Technology 2004, Vol. 2

Proceedings from symposia of the Technology 2004 Conference, November 8-10, 1994, Washington, DC. Volume 2 features papers on computers and software, virtual reality simulation, environmental technology, video and imaging, medical technology and life sciences, robotics and artificial intelligence, and electronics

Ninth European Powder Diffraction Conference – Prague, September 2-5, 2004

Zeitschrift für Kristallographie. Supplement Volume 23 presents the complete Proceedings of all contributions to the IX European Powder Diffraction Conference in Prague 2004: Method Development and Application, Instrumental, Software Development, Materials Supplement Series of Zeitschrift für Kristallographie publishes Proceedings and Abstracts of international conferences on the interdisciplinary field of crystallography

Anisotropic cobalt-based nanostructures: synthesis and characterization

Verschiedene Arten Kobalt-basierter magnetischer Nanostrukturen wurden gezielt hergestellt, um ihre Eigenschaften in modernen Anwendungen zu verbessern. Zum Beispiel werden magnetische Nanodrähte bestehend aus 3d-Übergangsmetallen derzeit als potentiel-le Kandidaten für Permanentmagnete ohne seltene Erden und für Anwendungen in der Ka-talyse untersucht. Die vorliegende Dissertation schlägt mögliche Ansätze für das magneti-sche Härten vor, die eine Kombination aus Form-, magneto-kristalliner und Austauschaniso-tropie der 3d-Metalle ausnutzen. Zunächst ist eine neuartige Methode für das magnetische Härten von Fe30Co70 Nanodrähten untersucht worden. Der Durchmesser der in anodisierten Aluminiumoxid Templaten elektrochemisch gewachsenen Nanodrähte beträgt dabei 20 nm und 40 nm bei einer von Länge 6 µm und 7,5 µm. Detaillierte strukturelle und magnetische Untersuchungen ergaben dabei eine 3-4 nm dicke, natürlich gebildete ferrimagnetische FeCo Oxidschicht an den Enden der Nanodrähte. Diese erhöhen die Koerzitivfeldstärke um 20% bei T = 10 K. Diese Zunahme der Koerzitiv¬feldstärke wird erreicht durch magnetisches Pin-nen, welches die Vortexbildung an den beiden Enden unterdrückt. Andererseits sind Co80Ni20 Nanostäbchen mit einem mittleren Durchmesser von 7 nm und einer mittleren Länge von 53 nm kolloidal-chemisch mit einem Polyolprozess syntheti-siert worden. Die Strukturanalyse zeigt kristalline Stäbchen mit einer kristallographischen Orientierung der c-Achse der hexagonalen dicht gepackten (hcp) Phase parallel zur langen Achse der Co80Ni20 Legierungsstäbchen. Weiterhin sind die Stäbchen mit einer dünnen, Co-reichen Oxidhülle mit kubisch-flächenzentrierten (fcc) Struktur ummantelt. Diese Hülle för-dert ein größeres Energieprodukt der magnetischen Hysterese aufgrund des Auftretens der Austauschanisotropie zwischen der antiferromagnetischen Oxidhülle und dem ferromagneti-schen Kern. In einer dritten Studie wurden Kobaltoxid-Nanopartikel untersucht, die gleichzeitig gu-te katalytische und magnetische Eigenschaften zeigen. Ein neues Syntheseverfahren ist ent-wickelt worden, um die magnetischen Eigenschaften der Kobalt-Nanokristalle zu kontrollie-ren. CoO-Co3O4 Kern-Hülle-Oktaeder mit 20 nm, 40 nm und 85 nm Kantenlänge wurden erfolgreich durch ein thermisches Zersetzungsverfahren hergestellt. Die Partikel weisen scharfe Kanten sowie fast atomar glatte {111}–Facetten auf. Sie bestehen aus einen CoO-Kern und einer 2-4 nm dicken Co3O4 Hülle. Die Grenzschicht zwischen diesen beiden Oxi-den ist stark verspannt, was zu ferromagnetischer Ordnung bis mindestens 400 K führt, die weit oberhalb der antiferromagnetischen Ordnungstemperatur der beiden Materialien liegt. Darüber hinaus wurden weitere Untersuchungen an verschiedenen Arten von Nano-partikeln für andere Anwendungen (z.B. Hyperthermie, Abfallbehandlung, Kontrastmittel) im Rahmen dieser Dissertation durchgeführt. Diese sind in den Anhängen II-IV zusammen-gefasst.Different types of cobalt-based magnetic nanoparticles have been designed to im-prove their performances in modern applications. For example, 3d transition metal-based magnetic nanowires are currently considered as potential candidates for rare-earth-free permanent magnets and for applications in catalysis. This thesis describes possible ap-proaches for the design of optimized architectures on the nanoscale exploiting the combi-nation of shape, magnetocrystalline and exchange anisotropy in 3d-metals. First, in a novel approach for the magnetic hardening, electroplated Fe30Co70 nanowires in anodic alumi-num oxide templates with diameters of 20 nm and 40 nm (length 6 μm and 7.5 μm, re-spectively) are synthesized and thoroughly characterized by structural and magnetic tech-niques. A 3–4 nm thick, naturally formed ferrimagnetic FeCo oxide layer covering the tip of the FeCo nanowire increases the coercive field by 20% at T = 10 K. The increase of the coercive field is achieved by means of magnetic pinning by an antiferromagnet which suppresses vortex formation at the tips of the nanowires as suggested by micromagnetic simulations. Second, Co80Ni20 nanorods with a mean diameter of 7 nm and a mean length of 53 nm have been synthesized by colloidal chemistry using the polyol process. Structural anal-ysis shows crystalline rods with the crystallographic c-axis of the hexagonal close-packed (hcp) phase, i.e. the magneto-crystalline easy axis, parallel to the long axis of the Co80Ni20 alloy rods. Moreover, these are covered by a thin Co-rich oxidized face-centered cubic (fcc) shell. This shell promotes a larger hysteretic energy product by exchange anisotropy between the antiferromagnetic oxide shell and the ferromagnetic metallic core. In a third study, cobalt oxide nanoparticles have been examined having a good cata-lytic response and additional magnetic properties. A new synthetic procedure has been developed to master the magnetic properties of cobalt oxide nanocrystals. 20 nm, 40 nm, and 85 nm edge length CoO-Co3O4 core-shell octahedra have been successfully synthe-sized by a thermal decomposition method. The particles exhibit sharp edges as well as almost atomically flat {111} facets. They consist of a CoO core and 2-4 nm thick Co3O4 shell. The interface between these two oxides is heavily strained and gives rise to ferro-magnetism to at least 400 K, well above the antiferromagnetic ordering temperatures of both oxides. Additional studies of different types of nanoparticles for innovative applications (e.g. hyperthermia, waste treatment, contrast agents) have been performed in the course of this thesis and summarized in the appendices II-IV

