No / The marginal cost approach for the analysis of repair/replacement models was introduced by Berg in 1980 and has since been applied to many maintenance policies of various complexity. All models hitherto analysed in the literature by the marginal cost approach have one single decision variable only, this being, typically, the age of the current item at the time of ordering or replacement. This paper is concerned with the extension of the marginal cost technique to maintenance policies with several decision variables. After addressing the general framework appropriate for the multi-parameter case, we exemplify the workings of the technique by analysing a two-variable maintenance model involving replacement and minimal repair. We demonstrate that the marginal cost approach is an attractive and intuitively appealing technique also for models with several decision variables. Just as in the single-parameter situation, the approach is amenable to economic interpretation, a welcome feature for users of maintenance models with a prime interest in its economic (rather than its mathematical) aspects. As an added bonus of the marginal cost approach, in our example, some otherwise necessary tools from the theory of stochastic processes are dispensable.

In a production environment, physical and cyber-related failures become unavoidable because of the complexity of highly connected manufacturing systems and a finite equipment life cycle. The main purpose of this thesis is to investigate optimal maintenance outsourcing and replacement policies in the presence of cyber-threats, as well as policies to achieve channel coordination via cost subsidization. Although well-developed maintenance outsourcing literature has addressed many advanced and trending issues such as the costs and benefits of new technology adoptions, learning effects, forgetting effects, and systems with back-up machines, no study has looked at the effect of cyber threats on connected production systems. Besides filling this gap, this thesis addresses the most common replacement policies including preventive maintenance with minimal repairs and age replacement. The advent of the Internet of Things (IoT) has enabled the creation of "smart" manufacturing systems, However the resulting connected format makes these systems potential targets for cyber-attacks. Manufacturers have to face a difficult decision as to whether they should adopt costly security technologies or let the manufacturing systems be vulnerable to cyber-threats. This study develops a model addressing this dilemma by providing some insights into the effects of cost subsidization and installation of security systems on the system profit. Our findings suggest that a manufacturer can trade off cost subsidization to gain flexibility in the maintenance decision-making process. The study also provides evidence that, for a "smart" manufacturing system, the existence of a security system guarantees at least a marginal increase in system profit. With the help of an extensive numerical study, we provide guidelines for optimizing system profit and addressing the effect of various model parameters (such as a monetary parameter, failure rate and a cyber-attack related parameter) on the value of a security system.In the second part of this thesis, we build analytical models to deal with cyber-threats in the context of a production system that utilizes the age replacement policy. We propose two different scenarios involving cyber-threats. First, cyber-attacks do not disrupt the physical production system. In this case, we replace the broken components either when the system has a physical breakdown or when a predetermined amount of time (T) elapses. Second, we need to replace the system right after it suffers from a successful cyber-attack. Thus, we replace the system components if one of three following events happen, whichever comes first: (1) a successful cyber-attack, (2) a physical breakdown, or (3) a predetermined time (T) elapses. We analytically provide optimal policies to minimize the expected cost for these scenarios. Finally, we carry out sensitivity analyses to show the effect of different model parameters on the value of a cyber security system.

Die Gewährleistung der Verkehrssicherheit von Bäumen stellt eine zentrale Herausforderung für Städte und Gemeinden dar. Traditionelle, manuelle Inspektionsmethoden sind zeit- und ressourcenintensiv sowie anfällig für menschliche Fehler. Der folgende Artikel präsentiert ein innovatives System zur automatisierten Baumzustandsbewertung, welches moderne Kameratechnologien und Künstliche Intelligenz (KI) nutzt. Im Rahmen einer Machbarkeitsstudie wurden Bilddaten, welche durch verschiedene Kamerasysteme erzeugt wurden, analysiert. Basierend auf diesen Daten wurde ein YOLOv8-Modell trainiert, welches eine präzise Detektion von Bäumen und Schäden, wie beispielsweise Totholz, ermöglicht. Die Ergebnisse des vorgestellten Prototypensystems sind vielversprechend hinsichtlich Genauigkeit und Effizienz. Es zeigt das Potenzial, manuelle Inspektionen durch automatisierte Verfahren zu ergänzen oder zu ersetzen. Die präsentierten Resultate legen den Grundstein für nachhaltige und skalierbare Ansätze in der Baumpflege und können zur Steigerung der öffentlichen Sicherheit und Effizienz im urbanen Management beitragen.

