Research Publications/Outputs

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10-year statistical study of double stratopause structure as observed by lidar over a southern sub-tropical site, Reunion Island (21°S, 55°E)
(2006-07) Sivakumar, V; Faduilhe, D; Bencherif, H
The lidar data collected for about 10 year’s period from 1994 to 2004 are used for the present study. The recorded raw data is in the form of photon count profiles with a height resolution of 300 m and time resolution of 120s. The method of deriving the temperature profile from the measured photon count profile closely follows the method adopted by Hauchecorne and Chanin [1980]
130000-year-old fossil elephant found near Durban, South-Africa: preliminary-report
(Bureau Scientific Publications, 1993-04) Ramsay, PJ; Smith, AM; Lee-Thorp, JC; Vogel, JC; Tyldsley, M; Kidwell, W
A modern African elephant tusk was discovered within a late Pleistocene aeolianite at Reunion Rocks, south of Durban. Ionium dating indicates that the tusk is older than 112 kyr BP with stratigraphic control suggesting a date at ca. 130 kyr BP. Preliminary carbon stable-isotopic analyses indicate that the elephant was a grass-grazer. Strontium isotopic analyses indicate a marine signature: this implies that the tusk suffered marine diagenesis or that the elephant accumulated a marine strontium isotope signature by living along the coastline.
1910–2010: How infrastructure grew our nation
(South African Institution of Civil Engineering, 2010-10) Wall, K
One hundred years ago this year, South Africa was established by an Act of Union. That Act gave us the shape and the texture that defined us as a nation. And it is wonderful that, despite all the exclusions and discriminations since May 1910, we have survived intact as a state and still live within those same, unchanged borders. While articles in the daily press earlier this year discussed political and governance aspects of how far we have travelled as a nation over the last 100 years, the author in this article reflects on infrastructure development and service delivery over the last century. Engineering infrastructure has indeed revolutionised the way we live, work, study, play, dispose of wastes, travel and communicate. Aircraft and the motor car, with improved roads, have revolutionised inter-city travel; the Internet (and Wiki) have revolutionised how learners prepare assignments; computers (and software) have revolutionised data sorting and analysis; aerial photography and satellite imagery have revolutionised map-making – the list could go on.
1st review of the status of national air quality: 1994-2004
(2006-10) Taviv, I; Zunckel, M; Mahema, T; John, Juanette; Naidoo, Mogesh
Need for informed decision making, history of fragmented and un-coordinated monitoring, framework for NAQIS-SAAQIS (output of NAQMPII) and metadata collection (output of NAQMPII).
2 DOF resolution adjustment laser position sensor
(Massey University, 2008-12) Shaik, A; Tlale, NS; Bright, G
A low cost sensor system is envisaged that has 2 distinct routes for resolution enhancement in position detection. The main area for application of the sensor design would be in the food processing and packaging industry where position resolution of the end effector is in the millimeter to submillimeter range. The sensor concept consists of a grid of laser light detectors attached to the stationary base and a grid of lasers attached to the mobile end effector. The photo detectors on the base provide one level for position detection enhancement, i.e. the density of the sensor array. The second degree of freedom in improvement comes from the strategic positioning of a set of lasers attached to the end effector.
20-year LiDAR observations of stratospheric sudden warming over a mid-latitude site, Observatoire de Haute Provence (44°N, 6°E): Case study and statistical characteristics
(Copernicus Publications, 2007-11) Charyulu, DV; Sivakumar, V; Bencherif, H; Kirgis, G; Hauchecorne, A; Rao, DN
The present study delineates the characteristics of Stratospheric Sudden Warming (SSW) events observed over the Observatoire de Haute Provence (OHP: 44°N, 6°E). The study uses 20 years of Rayleigh LiDAR temperature measurements for the 1982-2001 period, which corresponds to 2629 daily temperature profiles. The characteristics of warming events are presented in terms of type of warming (major and minor), magnitude of warming, height of occurrence, day and period of occurrence with emphasis on wave propagation and isentropic transport conditions. The major and minor warming events are classified with respect to temperature increase and reversal in the zonal wind direction in the polar region using National Centre for Environmental Prediction (NCEP) reanalysis data. SSWs occur with a mean frequency of 2.15 events per winter season. The percentages of occurrence of major and minor warming events are found to be ~23 % and ~77 %, respectively. The observed major and minor SSW is associated with descent of stratopause layer by -6 to 6 km range. The height of occurrences of major SSW are distributed between 38 km and 54 km with magnitude in the 12.2-35.7 K temperature range, while the minor SSW appear in 42-54 km range, closer to the usual stratopause layer (~47 km) and with a slightly larger range of temperature magnitude (10.2-32.8 K). The observed major and minor events are examined in connection with Quasi-Biennial Oscillation (QBO) phases and presented.
