Showing items 1 - 20 of 21

Your selections:

Asymmetric price transmission: an empirical analysis of the relationship between UG-2 chrome ore, charge chrome, nickel and Chinese domestic 304 stainless steel cold rolled coil

  • Authors: Le Roux, Simon Petrus
  • Date: 2021
  • Subjects: Pricing , Chromium ores -- Prices -- South Africa , Nickel -- Prices -- South Africa , Austenitic stainless steel-- Prices -- China , Steel -- Prices -- South Africa , Non-Linear Autoregressive Distributive Lag (NARDL)
  • Language: English
  • Type: text , Thesis , Masters , MCom
  • Identifier: http://hdl.handle.net/10962/171336 , vital:42049
  • Description: The goal of this study was to determine whether asymmetric price transmission (APT) exists between the prices of South African UG-2 Chrome ore, Charge Chrome, Nickel and Chinese Domestic 304 Stainless steel Cold Rolled Coil prices. Monthly time series data for the period January 2009 to July 2019 was analysed. The Non-Linear Autoregressive Distributive Lag (NARDL) model was applied to test for the presence of price asymmetry between the four variables. Firstly, it was observed that the four variables are cointegrated in the long-run. Secondly, no evidence of price asymmetry was found to be present within the Stainless steel supply chain. The reason for this is most likely due to the extremely close-knit and highly concentrated nature of this industry at each level within the supply chain. The industry can be very opaque to external observers even though the distribution of pricing information is very efficient for participants within the industry.
  • Full Text:
  • Date Issued: 2021

A skin that took them through

  • Authors: Kgame, Mbali
  • Date: 2020
  • Subjects: South African fiction (English) -- 21st century , African fiction (English) -- History and criticism , Short stories, South African (English) -- 21st century , Diaries -- Authorship
  • Language: English
  • Type: text , Thesis , Masters , MA
  • Identifier: http://hdl.handle.net/10962/147638 , vital:38656
  • Description: This project comprises of interlinked fictional short stories capturing experiences of the “invisibilised’’ young people- the street kids, drug addicts, cashiers, childminders, the sick, first graduates etc. These stories are a way to interrogate the fallacy of a “free and fair” South Africa by noting events taking place within homes, communities and countrywide. Told in a playful, innocent, curious, childlike voice and reasoning, my work draws inspiration from Werewere Likings ‘The Amputated Memory,’ for its ability to narrate the current without divorcing the past. I draw inspiration from Liking’s way of writing family connectivity and employing an emerging voice of the narrator starting from being a child scribbling to later becoming an elder. Nana Kwame Adjei-Brenyah’s ‘Black Friday’ for scanning into young black people’s experiences in a society where their bodies move as misfits. My work also draws from Lesley Nneka Arimah’s ‘What It Means When a Man Falls from the Sky’ for the interlinked stories. Lastly the stories in this project take from Sindiwe Magona’s Mother to Mother for humanising bodies that have been reduced to frames.
  • Full Text:
  • Date Issued: 2020

Economic evaluation of chemical and biological control methods on four aquatic weeds in South Africa

  • Authors: Maluleke, Mary
  • Date: 2020
  • Subjects: Invasive plants -- Biological control -- Economic aspects -- South Africa , Introduced organisms -- Biological control -- Economic aspects -- South Africa , Aquatic weeds -- Biological control -- Economic aspects -- South Africa , Aquatic weeds -- Control -- Economic aspects -- South Africa , Aquatic resources -- Management , Cost effectiveness , Net present value , Herbicides -- Cost effectiveness , Working for Water Programme , Water conservation -- South Africa
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: http://hdl.handle.net/10962/145953 , vital:38481
  • Description: Invasive alien plants (IAPs) of various kinds pose a threat to ecosystems, biodiversity, conservation and overall economy. In a world experiencing exponential increase in IAPs – this issue has become endemic, especially for developing countries such as South Africa. South Africa is a water scarce country and IAPs increase water stress. Thus, South Africa must invest in a more realistic, environmentally and economically inclusive policy outlook on the management of IAPs including aquatic weeds. This is especially urgent when considering the changing global climate, which is predicted to further reduce the quantity and quality of potable water. The Working for Water Programme (WfW) in South Africa aimed at addressing the issue of IAPs in a way that protects the environment as well as produces maximum return to society through poverty alleviation. As such, the aquatic weeds management strategy put in place for four of South Africa’s aquatic weeds Pista stratiotes, Salvinia molesta, Azolla filiculoides and Myriophyllum aquaticum - should be one that is cost-effective, efficient and sustainable; yielding the best possible return on investment. Since these four weeds are already under complete biological control, in the absence of biological agents, the WfW programme would have used herbicides to control these weeds. As such, this thesis conducted a retrospective analysis of the relative herbicide cost-saving associated with the use of biological control. To do this, due to existing limitations, E. crassipes was used as a surrogate weed and its herbicide control costs were used as proxy for the herbicide control cost estimates of the four selected weeds; with reasonable conversion factors applied to cater for the biological difference of the five weeds. Using the cost benefit analysis (CBA) framework, the net present cost (NPC) of each control method was calculated to which the relative cost-saving was considered to represent the avoided cost of using biological control instead of chemical control on these weeds. The avoided cost was used as the main benefit component when deriving the relative benefit cost ratios (BCR). Two scenarios were used, one assuming no follow-up requirement and the other assuming one follow-up requirement for chemical control. Using an 8% discount rate, the study found that the estimated cost of the biological control method on all four aquatic weeds was about R7,843,205 while for chemical control the estimated costs would have costed R149,580,142, R268,264,838 and R881,711,738 for application by means of a boat, bakkie and knapsack. Chemical control cost estimates would have increased to about R164,538,052, R295,216,120 and R1,008,761,000 for boat, bakkie and knapsack approach respectively when including a possible follow-up programme. These would have led to positive BCRs of 90.24:1, 164.97:1 and 557.99:1 across the three chemical control approaches without a follow-up (with BCR of about 99.67:1, 182.00:1 and 631.56:1 for the boat, bakkie and knapsack approach respectively with the accepted follow-up programme). When running a sensitivity test with varying discount rates of 5% and 10%, these results remained robust. As such, failing to reject the dominant hypothesis in literature, the main conclusion of the study is that biological control is indeed the more cost-effective management option compared to chemical control with respect to herbicide cost-saving. Further, biological control is most-likely to produce more environmental cost-saving and water-saving over chemical control. The study recommends the continued use of the biological control investment on the four aquatic weeds under study as well as on emerging aquatic weeds such as Iris pseudacorus, Nymphaea mexicana and Sagittaria platyphylla in South Africa.
  • Full Text:
  • Date Issued: 2020

