School of Mechanical, Industrial and Aeronautical Engineering (ETDs)

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A study of the finite element method, with reference to the Adina finite element package
(University of the Witwatersrand, Johannesburg, 1983) Constancon, Charles Peter
This dissertation presents a theoretical and practical study of the finite element met hod using the ADINA finite element program. The package was applied to the analysis of three different problems, namely: A nonlinear static analysis; a free vibration analysis and a themal analysis. The first two analyses were supplemented with experimental results for the purpose of comparison whilst the last was compared with a closed form analytic solution. The first problem consisted of a materially nonlinear static analysis of a cast iron sheave wheel. The sheave was physically loaded with a rope up to failure of the rim. Strain gauges monitored strain at twenty-four locations. In order to simulate the nonlinear properties of the east iron, a Drucker Prager yield criterion was utilised and accordingly, a subroutine describing the elasto-plastic constitutive laws was interfaced with the ADINA package. Owing to self-imposed limitations on computer resources, the sheave was modelled as a two-dimensional body. The results correlated well in the linear region but deviated when plastic deformation was pronounced. It is suspected that this was due to a combination of approximations in modelling the geometry and the material. In the free vibration analysis, a simple portal frame was built in order to compare its natural mode shapes and frequencies with those obtained from a finite element simulation. This comparison proved satisfactory. The thermal analysis was executed primarily to test and gain first hand experience with the ADINAT package. A two-dimensional flat plate subjected to a sinusoidal temperature load was simulated. Although the application was simple, the accuracy of the FEM results confirmed that the package was operating correctly. In all these exercises ADINA package performed satisfactorily. Experience show that the programme was not user-friendly, however this is not considered a drawback in a research environment.
An investigation of factors contributing to long waiting of patients collecting repeat medication in a tertiary hospital pharmacy
(University of the Witwatersrand, Johannesburg, 2022) Oladipupo, Rekgopetse Victoria; Sunjka, B.
According to the World Health Organization (WHO) patient waiting time is identified as a key measurement to a responsive healthcare service and is an important indicator of quality of services offered by hospitals (NDoH, 2011) as it affects the patient’s responsiveness to the services received (NDoH, 2011; SA FAM PRACTICE, 2008; Tegabu, 2008; Pandit et, al. 2016). Long waiting times at healthcare facilities undermines the services rendered resulting in compromised or unfulfilled patient care (Afolabi & Erhun, 2003). This research studies the processes associated with the collection of repeat medication in a tertiary hospital pharmacy in order to identify value adding activities and non-value adding activities that could be impacting patient waiting time using the Lean thinking concept of driving out waste. A qualitative observational method was therefore employed to observe all the steps involved during the journey of the patient collecting repeat medication from the registration point until medication was issued at the pharmacy. Value stream mapping (one of Lean Thinking principle) was employed to analyze the processes that took place. Patient waiting time was also measured from the registration point to the pharmacy. On average patients had to wait a total 159 minutes before they could access services both at the registration point (67 minutes) and at pharmacy (92 minutes). The service time was 29 minutes at both registration point (11 minutes) and pharmacy (18 minutes). Of the 18 minutes pharmacy service time; eight minutes were found to be value-adding while 10 minutes were non-value-adding mainly due to prescriptions waiting on queue to be picked, waiting to be signed by the pharmacist and waiting to be issued out to the patient. Lack of a dedicated pharmacy service points exclusively for chronic repeat patients, manual dispensing, illegible doctor’s prescriptions, were found to prolong the time it takes the Pharmacist to complete a prescription. Post Basic Pharmacist Assistants performing duties that could be performed by a less qualified staff (e.g., Learner Basic Pharmacist Assistants) during peak hours was not value adding and thus decreasing productivity. The level of staff commitment in addressing issues of quality such as long waiting time was questionable. The demand / workload and capacity during the early hours of business at the registration point did not seem to match, thus resulting in bottlenecks at the patient registration point and throughout the system.
An Investigation of Factors Contributing to Long Waiting of Patients Collecting Repeat Medication in a Tertiary Hospital Pharmacy
(University of the Witwatersrand, Johannesburg, 2023-02) Oladipupo, Rekgopetse Victoria; Hattingh, Teresa; Sunjka, Bernadette
According to the World Health Organization (WHO) patient waiting time is identified as a key measurement to a responsive healthcare service and is an important indicator of quality of services offered by hospitals (NDoH, 2011) as it affects the patient’s responsiveness to the services received (NDoH, 2011; SA FAM PRACTICE, 2008; Tegabu, 2008; Pandit et, al. 2016). Long waiting times at healthcare facilities undermines the services rendered resulting in compromised or unfulfilled patient care (Afolabi & Erhun, 2003). This research studies the processes associated with the collection of repeat medication in a tertiary hospital pharmacy in order to identify value adding activities and non-value adding activities that could be impacting patient waiting time using the Lean thinking concept of driving out waste. A qualitative observational method was therefore employed to observe all the steps involved during the journey of the patient collecting repeat medication from the registration point until medication was issued at the pharmacy. Value stream mapping (one of Lean Thinking principle) was employed to analyze the processes that took place. Patient waiting time was also measured from the registration point to the pharmacy. On average patients had to wait a total 159 minutes before they could access services both at the registration point (67 minutes) and at pharmacy (92 minutes). The service time was 29 minutes at both registration point (11 minutes) and pharmacy (18 minutes). Of the 18 minutes pharmacy service time; eight minutes were found to be value-adding while 10 minutes were non-value-adding mainly due to prescriptions waiting on queue to be picked, waiting to be signed by the pharmacist and waiting to be issued out to the patient. Lack of a dedicated pharmacy service points exclusively for chronic repeat patients, manual dispensing, illegible doctor’s prescriptions, were found to prolong the time it takes the Pharmacist to complete a prescription. Post Basic Pharmacist Assistants performing duties that could be performed by a less qualified staff (e.g., Learner Basic Pharmacist Assistants) during peak hours was not value adding and thus decreasing productivity. The level of staff commitment in addressing issues of quality such as long waiting time was questionable. The demand / workload and capacity during the early hours of business at the registration point did not seem to match, thus resulting in bottlenecks at the patient registration point and throughout the system.
