347 research outputs found
Development and field-installation of a mathematical simulation model in support of irrigation canal management
Mathematical models / Simulation models / Flow / Hydraulics / Irrigation canals / Decision making / Research / Sri Lanka / Kirindi Oya
Tuning of Robust Distant Downstream PI Controllers for an Irrigation Canal Pool. II: Implementation Issues
Hydraulic mangement of filamentous algae in open-channel networks : case study in Southern France
International audiencePeriphyton constitutes the benthic compartment of aquatic environments such as artificial channels which are specific eco-systems for many reasons. Firstly, they have to fulfill hydraulic performance and water quality objectives. These objectives may be affected by filling problems due to algal developments and sanitary risks linked to toxins secreted by Cyanobacteria. Second, compared to natural streams, artificial channels have a relatively simple geometry and their hydraulic variables are easier to monitor. Also, cross regulators allow the managers to control discharges and water elevations. Periphyton dynamics depend on several factors and hydrodynamic is one of the most crucial one. In this article we analyze an original strategy for algal control currently used in a branch of the Canal de Provence (South of France). The management strategy consists of regular flushes causing increases of the bed shear stress from upstream to downstream and consequently algal filament cutting. This is achieved by increasing the discharge at the upstream end of the branch. We first show that turbidity can be used as an indicator for algal detachment. Then, a detachment model is proposed and coupled with the hydrodynamic simulation of the system. It can be fitted very satisfactorily on the turbidity measurements and can be used to improve the management strategy, such as reducing the discharge released
Photometry of a Galactic field at l = 232, b = -6. The old open cluster Auner 1, the Norma-Cygnus spiral arm and the signature of the warped Galactic Thick Disk
We perform a detailed photometric study of the stellar populations in a
Galactic Field at l = 232, b = -6 in the Canis Major (CMa) constellation. We
present the first U,B,V,I photometry of the old open cluster Auner1 and
determine it to be 3.25 Gyr old and to lie at 8.9 kpc from the Sun. In the
background of the cluster, at more than 9 kpc, we detect a young population
most probably associated to the Norma Cygnus spiral arm. Furthermore, we detect
the signature of an older population and identify its Turn Off and Red Giant
Branch. This population is found to have a mean age of 7 Gyrs and a mean
metallicity of Z = 0.006 . We reconstruct the geometry of the stellar
distribution and argue that this older population - often associated to the
Canis Major {\it galaxy}- belongs in fact to the warped old thin/thick disk
component along this line of sight.Comment: 19 pages, 7 eps figures (some degraded), accepted for publication in
the Astronomical Journa
SymTrees and Multi-Sector QFTs
The global symmetries of a -dimensional QFT can, in many cases, be
captured in terms of a -dimensional symmetry topological field theory
(SymTFT). In this work we construct a -dimensional theory which governs
the symmetries of QFTs with multiple sectors which have connected correlators
that admit a decoupling limit. The associated symmetry field theory decomposes
into a SymTree, namely a treelike structure of SymTFTs fused along possibly
non-topological junctions. In string-realized multi-sector QFTs, these
junctions are smoothed out in the extra-dimensional geometry, as we demonstrate
in examples. We further use this perspective to study the fate of higher-form
symmetries in the context of holographic large averaging where the
topological sectors of different large replicas become dressed by
additional extended operators associated with the SymTree.Comment: 69 pages + appendices + ref
The Luminosity & Mass Function of the Trapezium Cluster: From B stars to the Deuterium Burning Limit
We use the results of a new, multi-epoch, multi-wavelength, near-infrared
census of the Trapezium Cluster in Orion to construct and to analyze the
structure of its infrared (K band) luminosity function. Specifically, we employ
an improved set of model luminosity functions to derive this cluster's
