bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of wafer bonding and laser liftoff process on residual stress of GaN-based vertical light emitting diode chips
Authors: Wang Hong  , Yun Feng  , Liu Shuo  , Huang Ya-Ping  , Wang Yue  , Zhang Wei-Han  , Wei Zheng-Hong  , Ding Wen  , Li Yu-Feng  , Zhang Ye  , Guo Mao-Feng  ,   Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Shaanxi Provincial Key Laboratory of Photonics and Information Technology, Xi'an Jiaotong University, Xi'an 710049, China;,   Solid-State Lighting Engineering Research Center, Xi'an Jiaotong University, Xi'an 710049, China;,   Shaanxi Supernova Lighting Technology Co. Ltd. Xi'an 710077, China
Published: December 2020

Residual stress conditions in GaN-based LEDs will have a significant influence on device performance and reliability. In this paper, GaN-based vertical LEDs under different stress conditions are fabricated by bonding with three types of submounts (Al2O3 submount, CuW submount and Si submount), changing the soak temperature (290 ℃, 320 ℃, 350 ℃ and 380 ℃) and using different laser energy densities (875, 945 and 1015 mJ·cm-2). The warpage and Raman scattering spectra of those GaN-based LEDs are measured. The experimental results show that the residual stress conditions in GaN-based vertical LEDs are a consequence of the bonded submounts and bonded metal, and the soak temperature is the primary factor that determines the degree of residual stress in LED chips. In the laser lift-off process, changing laser energy density in an appropriate range has little influence on residual strain of LED chips, and the micro-cracks in GaN layer caused by LLO process will play a role in releasing the residual stress. The warpage of epitaxial sapphire substrate becomes large after boding with Si submount, the residual stress in GaN-based vertical LEDs is tensile stress and becomes larger with the soak temperature rising. When GaN epi wafer bonds with Al2O3 submount and CuW submount, the warpages becomes small and large respectively and the residual stress in chips is compressive stress. Because of the mismatch of coefficient of thermal expansion, the compressive stress in GaN-based LED chips increases for Al2O3 submount and drops for CuW submount with the soak temperature rising.
Biased random walks in the scale-free networks with the disassortative degree correlation
Authors: Hu Yao-Guang  , Wang Sheng-Jun  , Jin Tao  , Qu Shi-Xian  ,   Institute of Theoretical and Computational Physics, School of Physics and Information Technology, Shaanxi Normal University, Xi'An 710062, China
Published: December 2020

Random walk has been applied to exploring the effective transport strategy of data package in complex networks. Because the disassortative degree correlation is ubiquitous in technical networks including the internet, we study the biased random walks in the scale-free networks with the disassortative degree correlation. Computer simulation shows that the degree correlation changes the behavior of the random walk. Random walkers are located on small degree nodes with a low probability, and they can be distributed homogeneously on other nodes. We find out the optimal biased coefficient that ensures the most homogeneous distribution on large nodes. In the optimal case, the degree-correlated network exhibits a more efficient random walk than degree-uncorrelated networks. We propose the mechanism for the effect of the disassortative mixing on the random walk.
Effects of inhomogeneous magnetic field and magnetic impurity on the quantum correlation of spin-1 system
Authors: Qin Meng  , Li Yan-Biao  , Bai Zhong  ,   School of Physics, Nanjing University, Nanjing 210093, China;,   College of Sciences, PLA University of Science and Technology, Nanjing 211101, China
Published: December 2020

We investigate the effects of inhomogeneous magnetic field and magnetic impurity on the quantum correlation in spin-1 system by means of negativity and measurement-induced disturbance. Results show that the increase of the inhomogeneous magnetic field not only decreases entanglement, but also can induce the entanglement, and increases the value of critical nonlinear coupling Kc. The critical magnetic field for measurement-induced disturbance is higher than that for negativity, and the measurement-induced disturbance (MID) will not disappear with the decrease of nonlinear coupling |K|, so it can reveal all the properties of quantum correlation. Results also show that the effects of different magnetic impurity on MID are independent of each other. Under the magnetic impurity, the entanglement exists only if the couplings |J| are less than the nonlinear couplings |K|, while there will be the MID when the couplings |J| are greater than the nonlinear couplings |K|. It is just the minimum point for MID when |J| equals to |K|. Moreover, the size of the Chain will influence the quantum correlation also.
Ground state of a rotating spin-orbit-coupled Bose-Einstein condensate in a harmonic plus quartic potential
Authors: Chen Guang-Ping  ,   The School of Physics and Mech-tronic Engineering, Sichuan University of Art and Science, Dazhou 635000, China
Published: December 2020

