bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum phase transition of a Bose-Einstein condensate in an optical cavity driven by a laser field
Authors: Liu Ni  ,   Institute of Theoretical Physics, Shanxi University, Taiyuan 030006, China
Published: December 2020

When an atomic ensemble is coupled with a cavity field governed by the well-known Dicke model , an important quantum phase transition (QPT) from the normal phase to the superradiant phase occurs, which was predicted more than 30 years ago. In this paper, both the atom-photon nonlinear interaction and the driving field are added to the Dicke's Hamiltonian. With the method of Holstein-Primafoff transformation, the ground state energy is given by the theoretical calculation, and the rich phase figures are presented. Meanwhile, these properties are observed experimentally. We mainly dicuss the effects of the atom-photon nonlinear interaction and the driving field on QPT.
Effect of pro-proximity pulse voltage on the third-generation low light level image intensifiers halo effect
Authors: Ren Ling  , Shi Feng  , Guo Hui  , Cui Dong-Xu  , Shi Ji-Fang  , Qian Yun-Sheng  , Wang Hong-Gang  , Chang Ben-Kang  ,   Science and Technology on Low-light-level Night Vision Laboratory, Xi’an 710065, China;,   Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094, China;,   Xi’an Institute of Applied Optics, Xi’an 710065, China
Published: December 2020

In order to explore the proper working voltage for the third-generation low light level image intensifier, the influence of pro-proximity pulse voltage on image intensifier halo effect is investigated. The pulse voltage is applied to photocathode of image intensifier. Respectively change the high and low level voltage and duty ratio, image intensifier halo images are collected by high-resolution charge-coupled device (CCD). The gray distributions for pixel points on halo image central line are given and comparatively analyzed. The results show that as high level voltage and duty ratio increase, the number of pixel points whose gray value is 255 increases and the border between signal and background becomes clear. When high level voltage is above 200 V and duty ratio is above 60%, the pro-proximity voltage has not great influence on image intensifier halo effect. When low level voltage is above 2 V, photoelectrons escaping from photocathode cannot reach microchannel plate under low level voltage stage. The present investigation is beneficial to the exploration of the optimal working voltage for image intensifier and energy range of photoelectrons escaping from photocathode, and provides an experimental support for the improvement of the third-generation low light level image intensifier performance.
Effect of mixed solvents on P3HT:PCBM based solar cell
Authors: Yang Shao-Peng  , Li Na  , Li Guang  , Shi Jiang-Bo  , Li Xiao-Wei  , Fu Guang-Sheng  ,   College of Physics Science and Technology, Hebei University, Baoding 071002, China
Published: December 2020

We fabricate solar cells based on blends of poly(3-hexylthiophene) (P3HT) as the donor and [6, 6]-phenyl-C60-butyric acid methyl ester (PCBM) as the acceptor using various solvents such as pure chlorobenzene (CB), pure chloroform (CF) and mixed solvent (CB/CF) with different ratios.We investigate the influences of various solvents and mixed solvents with different ratios on the performances of solar cells. The results show that for the device by using a mixed solvent of CB/CF (3/1), its UV-Vis absorption spectrum and external quantum efficiency show a red-shift and its AFM image shows finely structured phase segregation between P3HT and PCBM. We obtain an open circuit voltage of 0.61 V, short circuit current density of 9 mA/cm2, fill factor of 57.9%, and power conversion efficiency of 3.2% under irratiation of light with a strength of 100 mW/cm2.
Experimental study of the interactions between a pulsating bubble and sand particles with different diameters
Authors: Zhang A-Man  , Xiao Wei  , Wang Shi-Ping  , Cheng Xiao-Ou  ,   College of Shipbuilding Engineering, Harbin Engineering University, Harbin 150001, China
Published: December 2020

The interactions between a spark generated bubble and sand particles with different diameters are studied in this paper using a high speed camera. And distance between the bubble and sand particle is varied. The experimental results show that there are two distinct phenomena during the interaction between the bubble and sand particle. On the one hand, the jet formed is much like that near a rigid wall; on the other hand, a mushroom-shape bubble will form, which will split into two bubbles and two jets with opposite directions along the axes will be generated afterwards. Thus, it is found that the sand particle has the characteristics of a rigid wall and an elastic material. In addition, as the distance d between the bubble and sand particle increases, the pulsating period of the bubble will rise to a peak before it reduces. For different sand particles, the distance corresponding to the peak decreases as the diameter of sand particle increases.
Effect of cylinder-electrode on magnetoelectric heating of ions
Authors: Ma Zhi-Bin  , Shen Wu-Lin  , Wu Jun  , Yan Lei  , Wang Jian-Hua  ,   School of Material Science and Engineering, Key Laboratory of Plasma Chemical and Advanced Materials of Hubei Province, Wuhan Institute of Technology, Wuhan 430073, China
Published: December 2020

