检索结果-南通市图书馆

SIMULATION OF SEDIMENT DEPOSITION IN A CAVITY WITH FREE SURFACE

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2010年第5期22卷 626-633页

作者： ZHANG Xiao-feng CUI Zhan-feng LU Xin-hua state key {2. of water Resource and hydropower engineering Science Wuhan University Wuhan 430072 China Yangtze River Scientific Research Institute Wuhan 430010 China

Studies of the flow and sediment movement in a cavity with free surface were mostly limited to physical modeling experiments. In this study, the sediment movement is characterized in detail using a 3-D turbulent numerical model. To close the Reynolds equations, the standard k-ε model is employed. The VOF method is adopted to capture the time varying free surface and the porosity method is introduced to deal with the irregular boundary and the varying bed deformation. The computation results agree well with the experimental data in major aspects such as the vertical distribution of the sediment concentration and the deposition topography in the cavity. The comparisons show that this model can well predict the flow structure and the sediment movement and also the river bed deformation in a cavity.

关键词： 3-D turbulent flow cavity flow free surface VOF porosity sediment transport

ANALYSIS OF SOLUBLE CHEMICAL TRANSFER BY RUNOFF water IN FIELD

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2008年第3期20卷 382-390页

作者： TONG Ju-xiu YANG Jin-zhong state key {2. of water resources and hydropower engineering Science Wuhan University Wuhan430072 China

In order to determine the main factors influencing soluble chemical transfer and corresponding techniques for reducing fertilizer loss caused by runoff in irrigated fields, a physically based two-layer model was developed with incomplete mixing theory. Different forms of incomplete mixing parameters were introduced in the model, which was successfully verified with previous published experimental data. According to comparison, the chemicals loss of fertilizer is very sensitive to the runoff-related parameter while it is not sensitive to the infiltration-related parameter. The calculated results show that the chemicals in infiltration water play an important role in the early time of rainfall even with saturated soil, and it is mainly in the runoff flow in the late rainfall. Therefore, prevention of shallow subsurface drainage in the early rainfall is an effective way to reduce fertilizer loss, and the coverage on soil surface is another effective way.

关键词： soluble chemical transfer runoff incomplete mixing sensitive infiltration

THEORETICAL ANALYSIS AND NUMERICAL SIMULATION OF TURBULENT FLOW AROUND SAND WAVES AND SAND BARS

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2009年第2期21卷 292-298页

作者： LIU Shi-he XIONG Xiao-yuan LUO Qiu-shi state key {2. of water Resource and hydropower engineering Science Wuhan University Wuhan 430072 China School of water Resource and hydropower Wuhan University Wuhan 430072 China Changjiang River Administration of Navigation Affairs MC Wuhan 430014 China

Natural rivers usually possess sand waves and sand bars. In this article, the rapid distortion theory was used to study the turbulent flow over sand waves. The results show that the pre-existing sheafing motion and upstream anisotropy of the turbulence flow would have significant effect on the turbulent structures, and hence the memory effect should be taken into consideration. Furthermore, the 2.D mathematical model was employed to simulate the unsteady flow around the Taiping Sand Bar in the lower reach of the Yangtze River and the time step effect on the unsteady flow simulation with the implicit scheme was discussed at the same time. The results show that the implicit scheme keeps effective until the time step reaches a certain number, and the calculated water levels and velocities are in agreement with the observed data.

关键词： sand wave sand-bar rapid distortion theory numerical simulation

COMPOSITE ELEMENT MODEL FOR ROCK MASS SEEPAGE FLOW

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2006年第2期18卷 219-224页

作者： CHEN Sheng-hong FENG Xue-min state key {2. of water resources and hydropower engineering Science Wuhan UniversityWuhan 430072 China

In this paper, the algorithm developed on the concept of the Composite Element Method （CEM） is proposed for the seepage flow in discontinuous rock masses, The basic idea is that if an element contains one or more discontinuity segments, it will be denoted as a composite element having a set of hydraulic potential values defined at its nodes. By the variation principle, the governing equation can be established to solve the unknown hydraulic potential values at the composite element nodes. The main advantage of the proposed model is that the generation of calculation mesh will not be restricted strongly by the number, the position and the orientation of the discontinuities, A numerical example is presented at the end of the paper, to show the validity of the proposed model.

