bluuebunny/crossref_metadata_2025 huggingface dataset:
Luminescent properties of Er3+/Yb3+ co-doped oxyfluoride glass ceramic microsphere with the tapered fiber-microsphere coupling system
Authors: Huang Jing  , Huang Yan-Tang  , Wu Tian-Jiao  , Huang Yu  , Zhang Pei-Jin  , Guo Chang-Lei  ,   College of Physics and Information Engineering, Fuzhou University, Fuzhou 350108, China;,   School of Information Science and Engineering, Xiamen University, Xiamen 361005, China
Published: December 2020

We prepare Er3+/Yb3+ co-doped oxyfluoride glass ceramic samples by high temperature calcination method (41.2SiO2-29.4Al2O3-17.6Na2CO3-11.8LaF3-0.5ErF3-2.5 YbF3), and also fabricate transparent microspheres each with a handle. We propose a new method of studying the luminescent properties of Er3+/Yb3+ co-doped oxyfluoride glass ceramic with the tapered fiber-microsphere coupling system. The method has characteristics such as low excitation optical power, easy preparation and testing. We couple the 976 nm laser into the microspheres with the coupler of optical tapered fiber, then the fluorescence and laser are connected to spectrum analyzer with the optical tapered fiber. The strong up-conversion fluorescences at 522, 545 and 657 nm are obtained, and the laser oscillation spectra generated by Er3+ ions at 1562 nm are also measured. The up-conversion luminescence mechanism of Er3+, the mechanism of high luminescence efficiency in Er3+/Yb3+ co-doped oxyfluoride glass ceramic microsphere, and the mechanism of higher laser oscillation threshold in the oxyfluoride glass ceramic microsphere than in the SiO2 matrix microsphere are all analyzed.
Lubricant transfer mechanism and process between slider and disk
Authors: Pan Deng  , Yan Hui  , Jiang Hong-Yuan  ,   School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

The increasing of areal density of hard disk drives promotes the decreasing of the slider flying height. Lubricant transfer between slider and disk, caused by reducing slider flying height, plays an important role in affecting slider flying stability. In this study, the improved coarse-grained, bead-spring model is used to investigate the mechanism of lubricant transfer between slider and disk by molecular dynamics simulation. The effects of lubricant thickness on disk surface, lubricant type, and local temperature difference on the slider surface on lubricant transfer are studied. We observe that the amount of lubricant transferred to the slider sharply increases with the increase of lubricant thickness value on the disk surface. Increasing the number of hydroxyl groups in an individual lubricant molecule can greatly reduce the volume of the lubricant transferred to the slider. In addition, the local temperature difference on the slider surface can increase the volume of lubricant transferred to slider. What is more, the increasing of the number of hydroxyl groups contained in an individual molecule can considerably improve the influence of the local temperature difference on the lubricant transfer between slider and disk.
Faultprevention technique of controlling redundant routes into sleeping based on health degree
Authors: Song Jia  , Luo Qing-Hua  , Peng Xi-Yuan  ,   Automatic Test and Control Institute, Harbin Institute of Technology, Harbin 150080, China
Published: December 2020

Wireless sensor networks (WSNs) are widely used in various measurement fields. However, their nodes are characteristic of constrained energy supply, limited hardware resource, large number of nodes, self-organization and dynamic topology, which make networks prone to malfunction. As a result, high reliability and low fault are the basic requirements of WSNs. To prevent too many active nodes and wasting more energy in redundant routing method for WSNs, a fault-prevention technique of controlling redundant routes into sleeping based on health degree is proposed. This technique uses sink node to collect the residual energy of each node, and to calculate energy consumption degree parameter and health degree parameter, and adopts a-star algorithm to control the redundant routes into sleeping mode. The simulation results of NS2 and actual node experimental results show that the present health degree based technique can balance the networks energy consumption and prolong the network lifetime significantly.
Net sensitivity for open and short model based on layout optimization
Authors: Wang Jun-Ping  , Qi Su-Yang  , Liu Shi-Gang  ,   School of Communication Engineering, Xidian University, Xi'an 710071, China;,   School of Microelectronics, Xidian University, Xi'an 710071, China
Published: December 2020

To maintain and improve the manufacturing yield of integrated circuit becomes a research hot spot in optimized circuit design and manufacturing technology, with the expansion of the integrated circuit scale and shrinkage of devices feature sizes. In order to reduce the yield loss caused by redundancy material defect and missing material defect, choosing a preferentially optimizing net becomes an important subject in the process of layout optimization. Layout optimization is an effective way to increase integrated circuit yield which is based on the critical area diminution. In the paper presented is a new kind of short circuit and open circuit sensitivity model, which is net-based and not only reflects the size of the short critical area between the single net and the nets around it, but also possesses open critical area. Because this model is based on single net and includes the information about the surrounding net, the short critical area between the single net and the net around it and the open critical area of its own can be reduced at the same time. In this way, the efficiency of layout optimization is enhanced. According to the experimental results, this sensitivity model can be used to choose the position for optimization.
Objective quantification of the water vapor path influencing precipitation in North China in summer
Authors: Ye Min  , Wu Yong-Ping  , Zhou Jie  , Wu Hao  , Tu Gang  ,   College of Physical Science and Technology, Yangzhou University, Yangzhou 225002, China;,   Laboratory for Middle-High Latitude Circulation and East Asian Monsoon Research, Jilin Institute of Meteorological Science, Changchun 130062, China
Published: December 2020

