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Bayesian Estimation of Large Precision Matrix Based on Cholesky Decomposition

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Acta Mathematica Sinica,English Series 2019年第5期35卷 619-631页

作者： Fan qun LI Xin Sheng zhang Institute of Statistics and Applied Mathematics Anhui University of Finance and Economics School of Management Fudan University

In this paper, we consider the estimation of a high dimensional precision matrix of Gaussian graphical model. Based on the re-parameterized likelihood, we obtain the full conditional distribution of all parameters in Cholesky factor. Furthermore, by imposing the prior information, we obtain the shrinkage Bayesian estimator of large precision matrix, and establish the asymptotic distribution of all parameters in the Cholesky factor. At last, we demonstrate our method through the simulation study and an application to telephone call center data.

关键词： Bayesian estimation Cholesky decomposition graphical model shrinkage

Interaction of an anticyclonic eddy with sea ice in the western Arctic Ocean:an eddy-resolving model study

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Acta Oceanologica Sinica 2013年第3期32卷 54-62页

作者： LI qun zhang Zhanhai WU Huiding Polar Research Institute of China State Oceanic Administration National Marine Environmental Forecasting Center State Oceanic Administration

The dramatic decline of summer sea ice extent and thickness has been witnessed in the western Arctic Ocean in recent decades, which has motivated scientists to search for possible factors driving the sea ice variability. An eddy-resolving, ice-ocean coupled model covering the entire Arctic Ocean is implemented, with focus on the western Arctic Ocean. Special attention is paid to the summer Maskan coastal current （ACC）, which has a high temperature （up to 5℃ or more） in the upper layer due to the solar radiation over the open water at the lower latitude. Downstream of the ACC after Barrow Point, a surface-intensified anticyclonic eddy is frequently generated and propagate towards the Canada Basin during the summer season when sea ice has retreated away from the coast. Such an eddy has a warm core, and its source is high-temperature ACC water. A typical warm-core eddy is traced. It is trapped just below summer sea ice melt water and has a thickness about 60 m. Temperature in the eddy core reaches 2-3℃, and most water inside the eddy has a temperature over 1℃. With a definition of the eddy boundary, an eddy heat is calculated, which can melt 1 600 km2 of 1 m thick sea ice under extreme conditions.

关键词： eddy-resolving anticyclonic eddy sea ice western Arctic Ocean Alaskan coastal current

Einstein Probe discovery of EP240408a: A peculiar X-ray transient with an intermediate timescale