关键词： Composite Element Method(CEM) rock mass seepage flow

Development of distributed time-variant gain model for nonlinear hydrological systems

在线全文

学校读者我要写书评

暂无评论

Science china Earth sciences 2005年第6期48卷 713-723页

作者： XIA Jun1, 2. WANG Gangsheng1, TAN Ge1, YE Aizhong2.& G. H. Huang3 1. key laboratory of {2. Cycle & Related Land Surface Processes, Institute of Geographic sciences and Natural resources Research, Chinese Academy of sciences, Beijing 100101, china 2. state key laboratory of water resources & hydropower engineering sciences, wuhan university, wuhan 4.0072, china 3. Faculty of engineering, {12. of Regina, 3737 Wascana Parkway, Regina, Sask., S4S 0A2. Canada Correspondence should be addressed to Xia Jun 1. key laboratory of {2. Cycle & Related Land Surface Processes Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences 100101 Beijing China 2. state key laboratory of water resources & hydropower engineering sciences Wuhan University 430072 Wuhan China 3. Faculty of engineering University of Regina 3737 Wascana Parkway S4S 0A2 Sask Regina Canada

In this paper, a rainfall-runoff modeling system is developed based on a nonlinear Volterra functional series and a hydrological conceptual modeling approach. Two models, i.e. the time-variant gain model (TVGM) and the distributed time-variant gain model (DTVGM) that are built on the platform of Digital Elevation Model (DEM), Remote Sensing (RS) and Unit Hydro-logical Process were proposed. The developed DTVGM model was applied to two cases in the Heihe River Basin that is located in the arid and semiarid region of northwestern china and the Chaobai River basin located in the semihumid region of northern china. The results indicate that, in addition to the classic dynamic differential approach to describe nonlinear processes in hy-drological systems, it is possible to study such complex processes through the proposed sys-tematic approach to identify prominent hydrological relations. The DTVGM, coupling the advan-tages of both nonlinear and distributed hydrological models, can simulate variant hydrological processes under different environment conditions. Satisfactory results were obtained in fore-casting the time-space variations of hydrological processes and the relationships between land use/cover change and surface runoff variation.

关键词： hydrological process, nonlinearity, time-variant gain model, distributed hydrological model.

MATHEMATICAL MODEL FOR THE FLOW WITH SUBMERGED AND EMERGED RIGID VEGETATION

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2009年第5期21卷 722-729页

作者： HUAI Wen-xin CHEN Zheng-bing HAN Jie ZHANG Li-xiang ZENG Yu-hong state key {2. of water resources and hydropower engineering Science Wuhan University Wuhan430072 China Department of engineering Mechanics Kunming University of Science and Technology Kunming 650051 China

The article summarizes previous studies on the flow in open channels with rigid vegetation, and constructs a mathematical model for submerged and emerged rigid vegetation. The model involves the forces balance in the control volume in one-dimensional steady uniform flow. For submerged vegetation, the whole flow is divided into four regions： external region, upper vegetated region, transition region and viscous region. According to the Karrnan similarity theory, the article improves the mixing length expression, and then gives an analytical solution to predict the vertical distribution of stream-wise velocity in the external region. For emerged vegetation, the flow is divided into two region： outer region and viscous region. In the two circumstances, the thicknesses of each region are determined respectively. The comparison between the calculated results and our experimental data and other researchers＇ data proves that the proposed model is effective.

