bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase measurement of femtosecond pulses at different wavelengths
Authors: Zhang Hui  , Lu Juan  , Wen Jin-Hui  , Lei Liang  , Jiao Zhong-Xing  , Lai Tian-Shu  ,   State Key Laboratory of Optoelectronic Materials and Technology, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China;,   School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China
Published: December 2020

The continuous development of femtosecond technique has made it convenient to generate ultrashort pulses with variant structures in different wave ranges. In this paper we optimize the modified-zero-additional-phase spectral phase interferometry for direct electric field reconstruction system, so as to measure femtosecond pulses with different features. Pulses delivered from two femtosecond sources as well as the pulses stretched by an 80 mm-thick BK7 glass block are characterized with this system. The experimental results show sufficiently the versatility of our system.
Chaotic ultra-wideband microwave signal generation utilizing an optical injection chaotic laser diode
Authors: Meng Li-Na  , Zhang Ming-Jiang  , Zheng Jian-Yu  , Zhang Zhao-Xia  , Wang Yun-Cai  ,   Institute of Optoelectronic Engineering, Taiyuan University of Technology, Taiyuan 030024, China;,   State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China
Published: December 2020

The ideal ultra-wideband (UWB) microwave pulses that fully comply with the indoor spectrum mask governed by Federal Communications Commission(FCC Indoor Mask)are generated by using continuous-wave optical injection to a chaotic laser diode. We firstly simulate and demonstrate the photonic generation of the chaotic UWB signal according to the rate equations of laser diode with optical feedback and injection. The simulations display that the -10 dB bandwidth of UWB signal increases with the increases of optical injection strength, frequency detuning, linewidth enhancement factor and with the decrease of bias current of the slave laser, and the UWB signal central frequency changes in a range from 5 to 8 GHz. We further experimentally obtain tunable chaotic UWB microwave signals with a rate up to 500 Mbit/s by tuning optical injection strength when the other parameters are fixed. The experimental results are in accordance with the theoretical analyses.
Applications of molecular dynamics simulation in nonlinear optics
Authors: Zhao Ke  , Liu Peng-Wei  , Han Guang-Chao  ,   College of Physics and Electronics, Shandong Normal University, Jinan 250014, China
Published: December 2020

Organic nonlinear optical molecular materials have a number of important applications in frequency transformation, electrooptic modulation, two-photon absorption and so on. In this paper, we introduce the main applications of molecular dynamics simulation in theoretical study on nonlinear optical properties of organic molecules, including the electric field poling effects, the local field factors, the nonlinear susceptibilities, and the two-photon absorption. In addition, the important roles played by molecular dynamics simulation in the study of solvent and aggregation effects are also illustrated in combination with the recent research.
Simulation of mixing process for size-type binary wet particulate systems in a rotating horizontal drum by discrete element method
Authors: Gao Hong-Li  , Chen You-Chuan  , Zhao Yong-Zhi  , Zheng Jin-Yang  ,   Department of Chemical and Biochemical Engineering, Zhejiang University, Hangzhou 310027, China;,   College of Mechanical and Electrical Engineering, Guangdong University of Petrochemical Technology, Maoming 525000, China
Published: December 2020

Using the four-equation of linear spring-dashpot discrete element method and considering effect of the liquid bridge, the mixing and segregation process of size-type binary wet particulate system in a rotating horizontal drum is simulated. The effect of interstitial liquid on the mixing and segregation process is discussed. To assess the accuracy of the simulation result, some comparisons are made with the experimental date in the literature. The simulation results show that the liquid bridge between particles plays an important role in mixing and segregation process, and that the cohesion force induced by liquid-bridge leads to the formation of agglomerates of particles. As a result, segregation may be mitigated and mixing may be enhanced, and the network distribution of the contact forces is more uniform in wet particulate system.
Jamming phenomena of a two-dimensional frictional granular system under isotropic confining
Authors: Zhang Guo-Hua  , Sun Qi-Cheng  , Huang Fang-Fang  , Jin Feng  ,   Department of Physics, University of Science and Technology Beijing, Beijing 100083, China;,   State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

In this paper, the jamming/unjamming processes of the system composed of 5000 elastic disks with small friction =110-4 are simulated by using the molecular dynamics method. The variations of sidewall pressure P and the height of the first peak of the pair correlation function, g1, with packing fraction are studied. The result shows that the P() curve exhibits an obvious stick-slip-like behavior. The normal force-force correlation function, the tangential force-force correlation function, and the position-position correlation function are found to jump simultaneously during the stick-slip process. By relaxing jammed states obtained as the system undergoes the compression process, we observe that the P is related to -c by the power scaling law P(-c)0.964, although the different sidewall pressures corresponds to different values of c.
Modeling of plasma pattern formation in 110 GHz microwave air breakdown
Authors: Zhou Qian-Hong  , Dong Zhi-Wei  , Chen Jing-Yuan  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

