bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on the scale-free topology model with strong intrusion-tolerance ability in wireless sensor networks
Authors: Liu Hao-Ran  , Yin Wen-Xiao  , Dong Ming-Ru  , Liu Bin  ,   School of Information Science and Engineering, Yanshan University, Qinhuangdao 066004, China;,   The Key Laboratory for Special Fiber and Fiber Sensor of Hebei Province, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

Considering that the scale-free topology in wireless sensor networks has poor ability of intrusion-tolerance, we use the Poisson network model with node batch arrival to construct a new scale-free topology model with intrusion-tolerance optimization. Additionally, the two adjustment factors about the residual energy and the node degree are introduced in the construction of the topology model. Then the scale-free topology whose power-law exponent can be adjusted in the range of (1, + ∞) is obtained. Finally, the power-law exponent is optimized by the network structure entropy, and its optimal value is derived. Results show that the new topology has a strong fault-tolerance. And it also can enhance the network intrusion-tolerance and has good energy-saving advantages.
Study on the cascade classifier in target detection under complex background
Authors: Gao Wen  , Tang Yang  , Zhu Ming  ,   Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   Key Laboratory of Airborne Optical Imaging and Measurement, Chinese Academy of Sciences, Changchun 130033, China
Published: December 2020

Method of target detection and tracking is one of the hot topics in image processing and computer vision field, which is significant not only in military such as imaging guidance and military target tracking, but also for civil use such as security and monitoring and the intelligent man-machine interaction. Treating the feature matching problem as a more general equinoctial classification question, can turn the intractable high-dimensional problem to a classification problem and deplete computer complexity. This method is based on the law of large numbers and Bayes rule. In this paper we propose a non-hierarchy structure classifier, for which the equation for calculation is theoretically derived, and apply 1bitBP feature to the classifier; and for further reducing the amount of calculation, we use integral image and square integral image to variance classifier as preprocessor, and then use non-hierarchy classifier to handle the patches which meet the variance demand and use the nearest neighbor to further improve the accuracy, and finally realize target detection and tracking based on cascade classifier. Our experimental results show that the method proposed is far superior in calculation amount and processing precision, and is robust to scale changing and rotation, so the method proposed in this paper is of high practical value.
Multistable phenomenon of the Y-type four-level atom-assisted optomechanical system
Authors: Han Ming  , Gu Kai-Hui  , Liu Yi-Mou  , Zhang Yan  , Wang Xiao-Chang  , Tian Xue-Dong  , Fu Chang-Bao  , Cui Cui-Li  ,   College of Physics, Jilin University, Changchun 130012, China;,   College of Optical and Electronical Information, Changchun University of Science and Technology, Changchun 130012, China;,   School of Physics, Northeast Normal University, Changchun 130024, China
Published: December 2020

We have studied the steady-state properties of a hybrid optomechanical system, where a Y-type four-level atomic ensemble is confined in a microcavity with an oscillating mirror in one end. We find that the hybrid system will have multistability for the oscillating mirror and the confined atoms as the elastic coefficient of the spring decreases. When the elastic coefficient is very large, the oscillating mirror hardly affects the optomechanical system, therefore the system and the atomic ensemble have a single steady-state solution. However, when the elastic coefficient is small enough, the multiequilibrium positions of the oscillating mirror will be found, and the steady-state behaviors of the atomic ensemble confined in the microcavity may be affected. As a result, the susceptibility of the atomic ensemble will have multiple steady-state solutions and the probe absorption and dispersion will be changed as well. It has also been found that the number of steady-state solutions of the entire system could be controlled by changing the value of the elastic coefficient. These results may have potential applications in the area of high-precision quantum measurement and quantum information processing.
Effect of Raman gain on the characteristic of soliton transmission in birefringence optical fiber
Authors: Qiao Hai-Long  , Jia Wei-Guo  , Wang Xu-Dong  , Liu Bao-Lin  , Menke Neimule  , Yang Jun  , Zhang Jun-Ping  ,   School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China
Published: December 2020

The coupled nonlinear Schrödinger (CNLS) equation including Raman gain has been utilized for birefringence fiber. Evolution process of the optical soliton pulse has been simulated by the fractional Fourier method when the optical soliton pulse transmission in a birefringence fiber has a different nature. Results show that the drift of soliton caused by nonlinear coupling effect can be suppressed by Raman gain, at the same time, the soliton pulse peak in the transmission is enhanced. The interaction between optical solitons can be effectively restrained by Raman gain in the birefringence fiber.
Generation of broadband multicolor femtosecond laser pulses by using cascading four-wave mixing in a CaF2 plate
Authors: Liu Qi-Fu  , Li Fang-Jia  , Liu Jun  ,   State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China;,   MOE Key Laboratory of Advanced Micro-structured Materials, Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
Published: December 2020

