Abstract:In order to investigate the influence of different model structures on runoff simulation in semi-arid and semi-humid basins with complex runoff generation mechanisms,the CASC2D model and GSSHA model were used to simulate eight flood events from 1964 to 2000 in the Luanchuan Basin using the same digital elevation model (DEM) data,land cover data,and soil data. The CASC2D model is based on the excess-infiltration mechanism,and the GSSHA model is based on the CASC2D model through addition of groundwater runoff and transformation of the Green-Ampt equation into the Richards equation to calculate the infiltration. The runoff simulation results show that the GSSHA model performs well in the Luanchuan Basin. Compared with the CASC2D model,the simulation of flood peak,runoff depth,and the deterministic coefficient are highly improved by the GSSHA model except for peak time error.

Abstract:To investigate the effects of macropore flow in farmland soil and colloid release caused by agricultural activities on the vertical migration of phosphorus and groundwater pollution,parallel soil column experiments were conducted using agricultural soil from the Taihu Lake Basin. The results show that the release of colloid (with a concentration of about 50 mg/ L) in soil accelerated the vertical migration of colloid and available phosphorus,and the leaching rate of available phosphorus at the soil column bottom (100cm in depth) reached 0.15kg/ (m²·d),about 15. 4% higher than it was with no obvious release of soil colloid. Furthermore,the existence of macropores (5% in volume) in soil significantly increased the leaching rate of available phosphorus,with a value of 29. 9 kg/ (m2·d) at the soil column bottom. The preferential flow caused by macropores played a critical role in the leaching of colloid and available phosphorus. However,the release of soil colloid accounted for 3. 2% of the increase of the leaching rate of available phosphorus when macropores existed. Soil colloid release altered the chemical characteristics of soil,such as pH and electric conductivity,and then influenced the transport of solutes in soil. Preferential flow caused by macropores and soil colloid release caused by agricultural activities exist across the agricultural area of the Taihu Lake Basin. Macropores and soil colloid accelerated the vertical infiltration of phosphorus,which increased the risk of groundwater pollution caused by phosphorus.

Abstract:A regional average Spearman Rho method that takes into account both temporal and spatial correlation was developed. The method was used to assess regional variation trends of annual precipitation,annual mean air temperature,and annual potential evapotranspiration in each subcatchment in the upper Yangtze River based on the CRU dataset. The results show that the positive spatial cross-correlations between sites are prevalent for each climatic element. The annual mean air temperature and potential evapotranspiration also exhibit positive temporal autocorrelations. Both correlations can lead to overestimation of the significance of regional trends. If the correlations are ignored,it is concluded that a significant climatic variation occurs in each subcatchment in the upper Yangtze River. The new method effectively reduces the effect of temporal and spatial correlation,and concludes that the climatic trends have not been statistically significant over the last century,and that the annual precipitation only significantly increased in the Jinsha River area,whereas it slightly decreased in the Chuanjiang area. Meanwhile,the annual mean air temperature and potential evapotranspiration increased significantly after 1960. The results of the study indicate that consideration of temporal and spatial correlation plays an important role in decreasing trend misjudgment.

Abstract:According to the requirements of subwatershed codification for distributed hydrological models, river and watershed codification methods described in literature were studied. It is found that only five coding methods can meet the requirements of distributed hydrological models: the topological property table coding method (TPTCM), binary-tree coding method (BCM), multi-tree coding method (MCM), Pfafstetter coding method (PCM), and stem-branch topological coding method (SBTOPO). The advantages and the disadvantages of the five methods were examined based on analysis of their coding rules. The second Songhua River was selected as the study area for subwatershed division and codification. The results show that the TPTCM, MCM, and SBTOPO are superior to the other two methods in one-way and multi-way confluence situations. The TPTCM can directly find and obtain the codes of adjacent inflow and outflow subwatersheds, and the BCM and SBTOPO can directly calculate their codes, but the PCM and MCM obtain their codes by searching the entire coding system. The PCM and SBTOPO are better than the other three methods in terms of analysis of the upstream and downstream relationships between any two subwatersheds. All five coding methods have their own advantages and disadvantages. A suitable coding method should be selected according to research contents and coding requirements of distributed hydrological models in practical applications.

