bluuebunny/crossref_metadata_2025 huggingface dataset:
Dispersion management optimization of multi-wavelength all-optical regeneration based on self-phase modulation
Authors: Zhang Jing  , Pan Wei  , Yan Lian-Shan  , Luo Bin  ,   Center for Information Photonics & Communications, Southwest Jiaotong University, Chengdu 610031, China
Published: December 2020

In connection with the multi-wavelength all-optical regeneration system based on self-phase modulation in fibers, the effect of the average fiber dispersion for the quality factor Q improvement of regenerator is analyzed and a dispersion management optimization method is proposed. The stability of performance of the regenerator will degrade because of dispersion discrepancy between different wavelengths. By choosing the fiber length of dispersion compensating fiber and single mode fiber to make the dispersion curve of combination of two kinds of fiber approximately fitting with the dispersion curve corresponding to the best performance of each wavelength respectively, and keeping the compound dispersion curve in the better dispersion region, the stability of performance of the regenerator is effectively improved if the input signal power and offset of the filter are properly adjusted. The optimization of multi-wavelength dispersion management can be realized.
Ne-like Ti X-ray laser driven by a single femtosecond laser
Authors: Zheng Bing-Song  , Sun Yan-Qian  , Chen Yu  , Ma Jing-Long  , Li Ying-Jun  ,   Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100190, China;,   State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083, China;,   State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083, China, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 1
Published: December 2020

A physical scheme is presented for Ne-like Ti x-ray laser driven by a single laser pulse. According to the self-similarity method, we analyze the properties of Ne-like Ti slab plasma generated by irradiation of femtosecond laser with various front edges. Scaling laws for the temperature, scale length, and electron density are obtained. The characteristics of scaling laws for different input parameters are analyzed. Our results show that x-ray laser can be generated by a single femtosecond laser. The femtosecond laser with a gentle front edge is profitable to drive x-ray laser. Our results provide a new schemc for experiments using a single laser pulse to drive the x-ray laser.
Bandwidth in qusai-phase-matched frequency doubling
Authors: Ren Ai-Hong  , Liu Zheng-Ying  , Zhang Rong-Zhu  , Liu Jing-Lun  , Sun Nian-Chun  ,   Research Center of Photoelectron, Sichuan University, Chengdu 610064, China
Published: December 2020

Based on the theory of quasi-phase-matched frequency doubling, the condition to generate the broadband second-harmonic is investigated. We analyze the conversion performances of the high efficiency broadband second-harmonic for type-0 (e+e→e) and type-Ⅰ(o+o→e) quasi-phase-matchad cases in periodically poled LiNbO3 crystal and 7mol% periodically poled MgO:LiNbO3 crystal. The results show that the central wavelengths of the fundamental wave and the bandwidth shift toward short waves in periodically poled MgO:LiNbO3 crystal, and the wider bandwidth is obtained in the type-0 quasi-phase-matched case.
Polarization-independent self-collimation bends and beam splitters in 32,4,3,4 Archimedean photonic crystals
Authors: Zhong Qi  , Han Kui  , Shen Xiao-Peng  , Tong Xing  , Wu Qiong-Hua  , Li Ming-Xue  , Wu Yu-Xi  ,   College of Science, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

By using equi-frequency contour analysis and finite-difference time-domain simulation, self-collimation for TE- and TM-polarizations are achieved at the same frequency in two dimensional 32,4,3,4 Archimedean photonic crystals. The bends and beam splitters are realized by truncating an air block in the photonic crystals. It is observed that the line defect can produce a tunable one-to-two beam splitter by controlling the width of the air block. A bend and a 1 ∶1 beam splitter for the TE- and TM- polarization are designed respectively, both have high efficiency. This study proposes a new design method for optical devices based on photonic crystals.
Approaching 100 nJ pulse energy output from a mode-locked photonic crystal fiber laser
Authors: Song You-Jian  , Hu Ming-Lie  , Xie Chen  , Chai Lu  , Wang Qing-Yue  ,   Key Laboratory of Opto-electronic Information Science and Technology of Ministry of Education, College of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

Pulse energy directly output from a mode-locked fiber laser approaching one hundred nanojoule is demonstrated. The fiber laser is based on a σ-shaped cavity design. A segment of single polarization Yb-doped large mode area photonic crystal fiber acts as gain medium. A semiconductor saturable absorber mirror is used for self-starting mode-locking operation. The fiber laser works in an all normal dispersion mode-locking regime with no intracavity dispersion compensation introduced in the laser. A long multi-pass cavity is used to reduce the repetition rate of the fiber laser. Direct output pulse energy of 97 nJ with an average power of 1.08 W is achieved at a low repetition rate of 11.1 MHz. The pulse duration is 4.17 ps,which can be extracavity dechirped to 740 fs.
Two-dimensional numerical simulation of laser-ablation of aluminum material by nanosecond laser pulse
Authors: Wen Bin  , Zhao Ji-Jun  , Zhang Peng-Bo  , Qin Ying  ,   Laboratory of Materials Modification by Laser, Electron, and Ion Beams and College of Advanced Science and Technology, Dalian University of Technology, Dalian 116024, China;,   Laboratory of Materials Modification by Laser, Electron, and Ion Beams and College of Advanced Science and Technology, Dalian University of Technology, Dalian 116024, China, School of Materials Science and Engineering, Dalian University of Technology, Dal;,   School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China
Published: December 2020

