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Development trends of the national secure PNT system based on BDS

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Science China Earth Sciences 2023年第5期66卷 929-938页

作者： Yuanxi YANG xia ren xiaolin JIA Bijiao SUN State Key Laboratory of Geo-Information Engineering Xi’an 710054China Xi’an Research Institute of Surveying and Mapping Xi’an 710054China

Satellite navigation systems are *** guarantee the positioning,navigation and timing(PNT)safety of core infrastructure,it is necessary to establish a secure PNT system with hybrid physical *** this paper,the augmentations of the BeiDou satellite system(BDS)itself are analysed,namely augmentations through the BDS inter-satellite link,BDS geostationary orbit(GEO)and inclined geostationary orbit(IGSO)satellites,and BDS PNT services supported by low earth orbit(LEO)***,taking BDS as the core component,the comprehensive PNT infrastructure seamlessly covering deep space and deep ocean is described,consisting of the deep space PNT constellation,the sea-floor PNT sonar beacon network,and the ground-based low frequency and very low frequency(VLF)long wave radio ***,the key technologies of resilient PNT application matching comprehensive PNT and various autonomous perception PNT information are discussed,such as resilient PNT sensor integration,the resilient PNT functional model and the resilient stochastic *** a future development direction,the key factors of intelligent PNT services are analysed,including the intelligent perception of PNT application scenes,the intelligent optimization of PNT functional and stochastic models and the intelligent fusion of multisource PNT information.

关键词： Secure PNT system Comprehensive PNT infrastructure Resilient PNT application Intelligent PNT application

Diffusion tensor interpolation profile control using non-uniform motion on a Riemannian geodesic

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Journal of Zhejiang University-Science C(Computers and Electronics) 2012年第2期13卷 90-98页

作者： Chang-II SON Shun-ren xia MOE Key Laboratory of Biomedical Engineering Zhejiang UniversityHangzhou 310027China Department of Electronics Kim Chaek University of TechnologyPyongyang 104919DPR of Korea

Tensor interpolation is a key step in the processing algorithms of diffusion tensor imaging (DTI), such as registration and tractography. The diffusion tensor (DT) in biological tissues is assumed to be positive definite. However, the tensor interpolations in most clinical applications have used a Euclidian scheme that does not take this assumption into account. Several Rie-mannian schemes were developed to overcome this limitation. Although each of the Riemannian schemes uses different metrics, they all result in a ‘fixed’ interpolation profile that cannot adapt to a variety of diffusion patterns in biological tissues. In this paper, we propose a DT interpolation scheme to control the interpolation profile, and explore its feasibility in clinical applications. The profile controllability comes from the non-uniform motion of interpolation on the Riemannian geodesic. The interpolation experiment with medical DTI data shows that the profile control improves the interpolation quality by assessing the reconstruction errors with the determinant error, Euclidean norm, and Riemannian norm.

关键词： Diffusion tensor (DT) DT imaging (DTI) DT interpolation Interpolation profile control Riemannian geodesic

L log L criterion for a class of multitype superdiffusions with non-local branching mechanisms

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Science China Mathematics 2019年第8期62卷 1439-1462页

作者： Zhen-Qing Chen Yan-xia ren renming Song Department of Mathematics University of Washington Seattle WA 98195 USA LMAM School of Mathematical Sciences & Center for Statistical SciencePeking University Beijing 100871 China Department of Mathematics University of Illinois Urbana IL 61801 USA

In this paper, we provide a pathwise spine decomposition for multitype superdiffusions with nonlocal branching mechanisms under a martingale change of measure. As an application of this decomposition,we obtain a necessary and sufficient condition(called the L log L criterion) for the limit of the fundamental martingale to be non-degenerate. This result complements the related results obtained in Kyprianou et al.(2012),Kyprianou and Murillo-Salas(2013) and Liu et al.(2009) for superprocesses with purely local branching mechanisms and in Kyprianou and Palau(2018) for super Markov chains.

关键词： multitype superdiffusion non-local branching mechanism switched diffusion spine decomposition martingale

Development of Comprehensive PNT and Resilient PNT

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Journal of Geodesy and Geoinformation Science 2023年第3期6卷 1-8页

作者： xia ren Yuanxi YANG Xi’an Research Institute of Surveying and Mapping Xi’an 710054China State Key Laboratory of Geo-Information Engi-neering Xi’an 710054China

Any single Positioning,Navigation and Timing(PNT)technology has its vulnerability and limits,even the powerful Global Navigation Satellite System(GNSS)is no *** provide continuous and reliable PNT information to users,the theory and technique of comprehensive PNT information system and resilient PNT application system have attracted great attention from Chinese *** try to summarize the progress and development of the synthetic PNT system,including the proposal,the modification and the improvement of the comprehensive PNT,as well as the follow-up resilient *** frame of China’s comprehensive PNT system consisted of comprehensive PNT infrastructure and comprehensive PNT application system is initially described;the achievements on some main PNT technologies are introduced;the conceptual models of resilient PNT are given;besides,existing researches on resilient function models and stochastic models are summarized according to different user scenarios.

