bluuebunny/crossref_metadata_2025 huggingface dataset:
The resonant behavior of fractional harmonic oscillator with fluctuating mass
Authors: Yu Tao  , Luo Mao-Kang  , Hua Yun  ,   Department of Mathematics, Sichuan University, Chengdu 610064, China;,   Science and Technology on Electronic Information Control Laboratory, Chengdu 610036, China
Published: December 2020

When moving in viscous medium, the mass of a Brownian particle is fluctuant and its damping force depends on the past velocity history. Therefore, in order to investigate the characteristics of Brownian motion in viscous medium, fractional harmonic oscillator is proposed in this paper for the first time so for as we know. First, the Shapiro-Loginov formula is fractionized to solve fractional stochastic differential equation with exponential correlative stochastic coefficients. Then, by using stochastic averaging method and fractional Shapiro-Loginov formula, the analytical expression of a system’s steady response amplitude is presented and the system’s resonant behavior is discussed accordingly. Finally, the reliability of theoretical results is tested by simulation experiments. All the research shows that: (1) Stochastic resonant behavior can be induced by mass fluctuation noise. (2) Parameter-induced resonance can be induced by memory damping force. (3) Under different parameter conditions, the system’s resonant forms are diverse.
Study of 2.9 THz quantum cascade laser based on bound-to-continuum transition
Authors: Wan Wen-Jian  , Yin Rong  , Tan Zhi-Yong  , Wang Feng  , Han Ying-Jun  , Cao Jun-Cheng  ,   Key Laboratory of Terahertz Solid-State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
Published: December 2020

The material of GaAs/AlGaAs bound-to-continuum terahertz quantum-cascade laser (THz QCL) was grown by gas source molecular beam epitaxy. A THz QCL device was fabricated with semi-insulating surface-plasmon waveguide. Its spectrum and light intensity-current-voltage characteristics were studied. The device emits about 2.95 THz, and yields a maximum temperature of 67 K in pulse mode. In continuous-wave mode, it displays a threshold current density of 230 A/cm2 at 9 K with maximum emitted power of 1.2 mW and lases up to 30 K.
Image lag modeling and correction method for flat panel detector in cone-beam CT
Authors: Huang Kui-Dong  , Zhang Ding-Hua  , Li Ming-Jun  , Zhang Hua  ,   Key Lab of Contemporary Design and Integrated Manufacturing Technology (Northwestern Polytechnical University), Ministry of Education, Xi’an 710072, China;,   School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

Cone-beam computed tomography (CT) has the notable features, viz high efficiency and high precision, and is widely used in the areas such as medical imaging and industrial non-destructive testing, but the presence of image lag reduces the quality of CT images. By referencing the multi-exponential decay model for the image lag and combining with the actual decay rule of the flat panel detector output signal, a new decay modeling and correction method for the image lag based on multi-exponential fitting is proposed. Firstly, an imaging experiment using cone-beam CT based on flat panel detector is carried out; the results show that the image lag decay of the pixels in the flat panel detector has a good consistency, and is irrelevant to the initial gray value. Then, the rapid image lag correction is achieved according to the image lag decay model, and the comparison of image quality of the projected images and slice images before and after image lag correction indicates that the edge sharpness of the part has been significantly improved after the lag correction. This method does not need to obtain the scintillation compositions and the decay time constants of the detector, and is easily applied to the practical cone-beam CT imaging systems for image lag detection and correction.
Dynamics of entangled trajectories in quantum phase space
Authors: Xu Feng  , Zheng Yu-Jun  ,   School of Physics, Shandong University, Jinan 250100, China
Published: December 2020

Quantum phase space theory is widely used to investigate physical, and chemical questions. It gives us a powerful tool to study the relations between the classical and quantum world. In quantum phase space theory, entangled molecular dynamics method is developed based on quantum Liouville equation. It is different from classical Hamilton dynamics, the trajectories are entangled i.e. not independent with each other. The quantum effect in the system can be described using the semiclassical theory, and give a vivid physical picture. The quantum tunneling, photodissociation, and self-correlation are investigated using the entangled trajectory. In this paper, we review the recent development in this field.
Broadband low-RCS metamaterial absorber based on electromagnetic resonance separation
Authors: Yang Huan-Huan  , Cao Xiang-Yu  , Gao Jun  , Liu Tao  , Li Si-Jia  , Zhao Yi  , Yuan Zi-Dong  , Zhang Hao  ,   School of Information and Navigation of AFEU, Xi’an 710077, China
Published: December 2020

