WIReDSpace

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Communities in WIReDSpace

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Now showing 1 - 5 of 20

Recent Submissions

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    Rescheduling gabapentinoids had negligible effects on prescribing behaviour by general practitioners in England
    (Wiley, 2023) Kamerman, Peter
    Purpose: To determine whether the rescheduling of gabapentinoids in England as Schedule 3 Controlled Substances in April 2019, changed prescribing behaviour for gabapentinoids by general practitioners. Methods: Data on the monthly number of prescription items and the monthly average dose per prescription item were analysed for the period April 2017 to April 2021 under three models: (i) a simple linear regression, (ii) a linear spline with a knot at April 2019, and (iii) a parallel slopes model with time before and after the rescheduling as a covariate. Best fit models were selected based on them having the lowest corrected Akaike's information criterion. Auto-regressive integrated moving average (ARIMA) models were also generated. Results: For gabapentin, the best fit model for the number of prescription items was the simple linear model, and for the dose per prescription item it was the parallel slopes model. For pregabalin, the best fit model was the linear spline for the number of prescription items and the dose per prescription item. For all models, the interval estimates for the slopes were consistent with no change or no meaningful change in prescribing behaviour after April 2019. Forecasts from ARIMA models for gabapentin and pregabalin were consistent with no change in the number of prescription items per month. However, forecasts for the dose per prescription item for gabapentin or pregabalin did not fully capture the post-April 2019 trajectories. Conclusion: The reclassification of gabapentinoids did not materially change the prescribing behaviour of these drugs by general practitioners in England.
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    Information-Theoretic Clustering Techniques for Correlated Sources in Network Content Caching
    (University of the Witwatersrand, Johannesburg, 2025-09) Rosen, Benjamin; Abu-Mahfouz, Adnan; Cheng, Ling
    Two powerful and complementary tools have been presented in literature to facilitate the paradigm shift planned for the Internet, where the focus is on storing information within the network infrastructure itself. The first involves Slepian-Wolf (SW) coding, in which the high degree of correlation between pieces of information are exploited to reduce the overall size of the data. Then, Coded Caching (CC) stores parts of the information at the user end during o!-peak hours when demand is low. Although this hybrid system results in an impressive reduction of bandwidth usage during peak hours, the SW coding operation in particular becomes prohibitively complex to implement. Clustering has been proposed in other fields pertaining to SW coding to solve this issue, but the assumptions and simplifications used there are not applicable in this scenario. This work solves the problem of clustering within a hybrid Slepian-Wolf Coded Caching (SW/CC) system by first looking at a simplified single-group model. To this end, two iterative algorithms are developed and compared to the Genetic Algorithm (GA) and Ant Colony Optimisation (ACO) meta-heuristic approaches. Then, the problem is extended to multiple groups, which presents a much greater challenge. The single group algorithms are expanded and improved to cater for the new paradigm, providing close-to-optimal approaches while still running in polynomial time. At the same time, necessary conditions for optimality are derived for both cases, allowing for solutions to be further improved. The iterative approaches in particular, when used in conjunction with the optimality tests, perform comparably to the benchmark meta-heuristic ones, but with more predictable performance and much lower complexity in both the single and multi group scenarios. Clustering the files in this way greatly reduces the complexity in this system, making it more feasible to implement in practical scenarios. More research can be done to improve these algorithms, generalise the problem to arbitrarily sized groups and allow for files to belong to more than one group.
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    Evaluation of the relationships between measured archery bow performance and archer sensations
    (University of the Witwatersrand, Johannesburg, 2025-06) Pietra, Francesco; Loveday, Philip; Reid, Robert
    Archery is a precision sport in which the athlete is required to hit the centre of the target with accuracy and consistency. In archery, the interaction between the archer and the bow is of fundamental importance to guarantee performance. Unfortunately, there is no literature to support archers in selecting their bows. It is not always clear if new designs improve performance, due to the complex interaction between the archer and the bow, and it is not simple to measure if the archer-bow combination is better. In this thesis, a mixed research methodology is utilised to evaluate the relationships between the performance, the design and the athletes’ sensations in using archery equipment. In the context of this thesis, the term performance refers to any measurable quantity related to the use of the bow (vibration and emitted sound on shooting, accuracy on target, behaviour of the bow on arrow release, etc.). The term design refers to the different ways of configuring the bow or the various options in choosing archery equipment. The proposed methodology is divided into four steps: selection of the design details to analyse; definition of a set of measurable quantities to evaluate change in performance due to change in design (objective metrics); definition of a set of metrics related to the archer experience with the various designs (subjective metrics); and analysis of the correlations between the defined metrics. The methodology was applied in three investigations, which were published as journal articles and are included in this thesis. The first paper explored the best distribution of stabilising weights for the barebow style, the second paper studied the effect of the introduction of damping on the shooting experience of the archers, and the third paper analysed the problem of the performance of different sets of archery limbs from objective and subjective points of view. This thesis describes how the methodological approach was tested and refined as it was applied to three investigations of increasing complexity. In each paper, the methodology demonstrated its capability of analysing complex problems that involve design, performance and athletes’ sensations in using sports equipment. The study of the correlations between objective and subjective metrics led to a deep understanding of the analysed problem, suggesting less-than-obvious relationships between metrics. An interesting