6,844 research outputs found
Nonparametric efficiency analysis under uncertainty Jati K. Sengupta*
No full textProduction and cost frontiers of a firm in an industry are directly affected by the uncertainty of market demand and the uncertainty of input availability. The nonparametric approach of data envelopment analysis is generalized here in both static and dynamic directions by incorporating these uncertainties. Keywords: production and cost efficiency; demand and supply uncertainty; growth and level efficiency _________________________ * Fax: 805-893-3797; e-mail: [email protected] 1
Spatio-temporal growth of disturbances in a boundary layer and energy based receptivity analysis
No full textIn fluid dynamical systems, it is not known a priori whether disturbances grow either in space or in time or as spatio-temporal structures. However, for boundary layers, it is customary to treat it as a spatial problem and some limited comparison between prediction and laboratory experiments exist. In the present work, the receptivity problem of a zero pressure gradient boundary layer excited by a localized harmonic source is investigated under the general spatio-temporal framework, using the Bromwich contour integral method. While this approach has been shown to be equivalent to the spatial study, for unstable systems excited by a single frequency source [T. K. Sengupta, M. Ballav, and S. Nijhawan, Phys. Fluids6, 1213 (1994)], here we additionally show, how the boundary layer behaves when it is excited (i) at a single frequency that corresponds to a stable condition (given by spatial normal-mode analysis) and (ii) by wideband frequencies, that shows the possibility of flow transition due to a spatio-temporally growing forerunner or wave front. An energy based receptivity analysis tool is also developed as an alternative to traditional instabilitytheory. Using this, we reinterpret the concept of critical layer that was originally postulated to explain the mathematical singularity of inviscid disturbance field in traditional instabilitytheory of normal modes
A general skew-t mixed model that allows different degrees of freedom for random effects and error distributions
No full textAbstract not availablePankaj K. Choudhary, Dishari Sengupta, Phillip Casse
Theory of tunneling conductance of graphene normal metal-insulator-superconductor junctions
No full textWe calculate the tunneling conductance of a graphene normal metal-insulator-superconductor (NIS) junction with a barrier of thickness d and with an arbitrary voltage applied across the barrier region. We demonstrate that the tunneling conductance of such a NIS junction is an oscillatory function of both d and . We also show that the periodicity and amplitude of such oscillations deviate from their universal values in the thin barrier limit as obtained in an earlier work [S. Bhattacharjee and K. Sengupta, Phys. Rev. Lett. 97, 217001 (2006)] and become a function of the applied voltage . Our results reproduce the earlier results on tunneling conductance of such junctions in the thin [S. Bhattacharjee and K. Sengupta, Phys. Rev. Lett. 97, 217001 (2006)] and zero [C. W. J. Beenakker, Phys. Rev. Lett. 97, 067007 (2006)] barrier limits as special limiting cases. We discuss the experimental relevance of our results
Theory of tunneling conductance of graphene normal metal-insulator-superconductor junctions
No full textWe calculate the tunneling conductance of a graphene normal metal-insulator-superconductor (NIS) junction with a barrier of thickness d and with an arbitrary voltage V0 applied across the barrier region. We demonstrate that the tunneling conductance of such a NIS junction is an oscillatory function of both d and V0. We also show that the periodicity and amplitude of such oscillations deviate from their universal values in the thin barrier limit as obtained in an earlier work [ S. Bhattacharjee and K. Sengupta Phys. Rev. Lett. 97 217001 (2006)] and become a function of the applied voltage V0. Our results reproduce the earlier results on tunneling conductance of such junctions in the thin [ S. Bhattacharjee and K. Sengupta Phys. Rev. Lett. 97 217001 (2006)] and zero [ C. W. J. Beenakker Phys. Rev. Lett. 97 067007 (2006)] barrier limits as special limiting cases. We discuss the experimental relevance of our results
Book review: Rakhshanda Jalil, Tarun K. Saint and Debjani Sengupta (Eds), Looking Back: The 1947 Partition of India, 70 Years On
No full text Rakhshanda Jalil, Tarun K. Saint and Debjani Sengupta (Eds), Looking Back: The 1947 Partition of India, 70 Years On. Hyderabad: Orient BlackSwan, 2017, 355 pp., ₹1095, ISBN: 9789386689566 (Hardbound). </jats:p
Uniform Bounds on Product Sylvester-Gallai Configurations
No full textIn this work, we explore a non-linear extension of the classical Sylvester-Gallai configuration. Let be an algebraically closed field of characteristic zero, and let ℱ = {F_1, …, F_m} ⊂ [x_1, …, x_N] denote a collection of irreducible homogeneous polynomials of degree at most d, where each F_i is not a scalar multiple of any other F_j for i ≠ j. We define ℱ to be a product Sylvester-Gallai configuration if, for any two distinct polynomials F_i, F_j ∈ ℱ, the following condition is satisfied: ∏_{k≠i, j} F_k ∈ rad (F_i, F_j) .
