bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on cascading invulnerability of multi-coupling-links coupled networks based on time-delay coupled map lattices model
Authors: Peng Xing-Zhao  , Yao Hong  , Du Jun  , Ding Chao  , Zhang Zhi-Hao  ,   Aeronautics and Astronautics Engineering College, Air Force Engineering University, Xi’an 710038, China;,   Science College, Air Force Engineering University, Xi’an 710051, China
Published: December 2020

The couplings among different networks facilitate their communications, while at the same time they also bring the risk of enhancing the wide spread of cascading failures to the coupled networks. Given that there is usually the time-delay during the spread of failures and more than one coupling link a node might possess, a cascading failure model for scale-free multi-coupling-link coupled networks is built in this paper, based on time-delay coupled map lattices (CML) model, which may be wider representative than previous models. Our research shows that in BA (Barabási-Albert) scale-free coupled networks, there is a threshold hT ≈ 3: when the coupling strength is bellow this threshold, the stronger coupling strength corresponds to a lower invulnerability; and vice versa, the stronger coupling strength would bring a higher invulnerability. In addition, our studies show that the presence of time-delay not only prolongs the failure spreading time during which measures can be taken to suppress cascading failures, but also has a significant influence on the eventual cascading size, for detail, if intra-layer time-delay τ1 and inter-layer time-delay τ2 can have any values, then the multiples of the two numbers will cause larger cascading size. We hope our research can provide a reference for building high-invulnerable coupled networks or the increase of the invulnerability of the coupled networks.
Virtual trajectory model for lane changing of a vehicle on curved road with variable curvature
Authors: Ren Dian-Bo  , Zhang Jing-Ming  , Wang Cong  ,   School of Automotive Engineering, Harbin Institute of Technology, Weihai 264209, China
Published: December 2020

In this paper, a virtual trajectory planning method for vehicle lane changing in automated highway system is studied, and a trajectory model for lane changing on variable curvature road is established with odd-order polynomial constraints. Assuming that the starting lane and the target lane have the same instantaneous center, the motion for lane changing of vehicle on the curved road can be decomposed into a linear centripetal motion and a circular motion around the instantaneous centre of the curved road. If the centripetal motion displacement and the rotational angular displacement meet the requirement of odd-order polynomial constraints, the boundary condition of the above two kinds of motion may be obtained from the constraints, such as time, location, and desired state of vehicle at the start and end of the lane changing behavior. By applying the boundary conditions, the polynomial coefficient is deduced, and the mathematical model of virtual trajectory for lane changing can be designed based on the polynomial models of centripetal displacement and angular displacement. Compared with the existing trajectory planning method for lane changing on curved road, the curvature change has been taken into consideration, and the trajectory model for lane changing has been generalized. Simulation results verify the feasibility of the trajectory planning method proposed in this paper for lane changing on a curved road with variable curvature.
Relationship between the quasi-linear diffusion coefficients and the key parameters of spatial energetic electrons
Authors: Zhang Zhen-Xia  , Wang Chen-Yu  , Li Qiang  , Wu Shu-Gui  ,   National Earthquake Infrastruction Service, China Earthquake Administration, Beijing 100045, China;,   School of Physics, Peking University, Beijing 100871, China
Published: December 2020

It has been proved that the ground-based electromagnetic wave can transfer into ionosphere and interact with high-energy particles. By changing the pitch angle and momentum, the particles are imposed to enter the bounce loss cone and drift loss cone, then electron precipitation takes place and the particle bursts form. In recent decades, the relationship has been observed among electromagnetic disturbance and particle bursts and seismic activity based on satellite data. Here, by wave-particle cyclotron resonant interaction combined with the observation range of LEO satellite (about 350–1000 km), the evolvement trend of the pitch angle quasi-linear diffusion coefficients induced by field-aligned electromagnetic waves, is studied with the change of VLF electromagnetic wave frequency, band width, energies of electron (0.1–20 MeV) and L shell (L=1.1–3). We also show the relationship between VLF electromagnetic wave frequency and minimum energy of precipitation electron induced by it, under certain pitch angle value. The relationship among these quantities may be used to provide theoretical explanation for satellite observations of energetic particle precipitation examples, to provide guidance for extracting information associated with earthquakes from the detection of high-energy particles on the satellite, and to lay the foundation on the data analysis of China seismo-electromagnetic satellite planned to launch at about the end of 2016.
Simulation study of two-dimensional electron gas in N-polar GaN/AlGaN heterostructure
Authors: Wang Xian-Bin  , Zhao Zheng-Ping  , Feng Zhi-Hong  ,   College of Information Engineering, Hebei University of Technology, Tianjin 300130, China;,   State Key Laboratory of ASIC and System, Shijiazhuang 050051, China
Published: December 2020

