bluuebunny/crossref_metadata_2025 huggingface dataset:
Ocean duct inversion using radar clutter and its noise restraining ability
Authors: Sheng Zheng  , Huang Si-Xun  ,   解放军理工大学气象学院，南京  211101
Published: December 2020

The five-parameter model is proposed and the parabolic equation numerical model of electromagnetic waves propagation is used to calculate the propagation loss of electromagnetic waves, then GA （genetic algorithm） is used to retrieve the duct parameter and the parameter of GA are discussed. The ability of restraining noise of retrieval algorithm is tested. Experimental results show that when the observation errors are less than 10%, the retrieval precise is credible, but when the observation errors are larger than 10%, the retrieval precise is bad. These results can provide useful information to practice inversion and radar designing.
Regional characteristics of temperature changes in China during the past 58 years and its probable correlation with abrupt temperature change
Authors: Gong Zhi-Qiang  , Wang Xiao-Juan  , Zhi Rong  , Feng Guo-Lin  ,   (1)常熟理工学院物理与电子工程学院，常熟  215500; (2)国家气候中心中国气象局气候研究开放实验室，北京  100081；中国科学院大气物理研究所东亚区域气候-环境重点实验室，北京  100029; (3)扬州大学物理科学与技术学院，扬州  225002；国家气候中心中国气象局气候研究开放实验室，北京  100081
Published: December 2020

Based on recent studies of nonlinear science, we reconstruct dynamics of National Centre of Environment Prediction （NCEP） daily temperature series from 1948 to 2005 of grids located in China with the time-delay method and then analyse the dynamics structure by using dynamical correlation factor exponent Q.Eight significant temperature change regions are obtained. The characteristics of temperature changes and frequencies of extreme temperature in these regions are discussed, and the probable correlations between temperature changes and frequencies of extreme temperature are studied. Results indicate that, 1） the temperature and frequencies of extreme high temperature in ZhunGe’Er and North China both increased during the past 58 years, while frequencies of extreme low temperature in South China decreased. Furthermore, north oscillation, south oscillation, North Pacific oscillation and El Nio-south oscillation have distinct influence on temperature changes in North China, North-East China, west of West-South China and east of West-South China, while El Nio has distinct influence on South China and South East China. 2） The reason for warming during the past 58 years might be the increase of frequencies of extreme high temperature and the decrease of frequencies of extreme low temperature. 3） The abrupt change of extreme high/low temperature in the 1970s is 3—4 years later than that of abrupt temperature change. That is to say, the process of abrupt temperature change might be the inter-grade of extreme temperature from one stationary period to another stationary one.
Approximate solution of homotopic mapping for generalized Boussinesq equation
Authors: Mo Jia-Qi  , Cheng Yan  ,   (1)安徽师范大学数学系，芜湖  241000；上海高校计算科学E-研究院SJTU研究所，上海  200240; (2)中国人民解放军炮兵学院基础部，合肥  230031
Published: December 2020

The generalized nonlinear Boussinesq equation is studied. Using the homotopic mapping perturbation method，firstly，the corresponding homotopic mapping transform is constructed；secondly，the suitable initial approximation is selected；and then by using the homotopic mapping，the approximate solution for the solitary wave is obtained. Finally，the small perturbation asymptotic expansions are obtained.
Nonlinear Ramsey interference on a two-component Bose-Einstein condensate
Authors: Li Sheng-Chang  , Duan Wen-Shan  ,   西北师范大学物理与电子工程学院，兰州  730070
Published: December 2020

Taking Rosen-Zener tunneling as the underlying process，a scheme to achieve nonlinear Ramsey interferometry with a two-component trapped Bose-Einstein condensate is proposed. Abundant nonlinear Ramsey interference fringes are observed in time domain by the numerical simulations and these fringes are very different from the sinusoidal pattern for linear Ramsey interference due to the dominant nonlinear interaction between atoms. Furthermore，Fourier transformation results show that the fundamental frequency of Ramsey fringes can exactly reflect the information of nonlinearity or asymmetry. This finding provides an opportunity to measure atomic properties via measuring the frequency of fringes.
Methods for calculating the main-axis Lyapunov exponents of a type of chaotic systems with delay
Authors: Zhang Xiao-Dan  , Liu Xiang  , Zhao Pin-Dong  ,   北京科技大学应用科学学院，北京  100083
Published: December 2020

In this paper，we propose a new method for calculating the main-axis Lyapunov exponents of a type of chaotic systems with delays，which we call Matrix iteration method. We discuss this new method theoretically by detailed analysis. Also，we introduce another method called Taylor expansion method. The method invented by Wolf is also introduced and we discuss the advantages and disadvantages of these three methods. Finally，we calculate the main-axis Lyapunov exponents of a type of chaotic systems with delay to test these method.
The mechanism of the influence of Bi(or Sb) and rare earth on high temperature performance of AZ91 magnesium alloy
Authors: Zhang Guo-Ying  , Zhang Hui  , Wei Dan  , Luo Zhi-Cheng  , Li Yu-Cai  ,   (1)沈阳工程学院基础教学部，沈阳  110136; (2)沈阳师范大学物理科学与技术学院，沈阳  110034
Published: December 2020

