Abstract:In this study, we took the Tunxi, Dongwan, and Wangkuai watersheds as typical watersheds and studied the effect of watershed subdivision on the Xin’anjiang model’s parameters, including S_M, C_S, C_I, and C_G. We used the simplex algorithm with suitable objective functions to calibrate the parameters of the model. The results of the study show that, with the increase of the number of watershed subdivisions, the homogenization degree of rainfall data decreases, S_M has an increasing trend, C_S has a decreasing trend, and C_I and C_G remain invariant. The number of qualified flood volume and flood peaks and the deterministic coefficient show an increasing trend with the increase of the number of watershed subdivisions. When the area of the sub-watershed is less than 1 000 km², the simulation accuracy improves significantly.

Abstract:This study focused on the spatio-temporal variation of precipitation in the cascade hydropower development zone in the lower reaches of the Jinsha River. The changing trends, periodic oscillation, and duration characteristics of multi-annual and seasonal precipitation were analyzed using linear trend analysis, Morlet wavelet analysis, and R/S analysis methods, based on monthly precipitation data of ten meteorological stations in the study area during the period from 1956 to 2011. The results show that the annual precipitation in the study area during the period from 1956 to 2011 has shown a fluctuant downward trend at a tendency rate of -1. 338 mm per year. The precipitation increased slightly in spring and decreased in summer, autumn, and winter, with significant spatial differences. The precipitation in summer and autumn accounted for 81. 1% of the annual precipitation, especially the precipitation in summer, which was the leading factor accounting for 57. 4% of the annual precipitation. The periodic oscillation of annual precipitation was concentrated in one to two years, expectant four years, eight years, 14 years, and 31 years, and especially in expectant eight years, which was verified by a 90% confidence level test. There was an obvious Hurst effect of the precipitation series in the study area, with a feature of persistence in general, and the precipitation will maintain a decreasing trend in the future.

Abstract:Differences in water quality standards in China and problems in implementation of these standards are systematically analyzed in this paper. The results show that various kinds of national water quality standards and industrial standards lack a connection and are not scientific. This leads to deviations and contradictions between standard limits. The current water resources quality standards established by the Ministry of Water Resources of China are not applicable to the protection of drinking water safety and evaluation of the present situation of water resources quality and pollutant discharge, and cannot meet the requirements of water resources protection at present in different water function zones of various water areas. Therefore, when revising the existing water resources quality standards, the administration departments should determine water environmental protection goals and strengthen coordination to build complete, scientific, and practical water quality standards.

Abstract:Based on the NAM model, which is a lumped hydrological model, the discharge at the Wudaogou Hydrological Station was simulated. Nine flood events with the largest peak flows from the period of 1985 to 2010 were chosen to calibrate the model parameters. Simulation results show that peak flow appeared in advance systematically, and the flood peak phase difference could not be decreased by adjusting model parameters. In order to obtain reasonable results, two improved models are proposed: one is a lumped NAM hydrological model that does not change model parameters but deals with area precipitation by shifting time weighted, and the other is a NAM hydrological model, which is based on sub-catchments and deals with simultaneously weighted area precipitation. Calculation results of the two improved models show that the flood peak phase difference decreases, and the coefficient of determination and the qualified rate increase.

Abstract:This paper focuses on several key issues of a BP neural network when it is applied to the comprehensive evaluation of water conservancy in a state of relative prosperity. Based on the analytic hierarchy process(AHP), 30 representative indicators were selected out of more than 100 water conservancy indicators, in order to build up a comprehensive evaluation system of water conservancy in a state of relative prosperity and grading standards as well. In practical application, the BP neural network has shortcomings, including the slow convergence and likely occurrence of local extreme values. To overcome these shortcomings, an LM-BP neural network model was established for comprehensive evaluation of water conservancy in a state of relative prosperity. In this case, training and testing samples were generated between standard thresholds using the random interpolation method. A concept of network fitness is proposed as well. The performance of the proposed model was evaluated using the network fitness, the average relative error, and three other statistical indicators. After the evaluation of the model achieved the expected accuracy and generalization ability, it was applied to the comprehensive evaluation of water conservancy in a state of relative prosperity in Wenshan Zhuang and Miao Autonomous Prefecture, and compared with traditional BP and RBF models. The results are as follows: (a)In both the training samples and testing samples, the LM-BP model had higher evaluation accuracy than traditional BP and RBF models by nearly an order of magnitude, indicating that the LM-BP model has high accuracy and generalization capability and is applicable to the comprehensive evaluation of water conservancy in a state of relative prosperity in Wenshan Zhuang and Miao Autonomous Prefecture. In addition, the LM-BP model has the advantages of fast convergence and a high degree of stability. (b)In the year 2010, water conservancy in a state of relative prosperity in Wenshan Zhuang and Miao Autonomous Prefecture and county-level administrative districts was at level I to II, the initial stages. It will reach level III in the year 2020 according to the prediction, which means that the water conservancy in the whole prefecture will basically achieve a state of relative prosperity.