By the self-consistent solution of the Schrödinger and poisson equations, the effects of GaN channel layer, AlGaN back barrier layer with and without Si doping and AlN interlayer on two-dimensional electron gas in N-polar GaN/AlGaN heterostructure are systematically studied. The results indicate that the increases of the thickness values of GaN channel layer and AlGaN back barrier layer and Al content value can improve the density of 2DEG to a certain degree, and the influences of different Si doping forms on 2DEG sheet density are not the same, also the confinement of 2DEG could be strengthened by increasing Al content value and thickness value of the AlGaN barrier layer. The AlN interlayer is a comparatively outstanding one in improving the performance of the 2DEG such as the 2DEG sheet density and confinement. When GaN channel layer thickness is less than 5 nm, there is no 2DEG in the simulation, when it exceeds 20 nm the 2DEG sheet density tends to be saturated. 2DEG has a tendency to be saturated when the thickness value of AlGaN back barrier is more than 40 nm. 2DEG sheet densities with uniform doping and delta doping in AlGaN back barrier are saturated when the doping concentration is more than 5×1019 cm-3. The 2DEG sheet density could be increased from 0.93×1013 cm-2 without AlN interlayer to 1.17×1013 cm-2 with 2 nm AlN interlayer.
Application of memristor-based spiking neural network in image edge extraction
Authors: Liu Yu-Dong  , Wang Lian-Ming  ,   School of Physics, Northeast Normal University, Changchun 130024, China
Published: December 2020

By simulating biological synapses with memristors according to the function and principle of biological visual system and by combining the memory characteristic of memristor with high-efficient processing ability in spiking neural network, a three-layer spiking neural network model for image edge extraction is constructed, in which the image edge information is represented by the variation of the memristor conductance. The edge extraction result obtained with this approach has the characteristics of continuity, smoothness, low false leak detection and edge positioning accuracy. Since the processing mechanism of this neural network conforms to the biological counterpart, it offers a new idea for the bionic implementation of biological visual system.
Synchronizing chaotic systems based on an arbitrary function matrix
Authors: Lin Li-Xiong  , Peng Xia-Fu  ,   Department of Automation, Xiamen University, Xiamen 361005, China
Published: December 2020

In this paper, we introduce a type of chaotic synchronization, where two chaotic systems are synchronized based on a function matrix. In particular, each drive system state synchronizes with a certain combination of response system states. Based on linear system theory and the pole placement technique, the scheme is given and illustrated with hyperchaotic Lorenz system and Lorenz chaotic system. Numerical simulations are carried out to verify the effectiveness of the proposed scheme.
A family of multi-wing chaotic attractors and its circuit implementation
Authors: Huang Yun  ,   Asset Management Department, Chongqing University of Posts and Telecommunications, Chongqing 400065, China
Published: December 2020

A novel method is presented generating multi-wing butterfly chaotic attractors in this paper. Based on Liu chaotic system, a multi-wing butterfly chaotic system is constructed via designing a new piecewise linear function. The equilibrium point, Lyapunov exponent spectra, bifurcation diagram, phase diagram, frequency spectrum and Poincaré mapping of the system are studied. Furthermore, an electronic circuit is designed to implement the system. The experimental results are in agreement with numerical simulation results, which verify the feasibility and availability of this method.
First principles study of the electronic and optical properties of silica glass with hydroxyl group
Authors: Shi Yan-Li  , Han Wei  , Lu Tie-Cheng  , Chen Jun  ,   College of Physical Science and Technology, Sichuan University, Chengdu 610065, China;,   Institute of Applied Physics and Computational Mathematics, Beijing 100088, China;,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The formation model of hydroxyl group in silica glass is studied by first-principles calculations combined with coupling plane wave pseudo-potential method. The electronic structures and optical properties of silica glass with and without hydroxyl group are systematically calculated, including electronic densities of states, charge difference densities, Bader charge, etc. And optical transition models are analyzed. Our results show that three-fold coordinated silicon in silica glass induces two defect energy levels in forbidden gap, which are at 7.8 eV and 8.8 eV, respectively. Also, we find that H atom can interact with five-fold coordinated Si and forms hydroxyl group, and causes the three-fold coordinated silicon atom to change from sp2 hybridization to sp3 hybridization. Such a kind of hydroxyl group influences the electronic structure and optical properties of silica glass, by forming a half-occupied electronic state at Fermi level, and also by generating an optical transition, of which the excitation energy is 6.2 eV.
Molecular dynamic study on thermal expansion of U1-xPuxO2
Authors: Wang Li-Li  , Wan Ming-Jie  , Ma Jiang-Jiang  , Jiang Gang  ,   Institute of Computer Application, China Academy of Engineering Physics, Miangyang 621900, China;,   Computational Physics Key laboratory of Sichuan Province, Yibin University, Yibin 644007, China;,   Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
Published: December 2020

