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Effects of activator powders on hybrid binders based on volcanic ash and portalnd clinker based cement
No full textConcrete remains the most widely used construction material worldwide. However, the high energy consumption and CO₂ emissions associated with Portland cement production have driven the search for more sustainable alternatives. Volcanic ash (VA), a naturally occurring pozzolan found in abundance in regions such as Tauranga, New Zealand, presents promising potential as a partial replacement for cement.
This thesis investigates the performance of value-added products from the Takitimu North Link (TNL) site, using chemical activation with sodium sulphate (Na₂SO₄) and calcium hydroxide (Ca(OH)₂) in hybrid binder systems. A central composite experimental design was employed to systematically vary the VA content and activator dosages.
Mortar mixes with 25%, 50%, 75%, and 100% VA replacement were tested (Series A), with particular focus on the 25% blend. This composition underwent further testing with varying activator dosages to determine the optimal Na₂SO₄/Ca(OH)₂ (NS/CH) ratio (Series B). Compressive strength tests were conducted at 7, 28, and 90 days to assess mechanical performance.
Additionally, microstructural characterization techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) were used to identify hydration products and evaluate binder densification.
The results showed that a 25% replacement of Portland cement with VA, activated with 14% Na₂SO₄ at an NS/CH ratio of 1, delivered optimal compressive strength and microstructural development. While higher replacement levels generally reduced early-age strength due to weaker pozzolanic activity, appropriate activator dosages improved long-term performance significantly.
Overall, the study demonstrates that chemically activated volcanic ash can substantially improve the sustainability profile of concrete by reducing Portland cement usage and its environmental impacts. The use of optimized hybrid binders incorporating volcanic ash offers a viable solution for developing sustainable, resilient, and cost-effective construction materials in New Zealand and other volcanic regions worldwide
Renewable integration options for remote New Zealand community
No full textAbout 35% of New Zealand’s population lives in rural and remote areas like Whitianga and its nearby settlements. These areas are facing growing electricity demand due to rising population, business activity, and the shift to cleaner transport such as EV and FCEV. This trend is expected to put additional pressure on existing electricity infrastructure and networks, many of which were not built to handle such loads. A potential solution is to utilize local renewable energy sources, such as solar, wind, and green hydrogen, to reduce reliance on the national grid and delay costly infrastructure upgrades.
The first part of the thesis investigates the dynamic behaviour of a PEM electrolyser as a likely component in future integrated renewable energy systems. A Python-based simulation compares the hydrogen production output of dynamic and static models of a PEM under variable solar PV inputs. For the PEM capacity selected, there was a modest difference in cumulative hydrogen output from the dynamic model compared to the static model using one-minute input data over a whole day. Potentially, the dynamic model provides a more accurate way to size electrolyser and associated units like compressor and hydrogen storage vessels with the fluctuating electrical input conditions.
The second part evaluates the use of rooftop solar PV, wind, and hybrid solar-wind systems integrated with green hydrogen into a single residential house to achieve various levels of self-sufficiency over a full year. The study models energy balance, hydrogen storage, and levelized cost of energy (LCOE) for a range of system sizes, showing that 100% self-sufficiency is achievable in all three options, but only at extremely high LCOE levels between 0.52 and 0.78 NZD/kWh. Among the options, the hybrid system of solar and wind performs best, achieving complete self-sufficiency (100%) at the lowest cost of 0.52 NZD/kWh while balancing energy generation and storage needs with demand.
