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A series of batch experiments were carried out to determine the degradation velocity of herbicide atrazine in different soil samples, and the correlation between the soil properties and degradation parameter was statistically analyzed. The result shows that the degradation process is very slow with a half-life varying from 239d to 330d, and that atrazine is little absorbed by soil samples. Therefore, the use of atrazine is of serious threats to shallow groundwater and surface water resources. From a comparison of degradation of atrazine in sterile and non-sterile soil samples, it is found that the function of biodegradation is almost the same as that of the chemical degradation, and that the degradation velocity of atrazine is normally distributed in experimental areas. Furthermore, the degradation of atrazine is found to be not significantly related to the properties and sorption parameter of soil samples at the level ¦Á=0.05.
Journal of Hohai University (Natural Sciences),2005,33(4):357¡«360
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A comparison was made on several spatial rainfall interpolation methods commonly used, including the Thiessen polygon method, the reverse distance weighting method and the ordinary Kriging method. In consideration of great influences of the elevation information, it was taken as an influencing factor of the second class, and introduced into the Co-Kriging method for spatial rainfall interpolation, and a new Co-Kriging method was put forward. The application of the three methods, the reverse distance weighting method, the ordinary Kriging method and the new Co-Kriging method, to rainfall interpolation calculation for the Yanduhe River Basin shows that the effect of the last one is obviously superior to the other two methods.
Journal of Hohai University (Natural Sciences),2005,33(4):361¡«365
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The intention of the paper is to formulate a simple estimation model of groundwater discharge from a nearshore unconfined aquifer to a lake by using a hydraulic method. It was supposed that the aquifer was of isotropic permeability with a constant thickness and obliquity and extended unlimitedly toward the lake with a gentle slope. The distributions of hydraulic gradient and specific discharge along the transect of the discharge zone were discussed. The result shows that the aquifer seepage varies with the inclination of the nearshore bottom of the lake. For a large shallow lake with a gentle slope bottom, the aquifer seepage mainly concentrates in the littoral zone where the Dupuit assumptions are invalid, and flows into the lake through the upper section of interface between the lake bottom and aquifer. Moreover, the width of the discharge zone, the thickness of the aquifer and the gradient of the lake bottom are closely related to each other.
Journal of Hohai University (Natural Sciences),2005,33(4):366¡«369
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A 2-D dynamic flood evolution model was established based on GIS raster data, and a case study was performed for Jingjiang flood diversion area of Hubei Province. With the help of the digital topographical map and Landsat ETM remote sensing image, the flood inundated area, water depth, flood inundated ground surface, and economic loss which might occur were calculated under different flood diversion schemes according to the flood diversion situation and its hydrological planning in 1954. The simulated results show that the flood inundation risk simulation model provides a scientific basis for formulation of diversion schemes, planning for land utilization, and scientific management of flood.
Journal of Hohai University (Natural Sciences),2005,33(4):370¡«374
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An unsteady water quality and water quantity model and the synchronous monitoring data of 9 pollution sources along the west channel were employed to determine the water quality degradation parameters of the river channel. By use of the 2-D model for analysis of water quality achievable for the control section, the relationship between the water quality of water source places and pollution sources was set up with the rising and ebb tides taken into account. Based on an investigation of main wastewater discharge outlets affecting the major water source places, the Xicun and Shimen water plants, along the west channel of Guangzhou City, an analysis of water quality achievable was performed for the two water plants. The result shows that, for the formulation of an optimal scheme for regulation of discharge outlets, in addition to the environmental factor, the social and economic factors should be taken into account. Moreover, the relationship between the water quality and pollutant discharge of the water source places under different schemes can also be used to determine the allowable quantity of pollutants discharged from outlets to ensure the water quality of the water source places.
Journal of Hohai University (Natural Sciences),2005,33(4):375¡«377
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By combination of the transformation theory with nonparametric statistical theory, the nonparametric transformed kernel estimate model was developed. Without requirement for selection of window width, the present model improves the precision in small sample estimation. The comparison of the estimated result by the developed model with that by the Monte-Carlo method shows that the nonparametric transformed kernel estimate model is robust.
Journal of Hohai University (Natural Sciences),2005,33(4):378¡«381
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An introduction was given to the operating condition of the pond-bed system and the technical process of its application to wastewater treatment in Jiangsu Shuangdeng Paper Company, and the mechanism of pollutant purification and eco-environmental benefits of the system were also analyzed. The results show that the man-made wetland pond-bed system has high removal rate of some characteristic pollutants, such as CODCr, BOD5, and SS, and also decreases the level of soil salinization by effluent water irrigation of reed. The reed growing in wetland can be taken as paper-making materials, which will produce a certain benefit. Meanwhile, the unique eco-environment formed by man-made wetland system improves the local landscape, and protects the wild habitat environment.