Femtosecond laser pulses with new properties have been required for the great progress of femtosecond laser spectroscopy experiments. For example, simultaneous multiple ultrashort femtosecond laser pulses with different frequencies are needed in multicolor pump-probe experiments. Here, we have designed a much more simple and compact system for multicolor femtosecond pulse generation by using cascaded four-wave mixing in a 0.5 mm thick CaF2 plate. Multicolor femtosecond pulses with a sub-10 fs Fourier transform limit pulse width have been obtained by using two oppositely chirped incident pulses. These ultrashort multicolor femtosecond pulses will be used as a new laser source in femtosecond laser spectroscopy.
Atmospheric temperature profiles estimated by the vertical wind speed observed by MST radar
Authors: Qing Hai-Yin  , Zhang Yuan-Nong  , Zhou Chen  , Zhao Zheng-Yu  , Chen Gang  ,   School of Electronic Information, Wuhan University, Wuhan 430072, China
Published: December 2020

Atmospheric temperature is an important parameter for studying the process of atmospheric dynamics and photochemistry, and is a significant sign of the atmospheric vertical stratification structure. It is a challenge in atmospheric science research to obtain temperature profiles with high space-time resolution all the time. MST (mesosphere-stratosphere-troposphere) radar, which is the modern large-scale ground-based radio remote sensing equipment, can measure 3D atmospheric winds with high space-time resolution and unattended 24 hours a day. This paper uses the time series of vertical wind observed by MST radar to make spectral analysis and calculate B-V (Brunt-Väisälä) frequency. Then this paper builds the discrete model of temperature inversion based on the relationship between B-V frequency and temperature. Compared with actual measurement of temperature from radiosondes, the agreement between the radiosonde profile and the profile from MST radar data is quite good. Furthermore, the Richardson number can also be obtained by using the B-V frequency and horizontal winds, which can judge the atmospheric stability, quantize many of the dynamic characteristics, and explain the wave phenomenon. So the acquisition of B-V frequency is MST radar's another outstanding contribution to atmospheric dynamics research. It can accurately calculate the atmospheric temperature profiles and attain dynamic stability parameters.
Experimental investigation of dredging thermal protection system of hypersonic vehicle leading edge
Authors: Sun Jian  , Liu Wei-Qiang  ,   Detachments Unit 92941 of CPLA, Huludao 125000, China;,   Science and Technology on Scramjet Laboratory, National University of Defense Technology, Changsha 410073, China
Published: December 2020

According to the characteristics of dredging thermal protection system (DTPS) of hypersonic vehicle leading edge, both the structure of embedded high conductivity materials and that of integrative plate of heat pipe are designed to complete the two kinds of comparative experiments so as to prove the feasibility of the DTPS. As a source of radiation heating, the spherical short arc xenon lamp is simulated for aerodynamic heating. The pure steel leading edge, the embedded copper leading edge, the plate pure steel leading edge, and the integrative plate for heat pipe leading edge are heated respectively. Temperature variations of stagnation point region and tail fins are measured. Experimental results show that DTPS of the embedded high conductivity materials can reduce the temperature of stagnation point region and increase the temperature of the tail fins. It also can achieve the aim of thermal protection of leading edge. The DTPS of integrative plate heat pipe whose working fluid is pure water also can protect the leading edge under the condition of low heat flux. At the huge pressure of vapor, DTPS of the integrative plate of heat pipe may be broken at high heat flux. It is shown that the working fluid of heat pipe can play a key role in the application range for the thermal protection effect.
A cellular automaton model for the road in front of elementary and middle school gates during students going to school
Authors: Chen Jing  , Pang Ming-Bao  , Yang Min  ,   Transportation Department, School of Civil Engineering, Hebei University of Technology, Tianjin 300401, China
Published: December 2020

Based on the studies on traffic bottleneck of road, interference area, and mixed traffic flow, a cellular automaton model for the roads in front of elementary and middle school gates during students going to school is established. Characteristics of traffic flow are discussed via the simulation experiment. Effects of the traffic flow and the traffic volume are analyzed including the proportion of student driving private cars, the proportion of school buses, and the command giving by traffic policeman on the scene. Results of examples given in this paper show that traffic safety can be ensured, the traffic jams can be suppressed, and the goal of achieving largest traffic flow and decreasing the passing time of vehicles can be realized by decreasing the proportion of student driving private cars, increasing the proportion of school buses, and assisting the traffic policeman to command on the scene.
An analytical solution for the interaction of two-dimensional currents and gravity short-crest waves
Authors: Wen Feng  , Wang Jian-Hua  ,   School of Naval Architecture, Ocean & Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
Published: December 2020

Short-crest wave and current coexist widely in the ocean environments. However, the interaction between them has been studied recently and the method of velocity potential function was generally applied. Unlike the previous study, this article considers that location variable‘x'and time variable‘t'are independent of each other and it does not take into account the capillary effect, thus leading to an addition of a first-order time item in the second-order velocity potential function. Based on the perturbation technique, a second-order analytical solution is derived. Comparisons between the result in this article, where variables‘x'and‘t'are dependent on each other and the capillary effect is considered, and Huang's solutions show the difference. The difference between wave profile and wave pressure on mudline will become apparent with the increase of wave height, indicating that the solutions obtained in this article will be much suitable for ocean conditions with larger wave height.
Separating the Z-pinch plasma X-ray radiation and attaining the electron temperature
Authors: Gao Qi  , Zhang Chuan-Fei  , Zhou Lin  , Li Zheng-Hong  , Wu Ze-Qing  , Lei Yu  , Zhang Chun-Lai  , Zu Xiao-Tao  ,   University of Electronic Science and Technology of China, Chengdu 610054, China;,   Institute of Nuclear Physics and Chemistry, CAEP, Mianyang 621900, China;,   Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

