检索结果-南通市图书馆

A new method of calculating crown projection area and its comparative accuracy with conventional calculations for asymmetric tree crowns

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

Journal of Forestry Research 2024年第4期35卷 171-188页

作者： Mingrui Zhang huiquan bi Xingji jin Michael McLean School of Forestry Northeast Forestry UniversityHarbin 150040People’s Republic of China Forest Science NSW Department of Primary IndustriesLevel 304PSQ12 Darcy StreetParramattaNSW 2150Australia School of Ecosystem and Forest Sciences The University of MelbourneMelbourne 3010Australia

This paper introduces a new method of calculating crown projection area(CPA),the area of level ground covered by a vertical projection of a tree crown from measured crown radii through numerical interpolation and *** novel method and other four existing methods of calculating CPA were compared using detailed crown radius measurements from 30 tall trees of Eucalyptus pilularis variable in crown size,shape,and *** four existing methods included the polygonal approach and three ways of calculating CPA as the area of a circle using the arithmetic,geometric and quadratic mean *** were made across a sequence of eight non-consecutive numbers(from 2 to 16)of measured crown radii for each tree over the range of crown asymmetry of the 30 trees through generalized linear models and multiple comparisons of *** sequence covered the range of the number of crown radii measured for calculating the CPA of a tree in the literature.A crown asymmetry index within the unit interval was calculated for each tree to serve as a normative *** a slight overestimation of 2.2%on average and an overall mean error size of 7.9%across the numbers of crown radii that were compared,our new method was the least biased and most *** CPA as a circle using the quadratic mean crown radius was the second best,which had an average overestimation of 4.5%and overall mean error size of 8.8%.These two methods remained by and large unbiased as crown asymmetry increased,while the other three methods showed larger bias of *** the conventional method of using the arithmetic mean crown radius to calculate CPA as a circle,bias correction factors were developed as a function of crown asymmetry index to delineate the increasing magnitude of bias associated with greater degrees of crown *** study reveals and demonstrates such relationships between the accuracy of CPA calculations and crown asymmetry and will help increase awa

关键词： Crown radius measurements Interpolated crown contour Projected crown area Multiple comparisons of means

在线全文

学校读者我要写书评

暂无评论

系统元件带有延时的最佳年代更换策略

应用数学 2007年第4期20卷 633-639页

作者：胡必锦重庆交通大学理学院信息与计算科学研究所重庆400074

Das等研究过关于年代更换策略的一种简单模型[1,2],但这个模型不具有现实性.本文考虑的年代更换模型是具有现实意义的.在我们的模型中,元件的寿命T为"功能衰减"变量U和延时变量H之和,即T=U+H.在U和H满足某些条件下,可得出:T∈IFR的结论... 详细信息

Das等研究过关于年代更换策略的一种简单模型[1,2],但这个模型不具有现实性.本文考虑的年代更换模型是具有现实意义的.在我们的模型中,元件的寿命T为"功能衰减"变量U和延时变量H之和,即T=U+H.在U和H满足某些条件下,可得出:T∈IFR的结论(引理1).此外,我们得到保证最佳年代更换策略的解的存在性与唯一性的充分条件,但不必要求T∈IFR(定理1).

关键词：年代更换模型最佳策略延时变量存在唯一性

Kullback-Liebler测度在地震记录反演中的应用

在线全文

学校读者我要写书评

暂无评论

应用数学 2006年第4期19卷 683-687页

作者：胡必锦重庆交通大学信息与计算科学研究所重庆400074

在地震记录反演中,盲目反褶积是一个相当困难的问题.讨论这个问题现有各种方法,如累积矩法等.本文利用Likas等处理图像恢复的变分法来讨论地震记录反演中的盲目反褶积问题.利用Kullback-Liebler信息测度获得一个非常有用的统计函数(即... 详细信息

在地震记录反演中,盲目反褶积是一个相当困难的问题.讨论这个问题现有各种方法,如累积矩法等.本文利用Likas等处理图像恢复的变分法来讨论地震记录反演中的盲目反褶积问题.利用Kullback-Liebler信息测度获得一个非常有用的统计函数(即变分函数),此函数的极值点就含有所要求的反射系数序列的信息,并且拟订出求此泛数极值点的一套算法.