The atomic structure models of α matrix and the symmetric ［0001］ tilt boundary in AZ91 magnesium alloy were set up by using the concept of coincidence-site lattice (CSL). The total structure energy of α matrix and the grain boundary (GB)，the environment sensitive embedding energies (EESE) of alloy elements and the interaction energies between the atom clusters were calculated by using recursion method. Calculation results show that the cluster formed by Al and RE in bulk AZ1 Magnesium alloy is rather stable，but the cluster of Al，Bi(or Sb) and RE atom is unstable. When Bi(or Sb) and RE atoms coexist in AZ91 magnesium alloy，Bi or Sb will combine with RE to form dispersed particles which are mainly RE2Bi (or RE2Sb ) and RE-Sb(or RE-Bi) distributed at the grain boundary，and Al11RE3 will form in the bulk in AZ91 magnesium alloy. The consumption of Al in magnesium alloy inhibits the formation of the discontinuous precipitate phase Mg17Al12. The melting points of compounds formed by RE and Al (or Bi，Sb) are high，thus the high temperature performance of AZ91 magnesium alloy would be obviously improved.
A novel zero-bit watermarking algorithm based on Logistic chaotic system and singular value decomposition
Authors: Song Wei  , Hou Jian-Jun  , Li Zhao-Hong  , Huang Liang  ,   北京交通大学电子信息工程学院，北京  100044
Published: December 2020

Based on chaotic system and singular value decomposition （SVD）, a novel zero-bit watermarking algorithm is presented. The proposed approach changed the traditional ways that copyright is protected by modifying the contents of images. Taking advantage of the characteristics of extreme sensitivity to initial values, Logistic mapping is used to find the hiding position of information, which enhances the schemes security. The invariant characters of SVD are applied to make the watermarks of registration center, which make the watermarked image distortion-free. and can protect the copyright effectively. Binary image is selected as watermark image so that the watermarks of existing zero-bit watermarking algorithms are no longer invisible and meaningless. The relationship between watermark capacity and security is also analyzed. Simulation of the algorithm was performed on different types of images, including standard test image, cartoon image, medical image, poem image, remote sensing image and natural scenery image, and the results were compared with existing algorithms. Results show that the propsed algrithm is simple and applicable, and can resist many attacks such as filtering, noising, JPEG compression, and shearing.
A new hyperchaotic system
Authors: Liu Ming-Hua  , Feng Jiu-Chao  ,   (1)华南理工大学电子与信息学院，广州  510641; (2)华南理工大学电子与信息学院，广州  510641；井冈山大学数理学院，吉安  343009
Published: December 2020

A new four-dimensional continuous-time autonomous hyperchaotic system is proposed in this paper，which is built by adding a nonlinear controller to a three-dimensional continuous-time autonomous chaotic system. The hyperchaotic system is analyzed by studying the Lyapunov exponent spectrum and bifurcation diagram. The system will take on periodic and complex periodic，chaotic and hyperchaotic behaviors with change of the parameter. Also，an electronic circuit is designed and realized，the experimental results verify the conclusions.
Lag synchronization of spatiotemporal chaos in a weighted network with ring connection
Authors: Li Yan  , Lü Ling  , Luan Ling  ,   (1)大连大学物理科学与技术学院，大连  116622; (2)辽宁师范大学物理与电子技术学院，大连  116029
Published: December 2020

Lag synchronization of spatiotemporal chaos in a weighted network with ring connection is studied in this paper. Spatiotemporal chaos systems are taken as the nodes of the network，and connections between the nodes are made through a weighted ring. According to stability theory，the condition to realize lag synchronization of the network is obtained by identifying the maximum Lyapunov exponent of the network. Lag synchronization exists in the whole network when the largest Lyapunov exponent is less than zero，and the coupling strength between the nodes can be given any weight value. Autocatalytic reaction-diffusion chaotic systems are taken as the nodes of the network，and simulation results show the effectiveness of the method.
A key generation algorithm for biometric cryptosystems based on TD-ERCS
Authors: Zhou Qing  , Hu Yue  , Liao Xiao-Feng  ,   重庆大学计算机学院，重庆  400030
Published: December 2020

Biometric cryptosystems are widely studied recently, which bind a cryptographic key with the biometric characteristic of a user in such a way that the key cannot be recovered without a successful biometric authentication. By now, the key is generated from extra random number generators, which makes the system more complex. A novel method is proposed, which generates the key from biometric characteristics directly, and makes the biometric cryptosystems much cheaper, simpler and more convenient. To make the keys secure enough, the TD-ERCS is adopted and revised in the proposed algorithm. Experiments show that the algorithm is sensitive to biometric characteristics, free of collision, and the generated keys seem also random. It is believed that such a algorithm can be practically used for various biometric cryptosystems.
The cellular automaton model for the nonlinear waves in the two-dimensional excitable media
Authors: Zhang Li-Sheng  , Deng Min-Yi  , Kong Ling-Jiang  , Liu Mu-Ren  , Tang Guo-Ning  ,   广西师范大学物理与电子工程学院，桂林  541004
Published: December 2020

In this paper，we have studied the nonlinear waves using the Greenberg-Hasting Cellular Automaton model. The dependence of the propagation speed of plane wave on the neighbor radius and the excitation threshold is analyzed with the no-flux boundary condition by computer simulation, and then the excitation condition is obtained. The orbit of the tip of spiral wave is affected by the number of refractory states and the excitation threshold, and then the mechanism is analyzed.
Pedestrian evacuation flow simulation based on cellular automata
Authors: Yue Hao  , Shao Chun-Fu  , Yao Zhi-Sheng  ,   (1)北京交通大学城市交通复杂系统理论与技术教育部重点实验室，北京  100044; (2)北京市城市规划设计研究院，北京  100045
Published: December 2020

Pedestrian facility planning and pedestrian flow management and control depend on the theory of pedestrian flow. Simulation of pedestrian evacuation flow is presented based on cellular automata （CA） in this paper. Two dynamic parameters are formulated to simplify tactically the decision-making process of pedestrians, which can reflect the pedestrian judgment on the surrounding conditions and decide the pedestrian’s choice of action. The relationships of evacuation time against pedestrian density and exit width for different sizes of systems are studied. Moreover, the effect of exits arrangement on evacuation time is analyzed. It is observed that there is a linear relationship between evacuation time and pedestrian density, however, there is a negative exponential one between evacuation time and exit width. And exits arrangement affects pedestrian evacuation time.
A study on the thermal conductivity of multiwalled carbon nanotube/polypropylene composite
Authors: Wang Jian-Li  , Xiong Guo-Ping  , Gu Ming  , Zhang Xing  , Liang Ji  ,   (1)清华大学工程力学系，北京  100084; (2)清华大学机械工程系，北京  100084
Published: December 2020

