bluuebunny/crossref_metadata_2025 huggingface dataset:
Femtosecond optical parametric conversion properties based on the BiB3O
Authors: Ma Jing  , Liu Ying  , Zhang Li-Jun  ,   Department of Physics, School of Science, Tianjin University, Tianjin 300072, China
Published: December 2020

Parametric properties in femtosecond optical parametric conversion process based on the new nonlinear crystal BiB3O6 (BIBO) are studied. The phase- matching conditions and effective nonlinear coefficients in the three principal optical planes of the BIBO crystal are calculated, optimum principal optical planes and phase -matching types are determined when using the fundamental frequency and the frequency doubling of the KLM Ti:sapphire laser as pump respectively, and temporal walk-off and spatial walk-off of three waves, and signal parametric gain and bandwidth are analyzed. We thereby provided a theoretical basis and experimental guide for obtaining the light source with high energy, wide tuning range, and short duration with femtosecond optical parametric technology based on the BIBO.
Fabry-Perot resonance on extraordinary transmission through one-dimensional metallic gratings with sub-wavelength under transverse electric wave excitation
Authors: Wang Ya-Wei  , Liu Ming-Li  , Liu Ren-Jie  , Lei Hai-Na  , Tian Xiang-Long  ,   (1)School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China; (2)School of Science, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

The transmission distribution of transverse electric wave (TE) through one-dimensional metallic gratings with sub-wavelenghth slits with dielectric added in different positions has been simulated by the FDTD (finite difference time domain) method, the extraordinary transmission can be produced at several special wavelengths. The simulation shows that the guided-mode-like resonance theory is the main reason giving rise to the first peak and the second peak. Based on the guided-mode-like resonance theory, from the Maxwell’s equations,we nade sure that the Fabry Perot resonance is the main cause producing the third peak by the effective index mehod. In a word, the guided-mode resonance theory and the Fabry-Perot-like resonance reveal the physical nature of the extraordinary transmission phenomenon which provides a complete theoretical basis for further study of the extraordinary transmission phenomenon of TE-polarized wave.
Analysis and imitation of dynamic properties for rigid-flexible coupling systems of a planar flexible beam
Authors: He Xing-Suo  , Li Xue-Hua  , Deng Feng-Yan  ,   Department of Engineering Mechanics, Northwestern Polytechnical University, Xian 710072, China
Published: December 2020

The finite element method is used for the system discretization and the coupling dynamic equations of flexible beam are obtained by Lagranges equations. The second order coupling terms between rigid large overall motion, arc length stretch, lateral flexible deformation kinematics and torsional deformation terms are included in the present exact coupling model to expand the theory of one-order coupling model. The dynamic response of the present model is compared with that of zero-order approximate model and one-order coupling model. Then the changes of dynamic stiffening terms due to the new coupling terms are discussed according to different models. At the same time, the effect of initial static deformation in the tip is considered to study the vibrant deformation of flexible beam. The difference between zero-order approximate model, one-order coupling model and the present exact model is revealed by the frequency spectrum analysis method and it is concluded that the speed of overall motion is a vital cause for the difference between different models. And we found that the dynamic stiffening phenomenon still exists in rigid-flexible coupling system while the overall motion is free. But the effect of dynamic stiffening in the present exact model is not as severe as that in the one-order coupling model.
Equatorial Rossby envelope solitary waves with β effect in a shear flow
Authors: Yang Lian-Gui  , Jiang Nan  , Song Jian  ,   (1)College of Sciences, Inner Mongolia University of Technology, Hohhot 010051, China; (2)School of Mathematical Science, Inner Mongolia University, Hohhot 010021, China; (3)School of Mechanical Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

With a simple model of shallow-water on an equatorial beta plane, the nonlinear equatorial Rossby waves in a shear flow with beta effect are investigated by the asymptotic method of multiple scales. The nonlinear Schrdinger equation, satisfied by large amplitude Rossby envelope solitary waves in shear basic flow with beta effect, is derived. The effects of basic flow shear and beta effect on the nonlinear equatorial Rossby waves are also analyzed.
Electrical properties and impedance analysis of Bi0.5Ba0.5FeO3 ceramic
Authors: Yuan Chang-Lai  , Liu Xin-Yu  , Huang Jing-Yue  , Zhou Chang-Rong  , Xu Ji-Wen  ,   School of Material Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China
Published: December 2020

