bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of disorder degree on the localization-delocalization transition in one-dimensional disordered system with long-range correlations
Authors: Deng Chao-Sheng  , Xu Hui  , Liu Xiao-Liang  , Wu Xiao-Zan  ,   中南大学物理科学与技术学院，长沙  410083
Published: December 2020

In order to reveal the effect of disorder degree on the localization-delocalization transition in one-dimensional disordered system with long-range correlations, the long-range power-law correlated energy sequence was modified. By using the renormalization group method, the Lyapunov exponent characterizing the localization-delocalization transition was calculated. The results showed that, compared with the correlation exponent, the disorder degree plays an opposite role in this transition. When the correlation exponent was fixed but the disorder degree increased, the extended states, which appeared at the center of energy band due to the influence of long-range correlations, were gradually converted to localized states. When the disorder degree increased to a critical value Wc, the whole eigenstates of the system became localized states, and the critical value Wc increased with the increase of correlation exponent.
The control of the crucial current in current-induced magnetization switching with an external magnetic field
Authors: Zhang Lei  , Ren Min  , Hu Jiu-Ning  , Deng Ning  , Chen Pei-Yi  ,   清华大学微电子学研究所，北京  100084
Published: December 2020

The current induced magnetization switching (CIMS) in a nano-scale pseudo-spin-valve (PSV) structure at low external magnetic filed is investigated using a macroscopic phenomenological model based on the magneto-dynamic equation. Magnetization reversal conditions and the corresponding critical currents are obtained by considering both the spin-dependent scattering at the ferromagnetic/nonmagnetic interfaces and the relaxation of spin accumulation in the ferromagnetic layer. The movement of the resistance-current hysteresis of the PSV structure at low external magnetic filed are explained by the calculation. The way to control the crucial current in the CIMS effect with an external magnetic field is also suggested.
Study on the dielectric properties and dielectric relaxation of Fe-doped CaCu3Ti4O12 ceramics
Authors: Mu Chun-Hong  , Liu Peng  , He Ying  , Zhang Dan  , Meng Ling  , Bian Xiao-Bing  ,   陕西师范大学物理学与信息技术学院，西安  710062
Published: December 2020

The CaCu3Ti4-xFexO12 (0≤x≤0.2) ceramics have been prepared by a standard solid-state reaction method, and the influence of Fe doping on the microstructure and dielectric properties of CaCu3Ti4-xFexO12 ceramics were investigated by the X-ray diffraction, scanning electron microscopy, dielectric spectroscopy and impedance spectroscopy. It has been found that complete solid solutions are formed for all of the compositions x. With the increase of Fe content, the semiconductivity of grain vanishes gradually and the dielectric constant decreases. For specimens with x≤0.04, the two dielectric relaxation process Ⅰ and Ⅱappeared in the frequency ranges of 106—108 and 103—104 Hz, respectively. These two dielectric relaxation process were considered to be associated with grain boundaries and interfacial polarization between the electrode and ceramic surface, respectively. In addition, the third dielectric relaxation Ⅲ was detected in the high-temperature dielectric spectroscopy of CaCu3Ti3.99Fe0.01O12 ceramic, which was caused by a hopping process of localized charge carriers. The activation energy of this thermally excited relaxation is 0.78 eV, as obtained by using the Arrhenius formula.
Investigation on the formation mechanism and diffusion of the electrode metal of oxidized Au/Ni/p-GaN ohmic contact in different alloying time
Authors: Ding Zhi-Bo  , Wang Kun  , Chen Tian-Xiang  , Chen Di  , Yao Shu-De  ,   北京大学物理学院，北京  100871
Published: December 2020

Using Rutherford backscattering (RBS)/channeling method, we investigated the microstructure evolution in oxydizing atmosphere of Ni/Au contact on p-GaN during annealing at constant temperature (500 ℃) but for different alloying time. The technique of RBS/channeling and simulation of RUMP program were used to investigate the diffusion of the electrode metal. It was found that Ni diffused to the interior of the sample, Au diffused to the surface of p-GaN after 60s alloying time and the epitaxial structures of Au also began to form on p-GaN at the same time. The O also diffused into the sample after 180 s alloying time. Considering a continuous decrease in the ρc, it is suggested that the epitaxial structures of Au on p-GaN and the formation of NiO play a critical role in forming low resistance ohmic contact to p-GaN. At 300 s alloying time at the same annealing temperature (500℃), the epitaxial structure of Au was impoved further and the O also diffused deeper into the sample, and the ohmic contact reached the optimal value.
Research on correlation of 1/fγ noise and hot carrier degradation in metal oxide semiconductor field effect transistor
Authors: Liu Yu-An  , Du Lei  , Bao Jun-Lin  ,   (1)井冈山学院数理学院，吉安  343009; (2)西安电子科技大学技术物理学院，西安  710071; (3)西安电子科技大学微电子学院,宽禁带半导体材料与器件教育部重点实验室,西安  710071
Published: December 2020

Metal oxide semiconductor field effect transistor (MOSFET) in high-, mid- and low-gate stresses of hot carrier degradation effect and its 1/fγ noise feature are studied. Based on the formation theories of interface traps and oxide traps in Si-SiO2 and the MOSFET 1/fγ noise mechanism, the process of exchange carrier between the defect in gate oxide and the free-carrier in the channel is simulated by the duo-phonon emission model. A unified physical model for hot carrier effect, material defect, electrical parameter and noise was built. Also, a method characterizing the MOSFET anti-hot carrier abilities with noise parameter Sfγ is presented. The model is testified by the experiment, which is designed based on the relation between hot carrier and noise. Experimental results well confirm the developed model.
Investigation on the improvement of the stability and uniformity of solution-based metal-induced crystallization poly-Si using surface-embellishment
Authors: Li He  , Li Xue-Dong  , Li Juan  , Wu Chun-Ya  , Meng Zhi-Guo  , Xiong Shao-Zhen  , Zhang Li-Zhu  ,   (1)南开大学光电子薄膜器件与技术研究所，天津  300071；南开大学光电子薄膜器件与技术天津市重点实验室，天津  300071；南开大学光电信息技术科学教育部重点实验室，天津  300071; (2)天津工程师范学院数理系，天津　300222
Published: December 2020

