bluuebunny/crossref_metadata_2025 huggingface dataset:
Chaos and the control of multi-time delay feedback for some nonlinear relative rotation system
Authors: Zhang Wen-Ming  , Li Xue  , Liu Shuang  , Li Ya-Qian  , Wang Bo-Hua  ,   Key Lab of Industrial Computer Control Engineering of Hebei Province, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

The dynamic equation of some nonlinear relative rotation system with two masses has been established, which contains a kind of nonlinear sick-slip friction. Chaotic motion and the control effect of multi-delay feedbacks of the nonlinear relative rotation system under external excitation are investigated. When the system is in chaos under external excitation, the multi-time delay is applied to control the chaotic motion. The chaotic critical conditions of parameters about Smale commutation are given in terms of Melnikov theory, while the influence of multi-delay feedbacks on the system movement state and chaotic critical conditions is studied. The control impacts of multi-time delay parameters on chaotic motion are studied by phase diagram, Poincare map and power spectrum, separately.
The influence of CO2 laser local irradiation on the laser damage resistance of fused silica
Authors: Liu Chun-Ming  , Yang Liang  , Yan Zhong-Hua  , Jiang Yong  , Wang Hai-Jun  , Liao Wei  , Xiang Xia  , He Shao-Bo  , Lü Hai-Bin  , Yuan Xiao-Dong  , Zheng Wan-Guo  , Zu Xiao-Tao  ,   School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China;,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The influence of CO2 laser local irradiation (CLLI) on the laser damage resistance of fused silica was studied. It is found that CLLI has no evident effect on the laser-induced damage threshold (LIDT) of fused silica when the temperature of irradiation center is low (1139 K). However, the influence of CLLI on LIDT becomes important when the temperature of irradiation center is higher (1638 K). AT first, LIDT decreases with r increasing from zero to rM, where r is the distance to irradiation center, and rM is the distance at which the residual stress-induced phase retardance reaches the maximum. Then, LIDT increases a little when r is larger than rM. The origin of this phenomenon is discussed. Due to the residual stress, re-initiated damage in irradiation region can result in the formation of fractures. The fractures due to the re-initiated damage at irradiation center transport along radial direction firstly, and then transport along the tangential direction near rM. This may be due to the maximum tensile hoop stress and radial stress dependence of radius. Cares should be taken for the optical cleaning when thermal oven annealing is used to eliminate the residual stress. Otherwise, crystallization can be induced by contamination during annealing. The contamination also has negative impact on the light transmission and LIDT.
Effects of pristine state on conductive percolation model of memristor
Authors: Li Zhi-Wei  , Liu Hai-Jun  , Xu Xin  ,   Department of Circuit and Systems, School of Electronic Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Due to its fitting the resistive switching behavior of memristor well, the percolation network model has recently attracted attention in the memristive mechanism field. However, the current 2D percolation network model lacks the pristine states analysis. In this paper, the original model is simplified to study the effects of pristine state on the forming process of conductive percolation channel with the increase of applied voltage. Intuitively, such a percolation network model not only demonstrates the dynamic process of local conducting channels formed in the physical meaning, which verifies that the resistance distribution of the memristor switching is not ideally bistable but can be fitted by Gauss curve; also it contributes to deciphering the unknown conductive mechanisms of memristor with the various types of percolation channel.
Thermal-induced optical changes in the amorphous Ge20Sb15Se65 film
Authors: Zong Shuang-Fei  , Shen Xiang  , Xu Tie-Feng  , Chen Yu  , Wang Guo-Xiang  , Chen Fen  , Li Jun  , Lin Chang-Gui  , Nie Qiu-Hua  ,   Laboratory of Infrared Material and Devices, Ningbo University, Ningbo 315211, China
Published: December 2020

The amorphous Ge20Sb15Se65 thin film was prepared by magnetron sputtering deposition technique. Effect of heat treatment temperature in the range of 150—400 ℃ on the optical properties of Ge20Sb15Se65 thin films has been investigated. The microstructure and optical properties of the films were characterized by UV-Vis, Raman spectroscopy and XRD, the optical constant was calculated using the Swanepoel method and Tauc's law from the optical transmission spectra. Results indicate that when the annealing temperature (Ta) is lower than the glass transition temperature (Tg), the optical band gap (Egopt) increases from 1.845 to 1.932 eV, and the refractive index decreases from 2.61 to 2.54, while the optical band gap decreases from 1.932 to 1.822 eV and the refractive index increases from 2.54 to 2.71 with a further increase of Ta. The results were explained in terms of the Mott and Davis model for amorphous materials and amorphous to crystalline structural transformations. It is well consistent with the results of structure analysis by XRD and Raman spectroscopy.
The effect of the interlayer CrN on adhesion characteristics of ta-C films on high-speed steel substrate
Authors: Han Liang  , Liu De-Lian  , Chen Xian  , Zhao Yu-Qing  ,   School of Technical Physics, Xidian University, Xi'an 710071, China;,   School of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