A convenient 3ω method was developed to measure the thermal conductivity of multiwalled carbon nanotube/polypropylene （MWCNT/PP） composite，in which the metal strip heater was substituted for a platinum wire，and the commercial lock-in amplifier was replaced by a Labview-based virtual measurement system. The experimental result showed that，the thermal conductivity of multiwalled carbon nanotube/styrene-butadiene rubber/polypropylene （MWCNT/SBR/PP） ternary composite varied slightly with MWCNT/SBR powder loading; the thermal conductivity of MWCNT/PP composite increased with the increasing MWCNT loading; the composite thermal conductivity was far less than that expected from the law of mixtures，but in good agreement with the effective medium approach by incorporating the thermal interfacial resistance between the MWCNT and the surrounding polymer matrix.
Density functional calculations on the structure, bonding and magnetic properties of the transition metal atom doped endohedral fullerene Ni@C20H20
Authors: Tang Chun-Mei  , Zhu Wei-Hua  , Deng Kai-Ming  ,   (1)河海大学理学院，南京  210098; (2)河海大学理学院，南京  210098；南京理工大学应用物理系，南京  210094; (3)南京理工大学应用物理系，南京  210094
Published: December 2020

The generalized gradient approximation （GGA） based on density functional theory（DFT）is used to analyze the structure, bonding and magnetic properties of the transition metal atom doped endohedral fullerene Ni@C20H20. The geometric optimization shows that the Ni atoms situated at the three possible positions off the cage center are all drawn back to the cage center. The binding energy and the energy gap calculations tell us that the cage center is the most thermodynamically and dynamically stable site for the Ni atom. It is discovered from the bonding analysis that the interaction between Ni and the cage could be neglected and the Ni atom keeps its atomic character. The electronic and magnetic properties reveal that the Ni atom with 2μB magnetic moments has no magnetism, while the cage with no magnetism still has no magnetic moment, mainly due to the zero electron transference between the Ni and the cage.
Optimization of frequency conversion system in inertial confinement fusion driver for frontally located beam smoothing elements
Authors: Yao Xin  , Gao Fu-Hua  , Gao Bo  , Zhang Yi-Xiao  , Huang Li-Xin  , Guo Yong-Kang  , Lin Xiang-Di  ,   四川大学物理科学与技术学院，成都  610064
Published: December 2020

There are many advantages for frontally located beam smoothing elements in terminal optical system of the inertial confinement fusion （ICF） driver, but it will also exert an influence on the working state of the frequency conversion system at the same time. This paper studies the influence from the viewpoints of system integration and optimization. Based on the non-linear transmission theory of high power laser and adopting coupled-wave differential equations and perturbation theory, we calculate the third harmonic conversion efficiency, optical characteristics in near and far field as well as the shape of focal spot when CPP is laid before the frequency conversion system. Then we put forward the method for the optimization of detuning angle and thickness of the frequency conversion crystal, in order to reduce influence on ICF system when CPP is laid before the frequency conversion system. The third harmonic conversion efficiency, contrast ratio and encircled energy before and after optimization are compared and analyzed. The results show that the optimization of frequency conversion system is very effective in reducing the impact on the beam quality and the third harmonic conversion efficiency when CPP is laid before the frequency conversion system.
Terahertz surface plasmon polariton couping on brass rods
Authors: Chen Hua  , Wang Li  ,   (1)东南大学物理系，南京  210096; (2)中国科学院物理研究所光物理实验室，北京  100190
Published: December 2020

In the experiment for studying the nature of coupling between suface plasmon （SP） wave and terahertz radiation by subwavelenth-sized brass rods, we found that the polarization of the THz field, size of rods, and slit between rods critically affect the coupling efficiency. By the method of Fourier transform of the time domain data, we found the coupling frequency in THz range. With equal slits between the brass rods, we demonstrated thar the transmission resonance is attributed to the combined effects of surface plasmon and cavity mode resonance when the electric vector is perpendicular to the grating wires, while the cavity mode resonance dominates the resonance transmission when they are parallel.
A 36 W intracavity-frequency-doubled diode-side-pumped Nd:YAG/KTP continuous wave green laser
Authors: Zhang Yu-Ping  , Zhang Hui-Yun  , He Zhi-Hong  , Wang Peng  , Li Xi-Fu  , Yao Jian-Quan  ,   (1)山东科技大学理学院,青岛  266510；天津大学精仪学院激光与光电子研究所，光电信息技术教育部重点实验室，天津  300072; (2)天津大学精仪学院激光与光电子研究所，光电信息技术教育部重点实验室，天津  300072; (3)天津大学精仪学院激光与光电子研究所，光电信息技术教育部重点实验室，天津  300072；电子科技大学中山学院电子工程系，广州 中山  528402
Published: December 2020

High-power and high efficiency continuous wave green laser has been realized by optimizing the plane-concave-plane resonator of three mirrors in an laser diode side-pumped configuration and KTP of Ⅱ-type phase-matching for frequency doubling. A maximum of 36.6 W continuous wave 532 nm green laser is obtained at pumping current of 36 A, corresponding to optical-to-optical conversion efficiency of 8.71％. The power stability of the laser is measured at output power of 33 W. During a half hour measurement time, the output power instability is 0.27%. The beam transfer factor is less than 8 measured by knife-edge method at output power of 33 W. Astigmatism compensation, misalignment sensitivity and mode profile inside resonator of three mirror folded resonator are also numerically simulated under high pump power.
Experimental research and theoretical study based on gain-guided soliton pulse fiber laser
Authors: Wang Lei-Ran  , Liu Xue-Ming  , Gong Yong-Kang  , Hu Xiao-Hong  , Wang Yi-Shan  , Lu Ke-Qing  ,   (1)中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室，西安  710119; (2)中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室，西安  710119；中国科学院研究生院，北京  100049
Published: December 2020

