bluuebunny/crossref_metadata_2025 huggingface dataset:
Bi-stability in a fifth-order voltage-controlled memristor-based Chua's chaotic circuit
Authors: Lin Yi  , Liu Wen-Bo  , Shen Qian  ,   College of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
Published: December 2020

Generally, the occurrence of multiple attractors indicates that the multi-stability existing in a nonlinear dynamical system and the long-time motion behavior are essentially different, depending on which basin of attraction the initial condition belongs to. Up to now, due to the emergence of multi-stability, some particular memristor-based nonlinear circuits whose dynamical behaviors are extremely related to memristor initial conditions or other initial conditions have attracted considerable attention. By replacing linear or nonlinear resistors with memristor emulators in some already-existing oscillating circuits or introducing memristor emulators with different nonlinearities into these oscillating circuits, various memristor-based nonlinear dynamical circuits have been constructed and broadly investigated. Motivated by these considerations, we present a novel fifth-order voltage-controlled memristor-based Chua's chaotic circuit in this paper, from which a wonderful phenomenon of bi-stability is well demonstrated by numerical simulations and PSIM circuit simulations. Note that the bi-stability is a special kind of multi-stability, which is rarely reported in the memristor-based chaotic circuits.
The proposed memristor-based Chua's chaotic circuit is constructed by inserting an inductor into the coupled resistor branch in series and substituting the Chua's diode with a voltage-controlled memristor in the classical Chua's circuit. Five-dimensional system model is established, of which the equilibrium point and its stability are investigated. Theoretical derivation results indicate that the proposed circuit owns one or three equilibrium points related to the circuit parameters. Especially, unlike the newly reported memristive circuit with bi-stability, the proposed memristor-based Chua's chaotic circuit has only one zero equilibrium point under the given parameters, but it can generate coexistent chaotic and periodic behaviors, and the bi-stability occurs in such a memristive Chua's circuit. By theoretical analyses, numerical simulations and PSIM circuit simulations, the bi-stability phenomenon of coexistent chaotic attractors and periodic limit cycles with different initial conditions and their formation mechanism are revealed and expounded. Besides, with the dimensionless system equations, the corresponding initial condition-dependent dynamical behaviors are further numerically explored through bifurcation diagram, Lyapunov exponents, phased portraits and attraction basin. Numerical simulation results demonstrate that the proposed memristive Chua's system can generate bi-stability under different initial conditions. The PSIM circuit simulations and numerical simulations are consistent well with each other, which perfectly verifies the theoretical analyses.
Development and testing of glass substrate Wolter-1 X-ray focusing mirror
Authors: Li Lin-Sen  , Qiang Peng-Fei  , Sheng Li-Zhi  , Liu Zhe  , Zhou Xiao-Hong  , Zhao Bao-Sheng  , Zhang Chun-Min  ,   University of Chinese Academy of Sciences, Beijing 100049, China;,   School of Science, Xi'an Jiaotong University, Xi'an 710049, China;,   State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119, China
Published: December 2020

The wolter-1 X-ray focusing mirror can reflect grazing incidence X-ray to the focal plane, which plays an important role in the astronomical detection and other fields due to its good image detecting capability. A geometric model of the optical system is established for theoretically deriving the optical path equations which is useful in this glass based focusing mirror designing, all the design parameters of the focusing mirror can be obtained by solving these equations. In the manufacturing process, the D263T glass is chosen to be the structural material of the focusing mirror due to its light weight and super smooth surface, after a slumping process, the flat glass mirror will have the shape of Wolter-1 X-ray focusing mirror. This slumping process has been used successfully in the manufacturing process of an American mission named The Nuclear Spectroscopic Telescope Array, which was launched in 2012. According to X-ray reflecting theory, the reflectivity of the Wolter-1 mirror can be improved significantly by coating metal film on the surface of the mirror. In this work, an iridium film is coated on the surface of the glass mirror through a vacuum evaporating process. In order to learn the influence of the focal spot caused by the mirror shape tolerance, the morphology of the mirror is tested by using a 3-D laser scan instrument. The results show that 50% of the total test points are located in the tolerance range of-10-10 m, in which the tolerance represents the difference between the actual lens profile and the ideal lens profile. Then the focal spot test is carried out with the help of a visible light test system:a laser collimator is installed in front of focusing mirror as an incidence light source, and a charge coupled device (CCD) is placed in the focal plane to gather the image of the focal spot, by calculating the gray level distribution of the focal spot image taken by the CCD, the energy distribution characteristic of focal spot can be obtained. The experimental results show that the focal length of the focusing mirror is 1.6 m, and the half-power surrounding diameter of the focal spot is 0.33 mm, corresponding to the angular resolution of 0.7 arc min.
Competition between different nonlinear optical effects of GaN-based thin-film semiconductors
Authors: Liao Jian-Hong  , Zeng Qun  , Yuan Mao-Hui  ,   1. Guangzhou Key Laboratory for Special Fiber Photonic Devices and Applications, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China;,   2. College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
Published: December 2020

