排序方式: 共有17条查询结果,搜索用时 312 毫秒
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Martha Tapas Ranjan Roy Priyom Jain Nirmala Khanna Kirti Mrinalni K. Kumar K. Vinod Rao P. V. N. 《Landslides》2021,18(6):2125-2141
Landslides - India ranks first in the world in terms of fatal landslides. Large vulnerable area (0.42 million km2), high population density and monsoon rainfall make India’s landslide... 相似文献
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Nirmala Kumari Amares Chattopadhyay Abhishek K. Singh Sanjeev A. Sahu 《Acta Geophysica》2017,65(1):189-205
The present study investigates the propagation of shear wave (horizontally polarized) in two initially stressed heterogeneous anisotropic (magnetoelastic transversely isotropic) layers in the crust overlying a transversely isotropic gravitating semi-infinite medium. Heterogeneities in both the anisotropic layers are caused due to exponential variation (case-I) and linear variation (case-II) in the elastic constants with respect to the space variable pointing positively downwards. The dispersion relations have been established in closed form using Whittaker’s asymptotic expansion and were found to be in the well-agreement to the classical Love wave equations. The substantial effects of magnetoelastic coupling parameters, heterogeneity parameters, horizontal compressive initial stresses, Biot’s gravity parameter, and wave number on the phase velocity of shear waves have been computed and depicted by means of a graph. As a special case, dispersion equations have been deduced when the two layers and half-space are isotropic and homogeneous. The comparative study for both cases of heterogeneity of the layers has been performed and also depicted by means of graphical illustrations. 相似文献
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The main objective of this study is to measure the effect of slope and grass-cover on infiltration rate, run-off and sediment
yield under simulated rainfall conditions in a badland area located in the upper Pravara Basin in western India. An automatic
rainfall simulator was designed following Dunne et al (1980) and considering the local conditions. Experiments were conducted on six selected experimental fields of 2 × 2m within
the catchment with distinct variations in surface characteristics — grass-covered area with gentle slope, recently ploughed
gently sloping area, area covered by crop residue (moderate slope), bare badland with steep slope, gravelly surface with near
flat slope and steep slope with grass-cover. The results indicate subtle to noteworthy variations amongst the plots depending
on their slope angle and surface characteristics. An important finding that emerges from the study is that the grass-cover
is the most effective measure in inducing infiltration and in turn minimizing run-off and sediment yield. Sediment yields
are lowest in gently sloping grass-covered surfaces and highest in bare badland surfaces with steep slopes. These findings
have enormous implication for this area, because over 2/3 area is characterized by bare and steep slopes. 相似文献
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Nirmala D. Desouza Baby Simon Muhammad S. Qureshi 《Meteorology and Atmospheric Physics》2011,114(3-4):107-121
The evolutionary characteristics of a dust storm over Oman on 2 February 2008 were studied by analyzing the weather associated with it. The National Center for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) reanalysis wind flow pattern at 1,000?hPa showed a clockwise and outward wind flow pattern over the study region, a manifestation of a high-pressure cold air mass. In addition, ground truth observations for surface temperature and surface winds showed cold northerly winds until the early morning of 2 February 2008. A strong wind shear resulted from differences in wind speed between warm air and trapped cold air. This vertical wind shear enhanced instability. Furthermore, the weakening of the inversion in the lower troposphere and the formation of a mixed layer due to transfer of horizontal momentum from upper air towards the surface led to strong surface winds. These strong winds lifted a large amount of dust particles off the ground, resulting in the dust event of 2 February 2008. 相似文献
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Nirmala Devidas Desouza Rajnish Kurchania Muhammad Shums Qureshi 《Meteorology and Atmospheric Physics》2013,122(1-2):47-54
