Abstract:Based on numerical simulations and flume experiments, the processes of sedimentation of suspended solids and resuspension of sediments in the region downstream of a sewage outlet in a river were analyzed at three velocity ratios(R=4. 5, 7. 2, and 9. 9, where R is the ratio of discharge velocity at the sewage outlet to the flow velocity in the river). Results show that the relative turbulence intensity and the area of the pollution zone increased with the velocity ratio; this also resulted in significant sedimentation of suspended solids and resuspension of sediments in the river. At the three velocity ratios, the sedimentation fluxes of suspended solids through the bottom horizontal plane have similar distributions: first increasing and then reaching respective stable values; and the total fluxes of suspended solids increased with the velocity ratio. At a low velocity ratio(R=4. 5), the resuspension fluxes of suspended solids increased slowly due to the existence of a critical incipient velocity(corresponding to R=5. 8), while at the medium velocity ratio(R=7. 2)and high velocity ratio(R=9. 9), the resuspension fluxes increased rapidly. As a result, the discharge velocity of the sewage significantly affected the sedimentation of suspended solids and resuspension of sediments in the region downstream of the outlet.

Abstract:Because the hydrological response of watersheds is comprehensively affected by physical geographical factors, such as geology, topography, landforms, vagetation, and soil, and underlying surface factors, such as land use, hydrological partition was conducted based on the geographical characteristics of underlying surface of watersheds. The underlying surface of watersheds was classified with remote sensing data and information on land cover and land use was obtained. By combining data of watershed agrotype and the topography index, the soil topography index was calculated. Furthermore, taking advantage of the remote sensing data and soil topography index, hydrological partition was conducted, the parameter C_N of the SCS model was calibrated in every hydrological subregion, and hydrological simulation was conducted. The results showed that the relative error was less with the proposed method than with the traditional method in 21 flood runoff simulations in the Tunxi Watershed and 32 flood runoff simulations in the Dongwan Watershed.

Abstract:Based on the sample entropy, this study analyzed the spatial distribution and dynamic change characteristics of the complexity of runoff series using long-term daily runoff data from the Yichang, Hankou, and Datong hydrological stations, which were determined to be the main hydrological control stations in the Yangtze River. The results showed that the complexity of runoff series showed obvious spatial differences and an increasing trend from upstream to downstream in the Yangtze River. There was a negative correlation relationship between the annual runoff and the sample entropy value at every station. The complexity of runoff series at the Yichang and Datong stations showed a continuous increasing trend, and an increasing trend after 2000 at the Hankou Station.

Abstract:Considering the poor performance of existing real-time correction methods of flood forecasting in small mountain watersheds, this study introduced the K-nearest neighbor algorithm into the real-time correction method of flood forecasting. The real-time correction model based on the K-nearest neighbor algorithm(the KNN method)was built and the Shabu Basin, in Anhui Province, was chosen as the experimental basin. Meanwhile, the real-time correction method of back-propagation neural networks(the BP method)and the traditional error autoregression method(the AR method)were also used to analyze the correction results of correction models with the evaluation indices of the flood peak relative error and the certainty coefficient. The results showed that the KNN method improved the most on the error correction of flood peak and the BP method was more accurate. The correction ability of the KNN method improved more when the historical flood data were added to the learning sample. The KNN method can effectively avoid the defect of the AR method, that the flood peak error cannot be controlled. The KNN method is well-adapted and sensitive, has high accuracy, and can be used as an effective tool to promote real-time correction in small mountain watersheds.

Abstract:A systematic study was carried out on paths and frequencies of typhoons affecting the coastal areas of Jiangsu and Zhejiang provinces. The results show that typhoons affecting the coastal areas of Jiangsu and Zhejiang provinces originate in the northwest Pacific and South China Sea, with more than 90% generated in the northwest Pacific. According to the extent of influence of typhoons on the coastal areas of Jiangsu and Zhejiang provinces, the paths of typhoons can be classified into three types, and their characteristics obtained. Typhoons land in the coastal areas of Jiangsu and Zhejiang provinces mainly from May to November each year, and the number of typhoons reaches its maximum in August. The significant period of typhoon frequency is five to six years. The number of typhoons and the accumulated cyclone energy have decreased since the 21st century. Typhoons along the coastal areas of Jiangsu and Zhejiang provinces are plentiful in the south and scarce in the north, typhoons land frequently in Zhejiang province and Shanghai City, and there is almost no typhoon landfall in Jiangsu province. Due to the influence of the special hydrological environment and terrain near Hangzhou Bay on the typhoon path, an area centered around Hangzhou Bay is a rare area without typhoons, where no typhoon was observed during the study period.

