Vibration covariate regression analysis of failure time data with the proportional hazards model

Please read the abstract in the section 00front of this documentDissertation (MEng (Mechanical Engineering))--University of Pretoria, 2006.Mechanical and Aeronautical Engineeringunrestricte

The possible influence of risk management, forecasting, and personnel training in physical asset management

CITATION: Schoeman, J. S. & Vlok, P. J. 2014. The possible influence of risk management, forecasting, and personnel training in physical asset management. South African Journal of Industrial Engineering, 25(2):96-104, doi:10.7166/25-2-740.The original publication is available at http://sajie.journals.ac.zaThe work presented in this paper highlights the possible effects of risk management, forecasting, and personnel training in the physical asset management environment. Each section is taken separately, and an argument is formed as to why it is important and what portion of the physical asset management five-year budget each should receive. This paper considers the long-term and short-term benefits in its conclusion that risk management should receive 60 per cent of the budget, personnel training 25 per cent, and forecasting the final 15 per cent.Hierdie studie beklemtoon die moontlike effekte wat risiko bestuur, voorspelling van voorvalle, en die opleiding van personeel kan hê binne die fisiese bate bestuur omgewing. Die afdelings word elk apart bespreek, en ’n argument word gevorm om te sê waarom die afdeling belangrik is en watter bedrag van ’n maatskappy se vyf- jaar begroting elk moet ontvang. Die finale besluit was dat risiko ’n totaal van 60 persent van die begroting moet ontvang omdat dit so ’n breë afdeling is, die opleiding van personeel vereis 25 persent, en die voorspelling van gebeure die laaste 15 persent.http://sajie.journals.ac.za/pub/article/view/740Publisher's versio

Advances in renewal decision-making utilising the proportional hazards model with vibration covariates

Increased competitiveness in the production world necessitates improved maintenance strategies to increase availabilities and drive down cost . The maintenance engineer is thus faced with the need to make more intelligent pre ventive renewal decisions . Two of the main techniques to achieve this is through Condition Monitoring (such as vibrat ion monitoring and oil anal ysis) and Statistical Failure Analysis (typically using probabilistic techniques) . The present paper discusses these techniques, their uses and weaknesses and then presents the Proportional Hazard Model as an solution to most of these weaknesses. It then goes on to compare the results of the different techniques in monetary terms, using a South African case study. This comparison shows clearly that the Proportional Hazards Model is superior to the present techniques and should be the preferred model for many actual maintenance situations.Verhoogde vlakke van mededinging in die produksie omgewing noodsaak verbeterde instandhouding strategies om beskikbaarheid van toerusting te verhoog en koste te minimeer. Instandhoudingsingenieurs moet gevolglik meer intellegente voorkomende hernuwings besluite neem. Twee prominente tegnieke om hierdie doelwit te bereik is Toestandsmonitering (soos vibrasie monitering of olie analise) en Statistiese Falingsanalise (gewoonlik m.b.v. probabilistiese metodes). In hierdie artikel beskou ons beide hierdie tegnieke, hulle gebruike en tekortkominge en stel dan die Proporsionele Gevaarkoers Model voor as 'n oplossing vir meeste van die tekortkominge. Die artikel vergelyk ook die verskillende tegnieke in geldelike terme deur gebruik te maak van 'n Suid-Afrikaanse gevalle studie. Hierdie vergelyking wys duidelik-uit dat die Proporsionele Gevaarkoers Model groter belofte inhou as die huidige tegnieke en dat dit die voorkeur oplossing behoort te wees in baie werklike instandhoudings situasies.http://sajie.journals.ac.z

Pleistocene range dynamics in the eastern Greater Cape Floristic Region: A case study of the Little Karoo endemic Berkheya cuneata (Asteraceae)

AbstractThe glacial–interglacial climate cycles of the Pleistocene played a significant role in dramatically altering species distributions across the globe. However, the climate of the Greater Cape Floristic Region is thought to have been decoupled from global fluctuations and the current Mediterranean climate remained relatively buffered during this period. Here we explore the roles of climate stability and the topographic complexity of the region on the range history of an endemic Little Karoo plant, Berkheya cuneata, using ensemble species distribution modelling and multi-locus phylogeography. The species distribution models projected onto downscaled climate simulation of the Last Glacial Maximum demonstrated a considerable range contraction and fragmentation into the western and eastern Little Karoo, separated by the Rooiberg inselberg. This population fragmentation is mirrored in the phylogeographic structuring of both chloroplast and nuclear DNA. These results suggest that sufficient climatic buffering coupled with regionally complex topography ensured the localised population persistence during Pleistocene climate cycles but these features have also promoted population vicariance in this, and likely other, Little Karoo lowland species