关键词： GNSS comprehensive PNT resilient PNT resilient function model resilient stochastic model

Supercritical superprocesses: Proper normalization and non-degenerate strong limit

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Science China Mathematics 2019年第8期62卷 1519-1552页

作者： Yan-xia ren renming Song Rui Zhang LMAM School of Mathematical Sciences & Center for Statistical Science Peking University Beijing 100871 China Department of Mathematics University of Illinois Urbana IL 61801 USA School of Mathematical Sciences Nankai University Tianjin 300071 China School of Mathematical Sciences Capital Normal University Beijing 100048 China

Suppose that X ={Xt, t≥0;Pμ} is a supercritical superprocess in a locally compact separable metric space E. Let φ0 be a positive eigenfunction corresponding to the first eigenvalue λ0 of the generator of the mean semigroup of X. Then Mt := e-λ0t〈φ0,Xt〉 is a positive martingale. Let M∞ be the limit of Mt. It is known(see Liu et al.(2009)) that M∞ is non-degenerate if and only if the L log L condition is satisfied. In this paper we are mainly interested in the case when the L log L condition is not satisfied. We prove that, under some conditions, there exist a positive function γt on [0,∞) and a non-degenerate random variable W such that for any finite nonzero Borel measure μ on E,lim/t→∞γt〈φ0,Xt〉=W, a.s.-Pμ.We also give the almost sure limit of γt〈f, Xt〉for a class of general test functions f.

关键词： superprocesses Seneta-Heyde norming non-degenerate strong limit martingales

Enigmatic earwig-like fossils from Inner Mongolia, China

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Insect Science 2010年第5期17卷 459-464页

作者： Jing-xia Zhao Dong ren Chungkun Shih College of Life Science Capital Normal University Beijing China

A new species of a new genus, Atopderma ellipta gen. et sp. nov. is described from the Middle Jurassic Jiulongshan Formation of Daohugou, Inner Mongolia, China. Because of poor preservation, the placement of these specimens is contentious, either Dermaptera or Coleoptera. However, we are inclined to attribute them to Dermaptera based on differences of five key characters. Detailed description and illustration of the specimens are given. Possible reasons for lacking good and complete abdomen preservation are also discussed.

关键词： Dermaptera Daohugou earwig-like fossil Middle Jurassic

Automatic mass segmentation on mammograms combining random walks and active contour

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Journal of Zhejiang University-Science C(Computers and Electronics) 2012年第9期13卷 635-648页

作者： Xin HAO Ye SHEN Shun-ren xia MOE Key Laboratory of Biomedical Engineering Zhejiang UniversityHangzhou 310027China Department of Signal and lnformation Processing China Jiliang UniversityHangzhou 310018China

Accurate mass segmentation on mammograms is a critical step in computer-aided diagnosis (CAD) systems. It is also a challenging task since some of the mass lesions are embedded in normal tissues and possess poor contrast or ambiguous margins. Besides, the shapes and densities of masses in mammograms are various. In this paper, a hybrid method combining a random walks algorithm and Chan-Vese (CV) active contour is proposed for automatic mass segmentation on mammograms. The data set used in this study consists of 1095 mass regions of interest (ROIs). First, the original ROI is preprocessed to suppress noise and surrounding tissues. Based on the preprocessed ROI, a set of seed points is generated for initial random walks segmentation. Afterward, an initial contour of mass and two probability matrices are produced by the initial random walks segmentation. These two probability matrices are used to modify the energy function of the CV model for prevention of contour leaking. Lastly, the final segmentation result is derived by the modified CV model, during which the probability matrices are updated by inserting several rounds of random walks. The proposed method is tested and compared with other four methods. The segmentation results are evaluated based on four evaluation metrics. Experimental results indicate that the proposed method produces more accurate mass segmentation results than the other four methods.

关键词： Active contour Random walks Mass segmentation Mammogram

Stable Central Limit Theorems for Super Ornstein–Uhlenbeck Processes,Ⅱ

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Acta Mathematica Sinica,English Series 2022年第3期38卷 487-498页

作者： Yan xia ren ren Ming SONG Zhen Yao SUN Jian Jie ZHAO LMAM School of Mathematical Sciences&Center for Statistical Science Peking UniversityBeijing100871P.R.China Department of Mathematics University of Illinois at Urbana-ChampaignUrbanaIL61801USA School of Mathematics and Statistics Wuhan UniversityWuhan430072P.R.China The Faculty of Industrial Engineering and Management TechnionHaifa3200003Israel School of Mathematical Sciences Peking UniversityBeijing100871P.R.China

This paper is a continuation of our recent paper(***.,24(141),(2019))and is devoted to the asymptotic behavior of a class of supercritical super Ornstein-Uhlenbeck processes(X_(t))t≥0 with branching mechanisms of infinite second *** the aforementioned paper,we proved stable central limit theorems for X_(t)(f)for some functions f of polynomial growth in three different ***,we were not able to prove central limit theorems for X_(t)(f)for all functions f of polynomial *** this note,we show that the limiting stable random variables in the three different regimes are independent,and as a consequence,we get stable central limit theorems for X_(t)(f)for all functions f of polynomial growth.

关键词： Superprocesses Ornstein–Uhlenbeck processes stable distribution central limit theorem law of large numbers branching rate regime

Scheduling a Bounded Parallel-Batching Machine with Incompatible Job Families and Rejection

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Journal of the Operations Research Society of China 2014年第4期2卷 499-510页

作者： Shi-Sheng Li ren-xia Chen College of Science Zhongyuan University of TechnologyZhengzhou 450007China

We study a scheduling problem with incompatible job families and rejection on a parallel-batching machine,where the objective is to minimize the makespan of all accepted jobs plus the total penalty of all rejected *** provide a polynomial-time algorithm for the case where all jobs have identical release dates and a pseudo-polynomial-time algorithm for the case where the number of distinct release dates is *** also present a 2-approximation algorithm and a polynomial-time approximation scheme for the general problem.

关键词： Parallel-batching scheduling Incompatible job families Rejection Approximation algorithm