bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical study on geometry and physical and chemical properties of oligochitosan
Authors: Li Xin  , Zhang Liang  , Yang Meng-Shi  , Chu Xiu-Xiang  , Xu Can  , Chen Liang  , Wang Yue-Yue  ,   School of Engineering, Zhejiang A&F University, Linan 311300, China;,   School of Science, Zhejiang A&F University, Linan 311300, China;,   Key Laboratory for Magnetism and Magnetic Materials, Ministry of Education Lanzhou University, Lanzhou 730000, China
Published: December 2020

By using the density functional theory with B3LYP/6-31G+(d) we compute the optimization, vibration frequencies, electron structures of gg conformation of oligochitosans, and study the average binding energies and the zero-point energy corrections using WB97XD method. We also analyze the thermodynamic properties of oligochitosans. Results show that the hydrogen-bond makes the oligochitosan become spiral; average binding energies tend to decrease and stability tends to improve with the increasing degree of polymerization (DP); the water degradation of oligochitosan is an exothermic reaction, so it is feasible to reduce the temperature to improve the degradation yield in experiment; in addition, the energy gap of oligochitosan quickly converges to 6.99 eV with the increase of DP; furthermore, the value of DP7 oligochitosan is in accordance with the convergence value. The HOMO and LUMO of oligochitosan show that chemical activity is mainly distributed in C2 amino, C6 hydroxyl groups, and both ends of oligochitosan chain. These results have instructive significance on the modeling, and can provide a theoritical basis for degradation process, chemical activity position, and size-dependence in physical chemical properties of oligochitosan.
Ferromagnetism of Zn0.97Cr0.03O synthesized by PLD
Authors: Xie Ling-Ling  , Chen Shui-Yuan  , Liu Feng-Jin  , Zhang Jian-Min  , Lin Ying-Bin  , Huang Zhi-Gao  ,   College of Physics and Energy Fujian Normal University, Fujian Provincial Key Laboratory of Quantum Manipulation and New Energy Materials, Fuzhou 350108, China
Published: December 2020

Four Zn0.97Cr0.03O films were deposited on quartz wafers in various oxygen environment (0, 0.05, 0.15 and 0.2 Pa) using pulsed laser deposition (PLD). The films were characterized by XRD, PL, XPS, magnetic and electrical properties. Experimental results indicate that: (1) All the films are well crystallized and display a pure orientation. (2) All the films have ferromagnetism, and the film deposited at 0.15 Pa has the biggest Ms. (3) There exist VZn, Oi, Zni, VZn- and VO defects in the four films above, and the percentage of resonance peak area for VZn to the total area of all defects as a function of oxygen pressure is similar to Ms, which means that the magnetizations of the samples are closely related to Zn vacancy VZn. There is a Cr3+ state in the four films when the content of Cr3+ is the largest at 0.15 Pa. To sum up, the experimental results indicate that the substitutive Cr in the oxidation state of t3 and the neutral Zn vacancy in the Zn0.97Cr0.03O films is the most favorable defect complex to maintain a high stability of ferromagnetic order, which is consistent with the calculated results by the first-principle calculations.
One-dimensional photonic crystal(1D PC)-based back reflectors for amorphous silicon thin film solar cell
Authors: Chen Pei-Zhuan  , Hou Guo-Fu  , Suo Song  , Ni Jian  , Zhang Jian-Jun  , Zhang Xiao-Dan  , Zhao Ying  ,   Institute of Photo-electronic Thin Film Devices and Technique, Key Laboratory of Photo-electronic Thin Film Devices and Technique of Tianjin, Key Laboratory of Photo-electronic Information Science and Technology of Ministry of Education, Nankai University, Tianjin 300071, China
Published: December 2020

New-type back reflectors based on one-dimensional photonic crystal (1D PC) for amorphous silicon thin film solar cells have been investigated, designed and fabricated. These 1D PCs consist of alternating amorphous Si (a-Si) and silicon dioxide (SiOx), of which the deposition process is compatible with current silicon thin film solar cells technology. Results indicate that the total reflectance of 1D PCs increases with the increase of period number. An average reflectance over 96% can be achieved in the range from 500 to 750 nm with 4 periods or more. Applying the 4-period 1D PC as back reflector in NIP amorphous silicon thin film solar cell with device-configuration of glass/1D PC/AZO/NIP a-Si:H/ITO, a conversion efficiency of 7.9% can be obtained, which is comparable to the AZO/Ag-based solar cell of 7.7% and is much better than the SS-based solar cell of 6.9% (a relative enhancement of 14.5%).
A novel frequency selective surface of hybrid-element type with sharply decreased stop-band
Authors: Wang Yan-Song  , Gao Jin-Song  , Xu Nian-Xi  , Tang Yang  , Chen Xin  ,   Key Laboratory of Optical System Advanced Manufacturing Technology, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
Published: December 2020

