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Development of a fast steering mirror of large diameter | High bandwidth fast steering mirror | Reference frames in allocentric representations are invariant across static and active encoding | eng_Latn | 28,800 |
Adaptive Modeling, Engineering Analysis and Design of Advanced Aerospace Vehicles | Achieving High Sustained Performance in an Unstructured Mesh CFD Application | Sliding Mode Observer Based Attitude Determination of Spacecrafts Without Angular Velocity Measurement | eng_Latn | 28,801 |
Previous research at Stanford University involving automatic aircraft landings using a high-precision form of differential GPS known as Carrier-Phase Differential GPS (CPDGPS) led to the development of a CPDGPS-based sensor system for automatic tractor control. With high accuracy and no drift in attitude (roll, pitch, and yaw) and/or position, CPDPGS offers a cost-effective sensor option for automatic guidance systems. Stanford researchers first experimentally demonstrated automatic steering of a medium-sized Deere 7800 tractor in the spring of 1996. Subsequent research included tractor control along spirals, arcs, and arbitrary curves, control on steeply sloped terrain, on-line identification of the steering valve’s ‘dead-zone’, and real-time identification/improvement of the tractor model. Typical controller accuracies under full engine load with implement lowered were near 0 cm mean and 4–6 cm S.D. in the tracking error of the control point on the tractor from the desired trajectory (as measured by CPDGPS). Unbiased low-noise attitude measurements were vital because the control point is not collocated with the GPS position antenna: an attitude measurement noise of only 1° (1 σ) is shown to introduce additional position uncertainty of up to 4 cm at the control point above the original GPS measurement (for a tractor of similar size to the one used in this research). In other words, accurate position information alone is not enough for a viable sensor system. These experimental results, enthusiastically received by farmers who have witnessed Stanford’s ‘GPS tractor’, show that CPDGPS could be the sole position and attitude sensor for a viable commercial tractor guidance system. | A brief review of research in agricultural vehicle guidance technologies is presented. The authors propose the conceptual framework of an agricultural vehicle autonomous guidance system, and then analyze its device characteristics. This paper introduces navigation sensors, computational methods, navigation planners and steering controllers. Sensors include global positioning systems (GPS), machine vision, dead-reckoning sensors, laser-based sensors, inertial sensors and geomagnetic direction sensors. Computational methods for sensor information are used to extract features and fuse data. Planners generate movement information to supply control algorithms. Actuators transform guidance information into changes in position and direction. A number of prototype guidance systems have been developed but have not yet proceeded to commercialization. GPS and machine vision fused together or one fused with another auxiliary technology is becoming the trend development for agricultural vehicle guidance systems. Application of new popular robotic technologies will augment the realization of agricultural vehicle automation in the future. Keywords: agricultural vehicle, guidance, machine vision, GPS DOI: 10.3965/j.issn.1934-6344.2009.03.001-016 Citation: Ming Li, Kenji Imou, Katsuhiro Wakabayashi, Shinya Yokoyama. Review of research on agricultural vehicle autonomous guidance. Int J Agric & Biol Eng, 2009; 2(3): 1 | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,802 |
Peter A. Parker*, Tianshn Liu tNASA Langley Research CenterHampton, Virginia 23681NThis paper presents an uncertainty analysis of I'the Single-Vector Force Balance Calibration System R(SVS). This study is focuscd (m the uncertainty Sinvolved in setting the independent variables during the x,y,zcalibration experiment. By knowing the uncertainly in Ythe calibration system, the flmdamenlal limits of thecalibration accuracy of a particular balance can be Subscriptsdetermined. A brief description of the SVS mechanical asystem is provided. A mathematical model is bkedeveloped to describe the mechanical system elements, fA sensitivity analysis of these parameters is carried out FPSthrough numerical simulations to assess the sensitivity IBSof the total uncertainty to the elemental error sources, igThese sensitivity coefficients provide valuable kinfimnation regarding the relative significance of theelemental sources of error. An example calculation of KEthe total uncertainty for a specific balance is provided. KESResults from this uncertainty analysis are specific to the LTSingle-Vector System. but the approach is broad in mclnature and therefore applicable to other measurementand calibration systems, me2Nomenclature me3 | The current approach used to apply uncertainty intervals to balance estimated loads is based on the root mean square error from calibration. Using the root mean square error, a constant interval is applied around the estimated load and it is expected that a predetermined percentage of the check-loads applied fall within this constant uncertainty interval. However, this approach ignores additional sources of uncertainty and assumes constant uncertainty regardless of the load combination and magnitude applied to the balance. Rigorous prediction interval theory permits varying interval widths but fails to account for the additional error sources that are unrelated to the mathematical modeling. An engineered solution is proposed that combines prediction interval theory and the need to account for the additional sources of uncertainty from calibration and check loading. Results from a case study using the in-situ load system show improved probabilistic behavior in terms of uncertainty interval capture percenta... | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,803 |
Vernalization and photoperiod requirements regulate the timing of the vegetative/reproductive transition in plants. Cereals adapted to cold winter climates regulate this developmental transition mainly through vernalization requirements, which delay transition from the vegetative to the reproductive growth stage. Recent research indicates that vernalization requirements also influence the expression of low-temperature (LT) tolerance genes in cereals exposed to acclimating temperatures. The objective of the present study was to determine if LT tolerance expression was also developmentally regulated by photoperiod response. The nonhardy, short day (SD) sensitive, wheat (Triticum aestivum L. em Thell) cultivar AC Minto, the LT tolerant, highly SD sensitive barley (Hordeum vulgare L.) cultivar Dicktoo, and a barley selection with very low sensitivity to SD were subjected to 8-h (SD) and 20-h (LD) days at cold acclimating temperatures over a period of 98 d. Final leaf number (FLN) was used to measure photoperi... | Short growing season and mid-summer heat and drought are limiting factors for spring cereal production in Canada, suggesting that higher and more stable yields may be possible if the seeding date occurred earlier in the spring. Field trials were conducted in southern Ontario in 2003 and 2004 to compare development and yield potential of frost (early April) and conventional (late April–early May) seeded hard red spring wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), and oat (Avena sativa L.) established using commercially available no-till planting equipment. Frost seeding had lower plant populations than conventional seeding, with pre-tillering plant population reductions for frost seeding averaging 44 plants m−2 (12%) for wheat and 27 plants m−2 (10%) for oats. In spite of lower plant population, frost seeding yields were higher than conventional seeding, with yield increases averaging 0.66 Mg ha−1 (24%) for wheat, 0.72 Mg ha−1 (20%) for oats, and 0.36 Mg ha−1 (11%, 2004 only) for barle... | ZY-3, which was launched on January 9, 2012, is the first stereo mapping satellite in China. The initial accuracy of direct georeferencing with the onboard three-line camera (TLC) imagery is low. Sensor geometric calibration with bundle block adjustment is used to improve the georeferencing accuracy. A new on-orbit sensor calibration method that can correct the misalignment angles between the spacecraft and the TLC and the misalignment of charge-coupled device is described. All of the calibration processes are performed using a multistrip data set. The control points are automatically matched from existing digital ortho map and digital elevation model. To fully evaluate the accuracy of different calibration methods, the calibrated parameters are used as input data to conduct georeferencing and bundle adjustment with a total of 19 strips of ZY-3 TLC data. A systematic error compensation model is introduced as the sensor model in bundle adjustment to compensate for the position and attitude errors. Numerous experiments demonstrate that the new calibration model can largely improve the external accuracy of direct georeferencing from the kilometer level to better than 20 m in both plane and height. A further bundle block adjustment with medium-accuracy ground control points (GCPs), using these calibrated parameters, can achieve external accuracy of about 4 m in plane and 3 m in height. Higher accuracy of about 1.3 m in plane and 1.7 m in height can be achieved by bundle adjustment using high-accuracy GCPs. | eng_Latn | 28,804 |
Anewdevicefore nding theazimuth ofa rigidbody isdescribed. Thedeviceisbased on thereading ofa rotating, vertically placed accelerometer. The functional relationship between the measured specie c force and the azimuth information is derived for leveled and tilted apparatus when the latter is at rest or when it is in a straight and level motion. A robust algorithm for extracting the azimuth from the accelerometer measurements is presented, an experimental setup is described, and test results are shown and analyzed. It is shown that the new device is accurate, has low sensitivity to common error sources, and yields the azimuth very fast. The device can be used for azimuth e nding in terrestrial missions as well as in orbiting spacecraft. | This paper presents an approach to seeker-azimuth determination using the gyro rotor and optoelectronic sensors. In the proposed method, the gyro rotor is designed with a set of black and white right spherical triangle patterns on its surface. Two pairs of optoelectronic sensors are located symmetrically around the gyro rotor. When there is an azimuth, the stripe width covering the black and white patterns changes. The optoelectronic sensors then capture the reflected optical signals from the different black and white pattern stripes on the gyro rotor and produce the duty ratio signal. The functional relationship between the measured duty ratio and the azimuth information is numerically derived, and, based on this relationship, the azimuth is determined from the measured duty ratio. Experimental results show that the proposed approach produces a large azimuth range and high measurement accuracy with the linearity error of less than 0.005. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,805 |
Triple-level-ceil(MLCx3) flash-memory chips are prevalent in current storage markets; however, the growing bit-error-rate and worsen reliability of TLC flash ceils impose challenges on the design of flash storage devices. This problem further exaggerates in the design of a reliable storage system which should be able top support the sudden-power-off-recovery functionalities. To guarantee the data integrity, the backup operation is necessary for supporting the sudden-power-off-recovery function, and it is typically adopted to avoid data corruption before programming TLC flash pages. Usually, the backup process results in a significant overhead and the degradation of programming performance. In contrast to the past work which relies on backup-based or RAID-like approaches to resolve the data integrity issue under any sudden power-off, a data-backup-free programming scheme is proposed to totally remove the needs of costly backup procedures as well as guarantee the data reliability. Our goal is to boost the system performance of TLC-based SSDs without harming the flash reliability. The capability of the proposed design is evaluated by a series of experiments, for which we have very encouraging results. Experimental results show that the proposed design can improve performance and reduce the number of block erasures by up to 78% and 76% respectively when compared to an existing backup-based approach. | Flash memory is now a critical component in building embedded or portable devices because of its nonvolatile, shock-resistant, and power-economic nature. With the very different characteristics of flash memory, mechanisms proposed for many block-oriented storage media cannot be directly applied to flash memory. Distinct from the past work, we propose an adaptive striping architecture to significantly boost the system performance. The capability of the proposed mechanisms and architecture is demonstrated over realistic prototypes and workloads. | ZY-3, which was launched on January 9, 2012, is the first stereo mapping satellite in China. The initial accuracy of direct georeferencing with the onboard three-line camera (TLC) imagery is low. Sensor geometric calibration with bundle block adjustment is used to improve the georeferencing accuracy. A new on-orbit sensor calibration method that can correct the misalignment angles between the spacecraft and the TLC and the misalignment of charge-coupled device is described. All of the calibration processes are performed using a multistrip data set. The control points are automatically matched from existing digital ortho map and digital elevation model. To fully evaluate the accuracy of different calibration methods, the calibrated parameters are used as input data to conduct georeferencing and bundle adjustment with a total of 19 strips of ZY-3 TLC data. A systematic error compensation model is introduced as the sensor model in bundle adjustment to compensate for the position and attitude errors. Numerous experiments demonstrate that the new calibration model can largely improve the external accuracy of direct georeferencing from the kilometer level to better than 20 m in both plane and height. A further bundle block adjustment with medium-accuracy ground control points (GCPs), using these calibrated parameters, can achieve external accuracy of about 4 m in plane and 3 m in height. Higher accuracy of about 1.3 m in plane and 1.7 m in height can be achieved by bundle adjustment using high-accuracy GCPs. | eng_Latn | 28,806 |
The purpose of this study was to assess the sagittal knee kinematics of rectus femoris transfer without hamstring lengthening. A retrospective review of seventeen children (29 knees) was performed. Gait analysis was performed prior to surgery and repeated at a minimum of one year after surgery. Sagittal knee kinematics were analyzed. Stance minimum knee flexion increased 7 degrees; swing maximum knee flexion increased 5 degrees; and swing minimum knee flexion increased 5 degrees. The present study confirmed previously reported increases in swing maximum knee flexion. Increases in stance minimum knee flexion and swing minimum knee flexion were also found. These findings have not been previously reported. | Background: Previous study has shown that children with cerebral palsy (CP) functioning at Gross Motor Function Classification System (GMFCS) levels III and IV do not benefit from distal rectus femoris transfer (DRFT) due to lack of improvement in stance knee extension. The fate of knees in such subjects who do not undergo DRFT is unknown. The purpose of this study was to compare knee kinematic outcomes in patients with CP and stiff knee gait who underwent single-event multilevel surgery with and without DRFT. Methods: Preoperative and postoperative gait analysis data were retrospectively reviewed for ambulatory (GMFCS levels I to IV) patients with CP with crouch and stiff knee gait whom underwent single-event multilevel surgery, including hamstring lengthening either with DRFT (N=34) or without DRFT (N=40). Statistical analyses included t tests and χ2 tests, and multiple regression analysis was performed to adjust for covariates. Data were stratified by GMFCS level groups I/II and III/IV. Results: Improved maximum knee extension in stance was seen for both the DRFT (P=0.0002) and no DRFT groups (P≤0.0006) at GMFCS levels I/II, and the no DRFT group at GMFCS levels III/IV (P=0.02). Excessive stance knee flexion persisted for those at GMFCS level III/IV after DRFT. Maximum knee flexion in swing was maintained after DRFT, but significantly decreased in the no DRFT group (P<0.002) for both GMFCS groups. Change in total knee range of motion improved after DRFT only in the GMFCS I/II group subjects with unilateral involvement (P=0.01). Timing of maximum knee flexion in swing improved for all patients regardless of DRFT or GMFCS level group (P<0.0001). Conclusions: In patients with CP functioning at GMFCS levels III and IV, DRFT results in persistent crouch postoperatively. Given the importance of maintaining upright posture in these patients, we do not recommend DRFT in patients functioning at GMFCS levels III and IV. Level of Evidence: Level III—retrospective comparative study. | Sensor fusion technique has been commonly used for improving the navigation of ::: autonomous agricultural vehicles by means of combining complimentary sensors mounted on such ::: vehicles for the position and attitude angle measurements. In this research, sensor fusion via an ::: Extended Kalman Filter (EKF) was used to integrate the attitude angle estimates from the Digital ::: Elevation Models (DEMs) and Terrain Compensation Module (TCM) sensor to improve the roll and ::: pitch angle measurements of a self propelled sprayer. The fusion algorithm was also developed to ::: improve the three-dimensional positioning of the sprayer, in particular the elevation measurements of ::: a GPS receiver mounted on the sprayer. Vehicle attitude and field elevation were measured at two ::: speeds, 5.6 km/h and 9.6 km/h, using a set of onboard sensors including a real-time kinematic-differential GPS receiver (RTK-DGPS), a TCM sensor and an Inertial Measurement Unit (IMU). A ::: second order auto-regressive (AR) model was developed to model the TCM roll and GPS-based ::: pitch errors. The derived error states were incorporated into the EKF algorithm and the measurement ::: noise covariance was estimated from the AR model, which limited the fine tuning of noise covariance ::: to the process noise covariance only. ::: The EKF estimations were compared with the IMU measurements to validate the performance of the ::: developed fusion algorithm. For the slow speed test data, the mean and standard deviation of the ::: errors of roll (Mean: -0.2244o, Std. Dev.:1.471o) and pitch (Mean: 0.0597o, Std. Dev.: 0.6621o) from ::: the EKF estimates were reduced considerably compared to that of the errors of roll (Mean: 0.2157o, ::: Std. Dev.: 2.4610o) and pitch (Mean: 0.0473o, Std. Dev.: 1.3230o) from DEM. Medium speed test ::: data also showed considerable improvement in the attitude angles estimated using the developed ::: EKF algorithm. The fusion algorithm for improving the elevation measurement of the GPS also ::: showed promising results. Thus, the fusion algorithm was effective in improving attitude and the ::: navigational accuracy of the self-propelled agricultural sprayer, which in turn will also facilitate the ::: automatic control of the implements that interact with the soil surface on undulated topographic ::: surfaces. | eng_Latn | 28,807 |
The technics for early diagnosis and airway management of acute epiglottitis in children continue to provoke disagreement. In 104 cases of children with acute epiglottitis, early diagnosis was confirmed by cervical roentgenograms, direct pharyngoscopy, or both. Airway maintenance was provided by nasotracheal intubation of conscious patients in most cases. No tracheostomies were performed. Blood cultures obtained after, rather than before, nasotracheal instrumentation resulted in a significant increase in positive Haemophilus influenzae cultures. | In the 1960s, managing croup was simple - put the child in the bathroom and run a hot shower. In most cases, the child's symptoms would be controlled. When the mist from the shower failed to control the croup, the parents would take the child to an emergency room. Often, the child would get better on the way to the hospital, thanks to the cool, outside air. At the hospital, a 'croupette' would be available for some children, and the health care providers hoped that the children would remain quiet in the strange tent filled with cold mist. Some hospitals even had special croup rooms where steam was piped in, and the whole room was filled with cold mist. Needless to say, nursing staff were not eager to work in these rooms. The last resort of treatment was a tracheotomy because the art of intubation had not yet been mastered. Two randomized studies failed to show the benefit of cool mist, and, today, it is rarely used (1,2). | ZY-3, which was launched on January 9, 2012, is the first stereo mapping satellite in China. The initial accuracy of direct georeferencing with the onboard three-line camera (TLC) imagery is low. Sensor geometric calibration with bundle block adjustment is used to improve the georeferencing accuracy. A new on-orbit sensor calibration method that can correct the misalignment angles between the spacecraft and the TLC and the misalignment of charge-coupled device is described. All of the calibration processes are performed using a multistrip data set. The control points are automatically matched from existing digital ortho map and digital elevation model. To fully evaluate the accuracy of different calibration methods, the calibrated parameters are used as input data to conduct georeferencing and bundle adjustment with a total of 19 strips of ZY-3 TLC data. A systematic error compensation model is introduced as the sensor model in bundle adjustment to compensate for the position and attitude errors. Numerous experiments demonstrate that the new calibration model can largely improve the external accuracy of direct georeferencing from the kilometer level to better than 20 m in both plane and height. A further bundle block adjustment with medium-accuracy ground control points (GCPs), using these calibrated parameters, can achieve external accuracy of about 4 m in plane and 3 m in height. Higher accuracy of about 1.3 m in plane and 1.7 m in height can be achieved by bundle adjustment using high-accuracy GCPs. | eng_Latn | 28,808 |