To obtain poly-Si with good uniformity and stability, a new method of solution-based metal-induced crystallization (S-MIC) with surface-embellishment wasproposed in this paper. A special solution that can embellish the surface of a-Si was employed to improve the conglutination between nickel and a-Si thin film. Before the nickel solution was spin coated, the special solution was spin coated on the a-Si sample at first. By controlling the nickel salt concentration, the poly-Si with grain size of 20—70 μm and good uniformity could be achieved. Furthermore, the nickel salt concentration is lower than that used in the traditional method of S-MIC by 1 or 2 orders of magnitude.
Electron transport properties of In0.53Ga0.47As/In0.52Al0.48As quantum wells with two occupied subbands
Authors: Shang Li-Yan  , Lin Tie  , Zhou Wen-Zheng  , Huang Zhi-Ming  , Li Dong-Lin  , Gao Hong-Ling  , Cui Li-Jie  , Zeng Yi-Ping  , Guo Shao-Ling  , Chu Jun-Hao  ,   (1)中国科学院半导体研究所，北京  100083; (2)中国科学院上海技术物理研究所红外物理国家重点实验室，上海  200083; (3)中国科学院上海技术物理研究所红外物理国家重点实验室，上海  200083；广西大学物理科学与工程技术学院，南宁  530004
Published: December 2020

Magnetotransport properties of two-dimensional electron gas have been investigated for three In0.53Ga0.47As/In0.52Al0.48As quantum well samples having two occupied subbands with different well widths. When the intersubband scattering is considered, we have obtained the subband density, transport scattering time, quantum scattering time and intersubband scattering time, respectively, by analyzing the result of fast Fourier transform of the first derivative of Shubnikov-de Haas oscillations. It is found that the main scattering mechanism is due to small-angle scattering, such as ionized impurity scattering, for the first subband electrons.
Effect of dual-synthetic antiferromagnet structre on giant magnetoresistance in spin valves
Authors: Su Xi-Ping  , Bao Jin  , Yan Shu-Ke  , Xu Xiao-Guang  , Jiang Yong  ,   北京科技大学材料物理与化学系，新金属材料国家重点实验室，北京  100083
Published: December 2020

The properties of dual-synthetic antiferromagnet (DSAF) structure Co90Fe10(5 nm)/Ru(x nm)/Co90Fe10(3 nm)/Ru(y nm)/Co90Fe10(5 nm) (in which x=0.45 y=0.45; x=0.45 y=1; x=1, y=1) were studied. The effect of DSAF structure on giant magnetoresistance (GMR) single spin-valve (SPV) structures was also studied. The study shows that the properties of DSAF are better than those of the conventional synthetic antiferromagnet Co90Fe10(5 nm)/Ru(0.5 nm)/Co90Fe10(3 nm). We demonstrated that the DSAF structure as a pinned layer dramatically enhances the GMR ratio in single SPV films at room temperature.
Effect of Ga2O3 on the spectroscopic properties of Tm3+-doped GeO2-Ga2O3-Li2O-BaO-La2O3 glasses
Authors: Lin Qiong-Fei  , Xia Hai-Ping  , Wang Jin-Hao  , Zhang Yue-Pin  , Zhang Qin-Yuan  ,   (1)华南理工大学光通信材料研究所,特种功能材料及制备新技术教育部重点实验室,广州   510640; (2)宁波大学光电子功能材料研究所,宁波  315211
Published: December 2020

Glasses with the compositions of (77-x)GeO2-xGa2O3-8Li2O-10BaO-5La2O3(x=4,8,12,16) doped with 8.0mol% of Tm3+ were fabricated. The spectroscopic properties and thermal stability were investigated experimentally with increasing Ga2O3 content from 4mol% to 16mol%. It is noted from differential thermal analysis curves that the thermal stability of the glasses are improved by increasing Ga2O3. According to Judd-Ofelt theory, the Judd-Ofelt strength parameters (Ω2，Ω4，Ω6) of Tm3+-doped GeO2-Ga2O3-Li2O-BaO-La2O3 were calculated, by which the radiative transition probabilities, fluorescence branching ratios and radiative lifetimes were obtained. The emission spectra of Tm3+-doped germanate glasses and the effects of Ga2O3 on the emission properties were investigated with 808nm laser diode excitation. The fluoroscopic intensity and the maximum stimulated emission cross section first decrease along with the increase of Ga2O3 content from 4mol% to 16mol%, and reach a minimum at Ga2O3 content of 12mol%, and then increase. The effects of Ga2O3 on the glass structure and the spectral parameters were also preliminarily investigated.
Photoluminescence of Ar+ implanted sapphire before and after annealing
Authors: Zhou Li-Hong  , Zhang Chong-Hong  , Li Bing-Sheng  , Yang Yi-Tao  , Song Yin  ,   (1)中国科学院近代物理研究所，兰州  730000；中国科学院研究生院，北京  100049; (2)中国科学院研究生院，北京  100049
Published: December 2020