We use nonlinear polarization rotation technology to realize the self-start passive mode-locking in the erbium-doped fiber ring laser of positive dispersion, which can generate a new kind of gain-guided soliton pulse. The laser generates picosecond pulses with a rectangular-shaped spectrum, the FWHM width of which can be greater than 19 nm. The gain-guided soliton formation mechanism may include laser gain, spectral filtering effect, cavity dispersion and other fiber nonlinear effects. In this paper we also study the chirp property, peak power and other parameters of the pulse. With further increasing the pump power，the laser can operate on dual-pulse output mode.
Chaotic synchronization performances of two unidirectionally coupled VCSELs subject to negative optoelectronic feedback
Authors: Wang Xiao-Fa  , Xia Guang-Qiong  , Wu Zheng-Mao  ,   西南大学物理学院，重庆  400715
Published: December 2020

Based on the framework of the spin-flip model （SFM）, the synchronization performance of two unidirectionally coupled vertical-cavity surface emitting lasers （VCSELs） subject to negative optoelectronic feedback has been theoretically investigated. The results show that, with the increase of the feedback intensity, the laser output power displays two different chaos regions, i. e., singles-polarization mode region and mixed mode region. The polarized mode in the single mode region can achieve good synchronization, but sharply decline in the quality of synchronization close to the mixed mode region. Within the mixed-mode region, the continuity and quality of synchronization of polarized modes are not ideal. The fact that the synchronization quality of the mixed mode is worse than that of the single mode, is on the contrary to reported results based on optical feedback. The reason may be due to that negative optoelectronic feedback has induced the competion between the polarized modes. In addition, we have found changes in internal parameters have a great impact on the selection of two chaotic regions.
Experimental investigation of the slow light and superluminal effects in high-quality three-dimensional colloidal photonic crystals
Authors: Liu Hai-Ying  , Meng Zi-Ming  , Dai Qiao-Feng  , Wu Li-Jun  , Lan Sheng  , Liu Song-Hao  ,   华南师范大学信息光电子科技学院,光子信息技术实验室,广州  510006
Published: December 2020

We investigated by time-of-flight technique the slow light and superluminal effects in high-quality three-dimensional （3D） colloidal photonic crystals （PCs） with opal structure, fabricated by pressure controlled isothermal vertical deposition technique. They produce high transmission in the pass bands and sharp band edges due to low volume density of defects and dislocations. The variation of the group velocity across the short-wavelength band edge was measured. Group velocity as low as 0.43c was observed near the band edge while group velocity as high as 1.34c was found in the band gap. We have also simulated the transportation of ultrashort pulses through 3D PCs and compared the simulation results with the experimental ones.
Effect of the GaAs/GaSb combination strain-buffer layer on self-assembled InAs quantum dots
Authors: Jiang Zhong-Wei  , Wang Wen-Xin  , Gao Han-Chao  , Li Hui  , He Tao  , Yang Cheng-Liang  , Chen Hong  , Zhou Jun-Ming  ,   北京凝聚态物理国家实验室，中国科学院物理研究所，北京  100190
Published: December 2020

Optical properties and surface structures of InAs/GaAs serf-assembled QDs grown on 2ML GaSb and x-ML GaAs combined strain-buffer layer are investigated systematically by photoluminescence (PL) and atomic force microscopy (AFM). The QD density varies from 1.2×10cm-2 to 8.0×10cm-2 due to the influence of the lattice mismatch. The combined layer favors the increasing of In incorporated into dots and the average height-to-width ratio，which resulted in the red-shift of the emission peaks.For the sample of 5ML GaAs thin film the ground state transition is shifted to nearly 1300nm at room temperature.
Improvement and precision analysis of the split-step Fourier method in solving the general nonlinear Schr?dinger equation
Authors: Zhao Lei  , Sui Zhan  , Zhu Qi-Hua  , Zhang Ying  , Zuo Yan-Lei  ,   中国工程物理研究院激光聚变研究中心,绵阳  621900
Published: December 2020

Many numerical approximations are introduced in solving the general nonlinear Schrdinger equation （GNLSE） using the split-step Fourier method （SSFM）. In addition, careful consideration of the spatial and the temporal step sizes and the temporal window is needed to ensure the numerical precision. Supercontinuum generation in photonic crystal fiber is analyzed to show the improvement and precision control. The nonlinear term is treated directly by an integral instead of any mathematical approximation. Then the integral term can be transformed to a convolution to be solved by the Fourier transform, which facilitates the accurate numerical computation of the nonlinear term. High precision is ensured since no factitious approximation is introduced. Computation precision with respect to the step size choice is analyzed. Criteria are proposed as follows. The temporal and spatial step sizes can be appropriately chosen from the spectrogram, and the temporal figure provides a criterion for the temporal step size. These conclusions present direct criteria for the difficuet job of step size choice in solving the GNLSE.
Theory and fabrication of long period fiber grating with rotary refractive index modulation induced by CO2 laser pulses
Authors: Zhu Tao  , Song Yun  , Rao Yun-Jiang  , Zhu Yong  ,   (1)重庆大学光电工程学院光电技术及系统教育部重点实验室,重庆  400044; (2)重庆大学光电工程学院光电技术及系统教育部重点实验室,重庆  400044；电子科技大学通信与信息工程学院宽带光纤传输及通信网络技术教育部重点实验室,成都  610054
Published: December 2020

