bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on unidirectional transmission of photonic crystal diodes based on heterostructure interface optimization
Authors: Cheng Li-Feng  , Ren Cheng  , Wang Ping  , Feng Shuai  ,   School of Opto-Electronic Information Science and Technology, Yantai University, Yantai 264005, China;,   School of Science, Minzu university of China, Beijing 100081, China
Published: December 2020

In recent years, all-optical diodes based on photonic crystal heterostructures have attracted much attention, and their good characteristics of one-way transmission are the long pursued target. In this paper, different optimized designs are proposed by modifying the photonic crystal structure at the heterostructure interface. And the all-optical diodes with high contrast, which have both efficient unidirectional transmission and beam splitting, are realized in wide bandwidths.
Widely tunable frequency-doubling microwaves generated using Brillouin-assisted carrier phase shift
Authors: Zheng Di  , Pan Wei  , Yan Lian-Shan  , Luo Bin  , Zou Xi-Hua  , Liu Xin-Kai  , Yi An-Lin  ,   School of Information Science and Technology, Southwest Jiaotong University, Chengdu 610031, China
Published: December 2020

An optically tunable frequency-doubling microwave generation technique based on stimulated Brillouin scattering (SBS) in optical fibers is proposed and experimentally demonstrated. Due to the strong dispersion characteristics in SBS, when a up/2 phase shift is imposed on the optical carrier of an amplitude-modulated signal by SBS, only a frequency-doubling microwave signal from the beating between the optical carrier and the 1st sidebands is generated. Due to the inherent narrowband character of SBS and the phase shift being only imported on to the optical carrier while the sidebands are kept unchanged, the frequency-doubling with large frequency tunability is realized, the operational bandwidth is just limited by other optical device deployed. In addition, all the required optical signals and pumps can be generated from the same laser source, the influence from the wavelength drifting is eliminated, so the stability of the system is established.
Ultrasonic imaging for appearance of vertical slot by reverse time migration
Authors: Xu Yan-Feng  , Hu Wen-Xiang  ,   Institute of Acoustics, Tongji University, Shanghai 200092, China
Published: December 2020

The problem in traditional industrial ultrasonic imaging methods is the difficulty to obtain the appearance or the shape of defects inside solid materials although the methods have the ability to detect and determine the position and lateral dimensions. These special defects, like the vertical slot or crack, are typical examples. Based on the multi-element array ultrasonic technique, the numerical and experimental studies on reverse time migration (RTM) ultrasonic imaging for metalic materials are carried out. In this paper, the objects in detecting and imaging experiments are aluminum samples with slot intersecting the bottom or interior slot, which cannot be effectively detected by traditional ultrasonic methods. First the single component ultrasonic field for RTM imaging is studied to obtain RTM ultrasonic imaging results based on numerical simulation and experimental measurements using a multi-element array ultrasonic testing system. Then, the RTM imaging techniques based on multi-component ultrasonic displacement field detection and converted shear wave separation are further studied, and a new approach using a multi-component laser interferometer is proposed. Numerical simulation results verify that the multi-component RTM imaging reconstructive method can overcome the shortcomings of single component method, and obtain better image quality.
A new robust adaptive beamforming and the one-dimensional search strategy
Authors: Wang Yan  , Wu Wen-Feng  , Fan Zhan  , Liang Guo-Long  ,   Science and Technology on Underwater Acoustic laboratory, Harbin Engineering University, Haerbin 150001, China;,   China Electronics Technology Group Corporation No.38 Research Institute, Hefei 230031, China
Published: December 2020

Adaptive beamforming methods will be degraded sharply in the presence of steering vector errors. The design methods of robust adaptive beamforming become more flexible when the convex optimization technique is used. However, this leads to high computational-complexity and more difficulties for engineering applications. To solve these problems, a robust adaptive beamforming based on the least square estimation is proposed, and a laconic solution method using one-dimensional search is derived. The standard Capon beamformer (SCB) is converted to a robust least-square problem based on the principle of generalized sidelobe canceller, and is then changed into a problem of second-order program. In order to reduce the amount of computation, a one-dimensional search method is deduced using the relationship between the primal and dual problems of second-order program, and Newton iteration method is adopted to obtain the optimal solution. The computational complexity of the proposed algorithm is in the same order of magnitude as that of the SCB. Simulation results demonstrate the robustness of the proposed algorithm in the case of steering vector mismatch and snapshot deficiency.
Simulation study on the propagation of solitary waves in a one-dimensional composite granular chain
Authors: Huang De-Cai  , Chen Wei-Zhong  , Yang An-Na  , Sun Min  , Hu Feng-Lan  , Zhao Min  ,   Department of Applied Physics, Nanjing University of Science and Technology, Nanjing 210094, China;,   Key Laboratory of Modern Acoustics of Ministry of Education, Institute of Acoustics, Nanjing University, Nanjing 210093, China;,   School of Electric and Information Engineering, Hefei Normal University, Hefei 230601, China
Published: December 2020

