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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

An assessment of the social consequences of water management devices on the poor in Samora Machel, Cape Town

Ntwana, Bukiwe January 2014 (has links)
Magister Administrationis - MAdmin / This study assesses the social consequences of water management devices in poor households in Samora Machel, a poor urban area characterised by high levels of unemployment and poverty. South Africa is currently faced with an increase in the roll out of water management technologies, mainly in poor areas, allegedly to manage water demand and help poor households manage their water consumption and prevent wastage. The water management device (WMD) limits access to the free basic water (FBW) allocation and automatically cuts it off when the allocation is finished. In 2009/2010 the City of Cape Town started rolling out the devices in Samora Machel, which previously used the conventional water meter that supplied the area with unlimited water access. WMDs limit water access to 350 litres of FBW per day. People living in Samora Machel claim that 350 litres is not enough and they are experiencing problems of frequent water cuts even before the allocated litres are used up. There have also been water leaks ever since the installation of the devices. Section 27(1)(b) of the Constitution of the Republic of South Africa, Act 108 of 1996, entrenches the right of access to sufficient water. The WMDs are criticised for infringing the right of access to sufficient water supply to poor households by leaking, cutting off water supply frequently and by limiting access to FBW supply. Moreover, critics argue that the WMDs are not water-demand management mechanisms; they are cost-recovery mechanisms that are introduced under the neo-liberal policies introduced by the post-apartheid government in 1994. This criticism is based on the fact that the WMDs are implemented in poor areas only, where water is needed more for basic survival, rather than in high-income areas, where water is mostly used for luxury purposes.
2

Manufacturing of Welded Rings : Evaluation of Post-Weld Operations / Tillverkning av svetsade ringämnen : Utvärdering av svetsfogsoperationer

Andersson, Jim January 2019 (has links)
Pipe and ring blanks can be produced in several different ways. Today's focus on environmental effects motivates companies to develop processes that are as efficient as possible in their production. Ringsvets AB is a company that produces pipe and ring blanks from a flat stock by rolling and welding the piece to make it stay in its desired form. The direct benefit of the method is the minimizing of material loss, and it has thereby both environmental and economical advantages. The downside of the method is that the processes involved changes the mechanical behavior of the ring, locally around the weld zone. The focus of this master thesis is the processes and how they affect the material, both microstructure and behavior. The processes involved are; rolling, welding, shaping, brushing, forging, heat treatment, and calibration. The purpose of this work was to elevate the knowledge and understanding of the processes at Ringsvets. The goals were to give a theoretical description of them along with practical test results and explanations of how and why they function in reality. A literature study has been conducted which provided a theoretical basis on how the material reacts on certain processes. Practical examination of samples from current production has been done to get evidence of how well the processes are used, and how well they function, in today's production. Lastly, the main focus of the thesis, an evaluation has been made; do theory and practice correlate, and should anything be changed to correlate better? The results showed that the first operations do not alter the material behavior to an unacceptable extent. Forging, on the other hand, gives the material a very high hardness in the weld zone, and that needs to be corrected. The following heat treatment should compensate for that in a perfect world, but does not in reality. The finished ring shows good properties in general but with places where the heat treatment has failed to correct the uneven behavior induced by earlier operations. The heat treatment requires some adjustments before it functions as intended. Some grainshas not been recrystallized which makes them very hard and non-ductile. Future tests using a higher temperature or a longer heat treatment time would reveal the best way to adjust the heat treatment to obtain the desired properties. Other changes in the processes could also be benecial. Interesting things to try and change would, for example, be the degree of deformation in the forging, which affects the recrystallization temperature. Notes should be taken that this examination is done on just one sample of just one size. Analyses of different samples of different sizes should be done to ensure of the accuracy of the examination.
3

Nickel Catalyzed Cycloaddition Reactions: Alkyne Cyclotrimerizations and Reductive Vinylidene Transfer Reactions

Sudipta Pal (5930111) 14 January 2021 (has links)
The advent of transition metal catalysis has greatly expanded the scope of viable cycloaddition reactions, allowing for the direct synthesis of highly functionalized and complex biologically active compounds. By manipulating various aspects of catalyst structure, including the supporting ligands and the central metal, the function of a catalyst can be modified. In this context, the catalytic properties of dinuclear complexes have not been greatly explored in cycloaddition reactions. Our research has focused on studying the catalytic properties of dinuclear complexes in cycloaddition reactions. Comparative studies between dinuclear and mononuclear Ni-complexes led us to discover and develop an efficient route to synthesize 1,2,4-trisubstituted benzene derivatives from terminal alkynes. The key organometallic intermediates in this process were isolated, and computational studies were performed to unravel a novel bimetallic mechanism for alkyne cyclotrimerizations. As an extension of this study, we have found that the dinuclear catalyst is capable of catalyzing the methylenecyclopropanation of olefins. The reaction uses 1,1-dichloroalkene as a vinylidene precursor along with Zn as a stoichiometric reductant. A wide range of monosubstituted terminal alkenes and relatively unhindered internal alkenes are viable substrates. Furthermore, to understand the mechanism of vinylidene transfer, various stoichiometric and stereochemical experiments were performed. Furthermore, we discovered that mononuclear and dinuclear Ni-complexes are highly efficient in achieving vinylidene insertions into Si–H bonds to synthesize Si-containing heterocyclic molecules. Ongoing efforts are directed toward optimizing the reaction conditions and elucidating the substrate scope of the reaction.

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