Plasma pattern formation in 110 GHz microwave air breakdown is investigated by numerical solution of fluid-based plasmas equations coupled with the Maxwell equations. It is found that the filamentary plasmas are observed at high pressure, the filamentary plasmas transit to diffuse plasma at medium pressure, and the diffuse plasma is obtained at low pressure. The plasmas region propagates toward the microwave source. The distribution of initial electrons influences merely plasmas pattern at first stage, but not final plasmas pattern. The movements in the directions parallel and vertical to electric field are different. Due to the strong electric field at the poles of the plasmas region, the plasmas are elongated in the direction of electric field, forming the filamentary plasmas at much low pressure in E plane.
Effect of magnetized secondary electron on the characteristics of sheath in Hall thruster
Authors: Duan Ping  , Li Xi  , E Peng  , Qing Shao-Wei  ,   Department of Physics, Dalian Maritime University, Dalian 116026, China;,   College of Physics Science and Technology, Dalian University, Dalian 116622, China;,   Department of Electrical Engineering, Harbin Institute of Technology, Harbin 150001, China;,   School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

In order to investigate the effects of the inner wall secondary electron emission on the performance of Hall thruster, a hydrodynamic model is used to study the characteristics of plasma sheath considering secondary electron magnetization. The Bohm criterion of the magnetized plasma sheath is obtained. The structures of plasma sheath in Hall thruster with different magnetic field magnitudes and directions, different secondary electron emission coefficients and different plasma species are discussed. Simulation results indicate that both particle density and wall potential increase while the sheath thickness decreases with the augment of secondary electron emission coefficient. The sheath potential and the particle density increase with the magnitude and azimuth angle of magnetic field increasing. Both the sheath thickness and the wall potential are different in different plasma species. These research results provide a theoretical explanation for the magnetism-ampere characteristic of the Hall thruster.
Characteristics of atmospheric pressure air uniform discharge generated by a plasma needle
Authors: Li Xue-Chen  , Yuan Ning  , Jia Peng-Ying  , Chang Yuan-Yuan  , Ji Ya-Fei  ,   College of Physics Science and Technology, Hebei University, Baoding 071002, China
Published: December 2020

Cold plasma generated by atmospheric air discharge has wide application prospect in industry because it does not need vacuum equipment and mass production is possible. In this paper, a stable uniform discharge is generated in open air by a plasma needle. Discharge mechanism is investigated by optical method, and plasma parameters are given by the spatially resolved measurement of emission spectrum from the discharge. Results show that the discharges have two modes. One is a corona discharge mode and the other is plasma plume mode. In the stable plasma plume mode, a strong emission area and a weak emission one can be distinguished from each other. The development velocity of the weak emission area is much faster than that of the strong emission area. Furthermore, the electron energy and the plasma density in the weak emission area are also bigger than those in the strong emission area. Therefore, the discharge in the strong emission area is dominated by Townsend mechanism, while that in the weak emission area is dominated by streamer discharge. Gas temperature and vibration temperature are also studied in this paper. The experimental results are of great importance to the industrial applications of atmospheric pressure discharge.
Simulation and experimental research of melt convection on dendrite morphology evolution
Authors: Shi Yu-Feng  , Xu Qing-Yan  , Liu Bai-Cheng  ,   Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

The existence of forced and natural melt convections in the liquid in front of dendritic tip will Change the thickness of diffusion layer, which can significantly influence the dendrite morphology. Using the cellular automaton method and considering the influences of melt convection and heat transfer on microstructure evolution, a new numerical model is established by coupling the Navier-Stokes equations, the heat transfer equation and the solute convection and diffusion equation. The influences of forced and natural melt convection on dendrite morphology evolution are investigated by this model. The three-dimensional simulations reproduce the equiaxed dendrite growth, and reveal the influence of convection on dendritic growth rate and tip radius. The effect of natural convection on columnar dendrite growth during directional solidification of NH4Cl-H2O solution is simulated via the model. Experimental validation of this solidification process is performed and compared with simulation results. The simulation results accord well with experimental measurements. Hence, the model is reliable and can be extended to the prediction of the behavior of dendrite growth in real alloys.
Simulation of incipient spallation experiments of high purity aluminum based on a single void growth model
Authors: Wang Yong-Gang  , Hu Jian-Dong  , Qi Mei-Lan  , He Hong-Liang  ,   Mechanics and Materials Science Research Center, Ningbo University, Ningbo 315211, China;,   School of Science, Wuhan University of Technology, Wuhan 430070, China;,   Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

