Abstract:In this study, the approaches adopted in the assimilation of hydrological remote sensing data were introduced. Emphasis was placed on the advantages and disadvantages of the commonly used methods in both variational and sequential data assimilation. Focusing on the assimilation of soil moisture and streamflow, the application progress of multisource observations including the soil moisture, streamflow, precipitation, evapotranspiration and snow cover in hydrological simulation and forecast was analyzed in detail. On this basis, the issues existed in the application of multisource observations in hydrological modeling were explored. Finally, future development trends of hydrological remotesensing data assimilation were proposed in terms of both data assimilation method and multisource data assimilation application. It is believed that the potential of remote sensing and insitu multisource data assimilation in improving the hydrological simulation and forecast will increase with the improvement of remote sensing observations and reversion techniques, the refinement of hydrological model structure and the optimization of data assimilation approaches. The integrated application of multisource observations in hydrological simulation and forecast will be the inevitable trend in the development of hydrological data assimilation.

Abstract:To address the problem that the calculation method of the design value combination of flood peak and flood volume under stationary conditions cannot be applied for the non-stationary case under changing environment, this paper firstly constructs the multi-dimensional joint distribution model with time-varying dynamic Copula function, which can comprehensively consider the non-stationarities of marginal distributions and correlation structure between variables of the flood peak and flood volume. Then the nonstationary evolution characteristics of the joint distribution of flood peak and flood volume over time are analyzed. Subsequently, based on the equivalent reliability method and the conditional expectation combination method, the calculation method of design value combination of the flood peak and flood volume under changing environment is proposed, which can be applied to estimate the expected design value of flood peak and flood volume combination with a given return period under the changing environment. Taking the flood peak and maximum 7-day flood volume series at the Huanglongtan Station as examples, a case study is conducted. The results show that the joint distribution characteristics of flood peak and flood volume changes significantly with time, and the expected combination design value of flood peak and flood volume corresponding to the specified return period is affected by engineering design lifetime with a decreasing trend as the design lifetime increases.

Abstract:To scientifically investigate the flood control capacity, the drainage capacity and their improvements in the hilly city, taking the Yushan Bay as an example, the hydrologic and hydrodynamic model of hilly city was established based on SWMM (storm water management model), which can consider the torrential flood and drainage network together. Aiming at the un-gauged area, the model calibration was realized through surveying historical overflow points and using the comprehensive runoff coefficient method. In this model, the flood-cutting channels were discretized into calculation units with each section length of 10 m, and their control zones were divided by the Tyson Polygon Method to realize the simulation of the flood-cutting channels with variable sections and multiple outlets. The calculated averages of the maximum one-hour discharge peaks were within the recommended range of the standard value. As the influences of previous rainfall in the study area and the discharge distributions in the flood-cutting channels were considered in the model, the rationality of calculating the discharge peaks of the flood-cutting channels was ensured. Then using the renovated dimensions of the flood-cutting channels, this study calculated the flood control and drainage capacity of the downstream core planning area, and presented an improvement scheme, which is increasing the pumping capacity of Jinjing River Pump Station and reducing the control water level of Yushan Lake to increasing its storage capacity.

Abstract:To study the characteristics of rainfall-runoff generation processes in the plain area of the Taihu Lake Basin, the Jintan hydrological experimental area was selected to carry out the observation of rainfall-runoff processes.The specific elements that affected the runoff generation during rainfall events were extracted and the whole hydrologic processes of two typical runoff generation events, which were dominated by saturation-excess and infiltration-excess mechanism respectively, were analyzed. The results indicate that the experimental area is dominated by the mechanism of saturation-excess and the phenomenon of infiltration-excess is rare. The runoff generation processes in the plain experimental area under the condition of long-duration light rainfall can be divided into four stages: soil water filling, surface depression filling & ditch outflow, whole area outflow, and recession after rainfall. The runoff coefficient in the ditch outflow stage is small and the outflow is mainly composed of the rainwater falling on the area of the ditch. The whole area outflow stage belongs to the infiltration-excess mechanism under the condition of soil moisture reservoir is saturated and the rainfall intensity threshold is about 0.1mm/min with a large runoff coefficient. The first two runoff-generation stages may occur simultaneously in the short-duration heavy rainfall. If the soil is not saturated at the whole area outflow stage, it is a traditional infiltration-excess dominated runoff event with a large proportion of infiltration. While if the soil is saturated, it belongs to the infiltration-excess mechanism under the condition of soil moisture reservoir is saturated.

