bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Z-pinch dynamic hohlraum shadowgraphy
Authors: Chen Fa-Xin  , Feng Jing-Hua  , Li Lin-Bo  , Yang Jian-Lun  , Zhou Lin  , Xu Rong-Kun  , Xu Ze-Ping  ,   Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

In order to obtain the dynamic evolution image of tungsten array for foam padding, and to research the form of interaction between tungsten plasma and foam column, a shadow imaging system of four-frame ultraviolet probe laser (266 nm) is designed on 1 MA pulse power device. The time resolution of the system is 2.5 ns, and static space resolution is superior to 70 μm. The radial shadowgraphy image reveals the whole process from the melting and expansion of solid wire to the interaction between the precursor plasma and the foam, from the pinch to rebound inflation. The image shows the continuous interaction between tungsten plasma and foam in the form of Raining within a time of about 50 ns, the plasma shell structure is not found in the whole period of pinch. The quantitative analysis indicates that the minimum pinching speed of the foam column is 1.0×106 cm/s, and maximum pinching speed is 6.0×106 cm/s, and the axial stagnation diameter is about 1 mm. Shadowgram mainly shows the inverse bremsstrunlung effect of interaction between laser and plasma through simulation calculating, and main tungsten plasma interacting with foam column image is shown through synchronizing radial power profile.
Numerical simulations of the phase transition property of the explosive percolation model on Erds Rnyi random network
Authors: Li Yan  , Tang Gang  , Song Li-Jiang  , Xun Zhi-Peng  , Xia Hui  , Hao Da-Peng  ,   Department of Physics, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

Based on the modified Newman and Ziff algorithm combined with the finite-size scaling theory, in this present work we analytically study the phase transition property of the explosive percolation model induced by Achlioptas process on the Erds Rnyi random network via numerical simulations for the basic percolation quantities including the order parameter, the average cluster size, the moments, the standard deviation and the cluster heterogeneity. It is explicitly shown that all these relevant quantities display a typical power-law scaling behavior, which is the characteristic of continuous phase transition at the percolation threshold despite the fact that the order parameter presents a certain feature of discontinuous transition at the same time. Strictly, the explosive percolation transition during the Erds Rnyi random network is a singular transition, which means that it is neither a standard discontinuous phase transition nor the continuous transition in the regular random percolation model.
A compact model of substrate resistance for deep sub-micron gate grounded NMOS electrostatic discharge protection device
Authors: Wu Xiao-Peng  , Yang Yin-Tang  , Gao Hai-Xia  , Dong Gang  , Chai Chang-Chun  ,   Key Laboratory of Ministry of Education for Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi’an 710071, China
Published: December 2020

The current controlled voltage source model of substrate parasitic resistance of deep sub-micron electrostatic discharge protection device is optimized by considering the effect of conductance modulation. A compact macro-model of substrate resistance is presented according to the characteristics of lightly doped bulk substrate and heavily doped substrate with a lightly doped epitaxial layer, which is scalable with the layout dimension. The experimental model parameters of devices with various spaces between source and substrate diffusion can be extracted by device simulation. The breakdown behavior of gate grounded negative-channel metal oxide semiconductor shows the effectiveness of this method. In the meantime, the simulation time-consuming of the compact model is only 7% that of the device simulation software.
A new fast magnetic resonance imaging method based on variabledensity spiral data acquisition and Bregman iterative reconstruction
Authors: Fang Sheng  , Wu Wen-Chuan  , Ying Kui  , Guo Hua  ,   Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China;,   Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, China;,   Department of Engineering Physics, Tsinghua University, Beijing 100084, China
Published: December 2020

Data acquisition time is a bottle neck for increasing imaging speed of magnetic resonance imaging. To solve the problem, a new fast magnetic resonance imaging method based on variable-density spiral acquisition and Bregman iterative reconstruction is proposed in this paper, under the framework of compressed sensing. The proposed method increases the acquisition speed by data undersampling. The resulting undersampling aliasing artifact is removed by utilizing the intrinsic property of variable-density spiral and Bregman iterative recosntruction. The proposed method is validated by both phantom experiemnt and in vivo experiment. The experimental results demonstrate that the proposed method can effectively remove aliasing artifact from data undersampling, and achieve an image with well-preserved image structure information. Therefore this method can be used for reducing data acquisition time.
Structrual analyses of Ga2+xO3-x thin films grown on sapphire substrates
Authors: Pan Hui-Ping  , Cheng Feng-Feng  , Li Lin  , Horng Ray-Hua  , Yao Shu-De  ,   Department of Technical Physics, School of Physics, Peking University, Beijing 100871, China;,   Department of Physics and Electionic Science, Qiannan Normal College for Nationalities, Duyun 558000, China;,   Graduate Institute of Precision Engineering, National ChengKung University, Taichung 40227, China
Published: December 2020