Based on the data of daily wind and specific humidity, surface pressure from NCEP/NCAR and the data of monthly average precipitation of 160 stations in China from National Climate Center, and according to correlation filed of precipitation with water vapor transport, the water vapor transport which is perpendicular to a cross section is defined as an objective indicator of vapor transport path, and six mainly vapor transport paths are found for North China. The results show that the confluent water vapor path, the water vapor path which outputs to the east, the water vapor path which inputs from the west and the water vapor path from the South China Sea have obvious inter-decadal variation, and the inter-decadal variation is basically the same as the inter-decadal variation of summer precipitation in North China. It is found that the water vapor path which outputs to the east and the water vapor path which inputs from the west have main influence on the precipitation in North China on summer though sliding correlation analysis. It is influenced by westerly. Second, the water vapor transport of water vapor path which is from the west of North China increases, at the same time which is from the southeast of the Pacific Ocean is enhanced obviously. Then water vapor which passes through the middle and lower Yangtze river and the South China and directly transports to the North China and Northeast China, results in heavy precipitation of North China and Northeast China and slight precipitation of the south and the Yangtze river. However, the water vapor from the bay of Bengal began to influence the precipitation in North China in summer from 2000.
Simulation of aerolian sand transport with SPH-FVM coupled method
Authors: Chen Fu-Zhen  , Qiang Hong-Fu  , Gao Wei-Ran  ,   No. 601 Xi'an Hi-Tech Institute, Xi'an 710025, China
Published: December 2020

To overcome the drawback of discrete particle model (DPM) and Euler-Euler two-fluid model (TFM) in solving gas-solid two phase flow, a new method called SPH-FVM coupled method is presented, and then it is used to simulate aerolian sand transport problems. Based on a pseudo fluid model the smoothed particle hydrodynamics (SPH) is used to solve the discrete particle phase by tracing the movement of each individual particle, and the finite volume method (FVM) is used to discretize the continuum flow field on the stationary mesh by capturing fluid characteristics. Two phases are coupled through contributions due to the effects of drag, pressure gradient and volume fraction, and then the coupled framework of SPH-FVM is established. The properties of SPH are redesigned to be suited for the discrete phase named SDPH. The relationship between SPH particles and discrete particles is illustrated, and the SPH discrete equations of pseudo fluid are derived. Saltation processes of sands in aerolian sand transport, sand movement under free-air wind, and creeping processes of dune, are simulated; while the particle trajectories, the distribution characteristics of mean downwind velocity, and the changes of gas velocity under the sand reaction are analyzed. Through comparison with experiments, it is shown that the accuracy of the new method is high, and it can also reduce the computational cost. This indicates that the new method can be applied to aerolian sand transport even to other gas-solid multiphase flows.
Effect of output capacitance time-constant on dynamic characteristics of V2-controlled buck converter
Authors: He Sheng-Zhong  , Zhou Guo-Hua  , Xu Jian-Ping  , Wu Song-Rong  , Chen Li  ,   Key Laboratory of Magnetic Suspension Technology and Maglev Vehicle, Ministry of Education, School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China
Published: December 2020

The second-order discrete iterative map model of V2-controlled Buck converter is established, based on which, the bifurcation diagrams with variation of output capacitance and its equivalent series resistance (ESR) are obtained, and the effect of output capacitance time-constant on the dynamic characteristics of V2-controlled Buck converter is investigated. It is found that with gradual reduction of output capacitance time-constant, the V2-controlled Buck converter shows the evolutive dynamic behavior from continuous conduction mode (CCM) period-1 to CCM period-2, CCM period-4, CCM period-8, CCM chaos, and discontinuous conduction mode (DCM) chaos. Jacobi matrix at a fixed point is also derived. According to this, the converter stability is analyzed by using characteristic values and maximum Lyapunov exponent, which validates the correctness of bifurcation analysis. Finally, the simulation and experimental circuits are set up, and the correctness of the theoretical analysis is verified by simulation and experimental results.
Structural, electronic and magnetic properties of ComAln(m+n ≤ 6) clusters
Authors: Qin Jian-Ping  , Liang Rui-Rui  , Lü Jin  , Wu Hai-Shun  ,   School of Chemistry and Materials Science, Shanxi Normal University, Linfen 041004, China
Published: December 2020