The propagation of solitary wave in a one-dimensional composite granular chain with heavy and light particles by turns is investigated by using molecular dynamics simulation. Under the condition of larger or smaller mass ratio of light to heavy particles, scattering effect is weaker and both particle velocity and solitary wave velocity decay slowly. In the intermediate range of mass ratio, the scattering effect becomes stronger, resulting in a faster decay of particle velocity and solitary wave velocity. Moreover, effect of increasing velocity happens when teh solitary wave travels across the heavy-light interface, indicating that the solitary wave velocity is increased. Effect of increasing velocity is enhanced when the mass ratio of light to heavy particles decreases. Due to the combined action of scattering effect and the effect of increasing velocity, the traveling time of solitary waves can be modulated by altering the mass ratio of light to heavy particle.
Quasi-static finite element calculation of interaction between graphene and nanoprobe
Authors: Zhang Bao-Lei  , Wang Jia-Xu  , Xiao Ke  , Li Jun-Yang  ,   The State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400038, China
Published: December 2020

Probes of nano scale are a type of important tools for the study on nano-film material. Dynamic explicit method accompanied by the intermittent feeding of probe to dissipate the energy is applied to avoid the difficulty of convergence in the finite element model for a system of probe, graphene, and substrate. And the results of a static state are obtained from this strategy. The functions of interface interaction forces are deduced from adhesion energy and the potential between atoms. The force functions are implanted into subroutines in Abaqus code to simulate the interactions among graphene layers, probe, and substrate. Results of simulations show good consistency with the data of experiments.
Stability of heated liquid film on an uneven substrate
Authors: Liu Mei  , Wang Song-Ling  , Wu Zheng-Ren  ,   School of Energy Power and Mechanical Engineering, North China Electric Power University, Baoding 071003, China
Published: December 2020

This paper studies mainly the evolution and linear stability of the nonlinear surface waves of a two-dimensional viscous liquid film along an uneven inclined non-uniformly heated wall. A long wave perturbation method is used to derive zero- and first-order evolutions equations of the nonlinear surface wave flowing on an uneven substrate. Based on the obtained evolution equations, the diagram of evolution progress for film surface wave on a sinusoidal corrugated substrate is drawn, the linear stability analysis is also studied, and the effect of various parameters on the flow stability of liquid membrane is analysed. Theoretical results demonstrate that the free surface of the film shows sine wave and has the same frequency as the substrate, and the film thickness will decrease gradually along the flow direction. Marangoni number gives a stabilizing effect, the stable zone increases with the increase of Marangoni number. While, Peclet number and the angle theta are unstable factors, the stable region decreases with the increase of them. Besides, the trends that Marangoni number, Peclet number and angle theta may impact on the stability of the film whice are consistent with one another, so a liquid film is easy to destabilize at the trough of the substrate.
Study on thermal characteristics of phonons in graphene
Authors: Ye Zhen-Qiang  , Cao Bing-Yang  , 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

Phonons are the main energy carriers for heat conduction in graphene. One of the most important and basic thermal properties is the relaxation time. In this paper, phonon relaxation times are investigated by a normal mode decomposition method to reveal the distinctions of the different phonon modes. The method is based on equilibrium molecular dynamics simulation. In the simulations, the heat current autocorrelation functions are obtained for each single phonon, and the relaxation times are extracted by fitting the functions. In addition, the relations among relaxation time, wave vector, frequency, and temperature are examined. It is found that the variation tendency of the relaxation time with wave vector is close to that of the dispersion with wave vector. For frequency and temperature, they are in agreement with the theoretical model: 1/=nTm. It is shown thatn is 1.56 for acoustic phonons, while for optical phonons, it varies slightly with frequencies; and m is slightly different for each mode. Finally, the contributions of different phonon modes to thermal conductivity are investigated. It is found that low frequency phonons dominate the heat conduction process because of the relatively high relaxation time and density of states.
Investigation on the electrical properties of anatase and rutile Nb-doped TiO2 by GGA(+U)
Authors: Yang Zhen-Hui  , Wang Ju  , Liu Yong  , Wang Kang-Kai  , Su Ting  , Guo Chun-Lin  , Song Chen-Lu  , Han Gao-Rong  ,   State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
Published: December 2020

Crystal structure, electronic properties, and stability of anatase and rutile Nb-doped TiO2 (Nb:TiO2) compounds with different doping concentrations are studied by the combination of GGA and GGA+U methods within the density functional theory based first-principle calculation. And the main research work and contents are listed as follows: The anatase Nb:TiO2 appears as a degenerated semiconductor which behaves as an intrinsic metal. Its metallic property arises from Nb substitution into the Ti site, providing electrons to the conduction band. In contrast, the rutile Nb:TiO2 shows insulating behaviors. Ionization efficiency of Nb in anatase Nb:TiO2 is higher than that in rutile. We expect that anatase Nb:TiO2 is a potential material for transparent conducting oxide (TCO) while rutile Nb:TiO2 is not. The doped systems show different electronic characteristics, such as band structure, Fermi energy, and effective mass of carriers at different doping levels. In higher dopant concentration nNb, the ionization efficiency decreases slightly. Calculated defect-formation energy shows that Ti-rich material growth conditions are not in favor of the introduction of Nb while Nb can be easily doped in Nb:TiO2 under O-rich growth conditions. Nb dopant is difficult to be doped at higher doping level for both anatase and rutile Nb:TiO2.
Research of the synergistic effects in Cu/N co-doped TiO2 surface：A DFT calculation
Authors: Li Zong-Bao  , Wang Xia  , Fan Shuai-Wei  ,   Department of Physics and Application Engineering & Key Laboratory of New Material Manufacture and Application, the Department of Education of Guizhou Province, Tongren University, Tongren 554300, China;,   Department of Biological and Chemical Engineering, Tongren University 554300, China;,   College of Science, China Three Gorges University, Yichang 443002, China
Published: December 2020