Ga2+xO3-x thin films grown on sapphire substrates by metal-organic chemical vapor deposition under different conditions (temperature pressure) are studied by rutherford backscattering spectrometry/channeling. The structural information and crystalline quality are further investigated by high resolution X-ray diffraction (HR-XRD). The results suggest that at the same growth-temperature the crystalline quality is improved with pressure decreasing, while χmin reaches a minimum 14.5% when the pressure decreases to 15 Torr (1 Torr=133.322 Pa). Then if the pressure is kept at 15 Torr, all films present similar crystalline qualities, which hints that the temperature is not a chief factor. Moreover, films prepared under the same condition are annealed at different temperatures: 700, 800 and 900 ℃. At first the crystalline quality is improved by increasing the annealing temperature and reaches a best χmin of 11.1%. Nevertheless, as the annealing temperature is further increased, the samples become decomposed. XRD spectra of annealed samples each reveal a strong peak of Ga2O3 (402), indicating that the epitaxial layer has a preferred orientation (402).
Chaotic signal denoising method based on independent component analysis and empirical mode decomposition
Authors: Wang Wen-Bo  , Zhang Xiao-Dong  , Wang Xiang-Li  ,   School of Science, Wuhan University of Science and Technology, Wuhan 430065, China;,   State Key Laboratory of Remote Sensing Science, Beijing 100101, China;,   State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China;,   State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China;,   School of Computer Science and Technology, Wuhan University of Technology, Wuhan 430063,China
Published: December 2020

According to the characteristics of empirical mode decomposition and denoise of independent component analysis, an adaptive denoising method of chaotic signal is proposed based on independent component analysis and empirical mode decomposition. First, the chaotic signal is decomposed into a set of intrinsic mode functions by empirical mode decomposition; then, the multi-dimensional input vectors are constructed based on the translation invariant empirical mode decomposition, and the noise of each intrinsic mode function is removed through the constructed multi-dimensional input vectors and the independent component analysis; finally, the denoisied chaotic signal is obtained by accumulating and reconstructing all the processed intrinsic mode functions. Both the chaotic signal generated by Lorenz map with different level Gaussian noises, and the observed monthly series of sunspots are respectively used for noise reduction using the proposed method. The results of numerical experiments show that the proposed method is efficient. It can better correct the positions of data points in phase space and approximate the real chaotic attractor trajectories more closely．
Improved discrete-time model for a digital controlled single-phase full-bridge voltage inverter
Authors: Wu Xuan-Lü  , Xiao Guo-Chun  , Lei Bo  ,   State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Enginerring, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

An improved discrete-time model for a digital controlled single-phase full-bridge voltage inverter is proposed in this paper. Based on state-space averaging in every switching cycle, the improved discrete-time model combines the advantages of the average model and the traditional discrete-time model, which can accurately analyze the digital control delay and sample-and-hold process inherently in digital controlled system. Consequently, under the accuracy premise, the improved discrete-time model can effectively simplify the traditional discrete-time modeling. As an example, an LC filter capacitor-voltage and inductor-current feed-back plus voltage-reference feed-forward control algorithm is analyzed based on the improved discrete-time model. The stability boundary and oscillation frequency are accurately predicted. Finally, theoretical results are verified by simulations and experiments.
Analysis of noisy chaotic time series prediction error
Authors: Wang Xin-Ying  , Han Min  , Wang Ya-Nan  ,   Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian 116023, China
Published: December 2020

For the noisy chaotic series prediction problem, traditional methods are quite empirical, and are lacking in the analysis of the composition of the prediction error, thereby ignoring the the difference between chaotic dynamics reconstruction and prediction model. Based on the composition of actual prediction error, the predictor bias error and input disturbance error are defined in this paper and two kinds of global forecasts, ensemble least-square method and regularization method are analysed. It is shown that the ensemble least-square method is suitable for the reconstruction of chaotic dynamics, but has a greater influence on the predictor error. On the other hand, the regularization method can improve the sensitivity of the predictor, but it can be influenced by the input perturbation error. Two simulation examples are used to demonstrate the difference between the chaotic dynamical reconstruction and the establishment of prediction model, and to compare the ensamble least-square method and the regularization method, and at the same time indicate that the actual prediction error is influenced both by the input disturbance error and by the predictor error. In practice, a balance should be stricken between the two, in order to optimize the model prediction accuracy.
Chaotic time series prediction model of wind power based on ensemble empirical mode decomposition-approximate entropy and reservoir
Authors: Zhang Xue-Qing  , Liang Jun  ,   School of Electrical Engineering, Shandong University, Jinan 250061, China;,   Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education (Shandong University), Jinan 250061, China
Published: December 2020

