237 research outputs found
A survey for near-infrared H2 emission in Herbig Ae/Be stars: emission from the outer disks of HD 97048 and HD 100546
We report on a sensitive search for H2 1-0 S(1), 1-0 S(0) and 2-1 S(1)
ro-vibrational emission at 2.12, 2.22 and 2.25 micron in a sample of 15 Herbig
Ae/Be stars employing CRIRES, the ESO-VLT near-infrared high-resolution
spectrograph, at R~90,000. We detect the H2 1-0 S(1) line toward HD 100546 and
HD 97048. In the other 13 targets, the line is not detected. The H2 1-0 S(0)
and 2-1 S(1) lines are undetected in all sources. This is the first detection
of near-IR H2 emission in HD 100546. The H2 1-0 S(1) lines observed in HD
100546 and HD 97048 are observed at a velocity consistent with the rest
velocity of both stars, suggesting that they are produced in the circumstellar
disk. In HD 97048, the emission is spatially resolved and it is observed to
extend at least up to 200 AU. We report an increase of one order of magnitude
in the H2 1-0 S(1) line flux with respect to previous measurements taken in
2003 for this star, which suggests line variability. In HD 100546 the emission
is tentatively spatially resolved and may extend at least up to 50 AU. Modeling
of the H2 1-0 S(1) line profiles and their spatial extent with flat keplerian
disks shows that most of the emission is produced at a radius >5 AU. Upper
limits to the H2 1-0 S(0)/ 1-0 S(1) and H2 2-1 S(1)/1-0 S(1) line ratios in HD
97048 are consistent with H2 gas at T>2000 K and suggest that the emission
observed may be produced by X-ray excitation. The upper limits for the line
ratios for HD 100546 are inconclusive. Because the H2 emission is located at
large radii, for both sources a thermal emission scenario (i.e., gas heated by
collisions with dust) is implausible. We argue that the observation of H2
emission at large radii may be indicative of an extended disk atmosphere at
radii >5 AU. This may be explained by a hydrostatic disk in which gas and dust
are thermally decoupled or by a disk wind caused by photoevaporation.Comment: Accepted by A&A. 16 pages, 7 figure
Tribological study on solid lubricants at high temperature used in expansion machine
Dans le cadre de la conception d’un expanseur dédié à la récupération d’énergie à l’échappement d’un moteur à combustion interne, une étude sur des lubrifiants solides a été menée afin de choisir le couple de matériaux adéquat pour le joint principal de la machine. Ce joint doit assurer à la fois une fonction d’étanchéité interne et limiter ainsi les pertes par fuites internes de l’expanseur. Il doit également présenter un coefficient de frottement la plus faible possible afin de réduire les pertes par friction. Ce joint est en effet sollicité par des contraintes en frottement plan dans un environnement sous vapeur d’eau à des températures pouvant atteindre 250°C. Ces températures rendent complexe l’utilisation d’huile et le recours à des matériaux auto lubrifiants est dès lors l’unique solution
A Comparison of Discrete and Soft Speech Units for Improved Voice Conversion
The goal of voice conversion is to transform source speech into a target
voice, keeping the content unchanged. In this paper, we focus on
self-supervised representation learning for voice conversion. Specifically, we
compare discrete and soft speech units as input features. We find that discrete
representations effectively remove speaker information but discard some
linguistic content - leading to mispronunciations. As a solution, we propose
soft speech units. To learn soft units, we predict a distribution over discrete
speech units. By modeling uncertainty, soft units capture more content
information, improving the intelligibility and naturalness of converted speech.
