bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation study on a negative refractive index material with high transmission at 748 THz——The violet end of the visible region
Authors: Zhuo Shi-Chuang  , Yan Chang-Chun  ,   徐州师范大学物理与电子工程学院，徐州  221116
Published: December 2020

A left-handed material composed of unit cells of three-layered square nanoflake with four edges gapped is proposed in this paper. The S-parameters of the unit cell are caculated in the numeric simulation, and the property parameters such as the retrieved complex refractive index n, permittivity ε and permeability μ,etc. are analyzed. It is shown that, the frequency band in which the refractive index of this structure being negative lies from blue in the visible region to near ultraviolet, and the peak of negative refractive index lies at 748 THz, namely the violet end of the visible region. And the figure of merit of the material is 154, so it may have practical applications because of its low loss and high transmission.
Particle distribution and numerical stability in smoothed particle hydrodynamics method
Authors: Liu Mou-Bin  , Chang Jian-Zhong  ,   (1)中北大学机电工程学院,太原 030051; (2)中国科学院力学研究所,北京 100190
Published: December 2020

Smoothed particle hydrodynamics(SPH) is a Lagrangian meshfree particle method, and has been widely applied to different areas including incompressible or pseudo-incompressible flows with multiphase interfaces and moving boundaries. In this paper, an instability problem has been identified when the conventional SPH method is applied to modeling the Poiseuille flow problem at long-term simulations. It is found that this instability resulted from the particle inconsistency inherent to the SPH method, which originates from the discrete particle approximation and is a fundamental cause for poor approximation accuracy. A new particle approximation approach has been used to restore the particle consistency. We show that this particle consistency restoring approach can produce stable solutions for both regular and irregular particle distributions even at long-term simulations.
Quantum chaos and the dynamic properties of single-particle coherence in Dicke model
Authors: Song Li-Jun  , Yan Dong  , Gai Yong-Jie  , Wang Yu-Bo  ,   (1)长春大学理学院，长春 130022; (2)长春理工大学理学院，长春 130022
Published: December 2020

The Dicke model displays quantum chaotic dynamic properties in the without-rotating-wave approximation. We explore the dynamic properties of the single-particle coherence in Dicke model by using the first-order temporal correlation function and numerical simulation. The results reveal that the first-order temporal correlation function decays very rapidly when the initial coherent state is centered in chaotic regions, but rather slowly when the initial coherent state is centered in regular regions. This indicates that the single-particle coherence is highly sensitive to initial states, and the classical chaos suppresses quantum coherence. The mean single particle coherence during the evolution is studied, and a better quantum-classical correspondence is obtained. Finally, the dynamics of single-particle coherence in the whole phase space is investigated, which reveals the chaotic and regular structures of the phase space more clearly.
Calculation of the metric in the five-dimensional spacetime
Authors: Shao Liang  , Li Miao  , Qin Zheng-Hui  , Han Jin-Zhu  , Shao Dan  ,   (1)江汉大学物理与信息工程学院,武汉  430056; (2)武汉科技大学理学院,武汉  430065
Published: December 2020

This paper introduces the Wheeler-Dewitt (W-D) equation in the five-dimensional R+R2 theory of gravity, and gets solutions of the W-D equation by separation of variables. Using the Kaluza-Klein theory, the Robertson-Walker metric is extended to the five-dimensional spacetime. With the field equations of the spacetime, the relationship between energy and the cosmological term can be obtained.
Arithmetic complexity of discrete map of converter based on symbol time series
Authors: Yang Ru  , Zhang Bo  , Zhao Shou-Bai  , Lao Yu-Jin  ,   (1)广州大学物理与电子工程学院，广州 510400; (2)华南理工大学电力学院，广州 510640
Published: December 2020

The converter topologically conjugates with its symbol time series. The research of converter can be reduced to the research of symbol time series, and more common results can be gotten. The complexity of converter is studied based on arithmetic complexity of symbol time series, characteristics are gotten from its inner structure. Compared with statistics complexity, arithmetic complexity can describe working cycling and catastrophe point, thus the theoretical basis for understanding the complexity characteristics of converter is provided.
Disorder effect on the focus image of phononic crystal panel with negative refraction
Authors: Li Xiao-Chun  , Gao Jun-Li  , Liu Shao-E  , Zhou Ke-Chao  , Huang Bo-Yun  ,   (1)中南大学粉末冶金研究院,长沙  410083; (2)中南大学物理科学与技术学院,长沙  410083; (3)中南大学物理科学与技术学院,长沙  410083；中南大学粉末冶金研究院,长沙  410083
Published: December 2020

By multiple-scattering theory (MST), disorder effect on the focus image in steel/water phononic crystal panel with negative refraction was investigated. It was found that sonic waves within certain frequency range can propagate along certain directions in periodic crystal and form a focus image with negative refraction characteristics. These directional pathways depend on the periodic scattering in the crystal and are different from the ordinary positional guide. Obstacles in pathways have a deep influence on the focus image. With the increasing of degrec of positional disorder of cylinders, the periodic scattering decreases, pathways are broken, and the focus image becomes blurred or disappears.
The effect of random noise for empirical mode decomposition of nonlinear signals
Authors: Yang Yong-Feng  , Wu Ya-Feng  , Ren Xing-Min  , Qiu Yan  ,   (1)西北工业大学动力与能源学院，西安  710072; (2)西北工业大学振动工程研究所，西安  710072
Published: December 2020