underlying Initial Mass Function (IMF) across the entire range of mass from OB
stars to sub-stellar objects down to near the deuterium burning limit. We
derive an IMF for the Trapezium Cluster that rises with decreasing mass, having
a Salpeter-like IMF slope until near ~0.6 M_sun where the IMF flattens and
forms a broad peak extending to the hydrogen burning limit, below which the IMF
declines into the sub-stellar regime. Independent of the details, we find that
sub-stellar objects account for no more than ~22% of the total number of likely
cluster members. Further, the sub-stellar Trapezium IMF breaks from a steady
power-law decline and forms a significant secondary peak at the lowest masses
(10-20 times the mass of Jupiter). This secondary peak may contain as many as
\~30% of the sub-stellar objects in the cluster. Below this sub-stellar IMF
peak, our KLF modeling requires a subsequent sharp decline toward the planetary
mass regime. Lastly, we investigate the robustness of pre-main sequence
luminosity evolution as predicted by current evolutionary models, and we
discuss possible origins for the IMF of brown dwarfs.Comment: 74 pages, 30 figures, AASTeX5.0. To be published in the 01 July 2002
ApJ. For color version of figure 1 and online data table see
http://www.astro.ufl.edu/~muench/PUB/publications.htm
The highly polarized open cluster Trumpler 27
We have carried out multicolor linear polarimetry (UBVRI) of the brightest
stars in the area of the open cluster Trumpler 27. Our data show a high level
of polarization in the stellar light with a considerable dispersion, from to . The polarization vectors of the cluster members appear to be
aligned. Foreground polarization was estimated from the data of some non-member
objects, for which two different components were resolved: the first one
associated with a dust cloud close to the Sun producing
and degrees, and a second component, the main source of
polarization for the cluster members, originated in another dust cloud, which
polarizes the light in the direction of degrees. From a detailed
analysis, we found that the two components have associated values for the first one, and for the other. Due the
difference in the orientation of both polarization vectors, almost 90 degrees
(180 degrees at the Stokes representation), the first cloud (
degrees) depolarize the light strongly polarized by the second one ( degrees).Comment: 12 Pages, 6 Figures, 2 tables (9 Pages), accepted for publication in
A
Trypanosomiase humaine africaine : étude d'un score de présomption de diagnostic au Congo
Une enquĂȘte cas-tĂ©moins a Ă©tĂ© rĂ©alisĂ©e au Congo afin de dĂ©finir une grille de score de prĂ©somption de la maladie du sommeil Ă #T.b. gambiense$, basĂ©e sur une sĂ©lection de critĂšres cliniques et Ă©pidĂ©miologiques de la trypanosomiase, utilisable par les structures sanitaires pĂ©riphĂ©riques. L'enquĂȘte a Ă©tĂ© rĂ©alisĂ©e sur 163 cas et 326 tĂ©moins. Les signes cliniques et les symptĂŽmes retenus sont :fiĂšvre, cĂ©phalĂ©es, prurit et lĂ©sions de grattage, diarrhĂ©e, oedĂšmes, adĂ©nopathies cervicales, troubles du sommeil, troubles de l'appĂ©tit, troubles sexuels, psychisme, signes neurologiques et autres troubles cliniques mineurs. Les autres critĂšres retenus sont les antĂ©cĂ©dents de trypanosomiase humaine africaine (THA) et l'existence d'un cheptel dans la concession. L'analyse des rĂ©sultats confirme qu'il n'existe pas de critĂšre ou groupe de critĂšres pathognomoniques. Aucun des critĂšres sĂ©lectionnĂ©s n'est suffisamment discriminant pour permettre une sĂ©lection des trypanosomĂ©s parmi les consultants. Une grille de score de prĂ©somption semble donc de peu d'utilitĂ© au niveau pĂ©riphĂ©rique; ceci est d'autant plus vrai si l'on considĂšre l'augmentation de la charge de travail. Le faible pouvoir discriminant des signes cliniques et des symptĂŽmes ainsi que des autres paramĂštres de la trypanosomiase africaine met en Ă©vidence la difficultĂ© de mise en place d'une stratĂ©gie d'intĂ©gration efficiente en tant qu'outil diagnostique prĂ©coce. (RĂ©sumĂ© d'auteur
Massive open star clusters using the VVV survey II. Discovery of six clusters with Wolf-Rayet stars
Context: The ESO Public Survey "VISTA Variables in the V\'ia L\'actea" (VVV)
provides deep multi-epoch infrared observations for an unprecedented 562 sq.
