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Exzellenz verbindet – be part of a worldwide network
No full textPresentations SA PhD Project Conference: Gauteng Province 11 October 2016
Managing the relationships
No full textPresentations SA PhD Project Conference: Gauteng Province 11 October 2016
Planning for NRF evaluation and rating
No full textPresentation DST-NRF Postdoctoral Forum: Cape Town 13-15 March 201
Effects Of Biological Handling Of Biomass On Energy, Environment And Food Sectors in the Eastern Cape
No full textGreen economy postdoctoral fellowships induction workshop 201
PD characteristics of typical MV XLPE power cable termination defects at VLF and power frequency test voltages
No full textIt has been reported in literature that newly installed cable accessories can pass
typical commissioning tests and yet show signi cant PD activity leading to premature
failure in the long term. This research report details the partial discharge (PD)
characterisation of three arti cial defects in MV cable terminations, at both power
and very low frequency (VLF). The defects included a semi-conductor feather, a
tram line in the cross-linked polyethylene (XLPE) insulation and an XLPE ring
cut. The experimental methodology involved subjecting the terminations to a
standard overvoltage withstand test, after which the PD activity was monitored,
at 0.1 Hz and at 50 Hz excitation frequencies. All the defects passed the overvoltage
test, despite some showing signi cant discharges. The defects gave distinct
phase-resolved PD patterns that are e ectively invariant of excitation frequency.
The PD magnitudes at power frequency were typically bigger than at VLF, while
the PD inception voltages tended to be lower at VLF. The PD magnitudes of
the semi-conductor feather defect surface discharges were found to increase with
increasing applied voltage, while no increase was observed for the tram line and
ring cut void discharges. The results show that common installation defects in MV
cable terminations can be suitably characterised using VLF PD measurementsNational Research Foundatio
A comparative analysis of development theories in ICTD research from developed and developing countries
No full textThe field of Information and Communication Technologies and Development
(ICTD) examines the relationship between contemporary information
and communication technology (ICT)s and societal development. By defi-
nition, such inquiry requires not only a deep understanding of the ICTs as
artefacts and systems themselves, but also direct engagement with the nature
of development. An initial review of ICTD literature indicates that there is a
lack of explicit engagement with the nature of development, and with existing
development theories from other fields, in ICTD literature. Rather, development
is often treated as a “black box” that can be incorporated into an ICTD
study without much further interrogation. This is problematic in light of (i)
the rich and complex historical discourse surrounding development, (ii) the
persistently contested nature of development in contemporary academic and
policy debates (particularly in the context of developing countries), and (iii)
the potentially pervasive practical and policy ramifications of differing conceptions
of development. Furthermore, conflicting theories of development are
to be expected in the field of ICTD itself, given its diversity in terms of (i)
the disciplines from which its scholars originate, (ii) sectors involved in the
field, and most importantly, (iii) the geographical spread of its scholars. Failing
to explicitly interrogate the development theories underlying ICTD studies
renders discourses in ICTD vulnerable to conceptual muddling, misinterpretation,
incommensurability, and most importantly, diminished relevance in a
world where there is undoubtedly diversity in how ‘development’ is understood.
The present study seeks to address the above-mentioned problematique
by examining engagement with development in ICTD literature against the backdrop of its scholars’ geographic diversity. This is done by comparatively
analysing the occurrence of development theories (drawn from broader discourses
on development) in ICTD literature from Global North (developed)
and Global South (developing) countries, respectively. A general pool of literature
is constructed from papers published in three leading ICTD journals —
Information Technology & International Development (ITID), the Electronic
Journal of Information Systems in Developing Countries (EJISDC), and Information
Technology for Development (ITD) — between 2008 and 2015. From
this pool, samples of literature from the Global North and literature from
the Global South are drawn. Directed content analysis is then employed to
qualitatively study the occurrence of development theories in the papers in
either sample. Finally, patterns arising within and across the two samples are
identified and discussed.
