bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication and characteristics of ZnO nanowires array gas sensor based on microfluidics
Authors: Hu Jie  , Deng Xiao  , Sang Sheng-Bo  , Li Peng-Wei  , Li Gang  , Zhang Wen-Dong  ,   Micro Nano System Research Center, College of Information Engineering, Taiyuan University of Technology, Taiyuan 030024, China;,   Key Laboratory of Advanced Transducers and Intelligent Control System of the Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, China;,   College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China
Published: December 2020

In this paper, ZnO nanowire (ZnO NW) array is prepared based on microfluidic technology. The crystalline structures and morphologies of as-synthesized ZnO NWs are characterized by X-ray diffraction and scanning electron microscopy. The results show that ZnO NW is high-quality crystalline and c-axis oriented. At the same time, the gas-sensing properties of ZnO NWs are investigated for different gases, such as acetone, methanol and ethanol. The measured results prove that ZnO NW shows a sensitivity of 8.26 at 475 ℃, and the response and recovery times can reach 9 and 5 s separately, when exposed to 200 ppm (1 ppm=10-6) acetone. Compared with the method of conventional hydrothermal technology, the ZnO NWs based on microfluidic technology shows high sensitivity and fast recovery time. Finally, the gas sensing mechanism of ZnO NWs is also discussed from the aspect of gain and lose electron of oxygen molecules on material surface.
Transformation of spiral wave to plan wave in the two layers of coupled excitable media
Authors: Li Wei-Heng  , Li Wei-Xin  , Pan Fei  , Tang Guo-Ning  ,   College of Physical Sicence and Technology, Guangxi Normal University, Guilin 541004, China
Published: December 2020

The dynamics of spiral waves in a two-layer coupled excitable medium is studied by using the Bär-Eiswirth model. The two layers of medium are connected via network, i.e., a excitable unit is selected in each column of an excitable medium as a central point, and all excitable units in the same column of a layer medium are connected only with the corresponding central point and its eight neighbors in the opposite medium. The numerical results show that when the coupling strength is appropriately small, the two coupled spiral waves via local coupling can achieve their synchronization. Increasing coupling strength will induce meandering and drifting of spiral waves, leading to a desynchrony between the coupled spiral waves. The spiral wave with the resting state, low frequency plan wave and irregular pattern are observed to coexist. The coupled spiral waves via the transformation of spiral wave to synchronous plane wave disappear if the coupling strength is appropriately chosen. The physical mechanisms behind these phenomena are discussed.
Objective identification study of midsummer rainy season in the northeast China
Authors: Fang Yi-He  , Gong Zhi-Qiang  , Zhao Lian-Wei  , Zhao Chun-Yu  , Li Qing-Quan  ,   Regional Climate Center of Shenyang, Shenyang 110166, China;,   Laboratory for Climate Studies and Climate Monitoring and Diagnose, National Climate Center, China Meteorological Administration, Beijing 100081, China
Published: December 2020

Owing to the fact that the objective identification methods of rainy season are not totally identical in the three provinces of Northeast China, no unified monitoring criterion of rainy season is available in this area. In order to implement the regional key climate monitoring and to meet the needs of the national weather service, from the angle of the whole region, based on the daily precipitation data of 102 observational stations, by comprehensively analyzing the daily precipitation series disposed by 5-point moving average, the objective identification method of midsummer rainy season in the northeast China is presented in this paper. Then based on the daily reanalysis data of wind field and geopotential height field provided by NCEP/NCAR, the atmospheric circulation fields of different levels before, during and after the midsummer rainy season are contrastively analyzed, and the rationality of the objective identification method is validated. Finally, the partition criterion of the beginning and ending dates are determined. Results show that: the average beginning and ending dates of midsummer rainy season in the northeast China respectively are June 26th and August 30th. The partition criterion of midsummer rainy season in the northeast China by using the objective identification method is reasonable.
Stochastic resonance in a piecewise nonlinear system driven by colored correlated additive and multiplicative colored noises
Authors: Jin Yan-Fei  , Li Bei  ,   Department of Mechanics, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

In this paper, we study the stochastic resonance in a piecewise nonlinear system driven by a periodic signal and colored noises, which is described by multiplicative and additive colored noises with colored cross-correlation. Using the two-state theory and the unified colored approximation, we can derive the analytical expressions of the steady-state probability density and the signal-to-noise ratio (SNR). Effects of colored noises and the periodic signal on SNR are presented. It is found that the conventional stochastic resonance and bona-fide stochastic resonance may exist in this system. Moreover, the value of the SNR peak decreases with increasing correlation time and correlation between the additive and multiplicative noises.
A novel image authentication and recovery algorithm based on dither and chaos
Authors: Wan Xing-Yuan  , Zhang Ji-Ming  ,   Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian 116024, China
Published: December 2020