For various applications, such as object recognition or tracking and especially when the object is partly occluded or articulated, 3D information is crucial for the robustness of the application. A recently developed sensor to acquire distance information is based on the Photo Mixer Device (PMD)for which a distance error based on different causes can be observed. This article presents an improved distance calibration approach for PMD-based distance sensoring which handles objects with different Lambertian reflectance properties. Within this scope the relation of the sources of distance errors were investigated. Where applicable they were isolated for relational studies with the actuating variables, i.e. integration time, amplitude and measured distance, as these are the only parameters available for the calibration. The calibration results of the proposed method excel the results of all other known methods. In particular with objects with unknown reflectance properties a significant reduction of the error is achieved. | Three-dimensional (3D) data acquisition and real-time processing is a critical issue in an artificial vision system. The developing time-of-flight (TOF) camera as a real-time vision sensor for obtaining depth images has now received wide attention, due to its great potential in many areas, such as 3D perception, computer vision, robot navigation, human–machine interaction, augmented reality, and so on. This paper survey advances in TOF imaging technology mainly from the last decade. We focus only on recent progress of overcoming limitations such as systematic errors, object boundary ambiguity, multipath error, phase wrapping, and motion blur, and address the theoretical principles and future research trends as well. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 28,809 |
Efficient optimization approach for fast GPU computation of Zernike moments | Sub-pixel Gear Parameter Measurement Based on Zemike Moment | Zernike polynomials and atmospheric turbulence* | eng_Latn | 28,810 |
Beyond Inventory and Mapping : LIDAR , Landscape and Digital Landscape Architecture | Brawn and technology under the urban canopy | Full-DOF Calibration of a Rotating 2-D LIDAR With a Simple Plane Measurement | eng_Latn | 28,811 |
Sea level observations using multi-system GNSS reflectometry | 5-cm-Precision aircraft ocean altimetry using GPS reflections | Performance on the Cognitive Reflection Test is Stable Across Time | eng_Latn | 28,812 |
3-stage variable length continuous-flow scan vector decompression scheme | Multiscan-based test compression and hardware decompression using LZ77 | Sensorless vector and direct torque control | eng_Latn | 28,813 |
Imaging polarimeters for solar extreme ultraviolet astronomy | Design of precise ultraviolet imaging polarimeters that rely on in-situ calibration | Design of precise ultraviolet imaging polarimeters that rely on in-situ calibration | eng_Latn | 28,814 |
Improvements in ERBS attitude determination without gyros | Sliding Mode Observer Based Attitude Determination of Spacecrafts Without Angular Velocity Measurement | Experimental investigation of axial fan erosion and performance degradation | eng_Latn | 28,815 |
Automated Calibration Machine for Spirometers | Temperature Control using Fuzzy Logic | An Uncalibrated Stereo Visual Servo System | eng_Latn | 28,816 |
Implementation of an adaptive, constant thermodynamic speed simulated annealing schedule | An Ensemble Based Simulated Annealing Library for Multiprocessors | Sliding Mode Observer Based Attitude Determination of Spacecrafts Without Angular Velocity Measurement | eng_Latn | 28,817 |
Continuous vehicle tracking as well as detecting accidents, are significant services that are needed by many industries including insurance and vehicle rental companies. The main goal of this paper is to provide methods to detect the position of car accident. The models consider GPS/INS-based navigation algorithm, calibration of navigational sensors, a de-nosing method as long as vehicle accident, expressed by a set of raw measurements which are obtained from various environmental sensors. In addition, the location-based accident detection model is tested in different scenarios. The results illustrate that under harsh environments with no GPS signal, location of accident can be detected. Also results confirm that calibration of sensors has an important role in position correction algorithm. Finally, the results present that the proposed accident detection algorithm can recognize accidents and related its positions. | An optimal calibration method for a micro-electro-mechanical inertial measurement unit (MIMU) is presented in this paper. The accuracy of the MIMU is highly dependent on calibration to remove the deterministic errors of systematic errors, which also contain random errors. The overlapping Allan variance is applied to characterize the types of random error terms in the measurements. The calibration model includes package misalignment error, sensor-to-sensor misalignment error and bias, and a scale factor is built. The new concept of a calibration method, which includes a calibration scheme and a calibration algorithm, is proposed. The calibration scheme is designed by D-optimal and the calibration algorithm is deduced by a Kalman filter. In addition, the thermal calibration is investigated, as the bias and scale factor varied with temperature. The simulations and real tests verify the effectiveness of the proposed calibration method and show that it is better than the traditional method. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,818 |
If a Kalman Filter (KF) is applied to Global Positioning System (GPS) baseband signal preprocessing, the estimates of signal phase and frequency can have low variance, even in highly dynamic situations. This paper presents a novel preprocessing scheme based on a dual-filter structure. Compared with the traditional model utilizing a single KF, this structure avoids carrier tracking being subjected to code tracking errors. Meanwhile, as the loop filters are completely removed, state feedback values are adopted to generate local carrier and code. Although local carrier frequency has a wide fluctuation, the accuracy of Doppler shift estimation is improved. In the ultra-tight GPS/Inertial Navigation System (INS) integration, the carrier frequency derived from the external navigation information is not viewed as the local carrier frequency directly. That facilitates retaining the design principle of state feedback. However, under harsh conditions, the GPS outputs may still bear large errors which can destroy the estimation of INS errors. Thus, an innovative integrated navigation filter is constructed by modeling the non-negligible errors in the estimated Doppler shifts, to ensure INS is properly calibrated. Finally, field test and semi-physical simulation based on telemetered missile trajectory validate the effectiveness of methods proposed in this paper. | The well-known conventional Kalman filter requires an accurate system model and exact stochastic information. But in a number of situations, the system model has an unknown bias, which may degrade the performance of the Kalman filter or may cause the filter to diverge. The effect of the unknown bias may be more pronounced on the extended Kalman filter (EKF), which is a nonlinear filter. The two-stage extended Kalman filter (TEKF) with respect to this problem has been receiving considerable attention for a long time. Recently, the optimal two-stage Kalman filter (TKF) for linear stochastic systems with a constant bias or a random bias has been proposed by several researchers. A TEKF can also be similarly derived as the optimal TKF. In the case of a random bias, the TEKF assumes that the information of a random bias is known. But the information of a random bias is unknown or partially known in general. To solve this problem, this paper proposes an adaptive two-stage extended Kalman filter (ATEKF) using an adaptive fading EKF. To verify the performance of the proposed ATEKF, the ATEKF is applied to the INS-GPS (inertial navigation system-Global Positioning System) loosely coupled system with an unknown fault bias. The proposed ATEKF tracked/estimated the unknown bias effectively although the information about the random bias was unknown. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,819 |
The single-source localization problem (SSLP), which is nonconvex by its nature, appears in several important multidisciplinary fields such as signal processing and the global positioning system. In this paper, we cast SSLP as a Euclidean distance embedding problem and study a Lagrangian dual approach. It is proved that the Lagrangian dual problem must have an optimal solution under the generalized Slater condition. We provide a sufficient condition for the zero-duality gap and establish the equivalence between the Lagrangian dual approach and the existing Generalized Trust-Region Subproblem (GTRS) approach studied by Beck et al. [“Exact and Approximate Solutions of Source Localization Problems,” IEEE Trans. Signal Process., vol. 56, pp. 1770-1778, 2008]. We also reveal new implications of the assumptions made by the GTRS approach. Moreover, the Lagrangian dual approach has a straightforward extension to the multiple-source localization problem. Numerical simulations demonstrate that the Lagrangian dual approach can produce localization of similar quality as the GTRS and can significantly outperform the well-known semidefinite programming solver for the multiple source localization problem on the tested cases. | Based on two orthogonal linear sparse arrays (LSA) which consist of the coupled-sensors (CSs), a high resolution and no ambiguity (HRNA) method is proposed to estimate the two-dimensional (2D) angles of single source. The HRNA method flrst constructs a new covariance matrix to achieve no ambiguity independent angles estimation by using the covariance matrix generated by each LSA, and then computes joint elevation and azimuth angles by utilizing both the estimated independent angles and triangular relationship. For large array aperture of the LSA, the HRNA method earns a high angle resolution; however, its independent angles estimation accuracy is slightly lower than the multiple signal classiflcation (MUSIC) with a uniform linear array (ULA). In order to enhance the independent angle estimation performance, flrst improved HRNA (FI-HRNA) method is developed based on the HRNA and MUSIC methods. Further, in order to decrease the computational cost, second improved HRNA (SI-HRNA) method is presented based on FI-HRNA and MUSIC methods. The proposed SI-HRNA method obtains high angle resolution, high angle estimation accuracy and low computational load. In addition, the spacing between two adjacent CSs is not limited, and thus the angle resolution and estimation accuracy can be set according to practical demand. Numerical experiment and comparison with the other existing algorithms verify the efiectiveness and superior performance of the method proposed in this paper. | Blunt trauma abdomen rarely leads to gastrointestinal injury in children and isolated gastric rupture is even rarer presentation. We are reporting a case of isolated gastric rupture after fall from height in a three year old male child. | eng_Latn | 28,820 |
the maching algorithm in the vision-aided navigation system must be real-time, high-precision and suitable for matching different images with some scaling and rotation. This paper proposed three algorithms based on SURF, SIFT and ASIFT features. The SURF algorithm is the better method than the SIFT and ASIFT in theory, because the use of integral image and basic Hessian-matrix approximation has greatly reduce the computational complexity. The experimental results show that the three algorithms can obtain similar detecting and matching performance, but the SIFT and ASIFT need too much time to realize real time. So, the SURF is more suitable for scene matching in the vision-aided navigation system. | If a physical object has a smooth or piecewise smooth boundary, its images obtained by cameras in varying positions undergo smooth apparent deformations. These deformations are locally well approximated by affine transforms of the image plane. In consequence the solid object recognition problem has often been led back to the computation of affine invariant image local features. Such invariant features could be obtained by normalization methods, but no fully affine normalization method exists for the time being. Even scale invariance is dealt with rigorously only by the scale-invariant feature transform (SIFT) method. By simulating zooms out and normalizing translation and rotation, SIFT is invariant to four out of the six parameters of an affine transform. The method proposed in this paper, affine-SIFT (ASIFT), simulates all image views obtainable by varying the two camera axis orientation parameters, namely, the latitude and the longitude angles, left over by the SIFT method. Then it covers the other four parameters by using the SIFT method itself. The resulting method will be mathematically proved to be fully affine invariant. Against any prognosis, simulating all views depending on the two camera orientation parameters is feasible with no dramatic computational load. A two-resolution scheme further reduces the ASIFT complexity to about twice that of SIFT. A new notion, the transition tilt, measuring the amount of distortion from one view to another, is introduced. While an absolute tilt from a frontal to a slanted view exceeding 6 is rare, much higher transition tilts are common when two slanted views of an object are compared (see Figure hightransitiontiltsillustration). The attainable transition tilt is measured for each affine image comparison method. The new method permits one to reliably identify features that have undergone transition tilts of large magnitude, up to 36 and higher. This fact is substantiated by many experiments which show that ASIFT significantly outperforms the state-of-the-art methods SIFT, maximally stable extremal region (MSER), Harris-affine, and Hessian-affine. | This paper demonstrates a practical application of coupling a hydrodynamic model with a wave model for the calculation of storm tide elevations in the St. Johns River (Northeastern Florida). Hurricane Floyd (1999) is chosen as the storm of interest due to its track which paralleled the northeast coast of Florida without making a direct landfall on the St. Johns River. The advanced circulation (ADCIRC) numerical code is applied as the hydrodynamic model for the computation of two-dimensional circulation resulting from astronomic tides and meteorologically induced storm surge. The simulating waves nearshore (SWAN) numerical code is applied as the wave model for the computation of wind-induced waves. Two model implementations are considered in order to investigate the effect of short wave contributions on the overall storm tide water level: (1) a one-way coupling procedure that transfers gradient of wave radiation stresses from SWAN to ADCIRC; and (2) a two-way coupling procedure that builds on the former to... | eng_Latn | 28,821 |
Oat plants grown at an agricultural research facility produce higher yields in Field 1 than in Field 2, under well fertilised conditions and with similar weather exposure; all oat plants in both fields are healthy and show no sign of disease. In this study, the authors hypothesised that the soil microbial community might be different in each field, and these differences might explain the difference in oat plant growth. They carried out a metagenomic analysis of the 16 s ribosomal 'signature' sequences from bacteria in 50 randomly located soil samples in each field to determine the composition of the bacterial community. The study identified >1000 species, most of which were present in both fields. The authors identified two plant growth-promoting species that were significantly reduced in soil from Field 2 (Student's t-test P < 0.05), and concluded that these species might have contributed to reduced yield. | SUMMARY The common approach to the multiplicity problem calls for controlling the familywise error rate (FWER). This approach, though, has faults, and we point out a few. A different approach to problems of multiple significance testing is presented. It calls for controlling the expected proportion of falsely rejected hypotheses -the false discovery rate. This error rate is equivalent to the FWER when all hypotheses are true but is smaller otherwise. Therefore, in problems where the control of the false discovery rate rather than that of the FWER is desired, there is potential for a gain in power. A simple sequential Bonferronitype procedure is proved to control the false discovery rate for independent test statistics, and a simulation study shows that the gain in power is substantial. The use of the new procedure and the appropriateness of the criterion are illustrated with examples. | Our current and future Free Space Optical (FSO) designs and performance will be presented; Acquisition, Tracking, and Pointing (ATP) will be a key focus along with the size, weight and power (SWaP) of our existing ground systems and our design targets for space applications. Without gimbals, Rislet prisms, steering mirrors, or off-optical-z-axis sensing, and with only five static non-moving optical elements, we simply move an optical fiber in the focal plane to track the input and output beam angles over the entire wide range pointing field in both azimuth and elevation. Our optical design uses only five statically mounted elements. Fine pointing accuracies are sustained over the entire field without the use of coarse pointing and control systems. The impacts on SWaP are significant, and greatly simplify the packaging and ATP control systems. Our bi-directional ground-links have operated from 1 to 10 Gbps with link distances from 1 to 10 km. The primary ground systems that were delivered had ATP fields of 10o or 30o in both azimuth and elevation. For the 30o system, the pointing resolution is 470 nano-radian, while the 10o system provides 147 nano-radian pointing resolution. We also discuss the performance of our ground links and anticipated performance for various space applications. | eng_Latn | 28,822 |
The paper proposes Lyapunov-based nonlinear guidance laws for the stabilization of missile trajectories around null line-of-sight rate between the missile and the maneuvering target. The guidance laws are based on a nonlinear formulation of the missile-target kinematics. This allows tackling the stabilization of the cascade structure around suitable trajectories leading to relatively small miss distances. Several cases of maneuvering targets are considered and fundamental relationships between the proposed guidance laws and the classical proportional navigation guidance are established. Numerical simulations demonstrate the effectiveness of the proposed guidance laws. | The missile guidance law utilizing variable structure control is proposed. The acceleration command input is determined considering the target acceleration as an uncertainty. The proposed guidance law uses only the information for the target acceleration bound; therefore, the precise measuring of target acceleration during the maneuver is not required, and the robustness to the target maneuver is achieved. It is also shown that the proposed guidance law can be classie ed into the augmented true proportional navigation or the augmented realistic true proportional navigation guidance law. Numerical simulations show that the proposed guidance law yields better performance compared to existing guidance laws. ROPORTIONAL navigation guidance (PNG) was e rst developed during the 1950s, and during the 1970s and 1980s various PNG laws such as pure proportional navigation (PPN), true proportional navigation (TPN), the optimal guidance law (OGL), generalized TPN (GTPN), and realistic TPN (RTPN) have been developed. 1;2 Lots of studies have been performed to obtain analytical solutions as well as to analyze the capture regions of the guidance laws. With the development of accurate avionic sensors, augmented proportional navigation (APN) and the predictive guidance law (PGL) utilizing the information about target acceleration were also proposed. By analyzing the various guidance laws, the characteristics of the guidance laws, capture regions, and pursuing performance were compared. 1;2 | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 28,823 |
EISCAT measurements were performed during the four ROSE rocket launches. The results are presented. It is shown that the upper altitude limit of instabilities observed by in-situ measurements agrees with calculations using EISCAT results of drift and ion sound speed and assuming the two-stream-instability mechanism. The EISCAT results together with the STARE observations were used to calculate the ion velocity and the ψ-values from the dispersion relation of two-stream-instabilities. A comparison of EISCAT, STARE and in-situ measurements is discussed. | Low-frequency electrostatic fluctuations in the ionospheric E region were detected by instruments on the ROSE rockets. The phase velocity and dispersion of plasma waves in the ionospheric E region are determined by band-pass filtering and cross-correlating data of the electric-field fluctuations detected by the probes on the ROSE F4 rocket. The results were confirmed by a different method of analysis of the same data. The results show that the waves propagate in the Hall-current direction with a velocity somewhat below the ion sound speed obtained for ionospheric conditions during the flight. It is also found that the waves are dispersive, with the longest wavelengths propagating with the lowest velocity. | In this paper, we present a pen-shaped input device forwearable computers which reproduce and recognizethree-dimensional (3D) hand motions with no externalreferences. The input device is equipped with inertialsensors. The inertial sensors measure accelerations andangular velocities produced by a user's handwritingmotion in 2D/3D spaces. The measurements fromgyroscopes are integrated once to produce the attitude ofthe system and are consequently used to remove theeffects of the gravity and the inclination of the system.The compensated acceleration measurements are doublyintegrated to yield the position of the system. Due to theintegration processes involved in reproducing thehandwriting trajectory, the accuracy of the positionmeasurement significantly deteriorates along with time.To reproduce handwriting trajectory of a stroke on asurface and even in the air, we propose algorithms tosegment a stroke, to compensate the integration errors,and to reconstruct 2D trajectory on the x-y plane from 3Dtrajectory in the air. Real experimental results areincluded to show the effectiveness and feasibility of theproposed algorithms. The proposed methods provide anew approach for implementing a small, user-friendlykeyboard alternative input device for wearable computers. | eng_Latn | 28,824 |
