M.Ing. / The importance of maintenance in industry and specifically in the electrical distribution industry has never really been challenged. Maintenance has none of the glamour of other functions such as Marketing or Research, nor has it enjoyed close attention received by other aspects of business such as production and sales. Yet management remains painfully aware of the consequences and cost to the business when the maintenance job is not properly executed. What has, in recent years, exacerbated matters somewhat (in the electrical distribution business) is the reluctance of utility undertakings to invest heavily in a business that is to undergo a vast transformation arising from the creation of the National Electricity Regulator (NER). This will entail the amalgamation of some 400 plus different electricity distributors, by far the most in the guise of municipal undertakings, into a few Regional Distributors and Metro's. During this phase of uncertainty, the electricity departments of many municipalities have been allowed to deteriorate as maintenance and refurbishment funds were moved into other areas that would remain within the control of the municipalities. Eskom also has allowed, to a certain extent, its own distribution infrastructure to deteriorate over the last decade or so due to a focus being placed on the distribution and delivery of electric power to remote and informal settlement areas. Now on the eve of the re-organisation of the electricity supply industry into Regional Distributors and Metro's, the existing network infrastructures are far from being in an ideal situation to cope with the added business constraints to be placed on the supply industry under the scope of Regulation. This dissertation looks at an integrated maintenance strategy for one component of the electricity infrastructure namely, the distribution substation. The Electricity Supply Industry (ESI) is on the brink of vast changes that will reform the industry. Already there are cracks developing in the existing supply infrastructure resulting in power blackouts in several major centres. With the coming of the Regional Electricity Distributors, additional constraints will be placed on the supply industry. It is vital that maintenance management in the ESI start to work proactively in optimising maintenance to achieve a best return on hard gained funding in the coming years.

M.Ing. (Engineering Management) / Please refer to full text to view abstract

M.Ing. / Until very recently reactive maintenance was still used in the mining industry. Equipment failures occurred without warning and resulted in catastrophic breakdowns and large production losses and maintenance cost. As a result, the mining industry turned to preventative maintenance that focused on changing parts before they fail. Although preventative maintenance was an improvement over reactive maintenance practices, equipment reliability did not necessarily improve. Next came predictive diagnostics, which monitored the health of components within assemblies, and thereby predicting the life expectancy of assemblies through vibration analysis, infrared thermography, lubrication and oil analysis and ultrasonic detection. However, the level of success could not be achieved. Many hours and a lot of money are spent in developing and implementing a maintenance management system, but without the correct approach, efficient maintenance might not be achieved. The overall objective of this dissertation is to introduce a logical approach to managing the maintenance of mining equipment over the economical life of the equipment. This concept can be defined as Life Cycle Management. The research included in this dissertation is partially aimed at developing the Life Cycle Management program for P&H MinePro Services A division of Joy Global (South Africa) (Pty) Ltd. The dissertation also includes case studies on the P&H Mining Equipment (Blast Hole Drills) and their alliance partners (LeTourneau Front-end Loaders). The dissertation focuses on the cradle to grave approach of maintenance for mining machinery, referred to as the Life Cycle Management of Mining Machinery.

No description available.