This paper presents a digital image tamper detection and recovery algorithm, which uses the dither and chaos technology. Certification of generated image and the repair information gained by low frequency sub-diagram and dither technology after wavelet transform can effectively reduce the amount of data. At the same time, the watermark is embedded in high frequency sub-diagram, so as to make the watermark invisible. Chaos technology is used to complete watermark embedding and encryption; and combined with the Chinese remainder theorem, the impact on the image quality can further be reduced. Experimental results show that the algorithm's watermark has high invisibility and robustness, and also can repair tampered images. So it has a high practical significance in the image authentication and recovery.
Theoretical study on a novel molecular mirror with a surface plasmon polariton field
Authors: Ding Jing-Xin  , Fang Yin-Fei  , Guo Chao-Xiu  , Yang Lan  , Xia Yong  , Yin Ya-Ling  , Yin Jian-Ping  ,   State Key Laboratory of Precision Spectröscopy, Department of Physics, East China Normal University, Shanghai 200062, China
Published: December 2020

We propose a new scheme for molecular mirror with a blue-detuned surface plasmon ploariton field excited on a microstructural metal film and study the dynamic process of reflection of cold molecules by Monte Carlo simulation. Our study shows that this mirror can realize a reflection of cold iodine molecular beam with a longitudinal temperature of 10 mK and a transverse temperature of 1 mK with a reflectivity of 55.89% when the incident laser is of a 10 ns pulse width and its intensity is I0=1.0 109 W/cm2; and the molecular reflectivity increases with increasing incident laser intensity.
High efficient CEP-stabilized infrared optical parametric amplifier made from a BBO single crystal
Authors: You Lang-Fang  , Ling Wei-Jun  , Li Ke  , Zhang Ming-Xia  , Zuo Yin-Yan  , wang Yi-Shan  ,   Institute of Laser technology, Tianshui Normal University, Tianshui 741001, China;,   State Key Laboratory of Transient Optics and Photonics, Chinese Academy of Sciences, Xi'an 710119, China
Published: December 2020

We demonstrate an efficient tunable phase-stabilized near-infrared optical parametric amplifier (OPA) made from a BBO (β -BaB2O4) single crystal in this paper. By using the seeded white-light continuum produced by CEP(carrier envelop phase)-stabilized femtosecond laser amplifier system which is seeded into the two stages of a type II OPA system, the pump-to-signal conversion efficiency of 34% can be achieved at 1350 nm. The CEP jitter of amplified pulses measured by an f–2f interferometer is 137 mrad in 30 minutes. This paper demonstrates a simple, feasible and efficient way to produce tunable femtosecond pulses with CEP control.
Generation of dark hollow beams used in sub-diffraction-limit imaging in coherent anti-Stokes Raman scattering microscopy
Authors: Liu Shuang-Long  , Liu Wei  , Chen Dan-Ni  , Niu Han-Ben  ,   College of Opto-Electronics Engineering, Shenzhen University, Shenzhen 518060, China
Published: December 2020

Profile of a dark hollow beam in sub-diffraction -limit imaging is of crucial importance for its spatial resolution when using the coherent anti-Stokes Raman scattering microscopy, as far as the imaging quality is concerned. Therefore, the generation of dark hollow beams through a vortex phase plate will be theoretically analyzed based on the Fresnel diffraction theory. Influences of different incidence conditions on the intensity distribution of the generated dark hollow beams are also investigated. And it is shown that a perfect dark hollow beam could be produced when a Gaussian beam is vertically incident upon a first-order vortex phase plate, with the incident light wavelength equal to that of the phase plate. However, both the circular symmetry of the incident beam's intensity distribution and the alignment between the centers of Gaussian beam and phase plate may affect the intensity distribution of the dark hollow beam, which will almost be in circular symmetry though it may shift some distance from the image center when at a small incident angle. Furthermore, the dark hollow beam's intensity distribution will scarcely change when the central wavelength deviation is very small from the incidence light and the phase plate. These results may be of great value in generation of perfect dark hollow beams in sub-diffraction –limit imaging by coherent anti-Stokes Raman scattering microscopy.
From Arctic high, Antarctic low to three-dimensional heteroclinic orbit connecting south pole and north pole
Authors: Liu Shi-Da  , Fu Zun-Tao  , Liu Shi-Kuo  ,   Department of Atmospheric and Oceanic Sciences and Laboratory for Climate and Ocean-Atmosphere Studies, School of Physics, Peking University, Beijing 100871, China
Published: December 2020

Under the steady condition, the spherical geostrophic wind relationship in spherical coordinates (λ,φ,r) is applied to illustrate that when isobars take the simplest zonal distribution, the Antarctic is at a low ambient pressure, while the Arctic is at high. However, when friction is incorporated into the geostrophic wind relationship, the closed vortex over Antarctic and Arctic will turn to a spiral vortex, and there will exist a three-dimensional heteroclinic orbit between Antarctic and Arctic on the spherical surface.
Lattice Boltzmann modeling of microscale oscillating Couette flow
Authors: Tao Shi  , Wang Liang  , Guo Zhao-Li  ,   State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China;,   Beijing Computational Science Research Center, Beijing 100084, China
Published: December 2020