Abstract:Based on review of research on suitable water levels for landscape functions and water demand for landscape environment, the concept and characteristics of the suitable water level for landscape functions of lakes are discussed. The suitable water level for landscape functions of lakes is affected by various factors, including flood control and drainage, municipal drainage, irrigation water supply, water resources of rivers and lakes, shipping, ecological water demand, and quantity of water diverted. In view of the landscape function of lakes and based on analysis of the main factors influencing the suitable water level for the landscape function of lakes during the flood season and dry season, quantitative calculation models of the suitable water level for the landscape function of lakes in the flood and dry seasons were established, through overall coordination of different functions of lakes. Then the suitable water levels for the landscape function of Wangmu Lake were calculated using the models. The results show that the modeled water level for the landscape function of Wangmu Lake in the flood season is 22. 5 m, which is higher than the water level needed for comprehensive utilization of water resources(21. 2 m). This modeled water level in the flood season not only improves the security of flood control and drainage, but also ensures the irrigation and shipping functions of the lake and existence of fish. The modeled water level for the landscape function in the dry season is 21. 9 m, with the distance between the leisure activity platform and the water surface being less than 0. 5 m, and the water quantity necessary for diversion into the lake being 9. 362×10⁶ m³. This water level not only helps optimize the water landscape, investment, and the water quantity diverted from other basins, but also ensures the feasibility of shipping and meets the requirement of minimum ecological water demand.

Abstract:Based on statistical data of the mass concentrations of Mg²⁺ and Li⁺ and the concentration ratio of Mg²⁺ to Li⁺ in saline lakes in the Tibet Plateau, the isolines of the mass concentrations of Li⁺ and the ratio of Mg²⁺ to Li⁺ in saline lake brines in Tibet were drawn. The spatial distribution pattern of the content and the quality of the lithium resources in saline lakes in Tibet and the relationships between the enrichment of lithium resources and the geological environment were analyzed. The distribution of lithium resources shows a zonation character. The concentration of Li⁺ in saline lakes is mainly influenced by the tectonic belt. The zone of carbonate saline lakes shows the lowest ratio of Mg²⁺ to Li⁺, with the high-quality and general saline lake brines with low ratios of Mg²⁺ to Li⁺ mainly distributed along the transition zone between the carbonate saline lakes and the sulfate saline lakes.

Abstract:The distribution patterns of horizontal displacements, dynamic earth pressures, and horizontal accelerations of retaining walls constructed with soilbags filled with natural river sand under different horizontal vibration accelerations were investigated through small-scale shaking table tests, and they were compared with those of retaining walls reinforced with horizontal woven geotextiles and traditional rigid retaining walls under the same horizontal vibration accelerations. The results show that, when the input acceleration is not more than 0. 3g, the displacement of the retaining wall constructed with soilbags is slightly larger than that of the rigid retaining wall. With the increase of the input acceleration, slippage of the entire rigid retaining wall occurs, and then overturning failure occurs, while the retaining wall constructed with soilbags can still remain stable, showing a good seismic performance. The displacement of the retaining wall reinforced with horizontal woven geotextiles, with a maximum value at half of the wall height, is always larger than those of the retaining wall constructed with soilbags and the rigid retaining wall, and the convex deformation of the upper part of the retaining wall reinforced with horizontal woven geotextiles is more significant with the increase of the input acceleration. Dynamic earth pressure coefficients of retaining walls show a nonlinear distribution along the wall height, with larger values in the upper part of retaining walls and smaller values in the lower part. With the increase of the input acceleration and wall height, the horizontal acceleration amplification ratio of the retaining wall constructed with soilbags increases, and is slightly lower than those of the retaining wall reinforced with horizontal woven geotextiles and the rigid retaining wall. According to failure and instability modes of retaining walls constructed with soilbags, the seismic performance of retaining walls constructed with soilbags can be improved greatly through reinforcement of some soilbags at top layers with geotextiles.