The 2011 municipal elections in South Africa and new trends since the 2009 national elections
(Operations Society of South Africa, 2011-09) Greben, JM; Elphinstone, CD; Holloway, Jennifer P
The CSIR has been involved in South African election night predictions since 1999 using a cluster prediction model based on the segmentation of the electorate according to voting behavior. In this paper these clusters are exploited in another way. Different clusters are related to different demographic groups, and an analysis is made how these different groups change their affiliation between subsequent elections. The changes in affiliation are determined by calculating a trend matrix, a new tool in elections that was introduced by one of the authors a few years ago. By comparing trend matrices between municipal (2006, 2011) and national elections (2004 and 2009) one can establish whether the observed trends are incidental or have a more generic character. It is felt that a better understanding of the voter behavior through such analyses can enhance the value of elections and thereby promote democracy.
2014 Election forecast - a post-election analysis
(Operations Research Society of South Africa (ORSSA), 2017-06) Ittmann, HW; Holloway, Jennifer P; Dudeni-Tlhone, Nontembeko
General elections are held every five years in South Africa. During the 12 to 24 hour period after the close of the voting booths, the expected final results are of huge interest to the electorate and politicians. In the past, the Council for Scientific and Industrial Research (CSIR) has developed an election forecasting model in order to provide the media and political analysts with forecasts of the final results during this period of peak interest. In formulating this model, which forecasts the election results as the results from voting districts (VDs) become available, some assumptions had to be made. In particular, assumptions were made about the clustering of previous voting patterns as well as the order in which VD results are released. This election forecasting model had been used successfully for a number of elections in the past and in these previous elections, with around 5% {10% of the results available, the predictions produced by the model were very close to the final outcome, particularly for the ANC, being the largest party. For the 2014 national election, however, the predictions, with close to 50% of the voting district results known (equivalent to an estimated 40% of the total votes), were still not accurate and varied by more than 1% for both the ANC and the EFF. This paper outlines a post-election analysis to determine the reasons for these discrepancies and how they relate directly to the model assumptions. The aim is to highlight how practical realities can affect the assumptions and consequently their impact on the forecasted results. Reference is made to previous election forecasts and the 2014 post-election analysis is presented.
The 2020 WMO symposium on climatological, meteorological and environmental factors in the COVID-19 pandemic: A special issue from symposium presentations
(2021-06) Sweijd, Neville; Zaitchik, BF
The COVID-19 pandemic has become one of the great historical events of the modern era, presenting a generational challenge to the world. Questions about the role of weather on SARS-CoV-2 transmission led to the gathering of scientists at an online event, the “International Virtual Symposium on Climatological, Meteorological and Environmental factors in the COVID-19 pandemic,” convened on 4–6 August 2020 under the auspices of the World Meteorological Organization. This collection of papers arise from the Symposium.
25m2 target-aligned heliostat with closed-loop control
(2007-09) Roos, TH; Zwane, NX; Kruger, E; Perumal, S; Cathro, R
A 252m target-aligned research heliostat with closed-loop control, with a theoretical concentration of 80 suns, has been built at CSIR in South Africa. The heliostat has four degrees of freedom: Azimuth, Elevation, Rotation and Pitch. A control system making use of a solar tracker has been developed and tested on a 1.252m target-aligned miniheliostat. A tracking accuracy of 3.3 milliradians was obtained. A good focal spot has been obtained with the 252m target-aligned research heliostat.
2D Methods for pose invariant face recognition
(IEEE, 2016-12) Mokoena, Ntabiseng; Djonon Tsague, Hippolyte; Helberg, A
The ability to recognise face images under random pose is a task that is done effortlessly by human beings. However, for a computer system, recognising face images under varying poses still remains an open research area. Face recognition across pose is the ability of a face recognition technology (FRT) to recognise face images in different viewpoints, i.e. recognition of face images that are out of the image plane. In this research work, a short literature survey of 2D techniques which are used to correct pose are discussed.The classification of these techniques is based on three categories, (1) Real-view based matching, (2) Image space pose transformation and (3) Feature space pose transformation. This paper discuss the types of databases used, approaches to correct pose, the types of features extracted.