Abstract:The standardized precipitation index SPI and remote sensing vegetation index (NDVI, EVI) were used to quantify the evolution characteristics of growing season vegetation and hydrological drought in the Three River Source Region (TRSR) from 1961 to 2018. The spatio-temporal evolution trends of drought and vegetation in the Three River Source Region from 1961 to 2018 were analyzed based on the Mann-Kendall trend test. In addition, the spatio-temporal evolution trend of vegetation, and the correlation between different drought variables and vegetation index was analyzed based on the Spearman's level correlation coefficient. The results show that the seasonal drought events in the study area occurred in 1963, 1966, 1984, 1992, 2000 and 2017, there was significant humidification in spring (mean trend characteristic value Z=2.28), and both the source of Lancang River and the middle of the source of Yangtze River in autumn faced a non-significant drought threat. In May, there was a significant increase of vegetation in northern of the Yellow River source, while there was an insignificant trend of vegetation degradation in the middle of Yangtze River source and Lancang River source in September. The variation trend of vegetation is that the north is stronger than the south and the west is stronger than the east from 2000 to 2018. Since the 21st century, drought events have a certain response relationship with vegetation, and SPI3 has a significant positive correlation with the vegetation index.

Abstract:In this study, with small shallow lakes in Huaihe River Basin as object, the biodiversity and distribution characteristics of ammonia-oxidizing bacteria (AOB) were analyzed. Simultaneously, to explore the role of different sources of nitrogen pollutants on the abundance and distribution characteristics of AOB, nitrate sources were investigated via molecular biological means and bacterial denitrification stable isotope technology. The results showed that the diversity and abundance of AOB were the highest in Desheng Lake, while those in the northern part of the Dazong Lake were the lowest, demonstrating that the complex pollution sources and surrounding environment of Desheng Lake and the dense aquatic plants in the center of Dazong Lake led to the increase of the diversity and abundance of AOB. Phylogenetic analysis of amoA gene showed that the two most abundant genera in Desheng Lake, Dazong Lake and Jiulongkou were Nitrosomonas (92.3%) and Nitrospirillum (7.7%). Based on the distribution of AOB, nitrate nitrogen and AOB changed consistent, and nitrate nitrogen in overlying water was high at the point with high AOB abundance. Isotope traceability analysis showed that long-term seine farming led to a decrease of δ15N (0.57%) and the long-term over accumulation of decaying plants led to an increase of δ15N (1.0%). The research is helpful for the further study of the nitrogen cycle and management of shallow lakes.

Abstract:To further understand the toxic effects of Phthalate Esters (PAEs) on electroactive biofilms (EABs), based on summarizing the current distribution situation of PAEs in natural water and wastewater treatment systems, this review analyzed the influence mechanism of PAEs and other toxic substances on biofilms, and proposed the potential influence mechanism of PAEs on the performance of EABs. The influence mechanism mainly includes three aspects: the influence on the colonization of electroactive microorganisms, the influence on succession of electroactive biofilms, and the influence on functions of electroactive biofilms.

Abstract:In this study, activated carbons were prepred by the modified grapefruit peel with different methods. The effects of the pH value, the dosage of activated carbon, the initial concentration of methylene blue and the adsorption time on the adsorption effect were investigated. The adsorption kinetics and adsorption mechanism were also discussed. The results showed that under the optimal conditions, the removal rates of methylene blue by four activated carbons were 84.5% (unmodified), 87.3% (modified by aluminum chloride impregnation method), 91.1% (modified by sodium sulfide activation), and 95.5% (modified by potassium hydroxide activation), respectively. Comparing the value of the equilibrium adsorption capacity of different activated carbons, the activated carbons prepared from modified pomelo peel with aluminum chloride and potassium hydroxide had a significantly improved adsorption ability. The analysis of adsorption kinetics showed that the adsorption process of methylene blue on four kinds of activated carbons all accorded with the quasi-second-order kinetic model. The surface of activated carbons prepared from modified pomelo peel with aluminum chloride and potassium hydroxide contained many organic functional groups, which was consistent with the higher initial concentration of methylene blue wastewater and high equilibrium adsorption of activated carbons.

