Thesis (M. Tech. (Civil Engineering)) -- Central University of Technology, free State, 2013 / According to the Road Traffic Management Corporation (RTMC) of South Africa, a large number of accidents involving motor vehicles occur annually on the arterial roads passing through the suburban residential areas of the cities of South Africa. This problem warrants planning and design interventions for the reduction of vehicular accidents and the consequent improvement of road safety on these city roads. Based on this premise, an investigation was conducted to explore the major causes of vehicular accidents, and to develop a set of urban planning and design guidelines to reduce vehicular accidents in suburban arterial roads of a city and to improve the road safety appreciably. The investigation was conducted by considering the suburban areas of Bloemfontein city of Free State, South Africa as the study area. A survey research methodology was followed for this purpose, and data was collected from both primary and secondary sources. Sample surveys were conducted in four different suburban areas of the city to collect primary data and to acquire firsthand information for understanding the scenario at grassroots level. The surveys included household surveys, in order to understand the demographic, socio-economic, and perceptual infrastructural conditions of the study area and their influence on vehicular accidents; road geometrical design parameter surveys; and traffic surveys to understand the road geometry and traffic-related scenarios in the city. In addition, structured statistical data was collected from secondary sources, such as published and unpublished literature and a range of other documents. The data collected was analysed statistically to find the major control parameters influencing vehicular accidents in the suburban arterial roads, and to establish relationships between vehicular accidents and the major control parameters. Based on the analyses, a theoretical linear multiple regression model establishing relationships between the vehicular accidents as the dependent variable and vehicular traffic-related variables (speed of vehicles and average daily traffic), road geometry design variables (road width and median width), and spatial variables (land use and land form in the form of the number of access points from residential areas to arterial routes), was developed to observe the number of accidents under varied simulated scenarios. The simulated model results were employed to develop various policy scenarios to reduce accidents and to improve road safety in the study area. The investigation revealed that, under the composite scenario of the reduction of number of accesses from residential areas to arterial roads, speed, and average daily traffic along with the increase of road width and median width, the occurrence of vehicular accidents in the arterial roads of suburban areas of the city would be reduced and road safety would be improved significantly. It was also observed that residential areas with limited vehicular access from residential areas to arterial roads would have fewer vehicular accidents than residential areas having unrestricted access. Consequently, the number of access points from residential areas to arterial roads in suburban areas of the city would need to be limited, depending on the functions and land use of the area, to improve road safety.

Thesis (M. Tech. (Engineering: Electrical)) -- Central University of technology, Free State, 2013 / The South African (SA) manufacturing industry requires developing similar levels of sophistication and expertise in automation as its international rivals to compete for global markets. To achieve this, manufacturing plants need to be managed extremely efficiently to ensure the quality of manufactured products and these plants must also have the relevant infrastructure. Furthermore, this industry must also compensate for rapid product introduction, product changes and short product lifespan. To support this need, this industry must engage in the current trend in automation known as reconfigurable manufacturing. The aim of the study is to develop a reconfigurable assembly system with enhanced control capabilities by utilizing virtual commissioning. In addition, this system must be capable of assembling multiple different products of a product range; reconfigure to accommodate the requirements of these products; autonomously reroute the product flow and distribute workload among assembly cells; handle erroneous products; and implement enhanced control methods. To achieve this, a literature study was done to confirm the type of components to be used, reveal design issues and what characteristics such a system must adhere to. Software named DELMIA was used to create a virtual simulation environment to verify the system and simultaneously scrutinize the methods of verification. On completion, simulations were conducted to verify software functions, device movements and operations, and the control software of the system. Based on simulation results, the physical system was built, and then verified with a multi agent system as overhead control to validate the entire system. The final results showed that the project objectives are achievable and it was also found that DELMIA is an excellent tool for system verification and will expedite the design of a system. By obtaining these results it is indicated that companies can design and verify their systems earlier through virtual commissioning. In addition, their systems will be more flexible, new products or product changes can be introduced more frequently, with minimum cost and downtime. This will enable SA manufacturing companies to be more competitive, ensure increased productivity, save time and so ensure them an advantage over their international competition.

