bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparative study between MEAM and Tersoff potentials on the characteristics of melting and solidification of carborundum
Authors: Zhou Nai-Gen  , Hong Tao  , Zhou Lang  ,   School of Materials Science and Engineering, Nanchang University, Nanchang 330031, China
Published: December 2020

Molecular dynamic simulations of bulk melting, surface melting and crystal growth of SiC are carried out. The atomic interactions in SiC are calculated by MEAM and Tersoff potentials separately. The results show that the bulk melting of SiC with MEAM potential exhibits its relations to temperature similar to that with Tersoff potential, while can be indicated by the mean atomic energy, Lindemann index and structure order parameter. The difference between them is the bulk melt point: MEAM is 4250 K, while Tersoff is 4750 K. At the same superheat degree, the velocities of surface melting of SiC separately, with MEAM and Tersoff potentials are in substantial agreement. But at the same absolute temperature, the surface melting of SiC with MEAM potential is faster than that which the Tersoff potential, which is due to the difference in thermodynamic melting point. The Measured value of the thermodynamic melting point of MEAM is 3338 K compared with 3430 K of Tersoff. On the crystal growth side, the crystal growth velocity of SiC with MEAM potential is related to the undercooling. The fastest velocity corresponds to the undercooling of 400 K. However, the crystal of SiC with Tersoff potential cannot grow in the undercooling of 0 K1000 K. Overall, the MEAM potential is better than Tersoff potential in the sense of describing the melting and solidification of carborundum.
Chaos quantum clonal algorithm for decision engine of cognitive wireless network
Authors: Chai Zheng-Yi  , Liu-Fang  , Zhu Si-Feng  ,   School of Computer Science and technology, Xidian University, Xi’an 710071, China;,   Key Laboratory of Intelligent Perception and Image Understanding of Ministry of Education, Xi’am 710071, China
Published: December 2020

By analyzing engine decision of cognitive wireless network, the mathematical model of engine decision is given, and then it is converted into a multi-objective optimization problem. A Chaos quantum clonal algorithm is proposed to solve the problem, and the algorithm convergent with probability 1 is proved, in which the quantum coding and logistic mapping are used to initialize the population. A quantum mutation scheme is designed with chaotic disturbances. Finally, the simulation experiments are done to test the algorithm under a multi-carrier system. The results show that compared with QGA-CE (quantum genetic algorithm based cognitive engine), this algorithm has a good convergence and an objective function value. It can adapt the parameter configuration and meet the real-time requirement for cognitive engine.
The simulation and revision of soil moisture over Tibetan Plateau
Authors: Yu Lian  , Wang Cheng-Hai  ,   College of Atmospheric Science, LanZhou University, Lanzhou 730000, China
Published: December 2020

In this paper, the soil moisture is simulated by RegCM3 over the Tibetan Plateau. The obtained results are as follows:(1) The simulated annual cycle of soil moisture is consistent with the observation, but the simulations of soil moisture with different land surface conditions are different. (2) In the area with sparse vegetation , the simulated soil moisture is larger than observation in summer and consistent with that in winter, while in the area with lush vegetation, simulated soil moisture is consistent with observation in summer and larger than that in winter. (3) The larger deviation of simulated soil moisture is corresponding to a large deviation of simulated precipitation and temperature.The soil moisture is revised with revised method, and the results show that the debiations of soil moisture and temperature are reduced. The systematic errors of temperature and precipitation are eliminated after revision. We believe that the revised soil moisture and temperature can provide more accurate data over Tibetan Plateau, and be used to calculate the permafrost distribution.
Analysis of decadal characteristics of leading teleconnections based on complex networks theory
Authors: Gong Zhi-Qiang  , Zhi Rong  , Hou Wei  , Wang Xiao-Juan  , Feng Guo-Ling  ,   Laboratory for Climate Studies of National Meteorological Bureau Climate Research Center, Beijing 100081, China;,   College of Physics and Electronic Engineering, Changshu Institute of Technology, Changshu 215500, China;,   Department of Physics Yangzhou University, Yangzhou 225002, China
Published: December 2020

We construct a complex network of the middle latitude circulation system of north hemisphere (NCNH). The decadal characteristic of leading teleconnection and its probable correlation with abrupt climate change are analyzed base on the circulation system network. Results show that (1) action centres of NAO, EUPA and WP have all moved during different periods in the recent 40 years and there has been a common abrupt change process as the end of the 1970s and beginning of the 1990s separately; (2) the new index which denotes the importance of teleconnection is defined using the node degree of NCNH. The temporal change of new index shows that the leading modes were PNA, EUPA and WP before the 1980s; index of NAO notably increased and all the five teleconnections were comparatively robust after 1980s; the index of AO notably increased and other modes comparatively decreased after 1987. So, center and index changes of decadal leading teleconnections may be another important phenomenon of abrupt climate change.
Constructing path curve for a class of generalized phase tracks of canard system
Authors: Ouyang Cheng  , Yao Jing Sun  , Wen Zhao-Hui  , Mo Jia-Qi  ,   Faculty of Science, Huzhou Teacher College, Huzhou 313000, China;,   Department of Mathemtics, Anhui Normal University, Wuhu 241003, China;,   School of Statistics and Applied Mathematics, Anhui University of Finance and Economics, Bengbu 233030, China
Published: December 2020