The Monte-Carlo method is used to investigate the effect of random noise on empirical mode decomposition of the nonlinear signals. The simulation results show that, the influence of noise is obvious for the low-level intrinsic mode function and unabvious for the high-level intrinsic mode function. With the increase of the intensity of white noise, the intrinsic mode function pure noise level will increase. When the intrinsic mode function pure noise levels is subtracted from the noise signal, about 80% of the noise influence will be reduced. The noise signals largest Lyapunov exponent is smaller than that of the noise-free signal.
Dynamical analysis of memristor chaotic oscillator
Authors: Bao Bo-Cheng  , Liu Zhong  , Xu Jian-Ping  ,   (1)南京理工大学电子工程系，南京  210094; (2)南京理工大学电子工程系，南京  210094；江苏技术师范学院电气信息工程学院，常州  213001; (3)西南交通大学电气工程学院，成都  610031
Published: December 2020

Memristor, which is a nonlinear resistor with memory function, is the fourth fundamental two-terminal circuit element besides the resistor, capacitor and inductor. A memristor based oscillator circuit, directly derived from Chuas oscillator by replacing Chuas diode with a flux-controlled memristor characterized by a smooth monotonically increasing nonlinearity, is presented in this paper. By using conventional dynamical analysis method, the dynamical behaviors of the new smooth memristor oscillator with the variations of circuit parameters and initial conditions are investigated. The research results demonstrate that the dynamical behavior of the smooth memristor oscillator not only depends on the circuit parameters, but also closely depends on the initial conditions of the circuit. Different from general chaotic systems, some novel nonlinear phenomenas, such as the transient chaos and state transitions and so on, can be found in the proposed system.
Analysis of coupling nonlinear dynamical behaviors between two stages in a cascade power-factor-correction converter
Authors: Zou Jian-Long  , Ma Xi-Kui  ,   西安交通大学电气工程学院，电力设备电气绝缘国家重点实验室，西安 710049
Published: December 2020

A cascade power-factor-correction (PFC) converter is a nonlinear system cascaded by a PFC converter and a direct current-direct current (DC-DC) converter. According to the nonlinear model of the cascade PFC converter derived, we simulate the interstage coupling nonlinear dynamical behaviors of the system, and the simulation results are verified experimentally. The results shows that with the decrease of the PFC output capacitance the bifurcation may appear, which results in the change of the DC-DC output voltage. Likewise, the dynamical behavior of the PFC stage may change with DC-DC load resistance. When the duty ratio of the DC-DC stage becomes saturated, the coupling process between the PFC stage and the DC-DC stage is very complicated.
Hopf bifurcation and stability of periodic solutions in a nonlinear relative rotation dynamical system with time delay
Authors: Liu Shuang  , Liu Bin  , Zhang Ye-Kuan  , Wen Yan  ,   (1)燕山大学工业计算机控制工程河北省重点实验室，秦皇岛  066004; (2)燕山大学工业计算机控制工程河北省重点实验室，秦皇岛  066004；燕山大学机械工程学院，秦皇岛  066004; (3)燕山大学机械工程学院，秦皇岛  066004
Published: December 2020

Hopf bifurcation in a nonlinear relative-rotation system with time delay is considerd, and the critical time delay associated with Hopf bifurcation is found. The time delays influence on the direction and stability of bifurcation are analyzed under the primary resonance condition with the aid of multiple scales. Finally, numerical simulations are performed to verify the analytical results.
Lattice hydrodynamic model for pedestrian traffic with the next-nearest-neighbor pedestrian
Authors: Wen Jian  , Tian Huan-Huan  , Xue Yu  ,   (1)广西大学物理科学与工程技术学院，南宁 530004; (2)玉林师范学院物理与信息科学系，玉林 537000；广西大学物理科学与工程技术学院，南宁 530004
Published: December 2020

Based on the lattice hydrodynamic model with bidirectional pedestrian flow, the lattice hydrodynamic model which considered the interaction of the next-nearest-neighbor pedestrians was proposed in this paper. By the linear stability analysis, the stability condition was obtained. By nonlinear analysis, the modified Korteweg-de Vries equation to describe the density wave of pedestrian congestion was given. Furthermore, numerical simulation was carried out to examine the performance of such a model and it shows consistency with the theoretical analysis results.
A coupling lattice model of traffic flow on two lanes and numerical simulation
Authors: Peng Guang-Han  ,   湖南文理学院物理与电子科学学院，常德415000
Published: December 2020

An improved coupling lattice model of two-lane traffic flow is proposed by taking into account the effect of the two-lane coupling and lane changing. And the lane changing rate of traffic flow is modified. The analysis of the modified lane changing rate shows that it is in better accordance with the real traffic than the previous ones. The linear stability condition of the extended model is obtained by using the linear stability theory. Numerical simulation also shows that our model can better reproduce the lane changing of traffic flow than previous ones by considering the information of two-lane coupling interaction. And there is unavoidable effect on the two-lane traffic flow from the coupling effect between the two lanes.
Study of temporary traffic bottleneck based on cellular automaton model
Authors: Sheng Peng  , Zhao Shu-Long  , Wang Jun-Feng  , Zuo Hang  ,   四川大学计算机学院，视觉合成图形图像技术国防重点学科实验室，成都 610064
Published: December 2020

In this paper, we propose a new cellular automaton model for studying the temporary bottleneck induced by a special accident. The difference in driver behavior between before and after the accident occurrences is taken into account to investigate the effect of the bottleneck on driving character. Simulation results show that the new model can reproduce some complicated traffic phenomena, such as the asymmetrically lane-changing and grabbing the entrance on the bottleneck, and a reasonable asymmetrically gear-alternating control regulation can enhance the outflow of the bottleneck.
Measurement of the thermal wave in metal films using femtosecond laser thermoreflectance system
Authors: Wang Hai-Dong  , Ma Wei-Gang  , Zhang Xing  , Wang Wei  ,   (1)北京大学微电子学研究院，北京 100871; (2)清华大学航天航空学院，热科学与动力工程教育部重点实验室，北京 100084
Published: December 2020