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 222-240页

作者： Wenda zhang Weimin Yuan Zhixing Ling Yong Chen Nanda Rea Arne Rau Zhiming Cai Huaqing Cheng Francesco Coti Zelati Lixin Dai Jingwei Hu Shumei Jia Chichuan Jin Dongyue Li Paul O’Brien Rongfeng Shen Xinwen Shu Shengli Sun Xiaojin Sun Xiaofeng Wang Lei Yang Bing zhang Chen zhang Shuang-Nan zhang Yonghe zhang jie An David Buckley Alexis Coleiro Bertrand Cordier Liming Dou Rob Eyles-Ferris Zhou Fan Hua Feng Shaoyu Fu Johan P.U.Fynbo Lluis Galbany Saurabh W.Jha Shuaiqing Jiang Albert Kong Erik Kuulkers Weihua Lei Wenxiong Li Bifang Liu Mingjun Liu Xing Liu Yuan Liu Zhu Liu Chandreyee Maitra Alessio Marino Itumeleng Monageng Kirpal Nandra Jeremy Sanders Roberto Soria Lian Tao Junfeng Wang Song Wang Tinggui Wang Zhongxiang Wang Qingwen Wu Xuefeng Wu Dong Xu Yanjun Xu Suijian Xue Yongquan Xue Zijian zhang Zipei Zhu Hu Zou Congying Bao Fansheng Chen Houlei Chen Tianxiang Chen Wei Chen Yehai Chen Yifan Chen Chenzhou Cui Weiwei Cui Yanfeng Dai Dongwei Fan Ju Guan Dawei Han Dongjie Hou Haibo Hu Maohai Huang Jia Huo Zhenqing Jia Bowen Jiang Ge Jin Chengkui Li Junfei Li Longhui Li Maoshun Li Wei Li Zhengda Li Tianying Lian Congzhan Liu Heyang Liu Huaqiu Liu Fangjun Lu Laidan Luo Jia Ma Xuan Mao Haiwu Pan Xin Pan Liming Song Hui Sun Yunyin Tan Qingjun Tang Yihan Tao Hao Wang Juan Wang Lei Wang Wenxin Wang Yilong Wang Yusa Wang Qinyu Wu Haitao Xu Jingjing Xu Xinpeng Xu Yunfei Xu Zhao Xu Changbin Xue Yulong Xue Ailiang Yan Haonan Yang Xiongtao Yang Yanji Yang Juan zhang Mo zhang Wenjie zhang Zhen zhang Zhen zhang Ziliang zhang Donghua Zhao Haisheng Zhao Xiaofan Zhao Zijian Zhao Hongyan Zhou Yilin Zhou Yuxuan Zhu Zhencai Zhu National Astronomical Observatories Chinese Academy of Sciences School of Astronomy and Space Sciences University of Chinese Academy of Sciences Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Institute of Space Sciences (ICE) CSIC Institut d’Estudis Espacials de Catalunya (IEEC) Max Planck Institute for Extraterrestrial Physics Innovation Academy for Microsatellites Chinese Academy of Sciences Department of Physics University of Hong Kong School of Physics and Astronomy University of Leicester School of Physics and Astronomy Sun Yat-sen University Department of Physics Anhui Normal University Shanghai Institute of Technical Physics Chinese Academy of Sciences Physics Department Tsinghua University Nevada Center for Astrophysics University of Nevada Las Vegas Department of Physics and Astronomy University of Nevada Las Vegas South African Astronomical Observatory Department of Astronomy University of Cape Town Department of Physics University of the Free State Université Paris Cité CNRS Astroparticule et Cosmologie Université Paris Cité CEA Paris-Saclay IRFU/DAp-AIM Department of Astronomy Guangzhou University Cosmic Dawn Center (DAWN) Niels Bohr Institute University of Copenhagen Department of Physics and Astronomy Rutgers the State University of New Jersey Institute for Cosmic Ray Research The University of Tokyo ESA/ESTEC Department of Astronomy School of Physics Huazhong University of Science and Technology INAF-Osservatorio Astrofisico di Torino Sydney Institute for Astronomy School of Physics The University of Sydney Department of Astronomy Xiamen University Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Department of Astronomy University of Science and Technology School of Astronomy and Space Sciences University of Science and Technology of China Institute of Deep Space Sciences Deep Space Exploration Laboratory Department of Astronomy School of Physics and Astronomy Yunnan University Shanghai Astronomical Observatory Chi

We report the discovery of a peculiar X-ray transient,EP240408a,by Einstein Probe （EP） and follow-up studies made with EP,Swift,NICER,GROND,ATCA and other ground-based multiwavelength *** new transient was first detected with Wide-field X-ray Telescope （WXT） on board EP on April 8th,2024,manifested in an intense yet brief X-ray flare lasting for *** flare reached a peak flux of 3.9×10-9erg cm-2s-1in 0.5-4 ke V,～300 times brighter than the underlying X-ray emission detected throughout the *** and more precise follow-up observations by EP/FXT,Swift and NICER confirmed the finding of this new *** X-ray spectrum is non-thermal in 0.5-10 ke V,with a power-law photon index varying *** X-ray light curve shows a plateau lasting for ～4 d,followed by a steep decay till becoming undetectable ～10 d after the initial *** on its temporal property and constraints from previous EP observations,an unusual timescale in the range of 7-23 d is found for EP240408a,which is intermediate between the commonly found fast and long-term *** counterparts have been found in optical and near-infrared,with the earliest observation at 17 h after the initial X-ray detection,suggestive of intrinsically weak emission in these *** demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far,by comparison with,in particular,jetted tidal disruption events,gamma-ray bursts,X-ray binaries and fast blue optical *** nature of EP240408a thus remains an *** suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of～10 *** detection and follow-ups of more of such objects are essential for revealing their origin.

