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Assessment of the suitability of the fall cone method and the Casagrande cup method for determining the liquid limit of South African soils
Full text linkThesis (Master:Civil Engineering)--Central University of TechnologyThe plasticity index (PI) is one of the most important soil variables in the design of soil related structures. Most engineers rely on PI values determined by commercial laboratories. Commercial laboratories strive to make their services competitive and affordable to their clients. The liquid limit (LL) is one of the variables used to determine the PI and is determined by laboratory soil tests, therefore it is important to determine the LL accurately.
Two techniques, the Casagrande percussion cup and fall-cone (penetrometer) methods, have been adopted as the standard LL measurement approaches globally. The Casagrande cup method is implemented in South Africa (SANS, 2011) as well as in the USA, whilst the fall-cone method is accepted in the UK (BS 1377-2, 1990).
According to many researchers such as Karlsson (1961), Sherwood and Ryley (1970), Weston (1978), Sampson (1983), Sridharan and Prakash (2000), Feng (2000), the Casagrande cup method is operator dependent, less reliable and soils of low plasticity tend to slide in the Casagrande cup while the LL cannot be measured. On the other hand, the fall-cone test is a simple shear strength test that is much less operator dependent and can measure the liquid limit for a soil of any plasticity accurately.
According to Sampson and Netterberg (1984), the British variant of the Casagrande cup produced LL results that directly correlated with the BS fall-cone LL results, while the SANS variant Casagrande cup correlated indirectly with BS fall-cone LL results with a constant difference of about 4 units. It is important to note that the indirect correlation, does not refer to an inverse correlation, but a correlation with an offset.
This indirect correlation was caused by the international variance of the base hardness of the Casagrande cup devices and lead to poor precision limits (Haigh, 2015; Sampson and Netterberg, 1984).
The aim of this research is to modify the standard British fall-cone method in order to produce a fall-cone procedure that is optimised for South African soils, in order to replace the Casagrande cup method for the determination of the liquid limit for South African soils.
To optimise the sample preparation procedure, the BS fall-cone cup was modified by removing the bottom plate of the cup and sharpening its bottom edges to form a specimen ring. The specimen ring LL results were compared to the results of the BS cup and showed that there was a negligible difference in results due to the removal of bottom plate.
To optimise the amount of sample required to perform the test, four specimen rings were manufactured with diameters 54mm, 35mm, 30mm and 22mm to test whether the smaller diameter LL results would differ from the standard diameter. The results showed that the 35mm specimen ring could be used for testing, while the 30mm and 22mm diameters showed the effects of mould confinement, where the soil heave created by the cone affected the penetration depth of the cone.
The indirect correlation would be corrected by adjusting the standard 20mm corresponding penetration. The 54mm and 35mm diameter rings in the modified fallcone tests showed a direct correlation with the SANS Casagrande cup when the corresponding penetration was adjusted from 20mm to 16mm.
Further tests were conducted where the cone weight was increased in order to investigate the correlation between the fall-cone and the SANS casagrande cup. However, this method was not considered since it was impractical to change the standard apparatus and move further from achieving an international standard.