It is well known that the key problem associated with network-based real-time kinematic (RTK) positioning is the estimation of systematic errors of GPS observations, such as residual ionospheric delays, tropospheric delays, and orbit errors, particularly for medium-long baselines. Existing methods dealing with these systematic errors are either not applicable for making estimations in real-time or require additional observations in the computation. In both cases, the result is a difficulty in performing rapid positioning. We have developed a new strategy for estimating the systematic errors for near real-time applications. In this approach, only two epochs of observations are used each time to estimate the parameters. In order to overcome severe ill-conditioned problems of the normal equation, the Tikhonov regularization method is used. We suggest that the regularized matrix be constructed by combining the a priori information of the known coordinates of the reference stations, followed by the determination of the corresponding regularized parameter. A series of systematic errors estimation can be obtained using a session of GPS observations, and the new process can assist in resolving the integer ambiguities of medium-long baselines and in constructing the virtual observations for the virtual reference station. A number of tests using three medium- to long-range baselines (from tens of kilometers to longer than 1000 kilometers) are used to validate the new approach. Test results indicate that the coordinates of three baseline lengths derived are in the order of several centimeters after the systematical errors are successfully removed. Our results demonstrate that the proposed method can effectively estimate systematic errors in the near real-time for medium-long GPS baseline solutions. | When using multiple reference station networks to support real-time kinematic positioning, the global positioning system (GPS) and/or GLONASS carrier-phase ambiguities associated with between-reference-receiver processing have to be resolved. At the initialisation stage it is not difficult to reliably resolve these ambiguities, in the post-processing mode, using data sets of several hours or days in length. However, due to significant residual atmospheric delays in the double-differenced measurements, it is a big challenge to resolve the ambiguities within the reference station network in real time, particularly in the case of the ambiguities of the newly risen satellites. Both temporal and spatial correlation characteristics for the atmospheric delays are discussed, and appropriate atmospheric delay prediction models are proposed. The experimental results show that the proposed bias prediction models can be used to reliably and efficiently resolve the integer ambiguities within reference station ne tworks in real time, on a single-epoch basis. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,825 |
H. Collins has challenged the empiricist understanding of experimentation by identifying what he thinks constitutes the experimenter’s regress: an instrument is deemed good because it produces good results, and vice versa. The calibration of an instrument cannot alone validate the results: the regressive circling is broken by an agreement essentially external to experimental procedures. In response, A. Franklin has argued that calibration is a key reasonable strategy physicists use to validate production of results independently of their interpretation. The physicists’ arguments about the merits of calibration are not coextensive with the interpretation of results, and thus an objective validation of results is possible. I argue, however, that the in-situ calibrating and measurement procedures and parameters at the Large Hadron Collider are closely and systematically interrelated. This requires empiricists to question their insistence on the independence of calibration from the outcomes of the experiment and rethink their position. Yet this does not leave the case of in-situ calibration open to the experimenter’s regress argument; it is predicated on too crude a view of the relationship between calibration and measurement that fails to capture crucial subtleties of the case. | The large ttbar production cross-section at the LHC suggests the use of top quark decays to calibrate several critical parts of the detectors, such as the trigger system, the jet energy scale and b-tagging. | Calibration data are often obtained by observing several well-understood objects simultaneously with multiple instruments, such as satellites for measuring astronomical sources. Analyzing s... | eng_Latn | 28,826 |
(i) A random simulation approach is proposed, which is at the centre of a numerical comparison of the performances of different GPS decorrelation methods. The most significant advantage of the approach is that it does not depend on nor favour any particular satellite–receiver geometry and weighting system. (ii) An inverse integer Cholesky decorrelation method is proposed, which will be shown to out-perform the integer Gaussian decorrelation and the Lenstra, Lenstra and Lovász (LLL) algorithm, and thus indicates that the integer Gaussian decorrelation is not the best decorrelation technique and that further improvement is possible. (iii) The performance study of the LLL algorithm is the first of its kind and the results have shown that the algorithm can indeed be used for decorrelation, but that it performs worse than the integer Gaussian decorrelation and the inverse integer Cholesky decorrelation. (iv) Simulations have also shown that no decorrelation techniques available to date can guarantee a smaller condition number, especially in the case of high dimension, although reducing the condition number is the goal of decorrelation. | In the high-precision application of Global Navigation Satellite System (GNSS), integer ambiguity resolution is the key step to realize precise positioning and attitude determination. As the necessary part of quality control, integer aperture (IA) ambiguity resolution provides the theoretical and practical foundation for ambiguity validation. It is mainly realized by acceptance testing. Due to the constraint of correlation between ambiguities, it is impossible to realize the controlling of failure rate according to analytical formula. Hence, the fixed failure rate approach is implemented by Monte Carlo sampling. However, due to the characteristics of Monte Carlo sampling and look-up table, we have to face the problem of a large amount of time consumption if sufficient GNSS scenarios are included in the creation of look-up table. This restricts the fixed failure rate approach to be a post process approach if a look-up table is not available. Furthermore, if not enough GNSS scenarios are considered, the table may only be valid for a specific scenario or application. Besides this, the method of creating look-up table or look-up function still needs to be designed for each specific acceptance test. To overcome these problems in determination of critical values, this contribution will propose an instantaneous and CONtrollable (iCON) IA ambiguity resolution approach for the first time. The iCON approach has the following advantages: (a) critical value of acceptance test is independently determined based on the required failure rate and GNSS model without resorting to external information such as look-up table; (b) it can be realized instantaneously for most of IA estimators which have analytical probability formulas. The stronger GNSS model, the less time consumption; (c) it provides a new viewpoint to improve the research about IA estimation. To verify these conclusions, multi-frequency and multi-GNSS simulation experiments are implemented. Those results show that IA estimators based on iCON approach can realize controllable ambiguity resolution. Besides this, compared with ratio test IA based on look-up table, difference test IA and IA least square based on the iCON approach most of times have higher success rates and better controllability to failure rates. | MLL1 regulates circadian promoters by depositing H3K4 trimethyl marks, whose levels are also modulated by the NAD+-dependent deacetylase SIRT1. SIRT1 is now shown to promote circadian deacetylation of MLL1, thus affecting MLL1's methyltransferase activity. | eng_Latn | 28,827 |
Previously, estimation of piled logs scattered in wide area is processed via hi-definition fixed camera which is not effective because the camera is attracted to be stolen. Therefore, the method to calculate area of segmented outdoor piled logs is now implemented on a smartphone which consists of an orientation sensor in order to benefit mobile usage and reduce cost of camera installation. The method is two-dimensional area calculation of piled logs with virtual ruler grid based on images taken through a calibrated smartphone camera. The result shows that the proposed method is able to alleviate time-consuming issue, the method accuracy is relatively 88% compared to measuring by a tape measure. | This paper presents a 3D shape measurement system using a fixed camera and a handheld 1D laser range finder based on Time-of-Flight method. The user of the system only has to sweep the slit light projected from the sensor onto the measured object to obtain its entire shape data. To achieve this, the relative 6DOF of rotation and translation between the sensor and the camera has to be estimated at each frame. We propose to estimate the perspective transformation matrix through matching of the range data and the captured slit light. We built the first prototype system and measured a 3D shape of a simple shaped object. | Results of several full scale RC (reinforced concrete) pile load tests were studied and analyzed to create a comparison between the MLT (maintained load test) and PDA (pile driving analyzer) methods. The ultimate pile capacities derived from analysis of PDA were consistently higher than results from the MLT. A coefficient of 0.9 or a 10% reduction is suggested to be applied to values derived from PDA. It is also observed that the longer the time interval, the greater the shaft friction contribution is towards the pile capacity. | eng_Latn | 28,828 |
In order to test the transmission performance of cross magnetic gear which used to the production line for flat, the test system is set up. Transmission performance in different materials, spaces, pole numbers and loads are studied. First, after analyzing the traditional test system, according to the testing requirements, the overall test system is established. The installation of the transmission components and sensor in test system are determined. And then transmission, data acquisition systems and analysis software are designed. Finally, in order to verify the performance of testing system, experiments under same loads and different spaces to compare the transmission torque are done. The results showed that the system met the requirements of testing reliable, high precision, strong anti-interference for the 42mm diameter of NdFeB magnetic gear during the process of 1:1 cross magnetic gear transmission testing. The torque testing accuracy is up to 0.01Nm and the relative error can be controlled within 0.82%. | The torque of magnetic coupling with different magnetic poles has been investigated by theoretical computations with both 2D and 3D modelling processes of the finite element analysis. The torque can be increased by increasing the number of poles for magnetic coupling between magnetic gears with 2 mm separation distance, provided that the number of poles is less than 10. However, the torque is inversely proportional to the number of poles when its number is larger than 10. This phenomenon is explained by analyzing the magnetic coupling strength of different poles. The 3D computer simulations are in excellent agreement with the experimental values. The 2D computer simulations can be improved by a "two magnetization vectors within a pole" technique; i.e. by properly rotating the angle between the two magnetization vectors. | Regular inspection of transmission lines is an essential work, which has been implemented by either labor intensive or very expensive approaches. 3D reconstruction could be an alternative solution to satisfy the need for accurate and low cost inspection. This paper exploits the use of an unmanned aerial vehicle (UAV) for outdoor data acquisition and conducts accuracy assessment tests to explore potential usage for offsite inspection of transmission lines. Firstly, an oblique photogrammetric system, integrating with a cheap double-camera imaging system, an onboard dual-frequency GNSS (Global Navigation Satellite System) receiver and a ground master GNSS station in fixed position, is designed to acquire images with ground resolutions better than 3 cm. Secondly, an image orientation method, considering oblique imaging geometry of the dual-camera system, is applied to detect enough tie-points to construct stable image connection in both along-track and across-track directions. To achieve the best geo-referencing accuracy and evaluate model measurement precision, signalized ground control points (GCPs) and model key points have been surveyed. Finally, accuracy assessment tests, including absolute orientation precision and relative model precision, have been conducted with different GCP configurations. Experiments show that images captured by the designed photogrammetric system contain enough information of power pylons from different viewpoints. Quantitative assessment demonstrates that, with fewer GCPs for image orientation, the absolute and relative accuracies of image orientation and model measurement are better than 0.3 and 0.2 m, respectively. For regular inspection of transmission lines, the proposed solution can to some extent be an alternative method with competitive accuracy, lower operational complexity and considerable gains in economic cost. | eng_Latn | 28,829 |
We present the results of hydrodynamical simulations of nonaxisymmetric gas flow past a gravitating compact object in two dimensions. Calculations were performed with uniform flow as well as with transverse velocity and density gradients. We find that the flow is highly nonsteady, exhibiting the "flip-flop" behavior seen in previous studies, in which accretion disks form with alternating directions of rotation. We investigate the periodicity of the flip-flop behavior and study the effects of spatial resolution on the results. We find that the flip-flop motion creates accretion torques that, in some cases, may be large enough to explain the erratic spin behavior observed in Be-type X-ray pulsars. | The BATSE all-sky monitor on the Compton Gamma Ray Observatory is a superb tool for the study of accretion-powered pulsars. In the first part of this thesis, I describe its capabilities for hard X-ray observations above 20 keV, present techniques for timing analysis of the BATSE data, and discuss general statistical issues for the detection of pulsed periodic signals in both the time and frequency domains. BATSE's 1-day pulsed sensitivity in the 20-60 keV range is ≈ 15 mCrab for pulse periods 2s≲Ppulse≲400s, covering most of the known accreting pulsars. Its sensitivity degrades substantially outside of this range. In the second part of this thesis, I present the results of several science investigations applying these techniques. Half the 42 known accreting pulsars have been detected with BATSE and are monitored whenever they are active. Except for a few which lie outside of BATSE's sensitivity range, the rest are all transient sources which may eventually be detected in outburst. The detected systems include four new transients discovered by BATSE, one of which is discussed in detail. A new technique used to localize this source, GRO J1948+32, is described. Observations of the 38-s pulsar OAO 1657-415 discovered that it is in a 10.4-d eccentric orbit and undergoes regular X-ray eclipses by its massive companion, making it only the seventh known eclipsing X-ray pulsar. Constraints placed by the pulsar mass function and the eclipse duration indicate that the undetected binary companion must be an OB supergiant. If the companion can be identified and its orbital velocity measured, the neutron star mass can be determined. The 7.7-s pulsar 4U 1626-67 was found to be in an extended spin-down state, ending over a decade of rapid, steady spin-up. It is only the second steady-state disk accreter known to have undergone a torque reversal. The other, the 2-min pulsar GX 1+4, underwent two torque reversals during our observations and is detected up to 160 keV. During spin-down, we find that pulsed flux and torque in GX 1+4 are anticorrelated, the opposite of what is predicted by the usual theories of magnetic accretion torques. | This paper presents a method for using optical flow measurements to estimate stride length for pedestrian navigation applications. Optical flow sensors, such as the detectors used in an optical computer mouse, measure the velocity of visual features traversing an imaging array. We consider the case in which the optical flow sensor is attached to the leg of a pedestrian and used to infer distance traveled. In this configuration, optical flow data are a projection of the velocity and angular velocity of the leg to which the sensor is attached; a dynamic motion model is needed to estimate leg states and to infer stride length from the optical flow data. In this paper, we consider a very simple dynamic walking model, called the Spring Loaded Inverted Pendulum (SLIP) model. In a hardware-based trial, the basic SLIP model estimated stride length with 10% error. We anticipate that refinements to the basic SLIP model will enable more accurate stride-length estimation in the future. | eng_Latn | 28,830 |
A contour control strategy has been studied in this paper to improve the contour error of CNC machine tools. First, a single axis controller is analysed and then a velocity feedforward controller is added in the velocity loop. To further reduce the contour error, a cross-coupled controller is adopted and an algorithm for an on-line estimation of the contour error in arbitrary curved contouring is proposed. These controller parameters are all optimised by an efficient robust optimisation technique using genetic algorithms. Experimental results are provided to illustrate the proposed methods. | Reduction of contour error and saving energy are major essential requirements in computer numerical control (CNC) machines. This paper introduces a novel adaptive sliding contouring control using a nonlinear sliding surface to achieve higher machining accuracy without any increase of consumed energy. The main objective of this approach is that control gains are automatically adapted based on the contouring error to simultaneously generate appropriate control signals. The proposed controller has constantly improved the machining accuracy and achieved a perfect performance with shorter rise time and lower overshoot. To verify the proposed approach, simulation results for a biaxial feed drive system demonstrate a significant contouring performance for circular and non-circular trajectories. The adaptive algorithm decreases a contour error by about 31% and 29% than sliding mode control without adaptation through circular and non-circular trajectories, respectively. | The Global Positioning System (GPS) is unreliable in dense urban areas, known as urban canyons, which have tall buildings or narrow streets. This is because the buildings block the signals from many of the satellites. Combining GPS with other Global Navigation Satellite Systems (GNSS) significantly increases the availability of direct line-of-sight signals. Modelling is used to demonstrate that, although this will enable accurate positioning along the direction of the street, the positioning accuracy in the cross-street direction will be poor because the unobstructed satellite signals travel along the street, rather than across it. A novel solution to this problem is to use 3D building models to improve cross-track positioning accuracy in urban canyons by predicting which satellites are visible from different locations and comparing this with the measured satellite visibility to determine position. Modelling is used to show that this shadow matching technique has the potential to achieve metre-order cross-street positioning in urban canyons. The issues to be addressed in developing a robust and practical shadow matching positioning system are then discussed and solutions proposed. | eng_Latn | 28,831 |
In this article, the processing steps applied to the raw GOCE science payload instrument data (level 0) in order to obtain input data for the gravity field determination (level 1b) are described. The raw gradiometer measurements, which are given at the level of control voltages, have to be transformed into accelerations and gradients. For the latter step, knowledge about the GOCE attitude is required, which is provided by the star trackers. In addition, the data of the satellite to satellite tracking instrument are used to date the measurements, after its clock error has been corrected. All intermediate steps of the processing flow are described. Together with the explanation of the processing flow, an overview of the main level 1b products is given. The final part of the article discusses the means of quality control of the L1b data currently used and gives an outlook on potential processor evolutions. | An innovative orbit determination method which makes use of gravity gradients for Low-Earth-Orbiting satellites is proposed. The measurement principle of gravity gradiometry is briefly reviewed and the sources of measurement error are analyzed. An adaptive hybrid least squares batch filter based on linearization of the orbital equation and unscented transformation of the measurement equation is developed to estimate the orbital states and the measurement biases. The algorithm is tested with the actual flight data from the European Space Agency Gravity field and steady-state Ocean Circulation Explorer. The orbit determination results are compared with the GPS-derived orbits. The radial and cross-track position errors are on the order of tens of meters, whereas the along-track position error is over one order of magnitude larger. The gravity gradient based orbit determination method is promising for potential use in GPS-denied spacecraft navigation. | ●The conditions are officially justified not as punishment for prisoners but as an administrative measure. Prisoners are placed in control units in administrative moves and since there are no rules governing such moves (in contrast to punitive moves), prisoners are denied any due process and prison officials can incarcerate any prisoner in a control unit for as long as they choose, without having to give any reason. | eng_Latn | 28,832 |
In this paper, the history of inertial navigation technology is introduced and advancement and present development status of the up-to-date inertial sensors are described as well as some state-of-the-art inertial measurement units and their superior specifications are presented. Meanwhile, the application fields of inertial navigation technology are explained, with emphasizing that the nautical applications and development of shipborne inertial navigation systems are expounded. In conclusion, as new inertial sensors springing up and maturing, the hybrid navigation system based on inertial navigation system would be one important orientation of navigation technology in the near future. | The influence of gravity disturbance vector can't be neglected in high-precision long-time inertial navigation system (INS). In this paper, proceeding from INS arrange equations, we establish an error model of INS with gravity disturbance vector, and discuss on the basis of a case study of single channel how gravity disturbance vector influences INS in three varying situations. The simulation result indicates that the gravity disturbance vector has a conspicuous influence on high-precision long-time INS. On the basis of the comprehensive treatise of the influence of gravity disturbance vector on high-precision long-time INS, combined with the actual situation, we put forward two methods of gravity disturbance compensation. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 28,833 |