A class of generalized phase tracks of canard system is obtained. Firstly, the solutions to the generalized Lienard system are considered. Then the possessed head canard solutions are constructed, and illustrated the examples to construct the canard. Using this same method, we may construct also more extensive canards.
The modified variational iteration method for air-sea coupled dynamical system
Authors: Cao Xiao-Qun  , Song Jun-Qiang  , Zhang Wei-Min  , Zhao Jun  , Zhu Xiao-Qian  ,   School of Computer Science, National University of Defense Technology, Changsha 410073, China
Published: December 2020

A air-sea coupled dynamical system describing the oscillating physical mechanism of ENSO is studied. Using the modified variational iteration method (MVIM), the approximate expansions of the solution for corresponding problem are obtained effectively. And the numerical results show that the approximate solutions from the MVIM method are highly accurate by comparson with the exact solution of the model in a special case.
Robust adaptive radial wavelet neural network control for chaotic systems using backstepping design
Authors: Miao Zhi-Qiang  , Wang Yao-Nan  ,   College of Electrical and Information Engineering, Hunan University, Changsha 410082, China
Published: December 2020

This paper designs an adaptive and robustness backstepping control law to realize the control of Rossler-like systems of uncertainties. First, a wavelet network is used for the identification the nonlinear part of the system to change it into parametric model with parametric and structural uncertainties; Then, for the parameter uncertainties, an adaptive control law is designed to online estimate the unknown parameters; for the structural uncertainties, a robust control law is designed to make the system robustness. Finally, The effective of this methodology is illustrated by the simulation results.
The modification of entropy production by heat condution in non-equilibrium thermodynamics
Authors: Dong Yuan  , Guo Zeng-Yuan  ,   Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
Published: December 2020

The entropy production is expressed as the product of the generalized force (driving force) and generalized flux, which plays a central role in classical non-equilibrium thermodynamics. This expression has shortcomings in two aspects: first, the decomposition into generalized fluxes and forces is arbitrary to some extent; more importantly, the entropy production is negative value calculated in heat wave propagation, which breaks the second law. In this paper, we carry out analyses based on the thermomass theory and show that the entropy production is induced by the dissipation of thermomass energy during heat condution. The generalized force of entropy production is not driving force but resistive force, having a unit of force in Newton’s mechanics. The modified expression for entropy production not only guarantees its positiveness in propagation of heat waves consistent with the extended irreversible thermodynamics, but also avoids the arbitrariness of decomposition.
Stochastic subspsace parameter identification and stability diagram of gas-liquid two-phase flow patterns
Authors: Li Hong-Wei  , Zhou Yun-Long  , Liu Xu  , Sun Bin  ,   College of Energy Resource and Mechanical Engineering, Northeast Dianli University, Jilin 132012, China
Published: December 2020

The characteristics of stability diagram of several typical flow patterns are studied, and the signals of flow patterns under 47 kinds of flowing conditions are identified with stochastic subspace parameter identification. The results show that the characteristic of a stability diagram can reflect the internal characteristics of complex time series, the characteristics of time series can be quantified by extracted straightness characteristics and the differences of characteristics of stability diagrams of three typical flow patterns. The characteristics of stability diagrams of bubble flow are the most confused and followed by Mist flows'. Slug flows' are the most regular. The extraction and recognition for characteristics of gray fluctuation sequence of gas-liquid two-phase images and the accurate classification for flow pattern samples provide a new path for the classification of multi-phase flow patterns. At the same time, the stability diagram analysis method provides a useful exploration for the further revelation of flowing mechanism of multi-phase flows.
MRCI calculations for BeCl electronic excited states
Authors: Liu Dong-Mei  , Zhang Shu-Dong  ,   Shandong Provincial Key Laboratory of Laser Polarization and Information Technology, Department of Physics, Qufu Normal University, Qufu 273165, China
Published: December 2020

Potential energy curves (PECs)for the ground state and several low-lying electronic excited states of BeCl molecule are calculated using the multi-reference configuration interaction (MRCI)method with the basis set of aug-cc-pVTZ where the Davidson correction is considered as an approximation to full CI. The symmetries and dissociation limits for these electronic states are determined through group theory. The PECs of ground state(X2+)and first excited state(A2)are fitted to the Murrell-Sorbie (MS)potential function, and from the fitting parameters the spectroscopic constants are determined to be De=3.74 eV, Re=0.18173 nm(0.17970), we=857.4 cm-1(847.2), wexe=5.03 cm-1(5.14), Be=0.7103 cm-1(0.7285), and e =0.0059 cm-1(0.0069)(where the values in parentheses are the cited experimental results)for X2+ state and De=3.02 eV, Re=0.18369 nm(0.18211), we=832.7 cm-1(822.1), wexe=5.93 cm-1(5.24), Be=0.6953 cm-1(0.7094), and e=0.0065 cm-1(0.0068)for A2 state of BeCl. All the calculation results are in good agreement with the experimental values. In addition, we use the Level program to calculate the radial Schrdinger equation of nuclear motion to obtain the vibrational levels for the X2+ and A2 states.
Eliminating the center spot of bottle beam generated by axicon-lens system
Authors: Zhang Qian-An  , Wu Feng-Tie  , Zheng Wei-Tao  ,   College of Information Science and Engineering, Huaqiao University, Quanzhou 362021, China
Published: December 2020