Samples available at https://ubisoft-laforge.github.io/speech/soft-vc/. Code
available at https://github.com/bshall/soft-vc/.Comment: 5 pages, 2 figures, 2 tables. Accepted at ICASSP 202
Une approche symbolique pour la vérification et le test des chorégraphies de services
L'ingénierie orientée services est un nouveau paradigme pour développer des logiciels distribués et collaboratifs. Un tel logiciel se compose de plusieurs entités, appelés services, chacun d'entre eux étant par exemple une application Web, un service Web, ou même un humain. Les services peuvent être développés indépendamment et sont composés pour atteindre quelques exigences. Les chorégraphies de service définissent ces exigences avec une perspective globale, basée sur les interactions entre des participants qui sont implémentés en tant que services. Cette thèse vise à formaliser des problèmes et tente d'élaborer un environnement intégré avec lequel les chorégraphies de services peuvent être développés correctement pour les deux types d'approches de développement: l'approche descendante et l'approche ascendante. Elle consiste à analyser la relation entre une spécification de chorégraphie et une implémentation de la chorégraphie au niveau du modèle et aussi au niveau de l'implémentation réelle. Particulièrement, il s'agit de la composition/décomposition des services, la vérification, et le test de l'implémentation de chorégraphie. Le premier point-clé de notre environnement intégré est de représenter le passage de valeurs entre les services en utilisant la technique symbolique et un solveur SMT. Cette technique nous permet de réduire les faux négatifs et de contourner le problème d'explosion combinatoire de l'espace d'états, ces problèmes sont durs à l'abstraction et à l'énumération des valeurs pour les approches existantes basées données. Le second point-clé est le test passif boîte noire de l'implémentation de chorégraphie. Il ne nécessite pas d'accéder au code source, ni de rendre indisponible l'implémentation pendant le processus de test. Notre environnement intégré est mis en œuvre dans nos outils qui sont disponibles en téléchargement ou à utiliser en ligne à l adresse http://schora.lri.fr.Service-oriented engineering is an emerging software development paradigm for distributed collaborative applications. Such an application is made up of several entities abstracted as services, each of them being for example a Web application, a Web service, or even a human. The services can be developed independently and are composed to achieve common requirements through interactions among them. Service choreographies define such requirements from a global perspective, based on interactions among a set of participants. This thesis aims to formalize the problems and attempts to develop a framework by which service choreographies can be developed correctly for both top-down and bottom-up approaches. It consists in analyzing the relation between a choreography specification and a choreography implementation at both model level and real implementation level. Particularly, it concerns the composition/decomposition service design, the verification, and the testing of choreography implementation. The first key point of our framework is to support value-passing among services by using symbolic technique and SMT solver. It overcomes false negatives or state space explosion issues due by abstracting or limiting the data domain of value-passing in existing approaches. The second key point is the black-box passive testing of choreography implementation. It does not require neither to access to source codes nor to make the implementation unavailable during the testing process. Our framework is fully implemented in our toolchains, which can be downloaded or used online at address: http://schora.lri.fr.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF
A Coloured Petri Nets Based Attack Tolerance Framework
International audienceWeb services provide a general basis of convenient access and operation for cloud applications. However, such services become very vulnerable when being attacked, especially in the situation where service continuity is one of the most important requirements. This issue highlights the necessity to apply reliable and formal methods to attack tolerance in Web services. In this paper, we propose a Coloured Petri Nets based method for attack tolerance by modelling and analysing basic behaviours of attack-network interaction, attack detectors and their tolerance solutions. Furthermore, complex attacks can be analysed and tolerance solutions deployed by identifying these basic attack-network interactions and composing their solutions. The validity of our method is demonstrated through a case study on attack tolerance in cloud-based medical information storage
Characterising the magnetic fields of the Herbig Ae/Be stars HD97048, HD150193, HD176386, and MWC480
Our knowledge of the presence and the role of magnetic fields in
intermediate-mass pre-main-sequence stars remains very poor.
We present the magnetic properties of four Herbig Ae/Be stars that have not
been previously studied in detail.
Our results for the three Herbig Ae/Be stars HD97048, HD150193, and HD176386
are based on multi-epoch low-resolution spectra obtained in spectropolarimetric
mode with FORS2 mounted on the VLT. New high-resolution polarimetric spectra
were obtained for MWC480 with the SOFIN spectrograph installed at the Nordic
Optical Telescope. We discuss 41 FORS2 low-resolution observations of the
Herbig Ae/Be stars HD97048, HD150193, and HD176386 and determine their
rotational periods. Using stellar fundamental parameters and the longitudinal
magnetic field phase curves, we place constraints on the magnetic field
geometry. Three high-resolution circularly polarised SOFIN spectra obtained for
MWC480 were measured using the moment technique where wavelength shifts between
right- and left-hand side circularly polarised spectra are interpreted in terms
of a longitudinal magnetic field .
