Alipurduar College

West Bengal, India

Alipurduar College

West Bengal, India

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Thakur P.,Alipurduar College
Pramana - Journal of Physics | Year: 2017

Recent observational predictions suggest that our Universe is passing through an accelerating phase in the recent past. This acceleration may be realized with the negatively pressured dark energy. Generalized Chaplygin gas may be suitable to describe the evolution of the Universe as a candidate of unified dark matter energy (UDME) model. Its EoS parameters are constrained using (i) dimensionless age parameter (H0t0) and (ii) the observed Hubble (H(z) - z) data (OHD) + baryon acoustic oscillation (BAO) data + cosmic microwave background (CMB) shift data + supernovae (Union2.1) data. Dimensionless age parameter puts loose bounds on the EoS parameters. Best-fit values of the EoS parameters H0, As and α (As and α are defined in the energy density for generalized Chaplygin gas (GCG) and in EoS) are then determined from OHD+BAO+CMB+ Union2.1 data and contours are drawn to obtain their allowed range of values. The present age of the Universe (t0) and the present Hubble parameter (H0) have been estimated with 1σ confidence level. Best-fit values of deceleration parameter (q), squared sound speed (c2 s ) and EoS parameter (ω) of this model are then determined. It is seen that GCG satisfactorily accommodates an accelerating phase and structure formation phase.

Paul B.C.,North Bengal University | Thakur P.,Alipurduar College
Journal of Cosmology and Astroparticle Physics | Year: 2013

We investigate the linear growth function for the large scale structures of the universe considering modified Chaplygin gas as dark energy. Taking into account observational growth data for a given range of redshift from the Wiggle-Z measurements and rms mass fluctuations from Ly-α measurements we numerically analyze cosmological models to constrain the parameters of the MCG. The observational data of Hubble parameter with redshift z is also considered. The Wang-Steinhardt ansatz for growth index γ and growth function f (defined as f = Ωmγ(a)) are considered for the numerical analysis. The best-fit values of the equation of state parameters obtained here is employed to study the growth function (f), growth index (γ) and equation of state (ω) with redshift z. The observational constraints on MCG parameters obtained here are compared with that of the GCG model for viable cosmology. It is noted that MCG also satisfactorily accommodates an accelerating phase followed by a matter dominated phase of the universe. © 2013 IOP Publishing Ltd and Sissa Medialab srl.

Ghosh S.,Jadavpur University | Das Burman A.,Indian Association for The Cultivation of Science | De G.C.,Alipurduar College | Das A.R.,Indian Association for The Cultivation of Science
Journal of Physical Chemistry B | Year: 2011

Interfacial and bulk properties of sodium dodecyl sulfate (SDS), polyoxyethylene (20) sorbitan monooleate (Tween-80), and their binary mixtures in aqueous medium have been investigated using surface tension, conductance, and fluorescence measurements at different temperatures. The critical micelle concentration (CMC), counterion binding, polarity index, aggregation number, thermodynamics of interfacial adsorption, and micellization are evaluated. The entropic contribution is found to be the predominant factor in micelle formation. The aggregation number and the polarity index of the micelle interior estimated by the pyrene fluorescence technique show interesting temperature dependence. The size and composition of the mixed micelles vary with the total concentration. The micellar compositions, activities of the individual components in the mixed species, and intersurfactant interactions are also estimated following regular solution theory, excess thermodynamic functions, and a molecular thermodynamic model. The surfactant mixtures are found to be nonideal with a lower degree of counterion binding compared to the individual members. Mixed micelles are nonspherical in nature at all temperatures when the mole fraction (α) of the ionic part in mixtures is high but transform to spherical when αSDS is ≥0.50. © 2011 American Chemical Society.

Paul B.C.,North Bengal University | Thakur P.,North Bengal University | Thakur P.,Alipurduar College | Ghose S.,North Bengal University
Monthly Notices of the Royal Astronomical Society | Year: 2010

We study a composition of normal and exotic matter which is required for a flat emergent universe scenario permitted by the equation of state (EOS) (p=Aρ-Bρ1/2) and predict the range of the permissible values for the parameters A and B to explore a physically viable cosmological model. The permitted values of the parameters are determined taking into account the H(z)-z data obtained from observations, a model-independent Baryon Acoustic Oscillation (BAO) peak parameter and cosmic microwave background shift parameter (WMAP7 data). It is found that although A can be very close to zero, most of the observations favours a small and negative A. As a consequence, the effective EOS parameter for this class of emergent universe solutions remains negative always. We also compared the magnitude [μ (z)] versus redshift (z) curve obtained in the model with that obtained from the union compilation data. According to our analysis the class of emergent universe solutions considered here is not ruled out by the observations. © 2010 The Authors. Journal compilation © 2010 RAS.