Provision of personal protective equipment and sanitary facilities to female construction site workers
(University of the Witwatersrand, Johannesburg, 2023-09) Nene, Simphiwe; Ozumba, Obinna; Sunjika, Bernadette
The study was based on an aspect of social justice, namely gender equality in the workplace for the female workers who work on construction sites. The area covered in this study was the health and safety of women in construction in the form of the provision of personal protective equipment (PPE) and sanitary facilities to female workers. This specific focus is largely overlooked. The study explored, female workers’ (end-user) perceptions and experiences on the provisions of sanitary and personal protective equipment through a qualitative approach. The main source of data collection was through semi-structured interviews and further supported with site observations in order to triangulate the interview responses. The results of the study found that the availability of PPE for females in the construction industry has improved as women are provided with female size PPE. However, quality and advanced gender sensitive PPE still needs attention. Sanitary facilities at established sites are generally up to standard. However, female workers still share these facilities with their male counter parts. Sanitary facilities at unestablished sites still need attention.
Control of Aerial Manipulators for Contact Inspection
(University of the Witwatersrand, Johannesburg, 2023-10) Matosse, James; Kuchwa-Dube, Chioniso
Aerial manipulators are flying robotic systems that consist of a multi-rotor vehicle tailored with one or more manipulators. These systems are promising for contact inspection of chemical plants, boilers, tunnels and chimneys without human intervention. They require sophisticated control algorithms for control and stabilisation of complex varying dynamics due to the flying, manipulating and interacting with the environment. The dynamics of an aerial manipulator are treated as two subsystems, the quadrotor and the manipulator. The quadrotor dynamics are extracted through the Newton-Euler algorithm using quaternion-based orientation instead of Euler angles. The manipulator dynamics are extracted using the recursive Newton-Euler equations for purposes of handling the floating-base effect. A classic impedance control is a widely used effective control for contact force tracking but it requires the location of the environment relative to the end-effector and the environmental stiffness to be known precisely, and mostly- the desired force as a constant. In contact inspection without human intervention, the environmental properties (geometrical and mechanical) are uncertain, causing the classic impedance control method to be less effective. Presented in this study are: an adaptive variable impedance control (AVIC) for force tracking combined with the integral linear quadratic regulator (LQR) for the quadrotor and proportional-derivative (PD) for the manipulator’s navigation control. AVIC has the capability to counteract for environmental uncertainties by varying the impedance parameter (damping coefficient) on-line corresponding to the force tracking error. This control has been utilised effectively in industrial robot manipulators for a stable force tracking performance. So far in the literature, AVIC together with integral LQR and PD controllers have not been applied to aerial manipulators as a control strategy. Since the aerial manipulator is a coupled system, a linearisation process was performed on the quadrotor dynamics coupled with the manipulator to achieve a fair approximation of the non-linear model. This study has improved force tracking abilities through the implementation of AVIC that allows the aerial manipulator to achieve a desired contact force on the inspected contour while the quadrotor remains in a stable position. Finally, the developed system was simulated using MATLAB/SIMULINK program and the attained results proved the effectiveness of the strategy in comparison to the classic impedance control.
The Development and Application of a Hybrid Metaheuristic Clustering Algorithm to the Capacitated Vehicle Routing Problem
(University of the Witwatersrand, Johannesburg, 2023-11) de Sousa, Andrea Vaz; Bührmann, Joke
The Vehicle Routing Problem (VRP) is an important combinatorial optimization problem in the field of operations research that remains a significant challenge for distribution and logistics operations globally. This research is concerned with a relatively simple variation of the VRP referred to as the Capacitated Vehicle Routing Problem (CVRP), and it focuses on the integration of metaheuristics into its solution. A Genetic Algorithm (GA) was selected and integrated into several CVRP solutions with various configurations of the algorithm. Additionally, a hybrid implementation was proposed, which augments the GA by incorporating conventional heuristics to seed the initial population with “good” solutions. The proposed hybrid solution was the best performing solution evaluated and yielded results comparable to the best-known solution for the smaller datasets. However, the solution quality with respect to the best known solutions decreased with an increase in the size of the problem. This may be attributed to premature termination of the algorithm. Overall, the solutions evaluated were not able to match the best-known solution for each dataset, however successive improvements in the results suggest that GAs are effective at solving the CVRP. Moreover, combining metaheuristics with other methods is also an effective strategy for improving the efficiency of the solution space exploration.