The third part presents a case study of the Whitianga township and region, exploring the integration of solar PV, Vehicle-to-grid (V2G), and green hydrogen to meet future energy demand. A techno-economic assessment examines residential, commercial, and transport energy needs from 2024 to 2050 and evaluates how a 32 MWp solar PV energy system can supply local demand while reducing reliance on the national grid and the need for local transformer upgrades. Two approaches were investigated: a centralised solar farm approach plus local hydrogen production & EV charging demand, and a decentralised residential rooftop solar approach supported by V2G electricity storage. The results indicate that the centralised approach has the lowest LCOE of 0.107 NZD/kWh, while the local grid upgrade remains unavoidable, even with higher solar penetration to the local grid. But in terms of payback period, the decentralised approach has a significant advantage, even with the higher investment cost, especially when V2G is incorporated into the energy management system. The initial investment amount can be recovered in 12.01 years with 20kWh of V2G battery storage
Rapid online detection of nitrate and quantification of nitrate removal via capacitive deionisation (CDI)
No full textAbstract
The increasing nitrate contamination in water poses significant environmental and public health challenges. With the rapid development of Capacitive Deionization (CDI) as a low-cost point-of-use (POU) solution to the problem, there was a rapid need for an online in-situ method for nitrate detection to support emerging POU technologies.
Due to these circumstances, it was necessary to investigate a new method for detecting nitrates, optimised for CDI’s requirements. Spectrophotometric based methods in small batch configuration (cuvette style) became our focus at the onset. A review of all the viable techniques reduced the design to the following common steps that needed to be converted into a viable miniature scale process: i) sample the liquid continuously, ii) pretreatment, iii) nitrate to nitrite reduction, iv) dye addition, v) colour development, vi) spectrophotometric measurement, and vii) dispense the waste.
With the aim of trialling a range of methods that had the potential of functioning as a continuous flow cell system within this design process, reverse engineering attempts were made using commercially available reagent sets from Palintest, and Hach Nitraver5 showing poor colour development. Thus, they were eliminated from further testing
Subsequent experiments employed the zinc reduction method, which offered a cost-effective means of nitrate concentration through its reduction to nitrite, followed by colorimetric analysis. Even though the zinc method demonstrated promising results, challenges such as sensitivity to reaction time, over-reduction of nitrite to ammonia, and variability in reproducibility limited its effectiveness. Additionally, side reactions and maintenance issues, including zinc oxidation and clogging, hinder its suitability for our continuous process.
Vanadium Chloride reduction method was finally chosen for its efficiency, rapid reaction time, and robustness under varying conditions. This method, combined with UV-VIS spectrophotometric analysis and MATLAB-based data processing, enabled real-time nitrate monitoring with over 93.05% accuracy. Key parameters such as residence time, flow rate, and heat transfer were optimised to enhance system performance. A reaction temperature of 85°C enabled complete reduction of vanadium species within 2 minutes, ensuring safe operation, consistent repeatability, and high precision. To address axial dispersion in flow-through systems, a novel sample-and-hold configuration was implemented, utilising seven parallel reactors with 17-second intervals to achieve discrete temporal resolution and accurate measurement. The system achieved a high-frequency sampling rate of 210 samples per hour (105 samples per CDI cycle), allowing near real-time tracking of nitrate fluctuations during semi-batch CDI operation.
A Stella model was developed to simulate nitrate removal via CDI, providing high resolution insight into nitrate adsorption and desorption dynamics. The model predicted transient nitrate responses that did not far exceed the system’s temporal resolution, which guided the implementation of a discrete sampling interval of 17 seconds. The integration of experimental validation with system simulation underscores the effectiveness of this combined approach in achieving accurate, real-time nitrate monitoring. The outcomes of this research contribute to the advancement of automated water quality analysis systems and offer a scalable, field-deployable solution for mitigating nitrate pollution in drinking water supplies
The virtual society: An examination of the concerns regarding a life in fully immersive virtual reality
No full textThis thesis argues that in the future, fully-immersive virtual societies could contribute positively to the prudential wellbeing of their citizens, even if they are aware that their reality is simulated. It builds upon the work of David Chalmers in Reality+ (2022), by further detailing how a virtual society might address the current trepidations many people have about living a life in virtual reality. Additionally, the thesis formulates a coherent model of a prudentially valuable virtual society, a model that can be critiqued and refined over time.
