The continual increase in electrical energy demand in South Africa has resulted in a precariously low reserve margin in supply from the primary utility, Eskom. This resulted in extensive load shedding throughout the country. Far-reaching measures had to be introduced in order to ensure a reliable supply of electricity. DSM interventions were shown to be very successful short term solutions for the mining industry, reducing the strain on the national grid. This resulted in an increasing number of investigations to broaden the base of DSM projects to other industries. One such intervention was the Usutu-Vaal water distribution scheme, situated near Standerton, South Africa. This scheme includes the Grootdraai, Tutuka, Grootfontein, Rietfontein and Naauwpoort pumping stations. With a combined installed capacity of 36.5MW and the extremely large water storage capacities, these pump stations have been identified as prime candidates for DSM interventions. This dissertation discusses the method followed for a DSM project intervention and the results of the implementation. The national grid was relieved by an average of 12.3 MW during the Eskom weekday peak period, by shifting the pumping load into the off-peak periods. Simulations have shown that an annual financial saving of approximately R4.7million may be expected. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

The continual increase in electrical energy demand in South Africa has resulted in a precariously low reserve margin in supply from the primary utility, Eskom. This resulted in extensive load shedding throughout the country. Far-reaching measures had to be introduced in order to ensure a reliable supply of electricity. DSM interventions were shown to be very successful short term solutions for the mining industry, reducing the strain on the national grid. This resulted in an increasing number of investigations to broaden the base of DSM projects to other industries. One such intervention was the Usutu-Vaal water distribution scheme, situated near Standerton, South Africa. This scheme includes the Grootdraai, Tutuka, Grootfontein, Rietfontein and Naauwpoort pumping stations. With a combined installed capacity of 36.5MW and the extremely large water storage capacities, these pump stations have been identified as prime candidates for DSM interventions. This dissertation discusses the method followed for a DSM project intervention and the results of the implementation. The national grid was relieved by an average of 12.3 MW during the Eskom weekday peak period, by shifting the pumping load into the off-peak periods. Simulations have shown that an annual financial saving of approximately R4.7million may be expected. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

The research initiatives addressed in this thesis are geared towards improving the performance of passive optical networks through the development of advanced dynamic bandwidth allocation protocols. In particular, the aim of the research undertaken is to enhance the quality of service offered by standard passive optical networks with reduced network costs. To that extent, a dynamic multi-wavelength protocol has been developed to increase the network upstream bandwidth and introduce multiple service levels to a fibre to the home-based giga-bit passive optical network. Simulation results have confirmed the reduction of the mean packet delay by adjusting the ITU-T standard G984 giga-bit passive optical network frame format by means of the introduction of extended wavelength band overlay based on the ITU-T Coarse- Wavelength Division Multiplexing grid to support the multi-wavelength functionality. To evaluate the multi-wavelength upstream operation of the newly implemented models in OPNET, 2-dimensional Dynamic Bandwidth Allocation algorithms have been introduced to manage the network resources in both the time and wavelength domains. Furthermore, the enhanced traffic allocation among the supported wavelengths in new protocol confirmed a performance improvement in the network total capacity and the mean packet delay, which demonstrates the network reliability and improves the quality of the provided service according to the subscriber service level agreement, with a minimum guaranteed bandwidth of 100 Mbit/s to fulfil applications and associated bandwidth requirements for the next generation access network.

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Design step for Sigma-Delta ADC is introduced. Suitable solution for performance improvement of the original Sigma-Delta ADC, which meets new requirements on resolution of 16 bits and signal bandwidth 20-50 kHz is presented. Advantage of using multi-bit quantization and DEM DWA method reducing the linearity requirements of the internal feedback DAC is shown.

Under senare år har vi med hjälp av robotar som använder rörelseplanering kunnat automatisera olika processer och uppgifter. Idag finns det väldigt få strategier för lokal rörelseplanering vid jämförelse med global rörelseplanering. Syftet med det här projektet har varit att analysera tre strategier för lokal rörelseplanering, dessa har varit Dynamic Window Approach (DWA), Elastic Band (Eband) och Timed Elastic Band (TEB).I projektet har styrkor, svagheter, beteenden och förbättringsmöjligheter för respektive strategi studerats närmare genom att utföra olika simulerade tester. I testerna mätes tid för att nå mål, antal kollisioner och antalet gånger som målet nåddes. Under projektet användes en virtuell allriktad robot från ABB för att testa strategierna. Testerna genomfördes på ett så rättvist sätt som möjligt, där alla strategier fick samma antal försök och hade samma information om robotens begränsningar.Resultatet visar att TEB är den snabbaste strategin, följt av DWA och sista Eband som var den långsammaste strategin. TEB var också den strategi som presterade bäst vid dynamiska hinder, däremot var den också den strategi som kolliderade mest i testerna, medan Eband kolliderade minst. / In recent years, we have been able to automate various processes and tasks with the help of robots that use motion planning. Today, there are very few strategies for local motion planning when compared to global motion planning. The purpose of this project has been to analyze three strategies for local motion planning, these have been Dynamic Window Approach (DWA), Elastic Band (Eband) and Timed Elastic Band (TEB).In the project, strengths, weaknesses, behaviours and opportunities for improvement for each strategy have been studied in more detail by performing various simulated tests. The tests measure time to reach the goal, the number of collisions and the number of succeeding attempts. During the project, a virtual omni-directional robot from ABB was used to perform the tests. The tests were performed in as fair a way as possible, where all strategies got the same number of attempts and had the same information about the robot's limitations.The results show that TEB is the fastest strategy, followed by DWA and last Eband that was the slowest strategy. TEB was also the strategy that performed best in dynamic obstacles, however, it was also the strategy that collided most of the tests, while Eband collided the least.

