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101.
A detailed grain-size analysis of twenty-two sandstone samples from the uppermost Gondwana succession of Salbardi area has
been carried out to interpret the depositional pattern. The sandstones are mainly medium to coarse grained, moderately sorted,
near-symmetrical to fine-skewed and mesokurtic in nature. Inter-relationship of various parameters shows bimodal nature of
sediments having dominance of medium sand. Based on the granulometric analysis, a fluvial environment of deposition is interpreted
for the succession. 相似文献
102.
N. Ranganath Ashok Kumar Padhi Ajoy Kumar Padhi Ashwini Kumar Rai 《Journal of the Geological Society of India》2009,74(5):591-596
Petrographic studies of Proterozoic pyriteferous granitoids forming basement for upper cretaceous Mahadek sediments from Wahkyn
area reveal interesting textural peculiarities of Pyrite. These pyrites also reveal interesting structural peculiarities.
The three textural pyrite varieties found in the granitoids are: framboidal, colloform and recrystallised which appear both
as composite aggregate as well as independent units. Various textures and variation in reflectivity, microhardness and elemental
distribution of the pyrites are described. Average Co/Ni ratio along with the textural manifestation of these pyrites attests
their sedimentary origin. 相似文献
103.
Sandipan Mukherjee Ravi Prakash Shukla Ashok Kumar Mittal Avinash Chandra Pandey 《Meteorology and Atmospheric Physics》2011,114(3-4):83-93
Mathematical analysis of a predominantly bimodal chaotic attractor, Lu system, was carried out to investigate a possible application of the model as a prototype of monsoon intra-seasonal oscillation (ISO). Bifurcation structures of the system are explored as the system parameter c and the forcing parameter F are varied. Stability criteria of equilibrium points of the forced Lu system are also explored in detail. A sensitivity study is carried out, by changing forcing parameter F, to explore relationships between some of the derived variables of the model and, based on such relationships, an empirical rule is used for extended range prediction. Analogous variables are also derived from the ISO data and prediction results are compared. Application of the prediction rule of regime transition to the observed ISO and chaotic model data is purely based on the bimodal characteristics of ISO and neglects some of the intricate mechanisms therein. We have found that a forced Lu system can be a good prototype in the prediction of peak anomaly of the monsoon ISO when growth rates around a threshold value are taken as predictors. 相似文献
104.
Simulation of CO<Subscript>2</Subscript> hydrate formation in cold aquifers: nonequilibrium approach
Khaled Jemai Mohammad Taghi Vafaei Bjørn Kvamme Ashok Chejara 《Arabian Journal of Geosciences》2017,10(5):113
In this paper, we focus on the geological storage of CO2 in reservoirs with zones that are cold enough to facilitate CO2 hydrate formation at local pressures. A 2D hydro-chemical mechanical model which has five layers (three layers with aquifers and two layers with cap rock in which we introduced two fractures) is created. We apply a reactive transport reservoir simulator, RetrasoCodeBright (RCB), in which hydrate is treated as a pseudo mineral. Following the recent modifications to account for hydrate dynamics in the code through a kinetic approach (Kvamme et al., Proceedings of the 7th International Conference on Gas Hydrates (ICGH 2011), 2011b), we have further improved the simulator to implement the nonequilibrium thermodynamic calculations. In the present study, we spot the light on the hydrate formation effects on porosity in different regions, as well as on the flow pattern. These simulations are based on classical relationships between porosity and permeability, but the outline of ongoing modifications is presented as well. A critical question in such systems is whether hydrate formation can contribute to stabilizing the storage, given that hydrates are pore filling and cannot be stable toward mineral surfaces. The implications of hydrate formation on the geo-mechanical properties of the model reservoir are other aspects addressed in this study. 相似文献
105.
Ashok Kumar Rakesh Kumar Arun K. Singh Sahendra Ram Pradeep K. Singh Rajendra Singh 《Arabian Journal of Geosciences》2017,10(18):411
Underground extraction of total thickness of a thick coal seam in single lift by bord and pillar method increases pillar height during retreat. Field studies found that the increase in pillar height affects the depillaring operation adversely, especially, during caving of the strong/massive roof strata. Dilution in strength due to the increased pillar height caused catastrophic failure of barrier pillars and goaf overriding. This warrants a systematic study of pillar strength variation for the different heights of pillar. A review of different pillar strength estimation approaches for an analysis of the dilution in strength of the heightened pillar suggested that numerical modelling provides a better option for such a systematic study. Accordingly, investigations are conducted on simulated models in laboratory adopting a recognised numerical modelling procedure. The observed nature of variations in pillar strengths with the increase in its height in the numerical models and empirical formula is found to be matched. But a mismatch is found between the strength values of the two approaches with an increase in height of the pillar. Considering validity of the empirical formulation in Indian coalfields, a relationship is developed to incorporate a correction in the strength values of the numerical models. The suggested correction on the basis of this simple study of the pillar strength variation would be helpful for the use of the established simulation tool during the depillaring of a thick coal seam. 相似文献
106.