We have designed and fabricated a broadband low radar cross section (RCS) metamaterial absorber with polarization-independent characteristic based on electromagnetic resonance. The absorbing mechanism is investigated by means of electric as well as magnetic field distributions and retrieval algorithm. Absorbing and RCS properties of this absorber are performed by waveguide experiment and free space measurements, respectively. Theoretical analysis indicates that the absorber can produce electric and magnetic resonances in different locations for fixed frequency, while for different frequencies, it can provide energy losses in different dielectric layers, which effectively lowers the electromagnetic couplings and consequently keep the strong absorbing properties in a wide frequency range. Experimental results show that the designed absorber with 3-layer structure achieves a frequency range which is 4.25 times as that of 1-layer absorber with absorptivity above 90%, its relative bandwidth for RCS reduction above 10dB is 5.1%. The cell size and thickness of the designed absorber are very small, i.e., 0.17 and 0.015 of the working wavelength. Thus the low-RCS property of the absorber is wide-angle and polarization-independent. In addition, the working frequency range of the absorber can be adjusted by properly designing the layers.
Average capacity of free-space optical systems for a Laguerre-Gaussian beam propagating through non-Kolmogorov turbulence
Authors: Jiang Yue-Song  , Wang Shuai-Hui  , Ou Jun  , Tang Hua  ,   School of Electrical and Information Engineering, BeiHang University, Beijing 100191, China
Published: December 2020

The propagation of vortex beam in atmospheric turbulence is of great importance in theoretical study and practical applications. Based on the Rytov approximation and extended Huygens-Fresnel integral, the analytical expressions for the spiral spectrum of the Laguerre-Gaussian (LG) beam propagating in a slant non-Kolmogorov turbulence channel have been derived and the average capacity of free space optical system is given. The average capaticy of free space optical system is examined and the effects of exponent parameter, wavelength, zenith angle, inner scale, outer scale, and structure constant on average capacity are also analyzed. Results obtained in this paper may be benefical to optical communication.
Discussion on the problem of random media matching with the PCF for RFL
Authors: Wang Hui-Qin  , Gong Qi-Huang  ,   Physics Experiment Center, Nanchang University, Nanchang 330031, China;,   State Key Laboratory for Mesoscopic Physics & Department of Physics, Peking University, Beijing 100871, China
Published: December 2020

To reduce the threshold is an important requirement for utilizing the random laser. RFL (random fiber laser) is a new random laser which user the photonic bandgap of PCF to lower the threshold by filling the random medium into a hollow-core PCF. Theoretical analysis shows that most of the emitted light is concentrated in the core of the fiber because of the controlling of the bandgap, which should enhance the interaction between the random medium and the localized light for the light oscillating back and for the thin core region, therefore the excitation efficiency of the random laser could be improved. However, the band gap of PCF filled with the random medium should be changed, so when choosing fiber to reduce the threshold for RFL, we should consider the matching between the new bandgap of the padded fiber and the gain frequency of the medium, and arrange the fiber and medium in pairs reasonably. If the PCF matches with the medium, the lasing may be enhancedly regulated and controlled and the threshold can be reduced greatly.
Variational multi-source image fusion based on the structure tensor
Authors: Zhao Wen-Da  , Zhao Jian  , Xu Zhi-Jun  ,   Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

This article describes the variational multi-source image fusion using the structure tensor algorithm, which can keep the image features and details very well. We first narrative the fusion gradient field based on structure tensor, then measure the characteristic graphs of each source image, and thus construct a weight value for the source image gradient according to the characteristic graph. Gradients with high image features are highlighted in the fusion gradient field, and thus image features in the sources are well preserved. By using variational partial differential equation, the fusion image is reconstructed from the target gradient field. From the actual experimental results, the average gradient value and entropy of the fused image are found to be higher than those obtained by using the wavelet transform algorithm, tower decomposition algorithm, and direct gradient fusion algorithm, and the visual effect of the fusion image is good enough to retain the feature of source images and details in it. Therefore, it can give qualified image information for target detection and identification.
Investigation of bidirectional dual-channel long-distance chaos secure communication based on 1550nm vertical-cavity surface-emitting lasers
Authors: Zhao Yan-Mei  , Xia Guang-Qiong  , Wu Jia-Gui  , Wu Zheng-Mao  ,   School of Physical Science and Technology, Southwest University, Chongqing 400715, China
Published: December 2020

Based on the chaos synchronization between two pairs of corresponding linear polarization modes in two 1550 nm vertical-cavity surface-emitting lasers (1550 nm-VCSELs) subject to optical injection of common chaotic signals, a novel bidirectional and dual-channel long-distance chaos secure communication system is proposed. The chaotic synchronization characteristics, bidirectional dual-channel communication performance, and the influences of the fiber channel on the message transmission are numerically investigated. Results show that, driven by a common chaotic signal generated from a driver VCSEL (D-VCSEL), two pairs of responding linear polarization modes in two response 1550nm-VCSELs (R-VCSELs) can be synchronized completely and isochronally. Meanwhile, the synchronization coefficients between the two pairs of responding linear polarization modes in D-VCSEL and R-VCSELs are low. Based on the high quality chaos synchronization between two pairs of responding linear modes in two R-VCSELs, bidirectional and dual-channel chaos secure communication can be achieved. After adopting a single mode polarization-maintaining fiber (or dispersion-shifted polarization-maintaining fiber), for 2.5 Gbit/s messages, the Q factor of the decryption signals after transmitting 60 km (or 200 km) can be more than 6.
A gradient representation of first-order Lagrange system
Authors: Mei Feng-Xiang  , Wu Hui-Bin  ,   School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081, China;,   School of Mathematics, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

