bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on the design and measurement of dual-directional multi-band metamaterial absorber
Authors: Han Song  , Yang He-Lin  ,   College of Physical Science and Technology, Central China Normal University, Wuhan 430079, China
Published: December 2020

Using the method of combination, we have made a communicational band (0.8 GHz to 3 GHz) dual-directional metamaterial absorber. Simulation and experimental results show that the absorber to the incident electromagnetic wave of different polarization and wide-angle has three stable absorbing bands(2.04, 2.34, and 2.65 GHz), and the absorptions can reach 92.3%, 95.3% and 94.7% respectively. This kind of absorber is very simple in design, having strong flexibility, perfect absorption, and easy processing, which works in a communicational band (0.8 to 3 GHz) so that it provides a new idea on electromagnetic shielding and anti interference.
Experimental research on retrieval efficiency of atomic spin wave based on electromagnetically induced transparency
Authors: Bian Cheng-Ling  , Zhu Jiang  , Lu Jia-Wen  , Yan Jia-Lu  , Chen Li-Qing  , Wang Zeng-Bin  , Ou Ze-Yu  , Zhang Wei-Ping  ,   Quantum Institute for Light and Atoms, State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, China;,   Research Center for Quantum Engineering, Beijing Institute of Aerospace Control Devices, Beijing 100854, China
Published: December 2020

The retrieve process of stored light field is important for quantum information, nonlinear optics, and quantum optics. Electromagnetically induced transparency (EIT) is one of the popular methods. In this paper we demonstrate the co-propagating and counter-propagating scheme of EIT retrieved in vapor 87Rb atomic cell. Result indicates that the retrieval efficiency depends on the spatial distribution of the atomic spin waves. Our experimental results may be useful to quantum information and nonlinear optics with vapor atomic ensemble.
A measurement method of cell gap for liquid crystal lens
Authors: Tang Xian-Zhu  , Chung Te-Chen  , Jen Ting-Hsien  , Lu Jian-Gang  , Shieh Han-Ping  ,   National Engineering Laboratory of TFT-LCD Materials and Technologies, Displays and Lighting Center, Shanghai Jiao Tong University, Shanghai 200240, China;,   Infovision Optoelectronics Co. Ltd., Kunshan 215301, China;,   National Chiao Tung University (NCTU), Hsinchu, Taiwan, China
Published: December 2020

There was a problem in current cell gap measurement of liquid crystal (LC) lens. A method was proposed by adopting interference of linearly polarized light in this paper. It was claimed that the incident light was monochromatic light with a uniform distribution of light intensity. The polarization axis of the analyzer was perpendicular or parallel to the polarization axis of polarizer. The difference between light and dark interference fringes was the biggest when the angle was equal to 45° between the rubbing direction of alignment layer in the LC lens and the polarization axis of polarizer. The cell gap of LC lens can be calculated by the transmittance of LC lens center and the max transmittance of its other locations. The tilt angle was equal to the pre-tilt angle of LC at the LC lens center. This method was simple and reliable. Its accuracy is relatively high due to the use of optical interference principle.
An algorithm for image reconstruction based on lp norm
Authors: Ning Fang-Li  , He Bi-Jing  , Wei Juan  ,   School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an 710072, China;,   State Key Laboratory of Integrated Services Networks, School of Telecommunication Engineering, Xidian University, Xi’an 710071, China
Published: December 2020

Image reconstruction is one of the key technologies in the fields of physical imaging, which include optical imaging, photoacoustic imaging, sonar imaging, magnetic resonance imaging, and celestial imaging etc. Compressive sensing theory, the new research spot in recent years, describes that a small group of non-adaptive linear projections of a sparse or compressible signal contains enough information for signal reconstruction. Compressive sensing has been applied in many physical imaging systems. In this paper, we propose a new image reconstruction algorithm based on lp norm compressive sensing by combining the penalty function and revised Hesse sequence quadratic programming, and using block compressive sensing. Several images, such as “cameraman”, “barbara” and “mandrill”, are chosen as the images for image reconstruction. First, we take different sampling rates for image reconstruction to verify the algorithm. When the sampling rate is as low as 0.3, the signal-to-noise ratio of the reconstructed image can reach up to 32.23 dB. Then, when the sampling rate is above 0.5, by comparing with OMP algorithm, reconstructed images can be obtained with a higher signal-to-noise ratio and a shorter imaging time. Especially, when the sampling rate is 0.7, the imaging time is reduced by 88%. Finally compared with the existing algorithm based on lp norm compressive sensing, simulation results show that the new algorithm can improve the signal-to-noise ratio of reconstructed images, and greatly reduce the imaging time.
Viscosity measurements using a cylindrical resonator
Authors: An Bao-Lin  , Lin Hong  , Liu Qiang  , Duan Yuan-Yuan  ,   Key Laboratory of Thermal Science and Power Engineering of MOE, Beijing Key Laboratory for CO2 Utilization and Reduction Technology, Tsinghua University, Beijing 100084, China;,   Heat Division, National Institute of Metrology, Beijing 100013, China
Published: December 2020

