Search is not available for this dataset
query
stringlengths 1
13.4k
| pos
stringlengths 1
61k
| neg
stringlengths 1
63.9k
| query_lang
stringclasses 147
values | __index_level_0__
int64 0
3.11M
|
|---|---|---|---|---|
Effects of Process Parameters on Structure and Hardness of Cu-SiO_2 Composite Coating Prepared by Ultrasonic Electrodeposition | The Cu-SiO2 composite coating was prepared by ultrasonic electrodeposition,and the effects of ultrasonic power and cathode current density on its structure and hardness were studied.The results show that the structure of the coating is improved first and then deteriorated with the increasing of ultrasonic power(from 0 to 500 W),and it gradually becomes coarse and loose as cathode current density changes from 3 to 18 A/dm2.The hardness of the composite coating tends to increase first and then decrease with the increasing of ultrasonic power and cathode current density. | We demonstrate an effective route for the in-situ chemical synthesis of gold nanoparticles on monolayer modified silicon ::: substrate. The formation of gold nanoparticles is based on the ability of the amino groups of the monolayer to bind ::: AuCl 4 - ions, followed by the reduction of AuCl 4 - to Au 0 with NaBH4. The particles size can be controlled by the ::: concentration of HAuCl 4 during the deposition-reduction process. By repeating the ion binding and reducing cycle, large ::: amount of gold nanoparticles can be generated on the monolayer. UV visible spectroscopy and scanning electron ::: microscope (SEM) confirm that the well-dispersed gold nanoparticles are formed on the substrate. From Atomic Force ::: Microscope (AFM) images, we find the particles with characteristic of 3-35nm are generated on the monolayer. ::: Therefore, this facile procedure can give a new choice to the formation of gold nanoparticles on the self-assembly ::: monolayer modified silicon substrate. | eng_Latn | 11,700 |
Why [CpW(CO)3]+ reduces H2 to dihydride. | The [CpW(CO)3]+ complex, with three pi acceptor ligands and a positive charge, is shown to have an unexpected reducing ability towards H2 because of a low lying triplet state energy. | The formation of Pt nanowires (NWs) by atomic layer deposition on highly ordered pyrolytic graphite (HOPG) is investigated. Pt is deposited only at the step edges of HOPG and not on the basal planes, leading to the formation of laterally aligned Pt NWs. A growth model involving a morphological transition from 0-D to 1-D structures via coalescence is presented. The width of the NWs grows at a rate greater than twice the vertical growth rate. This asymmetry is ascribed to the wetting properties of Pt on HOPG as influenced by the formation of graphene oxide. A difference in Pt growth kinetics based on crystallographic orientation may also contribute. | eng_Latn | 11,701 |
Free space optical communication over the Ghanaian Turbulent Atmospheric Channel | A thesis submitted to the Department of Electrical/Electronic Engineering, ::: College of Engineering in partial fulfillment of the requirements for the degree of ::: MSc Telecommunication Engineering, 2014 | Using ultrafast optical-pump terahertz-probe spectroscopy, we study the THz dynamics and electronic cooling in few-layer epitaxial and CVD graphene; a microscopic theory of carrier-carrier and carrier-phonon interactions accounts quantitatively for the observed dynamics. | eng_Latn | 11,702 |
The Krypton Yellow-Green Laser for the Treatment of Facial Vascular and Pigmented Lesions | There has been a bewildering increase in the number and types of lasers available to the modern surgeon for the treatment of a variety of lesions. Pigmented and vascular lesions lend themselves to laser therapy and are common presentations in the cosmetic practice. While many different lasers may be effective for the treatment of these lesions, each has its own advantages and disadvantages. A detailed understanding of the specific properties and the applicability of the different lasers is vital if one is to successfully incorporate these lasers into one's practice. In this article, we discuss the different types of lasers available for the treatment of these lesions, discuss the specific indications and limitations and present our experience with the krypton laser. | Chemical doping in graphene due to polymer molecules adsorption has attracted much recent interest because of the modification of electrical, magnetic, and optical properties of graphene. We show a reversible charge-transfer doping effect in graphene due to the reaction with poly(methyl methacrylate) (PMMA) residues. By helium ion irradiation and vacuum annealing without introducing an external dopant, reversible shifts in Raman G and 2D bands are observed as well as the change in the relative 2D band intensity to the G band. Chemical bonds between functional groups from PMMA residues and graphene could be formed due to He+ ion irradiation, and the desorption of functional groups from graphene is dominant during the vacuum annealing process. Meanwhile, PMMA residue on the graphene surface is mostly removed and the surface morphology becomes smooth after irradiation and annealing. Both electrical conductance and Raman band shifts show nonmonotonic dependence on the dose density, which remains after anneali... | eng_Latn | 11,703 |
Boundary conditions at the walls with thermionic electron emission in two temperature modeling of “thermal” plasmas | In this paper, we propose new boundary conditions for the electric potential, the electron energy equation, and the energy equation for heavy particles (ions and neutrals) at the hot walls with thermionic electron emission for two-temperature thermal arc models. The derived boundary conditions assume that the walls are made from refractory metals and, consequently, the erosion of the wall is small and can be neglected. In these boundary conditions, the plasma sheath formed at the electrode is viewed as the interface between the plasma and the wall. The derived boundary conditions allow the calculation of the heat flux to the walls from the plasma. This allows the calculation of the thermionic electron current that makes the model of electrode-plasma interaction self-consistent. | We present a concept for an ultrathin solar fuel device with a nanostructured back-contact. Using rigorous simulations, we show that the nanostructuring significantly increases the absorption in the semiconductor, CuBi2O4 in this case, by 47% (5.2 mA cm–2) through the excitation of plasmonic modes. We are able to attribute the resonances in the device to metal–insulator–metal plasmons coupled to either localized surface plasmon resonances or surface plasmon polaritons. Rounding applied to the metallic corners leads to a blue shift in the resonance wavelength while maintaining absorption enhancement, thus supporting the possibility for a successful realization of the device. For a 2D array, the tolerance of the polarization-dependent absorption enhancement is investigated and compared to a planar structure. The device maintains an absorption enhancement up to incident angles of 75°. The study highlights the high potential for plasmonics in ultrathin optoelectronic devices such as in solar fuel generation. | eng_Latn | 11,704 |
Experimental Observation of Carbon and Carbon-Metal Nanotoroids and New Carbon-Metal Superstructures at Nanoscale | We report on experimental observation (by AFM, STM and HRTEM methods) of nanotoroids for both carbon and carbon-metal superstructures produced by methods of arc discharge and laser ablation. Size of superstructures is ~ 10 nm for carbon and ~ 30 nm for carbon-metal (outer diameter), with inner diameter ~ 1/3 of the total. We also discovered carbon-metal nanocapsules with shapes like nanodisks, reminiscent of human erythrocytes, and sizes ~ 30 nm. The influence of pressure, humidity and temperature was investigated. Effect of reversible transition of topology (sphere - toriod) on the same sample were oserved depending on external parameters. New types of topologically closed carbon and carbon-metal nanostructures are discovered. We also discuss some technological aspects of the growth of such toroidal nanostructures. | Smooth and continuous diamond films have been heteroepitaxially grown on β‐type silicon carbide (β‐SiC) (001) surfaces. The smooth films can be obtained in the thickness of less than 6 μm which is the smallest in heteroepitaxial diamonds. The epitaxial growth is composed of three steps; (i) Bias enhanced nucleation on β‐SiC (001) grown on silicon (001), (ii) 〈001〉 fast growth mode for the selection of epitaxially oriented particles, and (iii) 〈111〉 fast growth mode for the smoothing of (001) surface. High quality silicon carbide (001) surface is effective for oriented diamond nucleation. The winnowing process of oriented particles and the surface adjustment are due to the high surface energy of diamond. | eng_Latn | 11,705 |
Spectrin-based membrane skeleton: a multipotential adaptor between plasma membrane and cytoplasm | Pages 1029–1065: Vann Bennett. “Spectrin-Based Membrane Skeleton: A Multipotential Adaptor Between Plasma Membrane and Cytoplasm.” Page 1056: Ref. 36 should read BENNETT, H., and J. CONDEELIS. Isolation of an immunoreactive analogue of brain fodrin that is associated with the cell cortex of Dictyostelium amoebae. Cell Motil. Cytoskeleton 11: 303–317, 1988. | The results of the theoretical investigation of the curvature influence of the strained graphene nanoribbon on its sensory ::: properties are presented in the given work. The attachment mechanisms of hydrogen atoms to the plane and the wavelike ::: graphene nanoribbon are studied by the tight-binding method. For the first time it was established, that the sensory ::: properties of nanoribbon improve with increase of the surface curvature. It was revealed, that the potential well depth of ::: interaction of the curved graphene with hydrogen atom is greater than the planar graphene. It was established, that the ::: difference of the potential minima of the C-H interaction energy increases exponentially with the curvature increase. | eng_Latn | 11,706 |
Study on Phase Transformation Behaviors, Shape Memory Effects and Mechanical Properties of TiNiMo Shape Memory Alloys | Phase transformation behaviors, shape memory effects and mechanical properties of TiNiMo shape memory alloys are investigated. It is found that a R phase transformation exists in TiNiMo alloy, and the adition of Mo will lower the martensite start (Ms) temperature of TiNi alloy, and that the Ms temperatures of Ti(50)Ni(48.5),Mo(1.5 )and Ti(50)Ni(48)Mo(2.0 )alloys are -85℃ and -103℃, respectively. The two alloys will gain 8.06% and 7.71% shape memory effects under 8.51% and 8.26% pre-strain, respectively. The yield strength and breaking strength of Ti(50)Ni(48)Mo(2.0 )alloy, measured to be 589MPa and 799MPa, are 73% higher and 31% higher than the corresponding strengths of Ti(50)Ni(48)Fe(2.0), respectively. Furthermore, Ti(50)Ni(48.5)Mo(1.5) alloy also exhibits excellent mechanical properties. Therefore TiNiMo alloys are very potential when used as new joint materials | In this paper TPMS(Tire pressure monitoring system) provides real time monitoring of the tires and plays an important role in vehicle safety. In this work we have investigate the MEMS pressure sensor structure, which is important in the successful of micromachined pressure sensor. MEMS pressure sensor structure based on graphene membrane has been designed using comsol finite element method software.Along with that design the stress distribution and deflection of rectangular and circular vacuum cavity for various pressure ranges and have been studied and compared. The width of the graphene membrane is 100 nm. The advantage predicts that it has a vastprobable for MEMS pressure sensor. | eng_Latn | 11,707 |
Reversible Charge-Transfer Doping in Graphene due to Reaction with Polymer Residues | Chemical doping in graphene due to polymer molecules adsorption has attracted much recent interest because of the modification of electrical, magnetic, and optical properties of graphene. We show a reversible charge-transfer doping effect in graphene due to the reaction with poly(methyl methacrylate) (PMMA) residues. By helium ion irradiation and vacuum annealing without introducing an external dopant, reversible shifts in Raman G and 2D bands are observed as well as the change in the relative 2D band intensity to the G band. Chemical bonds between functional groups from PMMA residues and graphene could be formed due to He+ ion irradiation, and the desorption of functional groups from graphene is dominant during the vacuum annealing process. Meanwhile, PMMA residue on the graphene surface is mostly removed and the surface morphology becomes smooth after irradiation and annealing. Both electrical conductance and Raman band shifts show nonmonotonic dependence on the dose density, which remains after anneali... | We present the results of a computer simulation study of the structure of the interface between liquid Ga and the (111) face of diamond, with which we reinterpret the findings from an x-ray reflectivity study of that interface [W. J. Huisman, J. F. Peters, M. J. Zwanenburg, S. A. de Vries, T. E. Derry, D. Abernathy, and J. F. van der Veen, Nature (London) 390, 379 (1997); Surf. Sci. 402–404, 866 (1998)]. That experimental study has been interpreted to show that the contact of Ga with the (111) face of diamond induces the formation of Ga2 molecules for several layers into the bulk liquid, with the axes of the Ga2 molecules in successive layers oriented perpendicular to the diamond surface. No driving force for the proposed formation of Ga2 molecules is identified. The simulations reported in this paper are based on a model that permits chemical binding of Ga, as a dimer, to the CC double bonds in the reconstructed (111) face of diamond, thereby identifying the driving force for dimerization. We show that ... | eng_Latn | 11,708 |
Universal deformation pathways and flexural hardening of nanoscale 2D-material standing folds | In the present work, we use atomic force microscopy nanomanipulation of 2D-material standing folds to investigate their mechanical deformation. Using graphene, h-BN and talc nanoscale wrinkles as testbeds, universal force–strain pathways are clearly uncovered and well-accounted for by an analytical model. Such universality further enables the investigation of each fold bending stiffness κ as a function of its characteristic height h 0. We observe a more than tenfold increase of κ as h 0 increases in the 10–100 nm range, with power-law behaviors of κ versus h 0 with exponents larger than unity for the three materials. This implies anomalous scaling of the mechanical responses of nano-objects made from these materials. | The paper introducess the implemented conditions which colling recycle of flexible base on Ying-DaLine.It over all xpounds the investigation of road condlitions of original pavement,indoor trial study,determination of trial lot plan as well as completion of trial lot etc. | eng_Latn | 11,709 |
Fluorescence excitation spectra of the bΠu1, b′Σu+1, cnΠu1, and cn′Σu+1 states of N2 in the 80–100nm region | Fluorescence excitation spectra produced through photoexcitation of N2 using synchrotron radiation in the spectral region between 80 and 100nm have been studied. Two broadband detectors were employed to simultaneously monitor fluorescence in the 115–320nm and 300–700nm regions, respectively. The peaks in the vacuum ultraviolet fluorescence excitation spectra are found to correspond to excitation of absorption transitions from the ground electronic state to the bΠu1, b′Σu+1, cnΠu1 (with n=4–8), cn′Σu+1 (with n=5–9), and c4′(v′)Σu+1 (with v′=0–8) states of N2. The relative fluorescence production cross sections for the observed peaks are determined. No fluorescence has been produced through excitation of the most dominating absorption features of the b-X transition except for the (1,0), (5,0), (6,0), and (7,0) bands, in excellent agreement with recent lifetime measurements and theoretical calculations. Fluorescence peaks, which correlate with the long vibrational progressions of the c4′Σu+1 (with v′=0–8) an... | In the present work, we use atomic force microscopy nanomanipulation of 2D-material standing folds to investigate their mechanical deformation. Using graphene, h-BN and talc nanoscale wrinkles as testbeds, universal force–strain pathways are clearly uncovered and well-accounted for by an analytical model. Such universality further enables the investigation of each fold bending stiffness κ as a function of its characteristic height h 0. We observe a more than tenfold increase of κ as h 0 increases in the 10–100 nm range, with power-law behaviors of κ versus h 0 with exponents larger than unity for the three materials. This implies anomalous scaling of the mechanical responses of nano-objects made from these materials. | eng_Latn | 11,710 |