Molecular dynamic simulation is performed to investigate the thermal properties of U1-xPuxO2 (x=0.07, 0.15, 0.25, 0.5) using the potential of partially ionic model at temperatures ranging from 300 to 3000 K and pressures in a range of 0-1.5 GPa. The results indicate that the lattice parameters decrease linearly with Pu ratio increasing under different temperatures. The linear expansion coefficient increases with Pu ratio increasing. The isothermal compressibility decreases with Pu ratio decreasing. In addition, the experience functions of lattice parameter and linear expansion coefficient are also derived.
Theoretical and experimental study of measuring gas temperature in vacuum environment using tunable diode laser absorption spectroscopy
Authors: Lan Li-Juan  , Ding Yan-Jun  , Jia Jun-Wei  , Du Yan-Jun  , Peng Zhi-Min  ,   State Key Laboratory of Power Systems, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China;,   Beijing Orient Institute for Measurement and Test, Beijing 100086, China
Published: December 2020

Measuring the temperature in vacuum environment is more complex than in atmospheric environment. For example, high vacuum will cause the thermocouple sensor surface desorption, and the mechanism of heat transfer is also different. Therefore, there are some uncertainties if the thermocouple is used to measure the gas temperature in vacuum condition. In the present paper, tunable diode laser absorption spectroscopy (TDLAS) is employed to measure the gas temperature and also explore the application prospect of TDLAS temperature measurement technology in vacuum environment. During the thermal vacuum experiments, the vacuum gas cell is immersed in the thermostatic bath, and the gas temperature is determined by TDLAS. Meanwhile, a standard Pt-resistance is used to measure the thermostatic bath temperature. The results show that the temperatures of the gas and thermostatic bath are highly consistent with each other, and the difference between the two temperatures is less than 0.2 ℃ when the thermostatic bath is stable.
Theoretical study on measuring underwater temperature based on coherent Rayleigh scattering
Authors: Ren Xiu-Yun  , Tian Zhao-Shuo  , Yang Min  , Sun Lan-Jun  , Fu Shi-You  ,   Information Optoelectronics Research Institute, Harbin Institute of Technology at Weihai, Weihai 264209, China;,   North China Sea Marine Technical Support Center, State Oceanic Administration, Qingdao 266033, China
Published: December 2020

The rapid measuring of the underwater temperature on a large scale is very important for marine monitoring, and it has vital significances in the civilian and military fields. In this paper, a new coherent Rayleigh scattering method to measure underwater temperature is presented. A wide-band photodetector is used to receive the heterodyne signal combined by the local oscillator laser and water Rayleigh backscattering light, and the water Rayleigh scattering spectrum can be acquired by transform analysis, then the water temperature can be obtained. Firstly, theoretical study and simulation are made on the basic principles of measuring underwater temperature based on Rayleigh scattering. Secondly, theoretical analysis and simulation are made on how to measure water Rayleigh scattering spectrum using coherent detection. Finally, the water temperature measurement accuracy based on Rayleigh scattering is analyzed, showing that for 1 MHz measurement accuracy of Rayleigh scattering spectrum half-width, about 0.35 K temperature measurement accuracy can be achieved.
Transient kinetics of graphene bombarded by fullerene
Authors: Xu Zhi-Cheng  , Zhong Wei-Rong  ,   Siyuan Laboratory, Department of Physics, Jinan University, Guangzhou 510632, China
Published: December 2020

Using non-equilibrium molecular dynamics method, we study the transient kinetics of graphene bombarded by fullerene through controlling the temperature and velocity. Our results show that fullerene (C60) with low velocity cannot pass through graphene at any temperature. However C60 with high velocity can pass through graphene at any temperature. Between low velocity and high velocity, we find that the probability of C60 passing through graphene increases with temperature, the reason is that the probability of destroying carbon-carbon bond at high temperature is higher than at low temperature. In this paper, we also discuss the potential applications in the surface cleaning of graphene and the production of nanopore.
Crystalline undulator radiation and motion behavior in the vicinity of the resonance line
Authors: Yang Jie  , Li Xiu-Ping  , Wang Shan-Jin  , Luo Shi-Yu  ,   College of Electronic Engineering, Dongguan University of Technology, Dongguan 523808, China
Published: December 2020