Viscosity is an important fluid transport property, and the viscosity data mostly are obtained from experimental measurements. The fixed path interference method with a cylindrical resonator is one of the most precise ways to gain the gaseous sound speed by measuring the resonance frequency and the half-width of the resonance peak. The gas viscosity affects the sound speed, leading to the offset of the resonance frequency and the increase of half-width of the resonance peak. Viscosity can be accurately acquired through the measurement of the resonance frequency and the half-width of the resonance peak, together with modifications due to the effect of the thermal boundary layer, the fill duct on the resonator shell, the transducer and the resonator shell vibration. In this paper, the way to acquire viscosity by the cylindrical resonator was developed and was verified by measuring argon (Ar) viscosity, and we find the result agreeing well with the data given in the literature.
The Bohm criterion for a plasma sheath with two species of charged dust particles
Authors: Zhao Xiao-Yun  , Zhang Bing-Kai  , Zhang Kai-Yin  ,   School of Physics and Electronics, Fuyang Teachers College, Fuyang 236037, China
Published: December 2020

The fluid model and the self-consistent dust charging model are used to investigate the Bohm criterion for the plasma sheath including two species of charged dust particles. Numerical calculation results are obtained using quasi-Newton method. Effects of two species of dust particles on the dust charging and the ion Mach number are discussed. As the number density of the fewer dust particles is enhanced, different changes will take place on the surface potential of the two species of dust particles. Either more number density or smaller radius of the fewer dust particle may result in a larger ion Mach number. In addition, the ion Mach number will reduce when the velocity of any kind of dust particles at the sheath edge increases.
Experimental study on current division of nested wire array Z pinches
Authors: Ye Fan  , Xue Fei-Biao  , Chu Yan-Yun  , Si Fen-Ni  , Hu Qing-Yuan  , Ning Jia-Min  , Zhou Lin  , Yang Jian-Lun  , Xu Rong-Kun  , Li Zheng-Hong  , Xu Ze-Ping  ,   Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The current division between the inner and the outer arrays is one of the key factors that impact the implosion dynamics and modes of nested wire array. This paper presents the first quantitative measurements of current division for nested wire array Z pinch on the Qiang Guang-I pulsed power facility. In experiments, the nested wire arrays, made of 3.8 μm-diameter tungsten wires, were 20 mm in height and 8 mm/16 mm in diameter for inner/outer array. Measurements for loads consisting of 42/21 wires in inner/outer array were compared with that of 21/42 in inner/outer array. Data of current versus time at various radial positions were obtained using magnetic probes until 20 ns before the current peak. Results show that the currents in inner and outer arrays increase during the rise of the driving current, the proportion of current in outer array decreases and that in inner array increases, while the current in outer array, for loads with 21/42 wires in inner/outer array, was larger than those with 42/21 wires in inner/outer array.
Isotropic compression of colloidal crystal in electric field between plate electrode
Authors: Li Xiao-Long  , Lu Ying  , Zhai Yong-Liang  , Wu Lan-Sheng  , Sun Wei  , Hu Shu-Xin  ,   Institute of Microstructure and Property of Advanced Material, Beijing University of Technology, Beijing 100124, China;,   Beijing National Laboratory for Condensed Matter Physics and CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

Colloidal crystals composed of polystyrene micro-spheres (negatively charged, with a diameter of 300 nm) are fabricated by injecting aqueous suspensions of the micro-spheres with different volume fractions into sample cells which are made by gluing together two glass plates. Whose surfaces are coated with conductive films. The colloidal crystals have a face-centered-cubic structure with their (111) planes parallel to the surface of the sample cells. Laser diffraction is used to measure the structural changes of the colloidal crystals in an electric field. Structures of the colloidal crystals are characterized by using the Kossel-line method. It is found that the colloidal crystals are compressed isotropically in the electrical field. The lattice constants of the colloidal crystals decrease with the increase of the electric field, maintaining their face-centered-cubic structure. Results can be explained by the combined action of the electric field force, electrostatic repulsion and electrohydrodynamic force. The electric field makes all of the micro-spheres migrate to the positive plate of the sample cell and leads to a compression in the direction along the electric field. Then the electrohydrodynamic force produces an attractive interaction between the micro-spheres in the direction perpendicular to the electric field.
Structural phase transition of Ru at high pressure and temperature
Authors: Lu Zhi-Peng  , Zhu Wen-Jun  , Lu Tie-Cheng  , Meng Chuan-Min  , Xu Liang  , Li Xu-Hai  ,   College of Physical Science and Technology, Sichuan University, Chengdu 610064, China;,   National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China;,   Department of Mathematics and Physics, Officer College of the Chinese People’s Armed Police Force, Chengdu 610213, China
Published: December 2020