Frequency selective radome is one of the most important applications of frequency selective surface (FSS). In order to obtain better stealth performance, a novel element FSS, based on a regular slot element FSS, is presented in this paper. The novel element consists of a slot element in the center and at least two slot strips placed on the periodic boundary. We call such FSS the “hybrid-element type FSS” because it exhibits characteristics of both slot type and patch type FSS. Simulation and optimization work is carried out by using a period moment method and a discrete particle swarm optimization method based on the application requirements of a missile radome. Simulation results show that the hybrid-element type FSS has much steeper transition section between pass-band and stop-band, and much lower transmittance in stop-band when compared with the corresponding slot type FSS. The new FSS also has much lower insertion loss in pass-band, much thinner thickness, much simple structure and fabrication process when compared with the ordinary two-layer FSS. Equivalent sample plate is fabricated using printed circuit method and tested using the free space method. Good fit between simulation and testing results verify the accuracy and feasibility of this novel FSS design. The hybrid-element type FSS is especially suitable for the stealth radome when woking frequencies of both sides are very close. It provides a simple and feasible approach for developing frequency selective radome.
Synthesis of nanoparticles in SiO2 by implantation of Cu and Zn ions and their thermal stability in oxygen atmoshphere
Authors: Xu Rong  , Jia Guang-Yi  , Liu Chang-Long  ,   School of Science, Tianjin University, Tianjin 300072, China;,   Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology, Institute of Advanced Materials Physics, Faculty of Science, Tianjin University, Tianjin 300072, China;,   Key Laboratory of Beam Technology and Material Modification of Ministry of Education, Beijing Normal University, Beijing 100875, China
Published: December 2020

Cu nanoparticles (NPs) embedded in silica were synthesized by implantation of 45 keV Cu ions at a fluence of 1.01017 cm-2, and then subjected to post irradiation with 50 keV Zn ions at fluences of 0.51017 cm-2 and 1.01017 cm-2, respectively. Zn post ion implantation induced modifications in structures, optical absorption properties of Cu NPs as well as their thermal stability in oxygen ambient have been investigated in detail. Results clearly show that Cu-Zn alloy NPs could be formed in the Cu pre-implanted silica followed by Zn ion irradiation at a fluence of 0.51017 cm-2, which causes an unique surface plasmon resonance (SPR) absorption peak at about 516 nm. Subsequent annealing in oxygen atmosphere results in the decomposition of Cu-Zn alloy NPs, at 450 ℃, and thus, ZnO and Cu NPs appear in the substrate. Further increase of annealing temperature to 550 ℃ could transform all the Zn and Cu into ZnO and CuO. Moreover, results also demonstrate that introduction of Zn into SiO2 substrate could effectively suppress the oxidation of Cu NPs, meanwhile, the existence of Cu could promote thermal diffusion of Zn towards substrate surface, which enhances the oxidation of Zn. The underlying mechanism has been discussed.
Multiscale permutation entropy analysis of electroencephalogram
Authors: Yao Wen-Po  , Liu Tie-Bing  , Dai Jia-Fei  , Wang Jun  ,   Nanjing General Hospital of Nanjing Military Command, Nanjing 210002, China;,   Image Processing and Image Communications Key Lab., Nanjing Univ. of Posts & Telecomm., Nanjing 210003, China
Published: December 2020

We carried out a detailed analysis and a comparison between normal and epileptic electroencephalogram (EEG) based on multiscale permutation entropy. The relationship between multiscale permutation entropy values of EEG and age, and the effect of scale factor on multiscale permutation entropy value were also discussed. By analyzing normal and epileptic EEG based on multiscale permutation entropy, we found that, at the same age, multiscale permutation entropy value of the normal group’s EEG is higher than that of the epileptic group by an average of 0.19, about 7.9%. In addition, for people of age 3 to 35, their multiscale permutation entropies are clearly maximum. When scale factor is smaller than 15, the value of their entropy would reduce no matter whether the age increases or decreases. The results indicate that multiscale permutation entropy can distinguish between normal and epileptic EEG and reflect the general process of human brain development.
Ensemble variational data assimilation method based on regional successive analysis scheme
Authors: Wu Zhu-Hui  , Han Yue-Qi  , Zhong Zhong  , Du Hua-Dong  , Wang Yun-Feng  ,   Jinling Institute of Technology, Nanjing 211169, China;,   Institute of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China;,   National Key Laboratory on Electromagnetic Environmental Effects and Electro-optical Engineering, PLA University of Science and Technology, Nanjing 211101, China
Published: December 2020

The ensemble variational data assimilation method may be subject to significant uncertainties due to the size of forecast ensemble. We found that this problem occurs because the analysis increment of this method is expressed as a linear combination of ensemble perturbation vectors or expansion of the orthogonal basis vectors. Though this method avoids introducing adjoint model while calculating the gradient of object function, the number of physical control variables is much larger than the sample size of forecast ensemble, which causes the assimilation results to be sensitive to the number of ensemble members. For this reason, the regional successive analysis scheme of ensemble variational method is proposed. By this scheme, the ratio between the number of physical control variables in analysis region and the sample size is decreased, so that it is expected that the problem can be solved. The results of numerical experiments using shallow water model show that the regional successive analysis scheme can give better assimilation results than traditional method, and the analysis precision is improved appreciably.
The 4-dimensional hyperchaotic memristive circuit based on Chua’s circuit
Authors: Yang Fang-Yan  , Leng Jia-Li  , Li Qing-Du  ,   Key Laboratory of Industrial Internet of Things and Networked Control, Ministry of Education, Chongqing University of Posts and Telecommunications, Chongqing 400065, China;,   Institute for Nonlinear Circuits and Systems of Chongqing University of Posts and Telecommunications, Chongqing 400065, China
Published: December 2020

