Effect of homogenisation conditions on recrystallisation in the Al-Mg-Mn alloy AA5454

The purpose of the present work is to understand the microstructure development and, particularly, to control the progress of recrystallisation in hot strip in the Al-Mg-Mn alloy AA 5454, which is typically used for the manufacture of structural automotive components. The chemical composition, together with the thermomechanical processing history of this material, has a strong influence on the microstructure of the product and the resulting properties as it is supplied to the customer. Electrical conductivity measurements, thermal analysis and electron microscopy have been carried out to characterise the evolution of precipitation state at various stages in the processing route. The conditions of the homogenisation heat treatment have been varied, and the effect on subsequent recrystallisation after hot rolling has been evaluated in both the as cast and rough rolled condition by optical microscopy techniques. Results indicate that the conditions of homogenisation heat treatment and roughing rolling are critical for the generation of a suitable recrystallised microstructure in AA 5454 hot strip. A new two stage homogenisation practice has been developed to expedite post-rolling recrystallisation in this alloy

Collusion in Growing and Shrinking Markets: Empirical Evidence from Experimental Duopolies

Publicado como un capítulo en: Jeroen Hinloopen (ed.). Experiments and Competition Policy. [S.l.]: Cambridge University Press, 2009, p.34-60. ISBN 9780511576201. ISBN 9781107403611. DOI http://dx.doi.org/10.1017/CBO9780511576201.003We study collusive behaviour in experimental duopolies that compete in prices under dynamic demand conditions. In one treatment the demand grows at a constant rate. In the other treatment the demand declines at another constant rate. The rates are chosen so that the evolution of the demand in one case is just the reverse in time than the one for the other case. We use a box-design demand function so that there are no issues of finding and co-ordinating on the collusive price. Contrary to game-theoretic reasoning, our results show that collusion is significantly larger when the demand shrinks than when it grows. We conjecture that the prospect of rapidly declining profit opportunities exerts a disciplining effect on firms that facilitates collusion and discourages deviation.Financial support from the Spanish Ministerio de Ciencia y Tecnologia (BEC 2003-00412), the Ministerio de Educación y Cultura (PB98-0465), the Barcelona Economics programme CREA, the British Academy and the University of Nottingham is gratefully acknowledged

The Law: The Boon and Bane of IT-enabled Peer-to-Peer Sharing and Collaborative Consumption Services

IT-enabled peer-to-peer (P2P) sharing and collaborative consumption services (SCCS) allow private persons to provide access for others to their cars, accommodation and other physical assets. Together they constitute the so called Share Economy. These services often operate in a legal gray area. The relationship between the law and SCCS is bidirectional. On the one hand, the development of new SCCS offerings has to comply with a broad body of existing regulations. On the other hand, new P2P SCCS businesses often discover legislative loopholes, thereby forcing the law to react. This article conceptualizes the complex relationship between the law and IT-enabled P2P SCCS by means of a framework. The applicability of the framework is demonstrated by analyzing a specific SCCS in the electric vehicle charging infrastructure domain. The framework should constitute an effective tool in the design of new and legal P2P SCCS offerings

Form-flexible handling and joining technology (formhand) for the forming and assembly of limp materials

The assembly of limp, elastic or differently shaped objects poses a huge challenge which needs to be met by machine tools and the corresponding processes of handling, forming and joining. These processes are often carried out manually. This technological gap triggered the present work at the Technische Universität Braunschweig. A novel form-flexible handling tool (FormHand) is presented which focuses on the automation of these production steps taking into consideration the material behavior. The combination of the flexibility of both industrial robot and the FormHand end-effector allows for new processes appropriate for these materials. This article investigates the used materials of the granular filler and the cushion textile, the working states of FormHand and the use of online sensors for an automated process application

Novel form-flexible handling and joining tool for automated preforming

The production rates of carbon fiber reinforced plastic (CFRP) parts are rising constantly which in turn drives research to bring a higher level of automation to the manufacturing processes of CFRP. Resin transfer molding (RTM), which is seen as a production method for high volumes, has been accelerated to a high degree. However, complex net-shape preforms are necessary for this process, which are widely manually manufactured. To face these challenges a new concept for the manufacturing of carbon fiber preforms with a form-flexible gripping, draping and joining end-effector is presented and discussed. Furthermore, this paper investigates the application of this concept, describes the initial build-up of a demonstrator, focusing on material selection and heating technology, and discusses test results with the prototype. This prototype already validates the feasibility of the proposed concept on the basis of a generic preform geometry. After a summary, this paper discusses future in-depth research concerning the concept and its application in more complex geometries. © 2015 by De Gruyter 2015

