1,373 research outputs found
L'évaluation de l'économie sociale, quelques enjeux de conceptualisation et de méthodologie
Ce texte vise à discuter d'un certain nombre d'enjeux qui se posent lorsqu'il est question d'évaluation des activités d'économie sociale (ÉS), notamment au plan des concepts et des méthodologies qui viennent en appui de l'évaluation. De plus, la contribution de l'ÉS à la démocratisation de l'économique fait que les enjeux de son évaluation se posent également en termes politiques. Afin de tenir compte de ces particularités de l'ÉS, la démarche d'évaluation doit donc déborder la seule perspective productiviste et ne pas se limiter à un cadre purement économique ou gestionnaire. L'évaluation est également l'un des lieux où s'exerce l'orientation et le contrôle des actions. Il s'agit donc d'un moment fort de la gouvernance des activités d'ÉS
Cosmic strings and Natural Inflation
In the present work we discuss cosmic strings in natural inflation. Our
analysis is based entirely on the CMB quadrupole temperature anisotropy and on
the existing upper bound on the cosmic string tension. Our results show that
the allowed range for both parameters of the inflationary model is very
different from the range obtained recently if cosmic strings are formed at the
same time with inflation, while if strings are formed after inflation we find
that the parameters of the inflationary model are similar to the ones obtained
recently.Comment: 12 pages, 0 tables, 4 figures, accepted for publication in JHE
Probing Cosmic Strings with Satellite CMB measurements
We study the problem of searching for cosmic string signal patterns in the
present high resolution and high sensitivity observations of the Cosmic
Microwave Background (CMB). This article discusses a technique capable of
recognizing Kaiser-Stebbins effect signatures in total intensity anisotropy
maps, and shows that the biggest factor that produces confusion is represented
by the acoustic oscillation features of the scale comparable to the size of
horizon at recombination. Simulations show that the distribution of null
signals for pure Gaussian maps converges to a distribution, with
detectability threshold corresponding to a string induced step signal with an
amplitude of about 100 \muK which corresponds to a limit of roughly . We study the statistics of spurious detections caused by
extra-Galactic and Galactic foregrounds. For diffuse Galactic foregrounds,
which represents the dominant source of contamination, we derive sky masks
outlining the available region of the sky where the Galactic confusion is
sub-dominant, specializing our analysis to the case represented by the
frequency coverage and nominal sensitivity and resolution of the Planck
experiment.Comment: 14 pages, 3 figures, to be published in JCA
Efficiency improvement of a ground coupled heat pump system from energy management
The installed capacity of an air conditioning system is usually higher than the average cooling or heating
demand along the year. So, most of the time, the system is working under its actual capacity. In this
contribution, we study the way to improve the efficiency of a ground coupled heat pump air conditioning
system by adapting its produced thermal energy to the actual thermal demand. For this purpose, an air
conditioning system composed by a ground coupled heat pump and a central fan coil linked to an office
located in a cooling dominated area was simulated, and a new management strategy aiming to diminish
electrical consumption was developed under the basic constraint that comfort requirements are kept.
This strategy takes advantage of the possibility of managing the air flow in the fan, the water mass flows
in the internal and external hydraulic systems, and the set point temperature in the heat pump to
achieve this objective. The electrical consumption of the system is calculated for the new management
strategy and compared with the results obtained for a conventional one, resulting in estimated energy
savings around 30%This work has been supported by the Spanish Government under projects "Modelado y simulacion de sistemas energeticos complejos" (2005 Ramon y Cajal program), "Modelado, simulacion y validacion experimental de la transferencia de calor en el entorno de la edificacion" (ENE2008-0059/CON). A. Sala is grateful to the financial support of grants DPI2008-06731-c02-01 (Spanish Government), and Generalitat Valenciana Prometeo/2008/088.Pardo García, N.; Montero Reguera, ÁE.; Sala Piqueras, A.; Martos Torres, J.; Urchueguía Schölzel, JF. (2011). Efficiency improvement of a ground coupled heat pump system from energy management. Applied Thermal Engineering. 31(2):391-398. https://doi.org/10.1016/j.applthermaleng.2010.09.016S39139831
CMBPol Mission Concept Study: Prospects for polarized foreground removal
In this report we discuss the impact of polarized foregrounds on a future
CMBPol satellite mission. We review our current knowledge of Galactic polarized
emission at microwave frequencies, including synchrotron and thermal dust
emission. We use existing data and our understanding of the physical behavior
of the sources of foreground emission to generate sky templates, and start to
assess how well primordial gravitational wave signals can be separated from
foreground contaminants for a CMBPol mission. At the estimated foreground
minimum of ~100 GHz, the polarized foregrounds are expected to be lower than a
primordial polarization signal with tensor-to-scalar ratio r=0.01, in a small
patch (~1%) of the sky known to have low Galactic emission. Over 75% of the sky
we expect the foreground amplitude to exceed the primordial signal by about a
factor of eight at the foreground minimum and on scales of two degrees. Only on
the largest scales does the polarized foreground amplitude exceed the
primordial signal by a larger factor of about 20. The prospects for detecting
an r=0.01 signal including degree-scale measurements appear promising, with 5
sigma_r ~0.003 forecast from multiple methods. A mission that observes a range
of scales offers better prospects from the foregrounds perspective than one
targeting only the lowest few multipoles. We begin to explore how optimizing
the composition of frequency channels in the focal plane can maximize our