In recent years, new optoelectronic materials such as GaN-based thin-film semiconductors and rare-earth-ion doped luminescent materials have aroused the interest of many researchers. The GaN-based semiconductors have wide and direct energy gaps which could be adjusted to cover the whole visible light spectrum region by doping. They have been successfully applied to fabrications of blue lasers and light emitting diodes. The rare-earth-ion doped luminescent materials have exhibited many advantages in luminescent properties such as intense narrow-band emissions, high conversion efficiency, wide emission peaks ranging from ultraviolet to near infrared, long lifetime ranging from nanoseconds to milliseconds, and good thermal stability. They have been widely applied in the fields of illumination, imaging, display, and medical radiology. So far, the studies on GaN-based thin-film semiconductors and rare-earth-ion doped luminescent materials focus mainly on their growth and linear optical properties. In contrast, the investigations of the nonlinear optical properties of these materials, which have potential applications in many fields, are still lacking. In this paper, GaN-based thin-film semiconductors, such as undoped GaN, Mg-doped GaN and InGaN/GaN multiple quantum wells, are successfully grown by metal-organic chemical vapor deposition. Their nonlinear optical properties are studied by using an 800-nm femtosecond laser light. The nonlinear optical properties are different when the laser light is focused on different positions of the samples. The competition between different nonlinear optical effects reflect directly the competition in stimulated luminescence energy. And particularly, it is closely related to the density of energy states, stimulated luminescence energy, and the sample band gap energy difference. In addition, the competition between different nonlinear optical effects, such as multiphoton-induced luminescence and second harmonic generation, is clearly revealed and is manifested in the dependence of the nonlinear optical signal on excitation intensity in this investigation. And also, the competition mechanism is preliminary studied in this paper.
Radiation induced parasitic effect in silicon-on-insulator metal-oxide-semiconductor field-effect transistor
Authors: Peng Chao1\2  , En Yun-Fei  , Li Bin  , Lei Zhi-Feng  , Zhang Zhan-Gang  , He Yu-Juan  , Huang Yun  ,   Science and Technology on Reliability Physics and Application of Electronic Component Laboratory, the Fifth Electronics Research Institute of Ministry of Industry and Information Technology, Guangzhou 510610, China;,   School of Electronic and Information Engineering, South China University of Technology, Guangzhou 510006, China
Published: December 2020

In this paper, we investigate the total ionizing dose (TID) effects of silicon-on-isolator (SOI) metal-oxide-semiconductor field-effect transistors (MOSFETs) with different sizes by using 60Co γ-ray. The SOI MOSFET contains a shallow trench isolation (STI) edge parasitic transistor and back gate parasitic transistor, in which STI oxide and buried oxide (BOX) are used as gate oxide, respectively. Although these parasitic effects are minimized by semiconductor device process, the radiation-induced trapped-charge can lead these parasitic effects to strengthen, thereby affecting the electrical characteristics of the main transistor. Since both the STI and BOX are sensitive to the TID effect, we try to distinguish their different influences on SOI devices in this work.The experimental results show that the characteristic degradation of device originates from the radiation-enhanced parasitic effect. The turning-on of the STI parasitic transistor leads the off-state leakage current to exponentially increase with total dose increasing until the off-state leakage reaches a saturation level. The threshold voltage shift observed in the narrow channel device results from the charge sharing in the STI, while the back gate coupling is a dominant contributor to the threshold voltage shift in short channel device. These results are explained by two simple models. The experimental data are consistent with the model calculation results. We can conclude that the smaller size device is more sensitive to TID effect in the same process.Furthermore, the influence of the negative bias at back gate and body on the radiation effect are also studied. The negative bias at back gate will partially neutralize the effect of positive trapped-charge in STI and that in BOX, thus suppressing the turning-on of STI parasitic transistor and the back gate coupling. The parasitic transistors share a common body region with the main transistor. So exerting body negative bias can increase the threshold voltage of the parasitic transistor, thereby restraining the TID effect. The experimental and simulation results show that the adjustment of the threshold voltage of parasitic transistor by body negative bias is limited due to the thin body region. The modulation of body negative bias in depletion region is more obvious in back gate parasitic transistor than in STI parasitic transistor. The weakening of parasitic conduction in the back channel is more noticeable than at STI sidewall under a body negative bias.
Observation of hydrodynamic phenomena of plasma interaction in hohlraums
Authors: Li Hang  , Yang Dong  , Li San-Wei  , Kuang Long-Yu  , Li Li-Ling  , Yuan Zheng  , Zhang Hai-Ying  , Yu Rui-Zhen  , Yang Zhi-Wen  , Chen Tao  , Cao Zhu-Rong  , Pu Yu-Dong  , Miao Wen-Yong  , Wang Feng  , Yang Jia-Min  , Jiang Shao-En  , Ding Yong-Kun  , Hu Guang-Yue  , Zheng Jian  ,   1. Laser Fusion Research Center, Chinese Academy of Engineering Physics, Mianyang 621900, China;,   2. Basic Plasma Key Laboratory of Chinese Academy of Sciences, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