An optical noncontact method eliminates the resonances generated by mechanical interaction of the HDA arm with a conventional pushpin. Errors due to air turbulence in a laser interferometer are avoided by using an encoder with one nanometer resolution. | The Q-filter cut-off frequency in a Disturbance Observer (DOB) is restricted by the model mismatch between the plant and its nominal model. DOB Robustness is usually poor when the cut-off frequency of Q-filter increases. In this paper, robustness of the DOB is improved by shaping the true plant with a cascaded frequency shaping filter, while the nominal plant model remains fixed. Once the shaping filter is optimally designed based on DOB robust stability, the cut-off frequency of Q-filter can be greatly increased without loss of stability. The proposed algorithm is implemented on a typical tracking problem, i.e., the spiral writing in hard disk drives. | Historically, the climate of the HKH has experienced significant changes that are closely related to the rise and fall of regional cultures and civilizations. Studies show well-established evidence that climate drivers of tropical and extra-tropical origin—such as the El Nino-Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), Indian Ocean Dipole (IOD), the Madden-Julian Oscillation (MJO), and the Arctic Oscillation—influence the region’s weather and climate on multiple spatio-temporal scales. | eng_Latn | 28,834 |
The knowledge of ground elevation is essential in most remote sensing applications especially for very high resolution ::: images. This ground elevation information can be retrieved from a pair of stereoscopic images, by correlation methods. ::: The improving resolution of Earth observation systems and their increasing stereoscopic capabilities open up new ::: horizons for automatic Digital Elevation Model (DEM) generation and allow buildings reconstruction to be considered. ::: To reach this goal, the correlation methods used for computing disparities has to be improved and adapted to urban ::: scenes. ::: This paper aims to describe a new method of DEM generation from a stereoscopic pair of high resolution images, ::: whether aerial or satellite, fitted to urban scenes, focusing on correlation improvement. The proposed framework relies ::: on a multiscale dense correlation method with a step of regularisation/interpolation and a step of filtering. It efficiently ::: improves the quality of disparity maps, by reducing the level of noise, and allows us to generate high quality DEM from ::: high resolution images. | The new French high resolution earth observing satellite PLEIADES-HR will be launched in 2011. A specific design and new technologies have been embarked to provide great agility. These capabilities offer new methods to perform the image quality activities during the commissioning period. Some of them depend on dedicated guidance of the satellite platform and specific targets on the Earth or beyond. For instance, one concerns the so-called AMETHIST method to compute the normalization coefficients of the radiometric model. Another one is based on a controlled slow-motion to get a reference image line whose deviation along the image will give information on radiometric noise or attitude perturbations. Another uses the stars to measure the line-of-sight dynamic stability or the instrument refocusing needs. These originals methods and some more are briefly presented in this paper after an introduction of PLEIADES-HR capacities. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 28,835 |
The laminar-to-turbulent boundary-layer transition on a high-speed rotating propeller was measured using Temperature-Sensitive Paint (TSP). The TSP formulation, the experimental set-up, the image acquisition, and processing procedure had been evaluated in a pretest. High resolution propeller images were obtained even at rotation speeds of 9600 rpm. Obtained temperature images clearly show the temperature steps due to the laminar-to-turbulent boundary layer transition. Based on the pretest results, a wind tunnel experiment was conducted in the low-speed wind-tunnel BLSWT of AIRBUS in Bremen at propeller rotation speeds up to 14400 rpm. The TSP results of the wind tunnel test visualized the development of laminar and turbulent regions on the propeller blade depending on propeller speed. | Differential Infrared Thermography (DIT) was applied and investigated for the detection of unsteady boundary layer transition locations on a pitching rotor blade airfoil and on a rotating blade under cyclic pitch. The paper demonstrates the unsteady transition detection with a high framing rate infrared camera and the differential infrared thermography method. DIT is based on image intensity differences between two subsequently recorded images. A pitching NACA0012 airfoil served as the first test object. The recorded images were used in order to investigate and to further improve evaluation strategies for periodically moving boundary layer transition lines. The gained knowledge has then been used for the optical measurement of unsteady transition locations on helicopter rotor blade models under cyclic pitch and rotation for the first time. Image de-rotation for tracking the blade was employed using a rotating mirror to increase exposure time without causing motion blur. The paper describes the challenges that occurred during the recording and evaluation of the data in detail. The results obtained were discussed and found to be encouraging to further improve the method towards the measurement of unsteady boundary layer transition lines on helicopter rotor models in forward flight condition without the need of blade instrumentation. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,836 |
Rationale ::: Non-daily, or intermittent smokers (ITS), are increasingly prevalent. Their smoking may be more situational than that of daily smokers (DS), and thus is hypothesized to be more influenced by cues. | An adjustable clamp for temporary occlusion of a blood vessel for use in microvascular surgery is disclosed. The clamp includes a pair of aneurysm clips which slide along a cylindrical bar. Frictional engagement is provided between the clips and other components of the clamp, with the result that the clips may be positioned along the bar at any desired spacing, and, once positioned, such positions will be maintained during use of the clamp. | Differential Infrared Thermography (DIT) was applied and investigated for the detection of unsteady boundary layer transition locations on a pitching rotor blade airfoil and on a rotating blade under cyclic pitch. The paper demonstrates the unsteady transition detection with a high framing rate infrared camera and the differential infrared thermography method. DIT is based on image intensity differences between two subsequently recorded images. A pitching NACA0012 airfoil served as the first test object. The recorded images were used in order to investigate and to further improve evaluation strategies for periodically moving boundary layer transition lines. The gained knowledge has then been used for the optical measurement of unsteady transition locations on helicopter rotor blade models under cyclic pitch and rotation for the first time. Image de-rotation for tracking the blade was employed using a rotating mirror to increase exposure time without causing motion blur. The paper describes the challenges that occurred during the recording and evaluation of the data in detail. The results obtained were discussed and found to be encouraging to further improve the method towards the measurement of unsteady boundary layer transition lines on helicopter rotor models in forward flight condition without the need of blade instrumentation. | eng_Latn | 28,837 |
Pointing errors can compromise the performance of laser systems and cause numerous operational problems. In this paper, alignment tolerances for a bistatic sensor pod are derived from first principles. The method applies to a sizeable class of problems but is particularly relevant to military applications like laser target designation and rangefinding. It yields exact or conservative estimates in most cases of practical interest. Various results are explored from the point-of-view of employment methods and military deployment. | Pointing errors can compromise the performance of laser systems and cause numerous operational problems. Alignment tolerances for a generic electro-optical system comprising a laser are derived from first principles. The method applies to a sizeable class of problems but is particularly relevant to military applications such as laser target designation and rangefinding. It yields exact or conservative estimates in most cases of practical interest. Various results are explored from the point of view of employment methods and military deployment. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,838 |
The insect visuomotor system combines a lightweight and high bandwidth sensor with fast processing algorithms for efficient information extraction that enables autonomous navigation in complex, obstacle laden environments. In this paper, an H ∞ loop shaping controller synthesis framework is introduced to analyze an information extraction approach from patterns of optic flow based on analogs of wide field motion sensitive interneurons in the insect visuomotor system. Local proximity and velocity estimates are obtained with an optic flow model that is based on parameterization of typical three-dimensional urban environments. The insect inspired visual navigation technique combines proximity and speed estimates with an H ∞ controller that provides robust stability in a cluttered environment as well as mitigates measurement noise and gusts. The loop shaping approach is used to demonstrate safe obstacle avoidance and terrain following behavior in simulation on an autonomous helicopter miro-air-vehicle for an urban-like environment subjected to gusts. | This paper describes the design, operation and performance test results of a miniature, low cost integrated GPS/inertial navigation system (INS) designed for use in UAV or UGV guidance systems. The system integrates a miniaturized commercial GPS with a low grade Micro-Electro-Mechanical (MEMS) inertial measurement unit (IMU). The MEMS IMU is a small self-contained package (< 1 cu inch) and includes a triad of accelerometers and gyroscopes with additional sensors integrated for temperature compensation and baro pressure altitude aiding. The raw IMU data is provided through a serial interface to a processor board where the inertial navigation solution and integrated GPS/inertial Kalman filter is generated. The GPS/Inertial software integration is performed using NAVSYS’ modular InterNav software product. This allows integration with different low cost GPS chips sets or receivers and also allows the integrated GPS/inertial navigation solution to be embedded as an application on a customer’s host computer. This modular, object oriented architecture facilitates integration of the miniature MEMS GPS/INS navigation system for embedded navigation applications. Test results are presented in this paper showing the performance of the integrated MEMS GPS/INS navigation system when used to perform guidance for a small Unmanned Ground Vehicle (UGV). Data is provided showing the position, velocity and attitude accuracy when operating with GPS aiding and also for periods where GPS dropouts occur and alternative navigation update sources are used to bound the MEMS inertial navigation error growth. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,839 |
Fixed-wing aircraft equipped with downward pointing cameras and/or LiDAR can be used for inspecting approximately piecewise linear assets such as oil-gas pipelines, roads and power-lines. Automatic control of such aircraft is important from a productivity and safety point of view (long periods of precision manual flight at low-altitude is not considered reasonable from a safety perspective). This paper investigates the effect of any unwanted coupling between guidance and autopilot loops (typically caused by unmodeled delays in the aircraft’s response), and the specific impact of any unwanted dynamics on the performance of aircraft undertaking inspection of piecewise linear corridor assets (such as powerlines). Simulation studies and experimental flight tests are used to demonstrate the benefits of a simple compensator in mitigating the unwanted lateral oscillatory behaviour (or coupling) that is caused by unmodeled time constants in the aircraft dynamics. | Miniature Air Vehicles (MAVs) equipped with lightweight, inexpensive cameras have recently been employed in a great variety of missions due to their increased capability and continued affordability. Unfortunately, MAVs often experience unintended motions due to atmospheric turbulence. As a result, MAV video streams are often characterized by high-frequency jitter, making it difficult for a human operator to obtain information from the video. This paper describes a tool, operating on a mobile ground station, that produces real-time stabilized MAV video by estimating the actual and intended video motion between frames to remove jitter. The difficulty of this problem is compounded by the noise introduced during transmission. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 28,840 |
The design, test and results of a positioning system consisting of a differential global positioning system (DGPS) receiver, a radar velocity sensor, a wheel velocity sensor and an electronic compass are discussed. The characteristics of the individual sensors were investigated and with these results a Kalman filter was designed to integrate the different signals into a single estimate of position, velocity and heading. Field tests were conducted to investigate both the real-time performance of the system and the robustness against distortions caused by malfunctioning of the sensors. An extended Kalman filter was found to improve accuracy of positioning and was able to bridge gaps in position information due to blockage of the GPS receiver. The position measurements from the GPS receiver had a standard deviation of 1·18 m. The use of a nine-state filter reduced the standard deviation of positioning to 0·71 m. On a track which ran along a line of trees and between buildings, the filter was able to maintain position for 12 s, while the GPS receiver lost satellite fix. | Sensor fusion technique has been commonly used for improving the navigation of ::: autonomous agricultural vehicles by means of combining complimentary sensors mounted on such ::: vehicles for the position and attitude angle measurements. In this research, sensor fusion via an ::: Extended Kalman Filter (EKF) was used to integrate the attitude angle estimates from the Digital ::: Elevation Models (DEMs) and Terrain Compensation Module (TCM) sensor to improve the roll and ::: pitch angle measurements of a self propelled sprayer. The fusion algorithm was also developed to ::: improve the three-dimensional positioning of the sprayer, in particular the elevation measurements of ::: a GPS receiver mounted on the sprayer. Vehicle attitude and field elevation were measured at two ::: speeds, 5.6 km/h and 9.6 km/h, using a set of onboard sensors including a real-time kinematic-differential GPS receiver (RTK-DGPS), a TCM sensor and an Inertial Measurement Unit (IMU). A ::: second order auto-regressive (AR) model was developed to model the TCM roll and GPS-based ::: pitch errors. The derived error states were incorporated into the EKF algorithm and the measurement ::: noise covariance was estimated from the AR model, which limited the fine tuning of noise covariance ::: to the process noise covariance only. ::: The EKF estimations were compared with the IMU measurements to validate the performance of the ::: developed fusion algorithm. For the slow speed test data, the mean and standard deviation of the ::: errors of roll (Mean: -0.2244o, Std. Dev.:1.471o) and pitch (Mean: 0.0597o, Std. Dev.: 0.6621o) from ::: the EKF estimates were reduced considerably compared to that of the errors of roll (Mean: 0.2157o, ::: Std. Dev.: 2.4610o) and pitch (Mean: 0.0473o, Std. Dev.: 1.3230o) from DEM. Medium speed test ::: data also showed considerable improvement in the attitude angles estimated using the developed ::: EKF algorithm. The fusion algorithm for improving the elevation measurement of the GPS also ::: showed promising results. Thus, the fusion algorithm was effective in improving attitude and the ::: navigational accuracy of the self-propelled agricultural sprayer, which in turn will also facilitate the ::: automatic control of the implements that interact with the soil surface on undulated topographic ::: surfaces. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,841 |
This paper explains development of the general mathematical model of trochoidal gearing that can be applied for gerotor pumps and cyclo reducers. The model analyzes geometry and physics of the gearing pair in trochoidal pump where the outer gear has one tooth more than the inner gear. The inner gear profile is described by peritrochoid equidistance and the outer gear profile by circular arc. Mathematical model of gearing with clearances is based on the principle of an ideal profile development. Minimum clearance height between teeth profiles in relation to instantaneous gear ratio is determined. The influence of gear profile geometrical parameters on gearing process, clearance height change, and pulsation of drive moment is analyzed and presented in numerical examples. Obtained results can be used for the design of the trochoidal gearing where accurate and silent operation is required. [DOI: 10.1115/1.4005621] | Gerotor pumps are widely used for fuel and lubricating oil distribution, since they provide an economic and compact solution for low-pressure fluid systems. Made of two internally coupled gears, their behavioral and operative performances are strictly tied to their geometrical designs. Traditionally, the external gear features circular lobes that give origin to a cycloidal profile for the internal rotor. In this paper, the use of profiles based on asymmetric lobes made of elliptic arcs is further explored and expanded. At first, a complete mathematical framework describing the pump geometry and its dynamic behavior is provided, while algorithms used to compute a selected number of performance indexes are presented and when possible, verified. Hence, a single-objective optimization procedure is applied to the traditional cycloidal profile, in order to minimize each of the following quantities: the flow rate irregularity, the expected wear rate, and the estimated rotor mass. Finally, a multi-objective optimization process based on evolutionary strategy is employed, to obtain several asymmetric profiles minimizing the combination of two or more performance indexes. The results are hence compared, and the merits associated with the use of asymmetric lobes are presented. | ZY-3, which was launched on January 9, 2012, is the first stereo mapping satellite in China. The initial accuracy of direct georeferencing with the onboard three-line camera (TLC) imagery is low. Sensor geometric calibration with bundle block adjustment is used to improve the georeferencing accuracy. A new on-orbit sensor calibration method that can correct the misalignment angles between the spacecraft and the TLC and the misalignment of charge-coupled device is described. All of the calibration processes are performed using a multistrip data set. The control points are automatically matched from existing digital ortho map and digital elevation model. To fully evaluate the accuracy of different calibration methods, the calibrated parameters are used as input data to conduct georeferencing and bundle adjustment with a total of 19 strips of ZY-3 TLC data. A systematic error compensation model is introduced as the sensor model in bundle adjustment to compensate for the position and attitude errors. Numerous experiments demonstrate that the new calibration model can largely improve the external accuracy of direct georeferencing from the kilometer level to better than 20 m in both plane and height. A further bundle block adjustment with medium-accuracy ground control points (GCPs), using these calibrated parameters, can achieve external accuracy of about 4 m in plane and 3 m in height. Higher accuracy of about 1.3 m in plane and 1.7 m in height can be achieved by bundle adjustment using high-accuracy GCPs. | eng_Latn | 28,842 |
Multisensor navigation data synthesis (MNDS) is the process of fusing outputs from inertial sensors with information from other sensors and information processing blocks into one representational form. This technique is anticipated to accomplish enhanced accuracy and more specific inferences than could be achieved by the use of a single sensor alone. Therefore, this research work expounds innovative filtering methodology for the multisensor navigation data synthesis for a ballistic missile application that augments navigation system performance. The premise and characteristics of strapdown inertial navigation system (SINS) integrated with the astronavigation system (ANS) based on the unscented particle filter (UPF) are investigated in this paper. Configuration of the integrated navigation system is presented with its canonical model, and system dynamic and stochastic models required for the filtering algorithm are presented. To exemplify integrated navigation filter mechanization is the foremost aspiration of this research. To validate and corroborate the designed MNDS technique, simulations are carried out that demonstrate the validity of this method on enhancing the navigation system's accuracy with estimation and compensation for the gyro's drift. This integrated system results in a significant reduction in impact-point dispersion of a re-entry vehicle. | A new quaternion-based method for the SINS/SAR (strap-down inertial navigation system/synthetic aperture radar) integrated navigation system is presented. This method overcomes the shortcomings due to the linear SINS error model used in the currently existing SINS/SAR integrated navigation systems. A quaternion-based matrix is derived for describing the attitude of SINS. Quaternion-based nonlinear error and observation models are established for the SINS/SAR integrated navigation system. An adaptive unscented particle filtering (UPF) algorithm is developed based on the quaternion-based nonlinear models for optimal data fusion in the SINS/SAR integrated navigation system. Experimental results demonstrate that the proposed quaternion based method can effectively reduce the navigation error and improve the navigational positioning precision. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,843 |
