bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on train traffic flow affected by the line curve of the moving block system
Authors: Chen Yong  , Wang Xiao-Ming  , Dang Jian-Wu  , Hu Xiao-Hui  ,   School of Electronic and Information Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
Published: December 2020

According to the characteristics of railway line and NaSch model a cellular automata model for simulating multi-train tracking of railway curve is proposed. The computer numerical simulation is carried out and the influence of different curve radius, outer rail superelevation curve and curve length on railway traffic flow are studied using the propose model. Simulation results show that the model can reflect accurately traffic flow situation of the special line; and the train line curve has a great influence on the running safety and reveals the traffic wave phenomena in running and stopping. With increasing curve radius, train delay time decreases gradually according to the simulation results. Reasonable selection of curve radius, the outer rail superelevation and curve length can significantly improve the line capacity and reduce the wheel rail wear, so that these can guarantee the safety and comfort of the train running. The results have certain guiding significance for the railway line design and operational management.
Investigation of information bandwidth oriented spectrum sensing method
Authors: Zhang Jing-Chao  , Fu Ning  , Qiao Li-Yan  , Peng Xi-Yuan  ,   Department of Automatic Test and Control, Harbin Institute of Technology, Harbin 150080, China
Published: December 2020

Existing spectrum sensing systems are commonly designed based on the famous Nyquist theorem. With the rapid development of radio frequency technology, the corresponding sampling frequency is so high that many problems may be brought about, such as the increasing hardware complexity, large volume of measurements and difficulties to meet the real time requirement etc. To tackle these problems caused by high sampling frequency, a novel scheme, adaptive modulated wideband converter, is proposed. By exploiting the band width of the narrow bands, the total sampling frequency is proved to be as low as four times of the sum of the narrow bands. There is a trade-off between the sampling complexity and the total sampling frequency for different choices of the repeating frequency of the random function. Sufficient conditions are derived to guarantee exact signal recovery from sub-Nyquist measurements. Conditions of full row rank of the equivalent unknown matrix are also explored to guarantee that the multiple signal classification can be adopted to implement the signal reconstruction. The simulations verify the analysis. This novel scheme can be used to implement front-end spectrum analysis for absorbing materials and detect the active channels in cognitive radio.
Variation of parameters and recovery in crystal lattice of 30CrMnSiNi2A
Authors: Yuan Shu-Qiang  , Shen Zheng-Xiang  , Zhou Chun-Hua  , Liu Feng-Tao  , Wang Fang  , Yang Hui  , Chen Jiong  ,   NingBo Institute, China North Material Science and Engineering Technology Group, NingBo 315013, China
Published: December 2020

Aiming at the peaks overlapping in the field of X-ray diffraction, a new method for peaks separation was developed, and the parameters and recovery behaviors of crystal lattice of 30CrMnSiNi2A were investigated using RU-200V X-ray powder diffractmeter, by which the relationship between lattice parameters and carbon content at different tempering temperatures was obtained. Results show that the variation of lattice parameters of 30CrMnSiNi2A is consistent with high-carbon martensite on the whole, however there are some differences in the rate of change. The lattice parameter a is independent of carbon content, and slightly decreases with the rise of tempering temperature, while the amplitude of change for the lattice parameter c and carbon content is large, and a steep drop is observed in the process of quenching to the tempering temperature at 180 ℃, while the amplitude becomes flat aferwards for a higher tempering temperature.
Quenching rate of laser-excited lithium atoms with argon molecules in photochemical reaction
Authors: Qu Ding-Rong  , Fan Feng-Ying  , Song Zeng-Yun  ,   Department of Engineering Physics, Tsinghua University, Beijing 100084, China
Published: December 2020

In this paper, collisional quenching rate for Li(2P) atoms with argon molecules is studied in photochemical isotope separations. In the weak laser irradiation, the absorption spectra and fluorescence emission spectra of lithium atom vapor is measured by changing the argon pressure. The quenching rate constant of (12.29±0.92)×10-18 m3·s-1 for Li(2P) atoms quenched with argon molecules have been determined. This value is much smaller than the spontaneous emission rate of Li(2P) atoms. The experimental result shows that in photochemical lithium isotope separation collisional quenching effect on the separation selectivity is very small and can be neglected.
Design of high-gain broadband low-RCS waveguide slot antenna
Authors: Zhao Yi  , Cao Xiang-Yu  , Zhang Di  , Yao Xu  , Li Si-Jia  , Yang Huan-Huan  , Li Wen-Qiang  ,   School of Information and Navigation of AFEU, Xi’an 710077, China
Published: December 2020

A novel design for high gain and low radar cross section (RCS) waveguide slot antenna is proposed. Low RCS screen composed of orthogonal array of complementary split ring resonator etched square patch artificial magnetic conductor (CSRR-AMC) is exploited on the antenna for radiation improvement and broadband RCS reduction. Measured results demonstrate that the operating bandwidth is increased by 100 MHz and the gain is enhanced by 3.2 dB with the proposed structure. Meanwhile, 10 dB RCS reduction is achieved over the range of 5.52–6.63 GHz, implying 20% relative bandwidth.
A time-domain Gauss-Newton inversion algorithm for solving two-dimensional electromagnetic inverse scattering problems
Authors: Liu Guang-Dong  , Zhang Kai-Yin  ,   College of Physical and Electronic Science, Fuyang Teachers College, Fuyang 236037, China
Published: December 2020