In indirect-drive inertial confinement fusion (ICF), laser beams are injected into a high-Z hohlraum and the laser energy is converted into intense X-ray radiation, which ablates a capsule located in the center of the hohlraum, and thus making it implode. To achieve high implosion efficiency, it is required that the hohlraum inner wall plasma movement, which will block further laser injection through the laser entrance hole (LEH), be suppressed. Evolution of hohlraum radiation nonuniformity caused by the plasma movement will result in implosion asymmetry which will prevent the ignition from happening. Therefore it is very important to study the hydrodynamic movement of high-Z plasma in ICF experiment.
In ICF hohlraum, various plasmas of laser spots, corona, radiation ablation and jets move in different ways driven by laser ablation and X-ray radiation ablation, which is hard to observe and study. An X-ray dual spectral band time-resolved imaging method is developed to clearly observe the motion of various plasmas in hohlraum. Based on the time-resolved X-ray framing camera, using the typical gold plasma emission spectrum, the gold microstrip MCP response spectrum, and the 1.5 μm Al or 3 μm Ti filter transmittance spectrum, the two narrow-band X-ray peaks at 0.8 keV and 2.5 keV are highlighted. The 0.8 keV X-ray shows the Planck spectrum of gold plasma, and 2.5 keV X-ray indicates the M-band of gold plasma.
In the vacuum hohlraum, jets are observed clearly, which are verified to be 4 times the sound speed experimentally. The generation mechanism of gold plasma jets in the ICF hohlraum is mainly due to collision rather than magnetic field, because it is estimated that thermal pressure is much bigger than magnetic pressure. In the gas-filled hohlraum, low-Z C5H12 gas can effectively eliminate high-Z gold jets and suppress the high-Z gold coronal plasma movement. The interface between the low-Z and high-Z substance is observed clearly, and gold plasma is accumulated obviously in the later period at the interface. Moreover, spike and filamentous structure occur at the interface between the two substances, which is probably caused by the hydrodynamic instability. The 0.8 keV rather than 2.5 keV X-ray is observed around inner wall, which originates from the low-temperature plasma driven by radiation ablation and is predicted by simulation code. Furthermore, the pressure balance between the two substances and the density steepness at the interface are also analyzed.
Image enhancement based on multi-guided filtering
Authors: Liu Jie  , Zhang Jian-Xun  , Dai Yu  ,   1. College of Computer and Control Engineering, Nankai University, Tianjin 300071, China;,   2. Institute of Robotics and Automatic Information System, Nankai University, Tianjin 300071, China
Published: December 2020

Image enhancement, as a basic image proicessing technique, contains much research content, such as enhance contrast, image restoration, noise reduction, image sharpening, distortion correction, etc. The purpose of image enhancement is to effectively highlight the useful information in target image and suppress noise as well. The conventional image enhancement methods are always powerless to tackle the complicated gradient distributions in natural images, and they are also difficult to retain the information about edges accurately. For improving the status of over-smoothing on boundaries, we propose an image enhancement method based on multi-guided filtering. We first synthetically analyze the property of joint filtering and propose the general image optimization model in which the variable parameter is filter kernel. Different filter kernel in the optimization model above generate different filtering method. That is to say, we can use this model to describe the image enhancement problems. The existing joint filters can be regarded as close form solutions of the optimization model above. Inspired by ensemble theory, we use multiple guided images in joint filtering instead of a single guided image to make full use of structure information. By doing so, the image enhancement based on multi-guided filtering can obtain more accurate filtering results. In order to keep the consistency among the multiple filtering outputs of multi-guided filtering method, we add a regularization term into a general image optimization model. We also take into consideration the consistency of pixels in the same image. The experimental results about the noise reduction and image enhancement show that the image enhancement based on multi-guided filtering can give rise to significant outputs. The peak-signal-to-noise ratio of output image of proposed method is higher than those from the traditional image enhancement methods. Therefore, the image enhancement based on multi-guided filtering can improve the quality of digital images efficiently and effectively. This provides a good precondition for subsequent image processing steps and has a prospect of very wide application.
In-situ measurement of diamagnetic response of potassium-adsorbed multi-layer FeSe ultrathin films on SrTiO3(001) substrate
Authors: Chen Chuan-Ting  , Yao Gang  , Duan Ming-Chao  , Guan Dan-Dan  , Li Yao-Yi  , Zheng Hao  , Wang Shi-Yong  , Liu Can-Hua  , Jia Jin-Feng  ,   Key Laboratory of Artificial Structures and Quantum Control(Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China;,   Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
Published: December 2020