From surfaces to objects : Recognizing objects using surface information and object models.

This thesis describes research on recognizing partially obscured objects using surface information like Marr's 2D sketch ([MAR82]) and surface-based geometrical object models. The goal of the recognition process is to produce a fully instantiated object hypotheses, with either image evidence for each feature or explanations for their absence, in terms of self or external occlusion. The central point of the thesis is that using surface information should be an important part of the image understanding process. This is because surfaces are the features that directly link perception to the objects perceived (for normal "camera-like" sensing) and because surfaces make explicit information needed to understand and cope with some visual problems (e.g. obscured features). Further, because surfaces are both the data and model primitive, detailed recognition can be made both simpler and more complete. Recognition input is a surface image, which represents surface orientation and absolute depth. Segmentation criteria are proposed for forming surface patches with constant curvature character, based on surface shape discontinuities which become labeled segmentation- boundaries. Partially obscured object surfaces are reconstructed using stronger surface based constraints. Surfaces are grouped to form surface clusters, which are 3D identity-independent solids that often correspond to model primitives. These are used here as a context within which to select models and find all object features. True three-dimensional properties of image boundaries, surfaces and surface clusters are directly estimated using the surface data. Models are invoked using a network formulation, where individual nodes represent potential identities for image structures. The links between nodes are defined by generic and structural relationships. They define indirect evidence relationships for an identity. Direct evidence for the identities comes from the data properties. A plausibility computation is defined according to the constraints inherent in the evidence types. When a node acquires sufficient plausibility, the model is invoked for the corresponding image structure.Objects are primarily represented using a surface-based geometrical model. Assemblies are formed from subassemblies and surface primitives, which are defined using surface shape and boundaries. Variable affixments between assemblies allow flexibly connected objects. The initial object reference frame is estimated from model-data surface relationships, using correspondences suggested by invocation. With the reference frame, back-facing, tangential, partially self-obscured, totally self-obscured and fully visible image features are deduced. From these, the oriented model is used for finding evidence for missing visible model features. IT no evidence is found, the program attempts to find evidence to justify the features obscured by an unrelated object. Structured objects are constructed using a hierarchical synthesis process. Fully completed hypotheses are verified using both existence and identity constraints based on surface evidence. Each of these processes is defined by its computational constraints and are demonstrated on two test images. These test scenes are interesting because they contain partially and fully obscured object features, a variety of surface and solid types and flexibly connected objects. All modeled objects were fully identified and analyzed to the level represented in their models and were also acceptably spatially located. Portions of this work have been reported elsewhere ([FIS83], [FIS85a], [FIS85b], [FIS86]) by the author

Plutonium Futures – The Science 2016, A topical conference on plutonium and actinides, supporting safe and secure plutonium research as part of the global energy mix

Plutonium Futures - The Science series of conferences provides an international forum for discussion of current research on physical and chemical properties of plutonium and other actinide elements in complex systems. In bringing the community together from diverse disciplines, the conference aims to enhance the dialogue among scientists and engineers on the fundamental properties of plutonium and their technological consequences. Scientists, engineers, academics and students from universities, national laboratories, and the nuclear industry are encouraged to participate and make technical contributions.JRC.G.I.5-Advanced Nuclear Knowledg

Reports to the President

A compilation of annual reports for the 1985-1986 academic year, including a report from the President of the Massachusetts Institute of Technology, as well as reports from the academic and administrative units of the Institute. The reports outline the year's goals, accomplishments, honors and awards, and future plans