1,326 research outputs found
Inhomogeneous imperfect fluid spherical models without Big-Bang singularity
So far all known singularity-free cosmological models are cylindrically
symmetric. Here we present a new family of spherically symmetric non-singular
models filled with imperfect fluid and radial heat flow, and satisfying the
weak and strong energy conditions. For large anisotropy in pressure and
heat flux tend to vanish leading to a perfect fluid. There is a free function
of time in the model, which can be suitably chosen for non-singular behaviour
and there exist multiplicity of such choices.Comment: 8 pages, LaTeX versio
Design and analysis of movable boundary allocation protocol
The increasing digital communications traffic will require very high speed networks. The use of high communication speed increases the ratio between end to end propagation delay and the packet transmission time. This increase causes rapid performance deterioration and restricts the utilization of the high system bandwidth in broadcast channel based systems. Using several parallel channels in place of a single channel improves this ratio. For a given system bandwidth the total system capacity is increased by bandwidth division and parallel communication. FTDMA protocols have been suggested for the parallel channel network and these protocols are suitable for different loads. In this thesis, the movable boundary allocation protocol has been suggested for the parallel communication architecture. This protocol is suitable for varying loads and yields a better throughput versus delay characteristics. The analysis demonstrates the potential for improvement in the system capacity and the average message delay when compared to conventional single channel system
Early Identification of Violent Criminal Gang Members
Gang violence is a major problem in the United States accounting for a large
fraction of homicides and other violent crime. In this paper, we study the
problem of early identification of violent gang members. Our approach relies on
modified centrality measures that take into account additional data of the
individuals in the social network of co-arrestees which together with other
arrest metadata provide a rich set of features for a classification algorithm.
We show our approach obtains high precision and recall (0.89 and 0.78
respectively) in the case where the entire network is known and out-performs
current approaches used by law-enforcement to the problem in the case where the
network is discovered overtime by virtue of new arrests - mimicking real-world
law-enforcement operations. Operational issues are also discussed as we are
preparing to leverage this method in an operational environment.Comment: SIGKDD 201
CONFLICT RESOLUTION BETWEEN AGENTS: A BELIEF-THEORETIC PERSPECTIVE
Information Systems Working Papers Serie
Neutrinos from Gamma Ray Bursts in the IceCube and ARA Era
In this review I discuss the ultra-high energy neutrinos (UHEN) originated
from Cosmic-Rays propogation (GZK neutrinos) and from Gamma Ray Bursts (GRBs),
and discuss their detectability in kilometers scale detectors like ARA and
IceCube.
While GZK neutrinos are expected from cosmic ray interactions on the CMB, the
GRB neutrinos depend on the physics inside the sources. GRBs are predicted to
emit UHEN in the prompt and in the later 'after-glow' phase.
I discuss the constraints on the hadronic component of GRBs derived from the
search of four years of IceCube data for a prompt neutrino fux from gamma-ray
bursts (GRBs) and more in general I present the results of the search for
high-energy neutrinos interacting within the IceCube detector between 2010 and
2013.Comment: Accepted for publication in Journal of High Energy Astrophysics.
arXiv admin note: text overlap with arXiv:1407.015
The Discovery of Sgr A*
The compact radio source Sgr A* is associated with a 3.6 million black hole
at the center of the Milky Way. The radio source was discovered in February
1974 by Bruce Balick and Robert L.Brown. The National Radio Astronomy
Observatory's Green Bank 35 km radio link interferometer was used. We discuss
other observations in the years 1965-1985 as well as early VLBI observations.
The name Sgr A* was used for the first time in 1982 by Robert L.Brown and has
become the accepted name in the intervening years.Comment: 8 pages,2 figures. Conference proceedings: "The central 300 parsecs
of the Milky Way", editors A.Cotera, H.Falcke, T.R.Geballe, S.Markof
Equating an expert system to a classifier in order to evaluate the expert system
A strategy to evaluate an expert system is formulated. The strategy proposed is based on finding an equivalent classifier to an expert system and evaluate that classifier with respect to an optimal classifier, a Bayes classifier. Here it is shown that for the rules considered an equivalent classifier exists. Also, a brief consideration of meta and meta-meta rules is included. Also, a taxonomy of expert systems is presented and an assertion made that an equivalent classifier exists for each type of expert system in the taxonomy with associated sets of underlying assumptions
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