Electron diffraction study of small bundles of single-wall carbon nanotubes with unique helicity | The selected-area electron diffraction technique has been used to investigate the structure of bundles of single-wall carbon nanotubes synthesized by the catalytic chemical vapor deposition method. The helicity and lattice packing of the single-wall carbon nanotubes within the bundles have been deduced from the experimental diffraction patterns on the basis of the geometry of the reciprocal space of carbon nanotubes and computer simulations based on the kinematical theory. We show that a precise helicity can be found within a given small bundle. We attribute this selectivity to the small number of nanotubes ~20‐30! in the bundles. | Summary In this abstract, we propose a new finite-difference scheme for solving wave equations. This scheme splits the multidimensional system into different directions and solves each direction implicitly. Unlike most splitting methods in the literature which produce numerical anisotropy in diagonal directions, this method gives perfect circular impulse responses and allows lateral velocity variations. In this paper, we prove that the proposed scheme is unconditionally stable. In the numerical examples, we show some impulse response tests and compare them with the results from some high-order explicit finite-difference methods. The new method allows larger time step and requires less memory storage during the reverse time | eng_Latn | 11,711 |
Investigation of diamond-like carbon films for protection and stabilization of selenium-containing photoreceptors in electrophotography | Abstract The possibilities of diamond-like carbon film applications for protection and stabilization of selenium-containing photoreceptors in electrophotography have been studied experimentally. We have determined the optimal conditions for deposition of diamond-like a-C:H films as well as their thickness at which the electrophotographic characteristics and the printing quality are not deteriorated as compared with control samples of a-Se. The effect of amorphous phase stabilization in the selenium photoreceptors when depositing the a-C:H layer has been revealed. The service life of copying cylinders with a protective a-C:H coating increases by a factor of 2–3. | Combining Landau diamagnetism and differential magnetic susceptibility to an electromagnetic wave, we theoretically predict a graphene-sheet periodic structure, which exhibits a left-handed property to an electromagnetic wave in the infrared region by modulating external fields. Our new mechanism, unlike the usual mechanism, does not use resonant behavior and is thus able to synthesize broadband left-handed metamaterial. | eng_Latn | 11,712 |
Subnanometer vacancy defects introduced on graphene by oxygen gas. | The basal plane of graphene has been known to be less reactive than the edges, but some studies observed vacancies in the basal plane after reaction with oxygen gas. Observation of these vacancies has typically been limited to nanometer-scale resolution using microscopic techniques. This work demonstrates the introduction and observation of subnanometer vacancies in the basal plane of graphene by heat treatment in a flow of oxygen gas at low temperature such as 533 K or lower. High-resolution transmission electron microscopy was used to directly observe vacancy structures, which were compared with image simulations. These proposed structures contain C═O, pyran-like ether, and lactone-like groups. | A report is presented, for the first time, on the observation of optical resonance modes in free-standing InGaAs/GaAs quantum dot microtubes at room temperature. The three-dimensionally confined optical modes, with wavelengths in the range of 1.1-1.3 mum and an intrinsic Q-factor of -2000, are directly related to the microtube surface geometry and, consequently, can be precisely engineered by varying the microtube surface. | eng_Latn | 11,713 |
Line defects and induced doping effects in graphene, hexagonal boron nitride and hybrid BNC | Effects on the atomic structure and electronic properties of two-dimensional graphene (G) and h-BN sheets related to the coexistence of dopants and defects are investigated by using density functional theory based methods. Two types of extended line defects are considered for pristine G and h-BN sheets. In these sheets, the presence of individual doping increases the charge transport character. The coexistence of dopants and defects tunes the band gap towards lower values and causes the direct–indirect band gap change. The relative stability and the electronic properties of various BxNyCz systems are analyzed in detail. We find that the structural properties of these types of systems strongly depend on the orientation of grain boundaries and whether these are parallel or perpendicular to the extended line defects. The electronic structure analysis of the different systems evidences the shift of absorption to the visible region. | We present first-principles studies on how to engineer band lineups of nanosized radial heterojunctions, Si/Ge core-shell nanowires. Our calculation reveals that band offsets of these one-dimensional nanostructures can be tailored by applying the axial strain. In particular, the valence band offset can be efficiently tuned in a wide range and even be diminished with applied strain. Two mechanisms contributing to this strain engineering of band offsets are discussed. Our proposed approach to control band offsets in nanosized heterojunctions may be of practical interest for nanoelectronics and photovoltaic applications. | eng_Latn | 11,714 |
Low-frequency optical dielectric response and rigidity transitions in network glasses | Self-organization occurring in ${\mathrm{As}}_{x}{\mathrm{S}}_{1\ensuremath{-}x}$ and ${\mathrm{As}}_{x}{\mathrm{Se}}_{1\ensuremath{-}x}$ glass alloy films reflects in their low-frequency optical dielectric response, and valuable information about the building blocks conforming their structure, can be derived from the analysis of the refractive-index dispersion data. The experimental results are discussed in the framework of the single-oscillator approach proposed by Wemple and DiDomenico, which provides a meaningful parametrization of the phenomena ruling the coupling between the photon-probe and the electron plasma in the near-infrared spectral region. Rigidity transitions occurring in both binary glassy systems are discussed in terms of the differences observed in the oscillator parameters, and these electronic evidences are linked to those arguments found in the literature, based on calorimetric and Raman measurements, that point to a segregated-phase view of glass materials. | Abstract This research is focused on the effects of nonlinear terms on the dynamical behavior of graphene reinforced laminated composite plates. Firstly, the governing equations of the graphene reinforced composite thin plate subjected to transverse excitations are derived by using the Hamilton's principle and the von Karman deformation theory. Then numerical method is applied to investigate the nonlinear behaviors of graphene reinforced composite plates. Bifurcation diagram, waveform and phase portrait are demonstrated to analyze the nonlinear dynamics of the graphene reinforced laminated composite plates. Furthermore, the effects of nonlinear terms on the dynamical behavior are discussed in detail, where both the stronger and weaker nonlinear characteristics of lower modes of the plate are presented. Moreover, some interesting phenomena are obtained in numerical simulation. | eng_Latn | 11,715 |
Quantitative measure of nanoscale adhesion hysteresis by ultrasonic force microscopy | Adhesion hysteresis is the difference between the work used on separating two surfaces and the work gained on bringing them back together. Although much effort has been invested into adhesion hysteresis investigations at macroscales and microscales, its measurements at the nanolengths or even molecular lengths are still not easy. In this paper we demonstrate how to obtain quantitative measures of local adhesion hysteresis from ultrasonic force microscopy investigations. We derive analytical models fitting all the experimental cases and apply them to experimental data. | We describe linear scaling methods for electronic structure calculations and quantum molecular dynamics simulations which are based on an orbital formulation of the electronic problem. In particular, we discuss some open problems which need to be addressed to improve the performance of these methods, and briefly review some applications to carbon and silicon systems, with a Tight-Binding framework. | eng_Latn | 11,716 |
A comparative study of a self strain-monitoring carbon nanotube film and carbon fibers under flexural loading by electrical resistance changes | With the increased use of composites for load-carrying structures, the ability to obtain strain and damage information is critical to maintain reliable structures in the field. A promising class of multifunctional composites with the ability to self-sense strain and/or damage is possible through the use of carbon fibers and carbon nanotubes. This paper presents a comparative study of two sensors for fiber-reinforced polymer composites: the sensors are the carbon fibers themselves, and a non-structural carbon nanotube (CNT) film applied through spray deposition. The changes in resistance of the sensors are compared under monotonic and cyclic flexural loading. Within the limits of this study and the current CNT sensor configuration, the carbon fibers are shown to have a higher sensitivity for strain and damage sensing. However, the CNT film appears to track the performance of GFRPs reasonably well for tensile strains. | Abstract We propose a new model which simulates the motion of free electrons in graphene by the evolution of strings on manifolds. In this model, molecules which constitute sheets of graphene are polygonal point-like structures which build ( N + 1 ) -dimensional manifolds. By breaking the gravitational-analogue symmetry of graphene sheets, we show that two separated child sheets and a Chern–Simons bridge are produced giving rise to a wormhole. In this structure, free electrons are transmitted from one child sheet to the other producing superconductivity. An analogue between “effective gravitons” and “Cooper pairs” is found. In principle, this phenomenology provides the possibility to construct superconductor structures by using the analogue of cosmological models. | eng_Latn | 11,717 |
Structure versus electron effects in the growth mode of pentacene on metal-induced Si(111)-square root(3) x square root(3) surfaces. | The growth of pentacene films on different metal (Ga, Pb, Bi, Ag) induced Si(111)-(square root(3) x square root(3))R30 degrees surfaces is investigated by scanning tunneling microscopy. On surfaces with high atomic surface roughness, such as GaSi-square root(3), beta-PbSi-square root(3), and alpha-BiSi-square root(3), pentacene forms an initial disordered wetting layer followed by the growth of crystalline thin films. The growth behavior is independent of the metallicity of the substrate surface in this regime. On the other hand, on surfaces with low adatom surface roughness, pentacene molecules form self-organized structures without forming a wetting layer. Moreover, the molecular orientation is critically dependent on the surface metallicity. This work reveals that the growth mode of pentacene on solid surfaces is determined by the combined effects of structural and electronic properties of the substrate. | Silicene and Graphene are similar and have $\pi$-$\pi^*$ bands. However band width in silicene is only a third of graphene. It results in a substantial increase in the ratio of Hubbard U to band width W, U/W $\sim$ 0.5 in graphene to $\sim 1$ in silicene. This enhancement, 2 dimensionality and phenomenology suggest a Mott insulator based ground state for silicene (G. Baskaran, arXiv:1309.2242). We lend support to the above proposal by showing, in an ab-initio calculation, that unlike graphene, silicene has two instabilities: i) a valence bond (Kekule) dimerization and ii) a weak two sublattice antiferromagnetic order. Presence of these instabilities, in the absence of fermi surface nesting, point to Mott localization, \textit{within the frame work of ab-initio scheme}. Substrate dependent structural reconstructions seen experimentally in silicene are interpreted as generalized Kekule bond order. | eng_Latn | 11,718 |
Electron-Electron Interaction in Nanographite Ribbons | We study the π electronic structure of graphite ribbons of a nanometer width by taking account of the long-range electron-electron interaction. The primary features like energy dispersion and bond order distribution are essentially determined by the nearest-neighbor transfer alone, meaning their strong dependency on the connectivity relation in the π electron network. The Coulomb interaction, on the other hand, is induced by the sites of longer distances as well, which means that the Coulomb repulsion reflects the site geometry in the atomic configuration. We focus on the geometry-dependent Coulomb interaction and discuss how it influences the electronic state near the Fermi level which is governed by the network topology. The Coulomb repulsion under the geometry of armchair ribbons works against the bond order distribution determined by the network topology. This may lead to a frustrated system especially for a quite narrow ribbon. The Coulomb interaction in zigzag ribbons tends to open a gap with/withou... | The coating of the surface on H13 steel die was prepared by electrical spark deposition. Its wear and corrosion resistance were studied. The results indicate that, the wear resistance of the sample with electric spark coating is 4.3 times higher than that of the untreated sample, while corrosion resistance is 2.21 times higher than that of the untreated sample. | eng_Latn | 11,719 |
Fermi Velocity Modulation in Graphene by Strain Engineering | Using full-potential density functional theory (DFT) calculations, we found a small asymmetry in the Fermi velocity of electrons and holes in graphene. These Fermi velocity values and their average were found to decrease with increasing in-plane homogeneous biaxial strain; the variation in Fermi velocity is quadratic in strain. The results, which can be verified by Landau level spectroscopy and quantum capacitance measurements of bi-axially strained graphene, promise potential applications in graphene based straintronics and flexible electronics. | FIELD: information technologies. SUBSTANCE: systems and methodologies are described that provide methods to efficiently search for a cell in a wireless communication system. In one aspect a scheme of repeated frequency use may be generated by application of frequency shifts to reference signals transmitted from cells, which ensure a coverage area for a unit B on the basis of the cell IDs or IDs of cell groups for cells. Then frequency shifts applied to reference signals may be used as the basis for multiplexing reference signals from different cells using frequency division multiplexing (FDM) or a combination of FDM with other multiplexing methods. To improve the detection process, other corrections of reference signals sent from appropriate cells, such as transmission capacity corrections, may be made additionally. EFFECT: maximisation of total speed, reliability of the system and minimisation of spent resources. 36 cl, 16 dwg | eng_Latn | 11,720 |
Optical properties of GaN synthesized by implantation of nitrogen ions into GaAs | Abstract Implantation of N ions with doses of 3 × 1 0 16 and 3 × 1 0 17 cm - 2 and energies of 100 keV into semiinsulating (1 0 0) GaAs substrates has been performed in order to synthesize the GaN compound. The samples have been annealed in a furnace at 750 °C for 30 min in N gas flow or under GaAs powder and then characterized by 300 and 77 K cathodoluminescence, infrared reflection, Raman spectroscopy and secondary ion mass spectroscopy measurements. All optical techniques have detected the presence of GaN phase in the samples. No noticeable dependence of CL spectra on annealing conditions leading to different As and N losses from the surface has been observed. SIMS measurements have been performed to show N atom redistribution after annealing. The results of the study are consistent with the presence of buried layers with differently oriented GaN nanocrystals. | The results of the theoretical investigation of the curvature influence of the strained graphene nanoribbon on its sensory ::: properties are presented in the given work. The attachment mechanisms of hydrogen atoms to the plane and the wavelike ::: graphene nanoribbon are studied by the tight-binding method. For the first time it was established, that the sensory ::: properties of nanoribbon improve with increase of the surface curvature. It was revealed, that the potential well depth of ::: interaction of the curved graphene with hydrogen atom is greater than the planar graphene. It was established, that the ::: difference of the potential minima of the C-H interaction energy increases exponentially with the curvature increase. | eng_Latn | 11,721 |
Mechanical Characterization of Graphene | The emergence of monolayer carbon atom sheets, graphene, as a next generation advanced material, has potential applications in promising fields such as composite materials and energy storage. Graphene has exceptional mechanical properties, the most notable of which are ultrahigh strength and yield strain. Both experimental techniques and simulations have been performed for understanding mechanical properties of graphene such as, strength, yield strain, friction, and fracture behavior. This chapter summarizes the most recent findings on the mechanical characterization of graphene. | As part of the LANL/VNIIEF collaboration a high velocity cylindrical liner driven Hugoniot experiment is being designed to be driven by a VNIEF Disk Explosive Magnetic (flux compression) Generator (DEMG). Several variations in drive current and liner thickness have been proposed. This presentation will describe the LANL 1D and 2D simulations used to evaluate those designs. The presentation will also propose an analysis technique to assess a high current drive systems ability to stably and optimally drive a cylindrical aluminum liner for this type of experiment. | eng_Latn | 11,722 |
