title: Tactical management of pasture fallows in western Australian cropping systems

authors: Doole, Graeme J.

subjects: land-use sequences

abstract: Agricultural systems in the Western Australian wheatbelt are increasingly moving towards specialist crop production due to elevated cereal prices, depressed markets for livestock products, and ongoing labour scarcity. However, the profitability of crop-only farms is threatened by increasing levels of herbicide resistance and declining soil fertility. This study determines the value of ungrazed pasture fallows grown tactically between crop phases to address these agronomic constraints. A novel metaheuristic optimisation technique, compressed annealing, is used to determine profitable flexible land-use sequences in a complex simulation model. Tactical use of single-year, ungrazed pasture phases is found to be more valuable than the use of break crops in crop-only systems. In contrast to previous analysis, it is identified that rotation of short periods of crop and pasture is more profitable than extended phases of both. Effective weed control without dependence on selective herbicides is the key agronomic characteristic determining the value of intermittent pasture phases. Accordingly, the number of single-year pasture phases employed in a sequence should increase with the severity of herbicide resistance. Compressed annealing is shown to be a practical method of identifying profitable land-use sequences that respond to information that unfolds dynamically.

text: Tactical management of pasture fallows in western Australian cropping systems Agricultural systems in the Western Australian wheatbelt are increasingly moving towards specialist crop production due to elevated cereal prices, depressed markets for livestock products, and ongoing labour scarcity. However, the profitability of crop-only farms is threatened by increasing levels of herbicide resistance and declining soil fertility. This study determines the value of ungrazed pasture fallows grown tactically between crop phases to address these agronomic constraints. A novel metaheuristic optimisation technique, compressed annealing, is used to determine profitable flexible land-use sequences in a complex simulation model. Tactical use of single-year, ungrazed pasture phases is found to be more valuable than the use of break crops in crop-only systems. In contrast to previous analysis, it is identified that rotation of short periods of crop and pasture is more profitable than extended phases of both. Effective weed control without dependence on selective herbicides is the key agronomic characteristic determining the value of intermittent pasture phases. Accordingly, the number of single-year pasture phases employed in a sequence should increase with the severity of herbicide resistance. Compressed annealing is shown to be a practical method of identifying profitable land-use sequences that respond to information that unfolds dynamically.

year: 2009

title: Mechanical properties and fracture behaviour of nanostructured and ultrafine structured TiAl Alloys synthesised by mechanical milling of powders and hot isostatic pressing

authors: Zhang, Deliang

subjects: fracture behaviour

abstract: Bulk nanostructured (grain sizes in the range of 50-200nm) and ultrafine structured (grain sizes in the range of 100-500nm) γ-TiAl based alloys with compositions Ti-47Al (in at%) and Ti–45Al–2Cr–2Nb–1B–0.5Ta (in at%), respectively, have been produced using a combination of high energy mechanical milling of mixtures of elemental powders and hot isostatic pressing at 800 and 1000oC respectively, and the microstructures of the samples have been characterised. At room temperature, the HIPed samples fractured prematurely at tensile stresses in the range of 200-300MPa and showed no ductility, very likely due to the relative high oxygen content (0.6wt%) in the samples and very low tolerance of TiAl based alloys on dissolved oxygen. At 800oC, the HIPed samples showed a yield strength in the range of 55-70MPa, a tensile strength in the range of 60-80MPa, a large amount of elongation to fracturing around 100% and clear strain softening. Examination of the fractured tensile test specimens at room temperature and 800oC showed that the level of the consolidation was fairly high, but the HIPed samples do contain a small fraction of interparticle boundaries with weak atomic bonding. The fracture of the HIPed samples in tensile testing at room temperature and 800oC, respectively, is predominately intergranular, and the large amount of plastic deformation prior to fracture at 800oC is achieved mainly through grain boundary sliding in conjunction with dislocation gliding, in agreement with the deformation mechanisms of nanostructured and ultrafine structured alloys generally agreed by researchers.