CrN/ta-C composite coating on a high-speed steel substrate is performed by magnetic filtered cathodic arc technique and magnetron sputtering technique. Adheision of ta-C film on the high-speed steel substrate is studied by changing the preparation process of a buffer layer of CrN. The results are as follows. With the increase of nitrogen flow, the buffer layer chromium nitride experiences the phase transition of Cr-Cr2N-CrN; the adhesion of the coating is improved with the increase of nitrogen flow, but when the nitrogen flow exceeds 30 sccm, the adhesion of coating will decline; the preferred orientation and grain structure of chromium nitride are changed by adjusting the substrate bias; the adhesion of the coating is improved with the increases of the bias voltage, but when the bias voltage exceeds 200 V, the the coating adhesion characteristics will be slightly reduced. The abrasion resistance of the test also shows that CrN coating can significantly improve the adhesion of the ta-C film on a substrate of high speed steel, and can also significantly improve the wear characteristics.
Numerical calculation of 3 mm wave extinction for expanded graphite
Authors: Zhou Ming-Shan  , Xu Ming  ,   School of Chemical Engineering, Yunnan Vocational and Technical College of National Defense Industry, Kunming 650023, China;,   School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

In order to explore the extinction and scattering characteristics of expanded graphite, which is a kind of 3 millimeter wave interference materials, the formula of extinction, scattering, absorption and backscattering cross sections (radar cross. section, RCS) are established based on the electromagnetic scattering theory of cylindrical conductor of finite length and finite conductivity by the method of moment. The extinction and scattering characteristics are calculated, and the influening factors of the characteristics including length, radius, conductivity and magnetic permeability of the expanded graphite are analyzed using Mathematica program. Results show that the expanded graphite has excellent extinction and scattering properties when its length and radius are 1.5 mm and 0.5 mm, respectively, and the properties can be improved when the conductivity and magnetic permeability of the expanded graphite are increased properly. This research provides a valuable insight into the improvement of interference performance of expanded graphite in 3 millimeter wave.
Polaron effect in a GaAs film: the fraction-dimensional space approach
Authors: Wu Zhen-Hua  , Li Hua  , Yan Liang-Xing  , Liu Bing-Can  , Tian Qiang  ,   Department of Physics, Beijing Normal University, Beijing 100875, China;,   Department of Fundamental Courses, Academy of Armored Force Engineering, Beijing 100072, China
Published: December 2020

Within the framework of the fraction-dimensional space approach, the binding energy and the effective mass of a polaron confined in a GaAs film deposited on Al0.3Ga0.7As substrate have been investigated. It is shown that the polaron binding energy and mass shift decrease monotonously with increasing film thickness. For the film thickness of Lw70 and the substrate thickness of Lb200 , the substrate thickness will influence the polaron binding energy and mass shift. The polaron binding energy and mass shift increase with increasing substrate thickness. In the region Lw70 or Lb200 , the substrate thickness has no influence on the polaron binding energy and mass shift.
The experiments for obtaining Huang-Rhys factor and energy transfer rate of Gd2(WO4)3:Eu nanophosphor
Authors: Meng Qing-Yu  , Liu Zhi-Xin  , Sun Wen-Jun  ,   Key Laboratory for Photonic and Electronic Bandgap Materials, Ministry of Education, School of Physics and Electronic Engineering, Harbin Normal University, Harbin 150025, China
Published: December 2020

In this paper, Gd2(WO4)3:Eu nanophosphors with different Eu3+ concentrations were synthesized through co-precipitation. The crystal structure and morphology of the nanophosphors were characterized by means of XRD and field emission scanning electron microscopy. Emission and excitation spectra (phonon sideband spectra) of each sample were measured, and concentration quenching curves were also drawn. The optimal doping concentration was confirmed to be 20 mol%. Huang-Rhys factor for each sample of different doping concentration was calculated by the phonon sideband spectra. Fluorescence lifetimes of the samples with different Eu3+ doping concentrations were measured. By fitting the fluorescence lifetime data of Eu3+ 5D0 level within the Auzel's model, the intrinsic lifetime for 5D0 level was determined and the generated phonon number in the quenching process was measured. The energy transfer rate of Eu3+ was derived from the fluorescence lifetime data, and the relationship between the energy transfer rate and the concentration was also given.
The defect luminescences of {100} sector in nitrogen-doped diamond
Authors: Wang Kai-Yue  , Zhu Yu-Mei  , Li Zhi-Hong  , Tian Yu-Ming  , Chai Yue-Sheng  , Zhao Zhi-Gang  , Liu Kai  ,   School of Materials Science and Engineering, Taiyuan University of Science and Technology, Taiyuan 030014, China;,   Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