Electronic cooling in epitaxial and CVD graphene | Using ultrafast optical-pump terahertz-probe spectroscopy, we study the THz dynamics and electronic cooling in few-layer epitaxial and CVD graphene; a microscopic theory of carrier-carrier and carrier-phonon interactions accounts quantitatively for the observed dynamics. | A CUDA implementation of the 3D viscous incompressible Navier-Stokes equations is proposed using as advection operator the BFECC (Back and Forth Error Compensation and Correction) schema. The Poisson problem for pressure is solved with a CG (Conjugated Gradient) preconditioning the system with FFTs (Fast Fourier Transforms). Study cases as Lid-Driven Cavity and Flow Past Circular Cilinder, both 2D and 3D, are solved in order to check accuracy and obtain performance meassurements. | eng_Latn | 11,723 |
Analysis on User's Electroencephalography for Automatic Detection of 3D Syndrome | Various contents utilizing 3D holographic image have been developed and this led to the need of research on problems which are related to 3D syndrome. It is now more urgent to find the mechanism to sort out such problems as some people show such symptoms as fatigue, dizziness and vomiting after watching 3D contents. This research, in this light, has been conducted to suggest an indicator for detecting 3D syndrome by extracting and analyzing the changes in user’s electroencephalogram of which result can be utilized for implementing the system which prevent and mitigate the syndromes which occur after watching 3D holography. | Characteristic features of the d-band in electronic structure of transition metals are quite effective as descriptors of their catalytic activity toward oxygen reduction reaction (ORR). With the promise of graphene-based materials to replace precious metal catalysts, descriptors of their chemical activity are much needed. Here, a site-specific electronic descriptor is proposed based on the pz (π) orbital occupancy and its contribution to electronic states at the Fermi level. Simple structural descriptors are identified, and a linear predictive model is developed to precisely estimate adsorption free energies of OH (ΔGOH ) at various sites of doped graphene, and it is demonstrated through prediction of the most optimal site for catalysis of ORR. These structural descriptors, essentially the number of ortho, meta, and para sites of N/B-doped graphene sheet, can be extended to other doped sp2 hybridized systems, and greatly reduce the computational effort in estimating ΔGOH and site-specific catalytic activity. | kor_Hang | 11,724 |
Energy absorption characteristics of single-walled carbon nanotubes | The excellent mechanical properties of carbon nanotubes make them potential candidates for engineering application. In this paper, the impact and failure behaviors of single-walled carbon nanotubes (SWCNTs) are investigated. The effects of diameter, length, and chirality on their energy absorption characteristics under lateral impact and axial crush are studied. By integrating the principle of molecular structural mechanics (MSM) into finite element method (FEM), the locations and directions of fracture process can be predicted. It is shown that the specific energy absorption (SEA) of SWCNTs is 1–2 order of magnitude higher than that of the ordinary metallic materials and composites in axial impact, indicating that carbon nanotubes are promising energy absorption materials for engineering applications. | Abstract For experiments with future hadron colliders involving multi-TeV proton beams, such as the LHC and SSC, sampling calorimeters with silicon as active medium satisfy the special experimental conditions. Defect formation processes and electrical behavior of neutron irradiated p + -n ion implanted silicon detectors were studied. A fast monolithic preamplifier to be employed at hadron calorimeters was investigated for noise as a function of the expected leakage current in an SSC/LCH silicon calorimeter. | eng_Latn | 11,725 |
Optimal electrode shape and size of doubly rotated quartz plate thickness mode piezoelectric resonators | Using the Stevens–Tiersten equation for slowly varying thickness modes in doubly rotated quartz plate piezoelectric resonators, we determine optimal electrode shape and size for these resonators. The electrodes obtained are optimal in that they satisfy Bechmann’s number in every direction. | For a nanowire quantum dot with the confining potential modeled by both the infinite and the finite square wells, we obtain exactly the energy spectrum and the wave functions in the strong spin-orbit coupling regime. We find that regardless of how small the well height is, there are at least two bound states in the finite square well: one has the σx$${\mathscr{P}}$$P = −1 symmetry and the other has the σx$${\mathscr{P}}$$P = 1 symmetry. When the well height is slowly tuned from large to small, the position of the maximal probability density of the first excited state moves from the center to x ≠ 0, while the position of the maximal probability density of the ground state is always at the center. A strong enhancement of the spin-orbit effect is demonstrated by tuning the well height. In particular, there exists a critical height $${V}_{0}^{c}$$V0c, at which the spin-orbit effect is enhanced to maximal. | eng_Latn | 11,726 |
Electrical rectification by magnetic edge states | Abstract We investigate electron channelling by inhomogeneous magnetic fields in hybrid semiconductor/ferromagnet structures. A novel type of rectifying behaviour is observed in the current–voltage characteristics measured along the drift path of magnetic edge states. This rectification effect is switched on by the application of the magnetic potential and changes sign with its polarity. We ascribe this non-linear behaviour to the anisotropic electron–phonon interaction arising from the asymmetry of the energy dispersion curves of snake orbits that results in electrons thermalising by emitting phonons along the electron drift direction. We present a theory to evaluate the electromotive force due to this phonon drag effect and compare it to the non-linear behaviour. | Abstract EPR investigations on light-emitting Manganese centres in device-near ZnS or ZnSe thin-film layers were done. Mn 2+ centres were detected in both basic modifications of ZnS. Assertion on the crystallinity could be made. The efficiency of EPR is demonstrated by some examples. | eng_Latn | 11,727 |
Microstructural characterization of Au-free Si/Ti/Al/Cu ohmic contacts in an AlGaN/GaN heterostructure | Abstract A complementary metal-oxide semiconductor (CMOS)-compatible Au-free Si/Ti/Al/Cu ohmic metallization scheme has been developed for AlGaN/GaN power transistors epitaxially grown on Si substrates. The Si/Ti/Al/Cu metallization exhibited a low specific contact resistance of 3.5 × 10 − 6 Ω cm 2 after optimizing the Si interface layer. The ohmic metal surface was smooth with a root-mean-square roughness of 24 nm. Physical characterization confirmed that Cu diffusion into the semiconductor was suppressed because locally segregated TiSi x alloys acted as a barrier. Shallow interfacial reactions of localized TiN alloys occurred in the AlGaN/GaN heterostructure. Without a designated diffusion barrier as in conventional Au-based metallization, the contact resistivity and surface morphology in Si/Ti/Al/Cu improved significantly, which helps address critical challenges associated with the fabrication of AlGaN/GaN power transistors on a Si CMOS platform. | Recently, there has been an increase in research relating to the search for new optoelectronic materials for photovoltaic devices and light-emitting diodes. This research focuses on developing materials that not only possess the required optoelectronic properties (high absorption, efficient photon emission, and high charge-carrier mobilities) but are also solution-processable, which can reduce fabrication costs. Ternary ionic crystal structures, such as lead-halide perovskites, have emerged as a class of such suitable materials. However, the most promising structures, which exhibit the highest device efficiencies, rely on toxic lead as a cationic species, thereby hindering commercial application. Here, we synthesize and characterize CsCuCl3 and Cs2CuCl4 nanocrystals. These nanocrystals exhibit bright broad band green emission from copper defects when excited below 300 nm. We show that by employing a variety of ratios of coordinating solvents during synthesis, we can tailor the morphology of the nanopartic... | eng_Latn | 11,728 |
Electrochemical intercalation into graphite seen as an electrocapillary process | Abstract The electrochemical intercalation of H 2 SO 4 into graphite leads to the well known graphite salts C + n HSO − 4 . χH 2 SO 4 (with n → 20), χ ≈ 2.5). The potential—charge relations observed during intercalation agree well with a model involving the extended graphene layer-intercalate interfacial capacitance. The components of this capacitance are studied, including the effect of Fermi level lowering. A computed electrocapillary curve is compared to the separation work of graphene layers. | We propose a novel method for speeding up stochastic optimization algorithms via sketching methods, which recently became a powerful tool for accelerating algorithms for numerical linear algebra. We revisit the method of conditioning for accelerating first-order methods and suggest the use of sketching methods for constructing a cheap conditioner that attains a significant speedup with respect to the Stochastic Gradient Descent (SGD) algorithm. While our theoretical guarantees assume convexity, we discuss the applicability of our method to deep neural networks, and experimentally demonstrate its merits. | eng_Latn | 11,729 |
Melt Rheology and Thermal Stability of Nanoclay Filled Poly(3hydroxybutyrate-co-4hydroxybutyrate) Biocomposites | Melt apparent shear viscosity for poly(3hydroxybutyrate-co-4hydroxybutyrate) composites filled with nanoclay was measured by means of a capillary rheometer at temperatures ranging from 140 to 160 °C and apparent shear rates varying from 13 to 1,198 s−1, and thermal stability was conducted on a thermogravimetric analyzer for the composites. The results showed that the effects of extrusion conditions and the nanoclay content on the flow behavior were obvious for the composite melts. The composite melts were pseudoplastic, and the non-Newtonian indexes increased with the temperature increasing. The sensitivity of apparent shear viscosity for the composite melts to temperature increased with the nanoclay content increasing, and decreased with the apparent shear rate increasing. With the nanoclay content increasing, the melt apparent shear viscosity and the thermal stability decreased for the composites. | Abstract This research is focused on the effects of nonlinear terms on the dynamical behavior of graphene reinforced laminated composite plates. Firstly, the governing equations of the graphene reinforced composite thin plate subjected to transverse excitations are derived by using the Hamilton's principle and the von Karman deformation theory. Then numerical method is applied to investigate the nonlinear behaviors of graphene reinforced composite plates. Bifurcation diagram, waveform and phase portrait are demonstrated to analyze the nonlinear dynamics of the graphene reinforced laminated composite plates. Furthermore, the effects of nonlinear terms on the dynamical behavior are discussed in detail, where both the stronger and weaker nonlinear characteristics of lower modes of the plate are presented. Moreover, some interesting phenomena are obtained in numerical simulation. | eng_Latn | 11,730 |
Poole-Frenkel conduction in amorphous solids | Abstract The nature of the electrical conduction process in amorphous solids, using as a basis the ionization of local defects by an applied field, is investigated. It is shown that the Poole-Frenkel effect is a limiting case of a more general analysis that can be extended to cover the experimentally available range of field stress and temperature. At low temperature conduction is by tunnelling emission out of the defects into the quasi-conduction band of the host material whereas at high temperatures thermal emission becomes dominant. Between the two regions a thermal-field emission process has been identified with the characteristic of ln J ∝ T −⅓. | We review the current understanding of the acoustic phonon contribution to thermal transport in nanostructures from nanoparticles to thin films and membranes. Confinement and cavity effects will be discussed as well as electrical and optical measurement methods. | eng_Latn | 11,731 |
An organically modified sol–gel membrane for detection of lead ion by using 2-hydroxy-1-naphthaldehydene-8-aminoquinoline as fluorescence probe | Abstract A fluorescent reagent, 2-hydroxy-1-naphthaldehydene-8-aminoquinoline (HNAAQ) was synthesized, and an organically modified sol–gel membrane for detection of lead ion by using HNAAQ as fluorescence probe was fabricated. Under the optimum conditions, by a coplanar effect and the degree of molecular conjugation due to the complexation of Pb 2+ with HNAAQ the relative fluorescence intensity I 100 / I 0 of the sensing membrane is linearly increased over the Pb 2+ concentration range of 1.9 × 10 −7 to 1.9 × 10 −4 mol/L with the detection limit of 8.3 × 10 −8 mol/L. The preparation of this organically modified sol–gel membrane and its characteristics were investigated in detail. | We demonstrate snake-like motion of graphene nanoribbons atop graphene and hexagonal boron nitride (h-BN) substrates using fully atomistic nonequilibrium molecular dynamics simulations. The sliding dynamics of the edge-pulled nanoribbons is found to be determined by the interplay between in-plane ribbon elasticity and interfacial lattice mismatch. This results in an unusual dependence of the friction-force on the ribbon’s length, exhibiting an initial linear rise that levels-off above a junction-dependent threshold value dictated by the pre-slip stress distribution within the slider. As part of this letter, we present the LAMMPS implementation of the registry-dependent interlayer potentials for graphene, h-BN, and their heterojunctions that were used herein, which provides enhanced performance and accuracy. | eng_Latn | 11,732 |
The curvature influence of the graphene nanoribbon on its sensory properties | The results of the theoretical investigation of the curvature influence of the strained graphene nanoribbon on its sensory ::: properties are presented in the given work. The attachment mechanisms of hydrogen atoms to the plane and the wavelike ::: graphene nanoribbon are studied by the tight-binding method. For the first time it was established, that the sensory ::: properties of nanoribbon improve with increase of the surface curvature. It was revealed, that the potential well depth of ::: interaction of the curved graphene with hydrogen atom is greater than the planar graphene. It was established, that the ::: difference of the potential minima of the C-H interaction energy increases exponentially with the curvature increase. | AIM: To assess the ability of galvanic skin response (GSR) to differentiate between tactile and painful stimulation in newborn infants, and to compare this with the ability of the premature infant ... | eng_Latn | 11,733 |
Indentation size effect for spherical nanoindentation on nanoporous gold | Abstract We find that the indentation size effect (ISE) occurs during spherical indentation on nanoporous gold (np-Au). The hardness increases as the indenter radius decreases at a fixed representative strain. We prepare np-Au samples with a ligament size of 26 nm by free-corrosion dealloying and perform multiple spherical nanoindentations with nominal indenter radii of 4, 12, and 50 μm. A nanomechanics model for the ISE during spherical indentation is developed, and the model accurately describes the hardness depending on the indenter radius. We also correlate the ISE trends of spherical and Berkovich indentations along with their differences in terms of the representative strain and the indentation work. | We examine the influence of Ni impurity in cuprates on the distribution of hole carriers by performing numerically exact diagonalization calculations for a model consisting of $\text{Cu}\text{ }3d$, $\text{Ni}\text{ }3d$, and $\text{O}\text{ }2p$ orbitals. Using realistic parameters for the system, we find that a hole is predominantly bound to $\text{O}\text{ }2p$ orbitals around the Ni impurity forming the Zhang-Rice doublet. This imposes strong restrictions on modeling Ni-substituted cuprates. We propose a resonant inelastic x-ray scattering experiment for $\text{Ni}\text{ }K$ edge to confirm hole binding around the Ni impurity. | eng_Latn | 11,734 |
Modeling of Electron Devices Based on 2-D Materials | The advent of graphene and related 2-D materials has attracted the interest of the electron device research community in the past 14 years. The possibility to boost the transistor performance and the prospects to build novel device concepts with 2-D materials and their heterostructures has awakened a strong experimental interest that requires continuous support from modeling. In this paper, we review the state of the art in the simulation of electron devices based on 2-D materials. We outline the main methods to model the electronic bandstructure and to study electron transport, classifying them in terms of accuracy and computational cost. We briefly discuss, how they can be combined in a multiscale approach to provide a quantitative understanding of the mechanisms determining the operation of electron devices, and we examine the application of these methods to different families of 2-D materials. Finally, we shortly analyze the main open challenges of modeling 2-D-based electron devices. | The 2D problem of excitation of a circular metamaterial cylinder by a filamentary source is numerically investigated. It is found that, for the minus one values of the relative permittivity and permeability, the field on the surface of the cylinder concentrates in a region that is located on the illuminated surface of the cylinder and that is small compared to the wavelength. | eng_Latn | 11,735 |
