Administrasi; Strategi; Taktik Dan Penciptaan Efisiensi

vii+130 hlm.: - ; 24 cm

White Peacock

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Friction and wear of selected metal ceramic and polycrystalline diamond sliding couples

A thesis submitted to the Faculty of engineering. University of Witwatersrand. Johannesburg, in fulfilment of the requirements for the Degree of Doctor of Philosophy Pretoria, 1995This thesis describes a study of the friction and wear characteristics of a range of oxide and silicon-based ceramics sliding against AlSI 440C stainless steel, as well as various sliding combinations of two types of De Beers polycrystalline diamond (PCD), namely Syndite and Syndax, To facilitate the former work, a high-speed reciprocating sliding test machine with computerized data acquisition and control was developed. It was confirmed that under water-lubricated sliding, the oxide ceramics (alumina, PSZ, 3YTZP, and Ce-TZP) showed higher friction coefficients and Weal' rates than the silicon-based ceramics (Sialon and silicon nitride). This was related to different levels of adhesion and the formation of metallic transfer films. For the zirconia ceramics, increased transformation toughening was associated with increased surface fracture damage and metallic film formation. In general, the metallic transfer films were beneficial, protecting the underlying ceramic and dominating the friction and wear behaviour. The superior performance of the silicon-based ceramics was related to the formation of lubricious tribofilms containing silicon oxides and hydroxides. Experiments with synthetic mine water as lubricant demonstrated that the presence of significant amounts of chloride and sulphate in the water generally reduced friction and wear. This was tentatively explained in terms of reduced adhesion and the promotion of iron oxide and hydroxide formation. It is suggested that the influence of sulphate may be more important in thi'3 regard than that of chloride. The tribological behaviour of self-mated Syndite PCD sliding couples is dominated by the formation of Co-rich trlbofilms, which nrc associated with increased friction coefficients and reduced load carrying capacity (LCC). Syndax, which employs silicon as the binder phase, shows lower friction coefficients anti higher LCe under both dry and water-lubricated sliding conditions. Mixed Syndax/Syndite couples show superior performance to self-mated Synditc tinder dry sliding conditions, but 110 improvements in the presence of water. The former effect is related to the preferential removal of Co 11'0111 the Syndite surface to the SyndaxGR 201

Bridging the digital divide in older adults: a study from an initiative to inform older adults about new technologies

Ya-Huei Wu,1,2 Souad Damnée,1,2 Hélène Kerhervé,1,2 Caitlin Ware,1,3 Anne-Sophie Rigaud1,2 1Department of Clinical Gerontology, Broca Hospital, Assistance Publique-Hôpitaux de Paris, 2Research Team 4468, Paris Descartes University, 3Centre de Recherche en Psychanalyse, Médicine et la Société, Paris Diderot University, Paris, France Purpose: In a society where technology progresses at an exponential rate, older adults are often unaware of the existence of different kinds of information and communication technologies (ICTs). To bridge the gap, we launched a 2-year project, during which we conducted focus groups (FGs) with demonstrations of ICTs, allowing older adults to try them out and to share their opinions. This study aimed at investigating how participants perceived this kind of initiative and how they reacted to different kinds of ICTs.Patients and methods: In total, 14 FGs were conducted with community-dwelling older adults, with a frequency of two FGs on the same topic once per trimester. Twenty-three older adults (four men and 19 women) attended at least one FG but only nearly half of them were regular attendants (ten participating in at least five sessions). Age of participants ranged from 63 years to 88 years, with a mean of 77.1 years. All of them had completed secondary education. The analyses of the data were performed according to inductive thematic analysis.Results: Four overarching themes emerged from the analysis. The first concerned participants’ motivation for and assessment of the project. The second theme identified the underlying factors of the “digital divide” between the younger and the older generations. The third theme concerned the factors of technology adoption among older adults. The fourth one identified participants’ attitudes toward assistive ICTs, designed specifically for older adults (“gerontechnologies”).Discussions and conclusion: This project encouraging older adults to be informed about different kinds of ICTs was positively rated. With regard to ICTs, participants perceived a digital divide. The underlying factors are generation/cohort effects, cognitive and physical decline related to aging, and negative attitudes toward technologies. However, more and more older adults adopt different kinds of ICTs in order to fit in with the society. Concerning assistive ICTs, they manifested a lack of perceived need and usefulness. Also, there was a negative image of end users of this kind of technologies. The so-called gerontechnologies specifically targeting older adults contain stigmatizing symbolism that might prevent them from adopting them. Keywords: assistive technologies, attitude, digital divide, gerontechnology, technology adoption, technology acceptanc