According to the chaotic feature of wind power time series, a combined short-term wind power forecasting approach based on ensemble empirical mode decomposition (EEMD)-approximate entropy and echo state network (ESN) is proposed. Firstly, in order to reduce the calculation scale of partial analysis for wind power and improve the wind power prediction accuracy, the wind power time series is decomposed into a series of wind power subsequences with obvious differences in complex degree by using EEMD-approximate entropy. Then, the forecasting model of each subsequence is created with least squares support vector machine (LSSVM), ESN and EEMD-ESN improved with the regularized high frequency parts. Finally, the simulation is performed by using the real data collected from a certain wind farm, the results show that the EEMD-ESN model is better in the training speed and forecasting accuracy, than those obtained from the least square support vector machine (LSSVM) model, which provides a new useful reference for the short-term forecasting of wind power in online engineering application.
Photoionization of odd-parity bound excited states of Sm atom
Authors: Yang Lu  , Dai Chang-Jian  , Zhao Yan-Hong  ,   Key Laboratory of Display Materials and Photoelectric Devices, Ministry of Education, Tianjin 300384, China; School of Science, Tianjin University of Technology, Tianjin 300384, China
Published: December 2020

The photoionization detection method is employed to systematically study the odd-parity bound-excited states of Sm atom. Three different excitation paths are designed to carry out three-step excitation and photoionization processes for the Sm atom in the same energy region. By scanning the wavelength of third-step dye laser not only the level energies of a large number of odd-parity bound-excited states are determined, but also the information about relative intensity of the corresponding transition is obtained. Comparison of the three groups of spectra corresponding to the three paths enables us to assign the J-value, the total angular momentum of the excited states of Sm atom uniquely. In addition, a small number of level energies measured with different methods previously are also confirmed in this work.
Experimental and theoretical study of ArCO cluster
Authors: Shan Xiao-Bin  , Zhao Yu-Jie  , Kong Rui-Hong  , Wang Si-Sheng  , Sheng Liu-Si  , Huang Ming-Qiang  , Wang Zhen-Ya  ,   National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China;,   Laboratory of Environmental Spectroscopy, Anhui Institute of Optics Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

The photoionization mass spectra and photoionization efficiency curves of ArCO clusters are obtained with synchrotron radiation mass spectrometry. By comparison with absolute photoabsorption spectra of CO, the photoionization efficiency curve of ArCO clusters in an energy region from 13.9 to 14.6 eV reflects mainly the properties of Rydberg series converging to the X2+ (v+= 1, 2 and 3) of CO+, and these of n= 3 vibration sequence of the series converging to the A2 state of CO+. In the energy region from 14.6 to 15.75 eV, the curve reflects mainly the absorption property of CO, but its five strong peaks shift toward blue due to the interaction between Ar and CO. In an energy region from 15.75 to 15.80 eV, the curve reflects mainly the absorption properties of Ar and CO. At the same time, ionization energy of ArCO, and dissociation energies of ArCO and ArCO + are also calculated using the theory of quantum chemistry.
Investigation of effective EM parameter based on impedance simulation
Authors: Wu Chao  , Lü Xu-Liang  , Zeng Zhao-Yang  , Jia Qi  ,   National Key Laboratory on Electromagnetic Environmental Effects and Electro-optical Engineering, PLA University of Science & Technology, Nanjing 210007, China
Published: December 2020

In order to calculate the equivalent EM parameter of mixed medium, in this paper, we proposes a new method of impedance simulation based on an equivalent circuit. First, the relationship between electromagnetic parameters and capacitance, inductance of material is set up, and then the model that can describe real composite accurately is established. The equivalent EM parameter could be obtained by calculating the equivalent impedance of mixed medium. Comparing this method with the classical formulae and finite-difference numerical method, it is proved that it can be used to calculate the equivalent EM parameter of material. In addition, introducing thin films to simulate the factor such as surface effect, the result of calculation would match with experimental results perfectly. This method has more advantages than classical formulae and numerical method.
Theoretical analysis of polarization eigenstate and magnetic sensitivity in a ring laser gyro
Authors: Wang Zhi-Guo  , Long Xing-Wu  , Wang Fei  , Zhang Bin  ,   Department of Opto-Electronic Engineering, College of Opto-Electronic Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Disturbance by ambient magnetic field is an important factor, which leads to measurement error of the laser gyro. In order to reduce the magnetic sensitivity, the polarization eigenstate in ring cavity is analyzed with matrix perturbation method, considering factors of small nonplanarity, mirror anisotropy and stress birefringence, gain and so on. The main factors affecting the magnetic sensitivity of the laser gyro are discussed. Ellipticities of eigen modes in clockwise and anti-clockwise direction caused by nonplanarity are identical and both are proportional to magnetic sensitivity. The influence of stress birefringence on ellipticity is related to mirror position, propagating direction of eigenmodes and main axis of stress. Nonplanarity is zero when ellipticities of eigen modes in clockwise and anti-clockwise direction are equal without stress birefringence in the passive cavity. A lower cavity loss is better to reduce the magnetic sensitivity of the laser gyro. The minimum magnetic sensitivity is not identical with peak gain for the laser gyro. Large phase and amplitude anisotropies of mirrors are useful to reduce magnetic sensitivity and ellipticity. These findings are significant for the reduction of magnetic sensitivity in ring laser gyros.
Bifurcation of a kind of nonlinear-relative rotational system with combined harmonic excitation
Authors: Meng Zong  , Fu Li-Yuan  , Song Ming-Hou  ,   Key Laboratory of Measurement Technology and Instrumentation of Hebei Province, Yanshan University, Qinhuangdao 066004, China;,   Key Laboratory of Industrial Computer Control Engineering of Hebei Province, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