A highly-efficient magnetoelectric heating not only improves ion temperature of electron cyclotron resonance (ECR) plasma, but also reforms the radial and axial distribution of ions, thereby promoting the application of ECR plasma to the etching of chemical vapor deposition diamond films. In this paper, a ring-electrode is replaced by a cylinder-electrode, and the effects of cylinder-electrode on the ion temperature and density are studied. The ion heating effects in the cases of cylinder-electrode and ring-electrode are compared. The results indicate that cylinder-electrode can produce higher ion temperature than ring-electrode at the same anode voltage. Ion temperature at each radial point changes a lot when the cylinder-electrode is used to heat ions. The ion temperature inside cylinder-electrode has a big radial variation while it has a good radial uniformity at downstream of cylinder-electrode. The effect of magnetoelectric heating on ion density is small. Using cylinder-electrode to heat ion is beneficial to the transport and axial uniformity of ions.
Analysis of imaging an extended X-ray source by using a Fresnel phase zone plate
Authors: Chen Xiao-Hu  , Wang Xiao-Fang  , Zhang Wei-Wei  , Wang Wen-Hui  ,   Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

To image a large-size object with a high spatial resolution in a kiloelectronvolt (keV) X-ray range, a method is proposed to analyze and simulate the imaging of an extended X-ray source by a Fresnel phase zone plate (FPZP), based on the translational invariance of the point spread function in a 1 mm square area on the objective plane. Using this method, the imaging of an extended source of a different size is simulated under a typical experimental condition of image-to-source magnification of 10 for an FPZP of an outmost zone width of 0.35 μm. The results show that the image contrast decreases with the increase of the source size, and the zeroth-order and the minus first-order diffractions of the FPZP contribute mainly to the image background enhancement and the contrast decrease. The spatial resolution to the objective plane is also found to be reduced. For a 1-mm-square-shape source with a sinusoidal-distribution intensity modulation of contrast 1, the image modulation contrast is below 0.4, and the spatial resolution is 0.75 μm.
Influence of SiC intermediate layer on adhesion property of F-DLC film
Authors: Pan Yue  , Zhao Qiang  , Jiang Ge  , Zhou Yang  , Jiang Mei-Fu  , Yang Yi-Shang  ,   School of Physical Science and Technology, Suzhou University, Suzhou 215006, China;,   School of Physical Science and Technology, Sichuan University, Chengdu 610065, China
Published: December 2020

Two kinds of films are deposited on 316L stainless steel substrates by radio frequency reactive magnetron sputtering technique. One is fluorinated diamond-like carbon film (F-DLC) deposited on the 316L stainless steel substrate directly and the other is F-DLC with SiC intermediate layer. This paper focuses on the changing regulation of film adhesion with preparation condition. As the result, the adhesion of fluorinated diamond-like carbon film with SiC intermediate layer is obviously much better than that of F-DLC, and the adhesion is dependent on preparation condition of preparation SiC intermediate layer. The adhesion of F-DLC can reach 8.7 N with 200 W RF input power and 5 min deposition time, which is much bigger than the adhesion of F-DLC without intermediate layer (4 N). The mechanism of the preparation condition of SiC influencing the adhesive force of F-DLC is studied by investigating the deposition rate curve, surface morphology and infrared spectrum.
On glass forming ability and thermal stability of Zr57Cu20Al10Ni8Ti5 bulk metallic glass by substituting each component with 1 at% Ag
Authors: Cui Xiao  , Xu Bao-Chen  , Wang Zhi-Zhi  , Wang Li-Fang  , Zhang Bo  , Zu Fang-Qiu  ,   Liquid/Solid Metal Processing Institute, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China
Published: December 2020

Each component element of Zr57Cu20Al10Ni8Ti5 bulk metallic glass is substituted by 1 at% Ag element. Variations of glass forming ability and thermal-stability are studied using differential scanning calorimetry which gives the thermal-dynamic parameter of the bulk metallic glass, combined with X-ray diffraction of different diameter rods (Φ8, Φ10 and Φ12) which are prepared by copper mould suction casting, The results show that the glass forming ability and thermal-stability are greatly improved by substituting Ti element and the critical cooling rate is significantly reduced. While, no obvious law is found when substituting other elements. By analyzing the relevant data on glass forming ability, Inoue's atomic size rule show inconformity in this work, however, the mixing enthalpy rule dose not show conformity obviously. By calculating the packing density, we find that the packing density is obviously improved when substituting 1 at% Ti with Ag. Dynamic analysis is used and the mechanism of element substitution is also investigated on the aspects of crystallization activation energy and crystallization rate constant.
Study on the mechanical properties of carbon nanocones using molecular dynamics simulation
Authors: Li Ming-Lin  , Lin Fan  , Chen Yue  ,   College of Mechanical Engineering, Fuzhou University, Fujian 350108, China
Published: December 2020

