43 research outputs found
Dimensionnement hydrologique des retenues collinaires en Algérie
Dans les pays semi-arides et mĂ©diterranĂ©ens, la production agricole peut ĂȘtre intensifiĂ©e par la crĂ©ation de nombreuses retenues collinaires. Une sĂ©rie de manuels a Ă©tĂ© rĂ©alisĂ©e en AlgĂ©rie afin de permettre la construction rapide, et suivant des rĂšgles homogĂšnes, de centaines de retenues collinaires. Il a Ă©tĂ© ainsi Ă©laborĂ© en particulier un manuel pour le dimensionnement hydrologique des retenues dont les principes sont exposĂ©s dans le prĂ©sent article. Des abaques normalisĂ©s prĂ©sentant en compte les apports moyens des bassins versants ont Ă©tĂ© prĂ©parĂ©s suivant une variante gĂ©nĂ©ralisĂ©e du modĂšle MORAN, en utilisant les chroniques d'observations des stations hydromĂ©triques des diverses unitĂ©s gĂ©ographiques. Il a Ă©tĂ© construit, pour leur mise en application, des cartes des isolignes relatives aux apports annuels moyens et aux apports annuels de frĂ©quence 80% au dĂ©passement. (RĂ©sumĂ© d'auteur
Current Results of the EC-sponsored Catchment Modelling (CatchMod) Cluster
To support the Water Framework Directive implementation, much research has been commissioned at both national and European levels. CatchMod is a cluster of these projects, which is focusing on the development of computational catchment models and related tools. This paper presents an overview of the results of the CatchMod cluster to dat
The 2003-4 multisite photometric campaign for the Beta Cephei and eclipsing star 16 (EN) Lacertae with an Appendix on 2 Andromedae, the variable comparison star
A multisite photometric campaign for the Beta Cephei and eclipsing variable
16 Lacertae is reported. 749 h of high-quality differential photoelectric
Stromgren, Johnson and Geneva time-series photometry were obtained with ten
telescopes during 185 nights. After removing the pulsation contribution, an
attempt was made to solve the resulting eclipse light curve by means of the
computer program EBOP. Although a unique solution was not obtained, the range
of solutions could be constrained by comparing computed positions of the
secondary component in the Hertzsprung-Russell diagram with evolutionary
tracks.
For three high-amplitude pulsation modes, the uvy and the Geneva UBG
amplitude ratios are derived and compared with the theoretical ones for
spherical-harmonic degrees l <= 4. The highest degree, l = 4, is shown to be
incompatible with the observations. One mode is found to be radial, one is l =
1, while in the remaining case l = 2 or 3.
The present multisite observations are combined with the archival photometry
in order to investigate the long-term variation of the amplitudes and phases of
the three high-amplitude pulsation modes. The radial mode shows a
non-sinusoidal variation on a time-scale of 73 yr. The l = 1 mode is a triplet
with unequal frequency spacing, giving rise to two beat-periods, 720.7 d and
29.1 yr. The amplitude and phase of the l = 2 or 3 mode vary on time-scales of
380.5 d and 43 yr.
The light variation of 2 And, one of the comparison stars, is discussed in
the Appendix.Comment: 18 pages, 19 figures, accepted for publication in MNRA
Asteroseismology of the Beta Cephei star 12 (DD) Lacertae: photometric observations, pulsational frequency analysis and mode identification
We report a multisite photometric campaign for the Beta Cephei star 12
Lacertae. 750 hours of high-quality differential photoelectric Stromgren,
Johnson and Geneva time-series photometry were obtained with 9 telescopes
during 190 nights. Our frequency analysis results in the detection of 23
sinusoidal signals in the light curves. Eleven of those correspond to
independent pulsation modes, and the remainder are combination frequencies. We
find some slow aperiodic variability such as that seemingly present in several
Beta Cephei stars. We perform mode identification from our colour photometry,
derive the spherical degree l for the five strongest modes unambiguously and
provide constraints on l for the weaker modes. We find a mixture of modes of 0
<= l <= 4. In particular, we prove that the previously suspected rotationally
split triplet within the modes of 12 Lac consists of modes of different l;
their equal frequency splitting must thus be accidental.
One of the periodic signals we detected in the light curves is argued to be a
linearly stable mode excited to visible amplitude by nonlinear mode coupling
via a 2:1 resonance. We also find a low-frequency signal in the light
variations whose physical nature is unclear; it could be a parent or daughter
mode resonantly coupled. The remaining combination frequencies are consistent
with simple light-curve distortions.
The range of excited pulsation frequencies of 12 Lac may be sufficiently
large that it cannot be reproduced by standard models. We suspect that the star
has a larger metal abundance in the pulsational driving zone, a hypothesis also
capable of explaining the presence of Beta Cephei stars in the LMC.Comment: 12 pages, 7 figures, MNRAS, in pres
Dimensionnement hydrologique des retenues collinaires en Algérie
Dans les pays semi-arides et mĂ©diterranĂ©ens, la production agricole peut ĂȘtre intensifiĂ©e par la crĂ©ation de nombreuses retenues collinaires. Une sĂ©rie de manuels a Ă©tĂ© rĂ©alisĂ©e en AlgĂ©rie afin de permettre la construction rapide, et suivant des rĂšgles homogĂšnes, de centaines de retenues collinaires. Il a Ă©tĂ© ainsi Ă©laborĂ© en particulier un manuel pour le dimensionnement hydrologique des retenues dont les principes sont exposĂ©s dans le prĂ©sent article. Des abaques normalisĂ©s prĂ©sentant en compte les apports moyens des bassins versants ont Ă©tĂ© prĂ©parĂ©s suivant une variante gĂ©nĂ©ralisĂ©e du modĂšle MORAN, en utilisant les chroniques d'observations des stations hydromĂ©triques des diverses unitĂ©s gĂ©ographiques. Il a Ă©tĂ© construit, pour leur mise en application, des cartes des isolignes relatives aux apports annuels moyens et aux apports annuels de frĂ©quence 80% au dĂ©passement. (RĂ©sumĂ© d'auteur