The results reveal that conceptions of and engagement with development
in ICTD are dominated by ideas from development economics, Keynesian economics,
and neoliberal economics — i.e. conventional theories of development
— generally, and Sen’s capability approach (focussing on expanding people’s
freedoms), new growth theory (focussing on the centrality of the knowledge
economy), and the Millenium Development Goals (MDGs) specifically. Further
findings include a general lack of critical perspectives on how development
is defined, incoherency in authors’ conceptions of development, and the general
latency of modernist ideas of development. Global South authors were
also found to engage less with development than their counterparts from the
Global North. The study contributes to a growing body of literature on the
‘D’ in ‘ICTD’ and supports the conclusion there is an urgent need to promote
greater engagement with development theory in ICTD.National Research Foundatio
Quantitative microstructural evaluation of 12 Cr creep aged steels after welding
No full textThis dissertation focuses on the quantitative microstructural evaluation of new and creep aged X20 (12 Cr) stainless steel after welding. X20 stainless steel has been widely used in the high temperature and pressure pipework of coal-fired power plants. Consequently, this material has to withstand extreme conditions of high temperature and stress during service exposure. Under these conditions, creep deteriorates the strength of the material. The material’s resistance to creep damage due to its microstructure can be quantitatively described by the back-stress. There are four microstructural contributions to the back-stress: Precipitate Hardening, Sub-Boundary Hardening, Solid-Solution Hardening and Dislocation Hardening. Fusion welding is performed on creep aged materials when a component needs to be replaced. This high temperature process results in the formation of different microstructural regions within the weldment. These creep damaged components have a weldability limit as set by the life management strategy of the power plant company. Measuring techniques capable of quantifying the microstructural contributions (precipitates, subgrains and dislocations) were developed and evaluated in this study. These techniques were then used to characterise the different microstructural regions within a new and creep aged X20 steel weldment. Differences in the microstructure of the new and creep aged X20 steel was illustrated by the results of this study. The measured size and number densities of the precipitates in the creep aged X20 material showed that there is a decrease in PH during creep exposure. There was a decrease in SBH and DH stress for the creep aged X20 material due to coarsening of the subgrains and annealing of dislocations during creep exposure. The quantitative techniques demonstrated in this study opens up the possibility to perform life assessment on weldments with inhomogeneous microstructures by following a microstructural based approach.National Research Foundatio
High levels of genetic structure and striking phenotypic variability in a sexually dimorphic suckermouth catfish from the African Highveld
No full textUncovering biological diversity to more accurately understand diversity patterns, and ultimately the processes
driving diversification, is important not only from an evolutionary perspective but also a conservation
perspective. This is particularly pertinent in Africa’s rivers in which overall diversity, as well as how it arose, is
poorly understood in comparison with lacustrine environments. Here we investigate population divergence in the
sexually dimorphic suckermouth catfish species Chiloglanis anoterus (Crass, 1960) from the African Highveld, in
which we observe striking variability in exaggerated male caudal fins across its range. As this trait is likely to be
indirect evidence for sexual selection by female choice, a mechanism that has been shown to increase species
diversity in different taxa, we used an integrated approach to test if current diversity in this species is
underestimated. Results based on phylogenetic inference, population genetics and geometric morphometrics
indicate that the recognized species C. anoterus represents five distinct lineages that may be considered
confirmed candidate species. We suggest that diversification in these highland catfish has been facilitated
through geographical isolation in upper river catchments, and that sexual selection through female choice has
probably driven variation in male caudal fin morphology. In contrast to the relatively large range size of the
currently recognized species (C. anoterus), our findings highlight highly restricted ranges of the lineages
identified here, indicating that these highland habitats may harbour higher levels of endemic diversity than
previously thought
Microwave treatment: a facile method for the solid state modification of potassium-promoted iron on silica Fischer–Tropsch catalysts
No full textPotassium-promoted (0–1.5 wt%) iron–silica catalysts for Fischer–Tropsch synthesis (FTS) have been modified using microwave radiation. Radiation produced few or no modifications in the bulk properties, but surface and catalytic behaviour were markedly changed in K promoted 10 wt% of Fe/SiO2 (10Fe/SiO2) catalysts. The effect of potassium on CO adsorption was relatively insignificant in untreated catalysts, but was large in microwave-modified catalysts. Radiation induced an increase in CH4 formation in CO + H2 temperature programmed surface reactions. Microwave treatment promoted CH4 formation from graphitic carbon in these catalysts, while decreasing CH4 formation from α- and β-carbon species, and overall favoured strong CO adsorption onto the catalyst surface. Microwave effects were catalyst particle size and treatment duration-dependent. At low alkali concentration, microwaved samples showed improved ethene selectivities, higher alpha values and lower methane and light alkene selectivities. When 0.7 wt% K was added to the 10Fe/SiO2 catalyst, the α value increased from 0.59 to 0.66 after treatment of the sample with microwave radiation in the solid state.National Research Foundation (South Africa