Searching for new light source, especially short wave-length coherence light source has attracted extensive attention. The using of the crystalline undulator radiation as a short wave-length coherence light source is most likely to be one of the options. From the viewpoints of potential and field, the centrifugal force generated by periodic bent crystal is regarded as centrifugal potential, the particle motion equation is reduced to Mathieu equation with Duffing-type, and from the energy viewpoint the stability of the system is discussed. The behaviors of particles in the vicinity of the resonance are analyzed by perturbation method; the jump phenomena and instable behavior are revealed. The results show that the stability of the system is related to its parameters, and only properly adjusting these parameters, the bifurcation and instability for the system can be avoided in principle.
Experimental studies of multiple pulses in a passively ytterbium-doped fiber laser based on graphene-oxide saturable absorber
Authors: Huang Shi-Sheng  , Wang Yong-Gang  , Li Hui-Quan  , Lin Rong-Yong  , Yan Pei-Guang  ,   Shenzhen Key Laboratory of Laser Engineering, College of Electronic Science and Technology, Shenzhen University, Shenzhen 518060, 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 different multiple pulse phenomena are experimentally studied in a passively mode-locked ytterbium-doped fiber laser based on graphene-oxide saturable absorber (GOSA) with net normal dispersion cavity. At the same pump power with different polarization orientations, we observe the multiple pulse phenomena, including harmonic mode-locking of rectangular pulses, dissipative solitons, quasi-harmonic mode-locking, periodical peak modulation, multipulse bunches, multipulse cluster, and chaotic multipulse. The inserted 2 nm narrow bandwidth filter is important for limiting the gain bandwidth and shaping pulses. Adjusting the polarization controller is equivalent to changing the gain in the laser cavity, which is the main reason for the formation of different multiple pulses states. This is the first time that different multiple pulses states have been observed in an-normal-dispersion Yb-doped fiber laser with graphene-oxide saturable absorber. These results could extend the understanding of multiple pulse dynamics in GOSA mode-locked fiber lasers.
The human colorectal cancer tissue in vitro experimental study based on photoacoustic endoscopic system
Authors: Chen Bing-Zhang  , Yi Hang  , Yang Jin-Ge  , Chi Zi-Hui  , Rong Jian  , Hu Bing  , Jiang Hua-Bei  ,   School of Physical Electronic, University of Electronic Science and Technology of China, Chengdu 610054, China;,   West China Hospital, Sichuan University, Chengdu 610041, China;,   Department of Biomedical Engineering, University of Florida, Gainesville Florida 33063, USA
Published: December 2020

This paper developed a 4 array transducers photoacoustic endoscopic probe, and based on this, a photoacoustic endoscopic imaging system was build. Phantom experimental imaging was carried out, and the capability of location for endoscopic probe was demonstrated via analyzing the absorption of the light on the 4 sensors position. The in vitro human normal tissues and early colorectal cancer tissues was imaged using photoacoustic endoscopic system. The statistical analysis of the light absorbtion intensity distribution on different position proved that the photoacoustic endoscopic system has the ability to distinguish human normal tissues and early colorectal cancer tissues. This technology is expected to improve the accuracy of early diagnosis of colorectal cancer and has the potential clinical application.
A geoacoustic estimation scheme based on bottom backscatter signals from multiple angles
Authors: Zhou Tian  , Li Hai-Sen  , Zhu Jian-Jun  , Wei Yu-Kuo  ,   Acoustic Science and Technology Laboratory, College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Aiming at the disadvantages of current methods to estimate sediment geoacoustic parameters, a geoacoustic estimation scheme is presented, in which used are the bottom back reflection signals from multiple angles sampled with a multi-beam parametric array sub-bottom profiler. Firstly, the sediment thickness and sound speed are estimated with difference frequency backscatter signals separately from upper and lower sediment surfaces with vertical and outboard direction. Then, the sediment attenuation coefficient is estimated by use of the two backscatter signals with different difference frequencies from upper and lower sediment surfaces with vertical direction. Finally, the sediment property impedance is estimated with primary frequency backscatter signals from upper sediment surface with vertical direction and followed by the computation of the sediment density, thereby solving its coupling with sound speed. The efficiency is tested through pool experiment.
The study of fluid with free surface by many-body dissipative particle dynamics
Authors: Zhou Nan  , Chen Shuo  ,   School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, China
Published: December 2020

The dynamics of a drop on a mesoscopic scale is investigated by using the many-body dissipative particle dynamic (MDPD) method. The formation of liquid-vapor coexistence interface in the MDPD system is explored. The simulations of the pressure inside/outside the drop and the surface tension are carried out, and it is verified that Laplace’s law is satisfied in our simulation. Different contact angles are obtained by changing conservative interaction parameters between particles. The relationship between MDPD paremeters and contact angles is discussed. Based on the results, the flow behaviors of a drop moving in grooved microcannels are simulated. The results in this paper are useful in studying the fluid with free surfaces flow behavior on rough surface.
Experimental investigation of interactions between laminar or turbulent boundary layer and shock wave
Authors: Quan Peng-Cheng  , Yi Shi-He  , Wu Yu  , Zhu Yang-Zhu  , Chen Zhi  ,   College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Investigation on the interactions between laminar or turbulent layer and shock wave is performed in a Mach 3.4 supersonic wind tunnel, based on nanoparticle-tracer based planar laser scattering (NPLS) system and supersonic particle image velocimetry (PIV) system. The model geometry in this experiment is composed of two flats with different positions in the test section which can provide the flat with different kinds of boundary layer, and a shock wave generator–a 12° wedge. Boundary layer separation/attachment, induced suppression waves, induced shock wave and expansion fan were clearly presented by NPLS images, velocity field and vorticity field were given by PIV results. Instantaneous flow structures and temporal evolution of two different flow conditions were analysised and compared according to both NPLS and PIV results. The experimental results show that: the separation zone in the turbulent boundary layer is long and narrow, but it’s quite different in the turbulent boundary layer where it is oval-shaped; upstream of the oblique shock wave, a serious of suppression waves can be observed outside of the laminar boundary layer and they will focus into a unsteady induced shock wave, but in contrast, only a focused shock wave can be found outside of the turbulent boundary layer and it’s quite stable; the expansion fan downstream of the oblique shock wave is small in the laminar boundary layer, leading to a sufficient acceleration of the flow, and the attachment shock wave behind the expansion fan is extremely weak, however it is a totally different condition in the turbulent boundary layer with a wide expansion fan and a strong attachment shock wave.
Drag reduction mechanisms of 8-fold quasi-periodic short groove structures
Authors: Lang Sha-Sha  , Geng Xing-Guo  , Zang Du-Yang  ,   Key Laboratory of Space Applied Physics and Chemistry of the Ministry of Education, School of Science, Northwestern Polytechnical University, Xi’an 710129, China
Published: December 2020

