Organizations are expected by their shareholders to continually deliver above industry returns on capital invested and to remain competitive in the industry of choice through productivity, safety and quality. The maintenance function is a key area in which competitiveness through efficiencies and world–class performance can be attained by focusing on the prevention and reduction of long and costly equipment repair times. The question is: how can the mean time to repair of equipment already installed in the plant be reduced? To answer the above question correctly and comprehensively, the research explored mixed methods in finding answers. Quantitative methodology using a survey was used for data collection. Observations and interviews were held with maintenance personnel to uncover information that couldn’t have been obtained by means of a survey. The survey was limited to equipment performance measures, human factors, environmental factors, planning, spare parts, maintainability, procedures and training. To test consistency and accuracy of representation of the total population under study, a reliability test was done by using Cronbach’s alpha coefficient. To determine whether there are any differences between groups, an ANOVA test was used. Cohen’s d–value was used to determine practically significant differences between one set of data with another and correlation analysis was used to determine the relationships between the variables. The approach designed and delivered by this research flowed from the existing body of knowledge, case studies and survey findings. The approach adopts some of the elements of the failure mode and effects analysis (FMEA) procedure and differs from other work that has been done by others by taking into account the competency and experience of maintenance personnel and assigning to them factors which are used to compute anew MTTR of the equipment. The cost of implementing the recommended corrective actions for realising the new MTTR is determined and evaluated against an improved equipment availability that will be achieved as a result of the recommended corrective actions assuming that the failure rate of the equipment remains constant. This evaluation step imbedded within the approach is valuable for the maintenance function and management for decision making in ensuring that resources at the organization’s disposal are used productively. Validation and test results of the approach showed that the MTTR of equipment installed in the plant can be reduced. The results also indicated that through the use of the designed approach a regular pattern of repair or replacement times can be followed well in advance and that it is practical, user friendly and it also delivers on its objective of offering a structure for analysis and decision making aimed at reducing the MTTR. Included with this dissertation is feedback information that can be included in a maintenance job card feedback section to capture information about factors that can be improved to lower the MTTR as part of a continuous improvement process. Included also is a spare part development and management procedure that can be used by the maintenance function. Recommendations on training of maintenance personnel on the maintainability of equipment, the FMEA procedure and maintenance procedures are highlighted. Information that flowed from this approach will be valuable for continuous plant performance improvement and during the design, installation and operation stages of a blast furnace. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2012.

Organizations are expected by their shareholders to continually deliver above industry returns on capital invested and to remain competitive in the industry of choice through productivity, safety and quality. The maintenance function is a key area in which competitiveness through efficiencies and world–class performance can be attained by focusing on the prevention and reduction of long and costly equipment repair times. The question is: how can the mean time to repair of equipment already installed in the plant be reduced? To answer the above question correctly and comprehensively, the research explored mixed methods in finding answers. Quantitative methodology using a survey was used for data collection. Observations and interviews were held with maintenance personnel to uncover information that couldn’t have been obtained by means of a survey. The survey was limited to equipment performance measures, human factors, environmental factors, planning, spare parts, maintainability, procedures and training. To test consistency and accuracy of representation of the total population under study, a reliability test was done by using Cronbach’s alpha coefficient. To determine whether there are any differences between groups, an ANOVA test was used. Cohen’s d–value was used to determine practically significant differences between one set of data with another and correlation analysis was used to determine the relationships between the variables. The approach designed and delivered by this research flowed from the existing body of knowledge, case studies and survey findings. The approach adopts some of the elements of the failure mode and effects analysis (FMEA) procedure and differs from other work that has been done by others by taking into account the competency and experience of maintenance personnel and assigning to them factors which are used to compute anew MTTR of the equipment. The cost of implementing the recommended corrective actions for realising the new MTTR is determined and evaluated against an improved equipment availability that will be achieved as a result of the recommended corrective actions assuming that the failure rate of the equipment remains constant. This evaluation step imbedded within the approach is valuable for the maintenance function and management for decision making in ensuring that resources at the organization’s disposal are used productively. Validation and test results of the approach showed that the MTTR of equipment installed in the plant can be reduced. The results also indicated that through the use of the designed approach a regular pattern of repair or replacement times can be followed well in advance and that it is practical, user friendly and it also delivers on its objective of offering a structure for analysis and decision making aimed at reducing the MTTR. Included with this dissertation is feedback information that can be included in a maintenance job card feedback section to capture information about factors that can be improved to lower the MTTR as part of a continuous improvement process. Included also is a spare part development and management procedure that can be used by the maintenance function. Recommendations on training of maintenance personnel on the maintainability of equipment, the FMEA procedure and maintenance procedures are highlighted. Information that flowed from this approach will be valuable for continuous plant performance improvement and during the design, installation and operation stages of a blast furnace. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2012.