We consider the ground-state structure of a rotating Bose-Einstein condensate with spin-orbit coupling which is confined in a harmonic plus qurtic potential. Combined effects of spin-orbit coupling and rotation on the ground-state structure of such a system are investigated in detail. Results show that a large number of novel ground-state structures, such as stripe, two rows, snakeskin piebald, and so on, can be produced under the combination of anisotropic spin-orbit-coupling and rotation.
Research on particle swarm optimization algorithm with characteristic of quantum parallel and its application in parameter estimation for fractional-order chaotic systems
Authors: Huang Yu  , Liu Yu-Feng  , Peng Zhi-Min  , Ding Yan-Jun  ,   State Key Laboratory of Power Systems, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China;,   School of Control and Computer Engineering, North China Electric Power University, Baoding 071003, China
Published: December 2020

Parameter estimation for fractional-order chaotic systems is a multi-dimensional optimization problem, which is one of the important issues in fractional-order chaotic control and synchronization. With the characteristic of quantum parallel, a new quantum parallel particle swarm optimization algorithm is proposed for solving the problem of parameter estimation in fractional-order chaotic systems. A new method of quantum coding is presented with quantum parallel characteristic which can make the calculation number of each generation increase exponentially. On the basis of this method, a particle evolution equation composed of quantum current rotation angle, individual optimal rotation angle, and global optimum rotation angle is proposed, which can restraint the behavior of particles in quantum space, and also can improve the search capability of the algorithm. Numerical simulations of the fractional-order Lorenz system and the fractional-order Chen system are conducted and the results demonstrate the effectiveness, robustness and versatility of the proposed algorithm.
Progress of research on new hole transporting materials used in perovskite solar cells
Authors: Song Zhi-Hao  , Wang Shi-Rong  , Xiao Yin  , Li Xiang-Gao  ,   School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China;,   Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
Published: December 2020

Perovskite solar cells with a solid-state thin film structure have attracted great attention in recent years due to their simple structure, low production cost and superb photovoltaic performance. Because of the boost in power conversion efficiency (PCE) in short intervals from 3.8% to 19.3% at present, this hybrid cells have been considered as the next generation photovoltaic devices. It is expected that the efficiencies of individual devices could ultimately achieve 25%, which is comparable to the single-crystal silicon solar cell.In this article, the perovskite absorber, its basic device structure, and operating principles are briefly introduced. Since most of the high efficiency perovskite solar cells employ hole transporting materials (HTM), they could benefit the hole transport and improve the metal-semiconductor interface in the cells. This perspective gives analyses of some effective hole transporting materials for perovskite solar cell application. The hole transporting materials used in perovskite solar cell are classified into six categories according to their structures, including triphenylamine-based small molecule HTM, small molecule HTM containing N atom, sulfur-based small molecule HTM, sulfur-based polymer HTM, polymer HTM containing N atom and inorganic HTM. Emphasis is placed on the interplay of molecular structures, energy levels, and charge carrier mobility as well as device parameters. A critial look at various approaches applied to achieve desired materials and device performance is provided to assist in the identification of new directions and further advances.
Ultrafast electron diffraction technique and its applications
Authors: Pei Min-Jie  , Qi Da-Long  , Qi Ying-Peng  , 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
Published: December 2020

The real-time observation of atomic motion in space and time is of great importance for natural science research. Ultrafast electron diffraction (UED) technique, which is equipped with both the high temporal resolution of femtosecond laser pulses and the high spatial resolution of electron diffraction, can provide an effective approach to study the structural change of matter in atomic scale. In this review, we make an introduction of the development history, experimental methods, related applications and future prospects of UED technique.
Design of dually foveated imaging optical system
Authors: Feng Chi  , Chang Jun  , Yang Hai-Bo  ,   School of optoelectronics, Beijing Insitute of Technology, Beijing 100081, China;,   Science and Technology on Electro-optical Information Security Control Laboratory, Sanhe 065201, China
Published: December 2020

With the advances in technology, how to solve the problem of contradiction between the large field of view and high resolution of images becomes one of the research focus of many scientific researchers. In this paper we present the concept of dually foveated imaging optical system, based on the traditional singly foveated imaging system which simulates the human eye, by introducing a reflective liquid crystal spatial light modulator for modulating the aberrations of two fields of a view, so improving the corresponding aberrations and achieving high-resolution image of the two different fields of view, while the remaining fields of the view are of low-resolution image. In this way it can solve the contradiction between the large field of view and high resolution image. In this paper, we design a dually foveated imaging optical system with the following parameters: reference wavelength is 587 nm, the field of view is 60° (i.e., ± 30°), F/8, the focal length is 60 mm. Simulation is conducted by CODE V, achieving a 5° and 17° dual field high-resolution image, and the remaining field being of low-resolution image; and calculation shows the high diffraction efficiency of the system with sampling resolution of 32 × 32, verifying the scientificness and accuracy of the design method.
Tunable filtering properties of the ployphyly photonic crystal with double local states
Authors: Zhu Qi-Guang  , Dong Xin-Yu  , Wang Chun-Fang  , Wang Ning  , Chen Wei-Dong  ,   Key Laboratory for Special Fiber and Fiber Sensor of Hebei Province, School of Information Science and Engineering, Yanshan University, Qinhuangdao 066004, China;,   School of Liren, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