Recently, there has been a growing interest in chaotic memristive circuits. However, four-dimensional (4D) memristive system often can only exhibit common chaos with only one positive Lyapunov exponent. By replacing the resistor of Chua’s circuit with a memristor, we propose a new simple 4D memristive circuit in this paper. A major difference between our proposed system and the known chaotic or hyperchaotic system is that our modified system has infinitely many stable and unstable equilibria. We show that the system can exhibit rich complex dynamic behaviors, such as limit cycles, chaos and hyperchaos. Further numerical study and circuit simulation verify the existence of a hyperchaotic attractor in the memristive circuit, which gives a positive answer about whether there exists hyperchaos in 4D memristive systems.
Generation of the tunable vector ellipse hollow beam by using linearly polarized light beams
Authors: Chen Guo-Jun  , Zhou Qiao-Qiao  , Ji Xian-Ming  , Yin Jian-Ping  ,   Nantong Agricultural College, Nantong 226007, China;,   State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, China;,   Science College, Nantong University, Nantong 226007, China
Published: December 2020

A new scheme for generating a vector hollow beam is proposed by using π phase plates, in which two linearly polarized light beams with perpendicular polarizations pass through two π phase plates respectively, and then an elliptical hollow beam is generated by the superposition of two diffracted waves. The eccentricity of the ellipse can be adjusted by varying the geometric size of phase plates with rectangular diaphragm. And the conversion from the radial vector beam into the angular vector beam can be realized by adjusting directions of phase plates. The feasibility and potential applications in atom optics are analysed and discussed showing that our scheme has a good potential application in atom optics.
Research on the single-frequency super-resolution focusing of micro-structured antenna based on time reversal electromagnetic wave
Authors: Tu Hui-Lin  , Xiao Shao-Qiu  , Yang Zhi-Jie  , Wang Bing-Zhong  ,   Institute of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

The idea that single-frequency electromagnetically excited signal can possess the property of super-resolution focusing under time reversal technique is proposed in this paper. The feasibility of the idea is investigated from the channel theory. A micro-structured model with inter-element spacing of 1/4 wavelength is proposed based on the traditional coaxial probe antenna. Simulated results verify that in combination with time reversal technique, the model shows super-resolution focusing characteristics under single-frequency and broadband input signal excitation. The theoretical analysis and simulated results have great guiding significance for the super-resolution research of the single-frequency and multi-band antennas.
The influences of detuning on the duperfluid-nsulator phase transition in coupled dissipative cavity arrays
Authors: Bao Jia  , Tan Lei  ,   Institute of Theoretical Physics, Lanzhou University, Lanzhou 730000, China;,   Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou 730000, China
Published: December 2020

In this paper, based on the effective Jaynes-Cummings-Hubbard model Hamiltonian in the presence of detuning, we use the mean-field and the perturbation theory to figure out the superfluid order parameter of the system. By which we find that detuning from resonance allows one to drive the system from the superfluid into the insulator state of the polaritons and the reverse. In addition, combining with the properties of transportation of coupled dissipative cavity arrays with detuning, we discuss the influence of detuning on the number of superfluid polaritons and the lifetime of superfluid states. It suggests that the number of the superfluid polaritons will increase to its maximum and then reduce again along the negative part of detuning, which is similar to the spectrum of the transmission.
Capability of single optical buffer loop implementing all-optical time slot interchange based on nonlinear polarization rotation in semiconductor optical amplifier
Authors: Gao Song  , Sheng Xin-Zhi  , Feng Zhen  , Wu Chong-Qing  , Dong Hong-Hui  ,   Key Laboratory of Luminescence and Optical Information Technology of the Ministry of Education, School of Science, Beijing Jiaotong University, Beijing 100044, China;,   State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

Based on nonlinear polarization rotation (NPR) in semiconductor optical amplifier (SOA), a single optical buffer loop theoretically and experimentally demonstrates its switch capability to realize all-optical time slot interchange (TSI) on multiple optical packets (MOPs). Firstly, a series of prerequisites is theoretically deduced with a single optical buffer loop performing all-optical TSI on MOPs. And the corresponding equations which experimental parameters should satisfy are derived from these prerequisites for different cases of all-optical TSI. Accounting to the theoretical results, a single optical buffer loop based on NPR in SOA experimentally realizes all-optical TSI on three packets and four packets at data rate of 10 Gb/s. Experimental results are in accordance with those expected theoretically. These results will be very helpful to make all-optical TSI system more compact and more highly efficient, and have less expensive elements such as SOA, and also significant for developing the all-optical TSI technology.
Simulation of solidification with phase-change in viscoelastic moldfilling process
Authors: Wang Fang  , Li Jun-Lin  , Yang Bin-Xin  ,   School of Applied Science, Taiyuan University of Science and Technology, Taiyuan 030024, China
Published: December 2020