Single crystals of sapphire (Al2O3) with (0001), (1010) and (1120) orientations were implanted at 623 K with 110 keV Ar ions to fluence of 9.5×1016 cm-2. The ion-implanted Al2O3 samples were annealed at 873, 1073, 1273 and 1373K for 60 min in vacuum and in air, respectively. Photoluminescence (PL) spectra of the as-implanted samples showed an emission band at 506 nm, with excitation wavelength at 300 nm. The PL peak intensity of (0001) and (1010) orientation samples were maximum after annealing at 1073K in both vacuum and in air. The annealing in air at 873, 1073 and 1273K lead to much higher PL peak intensity compared to annealing in vacuum. In all the samples the emission band disappeared after annealing at 1373K both in vacuum and in air. The experimental results indicate that annealing temperature, annealing atmosphere and crystal orientation play important roles for the PL peak intensity at 506nm of sapphire implanted with Ar ions. The PL peak at 506nm after Ar-implantation and annealing is related with the population of interstitial Al atoms introduced by the ion bombardment and the formation of argon gas bubbles and the resolution of Ar atoms during annealing.
Simulation of physical properties of organic photovoltaic cell
Authors: Feng Wei  , Gao Zhong-Kuo  ,   天津大学材料科学与工程学院,天津  300072
Published: December 2020

We propose models of the incoherent optical absorption and exciton transport to simulate the processes of absorption and exciton diffusion in organic photovoltaic devices according to the optical principle and diffusion theory. The functional relation of optical absorption, and the power conversion efficiency versus the thickness of the film has been obtained. We demonstrate that the developed model can be useful for the modelling of the optical absorption and exciton separation in the optimization of devices of organic photovoltaic cells with high power conversion efficiency.
Optical gain in PbTe/CdTe quantum dots
Authors: Xu Tian-Ning  , Wu Hui-Zhen  , Si Jian-Xiao  ,   浙江大学物理系，杭州  310027
Published: December 2020

A theoretical model is developed to study the optical transition and optical gain of PbTe/CdTe quantum dots. The model is based on the k·p envelope function approach, and anisotropic band structure characteristics of PbTe are taken into consideration. The relationships of optical gain of PbTe/CdTe quantum dots vs dot size and injection carrier density are given. The theoretical results suggest that PbTe/CdTe quantum dots with dot size of 15—20nm are promising materials for mid-infrared lasers, which may produce optical gain higher than 5000cm-1 when the injection carrier density ranges (0.3—3)×1018cm-3. The optical gain decreases with dot size increasing. However, higher injection carrier density is required for PbTe/CdTe quantum dots with smaller sizes (<15nm). Therefore the optimal PbTe quantum dot sizes are 15—20nm.
A symbolic dynamics approach to the complexity analysis of event-related potentials
Authors: Liu Xiao-Feng  , Yu Wen-Li  ,   (1)山东科技大学机器人研究中心,青岛  266510; (2)西安交通大学生物医学工程系,西安  710049
Published: December 2020

The symbolic dynamics was introduced to analyze the complexity of cognitive event-related potentials (ERPs). This method was first applied to the case of the MIX(p) system, and then was compared with the approximate entropy which had been successfully used to analyze the biological and medical experimental data. The complexity of ERPs in the Oddball paradigm was calculated with the symbolic dynamics. It was found that the complexity of ERPs over the frontal, central, and parietal areas declined significantly during the processing of tasks, reached at the minimum corresponding to the latency of P300 component, and rose back after the response was performed. In addition, this method was sensitive to the discrimination between target stimuli and non-target stimuli. The results indicate that the complexity based on the symbolic dynamics can sensitively reflect the processing of the cognitive task, and will be a promising tool to analyze the neural activity associated with the cognitive task.
KdV equation with a forcing term for the evolution of the amplitude of Rossby waves along a slowly changing topography
Authors: Da Chao-Jiu  , Chou Ji-Fan  ,   (1)兰州大学大气科学学院,兰州  730000；西北民族大学计算机科学与信息工程学院,兰州  730124; (2)兰州大学大气科学学院,兰州  730000；中国气象局培训中心,北京  100081
Published: December 2020

Employing the weakly nonlinear method and perturbation method, the evolution ofthe amplitude of Rossby waves when the topography slowly changes is studied. AKdV equation with a forcing term governing this evolution is obtained from the quasi-geostrophic vorticity equation, and the forcing term is induced by the slowly changing topography.
Improved Q vector analyses from the perspective of field separation and its application in a torrential rain event
Authors: Cao Jie  , Gao Shou-Ting  , Zhou Yu-Shu  ,   (1)中国科学院大气物理研究所,北京  100029; (2)中国科学院大气物理研究所,北京  100029；中国科学院研究生院,北京  100049
Published: December 2020

According to the theory of separation and reconstruction of wind field, the Q vector is separated accordingly in limited area using the approach of harmonic-cosine series expansion. The rotational and divergent components of Q vector are introduced into diagnosing weather systems as an improvement in the traditional Q vector analyses. Through a case study of a torrential rain event, potential advantages of the improved Q analyses approach can be seen in dynamic identification of both the location and the position of heavy rain centers.
Noether’s theory for Birkhoffian systems in the event space
Authors: Zhang Yi  ,   苏州科技学院土木工程学院，苏州  215011
Published: December 2020

In this paper, the Noether symmetries and the Noether conserved quantities for Birkhoffian systems in the event space is studied. Firstly, the parametric equations for the Birkhoffian systems are established; secondly, the Noether's theorem and its inverse theorem for the systems are given, which are based upon the invariant properties of the Pfaffian action with respect to the action of the infinitesimal transformation; and finally, an examples is given to illustrate the application of the results.
Second-harmonic power generated in the absorbing and birefringent nonlinear medium
Authors: Yan Guo-Jun  , Chen Guang-De  , Wu Ye-Long  , Yang Jian-Qing  ,   西安交通大学理学院应用物理系,西安  710049
Published: December 2020