According to the experimental results of spectrum diagnosis made on Qiang-Guang-I generator, we report a method to separate and diagnose Z-pinch plasma radiation spectrum. Spectral lines and different continuums are separated from experimental results and electron temperatures can be acquired. Results show that continuums are superposed by radiation of high electron temperature plasma at the centre field (Te=290.7 eV ± 1.2 eV) and radiation of lower electron temperature plasma at shell region (Te=95.3 eV ± 8.3 eV). Spectral lines reflect the information of high electron temperature plasma at the centre field. According to the calculation by using NLTE model, the electron temperature of such a plasma is in the range of 299–313 eV. The diagnose result by spectral lines is identical with the continuum's results.
Study on the excited states of zinc porphyrinogen and anisotropy of 2, 2, 6, 6-tetramethylpiperidinooxy by the technology of electron paramagnetic resonance
Authors: Yin Chun-Hao  , Li Pei-Xin  , Hou Lei-Tian  , Xu Zhen-Kun  , Wu Cai-Ping  , Li Shao-Bo  ,   Surface And Magnetism Lab, School of Science, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

To investigate the energy transfer and electron transfer of the photo-induced excited state in porphyrin sensitizers, we built the “zinc porphyrin-2, 2, 6, 6-tetramethylpiperidinooxy-xylene” experimental system. Zinc porphyrin's UV-visible spectrum shows that the characteristic absorption line of zinc porphyrin consists of bands B and Q, which are generated by the transition of elections from the ground state to the excited state in molecules of zinc porphyrin. The electron paramagnetic resonance spectrum of the experimental system is produced under the UV-visible light irradiation, at a temperature of 143 K; and we have detected the enhanced electron paramagnetic resonance spectrum of 2, 2, 6, 6-tetramethylpiperidinooxy. Based on the theory of the molecular excited states, and the photophysical and photochemical theory as well as the theory of the chemical-induced electron spin polarization, we also analyze the experimental results. Our conclusion is that the enhanced electron paramagnetic resonance spectrum of 2, 2, 6, 6-tetramethylpiperidinooxy is caused by the energy transfer and electron transfer of the photo-induced excited state in the porphyrin sensitizers. The anisotropic characteristics of the phenomenon of electron paramagnetic resonance spectrum of 2, 2, 6, 6-tetramethylpiperidinooxy at low temperatures are due to the anisotropic hyperfine interaction between nitroxide electrons and nitrogen nuclear.
Surface plasmon enhancement effect in molecular excitation
Authors: Sun Xue-Fei  , Wang Lu-Xia  ,   Department of physics, University of Science and Technology Beijing, Beijing 100083, China
Published: December 2020

Enhancement effect of surface plasmon in the metal nano-particle is a hot topic in nano-material field. A system is investigated where a spherical metal nano-particle is placed near a dye molecule. Under the optical excitation of a polarized electric field the subsequent charge transfer dynamics for different relative positions are simulated by density matrix theory approach, where the Coulomb interaction of molecule and metal nano-particle is calculated in the framework of the dipole-dipole approximation. It is found that the enhancement effect is closely related to the relative distance between the molecule and metal nano-particle. Effect of enhancement due to the surface plasmon is discussed in detail for various coupling interactions, polarization of field, lifetime of plasmon, and non-resonant excitation; and the physical essence in the molecule-metal nano-particle coupled system is analysed.
Influence of temperature change on conductive characteristics of titanium oxide memristor
Authors: Xu Hui  , Tian Xiao-Bo  , Bu kai  , Li Qing-Jiang  ,   School of Electronic Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Nano-scaled titanium oxide memristors exhibit unstable conductive characteristics under the same test condition: restricting the possibility to have accurate reading and control of the transient resistance of the device. Moreover, the reliability and stability of memristor-based circuits cannot be guaranteed. Coexistence of dopant drift and tunnel barrier is one of possible origins which causes undesirable instability, and the ambient temperature has a close relationship with dopant drift. However, there have been no detailed researches which may improve the stability of memristors by controlling temperatures. Based on the coexistence of dopant drift and tunnel barrier, the connections between temperature and memristor conductive characteristics are analyzed, and the influences of changes of active area width and initially doped layer width on the critical temperature are studied. Simulations are performed in SPICE and the results are given in this paper. In conclusion, methods are proposed for enhancing the conductive stability of memristors, which include increasing the active area width, decreasing the initially doped layer width, keeping the temperature to be under the critical value, and stability. Our work may provide a basis for manufacturing memristors with stable performance and promoting the practical circuit in applications.
Circuit parameter calculation based on characteristic parameters and pseudo-impedance of damped oscillation signal
Authors: Zhang Wen-Hai  , Xiao Xian-Yong  , Yang Jing-Gang  , Li Yong  , Yuan Ming-You  , Xiong Qian  ,   College of Electrical Engineering and Information Technology, Sichuan University, Chengdu 610065, China;,   Leshan Electric Power Co.Ltd, State Grid, Leshan 614000, China;,   Yibin Power Supply Company, State Grid, Yibin 644000, China;,   Mianyang Power Supply Company, State Grid, Mianyang 621000, China;,   Ziyang Power Supply Company, State Grid, Ziyang 641300, China
Published: December 2020

