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SAR motion compensation based on the correction of residual attitude errors

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Science China(Physics,Mechanics & Astronomy) 2011年第10期54卷 1899-1905页

作者： NI Chong wang yanfei XU XiangHui ZHOU ChangYi Beijing Institute of Spacecraft System Engineering Beijing 100094 China Institute of Electronics Chinese Academy of Sciences Beijing 100190 China

As residual attitude errors are likely to affect the synthetic aperture radar (SAR) imaging, this paper presents a SAR motioncompensation algorithm based on the correction of residual attitude errors. The existing methods all use the antenna stableplatform to correct the attitude errors, and then compensate the trajectory deviations in the following imaging process. Besidescompensating the trajectory deviations, the modified method of this paper also considers the influence of residual attitude er-rors on the SAR imaging, and can compensate both the trajectory deviations and the residual attitude errors. Compared withthe existing methods, the modified method in this paper can more precisely compensate the imperfect motion on the SAR im-aging, especially good for the SAR system with a small platform, near operating distance and a narrow antenna beam. Such asystem causes severe residual attitude errors and needs to consider the influence of antenna beam pointing errors on the imag-ing. The validity of the modified method presented by this paper is demonstrated by the result of the experiment.

关键词： synthetic aperture radar residual attitude errors motion compensation

Diagnostic and modelling investigation on the ion acceleration and plasma throttling effects in a dualemitter hollow cathode micro-thruster

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Chinese Journal of Aeronautics 2021年第12期34卷 85-98页

作者： Zhongxi NING Chenguang LIU Ximing ZHU yanfei wang Bingjian AN Daren YU Plasma Propulsion Laboratory Harbin Institute of TechnologyHarbin 150001China

Hollow cathode discharges are widely used as neutralizers for the electric propulsion systems and recently developed into micro-thrusters for the small *** this work,a dualemitter hollow cathode thruster is developed,which can be operated in two different modes—the neutralizer mode and the micro-thruster *** characterizing this kind of new device,the Langmuir probe,Faraday probe,and retarding potential analyzer are used to determine the electron temperature,electron density,ion flux,and ion energy distribution *** operating parameters,including the thrust,and specific impulse,are also measured.A two-dimensional self-consistent extended fluid model is employed to calculate the spatial distribution of plasma parameters and the fluid field of electrons in the region around the *** comparing the diagnostic and modelling results,it is found that the change in the electric field and ionization zone is the essential reason for the different performances of the device in the neutralizer and micro-thruster *** in the electric field leads to an ion acceleration effect in the micro-thruster mode;moving of the ionization zone raises the plasma pressure in the orifice region of the hollow cathode,and thus leads to enhanced plasma throttling and gas expanding *** analyzing the above mechanisms,the possible methods for improving this kind of hollow cathode micro-thruster are discussed.

关键词： Extended fluid model Hollow cathodes Micro-thruster Plasma contactor Plasma throttling effect

High-resolution Load Profile Clustering Approach Based on Dynamic Largest Triangle Three Buckets and Multiscale Dynamic Warping Path Under Limited Warping Path Length

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Journal of Modern Power Systems and Clean Energy 2023年第5期11卷 1576-1584页

作者： Mi Wen Yue Ma Weina Zhang Yingjie Tian yanfei wang College of Computer Science and Technology Shanghai University of Electric PowerShanghaiChina Shanghai Electric Power Research Institute ShanghaiChina

With the popularity of smart meters and the growing availability of high-resolution load data, the research on the dynamics of electricity consumption at finely resolved timescales has become increasingly popular. Many existing algorithms underperform when clustering load profiles contain a large number of feature points. In addition, it is difficult to accurately describe the similarity of profile shapes when load sequences have large fluctuations, leading to inaccurate clustering results. To this end, this paper proposes a high-resolution load profile clustering approach based on dynamic largest triangle three buckets(LTTBs) and multiscale dynamic time warping under limited warping path length(LDTW). Dynamic LTTB is a novel dimensionality reduction algorithm based on LTTB. New sequences are constructed by dynamically dividing the intervals of significant feature points. The extraction of fluctuation characteristics is optimized. New curves with more concentrated features will be applied to the subsequent clustering. The proposed multiscale LDTW is used to generate a similarity matrix for spectral clustering, providing a more comprehensive and flexible matching method to characterize the similarity of load profiles. Thus, the clustering effect of a high-resolution load profile is improved. The proposed approach has been applied to multiple datasets. Experiment results demonstrate that the proposed approach significantly improves the Davies-Bouldin indicator(DBI) and validity index(VI). Therefore, better similarity and accuracy can be achieved using high-resolution load profile clustering.

