Refine
Year of publication
- 2003 (3) (remove)
Document Type
- Article (3)
Language
- English (3) (remove)
Has Fulltext
- no (3)
Is part of the Bibliography
- yes (3)
Keywords
- Semi-solid alloys (1)
- Suspension (1)
- Thixotropy (1)
- Yield stress (1)
Institute
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.
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.
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.