bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of light spot intensity and coverage to a triple-junction solar cell under non-uniform illumination
Authors: Liang Qi-Bing  , Shu Bi-Fen  , Sun Li-Juan  , Zhang Qi-Zi  , Chen Ming-Biao  ,   Institute for Solar Energy System, School of Engineering, Sun Yet-Sen University, Guangzhou 510006, China
Published: December 2020

The cells in high concentrated photovoltaic module are usually high efficiency triple-junction solar cells. Due to the non-ideal concentrators, the light intensity distribution on a solar cell is highly non-uniform, so the appropriate increase of the ratio between light spot size and cell area is a method to reduce the influence of non-uniform illumination on the electrical performance of the solar cell. The circuit network model is used to calculate the influences of light spot intensity distribution and size on a triple-junction solar cell. The light spot intensities and sizes, the cell efficiencies, and the temperature distributions of the cell under four design schemes (uniform illumination, non-uniform illumination, maximum cell efficiency, and maximum module efficiency) are compared. The results show that the cell efficiency in the maximum module efficiency design is not the maximum cell efficiency under the standard testing condition. The design to make the cell achieve the maximum efficiency obtains the minimum module efficiency. The design to achieve maximum module efficiency has a smaller size of concentrator, so the cost of the module goes up. The design to achieve the maximum cell efficiency has a bigger size of concentrator and a lowest cell temperature, so the cost of the module will reduce and the reliability will improve. Above all, the requirement of electricity quantity should be fully considered in the module design, in which an appropriate geometric concentration ratio and light spot coverage to solar cells should be chosen.
Measurement of device-independent quantum key distribution for the rotation invariant photonic state
Authors: Dong Chen  , Zhao Shang-Hong  , Dong Yi  , Zhao Wei-Hu  , Zhao Jing  ,   school of Information and Navigation, Air Force Engineering University, Xi'an 710077, China;,   Department of information security, Xi'an Communication College, Xi'an 710006, China
Published: December 2020

The original measurement of device-independent(MDI)quantum key distribution(QKD) is reviewed, and a modified protocol using rotation-invariant photonic state is proposed. Initial encoding and final decoding of information in our MDI-QKD implementation protocol can be conveniently performed in the polarization space, while the transmission is done in the rotation-invariant hybrid space. Our analysis indicates that both the secure key rate and transmission distance can be improved by our modified protocol owing to its lower error rate. Furthermore, our hybrid polarization-OAM qubits approach only needs to insert four q-plates in a practical experiment, and our simulation results show that the modified protocol is practical.
Boundary effects of Bose-Einstein condensation in a three-dimensional harmonic trap
Authors: Yuan Du-Qi  ,   Department of Physics and Information Technology, Baoji University of Science and Arts, Baoji 721016, China
Published: December 2020

By defining the characteristic length, the boundary effects of Bose-Einstein condensation in a three-dimensional harmonic trap are investigated using the Euler-MacLaurin formula. Results show that the condensed fraction of particles reduces due to the finite-size effects and the effects of finite particle number; the corrections of the condensation fraction and the condensation temperature have, respectively, a maximum value due to the boundary effect, hence it is very effective to optimize the parameters of the harmonic traps for improving the condensation fraction and the condensation temperature. In the jump of heat capacity exist the boundary effects and the effects of finite particle number, and the jump of heat capacity has a minimum because the parameters of harmonic traps are selected to be reasonable. The equation of state is derived for a finite ideal Bose gas system in a three-dimensional harmonic trap; the anisotropy (or isotropy) of the pressure is determined by the anisotropy (or isotropy) of the frequency of the harmonic potential.
The Langevin dynamics approach to generate solid interaction system
Authors: Deng Qi-Min  , Zou Ya-Zhong  , Bao Jing-Dong  ,   Department of Physics, Beijing Normal University, Beijing 100875, China
Published: December 2020

We have studied two probability potentials of a collinear oscillator atom chain and developed a Langevin dynamics approach for calculation. In the case of the harmonic chains, results of the Monte Carlo simulations are compared with the analytical solutions to verify the validity of this approach. In the case of 4-times coupled oscillator chains, the results of numerical simulations are used to the calculation of Hamiltonian. Then the system's energy distribution and the Maxwell-Boltzmann distribution are compared, and found to be in agreement with each other.
Collimating emission from photonic crystals based on the quasi-zero-effective-index
Authors: Zhao Hao  , Shen Yi-Feng  , Zhang Zhong-Jie  ,   Department of Physics, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

Transmission of light waves at the frequency near the edge of the band gap in two-dimensional square lattice photonic crystals is studied by using the plane wave expansion method (PWM) and finite difference in time domain (FDTD) method. It is found that, directional emission from two-dimensional photonic crystals can be realized if the effective refractive index is nearly zero. Moreover, the direction of the emitting beam is independent of the orientation of the crystal lattice, but dependent on the direction of the crystal surface. This is quite different from the self-collimation phenomenon in photonic crystals.
The pre-treatment of copper for graphene synthesis
Authors: Wang Lang  , Feng Wei  , Yang Lian-Qiao  , Zhang Jian-Hua  ,   Key Laboratory of Advanced Display and System Applications (Shanghai University), Ministry of Education, Shanghai 200072, China;,   School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China
Published: December 2020