The thermal wave phenomenon induced by the ultrafast laser heating in metal films has been studied by different experimental methods in the past. In our experiment, a femtosecond laser pump-probe system is used to study the ultrafast energy transport between the electrons and phonons. The experiments showed a weak wave peak in the electron temperature curve following the main peak caused by the laser pulse. The reproducibility of the results has been tested for different laser intensities and different film samples. This weak peak in electron temperature could be explained by the reflection of the thermal wave from the rear surface. The experimental results agree with the theoretical curves calculated by the hyperbolic two-step model. The speed of the thermal wave is about 5×105 m/s and the electron relaxation time is about 60 fs.
Influences of different types of piezoelectric shunting circuits on band gaps of phononic beam
Authors: Chen Sheng-Bing  , Han Xiao-Yun  , Yu Dian-Long  , Wen Ji-Hong  ,   国防科技大学三院机电工程研究所，长沙  410073
Published: December 2020

Piezoelectric patches connected with shunting circuits are periodically placed along a base beam, forming a one-dimensional phononic crystal. Different types of shunting circuits will determine the band structure of the beam. Resistive shunting circuits can restrain the beam’s modal vibrations to some extent and the band gaps of the beam can be changed by weakening the piezoelectric effect. LC shunting circuits can produce locally resonant gaps induced by LC circuits’ electromagnetic oscillations excited by piezoelectric patches. When resistors are added to the LC circuits, the LC circuits’ oscillation will be weakened and the attenuation amplitude in the band gaps will be lowered, but the scope of band gaps are widened.
Theoretical study of radiative recombination and the sub-sequent radiative decay processes in highly charged Au ions
Authors: Sang Cui-Cui  , Wang Yong-Jun  , Wan Jian-Jie  , Ding Xiao-Bin  , Dong Chen-Zhong  ,   西北师范大学物理与电子工程学院，兰州 730070
Published: December 2020

Using multi-configuration Dirac-Fock method and the corresponding packages GRASP92 and RATIP, as well as the newly developed RERR06, we have calculated the radiative recombination (RR) spectra for capturing a continuum electron into n| (n=4—8, l=0—3) subshell of Ni-like Au51+, Cu-like Au50+ and Zn-like Au49+ ions and their corresponding radiative decay spectra. The calculated RR spectra reproduce the experimental spectra excellently. It was found that for the Ni-like Au51+, Cu-like Au50+ and Zn-like Au49+ ions, the probability of capturing a free electron to n=4 subshell is the largest. Furthermore, the main characteristics of the relative decay spectra is the domination of the lines from the captured electrons radiatively decaying from the n=4 subshell.
Energies, fine structures, and Auger widths of the high-lying triply excited states of 2S(m) and 2D(m) (m=2—7) for the “hollow atom” lithium
Authors: Sun Yan  , Gou Bing-Cong  , Zhu Jing-Jing  ,   北京理工大学物理系，北京  100081
Published: December 2020

The relativistic energies and fine structures of the high-lying triply excited states 2l2l′nl″ 2S(m) and 2D(m) (m=2—7) for the “hollow atom” lithium are studied using the saddle-point variational method and the saddle-point complex-rotation method, including the mass polarization and relativistic corrections. The partial Auger widths and the total widths are also calculated. By the discussion of relativistic effect, we recalibrated the configurations of 2S(7) , 2D(6) and 2D(7).
Influence of the collision energy and isotopic variant on the stereodynamics of reaction H+BrF→HBr+F
Authors: Xu Yan  , Zhao Juan  , Wang Jun  , Liu Fang  , Meng Qing-Tian  ,   山东师范大学物理与电子科学学院，济南  250014
Published: December 2020

Quasi-classical trajectory calculations are carried out for the exothermic reaction H+BrF→HBr+F on the latest London-Eyring-Polanyi-Sato potential energy surface. The product angular distributions which reflect the vector correlation are calculated. Polarization dependent differential cross sections which are sensitive to many photoinitiated bimolecular reactions are presented in the center of mass frame. The calculated results suggest that the product rotational polarization becomes stronger as collision energy increases and the products were mainly backward scatteried. By comparing the product polarization of reactions D+BrF→DBr+F and H+BrF→HBr+F, the isotope effects have also been revealed.
Cross section invertion between double electron capture and transfer ionisation in low energy collision of highly charged ion(4≤q≤7) with He
Authors: Lü Ying  , Chen Xi-Meng  , Cao Zhu-Rong  , Wu Wei-Dong  ,   (1)兰州大学核科学与技术学院，兰州  730000; (2)中国工程物理研究院激光聚变研究中心，绵阳  621900
Published: December 2020

Based on the potential parameter Ω, which was defined as energy deposits ratio of incidence ion with target ion after double electron capture, the selection rule between double electron capture and transfer ionization of helium target induced by Aq+ (q=4,5,6,7) ions was studied. It is found that there is a cross point for the cross-section ratio curve of double electron capture and transfer ionization at Ω=10, and for ΩΩ≥10 the transfer ionization is a key reaction channel of double electron transfer.
Two inversion methods for electromagnetic scattering
Authors: Zhang Yu  , Yang Xi  , Gou Ming-Jiang  , Shi Qing-Fan  ,   (1)北京理工大学理学院，北京 100081; (2)北京理工大学信息与电子学院，北京 100081
Published: December 2020