Systems approach to improve utilisation of autonomous drilling at an open pit mine in South Africa
(University of the Witwatersrand, Johannesburg, 2024) Talane, Tabotabo; Botha, Andries
Mining companies have opportunities to feed the continuously growing global economy. However, these opportunities come with challenges. Technologies like drilling automation can help combat these challenges while improving operational efficiency. Although the importance of investing in technology is well appreciated, mining houses still struggle with the sustainable and effective use of introduced technologies. This study looks at the challenges faced by one of the open pit mines in South Africa. The case study mine has introduced ADS (autonomous drilling system) to aid in improving both health and safety, and operational efficiency, but utilisation of the system remains low. The aim of this study is to investigate potential causes of the problem and to come up with an actionable solution to tackle the challenges faced and improve the use of ADS. Six semi-structured interviews were conducted where experts in the field of autonomous drilling shared their insights into factors affecting the adoption of ADS. The interview data were recorded, transcribed and analysed using thematic content analysis. The analysis of the interview data yields seven themes: stakeholder engagement and buy-in; management support and trust; process management and KPIs (key performance indicators); ownership, accountability and influence; site capability; culture and attitude shift; and implementation approach. Using the systems approach and soft systems methodologies (SSM), the study found that effective stakeholder engagement and communication with workers early in the project can lead to a positive attitude towards the introduced system, improving its adoption. Further, management support becomes vital to build trust and team resilience, especially during challenging times. Additionally, the way of managing processes must evolve and adapt to accommodate the technology system introduced, and this requires a mindset shift from a leadership perspective. Operating standards and procedures of the entire drilling process, from planning to execution, also need to evolve with the introduction of technology to ensure that upstream processes become enablers of the effective use of the technology. Like standards and procedures, key performance indicators are those metrics that managers track, and they also need to be updated to allow accountability and ownership around the use of technologies like ADS. With commitment and drive from operational leaders, technology implementation can succeed. The correct implementation approach will increase the chances of success. The approach must be guided by an effective stakeholder engagement and requirements analysis. A proper approach in tandem with both management support and team commitment can result in the sustainable adoption of new technologies, including ADS.
Factors influencing innovation in public healthcare in South Africa: A critical analysis
(University of the Witwatersrand, Johannesburg, 2024) Nkosi, Mbali Rosemary; Siriram, Rajenlall
Healthcare innovation has proven to reduce morbidity and mortality rates by enhancing healthcare delivery. Most of the South African population depends on the public healthcare system for health needs. The morbidity and mortality rates in South Africa are much higher compared to other middle-income countries in the world. To enhance healthcare delivery in South Africa, understanding the factors that influence innovation in public healthcare is important. Therefore, this research aims to provide a comprehensive understanding of the factors influencing innovation in public healthcare in South Africa and the potential impact of innovation on the country's healthcare system. The main objectives of this study are to determine the level of successfully implemented innovation in public healthcare and the factors influencing it. Existing literature identifies several factors that influence innovation in public healthcare, including design empathy, technological infrastructure, decision-makers, human capital, and organisational culture. This study also investigates the readiness of the public health sector to embrace innovation and the strategies in place for implementing innovation in public healthcare. A gap was identified in the existing literature. There is evidence in literature is that healthcare innovation centres in South Africa and their impact on the adoption of innovation in public healthcare were only covered marginally by existing literature. To bridge this gap, this study provides results on the status of suitable research and development hubs for testing healthcare innovation prototypes in South Africa and their impact on the adoption of innovation in public healthcare. Currently, there are limited health innovation centres in South Africa. This study posits that an increase in the number of healthcare innovation centres would increase evidence-based innovation which would increase the uptake of innovation in public healthcare. A qualitative research approach was used to acquire descriptive information on the factors that influence innovation in healthcare through interviewing participants. Semi-structured interviews were used as the primary instruments of data collection. The interviews were then subjected to a thematic analysis. One of the significant findings of this research is that the lack of funding in public healthcare hinders innovation in the public healthcare system. Also, the rigorous regulatory requirements pertaining to healthcare innovation tend to cause uncertainty and delays, which in turn reduces the funding available for innovative proje
An Investigation Into The Propulsive Force Generation Of Multiple Flapping Surfaces
(University of the Witwatersrand, Johannesburg, 2024) Mabvuu, Never; Ho, Weihua
The aerodynamic performance of flapping NACA0012 airfoils was analyzed through numerical simulation, focusing on the effects of stagger, gap, phase difference, and the number of airfoils. The simulation was conducted under specific conditions: 𝑈∞ = 0.2𝑚/𝑠, f=2Hz, 𝛼0=200, C=0.04m, St=0.2 and Re= 8000). The problem was modeled in ANSYS Fluent using a transient viscous approach with absolute velocity formulation, employing the pressure-based coupled solver (PBCS). PRESTO! interpolation and second-order upwind discretization were applied for pressure, momentum, intermittency, turbulent kinetic energy, and specific dissipation rate. Mesh validation and independence studies confirmed that the results were driven by the physics setup, independent of mesh configuration. It was discovered that small stagger and gap at φ=1800 is not good for thrust production as the airfoils produced thrust less than a single airfoil with ∆Ctav = -0.94. However, lift production is increased and ∆Clav =1.2. At larger spacing ∆Ct, ∆Cl and η generally become constant. One of the worst performing cases (X=1.0C;Y=0.5C; ϕ= 1800 ) was improved by making the aft airfoil lead ( φ= -450 ). This explains why insects alter φ or frequency depending on the situation and flight requirements. The most effective X-Y- ϕ were found to be the ones at which flow separation is suppressed. For the 4 airfoils cases the fore pair performed better than the aft pair for the small spacing case. When spacing was increased the aft pair performed better than the aft pair.