A gradient representation of the first-order Lagrange system is studied. A condition under which the first-order Lagrange system can be considered as a gradient system is obtained. The stability of the system is discussed by using the property of the gradient system. Some examples are given to illustrate the application of the result.
Asymptotic analysis for effect of thermal inertia on thermal behaviors
Authors: Wang Ying-Ze  , Song Xin-Nan  , Liu Dong  ,   Department of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

The inertia effect induced by the motion of heat flow will have a significant impact on the heat transfer, when the heat pulse duration or the device structure has micro-scale characteristics. Based on the thermomass theory, the thermal wave equation is introduced to describe the motion of thermomass, and the generalized thermoelastic dynamic model involved in the thermal inertia is established by combining the constitutive relation of isotropic material. By taking into account the micro-scale characteristics for the transient heat transfer, the one-dimensional problem for the semi-infinite solid with the boundary subject to thermal impact is investigated by an analytic method, where the asymptotic solutions for thermoelastic response are obtained. With these solutions, the propagation of the thermal wave and thermal elastic wave and the distribution of the temperature, displacement and stresses are studied. By comparison with the same predictions of the L-S generalized thermoelasticity, the effect of thermal inertia on the thermal behaviors is revealed. The results show that the spatial thermal inertia induced by the motion of heat flux has an impact on the thermal behaviors, except for the temporal thermal inertia. All the velocities and wavefront locations of thermal wave and thermal elastic wave, and the time of each physical field begin to establish, the peak values of jumps and the intervals of two jumps are influenced by the spatial thermal inertia.
Interaction between bubble and free surface near vertical wall with inclination
Authors: Liu Yun-Long  , Wang Yu  , Zhang A-Man  ,   Collage of Shipbuilding and Engineering, Harbin Engineering University, Harbin 150001, China;,   Unit 92857 of PLA, Beijing 100161, China
Published: December 2020

Study on the interaction between bubble and free surface near an inclined vertical wall is carried out in this paper. Firstly, boundary element model for bubble dynamics based on incompressible potential flow is established, and the solid wall is modeled using the images of bubble and free surface. Then, through the numerical model, bubble dynamics near the walls with various inclination angles are studied respectively. We find that the inclination would lead discontinuity of the boundary condition of intersection between free surface and solid wall, which can affect its motion nonlinearly. Finally, the influence of the inclination angle on the bubble and spike dynamics is analyzed.
Dynamics of insoluble surfactant-laden thin films flow over inclined random topography
Authors: Li Chun-Xi  , Pei Jian-Jun  , Ye Xue-Min  ,   Key Laboratory of Condition Monitoring and Control for Power Plant Equipment, North China Electric Power University, Baoding Hebei 071003, China
Published: December 2020

For the flow of an insoluble surfactant-laden thin film and droplet on inclined random topography, the lubrication theory is used to derive the evolution equations of thin liquid film thickness and interfacial surfactant concentration. Characteristics of thin film flow and droplet spreading, as well as the influence of topography structure are numerically simulated with PDECOL code. Results show that under the action of gravitational component and Marangoni effects, the thin film flow and droplet spreading is accelerated; the capillary ridge emerges at the thin film edge and the droplet center; and at the bottom of the thin film and droplet, the depression is generated. While the deformation of liquid film free surface is more significant due to the effect of random topography. The increasing θ has a role of enhancing gravitational component and Marangoni effects, leading to the enhancement of the capillary ridge and depression. The increase of D promotes the thin film flow and droplet spreading, but causes the deformation amplified; and the increased k0 can induce the evolutions of thin film flow and droplet spreading to slow down and inhibit the formation of capillary ridge and depression. In addition, compared with the thin film flow, the impact of D and k0 on the speed of droplet spreading is relatively weak.
Influence of site-selective doping of Er3+ on the upconversion spectra in KPb2Br5
Authors: Ling Zhi  , Li Lan  , Zhang Xiao-Song  , Zhou Yong-Liang  , Wei Feng-Wei  , Feng Zhi-Jun  , Sun Jian  , Li De-Jun  ,   College of Science, Tianjin University of Technology, Tianjin 300384, China;,   Institute of Material Physics, Key Laboratory of Display Materials and Photoelectric Devices, Ministry of Education, Tianjin University of Technology, Tianjin 300384, China;,   College of Physics and Electronic Information, Tianjin Normal University, Tianjin 300387, China
Published: December 2020