The magnetism, stabilities and phase transition of Ru in hcp, fcc, bct and bcc structures are investigated with detailed first-principles calculations based on density-functional theory and quasiharmonic lattice dynamics approximation. Magnetic ground states and stability ranges of various phases are obtained. Calculated results indicate that the non-magnetic (NM)-hcp structure is the most stable in the entire pressure range at zero temperature, and the structural transition cannot be induced by pressure alone. NM-fcc structure is a metastable phase of bulk Ru, while both the NM-bcc and ferromagnetic (FM)-bct structures are dynamically unstable. At high pressure and temperature, a transformation from NM-hcp to NM-fcc structure will occur. Finally, the pressure-temperature phase diagram of Ru is presented.
Single-vacancy-induced transformation of electronic properties in armchair graphene nanoribbons
Authors: Zhang Zhen-Jiang  , Hu Xiao-Hui  , Sun Li-Tao  ,   SEU-FEI Nano-Pico Center, Key Lab of MEMS of Ministry of Education, Southeast University, Nanjing 210096, China
Published: December 2020

Using first principle and based on the density functional theory, we have studied the effect of the single vacancy on the electronic properties of armchair graphene nanoribbons (AGNRs). Results show that the system is the most stable when the vacancy is at edge site. It is found that AGNRs always become metallic, regardless of the vacancy position. As the vacancy concentration decreases, the influence of the vacancy position on band structures becomes weaker and weaker. As the ribbon width increases, the particular value characterizing the strength of metallicity decreases in oscillation. Vacancy-induced semiconductor to metal transition in AGNRs provides the theoretical direction for the application of graphene in the electrionic devices.
Photoluminescence properties of selenium nanocrystals on Si(100) substrate formed by rapid thermal annealing
Authors: Pan Shu-Wan  , Chen Song-Yan  , Zhou Bi  , Huang Wei  , Li Cheng  , Lai Hong-Kai  , Wang Jia-Xian  ,   College of Engineering, Huaqiao University, Quanzhou 362021, China;,   Department of Physics, Semiconductor photonics research center, Xiamen University, Xiamen 361005, China;,   Department of Physics and Electronic Information Engineering, Minjiang University, Fuzhou 350108, China
Published: December 2020

We have investigated the structure and photoluminescence (PL) properties of Se nanocrystals (NCs) obtained by rapid thermal annealing of a-Se films on Si substrate. The size of Se NCs in a trigonal phase increases linearly with increasing temperature. Moreover, three PL peaks located at 1.4, 1.7 and 1.83 eV are observed, which are attributed to the emission of defects in amorphous Se, donor-acceprter pair (DAP) recombination at the interface of amorphous Se and Se NCs, and interband transition of Se crystals, respectively.
Enhanced third harmonic generation by localized surface plasmon excitation
Authors: Zhu Hua  , Yan Zhen-Dong  , Zhan Peng  , Wang Zhen-Lin  ,   School of Physics, Nanjing University, Nanjing 210093, China
Published: December 2020

We experimentally achieved optical third harmonic generation (THG) from two-dimensional periodically arrayed gold-island films. The gold-island films were fabricated using micro-spherical lithography. By using a reflection-type optical system, these arrays can produce significant THG with the help of a spectrum-resolved femto-second laser. At the localized surface plasmon (LSP) excitation wavelength of the fundamental wave, THG is greatly enhanced due to the strong light localization effect. The radiation direction of THG satisfies the momentum matching condition.
Effect of interface energy anisotropy on the dendritic growth in directional solidification
Authors: Zhang Yun-Peng  , Lin Xin  , Wei Lei  , Peng Dong-Jian  , Wang Meng  , Huang Wei-Dong  ,   State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China;,   Beijing Hangxing Technology Development Co. Ltd., Beijing 100013, China
Published: December 2020

The dendritic growth patterns in directional solidification with different amplitudes of solid-liquid interface energy anisotropy were investigated using the two-dimensional cellular automata (CA) model. It is shown that when the preferred growth direction of the crystal was the same as the direction of thermal gradient, the solidification pattern would transform from seaweed to dendrite with the increase of amplitude of interface energy anisotropy. The amplitude of interface energy anisotropy could also influence the morphology of dendritic tips. As the amplitude of interface energy anisotropy increased, the dendritic tip radius, the liquid concentration ahead of the tip and the tip undercooling decreased. A power law relationship evisted between the stability parameter of dendritic tip and the amplitude of interface energy anisotropy in directional solidification. The primary arm spacing changed little with the increase of interface energy anisotropy. When the angle between the preferred growth direction of the crystals and the direction of thermal gradient was-40, and the amplitude of interface energy anisotropy increased, the solidification pattern would transform from seaweed to degenerated dendrite and finally to tilted dendrite.
Network controllability based on node overloaded failure
Authors: Xiao Yan-Dong  , Lao Song-Yang  , Hou Lü-Lin  , Bai Liang  ,   College of Information Systems and Management, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Liu and Barabasi applied the modern control theory to the network controllability of linear dynamical systems and proposed a method to calculate the minimal set of driver node which controls the states of all nodes in a linear time invariant complex network with any topology. The network controllability model solves the computable problems of the network controllability. Facing the problem of node overloaded failure in real networks, in the paper we investigate the model of network controllability based on node overloaded failure. Through the simulation of betweenness and Weibull failure model, the results demonstrate that the difficulty in maintaining the controllability of SF network is significantly greater than that of ER network. In the target failure mechanism, even if the failure signals input rarely to the networks, they can greatly increase the difficulty of network controllability. Besides, the node failure based high betweenness centrality is more efficient than failure based high degree on damaging network controllability, which indicates the nodes with high betweenness centrality play an important role in maintaining the network controllability. Furthermore, taking the reasonable measures for different load failure model can prevent the networks from inducing a step uncontrollable phenomenon.
Entransy dissiaption minimization for isothermal throttling process
Authors: Xia Shao-Jun  , Chen Lin-Gen  , Ge Yan-Lin  , Sun Feng-Rui  ,   Institute of Thermal Science and Power Engineering, Naval University of Engineering, Wuhan 430033, China;,   Military Key Laboratory for Naval Ship Power Engineering, Naval University of Engineering, Wuhan 430033, China;,   College of Power Engineering, Naval University of Engineering, Wuhan 430033, China
Published: December 2020