The structure of asymmetric LPFG with rotary refractive index modulation （R-LPFG） along the fiber axis is proposed and fabricated by using high frequency CO2 laser pulses. The transverse refractive index distribution of LPFG with asymmetric refractive index modulation in the cross-section is divided into multilayer circular waveguides, which are then discretized according to the magnitude of index. The mode coupling characteristics of this asymmetric LPFG is discussed by adopting coupled-mode equation sets and the revised Bragg condition. It’s observed that the transmission spectrum has different features depending on the rotation angle. For small angles, resonance peak is unique, however, when the angle becomes greater, the resonance peak will be split into two, which is different from the transmission spectrum of previous LPFGs. Moreover, the two split peaks have almost the same temperature sensitivity because they originated from the same two coupling modes. The high sensitivity torsion meter and strain meter without temperature compensation can be designed by adopting the wavelength spacing between the two split peaks.
Microbubble displacement under ultrasonic chirp excitation
Authors: Hu Yi  , Ge Yun  , Zhang Dong  , Zheng Hai-Rong  , Gong Xiu-Fen  ,   (1)南京大学声学研究所,近代声学教育部重点实验室,南京  210093; (2)中国科学院深圳先进技术研究院,深圳  518067
Published: December 2020

Ultrasound radiation force has been shown promising in facilitating ultrasonic molecular imaging and target drug delivery. A chirp excitation technique is developed to improve the translational displacement of microbubbles in this study. Based on a modified RP equation and a particle trajectory equation, we investigate the dependence of the translation of microbubble clouds on the chirp parameters （center frequency and frequency shift） and bubble radius distribution. Results demonstrate that the chirp excitation performs better than the traditional sinusoidal excitation in displacing widely distributed microbubbles and bubble clouds with radius far from resonant size. For example, for Gaussian size-distributed microbubble clouds with mean radius 3.5 μm and variance of 1, a 1 MHz center frequency chirp with frequency range 0.75 MHz induces about 12% more microbubbles displaced over a distance of 30 μm during 200 μs insonification, compared with a 1 MHz sinusoidal excitation with equal acoustic pressure.
Ultrafast rising of output electric impulse of lock-on model of semi-insulated GaAs photoconductive switches
Authors: Shi Wei  , Qu Guang-Hui  , Wang Xin-Mei  ,   西安理工大学物理系，西安  710058
Published: December 2020

In the lock-on model of semi-insulating GaAs photoconductive switches，the output current pulse has ultra-fast rise character，the rise time can be even less than that of the laser pulse. Fluid model is used to simulate the transport of photo-induced carrier. The results show that photo-activated charge domain formed in the transport process of carriers is the main cause of ultra-fast rise time. Further studies on the establishment of photo-activated charge domain and the absorption process show：1. The photo-activated charge domains during the establishment enhance the electron density gradient. 2. When the photo-activated charge domains are absorbed by the anode，rapid decline of bias electric voltage will accelerate the rise rate of output current pulse. Due to the two processes, the output current pulse in the lock-on model shows ultra-fast rise character.
Study on the Kelvin-Helmholtz instability in two-dimensional incompressible fluid
Authors: Wang Li-Feng  , Ye Wen-Hua  , Fan Zheng-Feng  , Li Ying-Jun  ,   (1)北京应用物理与计算数学研究所,北京  100088; (2)北京应用物理与计算数学研究所,北京  100088；浙江大学物理系，杭州  310028; (3)中国矿业大学（北京）,北京  100083; (4)中国矿业大学（北京）,北京  100083；北京应用物理与计算数学研究所,北京  100088
Published: December 2020

A weakly nonlinear model is proposed for the Kelvin-Helmholtz instability by expanding the perturbation velocity potential to third order. It is found that there is an important resonance in the process of mode coupling. This resonance makes the coupling processes very complex and interesting. Single-mode perturbation enters nonlinear stage quickly and produces lots of harmonics. The resonance reinforces the action of nonlinear process. The second and third harmonic generation efficiency of a single-mode disturbance is computed, as well as the nonlinear correction to the exponential growth of the fundamental modulation. Our simulations support the weakly nonlinear results from our analytic model. The nonlinear threshold phenomenon is also analyzed.
Experimental study on the effect of applied magnetic field on plane wave attenuation by microwave plasma plume
Authors: Yang Juan  , Long Chun-Wei  , Chen Mao-Lin  , Xu Ying-Qiao  , Tan Xiao-Qun  ,   (1)西北工业大学航天学院，西安  710072; (2)西北工业大学机电学院，西安  710072
Published: December 2020

The effect of applied magnetic field on the plane wave attenuation by microwave plasma plume inside a closed and evacuated quartz vessel is studied though spatially propagating wave method. The objective is to analyze how the operating parameters affect the wave attenuation in plasma and to find the mechanism which controls the interaction between plasma and plane wave. The experimental results show that under the present experimenal condition and in the cases without and with applied field, collisions are the reason leading to plane wave attenuation in the plasma. Plasma resonance absorption and upper hybrid resonant absorption mechanisms can not be found. To increase the plane wave attenuation in magnetized plasma, magnetic flux density should be set to make the wave test frequency and upper hybrid frequency identical.
Physical analysis of a one-surface multipactor model based on the structure of MILO
Authors: Ying Xu-Hua  , Hao Jian-Hong  ,   华北电力大学电气与电子工程学院，北京  102206
Published: December 2020

According to the interaction cavity structure of high-power microwave sources（HPM）, using magnetically insulated transmission line oscillator （MILO） as example, a one-surface multipactor discharge model is presented. Through the calculations of the susceptibility curves and the secondary electron evolution by using statistics and Monte Carlo simulation method, we analyzed the influence of the parameters of RF on multipactor discharge. Finally, measures for reducing and inhibiting multipactor discharge are proposed.
Experimental study on self-organized hexagonal superlattice pattern in dielectric barrier discharge in argon/air
Authors: Dong Li-Fang  , Xie Wei-Xia  , Zhao Hai-Tao  , Fan Wei-Li  , He Ya-Feng  , Xiao Hong  ,   河北大学物理科学与技术学院，保定  071002
Published: December 2020

