A target group tracking algorithm based on a hybrid sensor network
Power control and channel allocation optimization game algorithm with low energy consumption for wireless sensor network
Radiating frequency of three-loop mesoscopic LC circuit with mutual inductance obtained by IEO method
Dynamical effects of switching a super-critical well potential on pair creation from a vacuum
The dynamical effects on electron-positron pair creation from a vacuum caused by the switching processes of a super-critical well potential are investigated in detail. The results show that only when the switching on and switching off time both increase will the final pair yield converge to the integer of embedded bound states nearly exponentially. But a single adiabatic switching on or switching off cannot lead to an integer pair yield. If the potential is turned on abruptly, associated with the discrete and embedded bound states, there is multi-frequency oscillation around the pair number's saturation. The slowly switching on can suppress the amplitude of this oscillation and reduce the final pair yield. The switching off can also reduce the final pair number in the same order of magnitude. The evolution of a single-pair number shows a robust long range correlation between particle and antiparticle. For an adiabatic switching case, the single-pair dominates the early pair creation, their upper limit value is equal to the integer, and these single-pairs will totally disentangle during the switching off.
Quantum pseudodots under the influence of external vector and scalar fields
Dynamic quantum secret sharing protocol based on two-particle transform of Bell states
Controlling a sine wave gating single-photon detector by exploiting its filtering loophole
Concept study of measuring gravitational constant using superconducting gravity gradiometer
Newton's gravitational constant G is the least known fundamental constant of nature. Since Cavendish made the first measurement of G with a torsion balance over two hundred years ago, the best results of G have been obtained by using torsion balances. However, the uncorrected anelasticity of torsion fibers makes the results questionable. We present a new method of G measurement by using a superconducting gravity gradiometer constructed with levitated test masses, which is free from the irregularities of mechanical suspension. The superconducting gravity gradiometer is rotated to generate a centrifugal acceleration that nulls the gravity field of the source mass, forming an artificial planetary system. This experiment has a potential accuracy of G better than 10 ppm.
Correlation method estimation of the modulation signal in the weak equivalence principle test
In a test of the weak equivalence principle (WEP) with a rotating torsion pendulum, it is important to estimate the amplitude of the modulation signal with high precision. We use a torsional filter to remove the free oscillation signal and employ the correlation method to estimate the amplitude of the modulation signal. The data analysis of an experiment shows that the uncertainties of amplitude components of the modulation signal obtained by the correlation method are in agreement with those due to white noise. The power spectral density of the modulation signal obtained by the correlation method is about one order higher than the thermal noise limit. It indicates that the correlation method is an effective way to estimate the amplitude of the modulation signal and it is instructive to conduct a high-accuracy WEP test.
Topological classification of periodic orbits in Lorenz system
Double compound combination synchronization among eight n-dimensional chaotic systems
Phase transitions of the five-state clock model on the square lattice
Using the tensor renormalization group method based on the higher-order singular value decomposition, we have studied the phase transitions of the five-state clock model on the square lattice. The temperature dependence of the specific heat indicates the system has two phase transitions, as verified clearly by the correlation function at three representative temperatures. By calculating the magnetic susceptibility, we obtained only the upper critical temperature as Tc2=0.9565(7). Investigating the fixed-point tensor, we precisely locate the transition temperatures at Tc1=0.9029(1) and Tc2=0.9520(1), consistent well with the Monte Carlo and the density matrix renormalization group results.
Transport of velocity alignment particles in random obstacles
Efficient image encryption scheme with synchronous substitution and diffusion based on double S-boxes
Calibration and data restoration of light field modulated imaging spectrometer
A light field modulated imaging spectrometer (LFMIS) can acquire the spatial-spectral datacube of targets of interest or a scene in a single shot. The spectral information of a point target is imaged on the pixels covered by a microlens. The pixels receive spectral information from different spectral filters to the diffraction and misalignments of the optical components. In this paper, we present a linear spectral multiplexing model of the acquired target spectrum. A calibration method is proposed for calibrating the center wavelengths and bandwidths of channels of an LFMIS system based on the liner-variable filter (LVF) and for determining the spectral multiplexing matrix. In order to improve the accuracy of the restored spectral data, we introduce a reconstruction algorithm based on the total least square (TLS) approach. Simulation and experimental results confirm the performance of the spectrum reconstruction algorithm and validate the feasibility of the proposed calibrating scheme.
Configuration interaction calculations on the spectroscopic and transition properties of magnesium chloride
Forbidden transition properties of fine-structure 2p3 4S3/2-2p3 2D3/2,5/2 for nitrogen-like ions
Based on relativistic wave functions from multiconfiguration Dirac-Hartree-Fock and configuration interaction calculations, E2 and M1 transition probabilities of 2p3 4S3/2-2p3 2D3/2,5/2 are investigated in the nitrogen-like sequence with 7 ≤ Z ≤ 16. The contributions of the electron correlations, Breit interaction, and the quantum electrodynamic (QED) effects on the transition properties are analyzed. The present results can be used for diagnosing plasma. In addition, several N-like ions can also be recommended as a promising candidate for a highly charged ion (HCI) clock with a quality factor (Q) of transition as high as 1020.