Ba0.5Bi0.5FeO3 ceramic was fabricated by conventional solid-state reaction method. The microstructures and electrical properties were characterized by X-ray diffraction, scanning electron microscopy, direct current (DC) resistance-temperature measurement and alternative current (AC) impedance analysis. According to the analysis, Ba0.5Bi0.5FeO3 ceramic is a cubic perovskite-type compound, and its grain size is about 1.0 μm. In the measured temperature range of 16—280 ℃, Ba0.5Bi0.5FeO3 ceramic shows obvious negative temperature coefficient thermistor characteristic, and the thermistor constant and activation energy of the ceramic are 6490 K and 0.558 eV, respectively. The temperature dependence of dielectric constant reveals that below 280 ℃ no phase transition occurs. The AC impedance characteristic in the ceramic can appropriately be modeled in terms of an equivalent electrical circuit comprising of a series combination of three parallel RQ components in connection with the grain, grain shell and grain boundary effects. The fitting results are in good agreement with the experimental data. The components of grain, grain shell and grain boundary, showing NTC characteristic, have the order of resistive contribution of Rg>Rs>Rgb. In the temperature range 25—115 ℃, the significant mismatch between the peaks of parameters Z″(ω) (imaginary part of impedance) and M″(ω) (imaginary part of electric modulus) suggests a development of persistent localized conduction in Ba0.5Bi0.5FeO3 ceramic.
Effect of electron temperature anisotropy on BN dielectric wall sheath characteristics in Hall thrusters
Authors: Qing Shao-Wei  , Ding Yong-Jie  , Duan Ping  , Wang Xiao-Gang  , Yu Da-Ren  ,   (1)Dalian Maritime University, Dalian 116026, China; (2)School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China; (3)State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871, China
Published: December 2020

The effect of electron temperature anisotropy on BN dielectric wall sheath characteristics in Hall thruster plasma is studied by using a one-dimensional fluid sheath model with the help of emitted electron velocity distribution and multi-species mixed ion effects. Analytic results show that, in comparison with that of a pure univalent xenon plasma, the sheath potential drop and the critical secondary electron emission coefficient are decreased in mixed valence xenon plasmas, while the primary electron flux at the wall is increased. The electron temperature anisotropy in Hall thrusters thus significantly enhances the electron energy emission coefficient, and further reduces the sheath potential drop while intensifies the electron-wall interaction. Numerical results also indicate that the electron temperature anisotropy influences the potential distribution of space charge saturated sheath remarkably.
Laser time fiducial for precise physical experiment in Shenguang-Ⅲ prototype facility
Authors: Lin Hong-Huan  , Jiang Dong-Bin  , Wang Jian-Jun  , Li Ming-Zhong  , Zhang Rui  , Deng Ying  , Xu Dang-Peng  , Dang Zhao  ,   Research Center of Laser Fusion, China Academy of Engineering Physis, Mianyang 621900, China
Published: December 2020

Using comb laser pulses synchronized with the main pulse output by large laser facility as time fiducial to scale the reaction process between high power laser pulse and target is very important for the realization of precise measurement and simulation in the intense field experiment. We demonstrate a fiber multiharmonic time fiducial laser pulse generation system using optic-electric modulation and optical pulse stacking. A unit optical pulse with a width of 150 ps generated by modulation was stacked in a fiber stacker to form a 1053 nm comb pulse. The pulse was then amplified and frequency-converted to generate green (527 nm) and UV (351 nm) fiducials. The system can stably provide Shenguang-Ⅲ prototype facility with multi-frequency laser time fiducials which is essential for the precise physical experiment. In addition, the system is highly adaptive since it can generate fiducial signals with variable pulse intervals and amplitudes flexibly according to the requirements of different physical experiments.
Numerical simulation on the effect of shielding gas on the plasma cutting arc
Authors: Li Hui  , Zhou Qian-Hong  , Guo Wen-Kang  ,   (1)Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei 230027, China; (2)Institute of Applied Physics and Computational Mathematics, Beijing 100088, China;Institute of Modern Physics, Fudan University, Shanghai 200433, China; (3)Institute of Modern Physics, Fudan University, Shanghai 200433, China
Published: December 2020

By comparing two diffierent torch geometries, it was found that the shielding flow has no significant effect on plasma velocity and temperature,except in the shock wave region. The shielding flow decreases the shock wave, and increases the arc voltage due to cooling. In the impinging geometry, shielding flow will crash the plasma jet after the nozzle exit and slightly increase the pressure in the torch. It was also shown that the component of shielding gas has no significant effect on plasma cuttingarc. The mole fraction of oxygen decreases very slowly along the axis and is still more than 90% at 10 mm downstream the nozzle exit.
Defect mode properties of two-dimensional unmagnetized plasma photonic crystals with line-defect under transverse magnetic mode
Authors: Kong Xiang-Kun  , Liu Shao-Bin  , Zhang Hai-Feng  ,   College of Information Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;,   College of Information Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;Nanjing Branch, Artillery Academy of the Chinese People??s Liberation Army, Nanjing 211132, China;,   College of Information Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;Zhenjiang Watercraft Collegeg, Zhenjiang 212003, China
Published: December 2020

The piecewise linear current density recursive convolution finite-difference time-domain method of plasma is used to study the defect mode properties of transverse magnetic wave propagation in the two-dimensional unmagnetized plasma photonic crystals with a line-defect layer. In frequency domain, the transmission coefficients of electromagnetic differential Gaussian pulses are computed, and the effect of lattice constant, dielectric column radius, periodic constant, parameters of plasma and parameters of line-defect layer on defect mode properties of two-dimensional unmagnetized plasma photonic crystals are analyzed. The results illustrate that the frequency of defect mode cannot be tuned by changing periodic constant, position of the defect layer and plasma collision frequency, but be tuned by changing relative permittivity and radius of dielectric column in the defect layer, and central distance between defect layer and dielectric layer with the width of prohibit band gaps fixed. Furthermore, the defect mode and the width of prohibit band gaps can also be tuned by changing lattice constant, dielectric column radius and plasma frequency.
Characteristics of dielectric barrier discharge with different dielectric layer structures
Authors: Liu Wei-Yuan  , Yue Han  , Wang Shuai  , Liu Zhong-Wei  , Chen Qiang  , Dong Li-Fang  , Yang Yu-Jie  ,   (1)College of Physics Science and Technology, Hebei University, Baoding 071002, China; (2)Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Beijing 102600, China
Published: December 2020

