bluuebunny/crossref_metadata_2025 huggingface dataset:
A compact and tunable photonic crystal switch based on defect resonance
Authors: Wu Fang-Fang  , Shen Yi-Feng  , Wang Yong-Chun  , Han Kui  , Zhou Jie  , Zhang Yuan  , Chen Qiong  ,   Department of Physics, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

The transmission characteristics of a 2D photonic crystal waveguide with point defects were investigated by the plane wave expansion method (PWM) and finite difference time domain (FDTD) method. It was found that by introducing two resonant cavities (point defects) in the photonic crystal waveguide, light waves near the resonance frequencies can be totally reflected back to the waveguide. Since the resonance frequencies change with the variation of the refractive index of point defects, this phenomenon may be used to design a tunable optical switch.
The structure of silicon quantum dots and key factors for emission in different environment
Authors: Huang Wei-Qi  , Lü Quan  , Wang Xiao-Yun  , Zhang Rong-Tao  , Yu Shi-Qiang  ,   Key Laboratory of Photoelectron Technology and Application of Guizhou Province, Instituteof Nanophotonic Physics, Guizhou University, Guiyang 550025, China
Published: December 2020

Silicon quantum dots fabricated by nanosecond pulse laser in nitrogen, oxygen or air environment have enhancement in photoluminescence emission. The stimulated emission was observed at about 700 nm. It is difficult to recognize the difference between the photoluminescence peaks from samples in different environments, which is because of the same structure of the electron states in the band gap for different samples. The calculation results show that the same structure of the localized states forms in the band gap when silicon dangling bonds on surface of quantum dots are passivated by nitrogen or oxygen. It is the localized states that could catch the electrons from the conduction band to form metastable states, which is the key factor to enhance photoluminescence emission.
Experimental study on nonlinear absorption and Kerr effect in undoped GaP induced by femtosecond laser
Authors: Liu Feng  , Xing Qi-Rong  , Hu Ming-Lie  , Li Yan-Feng  , Wang Chang-Lei  , Chai Lu  , Wang Qing-Yue  ,   (1)Ultrafast Laser Laboratory, College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China; (2)Ultrafast Laser Laboratory, College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China;Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin
Published: December 2020

A modified Z-scan experimental setup based on a Yb-doped photonic crystal fiber amplifier was used to achieve polarization-resolved measurement of the nonlinear properties of bulk intrinsic GaP. The experiment results reveal that three-photon absorption dominated the nonlinear absorption processe at room temperature. The anisotropy and crystal orientation dependence of the nonlinear absorption and nonlinear refractive index was experimentally studied and the nonlinearities showed saturation at high pump intensities.
Quantum efficiency recovery of reflection-mode NEA GaN photocathode
Authors: Guo Xiang-Yang  , Du Xiao-Qing  , Chang Ben-Kang  , Qiao Jian-Liang  , Qian Yun-Sheng  , Wang Xiao-Hui  ,   (1)College of Optoelectronic Engineering, Chongqing University, Chongqing 400030, China; (2)School of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094, China; (3)School of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094, China;Department of electronic & electric Engineering,  Nanyang Institute of Technology,  Nanyang 473004,  China
Published: December 2020

In order to investigate the decay tendency and the recovery status of the quantum efficiency of reflection-mode NEA GaN photocathode, the quantum efficiency curves have been studied after the photocathode was fully activated, stored in system and supplemented with Cs. The quantum efficiency decay and recovery processes of reflection-mode NEA GaN photocathode were observed and the mechanism was discussed. The quantum efficiency value of reflection-mode NEA GaN photocathode can be recovered up to more than 94% of the best value in the shortwave region between 240nm and 300nm, and more than 88% in the long wave region between 300nm and 375nm after Cs supplement. Based on the changes of surface potential barrier profiles of the reflection-mode NEA GaN photocathode before and after the quantum efficiency degradation and the quantum yield formula, the decay characteristic and the recovery status of quantum efficiency curve after supplement with Cs have been related to the changes of surface barrier shapes.
Generation of 9.5 fs pulse by use of chirped mirrorsin Ti:sapphire laser cavity
Authors: Chai Lu  , Fan Zheng-Xiu  , Wang Qing-Yue  , Wang Yan-Zhi  , Dong Hong-Cheng  , Song You-Jian  , Hu Ming-Lie  , Shao Jian-Da  , Jin Yun-Xia  , He Hong-Bo  , Yi Kui  ,   Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics,The Chinese Academy of Sciences, Shanghai 201800, China;,   Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics,The Chinese Academy of Sciences, Shanghai 201800, China;Graduate School of the Chinese Academy of Sciences, Beijing 100049, China;,   Ultrafast Laser Laboratory, College of Precision Instruments and Opto-electronics Engineering, Key Laboratory ofOpto-electronic Information Science and Technology of Ministry of Education, Tianjin University, Tianjin 300072, China
Published: December 2020