When generating a bottle beam by using an axicon-lens system, diffraction factors often cause a bright spot in the center of bottle beam. This central bright spot is unfavorable for the using of bottle beam in constructing hollow optical tweezers system. In the article, we propose a new method of phase modulation, by adding a spiral phase plate (SPP) to optical path to make the bottle beam center have phase singularity,thereby eliminating the bright spot well. Theoretical analysis and numerical stimulation are shown to agree with the experimental results.
A method to compensate the tuned nonlinearity of DFB diode laser in the laser self-heterodyne coherent measuring system
Authors: An Ying  , Du Zhen-Hui  , Liu Jing-Wang  , Xu Ke-Xin  ,   State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China;,   College of Information Engineering, Hebei United University, Tangshan 063009, China;,   North China Institute of Aerospace Engineering, Langfang 065000, China
Published: December 2020

The measuring accuracy of self-heterodyne coherent measuring system can be deteriorated by the tuning nonlinearity of the diode laser with injection current. The tuning characteristics of a DFB laser were analyzed, and a mathematical model for compensating Mach-Zehnder interferometer based self-heterodyne system was presented. The dynamic frequency modulation coefficient of the model was built by prior beat frequency of foregone optical path difference. The relative error of predicted beat frequency is reduced about 3%. This method could simplify the setup of the system, and is especially suited for online tunable laser measurement system.
A new method to estimate the parameter of 1/f Noise of high power semiconductor laser diode based on sparse decomposition
Authors: Li Yang  , Guo Shu-Xu  ,   College of Electronic Science and Engineeing, Jilin University, Changchun 130012, China
Published: December 2020

Considering that the power spectral density of 1/f noise signal varies inversely with frequency and sparse decomposition is able to create dictionaries according to signals' own features, in this paper we propose a new method to estimate the parameter of 1/f noise of high power semiconductor laser diode based on sparse decomposition, and create a dictionary whose feature is similar to 1/f noise. Sparse decomposition of white noise and 1/f noise aliased signal is implemented by Matching-Pursuit(MP)algorithm. The experimenat results indicate that sparse decomposition could effectively estimate the parameter of 1/f noise signal covering white noise and the estimated parameter is in accordance with the measured result of spectrum analyzer. Finally, the superiority of the dictionary created in this paper is illustrated by comparing with a different dictionary.
On the methodology of measuring high-speed flows using tunable diode laser absorption spectroscopy
Authors: Zhang Liang  , Liu Jian-Guo  , Kan Rui-Feng  , Liu Wen-Qing  , Zhang Yu-Jun  , Xu Zhen-Yu  , Chen Jun  ,   Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

Based on the laser Doppler effect, real-time and on-line measurements of velocity in high-speed flows can be realized using tunable diode laser absorption spectra (TDLAS). The fundamental theory and the method to measure the velocity are presented. A dual-beam system used in the experiments is described. The water vapor absorption feature at 1398 nm is utilized to detect the flows generated within a wind tunnel. The DFB laser is quickly tuned at a rate of 10 kHz to obtain the spectra of the transient flows by using scanned-wavelength direct absorption spectroscopy. The ways to calibrate the frequency and calculate the Doppler shift (DS) are also introduced. The measured velocity is compared with the calculated velocity, and they are in good agreement with each other, which proves that the way combining DS with TDLAS to measure the velocity in high-speed flows is reasonable. The system capability and possible factors to induce measurement deviations are analyzed to improve the system performance in the future.
Theoretical analysis of a thermal-optical tunable filter based on Vernier effect of cascade microring resonators
Authors: Ren Guang-Hui  , Chen Shao-Wu  , Cao Tong-Tong  ,   State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

A thermal-optical tunable filter based on the Venier effect of cascade microring resonator, which can expand the Free-Spectrum-Range (FSR) and the tuning range, is designed and simulated. The FSR of the filter with a radius of 48 m for the first order and 50 m for the second order microring can be expanded to 76.5 nm, which is at present the largest FSR to our best knowledge. A tuning range covering all of the above mentioned FSR can be reached under 103.1 mW heating power, which is also the largest one for silicon based thermal-optic tunable microring resonator filers. The response time, calculated by finite-element-method, of the designed tunable filter with 50 m radius ring is 3.5 s for the rise edge and 0.8 s for the fall edge.
Locally resonant elastic wave band gaps in flexural vibration of multi-oscillators beam
Authors: Wen Qi-Hua  , Zuo Shu-Guang  , Wei Huan  ,   New Energy Vehicle Engineering Centre, Tongji University, Shanghai 201804, China
Published: December 2020