In this paper, the microscale non-equilibrium gas flow, and the oscillating Couette and Poiseuille flows, have been investigated by an effective MRT-LBM. The Knudsen layer model is introduced into lattice Boltzmann method (LBM) for the relaxation time correction. In the simulations the plate or external force oscillates in the form of sine curve, and the Couette flow contains a singular oscillation and a double-plate oscillation. It is revealed that the corrected MRT-LBM model can well handle the simulation of microscale non-equilibrium gas flow. For the Couette flow, the wall slip phenomenon is obvious for a larger Kn number, and the streamwise velocity profiles appear to be of a nonliner character when St number increases. When the two plates oscillate, the streamwise velocity profiles almost overlap with each other at small Kn and St. In the Poiseuille flow case, the extent of phase lag decreases as St exceeds a certain value. Compared to the Kn number, St has a bigger impact on the emerging of phase lag in the oscillating Couette and Poiseuille flows.
Stick-slip transition of a water droplet vibrated on a superhydrophobic surface
Authors: Zhou Jian-Chen  , Geng Xing-Guo  , Lin Ke-Jun  , Zhang Yong-Jian  , Zang Du-Yang  ,   Functional Soft Matter and Materials Group, Key Laboratory of Space Applied Physics and Chemistry of Ministry of Education, School of Science, Northwestern Polytechnical University, Xi'an 710129, China;,   School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

We have studied the vibration behavior of a water droplet vibrated on a superhydrophobic surface via a high-speed camera. The resonance frequencies of the droplet satisfy the Rayleigh equation, suggesting that the droplet on a superhydrophobic surface can be regarded as a free droplet. Its real oscillation frequency is half of the driving frequency when it is vibrated at low frequencies(<200 Hz). It shows large shape deformation from a compressed puddle to a stretched spheroid. The three-phase contact line exhibits a stick-slip behavior. However, when the droplet is vibrated at frequencies greater than 200 Hz, the three-phase contact line is pinned to the substrate and the droplet is vibrated at the same frequencies as the external driving frequencies. It is found that the oscillation of the contact line and the large shape deformation of the droplet are responsible for the distinct behavior at low frequency.
Anylasis and comparison of several methods for calculation of positron bulk lifetime in perfect crystals
Authors: Huang Shi-Juan  , Zhang Wen-Shuai  , Liu Jian-Dang  , Zhang Jie  , Li Jun  , Ye Bang-Jiao  ,   State Key Laboratory of Particle Detection and Electronics(IHEP &USTC), University of Science and Technology of China, Hefei 230026, China;,   Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China;,   Institute of Plasma Physics, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

Positron annihilation lifetime spectroscopy, which takes positron lifetime as a detected object, has been widely applied to the study on micro-defects of semiconductors and other materials, and is very sensitive to the type of crystal structure, defect types, and temperature, and so on. Therefore, the analysis of fast and accurate calculation of positron lifetime theoretically combined with the experimental data is particularly necessary. In this paper, the superposed neutral atom model, the pseudo-potential model, and the full-potential model are used to deal with the positron local potential. While the positron wave function is solved self-consistently by the finite difference method, the positron-electron correlation potential and its enhancement factor are handled within the frame work of the local density approximation and the generalized gradient approximation. We have respectively calculated the positron bulk lifetime of three kinds of single crystal solid: the alpha iron of a body-centered cubic structure, the aluminum of a face-centered cubic structure, and the silicon of a double face-centered cubic structure. Calculation results agree well with the published experimental data. At the same time, the impact on positron bulk lifetime due to electron density grid point accuracy, positron-electron correlation potential and enhancement factor is analyzed carefully. Finally, we discuss the advantages and disadvantages of the three methods for calculating the positron bulk lifetime. In summary, an effective and reasonable calculation for the positron bulk lifetime should take into account the electron density, positron-electron correlation potential, and enhancement factor, etc. especially the enhancement factor.
Effects of comprehensive information of the nearest following vehicle on traffic flow instability
Authors: Zeng You-Zhi  , Zhang Ning  ,   School of Economics and Management, Beihang University, Beijing 100191, China
Published: December 2020

Based on the condition of inhibiting traffic flow instability, this paper studies the effects of comprehensive information of the nearest following vehicle obtained by drivers' rear view behavior on traffic flow instability. Research shows that in the real practice the probability of paying attention to the information of the preceding vehicle is greater than that of paying attention to the information of the following vehicle, and the drivers' sensitive coefficient is assumed to be greater than 0, many conclusions such as the following can be obtained: 1) the information of the nearest following vehicle headway may reduce traffic flow instability, and the larger the attention probability, the smaller the traffic flow instability; on the contrary, the information of the velocity difference between the vehicle and the nearest following vehicle may increase the traffic flow instability, so the larger the attention probability, the bigger the traffic flow instability; 2) the instability reduction effect due to the comprehensive information from the nearest following vehicle is greater than the increasing effect on the traffic flow instability; 3) the bigger the driver's sensitive coefficient of the distance difference, the bigger the reducing effect of the information of the nearest following vehicle on traffic flow instability; 4) the bigger the driver's sensitive coefficient of the velocity difference, the bigger the increasing effect of the information of the nearest following vehicle on traffic flow instability.
Probabilistic analysis of the lateral diffusion of secondary electrons in multicarrier multipactor
Authors: Song Qing-Qing  , Wang Xin-Bo  , Cui Wan-Zhao  , Wang Zhi-Yu  , Ran Li-Xin  ,   Laboratory of Applied Research on Electromagnetics, Zhejiang University, Hangzhou 310027, China;,   Xi'an Institute of Space Radio Technology, Xi'an 710100, China;,   Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