International Atomic Energy Agency (IAEA) safeguards are one method of proliferation resistance which is applied at most nuclear facilities worldwide. IAEA safeguards act to prevent the diversion of nuclear materials from a facility through the deterrence of detection. However, even with IAEA safeguards present at a facility, the country where the facility is located may still attempt to proliferate nuclear material by exploiting weaknesses in the safeguards system. The IAEA's mission is to detect the diversion of nuclear materials as soon as possible and ideally before it can be weaponized. Modern IAEA safeguards utilize unattended monitoring systems (UMS) to perform nuclear material accountancy and maintain the continuity of knowledge with regards to the position of nuclear material at a facility. This research focuses on evaluating the reliability of unattended monitoring systems and integrating the probabilistic failure of these systems into the comprehensive probabilistic proliferation resistance model of a facility. To accomplish this, this research applies reliability engineering analysis methods to probabilistic proliferation resistance modeling. This approach is demonstrated through the analysis of a safeguards design for the Example Sodium Fast Reactor Fuel Cycle Facility (ESFR FCF). The ESFR FCF UMS were analyzed to demonstrate the analysis and design processes that an analyst or designer would go through when evaluating/designing the proliferation resistance component of a safeguards system. When comparing the mean time to failure (MTTF) for the system without redundancies versus one with redundancies, it is apparent that redundancies are necessary to achieve a design without routine failures. A reliability engineering approach to probabilistic safeguards system analysis and design can be used to reach meaningful conclusions regarding the proliferation resistance of a UMS. The methods developed in this research provide analysts and designers alike a process to follow to evaluate the reliability of a UMS.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The aim of this thesis is to compare the aviation derived reliability metric known as the Maintenance Free Operating Period (MFOP), with the traditionally used, and commonly found, reliability metric Mean Time Between Failure (MTBF), which has over the years shown some innate disadvantages in the field of maintenance. It will be shown that this is mainly due to MTBF’s inherent acceptance of failure and the unscheduled maintenance therewith directly connected. Moreover, MFOP is successfully applied to a mining specific case study, as to date, no other application of the MFOP concept to the mining sector is known. An extensive literature study is presented, which covers concepts relevant to the overall study and which helps to contextualise the problem, revealing the major shortcomings of the commonly accepted MTBF metric. A methodology to analyse systems MFOP performance, making use of failure statistics to analyse both repairable and non-repairable systems, is presented. Validation makes use of a case study which applies the MFOP methodology to a system, specifically in the mining sector. It was shown that MFOP could be applied to the data obtained from the mining sector, producing estimates which were accurate representations of reality. These findings provide an exciting basis on which to begin to facilitate a paradigm shift in the mind set of maintenance personnel, setting reliability targets and dealing with unscheduled maintenance stops. KEYWORDS: Maintenance Free Operating Period, Mean Time Between Failure, Maintenance, Mining / AFRIKAANSE OPSOMMING: Die doel van hierdie tesis is om die Onderhoudvrye Bedryf Tydperk (OBT), ’n betroubaarheidsmaatstaf afkomstig van die lugvaart industrie, te vergelyk met die Gemiddelde Tyd Tussen Falings (GTTF) maatstaf wat tradisioneel in algemene gebruik is, maar wat oor die jare inherente nadele met betrekking tot instandhouding geopenbaar het. Dit sal bewys word dat hierdie nadele hoofsaaklik ontstaan as gevolg van die GTTF se inherente aanvaarding van failure en die ongeskeduleerde instandhouding wat daarmee gepaard gaan. OBT word ook suksesvol aangewend in ’n mynwese-spesifieke gevallestudie, wat aaangegaan is aangesien geen ander sooortgelyke aanwending in die mynwese sektor tot datum bekend is nie. ’n Breedvoerige literatuurstudie word voorgelê wat relevante konsepte dek en die probleem binne konteks plaas, en daardeur die hoof tekortkominge van die algemeen aanvaarde GTTF metriek ontbloot. ’n Metodologie waardeur analise van die stelsel werkverrigting van die OBT uitgevoer kan word met gebruik van onderbrekings statistiek om herstelbaar sowel as onherstelbare stelsels te analiseer, word voorgestel. Geldigheid word getoets deur ’n gevallestudie wat die OBT metodologie aangewend word spesifiek vir ’n stelsel in die mynwese Dit is bewys dat OBT toegepas kan word op data afkomstig van die mynwese sector, en skattings lewer wat akkurate voorstellings is van die werklikheid. Hierdie bevindinge is opwindend, en dit dien as die basis vir ’n die aanwending van ’n paradigmaskuif in die benadering van instandhoudingspersoneel tot die daarstelling van teikens vir betroubaarheid en ook in hul hantering van ongeskeduleerde instandhoudingsophoud. SLEUTELWOORDE: Onderhoudvrye Bedryf Tydperk, Gemiddelde Tyd Tussen Falings, Onderhoud, Mynbou