A gas-liquid two-phase model for the simulation of viscoelastic fluid mold filling process with the consideration of phase change is proposed, in which the governing equations for the melt and air in the cavity, including the mass conservation, momentum conservation and energy conservation equations, are unified into one system of equations. A revised enthalpy method, which can be used for both the melt and air in the mold cavity, is proposed to describe the phase change during the mold filling. Finite volume method on non-staggered grid is used to solve the system. The level set method is used to capture the interface evolution in the mold filling process. The distributions of physical quantities such as velocity, pressure and temperature and so on are given. The "frozen skin" layers under different temperatures and velocities are discussed in detail. Numerical results show that increasing the temperatures of the melt and cavity is a better way to get rid of the "frozen skin" layer than increasing the injection velocity.
Lagrangian coherent structure and transport in unsteady transient flow
Authors: Lei Peng-Fei  , Zhang Jia-Zhong  , Wang Zhuo-Pu  , Chen Jia-Hui  ,   School of Energy and Power Engeneering, Xi’an Jiaotong University, Xi’an 710049, China
Published: December 2020

Unsteady transient phenomena in flow over impulsively started circular cylinder, such as the generation of separation, burst of separation bubble, vortex shedding, etc., are studied from Lagrangian viewpoint. The transient flow is solved numerically by using characteristic-based split scheme with dual time stepping. Then Lagrangian coherent structures (LCSs) are extracted to study the transport and mixing of these transient phenomena. Results show that the variation of drag is closely related to the evolutions of separation bubbles and vortex shedding. The evolutions of the symmetric bubbles in streamwise induce high pressure distribution at rear of cylinder and result in drag reduction of the circular cylinder. As separation bubbles become asymmetric, the transport between separation bubbles and main flow is enhanced and thus can reduce the separation region and suppress flow separation as well. The results also show that the shedding vortices are induced by the transpor between separation bubble and main flow. Compared with streamline patterns, LCSs have huge advantages in describing the dynamic features of the unsteady phenomena.
Effects of Ba-doping and process conditions on the structure and magnetic properties of BiFeO3 ceramics
Authors: Liu Feng-Jin  , Chen Shui-Yuan  , Huang Zhi-Gao  ,   Fujian Provincial Key Laboratory of Quantum Manipulation and New Energy Materials, College of Physics and Energy, Fujian Normal University, Fuzhou 350108, China
Published: December 2020

Multiferroic Bi1-xBaxFeO3 (named as BBFO-x, x=0, 0.05, 0.15) are prepared by the sol-gel method through rapid thermal process. The effects of Ba-doping and process conditions on the structures and magnetic properties of the samples are investigated. The experimental results indicate that the process requirements of the pure BBFO-x samples are rigorous. The samples annealed at 800 ℃ for 450 s possess the best structures and magnetic properties. X-ray diffraction results show that Ba-doping causes lattice deformations, but does not change the macroscopic lattice structures of the samples, which is further proved by the Raman spectra of the samples. Besides, Ba-doping is beneficial to enhancing the magnetization of the sample, which is attributed to both the destruction of long-rang antiferromagnetic spiral magnetic structure and the possible spin coupling resulting from the valent state change of the Fe ions. These achievements provide experimental foundation for further studying the microstructure and magnetoelectric coupling effect in such single phase multiferroics.
Propagation of electromagnetic signals in the time-varying plasma
Authors: Yang Min  , Li Xiao-Ping  , Liu Yan-Ming  , Shi Lei  , Xie Kai  ,   School of Aerospace Science and Technology, Xidian University, Xi’an 710071, China
Published: December 2020

Because the boundary layer of the plasma sheath formed around the hypersonic vehicle flying in atmosphere is turbulent, the parameters of plasma sheath, such as the electron density, become time-varying. Both the amplitude and phase of electromagnetic (EM) signal are modulated by the time-varying plasma. By using a large volume uniform plasma generator, an experimental system for the propagation of EM signals in the time-varying plasma is built. The propagation experiment of the monochromatic signals and binary phase shift keying signals in S band of plasma is conducted. The modulations of the amplitude and phase of EM signal are proved, and the rotation of constellation of the multiple phase shift keying (MPSK) signal is observed. The experimental and simulation results demonstrate that the frequency of parasitic modulation is the same as that of time-varying plasma and the parasitical modulation intensity varies in proportion to the ratio of the electron density profile to the carrier frequency. Even if the carrier frequency is higher than the plasma frequency, the parasitical modulation will make the constellation of the MPSK signals circumvolve, and the bit error rate higher.
Characteristics of wall materials secondary electron emission and sheath in Hall thruster
Authors: Duan Ping  , Qin Hai-Juan  , Zhou Xin-Wei  , Cao An-Ning  , Liu Jin-Yuan  , Qing Shao-Wei  ,   Department of Physics, Dalian Maritime University, Dalian 116026, China;,   School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China;,   Institute of Power Engineering, Chongqing University, Chongqing 400030, China
Published: December 2020