The mechanical behaviors of carbon nanocone (CNCs) with equivalent number of atoms under uniaxial extension and uniaxial compress are investigated using classical molecular dynamics simulations, exploring the Brenner and Lennard-Jones potentials to represent the interatomic interaction. The mechanical properties including elastic strain limit, ultimate longitudinal loading, and configuration evolution of CNC, are obtained and compared with those of carbon nanotube that consists of equivalent atoms. Under tension, CNC with larger apex angle presents a higher failure strength in general, as well as a larger maximum strain. However, the failure strength of the CNC with largest conical angle of 112.88° is the smallest one. The carbon nanotube with (15, 0) and 4 nm length presents a moderate strength and strain. Under compression, CNCs with conical angle of 112.88° and 83.62° have true chiral inversion without the chemical bond break. However, the other CNC exhibits unstable uniaxial compress and sudden lateral bend under compression. The force that buckles these carbon nanostructures decreases as the conical angle increases, except for the CNC of 38.94°. Results in the present study show that a certain CNC possesses more excellent mechanical properties than the equivalent CNT and is expected to substitute CNT and to be applied to some engineering fields such as nanosensors and nanoscale composites.
Performance of steel reinforced high strength concrete investigated in the gas gun experiment
Authors: Jiang Guo-Ping  , Huan Shi  , Hao Hong  , Du Yong-Feng  , Jiao Chu-Jie  ,   Earthquake Engineering Research Test Center, Guangzhou University, Guangzhou 510405, China
Published: December 2020

The shock properties of C100 concrete are investigated by gas gun planar impact technique. The manganin pressure gauge is used to measure the pressure-time curves of the samples. The physical quantities are all obtained by the Lagrange method. Moreover, it is observed from the measured pressure-time curves that the decay factor is smaller in the steel reinforced high strength concrete. The dynamic response is analyzed.
Theory study of rare earth (Ce, Pr) doped GaN in electronic structrue and optical property
Authors: Li Qian-Qian  , Hao Qiu-Yan  , Li Ying  , Liu Guo-Dong  ,   School of Material Science and Engineering, Hebei University of Technology, Tianjin 300130, China
Published: December 2020

Using the pseudopotential plane-wave method within the density functional theory as implemented in the Vienna ab-initio simulation package, we investigate the crystal parameters, electronic structures and optical properties of rare earth Ce and Pr doped GaN. The local spin density approximation with Hubbard-U corrections method is used to treat the correlation effect of strongly localized rare-earth 4f electron states. The results show that the crystal parameters increase after doping Ce and Pr in GaN. The Ce impurity introduces defect level in the gap while for Pr the level lies near the valence band maximum, and the defect levels are contributed by Ce and Pr 4f electron states. In addition, the dopings of Ce and Pr give rise to spin polarization and magnetic-order. For GaN:Ce, there appear two new peaks, one is in the low energy region of imaginary dielectric function and the other is in the low energy region of absorption coefficient. These new peaks are probably related to the defect level in the gap. For GaN:Pr, red shifts of the dielectric peak and absorption edge duo to bandgap narrowing are observed.
0.7 structure of conductance quantization in quantum point contact
Authors: Jiao Hui-Cong  , An Xing-Tao  , Liu Jian-Jun  ,   College of Physical Science and Information Engineering, Hebei Normal University, Shijiazhuang 050024, China;,   School of Sciences, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018, China;,   Physics Department, Shijiazhuang University, Shijiazhuang 050035, China
Published: December 2020

In the paper, we study electronic transport property through a quantum point contact with the saddle-point potential. Our numerical approach is based on the Green's function technique which is evaluated at the Hartree-Fork level. We reproduce relevant features of 0.7 structure when the strength of electron-electron interaction has changed. Besides, we calculate spin accumulation and noise factor at zero temperature. We deepen the understanding of the effect of strong correlation interaction on spin transport in nanometer semiconductor device.
Investigation on three-photon-absorption fitting method and three-photon-absorption-induced optical stabilication effect of a fluorene derivative
Authors: Liu Jun-Hui  , Li Guo-Feng  , Wang Yuan-Xu  ,   Institute for Computational Materials Science, Department of Physics, Henan University, Kaifeng 475004, China
Published: December 2020

Three-photon absorption coefficient obtained by current nonlinear transmittance method has large fitting error because of uneven laser radiation distribution. Relatively small three-photon absorption cross section values of present nonlinear molecules restrict their practical applications. In this paper, an accurate three-photon absorption coefficient fitting method is presented, which is applicable for a variety of laser distributions. A fluorene-based derivative, 2, 7-bis(4-methoxyphenylacetylene)-9-thoine-fluorene, is synthesized. Apparent three-photon-absorption-induced optical stabilization effect is shown.
Improvement of light extraction efficiency of GaN-based blue light-emitting diode by disorder photonic crystal
Authors: Chen Xin-Lian  , Kong Fan-Min  , Li Kang  , Gao Hui  , Yue Qing-Yang  ,   School of Information Science and Engineering, Shandong University, Jinan 250100, China;,   School of Physics Science and Technology, University of Jinan, Jinan 250022, China
Published: December 2020

