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Joint number and DOA estimation via the eigen-beam mCapon method for closely spaced sources

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Science China(Information Sciences) 2015年第12期58卷 217-219页

作者： GAO Yang xu jia jia Xin Academy of Equipment School of Information and Electronics Beijing Institute of Technology

Dear editor,The source number and direction of arrival(DOA)estimation are two important subjects in array signal processing[1,2].Many algorithms for estimating these parameters have been proposed in the past

关键词： DOA Joint number and DOA estimation via the eigen-beam mCapon method for closely spaced sources MUSIC

A priori Estimates and Existence for a Class of Fully Nonlinear Elliptic Equations in Conformal Geometry

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Chinese Annals of Mathematics,Series B 2006年第2期27卷 169-178页

作者： xu-jia WANG Dedicated to the memory of Shiing-Shen Chern

In this paper we prove the interior gradient and second derivative estimates for a class of fully nonlinear elliptic equations determined by symmetric functions of eigenvalues of the Ricci or Schouten tensors. As an application we prove the existence of solutions to the equations *** the manifold is locally conformally flat or the Ricci curvature is positive.

关键词： Conformal geometry Elliptic equation Ricci curvature

Schauder Estimates for Elliptic and Parabolic Equations

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Chinese Annals of Mathematics,Series B 2006年第6期27卷 637-642页

作者： xu-jia WANG Centre for Mathematics and its Applications Australian National University Canberra ACT 0200 Australia

In this note the author gives an elementary and simple proof for the Schauder estimates for elliptic and parabolic equations. The proof also applies to nonlinear equations.

关键词： Schauder estimate Elliptic equation Parabolic equation

Nonuniqueness of Solutions of a Class of0-minimization Problems

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Journal of the Operations Research Society of China 2021年第4期9卷 893-908页

作者： jia-Liang xu Hua Loo-Keng Center for Mathematical Sciences Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China

Recently,finding the sparsest solution of an underdetermined linear system has become an important request in many areas such as compressed sensing,image processing,statistical learning,and data sparse *** this paper,we study some theoretical properties of the solutions to a general class of0-minimization problems,which can be used to deal with many practical *** establish some necessary conditions for a point being the sparsest solution to this class of problems,and we also characterize the conditions for the multiplicity of the sparsest solutions to the ***,we discuss certain conditions for the boundedness of the solution set of this class of problems.

关键词： 0-minimization Sparsity Nonuniqueness Boundedness

The J_2 invariant relative configuration of spaceborne SAR interferometer for digital elevation measurement

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Acta Mechanica Sinica 2010年第4期26卷 643-651页

作者： Ming xu Ying-Hong jia Shi-Jie xu Department of System Engineering DFH Satellite Co. Ltd. EO. Box 5616 Beijing 100094 China

A 3-craft formation configuration is proposed to perform the digital elevation model （DEM） for the distributed spacebome interferometric synthetic aperture radar （InSAR）, and it is optimized by the modified ant colony algorithm to have the best compatibility with J2 invariant orbits created by differential correction algorithm. The configuration has succeeded in assigning the across-track baseline to vary periodically and with its mean value equal to the optimal baseline determined by the relative height measurement accuracy. The required relationship between crafts＇ magnitudes and phases is formulated for the general case of interferometry measure from non-orthographic and non-lateral view. The J2 invariant configurations created by differential correction algorithm are employed to investigate their compatibility with the required configuration. The colony algorithm is applied to search the optimal configuration holding the near-constant across-track baseline under the J2 perturbation, and the absolute height measurement accuracy is preferable as expected.

关键词： InSAR Digital elevation model (DEM) J2 invariant orbit Differential correction algorithm Formation flying

Mass Spectrometric Fragmentation of 1-(Benzyloxycarbonyl)amino-2-alkyl/cycloalkyl Thioacetates:a Thioester Pyrolysis-type Rearrangement under Electron Impact Ionization

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Chinese Chemical Letters 2006年第8期17卷 1069-1072页

作者： Shu xu jia Xi xu Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education College of Chemistry and Molecular Engineering Peking University Beijing 100871

The mass spectrometric fragmentation of 1-（benzyloxycarbonyl）amino-2-alkyl/cycloalkyl thioacetates has been studied with the aid of mass-analysed ion kinetic energy spectrometry under electron impact ionization. All compounds show a tendency to eliminate a ketene, thioacetic acid, and benzyl carbamate molecule, or an acetyl and benzyloxy radicals. A thioester pyrolysis-type rearrangement under electron impact ionizations was observed.