<p>Embedded plates are used to support the external attachments such as heavy piping, brackets, sprinkler systems, or other equipment in nuclear power plants. The plates are welded with deformed reinforcing bars or deformed wires and anchored to reinforced concrete walls. The ACI code (ACI 318-19/ACI 349-13) provides design equations to calculate the anchor strength in concrete under tension load. These empirical equations are based on experiments conducted on headed studs, hooked bars, headed bolts, and adhesive anchors. With the lack of experimental data and code provisions on straight deformed reinforcing bars or deformed wires used as anchors, it is believed that anchoring bars with the embedment length as per code prescribed development length will provide sufficient strength to transfer tensile forces to the concrete, ignoring other failure modes such as concrete breakout. </p> <p>In this study, eight large scale group anchor tests were performed to evaluate their concrete breakout strength as per ACI 349-13. The test specimens were made with deformed reinforcing bar anchors (DRAs) and deformed wire anchors (DWAs). The tests included the effect of different bar types, bar sizes, and anchor spacings on the breakout capacities of such connections. The mean average back-calculated effective <i>k </i>value is 33.25 for DRAs and 36.26 for DWAs. The experimental study confirms that the axial tension capacity of embedded plates anchored to concrete using deformed reinforcing bars or deformed wires can be limited by concrete breakout strength.</p>

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In South Africa a large number of dams owned by the Department of Water Affairs (DWA) need to be rehabilitated. This study investigated the decision process involved in the prioritisation of dams for rehabilitation. DWA developed a risk analysis methodology for defining the risks associated with dam safety, expressed as the combination of the probability and consequences of dam failure. These risks are evaluated usingmultiple acceptability criteria to assess risk to human life and the economic, social, socio-economic and environmental impacts of dam failure. In this study, the criteria used in the decision process to evaluate the acceptability of life safety risks were evaluated by comparing to international best practice methods, where the acceptability of risk to human life is commonly assessed as the expected number of fatalities against life safety criteria presented as FN-criteria on an FN-diagram. Damrehabilitation should reduce the probability of dam failure, thereby reducing the risk to society in terms of the expected lives lost. However, the rehabilitation works come at a cost and the level of these investments are usually large. In addition, the rehabilitation of South African government owned dams are financed by society and these financial resources are limited. Thus investments into dam rehabilitation works should be worthwhile for society. Society’s Willingness to Pay (SWTP) for safety was applied to South African dam safety to determine the acceptable level of expenditure into life safety that is required by society. Investments into improved safety levels are not always dictated by society, but could also be driven by the decision maker or owner requiring an economically optimal solution for the rehabilitation. Economic optimisation accounts for considerations additional to life safety, including economic motivations, damage costs of dam failure as well as compensation costs for lives lost. Often economic optimisation would govern the decision problem. Also, the DWA current evaluation does not take the cost of rehabilitation into account in any way. Thus, FN-criteria that primarily evaluates life safety, but also incorporates a measure of economic efficiency, were suggested in this study. / AFRIKAANSE OPSOMMING: In Suid-Afrika moet ’n groot aantal dammewat deur dieDepartement vanWaterwese (DWA) besit word gerehabiliteer word. Hierdie studie het die besluitnemingsproses ondersoekwat toegepasword om damme te prioritiseer vir rehabilitasiewerke. DWA het ’n bestaande metodologie wat gebaseer is op risiko-analise. Die risikos wat verband hou met damveiligheid word deur die metode bepaal en word uitgedruk as die kombinasie van waarskynlikheid en die beraamde gevolge van damfaling. Hierdie risikosword geëvalueer teenoor verskeie kriteriawat die aanvaarbaarheid van risikos teenoor menselewens en die ekonomiese, sosiale, sosio-ekonomiese en omgewingsimpakte van damfalings assesseer. In hierdie studie word die kriteria wat gebruik word in die besluitnemingsproses om die aanvaarbaarheid van risikos teenoor menselewens te bepaal geëvalueer deur die kriteria te vergelyk met metodes wat internasionaal as beste praktyk beskou word. Internasionaal word die aanvaarbaarheid van risikos teenoor menselewens oor die algemeen as die verwagte aantal sterftes teenoor lewensveiligheidskriteria FN-kriteria op ’n FN-diagram geassesseer. Dam rehabilitasiewerke behoort die waarskynlikheid van damfaling te verminder, sodoende verminder die risiko teenoor die samelewing in terme van verwagte sterftes. Die rehabilitasiewerke vereis finansiële beleggings, en hierdie beleggings is gewoonlik groot. Verder word die rehabilitasie van Suid-Afrikaanse damme wat deur DWA besit word deur samelewing gefinansier en hierdie finasiële hulpbronne is beperk. Dus moet hierdie beleggings die moeite werd wees vir die samelewing. Die samelewing se bereidwilligheidomte betaal ("SWTP") vir veiligheid word toegepas in Suid- Afrikaanse damveiligheidomdie aanvaarbare vlak van beleggings vir ’n verbeterde veiligheid teenoor menselewens wat deur die samelewing vereis word te bepaal. Beleggings in verbeterde damveiligheidsvlakke word egter nie altyd bepaal deur die samelewing nie,maar kan ook gedryf word deur die besluitnemer of eienaar wat ’n ekonomies optimale oplossing vir die rehabilitatiesewerke vereis. Ekonomiese optimering neem oorwegings addisioneel tot lewensveiligheid in ag, insluitend ekonomiese motiverings, skade kostes as die dam faal, sowel as vergoedingskostes vir die verwagte sterftes. Ekonomiese optimering beheer dikwels die besluitnemingsprobleem. Verder neem die huidige DWA besluitnemingssproses in geen manier die kostes van rehabilitasie in ag nie. Dus word FN-kriteria wat hoofsaaklik veiligheid teenoor menselewens evalueer,maar wat ook ’n mate van ekonomiese doeltreffendheid insluit, voorgestel in hierdie studie.