This paper mainly studied the circuit parameter calculation theory and the methods based on damped oscillations in transient signals. The methods can be used for the location and origin of faults by calculating the circuit parameters of transient fault signals' path when the fault occurs in the power system transmission lines. It is important in theoretical and practical engineering to locate faults in powerlines by calculating circuit parameters based on damped oscillations which are the main component of the transient signals. In R-L and R-C circuits, relations of the characteristic parameters in damped oscillation voltage and current in time domain, with the circuit parameters as well as the component parameters are deduced. And the impedance characteristic of the circuit under damped oscillation is analyzed, which is defined as a pseudo-impedance based on the definition that impedance is steady and sinusoidal. Relations between the pseudo-impedance and circuit parameters are also found. Relations between component parameter and pseudo-impedance in series or parallel are also analyzed. So methods for circuit parameter calculation are proposed separately based on the characteristic parameters and pseudo-impedance, each of which is a kind of characteristic of the damped oscillation signal. Specific calculation methods are also proposed combining with the state-of-the-art signal analysis for damped oscillation signal. Analyses in this paper may lay an important foundation for practical engineering application. The proposed theory and methods are verified based on simulation of fault signals produced by MATLAB. The equivalent circuit of an actual distribution system is simulated by using PSCAD/EMTDC. Actual fault signals reappear in the simulation. Location of single-line-to-ground fault using damped oscillation signal proposed in the paper is proved feasible.
A universal emulator of mem-elements
Authors: Li Zhi-Jun  , Zeng Yi-Cheng  , Tan Zhi-Ping  ,   College of Information Engineering, Xiangtan University, Xiangtan 411105, China;,   Dept. of Optoelectronic Engineering, Xiangtan University, Xiangtan 411105, China
Published: December 2020

According to HP memristor model, a grounded memristor emulator is proposed in this paper. Based on the proposed memristor emulator, a universal emulator of mem-elements is implemented with common off-the-shelf components. This universal emulator can transform the grounded memristor into a floating memristor, or a floating meminductor, or a floating memcapacitor by connecting different components to it. Because the universal emulator is floating, it is not confined to be grounded and can be connected between any two voltages. In order to verify theoretical presumptions about the universal emulator, Pspice simulations are conducted on this circuit.
Study of ZnO photoconductive X-ray detector
Authors: Zhao Xiao-Long  , Kang Xue  , Chen Liang  , Zhang Zhong-Bing  , Liu Jin-Liang  , Ouyang Xiao-ping  , Peng Wen-Bo  , He Yong-Ning  ,   The School of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China;,   Radiation Detection Research Center, Northwest Institute of Nuclear Technology, Xi'an 710024, China
Published: December 2020

Ag-ZnO-Ag X-ray detectors based on ZnO film and nanowires are both fabricated in this paper. Results of continuous X-ray radiation measurement show that the two detectors have high responsivity: the responsivity of the ZnO film device is about 0.12 μC/Gy under a 100 V bias voltage, and that of the ZnO nanowires device is about 0.15 μC/Gy under a 50 V bias voltage. Surface effect due to the absorption and desorption of oxygen on the ZnO surface, which makes the carrier lifetime increase, is decisive to the high responsivity. ZnO film and nanowires have their potential applications in the X-ray dose rate measurement.
Analysis of low-frequency noise in the amorphous indium zinc oxide thin film transistors
Authors: Liu Yuan  , Wu Wei-Jing  , Li Bin  , En Yun-Fei  , Wang Lei  , Liu Yu-Rong  ,   Science and Technology on Reliability Physics and Application of Electronic Component Laboratory, CEPREI, Guangzhou 510610, China;,   State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China;,   School of Electronic and Information Engineering, South China University of Technology, Guangzhou 510640, China
Published: December 2020

Properties of low-frequency noise in the amorphous InZnO thin film transistors have been investigated in this paper. Due to the emission and trapping processes of carriers between trapping states located in the interface between the IZO layer and gate insulator, the drain current spectral density shows a 1/fγ(γ =0.75) low-frequency noise behavior. In addition, the normalized drain current spectral density is decreased linearly with the increase of gate length and width. This property confirms that the low-frequency noise in the IZO TFTs is due to the flicker noise in the channel, the contribution of source/drain contact and parasitic resistances can be ignored. Finally, based on the number fluctuation theory and the mobility fluctuation theory, the γ and average Hooge's parameters have been extracted to estimate the quality of devices and materials.
Influence of the observation distance on the lightning channel temperature studied by means of spectroscopic diagnosis
Authors: Wang Rui-Yan  , Yuan Ping  , Cen Jian-Yong  , Wang Xue-Juan  , Wang Jie  ,   Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China;,   Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