The flexural vibration behavior of elastic wave across a slender beam with locally resonant multi-oscillators structure is studied by using the transfer-matrix method and the finite element method. A simplified model is proposed, and the formulas of start and end frequencies of band gap are deduced. The more abundant and wider flexural elastic wave band gaps are found in this locally resonant multi-oscillator beam than in one oscillator beam, which can be used in the reduction of multiple-frequency vibration and noise. The frequency response of vibration in the band gap frequency range has obvious attenuation. The results of simplified model are in good agreement with results from the theory model. The research project will provide a new way for vibration reduction of beam structure.
The irrotational progressive gravity waves propagating on uniform currents in Lagrangian analysis and experiments Part 1. Theoretical analysis
Authors: Chen Yang-Yih  , Hsu Hung-Chu  , Chang Hsien-Kuo  ,   Department of Marine Environment and Engineering, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, China;,   Department of Hydraulic and Ocean Engineering, National Cheng Kung University, Tainan 701, Taiwan, China;,   Research Center of Ocean Environment and Technology, Nation Cheng Kung University, Tainan 701, Taiwan, China;,   Department of Civil Engineering, National Chiao Tong University, Hsinchu 300, Taiwan, China
Published: December 2020

A third-order Lagrangian solutions is found directly by the full Lagrangian parametric governing equations, with the parameters of identifying each water particle which is obtained in mass conservation from taking the wavelength-averaged level of the vertical displacement of water particles along the direction of the wave propagation and is just the position of particle in the original still water, for the irrotational free surface progressive gravity waves propagating on uniform current in the three dimension. It is found that the effect of wave-current interaction is occurred in Lagrangian velocity potential, so that the pressure is not affected by the uniform current in the wave-current field. The drift velocity, Lagrangian mean level of particle and its motion period longer than the wave period which are exponentially decreasing with the depth of particle's level and the pathlines of particle and the streakline are then all presented, these are to be excluded in Eulerian solution. Furthermore, the forms of the helical pathlines of particles varying with the direction and speed of the uniform current are appeared to be turned from the wave velocity and current velocity component in co-direction to in anti-direction, even become into a closed orbit. The special case when the wave-current field is at the steady motion is also interpreted its consequential charateristics. The present solution can be reduced to that of the pure progressive waves as no current exists.
X-ray generation in repetitive pulsed discharge in atmospheric air with a point-to-plane gap
Authors: Zhang Cheng  , Shao Tao  , Niu Zheng  , Zhang Dong-Dong  , Wang Jue  , Yan Ping  ,   Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China;,   Key Laboratory of Power Electronics and Electric Drive, Chinese Academy of Sciences, Beijing 100190, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100039, China
Published: December 2020

Research on the characteristics of X-ray emission in repetitive pulsed discharge is associated with the behavior of runaway electrons and the mechanism of nanosecond pulsed discharge. In the experiments, X-ray emission in the repetitive pulsed discharge with a rise time of ～15 ns and an FWHM of 30-40 ns in atmospheric air is directly measured by a detection system consisting of NaI scintillator and a photomultiplier tube, and the energy range of the X-ray detector is demonstrated to be between 10 and 130 keV. Results show that main part of the energy of X-ray is from 20 keV to 90 keV, and a little X-ray with an the energy of less than 20 keV or more than 90 keV is detected. X-ray emission increases with the increase of pulse repetition frequency, and it has a peak value with the variation of air gap spacing. There is a maximum value of X-ray emission when the nanosecond discharge appears in a diffuse mode.
Study on the deposition of aluminum-doped zinc oxide films using direct-current pulse magnetron reactive sputtering technique
Authors: Chen Chao  , Ji Yong  , Gao Xiao-Yong  , Zhao Meng-Ke  , Ma Jiao-Min  , Zhang Zeng-Yuan  , Lu Jing-Xiao  ,   School of Physics and Engineering, Zhengzhou University, Zhengzhou 450052, China
Published: December 2020

Aluminum-doped zinc oxide (AZO) films have potential applications in photoconducting and piezo-electric devices, and gas and piezo sensors. Although the film structure and optical properties are intensively studied, the effect of gas flow ratio of O2 to Ar (GFR) on the film structure and optical properties has not been reported in terms of macrostress and lattice strain. In this paper, a series of AZO films is deposited on glass substrates by direct-current pulse magnetron reactive sputtering under different GFRs. The influence of the GFR on the crystalline structure, the surface topography, and the optical properties of the film is systematically studied in terms of macrostress and lattice strain by using X-ray diffractometry, scanning electron microscopy and spectrophotometry, respectively. The as-deposited AZO films are polycrystalline and (103) oriented, which can be attributed to the change in crystalline face energy during the accompanied thermal annealing for 3 h. The film tensile stress first increases to a maximum value, and then decreases gradually with GFR values increasing. It is noted that the transition from tensile to compressive stress occurs with GFR increasing. This result is different form that of lattice strain. The film transmissivity in the visible region first decreases and then increases with GFR increasing, which is attributed mainly to the scattering of grain boundary induced by the grain size.
Study on electronic transport and magnetic properties for antiperovskite Mn3CuNx thin films fabricated with different N2 flow rates
Authors: Na Yuan-Yuan  , Wang Cong  , Chu Li-Hua  , Ding Lei  , Yan Jun  ,   Center for Condensed Matter and Materials Physics, Key Laboratory of Micro-Naro Measurement, Manipulation and Physics, Beihang University, Beijing 100191, China
Published: December 2020

