197,491 research outputs found
Co-registration of lunar imagery and digital elevation model constrained by both geometric and photometric information
No full textA technical framework for construction of new-generation lunar global control network using multi-mission data
No full textDeterminação de propriedades mecânicas de materiais viscoelásticos através de ajuste de modelo
Get PDFDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2013.Dentre as várias formas de controle vibrações, os métodos passivos são largamente utilizados na indústria. Neste contexto, o uso de materiais viscoelásticos tornou-se uma prática comum devido à simplicidade de aplicação e aos bons resultados de atenuação obtidos. As propriedades dos materiais viscoelásticos têm características particulares, pois possuem comportamento elástico e viscoso simultaneamente, e suas propriedades variam com frequência e temperatura. Maiores dissipações de energia vibratória são obtidas com estes materiais quando usados em camadas constritas, conforme observadas em aplicações aeronáuticas e automotivas devido à boa relação entre massa adicionada e dissipação obtida. Este trabalho apresenta uma revisão detalhada da determinação experimental das propriedades dinâmicas de materiais viscoelásticos em função da frequência e da temperatura as quais são submetidos. As simulações numéricas dos corpos de prova tipo viga em configuração Oberst foram realizadas pelo método de elementos finitos. As propriedades foram obtidas através do ajuste dos resultados do modelo numérico aos resultados experimentais obtidos. Os resultados obtidos neste trabalho são comparados aos fornecidos por um fabricante.Abstract : Among the various forms of vibration control, passive methods are widely applied in the industry. In this context, the use of viscoelastic materials has become a common practice because of the simplicity of application and the good damping attenuation achieved. The properties of the viscoelastic materials have particular characteristics because they have both viscous and elastic behavior and their properties are dependent of temperature and frequency. Higher dissipation levels of vibrational energy are obtained with these materials when it used with constrained layers, as observed in aeronautical and automotive applications, due to the good relationship between the added mass and dissipation obtained. This study presents a detailed review of the experimental determination of the dynamic properties of the viscoelastic materials as a function of frequency and temperature which are submitted. The numerical simulations of beam type specimens in Oberst configuration were performed by finite element method. The properties were obtained by fitting the results of the numerical model to the experimental results. The results of this study are compared to those provided by a manufacturer
Numerical analysis of dynamic hysteresis in tape springs for space applications
No full textAntennas for small satellites are often simple tape springs, which have great advantages in terms of cost and space- and energy consumption. However, they are liable to unwanted vibrations, which can jeopardize a satellites' mission. Vibrations of thin elastic structures
in space lead to energy dissipation, which is able to change the attitude behavior of a satellite in orbit.
The present study investigates the dynamical system of a metal tape spring using a nite element model based on Oberst et al. (2018) and time domain simulations. Mesh convergence studies for element and method
selection have been conducted. It is found that linear shell elements
S4 provide good enough results for the dynamic analysis. The Hilber-
Hughes-Taylor implementation and ABAQUS/Implicit are employed.