Recently, a new mechanism of secondary electron multipaction, termed “long-term” multicarrier multipactor, was found in wideband high-power systems used in vacuum environments. Due to the long-term accumulation of secondary electrons between consecutive periods of the multicarrier signal, the long-term multicarrier multipactor has relatively low discharge threshold and is difficult to predict, thus causes potential reliability problems in space and accelerator applications. In this paper, we propose a stochastic approach to the analytical analysis of the multicarrier multipactor discharge occurring in inhomogeneous electric fields. By introducing the random walk and Levy walk theory, the probabilistic model of the lateral diffusion of secondary electrons in the process of a multipactor discharge is derived. Based on the derived probability density, the purely theoretical calculation of the accumulation of secondary electrons of a multicarrier multipactor in a rectangular waveguide supporting TE10 mode is given. The theoretical results comply well with the results achieved by the time-consuming particle simulation, with reducing computational time by about one- order of magnitude. The presented probability density of the lateral diffusion of secondary electrons can have applications in high-power electronics and electromagnetism.
System size stochastic resonance in asymmetric bistable coupled network systems
Authors: Sun Zhong-Kui  , Lu Peng-Ju  , Xu Wei  ,   Department of Applied Mathematics, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

In this paper, the noise-induced dynamics is studied in an asymmetric bistable coupled network system modulated by different signals. According to the Gaussian approximation and the slaving principle, the asymmetric bistable coupled network system is reduced to a low-dimensional model with two potentials, by which the phenomenon of system size stochastic resonance is studied theoretically and numerically. Under the assumption of adiabatic limit, the expressions of signal-to-noise ratio (SNR) are found by virtue of Fokker-Planck equation with respect to cosine signal and rectangle signal, based on which the system size stochastic resonance is investigated. Further, the effects of the noise strength, the asymmetry and the amplitude of the signal on the system size stochastic resonance are well discussed. It is demonstrated that the SNR shows a non-monotonic dependence on the number of coupled systems, which is demonstrated that there is a resonance with respect to the number of coupled systems.
Adaptive sliding-mode control of chaotic permanent magnet synchronous motor system based on extended state observer
Authors: Chen Qiang  , Nan Yu-Rong  , Xing Ke-Xin  ,   College of Information Engineering, Zhejiang University of Technology, Hangzhou 310023, China
Published: December 2020

An adaptive sliding-mode control scheme based on extended state observer (ESO) is proposed for permanent magnet synchronous motor (PMSM) chaotic system with some immesureable states. The adaptive sliding-mode control and extended state observer theory are combined in the developed controller, and thus the restriction that all the states in the PMSM should be completely measured is canceled. Through a simple coordinate transformation, the PMSM chaotic model is transformed into a Brunovsky canonical form, which is more suitable for the sliding-mode controller design. In the presence of unknown states and upper bound of nonlinear uncertainty, the ESO is employed to estimate the unknown states and the nonlinear uncertainty. Then, the adaptive sliding-mode controller is designed to ensure that the system states can converge to zero rapidly and stably. Simulation results show that the proposed controller can improve the chattering problem of the sliding-mode control and enhance the robustness of the system.
Wave function fractal dimensions for the periodically kicked free top
Authors: Zhou Jie  , Yang Shuang-Bo  ,   Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China
Published: December 2020

In this paper we study the fractal dimensions of wave function for the periodically kicked free top. We find that when kicking strength coefficient is less than or equal to 1 (≤ 1), the motion in classical phase space is regular, the fractal dimension is about 1, and as kicking strength increases, the motion in classical phase space becomes chaotic and the fractal dimension also increases. And we also find that when kicking strength is greater than or equal to 6 (≥ 6), the phase space becomes completely chaotic, the fractal dimension reaches its maximum value 1.5 and will keep this value.
A deployment strategy for coverage control in wireless sensor networks based on the blind-zone of Voronoi diagram
Authors: Fang Wei  , Song Xin-Hong  ,   Key Laboratory of Advanced Process Control for Light Industry (Ministry of Education), School of Internet of Things Engineering, Jiangnan University, Wuxi 214122, China
Published: December 2020