By means of a single void growth model, finite element simulations of incipient spallation experiments of high-purity aluminum under different plate impact velocities are carried out. The relationship between the influence of void growth in the sample on wave propagation and the feature of free surface velocity profile is discussed. By analyzing the change of stress field around the void, the occurrence of pullback signal in free surface velocity profiles is attributed to the local unloading wave effect caused by void growth in the sample, which cannot indicate the whole spallation of materials. Free surface velocity profiles and relative void volumes are simulated for different impact velocities and the simulation results are in good agreement with experimental results, which indicates that the stochastic damage evolution in incipiently spalled sample can be described by a single void growth in cell model.
Monte Carlo simulations of the relaxation dynamics of the spatial relaxation modes in the molecule-string model
Authors: Fan Xiao-Hui  , Zhao Xing-Yu  , Wang Li-Na  , Zhang Li-Li  , Zhou Heng-Wei  , Zhang Jin-Lu  , Huang Yi-Neng  ,   Laboratory of Phase Transitions and Microstructures in Condensed Matter Physics of Xinjiang, College of Physical Science and Technology, Yili Normal University, Yining 835000, China;,   National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing 210093, China;,   Research Department, Xinjiang Educational University, Urumqi 830043, China
Published: December 2020

According to the molecule-string model for glass transition, a more exact Monte Carlo protocol to simulate all the spatial relaxation modes (SRMs) of the string are proposed. The variations of the simulated relaxation times of the SRMs with temperature and string length are consistent with the predictions of the string relaxation equation of the model, i.e. the theretical predictions and the simulation results verify each other. It should be pointed out that the necessary condition of molecule string used as a collective unit in liquid is that the qualitative characteristics of the SRMs cannot be changed when the inter-string interactions are taken into account. This needs to study the coupling between the SRMs, but till now, the corresponding exact solutions have not been achieved, and only the self-consistent relaxation mean-field method is vailable. Therefore, the present simulation protocol will provide a necessary basis to study the coupling between the SRMs of neighboring strings, including the feasibility of the mean-field method.
A Brownian dynamic simulation to verify the effective hard-sphere model criterion for the formation of charged colloidal crystals
Authors: Gu Ling-Yun  , Xu Sheng-Hua  , Sun Zhi-Wei  ,   Key Laboratory of Microgravity, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The mechanism for the formation of colloidal crystals in charge-stabilized colloids is more complicated than that of hard-sphere colloidal crystals. And there is still lack of available criterion for the formation of charged colloidal crystals. The effective hard-sphere model suggests a criterion in which the effective diameter is used as a crucial parameter. In order to test the validity of this criterion, the characteristics of charged colloidal crystals with different effective diameters are investigated using Brownian dynamics simulations in this study. The crystallization behaviors with different geometric particle diameters and repulsive forces are also studied with some fixed effective diameters. In the simulation, the time evolution of crystallization process and the crystal structure during the simulation are characterized by means of the radial distribution functions and bond-order parameters. The results show that the effective hard-sphere model criterion has its reasonableness to some extent. However, the effective diameter cannot be used as the only parameter that influences the formation of charged colloidal crystals. The influence of other parameters should also be taken into account, which indicates that the criterion is one-sided.
Thermal stability of Si-doped glow discharge polymer films
Authors: Zhang Ying  , He Zhi-Bing  , Li Ping  , Yan Jian-Cheng  ,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China;,   Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
Published: December 2020

The Si-doped glow discharge polymer (Si-GDP) films are deposited by glow discharge polymerization technology at different tetramethylsilane (TMS) flows. The chemical structure, the composition and the thermal stabilities of Si-GDP films are analyzed by the Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and thermal gravimetric analysis. The results show that the Si content increases from 0 to 16.62%, when the flow of TMS changes from 0 to 0.06 cm3/min. The relative content of SiC, SiH, SiO, SiCH3 increases with TMS flow rate increaseing. As TMS flow increases, the thermal stability of Si-GDP film becomes good.
A first principles study on tetragonal distortion, magnetic property and elastic constants of Pd2 CrAl Heusler alloy
Authors: Zhao Kun  , Zhang Kun  , Wang Jia-Jia  , Yu Jin  , Wu San-Xie  ,   School of Materials Science and Engineering, Southeast University, Nanjing 211189, China;,   Key Laboratory of Advanced Metallic Materials of Jiangsu Province, Southeast University, Nanjing 211189, China;,   School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
Published: December 2020

Tetragonal distortion, magnetism and elastic constants of Pd2CrAl Heusler alloy are calculated by first principles based on the density function theory with projector augmented wave pseudopotential. Analysis of tetragonal distortion shows that there is a local minimum total energy at c/a1.20, which corresponds to a stable martensitic phase. The magnetic moments of formula unit cells for L21 and tetragonal structure are 3.825B and 3.512B, respectively. There is very strong hybridization between Pd and Cr, and magnetism originates mainly from the 3d-t2g and 3d-eg subbands of Cr atom in the two structures. Elastic constants of both L21 and tetragonal structure of Pd2CrAl satisfy their stability conditions, respectively.
Giant magnetoresistance in IrMn based antiferromagnetic spin valve
Authors: Jia Xing-Tao  , Xia Ke  ,   Department of Physics, Beijing Normal University, Beijing 100875, China
Published: December 2020