ability to perform component separation, with a range of typically 40 < nu <
300 GHz preferred for ten channels. Foreground cleaning methods are already in
place to tackle a CMBPol mission data set, and further investigation of the
optimization and detectability of the primordial signal will be useful for
mission design.Comment: 42 pages, 14 figures, Foreground Removal Working Group contribution
to the CMBPol Mission Concept Study, v2, matches AIP versio
Small-Angle CMB Temperature Anisotropies Induced by Cosmic Strings
We use Nambu-Goto numerical simulations to compute the cosmic microwave
background (CMB) temperature anisotropies induced at arcminute angular scales
by a network of cosmic strings in a Friedmann-Lemaitre-Robertson-Walker (FLRW)
expanding universe. We generate 84 statistically independent maps on a 7.2
degree field of view, which we use to derive basic statistical estimators such
as the one-point distribution and two-point correlation functions. At high
multipoles, the mean angular power spectrum of string-induced CMB temperature
anisotropies can be described by a power law slowly decaying as \ell^{-p}, with
p=0.889 (+0.001,-0.090) (including only systematic errors). Such a behavior
suggests that a nonvanishing string contribution to the overall CMB
anisotropies may become the dominant source of fluctuations at small angular
scales. We therefore discuss how well the temperature gradient magnitude
operator can trace strings in the context of a typical arcminute
diffraction-limited experiment. Including both the thermal and nonlinear
kinetic Sunyaev-Zel'dovich effects, the Ostriker-Vishniac effect, and the
currently favored adiabatic primary anisotropies, we find that, on such a map,
strings should be ``eye visible,'' with at least of order ten distinctive
string features observable on a 7.2 degree gradient map, for tensions U down to
GU \simeq 2 x 10^{-7} (in Planck units). This suggests that, with upcoming
experiments such as the Atacama Cosmology Telescope (ACT), optimal
non-Gaussian, string-devoted statistical estimators applied to small-angle CMB
temperature or gradient maps may put stringent constraints on a possible cosmic
string contribution to the CMB anisotropies.Comment: 17 pages, 9 figures. v2: matches published version, minor
clarifications added, typo in Eq. (8) fixed, results unchange
MASCOTTE: Model for AnalySing and foreCasting shOrT TErm developments
MASCOTTE is the new version of the Banque de France's macro-econometric forecasting model. Following the last rebasing of National Accounts (currently at 1995 price), the previous version of the model was simplified, re-specified and re-estimated. The model is essentially used for making macro-economic projections of the French economy over a two-to-three year horizon, which requires an accounting framework as close as possible to the French National Accounts. The main agents are companies, households, general government and the rest of the world. The new version now includes a supply block derived from the explicit optimisation behaviour of companies using a Cobb-Douglas technology under imperfect competition, and a new Wage Setting schedule. Full homogeneity of the nominal side of the model ensures the independence between the nominal equilibrium and the real equilibrium, the latter being only determined in the long run by relative prices. Furthermore, as regards the specification of equations, special attention was paid to the consequences of changes in short-term interest rates.Macro-economic model ; Applied econometrics ; Forecasting ; France
Le modèle de prévision MASCOTTE pour l’économie française : principales propriétés et résultats de variantes.
In-situ surface technique analyses and ex-situ characterization of Si1-xGex epilayers grown on Si(001)-2 ×1 by molecular beam epitaxy
Si1-xGex epilayers grown by Molecular Beam Epitaxy on Si(001) at 400 ○C have been analyzed in-situ by surface techniques such as X-ray and Ultraviolet Photoelectron Spectroscopies (XPS and UPS), Low Energy Electron Diffraction (LEED) and photoelectron diffraction (XPD). The Ge surface concentrations (x) obtained from the ratios of Ge and Si core level intensities are systematically higher than those obtained by the respective evaporation fluxes. This indicates a Ge enrichment in the first overlayers confirmed by Ge-like UPS valence band spectra. The structured crystallographic character of the epilayers is ascertained by LEED and XPD polar scans in the (100) plane since the Ge Auger LMM and the Si 2p XPD intensity patterns from the Si1-xGex epilayers are identical to those of the Si substrate. The residual stress in the epilayer is determined by ex-situ X-ray diffraction (XRD) which also allows, as Rutherford Back Scattering (RBS), Ge concentration determinations
Searching for Signatures of Cosmic Superstrings in the CMB
Because cosmic superstrings generically form junctions and gauge theoretic
strings typically do not, junctions may provide a signature to distinguish
between cosmic superstrings and gauge theoretic cosmic strings. In cosmic
microwave background anisotropy maps, cosmic strings lead to distinctive line
discontinuities. String junctions lead to junctions in these line
discontinuities. In turn, edge detection algorithms such as the Canny algorithm
can be used to search for signatures of strings in anisotropy maps. We apply
the Canny algorithm to simulated maps which contain the effects of cosmic
strings with and without string junctions. The Canny algorithm produces edge
maps. To distinguish between edge maps from string simulations with and without
junctions, we examine the density distribution of edges and pixels crossed by
edges. We find that in string simulations without Gaussian noise (such as
produced by the dominant inflationary fluctuations) our analysis of the output
data from the Canny algorithm can clearly distinguish between simulations with
and without string junctions. In the presence of Gaussian noise at the level
expected from the current bounds on the contribution of cosmic strings to the
total power spectrum of density fluctuations, the distinction between models
with and without junctions is more difficult. However, by carefully analyzing
the data the models can still be differentiated.Comment: 15 page
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