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71.
Prakash K. Singh 《Journal of the Geological Society of India》2012,80(6):759-770
This paper entails the results of the investigations undertaken to assess the oil potential of two lignite deposits, Rajpardi and Vastan, from Gujarat, western India. They are ‘Low rank B’ type lignite. Petrographically, they are enriched in huminite and are low in liptinite and inertinite. Their elevated hydrogen content, in relation to carbon, has probably made them perhydrous in nature and oil prone. The reactivity of these coals during liquefaction has also been discussed in the light of petrofactor. Good correlation has been noticed between oil yield and conversion (r2 = 0.999) in both the lignite deposits. The VRr (0.24–0.35% in both lignites), H/C atomic ratio (0.11–1.39 in Rajpardi and 1.09–1.88 in Vastan), reactive maceral content (91.6–99.8 vol % mmf in Rajpardi lignite and 75.5–99.7 vol % in Vastan lignite) and VMdaf (64.8–67.9 wt % in Rajpardi lignite and 42.1–80.0 wt % in Vastan lignite) of these lignites have a favourable range required for a coal to generate oil. Huminite is seen to play a vital role in conversion and maintains a good correlation with it. The calculations show that these lignites have a high conversion (> 95%) and oil yield (> 65%). 相似文献
72.
A. J. Prakash P. Palroy D. D. Misra 《Fragblast: International Journal for Blasting and Fragmentation》2004,8(1):51-60
This paper presents the influence of various discontinuities, natural or artificial, on magnitude and frequencies of blast induced ground vibrations. These discontinuities were geological faults, a pond, a shaft incline, a trench and a pre-split plane interposed in the path of vibration propagation. In the post-trench region, ground vibrations in terms of peak particle velocity were significantly reduced and dominant frequencies in higher bands were consequently observed. Depth of trench with respect to blastholes were varied and consequent vibration characteristics were analyzed. The techniques of creating a trench and pre-split plane were successfully implemented in controlling vibration and in increasing the explosives charge to meet the scheduled production target of an opencast mine. Comparisons of ground vibration characteristics affected by a trench and a pre-split plane of the same depth are described in the text. The findings lead to the conclusion that such experimental data are necessary for production blasting in open cast mines under constrained conditions. 相似文献
73.
The geoeffective magnetic cloud (MC) of 20 November 2003 was associated with the 18 November 2003 solar active events in previous
studies. In some of these, it was estimated that the magnetic helicity carried by the MC had a positive sign, as did its solar
source, active region (AR) NOAA 10501. In this article we show that the large-scale magnetic field of AR 10501 has a negative
helicity sign. Since coronal mass ejections (CMEs) are one of the means by which the Sun ejects magnetic helicity excess into
interplanetary space, the signs of magnetic helicity in the AR and MC must agree. Therefore, this finding contradicts what
is expected from magnetic helicity conservation. However, using, for the first time, correct helicity density maps to determine
the spatial distribution of magnetic helicity injections, we show the existence of a localized flux of positive helicity in
the southern part of AR 10501. We conclude that positive helicity was ejected from this portion of the AR leading to the observed
positive helicity MC. 相似文献
74.
CS Suma K Srinivasamoorthy K Saravanan S Gopinath R Prakash A Faizal Khan 《Arabian Journal of Geosciences》2016,9(18):703
An attempt has been made in Chinnar sub basin of Dharmapuri district, South India to isolate the geochemistry of uranium occurrences in groundwater. The geology of the area is mainly of charnockite and granite gneiss. Groundwater samples were collected for two different seasons post and pre monsoon in two different litho units (granite gneiss and charnockite) and analysed for major, minor and uranium concentrations. Higher uranium (18.45 μg L?1) has been recorded during pre monsoon season in granite gneiss with increasing pH. The saturation index calculation for the groundwater isolated minerals like uaraninite, coffinite, haiweeite and soddyite to be precipitating and uranium oxides like UO2.25, UO2.25beta, UO2.33beta as oversaturated. The Eh-pH diagram attempted represents solubility of uraninite within the pH range of 6.0 to 8.0. The study isolate uranium in groundwater of the study area is controlled by the presence of (U4O9) uranium oxide. 相似文献
75.
Prakash Mehra Michael N. Tsimplis R. G. Prabhudesai Antony Joseph Andrew G. P. Shaw Y. K. Somayajulu Paolo Cipollini 《Ocean Dynamics》2010,60(4):819-833
The contribution of atmospheric pressure and local wind to sea level variability at Goa (West coast of India) for the period
2007–2008 is investigated. Sea level data from a tide gauge are compared with measured local surface meteorological as well
as oceanographic data. Multilinear regression analysis is used to resolve the dependence of sea level on various forcing parameters.
The multilinear regression analysis performed over approx. 2-year data shows that the local surface meteorological data and
water temperature account for the sea level variability only up to 6%. The accounted sea level variability increases to 25%,
when the local wind and the surface currents obtained from satellite altimetry in the near vicinity of the study area are
incorporated in the regression analysis. The contribution of local wind increases substantially when the regression is performed
over a 2-month duration, and it is variable within the year. During the summer monsoon season (May–September), the sea level
variability attributable to wind is up to 47% and 75%, respectively, for 2007 and 2008; however, it reduces to <20% during
the winter monsoon (November–February) season. A significant part of the variability observed in sea level remains unaccounted
for and is attributed to remote forcing. 相似文献
76.
