254 research outputs found
Solar hybrid road: from concept to modeling and lab scale mock-up experiments
International audience; We present in this paper the concept of solar hybrid road and the numerical model studied and develop to compute its thermal state at any time step. The aim of these new structures is to collect part of the solar radiation during the summer period, to prevent from icing at the surface during the winter period. As it is reversible, it will help also to prevent from a too high structure temperature (in particular closed to the surface) in summer season. Two types of modifications, compared to traditional structures are presented. The first one concerns the insertion of a porous layer allowing a heat fluid to exchange thermal energy. The second one concerns the use of a semi-transparent material at pavement surface allowing the solar radiation to penetrate deeper in the structure. The numerical model of this multi-physics problem develop with the finite element method is presented and discussed. A validation on two test cases is proposed. First results on energy harvesting evaluation for few locations (i.e. climatic conditions) in France are presented and discussed. Finally, conclusion and perspectives are proposed.
Document type: Conference objec
Research Quality, Publications and Impact in Civil Engineering into the 21st Century. Publish or Perish, Commercial versus Open Access, Internet versus Libraries?
A research project is only completed when it has been published and shared with the community. Referees and peer experts play an important role to control the research quality. While some new electronic tools provide further means to disseminate some research information, the quality and impact of the works remain linked with some thorough expert-review process and the publication in international scientific journals and books; unethical publishing standards are not acceptable. The writer argues herein that the new electronic aids do not replace scholarship nor critical thinking, although they impact on the working environment of civil engineers
Thermographic monitoring of asphalt concrete surface with phase change materials inclusions for icing delays purposes
International audienceIf de-icers still are the main solution to avoid black ice occurrence and snow accumulation on pavements, some alternatives based on transportation infrastructure modifications have been tested over the past years. They aim at the reduction of environmental impacts and at coping with budgets constraints and cuts, including in winter maintenance. Among existing ones, the implementation of phase changes materials (PCM) into the infrastructure was evaluated to delay the occurrence of water in its solid phase on the surface. Additional results were obtained with an asphalt concrete in simulated winter conditions, indicating a tenuous thermal effect at the surface
Sex and gender differences in tobacco smoking among adolescents in French secondary schools
Aim. We investigated the relationship between sex (genetic/biological) and gender (environmental/ cultural) factors in relation to adolescent tobacco smoking. Methods. A representative sample of 11,582 students from French secondary public schools participated in the study by completing a self-administered, standardised questionnaire. Results. Using the WHO classification for smoking in the youth, 15.6% of the adolescents were regular smokers, 7.7% occasional smokers, 17.9% experimental smokers and 4.8% ex-smokers, with no statistically significant gender difference. Taking non-smoking as a reference, puberty had a much greater effect on the likelihood of being a regular smoker [OR=18.0 (95% Confidence Interval: 9.6- 32)] than of being an experimental/occasional smoker [OR=3.7 (2.9-4.6)] among girls. For boys, the effect of puberty was not as great [OR=4.7 (3.5-6.5)] for regular vs. [OR=2.1 (1.8-2.5)] for experimental/occasional smokers). Similarly, illicit drug use had a larger effect on the likelihood of being regular smoker vs. non-smoker [OR=15.0 (12.0-20.0) in boys and 12 (8.8-16.0) in girls] than of being experimental/occasional smoker vs. a non-smoker [OR=4.8 (3.7-6.1) and 2.9 (2.1-3.9) respectively]. Other factors related to regular smoking were exposure to passive smoking and regular alcohol consumption. Living with both parents was a protective factor for life and regular smoking in both genders. Conclusions. Our results show that influential factors of sex-related (puberty), gender-specific (environmental tobacco smoking, alcohol consumption, drug abuse) or sex/gender (regular sexual intercourse) are related to the smoking behaviour in French adolescents
Fundamental Properties of Stars using Asteroseismology from Kepler & CoRoT and Interferometry from the CHARA Array
We present results of a long-baseline interferometry campaign using the PAVO
beam combiner at the CHARA Array to measure the angular sizes of five
main-sequence stars, one subgiant and four red giant stars for which solar-like
oscillations have been detected by either Kepler or CoRoT. By combining
interferometric angular diameters, Hipparcos parallaxes, asteroseismic
densities, bolometric fluxes and high-resolution spectroscopy we derive a full
set of near model-independent fundamental properties for the sample. We first
use these properties to test asteroseismic scaling relations for the frequency
of maximum power (nu_max) and the large frequency separation (Delta_nu). We
find excellent agreement within the observational uncertainties, and
empirically show that simple estimates of asteroseismic radii for main-sequence
stars are accurate to <~4%. We furthermore find good agreement of our measured
effective temperatures with spectroscopic and photometric estimates with mean
deviations for stars between T_eff = 4600-6200 K of -22+/-32 K (with a scatter
of 97K) and -58+/-31 K (with a scatter of 93 K), respectively. Finally we
present a first comparison with evolutionary models, and find differences
between observed and theoretical properties for the metal-rich main-sequence
