bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoluminescence spectra of 1 MeV electron beam irradiated In0.53Ga0.47As/InP quantum well and bulk materials
Authors: Ma Li-Ya  , Li Yu-Dong  , Guo Qi  , Ai Er-Ken  , Wang Hai-Jiao  , Zeng Jun-Zhe  ,   Key Laboratory of Functional Materials and Devices for Special Environments of CAS; Xinjiang Key Laboratory of Electronic Information Materials and Devices; Xinjiang Technical Institute of Physics and Chemistry of CAS, Urumqi 830011, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Minimizing the impact of radiation-induced degradation on optoelectronic devices is important in several applications. Satellites and other spacecraft that fly in near-earth orbits (below 3.8 earth radius) are extremely susceptible to radiation damage caused by the high flux of electrons trapped in the earth’s magnetosphere. Optoelectronic devices are particularly vulnerable to displacement damage caused by electrons and protons. Effects of 1 MeV electron beam irradiation on the photoluminescence properties of In0.53Ga0.47As/InP quantum well (QW) and bulk structures, which are grown by metal-organic vapor phase epitaxy, are investigated. Samples are irradiated at room temperature using an ELV-8II accelerator with 1 MeV electron at doses ranging from 5×1012 to 9×1014 cm-2, and a dose rate of 1.075×1010 cm-2·s-1. Photoluminescence measurements are made using a 532 nm laser for excitation and a cooled Ge detector with lock-in techniques for signal detection. Photoluminescence intensity of all the structures is degraded after irradiation, and its reduction increases with increasing total dose of irradiation. Electron beam irradiation causes a larger reduction in the photoluminescence intensity and carrier lifetime of the bulk than that of quantum well. Photoluminescence intensity of five-layer quantum wells degenerates to 9% that before irradiation as the fluence reaches 6×1014 cm-2. As the electron beams bombard into the sample, the destruction of the lattice integrity will cause the decrease in the number of excitons and intensity of photoluminescence. Electron beam irradiation introduces defects in the samples, increases the density of the nonradiative recombination centers, and results in the decrease of carrier mobility. In a quantum well structure, due to the two-dimensional confinement, the probability of carrier nonradiative recombination at radiation-induced defect centers will be reduced. The reduction of photoluminescence intensity in the bulk is severer than in the quantum well while the cross-sectional area which is sensitive to radiation is kept the same. The number of interface defects which are produced by electron irradiation will increase with the number of layers in quantum well and the heterojunction interface of quantum wells, so is the degration of photoluminescence intensity. The degration is mainly due to the increase of non-radiative centers in the samples. By comparing the different structures, the quantum well structure shows a better radiation resistance.
Study on underwater acoustic scattering of a Bessel beam by rigid objects with arbitrary shapes
Authors: Li Wei  , Li Jun  , Gong Zhi-Xiong  ,   School of Naval Architecture and Ocean Engineering, Huazhong University Of Science and Technology, Wuhan 430074, China;,   Hubei Key Laboratory of Naval Architecture & Ocean Engineering Hydrodynamics (HUST), Wuhan 430074, China;,   Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration (CISSE), Shanghai 200240, China
Published: December 2020

Study on underwater acoustic scattering is very important for detection, location, and recognition of underwater targets. In the past decades, most investigations in this respect were focused on the case of plane wave incidence. But the Bessel beam is a kind of approximate non-diffracting beam with an excellent directing property, so more attention should be paid on it. So far, according to the literature, the studies about underwater acoustic scattering of a Bessel beam mainly focused on spheres and spherical shells using the partial wave series form. When the scatterers become complex objects, the partial wave series form fails to deal with these kinds of problems. To overcome this shortage, the T-matrix method has been introduced to calculate the underwater scattering of a Bessel beam by complex rigid objects. #br#In this paper, the underwater acoustic scattering of a Bessel beam by rigid objects with arbitrary shapes calculated by T-matrix method is studied. By means of the harmonic expansion of Bessel beam, the expression of the incident coefficient can be derived. Through the transmission matrix that relates the known coefficients of expansion of an incident wave to the unknown expansion coefficients of the scattered field, the acoustic scattering formula of a Bessel beam by a rigid scatterer with arbitrary shape is established. In this paper, the backscattering fields of rigid spheroids and finite cylinders with two spheroidal endcaps are discussed, and the backscattering form function modulus |F| is curved as a function of dimensionless frequency ka. Subsequently, the peak to peak intervals in backscattering form function caused by the interference of the specular wave and the Franz wave are also analyzed in geometry. The calculated results show that the frequency interval obtained from the curves agrees well with those obtained by geometric analysis for the rigid objects. Meanwhile, for both the rigid spheroid and finite cylinder, the highlight model is successfully applied to explain the phenomenon in which the amplitude of backscattering form function changes with the cone angle of the Bessel beam. From the above numerical results and analysis, the T-matrix method has been successfully introduced to calculate the acoustic scattering of the Bessel beam by complex objects, which extends the application of the T-matrix method and provides a useful tool to explore the characteristics of the Bessel beam.
Discrete element simulation of impact disaggregation for wet granule agglomerate
Authors: Jiao Yang  , Zhang Xin-Xi  , Kong Fan-Cheng  , Liu Hair-Shun  ,   College of Science, China University of Mining & Technology, Xuzhou 221116, China;,   School of Chemical Engineering and Technology, China University of Mining & Technology, Xuzhou 221116, China;,   Department of aerial ammunition, Air Force Logistics College, Xuzhou 221000, China
Published: December 2020