The first section describes several components of life in non-virtual reality that are considered by sceptics to be lacking or non-existent in virtual reality. For each example, it is argued that a virtual society can find a means to incorporate them. The second section discusses the position that utopian societies are "too good" to be prudentially valuable, and provides counterarguments against some of the reasons behind that perspective, in the context of a virtual utopia. Lastly, the third section offers five 'axioms of virtual abuse prevention'; design objectives that may help protect a prudentially valuable virtual society from corruption, abuses of power, and the suffering that may result
The PEAR Tool: evaluating portion sizes of food and beverages in food advertising to children using Google Street View
No full textPrevious research has established where and what types of advertising are in children’s neighbourhoods. However, no prior research has evaluated the portion sizes in advertisements or how these compare with national dietary recommendations. This study aimed to evaluate portion sizes in advertising on bus shelters surrounding schools in Auckland, New Zealand using images captured on Google Street View. Portion sizes for 265 foods or beverages in 172 advertisements on bus shelters within 500 m of Auckland schools were analysed to determine the discrepancy with nutritional guidelines. School type, decile, distance from school boundary, Walk Score® and Transit Score were analysed. Advertised foods and beverages were exaggerated in all but one advertisement. The main findings demonstrate 1) advertised food and beverage products are enlarged, and 2) advertised portion sizes exceed those deemed appropriate in national nutrition guidelines. Stricter advertising policies with revised definitions are needed to improve the food environments surrounding schools
Re-evaluating fatigue measurement: A comparative study of subjective and objective fatigue tests
No full textFatigue poses a significant risk in hazardous industries, with forestry being a particularly under-examined domain. Despite the availability of subjective and objective fatigue tests, inconsistencies in their application, selection rationale, and performance remain largely unaddressed in existing literature. This paper investigates the utility and challenges of subjective and objective fatigue assessments through a review of existing literature and two case studies: one intensive longitudinal study with a single participant and another broader study involving 31 participants. Our results reveal strong internal consistency across subjective tests but variable outcomes for objective tests, raising questions about test sensitivity and context-specific reliability. We argue for clearer guidance on fatigue test selection and propose criteria to inform future research in complex, real-world settings like forestry
Narrative persuasiveness without a narrative essence: A rejoinder to Talbi’s “Recognizing Something Human”
No full textMerel Talbi’s (2024a) main article, “The Epistemic Import of Narratives,” concerns how narratives of personal experience can be persuasive in reaching across a significant social or political divide. A primary goal of the article was to defend their role and value against the assumption that our form of argument must be based on logic and science. At the same time, she alerts us to some dangers associated with the use of such narratives, which she develops in her response (2024b) to us (2024b), a theme that we shall discuss, recognising the political context in which these situations occur. What she identifies as the main difference between us about the persuasiveness of narratives of personal experience may be framed as a question: what are the relative contributions of the narrative form and the personal quality?
We shall return to that question by way of a reframing which avoids the assumption that there is an essence of narrative structure. En route to that topic we shall look at ideas about how narratives may mesh well with the structure of the human mind. That will include Schechtman’s (2024) ideas about fiction as a process which mirrors the way human memory works. It will also include the thought that the self is a product of narrative self-creation. This may suggest that narratives can be persuasive given that they mesh well with our makeup. However our makeup is described, we hold that there is no essence of narrative structure that explains persuasiveness, for it comes down to the particularities of the situation. Narratives can occur in a variety of situations and a variety of forms; accounting narratives represent one kind of narrative with a distinct form and function. While there is no essence of a narrative that is linked to persuasiveness, narratives in particular situations certainly can be persuasive, as indeed they are designed to be
Navigating protection and presence: Trade-offs around data suppression for small Pacific populations
No full textIntroduction: Datasets, their analytics and their interpretation are key decision support tools for Pacific Island communities, with the potential to shape public policy, healthcare, and social interventions in the Pacific ‘Blue Continent’. However, in the case of numerically small island populations, privacy concerns have motivated widespread use of data suppression. While suppression safeguards privacy, it also risks erasing the visibility of these populations, leading to ‘statistical invisibility’ that obscures the social, health, and economic challenges. This study critically reviews the practice of data suppression, emphasizing its rationale in privacy protection, but also highlighting the impacts on resource allocation, advocacy, and equitable policy-making for Pacific populations.