A dielectric barrier discharge device with two glass dielectric layers, one of which is covered with an indium tin oxide (ITO) conductive layer, was designed. Its discharge characteristics was studied and compared with that in dielectric barrier discharge devices with two glass dielectric layers and single glass layer. The charge transport in two dimensions, zero dimension, and three dimensions were realized by the above three devices respectively. Single steady filament is obtained in the two devices with two glass layers. Different from the single filament obtained in the device with two glass dielectric layers without ITO conductive layer, the single filament obtained by using the device of two glass dielectric layers with ITO conductive layer in one side was "T" shapes, its halo was twice as much as that of the former, its current was greater, and the phenomenon of discharge interval changing alternatively between long and short was more evident. Moreover, the discharge intensity also varied alternatively between strong and weak. The analysis indicated that the differences of the wall charge transport and secondary electron emission between different dielectric structures lead to different discharge characteristics.
Effects of the vacancy point-defect on electronic structure and optical properties of LiF under high pressure: A first principles investigation
Authors: He Xu  , He Lin  , Tang Ming-Jie  , Xu Ming  ,   College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 610068, China
Published: December 2020

By using the ultra-soft pseudo-potential approach of the plane wave based on the density-functional theory, the electronic structures and optical properties of LiF with Li-1 and F+1 vacancies are calculated. The results indicate that: (1) the presence of the vacancy causes defective states within the band gap of LiF; (2) the optical absorption of LiF in the visible-light region is not influenced by the vacancy point-defect (absorption coefficients are still zero); (3) in the ultra-violet region, the weak absorption induced by the Li-1 vacancy, appears within ~99—114nm, and the relatively strong absorption induced by the F+1 vacancy exists in the range of 99—262nm; (4) effects of the Li-1 and F+1 vacancy on reflectivity and loss-function show mainly in the ultra-violet region, which is similar to those of optical absorption.
Energy band structure of uniaxial-strained silicon material on the (001) surface arbitrary orientation
Authors: Ma Jian-Li  , Zhang He-Ming  , Song Jian-Jun  , Wang Guan-Yu  , Wang Xiao-Yan  ,   Key Laboratory of Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi’an 710071, China
Published: December 2020

The strain tensor arising from uniaxial stress along an arbitrary direction on the (001) surface of Si is calculated. With these uniaxial strain tensor, the band structure of silicon material under arbitrary uniaxial stress on the (001) surface is calculated using K ·P perturbation theory coupled with linear deformation potential theory. The relation between energy band structure and stress parameters (type, direction, magnitude) was obtained. Finally, the uniaxial stress induced band structure change, such as that of the conduction band (CB) and the valence band (VB) edge levels, CB and VB splitting energy and the bandgap is demonstrated. Results of these band structure can be used as a guide for the design and the selection of the optimum strain and crystal orientation configuration of uniaxial strained silicon devices.
First principles studies of nitrogen doped tetrahedral amorphous carbon
Authors: Ma Guo-Jia  , Zhu Jia-Qi  , Gong Shui-Li  , Gao Wei  ,   Center for Composite Materials, Harbin Institute of Technology, Harbin 150080, China;,   Center for Composite Materials, Harbin Institute of Technology, Harbin 150080, China;National Key Laboratory of Science and Technology on Power Beam Processes, Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024, China;,   National Key Laboratory of Science and Technology on Power Beam Processes, Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024, China
Published: December 2020

The microstructures and electronic structures of nitrogen doped tetrahedral amorphous carbon (ta-C ∶N) have been simulated and investigated using molecular dynamics within the framework of density functional theory. There are no obvious relation between the coordination of nitrogen and the density of ta-C ∶N. The most common form of nitrogen bonding was found to be three coordinated. Two coordinated and a small quantity of four coordinated nitrogen atoms were also found. The addition of nitrogen caused a big increase in the sp2 fraction of carbon. The states near Fermi level increased in density as the contents of nitrogen atoms increased. Fermi level was not found to shift obviously.
Theoretical studies on spin-vibronic spectra of CH3 O(X2 E)
Authors: Zhang Shi-Yang  , Mo Yu-Xiang  ,   Department of Physics, Key Laboratory for Atomic and Molecular Nanosciences of Ministry of Education, Tsinghua University, Beijing 100084, China
Published: December 2020

We made an ab initio study of the spin-vibronic couplings in CH3O (X2E) based on diabatic model. The diabatic potential energy curves were calculated at the level of CASPT2/cc-pvtz. The calculated spin-vibronic energy levels are compared with the experimental data, which indicates that the present calculation has higher accuracy than the previously reported ones.
Synthesis and thermoelectric properties of thermoelectric materials of the skutterudites In0.3Co4Sb12-xSex
Authors:   State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China
Published: December 2020

