TY - JOUR A1 - Baroud, G. A1 - Wu, J.Z. A1 - Bohner, M A1 - Sponagel, Stefan A1 - Steffen, T. T1 - How to determine the permeability for cement infiltration into osteoporotic cancellous bone JF - Medical Engineering & Physics. 25 (2003), H. 4 N2 - Cement augmentation is an emerging surgical procedure in which bone cement is used to infiltrate and reinforce osteoporotic vertebrae. Although this infiltration procedure has been widely applied, it is performed empirically and little is known about the flow characteristics of cement during the injection process. We present a theoretical and experimental approach to investigate the intertrabecular bone permeability during the infiltration procedure. The cement permeability was considered to be dependent on time, bone porosity, and cement viscosity in our analysis. In order to determine the time-dependent permeability, ten cancellous bone cores were harvested from osteoporotic vertebrae, infiltrated with acrylic cement at a constant flow rate, and the pressure drop across the cores during the infiltration was measured. The viscosity dependence of the permeability was determined based on published experimental data. The theoretical model for the permeability as a function of bone porosity and time was then fit to the testing data. Our findings suggest that the intertrabecular bone permeability depends strongly on time. For instance, the initial permeability (60.89 mm4/N.s) reduced to approximately 63% of its original value within 18 seconds. This study is the first to analyze cement flow through osteoporotic bone. The theoretical and experimental models provided in this paper are generic. Thus, they can be used to systematically study and optimize the infiltration process for clinical practice. KW - Osteoporose KW - Permeabilität KW - Viskose Strömung KW - Viskosität KW - Vertebroplastie KW - Cement infiltration KW - Vertebroplasty KW - Osteoporosis KW - Permeability KW - Experiment KW - Analysis KW - Viscous flow Y1 - 2003 SN - 1350-4533 SP - 283 EP - 288 ER - TY - JOUR A1 - Kühn, Raoul-Roman A1 - Haugner, Werner A1 - Staat, Manfred A1 - Sponagel, Stefan T1 - A Two Phase Mixture Model based on Bone Observation N2 - An optimization method is developed to describe the mechanical behaviour of the human cancellous bone. The method is based on a mixture theory. A careful observation of the behaviour of the bone material leads to the hypothesis that the bone density is controlled by the principal stress trajectories (Wolff’s law). The basic idea of the developed method is the coupling of a scalar value via an eigenvalue problem to the principal stress trajectories. On the one hand this theory will permit a prediction of the reaction of the biological bone structure after the implantation of a prosthesis, on the other hand it may be useful in engineering optimization problems. An analytical example shows its efficiency. KW - Knochen KW - Knochenbildung KW - Knochenchirugie KW - Strukturanalyse KW - Schwammknochen KW - Knochendichte KW - Wolffsches Gesetz KW - bone structure KW - bone density KW - Wolff's Law KW - cancellous bone Y1 - 2004 ER - TY - JOUR A1 - Vu, Duc-Khoi A1 - Staat, Manfred T1 - An algorithm for shakedown analysis of structure with temperature dependent yield stress N2 - This work is an attempt to answer the question: How to use convex programming in shakedown analysis of structures made of materials with temperature-dependent properties. Based on recently established shakedown theorems and formulations, a dual relationship between upper and lower bounds of the shakedown limit load is found, an algorithmfor shakedown analysis is proposed. While the original problem is neither convex nor concave, the algorithm presented here has the advantage of employing convex programming tools. KW - Einspielen KW - Temperaturabhängigkeit KW - Fließgrenze KW - Shakedown KW - shakedown analysis KW - yield stress Y1 - 