Metrological procedures require a leveling staff calibration for an estimation of a true staff scale. The calibration process is usually realized on laboratory comparators. Two automatic comparators for digital level calibration were built by the staff of Department of Geomatics. This article brings some information about properties of developed systems and about a control software for the comparators. | Today, digital levels are commonly used in precise levelling. Every level at the market has its specific error pattern, and knowledge about this is essential to obtain precise height readings. To identify and investigate the error pattern of digital levels, a vertical comparator was developed at the Graz University of Technology. System calibration is used to calibrate the level and the staff together. This paper reports about the design of and experiences with the vertical comparator. The standard uncertainty of this comparator is ±3μm (computed in accordance with GUM, k=2). The vertical comparator can be used for both, the quality control of digital levels and the routine system calibration which also yields the scale value of the system. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 28,844 |
Earth-observing satellite sensors are calibrated in the laboratory against blackbody and lamp-based uniform optical ::: radiation standards. These sources and additional characterization tests fail to approximate the spatially, spectrally, and ::: temporally complex scenes viewed on-orbit by these sensors. The lack of appropriate diagnostic tools limits the ability ::: of researchers to fully characterize and understand the radiometric performance of sensors before deployment. The ::: consequences of these limitations are that problems in a sensor's performance, e.g. optical crosstalk, scattered light, ::: earth-shine, are often first observed on-orbit. Advanced radiometric characterization artifacts, able to produce realistic ::: spectral distributions and spatial scenes in the laboratory, would enable more complete instrument characterization, with ::: the resulting potential benefit of improved on-orbit performance. | The pre-launch characterization and calibration of remote sensing instruments should be planned and carried out in conjunction with their design and development to meet the mission requirements. The onboard calibrators such as blackbodies and the sensors such as spectral radiometers should be characterized and calibrated using SI traceable standards. In the case of earth remote sensing, this allows inter-comparison and intercalibration of different sensors in space to create global time series of climate records of high accuracy where some inevitable data gaps can be easily bridged. The recommended best practice guidelines for this pre-launch effort is presented based on experience gained at National Institute of Standards and Technology (NIST), National Aeronautics and Space Administration (NASA) and National Oceanic and Atmospheric Administration (NOAA) programs over the past two decades. The currently available radiometric standards and calibration facilities at NIST serving the remote sensing community are described. Examples of best practice calibrations and intercomparisons to build SI (international System of Units) traceable uncertainty budget in the instrumentation used for preflight satellite sensor calibration and validation are presented. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,845 |
We present a method for simultaneously obtaining registration and super-resolution from a sequence of low resolution images, based on a coordinate-descent approach. The novelty of the algorithm resides on the registration step, which can be applied easily to any parametric global motion model. We prove the validity of the model with synthetic and real data experiments, being of special interest the good performance achieved in the difficult case of images registered under a projective transformation. | Classical multi-image super-resolution (SR) algorithms, designed for CCD cameras, assume that the motion among the images is global. But CMOS sensors that have increasingly started to replace their more expensive CCD counterparts in many applications do not respect this assumption if there is a motion of the camera relative to the scene during the exposure duration of an image because of the row-wise acquisition mechanism. In this paper, we study the hitherto unexplored topic of multi-image SR in CMOS cameras. We initially develop an SR observation model that accounts for the row-wise distortions called the "rolling shutter" (RS) effect observed in images captured using non-stationary CMOS cameras. We then propose a unified RS-SR framework to obtain an RS-free high-resolution image (and the row-wise motion) from distorted low-resolution images. We demonstrate the efficacy of the proposed scheme using synthetic data as well as real images captured using a hand-held CMOS camera. Quantitative and qualitative assessments reveal that our method significantly advances the state-of-the-art. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 28,846 |
O heighten his understanding of the fluid dynamics and aerodynamics pertinent to the early stages of the atmospheric flight-vehicle design process, the aerodynamicist has at his disposal three standard tools: analytical methods, computational procedures, and experimentation. Some of the advantages and disadvantages of each design tool are summarized in Fig. 1. Analytical methods provide quick, closed-form solutions, but they require unduly restrictive assumptions, can treat only simple configurations, and capture only the idealized aerodynamics. Through experimentation, representative or actual configurations can be tested and representative and complete aerodynamic data can be produced. Experimentation is costly, however, both in terms of the model and actual test time. In addition, the limited conditions that can be attained in wind tunnels restrict the scope of ex | An intense research effort over the last few years has produced several competing and apparently diverse methods for generating meshes. This paper reviews recent progress and emphasizes the central themes that we can expect to form a solid foundation for future developments in mesh generation. | The application of a video-based motion analysis system for goniometry of finger joints during measurement of the fingertip motion area has been assessed. The results indicate that the motion analysis system is reliable for angular measurements of finger joints that are comparable with those obtained by conventional goniometer. The advantages of using the motion analysis system is that it can record and show the changes in angle of all finger joints continuously during finger motion. | eng_Latn | 28,847 |
The psi-angle model of nonlinear inertial navigation system(INS) alignment for large misalignment error was discussed,and the principle of the unscented Kalman filter(UKF) was analyzed.The UKF was used to estimate the psi-angle of INS alignment and simulation for the INS alignment on stationary base is presented.Simulation results show that the UKF is faster in alignment time and more accurate in estimation precision than the EKF in the case of large uncertainties in heading and low uncertainties in tilt angle.The UKF has better performance for low uncertainties of three psi-angles too. | In this paper, considering the performance of short-time working, inertial flight and high impulse of launch for projectile, an improved square root unscented Kalman filter (UKF) is used. According to the special motional rule of projectile, only use three low-cost MEMS accelerometers as inertial measurement unit to measure the specific force, and construct the linear state equation and nonlinear measurement equation of nonlinear system. Use the square root UKF to estimate the state of system, which effectively enhances the stability of filter and restrains the divergence of filter. Reduce the number of sigma points from 2n+1 to n+2, which improves the computational efficiency and real-time performance of filter. The experimental results in a three-axis flight test rotary table show that the improved square root UKF obtains the good precision of estimation and satisfies the request of real-time response. | In this paper, considering the performance of short-time working, inertial flight and high impulse of launch for projectile, an improved square root unscented Kalman filter (UKF) is used. According to the special motional rule of projectile, only use three low-cost MEMS accelerometers as inertial measurement unit to measure the specific force, and construct the linear state equation and nonlinear measurement equation of nonlinear system. Use the square root UKF to estimate the state of system, which effectively enhances the stability of filter and restrains the divergence of filter. Reduce the number of sigma points from 2n+1 to n+2, which improves the computational efficiency and real-time performance of filter. The experimental results in a three-axis flight test rotary table show that the improved square root UKF obtains the good precision of estimation and satisfies the request of real-time response. | eng_Latn | 28,848 |
Our research is aimed to increase accuracy and enhance data quality of inertial sensors. Inertial navigation systems (INSs) combine physical and cyber components such as micromachined sensing elements, processing and interfacing application-specific integrated circuits, software, etc. Our goals are to develop physics-consistent tools and algorithms for inertial measurement units (IMUs). Using the measured accelerations and velocities, post-processing is performed to reduce noise and errors in the measured and estimated physical quantities. These features ensure accurate estimates on position, orientation, and trajectory. Basic and applied results are experimentally validated using an Inertial Measurement Platform which consists of an IMU and microcontroller. Our findings both contribute to engineering solutions and empower transformative technologies towards technology transfer for cyber-physical systems. The proposed solutions can be applied to enable cloud information fusion and data management. We performed and demonstrated analytical and laboratory studies to validate methods, algorithms, and technology components. | Preface. 1. SINGLE DEGREE OF FREEDOM SYSTEMS. Introduction. Spring-Mass System. Spring-Mass-Damper System. Forced Response. Transfer Functions and Frequency Methods. Measurement and Testing. Stability. Design and Control of Vibrations. Nonlinear Vibrations. Computing and Simulation in Matlab. Chapter Notes. References. Problems. 2. LUMPED PARAMETER MODELS. Introduction. Classifications of Systems. Feedback Control Systems. Examples. Experimental Models. Influence Methods. Nonlinear Models and Equilibrium. Chapter Notes. References. Problems. 3. MATRICES AND THE FREE RESPONSE. Introduction. Eigenvalues and Eigenvectors. Natural Frequencies and Mode Shapes. Canonical Forms. Lambda Matrices. Oscillation Results. Eigenvalue Estimates. Computational Eigenvalue Problems in Matlab. Numerical Simulation of the Time Response in Matlab. Chapter Notes. References. Problems. 4. STABILITY. Introduction. Lyapunov Stability. Conservative Systems. Systems with Damping. Semidefinite Damping . Gyroscopic Systems. Damped Gyroscopic Systems. Circulatory Systems. Asymmetric Systems. Feedback Systems. Stability in the State Space. Stability Boundaries. Chapter Notes. References. Problems. 5. FORCED RESPONSE OF LUMPED PARAMETER SYSTEMS. Introduction. Response via State Space Methods. Decoupling Conditions and Modal Analysis. Response of Systems with Damping. Bounded-Input, Bounded-Output Stability. Response Bounds. Frequency Response Methods. Numerical Simulations in Matlab. Chapter Notes. References. Problems. 6. DESIGN CONSIDERATIONS. Introduction. Isolators and Absorbers. Optimization Methods. Damping Design. Design Sensitivity and Redesign. Passive and Active Control. Design Specifications. Model Reduction. Chapter Notes. References. Problems. 7. CONTROL OF VIBRATIONS. Introduction. Controllability and Observability. Eigenstructure Assignment. Optimal Control. Observers (Estimators). Realization. Reduced-Order Modeling. Modal Control in State Space. Modal Control in Physical Space. Robustness. Positive Position Feedback Control. Matlab Commands for Control Calculations. Chapter Notes. References. Problems. 8. VIBRATION MEASUREMENT. Introduction. Measurement Hardware. Digital Signal Processing. Random Signal Analysis. Modal Data Extraction (Frequency Domain). Modal Data Extraction (Time Domain). Model Identification. Model Updating. Chapter Notes. References. Problems. 9. DISTRIBUTED PARAMETER MODELS. Introduction. Vibrations of Strings. Rods and Bars. Vibration of Beams. Membranes and Plates. Layered Materials. Viscous Damping. Chapter Notes. References. Problems. 10. FORMAL METHODS OF SOLUTION. Introduction. Boundary Value Problems and Eigenfunctions. Modal Analysis of the Free Response. Modal Analysis in Damped Systems. Transform Methods. Green's Functions. Chapter Notes. References. Problems. 11. OPERATORS AND THE FREE RESPONSE. Introduction. Hilbert Spaces. Expansion Theorems. Linear Operators. Compact Operators. Theoretical Modal Analysis. Eigenvalue Estimates. Enclosure Theorems. Oscillation Theory. Chapter Notes. References. Problems. 12. FORCED RESPONSE AND CONTROL. Introduction. Response by Modal Analysis. Modal Design Criteria. Combined Dynamical Systems. Passive Control and Design. Distribution Modal Control. Nonmodal Distributed Control. State Space Control Analysis. Chapter Notes. References. Problems. 13. APPROXIMATIONS OF DISTRIBUTED PARAMETER MODELS. Introduction. Modal Truncation. Rayleigh- Ritz-Galerkin Approximations. Finite Element Method. Substructure Analysis. Truncation in the Presence of Control. Impedance Method of Truncation and Control. Chapter Notes. References. Problems. APPENDIX A: COMMENTS ON UNITS. APPENDIX B: SUPPLEMENTARY MATHEMATICS. Index. | This paper describes the design, operation and performance test results of a miniature, low cost integrated GPS/inertial navigation system (INS) designed for use in UAV or UGV guidance systems. The system integrates a miniaturized commercial GPS with a low grade Micro-Electro-Mechanical (MEMS) inertial measurement unit (IMU). The MEMS IMU is a small self-contained package (< 1 cu inch) and includes a triad of accelerometers and gyroscopes with additional sensors integrated for temperature compensation and baro pressure altitude aiding. The raw IMU data is provided through a serial interface to a processor board where the inertial navigation solution and integrated GPS/inertial Kalman filter is generated. The GPS/Inertial software integration is performed using NAVSYS’ modular InterNav software product. This allows integration with different low cost GPS chips sets or receivers and also allows the integrated GPS/inertial navigation solution to be embedded as an application on a customer’s host computer. This modular, object oriented architecture facilitates integration of the miniature MEMS GPS/INS navigation system for embedded navigation applications. Test results are presented in this paper showing the performance of the integrated MEMS GPS/INS navigation system when used to perform guidance for a small Unmanned Ground Vehicle (UGV). Data is provided showing the position, velocity and attitude accuracy when operating with GPS aiding and also for periods where GPS dropouts occur and alternative navigation update sources are used to bound the MEMS inertial navigation error growth. | eng_Latn | 28,849 |
The accuracy that can be achieved by a single GPS receiver in stand-alone mode is around 10 metres with SA switched off; this is not adequate for most hydrographic studies. This study aims to improve this level of accuracy using a single geodetic receiver in stand-alone mode by applying a phase smoothing algorithm. The algorithm described in this study requires that the measurements be started from a known point for initialisation. The test site selected for the study is Halic bay, Istanbul. After GPS data were collected on a geodetic point for initialisation, the receiver was moved to a hydrographic vessel and trial measurements were performed along several survey profiles. The position of the vessel was calculated at every epoch using the carrier phase smoothing algorithm. In order to analyse the accuracy of the results, a second receiver collected data on another known point on the seashore during the whole session. The position of the vessel was accurately determined using a kinematic positioning method considering the data collected by both receivers. The results produced show that an accuracy of less than a metre can be achieved using the approach considered in this study. | Tests of various types of inexpensive Global positioning system (GPS) receivers were performed in order to asses the utility of the technique for archeo-geophysical surveying. It is demonstrated that under favorable conditions a 30 cm relative uncertainty of the kinematical positioning is achievable and that under conditions, where a degradation of the GPS fixes occurs during the scans, it is possible to compensate for the errors, and refine the results by post-processing of the measurement data. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 28,850 |
A methodology for designing critical systems subject to magnitude- and rate-limited reference inputs is proposed. The worst-case tracking error is minimized under the constraint on the control effort. The LMI-based technique developed by Chilali and Gahinet is utilized to assign the resulting closed-loop poles into the intersection of vertical strips and a conic sector. The optimal pole region is searched by means of the simple genetic algorithm. An illustrative design example of the position control system for a two-inertia system is provided to demonstrate the proposed design methodology. | This paper proposes a robust controller design method for an norm-bounded uncertain linear system with disturbance. At First, we derive the necessary and sufficient condition for regional pole assignment for uncertain linear system, then derive the criteria of H 2 /H ∞ performance of uncertain linear system with disturbance. Hence combining them, we get the mixed H 2 /H ∞ controller control with regional assignment for norm-bounded uncertain linear system with disturbance. The problem of the robust controller designed is changed into an optimization problem, and the robust controller is parameterized by the solution of the optimization. Since the optimization problem conditions are expressed in term of linear matrix inequalities, so it makes the proposed method practical utility. Finally the numerical example illustrates the effectiveness of the proposed approach. | Smartphones may be seen as miniature toolboxes to perform Physics experiments. In this paper, we present three different “optics workbenches" mainly based on the light meter of a smartphone. One is aimed at the precise study of Malus law and other effects associated to linearly polarized light, the second allows quantifying the light intensity distribution of diffraction or interference patterns projected on a screen, and the third demonstrates the so-called inverse square law obeyed by the light from a point-like source. These experiments allow to quantitatively demonstrate three fundamental laws of optics using quite inexpensive equipment. | eng_Latn | 28,851 |
The technology of distributed FBG acceleration sensor has become one of the most practical applications in feeble vibration measure and fault diagnosis.A measurement system of vibration acceleration using fiber Bragg grating is presented.The sub-carrier frequency modulation and wavelength division multiplex technology are used in this system.Acceleration sensing probe structure based on dual fiber Bragg gratings is designed.This sensing probe is characterized by small volume,light weight,high sensitivity and resolution,and it has high ability to resist electromagnetic interference.This probe can automatically realize temperature compensation and phase compensation. | A novel dual FBG (DFBG) accelerometer based on lantern shape metallic shells is designed and analyzed. The DFBG accelerometer is based on the push–pull structure, which is used to eliminate common noises and disturbances. The axial size of the DFBG accelerometer is shortened by special combination of the mass and the elastic shells. The size of the optimized DFBG accelerometer is only 24 mm $\times 24$ mm $\times 24$ mm. Vibration trial results show that the average acceleration sensitivity is about 9.4 pm/g between 30 and 300 Hz, the resonant frequency is about 1175 Hz, the orthogonal crosstalk beyond 100 Hz is −20.6 dB, and the background phase noise is −70 dB re rad/ $\sqrt {{\mathbf{Hz}}}$ for interferometric detection method, which corresponds to a minimum detectable acceleration $6\times 10^{-3}$ g. This DFBG accelerometer has great superiority in composing small 3-D FBG accelerometers and ultra-large scale vector sensor arrays. | An approach has been developed for real-time vibration monitoring of a composite cantilever beam. The fiber Bragg grating (FBG) sensor has an advantage to be embedded or bonded to the structure compared with other sensors such as piezoelectric sensor or strain gage, thus allowing the measurement of parameters like strain and temperature. In this paper the vibration sensor system with a FBG embedded in a composite smart structure is proposed. This system can assort vibration direction and sensing vibration amplitude just by measuring output voltage. The sensing resolution is decided by the slope of the filter used in the system. | eng_Latn | 28,852 |
Green sand property on line test and control system | To control green sand quality which is directly related to the casting quality and to meet the ever increasing demands for better, faster, and cheaper casting production, a green sand property on line test and control system has been developed based on the relationships between the sand properties and the sand composition. This system can be used to test the properties of the moulding sand on line, such as sand compactability, green compressive strength, and sand temperature, and to control the actual sand compactability within the preset production adapted tolerance zone by controlling water addition using the test results. Excellent results have been achieved in its practical application. | Some performance simulation results of a remote-positioning system on a multitarget real-time context for oceanic instruments tracking are discussed and several indicators are considered to fine-tune the system's design requirements. Results show that, within the particular extent of practical applicability, an equilibrium between the performance indicators considered can be achieved. > | eng_Latn | 28,853 |
Detecting Vortex Formation and Shedding in Cylinder Wakes Using Lagrangian Coherent Structures | The wake behind a circular cylinder is studied to investigate the complex vortex shedding physics in the near-wake region. Both the Q criterion and a Lagrangian coherent structure analysis are applied to flowfields acquired from a numerical simulation, as well as from experimental particle image velocimetry to determine the properties of the wake. A rate-of-strain filter is applied to the finite-time Lyapunov exponent field to filter out ridges corresponding to local shear, and yields ridges along which fluid trajectories separate hyperbolically. This strain filter reveals a sudden loss of hyperbolicity along a Lagrangian coherent structure as a new vortex begins to form. The Lagrangian coherent structures are also shown to identify and track topological Lagrangian saddle points in the cylinder near wake. This information characterizes the behavior of the vortices as they form, shed, and convect downstream. In particular, a Lagrangian saddle point is observed to remain attached to the cylinder surface unt... | Abstract According to the method described in reference [1], we have designed a series of corrector systems for Cassegrain telescopes automatically with an electronic computer. The calculations were carried out under the following two conditions: the primary and secondary mirrors have strictly conical surfaces, and the telescope is strictly free from third-order spherical aberration when the corrector systems are taken off. Results in this papercan be converted proportionally to real telescopes of any aperture, while the aberrations expressed in seconds of arc remain unchanged. | eng_Latn | 28,854 |
