bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple speckle patterns differential compressive ghost imaging
Authors: Zhong Ya-Jun  , Liu Jiao  , Liang Wen-Qiang  , Zhao Sheng-Mei  ,   Institute of Signal Processing and Transmission, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
Published: December 2020

Equipment requirement, quality of reconstructed image, and reconstruction time are important factors in the realization of thermal-light ghost imaging system. In this paper, we propose a new ghost imaging scheme with multiple speckle patterns, named multiple speckle patterns differential compressive ghost imaging scheme. In this scheme, the high temporal resolution requirements for detectors is reduced by continuously detecting multiple independent speckle patterns. We eliminate the background and other noises in ghost imaging system by using differential ghost imaging method. And the reconstruction time is effectively reduced simultaneously to improve the reconstructed image quality by introducing the compressive sensing techniques. Numerical results show that for the two-level grayscale “N” image, the mean square error, in using the proposed scheme with 8000 measurements, is reduced by 96.9%, and the peak signal to noise ratio has improved by 15.1 dB, in comparison with those using the original multiple speckle patterns ghost imaging scheme with 35000 measurements. For the eight-level grayscale “Pepper” image, the peak signal to noise ratio is enhanced by 11.4 dB. The proposed scheme also can decrease the requirements of detection equipment to improve the image quality, and reduce the reconstruction time. Therefore, it may have a broad application prospect.
Laser diode double-end-direct-pumped slab laser with hybrid resonator
Authors: Mao Ye-Fei  , Zhang Heng-Li  , Xu Liu  , Deng Bo  , Sang Si-Han  , He Jing-Liang  , Xing Ji-Chuan  , Xin Jian-Guo  , Jiang Yi  ,   School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, China;,   Institute of Crystal Materials, Shandong University, Jinan 250100, China
Published: December 2020

To reduce the influence of thermal lensing and attain the high power laser with high beam quality, a laser diode stack dual-end-direct-pumped Nd:YVO4 slab laser with negative branch confocal folded hybrid cavity has been developed. Its maximum output power is 416 W, optical conversion efficiency is 54.3%, and slope efficiency is 61.6%. When the output laser power is 370 W, M2 values in the unstable resonator direction and stable resonator direction are 3.9 and 4.7, respectively.
Quantitative analysis of flow structures in compression ramp based on flow visualization
Authors: Wu Yu  , Yi Shi-He  , He Lin  , Quan Peng-Cheng  , Zhu Yang-Zhu  ,   College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Flow visualization studies on the laminar boundary layer flows over a 25° compression ramp are carried out via NPLS technique in a Mach 3.0 wind tunnel; fine flow structures such as boundary layer, shear layer, and shock waves may be visualized clearly. Based on the visualized data, quantitative analysis is conducted using intermittency, spatial correlations, and fractal theory. The intermittency function γ of the boundary layer and the interaction region is calculated, and the size of coherent structures and the structure angle θ for the boundary layer are obtained, so that the fractal dimension of the boundary layer in streamwise can be provided. Experimental data in the present paper have been compared with the results of Ringuette and Bookey, and the quantitative characteristics of flow structures are discussed in detail.
Study of laser action in dye-doped polymer dispersed cholesteric liquid crystal film
Authors: Dai Qin  , Wu Jie  , Wu Xiao-Jiao  , Wu Ri-Na  , Peng Zeng-Hui  , Li Da-Yu  ,   School of Science, Shenyang Ligong University, Shenyang 110159, China;,   State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
Published: December 2020

In this work, laser dye DCM, nematic liquid crystal TEB30A, chiral dopant S-811 and PVA are used to prepare polymer dispersed cholesteric liquid crystal (LC) films by the method of microcapsule. Lasing mechanism and temperature-tunable characteristics of the films are investigated. The diameters of large droplets in the films are about 80 μm and LC molecules are planar-textured in the droplets when viewed between crossed polarisers through a polarization microscope. Pumped by the 532 nm Nd:YAG laser, narrow linewidths in laser emissions are obtained at 634.5 nm and 680.2 nm, and the linewidths are of 0.25 nm and 0.29 nm, respectively. The device is then compared with a dye-doped cholesteric liquid crystal laser. The wavelength of output laser will blueshift when the temperature of the device is increased, and a 22.8 nm tunable lasing, from 666.7 nm to 643.9 nm, is obtained. Analysis concludes that the lasing mechanism of the film is band-edge lasing, and the emission wavelengths are corresponding to the two edges of the photonic band gap.
Synthesis and characterization of flower-like MoS2 microspheres by hydrothermal method
Authors: Fu Chong-Yuan  , Xing Song  , Shen Tao  , Tai Bo  , Dong Qian-Min  , Shu Hai-Bo  , Liang Pei  ,   College of Optical and Electronic Technology, China Jiliang University, Hangzhou 310018, China
Published: December 2020