Journal of Hohai University (Natural Sciences),2005,33(4):382¡«385
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In regard to some problems of AVSW-AT2000 model in the treatment of flat areas and depressions based on DEM, such as unable to form an integral drainage network with unreasonable river branches occurring, etc., a comparative analysis was made of DEM algorithms for pretreatment of flat areas and depressions in the process of automatic extraction of drainage networks. The DEM preprocessing algorithm, presented by Ao Tianqi, et al. was applied to practical simulation. The result shows that the algorithm overcomes the disadvantages of AVSW-AT2000 model. The drainage network and outlet information derived by the algorithm are in good agreement with digital stream networks.
Journal of Hohai University (Natural Sciences),2005,33(4):386¡«390
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In consideration of the fact that the conventional prediction model for dam safety monitoring is easily affected by the correlation of environmental factors, and the fact that it needs a long time of network training and easily converges to local optimum points, a rough set prediction model is developed by extraction of main affecting factors and decision rules from pretreatment of rough sets of original monitoring data and reasoning of decision rules under uncertainty. Compared with the conventional method, the present model is independent on a special mathematical model, and the predicted results are intervals under certain reliability, which are in accordance with measured data.
Journal of Hohai University (Natural Sciences),2005,33(4):391¡«394
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A kind of learning algorithm of adaptive fuzzy system (AFS) based on the simulated annealing algorithm (SAA) was presented to improve the stability and reliability of dam safety automatic monitoring. According to the algorithm, a non-linear monitor model and a fault auto-diagnosis system for dam safety monitoring were developed. A case study shows that the present system, just as SAA, brings the nonlinear fitting of AFS into full play, and has the capacity of global optimal search, realizing the on-line diagnosis and real-time separation of faults effectively.
Journal of Hohai University (Natural Sciences),2005,33(4):395¡«398
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Based on the basic principle of inter-basin compensation benefit calculation, the compensation benefit simulation model for cascade reservoirs on the mainstream of the Yellow River was adopted to calculate the power generation compensation benefit for the cascade reservoirs on the Long-Qing section of the upper Yellow River after a volume of water diversion 40¡Á10ª¬8?mª¬3 in the first stage of the South-to-North Water Transfer West Route Project. The result shows that, under the present installed capacity, the power generation of 25 cascade power plants on the Long-Qing section can increase by 88ª±52¡Á10ª¬8 kW¡¤h for such a volume of water diversion, and that the annual power generation compensation benefit resulted from saving of fuel and decrease of operational cost can reach 8ª±55¡Á10ª¬8?Yuan.
Journal of Hohai University (Natural Sciences),2005,33(4):399¡«403
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The pressures acting on the gate were divided into two parts: the fluctuating pressure of flow on the stationary gate and the hydrodynamic pressure due to gate vibration-induced additional disturbed flow. The temporal-spatial correlation of fluctuating pressures obtained by model experiments between different nodes was analyzed by the coherence function defined in frequency domain with consideration of different levels of correlation for different frequency components, and the nodal load of the fluctuating pressure could be obtained. Then, the computation method for flow-induced vibration response of gates with model experiment and numerical calculation combined together was developed based on the random vibration theory. As an example, the response of radial gate of Shuangkoudu hydropower station was analyzed. The result shows that the present method meets the requirement of engineering, and can be applied to flow-induced vibration analysis of other hydraulic structures.
Journal of Hohai University (Natural Sciences),2005,33(4):404¡«408
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According to the process of construction and mechanism of compaction of RCCDs, it was considered that the elastic modulus was exponentially attenuated along the depth of layers. By decomposition of single roller compacted layer into multi layers, the relationships between the intra-layer elastic modulus and the elastic moduli of dam body and layer interface were derived by use of the stiffness partition method. With the stiffness partition method and FEM, the elastic modulus distribution in layers of different thickness and strength was studied. It is concluded that the coefficient of exponential attenuation of elastic modulus inversely varies with the thickness of layers and the ratio of the elastic modulus of layer interface and that of the dam body.
Journal of Hohai University (Natural Sciences),2005,33(4):409¡«412
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A case study was performed on the Kezier Dam site. Based on the principles of maximum contribution and structure consistency, an effective peak acceleration (EPA)-based scenario earthquake method was put forward by combination of the virtues of the probability and determinacy seismic hazard analysis methods. The scenario earthquake parameters of the Kezier Dam site, including the magnitude, epicentral distance and response spectrum, for a transcendental probability of 2£¥ for 100 years were given. The response spectrum of scenario earthquake obtained was compared with the response spectrum prescribed by seismic design codes and the probability-consistent response spectrum, and the rationality of the scenario earthquake method was verified.