Thermoelectric materials of the skutterudites In0.3Co4Sb12-xSex(x=0—0.3) were prepared by melt-annealing and spark plasma sintering. The existence forms of the element In were investigated, and the effect of doping Se in In filled-skutterudites on the structure and thermoelectric properties were also studied systematically. The element In could be filled into the hole structure of skutterudite, and the excessive In exists as InSb in the boundary of grains. After the substitution of Se for Sb, the lattice parameters decrease, and the filling fraction limit of In decreases. All the compounds of In0.3Co4Sb12-xSex(x=0—0.3) show n-type conduction. With the Se doping amount increasing, the carrier concentration and electrical conductivity decrease, and the Seebeck coefficient increases, and the power factor decreases slightly. Since the introduction of Se substitution brings about quality fluctuation and lattice distortion in structure, moderate amount of Se substitution can lower the thermal conductivity largely. The maximum ZT values of both In0.3Co4Sb12 and In0.3Co4Sb11.95Se0.05 samples reach above 1.0.
Tunnelling and storage of charges in a-SiNx/nc-Si/a-SiNx structures
Authors: Wang Xiang  , Huang Rui  , Song Jie  , Guo Yan-Qing  , Chen Kun-Ji  , Li Wei  ,   (1)Department of Physics and Electronic Engineering, Hanshan Normal University, Chaozhou 521041, China; (2)Department of Physics and Electronic Engineering, Hanshan Normal University, Chaozhou 521041, China;Department of Physics, Nanjing University, Nanjing 210093, China; (3)Department of Physics, Nanjing University, Nanjing 210093, China
Published: December 2020

The a-SiNx/nc-Si/a-SiNx sandwiched structures are fabricated in a plasma enhanced chemical vapour deposition (PECVD) system on n-type Si substrate. The nc-Si layer in thickness of 5 nm is fabricated from hydrogen diluted silane gas by layer-by-layer deposition technique. The thicknesses of tunnel and control SiNx layer are 3 nm and 20 nm, respectively. Conductance-voltage and capacitance-voltage measurements are used to study the charges tunnelling and storage in the sandsiched structures. Distinct frequency-dependent conductance peaks due to charges tunneling into the nc-Si dots and capacitance-voltage hysteresis characteristic due to charges storage in the nc-Si dots are observed in the same sample. The experimental results demonstrate that by controlling the thickness of tunnel and control SiNx layers charges can be loaded onto nc-Si dots via tunnelling and be stored in a-SiNx/nc-Si/a-SiNx structures.
First principles study on structure and property of Si2 CN4(010) surface
Authors: Lu Shuo  , Zhang Yue  , Shang Jia-Xiang  ,   School of Materials Science and Engineering,Beihang University,Beijing 100191,China
Published: December 2020

The structure and property of Si2CN4(010) surface with different terminations were studied systemically by first principles calculation. The calculated cleavage energies of each possible surface showed that the Si—NⅡ bond located at the SiN layer was the strongest,while the Si—NⅠ bond connected with the carbodiimide was the weakest. As a result,the surface with the Si/NⅠ termination was the easiest to form. We have compared the atomic structure and electronic properties of un-optimized and optimized surface models. During the optimization of structure,the unsaturated surface atom,especially the NⅠ atoms at the surface would bond with each other to decrease the surface energies,since there are prominent density of states existing at the Fermi level of NⅠ atom. At the same time,the unsaturated C atoms do not have the tendency of bonding with each other,since their electronic state are more stable than NⅠ atom.
Coulomb oscillations effect in dual gate controlled silicon nanowire
Authors: Zhang Xian-Gao  , Fang Zhong-Hui  , Chen Kun-Ji  , Qian Xin-Ye  , Liu Guang-Yuan  , Xu Jun  , Huang Xin-Fan  , He Fei  ,   (1)State Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093, China; (2)Wuxi China Resources Huajing Micro Electronics Co. Ltd., Wuxi 214061, China
Published: December 2020

The tunable single electron effect and Coulomb oscillations were observed in Si nanowire transistors. By measuring the channel current as function of applied back-gate and side-gate voltage, the tunable single electron effect and Coulomb oscillations are investigated. From the differential conductance characteristics, the Coulomb diamonds are clearly observed due to the gate voltage-induced quantum dots formation in the Si nanowire.
Theoretical research on the electronic structure and transport properties of nitrogen doping chiral carbon nanotubes
Authors: Wei Yan  , Hu Hui-Fang  , Wang Zhi-Yong  , Cheng Cai-Ping  , Chen Nan-Ting  , Xie Neng  ,   College of Physics and Microelectronic Sciences, Hunan University, Changsha 410082, China
Published: December 2020

