Abstract:In order to obtain information on the water regime of the Huaihe River Basin, the rainfall and runoff in the catchment upstream of the Wangjiaba sub-basin, in the main stream of the Huaihe River, were analyzed and simulated. Historical data from 1985 to 2007 in the basin were used for rainfall-runoff analysis. The distributed SWAT model was used for monthly rainfall-runoff simulation, and the SCE-UA algorithm was used for automatic calibration of parameters. The results show that 50% of annual rainfall was concentrated in the period from June to August. The mean monthly runoff and runoff coefficients of the Xixian and Huangchuan sub-basins in the southern mountainous area were higher than those of the Bantai sub-basin in the northern plain area. The determination coefficients of the simulation results of monthly runoff in the Xixian, Huangchuan, Bantai, and Wangjiaba sub-basins were 0. 77, 0. 81, 0. 69, and 0. 80, respectively. The rainfall in the upstream area of the Huaihe River areas shows a significantly seasonal centrality. The characteristics of runoff of the southern mountainous area and northern plain area are different due to terrain difference. The water conservancy facilities have significant influence on the change of rainfall-runoff processes, resulting in the simulated results of the Bantai sub-basin being inferior to those of other sub-basins. The study area is a runoff data-deficient area, and the distributed hydrological model adequately reflects the given information of the underlying surface, which can offset this deficiency.

Abstract:A comparative study was conducted on the Mode'le du ge'nie rural(GR)model, the Xin’anjiang(XAJ)model, and a water balance model with double parameters(WBM-DP)at daily and monthly time-scales in the Ganjiang River Basin and 18 sub-catchments. The results show that, in the study areas, the coefficient of determination of the GR model exceeded 0. 85 and the relative error of the total runoff volume was within ±10% during the calibration and validation periods. At the daily time-scale, the GR model had slightly higher accuracy than the XAJ model, and it had greater stability, a simpler structure, and less uncertainty with regard to parameters. At the monthly time-scale, the accuracy and complexity of the GR model were consistent with those of the WBM-DP model.

Abstract:Taking Chengzi Township in Chifeng City as an example, with the support of GIS technology, we extracted elevation and slope information using DEM maps and conducted spatial overlay analysis with the spatial pattern maps of land use in the years 2001 and 2011, in order to systematically analyze the terrain gradient features of the spatial pattern distribution and changes of land use in the study area over the last ten years, and to explore the impacts of terrain factors on the selection of land use modes and the spatial patterns of land use. The study results are as follows: (a)Terrain factors play a dominant role in the spatial pattern of land use in the vertical direction. With an increase of the elevation, the woodland changes into the main land use type, the relative area of cultivated land in various elevation ranges increases initially, and then decreases, and the proportions of urban village, industrial and mining lands, traffic and transportation lands, water areas, and water conservancy facilities lands decrease gradually. Meanwhile, the diversity of land use diminishes. The land use type that is closely associated with human society’s production activities and living is mostly distributed over 0° to 3° slopes, and urban village and industrial and mining lands are mainly distributed over slopes of below 8°, indicating that they are greatly influenced by terrain factors and have high selectivity of slopes. (b)Terrain factors have a significant impact on the conversion of different land use types in the study area. There are certain differences in the conversion of land use types in different terrain areas. Low-terrain areas are the areas where the spatial pattern of land use changes most significantly, indicating that the spatial pattern of land use is affected by the joint action of natural conditions and human activities, and terrain is the background factor in the formation of the spatial patterns of land use.

Abstract:In order to improve the effect of air reaeration in the anaerobic phase of wastewater treatment, we used a combination of the siphon theory, the seepage theory, the theory of draft tubes in hydropower stations, and the wastewater biological treatment technology to develop an anaerobic/potential energy increasing oxygen ecological purification technology based on traditional anaerobic/aerobic technology. Case studies in industrial wastewater including grease wastewater and coking wastewater show that the technology is effective in pollutant purification.

Abstract:In this study, aerobic granular sludge was cultivated in a sequencing batch reactor(SBR)with glucose and sodium acetate as the carbon sources. The shock-loading effects of varying Cu²⁺ concentrations(0, 1, 3, 5 and 10 mg/L)on the physicochemical characteristics of the aerobic granular sludge were studied. The results show that the physicochemical characteristics of the aerobic granular sludge were affected as the concentration of Cu²⁺ increased from 0 to 10 mg/L. Cu²⁺ with concentrations of 1 and 3 mg/L had a slight effect on the removal efficiencies of COD and NH⁺₄-N, while Cu²⁺ with concentrations of 5 and 10 mg/L had a significant effect on the removal efficiencies of COD and NH⁺₄-N. As the concentration of Cu²⁺ increased, filamentous bacteria in the aerobic granular sludge increased gradually, the concentration of sludge decreased continuously, and the settling property deteriorated rapidly. In addition, a decrease in the density degree, a loosening structure, and polarization of particle size of the aerobic granular sludge were found in the SBR, and the granular sludge disintegrated when the Cu²⁺concentration was 10 mg/L.

