1,606 research outputs found
Implementation of stability-based transition model by means of transport equations
A natural laminar-turbulent transition model compatible with Computation Fluid Dynamics is presented. This model accounts for longitudinal transition mechanisms (i.e. Tollmien-Schlichting induced transition) thanks to systematic stability computation on similar boundary profiles from Mach zero to four both on adiabatic and isothermal wall. The model embeds as well the so-called “C1-criterion” for transverse transition mechanisms (i.e. cross-flow waves induced transition). The transition model is written under transport equations formalism and has been implemented in the solver elsA (ONERA-Airbus-Safran property). Validations are performed on three dimensional configurations and comparisons are shown against a database method for natural transition modeling and experiments
On Two Theorems About Symplectic Reflection Algebras
We give a new proof and an improvement of two Theorems of J. Alev, M.A.
Farinati, T. Lambre and A.L. Solotar : the first one about Hochschild
cohomology spaces of some twisted bimodules of the Weyl algebra W and the
second one about Hochschild cohomology spaces of the smash product G * W (G a
finite subgroup of SP(2n)), and as an application, we then give a new proof of
a Theorem of P. Etingof and V. Ginzburg, which shows that the Symplectic
Reflection Algebras are deformations of G * W (and, in fact, all possible
ones).Comment: corrected typo
Closedness of star products and cohomologies
We first review the introduction of star products in connection with
deformations of Poisson brackets and the various cohomologies that are related
to them. Then we concentrate on what we have called ``closed star products" and
their relations with cyclic cohomology and index theorems. Finally we shall
explain how quantum groups, especially in their recent topological form, are in
essence examples of star products.Comment: 16 page
Reduction of CO2-emissions in ceramic tiles manufacture by combining energy-saving measures
Ceramic tile manufacture requires a great quantity of energy, mainly in the form of heat.
The heat is principally used in the kilns and dryers, and it is obtained by natural gas
combustion.
The increasing cost of natural gas, as well as the application of a new gas tax, the new
legislation in regard to emissions trading, and the difficult current economic situation
have driven the ceramic tile sector to implement energy-saving actions in the production
process with the twofold aim of reducing energy costs and abating carbon dioxide
emissions.
One such course of action is the European project REDUCER, funded by the European
Commission and led by Azulev S.A.U., in which the Instituto de Tecnología Cerámica
(ITC) also participates. This project seeks to implement energy-saving actions in
company kilns and dryers in order to lower natural gas consumption and reduce carbon
dioxide emissions in the tile manufacturing process.
One of the saving actions envisaged is the installation of a system of waste heat recovery
from one of the company kilns to the tile body dryers. This new waste heat recovery
system is to be added to and will complement the already existing system at the
company, thus achieving maximum heat recovery from the kiln stacks. The recovered
heat will go entirely to the green tile body dryers, thus reducing natural gas consumption
in the dryers.
The designed installation seeks to recover 600 kW heat from the stacks of one of the
kilns, entailing a natural gas saving of more than 120 k€/year and suppressing the
emission into the atmosphere of 720 tons of CO2/year, savings that are to be added to
those attained with other energy-saving measures.
This paper describes the energy-saving actions implemented at the company, as well as
the resulting energy savings
Do Multinational enterprises push up wages of domestic firms in the Italian Manufacturing sector?