DEVELOPMENT OF CURVE BASED CRYPTOGRAPHY | Methods and apparatus for inspecting surfaces are disclosed. The present invention provides a system which is particularly useful for inspecting the inner race of a bearing and uses two video probes to create dual displayed views of the inner surface. The bearing is slowly rotated and the entire surface of the inner race is visually inspected by viewing the images collected by the video probes. Preferably, a motorized stand and frame are provided that automatically rotate the bearing and automatically insert the video probes into the bearing respectively. The magnification provided by the video probes permits the detection of flaws invisible to the human eye, and in certain embodiments a scale on or adjacent to the video images is also provided so that the size of the defects viewed can also be accurately determined. | This paper deals with a control strategy for underactuated underwater vehicle moving in 6-degrees of freedom whose target is the tracking of a space trajectory. The control algorithms proposed build upon Lyapunov's method and backstepping technique, which force the vehicle follow any smooth time-varying bounded trajectory, despite of the uncertainty in the damping coefficient and absence of the force of sway and heavy. The error of tracking and parameter estimation are ultimately confined to a ball that can be made arbitrarily small. | yue_Hant | 28,855 |
Optical lens focusing system rotation and deflection mechanism | The utility model discloses an optical lens focusing system rotation and deflection mechanism, particularly relates to a focusing system rotation and deflection mechanism applied to the high pixel camera optical lens, which comprises a base, wherein the base is provided with a drive unit, a swing arm is arranged in the base, one end of the swing arm is fixedly provided with a focusing lens, and the other end of the swing arm is hinged with a guide rod, and the base is also provided with a driven unit which can drive the swing arm to rotate to be hidden after the swing arm is driven by the drive unit to move up and down along the guide rod and then move downward in place. The utility model is applicable to the fields of the digital camera or the cell phone and the like. | The paper proposes a mathematical model to optimize wind power turbine maintenance by minimizing the total costs with preventive maintenance, corrective maintenance and costs due to energy losses. Objective function is an economic function and is represented by the total costs associated with actions of preventive maintenance, corrective maintenance and production losses due to interruption of equipment operation during maintenance activities. Furthermore, a study case is presented to show the implementation of the proposed mathematical model. | eng_Latn | 28,856 |
About the self-calibration of a rotating and zooming camera: Theory and practice | This paper deals with the uniqueness of the self-calibration of a rotating and zooming camera theoretically. We assume that the principal point and the aspect ratio are fixed but the focal length changes as the camera moves. In this case, at least one inter-image homography is required in order to compute the internal calibration parameters as well as the rotation. We analyze the effects of the deviation of the principal point on the estimation of the focal length and the rotation. The more the camera changes its zoom, the larger the effects are, and the larger the rotation angle is, the smaller the effects are. Thus, we may take the image center as the principal point in practical applications. Experiments using real images are given. | In this paper the methods of static and dynamic analysis of the closing rotor balancing device of the multistage centrifugal pump are represented. On an example of the feed pump PE 600-300 static and dynamic characteristics are determined. Defined the resonance frequencies and investigated stability of the system “pump rotor – automatic balancing device – pressure difference regulator”. The dependence for the pressure difference and conditions to ensure reliable operation of the locking rotor balancing device are determined. | eng_Latn | 28,857 |
Multi-method absolute paleointensity determinations on a Pliocene multiple-polarity record from the Lesser Caucasus | We report high technical quality absolute paleointensity determinations from a Pliocene sequence of 20 consecutive lava flows sampled in South Georgia named Apnia, which record either the Gilbert-Gauss polarity reversal or a composite transition from chron C2Ar to subchron C2An-2n. Paleointensity determinations with the multispecimen (MSP) technique were performed on 12 samples with both the original method (MSP-DB) and the extended protocol with corrections (MSP-DSC). Six MSP-DB and eight MSP-DSC determinations passed the proposed quality criteria. MSP-DB yielded higher intensity values than MSP-DSC. In order to provide additional reliability to the results, we have carried out a consistency test by means of a multi-method approach. We have compared the MSP intensities with Thellier-type intensities obtained from the reinterpretation of determinations performed in previous study. The match of both types of paleointensity determinations gives the results an added reliability. Paleointensity results have b... | AbstractIn a physical activity study, the 7-day physical activity log viewed as an alloyed gold standard was used to correct the measurement error in the physical activity questionnaire. Due to correlations between the errors in the two measurements, the usual regression calibration may result to a biased estimate of the calibration factor. We propose a method of removing the correlation through orthogonal decomposition of the errors, then the usual regression calibration can be applied. Simulation studies show that our method can effectively correct the bias. | eng_Latn | 28,858 |
Stabilized transverse Zeeman laser as a new light source for optical measurement | The light emitted by a stabilized 633-nm He–Ne transverse Zeeman laser (STZL) is composed of two linearly polarized components that are perpendicular to each other. Optical frequencies of the two components are different, and therefore the light changes its polarization with time. The change is represented on the Poincare sphere as a spin along the equator containing S2 and S3 axes of the sphere. Three types of polarimetry and two types of interferometry using an STZL are proposed and experimentally demonstrated. Comparisons of these techniques with the existing ones are also reported. | Previous work highlighted experiments contrasting immersion test results on rail to scans made with a rail search unit, ideally as a means of indicating areas of modeling that most need improvement. Some interesting flaw/beam orientation effects were noted. This foray into using a linear phased array inspection for the same rails indicates that using a phased array transducer can duplicate various orientation effects, resulting in better detection. | eng_Latn | 28,859 |
Mathematical Modeling for the Physical Relationship between the Coordinate Systems of IMU/GPS and Camera | When extracting geo-referenced 3D data from cameras mounted on Mobile Mapping Systems, one of important properties for accuracy of extracted data is the alignment of the relative translation(lever-arm) and rotation(bore-sight) between the coordinate systems of Inertial Measurement Unit(IMU)/Ground Positioning System(GPS) and cameras. Since the conventional method calculates absolute camera orientation using ground control points (GCP), the alignment is determined in one Coordinated System (GPS Coordinated System). It basically require GCP. We proposed a mathematical model for the alignment using the initially uncoupled data of cameras and IMU/GPS without GCPs. | The question of predicting accuracies in orthophoto products is not a clear-cut problem in error propagation. When one investigates the problem, he finds that there are several interconnecting factors all of which influence the accuracy of the final product. The non-normal probability density functions of these various factors, and the fact that, for prediction of output accuracies, a multivariate density function must be determined which is grossly non-normal, dictate that the solution be determined numerically. This numerical accuracy prediction procedure for orthophoto map products is the topic of this paper. | eng_Latn | 28,860 |
Effects of Geodetic Uncertainties on a Damped Inertial Navigation System | Gravity uncertainties are an inexorable source of error in all inertial navigation systems and are particularly important in high-quality inertial navigation systems. In this paper the steady-state rms errors that are excited in a damped inertial navigation system are analytically determined for four gravity uncertainty models and two vehicle maneuver models. The statistical approach used in this paper is compared with an alternate scheme (?direct simulation?) that does not require statistical models for gravity uncertainties. | The calculation of groud leveling up is a very huge work,and the computational accuracy is restricted because of the irregularity of ground.Using spatial interpolation and the accuracy of model checking up,we choose a planning area as test region.We choose IDW as the best interpolation method.Then we work out the cutfill elevation of evry grid,cutfill area and cutfill zero line for the whole region,and figure out total volume. | eng_Latn | 28,861 |
Detection of a gravitational oscillation in length-of-day | A high resolution length-of-day data set spanning approximately the last 42 years is found to contain an oscillation with a period of 5.8 ± 0.8 years. This oscillation is interpreted to represent a normal mode of the Earth that arises due to gravitational coupling between the mantle and inner core. In order to match the observed period of the oscillation, the strength of the gravitational coupling between the mantle and inner core must be ∼ 3.0 × 1020 N m. This coupling constant depends on the heterogeneous density distribution of the mantle, including flow-induced deformation of the core–mantle boundary. The existence of this normal mode requires that the relaxation time of the inner core be sufficiently long (on the order of a few years or more) that a perturbation from equilibrium results predominantly in solid-body rotation, not viscous deformation, of the inner core. The inferred lower bound for the viscosity of the inner core is of the order of 1017 Pa s. | The servo design and model of the W. M. Keck telescopes autoguider is presented. Telescope servo models often do not include the guider loop and therefore do not take advantage of traditional control analysis and test techniques to improve performance. Guide camera dynamics, computational and transport lags, and compensation networks are discussed. A means of measuring the actual frequency response characteristics of the guide loop is presented and the results are compared to those predicted by the model. Guide performance as a function of integration time is illustrated. An improved compensation network is developed and its performance examined.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. | eng_Latn | 28,862 |
Device and method for downloading and displaying a images of global position information in navigation system | PURPOSE: An apparatus and a method for downloading and reproducing an image related to the position information in a navigation system are provided to seize the overall panorama by identifying the real image of the following object in advance using the current position information and the traveling direction. CONSTITUTION: A method for downloading and reproducing an image related to the position information in a navigation system includes the steps of: generating the node message for guiding the following node point when the mobile terminal reaches to the node point; transmitting the partial image information of the node image information corresponding to the traveling direction of the mobile terminal by inspecting the traveling direction of the mobile terminal; and subsequently transmitting the partial image information of the adjacent direction of the mobile terminal after the partial image information of the traveling direction is transmitted. | This paper calculates GPS control network from different accuracy of prior coordinates, inspects the accuracy influence of the prior coordinates to final adjustment with coordinate after the precision of the unknown point coordinates, analyzes and summarizes the importance of the prior coordinates in the calculating of the whole GPS control network data. Through the translation of the simulation design GPS point, this paper tests the effects of the baseline length and the direction of change on the accuracy of the reliability of the whole network. | eng_Latn | 28,863 |
Control of underactuated free floating robots in space | The underactuated free floating robot in space is a nonlinear system where velocity and acceleration constraints are both nonintegrable, therefore it is a second-order nonholonomic system. Some of the existing nonholonomic control methods will not be directly applicable to such systems as it is extremely difficult, if not impossible, to find the control Lie brackets. In this paper, by investigating the system dynamics in depth, we propose a simple velocity-based method to control the unactuated joints and a multistep composite strategy to implement orientation tracking tasks. The proposed algorithm is of significance in controlling of space robots when some joints fail to function, or they are intentionally set to be passive for energy efficiency and safety purposes. | Aiming at the requirements in running efficiently and high accuracy handling data timely,the login system,communication module,database storage and reading,relay verification module,report generation and printing.were designed.The working principle and composition of the calibration device were introduced.The upper computer software of microprocessor relay protection's trippingoperation-board intelligent calibration device was developed based on graphical LabVIEW language and database programming technology to realize the function of each part.The results indicate that the software can complete returning the relay operating board calibration value and action value efficiently,and has a multi-function interface.The software has been successfully applied in this device. | eng_Latn | 28,864 |
Imaging tools to measure treatment response in gout | Imaging tests are in clinical use for diagnosis, assessment of disease severity and as a marker of treatment response in people with gout. Various imaging tests have differing properties for assessing the three key disease domains in gout: urate deposition (including tophus burden), joint inflammation and structural joint damage. Dual-energy CT allows measurement of urate deposition and bone damage, and ultrasonography allows assessment of all three domains. Scoring systems have been described that allow radiological quantification of disease severity and these scoring systems may play a role in assessing the response to treatment in gout. This article reviews the properties of imaging tests, describes the available scoring systems for quantification of disease severity and discusses the challenges and controversies regarding the use of imaging tools to measure treatment response in gout. | When extracting geo-referenced 3D data from cameras mounted on Mobile Mapping Systems, one of important properties for accuracy of extracted data is the alignment of the relative translation(lever-arm) and rotation(bore-sight) between the coordinate systems of Inertial Measurement Unit(IMU)/Ground Positioning System(GPS) and cameras. Since the conventional method calculates absolute camera orientation using ground control points (GCP), the alignment is determined in one Coordinated System (GPS Coordinated System). It basically require GCP. We proposed a mathematical model for the alignment using the initially uncoupled data of cameras and IMU/GPS without GCPs. | eng_Latn | 28,865 |
Establishment shot detection using qualitative motion | In this paper, we developed a technique to detect a special kind of shot, namely establishment shot, which is used to introduce a new scene to the audience or remind the audience of a known environment. The detection of establishment shot aids in various middle-level issues such as analyzing the story units of a movie. An establishment shot is usually realized by using camera motions such as panning, tilting or lateral translation. As it possesses similar motion features to those of another kind of shot called object-tracking shot, the two can be easily confused. An object-tracking shot is important for indexing on its own; it keeps the target of interest in the field of view. In this paper, we developed a technique to differentiate these two kinds of shots. The technique developed does not require accurate egomotion estimation, and can handle arbitrary camera movement including zoom as well as multiple independent motions. | In this work. an equipment to simulate several t orque-sped characteristics is studied. The proposed system may be used either as a load to test AC drives or as a mechanical power source for variable speed electric power generation systems studies. This simulator consists on a separ ate1 y-exci ted JX machi ne whose the armature circuit are fed by a four-quadrant chopper. The contr 01 al gor i thm perf or ms tasks related to set-point t orque determination through the measurements of the speed and acceleration rate calculation. The proposed system is described in detail and the design aspects are presented. The digital simulation results are compared with the experimental results to warrant the ability of the contr ol strategies. | eng_Latn | 28,866 |
Design of control system for water conductance instrument based on software temperature compensation | Design of Control System for Water Conductance Instrument controlled by LPC2131 MCU which has the control capability of ARM is introduced in this paper,and the problem which is about the temperature excursion is solved.The design adopts the bi-directional pulsed voltage as its source,which reduces the negative of capacitive and polarization effects at the electrodes.Software arithmetic is designed to compensate the offset of temperature coefficients of Water Conductance Instrument.With this method,the signal is digitally corrected by microprocessor based on the compensation coefficients determined from pretest data.The error problem of temperature compensation in the process of water conductivity measurement is better solved. | Our goal is to characterize the space-varying absorption coefficient from observations of diffuse light propagating through tissue. Sensor array measurements from illumination with several sources leads to an inverse problem which, due to the physics and the restriction of sensors to the surface, is ill-posed and underdetermined. Accurate, reliable solutions require a priori constraints. Here we adopt an admissible solution approach, with convex constraint functions defining admissibility conditions, implemented via the ellipsoid algorithm. The joint use of measurement-model agreement, amplitude, and total variation type constraints produces more accurate reconstructions in a variety of simulation scenarios. | eng_Latn | 28,867 |
IMPROVEMENT AND CONFIRMATION OF A NEW AUTOMATIC SYSTEM FOR AC-DC CALIBRATION AT NIS, EGYPT | The recent Improvements in AC-DC transfer capabilities at National Institute for Standards (NIS), Egypt, include an automated AC-DC transfer comparator system with international confirmation of the results through bilateral intercomparison with NPL, England. The system can be used to measure additional characteristics of thermoelements and operates over a frequency range from 20 Hz to 100 kHz for a voltage level from 0.5 V to 1 kV. The results of bilateral intercomparison including the proficiency test of the new system are reported. The expanded uncertainty assigned to the NIS working standard is given and its components are briefly discussed. The results show that the agreement between the two laboratories is better than the expected uncertainties | A method for the algebraic approximation of attractors recently developed by Foias and Temam is adapted for application to autonomous galloping oscillators. We compare results obtained by algebraic approximation on the one hand and numerical integration on the other. We conclude with an assessment of the limitations of the method as applied to our systems. | yue_Hant | 28,868 |
Study on high precision measurement of oil consumption in drilling platform field | This Paper analyzed affections in precision measurement of system oil consumption from sensor system,put forward a error compensation algorithm in system measurement,and established mathematical model.This compensation algorithm is implemented in VC++ experimental platform.We do experiment of oil in and out.It showed relative error of system measurement is controlled in the range of 0.6 percent,and precision is high. | A new modeling method based on sample data is described in this paper,through physics and sample date analysis on displacement vs.voltage characteristics of x-y plane of cylindrical piezoelectric scanner used in scanning probe microscope(SPM).Through sample data statistical analysis,and considering the error factors such as scan speed,scan angle,nonlinearity and coupling,a model represented by a binomial plus some error expressions is constructed.A nonlinearity correction expression based on the model is deduced.With the software Matlab this nonlinearity correction is simulated.The result of simulation indicates that it can eliminate the errors effectively.The ascendency of the method is that there are no polarization mechanism analysis and fewer number of model parameters.The method is practical applied to engineering. | eng_Latn | 28,869 |