Hall thruster plasma discharge channels interact with wall forming sheath, and different secondary electron emission coefficients of wall material can considerably affect sheath characteristics. In this paper, we establish a two-dimensional physical model in wall sheath area to study the secondary electron emission characteristics of three different wall materials which are boron nitride (BN), silicon carbide (SiC) and aluminium oxide (Al2O3), and SiC material secondary electron emission model is improved. On the basis of improved secondary electron emission model, the relationship between the wall secondary electron emission coefficient and both electron temperature and magnetic field intensity is discussed by the particle in cell simulation method, and the different sheath properties of three materials (BN, SiC and Al2O3), are also investigated. The results show that fitting curve is consistent with the experimental results; at the same electron temperature, the values of secondary electron emission coefficient and electron density of three materials (BN, SiC and Al2O3) increase but the values of sheath electric field and sheath potential drop decrease in their sequence. The BN material has the appropriate secondary electron radiation coefficient, which makes the thruster work steadily under low current condition.
Richtmyer-Meshkov instability induced by the interaction between shock wave and SF6 isosceles trapezoid cylinders
Authors: Sha Sha  , Chen Zhi-Hua  , Xue Da-Wen  , Zhang Hui  ,   Beijing Insititute of Electronic System Engineering, Beijing 100854, China;,   Key Laboratory of Transient Physics, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

Based on the large eddy simulation, combined with the 5th order weighted essentially non-oscillatory scheme and the immersed boundary method, the interaction between planar shock wave and two isosceles trapezoid SF6 cylinders is numerically simulated. Our numerical results clearly show that the deformations of isosceles trapezoid cylinders are induced by the Richtmyer-Meshkov instability due to the interaction of shock wave with them. The reflecting, refracting and diffracting process of incident shock are discussed in detail, and the complex wave structures induced during these processes are revealed. In addition, the mixing mechanism of SF6 gas and air is expatiated. Furthermore, the efforts are made to understand the difference in the evolution of the interface between these two isosceles trapezoid cylinders by analyzing the variation of four characteristic scales.
The laser uniformity of polar drive design on the SG-Ⅲ prototype facility
Authors: Li Ping  , Zhao Run-Chang  , Wang Wei  , Geng Yuan-Chao  , Pu Yu-Dong  , Su Jing-Qin  ,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

In this paper, the train of thought and contents of studying the polar drive for SG-Ⅲ prototype facility are teased out, and the beam approximation principle regarding the illumination uniformity on the target is proposed. Based on such a principle, the increase-by-degrees design method is developed and numerically simulated as well. The required laser parameters of target symmetrical illumination are optimally designed under various conditions. The investigation results are experimentally demonstrated on SG-Ⅲ prototype facility, showing that they are in excellent agreement with the designed illumination uniformity on the target. The obtained conclusions can give powerful guidance for the theoretical and experimental study of polar drive in the future.
Runaway electron beams in nanosecond-pulse discharges
Authors: Zhang Cheng  , Ma Hao  , Shao Tao  , Xie Qing  , Yang Wen-Jin  , 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;,   University of Chinese Academy of Sciences, Beijing 100049, China;,   State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Baoding 071003, China
Published: December 2020

Conventional discharge (Townsend and streamer mechanisms) theories are not able to well explain the phenomenon in nanosecond-pulse discharges. Recently, much attention has been paid to the runaway breakdown due to high-energy electrons in nanosecond-pulse discharges, and some experimental data confirm that high-energy runaway electron beam is an important characteristic parameter for nanosecond-pulse discharges. In this paper, two designed collectors are used for detecting runaway electron beams in nanosecond-pulse discharges. These collectors are used to measure the runaway electron beams in discharges driven by a nanosecond-pulse generator with a pulse width of 3-5 ns and a rise time of 1.2-1.6 ns. The measuring principle of both two collectors is similar to that of Faraday cup, where high-energy electrons are collected by a metal cone, and converted into an electric signal that can be recorded by an oscilloscope. Furthermore, optimal designs of collectors are conducted in order to improve the impedance matching characteristics and to obtain better recording data. Using the above two collectors, characteristics of runaway electron beams are investigated. Experimental results show that runaway electron beams can be effectively measured by the collectors, and the optimized collector has a shorter time resolution and higher amplitude of the runaway electron beam current. When the applied voltage is 80 kV, the electron beam current can be measured with an amplitude of 160 mA and a full width at half maximum of less than 1 ns. In addition, experimental results with pulse sequences prove that the collectors have excellent reliability, and both the transient response and the time resolution are stable.
Online and offline test method of total dose radiation damage on static random access memory
Authors: Cong Zhong-Chao  , Yu Xue-Feng  , Cui Jiang-Wei  , Zheng Qi-Wen  , Guo Qi  , Sun Jing  , Wang Bo  , Ma Wu-Ying  , Ma Li-Ya  , Zhou Hang  ,   Xinjiang Key Laboratory of Electronic Information Materials and Devices CAS Key Laboratory of Special Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In this paper, for the study of static random access memory (SRAM), the online-test and offline-test are carried out on the total dose radiation damages. The differences between the two kinds of test methods and physical mechanisms are investigated. The results show that SRAM present multiple failure mode, the online-test only includes one fixed failure mode and the offline-test includes multiple failure mode. Due to the restrictions on signal integrity at test frequency, the online dynamic current test value is significantly less than offline test value. Since the existence of imprinting effect, the online-test static current is significantly less than offline-test value when the device-stored data are opposite to irradiation data. The parameters that cannot be detected online, may lapse prior to the data that could be detected online. The results are significantly important for studying the total dose radiation effect and the experimental evaluation of SRAM under radiation environment.
Ripples of multilayer graphenes：a molecular dynamics study
Authors: Chang Xu  ,   School of Physics and Electrical Information, Shangqiu Normal University, Shangqiu 476000, China
Published: December 2020