A simulation study of water property changes using geometrical alteration in SPC/E
Relativistic R-matrix calculations for L-shell photoionization cross sections of C Ⅱ
Simultaneous study of the lower order harmonic and photoelectron emission from an atom in intense laser pulse
Theoretical study on twisted intramolecular charge transfer of 1-aminoanthraquinone in different solvents
Structural evolutions and electronic properties of AunGd (n=6-15) small clusters: A first principles study
Ultra-thin circularly polarized lens antenna based on single-layered transparent metasurface
Rapid measurement of transmission matrix with the sequential semi-definite programming method
This paper puts forward for the first time a combined transmission matrix (TM) method to measure the monochromatic TM of scattering media without a reference beam. This method can be named a sequential semi-definite programming method which combines the sequential algorithm and the semi-definite programming method. Firstly, each part of the TM is calculated respectively in proper sequence. Then every part of TM is combined to form a complete TM in accordance with a certain rule. The phase modulation of the incident light is achieved by using a high speed digital mirror device with the superpixel method. We have experimentally demonstrated that the incident light field is focused at the target through scattering media using the measured TM to optimize the wavefront of the incident light. Compared with the semi-definite programming method, our method takes less computational time and occupies less memory space. The sequential semi-definite programming method shows potential applications in imaging through biological tissues.
Cavity-induced ATS effect on a superconducting Xmon qubit
We couple a ladder-type three-level superconducting artificial atom to a cavity. Adjusting the artificial atom to make the cavity be resonant with the two upper levels, we then probe the lower two levels of the artificial atom. When driving the cavity to a coherent state, the probe spectrum shows energy level splitting induced by the quantized electromagnetic field in the cavity. This splitting size is related to the coupling strength between the cavity and the artificial atom and, thus, is fixed after the sample is fabricated. This is in contrast to the classical Autler-Townes splitting of a three-level system in which the splitting is proportional to the driving amplitude, which can be continuously changed. Our experiment results show the difference between the classical microwave driving field and the quantum field of the cavity.
Three-mode optomechanical system for angular velocity detection
We propose a scheme for measuring the angular velocity of absolute rotation using a three-mode optomechanical system in which one mode of the two-dimensional (2D) mechanical resonator is coupled to an optical cavity. When the total system rotates, the Coriolis force acting on the 2D mechanical resonator due to the absolute rotation will affect the mechanical motion and thus change the phase of the output field from the cavity. The angular velocity of the absolute rotation can be estimated by monitoring the spectrum of the output field from the cavity via homodyne measurement. The minimum measurable angular velocity, which is determined by the noise spectrum, is calculated. The working range of the gyroscope for measuring angular velocity is discussed.
Tripartite continuous-variable entanglement of NOPA system
High power external-cavity surface-emitting laser with front and end pump
Construction of two-qubit logical gates by transmon qubits in a three-dimensional cavity
Enhancement and modulation of terahertz radiation by multi-color laser pulses
Influences of adsorptions of some inorganic molecules on electronic, optical, and thermodynamic properties of Mg12O12 nanocage: A computational approach
Tunable graphene-based mid-infrared band-pass planar filter and its application
Analysis of resonance asymmetry phenomenon in resonator integrated optic gyro
Generation and evolution of multiple operation states in passively mode-locked thulium-doped fiber laser by using a graphene-covered-microfiber
Lamb wave signal selective enhancement by an improved design of meander-coil electromagnetic acoustic transducer
Interaction between encapsulated microbubbles: A finite element modelling study
Experimental and numerical study on energy dissipation in freely cooling granular gases under microgravity
Energy dissipation is one of the most important properties of granular gas, which makes its behavior different from that of molecular gas. In this work we report our investigations on the freely-cooling evolution of granular gas under microgravity in a drop tower experiment, and also conduct the molecular dynamics (MD) simulation for comparison. While our experimental and simulation results support Haff's law that the kinetic energy dissipates with time t as E(t)~(1+t/τ)-2, we modify τ by taking into account the friction dissipation during collisions, and study the effects of number density and particle size on the collision frequency. From the standard deviation of the measured velocity distributions we also verify the energy dissipation law, which is in agreement with Haff's kinetic energy dissipation.