Nitrogen is one of the most commonly-observed impurities in diamond, and affects the luminescence of these defects greatly. The complexes could be obtained from the nitrogen atom trapping the native defects such as self-interstitials, vacancies. In this study, a high-pressure and high-temperature synthesized nitrogen-doped diamond was characterized by cathode luminescence (CL) image, and the results showed that the blue region of this sample is the {100} growth sector. The {100} sector was then electron-irradiated in transmission electron microscope (TEM) and subsequently annealed at high temperatures so as to introduce the native defects to further form the nitrogen-containing complexes. All the optical properties of these defects in diamond were investigated by the low temperature photoluminescence (PL) spectra. The PL of {100} sector dominated the strong luminescence of nitrogen-vacancy (NV) complexes together with a weak 503 nm signal.
A study of spectral response for reflection-mode GaN photocathodes in UVA band
Authors: Hao Guang-Hui  , Chang Ben-Kang  , Chen Xin-Long  , Wang Xiao-Hui  , Zhao Jing  , Xu Yuan  , Jin Mu-Chun  ,   Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science & Technology, Nanjing 210094, China
Published: December 2020

In order to understand the spectral response characteristic of the NEA GaN photocathodes at UVA band, three samples grown by MOCVD with different emission layer thickness and doping concentration were activated in the ultra-high vacuum system, and their spectral response were tested online. We fit the experimental quantum efficiency with illumination wavelength between 0.25—0.35 μ by the use of reflection-mode GaN photocathode quantum efficiency formula and the least square approximation method. The back-interface compound rate and the slope of fitting line L are gained and the reflection-mode GaN photocathodes quantum efficiency is simulated with incident light wavelength at 0.35 μ. The results show that the back-interface compound rate and the slope of the fitting line L can reflect GaN photocathode response performance. When the back-interface compound rate of GaN photocathode is less than 105 cm/s and the thickness of the emission layer is set between 0.174—0.212 μ, the photocathode has optimal spectral response performance.
The influence of bias conditions on ionizing radiation damage of NPN and PNP transistors
Authors: Li Xing-Ji  , Lan Mu-Jie  , Liu Chao-Ming  , Yang Jian-Qun  , Sun Zhong-Liang  , Xiao Li-Yi  , He Shi-Yu  ,   School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;,   School of Astronautics, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

Bipolar junction transistors (BJTs), as important electronic components in analog or mixed-signal integrated circuits (ICs) and BiCMOS (Bipolar Complementary Metal Oxide Semiconductor) circuits, are employed in the space environment. Therefore, the research on characteristics and mechanisms of ionization damage in the BJTs is very important. Lower energy electrons are used as irradiation source to study the ionization damage in NPN and PNP transistors. Various bias conditions are imposed on the emitter-base junction to reveal the different bias conditions that contribute to the radiation effect on NPN and PNP transistors during irradiation processing. The semiconductor parameter analyzer, Keithley 4200-SCS, is used to measure the change of electrical parameters of transistors with increasing electron irradiation fluence in situ. Based on the measurement results, we find the degradation of transistors is severe under reverse emitter-base bias, and is lowest under forward emitter-base bias, while it is medium under zero emitter-base bias at a given irradiation fluence.
The network model of urban subway networks with community structure
Authors: Ding Yi-Min  , Ding Zhuo  , Yang Chang-Ping  ,   Faculty of Physics and Electronic, Hubei University, Wuhan 430062, China;,   School of Business Administration, South China University of Technology, Guangzhou 510640, China
Published: December 2020

In this paper, we present the empirical investigation results for the urban subway networks in China. The results show that all the urban subway networks have high clustering coefficient and small character path length, which exhibit a small-world behavior, the degree distributions take multiplicative exponential function forms. Otherwise, these networks are hierarchically organized by overlapping cliques, which are all the globally coupled networks. To explain these results, we introduce a network model, which is in good agreement with the empirical results; in addition, this model can explain the evolutionary procedure of other networks, such as the urban bus transport networks or the film actor networks.
Diagnosis and application of potential shear deformation wave-activity density in the torrential rain of Typhoon Morokat (2009)
Authors: Chu Yan-Li  , Wang Zhen-Hui  , Ran Ling-Kun  , Hao Shou-Chang  ,   Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science & Technology, Nanjing 210044, China;,   Institute of Urban Meteorology, CMA, Beijing 100089, China;,   Institute of Atmospheric Physics, CAS, Beijing 100029, China;,   Shanxi Provincial Meteorological Service, Taiyuan 030002, China
Published: December 2020

