365 research outputs found
U.S.-German-European Community Economic Relations: The Need for Common Approaches to Common Problems. Department of State Bulletin, 20 May 1974
Funktionale Sicherheit nach ISO 26262 in der Konzeptphase der Entwicklung von Elektrik/Elektronik Architekturen von Fahrzeugen
Die Entwicklung von softwarebasierten Fahrzeugsystemen unter Befolgung des neuen Standards IO 26262 erfordert ein gemeinsames Verständnis sowie die Verzahnung des Vorgehens in beiden Domänen. Ziel dieser Arbeit ist die Berücksichtigung von Anforderungen der funktionalen Sicherheit während der Modellierung von Elektrik/Elektronik Architekturen, ihre formale Zuteilung zu Modellinhalten sowie die Unterstützung nebenläufiger und nachfolgender Aktivitäten der Fahrzeugentwicklung
Qualifizierung einer Messtechnik zur Erfassung freier Grenzflächen bei Flüssigmetallen
The attempt to detect liquid metal surfaces is confronted with a number of difficulties. The main problems are the high reflectivity in vacuum at simultaneously high flow velocities and rapid surface motions. Currently no measurement methods for this problem providing unique results exist. In Order to develop such a method, a projection method has been modified by adding a second (transparent) screen. The development is completed by measurement of the circular hydraulic jump phenomena (GaInSn)
Qualifizierung einer Messtechnik zur Erfassung freier Grenzflächen bei Flüssigmetallen
Die Erfassung freier Grenzflächen bei Flüssigmetallen, wie sie in zukünftigen Anlagen der Kern- und Fusionstechnik eingesetzt werden sollen, ist einer Reihe von Schwierigkeiten unterworfen. Hauptprobleme bereiten die hohe Reflektivität der Oberfläche und die große Geschwindigkeit der Oberflächenbewegung. Die Beobachtung bestehender Flüssigmetalloberflächen, wie der Flüssigmetalltargets MYRRHA und GSI im KALLA-Labor des Forschungszentrums in Karlsruhe, sowie die Untersuchungen für HILIFE-II von Konkachbaev 2000 und IFMIF von Itoh 1998, legen eine zu fordernde Genauigkeit von ±0.3mm bei 100Hz nah. Für diese Anwendungstypen bestehen keine bekannten Messverfahren. Die Entwicklung des DLP-Verfahrens basiert auf der Ergänzung eines Projektionsverfahrens um einen zweiten (transparenten) Schirm, wobei die abgebildeten Laserquerschnitte von einer Hochgeschwindigkeitskamera als mit der Intensität und Farbe codierte Oberflächeninformation erfasst werden. Dies erlaubt die Erreichung der geforderten Genauigkeiten und konnte durch einen entsprechenden sequentiellen aufgebauten Validierungsprozess nachgewiesen werden. Die Qualifizierung wird durch eine raum- und zeitaufgelöste Erfassung des rotationssymmetrischen hydraulischen Sprungs mit eutektischen Gallium Indium Zinn abgeschlossen
Critical Tasks Facing Western Europe and the United States in a Period of Change and Transition. Address by Martin J. Hillenbrand, Assistant Secretary for European Affairs. Department of State Bulletin, 7 June, 1971
No abstract
AB Doradus C: Age, Spectral Type, Orbit, and Comparison to Evolutionary Models
We expand upon the results of Close et al. 2005 regarding the young, low-mass
object AB Dor C and its role as a calibration point for theoretical tracks. We
present an improved spectral reduction and a new orbital solution with two
additional epochs. Our improved analysis confirms our spectral type of M8 (+/-
1) and mass of 0.090+/-0.003 solar masses for AB Dor C. Comparing the results
for AB Dor C with other young, low-mass objects with dynamical masses we find a
general trend where current evolutionary models tend to over-predict the
temperature (or under-predict the mass) for low mass stars and brown dwarfs.