A new kind of hairpin-like vortical structure induced by cross-interaction of sinuous streaks in turbulent channel
Walking of spider on water surface studied from its leg shadows
Theoretical analysis on deflagration-to-detonation transition
Research progress of third-order optical nonlinearity of chalcogenide glasses
Liquid phase epitaxy magnetic garnet films and their applications
Observation of double pseudowaves in an ion-beam-plasma system
Pseudowaves, known as burst-ion signals, which are different from plasma normal modes, exist frequently in ion-wave excitation experiments when launching the waves by applying a pulsed voltage to a negatively biased grid. In previous experiments, only one kind of the pseudowave was observed. In this paper, we report the observation and identification of double pseudowaves in an ion-beam-plasma system. These pseudowaves originate from two ion groups:the burst of the beam ions and the burst of the background ions. It was observed that the burst of the background ions was in the case of high ion beam energy, while the burst of the beam ions was in the case of low ion beam energy. By observing the dependence of the signal velocities on the characteristics of the excitation voltage, these pseudowaves can be identified. It was also observed that the burst ion signal originating from the background ions can interact with slow beam mode and that originating from the beam ions can interact with fast beam mode.
Factors affecting improvement of fluorescence intensity of quartet and doublet state of NO diatomic molecule excited by glow discharge
We report on the observation of new fluorescence emission spectral transitions obtained from NO diatomic molecule in the region from ultraviolet (UV) to near infrared (NIR) in a low power glow discharge system. This glow discharge electronic excitation populates different quartet and doublet states of NO in its proximity such as the A2Σ (υ=2), b4Σ- (υ=3), B2Π (υ=4), and X2Π (υ=33-32) states. Due to inter-system crossing, emission lines originating from these levels to lower lying states are recorded and spectral line assignments are performed. The observed systems include b4Σ--a4Π, B2Π-a4Π, a4Π-X2Π, A2Σ-X2Π, X2Π-X2Π (33-15), X2Π-X2Π (33-17), X2Π-X2Π (33-20), and X2Π-X2Π (33-18). This new information will conduce to the better understanding of the interesting features of NO molecule. Such parameters that affect the recording of low density of NO molecules are also discussed In addition to the factors such as the time evolution, argon gas concentration relative to NO mixture, the percentage of NO molecular gas concentration, discharge electric current signals and discharge applied voltage are studied. Those factors would enhance the fluorescence signal intensity of NO molecules. The recent results might be significant as reference data for optimizing the glow discharge spectrometer and diagnostics of NO gas.
Properties of long light filaments in natural environment
The multiple filamentation of terawatt femtosecond (fs) laser pulses is experimentally studied in a natural environment. A more than 30-m long plasma filament with a millimeter diameter is formed by the collimated fs laser pulse freely propagating in an open atmosphere. This study provides the first quantitative experimental data about the electron density of a long range light filament in the atmosphere. The electron density of such a filament is quantitatively detected by using an electric method, showing that it is at the 1011-cm-3 level.
Influence of channel length on discharge performance of anode layer Hall thruster studied by particle-in-cell simulation
Electrical and thermal characterization of near-surface electrical discharge plasma actuation driven by radio frequency voltage at low pressure
Similarity principle of microwave argon plasma at low pressure
Synthesis of Pr-doped ZnO nanoparticles: Their structural, optical, and photocatalytic properties
Undoped and praseodymium-doped zinc oxide (Pr-doped ZnO) (with 2.0-mol%-6.0-mol% Pr) nanoparticles as sunlight-driven photocatalysts are synthesized by means of co-precipitation with nitrates followed by thermal annealing. The structure, morphology, and chemical bonding of the photocatalysts are studied by x-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive x-ray emission spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR), respectively. The optical properties are studied by photoluminescence (PL) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). We find that Pr doping does not change the crystallinity of ZnO; but it reduces the bandgap slightly, and restrains the recombination of the photogenerated electron-hole pairs. The photocatalytic performance of the photocatalysts is investigated by the photodegradation reaction of 10-mg/L rhodamine B (RhB) solution under simulated sunlight irradiation, showing a degradation rate of 93.75% in ZnO doped with 6.0-mol% Pr.
Influences of total ionizing dose on single event effect sensitivity in floating gate cells
First principles study on lattice vibration and electrical properties of layered perovskite Sr2M2O7 (M=Nb, Ta)
In this paper, we performed calculations to investigate the dielectric, piezoelectric properties, Born effective charge (BEC), and spontaneous polarization of Sr2M2O7, the method used in our study was a well-known density functional theory based on first-principles. The optimized results were in good agreement with previous experiments and calculations, which indicates that our calculated method is reasonable. The research we have done suggested that greater piezoelectric components of Sr2Nb2O7 were e31 and e33, and the contributions were derived from the A1. By studying the Born effective charge, it could be seen that the valence of ions changed, and the O of Sr2Nb2O7 were most obviously that caused by the covalent character of ions and the hybridization of O-2p and Nb-4d. The spontaneous polarization of Sr2Nb2O7 in the direction is 25 μC/cm2, while for Sr2Ta2O7, there was no spontaneous polarization in the paraelectric state. Finally, the effect of pressure on the piezoelectric properties were also investigated, the polarization of Sr2Nb2O7 decreased linearly with the increase after pressure. All our preliminary results throw light on the nature of dielectric, piezoelectric properties, Born effective charge, and spontaneous polarization of Sr2M2O7, it was helpful for experimental research, the development of new materials, and future applications.
