2,735 research outputs found
Analyse aérodynamique et acoustique d'une architecture boxwing dans le cadre du projet PARSIFAL
International audienceThe present paper summarizes the main results obtained from the CFD analysis of a reference boxwing configuration designed during the initial phase of the PARSIFAL project, with focus on the assessment of its aerodynamic performance in the transonic regime. For such purpose, high-fidelity RANS computations have been carried out and a detailed inspection of the different drag sources, induced, wave and viscous drag components, is presented. In addition, preliminary results from the acoustic analysis of such innovative aircraft configuration are also discussed, concerning the impact of the engine location
Sizing nanomatter in biological fluids by fluorescence single particle tracking
Accurate sizing of nanoparticles in biological media is important for drug delivery and biomedical imaging applications since size directly influences the nanoparticle processing and nanotoxicity in vivo. Using fluorescence single particle cracking we have succeeded for the first time in following the aggregation of drug delivery nanoparticles in real time in undiluted whole blood. We demonstrate that, by using a suitable surface functionalization, nanoparticle aggregation in the blood circulation is prevented to a large extent
Concepts of Operations for Asteroid Rendezvous Missions Focused on Resources Utilization
Several asteroids are the targets of international robotic space missions currently manifested or in the planning stage. This global interest reflects a need to study these celestial bodies for the scientific information they provide about our solar system, and to better understand how to mitigate the collision threats some of them pose to Earth. Another important objective of these missions is providing assessments of the potential resources that asteroids could provide to future space architectures. In this paper, we examine a series of possible mission operations focused on advancing both our knowledge of the types of asteroids suited for different forms of resource extraction, and the capabilities required to extract those resources for mission enhancing and enabling uses such as radiation protection, propulsion, life support, shelter and manufacturing. An evolutionary development and demonstration approach is recommended within the framework of a larger campaign that prepares for the first landings of humans on Mars. As is the case for terrestrial mining, the development and demonstration approach progresses from resource prospecting (understanding the resource, and mapping the 'ore body'), mining/extraction feasibility and product assessment, pilot operations, to full in-situ resource utilization (ISRU). Opportunities to gather specific knowledge for ISRU via resource prospecting during science missions to asteroids are also examined to maximize the pace of development of needed ISRU capabilities and technologies for deep space missions
Infrared to millimetre photometry of ultra-luminous IR galaxies: new evidence favouring a 3-stage dust model
Infrared to millimetre spectral energy distributions have been obtained for
41 bright ultra-luminous infrared galaxies. The observations were carried out
with ISOPHOT between 10 and 200 micron and supplemented for 16 sources with
SCUBA at 450 and 850 micron and with SEST at 1.3 mm. In addition, seven sources
were observed at 1.2 and 2.2 m with the 2.2 m telescope on Calar Alto.
These new SEDs represent the most complete set of infrared photometric
templates obtained so far on ULIRGs in the local universe.Comment: 23 pages, 11 figures, accepted for publication in Astronomy &
Astrophysic
Opportunities and Strategies for Testing and Infusion of ISRU in the Evolvable Mars Campaign
HE Evolvable Mars Campaign (EMC) is developing the plans and systems needed for a robust, evolutionary strategy to explore cis-lunar space, the Mars sphere of influence (including the moons of Mars), and the surface of Mars. Recently, the emphasis of NASA's plans has changed to focus on the prolonged pioneering of space, rather than focusing on a single crewed mission as the ultimate goal. A sustainable, pioneering vision of space would include in-situ resource utilization (ISRU) in multiple forms and at multiple destinations: atmospheric capture of Mars CO2 and/or volatiles for consumables and propellants, regolith for bulk and refined materials, and in-situ manufacturing at the Moon, Mars, and other bodies. These resources would enable a reduction in the logistical needs from Earth for future missions, thus preparing the way for a sustained presence on Mars. Although the EMC initially relies only on propellant production for the Mars ascent vehicle via ISRU, one of its primary objectives is to prospect at every EMC destination to understand the potential for ISRU; this will permit true pioneering to be enabled after the first crew arrives at Mars. Recent and ongoing analysis has considered the possible prospecting measurements that can be performed at the asteroid returned to cis-lunar space by the Asteroid Robotic Redirect Mission (ARRM), at the lunar surface, at Phobos and Deimos, and on the surface of Mars to identify available resources for future use. These opportunities will be available on missions currently in the Evolvable Mars Campaign construct, and will also facilitate the testing and demonstration of resource acquisition, processing, storage, and useage technologies that can play a role in later missions. This analysis has also led to the identification of several objectives that should be targeted during the missions building up to and including the initial crewed missions. These objectives are mapped to strategies for incorporating ISRU to support resource cycle closure and reduce mass requirements from Earth. This analysis has yielded engineering