Graphene synthesis by chemical-vapor-deposition (CVD) has attracted great interest. As the substrates for graphene growth, copper has become a common choice because its capacity could produce high-quality and uniform monolayer graphene. Morphology and surface conditions of the copper foil have great influence on the quality of the graphene grown on it. Here we report a rapid and effective copper pre-treatment method to improve the quality of graphene. After a pre-etching in 1 mol/L Fe(NO3)3 aqueous solutions for 90 s, the quality of the copper foil surface has been improved. Compared with the HCl treatment and electro-chemical polishing, Fe(NO3)3 pre-etching can generate a better result and has been verified to have general applicability for different types of copper foils.
Electroluminescent energy transfer of hybrid quantum dotsdevice
Authors: He Yue-Di  , Xu Zheng  , Zhao Su-Ling  , Liu Zhi-Min  , Gao Song  , Xu Xu-Rong  ,   Institute of Optoelectronics Technology, Beijing Jiaotong University, Key Laboratory of Luminescence and Optical Information (Beijing Jiaotong University), Ministry of Education, Beijing 100044, China
Published: December 2020

The hybrid quantum dot (QD) electroluminescent devices are fabricated by mixing every two kinds of QDs in the red, green, blue three types of QDs in a ratio 1:1, which are based on the structure of ITO/PEDOT:PSS/QDs/Al. In the systematical investigation of the electroluminescent spectrum, when the voltage increases, we find that the luminance intensity of the controlling devices continues to grow, while the hybrid QD devices first increase then decrease, showing that there is an energy transfer in the hybrid QD devices. And we also obtain the relationships among the energy transfer efficiency, the critical energy transfer distance, the donor-acceptor distance, and the electric field.
Theoretical calculation of electron transport properties of the Au-Si60-Au molecular junctions
Authors: Liu Fu-Ti  , Cheng Yan  , Chen Xiang-Rong  , Cheng Xiao-Hong  , Zeng Zhi-Qiang  ,   College of Physics and Electronic Engineering, Yibin university, Yibin 644007, China;,   College of Physical Science and Technology, Sichuan University, Chengdu 610064, China;,   Computational Physics Key Laboratory of Sichuan Province of Yibin university, Yibin 644007, China
Published: December 2020

The ground structure of Si60 clusters, which was obtained by optimization when using the density functional theory method, is a fullerene structure with C1 point group, a diameter 1.131 nm, the average bond length 0.239 nm, and the difference between the energies of the lowest unoccupied molecular orbital and the highest occupied molecular orbital is 0.72 eV. A Si60 cluster with optimized structure is sandwiched between two semi-infinite Au(100)-44 electrodes, and the Au-Si60-Au molecular junctions is constructed, whose electron transport properties is investigated with a combination of density functional theory and non-equilibrium Green's function method. When the distance between the two electrodes is 1.74 nm, the equilibrium conductance of the junctions is 1.93 G0 (G0=2e2/h). In the range of voltage from -2.02.0 V, we have calculated the current and conductance under different voltages, and find that the Ⅰ-Ⅴ curve of the junctions show linear characteristics. We also analyze the properties of transport from transmission and frontier molecular orbitals, and discuss the relationship of transfer charge with conductance.
Error analysis and reconstruction for diffractive optic imaging spectrometer using the multiple iterations
Authors: Li Na  , Jia Di  , Zhao Hui-Jie  , Su Yun  , Li Tuo-Tuo  ,   School of Instrumentation Science and Opto-electronics Engineering, Beihang University, Beijing 100191, China;,   Beijing Institute Of Space Mechanics & Electricity, Beijing 100094, China
Published: December 2020

Diffraction imaging spectrometer cannot acquire imaging spectral data without calculation and inversion. In this paper, the imaging process of the diffraction imaging spectrometer and the principle of the data error from both space and spectra are analyzed. To solve the problems of low definition of the reconstruction and the ringing in it occurring under the condition that the point spread function (PSF) is larger, a new algorithm is proposed based on improved inverse Wiener filtering. The improved method regards the reconstruction result of Wiener filtering as a new fuzzy image, and recalculates the PSF of the new fuzzy image based on the analysis of the diffraction characteristics and error. Inverse iterative Wiener filtering is used to improve the definition of the reconstruction, and then the noise needs to be removed according to the distribution of the spatial and spectral features. Simulated diffraction imaging spectral data are used to verify the correctness of the algorithm proposed in this paper. A reconstruction without ringing can be obtained when the standard deviation of PSF is 2.5, and both of the definition and detail ability are higher than those of the traditional reconstruction. The reconstruction using the improved algorithm proposed in this paper can satisfy the applications of the diffraction imaging spectral data.
Research on electrostatic discharge characteristics of tunnel field effect transistors
Authors: Wang Yuan  , Zhang Li-Zhong  , Cao Jian  , Lu Guang-Yi  , Jia Song  , Zhang Xing  ,   Institute of Microelectronics, Peking University, Beijing 100871, China;,   Innovation Center for MicroNanoelectronics and Integrated System, Beijing 100871, China
Published: December 2020

