29,496 research outputs found
Network traffic behaviour near phase transition point
We explore packet traffic dynamics in a data network model near phase
transition point from free flow to congestion. The model of data network is an
abstraction of the Network Layer of the OSI (Open Systems Interconnection)
Reference Model of packet switching networks. The Network Layer is responsible
for routing packets across the network from their sources to their destinations
and for control of congestion in data networks. Using the model we investigate
spatio-temporal packets traffic dynamics near the phase transition point for
various network connection topologies, and static and adaptive routing
algorithms. We present selected simulation results and analyze them
Integrality of quantum 3-manifold invariants and rational surgery formula
We prove that the Witten-Reshetikhin-Turaev (WRT) SO(3) invariant of an
arbitrary 3-manifold M is always an algebraic integer. Moreover, we give a
rational surgery formula for the unified invariant dominating WRT SO(3)
invariants of rational homology 3-spheres at roots of unity of order co-prime
with the torsion. As an application, we compute the unified invariant for
Seifert fibered spaces and for Dehn surgeries on twist knots. We show that this
invariant separates integral homology Seifert fibered spaces and can be used to
detect the unknot.Comment: 18 pages, Compositio Math. in pres
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Building on a Solid Baseline: Anticipatory Biases in Attention.
A brain-imaging paper by Kastner and colleagues in 1999 was the first to demonstrate that merely focusing attention at a spatial location changed the baseline activity level in various regions of human visual cortex even before any stimuli appeared. The study provided a touchstone for investigating cognitive-sensory interactions and understanding the proactive endogenous signals that shape perception
Structure of the QCD Vacuum As Seen By Lattice Simulations
This talk is a review of our studies of instantons and their properties as
seen in our lattice simulations of SU(2) gauge theory. We have measured the
topological susceptibility and the size distribution of instantons in the QCD
vacuum.
We have also investigated the properties of quarks moving in instanton
background field configurations, where the sizes and locations of the
instantons are taken from simulations of the full gauge theory. By themselves,
these multi-instanton configurations do not confine quarks, but they induce
chiral symmetry breaking.Comment: 18 pages, LaTeX, 8 figures, uses epsf, Talk given at YKIS9
Universal contact for a Tonks-Girardeau gas at finite temperature
We determine the finite-temperature momentum distribution of a strongly
interacting 1D Bose gas in the Tonks-Girardeau (impenetrable-boson) limit under
harmonic confinement, and explore its universal properties associated to the
scale invariance of the model. We show that, at difference from the unitary
Fermi gas in three dimensions, the weight of its large-momentum tails -- given
by the Tan's contact -- increase with temperature, and calculate the
high-temperature universal second contact coefficient using a virial expansion.Comment: 6 pages, 2 figure
Effects of population mixing on the spread of SIR epidemics
We study dynamics of spread of epidemics of SIR type in a realistic
spatially-explicit geographical region, Southern and Central Ontario, using
census data obtained from Statistics Canada, and examine the role of population
mixing in epidemic processes. Our model incorporates the random nature of
disease transmission, the discreteness and heterogeneity of distribution of
host population. We find that introduction of a long-range interaction destroys
spatial correlations very easily if neighbourhood sizes are homogeneous. For
inhomogeneous neighbourhoods, very strong long-range coupling is required to
achieve a similar effect. Our work applies to the spread of in influenza during
a single season and our model is applicable to other geographic regions, if
suitable data is available
Estimating the Indirect Gaming Contribution of Bingo Rooms
Using data from two repeater market hotel casinos, the relationship between bingo and slot business volumes is explored. Contrary to conjecture supplied by industry executives, the results fail to demonstrate a statistically significant relationship between daily bingo headcount and coin-in. This result was found in three different analyses, including one· attempt to estimate the impact of bingo headcount on low-denomination coin-in. This study advances the literature by challenging the assumption that bingo rooms produce substantial indirect slot profits. Given the minimal direct contribution to property cash flows, if any, the results suggest that bingo rooms are not always the highest and best use of valuable casino floor space
Long-Period Building Response to Earthquakes in the San Francisco Bay Area
This article reports a study of modeled, long-period building responses to ground-motion simulations of earthquakes in the San Francisco Bay Area. The earthquakes include the 1989 magnitude 6.9 Loma Prieta earthquake, a magnitude 7.8 simulation of the 1906 San Francisco earthquake, and two hypothetical magnitude 7.8 northern San Andreas fault earthquakes with hypocenters north and south of San Francisco. We use the simulated ground motions to excite nonlinear models of 20-story, steel, welded moment-resisting frame (MRF) buildings. We consider MRF buildings designed with two different strengths and modeled with either ductile or brittle welds. Using peak interstory drift ratio (IDR) as a performance measure, the stiffer, higher strength building models outperform the equivalent more flexible, lower strength designs. The hypothetical magnitude 7.8 earthquake with hypocenter north of San Francisco produces the most severe ground motions. In this simulation, the responses of the more flexible, lower strength building model with brittle welds exceed an IDR of 2.5% (that is, threaten life safety) on 54% of the urban area, compared to 4.6% of the urban area for the stiffer, higher strength building with ductile welds. We also use the simulated ground motions to predict the maximum isolator displacement of base-isolated buildings with linear, single-degree-of-freedom (SDOF) models. For two existing 3-sec isolator systems near San Francisco, the design maximum displacement is 0.5 m, and our simulations predict isolator displacements for this type of system in excess of 0.5 m in many urban areas. This article demonstrates that a large, 1906-like earthquake could cause significant damage to long-period buildings in the San Francisco Bay Area
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