This paper analyzes the effects of foreign direct investment on wages paid by domestic firms in the Italian manufacturing sector over the period 2002–2007. In particular, the authors investigate the im-pact of multinational enterprises on wages paid by local firms which operate in the same industry, known and horizontal wage spillovers, or have linkages with multinational enterprises in both downstream and upstream industries, known as vertical wage spillovers. By using a large panel dataset, consisting of 551,000 observations, the authors find evidence of wage spillovers only at inter-industry level and, more specifically, for those firms who supply their goods to multinational enterprises, described as backward wage spillovers. Moreover, findings suggest that the wage spillover effect is strongly affected by the technological gap between local and foreign firms: only workers employed in domestic firms with a low-medium technological absorptive capacity seem to benefit from the presence of multinational enterprises in terms of higher wages
The interstellar medium towards the Ara OB1 region
We present high resolution (R ~ 4 km/s) absorption measurements of the
interstellar NaI and CaII lines measured towards 14 early-type stars of
distance 123 pc - 1650 pc, located in the direction of the Ara OB1 stellar
cluster. The line profiles can broadly be split into four distinct groupings of
absorption component velocity, and we have attempted to identify an origin and
distance to each of these interstellar features. For gas with absorption
covering the velocity range -10 km/s < V_helio < +10 km/s, we can identify the
absorbing medium with local gas belonging to the Lupus-Norma interstellar
cavity located between 100 and 485 pc in this galactic direction. Gas with
velocities spanning the range -20 km/s < V_helio < +20 km/s is detected towards
stars with distances of 570-800 pc. We identify a wide-spread interstellar
feature at V_helio ~ -15 km/s with the expanding HI shell called GSH 337+00-05,
which is now placed at a distance of ~530 pc.Comment: 12 pages, 5 figures, accepted for publication in Astrophysics & Space
Scienc
Observational Constraints on Interstellar Grain Alignment
We present new multicolor photo-polarimetry of stars behind the Southern
Coalsack. Analyzed together with multiband polarization data from the
literature, probing the Chamaeleon I, Musca, rho Opiuchus, R CrA and Taurus
clouds, we show that the wavelength of maximum polarization (lambda_max) is
linearly correlated with the radiation environment of the grains. Using
Far-Infrared emission data, we show that the large scatter seen in previous
studies of lambda_max as a function of A_V is primarily due to line of sight
effects causing some A_V measurements to not be a good tracer of the extinction
(radiation field strength) seen by the grains being probed. The derived slopes
in lambda_max vs. A_V, for the individual clouds, are consistent with a common
value, while the zero intercepts scale with the average values of the ratios of
total-to-selective extinction (R_V) for the individual clouds. Within each
cloud we do not find direct correlations between lambda_max and R_V. The
positive slope in consistent with recent developments in theory and indicating
alignment driven by the radiation field. The present data cannot conclusively
differentiate between direct radiative torques and alignment driven by H_2
formation. However, the small values of lambda_max(A_V=0), seen in several
clouds, suggest a role for the latter, at least at the cloud surfaces. The
scatter in the lambda_max vs. A_V relation is found to be associated with the
characteristics of the embedded Young Stellar Objects (YSO) in the clouds. We
propose that this is partially due to locally increased plasma damping of the
grain rotation caused by X-rays from the YSOs.Comment: Accepted for publication in the Astrophysical Journa
The W51 Giant Molecular Cloud
We present 45"-47" angular resolution maps at 50" sampling of the 12CO and
13CO J=1-0 emission toward a 1.39 deg x 1.33 deg region in the W51 HII region
complex. These data permit the spatial and kinematic separation of several
spectral features observed along the line of sight to W51, and establish the
presence of a massive (1.2 x 10^6 Mo), large (83 pc x 114 pc) giant molecular
cloud (GMC), defined as the W51 GMC, centered at (l,b,V) = (49.5 deg, -0.2 deg,
61 km/s). A second massive (1.9 x 10^5 Mo), elongated (136 pc x 22 pc)
molecular cloud is found at velocities of about 68 km/s along the southern edge
of the W51 GMC. Of the five radio continuum sources that classically define the
W51 region, the brightest source at lambda 6cm (G49.5-0.4) is spatially and
kinematically coincident with the W51 GMC and three (G48.9-0.3, G49.1-0.4, and
G49.2-0.4) are associated with the 68 km/s cloud. Published absorption line
spectra indicate that the fifth prominent continuum source (G49.4-0.3) is
located behind the W51 molecular cloud. The W51 GMC is among the upper 1% of
clouds in the Galactic disk by size and the upper 5-10% by mass. While the W51
GMC is larger and more massive than any nearby molecular cloud, the average H2
column density is not unusual given its size and the mean H2 volume density is
comparable to that in nearby clouds. The W51 GMC is also similar to other
clouds in that most of the molecular mass is contained in a diffuse envelope
that is not currently forming massive stars. We speculate that much of the
massive star formation activity in this region has resulted from a collision
between the 68 km/s cloud and the W51 GMC.Comment: Accepted for publication by the Astronomical Journal. 21 pages, plus
7 figures and 1 tabl
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