According to the parameter-free first principles calculations, we investigate the spin polarized transport in antiferromagnetic spin valve (AFSV) based on noncollinear IrMn. The giant magnetoresistance (GMR) in Co/IrMn/Cu(111) with L12-type IrMn shows three-fold rotational symmetry, which is easy to be distinguished from the GMR of normal ferromagnetic spin valves. Moreover, GMR based on -phase IrMn with current-in-plane (CIP) structure shows that GMR is 7.7%, around two time larger than that in current-pendicular-to-plane (CPP) structure (3.4%). Our study demonstrates that the AFSV CIP structure possesses a larger GMR effect than the CPP structure, and the GMR effect in AFSV based on noncollinear antiferromagnetic structure is larger than that based on collinear antiferromagnetic structure such as FeMn.
Influences of the size and breadth of potential barrier on electronic scattering cross-section in spherical nanometer system
Authors: Wu Qiang  , Zheng Rui-Lun  ,   School of Electrical and Electronic Engineering, Chongqing University of Arts and Sciences, Chongqing 402160, China
Published: December 2020

Under the condition of the spherical square potential model and the effective mass approximation, the electronic scattering cross-section and the electronic probability distribution are obtained in an open-type spherical nanometer system, and the influences of the size and the width of potential barrier on electronic scattering cross-section, resonance energy and resonance width are discussed. The results show that there exist one maximum and one minimum in the distribution curve of the electronic scattering cross-section versus energy, and the maximum of electronic energy probability distribution curve is between the maximum and the minimum of energy in the scattering cross-section curve; the scattering cross-section increases with the increase of r0, the inner radius, and the scattering cross-section curve will change from smoother to sharper with the increase of r0; the scattering cross-section will enlarge with , the width of potential barrier, but it will become abnormal when is between 1.4aCdS and 1.7aCdS; when =1.6aCdS, the scattering cross-section is extremely small; El, the electronic resonance energy changing with , is related to the electronic state, while l, the electronic resonance width will decrease with the increase of ; no matter what is, both El and l satisfy the uncertainty principle of energy and time.
First principles study of electronic and optical properties of Er-doped silicon nanoparticles with different densities
Authors: Wang Ying-Long  , Wang Xiu-Li  , Liang Wei-Hua  , Guo Jian-Xin  , Ding Xue-Cheng  , Chu Li-Zhi  , Deng Ze-Chao  , Fu Guang-Sheng  ,   College of Physics Science and Technology, Hebei University, Baoding 071002, China
Published: December 2020

The structural stability, the electronic and the optical properties of Er-doped silicon nanoparticles are investigated by first principles based on the density functional theory. The results show that the structure is more stable when the doping concentration of Er atoms is smaller in silicon nanoparticles. The doping of Er atom in silicon nanoparticle introduces the impurity levels which result in the narrowing of band gap. A strong absorption peak occurs in the low-energy region of Er-doped silicon nanoparticles, and the intensity of the absorption peak decreases gradually, even disappears with doping concentration decreasing. The study provides the theoretical basis for the design of silicon-based materials.
Effects of curvature on the electronic structures of single-walled carbon nanotubes
Authors: Qin Wei  , Zhang Zhen-Hua  , Liu Xin-Hai  ,   School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410004, China
Published: December 2020

Based on the energy dispersion relation involving curvature effects for the single-walled carbon nanotube (SWCNT), the electronic velocity and the effective mass of the lowest conduction band for the SWCNT are computed and they are compared with the results without consideration of the curvature effects. The analysis shows that the influences of the curvature effect on the electronic velocity and effective mass depend on type of SWCNT, that is, the metallic zigzag-SWCNT is most sensitive to curvature effect, armchair-SWCNT is second most sensive to curvature effect, and the semiconducting zigzag-SWCNT is poorly sensitive to curvature effect. These findings suggest that curvature effects have the largest effect on the electronic structure and the low-bias transport behaviors of the metallic zigzag-SWCNT,a moderate effect on those of the armchair-SWCNT, and the smallest effect on those of the semiconducting zigzag-SWCNT, which are in good agreement with experimental measurements and the calculated results from the density-functional theory.
Electronic structure and magnetism of Cr-doped ZnO nanowires
Authors: Zhang Fu-Chun  , Zhang Wei-Hu  , Dong Jun-Tang  , Zhang Zhi-Yong  ,   College of Physics and Electronic Information, Yan’an University, Yan’an 716000, China;,   School of Information Science and Technology, Northwest University, Xi’an 710127, China
Published: December 2020

According to the spin-polarized density functional theory, we study the electronic structures, the magnetic and the optical properties of Cr-doped ZnO nanowires. The calculated results show ferromagnetic coupling for Cr atoms substitution for Zn atoms in ZnO nanowires along the [0001] direction, and the antiferromagnetic coupling with Cr-doped in ZnO nanowires along the [1010] and [0110] directions. The results reveal that the magnetic coupling state near the Fermi level gives rise to such a spin splitting phenomenon near the Fermi level, which indicates that Cr 3d and O 2p orbitals have intense hybrid effects. In addition, the spin electronic density results indicate that system magnetic moments are generated mainly by the unpaired 3d electrons of Cr atoms and are also related to the electron configuration. Moreover, the results of optical properties show that the obvious absorption peaks are observed in the far ultraviolet and the near ultraviolet regions and there is a red shift phenomenon in the ultraviolet region. These results indicate that the Cr-doped ZnO nanowires could be a promising dilute magnetic semiconductor material.
Hydrothermal controlled synthesis and luminescence properties of NaLa(MoO4)2∶Eu3+ microcrystals
Authors: Sun Jia-Yue  , Cao Chun  , Du Hai-Yan  ,   School of Science, Beijing Technology and Business University, Beijing 100048, China
Published: December 2020