Design of Digital Acquisition Circuit for Inertial Sensor Based on FPGA | In order to realize high-speed analog sampling and noise analysis, the paper put forward a design scheme of the high-speed data acquisition and analysis system based on FPGA, the system uses Cyclone series FPGA with high-speed A/D converter, and using fast Fourier analysis core of the Altera Company. The ADC model is AD9643 chip. The test results show that the prototype can simultaneously collect three output signals, and real-time processing to the host computer display. The measured gyro resonance frequency is stable at 324.88 kHz, fluctuation range is 9Hz, and the mean square deviation of the peak value is 0.008 V on the output voltage of reference point. The detection system is stable and has high precision. The digital detection circuit can be applied to the signal processing of MEMS gyroscope, which can improve the stability and anti-jamming of MEMS gyroscope. | The authors report the realisation of a contradirectional EDFA whose 1480 nm pump beam, generated by a DFB laser diode, is recycled in it by a photoinduced intracore fibre bragg grating. Insertion of the fibre grating does not introduce any extra input coupling loss and, for the same gain and noise figure values, allows a 20% decrease of the pump power compared to the EDFA without a fibre grating. | eng_Latn | 28,870 |
Algorithm Research on SINS/GPS Integrated Alignment of Large Misalignment Angles | In the case of large misalignment angles,quaternion error equation and nonlinear filtering can improve the performance of the in-flight alignment of SINS.Iterative filtering can obtain higher alignment precision than extended Kalman filtering.Separate-biased algorithm of extended Kalman filtering is utilized to reduce the large computational cost of iterative filtering.The idea of iterative filtering is introduced to put forward a non-linear filtering algorithm,which is not only of the same accuracy as iterative filtering but also of lower computational cost.The non-linear filtering algorithm is applied to the SINS/GPS integrated alignment based on quaternion error equations.Effectiveness is indicated by numerical emulation. | Sooner or later each manufacturer, because of the rising level of competition on the market, will have to find a way to decrease the expenses and to increase the profit. Optimization is the way to make that. In this paper optimization of metal masts construction using ANSYS Mechanical and IOSO algorithms will be discussed. Loads are automatically calculated according to the Code of Rules 20.13330.2011 and load*bearing elements are checked for strength and stability according to the Code of Rules 16.13330.2011. After the optimization run a Pareto set is created which allows to manually choose an optimal variant of construction. | eng_Latn | 28,871 |
Total internal reflectance fluorescence (TIRF) measurements of tracer diffusion through swollen supported polymer films | This work introduces a new method for tracer diffusion studies which emphasizes interfacial effects. Total internal reflectance fluorescence (TIRF) was employed to monitor rhodamine dye tracer diffusion normal to the interface in PDMS films whose swelling in THF was constrained by adhesion to a rigid support. In these constrained films, the tracer diffusivities were equal to or lower than those in freely swollen samples, with the difference most pronounced in samples of relatively low crosslink density. This indicated that swelling was reduced by adhesion to the substrate. In the supported films, tracer diffusion deviated from Fickian kinetics, suggesting that the region of the film near the substrate contained relatively less solvent at equilibrium than did the bulk film. | This paper deals with the transfer alignment problem of strapdown inertial navigation systems, using the velocity information and angular rate information of the ship. Major error sources for velocity-plus-angular rate matching is unmodeled ship body flexure dynamics. To reduce this alignment error, a two-stage strong tracking filter (TSTF) is designed. This TSTF is derived by merging the optimal two-stage Kalman filter with strong tracking filter. The ship body flexure is modeled as time-varying noise and its stochastic properties are estimated by TSTF. The simulation results show that the proposed method is effective to estimate the misalignment angles of the slave inertial navigation systems. | eng_Latn | 28,872 |
The control to picosecond accelerator based on Kingview 6.5 | This paper describes the features and applications of ADAM5000TCP and ADAM5511 in control system of picosecond accelerator,and mainly recounts the skillful data processing of Kingview 6.5 used as upper-layer platform,including the linear form,database,file and bit operation.Actually experience indicates that the adoption has minimized the efforts and guaranteed the real-time character and practicability of control system. | ABSTRACTThis paper aims to develop, assess, and numerically implement analytical models for the newly introduced Quintuple Friction Pendulum Isolator (QFPI) which can identically capture its real e... | eng_Latn | 28,873 |
Absolute gravimetry in Antarctica: Status and prospects | Abstract Twenty-three absolute gravity measurements at 12 stations have been performed in the Antarctic up to 2004. We review the measurements, and present a catalogue of gravity values. Four of the sites have repeated occupations. Gravity is sensitive both to elevation change and to changes in density distribution caused by past and present changes in the Antarctic ice mass. Thus, repeated absolute gravity measurements, especially when collocated with observations of vertical displacement from precise positioning systems, can provide information on the time evolution of the Antarctic ice sheet. We compare the observed gravity change with observed vertical motion, and with predictions from various models of the glacial isostatic adjustment and of present glacier mass balance. | This article through 2604 working face floor to probe bottom water of mine transient in Wangcun Coal Mine,analysed the advantages of transient electromagnetic methodof theoretically,and etting observation point through 2604 face,using Terra TEM transient electromagnetic instrument for observation,through on-site practice to explain this reasonable and accuracy method.Therefore,by transient electromagnetic method in the prediction of bottom water has good application value. | eng_Latn | 28,874 |
Optimization of Adjustable Let off Motion | Structure and working mechanism of adjustable let off motion are introduced ,taking looms 1515 as an example ,to which reliabity analysis and specification is given.The above said let off motion can meet the requirement of weft on warp let off,and more the let off can be fine tuned as well,keeping constant tension of warp let offs. | The servo design and model of the W. M. Keck telescopes autoguider is presented. Telescope servo models often do not include the guider loop and therefore do not take advantage of traditional control analysis and test techniques to improve performance. Guide camera dynamics, computational and transport lags, and compensation networks are discussed. A means of measuring the actual frequency response characteristics of the guide loop is presented and the results are compared to those predicted by the model. Guide performance as a function of integration time is illustrated. An improved compensation network is developed and its performance examined.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. | eng_Latn | 28,875 |
Intelligent power modules for driving systems [IGBTs] | A major challenge for systems engineers is the selection, drive system, optimum operation and implementation of the protection functions of power semiconductor devices. This article describes the Intelligent Power Module (IPM) for driving 3-phase asynchronous machines for the voltage range to 1200 V. Special detailed consideration is given to the continuous protection concept, comprising overvoltage, overload, short circuit, temperature and undervoltage protection, and the drive concept for the relevant frequency range of the IGBTs up to 20 kHz. | When extracting geo-referenced 3D data from cameras mounted on Mobile Mapping Systems, one of important properties for accuracy of extracted data is the alignment of the relative translation(lever-arm) and rotation(bore-sight) between the coordinate systems of Inertial Measurement Unit(IMU)/Ground Positioning System(GPS) and cameras. Since the conventional method calculates absolute camera orientation using ground control points (GCP), the alignment is determined in one Coordinated System (GPS Coordinated System). It basically require GCP. We proposed a mathematical model for the alignment using the initially uncoupled data of cameras and IMU/GPS without GCPs. | eng_Latn | 28,876 |
Operational stability enhancement of white OLEDs with single solution‐processed emitting layer fabricated by “self‐layered technique” | — We achieved operationally stable white OLEDs with a single solution processed EML fabricated using a self-layered technique. An LT70 of 10 khr at an initial luminance of 1000 cd/m2 was obtained by suppressing the exciplex formation between the EML and ETL, preventing Li diffusion into the EMLs, and using red dopants with shallow LUMO levels and stable host materials. | The invention belongs to the field of photogrammetry and computer simulation, in particular relates to a planar and three-dimensional precision estimation method of a low earth orbit satellite, and discloses a completely novel low earth orbit satellite posture simulation method for solving conventional technical defects, making up the blank of the aspect in China, and providing the analysis basis for advanced researches on low earth orbits. According to the technical scheme of the invention, the low earth orbit satellite imaging process is analyzed, corresponding imaging equations are established on the basis, and the positioning precision is obtained through the comparison of imaging equation results with errors and imaging equation results without errors. | eng_Latn | 28,877 |
Endotracheal stenting therapy in dogs with tracheal collapse. | Tracheal collapse in dogs is a common respiratory disorder, typically presenting with a history of chronic cough, increasing respiratory difficulties, and episodes of dyspnoea. Medical treatment is the therapy of choice and surgical repair is considered when patients do not respond well. Minimally invasive endotracheal stenting is a promising new therapy under investigation, but there remain significant challenges to overcome potential complications. The purpose of this article is to provide a comparative overview of intra-luminal stenting of the trachea in human and veterinary medicine. The currently available stents and their potential clinical application to the veterinary patient will be discussed. | This paper deals with the transfer alignment problem of strapdown inertial navigation systems, using the velocity information and angular rate information of the ship. Major error sources for velocity-plus-angular rate matching is unmodeled ship body flexure dynamics. To reduce this alignment error, a two-stage strong tracking filter (TSTF) is designed. This TSTF is derived by merging the optimal two-stage Kalman filter with strong tracking filter. The ship body flexure is modeled as time-varying noise and its stochastic properties are estimated by TSTF. The simulation results show that the proposed method is effective to estimate the misalignment angles of the slave inertial navigation systems. | eng_Latn | 28,878 |
Instability of Taylor-Couette Flow of Electrorheological Fluid | A linearized instability analysis of Taylor–Couette flow between two rotating concentric cylinders of an electrorheological (ER) fluid is carried out. The ER fluid exhibits a yield stress in addition to the plastic viscosity when an extra electric-field is applied. It can be found that the yield stress plays a dual role in the flow instability. The possibility of the yield surface falling between the cylinders is analysed. Although small waves appeared on the yielded surface is considered, the yielded surface, which has been treated as a free surface, has little effect on the flow instability. The effects of axisymmetric perturbation on the flow instability are presented due to the axisymmetric of the basic flow. The parameter β in the yield stress formula of the ER fluid is shown to have distinct effects on the flow instability characteristics. | This paper deals with the transfer alignment problem of strapdown inertial navigation systems, using the velocity information and angular rate information of the ship. Major error sources for velocity-plus-angular rate matching is unmodeled ship body flexure dynamics. To reduce this alignment error, a two-stage strong tracking filter (TSTF) is designed. This TSTF is derived by merging the optimal two-stage Kalman filter with strong tracking filter. The ship body flexure is modeled as time-varying noise and its stochastic properties are estimated by TSTF. The simulation results show that the proposed method is effective to estimate the misalignment angles of the slave inertial navigation systems. | eng_Latn | 28,879 |
Influence of track irregularity to wheel set longitudinal vibration | The wheel set longitudinal degree of freedom of movement was ignored in the general dynamic simulation analysis of railway vehicles.We can say that wheel set longitudinal vibration hasbeen ignored by researchers for a long time.But in recent research,we find that although the acute vibration in longitudinal of the wheel set has a little influence on the lateral stability of the whole vehicle,it has a big influence on the vertical dynamic performance of the whole vehicle.The longitudinal and nodding vibration of the car body will occurr and even lead the vertical dynamic to worsen when there is a big wheel set longitudinal vibration.Farther research finds that the wheel set longitudinal vibrate is heavily related with the track vertical profile track irregularity and lateral track irregularity.Only when the above two track irregularities were exited together,the wheel set longitudinal vibration resonance couldn’t happen.Wheel set longitudinal vibration resonance on the slick track will not occur. | According to the characteristics of the high precise GPS deformation monitoring, basing on the first period observation results of the monitoring network,the similar single-difference model of solving GPS monitor point deformation information at single epoch is built,and the receivers'antenna phase center offsets are discussed.This model avoids the troublesome problem of cycle slip detecting and repairing,and is not only applicable to the static and dynamic monitoring modes, but also suitable for the single receivers.The correctness of the similar single-difference model is verified with the practical data in Three Gorge Area. | eng_Latn | 28,880 |
Compensating well log for eccentered sensors and reducing whirling | Signals from a downhole sensor 24 on a drill collar 20 eccentrically rotating within a bore hole are corrected to generate a well log which more accurately represents the condition which the sensor 24 would have generated had the collar 20 been rotating centrally. The sensor signals are generated at time intervals of less than half the period of rotation of the collar 20. The frequency components of the time-varying sensor signals are extracted, and the frequency component attributable to the eccentric rotation determined. This frequency component may be used to modify the average sensor signal to produce a more accurate well log. The technique may also be used to determine actual rotational speed of the collar 20, the spacing between the sensor 24 and the borehole wall, and a whirling condition in real time to enable drilling parameters to be adjusted. The sensor may be nuclear, gamma, neutron, acoustic or electromagnetic. | A new modeling method based on sample data is described in this paper,through physics and sample date analysis on displacement vs.voltage characteristics of x-y plane of cylindrical piezoelectric scanner used in scanning probe microscope(SPM).Through sample data statistical analysis,and considering the error factors such as scan speed,scan angle,nonlinearity and coupling,a model represented by a binomial plus some error expressions is constructed.A nonlinearity correction expression based on the model is deduced.With the software Matlab this nonlinearity correction is simulated.The result of simulation indicates that it can eliminate the errors effectively.The ascendency of the method is that there are no polarization mechanism analysis and fewer number of model parameters.The method is practical applied to engineering. | eng_Latn | 28,881 |
INERTIAL DIRECTIONS BUILDER WITH DUAL AUTOCOMPENSATION OF INFLUENCE OF EXTERNAL INTERFERENCE | The analytical structure of pointer of direction is built on the base of triaxial astatic gyroscope with twochannel autoindemnification of influence of external noises. The correlation for determination of девиации of ax of figure in the first two approaching was gotten. | THE INVENTION CONCERNS A CONTROL CIRCUIT FOR ANAEROBIC REACTOR SYSTEM. THE TOUR INCLUDES FILTER 16 ESTIMATE THAT RECEIVES INPUT SIGNAL SENSOR PRODUCTS AN ESTIMATE OF THE PRESENT VALUE A VARIABLE IN THE SYSTEM, COMPARE THAT ESTIMATE FOR A SIGNAL SENSOR THE VARIABLE AND PRODUCT OF THAT COMPARISON, SIGNAL ERROR dIFFERENCE IS TO COMBINE THE RECEIVED SIGNAL and reapplied INTEGRATOR, A DISPOSAL OF A BIAS LONG TERM THAT MAY BE PRESENT IN AT LEAST ONE OF SIGNALS rECEIVED, SUCH ELIMINATOR INCLUDING HIGH PASS FILTER BY 53 OR rECEIVED INPUT SIGNALS ARE TRANSMITTED TO THE iNTEGRATOR 58, SUCH FILTER HIGH PASS THAT REJECTING THE BIAS PERSISTS FOR A PERIOD CONSIDERABLY LONGER THAN THE TIME cONSTANT SYSTEM. APPLY THE iNVENTION INCLUDING THE TREATMENT OF WASTE WATER. | yue_Hant | 28,882 |
A Novel Algorithm for Improving the Accuracy of Attitude and Heading Angle Measurement of Electronic Compass | This paper studied the measurement precision of the electronic compass used in VSAT(very small aperture terminal).The basic principle of the measurement was discussed in detail,and the error mathematical model of the measurement was derived.The cause for the increase of the roll angle measurement error with the increases of the pitch angle was analyzed and a novel method for improving the measurement precision was proposed based on the above analysis.The simulation and experiment results show that the novel method can remove the influence of pitch angle on the roll angle measurement and can improve the accuracy of heading measurement effectively.The application of the novel method shows that the roll angle accuracy is approximately 0.2°and the heading angle accuracy is approximately 0.5°with a turntable pitch angle of 30°. | In this paper,the comments of problems in meteorological application of neural network and its causes of formation are given.The principles and experiences of neural network structure designs and also discussed.An approach named false sample verification method is proposed to diagnose modeling problems.Finally,the principles of prediction ensemble are briefly reviewed.It is suggested that by using the method of constructing the differences among factor subsets to generate individuals for prediction ensemble,then the problems of smaller samples and factor selection may be solved. | eng_Latn | 28,883 |
Large Area of Transformation Parameters for Solving the Network RTK | Mainly on using multiple base stations network RTK technology of Nanning city of continuous operation of the integrated system of satellite positioning services,introduced a regional solution for network RTK converted seven parameters of the method,compared network RTK surveying and measurement results to "CGQC2000",and made network RTK surveying urban 56 different grades of handle.The application is based on the seven parameters of large regional network RTK coordinates transformation parameters for coordinate conversion,data processing and analysis of precision,while at the same time applied to the 2009 Nanning map patch test project,and achieved good results. | Abstract We present a new explicit Runge–Kutta method of fourth algebraic order with minimum error of the fifth algebraic order (whose limit is zero, when the step-length tends to zero) and infinite order of dispersion and dissipation. The numerical results of a wide range of methods when these are applied to well-known periodic orbital problems show the efficiency of the new constructed method. | eng_Latn | 28,884 |
Contour error compensation method for computer numerical controlled non-circular grinders | A contour error compensation method for computer numerical controlled (CNC) non-circular grinders is introduced. The compensation method collects set and actual positions of each axis from servo controllers during the dry run process and calculates compensation data for the interpolator of the CNC system. It can be executed quickly and iteratively without real grinding. It can also be integrated in existing CNC systems without modifying interpolation or servo control algorithms. Brief introductions to the servo controller simulation model and contour error displaying module when developing the compensation method are also given. Grinding results demonstrate high contour accuracy of a cam workpiece and efficiency of the compensation method. | According to the characteristics of the high precise GPS deformation monitoring, basing on the first period observation results of the monitoring network,the similar single-difference model of solving GPS monitor point deformation information at single epoch is built,and the receivers'antenna phase center offsets are discussed.This model avoids the troublesome problem of cycle slip detecting and repairing,and is not only applicable to the static and dynamic monitoring modes, but also suitable for the single receivers.The correctness of the similar single-difference model is verified with the practical data in Three Gorge Area. | eng_Latn | 28,885 |
Differential measure of matched linear accelerometers as a sensing strategy for the development of a vestibular prosthesis | We propose using a matched pair of linear diaphragm accelerometers in order to capture angular velocity data for use in a vestibular prosthesis. Each sensor transduces linear acceleration into deflection of the membrane. This deflection changes the distance between the plates and concordantly their capacitance. Through analytic equations of motion and finite element analysis we show that such a sensor design will allow for sufficient sensitivity for a vestibular prosthesis. By placing two accelerometers in such a way that they are parallel, within the same plane, and share a perpendicular axis, we can derive angular acceleration, and through signal processing, angular velocity. In such a configuration, linear accelerations will be rejected by taking the difference between the measured capacitances, while angular acceleration data will be accepted. Physical analysis shows that this scheme will generate the requisite data. | The main result of this paper identities certain derived cones to the reachable sets of nonsmooth control systems in terms of quasitangent variational inclusions that generalize the classical variational equation in the theory of O.D.E.. This result extends to nonsmooth control systems an earlier result of the second author. | eng_Latn | 28,886 |
