As the most basic precipitation collection equipment in the field of hydrometeorology, the tipping bucket rain gauge has the characteristics of practicality and good stability, but there are some deficiencies in the research on the tipping characteristics and mechanism of the tipping bucket rain gauge and the causes of the mechanical error of the tipping bucket rain gauge. In this study, the mechanism of the tipping process of tipping bucket rain gauge was explored by means of combination of numerical simulation and indoor experiment with high-speed camera. The results show that during the turnover process, the time from start to stop is about 0.35-0.40 s, the time t₁ from start to level is relatively high, about 80%-85%, and the time t₂ from level to stop is only about 0.05 s, and there is a slight rebound after the turnover touches the adjusting nut. During t₁ period, water will be continuously injected into the tipping bucket, which is the fundamental reason for the change of additional water volume and mechanical error of rain gauge with rain intensity. The tipping bucket will pour out the water in a very short time (about 0.4 s), and because the tipping bucket will cause slight rebound when touching the stop bolt, it will cause the "double peak" phenomenon of the tipping flow of the rain gauge tipping bucket when pouring out the water, and it will increase with the small installation inclination of the tipping bucket on the left and right. The research results can provide basic theoretical support for the improvement of tipping bucket rain gauge in the future.

The ecological security of rivers is not only closely related to the physical, chemical and biological integrity of the river itself, but also affected by the natural, economic and social conditions of the regions through which it flows. Based on the "driving force-pressur-state-function-response" (DPSFR) framework and matter-element extension model, a river ecological security evaluation system was constructed. Taking Hongru River as an example, it was divided into 10 evaluation units according to the spatial differences such as physical geography and water conservancy projects, and the river ecological security evaluation and spatial differentiation characteristics research were carried out. The results show that the ecological safety level of the Hongru River in 2017 was in a critical safety state, and there was a tendency to develop to an unsafe level. Its spatial differentiation characteristics were that the upstream was better than the downstream, and the tributaries were better than the mainstream, especially in the functional and response layers. Among the indicators, total phosphorus, per capita comprehensive water consumption, river longitudinal connectivity, and water quality assessment cross-section compliance rate are the main factors affecting the spatial distribution of ecological security differences in Hongru River. The response is a criterion layer that is significantly related to the spatial differentiation of the ecological security of the Hongru River.

Aiming at the topology optimization of large-scale offshore wind power collection system, an improved partheno genetic algorithm was proposed. The calculation model of the present value of the life cycle cost of the power collection system was established. Taking the minimum of the sum of present value as the goal, the population generation mode meeting the current carrying capacity constraints of the submarine cable and the elimination coefficient related to the number of crossing points were designed to avoid the submarine cable crossing. The topology of the power collection system with 35 kV and 66 kV voltage levels was optimized and compared. The example results show that the total cost of the improved partheno genetic algorithm can be reduced by 14.2% compared with the traditional algorithm; Compared with 35 kV, 66 kV voltage level has better comprehensive benefits, which can provide reference for the planning and design of large-scale offshore wind farm power collection system.

In practical engineering, there are few samples of arrester failures, and it is difficult for intelligent algorithms such as neural networks to make accurate judgments. To this end, a fault diagnosis method of arrester based on Bayesian network was proposed. Firstly, the principal component analysis was used to extract 21 characteristic parameters that affect the operation of arrester. And then the extracted characteristic parameters was chosen to establish two-layer information architecture defect diagnosis model. The classification probability of different categories was calculated according to the existing real-time data. If the first classification result indicated that the arrester is abnormal, new detection evidence was added for the second diagnosis. Finally, 6 arresters under the same voltage level in a certain area were selected to analyze and verify the validity and correctness of the proposed method.

Under the influence of climate change and land use/land cover (LULC) change, the combined influence of multiple factors has significantly increased the difficulty of probable maximum flood (PMF) estimation. A PMF estimation framework was proposed, integrating post-processing of climate model results, probable maximum precipitation (PMP) estimation and future LULC change setting under climate change scenarios, impact analysis of base flow/antecedent rainfall, and similarity-based PMP spatio-temporal distribution. This new framwork was applied to the Upper Nujiang River Basin. The results show that the uncertainty of base flow/antecedent rainfall and PMP spatio-temporal distribution are important factors affecting PMF for basins, and the dual-drive of climate change and LULC change has a greater impact on PMF, and the amplitude of change increases with the degree of change.