First principles density functional theory calculations are carried out to investigate the interactions between implanted copper and nitrogen atoms at the anatase TiO2 (001) surface. The doped configurations and formation energies of Cu on TiO2 (001) and TiO2 (101) surfaces, N on TiO2 (001) and Cu/TiO2 (001) surfaces have been considered, and the perfected structures are obtained. Compared with the S/TiO2 (001) perfected structure, the analyses of the band structure and density of states of Cu/N-TiO2 (001) show that the band gap is decreased obviously when the CuO2 state occurrs; this could improve the photocatalytic activity significantly.
New complexion two-soliton solutions to a kind of nonlinear coupled system
Authors: Taogetusang  , Yi Li-Na  ,   College of Mathematical Science, Inner Mongolia Normal University, Huhhot 010022, China
Published: December 2020

A function transformation is presented to change a kind of nonlinear coupled system into a set of two elliptic equations of the first kind. Then new infinite sequence complexion two-soliton solutions to a kind of nonlinear coupled system are constructed by new solutions and Bäcklund transformation of elliptic equation of the first kind.
Opinion evolution model of social network based on information entropy
Authors: Huang Fei-Hu  , Peng Jian  , Ning Li-Miao  ,   College of Computer Science, Sichuan University, Chengdu 610065, China
Published: December 2020

With the development of network services, social networking has become a new medium of information dissemination. Thus, many scholars pay close attention to the evolution of network public opinion which has great significance and practical value. In this paper, an opinion evolution model of social network based on information entropy is proposed, which is helpful to investigate the evolution of network public opinion. The model has two characteristics: firstly, it can reflect the psychological process when an individual makes a choice facing with two opposite views; secondly, it can reflect the influence of subjective and objective factors when the individual forms new ideas. In the simulation, some issues are discussed which includes the effects of the public opinion environment on the individual opinion evolution, the influences of the initial opinion and self-confidence on the individual opinion evolution, and the effects of leaders' opinions on the opinion evolution of populations. From the experimental results it follows that the model works well and can reflect the characteristics of individuals in real social networks. For example, the formation of the individual's opinion will be affected by public opinion environment, and an individual will not accept the opinions from others if he is very confident, and the opinion evolution of populations will be influenced when there exist the leader's opinions in network.
Systematic calculations on cluster radioactivity half-lives of trans-lead nuclei with effective liquid drop model
Authors: Sheng Zong-Qiang  , Shu Liang-Ping  , Meng Ying  , Hu Ji-Gang  , Qian Jian-Fa  ,   School of Science, Anhui University of Science and Technology, Huainan 232007, China;,   School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009, China
Published: December 2020

The cluster radioactivities of trans-lead nuclei are systematically investigated by using the effective liquid drop description with the varying mass asymmetry shape and effective inertial coefficient. An effective nuclear radius constant formula is used instead of the original empirical formula in calculation. The calculated half-lives are in good agreement with the available experimental data. The root-mean-square deviation between the calculated logarithmic half-lives and the experimental ones is only 0.895. From the plots of the calculated lgT1/2 values versus the neutron (or proton) number of daughter, the shell effect of neutron magic number N=126 (or proton magic number Z=82) can be clearly seen. The odd-even-stagger can be clearly seen in the odd clusters 25Ne, 29Mg. The calculated half-lives conform to the Geiger-Nuttall law. We obtain some important conclusions about the Geiger-Nuttall law from the calculated results.
Determination of thorium fission rate by off-line method
Authors: Feng Song  , Liu Rong  , Lu Xin-Xin  , Yang Yi-Wei  , Wang Mei  , Jiang Li  , Qin Jian-Guo  ,   Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China;,   Department of Engineering Physics, Tsinghua University, Beijing 100084, China
Published: December 2020

Thorium fission reaction rate is an important datum in uranium-thorium fuel cycle. In order to measure the thorium fission rate on the thorium sample equipment which is set up by the conceptual design of the subcritical reactor and to check the thorium data, the off-line activation γ measurement method of thorium fission rate is developed. Combined with thorium fission yield data of 85mKr, the 232Th fission reaction rate distribution in thorium sample device can be obtained by measuring the 151.16 keV feature gamma rays emitted by fission fragment 85mKr. Details of the principles and factors of this method are discussed, and the verification experiment is carried out on a depleted uranium shell of R13.1/30.0 cm with D-T neutrons. The relative uncertainty of experiment is 5.3%-5.5% for thorium fission reaction rates. The experiment is simulated using MCNP5 with ENDF/B-VI and ENDF/B-VII libraries, simulation results and experimental results accord well with each other within the experimental uncertainty, showing that this approach developed in this paper can work well for determining the thorium fission rate.
First-principles study of 3d transition metal Co doped core-shell silicon nanowires
Authors: Liao Jian  , Xie Zhao-Qi  , Yuan Jian-Mei  , Huang Yan-Ping  , Mao Yu-Liang  ,   Key Laboratory for Micro-Nano Energy Materials and Devices of Hunan Province, Faculty of Materials, Optoelectronic and Physics, Xiangtan University, Xiangtan 411105, China;,   Key Laboratory for Computation and Simulation in Science and Engineering of Hunan Province, Faculty of Mathematics and Computational Science, Xiangtan University, Xiangtan 411105, China
Published: December 2020