Apurinic endonuclease activity in human fibroblasts had been previously resolved into aflow-through and a high-salt eluate species by phosphocellulose chromatography (Kuhnlein, U. et al., Nucl. Acid. Res. 5: 951-960, 1978). Enzyme activity in the flow-through species amounted to 20-30% that of the high-salt eluate species. The flow—through enzyme species was not found in-eel I lines of xeroderma pigmentosum complementation group D. In this thesis, apurinic endonuclease activity was analysed in Hela ceflls. Specific enzyme activity in crude extracts "of Hela cells was in the range of 400-800 units/mg protein, similar to that of , human fibroblasts which was between 380-680 units/mg protein. Three species of endonuclease activity for apurinic DNA were resolved by phosphocellulose chromatography. They were designated as Peak I, Peak If, and Peak III. Peak I did not adsorb to the phosphoceIIuIose column at' 10 mM KP04 (pH 7.4) (flow-through activity), Peak II eluted from the column at about 210 mM KP0₄ (pH 7.4) and Peak I I I at 260 mM KPO₄ (pH 7.4). Based on their affinity to phosphoceIIuIose, we presumed Peak I and Peak III corresponded to the flow-through and high-salt eluate species in human fibroblasts respectively. Under our experimental conditions, the flow-through enzyme activity in both Hela cells and normaS human fibroblasts was only 2-4% of the activity of high-salt eluate species. We suspect that tissue culture conditions may affect the cellular level of the flow-through species of apurinic endonuclease. Peaks l-lII were optimally active at pH 7.5-8.0 and 5-10 mM MgCI, They were 'inhibited by increasing concentrations of KCI and NaCI except Peak III which was slightly stimulated by 20-40 mM KCI. The three species were distinguished by their thermosensitivities in a 50 mM KPO. buffer. Peak I was stable at 45°C. Peak III was heat-labile, having a half-life of 2-3 min at 45°C. Peak II seemed to contain two components, one with a ha If-life of 2-3 min at 45°C, and the other with a half-life of 25 min. In human fibroblasts, both the flow-through and high-salt eluate species of apu-rinic endonuclease were reported to be stimulated to 2.5-fold by 10 mM KCI. They had a ha If-life of 6 min at 45°C in a 230 mM KP0₄ (pH 7.4) buffer. Thus, Peaks I-lI I and enzyme species from human fibroblasts had a similar pH optimum, and Mg²⁺ requirement, but they differed in their thermosensitivities and inhibition by higher salt concentration. We do not know as yet whether these differences reflect the neoplastic nature of Hela cells or the different tissue origins of Hela cells and human fibroblasts. When either Peak I or Peak I I I was rechromatographed on the phosphoceIIulose column, activity was recovered in both the flow-through and high-salt eluate fractions. The result suggested an interconversion phenomenon between the flow-through and high-salt eluate species of apurinic endonuclease, This was further supported by molecular weight determinations of the apurinic endonucI eases In Peaks l-lII. Apurinic endonuclease activity in Peak III and Peak II had a molecular weight of 35,000-40,000 and 22,000-25,000 respectively. Peak I had two components with molecular weights similar to those of Peak II and Peak III. An understanding of the conversion between the different apurinic endonuclease species may help in elucidating the molecular defects of xeroderma pigmentosum complementation group D. Apurinic endonuclease activity in Peaks l-lII was found to be associated with a high molecular weight complex. The complex could be dissociated by high salt treatment. The possible biological significance of the high molecular weight complex Is discussed. We also found that apurinic endonuclease could adsorb to the Sephadex gel. The adsorption would lead to an aberrant estimation of molecular weight of the protein. The problem was solved with an elution buffer of high ionic strength. / Medicine, Faculty of / Medical Genetics, Department of / Graduate

<p>Prior literature on trust repair has focused primarily on exploring the effectiveness of different trust repair tactics in various contexts and the study of repair of trust as a process has been neglected. The literature has also suggested the presence of the humpty-dumpty effect in trust repair i.e. trust cannot be completely repaired once broken, though the claim has been more philosophical than empirical. In this dissertation, we explore the effect of tactic composites instead of analyzing the effect of each tactic separately (as has been the trend in the literature) that can be incorporated by the trustee to repair trust. We also develop multiple pathways that can potentially repair trust completely (specifically, redirect and replenish pathways) and one pathway that can restore the relationship by reestablishing cooperation but without repairing trust (redefine pathway). We structure the tactic composites within these pathways to explore the possibility of complete trust repair. Our results from a policy-capturing technique study and an experimental study show that in the redirect pathway, factual or symbolic evidence backed denial (but not denial alone) increases believability of the innocence claim by the trustee and can repair trust by improving the level of broken trustworthiness of the trustee. In the replenish pathway, only tactic composites that showcase regret through verbal tactics and repentance through behavioral tactics are able to make the trustor perceive that the trustee experiences remorse for the transgression, and only tactics that cater to individual and relational disequilibrium can increase perceived norm restoration in the eyes of the trustor. Both perceived remorse and norm restoration improved the levels of the broken trustworthiness. Finally, in the redefine pathway, strong control systems were better than weak control systems to restore cooperation, even though they had a negative relationship with the level of post-intervention trust. We also tested the potential of complete trust repair through the redirect pathway but did not find conclusive evidence. We discuss the limitations of the empirical studies and make suggestions for future research.</p>

