TUT DIGITAL OPEN REPOSITORY

By introducing a state feedback control to a proposed four-dimensional chaotic system, an extremely complex four-wing chaotic attractor is derived having larger positive Lyapunov Exponent (LE) than other chaotic systems. Spectral analysis shows that the system in the four-wing chaotic mode has very broad frequency bandwidth, verifying its random nature, and indicating the prospect for engineering applications such as secure communications. Finally, an analog circuit, implementing the new four-wing chaotic system, is presented.

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants widely detected in water and sediment worldwide. Despite growing concerns about their ecological and health risks, their distribution in African aquatic environments remains understudied. This study addresses the knowledge gap in PFAS contamination by analysing the spatial and temporal distribution of 18 PFAS in Apies River water and sediment in Pretoria, South Africa. Surface water and sediment samples were collected upstream and downstream of the Apies River during dry seasons. The analysis of PFAS concentrations was conducted using liquid chromatography-tandem mass spectrometry. Statistical analysis, including paired t-tests, non-metric multidimensional scaling, and hierarchical cluster analysis, were applied to determine spatial and temporal trends. The study revealed significant spatial variations in PFAS contamination, with upstream locations consistently exhibiting higher concentrations than downstream. In surface water samples, L_PFBS, 4:2 FTS, 6:2 FTS, and L_PFHpS showed statistically significant differences (p<0.05) between sites. Perfluorocarboxylic acids were the dominant PFAS class in surface water (50.47–57.15%), whereas perfluorosulfonic acids were more prevalent in sediments. Upstream sediment had higher L_PFHpS (43.00 ng/g), L_PFDS (38.89 ng/g), and L_PFHxS (23.91 ng/g) than downstream (31.96, 27.84, and 18.02 ng/g, respectively). The findings reveal contamination sources and partitioning between surface water and sediments, aiding in water quality management and pollution mitigation strategies.

Climate change poses significant challenges to informal street vendors, particularly in urban settings where they operate in vulnerable environments. These challenges include economic instability, health risks, and sociopolitical exclusion, which are further exacerbated by extreme weather events and inadequate policy support. This review focuses on understanding these impacts by synthesizing lessons and exploring potential solutions from South Africa and other regions that could be implemented by governments and street vendors. A systematic review was conducted, following PRISMA guidelines, to synthesize findings from 48 studies published between 2015 and 2024. This review employed qualitative and quantitative analysis using thematic coding in ATLAS.ti and Microsoft Excel version 2024. Comparative analyses across regions and time periods were conducted to identify differences in impacts and adaptation strategies. Among the 48 studies, 52% were conducted in Africa and 50% in Asia, making these the most frequently represented regions in research on climate change and informal street vendors. Most of the publications were between 2021 and 2024 (52%). This review further highlights that climate change has led to significant economic losses, reduced working hours, and increased operational costs for informal vendors. Health impacts, such as respiratory illnesses and heat stress, are prevalent, particularly among vendors exposed to air pollution and extreme temperatures. Gender-specific vulnerabilities were noted, with women facing compounded challenges due to caregiving responsibilities and inadequate access to sanitation facilities. While Asian vendors have adopted technological solutions like mobile payment systems and cooling devices, these may not be currently feasible for South African vendors. Instead, tailored interventions that consider the local context and available resources are necessary to effectively support South African street vendors. Key recommendations include integrating vendors into urban resilience planning such as encouraging the use of cleaner and more sustainable transportation, improving access to healthcare, and providing financial support. Additionally, governments and communities should pilot the solutions identified in this review and publish their findings to inform future policies and practices.

