检索结果-南通市图书馆

Review on hidden trouble detection and health diagnosis of hydraulic concrete structures

Science China(Technological Sciences) 2007年第z1期50卷 34-50页

作者： WU ZhongRu1,2?, LI Ji1, GU ChongShi1,2 & SU HuaiZhi1,2.1 College of Water Conservancy and Hydropower engineering, Hohai university, Nanjing 210098, China 2 National engineering Research Center of Water Resources Efficient Utilization and engineering Safety, Nanjing 210098, China College of Water Conservancy and Hydropower engineering Hohai University Nanjing 210098 China National engineering Research Center of Water Resources Efficient Utilization and engineering Safety Nanjing 210098 China

A large number of hydraulic concrete structures have hidden defects such as cracks, erosion, freeze and thaw, thermal fatigue, carbonization. These hidden defects seriously affect the strength, stability and durability of structures. These problems are studied mainly by single monitoring or diagnosis methods at present. The integration of multiple monitoring and diagnosis methods is not applied widely. Besides, the analysis theory on these problems is not developed very well. The systemic study on the aging mechanism of hydraulic concrete structures, time- variation model and health diagnosis is still not enough. The support for engineering practice is limited. Aimed at these major scientific and technological problems and combined with specific projects, study on detection of hidden defects and health diagnosis of hydraulic concrete structure has been carried out. This study includes the following content: field non-destructive examination of hidden defects of hydraulic concrete structures, seepage detection, the construction of in-situ sensing system, the combination of field detection and in-situ monitoring, the mechanism of crack, freeze and thaw, erosion and carbonization of hydraulic concrete structure, mechanism of combination aging; time-variation model of hydraulic concrete structure, theories and methods for health diagnosis of hydraulic concrete structures.

关键词： hydraulic concrete structure hidden trouble detection health diagnosis

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

Theory on real-time control of construction quality and progress and its application to high arc dam

引用

Science China(Technological Sciences) 2010年第10期53卷 2611-2618页

作者： ZHONG DengHua1, REN BingYu1, LI MingChao1, WU BinPing1 & LI MingChuan2.1 department of Hydraulic and Hydroelectric engineering, School of Civil engineering, Tianjin university, Tianjin 300072, China 2 Ertan Hydropower Development Company, Ltd., Chengdu 610051, China 1. department of Hydraulic and Hydroelectric engineering School of Civil Engineering Tianjin University Tianjin 300072 China2. Ertan Hydropower Development Company Ltd. Chengdu 610051 China

A complete scheme for solving the key scientific problems associated with high-standard,high-intensity continuous construction of high arch dams was presented. First,based on a coupling analysis of construction system decomposition and coordination for a high arc dam,a mathematical model for real-time control of construction quality and progress that considers complex constraints was developed. Second,a method of progress control was proposed based on a dynamic simulation. Third,a dynamic quality control mechanism was established based on construction information collected using a PDA. Fourth,a system for integrating collected information,progress simulation and quality control analyses under a network environment was developed. Finally,these methods were applied to a practical project to show that each aspect of a construction process can be managed effectively and that real-time monitoring and feedback control can be realized. Our methods provide new theoretical principles and technical measures for quality and progress control in the high arc dam construction process.

关键词： construction quality construction progress dynamic simulation real-time control network high arc dam

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

A preliminary study on vegetation-erosion dynamics and its applications

引用

Science China Earth Sciences 2005年第5期48卷 689-700页

作者： WANG Zhaoyin 1,2 , WANG Guangqian 1 , LI Changzhi 1 & WANG Feixin 1 1. department of Hydraulic engineering, Tsinghua university, Beijing 100084, China 2. International Research and Training Center on Erosion and Sedimentation, Beijing 100084, China 1. department of Hydraulic engineering Tsinghua University 100084 Beijing China 2. International Research and Training Center on Erosion and Sedimentation 100084 Beijing China

Vegetation-erosion dynamics is a new interdisciplinary science, studying the laws of evolution of watershed vegetation under the action of various ecological stresses. Introducing a qualitative expression of ecological stresses in this paper, the present authors establish the cou- pled differential equations for the vegetation-erosion process and derive a theoretical solution. The model is applied to the Anjiagou watershed on the Loess Pateau and the Xiaojiang water- shed and its sub-watersheds on the Yunnan Plateau. The calculated results agree well with the vegetation development processes. Abstracted from the differential equations the so-called vegetation-erosion chart is worked out, with which we can predict the development trend of vegetation under no human stresses. It is demonstrated that the erosion control is important for vegetation development and reforestation must be a long-term strategy. On the Yunnan Plateau with relatively high precipitation and temperature, vegetation can be greatly improved if erosion is controlled. On the dry and cold Loess Pateau suffering from high rate of soil erosion, however, vegetation can effectively control erosion but erosion reduction exhibits low effectiveness on vegetation development. Vegetation in the area is not stable and management is always needed to maintain the vegetation.

关键词： vegetation-erosion dynamics, human activities, coupled differential equations, erosion control, vigor ofvegetation.