Les convertisseurs analogiques-numériques fondés sur le principe de la modulation §¢ sont capables de fonctionner à des résolutions très élevés. L'utilisation en interne d'un CAN et d'un CNA multibit permet de réduire le taux de suréchantillonnage, les contraintes imposées par les circuits actifs, amé- liore la stabilité de la boucle du modulateur, mais rend celui-ci très sensible aux imperfections des composants du convertisseur numérique analogique (CNA) interne situé dans le chemin de retour. Les erreurs statiques dues aux non idéalités des circuits constitutifs de ce CNA peuvent être corrigées au moyen de techniques d'appariement dynamique des composants (DEM). Ce travail de thèse est consacré entre autre à l'étude théorique de ces techniques de correction des défauts des cellules des CNA multibits. Après avoir rappelé le principe de la conversion §¢ d'une part, et les différentes sources d'erreurs dominantes dans le cas multibit d'autre part, les techniques d'appariement existantes sont analysées et comparées. Nous soulignons les avantages, les inconvénients, et les domaines d'applications préférentiels de chacune. Le coeur du travail consiste en la proposition de quatre nouvelles techniques d'appariement dynamique. Les deux premières dérivent de la méthode de la moyenne des données (DWA), l'une pour le cas passe-bas du premier ordre, l'autre dans le cas passe-bande du second ordre. Les deux dernières propositions (appelées MDEM et STDEM) dérivent des deux algorithmes de tri (SDEM) et d'arborescence (TDEM) : elles conviennent à une mise en forme des erreurs d'ordre élevé et sont destinées aux applications passe-bas et passe-bande de haute performance. Ces quatre méthodes proposées ont été mises en équation et leurs performances confirmées par diverses simulations. Une implantation des algorithmes MDEM et STDEM a été faite au niveau cellule standard jusqu'à l'étape finale de routage en technologie CMOS 0.35 ¹m. L'ensemble des résultats des simulations au niveau système et au niveau transistor conforme l'avantage des techniques développées dans ce travail en termes de surface occupée et aussi de fréquence maximale d'application, si on les compare avec les algorithmes conventionnels de SDEM. Dans une dernière partie, les erreurs dynamiques du CNA, en particulier l'effet de la gigue d'horloge, le glitch, la dissymétrie des temps de transition, l'injection de charge (CFT) et la métastabilité du quantificateur sont également analysés. A l'issue de ces réflexions, une nouvelle cellule de CNA incluant un bloc limitant la plage dynamique de la commande d'entrée (SRD) est proposée. Elle possède une structure de remise à zéro partielle (semi-RZ) qui permet de bénéficier à la fois de l'avantage de la cellule RZ et non RZ. De plus, l'effet du retard du bloc de DEM est compensé par une modification dans l'architecture convenant aux applications passe-bande haute fréquence.