A new type of hexagonal superlattice pattern is observed under three different boundary conditions by using a dielectric barrier discharge device with water electrode. The power spectrum of hexagonal superlattice pattern and its angular distributions are shown. The phase diagram of the hexagonal superlattice pattern as a function of air concentration and applied voltage is obtained. The correlation measurements indicate that the hexagonal superlattice pattern is an interllacing of two different transient sublattices. The selection of pattern formation in quadrangular boundary with different area is studied. It is found that the hexagonal superlattice pattern is a typical type of nonlinear self-organized pattern, and the formation of square superlattice pattern is dependent upon the boundary conditions.
Trap capture properties of space charge and void breakdown charge in a cellular polypropylene electret film
Authors: Zhao Min  , An Zhen-Lian  , Yao Jun-Lan  , Xie Chen  , Xia Zhong-Fu  ,   同济大学波耳固体物理研究所，上海  200092
Published: December 2020

The following aspects have been indicated by systematic studies on the cellular polypropylene (PP) electret film. Trap capture properties of space charges changed with their injected amount or surface potential of the sample. The space charges were captured largely in the deep traps of the sample surface and the second-deep traps of the near-surface region at small amount of charge injection. They would fill these traps in the surface layer (surface and near-surface region) and the shallow traps in bulk at the same time in the case of greater amount of charge injection. The charge detrapping temperatures of the three kinds of trap centers are about 160℃，138℃ and 92℃，respectively. The charges formed due to void breakdown (called the void breakdown charges) were captured not only in the surface layers of voids which have similar traps as the surface layer of the sample，but also there were numerous void breakdown charges which penetrated the void surface layer，entered into the bulk，and were captured by the shallow bulk traps.
First-pricinples design on atomic scale for new lightweight hydrogen storage materials
Authors: Zhou Jing-Jing  , Chen Yun-Gui  , Wu Chao-Ling  , Zheng Xin  , Fang Yu-Chao  , Gao Tao  ,   (1)四川大学材料科学与工程学院，成都  610064; (2)四川大学原子与分子物理研究所，成都  610064
Published: December 2020

Many new lightweight hydrogen storage materials developed in recent yesrs were reviewed, including carbon nanotubes, microporous metal-organic frameworks materials, complex aluminum/ boracium hydrides, metal-nitrogen-hydrogen systems, and metal-organic complexes, etc. Novel results and important progress studied through the state-of-the-art first-pricinples about the above materials were introduced, and the applications of the materials were analyzed and discussed in combination with experimental results. The relationship between these lightweight hydrogen storage materials were generalized, which suggests the methods of the design of material in the field of energy storage, and promotes new idea for research.
Evolution of stacking-fault-tetrahedron-like structures in copper crystal
Authors: Fang Bu-Qing  , Lu Guo  , Zhang Guang-Cai  , Xu Ai-Guo  , Li Ying-Jun  ,   (1)北京应用物理与计算数学研究所计算物理实验室，北京  100088; (2)中国矿业大学（北京），北京  100083
Published: December 2020

Transformation of various intrinsic Frank loops into stacking-fault-tetrahedron（SFT）-like structures in single crystal copper is investigated using the molecular dynamics（MD） method. We got stable SFT structures and explained their formation via a unified theory.Simulation results show that there is a critical size for the Frank loops at zero temperature. When being smaller than this critical size, Frank loops can not transform into SFT. Hexagonal and trapezoidal Frank loops exhibit oscillations in the relaxation processe, which is due to the elastic interactions between dislocations as well as the delay effects in the propagation of elastic waves.
The electronic theory of the mechanism of the role of Sc in Al-Zn-Mg-Cu ultra high strength aluminium alloys
Authors: Liu Gui-Li  , Fang Ge-Liang  ,   (1)沈阳工业大学建筑工程学院，沈阳  110023; (2)沈阳师范大学物理科学与技术学院，沈阳  110034
Published: December 2020

The atomic cluster models of α-Al, Al3Sc,η phase in Al-Zn-Mg-Cu ultra high strength aluminum alloys have been constructed by cell translation and the atomic cluster models of the interfaces α-Al /liquid Al and α-Al /Al3Sc have been set up by self-programmed software. The electronic structure parameters such as the density of states, the bonding energy of atom, the Fermi energy of the microscopic structure in alloys, the interaction energy between Sc and vacancy, have been calculated by recursion method. The physical nature of grain refinement and corrosion behavior of Al-Zn-Mg-Cu alloys has been explained according to the calculated electronic structure parameter. The results show that the energy given off by Al3Sc precipitating from liquid Al is less than that by α-Al and Al3Sc can precipitate from liquid Al prior to α-Al. Because of the lower interface energy of α-Al /Al3Sc compared with α-Al /liquid Al, the Al3Sc phase may offer the condition for the nucleation and growth of α-Al, which increases the nucleation rate of α-Al and refines the grain. The calculated results also indicate that Sc can attract the vacancy, decreasing the diffusion ability of vacancy and solute atoms, which makes the precipitate free zone along grain boundaries become narrower, and decreases the potential difference between grain and grain boundary, leading to the improvement of the corrosion resistance.
Molecular dynamics simulation of the structure characteristic of diamond-like carbon films influence by oblique incidence ion-beam-assisted deposition
Authors: Kai Hua  , Li Yun-Chao  , Guo De-Cheng  , Li Shuang  , Li Zhi-Jie  ,   内蒙古民族大学物理与电子信息学院，通辽  028043
Published: December 2020