The mechanism of generating double defect modes in a photonic crystal with double local states is analyzed based on the tight-binding method. The optical transmission characteristic of a one-dimensional photonic crystal is studied using the transfer matrix method. And the relationship between the transmission spectrum and structural parameters of the photonic crystal is obtained. The mesoscopic calender effect is discussed when the photonic crystal is exerted on by a homotaxial stress on the basis of these theories. Therefore, a multichannel filter with a simple structure which can be modulated by the stress in the near infrared band is designed. Numerical simulation results show that the defect modes may produce a red shift with the increase of the dielectric layers' refractive index or thickness. When the uniaxial tensile stress is applied on the ployphyly photonic crystal with double local states, all defect peaks will move to the direction of the long wavelength, and the values of these defect peaks remain unchanged basically. Through numerical fitting, the relationship between these defect peaks' central wavelengths and the size of the strain produced by the homotaxial tensile stress on the photonic crystal is linear. This kind of photonic crystal filter with a simple structure has good tunability and has practical application value in the manufacture of a series of exquisite photonic crystal lasers, wavelength division multiplexers and other precision instruments.
Energetic stochastic resonance in gain-noise model for single-mode laser
Authors: Zhang Liang-Ying  , Jin Guo-Xiang  , Wang Zhi-Yun  , Cao Li  ,   School of Physics and Electronic Engineering, Xiangfan University, Xiangyang 441053, China;,   Hubei Province Key Laboratory of Intelligent Robot, Wuhan Institute of Technology, Wuhan 430073, China
Published: December 2020

This paper studies the work which is done by periodical external force to the gain-noise model for a single-mode laser. Result shows that the work exhibits a maximum as the angular frequency of the periodical external force varies, and the energetic stochastic resonance occurs; and the influence of system parameter and noise intensity on the resonance peak is discussed in detail.
Effects of laser irradiation on the photoelectric properties of thermal-annealed metal/fluorine-doped tin oxide transparent conductive films
Authors: Huang Li-Jing  , Ren Nai-Fei  , Li Bao-Jia  , Zhou Ming  ,   School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China;,   School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China;,   Jiangsu Provincial Key Laboratory of Center for Photon Manufacturing Science and Technology, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

Three kinds of bilayer films, i.e. aluminum (Al)/fluorine-doped tin oxide (FTO), copper (Cu)/FTO and silver (Ag)/FTO, are prepared by coating a commercial FTO glass with sputtered metal layers, and subsequently thermally annealed. Then all the as-annealed bilayer films are irradiated using a 532 nm nanosecond pulsed laser. X-ray diffraction (XRD) analysis confirms that all the laser-irradiated films have underwent laser annealing, resulting in an improvement in their photoelectric properties. More significantly, after laser irradiation, the as-annealed Ag/FTO film exhibits the highest increment in average transmittance (400–800 nm) that is increased from 72.6% to 80.5%. This should be attributed mainly to the formation of laser-induced grating structures that have anti-reflection effect on their surfaces. It is also found that the laser irradiation decreases the sheet resistance of the as-annealed Ag/FTO film from 5.6 to 5.3 Ω/sq. The annealing caused by thermal effect of laser irradiation gives rise to an increase in grain size, thereafter reduces carrier scattering at grain boundaries and enhances carrier mobility, which should be responsible for the improvement in conductivity. The calculated results show that after laser irradiation the figure of merit of the as-annealed Ag/FTO film is greatly increased from 0.73×10-2 to 2.16×10-2Ω-1, indicating a significant enhancement in the overall photoelectric property of the film. Laser irradiation can simultaneously achieve fabrication of grating structures and laser annealing, providing a new idea for performance optimization of metal-layer-composited transparent conductive films.
Study of structure parameters effect on performance of optical en/decoder based on parallel-cascaded microring resonators
Authors: Ji Zhe  , Jia Da-Gong  , Zhang Hong-Xia  , Zhang De-Long  , Liu Tie-Gen  , Zhang Yi-Mo  ,   Key Laboratory of Opto-electronics Information Technology, Ministry of Education, Tianjin University, Tianjin 300072, China
Published: December 2020

Optical en/decoder is one of the most crucial factors affecting the performance of the optical code division multiple access (OCDMA). The autocorrelation peak to maximum wing ratio (P/W) and cross-correlation ratio (P/C) are two important parameters to quantitatively evaluate the performance of the en/decoder.Based on the SOI parallel-cascaded coupled micro-ring reflector, a mathematical model of two-dimensional coherent optical en/decoder is established. Influences of the structure parameters including the coupling coefficient, the loss factor, the array distance, and the channel spacing on P/W and P/C ratios are discussed in detail. Results show that for the micro-ring with a radius of 50 μm, when the ring-bus and ring-ring coupling coefficients are 0.6–0.7 and 0.1–0.2, respectively, the propagation loss is lower than 2 dB/cm, the array distance is greater than 3 mm, and when the channel spacing is given between 25–36 GHz, the proposed structure can have an optimal performance of en/decoding.
A meshfree method based on point interpolation for dynamic analysis of rotating cantilever beams
Authors: Du Chao-Fan  , Zhang Ding-Guo  ,   School of Sciences, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

