Abstract:On the basis of the original Xin’anjiang model, this study solved the matching problem between sub-catchment and grid channel, and enabled the model to calculate channel routing according to actual river conditions. A hybrid rainfall-runoff model(named XAJ-DCH)was further proposed by coupling the XAJ model with diffusion wave method and Muskingum-Cunge-Todini(MCT)method by accounting for the lateral inflow. The flood prediction capabilities of the traditional XAJ model and the XAJ-DCH model were compared at hourly scale for the Chengcun catchment. The performance of both models is comparable and satisfactory, and thus, the rationality of the new model is verified. By improving the channel routing method in the Xin’anjiang model, the spatiotemporal variability can be further considered. Furthermore, compared with the Xin’anjiang model, the XAJ-DCH model can not only be used to simulate the discharge at the outlet station, but also to predict the water level and discharge of the interior station in the catchment. In addition, the diffusion wave method was introduced into the XAJ-DCH model, which can improve the prediction accuracy in hydraulically mild slope area by accounting for the backwater effects.

Abstract:This study mainly analyzed the effect of hydraulic project on baseflow by the Lyne-Holick filter method, based on the runoff data that was monitored in three hydrological stations, Xiaheyan, Qingtongxia, and Shizuishan, from 1951 to 2000. Results show that baseflows of three hydrological stations were generally similar before the construction of Qingtongxia hydraulic project, all about(184-214)×10⁸m³. Moreover, baseflow data was decreased to(111-187)×10⁸m³ since construction of the project, which indicated that the decrease ratio was nearly 24%. Results by the Mann-Kendall method also shows that, the decrease of baseflow reached its maximum value at the Qingtongxia hydrological station, and the point of abrupt change was observed between 1962 and 1964, which was coincident with the construction of Qingtongxia project. The baseflow index(BFI)of Qingtongxia hydraulic station showed an obvious downtrend in wet years with about 13% and the decrease ratio of BFI was approximately 20% in ordinary years, which provide a valid evidence that the hydraulic projects have strong influence on baseflow.

Abstract:In order to make the runoff close to the natural state and make the change of ecological flow within the acceptable range, by setting appropriate upper and lower limits of ecological flow and considering the ecological overflow and water shortage rate as well as the comprehensive water shortage rate as targets, an ecological scheduling model in reservoir group operation of Zhuozhang river basin was established. This model was solved according to the large-scale system decomposition-coordination technology and DP method. The difference between results with the minimum ecological overflow, water shortage rate and the minimum ecological water shortage rate was compared and analyzed. The results verified the effectiveness of system coordination. Within the capacity of reservoir regulation and storage, the model solved the imbalance of inter-annual water shortage in time and completed the ecological water supply task jointly undertaken by the downstream in space. Taking the minimum ecological overflow and water shortage rate as the ecological target, the lower monthly average water shortage rate and higher ecological satisfaction degree can be obtained compared with the traditional minimum ecological water shortage rate. The monthly average water shortage rate of Zhangze, Houwan and Guanhe reservoirs was reduced by 0. 25%, 0. 62% and 0. 03% respectively, and the annual average ecological satisfaction degree was increased by 2. 5%.

Abstract:In this study, numerical simulations were carried out to analyze the effects on flood diversion by the Garden Lake in the case of a flood with ahundred-year return period. The results show that when the Garden Lake is in operation, that is to say, at the time that the flood gates are kept open, the Garden Lake flooding area plays a role of cutting the peak of discharge in the upstream of Huaihe River and shifting the peak of water level in the downstream of Huaihe River. In addition, the extreme values of flow velocity in the Garden Lake flooding area appear near the downstream sluice gate. Especially at the beginning of the inversed discharging flood, the flow velocity at the downstream sluice gate can reach up to 0. 7 m/s. Last but not the least, the results reveal that properly delaying the operation of Gargen Lake flood area, despite of increasing the maximum water level of mainstream of Huaihe River, can effectively slow down the inundating process of the flooding area of the Garden Lake, which is conducive to improving the ability of the Huaihe River to regulate and store floods.