Abstract:To study the impact of spatial randomness of the gradation parameter on the deformation and stress of rockfill dams, the fractal model was selected to describe the gradation distribution. The exponential model and the Gauss model were introduced as the variogram model to analyze the spatial varying structure of gradation fractal dimension D, and some geological statistical methods such as the Kriging method were introduced to simulate the spatial random distribution of gradation parameters of rockfill material and transition material in the Lianghekou core-wall rockfill dam. With the combination of stochastic modeling and finite element method, this paper carried out 500 deformation and stress simulations for the dam to obtain the convergent results and compared the results with the deterministic finite element method. It is determined that when the spatial variability of rockfill materials is considered, the maximum displacement in horizontal direction and the maximum settlement will increase. Therefore, when the spatial variability is not considered, the probability of underestimating dam stress and deformation will exceed 50%. The calculation method considering the spatial random distribution of gradation parameter has good application value for the design and deformation control of high rockfill dams.

Abstract:In order to explore the enhancement effect of new materials on the performance of steel structures, the flexural behavior of steel beams under load is analyzed by strengthening and transforming the steel beams with Reinforced Reactive Powder Concrete (RPC). Through the bending test of the test beam under the secondary load, the failure process of the beam was analyzed. Then, the influences of initial load, RPC strength, and section steel strength on the bearing capacity of beam were studied. The test results were verified by the finite element simulation. The research shows that under the influence of different parameters, the bending capacity of the steel beam wrapped by reinforced RPC is 1.7~2 times higher than that of the pure steel beam and the specimen shows better ductility during the failure process. Meanwhile, no bond failure occurs at the interface between the section steel and the RPC, and both can work well together. The ultimate bearing capacity of the beam decreases with the increase of the initial load and increases with the increase of RPC strength and section steel strength. According to the experimental results, the calculation formula for the flexural bearing capacity of steel beam wrapped by reinforced RPC under the secondary load and the RPC strength reduction formula are proposed. The experimental value, the calculated value and the simulated value are in good agreement.

Abstract:In this paper, based on the technologies of global navigation satellite system (GNSS) positioning and attitude sensing technology, a vehicle-mounted leveling control device of bulldozer was developed. The device in the driver’s cab displays the bulldozing elevation, blade attitude and elevation difference compared with the designed paving plane in real time, which can effectively guide the driver to adjust the blade operation. An integrated real-time monitoring technology was proposed for the earthwork filling and leveling of embankment with remote coordination of all parties involved in the project construction. Accordingly, the corresponding software system was also developed, which can realize the remote monitoring of pavement thickness and flatness during the whole process of embankment earthwork filling and realize the monitoring mode of “driver-manager-supervisor-owner collaboration”. The application in an actual project shows that the absolute error of system accuracy is within 3 cm, the monitored pavement thickness is 76.5 cm and less than the design thickness, and the paving flatness meets the control requirements. The system can effectively improve the quality of earthwork filling and paving of embankment, and ensure that the pavement thickness and flatness are always under real control.

Abstract:Microgrid operators, load aggregators and large power users were selected as the diversified trading subjects on the distribution side. Based on the comprehensive consideration of the balanced relationship between demands and interests among the three, the transaction framework of distribution side power market was preliminarily constructed under blockchain technology. On the bottom layer, blockchain core technologies were adopted to realize the trust, security and transparency, which gives full play to the advantages of its function of distributed ledger. On the upper layer, considering the different trading needs of market players, smart contract models of the multi-party transaction with the goal of maximization of interests were achieved by the gambling balance. Then the transaction contracts were recorded in the underlying ledger of the blockchain. Finally, based on the example analysis, the research results verified the feasibility of the smart contract model, and the flow of power market transactions on the distribution side under the blockchain technology was realized through simulation.

Abstract:In order to improve the accuracy of wind power prediction, a new short-term wind power prediction method based on the variational mode decomposition (VMD) and the improved least squares support vector machine (LSSVM) is proposed. Firstly, VMD is used to decompose the historical power data into the trend component, detail component and random component to reduce the complexity and instability of original data. Then the IBA-LSSVM prediction model is established, the parameters of the least squares vector machine are optimized by the improved bat algorithm (IBA), and each sub mode is predicted separately. The final predicted wind power is obtained by superimposing the prediction results of sub modes. Finally, the power of a wind power plant in Ningxia is predicted by the proposed prediction method. The effectiveness of the model is proved by the error analysis of the prediction results. The comparison of different prediction methods verifies that the proposed model has higher prediction accuracy.