Two inversion methods for electromagnetic scattering, the deterministic gradient search method and the Monte Carlo random search method， are proposed in this paper. Firstly, the fundamental principles of the two methods are introduced. Inversion properties including the positioning capability of the scattering body, inversion accuracy and inversion time of the two methods are analyzed and compared. Simulation results demonstrates that the deterministic gradient search method can be used for scattering body positioning and the results using Monte Carlo random search method have high-precision at the same time have high speed. Successive applications of both methods fully realize the advantages of the two methods and improve the inversion result.
High power narrow linewidth single-frequency line-polarized fiber amplifier based on master-oscillator power amplifier technology
Authors: Qi Yun-Feng  , Liu Chi  , Zhou Jun  , Chen Wei-Biao  , Dong Jing-Xing  , Wei Yun-Rong  , Lou Qi-Hong  ,   中国科学院上海光学精密机械研究所，上海市全固态激光器与应用重点实验室，上海  201800
Published: December 2020

High power single-frequency (SF) lasers are of great significance in science, industry, and defense applications such as gravitational wave detection, free apace optical communication, range finding, lidar, parametric wavelength conversion in resonant cavities. We report on a high power single-frequency linearly polarized radiation with a nearly diffraction-limited beam quality by use of a two-stage fiber master-oscillator power amplifier system. The master oscillator is an SF distribution feedback fiber laser with polarization maintaining (PM) and single mode (SM) fiber pigtailed output power of about 10 mW at 1064 nm, and its line-width is of 20 kHz. This light power is amplified to about 1 W by the first stage of all-fiber SM/PM amplifier and then seeded at the second stage of high power main amplifier with large mode area (LMA) ytterbium-doped fiber (YDF). The pumping diode laser of the main amplifier is fiber-coupled (the core diameter is 400 μm and corresponding numerical aperture is 022) with a max emitting power as high as 190 W at 976 nm. By employing the co-pump configuration with a space coupling efficiency of about 85%, we demonstrate that the power output from the LMA/PM YDF (core diameter is 20 μm, inner cladding diameter is 400 μm) reaches 128 W and its corresponding overall slope-efficiency is 85% of the launched pump power. The beam profile is diffraction-limited and linearly polarized with a polarization extinction ratio over 12 dB. There is observed neither amplified spontaneous emission nor stimulated Brillouin scattering phenomenon, which means that the substitution of the pump source with the more powerful one can further enhance power output if LMA YDF with a larger core size, shorter fiber length and higher doping efficiency is used.
Influence of current aperture size on threshold in double oxide confined vertical-cavity surface-emitting lasers
Authors: Zhao Hong-Dong  , Zhang Wei-Hua  , Li Wen-Chao  , Liu Hui-Li  , Sun Mei  ,   河北工业大学信息工程学院，天津 300401
Published: December 2020

In this paper, the coupling equations for electric field, carrier density, optical-field and temperature are simulated self-consistently in double oxide confined vertical cavity surface emitting laser therefore the characteristics threshold are studied. The potentials near the oxide layers and the activity region are obtained and the effect of current aperture edge is simulated. The distributions of threshold injected current density, carrier density, fundamental mode and temperature for different radii of double oxide confined current aperture are obtained. An appropriately confined radius of current aperture for minimum threshold injected current is found, and the structure of vertical cavity surface emitting laser is designed.
Spectrum broadening of ultrashort ultraviolet pulse in dual-color laser field
Authors: Wu Hong  , Wang Yan-Ling  , Ding Liang-En  ,   华东师范大学物理系，精密光谱科学与技术国家重点实验室，上海  200062
Published: December 2020

When collinear dual-color intense laser pulses are overlapped in time, a strong coupling interaction occurs between their plasma filaments. Due to the cross phase modulation, strong non-linear effects are generated and the spectrum width of the ultrafast ultraviolet (UV) pulse is further broadened. The original UV pulse with a bandwidth of 15 nm and energy of 045 mJ is obtained by tripling the frequency of a Ti:sapphire laser system. The UV pulse and the near inferred pulse of 71 mJ can induce plasma filaments separately after focusing within an argon gas cell, leading to an obvious modulation of the UV spectrum. The full width at half maximum of UV spectrum increases to 64 nm which is 4 times the width of spectrum before focusing and 25 times the width of single ultraviolet filament broadening. In this experiment, we mainly study the frequency spectrum evolution of dual-color co-filament in argon gas under the condition of different time delays, coupling locations and gas pressures. Optimizing these factors can yield a valid approach to achieving extremely ultrafast pulses in the range of ultraviolet.
Sensitive temperature sensor based on phase properties of photonic crystal
Authors: Huang Qin  , Leng Feng-Chun  , Liang Wen-Yao  , Dong Jian-Wen  , Wang He-Zhou  ,   中山大学光电材料与技术国家重点实验室，广州  510275
Published: December 2020

It is revealed in the present paper that the reflectance around the defect mode of one-dimensional defective photonic crystal (PC) in an asymmetric structure approaches to 1, while the phase-shift depends on the number of the coupled-defect layers, i.e., the phase shift is 2π for every sub-peak of the defect mode. When the defect layer is a temperature sensitive material, very small change of temperature will cause a significant phase change. Secondly, it is demonstrated that the relationship of phase and temperature has a linear range. According to the above characteristics, a highly sensitive temperature sensor is designed based on the phase property of photonic crystal. Moreover, this principle of PC phase sensing can be extended to study other sensors, such as the two-dimensional PC, which is suitable for optical integration.
Signal impairment analysis of optical controlled apparatus caused by semiconductor optical amplifier
Authors: Wang Yong-Jun  , Wu Chong-Qing  , Wang Zhi  , Wang Ya-Ping  , Xin Xiang-Jun  ,   (1)北京交通大学光信息科学与技术研究所，发光与光信息技术教育部重点实验室，北京  100044; (2)北京邮电大学电子工程学院，信息光子学与光通信教育部重点实验室，北京  100876
Published: December 2020