Power consumption has been the major bottleneck in the development of integrated circuits with reduced critical dimensions and improved integrated level. Tunnel field effect transistor (TFET) has been investigated as one of the promising replacements for traditional metal oxide semiconductor field effect transistor (MOSFET), owing to the introduction of band to band tunneling (BTBT) mechanism based on which a smaller subthreshold slope is achieved. However, a thinner oxide layer and a shorter channel length in TFET may induce localization of high current density, high electrical field distribution, and generation of heat, which abate the probability to survive electrostatic discharge (ESD). Besides, the novel BTBT operating principles also present a challenge to TFET ESD protection design. In this paper transmission line pulse test method is adopted to analyze the working principle of conventional TFET at onset, holding, discharge, and second breakdown during an ESD event. Based on these a new TFET ESD device protection design is proposed and characterized with a deeply doped n+ pocket near the source region beneath the gate, which can make effective adjustments of contact potential barrier, reduce tunneling junction width, thus better ESD design windows are obtained.
A new method for calculating vorticity and Divergence using global wind field
Authors: Guan Ji-Ping  , Huang Si-Xun  , Zhang Li-Feng  ,   College of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China
Published: December 2020

Vorticity and divergence can be calculated using wind field in numerical forecast. The issue involves the problem of calculating differentiation using observation data, and it is ill-posed in mathematics. In a limited domain, the one-dimensional numerical differentiation can be used to calculate vorticity and divergence, but the method requires that the data along the boundary be accurate. This paper suggests a new method of calculating vorticity and divergence using the periodical function's one-dimensional numerical differentiation algorithm, and comparison is made with usually used difference method. The stream function and velocity potential are calculated using vorticity and divergence, and the initial wind field is reconstructed using the stream function and velocity potential. Results show that the algorithm proposed in this paper is stable, feasible, and its accuracy is superior to the difference method. It provides a new idea that the method mag be used in global meteorology data diagnosis analysis and forecast.
Numerical investigation on the interaction between multi-Compacton of K(m,n,p) equation
Authors: Wang Guang-Hui  , Wang Lin-Xue  , Wang Deng-Shan  , Liu Cong-Bo  , Shi Yu-Ren  ,   College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China;,   School of Applied Science, Beijing Information Science and Technology University, Beijing 100192, China
Published: December 2020

We numerically investigate the interaction between multi-compactons of the K(m,n,p) equation by a finite difference scheme that is of the second-order accuracy and absolutely stable in linearization sense. By adding an artificial dissipation term, it works well for preventing the break-up phenomena of the numerical solutions. Firstly, we simulate the long-time evolution behaviors of the single-compacton to verify the validity of the numerical method. It is shown that the numerical method is effective for solving this problem. Secondly, we study the nonlinear interaction between two-compacton and three-compacton by this numerical method. The numerical results indicate that the wave-frame and wave-velocity after collision are nearly the same as before collision. However, compacton-anticompacton pair induced behind the wave arises with small amplitudes.
Stability of information spreading over social network
Authors: Wang Chao  , Liu Cheng-Yuan  , Hu Yuan-Ping  , Liu Zhi-Hong  , Ma Jian-Feng  ,   School of Computer Science and technology, Xidian University, Xi'an 710071, China;,   Shaanxi Key Laboratory of Network and System Security, Xidian University, Xi'an 710071, China
Published: December 2020

Social networks have been developed into one of the most important media for information propagation, and it is necessary to disclose how the information disseminates over social networks. In this paper, we explore the spreading mechanism including information stifling and forgetting, establish a spreading model, and elaborate the spreading rules. According to the spreading model, we build the mean field equation, calculate the two equilibriums and the basic reproduction number R0, and prove theoretically the asymptotical stability of the equilibriums. We analyze the effects of stifling mechanism and forgetting mechanism on the information spreading process, and validate the results of theoretical analysis by numerical simulations.
Highly accurate computation of finite-time Lyapunov exponent
Authors: Cao Xiao-Qun  , Song Jun-Qiang  , Ren Kai-Jun  , Leng Hong-Ze  , Yin Fu-Kang  ,   School of Computer Science, National University of Defense Technology, Changsha 410073, China;,   Science and Technology on Parallel and distributed Processing Laboratory, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Aiming at the shortcomings of current method of calculating finite-time Lyapunov exponent (FTLE), such as low accuracy, inability to obtain boundary values, etc., a method of highly accurately computing FTLE is proposed based on dual number theory. Firstly, the weakness and disadvantages of the finite difference method used widely for computing FTLE are described. Secondly, the dual number theory is introduced to evaluate the derivatives accurately and efficiently, and its distinct virtues are also presented. The computation of Cauchy-Green deformation tensors for a dynamical system is transformed into a numerical integration problem of solving the nonlinear ordinary differential equation in dual number space by the new method. Finally, the proposed method is applied to typical pendulum system and nonlinear Duffing oscillator separately. The results of simulation experiments indicate that the new method is effective, convenient and accurate for computing the field of FTLE, from which Lagrangian coherent structures can be identified successfully.
Effects of arrangement of heterogeneous neurons on frequency synchronization of a ring-coupled neuronal network
Authors: Sun Xiao-Juan  , Yang Bai-Hua  , Wu Ye  , Xiao Jing-Hua  ,   School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, China
Published: December 2020

