As a widely used function in hydrologic frequency and flood computation, the Gamma function has many calculation methods, and the scope of application and computation accuracy also vary. In order to explore a high-precision Gamma function computation method suitable for hydrological computation, different Gamma function asymptotic expansion formulas such as Stirling series and its derived approximation formula are used for computation and analysis. Comparing the accuracy and application range of various methods, the results show that the piecewise polynomial method has the smallest truncation error and the highest accuracy; The second is the Ramanujan asymptotic expansion and the Stirling first tetranomial. The recommendatory high-precision Gamma function computation method can effectively improve the computation accuracy of hydrological results, which can provide fast and accurate results for the planning and design of various hydro projects to determine project scale and management decisions.

The Shiliushubao landslide is one of the giant landslides with complex structure in the Three Gorges Reservoir area. Since the dam was filled with water, the landslide has shown signs of revival, causing loss of life and property to several people around. In order to study the deformation failure mode and response mechanism of Shiliushubao landslide under the fluctuation of reservoir water level, the large-scale physical model test was used to accurately control the fluctuation condition of the experimental reservoir water level, and the displacement sensor, earth pressure sensor and pore water pressure were embedded in the slope. The sensor was used to analyze the experimental phenomenon. The results show that the influence of the reservoir water level fluctuation is mainly concentrated at the foot of the front edge of the landslide, and the rapid decline of the reservoir water level has a significantly greater effect on the landslide deformation than the increase of the reservoir water level; The mechanical response of the slope body has a hysteresis, and the effective soil stress increases when the reservoir water rises, the anti-sliding force of the sliding belt increases, and with the increase of the rising rate, the penetration force directed into the slope is larger, which is conducive to the stability of the landslide; Under the condition of the reservoir water level, the deformation and failure mode of the Shiliushubao landslide is sorted as: original slope → Erosion and erosion expansion at the foot of the slope → formation and expansion of the fissure at the foot of the slope → formation of the fissure on the slope surface → local slump, which is a hydrodynamic pressure landslide. The test revealed the deformation mechanism under the condition of reservoir water level, and provided a reference for the study of similar landslides.

For the long-distance water supply project where the pump station pressurizes before the high point and gravity flows after the high point, when the end valve is closed in a straight line in case of power failure in an accident, a longer valve closing time is required to meet the pressure control standard, which virtually increases the scale of the protective measures and increases the investment. In order to solve this problem, a broken line valve closing rule is proposed to reduce the volume of protective measures while optimizing the pressure. The characteristic line method is used to check each scheme through FORTRAN programming, and the general rule is summarized by analyzing the influencing factors of the main parameters. The case results show that the broken line valve closing can reduce the volume of protective measures and reduce the project cost compared with the straight line valve closing within the same valve closing time under the premise of ensuring that the pressure meets the requirements.

In the weak current network, due to the large impedance characteristics of the power grid, the impedance parameters in the line change the key parameters of the rectifier control, affecting the overall performance of the rectifier, which may lead to the unstable output of the rectifier, and the output presents the characteristics of sub-synchronous oscillation. On the basis of not increasing the hardware compensation system, this paper proposes a control strategy that can effectively suppress the sub-synchronous oscillation. Based on the mathematical model, the AC current component of the sub-synchronous oscillation is extracted through the low-frequency filter. After d/q transformation, the d/q current component of the sub-synchronous oscillation is PI closed-loop controlled. The output value of the PI regulator of the subsynchronous oscillation component is decoupled and compensated, and then multiplied by the compensation coefficient to obtain the d/q compensation component of the voltage. The output of the original current inner loop is compensated. A simulation and test results show that the control strategy is effective and feasible, which can suppress sub-synchronous components.

The expansion of cities and towns has caused a large amount of waters to be compressed, occupied or even disappeared, and the risk of floods in the region has increased sharply. This study is based on Hengyang, a typical city in midstream of Xiangjiang River. Based on expansion speed index and intensity index of Xiangjiang midstream from 2001 to 2016, the linkage relationship between the two is quantitatively analyzed, and the response of water system change under the background of urban expansion is analyzed. The results show that the urban development in midstream of Xiangjiang River can be divided into three stages. The urban expansion is characterized by a high speed and then a low intensity. During the study period, the total number of river systems showed a declining trend, and the channel morphology showed a shrinking state. The change of the structure of river systems was more severe than the change of the number. The basin with few river systems and single structure had a sharp decline. Urban expansion has a close relationship with the change of river system, and has a greater impact on the change of the number of river systems. And it is highly related to the basin with few water systems and single structure. It can be seen that human activities such as urban construction and expansion should minimize the adverse impact on such watersheds.