In a previous study of Oberst and Tuttle (2018) hystereses in the system's response during an excitation amplitude sweep have been experimentally observed, which are repeated here for the numerical model. Similar to the experimental study, hysteresis curves can be generated (Oberst and Tuttle, 2018). Whether the dynamics as well as the static hysteresis curves in opposite and equal sense bending direction obtained from the numerical model are similar to those determined experimentally needs to be studied in the near future
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
Methode und Implementation eines inertialen Bündelblockausgleichs
No full textDie Rotationselemente eines planetaren Körpers geben seine Orientierung im Raum in Bezug auf den internationalen Himmelsreferenzrahmen (engl. ICRF) an. Sie sind notwendig für die Berechnung von Kontrollpunktnetzen (KPN) und für die Erstellung von z.B. Karten oder Geländemodellen des Körpers. Diese Arbeit beschreibt den Bündelblockausgleich im inertialen Referenzrahmen. Das ist eine Methode, um Rotationselemente planetarer Körper direkt und analytisch anhand photogrammetrischer Messungen zu bestimmen. Simultan wird ein KPN berechnet und die externen Orientierungen der Kamera werden verbessert. Im Gegensatz zum klassischen körperfesten Bündelblockausgleich ist hier die bestehende Abhängigkeit zwischen dem Rotationsmodell des Körpers und der Kameraorientierung aufgelöst. Die Methode wurde anhand einer Simulation getestet und auf zwei reale Datensätze angewandt. Die Amplitude der erzwungenen Libration, die sich auf die Orientierung des Hauptmeridians auswirkt, wurde für den Marsmond Phobos bestimmt. Mittels Bilddaten aus den Missionen Viking und Mars Express ist eine Amplitude von 1, 13° (±0, 13) berechnet worden, das zugehörige KPN mit 680 Punkten hat eine Unsicherheit von Ø 55 m . Die Amplitude stimmt mit den Ergebnissen von Willner et al. (2010) und Oberst et al. (2014), die durch indirekte Methoden erhalten wurden, überein. Die Polachsenorientierung von Vesta wurde mittels Bilddaten aus der aktuellen Dawn Mission bestätigt. Das berechnete KPN mit 82 806 Punkten wurde verglichen mit dem Ergebnis von Preusker et al. (2012) aus einem körperfesten Bündelblockausgleich; beide Lösungen sind innerhalb des mittleren Schnittfehlers von 10 m plausibel. Die Software wurde mit Schwerpunkt auf große Datensätze implementiert. Dabei konnte erreicht werden, dass die Kosten für Speicher und Laufzeit nur von der Anzahl der Bilder abhängig sind. Beim Vesta-Beispiel mit 5440 Bildern werden im Vergleich zu einer Referenz-Software 164 von 168 Stunden eingespart. Die Methode ist geeignet, um Rotationsmodelle von planetaren Körpern mit fester Oberfläche zu studieren und zu verbessern.The rotational elements of a planetary body state its orientation in space with respect to the International Celestial Reference Frame (ICRF). They are used for computing control point networks (CPNs) and for creating e.g. maps or terrain models of the body. This work describes the inertial frame bundle block adjustment. It is a method to determine rotational elements of planetary bodies in a direct and analytical way from image point measurements. Simultaneously with the rotational parameters, a corresponding CPN is computed and the external orientation data of the camera are improved. In contrary to the classical photogrammetric bundle block adjustment, here the interdependence of the body’s rotational model and the camera’s external orientation is resolved. The method was tested on simulated data and applied to two real science cases. The amplitude of forced libration, which contributes to the orientation of the prime meridian, was determined for the Martian moon Phobos. Using combined images of the missions Viking and Mars Express, an amplitude of 1.13° ± 0.13 was computed together with a CPN of 680 points and an uncertainty of Ø 55 m. The amplitude is in agreement with previous results, derived by indirect methods (e.g. Willner et al., 2010; Oberst et al., 2014). Secondly, the pole axis orientation of Vesta was confirmed using images of the current Dawn mission. The computed CPN of 82 806 points is compared with the body-fixed solution of Preusker et al. (2012), showing that both networks are plausible within the average intersection error of 10 m. The software which was implemented is focusing on the application to large data sets. It could be achieved that the costs of memory and running time depend only on the number of images. In the example of Vesta with 5440 images, 164 hours (out of 168) are saved with respect to a reference adjustment software. The method is suitable to study and refine rotational models of bodies with solid surfaces
Pläne und Ansichten / 48/A Grosse Gletscher oder Eÿs Berg, aus dem Ursprung der Rhosne, an der Furca, zu oberst in Wallis
No full textOhne Titel, Legende unten ("A. Grosse Gletscher oder Eÿs Berg, aus dem ursprung der Rhosne, an der Furca, zu oberst in Wallis ...")Numerierung unten rechts: "4"Ursprungswerk: "Verschiedene rare Berg-Prospect des Schweyzer Lands" gezeichnet von J. M. Füssli (Augsburg : J. Wolff
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