Thesis (M. Tech. (Electrical Engineering )) - Central University of Technology, Free State, 2014 / Remote rural electrification via grid-extension is a challenging solution due to high connection costs and low electricity consumption rate. As a result, it is difficult to recover the initial investment costs. Therefore, electrification is made possible by means of the commonly used off-grid approaches such as solar, wind, diesel generator and conventional micro-hydro. However, owing to non-continuous availability of sunlight and wind, high cost of diesel fuel, and requirements for construction of diversion weirs, these off-grid approaches might not offer a cost-effective and reliable solution to low income rural residents. There are many rural communities throughout the world without access to grid electricity and with access to flowing water. An off-grid micro-hydrokinetic river (MHR) system is one of the promising technologies to be used in remote rural areas with flowing water. It can bring sustainable improvement to their quality of life due to its high energy density and minimal environmental impact. This technology is still in the development stage and there is a lack of application, especially in rural areas. Hence, this study investigates the current status of MHR technology in rural applications. To demonstrate the economic feasibility of an off-grid MHR system, a rural site with multiple energy sources within South Africa has been used. The economic benefit offered by this proposed system at the selected site is compared to the economic benefits offered by other commonly used standalone systems such a solar, wind and diesel generator (DG). This economic comparison has been performed by making use of a Hybrid Optimization Model for Electric Renewable (HOMER) simulation tool. Grid extension has also been used as a comparison method for obtaining an economical distance between grid lines and the remote rural site. The results highlighted the acceptable economic performance of the MHR system. Finally, most of the available modelling and simulation tools for mechanical and electrical systems are not equipped with hydrokinetic modules. Hence, an MHR system model has been developed in MATLAB/Simulink in order to study its dynamic performance as submitted to variable water resource. Its performance has then been compared to the performance of a wind system counterpart for generating the same amount of electrical power. This proved/verified that the proposed system can generate electricity markedly cheaper than a wind system even in areas with adequate wind resource within South Africa.

Thesis (M. Tech. (Engineering: Mechanical)) -- Central University of Technology, Free State, / The Centre for Rapid Prototyping and Manufacturing (CRPM) at the Central University of Technology, Free State (CUT) manufactures implants using Electro Optical Systems (EOS) titanium Ti-6Al-4V alloy powder (further referred to as EOS Ti64 powder) by means of Direct Metal Laser Sintering (DMLS) process on the EOSINT M 270 machine. For this reason, there is a need to characterise and acquire knowledge of the basic properties of direct metal laser sintered EOS titanium Ti-6Al-4V alloy samples (further referred to as DMLS Ti64 samples) under static tensile loading in order to provide the CRPM with engineering design data. The first objective of this Master’s study is to acquire the characteristics of EOS Ti64 powder in order to ascertain its suitability in the DMLS process. Secondly, the study aims to assess tensile properties and elastic constants of DMLS Ti64 samples produced from the set process parameters of EOSINT M 270 machine. Thirdly, it is to investigate microstructures of DMLS Ti64 samples subjected to different heat treatment techniques which will eventually assist in the determination of a suitable heat treatment technique that will yield higher ductility. Finally, the study aims to validate the static behaviour of DMLS Ti64 samples subjected to the static tensile loading up to a yield point in order to determine failure due to yielding. The samples were manufactured at CRPM Bloemfontein. The metallographic examinations, heat treatment and the determination of mechanical properties were done at the CSIR in Pretoria. Optical Microscope (OM) and Scanning Electron Microscope (SEM) were used to determine microstructures of DMLS Ti64 samples while Energy Dispersive X-Ray (EDX) analyses were performed using SEM. The samples were heat treated at temperatures of 700, 1000 and 1100°C respectively, and subsequently either cooled with the furnace, air or were water quenched. The mechanical property tests included tensile, hardness and determination of elastic constants. The static behaviour of DMLS Ti64 samples under static tensile load up to a yield point was predicted and verified using ABAQUSTM Finite Element Analysis (FEA). The stress-strain curves from ABAQUSTM were interpreted using