Methods: We explored the rationale behind data suppression, and its legal and regulatory context. Using case studies including the U.S. Census Bureau, Centers for Disease Control and Behavioral Risk Factor Surveillance System, we assess the impact of suppression thresholds and privacy-preserving methods on Pacific Island communities. We present a novel analysis of data suppression impacts on ICD code suppression across different levels of geographical units in the Pacific to illustrate disproportionate impacts. We review alternative privacy-preserving methods, including data smoothing, statistical masking, and synthetic data generation, that could mitigate the effects of suppression without compromising individual privacy.
Finding and Conclusions: We recommend inclusive and transparent data practices needed to prevent data suppression compounding systemic marginalization of small Pacific populations. By critically evaluating current practices and proposing alternative strategies grounded in ‘Critical Data Theory’ and Pacific knowledge epistemology, this paper aims to inform policies that balance protection of individual privacy with the accurate representation of small, geographically dispersed populations
“Pushing an irritational button”: Asian psychologists making sense of racialization in psychology training in Aotearoa/New Zealand
No full textThe monocultural psychology training in Aotearoa New Zealand deliberately centers White racial framing which enables those who benefit from Whiteness to uphold an imposed hierarchy of racially inferior (Māori) and superior (Pākehā) groups. In Aotearoa, we are faced with a reality that Asian (as a diverse group from East Asia, Southeast Asia, and South Asia) knowledge sources and the intake of Asian students into psychology training are scarcely prioritized. In this study, we utilized counter-storytelling as a critical race praxis to illuminate the various forms of Asianization (Asian racialization) as a subframe of White racial framing. Employing interpretative phenomenological analysis, we explored the subjective experiences of four Asian psychologists as they made sense of racism and the formation of their racialized identity within psychology training. Our analysis uncovered three main themes with subordinate themes: (1) the White mold of psychology (encountering White ideals of psychology and pursuing perceived benefits of Whiteness); (2) bearing the brunt of Asianization (ranging from being achievers yet forgotten to being perceived as a threat and unassimilable); and (3) relating to Māori (expressing identity validation and empathy yet experiencing lateral violence). We observed the manifestation of White racial framing across various cognitive (e.g., the prioritization of western knowledge and the promotion of colorblind norms), emotional (e.g., White fragility), and behavioral aspects (e.g., expectations placed on minoritized ethnic groups to assimilate), all of which contribute to Asianization archetypes (viz., the forgotten Asian, the irritational button, and the unassimilable foreigner)
Counting ourselves: Findings from the 2022 Aotearoa New Zealand trans and non-binary health survey
No full textCounting Ourselves is a comprehensive national survey of the health and wellbeing of trans and non-binary people aged 14 and older living in Aotearoa New Zealand. The survey takes place every four years.
We report findings from 2,631 trans and non-binary people who completed our second survey in 2022. This is more than double the 1,178 survey participants from our first survey in 2018 and gives us very strong data about a range of trans and non-binary people living in Aotearoa New Zealand.
The 2022 survey participants lived in all regions of Aotearoa New Zealand and ranged in age from 14 to 86. Most were either youth aged 14–24 (53%) or adults aged 25–54 (43%). Over half (56%) of participants were non-binary, with an equal mix of trans men (22%) and trans women (22%). Compared with the general population, the survey had a higher proportion of European participants (77%), a similar proportion of Māori (14%), and a lower proportion of Asian (7%) and Pasifika (2%) participants.
More than two out of five (42%) of our participants were disabled. This included people who identified as Deaf or disabled (29%) and/or who met the definition of disability used in Stats NZ’s population surveys (38%). This was higher than the Stats NZ measure of disability in the general population (10%).
Throughout the report we identify statistically significant differences between participants based on age, gender, ethnicity, location, or disability. In 2025, the Counting Ourselves team hopes to produce fact sheets, articles, and other resources looking at the key findings for Māori, Pasifika, Asian, and disabled trans and non-binary people.
In this report we use the term gender affirming healthcare to refer to any healthcare interventions that trans or non-binary people may require to affirm their gender. We also use the term unmet need to describe the percentage of all participants who wanted but had not had a type of gender affirming healthcare