To investigate the interaction between high-power pulsed laser and metal materials,we established a two-dimensional numerical model. The laser-induced two-dimensional temperature distribution was simulated using a finite difference method. From comparison of temperature evolution under different pulse time,spot sizes and energies,it can be seen that the rise of temperature in the initial period is faster than that in the later periods. Isothermal diagram shows that the temperature rising rate is fastest in the center of laser irradiating zone and that the ablation depth is in the range of 1—5 μm. As the laser pulse duration becomes longer,the ablation zone becomes narrower and deeper. As the laser spot diameter increases,the ablation zone becomes wider and shallower. The present numerical results indicate that: (1) the ablation shape and depth sensitively depend on the laser shape,pulse duration and power density, (2) with laser power density in the order of 109 W/cm2,the ablation area is roughly of the orgc of the laser spot. These results are helpful for designing relevant laser parameters in experiments.
Electrical conduction mechanism in polar molecule dominated electrorheological fluid
Authors: Cui Ping  , Lu Yang  , Ji Ai-Ling  , Sun Gang  , Lu Kun-Quan  , Wang Xue-Zhao  , Shen Rong  ,   (1)Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (2)Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China; (3)Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
Published: December 2020

Polar molecule dominated electrorheological (ER) fluid is a new type of ER material with high shear stress. The alignment of polar molecules adsorbed on the dielectric particles in the direction of the high local field between the particles plays a decisive role in such new ER fluids. In measuring the current density of ER fluid composed of Ca—Ti—O particles, it was found that the conductive behavior of the fluid exhibits Poole-Frenkel character, which is one of the particular features for polar molecule dominated electrorheological fluids. By heating the Ca—Ti—O particles at 500 ℃ to remove the polar molecules adsorbed on the particles, however, the current density of ER fluid fabricated with pure Ca—Ti—O particles has linear dependence on the electric field approximately, same as in the traditional ER fluids.
The theory of nonlinear interfacial-internal wave propagation in three-layer fluid systems
Authors: Wen Wen-Ying  , Chen Xiao-Gang  , Song Jin-Bao  ,   (1)College of Science, Inner Mongolia University of Technology, Hohhot 010051, China; (2)Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
Published: December 2020

Based on the small steepness parameter assumption, the three-layer incompressible, inviscid and irrotational fluid system of arbitrary depth is discussed by using the perturbation method, and a unified theory of nonlinear interfacial-internal wave propagation and the approximate nonlinear evolution equations (NEEs) for interfacial-internal elevations are given on the basis of the rigid upper boundary and the flat impermeable bottom. At last we also discuss on NEEs arising from various limiting cases of fluid depth. It is also noted that the theories obtained from the present work include the theoretical results derived by Yoshimasa Matsuno (1993) as special cases.
Growth and structure characterization of Cr4+ doped Ca2GeO4 laser crystal
Authors: Zhang Shan-Li  , Zeng Fan-Ming  , Wang Xin-Tong  , Li Chun  , Wang Cheng-Wei  , Zhang Ying  , Lin Hai  , Qin Jie-Ming  , Liu Jing-He  ,   Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

A new kind of Cr4+ :Ca2GeO4 infrared tunable laser crystals were synthesized by flux growth method with CaCl2 as solvent. The structure of Cr4+ :Ca2GeO4 was characterized by x ray diffraction, Raman spectroscopy (RS) and x ray photoelectron spectroscopy(XPS). The results showed that the obtained crystal was γ-Cr4+ :Ca2GeO4 single crystal with monoclinic structure belonging to olivine structure, and the lattice parameters are: a=5.3209 (1 =0.1 nm), b=6.6648 , c=11.2606 . The result that (GeO4)4- exists in the crystal was verified by RS measurement and its vibration was determined. We can see from the XPS measurement that Cr in the crystal is in the form of Cr4+ and no other valence states exist.
Synthesis and characterization of Sb2Te3 nanostructures
Authors: Zhu Hang-Tian  , Liu Quan-Lin  , Liang Jing-Kui  , Rao Guang-Hui  , Zhang Fan  , Luo Jun  ,   (1)Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (2)Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China; (3)School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
Published: December 2020

Single-crystalline Sb2Te3 nanostructures, of which the bulk is one of the best thermoelectric materials at room temperature, are synthesized by chemical vapor deposition. The composition, crystal structure, and growth mechanism of the sample are investigated. According to our experimental results, Sb2Te3 normally grows into hexagonal nanoplates without using catalyst, but single-crystalline nanowires can be fabricated with Au nanoparticles as the catalyst. The growth mechanism of Sb2Te3 nanostructures is closely related to its anisotropic crystal structure. Sb2Te3 has a rhombohedral structure, which exhibits a layered anisotropy with the Te and Sb atom layers arranged along the c-axis. Moreover, there are two adjacent Te layers connected by van der Waals bonds. Therefore, Sb2Te3 prefers to grow into hexagonal plates in the ab-plane. When Au nanoparticles are used as the catalyst, the growth direction of the precipitated Sb2Te3 is restricted, leading to the formation of Sb2Te3 nanowires.
Training effect in the ferromagnetic/antiferromagnetic bilayers
Authors: Xu Mian  , Pan Jing  , Shen Ying  , Hu Jing-Guo  ,   Department of Physics, Yangzhou University, Yangzhou 225002, China
Published: December 2020