Unconventional lattice dynamics in few-layer h-BN and indium iodide crystals Hot!
Unusual quadratic dispersion of flexural vibrational mode and red-shift of Raman shift of in-plane mode with increasing layer-number are quite common and interesting in low-dimensional materials, but their physical origins still remain open questions. Combining ab initio density functional theory calculations with the empirical force-constant model, we study the lattice dynamics of two typical two-dimensional (2D) systems, few-layer h-BN and indium iodide (InI). We found that the unusual quadratic dispersion of flexural mode frequency on wave vector may be comprehended based on the competition between atomic interactions of different neighbors. Long-range interaction plays an essential role in determining the dynamic stability of the 2D systems. The frequency red-shift of in-plane Raman-active mode from monolayer to bulk arises mainly from the reduced long-range interaction due to the increasing screening effect.
First-principles study of the (CuxNi1-x)3Sn precipitations with different structures in Cu-Ni-Sn alloys
The effect of dislocations on the thermodynamic properties of Ta single crystal under high pressure by molecular dynamics simulation
The thermodynamic properties of Ta metal under high pressure are studied by molecular dynamics simulation. For dislocation-free Ta crystal, all the thermodynamic properties considered are in good agreement with the results from experiments or higher level calculations. If dislocations are included in the Ta crystal, it is found that as the dislocation density increases, the hydrostatic pressure at the phase transition point of bcc→hcp and hcp→fcc decreases, while the Hugoniot temperature increases. Meanwhile, the impact pressure at the elastic-plastic transition point is found to depend on the crystallographic orientation of the pressure. As the dislocation density increases, the pressure of the elastic-plastic transition point decreases rapidly at the initial stage, then gradually decreases with the increase of the dislocation density.
Analysis of meniscus beneath metastable droplets and wetting transition on micro/nano textured surfaces
Fabrication of seeded substrates for layer transferrable silicon films
The properties of surface nanobubbles formed on different substrates
The properties and stability of the reported surface nanobubbles are related to the substrate used and the generation method. Here, we design a series of experiments to study the influence of the hydrophobicity of the substrate and the production method on the formation and properties of nanobubbles. We choose three different substrates, dodecyltrichlorosilane (DTS) modified silicon, octadecyltrichlorosilane (OTS) modified silicon, and highly oriented pyrolytic graphite (HOPG) as nanobubble substrates, and two methods of ethanol-water exchange and 4-℃ cold water to produce nanobubbles. It is found that using ethanol-water exchange method could produce more and larger nanobubbles than the 4-℃ cold water method. The contact angle of nanobubbles produced by ethanol-water exchange depends on the hydrophobicity of substrates, and decreases with the increase of the hydrophobicity of substrates. More interestingly, nanoscopic contact angle approaches the macroscopic contact angle as the hydrophobicity of substrates increases. It is believed that these results would be very useful to understand the stability of surface nanobubbles.
Dirac states from px,y orbitals in the buckled honeycomb structures: A tight-binding model and first-principles combined study
Dirac states composed of px,y orbitals have been reported in many two-dimensional (2D) systems with honeycomb lattices recently. Their potential importance has aroused strong interest in a comprehensive understanding of such states. Here, we construct a four-band tight-binding model for the px,y-orbital Dirac states considering both the nearest neighbor hopping interactions and the lattice-buckling effect. We find that px,y-orbital Dirac states are accompanied with two additional narrow bands that are flat in the limit of vanishing π bonding, which is in agreement with previous studies. Most importantly, we analytically obtain the linear dispersion relationship between energy and momentum vector near the Dirac cone. We find that the Fermi velocity is determined not only by the hopping through π bonding but also by the hopping through σ bonding of px,y orbitals, which is in contrast to the case of pz-orbital Dirac states. Consequently, px,y-orbital Dirac states offer more flexible engineering, with the Fermi velocity being more sensitive to the changes of lattice constants and buckling angles, if strain is exerted. We further validate our tight-binding scheme by direct first-principles calculations of model-materials including hydrogenated monolayer Bi and Sb honeycomb lattices. Our work provides a more in-depth understanding of px,y-orbital Dirac states in honeycomb lattices, which is useful for the applications of this family of materials in nanoelectronics.
