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831.
832.
S. R. Das Gupta 《Astrophysics and Space Science》1978,56(1):13-20
The transfer equations for non-coherent scattering arising from interlocking of principal lines without redistribution is exactly solved in a very simple way by Laplace tranform and Wiener-Hopf technique which are easily applied by the use of the new representation ofH-functions obtained recently by the author (1977). The emergent intensity in therth line is expressed in terms of anH-function and a Cauchy type integral admitting of closed form evaluation. 相似文献
833.
D. B. Vaidya B. G. Anandarao J. N. Desai R. Gupta 《Journal of Astrophysics and Astronomy》2000,21(1-2):91-99
It has long been established that the ratio of total to selective extinction is anomalously large (>- 5) in certain regions
of the interstellar medium. In these regions of anomalous extinction the dust grains are likely to be irregular in shape and
fluffy in structure. Using discrete dipole approximation (DDA) we calculate the extinction for porous and fluffy grains. We
apply DDA first to solid spheroidal particles assumed to be made of a certain (large) number of dipoles. Then we systematically
reduce the number of dipoles to model the porous grains. The aggregates of these particles are suggested to form the fluffy
grains. We study the extinction for these particles as a function of grain size, porosity and wavelength. We apply these calculations
to interpret the observed extincttion data in the regions of star formation (e.g. the Orion complex). 相似文献
834.
In both sand quarry faces and boreholes the Old Alluvium of Singapore is a matrix supported pebbly sand with minor beds of better sorted sands and clays. The beds can be grouped into four textural classes (pebbles, coarse sand with fine pebbles, medium to coarse sand, clay, and silt), each with characteristic sedimentary structures. The deposit appears to be the proximal facies of an ancient braided river alluvium of possible Pleistocene age. This widespread but scattered alluvium is found both on land and offshore on the Sunda Shelf in Southeast Asia. It is believed to have been deposited during low sea levels. In Singapore, the mineralogy of the grains forming the Old Alluvium suggests a mixed provenance of granitic and low-grade metamorphic origin. The volume and freshness of the deposited material indicate an environment of considerable relief, seasonal rainfall, and extremely active erosional processes, conditions considerably different from the current ones. The Old Alluvium was probably deposited by seasonal rivers which experienced periodic large floods. Such regional conditions could have prevailed over much of Southeast Asia at the time of deposition of the Old Alluvium. 相似文献
835.
We employ Friden's algorithm based on the maximum likelihood principle to restore one-dimensional star image data in the presence of noise. The algorithm is made iterative and its performance discussed. 相似文献
836.
837.
838.
Bhattacharjee Sutapa Kumar Pramod Thakur Praveen K. Gupta Kshama 《Natural Hazards》2021,105(2):2117-2145
Natural Hazards - Urban flooding and waterlogging are causing menace in many cities around the world from the perspective of day-to-day functioning, health and hygiene, communication, and the... 相似文献
839.
840.