Characterization and evaluation of the factors affecting the geochemistry of groundwater in Neyveli,Tamil Nadu,India   总被引：1，自引：0，他引：1  

M. Jayaprakash  L. Giridharan  T. Venugopal  S. P. Krishna Kumar  P. Periakali 《Environmental Geology》2008,54(4):855-867

In order to achieve a better understanding of the nature of the factors influencing ground water composition as well as to specify them quantitatively, multivariate statistical analysis (factor analysis) were performed on the hydrochemical data of this area. R-mode factor analysis was carried out on the geochemical results of the 79-groundwater samples and the factor scores were transferred to areal maps. Fundamental chemical parameters of the groundwater have been compounded together for characterizing and interpreting a few empirical hydrogeochemical factors controlling the chemical nature of water. R-mode factor analysis reveals that the groundwater chemistry of the study area reflects the influence of anthropogenic activities, silicate weathering reactions, precipitation, dissolution and subsequent percolation into the groundwater. The data have been put into few major factors and the seasonal variation in the chemistry of water has been clearly brought out by these factors. Factor scores were transferred to contour diagrams and the factor score analysis has been used successfully to delineate the stations under study with various factors and the seasonal effect on the sample stations.  相似文献   

The 26 July 2005 heavy rainfall event over Mumbai: numerical modeling aspects     

Sandeep Sahany  V. Venugopal  Ravi S. Nanjundiah 《Meteorology and Atmospheric Physics》2010,109(3-4):115-128

The performance of the Advanced Regional Prediction System (ARPS) in simulating an extreme rainfall event is evaluated, and subsequently the physical mechanisms leading to its initiation and sustenance are explored. As a case study, the heavy precipitation event that led to 65 cm of rainfall accumulation in a span of around 6 h (1430 LT–2030 LT) over Santacruz (Mumbai, India), on 26 July, 2005, is selected. Three sets of numerical experiments have been conducted. The first set of experiments (EXP1) consisted of a four-member ensemble, and was carried out in an idealized mode with a model grid spacing of 1 km. In spite of the idealized framework, signatures of heavy rainfall were seen in two of the ensemble members. The second set (EXP2) consisted of a five-member ensemble, with a four-level one-way nested integration and grid spacing of 54, 18, 6 and 1 km. The model was able to simulate a realistic spatial structure with the 54, 18, and 6 km grids; however, with the 1 km grid, the simulations were dominated by the prescribed boundary conditions. The third and final set of experiments (EXP3) consisted of a five-member ensemble, with a four-level one-way nesting and grid spacing of 54, 18, 6, and 2 km. The Scaled Lagged Average Forecasting (SLAF) methodology was employed to construct the ensemble members. The model simulations in this case were closer to observations, as compared to EXP2. Specifically, among all experiments, the timing of maximum rainfall, the abrupt increase in rainfall intensities, which was a major feature of this event, and the rainfall intensities simulated in EXP3 (at 6 km resolution) were closest to observations. Analysis of the physical mechanisms causing the initiation and sustenance of the event reveals some interesting aspects. Deep convection was found to be initiated by mid-tropospheric convergence that extended to lower levels during the later stage. In addition, there was a high negative vertical gradient of equivalent potential temperature suggesting strong atmospheric instability prior to and during the occurrence of the event. Finally, the presence of a conducive vertical wind shear in the lower and mid-troposphere is thought to be one of the major factors influencing the longevity of the event.  相似文献   

Particle diffusion and adiabatic expansion of plasmoids     

M. S. Sindhu  G. Renuka  C. Venugopal 《Journal of Earth System Science》1995,104(1):37-47

In this paper neutral point (coalescence) instability (NPI) of plasmoids (PMD) associated with tailward streaming O⁺, H⁺ and e⁻ particles and diffusion region (spatial extent and particle life time) are studied. Also, radial and pitch angle diffusion studies have been carried out in the near-earth region (10 and 11 R_E during substorm onset. Our study revealed that coalescence instability is favoured by a heavier ion like O⁺ and the time required for a heavier ion to reach from one X point to an adjacent X point is minimum. Near an X type neutral line (diffusion region) ions spend a fairly long time and gain a significant amount of energy. Radial and pitch angle diffusion studies showed that higher energy particles are largely confined near the reconnection region (near-earth region) and lower energy particles are rapidly depleted from the near-earth region during substorm onset.  相似文献   

Land use/cover classification using enhanced IRS-1A LISS 1 data — A case study of Calcutta Metropolitan District,India — 1989     

G. Venugopal  Kevin M. Turcotte 《GeoJournal》1993,29(2):139-141

The land use/cover in any urban area is dynamic in nature. Maps of existing land use/covers have to be updated periodically to monitor changes. To speed up mapping and decision making, remotely sensed satellite data have been advocated. This study used the IRS-1A LISS 1 satellite data for delineation of selected urban features in Calcutta Metropolitan District. Due to lack of ground information, some known features have been used as reference categories to classify the study area.The satellite data was transformed through a principal components analysis and two new bands of data were created and combined with the original four band data. Both supervised and unsupervised methods were used for spectral signature collection. Thirty-six classes derived from Isodata clustering, after comparing with the selected known features, these were grouped to form five generalized land use/cover categories. The spatial distribution of these land use/cover categories have been explained in this study.  相似文献   