Using density functional theory and nonequilibrium Greens function, the electronic structure and transport properties of chiral (6, 3) single-walled carbon nanotubes substituted by nitrogen atoms were investigated. The results show that the configurations and the concentration of the doped atoms have complicated effects on the transport properties of the chiral single-walled carbon nanotubes. The electronic structures of the carbon nanotubes are changed obviously. The transportation properties are degraded by the doping of nitrogen atoms and change significantly with the positions of impurity atoms in the structure. The currents-voltage curve shows nonlinear variation. Under certain conditions the metallic single-walled carbon nanotubes may be converted into semiconductors.
Effects of additional permanent magnet on the levitation force of single domain GdBCO bulk superconductor
Authors: Ma Jun  , Yang Wan-Min  , Li Guo-Zheng  , Cheng Xiao-Fang  , Guo Xiao-Dan  ,   (1)College of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062, China; (2)College of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062, China;Department of Physics, Qinghai Normal University, Xining 810008, China
Published: December 2020

Effects of additional permanent magnet on the levitation force of a single domain GdBCO bulk superconductor have been investigated with a cylindrical permanent magnet in their coaxial configuration under zero field cooled state at liquid nitrogen temperature. The magnetic polarity N of cylindrical permanent magnet is pointed to the GdBCO bulk superconductor, and the two additional permanent magnet of rectangular parallelepiped shape are fixed on two sides of the GdBCO bulk superconductor in different arrangments. It was found that the levitation force can be improved to about 61.5 N, which is more than 2 times higher than that (29.8 N) of the system without the additional permanent magnet, when the magnetic polarity N of two additional permanent magnets points to the GdBCO bulk superconductor in horizontal direction. The levitation force is reduced to 19.6N, which is about 65.8% of the levitation force 29.8N of the system without the additional permanent magnets, when the magnetic polarity N of two additional permanent magnet are antiparallel to the magnetic polarity N of the cylindrical permanent magnet. The results indicate that the levitation force of high temperature bulk superconductors can be effectively improved by introducing additional permanent magnet based on reasonably designing the system configuration, which is very important during the practical design and applications of superconducting magnetic levitation systems.
A Gires-Tournois mirror for dispersion compensation in the Ti-sapphire laser system
Authors: Zhang Qing  , Ye Peng  , Wei Zhi-Yi  , Ma Qun  , Zhang Shu-Na  , Zhang Yue-Guang  , Yuan Wen-Jia  , Shen Wei-Dong  , Luo Zhen-Yue  , Liu Xu  ,   (1)Laboratory of Optical Physics,Institute of Physics, Chinese Academy of Sciences, Beijing 100190,China; (2)State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027,China
Published: December 2020

A Gires-Tournois(GT) mirror with a group delay dispersion (GDD) of -60 fs2 in one reflection was designed according to the requirement of dispersion compensation in the Ti-sapphire femtosecond laser system. It was manufactured by ion assisted deposition combined with the optical monitoring in transmission. The reflectance of the mirror was measured by a spectrophometer working in the range from 650 nm to 950 nm with a resolution of 1 nm. The results were consistent with the design. Furthermore, a home-made white light interferometry system was employed to test the reflection GDD and the result also agreed well with the design. The experimental GDD oscillation was less than ± 20 fs2. The GT mirror was applied in the Ti-sapphire femtosecond laser system and a good clamping result was obtained. Finally a 29 fs ultra-short pulse was acquired.
Thermal transport in L-shaped graphene nano-junctions
Authors: Bao Zhi-Gang  , Chen Yuan-Ping  , Ouyang Tao  , Yang Kai-Ke  , Zhong Jian-Xin  ,   Institute for Quantum Engineering and Micro-Nano Energy Technology, Faculty of Materials, Optoelectronics and Physics, Xiangtan University, Xiangtan 411105, China
Published: December 2020

By using nonequilibrium Green’s function method, the thermal transport properties of L-shaped graphene nano-junctions consisting of a semi-infinite armchair-edged nanoribbon and a semi-infinite zigzag-edged nanoribbon were studied. It is shown that the thermal conductance of the L-shaped graphene nano-junctions depends on the included angles and the widths of the graphene nanoribbons. As the angle of L-shaped graphene nano-junctions increases from 30° to 90° and further to 150°, the thermal conductance obviously increases. For the right-angle L-shape graphene nano-junction, the thermal conductance undergoes a transition with the increasing of the widths of the armchair nanoribbons. The thermal conductance decreases at low temperature region and increases at high temperature region. Meanwhile the thermal conductance of L-shape graphene nano-junction with included angle 150° decreases by increasing the widths of zigzag-edged nanoribbons in both low and high temperature regions. These thermal transport phenomena can be reasonably explained by analyzing the phonon transmission coefficient. We illustrate the mechanisms of thermal transport for different L-shaped graphene nano-junctions. The results provide significant physical models and theoretical basis for designing the thermal devices based on the graphene nano-junctions.
Composition and crystal structure of N doped TiO2 film deposited with different O2 flow rates
Authors: Ju Dong-Ying  , Ding Wan-Yu  , Chai Wei-Ping  , Wang Hua-Lin  ,   (1)Department of Material Science and Engineering, Saitama Institute of Technology, Fukay 369-0293, Japan; (2)Engineering Research Center of Optoelectronic Materials and Devices of Education Department of Liaoning Province, School of Materials Science and Engineering, Dalian Jiaotong University, Dalian 116028, China
Published: December 2020