This paper analyzes the signals impairment in the semiconductor optical amplifier (SOA) based optical buffer for optical packets switching networks, including the shape distortion of single pulse and the pattern dependent distortion of the continuous bit stream due to the SOAs nonlinearity and the limitation of its carrier lifetime, the deterioration of signal-to-noise ratio caused by the accumulation of amplified spontaneous emmision noise of the SOA, and the power leakage. The theoretical analysis and experimental results indicate that the buffered circle is restricted to 20—30, as determined by the signals impairment when a negative control optical pulse with high power is injected into SOA.
Low-dispersion high-birefringence effect of squeezed hexagonal lattice elliptical hole photonic crystal fiber
Authors: Zhang Ya-Ni  ,   宝鸡文理学院物理与信息技术系，宝鸡 721007；中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室，西安 710119
Published: December 2020

A new type of photonic crystal fiber for realizing the effect of low dispersion high birefringence is proposed. The fiber is composed of a solid silica core and a cladding with squeezed-hexagonal-lattice elliptical air-hole along the fiber length. Dispersion and birefringence are investigated simultaneously by using the full vectorial plane wave method. Simulations indicate that the wavelength for realizing low-dispersion high-birefringence can be controlled by artificially choosing the structure parameters of photonic crystal fiber, such as the hexagonal lattice squeezing ratio, the relative air hole spacing and the air hole ellipticity. The optimal and feasible parameters of the fiber with low-dispersion high-birefringence are given, with the result of the total dispersion being within ±5 ps·nm-1km-1 over an ultra broad wavelength range from 1360 to 1670 nm and the corresponding high birefringence being about 15×10-2 at 1550 nm.
Nucleation and coagulation of nanoparticles in a planar jet
Authors: Liu Yan-Hua  , Gan Fu-Jun  , Zhang Kai  ,   (1)澳大利亚皇家墨尔本理工大学航空学院，墨尔本 3083; (2)浙江大学力学系，杭州 310027
Published: December 2020

The nucleation and coagulation of nanoparticles in the binary system of water vapor (relative humidity 70%) and sulfuric acid vapor (5×10-6) were detailedly studied by performing numerical simulation in a planar jet (Re=8300). The large eddy simulation was utilized to calculate the flow field, and the particle field is obtained by using the direct quadrature method of moment to solve the particle general dynamic equation. The distributions of particle number concentration, volume concentration and average diameter were discussed. The result shows that the growth of the calculated momentum thickness is consistent with the previous experimental data. The interface of the jet will roll up and generate the coherent vortices which will lead to an obvious decrease of the specie concentration of sulfuric acid vapor and increase of number concentration of nanoparticles in the vortex core. The appearance of the coherent vortices increases the possibility of particle collision and enhances the particle coagulation. The nanoparticle nucleation is enhanced in the vortex core where high particle number concentration will accelerate the particle coagulation.
Experimental studdy on relation between volume fraction of sandpiles and flow rate of forming sandpiles
Authors: Kong Wei-Shu  , Hu Lin  , Zhang Xing-Gang  , Yue Guo-Lian  ,   贵州大学理学院,贵州光电子技术与应用重点实验室,贵阳  550025
Published: December 2020

The function of volume fraction η versus flow rate Q was determined. It is found that η decreases exponentially with increase of Q. The volume fraction η will reach saturation when Q is reduced or increased　to certain extent. The increase of η slows down rapidly with decrease of Q when D/d decreases to a critical value. The decrease of η slows rapidly with increase of Q when d decreases to a critical size. The phenomenon is explained by the dissipation of granules, effect of air, effect of bottleneck and collision theory.Theoretical result about η-Q is in agreement with the experimental result.
Quantum theory of neutron double-slit diffraction
Authors: Liu Xiao-Jing  , Zhang Bai-Jun  , Li Hai-Bo  , Liu Bing  , Zhang Chun-Li  , Guo Yi-Qing  , Zhang Bing-Xin  ,   (1)吉林师范大学物理学院，四平  136000; (2)中国科学院高能物理研究所，北京  100049
Published: December 2020

By solving Schrdinger equation exactly, we obtain the neutron wave function in the slit. With the Kirchhoff’s law, we obtain the neutron diffraction function. Finally, we obtain the mathematical relation between the relative diffraction intensity of neutron double-slit diffraction and the diffraction position. The calculation result is in accordance with the experimental data.
Theoretical investigation of the electronic structure and thermoelectric transport property of Mg2Si
Authors: Peng Hua  , Wang Chun-Lei  , Li Ji-Chao  , Wang Hong-Chao  , Wang Mei-Xiao  ,   山东大学物理学院，晶体材料国家重点实验室,济南  250100
Published: December 2020

Full-potential linearized augmented plane wave method and Boltzmann transport properties have been used to investigate the crystal structure and electronic structure of Mg2Si. Electronic conductivity, Seebeck coefficient and power factor are calculated. Energy band structure shows that Mg2Si is an indirect semiconductor with energy band gap of about 020 eV. Transport properties versus the doping level have been calculated for the n type and p type doped materials at 700 K. The optimal carrier concentration corresponding to the maxima of power factor are obtained, which are 7749×1019 cm-3 and 1346×1020 cm-3 for the p-doping and n-doping respectively. Maximum ZT value of 093 has been estimated in combination with experimental data of thermal conductivity. From the transport properties at different temperatures, we found that the ratio of power factor to relaxation time is enhanced when the temperature increases. Optimum doping level of materials used in middle and high temperature range is higher than that of materials used in low temperature.
A low coverage investigation on Al adsorption on the (111) surface of Pt, Ir and Au
Authors: Zhang Jian-Jun  , Zhang Hong  ,   四川大学物理科学与技术学院,成都  610065
Published: December 2020