According to the requirement of Ti: sapphire laser, the optimized chirped mirrors(CM) are designed to provide group delay dispersion (GDD) of around -60 fs2 with bandwidth 200 nm at a center wavelength of 800 nm. The CMs are manufactured by time controlled ion beam sputtering.The GDD is determined by using a home-built white light interferometer. The measurement results show that the manufactured CM can meat our requirement. By balancing the intra-cavity dispersion with our manufactured chirped mirrors, 12 fs and 9.5 fs pulses have been obtained respecitively.
Composite defect electromagnetic band gap cavity
Authors: Bai Ning-Feng  , Hong Wei  , Sun Xiao-Han  ,   Research Center for Electronic Device & System Reliability, Southeast University Nanjing 210096,China
Published: December 2020

We demonstrate an approach to create a high Q factor two-dimensional (2D) electromagnetic band gap (EBG) structure with composite defects in the center of the structures. By theoretical calculation, we show that a single-mode 2D EBG structure can be created with different ratios of diameter, d, to the lattice period, Λ, in this structure. This structure can achieve high Q factor and single mode operation with large d/Λ of the defect at the first circle around the removed rod in the center. With our structure, the single mode operation can be achieved within d/Λat the defect rods and d/Λat the others. In comparison, the condition of d/Λ should be strictly satisfied for the traditional design. These results provide very important guidelines for designing of the 2D EBG structure which can be used in traveling-wave tube device.
Using conditional nonlinear optimal perturbation method in parameter optimization of land surface processes model
Authors: Li Hong-Qi  , Guo Wei-Dong  , Sun Guo-Dong  , Zhang Yao-Cun  ,   (1)LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; (2)School of Atmospheric Sciences, Institute for Climate and Global Change Research, Nanjing University, Nanjing 210093, China; (3)School of Atmospheric Sciences, Institute for Climate and Global Change Research, Nanjing University, Nanjing 210093, China;RCE-TEA, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
Published: December 2020

In this paper, we attempted to entend the application of conditional nonlinear optimal perturbation(CNOP) to the optimization of parameters in land surface model. We used the common land model and data of Tongyu station,which is a reference site of the CEOP in the semi-arid regions, and used three key parameters (soil color, soil sand/lay proportion and leaf area index) as parameters to be optimized. Two experiments are designed in our work, namely the single-parameter optimization and the triple-parameter optimization. Notable improvements in simulating sensible heat flux (SH), latent heat flux (LH), soil temperature (TS) and moisture (MS) at shallow layers were achieved by using the optimized parameters. In addition, the latter experiment shows a better performance than the former. All results above illustrate that the application of CNOP method can be extended to parameters optimization of land surface model. And what is more, due to its other advantages, such as the clear mathematical meaning, the simple design structure, and the fast computing speed, it shows a great potential for further applications in parameters optimization of related problems.
The variational iteration solution method for a classof nonlinear disturbed evolution equations
Authors: Mo Jia-Qi  ,   Department of Mathematics, Anhui Normal University, Wuhu 241003, China; Division of Computational Science, E-Institutes of Shanghai Universities, Shanghai 200240, China
Published: December 2020

Using the generalized variational iteration method, a class of nonlinear disturbed evolution equations are studied. Firstly, a functional is introduced, then its variational is computed, and the iteration expansion is finally constructed. The approximate and exact analytic solutions to the problem are obtained.
Quantum turbo product codes
Authors: Xiao Hai-Lin  , Ouyang Shan  , Xie Wu  ,   School of Information and Communication, Guilin University of Electronic Technology, Guilin 541004, China
Published: December 2020

Quantum communication is a growing interdisciplinary field which combines classical communications and quantum mechanics. Quantum error correction coding is one of the key techniques in quantum communication. Nearly all of the classical error correction coding schemes have been transplanted to the domain of quantum communication, and the quantum counterparts of classical error correction coding techniques have been found. Based on the classical turbo product codes (TPCs) which is one of the most outstanding schemes in classical coding region, a new structure of the CSS-type quantum convolutional codes (QCC) as stabilizer sub-code of the quantum turbo product codes (QTPC) is presented. Firstly, CSS-type QCC stabilizer generator is constructed with the help of group theory and the basic principle of stabilizer coders, and the corresponding networks are described. Secondly, the interleaved coded matrix of the QTPC is obtained by quantum permutation SWAP gate definition. Finally, the corresponding relation between the quantum trace distance of QTPC decoding and the distance of classical TPCs decoding is obtained, and the scheme of QTPCs coding and decoding is completed. The coding and decoding of QTPCs have a highly regular structure and a simple design idea, and the networks are easy to realize.
The single solitary wave with double kinks of the combined KdV equation and its stability
Authors: Shi Yu-Ren  , Zhang Juan  , Yang Hong-Juan  , Duan Wen-Shan  ,   College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China
Published: December 2020

Based on the ideas of the hyperbola function expansion method, we obtained some analytical solutions of the combined KdV-mKdV (cKdV) equations by introducing new expansion functions.One of the single soliton solutions has the kink-antikink structure, and this solution reduces to the kink-like solution and the bell-like solution under different limitations. Theoretical analysis shows that the cKdV equation has both propagated-type and non-propagated-type solitary wave solutions. We also investigated the stability of the single solitary wave solution with double kinks numerically. The results indicate that the solution may be stable or unstable, depending on different sets of parameters.
Circuit design of tabu learning neuron models and their dynamic behavior
Authors: Li Chun-Guang  , Chen Jun  ,   (1)Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China; (2)Department of Physics and Electronic Engineering, Dingxi Teachers College, Dingxi 743000, China; Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
Published: December 2020