MDSolid program. The point of interest was Von Mises yield stress at 0.2% offset, in order to determine failure due to yielding. EOS Ti64 powder particles were spherical in shape and the alpha and alpha+beta phases were identified. As-laser sintered samples possess a very fine and uniform alpha case with islands of martensitic plates; samples were brittle and showed low levels of ductility with an average elongation of 2.6% and an area reduction of 3.51%. Ultrasonic test results showed that DMLS Ti64 samples have Young’s modulus of 115 GPa, Shear modulus of 43 GP, a bulk modulus of 109 GPa and Poisson’s ratio of 0,323 while the density was 4.4 g/cm3. Slow cooling of DMLS Ti64 samples from 1000 and 1100oC resulted in a microstructure constituted more by the alpha phase of lower hardness than those from 700oC and as-laser sintered samples. High hardness was obtained by water quenching. The water quenched samples showed martensitic transformation and high hardness when compared to furnace cooled samples. Beta annealing tailored a microstructure of as-laser sintered samples into a lamellar structure with different lath sizes as per cooling rate. Beta annealing improved ductility levels up to 12.67% elongation for samples furnace cooled for 4 hours and even higher to 18.11% for samples furnace cooled for 34 hours, while area reduction increased to 25.94% and 33.39%, respectively. Beta annealing conversely reduced yield strength by 19.89% and ultimate tensile strength was reduced by 23.66%. The calculated maximum Von Mises stresses found were similar to the FEA interpreted results. The average percentage error, without the stress concentration factor, was approximately 8.29%; with the stress concentration factor included, it was 0.07%. The small reaction forces induced in both x-axis and z-axis contributed to this error of 0.07% between the calculations and ABAQUSTM FEA results. Samples that were not heat treated fell outside the Von Mises criterion and failed due to yielding. This justified the brittleness found in the tensile test results where elongation and area reduction were 2.6% and 3.51% respectively. However, all samples that were heat treated fell within the Von Mises criterion. The objectives of this study were achieved; the mechanical properties were similar to those of standard specification for wrought annealed Ti-6Al-4V alloy for surgical implant applications and EOS GmbH manufacturer’s material data sheet. DMLS Ti64 samples must be beta annealed in order to attain higher levels of ductility. A recommendation was made to further investigate the effect of heat treatment on the other mechanical properties. Furthermore, detailed results of basic properties of DMLS Ti64 samples are provided in the appendices in chart format and were written on a CD disc.

Thesis (D. Tech.(Human Resources Management)) -- Central University of Technology, Free State, 2014 / How to address the apparent failure of South African municipalities to deliver service that meets citizens’ expectations, poses a major challenge. The often violent protests that have resulted in deliberate destruction of private and public property, and sometimes fatalities, have been used by the public to demonstrate their dissatisfaction with the poor quality of service received from municipalities. With all these incidents, and no visible solutions yet in place, one can bluntly say that some South African municipalities have failed to deliver quality service to citizens, and they appear to be at a loss of how to change this state of affairs. This study proposes that the poor service delivery of municipalities in South Africa can be attributed to their human resource practices, which have been rendered ineffective by political interference. Borrowing from organisational justice theory, the researcher argues that political interference in human resource management (HRM) in municipalities in South Africa will lead to low employee perceptions of HRM fairness (or justness) (PHF) in the practices of municipalities, and this, in turn, will lead to low levels of employee organisational commitment (EOC) and employee motivation (MOT), conditions which are enough to make municipal employees develop negative or unacceptable employee citizenship behaviour (ECB), which may affect the quality of service delivery (QSD) that municipalities render to customers. This theory was tested using ten (10) emergent hypotheses. The theory was partially validated with empirical data collected from nine municipalities in the Free State province. Key findings of the study point to political interference in the HRM practices of municipalities, employees’ perception of HRM practices of municipalities as largely unfair, and service delivery that does not meet citizens’ expectations. These and other findings are presented and fully discussed in this research report. The report also provides recommendations for practice and further research.