We design two types of 8-fold quasi-period short groove structures which are arranged in single row and three rows respectively The flow field in the turbulent boundary layer and the total stress over these groove surfaces are numerically simulated by using Reynolds average Navier-Stokes equation and turbulence model. It is shown that the 8-fold quasi-periodic structure has good drag reduction effect compared with the periodic and disorder structures, especially for structure arranged in three rows. The results are also confirmed by the sheer stress measurements which are performed on substrates with the designed structures. By analyzing the distribution of flow field, we find that the quasi-periodic structure effectively inhibits the intensity of vortex, reduces the turbulent dissipation rate, and keeps the stripe phase stable. Furthermore, by using the two-dimensional grating model, it is found that the 8-fold quasi-periodic structure can reduce spectrum intensity in the large angle direction, revealing that the inhibition of the extension of coherence disturbance waves is responsible for the drag reduction effect, which is also confirmed by the flow field analysis.
Experimental study on mode instability in high power all-fiber master oscillator power amplifer fiber lasers
Authors: Tao Ru-Mao  , Zhou Pu  , Wang Xiao-Lin  , Si Lei  , Liu Ze-Jin  ,   College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Mode instability (MI) is an abrupt mode change when the average output power increases above a certain threshold power, which results in degrading beam quality and restricting the enhancement of power output for diffraction-limited high power fiber laser. The experimental study on MI in all-fiberized master oscillator power amplifer (MOPA) is presented in detail for the first time. It is revealed that MI in all-fiberized MOPA results in reducing the slope efficiency. The theoretical threshold power of MI for 20/400 step-index large-mode-area double-cladding Yb-doped fiber is about 1 kW and MI is rooted mainly from the thermal effect.
Study of laser plasma interactions using one-dimensional particle-in-cell code in kinetic regime
Authors: Zou Chang-Lin  , Ye Wen-Hua  , Lu Xin-Pei  ,   State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074, China;,   Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

Stimulated Raman scatting (SRS), which is one of the parametric processes of laser-plasma interactions, is examined by an explicit, electromagnetic, relativistic kinetic particle-in-cell code in one dimension. The code algorithm and implementation details are discussed. It is found that kinetic effects are important to SRS instability. Time-averaged reflectivity onsets at threshold intensity, and saturates at higher intensity. Backward SRS bursts in sub-picosecond, periodically. Kinetic ions initially delay the growth of SRS. Electron trapping results in the SRS bursts. The saturation of SRS results from the nonlinear frequency shift of Langmuir wave. Work is underway to add binary Coulomb collision to parallelize it, and to extend the code to 2D3V.
First-principles study of magnetic ground state of quantum paraelectric EuTiO3 material
Authors: Li Cheng-Di  , Zhao Jing-Long  , Zhong Chong-Gui  , Dong Zheng-Chao  , Fang Jing-Huai  ,   School of Sciences, Nantong University, Nantong 226007, China;,   School of Physical Sciences and Technology, Suzhou University, Suzhou 215006, China
Published: December 2020

Magnetic ground state of perovskite structure quantum paraelectric EuTiO3 has been known to have a planar anisotropic G-type antiferromagnet structure according to the experimental study. In this paper, based on density functional theory, first-principles computations are performed to investigate the magnetic properties and spin-exchange interaction of EuTiO3 in both of the quantum paraelectric phase and ferroelectric tetragonal phase under stress. By analyzing the energies of different magnetic structures and paths of spin exchange coupling as well as the effect of stress on the magnetic exchange paths change, it is found that when the system of EuTiO3 is free, it has a G-type antiferromagnetic structure with uniaxial anisotropic spin along [110] direction. Furthermore, in this structure, Eu 4f electron spin achieves antiferromagnetic super-exchange coupling via O 2p state at face-centered position. However, in the ferroelectric tetragonal phase structure induced by applied stress field, Eu 4f electron spin achieves ferromagnetic exchange coupling in [110] direction due to the variation of Eu-O-Eu bond angle in spin exchange path.
Conserved quantities and approximate solutions of a two-dimensional charged coupled oscillator system
Authors: Lou Zhi-Mei  ,   Department of Physics, Shaoxing University, Shaoxing 312000, China
Published: December 2020