star HD173701. We conclude that the constraints presented in this study will
have strong potential for testing stellar model physics, in particular when
combined with detailed modelling of individual oscillation frequencies.Comment: 18 pages, 12 figures, 7 tables; accepted for publication in Ap
The solar-like CoRoT target HD 170987: spectroscopic and seismic observations
The CoRoT mission is in its third year of observation and the data from the
second long run in the galactic centre direction are being analysed. The
solar-like oscillating stars that have been observed up to now have given some
interesting results, specially concerning the amplitudes that are lower than
predicted. We present here the results from the analysis of the star HD
170987.The goal of this research work is to characterise the global parameters
of HD 170987. We look for global seismic parameters such as the mean large
separation, maximum amplitude of the modes, and surface rotation because the
signal-to-noise ratio in the observations do not allow us to measure individual
modes. We also want to retrieve the stellar parameters of the star and its
chemical composition.We have studied the chemical composition of the star using
ground-based observations performed with the NARVAL spectrograph. We have used
several methods to calculate the global parameters from the acoustic
oscillations based on CoRoT data. The light curve of the star has been
interpolated using inpainting algorithms to reduce the effect of data gaps. We
find power excess related to p modes in the range [400 - 1200]muHz with a mean
large separation of 55.2+-0.8muHz with a probability above 95% that increases
to 55.9 +-0.2muHz in a higher frequency range [500 - 1250] muHz and a rejection
level of 1%. A hint of the variation of this quantity with frequency is also
found. The rotation period of the star is estimated to be around 4.3 days with
an inclination axis of i=50 deg +20/-13. We measure a bolometric amplitude per
radial mode in a range [2.4 - 2.9] ppm around 1000 muHz. Finally, using a grid
of models, we estimate the stellar mass, M=1.43+-0.05 Msun, the radius,
R=1.96+-0.046 Rsun, and the age ~2.4 Gyr.Comment: 12 pages, 15 figures, accepted for publication in A&
Iron and Nickel spectral opacity calculations in conditions relevant for pulsating stellar envelopes and experiments
Seismology of stars is strongly developing. To address this question we have
formed an international collaboration OPAC to perform specific experimental
measurements, compare opacity calculations and improve the opacity calculations
in the stellar codes [1]. We consider the following opacity codes: SCO,
CASSANDRA, STA, OPAS, LEDCOP, OP, SCO-RCG. Their comparison has shown large
differences for Fe and Ni in equivalent conditions of envelopes of type II
supernova precursors, temperatures between 15 and 40 eV and densities of a few
mg/cm3 [2, 3, 4]. LEDCOP, OPAS, SCO-RCG structure codes and STA give similar
results and differ from OP ones for the lower temperatures and for spectral
interval values [3]. In this work we discuss the role of Configuration
Interaction (CI) and the influence of the number of used configurations. We
present and include in the opacity code comparisons new HULLAC-v9 calculations
[5, 6] that include full CI. To illustrate the importance of this effect we
compare different CI approximations (modes) available in HULLAC-v9 [7]. These
results are compared to previous predictions and to experimental data.
Differences with OP results are discussed.Comment: 4 pages, 3 figures, conference Inertial Fusion Sciences and
Applications, Bordeaux, 12th to 16th September 2011; EPJ web of Conferences
201
A more realistic representation of overshoot at the base of the solar convective envelope as seen by helioseismology
The stratification near the base of the Sun's convective envelope is governed
by processes of convective overshooting and element diffusion, and the region
is widely believed to play a key role in the solar dynamo. The stratification
in that region gives rise to a characteristic signal in the frequencies of
solar p modes, which has been used to determine the depth of the solar
convection zone and to investigate the extent of convective overshoot. Previous
helioseismic investigations have shown that the Sun's spherically symmetric
stratification in this region is smoother than that in a standard solar model
without overshooting, and have ruled out simple models incorporating
overshooting, which extend the region of adiabatic stratification and have a
more-or-less abrupt transition to subadiabatic stratification at the edge of
the overshoot region. In this paper we consider physically motivated models
which have a smooth transition in stratification bridging the region from the
lower convection zone to the radiative interior beneath. We find that such a
model is in better agreement with the helioseismic data than a standard solar
model.Comment: 18 pages, 4 tables, 24 figures - to appear in MNRAS (version a:
equation 9 corrected
Enhanced lithium depletion in Sun-like stars with orbiting planets
The surface abundance of lithium on the Sun is 140 times less than
protosolar, yet the temperature at the base of the surface convective zone is
not hot enough to burn Li. A large range of Li abundances in solar type stars
of the same age, mass and metallicity is observed, but theoretically difficult
to understand. An earlier suggestion that Li is more depleted in stars with
planets was weakened by the lack of a proper comparison sample of stars without
detected planets. Here we report Li abundances for an unbiased sample of
solar-analogue stars with and without detected planets. We find that the
planet-bearing stars have less than 1 per cent of the primordial Li abundance,
while about 50 per cent of the solar analogues without detected planets have on
average 10 times more Li. The presence of planets may increase the amount of
mixing and deepen the convective zone to such an extent that the Li can be
burned.Comment: 13 pages, 2 figure
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