Tshwane University of Technology
  • Pretoria, Gauteng, South Africa
Recent publications
To eliminate slip rings, brushes, and terminate gear-box mechanism, ferrite permanent magnet (PM) based counter rotating dual rotor PM flux switching generator (CRDRPMFSG) for direct drive counter rotating wind turbine (D <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> CRWT) application is proposed in this paper. Initially, the mechanism of gearless and brushless counter rotating wind power generation is discussed, and a simplified formulation opted for the slot/pole combinations. The proposed CRDRPMFSG encapsulate inner and outer machines with circumferentially magnetized PM enclosed by non-overlapped armature windings; thus, offering reduced overhang with compact design. However, co-axially linking the inner and outer machines through a shared stator yoke results in serious issues of magnetic coupling due to dual air-gap fields. To this end, eight topologies with various slot/pole combinations are comprehensively investigated using finite element analysis (FEA) for magnetic coupling effects and its influence on electromagnetic performance. From the analysis, it is shown that magnetic coupling level influence electromagnetic performance i.e., average torque, ripple rate, power factor, efficiency, losses, and output power. Moreover, it is noted that coupling level can be reduced by adopting same stator teeth in inner and outer machines or same stator teeth with different rotor poles. Finally, the predicted FEA calculations are verified experimentally with four benchmarked CRDRPMFSG prototypes.
COVID-19-related alcohol sales bans and stay-at-home orders prompted the alcohol industry in South Africa to increase their online alcohol sales promotions. We investigated changes in alcohol-related behaviour and the drivers of illegal alcohol sales through a self-reported Facebook survey that ran from July to November 2020. Questions included socio-demographics and comparison of alcohol purchasing behaviour and intake during 2019 and 2020. Statistical tests were applied to find associations between illegal alcohol purchasing and alcohol-related behaviours. A total of 792 participants took part in the survey, 69.7% of whom were female. During lockdown periods, most participants (55.3%) bought alcohol illegally from illegal outlets or friends. Online alcohol-delivery marketing increased by 20 percentage points from 2019 to 2020, with participants stating that they saw a lot of advertisements per day and 80% of persons under 25 years were not asked to verify their age in 2020 upon delivery. Home-brewed beer and vodka intake increased in 2020 during the alcohol sales bans. Men from the Western Cape who engaged in daily or weekly heavy episodic drinking were more prone to purchase alcohol illegally. The Western Cape, which is South Africa’s most prolific wine-producing region, had the highest odds of people buying alcohol illegally, with wine being found to be the most frequently bought alcohol online and consumed by these participants. There is a need for further research into the differences in alcohol-related behaviour affecting illegal alcohol purchasing according to income group, proximity to alcohol producers and underage alcohol sales and marketing through online applications.
We report on the detection of an organic pollutant mostly found in local streams and wastewater treatment plants, specifically on triclosan detected in the Umbogintwini Industrial Complex (UIC), located on the south coast of Durban, KwaZulu-Natal in South Africa. Triclosan was successfully extracted from effluent samples using molecularly imprinted membrane adsorbents (MIMs) before quantification and removal using high-performance liquid chromatography (HPLC). This was done through fabrication of a polyvinylidene fluoride polymer using selective microparticles and molecularly imprinted polymers by means of phase inversion and an immersion precipitation method which results in enhanced hydrophilicity and membrane performance. The optimisation of experimental parameters – i.e. contact time and sample size – was performed through different stages of analysis. The synthesised MIMs exhibited an outstanding adsorption efficiency of 97% for triclosan in relation to those of non-imprinted membranes (NIMs) and pristine membranes at 92% and 88%, respectively. The analytical method employed had limits of detection and quantification of 0.21 and 0.69 parts per billion (ppb or μg/L) in wastewater effluent, respectively. The obtained efficiency results show great potential for future use of membrane and molecular imprinting technology, and that MIMs can be adopted as adsorbents for water treatment. The fast and highly selective methodology presented in this work could also be employed for the examination of persistent organic pollutants in the future to combat water scarcity in South Africa.