Considering the absorption of the nonlinear medium to the second-harmonic (SH) wave and using the complete boundary conditions for the reflections of the fundamental and SH waves at the input and output faces of the nonlinear medium, a formula for calculating the second-harmonic power generated in the absorbing and birefringent nonlinear medium was derived from the Maxwell's equation that the SH field E2 satisfies. The result shows that the formula for calculating the second-harmonic power generated in the nonzero absorption medium can be used for calculating the second-harmonic power generated in the absorptive medium if the complex refractive index, instead of the ordinary refractive index is used.
The homotopy analysis method for solving a class of combustion models
Authors: Wu Qin-Kuan  ,   南京工程学院数学研究所，南京  211167
Published: December 2020

A type of nonlinear combustion model is studied. Using the homotopy analysis method, the approximation solution is obtained.
N-soliton interactions of Bose-Einstein condensates in external potentials
Authors: Zong Feng-De  , Zhang Jie-Fang  ,   浙江师范大学非线性物理研究所，金华  321004
Published: December 2020

In this paper, a perturbed complex Toda chain has been employed to describe the adiabatic interactions in an N-soliton train of the Gross-Pitaevskii equation. Perturbations induced by weak quadratic and periodic external potentials are analytically and numerically studied. It is found that the perturbed complex Toda chain adequately models the N-soliton train dynamics for both types of potentials. As an application of the developed theory, we consider the dynamics of a train of matter-wave solitons confined in a quadratic trap and optical lattice, as well as tilted periodic potentials. In the last case, we demonstrate that there exist critical values of the strength of the linear or periodic potential for which one or more localized states can be extracted from a soliton train. In addition, some interesting results in the experiments and applications of the Bose-Einstein condensates are also obtained.
Coherent state of three-particle Calogero-Sutherland model
Authors: Li Wen-Bo  , Li Mi-Shan  , Li Ya-Ling  , Wen Xiao-Yang  , Yuan Guang-Jun  , Zhang Chi  , Yang Tao  ,   北京交通大学物理系，北京  100044
Published: December 2020

The three-particle CSM (Calogero-Sutherland model) is solved by the pseudo-angular-momentum method. Analytic expressions of the eigenstate and coherent states are obtained.
Quantum secret sharing of an arbitrary two-particle entangled state via non-maximally entangled channels
Authors: Liu Yu-Ling  , Man Zhong-Xiao  , Xia Yun-Jie  ,   曲阜师范大学物理工程学院,曲阜  273165
Published: December 2020

In this paper, a quantum secret sharing scheme is proposed for an arbitrary two-particle entangled state among N agents. The scheme adopts the non-maximally entangled Bell states as quantum channels and the generalized Bell states as the measurement basis. By introducing an auxiliary particle and making selective measurement on it, the receiver can obtain the original quantum state with a probability less than unity.
Influences of time delay on logistic growth process driven by colored correlated noises
Authors: Han Li-Bo  ,   长江大学物理科学与技术学院，荆州  434023
Published: December 2020

The small time-delay approach is applied to logistic growth model when time-delayed feedback and colored correlated noises are included in the system. The steady state probability distribution Pst(x) of the tumor cell number is obtained. It is found that a configuration transition of multiple peaks to a single peak occurs due to the variation of delay time τ. An extremum appears in the curves of the mean of the steady-state tumor cell number 〈x〉, the second moment 〈x2〉, and the normalized variance Var versus λ. The positions and the peak values of the extrema can be effected by the time delay.
Detecting faint variation in signal by synchronization of Duffing system
Authors: Qin Wei-Yang  , Su Hao  , Yang Yong-Feng  ,   西北工业大学工程力学系，西安  710072
Published: December 2020

For nonlinear Duffing system, a derived synchronization system is built and the method is proved. By the synchronization, the faint difference in stimulating signal of Duffing system can be detected. In simulation, when there occurs chaos in the original system, the responses of the original and derived system will exhibit synchronization for identical input signal and non-synchronization for different input signal. When the system is in quasi-periodic motion, the synchronization is still sensitive to the faint variation in the input signal. The simulation results prove the effectiveness of the method.
Chaotic time series prediction based on multi-kernel learning support vector regression
Authors: Zhang Jun-Feng  , Hu Shou-Song  ,   南京航空航天大学自动化学院,南京  210016
Published: December 2020

Multi-kernel learning support vector regression (MKL-SVR) are proposed for chaotic time series prediction to solve the problems of kernel selection and hyper-parameter determination when using the standard SVR. The algorithm is realized through quadratic constrained quadratic programming (QCQP) in the hybrid kernel space, which not only reduces the number of support vectors, but also improves the prediction performance. Finally, it is applied to Mackey-Glass, Lorenz and Henon chaotic time series prediction. The results indicate that the proposed method can effectively increase the prediction precision, accelerate the convergency of cascade learning and enhance the generalization of prediction model.
Narrowband interference suppression in chaos-based communications based on set-membership estimation
Authors: Fan Yong-Quan  , Zhang Jia-Shu  ,   (1)西南交通大学信号与信息处理重点实验室，成都  610031; (2)西南交通大学信号与信息处理重点实验室，成都  610031；西华大学数学与计算机学院，成都  610039
Published: December 2020

