检索结果-南通市图书馆

THE ALGORITHMS AND APPLICATIONS FOR DETERMINING PERMEABILITY COEFFICIENTS BY PULSE SPECTRUM TECHNIQUE

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2002年第2期14卷 112-115页

作者： Wang Ling-ling college of water Conservancy and hydropower engineering, hohai university, nanjing 210098, china college of water Conservancy and hydropower engineering Hohai University Nanjing 210098 China

The determination of inhomogeneous permeability coefficient was studied as a parameter-control inverse problem for parabolic-type equation in this paper. By virtue of PST, the solution of the inverse problem is converted into an iteration procedure of solving a direct problem and solving a Fredholm integral equation of the first kind. Besides, Tikhonov normalization method is introduced to treat the uncertainty caused by the integral equation. Thus an algorithm for determining inhomogeneous permeability coefficient has been formulated and implemented. Numerical results show: (1) The algorithm presented in the paper is suitable to strongly inhomogeneous seepagel; (2) The additional information needed for solution is merely the seepage velocity on partical boundary, so that drill works can be reduced remarkably; (3) The algorithm is applicable to determining inhomogeneous transmission coefficients in groundwater engineering or other engineering.

关键词： inverse problem Pulse Spectrum Technique (PST) permeability coefficient parameter identification

Influence of fractality of fracture surfaces on stress and displacement fields at crack tips

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2008年第S2期51卷 95-100页

作者： BAO TengFei,WU ZhongRu,GU ChongShi & GU YanLing college of water Conservancy and hydropower engineering,hohai university,nanjing 210098,china college of water Conservancy and hydropower engineering Hohai University Nanjing 210098 China

In the classic theory of fracture mechanics,expressions for calculating the stresses and displacements in the vicinity of the crack tip are deduced on the basis of the assumption that a fracture surface is a smooth surface or that a crack is a smooth *** fact,the surface of a crack formed during the fracture is usually very *** the real asymptotic form of the stress and displacement fields at the crack tip is different from the classic *** the irregularity of a real fracture surface or a real crack profile,the crack is taken as a fractal one,and then the real asymptotic form at the crack tip is developed by applying Griffith's energy balance principle and fractal *** the developed asymptotic form,it is discovered that the fractality of the crack reduces the stress singularity at the crack tip.

关键词： fracture surface crack fractal stress and displacement fields

EFFECTS OF HYDRAULIC AND GEOMETRIC PARAMETERS ON DOWNSTREAM CAVITY LENGTH OF DISCHARGE TUNNEL SERVICE GATE

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2009年第6期21卷 774-778页

作者： MOHAGHEGH A college of water Conservancy and hydropower engineering Hohai University

Aerators on discharge tunnel outlets may be regarded as an effective protection against cavitation erosion. The air entrainment of aerators is governed by a number of independent parameters, including the bottom slope of releasing free-surface flow tunnel downstream of service gate, the end top slope of pressure tunnel, the height of step, and the Froude number at take-off. During eight phases of experiments, the effects of above-mentioned parameters were observed on the cavity length downstream of the fully open operating service gate of a discharge tunnel. The results show that, the bottom slope of releasing free-surface flow tunnel has obvious effect on the cavity length as well as the Froude number at gate take-off. The effect of the step height variations on the cavity length could be considered for higher discharges and steeper tunnel top slope, particularly in higher discharges, resulting in shorter cavity length downstream of service gate.

关键词： cavitation erosion cavity length discharge tunnel service gate

AN IMPROVED ALGORITHM FOR DPIV CORRELATION ANALYSIS

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2007年第1期19卷 62-67页

作者： WU Long-hua college of water Conservancy and hydropower engineering Hohai University Nanjing 210098 China

In a Digital Particle Image Velocimetry （DPW） system, the correlation of digital images is normally used to acquire the displacement information of particles and give estimates of the flow field. The accuracy and robustness of the correlation algorithm directly affect the validity of the analysis result. In this article, an improved algorithm for the correlation analysis was proposed which could be used to optimize the selection/determination of the correlation window, analysis area and search path. This algorithm not only reduces largely the amount of calculation, but also improves effectively the accuracy and reliability of the correlation analysis. The algorithm was demonstrated to be accurate and efficient in the measurement of the velocity field in a flocculation pool.