Using Monte Carlo method to study the magnetic training effect in the ferromagnetic/antiferromagnetic bilayers, it was shown that the magnetic relaxation of the net magnetization induced by cold magnetic field which exists in the interface between ferromagnetic and antiferromagnetic bilayer can result in the training effect in the exchange bias and coercivity of the system. Further studies have shown that the doping in antiferromagnetic layer can modulate the training effect in the exchange bias, because the doping in antiferromagnetic layer can effectively change the magnetic relaxation process of the net magnetization induced by the cold field.
Physical origin of transient Kerr peak induced by circularly polarized laser in ferromagnetic films
Authors: Chen Da-Xin  , Chen Zhi-Feng  , Xu Chu-Dong  , Lai Tian-Shu  ,   State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
Published: December 2020

The magnetization dynamics of in-plane anisotropic FePt and perpendicularly anisotropic GdFeCo films induced by circularly polarized laser excitation is investigated using femtosecond time-resolved pump-probe Kerr spectroscopy. It is found that a transient Kerr peak occurs near zero-time delay, respectively for each sample. The origin of the peaks is analyzed. It is pointed out that the transient Kerr peaks are not related to ferromagnetism and may originate from paramagnetic magnetization of free electrons in the samples, while the magnetic field that magnetizes the free electrons comes from inverse Faraday effect of the circularly polarized pump laser. The calculation results based on the paramagnetic magnetization model support such a viewpoint. Based on our points, the duration of magnetic pulses induced by inverse Faraday effect should be the same as that of the pump laser pulses.
Spatial configurations and X-ray absorption of Ti catalyzing on NaAlH4 surfaces: Car-Parrinello molecular dynamics and density functional theory study
Authors: Gao Tao  , Zhou Jing-Jing  , Chen Yun-Gui  , Wu Chao-Ling  , Xiao Yan  ,   (1)Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China; (2)School of Materials Science and Engineering, Sichuan University, Chengdu 610065, China
Published: December 2020

A theoretical study on the spatial configurations of the catalytic dehydrogenation of the pre- and post- Ti-doped NaAlH4(001)2×2×1 supercell surface crystals was performed by using the Car-Parrinello molecular dynamics (CPMD) method at 333 K (60 ℃). It was be found that two of the Al—H bond lengths increased from approximately 1.64 to 1.74 and 1.93  respectively in the AlH4 groups of the Ti-doped alloy. Compared with this change, the four Al—H bond lengths almost kept invariant in the AlH4 group of un-doped alloy, which means that it was easier to dehydrogenate for the Ti-doped alloy than un-doped alloy. There was no bonding tendency between atom Ti and Al observed, which is probably because the temperature in the simulation process is not high enough. Based on the obtained surface crystal configuration, the Ti K-edge x ray absorption near-edge structure (XANES) spectra of the TiAl3, TiH2 crystals and Na8Ti8Al16H64(001) surface crystal have been calculated by using the full-potential linearized augmented plane wave method (FPLAPW). It was also found that the atom Ti may not only exist in the mixture of TiAl3 and TiH2 but also probably partially substitute for the Na atoms in NaAlH4 surface crystal, by comparing the experimental XANES and edge x ray absorption fine structure (EXAFS) spectra.
New GMF+RAIN model based on rain rate and application in typhoon wind retrieval
Authors: Zhang Liang  , Huang Si-Xun  , Zhong Jian  , Du Hua-Dong  ,   Institute of Meteorology, University of Science and Technology of People's Liberation Army, Nanjing 211101, China
Published: December 2020

This paper firstly selects three typhoon cases (SHANSHAN, YAGI, XANGSANE) which occurred in 2006, and analyzes the distribution characteristic of the normalized radar cross-section (NRCS, σo), which were received by QuikSCAT scatterometer in the case of rain effect. Secondly, in order to account for the effects of rain to σo, we follow the theory of atmospheric radiation transfer and introduce two different types of rain radiation transfer models (called SY model and AMSR model, respectively), then combine these two models with NSCAT2 GMF to produce an improved GMF suitable for the case of rain effect (called GMF+RAIN). Lastly, based on this GMF+RAIN, we use the ambiguity removal method which integrates 2DVAR (two-dimensional variational assimilation) with MSS (multiple solution scheme) to retrieve the YAGI and XANGSANE typhoon wind fields which had different intensity. The new approach which combines GMF+RAIN with 2DVAR+MSS improves the result, which further verifies the effectiveness of GMF+RAIN. This new approach also makes the scatterometer data more effective and valuable for application in the research of typhoon.
Long-range correlation and group-occurrence of return intervals of extreme events
Authors: Wang Qi-Guang  , Hou Wei  , Zheng Zhi-Hai  , Feng Ai-Xia  , Deng Bei-Sheng  ,   College of Atmospheric Scicences, Lanzhou University, Lanzhou 730000, China;,   College of Atmospheric Scicences, Lanzhou University, Lanzhou 730000, China, Key Laboratory of Regional Climate-Environment Research for Temperate East Asia of theInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China, Labora;,   Key Laboratory of Regional Climate-Environment Research for Temperate East Asia of theInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China, Laboratory for Climate Studies, National Climate Center, China Meteorological Admin
Published: December 2020

