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Santiniketan, India

Majumdar P.,Muc Womens College | Samanta S.K.,Visva Bharati
Computers and Mathematics with Applications | Year: 2010

In this paper, we define generalised fuzzy soft sets and study some of their properties. Application of generalised fuzzy soft sets in decision making problem and medical diagnosis problem has been shown. © 2009 Elsevier Ltd. All rights reserved.

Nandy S.K.,A.K.P.C. Mahavidyalaya | Mahapatra T.R.,Visva Bharati
International Journal of Heat and Mass Transfer | Year: 2013

The objective of the present study is to analyze the effects of velocity slip and heat generation/absorption on magnetohydrodynamic (MHD) stagnation-point flow and heat transfer over a stretching/shrinking surface, with convective boundary conditions, in the presence of nanoparticle fractions. The effects of Brownian motion and thermophoresis are also considered. The velocity, temperature and nanoparticle concentration profiles are analyzed with respect to the involved parameters, namely, slip parameter (δ), magnetic parameter (M), source/sink parameter (λ), Brownian motion parameter (Nb), thermophoresis parameter (Nt), Prandtl number (Pr), Lewis number (Le), Biot number (γ) and ratio of the rate constants of stretching/shrinking velocity to the free stream velocity (α). The numerical results indicate that for the stretching sheet, the velocity at a point decreases with the increase in the values of δ and M; whereas both temperature and nanoparticle concentration increase with the increase in δ and M. It is also observed that the temperature of the fluid increases with the increase in heat source parameter (i.e. λ > 0). Different from a stretching sheet, it is found that for a shrinking sheet the solutions are non-unique. A comparative study between the previously published results and the present results for a special case is found to be in good agreement. © 2013 Elsevier Ltd. All rights reserved.

This paper deals with capitalist agricultural development in West Bengal, India. Based on a field study of two regions at different ends of the development spectrum, it shows the class-specific nature of agrarian development. Farms based on hired labour adopt more capital-intensive techniques, operate on a much larger scale and have higher yields in comparison to farms based on family labour, regardless of their size. Differentiation of the peasantry is intense where the adoption of capital-intensive technology is high. The paper concludes that the arguments of A.V. Chayanov and A.K. Sen, which seek to explain the inverse relation between farm size and productivity in terms of the superior efficiency of farms based on family labour compared to capitalist farms, are not borne out by our findings. Moreover, in the advanced region of Bardhaman, farmers of all economic classes are found to be subject to a form of compulsive exchange or stressed commerce brought about by traders external to the region. © 2011 Blackwell Publishing Ltd.

Ghosh S.,Visva Bharati
Journal of the Optical Society of America B: Optical Physics | Year: 2013

The group index and its lineshape parameters of a relatively weak double-resonance probe pulse (signal) propagating through an open doubly driven M-type five-level atomic system are analytically formulated. It is shown for the first time, to our knowledge, that the group velocity status of the signal can be altered (between superluminal and subluminal propagation) by the combined effect of atomic coherence and linear AC Stark shift through coherent coupling. The distinct feature in this scheme is that, although it does not rely on electromagnetically induced transparency, a double-switching effect (i.e., from superluminal to subluminal and vice versa) is observed with negligible absorption/gain at two different frequency regimes. © 2013 Optical Society of America.

Ghosh S.,Visva Bharati
Journal of the Optical Society of America B: Optical Physics | Year: 2012

A detailed analytical description of a Doppler-free probe response (absorption and dispersion) is presented for a coherently prepared four-level atomic tripod driven by two coupling fields. Under the density matrix formalism the field-dependent and field-independent coherence are introduced through the off-diagonal matrix elements. Field-dependent coherence appears due to the interference between the probability amplitudes of finding the atom in energy levels associated with the allowed transition, while field-independent phases measure the atomic coherence for a coherently prepared lower state triplet. The double-control coherent effects on the probe response are investigated by controlling the relative driving contribution (coherence) of the two coupling fields, whereas the driving contribution can be controlled by the use of field-independent coherence, along with two coupling parameters like Rabi frequency and detuning of the respective coupling field. We report on the possibility of modifying the Rabi splitting into a perfect electromagnetically induced transparent window at probe resonance by a coherent double-control mechanism in an on-resonance coupling situation. Moreover, for off-resonance coupling, we exhibit the enhancement of multiphoton (two- or three-photon) absorption via coherent control of multiresonance processes. © 2012 Optical Society of America.

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