关键词： Load profile clustering largest triangle three buckets(LTTB) dynamic time warping(DTW) spectral clustering

Distribution of populations in excited states of electrodeless discharge lamp of Rb atoms

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Chinese Science Bulletin 2013年第16期58卷 1876-1881页

作者： TAO ZhiMing wang yanfei HONG YeLong wang DongYing ZHANG ShengNan ZHUANG Wei CHEN JingBiao State Key Laboratory of Advanced Optical Communication System and Network Institute of Quantum Electronics School of Electronics Engineering & Computer Science Peking University Department of Physics Bijie University

The intensity of fluorescence spectral lines of Rb atoms in the region of 350-1110nm is measured in eletrodeless discharge lamp. The population ratio between the excited states is calculated according to the spontaneous transition probabilities with rate equations. At the same time, the population density of energy level is also obtained. The results provide the potential applications of electrodeless discharge lamp in atomic filter and optical frequency reference at higher excited states without a pumping laser.

关键词：原子激发态无极灯铷原子种群分布人口密度无极放电灯原子滤光器概率计算

SYNTHETIC BANDWIDTH METHOD AND EXPERIMENTAL RESEARCH BASED ON A WIDEBAND MULTI-CHANNEL SAR

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Journal of Electronics(China) 2013年第2期30卷 130-137页

作者： Jia Yingxin wang yanfei Institute of Electronics Chinese Academy of Sciences

Synthetic bandwidth technique is used to increase frequency bandwidth of the system and provides an effective way to achieve the ultra high resolution in the field of Synthetic Aperture Radar (SAR). But in the actual SAR system, the synthesis result will be seriously deteriorated by the inner-channel and inter-channel phase error. A frequency domain synthetic bandwidth method based on transfer function extracting technique is proposed in an actual SAR system which consists of single wideband transmit channel and 8-way down-conversion receive sub-channels. The method can accurately get the amplitude and phase characteristics of the sub-channel and compensate the amplitude-phase errors. The final experimental results demonstrate the validity and feasibility of the method and the range resolution down to 0.1 m is obtained.

关键词： Synthetic Aperture Radar (SAR) Synthetic bandwidth Amplitude-phase errors

A unifying approach in simulating the shot peening process using a 3D random representative volume finite element model

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Chinese Journal of Aeronautics 2017年第4期30卷 1592-1602页

作者： Dianyin HU Ye GAO Fanchao MENG Jun SONG yanfei wang Mengxi REN Rongqiao wang School of Energy and Power Engineering Beihang University Beijing 100083 China Collaborative Innovation Center of Advanced Aero-Engine Beijing 100083 China Beijing Key Laboratory of Aero-Engine Structure and Strength Beijing 100083 China Mining and Materials Engineering McGill University Montreal QC H3A 0C5 Canada Experimental School of Beihang University Beijing 100083 China School of Automation Science and Electrical Engineering Beihang University Beijing 100083 China

Using a modified 3D random representative volume（RV）finite element model,the effects of model dimensions（impact region and interval between impact and representative regions）,model shapes（rectangular,square,and circular）,and peening-induced thermal softening on resultant critical quantities（residual stress,Almen intensity,coverage,and arc height）after shot peening are systematically examined.A new quantity,i.e.,the interval between impact and representative regions,is introduced and its optimal value is first determined to eliminate any boundary effect on shot peening ***,model dimensions are respectively assessed for all model shapes to reflect the actual shot peening process,based on which shape-independent critical shot peening quantities are ***,it is found that thermal softening of the target material due to shot peening leads to variances of the surface residual stress and arc height,demonstrating the necessity of considering the thermal effect in a constitutive material model of shot *** study clarifies some of the finite element modeling aspects and lays the ground for accurate modeling of the SP process.