Based on previous studies of the interaction between wave and flow, combining the vertical component of disturbance convective vorticity vector, the disturbance horizontal divergence and the vertical gradient of disturbance generalized potential temperature, We define a new disturbance thermodynamic shear advection parameter in this paper. This parameter means a typical wave action density, its equation of tendency is a typical wave action equation, which could describe the development or evolution of mesoscale disturbance. With the wave action density and the wave action equation, we have conducted a diagnostic analysis of the heavy-rainfall event caused by landfall typhoon "Morakot" in 2009. Results show that the abnormal values of the wave action density (namely the disturbance thermodynamic shear advection parameter) will always change with the development of the observed precipitation regions, both their horizontal distribution and their temporal evolution are quite similar. Statistical analysis reveals a certain correspondence between the wave action density and the observed 6-hour accumulated surface rainfall in the summer of 2009, and they are intimately related to each other. The wave action density may be used to describe the typical vertical structure of dynamic and thermodynamic fields of a precipitation system, so it is closely related to the occurrence and development of the precipitation system and may have certain relation with the surface rainfall regions. The calculation of the wave action flux divergence shows that at the time around the landing of typhoon "Morakot" in the southeastern China coastal region, the potential vorticity of disturbance ageostrophic wind is the main forcing term affecting the local variation of wave action density. The contribution of the coupled term between the first-order disturbance advection and disturbance shear to the local variation of wave action density is secondary. While the exchange of disturbance momentum and disturbance heat between the basic state and disturbance has relatively weak influence on the development and evolution of disturbance. After the landing of typhoon "Morakot" in the southeastern China coastal region, these forcing terms and the wave action itself are apparently weakened.
Analysis of the summer precipitation of 2012 in East China and its possibility of decadal shift
Authors: Gong Zhi-Qiang  , Zhao Jun-Hu  , Feng Guo-Lin  ,   National Climate Research Center CMA, Beijing 100081, China
Published: December 2020

Considering the abnormal precipitation in north-west and drougtin south China during the summer of 2012, we have analyzed the decadal precipitation distribution and the chief probably-influencing factors in recent 50 years, in order to make a discussion of the possibility of decadal change of summer precipitation in East China since the summer of 2012. Research results show that the north Pacific decadal oscillation (PDO) is in cold phase, and the north cold air active and the west Pacific subtropical high (WPSH) are both in weak phase during the summer of 1961-1978. This situation is beneficial to the strong east Asia summer monsoon (EASM) and the north expansion of the low latitude water vapor, causing the summer precipitation in northern China more than normal in this decadal. While the situation is in quite opposite way during 1979-1992 (which causes the decadal change of summer precipitation in east China) that the precipitation is less than normal in northern China during the late period. Meanwhile, since in the late 2010 PDO changed from the warm phase to cold phase, the sea surface temperature was warmer in north Pacific and colder in west Pacific than normal, while the west Pacific subtropical high and the north region cold air active both changed from strong phase to weak phase, and the EASM became stronger, quite similar to that in 1961-1978. All of the cases showed that there might be once more a decadal change of summer precipitation in East China since the summer of 2012. Furthermore, the yearly variation of indices of PDO, EASM, WPSH and Baikal Height (BH) showed that the abnormal precipitation distribution and the chief influencing factors are not only the yearly variables but also the probable signal of decadal change in the following years.
Generalized Hojman conserved quantity deduced from generalized Lie symmetry of Appell equations for a variable mass mechanical system in relative motion
Authors: Jia Li-Qun  , Sun Xian-Ting  , Zhang Mei-Ling  , Zhang Yao-Yu  , Han Yue-Lin  ,   School of Electric and Information Engineering, Pingdingshan University, Pingdingshan 467000, China;,   Mathematics Teaching and Research Group, Changzhou No.1 High School, Changzhou 213003, China;,   School of Science, Jiangnan University, Wuxi 214122, China
Published: December 2020

Generalized Lie symmetry and generalized Hojman conserved quantity of Appell equations for a variable mass holonomic system in relative motion are studied. The determining equation of generalized Lie symmetry of Appell equations for a variable mass holonomic system in relative motion under the infinitesimal transformations of groups is given. The expression of generalized Hojman conserved quantity deduced directly from generalized Lie symmetry for a variable mass holonomic system in relative motion is gained. Finally, the problem of dynamical system with three degree of freedom is studied by using the results of this paper.
A chaotic secure communication method based on chaos systems partial series parameter estimation
Authors: Liu Le-Zhu  , Zhang Ji-Qian  , Xu Gui-Xia  , Liang Li-Si  , Wang Mao-Sheng  ,   College of Physics and Electronic Information, Anhui Normal University, Wuhu 241000, China
Published: December 2020

We proposed a chaotic secure communication method, namely the partial series of the chaos system for parameter estimation and the other series for secure communications. Parameter estimation could be obtained from the partial series of chaos system with the chaotic ant swarm optimization algorithm, to understand all of the information of the chaos system. In the process of parameter estimation, the introduced parameter space and ant swarm space transformed into each other through space transformation function. Numerical simulation validated the feasibility of the chaos system partial series parameter estimation and the chaotic secure communication method.
Chaotic synchronization control of Chua’s circuit by injected feedback based on the symbolic function
Authors: Ma Mei-Ling  , Min Fu-Hong  , Shao Shu-Yi  , Huang Miao-Yu  ,   School of Electical and Automation Engineering, Nanjing Normal University, Nanjing 210042, China
Published: December 2020