The circuit design and implementation of neuron models have attracted much attention in recent years due to its importance in both theoretical studies and applications. In this paper, we designed electronic circuits for the recently proposed tabu learning chaotic neuron model, including the circuit design of single tabu learning neuron, a two-neuron system with linear proximity function, as well as a two-neuron system with quadratic proximity function. We used the electronic workbench (EWB) software to perform simulations of the designed circuits. We also studied the nonlinear behavior, especially the Hopf bifurcation and chaos, of the designed circuits. The consistency between the nonlinear behavior in the designed circuits and that in the numerical simulations demonstrates the correctness of the circuits design.
Fast-scale instability and dynamic parameter resonance of power factor correction Boost converter
Authors: Cheng Wei-Bin  , Kang Si-Min  , Wang Yue-Long  , Tang Nan  , Guo Ying-Na  , Huo Ai-Qing  ,   School of Electronic Engineering, Xian Shiyou University, Xian 710065, China
Published: December 2020

Based on the multiplication of dynamic eigenvalue coefficient and its dynamic stabilizing capability, fast-scale instability and its asymmetry in power factor correction (PFC) Boost converter with continuous peak current control mode are investigated. To realize higher power factor and less harmonic distortion, a kind of compensation strategy is proposed to make the input current a sinusoidal wave, and it is optimized with parameter resonance. The formulas are deduced,and the overall optimization is carried out. The results of digital simulation shows that the overall compensating strategy has the most powerful dynamic ability to ensure the quick stabilization during every stroboscopic period, and the fast-scale instability is controlled, and the approximate unit power factor and the best compensating effects are obtained finally, resulting in the increase of the conversion efficiency of PFC Boost converter.
Multivariate chaotic time series phase space reconstruction based on extending dimension by conditional entropy
Authors: Zhang Chun-Tao  , Ma Qian-Li  , Peng Hong  , Jiang You-Yi  ,   (1)College of Computer and Engineering, South China University of Technology, Guangzhou 510006, China; (2)College of Mathematic and Computer Science, Chongqing Three Gorges University, Wanzhou 404000, China; (3)College of Mathematic and Computer Science, Chongqing Three Gorges University, Wanzhou 404000, China; College of Computer and Engineering, South China University of Technology, Guangzhou 510006, China
Published: December 2020

For multivariate chaotic time series, a method of conditional entropy extending dimension(CEED) in the reconstructed phase space is proposed. First, the delay time of any variable time series is selected by mutual information method, and then the embedding dimension of phase space is extended by the conditional entropy. This method can ensure the independence of reconstructed coordinates from low space to high space and eliminate the redundancy of phase space, because the largest condition entropy is choosen. The effective input vector for the prediction of multivariate time series is given. Simulations of the Lorenz system and Henon system show that the neural network predictions of multivariate time series are much better than the prediction of univariate and existing multivariate. Therefore, CEED is effective for multivariate chaotic systems.
A nuclear micro-battery based on silicon PIN diode
Authors: Qiao Da-Yong  , Chen Xue-Jiao  , Ren Yong  , Zang Bo  , Yuan Wei-Zheng  ,   Micro and Nano Electromechanical Systems Laboratory, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

Due to the use of heavily doped N type silicon substrate, the nuclear micro-battery based on silicon PN diode suffers from the small minority carrier life-time and small depletion region width, and can not achieve high energy transfer efficiency. A nuclear micro-battery utilizing silicon PIN diode as the energy transfer structure was demonstrated with achieves higher electrical power output. Theoretical model was built to predict the power output performance of this kind of micro-nuclear battery and structure optimization was performed in terms of the stopping range of beta particles, the depletion region width, the minority carrier life-time and the body resistance. Prototypes of PIN energy transfer structure were fabricated and were illuminated by using beta radioisotopes 63Ni,147Pm and alpha radioisotope 241Am as the radiation sources, and proved to be effective to improve the energy transfer performance.
Effect of asymmetrical micro electrode surface topography on alternating current electroosmosis flow rate
Authors: Jiang Hong-Yuan  , Li Shan-Shan  , Hou Zhen-Xiu  , Ren Yu-Kun  , Sun Yong-Jun  ,   (1)School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001,China; (2)School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001,China; State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou 310027, China
Published: December 2020

AC Electroosmosis(ACEO) induced by electric field is the basic approach for non-mechanical microfluid pumping. Traditional ACEO theory is based on electric double layer (EDL) theory, and gives electric-flow field coupling equations for ACEO flo w rate. But there is a big deviation between the calculation data and experimental velocities. In this paper, electrode surface topography is included to solve ACEO flow rate. Withelectrode surfaceroughness as the characteristic parameter, equivalent EDL model is set up to modify the classical EDL model. The relationship between flow rate and electrode surface roughness is studied. Experiment results agree with the simulation very well, proving the feasibility ofequivalent EDL model.
Transverse superresolution and extended axial focal depth realized by three-zone annular phase pupil filter
Authors: Zhou Chang-He  , Yu Jun-Jie  , Wang Wei  ,   (1)Laboratory for Information Optics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China; (2)School of Mathematics and Physics, Anhui University of Technology, Ma'anshan 243002, China
Published: December 2020