High–quality single–crystal diamond–graphite–diamond membranes and devices | Implantation of hydrogen ions into synthetic single–crystal diamonds followed by subsequent high–temperature annealing and anodic etching of implanted crystals was used to obtain structurally perfect 30–nm thick diamond membranes with optically active NV− centres (area up to several tens mm²) appropriate for use in integral magnetometers and quantum–informatics optoelectronic circuits. | Abstract Calculations employing the simple Monte Carlo model of gamma-ray interaction in a silicon ΔE -detector provide a very reliable energy spectrum of Compton-scattered electrons. This makes it possible to determine the thickness of a Si ΔE -detector with a good accuracy. | eng_Latn | 11,736 |
Research update: strain and composition effects on ferromagnetism of Mn0.05Ge0.95 quantum dots | Mn0.05Ge0.95 quantum dots (QDs) samples were grown by molecular beam epitaxy on Si substrates and 15-nm-thick fully strained Si0.8Ge0.2 virtual substrates, respectively. The QDs samples grown on the Si0.8Ge0.2 virtual substrates show a significant ferromagnetism with a Curie temperature of 227 K, while the QDs samples grown on the Si substrates are non-ferromagnetic. Microstructures of the QDs samples were characterized by high resolution transmission electron microscopy and synchrotron radiation X-ray diffraction. Interdependence between microstructure and ferromagnetism of Mn-doped Ge QDs was investigated. For the QDs sample grown on the strained Si0.8Ge0.2 virtual substrate, although the ferromagnetic phase Mn5Ge3 clusters were found to be formed in small dome-shaped dots, the significant ferromagnetism observed in that sample is attributed to ferromagnetic phase Mn-doped large dome-shaped Ge QDs, rather than to the ferromagnetic phase Mn5Ge3 clusters. The fully strained Si0.8Ge0.2 virtual substrates w... | Abstract We propose a new model which simulates the motion of free electrons in graphene by the evolution of strings on manifolds. In this model, molecules which constitute sheets of graphene are polygonal point-like structures which build ( N + 1 ) -dimensional manifolds. By breaking the gravitational-analogue symmetry of graphene sheets, we show that two separated child sheets and a Chern–Simons bridge are produced giving rise to a wormhole. In this structure, free electrons are transmitted from one child sheet to the other producing superconductivity. An analogue between “effective gravitons” and “Cooper pairs” is found. In principle, this phenomenology provides the possibility to construct superconductor structures by using the analogue of cosmological models. | eng_Latn | 11,737 |
Alloy nanowires: Invar inside carbon nanotubes | Invar (Fe65Ni35), a ‘zero’ ::: thermal expansion alloy consisting of Fe and Ni, has been successfully ::: introduced into carbon nanotubes by pyrolysing, at 800 °C, aerosols of ::: NiCp2/FeCp2 mixtures dissolved in ::: C6H6; scanning electron microscopy (SEM) and ::: high-resolution transmission electron microscopy (HRTEM) studies reveal the ::: presence of flake-like structures (ca. 1–2 mm2) ::: consisting of filled/aligned carbon nanotubes (⩽200 μm in length and ::: ⩽80 nm in diameter) in a carpet pile-like configuration; analysis of ::: the filling material (⩽500 nm in length and ⩽40 nm in diameter) by ::: X-ray powder diffraction and high-resolution electron energy loss ::: spectroscopy (HREELS) line scans, confirmed that Invar was formed; this ::: appears, to the best of our knowledge, to be the first report of mixed ::: metal alloy nanowires forming inside carbon nanotubes. | The synthesis of new low-dimensioned solids relies on difficult chemistry that simultaneously takes into account many different factors, some of them largely conflicting. The design of chainlike niobium and tantalum chalcogenides reported here illustrates the experimental approaches that can be used to stabilize chainlike arrangements or to strengthen low-dimensional character when starting from a given compound. | eng_Latn | 11,738 |
High Mobility Flexible Graphene Field-Effect Transistors with Self-Healing Gate Dielectrics | A high-mobility low-voltage graphene field-effect transistor (FET) array was fabricated on a flexible plastic substrate using high-capacitance natural aluminum oxide as a gate dielectric in a self-aligned device configuration. The high capacitance of the native aluminum oxide and the self-alignment, which minimizes access resistance, yield a high current on/off ratio and an operation voltage below 3 V, along with high electron and hole mobility of 230 and 300 cm2/V·s, respectively. Moreover, the native aluminum oxide is resistant to mechanical bending and exhibits self-healing upon electrical breakdown. These results indicate that self-aligned graphene FETs can provide remarkably improved device performance and stability for a range of applications in flexible electronics. | We study the topological states which appear at the interface between a topological insulator (TI) and a conventional insulator (CI) using effective Hamiltonians which accurately describe the band structure of the Bi$_2$Se$_3$ family. Due to the hybridization between the TI and the CI states, the band-gap that appears in the interface Dirac cone decreases and ultimately vanishes by tuning the interface-hopping amplitude or by selecting a CI of appropriate band effective mass. More importantly, we find that a topologically trivial TI slab can be made non-trivial and vice-versa by tuning of such an interface-hopping amplitude or by tuning the CI band effective-mass; namely, a topological phase transition can be induced in such heterostructures indicated by the presence or absence of gapless linear edge modes. We discuss the relevance and realization of our results and conclusions in future experiments. | eng_Latn | 11,739 |
Quantum optical oscillations of the Fermi level in a graphene-based Schottky junction | The strong movility of charge carriers in graphene allows the introduction of high doping concentration in this material and, this way, the Fermi level can be tunned over a large range of energies. The above situation acquires a complex character in presence of strong electron–photon interaction that induces new quantum phases. In this context, this work describes the possible quantum oscillatory behavior of the Fermi level for a graphene-silicon Schottky junction under circular polarized radiation in the terahertz regime. The reported quantum optical oscillations of the Fermi level are related to intraband optical transitions of intrinsic photon-dressed electrons in the graphene sheet, which promote shiftings of the spectral singularities in the density of states (DOS). In addition, the oscillatory effect is strongly accented in the number of oscillations and modulation by the induction of electrons from the semiconductor to the graphene sheet via a gate potential. | The paper presents the information on specific design, accuracy characteristics, and results of testing of a prototype fiber-optic gyro of accuracy grade 0.01°/h, with sensing element spool diameter of 150 mm, designed by Concern RCSI Elektropribor, JSC. The device is compared to a number of sensors of similar accuracy grade, designed by various Russian and international companies. | eng_Latn | 11,740 |
Composition ratio dependent refractive index and optical bandgap of nonstoichiometric Si1−xGex on silicon | Nonstoichiometric Si 1−x Ge x films fabricated by plasma enhanced chemical vapor deposition (PECVD) with different flounce ratios are demonstrated to show the composition ratio dependent optical properties, including refractive index, bandgap and optical absorption. By increasing the fluence ratio from 0.2 to 0.5, the refractive index of Si 1−x Ge x film raises from 3.527 to 3.927, with the absorption coefficient enlarging from <<1cm−1 to 31.12 cm−1. | A simple structural model is proposed for the zigzag interface formed by contacting two-dimensional graphene-like compounds AB and CD (both free and formed on a metal). For the graphene–hexagonal boron nitride system, analytical expressions for the electron spectrum, density of states, and atom occupation numbers at the interface are obtained. The results of calculating the densities of states and occupation numbers within two alternative approximations are in good agreement. | eng_Latn | 11,741 |
Ultra-wideband (UWB) Monopole Antenna with Dual Notched Bands by Combining Electromagnetic-Bandgap (EBG) and Slot Structures | A novel design technique, which combines mushroom-shaped electromagnetic-bandgap (EBG) structures and a slot together, is proposed for ultra-wideband (UWB) band-notched antenna. The implementation of the slot can not only create its own notched band, but also enhance the filtering performance at the other notched band generated by EBG structures. This is caused by the increased current density in the two ends of the slot. The location of the two notched bands are determined by the position and size of the EBG and the length of the slot, respectively. However, the parameters of the EBG structures and slot has little effect on the antenna performance. The simulated results demonstrate that the proposed antenna exhibits a good wideband radiation performance from 2.64 to 12.9 GHz along with two separated notched bands at WLAN (4.8-5.9 GHz) and X-band downlink satellite communication band (7.1-7.8 GHz). As a result, the proposed design is a promising candidate for modern UWB antennas. | We present molecular dynamics calculations on the evolution of Ni nanowires stretched along the (111) and (100) directions, and at two different temperatures. Using a methodology similar to that required to build experimental conductance histograms, we construct minimum crosssection histograms H(Sm). These histograms are useful to understand the type of favorable atomic configurations appearing during the nanowire breakage. We have found that minimum crosssection histograms obtained for (111) and (100) stretching directions are rather different. When the nanowire is stretched along the (111) direction, monomer and dimer-like configurations appear, giving rise to well-defined peaks in H(Sm). On the contrary, (100) nanowire stretching presents a different breaking pattern. In particular, we have found, with high probability, the formation of staggered pentagonal nanowires, as it has been reported for other metallic species. | eng_Latn | 11,742 |
REACTION OF gem-DIHALIDES WITH NICKEL(O) COMPLEXES: SELECTIVE METHYLENE INSERTION INTO C–H BOND OF OLEFINS | The reaction between methylene dihalides and ethylene assisted by the nickel(O)-triphenylphosphine complex has been found to give propylene, which was formed by selective methylene insertion into the olefinic C–H bond of ethylene. Similarly propylene and methylene dibromide gave isobutylene. | Recently Geis fabricated a composite cold cathode emitter made of diamond doped by substitutional nitrogen on a roughened metallic substrate, which is characterized by high field emission currents at very low power. Using an internal field emission mechanism through the Schottky barrier at the metal diamond interfaces to populate the conduction band of diamond, we have developed a quantitative theory to describe the operation of such a device. The calculated I-V characteristics are in good agreement with the experimental results of Geis, et al. | yue_Hant | 11,743 |
3D printed long period gratings for optical fibers. | We demonstrate a simple technique for implementing long period grating (LPG) structures by the use of a 3D printer. This Letter shows a way of manipulating the mode coupling within an optical fiber by applying stress through an external 3D printed periodic structure. Different LPG lengths and periods have been studied, as well as the effect of the applied stress on the coupling efficiency from the fundamental mode to cladding modes. The technique is very simple, highly flexible, affordable, and easy to implement without the need of altering the optical fiber. This Letter is part of a growing line of interest in the use of 3D printers for optical applications. | Characteristic features of the d-band in electronic structure of transition metals are quite effective as descriptors of their catalytic activity toward oxygen reduction reaction (ORR). With the promise of graphene-based materials to replace precious metal catalysts, descriptors of their chemical activity are much needed. Here, a site-specific electronic descriptor is proposed based on the pz (π) orbital occupancy and its contribution to electronic states at the Fermi level. Simple structural descriptors are identified, and a linear predictive model is developed to precisely estimate adsorption free energies of OH (ΔGOH ) at various sites of doped graphene, and it is demonstrated through prediction of the most optimal site for catalysis of ORR. These structural descriptors, essentially the number of ortho, meta, and para sites of N/B-doped graphene sheet, can be extended to other doped sp2 hybridized systems, and greatly reduce the computational effort in estimating ΔGOH and site-specific catalytic activity. | eng_Latn | 11,744 |
Novel electrically conductive graphite material | A novel electrically conductive graphite material is characterized in that: the electrically conductive graphite material comprises a carbon material having a dimension equal to or less than 200nm, wherein the carbon material is graphene selected from a single layer graphene or multi-layer graphene, and a part of carbon atoms in the graphene are replaced by nitrogen atoms; and a metal material mixed or laminated with the carbon material, wherein the metal material comprises one of metal particles and metal lines. The material has a reasonable combination, favorable electrical conductivity, and is durable. | This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) grant EP/K02924X/1. E.O.R. is supported by an EPSRC DTA studentship (University of Cambridge), and F.D.D. is supported by the Honorary Vice-Chancellor’s Award and a Qualcomm/DTA Studentship. | eng_Latn | 11,745 |
Cavity Backed Substrate Integrated Waveguide Horn Antenna with Enhanced Gain for 5G Applications | In this paper, cavity-backed substrate integrated waveguide (SIW) H-plane horn antenna with enhanced gain for 5G applications is proposed. A coaxial probe has been used to feed the SIW H-plane horn antenna. A metallic cavity has been used to enhance the gain of the antenna. The antenna with cavity shows almost 2 dB enhanced gain over the bandwidth as compared to SIW H-plane horn antenna without cavity. The impedance bandwidth for $\vert\mathbf{S}_{11}\vert is 5% (from 25.2 to 26.5 GHz). A peak gain of 10.4 dBi at 25.5 GHz has been achieved. This antenna finds applications in wireless communication systems for 5G. | So far, the strategies for the synthesis of biomimetic dental enamel-like hydroxyapatite [Ca10(PO4)6(OH)2, HAp] have attracted great interest due to the extremely high orientation of HAp crystals. In the present study, a facile method via hydrothermal treatment of the hillebrandite [Ca2(SiO3)(OH)2] nanobelts as hard-templates in trisodium phosphate aqueous solutions was developed to synthesize the dental enamel-like HAp nanorod arrays, in the absence of any proteins, surfactants, organic solvents or organic molecule directing reagents. The morphology observations demonstrated that the highly oriented HAp arrays were constructed of uniform nanorods parallel to each other along the c-axis. A possible hard-template transformation mechanism based on the crystal structure and morphology of the hillebrandite nanobelts was proposed. | eng_Latn | 11,746 |
Ballistic simulation of Ratchet effect in antidot lattices patterned on graphene | In this contribution, we investigate the mechanism governing the Ratchet effect in patterned monolayer graphene, at the ballistic nanoscale. Still smaller than currently achievable and manifacturable devices, the simulated structures serve to exemplify the dependence of charge scattering on the arrangement of lattice defects, i.e. clusters of atomic vacancies of triangular shape. The ballistic Ratchet effect is seen as cumulative multimode scattering of carriers in correspondence of the lattice discontinuities. An atomistic model, based on the Scattering Matrix method and making use of TB approximation, has been applied. The latter, in contrast with continuum models, like Dirac or Kubo-Drude derived formulas, is capable of describing abrupt discontinuities at sub-micrometric scales, where graphene is likely to preserve its outstanding properties. We believe that this work is a first step in the direction of engineering and design of devices based on the ballistic Ratchet effect, like RF and THz detectors. | We argue that in the measured $p_T$ domain of RHIC, collisional rather than the radiative energy loss is the dominant mechanism for jet quenching. Accordingly we calculate nuclear suppression factor for light hadrons by taking only the elastic energy loss in sharp contrast with the previous calculations where only the radiative loss are considered. | eng_Latn | 11,747 |