This paper studies the long range correlation of the return intervals of extreme events using the method of percent threshold. In view of return intervals of the extreme events, the long range-correlations of return intervals are studied by simulated time series when the extreme events happened. It is found that the constructed extreme event time series also have the characteristics of long-range correlation if the original time series have one. Meanwhile, the scaling exponents of the two time series are very close, it is very different from the return intervals of stochastic series. The probability density function of time series with long-range correlation has significant difference from the stochastic time series. It was found that there is a group-occurrence phenomenon in the return time series with long-range correlation, so a so-called group occurrence index is defined and computed, the stability of the index is also studied. The results show that the reason of the group occurrence of extreme events series is attributed to the long-range correlation of time series.
Optical variability periodicity analysis of BL Lac object S5 0716+714 based on bispectrum estimation
Authors: Tang Jie  , Zhang Xiong  ,   (1)Department of Physics, Shaanxi University of Technology, Hanzhong 723001, China; (2)Department of Physics, Yunnan Normal University, Kunming 650092, China
Published: December 2020

Large and rapid variability is one of the defining properties of BL Lac objects. Variability in BL Lac objects has always served as a powerful and important tool for inquring into the physics of these unusual objects. From an extensive seach in the literature we have collected a total of data points of effective observations of BL Lac object S5 0716+714 in V, R and I bands from 1994 to 2008. Then these data are processed on 30 days baseline by autoregressive bispectrum model. In order to eliminate noise interference to extract useful information in the background of Gaussian noise, we propose a method of signal analysis and processing,which analyzes the additive Gaussion noise signal based on autoregressive bispectrum model. Bispectrum is not sensitive to Gaussian noise, it not only suppresses the Gaussion noise in the signal and greatly improves the signal to noise ratio, but also can identify the periodical variations of BL Lac objects. Our results show that the long term periods of variation are 3.33 years and 3.47 years. The conclusion is consistent with 3.3 years period which was found by Raiteri et al. The brightness peak was observed in 2007, so we expect the next burst in 2011—2012.
Infrared absorption of liquid-hydrogen planar cryotargets
Authors: Bi Peng  , Liu Yuan-Qiong  , Tang Yong-Jian  , Yang Xiang-Dong  , Lei Hai-Le  ,   (1)Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China; (2)Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China;Research Centre of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China; (3)Research Centre of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Using a home-made cryotarget system and infrared spectroscopy system, we measure the infrared absorption spectra of liquid hydrogen at low temperaturs. It is found that the fundamental vibration frequency of hydrogen molecule is 4237.3 cm-1. As liquid hydrogen cools from 19.75 K down to 16.75 K, the infrared absorption is enhanced. The vibration frequency of hydrogen molecules is calculated on the basis of non-harmonic approximation in order to explain the experimental ones.
Multi-soliton solutions and fractal structures in a (2+1)-dimensional soliton system
Authors: Zhou Zhen-Chun  , Ma Song-Hua  , Fang Jian-Ping  , Ren Qing-Bao  ,   Department of Physics, Lishui University, Lishui 323000, China
Published: December 2020

By the projective equation approach and the variable separation method, a series of excitations of the (2+1)-dimensional asymmetric Nizhnik-Novikov-Veselov system is derived. Based on the derived solitary wave excitation, we obtain multi solitons and fractal solitons of the system.
A new boundary treatment algorithm for dissipative particle dynamics
Authors: Chang Jian-Zhong  , Liu Mou-Bin  ,   (1)Key Laboratory for Hydrodynamics and Ocean Engineering, of Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China;The State Key Laboratory for Nonlinear Mechanics, of Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190,; (2)School of Mechatronic Engineering, North University of China, Taiyuan 030051, China
Published: December 2020

Dissipative particle dynamics (DPD) is a meso-scale, Lagrangian particle method, and has been successfully applied to different areas including micro- and nano-fluidics, bio- and chemical technologies. The treatment of solid matrix and the implementation of solid boundary conditions have been an important task for the development and application of the DPD method. This paper presents a new method of treating complex solid boundary. Solid grains in complex flow geometry can be represented by freezing randomly distributed DPD particles which have reached an equilibrium state. To increase computational efficiency, only the boundary DPD particles within one cut-off distance from the flow region are frozen. A thin layer in the flow region next to the solid boundary is used to bounce mobile DPD particles in this layer back to the flow region. The DPD method and this new boundary treatment algorithm are used to model the Poiseuille flow and a flow problem in a complex porous media. It is demonstrated that this new boundary treatment algorithm can effectively model complex solid matrix and correctly implement non-slip boundary condition.
Single soliton of double kinks of the mKdV equation and its stability
Authors: Shi Yu-Ren  , Zhang Juan  , Yang Hong-Juan  , Duan Wen-Shan  ,   College of Physics and Electronic Engineering,Northwest Normal University,Lanzhou 730070,China
Published: December 2020

