39 research outputs found
Influence of particle size and contact angle on the flotation of chalcopyrite in a laboratory batch flotation cell
No full textAbstract not availableS. Muganda, M. Zanin, S.R. Gran
Flotation behaviour of sulphide mineral size fractions with controlled contact angle
No full textThe flotation response of chalcopyrite has been characterized as a function of particle size and advancing contact angle. The advancing contact angle of individual size fractions was manipulated to different values, measured using the Washburn technique. A flotation feed sample was constituted from the individual size fractions. Parameters such as frother concentration, impeller rotational speed, and superficial gas velocity were the same in each flotation test. The chalcopyrite sample, in the absence of any steps to intentionally manipulate the contact angle, displayed advancing contact angles which varied with particle size fraction. In the presence of a standard thiol collector, the advancing contact angle was also particle size dependent, with the -20 micron fraction displaying the lowest contact angle. Flotation tests showed that the chalcopyrite size fractions above 20 microns floated independently of each other, and that the flotation response was the same for the same particle contact angle and size fraction across different flotation tests. The flotation response was characterized by the maximum recovery at infinite flotation time and the distributed rate constant, assuming a single floatable fraction existed within each size fraction. When the distributed and undistributed rate constants were compared, the latter gave a greater dependency on contact angle as it took into account the non-floating fraction. The two rate constants converged at high advancing contact angles as the non-floating fraction approached zero. Further work on mineral floatability characterization will lead to the development of calibration curves of rate constant against particle size and contact angle, a tool that could be used to benchmark flotation response.S. Muganda, M. Zanin and S. Gran
Benchmarking the flotation performance of ores
No full textA porphyry copper ore containing chalcopyrite as the principal copper bearing mineral, and pyrite as the only other sulphide mineral, was treated in batch flotation tests under well defined physical conditions. The size-by-size flotation response was benchmarked against established calibration curves to infer an operational contact angle of the sulphide minerals as a function of particle size. The inferred operational contact angle values of the sulphide minerals were validated by independent measurements of contact angle on the concentrates and, in the case of chalcopyrite, by an indirect approach using Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Recovery, flotation rate, and inferred operational contact angle increased with collector addition across all size fractions, with the intermediate and coarse size fractions benefitting the most from increased collector addition. The directly measured and inferred operational contact angles were in reasonable agreement, with an R2 value of 0.7 across all size fractions. There was good agreement between the advancing contact angle values determined using ToF-SIMS and those calculated from direct contact angle measurement on the 53-75 μm size fraction for the case of chalcopyrite. A method for benchmarking flotation response has been developed, which may lead to better flotation process diagnostics and modelling.S. Muganda, M. Zanin, S.R. Gran
Sites of transformation: queer and feminist leadership in Kenya’s social justice movements
No full text
This essay seeks to explore the role of queer and feminist leadership in transforming Kenya’s social justice movements. It examines how Gen Z leaders confront structural barriers and navigate tensions within their movements while advocating for systemic change in broader society; exploring how activists navigate power, identity, and systemic oppression in their pursuit of social justice. Additionally, it touches upon how digital activism serves as spaces for visibility, solidarity, and mobilisation, while also being sites of threat and violence. Grounded in the author's personal lived experiences navigating queer identities within various movements and that of two other activists, this essay situates queer and feminist leadership within decolonial and intersectional theories.