Raman spectroscopy of acoustic phonons in periodic and Fibonacci superlattices | Abstract Results of Raman scattering experiments on (a) periodic superlattices made up of GaAs/InxGa1−xAs layers with high indium concentrations, (b) GaAs/Ga1−xAlxAs Fibonacci superlattices, are presented. We discuss the observed peak positions and intensities using the continuum theory of acoustic wave propagation in layered media and the photo-elastic coupling model. | Abstract Understanding the atomistic mechanisms of tensile failure in carbon fibers is important for fiber manufacturing and applications. Here we design structural faults with atomistic details, pertaining to polyacrylonitrile (PAN) derived fibers, and probe them using large-scale molecular dynamics simulations to uncover trends and gain insight into the effect of local structure on the strength of the basic structural units (BSUs) and the role of interfaces between regions with different degrees of graphitization. Besides capturing the expected strength degrading with increasing misalignment, the designed basic structural units reveal atomistic details of local structural failure upon tensile loading. Fracture initiation is nearly always associated with the interface of the misoriented crystallite and its environment. | eng_Latn | 11,748 |
Wave Packet Dynamics at an Extended Seam of Conical Intersection: Mechanism of the Light-Induced Wolff Rearrangement. | Quantum dynamics calculations on a model surface based on CASPT2//CASSCF calculations are carried out to probe the traversal of a wave packet through an extended seam of conical intersection during the light-induced Wolff rearrangement of diazonaphtoquinone. The reaction is applied in the fabrication of integrated circuits. It consists of nitrogen elimination and ring rearrangement to yield a ketene. After excitation, the wave packet relaxes and reaches the extended seam. A fraction of the wave packet decays to the ground state at a region of the seam connected to a carbene intermediate, while the remaining part decays at a region leading to the ketene. The passage of the wave packet through the extended seam explains the competition between concerted ketene formation and a stepwise mechanism involving a carbene. The two primary photoproducts are formed in the first 100 fs of the simulation, in agreement with recent ultrafast spectroscopy measurements. | This is a status report about the ongoing work on the realization of quantum field theory on curved graphene spacetimes that uses Weyl symmetry. The programme is actively pursued from many different perspectives. Here we point to what has been done, and to what needs to be done. | eng_Latn | 11,749 |
Low-dimensional solids: an interface between molecular and solid-state chemistry? The example of chainlike niobium and tantalum chalcogenides | The synthesis of new low-dimensioned solids relies on difficult chemistry that simultaneously takes into account many different factors, some of them largely conflicting. The design of chainlike niobium and tantalum chalcogenides reported here illustrates the experimental approaches that can be used to stabilize chainlike arrangements or to strengthen low-dimensional character when starting from a given compound. | As electronic devices and integrated circuits get smaller and smaller, eventually quantum-mechanic effects take over. As Saito discusses in his Perspective, results reported by ::: Collins ::: et al. ::: in the same issue demonstrate the use of carbon nanotubes to create nanometer-scale devices known as diodes. Rather than fighting the effects of quantum mechanics, such devices make excellent use of quantum effects on the nanometer scale. | eng_Latn | 11,750 |
Fabrication and Test of Carbon Nanotubes Field Emission Cathode Made by Spin-Coating Technique | A novel fabrication process of carbon nanotubes cathode emitters is presented in the work.Single-walled carbon nanotubes(SWNTs) with high purity have been synthesized by dc arc discharge evaporation of a carbon electrode including Ni and Y_2O_3 catalysts in H_2-He mixture gas.As-grown SWNTs are purified by gas phase oxidation in air at 350 ℃ and then mixed uniformly with alcohol.We obtain SWNTs cathode film by spin-coating,drying and annealing the SWNTs suspension on the Si substrate.The tests show that the emitter made by the simple method has good properties of electron field emission,following the Fowler-Nordheim behavior. | Smooth and continuous diamond films have been heteroepitaxially grown on β‐type silicon carbide (β‐SiC) (001) surfaces. The smooth films can be obtained in the thickness of less than 6 μm which is the smallest in heteroepitaxial diamonds. The epitaxial growth is composed of three steps; (i) Bias enhanced nucleation on β‐SiC (001) grown on silicon (001), (ii) 〈001〉 fast growth mode for the selection of epitaxially oriented particles, and (iii) 〈111〉 fast growth mode for the smoothing of (001) surface. High quality silicon carbide (001) surface is effective for oriented diamond nucleation. The winnowing process of oriented particles and the surface adjustment are due to the high surface energy of diamond. | eng_Latn | 11,751 |
Synthesis of isothiocyanato-1-[1-(2-benzo[b]thienyl)cyclohexyl]piperidines, potential irreversible ligands at the dopamine re-uptake site | Isomeric isothiocyanate derivatives 2–7 of the potent dopamine re-uptake (DA) inhibitor 1-[1-(2-benzo-[b]thienyl)cyclohexyl]piperidine (BTCP 1) have been synthesized as potential irreversible ligands for this site. NaNO2–CF3CO2H provided a mild procedure for mononitration of the benzo[b]thienyl ring of 1 as a route to aryl isothiocyanates 5–7. Novel methodology, utilizing 3,3-ethylenedioxypentane-1,5-diol dimethanesulfonate ester is described for the synthesis of piperidone 13, a precursor for 4-isothiocyanatopiperidine 2. NaBH4 or LiAlH4 reduction of 4-(2-benzo[b]thienyl)-4-hydroxycyclohexanone 18 and 4-(2-benzo[b]thienyl)-4-(piperidino)cyclohexanone oxime 35 gives the corresponding cis-diol 21 and cis-cyclohexane-1,4-diamine 36 as the major isomers which have been investigated as precursors to the cyclohexane ring isothiocyanates 3 and 4. Alternative routes to 3 and 4 are compared and their stereochemical outcome investigated. | Chemical doping in graphene due to polymer molecules adsorption has attracted much recent interest because of the modification of electrical, magnetic, and optical properties of graphene. We show a reversible charge-transfer doping effect in graphene due to the reaction with poly(methyl methacrylate) (PMMA) residues. By helium ion irradiation and vacuum annealing without introducing an external dopant, reversible shifts in Raman G and 2D bands are observed as well as the change in the relative 2D band intensity to the G band. Chemical bonds between functional groups from PMMA residues and graphene could be formed due to He+ ion irradiation, and the desorption of functional groups from graphene is dominant during the vacuum annealing process. Meanwhile, PMMA residue on the graphene surface is mostly removed and the surface morphology becomes smooth after irradiation and annealing. Both electrical conductance and Raman band shifts show nonmonotonic dependence on the dose density, which remains after anneali... | eng_Latn | 11,752 |
Fabrication and optical characterization of III‐nitride air‐bridge photonic crystal with GaN quantum dots | We report the fabrication of III-nitride air-bridge photonic crystals with GaN quantum dots for the first time. Photonic crystals with various periodicities and airhole diameters were fabricated. Abrupt vertical profiles and high aspect ratio (∼3) were achieved with excellent reproducibility even to the structure with periodicity as small as 150 nm. The fabrication of air-bridge structure utilizing photoelectrochemical etching of SiC was demonstrated. Strong photoluminescence enhancement by a factor of 5 was observed from GaN QDs embedded in the air-bridge PC layer. This is due to the coupling of PL light with photonic bands above the light cone, thus results in the enhanced light extraction efficiency. These results will lead to the realization of high efficiency quantum dots based emitting devices in blue and ultraviolet range. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) | The performance of N-doped graphene on Li-ion battery has been investigated systematically by means of a density functional theory method. Pyridinic N doping, graphitic N atoms and 5-8-5 double vacancies have been selected as the functional defects to study their influence on Li storage compared to the pristine graphene. It has been confirmed that introducing pyridinic N atoms with p-type doping is a suitable method, especially for graphene doped with 4 pyridinic N atoms, whose structural distortion induced by Li intercalation is small and supplies strong force for Li adsorption. The diffusion barrier for this model is lower than for pristine graphene, both for the side and center diffusion routes, contributing to the high mobility. In addition, we point out that the strong catch force for Li will cause more Li to stay on the pyridinic N-doped graphene during the charge-discharge cycles, leading to a faster decrease of capacity compared to pristine graphene. | eng_Latn | 11,753 |
Heat exchangers for solar concentrators | Abstract The theoretical analysis of three types of heat exchangers for use with solar concentrators is developed. Under the assumptions of an incompressible inviscid fluid, constant energy rate input per unit area, and losses to the surroundings, an expression for the temperature field, and average exit temperature is given. An expression for a dimensionless temperature modulus, to aid in the determination of a fluid exit temperature, is derived and plotted for the three types of heat exchangers. | The melting transition of methane adsorbed in nanopores has been studied and compared in two types of structures: carbon slits pores and square shaped channels. We show that the nano-confinement not only modifies the temperatures of phase transformation but also induces strong space heterogeneity of the adsorbate. We emphasize the role of the structural heterogeneity on the mechanism of melting: in nanometric pores, each adsorbed layer exhibits different mechanisms of structural transformation and the notion of a unique transition temperature is not well defined. | eng_Latn | 11,754 |
Nanoscale Dielectric Capacitors Composed of Graphene and Boron Nitride Layers: A First Principles Study of High-Capacitance at Nanoscale | We investigate a nanoscale dielectric capacitor model consisting of two-dimensional, hexagonal h-BN layers placed between two commensurate and metallic graphene layers using self-consistent field density functional theory. The separation of equal amounts of electric charge of different sign in different graphene layers is achieved by applying electric field perpendicular to the layers. The stored charge, energy, and the electric potential difference generated between the metallic layers are calculated from the first-principles for the relaxed structures. Predicted high-capacitance values exhibit the characteristics of supercapacitors. The capacitive behavior of the present nanoscale model is compared with that of the classical Helmholtz model, which reveals crucial quantum size effects at small separations, which in turn recede as the separation between metallic planes increases. | We report an angle-resolved photoemission investigation of optimally-doped Ca$_{0.33}$Na$_{0.67}$Fe$_2$As$_2$. The Fermi surface topology of this compound is similar to that of the well-studied Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ material, except for larger hole pockets resulting from a higher hole concentration per Fe atoms. We find that the quasi-nesting conditions are weakened in this compound as compared to Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$. As with Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ though, we observe nearly isotropic superconducting gaps with Fermi surface-dependent magnitudes. A small variation in the gap size along the momentum direction perpendicular to the surface is found for one of the Fermi surfaces. Our superconducting gap results on all Fermi surface sheets fit simultaneously very well to a global gap function derived from a strong coupling approach, which contains only 2 global parameters. | eng_Latn | 11,755 |
Light emission from Na/Cu(111) induced by a scanning tunneling microscope | Measurements of light emission from a scanning tunneling microscope probing a Na overlayer on the (111) surface of Cu are reported along with the results of a model calculation that essentially agree with the experimentalones. The observed light-emission spectra show two characteristic features depending on the bias voltage. When the bias voltage is smaller than the energy of the second quantum well state formed outside the Na overlayer the light emission is due to a plasmon-mediated process, while for larger biases light emission is mainly caused by quantum well transitions between the two levels. | We have developed a new theoretical formalism for phonon transport in nanostructures using the nonequilibrium phonon Green's function technique and have applied it to thermal conduction in defective carbon nanotubes. The universal quantization of low-temperature thermal conductance in carbon nanotubes can be observed even in the presence of local structural defects such as vacancies and Stone-Wales defects, since the long wavelength acoustic phonons are not scattered by local defects. At room temperature, however, thermal conductance is critically affected by defect scattering since incident phonons are scattered by localized phonons around the defects. We find a remarkable change from quantum to classical features for the thermal transport through defective CNTs with increasing temperature. | eng_Latn | 11,756 |
Imaging Material Components of an Integrated Circuit Interconnect | Two regions of interest on a copper/tungsten integrated circuit interconnect were imaged using two techniques: (a) the absorption spectrum was measured at 15 x-ray energies between 1687 and 1897 eV, and (b) the x-ray fluorescence spectrum was recorded with incident photon energies of 1822, 1797, and 1722 eV. The energies were chosen to optionally excite tungsten and tantalum above their M5 edges yet stay below the silicon K edge. Four materials in the circuits, tantalum, tungsten, silica, and copper were mapped using both techniques. The two sets of images agree in their main features, but differ for finer features. | The literature concerning microstructure formation in Compacted Graphite Iron (CGI) is reviewed. CGI has an intermediate graphite morphology between Lamellar Graphite Iron (LGI) and Spheroidal Grap ... | eng_Latn | 11,757 |
Size-, position-, and separation-controlled one-dimensional alignment of nanoparticles using an optical near field | Particles several tens of nanometers in size were aligned in the desired positions in a controlled manner by using capillary force interaction and suspension flow. Latex beads 40-nm in diameter were aligned linearly around a 10-μm-hole template fabricated by lithography. Further control of their position and separation was realized using colloidal gold nanoparticles by controlling the particle-substrate and particle-particle interactions using an optical near field generated on the edge of a Si wedge, in which the separation of the colloidal gold nanoparticles was controlled by the direction of polarization. | This manuscript presents a summary on the parallel session V "Particles in the Cosmos" of the Neutrino Oscillation Workshop -- NOW 2018. The topics covered by the session are a combination of new theoretical approaches and ideas and a selection of recent experimental results and upcoming projects. | eng_Latn | 11,758 |
The Hypergraphite: A possible extension of graphitic network | We propose a class of networks which can be regarded as an extension of the graphitic network. These networks are constructed so that surface states with non-bonding character (edge states) are formed in a tight-binding model with one orbital for each atomic site. Besides, for several networks, the tight-binding electronic structures become a zero-gap semiconductor. These properties have been found in the $\pi$-electron system of the graphene. Thus, we call these networks hypergraphite. | Abstract A new class of connected digraphs is introduced — the class of quasi-initially connected digraphs. They are enumerated in the labelled case. Using the apparatus developed for labelled quasi-initially connected digraphs respective results for other classes of labelled connected digraphs were obtained. | eng_Latn | 11,759 |
Microstructure and Properties of Low-carbon High Strength Dual Phase Steel Wire | Microstructure and properties of dual-phase steel wire were studied.It is shown that with the incresaing of subcritical quenching temperature,the substructure of martensite in dual-phase microstructure changes form twin-type to dislocation type,and the deformation capability and drawing properties of both phases are improved.The amount of deformation is a key factor that effect the amount of dislocation and the forming dislocation cell in dual-phase microstructure.After the steel wire of subcritical quenching at a higher temperature was deeply drawn to 79%,very high tensile strength with satisfactory numbers of bending and twising was gained. | Abstract We propose a new model which simulates the motion of free electrons in graphene by the evolution of strings on manifolds. In this model, molecules which constitute sheets of graphene are polygonal point-like structures which build ( N + 1 ) -dimensional manifolds. By breaking the gravitational-analogue symmetry of graphene sheets, we show that two separated child sheets and a Chern–Simons bridge are produced giving rise to a wormhole. In this structure, free electrons are transmitted from one child sheet to the other producing superconductivity. An analogue between “effective gravitons” and “Cooper pairs” is found. In principle, this phenomenology provides the possibility to construct superconductor structures by using the analogue of cosmological models. | eng_Latn | 11,760 |