Thesis (Phd.) - Central University of Technology, Free State, 2008 / This study investigates whether five former Model C schools in Bloemfontein are inclusive of diverse cultures found among their learner population. In apartheid South Africa segregation on the basis of racial and cultural difference was policy. Therefore, post apartheid legislation and policies, coupled with the fact that inclusion is not always understood or welcomed where people are used to segregated systems necessitated this investigation. The study was qualitative in nature and Buskens-Meulenberg’s Free Attitude Interview (FAI) was used as a main source of data collection. Principals of the five former Model C schools that formed part of this study and three university students who are former Model C schools learners were interviewed using open ended questions. It was important to employ the Free Attitude Interview because it meant the interviewees were free to talk about anything they felt like, as long as it was within the framework of the starting question. Secondly, it allowed for reflection on the dominant discourse and also gave a voice to the dominated discourse. To arrive at the findings data was analyzed and interpreted using Fairclough’s Textual Oriented Discourse Analysis (TODA). This method of analysis allowed the researcher to look not only at the text of the interviews but also at their discursive practices. The following findings emerged from the data analysis. The general finding from the data collected from both the principals and students was that these schools expected learners from diverse cultural backgrounds to adapt to the existing ‘school culture’ which is white middle class. The curriculum delivery, staff provisioning, and everything within the schools was found to reflect ‘white middle class culture’. The interviews from both the principals and students indicated that instead of being inclusive of all learners these schools go out of their way to assimilate children from other cultures especially black children. While this is the case it is also clear that the two groups of respondents view this differently. To the white school principals this is an accepted and normal way consciously encouraged and promoted. On the other hand this is a sore point to the black students which led them to feel that they did not belong in these schools and left them with feelings of alienation. I therefore argue that in spite of the rhetoric endorsing equity, redress, justice and respect for difference including cultural diversity, little has changed in terms of educational outcomes. Young black children who go to these former Model C schools still face exclusionary practices despite the fact that these schools have been open to all racial groups and they are physically there. While I have taken care not to generalize from the findings, – since this was never the intention of the study - I nevertheless drew the conclusion that these schools are actually not inclusive of learners from diverse cultural backgrounds. Adhering to the ‘ethos’ of the school and thereby maintaining the status quo seems to be the main objective of the schools (principals). In-fact black learners in these schools continue to experience exclusion and explicit racism. The study concludes that power structures in these schools – management and governance -, curriculum and the way it is delivered and all other activities within the school are used to reinforce domination of the learners from cultural backgrounds other than that of the school. From the findings the study recommend that for these schools to be truly inclusive of learners from diverse cultural backgrounds the Department of Education should take a leading role in ensuring that transformation takes place in these schools and they become inclusive of all learners. For this nation to be a true rainbow nation the Department of Education should not leave the transformation of these schools to the School Management Teams and Governing Bodies. Recommendations on what schools themselves can do to ensure that they accommodate, acknowledge and reflect cultural diversity and as such are inclusive of all learners are also given. Furthermore suggestions for relevant future research, based on the findings are made.

Thesis (Ph.D Ed.) -- Central University of Technology, Free State, 2007 / Since the advent of multicultural democratic governance in 1994, transformation has become crucial in South African higher education. This study is focused on the current discourses in Free State higher education institutions, especially after the mergers of the formerly black institutions and their white counterparts. The learning guide has been used to capture those debates, hence the location of its positioning between the dominant and the dominated discourses. The realisation that African culture and knowledge was being sidelined to the margins of the centre of knowledge production at higher education institutions necessitated this study. The study was qualitative, and has used Buskens-Meulenberg’s Free Attitude Interview (FAI) as an instrument to collect data. The in-depth interview with open-ended questions was used to put into practice Buskens-Meulenberg’s FAI and collect data from the respondents. In-depth interviews with-open ended questions were employed to obtain data from the nine academic respondents who constituted the sampled population. The instrumentation and the mode of data collection were important for this study because of their compatibility with critical theory and qualitative research, giving a “voice” and “space” for the voiceless – the subaltern culture, the formerly and still marginalised and peripheralised, the excluded – to be heard. Textually Oriented Discourse Analysis (TODA) was used in the analysis and interpretation of