Abstract:To eliminate the impacts of cloud interference on the accuracy and applicability of water body extraction based on the satellite remote sensing, a reconstruction method for the continuous water body is developed by combining the high-precision terrain information and the GF-1 satellite imageries. Firstly, the GF-1 satellite imageries and high-precision contour terrain data are preprocessed and then, a buffer zone is set up to extract the part of the water body that is not covered by clouds through multiple iterations. Thereafter, the water level of water body is determined through image operations, such as the geographic referencing of two kinds of data and the statistical operation, so that the water surface area under the influence of clouds can be restored. The results show that the developed method can effectively eliminate the influence of clouds. According to the water body extraction results from seven cloud-interfered images, the average relative error of the extracted water areas is less than 5%. Comparing to the reference values, the average bias of the extracted water areas is 0.0809km2 , which indicates that this method can accurately restore the water area under the conditions of cloud interference and has a high potential for extracting water bodies from cloud influenced images.

Abstract:The sudden shortterm severe precipitation, frequently caused by mesoscale and microscale weather systems, is very complicated to forecast quantitatively. This study develops a seamless quantitative precipitation forecasting (QPF) model based on the rapid rolling update technique. In the developed model, the quantitative precipitation nowcasting (02h) is based on the improved optical flow method, the shortterm quantitative precipitation forecasting (212h) is based on the GRAPES3km and realtime frequency matching correction method, and the short and medium range quantitative precipitation forecasting (12240h) is based on the generation technique of optimal background precipitation field. According to forecasting skills of three methods in different forecasting time, the forecast fusion technology based on the empirical weight function is developed for the seamless quantitative precipitation forecasting (0240h) with the realtime precipitation verification and QPF. The 24hour quantitative precipitation forecast from May 2018 to October 2018 is taken as the experimental case to test the developed model, and the result is compared with forecasts of the traditional model. Results show that the 24hour precipitation forecast accuracy of the developed model is higher than that of the traditional forecast model, especially for the shortterm quantitative sudden severe precipitation forecasting caused by mesoscale and microscale weather systems. It is conducive to the flood forecasting, disaster prevention and control of small to mediumsized rivers.

Abstract:Distributed Watershed Hydrological Models with physical basis usually use the DEM grid as the calculation unit, which can homogenize the terrain information so that the extracted slope is non true value, and the non true value corresponding to different scale grids is significantly different, which leads to significant differences in simulation results based on different scale distributed models. In view of the influence of different resolutions on the simulation results, a normalized expression method of the relationship between grid scale and the extracted watershed slope and the corresponding slope correction method are proposed. The slope correction coefficient which can be used in the calculation formula of model velocity is introduced in the correction method. The results show that the influence of cell size on the simulation results is consistent with that on the extracted watershed slope, and the proposed method can effectively eliminate the influence of grid equalization on the simulation results of distributed hydrological model.

Abstract:To analyze the influence of the environmental remediation project on the discharge capacity of the Pukou section of the Yangtze River, a twodimensional hydrodynamic model of the engineering section was established based on MIKE21 FM. The Moghadam roughness formula for submerged vegetation in the open channel was used to simulate the water resistance of vegetation and the influence of vegetation on the floodplains roughness and flood resistance was studied. Water level and velocity were selected as the observation indexes to analyze the changes of water surface line and the velocity distributions of floodplains and main channel with and without the vegetation on floodplains. The influence of vegetation on the flood discharge capacity under different discharge conditions was studied. The results show that the vegetation causes the upstream water level to rise, the water velocity of floodplains to decrease and the water velocity of main channel to increase. When the water depth of floodplains is less than the critical water depth (1.3m), the upstream banked up water level increases with the increase of the discharge. When the water depth of floodplains is greater than the critical water depth, the upstream banked up water level decreases with the increase of the discharge.

Abstract:To study the cumulative effects of ecological water conveyance on groundwater in the lower Tarim River, a numerical model of local groundwater under the intermittent conveyance in a typical plain section of the lower Tarim River was established, taking the Alagansection and the 12th-18th ecological water conveyances as examples. Due to the lack of actual evapotranspiration data in this area, this study adopted the advectionaridity model based on the complementary relationship theory to calculate the actual monthly maximum evapotranspiration rates. After the calibration and verification, this model can be applied to evaluate the cumulative effect of ecological water conveyances on the groundwater. It is an effective method to describe the spatial and temporal response of groundwater to the ecological water conveyance. The spatiotemporal distribution pattern of groundwater before and after the water conveyance is revealed by two indicators, the effective response distances of groundwater to water conveyance and the response areas. The results showed that the maximum response distance from the groundwater to the channel was extended from 812m to 1100m. The response areas of middle and high level were 1.61 times of that of low water level. The effective range of water conveyance was mainly distributed within the range of 1000~2000m from the channel.

