Abstract:Based on the CMORPH-Gauge merged data and observed rain gauge data, the daily area rainfall of 15 sub-catchments in the Huaihe River Basin was calculated during flood seasons(June to September)from 2008 to 2011, using the Thiessen polygon method and the grid arithmetic average method. Comparative statistical analysis was conducted on the results of the two methods. The results show that the two sets of area rainfall of the 15 sub-catchments exhibited systematic differences and a significant linear correlation. The daily area rainfall also showed systematic difference. The area rainfall based on rain gauge data was generally greater than that based on the CMORPH-Gauge merged data. There was a strong correspondence for the magnitude between the two sets of area rainfall. The overall correspondence ratio was 78. 8%, with the ratio of rainfall values that differed by an order of magnitude being 20. 5%. The correspondence ratio for the light-rainfall magnitude reached 91. 4%.

Abstract:The bias-corrected and spatially and temporally downscaled(BCSD)method was used to downscale 20 GCM in IPCC AR4 in an A1B scenario in the source region of the Yellow River based on the data of daily precipitation, daily temperature, maximum temperature, and minimum temperature from 16 meteorological stations during the baseline period from 1961 to 1990. The performance and the confidence of BCSD are demonstrated in brief. The downscaling results show that, in the future, in the source region of the Yellow River, the temperature will increase by 0. 032℃ per year and the precipitation will increase by 0. 50 mm per year, with fluctuations and a slightly increasing trend, in the A1B scenario. Meanwhile, the temperature and precipitation are increasing significantly in the southeastern area, indicating that the climate there is becoming warm and humid.

Abstract:In order to evaluate the impact of hydropower exploitation on a river’s ecological environment, we established an evaluation index system, which includes 22 factors falling within the scopes of the water environment, ecological environment, and social environment, based on the unique geographical and climatic conditions and social and economic development in Tibet. With comprehensive consideration of various factors, we determined the standards for classification of the indices. We used the comprehensive index method to construct the evaluation model, and classified the evaluation results into five categories: insignificant influence, less insignificant influence, moderate influence, less significant influence, and significant influence. A case study at the Manla Hydropower Station showed that the exploitation of hydropower had little impact on the station, and the application results were consistent with the actual situation.

Abstract:Research achievements on the estimation of loss of life caused by dam breaks are summarized in this paper, with consideration of the complexity of such estimation. Warning and evacuation processes were studied. Warning and evacuation models as well as a mortality estimation model were established to estimate the number of exposed people. The idea of dividing the hazard zones based on flood characteristics is proposed on the basis of historical data on dam breaks in China. Criteria for dividing the hazard zones and mortality functions were established, as were a method and estimation formulas for estimating the loss of life caused by dam breaks in China. An application shows that the proposed method and estimation formulas can objectively evaluate the loss of lives caused by dam breaks in China.

Abstract:Based on analysis of the flow-dividing characteristics and riverbed evolution of the Xiaohuangzhou bifurcated reach of the Yangtze River, the influence of the evolution of the Xiaohuangzhou bifurcated reach on the Xinjizhou bifurcated reach downstream of the Yangtze River was studied using a mathematical model. According to the results, the evolution of the Xiaohuangzhou bifurcated reach has a significant influence on the flow-dividing characteristics of the downstream Xinjizhou bifurcated reach. In the current situation, the recession of the left branch of the Xiaohuangzhou bifurcated reach will lead to the recession of the left branches of the Xinshengzhou and Xinjizhou bifurcated reaches and development of the left branch of the Xinqianzhou reach, while development of the left branch of the Xiaohuangzhou bifurcated reach will lead to development of the left branches of the Xinshengzhou and Xinjizhou bifurcated reaches and a small change in the left branch of the Xinqianzhou bifurcated reach.