A single-unit-cell layer FeSe ultrathin film grown on SrTiO3(001) substrate exhibits remarkable high-temperature superconductivity, which has aroused intensive research interest. Electron transfer from the substrate to the FeSe layer has been shown to play an indispensable role in enhancing the extraordinary superconductivity. With this idea, researchers have tried to search for new high-temperature superconducting material systems including K-adsorbed multi-layer FeSe ultrathin films, on which superconducting-like energy gaps have been observed with scanning tunneling spectroscopy and photoelectron spectroscopy. However, the high-temperature superconductivity of the multi-layer FeSe ultrathin films has not yet been confirmed by directly observing the zero resistance or Meissner effect. With a self-developed multi-functional scanning tunneling microscope (STM+), which enables not only usual STM functionality, but also in situ two-coil mutual inductance measurement, we successfully observe the diamagnetic response of a K-adsorbed multilayer FeSe ultrathin film grown on a SrTiO3(001) substrate, and thus determine its transition temperature to be 23.9 K. Moreover, we calculate the penetration depth of the film from the measured results and find that its low-temperature behavior exhibits a quadratic variation, which strongly indicates that the order parameter of the superconducting K-adsorbed multi-layer FeSe ultrathin film has an S± pairing symmetry.
Effect of edge inclination of single crystal diamond on homoepitaxial growth
Authors: Geng Chuan-Wen  , Xia Yu-Hao  , Zhao Hong-Yang  , Fu Qiu-Ming  , Ma Zhi-Bin  ,   Provincial Key Laboratory of Plasma Chemistry and Advanced Materials, School of Materials Science and Engineering, Wuhan Institute of Technology, Wuhan 430074, China
Published: December 2020

Polycrystalline diamond is easy to appear at the edge of single crystal diamond grown by homogeneous epitaxial growth, which makes it difficult to enlarge the two-dimensional surface area of single crystal diamond. In this study, the microwave plasma chemical vapor deposition (MPCVD) is used, the edge of the single crystal diamond (100) crystal face is finely cut and polished to form an inclined surface which is different from the (100) crystal plane at different angles. After being pretreatment, homogeneous epitaxial growth is carried out in a double-substrate waveguide-type MPCVD device with CH4/H2 reaction gas. At the same time, the variation of plasma near the inclined plane of (100) crystal edge is analyzed by optical emission spectroscopy to study the effect of the tilting on the growth of the diamond edge. The experimental results show that the angle of the inclined surface of the edge has an effect on the quality of single crystal epitaxial growth of the edge. As the angle of the inclined surface of the single crystal diamond increases, the quantity of edge polycrystalline diamond first decreases and then increases. At an oblique angle of 3.8°, the edge exhibits complete single crystal epitaxial growth characteristics, which conduces to expand the surface area of single crystal diamond. According to the analysis, the inclined surface at different angle changes the surrounding electric field strength and plasma density of the edge, resulting in the change of carbon-containing precursors reaching the surface of the substrate. When the concentration of carbon-containing precursors on the inclined step surface is higher than the growth threshold of layered step, excessive carbon-containing precursors will constantly collide with each other and accumulate to form polycrystalline diamond on the step. When the concentration is lower than the growth threshold of layered step, the carbon-containing precursors on the surface of the substrate will be laid out to form a layered step. Therefore, the edge effect during the growth of single crystal diamond is weakened at the tilt angle of 3.8°, which leads the concentration of carbon-containing precursors on the inclined step surface to be lower than the growth threshold of layered step.
Model and applications of transition metal dichalcogenides based compliant substrate epitaxy system
Authors: Zhou Yu-Zhi  ,   1. Institute of Applied Physics and Computational Mathematics, Beijing 100094, China;,   2. Deng JiaXian Innovation Center, Institute of Applied Physics and Computational Mathematics, Beijing 100088, China;,   3. CAEP Software Center for High Performance Numerical Simulation, Beijing 100088, China
Published: December 2020