Eu3+ doped NaLa(MoO4)2 microcrystals with different sizes are synthesized by a mild hydrothermal method, and the morphologies of the microcrystals can be easily controlled by adjusting the volume ratio of ethylene glycol to water and the aging time. Uniform high-quality shuttle-like microcrystals with an average length of 2.0 m are obtained under the hydrothermal condition of 180℃ for 16 h. From the emission spectra of NaLa(MoO4)2∶Eu3+ microcrystals, it is concluded that the dopant Eu3+ ion occupies a La3+ site. It is indicated that the concentration quenching of the emission peak at 613 nm of Eu3+ is ascribed to the electric dipole-electric quadrupole interaction, and the cross relaxation process of Eu3+(5D1 ) + Eu3+(7F0 ) Eu3+( 5D0 ) + Eu3+(7F3) appear.
The non-adiabatic effects of NaI molecule
Authors: Yao Hong-Bin  , Zheng Yu-Jun  ,   School of Physics, Shandong University, Jinan 250100, China;,   Department of Basic Courses, Xinjiang Polytechnical College, Urumqi 830091, China
Published: December 2020

We investigate the dynamic evolution of wave packet under the coupled diabatic potentials via employing the time-dependent wave packet approach. The wave packet splits in the crossing region due to the influence of non-adiabatic effects. In our studies, it is found that the non-adiabatic effects are very important to the dissociation of NaI molecule, and it becomes markedly with the increase of evolutionary time. Moreover, our study shows that the mean packet position 〈R(t)〉 and the classical trajectory R(t) are nearly coincident and the dissociation probability is dependent on the laser wavelength.
Design of X-band tri-axial relativistic klystron amplifier
Authors: Liu Zhen-Bang  , Huang Hua  , Jin Xiao  , Chen Huai-Bi  ,   Department of Engineering Physics, Tsinghua University, Beijing 100084, China;,   Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

In this paper, we analyze the interaction between electron beam and microwave in the coaxial cavity, and obtain the coupling coefficient of the coaxial cavity and the electronic load conductance. The X-band tri-axial relativistic klystron amplifier is designed and simulated. Simulation results show that coaxial cavity can increase the efficiency. With an input microwave power of 70 kW, electron beam voltage of 600 kV, and electron beam of 5 kA, we obtain a microwave with a power of 1.1 GW, frequency of 9.37 GHz, and an efficiency of 37%.
Use of the two-point-source -P1 approximation model for recovery of optical parameters in biological tissue
Authors: Qi Bei-Bei  , Liu Ying  , Jia Guang-Yi  , Liu Xiao-Jun  ,   College of Science, Tianjin University, Tianjin 300072, China;,   Key Laboratory of Opto-electronic Information Science and Technology of Ministry of Education, College of Precision Instrument and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

Based on a theoretical model for spatial diffusion reflection with two-point-source -P1 approximation to the radiative transport equation for a semi-infinite homogeneous turbid medium, the optical absorption coefficient a, reduced scattering coefficient ' s, and the second-order parameter of the medium are recovered from the measurement data of the reflectance by the nonlinear least squares method. The results show that the two-point-source -P1 approximation can give more satisfactory results for describing irradiance distribution close to source when the source-detector separation is larger than one transport mean free path. We can also obtain the anisotropy factor g according to the relationship between and ' s. This study is of great significance for the measurement of the optical properties of biological tissues and the application of diffuse reflectance spectroscopy technology.
The self-trapping of superfluid Fermi gases in the Bose-Einstein condensation regime and in unitarity
Authors: Wang Wen-Yuan  , Yang Yang  , Meng Hong-Juan  , Ma Ying  , Qi Peng-Tang  , Ma Yun-Yun  , Duan Wen-Shan  ,   Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China
Published: December 2020

In the mean-field theory and two-mode approximation, we study the self-trapping of superfluid Fermi gases in the BEC regime and in unitarity by observing the evolution of the population imbalance with time and the variation of the average of population imbalance with several non-linear interaction parameters. The high-frequency modulations of both the symmetric double-well potential and the potential well are studied. The boundary conditions of the self-trapping and non-self-trapping are given. We find that high-frequency modulation in a certain range of modulation can make the self-trapping phenomenon easier to achieve. Finally, we study the influence of the initial value on self-trapping, and find that the increase of the absolute of the initial value can make the self-trapping more conducive to the realization.
Parameter joint estimation of phase space reconstruction in chaotic time series based on radial basis function neural networks
Authors: Chen Di-Yi  , Liu Ye  , Ma Xiao-Yi  ,   Department of Electrical Engineering, College of Water Resources and Architectural Engineering, Northwest A & F University, Yangling 712100, China
Published: December 2020