The spectra for first return strokes of cloud-to-ground lightning discharge were obtained by a slit-less spectrograph at the Qinghai plateau of China. In this paper, the effect of the observation distance on diagnosis results of channel temperature was calculated and discussed by applying the Beer-Lambert law and considering the attenuation of spectral line intensity in transmission. Results show that there is some difference in channel temperature obtained at different observation distances. The observation distance is further enlarged, then the temperature obtained will be lower. Furthermore, at further increased distance we take observation, the bigger the error will be. So the correction for the temperature is more important for longer observation distance. According to our calculation and analysis, a semi-empirical formula has been obtained, which shows a relationship between the lightning channel temperature and the observation distance. The influence of the observation distance on lightning channel temperature could be eliminated by using the semi-empirical formula.
The variational iteration method for characteristic problem of strong damping generalized sine-Gordon equation
Authors: Xu Yong-Hong  , Shi Lan-Fang  , Mo Jia-Qi  ,   Department of Mathematics & Physics, Bengbu College, Bengbu 233030, China;,   College of Mathematics and Statistics, Nanjing University of Information Science & Technology, Nanjing 210044, China;,   Department of Mathematics, Anhui Normal University, Wuhu 241003, China
Published: December 2020

A class of nonlinear strong damping sine-Gordon disturbed evolution differential equation is studied which appears widely in mathematics and mechanics. Firstly, we introduce a traveling wave transformation, and obtain the exact solution of degenerate equation. Then a functional calculating method for variational iteration is constructed, thus an iterative expansion is found. Finally, the approximate traveling wave analytic solutions for the original strong damping generalized sine-Gordon disturbed evolution equation are found. The arbitrary order approximate solutions, and the simple variational iteration method are obtained with higher accuracy. The approximate analytic solution can make up for the imperfection of the simple numerical simulation solution.
Dynamical modeling and multi-periodic behavior analysis on pulse train controlled DCM-DCM BIFRED converter
Authors: Shi Guo-Dong  , Zhang Hai-Ming  , Bao Bo-Cheng  , Feng Fei  , Dong Wei  ,   School of Information Science and Engineering, Changzhou University, Changzhou 213164, China
Published: December 2020

According to four different operating modes of a BIFRED converter, a piecewise smooth linear time-varying model for pulse train (PT)-controlled BIFRED converter operating in dual discontinuous conduction modes (DCM-DCM) is established, from which time-domain waveforms and phase portraits under different loads are obtained by numerical simulations. By analyzing the variation of the charge of an output capacitor in a switching period, a one-dimensional approximate discrete mapping model for PT-controlled DCM-DCM BIFRED converter is derived, in which the multi-periodic behaviors with the variations of the load resistance and the input voltage are studied, and the stability analysis and the estimations of the load resistance ranges are performed. Research findings indicate that the dynamical behaviors depicted by the one-dimensional approximate discrete mapping model are in good agreement with those described by the piecewise smooth linear time-varying model, well revealing the complicated multi-periodic behaviors existing in the PT-controlled DCM-DCM BIFRED converter. By PSIM circuit simulations and physical circuit experimental measurements, the waveforms obtained are consistent with the results of theoretical analysis, effectively validating the feasibility of the two dynamical models.
Control and synchronization in chaotic systems based on fast linear predictive control
Authors: Zhang Yuan  , Xu Qi  , Sun Ming-Wei  , Chen Zeng-Qiang  ,   College of Computer and Control Engineering, Nankai University, Tianjin 300071, China;,   Military Traffic Institute, Tianjin 300161, China
Published: December 2020

A kind of fast linear generalized predictive control (GPC) algorithm is proposed based on the extended state observer for chaotic (hyperchaotic) systems. The linear extended state observer is employed to estimate and compensate the nonlinear dynamics and the existing uncertainties of the chaotic (hyperchaotic) systems so that an integrator can be obtained to serve as the model for GPC design. Using this scheme, the computational complexity can be substantially reduced. A step coefficient matrix can be derived analytically and a future output prediction can be explicitly calculated by only using the last two samples of the output. Therefore, the self-tuning algorithms and the Diophantine equation can be completely avoided. The proposed method can be used to control nonlinear targets in a straightforward manner. Simulation results show the effectiveness of this linear algorithm.
First-principles study on saturated adsorption of alkali metal atoms on silicene
Authors: Huang Yan-Ping  , Yuan Jian-Mei  , Guo Gang  , Mao Yu-Liang  ,   Faculty of Materials, Optoelectronic and Physics, Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Xiangtan University, Xiangtan 411105, China;,   Faculty of Mathematics and Computational Science, Hunan Key Laboratory for Computation and Simulation in Science and Engineering, Xiangtan University, Xiangtan 411105, China;,   State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310027, China
Published: December 2020

