In order to study the adjustment characteristics and response of the important shoals in the bar area of the Yangtze River estuary under the influence of sediment discharge decreasing and human activities, this article took the Hengsha shoal, the Jiuduansha shoal and the eastern Nanhui beach as examples. The measured hydrological and topographic data were used to investigate the morphological adjustment of the shoals and the response to changed environment. The results show that in recent years, the two-dimensional geomorphology of the shoals were shrank in the bar area of the Yangtze River estuary, and the tail of the shoals stop progradation in general. The Hengsha shoal and Jiuduansha shoal had different degrees of tidal creeks development; Empirical relationships were developed between the areas of the Hengsha shoal and the previous seven-year average fluvial erosion intensity during flood seasons. This relationship can be used to reflect the change tendency of shoal’s area with the altered flow and sediment regime; The estuarine regulation project can restrain some part of the shoal’s erosion, which was caused by the variation of the flow and sediment conditions. However, the estuarine regulation project may have a slow and long-term cumulative impact on the surrounding regions.

Analyzing the hydrological response of mining activities in the Loess Plateau will help to promote ecological protection and high-quality development in mining areas. This paper selected four typical small watersheds of Baima River, Songta River, Xinshui River and Zhouchuan River on the Loess Plateau, and conducted a study on the applicability of 8 base flow segmentation methods in the Loess Plateau. The difference of anomaly cumulative percentages (DACP) based on paired watersheds was employed to analyze the impact of mining disturbances on the base flow process in the basin. The results show that the Chapman-Maxwell filtering method and the Eckhardt filtering method have the best applicability in the typical small watersheds of the Loess Plateau, the segmented base flow is relatively stable, and the base flow hydrograph conforms to the precipitation and runoff mechanism and the water regression process of the watershed; The base flow of the four small watersheds showed significant downward trends from 1956 to 2012 as a whole; With the increase of mining disturbance intensity, the DACP index of base flow increased, and mining disturbance increased the base flow of the basin.

A CVMD-GRU-DenseNet model for short-term load forecasting based on a decomposition-prediction-reconstruction framework is proposed to aim at the nonlinear and multi-period characteristics of power load time series. In the decomposition stage, the optimal decomposition number of VMD is determined according to the correlation entropy between subsequences to improve the decomposition quality. In the prediction stage, the input features are selected according to the characteristics of each sub-sequence. The GRU neural network and the DenseNet model are employed to forecast the regular low-frequency and highly random high-frequency components, respectively. Finally, the prediction results for each element are reconstructed into a load prediction curve. The short-term load forecasting results of four seasons for a city in Hubei Province show that the proposed method can effectively improve forecasting accuracy and has strong generalization ability.

Using the daily meteorological dataset of basic meteorological elements of China National Surface Weather Station (V3.0) as a control, the reproducibility of the spatial and temporal distribution characteristics of hourly precipitation in North China during the warm season (June-September) by the China Hourly Merged Precipitation Analysis (CHMPA) and the CPC MORPHing technique (CMORPH) were compared and analyzed. The hourly precipitation and daily variation characteristics of the warm season in North China were further investigated. Results show that the spatial and temporal distribution of precipitation in CHMPA and CMORPH during 2008-2018 is basically consistent with the observation, the estimation of precipitation by CHMPA is generally smaller than the observation, while CMORPH is larger than the observation. The CHMPA data has high spatial resolution and little difference with the actual observation, which is more conducive to the diagnosis analysis of strong convective weather. The overall warm season hourly precipitation in North China is characterized by more precipitation in the southeast and less in the northwest, with normal rain mostly occurring in the plateau area and flash heavy rain mostly occurring in the transition area between the plateau and the plain and the plain area. The warm season precipitation in North China has obvious daily variation characteristics. The large value of precipitation center appears in the afternoon near the mountains, then gradually moves southeast and causes large precipitation in the western part of the North China Plain at night, and the precipitation center reaches the central part of the plain in the early morning of the next day. The precipitation gradually weakened in North China from early morning to noon the next day. The peak of precipitation and precipitation frequency occurs mostly from midday to late afternoon in the plateau area and from midnight to early morning in the plain area. The results provide a theoretical reference for precipitation research and forecast in North China.

Malfunctions resulting from rub-impact between moving and stationary parts of bulb tubular unit will jeopardize the safety and stability of hydropower units. Aiming at the bulb tubular unit shaft rubbing system, a coupled bending-torsional rotor-runner system with faulty oil receiver under multi-vibration source and corresponding differential equation were established. The Floquet theory was applied to investigate the stability of periodic solution. The results reveal that when faulty oil receiver is taken into account, the system dynamic feature alters dramatically, which aggravates the possibility of system instability and alternates frequency transition between steady and non-steady state. This fault aggravates the unsteady vibration characteristics of different rotating parts, especially for the runner structure response trend, which needs to be paid enough attention. The results can provide useful references for safe operation and stability analysis of bulb tubular units.