关键词：盲目反褶积地震记录 K-L信息测度算法

在线全文

学校读者我要写书评

暂无评论

寿命分布的残余熵

工程数学学报 2009年第3期26卷 451-455页

作者：胡必锦重庆交通大学信息与计算科学系重庆400074

本文讨论基于寿命分布类的特性,研究不同于现有文献的另一类残余寿命熵的特性,并在一定的条件下得到残余寿命熵的上界。同时,作为一种应用,讨论一类依赖于参数α的指数型寿命模型的残余寿命熵,并得出当参数α大于1时,相应的残余寿命熵... 详细信息

本文讨论基于寿命分布类的特性,研究不同于现有文献的另一类残余寿命熵的特性,并在一定的条件下得到残余寿命熵的上界。同时,作为一种应用,讨论一类依赖于参数α的指数型寿命模型的残余寿命熵,并得出当参数α大于1时,相应的残余寿命熵受一个单调下降到零的函数的控制。

关键词：寿命分布类残余熵上界指数型寿命模型

在线全文

学校读者我要写书评

暂无评论

系统的最佳随机维护策略

应用数学 2009年第3期22卷 509-513页

作者：胡必锦重庆交通大学信息与计算科学系重庆400074

系统进行有计划的预防性维护时,要求设计一个具有周期T的维护时间表.有一个重要的问题就是这种维护时间表是否具有最佳周期.本文给出最佳随机维护策略问题有解存在的必要条件,并得到结论:当失效时刻Y服从指数分布时,对维护次数N的任意... 详细信息

系统进行有计划的预防性维护时,要求设计一个具有周期T的维护时间表.有一个重要的问题就是这种维护时间表是否具有最佳周期.本文给出最佳随机维护策略问题有解存在的必要条件,并得到结论:当失效时刻Y服从指数分布时,对维护次数N的任意概率分布,最佳随机维护策略问题都无解.

关键词：预防不完全维护最佳周期存在性

Structural Characteristics and Influencing Factors of Carbon Emission Spatial Association Network:A Case Study of Yangtze River Delta City Cluster,China

在线全文

学校读者我要写书评

暂无评论

Chinese Geographical Science 2024年第4期34卷 689-705页

作者： bi Xi SUN Renjin hu Dongou SHI Hongling ZHANG Han School of Economics and Management China University of Petroleum(Beijing)Beijing 102249China China Petroleum Planning&Engineering Institute Beijing 100083China

City cluster is an effective platform for encouraging regionally coordinated *** reduction of carbon emissions within city cluster via the spatial association network between cities can help coordinate the regional carbon emission management,realize sustainable development,and assist China in achieving the carbon peaking and carbon neutrality *** paper applies the improved gravity model and social network analysis(SNA)to the study of spatial correlation of carbon emissions in city clusters and analyzes the structural characteristics of the spatial correlation network of carbon emissions in the Yangtze River Delta(YRD)city cluster in China and its influencing *** results demonstrate that:1)the spatial association of carbon emissions in the YRD city cluster exhibits a typical and complex multi-threaded network *** network association number and density show an upward trend,indicating closer spatial association between cities,but their values remain generally ***,the network hierarchy and network efficiency show a downward trend but remain high.2)The spatial association network of carbon emissions in the YRD city cluster shows an obvious‘core-edge’distribution *** network is centered around Shanghai,Suzhou and Wuxi,all of which play the role of‘bridges’,while cities such as Zhoushan,Ma'anshan,Tongling and other cities characterized by the remote location,single transportation mode or lower economic level are positioned at the edge of the network.3)Geographic proximity,varying levels of economic development,different industrial structures,degrees of urbanization,levels of technological innovation,energy intensities and environmental regulation are important influencing factors on the spatial association of within the YRD city ***,policy implications are provided from four aspects:government macro-control and market mechanism guidance,structural characteristics of the‘core-edge’network,reconfigura

关键词： carbon emission spatial association network social network analysis(SNA) quadratic assignment procedure(QAP)model Yangtze River Delta city cluster China

High-Voltage and Fast-Charging Lithium Cobalt Oxide Cathodes: From Key Challenges and Strategies to Future Perspectives

在线全文

学校读者我要写书评

暂无评论

Engineering 2024年第6期37卷 105-127页

作者： Gongrui Wang Zhihong bi Anping Zhang Pratteek Das hu Lin Zhong-Shuai Wu State Key Laboratory of Catalysis Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023China Dalian National Laboratory for Clean Energy Chinese Academy of SciencesDalian 116023China

