Research Outputs

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Lock-out, lock-in, and networked sovereignty: resistance and experimentation in Africa's trajectory towards AI
(Brazilian Institute of Information in Science and Technology, 2024) Gagliardone, Iginio
The conception of digital sovereignty has been associated, especially in the early stages of the diffusion of the Internet, with efforts to keep specific data and information outside of a state’s jurisdiction. AI sovereignty responds to an almost opposite logic, indicating the ability of a state to access and make use of data that are produced within its jurisdiction. These two strategies –which I refer to as lock-out and lock-in sovereignty –share some common roots (e.g. the attempt to protect and enhance specific cultural attributes recognised as important by a national community), but they also point to different technical, economic, and political characteristics needed to enforce one or the other type of sovereignty. The article examines key elements that set these concepts, and their implementation, apart and how they intersect with both existing and potential articulations of national sovereignty in Africa. In particular it opposes a negative –and still pervasive –definition of sovereigntyapplied to African states, based on the Westphalian ideal and “measuring the gap between what Africa is and what we are told it ought to be” (Mbembe 2019, p.26); and the possibilities disclosed by re-appropriating practices of “networked sovereignty” (Mbembe, 2016).
An assessment of the artificial modelling elements approach to the pressure-driven analysis of water distribution networks
(IWA Publishing, 2023) Tanyimboh, Tiku T.; Sivakumar, P.; Gorev, Nikolai B.; Nivedita, S.; Suribabu, C. R.; Gupta, Rajesh
EPANET 2.2 is a newly introduced upgraded version of EPANET 2 that can be used for both pressure-driven analysis (PDA) and demanddriven analysis (DDA) of water distribution networks. Moreover, it has certain limitations concerning the minimum and required pressure head parameters used for PDA, which leads to inaccurate simulation results. Another limitation of the PDA option of EPANET 2.2 is its inability to simultaneously consider pressure-dependent demands with pressure-independent fire demands. In this article, the reason for the spurious convergence is identified, and it is shown that the spurious convergence of EPANET 2.2 can be addressed by extending the energy balance convergence criterion to include the virtual demand links employed in the EPANET 2.2 formulation of PDA. On the other hand, interest in the methods that use artificial modelling elements in EPANET 2 for PDA is increasing rapidly. The implementation of the method presented in this paper (termed the alternative PDA approach) allows an extended period simulation of large networks with complex demand patterns, multiple tanks, reservoirs, pumps, valves, and thousands of pipes. Two benchmark networks and two real-world networks were analysed by both the alternative PDA approach and EPANET 2.2 and the results were compared.
Adaptive-Mode PAPR Reduction Algorithm for Optical OFDM Systems Leveraging Lexicographical Permutations
(MDPI, 2023-06) Niwareeba, Roland; Cox, Mitchell A.; Cheng, Ling
In direct current optical orthogonal frequency division multiplexing (DCO-OFDM) systems, the high peak-to-average power ratio (PAPR) has been a significant challenge. Recently, lexicographical symbol position permutation (LSPP) using random permutations has been introduced as an efficient solution to reduce high PAPR. In this paper, we aim to evaluate the effectiveness of LSPP by comparing both adjacent and interleaved lexicographical permutation sequences with random lexicographical permutation sequences. Our findings demonstrate that random permutation yields superior PAPR reduction performance results when compared to adjacent and interleaved permutation. However, in scenarios with a limited number of sub-blocks, the use of adjacent and interleaved permutation becomes more favorable, as they can eliminate the possibility of generating identical permutation sequences, a drawback of random permutation. Additionally, we propose a novel algorithm to determine the optimal number of candidate permutation sequences that can achieve acceptable PAPR reduction performance while adhering to computational complexity constraints defined by the system requirements.
