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   

Obituary     

Sudipta Sengupta 《Journal of the Geological Society of India》2009,74(2):277-278

  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   

A numerical study on the role of atmospheric forcing on mixed layer depth variability in the Bay of Bengal using a regional ocean model     

Dandapat  Sumit  Chakraborty  Arun  Kuttippurath  Jayanarayanan  Bhagawati  Chirantan  Sen  Radharani 《Ocean Dynamics》2021,71(10):963-979

Ocean Dynamics - This study investigates the role of driving atmospheric forces [winds, net heat flux, and evaporation–precipitation (E–P)] and the possible mechanisms on the mixed...  相似文献   

Anisotropic cosmological models with bulk viscosity for variable <Emphasis Type="Italic">G</Emphasis> and Λ     

Subenoy Chakraborty  Anusua Roy 《Astrophysics and Space Science》2008,313(4):389-392

In this paper we have considered axially symmetric Bianchi-I, Kantowski Sachs and Bianchi-III space-time models with bulk viscosity, where the gravitational constant G and the cosmological term Λ vary with time. In Einstein equations this variation in G and Λ are taken in such a way as to preserve the energy momentum tensor. Solutions are obtained with the cosmological term varying inversely with square of time.  相似文献   

Cancer risks from exposure to vehicular air pollution: a household level analysis of intra-ethnic heterogeneity in Miami,Florida     

Jayajit Chakraborty  Timothy W. Collins  Sara E. Grineski 《Urban geography》2017,38(1):112-136

Quantitative environmental justice (EJ) research has relied on aggregated data from census units to determine disproportionate hazard exposure. Additionally, variables typically used to analyze ethnic inequities in exposure (e.g., percent Hispanic) are too broad and assume a degree of homogeneity that may not exist, given the diversity of ethnic minority populations. We address these limitations through a study that utilizes primary household level survey data and cancer risk estimates from the National-Scale Air Toxics Assessment (NATA) to analyze intra-ethnic inequities in exposure to vehicular air pollutants in the Miami metropolitan area, Florida. Our analysis disaggregates the Hispanic category based on five characteristics (language proficiency, U.S. citizenship, nativity, unemployment status, and national origin) and finds that risk burdens are significantly higher for Hispanic respondents who are foreign-born, unemployed, and of Cuban origin. Findings highlight the advantages of downscaling EJ analyses to the household level and considering intra-ethnic heterogeneity in EJ research and policy.  相似文献   

Lagoon–tidal flat sedimentation in an epeiric sea: Proterozoic Bhander Group,Son Valley,India     

Chandan Chakraborty 《Geological Journal》2001,36(2):125-141

The Bhander Group, the uppermost stratigraphic unit of the Proterozoic Vindhyan Supergroup in Son Valley, exhibits in its upper part a 550 m thick, muddy siliciclastic succession characterized by features indicative of deposition in a wave‐affected coastal, lagoon–tidal flat environment suffering repeated submergence and emergence. The basic architecture of the deposit is alternation of centimetre‐ to decimetre‐thick sheet‐like interbeds of coarser clastics (mainly sandstone) and decimetre‐thick mudstones. The coarser interlayers are dominated by a variety of ripple‐formed laminations. The preserved ripple forms on bed‐top surfaces and their internal lamination style suggest both oscillatory and combined flows for their formation. Interference, superimposed, ladder‐back and flat‐topped ripples are also common. Synsedimentary cracks, wrinkle marks, features resembling rain prints and adhesion structures occur in profusion on bed‐top surfaces. Salt pseudomorphs are also present at the bases of beds. The mudstone intervals represent suspension settlement and show partings with interfaces characterized by synsedimentary cracks. It is inferred that the sediments were deposited on a coastal plain characterized by a peritidal (supratidal–intertidal) flat and evaporative lagoon suffering repeated submergence and emergence due to storm‐induced coastal setup and setdown in addition to tidal fluctuations. The 550 m thick coastal flat succession is surprisingly devoid of any barrier bar deposits and also lacks shoreface and shelfal strata. The large areal extent of the coastal flat succession (c. 100,000 km²) and its great thickness indicate an extremely low‐gradient epeiric basin characterized by an extensive coastal flat sheltered from the deeper marine domain. It is inferred that the Bhander coastal flat was protected from the open sea by the Bundelkhand basement arch to the north of the Vindhyan basin, instead of barrier bars. Such a setting favoured accumulation of a high proportion of terrigenous mud in the coastal plain, in contrast to many described examples from the Proterozoic. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Scalar-tensor theory of gravity and generalized second law of?thermodynamics on?the?event horizon     

Nairwita Mazumder  Subenoy Chakraborty 《Astrophysics and Space Science》2011,332(2):509-513

Here we consider our universe as homogeneous spherically symmetric FRW model and analyze the thermodynamics of this model of the universe in scalar-tensor theory. Assuming the first law of thermodynamics validity of the generalized second law of thermodynamics (GSLT) at the event horizon is examined in both the cases when the universe is filled with perfect fluid and the holographic dark energy.  相似文献   

Seasonal and Monthly Variation of Vertical Structure of Temperature,Salinity and Heat Flux of the Bay of Bengal     

Bishnu Kumar  Sourav Sil  P. C. Pandey  Arun Chakraborty 《Marine Geodesy》2013,36(1):76-99

Seasonal and monthly variations of heat flux have been investigated in this study using the Modular Ocean Model of version 3 (MOM 3) simulations and 52 years Simple Ocean Data Assimilation (SODA) products. These variations of the heat flux in different boxes of the Bay of Bengal (BOB) in different depths show the different behavior of the boxes. It is seen that the model and SODA results are comparable. The basin shows north-south variation in the surface from winter to spring whereas there is east-west variation in the mixed layer throughout the year except winter. The remote effect caused by warm water penetration from Pacific Ocean through the Strait of Malacca and coastal Kelvin waves keeps the basin warm most of the year. This article addresses the mechanisms of the seasonal variation of the vertical structure of the temperature and heat flux components.  相似文献   

Compositionally zoned crystals and real-time degassing data reveal changes in magma transfer dynamics during the 2006 summit eruptive episodes of Mt. Etna     

Maren Kahl  Sumit Chakraborty  Fidel Costa  Massimo Pompilio  Marco Liuzzo  Marco Viccaro 《Bulletin of Volcanology》2013,75(2):1-14

One of the major objectives of volcanology remains relating variations in surface monitoring signals to the magmatic processes at depth that cause these variations. We present a method that enables compositional and temporal information stored in zoning of minerals (olivine in this case) to be linked to observations of real-time degassing data. The integrated record may reveal details of the dynamics of gradual evolution of a plumbing system during eruption. We illustrate our approach using the 2006 summit eruptive episodes of Mt. Etna. We find that the history tracked by olivine crystals, and hence, most likely the magma pathways within the shallow plumbing system of Mt. Etna, differed considerably between the July and October eruptions. The compositional and temporal record preserved in the olivine zoning patterns reveal two mafic recharge events within months of each other (June and September 2006), and each of these magma supplies may have triggered the initiation of different eruptive cycles (July 14–24 and August 31–December 14). Correlation of these observations with gas monitoring data shows that the systematic rise of the CO₂/SO₂ gas values is associated with the gradual (pre- and syn-eruptive) supply of batches of gas-rich mafic magma into segments of Etna’s shallow plumbing system, where mixing with pre-existing and more evolved magma occurred.  相似文献