Evolution of the IBDM Structural Latch Development into a Generic Simplified Design

This paper presents the evolution in the development of the structural latch for the International Berthing Docking Mechanism (IBDM, see Figure 1). It reports on the lessons learned since completion of the test program on the engineering development unit of the first generation latching system in 2007. The initial latch design has been through a second generation concept in 2008, and now evolved into a third generation of this mechanism. Functional and structural testing on the latest latch hardware has recently been completed with good results. The IBDM latching system will provide the structural connection between two mated space vehicles after berthing or docking. The mechanism guarantees that the interface seals become compressed to form a leak-tight pressure system that creates a passageway for the astronauts

Producing Crack-Free, High Density M2 HSS Parts by Selective Laser Melting: Pre-Heating the Baseplate

Cracks and delamination, resulting from residual stresses are a barrier in the world of Additive Manufacturing and Selective Laser Melting (SLM) that prohibits the use of many metals in this field. By preheating the baseplate, thermal gradients are lowered and stresses can be reduced. In this work, some initial tests were performed with M2 Tool Steel. Results show that pre-heating enables the production of dense M2 parts. The influence of pre-heating on density and mechanical and physical properties is investigated. The paper shows many promising results for the production of SLM parts in materials that are very sensitive to crack formation and delamination. When using a pre-heating of 200°C, crack-free parts were produced with a relative density of 99.8%.Mechanical Engineerin

Surgical Implications of Coronary Arterial Anatomy in Adults with Congenital Cardiac Disease

In adults with congenital heart disease coronary arterial anatomy, normal as well as anomalous, may have implications in surgical reconstruction of an underlying cardiac structure

The Projected Rotational Velocity Distribution of a Sample of OB stars from a Calibration based on Synthetic He I lines

We derive projected rotational velocities (vsini) for a sample of 156 Galactic OB star members of 35 clusters, HII regions, and associations. The HeI lines at $\lambda\lambda$4026, 4388, and 4471A were analyzed in order to define a calibration of the synthetic HeI full-widths at half maximum versus stellar vsini. A grid of synthetic spectra of HeI line profiles was calculated in non-LTE using an extensive helium model atom and updated atomic data. The vsini's for all stars were derived using the He I FWHM calibrations but also, for those target stars with relatively sharp lines, vsini values were obtained from best fit synthetic spectra of up to 40 lines of CII, NII, OII, AlIII, MgII, SiIII, and SIII. This calibration is a useful and efficient tool for estimating the projected rotational velocities of O9-B5 main-sequence stars. The distribution of vsini for an unbiased sample of early B stars in the unbound association Cep OB2 is consistent with the distribution reported elsewhere for other unbound associations.Comment: Accepted for publication in The Astronomical Journa

Atmospheric parameters and rotational velocities for a sample of Galactic B-type supergiants

High resolution optical spectra of 57 Galactic B-type supergiant stars have been analyzed to determine their rotational and macroturbulent velocities. In addition, their atmospheric parameters (effective temperature, surface gravity and microturbulent velocity) and surface nitrogen abundances have been estimated using a non-LTE grid of model atmospheres. Comparisons of the projected rotational velocities have been made with the predictions of stellar evolutionary models and in general good agreement was found. However for a small number of targets, their observed rotational velocities were significantly larger than predicted, although their nitrogen abundances were consistent with the rest of the sample. We conclude that binarity may have played a role in generating their large rotational velocities. No correlation was found between nitrogen abundances and the current projected rotational velocities. However a correlation was found with the inferred projected rotational velocities of the main sequence precursors of our supergiant sample. This correlation is again in agreement with the predictions of single star evolutionary models that incorporate rotational mixing. The origin of the macroturbulent and microturbulent velocity fields is discussed and our results support previous theoretical studies that link the former to sub-photospheric convection and the latter to non-radial gravity mode oscillations. In addition, we have attempted to identify differential rotation in our most rapidly rotating targets.Comment: Submitted to MNRAS, 16 page

The VLT-FLAMES survey of massive stars: Nitrogen abundances for Be-type stars in the Magellanic Clouds