The Gauss-Newton inversion (GNI), an iterative algorithm, is developed from the frequency domain to the time domain in order to simultaneously reconstruct the electrical permittivity and electric conductivity of a two-dimensional object of interest by directly using the ultra-wideband time-domain measurement data. The resulting forward problem is solved by the finite difference time domain method, while the ill-posedness of the corresponding inverse problem is restrained by an adaptive regularization technique at each iteration. Furthermore, the modified GNI algorithm is applied to four types of numerical examples where a noise model is considered, and the simulated results preliminarily demonstrate its feasibility and robustness. The reconstructed images present super resolution, thus it is expected to be used in the engineering practice such as the detection of the early-stage breast cancer.
A 147 fs mode-locked erbium-doped fiber laser with a carbon nanotubes saturable absorber in evanescent field
Authors: Dong Xin-Zheng  , Yu Zhen-Hua  , Tian Jin-Rong  , Li Yan-Lin  , Dou Zhi-Yuan  , Hu Meng-Ting  , Song Yan-Rong  ,   Institute of Information Photonics Technology, College of Applied Sciences, Beijing University of Technology, Beijing 100124, China
Published: December 2020

A saturable absorber of 3.9% modulation depth was prepared on the surface of a fiber clad with single-walled carbon nanotubes (SWCNT) using chemical corrosion method. An all-fiber Er-doped fiber laser was setup with a ring cavity, and was mode-locked successfully by evanescent field mode-locking using prepared saturable absorber of single-walled carbon nanotubes. A 147 fs mode-locking pulse is obtained near 1556 nm with a 3 dB bandwidth of 24 nm. The output power is 21 mW at a pump power of 520 mW, corresponding to a pulse energy of 0.14 nJ with a repetition rate of 150 MHz.
Visible supercontinuum generation in dual-concentric-core-like photonic-crystal fiber
Authors: Zhang Xin-Ben  , Luo Xing  , Cheng Lan  , Li Hai-Qing  , Peng Jing-Gang  , Dai Neng-Li  , Li Jin-Yan  ,   Wuhan National Laboratory for Optoelectronics, School of Optcal and Electronic Information, Huazhong University of Science and Technology Wuhan 430074, China
Published: December 2020

We report the visible supercontinuum (SC) generation in the double zero dispersion multi-core photonic crystal fiber (PCF), pumped by picosecond pulses from Yb-doped fiber laser. Such a dual-concentric-core-like PCF provides two closely spaced zero-dispersion wavelengths (ZDW). The redshift solitons will be canceled out at the vicinity of the second ZDW, and the steady solitons will cause considerable dispersive waves at the edges of the output SC which spans from 550 to 1700 nm at an average pump power 1 W. Moreover, the optical field is transferred from the inner core to the outer core. Experimental results agree well with the theoretical calculations.
Investigation of a novel all-solid large-mode-area photonic quasi-crystal fiber
Authors: Liao Wen-Ying  , Fan Wan-De  , Li Yuan  , Chen Jun  , Bu Fan-Hua  , Li Hai-Peng  , Wang Xin-Ya  , Huang Ding-Ming  ,   School of Physics, Nankai University, Tianjin 300071, China
Published: December 2020

Large-mode-area single-mode fibers play an important role in the field of high power lasers, high power delivery, and high sensitivity sensor. A novel all-solid large-mode-area single-mode photonic quasi-crystal fiber with extremely low loss is proposed. This kind of fiber contains a hexagonal quasi-crystal array of slightly fluorine-doped silica rods in a silica background. Its structure and properties are simulated numerically in virtue of finite element method. Effects of variation of d/Λ, or Λ on fiber loss and effective mode-area properties are investigated. Numerical results demonstrate that an effective mode-area of 5197 μm2, low confinement loss of 10-5 dB/km for fundamental mode and high confinement loss of 100 dB/km of second-order mode at a wavelength of 1064 nm. Numerical simulations show that this fiber can operate effectively in single-mode and remove the conflict between large-mode-area and low loss. Moreover, the bending loss for a bending radius of 10 cm is as low as 0.01 dB/m. This fiber can increase the thermal damage threshold of the PQF, decrease the coupling loss and simplify the fabrication process. The design of new fibers is highly meaningful for the development of high power delivery, fiber lasers, and fiber amplifiers.
Propagation of nonlinear waves in the bubbly liquids
Authors: Wang Yong  , Lin Shu-Yu  , Zhang Xiao-Li  ,   Institute of Applied Acoustics, Shaanxi Normal University, Xi’an 710062, China
Published: December 2020