Based on the combination of linear contact model, Coulomb slip contact model and parallel bond contact model, a discret element model (DEM) of wet granule agglomerates with coating structure is constructed. Disaggregation processes of wet agglomerates in impacting to a horizontal plate are performed by applying particle flow code (PFC). Three failure patterns are obtained corresponding to those in experiment. The variation of velocities and rupture characteristics of liquid bridge in disaggregation process are investigated. Effects of impact velocity, gravity of adhered granules, and rotation of core granule are analyzed. DEM simulations show that there are three disaggregation patterns in the coating structure of agglomerates: impact disaggregation, gravity-impact disaggregation and shear-impact disaggregation, depending on the size of primary particles and the rotation of the core granules. With the enlargement of size, gravity plays an increasingly important role and the impact disaggregation pattern shifts to gravity-impact disaggregation. The rotation of core can generate a shear force to separate the fine and disaggregation pattern to turn to shear-impact disaggregation. Impacting results in a heterogeneous distribution of granule velocities and a tendency of relative movement in agglomerates. Relative movement will bring about the stretch of liquid bridge between granules. If the maximum separation distance of wet granules exceeds the rupture distance of liquid bridge, disaggregation happens. The ruptures of liquid bridge start from impact point and expand to outward, from bottom to up, from inside to outside in coating agglomeration. It is found that the rupture of liquid bridge needs time for accumulation and goes through three stages termed as slow rupture stage, quick rupture stage and entire rupture stage. With the increase of impact velocity, particle gravity, and rotating speed of core granules, disaggregation processes of wet granule agglomerates become fast and thorough. Impact velocity plays a primary role in disaggregation. DEM simulations are consistent with the experimental results.
Design of two-cascade optical antenna for indoor visible light communication
Authors: Zhang Yi-Lun  , Lan Tian  , Gao Ming-Guang  , Zhao Tao  , Shen Zhen-Min  ,   Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology, Key Laboratory of Photoelectronic Imaging Technology and System, Ministry of Education, School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

White light emitting diode (LED) is expected to replace the incandescent lamp and becomes the next generation of lighting source because of its long life expectancy, high tolerance to humidity, and low power consumption. It is proposed that for the indoor visible light communication system white LED should be used as both lighting source and base station for its properties of high brightness and high speed modulation. Indoor visible light communication has a very wide area of applications, but there is a lack of research on receiver optical antenna that functions as an energy concentrator so as to increase received power. In order to meet the needs of high gain and meanwhile large field of view of receiver optical antenna for indoor visible light communication, two-cascade optical antenna is designed. It is shown that the field of view from 40 to 60 degrees can meet the requirements for high speed communication by analyzing the relationship between signal-to-noise ratio and data rate of different fields of view. The performances of the traditional optical antenna of Fresnel lens and the compound parabolic concentrator are simulated and analyzed by TacrePro. The gains of the designed two-cascade optical antenna are discussed at different incident angles. The results show that two-cascade optical antenna has better performance than traditional receiver optical antenna. The distribution of received power of two-cascade optical antenna is analyzed by using Matlab. The received average power by using two-cascade optical antenna is about 7 dBm larger than that without any optical antenna. The designed optical antenna provides a field of view of 40 degrees and enough gain for indoor visible light communication system.
Extraordinary optical transmission through bilayer metallic nano-grating for s-polarization light
Authors: Chu Jin-Kui  , Wang Qian-Yi  , Wang Zhi-Wen  , Wang Li-Ding  ,   School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, China
Published: December 2020