This paper presents the set-membership estimation for narrowband interference (NBI) suppression in chaos-based communications. The proposed NBI suppression methods under known or unknown model parameters of interference signals are derived in terms of the optimal bounding ellipsoid criteria and the bounded property of chaotic carriers, respectively. Compared to the mean phase space volume (MPSV) based Kalman filtering and the recursive least square (RLS) algorithms, the proposed NBI suppression method estimates interference signals using only a few observations with the selective updating features, so that the computation is effectively reduced. Simulations results on AR and single tone interference suppression in chaotic parameter modulation (CPM) and differential chaotic shift keying (DCSK) communication systems show that the proposed NBI suppression methods can efficiently eliminate the narrowband interference signal in CPM and DCSK communication systems, and the computation is smaller than that of MPSV-based Kalman filtering and RLS algorithms.
Mechanism of period-doubling bifurcation in DCM DC-DC converter
Authors: Wang Xue-Mei  , Zhang Bo  , Qiu Dong-Yuan  ,   (1)华南理工大学电力学院,广州  510640; (2)华南理工大学电力学院,广州  510640；湖南工业大学电气与信息工程学院，株洲  412008
Published: December 2020

The period-doubling bifurcation in DC-DC converters has been investigated widely. However, the studies main focus on the models of bifurcations and the identification of strange attractors, the essential mechanism causing period-doubling bifurcation was not analyzed. This paper deduces mathematically the conditions of producing the period-doubling bifurcation in discontinuous current mode (DCM) Boost and Buck converters based on voltage feedback control. It exposes the mechanism of the period-doubling bifurcation in DC-DC converters and perfects the theoretical analysis method, puting forward an analytic method for studying the period-doubling bifurcation.
A method of detecting the unpredictability of chaotic signals based on periodic orbit statistics
Authors: Jin Jian-Xiu  , Qiu Shui-Sheng  , Xie Li-Ying  , Feng Ming-Ku  ,   华南理工大学电子与信息学院，广州  510640
Published: December 2020

A method of detecting the unpredictability of chaotic signals is put forward based on periodic orbit statistics. Chaotic time sequences come from analog circuit and numerical simulation respectively. Hot saddle periodic orbits are found and its regression spectrum and regression frequency are investigated. The results show that the method is adequate for detecting the unpredictability of chaotic systems.
Multi-stable synchronization manifold in generalized synchronization of chaos
Authors: Yu Xiang  , Zhu Shi-Jian  , Liu Shu-Yong  ,   海军工程大学振动噪声研究所，武汉  430033
Published: December 2020

The phenomenon of multi-stable synchronization manifold (SM) in generalized synchronization (GS) refers to the coexistence of multiple chaotic response attractors, which all synchronize with the same driving dynamics in the sense of GS. In this paper, the multivalue characteristic of SM is investigated in the general sense on the basis of establishing the functional relationship between the driving and response systems. The stability of SM is studied and the conditions ensuring the existence of the multi-stable SM are deduced. A Genesio-Rssler coupled system and a coupled Duffing system with quadric and cubic nonlinear terms are analyzed as examples and the results show that there exist only one stable SM in the former, while the bifurcation evolves from bistable SM to single-stable SM with the increase of coupling strength in the latter.
Synchronization of chaotic Liu system with uncertain parameters
Authors: Wang Hua  , Han Zheng-Zhi  , Zhang Wei  , Xie Qi-Yue  ,   上海交通大学电子信息学院，上海  200240
Published: December 2020

Based on the control Lyapunov function (CLF), a method of synchronizing chaotic Liu system with uncertain parameters is proposed. The feedback control law presented does not depend on the parameters but on the boundary of the parameters. It shows that the feedback is simple and robust. Simulation studies on Liu chaotic system also verify the effectiveness of the proposed scheme when the parameters vary largely.
Prediction of chaotic time series based on robust fuzzy clustering
Authors: Liu Fu-Cai  , Zhang Yan-Liu  , Chen Chao  ,   燕山大学电气工程学院自动化系，秦皇岛  066004
Published: December 2020

We propose a new method for fuzzy modeling based on a robust fuzzy-clustering algorithm. The induced local spatial similarity improved the system's robustness to noise and outsider and predicted the robustness of the modeling system. Starting from an initial fuzzy partition of input space by a nearest-neighbor clustering method to get the number of rules and the initial clustering center, we can compute and optimize the fuzzy membership and the clustering center with a robust fuzzy-clustering algorithm and get the high precision T-S model. The obtained parameters were identified by the least square method and further optimized by selective recursive least square. The proposed method was applied to simulations of chaotic Mackey-Glass time series modeling and prediction. The results demonstrated the robustness, effectiveness and practicability of the method.
Chaotic properties of mechanically and electrically coupled nonlinear dynamical systems
Authors: Zhang Qi-Chang  , Tian Rui-Lan  , Wang Wei  ,   (1)天津大学机械学院力学系，天津  300072; (2)天津大学机械学院力学系，天津  300072；天津大学内燃机燃烧学国家重点实验室，天津  300072
Published: December 2020

Based on the Silnikov criterion, the chaotic properties of mechanically and electrically coupled nonlinear dynamical systems were discussed. Using Cardano formula and series solution of differential equation, the eigenvalue problem and existence of homoclinic orbit were studied respectively. A rigorous proof of the existence of Silnikov-sense Smale horseshoe chaos was presented and some conditions leading to chaos were obtained. The space trajectory, Lyapunov exponent and Lyapunov dimension were investigated via numerical simulation, which showed that chaotic attractors exist in the non-linear dynamical systems.
Quantum Generalized Reed-Solomon codes
Authors: Li Zhuo  , Xing Li-Juan  ,   西安电子科技大学综合业务网国家重点实验室，西安  710071
Published: December 2020