High-purity flower-like MoS2 microspheres have been successfully synthesized by hydrothermal method using Na2MoO4 and CH3CSNH2 as precursors, and H4O40SiW12 as an additive. Samples are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). XRD and EDS patterns show that the as-prepared samples are MoS2, which have good crystallinity with a well-stacked layered structure. SEM images show that the as-prepared MoS2 are composed of flower-like microspheres with a mean diameter about 300 nm, the structures of which are constructed from dozens of hundreds of MoS2 nano-sheet with a thickness of several nanometers. It is also found that the silicotungstic acid plays an important role in the formation of the flower-like MoS2 microspheres, which could affect the size and morphology of the MoS2. Flower-like MoS2 is not found in the as-prepared product without adding silicotungstic acid. A formation mechanism of MoS2 microspheres is tentatively given.
Molecular dynamics study on the phase transition of high density helium
Authors: Zhang Bao-Ling  , Song Xiao-Yong  , Hou Qing  , Wang Jun  ,   North China University of Water Resources and Electric Power, Zhengzhou 450045, China;,   Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, China
Published: December 2020

The melting curve of helium has been calculated over the temperature range of 0–1000 K using molecular dynamics method. Comparisons of the calculated melting curve and the experimental data show that the consistence between the melting curve and the experimental data may reach 500 K. When the temperature is above 600 K, no reliable experimental data have been found for comparison. In addition, the pressures inside the helium bubbles of various sizes existing in metal titanium are calculated and have a comparison with the melting curve. Results show that, at low temperatures, the helium bubbles may be in solid state as the temperature decreases. When the temperature is above 300 K, no solid helium bubble may exist.
Simulation of precipitate splitting in an alloy (Ⅱ): Elastic energy collapse
Authors: Liu Lei  , Chen Zheng  , Wang Yong-Xin  ,   State Key Laboratory of Solidification Processing, Northwesten Polytechnical University, Xi'an 710072, China;,   School of Materal Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

The phenomenon of elastic energy collapse (EEC) accompanying the variation of the structure and temperature during the growth of a nucleus is discovered while we study the precipitate splitting in an alloy. There are two ways to introduce the EEC, one is the instantaneous elastic energy collapse (IEEC) and the other is the gradual elastic energy collapse (GEEC). Simulation shows that whether the precipitate is splitted is related to the time when EEC emerges, and that the kind of splitting of the precipitate depends on the rate of EEC. For IEEC, if it is introduced when the diameter of a nucleus reaches about 80l–90l (l=12.18 nm) the precipitate is splitted to 4 blocks. For GEEC, if it is intoduced when the time is larger than τ = 7.5× 103 s, the precipitate is splitted to 2 blocks.
Study on surface relief related to reverse martensitic transformation in Mn-based high-temperature antiferromagnetic shape memory alloy
Authors: Yuan Feng  , Liu Chuan  , Geng Zheng  , Cui Yan-Guang  , Wang Lin  , Wan Jian-Feng  , Zhang Ji-Hua  , Rong Yong-Hua  ,   School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, China
Published: December 2020

Evolution of surface relief and its intrinsic mechanism associated with martensitic transformation (MT) during heating and cooling in Mn79.5Fe15.6Cu4.9 high-temperature antiferromagnetic shape memory alloy (SMA) have been investigated in nano-scale by means of in-situ atomic force microscopy (AFM), X-ray diffraction (XRD), and dynamic mechanical analyzer (DMA). Experimental results show that the N-type surface relief originates from the reverse MT and is completely made of matrix which is different from the conventional ones. The reverse MT exhibits untwinning shear and the reverse shearing of twinned martensites mainly contribute to the surface relief. The measured surface relief angles are less than 1°, which are determined by the small difference of lattice constants between fcc and fct structures. Surface relief has a good recovery property because of the crystallographic reversibility rule in SMAs, implying that this kind of alloy has a good surface morphology memory effect.
Study on cation distribution and magnetic moment of Ti ions in spinel ferrites Ni1-xTixFe2O4
Authors: Xu Jing  , Qi Wei-Hua  , Ji Deng-Hui  , Li Zhuang-Zhi  , Tang Gui-De  , Zhang Xiao-Yun  , Shang Zhi-Feng  , Lang Li-Li  ,   Hebei Advanced Thin Film Laboratory, Department of Physics, Hebei Normal University, Shijiazhuang 050024, China;,   School of Science, Hebei University of Engineering, Handan 050038, China;,   Department of Physics and Electronic Science, Liupanshui Normal University, Liupanshui 553004, China
Published: December 2020