Aluminium adsorptions on Pt(111),Ir(111) and Au(111) surface are studied systematically by using the density function theory. Four highly symmetric sites, namely face-centered cubic(fcc)-hollow,hexagonal close-packed(hcp)-hollow, top and bridge sites, are adopted. We calculate atomic geometry， average binding energy and differences in electron density among the three systems. The Mulliken charge population analyses and the projected densities of states of the three systems are also discussed. It is found that the hcp-hollow site is the energetically favorable site for Pt(111)and Ir(111) surfaces, but the energetically favorable site is the fcc-hollow site for Au(111) surface.
Analysis on transport sensitivity for a carbon atomic wire attached with side groups
Authors: Qiu Ming  , Zhang Zhen-Hua  , Deng Xiao-Qing  ,   长沙理工大学物理与电子科学学院，长沙  410114
Published: December 2020

Based on the local atomic-orbital density functional theory plus the nonequilibrium Green’s function approach, we study the transport sensitivities of a carbon atomic wire attached, respectively with seven kinds of commonly seen side-groups NO2, CN, CHO, Br, C6H5, C5H4N, NH2. The calculated results show that the transport current is most sensitive to attached C6H5 and CHO groups, less sensitive to attached CN and C5H4N groups. Under certain bias values, the currents have a substantial decline and would reached to 1/2, or even 1/3 the magnitude as the unattached system C6. But the transport of the carbon atomic wire is little influenced by the attached NO2, NH2, and Br. The intrinsic origins of side-group effects on the transport current in the wire are the suppression of the transmission eigen-channel, change of the Mulliken population, diminution of the delocalization of highest occupied molecular orbital or lowest unoccupied molecular orbital, and alteration of the resonant molecular orbital.
Band structures of strain-deformed BC3 nanotubes
Authors: Han Wen-Peng  , Liu Hong  ,   南京师范大学物理系，南京  210046
Published: December 2020

By using the tight-binding energy band theory, we study the band structures of BC3 nanotubes under stretching and compressing deformations, the conductivity band turns more and more close to the valence band of the BC3 nanotubes and eventually they overlap each other with the increase of tension. Furthermore, the results obtained show that the overlap under compressing is bigger than that under stretching. The biggest overlap under compressing is up to 05 eV, but it is only 02 eV under stretching. In addition, for armchair BC3 nanotubes, the results of band structures show that with the increase of tension, the BC3 nanotube transforms into an indirect semiconductor from a direct semiconductor, and then leads to the band overlap. The armchair BC3 nanotube is an unstable narrow-gap semiconductor, because a little compress (et=-0003) can convert it transform into an indirect semiconductor from a direct semiconductor. For zigzag BC3 nanotubes, a slight deformation can turn into a direct semiconductor having only one allowed wave vector from a direct semiconductor having all wave vectors, owing to the existence of two flat conductivity and valence bands.
The statistical properties and electronic transfer coefficients of Fibonacci sequence
Authors: Liu Xiao-Liang  , Huang Xiao-Mei  , Xu Hui  , Ren Yi  ,   (1)长沙电力职业技术学院电力工程系，长沙  410131; (2)中南大学物理科学与技术学院，长沙  410083; (3)中南大学物理科学与技术学院，长沙  410083；中南大学冶金科学与工程学院，长沙  410083
Published: December 2020

For the Fibonacci sequence constructed by following the inflation rule A→AB and B→A, using the one-dimensional random walk model and Hurst’ analysis, we calculate numerically the auto-correlation function, the pseudo standard deviation of displacement defined by ourselves and the rescaled range function and investigate systematically the statistical properties. The results are compared with that of one-dimensional random binary sequence. We show that the Fibonacci sequence presents correlated behavior as well as scaling invariability and self-similarity. In addition, basing on the tight-binding model of the single electron and transfer matrix method, we study the charge transfer properties of Fibonacci sequence and discuss specially the dependence of electron transmission on energy and the length of the sequence. We find some resonant peaks can survive in relatively longer Fibonacci sequences than in random sequences, which also implies that there are long-range correlations in Fibonacci sequences.
Electrical transport properties of Ca3－xAgxCo4O9(x=0—0.05) oxide
Authors: Zhang Fei-Peng  , Zhang Xin  , Lu Qing-Mei  , Zhang Jiu-Xing  ,   北京工业大学材料科学与工程学院,新型功能材料教育部重点实验室，北京  100124
Published: December 2020

The electrical transport properties of Ca3Co4O9 could be modified by doping in the Ca site. The Ca site doped Ca3-xAgxCo4O9(x=0—005) bulk samples were fabricated by citric acid sol-gel and spark plasma sintering method. The resulting samples were analyzed by X-ray power diffraction, scanning electron microscopy and electrical constant measurement. The results showed that all samples were single phased, the prefered orientation was lowered by Ag doping for Ca. The x=003 sample exhibited highest grain orientation among doped samples, which exhibited layered microstructure. Its electrical resistivity was increased and then decreased slightly by Ag doping, but the transport mechanism was not changed. However, the doped samples exhibited high electrical resistivity caused by changed electronic structure by Ag doping for Ca. The x=004 sample exhibited highest electrical resistivity in the measuring temperature region with the highest value 146 mΩ·cm at 973 K.
Preliminary studies on the mechanism of radiation production in aluminum wire array Z-pinch implosion
Authors: Xiao De-Long  , Ning Cheng  , Lan Ke  , Ding Ning  ,   北京应用物理与计算数学研究所,北京  100094
Published: December 2020