With the world economy becoming unpredictable, it has become a necessity for businesses to relook at the way they do business. The world has become competitive and companies that aim to become profitable have seen the need to find ways to improve efficiencies and increase productivity to stay relevant. There has been an adoption of strategies that are aimed at improving the efficiencies in companies such as Total Productive Maintenance (TPM). The strategy is aimed at improving equipment efficiencies and increase productivity through the transfer of certain skills from maintenance personnel to operators. The aim is that the operators perform some of the activities that the maintenance people used to do and they do the more complex tasks. By transferring these skills to operators there is constant cleaning, inspections and lubricating of equipment. This frees up time for maintenance people to do planning and other jobs that require time and higher skills levels. The implementation of these activities allows companies to tap into unused capacity that was always hidden by breakdowns and unplanned stops. The process however requires commitment from management and all stakeholders involved in the organisation. There are prescribed implementation processes that can be followed or companies can follow their own processes but the fundamentals of involving people from the onset must be followed. The involvement of stakeholders creates commitment at all levels and in order to sustain this initiative people must be committed to it. The inclusion of the activities transferred from maintenance people to operators, will reinforce the knowledge and habits required from operators and perhaps sustain the initiative. / MBA, North-West University, Potchefstroom Campus, 2015

With the world economy becoming unpredictable, it has become a necessity for businesses to relook at the way they do business. The world has become competitive and companies that aim to become profitable have seen the need to find ways to improve efficiencies and increase productivity to stay relevant. There has been an adoption of strategies that are aimed at improving the efficiencies in companies such as Total Productive Maintenance (TPM). The strategy is aimed at improving equipment efficiencies and increase productivity through the transfer of certain skills from maintenance personnel to operators. The aim is that the operators perform some of the activities that the maintenance people used to do and they do the more complex tasks. By transferring these skills to operators there is constant cleaning, inspections and lubricating of equipment. This frees up time for maintenance people to do planning and other jobs that require time and higher skills levels. The implementation of these activities allows companies to tap into unused capacity that was always hidden by breakdowns and unplanned stops. The process however requires commitment from management and all stakeholders involved in the organisation. There are prescribed implementation processes that can be followed or companies can follow their own processes but the fundamentals of involving people from the onset must be followed. The involvement of stakeholders creates commitment at all levels and in order to sustain this initiative people must be committed to it. The inclusion of the activities transferred from maintenance people to operators, will reinforce the knowledge and habits required from operators and perhaps sustain the initiative. / MBA, North-West University, Potchefstroom Campus, 2015

Reliability-Cenetred Maintenance (RCM) is a well-known maintenance process developed in the aviation industry. It has yielded great success and hence was the process adapted to be used in the more industrial environments, such as the process developed by Moubray (1997) called RCM2. The RCM process is considered by many to be a very effective and comprehensive maintenance process that can, if implemented correctly, improve reliability and plant availability substantially. However, many maintenance practitioners and maintenance experts who have used RCM will tell you that it is an overcomplicated process and that it is difficult to implement. In many cases the process is abandoned and left incomplete due to the amount of resources required and the slow initial results delivered by the process. This dissertation investigates the reason for this and considers the viability of implementing the RCM process on an industrial level. The Hot Strip Mill (HSM) at the ArcelorMittal Vanderbijlpark plant was used as a case study. The viability of using RCM to improve the HSM maintenance practices was investigated. A suggested maintenance improvement plan was developed that is more suitable for the HSM maintenance environment and culture. / MSc (Development and Management Engineering), North-West University, Potchefstroom Campus, 2015

In transactional systems development literature, maintenance is reported as being a phase in the software development life cycle. In practice, this phase is often neglected as it occurs post-deployment and other ongoing projects take a higher priority. In data warehouse (DW) systems development literature, maintenance is not reported as being a phase but an ongoing iteration to the DW development project. It should therefore not be treated as a phase by DW systems professionals. Although there is this fundamental difference in the approach to maintenance, transaction systems maintenance and DW maintenance share many of the same challenges. DW literature and methodologies inherently contain utilities and methods to assist in alleviating these challenges in a DW system. Transactional systems do not deal with these challenges inherently. Research aspects were extracted from the literature review conducted. The literature review conducted demonstrates what the challenges in maintenance are, how the challenges of transactional systems compare to the challenges of DW maintenance and how the utilities and methods used in DW methodologies can inherently assist in managing these challenges from DW perspective. These research aspects were used to formulate an interpretive questionnaire. This research portion of the study explores the use of DW systems development and maintenance methodologies in the industry among DW professionals. This is done by conducting an interpretive study using the interpretive questionnaire developed from the literature review. The interpretive questionnaire focusses on maintenance and dealing with the challenges thereof. Many themes evolved from the analysis of the interpretive study by using the content analysis method. The final conclusions of this study is drawn by comparing and combining the information gathered from the literature review with the information gathered from the interpretive study. Gaps are identified between practice and literature and recommendations are made based on these gaps. / MSc (Computer Science), North-West University, Potchefstroom Campus, 2015

