Central University of Technology

About: Central University of Technology is a education organization based out in Bloemfontein, South Africa. It is known for research contribution in the topics: Higher education & Population. The organization has 852 authors who have published 1478 publications receiving 13171 citations. The organization is also known as: Technikon Free State & Central University of Technology Free State.

Design of conformal cooling for plastic injection moulding by heat transfer simulation

Abstract: The cooling channels of a mold for plastic injection have to be as close as possible to the part geometry in order to ensure fast and homogeneous cooling. However, conventional methods to manufacture cooling channels (drilling) can only produce linear holes. Selective laser melting (SLM) is an additive manufacturing technique capable to manufacture complex cooling channels (known as conformal cooling). Nevertheless, because of the high costs of SLM the benefits of conformal collings are still not clear. The current work investigates two designs of conformal coolings: i) parallel circuit; ii) serial circuit. Both coolings are evaluated against to traditional cooling circuits (linear channels) by CAE simulation to produce parts of polypropylene. The results show that if the conformal cooling is not properly designed it cannot provide reasonable results. The deformation of the product can be reduced significantly after injection but the cycle time reduced not more than 6%.

The Etiology of Bioaerosols in Food Environments

Abstract: The past two decades have been characterised by a significant increase in the worldwide scientific database on bioaerosols in indoor and outdoor environments. Recently, the threats of bioterrorism as well as issues such as SARS and avian influenza have gained more public attention. New techniques and analytical methods have been used towards the precise identification of the sources of microbial contamination, as well as in the evaluation and assessment of potential hazards. In spite of the tremendous scientific progress made by developed countries, the state of knowledge about the biological origin of indoor air pollution in food processing environments remains relatively narrow and insufficient in developing countries. Airborne microorganisms, when they appear at the centre of interest, they are usually related to occupational studies, health complaints, and/or bioterrorism. This passive attitude towards bioaerosols in developing countries, especially in food processing environments, has increased as a ...

Additive manufacturing of TiAl-based alloys

Abstract: The ever-increasing demand for developing lightweight, high-temperature materials that can operate at elevated temperatures is still a subject of worldwide research and TiAl-based alloys have come to the fore. The conventional methods of manufacturing have been used successfully to manufacture the TiAl-based alloy. However, due to the inherent limitations of the conventional methods to produce large TiAl components with intricate near-net shapes has limit the widespread application and efficiency of the TiAl components produced using conventional methods. Metal additive manufacturing such as Electron Beam Melting technology could manufacture the TiAl alloys with intricate shapes but lack geometrical accuracy. Laser powder bed fusion (LPBF) technology could manufacture the TiAl-based alloys with intricate shapes with geometrical accuracy. However, the inherent high rate of heating and cooling mechanisms of the LPBF process failed to produce crack-free TiAl components. Various preheating techniques have been experimented, to reduce the high thermal gradient and residual stress during the LPBF process that causes the cracking of the TiAl components. Although these techniques have not reached industrial readiness up to now, encouraging results have been achieved.

Factors contributing to non-value adding activities in South African construction

Abstract: Purpose – Non-value adding activities (NVAAs) are considered to be problematic in the management of projects. Reported research findings suggest that these NVAAs consume resources without necessarily adding value to completed tasks. The main aim of the research is to provide insights and plausible explanations concerning how NVAAs can propagate poor performance in South Africa. Design/methodology/approach – The paper reports on a quantitative survey conducted among public sector clients, consulting engineers, and civil engineering contractors in South Africa. Using a framework that was developed from the literature reviewed, the study proposed three conceptual qualitative models that were based on system dynamics. Findings – The study suggests that NVAAs that are prevalent in South African construction can impact project performance negatively in the form of cost and time overruns. It can also be argued that although there is commonality between NVAAs that are identified in South Africa and other countrie...

Challenges Faced by Students with Special Educational Needs in Early Childhood Development Centers in Zimbabwe as Perceived by ECD Trainers and Parents

Abstract: The study sought to determine perceived challenges faced by: (a) students with special needs in Early Childhood Development (ECD) centres in Zimbabwe; (b) teachers of students with special needs in ECD centers in Zimbabwe; and (c) to assess how these perceived challenges could be addressed. A survey design was used to assess these perceived challenges. Data were collected using questionnaires, interviews and observations check list. A random sample of 50 ECD teachers (40 female, 10 male) and 20 parents (10 male, 10 female) of children with special needs were used in this study. Data were analysed using descriptive statistics and themes derived from research questions used in this study. The study found that children with special needs in ECD centers were being taught by untrained teachers; these children were used as surrogate mothers at the centers; and the school curriculum was inappropriate; and the physical environment was poor. Students with special needs are learning u nder very challenging conditions in these centers.