Due to the inherent property of the Chua’s circuit, it is difficult to obtain the three state variables directly from the circuit, and the general control method is hard to apply to the circuit. For these chaotic circuits which have energy storage elements, a simple circuit is designed to get the state variables. In addition, an injected feedback method to realize the synchronization is proposed, which can control the circuits with unknown differential variables of the state variables. Two chaotic systems which have different motions are investigated using the symbolic function. All results obtained from the circuits are verified by the effectiveness and feasibility of the above method.
Research and simulation on cellular automaton model of mixed traffic flow at intersection
Authors: Zhang Xing-Qiang  , Wang Ying  , Hu Qing-Hua  ,   Key Laboratory for Urban Transportation Complex Systems Theory and Technology of Ministry of Education, School of Traffic and Transportation, Beijing Jiaotong University, Beijing 100044, China ;,   West Zone Office of TEDA, Tianjin 300462, China
Published: December 2020

In this paper, right-turning vehicle and straight-going bicycle are regarded as the objects for studying the mixed traffic flow characteristics at the intersection. Based on vehicle-bicycle interference characteristics, and the coupling between the vehicle cellular automaton model and the bicycle cellular automaton model, a kind of cellular automaton model (NS-BCA) is presented to analyze the mixed traffic flow of intersection, in which the delay rules of bicycle through vehicle, the gap rules of vehicle through bicycle, and the disposal rules of the occupied conflict zone are taken into consideration. The mixed traffic flow of the right-turning vehicle and the straight-going bicycle is simulated, and the vehicle-non vehicle interference mechanism in mixed traffic flow at the intersection is investigated according to the relationship between traffic volume and arriving rate, transformation of traffic flow phases, the relationship among traffic flow phase, arriving rate and state of mixed traffic flow.
Dynamic characteristics of 1550 nm vertical-cavity surface-emitting laser subject to polarization-rotated optical feedback：the short cavity regime
Authors: Wang Xiao-Fa  , Li Jun  ,   School of Optoelectronics Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China;,   Basic Ministry, Chongqing Medical and Phamaceutical college, Chongqing 401331, China
Published: December 2020

Based on the extended spin-flip model (SFM), we investigate theoretically the dynamic characteristics of 1550nm vertical-cavity surface-emitting laser subject to polarization-rotated optical feedback: the short cavity regime. Results show that increasing the feedback strength will result in multiple polarization switching (PS) phenomena, and there will appear rich dynamics under the condition of medium feedback intensity, such as single period, period-doubling, quasi-periodic and chaotic states. At the same time, the increase of injection current will result in the reduction of working area of Y direction polarization mode. As the feedback delay time increases, under the condition of weak optical feedback polarization mode, the hopping phenomenon will take place at a particular frequency; the frequency of mode hopping will increase with the increase of moderate feedback strength, and the laser shows a variety of new dynamic characteristics, such as single period, pulse envelope, quasi-periodic and chaotic states, by taking a beat frequency signal. These dynamic characteristics are very sensitive to the phase change so the beat frequency effect between external cavity modes plays a key role. In addition, the hopping phenomenon between various dynamic states can also be found along with the mode hopping.
Assembling of gold nanorods by femtosecond laser fabrication
Authors: Zhang Ran  , Xiao Xin-Ze  , Lü Chao  , Luo Yang  , Xu Ying  ,   State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China;,   Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
Published: December 2020

Metal nanoparticle is of great importance for the study of surface plasmon resonance, and its functional assembly can show more excellent overall collaborative performance. We propose an efficient assembly of gold nanoparticles (GNP) through femtosecond laser fabrication without introducing additional modifier, which can not only retains the particle’s surface plasma resonance characteristic, but also realizes the assembling pattern of arbitrary subtle shape. We apply the assembly in microfluidic chip for surface-enhanced Raman scattering detection and achieve a very good enhancement. It provides a new approach for the preparation of plasma devices.
Influence of non-Kolmogorov turbulence on the spreading of Gaussian array beams
Authors: Lu Lu  , Ji Xiao-Ling  , Deng Jin-Ping  , Ma Yuan  ,   Department of Physics, Sichuan Normal University, Chengdu 610066, China
Published: December 2020

The expressions for the Rayleigh range zR, the turbulence distance zT and the far-field angle θ of Gaussian array beams propagating through non-Kolmogorov turbulence are derived. Influence of generalized exponent factor α of the atmospheric power spectrum and the type of beam combinations on the spreading of Gaussian array beams is studied. It is shown that for both coherent and incoherent combinations, the dependence of zR, zT and θ on α is not monotonic. When α=3.108, zR and zT reach their minima, and θ reaches its maximum. This means that the spreading is largest, and the spreading is enormously affected by turbulence when α=3.108. For the incoherent combination the spreading is larger than that for the coherent combination, but for the incoherent combination the spreading is less affected by turbulence than that for the coherent combination. It may be that, for the small free-space diffraction we have zT zR, i.e., the spreading is affected by turbulence within the Rayleigh range; for the large free-space diffraction we have zT > zR, i.e., the spreading is less affected by the turbulence within the Rayleigh range.
Development of high efficiency Tm3+-doped fiber and Tm3+-doped fiber laser
Authors: Xing Ying-Bin  , Ye Bao-Yuan  , Jiang Zuo-Wen  , Dai Neng-Li  , Li Jin-Yan  ,   Wuhan National Laboratory of Optoelectronics, Wuhan 430074, China
Published: December 2020