Bacterial communities present in the host digestive tract are important for the breakdown and absorption of nutrients required by the host. Changes in diet and the environment are major factors affecting the composition and diversity of the fecal microbiome. In addition to changes in ambient temperature and rainfall, primates living in seasonal temperate environments also need to adapt to seasonal changes in food resource quantity and quality. However, there is a lack of information about the fecal microbiome in African strepsirrhines relative to other primate taxa. We examined the effects of seasonal dietary and environmental changes on fecal microbial alpha diversity and composition in wild greater thick-tailed galagos (Otolemur crassicaudatus) at Lajuma Research Centre, South Africa. We collected fecal samples and assessed food availability and weather in summer and winter across 1 year and used 16S rRNA next-generation sequencing to characterise the fecal microbiome of 49 animals. We found significant increases in rainfall, ambient temperature, and food availability in summer compared with winter. However, we found no significant changes in body mass or in the overall diversity of bacterial species present in fecal samples between the two seasons. We found significant decreases in the abundance of certain bacterial families in winter, suggesting a change in diet. Our findings suggest that greater thick-tailed galagos can find food resources to maintain their body mass throughout the year. Our insights into the seasonal fecal microbiome of greater thick-tailed galagos add to the growing knowledge and understanding of fecal microbiomes in primates and how they help primates cope with changes to their environments.
Quantitative analysis of materials from Heavy Ion PIXE spectra remains impeded by the lack of reliable X-ray production cross section (XPCS) data. Although efforts at experimental Heavy Ion induced XPCS measurements still continue, Multiple Ionisation (MI) effects, which are not fully described by theory, render simulations of heavy ion PIXE data unreliable for large Z1/Z2 collisions, especially at low energies. This is also exacerbated by the random selection of projectile-target combinations for measured and reported experimental data available to validate theory. This study explored heavy ion induced X-ray production cross section deviations from those induced by protons at the same ion velocity. This enabled evaluations of the degree to which cross sections are enhanced through MI effects, with the aim of predicting XPCS due to heavy ion impact. The evaluation was carried out through the scaling of experimental heavy ion to theoretical proton cross section ratios (R), which were then used for the interpolation of XPCS in the same target element for ‘missing’ projectiles within the range of evaluation. Here we present measurements of heavy ion induced total L-shell XPCS in Bi, carried out to determine HI/p MI induced deviations due to C, F, Cl and Ti projectiles at an ion velocity range of (0.2–1.0) MeV/nucleon.
After many years of apartheid rule, South Africa held its first democratic elections in 1994. As evident in the Constitution of the Republic of South Africa 1996, a commitment to establish developmental and human rights became an imperative doctrine. Three government spheres were established here: national, provincial and local. The latter is the sphere closest to the public and is constitutionally mandated to render and deliver sustainable essential services. Since 1994, significant strides have been made by the local sphere of government with both successes and failures. South Africa’s legal and policy framework transformation took place between 1993 and 2000 through changes in legislation, proclamations, white papers and by-laws. However, the elements of bad governance since 1994 have created a loss of confidence and service delivery hindrances in South African local government. Much of the population, especially the previously marginalised, face inadequate health services, unclean water and poorly maintained infrastructure and housing because some state institutions have become paralysed due to corruption and maladministration. This article aims to delve into the constitutional and legislative framework of local government in South Africa. The premise from which this article moves is that the quality of governance at the local government level directly impacts service delivery and is, therefore, critical to understanding some of the constitutional and legislative underpinnings driving local government. Municipalities should ensure that all actions and conducts comply with the statutes (acts of parliament, legislations and laws) and regulatory documents (white papers, official rules and regulations and by-laws) to local government.