Analysing the disciplinary power of proactive monitoring bodies
(Emerald, 2025-07) Flowers, Kevin; van Zijl, Wayne; Ram, Jaywant; Warren Maroun
Purpose – The important role of regulatory monitoring bodies in enhancing financial statement quality is increasingly being studied. Prior research focuses on developed economies and often adopts a relatively unproblematic regulatory perspective to explain how these bodies foster compliance. This paper adopts a more critical approach by investigating the forces and processes at work by utilising a Foucauldian disciplinary power perspective on the proactive monitoring unit (PMU) regulating South African listed companies on the Johannesburg Stock Exchange. Design/methodology/approach – Seventeen semi-structured, open-ended interviews were conducted with expert financial statement preparers, auditors, regulators and academics. Open, axial and selective coding were used to analyse the interview data. Findings – The PMU isindicative of an enclosure mechanism that monitors and controlsthe financial reporting space of listed companies. Consequently, preparers and auditors resemble well-trained individuals who follow the PMU’s guidance without question. The PMU’s constant gaze, combined with the negative reputational impact of an adverse review for individual preparers and auditors, results in them presenting their financial statements in conformity with the PMU’sinterpretation. However, complete panoptic control is not achieved, as there is some resistance. Originality/value – This is one of the first studies to examine how an external monitoring body, the PMU, functions in a real-world setting. There is a limited understanding of what drives companies to comply with monitoring bodies that do not enjoy the direct force of law. This paper makes use of the novel Foucauldian framework to contribute towards understanding the disciplinary power that may be applied by the PMU.
Testing the suitability of portable X-Ray Fluorescence (pXRF) analysis of dried herbarium specimens to detect Ni hyperaccumulators in South Africa
(Elsevier, 2023-07) Balkwill, Kevin; Samojedny Jr. Thomas J.; Rajakaruna, Nishanta; Siebert, Stefan J.
Metal hyperaccumulators accumulate particular metals or metalloids in their leaves to concentrations hundreds or thousands of times greater than is normal for most plants. Globally, Ni is the most often hyperaccumulated metal, with 532 hyperaccumulator species documented to date. Hyperaccumulators have attracted much attention as potential candidates for green technologies, including phytoremediation and agromining. In South Africa, six serpentinite-associated plants in the genera Berkheya and Senecio hyperaccumulate Ni (to > 0.1% of leaf tissue dry weight). It is surprising that only six of about 70 Berkheya and 290 Senecio species native to South Africa hyperaccumulate Ni, given about ∼10–20% of taxa from each genus occur on serpentinite. While it is costly and time consuming to field collect and chemically analyze leaves of all species in these genera, a novel method (portable X-Ray Fluorescence or pXRF analysis of herbarium specimens) allows for rapid (100 s of specimens/day) and non-destructive measurement of Ni in dry herbarium specimens. We tested the accuracy of this approach on known Ni hyperaccumulators vouchered at two South African herbaria (C.E. Moss Herbarium (J) of the University of the Witwatersrand and A.P. Goossens Herbarium (PUC) from North-West University). While the absolute concentrations of Ni determined by ICP-MS and pXRF were not always directly in agreement, we had 100% success in confirming those that were known to hyperaccumulate Ni with those that did not. We propose pXRF as a cheap, effective, and efficient approach to rapidly screen herbarium specimens across South Africa to discover additional metal hyperaccumulators for much-needed remediation purposes.
The valorisation of platinum group metals from flotation tailings: A review of challenges and opportunities
(Elsevier, 2023-06) Gibson, Borbor A.K.K.; Nwaila, Glen; Manzi, Musa; Ndlovu, Sehliselo; Ghorbani, Yousef; Petersen, Jochen
Flotation tailings from South Africa’s platinum group minerals (PGM) represent complex polymetallic orebodies comprising a low-grade platinum group elements (PGE) content and complex mineralogical composition. Nevertheless, given the valuable mineral potential in the tailings, it is understandable that the substantial historic tailings deposits and sizeable annual production volume from primary processes represent a potential secondary resource. For several decades, valorising the PGM tailing materials received very little interest due to limitations associated with extractive metallurgical technology to achieve economically viable PGE extraction. The early 21st century saw the coming online of technologies, including but not limited to ultrafine grinding, suitable to meet challenges in primary metallurgical treatment processes to recover valuable minerals from ultrafine particle fractions, which could not otherwise be recovered. More so, such processes were critical in improving the liberation of partially liberated particles without compromising additional ultrafine generation. These technologies led to the development of re-treatment pilot tests and subsequent industrial re-treatment recovery processes. The current industrial re-treatment approach – via tertiary scavenging flotation circuits – renders profit in small increments up to 1 ~ 2% additional recovery relative to the primary plant head grade. These small increments relate to about ~12–30% PGE recovery of the feed grade to the re-treatment circuit, thereby enhancing the primary plant’s overall economics as well as aiding the supply of critical metals to meet global demands. With a focus on South Africa, this review provides an overview of (a) the current and future drivers of the precious metals global demand; (b) proffers discussion on the PGM characteristic mineralogy and the metallurgical value chain; (c) relates the parent orebodies (“reefs”) mineral characteristics to the inherent processed tailings; (d) estimates the economic potential these massive processed waste materials contain, (e) provides an overview of existing technologies that are industrially used in tailing re-treatment plants; and (f) outlines a comprehensive understanding of the nature of value minerals rejection to tailings.