Either way you die: a collection of short stories

Explored Vygotsky’s concept of mediation in a biliteracy project in the foundation phase of a township school

  • Authors: Frans, Nompumelelo Grace
  • Date: 2020
  • Subjects: Literacy -- South Africa -- Case studies , Education, Elementary -- South Africa -- Case studies , Education, Bilingual -- South Africa -- Case studies , Vygotskiĭ, L S (Lev Semenovich), 1896-1934 , Biliteracy Project (South Africa)
  • Language: English
  • Type: text , Thesis , Masters , MA
  • Identifier: http://hdl.handle.net/10962/147204 , vital:38602
  • Description: The research reported on in this thesis explored teacher mediation when a biliteracy approach through task-based teaching and learning is used in a Foundation Phase classroom in a township school in the Eastern Cape. It is an action research aimed at understanding and systematically investigating how and what it means to work with bilingual mediation to ensure cognition, with emphasis on task design, facilitation for cognition, mediation forms and language use. This thesis was motivated by three issues that are still not being adequately addressed: the low level of cognitive work in South African schools, the failure to use the home languages of children throughout schooling as a medium of instruction and assessment (while providing excellent access to English as subject), and a top-down approach to both policy development and teacher professionalisation. These three issues drove me to explore theories that can help address them, and that is how I came to rely mostly on mediation, biliteracy and a task-based approach to teaching. For this research, on data handling I prepared and taught six lessons, but only three of the six lessons were recorded, transcribed and analysed for empirical data. I chose data handling, as in my previous experience I found it to include all the mathematical problem-solving skills which involve addition subtraction, analysing and comparing information. It also offered opportunities for language use, and meaningful interactive co-construction and acquiring of knowledge in the process of teaching and learning. This turned into a form of theory-driven action research, which was also developmental. I was critically reflective on my practices, and my facilitation for cognition and how I use language to make cognition possible. I also looked at the types of activities that I gave learners to help reach maximum development. The data collected from the classroom interactions, shows how I, in some instances, would take decisions, implement them and then find them not to be effective. It also shows some of the challenges I came across, from myself and the learners. Learners challenges were, unfamiliarity with the systematic build-up of data handling, filling in tables, transferring information from one form into a different form, and constructing and analysing bar graphs. This was part of pedagogynot the policy, which indicated inadequate teacher development. This could be because data handling is allocated minimal weighting from the CAPS document, and teachers do not go as in depth as they need to in dealing with data handling. My challenge was to prepare the grade 3 class for more data handling encounters in the higher grades. I had to ensure they grasped data handling concepts in their mother tongue before the switch to English as LoLT, as prescribed by policy. Learners proved to have little or no knowledge with regards to data handling concepts, which meant I had to start from the basics, as I had nothing to build on, and then progress to grade 3 level in one year. This study suggests that for any concept that has to be taught, cognition must be a priority, and strategies on how to facilitate that needs to be well thought out. Teachers need to be aware of theories that can positively impact on their practices. Teacher development is key to improvement of education, especially in the Eastern Cape. That cannot be done in isolation, but in partnership with relevant stakeholders.
  • Full Text:
  • Date Issued: 2020

Modelling and investigating primary beam effects of reflector antenna arrays

  • Authors: Iheanetu, Kelachukwu
  • Date: 2020
  • Subjects: Antennas, Reflector , Radio telescopes , Astronomical instruments -- Calibration , Holography , Polynomials , Very large array telescopes -- South Africa , Astronomy -- Data processing , Primary beam effects , Jacobi-Bessel pattern , Cassbeam software , MeerKAT telescope
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/147425 , vital:38635
  • Description: Signals received by a radio telescope are always affected by propagation and instrumental effects. These effects need to be modelled and accounted for during the process of calibration. The primary beam (PB) of the antenna is one major instrumental effect that needs to be accounted for during calibration. Producing accurate models of the radio antenna PB is crucial, and many approaches (like electromagnetic and optical simulations) have been used to model it. The cos³ function, Jacobi-Bessel pattern, characteristic basis function patterns (CBFP) and Cassbeam software (which uses optical ray-tracing with antenna parameters) have also been used to model it. These models capture the basic PB effects. Real-life PB patterns differ from these models due to various subtle effects such as mechanical deformation and effects introduced into the PB due to standing waves that exist in reflector antennas. The actual patterns can be measured via a process called astro-holography (or holography), but this is subject to noise, radio frequency interference, and other measurement errors. In our approach, we use principal component analysis and Zernike polynomials to model the PBs of the Very Large Array (VLA) and the MeerKAT telescopes from their holography measured data. The models have reconstruction errors of less than 5% at a compression factor of approximately 98% for both arrays. We also present steps that can be used to generate accurate beam models for any telescope (independent of its design) based on holography measured data. Analysis of the VLA measured PBs revealed that the graph of the beam sizes (and centre offset positions) have a fast oscillating trend (superimposed on a slow trend) with frequency. This spectral behaviour we termed ripple or characteristic effects. Most existing PB models that are used in calibrating VLA data do not incorporate these direction dependent effects (DDEs). We investigate the impact of using PB models that ignore this DDE in continuum calibration and imaging via simulations. Our experiments show that, although these effects translate into less than 10% errors in source flux recovery, they do lead to 30% reduction in the dynamic range. To prepare data for Hi and radio halo (faint emissions) science analysis requires carrying out foreground subtraction of bright (continuum) sources. We investigate the impact of using beam models that ignore these ripple effects during continuum subtraction. These show that using PB models which completely ignore the ripple effects in continuum subtraction could translate to error of more to 30% in the recovered Hi spectral properties. This implies that science inferences drawn from the results for Hi studies could have errors of the same magnitude.
  • Full Text:
  • Date Issued: 2020

