检索结果-南通市图书馆

Area-corrected species richness patterns of vascular plants along a tropical elevational gradient

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2017年第4期14卷 694-704页

作者： XU Xiang zhang hua-yong LUO Jian zhang Dong-jie MAAthen North China Electric Power University Research Center for Engineering Ecology and Nonlinear Science Queen Mary University of London School of Electronic Engineering and Computer Science

The relationship and elevation is a hot issue between species richness in ecology and has been documented extensively. It is widely accepted that area size can significantly affect this relationship and thus mask the effects of other predictors. Despite the importance of the relationship between species richness and elevation while accounting for the area effect, it is insufficiently studied. Here, we evaluated area-corrected species richness patterns of all vascular plants as well as six vascular plant subgroups （seed plants, ferns, trees, shrubs, herbs and vines） along a tropical elevational gradient （Hainan Island, China）. If assessed in equal-elevation bands, uncorrected species richness showed bell-shaped curves, while area-corrected species richness assessed in equal-area bands appeared to increase monotonically due to the small proportion of highlands on Hainan Island. The mid-domain effect （MDE） was significantly correlated with both uncorrected and area-corrected species richness. On Hainan Island, the use of equal-area elevational bands increased the explanatory power of *** findings provide useful insights to adjust for the area effect and highlight the need to use equal- area bands along the elevational gradient.

关键词： Hainan Island Species-area relationship Mid-domain effect Vascular plant diversity Growthform

ESL-SELO:A Robust Image Denoising Algorithm with Penalty

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2017年第3期33卷 753-770页

作者： Guo-hua WANG San-guo zhang Peng-jie DAI School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049China Key Laboratory of Big Data Mining and Knowledge Management Chinese Academy of SciencesBeijing100049China School of Business Remin University of ChinaBeijing 100872China

Robust image recovery methods have been attracted more and more attention in recent decades for its good property of tolerating system errors or measuring noise. In this paper, we propose a new robust method （ESL-SELO） to recover nosing image, which combine exponential loss function and seamless-L0 （SELO） penalty function to guarantee both accuracy and robustness of the estimator. Theoretical result showed that our method has a local optimal solution and good asymptotic properties. Finally, we compare our method with other methods in simulation which shows better robustness and takes much less time.

关键词： denoising algorithm penalty function robust SELO

Highly Transparent and Colorless Polyimide Film with Low Dielectric Constant by Introducing Meta-substituted Structure and Trifluoromethyl Groups

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2021年第4期39卷 455-464,I0006页

作者： Hong-Tao Zuo Feng Gan jie Dong Peng zhang Xin Zhao Qing-hua zhang State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghai 201620China Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China

An effective design strategy for preparing highly transparent polyimide film with low dielectric constant is *** key to the strategy is to simultaneously introduce meta-substituted structure and trifluoromethyl in polymer *** using this design strategy,a highly transparent polyimide film with low-k was synthesized from 3,5-diaminobenzotrifluoride(m-TFPDA)and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)through a two-step *** obtained m-TFPDA/6FDA(CPI)film(~30 pm)possesses high optical transparency(λ_(cutoff)=334 nm,T_(450nm)=85.26%,Haze=0.31)and is close to colorless(L^(*)=96.03,a^(*)=-0.34,b^(*)=2.12,yellow index=3.96).The intrinsic k and dielectric loss value of the film are 2.27 and 0.0013 at 10 kHz,*** importantly,such low dielectric performance could remain stable up to 280℃,and the film shows a low moisture rate(~0.51%),which helps to maintain the low-k property stability in different humid ***,the film also shows good thermal stability and mechanical properties,with a glass transition temperature(T_(g))of 296℃and the 5 wt%decomposition temperature(T_(d,s%))of 522℃under N_(2).The tensile strength and tensile modulus of the film are 85.1 MPa and 1.96 GPa,*** addition,the film is soluble in common solvents,which allows simple solution processing and low-cost,continuous roll-to-roll *** design strategy is beneficial to improving the transparency,lightening yellow color,lowering the dielectric constant and meanwhile maintaining the comprehensive properties of polyimide films,which is mainly due to the introduced meta-substituted and trifluoromethyl structures effectively inhibiting the transfer of charge transfer complex(CTC)effects and increasing the free volume of *** design strategy could also be extended to other high-performance polymer systems.

关键词： Polyimide film Transparent Colorless Low dielectric constant

Variable Selection of Generalized Regression Models Based on Maximum Rank Correlation

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2014年第3期30卷 833-844页

作者： Peng-jie DAI Qing-zhao zhang Zhi-hua SUN School of Business Renmin University of China Department of Mathematics University of Chinese Academy of Sciences

In this paper, we investigate the variable selection problem of the generalized regression models. To estimate the regression parameter, a procedure combining the rank correlation method and the adaptive lasso technique is developed, which is proved to have oracle properties. A modified IMO （iterative marginal optimization） algorithm which directly aims to maximize the penalized rank correlation function is proposed. The effects of the estimating procedure are illustrated by simulation studies.

关键词： maximum rank correlation estimation adaptive LASSO oracle properties generalized regression models.