N doped TiO2 films were deposited in direct current pulsed magnetron sputtering system at room temperature. We have studied the influence of O2 flow rate on the crystal structure of deposited films by using stylus profilometer, X-ray photoelectron spectroscope, X-ray diffractometer, and ultraviolet-visible spectrophotometer. The results indicate that the growth behavior and crystal structure of N doped TiO2 film is dominated by the O2 flow rate. It was found that the chemical stiochiometry is close to TiO1.68±0.06N0.11±0.01 for all film samples, in which the N mainly exists in substitutional doped state. When O2 flow rate is 2 sccm (1 sccm=1 mL/min), N doped TiO2 film has amorphous structure with high growth rate, which contains both anatase phase and rutile phase crystal nucleuses. In this case, the film displays the mix-phase of anatase and rutile and the band gap is 2.86eV after annealing treatment. The film growth rate decreases with increasing O2 flow rate. After annealing treatment, the band gap of N doped TiO2 films decreases with increasing O2 flow rate. While N doped TiO2 film is anatase phase when O2 flow rate is 12sccm. In this case, the band gap is 3.2eV after annealing treatment. It should be noticed that no TiN phase appears for all samples before and after annealing treatment.
Influence of the high-repetition-pulsed laser beam size on the damage characteristics of absorbing glass
Authors: Han Jing-Hua  , Feng Guo-Ying  , Yang Li-Ming  , Zhang Qiu-Hui  , Fu Yu-Qing  , Niu Rui-Hua  , Zhu Qi-Hua  , Xie Xu-Dong  , Zhou Shou-Huan  ,   (1)College of Electronics and Information Engineering, Sichuan University, Chengdu 610064, China; (2)College of Electronics and Information Engineering, Sichuan University, Chengdu 610064, China;Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China; (3)Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The influence of the beam size of pulsed laser on damage morphology of absorbing glass, as well as the mechanism of the damage produced by high-repetition-pulsed laser (kHz magnitude), is investigated. We show that the damage morphology changes greatly with the decrease of the beam size under the condition that the energy of each individual pulse,the number of the pulses incident on the glass and the repetition frequency are kept invariant. The damage is induced by melting of the glass material due to dispersed energy of the incident laser with large beam size. With decreased beam size of laser, the material will break resulting from the melting and evaporating of glass induced by the densing and increasingly deposited laser energy in glass material. When the beam size is further reduced, too intensive laser will penetrate the dielectric material on the surface of glass. As a result, the laser induced plasma shock wave occurs. In addition, the super-heated liquid at the center where the laser beam interacts with glass will be produced as a consequence of the tremendous deposited laser energy. When the threshold of phase explosion is reached, the mixture of the evaporated, melted and original solid materials will blast outwards. Consequently, characteristic morphology made up of three regions covered with solid granules of original glass material and the re-crystallized material of the evaporated and melted glass will form around the damage crater.
In situ growth and characterization of Cu2ZnSnS4 thin films by reactive magnetron co-sputtering for solar cells
Authors: Zhang Kun  , Liu Fang-Yang  , Lai Yan-Qing  , Li Yi  , Yan Chang  , Zhang Zhi-An  , Li Jie  , Liu Ye-Xiang  ,   School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China
Published: December 2020

Cu2ZnSnS4 (CZTS) thin films have been first in situ grown by reactive magnetron co-sputtering and its characterizations has been carried out by energy dispersive spectroscopy(EDS), X-ray diffraction(XRD), scan electron microscope(SEM), optical transmittance and electronic measurement. It was observed that the grown film shows homogeneous, compact surface morphology, and consists of large columnar grains throughout the thickness. The atom ratio Cu/(Zn+Sn) is about 1, while Zn/Sn is larger than 1 and decreases with the increase of substrate temperature. XRD analysis indicates that the grown film exhibits strong preferential orientation along (112) plane and the structural properties depend on growth temperature and Cu/(Zn+Sn) ratio. The in situ grown CZTS film has an optical absorption coefficient higher than 104 cm-1, and the optical band gap becomes narrow with the increase of substrate temperature and achieves (1.51±0.01)eV at 500℃. The conduction type of the CZTS films is p-type and the value of carrier concentration is comparable with values of device quality CIGS.
Biot-Savart law and the formation mechanism of Somali low-level jet
Authors: Feng Shi-De  , Feng Tao  ,   (1)Beijing Meteorological Bureau, Beijing 100089, China; (2)Laboratory of Cloud-Precipitation Physics and Severe Storms, State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
Published: December 2020

