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Near-field 3D imaging approach combining MJSR and FGG-NUFFT

Journal of Systems Engineering and Electronics 2019年第6期30卷 1096-1109页

作者： WANG Shuzhen FANG Yang ZHANG Jin’gang LUO Mingshi LI qing School of Computer Science and Technology Xidian UniversityXi’an 710071China School of Electronics and Information Northwestern Polytechnical UniversityXi’an 710072China Institute of Optics and Electronics Chinese Academy of SciencesChengdu 610209China College of Materials Sciences and Opto-Electronic Technology University of Chinese Academy of SciencesBeijing 100049China College of Computer Science Xi’an Shiyou UniversityXi’an 710065China The Fourth Research Institute of Telecommunications Technology Co. LtdXi’an 710061China

A near-field three-dimensional(3 D)imaging method combining multichannel joint sparse recovery(MJSR)and fast Gaussian gridding nonuniform fast Fourier transform(FGGNUFFT)is proposed,based on a perfect combination of the compressed sensing(CS)theory and the matched filtering(MF)*** approach has the advantages of high precision and high efficiency:multichannel joint sparse constraint is adopted to improve the problem that the images recovered by the single channel imaging algorithms do not necessarily share the same positions of the scattering centers;the CS dictionary is constructed by combining MF and FGG-NUFFT,so as to improve the imaging efficiency and memory ***,a near-field 3 D imaging model of joint sparse recovery is constructed by combining the MF-based imaging ***,FGG-NUFFT and reverse FGG-NUFFT are used to replace the interpolation and Fourier transform in MF-based imaging methods,and a sensing matrix with high precision and high efficiency is constructed according to the traditional imaging ***,a fast imaging recovery is performed by using the improved separable surrogate functionals(SSF)optimization algorithm,only with matrix and vector ***,a 3 D imagery of the near-field target is obtained by using both the horizontal and the pitching interferometric phase *** paper contains two imaging models,the only difference is the sub-aperture method used in inverse synthetic aperture radar(ISAR)*** to traditional CS-based imaging methods,the proposed method includes both forward transform and inverse transform in each iteration,which improves the quality of *** experimental results show that,the proposed method improves the imaging accuracy by about O(10),accelerates the imaging speed by five times and reduces the memory usage by about O(10~2).

关键词： interference imaging joint sparse recovery compressed sensing(CS) matching filtering(MF) fast Gaussian gridding nonuniform fast Fourier transform(NUFFT) near-field 3D imaging

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Enhanced EVD based channel estimation and pilot decontamination for Massive MIMO networks

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The Journal of China Universities of Posts and Telecommunications 2015年第6期22卷 72-77页

作者： Guo Mangqing Xie gang Gao Jinchun Liu yuan'an Beijing Key Laboratory of Work Safety Intelligent Monitoring Beijing University of Posts and Telecommunications Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications

The enhanced eigenvalue decomposition （EEVD） based channel estimation algorithm, which could solve the pilot contamination problem in massive multiple-input and multiple-output （Massive MIMO） channel estimation when the number of antennas at base stations （NABT） tends to infinity, is proposed in this paper. The algorithm is based on the close relationship between covariance matrix of received pilot signal and the channel fast fading coefficient matrix, i.e. the latter is the eigenvector matrix of the former when NABT tends to infinity. Therefore, we can get a set of normalized base vectors from the eigenvalue decomposition （EVD） of sample covariance matrix in practical Massive MIMO networks. By multiplying the received pilot signal with conjugate transpose of normalized base vector matrix, the channel matrix is projected to a lower dimensional matrix, and the intra-cell and inter-cell interference can be eliminated completely when NABT tends to infinity. Thus, we only need to estimate the lower dimensional projected matrix during the channel estimation. Simulation results show that the mean square error （MSE） performance of channel estimation is improved with approximately two orders of magnitude when the signal-to-noise ratio （SNR） is 40 dB, compared with EVD based channel estimation algorithm. And the signal-to-interference ratio （SIR） is improved greatly as well. The increment of SIR becomes larger and larger as SNR increasing.