An important factor that causes the nonlinearity in the bubbly liquids when the acoustic wave is propagating is the bubbles. So we study the nonlinear propagation of acoustic waves in the bubbly liquids. The influence of the gas content is introduced into the equation of the wave propagation in the liquid, so one can get the model of wave propagation in the bubbly liquids. Through numerical simulation of the model one can get the gas content, the pressure amplitude of driving sound and the acting time of the driving sound can all affect the distribution of the sound field and the pressure amplitude of the wave in the bubbly liquids. The bubbles in the liquid will “block” the acoustic wave to propagate and “gather” the energy near the sound source field. For continuous and high power driving sound, the bubbles in the liquid will “block” the wave propagation and the transmission of energy.
Robust source localization based on mode subspace reconstruction in uncertain shallow ocean environment
Authors: Liu Zong-Wei  , Sun Chao  , Xiang Long-Feng  , Yi Feng  ,   Institute of Acoustic Engineering, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

Existing localization methods have mismatch problem when applied to the real uncertain ocean, and this will lead to performance degradation. In normal mode models, some modal eigenfunctions remain to be more correlated than others in the presence of environmental uncertainties. Based on this, we have proposed a mode subspace reconstruction robust localization method, which uses stable modes to reconstruct the replica vector to grantee the localization performance. The data from simulation and experiment are used to verify the effectiveness of the proposed method. Performances of the matched field processor (MFP) and the robust ML (maximum localization) estimator are also given here for comparison. Results show that: (1) the generally used MFP method has a low localization performance even at high SNR values; (2) the proposed method outperforms the robust ML estimator and the generally used MFP.
Characteristics of mapping domain of the acoustic field interference structures radiated by a moving target
Authors: Lin Wang-Sheng  , Liang Guo-Long  , Wang Yan  , Fu Jin  , Zhang Guang-Pu  ,   Science and Technology on Underwater Acoustic Laboratory, Harbin Engineering University, Harbin 150001, China;,   Science and Technology on Sonar Laboratory, Hangzhou Applied Acoustics Research Institute, Hanzhou 310012, China
Published: December 2020

In shallow water exist the stable and significant interference characteristics of low frequency sound propagation, which contain the information of the sound source state and waveguide peculiarity. A simplified mapping method for describing the scalar and vector sound field interference structure radiated by a moving target, and an indicatory mechanism of the target state implicated in the energy distribution of the mapping domain are investigated in this paper. The mapping characteristics of two-dimensional Fourier transform of the vector sound field time (space) frequency interference spectrum are analyzed theoretically. Relations among waveguide invariant, range-rate, heading angle, and energy ridge slope of the mapping domain for time-frequency interference spectrum produced by a uniformly moving target are derived. Indication of target attacking or moving away, and the degree of threatening through symbols or the absolute value change of mapping domain’s ridge slope are demonstrated. Then numerical simulation and sea trial research are carried out. Experimental results with theoretical analysis and simulation results are in good agreement with each other. Research results show that the scalar and vector field time (space) frequency interference structure can be simplified by the two-dimensional Fourier transform. The mapping domain ridges, range-rate, heading angle and waveguide invariant show an analytic relationship among them. Variation embodied in the form of scalar and vector field interference structure obtained after mapping are more consistent with each other. The ridge of mapping domain can indicate the moving state of target concisely.
Multiphysics-based simulation on heat conduction mechanism of TFC head and its influencing factors
Authors: Ao Hong-Rui  , Chen Yi  , Dong Ming  , Jiang Hong-Yuan  ,   Department of Machine Design, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

In order to precisely control the flying height of TFC head with consideration of microscale thermal effect, the thermal conducting characteristics and the influencing factors on TFC slider which is in an operation and multi-physics field condition were analyzed. In consideration of rarefaction effect of ultra-thin film at the head/disk interface, the models of slider heat conduction, air bearing surface heat transfer, and gas flow were established; the thermal deformation mechanism and the effect of thermal conduction on dynamic characteristics of slider were analyzed by using finite element method. Results show that the thermal conducting model and the proposed modification of Reynolds equation in this study are suitable for solving the problems of thermal deformation and dynamic characteristics of head slider. The main parameters that influence the thermal property of slider can be considered to be the heater height, heat generation rate, and the heat conductivity coefficient of the material. The change of the slider flying height is determined by the air bearing force and the air bearing surface thermal extrusion at the head/disk interface. Simulation results provide a basis for the design of heater in head slider and analysis of dynamic characteristics of air bearing.
Discrete element simulation of mechanical properties of wet granular pile
Authors: Zhao La-La  , Zhao Yue-Min  , Liu Chu-Sheng  , Li Jun  ,   School of Mechanical and Electrical Engineering, China University of Mining & Technology, Xuzhou 221116, China;,   School of Chemical Engineering and Technology, China University of Mining & Technology, Xuzhou 221116, China
Published: December 2020