In this paper, we discuss the effects of heterogeneous neuron arrangement on the frequency synchronization of a ring-coupled FitzHugh-Nagumo neuronal network. The obtained numerical results reveal that the threshold of coupling strength for frequency synchronization may be different for different arrangements of the heterogeneous neurons on a ring. On average, the closer to each other the neurons which are less heterogeneous on a ring, the larger the critical coupling strength needed for neuronal network to achieve frequency synchronization is; the closer to each other the neurons which are more heterogeneous, the smaller the critical coupling strength needed for neuronal network to achieve frequency synchronization is. Furthermore, we give the underlined mechanism for this phenomenon by analyzing the process of frequency synchronization.
Phase field crystal study on asymmetrical tilt subgrain boundaries
Authors: Lu Na  , Wang Yong-Xin  , Chen Zheng  ,   State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

With the phase field crystal approach, the structure of asymmetrical tilt subgrain boundaries and their motion micmechanism under stress are studied. The effects of temperature, inclination angle and stress direction on structure and migration process are also analyzed and discussed. Simulated results show that the subgrain boundary is composed of a row of edge dislcations with the same bugers vectors and the double-array dislocations with a vertical distribution. The motion process of asymmetrical tilt subgrain boundaries contains dislocation glide and climb, dislocation separation, dislocation reaction, individual dislocation decomposition and dislocation annihilation. The decrease of temperature and the increase of inclination angle hinder the subgrain boundary migration process. The change of stress direction causes the variation of dislocation motion and thus lead to the change in migration manner of subgrain boundary.
Accurate measurement of templates and imprinted grating structures using Mueller matrix ellipsometry
Authors: Chen Xiu-Guo  , Liu Shi-Yuan  , Zhang Chuan-Wei  , Wu Yi-Ping  , Ma Zhi-Chao  , Sun Tang-You  , Xu Zhi-Mou  ,   State Key Laboratory for Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China;,   College of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China;,   School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

In order to control nanoimprint lithography (NIL) processes for achieving good fidelity, the fast, low-cost, non-destructive and accurate measurement of geometric parameters of templates and imprinted grating structures is of great importance. Compared with conventional ellipsometric scatterometry, which only obtains two ellipsometric angles and has 2 changeable measurement conditions, i.e., the wavelength and the incidence angle, Mueller matrix ellipsometry (MME) can provide up to 16 quantities of a 4×4 Mueller matrix in each measurement with 3 changeable measurement conditions, i.e., the wavelength, the incidence angle and the azimuthal angle. Therefore, MME can acquire much more useful information about the sample. It is expected that much more accurate measurements of nanostructures can be achieved by choosing proper measurement configurations and completely using the rich information hidden in the measured Mueller matrices. Accordingly, the templates and imprinted grating structures in NIL processes are measured using an in-house developed Mueller matrix ellipsometer. We experimentally demonstrate that more accurate quantification of geometric parameters, such as line width, line height, sidewall angle and residual layer thickness, can be achieved by performing MME measurements in the optimal configuration and meanwhile by incorporating depolarization effects into the optical model. Moreover, as for the imprinted grating structures, the residual layer thickness variation over the illumination spot can also be directly determined by MME. The comparison between MME-extracted template and imprinted resist profiles also indicates an excellent fidelity of the nanoimprint pattern transfer process.
Femtosecond pulse shaping technology and its applications
Authors: Yao Yun-Hua  , Lu Chen-Hui  , Xu Shu-Wu  , Ding Jing-Xin  , Jia Tian-Qing  , Zhang Shi-An  , Sun Zhen-Rong  ,   State Key Laboratory of Precision Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062, China;,   School of Sciences, Nantong University, Nantong 226007, China
Published: December 2020

By controlling the spectral amplitude, phase and polarization of the femtosecond laser pulse in the frequency domain, a shaped femtosecond laser pulse with almost arbitrary pulse shape in time domain can be obtained, and this femtosecond laser pulse shaping technique provides a new experimental tool to study the nonlinear interaction between light and atoms or molecules. In this paper, we introduce the development history, technical method, control technique and relevant applications of the femtosecond laser pulse shaping technique, and also carry out a prospect on the research trends of this technique.
Efficient generation of third harmonic radiation of air filament induced by plasma grating
Authors: Liu Zuo-Ye  , Shi Yan-Chao  , Hu Bi-Tao  ,   School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China
Published: December 2020

