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Research Commons is the University of Waikato's open access research repository, housing research publications and theses produced by the University's staff and students.

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A quality framework for infrastructure as code in the modern DevSecOps era
(The University of Waikato, 2026) Konala, Pandu; Kumar, Vimal; Bainbridge, David; Haseeb, Junaid
Infrastructure as Code (IaC) is transforming how organisations deploy and manage their infrastructure through version-controlled scripts. While this creates opportunities for automation, it also introduces quality and security concerns. Many IaC analysis tools focus on one or two platforms and rely on pattern-based detection, but do not take advantage of the information contained within repository metadata and the relationships between repositories. A survey of current IaC analysis tools reveals shortcomings in their ability to conduct comprehensive quality assessments, allowing security smells to propagate through dependency chains and code reuse patterns without being identified. This thesis presents a systematic process for assessing the quality of IaC scripts. It introduces a nine-category framework that extends the principles of traditional software quality to infrastructure code. The categories include aspects such as metadata and platform-specific characteristics that were not addressed in previous works. This work also utilises policy-based weighted mechanisms to allow organisations to place their own emphasis on the various categories when conducting assessments. Building on this framework, the research assesses security smells by utilising metadata-assisted methods for detecting vulnerabilities in the supply chain of dependencies. Our findings show that vulnerable dependency chains affect multiple downstream repositories. For platforms that lack fork metadata, similarity-based methods are employed to identify the paths through which security smells diffuse. Clone detection proved effective at tracing these diffusion paths across such platforms. This work also demonstrates the applicability of the framework to the evaluation of AI-generated infrastructure code. The results showed that 15 out of the 16 tested AI models produced code that scored below human-written repositories. However, structured prompts with quality and compliance integration enabled the top-performing AI models to produce code that exceeded human-written implementations in meeting industry benchmarks for security. Together, these findings support the usefulness of the proposed framework for the integration of quality assurance into modern DevSecOps workflow practices.
Sulfur metabolism in Neisseria gonorrhoeae
(The University of Waikato, 2026) van Niekerk, Stacy; Hicks, Joanna
Elucidating essential pathways for the pathogenicity of Neisseria gonorrhoeae is crucial for the discovery of novel therapeutics required to combat the threat of extensively drug-resistant gonorrhoeae. Sulfur metabolic pathways have been proposed as attractive targets as they are absent in mammals, and cysteine, the central node in sulfur metabolism, is critical to a broad range of cellular functions. Accordingly, the acquisition of sulfur sources to fulfil cysteine requirements is a crucial determinant of bacterial survival. Compared to our understanding of how N. gonorrhoeae acquires essential nutrients such as carbon, zinc, and iron, sulfur acquisition and metabolism remain poorly defined. Here, we investigate the metabolic flexibility of N. gonorrhoeae with respect to sulfur acquisition and examine how the gonococcus adapts to conditions of sulfur limitation. By integrating bioinformatic analyses with experimental growth data and enzyme kinetic assays, we mapped the sulfur metabolic network in N. gonorrhoeae. We confirm that direct acquisition of cystine (and cysteine) supports growth and further demonstrate that cystine uptake is essential for colonization of epithelial cells under aerobic conditions. In the absence of cysteine, N. gonorrhoeae exhibits a limited capacity to utilize alternative sulfur sources, with only glutathione supporting proliferation, albeit inefficiently, via an unidentified mechanism. Growth under these conditions was restored by further supplementation with thiosulfate or methionine, indicating that glutathione utilization is constrained by downstream metabolic limitations, likely associated with inefficient cysteine liberation and restricted hydrogen sulfide availability required for methionine biosynthesis. This limited capacity to utilize alternative sulfur acquisition strategies is notable given that cysteine availability within the host is tightly regulated and maintained at low concentrations. Transcriptomic analyses across cysteine-independent growth conditions revealed the sulfur landscape influences transcriptional responses in a metabolite specific manner. More specifically, in response to sulfur starvation, N. gonorrhoeae does not appear to overcome this limitation through diverse acquisition strategies but instead adjusts cellular processes to compensate for inefficient sulfur acquisition via resource reallocation, where possible. By defining the sulfur metabolic network and uncovering the transcriptional responses, we conclude that N. gonorrhoeae exhibits metabolic inflexibility when its preferred substrate, cysteine, is unavailable, with proliferation supported by condition-specific adaptive responses rather than broad metabolic versatility. These findings provide valuable insights into how the gonococcus adapts to nutrient scarcity and advances our understanding of the fundamental physiology of this host-adapted pathogen.
Managing incivility in the public sector
(Hāpai Public | Institute of Public Professionals Aotearoa New Zealand, 2026) Zhou, Ao (Ollie); Haider, Alina; Duan, Daniel
Workplace incivility – everyday rudeness, dismissiveness, or disrespect – may seem minor, but its effects are far from trivial. Defined as “low-intensity behaviour with an ambiguous intent to harm”, incivility can damage wellbeing and productivity for both individuals and teams. How is incivility tackled in the Aotearoa New Zealand public sector?
On the processing of a powder metallurgy low-cost Ti alloy via different induction sintering strategies
(MDPI, 2026) Bolzoni, Leandro; Roduit, Valentin; Carreno-Morelli, Efrain; Yang, Fei; Raynova, Stiliana (Stella) Rousseva
Reducing the cost of Ti alloys, both from a processing and compositional point of view, is a pathway forward for harnessing more extensively the industrial and environmental benefits associated with their uses, and it is an outstanding manufacturing challenge. Thus, this study investigated the manufacturing of a low-cost Ti alloy using different induction sintering strategies where both aspects are designed to reduce the final cost. The primary conclusion is that induction sintering of Ti alloys by cycling the temperature above and below the allotropic phase transformation (i.e., beta transus) suffices for the need for high green density values, which are commonly achieved using more expensive methods. This is due to faster densification kinetics. The fast uniform heating of the alloys leads to homogenous pore distribution in the entire volume and the dissolution of the alloying elements, especially during cycling sintering due to the fine particle size of the alloying elements. Consequently, despite the low homologous sintering temperatures used, the induction sintered low-cost Ti alloys do not fail catastrophically, although the ability to sustain plastic deformation is affected by the features of the residual porosity.
Supercapacitor assisted multilevel inverter topology for off-grid renewable energy systems
(IEEE, 2024) Naligama, Chamila Anuradha; Kularatna, Nihal; Steyn-Ross, D. Alistair; Gunawardane, Kosala
Supercapacitor assisted (SCA) techniques are a new family of power electronic building blocks for renewable energy systems based on the theory published as SCA-loss management (SCALoM) concept. SCA inverter is a unique application of SCALoM theory, capable of meeting any capacity of off-grid inverter requirement, based on a combination of an even number of smaller inverters with suitably sized supercapacitor banks. SCA-inverter technique reduces input loop losses and transistor voltage stresses while providing DC-UPS capability without using batteries. This paper discusses the technical background of the SCA-inverter arrangement of operating seamlessly without common load balancing issues observed in other multi-inverter systems and techniques. The experiment results of two/four-SCA-inverter arrangement show stable operation of the inverter systems, both in switching transients of the supercapacitor banks and steady state operation. Four-SCA-inverter arrangement shows up to 2.5% efficiency improvement by equally partitioning the load into four inverters with no load balancing issues. As the four supercapacitor modules are switched at millihertz order frequency, it eliminaties the need for any EMC filters and dynamic losses in the frontend SCA arrangement are negligible.