Polymers are soft materials with large molecular chains, which are softened during frictional wear, leading to bulk detachment of materials and poor wear resistance in addition to their low mechanical strength and hardness. This study developed polypropylene nanocomposites containing hydrothermal assembled graphene and boron nitride (BN@GNs) with good mechanical properties and wear resistance. To ensure good dispersion of the nanoparticles in the polypropylene (PP) matrix, they were functionalized and preparation of masterbatch using polypropylene maleic anhydride (PPMA) was adopted, while the polymer nanocomposites for this study were developed via melt compounding. The addition of the nanoparticles in the PP matrix promoted its wear resistance as all the developed nanocomposites showed a low coefficient of friction (CoF). The wear rate of the nanocomposites was dramatically reduced to a minimum of 2.05 × 10 ⁻⁴ mm ³ /Nm for the PP/3wt%BN@GNs nanocomposite from around 24.9 × 10 ⁻⁴ mm ³ /Nm for the pure PP. The nanoindentation test results of the nanocomposites also revealed improvement in their nanomechanical characteristics. For instance, PP/3wt%BN@GNs nanocomposite showed an ideal increase of about 124% nano-hardness and 65.7% nano-elastic modulus when compared to pure PP. In comparison to pure PP, all of the developed nanocomposites displayed lower nano-percentage creep and nanoindenter’s tip penetration depth, which suggest greater plastic deformation resistance.
Plants of the genus Cordia (Boraginaceae family) are widely distributed in the tropical regions of America, Africa, and Asia. They are extensively used in folk medicine due to their rich medicinal properties. This review presents a comprehensive analysis of the isolation, structure, biogenesis, and biological properties of quinones from Cordia species reported from 1972 to 2023. Meroterpenoids were identified as the major quinones in most Cordia species and are reported as a chemotaxonomic markers of the Cordia. In addition to this property, quinones are reported to display a wider and broader spectrum of activities, are efficient scaffold in biological activity, compared to other classes of compounds reported in Cordia, hence our focus on the study of quinones reported from Cordia species. About 70 types of quinones have been isolated, while others have been identified by phytochemical screening or gas chromatography. Although the biosynthesis of quinones from Cordia species is not yet fully understood, previous reports suggest that they may be derived from geranyl pyrophosphate and an aromatic precursor unit, followed by oxidative cyclization of the allylic methyl group. Studies have demonstrated that quinones from this genus exhibit antifungal, larvicidal, antileishmanial, anti‐inflammatory, antibiofilm, antimycobacterial, antioxidant, antimalarial, neuroinhibitory, and hemolytic activities. In addition, they have been shown to exhibit remarkable cytotoxic effects against several cancer cell lines which is likely related to their ability to inhibit electron transport as well as oxidative phosphorylation, and generate reactive oxygen species (ROS). Their biological activities indicate potential utility in the development of new drugs, especially as active components in drug‐carrier systems, against a broad spectrum of pathogens and ailments.
Water pollution caused by emerging organic pollutants such as the halogenated organophosphate flame retardants, has exacerbated the issue of water scarcity. An eco-friendly technology, e.g., the adsorption technique, requires the use of affordable and safe adsorbents. Agricultural waste materials are promising adsorbents for wastewater remediation due to their relative abundance, biodegradability, non-toxic and cost-effective properties. However, most agricultural wastes are not ideal for adsorption in their raw forms and may require physical or chemical pre-treatments/modification, in order to increase the materials' compatibility and natural adsorption properties. Cellulose is an important constituent of plant residues that can be used as a precursor for the production of greener and sustainable industrial nanomaterials. Therefore, in this review, a discourse on the most recent approach/strategies for the modification of a range of agricultural wastes is presented. The result from their applications showed agricultural wastes has great prospects as adsorbents. The challenges encountered in the synthesis of plant-based adsorbents and the development of 3-D structured nanocomposites from cellulose, to circumvent these difficulties is extensively reviewed. Furthermore, the prospects in the application of cellulose beads/ZnO nanocomposites (CB-ZnO) derived from the maize tassel, for the adsorption of the halogenated organophosphate esters from aqueous matrices are presented in this review
The study investigated the effect of paraffin wax, expanded graphite, and their dispersion on the properties of the blend of polypropylene (PP) and ethylene vinyl acetate (EVA). The idea is to reduce interfacial tension in blends of PP and EVA while enhancing the properties of blends in the process. The chosen optimum contents of the paraffin wax and EG in the 80/20 PP/EVA blend were 10 and 6 wt.%, respectively. The morphological features show that the expanded graphite (EG) particles had high affinity for each other. Moreover, EG filler particles are localized inside the minor EVA phase and some at the interface. Rheological properties revealed that the flow of the binary composites increased when 10 wt.% wax is added suggesting that wax enhanced the processability of the composites. The Cole-Cole plots deviated from the semi-circular arc suggesting heterogeneity in the blend and PP/EVA/Wax/EG composite. The addition of paraffin wax and EVA delayed crystallization of PP, while earlier crystallization of PP was promoted by the presence of EG. Generally, all samples caught fire after 10 s, started dripping and are thus given a V-2 rating according to the Underwriters Laboratories test standard 94 results (UL-94).