In this paper, the dependences of the third harmonic generation (THG) of a probe filament on the relative position of the probe filament interacting with the plasma grating and the position of the plasma grating interacting with the probe filament are investigated. The phase matching between the third harmonic of the probe filament and the fundamental wave of the plasma grating is earlier to achieve when the head of the probe filament interacts with the plasma grating, inducing the enhancement of the third harmonic generation, while the phase mismatching happens when the trail of the probe filament interacts with the plasma grating. The distribution of the clamping laser intensity inside the plasma grating results in the dependence of the THG on the positions of the plasma grating interacting with the probe filaments. It is an effective method of promoting the THG by setting the crossing angle between the probe filament and the plasma grating to be very small.
Simulations of electrical asymmetry effect on N2-H2 capacitively coupled plasma by particle-in-cell/Monte Carlo model
Authors: Hao Ying-Ying  , Meng Xiu-Lan  , Yao Fu-Bao  , Zhao Guo-Ming  , Wang Jing  , Zhang Lian-Zhu  ,   College of Physics Science and Information Engineering, Hebei Normal University, Shijiazhuang 050024, China
Published: December 2020

A N2-H2 capacitively coupled rf discharge has potential applications in etching of organic low dielectric constant (low-k) material for microelectronics technology. In this paper, we investigate the characteristic and electrical asymmetry effect (EAE) on the N2-H2 capacitively coupled plasma used for low-k material etching by particle-in-cell/Monte Carlo (PIC/MC) model, in which the two frequency sources of 13.56 MHz and 27.12 MHz are applied separately to the two electrodes in geometrically in symmetry. It is found that the plasma density profiles, the ion flux density profiles and the energy distribution of ion bombarding electrodes can be changed by adjusting the phase angle θ between the two harmonics. When the phase angle θ is 0°, the density of primary ion (H3+) near low frequencie electrode (LFE) (wafer) is smallest, whereas flux and average energy of ion (H+, H3+, H2+) bombarding LFE are biggest; if the phase angle θ is tuned from 0° to 90°, the dc self-bias increases almost linearly from -103 V to 106 V, ion flux bombarding the LFE decreases by ±18%, the maximum of the ion bombarding energy at the LFE decreases by a factor of 2.5. For the N2-H2 capacitively coupled rf discharge, for the case of two frequencies (13.56 MHz/27.12 MHz) applied separately to the two electrodes, can realize separate control of ion energy and flux via the EAE, and is generally in qualitative agreement with experimental and modeling investigation on the Ar and O2 plasma for a dual-frequency voltage source of 13.56 MHz and 27.12 MHz is applied to the powered electrode. This work supplies a references basis for experimental research and technology that the EAE on the H2-N2 plasmas is used for organic low-k material etching process.
Electronic and magnetic properties of fluorinated graphene sheets with divacancy substitutional doping
Authors: Xu Lei  , Dai Zhen-Hong  , Sui Peng-Fei  , Wang Wei-Tian  , Sun Yu-Ming  ,   Institute of Opto-electronic Information Science and Technology, Yantai University, Yantai 264005, China
Published: December 2020

According to the first principles, we investigate the structure, electronic, and magnetic properties of fluorinated graphene doped with external X (Al, P, Ga, As, Si) atoms at double vacancies, and find that like double vacancy doping of graphene, this kind of the fluorinated graphene divacancy substitution is also an ideal choice for substitutional doping. The results show that the electronic property and magnetic property of the fluorinated graphene both have large changes: the fluorinated graphene doped with Al (Ga) atoms can cause the semiconductor-to-metal transitions and induce magnetic moments. The fluorinated graphene doped with P (As) atoms becomes spin-polarized semiconductor. The Si doped fluorinated graphene keeps the semiconductor properties unchanged and has no magnetic moments. Through the further discussion about the mechanism of magnetism the relation between the doping concentration and magnetic property is obtained, and the magnetic properties in different doping situations are found to be caused by the different orbital electrons of different atoms. The divacancy substitutional doping behaviors enrich not only the doping ways of fluorinated graphene materials, but also its distinctive electronic and magnetic characteristics, which make this doping structure have potential applications in future electronic devices.
Optical properties of Ti/TiO2 caped Tb3+-doped ZnO nanofibers
Authors: Mao Yan-Zhe  , Liu Yan-Xia  , Li Jian  , Li Hui  , Pan Xiao-Jun  , Xie Er-Qing  ,   School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China;,   Jiuquan Satellite Launch Center, Jiuquan 732750, China
Published: December 2020