Based on DFT-GGA calculations, we investigate systematically the structural, electronic and magnetic properties of ComAln (m+n ≤ 6) clusters. The calculated results show that the most stable structure of ComAln (m+n ≤ 6) clusters prefers to form the maximized number of Co–Al bonds, and is more similar to the most stable structure of pure cobalt clusters. With increasing Al atom numbers, the average magnetism of the clusters is reduced linearly. The magnetism of the ComAl (m=2–5) clusters is 4 μB smaller than that of Com+1 clusters, this agrees well with the recent Stern-Gerlach's experimental result of magnetism detection for a larger size of CoNAlM cluster. Reduction of the magnetism of ComAln clusters is mainly attributed to the non-magnetic Al element embeded and the weakening of spin polarization of the Co atoms.
A time reversal parabolic equation based localization method in evaporation duct
Authors: Feng Ju  , Liao Cheng  , Zhang Qing-Hong  , Sheng Nan  , Zhou Hai-Jing  ,   Institute of Electromagnetics, Southwest Jiaotong University, Chengdu 610031, China;,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: December 2020

Evaporation duct is a multipath environment on the sea, which tends to distort the signals, causes lower localization accuracy or even affects the normal work of radar when using the traditional localization algorithms. This paper presents a localization method in time reversal parabolic equation based on the radiation pattern loading. It could effectively handle the effects of evaporation duct and adaptively compensate the signal distortion, form time reversed waves matched with the propagation environment, and lead to a robust focusing and localization of the target. This method uses multipath effects flexibly to increase the effective aperture of antenna array for super resolution. In addition, it has a good tolerance in element spacing leading to a sparse array configuration which is more practical on the sea and widens its application fields. Simulation results show that the azimuth resolution in evaporation duct with the same aperture array has been improved 2 times more than in the free space by using this method; when 30λ is adopted as the element spacing, the sidelobe levels can be kept below -8.96 dB, so ghost images are effectively suppressed. The proposed method has strong robustness and high accuracy, thus may be useful in many practical applications, such as communication, search and rescue, pre-warning system on the sea, etc.
Experimental study on mode hopping triggered by transient characteristics of saturable absorber gratings in Er-doped fiber ring lasers
Authors: Xiong Shui-Dong  , Xu Pan  , Ma Ming-Xiang  , Hu Zheng-Liang  , Hu Yong-Ming  ,   School of Optoelectronic Science and Technology, National University of Defense Technology, Changsha 410073, China
Published: December 2020

It is preferred to insert a saturable absorber grating in Er-doped fiber ring lasers for obtaining a stable single-longitudinal-mode laser operation; however, mode hopping is hardly avoided in various applications. A new mode hopping mechanism is found by utilizing the interferometric phase-demodulation method to transfer the optical frequency hops to the phase changes in real time. The regular mode hops triggered by fast cavity-length modulation are measured, and the characteristics and the origin of the mode hopping are obtained. Experimental results show that this kind of mode hopping, usually occurring between two neighboring longitudinal modes, may appear near the maximum slope of the modulation curve, and the laser frequency with shift about the space of the longitudinal modes before mode hopping. In addition, both the threshold frequency of the optical frequency modulation and the minimal frequency shift, which can triggered a mode hop, increase with the pump power at the same modulation amplitude. These experimental results can provide the stable operation condition if vibration or modulation exists, and they are helpful for optimal designing of the isolated assemblage or determining the operation range under the modulation condition.
Experimental study on propagation properties of spherically aberrated beams through atmospheric turbulence
Authors: Li Xiao-Qing  , Wang Tao  , Ji Xiao-Ling  ,   Department of Physics, Sichuan Normal University, Chengdu 610068, China;,   College of Physical Science and Technology, Sichuan University, Chengdu 610064, China
Published: December 2020

The propagation properties of spherically aberrated beams through atmospheric turbulence are studied experimentally, where the spherically aberrated beams are generated by a spatial light modulator (SLM), and the atmospheric turbulence is simulated by the rotary random phase plate. It is shown that both for the positive and negative-spherical aberrated beams, the intensity distribution is multi-annular in free space, but it becomes a Gaussian-like profile in turbulence. The positive spherical aberration results in a beam spreading, while the negative spherical aberration causes a beam focusing. The larger the positive spherical aberration, the worse the power in the bucket. However, the dependence of the negative spherical aberration on the power in the bucket is non-monotonic. In particular, the effect of spherical aberration on beam spreading decreases due to turbulence.
Observation and study of precursor infrasound waves emitted before several strong earthquakes
Authors: Yang Yi-Chun  , Guo Quan  , Lü Jun  , Teng Peng-Xiao  ,   Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