Journal of Hohai University (Natural Sciences),2005,33(4):413¡«417
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With the axial displacement of anchor rods taken as a degree of freedom, a combined element model for anchored rock mass with consideration of interface properties was developed for numerical simulation of the rock mass, and the corresponding formulas were deduced for combined elements. Case study shows that, with the model used for anchored rock mass analysis, the anchor rod may go through anywhere of the block element. As a result, the present model makes it easy to truely reflect the complicated geometric layout and operational characteristics of anchor rods.
Journal of Hohai University (Natural Sciences),2005,33(4):418¡«421
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Under the assumption that concrete is a three-phase composite, which is composed of mortar matrix, aggregate and their interface, and that the mesomechanical property of concrete satisfies the Weibull distribution, the damage model of mesomechanics is used to investigate the macromechanical property of concrete. Numerical simulation is made of the failure process of concrete specimens under uniaxial tension and compression by compilation of an FEM program. The result shows that the model can be used to study the mechanism of concrete failure and size effect of concrete structures under uniaxial loads.
Journal of Hohai University (Natural Sciences),2005,33(4):422¡«425
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Based on the concept of basic internal force and generalized constraint matrix, a new method was proposed for calculation of the internal force of truss structures. By use of topological variation and responses of trusses, all the information needed for structure analysis was obtained at the same time of generation of the truss structure, and the structure calculation can be performed conveniently in different cases. Without requirement for establishment of simultaneous equations for solution, the method is simple in operation, and convenient in programming.
Journal of Hohai University (Natural Sciences),2005,33(4):426¡«429
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Based on Coulomb¡¯s earth pressure theory, the first-order differential equation for passive earth pressure on the retaining wall was set up for movement modes of rotation around base (RB) and rotation around top (RT) by analysis of slice elements extracted from sliding soil wedge, and the formulas for calculation of the unit earth pressure, the resultant earth pressure and the action point of resultant pressures were given. The comparison of the calculated results by the present formulas, the formulas for the translation (T) mode, and Coulomb¡¯s theory shows that the unit earth pressure is nonlinearly distributed, and that the distance from the action point of resultant pressures to the base of wall increases with the order of RB mode, T mode, and RT mode. It is also indicated that the calculated results of the resultant pressure under various modes of movement are in accordance with those from Coulomb¡¯s earth pressure theory for q0=0, and that the result from Coulomb¡¯s earth pressure theory is smaller than the calculated result of RT mode and greater than that of RB mode for q0>0.
Journal of Hohai University (Natural Sciences),2005,33(4):430¡«433
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Wave impedance inversion is essential in predicting reservoir properties and sand-body distribution, and plays an important role in seismic survey. In consideration of the fact that the fast simulated annealing (FSA) algorithm for wave impedance inversion may prevent the objective function from getting into local extreme ranges, and obtain the global optimum solution, the algorithm was adopted in this study, and the effectiveness of the algorithm was verified by trial calculation of theoretical model and inversion of measured data. The result indicates that the FSA result does not depend on the initial value, that the convergent speed of FSA is higher than that of the conventional simulated annealing (SA) algorithm, and that the FSA result of wave impedance inversion is coincident with well-logging data in boreholes.
Journal of Hohai University (Natural Sciences),2005,33(4):434¡«437
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In accordance with the characteristics of hydraulic mass concrete structures, the method for crack detection was discussed. A model for the relationship between the crack depth of concrete and its correlative parameters was developed based on BP neural network, and the measured data were used to train and test the network model. Case study shows that the application of BP neural network to crack detection is feasible and effective.
Journal of Hohai University (Natural Sciences),2005,33(4):438¡«441
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Based on field investigation and theoretical analysis of geological characteristics of the Hongfeng multiple arch tunnel of the Jinliwen Highway, the current situation and variation characteristics of the stress field, deformation field and plastic failure zone of surrounding rock during the excavation and strengthening of the tunnel were analyzed. The results show that the strain rate and the displacement of surrounding rock are low during excavation, and that the deformation of surrounding rock with the liner currently used meets the requirement of stability. It is also indicated that the tensile stress in surrounding rock increases with the extension of the excavated area, and the tensile strength of the liner is satisfactory except at some positions.
Journal of Hohai University (Natural Sciences),2005,33(4):442¡«446
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The elastic-plastic loading and deformation process of the statically-indeterminate beam fixed at two ends under uniformly-distributed loads was analyzed by use of the unit-load method, and formulas for bending moment and displacement at different loading stages were derived. The result of analysis shows that the deformation process can be divided into four stages, including the stage of elastic deformation of the whole beam, the stage of plastic deformation occurring in the region close to two fixed ends, the stage of unloading in plastic regions with two plastic hinges at the fixed ends, and the stage of plastic deformation till the occurrence of plastic yield at the middle of the beam with two plastic hinges at the fixed ends.