Background Undernutrition, including stunting, continues to impact child health globally. Stunting remains persistent in low and middle-income countries, including South Africa. The Eastern Cape Province has a high stunting prevalence. Contributing factors include poor infant and young child feeding, lack of infant and young child feeding knowledge, and detrimental cultural-specific practices. Understanding specific barriers preventing improved infant and young child feeding is important to ensure the United Nations’ sustainable development goals are met by 2023. The Health Belief Model contributes to developing effective, cultural-specific nutrition education, resulting in positive behaviour change. Applying design thinking while developing education material encourages engagement with local stakeholders/communities to deliver cultural-specific content. This paper outlines the protocol designed to develop material for a community-based, cultural-specific infant and young child feeding education for mothers/caregivers living in rural areas of the Eastern Cape Province, South Africa. Methods The study will be conducted in three phases. Phase 1 will use qualitative and quantitative secondary data to conduct a situational analysis of socio-demographic factors, anthropometric profiles, and feeding practices of infants and young children (0–24 months). In Phase 2, a knowledge, practices, and perceptions questionnaire will be developed to quantify infant and young child feeding knowledge, practices and perceptions and to measure the impact of the intervention. Published literature, focus group discussions, and expert opinion will be used. Phase 3 will use the Health Belief Model to develop a conceptual framework, with design thinking constructs as a method to develop the content of the infant and young child feeding education material. Discussion This study will provide a detailed analysis of the situation in the community, develop a questionnaire to quantify the effect of knowledge, practices and perceptions on nutrition, and ultimately provide cultural-specific infant and young child feeding education material. It is anticipated that, when implemented, this approach will positively improve maternal/caregiver knowledge, practices and perceptions, provide valuable information on the impact of culture, and ultimately result in improved child growth and diet.
Two ruthenium polypyridyl complexes of the type [Ru(N^N)2(curc)](PF6) where curc = curcumin; [(1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl-1,6-heptadiene-3,5-dione)] and N^N = 2,2′-bipyridine (bpy, R1) and 1,10-phenanthroline (phen, R2) were synthesized. Spectroscopic methods and elemental analyses were employed to characterize them. It was revealed by the T Single-crystal X-ray crystallography that the solid-state structure of compound R1 as the hexafluorophosphate to be triclinic with space group P-1, a = 12.7668(4) Å, b = 13.9159(5) Å, c = 24.1777(8) Å, β = 91.466(2)o, V = 4233.1(2) Ǻ3, Z = 6. Four nitrogen atoms of the polypyridyl ligands and two oxygen atoms of the β-diketone group, respectively, formed the coordinates of Ru(II) center, and in turn forming a distorted octahedral geometry. The experiments have been compared to be in agreement with the theoretical vibrational wave numbers of the synthesized compounds. Density functional theory (DFT) at the ωB97XD/gen/def2svp/LanL2DZ level of theory has been further utilized in evaluating the structural and electronic properties. Against two different GBM proteins (6bft and 6s79), the binding affinities of the studied compounds and the standard drug (temozolomide) were obtained through the in silico molecular docking approach. R1@6bft, R1@6s79, R2@6bft and R2@6s79 reflect higher binding affinities of − 7 kcal/mol, − 10 kcal/mol, − 8 kcal/mol and − 12 kcal/mol, respectively, in comparison to the commercial drug with binding affinities of − 5 kcal/mol (Temo@6bft) and − 6.0 kcal/mol (Temo@6s79). With the results obtained, it is evident to mention that the compounds and their derivatives could be used as a potential chemotherapeutic drug for the treatment of glioblastoma or as a precursor for the synthesis of other pharmaceutical products.