Study on the precursor infrasound waves emitted before the occurrence of strong earthquakes has been performed, so as to discover the relationship among position, arriving time, intensity of the infrasound wave and earthquakes. With the special kind of infrasound microphone CASI-ICM-2011, a kind of infrasound waves with frequencies from 0.001 Hz to 0.01 Hz, peak sound pressure level from 50 Pa to 200 Pa, continuous time period from half hour to 4 hours, and propagation speed from 10 m/s to 30 m/s, arising no more than two weeks, was received before a series of earthquakes over Ms6.0 occur. Amplitude of the signal is higher when the earthquake is stronger. In the far field the sensor network was spread in north-east China with automatic data uploading to a central server computer in Beijing. Precursor infrasound waves emitted 4 days before Ms7.0 Lu-san earthquake have been positioned perfectly as a sound cloud map, also the infrasound wave emitted 12 days before Ms7.7 Pakistan earthquake has been positioned. A long-time continuous signal over 8 years has been analysed without a bit gap, showing several effective signals accompanying earthquakes. Law of the infrasound generation has been discussed with a suggestion for the mechanism that the infrasound could be radiated by a large scale surface vibration near one million square kilometers in earthquake developing. Two demonstrative signals received after Ms8.8 Chile earthquake and Yu-shu earthquake were provided to prove this suggestion. The detected signal shows that the infrasound wave arrives accompanying S wave at the same time. One model is provided as a piston sound source to simulate very low frequency infrasound radiated by large surface vibration. All the presented signals in this paper should be useful for precursor information obtained for close earthquake prediction.
Underwater acoustic target classification and auditory feature identification based on dissimilarity evaluation
Authors: Yang Li-Xue  , Chen Ke-An  , Zhang Bing-Rui  , Liang Yong  ,   Department of Environmental Engineering, School of Marine Engineering, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

The purpose of this study is to explore perceptual classification of underwater acoustic targets and auditory features used by human being. First, we design a paired comparison experiment. Then we use the CLASCAL algorithm to model the dissimilarity ratings as a perceptual space, and analyze the properties in three common dimensions, specialties, 3 subjects' latent classes and their roles in target perceptual classification. Finally, based on the gammatone filterbank, we find some auditory features that can effectively underlie 3 common dimensions and beat properties, so as to use them to construct a binary decision tree to classify some new samples; thus we can provide some guidance about how to use these features in practical applications.
Constant-excitation caused response in a class of parametrically excited systems with two degrees of freedom
Authors: Hou Lei  , Chen Yu-Shu  , Li Zhong-Gang  ,   School of Astronautics, Harbin Institute of Technology, Harbin 150001, China;,   School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

This paper focuses on the response in parametrically excited systems caused by constant excitation. Taking a maneuvering cracked rotor system as an example, we formulate the vibration equations with two degrees of freedom, in which the breathing of the crack constitutes parametric excitation, and the maneuver load of the maneuvering rotor is simplified as a constant excitation, and it is supposed that the rotor system is balanced without the consideration of eccentricity. By solving the equations with harmonic balance method, each order of harmonic components related with the rotating speed and the constant excitation is derived to analyze the corresponding resonance of the system. Results show that the constant excitation plays a decisive role in the parametrically excited primary and super-harmonic resonances of the system that agrees with the gravity dominance in common cracked rotor systems without maneuver load. And the stronger the constant excitation, the greater the resonances. Moreover, the orientation of the constant excitation makes a great impact on the parametrically excited primary resonance, but does not have a significant effect on the parametrically excited super-harmonic resonances. Results implies that constant excitation may increase the parametrically excited super-harmonic resonances of the cracked rotor systems, which is disadvantageous to the operating of the system. From another point of view, however, constant excitation can be used for early detection of crack faults in rotor systems.
Study of the solid-solid phase change in polyalcohol binary systems
Authors: Wang Xiao-Wu  , Xu Hai-Hong  ,   Department of Physics, South China University of Technology, Guangzhou 510640, China
Published: December 2020

Many polyalcohols can change from one crystal structure to another in solid state at certain temperatures. A lot of papers reported their phase transition enthalpy, transition temperatures, and phase diagrams. This paper investigates the relation between transition enthalpy and hydrogen bond for the NPG (Neopentylglycol) and PE (Pentaerythritol) binary system on the basis of infrared spectrum experimental data and calorimetric results. It is shown that in the binary system some of the associated hydrogen bonds become weaker and are easier to break up. When temperature rises to a certain value, the hydrogen bonds, which retain in the course of phase transformation from the phase of NPG in PE to the plastic phase, will break up and form the second endothermal peak on the calorimetric curve. The number of retained hydrogen bonds is larger for the binary system NPG/PE with higher NPG concentration, and as a result, the corresponding enthalpy for the second endothermal peak is larger. While the influence of NPG on the retained hydrogen bonds is larger for binary system NPG/PE with higher NPG concentration, and the corresponding temperature of the second endothermal peak is lower.
Study on the effect of In-2N co-doping at preferential locality on the photoelectric function of ZnO (GGA+U)
Authors: Hou Qing-Yu  , Wu Yun  , Zhao Chun-Wang  ,   College of Sciences, Inner Mongolia University of Technology, Hohhot 010051, China;,   Chemistry department, Inner Mongolia Vocational College of chemistry Engineering, Hohhot 010071, China
Published: December 2020