We construct a family of quantum error-correcting codes with parameters ［［n，n-2k，k+1］］q which are defined in q-dimensional quantum systems，where q is an arbitrary prime power. These codes are optimal in the sense that the minimum distance is maximal. It is shown that codes exist for all n satisfying 2≤n≤q or q2-q+2≤n≤q2.
Agreement of two entropy-based measures on quantifying the complexity of short-term heart rate variability signals from professional shooters
Authors: Zhuang Jian-Jun  , Ning Xin-Bao  , Zou Ming  , Sun Biao  , Yang Xi  ,   (1)南京大学电子科学与工程系生物医学电子工程研究所，南京  210093; (2)南京体育学院运动系，南京  210014; (3)南京体育学院运动系，南京  210014；南京森林公安高等专科学校侦查系，南京  210046
Published: December 2020

Using two entropy-based measures, namely the approximate entropy and sample entropy measures, we studied the complexity of heart rate variability signals obtained from professional shooting athletes in the situations of rest and practice match. The results demonstrate that the values of two measures calculated from the resting signals are both greater than those calculated from the training signals, which means that the signals collected during the match are more regular compared to those acquired in a resting state. For a better application of the two methods, we further investigated the influences of two factors: threshold r and data length N, on the performance of the algorithms. Although both approaches have the ability to discriminate the complexity of heart beat interval series from different states of the shooters, provided that the parameters required by the algorithms are chosen within a proper range, it still seems that sample entropy method is more appropriate in quantifying the short-term heart rate variability signals for shooting athletes, especially when the time series are only several hundred points long.
Adaptive projective synchronization and parameter identification of a class of delayed chaotic neural networks
Authors: Wang Xing-Yuan  , Zhao Qun  ,   大连理工大学电子与信息工程学院，大连  116024
Published: December 2020

This paper deals with the adaptive projective synchronization problem of a class of delayed neural networks. Based on Lyapunov stability theory, a new control method is proposed to achieve parameter identification and projective synchronization simultaneously. Numerical simulations were conducted to verify the effectiveness of this method.
Control of spiral wave and turbulence in the time-varied reaction-diffusion system
Authors: Ma Jun  , Jin Wu-Yin  , Yi Ming  , Li Yan-Long  ,   (1)华中师范大学物理系，武汉  430079; (2)兰州理工大学机电学院，兰州  730050; (3)兰州理工大学物理系，兰州  730050
Published: December 2020

We investigated the external electric field-induced transition of the spiral wave and turbulence in a class of time-varied reaction-diffusion systems. In our numerical simulation, a modified Fitzhugh-Nagumo model, which was used to describe the excitable and/or oscillatory media under appropriate parameters, was investigated. The effect induced by the random and/or other uncertain factors (for example, external and interior noise, gas pressure, temperature gradient and deformation of media etc.) was considered. The amplitude of the fluctuations of parameters was selected at appropriate values so that stable rotating spiral wave, meandering spiral wave and turbulence could be observed respectively. The external electric field was introduced into the media after a transient period allowing for parameter fluctuations. It was found that only the breakup of spiral wave was observed and the whole media could not reach homogeneous state when weak electric field and parameter fluctuation were used. It was confirmed that the breakup of spiral wave happens and then the whole media becomes stably homogeneous when appropriately strong intensity of external electric field is applied to the whole media together with the action of parameter fluctuation. The snapshots of the activator are used to investigate the transition of the patterns in the presence of external electric field and under parameter fluctuation, and relevant theoretical discussion is given in the precent paper.
Reducing frequency phenomenon in Buck converters with one cycle control
Authors: Wang Fa-Qiang  , Zhang Hao  , Ma Xi-Kui  ,   西安交通大学电气工程学院电力设备电气绝缘国家重点实验室，西安  710049
Published: December 2020

This paper deals with the reducing frequency phenomenon in Buck converters with one cycle control. The critical conditions of its occurrance and operation modes are derived. The results show that the reducing frequency phenomenon occurs because the output voltage of the integrator does not rise to the reference voltage Vref within n clock periods so that the integrator can not be reset in n clock periods but must be reset in the (n+1)th clock period. Furthermore, the converters are stable both in CCM and DCM when the reducing frequency phenomenon occurs. Meanwhile, the ratio of the intervals with the reference voltage Vref between CCM and DCM is held constant. In addition, the ripple of the output voltage is increasing with the decrease of the circuit operating frequency. Finally, these theoretical results are verified by the numerical simulation and circuit experiment.
Coherence resonance in neural networks with small-world connections
Authors: Zhou Xiao-Rong  , Luo Xiao-Shu  ,   广西师范大学物理与电子工程学院，桂林  541004
Published: December 2020

The nonlinear response of small-world biological nerve network in the Hodgkin-Huxley model in the absence of external periodic signal is studied. Simulation results show the ordered degree of spike sequence may reach a maximum when the strength of noise is a certain limited value. Namely, coherence resonance phenomenon is produced in small-world biology nerve network. The number of minima of coherence resonance coefficient cv is more than one. This indicates that coherence resonance may occur in different scales of networks.
Study of modular transfer function-based optieal low-pass filter evaluation model and experiment
Authors: Qi Xun-Jun  , Lin Bin  , Cao Xiang-Qun  , Chen Yu-Qing  ,   (1)浙江大学现代光学仪器国家重点实验室，国家光学仪器工程技术研究中心，杭州  310027; (2)浙江大学现代光学仪器国家重点实验室，国家光学仪器工程技术研究中心，杭州  310027；安徽师范大学物理与电子信息学院，芜湖  241000
Published: December 2020

