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21.
D. K. Ghosh 《Environmental Geology》1990,16(1):15-22
Geological contributions to the stability of rockcut caves and evaluation of stone block as a construction material are discussed. Rock alteration and microfissuring are proposed to be coded by a deterioration index and usable stone blocks are evaluated on joint frequency measured in the field. 相似文献
22.
In the history of superposed deformations of the iron formations at the western border of the Kolar Gold Field in S India, an important event was the successive growth of broadly coaxial plane noncylindrical folds in course of a progressive deformation concomitant with development of ductile mesoscopic shear zones. The noncylindrical folds were initiated as active folds by the creation of a buckling instability at successive stages on newly developed foliation surfaces. The nucleation of noncylindrical folds and the subsequent axial-plane folding of the tightened mature folds are explained by the mechanical inhomogeneity of the rocks and the heterogeneous character of strain. The correlation between increasing tightness and increasing noncylindricity of the folds indicates that the initial curvatures of hinge lines were accentuated by an extension parallel to the subhorizontal stretching lineation. From the patterns of deformed lineations over folds of varying tightnesses, it is concluded that the passive accentuation of hinge-line curvatures was mostly achieved when the folds had already become isoclinal or very tight. 相似文献
23.
The stratosphere holds a variety of particulates like polar stratospheric clouds (PSCs) and sulphate aerosols which catalyse chemical reactions. These reactions cause changes in the composition of the stratosphere, including the redistribution of active chlorine which might lead to ozone destruction. As a result during recent years a lot of effort has been directed towards the quantification of the uptake of trace gases like ClONO2, HCl, etc. into these particulates. However, it has been observed that many of the two and three dimensional models used in such studies are constrained by the lack of adequate rate constant data. This paper describes a theoretical approach to estimate the reaction rate constants for 23 gases on both types of polar stratospheric clouds (type I and II). It is found that for gases like N2O5, ClONO2 and HCl, diffusional uptake is important and contributes significantly to the heterogeneous reaction rate. A complete Lennard-Jones calculation is used to accurately compute the trace gas diffusion coefficients. 相似文献
24.
Seismic Passive Earth Pressure Behind Non-vertical Retaining Wall Using Pseudo-dynamic Analysis 总被引:3,自引:0,他引:3
Priyanka Ghosh 《Geotechnical and Geological Engineering》2007,25(6):693-703
This paper shows a detailed study on the seismic passive earth pressure behind a non-vertical cantilever retaining wall using
pseudo-dynamic analysis. A planar failure surface has been considered behind the retaining wall. The effects of soil friction
angle, wall inclination, wall friction angle, horizontal and vertical earthquake acceleration on the passive earth pressure
have been explored. Unlike the Mononobe–Okabe method, which incorporates pseudo-static analysis, the present analysis predicts
a nonlinear variation of passive earth pressure along the wall. The results have been thoroughly compared with the existing
values in the literature. 相似文献
25.
Yearly changes in the seasonal frequency and duration of short-term acid pulses in some Nova Scotia, Canada streams 总被引:1,自引:0,他引:1
The seasonal frequency and duration of low pH events at three sites located in southwestern Nova Scotia were analyzed using
measured and synthetic daily pH data. The basins varied in size from 0.3 to 300 km2 and were subject to frequent snowmelt events in winter and spring, as well as occasional runoff events during summer and
fall. Results showed that, in order to fill in missing data from periods where collection was interrupted, statistical approximations
using discharge were not totally acceptable, as generated data consistently missed the extreme values measured. Despite a
lack of totally accurate event pH estimates for periods where daily data were missing, analysis showed that in this region,
low pH episodes can occur year-round including summer. The highest probabilities of low pH episodes nevertheless occurred
in the winter and spring when snowmelts were frequent.
Received: 12 November 1999 · Accepted: 18 July 2000 相似文献
26.
M. L. Ghosh 《Pure and Applied Geophysics》1963,54(1):31-52
Summary In this paper the problem of a point source of stress moving over the surface of a thick aelotropic plate resting of a rigid foundation has been considered. Following the method ofAleksandrov & Vorovich (1960) the stress componentsZ
x andZ
z have been expanded in series of ascending powers of 1/h when the source velocity is less than (c
44/)1/2. When the velocity exceeds (c
44/)1/2 it has been shown that two cracks are produced in different directions and their successive reflections at the upper and lower surface are also obtained. 相似文献
27.
Summary Offshore areas are sometimes found in which seismic record assumes the appearance of a sine wave or a simple combination of sine waves. It is more interesting to note that the dominant frequency on the singing records is the third harmonic of a fundamental whose wave length is four times the water depth. In this paper it has been proved that this peculiar phenomenon happens due to the slope of the sedimentary layer near the observational points. Using the method introduced byCovert (1958) of finding the Green's function for built in bodies, pressure field has been obtained in the water layer for a two dimensional point source in the same medium and it has been proved that due to the slope of the sedimentary layer singing is caused by waves of wave-length equal to four times the water depth. 相似文献
28.
29.
We constructed a grid of relativistic models for standard high-relative-luminosity accretion α-disks around supermassive Kerr black holes (BHs) and computed X-ray spectra for their hot, effectively optically thin inner parts by taking into account general-relativity effects. They are known to be heated to high (~106–109 K) temperatures and to cool down through the Comptonization of intrinsic thermal radiation. Their spectra are power laws with an exponential cutoff at high energies; i.e., they have the same shape as those observed in active galactic nuclei (AGNs). Fitting the observed X-ray spectra of AGNs with computed spectra allowed us to estimate the fundamental parameters of BHs (their mass and Kerr parameter) and accretion disks (luminosity and inclination to the line of sight) in 28 AGNs. We show that the Kerr parameter for BHs in AGNs is close to unity and that the disk inclination correlates with the Seyfert type of AGN, in accordance with the unification model of activity. The estimated BH masses Mx are compared with the masses Mrev determined by the reverberation mapping technique. For AGNs with luminosities close to the Eddington limit, these masses agree and the model under consideration may be valid for them. For low-relative-luminosity AGNs, the differences in masses increase with decreasing relative luminosity and their X-ray emission cannot be explained by this model. 相似文献
30.
N. Rama Rao P. K. Garg S. K. Ghosh 《Journal of the Indian Society of Remote Sensing》2006,34(1):69-78
Motivated by the increasingly availability and importance of hyperspectral remote sensing data, this study aims to determine
whether current generation narrowband hyperspectral remote sensing data could be used to estimate vegetation Leaf Area Index
(LAI) accurately than the traditional broadband multispectral data. A comparative study has been carried out to evaluate the
performance of the narrowband Normalized Difference Vegetation Index (NDV1) derived from Hyperion hyperspectral sensor with
that of derived from IRS LISS-III for the estimation of LAI of some major agricultural crops (e.g. cotton, sugarcane and rice)
in part of Guntur district, India. It has been found that the narrowband NDVI derived from Hyperion has shown better results
over its counterpart derived from broadband LISS-III. Linear regression models have been used which with selected subsets
of individual Hyperion bands performed better to predict LAI than those based on the broadband datasets, although the potential
to overfit models using the large number of available Hyperion bands is a concern for further research. 相似文献