Abstract:In order to consider the importance of the economic benefit,virtual water consumption,fairness difference of water use per person,and nutrition factors in the regional planning of production of agricultural and livestock products,the optimized allocation problem of water resources based on the virtual water and nutrition was studied. A multi-objective optimization model with the maximum economic benefit,the minimum fairness difference of water use per person,and the minimum virtual water consumption,meeting the constraints of nutrition factors,was established. The model was solved using the variable fuzzy decision-making theory and an optimal scheme for production of each kind of agricultural and livestock product was obtained. The model was run based on data from the Shiyang River Basin,and the results show that the scheme obtained from the model is the optimal scheme.

Abstract:In this paper,research on defects of geomembrane (GM) used in practical engineering in China and abroad is summarized and evaluated from the aspects of geomembrane defect types and test methods,theory of defect analysis and defect calculation model,principles and measures of defect prevention,cushion layer properties and interface flow,the rate of leakage under different contact conditions and cushion layers,and factors of leakage induced by geomembrane defects. Analysis shows that,due to the complexity and uncertainty of geomembrane defects,current research is mainly based on experiments,accompanied by theoretical analysis and numerical simulation,producing different results from the theoretical results. Some key problems related to geomembrane defects that require further research are put forward so that an overall recognition and effective control of geomembrane defects can be realized as early as possible.

Abstract:Research progress and development trends in numerical simulation methods for analyzing the dynamic response and failure process of dams under blast and impact loads are reviewed. Research findings regarding the dynamic response and failure process of dams under blast loading obtained through the existing numerical simulation methods for the computation of explosion mechanics are focally summarized. It is pointed out that the dam dynamic response analysis under blast loading involves an explosion,the formation and propagation of a shockwave,the interaction between the shockwave and the dam body,and the dynamic response of the dam body. The classification and characteristics of the blast loads exerted on dams and their damage effects on dams are summarized,and issues that require more attention in dam explosion simulation under explosion conditions are pointed out. Based on current research,the latest research achievements of computational mechanics should be absorbed into future research to develop high-precision numerical methods and high-efficiency numerical solution systems,and to realize the entire process simulation of the dam dynamic response to explosions.

Abstract:In order to investigate the patterns of adsorption of phosphorus by sediment under different hydrodynamic actions,the adsorption of phosphorus and the vertical distribution of phosphorus were investigated through experiments in an elongated annular flume. The effects of velocity,initial phosphorus concentration,and sediment concentration were investigated. The results show that the vertical distribution of velocity in the elongated annular flume matched the logarithm law. The concentration of soluble reactive phosphate was distributed unevenly along the depth,and the maximum value appeared in the middle of the depth. The adsorption pattern of phosphorus under different velocity conditions depends on the mass concentration of soluble phosphorus. The amount of adsorption per unit mass of sediment decreased as the velocity increased when the phosphorus concentration was low,while it increased when the phosphorus concentration was high. The adsorption amount of phosphorus per unit mass of sediment increased as the sediment concentration decreased or the initial phosphorus concentration increased. The first- order and second-order dynamic equations can be used to describe the adsorption behavior of sediment in the Huaihe River. With the deposition of suspended sediment,the phosphorus concentration increased to a maximum at 0. 25 h and then decreased.