The mechanism of energy conversion and radiation emission of aluminum wire array Z-pinch implosion has been studied by using a one-dimension non-equilibrium magnetohydrodynamic code. The energy transfer processes have been discused carefully, which shows that the accelerator feeds its stored energy to plasma via Poynting energy flux, and plasma kinetic energy is converted to plasma internal energy through pdV work and shock heating, thus producing radiation via several atomic processes including line radiation, recombination radiation and bremsstrahlung radiation. With the information of atomic populations, the mechanism of producing radiation has been anzlyzed. It is shown that in the implosion stage the ionization and excitation processes dominate, leading to the dominant yield of line radiation.While at stagnation most ions are in naked states, so the recombination radiation is the main radiation source. Corresponding to the two peak fractional populations of H-like and He-like ions, the line radiation also exhibits two radiation peaks at the time near peak compression. In the expansion stage, it is the radiative recombination that dominates the atomic processes, thus decreasing the share of line radiation in total radiation.
The mechanism of structure phase transition from α Fe to ε Fe under uniaxial strain: First-principles calculations
Authors: Lu Zhi-Peng  , Zhu Wen-Jun  , Lu Tie-Cheng  , Liu Shao-Jun  , Cui Xin-Lin  , Chen Xiang-Rong  ,   (1)北京师范大学物理系，北京 100875; (2)四川大学物理科学与技术学院，成都 610064; (3)中国工程物理研究院流体物理研究所，冲击波物理与爆轰物理国防科技重点实验室，绵阳 621900; (4)中国工程物理研究院流体物理研究所，冲击波物理与爆轰物理国防科技重点实验室，绵阳 621900；四川大学物理科学与技术学院，成都 610064; (5)中国工程物理研究院流体物理研究所，冲击波物理与爆轰物理国防科技重点实验室，绵阳 621900；四川大学物理科学与技术学院，成都 610064；中国人民武装警察部队成都指挥学院，成都 610213
Published: December 2020

We performed first-principles calculations for the pressure-induced martensitic phase transition from the ground state ferromagnetic body-center cubic (bcc) phase to a nonmagnetic hexagonal close-packed (hcp) phase of Fe under uniaxial strain along the ［001］ direction of bcc phase based on density-functional theory, employing the pseudopotentional and plane-wave method. The calculated results show that the transition path under unixial strain is significantly different from that under hydrostatic pressure. A sudden drop of the magnetic moment is observed at a critical point on the transition path, which results in a discontinuous derivative in the total energy and volume curve. This is a feature of a magnetic first-order phase transition, which indicates that magnetism is the primary stabilizing mechanism of the bcc structure. The enthalpy barrier for bcc-to-hcp transformation decreases as the uniaxial strain (the pressure) increases. The physical origin of the influence of uniaxial strain on the phase transition is discussed.
Molecular dynamics simulation of CO2 separation from integrated gasification combined cycle syngas via the hydrate formation
Authors: Yan Ke-Feng  , Li Xiao-Sen  , Chen Zhao-Yang  , Xu Chun-Gang  ,   中国科学院广州能源研究所，中国科学院可再生能源与天然气水合物重点实验室，广州  510640；中国科学院广州天然气水合物研究中心，广州  510640
Published: December 2020

Molecular dynamics (MD) simulation is used to study the microscopic mechanism of CO2 separation from integrated gasification combined cycle(IGCC) syngas (CO2/H2) via the hydrate formation. The stable structures and microscopic properties of CO2 hydrate, H2 hydrate, and CO2/H2 hydrate from one stage separation for IGCC syngas are investigated systematically. The binding energy for loading the hydrate structure with the guest molecules, ΔEn, was analyzed. It was shown that the binding between CO2 and water is more stable than that between H2 and water. That is, CO2 can more easily form the hydrate. Therefore, CO2 in the CO2/H2 gas mixture more easily transfers into the hydrate phase. Based on this, CO2 can be separated from the IGCC syngas. The binding energy for loading the single cavity with the guest molecules, ΔEGH, was analyzed. It was found that the gas mixture can form structure Ⅰ(SⅠ) hydrate, in which CO2 molecules preferably occupy the big cavity and then occupy the small cavity, and H2 molecules only occupy the small cavity. The simulation was carried out at pressure of 85 MPa and temperature of 2737 K for the stable structure of the CO2/H2 hydrate in one stage separation for IGCC syngas. From the ΔEn and ΔEGH of the systems with H2 single and double occupancy in the small cavity, it is concluded that the configurations with the single occupancy is most stable. The stable structure of the hydrate in one stage separation is attained by MD. It provides a theoretical evidence of CO2 separation for formation hydrate in IGCC syngas.
Field emission properties of amorphous carbon nanodot arrays in a novel anodic aluminum oxide template by self-assembly technique
Authors: Wu Zhi-Guo  , Zhang Peng-Ju  , Xu Liang  , Li Shuan-Kui  , Wang Jun  , Li Xu-Dong  , Yan Peng-Xun  ,   (1)兰州大学物理科学与技术学院，兰州  730000; (2)兰州大学物理科学与技术学院，兰州  730000；中国科学院兰州化学物理研究所固体润滑国家重点实验室，兰州  730000; (3)兰州理工大学甘肃省有色金属新材料省部共建国家重点实验室,兰州  730050; (4)兰州理工大学甘肃省有色金属新材料省部共建国家重点实验室,兰州  730050；兰州大学物理科学与技术学院，兰州  730000
Published: December 2020