When linearly polarized light is focused using a high numerical aperture lens with three-zone annular phase pupil filter, vector diffraction method was applied to study the optical intensity distribution in transverse and axial directions. Numerical simulation results show that optical intensity distribution in transverse and axial directions need to be treated simultaneously. When three-zone annular phase pupil filter is added in front of a high numerical aperture lens, transverse super resolution, extended axial focal depth and flat-top focusing can be achieved at the same time. Furthermore, When phase modulation depth is changed, the phenomenon of axial focal shift can be found. The structure of three-zone annular phase pupil filter was optimized and the optimized results were given.
Electromagnetically induced transparency in squeezed vacuum
Authors: Lü Chun-Hai  , Tan Wen-Ting  , Tan Lei  ,   Institute of Theoretical Physics, Lanzhou University, Lanzhou 730000, China
Published: December 2020

We studied the electromagnetically induced transparency, where the three-level atom of Λ-type is put in two statistically independent squeezed vacuums. We start from the master equation containing the decay of the atom to the squeezed vacuums, and solve the non-diagonal density matrix element analytically, finding that it is strongly dependent on the squeezing degree and the phase of the squeezed vacuum. There is also a dependence on the intensity and phase of the probe beam, which would not appear in the normal vacuum case. By coupling with squeezed vacuums, the atom would not only experience electromagnetically induced transparency and slow group velocity, but also induce a fast group velocity,backward group velocity and a gain in the probe light field. Besides, the absorption and gain can be modulated by the intensity of probe light.
All-fiber ultrashort Yb3+ doped fiber laser self-started by spectral filter
Authors: Zhang Pan-Zheng  , Fan Wei  , Wang Xiao-Chao  , Lin Zun-Qi  ,   National Laboratory on High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
Published: December 2020

Theory of the passively mode-locked Yb3+ doped fiber ring laser self-starting through spectral filter is presented. The all-fiber Yb3+ doped fiber ring laser generating ultrashort pulses are designed and fabricated. High concentration Yb3+ doped fiber was employed as gain medium, which was pumped by a 980 nm diode laser. In the all-normal-dispersion cavity, a spectral filter was spliced to reduce the large emission peak at 1030 nm of Yb3+ ion and to generate an additional pulse shaping through spectral filtering of chirped pulse. Self-starting and stable mode-locking centered at 1053 nm was achieved by nonlinear polarization evolution along with spectral filtering from the filter. The mode-locking threshold was 300 mW, with the slope efficiency of 18.3%, the maximum output power was 53.07 mW, corresponding to the maximum pulse energy of 3.2 nJ. The center wavelength of the mode-locked pulse was 1053.6 nm, with 3 dB bandwidth of 10.84 nm at the repetition rate of 16.45 MHz. The picosecond mode-locked pulse can be dechirped to 188 fs using grating pair outside the cavity.
Output characteristics of wavelength tunable fiber lasers based on sampled Bragg gratings
Authors: Liu Yan  , Wang Lei-Shi  , Tao Pei-Lin  , Feng Su-Chun  , Yin Guo-Lu  , Ren Wen-Hua  , Tan Zhong-Wei  , Jian Shui-Sheng  ,   Key Laboratory of All Optical Network and Advanced Telecommunication Network of Ministry of Education, Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

A simulation model of the fiber DBR (distributed Bragg reflector) laser with two sampled Bragg gratings (SBGs) as reflectors is established, with which the characteristics of the laser are analyzed in detail. The analysis mainly focuses on the change of the laser output characteristics with the wavelength and reflectivity of the front and back sampled fiber gratings. Because of the multi-channel reflection of SBGs, the side mode of such laser is always very obvious. The method for improving the SMSR(side mode suppression ratio) is suggested. And the wavelength tuning mechanism is also studied. Experiment has been carried out to confirm the analysis.
Characteristics of subluminal for optical resonators
Authors: Zhang Jing  , Zhang Yun-Dong  , Zhang Xue-Nan  , Yu Bo  , Wang Jin-Fang  , Wang Nan  , Tian He  , Yuan Ping  ,   State Key Laboratory of Tunable Laser Technology, Institute of Opto-Electronics, Harbin Institute of Technology University, Harbin 150080, China
Published: December 2020

The insertion loss of fiber couplers in the two fiber rings waveguide system is studied. The peak power is the same by matching coupler strength of two couplers at the resonant area. The peak transmittance is inversely proportional to the group refractive index regardless of the two reflection values. Group delay increases at the expense of reduction of the peak transmissivity. The three rings waveguide structure manifests the subluminal properties accompanying normal dispersion by doping gain media. Group delay is analyzed in the frequency domain and the time domain, respectively. This study could be regarded as the significant theoretical foundation for applications in the field of controllable light velocity theory, sensors, filters, optical buffers and so on.
Experiments on quasi-two-dimensional dipolar vortex streets generated by a moving momentum source in a stratified fluid
Authors: Zhu Min-Hui  , Wang Xiao-Qing  , Chen Ke  , You Yun-Xiang  , Hu Tian-Qun  ,   (1)State Key Laboratory of Microwave Imaging Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China; (2)State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai 200030, China
Published: December 2020

