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Natural Hazards - The state of Sikkim in India has many steep slopes and has been susceptible to landslides. Since 1968 there have been innumerable losses of lives and properties due to landslides.... 相似文献
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A. Roy B. S. S. Devi B. Debnath M. S. R. Murthy 《Journal of the Indian Society of Remote Sensing》2010,38(3):387-399
Development of forest connectivity and corridors are critical for biodiversity conservation and also ensures energy and genetic
exchange across greater spatial extent. A model has been developed to geospatially identify the potential ecological corridors
based on the vegetation type and land cover data in association with spatial disturbance profile. The model formulates the
route of least impedance due to (1) disturbance (a function of fragmentation, juxtaposition, Interspersion & proximity to
roads/settlements) and (2) vegetation type and land cover. This is because the movement of genetic information and materials
follow the path of least resistance across a landscape. The paper explores the utility of the approach to spatially generate
ecological corridors connecting 14 protected areas of Orissa. The model has been able to identify the potential route connecting
the different protected regions with 85–87% of the corridor in the natural areas. Of the 14 protected areas, only 12 could
be connected by the model as they confirm to the criteria for the corridor establishment. 相似文献
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Sourav Palit Sandip Kumar Chakrabarti Dipak Debnath A. R. Rao Anuj Nandi Vipin K. Yadav V. Girish 《Experimental Astronomy》2009,27(1-2):77-93
We present the results of simulations of shadows cast by a zone plate telescope which may have one to four pairs of zone plates. From the shadows we reconstruct the images under various circumstances. We discuss physical basis of the resolution of the telescope and demonstrate this by our simulations. We allow the source to be at a finite distance (diverging beam) as well as at an infinite distance (parallel beam) and show that the resolution is worsened when the source is nearby. By reconstructing the zone plates in a way that both the zone plates subtend the same solid angles at the source, we obtain back high resolution even for sources at a finite distance. We present simulated results for the observation of the galactic center and show that the sources of varying intensities may be reconstructed with accuracy. Results of these simulations would be of immense use in interpreting the X-ray images from recently launched CORONAS-PHOTON satellite. 相似文献
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Surajit Chattopadhyay Ujjal Debnath Goutami Chattopadhyay 《Astrophysics and Space Science》2008,314(1-3):41-44
In this letter, we have assumed that the Universe is filled in tachyonic field with potential, which gives the acceleration
of the Universe. For certain choice of potential, we have found the exact solutions of the field equations. We have shown
the decaying nature of potential. From recently developed statefinder parameters, we have investigated the role of tachyonic
field in different stages of the evolution of the Universe. 相似文献
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In this work, we have discussed the Maxwell’s electrodynamics in non-linear forms in FRW universe. The energy density and pressure for non-linear electrodynamics have been written in the electro-magnetic universe. The Einstein’s field equations for flat FRW model in loop quantum cosmology have been considered if the universe is filled with the matter and electro-magnetic field. We separately assumed the magnetic universe and electric universe. The interaction between matter and magnetic field have been considered in one section and for some particular form of interaction term, we have found the solutions of magnetic field and the energy density of matter. We have also considered the interaction between the matter and electric field and another form of interaction term has been chosen to solve the field equations. The validity of generalized second law of thermodynamics has been investigated on apparent and event horizons using Gibb’s law and the first law of thermodynamics for magnetic and electric universe separately. 相似文献
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Santanu Mondal Sandip K. Chakrabarti Dipak Debnath 《Astrophysics and Space Science》2014,353(1):223-231
Accretion flows having positive specific energy are known to produce outflows and winds which escape to a large distance. According to Two Component Advective Flow (TCAF) model, centrifugal pressure dominated region of the flow just outside the black hole horizon, with or without shocks, acts as the base of this outflow. Electrons from this region are depleted due to the wind and consequently, energy transfer rate due to inverse Comptonization of low energy photons are affected. Specifically, it becomes easier to cool this region and emerging spectrum is softened. Our main goal is to show spectral softening due to mass outflow in presence of Compton cooling. To achieve this, we modify Rankine-Hugoniot relationships at the shock front when post-shock region suffers mass loss due to winds and energy loss due to inverse Comptonization. We solve two-temperature equations governing an accretion flow around a black hole which include Coulomb exchange between protons and electrons and other major radiative processes such as bremsstrahlung and thermal Comptonization. We then compute emitted spectrum from this post-shock flow. We also show how location of standing shock which forms outer boundary of centrifugal barrier changes with cooling. With an increase in disc accretion rate \((\dot{m}_{d})\) , cooling is enhanced and we find that the shock moves in towards the black hole. With cooling, thermal pressure is reduced, and as a result, outflow rate is decreased. We thus directly correlate outflow rate with spectral state of the disc. 相似文献
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Ritabrata Sarkar Samir Mandal Dipak Debnath Tilak B. Kotoch Anuj Nandi A. R. Rao Sandip K. Chakrabarti 《Experimental Astronomy》2011,29(1-2):85-107
Hard X-ray detectors in space are prone to background signals due to the ubiquitous cosmic rays and cosmic diffuse background radiation that continuously bombards the satellites which carry the detectors. In general, the background intensity depends on the space environment as well as the material surrounding the detectors. Understanding the behavior of the background noise in the detector is very important to extract the precise source information from the detector data. In this paper, we carry out Monte Carlo simulations using the GEANT-4 toolkit to estimate the prompt background noise measured with the detectors of the RT-2 Experiment onboard the CORONAS-PHOTON satellite. 相似文献
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The Likelihood Ratio (LR) Model has been applied as an improvement upon the Frequency Ratio (FR) that computes the ratio of the percentage of the landslide pixels to the percentage of the non-landslide pixels instead of the total number of pixels used in the denominator as in case of the FR. The comparative assessment of the two techniques is made through spatial modelling of GIS vector data using the ArcGIS software. Two different Landslide Information Values were computed for each polygon element of the study area employing the two FR techniques that categorized the study area into five classes of vulnerability using natural breaks (Jenks) technique. Subsequently, vulnerability zonation maps were prepared showing the different levels of landslide vulnerability. The LR technique yielded significantly higher vulnerability assessment accuracy (77%) as compared to the standard FR (71%). 相似文献