Investigations on mesa width design for 4H-SiC trench super junction Schottky diodes
Optoelectronic properties of bottom gate-defined in-plane monolayer WSe2 p-n junction
Monolayer transition-metal dichalcogenides (TMDs) are considered to be fantastic building blocks for a wide variety of optical and optoelectronic devices such as sensors, photodetectors, and quantum emitters, owing to their direct band gap, transparency, and mechanical flexibility. The core element of many conventional electronic and optoelectronic devices is the p-n junction, in which the p- and n-types of the semiconductor are formed by chemical doping in different regions. Here, we report a series of optoelectronic studies on a monolayer WSe2 in-plane p-n photodetector, demonstrating a low-power dissipation by showing an ambipolar behavior with a reduced threshold voltage by a factor of two compared with the previous results on a lateral electrostatically doped WSe2 p-n junction. The fabrication of the device is based on a polycarbonates (PC) transfer technique and hence no electron-beam exposure induced damage to the monolayer WSe2 is expected. Upon optical excitation, the photodetector demonstrates a photoresponsivity of 0.12 mA·W-1 and a maximum external quantum efficiency of 0.03%. Our study provides an alternative platform for a flexible and transparent two-dimensional photodetector, from which we expect to further promote the development of next-generation optoelectronic devices.
Effect of Au/Ni/4H-SiC Schottky junction thermal stability on performance of alpha particle detection
Quantum spin Hall insulators in chemically functionalized As (110) and Sb (110) films
Behavior of fractional quantum Hall states in LLL and 1LL with in-plane magnetic field and Landau level mixing: A numerical investigation Hot!
By exactly solving the effective two-body interaction for a two-dimensional electron system with layer thickness and an in-plane magnetic field, we recently found that the effective interaction can be described by the generalized pseudopotentials (PPs) without the rotational symmetry. With this pseudopotential description, we numerically investigate the behavior of the fractional quantum Hall (FQH) states both in the lowest Landau level (LLL) and first excited Landau level (1LL). The enhancements of the 7/3 FQH state on the 1LL for a small tilted magnetic field are observed when layer thickness is larger than some critical values, while the gap of the 1/3 state in the LLL monotonically reduced with increasing the in-plane field. From the static structure factor calculation, we find that the systems are strongly anisotropic and finally enter into a stripe phase with a large tilting. With considering the Landau level mixing correction on the two-body interaction, we find the strong LL mixing cancels the enhancements of the FQH states in the 1LL.
Multi-carrier transport in ZrTe5 film
Single-layered zirconium pentatelluride (ZrTe5) has been predicted to be a large-gap two-dimensional (2D) topological insulator, which has attracted particular attention in topological phase transitions and potential device applications. Herein, we investigated the transport properties in ZrTe5 films as a function of thickness, ranging from a few nm to several hundred nm. We determined that the temperature of the resistivity anomaly peak (Tp) tends to increase as the thickness decreases. Moreover, at a critical thickness of~40 nm, the dominating carriers in the films change from n-type to p-type. A comprehensive investigation of Shubnikov-de Hass (SdH) oscillations and Hall resistance at variable temperatures revealed a multi-carrier transport tendency in the thin films. We determined the carrier densities and mobilities of two majority carriers using the simplified two-carrier model. The electron carriers can be attributed to the Dirac band with a non-trivial Berry phase π, while the hole carriers may originate from surface chemical reaction or unintentional doping during the microfabrication process. It is necessary to encapsulate the ZrTe5 film in an inert or vacuum environment to potentially achieve a substantial improvement in device quality.
Characterization of ion irradiated silicon surfaces ablated by laser-induced breakdown spectroscopy
Nonlinear uniaxial pressure dependence of the resistivity in Sr1-xBaxFe1.97Ni0.03As2 Hot!
Nematic order and its fluctuations have been widely found in iron-based superconductors. Above the nematic order transition temperature, the resistivity shows a linear relationship with the uniaxial pressure or strain along the nematic direction and the normalized slope is thought to be associated with nematic susceptibility. Here we systematically studied the uniaxial pressure dependence of the resistivity in Sr1-xBaxFe1.97Ni0.03As2, where nonlinear behaviors are observed near the nematic transition temperature. We show that it can be well explained by the Landau theory for the second-order phase transitions considering that the external field is not zero. The effect of the coupling between the isotropic and nematic channels is shown to be negligible. Moreover, our results suggest that the nature of the magnetic and nematic transitions in Sr1-xBaxFe2As2 is determined by the strength of the magnetic-elastic coupling.
Typicality at quantum-critical points Hot!
We discuss the concept of typicality of quantum states at quantum-critical points, using projector Monte Carlo simulations of an S=1/2 bilayer Heisenberg antiferromagnet as an illustration. With the projection (imaginary) time τ scaled as τ=aLz, L being the system length and z the dynamic critical exponent (which takes the value z=1 in the bilayer model studied here), a critical point can be identified which asymptotically flows to the correct location and universality class with increasing L, independently of the prefactor a and the initial state. Varying the proportionality factor a and the initial state only changes the cross-over behavior into the asymptotic large-L behavior. In some cases, choosing an optimal factor a may also lead to the vanishing of the leading finite-size corrections. The observation of typicality can be used to speed up simulations of quantum criticality, not only within the Monte Carlo approach but also with other numerical methods where imaginary-time evolution is employed, e.g., tensor network states, as it is not necessary to evolve fully to the ground state but only for sufficiently long times to reach the typicality regime.