A class of isothermal throttling process with generalized mass transfer law is investigated, and the optimality condition for the minimum mass entransy dissipation of the process is obtained by applying optimal control theory. The results for special cases with mass transfer laws [g∝(Δp)m] and [g∝Δ(μ)] are further obtained based on the general optimization result, and the obtained results are also compared with other mass transfer strategies of the minimum entropy generation, constant pressure ratio and constant pressure difference. Numerical examples for the cases with the mass transfer laws [g∝(Δp)1/2], [g∝Δ(p)] and [g∝Δ(μ)] are also provided. The results obtained herein can provide some theoretical guidelines for the optimal design and operation of real throttling processes and devices.
Analysis statistical fluctuation of passive untrusted source for quantum key distribution system
Authors: Jiao Rong-Zhen  , Ding Tian  , Wang Wen-Ji  , Ma Hai-Qiang  ,   Science School, Beijing University of Post and Telecommunication, Beijing 100876, China
Published: December 2020

The performance of active decoy-state quantum key distribution (QKD) system with an untrusted source is compared with that of passive decoy-state QKD. The key generation rate with the change of the secure transmission distance is shown under the condition of active decoy-state (or passive decoy-state) QKD where we pick the data size to be N=1012. The security characteristics of the passive scheme are studied with statistical fluctuation of the counting rate and the intensity of the practical source. At communication wavelength 1310 nm or 1550 nm, The security range of communication distance is [73.2 km, 96.5 km] or [104.5 km, 137.9 km] respectively. This analysis will provide important theoretical parameters for practical QKD experiment.
Study on the weak sinusoidal signal detection property using Duffing chaos system
Authors: Fan Jian  , Zhao Wen-Li  , Wang Wan-Qiang  ,   School of Mechanical Engineering, Hebei University of Technology, Tianjin 300401, China;,   College of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou 310018, China;,   Department of Mechanical Engineering, Taizhou University, Taizhou 318000, China
Published: December 2020

Chaotic detection method can be used to pick out the weak sinusoidal signal submerged in noise. Three types of detection properties of this method are proposed in this paper, i.e., sharp change ability of phase diagram, maintenance zone of chaos, and the sufferance with noise of the chaos critical point. After analyzing the factors influencing these three properties, two different chaotic systems are compared according to the three properties.
Modified function projective synchronization for a class of partially linear fractional order chaotic systems
Authors: Yang Ye-Hong  , Xiao Jian  , Ma Zhen-Zhen  ,   College of Mathematics and Statistics, Chongqing University, Chongqing 401331, China
Published: December 2020

In this paper, a method of modified function projective synchronization for a class of partially linear fractional order chaotic systems is proposed. This kind of system can be constructed by single variable coupling response system. The modified function projective synchronization controller is designed by Routh-Hurwitz conditions. Theoretical analyses and numerical simulations of two chaotic systems verify the effectiveness of the proposed method.
Magnetic exchange force microscopy using ferromagnetic resonance
Authors: Xue Hui  , Ma Zong-Min  , Shi Yun-Bo  , Tang Jun  , Xue Chen-Yang  , Liu Jun  , Li Yan-Jun  ,   Key Laboratory of Instrumentation Science and Dynamic Measurement, North University of China, Ministry of Education, Taiyuan 030051, China;,   Department of Applied Physics, Osaka University, Suita, Yamada-Oka, Osaka 565-0871, Japan
Published: December 2020

Electron spin is very important for investigating magnetic properties of nano-structure surface on the atomic scale. Magnetic exchange force microscope (MExFM) which is a significant method of measuring exchange force of electron spin, is adopted. However, the external magnetic field is necessary for the MExFM, which will damage the structure of the sample surface; further, cross-talk between topography and spin information becomes serious for separating the two signals in MExFM measurement. These shortcomings will restrict the application of MExFM. In order to solve these problems, we develop a new method to separate the topography from the spin information using ferromagnetic resonance by microwave radiation combined MExFM and atomic force microscopy. We demonstrate that the topography and spin information can be completely separated from each other using this method theoretically and experimentally. MExFM using ferromagnetic resonance effect is very useful for developing spintronic devices and new-generation magnetic materials.
Energy transfer between WO42- groups and Eu3+ in CaWO4：Eu3+ phosphor
Authors: Liang Feng  , Hu Yi-Hua  , Chen Li  , Wang Xiao-Juan  ,   School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China
Published: December 2020