Based on the phenomenon of the s-polarization extraordinary optical transmission through subwavelength metallic grating on a dielectric film, the same phenomenon in bilayer metallic nano-grating has been found. In order to analyze the s-polarization transmission in this specific structure, the rigorous coupled-wave analysis and finite-different time-domain method is applied: the former is used for analyzing the transmission of the structure exactly and the latter is used for acquiring the optical field distribution of the structure. Using the equivalent refractive method, the equivalent mechanical model of the bilayer metallic grating is founded, which is as much of extraordinary optical transmission as the original model, to discover the relationship between the polymer and the s-polarization transmission. The comparison of distribution of field-intensity for two bilayer structures, with or without the polymer, illustrates that the existence of the polymer is the main reason to the s-polarization transmission peak appearance. Because the existence of the polymer can be treated as a waveguide and the s-polarization is coupled by metal grating and then turns to a surface wave, there is a resonant phenomenon occurred in the polymer area under the incident light with particular wavelength. In addition, the effect of geometrical parameters of the polymer, such as the refractive index and the thickness of the polymer, the effect of the thickness of the metal film on s-polarization transmittance are discussed. Increasing the refractive index of the polymer leads to the red shift of transmission peak both in the original bilayer model and the equivalent model, which indicates that the two models have the same property. The transmission peak can be explained by the Fabry-Perot-like resonance, and the red shift of transmission peak is result from the change of the resonance condition due to the refractive index increase. The polymer thickness increase results in the addition of the resonance modes and the corresponding transmission peaks. The cycle of the peak is calculated and the result is similar to the length of the Fabry-Perot-like cavity. However, the thickness of metal layer does not impact the position of the s-polarization transmission peak. In conclusion, the polymer which sustains a waveguide elecromagnetic mode is necessary for the extraordinary optical transmission, and the existence of Fabry-Perot-like resonance in the polymer film is the main reason of the resonant peak appearing.
Research progress on preparation, manipulation, and remote sensing applications of high-order orbital angular momentum of photons
Authors: Chen Li-Xiang  , Zhang Yuan-Ying  ,   Department of Physics, Xiamen University, Xiamen 361005, China
Published: December 2020

Photons are an ideal candidate for encoding both classical and quantum information. Besides spin angular momentum associated with circular polarization, single photon can also carry other fundamentally new degree of freedom of orbital angular momentum related to the spiral phase structure of light. The key significance of orbital angular momentum lies in its potential in realizing a high-dimensional Hilbert space and in encoding a high-dimensional quantum information. Since Allen et al. [Allen L, Beijersbergen M W, Spreeuw R J C, Woerdman J P 1992 Phys. Rev. A 45 8185] recognized the physical reality of photon orbital angular momentum in 1992, rapidly growing interest has been aroused in orbital angular momentum (OAM) from both classical and quantum points of view. Here we present an overall review on the high-order orbital angular momentum of photon, including its preparation and manipulation based on some specific techniques and also its applications. The spatial light modulator is a commercial device that has been widely employed to generate the OAM beams. We make and identify the optical OAM superposition with very high quantum numbers up to l=360. Recently, the metallic spiral phase mirrors were also developed to produce high-order OAM beams up to l=5050. In addition, the Q-plates made of anisotropic and inhomogeneous liquid crystals were invented to generate high-order OAM beams in a polarization-controllable manner, and the OAM superposition of l=± 50 were achieved. Owing to high rotational symmetry, these high OAM beams have been found to have more and more important applications in the fields of high-sensitivity sensing and high-precision measurements. Two fascinating examples are discussed in detail. The first example is that the research group led by Prof. Zeilinger has prepared and observed the quantum entanglement of high orbital angular momenta up to l=±300 by the technique of polarization-OAM entanglement swapping, and they demonstrated that the angular resolution could be significantly improved by a factor of l. Their result was the first step for entangling and twisting even macroscopic, spatially separated objects in two different directions. The second example is that the research group led by Prof. Padgett has demonstrated an elegant experiment of rotational Doppler effects for visible light with l=±20 OAM superposition. They showed that a spinning object with an optically rough surface might induce a Doppler effect in light reflected from the direction parallel to the rotation axis, and the frequency shift was proportional to both the disk's angular speed and the optical OAM. The potential applications in noncontact measurement of angular speed and in significant improvement of angular resolution for remote sensing will be particularly fascinating.
The mechanisms of electric-dipole spin resonance in quasi-one-dimensional semiconductor quantum dot
Authors: Li Rui  ,   Quantum Optics and Quantum Information Division, Beijing Computational Science Research Center, Beijing 100094, China
Published: December 2020

Because of the long coherence time and the easy way to achieve the qubit scalability, quantum dot spin qubit has obtained considerable attentions recently. Single spin manipulation is usually achieved using the traditional electron spin resonance technique. This method not only needs a static Zeeman field, but also needs an ac magnetic field which is perpendicular to the static one. However, it is not easy to produce a local ac magnetic field experimentally. Recently, instead of an ac magnetic field, an ac electric field can also be used to manipulate an electron spin, an effect called electric-dipole spin resonance. As is well-known, there is no direct interaction between the spin and the electric field. Thus, the electric-dipole spin resonance must be mediated by some mechanisms. These mediums in the quantum dot can be: the slanting magnetic field, the spin-orbit coupling, and the electron-nucleus hyperfine interaction. This paper summarizes three main mechanisms of the electron-dipole spin resonance in semiconductor quantum dot.
New super junction lateral double-diffused metal-oxide-semiconductor field-effect transistor with the P covered layer
Authors: Li Chun-Lai  , Duan Bao-Xing  , Ma Jian-Chong  , Yuan Song  , Yang Yin-Tang  ,   Key Laboratory of the Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071, China
Published: December 2020