the texts through which the findings mentioned below were arrived at. The study was able to uncover the importance of the Africanisation of higher education in South Africa which seemed to be excluded in the agenda of the powers that be on the transformation of higher education. Critical theory was essential for this study because of its emancipatory underpinnings. The quantitative paradigm could not be used because of its tendency to maintain the status quo, which in the context of this study could entrench and perpetuate the exclusion and marginalisation of the subaltern culture from the centre of knowledge production. The study has taken care of the basics of TODA, namely ensuring that “textual or conversational structures” derive their framework from the cognitive, social, historical, cultural, or political contexts and in this way has prevented the interpretation of texts based only on surface structures and meanings of isolated and abstract sentences, especially from experts of the dominant discourse. This helped the study to obtain the following findings from the respondents: (i) Although the dominant discourse was diplomatic about benefiting financially from the compilation of learning guides, all indicators essentially pointed towards the existence of monetary gains from the process, even though the guides were purported to be less expensive compared to textbooks. (ii) Learning guides were only effective to the extent of helping students pass their courses, but on the other critical outcomes as outlined in the resource-based learning method document, they were lacking (see Chapter Four). (iii) The dominant discourse generally felt that it would be impossible for all the different cultures of South Africa to be incorporated into the curriculum of higher education. However, for the dominated culture, inclusion of indigenous knowledge systems in curriculum was non-negotiable and fundamental to any meaningful transformation of higher education in South Africa. (iv) The learning guide was regarded by the dominant discourse as neutral in the current debates in Free State higher education. The dominated discourse thought otherwise. In Chapter Four the dominated discourse clearly substantiated their position of learning guides as a tool for domesticating the dominated culture for the maintenance of the status quo. Considering the above findings, the study concluded that higher education transformation still had a long way to go before it bore any meaningful fruits for the downtrodden and poor people of South Africa, who happen to be Black. Under the present arrangement African culture will be dominated, demolished and diminished, and Eurocentricism will continue to reign supreme. A constant inflow of black academics with higher education qualifications (Ph.D.) may eventually tip the scales of justice may provided they continue with emancipatory discourses among the subaltern culture. In view of the above findings and conclusions, the study recommends that policy makers should intervene and formulate African cultural friendly policies as a matter of urgency and stop being advocates of Eurocentricism. In the same way that there are assessment mechanisms for quality control and assurance, there should be mechanisms for assessing higher education institutions on transformation issues. This can assist in a swift integration of the two cultures at the merged institutions for the emergence of a new African Institutional Identity. Moreover, this can only happen if African intellectuals establish Indigenous Knowledge Systems as a centre and a space for the subaltern and alternative “voice” to be heard.

Thesis (M.Tech.)(Nuclear Medicine) -- Central University of Technology, free State, 2007 / In the South African Health Services (SAHS) it is each health worker’s responsibility to find ways to reduce health care cost and improve health service to the public. The measurement of radioactive iodine uptake (RAIU) by the thyroid gland for diagnostic purposes has been used as early as the 1940s. The 24-hour (hr) iodine-131 (131I) uptake measurement is traditionally used for the calculation of the 131I administered activity for therapy dosage. This entails that the patient’s hospitalisation is prolonged, which increases the costs. The literature also indicates that the 24-hr 131I uptake value can be discarded and only the 6-hr 131I uptake measurement is needed to calculate administered activity for therapeutic dosages for Graves’ patients. Therefore, if it can be confirmed that the 6-hr 131I uptake measurement alone is needed, the SAHS could decrease hospitalisation costs. The overall goal of the investigation was to analyse the 6-hr and 24-hr 131I uptake measurements of patients with Graves’ disease at the Universitas Hospital. The aim was to determine the relationship between the 6-hr and 24- hr RAIU values to establish the therapeutic dosage for Graves’ disease. To achieve the aim, three objectives were set. First, to serve as a background to the investigation, a literature survey relating to the RAIU measurements of patients with Graves’ disease was made. Second, a retrospective analysis was performed by collecting the 6-hr and 24-hr 131I uptake measurements of patients with proven Graves’ disease at the Universitas Nuclear Medicine Department (UNMD). Finally, the data obtained from the retrospective analysis was analysed, summarised and compared to answer the investigation questions. The investigation group included patients with confirmed Graves’ disease who had undergone both the 6- and 24-hr 131I RAIU at the Universitas Hospital from the beginning of 2004 to the end of 2005. Graves’ disease is confirmed by the following factors at the UNMD, namely: Suppressed TSH, elevated T4 and T3 values, an increased uptake on the 99mTc-pertechnetate scan and