Abstract:In order to explore the effects of effective microorganisms(EM)on the improvement of water quality of crab ponds and survival rate of crabs, an experimental study on EM application was conducted in the Crab Cultural Park in the Gaochun District of Nanjing City. The results show that applying EM to Eriocheir sinensis culture can effectively decrease the concentration of pollutants in the water and increase the survival rate of crabs, but overdoses of EM should be avoided. With an EM concentration of 1. 5 mg/L in the crab pond, the concentrations of NH⁺₄-N, NO^-₂-N, COD, and TP decreased by 12. 7% to 29. 2%, and the survival rate of crabs increased by 2. 4%, compared with the control group. However, when the concentration of EM in the crab pond increased to 6. 0 mg/L, the concentrations of NH⁺₄-N, COD, and TP decreased by 1. 1%, 14. 4%, and 0. 03%, respectively, while the concentration of NO^-₂-N and the survival rate of crabs increased by 15. 6% and 1. 0%, respectively. A high EM dosage of 6. 0 mg/L resulted in poorer performance in improving the water quality and survival rate than a small EM dosage of 1. 5 mg/L, and even caused accumulation of NO^-₂-N.

Abstract:The safety and durability of the steel box girder of cable-supported bridges has become a compelling subject in steel bridge safety operation. This paper provides a review on the research status and main results of fatigue damage in steel box girders in China, presents an analysis of the difficulties and pressing issues in previous research, and puts forward prospects and suggestions for the future development.

Abstract:In order to evaluate the fatigue stress level of the structural details of a steel box girder under the wheel load, the local fatigue stress of nine structural details were studied based on the stress influence line. The greatest stress amplitude was corrected according to the principle of damage equivalence, and the structural details of the steel box girder were divided. The results show that the vehicle load has little influence on the fatigue stress of the nine structural details of the steel box girder. At the intersection of the diaphragm plate, the roof, and the longitudinal rib, the influence on the stress occurred in the interval of the diaphragm plate. At the intersection of the diaphragm plate and the longitudinal rib, and at longitudinal rib joints and roof joints, the influence on the stress occurred at half of the interval of the diaphragm plate. The corrected equivalent stress amplitude was the greatest at the joint of the diaphragm plate and the longitudinal rib, and the smallest at longitudinal rib joints. With consideration of stress and construction quality, the fatigue stress of the structural details of the steel box girder can be classified into five levels, and the corresponding levels of the nine fatigue structural details are also provided.

Abstract:In order to evaluate the fatigue life of a steel bridge deck, stress measuring points were set near the weld of the roof connected to the U-rib and the arc-shaped notch of the diaphragm plate across a quarter of a bridge’s steel box girder, and the fatigue stress was monitored for 24 hours. According to the measured data, the fatigue stress spectra were calculated with the rain-flow counting method. Based on the BS 5400 specification, the fatigue damage state of the stress measuring points was evaluated. The results show that the stress level of the measuring points near the arc-shaped notch of the diaphragm plate was relatively high. Each stress measuring point was mainly a low-rising stress cycle and the cycles of 2 to 10 Mpa stress amplitude accounted for more than 90%. However, the maximum stress amplitude exceeded the limit of fatigue damage stipulated by the BS 5400 specification. Fatigue life analysis shows that fatigue cracks in the weld of the roof connected to the U-rib easily occurred near the roof area at the welding hole, and the fatigue life of the weld of the diaphragm plate connected to the U-rib’s web was short.

Abstract:According to measured traffic flow statistics from the Nanjing Third Yangtze River Bridge, in Jiangsu Province, a vehicle load spectrum in a random state was developed based on the theory of fatigue damage equivalence, and a full-bridge dynamic response analysis was conducted using finite element numerical simulation. Through calculation of the displacements and vibration response time-history curves of internal forces in different sections of the main beam of the bridge under the influence of measured vehicle flow, the changes of internal forces and dynamic magnification factors were analyzed. The results show that, under the influence of random traffic, the absolute values of the bending moment and axial force were at their maximum at the bottom of the tower of the main beam. The mid-span bending moment and axial force changed most significantly. At one quarter of the span, the displacement vibration was most intense. The dynamic magnification factor ranged from 1. 00 to 1. 03 at the maximum stress amplitude at mid-span, one quarter of the span, and near the tower bottom. The dynamic magnification factor was more stable than in the case considering only the bending moment or the axial force, and was consistent with that of the current specifications in China.