A draft SANS fall-cone procedure manual was compiled from the research conducted and the results obtained in this dissertation and is attached as Annexure A. This manual will be submitted to SABS for the approval of the modified fall-cone as a South African standard method
Assessing the recency of HIV infections and estimating HIV incidence in two rural districts of Lesotho
Full text linkThesis (Master: Health Sciences: Biomedical Technology)--Central University of TechnologyBackground HIV recency assays are used to distinguish recently acquired infection from long-term infection among individuals newly diagnosed with HIV and thus identify hotspots of transmission. Additionally, since 2015, UNAIDS and the World Health Organisation (WHO) advise the use of HIV recency assay together with HIV viral load (VL) quantification as an incidence measure. Objectives Based on randomly selected samples of new HIV infections in two districts of Lesotho, we determined recent HIV infections, described and assessed risk factors for these recent infections, and estimated HIV incidence. Methods A total of 243 samples had been collected from newly diagnosed HIV- positive patients during a door-to-door HIV testing campaign from August 2018 to May 2019 in randomly selected rural villages of two districts in Lesotho (Butha-Buthe and Mokhotlong). The MSc candidate tested these samples for HIV recency using the Asanté HIV-1 Rapid Recency Assay and VL using the Roche Cobas System, according to the recent infection testing algorithm recommended by WHO. Moreover, she extracted the clinical and socio-demographic information from the trial database and conducted the descriptive (characteristics and incidence calculation) as well as inferential statistical analyses (risk factor analysis). Results Participants were recruited from August 2018 to May 2019. Among the 11,291 participants tested for HIV, 243 (2.2%) samples of new HIV diagnoses were available for recency and VL testing. Among the 243 samples, we found 18 (7.4%; 95% confidence interval 4.4%-11.5%) recent infections, while 225 (92.6%) were classified as long-term HIV infections. The majority of the participants were female (142 [58%]) with a median age of 37 years (interquartile range [IQR] 31-50 years). Although some characteristics showed a certain trend, only female gender was predictive for a recent HIV infection (adjusted odds ratio 3.74 (95% confidence interval 1.05-13.36); p-value 0.041). The estimated annual incidence was Ia = 0.29%. Conclusion During door-to-door testing among a general population sample in two rural districts of Lesotho, 7.4% of newly diagnosed HIV infections were recent (< 6 months) as well as a significant incidence rate. Women were more likely to have acquired HIV recently. Our results imply significant ongoing transmission in these rural communities
Association between carotid intima-media thickness and patient outcomes in coronary artery disease in central South Africa
Full text linkThesis (Master: Health Sciences: Clinical Technology)--Central University of TechnologyObjectives Atherosclerosis is responsible for significant cardiovascular morbidity and mortality. Carotid intima medial thickness (CIMT) is a useful non-invasive tool to detect atherosclerosis to diagnose cardiovascular disease. The aim of the study was to assess the correlation between pre-operative CIMT measurements and intra- and post-operative surgical outcomes in acute coronary syndrome (ACS) patients undergoing coronary artery bypass graft (CABG) surgery. Methods This retrospective analytical cohort included 89 patients diagnosed with ACS who received CABG surgery. Patients were divided into two cohorts: group 1 (normal CIMT <0.07cm) and Group 2 (abnormal CIMT ≥0.07cm). B-mode ultrasound was used to measure the CIMT in all patients. Pre-, intra- and post-operative data and complications were recorded for each patient. Results The study included 77 (86.5%) males and 12 (13.5%) females. Pre-operative mean body mass index (BMI) was significantly higher (p=0.03) in group 2 than in group 1 (29.2 kg/m2 vs 26.6 kg/m2 ). Patients in group 2 had significantly more diabetes (p=0.008), hypertension (p=0.009) and an increased NT proBNP (p=0.02) than patients in group 1. The intra-operative and post-operative outcomes between groups were comparable, with no significant differences. Conclusion The study showed no correlation between abnormal CIMT and increased adverse intra- and postoperative patient outcomes. Therefore, based on the results of this study, CIMT should not be considered a tool to predict adverse events in patients undergoing CABG surgery
The Influence Of Using Mobile Technologies During Project Execution On Perceived Managerial Competencies Of Emerging Construction Firm Owners/ Managers In The Free State Province
Full text linkDissertationThe exponential growth in the utilisation of mobile technologies (MTs) for cost reduction and improving organisational efficiency is widely acknowledged in entrepreneurship literature. Despite this promise, the exact effect of MTs on the managerial competencies of small, micro, and medium enterprises is yet to be fully comprehended by emerging construction firms (ECFs). To address this gap, the current study drew on a quantitative approach and survey conducted on 252 emerging construction firms' owners/managers in the Free State province of South Africa to establish how mobile technology adoption during project execution impacted the perceived managerial competencies (MCs) of these entrepreneurs.