The concept of compliant substrate epitaxy was first proposed by the scientists engaged in crystal growth in the early 1990s. The core idea is to take advantage of such an ultra-thin substrate that the film and the substrate generate strain together to relieve the lattice mismatch during the epitaxy growth. The quality of the epitaxial film is improved due to the reduction of the mismatch dislocation density. However, the preparation of the artificial ultra-thin substrate with good quality requires rather complicated fabrication process. On the other hand, many transition metal dichalcogenides naturally form the compliant substrates, due to their layered structure and weak van der Waals interlayer interaction. In this paper, we introduce the transition metal dichalcogenides based compliant substrate epitaxy model and relevant applications. Through combining density functional theory, linear elasticity theory and dislocation theory, we introduce the model comprehensively by using the Au-MoS2 as a prototypical example. And we explain the experimental results of Au growing on MoS2 from the early transition electron microscopy. In addition, we introduce the experimental work related to the model, especially the Au-mediated exfoliation of large, monolayer and high-quality MoS2. Future directions and relevant important problems to be solved are also discussed.
Bénard-von Kármán vortex street in dipolar Bose-Einstein condensate trapped by square-like potential
Authors: Xi Zhong-Hong  , Yang Xue-Ying  , Tang Na  , Song Lin  , Li Xiao-Lin  , Shi Yu-Ren  ,   1. College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China;,   2. Key Laboratory of Atomic and Molecular Physics and Functional Material of Gansu Province, Lanzhou 730070, China;,   3. College of Physics and Hydropower Engineering, Gansu Normal University for Nationalities, Hezuo 747000, China
Published: December 2020

Bénard-von Kármán vortex street in dipolar Bose-Einstein Condensate (BEC) trapped by a square-like potential is investigated numerically. In the frame of mean-field theory, the nonlinear dynamic of the dipolar BEC can be described by the so-called two-dimensional Gross-Pitaevskii (GP) equation with long-range interaction. In this paper, we only consider the case that all the dipoles are polarized along the z-axis, which is perpendicular to the plane of disc-shaped BEC. Firstly, the stationary state of the BEC is obtained by the imaginary-time propagation approach. Secondly, the nonlinear dynamic of the BEC, when a moving Gaussian potential exists in such a system, is numerically investigated by the time-splitting Fourier spectral method, in which the stationary state obtained before is set to be the initial state. The results show that when the velocity of the cylindrical obstacle potential reaches a critical value, which depends on interaction strength and the shape of the potential, the vortex-antivortex pairs will be generated alternately in the super-flow behind the obstacle potential. However, in general, such a vortex-antivortex pair structure is dynamically unstable. When the velocity of the obstacle potential increases to a certain value and for a suitable potential width, a stable vortex structure called Bénard-von Kármán vortex street will be formed. While this phenomenon emerges, the vortices in pairs created by the obstacle potential have the same circulation. The pairs with opposite circulations are alternately released from the moving obstacle potential. For larger potential width and velocity, the shedding pattern becomes irregular. We also numerically investigate the effects of the dipole interaction strength, the width and the velocity of the obstacle potential on the vortex structures arising in the wake flow. As a result, the phase graph is presented by lots of numerical calculations for a group of given physical parameters. Thirdly, the drag force on the obstacle potential is also calculated and the mechanical mechanism of vortex pair is analyzed. Finally, we discuss how to find the phenomenon of Bénard-von Kármán vortex street in dipolar BEC experimentally.
Multiple ionization effect of Au induced by different ions
Authors: Liang Chang-Hui  , Zhang Xiao-An  , Li Yao-Zong  , Zhao Yong-Tao  , Zhou Xian-Ming  , Wang Xing  , Mei Ce-Xiang  , Xiao Guo-Qing  ,   1. Ion Beam and Optical Physical Joint Laboratory of Xianyang Normal University and Institute of Modern Physics, Chinese Academy of Sciences, Xianyang 712000, China;,   2. School of Science, Xi'an Jiaotong University, Xi'an 710049, China;,   3. Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
Published: December 2020

We report the experimental data of characteristic X-ray spectra produced by the impact of H+, Ar8+, Ar12+, Kr13+ and Eu20+ ions with different kinetic energies on Au surface in the National Laboratory of Heavy Ion Research Facility in Lanzhou, China. The energy shifts of X-ray spectra are analyzed and the ratio of X-ray yield is calculated. The results show that H+ can excite the characteristic X-ray spectra of Mζ and Mα of Au, while Ar8+, Ar12+, Kr13+ and Eu20+ can excite the characteristic X-ray spectra of Mζ, Mα, Mγ and Mδ of Au, because the inner shells of target atom are multiply ionized by heavy ions impact, so that the relative intensity ratio of the X-rays changes when the heavy ions are incident. There are different energy shifts of Au M X-ray due to multiple ionization effect in collision. When the ion incident energy is lower, the degree of multiple ionization of the inner shells of the target atom is almost independent of the incident energy, when the ion energy is higher, the degree of multiple ionization increases with incident ion energy increasing. At the same time, the degree of multiple ionization also depends on the number of holes in the outer shell of the ion and its atomic number. That the ratio of X-ray yield increases with the increase of the atomic number of the incident ion further indicates that the degree of multiple ionization increases with atomic number of the incident ion increasing. The multiple ionization and electron configuration of the inner shells of the atom can be determined by the energy shift and spectra broadening. These measurements provide basic data for further studying the multiple ionization mechanism of the inner shells of the atom. But due to the limitation of the resolution of the detector, the spectral broadening data cannot be measured. It is necessary to use a higher-resolution detector to further study the multi-ionization effect of the inner shells of the atom.
Single-molecule electroluminescence and its relevant latest progress
Authors: Zhang Yao  , Zhang Yang  , Dong Zhen-Chao  ,   Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