Non-isothermal reduction kinetics of titanomagnetite by hydrogen

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2013年第12期20卷 1134-1140页

作者： jie Dang Guo-hua zhang Xiao-jun Hu Kuo-chih Chou State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing School of Metallurgical and Ecological Engineering University of Science and Technology Beijing

Reduction of titanomagnetite （TTM） powders by H2-Ar gas mixtures was investigated under a non-isothermal condition by using a thermogravimetric analysis system. It was found that non-isothermal reduction of TTM proceeded via a dual-reaction mechanism. The first reaction was reduction of TTM to wustite and ilmenite, whereas the second one was reduction of wiistite and ilmenite to iron and titanium dioxide. By using a new model for the dual reactions, which was in an analytical form and incorporated different variables, such as time, temperature, particle size, and hydrogen partial pressure, rate-controlling steps for the dual reactions were obtained with the apparent activation energies calculated to be 90-98 and 115-132 kJ/mol for the first and second reactions, respectively.

关键词： titanomagnetite ore reduction hydrogen reaction kinetics

Analysis of fluidized zone in transparent soil under jet induced by pipe leakage

在线全文

学校读者我要写书评

暂无评论

Water Science and Engineering 2023年第2期16卷 203-210页

作者： Li-jie Jiang Bin zhang Sai-hua huang Yu Shao College of Water Resources and Environmental Engineering Zhejiang University of Water Resources and Electric PowerHangzhou 310018China Key Laboratory for Technology in Rural Water Management of Zhejiang Province Hangzhou 310018China College of Civil Engineering and Architecture Zhejiang UniversityHangzhou 310058China

Jets caused by burst tubes erode the surrounding soil, eventually leading to issues such as ground collapse. It is therefore highly important to study the mechanisms of soil erosion caused by jets after pipeline leakage. To investigate the water-soil interaction mechanisms of pipe leakage, this study used transparent soil and developed a three-dimensional experimental device to observe the fluidization process. Changes in the boundary of the fluidization transition area were investigated, and a formula for calculating the soil damage area was derived. The results showed three different shapes of the fluidized cavity appearing in the fluidization process. The particles initially moved upward and then gradually transitioned into a state of backflow. The effects of particle size, upper load, and porosity on fluidization were also analyzed. It was found that soil with a large particle size and a lower porosity under a heavy upper load can effectively restrain fluidization. Therefore, large-diameter and dense soil can be used as pipe-covering material.

关键词： Water-soil interaction Fluidized cavity Transparent soil Particle image velocimetry Pipe leakage

高锰钢表面等离子熔覆低碳铁-铬-镍合金涂层的组织和耐磨性能

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

电镀与涂饰 2017年第6期36卷 324-327页

作者：袁磊胡永俊万俊张天成晓玲李风揭晓华张海燕肖小亭广东工业大学材料与能源学院广东广州510006

采用等离子熔覆技术在高锰钢表面原位反应制备了低碳Fe–Cr–Ni合金涂层。利用金相显微镜、扫描电镜和X射线衍射仪分析了熔覆层和热影响区的显微组织、形貌以及相组成,讨论了它们的形成机制,并用摩擦试验机测试了涂层和基体的耐磨性。... 详细信息

采用等离子熔覆技术在高锰钢表面原位反应制备了低碳Fe–Cr–Ni合金涂层。利用金相显微镜、扫描电镜和X射线衍射仪分析了熔覆层和热影响区的显微组织、形貌以及相组成,讨论了它们的形成机制,并用摩擦试验机测试了涂层和基体的耐磨性。结果表明,制得的Fe–Cr–Ni合金涂层无裂纹,与基体表现为冶金结合,由γ(Fe–Cr–Ni固溶体)相与M7C3等碳化物组成。根据γ相形貌,熔覆层组织由上到下依次为等轴晶、树枝晶、胞状晶和平面晶。热影响区组织为魏氏体。基体为奥氏体和少量珠光体组织。Fe–Cr–Ni合金涂层的显微硬度最高为723 HV,约为基体的3倍。涂层的磨损量远小于基体的磨损量,Fe–Cr–Ni合金涂层可显著改善高锰钢的硬度和耐磨性。

关键词：高锰钢铁铬镍合金等离子熔覆显微组织显微硬度耐磨性

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

在线全文

学校读者我要写书评

暂无评论

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 ${\bm~{Einstein~~Probe}}$

Bioinspiration:Pull-Out Mechanical Properties of the Jigsaw Connection of Diabolical Ironclad Beetle’s Elytra

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2023年第1期36卷 86-94页

作者： jie Wei Bo-hua Sun School of Sciences Xi’an University of Architecture and TechnologyXi’an 710055China School of Civil Engineering Xi’an University of Architecture and TechnologyXi’an 710055China Institute of Mechanics and Technology Xi’an University of Architecture and TechnologyXi’an 710055China

In engineering,connections between components are often weak *** connection methods can easily reduce the strength of components,resulting in unpredictable failure *** nature,numerous connection methods for biological structures with excellent mechanical properties have *** the connection methods of organisms in nature can inspire new ideas for bionic connection *** the diabolical ironclad beetle is under pressure,the elytra are not easy to separate,which ensures the stability of the beetle’s external structure,thus making the beetle extremely resistant to *** reason for this is the interlocking and toughening effect of the unique jigsaw connection between the ***,in this paper,a theoretical analysis model is established and used to analyze the mechanical behavior of the diabolical ironclad beetle’s jigsaw connection during the drawing process and determine the influences of factors such as quantity,angle,and geometric characteristics on the mechanical properties of the jigsaw *** results of the theoretical analysis are then compared with the results of experiments and ABAQUS finite element simulation.

关键词： Theoretical analysis Bionics Jigsaw connection 3D Printing Finite element