increased 6- and 24-hr 131I RAIU values. The UNMD statistics show that 178 patients were diagnosed with Graves’ disease during this period. The patients of the investigation group included both male and female patients from different races, ranging from 15-75 years. In order to increase the validity of the investigation, all factors that could influence the accuracy of the 131I thyroid uptake test were excluded. After the exclusion and inclusion criteria had been applied, the final investigation group was made up of 124 Graves’ disease patients. The data obtained from the patient files was noted on the different data sheets (see Appendix A) for further analysis. The information from these data sheets was then used to obtain the investigation results. The Department of Biostatistics of the University of the Free State (UFS) was consulted for recommendations regarding the management of data and the processing of results. All values were summarised by means and Standard Deviations (SD) or percentiles. Mean or median differences were calculated with a 95% Confidence Interval (CI). A regression analysis was made between the 6-hr and 24-hr 131I RAIU values. The highest RAIU value is the best to calculate the therapeutic dosage, as this gives a true reflection of the thyroid function of a Graves’ disease patient. In the investigation group the median of the 24-hr 131I RAIU values was higher than the 6-hr 131I RAIU values. The findings showed that the 24-hr 131I RAIU in most of the investigation group was the highest value and most effective to calculate the 131I therapeutic dosage. At a time when research-based practice is taking on an increasingly important role, it is essential for nuclear medicine departments to make evidence-based recommendations. This investigation found that the correlation between the 6-hr and 24-hr RAIU clearly justified the cost spent on Graves’ disease patients who must stay overnight for the 24-hr 131I RAIU procedure.

Thesis (M. Tech.) -- Central University of Technology, Free State, 2008 / Blood transfusions carry a number of risks, one of which is transmitting HIV/AIDS from an infected donor. Since HIV is sexually and parenterally transmitted, the initial HIV risk management of donated blood in the early 1980‟s consisted of screening by visual assessment and completion of a lifestyle questionnaire, followed by deferral of practicing homosexual and bisexual male donors and intravenous drug addicts. The visual assessment was replaced by tests for antibodies directed against HIV, from the middle 1980‟s. In the early 1990‟s HIV was increasingly found in the black population of South Africa, particularly among black women. By 1998 0.26% of the received donations returned a positive test for HIV-1. In 1999 the South African Blood Transfusion Service (SABTS) Blood Safety Policy was introduced, including a donation HIV-risk categorization model which used the donor ethnic group, gender and donation history as indicators of the risk of exposure to HIV. The unacceptable use of the donor ethnic group as an indicator was the motivation to seek a suitable alternative donation risk categorization model which excludes the donor‟s ethnic group. The use of a more acceptable model with a high level of accuracy in predicting the risk of exposure to HIV has the potential of contributing to the reduced risk of HIV transmission through blood transfusion in South Africa. The aim of this study was to compare the suitability of four alternative models based on the information obtained from donors. Donations from new and lapsed donors were categorized in the highest applicable risk category in each model. The study was divided into two phases to achieve the aim. The first phase needed to determine suitable parameters for a model which uses the donor‟s age as an indicator. For this phase the ages of the regular donors returning an HIV-positive test result, were analysed. The second phase was to evaluate the effectiveness of the four suggested alternative blood donation risk categorization models against the model introduced by the SABTS in 1999. During this phase the donor demographic data and donation histories of donors who made donations at the Bloemfontein branch of the South African National Blood Service (SANBS) between October 2004 and September 2005, were analysed statistically. This phase honed in on two aspects to evaluate the effectiveness of the alternative models. Firstly the percentages of HIV-positive donations found in each risk category of each model, were determined as indicators of the residual risk of HIV-positive donations within the window period. Secondly the percentages of the collected blood donations allocated to each risk category within each model, were analysed to give an indication of the availability of “safe” blood associated with each of the models. The first phase of the study highlighted the difference in the age-group prevalence between male and female regular donors who returned an HIVpositive test result. Potentially suitable parameters for an Age-based Model were formulated by comparing this data with the ages of the donors who donated in Bloemfontein during the twelve months covered by this study. The second phase compared a Donation Interval Model, a Combination Model (using donation interval, gender and ethnic group as indicators), the SANBS 2005 Model (using age and gender as indicators) and an Agebased Model (using age and gender as indicators) with the SABTS 1999 Model (using gender and ethnic group as indicators). This study has shown that each of the models analysed has its advantages and disadvantages. The SANBS 2005 Model proved the best model without an ethnic indicator, for SANBS. Several recommendations regarding further investigation emanating from the results of this study were made.