Sub-wavelength photonic crystal can effectively improve the light extraction efficiency (LEE) of the light emitting diode (LED). However, it is inevitable to have defects, (namely disorder structures) during its fabrication. In this study, the LED model with ideal quadrate photonic crystal is optimized by using the finite-different time domain method. Three different LED structures with various disordered photonic crystals are further simulated. We investigate the influences of several stochastic variables (including position, radius, and depth of an air hole) of the photonic crystal on the LEE of GaN based blue LEDs. It can be found that regarding photonic crystal LED whose air hole radius is optimized to 80 nm, the stochastic variables of the position and radius will reduce its LEE. However, an opposite trend is found when this radius is replaced by 60 nm, which is not optimized. Furhermore, the LEE fluctuates inside to an extent of 53.8% as two stochastic variables (including the randomized position and the randomized radius) change from 0 nm to ±20 nm. The influence of the stochastic variables of the depth of air hole can be neglected since this variation is very small. The results in this paper have an important reference value for designing and fabricating high-performance blue light photonic crystal LED.
Numerical simulation of coupled thermo-mechanical process of friction stir welding in quasi-steady-state
Authors: Yin Peng-Fei  , Zhang Rong  , Xiong Jiang-Tao  , Li Jing-Long  ,   School of Science, Northwestern Polytechnical University, Key Laboratory of Space Applied Physics and Chemistry, Ministry of Education, Xi’an 710072, China;,   School of Material Science and Engineering, Northwestern Polytechnical University, Shaanxi Key Laboratary of Friction Welding Technologies, Xi’an 710072, China
Published: December 2020

The flow field of plastic deformation and the temperature field during the process of friction stir welding can directly affect the structure evolution of the welded joint, and also have a great influence on mechanical properties of the final joint. In this respect, therfore, a lot of researches have been carried out. The recent research results show that this process is an extremely complex coupled thermal-mechanical process, the temperature field couples together with the flow field of plastic deformation of the material. In this paper, the coupled process is simulated based on hydromechanics and heat transfer theory; the flow field of plastic deformation and the temperature field are calculated; an experiment is designed to measure the temperature field, which indicates that the computed results can exactly describe the coupled thermal-mechanical condition of the friction stir welding in quasi-steady-state.
Preparation of vanadium oxide thin films by oxidation with rapid thermal processing
Authors: Gao Wang  , Hu Ming  , Hou Shun-Bao  , Lü Zhi-Jun  , Wu Bin  ,   School of Electronic Information Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

Vanadium thin films are deposited by magnetron sputter. Then VOx thin films are fabricated by a series of rapid thermal processes (RTPs) in pure oxygen environment. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscope are employed to analyze crystalline structure of the thin film, phase composition and surface morphology. Electrical and optical properties of VOx thin film are measured by the four-point probe method and THz time-domain spectroscopy technology, respectively. The results reveale that the VOx thin film which is composed mainly of V2O5 and VO2 has the properties of phase transition to a certain extent within the RTP condition of heat preservation temperature and time, and the overall valence of vanadium remains unchanged, no matter whether the RTP condition is the same. The best performance VOx thin film can be obtained under the moderate RTP condition, such as 500 ℃ 25 s, and this film can also modulate the THz wave.
Approximate symmetry reduction for initial-value problem of perturbed diffusion equations
Authors: Li Ji-Na  , Zhu Xiao-Ning  , Cheng Li-Fang  ,   College of Science, Zhong yuan University of Technology, Zhengzhou 450007, China;,   Department of General Studies, Henan Business College, Zhengzhou 450044, China
Published: December 2020

In this paper, the approximate symmetry reduction for the initial-value problem of perturbed diffusion equations with source term is studied by the approximate generalized conditional symmetry. The classification of governing equations is given, and the Cauchy problem of partial differential equations is reduced to initial-value problem of ordinary differential equations. Finally, the approximate solution is obtained by solving the reduced system of equations.
Study of directed networks-based Email virus propagation model and its concussion attractor
Authors: Deng Qi-Xiang  , Jia Zhen  , Xie Meng-Shu  , Chen Yan-Fei  ,   College of Science, Guilin University of Technology, Guilin 541004, China;,   Guangxi Key Laboratory of Spatial Information and Geomatics, Guilin 541004, China
Published: December 2020

According to directed Email networks and the spread characteristics of Email virus, we study the behavior of the virus shock propagation in Email networks by using the mean field method to build delay differential equation model of viral spread. Then, the sufficient condition about the existence of shock solution's global attractor is given in theory. The existence and control of attractor are proved by numerical experiments. Our research indicates that spread probability between subgraphs determines the existence of attractor, and effective rate of spread determines the amplitude of attractor. Therefore these two parameters are significant in prediction of the scale of viral spread in networks.
Problem and analysis of stability decidable theory for a class of fractional order nonlinear system
Authors: Li Li-Xiang  , Peng Hai-Peng  , Luo Qun  , Yang Yi-Xian  , Liu Zhe  ,   Information Security Center, Beijing University of Posts and Telecommunications, Beijing 100876, China
Published: December 2020

The research on the stability theory of fractional order nonlinear system has an important value for the application of synchronization and the control of fractional order chaotic system. The discussion that the stability discrimination of fractional order nonlinear system is converted into that of corresponding integer order nonlinear system has an important significance. In this paper, through the examples, for time-varying coefficient matrix, we point out the existing mistake of the discrimination theorem that states that if the integer system is stable, then its corresponding fractional system with order less than one is also stable. We also analyze the causes of the mistake.
Design and implementation of an arbitrary poincare plane section circuit in three-dimensional space
Authors: Chen Hong  , Wu Ling  ,   Electronic Engineer College, Heilongjiang University, Harbin 150080, China
Published: December 2020