Different concentrations of Er3+ doped in KPb2Br5 powders are prepared by solid-state reaction method. The upconversion spectra under the excitation of 980 nm laser are characterized and show the concentration-related change in emission band. With the doping concentration of 2.5 mol%, the sample exhibits mainly two green emission peaks at 530 nm and 550 nm, which correspond to the transitions of 2H11/2 and 4S3/2 levels to ground state 4I15/2 respectively. When the doping concentration of Er3+ is increased to 5 mol%, the upconversion emission is dominated by 490 nm, related to the transition of 4F7/2 to 4I15/2. Increasing the doping concentration up to 7.5 mol%, the emission quenching is observed throughout and the emission band appears mainly at 690 nm which comes from the transition of 4F9/2 to 4I15/2. The influence of possible substitution of Er3+ on lattice constant and upconversion emission properties of KPb2Br5 are discussed based on the first-principles calculation and Judd-Ofelt theory. The results show that the substitution of Er3+ in KPb2Br5 is dominated for Pb(1) in low concentration. When increasing the Er3+ doping concentration, it may substitute for Pb(2) Pb(1) and Pb(2) sites. The impact of the symmetry of the crystal field on the site-selective doping of Er3+ is proposed to explain the variation of upconversion luminescence spectrum.
Influence of the growth conditions on the transparent conductive properties of ZnO：Al thin films grown by pulsed laser deposition
Authors: Han Jun  , Zhang Peng  , Gong Hai-Bo  , Yang Xiao-Peng  , Qiu Zhi-Wen  , Zi Min  , Cao Bing-Qiang  ,   Key Lab of Inorganic Functional Material in Universities of Shandong, School of Material Science and Engineering, University of Jinan, Jinan 250022, China
Published: December 2020

The influences of aluminum doping, oxygen pressure, and substrate temperature on the transparent conductive properties of ZnO:Al (AZO) films grown by pulsed laser deposition (PLD) were investigated using scanning electron microscope, atomic force microscope, X-ray diffraction, Hall effect measurements, and optical transmission spectrum. When the aluminum doping concentration is over 0.5 wt%, all the PLD grown AZO films are degenerated and the aluminum donors are thermal ionized even at a low temperature of 80 K. As a result, the bandgap of AZO film shows blue shifts due to the Bernstein-Moss effect as further confirmed by optical transmission spectrum. The influences of the oxygen pressure and substrate temperature on the transparent conductive property of AZO films were further studied. When the oxygen pressure is 1 Pa and the substrate temperature is 200 ℃, the best conductivity property of AZO thin film is obtained with Hall mobility of 28.8 cm2/V·s and film resistivity of 2.7×10-4 Ω·cm. Moreover, the light transmittance in the visible range exceeds 85%. However, as the oxygen pressure and temperature continue to increase, the film resistivity will increase.
SiBN ceramics, a stealth material at high temperature
Authors: Lu Ai-Jiang  ,   Physics department of Science College, Donghua University, Shanghai 201620, China
Published: December 2020

Silicon boron nitride (SiBN) has been paid attention extensively due to its high melting point and anti-oxidation, which is also the reason that one of the research focus is its physical property of this material at high temperatures. It has been reported that amorphous SiBN ceramics could be modeled based on the the atomic structure of -Si3N4. In this paper, the molecular dynamics and DFT calculation were employed to explore the structural model of SiBN, to reveal the electronic and optical properties of SiBN at high temperatures. It is worth noting that, different from -Si3N4, the absorption of SiBN at visible light and higher frequency decreases at higher temperatures, and the reflectance decreases to 1% or so. Such results could not be found in single crystalline Si3N4. These indicate the possibility of SiBN used as the stealth coating. It also could be a good candidate in the optoelectronic application of amorphous materials in the near future.
Growth of vanadium dioxide thin films on Pt metal film and the electrically-driven metal–insulator transition characteristics of them
Authors: Qiu Dong-Hong  , Wen Qi-Ye  , Yang Qing-Hui  , Chen Zhi  , Jing Yu-Lan  , Zhang Huai-Wu  ,   State Key Laboratory of Electronic Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China;,   National Key Laboratory of Science and Technology on Communication, University of Electronic, Science and Technology of China, Chengdu 610054, China
Published: December 2020

High-quality VO2 thin films are deposited on the metal platinum (Pt) electrode buffered by silicon dioxide (SiO2) using radio frequency magnetron sputtering. The effect of the thickness of SiO2 on the the crystal structure, morphology and metal-insulator transition (MIT) performance of the films are discussed. Results show that SiO2 buffer layer with a thickness of 0.2 μm can effectively eliminate huge stress between the VO2 film and the metal film; and the VO2 thin film with the distinct MIT are deposited. When the buffer layer reaches more than 0.7 μm, the VO2 film has a distinct (011) preferred orientation, the smooth surface and compact nanostructure, and the resistance change reaches more than three orders of magnitude. At the same time, Pt-SiO2/VO2-Au sandwiched structure is achieved to test the current versus voltage curves, in which can be seen several distinct steps of current caused by the voltage perpendicular to the plane of a VO2 film. The result confirms the electrically-driven metal-insulator transition. Due to the high-quality VO2 and the flexible device structure, the VO2/Pt-SiO2 can be widely used for large-scale integrated electronic control devices.
Theoretical study on degradation phenomenon on AlGaN/GaN resonant tunneling diode
Authors: Chen Hao-Ran  , Yang Lin-An  , Zhu Zhang-Ming  , Lin Zhi-Yu  , Zhang Jin-Cheng  ,   Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi’an 710071, China
Published: December 2020