According to density functional first-principles calculations, we study the substitutional doping of Co atoms in core-shell silicon nanowires. By comparing the formation energies, we find that all the doping configurations obtained from shell-chain doping, core doping, and whole shell doping are stable, and core-shell doping silicon nanowire has the highest structural stability. All the doped configurations show metallic property, and the conductance channels increase with the increasing of doping concentration. Co-doped silicon nanowires show ferromagnetic, possessing magnetic moment. Bader charge analysis shows that charge is transferred from Si atoms to Co atoms in doped silicon nanowires. In transition metal Co atom, charge is transferred from 4s orbital to 3d and 4p orbital. The reducing of unpaired electron in 3d orbital and part of charge transferring from up-spin to down-spin in 4s, 3d and 4p orbital, makes magnetic moments in Co atom reduced.
Fast computation of electromagnetic scattering characteristics from conducting targets using modified-physical optics and graphical electromagnetic computing
Authors: Zhu Yan-Ju  , Jiang Yue-Song  , Zhang Chong-Hui  , Xin Can-Wei  ,   School of Electronic Information Engineering, Beihang University, Beijing 100191, China
Published: December 2020

A novel high-frequency radar cross section prediction method is introduced to solve the scattering from electrically large conductive target. It can be realized by combining a modified-vector physical optics algorithm and a graphical electromagnetic computing algorithm. In consideration of the traditional physical optics algorithm which needs to compute the edge diffraction, the radar cross section of the target cannot be calculated directly, but it is needed to first calculate the diffraction contribution, then to add the scattering contribution, therefore the radar cross section of the target can be finally obtained. By using the improved graphical electromagnetic computing, the surface normals, thus the surface current, can be directly corrected. Therefore the diffraction at the edges is taken into account, thereby improving the efficiency of the algorithm. The central processing unit running time involves only the time needed to compute the electromagnetic part, with leaving the geometric part to the graphics hardware. The line integrals are computed over an arbitrary shape in real time. Numerical results demonstrate the good accuracy and efficiency of the modified method.
A new full waveform analysis approach using simulated tempering Markov chain Monte Carlo method
Authors: Yin Wen-Ye  , He Wei-Ji  , Gu Guo-Hua  , Chen Qian  ,   Department of Optoelectronic Technology, Nanjing University of Sciences and Technology, Nanjing 210094, China
Published: December 2020

To reconstruct the target shape distribution in the distance, full waveform analysis algorithm is utilized by extracting and analyzing the number of the peaks, the time of the peak maximum and other parameters. A novel fast full waveform analysis algorithm (simulated tempering Markov chain Monte Carlo algorithm, STMCMC) is proposed, which is able to process the waveform data automatically. For the different types of the parameters, simulated tempering strategy and the Metropolis strategy are presented. In simulated tempering strategy, due to the demand of speed or accuracy, active intervention tempering is used to control the process of solving the vector parameters. On the other hand, the Metropolis strategy is adopted for non-vector parameters to reduce computation amount. Both the strategies are based on Markov chain algorithm, and meanwhile can hold the convergence of the Markov chain, which makes the STMCMC algorithm robust.
Conformal invariance and conserved quantity of Mei symmetry for Appell equations in nonholonomic systems of Chetaev’s type with variable mass
Authors: Zhang Fang  , Li Wei  , Zhang Yao-Yu  , Xue Xi-Chang  , Jia Li-Qun  ,   College of Electric and Information Engineering, Pingdingshan University, Pingdingshan 467002, China;,   School of Mathematics and Physics, Henan University of Urban Construction, Pingdingshan 467002, China;,   School of Science, Jiangnan University, Wuxi 214122, China
Published: December 2020

Conformal invariance and conserved quantity of Mei symmetry for Appell equations of nonholonomic system of Chetaev's type with variable mass are studied. The conformal invariance and Mei symmetry for Appell equations of nonholonomic systems of Chetaev's type with variable mass are defined under the infinitesimal transformation of group, and the determining equations of conformal invariance of Mei symmetry for the system are given. Then, the expression of the corresponding conserved quantity of the system is derived. Finally, an example is given to illustrate the application of the results.
Analytical calculation and evolutionary regression method for isentropic exponent of hydrogen gas at the throat of critical nozzle
Authors: Ding Hong-Bing  , Wang Chao  , Zhao Ya-Kun  ,   Key Laboratory of Process Measurement and Control of Tianjin, School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China
Published: December 2020