Abstract:By analyzing the social and economic conditions of Hefei City, the water quality, water resources per capita, GDP per capita, disposable income per capita, and population density, which can reflect the function and scarcity of water resources as well as the affordability of water price, were chosen as the impact factors of resource water price. Cloud model was established on the basis of upper limit of resource water price that was determined by the affordability index of water price and water supply factors, and the weight of each index was determined in combination with the excess multiple method. According to the analysis, the resource water price during 2014—2017 in Hefei City was 3. 06 yuan/m³, 3. 70 yuan/m³, 4. 28 yuan/m³ and 5. 35 yuan/m³, accordingly. With the development of economy, the resource water price has a rise and the water resource is more important for the development of society and economy.

Abstract:In order to improve the availability of bacteria and cementation solution for better solidification effect, the low-pH one-phase method was used to analyze and discuss the effects of two different bacterial grouting strategies, i. e. , multiple injection of low concentration bacteria and single injection of high concentration bacteria, on the solidification efficiency of microbially induced calcite precipitation(MICP)technology. Liquid solution, sand layer filtration and sand column bio-cementation experiment were carried out, and thereafter, three aspects including the calcium carbonate production, the grouting waiting period and the bio-cementation effect were evaluated. The result shows that with the same amount of bacteria used, the calcium carbonate produced by multiple injection of low concentration bacteria(OD=0. 45, activity=3 U/mL)is 3 times more than that produced by the single injection of high concentration bacteria method(OD=3. 6, activity=24 U/mL). When the pH of the all-in-one solution decreases to 4, the low concentration bacteria are not easy to flocculate and can provide a longer grouting period. This also results in a more uniform calcium carbonate distribution. It is found that when the calcium carbonate content is about 13%±1%, the unconfined compressive strength of bio-cementation sand column is about 2. 5 times greater than that treated with single injection of high concentration bacteria.

Abstract:In this study, a new device for the internal excitation test of soft soil was designed, and an instantaneous optical measurement system for the internal excitation response of soft soil based on digital image correlation(DIC)technology was developed. The relationship between the soil amplitude and the distance from the source, vibration frequency and confining pressure was studied. The results show that the soil amplitude decreases with the increasing distance from the source, and the amplitude attenuation curve is fitted in the form of power function. The affected range and degree of internal excitation can be visually and accurately represented by the affected zone of internal excitation based on DIC technology. The affected zone increases with the increasing vibration frequency, and significantly decreases with the increase of confining pressure.

Abstract:In this study, the reliability calculation results of slope are analyzed based on the Bayesian theory to improve the accuracy. At the first step, the prior distribution and like hood function were formulated according to the stability parameters of 21 slopes in critical state. Then, the posterior distribution was constructed using the Bayesian theory. The proposed method was implemented in evaluating the stability of a loess slope at the sewage outlet of Xi’an Xianyang International Airport in Jingyang County, Shaanxi Province. Results show that the means of the posterior distributions can be well calculated with lower variance and higher accuracy using the new method. In addition, when applying fluctuations of 5%, 10% and 15% in the values of stability parameters of the prior distribution, the posterior expected loss showed an increasing tendency, but within 20% in all three situations. These results indicate that the proposed method is quite robust and is capable of providing more accurate stability analysis results for loess slopes.

Abstract:Based on the elevation data of tidal flat profiles from field survey conducted in 2007 along the Jiangsu Coast, together with the numerical simulation results, the morphological characteristics of tidal flat profiles in different sections and their response to tides, waves and sediment supplies were compared and analyzed. Results show that the profile of tidal flats dominated by tidal current tends to be convex. With the increase in sediment supply, the profile can further develop into a sloping convex combination or double convex one. An increasing sediment supply attributes to a gentler and wider tidal flat profile. Besides, the tide-dominated tidal flat profile with a constant sediment supply tends to be steeper with a larger tidal range. Finally, the profile of wave-dominated tidal flats lacking sediment supply tends to be concave or linearly sloping, and a larger wave height results in a steeper tidal flat profile.