In this paper we study theoretically the degradation phenomenon of GaN-based resonant tunneling diode (RTD). The effects of trapping centers on GaN-based RTD are calculated and studied by self-consistently solving the Poisson-Schrödinger aligns when three experimentally obtained deep-level trapping centers are introduced into the AlGaN/GaN/AlGaN quantum well. Results show that the degradations of negative differential resistance (NDR) characteristic in GaN-based RTDs are actually caused by the combined action of the activation energy and the defect density. The deep-level trapping center with high activation energy plays a dominating role in the degradation of NDR characteristics because the probability of ionization is exponentially proportional to the activation energy.
Analysis of the finite-temperature phase transition of Heisenberg antiferromagnetic compound LiVGe2O6
Authors: Huang Hai  , Li Wei-Feng  ,   Mathematics and Physics Department, North China Electric Power University, Beijing 102206, China
Published: December 2020

The susceptibility and nuclear magnetic resonance measurements on quasi-one-dimensional spin-1 Heisenberg antiferromagnet LiVGe2O6 indicate that this material shows a phase transition from paramagnetic state to antiferromagnetic Nel state at about 22 K, and there exists a gap in the low-temperature magnetic excitation spectrum. Based on the model Hamiltonian of LiVGe2O6, we propose a low-energy field theoryGinzburg-Landau theory for this compound. From this theory, we study the finite-temperature phase transition induced by spontaneous symmetry breaking and then calculate the finite-temperature susceptibility of LiVGe2O6. All the theoretical calculations are consistent with the experimental results.
Investigation of magnetic properties of FeCoAlON thin films with stripe domain structure
Authors: Wang Rui  , Zheng Fu  , Luo Fei-Long  , Lou Yuan-Fu  , Wang Ying  , Cao Jiang-Wei  , Bai Jian-Min  , Wei Fu-Lin  , A. S. Kamzin  ,   Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education Research Institute of Magnetic Materials, Lanzhou University, Lanzhou 730000, China;,   Ioffe Physico-Technical Institute of Russian Academy of Sciences, St. Petersburg 194021, Russian Federation
Published: December 2020

The FeCoAlON thin films were prepared by magnetron sputtering. Effect of element addition of Al, O, and N on magnetic materials was studied. Experiment demonstrated that with increasing Al, O and N, the film structure changed from polycrystalline to amorphous, and the films showed soft magnetism. When N content in the film is high, the films show stripe domain structure. The condition and mechanism for the occurrence of stripe domain structure were discussed in detail, and we found that the frequency response of permeability of the films show characteristics of multi-peak resonance.
Relationships between synthesizing parameters, morphology, and contact angles of ZnO nanowire films
Authors: Jing Wei-Xuan  , Wang Bing  , Niu Ling-Ling  , Qi Han  , Jiang Zhuang-De  , Chen Lu-Jia  , Zhou Fan  ,   State Key Laboratory for Manufacturing Systems Engineering at Xi’an Jiaotong University, Xi’an 710049, China
Published: December 2020

Synthesizing parameters in the hydrothermal method can affect directly the morphology and the contact angles of ZnO nanowires films, and thus the controllable wettability. In this paper effects of characteristic parameters on the properties of random rough surfaces are simulated, including arithmetical mean deviation of the profile, skewness, kurtosis and correlation length. Batches of ZnO nanowires films with varied morphology were synthesized in different concentrations of seed layer solution and growth solution, as well as growth time spans. Sampling length was determined and characteristic parameters of the profiles of ZnO nanowires films were extracted based on SEM micrographs and specific operators of Matlab software. With vertical and lateral parameters of the morphology introduced into Wenzel model, relationships between synthesizing parameters, morphology, and contact angles of ZnO nanowires films were established. It is conculded that the sampling length was determined to be 5 μm, crystallization between ZnO nanowires occurred as the concentration of growth solution was larger than 0.125 mol/L, resulting in hydrophobic ZnO nanowires films; different concentrations of seed layer solution and growth time spans led to hydrophilic ZnO nanowire films. These results can be used to immobilize various enzymes on ZnO nanowires films and further to improve the property of ZnO nanowires-based bio-sensors.
Equivalent circuit analysis model of charge-controlled memristor and its circuit characteristics
Authors: Hu Feng-Wei  , Bao Bo-Cheng  , Wu Hua-Gan  , Wang Chun-Li  ,   School of Information Science and Engineering, Changzhou University, Changzhou 213164, China;,   Department of Electronic Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

Memristor realized physically is recently a basic two-terminal circuit element with memory property. Based on Taylor series form of φ-q relationship, a charge-controlled memristor equivalent circuit analysis model is built. A charge-controlled memristor model with cubic nonlinearity is taken, as an example, to make a theoretical analysis of circuit characteristics, such as voltage-current relationship, active-passive property, and so on, of the charge-controlled memristor with different parameters. Results indicate that the voltage-current relationship of the charge-controlled memristor has an italic “8” shaped hysteresis loop characteristic, and the charge-controlled memristor shows passivity and activity accompanied with the variations of parameter symbols, resulting in the occurrence of the corresponding variations of circuit characteristics; compared with the passive memristor, the active memristor is more suitable for use as a second harmonic signal generation circuit. An experiment circuit is built based on the equivalent circuit of the charge-controlled memristor characteristic analysis, and the experimental results well verify the theoretical analysis.
Characteristics of lightning radiation source distribution and charge structure of squall line
Authors: Liu Dong-Xia  , Qie Xiu-Shu  , Wang Zhi-Chao  , Wu Xue-Ke  , Pan Lun-Xiang  ,   Key Laboratory of Middle Atmosphere and Global Environment observation, Institute of Atmospheric Physics, Chinese Academy of Science, Beijing 100029, China;,   College of Atmosphere Sciences, Lanzhou University, Lanzhou 730000, China
Published: December 2020