Experiments were carried out in a stratified fluid with a momentum source modeled by a horizontally moving jet. The generation mechanism was investigated and the evolution characteristics were analyzed for the quasi-two-dimensional dipolar vortex streets generated by such a moving momentum source in the stratified fluid. The conditions of different Reynold and Froude number (Re, Fr) combinations under which the dipolar vortex street can be generated by moving momentum source were determined by use of data based on the present series of experiments. Moreover, the dependence of the dimensionless formation time and inverse dimensionless average wavelength of the dipolar vortex street on Fr for different values of Re was obtained. The results show that these parameters are independent of Re and approximately follow some exponential laws of Fr.
Numerical simulation of microwave power absorption of large-scale surface-wave plasma source
Authors: Lan Chao-Hui  , Hu Xi-Wei  , Liu Ming-Hai  ,   (1)College of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China; (2)Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

A full-size three-dimensional model of large-scale rectangular surface-wave plasma (SWP) source was built, the power deposition problems of SWP source based on collision mechanism were investigated through numerical simulations. The microwave reflectivity curves varying with plasma parameters were obtained, and the influence of different antenna arrays on power deposition is analyzed. The results show that the power deposition of uniformly discharged SWP source mainly depends on plasma property, and too big or too small plasma density is unfavorable to the energy absorption. In the range of working gas pressure, SWP source can achieve effective power deposition only through collision mechanism, and the absorption rate of microwave can reach more than 80%, which agrees with the existing experimental result. The results also show that compact and intensive surface wave is more favorable to the absorption of microwave.
Analysis of high-resolution X-ray imaging of an inertial-confinement-fusion target by using a Fresnel zone plate
Authors: Wang Xiao-Fang  , Wang Jing-Yu  ,   Key Laboratory of Basic Plasma Physics of Chinese Acadmy of Sciences, Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

Aiming at 1μm high resolution in imaging an inertial confinement fusion (ICF) target, a method is developed for analyzing the direct imaging by a Fresnel zone plate (FZP), and numerical calculations are carried out to study the FZP imaging characteristics in thekeV X-ray range. For the Ti K α line (photon energy 4.51keV, wavelength 0.275nm), the FZP parameters are suggested, for which the technical requirement of fabricating the outmost zone is relatively low. The influence of the target size on the imaging is studied for the first time. It is shown that the FZP has a large effective field of view and the image quality can be guaranteed even for a target of several millimeters. The influence of the spectral bandwidth of a polychromatic incident light on the imaging is also studied. Monochromatic imaging can be obtained due to the achromatic property of the FZP. However, if the bandwidth is larger than a certain limit, the image contrast will be degraded. These results indicate the feasibility of applying an FZP in high-resolution X-ray imaging of an ICF ignition target and put forward the requirements as well.
Variable charge molecular dynamics simulation of vitreous silica
Authors: Ma Ying  ,   Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, Faculty of Materials, Optoelectronics and Physics, Xiangtan University, Xiangtan 411105, China
Published: December 2020

Variable charge molecular dynamics simulations of vitreous silica have been performed based on the iterative fluctuation charge model. The vitreous silica was formed using the standard melt-quench process. The pair distribution function, angle distribution and frequency spectrum were then obtained. The results are in good agreement with experimental data. More importantly, our results show that the atomic charge in vitreous silica is significantly different from those in the crystalline silica, and larger fluctuations are observed.
Interpretation of dehydrogenation ability of high-density hydrogen storage materials by density functional theory
Authors: Zhang Hui  , Xiao Ming-Zhu  , Zhang Guo-Ying  , Lu Guang-Xia  , Zhu Sheng-Long  ,   (1)College of Physics Science and Technology, Shenyang Normal University, Shenyang 110034, China; (2)State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
Published: December 2020

A first-principles plane-wave pseudopotential method based on the density functional theory was used to investigate the dehydrogenation properties and its influence mechanics on several high-density hydrogen storage materials (MgH2, LiBH4,LiNH2 and NaAlH4) and their alloys. The results show that MgH2, LiBH4, LiNH2 and NaAlH4 high-density hydrogen storage materials are relatively stable and have high dehydrogenation temperature. Alloying can reduce their stability, but the stability of a system is not a key factor to the dehydrogenation properties of high-density hydrogen storage materials. The width of band gap of hydrogen storage materials can characterize the bond strength basically, the wider the energy gap is, the harder the bond breaks, and the higher the dehydrogenation temperature is. The bonding peak of the valence band top of LiNH2 is attributed mainly to the Li—N bonding, the N—H bond constitutes the low peak, which makes the dehydrogenation temperature of LiNH2 high, though LiNH2 has a narrow band gap in respect to LiBH4 and NaAlH4, which makes the ammonia release in the dehydrogenation process. Alloying makes the band gap narrow, and the Fermi level goes into the conduction band, which improves the dehydrogenation properties. It was found from the charge population analysis that B—H bond in LiBH4 is the strongest, H—N bond in LiNH2 is the weakest, so LiNH2 is relatively easy to release hydrogen. After alloying, the bond strength of X—H is weakened in every hydrogen storage material, and the N—H bond strength in LiMgNH2 is the lowest. Therefore, it is perspective to develop LiNH2 as hydrogen storage from the lowering of dehydrogenation temperature.
Drain-induced barrier-lowering effects on threshold voltage in short-channel strained Si metal-oxide semiconductor field transistor
Authors: Qu Jiang-Tao  , Wang Xiao-Yan  , Zhang He-Ming  , Wang Guan-Yu  , Song Jian-Jun  , Qin Shan-Shan  ,   Key Laboratory for Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi’an 710071, China
Published: December 2020

