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1.
In this paper, we have constructed a five dimensional LRS Bianchi type I cosmological model with wet dark fluid (WDF) in general relativity with the matter field described as bulk viscosity. It is found that in presence of bulk viscosity an inflationary effective stiff fluid cosmological model is obtained, whereas in absence of bulk viscosity the wet dark fluid degenerate to stiff fluid. Some physical and geometrical properties of the model are also discussed. 相似文献
2.
3.
Hydrogeology Journal - The study defines the hydrogeological framework of the Quaternary aquifer of south Bengal Basin, India, and the impact of urbanisation on the groundwater resources in and... 相似文献
4.
Rahul Sharma S. Jai Sankar Sudeshna Samanta A. A. Sardar D. Gracious 《Geo-Marine Letters》2010,30(6):617-626
Factors such as non-uniform illumination of seafloor photographs and partial burial of polymetallic nodules and crusts under
sediments have prevented the development of a fully automatic system for evaluating the distribution characteristics of these
minerals, necessitating the involvement of a user input. A method has been developed whereby spectral signatures of different
features are identified using a software ‘trained’ by a user, and the images are digitized for coverage estimation of nodules
and crusts. Analysis of >20,000 seafloor photographs was carried out along five camera transects covering a total distance
of 450 km at 5,100–5,300 m water depth in the Central Indian Ocean. The good positive correlation (R2 > 0.98) recorded between visual and computed estimates shows that both methods of estimation are highly reliable. The digitally
computed estimates were ∼10% higher than the visual estimates of the same photographs; the latter have a conservative operator
error, implying that computed estimates would more accurately predict a relatively high resource potential. The fact that
nodules were present in grab samples from some locations where photographs had nil nodule coverage emphasises that nodules
may not always be exposed on the seafloor and that buried nodules will also have to be accounted for during resource evaluation.
When coupled with accurate positioning/depth data and grab sampling, photographic estimates can provide detailed information
on the spatial distribution of mineral deposits, the associated substrates, and the topographic features that control their
occurrences. Such information is critical for resource modelling, the selection of mine sites, the designing of mining systems
and the planning of mining operations. 相似文献
5.
Application of geostatistics in estimating recoverable reserves of beach sand deposit is rare. This paper made an attempt to estimate local recoverable reserves using disjunctive kriging and discrete Gaussian model considering support and information effects for a beach sand deposit located in the eastern part of India. The dependence of different selective mining unit (SMU) sizes and different production sampling strategies on the estimated tonnage, metal quantity, and the ore tonnage versus metal quantity relationships has been examined. The results of the study show that nonlinear geostatistics should be used for more precise assessment of the grade, ore tonnage, and metal quantity and their relationships, which are necessary for recoverable reserve estimation. In selective mining operation, both support and information effects have significant influence on recoverable reserve. Recoverable reserve estimation based on SMU involves estimating grade distributions of mining unit with much bigger support than the available drill core sample data. Information effect comes into picture from the real scenario where the actual grades of the blocks remain unknown even during mining. At the mining stage, discrimination of ore and waste blocks is carried out based on estimated grades of the production samples and it is likely that the blocks might be misclassified as either ore or waste and thus sent to wrong destination. Information effect modeling makes the estimation more reliable by taking care of misclassification. 相似文献
6.
Arsenic is present in groundwater at Siliguri–Jalpaiguri area, West Bengal, India. This is the place where Tista river descending
from the Himalayas meets the alluvial plain. The area represents alluvial fan and floodplains of Tista, Mahananda-Balasan,
Jaladhaka and its tributaries. In the river sediment samples, para- and ferro-magnetic minerals within 0.3–0.05 mm fraction
contain 9–80 ppm of arsenic. The study indicates that iron bearing minerals viz. biotite, hornblende as well as iron coated
grains of the sediment are major contributors towards arsenic budget. Though magnetite as a mineral shows maximum arsenic
content (22 ppm), it is volumetrically not of much significance. Measurement of groundwater collected from tube wells shows
up to 0.05 ppm of arsenic. These arsenic contaminated tube wells occur in a linear fashion along the course of the rivers.
Moreover, localization of contaminated tube wells coincides with the change of channel gradient as observed in longitudinal
section. The study enumerates a cause–effect relationship of arsenic occurrence with river gradient and fluvial sedimentation. 相似文献
7.
