10,006 research outputs found
Predicting Intermediate Storage Performance for Workflow Applications
Configuring a storage system to better serve an application is a challenging
task complicated by a multidimensional, discrete configuration space and the
high cost of space exploration (e.g., by running the application with different
storage configurations). To enable selecting the best configuration in a
reasonable time, we design an end-to-end performance prediction mechanism that
estimates the turn-around time of an application using storage system under a
given configuration. This approach focuses on a generic object-based storage
system design, supports exploring the impact of optimizations targeting
workflow applications (e.g., various data placement schemes) in addition to
other, more traditional, configuration knobs (e.g., stripe size or replication
level), and models the system operation at data-chunk and control message
level.
This paper presents our experience to date with designing and using this
prediction mechanism. We evaluate this mechanism using micro- as well as
synthetic benchmarks mimicking real workflow applications, and a real
application.. A preliminary evaluation shows that we are on a good track to
meet our objectives: it can scale to model a workflow application run on an
entire cluster while offering an over 200x speedup factor (normalized by
resource) compared to running the actual application, and can achieve, in the
limited number of scenarios we study, a prediction accuracy that enables
identifying the best storage system configuration
Continuous Uniform Finite Time Stabilization of Planar Controllable Systems
Continuous homogeneous controllers are utilized in a full state feedback setting for the uniform finite time stabilization of a perturbed double integrator in the presence of uniformly decaying piecewise continuous disturbances. Semiglobal strong Lyapunov functions are identified to establish uniform asymptotic stability of the closed-loop planar system. Uniform finite time stability is then proved by extending the homogeneity principle of discontinuous systems to the continuous case with uniformly decaying piecewise continuous nonhomogeneous disturbances. A finite upper bound on the settling time is also computed. The results extend the existing literature on homogeneity and finite time stability by both presenting uniform finite time stabilization and dealing with a broader class of nonhomogeneous disturbances for planar controllable systems while also proposing a new class of homogeneous continuous controllers
Isotopic Production Cross Sections in Proton-Nucleus Collisions at 200 MeV
Intermediate mass fragments (IMF) from the interaction of Al,
Co and Au with 200 MeV protons were measured in an angular range
from 20 degree to 120 degree in the laboratory system. The fragments, ranging
from isotopes of helium up to isotopes of carbon, were isotopically resolved.
Double differential cross sections, energy differential cross sections and
total cross sections were extracted.Comment: accepted by Phys. Rev.
Investigating the Magnetic Structure of Interplanetary Coronal Mass Ejections using Simultaneous Multi-Spacecraft In situ Measurements
In situ measurements from spacecraft typically provide a time series at a
single location through coronal mass ejections (CMEs) and they have been one of
the main methods to investigate CMEs. CME properties derived from these in situ
measurements are affected by temporal changes that occur as the CME passes over
the spacecraft, such as radial expansion and ageing, as well as spatial
variations within a CME. This study uses multi-spacecraft measurements of the
same CME at close separations to investigate both the spatial variability (how
different a CME profile is when probed by two spacecraft close to each other)
and the so-called ageing effect (the effect of the time evolution on in situ
properties). We compile a database of 19 events from the past four decades
measured by two spacecraft with a radial separation <0.2 au and an angular
separation <10{\deg}. We find that the average magnetic field strength measured
by the two spacecraft differs by 18% of the typical average value, which
highlights non-negligible spatial or temporal variations. For one particular
event, measurements taken by the two spacecraft allow us to quantify and
significantly reduce the ageing effect to estimate the asymmetry of the
magnetic field strength profile. This study reveals that single-spacecraft time
series near 1 au can be strongly affected by ageing and that correcting for
self-similar expansion does not capture the whole ageing effect.Comment: Accepted for publication at ApJ. 18 pages, 6 figures, 2 table