The antiperovskite Mn3CuNx thin films are successfully deposited on single crystal Si (100) substrates using facing target magnetron sputtering. The effects of nitrogen content on the structures and physical properties of the Mn3CuNx thin films are investigated. The crystal structure, composition, surface morphology and the temperature dependence of resistivity and magnetization are characterized by X-ray diffraction, Auger electron spectroscopy, atomic force microscope, X-ray photoelectron spectroscopy, physical property measurement systems and superconducting quantum interference device. It is found that the thin film has an antiperovskite structure and a preferred orientation along (200) plane. The surface roughness and particle size increase with N content increasing. N content has little influence on the electronic transport behavior of the film. All the films display semiconductor-like behaviors, i.e. their resistivities monotonically decrease considerably, which is different from the bulk counterpart. The film undergoes a magnetic transition from ferrimagnetic to paramagnetic with the increase of temperature. Moreover, the Curie temperature (TC) increases as the N content decreases, owing to the effect of N deficiency on the interaction of Mn6N octahedron.
Study on the localized surface plasmon resonance properties of bimetallic gold and silver three-layered nanotubes
Authors: Cong Chao  , Wu Da-Jian  , Liu Xiao-Jun  , Li Bo  ,   School of Physics, Nanjing University, Nanjing 210093, China
Published: December 2020

The localized surface plasmon resonance (LSPR) properties of bimetallic gold and silver three-layered nanotubes such as SiO2-Ag-Au and SiO2-Au-Ag nanotubes have been investigated with the variations of Au or Ag shell thickness and size of the core by means of Finite Difference Time Domain (FDTD) method. With increase in the core size, it is found that the LSPR peaks show red-shift. We also observe with increasing the thickness of the Au or Ag shell that the LSPR peaks show blue-shift. Furthermore, the modulation of LSPR due to Ag shell is more significant compared with that due to Au shell. We have ascribed the variations of the LSPR peaks to the plasmon hybridization and the competition between the changes of conduction and oscillation electrons.
Study of Fermi resonance using the method of varying solution refractive index
Authors: Yang Jian-Ge  , Sun Cheng-Lin  , Yang Yong-Bo  , Gao Shu-Qin  , Jiang Yong-Heng  , Li Zuo-Wei  ,   State Key Laboratory of Superhard Materials, Changchun 130012, China;,   College of Physics, Jilin University, Changchun 130023, China;,   Air Force Aviation University, Changchun 130022, China
Published: December 2020

Fermi resonance (FR) plays an important role in the spectral line identification and assignment in spectral analysis. It contains a wealth of physical laws which are urgently needed for research. In the present paper, we propose a new method of varying the refractive index of the solution to study the FR, which is based on the model of Onsager. The basic principle of this method is to use Raman scattering intensity (Raman scattering coefficient) changing with the refractive index of solution to study the FR. With this method we not only can give the relationship between the FR parameters and the refractive index of solution, but also find new spectrum phenomena (including the asymmetric shift of Fermi doublet and the FR tuned fundamental freguency of the overtone). In this article we provide a new research method to study the FR.
The investigation of lithium insertion mechanism for Sn3InSb4 alloy based on first-principle calculation
Authors: Ru Qiang  , Li Yan-Ling  , Hu She-Jun  , Peng Wei  , Zhang Zhi-Wen  ,   Laboratory of Quantum Information Technology, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006, China
Published: December 2020

The mechanism of Li insertion into Sn3InSb4 alloy is investigated by means of the first-principle plane-wave pseudo-potential method. The lithium intercalation formation, the theoretical capacity, the volume expansion ratio and the electronic structures are calculated. In the intercalation process, lithium atoms firstly fill the interstitial sites, and then lithium atoms continue to replace the metal atoms. Large expansion ratio from 11.74% to 43.40% would lead to the bad cycle stability for Sn3InSb4 alloy as the lithium battery electrode material. The conduct electricity is improved with lithium content increasing, then the conduct electricity decreases with interstitial sites being filled with lithium atoms and Sn-replacement reaction occurring.
Numerical study of the death and breakup of spiral wave in the networks of thermosensitive neurons
Authors: Ma Jun  , Xie Zhen-Bo  , Chen Jiang-Xing  ,   Department of Physics, Lanzhou University of Technology, Lanzhou 730050, China;,   Key Laboratory of Gansu Advanced Control for Industria Processes, Lanzhou 730050, China;,   Department of Physics, Hangzhou Dianzi University, Hangzhou 310018, China
Published: December 2020

