441 research outputs found
Market Structure and Instability Artifacts in Heterogeneous Agent Models: Lessons from Implicit Discretizations of Stiff Equations
Imaging and photometry of U Antliae and AQ Andromedae using the Herschel space telescope
Die vorliegende Magisterarbeit beinhaltet die Beobachtungsauswertung und die Datenreduktion zweier Asymptotic Giant Branch (AGB) Sterne, U Ant und AQ And, welche mithilfe des Herschel Weltraumteleskops aufgezeichnet wurden. Die Ergebnisse dieser Datenreduktion werden mit der Modellierung in DUSTY verglichen, welche den Strahlungstransport in staubigen Umgebungen rund um Sterne simuliert. Mit den Ergebnissen ist es möglich, RĂŒckschlĂŒsse ĂŒber die aktuelle und anschlieĂende Entwicklung der Sterne zu ziehen.
Im ersten Teil erhÀlt der interessierte Leser eine Einleitung zu AGB-Sternen und ihren
Eigenschaften. Dadurch erkennt der Leser, wie wichtig es ist, die Entwicklung dieser
SpÀtstadien-Objekte zu studieren.
Das Herschel Weltraumteleskop ist im Kapitel 2 beschrieben und besonderes Augenmerk ist auf das SPIRE Instrument gelegt. Ein eigenes Kapitel erlĂ€utert die technischen Eigenschaften sowie die Reduktion der Objekte fĂŒr SPIRE. Das Reduktionskapitel prĂ€sentiert in groĂem Umfang die Datenstruktur, das Map-making sowie den Quellcode, um den Leser bei nachfolgenden Arbeiten zu unterstĂŒtzen.
Kapitel 3 âScience Objectsâ stellt die wichtigen Eigenschaften und Merkmale von beiden
Objekten, U Ant und AQ And, dar. ZusĂ€tzlich gibt es eine PublikationsĂŒbersicht, die
dem Leser eine Zusammenfassung der Publikationen mit Schwerpunkt âdetached shellâ-
Beobachtung gibt.
Das abschlieĂende Kapitel befasst sich mit den Ergebnissen von der Beobachtung und
der Modellierung von U Ant und AQ And. Die Ergebnisse der Beobachtung und die
Aperturphotometrie befinden sich in einem separaten Kapitel. Schlussendlich sind die
Resultate der Modellierung in einem Kapitel zusammengefasst und werden im Kapitel
âConclusion and interpretationâ diskutiert.In this master thesis the observation evaluation and data reduction of two Asymptotic
Giant Branch (AGB) stars, U Ant and AQ And, observed with the Herschel space telescope, is presented. The results from the data reduction will be compared with the
modeling in DUSTY, which simulates the radiation transport in dusty environments
around stars. With these results it is possible to draw conclusions about the current and
subsequent evolution of the stars.
The first part gives the interested reader an introduction to AGB-stars and their properties. So the reader will know, why it is important to study the evolution of these
late-stage-objects.
The Herschel space telescope is described in chapter 2, with special focus on the SPIRE
instrument. A dedicated chapter outlines the technical functionality and data reduction
part of the objects for SPIRE. The reduction process chapter presents in extended
scope the data structure, the map-making as well as the final source code to support the readerâs subsequent workings.
Chapter 3 âScience Objectsâ introduces the important properties and features of both
science objects, U Ant and AQ And. In addition an overview of publications about
(detached) shell-detection is given.
The final chapter outlines the results of U Ant and AQ And from the observations and
the modeling. The final maps from the observation as well as the aperture photometry
can be found in a separate chapter. Furthermore the modeling outcomes are summed up in one chapter per object and are discussed in chapter âConclusion and interpretationâ
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Determination of the corrosion progress of zirconium oxide containing refractories based on the natural intrinsic gamma radiation of the material
The determination of the corrosion progress of refractory blocks is interesting for the operation of glass furnace tanks under safety and economic aspects. The measuring principle, based on the very small natural radiation of impurities of the zirconium raw materials for refractory production, has been known since the beginning of the seventies of the last century and could now be developed through improvements of measuring technology and sensors. Smaller changes to a laboratory test setup from medical technology were made both in the hardware and the software, to enable measurements of the intrinsie radiation of fused-cast AZS refractory materials in hot and dusty environment on glass melting furnaces during operation.
Î measuring schedule was developed and calibrating measurements were carried out with blocks of different zirconia content. First practical tests were made on cold glass furnaces. The final adaptation of the equipment was done with measurements on operating glass furnaces. The measurements of the corrosion progress and/or the residual thickness of refractory blocks based on the natural intrinsic gamma radiation could be done with the expected accuracy and can be used to support the operator of glass melting tanks
Analyzing Heterogeneous Agents Models : Avoiding the Explicit Discretization of Stiff Equations (Enlarged Abstract)
Beyond backscattering: Optical neuroimaging by BRAD
Optical coherence tomography (OCT) is a powerful technology for rapid
volumetric imaging in biomedicine. The bright field imaging approach of
conventional OCT systems is based on the detection of directly backscattered
light, thereby waiving the wealth of information contained in the angular
scattering distribution. Here we demonstrate that the unique features of
few-mode fibers (FMF) enable simultaneous bright and dark field (BRAD) imaging
for OCT. As backscattered light is picked up by the different modes of a FMF
depending upon the angular scattering pattern, we obtain access to the
directional scattering signatures of different tissues by decoupling
illumination and detection paths. We exploit the distinct modal propagation
properties of the FMF in concert with the long coherence lengths provided by
modern wavelength-swept lasers to achieve multiplexing of the different modal
responses into a combined OCT tomogram. We demonstrate BRAD sensing for
distinguishing differently sized microparticles and showcase the performance of
BRAD-OCT imaging with enhanced contrast for ex vivo tumorous tissue in
glioblastoma and neuritic plaques in Alzheimer's disease
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