Abstract:To improve the hydrodynamic power and reciprocating water flow in the plain river network area, the appropriate timespace hydrodynamic reconstruction of river network is carried out through the combined control of regional sluices and pumps to promote the directional and orderly flow of rivers, thereby maintaining a good water environment. Taking the Wennan river network in the central city of Shanghai as the research object, a variety of control plans based on hydrodynamic reconstruction goals are proposed, and the hydrodynamic improvement effect of each plan is compared and analyzed through the model calculation. The results show that by raising the sluicepump control water level, the opening height of the Hongkougang and Yangshupu gates, and the water diversion intensity of Mudugang and Pengyuepu pump, the average velocity of 78.6% of the cross sections has been increased and the average flow velocity has increased by 16.7%, which indicates that the hydrodynamics of the river network is effectively improved. In response to the phenomenon of reciprocating flow in the Zoumatang river, by regulating the drainage method of the river network, an emergency dispatch plan of “from south to northeast” is proposed. This plan increases the average flow velocity of the representative section by 60.4% during the simulation period, and the cumulative duration of directional flow increases by 60%.

Abstract:To reveal the effect of different water and carbon managements on the N2O production in the paddy soil, a combined watersaving irrigation with the straw returning and organic fertilizer application was adopted to observe the profile distribution characteristics of N2O concentration in paddy soil with the microlevel technology under different water and carbon managements. Results show that within 16 days after fertilization, N2O concentration in the controlled irrigation paddy soil is lower than the conventional irrigated soil in different depth, from 8 day the controlled irrigation paddy soil is significantly higher than the conventional irrigated soil (p<0.05), and the law is basically same under two carbon managements. N2O concentration in the shallow layer (01cm) of the controlled irrigation paddy soil is not significantly affected by the straw returning and the organic fertilizer application, while in the deeper depth (13 cm), the straw returning is significantly higher than the organic fertilizer application (p<0.05). The effect of two carbon managements on N2O concentration in the conventional irrigation paddy soil is not obvious. N2O concentration of organic fertilizer application under the controlled irrigation is lower than others, after the tiller fertilizer, the mean concentration of N2O in CM is 35.1% and 24.8% lower than it in CS and FM (p<0.05), and CM is slightly lower than FS. After the panicle fertilizer, the mean concentrations of N2O are CM is 45.5%, 33.7% and 18.8% lower than CS, FS and FM (p<0.05).

Abstract:In this paper, the convolution type nonviscous damping model with exponential kernel function is used to establish the vibration equation of nonviscous damping structures under the seismic excitation. By introducing the state variables, the statespace expression of the vibration equation of nonviscous damping structure is derived. Taking a gravity dam as an example, the seismic response of the nonviscous damped dam is solved by the refined timedomain integration method under the Koyna seismic excitation, and the response time history of the dam is given for different values of the relaxation parameter μ. The results show that the peak response of the nonviscous damping model is larger than that of the viscous damping model whether it is empty or full, and the peak response of the nonviscous damping model is increased with the decrease of μ, which indicates that the damping effect of the viscous damping model is larger than that of the nonviscosity damping model. Therefore, the peak response of concrete gravity dam may be underestimated by using the viscous damping model in the seismic response analysis, thereby affecting the safety and rationality of the structural design scheme.

Abstract:The fully nonlinear Boussinesq model, called FUNWAVETVD, was used to simulate wave flume laboratory experiment to study the propagation and transformation of infragravity wave over fringing reef under irregular wave conditions. Based on the validation of predicted significant wave heights of short wave and infragravity wave and mean water levels, the crosscorrelation analysis and wavelet bispectrum were adopted to investigate the generation and propagation of infragravity wave and the related nonlinear energy transformation respectively. The results suggest that the infragravity wave can get energy from the peak frequency band in front of the reef. As the water depth on the forereef goes shallower, the nonlinear interaction goes stronger, the bound wave grows and the significant wave energy transfers from the peak frequency to lower and higher frequency bands. The infragravity wave on the reef flat is mainly generated by the moving breakpoint mechanism, and the energy transformation only occurs between low frequency band at the end of the reef flat.