关键词： Digital Particle Image Velocimetry (DPIV),correlation analysis improved algorithm

Detection of subcritical crack propagation for concrete dams

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2009年第12期52卷 3654-3660页

作者： BAO TengFei1 ,2&YU Hong 1,2 1college of water Conservancy&hydropower engineering,hohai university,nanjing 210098,china 2National engineering Research Center of water Resources Efficient Utilization and engineering Safety,nanjing 210098,china college of water Conservancy & hydropower engineering Hohai University Nanjing 210098 China National engineering Research Center of water Resources Efficient Utilization and engineering Safety Nanjing 210098 China

Subcritical propagation of cracks is a warning sign of *** such propagation is detected at an early stage,timely maintenance measures can be taken to prevent the failure of *** detect the subcritical propagation of a crack,the crack needs to be monitored continuously in a long term, which is not realistic under certain ***,cracks in concrete dams can be monitored continuously by dam monitoring to offer possible detection for subcritical *** this paper, with measured crack openings from dam monitoring,a state equation for characterizing crack development is established based on the grey system *** relation between the stability of the equation and the subcritical crack propagation is investigated,then a criterion is proposed for detecting subcritical *** example demonstrates the validity of the criterion and its potential for practical application.

关键词： crack subcritical propagation criterion concrete

Research on stability of the accumulated rock-soil body of reservoir bank under rainfall condition

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2009年第9期52卷 2528-2535页

作者： GU ChongShi1,2,WU HaiZhen1,2 & SU HuaiZhi1,2 1 college of water Resources and hydropower engineering,hohai university,nanjing 210098,china 2 National engineering Research Center of water Resources Efficient Utilization and engineering Safety,hohai university,nanjing 210098,china 3 Jiangxi water Conservancy Research Institute,Nanchang 330029,china 1. college of water Resources and hydropower engineering Hohai University Nanjing 210098 China 2. National engineering Research Center of water Resources Efficient Utilization and engineering Safety Hohai University Nanjing 210098 China 3. Jiangxi water Conservancy Research Institute Nanchang 330029 China

The shear strength parameters property of rock-soil aggregates in embankment slope of reservoir,that is,the relationship between cohesion and gravel content,between friction angle and gravel content,and the relationship between cohesion and water content,between friction angle and water content,is studied based on the direct shear test results,the shear strength change law of the rock-soil aggregates is given,and the unsaturated shear strength formulation of rock-soil aggregates that could consider suction and saturation degree influence is put forward in this paper,through which the sliding or failure physical mechanism of this type of slope under the condition of rainfall infiltration is studied. Also the 3D unsteady saturated-unsaturated seepage field and its FEM resolving mode are established based on the analysis of the slope rainfall infiltration process. Case study with this method indicates that the minimum safety factor of the accumulated rock-soil aggregates dose not arrive at the moment of rainfall cessation,but appears several hours after the rainfall cessation,this phenomenon is in accordance with the practical slope engineering's failure process and could explain appropriately the slope failure caused by rainfall infiltration. Research results in this paper have an important reference value for the research on stability of the accumulated rock-soil aggregates in embankment slope of reservoir,and can enrich the stability analysis method and relevant theory of reservoir embankment slope.