Based on density functional first-principles calculations, we study the stability, micro-geometry, and electronic properties of alkali metal atoms adsorbed on silicene, and perform the comparison between pure and hydrogen-saturated silicenes. We found that all the formation energies of SiX(X=Li, Na, K and Rb) are negative, indicating that the relative structural stability of these new compounds is higher than silicene. Bader charge analysis shows that electric charge is transferred from Si atoms to H atoms in SiH compound, but in SiX the direction of charge transfer is opposite, i.e., the charge is transferred from alkali metal atoms to Si atoms. From the viewpoint of chemical bonding, it can be regarded that valence bond is formed between Si atoms and H atoms, and the bonds between Si and alkali metal atoms are mainly ionic, but there exists covalent contribution. From the band structure calculations, it is also found that the new type compound SiLi is a semiconductor with a direct band gap of 0.34 eV; however, all the other compounds of SiX(X=Na, K and Rb) exhibit metallic property.
Evolution of average cluster size in supsonic cluster jet under high gas backing pressure
Authors: Xu Yi  , A. S. Boldarev  , Dong Eon Kim  , Chen Guang-Long  ,   School of Fundamental Studies, Shanghai University of Engineering Science, Shanghai 201620, China;,   Keldysh Institute of Applied Mathematics Russian Academy of Science, Moscow 125047, Russia;,   Department of Physics & Center for Attosecond Science and Technology(CASTECH), Pohang University of Science and Technology (POTECH), Pohang, Kyungbuk 790-784, Korea;,   Max Planck Center for Attosecond Science, Pohang, Kyungbuk 790-784, Korea
Published: December 2020

Evolution of the average cluster size at the center of a cluster jet from the nozzle throat along the gas flow is investigated using simulations. The simulation is performed for the cluster jet from the expansion of Ar gas into vacuum through a long conical nozzle (with the length L of 30 mm) under a high backing pressure (～ 5×106 Pa). Results indicate that the cluster size increases gradually until it is close to the maximum with the increase of the distance from the nozzle throat, and the part of the jet with large-size clusters is located at the distance greater than 20 mm from the nozzle throat. Based on the simulation results about the evolution of the cluster size and the atom density in a cluster jet, the optimization of a nozzle length has been discussed under a given condition. This work shows that a proper nozzle length is about 20 mm for a usual conical nozzle with an opening angle of about 8.5 degree and a throat diameter of about 0.5 mm.
Theoretical and experimental studies on the self-reconstruction property of non-diffracting Mathieu beam
Authors: Li Dong  , Wu Feng-Tie  , Xie Xiao-Xia  , Sun Chuan  ,   College of Information Science and Engineering, Huaqiao University, Fujian Key Laboratory of Optical Beam Transmission and Transformation, Xiamen 361021, China
Published: December 2020

Self-reconstruction properties of the Mathieu beam are studied theoretically and experimentally. By means of the Mathieu-Hankel wave's theory, the self-reconstruction mechanism of Mathieu beam is analyzed. Based on the Fresnel diffraction theory, an analytical expression for the optical field of a Mathieu beam partially blocked by a circular opaque obstacle is derived, and the self-reconstruction process of Mathieu beam is simulated based on the analytical expression. Using a cylindrical lens and an axicon system to generate Mathieu beam, the self-reconstruction properties of the Mathieu beam partially blocked by a circular opaque obstacle on axis and off axis are verified. Experimental results agree well with the theoretical analysis.
Research on semi-supervising learning algorithm for target model updating in target tracking
Authors: Gao Wen  , Tang Yang  , Zhu Ming  ,   Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   Key Laboratory of Airborne Optical Imaging and Measurement, Chinese Academy of Sciences, Changchun 130033, China
Published: December 2020

Target detection and tracking technique is one of the hot subjects in image processing and computer vision fields, which has significant research value not only in military areas such as imaging guidance and military target tracking, but also for civil use such as security and monitoring and the intelligent man-machine interaction. In this paper, for target deformation, scale changing, rotation, and other issues in the long-term stable target tracking, a bootstrapping feedback learning algorithm is proposed, which may improve the target model and the classifier discriminating capacity as well as the fault tolerance ability; and it also makes fewer errors during the updating, and then the proof of convergence of the algorithm is given. Experimental results show that among the same tracking algorithms, utilization of the learning method to update the target model and classifier is more stable and more adaptable than unusing it in the processes of target scale changing, deformation, rotation, perspective changing and fuzzy. And compared with the existing conventional method, this method has a better robustness, and a high value in practical application and research.
Influence of uneven wall changing over time on the characteristics of liquid surface wave evolution
Authors: Wang Song-Ling  , Liu Mei  , Wang Si-Si  , Wu Zheng-Ren  ,   School of Energy Power and mechanical Engineering, North China Electric Power University, Baoding 071000, China
Published: December 2020