ZnO:Tb nanofibers are fabricated by electrospinning method. X-ray diffraction and Raman results show that the sample is of hexagonal phase. The positions of doped diffraction peaks shift toward the small angle and the shift does not change with Tb content. Photoluminescence (PL) spectra of Tb-doped ZnO nanofibers show a strong defect-related emission and indicate that the doping affects the crystallinity of ZnO. It is found that Ti-capped can enhance the ultraviolet emission of ZnO nanofiber, while the defect-related emission is depressed. The enhancement in ultraviolet emission is mostly attributed to the surface plasmon coupling effect at the interface. The PL results indicate that the ZnO is not a proper matrix for Tb3+ ion.
Research progress of memristors and memristive mechanism
Authors: Liu Dong-Qing  , Cheng Hai-Feng  , Zhu Xuan  , Wang Nan-Nan  , Zhang Chao-Yang  ,   Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, National University of Defense Technology, Changsha 410073, China;,   State Key Laboratory of High Performance Computing, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Memristors are the fourth basic circuit element in addition to the three classical elements: resistor, capacitor, and inductor, which have great application prospects in the fields of information storage, logic operations and neuromorphic networks. The recent development of memristors and memristive mechanism is reviewed, including connotations and characteristics of memristors, memristive mechanism, types of memristive mateirals, and application prospects of memristors. Finally, the key problems and development proposals are presented and a prospect on the development trend is also given.
Optimizations for robust low sidelobe beamforming of bistatic multiple-input multiple-output virtual array
Authors: Huang Cong  , Sun Da-Jun  , Zhang Dian-Lun  , Teng Ting-Ting  ,   Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China;,   College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Two-dimensional estimation for direction of arrival and direction of departure is required in the target location of bistatic multiple-input multiple-output (MIMO) system. In view of the huge calculation of array covariance matrix processing and the sensitivity to the array manifold mismatch, a beam optimization algorithm which can resist array manifold mismatch is proposed based on the virtual array of bistatic MIMO. Optimization for beam pattern through the second-order cone programming is used in the algorithm. The waveform diversity technology and location of bistatic system are combined. The relationship between direction of arrival at and direction of departure from the ellipse locating line is used to convert the two-dimensional synthesis direction vector into one-dimensional virtual array manifold. It is proved that the beam pattern of virtual array manifold transformed in bistatic MIMO can be equivalent to the combination of the beam pattern of transmitting array mapping on the receiving array angle domain and the beam pattern of receiving array. The algorithm can not only control the side lobe and null the beam pattern but also improve the ability to resist array manifold mismatch. The validity of the method is verified by the computer simulation of the optimized beam pattern and spectrum.
Recognition of hail and rainstorm based on the radar reflectivity image features
Authors: Lu Zhi-Ying  , Liu Hai  , Jia Hui-Zhen  , Yin Jing  ,   Department of Electrical Engineering and Automation, Tianjin University, Tianjin Key Laboratory of Process Measurement and Control, Tianjin 300072, China;,   Tianjin Meteorological Bureau, Tianjin 300074, China
Published: December 2020

Based on radar reflectivity image features, an automatic recognition method is proposed to identify the hail and rainstorm. We extract the image features of hail echo areas and rainstorm echo areas from radar reflectivity images. By analyzing both the differences in single feature between hail and rainstorm and the classified complementarity among different features, we determine the effective image features, including the intensity and texture features, to identify the hail and rainstorm. The hail and rainstorm objective recognition model can be established through the data mining of the extracted sample features and sounding data by using the Rough Set Theory. Through the test and identification of the 362 test samples, the hit ratio of hail reaches 93.29% and the hit ratio of rainstorm reaches 89.07%. The false alarm ratios of hail and rainstorms can be also at a low level. Compared with those from the PUP system, the experimental results from the present system show that it has a good effect to identify and classify hail and rainstorm by using the radar reflectivity image features.
Oscillation and fission behavior of bright-bright solitons in two-species Bose-Einstein condensates trapped in an optical potential
Authors: He Zhang-Ming  , Zhang Zhi-Qiang  , Zhu Shan-Hua  , Liu Wen-Juan  ,   College of Science, Hunan University of Technology, Zhuzhou 412007, China;,   Department of Basic Course, Zhengzhou College of Science & Technology, Zhengzhou 450064, China
Published: December 2020

We have studied the dynamic behavior of bright-bright solitons in two-species Bose-Einstein condensates trapped in an optical lattice. It is shown that the directions of motion and oscillations of the bright-bright solitons can be effectively controlled by adjusting the lattice spacing and height, respectively. Especially, two separated solitons can be localized in the optical lattice, and the fission of each localized soliton is newly observed due to the increase of the lattice height.
The temperature measurement for the ultracold Cs2 molecules formed by photoassociation
Authors: Zhao Yan-Ting  , Yuan Jin-Peng  , Ji Zhong-Hua  , Li Zhong-Hao  , Meng Teng-Fei  , Liu Tao  , Xiao Lian-Tuan  , Jia Suo-Tang  ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China;,   Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Science, Xi'an 710600, China
Published: December 2020

Ultracold Cs2 molecules have been formed by photoassociation. Using the multiphoton ionization technique, we measure the time-evolution of expanding process in ultracold Cs2 molecule system and obtain the decay curve of photoionization signals. Based on a simple case, where the initial distribution of atomic or molecular sample is a Gaussian function of position and of velocity, we get the sample's temperature by theoretical simulation. The result shows a reasonable agreement with the result of release-recapture method in cold atom sample. This method avoids the disadvantage of detecting the weakly fluorescence and can be widely used for measuring the temperature in cold atom or cold molecule system.
Low threshold distributed feedback laser based on scaffolding morphologic and holographic polymer dispersed liquid crystal gratings
Authors: Liu Li-Juan  , Huang Wen-Bin  , Diao Zhi-Hui  , Zhang Gui-Yang  , Peng Zeng-Hui  , Liu Yong-Gang  , Xuan Li  ,   State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

