50,030 research outputs found
Thermodynamic consistency of liquid-gas lattice Boltzmann simulations
Lattice Boltzmann simulations have been very successful in simulating
liquid-gas and other multi-phase fluid systems. However, the underlying second
order analysis of the equation of motion has long been known to be insufficient
to consistently derive the fourth order terms that are necessary to represent
an extended interface. These same terms are also responsible for thermodynamic
consistency, i.e. to obtain a true equilibrium solution with both a constant
chemical potential and a constant pressure. In this article we present an
equilibrium analysis of non-ideal lattice Boltzmann methods of sufficient order
to identify those higher order terms that lead to a lack of thermodynamic
consistency. We then introduce a thermodynamically consistent forcing method.Comment: 12 pages, 8 figure
Pressure-control purge panel for automatic butt welding
Modification of a purge panel for use in an automatic butt weld reduces the drop in pressure between the regulators and the weld head and tube purge fitting. The invention affects air regulators for plants, regulating circuits for pneumatic valves, and automatic welding machines
Combustor liner construction
A combustor liner is fabricated from a plurality of individual segments each containing counter/parallel Finwall material and are arranged circumferentially and axially to define the combustion zone. Each segment is supported by a hook and ring construction to an opened lattice frame with sufficient tolerance between the hook and ring to permit thermal expansion with a minimum of induced stresses
Stable Marriage with Multi-Modal Preferences
We introduce a generalized version of the famous Stable Marriage problem, now
based on multi-modal preference lists. The central twist herein is to allow
each agent to rank its potentially matching counterparts based on more than one
"evaluation mode" (e.g., more than one criterion); thus, each agent is equipped
with multiple preference lists, each ranking the counterparts in a possibly
different way. We introduce and study three natural concepts of stability,
investigate their mutual relations and focus on computational complexity
aspects with respect to computing stable matchings in these new scenarios.
Mostly encountering computational hardness (NP-hardness), we can also spot few
islands of tractability and make a surprising connection to the \textsc{Graph
Isomorphism} problem
Timelike vs spacelike DVCS from JLab, Compass to ultraperipheral collisions and AFTER@LHC
Timelike and spacelike virtual Compton scattering in the generalized Bjorken
scaling regime are complementary tools to access generalized parton
distributions. We stress that the gluonic contributions are by no means
negligible, even in the medium energy range which will be studied intensely at
JLab12 and in the COMPASS-II experiment at CERN. Ultraperipheral collisions
with proton or ion beams may also be used at RHIC and at collider or fixed
target experiments at LHC.Comment: 7 pages, Presented at the Low x workshop, May 30 - June 4 2013,
Rehovot and Eilat, Israe
NLO QCD corrections for DVCS and TCS
The inclusion of QCD corrections to the Born amplitude of deeply virtual
Compton scattering in both spacelike (DVCS) and timelike (TCS) regimes modifies
the extraction process of generalized parton distributions (GPDs) from
observables. In particular, gluon contributions are by no means negligible even
in the medium energy range accessible at JLab12. We emphasize the
complementarity of spacelike and timelike measurements and raise the question
of factorization scale dependence of the O(alpha_S) results.Comment: 6 pages, 6 figures, Proceedings of the conference Photon 2013, 20-24
May 2013 Paris, France, to be published in Proceedings of Scienc
On timelike and spacelike deeply virtual Compton scattering at next to leading order
We study timelike and spacelike virtual Compton scattering in the generalized
Bjorken scaling regime at next to leading order in the strong coupling
constant, in the medium energy range which will be studied intensely at JLab12
and in the COMPASS-II experiment at CERN. We show that the Born amplitudes get
sizeable O(\alpha_s) corrections and, even at moderate energies, the gluonic
contributions are by no means negligible. We stress that the timelike and
spacelike cases are complementary and that their difference deserves much
special attention
The last glacial-interglacial cycle in Lake Ohrid (Macedonia/Albania): testing diatom response to climate
Lake Ohrid is a site of global importance for palaeoclimate research. This study presents results of diatom analysis of a ca. 136 ka sequence, Co1202, from the northeast of the lake basin. It offers the opportunity to test diatom response across two glacial-interglacial transitions and within the Last Glacial, while setting up taxonomic protocols for future research. The results are outstanding in demonstrating the sensitivity of diatoms to climate change, providing proxy evidence for temperature change marked by glacial-interglacial shifts between the dominant planktonic taxa, Cyclotella fottii and C. ocellata, and exact correlation with geochemical proxies to mark the start of the Last Interglacial at ca. 130 ka. Importantly, diatoms show much stronger evidence in this site for warming during MIS3 than recorded in other productivity-related proxies, peaking at ca. 39 ka, prior to the extreme conditions of the Last Glacial maximum. In the light of the observed patterns, and from the results of analysis of early Holocene sediments from a second core, Lz1120, the lack of a response to Late Glacial and early Holocene warming from ca. 15-7.4 ka suggests the Co1202 sequence may be compromised during this phase. After ca. 7.4 ka, there is evidence for enhanced nutrient enrichment compared to the Last Interglacial, following by a post-Medieval cooling trend. Taxonomically, morphological variability in C. fottii shows no clear trends linked to climate, but an intriguing change in central area morphology occurs after ca. 48.7 ka, coincident with a tephra layer. In contrast, C. ocellata shows morphological variation in the number of ocelli between interglacials, suggesting climatically-forced variation or evolutionary selection pressure. The application of a simple dissolution index does not track preservation quality very effectively, underlining the importance of diatom concentration data in future studies
Noise measurements for various configurations of a model of a mixer nozzle externally blown flap system
Noise data were taken for variations to a large scale model of an externally blown flap lift augmentation system. The variations included two different mixer nozzles (7 and 8 lobes), two different wing models (2 and 3 flaps), and different lateral distances between the wing chord line and the nozzle centerline. When the seven lobe was used with the trailing flap in the 60 deg position, increasing the wing to nozzle distance had no effect on the sound level. When the eight lobe nozzle was used there was a decrease in sound level. With the 20 deg flap setting the noise level decreased when the distance was increased using either nozzle
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