Abstract:A numerical model of open-channel flow over a rough bed was established based on double-averaged NS(DANS)equations. The turbulence was simulated by a modified Spalart-Allmaras(S-A)turbulence model, and the form-induced stress was calculated with a sub-layer-scale eddy viscosity model. The results show that the form-induced stress within the roughness layer cannot be ignored, and it decreased rapidly with the distance above the top of the roughness layer. The form-induced stress accounted for the dispersion of the velocity profiles and caused a slight reduction of the mean velocity. It also significantly decreased the Reynolds stress at the top of the roughness layer. In addition, this study shows that the velocity profile, the Reynolds stress profile, and the form-induced stress profile are affected by the distribution of the porosity. A smoother profile of porosity has less impact on the flow and turbulence characteristics.

Abstract:In order to study the effects of a group of bridges built across the Yongjiang River, a tidal river, on the flood and tide control of the river, a two-dimensional numerical model was established for the unsteady flow of the Yongjiang River based on the Delft3D model. The established model was calibrated and verified by the field observation data and used to study the influence of the group of bridges on the flow velocity and water level of the river under different flood and tide conditions. The results show that a single bridge has an effect on the flow near the bridge, while a group of bridges have a much greater accumulative influence on the flow velocity and water level and increase the influenced area. The effects of the bridges on water flow under different flood and tide conditions were compared. It was found that the effects of the bridges were more significant under the conditions of a spring tide and a small flood than under the conditions of a large flood and a neap tide.

Abstract:In order to improve the utilization rate of rainfall in Nanjing City, rainfall data forecasted by the National Meteorological Center over a forthcoming four-day period and observed rainfall data from the Nanjing Meteorological Station for the period from June 26 to October 28, 2011 were collected. The accuracy of rainfall forecasts and their applications to rice irrigation decision-making were analyzed. The results show that the accuracy was high in forecasting light rainfall and no rainfall, and the calculated irrigation water could be applied with a low risk of wasting irrigation water. When moderate rainfall and heavy rainfall were forecasted, there was a high probability of the occurrence of rainfall, and two-day delayed irrigation could be applied. Supplementary irrigation could be applied if there was no rainfall or if the rainfall could not meet the requirements of crop growth.

Abstract:According to theory and practice, based on consistent principles, the optical density nonlinear correction problem in particle concentration measurement was solved based on the generalized Lambert-Beer law. The problem of the effect of particle size on particle concentration measurement was solved using the size index. In addition, the extinction coefficient of the mixed particles was processed reasonably well. Solving these problems is the key to developing the desktop photoelectric sediment analyzer.

Abstract:In order to improve the construction speed of a concrete dam, a method of fast construction using thick pouring layers and short layer intervals was used. Based on the construction process of an RCC gravity dam located in Southwest China, the concrete stress was calculated with the deformation method according to the measured strain during the construction and initial running periods. The results accurately reflect the stress development under the condition of fast construction during the construction and initial running periods, providing valuable references for similar engineering construction projects.

Abstract:In dykes with fabriform sand, friction often exists between two adjacent geotextile bags and between a geotextile bag and the sand, and the transverse tension and the longitudinal tension of the geotextile bag are anisotropic. Based on these characteristics, a three-dimensional finite element method was used to simulate a dyke with fabriform sand, and the experimental data were adopted to analyze the stability of the dyke and its influencing factors. The results show that the integral safety factor increased significantly as the tensile strength of the geotextile bags and the filled soil strength increased. As the depth of the filled soil increased, the integral safety factor decreased rapidly at first, and then tended to become stable.

Abstract:According to research on mode Ⅰ and mode Ⅱ crack damage coupled with fractures, a damage evolution equation that is more suitable for mode Ⅱ cracks was established based on the damage equation of a mode Ⅰ crack. Then, the calculation method for the damage area was obtained. The variation of the direction in which the crack developed was studied using the damage gradient, over a period ranging from damage to cracking of the mode Ⅱ crack. Finally, the propagation angle of the mode Ⅱ crack was determined to be 79°. This propagation angle was compared with that obtained by the classic criterion. The results show that the method used in this study is feasible.