Based on strained silicon metal-oxide semiconductor field transistor (MOSFET) structure, the distribution of surface potential is obtained by solving two-dimensional Poisson equation, and the threshold voltage model is built. According to calculation results, the dependence of threshold voltage on germanium content of relaxed Si1－βGeβ, channel length, voltage of drain, doping content of substrate and channel are studied in detail, and the influence of drain-induced barrier-lowering on scaled strained silicon MOSFET is obtained, which can provide important reference for the design of strained silicon MOSFET device and circuit.
Preparation of Fe-based thick amorphous composite
Authors:   (1)Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (2)Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education, North China Electric Power University, Beijing 102206, China
Published: December 2020

A thick Fe-based amorphous composite coating (1—5mm) was prepared in situ by tungsten inert gas (TIG) cladding method. The auxiliary cooling system was used to improve the solidification rate of molten alloy and decrease the dilution from the substrates. The microstructure of the composite coating was investigated by X-ray differaction, optical microscope and transmission electron microscope. In addition, the micro-hardness of the coating was also measured. The results show that the composite coating is composed of the amorphous phase and the nano-crystalline grains encapsulated by amorphous transition layer, whose content is more than 50 percent. The composite coatings have been found to have good bonding strength and high wear resistance, the maximum value of the micro-hardness is up to 1600HV0.3. The microstructure of the transition layer with good elastic-plastic properties leads to the higher impact resistance. At last, the relations between the microstructure and micro-hardness properties were discussed in detail, and the main reason for high hardness is the cooperation of the amorphous phase and nano-crystalline phase in the composite coatings.
The hole concentration and strain relaxation of ultrathin GaMnAs film
Authors: Chen Chang  , Luo Dai-Sheng  , Gong Min  , Ma Yao  , Gao Bo  , Shi Rui-Ying  , Su Ping  , Meng Xiang-Hao  , Shi Tong-Fei  , Cao Xian-Cun  ,   Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China;,   School of Electronic and Information Engineering, Sichuan University, Chengdu 610064, China;,   School of Physical Science and Technology, Sichuan Province Key Laboratory of Microelectronics, Sichuan University, Chengdu 610064, China;,   School of Physical Science and Technology, Sichuan Province Key Laboratory of Microelectronics, Sichuan University, Chengdu 610064, China;School of Electronic and Information Engineering, Sichuan University, Chengdu 610064, China;,   State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China
Published: December 2020

The hole concentration and strain relaxation degree in the diluted magnetic epitaxial film of GaMnAs are affected by the Mn concentration. The result from Raman scattering spectrum experiment has shown that the hole concentration in ultra-thin GaMnAs sample with Mn concentration of 3% is greater than that in sample with Mn concentration of 2% , while the hole concentration in sample with Mn concentration of 4% is less than that in sample with Mn concentration of 3%. Based on the theory of strain relaxation and investigation by HRXRD, it was indicated the samples with Mn concentration of 2% and 3% are in quasi-coherence or with low relaxation degree, respectively. On the other hand, the sample with Mn concentration of 4% obviously has a greater relaxation degree than that with 3% concentration. Therefore, it is suspected that the status of quasi-coherence or low relaxation degree hardly affects the hole concentration with the change of the Mn concentration. However, the strain relaxation status of large relaxation degree results in more defects in the epitaxial layer which affects the energy band and level thus decreases the hole concentration dramatically.
Gate tunneling current predicting model of strained Si for scaled metal-oxide semiconductor field effect transistor
Authors: Wu Tie-Feng  , Zhang He-Ming  , Wang Guan-Yu  , Hu Hui-Yong  ,   (1)Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, School of Micro-Electronics, Xidian University, Xi’an 710071, China; (2)Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, School of Micro-Electronics, Xidian University, Xi’an 710071, China;School of Information and Electronic Technology, Jiamusi University, Jiamusi 154007, China
Published: December 2020

