Abstract:Contaminants in overlying water and sediments of 19 sections from Zhengyangguan to Laozishan in the main stream of Huaihe River were sampled for seven times from 2014 to 2017. The total phosphorus(TP)and main heavy metals, such as As, Cu, Pb, and Zn, in the overlying water and sediment were analyzed to reveal the spatial and temporal distribution characteristics and their main influence factors, and then, this study evaluated the environmental effect for each pollutant. The results show that the concentration of contaminants in the sediment in November is lower than that in June. Meanwhile, the concentrations of various contaminants are decreasing with time, especially TP and As. The analysis of pollutant sources shows that TP in the sediment is affected by the non-point source, while heavy metals are affected by the point source. TP and four heavy metals in the sediment of Huaihe River do not have ecological risk within the monitoring range.

Abstract:To alleviate the shortage of fresh water resources in the northern China where large-scale brackish water is widely distributed, a multi-stage freezing desalination experiment of brackish water was carried out to reveal the mechanism of water quality changes during freezing out processes. The experiment indicates that the methods of freezing and icing can effectively dilute the brackish water and the desalination rate of ice melt water can reach more than 60%. In the multi-stage processes of salty water freezing, the different freezing rate of various ions can lead to changes of ion composition in ice-melting water at all levels. The conclusion is that the method of multi-stage freezing and desalination of saltwater can be widely promoted and applied in the local for mitigating the predicament of local water shortage and the potential harm of primary salty water irrigation to the environment. The advantages of this desalination are that it can make fully use of natural cold energy in winter and realize well economic and environmental achievements. In addition, it seems to be very simple and practicable, which can be implemented in small-scale households or on a large scale. It is one of the effective ways to solve the difficulties of domestic water use and agricultural water use during the spring drought.

Abstract:When the algorithm based on the normal distribution is applied in the sliding window, the detection model will yield an extreme outlier and exhibit unstable phenomenon. To address this issue, this study proposed an algorithm based on the Cauchy distribution for detecting outliers in hydrological time series. Test results indicate that using the median and median absolute deviation in the sliding window instead of the mean and standard deviation can well eliminate the influence of extreme outliers. The setup of the sliding window and the confidence in the algorithm were analyzed. Examples were used to verify this method and the results indicate that the detection rate of the proposed algorithm maintains a high level when the window and confidence settings are appropriate. The comparison with other algorithms shows that the proposed algorithm exhibits good applicability and robustness for dealing with time series with severe local fluctuations.

Abstract:Based on the environmental Gini coefficient, this study investigated the allocation of regional flood drainage rights in the Sunan Canal. The population, GDP, and land area of urban flood control regions along the canal are selected as the control indexes, and the environmental Gini coefficient is calculated by drawing the Lorentz curve. In the case of a certain total amount of flood drainage right, the objective function is to minimize the sum of the environmental Gini coefficients of indicators, and reasonable constraints are set. According to the optimal allocation model of flood drainage right, the optimal allocation scheme of each region is calculated. The results show that after the optimal allocation based on population, GDP and land area is better than the current situation, the environmental Gini coefficients, which are 0. 000 2, 0. 144 1 and 0. 079 6 respectively, are better than the current allocation, and the average variation range of environmental Gini coefficient is 0. 026 3. The allocation model based on the environmental Gini coefficient can consider the actual situation of each region and is conducive to the overall planning of the relationship between urban flood control and regional flood control. On the premise of ensuring the city safety, the optimal allocation of flood drainage right alleviates the pressure of flood control in the Sunan Canal.