In order to obtain a more accurate calculation model of punching shear capacity of FRP reinforced two-way concrete slab, taking the FRP reinforced two-way concrete slab as the research object, using the research methods of literature review, data statistics, model analysis and regression calculation, and with the help of the commonly used calculation model of punching shear capacity of FRP reinforced two-way concrete slab, based on the collected punching test data of 98 FRP reinforced two-way concrete slabs, the inversion method of critical punching section coefficient of two-way slabs was used to establish a new calculation model of punching bearing capacity of FRP reinforced two-way concrete slabs. The model has high accuracy in predicting the punching bearing capacity of FRP reinforced concrete structures under concentrated load. The predicted results are in good agreement with the experimental database. The model has guiding significance for the design of punching shear capacity of FRP reinforced two-way concrete slab, which provides an important reference for further improving the accuracy of punching shear capacity calculation model of FRP reinforced two-way concrete slab in the future.

To solve the disadvantage of high cost and low efficiency in the traditional three-way crack detection methods, a three-dimensional crack change detection method based on binocular vision was proposed. Three-dimensional equivalent model of crack change was established, and the calculation of crack changes was equivalent to the calculation of changes between targets. Three-dimensional reconstruction of cracks was carried out through feature point code matching, spatial coordinate system transformation, three-dimensional coordinate calculation, and the three-dimensional situation of the fracture change was obtained. To verify the accuracy of the method, a unidirectional displacement test was carried out. The results show that the maximum measurement error of the opening and dislocation of the crack is within 0.2 mm, and the maximum measurement absolute error of settlement of the crack is within 0.3 mm, which meets the requirements for crack detection in technical specification for earth-rockfill dam safety monitoring.

Taking Shiping large irrigation area in Yunnan Province as an example, this paper studied the economic value of irrigation water and analyzed the influencing factors of crops in the irrigation area through the benefit sharing coefficient method and residual value method. It is found that the economic value of irrigation water for cash crops and fruits is higher than that for food crops. At the same time, it is recommended to use the benefit sharing coefficient method to calculate the benefits in irrigation district planning. The results of this study can guide similar irrigation district planning and help the construction of high standard modern irrigation districts.

Coral sand is an important material for island and reef engineering construction. Its physical and mechanical properties in different marine environments directly affect the design, construction and long-term operation of island and reef structures. In order to study the shear mechanical properties of coral sand under the influence of temperature and salinity, the triaxial drainage shear tests of coral sand in the South China Sea were carried out at different temperatures and salinity by using the self-developed temperature controlled pile-soil interface triaxial tester. The results show that similar to ISO standard sand, the shear stress-strain curves of coral sand have peaks, presenting its characteristics of strain softening; The shear strength of coral sand is not significantly affected by temperature, but it is sensitive to salinity. Compared with fresh water environment, the peak shear strength of coral sand in salt water environment decreases by 2.5%-8.5%, and the lower of confining pressure, the greater of decrease range; Salinity has a deterioration effect on the cohesion of coral sand, and its reduction range is about 30%, but the effect on the internal friction angle of coral sand is not obvious.

To determine the key water quality indicators for influencing the Weihe River tributaries of Chanhe, Bahe, Fenghe and Zaohe Rivers and the minimum water quality index (W_WQImin) is of great significance for simplifying water quality evaluation. The research set up a total of 30 sampling points in the 4 rivers and collected water quality samples in April, August, and December 2019, respectively. Fifteen water quality indicators were analyzed by laboratory experiment and mathematical statistics. It was found that the content of DO in Fenghe River was obviously highest, and the contents of EC and nitrite in Zaohe River and the Bahe River reach after the convergence of Chanhe River were higher than other rivers. In addition, based on 15 water quality indicators, the water quality index (W_WQI) was calculated to evaluate the temporal and spatial changes of water quality of the 4 rivers. This study shows that the water quality indices were generally above the medium level (W_WQI≥51) in all four rivers, and the water quality of the Fenghe River was better among the four rivers. On time scale, the water quality in the spring of 2019 was better than the other two periods. Besides, stepwise multiple linear regression analysis and empirical method were used to determine the appropriate minimum water quality index (W_WQImin), which contains DO, ammonia nitrogen, COD_Mn, turbidity, nitrate nitrogen, $\mathrm{SO}_{4}^{2-}$, and EC. Compared with the W_WQI based on 15 water quality indicators, the relative error (P_PE) is only 4.78%, the linear correlation coefficient R² reaches 0.95, and the root mean square error (R_RMSE) is only 3.99. Finally, the spatial and temporal distribution of W_WQI and the appropriate W_WQImin in the 4 rivers are consistent. Therefore, it can be considered that the selected appropriate W_WQImin can be replaced of WQI, which is more efficient for time-saving, low-cost and high-efficiency water quality evaluation in the basin near the Chanhe, Bahe, Fenghe and Zaohe Rivers.