Discrete element method (DEM) simulations for pile-up processes of different particle systems were performed based on linear cohesion contact model. Effects of particle shape and liquid bridge force between wet particles on the piling form were analyzed. The significant central dip profiles of normal force acting on the base surface, normal force and tangential force between particles were predicted. Effects of particle shape and cohesion energy density on the forces on the base surface and inter-particles were described. The results show that particle shape and the liquid bridge force have significant impacts on the piling form. With the increase of the cohesion energy density the angle of repose for each granular pile increases. But the angle of repose of cubical particles is bigger than that of spherical particles under the same condition. Particle shape and the liquid bridge force also significantly affect the change and the maximum amplitude of the forces acting on the base surface and the forces between the particles. The maximum amplitude of the forces increases with the increase of the cohesion energy density, and the value of the maximum force on cubical particles is bigger than that on spherical particles. When the value of cohesion energy density is very large, the mechanical properties of granular piles become more complicated, so that the liquid bridge force has a larger impact on the packing characteristic of particles than the impact on particle shape.
Shear test and physical mechanism analysis on size effect of granular media
Authors: Fang Ying-Guang  ,   School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510641, China;,   State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou 510641, China
Published: December 2020

Shear test samples of different grain sizes are prepared by using mineral particles of soil, and a series of tests of quick direct shear and tri-axial shear are performed to study the size effect of granular media. Deformation curves and shear stress strength are given of test samples with particles of different size and volume fraction. On the basis of the ratio of micro-acting forces between particles to gravity and the cell element model, physical mechanism of grain size effect is, for the first time as far as we know, explained on the micro-level and mecro-level respectively. Test results show that the deformation characteristic of granular media is enhanced and its shear stress strength increases with increasing volume fraction and decreasing of particle size, and the effect of volume fraction on the deformation characteristics and strength is more notable than that of grain size. According to mechanism analysis on size effect, parameter ratio of micro-acting forces to gravity is suggested to assess aggregation and friction effects of particles in the media, and mecro-mechanism is interpreted as strain gradient and micro-cracks of deformation coordination leading to grain size effect. The cell element model presented in this paper can greatly reduce the degrees of freedom of granular media and provides an available way for calculation modeling in industry and engineering design.
Numerical study of the erosion of the EAST tungsten divertor targets caused by edge localized modes
Authors: Huang Yan  , Sun Ji-Zhong  , Sang Chao-Feng  , Ding Fang  , Wang De-Zhen  ,   School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China;,   School of Information Science and Engineering, Dalian Polytechnic University, Dalian 116034, China;,   Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

Edge localized modes (ELMs) in company with high-confinement mode (H-mode) will release high energy plasma fluxes to the scrape of layer (SOL). Large portions of these high heat fluxes will eventually irradiate the divertor target plates, and may erode, even melt them. In this paper, we develope a one-dimensional heat conductivity model including evaporation, radiation, melting processes of tungsten to study the erosion of the divertor tungsten targets caused by ELMs in EAST at the current and possible future operation parameters. Based on both experimental data of heat fluxes on the carbon-fibre composites divertor in EAST and possible future data of high heat fluxes, the surface temperature of slab-shaped tungsten is evaluated numerically by solving the one-dimensional model. It is found that the current Type I ELMs do not cause any noticeable changes of the tungsten target, the surface temperature being raised only several tens of degrees. Simulation results show that ELMs will not become a problem for EAST tungsten wall for the time being and the near future as long as much more severe transient events, e.g., disruption, can be avoided. When deposition energy is increased to 1 MJ/m2 with a duration of 600 μs, the tungsten plate will melt for a layer as thick as 6.8 μm.
Influence of Ce doping concentration on the luminescence properties of LaCl3：Ce scintillation crystals
Authors: Ren Guo-Hao  , Pei Yu  , Wu Yun-Tao  , Chen Xiao-Feng  , Li Huan-Ying  , Pan Shang-Ke  ,   Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800, China;,   Guoju Electronics Ltd., China, Suzhou 215000, China
Published: December 2020

LaCl3:Ce is an excellent rare earth halide scintillation crystal discovered in the beginning of this century. Pure LaCl3 crystal and LaCl3 crystal doped with several different Ce concentrations were grown by vertical Bridgman method. Their transmission and luminescence as well as decay time were measured and compared with each other. It was found that the cut-off edge, emission wavelength as well as decay time for pure LaCl3 crystals are respectively 215 nm, 405 nm and 1 s. This emission is explained by the self trapped exciton (STE) of LaCl3. However, with the increase of Ce concentration in the crystal, the cut-off edge of LaCl3:Ce crystal shifts to about 300 nm, and the luminescence is dominated by the emission originating from 5d-4f transition of Ce ions. Meanwhile, the increase of the luminescence intensity of Ce3+ ion emission is accompanied with the expense of STE emission, this anti-correlation between the Ce3+ and STE luminescence intensity is interpreted by the energy transfer from STE to Ce ions in LaCl3:Ce scintillation crystals.
Quasi-equilibrium growth of monolayer epitaxial graphene on SiC (0001)
Authors: Yu Cui  , Li Jia  , Liu Qing-Bin  , Cai Shu-Jun  , Feng Zhi-Hong  ,   National Key Laboratory of ASIC, Hebei Semiconductor Research Institute, Shijiazhuang 050051, China
Published: December 2020

