Refine
Year of publication
Document Type
- Article (50)
- Book (28)
- Part of a Book (16)
- Conference Proceeding (4)
- Doctoral Thesis (2)
Has Fulltext
- no (100) (remove)
Is part of the Bibliography
- yes (100)
Keywords
- Autarkie (2)
- Container (2)
- Energie (2)
- Solarthermie (2)
- Energiekonzept (1)
- Erfolgsfaktor (1)
- Hackschnitzel (1)
- Innovationsmanagement (1)
- Klimazonen (1)
- Regenerativ (1)
Institute
- Institut für Duale Studiengänge (100) (remove)
Semi-solid metal alloys, as used in thixoforming, have a special microstructure of globular grains suspended in a liquid metal matrix. The complex rheological properties are strongly influenced by the local solid fraction, particle shape, particle size and state of agglomeration. There is a high demand for models and software tools allowing the simulation of semi-solid casting processes. The material under investigation is a tin-lead alloy (Sn-15%Pb) which exhibits a similar microstructure to aluminium alloys. The experiments were performed with a concentric cylinder rheometer of the Searle type. Initially, the liquid alloy is cooled down to the semi-solid range under constant shearing and then kept under isothermal conditions for further experimentation. Based on the experimental data, a single-phase model has been derived where the semi-solid alloy is regarded as a homogeneous material with thixotropic properties and the microstructure is characterised by a structural parameter. The model consists of two parts: the equation of state, including a finite yield stress, and a rate equation for the structural parameter. The model equations are employed in numerical software and used for the simulation of characteristic filling cases and the comparison with the conventional filling.
Semi-solid metal alloys, as used in thixoforming, have a special microstructure of globular grains suspended in a liquid metal matrix. The material under investigation is a tin–lead alloy (Sn–15% Pb) which exhibits a similar microstructure as aluminum alloys. The experiments were performed with concentric cylinder rheometers. Initially, the liquid alloy is cooled down to the semi-solid range under constant shearing and then kept under isothermal conditions for further experimentation. The microstructure is characterized in dependence of the shearing time. The rheological techniques consisted of step change of shear rate and shear stress ramp experiments for different solid fractions (40–50%). Based on the experimental data a single phase model has been derived, where the semi-solid alloy is regarded as a homogeneous material with thixotropic properties and the microstructure is characterized by a structural parameter. The model consists of two parts: the equation of state, including a finite yield stress, and a rate equation for the structural parameter. The model equations are employed into numerical software and used for the simulation of a characteristic thixocasting process. The results are compared to real experiments.
Semi-solid metal alloys, as used in industrial thixoforming, have a special microstructure of globular grains suspended in a liquid metal matrix. The complex rheological properties are strongly influenced by the local solid fraction, particle shape, particle size and state of agglomeration. It was analysed how the microstructure develops in dependence of the shear rate and cooling rate during the solidification and it was observed that the average particle size increased with increasing shear rate and decreasing cooling rate. In order to account for those phenomena, the rate of crystal growth and the relationship between average particle diameter and viscosity was modelled by applying the Sherwood two-film model for the mass transport. The dependence of the viscosity from the particle size were modelled with a modified Krieger–Dougherty model. Based on the rheological and microstructural observations an evaluation method was elaborated that allows for the construction of objective master curves that are independent of the particle growth during the experimentation. The isothermal experiments for the characterisation of the rheological behaviour consisted of step-change of shear-rate and yield-stress experiments. From the experimental data the steady-state flow curves could be determined as well as the time-dependent relaxation of the shear stress after a change of shear rate. The steady-state rheological behaviour was found to be shear thinning. Nevertheless, immediately after a shear-rate change an overshoot was observed that resulted from a short-time shear-thickening behaviour. The yield stress was found to strongly depend on the microstructure and the degree of agglomeration of the solid phase. With increasing rest time the yield stress was increasing strongly, because of the agglomeration of the solid particles. Based on the step-change of shear-rate experiments a single-phase flow has been developed that consists of a modified Herschel–Bulkley approach and accounts for the thixotropic as well as for the yield-stress behaviour of the alloys.
Companies and R&D institutions increasingly collaborate not only in isolated projects but also in knowledge-based networks. In those networks, participants combine expertise and applied problems to generate both ‘problem-solving knowledge’ and specialized knowledge: during the process of common problem-solving each partner acquires some of the specialized knowledge of the other partners as well as the newly generated problem-solving knowledge. This article examines the basic principles involved and provides a simple mathematical description of the step-by-step accumulation of knowledge through the solving of applied problems in a knowledge-based network. The rate of increase of the total amount of available knowledge in the network is derived and implications for the orientation of R&D institutes and companies are set out.