The results indicate that the adoption of MTs during project execution has a positive and statistically significant effect on the communicative and social competencies of ECF owners and managers, with MT adoption during project execution explaining 65.1% of the variance of communicative competencies and 71.2% of social competencies. The results further demonstrate that the type of device used (laptops and tablets) used moderated the strength of the MT adoption-MC relationship. The study recommends the wider rollout of other mobile technologies to improve managerial competencies in ways that optimise the efficiency of project-related operations. The study contributes to the broad project management theory and literature, especially project execution, by exploring how mobile technology adoption facilitates enhanced communication and social competencies that improve organisational efficiency of ECFs
An investigation into the effects of gender-based violence in primary schools of Warmbaths circuit, Waterberg region
Full text linkThesis (Master: Education leadership and Management)--Central University of TechnologySchools should provide a warm, loving and supportive environment where children can learn and become responsible citizens in the future. Instead, incidents of violence and murder caused by school-related gender-based violence have turned some South African schools into scenes of death and destruction. Major educational challenges caused by gender-based violence in schools are now affecting the majority of students in the country, putting their safety at risk. The aim of this study was to examine how gender-based violence affects primary school learners and how it severely limits their rights and participation in the educational environment. The questionnaire and interview were completed by a sample of six primary school learners (3 male learners and 3 female learners) and nine primary school educators (3 male and 6 female educators) in Warmbaths area. According to the study, gender-based violence is an issue in these regions. Findings also involve the magnitude of learner‘s experiences of SRGBV, the effects of SRGBV behaviour on learners, a general understanding of the consequences of SRGBV, male educators as perpetrators of SRGBV and the overall performance of school duties in the school environment. Effective measures for preventing the spread of the scourge have been identified. Suggestions and recommendations of the study involve improved parental involvement and policy evaluation to maintain positive engagement. Results showed that male learners were more likely to engage in violent behaviour than female learners and that female learners were more likely to experience gender-based violence at school. The plague can be stopped from spreading if effective steps are taken. The focus of the study was on how gender-based violence in schools affected student learning and educator effectiveness. To foster open dialogue and learn more about how school-related violence affects relationships between learners, educators, and their environment, data were acquired using semi-structured interviews with open-ended questions. When discussing violence issues at their individual schools, participants' identities were protected and made comfortable by the use of pseudonyms. The studies additionally encouraged collaboration among all parties, such as the Ministry of Education, to deal with the difficulty of gender-primarily based totally violence in schools
Optimal energy management of hybrid energy system for a commercial building
Full text linkThesis (Phd: Engineering: Electrical Engineering)--Central University of TechnologyHigh consumption of electricity in commercial buildings, is a global challenge, faced by many countries in the world. The high consumption of purchased electricity from the utility, results in high electricity bills for commercial consumers. The cost of energy consumed by the commercial buildings is high as an optimal power flow strategy to the load is not applied. The optimised on-site grid-tied hybrid renewable energy system under time of use tariff, has been found as the attractive option for solving this problem. As a result, this research work has focused on the development of an optimal energy management model, to minimise the electricity cost of a commercial building supplied by the on-site grid-tied hybrid photovoltaic-battery-diesel generator (PV-Battery-DG) hybrid renewable energy system (HRES), under time of use tariff. The selected solution methodology has consisted of a review of related literature, selection of an appropriate case study, optimal sizing of on-site grid-tied HRES, using Hybrid Optimization Model for Electric Renewable (HOMER), development of on-site grid-tied HRES model and simulations using realistic and measured data, as well as an economic impact assessment of scheduled grid load shedding, on commercial consumers. The optimum sizes are 18 kW for the PV, 18 kW for the DG, 6 Surrette 6CS25PS batteries and 15 kW for the bidirectional converter. The most economic NPC for the gridtied PV-Battery-DG configuration, obtained in this study, is 169/kWh and the operating cost is $5212, for 25-year period. The daily economic analysis results, indicate that the optimal energy management of the hybrid system has a potential daily savings of 49.51%, based on the data provided and the assumptions made. Results have shown that the proposed grid-tied hybrid PV-Battery-DG HRES has the potential of mitigating the South