Analysis of stirred mill performance using DEM simulation: Part 2 - Coherent flow structures, liner stress and wear, mixing and transport

Stirred Mills are becoming increasingly used for fine and ultra-fine grinding. This technology is still poorly understood when used in the mineral processing context. This makes process optimisation of such devices problematic. 3D DEM simulations of the flow of grinding media in pilot scale tower mills and pin mills are carried out in order to investigate the relative performance of these stirred mills. In the first part of this paper, media flow patterns and energy absorption rates and distributions were analysed to provide a good understanding of the media flow and the collisional environment in these mills. In this second part we analyse steady state coherent flow structures, liner stress and wear by impact and abrasion. We also examine mixing and transport efficiency. Together these provide a comprehensive understanding of all the key processes operating in these mills and a clear understanding of the relative performance issues. (C) 2006 Elsevier Ltd. All rights reserved.

Effect of growing site, moisture stress and seed size on viability and dormancy of Sporobolus pyramidalis (giant rats tail grass) seed

Sporobolus pyramidalis P. Beauv (giant rats tail grass) is a serious agricultural and environmental weed in tropical and subtropical areas of Australia. Infestations of this unpalatable plant reduce the productivity of pastures and the profitability of industries dependent on grazing animals. This paper reports a series of studies undertaken to assist in the development of control strategies for this species. In particular, these studies measured the viability and dormancy status of fresh seed of S. pyramidalis and the decline of dormancy with time. Variability in these characteristics was determined in seeds collected from several sites within south-east Queensland. The effect of moisture availability during the inflorescence and seed production phases on seed viability and dormancy was also determined. The dormancy of freshly collected seed from several sites ranged from 15 to 95%, but decreased to negligible levels after 4-6 months. Seeds that matured under conditions of high moisture availability were initially more dormant than seeds matured where moisture was less readily available. The proportion of viable seeds was significantly lower in smaller than larger seeds even though viability for all seed sizes exceeded 90%. This study has shown that seed of S. pyramidalis generally has high viability with a large proportion of the seed germinable soon after maturity.

Perceptions of organizational change: A stress and coping perspective

Few organizational change studies identify the aspects of change that are salient to individuals and that influence well-being. The authors identified three distinct change characteristics: the frequency, impact and planning of change. R. S. Lazarus and S. Folkman's (1984) cognitive phenomenological model of stress and coping was used to propose ways that these change characteristics influence individuals' appraisal of the uncertainty associated with change, and, ultimately, job satisfaction and turnover intentions. Results of a repeated cross-sectional study that collected individuals' perceptions of change one month prior to employee attitudes in consecutive years indicated that while the three change perceptions were moderately to strongly intercorrelated, the change perceptions displayed differential relationships with outcomes. Discussion focuses on the importance of systematically considering individuals' subjective experience of change.

Are country and culture values interchangeable? A case example using occupational stress and coping

Cross cultural research in occupational stress and coping has produced a wealth of knowledge. Although advances have been made, there are still problems to be solved. One of these problems is the confusion generated in the literature by researchers claiming that nation or country represents cultural values, and the use of the two terms interchangeably. It remains unclear whether this practice is correct. The present article reported on this by using 511 full-time employees from Australia, Singapore and Sri Lanka to study occupational stress and coping. Results revealed that cultural value paradigms (i.e. Individualism–Collectivism) were distributed across the three nations such that over 60% of participants were either high or low in both I–C paradigms. The findings also indicated that the relationship between cultural value paradigm and country impacted on stress and coping differently. The study shows that significant differences exist within countries as well as between countries, such that any attempt to equate ‘culture’ with ‘country’ becomes problematic. Therefore these findings established that country or nation is not the same as culture values and cannot be used interchangeably.