1,721,150 research outputs found
Analysis of End-of-Life Process Data to enable Design Knowledge for Circularity
No full textThe concept of Circular Economy (CE) is gaining increasing attention as an indispensable renewal of linear economy without neglecting sustainable development goals. Closing resource loops and keeping resources in the system at the highest level of use for as long as possible are cited as the main goals of CE. However, due to missing information exchange, the lack of consistency between the existing End-of-Life (EOL) infrastructure and the respective product designs hinders a successful circularity of resources. This research provides a modular method to collect, process, and apply EOL process data to provide the Beginning-of-Life (BOL) with important EOL-knowledge through a CE adapted product design assessment. EOL-data is collected using a Circular Value Stream Mapping (CVSM), EOL-information is processed using a digital state flow representation, and EOL-knowledge is applied by providing a graphical user interface for designers. The method is verified by a simulation model that serves as a decision-support tool for product designers in the context of a PET bottle case study in Luxembourg. The goal is to anticipate a circular flow of resources by reflectively aligning product design with the relevant EOL infrastructure. Within the linear economy, the focus has been on improving production processes while neglecting what happens to a product after its use. The developed method makes it possible to consider not only the requirements of users but also the actual end users, the EOL process chains, when designing products
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Erfolgreiches Lieferantenmanagement durch eindeutige Schnittstellendefinition
No full textIn schlanken Werken montieren externe Dienstleister ausgewählte
Baugruppen und liefern sie direkt an die Hauptmontagelinie.
Dabei sind zahlreiche technische und organisatorische
Schnittstellen zu definieren, um den Wissenstransfer
in beide Richtungen effektiv und sicher zu gestalten und
dabei gleichzeitig das Know-how beider Seiten zu schützen.
Dieser Beitrag beschreibt exemplarisch erfolgreich angewandte
Methoden zur Einbindung externer Dienstleister in
mehreren Werken in der Automobilindustrie
Laser Welding of Metals to Polymers Under the Special Influence of Surface Pretreatment on Interfacial Thermal Transfer
Get PDFJoining of metals to polymers is increasing among various industries because of its ability to produce lightweight hybrid products with tailored properties. Common joining methods, such as adhesive bonding and mechanical fastening, require adding a third material which might involve hazardous chemicals or add extra weight and stress concentration points to the component. On the other hand, Laser-Assisted Metal – Polymer joining (LAMP) is a contactless, rapid, highly precise and energy-efficient technique, that produces autogenous and miniaturized joints. It was already demonstrated that surface pretreatment prior to the welding process has a significant impact on the joint performance by modifying surface chemistry and topography, promoting chemical bonding and mechanical interlocking. This research aims at expanding the understanding of the effects of surface properties on the joint’s performance by investigating their influence on interfacial thermal transfer.
While increased surface roughness of metallic partner is expected to improve LAMP joint performance by promoting mechanical interlocking, it is hypothesized that a smoother surface would improve the joint quality by enhancing the interfacial thermal transfer during the welding process, resulting in a larger area of molten polymer at the interface and a better joint performance.
In this research, aluminum (Al1050) and titanium (Ti64) were joined with polyamide (PA6.6). Initially, laser welding parameters were optimized and kept constant during all surface pretreatments’ investigations. Preliminary surface pretreatments, using short-pulsed laser ablation and atmospheric plasma pretreatment, were conducted on Al1050 – PA6.6 to analyze the effects of surface composition and topography on joint quality and performance, and to optimize interfacial adhesion. Results show a correlation between increased surface oxidation and surface energy with improved interfacial adhesion and joint resistance to shear failure. Compared to plasma pretreated surfaces, laser ablation of metals results in a very rough surface which exhibits perfect wettability to both water and diiodomethane. This promotes mechanical interlocking and interfacial adhesion, resulting in a relatively stronger joint failing in a cohesive failure mode. Results confirm that an improvement of the assembly’s shear resistance to failure can certainly be achieved without an increase in surface roughness and interfacial interlocking, as observed in case of plasma pretreatment.
Design of Experiments (DoE) techniques were utilized for both material combinations in order to optimize laser ablation process and to investigate the effects of pretreatment parameters on surface properties, interfacial thermal transfer, joint quality and resistance to failure. Laser ablation parameters influenced the surface topography with no significant effect on the surface composition, and all laser-ablated surfaces showed perfect wettability to both water and diiodomethane. While all ablated surfaces demonstrate cohesive failure mode, smoother ablated surfaces results in a better interfacial thermal transfer as indicated by the Thermal Contact Resistance (TCR) calculations and measurements, based on Cooper–Mikic–Yovanovich (CMY) model and layered Laser Flash Analysis (LFA) investigations, respectively. Results show that a smoother ablated surface results in better interfacial thermal transfer, melting a larger area of polymer which increases the joint quality and resistance to shear load.LaserSTAM
Variations on the Author
Get PDF“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
Development of an intelligent, robot-supported assistance system for the disassembly of industrial products
Get PDFTechnical assistance systems are used in many aspects of our private environment to simplify our daily lives. Such assistance would also be desirable in our working environment,
especially in physically demanding activities such as dismantling products for maintenance, corrective maintenance, or remanufacturing.