Abstract:In this study, the flow of gas and leachate to vertical wells in landfills was investigated. Neglecting the flow of landfill gas and leachate in the vertical direction, and based on the degradation of organic matter, gas-leachate constitutive relationship, and gas-leachate continuous conditions, the flow equation under the condition of a plane axisymmetric gas-leachate coupling effect was established with gas pumping and leachate recirculation. The analytical solution in the unsteady state of the simplified equation is presented under conditions of passive and active extraction wells. The results show that the pore water pressure and gas pressure increased with the distance from the extraction well. The pore water pressure dispersed as time went on, and the gas pressure increased to its peak value initially, and then dispersed. The gas pressure that considered the gas-leachate coupling effect was relatively higher. The coupling effect on gas pressure was reduced with the increase of gaseous permeability, and become more significant with the increase of liquid permeability.

Abstract:According to the special cement type, water-to-cement ratio, mix proportion, and particle size distribution of aggregates, the CEMHYD3D hydration model was used to rebuild the representative volume element(RVE)model of a microstructure(cement)based on the micro scale, and the hard core/soft shell model was developed to build the RVE model of the mesostructure based on the meso scale. Then, numerical homogenization methods based on the Rankine criterion and the damage model, which are respectively suitable for mico and meso scales, were studied. Hierarchical analysis and prediction methods for concrete mechanical properties are proposed. The results of an example show that the proposed method can satisfactorily analyze and predict the macro mechanical properties of concrete. The developed reconstruction microstructure method can also be used to explore the aging and degradation mechanisms for concrete with simulations of physical and chemical processes at a micro scale.

Abstract:In this study, the interaction between the main crack and secondary crack was investigated using the Reduced XFEM, which is constructed with a new type of crack tip enrichment function. The effect of the secondary crack on the stress intensity factor(SIF)of the main crack was studied, and the SIF was calculated with the interaction energy integral method at crack tips. The calculation results show that the existence of the secondary crack decreases the SIF of the main crack. The SIF of the main crack decreases significantly with the increasing length of the secondary crack. The changes of the distance from the main crack to the secondary crack and the SIF of the main crack follow certain rules: the SIF of the main crack shows a scoop-shaped distribution as the distance increases, and it changes insignificantly, being close to a single crack state, as the distance reaches a certain value.

Abstract:In order to scientifically and rationally design excavations, we analyze the deformation and soil pressure distribution of an elliptical excavation support. The results show that there are four soil pressure changing points on the elliptical excavation support, similar active soil pressure and similar positive soil pressure change at these points, and there is a proportional relationship between the similar active soil pressure and similar positive soil pressure, in contrast to the classical theory. According to the distribution modes of soil pressure acting on the elliptical excavation support, we propose three methods for determining the soil pressure.

Abstract:Experiments on axial compression behaviors of 13 steel-polyurethane composite tube(SPCT)specimens were conducted to study the application of polyurethane to steel composite tubes. The results show that, under the axial compression, the SPCT was shaped like a bow drum. When local buckling occurred in the steel tube, polyurethane could effectively delay the buckling and deformation. Over the whole loading process, the bonding performance between polyurethane and steel was so good that peeling did not occur. It can be seen from the load-displacement curve and test process that the load-displacement curve is generally composed of elastic, elastic-plastic, descending, and strengthening phases, indicating that the SPCT has sound ductility and a reserve of strength to resist dynamic loads such as earthquakes. With the decrease of L/D, the limiting load of the specimen had an increasing trend, but the trend was not significant. The confining parameter ξ is an important factor influencing the specimen. When ξ increased, the specimen’s carrying capacity increased significantly, and vice versa.

Abstract:In the design of an observer-based LMI(linear matrix inequality)controller, bivariate values appear in one linear matrix inequality. To solve this problem, we propose an initial value-iteration method in this paper. Of the bivariate values, one is a positive definite matrix variable and the other is a scalar. Considering these two characteristics, we take the positive definite matrix variable as the initial value, in order to ensure the astringency of the iteration and to meet the requirements of positive definite matrices. Simulation analysis shows that the designed controller can guarantee the control trend, which was far from the expected control result. We subsequently put forward the concept of a regulatory factor. As a case study, the simulation analysis of a three-storey benchmark building shows that the proposed method is feasible.

