检索结果-南通市图书馆

The effect of texture and irrigation on the soil moisture vertical-temporal variability in an urban artificial landscape： a case study of Olympic Forest Park in Beijing

引用

Frontiers of Environmental Science & Engineering 2015年第2期9卷 269-278页

作者： Xiaofeng zhang xu zhang Guanghe LI School of Environment Tsinghua University Beijing 100084 China

Soil moisture variability in natural landscapes has been widely studied; however, less attention has been paid to its variability in the urban landscapes with respect to the possible influence of texture stratification and irrigation management. Therefore, a case study was carried out in the Beijing Olympic Forest Park to continuously monitor the soil in three typical profiles from 26 April to 11 November 2010. The texture stratification significantly affected the vertical distribution of moisture in the non- irrigated profile where moisture was mostly below field capacity. In the profile where irrigation was sufficient to maintain moisture above field capacity, gravity flow led to increased moisture with depth and thus eliminated the influence of texture. In the non-irrigated sites, the upper layer （above 80 cm） exhibited long-term moisture persis- tence with the time scale approximating the average rainfall interval. However, a coarse-textured layer wea- kened the influence of rainfall, and a fine-textured layer weakened the influence of evapotranspiration, both of which resulted in random noise-like moisture series in the deeper layers. At the irrigated site, frequent irrigation neutralized the influence of evapotranspiration in the upper layer （above 60 em） and overshadowed the influence of rainfall in the deeper layer. As a result, the moisture level in the upper layer also behaved as a random noise-like series; whereas due to deep transpiration, the moisture of the deep layer had a persistence time-scale longer than a month, consistent with characteristic time-scales found for deep transpiration.

关键词： moisture vertical distribution moisture tem-poral variation texture stratification irrigation meteorolo-gical forcing urban landscape

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

An improved analytical model of cutting temperature in orthogonal cutting of Ti6Al4V

引用

Chinese Journal of Aeronautics 2019年第3期32卷 759-769页

作者： Chenwei SHAN xu zhang Bin SHEN Dinghua zhang Key Laboratory of Modern Design and Integrated Manufacturing Technology of Ministry of Education Northwestern Polytechnical University 206 Institution North Electronics Research Institute Co. Ltd

Cutting heat has significant effects on the machined surface integrity of titanium alloys in the aerospace field. Many unwanted problems such as surface burning, work hardening, and tool wear can be induced by high cutting temperatures. Therefore, it is necessary to accurately predict the cutting temperature of titanium alloys. In this paper, an improved analytical model of the cutting temperature in orthogonal cutting of titanium alloys is proposed based on the Komanduri-Hou model and the Huang-Liang model. The temperatures at points in a cutting tool, chip, and workpiece are calculated by using the moving heat source method. The tool relief angle is introduced into the proposed model, and imaginary mirrored heat sources of the shear plane heat source and the frictional heat source are applied to calculate the temperature rise in a semi-infinite medium. The heat partition ratio along the tool-chip interface is determined by the discretization method. For validation purpose, orthogonal cutting of titanium alloy Ti6Al4V is performed on a lathe by using a sharp tool. Experimental results show to be consistent well with those of the proposed model,yielding a relative difference of predicted temperature from 0.49% to 9.00%. The model demonstrates its ability of predicting cutting temperature in orthogonal cutting of Ti6Al4V.

关键词： Cutting temperature Moving heat source method Orthogonal cutting Relief angle Titanium alloy

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Decentralized robust stabilization of discrete-time fuzzy large-scale systems with parametric uncertainties: a LMI method

引用

Journal of Systems Engineering and Electronics 2006年第4期17卷 836-845页

作者： zhang Yougang xu Bugong Coll. of Automatic Science & Engineering South China Univ. of Technology Guangzhou 510640 P. R. China

Decentralized robust stabilization problem of discrete-time fuzzy large-scale systems with parametric uncertainties is considered. This uncertain fuzzy large-scale system consists of N interconnected T-S fuzzy subsystems, and the parametric uncertainties are unknown but norm-bounded. Based on Lyapunov stability theory and decentralized control theory of large-scale system, the design schema of decentralized parallel distributed compensation （DPDC） fuzzy controllers to ensure the asymptotic stability of the whole fuzzy large-scale system is proposed. The existence conditions for these controllers take the forms of LMIs. Finally a numerical simulation example is given to show the utility of the method proposed.

关键词： fuzzy large-scale system parametric uncertainties decentralized Parallel distributed compensation linear matrix inequalities.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Heat Equation with Memory in Anisotropic and Non-Homogeneous Media

引用

Acta Mathematica Sinica,English Series 2011年第2期27卷 219-254页

作者： Jiongmin YONG xu zhang Department of Mathematics University of Central Florida FL 32816 USA Key Laboratory of Systems and Control Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 P. R. China Yangtze Center of Mathematics Sichuan University Chengdu 610064 P. R. China

A modified Fourier＇s law in an anisotropic and non-homogeneous media results in a heat equation with memory, for which the memory kernel is matrix-valued and spatially dependent. Different conditions on the memory kernel lead to the equation being either a parabolic type or a hyperbolic type. Well-posedness of such a heat equation is established under some general and reasonable conditions. It is shown that the propagation speed for heat pulses could be either infinite or finite, depending on the different types of the memory kernels. Our analysis indicates that, in the framework of linear theory, heat equation with hyperbolic kernel is a more realistic model for the heat conduction, which might be of some interest in physics.