Amorphous carbon nanodot arrays were successfully prepared through filtered cathodic arc plasma (FCAP) technique, and via a special widen process, the negative effect of the anion impurities distributed in the anodic aluminum oxide (AAO) template was avoided during carbon ions deposition. The morphology of the samples was studied by a field emission scanning electron microscopy (FESEM). The AAO template prepared by multi-steps combining anodization process and pore-widening process has special pore openings. The nanodot arrays are uniformly distributed and in good agreement with the AAO pore arrays. The diameter of the as-prepared nanodot is about 100 nm, and the density was estimated to be 1010 cm-2. Field emission properties of the nanodot arrays were investigated and a low threshold field of 37 V/mm at 10 mA/cm2 was obtained.
Simulation of pedestrian evacuation flow with affected visual field using cellular automata
Authors: Yue Hao  , Shao Chun-Fu  , Duan Long-Mei  , Guan Hong-Zhi  ,   Jilin Provincial Highway Survey and Design Institute, Changchun 130021, China;,   Key Laboratory for Urban Transportation Complex Systems Theory and Technology of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China;,   Key Laboratory for Urban Transportation Complex Systems Theory and Technology of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China; Transportation Research Center, Beijing University of Technology, Beijing 100124, China;,   Transportation Research Center, Beijing University of Technology, Beijing 100124, China
Published: December 2020

Simulation of pedestrian evacuation flow with affected visual field is carried out on the basis of cellular automata. The room to be evacuated is divided into exit visible area, wall visible area and blind area by pedestrian sight radius, and two basic dynamic parameters in the dynamic parameters model are used to simulate the varied movement characteristics of pedestrian in different evacuation areas, including normal evacuation movement, movement along the wall and movement in fixed direction. The effect of pedestrian sight radius on evacuation time is studied with evacuation signs on the wall and pedestrian stochastically moving to find the wall in fixed directions and then moving along the wall. It is observed that the evacuation time depends not only on the pedestrian sight radius but also on the length and utilization rate of exit.
Study on the electronic structures of CsI crystal with F-type color center
Authors: Pu Chun-Ying  , Liu Ting-Yu  , Liu Chang-Jie  , Bai Xiao-Ming  , Li Chun-Ping  , She Hui  ,   (1)解放军空军航空大学基础部物理教研室，长春  130024; (2)解放军空军航空大学基础部物理教研室，长春  130024；上海理工大学理学院，上海  200093; (3)上海理工大学理学院，上海  200093
Published: December 2020

The electronic structures of the perfect CsI crystal and the crystal containing iodine vacancy and F, F2 color centers are studied within the framework of the fully relativistic self-consistent Dirac-Slater theory, by using a numerically discrete variational (DV-Xα) method. Calculated results reveal that the existence of the iodine vacancy results in the band gap widening and does not introduce the new energy level in the forbidden band. However, the crystal containing F color centers and F2 color centers have their donor energy levels introduced in the forbidden band. The transition energy from energy level of F color center and F2 color center to the bottom of conduction band is 169 eV (736 nm) and 115 eV, respectively, which are consistent with the experimental results. This result indicates that the 750 nm absorption band originates from the F color center and the 11 eV absorption band originates from F2 color center.
Design and preparation of black-nickel film on the radiometer chip
Authors: Yu Bing-Xi  , Zheng Na  , Liang Zhong-Zhu  , Li Ya-Nan  , Liang Jing-Qiu  , Fang Wei  , Wang Wei-Biao  ,   Northeast Institute of Geography and Agricultural Ecology, Chinese Academy of Sciences, Changchun 130012, China;,   State Key Laboratory of Applied Optics,Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   State Key Laboratory of Applied Optics,Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; Graduate University of the Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The black-nickel film on the flat type radiometer chip was investigated, and a black-nickel film which can be applied in this chip was prepared using electroplating method. The analyses of absorption of radiometer chip indicated that the absorption rate of the chip is proportional to the surface roughness. The black-nickel film was prepared and tested, and surface morphology testing showed that this film has microstructures of the scale 50 nm—1.5 μm. Infrared absorption measurement indicated that the absorptivity of the film in the 1.4—8 μm range is higher than 0.989. This high absorptivity black-nickel film improves the performance of the chip.
Soft X-ray spectromicroscopy dual-energy contrast image for element spatial distribution analysis
Authors: Zhang Xiang-Zhi  , Xu Zi-Jian  , Zhen Xiang-Jun  , Wang Yong  , Guo Zhi  , Yan Rui  , Chang Rui  , Zhou Ran-Ran  , Tai Ren-Zhong  ,   Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China
Published: December 2020

The detection of chemical speciation with spatial resolution of 30 nm has been implemented at BL08U soft X-ray spectromicroscopy endstation of Shanghai Synchrotron Radiation Facility. For each specimen, we scan two absorption images separately at two energies E1 and E2 near the absorption edge of the element with E1>E2. After calculating the signal ratio of each pair of the corresponding pixels’ optical density in the two absorption images, we can obtain the map of the spatial distribution of that element. Compared with the conventional analysis method of K-edge subtraction (KES), our ratio analysis method is more sensitive and accurate in identifying the spatial distribution of the interested elements, and the definition of the contrast threshold determining whether a pixel contains the interested element, is simpler and clearer in physics. Through the analysis and calculation of the spatial distributions of the oxygen element on a pre-oxidized polyacrylonitrile fiber cross-section, we can verify the effectiveness of the ratio analysis method compared to the traditional KES method. This ratio method provides a new analysis tool for fast mapping the distribution of trace elements.