关键词： X-ray transients ${\bm~{Einstein~~Probe}}$

The hit-to-lead optimization of 1,2,3,4,4a,9a-hexahydro-1H-xanthenes as glucocorticoid receptor antagonists

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Chinese Chemical Letters 2014年第5期25卷 693-698页

作者： Yan-Hui Zhu Meng zhang qun-Yi Li Qing Liu jie zhang Yun-Yun Yuan Fa-Jun Nan Ming-Wei Wang The National Center for Drug Screening Shanghai Institute of Materia MedicaChinese Academy of Sciences The CAS Key Laboratory of Receptor Research Shanghai Institute of Materia MedicaChinese Academy of Sciences

The structure–activity relationship（SAR） study of a 1 2 3 4 4a 9a-hexahydro-1H-xanthene series of selective,human glucocorticoid receptor a（hGRa） antagonists is *** were screened using hydroxyapatite-based GR binding and MMTV-Luc co-transfection reporter gene *** different regions of the scaffold were modified to assess the effects on hGRa antagonism and related *** 8d exhibits an 8-fold better bioactivity than the original hit 1a,as well as an improved chemical stability,which make it a promising lead for the subsequent optimization.

关键词： Glucocorticoid receptor Antagonist 1 2 3 4 4a 9a-Hexahydroxanthene Structure–activity relationship Lead optimization

Moderate wetting and drying increases rice yield and reduces water use, grain arsenic level, and methane emission

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The Crop Journal 2017年第2期5卷 151-158页

作者： Jianchang Yang qun Zhou jianhua zhang Key Laboratory of Crop Genetics and Physiology of Jiangsu Province/Co-Innovation Center for Modern Production Technology of Grain Crops Yangzhou University Yangzhou 225009 China School of Life Sciences and State Key Laboratory of Agrobiotechnology The Chinese University of Hong Kong Hong Kong China

To meet the major challenge of increasing rice production to feed a growing population under increasing water scarcity,many water-saving regimes have been introduced in irrigated rice,such as an aerobic rice system,non-flooded mulching cultivation,and alternate wetting and drying(AWD).These regimes could substantially enhance water use efficiency(WUE) by reducing irrigation ***,such enhancements greatly compromise grain *** work has shown that moderate AWD,in which photosynthesis is not severely inhibited and plants can rehydrate overnight during the soil drying period,or plants are rewatered at a soil water potential of-10 to-15 k Pa,or midday leaf potential is approximately-0.60 to-0.80 MPa,or the water table is maintained at 10 to 15 cm below the soil surface,could increase not only WUE but also grain *** in grain yield WUE under moderate AWD are due mainly to reduced redundant vegetative growth;improved canopy structure and root growth;elevated hormonal levels,in particular increases in abscisic acid levels during soil drying and cytokinin levels during rewatering;and enhanced carbon remobilization from vegetative tissues to *** AWD could also improve rice quality,including reductions in grain arsenic accumulation,and reduce methane emissions from *** of moderate AWD with an appropriate nitrogen application rate may exert a synergistic effect on grain yield and result in higher WUE and nitrogen use *** research is needed to understand root–soil interaction and evaluate the long-term effects of moderate AWD on sustainable agriculture.

关键词： Alternate wetting and drying(AWD) Grain yield Nitrogen use efficiency Rice Water use efficiency

Influence of Indian Ocean Dipole on Tropical Cyclone Activity over Western North Pacific in Boreal Autumn

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Journal of Ocean University of China 2019年第4期18卷 795-802页

作者： ZHOU qun WEI Lixin zhang Runyu National Marine Environmental Forecasting Center Ministry of Natural Resources Beijing 100081 China

In this study, we investigated the influence of the Indian Ocean Dipole (IOD) on the interannual variability of tropical cyclone (TC) activity over the western North Pacific (WNP) during autumn (September November) from 1961 2015. We found the number of TCs making landfall in China to be significantly negatively correlated with the IOD index, which can be attributed to shifts in the location of TC formation together with the abnormal steering flow at 500 hPa. During negative IOD autumns, TC genesis regions move obviously westward due to the westward retreat of the WNP monsoon trough. The TC activity is remarkably enhanced near South China coastal areas, which is due to a contiguous 500-hPa subtropical ridge. In contrast, during positive IOD autumns, TC genesis positions obviously shift eastward and more TCs tend to exhibit recurvature around 130 E or a westward path south of 15 N led by an equatorward movement of the 500-hPa subtropical ridge with a break near 125 E. In our examination of large-scale circula- tion, we found a pair of equator-symmetric anticyclones in the lower troposphere resulting from variations in the large-scale Walker circulation induced by the anomalous sea surface temperature (SST) associated with a positive IOD. The resulting Philippines anti- cyclonic anomalies are closely related to the variability of the monsoon trough over the WNP region. Furthermore, the variations in the steering flow can be explained by the suppressed (enhanced) convective activities around the Philippines and the weakened (strengthened) local meridional circulation over East Asia in positive (negative) IOD years.