Reliability-Cenetred Maintenance (RCM) is a well-known maintenance process developed in the aviation industry. It has yielded great success and hence was the process adapted to be used in the more industrial environments, such as the process developed by Moubray (1997) called RCM2. The RCM process is considered by many to be a very effective and comprehensive maintenance process that can, if implemented correctly, improve reliability and plant availability substantially. However, many maintenance practitioners and maintenance experts who have used RCM will tell you that it is an overcomplicated process and that it is difficult to implement. In many cases the process is abandoned and left incomplete due to the amount of resources required and the slow initial results delivered by the process. This dissertation investigates the reason for this and considers the viability of implementing the RCM process on an industrial level. The Hot Strip Mill (HSM) at the ArcelorMittal Vanderbijlpark plant was used as a case study. The viability of using RCM to improve the HSM maintenance practices was investigated. A suggested maintenance improvement plan was developed that is more suitable for the HSM maintenance environment and culture. / MSc (Development and Management Engineering), North-West University, Potchefstroom Campus, 2015

In transactional systems development literature, maintenance is reported as being a phase in the software development life cycle. In practice, this phase is often neglected as it occurs post-deployment and other ongoing projects take a higher priority. In data warehouse (DW) systems development literature, maintenance is not reported as being a phase but an ongoing iteration to the DW development project. It should therefore not be treated as a phase by DW systems professionals. Although there is this fundamental difference in the approach to maintenance, transaction systems maintenance and DW maintenance share many of the same challenges. DW literature and methodologies inherently contain utilities and methods to assist in alleviating these challenges in a DW system. Transactional systems do not deal with these challenges inherently. Research aspects were extracted from the literature review conducted. The literature review conducted demonstrates what the challenges in maintenance are, how the challenges of transactional systems compare to the challenges of DW maintenance and how the utilities and methods used in DW methodologies can inherently assist in managing these challenges from DW perspective. These research aspects were used to formulate an interpretive questionnaire. This research portion of the study explores the use of DW systems development and maintenance methodologies in the industry among DW professionals. This is done by conducting an interpretive study using the interpretive questionnaire developed from the literature review. The interpretive questionnaire focusses on maintenance and dealing with the challenges thereof. Many themes evolved from the analysis of the interpretive study by using the content analysis method. The final conclusions of this study is drawn by comparing and combining the information gathered from the literature review with the information gathered from the interpretive study. Gaps are identified between practice and literature and recommendations are made based on these gaps. / MSc (Computer Science), North-West University, Potchefstroom Campus, 2015

