In order to study the response relationship between sediment discharge ratio (SDR) and influencing factors under actual water and sediment conditions, based on the measured water and sediment data of the Three Gorges Reservoir (TGR) from 2003 to 2018, this paper discussed the response relationship between SDR and various influencing factors on the basis of analyzing the characteristics of water and sediment from the reservoir, and established the formula of SDR in the main flood season. The results show that the correlation between SDR and single factor is not obvious, indicating that the SDR is affected by multiple factors. From the perspective of reservoir operation and regulation, the SDR is negatively related to the flood detention time, and the sediment discharge efficiency should be improved by shortening the flood detention time; From the perspective of incoming water and sediment, the greater the amount of sediment entering the reservoir, the greater the sediment discharge ratio of fine sediment is; Coarse sediment, on the contrary, is characterized by more coming and less discharging. In the main flood season, the relationship between the SDR and the proposed expression is good. This study can provide reference for the operation of TGR.

In view of the frequent occurrence and serious loss of urban waterlogging disasters in recent years, this paper focuses on the current situation of engineering of waterlogging drainage, and takes Lu'an City, Anhui Province, which experienced waterlogging disasters in 2016 and 2020 as the research object. Considering the connection relationship between drainage network and drainage channel systematically, the study analyzes and determines the engineering weakness that cause urban waterlogging from the aspects of the standard of drainage network corresponding to the location of water logging points, the relationship between ground elevation and the design water level of the corresponding receiving rainwater river, the drainage capacity of the river, and the operation conditions of the drainage pumping station, based on the tracking of rainwater discharge process of pipe network-inland river-outland river. The results show that the elevation of water logging point in the old urban area of Lu'an City has the condition of flowing into the river by gravity, and the drainage channel and drainage pumping station can meet the drainage requirements. The main engineering reason for the occurrence of waterlogging is that most drainage network have low standards and can not drain rainwater into the river in time. On this basis, it is further considered that the implementation of the drainage network rectification in the old urban area is difficult and long cycle. In order to minimize the risk of waterlogging before rectification, it is proposed to reduce the operation water level of the drainage pumping station at the estuary of the outland river, so as to improve the ability of urban drainage and disaster reduction.

The low voltage winding interturn insulation fault of dry-type transformer is not easy to find directly through the appearance of the phenomenon, and is difficult to real-time monitoring, seriously affecting the safe and stable operation of power systems. In view of the lack of fault detection methods due to insufficient research on the electromagnetic characteristics of single-turn interturn short-circuit faults in low-voltage windings of dry-type transformers, and the difficulty in setting interturn short-circuit faults in practical projects, finite element simulation software was used to establish a field-circuit coupling model which is consistent with the actual dry-type transformer, and the accuracy of the model was verified under rated operating conditions. On this basis, the variation rules of electromagnetic parameters of short-circuit turns at different positions were explored when interturn short-circuit faults occur in low-voltage windings. The distribution of electromagnetic force on short-circuit turns when interturn short-circuit faults occur in windings at different positions was simulated. The results show that when the interturn short circuit occurs at different positions of the winding, the maximum magnetic density appears in the outermost short-circuit turn; the outermost short-circuit turn is subjected to the largest radial force, and the innermost short-circuit turn is subjected to the largest axial force. Therefore, it provides a theoretical basis for on-line monitoring and protection technology of dry-type transformer interturn insulation, which is conducive to the research and implementation of measures to improve short-circuit resistance.

With many hydropower resources, Southwest China is a crucial area for current and future hydropower construction. However, most southwestern regions have deep overburden problems and high seismic intensity. The impact of these problems on the regular operation of high-face rockfill dams cannot be ignored. This paper established two-dimensional finite element models of 100 m, 200 m, and 300 m high-face rockfill dams on 100 m-deep overburden. Under the action of long-period ground motion and conventional ground motion, the elastic-plastic constitutive model was used to study the dynamic response characteristics of face rockfill dams with different heights on the same deep overburden. Compared with conventional ground motions, the results show that long-period ground motions significantly influence the acceleration of deep overburdened high-face rockfill dams. As the height of the dam body increases, the peak acceleration of the dynamic response of the dam body gradually decreases. Moreover, under the action of long-period ground motion, the higher the dam body is, the greater the displacement increment of the dam body in a short time. In this way, the resulting deformation is also more significant, which is not conducive to the seismic stability of the dam. Therefore, when building panel rockfill dams in areas with deep overburden and frequent long-period earthquakes, the effect of long-period ground shaking should be considered as a part of seismic stability evaluation.

