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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.
A suspension of PMMA spheres in a density matched saccharose solution is investigated with a classical Searle rheometer and a NMR (Nuclear Magnetic Resonance) spectrometer. Here the NMR is used to measure the radial distribution of the PMMA spheres in the rotating cell, in addition to the local velocity profile of the suspension. The influence of particle concentration on the wall depletion is studied. Further analysis are carried out with computational fluid dynamics software. The velocity field as well as the solid distribution in the couette flow is simulated with a two-phase model including the Darcy law and compared to the experimental data.
Investigation of the use of ceramic materials in innovative light water reactor – fuel rod concepts
(2001)
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.
Data warehouse systems have become a basic technological infrastructure in management decision making. Nevertheless, the overall utility of data warehouses remains unmeasured in most practical cases. As a consequence of this, IT-managers do not possess appropriate means to evaluate warehouse benefits in order to decide about investments in warehousing technology. This paper develops a controlling instrument for data warehouse systems based on the Balanced Scorecard (BSC) approach. On the basis of the technological aspects of data warehouse systems, the BSC perspectives are developed and populated with relevant objectives and measures for datawarehouse success. These perspectives are integrated into a consistent data warehouse scorecard. Finally, this instrument provides a holistic approach to drive the performance of data warehouse systems.
Building on Hofstede's finding that individualism and social hierarchy are incompatible at the societal level, the authors examined the relationship between individualism-collectivism and orientations toward authority at the individual level. In Study 1, authoritarianism was related to three measures of collectivism but unrelated to three measures of individualism in a U.S. sample (N = 382). Study 2 used Triandis's horizontal-vertical individualism-collectivism framework in samples from Bulgaria, Japan, New Zealand, Germany, Poland, Canada, and the United States (total N = 1,018). Both at the individual level and the societal level of analysis, authoritarianism was correlated with vertical individualism and vertical collectivism but unrelated to horizontal collectivism. Horizontal individualism was unrelated to authoritarianism except in post-Communist societies whose recent history presumably made salient the incompatibility between state authority and self-determination.
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.
Every modern institution involved in higher education needs a Learning Management System (LMS) to handle learning and teaching processes. It is necessary to offer e.g. electronic lecture materials to the students for download via the internet. In some educational contexts, it is also necessary to offer internet tutorials to be able to give the students more personal support and accompany them through the whole lecture period. Many organisations have introduced commercial LMS and gained the experience that monolithic solutions do not fulfil the dynamic requirements of complex educational institutions and are very cost-intensive. Therefore, many universities face the decision to stick to their commercial LMS or to switch to a potentially more cost-effective and flexible solution, for instance by adopting available Open Source LMS. Since we have made profound experience in developing and operating an Open Source LMS, this contribution enlightens the main characteristics of this alternative. This paper describes a use case dealing with a full product lifecycle (development, deployment, use and evaluation) of an Open Source LMS at the University of Muenster (Germany). It identifies relevant instruments and aspects of system design which software architects in practical application domains should pay attention to.
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.
Model Driven Architecture (MDA): Integration and Model Reuse for Open Source eLearning Platforms
(2005)
Business-driven development favors the construction of process models
at different abstraction levels and by different people. As a consequence, there is a demand for consolidating different versions of process models by merging them. In this paper, we study a basic scenario, derive requirements and present a prototype for detecting and resolving changes between process models.
The purpose of this study was to evaluate which mode of birth first-time mothers in Germany and in the USA prefer and how this desire is related to maternal well-being and sense of coherence. The paper describes emotional well-being postpartum in relationship to mode of birth. For data collection a prospective cohort study was conducted in both countries. A self-administered questionnaire including validated instruments (WHO-5 Well-Being Index, Sense of Coherence Scale and Edinburgh Postnatal Depression Scale) was used. Results showed that only a few of the pregnant women in Germany and the USA preferred to deliver by caesarean section. There was a relationship between women's well-being, women's sense of coherence and the preferred mode of birth. The majority of women who wanted a caesarean section delivered in this way. No relationship was found between women's well-being and the type of birth experienced. Well-being in both samples generally decreased after giving birth, but there was a difference between German and American first-time mothers on the postpartum well-being and depression scores. German mothers had a higher postnatal quality of life and lower postnatal depression scores. To give families the opportunity for a healthy start, midwives and obstetricians should try to enhance women's well-being and they should give some thought to health professionals' decision-making processes. Expanded postpartum care might have an impact on women's depression scores..
When speaking about eBusiness as applied to the healthcare market two questions arise immediately. Firstly, what is eBusiness? Secondly, why is eBusiness in healthcare different from eBusiness in other sectors?
Within the arena of eBusiness in healthcare, the focus is on purchasing and selling online as the most advanced application. In this book, the Authors consider both the perspective of the healthcare providers and that of the suppliers, showing the interdependencies between the two and developing concepts for a new synergistic cooperation.
eBusiness in Healthcare raises awareness of and interest in electronically mediated business processes in healthcare to a large audience including healthcare informaticians, medical business managers, clinicians, pharmacists and scientists. By taking an international approach to the topic the authors demonstrate the many similarities of eBusiness problems and their solutions among different countries which permits analysis of the differences that are often defined by the national healthcare systems and their rules. Case studies from healthcare institutions and from suppliers in the US, the UK and Germany will illustrate the achievements, barriers and future plans, thus enabling newcomers to learn from previous experience.
Clinicians will gain significant insight by this book which demonstrates the interconnection between patient care processes and management issues at the level of medical supplies. The book also makes a plea for a multidisciplinary effort, to enable the right product to be procured for the right patient. As a rather new discipline, eBusiness in healthcare needs further scientific backing. Against this background, this book will not only provide answers but will also raise questions for future research. Managing change and innovation and establishing the critical mass for eBusiness in healthcare is a major undertaking. The aim of this book is to support this process.
Hedonism
(2009)
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.