Supply Chain Risk Management in Manufacturing Small and Medium Enterprises: A Systematic Literature Review
(University of the Witwatersrand, Johannesburg, 2024) Pungula, Vusumuzi; Sunjka, B.
Background: Small and Medium Enterprises (SMEs) are becoming major actors in the manufacturing sector due to the rising complexity of global supply chains. However, they still face enormous risks from supply chain disruptions and market dynamics, which can have costly effects. SMEs sometimes lack the means and expertise to execute comprehensive risk management plans intended for larger businesses, despite their significance. Research on Supply Chain Risk Management (SCRM) specifically for small and medium-sized enterprises (SMEs) is noticeably lacking, especially in the manufacturing sector. Purpose: The aim of the study was to systematically review how SCRM has been developing in manufacturing SMEs globally over the past two decades, and provide insights for policymakers, industry associations, and SMEs themselves. Method: A Systematic Literature Review (SLR) was conducted by utilizing a qualitative research approach. Seven key phrases were formulated to guide the search for relevant articles published between 2000 and 2023. A thorough screening process was employed to select 38 articles that met inclusion criteria, and data analysis was performed using NVivo software on these articles. Following this, thematic analysis and textual narrative synthesis methods were employed for data analysis and synthesis. The discussion of the identified themes provides comprehensive insights to policymakers, industry associations, and SMEs into the current status of SCRM research in manufacturing SMEs globally. It highlights the importance of effectively addressing risk variables, developing tailored SCRM approaches, and striking a balance between risk reduction efforts and strategic opportunities within supply chains to enhance resilience and ensure operational continuity. Results: The review revealed a significant increase in SCRM research pertaining to manufacturing SMEs over the past decade. Trends analysis indicated a growing emphasis on SCRM in various disciplines, highlighting its increasing significance. Thematic analysis identified eight key themes, including the current status of SCRM research and factors influencing SCRM strategies in manufacturing SMEs. Conclusion: Based on the comprehensive review of literature, several key conclusions can be drawn. There is prevalent recognition of the importance of SCRM within SMEs, emphasizing the need for proactive risk mitigation strategies tailored to the SME context. While formal risk management approaches are increasingly adopted, the context-specific nature of risk management practices highlights the importance of tailored approaches. Technological advancements play a significant role in enhancing SCRM strategies, alongside the integration of green supply chain management practices.
Bodies of cunicularity in supersonic flow
(University of the Witwatersrand, Johannesburg, 2024) Myburgh, Sabrina Gabrielle; Law , Craig
Prior studies outlined the success of using randomised High Porosity Cellular Material cyl- inders both numerically and experimentally, however showed limited applicability to real-life aerodynamics applications. The primary effect of supersonic flow over porous media is to attenuate the bow wave by reducing the angle of incidence and redistributing the flow field, significantly reducing wave drag. The aim of this work was to investigate the drag-reduction effect of organised porosity within conic bodies of revolution on the supersonic flow field. Various organised porous cone-cylinders were developed to investigate the effect of the porous structure on the flow field, including shock waves, momentum changes and flow structures in and around the por- ous body. Several conic profiles were investigated. A numerical and experimental investigation was carried out in steady, supersonic flow at Mach 3.5 (Re = 3.9 × 10−5). The conic models had a porosity of ≈ 60%. The blow down supersonic wind tunnel facility at the University of the Witwatersrand was used for the exper- imentation, where schlieren photographs were captured along with drag force measurements of the solid and porous baseline cones. Numerical CFD simulations were carried out for a wider range of porous configurations using ANSYS Fluent R22.2. The numerical, experi- mental and literature Cd and flow visualisation were used to validate the numerical method, showing good agreement across data sets. Certain cunicular arrangements effectively reduced the drag in some shapes, while others worsened the drag. The greatest drag reduction of 40% was achieved in the cunicular BS4 Ellipsoid. The change in drag was associated with three sources, namely wave drag, jet v interaction, and momentum addition by the jet. These changes resulted from the flow inter- actions occurring within the inlet, internal and venting structures. Changes in drag depended on several factors, including vent geometry, expansion ratio, exit angle, inlet geometry and the crossflow condition, to name a few. Wave drag reduction was dependent on shock at- tenuation and reducing the wave angle, which was generally ensured by the conic surface pores absorbing energy from the bow wave. The jet interaction and momentum recovery were dependent on vent expansion ratio, exit angle and crossflow condition. The jet interaction had the greatest increase on the drag of the system, however, the effects of this were mitigated by using low vent angles with correct expansion ratios to maximise momentum recovery from the jet. The effect of the combined system was specific to the particular case, where the solid cone shape greatly influenced the overall performance. The effect on drag reduction was cumulative, sensitive and highly dependent on the individual case. The cunicular system is a viable drag reduction mechanism in conic bodies, however careful balancing of the porous inflow, outflow, bow wave and venting conditions is required in order to achieve significant drag reduction.