Using the classical molecular dynamics simulations, we have investigated the thermally-excited ripples of the multilayer graphenes at different temperatures, and compared them with those of the single- and doublelayer graphene. It is found that: 1) the ripples in multilayer graphene are intrinsic with a characteristic size of about 100 at room tempe- rature, increasing with increase of temperature; at the same time, the ripples height also increases with the temperature; 2) the ripples intralayer height-height correlation functions for the multilayer graphene follow a power-law behavior, Gh(q) q-; the scaling exponent decreases as temperature increases. Moreover, the scaling exponents are different for different types of multilayer graphene even at the same temperature. All these phenomena result from the anharmonic effects which are induced by the temperature and the interlayer interactions.
Molecular dynamics investigation of thermite reaction behavior of nanostructured Al/SiO2 system
Authors: Zhang Jin-Ping  , Zhang Yang-Yang  , Li Hui  , Gao Jing-Xia  , Cheng Xin-Lu  ,   College of Information Engineering, Huanghe Science and Technology College, Zhengzhou 450006, China;,   Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
Published: December 2020

In this study we have investigated the thermite reaction of Al/SiO2 layered structure by classical molecular dynamics simulation in combination with the reactive force field function. Under the adiabatic conditions, we simulate the structural changes and energetic properties of the system at six different initial temperatures (600, 700, 800, 900, 1000 and 1100 K). These results show that the thermite reaction of Al/SiO2 is the self-heating reduction-oxidation (redox) reaction. When the initial temperatures are 900 and 1000 K, the Al layers change into liquid-like structure under melting points. The thermite reaction happens with a much faster rate. At other initial temperatures such as 600, 700, 800 and 1100 K, the thin Al-O layer at the interface is quite weak for the higher initial temperature. The adiabatic reaction temperature increases and the effective reaction time decreases with the increasing of the initial temperature. the reaction self-heating rates are 3.4, 3.5, 4.7 and 5.4 K/ps for the initial temperatures of 600, 700, 800 and 1100 K, respectively. The results reveal that the thermite reaction self-heating rates depend on the thickness of interfacial diffusion barrier in the nanoparticle. In addition, the thermite reaction of the Al/SiO2 system leaves the Si, which accord well with the experimental result.
A theoretical study on coalescence-induced jumping of partially wetted condensed droplets on nano-textured surfaces
Authors: Liu Tian-Qing  , Sun Wei  , Li Xiang-Qin  , Sun Xiang-Yu  , Ai Hong-Ru  ,   School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China
Published: December 2020

Partially wetted (PW) droplets specially exist on textured surfaces with proper nano-structural parameters. Such tiny drops can depart from surfaces by coalescence-induced jumping, and become the main medium for dropwise condensation heat transfer. Therefore, it is of great importance to study the relationship between nano-structural parameters and PW drop post-merging jumping. In this study, the principle of minimum energy increasing during condensed droplets growth was used to judge if a condensed drop is in PW state. The initial shape of a coalesced droplet was determined based on the conservation of PW drop interface free energy and viscous dissipation energy before and after two or more PW condensed droplets merge. The dynamic equation describing the shape conversion of the post-coalescence droplet was then solved. Whether jumping or not of a merged drop was determined by whether the base radius of the droplet can reduce to 0 and if existing a up moving speed of drop gravity center at this moment. The calculation results show that PW droplets can form only on the textured-surfaces with certain nano-pillar height and relatively larger ratio between pillar diameter and pitch, dn/s, while completely wetted droplets easily form on the surfaces with low pillar height and dn/s less than 0.1. Meanwhile, post-coalescence jumping of PW droplets closely relates to nano-structural parameters. Not all PW drops can jump after merging. Instead, self-propelled jumping of PW drops takes place only on the surfaces with relatively higher nano-pillar height and suitable dn/s. Moreover, PW drop size and the scale ratio between two PW droplets to merge also have significant effect on the coalescence-induced jumping. It is difficult for a merged drop to jump spontaneously if the size of PW drops is too large or too small, or the scale ratio of two PW drops is too small. Finally, post-coalescence jumping of multi-droplets is easier than that of two drops since more surplus interface free energy exists in the former case. The calculation results of this model are well consistent with the experimental observations in literatures for whether the post-coalescence condensed drops jump on nano-textured surfaces, with accuracy of 95%. In conclusion, coalescence-induced jumping takes place only when PW droplets with suitable size on the textured surfaces with proper nano-structural parameters.
Effect of magnetic field assisted heat-treatment on field emission properties of metalized multi-walled carbon nanotubes cathodes
Authors: Ye Yun  , Chen Tian-Yuan  , Guo Tai-Liang  , Jiang Ya-Dong  ,   College of Physics and Telecommunication Engineering, Fuzhou University, Fuzhou 350002, China;,   State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