Abstract:In this study, the water footprint of agricultural production, water footprint of consumption and virtual water flows were quantified, and the related environmental impacts of water consumption on human health, ecosystem equality and resources were evaluated. Results indicated that the water footprint of agricultural production, water footprint of consumption, virtual water exports and virtual water imports were 110. 97×10⁸, 37. 98×10⁸, 74. 99×10⁸ and 2. 00×10⁸ m³, respectively. Milk, oil-bearing crops and beef were dominated products of virtual water imports, while the water footprint of production, water footprint of consumption and virtual water exports were mainly influenced by rice and wheat. For water footprint of production, water footprint of consumption, virtual water exports and virtual water imports, related impacts on human health were 26. 02×10⁴, 9. 30×10⁴, 17. 58×10⁴ and 0. 87×10⁴ DALY, impacts on ecosystem equality were 19. 02×10⁸, 6. 69×10⁸, 12. 85×10⁸ and 0. 53×10⁸ m²·a and impacts on resources were 0, 1. 47×10¹⁴, 0 and 1. 47×10¹⁴ J. In addition, the applications of water-saving technology and cultivation of new crop variation would contribute to the decrease of water footprint of production and the changes of consumption pattern from water-intensive animal products to water-extensive crop products, which would be helpful in decreasing regional water footprint of consumption. Virtual water imports increased the regional water availability and virtual water exports mean water losing for Jiangsu province. The adjustment of trade pattern and change of trade partner would be helpful in alleviating regional water stress. The environmental impacts related to water consumption in Jiangsu province was influenced by the volumes of water footprint and virtual water flows. Therefore, the decrease of water consumption, smaller ratio for agricultural water withdrawal and change of importing regions would be helpful in decreasing regional environmental impacts.

Abstract:The samples of layered rock mass with soft interlayers were made according to the geological structure of a hydropower project, and the triaxial rheological mechanics test was carried out under the action of seepage pressure by the automatic triaxial rheological servo system. The rheological properties and accelerated rheological properties of layered rock mass with soft interlayers are studied in this work. The long-term strength of rock mass is obtained according to the steady rheological rate of rock mass under different stress levels. It can provide reference for parameter identification of engineering rheological numerical tests of rock mass. According to the structural characteristics of layered rock mass with soft interlayers, a rheological model for the layered rock mass is proposed, which can reflect the rheological properties of layered composite rock mass. By introducing damage variables into the model, the rheological model can accurately reflect the rheological deformation characteristics of layered rock mass under different stress levels. Thereafter, the parameters of the proposed nonlinear damage rheological model were identified by the rheological test curve. The fitting curve fits well with the rheological test results, which verifies the applicability of the nonlinear damage rheological model to the layered rock mass.

Abstract:To improve the activity of volcanic rock powder in Hotan area of Xinjiang so as to expand its application to concrete works, this study adopted a commonly used machine grinding method, called the ball-milling method, to refine powder materials and improve their particle distribution. For volcanic rock powders of four sizes, this study investigated the specific surface area with the Blaine method, analyzed the particle grading and distribution with the laser particle size method, verified the change of macro-mechanical properties after the addition of volcanic rock powder with multi-age mortar strength index method, and analyzed the micro morphology and products with SEM and EDS, to reveal the micro change, the macro strength, and the relationship of activity improvement of volcanic ash. The test results show that the machine grinding method can effectively improve the particle distribution of volcanic rock powder, that is to say, the particle size with the passing rate of less than 50% will be reduced by 0. 6-0. 8 μm when the specific surface area is increased by about 80 m²/kg. With the increasing of age, the bending strength and compressive strength of cementitious system added with volcanic rock powder can be continuously improved on a macro level and the increasing rate of bending strength is faster. However, the strength increasing rate is slowed down with fining volcanic rock powder. Through the change of above macro-mechanical properties, the micro observation and analysis with SEM and EDS, the main reason that machine grinding can improve the activity of volcanic rock powder is the filling effects of micro aggregates from refined particles and the improvement of its hydration reaction capacity after addition with the cement-based system.

Abstract:In allusion to the problems in anti-seismic measures for the crest of earth and rockfill dam, a new kind of seismic strengthening measure has been put forward with the Hardfill materials. The rigid-body limit equilibrium method and dynamic finite element method were used to calculate and analyze the effect of Hardfill seismic strengthening measure in high rockfill dam. Improvements on the stability of dam against sliding, permanent deformation and dynamic strength of materials had been discussed using the Hardfill aseismatic reinforcement. In addition, adverse effects of Hardfill were studied by calculating the acceleration, stress and deformation of the dam. The results indicate that the Hardfill reinforcement will enhance the overall stability, inhibit permanent deformation significantly, and improve the dynamic strength safety coefficient, without adverse effect to the operation of the dam.