text: Mechanical properties and fracture behaviour of nanostructured and ultrafine structured TiAl Alloys synthesised by mechanical milling of powders and hot isostatic pressing Bulk nanostructured (grain sizes in the range of 50-200nm) and ultrafine structured (grain sizes in the range of 100-500nm) γ-TiAl based alloys with compositions Ti-47Al (in at%) and Ti–45Al–2Cr–2Nb–1B–0.5Ta (in at%), respectively, have been produced using a combination of high energy mechanical milling of mixtures of elemental powders and hot isostatic pressing at 800 and 1000oC respectively, and the microstructures of the samples have been characterised. At room temperature, the HIPed samples fractured prematurely at tensile stresses in the range of 200-300MPa and showed no ductility, very likely due to the relative high oxygen content (0.6wt%) in the samples and very low tolerance of TiAl based alloys on dissolved oxygen. At 800oC, the HIPed samples showed a yield strength in the range of 55-70MPa, a tensile strength in the range of 60-80MPa, a large amount of elongation to fracturing around 100% and clear strain softening. Examination of the fractured tensile test specimens at room temperature and 800oC showed that the level of the consolidation was fairly high, but the HIPed samples do contain a small fraction of interparticle boundaries with weak atomic bonding. The fracture of the HIPed samples in tensile testing at room temperature and 800oC, respectively, is predominately intergranular, and the large amount of plastic deformation prior to fracture at 800oC is achieved mainly through grain boundary sliding in conjunction with dislocation gliding, in agreement with the deformation mechanisms of nanostructured and ultrafine structured alloys generally agreed by researchers.

year: 2011

title: Whakapapa Ora: An exploration of Māori Identity through Whakapapa

authors: Ngawhare, Rauna Maria

subjects: Whakapapa

abstract: This thesis set out to explore Māori identity through access to whakapapa. As whānau, hapū, and iwi, we have a responsibility to future generations to ensure access to whakapapa is inclusive. Therefore, access to whakapapa in today’s world must also consider contemporary approaches, including the use of technology to engage the next generation in learning about, and connecting with, whakapapa. 

The research is centred on the question ‘How can whakapapa be accessed safely in culturally appropriate ways that evolve with twenty-first-century systems?’ I use contemporary pūrākau to review traditional access to whakapapa, supported by a Kaupapa Māori approach to frame the research. Kaupapa Māori Theory, Ngā Takepū, and Pūrākau Methodology (underpinned by Qualitative Methodology and Thematic Analysis) give an overview of the methodologies and methods used herein. Five semi-structured interviews with whānau affiliated to Ngāti Kahungunu ki Heretaunga and Taranaki iwi were conducted. Each share their lived experiences as Māori to support an understanding of identity through whakapapa.  

The results suggest whānau Māori who access whakapapa (in its many forms), will undergo a process of decolonisation. This requires adequate support in the form of kaitiakitanga, necessary to gain a better understanding of Te Ao Māori tikanga and kawa. Whakapapa access develops this process. However, further research is required to fully appreciate ‘Whakapapa Ora’ as a foundation for safe access to whakapapa in the twenty-first century.

text: Whakapapa Ora: An exploration of Māori Identity through Whakapapa This thesis set out to explore Māori identity through access to whakapapa. As whānau, hapū, and iwi, we have a responsibility to future generations to ensure access to whakapapa is inclusive. Therefore, access to whakapapa in today’s world must also consider contemporary approaches, including the use of technology to engage the next generation in learning about, and connecting with, whakapapa. 

The research is centred on the question ‘How can whakapapa be accessed safely in culturally appropriate ways that evolve with twenty-first-century systems?’ I use contemporary pūrākau to review traditional access to whakapapa, supported by a Kaupapa Māori approach to frame the research. Kaupapa Māori Theory, Ngā Takepū, and Pūrākau Methodology (underpinned by Qualitative Methodology and Thematic Analysis) give an overview of the methodologies and methods used herein. Five semi-structured interviews with whānau affiliated to Ngāti Kahungunu ki Heretaunga and Taranaki iwi were conducted. Each share their lived experiences as Māori to support an understanding of identity through whakapapa.  

The results suggest whānau Māori who access whakapapa (in its many forms), will undergo a process of decolonisation. This requires adequate support in the form of kaitiakitanga, necessary to gain a better understanding of Te Ao Māori tikanga and kawa. Whakapapa access develops this process. However, further research is required to fully appreciate ‘Whakapapa Ora’ as a foundation for safe access to whakapapa in the twenty-first century.

year: 2019