Using DEM to model ore breakage within a pilot scale SAG mill

The best accepted method for design of autogenous and semi-autogenous (AG/SAG) mills is to carry out pilot scale test work using a 1.8 m diameter by 0.6 m long pilot scale test mill. The load in such a mill typically contains 250,000-450,000 particles larger than 6 mm, allowing correct representation of more than 90% of the charge in Discrete Element Method (DEM) simulations. Most AG/SAG mills use discharge grate slots which are 15 mm or more in width. The mass in each size fraction usually decreases rapidly below grate size. This scale of DEM model is now within the possible range of standard workstations running an efficient DEM code. This paper describes various ways of extracting collision data front the DEM model and translating it into breakage estimates. Account is taken of the different breakage mechanisms (impact and abrasion) and of the specific impact histories of the particles in order to assess the breakage rates for various size fractions in the mills. At some future time, the integration of smoothed particle hydrodynamics with DEM will allow for the inclusion of slurry within the pilot mill simulation. (C) 2004 Elsevier Ltd. All rights reserved.

Making decisions with the future in mind: Developmental and comparative identification of mental time travel

Mechanisms that produce behavior which increase future survival chances provide an adaptive advantage. The flexibility of human behavior is at least partly the result of one such mechanism, our ability to travel mentally in time and entertain potential future scenarios. We can study mental time travel in children using language. Current results suggest that key developments occur between the ages of three to five. However, linguistic performance can be misleading as language itself is developing. We therefore advocate the use of methodologies that focus on future-oriented action. Mental time travel required profound changes in humans' motivational system, so that current behavior could be directed to secure not just present, but individually anticipated future needs. Such behavior should be distinguishable from behavior based on current drives, or on other mechanisms. We propose an experimental paradigm that provides subjects with an opportunity to act now to satisfy a need not currently experienced. This approach may be used to assess mental time travel in nonhuman animals. We conclude by describing a preliminary study employing an adaptation of this paradigm for children. (c) 2005 Elsevier Inc. All rights reserved.

Older people with hearing impairment: A literature review of the spouse's perspective

Spouses of older people with hearing impairment frequently urge their hearing impaired partners to seek help for their hearing difficulties. Only a minority of individuals with hearing impairment are self-motivated, with the majority of clients, especially older clients, presenting at audiology clinics under the persuasion or influence of their spouse or significant other. This highlights the important role that spouses play in initiating aural rehabilitation and indicates that spouses of older people with hearing impairment may become so frustrated with their partners' hearing loss that they are often the primary reason why the hearing impaired person presents for audiological services. To date, however, the number of studies addressing the effect of hearing loss on significant others is limited. Those studies that have investigated the effect of hearing impairment on families are commonly focused on the person with the impairment and most commonly, the significant other has merely been used as a proxy to describe the perceived problems of his or her spouse. Further, there has been no systematic indepth investigation of the needs of spouses of older people with hearing impairment, including the effect of retirement and the increase in time spent together, with the majority of studies focusing primarily on younger spouses of workers affected by noise-induced hearing loss. The cumulative effect of experiencing many years of hearing difficulties with a partner may also influence the extent to which older spouses are affected by hearing impairment. The primary purpose of this article is therefore to critically review the existing literature on the effects of hearing impairment on spouses. It will also provide a rationale for the importance of this topic as a clinical issue and suggest some future directions for research in this area.

Making media work in space: An interdisciplinary perspective on media and communication requirements for current and future space communities

As humans expand into space communities will form. These have already begun to form in small ways, such as long-duration missions on the International Space Station and the space shuttle, and small-scale tourist excursions into space. Social, behavioural and communications data emerging from such existing communities in space suggest that the physically-bounded, work-oriented and traditionally male-dominated nature of these extremely remote groups present specific problems for the resident astronauts, groups of them viewed as ‘communities’, and their associated groups who remain on Earth, including mission controllers, management and astronauts’ families. Notionally feminine group attributes such as adaptive competence, social adaptation skills and social sensitivity will be crucial to the viability of space communities and in the absence of gender equity, ‘staying in touch’ by means of ‘news from home’ becomes more important than ever. A template of news and media forms and technologies is suggested to service those needs and enhance the social viability of future terraforming activities.

Structural change in macroeconomic time series: A complex systems perspective

We demonstrate that the process of generating smooth transitions Call be viewed as a natural result of the filtering operations implied in the generation of discrete-time series observations from the sampling of data from an underlying continuous time process that has undergone a process of structural change. In order to focus discussion, we utilize the problem of estimating the location of abrupt shifts in some simple time series models. This approach will permit its to address salient issues relating to distortions induced by the inherent aggregation associated with discrete-time sampling of continuous time processes experiencing structural change, We also address the issue of how time irreversible structures may be generated within the smooth transition processes. (c) 2005 Elsevier Inc. All rights reserved.

Doom and gloom or a time for optimism: Potential aspirants' views about school leadership - now and for the future

Principal recruitment has attracted national and international attention in recent years (eg. Barty et al, 2005 in Australia; Earley et al, 2002 in the UK; Brooking et al, 2003 in New Zealand; Williams, 2003 in Canada). Importantly, Australian research in both state and non-state schools suggests that potential principal aspirants are less enthusiastic than might be expected in their desire to become principals (D’Arbon et al, 2002; Cranston et al, 2004; Lacey, 2002). Given the importance of ensuring we have quality leaders for our schools in the future, the research reported here (which is on-going) examined the views of potential aspirants (primary and secondary deputy principals) from one large government education system in Australia about the principalship and their intentions in seeking promotion (or otherwise) to such positions and the reasons driving these intentions. Data were collected via the Aspiring Principals Questionnaire (APQ) – especially developed for the study – comprising 38 closed items mainly of a Likert-type format, 5 open-ended items linked to particular closed items allowing participants to add their own suggestions/ideas, expand/elaborate on responses; and 4 further more general open-ended items. A number of system-level policy and practice recommendations have been developed from the findings.