On the stability of almost perpendicularly propagating ion cyclotron waves     

Chandu Venugopal 《Planetary and Space Science》1984,32(2):219-226

The dispersion relation for the near perpendicular propagation of the electromagnetic ion cyclotron wave, having a wavelength much larger than the ion Larmour radius r_L and a frequency $\text{ω ≈ Ω}{}^{\mathrm{+}}\text{(Ω}{}^{\mathrm{+}}$ is the ion cyclotron frequency), has been derived for a plasma consisting of a hot and a cold ion component. The hot ions and electrons have been described by loss-cone distribution functions; an ordering of the parameters was used to derive the cold ion contributions. Two modes, one with an increasing frequency and another with a constant frequency can propagate in the plasma. The two modes interact resulting in an instability of the former in the wavelength range k_⊥r_⊥ = 0.4?0.6 (for n_C/n_H = 0) and from k_⊥r_L = 0.5?0.8 (for n_C/n_H = 1.0) for a propagation angle of 70°. The instability of the mode is found to decrease with increasing cold ion densities and propagation angles.  相似文献   

A search for the variability of radio source 3C 120 at 327 MHz     

V. A. Sanamyan  V. R. Venugopal 《Astrophysics》1975,11(1):102-103

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On-line learning control of autonomous underwater vehicles usingfeedforward neural networks     

Venugopal  K.P. Sudhakar  R. Pandya  A.S. 《Oceanic Engineering, IEEE Journal of》1992,17(4):308-319

A neural-network-based learning control scheme for the motion control of autonomous underwater vehicles (AUV) is described. The scheme has a number of advantages over the classical control schemes and conventional adaptive control techniques. The dynamics of the controlled vehicle need not be fully known. The controller with the aid of a gain layer learns the dynamics and adapts fast to give the correct control action. The dynamic response and tracking performance could be accurately controlled by adjusting the network learning rate. A modified direct control scheme using multilayered neural network architecture is used in the studies with backpropagation as the learning algorithm. Results of simulation studies using nonlinear AUV dynamics are described in detail. The robustness of the control system to sudden and slow varying disturbances in the dynamics is studied and the results are presented  相似文献   

Observations of radio flares in the region of the Pleiades at 327 MHz     

V. A. Sanamyan  V. R. Venugopal  O. S. Chavushyan 《Astrophysics》1978,14(2):163-168

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Simulating the daily discharge of the Mandovi River,west coast of India     

K. Suprit  D. Shankar  V. Venugopal  N.V. Bhatkar 《水文科学杂志》2013,58(4):686-704

Abstract

A hydrological modelling framework was assembled to simulate the daily discharge of the Mandovi River on the Indian west coast. Approximately 90% of the west-coast rainfall, and therefore discharge, occurs during the summer monsoon (June–September), with a peak during July–August. The modelling framework consisted of a digital elevation model (DEM) called GLOBE, a hydrological routing algorithm, the Terrestrial Hydrological Model with Biogeochemistry (THMB), an algorithm to map the rainfall recorded by sparse raingauges to the model grid, and a modified Soil Conservation Service Curve Number (SCS-CN) method. A series of discharge simulations (with and without the SCS method) was carried out. The best simulation was obtained after incorporating spatio-temporal variability in the SCS parameters, which was achieved by an objective division of the season into five regimes: the lean season, monsoon onset, peak monsoon, end-monsoon, and post-monsoon. A novel attempt was made to incorporate objectively the different regimes encountered before, during and after the Indian monsoon, into a hydrological modelling framework. The strength of our method lies in the low demand it makes on hydrological data. Apart from information on the average soil type in a region, the entire parameterization is built on the basis of the rainfall that is used to force the model. That the model does not need to be calibrated separately for each river is important, because most of the Indian west-coast basins are ungauged. Hence, even though the model has been validated only for the Mandovi basin, its potential region of application is considerable. In the context of the Prediction in Ungauged Basins (PUB) framework, the potential of the proposed approach is significant, because the discharge of these (ungauged) rivers into the eastern Arabian Sea is not small, making them an important element of the local climate system.

Editor D. Koutsoyiannis; Associate editor S. Grimaldi

Citation Suprit, K., Shankar, D., Venugopal, V. and Bhatkar, N.V., 2012. Simulating the daily discharge of the Mandovi River, west coast of India. Hydrological Sciences Journal, 57 (4), 686–704.  相似文献   

Monitoring the Effects of Biological Control of Water Hyacinths Using Remotely Sensed Data: A Case Study of Bangalore, India   总被引：2，自引：0，他引：2  

G. Venugopal 《Singapore journal of tropical geography》1998,19(1):91-105

Native to South America, water hyacinths were brought to India as ornamental plants and are now considered as one of the most dreaded aquatic weeds in the country. This plant has infested more than 200,000 ha of fresh water bodies in the country. The Indian Institute of Horticultural Research resorted to biological methods to control these weeds and received favorable results, however, these weeds tend to reinfest the fresh water bodies. For an effective weed control, the infestation needs to be monitored and remotely sensed data have been recommended for this purpose. In this research, SPOT multitemporal data have been used to monitor the infestation of water hyacinths in Bangalore, India. Using Normalised Difference Vegetation Index (NDVI), this study delineated areas of clearing and new infestation in the fresh water tanks in the study area. This study concluded that host specific weevils can eradicate water hyacinths in large areas but that reinfestation remains an ongoing problem.  相似文献