The experimential evidences confirm that spiral waves are observed in the disinhibited mammalian neocortex. The scheme of ceullar networks is used to simulate the formation and the evolution of spiral wave in the neocortical slices. The regular networks of neurons are constructed in the two-dimensional space, the dynamical properties of thermosensitive neurons is described by temperature factor, and the effect of membrane temperature on the evolution of spiral wave is investigated in detail. A statistical factor of synchronization is defined to measure the critical condition inducing phase transition of spiral wave (death or breakup) by the factor of temperature of membrane. It is confirmed that spiral wave is removed and the whole networks become homogeneous and synchronous completely when the membrane temperature exceeds a certain threshold; the breakup of spiral wave is induced in the presence of weak channel noise being considered. Furthermore, it is suggested that the mechanism of temporary heat stupor could be the blocking of spiral wave propagation in some functional domain.
Research on synthesis of high-quality and large-scale graphene films by chemical vapor deposition
Authors: Wang Wen-Rong  , Zhou Yu-Xiu  , Li Tie  , Wang Yue-Lin  , Xie Xiao-Ming  ,   Science and Technology on Microsystem Laboratory, State Key Laboratories of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai 200050, China;,   State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai 200050, China
Published: December 2020

Graphene has received great interest because of its peculiar band structure and excellent physical properties. But today, the development of graphene is limited to its size and quality. In this paper, single- and multilayer graphene films were synthesized on copper foils by chemical vapor deposition(CVD) using methane at ambient pressure. Experiment results find the high temperature, low concentration of methane gas, shorter growth time and suitable gas flow are the key to get high-quality and large-scale graphene films. Raman spectra, scanning electron microscope(SEM) and transmission electron microscope(TEM) characterization indicate the graphene films are mostly single-layer, only with rare area having multilayer around copper boundaries. Further electrical tests show the graphene films grown by CVD method represent semiconductor behaviors under low temperature and the sheet resistance of graphene films is decreasing with the external magnetic field increasing.
Optimized analysis and experimental study for two-layer contact of crystalline silicon solar cells
Authors: Li Tao  , Zhou Chun-Lan  , Liu Zhen-Gang  , Zhao Lei  , Li Hai-Ling  , Diao Hong-Wei  , Wang Wen-Jing  ,   The Key Laboratory of Solar Thermal Energy and Photovoltaic System, Institute of Electrical Engineering, CAS, Beijing 100190, China
Published: December 2020

Compared with single-layer contact, optimized two-layer contact of front side could diminish power losses distinctly and improve the electrical performance of crystalline silicon solar cell. In this paper, the optimized analysis and experimental study for two-layer contact of crystalline silicon solar cell are carried out. The model of two-layer contact is established by abstracting the cross-section of two-layer contact into semi-elliptical shape closer to the realistic situation according to the SEM observation . The electrical losses and the optical losses of two-layer contact are analyzed in theory. In combination with experimental screen-printed contact thickened by light-induced electroplating solar cell, the relationship between the optimum thickening contact thickness by light-induced electroplating and the screen-printed contact width is achieved in theory and experiment. The corresponding theory and experimental results are in good agreement with each other. Due to involving no concrete technology of contact preparation, the theoretical model of two-layer contact is generally appticable for many types of two-layer contact structurs in consequence.
Propagating properties of a upward positive leader in a negative triggered lightning
Authors: Wang Cai-Xia  , Qie Xiu-Shu  , Jiang Ru-Bin  , Yang Jing  ,   Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Science, Beijing 100029, China;,   Beijing Information Science and Technology University, Beijing 100192, China;,   Graduate School, Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Propagating properties of a upward positive leader are analyzed by using the data from the artificially triggered lightning experiment in Shandong 2009, including the high-speed camera records and simultaneous surface electric field fast change measurements at 30 m, 60 m and 480 m from the channel. The tip of the leader is brighter, and the leader's 2-D partial propagating speed along its channel irregularly changes in a wide range. This indicates that the upward positive leader exhibits obviously stepped characteristics. The average speed is 9.8×104 m/s from 340 m to 705 m at the beginning stage of the leader propagating. The upward positive leader is initiated at a speed of 3.8×104 m/s. The partial speed shows an increasing tendency with height increasing. The electric field change waveform of upward positive leaders has a regularly stepped shape. The step interval of 28 steps recorded ranges from 14 μs to 39 μs with a geometrical mean value of 25.1 μs. The induced step length varies from 0.9 m to 3.7 m with a geometrical mean value of 1.7m. The electric field change of upward positive leaders includes the slowly stepped change and pulsed change. The high-speed camera records and electric field measurements show that the channel of the leader tip bending can eliminate or weaken the stepped property of the electric field change. The positive step leader has a similar propagating mechanism to that the negative leader has, that is a step of leader originates from a bi-directional streamer front end of the leader tip.
A study of basin of attraction of the simplest walking model based on heterogeneous computation
Authors: Li Qing-Du  , Zhou Hong-Wei  , Yang Xiao-Song  ,   Key Laboratory of Network Control & Intelligent Instrument of Ministry of Education, Chongqing University of Posts and Telecommunications, Chongqing 400065, China;,   School of Mathematics and Statistics, Huazhong University of Science and Technology, Wuhan 430074, China;,   Institute for Nonlinear Circuits and Systems, Chongqing University Posts and Telecommunications, Chongqing 400065, China
Published: December 2020