Using the Lagrange principle of dissipative system, the nonlinear dynamic equation of a relative rotation with combined harmonic excitation is established, which contains nonlinear stiffness and nonlinear damping. The stability and bifurcation characteristics of autonomous system are analyzed by constructing Lyapunov function. Bifurcation response equation of non-autonomous system under the combined harmonic excitation is obtained by the method of multiple scale. Finally, numerical method is employed to analyze the effects of external excitation, system damping and nonlinear stiffness on the process that the system enter into chaos motion via period-doubling bifurcation by bifurcation diagram, time domain waveform, phase trajectory and Poincaré map.
Mosaic structure in epitaxial GaN filmvarying with thickness
Authors: Zhang Yun  , Xie Zi-Li  , Wang-Jian  , Tao Tao  , Zhang Rong  , Liu Bin  , Chen Peng  , Han Ping  , Shi Yi  , Zheng You-Dou  ,   School of Electronics and Engineering, Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Nanjing University, Nanjing 210093, China
Published: December 2020

In this article. We report on the study of mosaic structures of different thick GaN films grown on sapphire (0001) by metalorganic chemical vapor deposition (MOCVD), using high resolution x-ray diffraction. The result from the symmetrical reflections show that the mosaic vertical and lateral correlation lengths that are calculated by two methods increase with film thickness increasing, and the vertical correlation lengths are close to the film thickness, and the same trend in the lateral correlation lengths derived from the reciprocal space maps. By the help of asymmetrical reflections and Williamson-Hall extrapolation method, the tilt and twist mosaic drop with thickness increasing at different rates. All this shows that the increase in thickness lads to the more uniform and neat grain arrangement and the higher-quality epitaxial wafers.
Rolling effects on electronic characteristics for graphene nanoribbons
Authors: Li Jun  , Zhang Zhen-Hua  , Wang Chen-Zhi  , Deng Xiao-Qing  , Fan Zhi-Qiang  ,   School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114, China
Published: December 2020

Graphene nanoribbons (GNRs) are important nanomaterials. A carbon nanotube can be viewed as a GNR rolled into a seamless cylinder. By using the first-principles method based on the density-functional theory, the rolling deformation-dependent electronic characteristics of GNRs, including the band structure (particularly the bandgap), density of states (DOS), and transmission spectrum, are studied systematically. It is found that before all types of GNRs are rolled into carbon nanotubes, they are not sensitive to the rolling deformations, which means that for electronic structures and transport properties, GNRs have a very strong ability to resist the rolling deformations. After GNRs are rolled into nanotubes, zigzag-edge GNRs (ZGNRs) and armchair-edge GNRs (AGNRs) present distinct differences in property, ZGNRs almost maintain unchanged metallic behaviors or become quasi-metallic. But for AGNRs, their electronic characteristics experience large variations, and transformations occur between the quasi-metal and semiconductor with various bandgaps, which might be closely related to the periodical boundary conduction along the direction of tubular circumference of a carbon nanotube and variation of quantum confinement. These studies presented here are of significance for understanding the rolling effects on electronic characteristic and relationship of electronic characteristics between GNRs and carbon nanotubes (structure-property relationship).
Ab initio study of the bcc-to-hcp transition mechanism in Fe under pressure
Authors: Lu Zhi-Peng  , Zhu Wen-Jun  , Lu Tie-Cheng  ,   College of Physical Science and Technology, Sichuan University, Chengdu 610064, China;,   Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China;,   Department of Mathematics and Physics, Officer College of the Chinese People's Armed Police Force, Chengdu 610213, China
Published: December 2020

We perform ab initio calculations on two different transition mechanisms of the bcc-to-hcp phase transition in Fe under pressure distinguished by the occurrence of the metastable fcc intermediate phase on the transition path, that is, the bcc-hcp and the bcc-fcc-hcp. The calculated results indicate that the occurrence of the fcc intermediate state during the transition is energetically unfavorable, which is consistent with the recent in situ XRD experiments. The enthalpy barrier of the fcc-hcp increases with pressure increasing, which indicates that the pressure tends to impede the transformation from fcc to hcp phase in Fe. The details of the structural and magnetic behaviors of the intermediate states during the transition are investigated, which indicates that there are complex magnetism transitions during the phase transition. The physical origins of the influence of magnetism on the phase transition are discussed. Moreover, the origin of the occurrence and evolution of the fcc metastable structure during the transition in the MD simulations are also discussed.
Molecular dynamics simulation of the thermophysical properties of phase change material
Authors: Rao Zhong-Hao  , Wang Shuang-Feng  , Zhang Yan-Lai  , Peng Fei-Fei  , Cai Song-Heng  ,   Key Laboratory of Enhanced Heat Transfer and Energy Conservation of the Ministry of Education, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China
Published: December 2020