Spinel ferrite samples TixNi1-xFe2O4 (x=0, 0.1, 0.2, 0.3, 0.4) were prepared using conventional solid reaction method. The sample exhibit a single-phase cubic spinel structure with a space group obtained Fd3m. The lattice parameter a increases with the increase of Ti doping level x. But the specific saturation magnetizations, σs, gradually decrease with increasing Ti doping level x at 10 K and 300 K. It is interesting that when the doping level x≥0.2, two transition temperatures, TL and TN, are found: when the temperature is lower than TN, the magnetization is obviously decreased, while at the temperature TL, dσ/d T reaches a maximum value. This phenomenon indicates that an additional antiferromagnetic structure arises in the traditional spinel phase of ferrites which results from Ti doping, that Ti ions will show the form of Ti3+ and Ti2+ cations which have magnetic moments, and that the magnetic moments of the Ti cations are opposite to those of the Fe and Ni cations. The dependence of the magnetic moments of the samples on the Ti doping level x at 10 K was fitted successfully using the quantum-mechanical potential barrier model proposed earlier by our group. In the fitting process, the distributions of Ti, Ni and Fe cations in the samples are obtained. It is found that 80% of the Ti cations will occupy the [B] sites in Ti2+ form.
Photoluminescence properties and energy transfer from Ce3+ to Mn2+ in Na2SrMg(PO4)2
Authors: Xiong Xiao-Bo  , Yuan Xi-Ming  , Liu Jin-Cun  , Song Jiang-Qi  ,   Engineering Research Center of Nano-Geomaterials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, China;,   Hubei Key Laboratory of Forensic Science, Laboratory Center, Hubei University of Police, Wuhan 430034, China
Published: December 2020

Na2SrMg(PO4)2: Ce3+, Mn2+ phosphor was prepared by high temperature solid state reaction. Its luminescence properties and energy transfer from Ce3+ to Mn2+ were investigated. The emission bands of Ce3+ and Mn2+peaking at 334 nm and 617 nm were attributed to 5d→4f transition of Ce3+ and 4T1(4G)→6A1(6S) transition of Mn2+, respectively. Dependence of Ce3+ and Mn2+ luminescence properties on their concentrations was investigated as well. With the increase of Mn2+ content, the emission intensity of Ce3+ could be observed to decrease, however, the emission intensity of Mn2+ was found to increase. It is indicated that the luminescence of Mn2+ could be sensitized by energy transfer from Ce3+ to Mn2+ in Na2SrMg(PO4)2 host. According to the Dexter's energy transfer formula of multipolar interaction, it is demonstrated that the energy transfer between Ce3+ and Mn2+ is due to the electric dipole-quadripole interaction of the resonance transfer.
Cellular automaton simulation of the molten pool of laser solid forming process
Authors: Wei Lei  , Lin Xin  , Wang Meng  , Huang Wei-Dong  ,   School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an 710072, China;,   State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

A two-dimensional multiscale model is presented for simulating laser melting process, which is the same as laser solid forming (LSF) without the addition of metallic powders into the molten pool. The metallurgical process in molten pool is simulated, including the temperature distribution, the pool shape, and the solidification microstructure. The shape of the molten pool and the microstructure in Fe-C single crystal substrate at a laser scanning speed of 15 mm/s is simulated. Results reveal the instability from planar interface to cell\ dendrite morphologies in the molten pool. At the bottom of the molten pool, the growth morphology is planar interface, which is also called bonding zone. Epitaxial dendrite arrays can be seen to grow above the bonding zone.
Increase in light extraction efficiency of vertical light emitting diodes by a photo-electro-chemical etching method
Authors: Gong Zhi-Na  , Yun Feng  , Ding Wen  , Zhang Ye  , Guo Mao-Feng  , Liu Shuo  , Huang Ya-Ping  , Liu Hao  , Wang Shuai  , Feng Lun-Gang  , Wang Jiang-Teng  ,   Shaanxi Provincial Key Laboratory of Photonics & Information Technology, Key Laboratory of Physical Electronics and Devices of Ministry of Education, 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

The rate of photo-electro-chemical (PEC) etching on N-polar n-GaN using vertical light emitting diodes (V-LEDs) has been investigated in detail, by varying the etching parameters (etchant concentration, etching duration and light intensity). V-LED with optimal hexagonal pyramid structure (the side-wall angle is 31°) has been fabricated, and then the influence of the PEC etching on the electrical and optical properties of V-LED has been analyzed. After PEC etching, the sample has good ohmic contact with the electrode and has lower contact resistance than a reference sample. The electrical characteristics have a better improvement. And the light output power has improved obviously after PEC etching, which shows 86.1% enhancement at 20 mA. Effect of side-wall angle of the pyramids on light extraction efficiency (LEE) in V-LEDs is theoretically calculated by finite difference time domain (FDTD) method. Simulation results show that the LEE is significantly increased for the sidewall angle between 20° and 40°, and the maximum enhancement is realized at a side-wall angle of 23.6° (the total reflection angle at the GaN/air interface).
Leveraging neighborhood “structural holes” to identifying key spreaders in social networks
Authors: Su Xiao-Ping  , Song Yu-Rong  ,   School of Computer and Software Engineering, Nanjing Institute of Industry Technology, Nanjing 210046, China;,   College of Automation, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
Published: December 2020