Research on the interaction and interconversion between electrons and photons on an individual molecular scale can provide scientific basis for the future developing of information and energy technology. Scanning tunneling microscope(STM) can offer abilities beyond atomic-resolution imaging and manipulation, and its highly localized tunneling electrons can also be used for exciting the molecules inside the tunnel junction, generating molecule-specific light emission, and thus enabling the investigation of molecular optoelectronic behavior in local nano-environment. In this paper, we present an overview of our recent research progress related to the single-molecule electroluminescence of zinc phthalocyanine (ZnPc) molecules. First, we demonstrate the realization of single-molecule electroluminescence from an isolated ZnPc by adopting a combined strategy of both efficient electronic decoupling and nanocavity plasmonic enhancement. By further combining the photon correlation measurements via the Hanbury-Brown-Twiss interferometry with STM induced luminescence technique, we demonstrate and confirm the single-photon emission nature of such an electrically driven single-molecule electroluminescence. Second, by developing the sub-nanometer resolved electroluminescence imaging technique, we demonstrate the real-space visualization of the coherent intermolecular dipole-dipole coupling of an artificially constructed non-bonded ZnPc dimer. By mapping the spatial distribution of the photon yield for the excitonic coupling in a well-defined molecular architecture, we can reveal the local optical response of the system and the dependence of the local optical response on the relative orientation and phase of the transition dipoles of the individual molecules in the dimer. Third, by using a single molecular emitter as a distinctive optical probe to coherently couple with the highly confined plasmonic nanocavity, we demonstrate the Fano resonance and photonic Lamb shift at a single-molecule level. The ability to spatially control the single-molecule Fano resonance with sub-nanometer precision can reveal the coherent and highly confined nature of the broadband nanocavity plasmon, as well as the coupling strength and the anisotropy of the field-matter interaction. These results not only shed light on the fabrication of electrically driven nano-emitters and single-photon sources, but also open up a new avenue to the study of intermolecular energy transfer, field-matter interaction, and molecular optoelectronics, all at the single-molecule level.
A noval method of constructing shallow water sound speed profile based on dynamic characteristic of internal tides
Authors: Qu Ke , Piao Sheng-Chun , Zhu Feng-Qin ,   Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China,   Key Laboratory of Marine Information Acquisition and Security (Harbin Engineering University), Ministry of Industry and Information Technology, Harbin 150001, China,   College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China,   Guangdong Ocean University, Guangdong Key Laboratory of Coastal Ocean Variation and Disaster Prediction, Zhanjiang 524088, China
Published: December 2020

In order to provide constraint to the number of inversion parameters, sound speed profile is often modeled by empirical orthogonal functions (EOFs). However, the EOF method, which is dependent on the sample data, is often difficult to apply due to insufficient real-time in-situ measurements. In this paper, we present a novel basis for reconstructing the sound speed profile, which can be obtained by using historical data without real-time sample. By deducing the dynamic equations and the state function of water particle, the hydrodynamic mode bases (HMBs) can be calculated from historical data without real-time in-situ measurement, and a method of constructing the sound speed profile is established by using the dynamic characteristics of seawater. The use of the World Ocean Atlas 2013 (WOA13) can obtain the seasonal profiles of temperature and salinity, and then the HMB which represents the dynamic characteristic of internal tides is obtained and analyzed. Unlike EOF, the HMB and its projection coefficients are directly related to the sea dynamic features and have a more explicit physical meaning. According to the orthogonality analysis of hydrodynamic mode, the first-order coefficient can be used to describe the depth change of sound speed iso-lines and the second-order coefficient can be used to describe the change of sound speed gradient. Based on the conductance-temperature-depth profiles and broadband data from underwater explosion collected in the East China Sea experiment of the Asian Seas International Acoustic Experiment, the HMB is tested and compared with the EOF in the sound speed profile reconstruction and matched field tomography. The results show that the sound speed profile in shallow water area can be expressed by the HMB with proper precision. By means of the conventional matched field tomography, the valid sound speed profile can also be obtained in the form of HMB coefficients. The result of transmission loss prediction and tomography from HMB are as good as those from EOF, while the HMB has less dependent on real-time in-situ measurement. The HMB is easy to obtain and closely related to the physical characteristics of seawater, it can be used as an efficient alternative to EOF for monitoring the marine dynamic phenomena in sea areas with insufficient real-time in-situ measurement.
Effects of radial electric field on confinement of high energy particles in advanced fusion mirror reactor
Authors: Shi Li-Ming , Wu Xue-Ke , Wan Di , Li Hui-Dong , Fan Qun-Chao , Wang Zhong-Tian , Feng Hao , Wang Zhan-Hui , Ma Jie ,   Key Laboratory of High Performance Scientific Computation, School of Science, Xihua University, Chengdu 610039, China,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Laser Spectroscopy Laboratory, College of Physics and Electronics Engineering, Shanxi University, Taiyuan 030006, China
Published: December 2020