Abstract:In order to study the impact of different junction angles and discharge ratios on the backwater characteristics at open-channel confluences, a three-dimensional numerical model was established by using the Volume of Fluid(VOF)method for the free surface capture and adopting the Reynolds Stress Model(RSM)for the governing equations closure. The 3D pattern of backwater was analyzed after the simulations of 21 combined conditions for 3 different discharge ratios and 7 different junction angles. The results indicate the raising of water level in the upstream area and the dropping of water level in the junction area because of the tributary convergence. Under a same discharge ratio, the upstream water level increases as the junction angle increases, and the drop of the water surface in the downstream becomes more obvious. The minimum and maximum ratios of the upstream water depth to downstream water depth were calculated, which indicate that both the minimum and maximum depth ratios increase with a greater junction angle or a smaller discharge ratio among the ranges of junction angle and discharge ratio in the current study. The variation range of the depth ratio was also analyzed. Under a same discharge ratio, a greater junction angle leads to a larger variation range of water level around the junction area. Under a same junction angle, a greater discharge ratio leads to a smaller variation range of water level around the junction area.

Abstract:A wave forecasting algorithm is established based on the stacking ensemble machine learning method. The algorithm includes two sublayers. The multi-layer perceptron model and the random forest model are used in the first sublayer, and the extreme randomized tree model is used in the second sublayer. To suppress the numerical oscillation of the predicted results, the neighborhood averaging method is introduced into the algorithm. Toestablish relations between the wind speed and the significant wave height, the wind speed and China wave(CWAVE)data from January to September 2016 in the offshore area of the Yangtze River Estuary are used. By using the wind data from October to November 2016, the corresponding significant wave height is predicted by the wave forecasting algorithm. The results show that the values of R² between the predicted wave height and CWAVE data are larger than 0. 97 in the 45 days from 1 October, the mean error is less than 0. 08 m, and the mean relative error is less than 0. 05. The trends of the variations of the significant wave height can be accurately predicted by the algorithm. However, the error increases in the last 15 day, which is due to lack of cold wave data in the training set.

Abstract:Based on the investigation and monitoring of sedimentary environment, dynamic conditions and topography of the Nansha beach in Zhujiajian, the longshore sediment transport is calculated and analyzed by using different wave energy flow methods. The results show that the main type of beach sediments is sand, and the depositional substance is mostly from efflorescent rock. Affected by waves, tides, tidal currents and sedimentary environment, the seasonal variation of beach profile is obvious, which is the erosion in summer and the deposition in winter. The characteristic that is erosion in the east and deposition in the west is closely related to the coastal sediment transport. The calculation results of longshore sediment transports show that the net volume of sediment transport is between 43. 85×10³ m³/a and 172. 77×10³ m³/a. The direction of longshore sediment transport from east to west is mainly caused by ESE and SE incident waves, and the direction from south to north is caused by S incident waves. Without considering the impact of human activities on the beach, the longshore sediment transport plays a key role in the long-term evolution.

Abstract:This study reviewed the current research progress of load modeling and pointed out the new circumstances faced by the load modeling. Then, this study put forward a research framework for the generalized synthesis electric load modeling containing active loads and discussed the research scheme in detail. The proposed research framework focuses on solving two key scientific problems, one of which is the coordination of the accuracy and conciseness for the model structure of active loads, and another is the coordination of the time variation and robustness for the parameters of load model. Thus, this study indicates a feasible technical route for building an accurate generalized synthesis electric load model considering the electrical characteristics of active loads.

Abstract:Firstly, the necessity of power electronization is explained from the development history of the power electronics and the challenges in power generation, transmission, distribution, and consumption. Secondly, the driving factors of power electronization, such as politics, economy, and technology, are elaborated in three aspects, including energy security and political construction, the resource and environmental benefits, and the transformation of power generation, transmission, distribution and consumption. Finally, the development trends and main restrictive factors of power electronization in power system are analyzed, and related study directions are summarized to provide some references and suggestions for future study.