The identifying of influential nodes in large-scale complex networks is an important issue in optimizing network structure and enhancing robustness of a system. To measure the role of nodes, classic methods can help identify influential nodes, but they have some limitations to social networks. Local metric is simple but it can only take into account the neighbor size, and the topological connections among the neighbors are neglected, so it can not reflect the interaction between the nodes. The global metrics is difficult to use in large social networks because of the high computational complexity. Meanwhile, in the classic methods, the unique community characteristics of the social networks are not considered. To make a trade off between affections and efficiency, a local structural centrality measure is proposed which is based on nodes' a nd their ‘neighbors’ structural holes. Both the node degree and “bridge” property are reflected in computing node constraint index. SIR (Susceptible-Infected-Recovered) model is used to evaluate the ability to spread nodes. Simulations of four real networks show that our method can rank the capability of spreading nodes more accurately than other metrics. This algorithm has strong robustness when the network is subjected to sybil attacks.
New complexion two-soliton solutions of a class of nonlinear evolution equation
Authors: Taogetusang  , Yi Li-Na  ,   The College of Mathematical Science, Inner Mongolia Normal University, Huhhot 010022, China
Published: December 2020

New infinite sequence complexion two-soliton solutions of a kind of nonlinear evolution equation are constructed with the help of function transformations and two kinds of elliptic equations. Step one，according to two function transformations, a kind of nonlinear evolution equation is changed into a nonlinear ordinary differential equation of second order. Step two, using function transformation, the nonlinear ordinary differential equation of second order is transformed into a set of nonlinear ordinary differential equations of first order, and the first integral of the set of equations is obtained. Finally, the first integral with new solutions and Bäcklund transformation of two kinds of elliptic equations are used to search for new infinite sequence complexion two-soliton solutions of a kind of nonlinear evolution equation.
Stochastic resonance of an underdamped linear harmonic oscillator with fluctuating mass and fluctuating frequency
Authors: Zhong Su-Chuan  , Yu Tao  , Zhang Lu  , Ma Hong  ,   College of Aeronautics and Astronautics, Sichuan University, Chengdu 610064, China;,   College of Mathematics, Sichuan University, Chengdu 610064, China
Published: December 2020

When Brownian particle moves in a viscoelastic medium, the surrounding molecules not only collide with the Brownian particle but also adhere to the Brownian particle randomly, thereby changing the mass of the Brownian particle. We investigate the stochastic resonance phenomenon in an underdamped linear harmonic oscillator with fluctuating mass and fluctuating frequency under an external periodic force. The exact expressions of the first moment and the amplitude of the output signal are obtained by using the Shapiro-Loginov formula and the Laplace transform technique. We establish the necessary and sufficient conditions for the emergence of the stochastic resonance phenomenon induced by the mass fluctuation noise intensity and frequency fluctuation noise intensity. Furthermore, based on the necessary and sufficient conditions, the output amplitude shows a non-monotonic dependence on the noise intensity, which means that the stochastic resonance phenomenon happens.
Stochastic resonance of asymmetric bistable system with α stable noise
Authors: Jiao Shang-Bin  , Yang Rong  , Zhang Qing  , Xie Guo  ,   Faculty of Automation and Information Engineering, Xi'an University of Technology, Xi'an 710048, China
Published: December 2020

In this paper we take the asymmetric bistable system excited by weak periodic signal as a model and regard signal-to-noise ratio gain as an index to investigate the stochastic resonance phenomenon stimulated by additive and multiplicative α stable noise. Stochastic resonance phenomenon stimulated by only additive α stable noise is also investigated here. The laws for the resonance system parameters a, b, asymmetric skewness r and intensity amplification factor Q or D of α stable noise to act on the resonant output are explored under different stability index α and skewness parameter β of α stable noise. The results show that no matter whether under the joint action of additive and multiplicative α stable noise or under the action of only additive α stable noise, weak signal detection can be realized by tuning the system parameters a, b and r. The intervals of a, b and r which can induce stochastic resonances are multiple, and do not change with α nor β. Moreover, when investigating the noise-induced stochastic resonance, it is found that stochastic resonance can also be realized by tuning the intensity amplification factor of α stable noise. And the interval of D does not change with α nor β. The results will contribute to a reasonable selection of parameter-induced stochastic resonance system parameters and noise intensity of noise-induced stochastic resonance under α stable noise.
Spectral interferometry based absolute distance measurement using frequency comb
Authors: Wu Han-Zhong  , Cao Shi-Ying  , Zhang Fu-Min  , Qu Xing-Hua  ,   State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China;,   Division of Time and Frequency Metrology, National Institute of Metrology, Beijing 100013, China
Published: December 2020