For scaled metal-oxide semiconductor field effect transistor (MOSFET) devices, normal operation is seriously affected by the static gate tunneling leakage current due to the ultra-thin gate oxide of MOSFET, and the novel MOSFET devices based on strained Si are similar to bulk Si devices in the effects. To illustrate the impact of gate leakage current on performance of novel strained Si device, a theoretical gate tunneling current predicting model by integral approach following the analysis of quasi-two-dimensional surface potential is presented in this study. On the basis of theoretical model, performance of MOSFET device was quantitatively studied in detail using ISE simulator, including different gate voltages and gate oxide thickness. The experiments show that simulation results agree well with theoretical analysis, and the theory and experimental data will contribute to future VLSI circuit design.
Structure and magnetic properties of Pr2Fe14(C, B)/α-(Fe, Co)-type nanocomposite ribbons
Authors: Li An-Hua  , Lai Bin  , Wang Hui-Jie  , Zhu Ming-Gang  , Li Wei  ,   Division of Functional Materials, Central Iron and Steel Research Institute, Beijing 100081,China
Published: December 2020

The phase evolution, microstructure and magnetic properties of PrxFe82-x-yTiyCo10B4C4 (x=9—10.5; y=0, 2) melt-spun ribbons have been investigated. All ribbons are mainly comprised of the 2 ∶14 ∶1, 2 ∶17 and α-(Fe, Co) phases. For the group of Ti-free ribbons (y=0), the coercivity increases with increasing x while the remanence decreases with increasing x. When 2 at.%Ti is substituted for Fe in the Ti-free ribbons, the magnetic properties are remarkably enhanced. The coercivity and squareness of demagnetization curve of the Ti-substitution ribbons are substantially improved without a sacrifice of remanence (except for x=9), the remanence even obviously increases at x=10.5. The optimal magnetic properties of Br=9.6 kGs (1 Gs=10-4T), iHc =10.2 kOe (1 Oe=79.5775 A/m), (BH)max＝17.4 MGOe have been obtained in Ti-substituted Pr10.5Fe69.5Ti2Co10B4C4 group. The volume fraction of the 2 ∶14 ∶1 phase increases with increasing x, which leads to an increase of coercivity. Ti-substitution suppresses the grain growth of α-(Fe, Co) phase during annealing process, which makes the volume ratio of magnetically hard phase and soft phase and grain size tend to have optimal values, and the intergranular exchange coupling substantially enhances.
Effect of microstructure on the ferroelectric properties of Eu-doped Bi4Ti3O12 ferroelectric thin film
Authors:   (1)Department of Electronic Engineering, Hunan University of Science and Engineering, Yongzhou 425100, China; (2)Department of Electronic Engineering, Hunan University of Science and Engineering, Yongzhou 425100, China;Faculty of Material and Photoelectronic Physics, Xiangtan University, Xiangtan 411105, China; (3)Faculty of Material and Photoelectronic Physics, Xiangtan University, Xiangtan 411105, China
Published: December 2020

Eu-doped bismuth titanate Bi3.15Eu0.85Ti3O12 (BET) ferroelectric thin film was prepared on the Pt/Ti/Si(111) substrates by metal-organic decomposition (MOD) at different annealing temperatures of 600℃, 650℃ and 700℃. The structure and ferroelectric properties of BET thin film were analyzed. The nanoscale domain switching was investigated by scanning probe microscopy (SPM) via direct observation. When the polarizing voltage increases to +6V, the ferroelectric c-domain suffers 180° domain switching. The ferroelectric r-domain can not be reversed due to its highly tetragonal structure even if the polarized voltage value increases to +12V. The ferroelectric properties of the BET thin films are dependent on the polarization of ferroelectric c-domain. With the increasing annealing temperature, the area of c-domain becomes larger, and the remnant polarization (2Pr) values of BET films increase. The value of 2Pr reaches 84μC/cm for BET thin film annealed at the temperature of 700℃.
Optical and electrical properties of CuS nanoparticles in terahertz frequency
Authors: Yang Yu-Ping  , Feng Shuai  , Feng Hui  , Pan Xue-Cong  , Wang Yi-Quan  , Wang Wen-Zhong  ,   (1)Key Laboratory of Optical Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (2)School of Science, Minzu University of China, Beijing 100081, China
Published: December 2020

The spectral response of the mixture composed of CuS nanoparticles and polyethylene powder was measured by the terahertz time-domain spectroscopy (THz-TDS). The low-frequency optical properties of pure CuS nanoparticles, including absorption coefficient, complex dielectric constants as well as conductivity, were calculated by the effective medium theory. The Lorentz theory of dielectric response and the Drude-Smith model of conductivity provide good fits on the measured dielectric function as well as conductivity, respectively. In addition, some terahertz optical properties, such as the frequency of the lattice vibration and the time constant for the carrier scattering, are also obtained by the fitting. Our investigation could help to reveal the material properties in the terahertz range and to find out the promising physical effect for special application.
Approximate solution to Sinh-Gordon equation via the homotopy analysis method
Authors: Ye Wang-Chuan  , Li Biao  , Wang Jia  ,   Department of Mathematics, Ningbo University, Ningbo 315211, China
Published: December 2020

In this paper, approximate solution of the Sinh-Gordon equation is obtained via the homotopy analysis method. The obtained solution contains an auxiliary parameter which provides a convenient way to control the convergence region and rate of the series solutions.
Feedback sum-product decoding of sparse quantum codes for X-Z Pauli channels
Authors: Peng Jin-Ye  , Wang Yun-Jiang  , Wang Xin-Mei  , Bai Bao-Ming  ,   (1)School of Electronics and Information, Northwestern Polytechnical University, Xi’an 710072, China; (2)State Key Lab of Integrated Service Networks, Xidian University, Xi’an 710071, China
Published: December 2020