Passive dynamic walking becomes an important development for walking robots due to its simple structure and high energy efficiency, but it often falls. The key to this problem is to ascertain its stable gaits and basins of attraction. In order to handle the discontinuity, massive numerical computation is unavoidable. In this paper, we first propose an algorithm to compute Poincar maps in heterogeneous platforms with CPU and GPU, which can take the best performance of the newest heterogeneous platforms and improve the computing speed by more than a hundred times. With this algorithm, we study the simplest walking model by sampling massive points from the state space. We obtain high resolution images of the basin of attraction, and reveal its fractal structure. By computing the relation between the stable gaits and their basins and by varying the slop k, we find a new three-period stable gait and a period-doubling route to chaos, and we also study the new gait and its basin.
Variation of adhesive force in the nanoscale contact
Authors: Duan Fang-Li  , Wang Guang-Jian  , Qiu He-Bing  ,   State Key Laboratory of Mechanical Transmissions, Chongqing University, Chongqing, 400030 China
Published: December 2020

Intermolecular attractive forces lead to the adhesion problem in M/NEMS. The Van der Waals formula for the interaction between macroscopic objects can be used only in the situation with no deformation. As to the adhesive contact between elastic bodies it is still unknown how the attractive force contributes to the normal force on the interface. In this paper large-scale molecular dynamics simulation is performed to study the adhesive contact between a rigid spherical tip and an elastic flat substrate. We study the effect of atomic-scale surface roughness on the adhesive properties, including pull-off force between tips and substrate, the variation of adhesive force with applied load, and the distribution of contact stress. The results show that the adhesive force varies linearly with the applied load for the atomic-scale smooth contact. But for the atomic-scale rough contact the variation of adhesive force with applied load can be divided into two phases, which are distinguished by different increasing slops. Compared with the smooth contact, the rough contact has a small pull-off force, but exhibits a large adhesive force during the contacting process. Our simulations indicate that the pull-off force cannot characterize the contribution of attractive interaction to the normal force on the interface in the case of an elastic adhesion contacting.
Study of growth of [111]-oriented CdTe thin films by MBE
Authors: Zhang Bing-Po  , Cai Chun-Feng  , Cai Xi-Kun  , Wu Hui-Zhen  , Wang Miao  ,   Department of Physics, State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China
Published: December 2020

In this study, CdTe(111) thin films were epitaxially grown on freshly cleaved BaF2 substrate using molecular beam epitaxy (MBE). In situ characterization of reflection high energy electron diffraction (RHEED) reveals the growth mode of transition from 2D to 3D. XRD analysis results verify the single crystalline property of the as-grown films. Theoretical method is adopted to fit the measured near infrared transmission spectrum, revealing a CdTe energy gap of 1.511 eV at room temperature.
A new phenomenon of photoconductive InSb detector under the irradiation of out-band laser
Authors: Zheng Xin  , Jiang Tian  , Cheng Xiang-Ai  , Jiang Hou-Man  , Lu Qi-Sheng  ,   College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

A new phenomenon is observed when a photoconductive InSb detector with 0.228eV band gap is irradiated by 10.6 μm laser, whose photon energy is 0.12 eV. The detector is heated by this out-band laser, due to the absorption of laser energy. However, a transformation temperature T0 exists in this process. When the temperature of the detector, T, is lower than T0, the number of carriers remains constant but the conductivity changes because of a change in mobility. The mobility decreases with the increase of temperature and varies as T-2.35. At T>T0, the concentration of thermally-activated carrier increases with temperature, which is proportional to exp (-Eg/2k0T). As a result, the influence of carrier concentration becomes more and more important. As a result, the output of the detector decreases. In a word, the output voltage of photoconductive detector results from the temperature dependence of mobility and concentration of carriers. This work provides an experimental basis for improving the carrier transport model.
Determination of optical constants and thickness of photoactive layer in polymer oslar cells by single transmission measurement
Authors: Huang Zhuo-Yin  , Li Guo-Long  , Li Kan  , Zhen Hong-Yu  , Shen Wei-Dong  , Liu Xiang-Dong  , Liu Xu  ,   State Key Labs of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
Published: December 2020

We present a simple and accurate method of determininy the optical constant and physical thickness of the photoactive layer in a polymer solar cell. The applicabilities of the physics models including Forouhi-Bloomer and Lorentz-Oscillator models in transmission curve fitting are compared. This method is used to calculate the optical constants and film thicknesses of poly(3-hexylthiophene) (P3HT) /[6,6]-phenyl C61-butyric acid methyl ester (PCBM) and poly[2- methoxy-5-5(2'-ethyl-hexyloxy)-1,4-phenylenevinylene](MEH-PPV)/PCBM bulk heterojunction, The calculated transmission curves fit to the experimental ones well. The results accord with those reported in the literature and from the step profiler, and their error is less than 4%. The optical constant and the physical thickness of polymer solar cell after the optimization process including thermal annealing and adding high-boiling-point additive are studied, and the results are consistent with the voltage-current characteristics of the cell. This method is suited for bulk heterojunction films and can be used in polymer solar cell optimization and detection system.
Effects of surface modification on nonlinear optical performance of gold nanoparticles
Authors: Zheng Li-Si  , Feng Miao  , Zhan Hong-Bing  ,   College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108, China
Published: December 2020