Spectral interferometry using frequency comb has become a powerful approach to absolute distance measurement. In this paper, we analyze the principle of spectral interferometry in detail. With the consideration of dispersion, pulse chirp and the power ratio of the reference pulse and the measurement pulse, we develop a Gaussian model, which can be used to determine distances. The frequency of the spectral interference fringe is of key importance. The distances can be directly determined by the frequency of the spectral interference fringe through one-step fast Fourier transform with no filters during the data processing. The simulation results show that the maximum deviation is 1.5 nm when the distance is 1.5 mm theoretically. The comb consists of hundreds of thousands of teeth in the spectral domain, and each tooth can be regarded as a cw laser. We propose a method based on the phases of two close modes. The principle is introduced, and the maximum deviation is 8.7 nm with a distance of 1.5 mm while the minimum deviation is 0.3 nm corresponding to distance of 0.5 mm. We theoretically show that the linear pulse chirp can be used for distance measurement. The measurement principle is analyzed, and the simulation shows that the maximum deviation is 5.3 nm when the distance is 1.2 mm.
Investigation on the influences of linear chirp with different input pulse intensities on BaF2 cross-polarized wave generation
Authors: Li Gang  , Liu Hong-Jie  , Lu Feng  , Wen Xian-Lun  , He Ying-Ling  , Zhang Fa-Qiang  , Dai Zeng-Hai  ,   Science and Technology on Plasma Physics Laboratory, Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Cross-polarized wave (XPW) generation based on BaF2 crystal is one of the most important tools in improving the contrast of ultra-intense femtosecond laser pulses at present. In this paper, the influences of linear chirp with different input pulse intensities on BaF2 XPW generation, including conversion efficiency, spectrum broadening, and pulse duration reduction are in detail simulated and discussed. Especially, the influence of linear chirp on spectrum broadening is comparatively investigated under unsaturated and intense input pulses. While the amount of spectrum broadening relative to linear chirp is symmetrical with respect to the zero chirp point under unsaturated input pulse, the results show that it is no longer those in the case under intense input pulse, and the intrinsic reason is explained in detail in this paper.
A blending crossover differential evolution approach to camera space manipulation parameter optimization
Authors: Xie Yu  , Zhao Chun-Xia  , Zhang Hao-Feng  , Yan Xue-Jun  , Chen De-Bao  ,   School of Computer Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China;,   School of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000, China
Published: December 2020

A blending crossover differential evolution algorithm is proposed to increase the precision of camera-space manipulation (CSM) system. In this approach, six view parameters and flattening parameter are assembled into a single parameter of blending crossover differential evolution; the positioning precision of camera-space manipulation is set to be a fitness function.The CSM system can obtain the optimal parameter combination by evolutionary iteration.Experimental results of a virtual robot system show the robot positioning precision is improved by blending crossover differential evolution algorithm.
Spontaneous evolution of Cs 47D Rydberg atoms at different fine levels
Authors: Duan Jun-Yi  , Wang Yong  , Zhang Lin-Jie  , Zhao Jian-Ming  , Li Chang-Yong  , Jia Suo-Tang
Published: December 2020

The spontaneous evolution from Rydberg atoms in different fine states to plasmas is investigated. Two-photon excitation is used to excite ultracold cesium atoms from 6S1/2 to 47D3/2 and 47D5/2 Rydberg states, respectively. The ramp electric field is used to ionize the Rydberg atoms and drive the ions to the micro-channel plate detector. In this experiment, The atom number of 47D5/2 state, which has a high oscillator strength compared with 47D3/2, is about 7 times larger than that of 47D3/2 state. Based on the different initial atom numbers of two fine states, the evolutions of plasma and Rydberg atoms are observed. The initial ionization time of Rydberg atoms and avalanche ionization rate of different states are presented. The initial ionization of Rydberg atoms is ascribed to the combining effect of state transfer from repulsive interaction to attractive interaction induced by the blackbody radiation and superradiation and Rydberg atoms collision. Moreover, the avalanche ionization and production of plasma are explained as being due to the rapid collision between Rydberg atoms and electrons in a local potential trap produced by positive ions.
Electromagnetic scattering characteristics of double S-shape exhaust nozzle with different coating medium parts
Authors: Gao Xiang  , Shi Yong-Qiang  , Yang Qing-Zhen  , Chen Li-Hai  ,   School of Power and Engergy, Northwestern Polytechnical University, Xi'an 710072, China;,   No.94638 PLA, Nanchang 330201, China
Published: December 2020

As one of the strong electromagnetic scattering source of the aircraft, the radar cross section (RCS) of the nozzle can be reduced by the special geometry and coating microwave absorbing material at the backward direction of the aircraft. In order to simulate the radar scattering characteristics of six coating models and one metal surface model of double S-shape nozzle, the mode combining impedance boundary condition with iterative physical optics (IPO) method is built. Forward and back-forward IPO method and open MP, MPI parallel computing technology are added to accelerate the convergence and reduce computational time. Besides, the ray tracing method is also adopted to improve the efficiency of geometric blanking judgment. The RCS variation regulations of 7 models under X waveband are obtained. The results indicate that coating medium can effectively diminish the RCS of double S-shape exhaust system. Proper coating method can not only reduce the RCS of exhaust system significantly, but also be economical, easy to coat and light-weight. Compared with all parts coating medium model, the model which is only coated at nozzle outlet can reduce microwave absorbing material cost by 73.6% and ensure that the maximal increment of RCS is less than 15.6%. Comparing with the metal model case, The RCS will decrease by at least 18.5%. The improved IPO method can be applied to the RCS evaluation of cavity and the study of coating absorbing material method, and provide technical support for the coating medium model experiment.
Propagation evolution of the off-axis ellipse vector beam
Authors: Li Yang  , Zhu Zhu-Qing  , Wang Xiao-Lei  , Gong Li-Ping  , Feng Shao-Tong  , Nie Shou-Ping  ,   Key Laboratory of Optoelectronic Technology of Jiangsu Province, School of Physical Science and Technology, Nanjing Normal University, Nanjing 210023, China;,   Key Laboratory of Optical Information Science and Technology of Ministry of Education, Institute of Modern Optics, Nankai University, Tianjin 300071, China
Published: December 2020

