90,526 research outputs found

    In Re: Rajesh Mehta

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    United States District Court for the District of New Jerse

    Visual perception based bit allocation for low bitrate video coding

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    Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (leaves 45-47).by Rajesh Suryadevara.M.S

    The Culture of Science: How the Public Relates to Science across the Globe

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    edited by Martin W. Bauer, Rajesh Shukla and Nick Allum, published by Routledge, 711 Third Avenue, New York, NY 10017, 201

    Why we should thank Donald Trump for making a Hillary Clinton presidency possible.

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    Now that the imminent danger of a Donald Trump victory in November is not so imminent, Rajesh Venugopal writes that perhaps now we can look beyond the fear and outrage to reflect on the legacy that Trump’s candidacy leaves behind

    Reflections on a masterclass: poverty, social welfare and data in Sri Lanka

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    As part of the first ever Colombo Development Dialogue held in April 2018, a masterclass with Dr Rajesh Venugopal was organised by South Asia Centre, LSE in collaboration with UNDP in Sri Lanka. Amayaa Wijesinghe, of the University of Colombo, reports her experience

    Variation of the gas and radiation content in the sub-Keplerian accretion disk around black holes and its impact to the solutions

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    We investigate the variation of the gas and the radiation pressure in accretion disks during the infall of matter to the black hole and its effect to the flow. While the flow far away from the black hole might be non-relativistic, in the vicinity of the black hole it is expected to be relativistic behaving more like radiation. Therefore, the ratio of gas pressure to total pressure (beta) and the underlying polytropic index (gamma) should not be constant throughout the flow. We obtain that accretion flows exhibit significant variation of beta and then gamma, which affects solutions described in the standard literature based on constant beta. Certain solutions for a particular set of initial parameters with a constant beta do not exist when the variation of beta is incorporated appropriately. We model the viscous sub-Keplerian accretion disk with a nonzero component of advection and pressure gradient around black holes by preserving the conservations of mass, momentum, energy, supplemented by the evolution of beta. By solving the set of five coupled differential equations, we obtain the thermo-hydrodynamical properties of the flow. We show that during infall, beta of the flow could vary upto ~300%, while gamma upto ~20%. This might have a significant impact to the disk solutions in explaining observed data, e.g. super-luminal jets from disks, luminosity, and then extracting fundamental properties from them. Hence any conclusion based on constant gamma and beta should be taken with caution and corrected.Comment: 22 pages including 8 figures; published in New Astronom

    Transition from radiatively inefficient to cooling dominated phase in two temperature accretion discs around black holes

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    We investigate the transition of a radiatively inefficient phase of a viscous two temperature accreting flow to a cooling dominated phase and vice versa around black holes. Based on a global sub-Keplerian accretion disc model in steady state, including explicit cooling processes self-consistently, we show that general advective accretion flow passes through various phases during its infall towards a black hole. Bremsstrahlung, synchrotron and inverse Comptonization of soft photons are considered as possible cooling mechanisms. Hence the flow governs a much lower electron temperature ~10^8 - 10^{9.5}K compared to the hot protons of temperature ~10^{10.2} - 10^{11.8}K in the range of the accretion rate in Eddington units 0.01 - 100. Therefore, the solutions may potentially explain the hard X-rays and the gamma-rays emitted from AGNs and X-ray binaries. We finally compare the solutions for two different regimes of viscosity and conclude that a weakly viscous flow is expected to be cooling dominated compared to its highly viscous counterpart which is radiatively inefficient. The flow is successfully able to reproduce the observed luminosities of the under-fed AGNs and quasars (e.g. Sgr A*), ultra-luminous X-ray sources (e.g. SS433), as well as the highly luminous AGNs and ultra-luminous quasars (e.g. PKS 0743-67) at different combinations of the mass accretion rate and ratio of specific heats.Comment: 13 pages including 8 figures; couple of typos corrected; to appear in Research in Astronomy and Astrophysic
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