Lightning information indicates the intensity and the development of severe convection. The characteristics of lightning activity and charge structure of a squall line over Beijing on 13 June 2010 are analyzed by using the SAFIR3000 lightning detection data, Doppler weather radar and precipitation data. Results show that the lightning radiation sources are the major part in the convective leading region with a high reflectivity in front of the squall line, and the number of lightning radiation sources gradually increases in the back of stratiform region only at the dissipating stage. The correlation coefficient between the total lightning and convective precipitation is found to be 0.82, and that of intra-cloud lightning and convective precipitation is 0.76. It is inferred that the lightning is closely related to dynamical and microphysical processes of the squall line. According to the lightning radiation distribution, the charge structure of squall line is also discussed. At the mature stage of the squall line, the lightning radiation sources have two layers with the upper level centered at 11 km and the lower level at 6 km. Based on the bidirectional leader of lightning propagation and by assuming VHF source density maxima being most likely associated with the positive charge region, it is concluded that the squall line is characterized by a tripole charge structure with a middle charge region between the levels of 8 km and 10 km, and the two positive charge regions at the levels of 10 to 12 km and 4 to 7 km above the ground, respectively.
The study of conserved quantities and symmetries for two-dimensional isotropic harmonic charged oscillator moving in homogeneous magnetic field
Authors: Lou Zhi-Mei  ,   Department of Physics, Shaoxing University, Shaoxing 312000, China
Published: December 2020

The kinematic differentiation equations of two-dimensional isotropic harmonic charged oscillator moving in a homogeneous magnetic are obtained by using Newton’s second law. Two integrals (conserved quantities) are obtained by directly integrating the kinematic differentiation equations. The relationship between the Lagrangian and the conserved quantity is established through the Legendre transformation, thereby obtaining a Lagrangian function of the system. The Noether symmetry and Lie symmetry of the infinitesimal transformations corresponding to the conserved quantities are studied. Finally, the kinematical equations of the system are obtained.
Entanglement properties of two atoms interacting with weak coherent states trapped in two distant cavities connected by an optical fiber
Authors: Wang Zhong-Qing  , Zhao Xiao-Qi  , Zhou Xian-Ju  ,   School of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065, China
Published: December 2020

Considering a system comprised of two-level atoms resonantly interacting with weak coherent states trapped in two distant cavities connected by an optical fiber initially, we study the entanglement properties of the atom-atom, the cavity-cavity and the atom-cavity. Then the influences of the ratio between fiber-cavity and atom-cavity coupling intensity, the intensity and the phase of the cavity field on the entanglement properties are investigated numerically. It is shown that the entanglements of the atom-atom, the cavity-cavity and the atom-cavity vary with time in the periodical or approximately periodical manner; the entanglement can be transferred from cavity-cavity to atom-atom reciprocally. Compared with the entanglements of atom-atom and cavity-cavity, the varying period of atom-cavity entanglement is short. The ratio of fiber-cavity coupling intensity to atom-cavity coupling intensity and the phase of cavity field affect the entanglement properties greatly. The great entanglement can be achieved by using a smaller ratio of coupling intensity between fiber-cavity and atom-cavity.
Chaos analysis of the rational Bézier biquadratic surface in the unit area
Authors: Yu Wan-Bo  , Zhou Yang  ,   School of Information, Dalian University, Dalian 116622, China
Published: December 2020

In the paper, the chaotic characteristics of two functions are studied by a quadratic surface mapping in spatial unit area. When a surface is the standard surface in spatial unit area and another surface is generated randomly, the probability that the two functions are in the chaos can be greater than one-tenth, so this is a better method of generating chaos. The chaotic characteristics are analyzed by calculating the Lyapunov exponent and drawing the bifurcation diagram. According to the bifurcation diagram of the changing parameter and the characteristics of the regional distribution of the chaotic surface control points, the chaotic mapping function can be found and a lot of two-dimensional chaotic attractor graphics can be obtained. Besides, gray scale image is regarded as a discrete two-dimensional function for the first time. The study of image as an iteration expression shows some chaotic characteristics. The study shows that the same or similar image converges to the cycle point easily, which can be used in some research areas such as image recognition.
Characteristics of time-delay complex Lorenz chaotic system and its self-synchronization of time delay
Authors: Zhang Fang-Fang  , Liu Shu-Tang  , Yu Wei-Yong  ,   College of Control Science and Engineering, Shandong University, Jinan 250061, China
Published: December 2020