The propagation characteristics of the off-axis ellipse vector beam (OEVB) are studied in this paper. The analytic expressions of the electric field and the intensity after OEVB propagating in free-space are derived. Numerical results indicate that the intensity distribution of OEVB is asymmetric and the intensity distribution after propagating is determined by propagation distance, dislocation displacement and ellipticity. In addition to expanding, the intensity distribution of OEVB tends to steady-state distribution finally and the dark core of vector beam disappears gradually during propagation. The major axis and minor axis of the ellipse intensity distribution in the steady-state are exchanged with each other as compared with in the initial plane. The results can help us to understand the dynamic propagation characteristics of the ellipse vector beam under the off-axis situation, and they can also guide the calibration of the ellipse vector beam in practice.
A closed-loop aberration compensating method of optics system based on holography
Authors: Tang Yan-Qiu  , Sun Qiang  , Zhao Jian  , Yao Kai-Nan  ,   Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   University of China Academy of Sciences, Beijing 100049, China
Published: December 2020

We propose a holographic adaptive optics system based on holographic wavefront sensor and 21-element deformable mirror, and analyze the wavefront correction ability of the system in this paper. The principle of holographic wavefront sensor is described, and its numerical model is provided by fast Fourier transform algorithm in the thin hologram approximation. Then, the wavefront correction ability of 21-element deformable mirror is analyzed with its numerical model. Finally, the aberration compensation of the system is simulated and an experimental device is set up to verify the feasibility of the proposed adaptive optics system.
Progress in gain-guided and index-antiguided large mode area fiber laser pump technology
Authors: Shen Xiao  , Zou Hui  , Zheng Rui-Lin  , Zheng Jia-Jin  , Wei Wei  ,   College of opto-electronic engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
Published: December 2020

In this paper, we introduce a new type of gain guided and index antiguided (GG-IAG) large mode area (LMA) fiber structure, basic theory and its important applications in fiber laser fields. We draw a conclusion that the side pump technology is the most appropriate scheme for GG-IAG LMA fiber after comprehensively analyzing the laser output characteristics and the thermal effect of the fiber under different pump conditions. The theoretical simulations of GG-IAG fiber side pump technology and the side pump experiment process are performed by the V groove technology, which is conducible to the experiment research in relevant fields. Finally, the suggestion of how to reduce the difference between the experimental results and the theoretical results is made and its relevant reason is also discussed.
Stochastic multi-resonance of the single-mode laser system driven by the noise with periodic force modulation
Authors: Zhang Rui-Fang  , Cheng Qing-Hua  , Xu Da-Hai  ,   School of Physics Science and Technology, Yangtze University, Jingzhou 434023, China;,   Research Center for Applied Physics and Information Technology, Yangtze University, Jingzhou 434023, China
Published: December 2020