As one of the most promising renewable energy resources, the hydrogen has been used in the fields such as aerospace, industry, and fuel cells. Critical nozzles are widely used for mass flow-rate measurement of high hydrogen gas, since the flow measurement process is not affected by its downstream flow disturbance. The flow rule of real hydrogen gas through a critical nozzle is complicated and the thermophysical property of hydrogen at the nozzle throat is vital to the accurate measurement of hydrogen flow. In this paper, based on explicit Helmholtz energy and entropy-enthalpy equations, the basic flow parameter and isentropic volume change exponent are analytically calculated. In addition, an accurate explicit equation is determined by the nonlinear regression analysis where the ways of selection, exchange and mutation derived from evolutionary algorithm are introduced to search for optimal population individual. The regression standard deviation is 0.0089%, mean residual deviation is 0.0285%, and maximum residual deviation is 0.1781%. The result shows that it not only can rapidly find the optimal solution which has the lowest number of equation items and the great overfitting suppression capability, but also has a high computation accuracy. This algorithm can also be applied to modeling flow characteristic parameters for every other flow device.
Two-dimensional magneto-hydrodynamic description of field reversed configuration
Authors: Li Lu-Lu  , Zhang Hua  , Yang Xian-Jun  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: December 2020

Magnetized target fusion (MTF) is an alternative approach to fusion, of which the plasma lifetime and density are those between inertial confinement fusion and magnetic confinement fusion. Field-reversed configuration (FRC) is a candidate target plasma of MTF. In this paper, a two-dimensional magneto-hydrodynamic code MPF-2D is developed, and it is used to simulate the formation process of FRC on experimental devices FRX series at Los Alamos National Laboratory. In addition, design parameters of FRC on Yingguang-1 device are also evaluated, which will be constructed in 2015 at the Institute of Fluid Physics, China Academy of Engineering Physics.
Effect of predeformation on the transition from hexagonal phase to square phase near the melting point using phase field crystal method
Authors: Yun Jiang-Juan  , Chen Zheng  , Li Shang-Jie  , Zhang Jing  ,   State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

The two-mode phase field crystal (PFC) method is used to calculate the phase diagram. And in this paper it is used to simulate the effects of predeformation degree and isothermal temperature on the hexagonal grain boundary evolution and on the hexagonal/square phase transition. Results show that when there is no predeformation in the initial phase, the grain boundary defect causes the pre-melting around the melting point; predeformation increases and the interaction between deformation and defects induces the pre-melting around the melting point; and the predeformation further increases, deformation induces liquid phase and square phase simultaneously at the distortion place. The bigger the predeformation and the closer to melting point the maintained temperature, the more obvious the growth of liquid phase is; on the contrary, the square phase grows obviously. The distortion energy is released with time and the phase of grain finally becomes square phase. It can be concluded that keeping the hexagonal phase isothermal near the melting temperature, the liquid phase appears at the grain boundary or at the other defects because the predeformation leads to the increase of atom activity, thus increasing atom disorder degree. Then with the release of distortion energy, the grain phase finally transforms into an equilibrium square phase. In this way the hexagonal/square transition time is extended.
Epitaxial growth micro-structure and magnetic studies of FePt nanoparticles：MgO multi-layer composite thin films
Authors: Wu Jian-Bang  , Zhou Min-Jie  , Wang Xue-Min  , Wang Yu-Ying  , Xiong Zheng-Wei  , Cheng Xin-Lu  , Marie-José Casanove  , Christophe Gatel  , Wu Wei-Dong  ,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China;,   Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610064, China;,   Centre d'Elaboration de Matériaux et d'Etudes Structurales, CNRS, Toulouse 31055, France
Published: December 2020

The FePt：MgO multi-layer nanocomposite thin films are deposited on MgO (100) substrates by using pulsed laser deposition method. The composition of FePt is Fe48Pt52. FePt nanoparticles (NPs) are embedded in MgO epitaxial layer periodically. The results of in-situ reflection high energy electron diffraction show that MgO epitaxial layers grow into the layer-by-layer mode and FePt NPs grow into the island mode. The alternation of the two growth modes is achieved in the whole deposition process. The high resolution transmission electron microscope results show that the phase of FePt is converted from the disordered face-centered cubic structure into the ordered face-centered tetragonal L10 structure after annealing. The perfect crystalline FePt NPs (around 5 nm in diameter) are flat-hexagonal in shape and array layer by layer on MgO matrix. The M-H loop of the film shows that the ordering degree and magnetism are enhanced after annealing.
Influence of annealing on green luminescence from Cu：ZnO thin films
Authors: Jia Xiang-Hua  , Zheng You-Jin  , Yin Long-Cheng  , Huang Hai-Liang  , Jiang Hong-Wei  , Zhu Rui-Hua  ,   Key Laboratory of Superhard Materials, Mudanjiang Normal College, Mudanjiang 157012, China
Published: December 2020