In order to design the lateral double-diffused metal-oxide-semiconductor field-effect transistor (LDMOS) with low loss required for a power integrated circuit, a new super junction LDMOS with the P covered layer which is based on the existing N buffered super junction LDMOS is proposed in this paper for the first time. The key feature of the proposed structure is that the P-type covered layer is partly above the N-type of the super junction layer, which is different from the N buffered super junction LDMOS. In this structure, the specific on-resistance of the device is reduced by using the high doped super junction layer; the problem of the substrate-assisted depletion which is produced due to the P-type substrate of the N-channel super junction LDMOS is eliminated by completely compensating for the charges of the N-type buffered layer and the P-type covered layer, thus improving the breakdown voltage. The charges of the N-type and P-type pillars are depleted completely. A new transmission path at the on-state is formed by N buffered layer to reduce the specific on-resistance, which is similar to the N buffered super junction LDMOS. However, the effect of N-type buffered layer of N buffered super junction LDMOS is not fully used. The drift region of the device is further optimized by the proposed device to reduce the specific on-resistance. The charge concentration of the N-type buffered layer in the proposed device is improved by the effect of charge compensation of the P covered layer. It is clear that high breakdown voltage and low specific on-resistance are realized in the proposed device by introducing the P-type covered layer and the N-type buffered layer. The results of the 3 D-ISE software suggest that when the drift region is on a scale of 10 μm, a specific on-resistance of 4.26 mΩ·cm2 obtained from P covered super junction LDMOS by introducing P covered layer and N buffered layer is reduced by about 59% compared with that of conventional super junction LDMOS which is 10.47 mΩ·cm2, and reduced by about 43% compared with that of N Buffered super junction LDMOS which is 7.46 mΩ·cm2.
Dynamics of complex vesicles in shear flow
Authors: Deng Zhen-Yu  , Zhang Lin-Xi  ,   Department of Physics, Zhejiang University, Hangzhou 310027, China
Published: December 2020