Nowadays although the study of In-N co-doping effect on the photoelectric function of ZnO is relatively common, all of the In-N co-doped ZnO are of random doping, and the preferential locality doping using the unpolarized structure of ZnO has not been considered so far. Therefore, in this paper, based on the density functional theory using first-principles plane-wave ultrasoft pseudopotential method, the un-doped and the In-N heavily co-doped Zn1-xInxO1-yNy (x= 0.0625, y=0.125) in different orientations have been set up, and band structures and density of states have been calculated respectively. The calculated results show that the In-N atoms along the c-axis orientation has the advantages of high stability over those in the vertical c-axis direction, the band gap is narrower, the effective mass is smaller, the mobility is greater, and the hole concentration is higher, so that the conductivity of ZnO is higher in the In-N heavily co-doped materials. We believe that these results may be helpful to the design and preparation of the conductivity of In-N heavily co-doped ZnO.
Study on electron transfer in a heterogeneous system using a density matrix theory approach
Authors: Wang Lu-Xia  , Chang Kai-Nan  ,   Department of physics, University of Science and Technology Beijing, Beijing 100083, China
Published: December 2020

Heterogeneous structure of a molecule semiconductor is the essential part of dye-sensitized solar cell, and the charge injection in it is the key factor of efficiency of solar energy conversion. A heterogeneous system is investigated where a metal nano-particle is used to decorate the structure of dye molecules and TiO2 semiconductor. Photoinduced charge injection dynamics from the molecule dye to TiO2 lattice is studied using density matrix theory. Simulations can account for the semiconductor lattice structure, the reflection of electron wave function in the lattice boundary, as well as the plasmon effect of the metal nano-particles. The compound treatment of density matrix theory and wave function approach is verified to be an efficient way for calculating the plasmon effect in the heterogeneous system. It is found that the plasmon enhancement due to the photoexcitation of metal nano-particles can reach as high as 3 orders of magnitude, which is shown to be an efficient way of improvement of charge conversion. The approach of density matrix theory and wave function treatment makes it possible to simulate the charge transfer in large-scale bulk semiconductor, the result of which is helpful for the theoretical analysis of plasmon enhancement in charge transfer dynamics.
Spectroscopic ellipsometry study of the Zn3N2 films prepared by radio-frequency sputtering
Authors: Chen Ren-Gang  , Deng Jin-Xiang  , Chen Liang  , Kong Le  , Cui Min  , Gao Xue-Fei  , Pang Tian-Qi  , Miao Yi-Ming  ,   College of Applied Sciences, Beijing University of Technology, Beijing 100124, China
Published: December 2020

Zinc nitride (Zn3N2) thin films were deposited on glass substrates by reactive radio-frequency magnetron sputtering from a pure Zn target in nitrogen-argon ambient. X-ray diffraction analysis indicates that the films just after the deposition are polycrystalline with a preferred orientation of (400). With increasing substrate temperature, the grain size in zinc nitride film increases from 26.5 nm (100 ℃) to 33.6 nm (200 ℃), and then decreases to 17.8 nm (300℃). Atomic force microscopy reveals that the film surface morphology is dependent on the substrate temperature. With reflective spectroscopic ellipsometry, the ellipsometric parameters ψ and Δ of Zn3N2 films are measured. Then, a new model for Zn3N2 films is built. With the Tauc-Lorentz dispersion formula, the ellipsometric data are fitted, and both the thickness and optical constants (refractive index and extinction coefficient) of the films are obtained at a wavelength of 430–850 nm. The optical band gap is calculated from the extinction coefficient by using the Tauc formula, and a direct band gap of 1.73–1.79 eV is obtained.
Conformal invariance and Hojman conserved quantity of Lie symmetry for Appell equations in a holonomic system
Authors: Sun Xian-Ting  , Zhang Yao-Yu  , Zhang Fang  , Jia Li-Qun  ,   Electric and Information Engineering College, Pingdingshan University, Pingdingshan 467002, China;,   School of Science, Jiangnan University, Wuxi 214122, China
Published: December 2020

The conformal invariance and Hojman conserved quantity of Lie symmetry for Appell equations in a holonomic system are studied. Under the special infinitesimal transformations in which the time is not variable, the Lie symmetry and conformal invariance of differential equations of motion for a holonomic system are defined, and the determining equations of the conformal invariance of Lie symmetry and the Hojman conserved quantity for the system are given. Finally, an example is presented to illustrate the application of the results.
Parameters estimation for a one-dimensional time fractional thermal wave equation with fractional heat flux conditions
Authors: Fan Wen-Ping  , Jiang Xiao-Yun  ,   School of Mathematics, Shandong University, Jinan 250100
Published: December 2020

An inversion problem of estimating parameters for a one-dimensional time fractional thermal wave equation with fractional heat flux conditions and Caputo fractional derivatives is investigated. To begin with, the analytical solution of the direct problem is obtained. Then, based on the parameter sensitivity analysis, the least-squares method is used to estimate both the fractional order α and the relaxation time τ simultaneously. Finally, two different heat flux distributions are given as different boundary conditions to perform the simulation experiments, respectively. By analyzing the degree of fitting curves, results show that the least-squares method performs well in parameter estimation for this fractional thermal wave equation. This study provides an effective method of estimating the parameters of fractional thermal wave equations.
Entanglement of one- and two-mode combination squeezed thermal states and its application in quantum teleportation
Authors: Liu Shi-You  , Zheng Kai-Min  , Jia Fang  , Hu Li-Yun  , Xie Fang-Sen  ,   College of Physics and Communication Electronics, Jiangxi Normal University, Nanchang 330022, China
Published: December 2020