Based on the idea of the hyperbola function expansion method, some analytical solutions of the modified Korteweg-de Vries (mKdV) equation are obtained by introducing new expansion functions. One of the single soliton solutions has a kink-antikink structure and it reduces to a kink-like solution and bell-like solution under different limitations. The stability of the single soliton solution with double kinks is investigated numerically. The results indicate that the soliton is stable under different disturbances.
The bound energy spectrum of position-dependent mass particle in the null potential
Authors: Dai Man-Yuan  , Nie Yi-You  , Sang Ming-Huang  , Wang Xian-Ping  , Yin Cheng  , Cao Zhuang-Qi  ,   (1)Department of Physics, Jiangxi Normal University, Nanchang 330022, China; (2)Department of Physics, Shanghai JiaoTong University, Shanghai 200240, China
Published: December 2020

The bound energy spectrum of a position-dependent mass particle which is trapped in a null potential is obtained by combining the point canonical transformation (PCT) method and the analytical transfer matrix (ATM) method. With the calculation for the transmission of a position-dependent mass particle passing through the null potential, the one-to-one correspondence between transmission resonance peak and eigenenergy is found and explained.
Calculation of energy density fluctuations for Fermi matter on black hole background
Authors: Zou Bo-Xia  , Yan Jun  , Li Ji-Gen  ,   Department of Physics, Sichuan Normal University, Chengdu 610066, China
Published: December 2020

In this paper, the propagator and the effective potential in quantum Thirring model are derived by using the functional integral method, and the energy density fluctuations for coupled Fermi matter are calculated in two-dimensional point matter black hole and dilaton black hole models separately. We find that energy density fluctuation outside dilaton black hole is stronger under the same physical conditions.
Lévy flights in a steep potential well displaying non-Gibbs-Boltzmann statistics
Authors: Shangguan Dan-Hua  , Lü Yan  , Bao Jing-Dong  ,   (1)Department of Physics, Beijing Normal University, Beijing 100875, China; (2)Department of Physics, Beijing Normal University, Beijing 100875, China;Institute of Applied Physics and Computational Mathematics,  Beijing 100094,  China
Published: December 2020

We study analytically and numerically the probability density function in the stationary state of non-linear oscillators which are subjected to Lévy white noise and confined by a steep symmetric potential. The probability density function transforms from unimodality to bimodality or from bimodality to trimodality when the potential transforms from single well to double well; especially, the probability density function shows a peak at the saddle point of the potential. This result is far from the Gibbs-Boltzmann statistics.
Synchronization of chaos for two-dimensional time-delayed chaotic systems with different structures
Authors: Sang Jin-Yu  , Wang Jiao  , Yue Li-Juan  ,   College of Physics, Northeast Normal University, Changchun 130024, China
Published: December 2020

Generalized synchronization of chaos is studied for two-dimensional time-delayed chaotic systems with different structurs. The auxiliary system method and the stability theory of functional differential equations are used. Compared with the conventional generalized synchronization approaches, the proposed method is convenient to realize generalized synchronization of chaos. Simulation results illustrate the validity of the method.
Anticipating projective response in coupled dynamical systems
Authors: Wang Jiao-Jiao  , Yan Hua  , Wei Ping  ,   School of Electronic Engineering, University of Electronic Science and Technology of China , Chengdu 611731, China
Published: December 2020

In this paper, we suggest an anticipating projective response scheme in coupled dynamical systems, from which a large class of different drive-response systems can be constructed by choosing different functions and changing the scaling factor. A specific case of the scheme, which is named the accelerative anticipating projective response scheme, is studied in detail. In this specific scheme, the amplitudes of the drive and response systems synchronize up to a scaling factor and the response system evolves with a faster speed. Further, the robustness of this scheme is proved under the existence of the small disturbance of the driving term, interference of the driving signal and parameter mismatches.
Modification of projective synchronization for a class of fractional order chaotic system by using a single driving variable
Authors: Li Jian-Fen  , Li Nong  , Chen Chang-Xing  ,   (1)Institute of Engineering, Air Force Engineering University, Xi'an 710038, China; (2)Institute of Sciences, Air Force Engineering University, Xi' an 710051, China
Published: December 2020

Designing a suitable response system to a class of fractional order chaotic systems, we can realize the modification of projective synchronization for these systems by only transmitting a single variable. Since chaos synchronization can be achieved by transmitting the single variable from driving system to response system, this method is more practical. Numerical simulation of fractional order unified chaotic system demonstrates the effectiveness of the proposed method.
Dislocated projective synchronization of Qi hyper-chaotic system and its application to secure communication
Authors: Min Fu-Hong  , Wang En-Rong  ,   School of Electronic Engineering and Automation, Nanjing Normal University, Nanjing 210042, China
Published: December 2020