Vesicles exposed to shear flow exhibit a remarkably rich dynamics. With the increase of shear rate, one can observe a tumbling-to-tank-treading transition. Besides, a complex oscillating motion, which has alternatively been called trembling, swinging, or vacillating breathing, has also been predicted theoretically and observed experimentally. While in biological systems, vesicles are always decorated by a large number of macromolecules, rendering the dynamics of vesicles in shear flow much more complex. As a powerful supplement to analytical techniques, the dissipative particle dynamics has been proved to be a useful tool in simulating nonequilibrium behaviors under shear. By replacing the conservative force in dissipative particle dynamics with a repulsive Lennard-Jones potential, the density distortion has been overcome and the no-slip boundary condition is achieved. In this article, a nonequilibrium molecular dynamic method is used to study the dynamics of two-dimensional complex vesicles in shear flow. The dynamical behaviors of the complex vesicles are closely related to shear rate and the size of small grafting vesicle. We first consider a vesicle with two small vesicles symmetrically grafted. At a weak flow, the complex vesicle maintains its equilibrium shape and undergoes an unsteady flipping motion, known as tumbling motion. At a moderate shear rate, the tumbling of the vesicle is accompanied with strong shape oscillation, which is consistent with Yazdani's simulation, in which a breathing-with-tumbling type of motion is observed, and is called trembling in this article. As the shear rate further increases, the vesicle is oriented at a fixed angle with respect to the flow direction, while the vesicle membrane circulates around its surface area, exhibiting a well-known tank-treading motion. For sufficiently large grafted vesicles and at a high enough shear rate, a transition from tank-treading to translating motion is observed, in which the flipping of the vesicle or the circulating of the vesicle membrane is hampered. A crossover regime, namely, the tank-treading/translating mixture motion is also found, where translating motion alternates with tank-treading chaotically. However, when a sufficient number of small vesicles are uniformly grafted to the vesicle, the newly observed translating motion is eliminated. This study can give a deeper insight into the complexity of vesicle motions in shear flow.
Decreasing trend of the middle atmospheric static stability in historical data from rocketsonde network
Authors: Wang Li-Ji  , Chen Ze-Yu  , Ling Chao  , Lü Da-Ren  ,   Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Brunt-Vaisala frequency squared (N2) measures the static stability of the atmosphere, and reflects the general structure of the atmosphere in term of vertical temperature gradient. For middle atmosphere the response of the middle atmospheric structure to the global warming still lacks investigation currently. The historical data from rocket sounding network in 1962-1991 are used to investigate the long-term trend of N2 in the middle atmosphere. For six stations spanning from the tropical latitudes to the northern mid-latitudes, our estimates show that, in the upper stratosphere and middle mesosphere, i. e., 48-60 km high, the significant decreasing of static stability is observed in an N2 anomalies averaged over 48-60 km range. For two tropical stations, long-term trend in N2 exhibits a similar magnitude, i.e., -0.11×10-4 s-2/decade; it is also observed that the trend increases with latitude, with trend estimates from -0.16×10-4 s-2/decade at 22°N (Barking Sand station) to -0.22×10-4 s-2/decade at 38°N (Wallops Island station).
Influence of earth's reflective radiation on space target for space based imaging
Authors: Yan Pei-Pei  , Ma Cai-Wen  , She Wen-Ji  ,   Xi'an Institute of Optics and Precision Mechanics, Chinese Academy Sciences, Xi'an 710119, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The space-based surveillance, which would mainly use the space-based visible, has great value for civil and military applications currently and for a fairly long future period. In space-based surveillance, the visible and near-infrared radiation characteristics of the space target are influenced by its attitude variation. This influence is especially prominent in space-based imaging. In some ways, solar radiation cannot arrive at the surface of the space target, or the arriving radiation is not uniformly distributed because of the space target's strong reflection at a particular position. In order to solve these problems, the visible and near-infrared illumination characteristics of the space target surface are analyzed. Moreover, a notion that earth's reflective radiation can be used as illumination for space target imaging is given, and an accurate modeling method is proposed. Firstly, based on diffuse reflectance model, a method of mathematically calculating the illumination at space target's position from earth's reflective radiation is established. And a formula for calculating illumination is derived. Secondly, the coordinates of sun and space target at any time can be obtained by the Satellite tool kit software, in which the complicated multiplying matrix and coordinate transformation algorithm introduced in some references are avoided. Thirdly, the method of estimating earth's reflective radiation region at arbitrary moment is introduced. The grid division method is generated and the uniform sampling is used in each small area. Fourthly, the position of a surface cell is transformed from the sphere reference frame into the J2000.0 inertial frame. The earth's reflective radiation can be calculated through numerical integration. Finally, the illumination from earth's reflective radiation to a sun synchronous orbit satellite in an imaging mission based on space is calculated by the given parameters. The results show that the earth's reflective radiation is luminous enough for space target imaging when the satellite passes through arctic. When the satellite moves on the orbit, we can obtain more detailed information about target satellites' bottom then the ground simulation imaging. The on-orbit imaging results demonstrate the validity of the modeling method, which could support the foundation of our space-based surveillance system theoretically and technically and could be used as a reference of space-based orbit measurement and determination in deep space exploration.
Studies of nonergodic criterion based on the fractional heat bath model
Authors: Lu Hong  , Lü Yan  , Bao Jing-Dong  ,   School of Science, Xihua University, Chengdu 610039, China;,   School of Applied Science, Taiyuan University of Science and Technology, Taiyuan 030024, China;,   Department of Physics, Beijing Normal University, Beijing 100875, China
Published: December 2020

The generalized Langevin equation with a power law memory kernel is derived via the gas/solid-surface model with fractional heat bath. Using Lapalce transformation, the dynamic evolution and long-time asymptotic behaviors of the gas particles occurring either in free or harmonic potentials are then investigated. In particular, the validity of three kinds of ergodic criteria is analyzed in detail, including the Khinchin criterion, Lee criterion, and the intrinsic and external behaviors. It is found that the Khinchin criterion holds for all ranges of diffusion and transport processes described by a generalized Langevin equation. Lee criterion is just applied to distinguish diffusion processes. Meanwhile, the intrinsic criterion and external behaviors can not only divide the nonergodicity into two classes but also reveal the underlying physical origins.
Inductorless chaotic circuit based on active generalized memristors
Authors: Yu Qing  , Bao Bo-Cheng  , Xu Quan  , Chen Mo  , Hu Wen  ,   School of Information Science and Engineering, Changzhou University, Changzhou 213164, China;,   College of Electronic and Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Published: December 2020

