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Applications of gauge duality in robust principal component analysis and semidefinite programming

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Science China Mathematics 2016年第8期59卷 1579-1592页

作者： MA ShiQian yang junfeng Department of Systems Engineering and Engineering Management The Chinese University of Hong Kong Department of Mathematics Nanjing University

Gauge duality theory was originated by Preund （1987）, and was recently further investigated by Friedlander et al. （2014）. When solving some matrix optimization problems via gauge dual, one is usually able to avoid full matrix decompositions such as singular value and/or eigenvalue decompositions. In such an approach, a gauge dual problem is solved in the first stage, and then an optimal solution to the primal problem can be recovered from the dual optimal solution obtained in the first stage. Recently, this theory has been applied to a class of semidefinite programming （SDP） problems with promising numerical results by Friedlander and Mac^to （2016）. We establish some theoretical results on applying the gauge duality theory to robust principal component analysis （PCA） and general SDP. For each problem, we present its gauge dual problem, characterize the optimality conditions for the primal-dual gauge pair, and validate a way to recover a primal optimal solution from a dual one. These results are extensions of Friedlander and Macedo （2016） from nuclear norm regularization to robust PCA and from a special class of SDP which requires the coefficient matrix in the linear objective to be positive definite to SDP problems without this restriction. Our results provide further understanding in the potential advantages and disadvantages of the gauge duality theory.

关键词： gauge optimization gauge duality polar function antipolar set singular value decomposition robust principal component analysis semidefinite programming

Solution set on the natural satellite formation orbits under first-order earth's non-spherical perturbation

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Acta Mechanica Sinica 2005年第5期21卷 503-510页

作者： Humei Wang Wei yang junfeng Li School of Aerospace Tsinghua University Beijing100084 China

Using the reference orbital element approach, the precise governing equations for the relative motion of formation flight are formulated. A number of ideal formations with respect to an elliptic orbit can be designed based on the relative motion analysis from the equations. The features of the oscillating reference orbital elements are studied by using the perturbation theory. The changes in the relative orbit under perturbation are divided into three categories, termed scale enlargement, drift and distortion respectively. By properly choosing the initial mean orbital elements for the leader and follower satellites, the deviations from originally regular formation orbit caused by the perturbation can be suppressed. Thereby the natural formation is set up. It behaves either like non-disturbed or need little control to maintain. The presented reference orbital element approach highlights the kinematics properties of the relative motion and is convenient to incorporate the results of perturbation analysis on orbital elements. This method of formation design has advantages over other methods in seeking natural formation and in initializing formation.

关键词： Orbital mechanics . Satellite formation flight .Orbital elements . Reference orbital elements . Perturbation

Effect of Mixed Dispersants on Suppression of the Gel Effect during Aqueous Adiabatic Terpolymerization of AM,NaAA,and DMC

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China Petroleum Processing & Petrochemical Technology 2023年第3期25卷 83-91页

作者： yang junfeng Zhou Manli Wang Meng Qingyuan Yakoo Chemical Co. LtdQingyuan 510640China Department of Polymer Science and Engineering South China University of TechnologyGuangzhou 510640China

Gelation adversely affects the aqueous adiabatic terpolymerization of acrylamide (AM), sodium acrylate (NaAA),and 2-methacryloyloxyethyl trimethylammonium chloride (DMC). Here, the mixed dispersants sorbitan monooleate (Span80) and polyoxyethylene sorbitan monooleate (Tween 80) were introduced to the terpolymerization system in an attemptto mitigate the gel effect. This enabled the preparation of high-performance amphoteric polyacrylamides, which werecharacterized by Fourier-transform infrared spectroscopy and thermogravimetric analysis. The influences of the dispersanttype and content as well as the hydrophilic-lipophilic balance (HLB) on the gel effect were examined, and the mechanismunderlying the suppression of the gel effect was considered. The obtained results indicated that the gel effect can beeffectively mitigated using an aqueous adiabatic terpolymerization system containing mixed Span 80/Tween 80 dispersantsat various contents. In particular, mixed dispersant contents of 0.6%–0.8% with HLB values of 5.0–6.0 afforded the optimalperformance (e.g., high viscosity, fast aqueous dissolution time, and the like).