African scheduled load shedding for a commercial consumer’s building. The optimal energy management of the proposed hybrid energy system under TOU has minimised both the grid consumption, as well as the consumer’s bill and the diesel fuel for running the DG. The main benefit of reduced electricity purchased from the grid, is the reduced electricity bill for the commercial consumers. Daily scheduled grid load shedding impacts differently on commercial consumers; this is due to the available renewable resources, battery SOC, as well as the amount of DG energy used. The author anticipates that, in future, Smart grid technologies will have a positive impact on commercial demand side management. These technologies may consist of communication systems, monitoring systems, control devices and on-site HRESs. They will enable a sustainable, efficient and secure electricity supply to a commercial building
Optimal water pump scheduling in an open reservoir water treatment system, incorporating evaporation and seepage effect
Full text linkThesis (Doctor :Engineering: Electrical Engineering)--Central University of TechnologyBulk water extraction and purification, in most countries, occurs in distant areas, where running rivers or lakes are available. To achieve the goal of obtaining potable water, water from dams or lakes is pumped into a treatment reservoir, to undergo purifying operations. Electrical energy is required for the supply of these electric pumps, to pump water from one level to another, during the process. Looking at the energy management point of view, the main problem is the rising cost of electrical energy used to pump water from the dam to the reservoirs. This could be owing to inadequate management of the pumping system, as well as the fact that water reservoir pumping systems are subject to exogenous variables, including evaporation, precipitation, seepage and leakage. A review of water-pump energy management steps in a bulk-water purification system, was conducted, to understand the problem and find the best possible solution in enhancing the energy usage in a water pumping system. This survey provides a complete overview of current control strategies in water pumping energy management activities. The review is led by the performance, operation, equipment and technology (POET) concept, which includes a review of current water pumping technologies, as well as advancements, ideas, evaluations and improvements. This POET framework discussed the long term viability of a broad energy management program, as an application of the commercial bulk water development scenario. The case study established that the POET based energy management system may save energy in a coordinated and effective manner. It may be able to successfully obtain the energy saving prospects of water pumping processes, as well as laying the groundwork for a future project in water treatment systems. This research proposes different energy management models, to meet the pumping water demand while minimizing the amount of energy required during the operation. The first model was based on the mathematical model for water pumping controller systems and is known as the research's baseline model. The system takes into consideration the impacts of evaporation, rainfall and seepage to make the model more realistic and it uses the flood switching principle, regulating the pumping operation of a water facility. To assess the initial model's performance, simulations were run in two scenarios: first, evaluating the flood switching control system without taking into account the effects of rainfall, evaporation, and seepage, and second, with all of these constraints taken into account. The second model was based on the principle of timer-setting control. When the effects of evaporation, rainfall, and seepage losses were all considered, the performance of the suggested electrical timer switching control system was evaluated. The simulation of the second model was carried out using two scenarios: first, a time control system was applied to a fixed water pump, and second, a timer-setting control system was incorporated with the VFD power control pump. The optimal switching control system was used in the third model. Evaporation, rainfall, and seepage losses were all elements taken into account in order to make the model more realistic. The simulation of the third model was divided into two categories: first, an optimal control system was applied to a fixed water pump, and second, the optimal control system combined with the VFD power control pump. The main objective of this research was to optimise the pumping operation of a water pumping system, with the aim of obtaining a lower energy consumption cost. MATLABSCIP optimization software was used to implement the developed models. Hence, the model's energy-saving capabilities were validated through simulation. In comparison to the baseline case, in which the developed model is simulated with the impacts of evaporation, rainfall and seepage; and then again without these disturbances, the results of the first model show an energy savings of 683ZAR per day, when the effect of evaporation, seepage and rainfall are all taken into consideration in a flood switching control system. The simulated results of the second model are compared to the baseline flood switching control system, to estimate the economic benefit of the developed model. As compared to the baseline case, where the flood switching control system is used to accommodate the load demand, the