Aims. We compare the predictions of evolutionary models for early-type stars with atmospheric parameters, projected rotational velocities and nitrogen abundances estimated for a sample of Be-type stars. Our targets are located in 4 fields centred on the Large Magellanic Cloud cluster: NGC 2004 and the N 11 region as well as the Small Magellanic Cloud clusters: NGC 330 and NGC 346. Methods. Atmospheric parameters and photospheric abundances have been determined using the non-LTE atmosphere code tlusty. Effective temperature estimates were deduced using three different methodologies depending on the spectral features observed; in general they were found to yield consistent estimates. Gravities were deduced from Balmer line profiles and microturbulences from the Si iii spectrum. Additionally the contributions of continuum emission from circumstellar discs were estimated. Given its importance in constraining stellar evolutionary models, nitrogen abundances (or upper limits) were deduced for all the stars analysed. Results. Our nitrogen abundances are inconsistent with those predicted for targets spending most of their main sequence life rotating near to the critical velocity. This is consistent with the results we obtain from modelling the inferred rotational velocity distribution of our sample and of other investigators. We consider a number of possibilities to explain the nitrogen abundances and rotational velocities of our Be-type sample.Comment: 14 pages, 9 figures, submitted to A&

Discovery of magnetic fields in the very young, massive stars W601 (NGC 6611) and OI 201 (NGC 2244)

Context: Recent spectropolarimetric observations of Herbig Ae/Be stars have yielded new arguments in favour of a fossil origin for the magnetic fields of intermediate mass stars. Aims: To study the evolution of these magnetic fields, and their impact on the evolution of the angular momentum of these stars during the pre-main sequence phase, we observed Herbig Ae/Be members of young open clusters of various ages. Methods: We obtained high-resolution spectropolarimetric observations of Herbig Ae/Be stars belonging to the young open clusters NGC 6611 (< 6 Myr), NGC 2244 (~1.9 Myr), and NGC 2264 (~8 Myr), using ESPaDOnS at theCanada-France-Hawaii Telescope. Results: Here we report the discovery of strong magnetic fields in two massive pre-main sequence cluster stars. We detected, for the first time, a magnetic field in a pre-main sequence rapid rotator: the 10.2 Msun Herbig B1.5e star W601 (NGC 6611; v sin i ~ 190 km/s). Our spectropolarimetric observations yield a longitudinal magnetic field larger than 1 kG, and imply a rotational period shorter than 1.7 days. The spectrum of this very young object (age ~ 0.017 Myr) shows strong and variable lines of He and Si. We also detected a magnetic field in the 12.1 Msun B1 star OI 201 (NGC 2244; v sin i = 23.5 km/s). The Stokes V profile of this star does not vary over 5 days, suggesting a long rotational period, a pole-on orientation, or aligned magnetic and rotation axes. OI 201 is situtated near the Zero-Age Main Sequence on the HR diagram, and exhibits normal chemical abundances and no spectrum variability.Comment: Accepted for publication as a letter in A&

Boron Abundances in Main Sequence B-type Stars: A Test of Rotational Depletion during Main Sequence Evolution

Boron abundances have been derived for seven main sequence B-type stars from HST STIS spectra around the B III 2066 A line. In two stars, boron appears to be undepleted with respect to the presumed initial abundance. In one star, boron is detectable but it is clearly depleted. In the other four stars, boron is undetectable implying depletions of 1 to 2 dex. Three of these four stars are nitrogen enriched, but the fourth shows no enrichment of nitrogen. Only rotationally induced mixing predicts that boron depletions are unaccompanied by nitrogen enrichments. The inferred rate of boron depletion from our observations is in good agreement with these predictions. Other boron-depleted nitrogen-normal stars are identified from the literature. Also, several boron-depleted nitrogen-rich stars are identified, and while all fall on the boron-nitrogen trend predicted by rotationally-induced mixing, a majority have nitrogen enrichments that are not uniquely explained by rotation. The spectra have also been used to determine iron-group (Cr, Mn, Fe, and Ni) abundances. The seven B-type stars have near solar iron-group abundances, as expected for young stars in the solar neighborhood. We have also analysed the halo B-type star, PG0832+676. We find [Fe/H] = -0.88 +/- 0.10, and the absence of the B III line gives the upper limit [B/H]<2.5. These and other published abundances are used to infer the star's evolutionary status as a post-AGB star.Comment: 31 pages, 14 figures. accepted to Ap