finding from the first study is that the number of arrows required to achieve statistical significance in evaluating the performance of the bow depends on the skill level of the archer, as studied by JL Park. Notably, even for an Olympic-level archer, the commonly recommended 30 arrows are insufficient to evaluate the change in performance of the bow, in contrast with archery manuals. Additionally, the study highlights the importance of distinguishing between mechanical vibrations (low frequency) and the sound of the bow on shooting (high frequency) when assessing the vibrations of the bow. The main finding of the second study is that the introduction of damping into the bow effectively reduces the high-frequency components of the mechanical vibrations—specifically, the sound during shooting—while exerting minimal influence on low-frequency vibrations. This reduction in high-frequency vibrations is perceptible to the archer, leading to an improved shooting experience. The primary findings of the third study reveal that archers can accurately judge the speed of the arrow with remarkable precision, but they are unable to reliably assess the smoothness of the bow limbs. Considering that the smoothness of the limbs is one of their key selling factors, finding that the archer is not capable of perceiving the smoothness is a finding worthy of future investigations. The methodology utilised in this thesis may be applied to investigating other topics in archery and can be adapted to other sports where there is a necessity to understand how a change in the design of sports equipment can impact athletes’ performance and athletes’ perception of the sports equipment.
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    Design, Implementation and Performance Evaluation of an Elastic Partitioned Global Address Space Storage (EPGASS)
    (University of the Witwatersrand, Johannesburg, 2025-10) Ohene-Kwofie, Daniel; Hazelhurst, Scott; Otoo, Ekow
    Advances in modern technologies, high-speed and more precise instrumentation for data acquisition, cutting-edge high-performance computing, improved simulation modelling, and the development of large data centres have collectively contributed to the rapid accumulation of massive datasets, commonly referred to as Big Data. While the processing speed of CPU/GPGPU in high-performance computing has steadily increased, the rate of data input and output (I/O), even with parallel I/O, has lagged behind the advances in computing speeds. Although a number of computing techniques have been adopted to bridge the CPU I/O gap, I/O still remains a major bottleneck to high performance data processing and large scale scientific applications. Recent advances in database management and data processing technologies focus on in-memory (or DRAM) data storage system to enhance performance. The challenge, however, lies in developing an I/O subsystem infrastructure that can match the computational speeds of advanced computing systems operating at the petascale and exascale levels. The thesis proposes an I/O subsystem infrastructure leveraging in-memory computing to meet the computational speeds of advanced computing systems at the petascale and exascale level, leveraging the Partitioned Global Address Space Model (PGAS) of computing on commodity hardware. The PGAS system is used to host an in-memory data store, providing high performance access to in-memory data. The proposed architecture is reminiscent of that of RAMCloud, but with some major differences. The architecture consists of a number of commodity nodes, that can grow into hundreds or thousands, whose physical memories are aggregated as a single global logical address space, with a fraction of these nodes serving as the I/O nodes, while the remaining nodes form the collection of compute nodes. The I/O nodes maintain in-memory data in the global address space and run thousands of threads, some of which persist the memory resident data onto Solid-State Device (SSDs), attached to the nodes. The thesis refers to this architecture as EPGASS: An Elastic Partitioned Global Address Space Storage. The major contribution of the thesis is the design, implementation, and application usage EPGASS. The study presents strategies to address challenges such as memory-to memory data copying, fault-tolerance, long-term persistence with asynchronous parallel data migration from memory-to-SSDs and vice versa and also from SSDs-to-hard disks (HDD), with a hierarchical storage approach. The thesis also discusses use-cases with diverse applications, including a novel approach to dense matrix-matrix multiplication and multidimensional index schemes, which minimise the communication overhead to improve algorithmic efficiency.
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    Voices of children on movement behaviours in the early years: reflections from six diverse country settings
    (Sage Publications, 2023-02) Kariippanon, Katharina E.; Hongyan, Guan; Aguilar-Farias, Nicolas; El Hamdouchi, Asmaa; Lubree, Himangi
    Little is currently known about young children’s perceptions and experiences of 24-hour movement behaviours (physical activity, sedentary behaviour, sleep), yet their voices play an important role in contributing to our understanding and ensuring that appropriate action is taken to promote healthy behaviours. With the release of the World Health Organisation’s Guidelines for physical activity, sedentary behaviours and sleep for children under 5 years of age, interest is gathering to examine how young children globally perceive and experience these movement behaviours in their daily lives. Conducting qualitative research with young children, however, presents a host of challenges including identifying suitable methods (interview type), developing appropriate questions (terminology, translation), building rapport (presence of caregivers/educators, incentives), and managing power dynamics, while adjusting to the restrictions imposed by COVID-19. Additional layers of complexity come into play when conducting an international study across culturally, linguistically, and socioeconomically diverse populations. This article describes the reflections of our research group as we considered the effect of diverse contextual influences in Australia, Chile, China, India, Morocco and South Africa, on how movement behaviours are conceptualised by young children. The complexities of working across these diverse contexts is discussed and the implications this has for methodological decisions and data interpretation are reflected upon. While the WHO Guidelines (2019) are universal, globally young children experience considerable differences in how their days are structured, along a continuum of highly supervised to independent play, with varying degrees of agency to make choices regarding their experience of movement behaviours. This suggests the need for a nuanced approach in how we further research and address movement behaviours across different country contexts, taking into consideration social and cultural norms.