关键词： Heat equation with memory anisotropic and non-homogeneous media well-posedness propagation speed

来源：

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

Distinct phase transitions and dielectric anomalies in two 4-methylanilinium salts

引用

Science China Chemistry 2012年第2期55卷 201-207页

作者： zhang Wen xu RuiJun Ordered Matter Science Research Center Southeast University Nanjing 211189 China

Solid-state phase transitions of 4-methylanilinium perchlorate （4-CH3C6H4NH3.C104, 1） and tetrafluoroborate （4-CH3C6H4- NH3-BF4, 2） were investigated with variable-temperature X-ray single-crystal structure analysis and thermal studies. Both 1 and 2 undergo first-order phase transitions and exhibit distinct dielectric anomalies at 385 and 247 K, respectively.

关键词： organic-inorganic hybrid compounds dielectricity phase transition crystal structure switchable molecular dielectrics

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Molecular-scale electronics： From device fabrication to functionality

引用

Chinese Chemical Letters 2017年第11期28卷 2058-2064页

作者： xu zhang Tao Li School of Chemistry Chemical Engineering Shanghai Jiao Tong University Shanghai 200240 China

By wiring molecules into circuits, ＂molecular electronics＂ aims at studying electronic properties of single molecules and their ensembles, on this basis exploiting their intrinsic functionalities, and eventually applying them as building blocks of electronic components for future electronic devices. Herein, fabricating reliable solid-state molecular devices and developing synthetic molecules endowed with desirable electronic properties, have been two major tasks since the dawn of molecular electronics. This review focuses on recent advances and efforts regarding the main challenges in this field, highlighting fabrication of nanogap electrodes for single-molecule junctions, and self-assembled-monolayers （SAMs） for functional devices. The prospect of molecular-scale electronics is also discussed.

关键词： Molecular electronics Nanogap electrodes Single-molecule junctions Self-assembled monolayers Functional molecular devices

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

On tame and wild bocses

引用

Science China Mathematics 2005年第4期48卷 456-468页

作者： zhang Yingbo xu Yunge Department of Mathematics Beijing Normal UniversityBeijing100875China Department of Mathematics Beijing Normal UniversityBeijing100875China Faculty of Mathematics & Computer Sciences Hubei University Wuhan430062China

We first give an alternative proof of the well-known Drozd's wild Theorem,which lowers down the dimension 43 to 20. Then we list more minimally wild bocses and discuss the possible differentials of the first arrow of ... 详细信息

关键词： Bocs, tameness, wildness, differential.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Profile of *** zhang

引用

Science China(Life Sciences) 2017年第9期60卷 1010-1012页

作者： xu, zhang Fourth Mil Med Univ Inst Neurosci Xian Shaanxi Peoples R China Chinese Acad Sci Inst Neurosci Beijing Peoples R China

*** zhang was conferred the Bachelor's degree of Medicine from Fourth Military Medical University in *** 1990 to 1994,he carried out his *** at the Department of Neuroscience,Karolinska Institute in ***,he was appointed as lecturer,associate professor and professor successively at the Institute of Neuroscience,Fourth Military Medical *** 1999,he was recruited as a principal investigator by the Institute of Neuroscience,Chinese Academy of *** received the outstanding young investigator award of National Natural Science Foundation of China in *** was elected as Academician of Chinese Academy of Sciences in 2015.

关键词：博士中国科学院院士国家自然科学基金第四军医大学科学研究所神经科学医学院研究员

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Conversion of CH4, steam and O_2 to syngas and hydrocarbons via dielectric barrier discharge

引用

Journal of Natural Gas Chemistry 2009年第1期18卷 94-97页

作者： Baowei Wang xu zhang Yongwei Liu Genhui xu Key Laboratory for Green Chemical Technology of the Ministry qf Education School qf Chemical Engineering and Technology. Tianjin University Tianjin 300072 China

The conversion of CH4 with oxygen and steam in a dielectric barrier discharge （DBD） was studied in the paper to discuss the effects of different factors, such as the content of feed-in gas, the applied voltage and frequency. The results showed that a lower ratio of CH4 to O2 always resulted in a higher conversion of CH4. When it was 2, the conversion reached 32.43% without steam introduced into the system. The main effect of steam was increasing the selectivity to CO. The reaction was accelerated and the selectivities to CO and hydrocarbons were enhanced by increasing the applied voltage. It was also observed that a higher frequency led to a lower current and then restrained the reaction.

关键词： methane steam oxygen dielectric barrier discharges plasma

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The Fundamental Plane of GRBs

引用

Research in Astronomy and Astrophysics 2023年第12期23卷 221-229页

作者： xu zhang Quan-Gui Gao Department of Physics Yuxi Normal UniversityYuxi 653100China Key Laboratory of Astroparticle Physics of Yunnan Province Kunming 650091China

Gamma-ray bursts(GRBs)exhibit powerful radiation and relativistic jets similar to ***,the central engine of GRBs remains *** this paper,we use the fundamental plane to analyze a sample of GRBs with measured *** extend,over~12 orders of magnitude,the correlation analysis and fundamental plane with a sample of X-ray binaries,active galactic nuclei(AGNs)including blazars,and brightest cluster *** fundamental plane of our de-beamed sample,with a measured mass(logL_(R)=(0.60±0.03)logL_(X)+(0.78±0.02)logM+7.23±0.95),closely aligns with the findings of previous work on *** finding suggests that GRBs adhere to the fundamental plane of AGNs and supports the theory proposed in previous work that the central engine of GRBs may be black *** observation provides a plausible explanation for the striking similarities between GRBs and AGNs.

关键词： (stars:)gamma-ray burst general-radiation mechanisms general-galaxies active

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：