Sectoral co-integration and portfolio diversification benefits: a business cycle examination of South African equity sectors

  • Authors: Hofisi, Tinashe S
  • Date: 2020
  • Subjects: Portfolio management -- South Africa , Investments -- South Africa , Investments, South African , Stocks -- South Africa
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: http://hdl.handle.net/10962/146379 , vital:38521
  • Description: The onset of globalisation and simultaneous changes in financial technology and financial reforms dissipated hurdles once faced in financial transactions among stock markets. Hence, stock markets around the world became increasingly integrated because there was a free flow of cross border investments. Consequently, international diversification diminished thereby undermining the ability of investors to diversify investments across borders. For that reason, recent literature on portfolio diversification is urging investors to shift their focus to domestic portfolio diversification as an alternative. On that account, this study aims to examine the co-integration and dynamic causalities between South African equity market sectors in order to ascertain the sectoral diversification opportunities available to domestic investors over time. The study was examined over the different phases of the business cycle as well as the full sample, i.e. 2004 – 2018, with a view to shedding light on the inter-sectoral diversification opportunities of domestic investors over the South African business cycle. The phases of the business cycle applied are a| expansion and boom; b| recession and recovery phase and c| stagnation phase. The Johansen co-integration and Granger-causality tests were employed. The hypothesis of the study is that, if sectors are not cointegrated, then diversification benefits can be reaped by constructing a portfolio that combines stocks from the respective sectors. On the whole, the findings of this study show that there are both long-run and short-run diversification opportunities across the different phases of the South African business cycle as well as the full sample. However, there are lesser diversification opportunities in the recession and recovery phase over both the long-run and short-run. These results indicate that domestic sectoral portfolio diversification is least effective when it is needed the most (i.e. in a period of heightened volatility such as recession and recovery phase). This study will contribute to the existing literature in two ways; firstly, to investors who intend to diversify their portfolios domestically rather than internationally and, secondly, after reasonably thorough research it was evident that there is scant literature on domestic sectoral diversification in South Africa. As a result, the study attempts to address this gap. Additionally, the essence of the business cycle in this study is to make investors aware of potential diversification opportunities when positioning their portfolios for the next shift in the business cycle.
  • Full Text:
  • Date Issued: 2020

The current nature of intra-regional trade in the proposed tripartite free trade area

  • Authors: Chibuta, Chisengele
  • Date: 2020
  • Subjects: Customs unions -- Africa, Southern -- Economic integration , Africa, Southern -- Economic policy , Africa, Southern -- Economic integration , Africa, Southern -- Economic conditions , Tripartite Free Trade Area , Free trade -- Africa, Southern
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: http://hdl.handle.net/10962/146744 , vital:38553
  • Description: This thesis examines and analyses the current nature of intra-regional trade between member states of the proposed Tripartite Free Trade Area in order to contribute to an understanding of the potential for intra-regional trade within the region to increase. Trade Complementarity Indexes were used to determine how well the structures of the three founding blocs’ major imports and exports match. The results show that there is a high degree of trade complementarity in the trade of the top 5 major products traded between the regional groups. With the proposed TFTA in place, high trade complementarity could lead to increased trade between the regional groups. Trade Intensity Indexes were used to determine how intensively the three founding blocs trade with one another. Results from the indexes help determine the extent to which the blocs currently view each other as important trading partners and the implications of this for the proposed TFTA. Results show that EAC and SADC as well as EAC and COMESA viewed each other as significant trading partners while SADC and COMESA did not for the majority of the years from 2001 to 2018. With the TFTA in place, intra-regional trade could be strengthened among the members who currently trade intensively because tariffs between them would be progressively eliminated as required by the TFTA Agreement. Revealed Comparative Advantage Indexes were used to gain insights on whether member states have any comparative advantage in their top 5 exports. Results from the indexes were used to determine whether member states have comparative advantage in similar or dissimilar major exports and the implications of this for the proposed TFTA. Results show that member states have revealed comparative advantage in similar products and these products present opportunities for joint-production among member states as well as sectors for product development once the proposed TFTA is in place. Revealed Trade Barrier Indexes were used to gain insights into the extent of ease of market access into each regional bloc’s market. Results from the indexes indicate whether major products imported from each other receive possibly discriminatory or preferential treatment. The results indicate that the majority of the top 5 imports sourced from each region receive preferential treatment. This indicates that there is ease of market access for the top 5 imports sourced from each other and this could promote increased intra-regional trade among member states in these product categories because tariff and non-tariff barriers to trade will be progressively eliminated once the TFTA is in place.
  • Full Text:
  • Date Issued: 2020

The exploration of ARF1 screening assays to determine the drug status of ARF1 in cancer and malaria