The Poincare section method is an effective method to simplify the analysis of complex dynamic system motion state. To achieve online observing system states conveniently, an arbitrary directional Poincare plane section physical electronic circuit in three-dimensional space is designed and realized. Firstly, the key problems of an arbitrary Poincare plane section circuit design are analyzed and studied in detail. And then the physical circuit is realized in classification. As Chua's circuit has rich dynamic behaviors, the typical Chua's circuit is chosen as the experimental dynamical system. And then a lot of the physical experiments with this Poincare plane section circuit are performed in real time. For example, Poincare plane section diagrams in different conditions of Chua's circuit are measured, and the test experiments in the same kind of chaotic state, with different plane sections chosen, are carried out. All Poincare section map diagrams and phase diagrams are measured by two double-channel oscilloscopes (analogue oscilloscope and digital oscilloscope). At the same time, computer simulation experiments are conducted by using Matlab. These results show the practicability and effectiveness of the Poincare plane section circuit.
Synchronization of "Hopf/homoclinic" bursting with "SubHopf/homoclinic" bursting
Authors: Wang Fu-Xia  , Xie Yong  ,   State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

Taking the modified Morris-Lecar neuron model for example, we consider the synchronous behaviour between "Hopf/homoclinic" bursting and "SubHopf/homoclinic" bursting. Firstly, the synchronization between two coupled bursting neurons with the same topological type is investigated numerically, and the results show that the coupling strength reaching the synchronization of the membrane potential of "Hopf/homoclinic" bursting is smaller than that of "SubHopf/homoclinic" bursting, that is to say, the former can reach complete synchrony of the membrane potential more easily than the latter. Secondly, we study the synchronous behavior of two coupled bursting neurons with different topological types by numerical analysis, and find that with the increase of the coupling strength the two different types of bursting neurons reach the bursting-synchrony first, and then they can reach complete synchrony of the membrane potential when the coupling strength is strong enough, and the type of synchronous state is inclined to the type of easy synchronization, namely, "Hopf/homoclinic" bursting. To our surprise, the slow variables exhibit phase synchronization instead of complete synchronization. Moreover, there is a linear relationship between the both slow variables. This point is distinctly different from the results of the existing documents.
Algorithm for finding horseshoes in three-dimensional hyperchaotic maps and its application
Authors: Li Qing-Du  , Tang Song  ,   Key Laboratory of Industrial Internet of Things & Networked Control of Ministry of Education, Chongqing University of Posts and Telecommunications, Chongqing 400065, China;,   Institute for Nonlinear Circuits and Systems, Chongqing University Posts and Telecommunications, Chongqing 400065, China
Published: December 2020

Topological horseshoe theory is fundamental for studying chaos rigorously, which, however, has rarely applied to hyperchaos. The reason is that it is too hard to find a topological horseshoe in a hyperchaotic system, due to the high dimension of the system and the multiple expansion directions in the state space. Therefore, in this paper a practical algorithm for three-dimensional (3D) hyperchaotic maps is proposed. Usually, a hyperchaotic system has a large negative Lyapunov exponent, its attractor is often contracted closely to a certain surface. Based on this feature, the algorithm first deducts the dimension along the direction of contraction to obtain a 2D projective system; then it detects a projective horseshoe with 2D expansion; finally, it constructs a 3D horseshoe for the original system. In order to verify the validity of the algorithm, it is applied to the classic hyperchaotic Lorenz system and the famous Saito hyperchaotic circuit, and their horseshoes with 2D expansion are successfully found from the Poincaré mapping.
Spatiotemporal chaos synchronization of complex networks by Backstepping design
Authors: Li Yu-Shan  , Lü Ling  , Liu Ye  , Liu Shuo  , Yan Bing-Bing  , Chang Huan  , Zhou Jia-Nan  ,   College of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029, China
Published: December 2020

Spatiotemporal chaos synchronization of complex networks by Backstepping design is investigated. Backstepping design is extended from synchronization between two chaotic systems to the synchronization of complex network constituted spatiotemporal chaotic systems. The relation between the configuration coefficient and the control gain is identified according to the stability theory. When the control input is added to any node of the network, the network synchronization is realized. Furthermore, simulation is made to verify the effectiveness of the synchronization mechanism.
The characteristics of elliptical optical soliton in anisotropic medium
Authors: Li Qiong  , Zhai Yong-Hui  , Liang Guo  , Guo Qi  ,   Laboratory of Nanophotonic Functional Materials and Devices, South China Normal University, Guangzhou 510631
Published: December 2020

Formation of elliptical optical soliton in rectangular lead glass is theoretically investigated, and an anisotropic diffraction effect is introduced into our theoretical model. Using the variational approach, we obtain an analytic elliptic soliton solution in a strongly nonlocal medium with anisotropy, which demonstrates that anisotropic diffraction effect has a great influence on the formation of the elliptical optical soliton. To confirm the analytic solution, we work out the numerical solution by the Newton iterative method. And the analytic solution accords with the numerical solution very well.
Experimental studies of slow wave based on the surface waves in a two-dimensional metamaterials waveguide
Authors: Wang Wu-Song  , Zhang Li-Wei  , Zhang Ye-Wen  , Fang Kai  ,   MOE Key Laboratory of Advanced Micro-structure Materials, Department of Physics, Tongji University, Shanghai 200092, China;,   School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000, China
Published: December 2020

