1,721,021 research outputs found
The use of Do-Not-Resuscitate-Order equivalents in pediatric palliative care medicine in Germany
No full textClassification of pores from micro-XCT data of additively manufactured components prepared by laser powder bed fusion.
No full textLaser powder bed fusion (PBF-LB/M) is a metal-based additive manufacturing (AM) process that utilizes a laser to melt powder particles selectively and form the desired product through a layer-by-layer fabrication process. It allows access to a vast new design space and can produce parts with far greater geometrical complexity than traditional methods. However, PBF-LB/M induces inevitable microstructural defects, such as voids and pores, that can adversely affect the quality and performance of the manufactured components. Hence, knowledge of pore formation, types, and suppression is essential for successful future AM applications. This research investigates the formation of different types of pores and their quantification from X-ray micro-computed tomography images of a formerly reported sample. It also examines the influence of the volumetric energy density (VED) on the size, shape, and location of pores for 316L stainless steel parts produced by the PBF-LB/M process
Neues aus der BAM 2019
No full textNeuentwicklungen im Fachbereich 8.3 "Radiologische Verfahren" der BA
X-ray back scatter techniques for additive manufacturing
No full textX-ray back scatter imaging is rarely applied compared to classical X-ray projection imaging. 20 years ago the company Philips developed “COMSCAN”, a first application case in the aircraft industry, which allowed even a depth resolution using back scatter imaging. The company AS&E in Boston offers back scatter imaging solutions for the security market. Their principle is to scan the object with a highly collimated X-ray needle beam from one side only and detect the backscattered radiation by a large area detector side by side with the collimation wheel. A new prototype is investigated at BAM for application and optimization in non-destructive testing. As modern industrial application field in-situ testing in additive manufacturing is targeted. The accessibility of the printed part during the production process is very limited. This prevent the application of a two sided X-ray inspection or Computed Tomography, were an rotation of the object is required to acquire projections from 360 degrees. An important advantage for the X-ray back scatter technique are also the materials used in additive manufacturing (polymers, ceramics, light metals like Aluminum or Titanium). These materials with lower density and lower Z values give better scatter signals than metals with higher densities and Z values. The back scatter intensity decreases with increasing density and Z value of the material. But the requirements on spatial resolution and contrast sensitivity are more stringent for non-destructive testing of additive manufactured parts compared to the security area. In NDT sizes of indications smaller than 1 mm have to be detected clearly. The investigation of these limits on a stateof-the-art prototype for X-ray back scattering using rotating collimated X-ray needle beams is a part of the BAM project “ProMoAM”. The contribution shows first results of the optimization for NDT and the achieved application limits for several example cases
Röntgenrückstreutechnik für die additive Fertigung
No full textNeben der klassischen Durchstrahlung wird die bildgebende Röntgen-rückstreuung bisher nur sehr begrenzt eingesetzt. Vor über 20 Jahren hatte Philips mit „COMSCAN“ eine erste industrielle Anwendung in der Luftfahrt gefunden, die sogar eine Tiefenauflösung besaß. Die Firma AS&E in Boston bietet Röntgenrückstreu-Anlagen für den Sicherheitsbereich an. In diesen wird mit einem hochkollimierten Nadelstrahl aus einem rotierenden Blendenrad ein Objekt einseitig abgetastet. Zur Detektion der gestreuten Strahlung aus dem Objekt werden großflächige Detektoren direkt neben dem rotierenden Nadelstrahlkollimator eingesetzt. Ein solcher Prototyp wird an der BAM für den Einsatz in der zerstörungsfreien Prüfung untersucht und optimiert. Als neues industrielles Einsatzgebiet wird dabei die in situ Überwachung in der additiven Fertigung avisiert. Hier ist die Zugänglichkeit zum entstehenden Werkstück in den 3D-Druckanlagen stark eingeschränkt, was den Einsatz einer zweiseitigen Durchstrahlung oder der Computer-Tomographie, bei der das Objekt rotiert wird, verhindert. Auch sind die in der additiven Fertigung eingesetzten Werkstoffe (Polymere, Keramik, Leichtmetalle wie Al oder Ti) für die Rückstreuung besser geeignet als Metalle höherer Dichte, da das Streusignal mit der Ordnungszahl und der Materialdichte abnimmt. Allerdings sind die Anforderungen an räumliche Auflösung und Kontrastempfindlichkeit in der zerstörungsfreien Prüfung additiv gefertigter Bauteil deutlich höher als im Sicherheitsbereich, da hier Bauteilfehler mit typischen Dimensionen kleiner als 1 mm sicher detektiert werden müssen. Die Untersuchung dieser Grenzen des derzeitigen Standes der Röntgenrückstreutechnik mit Nadelstrahl ist ein Teilbereich des mehrjährigen BAM-Themenfeldprojektes „ProMoAM“. Im Vortrag werden die ersten Ergebnisse der Optimierung sowie die gefundenen Anwendungsgrenzen an Beispielen erläutert
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Mikro-Computertomographie für die Werkstoffforschung
No full textPreisträgervortrag Georg-Sachs-Preis der DGM
Röntgencomputertomographie (CT) ist heute ein Standardwerkzeug in der Materialcharakterisierung. Im Vortrag zeigen wir ihre Anwendung für die Untersuchung magnetischer Funktionsmaterialien, additiv gefertigter Bauteile und deren Feedstockpulver und stellen erste CT-Ergebnisse biogener Feedstockpulver vor
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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