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Benchmarking flotation performance: Single minerals
No full textChalcopyrite, conditioned with sodium dicresyl dithiophosphate (DTP), was floated under standard and well-defined hydrodynamic conditions. The advancing contact angle values of the flotation feed and products were measured and the flotation response benchmarked against a calibration previously established for the chalcopyrite-amyl xanthate (KAX) system. Furthermore, the flotation response of pyrite, separately conditioned with KAX and DTP, was also evaluated under the same hydrodynamic conditions. When the advancing contact angle of chalcopyrite conditioned with DTP was the same (within 5°) as that of chalcopyrite conditioned with KAX, the flotation response was, within experimental error, the same. For both chalcopyrite and pyrite, heterogeneity of the advancing contact angle within the feed size fractions was demonstrated by significant differences in contact angle values measured on the flotation concentrate and tailings size fractions. The mean contact angle of the chalcopyrite and pyrite particles remained constant, within experimental error, through both flotation and sample preparation under the test conditions. The flotation response of chalcopyrite at 2% solids (w/w) was the same, within experimental error, as that at 30% solids (w/w) in the presence of silicate gangue, suggesting non-interaction of this gangue mineral with chalcopyrite under the test conditions. The operational advancing contact angles inferred for pyrite using the calibration established for the chalcopyrite-KAX system were, however, lower than the measured feed advancing contact angles, while the maximum recovery of pyrite was also lower than for chalcopyrite for the same feed advancing contact angle values, in the contact angle range less than 80°. The difference in flotation response between these two minerals for the same feed contact angle values was interpreted in terms of a difference in critical contact angle value for stable bubble-particle attachment. The critical advancing contact angle values for the pyrite size fractions were higher than values for chalcopyrite for size fractions above 20 μm. This difference in critical advancing contact angle was attributed to the difference in mineral specific gravity between chalcopyrite and pyrite.S. Muganda, M. Zanin and S.R. Gran
Exploring the digital maturity of a global engineering firm in the South African mining industry
No full textA research report submitted in partial fulfillment of the requirements for the degree of Master of Management in the field of digital Business to the Faculty of Commerce, Law and Management, Wits Business School, University of the Witwatersrand, Johannesburg, 2023The mining sector has long been perceived as a conservative innovation industry which is labour-intensive. However, this notion is rapidly changing, based on the sector's level of innovation and digital disruption. Studies show that digital technologies increase a firm's profits by 20% to 45%. Given this digital shift, most companies in the mining sector are investing heavily in digital transformation to drive growth and increase efficiencies. According to reports by Minerals Council South Africa and PwC, digital is becoming a game changer in the South African mining industry by increasing the use of innovative and latest technologies to run more efficient operations, improve health and safety, reduce maintenance and extraction costs, as well as bringing about skills improvement. Despite visible positive results, the South African mining industry's digital transformation journey has not been smooth. While some companies have successfully embraced digital transformation to enable sustainable business growth and efficiency, others have grappled with achieving the same results. The challenge for most organisations is to justify the massive investments by demonstrating the impact of digital maturity on the sustainable competitive advantage of their organisations. Therefore, this study aims to explore the effect of digital maturity on an organisation's sustainable competitive advantage through the lens of the dynamic capability theory. The literature review focused on digital transformation and maturity, sustainable competitive advantage and the dynamic capability theoretical framework. The research design method was qualitative; data collection was through semi-structured interviews with eight portfolio managers, five digital managers and the chief information officer selected from within the organisation. The data analysis was based on the thematic analysis process to deliver the initial codes, initial themes and the final themes emerging from the study. The study's findings demonstrate that mining organisations using dynamic capabilities (sensing, seizing and transforming) have a higher digital maturity, enabling the agility to scan and explore market and technology opportunities better than organisations with low digital maturity. They also have a high renewal and reconfiguration rate that poise them to successfully take advantage of the market and technology opportunities and respond to threats. Therefore, high level dynamic capabilities (sensing, seizing and transforming) offer a sustainable competitive advantage to an organisation in a changing market environment. However, mixed findings on the association between dynamic capabilities and organisation performance warrant further research. The first is the unclear conditions and the mechanisms under which dynamic capabilities affect organisational performance. Secondly, a detailed analysis of the high-level dynamic capabilities is required to establish the dynamic capabilities with the most effect on an organisation's sustainable competitive advantage.MM202
A generalized linear model for rating the premiums of a Micro Health Insurance Policy
No full textSubmitted in partial fulfillment of the requirements for the Degree of Bachelor of Business Science Actuarial at Strathmore UniversityThis study focuses on the modeling of a risk premium for a micro health insurance policy. It was carried out as a response to the gap highlighted by scholars and industry players which relates to the difficulty in developing insurance products which are both affordable and sustainable to cater for the needs of the low income market. which is a large segment in developing countries (KPMG, 20 13). It adopts the generalized linear model in the rating of premium factors to parameterize their