In this paper, we study the slow propagation characteristics of surface electromagnetic waves according to theoretical analysis in the MNG (μ-negative)-DPS (double-positive)-MNG waveguide, which is composed of two-dimensional (2D) metamaterials. The dispersion curves of this waveguide vary with circuit parameter (unit capacitors) of MNG metamaterial. At the cutoff frequency of the dispersion curve the group velocity of electromagnetic wave is equal to zero in theory. So we can obtain slow propagation of the surface waves at different cutoff frequencies just by changing the unit capacitor of the MNG metamaterial. Theoretical analysis also shows that the step changes in slow waves are obtained at some fixed frequencies through changing the unit circuit parameters. The experimental results are in good agreement with simulation results.
Mode-locked double-clad fiber laser with a carbon nanotubes saturable absorber
Authors: Wang Sha-Sha  , Pan Yu-Zhai  , Gao Ren-Xi  , Zhu Xiu-Fen  , Su Xiao-Hui  , Qu Shi-Liang  ,   Dept. of opt-electronics, Harbin institute of technology at Weihai, Weihai 264209, China
Published: December 2020

In this paper, the mode-locked laser pulse with a maximum power of 366 mW is achieved by using Yb-ions-doped double-clad fiber as the gain medium and single-walled carbon nanotubes (SWCNTs) as the saturable absorber (SA). The saturable absorber with a modulation depth of 27% is fabricated by spreading the well-dispersed SWCNTs on the D-shaped segment of the fiber, which is directly etched on the standard single-mode fiber by water-assisted femtosecond laser ablation. The ring-cavity structure fiber laser is fabricated based on the SWCNT-SA. The mode-locked pulse width of 93.8 fs, central wavelength of 1083.8 nm, and 3 dB bandwith of 8.6 nm at the repetition rate of 5.59 MHz are obtained in the optimized polarization state under a pump power of 4 W.
Investigation of tunable coherent XUV light source by high harmonics generation using intense femtosecond laser pulses in Ne
Authors: Lu Fa-Ming  , Xia Yuan-Qin  , Zhang Sheng  , Chen De-Ying  ,   National Key Laboratory of Science and Technology on Tunable Laser, Harbin institute of Technology, Harbin 150080, China;,   Department of Physics, Harbin institute of Technology, Harbin 150080, China
Published: December 2020

The buleshift properties of high-harmonic generation with phase matching of different filling pressures and laser intensities are experimentally investigated in this paper. The laser buleshift generated in gas cell, with about 0.13 nm in plateau and 0.07 nm in cutoff is obtained. The buleshift is influenced by simply changing the filling pressure and laser intensity, namely, by varying the density of free electrons in gas cell.
Characteristics of laser transmission in different types of aerosols
Authors: Wang Hong-Xia  , Zhu You-Zhang  , Tian Tao  , Li Ai-Jun  ,   Faculty of Science, Second Artillery Engineering University, Xi'an 710025, China
Published: December 2020

The characteristics of laser transmission in atmosphere are an important issue that must be considered for applications in laser engineering. For 1.06 μm and 10.6 μm laser, the single scattering parameters of aerosols are calculated based on the Mie scattering theory. For the transmission attenuation of the laser in aerosol, the Monte Carlo simulation model is established. For dust-like, water-soluble, oceanic and soot four types of aerosols, the relations of transmittance to visibility and propagation distance are computed and analyzed using the program written in MATLAB language respectively. The results show that single scattering calculation has a larger error when the visibility is low, and albedo is high. Using the Monte Carlo method to calculate the attenuation of the laser transmission in aerosol can reveal multiple scattering phenomenon. For the 1.06 μm laser, the attenuation capacity of soot aerosol is strongest, and for the 10.6 μm laser, the attenuation capacity of dust-like aerosol is strongest.
Field-tracing based numerical simulation technique for the investigation of ultra-small self-focusing optical fiber probe
Authors: Wang Chi  , Bi Shu-Bo  , Wang Li  , Xia Xue-Qin  , Ding Wei  , Yu Ying-Jie  ,   Dept.of Precision Mechanical Engineering, Shanghai University, Shanghai 200072, China;,   State key laboratory of precision measuring technology and instruments, Tianjin University, Tianjin 300072, China;,   Shanghai Institute of Optics and Fine Mechanics, CAS, Shanghai 201800, China
Published: December 2020