Firstly, we investigate the impact of cross-equatorial Somali low-level jet on the atmospheric circulation in the east of Tibet Plateau using lattice Boltzmann model simulation. Secondly, we study the relationship between thermal conditions on the bottom boundary and the formation of Somali jet based on Biot-Savart law using the data from National Centres for Environmental Prediction (NCEP). As the radiation from the Sun gradually moves from the southern meridian, the temperature on the ground surface of Somali Peninsular and Arabic Peninsular gradually increases. During the same period the surface temperature of the Northern Indian Ocean increases much slower. It is shown that this increase in the temperature difference between the land and sea is inductive to the formation and development of Rayleigh-Benard convection and leads to the increasing relative vorticity strength between positive and negative vertical vortices over the land and sea. According to Biot-Savart law, the increase in vorticity strength will induce correspondingly a large horizontal velocity. The pair of positive and negative vorticity fields over the two Peninsulars and the sea surface is effective in forming and maintaining this current. This mechanism is referred to as "Somali suction pump". It draws air continually from the Southern hemisphere and releases it at the coastal area of Somali.
Comparison of applications of different filter methods for de-noising detrended fluctuation analysis
Authors: Cheng Hai-Ying  , He Wen-Ping  , Zhang Wen  , Wu Qiong  ,   (1)Fundamental Education Department, Yancheng Institute of Technology, Yancheng 224002, China; (2)National Climate Center, China Meteorological Administration, Beijing 100081, China; (3)National Satellite Meteorological Center, China Meteorological Administration, Beijing 100081, China; (4)Tongda College, Nanjing University of Post and Telecommunications, Nanjing 210003, China
Published: December 2020

We studied the effects of continuous noises and random spikes on detrended fluctuation analysis, and found that the noises lead to the appearance of crossovers in the double logarithm curves when the linear fitting scale was less than a characteristic scale s×. To solve this problem, we use three kinds of filter methods, multi-stage Vondrak filter, N-point weighted moving average filter and fast Fourier filter, to filter high frequency from the analyzed time series. The results indicate that the evolution trend and intensity of high frequency series by multi-stage Vondrak filter is almost identical to those of real noises. Further investigation showed that multi-stage Vondrak filter can eliminate the phenomenon of crossover, and the DFA results of lowpass filtering time series are less dependent on the threshold of the filter periods. To some extent, N-points weighted moving average filter can partly eliminate the effect of noises on DFA, but can not completely eliminate the phenomenon of crossover caused by noises. Fast Fourier filter can almost totally eliminate the effect of noises on DFA when the period of filter adopts an appropriate value, but the filtering results have a stronger dependence on the period of filter, so it is difficult to select the period of filter in practical application. Therefore, comparatively speaking, multi-stage Vondrak filter is an effective measure to alleviate the effects of noises on the DFA results.
Dynamic optimal multi-indexes configuration for estimating the prediction errors of dynamical climate model in North China
Authors: Feng Guo-Lin  , Yang Jie  , Wang Qi-Guang  , Zhi Rong  ,   College of Atmospheric Scicences, Lanzhou University, Lanzhou 730000, China;,   College of Atmospheric Scicences, Lanzhou University, Lanzhou 730000, China;Key Laboratory of Regional Climate-Environment Research for Temperate East Asia of the Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;,   Key Laboratory of Regional Climate-Environment Research for Temperate East Asia of the Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;Laboratory for Climate Studies of China Meteorological Administration, National Cli;,   Laboratory for Climate Studies of China Meteorological Administration, National Climate Center, Beijing 100081, China
Published: December 2020

Based on the idea of using the historical-analogue information to revise the prediction errors of National Climate Centre numerical business model, for North China, based on analysis data of the CMAP from 1983 to 2009, 40 pieces of climate indices from NOAA, 27 years of the season prediction model results from 1983 to 2009 and 74 pieces of circulation characteristics materials provided by Weather Diagnostic Forecasting Room of National Climate Center, using the method of combining data analysis and numerical simulation of diagnostic tests, taking the advantage of the prediction error of the key information of similar model from the historical data, by identifying key factors, optimizing allocation of the different factors of different forecasting years, we established specific multi-factor dynamic optimal portfolios to revise prediction errors in different periods of the power-statistical model in North China, and constructed early environmental factors similar to field multiple objective criteria, to develop new technology of revising prediction errors from the power-statistical model based on dynamic optimal combination of multi-factor, and improved the prediction effect in the summer precipitation in North China and the forecasting skills. Results of independent sample return of 2005—2009 shows that, the score of similarity revised method has improved significantly compared with the score of systematic revised method. The method has a good prospect for summer precipitation forecast in North China, and is going to be put into operation.
Diffraction theory analysis and numerical simulation of non-modulation two-sided pyramid wavefront sensor
Authors: Wang Jian-Xin  , Bai Fu-Zhong  , Ning Yu  , Huang Lin-Hai  , Jiang Wen-Han  ,   Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China;Key Laboratory on Adaptive Optics of the Chinese Academy of Sciences, Chengdu 610209, China;,   Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China;Key Laboratory on Adaptive Optics of the Chinese Academy of Sciences, Chengdu 610209, China;College of Photon-Electron Science and Engineering, National University of;,   Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China;Key Laboratory on Adaptive Optics of the Chinese Academy of Sciences, Chengdu 610209, China;Graduate University of the Chinese Academy of Sciences, Beijing 100049, Chi,   null
Published: December 2020