Self-synchronization of time delay implies that the synchronization between the time-delay system and the original system keeps the structure and parameters of systems unchanged, thus these various problems produced by time-delay in practice are avoided. Taking a time-delay complex Lorenz system for example, we investigate its dynamic characteristics and the influence of of time lag factor. A nonlinear feedback controller is designed to realize the self-synchronization of time delay of the complex Lorenz system. Numerical simulations verify the effectiveness of the presented controller. The controller adopts some states to realize the synchronization of all states. It is simple in principle and easy to implement in engineering.
Theoretical study of adsorption of propanethiol on Au(111) surface at different coverages
Authors: Ran Run-Xin  , Fan Xiao-Li  , Yang Yong-Liang  , Fang Xiao-Liang  ,   State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

By applying the first-principles method based on the density functional theory, we study the non-dissociative adsorption of C3H7SH molecule and the dissociated adsorption of C3H7S group both on Au(111) surface at five kinds of coverages (1/16, 2/16, 3/16, 4/16, 1/3). It is found that both the tilt angle and the adsorption energy are affected by coverage. When the coverage increases to 1/3, the tilt angle of the molecular axis reduces 6°–10°, and the adsorption energy reduces 0.21 eV. At a saturated coverage, the absorption properties are especially studied for three Au(111) surface structures of (3×3), (2√3×2√3 ight)R30° and 2√3×3. For the non-dissociative adsorption of C3H7SH at the saturated coverage, both the adsorption configurations and adsorption energies are almost the same for the three surface structures. But for the dissociated C3H7S group, the adsorption energies of surface structures of (2√3×2√3 ight)R30° and 2√3×3 are about 0.05-0.07 eV higher than that of the (3×3) surface structure. Effects of the van der Waals interaction on the adsorption configuration and energy are investigated by the DFT-D2 method. For the non-dissociative adsorption of C3H7SH/Au(111) system at a saturated coverage of 1/3, the van der Waals interaction reduces the interaction distance between the adsorbate and the substrate, and corrects the adsorption energy by 0.53 eV, which is close to experimental result.
Research on proton-impact excitation process of hydrogen atom in Debye plasma
Authors: Sun Tian-Miao  , Qi Yue-Ying  , Ye Dan-Dan  , Ning Li-Na  ,   Jiaxing University, Jiaxing 314001, China
Published: December 2020

The high-energy H++H impact excitation process in Debye plasma is investigated using impact parameter Born approximation method. In the cases of several different values of Debye length D, the inter-nuclear distance R of matrix elements, the weighted probability at a collision energy of 160 keV/u, and impact excitation cross sections in an energy range of 100–1000 keV/u for direct 1s → 2p transition in H for both the unscreened and screened Coulomb interactions are calculated. It is demonstrated that the magnitude of impact excitation cross section gradually reduces as screening parameter increases. According to the excitation cross section formula and the calculated results, a detailed analysis of the reason for the reduction caused by excitation cross section is given in this paper. The effects of screened Coulomb interaction on the potential of between incident particles and excited electronic and on the hydrogenatomic structure (wave function and energy level) have very important influence on the excitation cross section.
Influence of gas bubbles in valve-less micropump chamber on periodic driving pressure
Authors: Jiang Dan  , Li Song-Jing  , Yang Ping  ,   School of Mechanical, Electronic and Industrial Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China;,   School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

The appearance of gas bubbles in a valve-less micropump is generally undesirable as they can lead to performance deterioration, life reduction and even complete failure of the micropump. In order to predict influence of gas bubbles in valve-less micropump chamber on periodic driving pressure, the mathematical models, including volume change of chamber, continuity equation, effective bulk modulus and resistance coefficients of the nozzle and diffuser, are given to describe dynamic characteristics of piezoelectric valve-less nozzle/diffuser micropump. The influence of different gas bubble volume in chamber on the valve-less micropump periodic driving pressure is analyzed. Pressure pulsations with two gas bubbles into the valve-less micropump chamber are simulated and tested. Simulation and experimental results are given. Comparison of the results shows that the mathematical model and simulation method can handle the prediction of pressure pulsations accompanying gas bubble in the valve-less micropump.
Nonlinear Ramsey interference with Gaussian pulse
Authors: Chen Chao  , Tian Gang  , Yu Shu-Juan  , Yang Shi-Ping  ,   College of Physics Science and Information Engineering, Hebei Normal University, Shijiazhuang 050024, China
Published: December 2020

According to the theory of nonlinear Rosen-Zener tunneling, we investigate the nonlinear Ramsey interference of Bose-Einstein condensate in a double-well potential with Gaussian pulse. Rich Ramsey fringes are shown by the numerical simulations. The influences on the fringes of the atom-atom interaction and the period of Gaussian pulse are discussed. We obtain the analytical expression for the fundamental frequency of Ramsey fringes by using Hamilton equation. The relation of the frequency to the interaction strength and the Gaussian-pulse period is found by analyzing the fringes through Fourier transformation. The numerical simulations are consistent with our theoretical predictions.
The effects of precipitant on the defect structures and properties of ZnO varistor ceramics
Authors: Wang Hui  , Lin Jia-Jun  , He Jin-Qiang  , Liao Yong-Li  , Li Sheng-Tao  ,   State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China;,   Electric Power Research Institute, CSG, Guangzhou 510080, China
Published: December 2020

