623 research outputs found
Inlet conditions for large eddy simulation of gas-turbine swirl injectors
Copyright © 2008 American Institute of Aeronautics and AstronauticsIn this paper, we present a novel technique for generating swirl inlets for large eddy simulation. The velocity a short distance downstream of the inlet to the main domain is sampled and the flow velocity data are reintroduced back into the domain inlet, creating an inlet section integrated into the main domain in which turbulence can develop.
Additionally, variable artificial body forces and velocity corrections are imposed in this inlet section, with feedback control to force the flow toward desired swirl, mean, and turbulent profiles. The method was applied to flow in an axisymmetric sudden expansion, with and without swirl at the inlet, and compared against experimental and literature large eddy simulation data and against similar results in the literature. The method generates excellent results for this case and is elegant and straightforward to implement
Measurement of the 187Re({\alpha},n)190Ir reaction cross section at sub-Coulomb energies using the Cologne Clover Counting Setup
Uncertainties in adopted models of particle+nucleus optical-model potentials
directly influence the accuracy in the theoretical predictions of reaction
rates as they are needed for reaction-network calculations in, for instance,
{\gamma}-process nucleosynthesis. The improvement of the {\alpha}+nucleus
optical-model potential is hampered by the lack of experimental data at
astrophysically relevant energies especially for heavier nuclei. Measuring the
Re187({\alpha},n)Ir190 reaction cross section at sub-Coulomb energies extends
the scarce experimental data available in this mass region and helps
understanding the energy dependence of the imaginary part of the
{\alpha}+nucleus optical-model potential at low energies. Applying the
activation method, after the irradiation of natural rhenium targets with
{\alpha}-particle energies of 12.4 to 14.1 MeV, the reaction yield and thus the
reaction cross section were determined via {\gamma}-ray spectroscopy by using
the Cologne Clover Counting Setup and the method of {\gamma}{\gamma}
coincidences. Cross-section values at five energies close to the
astrophysically relevant energy region were measured. Statistical model
calculations revealed discrepancies between the experimental values and
predictions based on widely used {\alpha}+nucleus optical-model potentials.
However, an excellent reproduction of the measured cross-section values could
be achieved from calculations based on the so-called Sauerwein-Rauscher
{\alpha}+nucleus optical-model potential. The results obtained indicate that
the energy dependence of the imaginary part of the {\alpha}+nucleus
optical-model potential can be described by an exponential decrease. Successful
reproductions of measured cross sections at low energies for {\alpha}-induced
reactions in the mass range 141{\leq}A{\leq}187 confirm the global character of
the Sauerwein-Rauscher potential
Instabilitäten von Infiltrationsfronten verursacht durch langzeitige Bewässerung mit behandelten Abwässern
Die Bewässerung von Agrarflächen mit behandelten Abwässern (TWW) ist eine weitverbreitete Praxis in ariden und semi-ariden Gebieten. In Israel liegt auf dieser Wasserressource ein besonderer Fokus, da Abwässer ganzjährig verfügbar sind, Frischwasserressourcen schonen und einen wichtigen Beitrag zur Wiederverwendung von Nährstoffen leisten. Vorangegangene Studien haben gezeigt, dass organische Stoffe die Benetzbarkeit von Mineraloberflächen beeinträchtigen und die Bodenstruktur verändern können. Auf Grund der erhöhten Restmenge an organischen Bestandteilen im TWW kann eine langzeitige Bewässerung im Boden zu Veränderungen der Struktur, Hydrophobizität, präferentiellen Fließwegen und dem Auswaschen von Pflanzenschutzmitteln und Nährstoffen führen. In dieser Studie wurden (i) eine neue Methode zur Quantifizierung von Wassergehaltsänderungen in ungestörten Bodenproben via Radiographie entwickelt und (ii) Instabilitäten von Infiltrationsfronten in Böden, die seit über zwanzig Jahren mit TWW bewässert wurden, detektiert. Wir untersuchten ungestörte Bodenproben von zwei Obstplantagen in Israel mit langzeitiger TWW-Bewässerung, wobei an einem Standort zusätzlich ein Teil mit Frischwasser bewässert wird. Die Proben umfassen zwei unterschiedliche Bodentexturen und zwei unterschiedliche Bewässerungsverfahren: Frischwasser und TWW. Des Weiteren wurden saisonale Abhängigkeiten (Trocken-/ Regenzeit) mit in die Studie eingeschlossen um die Persistenz der Effekte zu erfassen. Ungestörte, zylindrische Bodenproben wurden aus dem Oberboden (0-20 cm) genommen und Bewässerungsversuche innerhalb eines Röntgensystems durchgeführt. Durch Bildanalyse konnten die Ausbreitung der Infiltrationsfronten und räumliche Wassergehaltsänderungen als Funktion der Zeit erfasst werden. Die Versuche wurden mit unterschiedlichen Anfangswassergehalten wiederholt. In dieser Studie konnte gezeigt werden, dass die Stabilität der Infiltrationsfronten in diesen Böden von der Wasserqualität und dem initialen Wassergehalt abgängig sind. Darüber hinaus konnte dargelegt werden, dass langzeitige TWW-Bewässerung zu einer persistenten Veränderung der Benetzbarkeit führen kann, unabhängig von der Saison. Diese Studie liefert einen experimentellen Nachweis über die Notwendigkeit von optimiertem Bewässerungsmanagement um präferentielles Wasserfließen zu vermeiden