No description available.

DNA double strand breaks represent the single most dangerous type of damage that can afflict the genome. Given the severity of such a lesion, higher eukaryotes possess two distinct pathways to repair such damages. The work presented here focuses on the role of different protein complexes formed during within Non-Homologous End Joining (NHEJ). Specifically, how the C-terminal tails of XRCC4 and XLF regulate higher-order complex formation of end bridging filaments prior to terminal ligation and release of the intact DNA following repair. The crystal structure of full length XRCC4 was solved to 3.43Å and confirmed that the C-terminal tails or XRCC4 mediate tetramerization but are not required for end bridging of DNA ends. A cluster of residues that stabilized the XRCC4 multi helix bundle were mutated and determined to result in an XRCC4Mutational analysis and SEC-MALS further revealed that this 4-helix bundle stabilizes tetramers, interestingly tetramerization was found to not be required for bridging of DNA ends. Additional work aimed at determining the mechanism by which XLF binds DNA and how complex filaments are formed was carried out using a combination of structural and biochemical techniques. Mutational analysis of the yeast XLF homologue, Nej1, revealed that the tails of these proteins bind their DNA substrates through an extended interface that may involve wrapping DNA to further stabilize interaction. Also, it was determined that phosphorylation of key residues within this extended DNA binding domain results in a decreased affinity for DNA and may play a role in DNA repair pathway choice in Saccharomyces cerevisiae. Transmission electron microscopy showed that when bound to DNA, XLF is capable of forming DNA dependent filaments that are capable of bridging DNA ends in a linear manner. Addition of XRCC4 resulted in extensive remodelling of these filaments. Crystals of the XRCC4/XLF/DNA were optimized to diffract to a resolution of greater than 5Å, however further work will be required to determine the structure of this key NHEJ complex. Finally, attempts to determine the optimal combination of DNA substrates and NHEJ factors to crystallize the terminal repairosome were carried out and initial hit conditions have been identified. / Thesis / Doctor of Philosophy (PhD)

The purpose of this research was to investigate the potential application of additive friction stir deposition (AFSD) to repair corroded steel bridge members. AFSD is an emerging solid-state additive manufacturing (AM) technology with many advantageous qualities such as low porosity, low residual stresses, flexibility in material, and a high build rate allowing for large-scale deposits. Two parameters were studied to understand the quality of AFSD on corroded steel: surface roughness and surface cleanliness. Three rounds of depositions were done: AerMet100, a high-strength corrosion-resistant steel, deposited onto AISI 1018 plates, with varying degrees of section loss, sectioned from a bridge taken out-of-service; AISI 1018 steel deposited onto an A572 Gr. 50 plate with 12 holes of varying diameters and depths drilled into the plate to simulate surface roughness; and AISI 1018 steel deposited onto an A572 Gr. 50 plate with mill scale, corrosion, and an industrial three-coat bridge paint system. The repair quality of each deposition was studied using scanning electron microscopy, microhardness testing, and three-point bending. Results from these tests indicated the following: AFSD can sufficiently mix dissimilar steels and result in a fine-grained microstructure; depositing onto a rough surface appeared to aid bonding between the two materials with little to no adverse effects on the repair quality; and finally, depending on the chosen deposition parameters, AFSD can mix foreign surface material into the matrix or mechanically remove the bulk of the foreign surface material appearing to clean the surface during the deposition. / Master of Science / This research investigated the applicability of additive friction stir deposition (AFSD) to repair corroded steel bridge members. AFSD is an emerging technology that can deposit metals without melting and build a part layer by layer similar to 3D printing. Since this process uses relatively low temperatures, the deposited material is not melted thus reducing issues associated with rapid solidification of melted metal. Three studies were conducted to better understand the print quality of AFSD on corroded steel. First, steel was deposited onto a surface with varying sized holes drilled to different depths meant to simulate a corroded surface. Second, a high-strength corrosion-resistant steel was deposited onto a corroded steel plate cut from an old bridge. Last, steel was deposited onto a steel plate with varying prepared surfaces including paint and corrosion. The quality of the depositions was studied through microscopy and mechanical testing. Results from these tests indicated the following: AFSD can sufficiently bond two different types of steels; depositing onto a non-level surface appeared to aid bonding between the two steels; and finally, AFSD can deposit steel onto certain unclean surfaces.