Journal of Hohai University (Natural Sciences),2005,33(4):447¡«451
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It is found from an analysis of a group of typical experimental data about steel fiber reinforced concrete that the formula for calculation of KIC of steel fiber reinforced concrete, presented by ASTM, is ineffective to reflect the fracture characteristic of the reinforced concrete. Therefore, the necessity for consideration of the precritical crack propagation length was theoretically discussed, and a new formula for calculation of KIC of steel fiber reinforced concrete was derived by use of the double-K fracture criterion.
Journal of Hohai University (Natural Sciences),2005,33(4):452¡«454
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An analysis was made on the variation of groundwater level under vacuum preloading and the influence of boundaries on the effect of consolidation for further understanding the mechanism of consolidation by means of vacuum preloading, and a formula for calculation of the degree of consolidation of sand-wall foundation was derived with the factors of sand-drain resistance, smearing, bi-directional seepage, and deformation taken into account. During the finite element calculation, the double-yield surface model, presented by Yin Zongze, was combined with the modified Komamura-Huang model, and the methods for dealing with the boundary condition and initial condition were improved. Practice shows that, with consideration of dilatancy, contraction, and viscoplasticity of soil, the present method can well simulate the transfer of the vacuum degree in sand-drain and foundation soil.
Journal of Hohai University (Natural Sciences),2005,33(4):455¡«458
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The BQ value and RMR weight of rockmass of the Lanyoushan slope were obtained by uniaxial compression test, triaxial compression test, in-situ acoustic wave testing of rockmass, and in-situ PANDA testing of soft strata. Then, the mechanical parameters of rockmass were estimated by using the Hoek-Brown strength criterion. The results provide a basis for engineering design and construction of the Lanyoushan slope.
Journal of Hohai University (Natural Sciences),2005,33(4):459¡«462
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The Differential Interferometric Synthetic Aperture Radar (D-InSAR) extracts the 3-D earth surface information and its variation from the phase information of SAR, and can detect the little variation of earth and ice surface. The accuracy of displacement monitoring with the technique can reach up to cm-level or even better. In this paper, an introduction was given to the basic principle of D-InSAR, the general situation of its development, and its application to earth surface deformation monitoring. Finally, the further development and application of D-InSAR were discussed.
Journal of Hohai University (Natural Sciences),2005,33(4):463¡«465
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With the test data collected by the three-dimensional laser image scanner and total station, the three-dimensional laser scanning image combination model was figured out by the indirect adjustment model with constraint condition. Meanwhile, the rationality of the combination model was discussed with the scale factor taken into account. The result shows that the method for solution of the combination model is reasonable and valid, and that the laser scanning granularity of 18mm is of great influences on the precision of the combination model.
Journal of Hohai University (Natural Sciences),2005,33(4):466¡«471
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By use of the 2-D numerical model averaged in vertical direction, the numerical simulation was performed of the tidal current and pollutant diffusion in a typical sea area of radial sandy ridges with wide tidal range in the Yellow Sea to reveal the hydraulic condition and pollutant diffusion in this area, and further to find the perfect positions for pollutant discharge. In the study, the changed grid technology and the improved ¡°dry-wet¡± method were also used to deal with the moving boundary. By calculation of the residual current field of the studied area and the track of Lagrange water particles at several typical positions, the effects of residual current field on pollutant diffusion were analyzed, and the perfect positions for pollutant discharge were obtained as well.
Journal of Hohai University (Natural Sciences),2005,33(4):472¡«475
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Model tests were carried out on the stability of a new type concrete block revetment under regular and irregular waves in a wave flume. Based on an analysis of the mechanism of wave action on the revetment, formulae for block thickness under the actions of regular and irregular waves were obtained through a series of stability tests. The results show that the block thickness is in direct proportional to wave height and also related to the break parameter and block density in water. Compared with several thickness formulae for concrete blocks and slabs conventionally used, the present formulae give a reasonable result.
Journal of Hohai University (Natural Sciences),2005,33(4):476¡«481
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A nonlinear combined model for prediction of port throughput was presented based on the regression algorithm of support vector machines. The comparison of the predicted result of port throughput by the present method with those of other methods shows that the method developed in this paper is of strong capability in learning and mapping, and has high applicability in modeling for combined prediction of nonlinear systems with some uncertainties.
Journal of Hohai University (Natural Sciences),2005,33(4):482¡«484
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