In this paper, a feedback sum-product decoding algorithm of sparse quantum codes for X-Z Pauli channels is developed. Compared with the previous decoding algorithm, our feedback strategy exploits not just the syndrome but also the values of the frustrated checks on individual qubits of the code and the character of the channel model with the portion of each error to adjust the probability distribution of information nodes. Due to the smart adjustment, our decoding algorithm, on one hand, can break the symmetric degeneracy, and on the other hand, can feed back more useful information to the SPA decoder to help the decoder determine a valid output, thereby significantly improving the decoding ability of the decoder. Moreover, our algorithm, which is based on GF(4), overcomes the limitation caused by decoding in GF(2). Finally, we want to point out that, our method does not increase the measurement overhead in comparison wioth the previous methods, as the extra information comes for free from the requisite stabilizer measurement.
Anti-synchronization of different hyperchaotic systems based on adaptive active control and fractional sliding mode control
Authors: Liu Fu-Cai  , Li Jun-Yi  , Zang Xiu-Feng  ,   Key Laboratory of Industrial Computer Control Engineering of Hebei Province,West Campus of Yanshan University, Qinhuangdao 066004, China
Published: December 2020

Taking hyperchaotic Chen system and hyperchaotic Lorenz system as examples, we study the anti-synchronization of hyperchaotic systems with slow time-varying parameters. Firstly, taking advantage of active control concept, the non-linear parts of hyperchaotic systems are eliminated, and then based on Lyapunov stability theory, a kind of parameter adaptive control law is selected reasonably to achieve anti-synchronization of two hyperchaotic systems, which is a good solution to the time-varying parameters perturbation problem. Furthermore, hyperchaotic systems of different parameters with fractional order are studied via sliding mode control,which is proved to be valid theoretically. Numerical simulation experiments verify the effectiveness and feasibility of the proposed method.
Mechanism of polyalcohol solid—solid phase change
Authors: Wang Xiao-Wu  , Xu Hai-Hong  ,   Applied Physics Department, South China University of Technology, Guangzhou 510640, China
Published: December 2020

Many polyalcohols will change from one crystal structure to another at certain temperatures. A lot of works had reported their phase change enthalpy, phase change temperature and phase diagram. It is taken that their phase change enthalpy must be related to their hydrogen bond. This article investigated quantitatively the relation between phase change enthalpy and hydrogen bond of NPG (neopentylglycol), PG (pentaglycerino) and PE (pentaerythritol) on the basis of infrared spectrum experimental data and calorimetric results. It was shown that before phase change, all the —OH are associated and as a result NPG, PG and PE form layer structure. After phase change, NPG, PG and PE move along the layer and as a result some hadrogen bonds break. Therefore the phase change enthalpy equals the energy used to break hydrogen plus the energy used to increase the vibration frequency of other still associated —OH.
Molecular dynamics simulation for the impact of hydrazineon the water of pressurized water reactors
Authors: Shi Shun-Ping  , Li Yong  , Fan Yong-Sheng  , Chen Xu  , Zhou Wei  ,   (1)Sichuan University, Institute of Atomic and Molecular Physic, Chengdu 610062, China; (2)Sichuan University, Institute of Nuclear Science and Technology, Key Laboratory of Radiation Physics and Technology, Ministry of Education, Chengdu 610064, China
Published: December 2020

In this paper, we used molecular dynamics to simulate dynamic properties and micro-structure of the water-hydrazine particle system under various conditions:chamber condition of 1 atm, 298 K; pressurized water reactor (PWR) environment of 155 atm, 626 K; with number of water molecules of 256, numbers of hydrazine (N2H4) molecules of 0, 25, 50 and 75. And we have also explored the impact on the dissolved oxygen in water when hydrazine molecule is added to the system. The simulation results show that in the chamber ambient, when the number of molecules of hydrazine varies from 0 to 25, 50 and 75, the mean square displacement (MSD) in the particle system will increase with the number of particles of the hydrazine. The MSD for hydrazine molecule of number 0 will be ten less than that of 25, 50 and 75. Under the PWR environment, with hydrazine molecule number of 50, the MSD is about 4 times higher than that in chamber ambient. At the same time, under such condition, the MSD of particle system does not increase with the number of hydrazine molecules. The MSD with hydrazine molecule of 50 is higher than its counterpart with the number of molecules of 25 or 75. In addition, the micro-structure of particle systems, from the perspective of the radial distribution functions (RDF), will increase with the increase of concentration of hydrazine in chamber ambient. This conclusion goes along with the fact that hydrazine is easy to react with water to generate hydrazine hydrate. While in the pressurized water reactor environment, the radial distributions of the water with the number of hydrazine molecules of 25, 50 and 0 will have no big change. But the radial distributions with the number of hydrazine molecules of 75 increase significantly. It can be seen from simulation data that hydrazine added to PWR significantly inhibits the dissolved oxygen in water, but the inhibition does not increase in proportion to the increase of the concentration of hydrazine. This phenomenon and its causes are revealed comprehensively in this paper.