The interruption cost for one hour of a petrochemical plant is 33 times higher than that of the average interruption cost for industrial plants across all industries. In addition to the high cost of loss of production, interruptions to the operations of petrochemical and gas-toliquid plants pose safety and environmental hazards. Thus it is necessary to better understand the reliability requirements of petrochemical and gas-to-liquid plants. This study investigated the reliability of electrical distribution networks used in petrochemical and gas-to-liquid plants compared to those used in other industrial plants. A model was developed that can be used to establish the adequacy of the reliability of a distribution network in terms of the components and network topologies used. This model was validated against data that had been collected by the IEEE and applied to an actual petrochemical plant. Over 19 years’ worth of data regarding the trips that have occurred on the distribution network of an existing petrochemical plant was collected and manipulated in order to calculate the reliability indices associated with the equipment used to make up thisRecommended Practice for the Design of Reliable Industrial and Commercial Power Systems. The cost of loss of production and the capital costs associated with increased reliability were calculated for a section of the existing petrochemical plant. The reliability associated with different network topologies that could possibly be used to supply power to this section of the plant were modelled using an appropriate software package. The resulting total cost of ownership over the life of the plant associated with each topology was then calculated in order to establish which network topology is the most appropriate for petrochemical and gas-to-liquid plants. It was concluded the components that affect the reliability of an industrial distribution network are different to those that affect a utility distribution network. These components were listed and compared. It was found that the reliability indices that were calculated for the components that affect the reliability of a petrochemical plant were similar to those provided by the IEEE. 17 out of 20 of the indices that were calculated were within the required factor of deviation. Generally the failure rates of components used in petrochemical plants were very similar to those given in the IEEE Gold Book, while the MTTR’s for the components used in petrochemical plants were found to be slightly better than those given in the IEEE Gold Book. The effect of network topology was found to be significant, with small changes in the topology of a network resulting in large variations in the reliability of the network. It was also found that the most appropriate type of network topology to use in the design of the electrical distribution network of a petrochemical plant is the dual radial network. This is the most conservative of the commonly used network topologies and is the one that is currently used in the existing plant that was studied. Due to the high cost of loss of production in petrochemical plants it was established that any incremental improvement in the reliability of the dual radial network would be beneficial to the total cost of ownership of such a plant. Such incremental improvement of the reliability of the distribution network could be cost effectively achieved by adopting a conservative maintenance strategy and the establishment of a conservative spares inventory. Before this study was undertaken, there was no literature around the reliability of electrical distribution networks that focused specifically on petrochemical and gas-to-liquid plants. This study produced a set of reliability indices and a model that electrical engineers can use in the reliability analysis of petrochemical and gas-to-liquid plants. Furthermore it shows that, because the cost of loss of production in petrochemical plants is so high, the most conservative distribution network design and maintenance philosophies should always be used. distribution network. These reliability indices were compared to those given by the IEEE / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / unrestricted

This dissertation studies the effects of radiation-induced single-event upsets (SEUs) on field-programmable gate array(FPGA)-based circuits. It analyzes and quantifies a special case in data communication, that is, the synchronization issue of signals when they are sent across clock domains in triple modular redundancy (TMR) circuits with the presence of SEUs. After demonstrating that synchronizing errors cannot be eliminated in such case, this dissertation continues to present novel synchronizer designs that can guarantee reliable synchronization of triplicated signals. Fault injection tests then show that the proposed synchronizers provide between 6 and 10 orders of magnitude longer mean time to failure (MTTF) than unmitigated synchronizers. This dissertation also studies the reliability of block random access memory (BRAM) on FPGAs. By investigating several previous reliability models for single-error correction/double-error detection (SEC/DED) memory with scrubbing, this dissertation proposes two novel MTTF models that are suitable for FPGA applications. The first one considers non-uniform write rates for probabilistic write scrubbing, and the second one combines deterministic scrubbing and probabilistic scrubbing into a single model. The proposed models reveal the impact of memory access patterns on the reliability of BRAMs. Monte Carlo simulations then demonstrate the correctness of the proposed models. At last, the memory access patterns of a type of FPGA application, digital signal processing (DSP) is studied, and mitigation mechanisms for DSP applications are discussed.