This paper mainly studied the evolution of liquid surface waves along an uneven wall. Considering the characteristic of the uneven wall changing over time, the perturbation equation for the surface waves is derived by using the small parameter perturbation method to solve the control equations under the given boundary conditions. The method of derivative expansion is used to find the solution to the equation and numerical research is then carried out for the wall shape of a simple harmonic. By studying the influence of different parameters on the wavy wall, it can be found that when the frequency of the wall is small, the wavelengths of static waves and traveling waves are close to each other, promoting the merger between the surface waves, and the surface wave amplitude is obviously increased when the wall frequency and wall depth or Re increase. By contrast of the two cases of wavy wall and uneven wall, the surface wave on uneven wall has a periodical change at the same location with the increase of time, while the surface wave on wavy wall has an almost periodic change with a longer wavelength. Although the decrease of the wall amplitude and the wall frequency both can cause surface wave amplitudes reduced, the surface waveforms are different, for the surface wave on the wavy wall can be regarded as the superposition of wavy wall waveform and surface waveform caused by uneven wall.
Crystallization behaviors of deuterium in glass microsphere
Authors: Yin Jian  , Chen Shao-Hua  , Wen Cheng-Wei  , Xia Li-Dong  , Li Hai-Rong  , Huang Xin  , Yu Ming-Ming  , Liang Jian-Hua  , Peng Shu-Ming  ,   Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

To develop deuterium-tritium (DT) cryogenic targets that meet the inertial confinement fusion (ICF) experiment requirements, the DT crystal seeding growth process needs to be controlled to obtain single crystalline DT-ice, thus reducing the crystal defects formed during crystal growth and improving ice-layering. In this paper, the close-packed hexagonal (hcp) single crystal growth mode has been established through kinetic theory of crystal growth morphology. Experimentally, the target chamber temperature is controlled to within ± 3 mK and the deuterium (D2) crystal growth process can be observed by backlit shadowgraphy. Results show that slow cooling can reduce the crystal defects significantly at the 20–100 Pa conducting helium pressure. When the cooling rate reaches 2 mK/min, two single crystal growth modes are observed with good reproducibility. Experimental results conform with the proposed hcp single crystal growth model. Compared with the results from Lawrence Livermore National Laboratory (LLNL), the methods of D2/DT single crystal growth in the cryogenic target are proposed.
Axial backlighting of two-wire Z-pinch using an X-pinch as an X-ray source
Authors: Zhao Shen  , Zhu Xin-Lei  , Shi Huan-Tong  , Zou Xiao-Bing  , Wang Xin-Xin  ,   Department of Electrical Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

The axial backlighting of two-wire Z-pinch using an X-pinch as an X-ray source was conducted on PPG-1, a pulsed power generator with a current of 400 kA in amplitude and 100 ns in pulse width. Its time-resolved axial backlighting images are obtained. In the backlighting images all the physical processes similar to those occurring in the early stage of the wire-array Z-pinch are observed, including the expansion of the high-density wire core surrounded by low-density coronal plasmas, the motion of the coronal plasma toward the axis of the wire-array, and the formation of precursor plasma. The areal mass density of the plasma shown in the backlighting images is calibrated with step-wedge filters. And the time-resolved radial distributions of the areal mass density of the plasma from the two-wire Z-pinch are obtained.
Geometric stability and nitrogen adsorption properties of small BaxOy cluster-modified Ru(0001) surface
Authors: Yan Jing  , Xu Wei-Yun  , Guo Hui  , Gong Yu  , Mi Yi-Ming  , Zhao Xin-Xin  ,   School of Fundamental Studies, Shanghai University of Engineering Science, Shanghai 201620, China;,   College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, China;,   Automotive Engineering College, Shanghai University of Engineering Science, Shanghai 201620, China
Published: December 2020

Barium promoter is widely used in the secondary ammonia synthesis catalysis, which could greatly improve the performance of a catalyst. Although barium oxide is confirmed as the main component of barium promoter, the existence of metallic barium has been argued. In order to theoretically clarify this issue, the first principles calculations have been performed to study the geometric stability and the nitrogen adsorption properties of small BaxOy cluster-modified Ru(0001) surface. It is found that Ba2O cluster is more stable than other small clusters or atoms (BaO2, BaO, Ba and O) on the Ru(0001) surface under the condition that the pressure rate of H2O/H2 is below 1‰. This implies that BaO promoter could be partially reduced by hydrogen gas in the experiment. According to the results of the projected density of states and charge difference induced by modification of cluster, the O atom in Ba2O cluster gains electrons from dz2 orbit of the underlying Ru atom, and forms O–Ru bonds; while Ba atom in Ba2O clusters transfers electrons to the nearest Ru atoms and forms Ba-Ru metallic bonds. As the adsorption of nitrogen is an initial reactant in ammonia synthesis, we also study the nitrogen adsorption properties near the Ba2O cluster. Compared with the different chemical properties of O and Ba atoms, the adsorption properties of nitrogen molecules on the sites close to O and Ba atoms are similar. The nitrogen adsorption energies at the corresponding sites are calculated to be 0.88 and 0.78 eV, respectively. The bond lengths of nitrogen molecules are about 0.187 nm near O atom, and 0.190 nm near Ba atom, both of which are shorter than those on a clean surface (～ 0.197 nm). And the stretching vibrational frequency of a nitrogen molecule is calculated to be 1888 cm-1 near the O atom, 1985 cm-1 near the Ba atom, both of which are also less than those on a clean surface (～ 2193 cm-1). This suggests that Ba2O cluster may weaken the bond strength of nitrogen molecules. According to the charge difference induced by nitrogen adsorption, the electrostatic interactions of Ba2O clusters increase the occupation of π antibonding orbital and the electric polarization of the nitrogen molecule, and thus weaken the N–N bond.
Theoretical and experimental studies on N, Fe, La co-doped anatase TiO2 band adjustment
Authors: Wang Qing-Bao  , Zhang Zhong  , Xu Xi-Jin  , Lü Ying-Bao  , Zhang Qin  ,   School of Physics and Technology, University of Jinan, Jinan 250022, China;,   School of Space Science and Physics, Shandong University at Weihai, Weihai 264209, China;,   Department of mathematics and physics, Shandong Jiaotong University, Jinan 250023, China
Published: December 2020