Abstract:The present situation of observation and research on sea level variation in the Arctic Ocean were reviewed in this study, and the characteristics and mechanisms of the Arctic sea level variability based on the analysis of observation data and numerical simulation were summarized. It has been pointed out that the seasonal sea level variability is related to the seasonal variation of sea ice formation and melt, net precipitation minus evaporation and river runoff, and is dominated by halosteric effect. The inter-annual to decadal variability is closely related to the spatial distribution of freshwater caused by anomalous cyclonic and anticyclonic atmospheric circulation associated with the Arctic Oscillation. Halosteric change dominates the low-frequency sea level variability in the deep basin, and consequent ocean mass change dominates the sea level variation on the continental shelf and the average sea level change of the Arctic Ocean. The fast sea level rise in the Beaufort Gyre region recently can be explained by freshwater accumulation due to the enhancement of high and rapid sea ice decline in Beaufort Sea. The mean sea level of the Arctic Ocean will continue rising under the global warming. The influence of recent sea ice decline and the Greenland ice sheet melt on the Arctic sea level change needs further study. The shortage of data and uncertainty of observations still restrict the research on Arctic sea level variation and the high-resolution numerical simulation is expected to be an important tool for future research.

Abstract:Based on the results of full-scale flume tests, characteristics of combined wave and surge overtopping at relative freeboard were analyzed and classified. According to this classification, discharges of combined wave and surge overtopping measured from the full-scale flume test was fitted with the Weibull distribution, and distributions of individual overtopping volumes and instantaneous overtopping discharge were studied respectively. New empirical equations have been proposed to estimation the distribution of individual overtopping volumes and instantaneous overtopping discharge, which improved the estimation accuracy of them compared with the existing methods.

Abstract:In this study, a non-mechanism model for the output power of photovoltaic(PV)plant considering weather factors such as irradiance, etc. was established based on a two-layer feed-forward neural network. Firstly, a neural network-based model of output power of PV power plant was established by using weather factors as the inputs. Secondly, the combination of input features for the neural network model was selected. The impacts of different weather factors combinations to the model accuracy were compared to select the input combination of the power model. Then, the training algorithm, the number of hidden layer neurons, and the training times, were changed in the neural network to compare the estimation accuracy and simulation time, and thus the optimal network configuration and parameters of the power model were determined. Finally, the optimized power model of the PV power plant was validated based on the actual measured data. The result shows that the proposed power model has high accuracy.

Abstract:By constructing a differentiated technical-transformation model for substation, the technical upgrading scheme of secondary equipment was evaluated, and the differentiation and precision of secondary-equipment technical transformation were realized. Firstly, through analyzing history information records, relevant regulations and standards of secondary equipment, combined with the actual operation of substation, the evaluation index system of reforming scheme was constructed. Then, the evaluation rules were perfected, and the calculation model and quantification method of each index were given. Thirdly, the triangular intuitionistic fuzzy number was introduced, a new score function was defined to improve the fuzzy analytic hierarchy process(FAHP), and a non-additive multi-attribute decision-making model was established. Finally, in order to verify the validity of the improved model, an actual case of differential technical transformation was adopted, and the evaluation results are obtained with better discrimination.

Abstract:Aiming at the high complexity, poor flexibility and security problem in the traditional cross-domain access under the dynamic heterogeneous network environment, this paper proposed a multi-level security access model that introduced the risk management mechanism, where a dynamic risk threshold is set for each domain and a risk pre-audit is performed on both subject and object of the access. The model compares the number of access, the cumulative access risk values, and the maximum value within the set access period and then stipulates restriction conditions. For low-risk entities that frequently initiate access, a risk advance limit is offered, and further access is allowed in case of non-overdraft risk limit. After the access, the risk threshold of the domain will be adjusted dynamically to make it a certain dynamic adaptability.