Equivalently implementing a generalized memristor by using common components and then making a nonlinear circuit with a reliable property, are conducive to experimentally exhibit the nonlinear phenomena of the memristive chaotic circuit and show practical applications in generating chaotic signals. Firstly, based on a memristive diode bridge circuit, a new first-order actively generalized memristor emulator is constructed with no grounded restriction and ease to realize. The mathematical model of the emulator is established and its fingerprints are analyzed by the pinched hysteresis loops with different sinusoidal voltage stimuli. The results verified by experimental measurements indicate that the emulator uses only one operational amplifier and nine elementary electronic circuit elements and is an active voltage-controlled generalized memristor. Secondly, by parallelly connecting the proposed emulator to a capacitor and then linearly coupling with an RC bridge oscillator, a memristor based chaotic circuit without any inductance element is constructed. The dynamical model of the inductorless memristive chaotic circuit is established and the phase portraits of the chaotic attractor with typical circuit parameters are obtained numerically. The dissipativity, equilibrium points, and stabilities are derived, which indicate that in the phase space of the inductorless memristive chaotic circuit there exists a dissipative area where are distributed two unstable nonzero saddle-foci and a non-dissipative area containing an unstable origin saddle point. Furthermore, by utilizing the bifurcation diagram, Lyapunov exponent spectra, and phase portraits, the dynamical behaviors of the inductorless memristive chaotic circuit are investigated. Results show that with the evolution of the parameter value of the coupling resistor, the complex nonlinear phenomena of the coexisting bifurcation modes and coexisting attractors under two different initial conditions of the state variables can be found in the inductorless memristive chaotic circuit. Finally, a prototype circuit with the same circuit parameters for numerical simulations is developed, from which it can be seen that the prototype circuit has a simple circuit structure and is inexpensive and easy to practically fabricate with common components. Results of both the experimental measurements and the numerical simulations are consistent, verifying the validity of the theoretical analyses.
Multiple synchronous states in a ring of coupled phase oscillators
Authors: Huang Xia  , Xu Can  , Sun Yu-Ting  , Gao Jian  , Zheng Zhi-Gang  ,   Department of Physics, Beijing Normal University, Beijing 100875, China;,   Department of Mathematics and Physics, North China Electric Power University, Beijing 102206, China
Published: December 2020

A significant phenomenon in nature is that of collective synchronization, in which a large population of coupled oscillators spontaneously synchronizes at a common frequency. Nonlinearly coupled systems with local interactions are of special importance, in particular, the Kuramoto model in its nearest-neighbor version. In this paper the dynamics of a ring of Kuramoto phase oscillators with unidirectional couplings is investigated. We simulate numerically the bifurcation tree of average frequency observed and the multiple stable states in the synchronization region with the increase of the coupling strength for N4, which cannot be found for N3. Oscillators synchronize at a common frequency =0 when K is larger than a critical value of N=3. Multiple branches with 0 will appear besides the zero branch, and the number of branches increases with increasing oscillators for the system N3. We further present a theoretical analysis on the feature and stability of the multiple synchronous states and obtain the asymptotically stable solutions. When the system of N=2 reaches synchronization, the dynamic equation has two solutions: one is stable and the other is unstable. And there is also one stable solution for N=3 when the system is in global synchronization. For the larger system (N3), we study the identical oscillators and can find all the multiple branches on the bifurcation tree. Our results show that the phase difference between neighboring oscillators has different fixed values corresponding to the numbers of different branches. The behaviors in the synchronization region computed by numerical simulation are consistent with theoretical calculation very well. The systems in which original states belong to different stable states will evolve to the same incoherent state with an adiabatic decreasing of coupling strength. Behaviors of synchronization of all oscillators are exactly the same in non-synchronous region whenever the system evolves from an arbitrary branch according to the bifurcation trees. This result suggests that the only incoherent state can be attributed to the movement ergodicity in the phase space of coupled oscillators in an asynchronous region. When the system achieves synchronization, the phenomenon of the coexistence of multiple stable states will emerge because of the broken ergodicity. All these analyses indicate that the multiple stable states of synchronization in nonlinear coupling systems are indeed generically observable, which can have potential engineering applications.
Ultrahigh-resolution optical coherence tomography and its application in inspection of industrial materials
Authors: Tang Tao  , Zhao Chen  , Chen Zhi-Yan  , Li Peng  , Ding Zhi-Hua  ,   State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
Published: December 2020

Since many industrial materials have micro or submicro structures on the surface or subsurface, utrahigh-resolution is required in the inspection of these materials. Ultrahigh-resolution optical coherence tomography uses broadband light sources to achieve axial image resolutions on the scale of a few microns. We have been investigating an ultrahigh-resolution spectral-domain optical coherence tomography (SD-OCT) system using supercontinuum sources (SC) in free space. The effective SC spectrum has a full width at half maximum of 230 nm centered around 665 nm, and the imaging setup has an ultrahigh axial resolution of 0.9 μm in air, and a lateral resolution of 3.9 μm, with the system measurement range being 0.6 mm in axial direction. At a 50 μm axial position, the sensitivity can be 63 dB with 28600 axial scans per second at 2048 pixels per axial scan. Images of polystyrene microspheres solution with an average diameter of 5 μm and different sizes of industrial abrasive papers are presented to illustrate the performance of the system.
Photon spin splitting in magneto-optic Kerr effect
Authors: Wang Li-Cen  , Qiu Xiao-Dong  , Zhang Zhi-You  , Shi Rui-Ying  ,   Key laboratory of microelectronics, Sichuan University, Chengdu 610064, China;,   Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064, China
Published: December 2020

