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Liu Y.,State Key Laboratory of Hydrology Water Resources and Hydraulic Engineering | Liu Y.,CAS Nanjing Institute of Geography and Limnology
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2012

Water body can be extracted from a satellite image with normalized difference water index (NDWI). It is commonly known that the index varies if extracting water body using multi-temporal images. This study selected 33 cloud-free scenes of MODerate-resolution Imaging Spectroradiometer (MODIS) data over the Poyang Lake region located in a subtropical area of China. Both the data with and without radiometric correction were used to extract lake water surface. The NDWI thresholds varied from date to date for the cases using either corrected or uncorrected data. Comparison showed that there were large differences between the two kinds of thresholds. Approximate 90% of the difference could be explained by the temporal influences including sun-target-satellite geometry and atmospheric conditions. © 2012 IEEE. Source


Su H.,Hohai University | Su H.,State Key Laboratory of Hydrology Water Resources and Hydraulic Engineering | Wen Z.,Nanjing Institute of Technology | Wu Z.,Hohai University
Water Resources Management | Year: 2011

With systems engineering and artificial intelligent methods, an early-warning system of dam health (EWSDH) is developed. This system consists of integration control module, intelligent inference engine (IIE), support base cluster, information management and input/output modules. As a central processing unit of EWSDH, IIE is a decision support system for monitoring the operation characteristics and diagnosing unexpected behaviour of dam health. With the time-frequency domain localization properties and self-learning ability of wavelet networks based on wavelet frames, IIE builds some new monitoring models of dam health. The models are used to approximate and forecast the operation characteristics of dam. The methods of attributions reduction in rough sets theory are presented to diagnose adaptively the unexpected behaviour. The proposed system has been used to monitor dam health successfully. © 2011 Springer Science+Business Media B.V. Source


Shen Z.,State Key Laboratory of Hydrology Water Resources and Hydraulic Engineering | Ren H.,Hohai University
Advanced Materials Research | Year: 2012

According to the practical situation, the 3-D finite element model of Sandaowan underground powerhouse caverns on Taolai River is set up for analyzing the behaviors under earthquake action. Based on static stress field of the surrounding rock mass, and with the selection of appropriate seismic waves for dynamic time-history analysis method, the dynamic responses of underground powerhouse caverns are analyzed. It is shown that the time-history waveform of dynamic displacement of given points has a very similar variation regularity with that of acceleration, and the wave phases of both are almost synchronous. The dynamic displacements and principal stresses of the given points on rock walls are with the vibration of low-frequency characteristics, the acceleration response is with the vibration of high-frequency characteristics. Source


Hu S.,Nanjing Hydraulic Research Institute | Hu S.,State Key Laboratory of Hydrology Water Resources and Hydraulic Engineering | Hu L.,Nanjing Hydraulic Research Institute
Materials Research Innovations | Year: 2014

The size of concrete specimen is the main reason affecting the shear fracture toughness, so this research carried out five groups of experiments including 40 symmetrically loading specimens with different lengths and heights. Through P-CTSD (loading and crack tip sliding displacement curve), P-ε (loading and strain curve) and P-t (loading and time curve), the effects of length and height of specimens on shear fracture toughness were studied. Stability of specimen is strengthened by increasing length and weakened by increasing height. Size effect on fracture toughness is weakened by increasing of length and strengthened by the increasing of height. Fracture toughness will increase with the increasing of length and decrease with the increasing of height. © 2014 W. S. Maney & Son Ltd. Source


Huang Y.,Hohai University | Yu Z.,University of Nevada, Las Vegas | Yu Z.,State Key Laboratory of Hydrology Water Resources and Hydraulic Engineering | Zhou Z.,Hohai University
Journal of Hydrologic Engineering | Year: 2013

Groundwater inflow during tunnel excavation is a common problem in practice. How to accurately predict its occurrence during the construction is still a challenging problem for tunnel designers. A numerical method, basedon the coupled model involved in artery fractures described by a discrete fractured network model and ramification fractures and rock matrix describedby the equivalent continuum medium model, is developed to calculate the groundwater inflow of underground tunnel. The model is calibrated with the observed groundwater levels in the study domain. The results in the model calibration show that calculated and measured groundwater inflows agree well. Sensitivity analysis indicates that groundwater inflow increases with the increase of precipitation rate, hydraulic conductivity of rock matrix and fracture aperture. The effect of fracture aperture on groundwater inflow is predominant, owing to the occurring of many artery fractures around the tunnel, which leads to much groundwater flowing to the tunnel through these fractures. © 2013 American Society of Civil Engineers. Source

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