In view of the fact that one- and two-mode combination squeezed vacuum states may exhibit stronger squeezing in a certain range, we introduce one- and two-mode combination squeezed thermal states (OTCSTS) and investigate the property of entanglement in detail. Using the remarkable property of Weyl ordering, i.e., the order-invariance of Weyl ordered operator under similar transformations, we conveniently derive the analytical expression of entanglement degree-logarithmic negativity, and then present the condition of keeping entanglement for these squeezed thermal states. It is found that the OTCSTS possesses higher entanglement than the usual two-mode squeezed thermal states for any non-zero squeezing parameter. As an application, the quantum teleportation for coherent state is considered by using the OTCSTS as an entangled channel. It is shown that the teleportation fidelity can only be enhanced within a certain range of parameters, which is just the same as the condition of exhibiting stronger squeezing in one quadrature. In addition, the condition of realizing effective quantum teleportation (>1/2) is obtained analytically.
Study on quantum key distribution between different media
Authors: Zhou Fei  , Yong Hai-Lin  , Li Dong-Dong  , Yin Juan  , Ren Ji-Gang  , Peng Cheng-Zhi  ,   Department of Physics and State Key Laboratory of Low Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China;,   National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

This paper mainly solves the photon polarization encoding problem of quantum key distribution (QKD) between different media. The influence of the transmission rate of different photon component on quantum bit error rate (QBER) has been quantitatively analyzed, with a practical analysis of QBER of QKD between air and water. Furthermore, we have put forward a single-photon compensation scheme for eliminating such non-ideal BB84 protocol, as well as a more robust and practical dual-photon encoding scheme to offset such interfacial non-unitary noise. This takes an important step towards the air-sea-ground wide area quantum communication in the future.
Influence of synaptic plasticity on dynamics of neural mass model：a bifurcation study
Authors: Xia Xiao-Fei  , Wang Jun-Song  ,   School of Biomedical Engineering, Tianjin Medical University, Tianjin 300070, China;,   Department of Neuroscience and Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore 21218, MD, USA
Published: December 2020

Neural mass model is a typical nonlinear system with rich and complex dynamics. Up to now, most bifurcation researches of neural mass model (NMM) have focused on the influence of input or connection parameters between subpopulations on the dynamics of NMM. Actually, the synaptic strength is varied temporally, owing to synaptic plasticity, and plays a crucial role in regulating the dynamics of NMM. However, there are no researches on synaptic strength bifurcation analysis of NMM, and how excitatory and inhibitory synaptic plasticity exerts an influence on the dynamics of NMM is still little known. Motivated by this idea, the bifurcation analysis of excitatory and inhibitory synaptic strength of NMM is conducted in this study. Firstly, codimension-one bifurcation analyses of excitatory and inhibitory synaptic strengths are performed, respectively, through which the parameters regions of stability, bistablility, normal and abnormal oscillation are determined. Secondly, codimension-two bifurcation analysis is conducted, through which we can further gain an insight into the influence of the interaction between excitatory and inhibitory synaptic strengths on the dynamics of NMM. Finally, the bifurcation analysis results is verified by the simulation results. This study of bifurcation reveals two kinds of oscillation mechanisms: limit cycle oscillation mechanism and input-induced transition between two states of the bistability.
Laser characteristic effect on the trace gas detection
Authors: Zhang Rui  , Zhao Xue-Hong  , Zhao Ying  , Wang Zhe  , Wang Yan  ,   College of Precision Instruments and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China;,   College of Electronic Information and Automation, Tianjin University of Science and Technology, Tianjin 300222, China
Published: December 2020

In this paper, we study the effects of laser scanning step length and width characteristic on tunable diode laser absorption spectrum detection system, theoretically derive the principle of interaction between laser and gas absorption line, and analyse the principle of effects of step duration and height about scanning signal (ramp) on the laser central wavelength. After setting the simulation parameters, the curve between the number of ramp steps and the maximum scanning error is obtained. If the scanning signal has 4000 steps in one cycle, the error is less than 1‰ with full width at half maximum (FWHM) value being greater than 0.01 cm-1. The curves between laser linewidth and maximum amplitude or linewidth error are simulated, and also the relationship between laser linewidth and minimum FWHM is given with linewidth error maximum values being 1% and 0.5%. On condition that temperature coefficient n is 0.9 and air-broadened coefficient is 0.005, this paper gives the relationship among pressure, temperature and FWHM, from which the suitable pressure P and temperature T range are deduced. It can provide the relevant theoretical basis for selecting the laser and gas absorption lines and also for improving the system detection limit.
Design of the active zoom system with three-mirror
Authors: Shen Ben-Lan  , Chang Jun  , Wang Xi  , Niu Ya-Jun  , Feng Shu-Long  ,   School of Opto-Electronics, Beijing Institute of Technology, Beijing 100081, China;,   Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130022, China
Published: December 2020