In this paper, we propose a joint estimation method of two parameters for phase space reconstruction in chaotic time series, based on radial basis function (RBF) neural networks. And we obtain the best estimation values, according to some objective standards. Furthermore, The single-step and multi-step RBF prediction model is used to estimate the best embedding dimension and delay time, and Lorenz system is selected as an example. Finally, the estimation values are tested in the original model. The simulations show that we can obtain the best estimation values through the method, and the prediction accuracy is significantly improved.
Overdamped fractional Langevin equation and its stochastic resonance
Authors: Gao Shi-Long  , Zhong Su-Chuan  , Wei Kun  , Ma Hong  ,   College of Mathematics, Sichuan University, Chengdu 610065, China;,   College of Mathematics and Information Science, Leshan Normal University, Leshan 614000, China
Published: December 2020

By choosing an appropriate damping kernel function of generalized Langevin equation, fractional Langevin equation (FLE) is derived in the case of overdamped condition. With the theory of anomalous diffusion and the memory of fractional derivatives, the physical meaning of FLE is discussed. Moreover, the internal mechanism of stochastic resonance about FLE is obtained. Finally, the numerical simulation shows that in a certain range of the order, stochastic resonance appears in FLE, and it is evident that the SNR gain in fractional Langevin equation is better than that of the integer-order situation.
The similarity between the distribution functions of characteristic quantities for noise signal
Authors: Lin Ying-Lu  , Yan Zhen-Gang  , Yang Juan  , Wang Chun-Yong  , Bian Bao-Min  ,   Department of Information Physics and Engineer, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

For studying the statistical properties of characteristic quantities in noise signal, such as the amplitude of extreme, the amplituds of the rising edge and the falling edge, the interval between extreme points and the product value of the quantities,the background noise signal sequence values of photoelectric sensor in suspended particle counter are recorded by using the high-speed data acquisition card. The results show that the statistical distribution of these characteristic quantities match well with the form of the log-normal distribution, with natural number l used as the independent variable. The statistical distributions of characteristic quantities show a high degree of similar characteristics. Based on this statistical similarity the transform relationship between the independent variables corresponding to different characteristic quantities by power function can be derived. The similarity between statistical distribution functions of characteristic quantities can be understood as a kind of performance of statistical fractal characteristics for noise signal collections.
Method for improving the accuracy of step height measurement based on optical frequency comb
Authors: Zhang Ji-Tao  , Wu Xue-Jian  , Li Yan  , Wei Hao-Yun  ,   State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments and Mechanology, Tsinghua University, Beijing 100084, China
Published: December 2020

An improved method of step height measurement by optical frequency comb and tunable diode laser is presented. The tunable diode laser is phase locked to the optical frequency comb, so that the output wavelength of the laser can be locked and measured in a high accuracy. Based on the principle of variable synthetic wavelength chain, the step height can be measured by tuning the wavelength of the locked tunable diode laser. This method can be used to eliminate the effect of the synthetic wavelength error on the measurement uncertainty of the step height. The stability of the phase locked laser is tested by locking a tunable diode laser to an optical frequency comb for about 5000 s. It is shown that the frequency stability of the phase locked laser is 1.810-12. The uncertainty of the step height measurement by this method is estimated to be 7.9 nm accordingly. Moreover, the measurement result of the step height can be traced to the time and frequency standard.
Analysis of shape evolution for Pt isotopes with relativistic mean field theory
Authors: Wang Gang  , Fang Xiang-Zheng  , Guo Jian-You  ,   School of Physics and Material Science, Anhui University, Hefei 230039, China
Published: December 2020

The relativistic mean field theory is used to investigate the shape evolution of Pt isotopes. The calculated binding energy and deformation parameter 2 are consistent with those obtained in experiment. The potential energy surfaces and the single particle levels show the shape evolution for Pt isotopes. From N=88 to N=126, the shapes for Pt nuclei evolve from spherical shapes to X(5), and then to shapes of stable quadruple deformation, finally back to the spherical shapes. In detail, 166-172Pt are spherical. 174Pt and 192-196Pt possess the X(5) symmetry. 176-190Pt are deformed nuclei. 204Pt holds spherical shape. These results in agreement with the experimental observations.
Study on estimating efficiency of multistage depressed collector in traveling wave tubes
Authors: Li Fei  , Xiao Liu  , Liu Pu-Kun  , Yuan Guang-Jiang  , Yi Hong-Xia  , Wan Xiao-Sheng  ,   Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Science, Beijing 100190, China;,   Graduate University of Chinese Academy of Science, Beijing 100190, China
Published: December 2020