Using the linear approximation method, we calculate the intensity correlation function and the output signal-tonoise ratio (SNR) by adding a modulated wave to light intensity equation of a single mode laser system driven by the periodic force of modulating noise. Through the numerical calculation and analysis of the SNR, we find that the lowfrequency modulation frequency Ω, the high-frequency carrier frequency ω, and the frequency of periodic force Ωλ have a significant effect on the SNR. In particular, multi-peak stochastic resonances and strong single-peak resonance with low-frequency modulation frequency Ω appear in the SNR. When Ω ω, the system exhibits multi-peak resonance and the distance between the resonance peaks increases with the increase of Ωλ, but the position of peak is invariant. When Ω → ω, the output SNR R increases rapidly, the effect of Ωλ becomes weak or negligible, and multi-peak resonance disappears. When Ω = ω, a strong single-peak resonance appears in the system. In addition, the SNR varies with the decrease of amplitude of the multi-peak stochastic resonance, and with the SNR changes with carrier frequency the single-peak stochastic resonance appears in the system.
Experimental research of boresight error correction using returning signals from the illuminated targets through atmosphere
Authors: Tan Yi  , Geng Chao  , Li Xin-Yang  , Luo Wen  , Luo Qi  ,   Key Laboratory on Adaptive Optics, Chinese Academy of Sciences, Chengdu 610209, China;,   Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The relationship between boresight error and returning signal from the illuminated target is studied theoretically. The operating principle of a new-style adaptive-optics device, which is named adaptive fiber-optics collimator with the abilities to correct both laser beam transmission error and pointing error, is introduced. The laser beam pointing experimental setup with a laser propagation distance of 200 m through horizontal atmosphere is established. Based on returning signals from the illuminated two-dimensional and three-dimensional targets, the beam pointing closed loop using stochastic parallel gradient descent algorithm (SPGD) algorithm is achieved under different initial boresight errors. The experimental results indicate that the evaluation parameters of the residual boresight errors are less than 6% and 10.8% for the two-dimensional target and three-dimensional target, respectively, which are within the tolerance of theoretical analysis. Finally, the influence of SPGD parameter on moving-target pointing is analyzed.
Influence factors of quantitative analysis precision of greenhouse gases and carbon isotope ratio based on infrared spectroscopy
Authors: Li Xiang-Xian  , Xu Liang  , Gao Min-Guang  , Tong Jing-Jing  , Feng Ming-Chun  , Liu Jian-Guo  , Liu Wen-Qing  ,   Key Laboratory of Environment Optics and Technology, Chinese Academy of Sciences National Engineering Research Center for Environment Optical Monitoring Instrument, Hefei 230031, China
Published: December 2020

The quantitative analysis based on Fourier transform infrared (FTIR) technology is affected by the temperature and pressure properties of gas and the H2O cross section, so the applications of FTIR technology to high-precision measurement area of the greenhouse gases and isotope ratio are restricted. Firstly, the methods of correcting the gas property sensitivities and H2O cross sensitivity are studied, then the standard gas measurements are corrected with these sensitivity correcting functions established through experimental study. The standard deviations of CO, CO2, N2O, CH4 and δ13CO2 are all improved after correcting the sensitivities, and reduced by 1.80-3.38 times. These studies are significant for the applications of FTIR technology to the high-precision measurement area of greenhouse gases and isotope ratio.
Analysis of ionizing and department damage mechanism in proton-irradiation-induced scientific charge-coupled device
Authors: Wen Lin  , Li Yu-Dong  , Guo Qi  , Ren Di-Yuan  , Wang Bo  , Maria  ,   Key Laboratory of Functional Materials and Devices for Special Environments of CAS; Xinjiang Key Laboratory of Electronic Information Materials and Devices; Xinjiang Technical Institute of Physics and Chemistry of CAS, Urumqi 830011, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

A sort of homemade buried scientific charge-coupled device (CCD) is injected by 10 MeV protons, and measurements are carried out primarily on change of dark signal, charge transfer efficiency. Results show that parameters of CCD presented significantly decrease. Post-irradiation annealing is implemented and the results revel that CCD parameters recover to different extents. In this paper, analysed are the mechanism for the decrease of CCD parameters, and their dependences on process and structure in manufacture. The results above will provide helpful reference in characterization evaluation and technique development of future CCD.
Ultrasonic enhancement of the porosity of alginate scaffold
Authors: Lu Lu  , Ji Hong-Fei  , Guo Ge-Pu  , Guo Xia-Sheng  , Tu Juan  , Qiu Yuan-Yuan  , Zhang Dong  ,   Key Laboratory of Modern Acoustics (Nanjing University), Ministry of Education, Institute of Acoustics, Nanjing 210093, China;,   Department of Electronic Information, Nantong University, Nantong 226019, China;,   State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100080, China
Published: December 2020

Alginate scaffold with a three-dimensional (3D) porous structure can provide sufficient space for the cell to adhere, and has a good biocompatibility and mechanical strength. In this work, low-intensity pulsed ultrasound (LIPUS) is used to enhance the porosity of alginate scaffold based on acoustic cavitation. In the experiment, the alginate-calcium-based 3D scaffold culture system is fabricated with an optimum CaCl2/sodium alginate ratio of 3:5. The mechanical properties of alginate scaffold are measured and scanning electron microscopy is used to analyze the porosity of the scaffold. In addition, the microscopy observation of green fluorescent protein expression and the CCk-8 assessment are adapted to analyze the cell proliferation effect. Experimental results show that with LIPUS treatment under appropriate driving parameters (acoustic pressure 0.055 MPa and treatment time 20 min), the porosity of the 3D scaffold can be significantly improved, which would benefit the cell growth in the scaffold.
Influences of sound speed profile on the source localization of different depths
Authors: Su Lin  , Ma Li  , Song Wen-Hua  , Guo Sheng-Ming  , Lu Li-Cheng  ,   Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China;,   Key Laboratory of Underwater Acoustics Environment, Beijing 100190, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