ZnO thin films are prepared by sol-gel method on Si substrates. The structural and optical properties of the films annealed at different temperatures are analyzed by X-ray diffraction (XRD), scanning electron microscopy, X-ray photoelectron spectroscopy and photoluminescence. The results of XRD show that each of all the ZnO thin films has a wurtzite phase and is preferentially oriented along the c-axis direction. The sample annealed at 900℃ exhibits a better crystalline quality. Bright and stable structured green luminescence is achieved from the Cu-doped ZnO thin film. The intensity of the green emission increases significantly after annealing at 800℃, while starts to decrease with further increasing temperature. Green luminescence is correlated with the creation of Zn vacancies. Green emission peaks are found to be dependent on the relative concentration of defect centers. The substitution of Cu2+ by Cu+ will increase concentration of defects in the Cu:ZnO thin film and result in very strong green emission.
High-frequency magnetic properties of planar anisotropy carbonyl-iron particles（Retracted Article）
Authors: Huo Tian-Xu  , Qiao Liang  , Wang Tao  , Li Fa-Shen  ,   Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000, China
Published: December 2020

The effect of orientation degree on high-frequency magnetic properties of planar anisotropy carbonyl-iron particles is studied. We build the samples for planar carbonyl-iron particles, whose magnetic moments obey Gaussian distribution. Meanwhile, we obtain a new method about complex permeability by utilizing Landau-Lifshitz-Gilbert equation. Then the frequency-dependent complex permeability of sample is calculated using our method. The result shows that with the increase of orientation , the standard deviation of Gaussian distribution decreases and the orientation degree f increases. Furthermore, the real part of initial permeability of the planar carbonyl-iron sample becomes higher with the increase of orientation degree f. For comparison, we measured the orientation degree and complex permeability of the sample by Mssbauer spectroscopy and vector network analyzer respectively. It is found that our experimental data accord well with the simulation results.
Resolution characteristic of graded band-gap AlGaAs/GaAs transmission-mode photocathodes
Authors: Deng Wen-Juan  , Peng Xin-Cun  , Zou Ji-Jun  , Jiang Shao-Tao  , Guo Dong  , Zhang Yi-Jun  , Chang Ben-Kang  ,   Engineering Research Center of Nuclear Technology Application, Ministry of Education, East China Institute of Technology, Nanchang 330013, China;,   Engineering Research Center of New Energy Technology and Equipment of Jiangxi Province, East China Institute of Technology, Nanchang 330013, China;,   School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

The modulation transfer function (MTF) of graded band-gap AlGaAs/GaAs transmission-mode photocathodes is numerically solved from the two-dimensional continuity equations. According to the MTF model, we calculate the theoretical MTF of graded band-gap and uniform band-gap transmission-mode photocathodes, and analyze the effects of Al composition, wavelength of incident photon, and thickness values of AlGaAs and GaAs layer on the resolution. The calculated results show that compared with the uniform band-gap photocathode, the graded band-gap structure can increase the resolution of photocathode evidently. If the spatial frequency f ranges from 100 to 500 lp·mm-1, the increase of resolution is more pronounced. Let f=200 lp·mm-1, the resolution of graded band-gap photocathode generally increases 150%-260%. The resolution improvement of graded band-gap photocathode is attributed to the built-in electric field. While too high built-in electric field will influence the spectral response of long-wavelength photons due to higher Al composition in the AlGaAs/GaAs photocathodes.
A chaotic signal denoising method developed on the basis of noise-assisted nonuniformly sampled bivariate empirical mode decomposition
Authors: Wang Xiao-Fei  , Qu Jian-Ling  , Gao Feng  , Zhou Yu-Ping  , Zhang Xiang-Yu  ,   Naval Aeronautical Engineering Institute Qingdao Branch, Qingdao 266041, China;,   Naval Aeronautical Engineering Institute, Yantai 264001, China
Published: December 2020

According to the advantages of nonuniformly sampled bivariate empirical mode decomposition and the characteristics of noise after it, an adaptive chaotic signal denoising method is proposed based on the noise-assisted nonuniformly sampled bivariate empirical mode decomposition. Firstly, a complex signal is constructed for the noise-assisted nonuniformly sampled bivariate empirical mode decomposition, by using noisy chaotic signal and gaussian white noise as the real part and imaginary part respectively; secondly, the noise energy of each intrinsic mode function in the real part is estimated according to the energy of each intrinsic mode function in the imaginary part; and finally, from the above results, each intrinsic mode function in the real part is denoised by using the singular value decomposition. Noise energy estimate numerical experiment validates the feasibility of this method, and the denoising tests for Lorenz signal and monthly sunspot data indicate that our method shows advantages in both noise reduction and chaotic attractor topological configuration reversion.
A scale-free fault tolerant topology model in wireless sensor network for toleration of comprehensive fault
Authors: Liu Bin  , Dong Ming-Ru  , Liu Hao-Ran  , Yin Rong-Rong  , Han Li  ,   School of Electrical Engineering, Yanshan University, Qinhuangdao 066004, China;,   School of Information Science and Engineering, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