The effects of different precipitants (NH4HCO3 and NaOH) on the performances of ZnO varistor ceramics which were prepared by coprecipitation method were analyzed. There are noticeable influences for different precipitants to the microstructure and electrical performances of ZnO varistor ceramics. The change of microstructure is caused by the properties of precipitants themselves while the change of electrical performance is caused by the influence of precipitants to the grain boundary potential barrier properties. Besides, the donor impurity ion Na+ introduced by NaOH in the ZnO varistor ceramic will increase the free electron concentration in the grain. So the densities of intrinsic defects (zinc interstitial and oxygen vacancy) are restrained. The density of zinc interstitial is more sensitive to donor impurity ions compared with oxygen vacancy. Therefore the choice of precipitant is important when using coprecipitation method to prepare the powder of ZnO varistor ceramics. Even little impurity ions will result in the obvious change of the performance of varistor ceramics. The impurity ions should be avoided in the powder of ZnO varistor ceramics.
Chaotic laser parallel synchronization and its application in all-optical logic gates
Authors: Yan Sen-Lin  ,   Department of Physics and Electronic Engineering, Nanjing Xiaozhuang University, Nanjing 211171, China
Published: December 2020

We present a “master-slave-response” synchronization system of chaotic multiple-quantum-well lasers. And we study the applications of chaotic parallel synchronization for optical logic gates. An injection multiple-quantum-well laser drives two responding systems of multiple-quantum-well lasers to obtain chaotic synchronization while the injection multiple-quantum-well laser can synchronize the responding systems. We present theoretically the constructions of the fundamental all-optical gates based on the parallel synchronization of responding systems and define their computational principle. By modulating the driving light into the responding systems, all-optical logic gates characterizing logic function are realized by synchronizing or unsynchronizing appropriately the two chaotic states of responding systems. We present all-optical XNOR, NOR, NOT logic gates and their logic computational methods. Numerical simulation result validates the feasibility of the system.
Multi-reference calculations on the potential energy curves and spectroscopic properties of the low-lying excited states of BS+
Authors: Gao Xue-Yan  , You Kai  , Zhang Xiao-Mei  , Liu Yan-Lei  , Liu Yu-Fang  ,   College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007, China
Published: December 2020

The high-level quantum chemistry ab initio multi-reference configuration interaction method (MRCI) with reasonable aug-cc-p VQZ basis sets is used to calculate the potential energy curves of 5 -S states of BS+ radical related to the dissociation limit B+(1Sg)+S(3Pg) and B+(1Sg)+S(1D), where the ground state of X3 is determined. The spin-orbit interaction is firstly considered, which makes the calculated 5 -S states split in to 9 states. Calculated results show that avoided crossing rule exists between the states of the same symmetry. Analysis of electronic structures of -S states shows that the -S electronic states are multi-configuration in nature. Then the spectroscopic constants of the bound -S and states are obtained by solving the radial Schrdinger equation. All of these data will provide accurate information of the electron structure for further research on BS+ in theory and experiment.
Noether symmetries of dynamics for non-conservative systems with time delay
Authors: Zhang Yi  , Jin Shi-Xin  ,   College of Civil Engineering, Suzhou University of Science and Technology, Suzhou 215011, China;,   College of Mathematics and Physics, Suzhou University of Science and Technology, Suzhou 215009, China
Published: December 2020

The Noether symmetries and the conserved quantities of dynamics for non-conservative systems with time delay are proposed and studied. Firstly, the Hamilton principle for non-conservative systems with time delay is established, and the Lagrange equations with time delay are obtained. Secondly, based upon the invariance of the Hamilton action with time delay under a group of infinitesimal transformations which depends on the generalized velocities, the generalized coordinates and the time, the Noether symmetric transformations and the Noether quasi-symmetric transformations of the system are defined and the criteria of the Noether symmetries are established. Finally, the relationship between the symmetries and the conserved quantities are studied, and the Noether theory of non-conservative systems with time delay is established At the end of the paper, some examples are given to illustrate the application of the results.
Analytical modeling for drain current of strained Si NMOSFET
Authors: Zhou Chun-Yu  , Zhang He-Ming  , Hu Hui-Yong  , Zhuang Yi-Qi  , Lü Yi  , Wang Bin  , Li Yu-Chen  ,   Key Laboratory for Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi’an 710071, China
Published: December 2020

Based on the structure of strained Si/SiGe NMOSFET, a unified drain current model is presented in this paper. The model describes current characteristics from subthreshold to strong inversion as well as from the linear to the saturation operating regions with a smoothing function, and guarantees the continuities of the drain current and its derivatives.Furthermore, the model accuracy is enhanced by including carrier velocity saturation and channel length modulation effects. Comparisons between the model and the measured data show that the drain current model can describe the device characteristics well. The proposed model is useful for the design and simulation of digital and analogy circuits made of strained Si.