604 research outputs found
Scheduling Pipelined, Multi-Threaded Programs in Linux
A process causes latency when it performs I/O or communication. Pipelined processes mitigate latency by concurrently executing multiple threads--- sequences of operations--- and overlapping computation, communication, and I/O. When more than one thread is ready to run, the scheduler determines which thread in fact runs. This paper presents techniques for scheduling pipelines, with the following three findings. First, using Linux kernel version 2.6 and the NPTL threads package, we observe a 3-6% performance improvement over kernel version 2.4 and the LinuxThreads package. Second, we test techniques that both take advantage of prior knowledge about whether a program is I/O-bound or compute-bound and raise and lower priorities before the pipeline begins working. These techniques, referred to as fixed scheduling, further improve performance by 5% in the case of the compute-bound columnsort algorithm. In the I/O-bound algorithm, fixed scheduling failed to yield better performance than the default scheduling. Third, we test simple, adjusting methods that do not take advantage of prior knowledge about whether a program in compute-bound or I/O-bound but rather adjust scheduling as the pipeline progresses. These techniques, called adjusting scheduling, fail to yield better performance than the default scheduling in any of our test cases. In addition, we suggest new scheduling calls and other operating-system improvements
Extensions of adaptive slope-seeking for active flow control
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.To speed up gradient estimation in a slope-seeking controller two different modifications are proposed in this study. In a first approach, the gradient estimation is based on a locally identified black-box model. A further improvement is obtained by applying an extended Kalman filter to estimate the local gradient of an input—output map. Moreover, a simple method is outlined to adapt the search radius in the classical extremum- and slope-seeking approach to reduce the perturbations near the optimal state. To show the versatility of the slope-seeking controller for flow control applications two different wind tunnel experiments are considered, namely with a two-dimensional bluff body and a generic three-dimensional car model (Ahmed body).DFG, SFB 557, Beeinflussung komplexer turbulenter Scherströmunge
Photocatalytic degradation of diclofenac in wastewater using ironceramic composites
The photocatalytic degradation of diclofenac in model aqueous solution is investigated. The surface of composites were correlated with photocatalytic activity. Adsorption activity of the composites is related to the presence of surface active sites. The degradation under UV irradiation and photo-Fenton process using ironceramic composites is more effective than direct photolysis
Volumetrie der Schilddrüsenlappen mittels Real-time-Sonographie
Im direkten Vergleich mit der durch Submersion ermittelten wahren Schilddrüsengröße wurde bei Leichen mit einem Real-time-Gerät ein Verfahren zur Volumenbestimmung durch sonographische Messungen erarbeitet. Länge mal Breite mal Dicke des Schilddrüsenlappens, multipliziert mit dem Faktor π/6, entsprechen einem Rotationsellipsoid, während sich bei Multiplikation mit dem optimierten Korrekturfaktor f = 0,479 das bestmögliche rechnerische Volumen des Lappens ergibt. Die Richtigkeit dieser Bestimmung ist definitionsgemäß 100 %; der. durchschnittliche Fehler der Methode beträgt 16 %. Die Messungen sind einfach durchzuführen und verlangen keinerlei Zusatzeinrichtungen für Planimetrie oder Rechneroperationen. Die Volumetrie der Schilddrüse ist vor allem zur Therapiebeurteilung und zur Berechnung der Dosis bei einer Radiojodtherapie erforderlich.Thyroid volume as measured by real-time ultrasound in cadavers was compared with direct measurements obtained by submersion. Length × width × thickness of the thyroid lobe multiplied by factor π/6, correspond to a rotation ellipsoid, while the best calculated volume of the lobe is obtained by multiplying with the optimised correction factor f = 0.479. The correctness of this calculation is, by definition, 100 %; average error of the method is 16 %. The measurements are easy to do and require no additional equipment for planimetry or calculations. Volumetric analysis of the thyroid gland is especially necessary in assessing results of treatment and for measuring dosage in connection with radioiodine therapy
Mariner Mars 1969 project report. Volume 2 - Performance Final report
Performance of Mariner Mars 1969 mission by flight and Earth-based elements during launch and space flight phases - Vol.
Evidence for Quark-Hadron Duality in the Proton Spin Asymmetry
Spin-dependent lepton-nucleon scattering data have been used to investigate
the validity of the concept of quark-hadron duality for the spin asymmetry
. Longitudinally polarised positrons were scattered off a longitudinally
polarised hydrogen target for values of between 1.2 and 12 GeV and
values of between 1 and 4 GeV. The average double-spin asymmetry in
the nucleon resonance region is found to agree with that measured in
deep-inelastic scattering at the same values of the Bjorken scaling variable
. This finding implies that the description of in terms of quark
degrees of freedom is valid also in the nucleon resonance region for values of
above 1.6 GeV.Comment: 5 pages, 1 eps figure, table added, new references added, in print in
Phys. Rev. Let
The Q^2-Dependence of Nuclear Transparency for Exclusive Production
Exclusive coherent and incoherent electroproduction of the meson
from H and N targets has been studied at the HERMES experiment as a
function of coherence length (), corresponding to the lifetime of hadronic
fluctuations of the virtual photon, and squared four-momentum of the virtual
photon (). The ratio of N to H cross sections per nucleon,
known as nuclear transparency, was found to increase (decrease) with increasing
coherence length for coherent (incoherent) electroproduction. For
fixed coherence length, a rise of nuclear transparency with is observed
for both coherent and incoherent production, which is in agreement
with theoretical calculations of color transparency.Comment: 5 pages, 4 figure
Single-spin Azimuthal Asymmetries in Electroproduction of Neutral Pions in Semi-inclusive Deep-inelastic Scattering
A single-spin asymmetry in the azimuthal distribution of neutral pions
relative to the lepton scattering plane has been measured for the first time in
deep-inelastic scattering of positrons off longitudinally polarized protons.
The analysing power in the sin(phi) moment of the cross section is 0.019 +/-
0.007(stat.) +/- 0.003(syst.). This result is compared to single-spin
asymmetries for charged pion production measured in the same kinematic range.
The pi^0 asymmetry is of the same size as the pi^+ asymmetry and shows a
similar dependence on the relevant kinematic variables. The asymmetry is
described by a phenomenological calculation based on a fragmentation function
that represents sensitivity to the transverse polarization of the struck quark.Comment: 4 pages, 1 figure, replaced to correct eprint author field, 2nd
replacement to correct figure; upper limit of model predictions are
corrected. No correction to data or conclusion
The -dependence of the generalised Gerasimov-Drell-Hearn integral for the deuteron, proton and neutron
The Gerasimov-Drell-Hearn (GDH) sum rule connects the anomalous contribution
to the magnetic moment of the target nucleus with an energy-weighted integral
of the difference of the helicity-dependent photoabsorption cross sections. The
data collected by HERMES with a deuterium target are presented together with a
re-analysis of previous measurements on the proton. This provides a measurement
of the generalised GDH integral covering simultaneously the nucleon-resonance
and the deep inelastic scattering regions. The contribution of the
nucleon-resonance region is seen to decrease rapidly with increasing . The
DIS contribution is sizeable over the full measured range, even down to the
lowest measured . As expected, at higher the data are found to be in
agreement with previous measurements of the first moment of . From data on
the deuteron and proton, the GDH integral for the neutron has been derived and
the proton--neutron difference evaluated. This difference is found to satisfy
the fundamental Bjorken sum rule at GeV.Comment: 12 pages, 10 figure
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