Micromagnetism simulation on effects of soft phase size on Nd2Fe14B/α–Fe nanocomposite magnet with soft phase imbedded in hard phase
Detailed electronic structure of three-dimensional Fermi surface and its sensitivity to charge density wave transition in ZrTe3 revealed by high resolution laser-based angle-resolved photoemission spectroscopy
The detailed information of the electronic structure is the key to understanding the nature of charge density wave (CDW) order and its relationship with superconducting order in the microscopic level. In this paper, we present a high resolution laser-based angle-resolved photoemission spectroscopy (ARPES) study on the three-dimensional (3D) hole-like Fermi surface around the Brillouin zone center in a prototypical quasi-one-dimensional CDW and superconducting system ZrTe3. Double Fermi surface sheets are clearly resolved for the 3D hole-like Fermi surface around the zone center. The 3D Fermi surface shows a pronounced shrinking with increasing temperature. In particular, the quasiparticle scattering rate along the 3D Fermi surface experiences an anomaly near the charge density wave transition temperature of ZrTe3 (~63 K). The signature of electron-phonon coupling is observed with a dispersion kink at~20 meV; the strength of the electron-phonon coupling around the 3D Fermi surface is rather weak. These results indicate that the 3D Fermi surface is also closely connected to the charge-density-wave transition and suggest a more global impact on the entire electronic structure induced by the CDW phase transition in ZrTe3.
Effect of flash thermal annealing by pulsed current on rotational anisotropy in exchange-biased NiFe/FeMn film
High uniformity and forming-free ZnO-based transparent RRAM with HfOx inserting layer
The impacts of HfOx inserting layer thickness on the electrical properties of the ZnO-based transparent resistance random access memory (TRRAM) device were investigated in this paper. The bipolar resistive switching behavior of a single ZnO film and bilayer HfOx/ZnO films as active layers for TRRAM devices was demonstrated. It was revealed that the bilayer TRRAM device with a 10-nm HfOx inserted layer had a more stable resistive switching behavior than other devices including the single layer device, as well as being forming free, and the transmittance was more than 80% in the visible region. For the HfOx/ZnO devices, the current conduction behavior was dominated by the space-charge-limited current mechanism in the low resistive state (LRS) and Schottky emission in the high resistive state (HRS), while the mechanism for single layer devices was controlled by ohmic conduction in the LRS and Poole-Frenkel emission in the HRS.
Optical polarization response at gold nanosheet edges probed by scanning near-field optical microscopy
High-performance lens antenna using high refractive index metamaterials
Modulated thermal transport for flexural and in-plane phonons in double-stub graphene nanoribbons
Thermal transport properties are investigated for out-of-plane phonon modes (FPMs) and in-plane phonon modes (IPMs) in double-stub graphene nanoribbons (GNRs). The results show that the quantized thermal conductance plateau of FPMs is narrower and more easily broken by the double-stub structure. In the straight GNRs, the thermal conductance of FPMs is higher in the low temperature region due to there being less cut-off frequency and more low-frequency excited modes. In contrast, the thermal conductance of IPMs is higher in the high temperature region because of the wider phonon energy spectrum. Furthermore, the thermal transport of two types of phonon modes can be modulated by the double-stub GNRs, the thermal conductance of FPMs is less than that of IPMs in the low temperatures, but it dominates the contribution to the total thermal conductance in the high temperatures. The modulated thermal conductance can provide a guideline for designing high-performance thermal or thermoelectric nanodevices based on graphene.
Effect of FeS doping on large diamond synthesis in FeNi–C system
The large single-crystal diamond with FeS doping along the (111) face is synthesized from the FeNi-C system by the temperature gradient method (TGM) under high-pressure and high-temperature (HPHT). The effects of different FeS additive content on the shape, color, and quality of diamond are investigated. It is found that the (111) face of diamond is dominated and the (100) face of diamond disappears gradually with the increase of the FeS content. At the same time, the color of the diamond crystal changes from light yellow to gray-green and even gray-yellow. The stripes and pits corrosion on the diamond surface are observed to turn worse. The effects of FeS doping on the shape and surface morphology of diamond crystal are explained by the number of hang bonds in different surfaces of diamond. It can be shown from the test results of the Fourier transform infrared (FTIR) spectrum that there exists an S element in the obtained diamond. The N element content values in different additive amounts of diamond are calculated. The XPS spectrum results demonstrate that our obtained diamond contains S elements that exist in S-C and S-C-O forms in a diamond lattice. This work contributes to the further understanding and research of FeS-doped large single-crystal diamond characterization.