Photonic spin Hall effect (PSHE) of light, similar to the spin Hall effect of an electronic system, is the interaction between photon spin-orbit of spin splitting phenomenon in refractive index gradient field. PSHE provides a new way to manipulate photons and accurately measure relevant physical effects. This paper studies the photon spin splitting in the magneto-optic Kerr effect, and establishes the quantitative relationship between the magneto-optical Kerr rotation and the PSHE. We have observed the magneto-optic Kerr effect of the action of an iron film in the magnetic field. After finishing experiments, we firstly analyze the amplified shift of the spin changing with the magnetic intensity in the case of horizontal polarization and vertical polarization incidence. Then, the Kerr rotations changing with the incident angle for different magnetizations are measured separately. Finally, comparing the above two results, we obtain that the accurate magneto-optic Kerr rotation angle is 6.7×10-5o/μm. If the position sensor based on phase-locked amplifier (20 nm) is used to measure the magneto-optic Kerr rotation angle, its precision can be improved by one or two orders of magnitude. These results prove that the PSHE not only can be used to accurately measure the magneto-optic Kerr effect, but also have great significance in magnetic film research. Especially, in terms of magnetic-optic devices, PSHE can be used to achieve the superior performance of endurance cycling and data retention.
Analysis of all fiber acousto-optic tunable filter based on superimposed fiber Bragg gratings
Authors: Liu Chao  , Pei Li  , Wu Liang-Ying  , Wang Yi-Qun  , Weng Si-Jun  , Yu Shao-Wei  ,   Key Laboratory of All Optical Network and Advanced Telecommunication Network of Ministry of Education, Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

In this paper, an all fiber acousto-optic tunable filter based on superimposed fiber Bragg gratings (SFBG-AOTF) is demonstrated and studied. Compared to the normal fiber Bragg gratings based all fiber acousto-optic tunable filter, SFBG-AOTF can modulate the two optical resonant wavelengths of the gratings synchronously. The spectrum of SFBG-AOTF at various acoustic frequencies and under acoustically induced strains, has been analyzed theoretically. Based on simulation results, one can find that each order of the secondary reflection peak is symmetrical with respect to the two primary reflection peaks with SFBG as the center, and the resonant wavelength spacing between the primary reflection peak and the secondary reflection peak which is modulated by the former, is proportional to the acoustic frequency. But the resonant wavelength between the same order secondary reflection peaks which are modulated by two different primary reflection peaks, is independent of the acoustic frequency. The acoustically induced strains mainly affect the variation of the reflectivities of the primary and secondary reflection peaks. In the experiment, the spectra of SFBG-AOTF with acoustic frequencies of 390 and 710 kHz, are measured. The variation trend of the experimental results accords well with the simulated one.
Research on the method and experiment of path rainfall intensity inversion using a microwave link
Authors: Gao Tai-Chang  , Song Kun  , Liu Xi-Chuan  , Yin Min  , Liu Lei  , Jiang Shi-Tai  ,   College of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China;,   Unit No. 93721 of PLA, Shuozhou 038301, China
Published: December 2020

Accurate measurement of rainfall with high spatial and temporal resolution have important significance in meteorology, hydrology, agriculture, environment, flood warning and weather forecasting, etc. Based on the rain-induced power-law attenuation, an inversion method of the path rainfall intensity is proposed by using a microwave link. Starting from the atmospheric gas absorption attenuation model, a correction model of rainfall effective attenuation and a rainfall inversion model for line-of-sight microwave links are proposed, based on the microwave rain attenuation characteristics and raindrop size distribution statistics. A line-of-sight microwave link is designed and used to measure the rainfall, and the path average rain rate is inversed by means of rainfall inversion model, which is compared with a disdrometer. Results show that the correlation coefficient of rain rate inversed by microwave link with that of disdrometer is higher than 0.6 mostly, and the maximum value is 0.9647; the error of the accumulated rain amount is less than 0.5 mm, and the minimum value is 0.0827 mm; the relative error of the accumulated rain amount is less than 15%, the minimum value is 3.3415%. Experiments confirm the feasibility and accuracy of rainfall inversion obtained using a microwave link.
A far distance wideband geoacoustic parameter inversion method based on a modal dispersion curve
Authors: Guo Xiao-Le  , Yang Kun-De  , Ma Yuan-Liang  ,   School of Marine Science and Technology, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