degrees of the Galactic bulge, and adjacent regions of the disk. In this survey
nearly 150 new open clusters and cluster candidates have been discovered. Aims:
This is the second in a series of papers about young, massive open clusters
observed using the VVV survey. We present the first study of six recently
discovered clusters. These clusters contain at least one newly discovered
Wolf-Rayet (WR) star. Methods: Following the methodology presented in the first
paper of the series, wide-field, deep JHKs VVV observations, combined with new
infrared spectroscopy, are employed to constrain fundamental parameters for a
subset of clusters. Results: We affirm that the six studied stellar groups are
real young (2-7 Myr) and massive (between 0.8 and 2.2 10^3 Msol) clusters. They
are highly obscured (Av ~ 5-24 mag) and compact (1-2 pc). In addition to WR
stars, two of the six clusters also contain at least one red supergiant star.
We claim the discovery of 8 new WR stars, and 3 stars showing WR-like emission
lines which could be classified WR or OIf. Preliminary analysis provides
initial masses of ~30-50 Msol for the WR stars. Finally,we discuss the spiral
structure of the Galaxy using as tracers the six new clusters together with the
previously studied VVV clusters.Comment: 17 pages, 8 figurs, accepted in A&
Massive open star clusters using the VVV survey, I: presentation of the data and description of the approach
Context. The ESO Public Survey âVISTA Variables in the VĂa LĂĄcteaâ (VVV) provides deep multi-epoch infrared observations for unprecedented 562 sq. degrees of the Galactic bulge, and adjacent regions of the disk. Aims. The VVV observations will foster the construction of a sample of Galactic star clusters with reliable and homogeneously derived physical parameters (e.g., age, distance, and mass, etc.). In this first paper in a series, the methodology employed to establish cluster parameters for the envisioned database are elaborated upon by analysing four known young open clusters: Danks 1, Danks 2, RCW 79, and DBS 132. The analysis offers a first glimpse of the information that can be gleaned from the VVV observations for clusters in the final database. Methods. Wide-field, deep JHKs VVV observations, combined with new infrared spectroscopy, are employed to constrain fundamental parameters for a subset of clusters. Results. Results are inferred from VVV near-infrared photometry and numerous low resolution spectra (typically more than 10 per cluster). The high quality of the spectra and the deep wideâfield VVV photometry enables us to precisely and independently determine the characteristics of the clusters studied, which we compare to previous determinations. An anomalous reddening law in the direction of the Danks clusters is found, specifically E(J â H)/E(H â Ks) = 2.20 ± 0.06, which exceeds published values for the inner Galaxy. The G305 star forming complex, which includes the Danks clusters, lies beyond the Sagittarius-Carina spiral arm and occupies the Centaurus arm. Finally, the first deep infrared colour-magnitude diagram of RCW 79 is presented, which reveals a sizeable pre-main sequence population. A list of candidate variable stars in G305 region is reported. Conclusions. This study demonstrates the strength of the dataset and methodology employed, and constitutes the first step of a broader study which shall include reliable parameters for a sizeable number of poorly characterised and/or newly discovered clusters.Fil: ChenĂ©, A.-N.. Universidad de ValparaĂso; ChileFil: Borissova, J.. Universidad de ValparaĂso; ChileFil: Clarke, J. R. A.. Universidad de ValparaĂso; ChileFil: Bonatto, C.. Universidade Federal do Rio Grande do Sul; BrasilFil: Majaess, D. J.. Saint Marys University; CanadĂĄFil: Moni Bidin, C.. Universidad de ConcepciĂłn; ChileFil: Sale, S. E.. Universidad de ValparaĂso; ChileFil: Mauro, F.. Universidad de ConcepciĂłn; ChileFil: Kurtev, R.. Universidad de ValparaĂso; ChileFil: Baume, Gustavo Luis. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; ArgentinaFil: Feinstein Baigorri, Carlos. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; ArgentinaFil: Ivanov, V. D.. European Southern Observatory; ChileFil: Geisler, Doug. Universidad de ConcepciĂłn; ChileFil: Catelan, M.. The Milky Way Millennium Nucleus; ChileFil: Minniti, Dante. The Milky Way Millennium Nucleus; ChileFil: Lucas, P.. University Of Hertfordshire; Reino UnidoFil: de Grijs, R.. Peking University; ChinaFil: Kumar, M. S. N.. Centro de Astrofisica da Universidade do Porto; Portuga
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