This paper focuses on a new type of dislocated projective synchronization, in which, the state variables of drive system and resporse system, at least one pair is required not to synchronize in proportion to the original corresponding state variable, but to realige the projective synchronization in proportion to dislocation relation of vectors. Here a new Qi hyper-chaotic system is taken for example, which has 23 synchronized schemes. Using the Lyapunov stability theory, a nonlinear controller is presented and a kind of disorder projective synchronization for Qi system is successfully completed. Then this method is applied to secure communication through improved chaotic masking. The information signal is mixed with the chaotic signal before being transmitted, and is recovered without distortion through the synchronized receiver. Simulation results show that the scheme has a good performance.
Order patterns of spatiotemporal chaos
Authors: Guo Jing  , Wang Yue  , Shan Xiu-Ming  , Ren Yong  ,   Department of Electric Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

Based on piecewise monotone interval maps and linear coupling, we study order patterns of spatiotemporal chaos. The forbidden patterns are found to arise mainly from the reduction of curve intersections due to time invariance of chaotic maps. It is proved that linear couplings may destroy the time invariance, and create the conditions for increasing intersections. We analyze the effects of chaotic map, coupling strength and coupling number order patterns. Simulation results and illustrative examples all confirm the correctness of the theoretical results.
Randomness analysis of external cavity semiconductor laser as entropy source
Authors: Zhang Ji-Bing  , Zhang Jian-Zhong  , Yang Yi-Biao  , Liang Jun-Sheng  , Wang Yun-Cai  ,   Department of Physics, College of Science, Taiyuan University of Technology, Taiyuan 030024, China
Published: December 2020

In this paper, we employ chaotic light as an entropy source, generated by semiconductor lasers with optical feedback induced by external cavity, to generate 500 Mbit/s random number sequence and then study specifically the influence of external cavity length on randomness. The results indicate that the generated random sequence has an weak periodicity caused by the external cavity feedback under a single-channel chaotic source, and can only pass two or three tests of the National Institure of Standards and Technology(NIST) when the external-cavity round trip delay time is an integral multiple of the sampling time. On the other hand, the weak periodicity can be eliminated by using two different chaotic sources when their external cavity lengths are unproportional to each other, and the obtained random sequence can pass all tests of the NIST after XOR processing.
Excitation of Si2O molecule under external electric field
Authors: Xu Guo-Liang  , Liu Xue-Feng  , Xia Yao-Zheng  , Zhang Xian-Zhou  , Liu Yu-Fang  ,   College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007, China
Published: December 2020

The present work is devoted to the study of the excitation of two kinds of Si2O isomers. The results show that the is excitation energies, oscillator strengths, transition electric dipole moments and absorption spectra are affected evidently by external electric field. The triangular Si2O(C2v,1A1) has no visible light absorption spectrum under no external electric field, however, it has faint absorption spectrum(407.18—526.93 nm) in the visible region under external electric field. The linear Si-Si-O(C∞v,3Σ-) has absorption spectra in blue light region and in purple light both in the presence and in the absence of external electric field. One of the important results is that the linear Si-Si-O has strong blue light absorption spectrum(478.88—488.59 nm).
γ-irradiation damage of quartz fiber and its effects on near-infrared transmission characteristics
Authors: Jiang Hui  , Chen Bao-Xue  , Fu Chang-Song  , Sui Guo-Rong  , Mamoru Iso  ,   (1)Department of Chemical Engineering, Tokyo University of Agriculture and Technology, Tokyo 184-8588, Japan; (2)Department of Optical-Electrical and Computer Engineering, University Of Shanghai for Science and Technology Shanghai 200093, China; (3)Department of Optical-Electrical and Computer Engineering, University Of Shanghai for Science and Technology Shanghai 200093, China;Shanghai Aerospace Control Technology Institute, Shanghai 200233, China
Published: December 2020

Around the near-infrared wavelength at which optical fiber gyroscope works, the effects of 120 krad γ-irradiation on single-mode quartz fiber are studied experimentally from the following several aspects: return loss, polarization dependent loss, scattering loss, absorption loss, mode field distribution and guided-mode propagation constants. The gap defect energy level and its increment are estimated from near-infrared spectroscopy and stimulated raman scattering experiment. The medium density change is studied by x-ray diffraction. The photothermal effect of irradiated fiber with γ-ray is observed by a high sensitivity interference circuit. The test data show that the UV anneal has some repairing effect, revealing the possibility that UV annealing method can serve as a mannes of active reinforcement.
Influence of quadratic phase existing in the initial condition on the dynamics of femtosecond laser pulse filamentation
Authors: Ji Zhong-Gang  , Wang Zhan-Xin  , Liu Jian-Sheng  , Li Ru-Xin  ,   State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800,China
Published: December 2020

By employing a full-order dispersion model, we numerically investigat the filamentation of few-cycle laser pulse focused in argon. The focusing effect caused by lens is simulated by quadratic phases e－ik(ω)r2/2f and －ik(0)r2/2f, separately. We find that it is inaccurate to simulate the focusing effect by employing e－ik(0)r2/2f, especially for the propagation of few-cycle. So quadratic phase e－ik(ω)r2/2f must be used in order to accurately simulate the effect induced by lens.
Properties of novel variable optical attenuator based on electrowetting microprisms
Authors: Chen Tao  , Liang Zhong-Cheng  , Qian Chen  , Xu Ning  ,   College of Optoelectronic Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
Published: December 2020

