title: Resilience of New Zealand indigenous forest fragments to impacts of livestock and pest mammals

authors: Dodd, Mike B.

subjects: biodiversity

abstract: A number of factors have combined to diminish ecosystem integrity in New Zealand indigenous lowland forest fragments surrounded by intensively grazed pasture. Livestock grazing, mammalian pests, adventive weeds and altered nutrient input regimes are important drivers compounding the changes in fragment structure and function due to historical deforestation and fragmentation. We used qualitative systems modelling and empirical data from Beilschmiedia tawa dominated lowland forest fragments in the Waikato Region to explore the relevance of two common resilience paradigms – engineering resilience and ecological resilience – for addressing the conservation management of forest fragments into the future. Grazing by livestock and foraging/predation by introduced mammalian pests both have direct detrimental impacts on key structural and functional attributes of forest fragments. Release from these perturbations through fencing and pest control leads to partial or full recovery of some key indicators (i.e. increased indigenous plant regeneration and cover, increased invertebrate populations and litter mass, decreased soil fertility and increased nesting success) relative to levels seen in larger forest systems over a range of timescales. These changes indicate that forest fragments do show resilience consistent with adopting an engineering resilience paradigm for conservation management, in the landscape context studied. The relevance of the ecological resilience paradigm in these ecosystems is obscured by limited data. We characterise forest fragment dynamics in terms of changes in indigenous species occupancy and functional dominance, and present a conceptual model for the management of forest fragment ecosystems.

text: Resilience of New Zealand indigenous forest fragments to impacts of livestock and pest mammals A number of factors have combined to diminish ecosystem integrity in New Zealand indigenous lowland forest fragments surrounded by intensively grazed pasture. Livestock grazing, mammalian pests, adventive weeds and altered nutrient input regimes are important drivers compounding the changes in fragment structure and function due to historical deforestation and fragmentation. We used qualitative systems modelling and empirical data from Beilschmiedia tawa dominated lowland forest fragments in the Waikato Region to explore the relevance of two common resilience paradigms – engineering resilience and ecological resilience – for addressing the conservation management of forest fragments into the future. Grazing by livestock and foraging/predation by introduced mammalian pests both have direct detrimental impacts on key structural and functional attributes of forest fragments. Release from these perturbations through fencing and pest control leads to partial or full recovery of some key indicators (i.e. increased indigenous plant regeneration and cover, increased invertebrate populations and litter mass, decreased soil fertility and increased nesting success) relative to levels seen in larger forest systems over a range of timescales. These changes indicate that forest fragments do show resilience consistent with adopting an engineering resilience paradigm for conservation management, in the landscape context studied. The relevance of the ecological resilience paradigm in these ecosystems is obscured by limited data. We characterise forest fragment dynamics in terms of changes in indigenous species occupancy and functional dominance, and present a conceptual model for the management of forest fragment ecosystems.

year: 2011

title: Simulation of the powder forging process for titanium components using a porous metal plasticity model

authors: Velluvakkandi, Navaneeth

subjects: powder forging

abstract: Powder forging is a technique that has been used to produce fully dense near-net parts from metal powders.  Due to a “low cost titanium” product manufacturing initiative, targeting a reduction in the cost of titanium components, a titanium powder forging technique has gained significant interest.  In titanium powder forging, powder consolidation is a key factor that influences successful component manufacture.  Consolidation during titanium powder forging is dependent on the densification and deformation mechanisms involved.
In this study, a finite element method is used to model the densification and deformation behaviour of titanium powder compacts during powder forging.  The research focuses on developing a simulation capability and identifying a suitable constitutive model to simulate the powder forging process that can predict the relative density distribution.  The simulation is carried out in Abaqus software and the results are compared with experimental results.  A gamma particle radiography technique is used to compare the experimental density results with the simulated results.
The Gurson and Gurson-Tvergaard models are used to predict the relative density of porous titanium powder compacts during upset-powder forging and are used to include the effect of hydrostatic stresses and the extent of densification.  Three different modes of densification, related to powder forging were studied i.e. upset forging, hot-repressing and closed die forging.
The simulation results indicate that both models can be used to determine the relative density during powder forging.  By comparing the simulated results with the experimental results, it is found that the density prediction given by the Gurson-Tvergaard model showed closer agreement with the calculated parameters.

text: Simulation of the powder forging process for titanium components using a porous metal plasticity model Powder forging is a technique that has been used to produce fully dense near-net parts from metal powders.  Due to a “low cost titanium” product manufacturing initiative, targeting a reduction in the cost of titanium components, a titanium powder forging technique has gained significant interest.  In titanium powder forging, powder consolidation is a key factor that influences successful component manufacture.  Consolidation during titanium powder forging is dependent on the densification and deformation mechanisms involved.
In this study, a finite element method is used to model the densification and deformation behaviour of titanium powder compacts during powder forging.  The research focuses on developing a simulation capability and identifying a suitable constitutive model to simulate the powder forging process that can predict the relative density distribution.  The simulation is carried out in Abaqus software and the results are compared with experimental results.  A gamma particle radiography technique is used to compare the experimental density results with the simulated results.
The Gurson and Gurson-Tvergaard models are used to predict the relative density of porous titanium powder compacts during upset-powder forging and are used to include the effect of hydrostatic stresses and the extent of densification.  Three different modes of densification, related to powder forging were studied i.e. upset forging, hot-repressing and closed die forging.
The simulation results indicate that both models can be used to determine the relative density during powder forging.  By comparing the simulated results with the experimental results, it is found that the density prediction given by the Gurson-Tvergaard model showed closer agreement with the calculated parameters.

year: 2014

title: Help or hindrance? New Zealand audience perspectives on subtitled media

authors: Kirk, Victoria

abstract: This research presents a picture of audiences’ patterns of engagement with internationally subtitled media in Hamilton, New Zealand. Utilising an audience reception framework to investigate audiences’ interactions with, and evaluations of subtitled media, this research unites the disciplines of Audio Visual Translation and Screen and Media Studies in a specific locale, with an emphasis on the reception of audio visual translated media. Findings in this research also provide a discussion of the wider contexts of audience reception in New Zealand, by investigating local subtitled media in relation to media accessibility processes found in the distinctive cultural landscape of New Zealand. Ultimately, this research finds the situation in New Zealand regarding audiences and the reception of both local English and Māori language media, as well as international subtitled media, exhibits complex polarisations in both the local translation industry production and audience attitudes towards bilingual media. In contrast to this, is the proliferation of international media with subtitles, which is appreciated by Hamilton residents since it provides diverse, accessible, and enjoyable content through a variety of media platforms.

text: Help or hindrance? New Zealand audience perspectives on subtitled media This research presents a picture of audiences’ patterns of engagement with internationally subtitled media in Hamilton, New Zealand. Utilising an audience reception framework to investigate audiences’ interactions with, and evaluations of subtitled media, this research unites the disciplines of Audio Visual Translation and Screen and Media Studies in a specific locale, with an emphasis on the reception of audio visual translated media. Findings in this research also provide a discussion of the wider contexts of audience reception in New Zealand, by investigating local subtitled media in relation to media accessibility processes found in the distinctive cultural landscape of New Zealand. Ultimately, this research finds the situation in New Zealand regarding audiences and the reception of both local English and Māori language media, as well as international subtitled media, exhibits complex polarisations in both the local translation industry production and audience attitudes towards bilingual media. In contrast to this, is the proliferation of international media with subtitles, which is appreciated by Hamilton residents since it provides diverse, accessible, and enjoyable content through a variety of media platforms.

year: 2019