Abstract:In this work, by utilizing the monitoring data of a gravity retaining wall in the upperreservoir of Yixing PumpedStorage Hydropower Station, the variations of retaining wall displacement and their influence factors were studied. After that, a numerical simulation was conducted to investigate the displacements of rockfill dam and retaining wall with the consideration of the coupled effect of temperature. Here, the rheological model and wetting model (CwDw) proposed by Shen were used to model the rheological deformation and wetting deformation of rockfill materials. The results show that the rheological deformation, wetting deformation, and environmental temperature are three main influence factors for the displacement of retaining wall in the operation period. In the early stage of dam operation, there was a displacement for the retaining wall occurred towards upstream, which was mainly attributed to the relatively larger rheological deviator strain for rockfill materials near this place. The wetting deformation of rockfill materials was caused by rainfall infiltration and led to the increase of displacement of retaining wall towards downstream. The cycling variations of displacement were related to the environmental temperature. In addition, the calculated displacement and earth pressure agreed well with measured values, which indicates that the numerical method used in this study was effective.

Abstract:To discuss the influence of load conditions on the topology optimization for RC deep beams, and improve their current design methods as well, in this paper the optimal topology structures for RC deep beams with openings under different concentrated loading conditions and different load concentration conditions were separately evolved based on the evolutionary topology optimization algorithm. Then, the corresponding StrutandTie models were constructed according to these optimal topology structures. The diversities among these optimal topology structures and among these StrutandTie models were discussed next. The results show that all these StrutandTie models conform better to Michell structures which have full stress distribution. The loads are always transmitted from the loading point to the support in the form of pressure through the shortest straight struts when a concentrated load is applied on the top surface of the beams, while the loads are suspended on the main pressure arch by umbrella shaped ties and then transmitted to the support when a concentrated load is applied on the web or bottom of the beams. The optimal topological structures always evolve into arch structures or hybrid system of archandcompositestrut as the load concentration decreases, especially those are close to uniform loads applied on the beam. Furthermore, the RC deep beams under different load conditions may be designed with some hidden reinforced compression parts and tensile reinforcements in beam body by the light of the optimal topology structures in engineering designs.

Abstract:In view of the shortcomings of current TBM data mining capability and tunnelling parameters optimization of TBM performance prediction as well as the unmanned driving in future, this paper examines the feasibility of least squares support vector machine (LSSVM) technology in the parameter prediction of TBM tunnelling. Four important parameters including the cutter torque, cutter thrust, total propulsion and propulsion speed of the ascending section were extracted from the TBM excavation data of the Yinsong Diversion Project to model, and this study predicted the mean value of the stable section. The influence on model prediction performance was discussed from the aspects of model size and parameter selection. The numerical results show that the LSSVM model established by uniformly extracted samples from the original data, RBF kernel function and 10fold cross validation can predict above four parameters in the stable segment more accurately. Therefore, the LSSVM machine learning method is a scientific and feasible method to predict TBM tunnelling parameters.

Abstract:To study the flow law in the suction chamber of a centrifugal pump when conveying the gasliquid twophase medium, a transparent model pump was experimentally studied and the gasliquid twophase flow in the pump was numerically simulated based on the EulerianEulerian heterogeneous flow model. The twophase flow in the suction chamber was studied in detail by using the numerical calculation model verified by the experimental results. Thereafter, the variation law of flow patterns in the suction chamber was revealed, and the relationship between the flow pattern and the external characteristics of the pump was established. The results show that, there may be up to eight flow patterns in the suction chamber, while at a certain rotational speed, there will only be six flow patterns at most. The gas spiral length decreases with the increase of the liquid flow rate and increases with the increase of the rotational speed. The appearance of spiral flow greatly increases the turbulence intensity in the suction chamber and reduces the stability of the pump. When the flow pattern in the suction chamber is steady spiral bubble flow, the pump head of pump is relatively large. When the efficiency of centrifugal pump is the highest, the flow pattern in the suction chamber is steady non spiral bubble flow or pulsating non spiral bubble flow.