Abstract:An improved algorithm for water body area extraction based on pixel unmixing is proposed in order to reduce the impact of water body boundary pixels on water body area extraction. A fraction image of water abundance was obtained with the linear pixel unmixing model using ALOS data. The threshold method and the mathematical morphology method were used to extract pure water and water body boundary pixels. Through analysis of the composition of water body boundary pixels, an area correction algorithm for water body boundary pixels is proposed to correct the water body area. The research results show that, compared with the linear pixel unmixing model, the proposed method can improve the accuracy of water body area extraction by 6. 7% at most, and can reduce the impact of the water content of washlands on the calculation of water abundance of water body boundary pixels.

Abstract:The conventional hyperbolic travel time is based on the hypothesis that offset is not larger than the depth of the reflector and is not suitable for velocity analysis and normal move-out of seismic data for the long cable acquisition mode with a large degree of migration and multi-folds. Based on these facts, we propose a long-array non-hyperbolic normal move-out(NMO)method and used it for the first time to process seismic data from the South China Sea. We introduced two parameters into this method, which are non-uniformity s and anisotropy η, in order to meet the requirements of seismic data processing with long cable acquisition. The results of both synthetic and field data for the non-hyperbolic NMO show that the seismic traces of a large offset and a steep dip angle are approximately aligned and the profiles have clear images and a high signal-to-noise ratio.

Abstract:The study subject of the renormalization group theory is supposed to have a scaleless property in theory. In other words, the primitive cell level tends to be infinite. However, the level cannot be set at a very high value in actual engineering projects. In order to solve this problem, comparative studies of damage probability of limited primitive cell levels were carried out using the percolation model, the fault rupture model, the rock breaking model, and the structural damage probability model of a triangular prism unit for a gravity dam based on the renormalization group theory. The results of iterative computations show that level 3 of a primitive cell or three iterations can be applicable to actual engineering projects. A safety evaluation classification method for an overall structure is proposed based on the damage probability of a primitive cell of level 3. The steps of determing the overall safety of a gravity dam using the triangular prism model are presented. According to the key points and fixed points of the damage probability, three safety states of the overall structure were classified as follows: (a)a safe state; (b)an intermediate state, between safey and overall collapse; and(c)an overall collapse state.

Abstract:Although a low-pressure irrigation system can save power energy, it is prone to clogging. In this study, the constant water pressure was changed to dynamic pressure fluctuating with a certain frequency and amplitude, in order to increase the drip emitter’s anti-clogging capability during the runtime at a low pressure. The dynamic model of operating pressure was designed by taking the base pressure, fluctuation amplitude, and fluctuation cycle as variable parameters. With orthogonal experiments, the fluctuation parameters and flow properties were tested. The effects of three fluctuation parameters on the emitter flow were analyzed. The study results show that the water base pressure has the most significant effect on the emitter flow.

Abstract:In the calculation of reference crop evapotranspiration(ET₀)in China, meteorological data are difficult to access, and there is a low spatial resolution of the data on crop water requirements. To solve these problems, a grid computing model for ET₀ was developed using the FAO Penman-Monteith equation in a case study in Heilongjiang Province. A dataset of CRU(climatic research unit)CL 2. 0 with a resolution of 10 minutes was used to construct the model. This model was validated with observed meteorological data from 14 meteorological stations in Heilongjiang Province. The results show that the performance of the model is acceptable. The ET₀ calculated with the model agreed with that calculated using observed meteorological data. Results from the present research not only help refine the research results of ET₀ and crop water requirements in China, but also provide an innovative model for calculating ET₀ in regions lacking meteorological data.

Abstract:In order to investigate the effects of different irrigation water quality and quantity levels on the quality and yield of greenhouse tomatoes, principal component analysis was conducted for comprehensive evaluation of the effects of three types of water, which were sewage, reclaimed water, and fresh water, and the irrigation amount on the quality and yield of tomatoes. The results show that the accumulative contribution rate of four selected principal components was 89. 70%. There existed significant differences in vitamin C, nitrate, and soluble protein, but insignificant differences in soluble sugar, yield, and irrigation water utilization efficiency with different irrigation water quality and quantity treatments. Under the experimental conditions introduced above, the comprehensive evaluation results of the data handled by the membership function ranking showed that reclaimed water with an irrigation amount of 360 mm was the optimal irrigation condition. Average ranking results of the two sets of data showed that reclaimed water with irrigation amounts of 320 mm and 360 mm had a better effect.