The effect of magnetic field assisted heat-treatment on the field emission properties of metalized multi-walled carbon nanotubes (MWNTs) is investigated. The metalized MWNTs are prepared via an electroless plating method, and then the MWNTs/Ni cathodes are fabricated by screen printing. The morphology and composition of MWNTs/Ni were studied by transmission electron microscopy and energy dispersive X-ray detector, and the difference between MWNTs/Ni cathodes heat-treated with or without magnetic field was observed by scanning electron microscopy. The force of a single MWNT coated with Ni was simulated, and the results demonstrate that the magnetic field force could induce the rotation of MWNTs/Ni during magnetic field assisted heat-treatment. The field emission characteristics show that the MWNTs/Ni cathodes heat-treated with magnetic field has a low turn-on field of 0.80 Vm-1 and high field enhancement factor of 16068, which are attributed to the embossment of MWNTs/Ni from substrates under the magnetic field.
Mechanical properties of transition metals doped Mo：a first-principals study
Authors: Guo Yuan-Jun  , Liu Rui-Ping  , Yang Zhi  , Li Xiu-Yan  ,   College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China
Published: December 2020

For Mo doped with the transition metals W, Ti, Cu and Fe with the molar percentages of 2.08% and 4.17%, the generalized-stacking-fault energies and the cleavage energies along the direction [111] in (110) plane are calculated by the first principles method based on the density functional theory, and the shear information and the brittle-ductile influences of the transition metals on the Mo material are investigated. It is found that doping W and Ti atoms can make the shear deformation difficult to happen and the brittleness of Mo enhanced, however, doping Cu and Fe atoms can make the shear deformation easy to happen and the ductility of Mo enhanced. Moreover, with the increase of doping concentration, the influences of W and Fe atoms are more obvious. Doping W atoms can make the shear deformation more difficult to happen and the brittleness of Mo stronger. Doping Fe atoms can make the shear deformation easier to happen and the ductility of Mo stronger.
Theoretical study of optimal doping concentration in laser ceramics
Authors: Li Wei  , Chen Chang-Shui  , Wei Jun-Xiong  , Han Tian  , Liu Song-Hao  ,   Laboratory of Nanophotonic Functional Materials and Devices, South China Normal University, Guangzhou 510631, China
Published: December 2020

The ion-doped ceramic crystal is different from the single crystal in the respect of theoretical calculation method, because of the presence of grain boundaries. The populations at the active levels in both CW and pulsed regimes each as a function of the concentration of active impurities are deduced by means of the luminescence decay curve. Taking the Nd3+:YAG laser ceramic for example, we calculate the optimal doping concentration and compare our calculated results with reported experimental data, showing that our theoretical calculation is in line with the trend of the experimental data, and also we compare our results with the Nd3+:YAG single crystal theoretical data. showing that the ceramic crystal is superior to the laser doped laser crystal in the respect of population.
Upconversion luminescence properties in Er3+/Yb3+ codoped TiO2 films prepared by magnetron sputtering
Authors: Mao Xin-Guang  , Wang Jun  , Shen Jie  ,   Department of Materials Science, Fudan University, Shanghai 200433, China
Published: December 2020

The Er3+/Yb3+ codoped TiO2 films prepared by magnetron sputtering can emit the green light at 490 nm and the red light at 670 nm by using a 980 nm diode laser irradiation. The emission intensity of upconversion is influenced by ErxYb2-xTi2O7 crystal and concentration of Er3+/Yb3+. The experiment shows that an appropriate codoping proportion of Er3+/Yb3+ brings a notable enhancement of upconversion luminescence intensity. Er3+ plays a main role in the upconversion luminescence, and the sensitized ion Yb3+can greatly improve the efficiency of upconversion. The TiO2 film prepared by magnetron sputtering has a small density of phonon states, thus it inhibits the process of non-radiative transitions, which leads to the formation of green light at 490 nm and the intensity of red light being greater than green light.
Study on land-surface albedo over different types of underlying surfaces in North China
Authors: Yao Tong  , Zhang Qiang  ,   Gansu Key Laboratory of Arid Climatic Change and Reducing Disaster, Key Open Laboratory of Arid Climatic Change and Disaster Reduction of China Meteorological Administration, Institute of Arid Meteorology, China Meteorological Administration, Lanzhou 730020, China;,   College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China;,   Meteorological Bureau of Gansu, Lanzhou 730020, China
Published: December 2020

