Identification of groundwater contamination sources in Dindugal district of Tamil Nadu,India using GIS and multivariate statistical analyses     

S. Selvam  S. Venkatramanan  S. Y. Chung  C. Singaraja 《Arabian Journal of Geosciences》2016,9(5):407

The purpose of this research is to evaluate the groundwater quality in Dindugal district of Tamil Nadu based on the water quality index by geographic information system (GIS) and statistical analysis. This area consists of 80 functional tanneries around Dindigul town with a capacity to process about 200 Mt of hides and skins as leather. In 13 villages, as many as 1090 houses were damaged by tannery contamination. A total of 66 groundwater samples were collected to identify the geochemical sources and contamination. The order of major cations is Na > Ca > Mg > K, while that of anions is Cl > SO₄ > HCO₃ > F > PO₄. CaCl₂, MgCl₂, and (CaHCO₃)₂ types suggested that the mixing of high-salinity water was caused by irrigation return flow, domestic wastewater, and septic tank effluents, with existing water followed by ion exchange reactions. Moreover, Gibbs plots indicated that groundwater contamination was derived from the weathering of granitic gneisses as well as the leaching of evaporated and crystallized ions from agricultural and industrial effluents. The water quality index (WQI) exhibited 8 % of the groundwater samples were not suitable for drinking purpose. The GIS maps showed that the poor water quality decreased toward the southern part of the study area. WQI of TDS, fluoride, sodium, potassium, and bicarbonate were high in groundwater. Multivariate statistical analyses (principal component analysis (PCA), factor analysis (FA)) suggested that the groundwater chemistry was changed by the weathering of source rocks ion exchange and leaching of inorganic components and addition from anthropogenic effluents. Finally, it is thought that the monitoring and assessment works are very useful to understand the degree and sources of groundwater contamination.  相似文献   

Integrated system for site-specific earthquake hazard assessment with geotechnical spatial grid information based on GIS   总被引：1，自引：0，他引：1  

Han-Saem Kim  Choong-Ki Chung 《Natural Hazards》2016,81(2):981-1001

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The role of local atmospheric forcing on the modulation of the ocean mixed layer depth in reanalyses and a coupled single column ocean model     

Byju Pookkandy  Dietmar Dommenget  Nicholas Klingaman  Scott Wales  Christine Chung  Claudia Frauen  Holger Wolff 《Climate Dynamics》2016,46(9-10):2991-3006

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The Interannual Variations of the Summer Monsoon Onset overthe South China Sea     

An Xie  Yong-Seung Chung  Xia Liu  Qian Ye 《Theoretical and Applied Climatology》1998,59(3-4):201-213

Summary Interannual variations of the summer monsoon onset over the South China Sea (SCS) have been studied using data from over seventeen years (1979–1995) of NMC global analysis and of Outgoing Longwave Radiation (OLR) observed with NOAA polar-orbitting satellites. It was found that the summer monsoon onset in the SCS occurs abruptly with a sudden change of zonal wind direction from easterly to westerly and an exploding development of deep convection in the whole SCS region in the middle of May. Based on the criteria defined in this paper for the SCS summer monsoon onset, the average onset date over the SCS from 1979 to 1995 is around the fourth pentad of May. The airflow and general circulation over the SCS changes dramatically after the onset. The ridge of the subtropical high in the western Pacific in the lower troposphere weakens and retreats eastward from the SCS region with an establishment of westerly winds over the whole region. During the SCS monsoon onset, the most direct impact in the vicinity of the SCS are the equatorial westerlies in the Bay of Bengal through their eastward extension and northward movement. An indirect influence on the SCS onset is also caused by the enhancement of the Somali cross-equatorial flow and the vanishing Arabian High over the sea; the latter may be a signal for the SCS onset. There are quite significant interannual variations in the SCS onset. In the years of a delayed onset, the most profound feature is that the easterly winds stay longer in the SCS than on average. Deep convection activities are suppressed. The direct cause is the abnormal existence of the western Pacific subtropical high over the SCS region. Moreover, compared to the average, the equatorial westerlies in the Bay of Bengal are also weaker in the years of a delayed onset. No significant changes for the cross-equatorial flow at 105 °E are observed for these years. It has also been found that the interannual variations of the SCS onset are closely related with the ENSO events. In the years of a delay, the Walker circulation is weaker, and the sea surface temperature (SST) anomalies in the western Pacific are negative. Received April 14, 1997 Revised July 11, 1997  相似文献   

Electric imaging and laboratory resistivity testing for geotechnical investigation of Pusan clay deposits   总被引：3，自引：0，他引：3  

P. H. Giao  S. G. Chung  D. Y. Kim  H. Tanaka 《Journal of Applied Geophysics》2003,52(4):157-175

Large-scale reclamation works for new land development in the Nakdong River plain have been extensively carried out on soft clays. Several geotechnical characteristics of the clays could not be well evaluated, partly due to easy disturbance during drilling and sampling. Consequently, geophysical methods, seen as nondestructive testing tools, have been applied in geotechnical investigation of Pusan clays for the first time. In this study, the 2D electric imaging technique was employed to map the thick soft clay deposits in four reclamation sites. The Pusan clay deposit was very well mapped. Electric resistivity of Pusan clays was measured on over 50 core samples in the laboratory, and then correlated with other geotechnical parameters such as salinity, organic content, water content, plasticity, unit weight and sampling depth. Additionally, electric resistivity of about 20 natural clays collected worldwide was measured and compared to that of the Pusan clays as an initial effort in creating a database of clay electric resistivity to help further application of electric imaging in geotechnical investigation of clayey soils.  相似文献   