Sublimation of SiC substrates is a promising way to prepare high-quality graphene on large scale. Nowadays, growth of high-quality epitaxial graphene is still a crucial issue. In this work, monolayer epitaxial graphene is grown on Si-terminated 4H-SiC (0001) substrate. By introducing argon inert gas and silicon vapor as background atmosphere, the Si evaporation rate and condensation rate on the SiC surface is close to equilibrium and the growth of monolayer epitaxial graphene with very low speed is realized. The growth duration of monolayer epitaxial graphene is prolonged to 75 minutes from 15 minutes. It is found that the disorder-induced Raman D peak shows an obvious decrease as the growth speed decreases, indicating the improvement of crystal quality, which makes the electrical properties of the monolayer epitaxial graphene is improved. The maximum carrier mobility and sheet resistance have reached 1200 cm2/Vs and 604 /, respectively. The above results indicate that slowing down of growth speed by controlling of growth atmosphere is an efficient way to prepare high-quality epitaxial graphene.
Optimization method for extracting ocean wave parameters from HFSWR
Authors: Li Lun  , Wu Xiong-Bin  , Xu Xing-An  ,   Wuhan Digital Engineering Institute, Wuhan 430074, China;,   Electronic Information Institute of Wuhan University, Wuhan 430072, China
Published: December 2020

The principle of Doppler spectra detected by HFSWR (high-frequency-surface-wave radar) is given by a nonlinear integral equation from which can be extracted ocean wave parameters. By linearization, the equation can be transferred into a first kind of Fredholm integral equation approximately and can be displayed in a quadratic form. Conjunction gradient (CG) method is proposed to solve the optimization problem. Non-negative restriction is introduced to improve the involved CG algorithm and fit to the priori knowledge so that the ocean wave parameter is non-negative. Validity and accuracy of the proposed method are demonstrated by numerical simulation with different noise levels at one site and two sites.
Effect of source/drain preparation on the performance of oxide thin-film transistors
Authors: Xu Hua  , Lan Lin-Feng  , Li Min  , Luo Dong-Xiang  , Xiao Peng  , Lin Zhen-Guo  , Ning Hong-Long  , Peng Jun-Biao  ,   State Key Laboratory of Luminescent Materials and Devices, School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
Published: December 2020

Indium-zinc-oxide thin-film transistors (IZO-TFTs) are prepared with the multilayer structure of molybdenum-aluminum-molybdenum (Mo/Al/Mo) as the source/drain (S/D) electrode. Experiment demonstrates that the sputtering power of Mo (bottom layer of Mo/Al/Mo S/D) influences the performance of TFTs significantly. As the sputtering power increases, the Von runs negative shift, and the device uniformity degrades. XPS depth profile shows that the diffusion at the interface (IZO/Mo) occurs seriously. By decreasing the sputtering power, the diffusion can be suppressed and the devices are shown in normal off state (Von ～ 0.5 V, enhanced mode), with higher mobility (～ 13 cm2·V-1·s-1) and improved uniformity.
Calculation of system risk in a dynamical bank network system
Authors: Fan Hong  ,   Glorious Sun School of Business and Management Donghua University, Shanghai 200051, China
Published: December 2020

There have been many researches and rich results on the system risk in bank network systems that use complex network theory. Researches to date focus on the relationship between the contagion of the risk and the structure of the network after risk bursting, based on the assumptions that the accumulation of the system risk in network systems has approached the critical point of bursting and that the network is static (both the node and connection of the bank network are static).However, the problem why the system risk accumulates gradually and finally bursts in the network has not been addressed yet. The study on the system risk accumulation can only be conducted in dynamically evolving bank network systems; and the risk can be observed clearly only if the system risk is evaluated quantitatively. Therefore, a dynamically evolving complex bank network system, which has nodes of dynamic behavior and exhibits macroeconomic trends, is modelled first in the present paper. A lending-borrowing algorithm and a multi-term clearing algorithm for the dynamic bank network system are designed, and the method for calculating the system risk is proposed also. Finally, the system risk is calculated and analyzed by simulation. The curve of the system risk evolving with time is shown and the process of the accumulation of the system risk can be observed clearly. Researches in the present paper are to lay a foundation for the quantitative study of the system risk accumulation in dynamically evolving bank network systems.
Nondestructive detection of nano grating by generalized ellipsometer
Authors: Ma Zhi-Chao  , Xu Zhi-Mou  , Peng Jing  , Sun Tang-You  , Chen Xiu-Guo  , Zhao Wen-Ning  , Liu Si-Si  , Wu Xing-Hui  , Zou Chao  , Liu Shi-Yuan  ,   School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China;,   College of Sciences, Wuhan University of Science and Technology, Wuhan 430081, China;,   State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

The silicon nanometer structure grating and the photoresist nanometer structure grating were prepared. A fitting model was built on the new self-developed generalized ellipsometer. Then, the gratings was tested and fitted. Results proved that the machine could work well in nondestructive test of nano grating. Under the condition of the incident angle of 60 and the azimuth angle of 75, the measurement accuracy can be up to 99.97% for the three-dimensional morphology parameters such as key dimension and sidewall angle and so on, and the maximum error is less than 1%. This method is significant for the nondestructive test.
Application of the symmetry classification to the boundary value problem of nonlinear partial differential equations
Authors: Sudao Bilige  , Wang Xiao-Min  , Wuyun Morigen  ,   College of Sciences, Inner Mongolia University of Technology, Hohhot 010051, China
Published: December 2020