The Tm3+-doped fiber is the key of Tm3+-doped fiber laser, which has broad application prospects. In this paper, the silica-based Tm3+-doped fiber preform is manufactured by gas-solution co-doping method in MCVD(modified chemical vapour deposition) and the Tm3+-doped double-cladding fiber is also achieved, the core and cladding diameters of which are 10 μm and 125 μm respectively. We prepare the Tm3+ all-fiber laser using the Tm3+-doped fiber and when the laser is pumped by a 793 nm laser diode, the center wavelength is 2002 nm, maximum output is 31.7 W, and the slope efficiency of the fiber is 59.32%.
Multi-Gaussian beam model for ultrasonic surface waves with angle beam rectangular transducers
Authors: Duan Xiao-Min  , Zhao Xin-Yu  , Sun Hua-Fei  ,   School of Mathematics, Beijing Institute of Technology, Beijing 100081, China;,   School of Science, Dalian Jiaotong University, Dalian 116028, China;,   School of Mechanical and Vehicular Engineering, Beijing Institute of Technology, Beijing 100081, China;,   School of Materials Science and Engineering, Dalian Jiaotong University, Dalian 116028, China
Published: December 2020

Rayleigh waves propagating in an elastic surface are commonly used for the near surface flaw detection and material characterization. However, unlike the bulk wave case, there are seldom three-dimensional models to be provided for the Rayleigh waves. In the past decade, multi-Gaussian beam models have been gradually developed and perfectly applied to solve many complicated propagation problems of bulk waves. However, up to date they have not been extended to the simulation of the Rayleigh waves. By combining the Rayleigh wave Green function and the multi-Gaussian beam model, a three-dimensional Rayleigh wave model is presented to calculate the beam fields radiated from a rectangular transducer mounted on the Lucite wedge. Furthermore, some simulation results of the provided method are compared to those of a more exacted point source model. It is shown that the multi-Gaussian surface wave model has good capability in both computational accuracy and efficiency.
Molecular dynamics simulation of thermal conductivity of mesoporous α-Al2O3
Authors: Yuan Si-Wei  , Feng Yan-Hui  , Wang Xin  , Zhang Xin-Xin  ,   School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China;,   Beijing Key Laboratory of Energy Saving and Emission Reduction for Metallurgical Industry, University of Science and Technology Beijing, Beijing 100083, China;,   Beijing Gas and Heating Engineering Design Institute, Beijing 100032, China
Published: December 2020

In this paper, molecular dynamics simulation was performed to predict the thermal conductivities of ordered mesoporous α-Al2O3. A kind of porous structure was proposed to guarantee the electrical neutrality. Based on the Matsui potential, the nonequilibrium molecular dynamics method adapted by Mller-Plathe was used to calculate the lattice thermal conductivity of mesoporous alumina along the axial direction of pore at various temperatures. Effects of pore size and porosity were also investigated. It turns out that with increasing temperature the thermal conductivity of mesoporous α-Al2O3 rises first until the temperature reaches 200–400 K, then decreases almost linearly. In addition, as the pore size gets larger, the specific surface area decreases, and the thermal conductivity increases because the boundary scattering has been weakened. On the other hand, the number of phonons in the pore wall decreases greatly with increasing porosity, thus dramatically reducing the thermal conductivity of the mesoporous material. Range analysis shows that the porosity is more influential than the pore size on the thermal conductivity of mesoporous materials.
Effect of H3BO3 on structure and long persistence properties of Y1.98O3：Eu, Dy red long-afterglow phosphor
Authors: Xie Wei  , Wang Yin-Hai  , Quan Jun  , Zou Chang-Wei  , Liang Feng  , Shao Le-Xi  ,   Research Center of Chemistry & Materials Science, Zhanjiang Normal University, Zhanjiang 524048, China;,   School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China
Published: December 2020

The phosphor Y1.98O3: Eu0.013+, Dy0.013+ was prepared by high temperature solid reaction method. X-ray powder diffraction (XRD), scanning electronic microscope (SEM), photoluminescence spectra (PL), and single-photon counter system were used to investigate the structure, morphology, luminescent properties, and decay characteristics of the phosphor Y1.98O3: Eu0.013+, Dy0.013+ which was synthesized with different contents of H3BO3. Results show that the structure of the H3BO3-contained phosphors can keep Y2O3 matrix when the content of H3BO3 is below 8%(mol), and the particles size of phosphors increases during the addition of H3BO3. The luminescence of phosphors come from the transition of 5D0→7FJ of Eu3+, the main emission peaks at 612 nm and the intensity is increased linearly with the increase of H3BO3 content. Phosphors show better afterglow characteristics during the increase of H3BO3.The measurement of thermoluminescence(TL) reveals that the addition of H3BO3 increases the trap depth and trap concentration in the host, hence the afterglow characteristics become better.
Structural and electronic properties of hydrogenated bilayer boron nitride
Authors: Gao Tan-Hua  , Wu Shun-Qing  , Zhang Peng  , Zhu Zi-Zhong  ,   School of Electromechanical Engineering, Wuyi University, Wuyishan 354300, China;,   Department of Physics, Xiamen University, Xiamen 361005, China;,   Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen University, Xiamen 361005, China
Published: December 2020