关键词： channel estimation eigenvalue decomposition (EVD) Massive MIMO pilot contamination

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Effect of Structure Parameters on Power and Magnetic Field in Electromagnetic Soft-Contact Continuous Casting System

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Journal of Iron and Steel Research International 2008年第1期15卷 19-24页

作者： DENG An-yuan WANG En-gang HE Ji-cheng Key Laboratory of National Education Ministry for Electromagnetic Processing of Materials Northeastern UniversityShenyang 110004 Liaoning China

To design a power source system and mold for electromagnetic soft-contact continuous casting process and to theoretically estimate the heat losses from the charges and the system power, the effect of structure parameters on system power and magnetic flux density distribution was calculated using finite element method. The results show that as for electromagnetic soft-contact continuous casting system with partial-segment type mold, the power consumption is much more than that with a full-segment type mold; about 62% of electric power is dissipated in the mold, and the effective acting range of magnetic field is relatively narrow. Optimizing mold structure is a crucial measure of remarkably reducing mold power consumption and saving electric energy. Increasing slit number, width, and length can remarkably increase the magnetic flux density in the mold and can reduce the electric energy consumption. Among structure parameters, slit number and slit width are relatively more effective to reduce energy consumption. For a round billet electromagnetic continuous casting system with diameter of 178 ram, the reasonable slit number, width, and length are about 24--32, 0. 5--1.0 mm, and 160 mm, respectively.

关键词： continuous casting soft-contact mold electromagnetic field electric power structure parameter

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Global Optimization Method for Linear Multiplicative Programming

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Acta Mathematicae Applicatae Sinica 2015年第2期31卷 325-334页

作者： Xue-gang ZHOU Bing-yuan CAO Kun WU School of Mathematics and Information Science Key Laboratory of Mathematics and Interdisciplinary Sciences of Guangdong Higher Education Institutes Guangzhou University Department of Applied Mathematics Guangdong University of Finance School of Mathematical Science and Computing Technology Center South University

In this paper, a new global algorithm is presented to globally solve the linear multiplicative programming（LMP）. The problem（LMP） is firstly converted into an equivalent programming problem（LMP（H））by introducing p auxiliary variables. Then by exploiting structure of（LMP（H））, a linear relaxation programming（LP（H）） of（LMP（H）） is obtained with a problem（LMP） reduced to a sequence of linear programming problems. The algorithm is used to compute the lower bounds called the branch and bound search by solving linear relaxation programming problems（LP（H））. The proposed algorithm is proven that it is convergent to the global minimum through the solutions of a series of linear programming problems. Some examples are given to illustrate the feasibility of the proposed algorithm.

关键词： linear multiplicative programming global optimization linear programming branch and bound

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The spiral structure of the Milky Way

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Research in Astronomy and Astrophysics 2018年第12期18卷 9-28页

作者： Ye Xu Li-gang Hou yuan-Wei Wu Purple Mountain Observatory Chinese Academy of Sciences CAS Key Laboratory of FAST National Astronomical Observatories Chinese Academy of Sciences National Astronomical Observatories Chinese Academy of Sciences National Time Service Center Key Laboratory of Precise Positioning and Timing Technology Chinese Academy of Sciences

The morphology and kinematics of the spiral structure of the Milky Way are long-standing problems in *** this review we firstly summarize various methods with different tracers used to solve this *** astrometry of Galactic sources is gradually alleviating this difficult situation caused mainly by large distance uncertainties, as we can currently obtain accurate parallaxes(a few μas) and proper motions(≈1 km s-1) by using Very Long Baseline Interferometry(VLBI).On the other hand, the Gaia mission is providing the largest, uniform sample of parallaxes for O-type stars in the entire Milky *** upon the VLBI maser and Gaia O-star parallax measurements, nearby spiral structures of the Perseus, Local, Sagittarius and Scutum Arms are determined in unprecedented ***, we estimate fundamental Galactic parameters of the distance to the Galactic center,R0, to be 8.35 ± 0.18 kpc, and circular rotation speed at the Sun, Θ0, to be 240±10 km *** found kinematic differences between O stars and interstellar masers: the O stars, on average, rotate faster,>8 km s-1than maser-traced high-mass star forming regions.