To evaluate the performance of optical low pass filter (OLPF) accurately, a new 2D digital imaging system model including an OLPF was created for the first time using the modular transfer function (MTF). An evaluation function was also established based on this model. To manifest the model and its evaluation, three typical OLPFs were studied. The results show that the Δ value of each filter undergoes a slow and slight decrease and then rapidly increases when the ideal optical system cutoff frequency is increased. The optieal system embedded with the 2-chip-4-point type OLPF created a better image than those with the other two OLPF's when the F number is greater than 44; whereas the OLPF of 3-chip-8-point type worked best when the F number is lower than 44 When the F number of the optical system is 28, namely, with a spatial cutoff frequency of 649 lp/mm, the filter of 3-chip-8-point type performs better than that of the 2-chip-4-point and 3-chip-4-point types. The Δ value of the first filter is 283% and 375%, lower than that of the other two filters, respeatively. That is, the filter performance is 283% and 375% higher. Finally, spatial frequency test shows that the moiré fringe and false colors can be seen in the last two pictures, while in the first, these effects are well eliminated. The theoretical calculations agree with the experimental results.
Gaussian pulse shaping of exponential decay signal based on wavelet analysis
Authors: Chen Shi-Guo  , Ji Shi-Yin  , Liu Wan-Song  ,   (1)贵州教育学院物理系，贵阳  550003; (2)贵州师范大学理学院,贵阳  550001
Published: December 2020

Gaussian pulse shaping of exponential decay signal based on wavelet analysis is reported. The peak height of Gaussian shaping signal represents the energy of radiation particle and the peak position represents the time of radiation event occurring, respectively. The experimental results with simulating and sampling signals show that the exponential decay signal has been shaped into Gaussian signal, which indicates that Gaussian pulse shaping based on wavelet analysis is valid. The result may serve as the theoretical basic for studying digital realization of Gaussian pulse shaping.
High-frequency analysis of scattering from coated targets with electrically large size in half space
Authors: Li Xiao-Feng  , Xie Yong-Jun  , Wang Peng  , Yang Rui  ,   西安电子科技大学天线与微波技术国家重点实验室,西安  710071
Published: December 2020

The high-frequency method for solving the scattering of electrically large coated targets in half space is presented in this paper. In order to consider the influence of environment, the half-space physico-optical integral equation is deduced by introducing the half-space Green's function into the physico-optical method. Combined with the graphical-electromagnetic computing method, the shadow regions are eliminated quickly and the geometry information is attained by reading the color and depth of each pixel. Meanwhile, we use the impedance boundary conditions to account for the target covered RAM in half space, and the radar cross section of coated targets can be exactly calculated in half space. The numerical results show that this method is efficient and accurate.
A direct discrete-finite-difference time-domain implementation of electromagnetic scattering by magnetized ferrite medium
Authors: Yang Li-Xia  , Ge De-Biao  , Zhao Yue-Hua  , Wang Gang  , Yan Shu  ,   (1)江苏大学通信工程系，镇江  212013; (2)西安电子科技大学物理系，西安  710071
Published: December 2020

Based on the constitutive relation between the magnetic permeability and magnetic flux density, the constitutive relation of magnetized ferrite medium in frequency domain is transformed to the time domain by using the corresponding relation between the time-differential operator /t and jω. And the constitutive relation including the time-differential operator /t in time domain is presented. By the introduction of a direct-discrete method, the time-differential operator /t is dispersed. Then direct discrete-finite-difference time-domain(DD-FDTD) iterative formula are derived in the discrete time domain. To exemplify the availability of the algorithm, the backscattering radar scattering section of a magnetized ferrite sphere is computed, and the numerical results are the same as the reference values, and show that the DD-FDTD method is correct and efficient.
Dependence of spectral width of TM-polarization lasing modes on pumping intensity in two-dimensional random media
Authors: Wang Ke-Jia  , Zhang Qing-Quan  , Lü Jian-Tao  , Du Ze-Ming  , Liu Jin-Song  ,   华中科技大学，武汉光电国家实验室，光电子科学与工程学院，武汉  430074
Published: December 2020

The spectral width of transverse magnetic (TM) lasing modes in two-dimensional random media is theoretically investigated by using the time-dependent theory. The evolution curve of the spectral width of TM-polarization modes versus the pump intensity is obtained from which one can calculate some characteristic parameters of the emission, e.g. the threshold. The results show that, from the view of spectral width, the emission of the TM-polarization lasing modes have better out-put property than that obtained previously with TE-polarization.
Influence of dopants on nonvolatile holographic storage in lithium niobate
Authors: Fu Bo  , Zhang Guo-Quan  , Liu Xiang-Ming  , Shen Yan  , Xu Qing-Jun  , Kong Yong-Fa  , Chen Shao-Lin  , Xu Jing-Jun  ,   (1)南开大学弱光非线性光子学教育部重点实验室，天津  300457; (2)南开大学弱光非线性光子学教育部重点实验室，天津  300457；南开大学物理科学学院光子学中心，天津  300071; (3)南开大学弱光非线性光子学教育部重点实验室，天津  300457；中国工程物理研究院流体物理研究所，绵阳  621900; (4)枣庄学院物理系，枣庄  277160
Published: December 2020

By studying the ultraviolet-red two-color holographic storage performances of Mg-, Zn- and In-doped lithium niobate crystals, we found that the response time of the two-color recording could be shortened by as much as 3 orders of magnitude compared to that of one-color recording, and the two-color recording sensitivity was improved significantly, which was measured to be 11 cm/J in the crystal doped with Mg of 5 mol.%. Nonvolatile holographic storage was achieved in the crystals with doping concentrations above the damage-resistant threshold value. However, gratings on the deep centers and the shallow centers were out of phase in Mg- or Zn-doped lithium niobate, while those in In-doped lithium niobate were in phase. We consider that different defects induced by different dopants are responsible for the observed results.
Modulation of the azimuth of polarization of reconstruction beam on the diffraction efficiency of anisotropic gratings recorded in bacteriorhodopsin films by two parallel linearly polarized beams
Authors: Gao Peng  , Yao Bao-Li  , Han Jun-He  , Chen Li-Ju  , Wang Ying-Li  , Lei Ming  ,   (1)中国科学院西安光学精密机械研究所瞬态光学和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和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