In the applications of deep-space exploration, surveillance, threat detection and high resolution investigation on the ground, space optical systems need not only both the high resolution and width of view zoom system, but also the small size, light weight, low power and fast focusing system. As the traditional mechanical zoom system requires complex and precision mechanical motion, many problems are usually caused. Thus, based on active optics, the active optical elements are applied to the imaging system, and it is proposed that the optical element curvature radius should be variable to realize the transition among the different focal lengths. According to third-order aberration theory and dimension calculation of optical system requirement, the active zoom theory is studied, and the third-order aberration equation constraints are confirmed. Then the initial construction parameters of coaxial active zoom system are achieved by solving the equations. The system is optimized with using the optical design software ZEMAX. The system consists of the static primary mirror, the secondary and third mirror with the variable curvature radius, and the plane mirror with zero-power. As two times the light is obscured by the elements in the coaxial active zoom system, the amount of the energy on the image plane will be affected. For this reason, it is proposed that the unobstructed off-axis optimization should be necessary to the coaxial system. The off-axis system design theory is studied and the off-axis active zoom system is designed.
Simplification of Santillis second method of constructing Birkhoffian functions
Authors: Song Duan  ,   Physics of Medical Imaging Department, Eastern Liaoning University, Dandong 118001, China
Published: December 2020

The method of constructing Birkhoffian funcations of mechanical systems is investigated. The redundant term is discovered in Santilli's second method. As a result, a simpler construction formula for self-adjoint systems is obtained by cancelling the redundant term. An example is given to illustrate the application of the results.
Equation of state of solid krypton from correlated quantum chemistry calculations
Authors: Wu Na  , Yang Jiao  , Xiao Fen  , Cai Ling-Cang  , Tian Chun-Ling  ,   School of Physical Science and Technology, Southwest University, Chongqing 400715, China;,   Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The two-, three- and four-body interaction energies in face-centered cubic (fcc) krypton are evaluated using the many-body expansion method and the coupled cluster theory with full single and double excitations plus perturbative treatment of triples, and both self-consistent-field (SCF) Hartree-Fock energy and correlation one are accurately determined in a wide volume range (from 27 to 4 cm3/mol). All different three- and four-atom clusters existing in the first three and two nearest and two neighbor shells of fcc lattice are considered. It is found that the three-body interaction energy is positive at low compression, where the dispersive forces play a dominant role, with increasing the compression the three-body contribution becomes attractive, and the SCF energy overwhelms the dispersive one. At pressures higher than 30 GPa, the four-body contribution becomes important and significantly cancels the over-softening effects of the three-body potential. It shows that the combination of the four-body effects with two- and three-body interactions leads to an excellent agreement with the measurements from the equation of state in the whole experimental range of 0-130 GPa.
Effect of doping Pr on multiferroic properties of Bi5Fe0.5Co0.5Ti3O15 ceramics at room temperature
Authors: Wang Qin  , Wang Yi-Lun  , Wang Hao  , Sun Hui  , Mao Xiang-Yu  , Chen Xiao-Bing  ,   College of Physical Science and Technology, Yangzhou University, Yangzhou 225002, China
Published: December 2020

The polycrystalline Bi5-xPrxFe0.5Co0.5Ti3O15 (BPFCT-x: x=0.25, 0.50, 075, 0.80) ceramics are prepared by an improved solid state reaction method. X-ray diffraction structure analysis shows that the content of Pr has an influence on the microstructure of sample, but all the samples are layered perovskite structure. The remanent polarization (2Pr) first increases and then decreases with the increase of Pr content (x), so do the magnetic and ferroelectric properties. The remanent polarization reaches a maximum vaule of 6.43 μC/cm2, when x = 0.75. The remanent magnetization (2Mr) increases to a maximum value of 0.097 emu/g when x=0.75, and then decreases with the increase of Pr content (x). with the increase of Pr doping the ferroelectric and ferromagnetic properties of sample at room temperature can be obviously improved, and when x=0.75, multiferroic properties of the sample at room temperature is the best. The improvement in ferroelectric properties of sample is related to Pr doping. With the increase of Pr content (x), the defect concentration of the sample can be reduced, ferroelectric domain of movement can be improved, and the improvement in ferromagnetic property is possibly related to the lattice deformation which is affected by Pr.
Hydrothermal diffusion of Eu3+ in EuVO4@YVO4 core-shell nanoparticles and its influence on luminescent properties
Authors: Xie Di-Ni  , Peng Hong-Shang  , Huang Shi-Hua  , You Fang-Tian  , Wang Xiao-Hui  ,   Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

EuVO4@YVO4 core-shell nanoparticles (NPs) are synthesized, coated by poly(sodium 4-styrenesulfonate) and hydrothermally treated at 200 ℃ for 0-48 h. The photoluminescence (PL) intensity of as-prepared sample is enhanced by about 5 times after 48-hour hydrothermal treatment, and the average lifetime is raised up from 0.410 ms to 0.579 ms. Further studies of hydrothermal time-dependent PL decay curves provide evidence for the diffusion of Eu3+ in core-shell NPs, which could reduce the concentration quenching in particle core and hence enhance the PL efficiency. This thermal diffusion strategy based on ion-doped core-shell NPs could be used to prepare luminescent NPs with high efficiency if designed elaborately.
Analysis on the variational model of synthetic aperture radar sea surface wind retrieval
Authors: Jiang Zhu-Hui  , Zhou Xiao-Zhong  , You Xiao-Bao  , Yi Xin  , Huang Wei-Quan  ,   Beijing Institute of Applied Meteorology, Beijing 100029, China
Published: December 2020

