Paleomires of Eocene lignites of Bhavnagar,Saurashtra basin (Gujarat), western India: Petrographic implications     

Prakash K. Singh  Vijay K. Singh  M. P. Singh  P. K. Rajak 《Journal of the Geological Society of India》2017,90(1):9-19

The Tertiary basins of Gujarat have always been a potential target for their hydrocarbon resources. The lignite resources of the region have also been an important field of research. The present paper presents the results of the petrological study carried out on the lignites of the Saurashtra basin. For this purpose samples were collected from lower and upper lignite seams from the Surkha lignite mine of Bhavnagar, Saurashtra. These samples were subjected to detailed petrographic analysis (both maceral and microlithotype). The study reveals that these lignites are dominantly composed of huminite group macerals while liptinite and inertinite group macerals occur in subordinate amounts. These lignites have attained a thermal maturity up to 0.28-0.30 percent vitrinite reflectance (VRr) which classifies them as ‘low rank C’ coals. Moreover, Bhavnagar lower lignite seam shows relatively less gelification as compared to the upper seam which suffered relatively more biochemical degradation. These lignites are characterized by high gelification index (GI) and low tissue preservation index (TPI).With the help of petrography based facies models an attempt has been made to reconstruct the environment of the paleomire of these lignites.  相似文献   

Performance evaluation of a reverse-gradient artificial recharge system in basalt aquifers of Maharashtra,India     

Bhusari  Vijay  Katpatal  Y. B.  Kundal  Pradeep 《Hydrogeology Journal》2017,25(3):689-706

Hydrogeology Journal - Drinking water scarcity in rural parts of central India in basaltic terrain is common. Most of the rural population depends on groundwater sources located in the fractured...  相似文献   

Spatiotemporal trends of aridity index in Shiyang River basin of northwest China     

Xiaoling Su  Vijay P. Singh  Jiping Niu  Lina Hao 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(6):1571-1582

Drought/wetness conditions are fundamental not only for agricultural production but also ecology, human health, and economic activity. Dryness/wetness is a function of precipitation, temperature, vegetation and potential evapotranspiration. Regions with low moisture are often characterized by aridity which, in turn, reflects the degree of meteorological drought. Observed climatic data from eleven meteorological stations in and around Shiyang River basin, China, were used to calculate the aridity index (AI) which was defined as the ratio of potential evapotranspiration (ET₀) to precipitation (P). ET₀ was calculated using the Penman–Monteith method. The ordinary kriging method was used to interpolate the spatial variability of ET₀, P and AI. The Mann–Kendall test with a pre-whitening method was employed using the Yue and Wang autocorrelation correction to detect temporal trends. The Theil–Sen estimator was used to estimate the slopes of trend lines. Results showed a higher AI in the north basin and a lower AI in the Qilian Mountain region. Annual ET₀ and P had increasing trends with a slope of 0.672 and 0.459 mm per year, respectively, but trends were not statistically significant for most stations. While annual AI had a slight decreasing trend with a slope of ?0.01 per year, the trend was not statistically significant for all stations. The decreasing trends in winter AI (at a rate of ?0.313/a) was more significant than that in other seasons. The study indicates that the Shiyang River basin is getting slightly wetter, especially in winter.  相似文献   

Improvement in predictability of waves over the Indian Ocean     

Raj Kumar  Suchandra A. Bhowmick  Sulagna Ray  Vihang Bhatt  Suhe Surendran  Sujit Basu  Abhijit Sarkar  Vijay K. Agarwal 《Natural Hazards》2009,49(2):275-291

Accurate prediction of ocean surface waves is a challenging task with many associated difficulties. Availability of good quality wind and wave information from satellite platforms inspired the scientific community to assimilate such data in various spectral wave models for enhancing the accuracy of prediction. Over the Indian Ocean, which is the region of interest for the present study, wave heights in extreme situation can go up to 12–14 m, thereby increasing the probability of coastal hazards. This region is further governed by the southern ocean swells that propagate thousands of kilometers. These are, in general, not well captured by the spectral wave models. Therefore, assimilation of altimeter data in open ocean wave model WAM has been attempted with the aim of enhancing the quality of prediction of significant wave height. Further, simulated wave spectra have been assimilated in a coastal wave model SWAN. This assimilation has been found to significantly improve the prediction of the height of wind waves as well as swell waves. V. Bhatt and S. Surendran are former students of Meteorology and Oceanography Group, Space Applications Centre, ISRO, Ahmedabad.  相似文献   

Modelling suspended sediment concentration using artificial neural networks for Gangotri glacier          下载免费PDF全文