Thesis (M. Tech) --Central University of Technology, Free State, 2008 / Aphids (Hemiptera: Aphididae) are amongst the most destructive insects in agricultural crop production systems. This reputation stems from their complex life cycles which are mostly linked to a parthenogenetic mode of reproduction, allowing them to reach immense population sizes within a short period of time. They are also notorious as important and efficient vectors of several plant viral diseases. Their short fecund life cycles allow them to be pests on crops with a short growth period, e.g. lettuce (Lactuca sativa L.). It is common practice to provide this crop with some degree of protection from environmental extremes on the South African Highveld. Shadehouses are popular in this regard, but aphids are small enough to find their way into these structures, and their presence on lettuce is discouraged due to phytosanitary issues. In addition, the excessive use of insecticides is criticized due to the negative influence on human health, and because aphids can rapidly develop resistance. This necessitates the use of alternative control options in order to suppress aphid numbers. Biological control is popular in this regard and the use of predatory ladybirds (Coleoptera: Coccinellidae) is a popular choice. This study investigated the aphid and coccinellid species complex encountered under varying shadehouse conditions on cultivated head lettuce in the central Free State Province (South Africa). Their seasonality was also examined, along with variations in their population size throughout a one-year period. Finally, the impact of varying aphid populations on some physical characteristics of head lettuce was examined, and recommendations for aphid control (using naturally occurring coccinellid predators) were made. Two shadehouse structures were evaluated during this study. One was fully covered with shade netting and designed to exclude the pugnacious ant, Anoplolepis custodiens (Hymenoptera: Formicidae), while the other was partially covered with shade netting (on the roof area) allowing access to the ants. Six cycles of head lettuce were planted and sampled four times during each cycle. These were scheduled to monitor the seedling, vegetative and heading stage of lettuce. Four important aphid species were recorded on the lettuce, namely Acyrthosiphon lactucae, Nasonovia ribisnigri, Myzus persicae and Macrosiphum euphorbiae. Both structures harboured similar aphid and coccinellid species, but their population dynamics differed. A. lactucae dominated in the absence of A. custodiens in the fully covered structure (whole study), while N. ribisnigri dominated in the partially covered structure in the presence of these ants during the warmer months (December – January). M. euphorbiae replaced this species as the dominant species in the absence of A. custodiens (April – September). M. persicae occured during the winter (May – August) in the fully covered structure. Promising coccinellid predators were Hippodamia variegata and Scymnus sp. 1, and to a lesser extent, Exochomus flavipes and Cheilomenes lunata. However, the fully covered structure hampered the entrance of the larger adult coccinellid species, resulting in their lower occurrence. Aphid and coccinellid activity peaked during the summer months (October – January), and the fully covered structure attained the highest aphid infestation levels and coccinellid larval numbers during this time. On the other hand, aphid numbers were higher in the partially covered structure during the cooler months of the year (April – July) and this structure also harboured more adult coccinellids. In most cases, aphid infestation levels did not affect the amount of leaves formed. However, symptomatic damage in terms of head weight reduction did occur under severe infestation levels. Specific environmental conditions within a shadehouse structure concurrently contributed to this reduction, with less favourable conditions accelerating this condition. Results from this study have shown that even though the type of shadehouse structure does not influence the insect species complex found on lettuce, it does have an influence on detrimental and beneficial insect population dynamics. Aphid species infesting lettuce have been identified, along with coccinellid predators that could potentially be used in their control. Both types of structures had advantages and disadvantages, and therefore, decisions concerning shadehouses should not be focused on which type of structure to use, but rather which type of structure to use during different seasons of the year.