The phase change material (PCM), which is based on straight-chain alkanes, has received more and more attention for thermal management. To explore the mechanism of the thermal property of PCM from the microscopic scale, the molecular model of the PCM which consists of n-dodecane with amorphous structure is established in this study. The molecular dynamics (MD) simulation is performed with periodic boundary conditions and COMPASS force field. The melting temperature of n-dodecane is also determined by differential scanning calorimeter (DSC). The results show that the deviation of the isobaric heat capacity of the n-dodecane based PCM by MD method from the perviously reported value is 6.5%. The deviation of the simulated melting temperature of the PCM from the value from the DSC analysis is 7.6%. The simulated thermal conductivity of the PCM shows a slightly decreasing trend with pressure increasing, in a range of 0.1–0.4 W·m-1·K-1.
Acoustic phonon transport and thermal conductance in quantum waveguide with abrupt quantum junctions modulated with double T-shapedquantum structure
Authors: Peng Xiao-Fang  , Chen Li-Qun  , Luo Yong-Feng  , Liu Lin-Hong  , Wang Kai-Jun  ,   College of Science, Central South University of Forestry and Technology, Changsha 410004, China
Published: December 2020

By using the scattering matrix method, the transmission coefficient and thermal conductance of acoustic phonon through a quantum waveguide with abrupt quantum junctions modulated with double T-shaped quantum structure at low temperatures are studied. The results show that at very low temperatures, the double T-shaped quantum structure can enhance low-temperature thermal conductance; contrarily, at higher temperatures, the double T-shaped quantum structure can reduce low-temperature thermal conductance. However, in the whole low-temperature region, the low-temperature thermal conductance can be enhanced by adding the narrowest width c in the scattering region. Moreover, it is found that both the transmission coefficient and thermal conductance can be adjusted by changing the structural parameters of the the scattering region.
Studies on electrical properties of graphene nanoribbons with pore defects
Authors: Wei Xiao-Lin  , Chen Yuan-Ping  , Wang Ru-Zhi  , Zhong Jian-Xin  ,   Laboratory for Quantum Engineering and Micro-Nano Energy Technology, Department of Physics, Xiangtan University, Xiangtan, Hunan 411105, China;,   Laboratory of Thin Film Materials, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
Published: December 2020

In practical applications of graphene-based electronic devices, they may have some pore defects under energetic particle bombardment, or chemical corrosion, which will inevitably affect their electrical properties. These problems have recently aroused great concern and interest. In this paper, we systematically study the influence of shape (tripartite, tetragonal and hexagonal) of hole defect on the electrical property of zigzag graphene nanoribbon (ZGNR). The results show that the influence of the shape of the pore defects on the conductance and current characteristics of ZGNRs is significant, whicl may result from electron scattering for the different shapes of the poredefect boundary. In addition, due to defects in suspension adsorbed hydrogen or nitrogen atoms, caused by defects of the pore shape changes, it also affects the electrical properties of ZGNRs. This study will supply valuable theoretical guidances for graphene-based electronic device failure analysis and the design of the graphene pore structure.
Effects of stress on the hysteresis loss and coercivity of ferromagnetic film
Authors: Guo Zi-Zheng  , Hu Xu-Bo  ,   Department of Applied Physics, College of Science, South China Agricultural University, Guangzhou 510642, China
Published: December 2020

The JA-SW hybrid model is extended in order to include the strain or stress anisotropy. With this improved model, a simulation is carried out to study the effects of stress on magnetic hysteresis loss and coercivity of ferromagnetic film. It is shown that the hysteresis loss and coercivity are related to the external field orientation, the stress intensity and the stress direction. Hysteresis loss, or the coercive force does not entirely monotonially increase with the change of stress intensity. For example, when the external field is parallel to the easy axis, a valley appears in the curve. In addition, stress will cause the peak offset of the coercivity curve as the orientation angle of the external field changes. Extensive comparisons of results with literature data are made and the differences between them are explained.
First principles study of structures, static polarizabilities and optical absorption spectra of Cun-1Au (n=2–10) clusters
Authors: Qian Shuai  , Guo Xin-Li  , Wang Jia-Jia  , Yu Xin-Quan  , Wu San-Xie  , Yu Jin  ,   School of Materials Science and Engineering, Southeast University, Nanjing 211189, China;,   Jiangsu Key Laboratory of Advanced Metallic Materials, Southeast University, Nanjing 211189, China;,   School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
Published: December 2020