Thesis (MBA)--Stellenbosch University, 2005. / Some digitised pages may appear illegible due to the condition of the original hard copy / ENGLISH ABSTRACT: A critical success factor for investment in high capital intensive business is to ensure that there is an integrated physical asset management plan in place that is integrated with the business strategy. The three fundamental aspects in modern physical asset management are to have a balanced performance measurement framework, self assessment system and benchmark review process in place to integrate, control and continuously improve the return on asset investment. There is a general lack of "hands-on" structured integration and performance management in the physical asset management environment. The result is ineffective assets with high life cycle costs that will have a negative effect on the business return on investment. A literature study was done on the most resent physical asset management models and business performance measurement systems to identify if the necessary methods and business systems exist to effectively manage the physical asset management function. A self assessment review and benchmark was done on Ticor South Africa and Kumba Resources centres to identify the gap in performance and what the main criteria is for improvement. The process was also used to identify the barriers that exist to effectively implement and integrate physical asset management with a link into business strategy. Achieving success in any strategy implementation requires a team effort among all stakeholders. A shared understanding and collaboration of all the role players is required. Very often physical asset management is not seen as core business, but as a cost centre that cannot be done without. This leads to sub optimisation and increased asset life cycle cost. It also promotes the tendency to make short-term financial decisions that do not have any longterm sustainability. A further downside to it is that if the function is seen as a service department it will only be reactive to business strategy and does not form part of the business strategy. This leads to a very reactive situation where the actions are driven by fixing what is wrong just to stay in business. A uniform performance measurement framework must be implemented across all business functions to align the entire organisation with the business goals. All functions have an effect on overall business performance, but they seldom have conflicting goals. Physical asset managers are sometimes not properly prepared and skilled to ensure that an effective and efficient physical asset management function is being maintained. Training and learning should be a major focus to ensure optimum use of employee potential in meeting the functional goals. Ignored leadership is a recipe for poor performance and frustration. The degree to which a company's business functions and processes are aligned with customers' needs makes a significant impact on the bottom line. The key objectives for the physical asset management strategy should be drafted with customer "needs and wants" in mind. The objective must be to maximise long-term profitability of plant and equipment through utilisation of the allocated resources. The opportunities and improvement methods that are possible in the physical asset management environment are endless and the potential that exists can be missed by the likelihood of failure to implement it effectively. The lack of managerial support is in many cases the only cause of failure to link physical asset management with business strategy. Secondly, the weakness of some of the solutions offered and the lack of embedding the solutions that are generated also contribute to the failure of linking physical asset management with business strategy. "The secret of managing success is choosing the right direction despite the uncertainties and conjlicting stakeholder expectations, and taking the whole organisation with you." - John Woodhouse. / AFRIKAANSE OPSOMMING: 'n Kritiese faktor vir die suksesvolle belegging in kapitaal intensiewe besighede is om te verseker dat 'n geïntegreerde fisiese batebestuurplan in plek is wat met die besigheidstrategie integreer. Die drie fundamentele aspekte in moderne fisiese batebestuur is om 'n gebalanseerde prestasieraamwerk vir bestuur, self-evalueringstelsel en doelwit-bestuursproses in plek te hê, om dit te integreer, te beheer en deurlopend opbrengste op bate-belegging te verbeter. Daar is 'n algemene gebrek aan vaardighede om die gestruktureerde integrasie en prestasiebestuur in die fisiese batebestuursomgewing te verseker. Die resultaat is oneffektiewe bates met baie hoë lewensikluskoste wat die besigheid se opbrengs op kapitaal negatief sal beinvloed. 'n Literatuurstudie is gedoen om die nuutste fisiese batebestuurmodelle en prestasiebestuurstelsels te identifiseer en te analiseer. Die doel was om vas te stel of die nodige metodes en besigheidraamwerke bestaan waarmee die fisiese batebestuur funksie bestuur kan word. 'n Self-evaluering analise en doelwitmeting is gedoen op Ticor South Africa en Kumba Resources-sentra met die doel om die gapings in prestasie te identifiseer en kriteria vir verbetering te bepaal. In die proses is die hindernisse wat in die pad van effektiewe implementering en integrering van fisiese batebestuur met besigheidstrategie staan, geïdentifiseer. Spanwerk word benodig vir die suksesvolle implementering van besigheidstrategie. 'n Gedeelde verstandhouding en samewerking deur alle belanghebbendes word benodig. Fisiese batebestuur word gereeld uitgesonder as een van die nie-kern besigheidsfunksies en dat dit slegs 'n kostesentrum is waarmee nie weggedoen kan word nie. Dit lei tot die suboptimisering van die bate se lewensiklus-koste. Dit skep ook die tendens om slegs korttermyn finansiële besluite te neem, wat geen langtermyn volhoubaarheid het nie. 'n Verdere gevolg is dat die funksie slegs beskou kan word as 'n dienste-funksie en dat dit baie reaktief raak teenoor strategie verandering. Die funksie word ook nie deel van die besigheidstrategie nie. Dit lei tot 'n baie reaktiewe situasie waarin aksies en inisiatiewe slegs gedryf word deur die noodsaaklikste bates te herstel net om in besigheid te bly. 'n Uniforme prestasie-bestuursraamwerk moet geïmplementeer word regoor al die besigheidsfunksies om die totale organisasie se besigheidsdoelwitte in ooreenstemming te bring. Al die besigheidfunksies het 'n effek op oorhoofse besigheidprestasie, maar daar is baie selde doelwitte wat totaal in konflik met mekaar is. Fisiese batebestuurders is soms nie ten volle voorbereid of bevoeg om te verseker dat 'n effektiewe fisiese batebestuursfunksie onderhou word nie. Opleiding en mentorskap moet 'n fokuspunt wees om te verseker dat werknemerpotensiaal benut word in die bereiking van funksionele doelwitte. Leierskap wat agterweë bly is 'n resep vir lae prestasie en frustrasie. Die graad waartoe 'n besigheidfunksie en proses ooreenstem met sy kliente se behoeftes sal 'n beduidende impak op die netto prestasie van die besigheid hê. Die kern doelwitte van die fisiese batebestuurstrategie moet opgestel word deur die behoeftes van die kliente in ag te neem. Langtermyn winsgewendheid van aanlegtoerusting moet die doelwit wees tydens die allokasie van hulpbronne. Die geleenthede en verbeteringsmetodes beskikbaar in die fisiese batebestuuromgewing het oneindige potensiaal wat verlore kan gaan as nagelaat word om die funksie effektief te implementeer. Gebrek aan ondersteuning deur bestuur is in baie gevalle die rede hoekom die fisiese batebestuurfunksie nie geïntegreer is met die besigheidstrategie nie. Die swakpunte van sommige van die oplossings wat aangebied word en die onvermoë om oplossings te implementeer, dra by tot die mislukking om fisiese batebestuur met besigheidstrategie te verbind. "The secret of managing success is choosing the right direction despite the uncertainties and conflicting stakeholder expectations, and taking the whole organisation with you. " - John Woodhouse.