Abstract:In order to explore the formation conditions of transient saturated areas of a coarse-grained soil embankment slope with rainfall infiltration, and to investigate the effects of rainfall infiltration parameters on the development of the transient saturated areas, we designed various numerical calculation schemes using field and laboratory data and actual meteorological data, and conducted numerical simulation of the rainfall infiltration process of the coarse-grained soil embankment slope under the influence of rainfall infiltration parameters based on the theory of rainfall infiltration. The results show that the rainfall infiltration direction and formation of transient saturated areas were determined by the ratio of rainfall intensity(q)to saturated permeability coefficient(k_sat). When q/k_sat ≥1. 5, transient saturated areas with a certain depth formed at the embankment slope surface and slope toe. The formation of the transient saturated areas increased the possibility of embankment failure. The rainfall infiltration only caused the water level under the embankment slope surface to increase significantly, but had limited influence on the groundwater level below the central road. The expanding speed of the transient saturated areas was mainly determined by q and k_sat, while the formation time and expansion area of the transient saturated areas were influenced by q, rainfall duration, and saturated water content.

Abstract:In this study, the improved smoothed particle hydrodynamics(SPH)method was used to simulate the liquid sloshing in a prismatic tank under shaking excitation with different water depths and excitation frequencies. With this method, the roll-up and break-up of liquid caused by violent nonlinear sloshing can be simulated, and the simulation results were consistent with experimental data. Through changing the structure of the prismatic tank, the liquid sloshing in the prismatic tank with a baffle was simulated and the influence of the baffle on the liquid sloshing was analyzed. The results show that the water depth and the excitation frequency are the major factors influencing the characteristics of the liquid sloshing, and appropriately changing the structure of the tank can effectively suppress the liquid sloshing.

Abstract:Based on the linear shallow water approximation, this paper presents analytic solutions for oscillation within a closed regular pentagon-shaped harbor. The Boussinesq model was used to verify the equation. The results show that oscillations in the closed regular pentagon-shaped harbor are similar to those in a one-dimensional water flume, and the resonance is mainly due to the standing wave between different walls of the harbor.

Abstract:In this study, an East China Sea circulation model was built. Based on this, a small-scale circulation model including the domain of the Yangtze Estuary, Hangzhou Bay, and adjacent water areas was built. With this model, the oceanic current system and coastal current system of the East China Sea, and the flow structure off the Yangtze Estuary were accurately simulated. In order to study the anomalies, typical El Niñ o years were chosen to analyze the response relationship between the nearshore circulation off the Yangtze Estuary and El Niñ o events. The results show that there was a significantly responsive relationship between the nearshore circulation off the Yangtze Estuary and El Niñ o events. In the winter, the circulation at the Yangtze Estuary and adjacent water areas weakened significantly when the El Niñ o phenomenon occurred. The Taiwan warm current was greatly affected, with decreased flow velocity and narrowed flow amplitude, which weakened the impact of the Taiwan warm current on the nearshore circulation off the Yangtze Estuary.

Abstract:To overcome the inherent deficiencies in the particle swarm optimization(PSO)algorithm, such as premature convergence, and to take into account the effects of inertia weight on the identification accuracy, an improved PSO algorithm, which combines the adaptive inertia weight PSO algorithm with the global optimum location mutation PSO algorithm, is proposed in this paper, in order to identify the double-fed induction generator(DFIG)parameters. First, the identifiability of the DFIG parameters and the difficulties in identification are analyzed. Then, the identification steps based on this improved PSO algorithm are illustrated. Compared with the basic PSO algorithm, the adaptive inertia weight PSO algorithm, and the global optimum location mutation PSO algorithm, the proposed algorithm has faster convergence, smaller errors, and higher identification accuracy, even at a wide search range.

Abstract:This paper presents an active learning algorithm based on the Madaline network’s output sensitivity due to its input variation near a given sample. First, a portion of samples are used to train a Madaline network. Then, based on the sensitivity of the network, some other samples with higher sensitivity are actively selected and added into the training data to continue the training of the network. This process is repeated until the training requirement is met. Experiments verified the effectiveness and feasibility of the proposed active learning algorithm in treating discrete classification problems.