Optimale Garantiepolitik
(2006)
Die Fallstudie aus der Betriebswirtschaftslehre: Preisbündelung bei einer Bildungseinrichtung
(2006)
Die Rolle von Händlern bei der Bewältigung von Produktkrisen: Eine verhaltenspsychologische Analyse
(2009)
Ziel der Untersuchung ist es, einen Simulationsansatz zum quantitativen Vergleich der Ergebnisse verschiedener Verfahren der verbundorientierten Erfolgsbewertung von Artikeln in Handelssortimenten zu entwickeln und zu erproben. Die Hauptschwierigkeit liegt dabei darin, dass es keinen absoluten Gütemaßstab gibt: Niemand kann angeben, welches der tatsächliche verbundorientierte Beitrag eines Artikels zum Gesamterfolg eines Sortiments ist. Die statistische Analyse von realen Abverkaufsdaten des Handels, oder auch von in kontrollierten Experimenten
gewonnenen Abverkaufsdaten, kann deshalb kein schlüssiges Ergebnis liefern. Natürlich kann eine theoretische Analyse der verschiedenen Verfahren Argumente für oder gegen die Überlegenheit einzelner Verfahren liefern. Ihre Ergebnisse sind aber schwierig zu quantifizieren und damit zu interpretieren. Zur Erlangung quantitativer Resultate erscheint deshalb einzig die Methode der Simulation als geeignet.
Diese kann von fiktiven Situationen ausgehen, in denen der tatsächliche verbundorientierte Erfolgsbeitrag eines Artikels vorgegeben wird und damit bekannt ist. Durch eine sehr große Anzahl verschiedener Versuche sollte sich dann im statistischen
Mittel ein Hinweis zur Leistungsfähigkeit der Verfahren ergeben, eben diesen tatsächlichen Erfolgsbeitrag aus normalen Warenkorbdaten zu ermitteln. Dieser Weg wird im vorliegenden Beitrag beschritten.
In Abschnitt 2 wird zunächst das Ziel verdeutlicht, das Verfahren der verbundorientierten Erfolgsbewertung zu verfolgen. Im Anschluss daran werden die Funktionsweisen mehrerer Verfahren zur verbundorientierten Erfolgsbewertung vorgestellt, die im Schrifttum bekannt sind (Merkle 1981; Recht/Zeisel 1998; Städler/Fischer 2001). Auf eine theoretische Diskussion und Kritik der Verfahren kann dabei mit
Blick auf das Ziel der vorliegenden Untersuchung verzichtet werden. In Abschnitt 3 wird zunächst die Frage diskutiert, wie die Ergebnisse derartiger Verfahren überhaupt miteinander verglichen werden könnten. Dabei geht es u. a. um das Problem einer Untermauerung von Vorteilhaftigkeitsaussagen durch empirische Untersuchungen.
In Abschnitt 3.2 wird dann gezeigt, wie durch eine Simulation zumindest einige Anhaltspunkte zur Leistungsfähigkeit alternativer Verfahren gewonnen werden können. Für mehrere Verfahren wurde eine entsprechende Simulation durchgeführt, deren Ergebnisse in Abschnitt 4 vorgestellt und diskutiert werden. Abschnitt 5 enthält eine Zusammenfassung der Untersuchungsergebnisse und
einen Ausblick auf aufgeworfene Forschungsfragen.
Purpose
– The purpose of this paper is to present the current empirical research examining communication, compensation and logistics as elements of product crises management in retailing.
Design/methodology/approach
– The advantages and disadvantages of these three elements of crises response strategies are juxtaposed drawing on relevant empirical research. For each element of crises response the major findings of research are summarized and shown how it relates to crisis management. Needs for further research that would be necessary to solidify recommendations to retail managers are derived.
Findings
– The investigation finds that both communicative and compensatory response elements as well as the retailer's logistics can positively influence evaluations of customers directly and indirectly affected by product problems thus enhancing brand equity. This in turn will serve to increase consumers' trust in the retailer that could win him new customers and generally benefit his reputation.
Research limitations/implications
– Most of the discussed research rests on the assumption of a given (extraneous) crisis response strategy of the manufacturer. Potential problems concerning the co‐ordination or implementation of manufacturer and retailer strategies remain open to question. Additionally, further research should examine which strategies are appropriate to which crisis situation.
Practical implications
– Materially, over‐compensating customers often has a detrimental effect on solving the crisis. The impact of different compensation types on crisis resolution mostly depends on their respective signalling capabilities, the product problem constituting the crisis and consumer attributions. The use and the effects of a communicative crisis response largely depend on moderating factors such as the retailer's reputation or the existence of strong retail brands and consumer expectations. Elements of logistics seem to support the effects of communication and compensation on crisis resolution but are hardly capable of solving a product‐harm crisis.
Originality/value
– The role of retailers in product‐harm crisis management has been widely neglected in research although such crises are predominant. This paper outlines the current empirical work on how different crises response elements may contribute to solving a product‐harm crisis for retailers. It derives relevant avenues for further research as well as useful insights to practitioners considering to using such response elements in their own crisis management strategy.