Two kinds of gold nanoparticles with different surface-capping groups (Au-DT and Au-DT-CTAB), 1-dodecanthiol and cetyltrimethylammonium bromide (CTAB) are prepared by a two-phase method. Structures and linear optical properties of the materials are characterized using transmission electron microscopy and ultraviolet--visible absorption spectroscopy. The effects of surface modification on nonlinear optical (NLO) performance and optical limiting behavior of gold nanoparticles are investigated using the openZ-scan technique at a laser wavelength of 532 nm. The results show that Au-DT-CTAB shows an enhanced NLO effect in comparison with Au-DT. The secondary modification with CTAB can not only improve local field enhancement effect but also make the contribution of thermoelectrons to NLO performance of gold nanoparticles on laser irradiation.
Component wave analysis of borehole seismoelectric wavefields in a porous formation
Authors: Wang Zhi  , Hu Heng-Shan  , Guan Wei  , He Xiao  ,   Department of Astronautics and Mechanics, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

In this work, the axisymmetric seismoelectric logging response excited by a point-pressure source is formulated as an integral in the frequency-wavenumber domain. To analyze the properties of each constituent wavepacket in the seismoelectric logs, the poles and the branch points of the integrands are examined by the complex analysis. The electromagnetic wavenumber in the borehole fluid proves to be a removable branch point. The argument principle is used to search for the complex poles. After the excitation intensity as well as the dispersion curves has been obtained for each component wave for a typical sandstone formation, the ratio of the electric excitation intensity to the acoustic excitation intensity is evaluated. Especially it is found that the argument of this ratio of the Stoneley wave is sensitive to the permeability. The excitation curves corresponding to the branch points show that the compressional wave has a higher seismoelectric conversion efficiency than the shear wave and the mode waves.
Wavefunction and Fourier coefficients of excitons in quantum wells: computation and application
Authors: Lei Xiao-Li  , Wang Da-Wei  , Liang Shi-Xiong  , Wu Zhao-Xin  ,   Shaanxi Key Laboratory of Photonics Techonology for Information and Key Laboratory for Physical Electronics and Devices of the Ministry of Education, School of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China;,   Xi'an University of Post and Telecommnunications, Xi'an 710061, China
Published: December 2020

Excitonic dynamic equations, which are derived from the quasi-Boson approach, are useful tools in investigating the ultrafast optical responses of semiconductor nanostructures. To apply these equations to the exciton dynamics in semiconductor quantum wells, we need exciton wavefunctions and their representations in momentum space to obtain the coefficients in the excitonic dynamic equations. By discussing in detail the exciton wavefunctions and their momentum-space representations, we present a method of obtaining the essential coefficients in the excitonic dynamic equations. We finally use these coefficients to understand the nonlinear effects in the terahertz-pulse-induced intraexcitonic transitions caused by high exciton densities. The obtained theoretical results are in good agreement with recent experimental results.
Hamiltonian model-based H control of chaos in permanent magnet synchronous generators for wind power systems
Authors: Ren Li-Na  , Liu Fu-Cai  , Jiao Xiao-Hong  , Li Jun-Yi  ,   Key Laboratory of Industrial Computer Control Engineering of Hebei Province, West Campus of Yanshan University, Qinhuangdao 066004, China
Published: December 2020

Aiming at chaos in the wind turbine systems, the H control strategy is presented based on the Hamiltonian model, which makes systems disengage chaos and operate stably. Firstly, the permanent magnet synchronous generator of wind power system is transformed into a model which is similar to a Lorenz-like classical mathematic model through a series of transforms, and demonstrates existing chaos phenomena when its parameter values are in a certain range. Then, the Hamiltonian model of chaos system is established by taking full advantage of the physics structure of wind power system without the compensation of workless forces. Moreover, an H controller is investigated under the external disturbance. This controller is not only simple but also can reflect the interior structure and dynamic characteristics of system. The proposed strategy proves to be valid by simulations.
Full-order and reduced-order optimal synchronization of neurons model with unknown parameters
Authors: Wang Xing-Yuan  , Ren Xiao-Li  , Zhang Yong-Lei  ,   School of Electronic & Information Engineering, Dalian University of Technology, Dalian 116024, China
Published: December 2020

Based on Lyapunov stability theory, optimal control principle and step design methodology, nonlinear feedback controller and optimal controller are designed, in which the nonlinear feedback controller makes the trajectory error between two neuron systems tend to zero, and the optimal controller makes the spent energy meet minimum, which is spent in the process of synchronizing. In this paper, the uncertain cable model is taken as an example to illustrate the full-order optimal synchronization of two neurons. The uncertain cable model and the uncertain Hindmarsh-Rose (HR) model are taken to illustrate the reduced-order optimal synchronization of two neurons. In addition, the unknown parameters are identified successfully. Numerical Simulation results show the effectiveness of the strategy further.