A meshfree method based on polynominal point interpolation method (PIM) is proposed for dynamic analysis of a rotating cantilever beam; PIM is used to describe the deformation of the flexible beam. Its longitudinal and transverse deformations are both taken into consideration, and the coupling term of the deformation which is caused by the transverse deformation is included in the longitudinal deformation of the beam. The rigid-flexible coupling dynamic equations of the system are derived via employing Lagrange's equations of the second kind. Compared with the finite element method (FEM), only individual nodal data are required in the current method so that its preprocessor is easier, and the shape functions constructed have high-order continuities due to more nodes to be interpolated. Simulation results of the meshfree method are compared with those obtained by using FEM and assumption of modes method. It is demonstrated that the meshfree method can be extended to the field of multibody system dynamics.
A flexible dual-band metamaterial based on hairpin split-ring resonators
Authors: Liu Hai-Wen  , Zhu Shuang-Shuang  , Wen Pin  , Qin Feng  , Ren Bao-Ping  , Xiao Xiang  , Hou Xin-Yu  ,   Department of Information Engineering, East China Jiaotong University-RF communications and sensor networks, Jiangxi Province Key Laboratory 330013, China;,   Institute No. 207, China Aerospace Science and Industry Corporation, Beijing 100084, China
Published: December 2020

A miniaturization dual-band metamaterial (MM) model with a unit cell of hybrid-aligned hairpin split ring resonator (SRR) is proposed in this letter. The unit cell of this MM structure is a hairpin SRR, and the proposed dual-band MM is designed for security applications of wireless local-area networks (WLAN) at 2.4 GHz and worldwide interoperability for microwave access (WiMAX) at 3.5 GHz. Furthermore, a flexible substrate is adopted to improve the flexibility and practicability of the MM. Both simulated and measured results show that the center frequencies of the dual-band MM can be allocated by properly choosing the dimension parameters of the SRR. In addition, the MM are simulated at different angles of incidence, and the results reveal that the MM can operate quite well over a range of angles of incidence. Finlly, the current distribution in the MM has also been investigated to explain the mechanism of the dual-band resonance prodnced.
A review of the perovskite solar cells
Authors: Yao Xin  , Ding Yan-Li  , Zhang Xiao-Dan  , Zhao Ying  ,   Institute of Photo Electronics Thin Film Devices and Technology of Nankai University, Tianjin 300071, China
Published: December 2020

The efficiency of solar cells based on organic-inorganic hybrid perovskite materials has a rapid growth from 3.8% in 2009 to 19.3%. The perovskite material (CH3NH3PbX3) exhibits advantages of high absorbing coefficient, low cost, and easily synthesised, which achieved extremely rapid development in recent years and gains great concern from the academic circle. As we know, perovskite materials not only serve as light absorption layer, but also can be used as either electron or hole transport layer. Consequently, various structures are designed based on the function of the perovskite, such as the solid-state mesoscopic heterojunction, meso-superstructured planar-heterojunction, HTM-free and the organic structured layers. Besides, it is also attractive for its versatility in fabrication techniques: one-step precursor solution deposition, two-step sequential deposition, dual-source vapor deposition, and vapor-assisted solution processing etc. This review mainly introduces the development and mechanism of the perovskite solar cells performance and the fabrication methods of peroskite films, briefly describes the specific function and improvement of each layer, and finally discusses the challenges we are facing and the development prospects, in order to have a further understanding of perovskite solar cells and lay a solid foundation for the preparation of new structures of the perovskite solar cells.
Pre-synthesized quantum dot deposition approach to obtain high efficient quantum dot solar cells
Authors: Li Wen-Jie  , Zhong Xin-Hua  ,   Key Laboratory for Advanced Materials, Institute of Applied Chemistry, East China University of Science and Technology, Shanghai 200237, China
Published: December 2020