  • Authors: Ntlantsana, Apelele
  • Date: 2020
  • Subjects: ADP ribosylation , Golgi apparatus , Guanosine triphosphatase , G proteins , Malariotherapy , Malaria -- Research , Cancer -- Chemotherapy , Malaria -- Chemotherpay
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/167232 , vital:41458
  • Description: ARF GTPases are key regulators of the secretory and endocytic pathways. ARF1 is involved in the secretory pathway. ARF1 has been implicated in the endoplasmic reticulum to Golgi transport, function of the Golgi apparatus and transport from the trans-Golgi network to endosomes. ARFs cycle between active GTP-bound and inactive GDP-bound conformations. GDP/GTP cycling is regulated by large families of guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs). ARF GEFs facilitate the activation of ARFs by mediating the exchange of GDP for GTP, while ARF GAPs terminate ARF function by stimulating the hydrolysis of the terminal phosphate group of GTP. Based on existing evidence gained from gene manipulation and cell biological investigations, ARF1 has been shown to be fundamentally important for cancer cell proliferation and metastasis and may be a promising target for the development of anti-cancer drugs. Additionally, the conservation of ARFs in eukaryotic organisms leads to an interesting question of whether a single drug target can be used to target multiple diseases. In this case, can a human cancer drug employed for cancer therapy be used in anti-malarial drug therapies? To confirm the drug target status of ARFs using chemical validation experiments, novel inhibitory compounds are needed. This requires the development of complex in vitro protein- protein interaction assays that can be used to screen chemical libraries for ARF GTPase inhibitors. In this study, we developed a fluorescence resonance energy transfer (FRET) assay and a novel in vitro colorimetric plate-based assay to detect the activation status of truncated human and Plasmodium falciparum ARF1. In the case of the FRET assay, active (GTP-bound) and inactive (GDP-bound) ARF1 could be distinguished with Z-factor values >0.5, suggesting that further development of the assay format to identify GEF and GAP inhibitors may be feasible. In the case of the colorimetric assay, robust signals could be detected and the assay was useful for detecting the activation status of ARF1. However, although the activation of ARF1 by the Sec7 domains of the BIG1 and ARNO was detectable, signals were not robust enough to employ in screening campaigns.
  • Full Text:
  • Date Issued: 2020

Understanding the underlying resistance mechanism of Mycobacterium tuberculosis against Rifampicin by analyzing mutant DNA - directed RNA polymerase proteins via bioinformatics approaches

  • Authors: Monama, Mokgerwa Zacharia
  • Date: 2020
  • Subjects: Mycobacterium tuberculosis , Rifampin , Drug resistance , Homology (Biology) , Tuberculosis -- Chemotherapy
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/167508 , vital:41487
  • Description: Tuberculosis or TB is an airborne disease caused by the non-motile bacilli, Mycobacterium tuberculosis (MTB). There are two main forms of TB, namely, latent TB or LTB, asymptomatic and non-contagious version which according to the World Health Organization (WHO) is estimated to afflict over a third of the world’s population; and active TB or ATB, a symptomatic and contagious version which continues to spread, affecting millions worldwide. With the already high reported prevalence of TB, the emergence of drug-resistant strains has prompted the development of novel approaches to enhance the efficacy of known drugs and a desperate search for novel compounds to combat MTB infections. It was for this very purpose that this study was conducted. A look into the resistance mechanism of Rifampicin (Rifampin or RIF), one of the more potent first-line drugs, might prove beneficial in predicting the consequence of an introduced mutation (which usually occur as single nucleotide polymorphisms or SNPs) and perhaps even overcome it using appropriate therapeutic interventions that improve RIF’s efficacy. To accomplish this task, models of acceptable quality were generated for the WT and clinically relevant, RIF resistance conferring, SNPs occurring at codon positions D516, H526 and S531 (E .coli numbering system) using MODELLER. The models were accordingly ranked using GA341 and z-DOPE score, and subsequently validated with QMEAN, PROCHECK and VERIFY3D. MD simulations spanning 100 ns were run for RIF-bound (complex) and RIF-free (holo) DNA-directed RNA polymerase (DDRP) protein systems for the WT and SNP mutants using GROMACS. The MD frames were analyzed using RMSD, Rg and RMSF. For further analysis, MD-TASK was used to analyze the calculated dynamic residue networks (DRNs) from the generated MD frames, determining both change in average shortest path (ΔL) and betweenness centrality (ΔBC). The RMSD analysis revealed that all of the SNP complex models displayed a level instability higher than that of the WT complex. A majority of the SNP complex models were also observed to have similar compactness to the WT holo when looking at the calculated Rg. The RMSF results also hinted towards possible physiological consequences of the mutations (generally referred to as a fitness cost) highlighted by the increased fluctuations of the zinc-binding domain and the MTB SI α helical coiled coil. For the first time, to the knowledge of the authors, DRN analysis was employed for the DDRP protein for both holo and complex systems, revealing insightful information about the residues that play a key role in the change in distance between residue pairs along with residues that play an essential role in protein communication within the calculated RIN. Overall, the data supported the conclusions drawn by a recent study that only concentrated on RIF-resistance in rpoB models which suggested that the binding pocket for the SNP models may result in the changed coordination of RIF which may be the main contributor to its impaired efficacy.
  • Full Text:
  • Date Issued: 2020

Visualising Chinese presence: an analysis of the contemporary arts of Zambia and Zimbabwe