Nearly perfect quark–gluon fluid | A statistical analysis of data from ultra-relativistic heavy-ion collisions has uncovered the specific viscosities of the quark–gluon plasma — suggesting that the hottest matter in the current Universe behaves like a near-perfect fluid. | The results of the theoretical investigation of the curvature influence of the strained graphene nanoribbon on its sensory ::: properties are presented in the given work. The attachment mechanisms of hydrogen atoms to the plane and the wavelike ::: graphene nanoribbon are studied by the tight-binding method. For the first time it was established, that the sensory ::: properties of nanoribbon improve with increase of the surface curvature. It was revealed, that the potential well depth of ::: interaction of the curved graphene with hydrogen atom is greater than the planar graphene. It was established, that the ::: difference of the potential minima of the C-H interaction energy increases exponentially with the curvature increase. | eng_Latn | 11,761 |
New boron nitride whiskers: showing strong ultraviolet and visible light luminescence. | Boron nitride whiskers with a special structure have been synthesized by a thermal reaction process. The as-prepared BN whiskers have a length of tens of micrometers and a mean diameter of 500 nm. High-resolution TEM analysis shows that the as-prepared BN whiskers can be described as a nanofiber-interweaved network. Infrared and electron energy loss spectra reveal that the BN whiskers are composed of both sigma-sp2 and sigma-sp3 chemical bonds. The UV-vis absorption spectrum displays the energy band gap of the BN whiskers and multiple fine absorption peaks of the phonon-electron coupling. Both photoluminescence (PL) and cathodoluminescence (CL) measurements show the specially structured BN emits strong UV and visible luminescences, which is a promising material for deep-blue and UV applications. | The results of the theoretical investigation of the curvature influence of the strained graphene nanoribbon on its sensory ::: properties are presented in the given work. The attachment mechanisms of hydrogen atoms to the plane and the wavelike ::: graphene nanoribbon are studied by the tight-binding method. For the first time it was established, that the sensory ::: properties of nanoribbon improve with increase of the surface curvature. It was revealed, that the potential well depth of ::: interaction of the curved graphene with hydrogen atom is greater than the planar graphene. It was established, that the ::: difference of the potential minima of the C-H interaction energy increases exponentially with the curvature increase. | eng_Latn | 11,762 |
Microscopic structure of the Gamow-Teller resonance in 208Bi | The 2osPb(3He,t)20sBi reaction has been studied with the RCNP ring cyclotron at E(3He) = 450 MeV using the magnetic spectrometer Grand Raiden at 0 = 0”. The Gamow-Teller resonance is strongly excited at this bombarding energy. Its microscopic structure has been investigated by measuring the direct proton decay to the neutron-hole states in ‘07Pb. The branching ratio for proton emission of a few % is much smaller than that for the decay of the isobaric analog state. The total width of the Gamow-Teller resonance as well as its total and partial escape widths have been determined. Several recent theoretical estimates for the escape width differ from the measured values by factors of - 2.5. | The results of the theoretical investigation of the curvature influence of the strained graphene nanoribbon on its sensory ::: properties are presented in the given work. The attachment mechanisms of hydrogen atoms to the plane and the wavelike ::: graphene nanoribbon are studied by the tight-binding method. For the first time it was established, that the sensory ::: properties of nanoribbon improve with increase of the surface curvature. It was revealed, that the potential well depth of ::: interaction of the curved graphene with hydrogen atom is greater than the planar graphene. It was established, that the ::: difference of the potential minima of the C-H interaction energy increases exponentially with the curvature increase. | eng_Latn | 11,763 |
Efficient n-type doping in epitaxial graphene through strong lateral orbital hybridization of Ti adsorbate | Abstract In recent years, various doping methods for epitaxial graphene have been demonstrated through atom substitution and adsorption. Here we observe by angle-resolved photoemission spectroscopy (ARPES) a coupling-induced Dirac cone renormalization when depositing small amounts of Ti onto epitaxial graphene on SiC. We obtain a remarkably high doping efficiency and a readily tunable carrier velocity simply by changing the amount of deposited Ti. First-principles theoretical calculations show that a strong lateral (non-vertical) orbital coupling leads to an efficient doping of graphene by hybridizing the 2pz orbital of graphene and the 3d orbitals of the Ti adsorbate, which attached on graphene without creating any trap/scattering states. This Ti-induced hybridization is adsorbate-specific and has major consequences for efficient doping as well as applications towards adsorbate-induced modification of carrier transport in graphene. | In this paper, aimed at the neutron transport equations of eigenvalue problem under 2-D cylindrical geometry on unstructured grid, the discrete scheme of Sn discrete ordinate and discontinuous finite is built, and the parallel computation for the scheme is realized on MPI systems. Numerical experiments indicate that the designed parallel algorithm can reach perfect speedup, it has good practicality and scalability. | eng_Latn | 11,764 |
Interlayer Conductance of Graphene with Multiple Transfer Process | Electrical properties of multi-layer graphene are subject to variations due to random interlayer alignments. In this work we reported graphene interlayer conductance without special layer aligning. Ohmic contacts between two graphene layers are observed with resistance variations of more than one order. With Raman spectroscopy we identify that the lattice angle between twisted graphene layers is the key variation source. The angular dependence and temperature dependence of the interlayer conductance suggest that a phonon assistant tunneling mechanism is valid for the interlayer transport of graphene prepared by multiple transfer process. We finally derive that the multi-layer graphene resistance shows an exponential-like distribution due to the random interlayer misalignments. | The six papers in this session address performance limits and transport characteristics of devices on strained and III-V substrates. The session begins with a paper by Oh and Wong from Stanford. They discuss a physics-based compact model for heterostructure devices. Luisier and colleagues from Purdue next apply an advanced transport model to InAs HEMTs. Finally, an NEGF analysis for InGaAs DGFETs by Pal, Low, and Lundstrom is presented. Strain effects in group IV devices are the subject of the second half of the session. First, Pham and colleagues at Braunschweig Technical University employ multisubband simulation for strained DG PFET including magnetic effects. Results of a collaboration between Stanford, Braunschweig, and Intel that deal with the effect of orientation and strain on Ge and Si DG PFET's are presented next by Krishnamohan et al., Finally, Shi, Register and Banerjee from University of Texas Austin analyze strained, deeply scaled NFETs using quantum-scorrected Monte Carlo methods. | eng_Latn | 11,765 |
The release of hydrogen reaction of graphene modified NaAlH4. | In this experiment, we prepared a better performance graphene, by using butyrolactone and flavanone, promoting the graphite into high quality graphene strip. The obtained graphene were used to catalyze the hydrogen released by NaAlH4. The result proved that 5 wt% doped butyrolactone treated graphite and 2 wt% doped flavanone-treated graphite are good catalyst in NaAlH4's decomposition process. | An atomic model of the laser-produced Al plasma has been developed and used to analyze excitation processes of recombination pumping soft X-ray lasers. A soft X-ray gain for H-like Balmer-α line and He-like 3d-2p transition in short-pulse intense KrF laser ( I L = 10 14 –10 15 W/cm 2 , T = 10–100 ps)-produced Al plasmas are calculated for various laser temporal pulse shapes to find the condition for efficient production of population inversion. Results from different models are compared and requirements for the atomic model for X-ray laser design are discussed. | eng_Latn | 11,766 |
52.1: Invited Paper: FEM and in situ TEM Studies | Field emission microscopy (FEM) study of carbon nanotube (CNT) with various tip radii was performed to reveal the origin of different types of FEM patterns (“pentagon” and “dim” patterns) so far reported. Dynamic behaviour and degradation mechanism of field-emitting CNTs were also studied by in-situ transmission electron microscopy (TEM). | Related Article: Yuanyuan Zhang, Xuan Zhang, Jiafei Lyu, Ken-ichi Otake, Xingjie Wang, Louis R. Redfern, Christos D. Malliakas, Zhanyong Li, Timur Islamoglu, Bo Wang, Omar K. Farha|2018|J.Am.Chem.Soc.|140||doi:10.1021/jacs.8b06789 | kor_Hang | 11,767 |
Charged Topological Solitons in Zigzag Graphene Nanoribbons | Graphene nanoribbons with zigzag terminated edges have a magnetic ground state characterized by edge ferromagnetism and antiferromagnetic inter edge coupling. This broken symmetry state is degenerate in the spin orientation and we show that, associated with this degeneracy, the system has topological solitons. The solitons appear at the interface between degenerate ground states. These solitons are the relevant charge excitations in the system. When charge is added to the nanoribbon, the system energetically prefers to create magnetic domains and accommodate the extra electrons in the interface solitons rather than setting them in the conduction band. | This paper considers corona discharge problems with multiple conductors, such as those appearing in some electrostatic precipitators. A common precise condition is identified in which the previous approaches proposed in the literature fail. For dealing with these conditions, a novel, stabilized, and regularized formulation of the problem is proposed. Moreover, a Newton–Raphson scheme is defined for iteratively solving a nonstandard Petrov–Galerkin finite-element discretization of the problem. The presented approach is validated on a benchmark for which an analytical solution is known and its applicability to problems of industrial relevance is shown. | eng_Latn | 11,768 |
Suction Effects on the Transition and Reattachment of a Transitional Bubble | The effects of distributed suction on the transition and reattachment of the transitional bubble on an airfoil at a Reynolds number of 250,000 are investigated by analyzing the mean and fluctuating velocity profiles. It is found that suction delays separation and transition and decreases the turbulence intensity at these locations. Suction also affects the development of the turbulent boundary layer downstream of reattachment by causing the mean velocity profiles to be “fuller” and reducing the turbulence intensity in this region. Investigating the power spectra of the streamwise velocity fluctuations shows that suction suppresses the freestream disturbances upstream of the suction distribution. However, once suction begins, these disturbances amplify significantly. | The results of the theoretical investigation of the curvature influence of the strained graphene nanoribbon on its sensory ::: properties are presented in the given work. The attachment mechanisms of hydrogen atoms to the plane and the wavelike ::: graphene nanoribbon are studied by the tight-binding method. For the first time it was established, that the sensory ::: properties of nanoribbon improve with increase of the surface curvature. It was revealed, that the potential well depth of ::: interaction of the curved graphene with hydrogen atom is greater than the planar graphene. It was established, that the ::: difference of the potential minima of the C-H interaction energy increases exponentially with the curvature increase. | eng_Latn | 11,769 |
Spectral imaging of single CdSe/ZnS quantum dots employing spectrally- and time-resolved confocal microscopy | A spectrally- and time-resolved study of single CdSe/ZnS quantum dots (QDs) is presented. To this end a versatile, high sensitivy spectrograph is coupled to a confocal laser-scanning microscope. The spectrograph is built in-house and is especially developed for use in fluorescence microscopy. The high sensitivity is achieved by using a prism for the dispersion of light in combination with a state-of-the-art back-illuminated charge-coupled device (CCD) camera. The detection efficiency of the spectrograph, including the CCD camera, amounts to 0.77 ±0.05 at 633 nm. Full emission spectra with a 1–5 nm spectral resolution can be recorded at a maximum rate of 800 spectra per second. The spectrograph can easily be fiber-coupled to any confocal laser-scanning microscope. | Characteristic features of the d-band in electronic structure of transition metals are quite effective as descriptors of their catalytic activity toward oxygen reduction reaction (ORR). With the promise of graphene-based materials to replace precious metal catalysts, descriptors of their chemical activity are much needed. Here, a site-specific electronic descriptor is proposed based on the pz (π) orbital occupancy and its contribution to electronic states at the Fermi level. Simple structural descriptors are identified, and a linear predictive model is developed to precisely estimate adsorption free energies of OH (ΔGOH ) at various sites of doped graphene, and it is demonstrated through prediction of the most optimal site for catalysis of ORR. These structural descriptors, essentially the number of ortho, meta, and para sites of N/B-doped graphene sheet, can be extended to other doped sp2 hybridized systems, and greatly reduce the computational effort in estimating ΔGOH and site-specific catalytic activity. | eng_Latn | 11,770 |
Communication: Influence of graphene interlayers on the interaction between cobalt phthalocyanine and Ni(111). | The influence of graphene interlayers on electronic interface properties of cobalt phthalocyanine on Ni(111) is studied using both photoemission and X-ray absorption spectroscopy. A charge transfer associated with a redistribution of the d-electrons at the Co-atom of the phthalocyanine occurs at the interface to Ni(111). Even a graphene buffer layer cannot prevent the charge transfer at the interface to Ni(111); however, the detailed electronic situation is different. | Intraoperative distinction of lesional tissue versus normal brain parenchyma can be difficult in neurosurgical oncology procedures. We report the successful, real-time visualization of central nervous system (CNS) lymphoma using the 'Second Window Indocyanine Green' (SWIG) method for two patients who underwent craniotomy for pathology that was determined to be large B cell lymphoma. Indocyanine green (ICG), when administered intravenously the day prior to cranial surgery, is a re-purposed fluorophore that may afford safe, immediate visual confirmation of on-target tissue resection, thereby providing a valuable adjunct to intraoperative navigation and decreasing reliance on frozen pathology analysis. These first reported cases of SWIG for lymphoma in the CNS indicate that further study of fluorophores to improve biopsy targeting and yield is warranted. | eng_Latn | 11,771 |
Passive laser Q-switches on the basis of LiF color center crystals for alexandrite laser | Passive laser Q-switches on the basis of crystals of LiF with F 3 - - and LiF with F 3 - -like centers, and LiF:O, OH with new F 2 + -like centers were investigated. The paper presents power characteristics and radiation parameters of alexandrite lasers with different Q-switches. Operating potentials of Q-switches are determined. | The phase of graphene plasmon upon edge-reflection plays a crucial role on determining the spectral properties of graphene structures. In this article, by using the full-wave simulation, we demonstrate that the mid-infrared graphene plasmons are nearly totally reflected at the boundary together with a phase jump of approximately 0.27π, regardless of the environments surrounding it. Appling this phase pickup, a Fabry-Perot model is formulated that can predict accurately the resonant wavelengths of graphene nano-ribbons. Furthermore, we find that the magnitude of the phase jump will either increase or reduce when two neighboring coplanar graphene sheets couple with each other. This could be used to explain the red-shift of resonant wavelength of periodic ribbon arrays with respect to an isolated ribbon. We provide a straightforward way to uncover the phase jump of graphene plasmons that would be helpful for designing and engineering graphene resonators and waveguides as well as their associated applications. | eng_Latn | 11,772 |