Two-sided pyramid wavefront sensor (TSPWFS) is a kind of wavefront sensor with high spatial resolution and light energy utilization. To deeply study the principle of wavefront reconstruction of this wavefront sensor using wave optics theory, this paper deduces the diffraction theory of non-modulation TSPWFS and gives the analytic solution of linear reconstruction matrix for wavefront reconstruction. With numerical simulation the optimal distance between adjacent pupil image centers was determined. Also, wavefront reconstruction and closed-loop correction of static aberrations by using non-modulation TSPWFS as a wavefront sensor were simulated. The results show that non-modulation TSPWFS has three main advantages. i.e., it does not require measuring the response matrix in real optical setup, and can correct the optical systemic aberration, and can achieve stable closed-loop correction result. Additionally, non-modulation TSPWFS can be applied to a real adaptive optics system to detect wavefront.
Lie symmetry and Hojman conserved quantity of Nielsen equation in a dynamical system of the relative motion
Authors: Xie Yin-Li  , Jia Li-Qun  , Yang Xin-Fang  ,   School of Science, Jiangnan University, Wuxi 214122, China
Published: December 2020

Lie symmetry and Hojman conserved quantity for Nielsen equations in a dynamical system of the relative motion are investigated. The definition and the criterion of Lie symmetry of Nielsen equations in a dynamical system of the relative motion under the infinitesimal transformations of groups are given. The expressions of the determining equation of Lie symmetry of Nielsen equations and Hojman conserved quantity deduced directly from Lie symmetry in a dynamical system of the relative motion are obtained. An example is given to illustrate the application of the results.
Perturbed solution for a class of ENSOdelayed sea-air oscillator
Authors: Zhu Min  , Lin Wan-Tao  , Lin Yi-Hua  , Mo Jia-Qi  ,   (1)Department of Mathematics, Anhui Normal University, Wuhu 241003, China; (2)Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
Published: December 2020

A class of delayed oscillator of El Nio-Southern Oscillation (ENSO) coupling systems is considered. Using the delayed theory, perturbation and other methods, the asymptotic expansion of the solution for ENSO model is obtained and the asymptotic behavior of solution for the corresponding problem is studied.
FDTD numerical simulation of the trapping force of microspherein single optical tweezers
Authors: Hu Geng-Jun  , Li Jing  , Long Qian  , Tao Tao  , Zhang Gong-Xuan  , Wu Xiao-Ping  ,   (1)Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China; (2)Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
Published: December 2020

In this paper the model of trapping force on microsphere near focus in single optical tweezers is built by three dimensional finite-difference time-domain (FDTD) and Maxwell stress tensor methods. Fifth order Gaussian beam based on spherical vector wave function (VSWF) is adopted as simulation light source; the correct light field transmission is obtained. The influences of the wavelength, waist and polarization of light sources, the radius and refractive index of the microsphere on the optical trapping force are discussed. The influence of nearby microsphere and beam polarization on the trapping force of the trapped microsphere in single optical tweezers is analyzed. The effect of beam polarization working on the trapping force of the trapped microsphere is specially analyzed. As results of simulation, the trapping force acting on the microsphere by the circularly polarized beam is larger than that by the linearly polarized beam. The stability of the trapped microsphere in single optical tweezers will be disturbed by the nearby microsphere and lose its balance. Varying the beam polarization will lead to the change of the trapping force of the trapped microsphere.
The effect of Dzyaloshinskii-Moriya interaction on entanglement in one-dimensional XY spin model
Authors: Liu Sheng-Xin  , Li Sha-Sha  , Kong Xiang-Mu  ,   School of Physics and Engineering, Qufu Normal University, Qufu 273165 China
Published: December 2020

The effects of Dzyaloshinskii-Moriya (DM) interaction on the thermal entanglement of mixed-spin XY chain (1/2,3/2) and spin 1 XY chain are investigated through negativity. By calculating the entanglement between two particles, it was found that the DM interaction can not only increase the entanglement, but also make the entanglement of the particles reach a stationary value. The higher the temperature, the greater the DM interaction is required to make the thermal entanglement arrive at this stationary value. Under the same condition, the entanglement between two spin 1 particles is less than that between mixed-spin. The exchange-coupling interactions between the spins are helpful to strengthen the thermal entanglement, hence the exchange-coupling can be used to modulate the entanglement along with the DM interaction. When the exchange-coupling interaction is small, one can enlarge the DM interaction to increase the entanglement, whereas, when the DM interaction is small, one can increase the thermal entanglement through increasing the exchange-coupling interaction.
Performance analysis of decoy state quantum key distribution using two kinds of photon sources
Authors: Wang Han  , Yan Lian-Shan  , Pan Wei  , Luo Bin  , Guo Zhen  , Xu Ming-Feng  ,   Center for Information Photonics and Communications, School of Information Science and Technology, Southwest Jiaotong University ,Chengdu 610031, China
Published: December 2020

Since the single photon is easy to attenuate and be disturbed, its key generation rate and transmission distance in quantum communication systems are generally limited. In contrast, weak coherent pulse (WCP) and heralded single photon source (HSPS) exhibit higher feasibility than the single photon source in quantum key distributions (QKD). We compare the performances of QKD using these two kinds of photon sources and decoy state method, incorporating data-postprocessing methods including the Lütkenhaus scheme and Gottesman-Lo-Lütkenhaus- Preskill (GLLP) scheme. Simulation results indicate that QKD using HSPS can transmit longer distance than using WCP with lower overall quantum bit error rate (QBER) at the same transmission distance, albeit with relatively low key generation rate.