Field-tracing based numerical simulation technique is investigated to design and analyze ultra-small self-focusing optical fiber probe. Firstly, the concept and principle of the field-tracing are described. Secondly, the method is discussed to implement the field-tracing technique in the physical optical software of VirtualLab. Finally, an ultra-small self-focusing optical fiber probe is simulated in the field-tracing based optical software of VirtualLab. In this paper, we find that under the conditions of a fiber spacer length of 0.36 mm and the self-focusing fiber lens lengths of 0.1 mm, 0.11 mm and 0.12 mm, the working distances of the probe are 0.75 mm, 0.63 mm and 0.51 mm, and the focus spot sizes are 32 μm, 24 μm and 19 μm respectively. The simulation results are in good agreement with the experimental data, showing that the field-tracing based numerical simulation technique is an effective tool for investigating ultra-small self-focusing optical fiber probe.
Analysis of liquid sheet and jet flow mechanism after droplet impinging onto liquid film
Authors: Liang Gang-Tao  , Guo Ya-Li  , Shen Sheng-Qiang  ,   School of Energy and Power Engineering, Dalian University of Technology, Key Lab. for Ocean Energy Utilization and Energy Conservation of Education of Ministry, Dalian 116024, China
Published: December 2020

Physical and mathematical models are established to simulate the phenomenon of single droplet impinging onto flat liquid film by using the coupled level set and volume of fluid method, and influences of viscosity and surface tension on the morphology of the crown liquid sheet are discussed. Besides, the mechanism of jet flow in the neck region is revealed and the theory of kinematic discontinuity proposed by Yarin and Weiss is verified by analyzing the distributions of pressure and velocity after impingement. The research result shows that the effect of surface tension on the crown morphology is far stronger than that of viscosity. Generation of jet flow is due to the higher pressure difference, the effect of which becomes weak with impact evolution and the jet flow is developed into the crown gradually with the help of radial flow in the liquid film.
Particle-in-cell simulation of corona discharge in low pressure in stepped impedance transformer
Authors: Liu Lei  , Li Yong-Dong  , Wang Rui  , Cui Wan-Zhao  , Liu Chun-Liang  ,   Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049, China;,   Science and Technology on Space Microwave Laboratory, Xi'an 710100, China
Published: December 2020

The corona discharge process in low pressure N2 in stepped impedance transformer (SIT) is simulated using 3-D particle-in-cell (PIC) software (VORPAL). The evolution of the charged particle spatial distribution during the discharge is obtained. The two main discharge mechanisms, i.e., multipactor and corona discharge, are analyzed. From the simulation results, it can be found that the threshold voltage of breakdown of the SIT first decreases and then increases. In addition, with the increase of the pressure, the multipactor effect weakens while the corona discharge effect strengthens. Through the comparison of the threshold voltages between two kinds of wall materials, i.e., Ag and Cu, the critical pressures between the two discharge mechanisms are achieved.
The MCC numerical algorithm of the extraction of the surface-produced negative hydrogen ions
Authors: Yang Chao  , Liu Da-Gang  , Wang Hui-Hui  , Yang Yu-Peng  , Liao Fang-Yan  , Peng Kai  , Liu La-Qun  ,   School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

The physical mechanism of the negative hydrogen ion transportation and extraction is investigated, the charge exchange reaction and coulomb collision process are analysed thearelically, and the corresponding numerical calculation module is also designed. Therefore, using the finite difference time domain method to calculate the lorentz force of the negative hydrogen ions, and through Monte Carlo method to deal with the collision between negative hydrogen ions and other particles. Finally, it is successful to develop the 3D MCC algorithm of the transportation and extraction of the surface-produced negative hydrogen ions, and simulate the foreign popular ion source JAEA 10 A. The results show that with the increase of the filter magnetic fiel, the bigger the number of extracted ions, the smaller the number of ions in negative hydrogen ions source is, that with the filter magnetic filed is small, the greater the pressure, the bigger the number of extracted ions is, and that when the filter magnetic filed is big, the smaller the pressure, the bigger the number of extracted ions is.
Structural and optical characterization of film deposited by pulsed plasma thruster plume
Authors: Zhang Rui  , Zhang Dai-Xian  , Zhang Fan  , He Zhen  , Wu Jian-Jun  ,   College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

In order to study the characteristics of the films deposited by pulsed plasma thruster plume and assess contamination arising from the exhaust plume, the compositions of the pulsed plasma thruster plume are studied by means of mass spectrum analysis, the structural properties of the films deposited at different angles on the cathode side of the thruster are investigated by X-ray photoelectron spectroscopy, Fourier transform infrared absorption spectroscopy, and the optical properties of the films are studied by ultraviolet-visible light spectrophotometry. The results show that the plume consists primarily of C, F, CF, CF2, CF3, that low fluorine-carbon ration carbon fluorine films are deposited by pulsed plasma thruster plume, and that the chemical bondings and structures of these films present different trends in different regions with 30 degree angle as the boundary. These films basically show that they have strong absorption properties for wavelengths below 500 nm and have enhanced reflective characteristics. Due to influence of the characteristics of the deposited films, the optical properties of these films present signigicant angular dependences.
Process in preparation of metal-catalyzed graphene
Authors: Yu Hai-Ling  , Zhu Jia-Qi  , Cao Wen-Xin  , Han Jie-Cai  ,   Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, China
Published: December 2020