In this paper, we propose a blind-zone centroid-based scheme (BCBS) for solving the coverage problem of wireless sensor network in two-dimensional monitor area. In BCBS the monitor area is partitioned into several Voronoi polygons by using the Voronoi diagram and then each Voronoi polygon can be covered by one sensor. The next work in the BCBS is to obtain the blind-zone in the Voronoi polygon according to the positions of its vertexes in order to construct the polygon, which is approximately the shape of the blind-zone. The centroid of the polygon is then regarded as the candidate target position for the sensor nodes in order to improve the coverage rate. Experimental results show that the BCBS has advantages in the coverage rate, uniformity of the nodes distribution and the efficiency of the nodes coverage over the centroid-based scheme.
Tunable optimization of high-order harmonic generation driven by 5 fs laser pulses
Authors: Wang Li-Feng  , He Xin-Kui  , Teng Hao  , Yun Chen-Xia  , Zhang Wei  , Wei Zhi-Yi  ,   Beijing National Laboratory for Condensed Matter Physics, Insititute of Physics, the Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The characteristics of high-order harmonic generation (HHG) driven by 5 fs laser pulses interacting with argon under tightly focused geometry are investigated in this paper. By carefully optimizing parameters like dispersion, gas pressure and gas cell position, the enhanced HHG with nearly one order of magnitude in a range of 60-73 eV is observed. Based on single atom approximation and Maxwell propagation equations, numerical simulation is conducted to compare with the experimental characterization with proper parameter. It is proved that the phase-matching plays a crucial role in this phenomenon showing that the theoretical results are in agreement with the experimental results.
Asymmetry of hole states in vertically coupled Ge double quantum dot
Authors: Cui Wei  , Wang Chong  , Cui Can  , Shi Zhang-Sheng  , Yang Yu  ,   Yunnan Key Laboratory of Micro/Nano Materials and Technology, Yunnan University, Kunming 650091, China;,   Center for Optoelectronics Materials and Devices, Department of Physics, Zhejiang Sci-Tech University Hangzhou 310018, China
Published: December 2020

The two lowest single-particle hole states in the vertically coupled Ge/Si double layer quantum dots are investigated numerically by using the single-band heavy hole effective mass approximation and six-band Kronig-Penney model, respectively. The calculated results indicate that within the frame of several-band coupled model, the bonding-antibonding ground-state transition and a bonding-antibonding energy anti-crossover phenomenon are observed with interdot distance increasing. These results have not been observed previously in those single-band model calculations. The analysis of the wavefunction component of bonding-antibonding hole state shows that the contribution ratios of light, heavy and spin-orbital-split-off hole states to the characteristic hole wavefunction vary with the increase of the vertical coupled distance, resulting in the ground state wavefunction changing from bonding states to antibonding ones finally.
Electron transport through T-shaped double quantum dot molecule Aharonov-Bohm interferometer
Authors: He Ze-Long  , Bai Ji-Yuan  , Li Peng  , Lü Tian-Quan  ,   School of Electrical and information Engineering, Heilongjiang Institute of Technology, Harbin 150050, China;,   Institute of Condensed-Matter Science and Technology, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

Using non-equilibrium Green's function method, the charge and spin transport properties through T-shape double quantum dot molecule Aharonov-Bohm (A-B) interference are theoretically investigated. Resonance or anti-resonance can occur at the same location in conductance spectrum by controlling coupling or uncoupling between two quantum dots in T-shape double quantum dot molecule, which is the basis for designing quantum switches. When two identical T-shaped double quantum dot molecules are embedded in two arms of A-B interferometer, respectively, totally destructive interference can appear by taking appropriate magnetic flux. Spin current through the system can be regulated by adjusting quantum dot level, bias between two electrodes and Rashba spin-orbit interaction.
Numerical simulation of multipactor phenomenon on the surface of cylinder window disk
Authors: Zhang Xue  , Wang Yong  , Fan Jun-Jie  , Zhang Rui  ,   Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

A particle model that is based on Monte Carlo particle simulation arithmetic is built up to investigate the multipactor behavior on the surface of cylinder window disk in pill-box window. The regime of multipactor in the inhomogeneous electric field is obtained. The simulation results prove that the interaction between secondary electrons and window disk is sustained by magnetic field force on the upstream side. The multipactor phenomenon acts intensively in the area with a great electric field. The ponderomotive force does not devote any effort to multipactor on the upstream side. On the downstream side, the multipactor cannot be excited without strong enough surface electrostatic field because of the positive magnetic field force. With the increase of transmitting power, secondary electrons can obtain more energies. Due to the effect of ponderomotive force, the multipactor region transfers from the area with powerful electric field to the weak one on the downstream side. Besides, the resistance effect of electrostatic isolation on multipactor is also confirmed in the input port of cylinder waveguide.
On traffic flow model with weighted look-ahead potential
Authors: Zheng Wei-Fan  , Zhang Ji-Ye  , Wang Ming-Wen  , Tang Dong-Ming  ,   Traction Power State Key Laboratory, Southwest Jiaotong University, Chengdu 610031, China;,   School of Mathematics, Southwest Jiaotong University, Chengdu 610031, China;,   Institute of Information Research, Southwest Jiaotong University, Chengdu 610031, China
Published: December 2020