The structural and electronic properties of hydrogenated bilayer boron nitride (BN) were studied by employing the first-principles calculations. Six major polymorphic structures of hydrogenated bilayer BN are considered. Calculated results show that, among them, the AB-BN and AA-BN structures are the most stable ones. The analysis on the energy bands and electronic properties of the two most stable structures are then performed. Structures of AB-BN and AA-BN are both semiconducting with direct band gaps, and the gaps are 1.47 eV and 1.32 eV, respectively, calculated using the GGA method. Since GGA usually severely underestimates the band gap, the hybrid density functional calculations are then conducted, which suggests that the band gaps are 2.52 eV and 2.34 eV for AB-BN and AA-BN structures, respectively. In the most stable structures of AB-BN and AA-BN, B-N bonds show mainly covalent characters, while B-H and N-H bonds exhibit clear ionic characteristics. Moreover, the band gap of hydrogenated bilayer BN atomic sheet can be continuously modulated by biaxial strains. When the lattice constant is compressed by around 8%, the electronic character of the atomic sheet changes from semiconducting into metallic.
Charge and spin transport through parallel-coupled double-quantum-dot molecule A-B interferometer
Authors: Bai Ji-Yuan  , He Ze-Long  , Yang Shou-Bin  ,   School of Electrical and information Engineering, Heilongjiang Institute of Technology, Harbin 150050, China;,   Harbin Normal University, Harbin 150025, China
Published: December 2020

By using the nonequilibrium Green’s function technique, the charge and spin transport properties through an A-B interferometer that has a parallel-coupled double-quantum-dot molecule embedded in each arm, (named as parallel-coupled double-quantum-dot molecule A-B interferometer) are investigated. In the absence of magnetic flux, as compared with the A-B interferometer with two quantum dots embedded in each arm, electron tunnelling becomes far easier for parallel-coupled double-quantum-dot molecule A-B interferometer. When the magnetic field is introduced, one can observe in the conductance spectrum one Fano resonance and one anti-resonance, both of which will die away simultaneously when the magnetic flux takes a proper value. Besides, spin transport can be manipulated by tuning the bias voltage between the two leads, magnetic flux, and Rashba spin orbit interaction.
Study on porous silicon template for nanoimprint lithography
Authors: Zhang Zheng  , Xu Zhi-Mou  , Sun Tang-You  , Xu Hai-Feng  , Chen Cun-Hua  , Peng Jing  ,   School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China;,   College of Chemistry, Central China Normal University, Wuhan 430079, China;,   College of Science, Wuhan University of Science and Technology, Wuhan 430081, China
Published: December 2020

The template for naoimprint lithography having a nano-sized structure was usually fabricated by traditional lithography such as extreme ultraviolet (EUV) lithography, focused ion beam (FIB) lithography, electron beam (EB) lithography. However, these approaches are always time-consuming and inefficiency which limits the potential application in nanoimprint lithography. To find a simple and low-cost method to fabricate the mold for nanoimprint lithography, and to improve the application in nanoimprint lithography have become the research focus. Instead of being formed by traditional lithography, the anodic aluminum oxide (AAO), with highly regular structures and high pore density, is the mold to achieve periodic structures for nanoimprint lithography. In this work, we successfully transfer a 2D nanoporous array structure to the Si surface via the nanoimprint lithography and AAO. The pore diameter and the interpore distance of the porous silicon (PS) are well consistent with that of AAO template. The interval, the diameter, and the height of the hexagonal array structure are 350–560 nm, 170–480 nm, and 200 nm, respectively. We have tested the Raman spectrum under the excitation by lasers of wavelength 514 nm. According to the results, two samples each exhibits a peak at 520 cm-1 and no frequency shift is observed with the Si characteristic Raman peak, indicating that the PS was not extensively damaged by the ICP etching process. Raman intensity in the structured Si is almost enhanced by a factor of 12 as compared with the case on polished Si, which will greatly benefit the application of Si-based optical devices. Thus, we have realized the replica of the PS template and obtained a nanopillar soft template via the hot embossing lithography.
Helical conformation of polymer bottle brushes induced by entropy
Authors: Deng Zhen-Yu  , Weng Le-Chun  , Zhang Dong  , He Lin-Li  , Zhang Lin-Xi  ,   Department of Physics, Zhejiang University, Hangzhou 310027, China;,   Department of Physics, Wenzhou University, Wenzhou 325027, China
Published: December 2020