Cold-cathode emitter based on a metal-diamond tunneling junction | Recently Geis fabricated a composite cold cathode emitter made of diamond doped by substitutional nitrogen on a roughened metallic substrate, which is characterized by high field emission currents at very low power. Using an internal field emission mechanism through the Schottky barrier at the metal diamond interfaces to populate the conduction band of diamond, we have developed a quantitative theory to describe the operation of such a device. The calculated I-V characteristics are in good agreement with the experimental results of Geis, et al. | As electronic devices and integrated circuits get smaller and smaller, eventually quantum-mechanic effects take over. As Saito discusses in his Perspective, results reported by ::: Collins ::: et al. ::: in the same issue demonstrate the use of carbon nanotubes to create nanometer-scale devices known as diodes. Rather than fighting the effects of quantum mechanics, such devices make excellent use of quantum effects on the nanometer scale. | eng_Latn | 11,773 |
Single-wall carbon nanotube dispersions stabilised with N-trimethyl-chitosan | We report the noncovalent complexation of a biocompatible low substituted N-trimethyl chitosan (TMC), a cationic chitosan derivative, onto the graphitic surface of single-walled carbon nanotubes (SWCNTs). TMC was synthesized and characterized by 1H-NMR. A yield between the range of 34% and 56% was obtained with a degree of substitution of 19.7%. SWCNTs dispersed in TMC resulted in stable dispersions, which were further characterized by Atomic Force Microscopy (AFM) Raman Spectroscopy and ζ-potential. AFM and Raman spectroscopy studies confirmed that smaller diameter SWCNTs are preferentially dispersed by TMC molecules resulting in stable dispersions. In addition TMC coated CNTs have a high ζ-potential over a wide range of pH (2-12) exceeding values from 35 mV (pH 2) up to 10 mV (pH 12) respectively. The presence of TMC induces electrostatic repulsions which stabilize the CNTs against van der Waals attractions resulting in stable dispersions. Such complexes may have potential applications in nanomedicine | Recently Geis fabricated a composite cold cathode emitter made of diamond doped by substitutional nitrogen on a roughened metallic substrate, which is characterized by high field emission currents at very low power. Using an internal field emission mechanism through the Schottky barrier at the metal diamond interfaces to populate the conduction band of diamond, we have developed a quantitative theory to describe the operation of such a device. The calculated I-V characteristics are in good agreement with the experimental results of Geis, et al. | eng_Latn | 11,774 |
Novel phenyl migration of 1-phenylbenzo[b]thiophenium triflates in the thermolysis | Thermolysis of 1-phenylbenzo[b]thiophenium triflates at 180°C causes phenyl migration to give 2-phenylbenzo[b]thiophenes in high yields. Interestingly, the thermolysis of 1-phenylbenzo[b]thiophenium triflates having a substituent at the 2 position affords the corresponding 3-phenylbenzo[b]thiophenes. On the basis of the thermolysis of 2-(4-methylphenyl)-1-phenylbenzo[b]thiophenium triflate, a consecutive [1,5] sigmatropic rearrangement is proposed for the phenyl migration. | Abstract Monte Carlo simulation of the order–disorder transition revealed that the transition temperature of Co–Pt nanowires increases with wire diameter, approaching the bulk value if the size is large enough. The transition temperature is affected by the shape of cross-section, though the shape effect is less significant than the size effect. It is showed that the rise of transition temperature in nanowires is largely due to the decrease of surface area compared with nanoparticles. The phase separation and tetragonalization are discussed by introducing mixing parameter and asphericity parameter. It is also found that the order–disorder transition starts from the surface and then to the core, indicating that the order–disorder transition of nanowires is a surface-dominant phenomenon, governed by the atomic under coordination. | eng_Latn | 11,775 |
Three-Dimensional Model of Cosmic-Ray Lepton Propagation Reproduces Data from the Alpha Magnetic Spectrometer on the International Space Station | We study the compatibility of Alpha Magnetic Spectrometer (AMS-02) data on the cosmic-ray (CR) positron fraction with data on the CR electron and positron spectra provided by PAMELA and Fermi LAT. We do that in terms of a novel propagation model in which sources are distributed in spiral arm patterns in agreement with astrophysical observations. While former interpretations assumed an unrealistically steep injection spectrum for astrophysical background electrons, the enhanced energy losses experienced by CR leptons due to the larger average source distance from Earth allow us to reproduce the data with harder injection spectra as expected in a shock acceleration scenario. Moreover, we show that in this approach, and accounting for AMS-02 results, the contribution of nearby accelerators to the fluxes at very high energy can be significantly reduced, thus avoiding any tension with anisotropy upper limits. | Lithium aluminum silicate (LAS) nanoparticles have been successfully loaded on graphene nanosheets by adding a silane coupling agent KH-550 by sol–gel process, hydrothermal reaction, and heat treatment process. By regulating the complex permittivity of reduced graphene oxide (rGO) by LAS nanoparticles and KH-550, LAS/rGO-KH-550 possesses excellent microwave absorption performance. The maximum reflection loss of LAS/rGO-KH-550 reaches −62.25 dB at 16.48 GHz with thickness of only 2.7 mm, and the widest bandwidth is up to 6.64 GHz below −10 dB. The LAS/rGO-KH-550 has effective absorption (99.9%) below −20 dB at all X and Ku bands (8–18 GHz). Also, the added quantity of composites in the paraffin matrix is only 20 wt %. The results demonstrate that the interfacial polarization, the Debye dipolar relaxation, the well-matched characteristic impedance, and the quarter-wavelength matching all play important roles in improving the microwave absorption properties of LAS/rGO-KH-550 nanocomposites. Consequently, the... | eng_Latn | 11,776 |
Magnetic phase transition of second-stage NiCl2-graphite intercalation compound in an external magnetic field | The AC magnetic susceptibility of the second-stage NiCl2-graphite intercalation compound along the easy plane has been measured in the presence of an external magnetic field parallel and perpendicular to the easy plane. The experimental result suggests that the intermediate 2D XY-like phase exists in the temperature range of Tc1<or=T<or=Tc2 (Tc1=17.30K and Tc2=19.40K) without an external magnetic field. | The band profiles in InGaAsP single quantum well are investigated using the model solid theory under considering of the effect of strain.The band lineups for electrons and holes are tuned by changing Ga concentration x and As concentration y in the well on condition that the concentrations in the barrier are fixed.The results indicate that the variety of concentration influences evidently the band lineups,resulting in type-Ⅰ to type-Ⅱ transformation.When the well is multilayer,parabolic potential well can expediently carry out by controlling the compositions. | eng_Latn | 11,777 |
Size and shape dependent order–disorder phase transition of Co–Pt nanowires | Abstract Monte Carlo simulation of the order–disorder transition revealed that the transition temperature of Co–Pt nanowires increases with wire diameter, approaching the bulk value if the size is large enough. The transition temperature is affected by the shape of cross-section, though the shape effect is less significant than the size effect. It is showed that the rise of transition temperature in nanowires is largely due to the decrease of surface area compared with nanoparticles. The phase separation and tetragonalization are discussed by introducing mixing parameter and asphericity parameter. It is also found that the order–disorder transition starts from the surface and then to the core, indicating that the order–disorder transition of nanowires is a surface-dominant phenomenon, governed by the atomic under coordination. | Abstract In situ composites can be obtained either by unidirectional eutectic solidification or by unidirectional solid- state decomposition. Techniques in the latter category are dealt with in this review. The solid-state growth methods may be classified, according to the state of the starting material, into (a) eutectoid decomposition, (b) discontinuous precipitation, or (c) growth from the noncrystalline state. Common to the three processes is the duplex microstructure which occurs, permitting alignment during growth in a temperature gradient. The author reviews the theory of the transformation, the experimental techniques, and the empirical parameters which have been reported in the literature. Emphasis is placed upon the relationships between interphase spacing and growth rate, and upon the potential discrepancies between growth rate and pulling rate. | eng_Latn | 11,778 |
Nitrogen-Doped Nanoporous Graphenic Carbon: An Efficient Conducting Support for O2Cathode | Herein, we synthesize a nanoporous N-doped graphenic carbon with high surface area and a higher graphenization/graphitic degree by further developing the metallothermic reduction of gaseous CO2 by adding N2 into the gas flow. The N-doped nanoporous carbon is composed of both a highly porous graphenic and non-graphitic matrix and homogeneously dispersed ordered graphitic nanodomains, which constitute a very unique composite carbon structure. The resulting N-doped graphenic carbon exhibits much more favorable reactivity as a carbon conducting support in the O2 cathode of Li-O2 batteries, increasing the specific capacity of the GC electrode from 5300 to 9600 mAh g−1. The N-doped carbon also exhibits lower overpotentials during initial cycling for the charging process as well as an enhanced cycling performance compared to the undoped carbon. These results demonstrate that N-doping has a strong correlation with the enhanced performance of O2 cathode of Li-O2 batteries. | In this paper, the GMT–PO hybrid method accompanied by the iterative technique is applied successfully to calculate 3-D numerical diffraction coefficients (3-D NDC) of the irregular circular-cylinder edge. The computed RCS of the circular cylinder with 3-D NDC of the irregular edge is in good agreement with the measured data from the reference. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 108–110, 2001. | eng_Latn | 11,779 |
Atomic resolution STM imaging of a twisted single-wall carbon nanotube | We present atomically resolved scanning tunneling microscopy images of single-wall carbon nanotubes (SWNT's) embedded in a crystalline nanotube rope. Although they may be interpreted as of a chiral nanotube, the images are more consistently explained as an achiral armchair tube with a quenched twist distortion. The existence of quenched twists in SWNT's in ropes might explain the fact that both as-grown bulk nanotube material and individual ropes have insulatorlike conductivity at low temperature. | A new method of staining the keratin filament matrix allowing a visualization of the filaments in cross section of hair fibres has been developed. It differs from previously published methods in that the hair fibres are neither fixed with OsO 4 nor treated with sulfur bond breaking agents. High contrast is still obtainable in sections thicker than 60 nm | eng_Latn | 11,780 |
Emerging trends in flame retardancy of biofibers, biopolymers, biocomposites, and bionanocomposites | Recent advancements in natural fiber-reinforced polymer composites have engineered the need to procure alternatives to replace metals in automotives, construction, aerospace, defense, electronics, and gas and oil industries. However, application versatility of biomaterials has been limited due to poor flame retardancy. In line with the new CO2 emission policy and global ban on halogenated flame retardants, the automotive and aerospace industries require environmentally benign materials with nonhalogenated flame retardancy, that can provide the high FPI, and low FGI, required to reduce fatalities and destruction of properties during real fire situations. Researchers, therefore, postulate that versatility of application of biomaterials can be attained by improving their fire retardant properties. Hence, this paper reviews novel emerging technologies used in achieving flame retardancy in biofibers, biopolymers, biocomposites, and bionanocomposites. | Abstract This research is focused on the effects of nonlinear terms on the dynamical behavior of graphene reinforced laminated composite plates. Firstly, the governing equations of the graphene reinforced composite thin plate subjected to transverse excitations are derived by using the Hamilton's principle and the von Karman deformation theory. Then numerical method is applied to investigate the nonlinear behaviors of graphene reinforced composite plates. Bifurcation diagram, waveform and phase portrait are demonstrated to analyze the nonlinear dynamics of the graphene reinforced laminated composite plates. Furthermore, the effects of nonlinear terms on the dynamical behavior are discussed in detail, where both the stronger and weaker nonlinear characteristics of lower modes of the plate are presented. Moreover, some interesting phenomena are obtained in numerical simulation. | eng_Latn | 11,781 |
Electrochemical Deposition of Bismuth Micro- and Nanowires Using Electroplate and Lift Lithography | Patterned micro- and nanowires of several compositions in the solution series of Bi x Te y were electrochemically deposited using Electroplate and Lift (E&L) Lithography on Ultrananocrystalline Diamond (UNCD) templates. The composition of the deposited Bi x Te y wires was controlled by mixing saturated solutions of bismuth nitrate and tellurium in various ratios in the electroplating bath. All wires were electroplated via pulsed depositions at -1.4V vs. the saturated calomel electrode (SCE). The morphology and composition of all wires were studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). In general, the Bi x Te y wires were fine-grained and brittle, often fracturing during the liftoff process. By contrast, wires containing less than 5% Te are smooth, and strong enough to support their own weight without a supporting medium for a length of over 100 times the wire diameter. | Abstract This research is focused on the effects of nonlinear terms on the dynamical behavior of graphene reinforced laminated composite plates. Firstly, the governing equations of the graphene reinforced composite thin plate subjected to transverse excitations are derived by using the Hamilton's principle and the von Karman deformation theory. Then numerical method is applied to investigate the nonlinear behaviors of graphene reinforced composite plates. Bifurcation diagram, waveform and phase portrait are demonstrated to analyze the nonlinear dynamics of the graphene reinforced laminated composite plates. Furthermore, the effects of nonlinear terms on the dynamical behavior are discussed in detail, where both the stronger and weaker nonlinear characteristics of lower modes of the plate are presented. Moreover, some interesting phenomena are obtained in numerical simulation. | eng_Latn | 11,782 |
From current trace to the understanding of confined media | Abstract.Nanopores constitute devices for the sensing of nano-objects such as ions, polymer chains, proteins or nanoparticles. We describe what information we can extract from the current trace. We consider the entrance of polydisperse chains into the nanopore, which leads to a conductance drop. We describe the detection of these current blockades according to their shape. Finally, we explain how data analysis can be used to enhance our understanding of physical processes in confined media.Graphical abstract | Abstract : The report contains a brief analysis of the following items: (a) Two-dimensional steady flow (variational method), (b) One-dimensional unsteady flow (variational method), (c) Plasma with finite conductivity (exact solutions), (d) Approximate solutions and linearized equations, (e) New numerical methods, (f) Low conductivity plasma, (g) Applications, (h) Plasma acceleration and MHD power generation. A detailed discussion of future plans is given. (Author) | eng_Latn | 11,783 |
Manipulation and Characterization of Aperiodical Graphene Structures Created in a Two-Dimensional Electron Gas | We demonstrate that Dirac fermions can be created and manipulated in a two-dimensional electron gas (2DEG). Using a cryogenic scanning tunneling microscope, we arranged coronene molecules one by one on a Cu(111) surface to construct artificial graphene nanoribbons with perfect zigzag (ZGNRs) or arm-chairedges and confirmed that new states localized along the edges emerge only in the ZGNRs. We further made and studied several typical defects, such as single vacancies, Stone-Wales defects, and dislocation lines, and found that all these defects introduce localized states at or near the Dirac point in the quasiparticle spectra. Our results confirm that artificial systems built on a 2DEG provide rigorous experimental verifications for several long-sought theoretical predications of aperiodic graphene structures. | A Planar square stack coupled inductor coils on silicon substrate has been fabricated using MEMS technology. The fabrication process utilized a simple, cost effective process technique as well as CMOS compatible resulting to a reproducible and good controlled process. The basic characteristics of the coupled inductors were discussed in wide range of operating frequency. The analysis results showed that the geometry of the inductor coil strongly affects the basic characteristics of the coils. The results of the study have promised a good prospect for the development of fully integrated planar magnetic field generator for sensing and actuating purposes. | eng_Latn | 11,784 |