  • Authors: Zhang, Lifang
  • Date: 2020
  • Subjects: Art, Modern -- 21st century , Art, Modern -- 21st century -- Chinese influences , China -- Relations -- Zambia , China -- Relations -- Zimbabwe , Art and society -- Zambia , Social practice (Art) -- Zambia , Art and globalization -- Zambia , Art and society -- Zimbabwe , Social practice (Art) -- Zimbabwe , Art and globalization -- Zimbabwe
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: http://hdl.handle.net/10962/146618 , vital:38542
  • Description: With the revival and rapid growth of relations between China and African countries in the present century, the “China-Africa relationship” has become a topic of close attention globally and the media and politicians have been dominating the mainstream discourses with dichotomised narratives. China-Africa engagement has also spurred academic research, most of which is oriented toward large-scale economic, political, and strategic concerns. In this context, it is significant to conduct in-depth research exploring specific engagement between Chinese and African people on the ground. Contemporary artists based in Africa have started to represent, through artworks and performances, their experiences and expressions of relations between China and various African countries. However, an examination of twenty-first century connections between Africa and China in relation to the contemporary visual arts is a new area of study and only a limited number of scholarly works exist. To contribute to the research in this area, this thesis explores the ways in which artists engage with specific realities and lived-experiences of Chinese presence through their artistic practices, with a focus on a selection of artists from Zambia and Zimbabwe. Through visual analysis, interviews and field work, this thesis provides a systematic investigation of contemporary arts of Zambia and Zimbabwe in relation to Africa- China encounters, engaging with four aspects: the discursive field, the material presence, individual experiences of encounters, and the broader relational connections within the arts. This thesis argues that, motivated by the histories and realities of African societies, artists from Zambia and Zimbabwe, through their artistic practices, form part of the Africa-China engagement and insert their agencies in the south-south relations between Africans and Chinese. Therefore, this thesis demonstrates the value in approaching the broader discussion on Africa-China engagements from the perspective of contemporary art, arguing that, with the social concerns of the artists and the expressive capacity of creative forms, visual arts are able to embrace diversity, dynamics, complexities and contradictions, and, therefore, can develop the topic beyond the stereotypical narratives about Africa-China relations to a more nuanced understanding of African-Chinese encounters in specific contexts.
  • Full Text:
  • Date Issued: 2020

CubiCal: a fast radio interferometric calibration suite exploiting complex optimisation

  • Authors: Kenyon, Jonathan
  • Date: 2019
  • Subjects: Interferometry , Radio astronomy , Python (Computer program language) , Square Kilometre Array (Project)
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/92341 , vital:30711
  • Description: The advent of the Square Kilometre Array and its precursors marks the start of an exciting era for radio interferometry. However, with new instruments producing unprecedented quantities of data, many existing calibration algorithms and implementations will be hard-pressed to keep up. Fortunately, it has recently been shown that the radio interferometric calibration problem can be expressed concisely using the ideas of complex optimisation. The resulting framework exposes properties of the calibration problem which can be exploited to accelerate traditional non-linear least squares algorithms. We extend the existing work on the topic by considering the more general problem of calibrating a Jones chain: the product of several unknown gain terms. We also derive specialised solvers for performing phase-only, delay and pointing error calibration. In doing so, we devise a method for determining update rules for arbitrary, real-valued parametrisations of a complex gain. The solvers are implemented in an optimised Python package called CubiCal. CubiCal makes use of Cython to generate fast C and C++ routines for performing computationally demanding tasks whilst leveraging multiprocessing and shared memory to take advantage of modern, parallel hardware. The package is fully compatible with the measurement set, the most common format for interferometer data, and is well integrated with Montblanc - a third party package which implements optimised model visibility prediction. CubiCal's calibration routines are applied successfully to both simulated and real data for the field surrounding source 3C147. These tests include direction-independent and direction dependent calibration, as well as tests of the specialised solvers. Finally, we conduct extensive performance benchmarks and verify that CubiCal convincingly outperforms its most comparable competitor.
  • Full Text:
  • Date Issued: 2019

Movement of coastal fishery species in Southern Africa: research trends, characterisation of behaviours and a case study on fishery implications