Quantum dot sensitized solar cells (QDSCs) appear to be one of the promising photovoltaic candidates, due to the lower cost of obtaining materials and assembling processes, as well as the advantages of their QD sensitizers which exhibit properties of tailoring the absorbance spectrum to near-infrared (NIR) regions, the multiple exciton generation (MEG), hot electron extraction, etc. However, the difficulty of QDs penetrating into TiO2 mesoporous film remains to be an obstacle for the development of QDSCs, which comes from (1) their larger size (1-10 nm) compared with dye molecules, (2) steric hindrance from the long chain organic ligands on the surface, and (3) the lack of terminal functional group of the ligand with affinity to TiO2. These issues imply the importance of implementing an efficient QD deposition method in the fabrication process. Based on summarizing the advantages and shortcomings, this review demonstrates the development of the QD deposition approaches in direct growth deposition methods: the chemical bath deposition (CBD) method, the successive ionic layer adsorption and reaction (SILAR) method, and the pre-synthesized QD deposition methods: linker-assisted deposition (LA), direct absorption (DA) and electrophoretic deposition (EPD). As an overall comparison to be taken for all these deposition approaches, the pre-synthesized QD deposition method has outperformed the direct growth deposition method due to the use of pre-synthesized high quality QD sensitizers for better performance in surface chemistry. Especially, the LA approach in this method exhibits its excellence of fast and uniform QD deposition with high coverage, as well as in building high efficiency QDSC devices. Specifically, the improved structure of the sensitizers such as the inverted type-I, type-II core/shell structures and alloyed configuration through surface ion-exchange, has been employed to boost the charge injection and depress the charge recombination, benefited from LA pre-synthesized QDs deposition method. The advantages of the LA method are fully illustrated by the examples of the most recent work in the achievement of reaching the record efficiency of QDSCs. Finally, outlooks have been given on possible approaches to realize further improvement of fabricating the QDSCs with excellent performance at higher levels.
Quantum channel establishing rate model of quantum communication network based on entangled states
Authors: Chen Peng  , Cai You-Xun  , Cai Xiao-Fei  , Shi Li-Hui  , Yu Xu-Tao  ,   State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 211189, China
Published: December 2020

Targeting the quantum communication network based on entangled states, a network model is proposed. According to the model, the quantum channel establishing rate of basic links is then analyzed. For different quantum channel establishment methods, the quantum channel establishing rates of long relay links are also analyzed. Then the quantum channel establishing rates corresponding to the point-by-point method and segmentation method are calculated. Finally, the quantum channel establishing rate between two arbitrary points in a large-scale quantum entanglement communication network is analyzed based on the percolation model. The quantum channel establishing rate in a quantum communication network of n nodes is Ω (1/n).
Investigation of thermodynamic properties of weakly interacting Fermi gas in weakly magnetic field by using the N-E-V distribution and pseudopotential method
Authors: Li He-Ling  , Wang Juan-Juan  , Yang Bin  , Shen Hong-Jun  ,   School of Physics and Electrical Information Science, Ningxia University, Yinchuan 750021, China
Published: December 2020

Based on the fact that most of low temperature experiments of quantum systems are explored in an external field on condition that the particle numbers, volumes and energies of systems may be changed, the thermodynamic properties of weakly interacting Fermi systems in weak magnetic field are studied by using the statistical distribution of the completely open system with variable particle number, volume, and energy (N-E-V distribution). Firstly, the analytical expressions of internal energy and heat capacity, which are in the Fermi integral form, are obtained in the general case, and the analytical expressions and numerical results of energy and heat capacity are given under the extreme condition of supper-low temperature. The calculation results by the N-E-V distribution (with particle number density being variable) are compared with those by a pseudopotential method (with particle number density being unchanged). It can be found that the deviations of the internal energy and heat capacity calculated by the two different methods are very small, and the N-E-V distribution method can partially compensate for the error caused by the pseudo potential method. The most interesting point of the results obtained by the N-E-V distribution method is that there is a phase transition temperature in the weakly interacting Fermi system in weak magnetic field under the low temperature condition. The phase transition temperature is just in the range where occur the Fermi systems, Bose-Einstein condensation (BEC), Bardeen-Cooper-Schrieffer (BCS) phase transition, and BEC-BCS crossover, and does not vary with strength nor characteristic (attraction or repulsion) of the weak interaction, but it decreases with the strengthening of the external magnetic. When there is no external magnetic, the phase transition temperature is highest (more than 0.184 times Fermi temperature).
Analysis on the slow-scale bifurcation behaviors of one-cycle-controlled three-level Boost power factor correction converter
Authors: Liu Hong-Chen  , Guan En-Hui  , Wang Yun  , Zhao Dan  , Zhou Qi-Kun  , Xu Yong-Xiang  ,   School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China;,   Central Research Institute of Shanghai Electric Group, Shanghai 200070, China
Published: December 2020

In this paper, the slow-scale bifurcation phenomenon of the one-cycle-controlled three-level Boost power factor correction (PFC) converter is studied in depth, aiming at analyzing the influence of main circuit parameters on the stability of the system based on Floquet multiplier method. Firstly, the working principle of the circuit is analyzed, and a simplified model is derived according to the power balance principle. The periodic solutions are investigated using the harmonic balance method, and its stability is studied by the Floquet theory. By calculating the Floquet multiplier, the influence of the voltage compensator resistor Rvf on the slow-scale behavior of the system is analyzed. The simulation result verifies the correctness of the simplified model and theoratical analysis. Finally, the stability boundary composed of filter capacitor C and load resistor R as well as feedback resistor Rvf and capacitor Cvf is calculated and simulated under certain conditions. The circuit simulation result is consistent with the theoretical calculation. The results show that the correct choice of circuit parameters of three-level Boost PFC converter is very important for achieving its stable operation and improving the power factor.
Analysis of chaos in permanent magnet synchronous generator and optimal output feedback H∞ control
Authors: Yang Yi-Fei  , Luo Min-Zhou  , Xing Shao-Bang  , Han Xiao-Xin  , Zhu Huang-Qiu  ,   School of Electrical and Information Engineering, Jiangsu University of Technology, Changzhou 213001, China;,   Institute of Advanced Manufacturing Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Changzhou 213164, China;,   School of Electrical and Information Engineering, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