Nous avons dans cette thèse cherché à définir un formalisme simple pour pouvoir modéliser des systèmes où se combinent des phénomènes non-déterministes et des comportements aléatoires. Nous avons choisi d'étendre le formalisme de la réécriture pour lui permettre d'exprimer des phénomènes probabilistes, puis nous avons étudié la terminaison en temps moyen fini de ce modèle. Nous avons également présenté une notion de stratégie pour contrôler l'application des règles de réécriture probabilistes et nous présentons des critères généraux permettant d'identifier des classes de stratégies sous lesquelles les systèmes de réécriture probabilistes terminent en temps moyen fini. Afin de mettre en valeur notre formalisme et les méthodes de preuve de terminaison en temps moyen fini, nous avons modélisé un réseau de stations \WIFI~ et nous montrons que toutes les stations parviennent à émettre leurs messages dans un temps moyen fini. / In this thesis we define a new formalism that allows to model transition systems where transitions can be either probabilistic or non deterministic. We choose to extend the rewriting formalism because it allows to simply express non-deterministic behavior. Latter, we study the termination of such systems and we give some criteria that imply the termination within a finite mean number of rewrite steps. We also study the termination of such systems when the firing of probabilistic rules are controlled by strategies. In this document, we use our techniques to model the \WIFI~ protocol and show that a pool of stations successfully emits all its messages within a finite mean time.

Tillgänglighet är väsentligt för att skapa effekt med tekniska system. Detta leder till ett behov av att aktivt arbeta med uppföljning och nyckeltal för att kunna optimera organisation och design i syfte att uppnå den önskade effekten, utifrån tillgängliga resurser. En grund i detta är att ha en gemensam terminologi, god kommunikation och en förståelse för aktörernas roller.   Studien undersöker tillgänglighetsbegreppen och jämför definitionerna i litteratur med verkligheten. Syftet är att förtydliga och belysa problematiken kring begreppen för tillgänglighet och dess nyckeltal samt arbetet med detta. Detta görs bland annat genom att pröva om befintliga begrepp fortfarande är valida. Målsättningen är att arbetet skall styrka de uttalade behoven rörande en diskussion kring tillgänglighetsbegreppen och kunna vara en inledning till vidare studier.   Resultatet visar på att befintliga tillgänglighetsbegrepp är gångbara. Frågan som uppstår är rörande vilken typ av tillgänglighet som bör vara i fokus. Oavsett, är det utmanande att ur ett tillgänglighetsperspektiv, hantera multifunktionella plattformar med olika driftprofiler. Till detta finns det tolkningsdiskrepanser mellan litteraturen och verkligheten, samt inom och mellan organisationerna. Vidare noteras att ensade rutiner för uppföljning saknas och att detta främst är en chefs- och ledningsfråga. / Availability is essential to create effect with technological systems. This leads to a need to actively work on follow-up and key indicators to be able to optimize organization and design in order to achieve the desired effect, with the resources available. Fundamental to this is to have common terminology, good communication and an understanding of the roles of those involved.   This study examines the concepts of availability and compares the definitions from literature with reality. The aim is to clarify and highlight problems with concepts of availability, key indicators and the work being done on this. This is partly done by testing whether or not existing concepts are still valid. The objective is for this work to support needs expressed regarding a discussion of availability concepts, and to be a prelude for further studies.   The results of the study show that existing concepts of availability are still valid. The question that arises relates instead to which type of availability should be in focus. Nevertheless, it is quite clear that it is a challenging task, from an availability perspective, to manage multifunctional platforms with different operating profiles. Furthermore, there are also discrepancies both between literature and reality, and within and between organizations. It was also noted that there is a lack of uniform follow-up procedures, and that this is primarily an issue for commanders and management.