simulated results for the selected day of operation have shown that, using the proposed timer-setting control model with fixed speed motor pump, a 316 ZAR reduction in the operating cost is achieved, compared to the baseline flood switching control system. Looking further, when a VFD control motor pump is added to the timer-setting control system, the simulated result shows that a 1022 ZAR decrease in operating cost per day may be saved, when compared to the baseline flood switching control system. In a separate simulation of the third model, the results are compared to the baseline flood switching control system, to estimate the economic benefit of the developed model. When the optimal control system is employed to meet the load requirement, the simulated results for the chosen day of operation demonstrate that, when compared to the baseline flood switching control system, the proposed optimal control model with fixed speed motor pump, saves 1204 ZAR in operating costs. When a VFD control motor pump is introduced to the optimal control system, the simulated result shows that, when compared to the baseline flood switching control system, a 1725 ZAR reduction in operating cost per day may be achieved. These findings further revealed that the grid's energy demands are significantly reduced when the proposed optimal control models are combined with a VFD control motor pump in a water pumping system. As a result, the initial cost of acquiring energy is reduced. Further services, such as maintenance, could benefit from the savings. In the end, this may assist in lowering the initial cost of water sold to consumers
Mentor competencies and psychological mindsets in the context of a multinational corporation: an intervention-based study
Full text linkThesis (Doctor: Human Resource Management)--Central University of TechnologyGiven the fiercely competitive international business environment, organisations need to actively engage in attracting, recruiting, and retaining top talent. Mentoring as a key part of talent management is pertinent, especially in the context of multinational corporations that employ diverse employees from across the globe. To that end, mentoring programmes help to improve organisational effectiveness. The purpose of this study was to contribute both theoretically and empirically to positioning mentoring as a key component of talent management in a multi-national corporation, namely Abu Dhabi National Oil Company (ADNOC) with specific focus on the ADNOC Gas Processing (AGP) business unit. Using a mixed-methods research approach, the study targeted 15 AGP mentors that were currently part of AGP’s mentoring team. Data was collected through pre- and post-self-assessment questionnaires and structured interviews were conducted to ascertain the thoughts and feelings of participants. A three-month mentor development journey was developed and implemented based on the findings of the pre-assessment phase of the study. The empirical results from the study indicated that prior to the mentor development journey, mentees admitted to having deficiencies in most mentor competencies and aspects relating to psychological mindsets. After undergoing the mentor development journey, the mentees acknowledged they had improved their competencies in these fields. A mentoring framework was designed with the aim of addressing the mentoring gaps. The key focus of the framework was to enhance trust between mentor and mentee, to enhance the mentor’s appreciation of the mentee’s growing independence, to promote communication between mentor and mentee, as well as to develop the empathic listening skills of mentors
Finite element model of masonry structures on expansive soils
Full text linkThesis (Master: Engineering: Civil Engineering)--Central University of TechnologyThe ancient construction of masonry is still a prominent feature in the industry. Masonry is used particularly as a construction material for homes, schools, offices, and industrial buildings. To ensure that masonry structures are safe, they must comply with the Code of Practice for Unreinforced Masonry (SANS 0164-1:1980 as amended in 1986 and 1987), which states the necessary limitations for masonry design work. Therefore, the SANS devised several tests for different material choices. As these tests are mostly performed on physical structures, they are destructive, time-consuming, labour intensive and can be costly. Thus, alternative methods that will provide equivalent information faster, more accurately and less costly will be advantageous. This study was thus undertaken to design a finite element model to simulate the behaviour of masonry wall panels subjected to soil deformation so that rational material choices can be made to improve the susceptibility of cracking in masonry. In Phase 1, the material properties of five different mortar mixes were analysed in a controlled environment at the Central University of Technology Free State laboratory. In Phase 2, a finite element model was designed with the Prokon software program and refined using the mesh refinement method. The performance of different mortar material properties was analysed using the designed finite element model. Three experiments were performed on the five different mortar mixes. Three of the mortar mixes were sourced from the SANS 10164-1, and two from the ASTM C270- 1T. The experiments performed included the Young’s modulus test, determination of the bond strength test, and the application of the deformation test on physical