The permanent magnet synchronous generator (PMSG) is investigated and its mathematical model is established in two-phase synchronous rotating coordinates. Aiming at the fact that PMSG may present chaotic behaviors at certain values of parameters and under certain working conditions, the output feedback control gain matrix with the minimum performance index is obtained by solving the Riccatic equation and fed back to the system in order to improve the system performance with considering the disturbance. Results show that the optimal output feedback H∞ control based on Riccatic equation can respond to PMSG very quickly and accurately in the chaotic state when disturbance occurs.
Design of an adaptive sliding mode controller for synchronization of fractional-order chaotic systems
Authors: Pan Guang  , Wei Jing  ,   College of Marine Engineering, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

In this paper, the synchronization of fractional-order chaotic systems is investigated. Based on sliding mode control and adaptive control theory, a fractional order integral sliding surface with strong robustness is designed, and an adaptive sliding controller is proposed for synchronizing the fractional-order chaotic systems with retaining the nonlinear part. Numerical simulations on synchronizing the Chen chaotic systems, the Liu chaotic systems, and Arneodo chaotic systems are carried out separately. The simulation results show the validity and feasibility of the adaptive sliding controller.
Hybrid algorithm for weak signal detection in chaotic sea clutter
Authors: Xing Hong-Yan  , Zhang Qiang  , Xu Wei  ,   Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Key Laboratory of Meteorological Observation and Information Processing of Jiangsu Province, Nanjing University of Information Science and Technology, Nanjing 210044, China
Published: December 2020

According to the empirical mode decomposition (EMD) theory, a prediction method of support vector machine (SVM) is proposed based on particle swarm optimization. The ensemble EMD method is used to decompose the signal into some intrinsic mode function components which are taken as the input of the SVM to predict the data. All the predicted values are combined, and the weak signals submerged in chaos background, including the transient signal and periodic signal, are detected from the prediction error. Lorenz attractor and the data from the McMaster IPIX radar sea clutter database are used in the simulation. The results show that the proposed method can effectively detect the weak target from chaotic signal. When the signal-to-noise ratio is 102.8225 dB in the chaotic noise background, by using the new method the root mean square error can be reduced by five orders of magnitude, reaching 0.00000033092, while the conventional SVM can reach only 0.049 under the condition of -54.60 dB and the weak target detected in sea clutter has the harmonic characteristics, which shows the prediction model has a lower threshold and error.
Computational study of structures and electronic properties of SimGen (m+n=9) clusters
Authors: Wu Li-Jun  , Sui Qiang-Tao  , Zhang Duo  , Zhang Lin  , Qi Yang  ,   College of Science, Northeastern University, Shenyang 110819, China;,   College of Science, Shenyang Ligong University, Shenyang 110159, China
Published: December 2020

The researches of the structural and electronic properties of silicon and germanium clusters are of great significance for developing novel microelectronic materials. This paper aims to study the geometric structures and electronic properties of SimGen (m+n=9) clusters by combining genetic algorithm and density functional tight binding method. The study shows that there are two low energy stable atomic stacking configurations for SimGen(m+n = 9) clusters: one is a pentagon double cone stacking two small adjacent pyramids, the other is a tetrahedron close packing with a Ge atom on a bridge. Both stacking configurations are changed greatly with gradually increasing the Ge atom number in the cluster. The shape of the lowest-energy configuration changes from the pentagon double cone stacking two adjacent pyramids on the same side into the pentagon double cone stacking two adjacent pyramids on both sides of the up and down. With this change, the electron distribution and the gap of the highest occupied molecular orbital and the lowest unoccupied molecular orbital gap are obviously dependent on the difference in components of Ge and Si elements contained.
Ground state properties and excitation properties of ZnSe under different external electric fields
Authors: Li Shi-Xiong  , Wu Yong-Gang  , Linghu Rong-Feng  , Sun Guang-Yu  , Zhang Zheng-Ping  , Qin Shui-Jie  ,   School of Physics and Electronic Science, Guizhou Normal College, Guiyang 550018, China;,   Key Laboratory of Photoelectron Technology and Application of Guizhou Province, Guizhou University, Guiyang 550025, China
Published: December 2020