M & L Jaargang 12/6

GeneriekMiek Goossens Leven in de brouwerij of hoe iets ouds iets nieuws werd. [From old to new: the Christiaen Brewery in Koekelare.]Bijna twee eeuwen lang wist deze organisch gegroeide dorpsbrouwerij het West-Vlaamse Koekelare tegelijk aan werkgelegenheid te helpen, te lessen en te voorzien in burgemeesters. Het kan dan ook niet enkel toeval genoemd worden dat na het stilvallen van de activiteiten in 1968 en een sindsdien voortschrijdend verval, het controversieel industrieel-archeologisch relict vanaf 1984 een nieuwe bestemming tegemoet ging als gemeentelijk en cultureel polyvalent centrum. Terecht bedacht een Prijs dan ook dit eerste Vlaamse Monument.Ann Bergmans Van Lucca naar Brugge. Een Volto Santo in de Speelmanskapel. [From Lucca to Bruges. A Volto Santo in the Speelmanskapel.]Enige verwarring tussen de gekruisigde Christus-voorstelling en de legendarische vrouw-met-de-baard is niet geheel denkbeeldig, gezien de ooit bijzonder populaire aldus getooide Heilige Wilgefortis. De thans verdwenen muurschildering in de Brugse Speelmanskapel leverde alleszins het verrassende bewijs van een vroeg 15de-eeuwse beïnvloeding door het Italiaanse Lucca. Voor de Zuidelijke Nederlanden een unicum.Roger Deneef en Lutgart Vrancken De Hortus Thenensis. [The Hortus Thenensis.]Met merkelijk meer succes wist de Tiense Léon P. Ch. Van den Bossche vanaf 1883 zijn korte diplomatieke carrière te ruilen voor deze van gepassioneerd plantenverzamelaar: tot méér dan 3000 soorten in 1900, op een oppervlakte van nauwelijks 2,5 hectare, van wetenschappelijke geloofsbrieven voorzien door latere Nationale Plantentuindirecteur Emile De Wildeman. Een weelde, waarvan het Stadspark onverhoopt nog tastbare restanten blijkt te hebben bewaard.P. Vissers Mecenaat in de monumentenzorg, een (her)nieuw(d) gegeven. [Sponsoring historic preservation.]Van het 15de-eeuwse Brugse Oosterlingenhuis, pleisterplaats van Duitse Hanze-kooplui, bleven ingevolge brand en ingrijpende verbouwingen, slechts spaarzame fragmenten intact.Onlangs bij renovatiewerken vrij gelegde kinderbalken brachten alvast een zeldzaam overblijfsel aan het licht van persbrokaat, een uiterst fragiele decoratietechniek ... met een geëigende conserverende behandeling.Marjan Buyle Het plafond van het Oosterlingenhuis te Brugge. [The ceiling of the Oriental House in Bruges.]Van bij haar oprichting in 1984 ijverde de Stichting Monumenten- en Landschapszorg onverdroten voor een meer tastbare financiële inzet van de zakenwereld bij de behartiging van het cultureel erfgoed.Welke zijn nu de reeds bereikte resultaten en in welke mate varen àlle betrokken partijen wel bij deze transactie?SummaryM&L Binnenkran

Expressiveness modulo Bisimilarity of Regular Expressions with Parallel Composition (Extended Abstract)

The languages accepted by finite automata are precisely the languages denoted by regular expressions. In contrast, finite automata may exhibit behaviours that cannot be described by regular expressions up to bisimilarity. In this paper, we consider extensions of the theory of regular expressions with various forms of parallel composition and study the effect on expressiveness. First we prove that adding pure interleaving to the theory of regular expressions strictly increases its expressiveness up to bisimilarity. Then, we prove that replacing the operation for pure interleaving by ACP-style parallel composition gives a further increase in expressiveness. Finally, we prove that the theory of regular expressions with ACP-style parallel composition and encapsulation is expressive enough to express all finite automata up to bisimilarity. Our results extend the expressiveness results obtained by Bergstra, Bethke and Ponse for process algebras with (the binary variant of) Kleene's star operation.Comment: In Proceedings EXPRESS'10, arXiv:1011.601