关键词： Electron impact ionization mass spectrometry rearrangement thioacetate.

Several fourth-order force gradient symplectic algorithms

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Research in Astronomy and Astrophysics 2010年第2期10卷 173-188页

作者： jia xu Xin Wu Department of Physics Nanchang University Nanchang 330031 China

By adding force gradient operators to symmetric compositions, we build a set of explicit fourth-order force gradient symplectic algorithms, including those of Chin and coworkers, for a separable Hamiltonian system with quadratic kinetic en- ergy T and potential energy V. They are extended to solve a gravitational n-body Hamiltonian system that can be split into a Keplerian part H0 and a perturbation part H1 in Jacobi coordinates. It is found that the accuracy of each gradient scheme is greatly superior to that of the standard fourth-order Forest-Ruth symplectic integra- tor in T ＋ V-type Hamiltonian decomposition, but they are both almost equivalent in the mean longitude and the relative position for H0 ＋//1-type decomposition. At the same time, there are no typical differences between the numerical performances of these gradient algorithms, either in the splitting of T ＋ V or in the splitting of H0 ＋//1. In particular, compared with the former decomposition, the latter can dra- matically improve the numerical accuracy. Because this extension provides a fast and high-precision method to simulate various orbital motions of n-body problems, it is worth recommending for practical computation.

关键词： celestial mechanics -- methods: numerical

Walnut Staminate Flowers Can Be Explored as a Supplementary Plant Oil Source

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Journal of Integrative Plant Biology 2006年第4期48卷 377-380页

作者： Husen jia Yinong xu Key Laboratory of Photosynthesis and Environmental Molecular Physiology Institute of Botany the Chinese Academy of Sciences Beijing 100093 China

Fossil fuel Is currently the major energy source driving global socio-economy, but its stock Is being heavily depleted due to Increasing anthropogenic activities worldwide. There are also concerns regarding the burning of fossil fuels, which contributes to global climate warming and sir pollution. As such, the development of blodlesel as a non-toxic, blodegredable, and renewable alternative energy source using oil crops such as soybean and rapeseed has quickly emerged in the West countries. However, the production of oil crops In China Is far from sufficient to meet the demands of the country＇s population of 1.3 billion, and Increasing oil crop production Is Inhibited by a severe shortage of agricultural land, which currently averages 0.2 acre per person and, as such, Is less than half the world average. The current national policy in China regarding land use Is more towards revering cultivated lands in revins and hills to forestry, which presents an ideal opportunity to further develop plantations of walnut （Juglans regis L.） trees, a plant that is tolerant to drought and infertile soils and has a high oil content. Study In this paper shows that one ament of walnut staminate flowers produces about 0.168 g dry pollen, and the dry pollen contained 49.67% oil. Based on this discovery, oil yield obtained from staminate flowers Is estimated to reach 6.95% of that from walnut nuts. Thus walnut staminate flower is suggested to explore as supplementary plant oil source, and has a great opportunity to utilize as a biodlesel feedstock.

关键词： biodiesel feedstock oil walnut staminate flowers.

Experimental study of wave propagation characteristics on a simplified coral reef

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Journal of Hydrodynamics 2020年第2期32卷 385-397页

作者： jia-yi xu Shu-xue Liu Jin-xuan Li Wei jia State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian116024China

The wave transformation over slope topography is widely studied,but most of studies are for common coastal *** paper presents an experimental study of 2-D regular and irregular wave transformations on a simplified coral reef with a steep slope of 1:5 and a horizontal reef flat,focusing on the characteristics of the waves that break on the reef *** analyzed results show that the estimates of the wave breaking made by using the well-known previous formulae do not agree completely with the experimental *** the waves break on a reef flat,the relative breaking wave height(H/d)b is related to the incident deep-water wave steepness and the relative water depth db/***,a new criterion for breaking waves on a reef flat is ***,in view of the fact that the local Ursell number is commonly used to parameterize the wave nonlinearity,the relationships among the skewness,the asymmetry,and the local Ursell number are also *** data confirm that when the Ursell number is greater than 30,the absolute values of the skewness and the asymmetry on a reef flat are greater than those on a steep slope.

关键词： Coral reef bathymetry wave breaking wave height attenuation representative wave parameter nonlinear parameters