The Department of Basic Education (DBE) established the South African Mathematics Curriculum Framework (SAMCF) to enhance and balance the approach to teaching and learning mathematics (DBE, 2018:8). It is envisaged that the SAMCF will help teachers develop learners with mathematical understanding and improve learner performance. The establishment of the SAMCF was prompted by the consistent poor learner performance in mathematics. It is recommended that the curriculum framework must be horizontally aligned with the content standards and assessment to enable achievement of the intended learning outcomes (Webb, 1997:5). This study sought to investigate the alignment between Grade 9 mathematics content standards, the SAMCF, and summative assessment tasks in Mpumalanga. The study aimed to establish the fundamental basis for how these educational components are aligned prior to the full implementation of the SAMCF. A mixed methods research design and concurrent triangulation were employed to explore different perspectives to effectively guide the education system. Further, document analysis was conducted to obtain comprehensive findings about the research problem. Moreover, the National Research Council (NRC, 2001) and two alignment models, Webb’s (1997) alignment model and Porter’s (2002) alignment model were employed as theoretical frameworks to guide this study. The findings reveal that the content structure of the Grade 9 mathematics summative assessment tasks from the four secondary schools in Mpumalanga were not well aligned with the Grade 9 mathematics content standards. Most major concepts were not assessed in the summative assessment tasks. The calculated Porter’s alignment index between Grade 9 mathematics content standards and the summative assessment tasks was statistically significantly low at an average of 0,699. The study recommends that courses on alignment of educational components should be established and incorporated at tertiary level; and more alignment studies should be conducted to improve alignment and guide the education system.

Alkaline roasting of a low-grade alluvial silica-based columbite bearing mineral from the Rayfield–Jos deposits (located in South Jos, Plateau state, Federal Republic of Nigeria) was conducted with specific emphasis on the evaluation of thermodynamic reactions as well as the mineral phase evolution during the extraction of Nb and Ta. An isothermal roasting procedure was investigated in order to understand the effects of different soda ash to sample mass ratios as well as the roasting temperatures on the measure or rate of the recoveries of Nb and Ta complexes. Thus, the feasibility rate of a successful alluvial columbite mineral roasting was determined to be influenced by certain optimal process conditions or optimum values of the study parameters, such as alkali to sample mass ratio and, more essentially, the roasting temperature. Therefore, the thermodynamic feasibility of the alkali-carbothermic roasting procedure was also investigated and the resulting chemical reactions were evaluated using the HSC chemistry 9.0 software. Premised on this, the results obtained as well as the thermodynamic data realized from the study demonstrated the feasibility of successful dissolutions of Nb and Ta into a pregnant leached-liquor stream (PLS), without the use of the conventional harmful, hazardous, toxic, and environmentally unfriendly hydrofluoric (HF) acid.

The Republic of South Africa is known for having the most unequal society in the world with an economy that is characterised by obscene wealth and extreme poverty despite the economy being rooted in the Mineral energy complex and abundance of diverse range of wildlife. It then stands to reason that South Africa’s industrial deployment was characterised by the exclusion of an entire race of mainly persons of African descent in favour of the European counterparts to create isolated islands of opulence that is surrounded by a sea of misery even though it is one of the most industrialized countries in Africa, socioeconomic problems like poverty, unemployment, and social inequality still exist (Africa, 2021). The triple mandate of higher education institutions is widely recognized to include teaching and learning, research and development, and innovation in addition to community participation. This research adds to the body of knowledge already available about the function of universities in the fields of social, economic, political, and ecological studies. It examines how the three institutions located in the City of Tshwane work both independently and jointly to address the problems associated with unemployment in South Africa. This study identifies the distinctive elements in each HEI's approach to problem-solving by providing strategic insights into the ideas behind the three universities' approaches to a shared difficulty. This study evaluated the adequacy of the efforts made by the three Tshwane based institutions in addressing the clearly stated national concerns. The study focused on the three public universities in the City of Tshwane (TUT, Unisa, and UP) and examined how higher education institutions can lower unemployment. This may be examined by outlining distinct approaches and evaluating their adequacy in resolving the issue, a comparison of the three Higher Education Institutional approaches to and responses to unemployment, concerns may help address the more general challenges facing South Africa in the wake of apartheid.