2004 ER - TY - JOUR A1 - Staat, Manfred T1 - Direct FEM Limit and Shakedown Analysis with Uncertain Data N2 - The structural reliability with respect to plastic collapse or to inadaptation is formulated on the basis of the lower bound limit and shakedown theorems. A direct definition of the limit state function is achieved which permits the use of the highly effective first order reliability methods (FORM) is achieved. The theorems are implemented into a general purpose FEM program in a way capable of large-scale analysis. The limit state function and its gradient are obtained from a mathematical optimization problem. This direct approach reduces considerably the necessary knowledge of uncertain technological input data, the computing time, and the numerical error, leading to highly effective and precise reliability analyses. KW - Finite-Elemente-Methode KW - Einspielen KW - FEM KW - Einspielanalyse KW - shakedown KW - limit load KW - reliability analysis KW - FEM KW - direct method Y1 - 2000 ER - TY - GEN A1 - Bellenberg, Markus T1 - Optimierung einer Roboter-Schweißzelle als Basis eines E-Learning Systems T1 - Optimization of a Robot-welding Station as the Basis for an E-Learning System N2 - Ziel war die technische Überarbeitung und Optimierung des vorliegenden Prototypen, um eine Basis für ein E-Learning System (Internet unterstütztes Lernen) zu schaffen. Zu diesem Zweck wurde das Programm der Robotersteuerung neu erstellt, notwendige mechanische Änderungen an Roboterequipment und Materialförderung vorgenommen sowie eine neue Internet-Anbindung geschaffen. Wesentliche Ergebnisse der Arbeit sind: • Erzeugen roboterbasierter kreisinterpolierter Bahnschweißnähte • Kommunikation des Lernsystems via Internet • Lernorientierte Steuerungssoftware N2 - The main goal of this final thesis was the revision and optimization of the given prototype as a basis for an E-Learning environment. All components of the system, including specific technical aspects, are discussed in order to create the basis for future training documentation. Similarly, the programs for the robot motion sequences and welding processes were renewed in order to create well-structured, clear and properly documented software that is suitable for use in a formal training program. KW - Roboter KW - MAG-Schweißen KW - MIG-Schweißen KW - Schweißen KW - Mechatronik KW - Kawasaki KW - E-Learning KW - Roboter-Schweißen KW - welding KW - welded joint KW - mechatronics Y1 - 2002 ER - TY - GEN A1 - Balzar, Christoph Rupert T1 - Land in land N2 - [...] Darin suche ich „Zwischenräume“ in der digitalen Verschmelzung von Fotos unterschiedlicher Orte und durchleuchte diese neu geschaffenen Landschaften auf ihren Sinn für mich. Anhand der so ge-wonnenen Erkenntnisse belebe ich diese Plätze später mit Menschen, Tieren und Fundstücken, die mir das Schicksal auf meinen „Walkabouts“ durch den australischen Kontinent zugespielt hat und denen ich zu den neu entstandenen Orten passende Bedeutungen beimesse. [...] Neben meinen flächigen, fotografischen und installativen Werken stelle ich auch ein umfassendes Rahmen- und Begleitprogramm zur Ausstellung her, beispielsweise eine CI und eine Homepage. KW - Digitale Photographie KW - Photomontage KW - Naturphotographie KW - Aborigines KW - Fotografie KW - Digitale Montage KW - Bilderserie KW - Ureinwohner KW - Australien KW - Inszenierte Photographie KW - Photography KW - Digital montage KW - Series KW - Aboriginal people KW - Australia KW - Set-up photography Y1 - 2005 ER - TY - JOUR A1 - Kämper, Klaus-Peter A1 - Picard, Antoni A1 - Brill, Manfred A1 - Cassel, Detlev A1 - Jentsch, Andreas A1 - Merten, Sabine A1 - Rollwa, Markus T1 - The Virtual Clean Room - a new tool in teaching MST process technologies N2 - The Virtual Clean Room - a new tool in teaching MST process technologies University education in high-technology fields like MST is not complete without intensive