In this paper, we study the application of the symmetry classification to the boundary value problem of nonli-near partial differential equations. Firstly, by using differential characteristic set algorithm for the complete symmetry classification of partial differential equations, the complete symmetry classification of a given boundary value problem of nonlinear partial differential equations is proposed. Secondly, by using an extended symmetry, the boundary value problem of nonlinear partial differential equations is reduced to an initial value problem of the original differential equations. Finally, we numerically solve the initial value problem of the original differential equations by using Runge-Kutta method.
Delay consensus of leader-following multi-agent systems
Authors: Xie Yuan-Yan  , Wang Yi  , Ma Zhong-Jun  ,   School of Mathematics and Computing Science, Guilin University of Electronic Technology, Guilin 541004, China;,   School of Mathematics and Statistics, Zhejiang University of Finance and Economics, Hangzhou 310012, China
Published: December 2020

In recent years, there has been the increasing interest in the research on the consensus of multi-agent systems because of the need of application and the development of technology. In communication networks and engineering applications, due to signal propagation delays, time delay may exist in the consensus state of systems. In this paper, a concept on delay consensus is first defined, and then the problem of first-order delay consensus in leader-following multi-agent systems is discussed. By designing an appropriate control protocol and using the graph theory, matrix theory and Lyapunov stability theory, a sufficient condition is given to realize delay consensus of the multi-agent systems. Numerical simulations are given to verify the theoretical results.
Phase synchrony in the cerebral infarction electroencephalogram based on the degree of network-links
Authors: Hou Feng-Zhen  , Dai Jia-Fei  , Liu Xin-Feng  , Huang Xiao-Lin  ,   School of Science, China Pharmaceutical University, Nanjing 210009, China;,   Neurological Department, Nanjing General Hospital of Nanjing Military Command, Nanjing 210002, China;,   Institute of Biomedical Electronic Engineering, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
Published: December 2020

Recently, there has been increasing interest in applying graph theory to the quantitative analysis of brain functional networks, while phase synchronization (PS) analysis has been demonstrated to be a useful method to infer functional connectivity with multichannel neural signals, e.g., electroencephalogram (EEG). In this paper, we focus on the case that the number of channels in EEG data is not adequate for the use of graph theory analysis. The degree of network-links (DNLs), an index based on the PS analysis of all the EEG wave pairs, is proposed to study the relevant and the overall characteristics of the brain. With the help of a novel division to the frequency range 0.5–30 Hz, we analyze the DNLs in different frequency bands of the EEG signals. As a comparison, a frequency band analysis of the relative power spectrum is conducted. The results demonstrate that when the cerebral infarction (CI) patients and normal control people are analyzed, there is a need for the reasonable length of EEG data to quantify the differences between different dynamical systems; under a reasonable data length, the frequency band (19–24 Hz) yields the best accuracy for diagnosing CI, which lies within the classical beta band (13–30 Hz); furthermore, only in the 19–24 Hz band, as for the values of relative power spectrum, in each EEG channel, there presents a similar relationship between the CI group and control group. The experimental results suggest that 19–24 Hz should be the optimal range for the diagnosis of CI, further the DNLs calculated within this band serve as an assist indicator in the CI diagnosis.
Squeezing properties of atom laser from two-level atomic Bose-Einstein condensate interacting with two-mode light field
Authors: Li Ming  , Chen Cui-Ling  ,   College of Science, Guilin University of Technology, Guilin 541004, China;,   College of Mathematics and Statistics, Guangxi Normal University, Guilin 541004, China
Published: December 2020

The Hamiltonian operator of a system of two-level atomic Bose-Einstein condensate interacting with two-mode squeezed coherent light field is improved in terms of the lattice-liquid model. The squeezing properties of atom laser in this system are studied. Results show that the two quadrature components of the atom laser can be squeezed periodically, and the maximum depth depends greatly on the initial squeezing factor of the light field. The collapse-revival oscillatory frequency of the atom laser and the quantum Rabi frequency are largely determined by the interaction intensity between the light field and the atoms and by the circle frequency of the light field, respectively.
Ethanol vapor measurement based on tunable diode laser absorption spectroscopy
Authors: Geng Hui  , Liu Jian-Guo  , Zhang Yu-Jun  , Kan Rui-Feng  , Xu Zhen-Yu  , Yao Lu  , Ruan Jun  ,   Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

A method of detecting ethanol vapor concentration using a narrow bandwidth tunable diode laser is studied. The relatively narrow absorption feature in the vicinity of 7180 cm-1 is used as an identification of ethanol vapor. To eliminate the interference of water vapor, multidimensional linear regression analysis is used to solve the problem of multiple molecule absorptions. The detection limit is obtained to be 25 ppm·m experimentally.
Characteristics of the slow and fast light in the band-edge of gain spectrum of the fiber-optic parametric amplification
Authors: Zhao Jian-Peng  , Luo Bin  , Pan Wei  , Yan Lian-Shan  , Zhu Hong-Na  , Zou Xi-Hua  , Ye Jia  ,   School of Information Science and Technology, Southwest Jiaotong University, Chengdu 610031, China
Published: December 2020