A wireless sensor network in practice often suffers from environment damage and energy depletion. In order to solve the problem, this paper establishes a comprehensive fault model first. Then according to the demand for comprehensive fault tolerance ability and network lifetime, a relationship between the network node degree and the maximum node degree is obtained. And the relational expression between the two kinds of node degrees derived from the scale-free characteristics is acquired. Thus the optimal maximum node degree can be solved. Finally, based on the fitness function for the maximum node degree introduced, a scale-free fault tolerant topology evolution model is put forwarded which can effectively tolerate comprehensive fault. Simulation results show that the scale-free topology obtained has strong fault tolerance for environment damage and energy depletion. And it also can effectively prolong the network lifetime.
Cylindrical thermal concentrator：theory, simulation, and implement
Authors: Mao Fu-Chun  , Li Ting-Hua  , Huang Ming  , Yang Jing-Jing  , Jia Bang-Jie  ,   Wireless Innovation Lab of Yunnan University, Kunming 650091, China;,   Kunming Key Lab of Spectrum Sensing and Radio Monitoring, Kunming 650091, China
Published: December 2020

As a kind of ultra-efficient thermal energy harvesting cell, thermal concentrator has recently attracted great attention from researchers. An analytical expression which describes the temperature distribution in the concentrator is deduced from the heat conduction equation and coordinate transformation relations. The expression is validated by numerical experiments based on COMSOL. Influence of the anisotropy due to cladding and device geometry on the performance of the thermal concentrator is analyzed. It is demonstrated that the greater the anisotropy, the better the thermal concentration effect. Besides, increasing the aspect ratio between the cladding and the core radius also gives rise to a better performance. Based on the temperature distribution relations between the core and the background region, we further explore a method to practically realize such a thermal concentrator by using naturally available materials. It is suggested that different levels of thermal concentration can be achieved by arranging alternately two isotropic conductivities along the azimuth direction and tuning their thermal localizations respectively.
Bifurcation and chaos of some relative rotation system with triple-well Mathieu-Duffing oscillator
Authors: Liu Bin  , Zhao Hong-Xu  , Hou Dong-Xiao  ,   College of Electrical Engineering, YanShan University, Qinhuangdao 066004, China;,   Department of Control Engineering Northeastern University at Qinhuangdao, Qinhuangdao 066004, China
Published: December 2020

The dynamic equation of a nonlinear relative rotation system with a triple-well Mathieu-Duffing oscillator is investigated. Firstly, a codimension three-bifurcation characteristic is deduced by combining with the multi-scale method and singularity theory under the condition of nonautonomy. Secondly, the threshold value of chaos about Smale horseshoe commutation is given from Melnikov method. Finally, the numerical simulation exhibits safe basins and chaos, and the erosion process of safe basins, which is closely related to the process, leading to chaos.
Investigation on range distribution of Er ions implanted in silicon-on-insulator
Authors: Qin Xi-Feng  , Ma Gui-Jie  , Shi Shu-Hua  , Wang Feng-Xiang  , Fu Gang  , Zhao Jin-Hua  ,   College of Science, Shandong Jianzhu University, Jinan 250101, China
Published: December 2020

It is very important to take into consideration the distribution of range, range straggling, and lateral spread of ions implanted into semiconductor materials during designing and fabrication of semiconductor integration devices by means of ion implantation. Er ions with energies between 200 and 500 keV are implanted in SOI (silicon-on-insulator) samples. The mean projection range Rp and the range stragglings Rp of Er ions with a dose of 21015 cm-2 implanted in SOI samples are measured by Rutherford backscattering (RBS) technique. The obtained data are then compared with those predicted by TRIM codes. It is seen that the experimental data of Rp agree well with the theoretical values. However, there are great differences between the experimental data and the theoretical values of Rp.
Nanoindentation simulation of Ni-base single-crystal superalloy with the consideration of interface effect
Authors: Hu Xing-Jian  , Zheng Bai-Lin  , Hu Teng-Yue  , Yang Biao  , He Peng-Fei  , Yue Zhu-Feng  ,   institute of Applied Mechanics, Tongji University, Shanghai 200092, China;,   School of Mechanics and Civil&Architecture, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

Nanoindentation made by diamond indenter on pure Ni and the /'-phase in a Ni-base single-crystal superalloy is simulated respectively with molecular dynamics method. Elasticity modulus and hardness of the two models are calculated. Initiation and growth of dislocations and the influence of misfit dislocations of /'-phase in Ni-base single-crystal superalloy at different indentation depths are analyzed with center symmetry parameter. Results show that the relationship between indentation load and depth for the two models is similar when the indentation depth below 0.641 nm, indicating that the misfit dislocation on interface little affects the indentation. When the indentation depth reaches 0.995 nm, the dislocation nucleation can be found in misfit dislocations and the crystals that have slipped along {111}-oriented crystal surface in -phase. As a result, the indentation load of the latter model decreases and is smaller than that in pure Ni model before the indentation depth reaches 1.487 nm. When the indentation depth reaches 1.307 nm, owing to the inhibition caused by misfit dislocations at the interface, the indentation load for the /'-phase model in Ni-base single-crystal superalloy increases rapidly.
Density functional study on the different behaviors of Pd and Pt coating on graphene
Authors: Li Feng  , Xiao Chuan-Yun  , Kan Er-Jun  , Lu Rui-Feng  , Deng Kai-Ming  ,   Department of Applied Physics, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

