Estimation of heterogeneous reaction rates for stratospheric trace gases with particular reference to the diffusional uptake of HCl and ClONO2 by polar stratospheric clouds     

S. Ghosh  D. Lary  J. A. Pyle 《Annales Geophysicae》1995,13(4):406-412

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   

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   

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  

T. A. Clair  A. Ghosh Bobba  Krista Miller 《Environmental Geology》2001,40(4-5):582-591

 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   

Formation of cracks due to moving source over a thick crust     

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   

On the singing phenomenon in the offshore seismic experiments     

Ghosh  M. L. 《Pure and Applied Geophysics》1961,49(1):61-74

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   

"A study on the direct interpretation of dipole sounding resistivity measurements over layered earth"     

U. C. Das  D. P. Ghosh 《Geophysical Prospecting》1973,21(4):800-800

  相似文献   

X-ray emission from accretion disks in active galactic nuclei     

V. F. Suleimanov  K. K. Ghosh  R. A. Austin  B. D. Ramsey 《Astronomy Letters》2002,28(11):745-754

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 M_x are compared with the masses M_rev 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   

Estimation and comparison of leaf area index of agricultural crops using irs liss-III and EO-1 hyperion images     

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   

Reappraisal of the structure of the Western Iron Ore Group, Singhbhum craton, eastern India: Implications for the exploration of BIF-hosted iron ore deposits   总被引：1，自引：0，他引：1  

Gautam Ghosh  Joydip Mukhopadhyay 《Gondwana Research》2007,12(4):525-532

The middle to late Archean Iron Ore Group rocks occurring along the western margin (the Western Iron Ore basin) of the Singhbhum Granite massif in the Singhbhum craton were deformed during Iron Ore orogeny and are disposed in a horseshoe-shaped synclinal structure in the eastern part of the Indian shield. The Western Iron Ore basin hosts almost all the major high-grade iron ore deposits of eastern India. Contrary to the established view, present analysis emphasizes that the horseshoe fold in reality is a synclinorium consisting of a syncline–anticline fold pair which were later cross-folded along an east–west axis.

Structural analysis in the eastern anticline of the ‘horseshoe synclinorium’ suggests that the BIF hosting the high-grade iron ore bodies are disposed in three linear NNE–SSW trending belts, each showing an open synclinal geometry. Later cross folding produced development of widespread dome and basin pattern at the sub-horizontal hinge zones of these synclinal fold belts. The major iron ore deposits in the eastern anticline at the present level of erosion are preferentially localized within shallow elongated basinal structures only. The axis of the adjoining western syncline was similarly uplifted as partial culminations where cross-folded against E–W anticlinal axes. But here, the BIF-iron ore bodies are preferentially localized within elongated domal structures in contrast to the basinal sites in the adjacent eastern anticline. Such an inference based on structural analysis could probably be utilized as a potential tool for all future explorations, reserve estimation and recovery of the iron ore deposits in the terrain.  相似文献   

Tropospheric disturbance of 17–21 December 1974 and its effect on microwave propagation     

A. P. Mitra  Y. V. Somayajulu  S. P. Singal  S. C. Majumdar  T. R. Tyagi  B. M. Reddy  S. K. Agarwal  B. S. Gera  A. B. Ghosh  S. K. Sarkar 《Boundary-Layer Meteorology》1977,11(1):103-116

A number of troposphere-monitoring experiments were pressed into service during a large tropospheric disturbance which lasted for several days in December 1974. The experiments operated intensively included a monostatic Sodar system, a satellite radio beacon receiver at very low elevation angles, Meteorological Radiosondes, a 250-kW weather radar, a microwave LOS link and a microbarograph. This multi-pronged campaign yielded very useful results and the correspondences between various observations were striking. The Sodar and microwave link observations were visibly affected only when N reached a value of about –70 units; however, the satellite beacon observations showed anomalous behaviour even for lower N values. Rather spectacular coincidences occurred on one night: the large fading (up to 10 db) in the LOS link; highly disturbed conditions displayed in the entire Sodar range; the largest tropospheric effect on the satellite beacon system; and the most active superrefraction of the radar echoes. It was also noticed that these effects are obvious only during nights, while they remain masked or dampened in the sun-lit hours.  相似文献