Given our precision, there is a ~99% chance that the mass of AB Dor C is
underestimated by the DUSTY tracks in the HR diagram.Comment: 7 pages, 10 figures, proceedings for the workshop "Ultralow-mass star
formation and evolution", to be published in Astronomische Nachrichten -
Astronomical Note
Proper motion of very low mass stars and brown dwarfs in the Pleiades cluster
We report proper motion measurements for 25 very-low mass (VLM) star and
brown dwarf (BD) candidates of the Pleiades cluster previously identified by
Bouvier et al. (1998). Proper motions are measured with an accuracy of 9
mas/yr, compared to an expected tangential motion of about 50 mas/yr for
Pleiades members. Of the 25 candidates, 15 have a membership probability of 95%
or more and 7 are rejected as being field dwarfs. The 3 remaining candidates
exhibit independent evidence for membership (lithium absorption or long-term
proper motion). From the firm identification of Pleiades VLM and BD members,
the cluster's substellar mass function is revised to dN/dM \propto M^{-0.5} in
the mass range from 0.04 to 0.3 M_solar.Comment: 7 pages, 2 tables, 2 figures, accepted by A&
Modeling the Formation of Giant Planet Cores I: Evaluating Key Processes
One of the most challenging problems we face in our understanding of planet
formation is how Jupiter and Saturn could have formed before the the solar
nebula dispersed. The most popular model of giant planet formation is the
so-called 'core accretion' model. In this model a large planetary embryo formed
first, mainly by two-body accretion. This is then followed by a period of
inflow of nebular gas directly onto the growing planet. The core accretion
model has an Achilles heel, namely the very first step. We have undertaken the
most comprehensive study of this process to date. In this study we numerically
integrate the orbits of a number of planetary embryos embedded in a swarm of
planetesimals. In these experiments we have included: 1) aerodynamic gas drag,
2) collisional damping between planetesimals, 3) enhanced embryo cross-sections
due to their atmospheres, 4) planetesimal fragmentation, and 5) planetesimal
driven migration. We find that the gravitational interaction between the
embryos and the planetesimals lead to the wholesale redistribution of material
- regions are cleared of material and gaps open near the embryos. Indeed, in
90% of our simulations without fragmentation, the region near that embryos is
cleared of planetesimals before much growth can occur. The remaining 10%,
however, the embryos undergo a burst of outward migration that significantly
increases growth. On timescales of ~100,000 years, the outer embryo can migrate
~6 AU and grow to roughly 30 Earth-masses. We also find that the inclusion of
planetesimal fragmentation tends to inhibit growth.Comment: Accepted to AJ, 62 pages 11 figure
Stellar Activity in the Broad-Band Ultraviolet
The completion of the GALEX All-Sky Survey in the ultraviolet allows activity
measurements to be acquired for many more stars than is possible with the
limited sensitivity of ROSAT or the limited sky coverage of Chandra, XMM, or
spectroscopic surveys for line emission in the optical or ultraviolet. We have
explored the use of GALEX photometry as an activity indicator, using as a
calibration sample stars within 50 pc, representing the field, and in selected
nearby associations, representing the youngest stages of stellar evolution. We
present preliminary relations between UV flux and the optical activity
indicator R'_HK and between UV flux and age. We demonstrate that far-UV (FUV,
1350-1780{\AA}) excess flux is roughly proportional to R'_HK. We also detect a
correlation between near-UV (NUV, 1780-2830{\AA}) flux and activity or age, but
the effect is much more subtle, particularly for stars older than than ~0.5-1
Gyr. Both the FUV and NUV relations show large scatter, ~0.2 mag when
predicting UV flux, ~0.18 dex when predicting R'_HK, and ~0.4 dex when
predicting age. This scatter appears to be evenly split between observational
errors in current state-of-the-art data and long-term activity variability in
the sample stars.Comment: 37 pages, 12 figures. To appear in the Astronomical Journa
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