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    Using trickle ventilators coupled to fan extractor to achieve a suitable airflow rate in an Australian apartment: A nodal network approach connected to a CFD approach
    (Elsevier B.V., 2023-12-26) Boulic M; Bombardier P; Zaidi Z; Russell A; Waters D; van Heerden A
    The level of airtightness is increasing in newly built Australian apartments. Due to the COVID-19 pandemic, restrictions have forced many people to work from home. An appropriate ventilation rate is needed to decrease virus transmission and provide occupants with a healthy environment. As occupants tend not to open windows, they need to be informed about the potential benefit of using trickle ventilators, in connection with exhaust systems, to ventilate their apartments. In 2022, a provision for lower rates of continuous ventilation (10 L.s−1 for the bathroom exhaust system and 12 L.s−1 for the kitchen exhaust system) was considered for inclusion in the National Construction Code of Australia. This provision was not adopted; however, this is still a valid reference for good practice. Based on this provision for continuous ventilation, our study aims to investigate the airflow velocity and the ventilation efficiency to remove the carbon dioxide (CO2) generated across winter and summer seasons in a Melbourne apartment occupied by two adults and a child over four hours. The study's objectives are 1) to connect two modelling approaches (Computational Fluid Dynamics and nodal networks), and 2) to investigate the potential benefits of using trickle ventilators across winter and summer seasons. The results show that wind conditions have limited effects (4% decrease in the extracted air flow rate) if the extraction network output is protected from the wind. Comparing winter and summer conditions, we found that indoor airflows differed, highly influenced by the temperature difference between outside and inside. We observed that the airflow patterns were more inclined to create “CO2 pockets” during winter, which could increase virus transmission due to ineffective ventilation in this area. However, in winter, ventilation performed better in reducing the CO2 concentration in the kitchen/living room area and the whole apartment than it did during summer.
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    Metal-organic framework (MOF) membranes for gas separations : a thesis presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy in Chemistry at Massey University, Manawatu, New Zealand
    (Massey University, 2024-04-29) Zhang, Yiming
    The study presented in this thesis involves the design, preparation and evaluation of metal-organic frameworks (MOFs) for gas separation applications, with a focus on the development of MOF membranes with both high gas permeability and good selectivity. Here, two types of membranes, including crystal glass composite membranes (CGCMs) and mixed matrix membranes (MMMs), were prepared and characterized, followed by a comprehensive evaluation of their performance for CO₂ separation. Separating gases using membranes is appealing due to their efficiency and low energy requirements. Recently, glasses have been discovered that are produced by the melt-quenching of ZIFs. In chapter 2, we propose that useful membranes can be prepared by combining ZIF glasses with MOFs. We prepared these crystal-glass composite membranes by ball milling ZIF-62 with various crystalline MOFs followed by pressing into a tablet, heating to melt the ZIF-62 into a glass, and subsequent cooling. This fabrication process delivers membranes with homogenous dispersion of crystalline MOF particles in a ZIF glass matrix. As an alternative, we show how pre-forming ZIF-62 glass allows membranes to be formed with MOFs with relatively low stability. The resulting crystal-glass composite membranes show ultrahigh CO₂ permeance. MMMs offer great potential for gas separation through the integration of nanofillers into polymers with excellent processability. Among these, MOF-based MMMs have emerged as promising candidates for advanced gas separation applications. However, a major obstacle hindering their performance is the inherent interfacial incompatibility between MOFs particles and the polymer matrix. In this thesis, we present a viable solution utilizing a scalable ball milling approach to address this challenge, specifically targeting the interfacial incompatibility between MUF-16 and the polymer matrix. Significantly, our approach involves the production of MUF-16 with varying crystal sizes through ball milling prior to MMM fabrication. In chapter 3 and 4, we illustrate that the nanosizing of MUF-16 (nsMUF-16) enhances its dispersion within three different polymer matrices (Pebax, 6FDA-DAM and 6FDA-Durene), effectively minimizing non-selective voids around the particles. Importantly, MMMs incorporating nsMUF-16 consistently exhibit superior CO₂ separation performance compared to those utilizing micro-sized MUF-16. Overall, this study highlights a versatile methodology employing engineered approaches to develop high-performance membranes with enhanced interfacial compatibility for gas separation. Furthermore, this approach holds promise for extending the processability of other MOF adsorbents into matrix materials, thereby broadening the scope of potential applications in gas separation technologies. Due to the distinctive structural arrangement of MUF-15, where the phenyl rings of the ipa ligands protrude into the void space, there exists a potential for substituting the ipa ligand with various functional groups. This opens avenues for obtaining analogues of MUF-15. These functionalized variants, denoted as MUF-15-X (with X representing substituents such as F, Br, CH₃, and NO₂), offer the prospect of imbuing MUF-15 with diverse gas sorption properties. Consequently, our interest is piqued to explore the structural characteristics and gas separation capabilities of these analogues across different functional groups. In chapter 5, we present a comprehensive investigation into 6FDA-DAM-based MMMs incorporating MUF-15 and its analogues for CO₂ separation from CH₄. Notably, this study constitutes the pioneering utilization of MUF-15 analogues as fillers in MMMs specifically designed for CO₂/CH₄ separation. It introduces a spectrum of emerging MUF-15 derivatives as potential filler materials for MMM development and underscores the efficacy of pore structure functionalization in augmenting the separation performance of MMMs.
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    Effects of elevated atmospheric CO2 concentrations on carbon and nitrogen fluxes in a grazed pasture : a thesis presented in partial fulfilment of the requirements for the degree of Ph. D. in Plant Science at Massey University and the degree of Docteur en Sciences, speciality Sciences Agronomiques at the Institut National Polytechnique de Lorraine
    (Massey University, 2003) Allard, Vincent
    Predicting the response of grazed grasslands to elevated CO2 is of central importance in global change research as grasslands represent 20% of the worlds' land area and grassland soils are a major sink for carbon (C). Grasslands responses to elevated CO2 are strongly controlled by the availability of other nutrients and nitrogen (N) in particular. There have been many previous studies of N cycling in grasslands exposed to elevated CO2 but none of these experiments were grazed. In this thesis I present data on CO2 effects on N cycling from an experimental system (FACE: Free Air Carbon dioxide Enrichment) that enabled grazing to be included. The thesis focuses on the effects of elevated CO2 on the different processes involved in organic matter (OM) returns from the plant to the soil and the consequences for N availability. In Chapter 1, it was shown that elevated CO2 modified N returns by grazing animals by altering the partitioning of N between faeces and urine creating a potential for enhanced N losses at elevated CO2. Plant litter decomposition rates were, at the ecosystem scale, not affected by elevated CO2 (Chapter 3), but a marked increase in the organic matter fluxes, from roots, led to an accumulation of coarse OM in the soil (Chapter 4). In Chapter 5, using 14C and 15N labelling, I compared short-term (plant mediated) and long-term (soil mediated) effects of elevated CO2 on soil OM dynamics and concluded that soil OM accumulation under elevated CO2 was not caused by C or N limitation but probably by the availability of other nutrients. The thesis demonstrates that the inclusion of grazing animals can strongly modify N cycling under elevated CO2. As most grasslands are grazed, the prediction of grassland responses to elevated CO2 must be derived from systems in which animals are an integral part.