Coupled terms are present in the Lagrangian and the corresponding differential equations of a two-dimensional charged oscillator system are nonlinearly coupled. Firstly, the coupled terms in the Lagrangian are eliminated by transformation of coordinates; secondly, the conserved quantities in new coordinates are obtained by direct integral method, and the approximate solutions are obtained by Abdomina decomposition method. Finally, the conserved quantities and the approximate solutions can be expressed in original coordinates by using the inverse transform of the coordinates. The discussion of the approximate solutions is also given in this paper.
Stability and bifurcation control in inertial neuron networks with delays
Authors: Zhu Lin-He  , Zhao Hong-Yong  ,   Department of Mathematics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Published: December 2020

Based on the second order delay inertia neural network model, this paper puts forward the bifurcation control method: delay feedback control method. Applying the theory of delay differential equations, we give some stability and Hopf bifurcation conditions for the feedback control system. Examples are given to validate that the feedback controller can control the occurrence of bifurcation effectively, expand the stability domain, and change the convergence speed of the network as well.
An improved discrete arnold transform and its application in image scrambling and encryption
Authors: Wu Cheng-Mao  ,   School of Electronic Engineering, Xi'an University of Posts and Telecommunications, Xi'an 710121, China
Published: December 2020

To improve the image scrambling and encryption effect in traditional two-dimensional discrete Arnold transform, a new nonlinear transform for image scrambling is proposed which improves the classical discrete Arnold transform with quasi-affine properties, and can be applied in image scrambling and encryption researching. This method first makes good use of the construction thought in classical discrete standard map, and embeds the nonlinear expressions of output results of one congruence equation for classical two-dimensional discrete Arnold transform into the input item of the other congruence equation for two-dimensional discrete Arnold transform. Then a new transform with good nonlinear characteristics is constructed on the basis of classical two-dimensional discrete Arnold transform in order to quickly improve the scrambling effect of the gray image. In the end, through mathematical proof it is shown that the proposed transform no longer has the quasi-affine invariance properties in the existing two-dimensional discrete Arnold transform, but it is still a reversible mapping with periodic properties; and when it is applied in image scrambling encryption, the original image can be restored from the scrambling and encryption in gray image for its periodic properties or inverse transform. Some experimental results show that the proposed nonlinear transform is effective, and can obtain better scrambling and encryption quality than the existing discrete two-dimensional Arnold transform, meanwhile it is more practical than the standard Arnold transform in view of security.
Study of a spherical vibration-insensitive optical reference cavity
Authors: Ren Li-Qing  , Zhu Song  , Xu Guan-Jun  , Wang Zhao-Hua  , Deng Zhong-Xun  , Wei Ying-Chun  , Jin Hong-Ying  , Li Zeng-Sheng  , Gao Jing  , Liu Jie  , Zhang Lin-Bo  , Dong Rui-Fang  , Liu Tao  , Li Yong-Fang  , Zhang Shou-Gang  ,   Energy and Engineering College, Yulin University, Yulin 719000, China;,   National Time Service Center, Chinese Academy of Sciences, Xi'an 710600, China;,   Key Laboratory of Time and Frequency Primary Standard, Xi'an 710600, China;,   School of Physics and Information Technology, Shannxi Normal University, Xi'an 710062, China
Published: December 2020

We have investigated the vibrational sensitivity of a horizontal-mounted spherical reference cavity, which can be applied to develop an ultra-stable laser. Effects of different magnitudes of height and area as well as acceleration of the cavity support points on the length variation of the cavity are studied. When the cavity support points are totally constrained, the vibration sensitivity can be reduced to below 3.0×10-10/g. After performing extensive numerical simulations, we can find the optimal support position. According to the obtained results we present the mounting scheme of the spherical cavity. Taking into consideration the machining errors, near-horizontal mounting, and unsymmetrical mounting of the cavity, we can describe quantitatively the length variation of the cavity caused by these three factors. We also discuss the contribution of the second order effect to the length variation of the cavity.
A cross bus single microring electro-optical switch with U bend waveguide
Authors: Zhang Xin  , Li Zhi-Quan  , Tong Kai  ,   College of Electrical Engineering, YanShan University, Qinhuangdao 066004, China
Published: December 2020

A cross bus single microring electro-optical switch model is proposed based on the theory of coupling modes, electro-optical modulation, and transfer matrix. Simulation is carried out for the 1561 nm wavelength light signal. Result shows that the switch voltage is about 400 V, the interrupt is less than -30 dB and the insertion loss is less than 4 dB. The response time is only 5.4 ps, in which the rise and fall time on the microring is only 0.32 ps. Besides, since the electro-optical switch is controlled by a single-pole double-throw switch, the three states of the latter can be realized through adding driving voltage on microring and U bend waveguide. Unlike the tranditional microring switch, the above-mentioned one not only can realize the selection of light signal pathway, but also can let the two output ports have light signal sent out.
Theoretical and numerical studies on interactions between high-power microwave and plasma
Authors: Yuan Zhong-Cai  , Shi Jia-Ming  ,   State Key Laboratory of Pulsed Power Laser Technology, Institute of Electronic Engineering, Hefei 230037, China
Published: December 2020