Abstract:In order to study the fatigue performance of a steel bridge deck and a vertical stiffener connection fillet weld, a mechanical vibration fatigue testing machine was used to test nine specimens with constant amplitude fatigue loading, and the fatigue performance of the welds of the specimens was evaluated with two methods, the nominal stress and hot spot stress methods. The test results show that, under the fatigue load, the specimens’ fatigue crack initiation occurs on the weld toe, and then the cracks grow along the weld toe and finally extend in bilateral symmetrical manner along the plate transverse, which is perpendicular to the weld edge. With the nominal stress method, the test results are above the S-N curve in JSSC-G, which has a fatigue strength of 50 MPa. With the hot spot stress method, the test results are above the S-N curve in Eurocode 3 specification, which has a fatigue strength of 100 MPa. The results suggest that the fatigue strength of the fillet weld of the test specimens’ fatigue details should be set at 50 MPa for nominal stress and 100 MPa for hot spot stress.

Abstract:The effect of a sialic mineral admixture on the sulfate attack of cement-based material with limestone at low temperature was studied based on analysis of the visual appearance and strength changes of specimens, and erosion phases through erosion experiments. The results show that, with an increase of the content of the sialic mineral admixture, the integrity of the Portland cement specimens with limestone powder improved, and the strength loss ratios of the specimens decreased. When 15% and 30% of sialic mineral admixtures were added, the mineral powder had a greater effect in increasing the resistance to sulfate attack of the cement-based material with limestone than fly ash with the same content. Furthermore, the sialic mineral admixture could defer the sulfate attack of Portland cement with limestone powder at low temperature, and restrain the formation of thaumasite.

Abstract:In order to solve the problem of structural multi-damage identification, different modal strain energy damage index methods are studied and compared. First, three kinds of modal strain energy damage indices, the modal strain energy change index, the modal strain energy dissipation ratio index, and the modal strain energy based index, are described. Then, with consideration of the modal strain energy dissipation ratio index method, an improved equivalence equation is derived through improvement of the stiffness matrix, and a modal strain energy equivalence index is proposed. Finally, four kinds of modal strain energy damage indices are compared, and the impact of the measured noise is considered. Simulation results show that the modal strain energy-based index method can identify structural damage locations, and the proposed modal strain energy equivalence index can not only identify structural damage locations but can identify the damage extent with high accuracy.

Abstract:In order to explore the causes of the butterfly valve rib plate cracking of a turbine at a hydropower station, we calculated and anlayzed the strength and the vibration properties of the butterfly valve using the finite element software ANSYS. The strength analysis results show that the stress level of a 40-mm rib plate is very low. Obviously, high stress is not the reason for rib plate cracking. The results of modeling analysis show that the Karman vortices occurred at a 40-mm rib plate and a 90-mm cover plate. Referring to the results of FEM analysis, we conducted a site test for the butterfly valve at the hydropower station. The experimental results agreed with the calculated results. Hence, the cracks in the butterfly valve were caused by the Karman vortices.

Abstract:A field experiment was conducted in the Sucheng District, in Suqian of Jiangsu Province, in order to study the changes of the concentrations of nitrogen and phosphorus in surface drainage from a paddy field after a rainstorm with different irrigation and drainage modes, and to reduce agricultural non-point source pollution and improve the utilization efficiency of nitrogen fertilizer. The experimental results show that, compared with conventional irrigation and drainage modes, the controlled irrigation and drainage mode caused an 18. 7% reduction in total irrigation water, a 50. 6% reduction in total drainage water, and a 3. 6% reduction in rice yield. As the controlled irrigation and drainage mode increased the storage water depth in the paddy field, it caused drainage to decrease after the rainstorm, the drainage time to be delayed, and the total amounts of NH⁺₄-N, NO^-₃-N, TN, and TP losses in the surface drainage from the paddy field to decrease by 48. 15%, 49. 09%, 45. 54%, and 49. 10%, respectively, indicating a significant effect in water conservation and drainage reduction.

Abstract:Taking the advantage of strong convergence of the Newton method, we introduce the first-order sensitivity and second-order sensitivity to the method, and propose the Newton parameter identification method based on the second-order sensitivity. We applied the proposed method to parameter identification of electric loads. Through simulation, we compared the proposed method with the PSO algorithm. The results show that the proposed method has higher identification precision, utilizes a smaller amount of calculation, and is more robust.

Abstract:For accurate estimation of the main types of transformer faults with relatively fewer fault information samples, this paper presents an approach to transformer fault diagnosis based on the probability output of the least squares support vector machine(LSSVM)and DS evidence theory according to the ideas of intelligence complementarity and information fusion. This diagnosis method has the following features: it integrates multiple feature information of the operating state of the power transformer, outputs the probabilities of various transformer faults, and provides more available information for the maintenance and repair of the power transformer. This gives full play to the strong generalization ability of the LSSVM in the case of small samples. In case studies, the diagnosis accuracy of the proposed method reached 91. 1%, which was higher than that of the three-ratio method(with an accuracy of 75. 6%)and that of the LSSVM method(with an accuracy of 82. 2%). The proposed method effectively reduces the risk of misdiagnosis of transformer faults.