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Development of a digital twin for demo cooling system
Full text linkCO2 - based mechanically pumped fluid systems, known as Two-phase Accumulator Controlled Loop (2PACL) systems, have continued to enjoy extensive research and exploration at CERN. The system offers operational specifications that arise as a results of the High Luminosity upgrade. These include the need to operate at a colder temperature of -45˚C at the detector and -53˚C at the pump inlet and substantially higher varying loads. Furthermore, for redundancy, the systems now need to have multiple plants in parallel. To address challenges pertaining to scaling, the systems now have novel design elements such as the addition of the surface storage, flow-through mode for the accumulator, Back Pressure Regulator, new more intricate logic. This project considers simulations that have been developed for mechanically pumped fluid systems and then develops a full-scale model for the novel 2PACL systems developed at CERN, including the new of intricate logic and functionality. The literature survey revealed that there are no simulations to conduct a system-level study or a study of this new logic. No simulations are available for the new systems with parallel architecture and new logic associated with it for smooth handover. The project further explores how the critical control loops in the new systems may benefit from a procedural control design that considers plant uncertainty and sampling effects. Simulations conducted with the model are then validated against the measurements from corresponding experiments in Demo – CERN's 2PACL prototype, which cover startup, setpoint change, load change, and the swap and re-takeover test. The results are used to validate the model fidelity – both the discrete logic and trajectory behaviour
Modelling of Berry phase and Fermi-level topologies for emergent quantum phenomena prediction in selected solid state systems
Full text linkTopological materials host electronic states that remain robust against perturbations and offer routes to novel quantum functions. This thesis investigates three representative compounds - SrSi2, CoSi, and NbP - to reveal how external stimuli, namely tensile strain and electric fields, tune their electronic bands and topological traits. By combining first-principles calculations with model Hamiltonian experiments, we aim to uncover mechanisms behind quantum phase transitions (QPTs) and to establish design principles for materials with tailored quantum states. We perform density functional theory (DFT) calculations within the plane-wave pseudopotential framework using the Quantum ESPRESSO (QE) suite. Spin-orbit coupling (SOC) is included to capture relativistic effects critical for topological properties. We generate maximally localized Wannier functions (MLWFs) with Wannier90 and construct tight-binding (TB) models to compute Berry curvature, surface state spectra, and Fermi arc patterns via WannierTools. To probe QPTs in SrSi2, we employ the Quantum Lattice environment to simulate a renormalized graphene lattice, mapping analogies between external perturbations and topological responses in both systems
Understanding the burden of HIV-related cancers in South Africa's Eastern Cape Province: A 2002-2017 retrospective study
Full text linkBackground: The Human Immunodeficiency Virus (HIV)-related cancers in South Africa are a critical public health issue that echoes trends seen across other low-middle income countries (LMICs). These cancers include Kaposi sarcoma, non-Hodgkin's lymphoma, and cervical cancer. Understanding the HIV-related cancer trends and incidence is crucial for achieving improved health outcomes. Therefore, this study aims to understand the HIV- related cancers in the Eastern Cape province of South Africa Methods: This retrospective study used secondary analysis of data generated by the Eastern Cape Cancer Registry linked to the HIV database from the National Health Laboratory Services through probabilistic record linkage to identify and characterise cancer among people living with HIV. Included were cancer cases reported between 1st January 2002 and 31st December 2017 of adult men and women diagnosed with HIV-related cancers. Statistical analysis was done using STATA18.0. A join-point regression model was used to characterise the cancer trends. The Kaplan-Meier curve was used for survival analysis. Results: The sample comprised 1183 eligible cancer patient records, with 1044 (88.3%) females. The HIV prevalence among cancer patients was 74.5%. Specifically, 75.5% of males and 74.3% of females were living with HIV. The trends of Kaposi sarcoma showed an increase between 2002 and 2015 with an annual percentage change (APC) of 17.4%, and between 2015 and 2017, trends decreased with an APC of 22.6%. Cervical cancer trends decreased between 2002 and 2004 with an APC of 14.4%; from 2004 to 2017, there was a sharp increase of 33.2% APC. Kaposi sarcoma had the highest survival median of 3.1 years (p=0.06) for people living with HIV, followed by non-Hodgkin's lymphoma with 2.9 years (p=0.96), and lastly cervical cancer with 2.5 years (p=0.73). Conclusion: The growing burden of cervical cancer and Kaposi sarcoma among people living with HIV remains a problem in the Eastern Cape. Therefore, targeted interventions such as regular screening, early diagnosis, access to appropriate treatment, a system to track treatment adherence and survival rates, appropriate resource allocation, and targeted educational programmes are needed to address the burden
How social change leaders practice reflexivity in an integrated way and realise its emancipatory aim