The results of an investigation carried out during June 2005 to May 2007 on bloom-forming phytoplankton species composition and abundance in the Parangipettai and Coleroon coastal waters(Southeast coast of India) are reported.Air and surface water temperatures(℃) varied from 25.1 to 30.1 and 24.5 to 28.5,respectively,in the former waters and from 25.5 to 31.2 and 25.0 to 29.3 in the latter waters.The respective salinities varied from 6.0 to 28.5 and 5.0 to 33.1 and the respective pH ranged between 7.0 and 8.3 and 7.2 and 8.3.Correspondingly,the dissolved oxygen content varied from 3.1 to 7.5 and 3.1 to 7.9 mgL-1 while the light extinction coefficient(LEC) values ranged between 3.1 and 10.1 and 1.8 and 11.0.The content ranges of inorganic nutrients,i.e.,nitrate,nitrite,phosphate and silicate(μmolL-1),in the Parangipettai and Coleroon coastal waters were:6.5-27.0;1.0-8.9;0.1-3.0 and 15.0-140 and 10.1-23.4;1.2-8.9;0.2-3.1 and 55-125 respectively.The chlorophyll a contents in both waters ranged from 2.0-7.5 μgL-1.Presently,124 phytoplankton species representing different classes were recorded in the Coleroon coast,viz,Bacillariophyceae(77);Dinophyceae(19);Cyanophyceae(15);Chlorophyceae(10) and Chrysophyceae(3),whereas 117 phytoplankton species were recorded in the Parangipettai coast,viz,Bacillariophyceae(66);Dinophyceae(22);Cyanophyceae(19);Chlorophyceae(7) and Chrysophyceae(3).The phytoplankton cell abundance in the Parangipettai and Coleroon coastal waters varied from 290 to 111662 and 140 to 132 757 cells L-1,respectively,with peak diversity(3.38 and 3.52 bits ind-1.) recorded in summer.The maximum abundance occurred in summer coinciding with the stable hydrographical conditions.The seasonal distribution and abundance of phytoplankton are discussed in relation to hydrographical parameters.Totally 31 and 24 species of phytoplankton were found to be bloom-forming in the Parangipettai and Coleroon coastal waters,respectively.Presently Trichodesmium bloom was also observed,which appeared at the 10 fathom level of the coastal water and quickly spread to the marine zone of the Vellar estuary and near the mouth region of the mangrove waters.The Parangipettai and Coleroon coastal waters are subject to long term fluctuations in physico-chemical conditions depending upon the seasonal tidal range and freshwater influx,resulting in a continuous exchange of organic,inorganic,plant and animal matters. 相似文献
107.
108.
A simple and effective extension to the boundary element method for solving Laplace'S equation (?2u = 0) for boundary value problems is presented to solve steady confined and (or) steady unconfined seepage problems in zoned anisotropic mediums. Sample problems indicating the accuracy of results are given. 相似文献
109.
Ashok KR. Chakraborty 《Astrophysics and Space Science》1992,192(2):321-324
In this Letter the five-dimensional Kaluza-Klein cosmological model is studied in the presence of a massless scalar field, whose potential has a flat part. By use of the polynomial relation between the two scale factors, inflationary solutions are obtained. The results show that the scale factor corresponding to the extra dimension is either constant or varies inversely as some power of the usual scale factor. 相似文献
110.
Ashok K. Chugh 《国际地质力学数值与分析法杂志》1977,1(4):323-341
A numerical step-by-step procedure, analogous to the ‘Initial Stress Method,’ is presented for the analysis of a single-layer jointed rock beam subjected to gravity loads and in-plane in situ formation pressure. The joints are permitted to open at locations where the flexural stresses exceed flexural strength. The material properties may be different for each rock block and joint. A detailed algorithm is given for the solution of the problem. The results of several analyses indicating the relative effects of initial formation pressure, transverse load, stiffness of the joint material, and joint spacing on the response of a jointed beam are presented. The convergence characteristics of the numerical procedure are included. The joint material is assumed to be ‘no-tension’ type. Both the geometric and material non-linear effects are considered. 相似文献