The structures of Cun-1Au clusters are examined using the genetic algorithm, and the static polarizabilities and optical absorption spectra are investigated by first principles computations within the static and time-dependent versions of the density functional theory. The static polarizabilities decrease after being doped by one Au atom due to the strengthened screening effect of d electrons, which can also be weakened by three-dimensional structures. The optical spectra computed within the time-dependent density functional theory indicate that the screening effect also leads to the quenching of oscillator strengths. A deeper analysis of d-orbit indicates d-orbit is the main contributor in the optical excitation while its growing up is not directly influenced by the strengthened screening effect. The research on Cu6-nAun (n=0–6) clusters in a fixed size system verifies our arguments further. Our calculation results are in good agreement with the experimental data on the optical absorption spectra, which are closer to the experimental data than the earlier theoretical results.
Nanoring color filters based on Fabry-Pérot cavities
Authors: Lü Jiang-Tao  , Tao Wang  , Ma Zhen-He  , Si Guang-Yuan  ,   School of Control Engineering, Northeastern University at Qinhuandao, Qinhuangdao 066004, China
Published: December 2020

Coaxial nanoring structures have attracted extensive attention in recent years due to their peculiar optical properties. In this article, we investigate two different types of resonances in plasmonic Fabry-Pérot cavities, planar surface plasmon and propagating surface plasmon. Using nanoring arrays with the same periodicity and different gaps, we can tune propagating surface plasmons and finally filter individual colors out. With large periodicities, planar surface plasmon resonance can be fixed in the near infrared range to avoid any disturbance on propagating surface plasmon resonance which is located in visible frequencies. In this work, we filter a broadband white source into different colors by using nanoring arrays with a fixed periodicity of 1200 nm and varying gaps range from 10 nm to 180 nm (in steps of 10 nm). Compared with one-dimensional nanoslits or metal-insulator-metal (MIM) nanogratings, nanoring structures present polarization independence to the incident light, leading to more functional devices and broader applications (applicable to natural light, for instance). Finite-difference time-domain (FDTD) simulations accord well with measurements, which confirms our conclusions and supports our explanations.
High-quality Ge1-xSnx alloys grown on Ge(001) substrates by molecular beam epitaxy
Authors: Su Shao-Jian  , Zhang Dong-Liang  , Zhang Guang-Ze  , Xue Chun-Lai  , Cheng Bu-Wen  , Wang Qi-Ming  ,   College of Information Science and Engineering, Huaqiao University, Xiamen 361021, China;,   State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

As a new group-IV semiconductor alloy, Ge1-xSnx is a very promising material for applications in photonic and microelectronic devices. In this work, high-quality germanium-tin (Ge1-xSnx) alloys are grown on Ge(001) substrates by molecular beam epitaxy, with x=1.5%, 2.4%, 2.8%, 5.3%, and 14%. The Ge1-xSnx alloys are characterized by high resolution X-ray diffraction (HR-XRD), Rutherford backscattering spectra (RBS), and transmission electron micrograph (TEM). For the samples with Sn composition x 5.3%, the Ge1-xSnx alloys each exhibit a very high crystalline quality. The ratio of channel yield to random yield (min) in the RBS spectrum is only about 5%, and the full width at half maximum (FWHM) of the Ge1-xSnx peak in HR-XRD curve is 100''. For the sample with x=14%, the crystalline quality of the alloy is degraded and FWHM is 264.6''.
Spatiotemporal modulation induced coexistence of meandering spiral wave and travelling spiral wave
Authors: Qian Yu  ,   Nonlinear Research Institute, Baoji University of Arts and Sciences, Baoji 721000, China
Published: December 2020

Spiral dynamics induced by spatiotemporal modulation is investigated in the generic excitable Barkley model. The coexistence of meandering spiral wave and travelling spiral wave in the same medium is discovered under proper spatiotemporal modulation. The underlying mechanism behind this coexistence phenomenon is analyzed. And the two necessary conditions which are needed to observe the coexistence of meandering spiral wave and travelling spiral wave in the excitable Barkley model are discussed.
Wireless energy transfer system based on metglas/PFC magnetoelectric laminated composites
Authors: Yu Xin-Jie  , Wu Tian-Yi  , Li Zhen  ,   State Key Lab. of Power System, Dept. of Electrical Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

Wireless energy transfer has broad prospective applications. Current researches focus on electromagnetic induction and magnetic resonance. The former approach is sensitive to position and the latter has larger size, both of which affect the broad application of wireless energy transfer. Two layers of magnetostrictive effect materials and one layer of piezoelectric effect material are bound by epoxy resin, which generates magnetoelectric laminated composite. It is the first time that the output voltage, current and magnetoelectric factor have been deduced without DC magnetic bias. Three samples are implemented and the wireless energy transfer system based on them is developed. The tests on the samples verify the correctness of the theoretic analysis. Further experiments illustrate that there are double frequency characteristics for the magnetoelectric laminated composites; the resonant frequency is proportional to the reciprocal of the length of the composite; the open circuit voltage of the composite could reach 100 V (rms) under a magnetic field of 20 Oe; the maximum energy transferred is 520 mW, which is the highest record reported up to now, with the energy density 1.21W/cm3 and maximum transfer efficiency 35%; the rotation less than 30° has little effect on the output of the composites. Theoretical analyses and experimental results suggest that the magnetoelectric laminated composite based on Metglas/PFC is a very interesting approach to small volume and small power wireless energy transfer applications.
Study of the contact property between BZO and p-a-SiC in amorphous silicon solar cell
Authors: Wang Li  , Zhang Xiao-Dan  , Yang Xu  , Wei Chang-Chun  , Zhang De-Kun  , Wang Guang-Cai  , Sun Jan  , Zhao Ying  ,   Institute of Photo-Electronic Thin Film Devices and Technology of Nankai University, Tianjin 300071, China
Published: December 2020