Dust storms commonly occur during the pre-monsoon (summer) season in north and northwest parts of India. Characteristics of dust events of the pressure gradient type are well understood. However, comprehensive studies on mechanism of convective dust storms in India are few. A convective dust storm which occurred on 21 April 2010 in association with a western disturbance over North India was hence studied. In the absence of in situ data, we used available satellite data to study the event. Dust storm that occurred on 20 April 2010 on the surface of the Thar Desert transported dust to northern and northwestern parts of India (Rajasthan, Haryana, Delhi and some parts of Uttar Pradesh). This formed a background of aerosols that affected the thunderstorm formed in association with western disturbance and the strong updraft in the thunderstorm carried the dust lingering in the atmosphere to higher altitudes. Large amount of aerosols carried to higher altitude suppressed the chance of precipitation by affecting the cloud top microphysics. Enhancement in evaporation due to an increase in aerosol concentration and strong downdrafts during dissipation of the thunderstorm resulted in emission of dust particles which led to the convective dust event of 21 April 2010. 相似文献
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Nirmala Jain Ramdayal Singh Priyom Roy Tapas R. Martha K. Vinod Kumar Prakash Chauhan 《Arabian Journal of Geosciences》2018,11(16):455
We explored the utilization of Landsat-8 Operational Land Imager (OLI) data for mapping of hydrothermal alteration zones. The region in and around the cities of Dungarpur and Udaipur of Rajasthan state in India was selected for this study. The rock types of Dungarpur and Udaipur are serpentinites, talc-carbonate, talc-schist, and quartzite of the Aravalli Supergroup. Hydrothermally altered zones and resultant hydrous minerals play an important role in the genesis of these rocks. We aimed to identify possible locations of hydrothermally altered zones in regional context around Dungarpur and Udaipur using Landsat-8 OLI data. False-color composite maps and band ratios were prepared from Landsat-8 bands. Band ratios such as band 6/band 7 (short-wave infrared 1 (SWIR1)/short wave infrared 2 (SWIR2)), band 4/band 3 (red/green), and band 5/band 6 (near infrared (NIR)/SWIR1) and visual interpretation techniques were used to identify the hydrothermally altered zones. Spectroscopic analyses of field rock samples were done to validate the hydrothermal alteration zones delineated from the analysis of Landsat-8 data. We present the combined results of Landsat-8 and field spectroradiometer analysis which brings out the hydrothermal alteration zones associated with hydrous minerals (antigorite, lizardite, montmorillonite, vermiculite, talc, and saponite). The study demonstrates the utility Landsat-8 OLI (with field spectroradiometer data) in the mapping of hydrothermally altered zones as a key in understanding geological processes. 相似文献
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Veena Joshi Devidas Tambe Gorakh Dhawade 《Journal of the Geological Society of India》2009,73(3):355-370
One of the most serious limitations in studying the surface morphometry of a badland landscape is the nonavailability of a
very fine resolution data which is essential for such types of studies. Local relief of most of the badlands in India and
also from other parts of the world exhibit limited relief amplitude, often within a few meters. The paper reports a case study
carried out in a riverine badland formed along the Western Deccan Trap Region. An attempt has been made in the present paper
to extract the morphometric variables of the landscape from the DEMs derived from a high resolution field generated data,
because the accuracy of the DEM derived values are dependent on the pixel resolution of the DEM from which they are generated.
The size of the pixel resolution should be fixed differently for different landscapes depending on the landscape process in
the area. The local relief of the area is around 10 m and for such types of landscapes the topographical maps and also the
web-available DEMs are of very coarse resolutions which are not suitable for the analysis. Therefore two well defined tributary
catchments were chosen from the area under investigation and theodolite surveys were carried out, contours were generated
with 10 cm interval, DEMs were derived by using Arc GIS software. SRTM (Shuttle Radar Topography Mission) 90 m resolution
data were utilized to generate DEM for the whole basin. Hypsometric and the drainage basin parameters were extracted from
these data by using the same software. Fractal dimension of the whole basin and the sample basins were also obtained for the
same data. The morphometric data generated were used to understand the geomorphic processes operating in the area. 相似文献
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