A novel variable fiber optical attenuator (VFOA)using an electrowetting microprisms (EMPs) and and two self-focusing lenses is proposed . EMPs can change the wetting angle of solid-liquid interface technology by electronic control methods. The attenuation of the VFOA is analyzed by the theory and experimental measurements . Theoretical analysis and experimental results show that a good control effect of light attenuation in the small voltage range (such as 135—139 V),and the optical attenuation range can achieve in 2—60dB. With the merits of novel conception, easy production, low cost and simple structure, the device will be widely used in communications fields after the optimized design. Disadvantage of this device is high voltage, in order to reduce the operating voltage to achieve the purpose of actual use, screening of high dielectric constant material as the dielectric layer material is topic of future research.
Generalization of Berthelot geometric averaging rule for adhesion work of solid-liquid interface and its applications
Authors: Wang Xiao-Song  , Zhu Ru-Zeng  ,   State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The Zisman equation, the Fowkes equation and the Owens-Wendt equation, which are derived based on the Berthelot geometric averaging rule for the adhesion work of solid-liquid interface, are theoretical foundations of experimental measurements of surface tensions of solid-liquid interfaces. We generalize the Berthelot geometric averaging rule and obtain a generalized expression of the parameters in Zisman equation. We also obtain a generalized Fowkes equation and a generalized Owens-Wendt equation.
Electronic structure and high-temperature oxidation behavior of Nb alloy
Authors: Zhang Guo-ying  , Li Dan  , Liang Ting  ,   College of Physics Science and Technology, Shenyang Normal University, Shenyang 110034, China
Published: December 2020

In order to reveal the physical nature of high temperature oxidation of Nb alloy in electron level, the density of states, the atomic embedded energy, the atomic affinity energy and other electronic structure parameters of Nb alloy are calculated by using the recursive method. The high-temperature oxidation mechanism of Nb alloy is investigated. The results show that the diffusion rate and the solid solubility of oxygen are high in the Nb alloy, so oxygen can easily react with Nb to form oxides, which makes the oxidation resistance of Nb alloy poor at high temperatures. The calculated results of atomic embedded energy show that the stabilities of alloying elements (Ti, Si, Cr) are lower in the matrix than in the surface of Nb alloy, so they diffuse easily in to the surface of Nb alloy to form a surface layer enrichment with Ti, Si, Cr. Alloying elements Nb, Ti, Si, Cr have negative affinity energies to oxygen in alloy surface layer, thereby forming the corresponding oxide film, which has a protective effect for Nb alloy.
First-principle prediction of magnetic shape memory effect of Heusler alloy Mn2NiGe
Authors: Jiang Xue-Fan  , Luo Li-Jin  , Jiang Qing  , Zhong Chong-Gui  , Tan Zhi-Zhong  , Quan Hong-Rui  ,   (1)Department of Physics and Communication Technology,Guilin Teachers college,Guilin 541001,China; (2)Department of Physics,Suzhou University,Suzhou 215006,China; (3)Jiangsu Key Laboratory of Advanced Functional Materials,Changshu Institute of Technology,Changshu 215500,China; (4)School of Science,Nantong University, Nantong 226007,China
Published: December 2020

Tetragonal distortions,crystal structure,magnetism,electronic structure and pressure response of Hg2CuTi-type Mn2NiGe are calculated by the first-principles method based on the density functional theory. The calculations show that 1)in the process of transform from cubic to a tetragonal in structure,Mn2NiGe alloys exhibit a stable martensitic phase at c/ a≈1.34; 2)in austenite and martensite,Mn atoms are the main contributors to the magnetism in Mn2NiGe,and Mn2NiGe alloys show ferrimagnetism due to antiparallel but unbalanced magnetic moments of Mn(A) atom and Mn(B) atom; 3)in austenite and martensite,the direct d-d exchange interaction between Mn(A) atom and Mn(B) atom is weak because of small overlap of d-projected DOS of Mn(A) atom and Mn(B) atom nearby the Fermi level. This is the reason why the Mn2NiGe alloys show ferrimagnetism. We can predict the magnetic shape memory effect (MSME) in Mn2NiGe alloys based on the the results of calculation above.
Renormalized perturbation expansion of asymmetric Anderson model
Authors: Li Huan  ,   School of Physics,Peking University,Beijing 100871,China
Published: December 2020

We generalize Yamadas perturbation theory and develop a renormalized perturbation method to study the asymmetric Anderson model. We obtain the occupancy of the local electrons,the renormalization factor,the renormalized energy level,and the renormalized parameters,which are expanded by the bare parameters. We also calculate the density of states of local electrons and the conductance of impurity scattering. The results coveres the range from weak to strong coupling. We find that the approach we adopted is more convenient than Hewsons renormalization method in studying the asymmetric Anderson model.
p-AlGaN electron blocking layer with different Al fractions on green InGaN/GaN LEDs grown on Si substrates
Authors: Mao Qing-Hua  , Jiang Feng-Yi  , Cheng Hai-Ying  , Zheng Chang-Da  ,   Education Ministry Engineering Reserch Center for Luminescence Matirials and Devices,Nanchang University,Nanchang 330047,China
Published: December 2020