Highly conductive p-type microcrystalline silicon thin layer is inserted between the front layer (ZnO:B) and the window layer(p-a-SiC) in a p-i-n amorphous silicon solar cell, and the inserted layer is found to be able to eliminate the non-ohmic contact, which is caused by the difference in the work function between the ZnO:B and p-a-SiC. The properties of the p-type microcrystalline silicon are studied by varying layer thickness, hydrogen dilution ratio and B2H6/SiH4 ratio. The optimized p-type microcrystalline silicon film can have a dark conductivity as large as 4.2 S/cm at a thickeness of 20 nm. The p-i-n type amorphous silicon solar cell with the p-type microcrystalline silicon is shown to have a good open circuit voltage and fill factor compared with without the p-type microcrystalline silicon layer.
A class of asymptotic solution of sea-air time delay oscillator for the El Niño-southern oscillation mechanism
Authors: Ouyang Cheng  , Lin Wan-Tao  , Cheng Rong-Jun  , Mo Jia-Qi  ,   Faculty of Science, Huzhou Teachers College, Huzhou 313000, China;,   State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;,   Ningbo Institute of Technology, Zhejiang University, Ningbo 315100, China;,   Department of Mathematics, Anhui Normal University, Wuhu 241003, China
Published: December 2020

A class of coupled system of the El Niño-southern oscillation mechanism is studied. Using the singular perturbation theory and method, the outer solution and the initial layer corrective term of the model are solved. And then, the asymptotic expansion of the solution for the problem is obtained and the asymptotic behavior of solution is considered.
Femtosecond laser fine machining of energetic materials
Authors: Wang Wen-Ting  , Hu Bing  , Wang Ming-Wei  ,   Institute of Modern Optics, Key Laboratory of Optic Information Science and Technology, Ministry of Education of China, Nankai University, Tianjin 300071, China
Published: December 2020

In this article, the characteristics of femtosecond laser pulses and the interaction mechanism between them and materials are described, and the characteristics and advantages of femtosecond laser micromachining of energetic materials are discussed. The technology and development of the femtosecond laser machining of energetic materials are reviewed. The experimental and theoretical research of femtosecond laser machining of energetic materials and the corresponding research scheme and key techniques for further development are discussed.
A space audio cummunication system based on X-ray
Authors: Deng Ning-Qin  , Zhao Bao-Sheng  , Sheng Li-Zhi  , Yan Qiu  , Yang Hao  , Liu Duo  ,   State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences,Xi’an 710119, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In this paper, an X-ray communication program, which consists of a sender of grid controlled X-ray source and a receiver of X-ray single-photon detector based on micro-channel plate, is presented. With the detailed information about the signal modulation transmitter, the micro-channel-based X-ray single-photon detector as well as the signal receiving demodulator, a space audio communication system based on X-ray is built. The communication rate of more than 20 kbit/s is realized. According to the preliminary test result analyses of the X-ray space audio communication system test, the X-ray emission success rate restricts the communication speed by the influence of different X-ray intensities, signal shaping time and threshold settings respectively. Therefore, a scheme for further increasing X-ray communication performance is suggested.
Reflection and transmission characteristics of electromagnetic waves by the uniaxially anisotropic chiral slab
Authors: Dong Jian-Feng  , Li Jie  ,   Institute of Optical Fiber Communication and Network Technology, Ningbo University, Ningbo 315211, China
Published: December 2020

The reflection and transmission characteristics of electromagnetic waves by the uniaxially anisotropic chiral slab with the optical axis parallel to the interface are investigated. Formulas of the reflection and transmission coefficients (power) are derived. The curves of powers of the reflected and transmitted electromagnetic waves are presented for four cases of dielectric constants according to their signs. The effects of chirality parameter on the reflection and transmission are discussed. Especially, the dependences of pseudo-Brewster angles on the chirality parameter are plotted.
Design of incident angle-independent color filter based on subwavelength two-dimensional gratings
Authors: Hong Liang  , Yang Chen-Ying  , Shen Wei-Dong  , Ye Hui  , Zhang Yue-Guang  , Liu Xu  ,   Department of Optical Engineering, Zhejiang University, State Key Laboratory of Modern Optical Instrumentation, Hangzhou 310027, China
Published: December 2020