Maximizing access and minimizing barriers to research in low- and middle-income countries: open access and health equity
(Springer, 2023-11) Saloojee, Haroon; Pettifor, John M.
Access to published research has always been difcult for researchers and clinicians in low- and middle-income countries,because of the cost of and lack of access to the relevant publications. The dramatic recent increase in electronic research publications has resulted in a marked improvement in reader access to these publications through their mainly Open Access policies, however the costs of processing of submissions and publication have now become the burden of the researchers wishing to publish, rather than the readers. For many researchers working in LMIC, the Article Processing Charges (APC) are prohibitive, hampering the publication of research being conducted in and relevant to these countries. A number of grant funding agencies and international not-for-proft organizations are trying to address these issues by including funding for article publications in their grants, or by supporting publishing entities by subsiding the cost of publication, but more needs to be done by major journal publishers through markedly reducing the APC being charged to researchers in LMIC for open access facilities.
Chemical analysis of low grade gold from mine tailings after size fractionation and acid digestion using reverse aqua regia
(Nature Research, 2025-03) Chimuka, Luke; Tshilongo, James; Mashale, Kedibone Nicholine; Sehata, James; Ntsasa, Napo Godwill
The growing interest in reprocessing mine tailings for gold recovery requires a suitable quantification method that is accurate, rapid, and not harsh to the environment. Acid digestion is often used to determination of gold; however, it often faces the challenge of incomplete digestion due to the presence of minerals such as quartz, and homogeneity is compromised due to small sample masses, which can result in low bias. This study investigated a shorter acid digestion method employing reverse aqua regia, both in the presence and absence of hydrofluoric acid. Before digestion, the sample was subjected to gold depot analysis, which showed that 78% was free-milling gold and that only 0.8% was associated with pyrite, increasing the chances of accurate quantifications. Furthermore, the size screening test showed that most of the gold could be recovered on the −38 μm screen. This proposed method provided good linearity (5–100 µg. L−1) and low detection limits (0.139–0.183 µg.kg−1). The concentrations obtained by the acid digestion was 0.258 g.t−1 with the recoveries ranging between 80% and 82%, which fit the criteria set. The method also worked well for the certified reference materials (CRM), AMIS 610 (accurate value=0.068 g.t−1) and AMIS 646 (accurate value=0.166 g.t−1), which are of a similar matrix and are also lower in grade compared to the sample. The method was also evaluated for uncertainty (±value) using the bottom-up approach, and the expanded uncertainty (k=2) was reported to be 0.258±0.092 g.t−1, which was comparable to that offered by the fire assay with the ICP‒OES finish, which was 0.28±0.10 g.t−1. This implies that the acid digestion method is suitable for quantifying gold from mine tailings without large uncertainties.
Topological rejection of noise by quantum skyrmions
(Nature Research, 2025-03) Ornelas, Pedro; Forbes, Andrew; de Mello Koch, Robert
An open challenge in the context of quantum information processing and communication is improving the robustness of quantum information to environmental contributions of noise, a severe hindrance in real-world scenarios. Here, we show that quantum skyrmions and their nonlocal topological observables remain resilient to noise even as typical entanglement witnesses and measures of the state decay. This allows us to introduce the notion of digitization of quantum information based on our discrete topological quantum observables, foregoing the need for robustness of entanglement. We compliment our experiments with a full theoretical treatment that unlocks the quantum mechanisms behind the topological behavior, explaining why the topology leads to robustness. Our approach holds exciting promise for intrinsic quantum information resilience through topology, highly applicable to real-world systems such as global quantum networks and noisy quantum computers.
A Technique to Solve a Parabolic Equation by Point Symmetries that Incorporate Initial Data
(Springer, 2025-03) Jamal, Sameerah; Maphanga, Rivoningo
In this paper, we show how transformation techniques coupled with a convolution integral can be used to solve a generalised option-pricing model, including the Black–Scholes model. Such equations are parabolic and the special convolutions are extremely involved as they arise from an initial value problem. New symmetries are derived to obtain solutions through an application of the invariant surface condition. The main outcome is that the point symmetries are effective in producing exact solutions that satisfy a given initial condition, such as those represented by a call-option.

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