关键词： gel effect dispersants amphoteric polyacrylamide terpolymerization

A COMPARISON OF DIFFERENT CONTRACTION METHODS FOR MONOTONE VARIATIONAL INEQUALITIES

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Journal of Computational Mathematics 2009年第4期27卷 459-473页

作者： Bingsheng He Xiang Wang junfeng yang Department of Mathematics Nanjing University Nanjing 210093 China

It is interesting to compare the efficiency of two methods when their computational loads in each iteration are equal. In this paper, two classes of contraction methods for monotone variational inequalities are studied in a unified framework. The methods of both classes can be viewed as prediction-correction methods, which generate the same test vector in the prediction step and adopt the same step-size rule in the correction step. The only difference is that they use different search directions. The computational loads of each iteration of the different classes are equal. Our analysis explains theoretically why one class of the contraction methods usually outperforms the other class. It is demonstrated that many known methods belong to these two classes of methods. Finally, the presented numerical results demonstrate the validity of our analysis.

关键词： Monotone variational inequalities Prediction-correction Contraction methods.

Responses of zonal wind at -40°N to stratospheric sudden warming events in the stratosphere, mesosphere and lower thermosphere

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Science China(Technological Sciences) 2017年第6期60卷 935-945页

作者： yang junfeng XIAO CunYing HU Xiong XU QingChen National Space Science Center Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China

Based on the data at^40°N at different longitudes during different stratospheric sudden warming(SSW)events,the responses of zonal winds in the stratosphere,mesosphere and lower thermosphere to SSWs are studied in this *** variations of zonal wind over Langfang,China(39.4°N,116.7°E)by MF radar and the modern era retrospective-analysis for research and applications(MERRA)wind data during 2010 and 2013 SSW and over Fort Collins,USA(41°N,105°W)by lidar and MERRA wind data during 2009 SSW are *** show that the zonal wind at^40°N indeed respond to the SSWs while different specifics are found in different SSW events or at different *** zonal wind has significant anomalies during the *** Langfang,before the onset of 2010 and 2013 SSW,the zonal wind reverses from eastward to westward below about 60–70 km and accelerates above this region,while westward wind prevails from 30 to 100 km after the onset of2010 SSW,and westward wind prevails in 30–60 and 85–100 km and eastward wind prevails in 60–85 km after the onset of2013 *** Fort Collins during 2009 SSW,eastward wind reverses to westward in 20–30 km before the onset while westward wind prevails in 20–30 and 60–97 km and eastward wind prevails in 30–60 and in 97–100 km after the ***,simulations by the specified dynamics version of the whole atmosphere community climate model(SD-WACCM)are taken to explain different responding specifics of zonal wind to SSW *** is found that the modulation of planetary wave(PW)plays the main *** phases of PWs would lead to the different zonal wind along with longitudes and the different amplitudes and phases in different SSW events can lead to the different zonal wind responses.

关键词： stratospheric sudden warming(SSW) MF radar WACCM planetary waves

A real time transmission system of long distance for nuclear logging

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Nuclear Science and Techniques 2011年第6期22卷 366-371页

作者： CAO Ping SONG Kezhu yang junfeng State Key Laboratory of Particle Detection and Electronics Anhui Key Laboratory of Physical Electronics Department of Modern Physics University of Science and Technology of China Hefei 230026 China

Some specified chips in traditional Manchester-Ⅱencoding/decoding designs are used to guarantee strictly the stability of the input wave,otherwise the capacity of anti-interference and resilience are degraded *** this paper,a new Manchester-Ⅱencoding/ decoding system is used for nuclear logging by a 7 000 m armoring cable.A thorough hardware wave tracking decoding algorithm is proposed and realized in a FPGA hardware *** on-site measurements show that this transmission system can decode correctly in real time,with a bit error rate of better than 10^(-10).