We have made a low scattering holographic polymer dispersed liquid crystal (HPDLC) transmission grating with polymer scaffolding morphology, which was fabricated under the condition of low curing intensity and no liquid crystal droplet. We studied the amplified spontaneous emission (ASE) thresholds and relative intensities of PM567(4, 4-difluoro-1, 3, 5, 7, 8-pentamethyl-2, 6-diethyl-4-bora-3a, 4a-diaza-s-indacene), DCM (4-Dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran), and DCJTI(4-dicyanomethylene)-2-isopropyl-6-(1, 1, 7, 7-tetramethylzulolidyl-9-enyl)-4H-pyran). It is shown that the dye DCJTI has the best properties of ASE, the lowest threshold and the highest relative intensity among the three dyes. Results suggest that DCJIT is a promising material for low threshold, high slope efficiency lasers. Each dye was doped in HPDLC grating with polymer scaffolding morphology individually, and lasers with different wavelengths can be obtained by changing the period of the gratings. The excellent laser property is obtained from the DCJIT-doped laser. A spectral linewidth of 0.3 nm is observed at pump energy threshold 0.65 J/pulse and a conversion efficiency of 1.6% is achieved at the operating wavelength 635 nm. The laser performance is improved in some aspects such as threshold energy, conversion efficiency, and linewidth to some extent as compared with those reported previously.
Intensity noise analysis of a fibre laser after passing through an optical mode cleaner
Authors: Tai Zhao-Yang  , Hou Fei-Yan  , Wang Meng-Meng  , Quan Run-Ai  , Liu Tao  , Zhang Shou-Gang  , Dong Rui-Fang  ,   Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Science, Xian 710600, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The intensity noise in a 1560 nm single frequency fiber laser after passing through an optical mode cleaner is analyzed both theoretically and experimentally. Experimental measurement shows that in addition to the evident suppression of intensity noise by the mode cleaner, there exist induced observable periodic fluctuations in the analyzing frequency range of 2 to 12 MHz, as well as the amplification of the intensity noise at low frequencies. The above results cannot be explained by the present mode cleaner model for noise suppression. In this paper, we propose a new theoretical model, in which the mode cleaner is considered equivalent to a delay line and through it the phase-noise of the fiber laser is partially converted to the intensity noise. The phase-induced relative intensity noise (RIN) amplitude is jointly determined by the laser linewidth, the mode cleaner linewidth, and the analyzing frequency. The theoretical analysis shows a very good agreement with the experimental results. The noise suppression effect of the acoustic optical modulator is further analyzed by inserting it into the setup and providing a frequency modulation for it. We have observed an evident improvement of the mode cleaner locking, while the bandwidth of the laser is slightly suppressed from 26 to 16kHz, and the degradation of the measured intensity noise after the mode cleaner is also moderate. The theoretical analysis according to our proposed model fits well with this result. This result further confirms that the phase-induced intensity noise has no direct connection to the mode cleaner locking quality. Through the above analysis, a complete theoretical mode for analyzing the noise suppression by a mode cleaner is built.
Supercontinuum generation in photonic crystal fiber and tapered single-mode fiber
Authors: Wei Zhi  , Jin Guang-Yong  , Peng Bo  , Zhang Xi-He  , Tan Yong  ,   School of Science, Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

In order to study the thermal and stress fields in the multilayered structure of silicon-based positive-intrinsic-negative(PIN) photodiode irradiated by millisecond(ms)-pulsed laser, we use the thermal elasto-plastic constitutive theory and the equivalent specific heat method, to deal with the phase change latent heat. The multiple-heat-source, especially the influence of reflection from bottom-aluminum-electrode, and the effect of the nonlinearity of material parameters are taken into consideration. A 2-D simulation model is built by means of the finite element simulation software of COMSOL Multiphysics. The surface and the internal each layer showing changes of the transient distribution and evolution of the thermal and stress fields with space and time can be obtained. Because of taking account of the reflection of the aluminum electrode, the temperature of the aluminum electrode rises slightly. On this basis, we analyze the hard failure mechanism of ms-pulsed laser irradiated silicon-based PIN, and the mechanical damage before melting that leads to a malfunction of silicon-based PIN detector.
First-prinicples study of Mn-N co-doped p-type ZnO
Authors: Chen Li-Jing  , Li Wei-Xue  , Dai Jian-Feng  , Wang Qing  ,   State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China;,   School of Sciences, Lanzhou University of Technology, Lanzhou 730050, China
Published: December 2020

