Browsing by Subject "Network analysis"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Open Access
    The structure and evolution of the African air transport network
    (2025) Snaddon, David; Er, Sebnem; Britz, Stefan
    This dissertation studies the structure and evolution of the African Air Transport Network (AATN) from 2015 to 2023. With respect to the network's structure, a power-law distribution appropriately characterises the networks degree distribution. The ‘golden tri-angle' between Johannesburg O.R. Tambo, Cape Town, and Durban King Shaka plays a dominant role in the network's structure when considering airline seat capacity. Addis Ababa shows strong growth in node centrality, ending the period with the highest centrality across all observed centrality measures. Community detection reveals airport clusters that align with geographic regions, including African subregions and countries. k-coredecomposition reveals a growing core of the network spread across the continent with a higher concentration in West Africa. Longitudinal trends of network-wide indicators de-tail the network's evolution. A gradual decrease in the average clustering coefficient and degree assortativity coefficient but an increase in the Gini coefficient and largest degree suggest that the network aligns to a growing airline hub-and-spoke structure. During this period, the COVID-19 pandemic occurs and significantly affects the network's evolution, particularly in measures related to the sizing of the network, calling for an investigation into the changes from pre-pandemic to the end of recovery phase. When the network recovers, it does not revert back to its pre-pandemic structure completely, adding new routes and not reintroducing some old ones. Moreover, a similar magnitude of variability during the period is found in the global air transport network.
  • Thumbnail Image
    Item
    Open Access
    Tracking socioeconomic vulnerability using network analysis: insights from an avian influenza outbreak in an ostrich production network
    (Public Library of Science, 2014) Moore, Christine; Cumming, Graeme S; Slingsby, Jasper; Grewar, John
    BACKGROUND: The focus of management in many complex systems is shifting towards facilitation, adaptation, building resilience, and reducing vulnerability. Resilience management requires the development and application of general heuristics and methods for tracking changes in both resilience and vulnerability. We explored the emergence of vulnerability in the South African domestic ostrich industry, an animal production system which typically involves 3-4 movements of each bird during its lifetime. This system has experienced several disease outbreaks, and the aim of this study was to investigate whether these movements have contributed to the vulnerability of this system to large disease outbreaks. METHODOLOGY/PRINCIPAL FINDINGS: The ostrich production system requires numerous movements of birds between different farm types associated with growth (i.e. Hatchery to juvenile rearing farm to adult rearing farm). We used 5 years of movement records between 2005 and 2011 prior to an outbreak of Highly Pathogenic Avian Influenza (H5N2). These data were analyzed using a network analysis in which the farms were represented as nodes and the movements of birds as links. We tested the hypothesis that increasing economic efficiency in the domestic ostrich industry in South Africa made the system more vulnerable to outbreak of Highly Pathogenic Avian Influenza (H5N2). Our results indicated that as time progressed, the network became increasingly vulnerable to pathogen outbreaks. The farms that became infected during the outbreak displayed network qualities, such as significantly higher connectivity and centrality, which predisposed them to be more vulnerable to disease outbreak. Conclusions/Significance Taken in the context of previous research, our results provide strong support for the application of network analysis to track vulnerability, while also providing useful practical implications for system monitoring and management.