The radial electric field Er in a magnetic confined machine, such as the compact fusion reactor (CFR), the field-reserved configuration (FRC), and the tokamak, plays an essential role in affecting the confinement properties of the high energy particles. The parallel velocities of the high energy particles will be accelerated or decelerated by applying a radial electric field, which could change the loss rate of the high energy particles in the magnetic confined machines. Unlike the fourth-order Runge-Kutta method RK4, the recently-developed Boris method can strictly preserve energy conservation of the high energy particles in the case without radial electric field. The orbit of high energy α particle in compact fusion reactor (CFR) is simulated by solving the equations of motion numerically with the Boris Algorithm. The effect of radial electric field on the orbit of the high energy α particle is investigated and the confinement of plasma in different radial electric fields in the CFR machine is studied in the present paper. By changing the strength of the radical electric field and the particles' radical locations in the middle plane of the CFR configuration, the confinement property of the high energy α particle is studied. The numerical results indicate that both the positive radial electric field and negative electric field can significantly affect the confinement of the high energy α particle. When the radial electric field is increased to a threshold, the high energy α particle could be confined in the central region of the CFR machine for a long enough time. The threshold of the radial electric field depends on the initial parameters of the confined particle. Systematic investigations of the radical electronic field effect will conduce to greatly improving the performance of the designed CFR machines.
Resonance characteristics of independently tuned dual Fano of metal-dielectric-metal waveguide coupling square cavity with double baffles
Authors: Chen Ying , Cao Jing-Gang , Xie Jin-Chao , Gao Xin-Bei , Xu Yang-Mei , Li Shao-Hua ,   Hebei Province Key Laboratory of Test/Measurement Technology and Instrument, School of Electrical Engineering, Yanshan University, Qinhuangdao 066004, China,   Hebei Sailhero Environmental Protection Hi-tech Co., Ltd., Shijiazhuang 050000, China
Published: December 2020

A metal-dielectric-metal (MDM) waveguide coupling two square cavities with double baffles is designed in this paper based on the transmission characteristics of surface plasmon polaritons in subwavelength structure. The independent tuning of the dual Fano resonance is implemented by the interference between the wide-spectrum mode generated by the F-P (Fabry Perot) cavity and the two narrow-spectrum modes generated by the two square cavities. Moreover, the independent tuning of the dual Fano resonance can be achieved by changing the sizes of the two square cavities and filling medium. The coupled-mode theory (CMT) is adopted to analyze the transmission characteristics of the dual Fano resonance. The structure is simulated by the finite element method to quantitatively analyze the influence of structural parameters on the independent tuning of the dual Fano resonance and the refractive index sensing characteristics. The proposed sensor yields respectively sensitivity higher than 1020 nm/RIU and 1120 nm/RIU and a figure of merit of 3.29 × 105 and 1.17 × 106 by optimizing the geometry parameters. This structure provides an effective theoretical reference in the optical integration of ultra-fast optical switches, multi-function high-sensitivity sensors and slow-light devices.
Analytical theory on electromagnetic shielding effectiveness of infinite conductor plate with periodic aperture array under plane wave illumination
Authors: Bai Wan-Xin , Li Tian-Le , Guo An-Qi , Cheng Rui-Qi , Jiao Chong-Qing ,   State Key Laboratory of Alternate Elelctrical Power System with Renewable Energy Sources, North China Elelctric Power University, Beijing 102206, China
Published: December 2020