Helical formation is fairly ubiquitous in nature. Under certain circumstances, entropy may induce polymer chains to form helical structures. In this article, molecular dynamics is applied to illustrate the conformation behaviors of a polymer bottle brush adsorbed onto the surface of a cylinder with infinite length. The helical conformation of a polymer bottle brush is closely related to the number of branch chains as well as the adsorption energy between the polymer bottle brush and the cylinder. Once the adsorption energy is weak, the polymer bottle brush with enough branch chains may form an entropy-induced complete helical structure. Our results may give a deeper insight into polymer helical structural studies.
Design of a metallic photonic crystal high power microwave mode converter
Authors: Wang Dong  , Xu Sha  , Cao Yan-Wei  , Qin Fen  ,   Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics, CAEP, Mianyang 621900, China;,   The Equipment Research Institute of Second Artillery, Beijing 100085, China
Published: December 2020

Electromagnetic properties of a two-dimensional metallic photonic crystal in a transmission line is analyzed, and a compact TEM-TE11 high-power microwave mode converter which takes this type of sturcture for phase-shiftting is presented. An L band TEM-TE11 mode converter is optimized using the commercial software cst microwave studio. Its conversion efficiency is 98% at the center frequency of 1.58 GHz. Over the frequency range of 1.56–1.625 GHz, the conversion efficiency exceeds 90%, with a corresponding bandwidth of 4.1%. This mode converter has a gagawatt level power handling capability, thus it is suitable for narrow band high-power microwave application. Using magnetically insulated transmission line oscillator as a high-power microwave source, particle-in-cell simulation is carried out to test the performance of the mode converter. It is found that the proposed mode converter works well with this narrow band high power microwave device.
Automatic recognition of mid-altitude radial convergence and study on the relationship between the convergence and strong convective weather based on Doppler weather radar data
Authors: Wang Ping  , Niu Zhi-Yong  ,   School of Electrical and Automation Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

To identify the mid-altitude radial convergence of a strong convective weather automatically, we propose a method based on recognition of ‘positive-negative velocity region-pairs’ (region-pairs)in a single elevation angle of the Doppler radar radial velocity image. First of all, according to the principle of the radar detection, this paper explains the phenomenon that the convergence field formed by the airflow must produce a local maximum in positive or negative velocity region in the radial velocity image.The algorithms for recognizing these regions and matching the positive-negative pair are then devised.By searching a set of region-pairs with longitudinal extension, which are obtained from the multiple single elevation radial velocity images, we can judge whether there is a mid-altitude radial convergence in the convective storm, and estimate important parameters, such as the strength and extended thickness of the mid-altitude radial convergence.Finally, we determine the position of optimal section and present the cross-sectional view of the mid-altitude radial convergence. We have tested 384 samples with obvious mid-altitude radial convergence and 365 heavy rainfall samples without obvious mid-altitude radial convergence. Experimental results show that the recognition rate of obvious mid-altitude radial convergence is 100% and the false alarm rate is 0.Compared with the manual way by means of the cross-sectional view, the proposed method in this paper can more rapidly recognize the mid-altitude radial convergence (and reduce the recognition time from minutes to seconds). At the same time, it can present a great deal of quantitative information, including the strength, height, thickness, and position of the mid-altitude radial convergence.Furthermore, it shows the cross-sectional view automatically.We can obtain good results from the comparison between the mid-altitude radial convergence and strong convective weather by using the given parameters.We test and verify the strong correlation between the mid-altitude radial convergence and severe surface wind.Moreover, the height of the strongest mid-altitude radial convergence plays an important role in discrimination of strong hail and torrential rain. Also the strength of the mid-altitude radial convergence can be used to estimate the maximum dimensions of the hail.
Study on plasma characteristics from hypervelocity impacts by small space debris
Authors: Cai Ming-Hui  , Wu Feng-Shi  , Li Hong-Wei  , Han Jian-Wei  ,   Space Environment Effects Laboratory, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Dense plasma cloud can be produced by small debris impact on spacecraft surface, with the diffusion of plasma which can induce the electrostatic discharge (ESD) and electromagnetic interference (EMI). By this way, spacecraft will experience electrical anomalies. In this paper, a plasma drag particle accelerator is used to study the characteristics of impact-generated plasma due to crash of small debris with mass 10-5 g. The relation between plasma charge and debris velocity is acquired by analyzing experimental data. In addition, the diffusion velocity of the impact-generated plasma is observed by two retarding potential analyzers. By theoretical analysis, the change law of the electron density with time and dimension is calculated. Experiment results will be helpful to reveal the physical mechanism of spacecraft anomalies by small debris impacts.
Generalized parameter-adjusted stochastic resonance of Duffing oscillator based on Kramers rate
Authors: Leng Yong-Gang  , Lai Zhi-Hui  ,   School of Mechanical Engineering, Tianjin University, Tianjin 300072, China;,   Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin 300072, China
Published: December 2020

The stochastic resonance (SR) of two-dimensional Duffing oscillator is studied in this paper. We propose the generalized parameter-adjustment SR of Duffing oscillator. On the basis of Kramers rate, we build a discrimination function of the SR of Duffing oscillator, and we expound the generalized parameter-adjustment SR laws of Duffing oscillator under different noise intensity and signal frequency conditions. The general method of generating the generalized parameter-adjustment SR of Duffing oscillator is also given in this paper.