Software development is an area in which companies not only need to keep up with the latest technology, but they additionally need to continuously increase their productivity to stay competitive in the industry. One company currently facing these challenges is Storytel - one of the strongest players on the Swedish audiobook market - with about a fourth of all employees involved with software development, and a rapidly growing workforce. With the purpose of understanding how the Storytel Tech Department is performing, this thesis maps Storytel’s productivity defined through the Four Key Metrics - Deployment Frequency, Delivery Lead Time, Mean Time To Restore and Change Fail Rate. A classification is made into which performance category (Low, Medium, High, Elite) the Storytel Tech Department belongs to through a deep-dive into the raw system data existing at Storytel, mainly focusing on the case management system Jira. A survey of the Tech Department was conducted, to give insights into the connection between human and technical factors influencing productivity (categorized into Culture, Environment, and Process) and estimated productivity. Along with these data collections, interviews with Storytel employees were performed to gather further knowledge about the Tech Department, and to understand potential bottlenecks and obstacles. All Four Key Metrics could be determined based on raw system data, except the metric Mean Time To Restore which was complemented by survey estimates. The generalized findings of the Four Key Metrics conclude that Storytel can be minimally classified as a ‘medium’ performer. The factors, validated through factor analysis, found to have an impact on the Four Key Metrics were Generative Culture, Efficiency (Automation and Shared Responsibility) and Number of Projects. Lastly, the major bottlenecks found were related to Architecture, Automation, Time Fragmentation and Communication. The thesis contributes with interesting findings from an expanding, middle-sized, healthy company in the audiobook streaming industry - but the results can be beneficial for other software development companies to learn from as well. Performing a similar study with a greater sample size, and additionally enabling comparisons between teams, is suggested for future research.

Safety-critical applications employed in automotive, avionics and aerospace domains are placed under strict demands for performance, power efficiency and fault tolerance. Development of system hardware and software satisfying all criteria is challenging and time-consuming. System co-design based on specifications and desired high-performance requirements, is one solution to this problem, however, it remains a largely unexplored territory. Currently at KTH Royal Institute of Technology, a co-design framework in relation to theoretical system design models is being researched with the objective to move the embedded system design to a higher abstraction level. Presently, it focuses on correct-by-construction design of low power and reliable safety-critical systems. This thesis intends to assess the accuracy of this framework in comparison to conventional design approaches. The accuracy is evaluated empirically in terms of extra functional requirements - average total power consumption and Mean Time Between Failure (MTBF). A simple payload Central Direct Memory Access (CDMA) application is integrated with Xilinx Soft Error Mitigation (SEM) IP Core and source of system failure is a Single Event Upset (SEU) which occurs due to ionizing radiations. Measurements obtained from this reference system are compared to results determined theoretically from model related equations for the same system. Comparison of measured MTBF values with theoretical estimations shows that measured ones are higher by an average huge difference of 324.63%. Similarly for power consumption, measurements were found to be higher than estimated ones by 0.4465 Watts. In conclusion, it can be said that theoretical model design framework is not accurate and models must somehow take into account implementation dependent factors. Nevertheless, this case study provided a good insight and pathways for enhancements and optimizations to turn this reference into a dependable platform. Finally, future work required for desirable experiment system improvements are identified. / Säkerhetskritiska applikationer som används inom fordons-, flyg- och flygindustrin ställs strikta krav på prestanda, energieffektivitet och feltolerans. Utveckling av systemhårdvara och mjukvara som uppfyller alla kriterier är utmanande och tidskrävande. Systemdesign baserad på specifikationer och önskade högpresterande krav är en lösning på detta problem, men det är fortfarande ett i stort sett outforskat område. För närvarande vid KTH Royal Institute of Technology undersöks ett ramverk för samdesign i relation till teoretiska systemdesignmodeller undersöks med målet att flytta den inbyggda systemdesignen till en högre abstraktionsnivå. Nuvarande, den fokuserar på korrekt konstruktion av låg effekt och pålitliga säkerhetskritiska system. Denna avhandling avser att bedöma riktigheten i detta ramverk i jämförelse med konventionella designmetoder. Noggrannheten utvärderas empiriskt när det gäller extra funktionskrav - genomsnittlig total strömförbrukning och medeltid mellan misslyckande (MTBF). En enkel nyttolast central direktminnesåtkomst (CDMA) applikation är integrerad med Xilinx begränsning av en händelse (SEM) IP kärnan och källan till systemfel är en singelhändelse upprörd (SEU) som uppstår på grund av joniserande strålning. Mätningar erhållna från detta referenssystem jämförs med resultat som bestämts teoretiskt från modellrelaterade ekvationer för samma system. Jämförelse av uppmätta MTBF -värden med teoretiska uppskattningar visar att uppmätta värden är högre med en genomsnittlig enorm skillnad på 324,63%. På samma sätt för strömförbrukning befanns mätningarna vara högre än beräknade med 0,4465 Watt. Sammanfattningsvis kan man säga att det teoretiska ramverket för modelldesign inte är korrekt och att modellerna på något sätt måste ta hänsyn till implementeringsberoende faktorer. Ändå gav denna fallstudie en bra insikt och vägar för förbättringar och optimeringar för att göra denna referens till en pålitlig plattform. Slutligen identifieras framtida arbete som krävs för önskvärda experimentsystemförbättringar.