Abstract:Through water level control tests in two important growth stages of rice,the jointing-booting and heading- flowering stages,the change of total phosphorus (TP) mass concentration in surface and subsurface water of a paddy field were studied using lysimeters under alternative stresses of drought and waterlogging (ASDW) in individual stages and two consecutive growth stages. The results show that ASDW had a significant influence on the change of TP mass concentrations in surface and subsurface water of a paddy field,the TP mass concentration in surface water with the treatment of waterlogging after drought was much higher than it was with the treatment of drought after waterlogging,and the declining rate of phosphorus release amount was faster. The mean TP mass concentration in the waterlogging phase was higher than in the drought phase with all treatments of subsurface water. The TP mass concentration increased significantly after the abrupt alternation from drought to waterlogging. Compared with that during the individual growth stages with the treatment of ASDW,the change of TP mass concentration in the heading-flowering stage during the two consecutive growth stages with the treatment of ASDW was similar,the mean TP mass concentration in surface water was lower,and the mean TP mass concentration in subsurface water was higher.

Abstract:Considering economic and environmental pressure in mining in Jinchuan City,development of a new filling cementing material was carried out using acid slag with low activity at the Jiugang Company,and an early-strength filling cementing material,called consolidation powder,was obtained. In order to use the consolidation power in Jinchuan Mine,compressive strength tests on consolidation powder were carried out for four kinds of filling aggregates,including waste rock,rod milling sand,Gobi Desert sand,and river sand. The results show that the compressive strength of the cemented filling body of Gobi Desert sand for a curing period of three days is lower than the design compressive strength,and the compressive strength of the cemented filling bodies of the three other kinds of filling aggregates meet the strength requirements of a filling body for safe mining in Jinchuan Mine,indicating that the early-strength consolidation powder filling cementing material can replace cement for filling mining in Jinchuan Mine.

Abstract:In order to study the influences of rigid,half-rigid,and flexible boundaries on test results,unilateral loading tests on coarse-grained soil,with invariable horizontal stress and increasing vertical stress,were performed using the TSW-40 true triaxial apparatus developed by Hohai University. The results show that the restriction of the rigid boundary is clear on a cubic sample with the depth-width ratio of 1:1;using a half-rigid boundary on the top of a sample,with the rigid boundary in the vertical direction and the flexible boundary in the horizontal direction,can remarkably decrease the restriction of the boundary on the sample;the restriction of the rigid boundary on a sample can be effectively decreased by increasing the depth-width ratio of the sample;and half-rigid compound blocks and flexible water bags have a lesser influence on the test results.

Abstract:In order to establish an accurate equivalent model of a hybrid offshore renewable energy conversion farm, a non-mechanism equivalent modeling method is proposed. Based on transfer functions,a non-mechanism equivalent model was developed to describe the nonlinear relation between inputs and outputs. Then the decoupling parameter identification method was applied to the model,and parameters of transfer functions were identified using the ant colony algorithm. Furthermore,a phasor model of a hybrid offshore renewable energy conversion farm,consisting of wind,tidal,and wave turbines,was built in Matlab/ Simulink. With the model,the input and output data of the farm were acquired under the influences of wind,tidal,wave,and voltage disturbances. Finally,a transfer function model was built based on the collected data,and model parameters were identified. With the obtained parameters,the outputs of the equivalent model were calculated. The error between outputs of the equivalent model and the simulation model is very small,verifying the feasibility of the non-mechanism equivalent model in building the hybrid offshore renewable energy conversion farm.

Abstract:In previous modal analysis of a switched reluctance motor (SRM),the windings were treated simply as an additional mass and the influence of the stiffness of windings was ignored. In order to overcome the limitations,a finite element model of an SRM stator,which takes windings,the radiation rib,and the base into account,was constructed based on a three-dimensional (3D) physical model of SRM with a 6/4-pole structure. A modeling method in which the springs were used to simulate the flexible connection between the windings and stator core is presented. The validity of the modeling method was proven through finite-element modal analysis results of the SRM prototype. In order to reasonably consider the influence of the torque winding and suspension winding on the mass and stiffness of the stator of a bearingless SRM (BSRM) with double windings,the modeling method in which the springs were used to simulate the flexible connection was applied in 3D finite-element modal analysis for a BSRM with double windings. The results show that the modeling method in which the springs were used to simulate the flexible connection between the windings and stator core and the flexible connection between the torque winding and suspension winding is a effective method,it can take the influence of double windings into account,and it has high engineering practical value.