A novel design of reflective color filters based on a two-dimensional subwavelength grating structure is proposed, which exhibits an incident angle independent property with unpolarized incident light in the visible range. By using rigorous coupled-wave analysis method, the effects of the grating period, the groove depth and the size of the structure on the reflectance spectrum are investigated in detail. The structural parameters of the gratings are optimized, and a color filter with high angular tolerance is achieved. Simulation result shows that the maximal reflectance is 56% at 424 nm with a bandwidth of 45 nm, and that the grating can almost keep its reflectance, bandwidth and the peak position at the incident angle up to about 60° under unpolarized incident light. The peak position of the color filter can be tuned from 400 nm to 520 nm by changing structural parameters of the gratings, and keep its incident angle-independent property.
Multi-level authentication based on two-beam interference
Authors: He Wen-Qi  , Peng Xiang  , Meng Xiang-Feng  , Liu Xiao-Li  ,   College of Optoelectronics Engineering, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University, Shenzhen 518060, China;,   Department of Optics, School of Information Science and Engineering and Shandong Provincial Key Laboratory of Laser Technology and Application, Shandong University, Jinan 250100, China
Published: December 2020

A method of multi-level authentication based on two-beam interference is proposed. By verifying the "password" and "phase key" of one user simultaneously, the system can thus achieve the two-factor authentication on the user's identity. This scheme can not only check the legality of one user, but also verify his identity level as an authorized user and then grant the user the corresponding permissions to access the system resources. While operating the authentication process, which largely depends on an optical setup based on interference, a "phase key" and a password-controlled "phase lock" are firstly loaded on two spatial light modulators (SLMs), separately. Then two coherent beams are respectively, modulated by the two SLMs and then interfere with each other, leading to an interference pattern in the output plane. It is recorded and transmitted to the computer to finish the last step of the authentication process: comparing the interference pattern with the standard verification images in the database of the system to verify whether it is an authorized user. When it turns to the system designing process for a user, which involves an iterative algorithm to acquire an estimated solution of an inverse problem, we need to determine the "phase key" according to a modified phase retrieval iterative algorithm under the condition of an arbitrarily given "phase lock" and a previously determined identity level (corresponding to a certain standard verification image). The theoretical analysis and simulation experiments both validate the feasibility and effectiveness of the proposed scheme.
Generation of continuous-variable entanglement in a two-mode four-level single-atom driven by microwave
Authors: Song Ming-Yu  , Wu Yao-De  ,   College of Physical Science and Technology, Yangtze University, Jingzhou, 430023, China
Published: December 2020

In this paper, we discuss the generation and evolution of continuous-variable entanglement in a two-mode single-atom laser, where the atomic coherence is induced by two classical microwave fields, which drive the corresponding fine atomic transitions. The results show that the intensity of the microwave field can influence effectively the entanglement properties of the cavity field. In addition, our numerical results also show that the intensity and the period of entanglement between the two cavity modes as well as the total mean photon number of the cavity field can be increased synchronously by adjusting the corresponding frequency detuning.
Generation of ultra-wideband signals by directly current-modulating distributed feedback laser diode subjected to optical feedback
Authors: Liu Ming  , Zhang Ming-Jiang  , Wang An-Bang  , Wang Long-Sheng  , Ji Yong-Ning  , Ma Zhe  ,   Key Laboratory of Advanced Transducers and Intelligent Control System, Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China;,   Institute of Optoelectronic Engineering, Taiyuan University of Technology, Taiyuan 030024, China;,   The State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China
Published: December 2020

The chaotic ultra-wideband (UWB) pulse signals are generated by directly modulating semiconductor laser subjected to optical feedback. We simulate that the -10 dB bandwidth and the central frequency of the RF spectrum of the chaotic UWB signals are influenced by the bias current and feedback strength. The research results demonstrate that the -10 dB bandwidth of the RF spectrum of the UWB signals increases with the increases of the bias current of the semiconductor laser and the feedback, the central frequency also increases with the increases of the bias current and the feedback. In our experiments, chaotic UWB signals with steerable and flatted power spectrum are generated by directly modulating DFB-LD subjected to optical feedback. The power spectrum of UWB signals is fully compliant with the FCC indoor mask, while a large fractional bandwidth of 133% and a central frequency of 6.6 GHz are achieved. The central frequency and -10 dB bandwidth of the chaotic UWB signals are on a large scale tunable by adjusting the bias current and feedback power. In addition, the chaotic UWB signals transmit through a 34.08 km single mode fiber and the power spectrum does not have any discrete spectrum line.
Experimental research of high performance fiber and fiber laser at 1018 nm
Authors: Wang Yi-Bo  , Chen Gui  , Xie Lu  , Jiang Zuo-Wen  , Li Jin-Yan  ,   College of Optoelectronic Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China;,   Wuhan National Laboratory for Optoeletronics, Wuhan 430074, China
Published: December 2020

The effects of codopants and the deposition parameters such as gas flowrate and pressure in tube during the fabrication of fiber performs are studied. It is found that the fluorescence spectrum of Yb3+ can shift when codoping other elements, according to which, a double cladding Yb3+-doped fiber that is beneficial for 1018 nm laser is fabricated for the first time. When the fiber length is 7 m, an output of 22.8 W at 1018 nm is obtained. The optical-optical conversion efficiency is approximately 70%, and there are neither spontaneous radiation nor saturation.