Accurate and practical thruster modeling for underwater vehicles     

Jinhyun Kim  Wan Kyun Chung   《Ocean Engineering》2006,33(5-6):566-586

The thruster is the crucial factor of an underwater vehicle system, because it is the lowest layer in the control loop of the system. In this paper, we propose an accurate and practical thrust modeling for underwater vehicles which considers the effects of ambient flow velocity and angle. In this model, the axial flow velocity of the thruster, which is non-measurable, is represented by ambient flow velocity and propeller shaft velocity. Hence, contrary to previous models, the proposed model is practical since it uses only measurable states. Next, the whole thrust map is divided into three states according to the state of ambient flow and propeller shaft velocity, and one of the borders of the states is defined as critical advance ratio (CAR). This classification explains the physical phenomenon of conventional experimental thrust maps. In addition, the effect of the incoming angle of ambient flow is analyzed, and Critical Incoming Angle (CIA) is also defined to describe the thrust force states. The proposed model is evaluated by comparing experimental data with numerical model simulation data, and it accurately covers overall flow conditions within ±2 N force error. The comparison results show that the new model's matching performance is significantly better than conventional models'.  相似文献   

Undrained Shear Strength from Field Vane Test on Busan Clay     

S. G. Chung  G. J. Kim  M. S. Kim  C. K. Ryu 《Marine Georesources & Geotechnology》2007,25(3):167-179

An unusually thick and soft clay, which is called Busan clay, has been deposited throughout the Nakdong River estuary, South Korea. Although many reclamation works have been carried out in the area since early 1990s, large- and small-scale slope failures have taken place mostly during the soil placement on the clay. A case history briefly describes failure of a breakwater resulting from overestimation of the undrained strength, obtained from laboratory testing. An attempt has been made to examine the methods for determining the undrained strength from field vane testing. For this, the undrained strengths from field vane testing were obtained using different correction factors and compared with each other at five sites in the area. An alternative correction method applicable especially for Busan clay was found, using a range of corrected strength ratios. Further, relationships between the depositional environment and the undrained strength of the clay have also been investigated.  相似文献   

Assessment of Compressibility Behavior of Naturally Cemented Soft Clays     

S. G. Chung  K. Nagendra Prasad  T. S. Nagaraj  J. G. Chung  K. Y. Jo 《Marine Georesources & Geotechnology》2004,22(1):1-20

It Naturally cemented soft clays have components of strength and stiffness, which cannot be accounted for by classical soil mechanics (Leroueil and Vaughan 1990). This stems from the influence of structure caused by cementation due to environmental factors. It is necessary to evaluate the cementation bond strength at preyield and postyield stress levels of loading, to understand comprehensively the observed response from micromechanic considerations. This helps to better understand and evolve approaches to model the constitutive behavior in a consistent manner, according to the physical phenomenon of formation of cementation as an additional component to what is otherwise normally regarded as frictional behavior arising only from particulate nature of clays. Comparing the behavior of deep deposits of Pusan soft clays under stress with corresponding response of the same clay in its remolded state, it has been possible to take into account particulate and nonparticulate responses. The evolution of cementation bonding is modeled for different Pusan clays with the yield stress in oedometer compression as a normalizing parameter for obtaining the generalized relationship of cementation bonding with increase in stress. The already established model for determining the remolded behavior is appropriately modified to assess the behavior influenced by cementation. The model proposed consists of parameters, which are determined in routine investigations.  相似文献   

Online conservative generalized multiscale finite element method for highly heterogeneous flow models     

Wang  Yiran  Chung  Eric  Fu  Shubin  Presho  Michael 《Computational Geosciences》2021,25(5):1837-1853

Computational Geosciences - In this work, we consider an online enrichment procedure in the context of the Generalized Multiscale Finite Element Method (GMsFEM) for the two-phase flow model in...  相似文献   

On Blind Tests and Spatial Prediction Models   总被引：3，自引：0，他引：3  

Andrea G. Fabbri  Chang-Jo Chung 《Natural Resources Research》2008,17(2):107-118

This contribution discusses the usage of blind tests, BT, to cross-validate and interpret the results of predictions by statistical models applied to spatial databases. Models such as Bayesian probability, empirical likelihood ratio, fuzzy sets, or neural networks were and are being applied to identify areas likely to contain events such as undiscovered mineral resources, zones of high natural hazard, or sites with high potential environmental impact. By processing the information in a spatial database, the models establish the relationships between the distribution of known events and their contextual settings, described by both thematic and continuous data layers. The relationships are to locate situations where similar events are likely to occur. Maps of predicted relative resource potential or of relative hazard/impact levels are generated. They consist of relative values that need careful quantitative scrutiny to be interpreted for taking decisions on further action in exploration or on hazard/impact mitigation and avoidance. The only meaning of such relative values is their rank. Obviously, to assess the reliability of the predicted ranks, tests are indispensable. This is also a consequence of the impracticality of waiting for the future to reveal the goodness of our prediction. During the past decade only a few attempts have been made by some researchers to cross-validate the results of spatial predictions. Furthermore, assumptions and applications of cross-validations differ considerably in a number of recent case studies. A perspective for all such experiments is provided using two specific examples, one in mineral exploration and the other in landslide hazard, to answer the fundamental question: how good is my prediction?  相似文献