Research on the stochastic behavior of traffic flow is important to understand the intrinsic evolution rule of traffic system. On the basis of cellular automata model and traffic flow model with look-ahead potential, in this paper, a novel traffic flow model with weighted look-ahead potential is presented. By introducing the weighting coefficient into the look-ahead potential and endowing the potential of vehicle closer to itself with a greater weight, the modeling process is more suitable for the driver's random decision-making process which is based on the vehicle and enviroment situation in front of him in actual traffic. Complex high-density traffic behavior is reproduced by numerical simulations. The simulation results show that the weighting coefficient has an obvious effect on high-density traffic flux, and the weighted model is more conducive to keeping high traffic flux and road capacity while maintaining a high traffic density.
New infinite sequence complexion soliton-like solutions of (2+1)-dimensional Zakharov-Kuznetsov modified equal width equation
Authors: Yin Jun-Yi  ,   College of Information and Management Science, Henan Agricultural University, Zhengzhou 450002, China
Published: December 2020

The (G'/G)-expansion method is further studied, the solution to the second-order nonlinear auxiliary equation is changed into solving of one unknown quadratic equation and Riccati equation by two function transformations. An infinite sequence solution of auxiliary equation is obtained with the help of Bcklund transformation of Riccati equation and nonlinear superposition formula of the solution. In this way, the infinite sequence solution to the nonlinear evolution equation can be obtained by the (G'/G)-expansion method, this method is an extension of existing methods, which can get more infinite series solutions. Take the (2+1)-dimensional Zakharov-Kuznetsov modified equal width equation as an example to obtain the new infinite sequence solution. This method can be used to get the infinite sequence solution to other nonlinear evolution equations.
Approximate analysis of spatial fading correlation for multiple antenna system
Authors: Zhou Jie  , Wang Ya-Lin  , Hisakazu Kikuchi  ,   School of Electronic and Information Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China;,   Department of Electronic and Electrical Engineering, Niigata University, Niigata 950-2181, Japan
Published: December 2020

Spatial fading correlation (SFC) mainly depends on power azimuth spectrum (PAS) of arrival signals and the transceiver mode of multi-antenna arrays. This paper investigates in depth the approximate algorithm and its complexity in SFC of multi-antenna arrays in a mobile communication system. First, we derive the closed-form formulas for SFCs under three typical PAS: i. e. a uniform distribution, a Gaussian distribution and a Laplace distribution. Based on these theoretical formulas, we study the approximate algorithm when the angle spread in PAS for arrival signals is small. From this, we develop a multi-antenna reception channel model and analyze in detail the impact of the antenna array and electric wave propagation parameters we choose on the capacity of multiple-input multiple-output (MIMO) channel. By using theoretical calculations and simulation experiments, we find that in a particular situation the approximate algorithm provides a good approximation for SFC. Furthermore, a method is used to quantify the applicability and calculation efficiency while analyzing the MIMO multi-antenna array. Finally, it can be concluded that the approximate method has a good approximation in particular situations, and it will greatly reduce the theoretical computational complexity. The method we suggest will improve the efficiency of analyzing and simulating a complex MIMO multi-antenna system.
Numerical simulation of heat transfer in gas-particle two-phase flow with smoothed discrete particle hydrodynamics
Authors: Chen Fu-Zhen  , Qiang Hong-Fu  , Gao Wei-Ran  ,   Faculty 601, Second Artillery Engineering University, Xi'an 710025, China
Published: December 2020

Heat transfer between particles and that between gas phase and particle phase in gas-particle two-phase flow cannot be ignored. Smoothed discrete particle hydrodynamics, as a new method for solving the gas-particle two-phase flow, has been used in simulating the aerolian sand transport successfully. Based on the smoothed discrete particle hydrodynamics method, a heat conduction model is presented in this paper and is used to simulate the heat transfer processes and the particle evaporation in gas-particle two-phase flow. Firstly, the equations to be solved are presented in which the energy equations are introduced for each phase and the second derivative item in conduction is treated by combining a standard smoothed particle hydrodynamics first derivative with a finite difference approximation of a first derivative. The heat conduction between particle and gas is computed from temperature difference and heat transfer coefficient. The disc-type particle cluster problem and bubble fluidized bed are simulated and the results are in close agreement with the two fluid model simulation results. The vaporization law for discrete phase droplet is used to deal with the particle evaporation and then a jet evaporation is simulated. Numerical results all show a good agreement with the discrete particle model results. It is indicated that the new method is of good accuracy and practical applicability.
The ab initio and potential energy curve of SiF2(1A1)
Authors: Han Xiao-Qin  ,   Department of Physics, Shangqiu Normal College, Shangqiu 476000, China
Published: December 2020