The Effects of Rectilinear Acceleration and Deceleration on Shock Formation near a Stationary Boundary
(University of the Witwatersrand, Johannesburg, 2024) Morrow, Sean Robert
Inspired by the world land speed record vehicles the Thrust and Bloodhound supersonic cars (SSC), the focus of this dissertation is to investigate how rapid acceleration affects the formation of shock waves coming off an object travelling in ground effect. Due to the proximity of the ground, these shock waves are not able to freely propagate under the object and must interact with, and reflect off, the ground. Steady state and transient models of aerofoils, accelerating from Mach 0.05 to Mach 2.00 at a test run acceleration of 3 g and an extreme acceleration of 176 g are developed and compared to reveal that the transient shock wave development trails that of the constant velocity aerofoil. The main reason for this difference is that the transient flow is unable to fully develop and reach a state of equilibrium. The extreme acceleration allowed even less time for the flow to develop, and the difference in the shock location continuously increased throughout the acceleration. The same difference in shock location was evident when these models were decelerated back down to Mach 0.05. However, the extreme deceleration and increasing difference in shock location drastically changed the transonic and subsonic flow field, especially as flow features and shock waves from the higher velocity flow overtook the model. In each acceleration and deceleration case, the transient flow history effects subsided and the aerodynamic performance from the transient analysis converged with the aerodynamic performance from the steady state analysis. Under acceleration the transient performance converged at a higher steady state Mach number, while under deceleration the transient performance converged at a lower steady state Mach number. As the magnitude of the acceleration and deceleration increased the Mach number at which the results converged shifted to higher and lower Mach numbers respectively. Models with different orientations and ground clearances were also compared against each other and a case at free flight to determine the impact ground effect has on the formations and locations of the shock waves. Increasing ground effect was shown to promote the formation of shock waves under the inverted aerofoil and in general delay the propagation of the bow shock between the model and the ground. Once the bow shock propagations passed underneath the models, the resulting flow field converged with free flight conditions and ground effect no longer had an impact on the supersonic aerodynamic performance of these models. Under some conditions, the combination of ground effect and the transient effects of acceleration or deceleration can cause dangerous lift and pitch conditions.
Characterisation, Modelling, Finite element analysis, and optimisation of hyperelastic materials for Non-Pneumatic Wheels
(University of the Witwatersrand, Johannesburg, 2024) Bhartu, Saahil; Pietra, Francesco
This abstract concludes the exploration of hyperelasticity within the context of mechanical engineering. Through this section, we have delved into the substantial elastic deformations characteristic of hyperelastic materials, their capacity for energy conservation during deformation, and their inherently non-linear behaviour. The calibration of non-linear material models has been informed by a rigorously designed experimental regimen, where preferred methodologies and necessary precautions were identified to ensure the integrity of the data obtained. Theoretical foundations for the development of constitutive models have been established, with a discussion of prevalent models frequently employed in engineering applications. Practical modelling applications introduced have provided a tangible context for the utilization of hyperelastic material models. While our focus was predominantly on nearly or fully incompressible materials, foundational concepts for compressible behaviour were also addressed, setting the stage for further investigative pursuits. Polyurethane (PU) materials exemplify hyperelastic behaviour. Through computational simulation, we assessed the deformation in a structured wheel to be 4.6mm, utilizing a 9;5 and 2 parameter Mooney-Rivlin model for the PU material. Experimental testing was conducted measuring deformation to be 4.1mm From the results, the deformation patterns, stress distributions, and contact pressures were analysed, indicating the wheel’s ability to endure a contact pressure of 7.36MPa, deformation of 4.6mm, Von-Mises stress of 3.9MPa. This investigation not only corroborates the distinctive properties of hyperelastic materials but also illustrates how analysis results can inform and optimize design iterations. It demonstrates the practical applications of hyperelastic material models in design engineering, providing a comprehensive understanding that is indispensable for the modelling and analysis of hyperelastic components.
Development of an enterprise engineering strategy execution framework
(University of the Witwatersrand, Johannesburg, 2024) Mudavanhu, Thabani B.; Emwanu, Bruno
Even with a myriad of implementation models from consulting firms and academia – the success rate of Strategy Execution (SE) remains low. Extant literature in strategy execution exposes inadequacies of theoretical foundations for the assertions outlined in current SE models. In addition to this, where there is some explanation, the theory is inconsistent, and discipline biased which limits development of general application theory. Further to this ‘enterprises’ as the housing (the system of interest) from which a strategy is launched rarely receive the level of attention and rigor that technical systems do. Against this background, this study sought to understand how the success rate of SE can be improved through the application of Enterprise Engineering (EE) principles and practices. The premise being that the challenges in implementing strategies in any organisation are too an extent related to the design of the enterprise. Consequently, the common challenges attributed to the failure in SE can be linked to the enterprise design and as such organisations can, to an extent be designed to influence SE. Considering the complexity / greyness of the study area and limited literature in the relatively new discipline of EE, specifically enterprise ontology theory (the theoretical lens of this study), a structured literature review was used as the basis for a Delphi study. A two (2) round Delphi study was conducted with experts in the field to determine and validate the critical dimensions in Strategy Execution. Thirty-one (31) and twenty (25) experts participated in Delphi Round 1 and 2 respectively. The experts came from four regions of the world and were largely academics, board members and executive leaders and practitioners many of them tasked with either overseeing or leading strategy execution. The study revealed that there is a significant relationship between the design of an enterprise at the deepest level (the ontological layer) and the seven (7) aggregated themes that were synthesised in this study and are linked to constraining successful SE – (a) the strategy itself, (b) leadership, (c) people (the team); (d) effective communication; (e) organisational capabilities (f) organisational enablers and (g) organisational culture. The study proposed a generic enterprise engineering-based strategy execution (EEbSE) framework anchored in the deepest layer of an organisation, the ontological layer - the level where companies transact (cooperate and enter into agreements). Consequently, the study confirmed the proposition that ‘organisations can, to some degree, be designed or re-engineered for strategy execution’. This study demonstrates how EE can be useful in aiding Successful SE. An example of a key take-away include the need to check for execution readiness at the ontological layer and v eliminating any construction flaws (errors) that will later reflect as ‘common’ challenges. For example, lack of commitment [people issues] and lack of an implementation [culture issues] are flaws associated with SE that can be traced and re-engineered at the ontological level. This study adds to on-going work to confront the SE challenge and demonstrates the relevancy and pervasiveness of the application of EE.