The Hartree-Fork (HF) method with LANL2DZ basis set is used to investigate the equilibrium structures, atomic charge distributions, the highest occupied molecular orbital (HOMO) energy levels, the lowest unoccupied molecular orbital (LUMO) energy levels, energy gaps, dipole moments, harmonic frequencies and infrared intensities of ZnSe under different external electric fields ranging from -0.025 to 0.040 a.u. The excitation energies, transition wavelengths and oscillator strengths under the same external electric fields are calculated by the time-dependent-HF method. The results show that the bond length and electric dipole moment are proved to be first decreasing, and then increasing with the variation of the external field; the total energy is found to decrease linearly with the variation of external field; but the HOMO energy and energy gap are proved to increase with the variation of external field. The harmonic frequency and LUMO energy are found to first increase, and then decrease, but the infrared intensities are proved to first decrease, and then increase. The external electric field has significant effect on the excitation properties of ZnSe molecule. The excited energies from ground state to the first nine excited states are found to increase, and the transition wavelengths are decreasing with the variation of the external field. Meanwhile, the strongest excited state becomes very weak, and the weak excited state becomes strongest by the external field. The excitation properties of ZnSe material can be changed with external electric field.
Photon and photoelectron emission of the atom under the action of high-frequency laser pulse
Authors: Cui Xin  , Li Su-Yu  , Guo Fu-Ming  , Tian Yuan-Ye  , Chen Ji-Gen  , Zeng Si-Liang  , Yang Yu-Jun  ,   Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China;,   Department of Physics and Materials Engineering, College of Physics and Electronic Engineering, Taizhou University, Taizhou 318000, China;,   Data Center for High Energy Density Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

By numerically solving the time-dependent Schrdinger equation, we investigate the ionization probability, photoelectron spectrum, and harmonic emission spectrum of the atom under the action of high-frequency laser pulses. It is found that with the increase of incident laser pulse intensity, the ionization probability of the atom first increases to a maximum value gradually and then decreases, and in this process, both the photoelectron spectrum and high-order harmonic generation spectrum change from a single-peak structure to a multi-peak one. Through the time-frequency analysis of the harmonic emission spectrum, we also find that the harmonic emission is suppressed around the pulse peak, and it occurs at the rising edge and the falling edge, which interfere with each other, thus forming the multi-peak structure. Utilizing the laws of the changes of photoelectron and harmonic spectra with incident laser pulse intensity, we can diagnose the laser intensity at which the atomic ionization suppression occurs.
Single mode optoelectronic oscillator assisted by active ring resonance cavity filtering
Authors: Li Hong-Xia  , Jiang Yang  , Bai Guang-Fu  , Shan Yuan-Yuan  , Liang Jian-Hui  , Ma Chuang  , Jia Zhen-Rong  , Zi Yue-Jiao  ,   Department of Communications, College of Big Data and Information Engineering, Guizhou University, Guiyang 550025, China;,   Department of Physics, College of Science, Guizhou University, Guiyang 550025, China
Published: December 2020

In this paper, a single mode optoelectronic oscillator assisted by active ring resonance cavity filtering is presented and verified. Using the high Q optical comb frequency response to select the oscillation mode of an optoelectronic oscillator, the system can effectively suppress the side-mode and generate single mode signal. Theoretically, the optoelectronic oscillator oscillation mode and the frequency response of the active cavity are analyzed. The simulation results show that the active ring resonance cavity filtering is of benefit to the side-mode suppression and single mode output in an optoelectronic oscillator system. By comparing with experimental result, the theoretical prediction is verified. The output of a 20 GHz single-mode signal with a side-mode suppression ratio of 58.83 dB and a phase noise of -97 dBc/Hz at 10 kHz from carrier is also obtained. This scheme has the advantages of the existing optoelectronic oscillator side-mode suppression methods. In addition, it has more convenient manipulation, and good flexibility and tunability.
Experimental study of multiple optical parametric oscillator based on MgO:APLN and its evolution analysis of back conversion
Authors: Yu Yong-Ji  , Chen Xin-Yu  , Wang Chao  , Wu Chun-Ting  , Dong Yuan  , Li Shu-Tao  , Jin Guang-Yong  ,   Jilin Key Laboratory of Solid Laser Technology and Application, School of Science, Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

In this paper, a multiple optical parametric oscillator based on MgO:APLN is reported. The polarization structure of MgO:APLN and output coupler transmittance are optimized, with a high repetition rate of 200 kHz and 1064 nm laser pumping. The 1.57 μm and 3.84 μm cross period parameters light output can be achieved by a single poled crystal for the first time. The maximum average output powers of 2.4 W at 1.57 μm and 1.31 W at 3.84 μm are obtained, corresponding to optical-optical conversion efficiency of 11.54% and 6.25%, respectively. For the phenomenon of energy back conversion appearing in the multiple optical parametric oscillation process, the numerical evolution of multi-wave coupling process through the coupled wave equations is investigated, and the concept of “back conversion in energy transmission area” is induced, and indicates that the existence of back conversion in energy transmission area causes the weak gain parameters of optical parametric oscillator to be enhanced twice. The theoretical analyses are basically in agreement with the experimental results.
A new scheme of measuring Sagnac effect based on microwave resonant
Authors: Wu Qiong  , Yu Jin-Long  , Wang Ju  , Wang Wen-Rui  , Jia Shi  , Huang Gang-Bin  , Hei Ke-Fei  , Li Li-Juan  ,   Optical Fiber Communication Lab, School of Electronic and Information Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