关键词： Almen intensity Boundary effect Finite element modeling Residual stress Shot peening

Review of Hydrogen Embrittlement in Metals: Hydrogen Diffusion, Hydrogen Characterization, Hydrogen Embrittlement Mechanism and Prevention

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Acta Metallurgica Sinica(English Letters) 2020年第6期33卷 759-773页

作者： Xinfeng Li Xianfeng Ma Jin Zhang Eiji Akiyama yanfei wang Xiaolong Song Sino-French Institute of Nuclear Engineering and Technology Sun Yat-sen UniversityZhuhai 519082China State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong UniversityXi'an 710049China Department of Physics and Astronomy Washington State UniversityPullmanWA 99164USA Materials Design Division Institute for Materials ResearchTohoku UniversitySendai 980-8577Japan School of Chemical Engineering and Technology China University of Mining and TechnologyXuzhou 221116China

Hydrogen dissolved in metals as a result of internal and external hydrogen can affect the mechanical properties of the metals, principally through the interactions between hydrogen and material defects. Multiple phenomena such as hydrogen dissolution, hydrogen diffusion, hydrogen redistribution and hydrogen interactions with vacancies, dislocations, grain boundaries and other phase interfaces are involved in this process. Consequently, several hydrogen embrittlement(HE) mechanisms have been successively proposed to explain the HE phenomena, with the hydrogen-enhanced decohesion mechanism, hydrogenenhanced localized plasticity mechanism and hydrogen-enhanced strain-induced vacancies being some of the most important. Additionally, to reduce the risk of HE for engineering structural materials in service, surface treatments and microstructural optimization of the alloys have been suggested. In this review, we report on the progress of the studies on HE in metals, with a particular focus on steels. It focuses on four aspects:(1) hydrogen diffusion behavior;(2) hydrogen characterization methods;(3) HE mechanisms;and(4) the prevention of HE. The strengths and weaknesses of the current HE mechanisms and HE prevention methods are discussed, and specific research directions for further investigation of fundamental HE mechanisms and methods for preventing HE failure are identified.

关键词： Hydrogen embrittlement Hydrogen diffusion Hydrogen embrittlement mechanism prevention

Alternative splicing of inner-ear-expressed genes

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Frontiers of Medicine 2016年第3期10卷 250-257页

作者： yanfei wang Yueyue Liu Hongyun Nie Xin Ma Zhigang Xu Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology School of Life Sciences Shandong University Jinan 250100 China School of Control Science and Engineering Shandong University Jinan 250061 China

Alternative splicing plays a fundamental role in the development and physiological function of the inner ear. Inner-ear-specific gene splicing is necessary to establish the identity and maintain the function of the inner ear. For example, exon 68 of Cadherin 23 （Cdh23） gene is subject to inner-ear-specific alternative splicing, and as a result, Cdh23（＋ 68） is only expressed in inner ear hair cells. Alternative splicing along the tonotopic axis of the cochlea contributes to frequency tuning, particularly in lower vertebrates, such as chickens and turtles. Differential splicing of Kcnmal, which encodes for the a subunit of the Ca2＋-activated K~ channel （BK channel）, has been suggested to affect the channel gating properties and is important for frequency tuning. Consequently, deficits in alternative splicing have been shown to cause hearing loss, as we can observe in Bronx Waltzer Cov） mice and Sfswap mutant mice. Despite the advances in this field, the regulation of alternative splicing in the inner ear remains elusive. Further investigation is also needed to clarify the mechanism of hearing loss caused by alternative splicing deficits.

关键词： alternative splicing inner ear hearing loss hair cells

A super-resolution algorithm for synthetic aperture radar based on modified spatially variant apodization

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Science China(Physics,Mechanics & Astronomy) 2011年第2期54卷 355-364页

作者： NI Chong wang yanfei XU XiangHui ZHOU ChangYi CUI PengFei Institute of Electronics Chinese Academy of SciencesBeijing 100190 China Graduate University of the Chinese Academy of Sciences Beijing 100190 China

The existing spatially variant apodizations(SVAs) either cannot depress the sidelobes effectively or reduce the energy of the *** improve this,a modified SVA(MSVA) is put forward in this paper,which expands the traditional filter from 3-taps to 5-taps and sets relevant parameters according to different sampling rates to get the excellent result that satisfies constrained optimization theory.A modified super-SVA is also presented,which compares the result after the iteration with the original signal and makes the one whose amplitude is smaller as the initial value of the next *** method can eliminate the sidelobes produced by the intermediate operation,so that the following bandwidth extrapolation is more ***-MSVA is presented based on the modified SVA and modified super-SVA,which is suitable for any Nyquist sampling rate,can extrapolate the signal bandwidth many times through iteration with a commensurate improvement in resolution,as demonstrated by the result of the experiment.

关键词： synthetic aperture radar sidelobe suppression super-resolution SVA