Joevivek Vincent Jayaraj Chandrasekar Nainarpandian Jayangondaperumal Ramakrishnan Thakur Vikram Chandr Shree Purniema Krishnan 《海洋学报(英文版)》2019,38(5):151-160
To analyze the grain size and depositional environment of the foreshore sediments, a study was undertaken on wave refraction along the wide sandy beaches of central Tamil Nadu coast. The nearshore waves approach the coast at 45° during the northeast(NE) monsoon, at 135° during the southwest(SW) monsoon and at 90° during the non-monsoon or fair-weather period with a predominant wave period of 8 and 10 s. A computer based wave refraction pattern is constructed to evaluate the trajectories of shoreward propagating waves along the coast in different seasons. The convergent wave rays during NE monsoon, leads to high energy wave condition which conveys a continuous erosion at foreshore region while divergent and inept condition of rays during the SW and non-monsoon, leads to moderate and less energy waves that clearly demarcates the rebuilt beach sediments through littoral sediment transport. The role of wave refraction in foreshore deposits was understood by grain size and depositional environment analysis. The presence of fine grains with the mixed population, during the NE monsoon reveals that the high energy wave condition and sediments were derived from beach and river environment. Conversely, the presence of medium grains with uniform population, during SW and non-monsoon attested less turbulence and sediments were derived from prolong propagation of onshore-offshore wave process.These upshots are apparently correlated with the in situ beach condition. On the whole, from this study it is understood that beaches underwent erosion during the NE monsoon and restored its original condition during the SW and non-monsoon seasons that exposed the stability of the beach and nearshore condition. 相似文献
77.
Summary The potential technique of the perturbation has been employed to find the analytical expressions for the response of conducting bodies of irregular shapes. In Part I spherical bodies and in Part II cylindrical ones are considered. The conductivities are assumed to be finite and radially varying. The deformation of the boundaries in both the cases are considered to be of the typek
p
=r
0[1++f
1(, )] where is the perturbation parameter. Calculations have been made for uniform as well as non-uniform excitation fields. Since the models represent the geological ore-formation more closely, the results will find application in preparing type curves for induction prospecting.N.G.R.I. Contribution No. 70-194. 相似文献
78.
The Nature and Distribution of Particulate Matter in the Mandovi Estuary,Central West Coast of India
Pratima Mohan Kessarkar Venigalla Purnachandra Rao Ranjan Shynu Prakash Mehra Blossom E. Viegas 《Estuaries and Coasts》2010,33(1):30-44
Systematic seasonal variations of suspended particulate matter (SPM) along a 44-km transect of the Mandovi estuary reveal
that the concentrations of SPM are low at river-end stations, increase generally seaward, and are highest at sea-end stations
of the estuary. An estuarine turbidity maximum (ETM) occurs at sea-end stations during June–September when river discharge
is high and also in February–May when river discharge is low. These are the two windiest times of year, the former associated
with the southwest monsoon and the latter characterized by a persistent sea breeze. The salinity vs. SPM plot shows that high
SPM is a seaward deposit and skewed landward. Suspended matter comprised of floccules, fecal pellets, and aggregates that
consist of clay and biogenic particles occur everywhere in the estuary. Diatoms are the most common and are of marine type
at the sea-end and freshwater-dominated at river-end stations of the estuary. SPM is characterized by kaolinite- and smectite-rich
clay mineral suites at the river- and sea-end stations, respectively. Smectite concentrations increase seawards with the increase
in SPM content and are not influenced by salinity. Wind-driven waves and currents and biogeochemical processes at the mouth
of estuary likely play an important role in the formation of ETM in resuspension and transformation of SPM into floccules
and aggregates and in their upkeep or removal. 相似文献
79.
Efficient, robust simulation of groundwater flow in the unsaturated zone remains computationally expensive, especially for problems characterized by sharp fronts in both space and time. Standard approaches that employ uniform spatial and temporal discretizations for the numerical solution of these problems lead to inefficient and expensive simulations. In this work, we solve Richards’ equation using adaptive methods in both space and time. Spatial adaption is based upon a coarse grid solve and a gradient error indicator using a fixed-order approximation. Temporal adaption is accomplished using variable order, variable step size approximations based upon the backward difference formulas up to fifth order. Since the advantages of similar adaptive methods in time are now established, we evaluate our method by comparison with a uniform spatial discretization that is adaptive in time for four different one-dimensional test problems. The numerical results demonstrate that the proposed method provides a robust and efficient alternative to standard approaches for simulating variably saturated flow in one spatial dimension. 相似文献
80.
Temperature distribution in cylindrically symmetric coronal magnetic loops has been reinvestigated under various conditions: (a) loop with the pressure varying along the radial distance, and (b) loop with constant pressure, for cooler apex loops and hotter apex loops. This work is reinvestigation of our previous work published inAstrophysics and Space Science (Chandra and Prasad, 1993b). 相似文献