117,777 research outputs found
The Structure and Freezing of fluids interacting via the Gay-Berne (n-6) potentials
We have calculated the pair correlation functions of a fluid interacting via
the Gay-Berne(n-6) pair potentials using the \PY integral equation theory and
have shown how these correlations depend on the value of n which measures the
sharpness of the repulsive core of the pair potential. These results have been
used in the density-functional theory to locate the freezing transitions of
these fluids. We have used two different versions of the theory known as the
second-order and the modified weighted density-functional theory and examined
the freezing of these fluids for and in the reduced
temperature range lying between 0.65 and 1.25 into the nematic and the smectic
A phases. For none of these cases smectic A phase was found to be stabilized
though in some range of temperature for a given it appeared as a metastable
state. We have examined the variation of freezing parameters for the
isotropic-nematic transition with temperature and . We have also compared
our results with simulation results wherever they are available. While we find
that the density-functional theory is good to study the freezing transitions in
such fluids the structural parameters found from the \PY theory need to be
improved particularly at high temperatures and lower values of .Comment: 21 Pages (in RevTex4), 6 GIF and 4 Postscript format Fig
You Manage What You Measure: Using Mobile Phones to Strengthen Outcome Monitoring in Rural Sanitation
This paper addresses the sanitation challenge in India, where it is home to the majority of people defecating in the open in the world and also one of the top rapidly growing emerging economies. The paper focuses on the need for a reliable and timely monitoring system to ensure investments in sanitation lead to commensurate outcomes
Multimedia congestion control: circuit breakers for unicast RTP sessions
The Real-time Transport Protocol (RTP) is widely used in telephony, video conferencing, and telepresence applications. Such applications are often run on best-effort UDP/IP networks. If congestion control is not implemented in these applications, then network congestion can lead to uncontrolled packet loss and a resulting deterioration of the user's multimedia experience. The congestion control algorithm acts as a safety measure by stopping RTP flows from using excessive resources and protecting the network from overload. At the time of this writing, however, while there are several proprietary solutions, there is no standard algorithm for congestion control of interactive RTP flows. This document does not propose a congestion control algorithm. It instead defines a minimal set of RTP circuit breakers: conditions under which an RTP sender needs to stop transmitting media data to protect the network from excessive congestion. It is expected that, in the absence of long-lived excessive congestion, RTP applications running on best-effort IP networks will be able to operate without triggering these circuit breakers. To avoid triggering the RTP circuit breaker, any Standards Track congestion control algorithms defined for RTP will need to operate within the envelope set by these RTP circuit breaker algorithms
q-Deformation of the Krichever-Novikov Algebra
The recent focus on deformations of algebras called quantum algebras can be
attributed to the fact that they appear to be the basic algebraic structures
underlying an amazingly diverse set of physical situations. To date many
interesting features of these algebras have been found and they are now known
to belong to a class of algebras called Hopf algebras [1]. The remarkable
aspect of these structures is that they can be regarded as deformations of the
usual Lie algebras. Of late, there has been a considerable interest in the
deformation of the Virasoro algebra and the underlying Heisenberg algebra
[2-11]. In this letter we focus our attention on deforming generalizations of
these algebras, namely the Krichever-Novikov (KN) algebra and its associated
Heisenberg algebra.Comment: AmsTex. To appear in Letters in Mathematical Physic
Friedmann model with viscous cosmology in modified gravity theory
In this paper, we introduce bulk viscosity in the formalism of modified
gravity theory in which the gravitational action contains a general function
, where and denote the curvature scalar and the trace of the
energy-momentum tensor, respectively within the framework of a flat
Friedmann-Robertson-Walker model. As an equation of state for prefect fluid, we
take , where and viscous term as a
bulk viscosity due to isotropic model, of the form , where and are constants, and
is the Hubble parameter. The exact non-singular solutions to the
corresponding field equations are obtained with non- viscous and viscous
fluids, respectively by assuming a simplest particular model of the form of
, where ( is a constant). A big-rip
singularity is also observed for at a finite value of cosmic time
under certain constraints. We study all possible scenarios with the possible
positive and negative ranges of to analyze the expansion history of
the universe. It is observed that the universe accelerates or exhibits
transition from decelerated phase to accelerated phase under certain
constraints of and . We compare the viscous models with the
non-viscous one through the graph plotted between scale factor and cosmic time
and find that bulk viscosity plays the major role in the expansion of the
universe. A similar graph is plotted for deceleration parameter with
non-viscous and viscous fluids and find a transition from decelerated to
accelerated phase with some form of bulk viscosity.Comment: 19 pages, 3 figures, the whole paper has been revised to improve the
quality of paper. Some references added. arXiv admin note: text overlap with
arXiv:1307.4262 by other author
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