3,088 research outputs found
Joint Cache Partition and Job Assignment on Multi-Core Processors
Multicore shared cache processors pose a challenge for designers of embedded
systems who try to achieve minimal and predictable execution time of workloads
consisting of several jobs. To address this challenge the cache is statically
partitioned among the cores and the jobs are assigned to the cores so as to
minimize the makespan. Several heuristic algorithms have been proposed that
jointly decide how to partition the cache among the cores and assign the jobs.
We initiate a theoretical study of this problem which we call the joint cache
partition and job assignment problem.
By a careful analysis of the possible cache partitions we obtain a constant
approximation algorithm for this problem. For some practical special cases we
obtain a 2-approximation algorithm, and show how to improve the approximation
factor even further by allowing the algorithm to use additional cache. We also
study possible improvements that can be obtained by allowing dynamic cache
partitions and dynamic job assignments.
We define a natural special case of the well known scheduling problem on
unrelated machines in which machines are ordered by "strength". Our joint cache
partition and job assignment problem generalizes this scheduling problem which
we think is of independent interest. We give a polynomial time algorithm for
this scheduling problem for instances obtained by fixing the cache partition in
a practical case of the joint cache partition and job assignment problem where
job loads are step functions
Resonant Enhancement of Electronic Raman Scattering
We present an exact solution for electronic Raman scattering in a
single-band, strongly correlated material, including nonresonant, resonant and
mixed contributions. Results are derived for the spinless Falicov-Kimball
model, employing dynamical mean field theory; this system can be tuned through
a Mott metal-insulator transition.Comment: 4 pages, 3 figures, contribution to the SNS'2004 conferenc
Invariance of Charge of Laughlin Quasiparticles
A Quantum Antidot electrometer has been used in the first direct observation
of the fractionally quantized electric charge. In this paper we report
experiments performed on the integer i = 1, 2 and fractional f = 1/3 quantum
Hall plateaus extending over a filling factor range of at least 27%. We find
the charge of the Laughlin quasiparticles to be invariantly e/3, with standard
deviation of 1.2% and absolute accuracy of 4%, independent of filling,
tunneling current, and temperature.Comment: 4 pages, 5 fig
Quantum phase transition of condensed bosons in optical lattices
In this paper we study the superfluid-Mott-insulator phase transition of
ultracold dilute gas of bosonic atoms in an optical lattice by means of Green
function method and Bogliubov transformation as well. The superfluid-
Mott-insulator phase transition condition is determined by the energy-band
structure with an obvious interpretation of the transition mechanism. Moreover
the superfluid phase is explained explicitly from the energy spectrum derived
in terms of Bogliubov approach.Comment: 13 pages, 1 figure
NARROMI: a noise and redundancy reduction technique improves accuracy of gene regulatory network inference.
MOTIVATION: Reconstruction of gene regulatory networks (GRNs) is of utmost interest to biologists and is vital for understanding the complex regulatory mechanisms within the cell. Despite various methods developed for reconstruction of GRNs from gene expression profiles, they are notorious for high false positive rate owing to the noise inherited in the data, especially for the dataset with a large number of genes but a small number of samples.
RESULTS: In this work, we present a novel method, namely NARROMI, to improve the accuracy of GRN inference by combining ordinary differential equation-based recursive optimization (RO) and information theory-based mutual information (MI). In the proposed algorithm, the noisy regulations with low pairwise correlations are first removed by using MI, and the redundant regulations from indirect regulators are further excluded by RO to improve the accuracy of inferred GRNs. In particular, the RO step can help to determine regulatory directions without prior knowledge of regulators. The results on benchmark datasets from Dialogue for Reverse Engineering Assessments and Methods challenge and experimentally determined GRN of Escherichia coli show that NARROMI significantly outperforms other popular methods in terms of false positive rates and accuracy.
AVAILABILITY: All the source data and code are available at: http://csb.shu.edu.cn/narromi.htm
Off-Diagonal Long Range Order and Scaling in a Disordered Quantum Hall System
We have numerically studied the bosonic off-diagonal long range order,
introduced by Read to describe the ordering in ideal quantum Hall states, for
noninteracting electrons in random potentials confined to the lowest Landau
level. We find that it also describes the ordering in disordered quantum Hall
states: the proposed order parameter vanishes in the disordered
() phase and increases continuously from zero in the ordered
() phase. We study the scaling of the order parameter and
find that it is consistent with that of the one-electron Green's function.Comment: 10 pages and 4 figures, Revtex v3.0, UIUC preprint P-94-03-02
The Causes of Quasi-homologous CMEs
In this paper, we identified the magnetic source locations of 142 quasi-homologous (QH) coronal mass ejections (CMEs), of which 121 are from solar cycle (SC) 23 and 21 from SC 24. Among those CMEs, 63% originated from the same source location as their predecessor (defined as S-type), while 37% originated from a different location within the same active region as their predecessor (defined as D-type). Their distinctly different waiting time distributions, peaking around 7.5 and 1.5 hr for S- and D-type CMEs, suggest that they might involve different physical mechanisms with different characteristic timescales. Through detailed analysis based on nonlinear force-free coronal magnetic field modeling of two exemplary cases, we propose that the S-type QH CMES might involve a recurring energy release process from the same source location (by magnetic free energy replenishment), whereas the D-type QH CMEs can happen when a flux tube system is disturbed by a nearby CME
Resonant scattering on impurities in the Quantum Hall Effect
We develop a new approach to carrier transport between the edge states via
resonant scattering on impurities, which is applicable both for short and long
range impurities. A detailed analysis of resonant scattering on a single
impurity is performed. The results are used for study of the inter-edge
transport by multiple resonant hopping via different impurities' sites. It is
shown that the total conductance can be found from an effective Schroedinger
equation with constant diagonal matrix elements in the Hamiltonian, where the
complex non-diagonal matrix elements are the amplitudes of a carrier hopping
between different impurities. It is explicitly demonstrated how the complex
phase leads to Aharonov-Bohm oscillations in the total conductance. Neglecting
the contribution of self-crossing resonant-percolation trajectories, one finds
that the inter-edge carrier transport is similar to propagation in
one-dimensional system with off-diagonal disorder. We demonstrated that each
Landau band has an extended state , while all other states are
localized. The localization length behaves as .Comment: RevTex 41 pages; 3 Postscript figure on request; Final version
accepted for publication in Phys. Rev. B. A new section added contained a
comparison with other method
The Use of Dispersion Relations in the and Coupled-Channel System
Systematic and careful studies are made on the properties of the IJ=00
and coupled-channel system, using newly derived dispersion
relations between the phase shifts and poles and cuts. The effects of nearby
branch point singularities to the determination of the resonance are
estimated and and discussed.Comment: 22 pages with 5 eps figures. A numerical bug in previous version is
fixed, discussions slightly expanded. No major conclusion is change
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