Battery management of rechargeable zinc-air batteries

Last, but not least, I would like to thank the project partners and funding institutions. Only through the active support and valuable insights of 3e Batterie Systeme GmbH, Kunkel und Partner GmbH, EMG Automation and Stadtwerke Steinfurt the success of the projects and the cell technology is possible. Special thanks also go to the project funding Projektträger ETN, Leitmarktagentur.NRW, which is now funding the project after project number EFRE-0800072 in a follow-up project EFRE-0801585, making the research possible in the first place.The demand for energy storage is increasing massively due to the electrification of transport and the expansion of renewable energies. Current battery technologies cannot satisfy this growing demand because they are difficult to recycle, because the necessary raw materials are mined under precarious conditions, and because the energy density is insufficient. Metal-air batteries offer a high energy density because there is only one active mass inside the cell and the cathodic reaction uses the ambient air. Various metals can be used, but zinc is very promising because of its disposability, non-toxic behavior, and because operation as a secondary cell is possible. Typical characteristics of zinc-air batteries are flat charge and discharge curves. On the one hand, this is an advantage for the subsequent power electronics, which can be optimized for smaller and constant voltage ranges. On the other hand, the state determination of the system becomes more complex, since the voltage level is not sufficient to determine the state of the battery. In this context, electrochemical impedance spectroscopy is a promising candidate since the resulting impedance spectra depend on the state of charge, working point, state of aging, and temperature. Therefore, in this thesis, an electrochemical model of the zinc-air cell is developed and parameterized using measured electrochemical impedance spectra. The modification of the parameters enables to successfully determine the state of charge when the cell is being discharged and provide a charge termination detection. In addition, electrochemical impedance spectroscopy is combined with various artificial intelligence techniques to also determine successfully the state of charge during charging of the cell. Furthermore, an analysis of the oxygen consumption and the cell performance at different oxygen concentrations is performed, such that with a control of the electrolyte management a demonstrator consisting of several zinc-air cells could be successfully put into operation.La demanda de almacenamiento de energía está aumentando masivamente debido a la electrificación del transporte y la expansión de las energías renovables. Las actuales tecnologías de baterías no pueden satisfacer esta creciente demanda porque son difíciles de reciclar, porque las materias primas necesarias se extraen en condiciones precarias y porque la densidad energética es insuficiente. Las baterías metal-aire ofrecen una alta densidad energética porque sólo hay una masa activa dentro de la celda y la reacción catódica utiliza el aire del ambiente. Se pueden utilizar varios metales, pero el zinc es muy prometedor por su carácter desechable, su comportamiento no tóxico y porque es posible su funcionamiento como celda secundaria. Una característica típica de las baterías de zinc-aire son las curvas planas de carga y descarga. Por un lado, esto es una ventaja para su uso en electrónica de potencia, ya que puede optimizarse para rangos de tensión más pequeños y constantes. Por otro lado, la determinación del estado del sistema se vuelve más compleja, ya que el nivel de tensión no es suficiente para determinar el estado de la batería. En este contexto, la espectroscopia de impedancia electroquímica es un candidato prometedor, ya que los espectros de impedancia resultantes dependen del estado de carga, el punto de trabajo, el desgaste acutal y la temperatura. Por lo tanto, en esta tesis se desarrolla y parametriza un modelo electroquímico de la celda de zinc-aire utilizando los espectros de impedancia electroquímica medidos. La modificación de los parámetros permite determinar con éxito el estado de carga cuando la celda se está descargando y proporcionar una detección de ausencia de carga. Además, la espectroscopia de impedancia electroquímica se combina con varias técnicas de inteligencia artificial para determinar también con éxito el estado de carga durante la carga de la celda. Asimismo, se realiza un análisis del consumo de oxígeno y del rendimiento de la celda a diferentes concentraciones de oxígeno, de manera que, con un control de la gestión del electrolito, se podría poner en funcionamiento con éxito un moelo de demostración compuesto por varias celdas de zinc-aire.Tesis Univ. Granada.Projektträger ETNLeitmarktagentur.NRW EFRE-0800072 EFRE-0801585European Unio