wall panels. After conducting the experimental tests on the five different mortar mixes, an initial finite element model was designed using the finite element method approach based on mesh refinement. The mesh of the initial finite element model was refined to create five different mesh refinement models, each consisting of a different size mesh. The five mesh refinement models were used to design five finite element wall panels. The dimensions of the finite element wall panels were the same throughout, namely 8 × 10 bricks (1 830 × 790 mm). Theoretical parameters were assigned to each of the five different finite element wall panels to determine which wall panel supplied the most consistent results pertaining to the maximum and minimum stress in a wall panel, as well as the overall flow of stress. One finite element wall panel with a specified mesh refinement was selected from the five finite element wall panels for the analysis on the performance of different mortar material properties and standard cement brick properties. Each of the different mortar material properties and standard cement brick material properties was applied to the selected finite element model with specified mesh refinement. A deformation of 1 mm was applied to each finite element wall panel to determine the magnitude of stress found in a finite element wall panel designed using a specified mortar mix and standard cement brick properties. The tensile stress in each finite element wall panel was compared to the results of the three experiments performed. The finite element wall panels showed significant similarity to the experimental wall panels built. The stress distribution through each of the finite element wall panels during the mesh refinement process proceeded to illustrate stress differences among the brick and mortar elements. In the finite element wall panel where the mortar material properties with the least amount of strength was implemented the stress distribution in both the brick and mortar elements was remarkably low. In contrast to this result, the finite element wall panel with the higher mortar material properties of higher strength revealed a higher stress distribution in between the brick and mortar elements. The experimental wall panels that were built showed similar comparisons between the mortar with a high strength and a mortar with a lower strength. The experimental wall panel constructed with the higher strength mortar failed at a lower applied deformation than the experimental wall panel constructed with the mortar with lower compressive strength and higher flexibility. The results of these tests indicated that a mortar with a lower Young’s modulus, combined with a brick of higher strength, showed higher flexibility coefficient and lower stress distribution than a mortar with a higher Young’s modulus. Therefore, the use of a flexible mortar would reduce the stress in the wall panel and assist in masonry flexibility. The designed finite element model could make a significant contribution to the masonry industry in the construction of masonry structures on expansive soils. The finite element model could provide some level of confidence on the effect of masonry constructed on heaving soil, and thus determine the choice of adequate materials in such situations
Reflections By Pre-Service Economic And Management Sciences Teachers On Their Experiences Of Remote Learning In Curriculum Practice
Full text linkResearch ArticleCurriculum reformists were caught off-guard over the past two years by the unforeseen and extreme
pressure of the COVID-19 pandemic. This phenomenon threatened to engulf humans in despair.
Institutions of higher learning initiated moves to remote learning, as a measure to prevent the spread of
the virus while continuing to promote teaching and learning. Scholars were absorbed by grasping the
importance and application of a revolution in curriculum reform. The use of remote learning in
curriculum practice to improve teaching and learning is a recent initiative in the package of curriculum
and pedagogical reforms in South Africa. The aim of this paper is to reflect on adaptive experiences of
pre-service economic and management sciences teachers, their ability to adapt curriculum practice to
remote learning of this specific curriculum, and pedagogical reform of the use of remote learning in
schools. An architecture theory, which draws on the famous quotation of Adolf Loos's parable about “the
poor rich man” and whether they really understand the lesson, was used as the main lens for the study. An
interpretative phenomenological analysis approach, as a form of critical education science, was employed
to generate data. The basic purpose and essence of the IPA approach in a qualitative research study is to
examine the life experiences of the research participants and to allow them to narrate the research
findings through their lived experiences and critical reflections, thereby deliberately embracing diversity
as characterised by the unequal context of South African education. Phenomenological analysis was used
to arrive at the following findings. First, higher learning institutions are obligated to create practical
learning experiences for pre-service teachers. Second, the phenomenon that resulted in the necessity to
embrace remote learning impacted participants academically, socially and psychologically. The paper
concludes with the recommendation that the prefigured remote learning for professional teaching practice
should be reconfigured