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 the dynamics in a transitional boundary layer

引用

Communications in Nonlinear Science and Numerical Simulation 2001年第3期6卷 111-171页

作者： C. B. LEE and R. LEE department of Mechanics and engineering Science/State Key Laboratory for Studies of Turbulence and Complex Systems, Peking university, Beijing 100871, China department of engineering Mechanics, Tsinghua university, Beijing 100084, Chi department of Mechanics and engineering Science / State Key Laboratory for Studies of Turbulence and Complex Systems Peking University Beijing 100871 China department of engineering Mechanics Tsinghua University Beijing 100084 China

A model is presented to describe the dynamic physical processes that occur in a transitional boundary layer flow. The CS-solitons, the closed vortex, the secondary closed vortex and the chain of ring-like vortices are postulated to be the basic flow structures of the transitional boundary layer as well as the turbulent boundary layer. It is argued that the central features of transitional and developed turbulent boundary layer flows can be explained in terms of how the series vortices interact with each other, and with the CS-solitons. The physical process that leads to the regeneration of the new closed vortex along the border of the CS-soliton, as well as the processes of evolution of the vortices to high frequency vortices, is described. The model is supported by the important developments in a number of "kernel" experiments, which illustrate both transitional and developed turbulent boundary layer. An important aspect of the model is that it has been formulated to be consistent with accepted rational mechanics concepts that are known to provide a proper physical description of other flows.

关键词： boundary layer transition dynamic processes onset of turbulence

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

复杂工艺流程企业内部供应链产量联合优化

引用

系统工程学报 2001年第4期16卷 305-310页

作者：赵道致天津理工学院经济管理学院

建立了以利润最大化为目标函数的企业内部供应链多环节产量联合优化模型 ,证明了目标函数是凹函数 ,并给出了最优解的解法 .在优化模型中 ,利用投入产出模型分析了加工制造类企业各类需求项目之间的关系。

关键词：供应链联合优化成本分析投入产出复杂工艺流程企业目标函数

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

Phylogenetics and biogeography of eastern Asian–North American disjunct genus Pachysandra (Buxaceae) inferred from nucleotide sequences

引用

Journal of Systematics and Evolution 2009年第3期47卷 191-201页

作者： 1Zhihua JIAO 2,3Jianhua LI 1(School of Chemical and Environmental engineering, China university of Mining and Technology, Beijing 100083, China) 2(The Arnold Arboretum of Harvard university, cambridge, MA 02138, USA) 3(Adjunct Faculty of College of Life Sciences, Zhejiang university, Hangzhou 310029, China) (Adjunct Faculty of College of Life Sciences Zhejiang University Hangzhou 310029 China)

Pachysandra is an eastern Asian-North American disjunct genus with three species, two in eastern Asia (Pachysandra axillaris and Pachysandra terminalis) and one in eastern North America (Pachysandra procumbens). Although morphological and cytological studies suggest a close affinity of P. procumbens with P. axillaris, molecular data from nuclear and chloroplast DNA regions have provided conflicting signals. In this study, we tested previous phylogenetic hypotheses using sequences of nuclear ribosomal DNA internal transcribed spacers and chloroplast ndhF gene from multiple individuals of each of the three species. We also estimated the time of divergence between eastern Asia and eastern North America. Our results support the morphological and cytological conclusion that P. procumbens is more closely related to P. axillaris than to P. terminalis. The estimated time of divergence of P. axillaris and P. procumbens was 14.6±5.5 mya, consistent with estimates from many other eastern Asian-North American disjunct genera. The migration of Pachysandra populations from eastern Asia to North America might have occurred by way of the North Atlantic land bridge.

关键词： Buxaceae divergence time ndhF nrDNA ITS Pachysandra.

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Construction and application of formal ontology for mine

引用

中国有色金属学会会刊：英文版 2011年第S3期21卷 577-582页

作者： CHENG Gang 1, 2, ZHANG Yin-ling1, 2, WANG Fei 1 ,2, ZHANG Zhen-hui 3, GUO Yu-xiang1, 2.1. Key Laboratory of Mine Spatial Information Technologies of State Bureau of Surveying and Mapping, Henan Polytechnic university, Jiaozuo 454003, China 2. School of Surveying and land Information engineering, Henan Polytechnic university, Jiaozuo 454003, China 3. Qingdao Branch of Naval Aeronautical engineering Institute, Qingdao 266041, China Henan Polytech Univ Key Lab Mine Spatial Informat Technol State Bur Surveying & Mapping Jiaozuo 454003 Peoples R China Henan Polytech Univ Sch Surveying & Land Informat Engn Jiaozuo 454003 Peoples R China Naval Aeronaut Engn Inst Qingdao Branch Qingdao 266041 Peoples R China

Digital mine is the only way for the development of mining industry in China. Due to lack of appropriate standards and norms, and different awareness in the field of digital mine among academia and industry insiders, the meaning for digital mine is still unclear. Starting from the nature of mining and removing of views of specialized fields, this paper constructs formal ontology for digital mine and proposes the four levels for it. The ontology clarifies the concept world for digital mine, defines the meaning of concepts and relations clearly, provides a reference for the standard construction for digital mine and provides a unified semantic framework for the integration of heterogeneous mine data. Meanwhile, it can provide formal reasoning knowledge for expert system of digital mine and improve the intelligence and automation while the machine automatically interpreting and processing mine spatial data.