We grow green light emitting diodes (LEDs) on Si(111) substrates with p-AlGaN electron blocking layers (EBLs) which have different Al frations. The results show that the variation of quantum efficiency with current density displays a diversity. At lower current densities,the quantum efficiency of LED increases with Al fraction decreasing, at higher current densities, however, the quantum efficiency of LED increases with Al fraction decreasing, which is attributed to the complicated mechnism when electron and hole are recombined in the quantum well.
Low-operating-voltage polymer thin-film transistors based on poly(3-hexylthiophene)
Authors: Liu Yu-Rong  , Chen Wei  , Liao Rong  ,   School of Electronic and Information Engineering,South China University of Technology,Guangzhou 510640,China
Published: December 2020

Polymer-based thin film transistors (PTFTs) with poly(3-hexylthiophene) (P3HT) as semiconducting active layers are successfully fabricated on silicon substrates in air which are used as gate electrods. HfTiO film deposited by RF sputtering method is used as gate insulators,and gold metal is used as source and drain electrodes. The HfTiO surface is modified by using octadecyltrichlorosilane solution in the fabrication process. Experimental results indicate that the PTFTs show good saturation behaviors at low drive voltages (-2 cm2/V ·s. The frequency-dependence and hysteresis effect are observed in the C-V measurements for the metal-polymer-oxide-silicon (MPOS) capacitors,and discussed in detail to understand their physical mechanism.
Contact effect in organic thin film transistors
Authors: Sun Qin-Jun  , Xu Zheng  , Zhao Su-Ling  , Zhang Fu-Jun  , Gao Li-Yan  , Tian Xue-Yan  , Wang Yong-Sheng  ,   Institude of Optoelectronics Technology,Beijing Jiaotong University,Key Laboratory of Luminescence and Optical Information (Beijing Jiaotong University),Ministry of Education,Beijing 100044,China
Published: December 2020

The contact effect on the performances of organic thin film transistors (OTFTs) is studied here. We fabricate Bottom-gated top-contact Pentacene-OTFTs on heavily doped n type Silicon wafers with using Al modified by MoO3 as source and drain electrodes. Field effect mobility μef of the OTFT reaches 0.42cm2/V ·s,the threshold voltage and the on/off current ratio arrive at -5.0 V and 4.7×103 respectively. The electric potential distribution in the channel is qualitively investigated by means of middle probe method (MPM) and the output curve is simulated by the charge drift method. Considering the contact effect,the μef is greatly improved to 1.1 cm2/V ·s,which indicates the importance of the contact engineering in OTFTs.
Threshold voltage analytical model for strained Si SOI MOSFET with high-k dielectric
Authors: Li Jin  , Liu Hong-Xia  , Li Bin  , Cao Lei  , Yuan Bo  ,   Key Laboratory for Wide Band Gap Semiconductor Materials and Devices of Education,School of Microelectronics,Xidian University,Xi'an 710071,China
Published: December 2020

A strained Si fully depleted SOI MOSFET,which has the advantages of strained Si,high-k gate and SOI structure, is presented in this paper. A two-dimensional analytical model for the threshold voltage in strained Si fully depleted SOI MOSFET with high-k dielectric is proposed by solving Possions equation. Several important parameters are taken into account in the model. Relationships between threshold voltage,Ge Profile and thickness of strained silicon are investigated. The result shows that the threshold voltage decreases with Ge Profile and strained silicon thickness increasing. Relationships between threshold voltage,dielectric constant of high k gate and doping conceration of strained silicon are also investigated. The result shows that the threshold voltage increases with dielectric constant of high-k and doping conceration of strained silicon increasing. SCE and DIBL are analyzed finally,which also demonstrate that this novel device can suppress SCE and DIBL effect greatly.
Magnetic and electric properties of Co-doped Bi5Ti3FeO15 multiferroic ceramics
Authors: Hu Xing  , Wang Wei  , Mao Xiang-Yu  , Chen Xiao-Bing  ,   College of Physics Science and Technology,Yangzhou University,Yangzhou 225002,China
Published: December 2020

Multiferroic ceramics of Bi5Fe1-xCo x Ti3O15(x=0.0—0.6) are synthesized by the conventional solid state reaction, and their microstructure,magnetic and ferroelectric properties are investigated. X-ray diffraction patterns show that a four-layer Aurivillius phase is formed in each sample with a suggested structural transformation at heavy doping of Co ions. The Raman results demonstrate that Co ions enter into the lattice,occupy the B-sites in the BFCT-x and have an effect on the order occupancy of cations at B sites. It is found that the Co ion modification induces remarkable ferromagnetism (FM) at room temperature with a greatest remanent magnetization (2M r) of 2.3 memu/g at x=0.5,which is three orders of magnitude larger than that of Bi5Ti3FeO15(BFTO). All samples with Co doping have ferroelectricity (EM). The remanent polarization (2P r) reaches a value of 11 μC/cm2 at x=0.1,which is about 38.2% higher than that of BFTO,and then decreases when 0.2≤x≤0.4 and increases again at x=0.5 and 0.6. Of all materials,the sample of x=0.5 is best in both good FE and FM.