The assessment of exploration processes in the Upstream Industry to increase exploration efficiency and promote accelerated drilling decisions.
(University of the Witwatersrand, Johannesburg, 2024) Tshikovhi, Rilwele Mikovhe Muditambi; Botha, A.
During petroleum exploration, petroleum companies (operators) require efficient hydrocarbon detection and delineation methods to locate petroleum prospects and promote drilling (Selley, 1998). The two pre-drill surveys under investigation in this study are seismic surveys and controlled source electro-magnetic (CSEM) surveys which are used to study the subsurface during offshore petroleum exploration. Drilling dry holes is inevitable, however, a proper and thorough prospect evaluation can significantly increase the chance of success of a prospect (Milkov & Samis, 2020). The purpose of the research is to evaluate seismic and CSEM surveys as secondary hydrocarbon detection tools used to recommend drilling, and to also determine if any of these methods can encourage accelerated drilling decisions and significantly reduce exploration risk. A total of 49 seismic-based samples and 41 CSEM-based samples were used in the study. Survey anomalies were assessed against drilling results to determine the predictive strength of each survey. The Chi-test confirmed that there is a significant association between survey anomalies and attributes such as well results, predictive strength, fluid type and trap style. The researcher analysed the two datasets to determine the probability of an anomaly in each survey and the chance of success if each well is drill based on these surveys. The presence of an anomaly was defined as a positive anomaly (PA) and the absence of an anomaly was defined as a negative anomaly (NA). Fluid type and trap style were used to analyse the predictive ability of the survey anomalies. Seismic and CSEM surveys have indicated a high probability of discovering charged reservoirs in a structural trap as compared to stratigraphic traps, however, CSEM is slightly better than seismic surveys in defining these reservoirs. Both surveys have a low probability of predicting a charged stratigraphic reservoir, although seismic surveys have indicated higher chance of success as compared to CSEM. Positive anomalies observed in both surveys proved to be good indicators of gas-bearing reservoirs as compared to other hydrocarbon fluid. CSEM has a slightly higher chance of predicting oil than seismic surveys. A simplified process mapping for the current offshore exploration processes was conducted. A decision tree was used to analyse seismic and CSEM surveys as secondary tools with emphasis given to their hydrocarbon detection capabilities. Bayesian Theorem was used to calculate the posterior probabilities given that a well is drilled on a positive iii anomaly. The same was applied for wells drilled on negative anomalies. The results have indicated that CSEM has a higher probability of detecting hydrocarbon accumulations as compared to seismic surveys.
The improvement of the on-time delivery for “company x” e-commerce orders during the golden quarter
(University of the Witwatersrand, Johannesburg, 2024) Sukazi, Thobile Nomalungelo; Sunjka, Bernadette
E-commerce has revolutionized global business and consumer interactions, offering convenience and accessibility across various domains like Business-to-Business (B2B), Business-to-Consumer (B2C), and Consumer-to-Consumer (C2C). The COVID-19 pandemic has accelerated digital transformation, with South Africa's e-commerce market showing robust growth projections, fuelled by factors such as improved internet penetration and shifting consumer behaviours. The Omni-channel strategy has become standard, with leading players leveraging digital capabilities to maintain market share. Notably, the "Golden Quarter" of retail, encompassing events like Black Friday and Singles Day, presents a pivotal opportunity for retailers to boost profits through strategic promotional efforts. As the market matures, focus shifts to optimizing the final mile of delivery, aiming to improve efficiency and reduce costs. This project seeks to explore tailored strategies for final mile optimization in Company X, aligning with the broader goal of enhancing efficiency and customer experiences in South Africa's growing e-commerce sector. Despite being the second-largest wholesale food distributor in South Africa, Company X experienced significant on-time delivery performance declines, particularly in its discount retailer brand, Banner 3. The analysis identified logistical bottlenecks in the final mile as the primary contributor to these challenges, resulting in an average delay of 4.3 days in the order fulfilment process. Additionally, the study highlighted the importance of addressing these challenges to maintain customer satisfaction, loyalty, and competitiveness in the rapidly evolving South African e-commerce landscape. This study employs a comprehensive framework and systematic approach to investigate the research questions and objectives. A qualitative research design involves one-on-one interviews conducted digitally via Microsoft Teams. Ethics clearance (MIAEC 099/23) was obtained, ensuring transparency and participant understanding. The sampling strategy prioritizes quality over quantity, with six diverse participants selected to provide rich qualitative data. Data analysis follows Braun and Clarke's thematic analysis approach, incorporating triangulation methods and emphasizing thorough documentation to ensure validity and reliability. This research has thoroughly investigated Company X's final mile delivery challenges during the Golden Quarter, providing comprehensive insights and recommendations for enhancement. Key findings underscore the significance of accurate forecasts, planning collaboration, proximity to customers, fleet and technology utilization, customer service levels, and delivery types in optimizing delivery performance. Recommendations encompass advanced forecasting models, collaborative planning efforts, tailored customer promises, technological enhancements, and automation to address identified challenges and capitalize on opportunities for improvement. The proposed strategies offer a strategic roadmap for Company X to enhance efficiency, customer satisfaction, and competitiveness in the e-commerce landscape, aligning with the study's objectives and concluding the project successfully. The tailored recommendations contribute valuable strategies for improving efficiency, customer satisfaction, and competitiveness. Future research could focus on evaluating the implementation of these strategies and exploring emerging technologies to further optimize the delivery process and adapt to evolving market dynamics.