We prove that product Sylvester-Gallai configurations are inherently low dimensional. Specifically, we show that there exists a function λ : ℕ → ℕ, independent of , N, and m, such that any product Sylvester-Gallai configuration must satisfy: dim(span_(ℱ)) ≤ λ(d).
This result generalizes the main theorems from (Shpilka 2019, Peleg and Shpilka 2020, Oliveira and Sengupta 2023), and gets us one step closer to a full derandomization of the polynomial identity testing problem for the class of depth 4 circuits with bounded top and bottom fan-in
High Economic Growth, Equity and Sustainable Energy Development of India
No full textIndia has been experiencing sustained high economic growth in the recentyears. However, there exists substantial amount of unacceptable poverty among the people in the country. The expressions of symptoms of such poverty include among others inadequate educational and health attainment of the people and lack of access to basic amenities like modern clean energy, safe water and sanitation which are crucial determinants of capability development. There exists in fact significant amount of energy poverty among the people, particularly in the rural India which has more than 70% share of its population, in the form of use of traditional inefficient biomass as the primary fuel with injurious health effect and the lack of connectivity of the households with electricity. The eleventh five year plan of India which has recently been initiated has taken the approach of inclusive faster growth for the development of the Indian economy. This paper analyses the implications of this high inclusive growth in respect of the twin challenges of environmental sustainability of the energy use required by such growth and the removal of energy poverty, which have to be addressed in India's energy planning. The paper defines the concept of sustainable development and points out its resource accounting implications in respect of energy related resource use. It focuses in this context on the instrumental role of the efficiency of energy use and energy supply, fuel composition and technology in determining the strength of the linkage between the GDP growth and the growth of energy use and that between the energy use and the pollution intensity of energy. The paper also defines, on the other hand, the notion of energy poverty and discusses the problem of equity and energy development in a dual society like that of India. It then reviews the past trend and pattern of energy use and the future projections of energy requirement and supply with special reference to the twin issues of equity and environmental sustainability. In this context it makes a decomposition analysis of the past energy use and CO2 emissions in India for examining its environmental sustainability and if economic reforms of India could make any impact on it. It makes further a brief review of the methodologies of projections and policy planning for the future energy sector development in India as existing in the recent literature. Finally, the paper discusses certain selected issues of energy security and macroeconomic viability of such energy development in the background of the sustained steep rise of oil prices and high cost of carbon free new technologies. It concludes by highlighting certain policy issues relating to pricing, technology and institution for the attainability of inclusive growth and particularly for meeting the gaps in such attainment that would possibly remain as per the existing alternative projections for the future. However, this paper does not pay any special attention to the climate change related global policy issues that would affect India and gives priority to the national level issues relating to energy equity and energy related environmental sustainability of Indian development.
A new phosphorus selective ion exchange resin was tested, improving the REM NUT process for nutrient recovery as struvite
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