The pure CaWO4 and 1%Eu3+ doped CaWO4 phosphors are successfully prepared by the conventional solid state reaction method. The photoluminescence (PL) spectra, decay cures, and time-resolved PL spectra are measured at depend on different temperatures. Fluorescence spectra at room temperature (300 K) and low temperature (10 K) show that these two samples each have a broad band at about 430 nm, originating from the WO42- groups under 240 nm excitation, while the CaWO4:Eu3+sample exhibits the characteristic emission of Eu3+ corresponding to 5D0→7F1, 2, 3,4 transitions due to the absorbed energy transfer from WO42- groups to Eu3+ ions. And the red light at 616 nm of CaWO4: Eu3+ can be excited efficiently by UV (395 nm) and blue (465 nm) light. The decay curves at 300 K illustrate that the lifetime of WO42- group in pure CaWO4 is about 8.85 s but is shortened to 6.27 μs after Eu3+ions have been doped, which is a further good evidence for demonstrating the existence of WO42-–Eu3+ energy transfer process. The energy transfer efficiency (ηET)) and rate (ωET) between WO42- and Eu3+in CaWO4: 1%Eu3+ are 29.2% and 4:65×104 s-1 respectively, when T = 300 K. The energy transfer process is studied in detail by the time-resolved PL spectra, and the lifetime for the appearance of Eu3+ emission in CaWO4 decreases monotonically as temperature increases from 10 K to 300 K. The temperature dependence of luminescence decay time is performed and the results indicated that the lifetime of Eu3+ increases in a temperature range of 10-50 K, when the temperature is more than 50 K, thermal quenching of Eu3+ begins and the lifetime is shortened. However, the lifetime of WO42- reduces constantly with the increase of temperature.
Influence of screening effect on double differential cross section and single differential cross section for (e, 2e) process of helium
Authors: Yang Huan  , Xing Ling-Ling  , Zhang Sui-Meng  , Wu Xing-Ju  , Yuan Hao  ,   The Center of Basic Experiment, West Anhui University, Liu’an 237012, China;,   School of Mechanism and Electrical Engineering, West Anhui University, Liu’an 237012, China;,   Institute of Atomic and Molecular Physics, School of Materials and Chemical Engineering, West Anhui University, Liu’an 237012, China
Published: December 2020

The double differential cross sections for electron impact single ionization of helium at incident energies of 32.5, 36.5 and 40.7 eV are calculated by using the DS3C model. The calculated results are compared with the experimental date. The exchange effects are discussed. The single differential cross section for electron impact single ionization of helium is obtained by integrating the double differential cross sections over the angle of the ejected electron. The single differential cross sections of helium at incident energies of 32.5, 36.5, 40.7 and 50 eV are calculated by using the 3C model and the DS3C model. The calculated results are compared with the experimental date. The structure of the cross section is analysed and the contribution of exchange effect to the corss section is discussed.
Experimental studies of the surface plasmon polaritons waveguide filter in microwave band
Authors: Wang Wu-Song  , Zhang Li-Wei  , Ran Jia  , Zhang Ye-Wen  ,   MOE Key Laboratory of Advanced Micro-structure Materials, Department of Physics, Tongji University, Shanghai 200092, China;,   School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000, China;,   Department of Electrical Engineering, Tongji University, Shanghai 200092, China
Published: December 2020

Based on theoretical analysis, in this paper studied are the low pass and band stop filter effects of the μ-negative materials/double positive materials/μ-negative materials (MNG-DPS-MNG) surface plasmon polaritons waveguide with branch defect. The research results show that the defect is equivalent to a sub wavelength resonator. The central frequency of the band stop filter is determined by the resonator length and it is independent of the position where the resonator is located in the MNG region. The transmission dips of the waveguide are closely related to the coupling distance. So the filter characteristics of the surface plasmon polariton waveguide can be adjusted by changing the resonator length and number and the coupling distance. The experimental results are in good agreement with simulation results. These properties will have potential application value in the tunable single channel or multi-channel band stop filters.
Coherent diffractive imaging based on the multiple beam illumination with cross grating
Authors: Liu Cheng  , Pan Xing-Chen  , Zhu Jian-Qiang  ,   Joint Laboratory on High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800, China
Published: December 2020