This study aimed to investigate the sorption behaviour of South African coal seams with relation to the effect of temperature during CO 2 sequestration. The excess adsorption isotherms of CO 2 adsorption were undertaken using a high‐pressure volumetric system for four coals of different coal rank (denoted by Somkele [SK], anthracite KZN [AN], Tshikondeni [TD], and Syferfontein [SF]). The volumetric pressure step method was conducted at increments of system temperature of 35, 45, 55, and 65°C for pure CO 2 adsorption at incremental pressures up to 93 bar. The results showed that high temperatures have a very significant negative effect on the amount of CO 2 adsorbed on the coal samples. The high‐rank coal samples (SK and AN) demonstrated elevated CO 2 adsorption capacity across all tested temperatures due to their high vitrinite content. The medium‐rank coals (TD and SF) exhibited comparatively lower CO 2 adsorption capacity, attributed to the presence of adsorption hindrances such as higher ash content and volatile and mineral matter. The isosteric heat of adsorption revealed an increasing trend with coverage for all coal samples, with higher rank coals displaying greater slopes. The determined range of the isosteric heat of adsorption, spanning from 10 to 59 kJ/mol, indicated that the adsorption process is primarily of a physisorption nature. Three theoretical models (Langmuir, Freundlich, and Temkin) were evaluated and fitted to the sorption experimental data. The Temkin model exhibited superior fitting compared to the Langmuir and Freundlich isotherms. The Temkin isotherm parameters suggest that the adsorption of CO 2 onto coal is a physisorption process.
This study investigates the development of polyvinyl alcohol (PVA) and essential oil‐based biocomposite films incorporating halloysite nanotubes (HNTs) and cellulose nanocrystals (CNCs) as reinforcement materials for the packaging of papaya fruits to extend their postharvest shelf‐life. The fabrication process involves the dispersion of filler materials within the PVA polymer matrix, followed by the casting of the films using the solvent‐evaporation technique. The CNC isolated from the papaya peel exhibited rod‐like structures that were confirmed in the morphological studies. The films reinforced with HNT and CNC (5 wt%) had enhanced mechanical properties and exhibited a tensile strength of ~64.40 MPa. The findings of the study demonstrate that the fruits packed with biocomposite materials containing HNTs and CNCs as reinforcements and lemongrass essential oil as active material showed better performance when compared to the control. The edible quality and the storage life of the papaya fruits (TSS, firmness and weight loss %) under investigation were extended by 14 days at ambient temperature (25 °C ± 2 °C) and relative humidity (80%–85%), thus improving the postharvest shelf‐life of harvested papayas. Therefore, PVA‐based active packaging film prepared with lemongrass essential oil, HNTs and CNCs has great potential for the preservation of papaya during postharvest storage.
Before the COVID-19 pandemic, digital skills were becoming important for opera artists as technology continues transforming the performing arts industry worldwide. Digital performance in the opera industry emerged as a global phenomenon negatively affecting opera artists’ employability. Like opera artists from other emerging countries, South African opera artists are experiencing high unemployment due to changing industry skills. In the South African opera industry, the pandemic has fast-tracked the demand for digital skills for opera artists to produce work and reach global audiences. The absence of digital skills for opera artists in the performing arts industry has become a great concern. Framed within digital performance, this article discusses the importance of digital skills to South African opera artists to improve their employability. This article used a qualitative research approach to review scholarly writings and to undertake interviews with selected opera companies and opera artists. The findings confirm that South African opera artists’ lack of digital skills contributes to their increasing unemployment. This article finds that the swift advancement of technology creates a growing demand for digital performances, and thus digital skills are crucial for opera artists. This article concludes by affirming that acquiring digital skills can enable opera artists to adapt to the changing industry and expand their career opportunities.