In order to study the influence of mineral admixture on steam-cured concrete under freeze-thaw environment, CT technology was used to scan the steam-cured concrete after freeze-thaw cycle, and the sectional images were obtained. The three-dimensional reconstruction of steam-cured concrete was carried out by Fiji and Avizo software, and the pore structure characteristics of the samples were obtained. The results show that the compressive strength of steam-cured concrete decreases with the increase of freeze-thaw times, and the deterioration of pore structure is the main reason for the decrease of compressive strength; The mechanical properties and pore structure characteristics of steam-cured concrete mixed with mineral powder and fly ash are better than those of ordinary steam-cured concrete under the same freeze-thaw conditions. The mineral powder and fly ash have a certain effect on improving the pore structure of steam-cured concrete.

In order to explore the spatiotemporal characteristics of water quality and its correlation with land use type in the middle and lower reaches of the Chanba River, sampling and monitoring were conducted in April (wet period), August (flow period) and December (dry period) of 2019 based on seventeen sampling sites. The spatial-temporal characteristics of water quality and the identification of main pollution factors were analyzed by employing multivariate statistical, and the relationship between the land use type and water quality indexes was studied by the method of Spearman analysis. The results show that water quality had spatial and temporal characteristics in the middle and lower reaches of Chanba River in 2019. In terms of time, the concentration values of NH₃-N, TP and COD_Mn were maximum in flow period; The order of TP and COD_Mn was sorted as flow period > wet period > dry period. Spatially, the concentrations of NH3-N, TP and COD_Mn basically increased from the middle reaches to the lower reaches. Influenced by human activities along the river, the water quality was mainly polluted by nutrient and organic matter in the middle and lower reaches of Chanba river. Construction land had a positive correlation with pollutants and played a "source" role, while forest had a negative correlation with pollutants and played a "sink" role. The results can provide reference for water environmental management in Chanba River Basin.

In the hydraulic transition calculation of long-distance water transmission pipeline, the intake and exhaust coefficient of air valve is mostly constant. In order to explore the influence of the intake and exhaust coefficient of water hammer air valve on the change of pipeline pressure, the DN100 water hammer air valve was simulated by FLUENT software to obtain the mass flow at -9 kPa -11 kPa, and the dynamic intake and exhaust coefficient curves with different pressure differences were established. Taking Xishan primary water lift pump station as an example, dynamic value and fixed value were adopted for air valve inlet and exhaust coefficient respectively (mean value 0.55) to calculate and compare the transition process. The numerical simulation results show that the improved dynamic inlet and exhaust coefficient of the air valve has little impact on the negative pressure of the pipeline and great impact on the positive pressure. The improved dynamic inlet and exhaust coefficient effectively reduces the pressure fluctuation in the pipeline. In the actual operation of the pump station, it is necessary to pay attention to the positive pressure change of the pipeline, and strengthen protection. The calculation of water hammer prevention should be based on the measured data of air valve inlet and exhaust. The research results can provide some references for the hydraulic transition calculation of air valve in the operation of pump station.

Flood prediction and design calculation in ungauged region are often restricted by data of rainfall and runoff. Based on the DEM data extraction of Horton geomorphologic parameters in Luoyang river basin, geomorphic units line of Luoyang river was calculated, and the basin confluence and the response relation between geomorphic parameters was established. The three layers of evaporation and saturation excess runoff were used to construct Xin’anjiang model based on geomorphic unit line. Luoyang river basin flood simulation was carried out by combination of genetic algorithm with objective optimization. Compared with Xin 'anjiang model, the results show that the Xin’anjiang model based on geomorphic unit line can obtain better simulation results, which can provide reliable technical support for hydrologic analysis and calculation of small and medium-sized rivers in ungauged region.

In order to evaluate the quality of "stepped" concrete cut-off wall of Hejiagou reservoir dam, the ground penetrating radar was used to detect the whole cut-off wall, and the cross-hole ultrasonic method was used to detect the " steps" of the concrete cut-off wall. The detection shows that the overall quality of the cut-off wall is good. Core drilling and water pressure test were carried out in the areas where there may be abnormalities, and the quality of the cut-off wall was comprehensively evaluated in combination with the monitoring data of the osmometer in front of and behind the cutoff wall. The results show that no major quality defects are found on the cutoff wall, local abnormalities exist, and the overall working performance is normal. This comprehensive geophysical detection method can effectively reflect the actual quality of the "stepped" cutoff wall, and the comprehensive utilization of relevant technologies can provide reference for similar projects.