The ab initio configuration interaction method and coupled-cluster theory have been used to optimize the possible ground-state structures of SiF2. The method QCISD/6-311G(2df) is most suitable for the calculation of SiF2 by comparing the experimental value and the calculated value; and the calculated equilibrium structure, harmonic frequency, dissociation energy, force-constant are in good agreement with the experimental data. The potential energy functions of SiF2 have been derived from the many-body expansion theory. In the symmetry of stretching vibration and rotation potential energy diagram of SiF2, there is a saddle point in the reaction kinetics SiF+F→SiF2. A stable SiF2 molecule could be formed when F atom with an energy surpassing 4.38 eV. These are completely reported so far as we know for the first time. In addition, it is found that a stable SiF2 molecule could be formed through two equivalent channels of SiF+F→SiF2. And the reaction is endothermic with a threshold energy.
Effect of Pd in NiTi on the martensitic transformation temperatures and hysteresis: a first-principles study
Authors: Ma Lei  , Wang Xu  , Shang Jia-Xiang  ,   School of Material Science and Engineering, Beihang University, Beijing 100191, China
Published: December 2020

In this paper phase stability and functional properties of Pd-doped NiTi with different Pd concentrations (Ni24-nPdnTi24, n=2, 3, 4, 5, 6, 9, 12; CPd=4.2 at.%, 6.3 at.%, 8.4 at.%, 10.4 at.%, 12.5 at.%, 18.8 at.% and 25 at.%) are calculated by first-principles method. Results show that B19' is the most stable when CPd is less than 10.4 at.%, whereas B19 is the most stable for CPd is equal to or larger than 10.4 at.%. The formation energy decreases with increasing Pd concentration. With increasing CPd, the energy difference between austenite and martensite decreases slightly and increases for CPdCPdCPd=10.4 at.%, which agrees well with the experimental results.
Robust visual tracking algorithm based on bidirectional sparse representation
Authors: Wang Bao-Xian  , Zhao Bao-Jun  , Tang Lin-Bo  , Wang Shui-Gen  , Wu Jing-Hui  ,   School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

At present the visual tracking model based on sparse representation is mainly divided into two types: one is to use the template set to reconstruct candidate samples, which is called forward model; the other is to project the template set into a candidate space, which is called reverse model. What the two models have in common is to compute the sparse correlation coefficient matrix of candidate sample and template set. Based on this, the paper establishes a bidirectional cooperative sparse representation tracking model. Using L2-norm constraint item, the forward and reverse sparse correlation matrix coefficients could be uniformly convergent. In comparison to conventional unidirectional sparse tracking model, bidirectional sparse tracking model could fully excavate the sparse mapping relation of the whole candidate sample and template set. And the candidate that scores highest in the sparse mapping table for the positive and negative templates is the tracking result. Based on the accelerated proximal gradient fast method, the paper derives the optimum solution (in matrix form) of bidirectional sparse tracking model. As a result, it allows the candidates and templates to be calculated in parallel, which can improve the calculation efficiency to some extent. Numerical examples show that the proposed tracking algorithm has certain priority over against the conventional unidirectional sparse tracking methods.
Self-mixing interference effect based on fiber laser
Authors: Hao Hui  , Xia Wei  , Wang Ming  , Guo Dong-Mei  , Ni Xiao-Qi  ,   Key Laboratory for Opto-Electronic Technology of Jiangsu Province, School of Physical Science and Technology, Nanjing Normal University, Nanjing 210023, China;,   Institute of Quantum Electronics, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871, China
Published: December 2020

For the sensing applications based on the self-mixing interference technology of fiber laser, the self-mixing interference in the linear cavity fiber laser is theoretically analyzed through a four-mirror cavity model. The output power and frequency equation are deduced, and the behaviors of the laser under different optical feedback strengths are analyzed and simulated as well. The intensity of the laser is modulated by the length of the external cavity, and one fringe of the signal corresponds to the displacement of half wavelength of the target. Experimental setup is developed to validate the theoretical analysis. The obtained results provide both the theoretical and experimental basis for further studying self-mixing interferemetric sensing applications of fiber lasers.
Effect of curve groove on the spectral resolution for soft X-ray holographic flat-field gratings
Authors: Chen Huo-Yao  , Liu Zheng-Kun  , Wang Qing-Bo  , Yi Tao  , Yang Guo-Hong  , Hong Yi-Lin  , Fu Shao-Jun  ,   National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China;,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The soft X-ray spectrograph is an important instrument for plasma diagnostics. As the core optical element of spectrograph, holographic flat-field grating is fabricated by aspheric wave-front recording optics, so grooves on the surface are curve. The curve grooves of the grating would affect the spectral image properties, thus influencing spectral resolutions. In the design of recording optics, only the groove density distribution on the surface in meridian line should be guaranteed, so optimized recording optics is not unique. Thus gratings with different curvatures of grooves but with expected groove density distribution could be obtained. For holographic flat-field gratings used in a 0.8-6 nm region, we analyze the influences of different curve grooves on the spectral image by ray tracing, and find that the almost straight grooves which are obtained by means of cylinder mirror can obtain the better spectral images. The theoretical results show that the spectral resolutions of grating with almost straight grooves are obviously improved compared with curve grooves, the theoretical spectral resolutions increase from 626 to 953 at 3 nm and from 635 to 1222 at 5 nm, respectively.
A segmentation calculation method for plasma collision frequency considering the electro-magnetic wave driving effect
Authors: Liu Zhi-Wei  , Bao Wei-Min  , Li Xiao-Ping  , Liu Dong-Lin  ,   School of Aerospace Science and Technology, Xidian University, Xi'an 710071, China
Published: December 2020