No full textSocial change leaders seek to help those marginalised by some of the most pressing social problems of our time. The underlying assumptions informing how ‘help' is understood and given may, however, remain overlooked, producing disempowering rather than empowering outcomes for the ‘helped'. Such assumptions and related relationships and power imbalances can be examined through the practice of reflexivity. My literature review explores the meaning of reflexivity and reflexive leadership. I derive four calls of reflexivity from the literature: to question assumptions, to interrogate power relations, to relate with others and the Other, and to live with heart. The literature review also shows that reflexivity acknowledges the interconnected and embodied nature of experience. Yet while there is evidence of siloed, and mostly discursive, reflexive practice, there is a scarcity of literature on the integrated enactment of reflexivity that is inclusive of embodied as well as dialogical practices. While reflexivity's emancipatory effect is referenced in the literature, the mechanism by which reflexivity might achieve this aim is unclear. The resulting research question that responds to this gap in the literature is: How do social change leaders practise reflexivity in an integrated way, and how does this practice fulfil reflexivity's emancipatory aim? Aligned with positive organisational scholarship, I chose to study leaders within two social change organisations as positive cases in that they demonstrated apparent accomplishments in reflexive leadership, with empowering results for participants. I designed a phenomenological research methodology that gave precedence to experiential, embodied and relational research design elements. This took the form of arts-based methods (including clay work, photography, and drawing) combined with interviewing. I also designed and implemented three original arts-based methods: family mapping, dialogue writing and letter writing. Interpretive phenomenological analysis (IPA) informed the analysis of data, as well as the design of the study. In my findings, I discover that leaders take on a critically reflexive role in identifying and responding to the contextual threats and trauma that the intended participants of their social change interventions encounter. They design and then engage in numerous reflexive practices with participants which are mutually supportive to form an integrated whole. I call this integrated reflexive practice (IRP). The constituent practices are bodying (including inter-bodying); dialoguing; seeing, hearing and caring for; and the fostering of physical and emotional safety. Collectively these develop participant self-reflexivity. I show how these practices are reflexive and interrelated. I further show that IRP empowers participants by interrupting pathways from their contextual threats/trauma to habituated defensive action (characterised by the psychological defence mechanism of splitting), developing instead reciprocity and choice towards integration, which in turn leads towards participant empowerment. The study contributes to the literature on prosocial reflexive leadership by identifying a constellation of interrelated, mutually supportive reflexive practices that form a holistic whole. Trauma is flagged as an important contextual feature, which shapes both the need and opportunity for IRP. I also develop the concept of inter-bodying as a foundational aspect of such reflexive practice, involving the empathic sensitization to the other and to context, through conscious, physical presence. I offer practical implications for leaders, students and educators to develop IRP towards empowerment. These implications become increasingly relevant as leaders manage themselves and others in contexts of greater ambivalence and uncertainty
Resilience of small-scale farmers amidst the COVID-19 Pandemic: a case study of small-scale farmers in Limpopo Province, South Africa
No full textThis qualitative study examines the impact of COVID-19 lockdowns on small-scale farmers in Limpopo, South Africa. The closure of various market channels such as street vendors, restaurants, hotels and large social gatherings by the government left these farmers susceptible to market shocks, given their reliance on these channels. Over a span of 17 months, the study observed 21 farmers, exploring their adaptive strategies amidst the crisis. Farmer selection was based on their access to various markets: municipal markets, local informal markets, or alternative channels facilitated by intermediaries. The research underscores a pronounced correlation between market access and resilience. Farmers with market access demonstrated greater resilience compared to their counterparts lacking such access. The study further details the various coping mechanisms adopted by these farmers, including finding alternative markets, starting new businesses, changing crop patterns, and modifying their transport system. This research provides a deeper understanding of the intricate link between market access and farmer resilience, particularly for small-scale farmers facing both supply and demand disruptions. Furthermore, the study highlights that intermediaries can play a crucial role in strengthening farmers' resilience during crises. However, their effectiveness is dependent on the organisation's vision and goals. It also provides practical implications for improving market access and government response to crises. This includes government preparedness for similar future disruptions can be achieved by collaborating with the private sector to establish localised markets in rural communities. Also prioritising the development of these local markets is essential for bolstering both local food systems and farmers' resilience in the face of the shocks
Playing catch up: a critical examination of filmmaking and the film sector in Zambia