关键词：传输系统长距离核测井编码/解码曼彻斯特抗干扰能力抗灾能力解码系统

Nickel-Catalyzed Regio-and Stereoselective Defluorinative Arylation of gem-Difluorinated Cyclopropanes

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Chinese Journal of Chemistry 2024年第8期42卷 823-828页

作者： Shutao Qi Yunkai Hua Liangkai Pan junfeng yang Junliang Zhang Department of Chemistry Fudan University2005 Songhu RoadShanghai200438 China Fudan Zhangjiang Institute Shanghai201203 China School of Chemistry and Chemical Engineering Henan Normal UniversityXinxiangHenan 453007China

Comprehensive Summary,Herein,we report nickel-catalyzed cross-coupling of gem-difluorinated cyclopropanes with boronic acids,providing the corresponding arylated 2-fluoroallylic *** approach used commercially available phosphine ligand Xantphos to obtain monofluorinated alkenes with high regioselectivity and *** studies proposed a Ni(II)-fluoroallyl pathway and excluded the radical pathway.

关键词： Nickel Monofluoroolefin Cyclopropane Regioselectivity Stereoselectivity C-C coupling Cross-coupling Synthetic methods

The role of sediment resuspension duration in releaseof PAHs

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Chinese Science Bulletin 2008年第18期53卷 2777-2782页

作者： FENG JingLan SHEN ZhenYao NIU junfeng yang ZhiFeng State Key Laboratory of Water Environment Simulation School of Environment Beijing Normal University Beijing 100875 China

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants. Due to their low water solubility and high hydrophobicity, PAHs are rapidly sorbed onto particles and subsequently deposit in sediments once introduced into aquatic environment. In such a way, sediments become a huge sink for PAHs. During sediment resuspension, the potential exists for PAHs to be released from sediments into water. Sediment resuspension plays an important role in the transportation and fate of PAHs in the aquatic environment. In this study, release behavior of PAHs on yangtze River sediment during resuspension was investigated using a particle entrainment simulator (PES). The role of re- suspension duration on release of 16 PAHs was measured by resuspending sediment for 12 h at 0.2 and 0.5 N/m2, respectively. Results indicated that PAH concentrations in TSS increase over time with more increase of phenanthrene and 4-ring PAHs. Comparing with 0.2 N/m2 (30%), ∑PAHs concentra- tions in TSS demonstrated remarkable increase during 0.5 N/m2 resuspension (37%). Dissolved PAH concentrations increased throughout the duration with more increase of 2―3 ring PAHs (50%―88%). Dissolved PAH concentrations showed remarkable increase during 0.5 N/m2 resuspension (50%). Moreover, PAH concentrations in overlying water throughout the duration of resuspension were higher than toxic effects threshold values in drinking water developed by WHO, which may cause toxic effect on ecosystem.

关键词：多环化合物长江再悬浮 PAHs

Analysis of the correlation between horizontal wind and 11-year solar activity over Langfang, China

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Earth and Planetary Physics 2021年第3期5卷 270-279页

作者： Bing Cai QingChen Xu Xiong Hu Xuan Cheng junfeng yang Wen Li Key Laboratory of Science and Technology on Environmental Space Situation Awareness National Space Science CenterChinese Academy of SciencesBeijing 100190China College of Earth Sciences University of Chinese Academy of SciencesBeijing 100049China

In this study,long term observations of medium frequency(MF)radar at Langfang site(39.4°N,116.7°E)from 2009 to 2020 have been used to analyze the dependence of the 11-year solar cycle on horizontal winds in the local mesosphere and lower thermosphere(MLT).The results show that the zonal wind is positively correlated with solar activity during spring at 80–84 km,and during summer at 80–82 km;the meridional wind is positively correlated with solar activity during spring at 84–88 km and during summer at 84–90 *** contrast,the results show no correlation between the horizontal wind and solar activity in autumn and *** attempt to explain the correlations in terms of the changes in stratospheric temperature and the net flux of gravity waves during solar *** addition,annual and semiannual oscillations of the zonal/meridional wind were found by using the least squares fitting method on daily horizontal winds,which show negative correlations with solar activity at heights of 80–90 km.

关键词： MF radar MLT horizontal wind solar cycle