An empirical formula of collision frequency has been used for years to calculate the collision frequency of aircraft plasma sheath. But the formula ignores the influences of electron-electron impact, electron-ion impact, and electro-magnetic (EM) wave driving effect on the collision frequency. To remedy these deficiencies, this paper proposes a segmentation calculation method. Based on the plasma kinetic theory, combined with real flow conditions and synthesizing the influences of electron-electron impact, electron-ion impact and EM wave driving effect together, this method defines a new parameter, ionization-to-thermal motion ratio, to calculate the collision frequency segmentally. Theoretical analysis and simulation results demonstrate that this method is closer to the truth than the empirical formula when ITR is greater than 5.
Deformation behaviors of zircaloy-4 alloy under uniaxial compression
Authors: Li Hong-Jia  , Sun Guang-Ai  , Gong Jian  , Chen Bo  , Wang Hong  , Li Jian  , Pang Bei-Bei  , Zhang Ying  , Peng Shu-Ming  ,   Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999, China
Published: December 2020

Zirconium (Zr) has a hexagonal close-packed crystal structure, which exhibits elastic and plastic anisotropy. Internal stresses can be easily generated in the rolling process and the subsequent plastic deformation process. It is critical to evaluate the internal stresses and the deformation mechanisms of Zr alloy materials. The deformation behaviors of Zr alloy influence directly its service life and safety. In this work, compression deformation behaviors of zircaloy-4 (Zr-4) alloy have been studied by the in situ neutron diffraction technique combined with the elastic-plastic self-consistent (EPSC) simulation. A compressive external load is applied along the thickness direction of the rolled plate, which is called through-thickness compression. Electron back-scattered diffraction is used to analyze the texture evolution during the plastic deformation. Transmission electron microscopy (TEM) is used to measure the distribution of the defects in the deformed sample. The EPSC simulation provides the deformation mechanism quantitatively by fitting the in situ neutron diffraction data, and the simulated results is confirmed by the TEM observations. Results show that when the true strain is small (less than 0.55%), prismatic {1010}20> (a> type) slip dominates; however, as the plastic strain is increased, the percentage of pyramidal {1011}23> (c+a> type) slip becomes larger than that of prismatic {1010}20> (a> type) slip, and the pyramidal {1011}20> (a> type) slip and pyramidal {1012}20> (a> type) slip may exist.
Study on the influence of γ -ray total dose radiation effect on the threshold voltage and transconductance of the strained Si p-channel metal-oxide-semiconductor field-effect transistor
Authors: Hu Hui-Yong  , Liu Xiang-Yu  , Lian Yong-Chang  , Zhang He-Ming  , Song Jian-Jun  , Xuan Rong-Xi  , Shu Bin  ,   Key Lab of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071, China
Published: December 2020

In this work, the carrier microscopic transport process of biaxial strained Si p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) under γ -ray radiation has been studied. Effect of γ-ray on devices and the relationship between the variation of device electrical characteristics and the total dose are investigated. A model for considering the degradation of threshold voltage and transconductance due to the total dose radiation is established. Based on this model, numerical simulation has been carried out. Results show that the threshold voltage of PMOSFET decreases with increasing radiation dose. At a lower total dose, the threshold voltage decreases linearly. However, at a higher total dose, it becomes saturated. The degradation can be explained by the generation of trapped charges which increase the impact possibility of carriers in the channel and induce the reduction of mobility and transconductance accordingly. Finally, the simulation results are compared with the experimental data. A good agreement is observed, indicating the validation of our proposed model.
Study on the strained SiGe p-channel metal-oxide-semiconductor field-effect transistor with polycrystalline silicon germanium gate threshold voltage
Authors: Liu Xiang-Yu  , Hu Hui-Yong  , Zhang He-Ming  , Xuan Rong-Xi  , Song Jian-Jun  , Shu Bin  , Wang Bin  , Wang Meng  ,   Key Lab of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071, China
Published: December 2020

In this work, the strained SiGe p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) with poly-Si1-xGex gate has been studied. Based on the analysis of vertical electric field and potential distribution, the equipment oxide thickness of strained SiGe PMOSFET with poly Si1-xGex gate is established. The mechanism and the influence of hot carriers induced are studied. A model of the drift of threshold voltage is established; its relationships with the duration of the applied electrical stress, the voltage of gate, the Ge content of the poly Si1-xGex gate and the strained SiGe are also obtained. Based on the above results, the simulation results have been compared with the experimental data. The drift of threshold voltage is 0.032 V under 10000 s electrical stress. A good agreement is observed, which indicates the validation of our proposed model.