Charge accumulation and frequency characteristics of sequential tunneling. | This paper, as an addendum to Phys. Rev. B 46, 4714 (1992), provides a study of the finite frequency spectrum of noise current in sequential tunneling through double-barrier structures and the effect of space-charge accumulation | Using ultrafast optical-pump terahertz-probe spectroscopy, we study the THz dynamics and electronic cooling in few-layer epitaxial and CVD graphene; a microscopic theory of carrier-carrier and carrier-phonon interactions accounts quantitatively for the observed dynamics. | eng_Latn | 11,785 |
A novel reconfigurable multiband slot antenna fed by a coplanar waveguide using radio frequency microelectro‐mechanical system switches | Originally published Microwave Opt Technol Lett 53: 751–757, 2011. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53: 1685, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26162 ::: ::: ::: ::: (Original article DOI 10.1002/mop.25828) | Characteristic features of the d-band in electronic structure of transition metals are quite effective as descriptors of their catalytic activity toward oxygen reduction reaction (ORR). With the promise of graphene-based materials to replace precious metal catalysts, descriptors of their chemical activity are much needed. Here, a site-specific electronic descriptor is proposed based on the pz (π) orbital occupancy and its contribution to electronic states at the Fermi level. Simple structural descriptors are identified, and a linear predictive model is developed to precisely estimate adsorption free energies of OH (ΔGOH ) at various sites of doped graphene, and it is demonstrated through prediction of the most optimal site for catalysis of ORR. These structural descriptors, essentially the number of ortho, meta, and para sites of N/B-doped graphene sheet, can be extended to other doped sp2 hybridized systems, and greatly reduce the computational effort in estimating ΔGOH and site-specific catalytic activity. | eng_Latn | 11,786 |
Fabrication of graphene with CuO islands by chemical vapor deposition. | Graphene prepared on Cu foil by chemical vapor deposition was studied as a function of post growth cooling conditions. CuO islands embedded in the graphene film were discovered and studied by scanning electron microscopy, atomic force microscopy, and X-ray photoemission spectroscopy. It is shown that nanostructured holes can be formed within a graphene film by reduction using hydrogen cooling immediately after film growth. We also observe the formation of symmetrical oxide islands in these holes. This study provides an easy way to fabricate a graphene + CuO composite, and the method may be extended to other graphene based structures. | Microstructural studies and X-ray diffraction combined with pole figure characterizations have been carried out on the melt-grown YBa2Cu3O7-x and GdBa2Cu3O7-x samples. The crystallographic orientation of the domains in melt-grown samples are highlighted based on the above studies. | eng_Latn | 11,787 |
Tuning graphene nanoribbon field effect transistors via controlling doping level | By performing first-principles transport simulations, we demonstrate that n-type transfer curves can be obtained in armchair-edged graphene nanoribbon field effect transistors by the potassium atom and cobaltocene molecule doping, or substituting the carbon by nitrogen atom. The Dirac point shifts downward from 0 to −12 V when the n-type impurity concentration increases from 0 to 1.37%, while the transfer curves basically maintain symmetric feature with respect to the Dirac point. In general, the on/off current ratios are decreased and subthreshold swings are increased with the increasing doping level. Therefore, the performance of armchair-edged graphene nanoribbon field effect transistors can be controlled via tuning the impurity doping level. | The invention provides a TWDMPON uplink solution based on a tunable wavelength converter and a wavelength sharing method, comprising the tunable wavelength converter, a tunable optical filter and a circulator. The invention utilizes the tunable wavelength converter to uniformly convert an uplink time division multiplexed wavelength signal into a TWDM-PON system compatible wavelength signal, seamless compatibility of the TWDM-PON system and a traditional ONU (optical network unit) device is ensured, the outburst wavelength shift problem of the ONU is solved, and the layout cost of the ONU is effectively reduced. | eng_Latn | 11,788 |
Crystal defects in flux grown lithium ferrite, LiFe5O8 single crystals | With the increase of frequencies in microwave communications lithium ferrite single crystals attract growing interest. | Abstract In extension of an earlier note 1) we present some observations of different electric and magnetic switching phenomena in thin polycrystalline EuS film junctions. A possible explanation for qualitatively different nonllinearities of the current transport behavior in spite of very similar preparation conditions of the samples, is a narrow-band energetic structure with the Fermi level lying within such a band or between. | eng_Latn | 11,789 |
Microstructure of spray converted nanostructured tungsten carbide-cobalt composite | This paper reports the presence of face centered cubic cobalt precipitates inside tungsten carbide in nanocomposite of WC-Co synthesized by spray conversion processing. EDS was used to identify the presence and micro-diffraction was employed to determine the nature of the precipitates. There is entrapment of cobalt in tungsten carbide during the spray conversion process used to form WC/Co powder. During consolidation, at high temperatures, the cobalt attains enough mobility to precipitate inside WC. A vanadium containing compound was seen at the interfaces in samples which incorporated VC as a grain growth inhibitor. | Abstract We propose a new model which simulates the motion of free electrons in graphene by the evolution of strings on manifolds. In this model, molecules which constitute sheets of graphene are polygonal point-like structures which build ( N + 1 ) -dimensional manifolds. By breaking the gravitational-analogue symmetry of graphene sheets, we show that two separated child sheets and a Chern–Simons bridge are produced giving rise to a wormhole. In this structure, free electrons are transmitted from one child sheet to the other producing superconductivity. An analogue between “effective gravitons” and “Cooper pairs” is found. In principle, this phenomenology provides the possibility to construct superconductor structures by using the analogue of cosmological models. | eng_Latn | 11,790 |
Magnetic properties of amorphous ribbon | The magnetic properties of transition-metal amorphous alloys are discussed, with emphasis on methods to increase the value of the saturation induction at room temperature, and on the factors that control the low-field magnetic properties that are important in most engineering applications. | We describe the first time on the direct and facile method for noble metal/graphene nanocomposites from graphite without reductants. In our system, the irradiant white-light instead of the chemical reductant exerts the influence on the synthesis of noble metal nanoparticles on graphene. Noble metal salts adsorbed on the surfaces of graphene flakes which were functionalized with ionic surfactants were reduced by irradiation with white light. In particular, noble metal nanoparticles were more evenly distributed on the surface of graphene which was functionalized with SDS than with CTAB. | eng_Latn | 11,791 |
Dynamical behavior of fractal structures | We present a scaling theory for the vibrational properties of tenuous fractal objects and a numerical calculation of the density of states for percolation clusters and diffusion-limited aggregates. A microscopic elastic Hamiltonian is used, which contains bending energy terms and properly describes the elasticity of such structures. We find that the density of states is weakly divergent at low frequencies implying that fractal aggregates relax to a new configuration beyond a critical size. | An introduction to the theoretical description of the optical properties of metal nanoclusters and nanostructures is presented, divided into two parts. The first part is devoted to the methodology, the most appropriate depending the system size: classical electrodynamics for large systems and quantum mechanics for small to medium-sized systems. The second part describes a few applications and representative examples ranging from small bare clusters to large protected metal ones, with the goal of highlighting the most relevant concepts and physics involved. | eng_Latn | 11,792 |
Raman spectra of twisted CVD bilayer graphene | Abstract The Raman spectra of large-size, single-crystal, twisted bilayer graphene (tBLG) grains grown by chemical vapor deposition (CVD) are measured as a function of the rotation angle. The rotation angle between the graphene layers is determined using a combination of transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The 2D and G peaks follow the same trends as found previously. The low-frequency peaks ( | Computational methods based on the solution of the flow model are widely used for the analysis of low-speed, inviscid, attached-flow problems. Most of such methods are based on the implementation of the internal Dirichlet boundary condition. In this paper, the time-domain panel method uses the piecewise constant source and doublet singularities. The present method utilizes the time-stepping loop to simulate the unsteady motion of the rotary wing blade. The wake geometry is calculated as part of the solution with no special treatment. To validate the results of aerodynamic characteristics, the typical blade was chosen such as, Caradonna-Tung blade and present results were compared with the experimental data and the other numerical results in the single blade condition and two blade condition. This isolated rotor blade model consisted of a two bladed rotor with untwisted, rectangular planform blade. Computed flow-field solutions were presented for various section of the blade in the hovering mode. | eng_Latn | 11,793 |
Nanoionics: ionic charge carriers in small systems. | Ion-conduction phenomena are discussed that are governed by interfacial effects. In a given material the density of interfaces is crucial in such cases. Particular emphasis is laid on situations in which the spacing of interfaces matters, even locally. These then observed mesoscopic phenomena are at the heart of what may be called nanoionics. Effects do not only refer to enhancement or depression of conductivity or storage, mechanistic variations are also observed. | The energy wasted in wireless networks is a serious concern and the main challenge lies in determining when and where the energy is wasted. In this demo, we present Energino, an energy measurement and control system designed to deliver high performance while remaining a cheap solution. | eng_Latn | 11,794 |
Graphene-Composite Carbon Nanofiber-Based Electrodes for Energy Storage Devices | Abstract : The goal of this research project is to develop highly conductive graphene composite carbon nanofiber (CNF) webs with an electrical conductivity larger than 1000 S/cm. In addition, metal-oxide-nanostructures on the surface of CNF webs will also be developed. These highly conductive and surface-modified CNF webs will be utilized for high-performance electrodes of energy storage devices including flexible ones. | We built a pulse compressor using a comb-like dispersion-profiled fiber (CDPF). The CDPF consists of 12-segment fibers with the dispersion alternatively high and low. Using this compressor and a 17 dBm Erbium-doped fiber amplifier, the 10 GHz, 12 ps pulses generated from an actively mode-locked Er3+ doped fiber ring laser was compressed to ~ 2 ps without pedestal. We also show that compared with the high order soliton pulse compressor, the power efficiency can be doubled in supercontinuum generation by using the pump pulses compressed by this CDPF compressor. | eng_Latn | 11,795 |
A class of high-selectivity microstrip transversal bandpass filter using non-resonating nodes | A new type of high-selectivity microwave planar bandpass filter is reported. It exploits the use of non-resonating nodes to generate the maximum number of inter-resonator electromagnetic (EM) couplings in a transversal configuration. Furthermore, it is exclusively shaped by parallel-coupled transmission-line segments, thus leading to a compact and simple circuit. The operating principle of the proposed bandpass filter topology is described. Also, its experimental usefulness is confirmed with the development and testing of a microstrip filter prototype at 1.4 GHz that implements a quadruplet with cross couplings. | We present molecular dynamics calculations on the evolution of Ni nanowires stretched along the (111) and (100) directions, and at two different temperatures. Using a methodology similar to that required to build experimental conductance histograms, we construct minimum crosssection histograms H(Sm). These histograms are useful to understand the type of favorable atomic configurations appearing during the nanowire breakage. We have found that minimum crosssection histograms obtained for (111) and (100) stretching directions are rather different. When the nanowire is stretched along the (111) direction, monomer and dimer-like configurations appear, giving rise to well-defined peaks in H(Sm). On the contrary, (100) nanowire stretching presents a different breaking pattern. In particular, we have found, with high probability, the formation of staggered pentagonal nanowires, as it has been reported for other metallic species. | eng_Latn | 11,796 |
Investigations of dual-frequency nematic liquid crystals doped with dichroic dye | ABSTRACTIn this work, we studied and analysed a particular variety of liquid crystals, the so-called dual-frequency nematic liquid crystals (DFNLCs). The interest was to perform dielectric spectros... | By performing first-principles transport simulations, we demonstrate that n-type transfer curves can be obtained in armchair-edged graphene nanoribbon field effect transistors by the potassium atom and cobaltocene molecule doping, or substituting the carbon by nitrogen atom. The Dirac point shifts downward from 0 to −12 V when the n-type impurity concentration increases from 0 to 1.37%, while the transfer curves basically maintain symmetric feature with respect to the Dirac point. In general, the on/off current ratios are decreased and subthreshold swings are increased with the increasing doping level. Therefore, the performance of armchair-edged graphene nanoribbon field effect transistors can be controlled via tuning the impurity doping level. | eng_Latn | 11,797 |
Raman Scattering of Type-I Clathrate Compounds | Rattling motion of a guest ion in type-I clathrate compounds has been studied by Raman scattering measurements. The anomalous energy-decrease of guest atom vibration has been observed for Sr 8 Ga 16 Si 30- x Ge x and Ba 8 Ga 16 Si 30- x Ge x as well as A 8 Ga 16 Ge 30 with decreasing temperature. This result shows that the 4th order anharmonic potential is also important for the guest-ion motion of Sr- and Ba-clathrates. The energy of the guest mode observed by the Raman scattering is consistent with the Einstein temperature estimated by the specific heat measurements. It is confirmed that the off-center rattling plays an important role to suppress the lattice thermal conductivity. | We present the design for the chalcogenide nanofiber coated with a thin finite tellurite cladding. The effects of the thickness of the tellurite coating on the dispersion and the nonlinearity of the nanofiber are studied. | eng_Latn | 11,798 |
INTERACTION OF DISLOCATIONS WITH ELECTRONS AND WITH PHONONS | Abstract : The interaction parameter, B, of moving dislocations with electrons and with phonons in aluminum was determined in the temperature range 10 degrees K to 250 degrees K. A new technique was developed for measuring ultrasonic attenuation changes, the change in alpha, as a function of a dynamic bias stress. The numerical values of B were obtained from an analysis of the change in alpha, which does not require any knowledge of dislocation density or of other inaccurately known features of the dislocation network. The results indicate that the dislocation interaction with electrons is temperature independent and the interaction with phonons increases with increasing temperature. These results are consistent with theoretical predictions. (Author) | The present invention relates to a battery (1) with integrated discharge circuit comprising a battery cell (2) comprising a positive pole and a negative pole, a transistor (3) which comprises a control contact and two switching contacts which, with its switching contacts between the positive pole and the negative pole is connected to enable discharge of the battery cell (2) via the transistor (3), and a control circuit (4) which is adapted at the discharge of the battery cell (2) a discharge current (I | yue_Hant | 11,799 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.