However, the use of robot-supported assistance systems is prevented by the imponderabilities in the dismantling process of different products due to the lack of autonomy of the
technical systems.
In the course of this dissertation, the development of intelligent, robot-supported assistance systems that can support people in such complex processes in a target-oriented manner are considered, and the following research question is posed: What are the technical
requirements for such assistance systems and how can they be implemented?
In the reviewed scientific literature, no holistic approach has been identified for the development of these systems, but many approaches to partial aspects of such a system have
been collected across several research disciplines.
In order to address the research question, this dissertation discusses the theoretical fields
of technical assistance systems, human-robot systems, and the field of application in order
to define technical requirements. A demonstrator for experimental validation is implemented in the form of a multi-agent system in which various technical systems are integrated and interconnected by software. The function of the developed robot-based assistance system could be verified in concrete dismantling processes in conjunction with suitable man-machine communication interfaces.
Finally, this dissertation identifies further research questions that must be addressed before such systems can be introduced in the industrial environment.In vielen Bereichen des privaten Umfelds haben technische Assistenzsysteme ihren Platz
eingenommen und vereinfachen das tägliche Leben. Diese Tendenz wäre auch im Arbeitsleben wünschenswert, besonders in körperlich belastenden Tätigkeiten wie der Demontage von Produkten in der Wartung, Instandsetzung oder Refabrikation.
Doch der Einsatz robotergestützter Assistenzsysteme wird durch die Unwägbarkeiten im
Demontageprozess unterschiedlicher Produkte wegen der fehlenden Autonomie der technischen Systeme verhindert.
Im Rahmen dieser Dissertation wird daher die Entwicklung von intelligenten, robotergestützten Assistenzsystemen betrachtet, die den Menschen in solch komplexen Prozessen zielgerichtet unterstützen können. Dabei wird die folgende Forschungsfrage gestellt:
Welche technischen Anforderungen werden an ein solches Assistenzsystem gestellt und
wie können sie umgesetzt werden?
In der gesichteten wissenschaftlichen Literatur konnte für die Entwicklung dieser Systeme kein ganzheitlicher Ansatz ermittelt werden. Es wurden jedoch viele Ansätze zu
Teilaspekten eines solchen Systems, über mehrere Forschungsdisziplinen hinweg, zusammengetragen.
Zur Klärung der Forschungsfrage erfolgt in dieser Dissertation die Darstellung der Themengebiete der technischen Assistenzsysteme, der Mensch-Roboter-Systeme sowie des
Einsatzgebiets, um technische Anforderungen zu definieren. Deren Umsetzung in einem
Demonstrator zur experimentellen Validierung erfolgte in Form eines Multiagentensystems, in das verschiedene technische Systeme durch Software integriert und vernetzt wurden. Weiterhin wurde die notwendige technische Autonomie des Assistenzsystems auf
Basis zweier modellbasierten Planungssysteme sowie des zentralen Steuerungssystems
durch Software implementiert. In Verbindung mit geeigneten Mensch-Maschine-Kommunikationsschnittstellen, konnte die Funktion des Assistenzsystem in konkreten Demontageprozessen verifiziert werden.
Jedoch zeigte sich auch, dass für die Einführung solcher Systeme im industriellen Umfeld noch weitere herausfordernde Forschungsfragen bearbeitet werden müssen.Demontage von elektrischen Antriebssysteme
Modeling and Control of Laser Wire Additive Manufacturing
Get PDFMetal Additive Manufacturing (MAM) offers many advantages such as fast product manufacturing,
nearly zero material waste, prototyping of complex large parts and the automatization of the manufacturing process in the aerospace, automotive and other sectors. In the MAM, several parameters influence the product creation steps, making the MAM challenging. In this thesis, we modelize and control the deposition process for a type of MAM where a laser beam is used to melt a metallic wire to create the metal parts called the Laser Wire Additive Manufacturing Process (LWAM). In the dissertation, first, a novel parametric modeling approach is created. The goal of this approach is to use parametric product design features to simulate and print 3D metallic objects for the LWAM. The proposed method includes a pattern and the robot toolpath creation while considering several process requirements of LWAM, such as the deposition sequences and the robot system. This technique aims to develop adaptive robot toolpaths for a precise deposition process with nearly zero error in the product creation process. Second, a layer geometry (width and height) prediction model to improve deposition accuracy is proposed. A machine learning regression algorithm is applied to several experimental data to predict the bead geometry across layers. Furthermore, a neural network-based approach was used to study the influence of different deposition parameters, namely laser power, wire-feed rate and travel speed on bead geometry. The experimental results shows that the model has an error rate of (i.e., 2∼4%). Third, a physics-based model of the bead geometry including known process parameters and material properties was created. The model developed for the first time includes critical process parameters, the material properties and the thermal history to describe the relationship between the layer height with different process inputs (i.e., the power, the standoff distance, the temperature, the wire-feed rate and the travel speed). The numerical results show a match of the model with the experimental measurements. Finally, a Model Predictive Controller (MPC) was designed to keep the layer height trajectory constant, considering the constraints and the operating range of the parameters of the process inputs. The model simulation result shows an acceptable tracking of the reference height.Fabrication Additive par Dépôt de Fil (FAFil) project (Ref. 3477
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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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