关键词： Galaxy:structure Galaxy:kinematics and dynamics masers techniques:high angular resolution astrometry stars:formation

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Influence of semisolid forging ratio on the microstructure and mechanical properties of Ti14 alloy

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International Journal of Minerals,Metallurgy and Materials 2013年第3期20卷 266-272页

作者： Yong-nan Chen gang Liu Xue-min Zhang Yong-qing Zhao State Key Laboratory for Mechanical Behavior of Material Xi'an Jiaotong University School of Materials Science and Engineering Chang'an University Northwest Institute for Nonferrous Metal Research

The present work is focused on the microstructure and mechanical properties of Ti14 alloy with different semisolid deformation ratios during forging tests. The results revealed that the forging ratio had a significant effect on the precipitation of the alloy. Fewer plate-shaped Ti2Cu tended to precipitate on grain boundaries with higher forging ratios, and finally the plate-shaped Ti2Cu formed precipitate-free zones along grain boundaries with a forging ratio of 75%. The precipitation on grain boundaries was found to be controlled by a peritectic reaction. Large forging ratios accelerated the extrusion of liquid and resulted in less liquid along the prior grain boundaries, which reduced the peritectic precipitation in this region and formed precipitate-free zones during re-solidification. In addition, increasing the forging ratio could accelerate dynamic recrystallization, which is favorable for improving the semisolid formability. The tensile ductility increased with increasing forging ratio, and a mixed fracture mode, involving both cleavage and dimple fracture, was observed after forging with a forging ratio of 75%, which along grain boundaries during semisolid processing. is attributed to the presence of precipitate-free zones formed

关键词： titanium alloys semisolid forging microstructure precipitates mechanical properties

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High-temperature fracture behavior of MnS inclusions based on GTN model

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Journal of Iron and Steel Research International 2019年第9期26卷 941-952页

作者： Xin-gang Liu Can Wang qing-feng Deng Bao-feng Guo Key Laboratory of Advanced Forging and Stamping Technology and Science (Yanshan University) Ministry of Education of ChinaQinhuangdao 066004HebeiChina

The influence of the MnS plastic inclusion on the accumulation of internal damage was considered, and the Gurson– Tvergaard–Needleman (GTN) model was calibrated based on the finite element inverse method and image analysis method using ABAQUS and GTN models. The modified GTN damage model was used to simulate the initiation and propagation of cracks in an as-cast 304 stainless steel with MnS inclusions at 900 C. The simulation results agreed well with the experimental results, indicating that the model can be effectively applied to examine the high-temperature fracture behavior of MnS inclusions. The simulation and high-temperature tensile test results revealed that MnS inclusions increased the number of holes initiation and the probability of hole polymerization, reduced the crack propagation resistance, accelerated the occurrence of material fracture behavior, and were closely related to the stress state at high temperatures. When the stress triaxiality was low, the plastic strain in the metal matrix was high, and the MnS plastic inclusions accelerated the polymerization of the pores, making metal fracture failure more likely. On the other hand, when the stress triaxiality was high, the stress state in the metal matrix was biased to the tensile state, the plastic strain in the metal matrix was low, and the influence of MnS plastic inclusions on the fracture behavior was not evident.

关键词： MnS inclusion GTN model Tension High-temperature fracture behavior Crack initiation Crack propagation Stress

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Transformation character of ferrite formation by a ledge mechanism under a mixed-control model

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International Journal of Minerals,Metallurgy and Materials 2012年第5期19卷 428-433页

作者： Zhen-qing Liu Zhi-gang Yang Zhao-dong Li Chi Zhang Key Laboratory of Advanced Materials Department of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