In a traveling wave tube, efficiency of multistage depressed collector (MDC) is very important because it is closely related to total efficiency. The correct estimate of the efficiencies of MDC and TWT can help us predict TWT's whole function and provide a theoretical guidance for developing pertinent software, which therefore plays an important role in optimizing MDC and improving TWT total efficiency. Although formula for predicting MDC efficiency was given by Kosmahl in 1980, whose estimation is much higher than the measured value, a more accurate formula is still necessary. Firstly, the concept of dissipated common difference is used in this paper to estimate the efficiencies of MDC and TWT and then new estimate formulas are obtained by making a model of arithmetic triangular energy distribution for spent beam. It is expected that new formulas give predictions closer to the measured values than the Kosmahl's evaluation. Finally, expression for optimal MDC electrodes is given on the basis of two extreme values, i.e., maximal MDC efficiency and minimal total dissipated energies on all electrodes. The prediction from the expression is reasonable and accurate.
Analysis of figure of merit for thick pinhole imaging
Authors: Song Gu-Zhou  , Ma Ji-Ming  , Wang Kui-Lu  , Zhou Ming  ,   Northwest Institute of Nuclear Technology, Xi'an 710024, China
Published: December 2020

A figure of merit (FOM) for thick pinhole imaging and its formula are developed. The FOM can describe the total spatial resolution and sensitivity of thick pinhole imaging. Based on the penetration model, the root-mean-square of point spread function and the effective diameter at the center are derived. FOMs at the total and effective field of view are calculated. Based on the figures, the characteristics of thick pinhole imaging are discussed.
Polarization properties of one-dimensional photonic crystal tunneling mode containing metamaterials
Authors: Li Wen-Sheng  , Luo Shi-Jun  , Huang Hai-Ming  , Zhang Qin  , Shi Du-Fang  ,   Department of Basic Science Hubei University of Automotive Technology, Shiyan 442002, China
Published: December 2020

An (AB)N(BA)N-type one-dimensional photonic crystal is made from common material A(SiO2) and electric single-negative material B. Numerical calculation results indicate that there is a very sharp tunneling model at 1907.3 nm of the original band. When the incident angle increases, the transmittance and the full-width half-maximum of the tunneling mode remains the same, but its position is blue shifted. The value of |d/d| turns larger when the incident angel is in a range from 15 to 65. When permeability of B medium B increases from 5 to 10, the position of the tunneling model is only red shifted. When geometric thickness of the dielectric increases, the transmittance of the tunneling model remains unchanged, but its position is red shifted obviously and its full-width half-maximum increase slightly.
Theoretical research of the influence of operation mode of chemical oxygen-iodine laser on its pulsing
Authors: Li Guo-Fu  , Duo Li-Ping  , Jin Yu-Qi  , Yu Hai-Jun  , Wang Jian  , Wang De-Zhen  , Sang Feng-Ting  ,   Key Laboratory of Chemical Laser, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China;,   School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China
Published: December 2020

One-dimensional pre-mixed model for a pulsed chemical oxygen-iodine laser is presented according to the reaction mechanism in chemical oxygen-iodine laser. The influences of gas temperature of 150-450 K and pressure of 660-2660 Pa on single pulse energy, pulse duration and peak power are studied. The internal reason of the influences of pressure and temperature on laser characteristics is analyzed. The results show that the higher laser peak power can be obtained in the case of gas temperature of 150 K and pressure of 1330 Pa than in the case of 400 K and 2660 Pa. Thus an efficient pulsed chemical oxygen-iodine laser is promising if the abundant atomic iodine is generated instantaneously. The approach to atomic iodine generation does not disturb the state of supersonic flow.
Lattice Boltzmann method for an advective transport equation coupled with incompressible flow field
Authors: Su Jin  , Ouyang Jie  , Wang Xiao-Dong  ,   Department of Applied Mathematics, Northwestern Polytechnical University, Xi'an 710129, China
Published: December 2020

In this paper, an improved numerical scheme based on the lattice BGK method (LBM) is proposed for solving the advective transport equation coupled with an incompressible flow. We utilize the LBM to solve the equations of flow field and build a second order discrete scheme for the advective transport equations using the probability density function of LBM. Meanwhile, the validity of the method is verified by an advective transport in a planar channel flow. Numerical results show that the method reduces the numerical dissipation efficiently and it involves consistently smaller memory requirements compared with previous studies.
Effect of physical properties of polymer on ion implantation
Authors: Huang Yong-Xian  , Lü Shi-Xiong  , Tian Xiu-Bo  , Yang Shi-Qin  , Fu Ricky  , Chu K Paul  , Leng Jin-Song  , Li Yao  ,   State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China;,   Department of Physics and Materials Science, City University of Hong Kong, Hong Kong, China;,   Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