Adopting green technologies is crucial for a sustainable supply process and organization development. In this construct, the current study analyzes how green technology adoption (GTA) and knowledge management (KM) processes could minimize supply risk in large manufacturing companies. The current study utilizes research techniques based on the resource-based view and contingency theories to minimize supply chain risk. The present study selected green variables (learning, productivity, raw materials, and resource utilization) along with KM processes (acquisition, sharing, and utilization) to investigate these connections to achieve the research objective. The author collected the data (203) from manufacturing firms in Zhengzhou city and used PLS-SEM, fuzzy set qualitative comparative analysis (fsQCA) to examine the study aims. The relationship between the adoption of green technologies and the KM process, which may reduce supply risk, was verified via PLS-SEM. fsQCA is employed as a combined strategy with green technology and the KM dimension to examine supply risk. The study results showed a significant correlation between the KM process’s ability to reduce supply risk under the GTA. The results of the fsQCA specify the numerous dimensions of green implementation enablers, and the KM process produced superior results in terms of supply risk minimization. This research contributes to bridging gaps and understanding the interrelationship between green measurement and the supply risk process minimization. The current study provides practical and social justification for enlightening the relationship between GTA and the KM process, aiming to minimize the supply risk. Based on the study outcome and ground information, this study reported limitations and future research direction.
Improving the efficiency of the legume–rhizobia symbiosis in African soils for increased grain yield would require the use of highly effective strains capable of nodulating a wide range of legume plants. This study assessed the photosynthetic functioning, N2 fixation, relative symbiotic effectiveness (%RSE) and C assimilation of 22 jack bean (Canavalia ensiformis L.) microsymbionts in Eswatini soils as a first step to identifying superior isolates for inoculant production. The results showed variable nodule number, nodule dry matter, shoot biomass and photosynthetic rates among the strains tested under glasshouse conditions. Both symbiotic parameters and C accumulation differed among the test isolates at the shoot, root and whole-plant levels. Although 7 of the 22 jack bean isolates showed much greater relative symbiotic efficiency than the commercial Bradyrhizobium strain XS21, only one isolate (TUTCEeS2) was statistically superior to the inoculant strain, which indicates its potential for use in inoculant formulation after field testing. Furthermore, the isolates that recorded high %RSE elicited greater amounts of fixed N.
An ensemble of classifiers combines several single classifiers to deliver a final prediction or classification decision. An increasingly provoking question is whether such an ensemble can outperform the single best classifier. If so, what form of ensemble learning system (also known as multiple classifier learning systems) yields the most significant benefits in the size or diversity of the ensemble? In this paper, the ability of ensemble learning to predict and identify factors that influence or contribute to autism spectrum disorder therapy (ASDT) for intervention purposes is investigated. Given that most interventions are typically short-term in nature, henceforth, developing a robotic system that will provide the best outcome and measurement of ASDT therapy has never been so critical. In this paper, the performance of five single classifiers against several multiple classifier learning systems in exploring and predicting ASDT is investigated using a dataset of behavioural data and robot-enhanced therapy against standard human treatment based on 3000 sessions and 300 h, recorded from 61 autistic children. Experimental results show statistically significant differences in performance among the single classifiers for ASDT prediction with decision trees as the more accurate classifier. The results further show multiple classifier learning systems (MCLS) achieving better performance for ASDT prediction (especially those ensembles with three core classifiers). Additionally, the results show bagging and boosting ensemble learning as robust when predicting ASDT with multi-stage design as the most dominant architecture. It also appears that eye contact and social interaction are the most critical contributing factors to the ASDT problem among children.
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Mulatu Fekadu Zerihun
  • Department of Economics
Rasigan Maharajh
  • Institute for Economic Research on Innovation (IERI)
Mario Scerri
  • Institute for Economic Research on Innovation (IERI)
Yskandar Hamam
  • Department of Electrical Engineering
0001, Pretoria, Gauteng, South Africa
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