Modern soil phytolith assemblages used as proxies for paleoscape reconstruction on the South Coast of South Africa

South Africa continues to receive substantial attention from scholars researching modern human origins. The importance of this region lies in the many caves and rock shelters containing well preserved evidence of human activity, cultural material complexity and a growing number of early modern human fossils dating to the Middle Stone Age (MSA). South Africa also hosts the world's smallest floral kingdom, now called the Greater Cape Floristic Region (GCFR), with high species richness and endemism. In paleoanthropological research, improving our capacity to reconstruct past climatic and environmental conditions can help us to shed light on survival strategies of hunter-gatherers. To do this, one must use actualistic studies of modern assemblages from extant habitats to develop analogies for the past and improve paleoenvironmental reconstructions. Here, we present a phytolith study of modern surface soil samples from different GCFR vegetation types of the south coast of South Africa. In this study, the phytolith concentration and morphological distribution are related to the physicochemical properties of soils, the environmental conditions and the characterization of the vegetation for the different study areas. Our results show that phytolith concentration relates mostly to vegetation types and the dominant vegetation rather than to the type of soils. More abundant phytoliths from Restionaceae and woody/shrubby vegetation are also noted from fynbos vegetation and grass phytoliths are a recurrent component in all the vegetation types in spite of being a minor component in the modern vegetation. The grass silica short cells from these plants, however, suggest a mix of C3 and C4 grasses in most of the vegetation types with a major presence of the rondels ascribed to C3 grasses. The exceptions are riparian, coastal thicket and coastal forest vegetation, which are characterized by the dominance of C4 grass phytoliths

Dynamic residual life estimation of industrial equipment based on failure intensity proportions

There is a world-wide drive to optimize maintenance decisions in an increasingly competitive manufacturing industry. Preventive maintenance if often the most organized and cost efficient strategy to follow, but a decision still has to be made on the optimal instant to perform preventive maintenance. Use based preventive maintenance decisions have been optimized through statistical analysis of failure date while predictive preventive maintenance (condition monitoring) has been optimized by utilizing more sophisticated technology. Very little work has however been done to combine the advantages of the two schools of thought. This thesis originated from a realization of the potential improvement in maintenance practice by combining use based preventive maintenance optimization techniques with high technology condition monitoring. In this thesis an approach is developed to estimate residual life of industrial equipment dynamically by combining statistical failure analysis and sophisticated condition monitoring technology. The approach is based on failure intensity proportions determined from historic survival time information and corresponding diagnostic information such as condition monitoring. Combined Proportional Intensity Models (PIMs) for non-repairable and repairable systems, containing the majority of conventional PIM enhancements as special cases, with numerical optimization techniques to solve for the regression coefficients, are derived. In addition to the residual life estimation approach, a user-friendly graphical method with which residual life estimates can be presented was also developed. This method is natural and easy to comprehend, even by inexperienced data analysts. The residual life estimation approach is applied to a typical data set from a South African industry and results are compared to those obtained from a similar, established maintenance decision support tool. This comparison showed that the approach developed in this thesis is relevant, practical and marginally better than the established decision support tool for certain criteria.Thesis (PhD (Industrial Engineering))--University of Pretoria, 2006.Industrial and Systems Engineeringunrestricte

Die terugbetalingsvermoë van die landbouprodusent as evalueringskriterium vir produksiekredietverskaffing

M.Com. (Business Management)Please refer to full text to view abstrac

A simplified numerical decision-making methodology for physical asset management decisions