Land-surface albedo reflects the ability that land surface reflects solar radiation and plays a very important role in surface energy balance. By picking 10 different underlying surfaces including bare soil, cropland and grassland, the differences in the diurnal variation of land surface radiation and energy processes over North China are investigated using the data measured during July and September, 2008, provided by the Experimental Co-observation and Integral Research in Semi-arid and Arid Regions over North China, the characteristic of land-surface albedo and the response to precipitation are analyzed, and the relationships between land-surface albedo and solar altitude angle and soil humidity are studied. According to the average albedo, the sequence of albedo over all the underlying surfaces are arid meadow in the northeast of China>alpine meadow in the northwest of China>oasis farmland in the northwest>natural vegetation on the Loess Plateau>semi-arid meadow in the northeast of China>farmland in the northeast of China>fruit bearing forest in the northeast of China. And the albedo is smaller when the precipitation is much while it is bigger when the precipitation is less on the whole. The diurnal variation curves of albedo have three types: symmetric type, bigger in the morning and smaller in the noon and afternoon, biggest in the afternoon and smallest in the morning. In the selected 6 stations, the valley of albedo basically occurs on rainy days and the peak occurs on days which are not rainy but have strong solar radiation. The land-surface albedo decreases with the solar altitude angle increasing and tends to remain when the solar altitude angle is bigger than 40°. The land-surface albedo decreases obviously with soil moisture increasing in Yuzhong and farmland of Tongyu, then the grassland of Tongyu. And the land-surface albedos of Maqu, Miyun, Jinzhou have no significant change with the soil moisture.
A new type of conserved quantity deduced from conformal invariance in nonholonomic mechanical system
Authors: Wang Ting-Zhi  , Sun Xian-Ting  , Han Yue-Lin  ,   School of Science, Jiangnan University, Wuxi 214122, China;,   School of Electric and Information Engineering, Pingdingshan University, Pingdingshan 467002, China
Published: December 2020

Conformal invariance and a new type of conserved quantity in nonholonomic mechanical system are studied. The definition and determining equation of conformal invariance for the nonholonomic mechanical system are provided; and the necessary and sufficient conditions that the conformal invariance for a nonholonomic mechanical system should be of Lie symmetry are deduced. With the aid of a new structure equation that the gauge function satisfies, the system's corresponding new conserved quantity is obtained. Finally an example is given to illustrate the application of the results.
The traveling wave approximation method for solving solitary wave in Schrödinger disturbed coupled system
Authors: Xu Yong-Hong  , Han Xiang-Lin  , Shi Lan-Fang  , Mo Jia-Qi  ,   Department of Mathematics & Physics, Bengbu College, Bengbu 233030, China;,   Huzhou Teachers College, Huzhou 313000, China;,   College of Mathematics and Statistics, Nanjing University of Information Science & Technology, Nanjing 210044, China;,   Department of Mathematics, Anhui Normal University, Wuhu 241003, China
Published: December 2020

A class of the Schrödinger nonlinear disturbed coupled system is studied, using the specific technique to relate the exact and approximate solutions. Firstly, the corresponding non-disturbed coupled system is considered. The exact solitary wave solution is obtained by using the projection method. Then, the traveling wave approximation solution to the Schrödinger disturbed coupled system is found by using a functional mapping method.
Using time delay compensation scheme in dynamic output feedback controller for networked control systems
Authors: An Bao-Ran  , Liu Guo-Ping  ,   School of Astronautics, Harbin Institute of Technology, Harbin 150080, China;,   School of Engineering, University of South Wales, Pontypridd CF37 1DL, U.K.
Published: December 2020

This paper proposes a new method to design the dynamic output feedback controller for networked control systems (NCS) with communication delay in both forward and feedback channels. In order to remove the effects of the communication delay according to one's will, two different network delay compensation schemes are provided in two cases: the controlled plant whose state vectors can be measured and the one whose state vectors cannot be measured. Furthermore, another key part of this paper is to analyse the stability of the closed-loop networked control system. Finally, numerical simulation results show the effectiveness of the proposed method.
H∞ control for spacecraft chaotic attitude motion by liquid sloshing disturbance observer
Authors: Qin Li  , Liu Fu-Cai  , Liang Li-Huan  , Hou Tian-Tian  ,   Key Lab of Industrial Computer Control Engineering of Hebei Province, Yanshan University, QinHuangdao 066004, China
Published: December 2020

To investigate the control problem of chaotic motion in spacecraft system caused by the coupled effect of liquid fuel sloshing and small periodic disturbance inside or outside spacecraft, the H∞ control strategy based on neural network disturbance observer is presented, which makes liquid spacecraft disengage chaos and liquid fuel sloshing which are inhibited. Disturbance observer is designed to track and compensate the coupled disturbance caused by liquid sloshing, parameter uncertainty, and external disturbance based on the nonlinear approximation capability of neural network. Taking into account the problems of observation error and model inaccuracy, the H∞ control strategy can be applied to improve the robustness of the control system. Compared with the existing common control algorithm, the proposed strategy proves to be valid and better at adaptability and robustness by simulations.