UHV DC wall bushing is the neck-jamming technology of China’s power grid. At present, not only its core design and manufacturing technology still have many difficulties to be overcome, but also the state monitoring technology of its equipment operation is also a hot issue. This paper explores the application of an on-line monitoring technology based on vibration signals in UHV DC wall bushings. On the basis of analyzing the structure and common faults of UHV DC wall bushings, theoretical simulation research is carried out. It is found that when the outdoor insulation or inner insulation of the UHV DC wall bushing is damaged, the fundamental characteristic frequency of the bushing changes significantly. Afterwards, this paper carried out fault simulation and vibration tests on the cracking of capacitor core and the rupture of silicone rubber shed of the 800 kV UHV DC wall bushing. The results show that the fundamental characteristic frequencies of the bushing under different fault conditions are quite different. Therefore, the use of vibration monitoring technology can effectively identify the faults of UHV DC wall bushings, which can provide technical reference for UHV engineering construction and operation and maintenance personnel.

To address the challenges in oil leakage image recognition of peak regulation power equipment, a new method is proposed by introducing logical rule discrimination strategy into the task of image recognition. The technology of histogram equalization is adopted to improve original image. Then Mask RCNN network is introduced to obtain the preliminary location and contour information of storage device, ground and suspected oil area. Based on the above information, positional relationships between objects are judged, and logical expressions are adopted to determine the oil leakage area. Example analysis is conducted based on filed images of peak regulation power equipment. The results indicate that the proposed framework solves the problems in oil leakage area recognition, largely boosting model performance.

With the continuous accumulation of dam deformation monitoring data and the continuous increase of deformation measuring points, it often takes a lot of time to predict all deformation measuring points, which is easy to cause the problem of untimely feedback. Therefore, the fuzzy C-means clustering algorithm (FCM) was introduced to partition the dam according to the similarity of deformation laws. The whale optimization algorithm (WOA) was used to optimize the parameters of long short-term memory neural network (LSTM), and a dam deformation prediction model based on FCM-WOA-LSTM was established. The measured deformation data of a concrete double-curvature arch dam was used as sample data for prediction, and the prediction results were compared with those of LSTM model and SVM model. The results show that the average absolute error (M_MAE), mean square error (M_MSE) and root mean square error (R_RMSE) of the prediction results of FCM-WOA-LSTM model are the smallest among the three models, and the three evaluation indexes of the fitting section are close to those of the prediction section, respectively. Compared with the existing models, the FCM-WOA-LSTM model has higher prediction accuracy and better applicability.

The bedload sediment transport in the compound channel is affected by the presence of emergent rigid vegetation, and there were few studies available on this topic. The laboratory experiments and theoretical analysis were used to investigate the effect of emergent rigid vegetation in parallel arrangement on the threshold Shields number and the bedload transport intensity. The results show that the presence of emergent rigid vegetation in parallel arrangement increased the threshold Shields Number by 97.2%, and the bedload transport intensity reduced by more than 80%. The modified Engelund Formula that was applicable to the emergent rigid vegetation in parallel arrangement conditions was developed to calculate the bedload transport intensity. The formula was shown to have a high accuracy by applying it to the other studies.

In order to study the influence of high tidal current velocity on the dynamic characteristics of horizontal axis tidal turbine under free wave conditions, STAR-CCM+ was used to establish a numerical calculation method for the hydrodynamic characteristics of tidal energy turbines under sea wave conditions. The law of wave influence on the rotation of tidal energy turbines and the characteristics of wake flow generated during the rotation were obtained. The results show that the amplitude and frequency of the angular acceleration of the tidal energy turbine are affected by the waves, but the fluctuation amplitude is less than the wave amplitude, the variation frequency is higher than the wave frequency. The wake flow produced by the rotation of the hydraulic turbine will make the flow field around the next hydraulic turbine more chaotic, and will have an impact on the blade rotation, turbine shaft load and energy utilization efficiency. Based on the analysis of the changing trend of pressure fluctuation, it is considered that the wake flow has little effect on the fatigue damage of hydraulic turbine.