constraints, based on ISRU, that impact the evaluation of landing sites for missions to the surface of Mars. The terrain of a particular site must be sufficiently flat to permit ISRU systems, as well as ancillary systems such as power and propellant storage tanks, to be landed, moved into position, set up, and operated. Water must be accessible in a form that can be acquired via ISRU, in quantities that align with demands. The chosen method of acquiring and processing water should align with the available resources at a particular site, and that site must have sufficient quantities to meet the requirements (based on crew consumables and propellant demands). Lower altitude landing sites are preferred, as the increase in density can facilitate carbon dioxide acquisition from the atmosphere. Another preference is for sites with a greater ability to move regolith for civil engineering purposes; for example, this would be conducive to both bulk regolith uses (such as the manufacture of berms), and processed regolith uses (such as microwave sintering)
Dust enshrouded star-forming activity in Arp 299
We present mid-infrared spectro-imaging (5 - 16 microns) observations of the
infrared luminous interacting system Arp 299 (=Mrk171 =IC694+NGC3690) obtained
with the ISOCAM instrument aboard ISO. Our observations show that nearly 40% of
the total emission at 7 and 15 microns is diffuse, originating from the
interacting disks of the galaxies. Moreover, they indicate the presence of
large amounts of hot dust in the main infrared sources of the system and large
extinctions toward the nuclei. While the observed spectra have an overall
similar shape, mainly composed of Unidentified Infrared Bands (UIB) in the
short wavelength domain, a strong continuum at ~ 13 microns and a deep silicate
absorption band at 10 microns, their differences reveal the varying physical
conditions of each component. For each source, the spectral energy distribution
(SED) can be reproduced by a linear combination of a UIB "canonical" spectral
template and a hot dust continuum due to a 230-300 K black body, after
independently applying an extinction correction to both of them. We find that
the UIB extinction does not vary much throughout the system (A_V ~ 5 mag)
suggesting that most UIBs originate from less enshrouded regions. IC694 appears
to dominate the infrared emission of the system and our observations support
the interpretation of a deeply embedded nuclear starburst located behind an
absorption of about 40 mag. The central region of NGC3690 displays a hard
radiation field characterized by a [NeIII]/[NeII] ratio > 1.8. It also hosts a
strong continuum from 5 to 16 microns which can be explained as thermal
emission from a deeply embedded (A_V ~ 60 mag) compact source, consistent with
the mid-infrared signature of an active galactic nucleus (AGN), and in
agreement with recent X-ray findings.Comment: to be published in Astronomy and Astrophysics - 12 page
PAHs in the Halo of NGC 5529
We present sensitive ISO m observations of the edge-on
galaxy, NGC 5529, finding an extensive MIR halo around NGC 5529. The emission
is dominated by PAHs in this band. The PAH halo has an exponential scale height
of 3.7 kpc but can still be detected as far as kpc from the plane
to the limits of the high dynamic range (1770/1) data. This is the most
extensive PAH halo yet detected in a normal galaxy. This halo shows
substructure and the PAHs likely originate from some type of disk outflow. PAHs
are long-lived in a halo environment and therefore continuous replenishment
from the disk is not required (unless halo PAHs are also being destroyed or
removed), consistent with the current low SFR of the galaxy. The PAHs correlate
spatially with halo H emission, previously observed by Miller &
Veilleux (2003); both components are likely excited/ionized by in-disk photons
that are leaking into the halo. The presence of halo gas may be related to the
environment of NGC 5529 which contains at least 17 galaxies in a small group of
which NGC 5529 is the dominant member. Of these, we have identified two new
companions from the SDSS.Comment: 16 pages, 5 gif figures, accepted for publication in A&A, For pdf
with higher quality figures, see http://www.astro.queensu.ca/~irwi
Spatially-resolved spectrophotometric analysis and modelling of the Superantennae
We have performed spatially-resolved spectroscopy of the double-nucleated
Ultra-Luminous Infrared Galaxy IRAS 19254-7245, ``the Superantennae'', along
the line connecting the two nuclei. These data are analysed with a spectral
synthesis code, to derive the star formation and extinction properties of the
galaxy. The star formation history (SFH) of the two nuclei is similarly
characterized by two different main episodes: a recent burst, responsible of
the observed emission lines, and an older one, occurred roughly 1 Gyr ago. We
tentatively associate this bimodal SFH with a double encounter in the dynamical
history of the merger. We have complemented our study with a detailed analysis
of the broad band spectral energy distribution of the Superantennae, built from
published photometry, providing the separate optical-to-mm SEDs of the two
nuclei. Our analysis shows that: a) the southern nucleus is responsible for
about 80% of the total infrared luminosity of the system, b) the L-band
luminosity in the southern nucleus is dominated by the emission from an
obscured AGN, providing about 40 to 50% of the bolometric flux between 8 and
1000 microns; c) the northern nucleus does not show evidence for AGN emission
and appears to be in a post-starburst phase. As for the relative strengths of
the AGN and starburst components, we find that, while they are comparable at
FIR and sub-mm wavelengths, in the radio the Sy2 emission dominates by an order
of magnitude the starburst.Comment: 18 pages. Accepted for publication on A&
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