CITATION: Burnett, S. & Vlok, P. J. 2014. A simplified numerical decision-making methodology for physical asset management decisions. South African Journal of Industrial Engineering, 25(1):162-175, doi:10.7166/25-1-689.The original publication is available at http://sajie.journals.ac.zaThe management of physical assets has become a popular field recently, and is acknowledged in many disciplines worldwide. Physical Asset Management (PAM) is a complex subject that requires the participation of many disciplines. Maintenance management, together with accurate and effective decision–making, is vital for achieving successful PAM. The primary objective of this research project was to identify the possibility of simplifying maintenance-related decision-making. With the focus on numerical decision-making techniques, the secondary objective was to investigate the practicality and useability of combining appropriate techniques to create an easily useable and understandable methodology to support maintenance-related decisions. The results confirm the practicality and useability of a simplified numerical decision-making methodology. By concentrating on the core operational questions related to maintenance, and by combining the most appropriate techniques, a simplified numerical decision-making methodology can ease the decision-making process on an operational level. This can accomplish successful PAM in a proactive, preventive and simplified manner.Die onderwerp van Fisiese Bate Bestuur (FBB) het ‘n gewilde navorsingsveld geraak oor die afgelope paar jaar. FBB is ‘n komplekse onderwerp en vereis insette van verskeie dissiplines. Effektiewe bestuur van instandhouding sowel as doeltreffende besluitneming is noodsaaklik vir suksesvolle FBB. Die primêre doel van hierdie navorsingsprojek was om die moontlikheid van vereenvoudigde besluitneming met betrekking tot instandhouding, te ondersoek. Met die fokus op numeriese besluitnemingstegnieke was die sekondêre doel om die praktiese toepassing van ‘n gepaste tegniek-kombinasie te ondersoek om uiteindelik ‘n maklike, bruikbare en verstaanbare tegniek-kombinasie te skep wat instandhouding verwante besluite kan ondersteun. Die resultate bevestig die bruikbaarheid van ‘n eenvoudige numeriese besluitnemings tegniek-kombinasie om die besluitnemingsproses op operasionele vlak te verlig. Deur te konsentreer op instandhouding verwante kern operasionele vrae, en deur die mees gepaste tegnieke te kombineer, kan ‘n vereenvoudige numeriese besluitnemingsmetodologie die besluitnemingsproses op operasionele vlak verlig. Dit kan FBB suksesvol op ‘n pro-aktiewe, voorkomende en vereenvoudige manier uitvoer.http://sajie.journals.ac.za/pub/article/view/689Publisher's versio

Supply chain management : a framework of understanding

CITATION: Du Toit, D. & Vlok, P. J. 2014. Supply chain management: a framework of understanding. South African Journal of Industrial Engineering, 25(3):25-38, doi:10.7166/25-3-743.The original publication is available at http://sajie.journals.ac.zaThe topic of supply chain management (SCM) is complex to understand because it encompasses many different flows of activities, components, functions, and role-players. The literature is scattered across multiple functions, varies in scope, and is often confined to certain elements within SCM. This article aims to provide a literature overview of SCM. It is explained with the aid of a newly-developed framework of understanding that offers a graphical representation of the term. It unifies and condenses different components within SCM and shows the relationship between them. The framework was developed by identifying the main themes in the definitions for SCM, examining existing categorisations and frameworks in SCM, and analysing frameworks in other disciplines. The outcome of this article can be used as a guide to explain and orientate researchers and practitioners in the field.Die onderwerp van voorsieningskettingbestuur (VKB) is kompleks om te verstaan omdat dit baie verskillende komponente, vloei van aktiwiteite, funksies, en rolspelers insluit. Die literatuur oor VKB is versprei oor verskeie funksies, wissel in omvang, en word dikwels beperk tot sekere elemente binne VKB. Die doel van hierdie artikel is om ’n literatuur oorsig oor die onderwerp van VKB te voorsien. VKB word verduidelik met behulp van ’n nuut-ontwikkelde raamwerk van verstaan: ’n grafiese voorstelling van die term. Dit verenig die verskillende komponente binne VKB, en toon die verwantskap tussen hulle. Die raamwerk is ontwikkel deur die belangrikste temas in die definisies van VKB te bestudeer, en bestaande kategorisering en verwysingsmodelle te ontleed. Die uitkomste van die artikel kan gebruik word as ’n gids om navorsers en praktisyne te oriënteer in die veld.http://sajie.journals.ac.za/pub/article/view/743Publisher's versio

Psoralea karooensis (Psoraleeae, Fabaceae): a new species from the Klein Karoo region of South Africa

A new species of Psoralea is described. Psoralea karooensis C.H. Stirt., Muasya & Vlok is endemic to mountain streams in the Klein Karoo region of the Western Cape Province, South Africa. The new species is characterised by its flexuose habit of many stiff bare stems with the seasonal shoots arising apically in clusters and its greenish cream flowers borne at the apex of 10–12 mm long peduncles each ending in a trifid cupulum