Penetration of a plane electromagnetic wave through the apertures on a perfectly conducting flat plate is a classical electromagnetic problem. In some practical applications like electromagnetic shielding, where only the fields far from the apertures are concerned and the aperture sizes are small compared with a wavelength, the role of apertures can be represented by the equivalent electric and magnetic dipoles located in the centers of the apertures. In principle, the penetration field can be expressed as the superposition of the radiation fields of the dipoles. However, the direct superposition leads to a double series with complex form and poor convergence. On the other hand, this problem may also be solved by full wave numerical simulations. Even so, finding analytical solutions is still desirable considering that it is clear in physical significance and easy to implement. In this paper, the analytical formula of the penetration fields are derived for both TE and TM polarization mode with different angles of incidence. The derivation is carried out firstly by averagely distributing each dipole moment within each periodic unit. As a result, the dipole array is replaced with a flat sheet with uniform magnetization and polarization intensity. Then, the equivalent surface current and charge distributions are obtained directly from the polarization intensity. Finally, the penetration fields are treated as the radiation fields of the surface sources. It is shown that the amplitude of the penetration field is proportional to aperture magnetic polarization coefficient and wave frequency, and it is inversely proportional to the area of a periodic unit. In regard to the effect of the incidence angle, the amplitude of the penetration field is proportional to the cosine of the incidence angle for TE polarization. However, for the TM polarization, the relationship is a little complicated due to the coexistence of electric and magnetic dipoles: the field is not rigorously inversely proportional to the cosine of the incidence angle due to the existence of a correction term involving both the polarization coefficient and the sine of the angle. The formula is used to calculate the shielding effectiveness for several different aperture shapes and different incidence angles. The results are in good agreement with those from the full wave simulation software.
Analysis on complexity of optical variability based on approximate entropy in Sloan digital sky survey quasars
Authors: Tang Jie , Liu Xiao-Qin ,   School of Physics and Telecommunication Engineering, Shaanxi University of Technology, Hanzhong 723001, China,   Department of Pharmaceutical and Medical Technology, Hanzhong Vocational and Technical College, Hanzhong 723002, China
Published: December 2020

Variability is one of the most important observational features of quasars, and it is still not clear that the different quasars show different characteristic variability patterns. The optical variability of quasar is very complex, and optical variability has the non-linear characteristic of complex system. In this paper, the approximate entropy method is employed to analyze the complexities of variability in the Sloan digital sky survey (SDSS) stripe 82 quasars. Firstly, in order to show that the approximate entropy method has the effective ability to distinguish the different types of time sequences, the approximate entropy of periodic sequence, noise sequence, chaotic sequence and their mixed sequences are calculated by using the analog signals. The approximate entropy method proves to be an effective method to identify different types of time sequences. Then, we present the approximate entropy of optical variability of spectroscopically-confirmed quasars from the SDSS data release 7 spectroscopic catalog, and their complexities are analyzed. The results show that the maximum approximate entropy of quasars’ optical variability is only 0.58. The complexity of quasars’ optical variability is between the complexities of periodic sequence and white noise sequence. For nearly half of the samples, the complexities of their optical variability are basically consistent with the complexity of chaotic sequence. Quasars’ optical variability is neither completely periodic nor completely stochastic.
Broadband terahertz vortex beam generation based on metasurface of double-split resonant rings
Authors: Zhou Lu , Zhao Guo-Zhong , Li Xiao-Nan ,   Department of Physics, Capital Normal University, Beijing 100048, China,   Beijing Advanced Innovation Center for Imaging Theory and Technology, Beijing 100048, China,   Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Beijing 100048, China
Published: December 2020

Terahertz vortex beam generators have potential applications in optical micro-manipulation, terahertz communications and many other fields. A broadband vortex beam generator in a terahertz frequency range is proposed based on the metasurface of double-split resonant rings’ array. The designed structure consists of two layers, i.e., the top layer, which is a metasurface of double-split resonant rings, and the bottom layer, which is the dielectric layer of polymide. The numerical simulation of the cell structure array is performed by using the CST microwave studio. In order to obtain the best performance, the structure parameters of metasurface are continuously optimized and a set of optimal geometric parameters is finally determined. The simulation results show that the circularly polarized incident light can be converted into corresponding cross-polarized transmitted light. By rotating the metal resonant ring on the top layer, the cross-polarized transmitted light can be controlled to have the same amplitude and correspondingly different phases. The relationship between the phase change and the angle of rotation conforms to the P-B phase principle. These cell structures are arranged according to a specific order and can form the vortex phase plates for generating the vortex beams with different topological charges. Taking the topological charge numbers 1 and 2 for example, two kinds of vortex phase plates are designed. The characteristics of the circularly cross-polarized vortex beams generated by a circularly polarized wave perpendicularly incident on the vortex phase plates are numerically analyzed. The results show that the ideal vortex beams with different topological charge numbers are generated. The characteristics of vortex beams appear to be consistent with those theoretical results. Moreover, the vortex beams can be generated in a frequency range from 1.39 THz to 1.91 THz. The operating bandwidth is much wider than the previously obtained result of the transmission terahertz vortex phase plates. The transmission is higher than 20%, and the maximum value of transmission can reach 24%, which is close to the theoretical limit value of the single-layered transmission-type metasurface. This work provides a reference for generating the terahertz vortex beams based on metasurface. It is expected to possess a practical application in generating the device of terahertz vortex beam.