Research of interactions between high-power microwave and plasma is of importance for both microwave discharge and electromagnetic compatibility. Based on wave equations, fluid equations, and Boltzmann equations of plasma interactively, a theoretical model of interactions between high-power microwave and plasma was established. Combined with characteristic parameters of plasma, the model was solved numerically by the method of finite difference in time domain to analyze variations of plasma electron density and transmission property of high-power microwave. Results show that heating of electrons by incident high-power microwave makes nonlinear effects become obvious in the plasma, and gas breakdown increases plasma electron density which results in the enhancement of reflection of microwave and the of decrease transitivity. The model mentioned above and results related are instructive for protecting against high-power microwave and electromagnetic pulse.
Detection of heavy metal Cr in soil by the femtosecond filament induced breakdown spectroscopy
Authors: Gao Xun  , Du Chuang  , Li Cheng  , Liu Lu  , Song Chao  , Hao Zuo-Qiang  , Lin Jing-Quan  ,   School of science, Changchun university of science and technology, Changchun 130022, China;,   Changchun new industries optoelectronics technology Co., Ltd, Changchun 130103, China;,   School of Chemistry and Environmental Engineering, Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

In this paper, the element content detection of heavy metal Cr in soil is investigated experimentally by femtosecond filament induced breakdown spectroscopy (FIBS). The plasma filament length is measured using the fluorescence method, and the spatial distribution of Cr 425.5 nm spectral intensity is obtained at lens focal lengths 150 mm and 1000 mm. A calibration curve of the heavy metal element Cr in the soil is obtained based on experimental results. Results demonstrate that the relative deviation of the quantitative analytic result from the standard value is smaller than 5%, and the detection limit of Cr in soil is 7.85 ppm at the laser repetition rate 1 kHz. The femtosecond laser filaments induced breakdown spectroscopy is entirely feasible for quantitative detection of heavy metal element Cr in the soil.
First-principles study on phonon properties of iron-based fluoride superconductors SrFe1-xCoxAsF (x=0, 0.125)
Authors: Wang Wei  , Yin Xin-Guo  ,   School of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000, China
Published: December 2020

Using plane-wave pseudopotential method based on first-principles, we calculate the phonon spectra (including phonon dispersion curves and phonon density of states) and electron-phonon coupling constants of SrFe1-xCoxAsF (x=0, 0.125) in tetragonal nonmagnetic (NM) and orthorhombic striped antiferromagnetic (SAF) states. Results show that under striped antiferromagetic interaction the spin-phonon coupling is stronger than the electron-phonon coupling, leading to the decrease of phonon spectra width; and the increased effective phonon quality due to spin effects makes the frequencies of coupling vibration between Fe and As atoms reduced. In addition, doping and spin effects are two effective methods to enhance the electron-phonon coupling, however, the calculated superconducting transition temperature is far lower than the experimental measurement, which rules out the simple electron-coupling superconducting pairing mechanism in SrFe1-xCoxAsF.
Thermophysical properties and rapid solidification of Al-Cu-Ge alloys
Authors: Wang Xiao-Juan  , Ruan Ying  , Hong Zhen-Yu  ,   MOE Key Laboratory of Space Applied Physics and Chemistry, Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

Al-Cu-Ge alloy system, a typical ternary eutectic alloy system, has been used widely in the industries. Our research is helpful for better understanding its thermophysical properties and improving its structural performance. In this paper, the specific heat values and thermal expansion coefficients of Al55Cu10Ge35, Al70Cu10Ge20 and Al80Cu10Ge10 alloys are investigated. The microstructural characteristics and the solidification paths of these alloys under near-equilibrium solidification and rapid solidification conditions are studied comparatively. Their specific heat values increase as Al content increases and Ge content decreases. The softening temperature is 666 K, and the thermal expansion coefficient fluctuates around 1.5×10-5 K-1 in the temperature range of 370–650 K. Under a near-equilibrium solidification condition, the last formation microstructure is (Al)+(Ge) pseudobinary eutectic instead of ternary eutectic. This means that (Al), (Ge), and CuAl2 phases are difficult to nucleate simultaneously or grow cooperatively. In comparison, during rapid solidification, the nucleation of primary phase is depressed, pseudobinary eutectic and ternary eutectic are much easier to form in these alloys.
Preparation and properties of polycrystalline and nanocrystalline Sm3Co alloys
Authors: Liu Xue-Mei  , Liu Guo-Quan  , Li Ding-Peng  , Wang Hai-Bin  , Song Xiao-Yan  ,   State Key Lab of Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China;,   College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
Published: December 2020

