43,783 research outputs found
Statistics Of The Burst Model At Super-critical Phase
We investigate the statistics of a model of type-I X-ray burst [Phys. Rev. E,
{\bf 51}, 3045 (1995)] in its super-critical phase. The time evolution of the
burnable clusters, places where fire can pass through, is studied using simple
statistical arguments. We offer a simple picture for the time evolution of the
percentage of space covered by burnable clusters. A relation between the
time-average and the peak percentage of space covered by burnable clusters is
also derived.Comment: 11 Pages in Revtex 3.0. Two figures available by sending request to
[email protected]
Conductance spectra of metallic nanotube bundles
We report a first principles analysis of electronic transport characteristics
for (n,n) carbon nanotube bundles. When n is not a multiple of 3, inter-tube
coupling causes universal conductance suppression near Fermi level regardless
of the rotational arrangement of individual tubes. However, when n is a
multiple of 3, the bundles exhibit a diversified conductance dependence on the
orientation details of the constituent tubes. The total energy of the bundle is
also sensitive to the orientation arrangement only when n is a multiple of 3.
All the transport properties and band structures can be well understood from
the symmetry consideration of whether the rotational symmetry of the individual
tubes is commensurate with that of the bundle
Three-dimensional finite element analysis for high velocity impact
A finite element algorithm for solving unsteady, three-dimensional high velocity impact problems is presented. A computer program was developed based on the Eulerian hydroelasto-viscoplastic formulation and the utilization of the theorem of weak solutions. The equations solved consist of conservation of mass, momentum, and energy, equation of state, and appropriate constitutive equations. The solution technique is a time-dependent finite element analysis utilizing three-dimensional isoparametric elements, in conjunction with a generalized two-step time integration scheme. The developed code was demonstrated by solving one-dimensional as well as three-dimensional impact problems for both the inviscid hydrodynamic model and the hydroelasto-viscoplastic model
An Improved Private Mechanism for Small Databases
We study the problem of answering a workload of linear queries ,
on a database of size at most drawn from a universe
under the constraint of (approximate) differential privacy.
Nikolov, Talwar, and Zhang~\cite{NTZ} proposed an efficient mechanism that, for
any given and , answers the queries with average error that is
at most a factor polynomial in and
worse than the best possible. Here we improve on this guarantee and give a
mechanism whose competitiveness ratio is at most polynomial in and
, and has no dependence on . Our mechanism
is based on the projection mechanism of Nikolov, Talwar, and Zhang, but in
place of an ad-hoc noise distribution, we use a distribution which is in a
sense optimal for the projection mechanism, and analyze it using convex duality
and the restricted invertibility principle.Comment: To appear in ICALP 2015, Track
Increased Risk of Respiratory Mortality Associated with the High-Tech Manufacturing Industry: A 26-Year Study
Global high-tech manufacturers are mainly located in newly industrialized countries, raising concerns about adverse health consequences from industrial pollution for people living nearby. We investigated the ecological association between respiratory mortality and the development of Taiwan's high-tech manufacturing, taking into account industrialization and socioeconomic development, for 19 cities and counties-6 in the science park group and 13 in the control group-from 1982 to 2007. We applied a linear mixed-effects model to analyze how science park development over time is associated with age-adjusted and sex-specific mortality rates for asthma and chronic obstructive pulmonary disease (COPD). Asthma and female COPD mortality rates decreased in both groups, but they decreased 9%-16% slower in the science park group. Male COPD mortality rates increased in both groups, but the rate increased 10% faster in the science park group. Science park development over time was a significant predictor of death from asthma (p ≤ 0.0001) and COPD (p = 0.0212). The long-term development of clustered high-tech manufacturing may negatively affect nearby populations, constraining health advantages that were anticipated, given overall progress in living standards, knowledge, and health services. National governments should incorporate the long-term health effects on local populations into environmental impact assessments
Lagrangian Floer superpotentials and crepant resolutions for toric orbifolds
We investigate the relationship between the Lagrangian Floer superpotentials
for a toric orbifold and its toric crepant resolutions. More specifically, we
study an open string version of the crepant resolution conjecture (CRC) which
states that the Lagrangian Floer superpotential of a Gorenstein toric orbifold
and that of its toric crepant resolution coincide after
analytic continuation of quantum parameters and a change of variables. Relating
this conjecture with the closed CRC, we find that the change of variable
formula which appears in closed CRC can be explained by relations between open
(orbifold) Gromov-Witten invariants. We also discover a geometric explanation
(in terms of virtual counting of stable orbi-discs) for the specialization of
quantum parameters to roots of unity which appears in Y. Ruan's original CRC
["The cohomology ring of crepant resolutions of orbifolds", Gromov-Witten
theory of spin curves and orbifolds, 117-126, Contemp. Math., 403, Amer. Math.
Soc., Providence, RI, 2006]. We prove the open CRC for the weighted projective
spaces using an equality between open
and closed orbifold Gromov-Witten invariants. Along the way, we also prove an
open mirror theorem for these toric orbifolds.Comment: 48 pages, 1 figure; v2: references added and updated, final version,
to appear in CM
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