A mixed-control model was developed to study the transformation character of ferrite formation by a ledge mechanism. A nu- merical two-dimensional diffusion-field model was combined to describe the evolution of the diffusion field ahead of the migrating austenite/ferrite interface. The calculation results show that the bulk diffusion-controlled model leads to a deviation from experimental results under large solute supersaturation. In the mixed-control model, solute supersaturation and a parameter Z together determine the transformation character, which is quantified by the normalized concentration of carbon in austenite at the austenite/ferfite interface. By comparing with experimental data, thepre-exponential factor of interface mobility, M0, is estimated within the range from 0.10 to 0.60 mol-m·J^-1·s^-1 for the alloys with 0.1 lwt%-0.49wt% C at 700-740℃. For a certain Fe-C alloy, the trend of the transformation character relies on the magnitude of M0 as the transformation temperature decreases.

关键词： iron carbon alloys modeling ferrite ledge mechanism diffusion interfaces

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High-temperature corrosion of Sn-Bi-Zn-Ga alloys as heat transfer fluid

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Rare Metals 2021年第8期40卷 2221-2229页

作者： qing-Meng Wang Xiao-Min Cheng yuan-yuan Li Guo-Ming Yu Zhi Liu School of Materials Science and Engineering Wuhan University of TechnologyWuhan430070China School of Mechanical and Electrical Engineering Huanggang Normal UniversityHuanggang438000China

The new heat transfer alloy is highly reactive at high temperatures,and the corrosion of the container material determines the service life of the heat transfer *** high-temperature corrosion of Sn-Bi-Zn-Ga alloys as heat transfer fluid was *** microstructure and elemental distribution were studied by field emission scanning electron microscopy(FESEM)and energy dispersive spectroscopy(EDS).The thermal properties before and after corrosion were studied by differential scanning calorimetry(DSC).The results show that the corrosion kinetics of the studied materials follows the parabolic law and the thermal properties after corrosion are *** significantly improves the thermal conductivity.316 stainless steel exhibits excellent corrosion resistance due to its high Cr and Ni *** mechanism analysis shows that the oxidation of Ga has a smaller Gibbs free energy,and an oxide forms at the corrosion interface to prevent dissolution corrosion and oxidative corrosion of the container material.

关键词： Sn-Bi-Zn-Ga Heat transfer fluids Thermophysical properties High-temperature corrosion

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Regional changes in extreme heat events in China under stabilized 1.5℃ and 2.0℃ global warming

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Advances in Climate Change Research 2020年第3期11卷 198-209页

作者： ZHANG Gu-Wei ZENG gang Vedaste IYAKAREMYE YOU qing-Long Key Laboratory of Meteorological Disaster of Ministry of Education(KLME) Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)Nanjing University of Information Science and TechnologyNanjing210044China Department of Atmospheric and Oceanic Sciences Institute of Atmospheric SciencesFudan UniversityShanghai200433China

Extreme heat events(EHEs)have a significant impact on the social economy and human *** is a country with a large population and diverse terrain,and it is necessary to project future extreme heat changes in the *** study used a specially designed dataset,the Community Earth System Model(CESM)simulations,namely CESM low-warming,to investigate the EHEs in China under 1.5℃ and 2.0℃ global *** results indicate that the regional mean warming over China will exceed the global average,about 1.63℃ and 2.24℃ in 1.5℃ and 2.0℃ warmer *** to the present-day(1976–2005),the frequency and duration of the EHEs in South China are projected to increase the most among the *** example,the frequency of EHEs in South China at 1.5℃ and 2.0℃ warming will exceed 3 and 3.5 times the present-day ***,when global warming rises from 1.5℃ to 2.0℃,the increased impacts relative to the 1.5℃ warming level will be the lowest in South China(less than 40%),and the highest increased impacts are projected to appear in Northeast China(53%-84%)and Northwest China(53%–107%).The main reason for this situation is that compared with the 1.5℃ scenario,the upper zonal westerly in northern China weakens and the continental high pressure enhances under the 2.0℃ ***,limiting global warming at 1.5℃ instead of 2.0℃ is beneficial for eliminating extreme heat events,especially for Northeast China and Northwest China.

关键词： China Regional changes Extreme heat events 1.5℃and 2.0℃global warming CESM low-warming

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