A single shot PIE (ptychographic imaging engine) imaging method is proposed to overcome the disadvantages of common PIE algorithm. In this proposed method, a multiple beam illumination obtained with a cross grating is used to illuminate the object studied, and a CCD camera is adopted to record the diffraction pattern array of all the illumination beams simultaneously. The phase and the modulus images of the object can be faithfully reconstructed with stand PIE computation algorithm from the recorded data.
The role of intensity fluctuations in thermal ghost imaging
Authors: Liu Xue-Feng  , Yao Xu-Ri  , Li Ming-Fei  , Yu Wen-Kai  , Chen Xi-Hao  , Sun Zhi-Bin  , Wu Ling-An  , Zhai Guang-Jie  ,   Laboratory of Space Science Experiment Technology, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, China;,   Laboratory of Optical Physics, Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China;,   College of Physics, Liaoning University, Shenyang 110036, China
Published: December 2020

The quality of the image in ghost imaging with thermal light is of great importance in practical applications. Through theoretical analysis and simulation, we find that the intensity fluctuations of the field can greatly influence the visibility of thermal ghost imaging. According to this, we suggest a new scheme to improve the visibility by appropriately scaling the intensity and variance of the incident thermal field. The influence of this method on the signal-to-noise ratio is also studied. In addition, comparison is made with the high-order correlation ghost imaging, another means adopted in recent years to increase the visibility. Our analysis should help promote our understanding of thermal ghost imaging.
Analysis of unified unsymmetric lateral coupled-mode theory of optical waveguide
Authors: Pei Li  , Zhao Rui-Feng  ,   Key Laboratory of All Optical Network and Advanced Telecommunication Network, Ministry of Education, Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

Lateral coupled-mode theory of optical waveguide includes orthogonal coupled-mode theory and nonorthogonal coupled-mode theory. However, the two kinds of coupled-mode theories do not have unified analytical solutions. And they both do not deal with the asymmetric coupling power of unmatched-coupled waveguides deeply. On the one hand, a new kind of nonorthogonal coupled-mode equation is derived from the Helmholtz wave equation in this paper. And both of the orthogonal coupled-mode equations and the nonorthogonal coupled-mode equations are processed and solved uniformly. As a result, a unified solution is obtained. On the other hand, the asymmetric coupling power of unmatched-coupled waveguides is studied in detail, based on the obtained solution. The calculated results show that both of the maximum mutual-coupling power and the minimum self-coupling power can be approximated by the unified solution.
Robust adaptive beamforming based on semi-definite programming and rank-one decomposition
Authors: Wang Yan  , Wu Wen-Feng  , Fan Zhan  , Liang Guo-Long  ,   Science and Technology On Underwater Acoustic Laboratory, Harbin Engineering University, Harbin 150001, China
Published: December 2020

The performance of Capon beamformer degrades sharply in the presence of array steering vector mismatch. To solve this problem, a robust beamforming algorithm based on semi-definite programming and rank-one decomposition is proposed, which improves the robustness of the adaptive beamforming by estimating an actual steering vector. The constraints for estimating the steering vector are deduced under the requirement that the estimate does not weaken the ability to suppress interference and noise, and the analysis shows that the approach to formulating constraint using matrix pre-filter is reasonable. The optimization problem is constructed and converted into a semi-definite relaxation problem, and rank-one decomposition technique is adopted in order to obtain the optimal solution. The simulation results demonstrate that compared with the existing algorithms, the proposed algorithm offers high SINR (signal to interference plus noise power ratio) and accuracy of power estimation, with the sole prior information about the angular vector in which the actual signal lies.
Effects of size polydispersity on mechanical and geometrical properties of granular system
Authors: Feng Xu  , Zhang Guo-Hua  , Sun Qi-Cheng  ,   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

In this paper, the multi-disperse systems composed of 2048 frictionless particles with different size polydispersities are simulated by using the distinct element method, and effects of size polydispersity on mechanical and geometrical properties of these systems are studied under isotropic confining. The result shows that changing polydispersity can qualitatively affect the coordination number, shear modulus, static structure factor and orientational order correlation function, but it does not influence the cumulative force distribution. At small wave number k, static structure factor of mono-disperse systems shows the power scaling law S(k)∝0.2k-4/3. Moreover, the peak of orientational order correlation function exhibits an exponent scaling law g6 (r)∝ae-r/ξ6, and the scaling exponent ξ6 decreases with polydispersity increasing.
Observation and analysis of drop impact on wetted spherical surfaces with low velocity
Authors: Liang Gang-Tao  , Guo Ya-Li  , Shen Sheng-Qiang  ,   School of Energy and Power Engineering, Dalian University of Technology, Key Laboratory for Desalination of Liaoning Province, Dalian 116024, China
Published: December 2020

The phenomenon of liquid drop impact on wetted spherical surfaces with low impact velocity is observed using a high speed digital camera at 10000 frames per second. Drop rebound, partial rebound and spreading are observed and analyzed, considering the effect of viscosity. Influences of the sphere diameter, impact velocity and viscosity on the spreading characteristic parameter are discussed quantitatively. The experimental observations show that the drop rebound and partial rebound phenomena may occur at large viscosity and low impact velocity, which cannot be observed at small viscosity. The spreading area can be increased by increasing impact velocity. The results also reveal that the spreading factor increases with viscosity decreasing. At the sphere diameters ranging from 4 mm to 20 mm, it is found that with the increase of the sphere diameter, the spreading factor will be increased.
Molecular dynamics simulation study of polyimide/copper-nanoparticle composites
Authors: Sun Wei-Feng  , Wang Xuan  ,   Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Heilongjiang Provincial Key Laboratory of Dielectric Engineering, School of Electrical and Electronic Engineering, Harbin University of Science and Technology, Harbin 150080, China
Published: December 2020