关键词： reservoir bank slope rock-soil aggregates rainfall infiltration saturated/unsaturated seepage

Field experiments on greenhouse gas emissions and nitrogen and phosphorus losses from rice paddy with efficient irrigation and drainage management

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2011年第6期54卷 1581-1587页

作者： PENG ShiZhang1,2,YANG ShiHong1,2,XU JunZeng1,2 & GAO HuanZhi1,2 1State Key Laboratory of Hydrology-water Resources and Hydraulic engineering,hohai university,nanjing 210098,china 2college of water Conservancy and hydropower engineering,hohai university,nanjing 210098,china 1. State Key Laboratory of Hydrology-water Resources and Hydraulic engineering Hohai University Nanjing 210098 China2. College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China

Greenhouse gas emissions,nitrogen and phosphorous losses through ammonia volatilization,leaching and surface drainage from rice paddy under efficient irrigation and drainage were analyzed based on field experimental data in order to reveal the eco-environmental impacts of efficient irrigation and drainage on rice *** results showed that total methane emission from rice paddy under the controlled irrigation was reduced by more than 80% and total nitrous oxide emission increased by 15.9% compared with flooding *** comprehensive global warming potentials(GWP) of methane and nitrous oxide were 62.23 gCO2 m-2 for rice paddy under the controlled irrigation,reduced by 68.0% compared with flooding *** to large reduction in seepage and surface drainages,nitrogen and phosphorous losses through leaching were reduced by 40.1% and 54.8%,nitrogen and phosphorous losses through surface drainage were reduced by 53.9% and 51.6% from rice paddy under efficient irrigation and drainage compared with traditional irrigation and *** loss through ammonia volatilization was reduced by 14.0%.Efficient irrigation and drainage management is helpful to mitigate greenhouse gases emission,nitrogen and phosphorus losses and their pollution on groundwater and surface water.

关键词： efficient irrigation and drainage nitrogen and phosphorus greenhouse gas ammonia volatilization paddy field

Assessment model of dam operation risk based on monitoring data

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2007年第z1期50卷 144-152页

作者： WU ZhongRu1,2?, SU HuaiZhi1,2 & GUO HaiQing1 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 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

Although the dams produce remarkable social and economic benefits, the threat made by unsafe dams to the life and property of people who live in the lower river area is un-negligible. Based on the monitoring data which reflect the safety condition of dams, the risk degree concept is proposed and the analysis system and model for evaluating risk degree (rate) are established in this paper by combining the reliability theory and field monitoring data. The analysis method for risk degree is presented based on Bayesian approach. A five-grade risk degree system for dam operation risk and corresponding risk degree is put forward according to the safety condition of dams. The operation risks of four cascade dams on some river are analyzed by the model and approach presented here and the result is adopted by the owner.

关键词： dam monitoring data operation risk degree analysis model

Hybrid method of limit equilibrium and finite element internal force for analysis of arch dam stability against sliding

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2011年第4期54卷 793-798页

作者： BAO TengFei1,2,3,XU BaoSong1,2,3 & ZHENG XueQing1,2,3 1State Key Laboratory of Hydrology-water Resources and Hydraulic engineering,hohai university,nanjing 210098,china 2National engineering Research Center of water Resources Efficient Utilization and engineering Safety,nanjing 210098,china 3college of water Conservancy and hydropower engineering,hohai university,nanjing 210098,china 1. State Key Laboratory of Hydrology-water Resources and Hydraulic engineering Hohai University Nanjing 210098 China2. National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety Nanjing 210098 China3. College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China

A hybrid method of limit equilibrium and finite element internal force for analysis of arch dam stability against sliding is *** finite element internal force method(FEIFM) is used to provide more accurate thrust forces acting on the faces of a slip body,and the limit equilibrium method(LEM) is employed to evaluate the factor of safety of the slip *** method presented can deal with a slip body with large amount of geometrically complex slip *** addition,compared with the traditional LEM,it can meet the balance condition of the forces in the slip *** example shows that the factor of safety obtained by the method presented agrees well with the theoretical solution.A practical example is also presented to demonstrate the application of the method in the stability analysis of an arch dam *** results from the examples show that the method is promising in analysis of arch dam stability against sliding.

关键词： arch dam stability against sliding limit equilibrium method finite element internal force method