Density functional calculations are used to investigate the mechanism of the distinctly different behaviors of Pd and Pt coating on graphene. Geometric and electronic structural analysis indicates that the electrons on the dz2 orbital of Pd may transfer to the dxz+dyz orbital of Pd by the aid of the up electrons of the graphene. This charge-transfer mechanism enhances the interactions between the Pd coating and the graphene substrate, driving the Pd coating to grow on the graphene, while Pt does not have this behavior. Metal self-assembly hinders Pt atoms to cover the graphene.
Effects of optical phonon and built-in electric field on the binding energy of bound polarons in a wurtzite In0.19Ga0.81N/GaN quantum well
Authors: Zhao Feng-Qi  , Zhang Min  , Li Zhi-Qiang  , Ji Yan-Ming  ,   College of Physics and Electronic Information, Inner Mongolia Normal University, Inner Mongolia Key Laboratory for Physics and Chemistry of Functional Materials, Hohhot 010022, China
Published: December 2020

The energies and binding energies of the bound polarons in a wurtzite In0.19Ga0.81N/GaN quantum well are investigated by means of a modified Lee-Low-Pines variational method. Contributions of ground state binding energies and different branches of a longwave optical phonon mode to the energies and binding energies of the bound polarons as a function of the well width and impurity center position are given. Effects of the anisotropy of phonon frequency and built-in electric field in the system on the energies and binding energies, and the electron and impurity center-optical phonon interaction, are included in the calculations. Results show that the contributions of optical phonons and built-in electric field to the ground state energy and binding energy of the bound polarons in a wurtzite In0.19Ga0.81N/GaN quantum well are very large, and result in the reduction of energy and binding energy. The binding energy decreases monotonically with increasing well width, and the speed of decrease is fast in the narrower well while the speed of decrease is slow in the wider well. Contributions of different branches of phonons to the energies and binding energies as a function of well width are different. In the narrower well, contributions of the confined phonon (withoud built-in electric field) are smaller than those of the interface and half-space phonons, while in the wider well, contributions of the confined phonons are larger than those of the interface and half-space phonons. Contributions of the confined phonon (with built-in electric field) become larger, whereas those of the interface and half-space phonons become smaller, and the total contribution of phonons also have obvious change. Contributions of these optical phonons to the ground state energies and binding energies of the bound polarons in In0.19Ga0.81N/GaN quantum wells are larger than the corresponding values (about 3.11.6 meV and 1.50.3 meV) of those in GaAs/Al0.19Ga0.81As quantum wells. The binding energies in In0.19Ga0.81N/GaN quantum wells decrease monotonically with increasing location Z0 of the impurity center for a constant well width d =8 nm, and the decrease of speed becomes faster. As the position of the impurity center is increasing, the contributions of the the interface and half-space phonons decrease slowly, and those of the confined phonons increase slowly as well.
Electroluminescence from SnO2/p+-Si heterostructured light-emitting device：enhancing its intensity via capping a TiO2 film
Authors: Jiang Hao-Tian  , Yang Yang  , Wang Can-Xing  , Zhu Chen  , Ma Xiang-Yang  , Yang De-Ren  ,   State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China
Published: December 2020

Low-voltage (current) driven electroluminescence (EL) has been achieved in the light-emitting device (LED) with a SnO2/p+-Si heterostructure, which is formed by sputtering SnO2 film on a p+-Si substrate, followed by annealing at 800 ℃ in O2 ambient. Furthermore, by means of capping a TiO2 film onto the SnO2 film, the modified LED exhibits significantly enhanced EL. The densification of SnO2 film as a result of the TiO2-capping is responsible for reducing the non-radiative centers. Moreover, the large refractive index and appropriate thickness of TiO2-capped layer are favorable for the extraction of emitted light from SnO2 film. Such two effects of TiO2-capping contribute to the aforementioned enhanced EL.
Structural and electrical transport properties of Mg-doped n-type Sn-based type Ⅷ single crystalline clathrate
Authors: Meng Dai-Yi  , Shen Lan-Xian  , Li De-Cong  , Shai Xu-Xia  , Deng Shu-Kang  ,   Education Ministry Key Laboratory of Renewable Energy Advanced Materials and Manufacturing Technology, Yunnan Normal University, Kunming 650500, China;,   Photoelectric Engineering College, Yunnan Open University, Kunming 650050, China
Published: December 2020

Mg-doped Sn-based single crystalline samples Ba8Ga16-XMgXSn30(0 X 1.5) were grown from Sn flux to characterize their structural and electrical transport properties. Research results show that the prepared compounds are well indexed by the type-Ⅷ clathrate structure with a space group I43 m. With the increase in Mg content, the melting point of the corresponding compounds increases. On the contrary, the lattice constant decreases. The actual content of filling atomic Ba in doped samples is below the ideal value of 8.0, the occupancy of Ba in the dodecahedron is about 0.93 for the sample with X=1.5. All the samples show n-type conduction. The Mg atoms have an effect on the band structure of the materials, and the carrier concentrations in the doped samples are reduced. However, the absolute values of Seebeck coefficient and the resistivity of doped compounds increase, respectively. By calculation, the sample of X=1.5 obtains the maximum value of power factor 1.2610-3 Wm-1K-2 near 430 K.