Molecular dynamics simulations of polyimide/copper-nanoparticle composites are implemented to calculate the morphological structures, thermodynamic and mechanical properties, and to investigate their relationships with the nanoparticle dimension and simulation temperature. The results demonstrate that polyimide/copper-nanoparticle composites are of isotropic amorphous structures, in which the copper nanoparticles combine with polyimide matrix due to van der Waals effect and multi-layers of atoms on nanoparticle surface change into amorphous configurations, forming interface layers between them. The interface regions shrink and expand respectively with increased nanoparticle dimension and temperature. The polyimide/copper-nanoparticle composites exhibit the explicit increase of isometric heat capacity with larger nanoparticle dimension in moderated temperature dependence, resulting in lower heat capacities at relatively low temperature for nanocomposites with relatively small nanoparticle size, compared with polyimide system. The thermal pressure coefficients of polyimide/copper-nanoparticle composites are distinctly higher than those of polyimide system, and increase substantially with enlarged nanoparticle dimension and reduce slightly with elevated temperature. The thermodynamic properties of polyimide/copper-nanoparticle composites manifest obvious scale-effect and distinctly higher temperature stability than polyimide system. The mechanical properties of polyimide/copper-nanoparticle composites represent isotropic elastic constant tensors with distinctly lower Young modulus and Poisson ratio than those of polyimide system, which decrease and increase respectively with increasing simulation temperature, exactly contrary to polyimide system and with substantially higher temperature stability of Young modulus. The composites with larger nanoparticle dimension exhibit considerably higher Poisson ratio with slight change of Young modulus, indicating the remarkably different mechanical properties of new nanocomposites with Cu nanoparticle filler.
Electrical properties of single ZnO nanobelt in low temperature
Authors: Li Ming-Jie  , Gao Hong  , Li Jiang-Lu  , Wen Jing  , Li Kai  , Zhang Wei-Guang  ,   Department of Physics, School of Physics and Electronic Engineering, Harbin Normal University, Ministry of Education Key Laboratory for Photoelectric Bandgap Materials, Harbin 150025, China
Published: December 2020

ZnO nanobelts are synthesized using chemical vapors deposition method on silica substrate. The average width of the nanobelts is ～1 μm and the length is dozens of micron. Single ZnO nanobelt device is assembled using the micro-grid template method. The current-voltage characteristics are linear and the resistance and resistivity of the ZnO nanobelt are calculated to be ～3 MΩ and ～0.4 Ω·cm at room temperature, respectively. It is found that there are two different conduction mechanisms through the single ZnO nanobelt, according to the temperature dependence of the resistance of the single ZnO nanobelt at 20-280 K. In the higher temperature range (130-280 K) the thermally activated conduction is dominant. However, as the temperature comes down (<130 K), the nearest-neighbor hopping conduction mechanism instead of the thermally activated conduction turns into the dominant conduction mechanism through the single ZnO nanobelt.
Synthesis of gem diamond crystals by multiseed method using China-type cubic high-pressure apparatus
Authors: Hu Mei-Hua  , Bi Ning  , Li Shang-Sheng  , Su Tai-Chao  , Li Xiao-Lei  , Hu Qiang  , Jia Xiao-Peng  , Ma Hong-An  ,   School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China;,   School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000, China;,   State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China
Published: December 2020

In this paper, gem diamond synthesis is systematically studied using the multiseed method in China-type cubic high-pressure apparatus. High-quality Ib diamond crystals are synthesized in a growth cell with 3-5 diamond seeds, by adjusting the growth cell assembly and investigating the pressure and temperature regions of diamond synthesis. Because of several diamond seeds embedded in a growth cell, the synthesized diamond crystals possess the same morphology and quality. At the same time, the whole growth rate increases apparently. Using the multiseed method of diamond synthesis the growth cell volume can be effectively utilized, the efficiency of diamond synthesis can be enhanced, and the problem of low utilization rate is solved. Meanwhile, those also provide an effective support for the gem diamond industrialization synthesis.
Study on transmission characteristics of matching transformer in DC superconducting quantum interference device readout
Authors: Liu Ming  , Xu Xiao-Feng  , Wang Yong-Liang  , Zeng Jia  , Li Hua  , Qiu Yang  , Zhang Shu-Lin  , Zhang Guo-Feng  , Kong Xiang-Yan  , Xie Xiao-Ming  ,   State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China;,   Electronic Science and Technology Department, University of Science and Technology of China, Hefei 230027, China
Published: December 2020