Compared to the large slope of the gain spectrum, in this paper, the characteristics of the slow and fast light on the band-edge of gain spectrum of the narrow-band fiber-optic parametric amplification (FOPA) are analyzed. Firstly, we derive the analytical solution of the signal delay under the condition of small-signal gain. Secondly, the characteristics of 10 Gb/s pseudo-random binary sequence pulse signal delay are investigated experimentally under the condition of low pump power (<1 W). Finally, the factors that influence the signal delay, such as pump power, dispersion, nonlinear coefficient, etc. are analyzed. The results obtained in this paper provide a detailed theoretical reference for designing slow and fast delay line in band-edge of gain spectrum of FOPA.
Chirp spread spectrum of orthogonal frequency division multiplexing underwater acoustic communication system based on multi-path diversity receive
Authors: Wang Yi-Lin  , Ma Shi-Long  , Liang Guo-Long  , Fan Zhan  ,   Science and Technology on Underwater Acoustic Laboratory, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Aiming at the problem of traditional orthogonal frequency division multiplexing (OFDM) communication system performance degradation when the channel is subjected to complex multi-path and frequency-selective deeply fading, a chirp spread spectrum (CSS) of OFDM underwater acoustic communication system called CSS-OFDM is proposed in this paper. The CSS-OFDM system spreads the spectrum of traditional OFDM signals, whose sub-carriers are modulated into the same chirp rate, different center frequency orthogonal chirp signals with overlapped bandwidth. Dispreading after underwater acoustic coherent multi-path channel, at the receiving end, the multi-path signals will be expanded from each other in the frequency domain. Applying virtual time reversal mirror technology, the energies of the multi-path signals are focused to complete the multi-path channel diversity receiving. The system performance is improved not only by suppressing the frequency selective fading, but also taking full advantage of multi-path energy of the channel. The effectiveness and reliability of this system are verified through a number of simulations and lake trials.
Research and modeling of the lane-changing behavior on the approach
Authors: Wei Li-Ying  , Wang Zhi-Long  , Wu Rong-Hua  ,   School of Traffic and Transportation, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

In order to analyze the lane-changing behavior on the upstream of the intersections, based on the cellular automata traffic theory, a comprehensive lane-changing model for the traffic flow near the approach is proposed by combining the improved mandatory lane-changing model and discretionary lane-changing model. And the charts describing the scenarios of the space-time and traffic density for the traffic flow near the approach are obtained through simulation based on the comprehensive lane-changing model. Results show that the lane-changing rate at the approach is higher when the traffic density is in the ranges of [0, 0.2] and [0.4, 0.6]. The average vehicle speed is gradually reduced as lane-changing rate increases under median low vehicle stream density, but the variation of vehicle speed with lane-changing rate is not significant under high vehicle stream density.
Investigation of C atom doped armchair (n, n) single walled BN nanotubes with density functional theory
Authors: Wang Yan-Li  , Su Ke-He  , Yan Hong-Xia  , Wang Xin  ,   Key Laboratory of Space Applied Physics and Chemistry, Ministry of Education of China, School of Natural and Applied Sciences, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

Structures and properties of single walled (n,n) BN nanotubes doped with the C atom at different positions are studied by the DFT B3LYP/3-21G(d) theoretical method combined with the one-dimensional (1D) periodic boundary conditions. Their structure parameters, energies, stabilities, band structures and the energy gaps are explored. For the BN nanotubes doped with the C atom at different positions, the C atom concentrations x=1/4n (n=3–9) are examined. It is found that the N site tubes are almost undistorted and more stable. The band gaps are within 1.054–2.411 eV for the C atom doped at the B sites, and those are narrower and within 0.252–1.207 eV for the N sites. All of the doped tubes are shown to be semiconducting and have direct gaps.
Magnetic and electronic properties of fluorographene sheet with foreign atom substitutions
Authors: Gao Tan-Hua  ,   School of Electromechanical Engineering, Wuyi University, Wuyishan 354300, China
Published: December 2020

The magnetic and electronic properties of fluorographene doped with M (M=B, N, P, Si) atoms are studied by employing the first principles calculation based on the spin-polarized density functional theory. The results show that the fluorographene doped with B (or P) atoms can cause the semiconductor-to-metal transitions and the fluorographene with doped N (or Si) atoms is still the semiconductor; the substitutional B, P, and N atoms induce magnetic moments of adjacent carbon atoms. For Si atoms doped fluorographene sheet, semiconductor properties keep unchanged, but the band gap changes.
Effects of niobium on helium behaviors in tungsten：a first-principles investigation
Authors: Wang Xin-Xin  , Zhang Ying  , Zhou Hong-Bo  , Wang Jin-Long  ,   School of Physics and Nuclear Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
Published: December 2020