Acoustic propagation in shallow water is greatly influenced by the properties of the sea bottom. The dispersion characteristics of modes are relatively sensitive to the bottom parameters and have been used to invert the bottom parameters. Since the inversion error using a single wideband sound source increases with increasing range, a far distance inversion method based on the modal dispersion curve using a single hydrophone with two wideband sound sources is presented in this paper, in which a warping transform is applied so that it can accurately extract the modal dispersion curve from the warped signal spectrum. Experimental data used for the inversion are acquired using a hydrophone of vertical array in the South Sea of China during the Autumn in 2012. The transmitted signals are explosive signals, and the bottom sound speed and density are inverted by matching the theoretical arrival time differences of various modes and frequencies with those calculated using the experimental data. The attenuation coefficient is deduced using the transmission loss data recorded in the experiment. A genetic algorithm (GA) is used for optimization search for the parameter bounds. Inversion results demonstrate that the arrival time difference when using the bottom sound speed and density show a high consistency with those obtained using the experimental data. Moreover, the attenuation coefficient is nonlinear over the frequency band from 100 to 315 Hz. The validity of inverted parameters is evaluated by the posteriori probability distributions, and the numerical results of arrival time differences calculated using the inverted sound speed and density are in good agreement with those extracted from the other two wideband explosive signals at different distances. In addition, the theoretical transmission loss calculated using the inverted attenuation coefficient matches the experiment data very well. It is shown that the inversion scheme can provide a valid and stable environmental estimation.
Research of spin wave function and exchange coupling interactions in metal magnetic materials
Authors: Zheng Yong-Lin  , Lu Meng-Chun  , Guo Hong-Xia  , Bao Xiu-Li  ,   Institute of Electronics and Information Engineering, Chengdu University, Chengdu 610106, China;,   Institute of Condensed Matter Physics, Yangtze Normal University, Chongqing 408100, China
Published: December 2020

Exchange coupling is one of the most important fundamental interactions in ferromagnetic systems. Understanding of the parameters in this interaction may help describe numerous properties of metal magnetic materials. However, in the localized electron theory or itinerant electron theory there are also certain difficulties when utilizing this approximation method to study magnetic ordering problems for multi-atom systems. In realistic magnets exchange coupling is also related to the coexistence of localized and itinerant degrees of freedom. In this case Heisenberg exchange relationship has some limitations. If the exchange relationship only depends on the structure of the magnet, and is not related to energy differences between the phases, we can better avoid the Heisenberg exchange limits. Based on this, we use the general principle of the exchange coupling theory to analyse the usual approximation, and discuss the opportunity to calculate the parameters of such coupling rigorously without specific assumptions about the range of magnetic order or any approximation about the form of magnetization density. We propose a method for calculating the exchange coupling parameter to any approximation. The range of applicability of the above relation is discussed quantitatively for real magnetic systems (magnetic metal materials Gd, Fe, Ni) and spin waves, and the relevance for the exchange coupling is also analysed. This analysis for metal magnetic system (Fe, Ni and Gd) shows that the most significant improvement is obtained for exchange coupling between nearest magnetic atoms and for spin wave spectrum at finite wave vectors. It can be described by the relationship between the exchange coupling approximation and spin wave spectrum, and also interaction between the nearest neighbor magnetic atoms in ferromagnetic systems; these will give reasonable description to the large wave vectors part of spin wave spectra in any magnet with not fully localized magnetism. This point of view from the magnetism theory is consistent with the experimental results.
Study on the magnetic and magnetocaloric effects of Dy3Al5O12
Authors: Dong Xue  , Zhang Guo-Ying  , Xia Wang-Suo  , Huang Yi-Jia  , Hu Feng  ,   Department of Physics, College of Science, China University of Mining and Technology, Xuzhou 221008, China
Published: December 2020

The crystal field (CF)- and external magnetic field- split ground state of Dy3+ in Dy3Al5O12 (DyAG) has been calculated based on the quantum theory in this paper. The eight CF-split levels are obtained, which are all twofold degenerates and are removed by the external magnetic field. On the basis of the results, the magnetic moments and the magnetic entropy changes of DyAG are calculated in the temperature range of 3THe3Ga5O12(GdGG) is stronger at low temperatures and dependent on the temperature and external magnetic field. Besides, the variation of the adiabatic temperature change ΔT with T is theoretically anticipated and the anticipated results are comparied with that of GdGG. It is found that the maximum adiabatic temperature change ΔT of DyAG is 1.27 times larger than that of GdGG when T=11 K and He=1 T. However, it changes to 1.15 times that of GdGG when T=16 K and He=2 T. There are differences between the refrigerative properties of DyAG and GdGG when they are in different external magnetic fields and different temperature regions. At low temperature s(THe is higher, GdGG is a good selection. This study is helpful to select suitable materials for the magnetic refrigeration technology.