Growth of high-quality perovskite (110)-SrIrO3 thin films using reactive molecular beam epitaxy
Recently, 5d transition metal iridates have been reported as promising materials for the manufacture of exotic quantum states. Apart from the semimetallic ground states that have been observed, perovskite SrIrO3 is also predicted to have a lattice-symmetrically protected topological state in the (110) plane due to its strong spin-orbit coupling and electron correlation. Compared with non-polar (001)-SrIrO3, the especial polarity of (110)-SrIrO3 undoubtedly adds the difficulty of fabrication and largely impedes the research on its surface states. Here, we have successfully synthesized high-quality (110)-SrIrO3 thin films on (110)-SrTiO3 substrates by reactive molecular beam epitaxy for the first time. Both reflection high-energy electron diffraction patterns and x-ray diffraction measurements suggest the expected orientation and outstanding crystallinity. A (1×2) surface reconstruction driven from the surface instability, the same as that reported in (110)-SrTiO3, is observed. The electric transport measurements uncover that (110)-SrIrO3 exhibits a more prominent semimetallic property in comparison to (001)-SrIrO3.
A lattice Boltzmann-cellular automaton study on dendrite growth with melt convection in solidification of ternary alloys
A lattice Boltzmann (LB)-cellular automaton (CA) model is employed to study the dendrite growth of Al-4.0 wt%Cu-1.0 wt%Mg alloy. The effects of melt convection, solute diffusion, interface curvature, and preferred growth orientation are incorporated into the coupled model by coupling the LB-CA model and the CALPHAD-based phase equilibrium solver, PanEngine. The dendrite growth with single and multiple initial seeds was numerically studied under the conditions of pure diffusion and melt convection. Effects of initial seed number and melt convection strength were characterized by new-defined solidification and concentration entropies. The numerical result shows that the growth behavior of dendrites, the final microstructure, and the micro-segregation are significantly influenced by melt convection during solidification of the ternary alloys. The proposed solidification and concentration entropies are useful characteristics bridging the solidification behavior and the microstructure evolution of alloys.
Influence of dopant concentration on electrical quantum transport behaviors in junctionless nanowire transistors
Size effect of Si particles on the electrochemical performances of Si/C composite anodes
A series of Si/C composites were fabricated based on pitch and Si powders with particle sizes of 30, 100, 500, and 3000 nm. The size effects of the Si particles in the Si/C composites were investigated for lithium-ion battery anodes. The nanoscale Si and Si/C composites exhibited good capacity retentions. Scanning electron microscopy showed that exterior and interior cracks emerging owing to volume expansion as well as parasitic reactions with the electrolyte could well explain the performance failure.
Improved electrochemical performances of high voltage LiCoO2 with tungsten doping
The effects of tungsten W doping and coating on the electrochemical performance of LiCoO2 cathode are comparatively studied in this work. The amount of modification component is as low as 0.1 wt% and 0.3 wt% respectively. After 100 cycles between 3.0 V-4.6 V, 0.1 wt% W doping provides an optimized capacity retention of 72.3%. However, W coating deteriorates battery performance with capacity retention of 47.8%, even lower than bare LiCoO2 of 55.7%. These different electrochemical performances can be attributed to the surface aggregation of W between doping and coating methods. W substitution is proved to be a promising method to develop high voltage cathodes. Practical performance relies on detailed synthesis method.
Molecular dynamics simulations on the dynamics of two-dimensional rounded squares
The collective motion of rounded squares with different corner-roundness ζ is studied by molecular dynamics (MD) simulation in this work. Three types of translational collective motion pattern are observed, including gliding, hopping and a mixture of gliding and hopping. Quantitatively, the dynamics of each observed ordered phase is characterized by both mean square displacement and van Hove functions for both translation and rotation. The effect of corner-roundness on the dynamics is further studied by comparing the dynamics of the rhombic crystal phases formed by different corner-rounded particles at a same surface fraction. The results show that as ζ increases from 0.286 to 0.667, the translational collective motion of particles changes from a gliding-dominant pattern to a hopping-dominant pattern, whereas the rotational motion pattern is hopping-like and does not change in its type, but the rotational hopping becomes much more frequent as ζ increases (i.e., as particles become more rounded). A simple geometrical model is proposed to explain the trend of gliding motion observed in MD simulations.
Calculation and analysis of unbalanced magnetic pulls of different stator winding setups in static eccentric induction motor
In large-scale electric machines, unbalanced magnetic pull (UMP) caused by eccentricity usually results in stator-rotor rub, so it is necessary to investigate the amplitude and the influencing factors. This paper takes the squirrel-cage induction motor as an example. A magnetic loop model of an induction motor is established by an analytical method. The impact of stator winding setup (parallel branch and pole pairs) on each magnetomotive force (MMF) and unbalanced magnetic pull is analyzed. Using the finite element simulation method, the spatial and time distribution of flux density of the rotor outer circle under static eccentricity is obtained, and the unbalanced magnetic pull calculation caused by static eccentricity is completed. The conclusion of the influence of stator winding on the size of unbalanced magnetic pull provides reliable gist for motor noise and vibration analysis, and especially provides an important reference for large induction motor design.