Based on first-principles plane-wave ultrasoft pseudopotential density functional theory method,the lattice structure, formation energy, density of states and charge density of the ZnO:(Mn,N) system are calculated and studied theoretically. Results show that Mn and N co-doped ZnO system is more suitable for doping into a p-type system, for it has a lower impurity formation energy and higher chemical stability; Mn and N in a proportion of 1:2 doping system can effectively reduce the formation energy of the system and so it is more stable; when the system forms a double acceptor level defects, the p-type characteristic of the system is more obvious, for the solubility of impurities and the number of carriers in the system are increased. In addition, it is found that more impurities can go through the Fermi level density of states in the Mn-N co-doped system, while the 2p state density of N is widened and effective mass of holes is smaller and more delocalized.Moreover,compared with the Mn-N-doped system, the density of states of Mn-2N co-doped system is more dispersed near the Fermi level, and the non-localized characteristics are distinctive, thus it is expected to be a more effective means of p-type doping.
Hydrogen adsorption on one-dimensional graphene superlattices
Authors: Huang Xiang-Qian  , Lin Chen-Fang  , Yin Xiu-Li  , Zhao Ru-Guang  , Wang En-Ge  , Hu Zong-Hai  ,   State Key Lab for Artificial Microstructures and Mesoscopic Physics, Peking University, Beijing 100871, China;,   Collaborative Innovation Center for Quantum Matter, Beijing 100871, China;,   International Center for Quantum Materials, Peking University, Beijing 100871, China
Published: December 2020

One-dimensional (1D) graphene superlattices were formed on a prototypical high index surface-Cu(410)-O. Atomic hydrogen adsorption on the superlattice was studied by using Raman spectroscopy, low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Selective H adsorption due to the 1D modulation from the Cu substrate was observed in defect-free graphene area. Most H adatoms occupy the same positions in the 1D graphene superlattice stripes, as revealed by STM. This opens the possibility for further graphene property tuning through 1D superlattices. In addition to H monomers and dimers, a new type of trimer configuration was also observed.
Analysis on power spectrum and base-scale entropy for heart rate variability signals modulated by reversed sleep state
Authors: Liu Da-Zhao  , Wang Jun  , Li Jin  , Li Yu  , Xu Wen-Min  , Zhao Xiao  ,   College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, China;,   Image Processing and Image Communications Key Lab., Nanjing Univ. of Posts & Telecomm., Nanjing 210003, China
Published: December 2020

Heart rate variability(HRV) signals can provide the important information about the active state of heart. To set up a reversed sleep model, then, we analyze the 24-hours HRV signals modulated by the reversed sleep state using the power spectrum and base-scale entropy method, and study the effect of the interaction of autonomic nerve system and the chaotic intensity of HRV signals in the case of reversed sleep. Results show that because of the reversed sleep state, the activity rhythm of autonomic nerve is contrary to that in normal state. The variational trend of base-scale entropy is corresponding to that reversed in day and night. This means that the chaotic intensity of HRV signals is closely related to the reaction of autonomic nerve system. In further researches, it is found that the chaotic intensity of HRV signals is in positive correlation with the modulation intensity of sympathetic nerve, but in negative correlation with the modulation intensity of vagus.
Review on superconducting transition edge sensor based single photon detector
Authors: Zhang Qing-Ya  , Dong Wen-Hui  , He Gen-Fang  , Li Tie-Fu  , Liu Jian-She  , Chen Wei  ,   Tsinghua National Laboratory for Information Science and Technology, Tsinghua University, Beijing 100084, China;,   Institute of Microelectronics, Department of Micro/Nanoelectronics, Tsinghua University, Beijing 100084, China
Published: December 2020

Over the past decade, there have been increasing demand on and interest in high performance single photon detectors in many new applications in quantum information technology. Compared with conventional single photon detectors, superconducting transition edge sensor (TES) based single photon detectors have great advantages in the performance of detection efficiency, energy resolution, photon number resolving capability, dark count rate, etc. They have been successfully used in quantum optics experiments and quantum key distribution systems, and they will play a more important role in the research field of quantum information science and technology. In this paper we review the operating principle, fabrication process, performance, measurement system and the research progress on superconducting TES based single photon detectors.
Prediction method of flow instability based on multi-objective optimized extreme learning machine
Authors: Chen Han-Ying  , Gao Pu-Zhen  , Tan Si-Chao  , Fu Xue-Kuan  ,   Fundamental Science on Nuclear Safety and Simulation Technology Laboratory, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Extreme learning machine (ELM) is a recently proposed learning algorithm for single-hidden-layer feedforward neural networks, which has a fast learning speed while avoiding the problem of local optimal solution. However, the performance of ELM may be affected due to the random determination of the input weights and hidden biases. In this paper, a multi-objective optimized extreme learning machine (MO-ELM) is proposed to solve this problem. The algorithm uses the no-dominated sorting genetic algorithm II algorithm to select input weights and hidden biases. Both the learning errors and the mean square value of output weights are used as optimization objects. The MO-ELM algorithm is used in the multi-step forecast of irregular complex flow oscillations of natural circulation system in rolling motion, and the influences of learning errors and output weights on forecast results are analyzed. Experimental results show that MO-ELM can achieve good generalization performance with much more compact networks and provide a relatively accurate forecast method of flow rate, and the forecast results can be used as reference to nuclear power system operators.