The Tunisian traditional rabbit breeding system versus the commercial system: an epidemiological perspective
[EN] Rabbit breeding is practiced in many hot climate countries and contributes in terms of agricultural activities to rural development. In Tunisia two different rabbit breeding systems can be identified - the "traditional" (an integrated free range and underground system) and the "commercial" (employing sheds and wire net cages) practice. 24 Tunisian rabbitries (10 traditional and 14 commercial) were included in an epidemiological study aimed at comparing the prevalence of pathogenic bacteria responsible for upper respiratory and digestive diseases in the two breeding systems. A total of 128 adult rabbits (mean age of 9.4 months) were tested using deep nasal and rectal swabs. Symptoms of nasal discharge and/or diarrhea were recorded. 281 bacterial strains were isolated in total, 138 in commercial and 143 in traditional farms. The bacteria most frequently isolated (61.2%) were Gram-positive strains, which included Streptococcus sp. (22.8%), coagulase negative Staphylococcus sp. (17.8%) and coagulase-positive Staphylococcus (17.4%) strains. Among the Gram-negative isolated bacteria, Escherichia coli was the most frequent (12.5%), followed by Proteus sp. (5.7%). The two Salmonella strains isolated were Salmonella bongori (found in the commercial system), and Salmonella typhimurium definitive phage-type (DT) 104 (found in the traditional farming system). The absence of Pasteurella multocida in the list of isolated bacteria may be directly correlated to the method of conserving the samples (storage at freezing temperature). The coagulase-positive Staphylococcus strains were frequently isolated (73.5%) from healthy rabbits, but seldom from rabbits with rhinitis (18.4%) or diarrhea (8.2%). Staphylococcus aureus strains were recovered at a higher rate in commercial farms (21%) in comparison with traditional (11.9%) farms. However, this difference was not statistically significant. Four Staphylococcus aureus strains, all belonging to commercial farms, proved positive when tested for enterotoxin production. The antimicrobial susceptibility of isolated Staphylococcus aureus strains was also investigated. Most of the antibiotics tested were very effective: the highest level of susceptibility was observed with enrofloxacin (100%). The low performance of Tunisian traditional rabbit rearing has been linked to the high mortality rate, which may possibly be due to the increased presence of pathogens at the rabbit flock level. However, this was not confirmed by the results of our study due to the fact that the bacterial contamination seems to be comparable in both the traditional and the commercial breeding systems.Belli, P.; Fontana, E.; Sommariva, M.; Scarpelli, L.; Ricci, C.; Luzi, F.; Haddad, B. (2008). The Tunisian traditional rabbit breeding system versus the commercial system: an epidemiological perspective. World Rabbit Science. 16(4). doi:10.4995/wrs.2008.617SWORD16
On the Absorption of X-rays in the Interstellar Medium
We present an improved model for the absorption of X-rays in the ISM intended
for use with data from future X-ray missions with larger effective areas and
increased energy resolution such as Chandra and XMM, in the energy range above
100eV. Compared to previous work, our formalism includes recent updates to the
photoionization cross section and revised abundances of the interstellar
medium, as well as a treatment of interstellar grains and the H2molecule. We
review the theoretical and observational motivations behind these updates and
provide a subroutine for the X-ray spectral analysis program XSPEC that
incorporates our model.Comment: ApJ, in press, for associated software see
http://astro.uni-tuebingen.de/nh
Implementação de diagnóstico por PCR para Fusarium oxysporum f. sp. cubense (raça 4).
O mal-do-panamĂĄ Ă© um dos principais problemas fitossanitĂĄrios da bananeira, causado pelo Fusarium oxysporum f. sp. cubense. A Ășnica alternativa eficiente para o controle da doença tem sido a utilização de variedades resistentes, o que nem sempre Ă© possĂvel. O surgimento de novas raças Ă© preocupação constante
Isospin Diffusion in Ni-Induced Reactions at Intermediate Energies
Isospin diffusion is probed as a function of the dissipated energy by
studying two systems Ni+Ni and Ni+Au, over the
incident energy range 52-74\AM. Experimental data are compared with the results
of a microscopic transport model with two different parameterizations of the
symmetry energy term. A better overall agreement between data and simulations
is obtained when using a symmetry term with a potential part linearly
increasing with nuclear density. The isospin equilibration time at 52 \AM{} is
estimated to 13010 fm/
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