Fatigue Crack Propagation in AlSi10Mg Additive Manufactured Aeronautical Parts Processed by Laser Shock Peening
(University of the Witwatersrand, Johannesburg, 2024) Chinyama, Joel; Polese, Claudia
Additive manufacturing (AM) offers advantages for complex aeronautical parts, but inherent defects can reduce fatigue life. Post-processing techniques such as laser shock peening (LSP) can be used to introduce beneficial compressive residual stress that hinders crack propagation. This study investigates LSP as a method to improve fatigue performance in additively manufactured AlSi10Mg aeronautical parts. It examined how varying LSP treatment laser power intensity (1.5 – 4.5 GW/cm2) affects LSP's effectiveness and identified optimal LSP residual stress profiles for peak fatigue performance. The residual stress profiles that were used in this research were adopted from previous experimental work done on AM-manufactured AlSi10Mg alloys within the Wits AM/LSP group. Previous experimental work results on wrought AA2024-T351 (untreated and LSP-treated cases) indicated that LSP-treated samples have a fatigue life of at least four times longer as compared to as-built samples. AFGROW models with similar geometry, material properties and load conditions were used to predict the fatigue life of as-built and LSP-treated cases. An improvement in fatigue life of at least 3.8 times was observed, which was within an acceptable deviation from the experimental results. These results were used to validate AFGROW models for exploring different specimens. Fracture mechanics models (AFGROW) were used to compare the fatigue life of as-built and LSP-treated AlSi10Mg samples with different LSP power intensity parameters. The results showed that LSP treatment can significantly extend fatigue life, with the optimal laser power intensity found to be 3.0 GW/cm2. This improvement is attributed to the introduction of compressive residual stresses by LSP, which suppress crack initiation and propagation. The effectiveness of LSP was further explored in the context of the Cessna 172/175 horizontal stabilizer, a part that could benefit from AM for weight reduction and structural integrity. AFGROW models were developed to predict the fatigue life of the centre lightening hole in the forward spar, a critical location for crack initiation. The models incorporated a beta correction factor to account for the specific crack geometry and stress distribution. The beta correction factor was determined by comparing the stress intensity factors from the Finite Element Analysis (FEA) and AFGROW models. The results again demonstrated a significant increase in fatigue life (of at least six times) for LSP-treated parts compared to as-built parts. AFGROW models with a beta correction factor proved valuable for predicting fatigue life in components with complex geometries. This study confirms that LSP is an effective post-processing technique for mitigating fatigue crack propagation in AlSi10Mg AM aeronautical parts.
Financial Evaluation of Implementing In-Pit Crushing and Conveying Systems for Waste on Open Pit Mines
(University of the Witwatersrand, Johannesburg, 2024) Serepa, Ikaneng; Emwanu, B.
The South African mining industry has faced mounting challenges, especially rising expenses that threaten profitability. These escalating costs, driven by various factors including operational expenses such as mining costs, are critical. The distribution of mining costs across activities within the production cycle is crucial, with hauling operations in open pit mines representing a significant portion, as noted by Paricheh et al (2017) at 49%. Due to the substantial economic impact of hauling expenses on mining expenditures, there's a strong incentive to streamline these operations to lower overall costs effectively. Current research highlights a noticeable transition in the mining sector towards embracing in-pit crushing and conveying (IPCC) systems in open pit mines, acclaimed as a cost-effective substitute for conventional truck and shovel (CTS) systems (Awuah-Offei et al, 2009). This research assessed both the integration and financial viability of implementing a waste IPCC system in the loading and hauling operations of an open pit mine. A mixed-methods approach, combining quantitative data from production records and costs with qualitative insights from expert interviews was used. The findings of this research indicate that while the IPCC system can be integrated, there remains a degree of reliance on the CTS system for material transportation from the pit to the IPCC system. For the CTS system, 55 rigid dump trucks (RDTs) are required, constituting 57% of the initial capital expenditure of R1.27 billion. Conversely, the IPCC system requires only 31 RDTs, accounting for 29% of the initial capital costs of R1.37 billion. However, despite the substantial reduction in RDTs, the IPCC system requires significant investment in a crusher and conveyor belt system for waste management, which constitutes 32% of its capital costs. Examination of the operating costs over the life of the mine indicates that there are no cost advantages associated with operating an IPCC system compared to the CTS system. Operating expenses for the IPCC system exceed those of the CTS system by 58%, predominantly driven by the operational costs of the crusher and belt system, contributing to 67% of the IPCC system's costs. The financial assessment results show a positive and acceptable net present value (NPV), internal rate of return (IRR), and payback period for both systems. Nevertheless, the CTS system exhibits superior financial performance, with a NPV of R7.45 billion, an IRR of 83.1%, and a shorter payback period of 1.2 years, and is recommended as a viable option for the mine.
The development of cannabis in emerging markets- Evaluating the prospective value chain, market accessibility, and commercialisation
(University of the Witwatersrand, Johannesburg, 2024) Rapetsoa, Maisaaya Hellen; Emwanu, B.