We investigate the effects of niobium (Nb) on helium (He) dissolution and diffusion behaviors in tungsten (W) using a first-principles method. The results show that Nb can effectively reduce the solution energy of He in the bulk W, which is because of the charge density redistribution. This leads to a strong attraction between He and Nb in W, and thus Nb can serve as a He trapping centre in W. The trapping energy of He is 0.37 eV at the most stable site surrounding Nb atom. It is demonstrated that the diffusion barrier of He towards Nb will decrease with the decreasing of He-Nb distance. This suggests that the kinetic process in which He is trapped by Nb is feasible. Therefore, the presence of Nb will facilitate the nucleating and blistering of He in W.
Influences of Ga gradient distribution on Cu(In, Ga)Se2 film
Authors: Liu Fang-Fang  , Sun Yun  , He Qing  ,   Key Laboratory of Photoelectronic Thin Film Devices and Technique of Tianjin, Nankai University, Tianjin 300071, China
Published: December 2020

One of the traditional methods of preparing Cu (In, Ga) Se2 (CIGS) is the three-step co-evaporation. Using this technique, four elements of Cu, In, Ga, and Se form a parabolic Ga gradient distribution through their inter-diffusion and interaction. In this paper, CIGS films and solar cells with different Ga gradient distributions are prepared through adjusting the temperature of Ga source. The effects of different Ga gradients on structural and electrical properties of CIGS film surface and back surface are studied through a variety of measurement methods. The influences of surface conduction band offset value and back surface electric field on the performance of solar cell are investigated and analysed. Finally, an optimal Ga gradient distribution is obtained, where the spectral response is improved, and the solar cell shows better performance.
Investigation on the electron dynamics of periodic nano ripple formation on fused silica induced by temporally shaped femtosecond laser
Authors: Yang Qing  , Du Guang-Qing  , Chen Feng  , Wu Yan-Min  , Ou Yan  , Lu Yu  , Hou Xun  ,   State Key Laboratory for Manufacturing Systems Engineering, Key Laboratory of Photonics Technology for Information of Shannxi Province, School of Electronics and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

We investigate the electron dynamic process of periodic nano ripples formation on fused silica induced by temporally shaped femtosecond laser. The dynamic model for predictions of ripple period is proposed by introducing the mechanisms of non-linear ionization and surface plasmon polaritons (SPPs) interaction. The quantitative relation between nano ripple period and temporally shaped pulse separation is obtained by using the proposed model. It is revealed that the nano ripple period can be manipulated by adjusting the temporal intervals of the temporally shaped pulses due to the transient adjustment of the wavevector matching process during ripple formation via temporally shaped pulses. The theoretical predictions of the ripple period match well with the experimental data. This study provides the fundamental understanding of transient formation mechanism of ripples, and the precise manipulating of ripple period.
A fast single particle Monte-Carlo method of computing the breakdown threshold of multipactor in microwave device
Authors: Li Yong-Dong  , Yan Yang-Jiao  , Lin Shu  , Wang Hong-Guang  , Liu Chun-Liang  ,   Key Laboratory for Physical Electronics and Devices of Ministry of Education, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

To compute the breakdown thresholds of multipactor in microwave devices, a fast single particle Monte-Carlo (SP-MC) method is presented, which considers the random nature of secondary electrons and their initial energies, phases and angles. With Runge-Kutta method and Furman model, the motion of the electron and the secondary electron yield (SEY) of the wall of the device are computed. An effective SEY is regarded as a criterion to estimate whether multipactor occurs, which is computed by averaging the SEYs for all impacts. As an example, the multipactor in a transmission line composed of parallel plates is investigated with the presented SP-MC method, traditional Monte-Carlo method, statistical theory method and particle-in-cell method separately. The results obtained from the SP-MC method accord well with those from the statistical theory method and particle-in-cell method, including the results of the susceptibility zones, break thresholds on specific products of frequency and gap space. Moreover, the SP-MC method is more adaptive than the statistical theory method, more stable than the traditional Monte-Carlo method and much more efficient than the particle-in-cell method.
Preparation of boron nanowires using AuPd nanoparticles as catalyst and their field emission behavios
Authors: Yang Xiu-Qing  , Hu Yi  , Zhang Jing-Lu  , Wang Yan-Qiu  , Pei Chun-Mei  , Liu Fei  ,   Beijing Polytechnic, Beijing 100029, China;,   Key Laboratory of Display Material and Technology of Guangdong Province, State Key Laboratory of Photo-Electronics Materials and Technology, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China
Published: December 2020

Large-area boron nanowires are successfully prepared by chemical vapor deposition using different compositions of AuPd bimetal nanoparticles as catalysts. The lengths of the boron nanowires are in a range of 5–10 μm and their average diameter is 50 nm. Structural and morphology analysis indicate that these nanowires are single crystalline with a β-rhombohedral structure. The diameters of nanowires gradually decrease with the increase of the concentration of Pd in bimetal nanoparticles. Field emission results show that the field emission properties of boron nanowires can be tuned through using different diameters and densities of boron nanowires.