No full textThis study examined the development and the state of filmmaking in Zambia from 1964 to 2021. Using the Political Economy of Film as the theoretical lens, the study sheds light on the ways that filmmaking has evolved during three key dispensations in Zambian political economic history, namely, the (United National Independence Party) UNIP years (1964 –1991), the Movement for Multi-Party Democracy (MMD) years (1991 – 2011), and the Patriotic Front (PF) years (2011 – 2021). This was done with the assumption that a country's political and economic positionality can significantly affect the development of its film sector because it establishes the context in which filmmaking, a cultural, economic and meaning-making activity, occurs (Wasko, 2003; McQuail & Deuze, 2020). The study also sought to understand why Zambia did not develop a recognisable film sector in Africa despite having had a long history with filmmaking that dates to its colonial past. The examination was done in two layers, the first of which analysed film sector or industry-related elements as they have been experienced in post-colonial Zambia, while the second layer comprised a reading of selected Zambian film texts in the three epochs. The study appropriated the Small Nation Cinema approach (Hjort and Petrie, 2007) as an analytical frame, assuming that it could be used to examine the cinema of countries at the margins of film scholarship and the global film industry order. The qualitative study employed various data collection methods, including key informant (in-depth) interviews, observation and the analysis of selected Zambian productions. The study's findings show that the prevailing socio-political and economic conditions have influenced the context of film production in postcolonial Zambia. These conditions have determined the resources available for production and distribution and have influenced the state's overall approach to film in the different epochs. Further, filmmaking and the emerging screen industries continue to be plagued by old and new challenges, including the lack of funding or film financing, limited education and skills training in various aspects of film, little or no access to distribution channels, and an absence of government policy and support, necessary to develop filmmaking. The study also shows how television remains crucial to the development of screen production in the country but also highlights how this does not always serve the film industry well. Another key finding is that digitalisation, exemplified by the migration to digital broadcasting and the rise of over-the-top (OTT) platforms, is driving new optimism and opportunities in Zambian screen production. Lastly, a critical examination of selected film texts across the epochs reveals how didacticism and social value storytelling characterise many Zambian films. However, the study notes that this tendency is beginning to change as filmmakers embrace more narrative styles and aesthetic influences in recent years. Overall, the study highlights Zambian filmmaking and positions it as an activity of historical, cultural and, more recently, economic significance. It offers clear examples of filmic texts, textual practices, filmmakers, and information essential to appreciating Zambian filmmaking. By situating Zambia as a small cinema nation, the study expounds on how this ‘smallness' has affected the development of filmmaking in the country. The study also contributes to emerging national discourses on the development of the creative industries or the creative economy
Understanding the role of cybersecurity culture in the gig economy: the case of platform-based food delivery workers in Gauteng
No full textThe growth of gig economy platforms has coincided with increased cybersecurity threats and attacks. As gig platforms have evolved, so too have cybercriminals, with attacks such as malware, phishing, and social engineering becoming increasingly sophisticated and human centric. However, cybersecurity defence mechanisms are still centred around traditional technical controls. In response to this growing threat landscape, researchers argue that organisations should implement other mechanisms to counter the threat. Embedding a cybersecurity culture in organisations has gained prominence in recent studies. However, studies on the cybersecurity culture in the gig economy, focusing on food delivery workers, are needed, as there is currently limited literature on this phenomenon. This research report explored the nature of cybersecurity culture in the context of platform-based food delivery workers in Gauteng, South Africa. The main research question explored the following: How does the cybersecurity culture influence the cybersecurity behaviours of food delivery gig workers? The Cybersecurity Culture Model (CCM) was used as a sensitizing theoretical device to develop the initial interview guides, observation protocols, and the preliminary coding schemes. A qualitative research strategy was adopted using semi-structured interviews as the primary data source; furthermore, a qualitative research survey and publicly available documents and observations of the context were provided as secondary data sources. Fifteen (N=15) semi-structured interviews were performed with food delivery workers. Secondary data was acquired via online searches (N=11), web articles on the gig economy, three (N=3) online qualitative surveys, and contextual observations by interacting with food delivery workers at their pick-up sites. Data analysis was conducted using established guidelines for inductive data analysis using the NVivo 14 software. The research revealed significant barriers to implementing cybersecurity culture in the food delivery sector of the local gig economy. Workers receive minimal cybersecurity education and training, with limited management communication about security policies and procedures. Gig work apps present additional challenges, contributing to a virtually non-existent cybersecurity culture among food delivery workers in Gauteng, South Africa. Weak management initiatives, inadequate training, and absent security policies drive non-compliance, further complicated by conflicts between financial incentives, personal safety, and cybersecurity requirements. These findings highlight structural gig economy issues, underscoring the need for enhanced cybersecurity governance, comprehensive training programs, and integrated information security policies. Future research should examine platform providers' responsibilities in cybersecurity culture development and methods to align safety priorities with cybersecurity compliance
Power Domination in graphs