C/A code cross-correlation at a high doppler offset | C/A code cross-correlation affects signal acquisition and tracking in global positioning system (GPS) receivers. This paper investigates the cross-correlation–induced tracking errors, which can be substantial when the two Doppler frequencies are apart by an integer number of kilohertz. Carrier smoothing is an effective mitigation against the pseudorange errors, although the residual could still be significant if a short smoothing time constant is used. | an unmodified (perfect involute) gear pair was compared with that of gears with various profile modifications. relations were found between various profile rnodificatlons and the resulting dynamic loads. the gear's static transmission error, gave a very good estimation of gear dynamic loading. Cor- An effective error, obtained from frequency domain analysis of Design curves generated by dynamic simulation at several profile modlfi- catlons are given for gear systems operated at various applied loads. Optimum profile modifications can then be determined from the design curves to yield a minimum dynamic effect for a gear system and to provide up-to-date knowledge for better gear deslgn. NOMENCLATURE amplitude of ith frequency component | eng_Latn | 28,887 |
Lightweight Man-In-The-Middle (MITM) Detection and Defense Algorithm for WiFi-Enabled Internet of Things (IoT) Gateways | Man-In-The-Middle (MITM) attack is one of the well-known threats in computer security. With the convergence of smart objects and the Internet (Internet of Things), there has been the need to ensure confidentiality, integrity and availability of information. MITM targets the data flow between endpoints, and the confidentiality and integrity of the data itself. In this paper, we present a lightweight and real-time MITM detection and defense algorithm that can be implemented on WiFi-enabled IoT gateways. The algorithm works for statically assigned host IP addresses and also IP addresses assigned via DHCP. We employed Asynchronous Method Dispatch (AMD) to reduce performance overhead. Subsequently, we evaluated the performance of the algorithm with respect to CPU utilization, detection rate and network latency. | Abstract This paper describes the design and principle behind the demonstrated novel lamellar grating out-of-plane gyroscope design. The sensing mechanism is based on out-of-plane motion of movable light-reflecting beams changing the phase relationship between the light reflected off the two sets of beams. This phase relationship is manifested as an intensity change in the zeroth-order diffracted light. The device consists of two in-plane 180° out-of-phase vibrating masses with a set of overlapping light-reflecting beams behaving essentially as a lamellar grating. The commercial SOI-MUMPS process was used to fabricate a prototype. The gyroscope demonstrated a sensitivity of 17.8 μV/(°/s) and linearity error of less than 0.6%. Design issues were addressed and show promise to be overcome. Post-fabrication tuning and better optics design can improve the performance greatly with respect to the current prototype setup. | eng_Latn | 28,888 |
This adjustment factor is then multiplied by the estimated coefficients from the Schwartz et al. | The estimated coefficients and adjustment factor are multiplied. | The adjustment factor is not used in our calculations. | eng_Latn | 28,889 |
A 4-spot time-of-flight anemometer for small centrifugal compressor velocity measurements | Abstract : The application of laser anemometry techniques in turbomachinery facilities is a challenge dilemma requiring an anemometer system with special qualities. In this work we describe the use of a novel laser anemometry technique applied to a small 4.5 kg/s, 4:1 pressure ratio centrifugal compressor. Sample velocity profiles across the blade pitch are presented for a single location along the rotor. The results of the intra-blade passage velocity measurements will ultimately be used to verify CFD 3-D viscous predictions. | This paper presents a new methodology for the detection of critical situations for vehicle lateral dynamics, in order to improve the ESP systems. The principle of the approach rests on the modeling of the vehicle thanks to a bicycle model. The lateral tire forces are well known to be highly non-linear. However, in normal driving region, those force can be approximated as linear. The detection of the critical situation is done when the physical data provided by the sensors on the vehicle do not anymore match with the linear tire force. The problem of the detection of critical situation is so rewritten as a problem of a fault detection, where some dedicated approaches are given in the literature. Since the vehicle model depends on its longitudinal speed, an extension of the parity space approach for linear parameter varying system is handled. The results has been applied on a real vehicle within the INOVE project$^*$ in order to detect a loss of stability in the vehicle. | eng_Latn | 28,890 |
Projector recalibration of three-dimensional profilometry system. | In three-dimensional profilometry, the primary disadvantage of the monocular system equipped with a projector and a camera is that it is often highly dependent on the projector calibration. The projector calibration errors of the principal point and focal length are analyzed in this paper, and result in measuring the object deviation, including not only the rigid transformation, but also the scale transformation. Unfortunately, the deviation cannot be revealed by reprojection, the normal error analysis method. Here, a systematic recalibration method is proposed to correct the projector calibration errors of the principal point and focal length, where an accurate binocular three-dimensional measurement system is applied. The experimental results show that the method is effective. The three-dimensional measurement accuracy of the monocular system is improved approximately from 1.0 mm before projector recalibration to 0.10 mm afterward. | Abstract : JAYCOR determined that much of the pressure trace detail from the M-198 155mm howitzer with the M203 charge could be understood in terms of gas dynamics and the gun and ground geometry. The objective was to determine the feasibility of simulating the far field muzzle blast and to interpret the field data already taken. A lung model was also developed which gives a way of comparing various pressure traces in terms of the internal dynamics. The agreement seen between measured and predicted pressure traces is repeated in the lung response. A bio- mechanical workshop was also held in Albuquerque, New Mexico on lung modeling. (Author) | eng_Latn | 28,891 |
Pedicle violation and Navigational errors in pedicle screw insertion using the intraoperative O-arm: A preliminary report | Background ::: Use of computer-assisted insertion of pedicle screws has some advantages owing to the reportedly decreased incidence of pedicle breach and clinical events. Registration-based methods based on preoperative computed tomography imaging, 2D fluoroscopy, and 3D fluoroscopy are the most popular, however each has its limitations. O-arm–based navigation, which uses intraoperative acquisition and registration of navigated images, may overcome many of these disadvantages. We set out to study the clinical accuracy and navigational accuracy for pedicle screw insertion using our recently acquired O-arm and present our preliminary findings. | A NNE fault named F1 was found on the site of a proposed irrigation project.Through geological radar detection,seismo-geological investigation,the analysis of the engineering geological data,and the test of dislocation fault and overlying chronology of quaternary strata,we identify the activity,vertical displacement and slip rate of F1 fault.Then we assess the influence of F1 fault on the project and put forward the selection of sites and the design plan for the project.In this way,we provide a good example of the practical application of the identification of fault's activity to the selection of sites and the design plan for the construction project. | eng_Latn | 28,892 |
Does the crop factor affect the field of view (FOV)? I'm working on smartphone cameras. I want calculate Field Of View of different smartphone cameras using the formula : FOV = 2 arctan(SensorSize/2f) where: f is the focal length sensor size is the Height or Width or Diagonal of the sensor (in mm) In doing some research, I've found that there is another parameter to take in consideration, which is the crop factor. When using the formula for FOV, should I apply the given f (focal length), or should I apply the effective focal length which is (focal length x crop factor)? | What is crop factor and how does it relate to focal length? I'm reading that a 50mm lens is recommended as a first prime lens for DSLR owners as it's supposed to give a 'natural' perspective, but when used on (most) DSLRs, the view is cropped, as if you were zoomed in by 1.5-1.6x, so it's more of a telephoto lens when used on a DSLR. I've also read however that the 50mm lens gives the same perspective on a DSLR and a 35mm, and shouldn't really be considered to be 'equivalent' to an 80mm lens as the crop factor isn't really a magic focal length changer. Can someone explain how the image is different from (for example) a 50mm lens on a DSLR and an 80mm lens (assuming 1.6x crop factor) on a 35mm camera? | Rotating a gyroscope's output values into an earth-relative reference frame For whatever reason, I seem to have gotten myself twisted into quite a confusion on how to process data from my 3 axis gyro and 3 axis accelerometer to get gyro rotation values related to the earth's reference frame. i.e. Given my accelerometer measures gravity (we assume it's stable) along the sensors (x,y,z) reference frame, how do I adjust the values of my gyro, measured along the sensors same (x,y,z) reference frame such that I am actually measuring the rotating about the Earth's frame x (North), y (West), and z (downwards) direction? I just can't seem to wrap my head around the use of the rotation matrix. Do I simply employ a 3d rotation matrix, and multiply the vector, \$[gyro_x, gyro_y, gyro_z]^T\$, by a rotation matrix, R? I then assume the rotation angles, are somehow derived from the filtered accelerometer outputs, but I'm having trouble deciding on what those should be. I have yet to find a concise reference on how to move the rotation and acceleration values from the sensor reference frame into the earth global reference frame. Perhaps someone can help? Thanks | eng_Latn | 28,893 |
Movement of the Shoulder Complex The development of a measurement technique based on proposed ISB standards | ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion--Part II: shoulder, elbow, wrist and hand. | First ocean survey with synthetic aperture sonar on neutral trim tow-fish | eng_Latn | 28,894 |
What is the name of the line of latitude that is approximately 23 degrees 30 minutes North? | Latitude Geography Overview By Amanda Briney Updated July 25, 2016. Latitude is the angular distance of any point on Earth measured north or south of the equator in degrees, minutes and seconds. The equator is a line going around Earth and is halfway between the North and South Poles , it is given a latitude of 0°. Values increase north of the equator and are considered positive and values south of the equator decrease and are sometimes considered negative or have south attached to them. For example, if a latitude of 30°N was given, this would mean that it was north of the equator. The latitude -30° or 30°S is a location south of the equator. On a map, these are the lines running horizontally from east-west. Latitude lines are also sometimes called parallels because they are parallel and equidistant from each other. Each degree of latitude is about 69 miles (111 km) apart. The degree measure of latitude is the name of the angle from the equator while the parallel names the actual line along which degree points are measured. continue reading below our video Latitude and Longitude For example, 45°N latitude is the angle of latitude between the equator and the 45th parallel (it is also halfway between the equator and the North Pole). The 45th parallel is the line along which all latitudinal values are 45°. The line is also parallel to the 46th and 44th parallels. Like the equator, parallels are also considered circles of latitude or lines that circle the entire Earth. Since the equator divides the Earth into two equal halves and its center coincides with that of the Earth, it is the only line of latitude that is a great circle while all other parallels are small circles. Development of Latitudinal Measurements Since ancient times, people have tried to come up with reliable systems with which to measure their location on Earth. For centuries, both Greek and Chinese scientists attempted several different methods but a reliable one did not develop until the ancient Greek geographer, astronomer and mathematician, Ptolemy , created a grid system for the Earth. To do this, he divided a circle into 360°. Each degree comprised 60 minutes (60') and each minute comprised 60 seconds (60''). He then applied this method to Earth's surface and located places with degrees, minutes and seconds and published the coordinates in his book Geography. Although this was the best attempt at defining the location of places on Earth at the time, the precise length of a degree of latitude was unresolved for around 17 centuries. In the middle ages, the system was finally fully developed and implemented with a degree being 69 miles (111 km) and with coordinates being written in degrees with the symbol °. Minutes and seconds are written with ', and '', respectively. Measuring Latitude Today, latitude is still measured in degrees, minutes and seconds. A degree of latitude is still around 69 miles (111 km) while a minute is approximately 1.15 miles (1.85 km). A second of latitude is just over 100 feet (30 m). Paris, France for example, has a coordinate of 48°51'24''N. The 48° indicates that it lies near the 48th parallel while the minutes and seconds indicate just how close it is to that line. The N shows that it is north of the equator. In addition to degrees, minutes and seconds, latitude can also be measured using decimal degrees . Paris' location in this format looks like, 48.856°. Both formats are correct, although degrees, minutes and seconds is the most common format for latitude. Both however, can be converted between each other and allow people to locate places on Earth to within inches. One nautical mile , a mile type used by sailors and navigators in the shipping and aviation industries, represents one minute of latitude. Parallels of latitude are approximately 60 nautical (nm) apart. Finally, areas described as having low latitude are those with lower coordinates or are closer to the equator while those with high latitudes have high coordinates and are far. For example, the Arctic Circle, which has a high latitude is at 66°32'N. Bogota, Columb | Douglas MGR-1 Honest John Douglas M31/M50/MGR-1 Honest John The Honest John was the U.S. Army's first nuclear-armed surface-to-surface rocket. Development started in May 1950, when Restone Arsenal was tasked with the development of a large caliber unguided solid-fuel field artillery rocket with a capability for nuclear armament. In late 1950, Douglas was contracted to develop the new rocket, to be named Honest John. Flight testing began in June 1951, and in January 1953, the first limited-production Honest John rockets, designated Artillery Rocket XM31, reached U.S. Army units. In September 1953, the Honest John was reclassed as M31, and the first operational units were deployed in Europe in Spring 1954. The M31 Honest John was an unguided 762 mm artillery rocket, powered by a M6 solid-fuel rocket engine, and spin-stabilized in flight by two M7 spin motors. Of all U.S. nuclear weapons of the 1950's, the Honest John was the easiest to operate. The rocket was transported from the depot to the launching unit by truck and trailer in three parts (warhead, motor, fins). Assembling the rocket, and mounting it on the M289 launcher was then accomplished by six men with a crane in about five minutes. The rocket was then ready for aiming and firing to a range between 5.5 km (3.4 miles) and 24.8 km (15.4 miles). Because of its simplicity, Army units actually preferred the Honest John to the guided MGM-5 Corporal and MGM-18 Lacrosse missiles. Photo: U.S. Army M31 (MGR-1A) In 1954 production switched to the M31A1 model with a slightly improved M6A1 rocket motor. Further improvements of the rocket motor resulted in the M31A1C (late 1956), and the M31A2 (1959, M6A2 motor). Production of the M31 basic Honest John continued until 1960, with almost 7800 rockets built. As early as 1955, the Redstone Arsenal started looking for a major improvement of the Honest John, tentatively known as XM31E2. Contractual problems with Douglas, as well as technical difficulties of finding a new rocket configuration delayed the program, but in 1957 Douglas had completed the design of the improved Honest John, now known as XM50. Flight tests of the XM50 started in June 1958 and continued through July 1959. In 1960 production of the Honest John switched from the M31A2 to the XM50, and the first XM50 rockets reached operational units in 1961. The XM50 Improved Honest John had a significantly improved solid-rocket motor, being lighter and yielding higher thrust, and had completely new square-tipped fins for much improved stability. These changes almost doubled the range, and significantly increased the accuracy of the rocket. In December 1962, the XM50 was reclassified as M50. There was also a product-improved version designated M50A1. Photo: U.S. Army In June 1963, all Honest John rockets were redesigated in the MGR-1 series, as follows: Old Designation | eng_Latn | 28,895 |
What is a sextant used for? | Sextant | Define Sextant at Dictionary.com sextant noun 1. an astronomical instrument used to determine latitude and longitude at sea by measuring angular distances, especially the altitudes of sun, moon, and stars. 2. (initial capital letter) Astronomy. the constellation Sextans. Origin of sextant 1590-1600; < Latin sextant- (stem of sextāns) sixth part of a unit. See sext , -ant Can be confused Examples from the Web for sextant Expand Historical Examples About five minutes before local noon the sea captain goes to the bridge with sextant in hand. Lectures in Navigation Ernest Gallaudet Draper The flat bar which carries the nonius scale and index-glass of a quadrant, octant, quintant, or sextant. The Sailor's Word-Book William Henry Smyth Now read the angle of the height of that light by using your sextant. Lectures in Navigation Ernest Gallaudet Draper Without an English sextant you cannot take an altitude at all. Newton Forster Captain Frederick Marryat Prof. had forgotten his sextant and rode back to our main camp for it. A Canyon Voyage Frederick S. Dellenbaugh It would be like chucking the sextant and the compass overboard. Lefty Locke Pitcher-Manager Burt L. Standish The sun reached its height, and Lund busied himself with his sextant. British Dictionary definitions for sextant Expand noun 1. an optical instrument used in navigation and consisting of a telescope through which a sighting of a heavenly body is taken, with protractors for determining its angular distance above the horizon or from another heavenly body 2. a sixth part of a circle having an arc which subtends an angle of 60° Word Origin C17: from Latin sextāns one sixth of a unit Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Word Origin and History for sextant Expand n. instrument for determining latitude, 1620s, from Modern Latin sextans, said to have been coined c.1600 by Danish astronomer Tycho Brahe, from Latin sextans "a sixth," from sex "six" (see six ). So called because the sextans has a graduated arc equal to a sixth part of a circle. Online Etymology Dictionary, © 2010 Douglas Harper sextant (sěk'stənt) An instrument containing a graduated 60° arc and a movable pivoted arm corresponding to the radius of the arc's circle, used in celestial navigation to measure the altitude of a celestial body in order to determine the observer's latitude and longitude. A horizontally mounted telescope and two small mirrors are arranged so that the observer can, by moving the pivoted arm, sight the horizon and the reflected image of the celestial body in the same line, giving a reading along the arc that is used to look up the observer's position in a published table. The American Heritage® Science Dictionary Copyright © 2002. Published by Houghton Mifflin. All rights reserved. | 1000+ images about @Antarctica@ on Pinterest | Lands in, Frozen and Deception island Forward This is the ceremonial south pole marker, surrounded by flags of all countries who have a presence in Antarctica. The magnetic south pole marker is a temporary marker that has to be moved every year because the ice underneath moves about 30 feet per year. See More | eng_Latn | 28,896 |
How is Earth's axis tilt measured? | How was the tilt of Earth's axis calculated? | What is the best way to check you credit score? | eng_Latn | 28,897 |
How I can rotate unwrap, exactly, for example some menu or box to enter for example 90 degrees ?. This is possible?. Sorry for my English I hope you can understand me. I leave a picture hope it will help me understand. Blender version : 2.72 | I keep running into a problem: How can I rotate an UV island by exactly 90 or 180 degrees? The same applies for scaling it to double in size, etc. | This question is here just to avoid you choosing the wrong Ubuntu version number. So, this is not about: nor about nor nor nor nor . So in the answer below a simple guide as to what Ubuntu version is good for you, independent of future releases! | eng_Latn | 28,898 |
Local and Global Accessibility Evaluation with Tool Geometry | AbstractAccessibility analysis is an important step for the automatic generation of machining planning. One aim of accessibility analysis is to find a domain in which the tool can maneuver without colliding with the workpiece. Most approaches to accessibility analysis use rays or half-line projections that do not include tool geometry considerations. In this paper we present an approach for the global accessibility analysis that includes tool geometry. The paper demonstrates how local accessibility analysis forms an upper bound for the tool radius selection and how a global accessibility approach determines point and part accessibility. The results in this paper are limited to ball-endmill tool geometry. The paper also only considers tool – workpiece interference and collisions and does not consider tool holder geometry. Experiments on sample parts are shown to validate the approach. | Our goal is to characterize the space-varying absorption coefficient from observations of diffuse light propagating through tissue. Sensor array measurements from illumination with several sources leads to an inverse problem which, due to the physics and the restriction of sensors to the surface, is ill-posed and underdetermined. Accurate, reliable solutions require a priori constraints. Here we adopt an admissible solution approach, with convex constraint functions defining admissibility conditions, implemented via the ellipsoid algorithm. The joint use of measurement-model agreement, amplitude, and total variation type constraints produces more accurate reconstructions in a variety of simulation scenarios. | eng_Latn | 28,899 |
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