A snapback-free TOL-RC-LIGBT with vertical P-collector and N-buffer design
A reverse-conducting lateral insulated-gate bipolar transistor (RC-LIGBT) with a trench oxide layer (TOL), featuring a vertical N-buffer and P-collector is proposed. Firstly, the TOL enhances both of the surface and bulk electric fields of the N-drift region, thus the breakdown voltage (BV) is improved. Secondly, the vertical N-buffer layer increases the voltage drop VPN of the P-collector/N-buffer junction, thus the snapback is suppressed. Thirdly, the P-body and the vertical N-buffer act as the anode and the cathode, respectively, to conduct the reverse current, thus the inner diode is integrated. As shown by the simulation results, the proposed RC-LIGBT exhibits trapezoidal electric field distribution with BV of 342.4 V, which is increased by nearly 340% compared to the conventional RC-LIGBT with triangular electric fields of 100.2 V. Moreover, the snapback is eliminated by the vertical N-buffer layer design, thus the reliability of the device is improved.
Damage effects and mechanism of the silicon NPN monolithic composite transistor induced by high-power microwaves
Time-dependent crosstalk effects for image sensors with different isolation structures
Weighted total variation using split Bregman fast quantitative susceptibility mapping reconstruction method
Individual identification using multi-metric of DTI in Alzheimer's disease and mild cognitive impairment
Accurate identification of Alzheimer's disease (AD) and mild cognitive impairment (MCI) is crucial so as to improve diagnosis techniques and to better understand the neurodegenerative process. In this work, we aim to apply the machine learning method to individual identification and identify the discriminate features associated with AD and MCI. Diffusion tensor imaging scans of 48 patients with AD, 39 patients with late MCI, 75 patients with early MCI, and 51 age-matched healthy controls (HCs) are acquired from the Alzheimer's Disease Neuroimaging Initiative database. In addition to the common fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity metrics, there are two novel metrics, named local diffusion homogeneity that used Spearman's rank correlation coefficient and Kendall's coefficient concordance, which are taken as classification metrics. The recursive feature elimination method for support vector machine (SVM) and logistic regression (LR) combined with leave-one-out cross validation are applied to determine the optimal feature dimensions. Then the SVM and LR methods perform the classification process and compare the classification performance. The results show that not only can the multi-type combined metrics obtain higher accuracy than the single metric, but also the SVM classifier with multi-type combined metrics has better classification performance than the LR classifier. Statistically, the average accuracy of the combined metric is more than 92% for all between-group comparisons of SVM classifier. In addition to the high recognition rate, significant differences are found in the statistical analysis of cognitive scores between groups. We further execute the permutation test, receiver operating characteristic curves, and area under the curve to validate the robustness of the classifiers, and indicate that the SVM classifier is more stable and efficient than the LR classifier. Finally, the uncinated fasciculus, cingulum, corpus callosum, corona radiate, external capsule, and internal capsule have been regarded as the most important white matter tracts to identify AD, MCI, and HC. Our findings reveal a guidance role for machine-learning based image analysis on clinical diagnosis.
Electronic states and molecular orientation of ITIC film
Nanoforest-like CdS/TiO2 heterostructure composites: Synthesis and photoelectrochemical application
In this study, TiO2 nanoforest films consisting of nanotubes have been synthesized by a simple hydrothermal method and a subsequent sintering technique. The hydrothermal reaction time is important for the controlling of the nanotube diameter and the specific surface area of holistic TiO2 films. When the hydrothermal process reaction time is up to 8 hours, the diameter of the nanotube is about 10 nm, and the specific surface area of TiO2 nanoforest films reaches the maximum. CdS nanoparticles are synthesized on TiO2 nanoforest films by the successive ionic layer adsorption and reaction (SILAR) technique. The transmission electron microscope (TEM) and energy dispersive x-ray spectroscopy (EDX) mapping results verify that TiO2/CdS heterostructures are realized. A significant red-shift of the absorption edge from 380 nm to 540 nm can be observed after the pure TiO2 film is sensitized by CdS nanoparticles. Under irradiation of light, the current density of the optimal TiO2/CdS photoanode is 2.30 mA·cm-2 at 0 V relative to the saturated calomel electrode (SCE), which is 6 times stronger than that of the pure TiO2 photoanode. This study suggests that the TiO2 nanoforest consisting of interlinked pony-size nanotubes is a promising nanostructure for photoelectrochemical.
Evacuation flow of pedestrians considering compassion effect