In a magnetic flux modulated DC superconducting quantum interference device (SQUID) readout, the matching transformer could realize the function of signal amplification and impedance matching, which is the key element of a low noise SQUID readout. We use a simulated DC SQUID readout to test the characteristics of matching transformer, study the transmission characteristics of transformer with different turns, and confirm its best turn ratio. In the coupling network that the transformer picks up voltage signals of SQUID, We also study the transmission characteristics of transformers with different matching capacitances, realize the matching of the parameters and the optimization in the transformer coupling network. At room temperature, for the matching transformer with a turn ratio of 1:20, when matching capacitance is 1 μF, the gain of output voltage source could reach 21.2 and its bandwidth could reach 210 kHz. Finally, in magnetic flux modulation DC SQUID readout, we evaluate the performance of the matching transformer.
The multi-parameter observation of lightning M changes in northeastern part of the Qinghai-Tibet Plateau
Authors: Wu Bin  , Zhang Guang-Shu  , Wang Yan-Hui  , Li Ya-Jun  , Fan Xiang-Peng  , Yu Hai  , Zhang Rong  ,   Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Science, Lanzhou 730000, China;,   Guizhou Lightning Protection and Disaster Reduction Center, Guiyang 550002, China
Published: December 2020

The M change characteristics in continuing current process of negative cloud-to-ground lightning discharge and artificially triggering lightning discharge are comparatively analyzed using the synchronous data of optical channel high-speed video camera pictures, electric field changes on ground and the peak very high frequency radiation. The results indicate that M process could be identified accurately from synchronous data of optical channel luminance and electric field changes on ground. There are lots of rapid changes of electric field (MP) prior to and during classic M change. And the M changes caused by lots of MP changes. There is mostly no difference in waveform characteristics between M changes and K changes and their generated physical mechanisms are similar. MP change is a rapid change of electric field corresponding to the rapid flow of charge caused by the breakdown process in the stage of continuous current process and accompanied with channel sudden brightening and high intensity radiation. Most of the M changes are unipolar, positive or negative and a few are irregular and last within 0.1 ms. Only M change in close lightning discharge exhibits a classic U-shaped structure because of its waveform mostly caused by static electric field, and its duration is about from 0.2 to 0.8 ms. MP and K changes are all caused by the breakdown. The difference between MP and K changes is that the electric charges flow into the original return stroke channel in the process of MP change, but not in the process of K change.
Work done by a periodical external force on an overdamped harmonic oscillator with frequency fluctuation and energetic stochastic resonance
Authors: Zhang Liang-Ying  , Cao Li  , Wu Da-Jin  ,   School of Physics and Electronic Engineering, Xiangfan University, Xiangyang 441053, China
Published: December 2020

Characterization of the work done by a periodic external force on an overdamped harmonic oscillator with frequency fluctuation is studied. Results indicate that the instantaneous power with periodic variations of time shows asymmetry. It is also revealed that the work done by a periodic external force on the system in one period with the variation of multiplicative noise intensity exhibits non-monotonic behavior. Whether the system shows the coexistence of energetic stochastic resonance and suppression or not is determined by the sign of the correlation coefficient between the multiplicative noise and the additive noise.
The reliability of logical operation in a one-dimensional bistable system induced by non-Gaussian noise
Authors: Jin Xiao-Qin  , Xu Yong  , Zhang Hui-Qing  ,   Department of Applied Mathematics, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

Using success probability as a measure of logical stochastic resonance, we mainly studied the phenomenon of logical stochastic resonance (LSR) in a one-dimensional bistable system induced by non-Gaussian noise in this paper. And we explained the cause of this phenomenon via the method of the mean first-passage time. Results show that the resonance peak of the success probability can be achieved only when in an appropriate range of noise intensity or correlation time. Through an optimization of system parameters, we have improved the reliability of realizing logic operation in the system.
Laser-induced chlorophyll fluorescence lifetime measurement and characteristic analysis
Authors: Wan Wen-Bo  , Hua Deng-Xin  , Le Jing  , Liu Mei-Xia  , Cao Ning  ,   School of Mechanical and Precision Instrument Engineering, Xi’an University of Technology, Xi’an 710048, China
Published: December 2020

A laser-induced fluorescence lifetime measurement method is presented to evaluate living status for plant growth and the environmental monitoring. A 355 nm laser is used as excitation source for exciting chlorophyll fluorescence, and the fluorescence signals are received by a photomultiplier. Because the measured signal is the convolution of the reliable fluorescence decay signals, laser pulse and instrument response function, according to their characteristics, the time-resolved measurement method is used to estimate the chlorophyll fluorescence and background signals separately; the real fluorescence decay signals are separated by combining a novel deconvolution method, and the chlorophyll fluorescence lifetime can be retrieved. Experiment shows that the method proves to be a high accuracy and real-time monitoring chlorophyll fluorescence lifetime technique; and the chlorophyll solution fluorescence lifetime is measured for different concentrations. The result can prove that the chlorophyll concentration is related to its fluorescence lifetime, and the calibration curves of chlorophyll concentration and fluorescence lifetime is fitted.