2D numerical model for heat transfer on a laser deposited high entropy alloy baseplate using Comsol Multiphysics
(2021-12) Dada, A; Popoola, P; Mathe, Ntombizodwa R; Adeosun, S; Aramide, O
In an optimization study, cracks were observed in the microstructures of laser-deposited HEAs on a steel baseplate from residual stresses, thus, the optimization of crack-free microstructures was achieved by the optimization of the laser parameters by baseplate preheating attributed to the lowering of the thermal gradients of the deposition process. This study reports the finite element analysis on the temperature distribution by the moving laser modelled to achieve process optimization with the necessary boundary conditions. Simulation has been reported as a facilitating tool in predicting the behaviour of materials during process optimization. Comsol Multiphysics 4.4, was used to create a 2D transient heat transfer time-dependent model to simulate the temperature distribution and the laser heating of the A301 steel baseplate surface and determine the effect of temperature on the optimization process of the alloys. Gaussian profiles were used as the heat source distributed per time. The results are presented in terms of thermal fields and Gaussian temperature profiles. Which show the temperature distribution that occurred in the steel baseplate during fabrication and the high cooling rate of the laser additive manufacturing technique restricted thermal stresses, improving adhesion and facilitating the optimization process.
3-D breast anthropometry of plus-sized women in South Africa
(Taylor & Francis, 2011-09) Pandarum, R; Winnie, Y; Hunter, Lawrance
Exploratory retail studies in South Africa indicate that plus-sized women experience problems and dissatisfaction with poorly fitting bras. The lack of 3-D anthropometric studies for the plus-size women's bra market initiated this research. 3-D body torso measurements were collected from a convenience sample of 176 plus-sized women in South Africa. 3-D breast measurements extracted from the TC(2) NX12-3-D body scanner 'breast module' software were compared with traditional tape measurements. Regression equations show that the two methods of measurement were highly correlated although, on average, the bra cup size determining factor 'bust minus underbust' obtained from the 3-D method is approximately 11% smaller than that of the manual method. It was concluded that the total bust volume correlated with the quadrant volume (r = 0.81), cup length, bust length and bust prominence, should be selected as the overall measure of bust size and not the traditional bust girth and the underbust measurement. Statement of Relevance: This study contributes new data and adds to the knowledge base of anthropometry and consumer ergonomics on bra fit and support, published in this, the Ergonomics Journal, by Chen et al. (2010) on bra fit and White et al. (2009) on breast support during overground running.
3-substituted anilines as scaffolds for the construction of glutamine synthetase and DXP-reductoisomerase inhibitors
(Taylor & Francis, 2009-01) Mutorwa, M; Salisu, S; Blatch, GL; Kenyon, C; Kaye, PT
Access to a series of truncated ATP analogs, as potential anti-tuberculosis agents, has been explored via alkylation and acylation of 3-aminophenol, whereas chloroacetylation, using chloroacetyl chloride, and subsequent Arbuzov phosphonation of a series of 3-substituted anilines have afforded a series of phosphonate derivatives as potential antimalarial agents.
330 mJ single-frequency Ho:YLF slab amplifier
(Optical Society of America, 2013-04) Strauss, Hencharl J; Preussler, D; Esser, MJD; Koen, W; Jacobs, Cobus; Collett, OJP; Bollig, C
We report on a double-pass Ho:YLF slab amplifier which delivered 350 ns long single-frequency pulses of up to 330 mJ at 2064 nm, with a maximum M(sup2) of 1.5 at 50 Hz. It was end pumped with a diode-pumped Tm:YLF slab laser and seeded with up to 50 mJ of single-frequency pulses.
3D edge detection seismic attributes used to map potential conduits for water and methane in deep gold mines in the Witwatersrand basin, South Africa
(Society of Exploration Geophysicists, 2012-09) Manzi, MSD; Durrheim, RJ; Hein, KAA; King, N
Inrushes of ground water and the ignition of flammable gases pose risks to workers in deep South African gold mines. Large volumes of water may be stored in solution cavities in dolomitic rocks that overlie the Black Reef (BLR) Formation, while there are several possible sources for methane, namely, coal seams, kerogen found in some gold ore bodies, or methane introduced by igneous intrusions. Potential conduits that may transport water and methane to underground workings were mapped using 3D reflection seismic data. Edge detection attributes successfully identified many faults, some with displacements as small as 10 m. Faults that displace the Ventersdorp Contact Reef (VCR) and the BLR horizons were of special interest, as known occurrences of fissure water and methane in underground workings show a good correlation with faults that were imaged on the VCR and BLR horizons. Because there are uncertainties in determining the linkage of faults with aquifers and methane sources, it is considered prudent to assume that all structures that displace the VCR and BLR horizons are potential conduits.