Error analysis is carried out to test the variational model of synthetic aperture radar sea surface wind retrieval. On condition that the background error is maximum, the analysis error is lower than the background error, and with the increase of the background wind direction, the analysis error changes periodically; on condition that the background error gradually increase, the analysis error increases gradually and its deviation direction coincides with the background error deviation direction; under the condition of specific background field, the variational model is compared with the direct inversion model: when the background wind speed is low, the variational model error is slightly high, when the background wind speed is high, the variational model error is significantly low. Generally, the variational model wind speed error is less than 1.60 m/s, and the wind direction error is less than 17.15°, which are better than those of the direct inversion model.
Medical ultrasound imaging based on cross-correlation adaptive weighting
Authors: Zheng Chi-Chao  , Peng Hu  , Han Zhi-Hui  ,   Department of Biomedical Engineering, Hefei University of Technology, Hefei 230009, China
Published: December 2020

According to the cross-correlation between the ultrasonic echo signals of ultrasonic imaging system, ultrasonic imaging algorithm based on cross-correlation adaptive weighting is introduced. This method determines the weight on the correlation between the echo signals of scatters at different positions, and then the adaptive weighted imaging is performed. The sidelobe and the noise which has the low correlation are suppressed. Simulations to points object and speckle object pattern using Field Ⅱ show that the method of imaging fast, and it can give a high horizontal and longitudinal resolution. Compared with delay and sum (DAS) algorithm, the contrast of the image to point object is increased by 16 dB. The contrast of the image to sound-absorbing speckle is increased by 0.85 dB. The results of experiments in which the complete data sets are used, show that the resolution is better than that of DAS algorithm and the contrast is increased by 17 dB.
Application of digital filter weak constraint four-dimensional variational data assimilation on typhoon initialization Ⅱ. Digital filter weight chosen
Authors: Zhong Jian  , Fei Jian-Fang  , Dong Gang  , Cheng Xiao-Ping  , Sun Yi-Mei  ,   China Satellite Maritime Tracking and Control Department, Jiangyin 214431, China;,   Joint Laboratory of Ocean-based Flight Vehicle Measurement and Control, China Satellite Maritime Tracking and Control Department, Jiangyin 214431, China;,   Institute of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China
Published: December 2020

In Part I, the digital filter weak constraint four-dimensional variational (4D-Var) data assimilation is implemented with different digital filter weight settings through two typhoon cases. The results show that the influence of the digital filter weight on typhoon track and intensity prediction is large, and how to choose an appropriate digital filter weight is important. In this paper, seven different initial time typhoon cases in 2010 are selected to analyze the effects of different digital filter weight settings on typhoon track and intensity prediction. Based on the track and intensity prediction information of the seven cases, and the three-hour pressure tendency information for the whole domain and the area with 800 km radius from the typhoon center, a method of choosing digital filter weight is proposed for typhoon initialization with bogus data assimilation. Also, the ordinary digital filter weight setting is proposed, which is 1000 and obviously different from the operational and storm cases weight setting.
Study on orbital angular momentum of Laguerre-Gaussian beam in a slant-path atmospheric turbulence
Authors: Ke Xi-Zheng  , Chen Juan  , Yang Yi-Ming  ,   The Faculty of Automation & Information Engineering, Xi'an University of Technology, Xi'an 710048, China
Published: December 2020

Atmospheric turbulence can cause random variations of the refractive index, resulting in a spatial inhomogeneity. When a Laguerre-Gaussian beam is propagating through the atmospheric turbulence, spatial inhomogeneity can bring about the change of photon wave function that causes variations in the orbital angular momentum. This article discusses how turbulence media change the orbital angular momentum of photons as to form different photon states, when the Laguerre-Gaussian beam is propagating in a slant-path atmospheric turbulence, by calculating the weight of the spiral harmonic component of the beam energy. Analysis of the variations of orbital angular momentum of Laguerre-Gaussian beam in the turbulent medium has been carried out.
Conformal invariance of isoheight lines of the (2+1)-dimensional etching surfaces
Authors: Xun Zhi-Peng  , Tang Gang  , Xia Hui  , Hao Da-Peng  , Song Li-Jian  , Yang Yi  ,   Department of Physics, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

In order to study the statistical properties of the surface fluctuations in the Etching model more comprehensively and effectively, based on the Schramm Loewner evolution (SLE) theory, the contour lines of the saturated surface in the (2+1)-dimensional Etching model are investigated by means of numerical simulations. Results show that the isoheight lines of the (2+1)-dimensional Etching surfaces are conformally invariant and can be described in the frame work of the SLE theory with diffusivity =2.70 0.04, which belongs to the =8/3 universality class. The corresponding fractal dimensions of the isoheight lines are df =1.34 0.01.