Quasi-spherical collapse with cosmological constant     

Ujjal Debnath  Soma Nath  Subenoy Chakraborty 《Monthly notices of the Royal Astronomical Society》2006,369(4):1961-1964

The junction conditions between static and non-static space–times are studied for analysing gravitational collapse in the presence of a cosmological constant. We have discussed about the apparent horizon and their physical significance. We also show the effect of cosmological constant in the collapse and it has been shown that cosmological constant slows down the collapse of matter.  相似文献   

A Study of an Inhomogeneous Bianchi-I Model in Lyra Geometry     

Farook Rahaman  Subenoy Chakraborty  Jayanta Kr. Bera 《Astrophysics and Space Science》2002,281(3):595-600

The inhomogeneous Bianchi-I model based on Lyra's geometry has been studied in the cosmological theory in presence of a massless inhomogeneous scalar field whose potential has a flat part. The field equations are solved using separation of variables and it is shown that one of the time part of the field equations are solvable for any arbitrary other cosmic scale function. Solutions for a particular form of cosmic scale (time part) is presented. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Estimation of Raft Settlement Based on Linear Elastic Finite Element Analysis     

Bhartiya  Priyanka  Chakraborty  Tanusree  Basu  Dipanjan 《Geotechnical and Geological Engineering》2022,40(6):2907-2919

Geotechnical and Geological Engineering - A detailed parametric study based on linear-elastic three-dimensional finite element (FE) analysis with proper raft–soil interaction is performed for...  相似文献   

Hazardous air pollutants and flooding: a comparative interurban study of environmental injustice   总被引：1，自引：0，他引：1  

Sara Grineski  Timothy W. Collins  Jayajit Chakraborty  Marilyn Montgomery 《GeoJournal》2015,80(1):145-158

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Structure and stability of rotating fluid disks around massive objects. I. Newtonian formulation     

D. K. Chakraborty  A. R. Prasanna 《Journal of Astrophysics and Astronomy》1981,2(4):421-437

In this paper we have presented a very general class of solutions for rotating fluid disks around massive objects (neglecting the self gravitation of the disk) with density as a function of the radial coordinate only and pressure being nonzero. Having considered a number of cases with different density and velocity distributions, we have analysed the stability of such disks under both radial and axisymmetric perturbations. For a perfect gas disk with γ= 5/3 the disk is stable with frequency (MG/r³)^1/2 for purely radial pulsation with expanding and contracting boundary. In the case of axisymmetric perturbation the critical γ_c for neutral stability is found to be much less than 4/3 indicating that such disks are mostly stable under such perturbations. On leave of absence from Government College, Jagdalpur 494005.  相似文献   

General relativistic analysis of structure and stability of charged fluid disks around compact objects     

A. R. Prasanna  D. K. Chakraborty 《Journal of Astrophysics and Astronomy》1981,2(1):1-27

In this paper we give a detailed general relativistic formulation of the study of structure and stability of charged fluid disks around compact objects like black holes neglecting the self-gravitation of the disk itself. Having presented the general equations for equilibrium as well as for perturbations we solve explicitly the cases of rigidly and differentially rotating thin disks, with constant charge density and zero pressure, confined to the equatorial plane of the black hole. By using normal mode analysis we have analysed the stability of such disks under purely radial perturbations and find that the disks are generally stable. On leave of absence from Government College, Jagadalpur 494005  相似文献   

Analysis of temporal sar and optical data for rice mapping     

Indrani?ChoudhuryEmail author  M.?Chakraborty 《Journal of the Indian Society of Remote Sensing》2004,32(4):373-385

This study investigates the potential of multi-temporal signature analysis of satellite imagery to map rice area in South 24 Paraganas district of West Bengal. Two optical data (IRS ID LISS III) and three RADARSAT SAR data of different dates were acquired during 2001. Multi-temporal SAR backscatter signatures of different landcovers were incorporated into knowledge based decision rules and kharif landcover map was generated. Based on the spectral variation in signature, the optical data acquired during rabi (January) and summer (March) season were classified using supervised maximum likelihood classifier. A co-incidence matrix was generated using logical approach for a combined “rabi-summer” and “kharif-rabi-summer” landcover mapping. The major landcovers obtained in South 24 Paraganas using remote sensing data are rice, water, aquaculture ponds, homestead, mangrove, and urban area. The classification accuracy of rice area was 98.2% using SAR data. However, while generating combined “kharif-rabi-summer” landcovers, the classification accuracy of rice area was improved from 81.6% (optical data) to 96.6% (combined SAR-Optical). The primary aim of the study is to achieve better accuracy in classifying rice area using the synergy between the two kinds of remotely sensed data.  相似文献   

Tropical systematic and random error energetics based on NCEP (MRF) analysis-forecast system — A barotropic approach     

S. De  D. R. Chakraborty 《Journal of Earth System Science》2004,113(2):151-166

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Effect of modified Chaplygin gas in anisotropic universe     

Shuvendu Chakraborty  Ujjal Debnath 《Astrophysics and Space Science》2009,321(1):53-56

In this work, we have studied the model of modified Chaplygin gas and its role in accelerating phase of the universe for anisotropic model. We have assumed that the equation of state of this modified model is valid from the radiation era to ΛCDM model. We have obtained the possible relation between the hessence and the modified Chaplygin gas. We have also use the statefinder parameters for characterize different phase of the universe diagrammatically.  相似文献   

High-resolution satellite image segmentation using Hölder exponents     

Debasish Chakraborty  Gautam Kumar Sen  Sugata Hazra 《Journal of Earth System Science》2009,118(5):609-617

Texture in high-resolution satellite images requires substantial amendment in the conventional segmentation algorithms. A measure is proposed to compute the Hölder exponent (HE) to assess the roughness or smoothness around each pixel of the image. The localized singularity information is incorporated in computing the HE. An optimum window size is evaluated so that HE reacts to localized singularity. A two-step iterative procedure for clustering the transformed HE image is adapted to identify the range of HE, densely occupied in the kernel and to partition Hölder exponents into a cluster that matches with the range. Hölder exponent values (noise or not associated with the other cluster) are clubbed to a nearest possible cluster using the local maximum likelihood analysis.  相似文献