laboratory sessions. Students cannot fully grasp the complexity and the special problems related to the manufacturing of microsystems without a thorough hands-on experience in a MST clean room. KW - Virtuelle Maschine KW - VM KW - Mikrosystemtechnik KW - MST KW - virtual clean room Y1 - 2003 ER - TY - JOUR A1 - Picard, Antoni A1 - Brill, Manfred A1 - Cassel, Detlev A1 - Jentsch, Andreas A1 - Rollwa, Markus A1 - Kämper, Klaus-Peter A1 - Merten, Sabine T1 - Neue Medien für die praktische MST-Ausbildung N2 - Im Studiengang Mikrosystemtechnik des Fachhochschulstandortes Zweibrücken werden zwei neue moderne Anlagen für die Herstellung von mikrotechnischen Komponenten in Betrieb genommen: Ein Oxidationsofen für Herstellung dünner Oxidschichten auf Silizium-Einkristallen und eine Belichtungsapparatur für die Fotolithografie - das Besondere an diesen Anlagen: Sie existieren nur virtuell, d.h. als Animationen in einer Computerwelt. KW - Mikrosystemtechnik KW - Photolithographie KW - Mikrotechnik KW - mikrotechnische Komponenten KW - Oxidationsofen KW - Oxidschicht KW - multimediale Lernsoftware KW - micro technology KW - micro-technical components KW - oxidation furnace KW - oxide coating Y1 - 2002 ER - TY - CHAP A1 - Merten, Sabine A1 - Kämper, Klaus-Peter A1 - Brill, Manfred A1 - Picard, Antoni A1 - Cassel, Detlev A1 - Jentsch, Andreas A1 - Rollwa, Markus T1 - Vom virtuellen Wafer zum realen Drucksensor N2 - Das Technologiepraktikum „Virtuelle Sensor-Fertigung“ ist ein Beispiel für die medientechnische Aufbereitung von Lern- und Lehrmaterial unter didaktischen Gesichtspunkten. Studierende lernen einen Fertigungsprozess mit Hilfe von virtuellen Maschinen kennen, bevor sie die reale Prozesskette im Laborpraktikum im Reinraum durchführen. N2 - The technology course “Fabrication of a microsensor” represents a multimediabased approach towards education in high technology production in consideration of didactical aspects. The students learn the operation of a complex microfabrication line with the help of virtual fabrication machines before they perform the actual process in a hands-on training in an actual clean room. KW - Virtuelle Maschine KW - VM KW - Virtuelle Sensor-Fertigung KW - virtual fabrication of a microsensor Y1 - 2003 ER - TY - CHAP A1 - Merten, Sabine A1 - Kämper, Klaus-Peter A1 - Brill, Manfred A1 - Picard, Antoni A1 - Cassel, Detlev A1 - Jentsch, Andreas A1 - Rollwa, Markus T1 - Virtuelle Sensor-Fertigung: Hightech mit LabVIEW N2 - Eine neue Generation von Praktika an Hochschulen wächst heran. Moderne Wege beim Verstehen und Erlernen naturwissenschaftlicher Zusammenhänge sowie industrieller Fertigungsprozesse sind gefordert. Das Technologiepraktikum „Virtuelle Sensor- Fertigung“, entwickelt im Verbundprojekt INGMEDIA an den Fachhochschulen Aachen und Zweibrücken, trägt als neuartiges Lern- und Lehrmodul dieser Forderung Rechnung. Die Studierenden lernen einen vollständigen Fertigungsprozess mit Hilfe von virtuellen, in LabVIEW programmierten Maschinen kennen, bevor sie die reale Prozesskette im Reinraum durchführen. N2 - A new generation of university laboratory courses is presently being developed. Modern concepts for the understanding and learning of applied science and industrial fabrication processes are required. The technology course “Fabrication of a microsensor”, developed by the Universities of Applied Sciences Aachen and Zweibrücken in the joint research project INGMEDIA, represents a new approach towards education in high technology production. The students learn the operation of the complex microfabrication line with the help of virtual fabrication machines, programmed in LabVIEW, before they perform the actual process in a genuine clean room. KW - LabVIEW KW - Virtuelle Sensor-Fertigung KW - Fertigungsprozess KW - virtuelle Maschinen KW - virtual sensor fabrication KW - manufacturing process KW - virtual KW - virtual machines Y1 - 2003 ER -