No full textDomination in graphs has been studied since the 1800s. Many parameters related to domination have been defined and studied since then. Power domi-nation was first defined and studied in the early 2000s. It is an abstraction of how an electrical power system is monitored. In this thesis, we focus on power domination and its natural extension k-power domination. We also look at the propagation radius, which is essentially the number of steps it takes a power dominating set of vertices to monitor a graph. We show how ideas from domina-tion can be extended to power domination and k-power domination. We show how domination differs from k-power domination. We demonstrate how making small changes to a graph affects the domination and power domination number of the graph. The small graph changes we will present are: vertex removal, edge removal and edge contraction. We present upper and lower bounds for how much the power domination number can change and present examples that reach all of these bounds. We present a general bound on the power domination and k-power domination number of connected graphs. We also present a general bound on the power domination number of connected, claw-free, cubic graphs. In all cases we present examples that reach these bounds. We show that finding a power dominating set of a tree is equivalent to finding a spider partition of that tree. We also present a lower bound on the power domination number of a tree with respect to its number of branching vertices. We present an upper bound on the power domination radius with regards to the smallest degree of a vertex in a graph. We also present infinitely many graphs that reach this bound
A framework to internationalise South African small and medium enterprises through the Africa Continental Free Trade Agreement
No full textThis research investigates the use of the African Continental Free Trade Agreement to provide a complete framework for promoting the internationalisation of South African Small and Medium Enterprises. The African Continental Free Trade Agreement was established in 2012 and is one of the largest free trade areas in the world in terms of the number of participating countries and it became operational in January 2021. It offers significant prospects for Small and Medium Enterprises by reducing trade barriers, establishing a cohesive market among 54 African countries, and promoting intra-African trade. The research uses a qualitative research approach and semi-structured interviews to collect data from Small and Medium Enterprises that have benefited from the Department of Trade, Industry and Competition's Export Marketing and Investment Assistance incentive scheme, as well as the Department of Trade, Industry and Competition personnel responsible for export development and international trade. The data collected was qualitative, therefore, the researcher utilised thematic analysis, a method that specifically aims to identify, structure, and analyse themes within textual material. The study findings provide insight into a wide range of factors that influence internationalisation such as; barriers to market entry, financial constraints, lack of support mechanisms for Small and Medium Enterprises, collaborative networks for export growth, African Continental Free Trade Agreement as an enabler, access to market information, trade data as well as adapting to local conditions. This study is anticipated to be highly informative and impactful, addressing critical needs and offering substantial benefits to various stakeholders such as Small and Medium Enterprises, policymakers, and trade facilitators. Its significance lies in its potential to transform the landscape of Small and Medium Enterprises internationalisation in South Africa. The results demonstrated a dynamic landscape shaped by regulatory complexities, financial constraints, the potential of the African Continental Free Trade Agreement as a unifying market, and the critical role of support systems and adaptive strategies for successful Small and Medium Enterprise internationalisation. The study offers several recommendations, including prioritising harmonizing of regulatory standards across the continent, access to Small and Medium Enterprise-focused trade finance, improving logistics and trade infrastructure, institutional support and capacity building, and collaboration through trade shows. Future research should be on Sector Specific Regulations pertaining to South African Small and Medium Enterprises on African regional trade
A retrospective review of risk factors for recalcitrant peptic structures
No full textIntroduction: Peptic strictures (PS) are a common benign cause of dysphagia, but a scarcity of local data is available as regards identifying risk factors associated with recalcitrancy. Methods: Single centre retrospective audit of PS undergoing endoscopic management between 1st March 2018 and 1st March 2022, aiming to identify recalcitrancy risk factors. Results: Of 69 patients (37 male, 53.4%) with PS, 27 (39.1%) were diagnosed with recalcitrant strictures. Most strictures were positioned distally (53; 76.8%) with an associated hiatus hernia in 52 (75.4%). While comorbidities were not associated with recalcitrancy, younger age was a risk factor (recalcitrant stricture group median age 51 (IQR 38.5-61.0 years) versus non-recalcitrant group median age 62.5 (IQR 48.5-70.8 years); p=0.044). Although HIV status did not affect recalcitrancy risk, taking oral antiretrovirals (ARVs) was significantly associated with PS recalcitrancy (p=0.032; OR 4.55). Presenting degree of dysphagia (p<0.001; OR 16), requiring more than 3 dilatations (p<0.001), and smaller index residual oesophageal lumen (p<0.001) were all significantly associated with stricture recalcitrancy. Fourteen patients were temporarily stented (having a total of 24 stents placed). Thirteen patients had post endoscopic complications with most of these complications occurring amongst the recalcitrant group (n=11). Four complications occurred during endoscopy, two partial thickness tears managed endoscopically, a gastric perforation requiring an over-the-scope-clip closure and one sedation related hypoxia requiring a short period of bag-mask-valve ventilation and sedation-reversal. Two deaths occurred in the cohort; one from a suspected aspiration pneumonia five days after last dilatation and one from a suspected missed oesophageal perforation (2.3% immediate endoscopic intervention complication rate for 265 dilatations performed). Conclusion: Locally pill oesophagitis related to ARVs has been identified as a potential cause of recalcitrancy; identifying at-risk patients early may allow for management adjustments to improve outcomes