Deeply sequenced metagenome and metatranscriptome of a biogas-producing microbial community from an agricultural production-scale biogas plant
Bremges A, Maus I, Belmann P, et al. Deeply sequenced metagenome and metatranscriptome of a biogas-producing microbial community from an agricultural production-scale biogas plant. GigaScience. 2015;4(1): 33.Background
The production of biogas takes place under anaerobic conditions and involves microbial decomposition of organic matter. Most of the participating microbes are still unknown and non-cultivable. Accordingly, shotgun metagenome sequencing currently is the method of choice to obtain insights into community composition and the genetic repertoire.
Findings
Here, we report on the deeply sequenced metagenome and metatranscriptome of a complex biogas-producing microbial community from an agricultural production-scale biogas plant. We assembled the metagenome and, as an example application, show that we reconstructed most genes involved in the methane metabolism, a key pathway involving methanogenesis performed by methanogenic Archaea. This result indicates that there is sufficient sequencing coverage for most downstream analyses.
Conclusions
Sequenced at least one order of magnitude deeper than previous studies, our metagenome data will enable new insights into community composition and the genetic potential of important community members. Moreover, mapping of transcripts to reconstructed genome sequences will enable the identification of active metabolic pathways in target organisms
Search for decays with semileptonic tagging at Belle
We present the results of a search for the rare decays , where stands for and . The results are
obtained with pairs collected with the Belle
detector at the KEKB collider. We reconstruct one meson in a
semileptonic decay and require a single meson but nothing else on the
signal side. We observe no significant signal and set upper limits on the
branching fractions. The limits set on the , , , ,
, and channels
are the world's most stringent.Comment: Submitted to PR
Search for a dark vector gauge boson decaying to using decays
We report a search for a dark vector gauge boson that couples to
quarks in the decay chain , . No signal is found and we set a
mass-dependent limit on the baryonic fine structure constant of in the mass range of 290 to 520 MeV/. This analysis is
based on a data sample of 976 fb collected by the Belle experiment at
the KEKB asymmetric-energy collider.Comment: 6 pages, 4 figure
First Observation of Doubly Cabibbo-Suppressed Decay of a Charmed Baryon:
We report the first observation of the decay using a 980 data sample collected by the
Belle detector at the KEKB asymmetric-energy collider. This is the
first doubly Cabibbo-suppressed decay of a charmed baryon to be observed. We
measure the branching ratio of this decay with respect to its Cabibbo-favored
counterpart to be , where the uncertainties are
statistical and systematic, respectively.Comment: 6 pages, 3 figure
Measurement of the lepton polarization and in the decay
We report the first measurement of the lepton polarization
in the decay as
well as a new measurement of the ratio of the branching fractions , where
denotes an electron or a muon, and the is reconstructed in the modes
and .
We use the full data sample of pairs recorded
with the Belle detector at the KEKB electron-positron collider. Our results,
and
, are
consistent with the theoretical predictions of the Standard Model.Comment: 7 pages, 2 figures, submitted to Physical Review Letters; one figure
was removed from the first versio
Angular analysis of
We present a measurement of angular observables, , , ,
, in the decay , where
is either or . The analysis is performed on
a data sample corresponding to an integrated luminosity of
containing pairs, collected
at the resonance with the Belle detector at the
asymmetric-energy collider KEKB. Four angular observables,
are extracted in five bins of the invariant mass squared of the
lepton system, . We compare our results for with Standard
Model predictions including the region in which the LHCb collaboration
reported the so-called anomaly.Comment: Conference paper for LHC Ski 2016. SM prediction for
corrected and reference for arXiv:1207.2753 adde
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