Our search for periodicities resulted in P=0.693d for HD97048, P=1.317d for
HD150193, and P=0.899d for HD176386. The magnetic field geometry can likely be
described by a centred dipole with a polar magnetic field strength B_d of
several hundred Gauss. The longitudinal magnetic-field measurements of MWC480
reveal the presence of a strong kG field, which was undetected in our previous
low-resolution polarimetric observations with FORS1. A weak magnetic field was
detected in the circumstellar components of the Ca II H&K lines and the Na I D
lines, indicating a complex interaction between the stellar magnetic field and
the circumstellar environment.Comment: 8 pages, 9 figures, 5 tables, accepted for publication in A&
Recent studies of magnetic fields in Herbig Ae/Be stars
New determinations of the mean longitudinal magnetic field for several Herbig Ae/Be stars are presented. The longitudinal magnetic field measurements of MWC 480 reveal the presence of a strong kG field, which was undetected in our previous low‐resolution polarimetric observations with FORS 1. The magnetic field geometries of Herbig Ae/Be stars studied with spectropolarimetric time series can likely be described by centred dipoles with polar magnetic field strengths of several hundred Gauss. A number of Herbig Ae/Be stars with detected magnetic fields were recently observed with X‐shooter in the visible and near‐IR as well as with the high‐resolution near‐IR spectrograph CRIRES. These observations are of great importance to understand the relation between the magnetic field topology and the physics of accretion flow and accretion disk gas emission (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/89448/1/1022_ftp.pd
Evidence for CO depletion in the inner regions of gas-rich protoplanetary disks
We investigate the physical properties and spatial distribution of Carbon
Monoxide (CO) gas in the disks around the Herbig Ae/Be stars HD 97048 and HD
100546.
Using high-spectral-resolution 4.588-4.715 m spectra containing
fundamental CO emission taken with CRIRES on the VLT, we probe the
circumstellar gas and model the kinematics of the emission lines. By using
spectro-astrometry on the spatially resolved targets, we constrain the physical
size of the emitting regions in the disks. We resolve, spectrally and
spatially, the emission of the CO v(1-0) vibrational band and the
CO and vibrational bands in both targets,
as well as the CO band in HD 100546. Modeling of the CO emission
with a homogeneous disk in Keplerian motion, yields a best fit with an inner
and outer radius of the CO emitting region of 11 and 100 AU for HD
97048. HD 100546 is not fit well with our model, but we derive a lower limit on
the inner radius of 8 AU. The fact that gaseous [OI] emission was previously
detected in both targets at significantly smaller radii suggests that CO may be
effectively destroyed at small radii in the surface layers of these disksComment: v2: Letter format has been changed to Paper format; Change in the
focus of the paper towards CO depletion; Major changes in text; Change of
title. Submitted to A&A, 14/10/2008. Accepted by A&A, 17/04/200
GASPS observations of Herbig Ae/Be stars with PACS/Herschel. The atomic and molecular content of their protoplanetary discs
We observed a sample of 20 representative Herbig Ae/Be stars and five A-type
debris discs with PACS onboard of Herschel. The observations were done in
spectroscopic mode, and cover far-IR lines of [OI], [CII], CO, CH+, H2O and OH.
We have a [OI]63 micron detection rate of 100% for the Herbig Ae/Be and 0% for
the debris discs. [OI]145 micron is only detected in 25%, CO J=18-17 in 45%
(and less for higher J transitions) of the Herbig Ae/Be stars and for [CII] 157
micron, we often found spatially variable background contamination. We show the
first detection of water in a Herbig Ae disc, HD 163296, which has a settled
disc. Hydroxyl is detected as well in this disc. CH+, first seen in HD 100546,
is now detected for the second time in a Herbig Ae star, HD 97048. We report
fluxes for each line and use the observations as line diagnostics of the gas
properties. Furthermore, we look for correlations between the strength of the
emission lines and stellar or disc parameters, such as stellar luminosity, UV
and X-ray flux, accretion rate, PAH band strength, and flaring. We find that
the stellar UV flux is the dominant excitation mechanism of [OI]63 micron, with
the highest line fluxes found in those objects with a large amount of flaring
and greatest PAH strength. Neither the amount of accretion nor the X-ray
luminosity has an influence on the line strength. We find correlations between
the line flux of [OI]63 micron and [OI]145 micron, CO J = 18-17 and [OI]6300
\AA, and between the continuum flux at 63 micron and at 1.3 mm, while we find
weak correlations between the line flux of [OI]63 micron and the PAH
luminosity, the line flux of CO J = 3-2, the continuum flux at 63 micron, the
stellar effective temperature and the Brgamma luminosity. (Abbreviated version)Comment: 20 pages, 29 figures, accepted by Astronomy and Astrophysic
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