In this paper, a novel fabrication process of the nanocrystalline Sm3Co alloys and their fundamental properties were studied. The polycrystalline Sm3Co bulk material was prepared by the vacuum melting method. By using the polycrystalline Sm3Co bulk metal, the nanocrystalline Sm3Co alloys with an average grain size of about 8 nm was prepared by combined ball milling and spark plasma sintering. The crystal structure model was constructed and the magnetic and mechanical properties of the polycrystalline and nanocrystalline Sm3Co alloys were characterized and compared with each other in detail. Results show that the nanocrystalline alloys exhibit magnetic properties and high mechanical properties. Microhardness and elastic modulus of the nanocrystalline Sm3Co alloys are 4.87 GPa and 63.7 GPa, respectively, which are increased by 8.7% and 13.3% as compared with the polycrystalline alloys.
First principles calculations of solid phase transition of nitromethane
Authors: Zhang Li  , Chen Lang  ,   State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

The solid phase transition in crystals prepared from molecular energetic materials under extreme conditions is important for understanding the detonation mechanisms. By applying the first principles density functional calculations, a detailed theoretical study of the lattice parameters and molecular structures, equations of state, densities of state for solid nitromethane is reported. By analyzing the pressure dependence of lattice parameters, a sudden change of the lattice parameters occurs between 10-12 GPa, implying that a transition has taken place. It is also found that the maximum dihedral angle of H-C-N-O has increased from 155.3° to 177.5°, indicating that a rotation of the methyl group from a staggered to an eclipsed conformation occurs in the pressure range 11–12 GPa. Before the phase transition, the intramolecular O … H–C interactions are mainly of hydrogen bonds. After the phase transition, the intramolecular and intermolecular O … H interactions are mainly of the hydrogen bonds. Phase transition also affects the reduced ratio of band gap and the density of state near the Fermi level.
Multistage microstructural evolution caused by deformation in two-mode phase field crystals
Authors: Yun Jiang-Juan  , Chen Zheng  , Li Shang-Jie  ,   State Key Laboratory of Solidification Processing, Northwestern Polytechnic University, Xi'an 710072, China
Published: December 2020

The two-mode phase-field-crystal (PFC) method is used to calculate two-dimensional phase diagram and to simulate the process of multistage microstructural evolution in the transformation from hexagonal phase to square phase, which is induced by deformation. And the effect of misorientation and deformation on dislocation, grain boundary, crystal structure and morphology of the new phase is carefully analyzed. Simulation results show that both the nucleation site and growth direction of the square phase are affected by the direction of deformation. Under a tensile deformation, the nucleation of the square phase occurs preferentially in the deformation zone; while under compression deformation, the nucleation of the square phase may begin at dislocations and grain boundary. Moreover, the new phase grows towards the direction along which the degree of atomic mismatch decreases, i.e. the vertical direction of tensile deformation and the parallel direction of compressive deformation. Besides, the free energy varies with misorientation. In small misorientation, the dislocation climbing, slipping and annihilating will result in an energy peak; while in a big misorientation, the dislocation annihilates in several stages and thus offsetting the energy caused by deformation. Furthermore, the process of phase transformation is complex: It is not a pure phase transformation but a composite change of phase transformation and dynamic recrystallization.
Study on mechanical behavior of the transverse processing on a granular matter layer
Authors: Wu Di-Ping  , Li Xing-Xiang  , Qin Qin  , Guan Ben  , Zang Yong  ,   School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China
Published: December 2020

When the granular matter is being pushed a certain point can be found, before arriving at which the force increases linearly, and after that it increases exponentially. The granular matter is a large assemblage of solid grains, which are fundamentally different from any other type of matters, such as solid blue and liquids; they have different physical properties. The meso-scale of force chain bridges single particles and granular matter, and leads to unique properties and behaviours of granular matters, thus acts as the key issue in the study of granular matter. In this work, we first find the variation of different forces by simulation. We then propose a discrete element model based on rigorous Hertzian contact law and Mindlin-Deresiewicz contact theory for normal and tangential contact forces, respectively, and then point out that the change of force chain is the key to the granular dynamics. The force distribution and the force chain length distribution are calculated and analyzed to show the change rule and the origin of the drag force.
A method of removing baseline drift in ECG signal based on morphological filtering
Authors: Pang Yu  , Deng Lu  , Lin Jin-Zhao  , Li Zhang-Yong  , Zhou Qian-Neng  , Li Guo-Quan  , Huang Hua-Wei  , Zhang Yi  , Wu Wei  ,   College of Electrical Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China;,   National Engineering Research Center of Ultrasound Medicine, Chongqing 401121, China;,   Institute of Electronic Information, Sichuan University, Sichuan 610050, China
Published: December 2020

Removing baseline drift is an important step in preprocessing ECG signal. The traditional methods have disadvantages of large computation and poor results. This paper utilizes the morphology theory combined with the characteristics of ECG signal to propose a morphological method for removing the baseline drift, which uses different shapes and sizes to design a two-stage morphological filter and perform cascaded combination operations of closing-opening and opening-closing respectively. The proposed method is verified that it can maintain the morphological specificity, improve the SNR, reduce the MSE, and remove the noise efficiently.