In recent years, the significance of small businesses in the growth of developing economies has been acknowledged, along with their ability to foster social development, create employment opportunities, advance innovations, and contribute to economic growth. The agricultural sector serves as a catalyst in building a strong economy by increasing income and employment opportunities for the poor while nurturing natural resources. This is evidenced by the vision stated in the Government’s National Development Plan (NDP), which proposes to create close to 1 million jobs by 2030 within the agricultural sector. This study aimed to determine the “strategic interventions required to ensure that South Africa is aligned with the regulatory, social, economic, and knowledge base needed for the effective commercialisation of the cannabis market”. In doing so, knowledge experts were consulted through open-ended interviews to ascertain their views on the growth and trajectory of cannabis as an economic driver. This qualitative study adopted the Wengraf pyramid model to relate the “progression from the Central Research Questions (CRQ) differentiated into several Theory Questions (TQ) and the particular Interview Questions (IQ) and the non-verbal Interview Interventions (II)” (Wengraf, 2001). The selected qualitative method was best suited for this research as it assisted in breaking ground on themes that have limited literature, such as the current research. The data was collected from subject matter experts through open-ended interviews, allowing the participants to freely express and share their knowledge, views, and experiences. An ‘inductive content analysis’ method was used to analyze the data by transcribing and coding the information to identify common themes, links, and categories and gain more understanding of the data received. The study claimed that cannabis has the potential to uplift the economy and alleviate poverty through its commercialisation and that the legal frameworks or lack thereof pose a barrier to the growth and development of this market. The research revealed that there is a greater gap in the market where the knowledge, expertise, and financial instruments are being underutilized therefore rendering South Africa a laggard with considerable ramifications for our global competitiveness. With much at stake and our staggering economy, the common theme was that erratic and deliberate action is required especially in a market where other countries that have legalized cannabis appear to be well under control and thriving. Cannabis has become one of the biggest disruptors of mainstream industries over the last decade, impacting sectors from pharmaceutical, food, and wellness to cosmetics. The subject experts collectively agreed that South Africa is missing out on a multibillion-dollar opportunity.
Aerodynamic Force Variation on a Trailing MotoGP Motorcycle in a Corner
(University of the Witwatersrand, Johannesburg, 2024) Shaw, Craig Byrne; Boer, Michael
Motorcycle racing is a popular form of motor racing. The MotoGP category produces exciting and competitive races due to motorcycles following each other so closely. This has led to significant aerodynamic advancements being made in the MotoGP category over the past decade. Motorcycles and riders often race within the wake of a leading motorcycle as a result of this competitive racing. Racing in the wake provides an advantage on a straight due to the reduced drag force. This allows for greater acceleration and an opportunity to overtake the leading motorcycle. The effect of the wake on a trailing motorcycle in a corner has not been explored in depth. This research was focused on the aerodynamic force variation on a trailing motorcycle in the wake of leading motorcycle. The optimal position for the trailing motorcycle to gain an advantage over the leading motorcycle was determined subsequently. This was achieved using Computational Fluid Dynamics (CFD). The geometry of the motorcycle was obtained using 3D scans of a 1/18th scale model 2018 Repsol Honda RC213V. The geometry of the rider was drawn using CAD. Initial CFD models were created simulating the motorcycle and rider in a straight line to compare to existing published data for validation. The CFD cornering methodology was developed by Queens University in association with Siemens. The method makes use of rotating reference frames. This simulates the motorcycle and rider cornering at a constant velocity around a constant radius corner. Models were created for a singular motorcycle and rider at varying lean angles between 40 and 60 degrees with matched velocities and corner radii. The aerodynamic forces of drag, lift and side force were analysed on the motorcycle and rider for each case. The trends for these forces were determined relative to the changing lean angles. The drag on the motorcycle and rider increased non-linearly as the lean angle increased with the side force following a similar trend. The lift on the motorcycle and rider also increased non-linearly as the lean angle increased. These same CFD models were recreated with a second motorcycle and rider following a leading motorcycle to determine the effect the wake had on the aerodynamic forces. The second motorcycle and rider were positioned 1 characteristic length behind the leading pair on the same racing line. The drag on the trailing motorcycle and rider decreased as the lean angle increased. The lift on the trailing motorcycle and rider followed a similar trend to the leading pair with it increasing as the lean angle increased and the side force fluctuates as the lean angle increased. This resulted in the trailing motorcycle having a negative allowable change in forward acceleration relative to the leading motorcycle at lean angles lower than 60 degrees. The optimal position for a trailing motorcycle in a corner was determined by positioning the motorcycle and rider on various racing lines and following distances behind the leading motorcycle and rider. This created a grid pattern of the tested trailing positions. Two smaller racing line radii, three larger racing line radii and three different following distances were tested. The optimal trailing position at a 50 degree lean angle was found to be 1 characteristic length behind and on a racing line 1 characteristic width larger than the leading motorcycle. This position resulted in a positive allowable change in forward acceleration relative to the leading motorcycle around a corner radius of 125.86 m at 38.36 m/s. This iii position was tested around another two corner radii of 75 m and 150 m. This resulted in a negative allowable change in forward acceleration of around the 75 m radius corner and a greatly improved positive change in forward acceleration around the 150 m radius corner. From these results it was concluded that this optimal position is only viable around larger radius corners. It was approximated that this optimal position provides the trailing motorcycle an advantage around corner with radii larger than 86.8 m.