关键词： IOD tropical cyclone activity western North Pacific monsoon trough

Recent Progress on Two-Dimensional Nanoflake Ensembles for Energy Storage Applications

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Nano-Micro Letters 2018年第4期10卷 122-151页

作者： Huicong Xia qun Xu Jianan zhang College of Materials Science and Engineering Zhengzhou University

The rational design and synthesis of two-dimensional(2D) nanoflake ensemble-based materials have garnered great attention owing to the properties of the components of these materials, such as high mechanical flexibility, high specific surface area, numerous active sites,chemical stability, and superior electrical and thermal conductivity. These properties render the 2D ensembles great choices as alternative electrode materials for electrochemical energy storage systems. More recently,recognition of the numerous advantages of these 2D ensemble structures has led to the realization that the performance of certain devices could be significantly enhanced by utilizing three-dimensional(3D) architectures that can furnish an increased number of active sites. The present review summarizes the recent progress in 2D ensemble-based materials for energy storage applications,including supercapacitors, lithium-ion batteries, and sodium-ion batteries. Further, perspectives relating to the challenges and opportunities in this promising research area are discussed.

关键词： 2D nanoflakes Ensembles 3D architectures Supercapacitors Lithium-ion batteries Sodium-ion batteries

Assessing the Fishery Resource Status of China’s Coastal Waters Using Surplus Production Models

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Journal of Ocean University of China 2021年第5期20卷 1236-1244页

作者： zhang Qingqing LIU qun HAN Ya’nan College of Fisheries Ocean University of ChinaQingdao 266003China

Surplus production models(SPMs)are among the simplest and most widely used fishery stock assessment *** catch-effort data analysis(CEDA)and a surplus production model incorporating covariates(ASPIC)are softwares for analyzing fishery catch and fishing effort data using nonequilibrium *** China Fishery Statistical Yearbook,annual fishery production and fishing effort data of the Yellow Sea,Bohai Sea,East China Sea,and South China Sea have been published from 1979 till *** its catch and fishing effort data from 1980 to 2018,we apply the CEDA and ASPIC to evaluate fishery resources in Chinese coastal *** results show that the total maximum sustainable yield(MSY)estimate of the four China seas is 10.05-10.83 million tons,approximately equal to the marine fishery catch(10.44 million tons)reported in *** can be concluded that China’s coastal fishery resources are currently fully exploited and must be protected with a precautionary *** softwares produced similar results;however,the CEDA had a much higher R2 value(above 0.9)than ASPIC(about 0.2),indicating that CEDA can better fit the data and therefore is more suitable for analyzing the fishery resources in the coastal waters of China.

关键词： Chinese coastal waters fishery resources surplus production models(SPMs) catch-effort data analysis(CEDA) a surplus production model incorporating covariates(ASPIC) China Fishery Statistical Yearbook

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采用阻流器的近壁面海底管道绕流研究

大连理工大学学报 2025年第1期65卷 89-96页

作者：王杰刘政沅张彬滨宋朝周波大连理工大学船舶工程学院辽宁大连116024

为深入了解采用阻流器的海底管道自埋机制,基于Fluent软件,结合标准k-ε湍流模型,建立了高雷诺数下安装阻流器的近壁面海底管道绕流数值模型,研究了阻流器长度和间隙比对管道尾流与壁面边界层之间复杂的相互作用以及时空演化的影响.研... 详细信息

为深入了解采用阻流器的海底管道自埋机制,基于Fluent软件,结合标准k-ε湍流模型,建立了高雷诺数下安装阻流器的近壁面海底管道绕流数值模型,研究了阻流器长度和间隙比对管道尾流与壁面边界层之间复杂的相互作用以及时空演化的影响.研究结果表明采用阻流器可以显著增大管道与壁面之间流速以及管道附近脉动速度,但当阻流器长度达到临界值时,管道尾部会形成稳态结构.随着间隙比的增大,尾流演化可以分为4个区域:稳态结构、两次诱导壁面涡、单次诱导壁面涡、卡门涡街.适当的间隙比有利于诱导壁面旋涡的产生,从而加快管道周围沉积物冲刷.

关键词：阻流器海底管道壁面圆柱绕流湍流