On atomic scale, using molecular dynamics （MD） simulation, the influence of different ion-beam incident angles on the structure of diamond-like carbon （DLC） films was discussed in the process of ion-beam-assisted deposition （IBAD）. The study focused on the model of film surface, average density and SP3 hybridization fraction under different ion beam incidence angles. The results showed that horizontal kinetic energy of the incident atoms was enhanced by the oblique incident assist ions, thereby the horizontal migration of the C-atoms were also enhanced. The ratio of migration of C-atoms with ion-beam oblique incidence became greater than with verticalineidace, however, the density of the film and SP3 hybridization fraction became smaller. The effect of different ion-beam incident angle on the films structure varies with the variation of assistance/deposition atomic ratio （Ar/C） and incident energy. Thus films with different structures could be obtained when the incidence of ion-beam is oblique.
Small polaron property of polycrystalline Pr0.7(Sr1-xCax)0.3MnO3 series
Authors: Ma Yu-Bin  ,   北京大学物理学院，北京  100871
Published: December 2020

We have synthesized polycrystalline bars of Pr0.7（Sr1-xCax）0.3MnO3（x=0，0.1，…，1）with a sol-gel method using citrate as an agent, and grown epitaxial thin films of Pr0.7（Sr1-xCax）0.3MnO3 on （100）-oriented substrates of SrTiO3 （ STO ） by using pulsed laser deposition （ PLD ）. We systemically investigated their lattice structures and electronic transport property. Both polycrystalline and film samples have orthorhombic lattice structure, and their electronic transport behaviors nicely follow a adiabatic small polaron model in high temperature paramagnetic phase when T is larger than the Curie temperature TC. All resistivity data have been fitted by the small polaron model. The fitted results of polycrystalline samples qualitatively agree with that of corresponding film samples. With increasing contents of Ca, polaron hopping energy Ehop increases monotoniccaly, and ρ0 first decreases, then increases. The above results indicate that electronic transport property of high quality polycrystalline samples is less influenced by lattice defects and grain boundaries which are abundant in low quality samples, such that intrinsic small polaron transport behavior can appear in the former.
The effect of controlling laser field on broadband suppercontinuum generation
Authors: Zhang Qing-Bin  , Lan Peng-Fei  , Hong Wei-Yi  , Liao Qing  , Yang Zhen-Yu  , Lu Pei-Xiang  ,   华中科技大学，武汉光电国家实验室，武汉  430074
Published: December 2020

The effect of controlling laser field on broadband suppercontinuum generation is researched. By adjusting the wavelength of controlling field as much as ±0.2 μm at 1.6 μm, no effect has been found in suppercontinuum obviously, the cut off range and the bandwidth of suppercontinuum both vary less than 5%. With increasing of the intensity of the controlling field, the suppercontinuum is broadened. A 12 fs/800 nm and a 30 fs/1.6 μm pulses are combined to serve as the driving pulse with the relative phase of -0.1π and relative intensity of 20%, the short quantum path is selected and a 105 eV suppercontinuum is obtained.
The influence of doposition conditions on the structrure of ZnTe/ZnTe:Cu thin films and the properties of CdTe cells
Authors: Zhong Zheng-Xiang  , Zheng Jia-Gui  , Zhong Yong-Qiang  , Yang Fan  , Feng Liang-Huan  , Cai Wei  , Cai Ya-Ping  , Zhang Jing-Quan  , Li Bing  , Lei Zhi  , Li Wei  , Wu Li-Li  ,   (1)四川大学材料科学与工程学院，成都  610064; (2)中国工程物理研究院，绵阳  621900
Published: December 2020

Polycrystalline film of ZnTe/ZnTe:Cu is fabricated by co-vaporization. The influence of evaporation temperature on the structue of the film and Cu distribution in the film and performance of the cell fabricated with the films are studied by XRD,XPS, C-V and I-V analysis. The results indicate that, （1） the deposition temeperature has less effecton the structure of the film ZnTe/ZnTe:Cu, （2） the fact that the Cu concentration in the film deposited at 100℃ raises to a maximum and descend rapidly shows the function of ZnTe film in preventing Cu atoms diffusing in the film and the CdTe cell fabricated with the film shows a wider barrier （XD）,smaller capacitance, better diode characteristic and larger conversion efficiency.
Fullerene-doped hole transport NPB layer in organic light-emitting devices
Authors: Niu Lian-Bin  , Guan Yun-Xia  ,   重庆市高校光学工程重点实验室，重庆师范大学物理学与信息技术学院，重庆  400047
Published: December 2020

The effect of C60 doping in the hole transport NPB layer on the performance of the device was investigated by changing the C60 content from 0 to 20 wt%. The OLEDs had a structure of ITO/NPB:C60（0, 10, 15, and 20 wt %）/Alq3/LiF/Mg: Ag. The doping led to higher hole mobility in C60-doped NPB layer from 5 wt% to 15wt%. Moreover, the hole mobility decreased when the doping content is 20%. The higher hole mobility resulted in efficient hole injection and low driving voltage at high luminance. For example, the driving voltage is about 4V and the maximum luminance of the OLEDs is 11000 cd／m2 when the doping content is 15%.However, the driving voltage is about 6V and the maximum luminance of the OLEDs is 6500 cd／m2 when the doping content is 15%. The hole mobility change resulted in the different performance in the devices.
The effect of substrates on magnetic properties and structure of MnZn ferrite films by alternate deposition
Authors: Zhang Hong  , Liu Xi  , Wang Lan-Xi  , Cao Jiang-Wei  , Liu Xiao-Xi  , Wei Fu-Lin  ,   (1)兰州大学磁性材料研究所,兰州  730000; (2)兰州大学电子材料研究所,兰州  730000
Published: December 2020