Abstract:The interior point path-following method was applied to lower bound finite element limit analysis of the nonlinear programming problem. By applying the subiterative process in the Newton algorithm to solving nonlinear equations, the data storage format and solver of the displacement-based finite element method can be used directly, and large amounts of calculation can be performed element by element. The improved algorithm can be simply implemented with the existing displacement-based finite element program. An example shows that the subiteration algorithm can obtain high efficiency and precision.

Abstract:An experimental study on bonded prestressed steel-reinforced concrete frames at an early stage was conducted to investigate the constraint imposed by steel in the prestressed steel-reinforced concrete beam to concrete and its impact on the carrying capacity of the frame beam. Test results show that steel can effectively restrain concrete deformation in the core area, improve the brittleness of concrete under pressure when it is destroyed, and enhance the flexural bearing capacity of the beam. With regard to prestressed steel-reinforced concrete frame beams in bending, and with reference to the theory of confined concrete as described in the literature, a bearing capacity calculation method for prestressed steel-reinforced concrete frame beams considering regional constraints is proposed based on the superposition principle. The calculated results of the flexural bearing capacity of prestressed steel-reinforced concrete beams are compared with the test results in the limit state. The average ratio of the calculated results to the test results is 0. 98, demonstrating agreement between them.

Abstract:Based on the consolidation mechanism of the combined electroosmosis-vacuum preloading method, a field test was conducted on the hydraulically filled soft foundation treatment project in the Liangzi Lake Aquatic Ecological Exhibition Hall on Li Island, in Hubei Province. The performance of electric vertical drains(EVD)and the consolidation effect of electroosmosis were evaluated. The field test results show that the physico-mechanical properties and bearing capacity of the foundation soil are improved significantly after a 28-day treatment. The electroosmosis-vacuum preloading method using EVD can not only reduce the construction time and energy consumption, but also achieve the ideal consolidation effect.

Abstract:Subsidence deformation of dredger fill sea sand in Qidong City, Jiangsu Province, was studied using a consolidometer. Dredger fill sea sand with a subsidence coefficient of 1. 1%, which is less than the subsidence coefficient of the subgrade filling material of a highway, i. e. , 1. 5%, can be used as the subgrade filling material. Sea sand samples with different salt contents were prepared by adding different quantities of NaCl to investigate the effect of the salt content and pressure on the subsidence coefficient. It was found that the subsidence coefficient increased with the salt content and reached the maximum value when the pressure was 200 kPa.

Abstract:In order to obtain a real-time atmospheric water vapor field of high temporal and spatial resolution, based on the principle of remote sensing of atmospheric precipitable water vapor(PWV)using a ground-based GPS, the observed data at certain stations in the Hong Kong CORS network were processed. According to the different time spans in calculating PWV with ultra-rapid ephemeris, three schemes were designed. In each scheme, PWV data calculated with final precise ephemeris, ultra-rapid ephemeris, and radiosonde data were compared. The results show that the predicted PWV data of the ultra-rapid ephemeris agree with those of the final precise ephemeris, and its accuracy satisfies the requirements of real-time service, such as weather forecasting.

Abstract:In order to improve the accuracy of short-term electric load forecasting, a cycle forecasting method for short-term electric load forecasting is proposed based on a radial basis function network-style coefficients autoregressive model with an exogenous variable(RBF-ARX)model. First, the short-term electric load forecasting was regarded as a nonlinear time series prediction problem, and an autoregressive model(ARX model)of electric load forecasting was established based on historical load data. Then, the ARX model parameters were approximated with the RBF neural network and were estimated with an off-line structured nonlinear parameter optimization method(SNPOM). Finally, based on this, a cycle forecasting method for short-term electric load forecasting was established. The proposed method was used to predict the short-time electric load in a certain city of Hunan Province. The predicted results were compared with the actual load values. The results show that the proposed method has high accuracy, reliability, and practicability.

Abstract:Based on analysis of existing remote data integrity verification methods and using homomorphic hashing and pseudo-random numbers in the tag blocking stage, a data integrity verification method, supporting dynamic data and considering challenges to be unlimited, is proposed to deal with the problem of users’ data integrity verification in cloud storage. The effectiveness of this method is verified through security and performance analyses. With a guarantee of maintaining the remote data integrity, the method can reduce the redundancy of storage space and the bandwidth consumption in data communication.