关键词： Digital mine formalization ontology concept world semantic share

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

Description to wear debris boundaries by radar graph fractal method

引用

Chinese Science Bulletin 2007年第16期52卷 2285-2290页

作者： LIU HongTao1,2 & GE ShiRong1 1 Institute of Tribology and Reliability engineering,China university of Mining & Technology,Xuzhou 2.1008,China 2 College of Mechanical and Electrical engineering,China university of Mining & Technology,Xuzhou 2.1116,China Institute of Tribology and Reliability engineering China University of Mining and Technology Xuzhou 221008 China

In this paper,radar graph fractal method is introduced to describe wear debris boundaries. Research results show that it is a nice way to describe wear debris boundaries. Since the longest axis is selected as the first coordinate axis,its center point selected as the center point of the radar graph,and the co-ordinate value of wear debris boundary selected as the measure parameter,the limitations existing in Yard fractal measure method can be avoided. For any wear debris,its radar graph fractal dimension value is one and only,and as the wear debris shape changes from round to strip,the radar graph fractal dimension value also changes from low to high,showing strong uniqueness and independence. Due to the fact that the researched wear debris is gotten in different wear states,the results also prove that radar graph fractal dimension value is correlated with frictional pairs work condition and wear state. Radar graph fractal method is compared with Yard fractal measure methods,and results show that ra-dar graph fractal dimension values gotten from different wear debris have enough value grads to avoid effect of errors,and provide higher sensitivity for wear debris shape. This paper also discusses the influencing factors for radar graph fractal method. With the increase of the decomposing degree value,the radar graph fractal dimension tends to keep stable at one certain value,showing the typical characteristic of the fractal theory. All this proves that radar graph fractal method is an effective description method for wear debris boundaries.

关键词：磨粒边界雷达图表分形法

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

Thermal-stress Simulation of Direct-chill Casting of AZ31 Magnesium Alloy Billets

引用

Journal of Wuhan university of Technology(Materials Science) 2009年第3期24卷 376-382页

作者：胡红军 College of Materials Science and engineering Chongqing University National engineering Research Center for Magnesium Alloys Chongqing University College of Material Science and engineering Chongqing University of Technology

Two-dimensional （2D） transient coupled finite element model was developed to compute the temperature and stress field in cast billets, so as to predict the defects of the I-type billets made from AZ31 magnesium alloy and find the causes and solutions for surface cracks and shrinkages during direct-chill （DC） casting process. Method of equivalent specific heat was used in the heat conduction equation. The boundary and initial conditions used for primary and secondary cooling were elucidated on the basis of the heat transfer during the solidification of the billet. The temperature and the thermal-stress fields were simulated with the thermal-structural coupled module of ANSYS software. The influences of casting parameters on the distributions of temperature and stress were studied, which helped optimize the parameters （at pouring temperature of 680 ℃, casting speed of 2 min/s, heat-transfer coefficient of the second cooling equals to 5 000 W/m^2.℃^-1）. The simulation results of thermal stress and strain fields reveal the formation mechanism of some casting defects, which is favourable for optimizing the casting parameters and obtain high quality billets. Some measures of controlling processes were taken to prevent the defects for direct-chill casting billets.

关键词： magnesium alloy direct-chill casting temperature and stress fields numerical simulation solidification model

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 optimization of replica distribution in the unstructured overlays

引用

Science China(Information Sciences) 2012年第3期55卷 714-722页

作者： FENG GuoFu1,2 , LI WenZhong2, LU SangLu2, CHEN DaoXu2 & BUYYA Rajkumar3 1School of Information Science, Nanjing Audit university, Nanjing 210029, China 2State Key Laboratory of Novel Software Technology, Nanjing university, Nanjing 210093, China 3department of Computer Science and Software engineering, The university of Melbourne, Victoria 3010, Australia 1. School of Information Science Nanjing Audit University Nanjing 210029 China2. State Key Laboratory of Novel Software Technology Nanjing University Nanjing 210093 China3. Department of Computer Science and Software Engineering The University of Melbourne Victoria 3010 Australia

Replication is a widely used technique in unstructured overlays to improve content availability or system performance. A fundamental question often addressed by previous work focused on: how many replicas ought to be allocated for each data item given the fixed query rates and limited storage capability? In this paper, we have put forth two optimal replica distributions to achieve the highest success rate and the lowest message consumption. Especially, we have investigated the influence of item size on replica distribution. Our results show that Square-Root Replication, which is traditionally considered to be optimal, is not always the best choice. Our study offers a new deep understanding of resource managment in self-organized unstructured overlays.

关键词： unstructured overlay item size distribution query rate success rate expected search size

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

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：