  • Authors: Maggs, Jade Quinton
  • Date: 2018
  • Subjects: Fishery management -- Africa, Southern , Fisheries -- Africa, Southern , Fisheries -- Catch effort , Fisheries -- Environmental aspects , Fisheries --Monitoring , Biotelemetry , Sustainable fisheries -- Africa, Southern , Overfishing -- Africa, Southern
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/60574 , vital:27798
  • Description: Movement of fishes is an integral part of their daily life, but has significant implications for fishery management. As with nearly all coastal countries, South Africa relies on coastal fisheries as a renewable resource, but many stocks have been overexploited for decades. Although it has long been recognised that an understanding of fish movement is necessary for effective management, it is with some difficulty that the subject has been studied in the past. In recent years, however, improvements in technology have provided the means for more in-depth investigations into fish movement. This research has revealed a range of complex movement behaviours. Movement in fishes occurs on a variety of temporal and spatial scales leading to the characteristic patterns of distribution and abundance observed in marine ecosystems. Fishes move nearly constantly in search of food, shelter or reproductive opportunities. Observations of behaviours such as long-term site fidelity, longdistance migration and natal homing are enabling ecologists to understand patterns of distribution and abundance within a species' range. Fish movement around the South African coast has been studied on numerous occasions but this has largely been confined to studies on single species. Movement behaviour of multiple species has been studied, but this has been limited to spatially localised marine protected area research. There has been little attempt in southern Africa to synthesize interspecific movement behaviour over wide spatial scales.Unprecedented concern over the biological effects of overexploitation, together with rapid technological advances in biotelemetry, have provided the impetus for much research, on a global scale, into the movement of marine animals. I reviewed 101 marine and estuarine fish movement studies from southern Africa, published from 1928 to 2014, with the aim of synthesising research trends and findings. Trends showed an increasing emphasis on fish movement research in publications in the sub-tropical and warm-temperate biogeographic regions along the south and east coasts of southern Africa. Although 63% of publications featured only marine studies, research into fine-scale habitat use in estuaries has been on the increase, concomitant with increasing accessibility of biotelemetry. Overall, 26 fish families were identified in the surveyed literature with regionally endemic sparids featuring in 32% of the publications. Ten movement themes were identified in the surveyed literature, including broad-scale movement patterns, which featured in 68% of studies, followed by fine- scale habitat usage (33%) and protected areas (26%). The most prominent phenomenon, emerging from this research, is that of partial migration, which describes the occurrence of resident and migratory behaviour within a coexisting animal population. Substantial progress has also been made in unravelling the complexities of fine-scale movements in marine reserves and habitat usage in estuaries. While this knowledge has enabled more effective management of South Africa's multi-user, multi-species fisheries, focus should now be directed at improving our understanding of the commonalities in movement behaviour, the associated driving forces behind this behaviour and the extent of movement across reserve boundaries. Mark-recapture data, collected over the past 30 years by the Oceanographic Research Institute’s Cooperative Fish Tagging Project (ORICFTP), were used to investigate broad- scale movement patterns of 30 prominent coastal fishery species (Chapter 4). Fishes were tagged with plastic dart tags along the coastline of southern Africa from Angola to Mozambique. This exercise yielded more than 10000 recaptures. The 30 chosen species represented 14 families, although 12 species belonged to a single family (Sparidae). Overall, 67% of recaptures were reported from the original tagging locality and 73% were recorded within 5 km of the tagging locality. The remaining observations extended from 6-3000 km. Movements were assigned to four distance bins (0-5 km, 6-50km, 51-500km and >500 km) and modelled with an ordinal logistic regression. Species, life-stage (juvenile/adult) and time- at-liberty were included as predictor variables. Model coefficients were then included in a cluster analysis, which produced two primary groupings of species (Category I and II), with two sub-groupings (Category IIa and IIb). Category I species were characterised by wide-ranging movements, greatest median recapture length and highest trophic levels. Category II species were characterised by residency, lower median recapture length and lower trophic levels. These findings have implications for fisheries management. Exploitation of resident species may lead to localised depletion, but their diffuse spatial distribution may offer some resilience. In contrast, even localised targeting of migratory species may pose a population level risk if individuals are known to aggregate. Life-cycle diversity or intra-population variability describes the existence of alternative strategies or tactics among coexisting individuals within an animal population (Chapter 5). Partial migration is a specific case of life-cycle diversity where coexisting groups exhibit either resident or migratory (wide-ranging) behaviour within a single population. Mark- recapture data collected under the auspices of the ORICFTP were used to investigate the occurrence and nature of life-cycle diversity in the movement behaviour of five non- diadromous fish species around the coastline of southern Africa. Among the five species were three teleosts (Category I and IIa) and two elasmobranchs (Category I). A fish was considered to have remained resident if recaptured within 0-5 km after 365 days at liberty. A fish was considered to have undertaken a wide-ranging movement if recaptured more than 50 km away from the release site in 365 days or less. A total of 1848 individuals from the five study species were recaptured during the study, of which 73% of the observations were classified as being resident. Binomial logistic regression confirmed that species, life-stage (juvenile/adult) and ecoregion were significant (p < 0.001) predictors of the probability of wide-ranging behaviour. A Gaussian model confirmed that species and ecoregion were also significant (p < 0.001) predictors of direction and distance of wide-ranging movement. However, the direction and distance of wide-ranging movements in juveniles did not differ significantly (p > 0.05) to that of adults. The median growth rate was mostly greater in wide- ranging individuals; however, this was only statistically significant (p < 0.05) in two cases. These findings provide unequivocal evidence of life-cycle diversity in five fish species, with vastly different life-histories. This ecological phenomenon may provide species resilience at the population level and needs to be considered in fisheries management initiatives. The movement of fishes is a fundamental aspect to consider when designing fishery management regimes. Unfortunately, traditional management strategies have often disregarded movement behaviour to the detriment of fish populations (Chapter 6). As a case study, the management of Lichia amia (Category I: wide-ranging) was evaluated in the context of its movement behaviour. Long-term catch-per-unit-effort (CPUE) datasets were examined for three South African recreational fishery sectors. The CPUE was standardised using generalized linear models (delta-Gamma/hurdle approach) to reduce the effect of factors other than abundance. Factors that were available for this purpose were year, month and locality/zone. Year was included in every model as the primary objective was to detect trends in abundance over time. Although standardised CPUE for all sectors showed an overall long-term decline, there was considerable variability in trends between the different recreational sectors and between datasets. Contrasting trends between competitive shore angling and general shore angling datasets were ascribed to hyperstability in competitive CPUE data. Hyperstability in this case was mostly influenced by rapidly improving technology, techniques and communication networks amongst competitive anglers. Month and locality were significant factors explaining the probability of catching L. amia. This suggests that the predictable aggregatory behaviour of this species could further compound the observed CPUE hyperstability. Although the CPUE responded positively for six years after implementation of the first minimum size and bag limits, and for one year after the decommercialisation of the species, these regulations and their amendments failed to arrest a long-term decline in the CPUE despite the ample evidence for hyperstability. It is clear from this case study that the predictable nature of wide-ranging behaviour in L. amia has made the population vulnerable to exploitation. This has led to the demise in the population, which could have been worse if not for the occurrence of intra-population variability in its movement behaviour, which may provide some measure of resilience.
  • Full Text:
  • Date Issued: 2018

Quantification of pre-competitive sleep/wake behaviour in a sample of South African cyclists