Plasma immersion ion implantation (PIII) of polymer materials is inherently difficult because the voltage across the sheath is reduced by the voltage drop across the insulator due to dielectric capacitance and charge accumulating on the insulator surface. The spatiotemporal evolutions of plasma sheath, energy and dose of ions are simulated by particle-in-cell (PIC) model for ion implantation into insulator materials. Statistical results can be achieved through scouting each ion motion in the plasma sheath. Based on the PIC model, the secondary electron emission (SEE) coefficient is determined according to the instant energy of implanting ions. Effects of thickness, dielectric constant and SEE coefficient on sheath evolution, dose and energy of incident ions are studied. The ion implantation doses and the share of high-energy incident ions are basically equivalent to the case of implantation of conductor ions, when the polymer thickness is less than 200 m, relative dielectric constant is more than 7, and SEE coefficient is less than 0.5. The numerical simulation of ion implantation into polymer can effectively provide a scientific and experimental basis for PIII of insulators and semiconductors.
The three-dimensional numerical simulation study of H transmission and negative hydrogen ions production
Authors: Yang Chao  , Liu Da-Gang  , Wang Xue-Qiong  , Wang Xiao-Min  , Xia Meng-Zhong  , Peng Kai  ,   University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

The negative hydrogen ion source neutral particle transmission characteristics and the physical processes of the negative hydrogen ion extracted from plasma grid surface are analyzed. The influence of the extraction hole transfer rate which leads to hydrogen atom transmission is studied. A physical phenomenon of collision and reflection between H and different attribution conductor walls is explored. Then based on CHIPIC software platform, a full three-dimensional PIC-MCC simulation algorithm, in which the H transmission and the physical process of negative hydrogen ion production can be simulated, is successfully developed. It is verified by the simulation of JAEA 10A model. While the simulation reaches a steady state, the average energy of H is about 0.57 eV and H presents +Y drift. The non-uniform H beam bombarding the extraction wall leads to the spatial nonuniformity of negative hydrogen ions. These simulation results are consistent with those given in the literature, thereby verifying the reliability of the algorithm.
Model analysis of experiments of implosion symmetry on Shenguang-Ⅱ and Shenguang-Ⅲ prototype laser facilities
Authors: Jing Long-Fei  , Huang Tian-Xuan  , Jiang Shao-En  , Chen Bo-Lun  , Pu Yu-Dong  , Hu Feng  , Cheng Shu-Bo  ,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The analysis and control of implosion symmetry of fuel capsule is one of the most important issues in inertial confinement fusion (ICF), and many experiments and simulations on it have been done. Here we use a simple model on implosion symmetry in ICF to analyze the best lengths of the hohlraum and distortions of capsule on Shenguang-Ⅱ and Shenguang-Ⅲ prototype laser facility. It is shown that the calculated best lengths agree with the ones obtained in experiment and the calculated capsule distortions are also close to experimental measurements. The validated model may give some references to the future experiments of implosion symmetry on Shenguang-Ⅲ laser facility.
The mechanism of the anomalous variation of grain size for Fe-based nanocrystalline alloys
Authors: Yang Wei-Ming  , Liu Hai-Shun  , Dun Chao-Chao  , Zhao Yu-Cheng  , Dou Lin-Ming  ,   School of Sciences, China University of Mining and Technology, Xuzhou 221116, China;,   State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou 221008, China;,   School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

The magnetic properties of the Fe-based nanocrystalline alloys are determined mainly by their grain sizes, and the mechanism of the variation of grain size with annealing temperature is an important issue in the study of nanocrystalline alloys. In this paper, the relationships between grain size and annealing temperature for these alloys within the primary crystallization temperature (Tx1) and the secondary crystallization temperature (Tx2) for 1 h are investigated, and a corresponding model is proposed. The physical mechanism of the fact that the grain size first decreases and then increases with the increase of annealing temperature is explained by using this model. It is found that the grain size has a minimum value when these alloys are isochronally annealed at the temperature near 0.6 times that of the melting point. Theoretical analysis results are found to be in agreement with the experiments data within the investigated temperature range. This investigation provides a means to obtain the smallest grain size quickly.
Influence of radio frequency power on the structure and optical properties of glow discharge polymer films
Authors: Niu Zhong-Cai  , He Zhi-Bing  , Zhang Ying  , Wei Jian-Jun  , Liao Guo  , Du Kai  , Tang Yong-Jian  ,   Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China;,   The Centre of Laser Fusion Research, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Taking advantage of triple radio frequency, hydrocarbon polymer films are fabricated at different powers by the glow discharge polymerization technology. The deposition rates, the chemical structures, the atomic ratios and the optical properties are studied. The thicknesses of glow discharge polymer (GDP) films are measured by the surface profiler technology. The chemical compositions of GDP films are characterized by FT-IR spectra and element analysis. The optical properties of GDP films are investigated by UV-VIS spectra. With RF power increasing from 20 W to 60 W, the deposition rate of GDP films first increases 0.34 μ m/h, then decreases after the RF power reaches 40 W. In visible light area more than 500 nm, the optical transmittances of all GDP films are more than 90%.The optical band gaps of GDP films first decrease, then reaches the minimum at the RF power of 50 W, then increases when the RF power increases from 20 W to 60 W.