Based on the plane wave method (PWPP) of densiy functional theory (DFT) we model the N, Fe, La three elements co-doped anatase TiO2 crystal structure and calculate its band structure and density of states with Material Studio. By the sol-gel method, the intrinsic anatase TiO2 and the anatase TiO2 with N, Fe, La three elements co-doping are prepared and investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results indicate that the changes of the N, Fe, La co-doped TiO2 lattice volume and its bond length will result in a decline of the crystal symmetry and the effective separation of the electron-hole pair. Impurity level appearing at the bottom of the conduction band and at the top of valence band leads to the decrease of the TiO2 forbidden band width(1.78 eV to 1.35 eV, reduced by 25%), the red shift of light absorption edge, the increase of density of states as well as, the improve ment of electron transition probability and the photocatalytic efficiency of TiO2. Ion doping makes the particles in doped TiO2 become smaller, i.e. the size of particles in TiO2>N/Fe_TiO2>N/Fe/La_TiO2, the emission peak of the N/Fe/La: TiO2 is 425 nm and its energy gap is smaller than that of the intrinsic TiO2. The measured N/Fe/La: TiO2 photocatalytic ability is stronger than the N/Fe: TiO2, the origin can be due to the increasing number of the electronic states and the impurity energy levels.
Persistent currents in mesoscopic graphene rings with armchair edges
Authors: Dai Nan  , Deng Wen-Ji  ,   Department of physics, South China University of Technology, Guangzhou 510641, China
Published: December 2020

Based on the tight-binding model, the energy spectrum and persistent currents of mesoscopic graphene rings with armchair edges are studied analytically and numerically. Characters of the persistent currents changing with Aharonov-Bohm (A-B) magnetic flux in rings in different geometry are investigated in datail. The periodicity and special symmetry of energy spectrum and persistent currents changing with the magnetic flux are revealed. It is demonstrated that the persistent currents are determined by the geometric structures of the rings; the quantum states with small eigen-energies may carry much larger currents than those quantum states with eigen-energies far away from zero.
Long persistent and photo-stimulated luminescence properties of β-Sr2SiO4:Eu2+, La3+ phosphors
Authors: Cheng Shuai  , Xu Xu-Hui  , Wang Peng-Jiu  , Qiu Jian-Bei  ,   Key Laboratory of Advanced Materials of Yunnan Province, College of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China
Published: December 2020

A series of β-Sr2SiO4: Eu2+, La3+ phosphors have been synthesized via high temperature solid state reaction. Photoluminescence (PL), long persistent luminescence (LPL), and the photo-stimulated luminescence (PSL) suggest that Eu2+ ions occupy Sr(1) and Sr(2) sites. Significant enhancement of PL, LPL and PSL has been observed by co-doping La3+ in β-Sr2SiO4: Eu2+, La3+. Meanwhile, the introduction of La3+ ions increases significantly the intensities of the TL bands (T1 and T3 regions), and promotes the formation of a large number of traps in LPL and PSL. In addition, the observation of the PSPL(photo-stimulated long persistent luminescence) phenomenon demonstrates the occurrence of electrons which are retrapped by the shallow traps in the LPL process.
Study on the electromagnetic properties of thin-film solar cell grown with graphene using FDFD method
Authors: Zhou Li  , Wei Yuan  , Huang Zhi-Xiang  , Wu Xian-Liang  ,   Key Laboratory of Intelligent Computing and Signal Processing, Anhui University, Hefei 230039, China;,   School of Electronic and Information Engineering, Hefei Normal University, Hefei 230061, China
Published: December 2020

In recent years amorphous silicon solar cells have been receiving a great deal of interest due to their high energy conversion efficiency and low cost. The positions of absorption peak reflect the good absorption performance at specific frequency point or nearby spectra. However, the absorption peaks of amorphous silicon solar cell which are mainly determined by the properties of amorphous silicon and metal electrode, cannot be tuned. And the absorption efficiency can not be further enhanced also. Therefore, monolayer graphene film will be employed in the solar cells with periodic structure due to its remarkable electro-optic properties. With a suitable chemical potential applied, the dielectric constant of graphene can be tuned. This design mainly aims to tune the position of the absorption peak based on the graphene by using finite-difference frequency-domain method. Also, an approximate fitted function is developed in order to overcome the singularity in the exact expression. Numerical results show that the approximate closed form expression generates results within a maximum absolute error of 0.8%. Theoretical results provide the realistic organic thin-film solar cells with theoretical basis and technical support.