  • Authors: Steenekamp, Travis
  • Date: 2018
  • Subjects: Sleep deprivation , Cyclists Health and hygiene South Africa , Sleep Physiological aspects , Performance , Performance anxiety
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/59015 , vital:27408
  • Description: The quantification of athlete pre-competitive sleep behaviour is of interest owing to the possibility that sleep loss may have a negative effect on health and performance. The purpose of this study was to monitor and quantify the sleep/wake patterns of South African cyclists prior to competitive races. A total of 336 cyclists, male and female and of differing competition levels, cycling in either the 2015 Tsogo Sun Amashova or the 2016 Telkom 94.7 Cycle Challenge completed an altered version of the Competitive Sports and Sleep Questionnaire. The questionnaire asked cyclists to report on precompetitive sleep over the past year. A subset of 92 cyclists also recorded a Core Consensus Sleep Diary for the three nights leading up to the races. The questionnaire showed that 67% of the cyclists reported worsened sleep at least once prior to competition within the past 12 months. The sleep diary found that the cyclists’ average sleep duration the night before the races was 6h19min (±1h38min), which was significantly less than two and three nights prior to the races. Sleep quality was also shown to deteriorate significantly the night before the races. The contributing factors leading to worsened pre-competitive sleep were the time the cyclists had to wake-up as well as perceived increases in sleep latency and awakenings after sleep onset. Anxiety was found to be the major cause of sleep disturbances. While females were found to be significantly more likely to report having experienced poorer sleep before competition in the past year, the sleep diary showed no difference in sleep the night before the races between the sexes. Females were significantly more likely to report instances of unpleasant dreams and waking up during the night. Again, the sleep diary data did not corroborate these findings. Females were also found to report significantly more accounts of nervousness or thoughts about competition as being the cause of sleep problems. There was no difference in sleep loss the night before competition when comparing competition-level groups. The only significant difference was that recreational cyclists were more likely to report sleeping in foreign environments as a cause of sleep disturbances. Despite a large percentage of cyclists experiencing pre-competitive sleep loss, over half (55%) perceived sleep loss to have no impact on their performance. Analysis of pre-sleep behaviour also revealed that the cyclists engaged in several practices that may have a negative effect on subsequent sleep. The vast majority of the cyclists (61%) indicated having no specific strategy to help them sleep the night before competition. Fifteen percent of cyclists reporting using media devices to help them fall asleep, a practice that has been shown to disrupt sleep. In conclusion, most cyclists, regardless of sex and level of competition experience precompetitive sleep loss attributed largely to anxiety but with the perception that this loss in sleep does not negatively impact their performance.
  • Full Text:
  • Date Issued: 2018

Strength and conditioning practices of high school rugby coaches: a South African context

  • Authors: Robinson, Bradley Charles
  • Date: 2018
  • Subjects: Rugby football coaches South Africa , Rugby football Coaching , Rugby football Physiological aspects , Rugby football Training , High school students Social conditions
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/63459 , vital:28413
  • Description: Although the sport of rugby union is well established, the strength and conditioning practices of high school level players are not well known. Therefore, the purpose of this study was to examine the current strength and conditioning practices that coaches implement at South African high school level rugby. A secondary purpose was to compare practices between different types of schooling systems available in South Africa. An online survey or in person interview (depending on the school), adapted from previous strength and conditioning questionnaires, was conducted with 43 responses; including 28 schools among the top 100 rugby schools in South Africa for 2016 and 15 no-fee paying public schools in the Eastern Cape Province of South Africa. Results indicated that the top 100 rugby schools implement conditioning practices similar to the best-known international practices compared to no-fee paying schools who lacked the knowledge and skills in various strength and conditioning principles. It was found that all no-fee paying school coaches had insufficient qualifications to administer the correct training techniques. Coaches at all schools lacked the appropriate knowledge on injury prevention and scientifically based training programmes. It was concluded that education and skills around the best strength and conditioning practices for school level coaches needs to be improved and particularly in less privileged schools. The main goal being to reduce the risk of injury and improve performance across all sectors of the rugby playing population within the country. This was deemed crucial to the transformation goals set out by the South African Rugby Union, which would benefit from player development in lower socioeconomic schools.
  • Full Text:
  • Date Issued: 2018

Reliability analysis: assessment of hardware and human reliability

  • Authors: Mafu, Masakheke
  • Date: 2017
  • Subjects: Bayesian statistical decision theory , Reliability (Engineering) , Human machine systems , Probabilities , Markov processes
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/6280 , vital:21077
  • Description: Most reliability analyses involve the analysis of binary data. Practitioners in the field of reliability place great emphasis on analysing the time periods over which items or systems function (failure time analyses), which make use of different statistical models. This study intends to introduce, review and investigate four statistical models for modeling failure times of non-repairable items, and to utilise a Bayesian methodology to achieve this. The exponential, Rayleigh, gamma and Weibull distributions will be considered. The performance of the two non-informative priors will be investigated. An application of two failure time distributions will be carried out. To meet these objectives, the failure rate and the reliability functions of failure time distributions are calculated. Two non-informative priors, the Jeffreys prior and the general divergence prior, and the corresponding posteriors are derived for each distribution. Simulation studies for each distribution are carried out, where the coverage rates and credible intervals lengths are calculated and the results of these are discussed. The gamma distribution and the Weibull distribution are applied to failure time data.The Jeffreys prior is found to have better coverage rate than the general divergence prior. The general divergence shows undercoverage when used with the Rayleigh distribution. The Jeffreys prior produces coverage rates that are conservative when used with the exponential distribution. These priors give, on average, the same average interval lengths and increase as the value of the parameter increases. Both priors perform similar when used with the gamma distribution and the Weibull distribution. A thorough discussion and review of human reliability analysis (HRA) techniques will be considered. Twenty human reliability analysis (HRA) techniques are discussed; providing a background, description and advantages and disadvantages for each. Case studies in the nuclear industry, railway industry, and aviation industry are presented to show the importance and applications of HRA. Human error has been shown to be the major contributor to system failure.
  • Full Text:
  • Date Issued: 2017

Treatment of anaerobically digested brewery effluent in high rate algal ponds: an understanding of the microbial community structure in the ponds and the underlying mechanisms responsible for nutrient removal from the effluent

A study of South African computer users' password usage habits and attitude towards password security