Rajesh Joshi  Kireet Kumar  Vijay Pal Singh Adhikari 《水文研究》2016,30(9):1354-1366

The dynamics of suspended sediment involves inherent non‐linearity and complexity because of existence of both spatial variability of the basin characteristics and temporal climatic patterns. This complexity, therefore, leads to inaccurate prediction by the conventional sediment rating curve (SRC) and other empirical methods. Over past few decades, artificial neural networks (ANNs) have emerged as one of the advanced modelling techniques capable of addressing inherent non‐linearity in the hydrological processes. In the present study, feed‐forward back propagation (FFBP) algorithm of ANNs is used to model stage–discharge–suspended sediment relationship for ablation season (May–September) for melt runoff released from Gangotri glacier, one of the largest glaciers in Himalaya. The simulations have been carried out on primary data of suspended sediment concentration (SSC) discharge and stage for ablation season of 11‐year period (1999–2009). Combinations of different input vectors (viz. stage, discharge and SSC) for present and previous days are considered for development of the ANN models and examining the effects of input vectors. Further, based on model performance indices for training and testing phase, a suitable modelling approach with appropriate model input structure is suggested. The conventional SRC method is also used for modelling discharge–sediment relationship and performance of developed models is evaluated by statistical indices, namely; root mean square error (RMSE), mean absolute error (MAE) and coefficient of determination (R²). Statistically, the performance of ANN‐based models is found to be superior as compared to SRC method in terms of the selected performance indices in simulating the daily SSC. The study reveals suitability of ANN approach for simulation and estimation of daily SSC in glacier melt runoff and, therefore, opens new avenues of research for application of hybrid soft computing models in glacier hydrology. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Larmor radius effects on the instability of a stratified partially-ionized plasma in the presence of Hall currents and magnetic resistivity     

Vijay Mehta  P. K. Bhatia 《Astrophysics and Space Science》1988,148(2):207-219

Instability of a stratified layer of a partially-ionized plasma has been investigated in the simultaneous presence of the effects of Hall currents, magnetic resistivity, finite Larmor radius (FLR), and viscosity. The ambient magnetic field is assumed to be uniform and acting along the vertical direction. The solution is shown to be characterized by a variational principle, based on it the solution has been obtained for a plasma in which the density is stratified exponentially along the vertical. It is found that the viscosity, friction with neutrals, and FLR have all stabilizing influence on the growth rate of the unstable mode of disturbance. Magnetic resistivity and Hall currents are, however, found to have a destabilizing influence.  相似文献   

Forecasting of a nonlinear cascade for watershed runoff     

Chen Shengjia  Vijay P. Singh 《中国海洋湖沼学报》1989,7(2):169-177

Forecasting of a nonlinear cascade was developed for modeling watershed runoff, and was tested by computing the direct runoff hydrograph for two rainfall-runoff events on a small watershed in China. The forecasting model was superior to Dings variable unit hydrograph method and the method of limited differences for these two events.  相似文献   

Analytical solutions of kinematic equations for erosion on a plane II. Rainfall of finite duration     

Vijay P. Singh 《Advances in water resources》1983,6(2):88-95

This paper, part II of the series, derives analytical solutions to kinematic equations for erosion from a sloping plane subject to rainfall of finite duration. Both equilibrium and partial equilibrium cases are distinguished. Complete solutions of these cases have not appeared previously in hydrologic literature. Properties of these solutions are briefly discussed. Finally a procedure is suggested for estimating the parameters contained in these solutions.  相似文献   

Non-linear analysis of geomechanical problems using coupled finite and infinite elements     

T.G. Sitharam  I.V. Vijay Kumar 《Geotechnical and Geological Engineering》1998,16(2):129-149

In modeling of many geomechanics problems such as underground openings, soil-foundation structure interaction problems, and in wave propagation problems through semi-infinite soil medium the soil is represented as a region of either infinite or semi-infinite extent. Numerical modeling of such problems using conventional finite elements involves a truncation of the far field in which the infinite boundary is terminated at a finite distance. In these problems, appropriate boundary conditions are introduced to approximate the solution of the infinite or semi-infinite boundaries as closely as possible. However, the task of positioning the finite boundary in conventional finite element discretization and the definition of the boundary and its conditions is very delicate and depends on the modeller's skill and intuition. Moreover, such a choice is influenced by the size of the domain to be discretized. Consequently, the dimensions of the global matrices and the time required for solution of the problem will increase considerably and also selection of the arbitrary location of truncated boundary may lead to erroneous result. In order to over come these problems, mapped infinite elements have been developed by earlier researchers (Simoni and Schrefier, 1987). In the present work the applicability of infinite element technique is examined for different geomechanics problems. A computer program INFEMEP is developed based on the conventional finite element and mapped infinite element technique. It is then validated using selected problems such as strip footing and circular footing. CPU time taken to obtain solutions using finite element approach and infinite element approach was estimated and presented to show the capability of coupled modeling in improving the computational efficiency. Mesh configurations of different sizes were used to explore the enhancement of both computational economy and solution accuracy achieved by incorporation of infinite elements to solve elastic and elasto-plastic problems in semi-infinite/finite domain as applied to geotechnical engineering. © Rapid Science Ltd. 1998  相似文献   

Diverging overland flow     

Vijay P. Singh  Necati Agiralioglu 《Advances in water resources》1981,4(3):117-124

This study investigates divering overland flow utilizing kinematic wave theory, which does not appear to have been dealt with previously. Explicit analytical solutions are derived in dimensionless form for space-time invariant rainfall. Analytical solutions do not seem to be tractable for time-varying rainfall. Depending upon the duration of rainfall, equilibrium and partial equilibrium cases are distinguished explicitly. The effect of divergence parameter on the hydrograph shape is shown. The adequacy of kinematic approximation for characterization of diverging overland flow is tested against laboratory watershed results. The diverging overland flow model is found to yield results which compare well with observations and with those of a plane model.  相似文献