Mn1-xZnxFe2O4 films were prepared by alternative rf-sputtering from targets of MnFe2O4 and ZnFe2O4. The films were deposited on substrates such as single-crystal Si（100）, oxidized single-crystal Si（100）, single-crystal Si（100） with ZnFe2O4 underlayer and single-crystal MgO（100）. The deposited films are amorphous. After annealing in vacuum furnace at 550℃, the polycrystalline Mn-Zn ferrite crystallizes. The film with composition of Mn0.5 Zn0.5 FeO4 shows better magnetic properties: high magnetization Ms and lower coercivity Hc. The coercivity of the film deposited on MgO（100） substrate is the lowest. In this paper, the influences of substrate on film structure and the magnetic properties are investigated. It is believed that the magneto-elastic anisotropy resulting from stress in films dominates the coercivity of Mn-Zn ferrite films. The grain size may be refined to nanometer scale instrumentally by using suitable substrate; the stronger exchange coupling between grains would lead to a lower magneto-elastic anisotropy by averaging to the grains. Therefore, the soft magnetic properties of Mn-Zn ferrite films are improved.
The local structure and charge transfer properties of Co-doped ZnO thin films
Authors: Liu Xue-Chao  , Chen Zhi-Zhan  , Shi Er-Wei  , Yan Cheng-Feng  , Huang Wei  , Song Li-Xin  , Zhou Ke-Jin  , Cui Ming-Qi  , He Bo  , Wei Shi-Qiang  ,   (1)中国科学技术大学国家同步辐射实验室，合肥  230029; (2)中国科学院高能物理研究所，北京  100049; (3)中国科学院上海硅酸盐研究所，上海  200050; (4)中国科学院上海硅酸盐研究所，上海  200050；中国科学院研究生院，北京  100049
Published: December 2020

Zn0.95Co0.05O and Zn0.94Co0.05Al0.01O films were prepared by inductively coupled plasma enhanced physical vapor deposition with magnetic confinement system under different oxygen partial pressure. The local structure and charge transfer properties were investigated by X-ray absorption fine structure and resonant inelastic scattering spectroscopy at O-K, Co-K and Co-L edges. The Co K-edge and L-edge X-ray absorption fine structure revealed that Co2+ ions substituted for tetrahedrally coordinated Zn2+ ions without changing the wurtzite structure. The main defects were oxygen vacancies when the films were deposited under very low oxygen partial pressure. The resonant inelastic scattering spectroscopy indicated that the charge transfer between Co-3d and the electrons in Zn0.94Co0.05Al0.01O films was much stronger than that in Zn0.95Co0.05O. The oxygen partial pressure had an important effect in the charge transfer of Co-doped ZnO films.
Study on infrared absorption spectra of congruent lithium niobate crystals at low temperature
Authors: Shi Li-Hong  , Yan Wen-Bo  ,   (1)河北工业大学材料科学与工程学院，天津  300130; (2)弱光非线性光子学材料先进技术及制备教育部实验室，南开大学，天津  300457；天津城市建设学院物理系，天津  300384
Published: December 2020

Infrared absorption spectra of congruent lithium niobate crystals are measured at low temperature, and a new peak is found at 3200 cm-1 in the spectra. Results show that this peak has no relationship with hydrogen in the crystals, and that with the increase of the temperature, both the intensity and shape of the peak change in a complex way. Based on these results, we suggest that the new peak results from the electron transfer from small polarons （Nb4+Li） to free polarons （Nb5+Nb）. In addition, we find that this peak can be decomposed into three Gauss peaks, and the three components are attributed to three transfer processes with different energies.
Fabrication and properties of （100） oriented MgO by DC sputtering on Si substrate
Authors: Fu Xing-Hai  , Yin Yi  , Zhang Lei  , Ye Hui  ,   浙江大学现代光学仪器国家重点实验室,杭州\ 310027
Published: December 2020

MgO film was fabricated on （100） Si substrates with DC sputtering method, （100） highly preferred oriented MgO film and MgO/TiN bi-buffer layers were successfully obtained by optimizing the preparation parameters, and the preferred （100） orientation mechanism affected by temperature was also discussed in the paper. XRD, AFM, FESEM were used to investigate the crystalline orientation, surface morphology, as well as the cross-section morphology of MgO films deposited on substrates with and without buffer layers. Columnar structure of MgO film and a good epitaxial relationship between MgO and TiN films were shown in our samples. Refractive index of MgO film on Si was fitted with Sellmeier model in the visible wavelength range （1.692 @ 550 nm）, while on TiN/Si substrate, the refractive index was calculated to be 1.716 @ 550 nm （where part of the layer approaches to the air） with the help of an inhomogeneous model.
Study of structure and properties of Ba0.7Sr0.3TiO3 thin film with prefer-orientated MgO buffer layer on the silicon substrate
Authors: Yin Yi  , Fu Xing-Hai  , Zhang Lei  , Ye Hui  ,   浙江大学现代光学仪器国家重点实验室，杭州  300027
Published: December 2020

The （001） and （111）-oriented MgO buffer layers, on which ferroelectric Ba0.7Sr0.3TiO3（BST30） thin films were prepared subsequently, have been grown on Si （001） single-crystal substrates by sol-gel and magnetron sputtering methods. The microstructure of the thin films was investigated by XRD, AFM and SEM. The results showed that the （101）-prefer-oriented BST30 thin film was obtained on the thicker MgO（001） buffer layer, while only the competition between the （101） and （111） orientations of BST30 can be observed on the thinner MgO（111） buffer layer. With the increasing thickness of MgO（111） buffer layer, the BST30 thin film’s （101） orientation was restrained, whereas the （001） orientation was strengthened. The improved simplex method was utilized to obtain the optical constant （n） and thickness （d） of BST30 thin film and MgO buffer layer. It was also found that the MgO buffer layer can significantly decrease the leakage current and p-n junction effect of BST30 thin film.