关键词： Karman similarity theory mixing length submerged and emerged rigid vegetation velocity distribution

An efficient method for detecting concurrency errors in object-oriented programs

在线全文

学校读者我要写书评

暂无评论

Science china(Information sciences) 2012年第12期55卷 2774-2784页

作者： HE YanXiang 1,2.WU Wei 2.& CHEN Yong 2.1 School of Computers,wuhan university,wuhan 4.0072,china 2.state key laboratory of Software engineering,wuhan university,wuhan 4.0072,china 1. School of Computers Wuhan University Wuhan 430072 China2. State Key Laboratory of Software Engineering Wuhan University Wuhan 430072 China

Multicore and multi-threaded processors have become the norm for modern ***,concurrent programs have become more and more prevalent despite being difficult to write and *** errors are highly likely to appear in concurrent code,conventional error detection methods such as model checking,theorem proving,and code analysis do not scale smoothly to concurrent *** is an indispensable technique for detecting concurrency errors,but it involves a great deal of manual work and is *** paper presents an automatic method for detecting concurrency errors in classes in object-oriented *** method uses a heuristic algorithm to automatically generate test cases that can effectively trigger ***,each test case is executed automatically and a fast method is adopted to identify the actual concurrency error from anomalous run *** have implemented a prototype of the method and applied it to some typical Java *** shows that our method is more effective and faster than previous work.

关键词： concurrency error dynamic test data race atomicity violations test case generation

A 2.D HYDRODYNAMIC MODEL FOR THE RIVER,LAKE AND NETWORK SYSTEM IN THE JINGJIANG REACH ON THE UNSTRUCTURED QUADRANGLES

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2010年第3期22卷 419-429页

作者： ZHANG Xi-bing HU De-chao WANG Min state key {2. of water resources and hydropower engineering Science Wuhan University Wuhan430072 China Yangtze River Scientific Research Institute Wuhan 430010 China state key {2. of Hydroscience and engineering Tsinghua University Beijing 100084 China

The main river, the Dongting Lake and river networks in the Jingjiang reach of the Yangtze River constitute a complex water system, for which a full 2.D hydrodynamic model is established instead of the traditional 1-D or compound models for simulation of such complex systems, based on the latest developments of computer technologies and numerical methods. To better handle irregular boundaries and keep the computation cost well in a reasonable limit, unstructured grids of moderate scale are used. In addition, a dynamic boundary tracking method is proposed to simulate variable flow domains at different floods, especially, when the moderate scale gird can not describe flows in narrow river-network channels at low water levels. The t9 semi-implicit method and the Eulerian-Lagrangian Method （ELM） are adopted, which make the model unconditionally stable with respect to the gravity wave speed and Courant number restrictions. Properties and efficiency of the model are discussed, and it is concluded that the new model is robust and efficient enough for the simulation of a big, complex water system. Validation tests show that the simulation results agree well with field data. It takes about 0.96 h to complete the computation of a 76 d flood, which indicates that the model is efficient enough for engineering applications.

关键词： 2.D numerical model river network unstructured grid semi-implicit Eulerian-Lagrangian Method (ELM) boundarytracking

Hierarchical Classification of Chinese Documents Based on N grams

在线全文

学校读者我要写书评

暂无评论

wuhan university Journal of Natural {2. 2001年第Z1期6卷 416-422页

作者： Zhou Shui geng 1, Guan Ji hong 2. He Yan xiang 2.1. state key {2. of Software engineering, wuhan university, wuhan 4.0072, china 2. School of Computer Science, wuhan university, wuhan 4.0072, china state key {2. of Software engineering Wuhan University Wuhan China School of Computer Science Wuhan University Wuhan China

We explore the techniques of utilizing N gram information to categorize Chinese text documents hierarchically so that the classifier can shake off the burden of large dictionaries and complex segmentation processing, and subsequently be domain and time independent. A hierarchical Chinese text classifier is implemented. Experimental results show that hierarchically classifying Chinese text documents based N grams can achieve satisfactory performance and outperforms the other traditional Chinese text classifiers.

关键词： Chinese text classification N grams feature selection hierarchical classification