3D evaluation of fine-scale normalised DSMs in urban settings
(2020-09) Breytenbach, Andre
Humankind often needs to accurately model, identify and spatially quantify aboveground phenomena on the Earth’s surface for informed decision-making. Height data derived from digital elevation models (DEMs) is often used to achieve this. This study conducted a deterministic assessment of three normalised digital surface models (nDSMs) of different spatial resolutions, namely 2m, 4m and 12m, derived from VHR digital stereo aerial photography, tri-stereo Pléiades imagery and Tandem-X InSAR data, respectively. Covering a predominantly built-up area within a city landscape, the nDSMs were vertically and volumetrically compared to assess their quality and fit-for-use. In each case a consistent systematic evaluation was accomplished against a lidar derived reference surface at matching spatial resolutions (co-registered) using a semi-automated GIS routine. The relative height and volumetric errors were statistically analysed and described, including those computed individually over nine urban land cover/land use (LCLU) classes and several selected large buildings. Higher vertical accuracies were reported across single storey structures and areas with no to little or short vegetation, as apposed to substantially lower accuracies obtained over multi-levelled buildings and tall (dense) woody vegetation. Here significant underestimations of volumes exacerbated by lower spatial resolutions were also observed across each nDSM. Conversely, notable volume overestimations were found over predominantly grass-covered areas in especially the finer-scaled nDSMs. VHR elevation data is recommended to model and quantify aboveground elements spatially in 3D (e.g. buildings, earthworks and woody vegetation) in urban landscapes, but a sensitivity test beforehand remains critical to ensure more reliable outcomes for users and stakeholders alike.
3D mapping and photogrammetry sensor payload for unmanned aerial vehicles
(2023-11) Purdon, Kyla; Van Niekerk, T; Phillips, R; Marais, Stephen T
Unmanned Aerial Vehicles (UAVs) have shown great potential for data collection and monitoring of areas. Sensors such as LiDARs and cameras can be used on UAVs for high-resolution data collection and used for various applications like Digital Surface Models (DSM), photogrammetry, inspection systems, and maintenance applications. This paper describes the design and implementation of a sensor payload for UAVs using a LiDAR sensor, camera, Inertial Measurement Unit (IMU), and Global Positioning System (GPS). The payload collects data that can be used to georeference LiDAR and camera data, which can later be used to generate a georeferenced map and perform object detection and classification.
A 3D potential field model of the Pilanesberg Complex shape and structure
(2013-10) Lee, SA; Webb, SJ; Jones, MQW; Durrheim, RJ; Ganerød, M
The Mesoproterozoic Pilanesberg Complex, South Africa, is the world’s largest alkaline intrusion. While surface field relationships suggest an inward dipping structure, it is unclear how these dips extend to depth. The 3D geometry of the Pilanesberg Complex is also unknown. 2D and 3D forward and inversion modelling of gravity and magnetic data are used to set limits on the 3D shape of the Complex. Based on age and chemical affinity, it is known that the Pilanesberg Complex forms part of a larger system of alkaline intrusions that includes two dyke swarms that radiate to the north-west and south of the Complex, as well as smaller circular clinopyroxene intrusions throughout the Bushveld Complex. The Pilanesberg dyke swarms and the circular clinopyroxenite intrusions are reversely magnetised to that of the normally magnetised Pilanesberg Complex, suggesting that a magnetic reversal occurred during emplacement of the system.
3D primary grain shapes resulting from semi-solid metal processing
(2017-07) Curle, Ulyate A
The issue regarding globular grain shape and size has been a topic for semi-solid processing since the discovery of the technique. Semi-solid rheo-processing takes advantage of cooling a liquid metal alloy to the solid + liquid phase field, while it is subjected to some form of turbulence during cooling. It has been suggested that the grains grow into spherical globules by observations of 2D microstructures. It is also known that reducing the melt super-heat has the effect of reducing the globule (grain) size. Are these 2D globules also spherical in shape in 3D or are these 2D shapes remnants of the 3D shapes after sectioning along planes? An Al-Si-Mg alloy is semi-solid processed using a patented processing coil that induces contactless stirring while simultaneously being cooled. Primary aluminium grains are extracted by an etch technique from a sample volume of the casting. The grain size distribution and shapes are analysed. The 3D particles are pictured with scanning electron microscopy. Various interesting particle shapes are observed, from simple to complex. The particle geometry in 3D is compared to 2D optical light microscopy micrographs. It is found that the 2D globules are remnant shapes from the 3D particles after sectioning along random planes.

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