It is found in the data processing of matched filed source localization experiment that in the case of the slight mismatch of sound speed profile, the louder source below disappears while the weaker source above comes out. Based on the experimental phenomenon, the influences of the sound speed profile on the source localization of different depths are investigated. Firstly, the simulation is conducted in order to extract the influence of the uncertain factors in the sea test, from which it is further concluded that the deeper source is greatly affected. Then another simulation about the mismatch of the depth of the thermocline is conducted in the typical shallow-water negative gradient environment, from which a preliminary conclusion is drawn that the most sensitive depth to the mismatch of the sound speed profile is around 10 meters below the lower boundary thermocline. Finally, this pheonomenon is reasonably explained through a theoretical analysis from two aspects of the normal mode theory.
A geometric calibration mehtod of hydrophone array with known sources in near field under strong multipath
Authors: Wang Yan  , Zou Nan  , Liang Guo-Long  ,   Science and Technology on Underwater Acoustic Laboratory, Harbin Engineering University, Harbin 150001, China;,   College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China
Published: December 2020

In order to meet the demand of underwater acoustic array calibration in near field with strong reflection, a high-precision geometric calibration method with known sources is proposed. Colligating the principles of non-plane wave model of point source and the Taylor approximation, a two-dimensional geometry error model for near field is established. And then the line mapping relationship is obtained between geometric error of sensors and signal eigen vector. Cramer-Rao bound (CRB) of this mode is deduced and analyzed. The influence of multipath on geometric calibration is studied. The strong reflections are compared to the coherent sources at a known position, and the compensation strategy is realized. The results from theory and simulation show that the precision of geometry calibration technique with accessorial sources in near field is high and it is close to the CRB in the case of low SNR. The method has a certain tolerance for the position error of accessorial sources. And it is applicable for multipath. Pool test results further verify the correctness of these results.
On the accuracy and robustness of a new flux splitting method
Authors: Xie Wen-Jia  , Li Hua  , Pan Sha  , Tian Zheng-Yu  ,   College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

The high speed flow problems usually involve complex flow phenomena, such as strong shock waves, shock-shock interactions, and shear layers. Prediction of these problems requires robust, efficient and accurate numerical methods. A robust flux splitting method capable of capturing crisp shock profile and exact contact surface is presented. Here, the flux vector of the Euler equation is split into convective and pressure parts according to the Toro's formulation. The accuracy of the numerical method at the contact discontinuity is examined first. Sufficient conditions of shock stability for this new method are obtained through a linear perturbation analysis. Several carefully chosen test problems are numerically investigated, and the numerical results demonstrate the accuracy and robustness of the proposed scheme.
Numerical simulation of natural convection of square enclosure filled with Cu/Al2O3-water mixed nanofluid based on lattice Boltzmann method
Authors: Qi Cong  , He Guang-Yan  , Li Yi-Min  , He Yu-Rong  ,   School of Electric Power Engineering, China University of Mining and Technology, Xuzhou 221116, China;,   School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

As an effective heat transfer medium, Nanofluid is used widely in heat transfer field. However, due to the contradiction between the heat conductivity coefficient of nanofluid and the cost of nanoparticles, a new mixed nanofluid is developed. In order to investigate the natural convection heat transfer characteristics and the interaction mechanism between nanoparticles, the lattice Boltzmann equations of nanofluid flow and temperature fields are deduced by multi-scale technique based on considering the interaction forces between nanoparticles, and the lattice Boltzmann model of Cu/Al2O3-water mixed nanofluid is established by coupling the evolution equations of flow with temperature fields. Nanoparticles distribution in enclosure and interaction forces between nanoparticles are investigated, it is found that Brownian motion force is far bigger than any other forces, and the effects of temperature difference driving force and Brownian motion force on nanoparticles distribution are biggest. In addition, the effects of nanoparticles fractions and Rayleigh number on natural convection are investigated, and the natural convection heat transfer characteristics of mixed nanofluid (Cu/Al2O3-water) are compared with those of single metal nanoparticle nanofluid (Al2O3-water). It is found that the mixed nanofluid has a higher heat transfer characteristic than other common nanofluid.
Irradiation effect of deuterium or hydrogen on Cr/W mixed transitional layers prepared by double ion beam deposition
Authors: Feng Hong-Li  , Gou Cheng-Ling  , Yu Jian-Gang  , Han Wen-Jia  , Chen Zhe  , Cai Ya-Nan  , Zhu Kai-Gui  ,   School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191, China
Published: December 2020

Cr films with different thickness values on W substrates are prepared by double-ion-beam-deposition(DIBD) method. The deep distributions of Cr and W are analyzed by energy dispersive spectrometer. Hydrogen and deuterium irradiation of high energy and low flux are carried out in heavy ion accelerator. The changes of the sample surface morphology are analyzed by scanning electron microscopy. The injection range of hydrogen particles in double layers of Cr/W is simulated by simulation software SRIM. The experimental results demonstrate that a Cr/W mixture transitional layer is formed at the interface between Cr and W using DIBD method; hydrogen and deuterium of high energy and low flux tend to be retained in the Cr/W mixture transitional layer and form gas bubbles, while the Cr film is not easy to retain enough hydrogen or deuterium to form gas bubbles.