Study of subsurface geology in locating arsenic-free groundwater in Bengal delta,West Bengal,India 总被引:1,自引:0,他引:1
Over a large area of the Bengal delta in West Bengal, India, arsenic distribution patterns in groundwater were studied. One
hundred and ten boreholes at different target locations were made, subsurface sediments were logged and analysed, and arsenic
values in sediments vis-à-vis groundwater were compared. The study elucidates the subsurface geology of the western part of
Bengal delta and characterises the sediments that were intersected in different boreholes with contrasting values of arsenic
in groundwater. It reveals an existence of multiple aquifers stacked over each other. Depending on the color and nature of
aquifer-sands and their overlying clay beds six aquifer types (Type-1 to Type-6) are classified and described. Sediment-arsenic
for all the varieties of aquifer sands are near similar but the groundwater-arsenic of these six aquifers varies widely. Type-2
and Type-5 aquifers host arsenic-contaminated groundwater whereas the other four aquifers are arsenic-free. Type-2 and Type-5
aquifers are capped by a grey to dark grey soft organic matter-rich clay unit which makes these aquifers semi-confined to
leaky-confined. These contribute in releasing arsenic from the sediments. The results of this study are employed in a proposed
georemedial measure against this hazardous toxic element. 相似文献
8.
A core from the Cambay Shale Formation of the Cambay Basin, containing immature Type III organic matter, was pyrolysed at 300°C for different durations of time to different maturation levels. Fractionation effects were studied employing a three-step extraction technique after removal of the expelled pyrolysate. The extractable organic matter (EOM) obtained on extraction of the whole core is assumed to be that present in open pores, while that obtained on finely crushing the sample is assumed to be that present in closed pores. The EOM obtained from 1 cm chips is termed EOM from semi-open pores. The gross composition of the pyrolysates expelled during pyrolysis is not similar to the oils reservoired in the area, and there is no significant fractionation observed between expelled pyrolysates and unexpelled EOM. Our study indicates movement of fluids between closed, semi-open and open pores. In both systems, there is a higher concentration of EOM in open pores than in semi-open and closed pores, and the fraction of EOM in open pores is much greater in the artificial system than in the natural system. Fractionation effects on n-alkane and isoprenoid hydrocarbon-based parameters were also studied. n-Alkenes are present in semi-open and closed pores of the immature core and in the core after it was pyrolysed to 300°C for 6 and 48 h, but are absent in the open pores. n-Alkenes are present in closed pores in the naturally matured core. Presence of n-alkenes in the pyrolysates expelled during the 6 and 48 h experiments, but their absence in the open pores of the core, indicates that expulsion also occurs through temporary microfractures during laboratory pyrolysis, whereas in the natural system expulsion from closed pores seems to be only via semi-open and open pores. 相似文献
9.
Jagadish Prasad Sahoo Pradip Kumar Pradhan 《Geotechnical and Geological Engineering》2010,28(6):889-897
An experimental investigation was undertaken to study the effects of lime-stabilized soil-cushion on the strength behavior
of expansive soil. In the present investigation, a series of laboratory tests (Unconfined compression tests and CBR tests)
were conducted on both expansive soil alone and expansive soil cushioned with lime-stabilized non-expansive cohesive soil.
Lime contents of 2, 4, 6, 8 and 10% by dry weight of cohesive non-swelling soil was used in the stabilized soil cushion. Both
expansive soil and lime stabilized soil cushion were compacted to Standard Proctor’s optimum condition with thickness ratio
2:1. Tests on cushioned expansive soils were conducted at different curing and soaking periods i.e., 7, 14, 28 and 56 days.
The test results revealed that maximum increase in strength was achieved after 14 days of curing or soaking period with 8%
of lime content. 相似文献
10.
Binita Pathak Arup Borgohain Pradip Kumar Bhuyan Shyam Sundar Kundu S Sudhakar Mukunda M Gogoi Toshihiko Takemura 《Journal of Earth System Science》2014,123(4):651-663
In order to examine the spatial variability of the aerosol characteristics across the Brahmaputra valley, a land campaign was conducted during late winter (February 3–March 2) 2011. Measurements of particulate matter (PM, PM10, PM2.5) and black carbon (BC) concentrations were made onboard an interior redesigned vehicle. The length of the campaign trail stretched about 700 km, covering the longitude belt of 89.97°–95.55°E and latitude belt of 26.1°–27.6°N, comprising 13 measurement locations. The valley is divided into three sectors longitudinally: western sector (R1: 89.97°–91.75°E), middle sector (R2: 92.5°–94.01°E) and eastern sector (R3: 94.63°–95.55°E). Spatial heterogeneity in aerosol distribution has been observed with higher PM10 and PM2.5 concentrations at the western and middle sectors compared to the eastern sector. The locations in the western sector are found to be rich in BC compared to the other two sectors and there is a gradual decrease in BC concentrations from west to east of the Brahmaputra valley. Two hotspots within the western and middle sectors with high PM and BC concentrations have been identified. The associated physico-optical parameters of PM reveal abundance of PM2.5 aerosols along the entire valley. High population density in the western and middle sectors, together with the contribution of remote aerosols, leads to higher anthropogenic aerosols over those regions. Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS) slightly underestimates the measured PM10 and PM2.5 at the eastern sector while the model overestimates the measurements at a number of locations in the western sector. In general, BC is underestimated by the model. The variation of BC within the campaign trail has not been adequately captured by the model leading to higher variance in the western locations as compared to the middle and eastern locations. 相似文献