Paul B.C.,North Bengal University | Thakur P.,Alipurduar College | Saha A.,Jalpaiguri Government Engineering College
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We present cosmological models with modified Chaplygin gas (MCG) in the framework of Horava-Lifshitz (HL) theory of gravity. The equation of state (EOS) for a MCG is a three-variable equation determined by A, α, B. The allowed values of these parameters of the EOS are determined using the recent astrophysical and cosmological observational data. For this we consider H(z)-z, BAO peak, CMB shift parameter data to obtain a suitable range of values of the parameters for a viable cosmological model. Considering the suitable range of effective neutrino parameter (ΔN ν), the ranges of values of the B-parameter along with A S (defined by A, α, and B) and α are determined here by chi-square minimization. © 2012 American Physical Society.

Ghose S.,North Bengal University | Thakur P.,Alipurduar College | Paul B.C.,North Bengal University
Monthly Notices of the Royal Astronomical Society | Year: 2012

A class of emergent universe models is studied in the light of recent observational data. Significant constraints on model parameters are obtained from these observations. The density parameter for a class of models is also evaluated. Some of the models are in accordance with recent observations. Others are not of interest, yielding unrealistic present-day values of the density parameter. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Paul B.C.,North Bengal University | Ghose S.,North Bengal University | Thakur P.,North Bengal University | Thakur P.,Alipurduar College
Monthly Notices of the Royal Astronomical Society | Year: 2011

A specific class of flat Emergent Universe (EU) is considered and its viability is tested in view of the recent observations. Model parameters are constrained from Stern data for Hubble parameter and redshift [H(z) versus z] and from a model-independent measurement of BAO peak parameter. It is noted that a composition of exotic matter, dust and dark energy, capable of producing an EU, cannot be ruled out with present data. Evolution of other relevant cosmological parameters, viz. density parameter (Ω) and effective equation of state (EOS) parameter (ω eff), are also shown. © 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Pal B.B.,Kalyani University | Kumar M.,Alipurduar College
Advances in Intelligent Systems and Computing | Year: 2014

This paper presents an extended version of goal programming (GP) approach for modeling and solving farm planning problems having objectives with interval parameter sets by utilizing farming resources in the planning horizon. In the model formulation of the problem, the defined goals with interval parameters are converted into conventional goals by using interval arithmetic technique in interval programming and introducing under- and over-deviational variables to each of them. In the decision process, extended GP (EGP) approach, i.e. convex combination of both the modelling aspects, minsum GP and minmax GP are addressed in the achievement function for minimizing the possible regret towards goal achievement from the optimistic point of view in the inexact decision making environment. The potential use of the approach is demonstrated via a case example.

Incidence of whitefly, Bemisia tabaci population in tomato crop field was assessed. The population was initiated at about 48 standard meteorological weeks (SMW), improved at first slowly up to 1 SMW then steadily up to 5 SMW attaining the maximum at about 6 SMW which was maintained up to about 9 SMW. The population then declined at first slowly then abruptly. Incidence of tomato yellow leaf curl virus disease (TYLCV) was befitted with B. tabaci incidence. Maximum and minimum value of TYLCV was noted at about 15 and 50 SMW respectively. Abiotic conditions had significant negative influence on B. tabaci population. In case of relative humidity gradient a positive influence was observed. A time-fitted early-season cultivation of tomato crop was economically prudent to minimize white fly menace.

Bagchi B.,Alipurduar College
International Journal of Services and Operations Management | Year: 2014

This study comprehensively excavates the general relationship and causality between liquidity management and corporate profitability for Indian CPSEs (central public sector enterprises). Liquidity indices like current ratio, liquid ratio, absolute liquid ratio and cash conversion cycle are taken as explanatory variables, whereas, age of creditors, age of debtors, age of inventory and the natural logarithm of sales are taken as control variables. Profitability is measured in terms of return on total assets. The sample size is restricted to 48 Indian CPSEs listed on the National Stock Exchange (NSE) and Bombay Stock Exchange (BSE) of India and the secondary data for analysis is retrieved from CMIE (Centre for Monitoring Indian Economy) for a ten-year period from 2002-2003 to 2011-2012. Statistical and econometric tools like, descriptive statistics, unit root test, fixed effects regression model and Granger causality test are employed in the study. Granger causality test suggests the evidence of feedback causality running between current ratio, liquid ratio, absolute liquid ratio and cash conversion cycle with return on total assets, while, unidirectional causality is found to be running from firms' size to return on total assets. Copyright © 2014 Inderscience Enterprises Ltd.

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