Corrosion on bridges is a common issue since it can be caused by multiple agents such as marine environments or deicing chemicals. The damages caused by these agents, if left unmitigated, may lead to failure of the superstructures. If corrosion is present in the end regions of the beams, failure of the girders will likely be in shear, which is a sudden failure mode and not the preferred limit state. Therefore, it is beneficial to study repair practices and their advantages, as repairs are often more cost-effective than building entirely new structures. Repairing prestressed girders for shear is not common practice, but with the number of superstructures considered structurally deficient in the United States, additional consideration should be given to repair methods. In this study, two beams were extracted from two decommissioned bridges and were repaired using Carbon Fiber Reinforced Polymer (CFRP) to investigate how well proposed repairs functioned. One of the beams is an American Association of State Highway and Transportation Officials (AASHTO) Type II beam, while the second one is an adjacent box beam. Before repairs were done, the beams had their ends further damaged with accelerated corrosion induced via electrolysis to ensure that the beams would have enough deterioration in their shear span to simulate the worst-case scenario found in the field. Afterwards, the girders had their damage and residual strength estimated, and repairs were designed using guidelines from the American Concrete Institute (ACI) and AASHTO for CFRP repairs. Since the adjacent box beam could only be repaired in flexure, it failed in shear with a load similar to previous studies done in beams from the same bridge, which indicates that repairs for box beams need further investigation. The repairs on the AASHTO Type II beam worked well for shear, and both ends failed in flexure, which is an improved failure mode since failing in flexure is more ductile and predictable than shear failures. One end of the AASHTO Type II beam failed by concrete crushing and CFRP rupturing, and the other end failed by strand rupturing, which shows that the accelerated corrosion worked as was predicted. / Master of Science / Corrosion on bridges is a major problem across the United States, especially in marine environments and in cold areas where deicing chemicals are needed to ensure the safety of the drivers. These external agents typically accelerate the deterioration of bridges and lead to expensive repairs and sometimes total replacement of structures. In order to study repair methods for bridges that have been exposed to corrosive agents, bridge girders were extracted from two decommissioned bridges in Virginia. The level of damage in these girders was assessed and it was determined that more corrosion had to be induced into the girder to ensure repairs were needed. After that process, the strength of the girders was estimated using guidelines from the American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO), and the girders were repaired for shear using sheets of Carbon Fiber Reinforced Polymers (CFRP). These repairs were done by using two different wrapping schemes, one that enveloped the sides of the girder, and one that was only at the bottom of the girder. The girders then had their ends tested under three-point bending to evaluate the effectiveness of the repairs. The girder that had the sides repaired as well performed better since the failure mode of it changed from shear to flexure. The girder that only had its bottom repaired did not do as well since its failure mode was still shear.