Graphene, which is regarded as a new carbon material, has attracted much attention of scientists. Graphene holds the promise for applications in optoelectronics and microelectronics, owing to many unique physical and chemical properties. The large-scale applications are restricted by controllable synthesis of large-size graphene. In this paper we present the advantages and disadvantages of preparation processes of graphene. The recent advances in the process of metal-catalyzed graphene in terms of lay number control and large area synthesis are discussed. The graphene prepared by metal-catalyzed solid carbon source has large area and high quality and is thin and homogeneous. We review the latest progress in graphene transformation mechanism, point out the limitations of current study and prospect the future development in the graphene transformation mechanism.
Terahertz dual air core fiber directional coupler
Authors: Jiang Zi-Wei  , Bai Jin-Jun  , Hou Yu  , Wang Xiang-Hui  , Chang Sheng-Jiang  ,   Institute of Modern Optics, Nankai University, Tianjin 300071, China;,   School of Electronics and Information Engineering, Tianjin Polytechnic University, Tianjin 300160, China
Published: December 2020

A novel low-loss dual-core fiber directional coupler for terahertz raditional is proposed, Coupling properties, loss and group velocity dispersion of the fibers are investigated by the full-vector finite-element method (FEM). The simulation results demonstrate that the coupling length of this coupler is less than 1.8 cm between 1.55 and 1.80 THz, and the coupling broadband of 0.07THz can be realized. And the loss coefficient of the coupler is less than 0.02 cm-1. The directional coupler has potential applications in narrowband filtering, wavelength-division multiplexing, switching, polarization splitter and so on.
Empirical study on scaling of human behaviors in e-commerce
Authors: Dong Yu-Wei  , Cai Shi-Min  , Shang Ming-Sheng  ,   School of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China;,   Institute of Information Economy, Hangzhou Normal University, Hangzhou 310036, China
Published: December 2020

The detrended fluctuation analysis (DFA) method is used to analyze the human on-line activities in e-commerce. We comprehensively investigate the scale laws of browse and purchase behaviors, which have received little attention before. The time series of browse and purchase behaviors each obviously show a periodical character, and their probability density distributions each have a significant bimodal form. Based on the Fourier transform method, the power spectra of time series indicate that each of them obeys a stochastic process with a long-range self-similar feature (i.e., deviation far from the Poisson process). After identifying and filtering the influence of periodic trend based on power spectra, the detrended fluctuation analysis is used to study the scaling law of time series. Several interesting results can be found that their scaling behaviors on small and large scales show similar values that confirm the long-range correlations rooting in the time series of human on-line activities, and their average scaling exponent approximately equaling 1 suggests that the human online activity may be associated with a self-organized criticality. Although the empirical results are only the observed phenomena like those found in the Internet traffic and stock price fluctuation of financial market, we still think that they may provide an important insight to deeply understand the mechanism of human dynamic behaviors in e-commerce and predict their fluctuation trend for the potential business application.
Mechanism of dual-wavelength anti-jamming photoelectric smoke-detection
Authors: Sun Wu  , Deng Xiao-Jiu  , Li Yao-Dong  , Zhang Yong-Ming  , Zheng Sai-Jing  , Wang Wei-Miao  ,   College of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009, China;,   State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230027, China;,   Technical Center of Shanghai Tobacco Corporation, Shanghai 200082, China
Published: December 2020

Using the T-matrix method, detailed numerical computation and comparative analysis on the distributions of light scattering matrix of fire smoke particles and non-fire smoke particles are carried out. The results show that when the wavelength of incident light changes, the degrees of variation on elements of fire smoke particles are different from those of non-fire smoke particles. By using dual-wavelength pulsed laser as incident ligh, through detecting appropriate element of light scattering matrix and combining XOR logical operation, the fire smoke particles can be distinguished from non-fire smoke particles, thereby reducing the misinformation caused by non-fire smoke particles.
Entanglement properties in the system of atoms interacting with three coupled cavities which are in weak coherent states
Authors: Lu Dao-Ming  ,   Department of Electronic Engineering, Wuyi University, Wuyishan 354300, China
Published: December 2020

We study the entanglement dynamics of the system comprising three two-level atoms resonantly interacting with three coupled cavities which are in weak coherent states initially. The atom-atom entanglement and cavity-cavity entanglement are investigated. The influences of coupling constant between cavities and intensity of the cavity field on entanglement properties are discussed. The results obtained using the numerical method show that atom-atom entanglement and cavity-cavity entanglement are both strengthened with the increase of intensity of the cavity field; on the other hand, atom-atom entanglement is weakened and the entanglement between cavity A and cavity B is strengthened with the increase of the coupling constant between cavities, and the entanglement between cavity B and cavity C has a nonlinear relation with the increase of the cavity-cavity coupling coefficient. These results are different from those in the case that cavity field is in vacuum state initially.
Entanglement dynamics in Majorana representation
Authors: Cao Hui  ,   School of Physics, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

With the help of the newly proposed definition of entanglement, the entanglement dynamics of a system composed of two bosonic atoms trapped in a symmetric double-well potential is investigated. For any state of this system, the description of Majorana representation can be analytically derived. It is found that the entanglement dynamics depends on both the atomic interaction and the initial state of the system. Specifically, the atomic interaction determines the oscillation frequency of the entanglement degree, whereas the initial state controls the oscillation amplitude.