Significance in predicting the claim amount. The product being analyzed is a group micro health insurance policy in the Kenyan market, and claims data has been .obtained from three .schemes whose policies have been in force for at least three years since 2011. A policy covers not only the scheme's members but also their nuclear family. Factors rated include the claimant's age, gender, and their relation to the insured life. The impact of the interaction between these factors is also analyzed. The results show that for a group policy offering family cover, all the three factors are significant in the prediction of claim amounts and thus the risk premium. They also show that interactions between the claimant's age and gender and between their age and relation to the policy holder significantly improve the pricing model
Socio-technical factors impacting youth perspectives on digital transformation in resource-constrained environments: A study of Diepsloot youth
No full textA research report submitted in accordance with the requirements for the degree of Master of Arts in the field of ICT Policy and Regulation, LINK Centre, School of Literature, Language and Media, University of the Witwatersrand, Johannesburg, 2023.There has been a proliferation of tech hubs in Africa, with more than 80 in South Africa, forming a foundation for more inclusive digital innovation. However, we do not sufficiently understand the relationships between tech hubs, digital inclusiveness and poverty. This study explores the sociotechnical factors influencing access and use of the Internet to achieve social inclusion in resource-constrained environments. The literature reviewed focused on social influences on digital adoption, tech hub infrastructure, digital skills, and trends in Information Communication Technologies (ICT) policies. The study’s findings are categorised into themes using the sociotechnical systems (STS) theoretical framework. Each of the seven STS theoretical components (goals, culture, people, processes, infrastructure, technology and environment) were used as a lens to explore the social and technical factors that influence the perspectives of the youth on digital transformation. These themes were then mapped to the four dimensions of the research questions (social influence of digital adoption, institutional infrastructure for access, digital skills, and ICT policies for digital enablement) to highlight key findings and interpretations of the study. Under social influences, the youth demonstrated resilience driven by a need to improve their standard of living in a challenging environment. The institutional infrastructure, designed to support youth to access digital technologies, is constrained by a lack of resources. Tech hubs are using creative ways with the limited resources to cater to all their patrons, although there is room for improvement. In terms of digital skills, four youth profiles are highlighted to demonstrate a solid existence of digital skills and pursuit of tangible outcomes among the youth. In addition, the youth want to pursue entrepreneurship, meaning that tech hubs can potentially become mass training centres for digital entrepreneurship. Finally, a review of ICT policies revealed a chasm between the ICT policy objectives and activities on the ground, pointing to a lack of implementation and monitoring of ICT policies. Acting as a platform for digital foundations, tech hubs in marginalised environments must engage policymakers and reinforce their role in digital empowerment to influence policy development. This research is located in the qualitative interpretivist paradigm. A total of 21 in-depth interviews were conducted with 18 youth, with an equal representation of male and female, and three tech hub managers. Based on the researcher's analysis, access to the Internet offers the resilient youth a view into "a new world" that make them feel they can achieve anything they want. The high literacy level among the youth puts them in good stead for digital upskilling, and they are motivated to participate in the digital economy. However, ICT policy objectives concerning universal access look good on paper, but in reality, poor people are still offline. They are still excluded.MM202
Impact of firm-level factors on profitability of companies in Kenya.
No full textThis research evaluates the impact of finn-level factors on the performance of companies. These finn-level factors are examined as a set of determinants within business that explain profitability. The study thus adopts a quantitative approach based on a longitudinal study of publicly quoted companies in Kenya within each industry, for a period from 2004 to 2014, to determine how firm-level factors such as size, diversification, leverage, expense and growth impact a company's profitability, using ROA as a profitability measure . The study finds that leverage, firm size and expense ratios had the most significant impact in explaining profitability of listed Kenyan companies, their changes also contributed significantly to firm profitability changes across industries. Also, most of firm heterogeneity was found to exist among firms in the manufacturing and banking industries
Single-Step CMOS Compatible Fabrication of High Aspect Ratio Microchannels Embedded in Silicon
No full textThis paper presents a new method for the CMOS compatible fabrication of microchannels integrated into a silicon substrate. In a single-step DRIE process (Deep Reactive Ion Etching) a network of microchannels with High Aspect Ratio (HAR) up to 10, can be etched in a silicon substrate through a mesh mask. In the same single etching step, multidimensional microchannels with various dimensions (width, length, and depth) can be obtained by tuning the process and design parameters. These fully embedded structures enable further wafer processing and integration of electronic components like sensors and actuators in wafers with microchannels.Electronic Components, Technology and Material