When the linearly polarized object and reference beams with the same polarization direction are used for recording gratings in bacteriorhodopsin films, the azimuth of polarization of the reconstruction beam has an influence on the diffraction efficiency. By using Jones matrices to analyze this phenomenon, we find that the azimuth of polarization of the reconstruction beam makes a cosine modulation on the diffraction efficiency. The diffracted beam is linearly polarized only when the polarization of the reconstruction beam is parallel or perpendicular to that of the recording beams; otherwise, the diffracted beam becomes elliptically polarized. The azimuth of polarization of the reconstruction beam produces a positive cosine modulation on the peak diffraction efficiency, but a negative cosine modulation on the steady diffraction efficiency (with phase difference π). By adding auxiliary violet light during grating formation, the saturation of the grating can be restrained; as a result, the negative cosine modulation of the steady diffraction efficiency changes to the positive cosine modulation and also the steady diffraction efficiency is increased apparently.
The influence of injection current on transverse mode characteristics of vertical-cavity surface-emitting lasers
Authors: Yang Hao  , Guo Xia  , Guan Bao-Lu  , Wang Tong-Xi  , Shen Guang-Di  ,   北京工业大学北京市光电子技术实验室，北京  100022
Published: December 2020

The influence of transverse mode were researched with the injection current changing via experiments conducted with 980nm oxide-confined vertical cavity surface emitting lasers (VCSELs). Based on the spatio-temporal rate equation, the injection parameter dependence of the transverse mode characteristics of weak-index guiding VCSELs were theoretically researched by integrating the spatially dependent part. The result of the experiment indicated that the higher-order modes begin to emerge and exhibit strong competition with the injection current increased when the oxidized aperture was kept unchanged, and the distribution of the carrier transfers from the center to the edge. Furthermore, the main order becomes weaker because of the spatial hole burning. Compared with the appearance of higher-order modes with different oxidized aperture, the small injection aperture exhibits better single mode behavior.
Low temperature emission characteristics of an ytterbium sensitized erbium-doped tellurite glass
Authors: Li Xu-Jie  , Nie Qiu-Hua  , Dai Shi-Xun  , Xu Tie-Feng  , Shen Xiang  , Zhang Xiang-Hua  ,   (1)法国雷恩第一大学玻璃与陶瓷实验室,法国 雷恩  35042; (2)宁波大学信息科学与工程学院,宁波市新型功能材料及其制备科学实验室——省部共建国家重点实验室培育基地,宁波  315211
Published: December 2020

The 15 μm emission spectrum corresponding to the 4I13/2→4I15/2 transition and upconversion of Er3+ in tellurite glass in the temperature range from 8 to 300K is studied. The emission spectrum of Er3+: 4I13/2→4I15/2 transition is also analyzed using a peak-fit routine, and an equivalent four-level system is proposed to estimate the Stark splitting for the 4I15/2 and 4I13/2 levels of Er3+ in the tellurite glass. The results indicate that the 4I13/2→4I15/2 emission of Er3+ has considerable broadening due to a significant enhancement of the a' and b' emission peaks. Temperature-dependent FWHM are investigated, the results show that a monotonic increase of FWHM is observed for temperatures from 8 to 300K. Intense upconversion emission signals around 529, 545 and 669nm corresponding to the 2H11/2, 4S3/2, and 4F9/2 transitions, respectively, to the 4I15/2 ground state are generated and are measured as functions of temperature in the 8 to 300K range. The most remarkable result is observed in the green upconversion signal around 546 and 669nm which presented a maximum intensity enhancement of 2198 and 1556 times around 80K compared with that around 300K. Monotonic decrease is observed at temperatures above 80K. In the same temperature range the signal at 529nm diminishes to zero with lowering temperature.
Study on the focus performance of micro-focus Fresnel zone plate
Authors: Dong Jian-Jun  , Cao Lei-Feng  , Chen Ming  , Xie Chang-Qing  , Du Hua-Bing  ,   (1)中国工程物理研究院激光聚变研究中心，绵阳  621900; (2)中国科学院微电子研究所，北京  100029
Published: December 2020

The performance of micro-focus Fresnel zone plate(MFZP) with the outermost width of 150nm is tested using the Ti spectral line. Experimental data indicates that the image of pinhole with diameter of 125μm fully responses to a pixel of the X-ray CCD camera. Furthermore，the X-ray focal spot is tested with a magnification of 66 by using laser striking the Ti planar target. The MFZP's point spread function is simulated with the integral formula of Fresnel-Kirchhoff diffraction. The simulated results indicate that the MFZP strongly focuses at double foci. The same results are obtained when the object distance and image distance change but keeping the relation of the lens unchanged. The simulation and the experiment indicate that MFZP can be applied to point-to-point imaging of X-ray to realize high spatial resolution imaging for the laser plasmas.
Conductance enhancement phenomenon of graphene ribbons on highly oriented pyrolytic graphite surfaces studied by scanning probe microscopy
Authors: Wang Qi  , Zhao Hua-Bo  , Zhang Zhao-Hui  ,   北京大学物理学院，人工微结构与介观物理国家重点实验室，北京  100871
Published: December 2020

Based on comparative observations with the conducting atomic force microscope and the scanning tunneling microscope，conductance enhancement phenomenon of graphene ribbons on highly oriented pyrolytic graphite surfaces has been studied. According to measured data of local resistance on the samples，the phenomenon is attributed to the state of point contact of the conducting tip on the sample surface. It was demonstrated that the conductance of the point contact is proportional to the local density of electrons in the contacting surface area，so we conclude that the conductance enhancement phenomenon results from the high density of electrons on the graphene ribbons.