  • Authors: Friendman, Brandon
  • Date: 2014
  • Subjects: Computers -- Access control -- Passwords , Computer users -- Attitudes , Internet -- Access control , Internet -- Security measures , Internet -- Management , Data protection
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: vital:4700
  • Description: The challenge of having to create and remember a secure password for each user account has become a problem for many computer users and can lead to bad password management practices. Simpler and less secure passwords are often selected and are regularly reused across multiple user accounts. Computer users within corporations and institutions are subject to password policies, policies which require users to create passwords of a specified length and composition and change passwords regularly. These policies often prevent users from reusing previous selected passwords. Security vendors and professionals have sought to improve or even replace password authentication. Technologies such as multi-factor authentication and single sign-on have been developed to complement or even replace password authentication. The objective of the study was to investigate the password habits of South African computer and internet users. The aim was to assess their attitudes toward password security, to determine whether password policies a↵ect the manner in which they manage their passwords and to investigate their exposure to alternate authentication technologies. The results from the online survey demonstrated that password practices of the participants across their professional and personal contexts were generally insecure. Participants often used shorter, simpler and ultimately less secure passwords. Participants would try to memorise all of their passwords or reuse the same password on most of their accounts. Many participants had not received any security awareness training, and additional security technologies (such as multi-factor authentication or password managers) were seldom used or provided to them. The password policies encountered by the participants in their organisations did little towards encouraging the users to apply more secure password practices. Users lack the knowledge and understanding about password security as they had received little or no training pertaining to it.
  • Full Text:
  • Date Issued: 2014

The risks of civil engineering project development in emerging nations

  • Authors: Fyvie, Richard Michael
  • Date: 2010
  • Subjects: Engineering -- Management , Engineering firms -- South Africa , Construction industry -- Management , Project management -- South Africa , Civil engineering -- Africa
  • Language: English
  • Type: Thesis , Masters , MBA
  • Identifier: vital:8632 , http://hdl.handle.net/10948/1481 , Engineering -- Management , Engineering firms -- South Africa , Construction industry -- Management , Project management -- South Africa , Civil engineering -- Africa
  • Description: This research reviews the challenges and obstacles confronting multinational civil engineering consulting and contracting companies seeking to conduct project developments within Emerging Markets, specifically with regard to the regions of Africa and the Middle East. With the increasing convergence of the global economy towards an interconnected and co-dependant system, the emerging economies of previously underdeveloped parts of the world are now capturing the focus of the civil engineering industry as the primary area of operation. Multinational companies that historically were restricted to construction of the developed world must now adapt and reposition themselves with a footprint in these emerging markets, if they are to take advantage of the changing conditions within the global infrastructure construction industry. For companies historically unfamiliar with operating in Africa and the Middle East, a plethora of potential risks are associated with project development. This research incorporated a substantial literature study that determined a number of critical issues that directly and indirectly influence a company’s ability to complete a project within time and under budget. The literature bank was then tested against the expert opinions of four selected respondents utilising a case study research methodology, as detailed by Yin (1994: 1-17). The respondents represented two selected civil engineering consulting firms, one based in a developed country with an extensive interest in the Middle East, and the other based in an emerging country itself, with operations throughout Africa. The outcome of the research ii highlighted several internal risk factors affecting development in Africa and the Middle East, such as capacity, staff experience, available resources and corporate culture. External factors were, however, the primary focus of respondents’ feedback, and included the reliability of energy supply in the target country, the condition of the built infrastructure such as roads and ports, tax rates and cost of finance, the prevalence of corruption as well as the risk of civil conflict and political instability. The Project Risk Guideline was the final output of this research process, which represented a synthesis between the literature review, the case study investigations as well as synthesis of various accepted risk evaluation techniques. The Guideline is a stage-gate sequential process, and may be utilised by civil engineering consulting or contracting firms with an interest in risk profiling and mitigation for project developments in emerging nations.
  • Full Text:
  • Date Issued: 2010

Changes in energy use patterns in the Bushbuckridge Lowveld of the Limpopo Province, South Africa: eleven years on

  • Authors: Madubansi, Mainza
  • Date: 2004
  • Subjects: Energy consumption -- South Africa -- Limpopo
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4756 , http://hdl.handle.net/10962/d1007139 , Energy consumption -- South Africa -- Limpopo
  • Description: This research reports on the energy transition that has taken place in the Bushbuckridge district between 1991 and 2002. It is a follow up to a similar study that was done in 1991 investigating a number of aspects of energy use. It uses the 1991 study as a baseline and aims to explore how the passage of time, growth of the local population and changes in incomes and the availability of fuels have affected the patterns of fuel use in the region in the past eleven years. A structured interview approach was used for most aspects of the study. The interview schedule included sections on types, amounts and reasons for use and non-use of 13 different energy sources as well as data on income levels, household size and other economic parameters. Analysis of the consumption patterns of the different fuel types revealed that between the two survey periods, households in the sample settlements went through some pronounced changes in patterns of fuel use, particularly those that had acquired electricity. The introduction of electricity in the region had certainly played a major role in spurring the energy transition. Fuels that were previously used for lighting, powering entertainment appliances and refrigeration had been displaced by electricity. In terms of cooking and other thermal application, however, the vast majority of households in all the sample settlements continued using fuelwood and complemented it to a lesser extent with paraffin and electricity. In both surveys, the use or non-use of available fuels in the region was influenced by several factors. Common reasons for non-use of certain fuel types included expense, lack of appliances, the risk involved in using such fuels and the preference for other fuels. Reasons for use were mainly related to the low cost of the fuel and the fuel’s ability to meet particular end uses. Although incomes in the region had increased between 1991 and 2002, they were still below the poverty line. Activities from which households obtained their income remained the same. Old age pension, migrant wages and the informal sector remained the largest contributors of income to most households. Other indicators of relative wealth and poverty, like ownership of vehicles, bicycles and beds remained the same.
  • Full Text:
  • Date Issued: 2004
  • Disclaimer
  • Privacy
  • Copyright
  • Contact