The main principle of the existing optical gyroscope is based on the Sagnac effect. How to improve the measurement accuracy of the Sagnac effect is an important research topic of improving the gyro accuracy. The traditional optical gyro uses the short wavelength characteristic of light to improve the detection accuracy. But when considering the fact that the detection accuracy of the microwave phase/frequency is much higher than that of light wave phase/frequency, if the microwave can be used to detect the Sagnac effect, the detection accuracy higher than optical gyro accuracy can be obtained, which makes it possible to achieve high-accuracy microwave gyro. The Sagnac effect is detected by using the optoelectronic oscillator based light-carrying microwave structure. Experimental results prove the feasibility of detecting Sagnac effect by using microwave, which lays the foundation for realizing the high-precision microwave resonant gyroscope in the future.
Dynamic effective mass and power dissipation of the granular material under vertical vibration
Authors: Yu Tian  , Zhang Guo-Hua  , Sun Qi-Cheng  , Zhao Xue-Dan  , Ma Wen-Bo  ,   Department of Physics, University of Science and Technology Beijing, Beijing 100083, China;,   State Key Laboratory for Hydroscience and Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

The dependences of the dynamic effective mass() and power dissipation p() of tungsten particles system on frequency are studied under vertical vibration excitation. It is found that there appears a sharp resonance peak in each of spectra of the real part M1 (), the imaginary part M2 () of the effective mass, and the power dissipation for a given vibrating strength. With the increase of the pressure acting on the top surface of the particle, each peak frequency of the M1 (), M2 () and power dissipation moves to higher frequency, and the peak height also increases accordingly. Further study finds that the resonance frequency fg of the real part of the effective mass satisfies piecewise power-law with the change of pressure P acting on the top surface. At low P value, the power exponent is 0.3, and at high P value the power exponent decreases to 1/6. The reciprocal of quality factor of the granular system, 1/Q, decreases exponentially with the change of pressure P.
Experimental study of shock waves induced by a nanosecond pulsed laser in copper target
Authors: Wang Ji-Xun  , Gao Xun  , Song Chao  , Lin Jing-Quan  ,   School of Science, Changchun University of Science and Technology, Changchun 130022, China;,   School of Chemistry and Environmental Engineering, Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

In this paper, the shock waves induced by a nanosecond pulsed laser in copper target are studied and the relative pressures of shock waves are measured by using the piezoelectric polyvinylidene fluoride piezoelectric sensors. The evolutions of the relative pressures of shock waves with laser pulse energy and target thickness are discussed. Experimental results show that the pressure of shock wave is 2.1 MPa when the nanosecond pulsed laser with an energy of 500 mJ irradiates on a 2 mm thick copper target. When the laser energy increases from 200 to 500 mJ, the pressures of shock wave can increase 162% and 231%, with the target thickness values being 2 and 4 mm respectively. But when the thickness of the copper target increases from 2 to 6 mm, the pressures of shock waves with laser pulse energies of 400 and 500 mJ are reduced by 32% and 49%, respectively.
Critical value of volume ignition and condition of nonequilibriem burning of DT in inertial confinement fusion
Authors: Zhao Ying-Kui  , Ouyang Bei-Yao  , Wen Wu  , Wang Min  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: December 2020

In the local thermodynamic equilibrium approximation, we study the problems on low-temperature volume ignition of DT fuel. The temperature and compression threshold of volume ignition are given by solving the ion, electric and radiation energy equation. The ignitions points are affected by the albedo, DT mass, abundance ratio, etc. At the point of ignition, the temperature reduces with the increase of areal density. The trends of variations in radiation and electron temperature become closer to each other. The most important fact is that the subsequent development of the system can be given by analyzing the stationary solution based on the linear stability method. In other words, we can estimate whether the system can enter into a deep-burning state by using this method.
Optical properties of direct current glow discharge plasmas at high pressures
Authors: Wang Jian-Long  , Ding Fang  , Zhu Xiao-Dong  ,   Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China;,   Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

In this work, the parallel bright and dark plasma striations are observed in direct correct glow discharge plasmas at high pressures (>100 Torr, 1 Torr=1.33322×102 Pa), and the effect of working gas on the plasma optical property is studied by combining the measurements of optical emission spectra. With the increase of the methane concentration, the length of striations decreases and the corresponding electron excitation temperature reduces. As the concentration of methane increases, the species with the low ionization energy increases, and the average ionization energy of the species decreases. In this case, the electron accelerated in a smaller distance can obtain enough energy to excite the gas species and produce visible light emission, and thus the length of plasma striations becomes shorter. With the introduction of argon, the plasma striations appear clearly. The length of striations increases with the increase of argon content, which is also correlated with the higher ionization energy of argon, while the corresponding electron excitation temperature rises. The length of plasma striations shows a response to the electron temperature as working gas changes.