Lithium-ion batteries(LIBs)with the“double-high”characteristics of high energy density and high power density are in urgent demand for facilitating the development of advanced portable ***,the lithium ion(Li+)-storage performance of the most commercialized lithium cobalt oxide(LiCoO_(2),LCO)cathodes is still far from satisfactory in terms of high-voltage and fast-charging capabilities for reaching the double-high ***,we systematically summarize and discuss high-voltage and fast-charging LCO cathodes,covering in depth the key fundamental challenges,latest advancements in modification strategies,and future perspectives in this *** and elaborated discussions are first presented on key fundamental challenges related to structural degradation,interfacial instability,the inhomogeneity reactions,and sluggish interfacial *** provide an instructive summary of deep insights into promising modification strategies and underlying mechanisms,categorized into element doping(Li-site,cobalt-/oxygen-site,and multi-site doping)for improved Li+diffusivity and bulkstructure stability;surface coating(dielectrics,ionic/electronic conductors,and their combination)for surface stability and conductivity;nanosizing;combinations of these strategies;and other strategies(i.e.,optimization of the electrolyte,binder,tortuosity of electrodes,charging protocols,and prelithiation methods).Finally,forward-looking perspectives and promising directions are sketched out and insightfully elucidated,providing constructive suggestions and instructions for designing and realizing high-voltage and fast-charging LCO cathodes for next-generation double-high LIBs.

关键词： Lithium cobalt oxide High energy/power density Fast-charging High-voltage Lithium-ion battery

Recent advances and future prospects on Ni_(3)S_(2)-Based electrocatalysts for efficient alkaline water electrolysis

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

Green Energy & Environment 2024年第4期9卷 659-683页

作者： Shiwen Wang Zhen Geng Songhu bi Yuwei Wang Zijian Gao Liming jin Cunman Zhang Clean Energy Automotive Engineering Center School of Automotive StudiesTongji UniversityShanghai201804China

Green hydrogen(H_(2))produced by renewable energy powered alkaline water electrolysis is a promising alternative to fossil fuels due to its high energy density with zero-carbon ***,efficient and economic H_(2) production by alkaline water electrolysis is hindered by the sluggish hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Therefore,it is imperative to design and fabricate high-active and low-cost non-precious metal catalysts to improve the HER and OER performance,which affects the energy efficiency of alkaline water ***_(3)S_(2) with the heazlewoodite structure is a potential electrocatalyst with near-metal conductivity due to the Ni–Ni metal ***,the review comprehensively presents the recent progress of Ni_(3)S_(2)-based electrocatalysts for alkaline water ***,the HER and OER mechanisms,performance evaluation criteria,preparation methods,and strategies for performance improvement of Ni_(3)S_(2)-based electrocatalysts are *** challenges and perspectives are also analyzed.

关键词： Alkaline water electrolysis Hydrogen Electrocatalysts Ni_(3)S_(2)

A new mixed type crack propagation criterion in shale reservoirs

在线全文

学校读者我要写书评

暂无评论

Petroleum 2024年第1期10卷 85-92页

作者： Muru Ding Zhirong jin Yanjun Zhang jinghong hu Beijing Key Laboratory of Unconventional Natural Gas Geology Evaluation and Development Engineering China University of Geosciences Sinopec Jiangsu Oil Field Branch Oil & Gas Technology Research Institute Changqing Oilefiled CompanyPetroChina

Hydraulic fracturing is a mainstream technology for unconventional oil and gas reservoirs development all over the world. How to use this technology to achieve high-level oil and gas resource extraction and how to form complex fracture networks as hydrocarbon transportation channels in tight reservoirs, which depends to a large extent on the interaction between hydraulic and pre-existing cracks. For hydraulic fracturing of fractured reservoirs, the impact of natural fractures, perforation direction, stress disturbances, faults and other influencing factors will produce a mixed I&II mode hydraulic fracture. To forecast whether hydraulic fractures cross pre-existing fractures, according to elastic mechanics and fracture mechanics, a stress state of cracks under the combination of tensile(I) and shear(II) is presented. A simple mixed-mode I&II hydraulic fracture's crossing judgment criterion is established, and the propagation of hydraulic fractures after encountering natural fractures is analyzed. The results show that for a given approaching angle there exists a certain range of stress ratio when crossing occurs. Under high approaching angle and large stress ratio, it is likely that hydraulic cracks will go directly through pre-existing cracks. The reinitiated angle is always controlled within the range of approximately 30°among the main direction of penetration.

关键词： Crack propagation criterion Stress ratio Approaching angle Reinitiated angle Mechanical model