The precipitation data with high quality and high spatial and temporal resolution is of great significance to the research of hydrology, meteorology and other fields. At present, remote sensing and reanalysis of precipitation data are widely used, but there are problems such as low resolution, high uncertainty of accuracy, etc. In this paper, a random forest precipitation fusion algorithm considering covariates is proposed to fuse seven sets of precipitation products, namely CMA, CN05, ERA5, GLDAS, TRMM, IMERG and PERSIANN. Three typical sub-basins of the Yangtze River basin (Jinsha River, Sanxiaqujian and Poyang Lake) are selected to test the effect of random forest fusion data (RFF). The results show that for the accuracy of precipitation products, the accuracy of random forest fusion data is improved compared with the original precipitation products. For the accuracy assessment of different precipitation events, with the increase of rainfall intensity, the T_TS score of each precipitation product shows a decreasing trend, and the T_TS score of RFF is better than the original precipitation product. Data fusion of precipitation products through random forest model considering covariates can improve the accuracy of precipitation data and the reliability of different precipitation events, which provides support for hydrological simulation.

A new anti-seepage structure between the asphalt concrete slab and geomembrane is proposed, which eliminates the concrete connecting plate and adopts backfilling elastomeric epoxy mortar into drilling holes. The mechanical and impervious properties, as well as anchoring parameters of the connecting joints in the anchorage area, are experimentally studied. It is found that the torsional and anti-pulling performance of the proposed anchoring approach is reliable. The suggested double-channel anchoring approach is more compatible with the large deformation of the geomembrane under a pressure of 0.4MPa. According to the results, optimal drilling parameters are proposed, which have the features of good porosity, reliable impermeability and less impact on the asphalt slab, providing a reference for engineering design.

In order to ensure the service performance of underwater concrete structures, it is urgent to carry out the detections and quantitative analyses of underwater concrete structure defects. Aiming at the common failure forms of underwater concrete structures such as collapse and indentation in practical projects, model plates with different shapes and sizes of indentations were designed and made. Using the side scan sonar carried by the unmanned ship, the defect model plates were scanned at a constant speed in a test pool. The acoustic characteristics of the defect areas were summarized by extracting the echo intensity waveforms of different shaped defects along the transverse sections. Image segmentation, mathematical morphology processing, and edge feature extraction were carried out on the original sonar image of different sizes of defects to obtain clear and complete contours of the defect areas. Through the interpretation of the longitudinal length of the defect areas, the quantitative analyses of underwater concrete defects were realized, and the identification error ratios were within 10%. It provides a new method for detecting the defects of underwater concrete structures.

New energy grid connection is easy to cause voltage fluctuation, frequency oscillation and other problems. For this, the paper adopts a frequency division control strategy of hybrid energy storage unit, which based on the storage of photovoltaic grid-connected system as the research subject, thus improving the dynamic stability of DC bus voltage, and proposes an improved virtual synchronous generator. According to the characteristics of flexible adjustment of inertia parameters, the virtual inertia and parameters are adjusted adaptively to suppress the frequency and power oscillation caused by the disturbance. Finally, a simulation model of photovoltaic storage grid-connection is established. It verifies that the proposed strategy can not only stabilize the DC bus voltage and supplement the power deficiency under different operating conditions. At the same time, it can slow down the sudden change of the system frequency and reduce the overshoot, showing good grid-connected performance.

In order to analyze the Nitrogen pollution status and changes in the Yihe River Basin, a SWAT model was established, and the model was calibrated based on the monitoring data of Linyi Station. Its temporal and spatial distribution characteristics were analyzed and the key pollution sources were identified. The results show that the SWAT model has good applicability in the simulation research of runoff and pollution in the Yihe River Basin; The pollution is mainly concentrated in the flood season from July to September, and the ammonia nitrogen and total nitrogen load account for 73.34% and 81.58% of the whole year; The sub-basin in the southwest and close to the water system in the northeast are the main source area of pollution; The main sources of pollution in the basin are sewage discharge, agricultural fertilization and soil loss. Taking Nitrogen fertilizer reduction, returning farmland to forest and comprehensive management measures for the changes can effectively reduce the discharge of pollution load.

In order to realize the safe monitoring of the operation status of hydroelectric units and solve the problem of automated watch keeping, based on speech recognition technology, the normal status model of measurement points based on the operation monitoring information of generating units was established to implement abnormality detection. Firstly, the experimental data of the bearings of Western Reserve University were used to verify the correctness of the selected modeling method of deep convolutional neural network (CNN) and Gaussian mixture model (GMM). Secondly, a total of forty-two measurement points were arranged for the turbine set, and ten sensitive measurement points were selected for position classification based on the rise rate of RMS before and after overspeed. Then some data were selected as training data to get CNN model and unit sound features. The GMM model was obtained by further training. Finally, the scoring results of the test data were used to determine the machine operation status, i.e., the degree of deviation from the normal status was determined to achieve abnormal status detection. The experimental scheme was confirmed by manual annotation, thus verifying the feasibility of the method, which realizes the design of sound-based abnormality detection algorithm for hydropower units.