title: Microstructure development and properties of alumina–Ti aluminide interpenetrating composites

authors: Han, Ching Zen

subjects: pressureless sintering

abstract: Interpenetrating phase Al₂O₃–Ti₃Al composites have been fabricated by reaction sintering of 2 and 4-h discus milled composite powders containing Al and TiO₂ using controlled heat-treatment in non-oxidizing atmospheres. Pressureless sintering and hot pressing of the powders has been carried out under vacuum and argon at temperatures between 1278 °C and 1500 °C and a heating rate of 5 °C/min. Densification of the composites was investigated as a function of temperature. It was shown that lower porosity was obtained by hot pressing compared to pressureless sintering.

The microstructure development and mechanical properties of dense Al₂O₃–Ti₃Al composites fabricated by hot pressing of Al–TiO₂ powder blends were examined. Fully dense microstructures could be achieved by hot pressing at 1387 °C under vacuum. An increase of Vickers hardness was observed with increasing temperature, which can be attributed to the increase of density and the decrease in the level of porosity of the composites. The mechanical behaviour exhibited by the composites can be related to properties such as Al₂O₃ particle size and porosity level. Fracture toughness of 6.3 ± 0.8 MPa m1/2 and Vickers hardness of 13.6 ± 0.4 GPa were achieved for the fully dense composite produced by hot pressing discus milled powder.

text: Microstructure development and properties of alumina–Ti aluminide interpenetrating composites Interpenetrating phase Al₂O₃–Ti₃Al composites have been fabricated by reaction sintering of 2 and 4-h discus milled composite powders containing Al and TiO₂ using controlled heat-treatment in non-oxidizing atmospheres. Pressureless sintering and hot pressing of the powders has been carried out under vacuum and argon at temperatures between 1278 °C and 1500 °C and a heating rate of 5 °C/min. Densification of the composites was investigated as a function of temperature. It was shown that lower porosity was obtained by hot pressing compared to pressureless sintering.

The microstructure development and mechanical properties of dense Al₂O₃–Ti₃Al composites fabricated by hot pressing of Al–TiO₂ powder blends were examined. Fully dense microstructures could be achieved by hot pressing at 1387 °C under vacuum. An increase of Vickers hardness was observed with increasing temperature, which can be attributed to the increase of density and the decrease in the level of porosity of the composites. The mechanical behaviour exhibited by the composites can be related to properties such as Al₂O₃ particle size and porosity level. Fracture toughness of 6.3 ± 0.8 MPa m1/2 and Vickers hardness of 13.6 ± 0.4 GPa were achieved for the fully dense composite produced by hot pressing discus milled powder.

year: 2006

title: The impact of background and context on car distance estimation

authors: Zhang, Fan

subjects: Distance Estimation

abstract: It is well established that people underestimate the distance to objects depicted in virtual environments and two-dimensional (2D) displays. The reasons for the underestimation are still not fully understood. It is becoming more common to use virtual environment displays for driver training and testing and so understanding the distortion of perceived space that occurs in these displays is vital. We need to know what aspects of the display cause the observer to misperceive the distance to objects in the simulated environments. The research reported in this thesis investigated how people estimate distance between themselves and a car in front of them, within a number of differing environmental contexts.  Four experiments were run using virtual environment displays of various kinds and a fifth experiment was run in a real-world setting.
It was found that distance underestimation when viewing 2D displays is very common, even when familiar objects such as cars are used as the targets. The experiments also verified that people have a greater underestimation of distance in a virtual environment compared to a real-world setting. A surprising and somewhat counterintuitive result was that people underestimate distance more when the scene depicts forward motion of the observer compared to a static view.  The research also identified a number of visual features in the display (e.g., texture information) and aspects of the display (e.g., field of view) that affected the perception of distance or that had no effect. The findings should help the designers of driver-training simulators and testing equipment to better understand the types of errors that can potentially occur when humans view two-dimensional virtual environment displays.

text: The impact of background and context on car distance estimation It is well established that people underestimate the distance to objects depicted in virtual environments and two-dimensional (2D) displays. The reasons for the underestimation are still not fully understood. It is becoming more common to use virtual environment displays for driver training and testing and so understanding the distortion of perceived space that occurs in these displays is vital. We need to know what aspects of the display cause the observer to misperceive the distance to objects in the simulated environments. The research reported in this thesis investigated how people estimate distance between themselves and a car in front of them, within a number of differing environmental contexts.  Four experiments were run using virtual environment displays of various kinds and a fifth experiment was run in a real-world setting.
It was found that distance underestimation when viewing 2D displays is very common, even when familiar objects such as cars are used as the targets. The experiments also verified that people have a greater underestimation of distance in a virtual environment compared to a real-world setting. A surprising and somewhat counterintuitive result was that people underestimate distance more when the scene depicts forward motion of the observer compared to a static view.  The research also identified a number of visual features in the display (e.g., texture information) and aspects of the display (e.g., field of view) that affected the perception of distance or that had no effect. The findings should help the designers of driver-training simulators and testing equipment to better understand the types of errors that can potentially occur when humans view two-dimensional virtual environment displays.

year: 2014

title: Reconnecting whānau: Pathways to recovery for Māori with bipolar disorder

authors: Waitoki, Waikaremoana

subjects: mental health

abstract: While Māori are known to experience a higher burden of mental health and addiction problems compared to non-Māori (Baxter, 2008), little exploratory research has been conducted into Māori experiences of bipolar affective disorder. Bipolar disorder is at times regarded as a “life sentence”, with little hope of recovery. The recovery- focused mental health literature, however, argues wellness is achievable for even the most intractable conditions (Lapsley, Nikora, & Black, 2002; Mental Health Commission, 2001). The aim of this research was to gather information about the experiences of Māori who were diagnosed with bipolar affective disorder. Interviews were conducted with 22 Māori wāhine (women) and tāne (men), and using thematic analyses, themes relevant to their life stories were uncovered. This research sought to contribute to the realisation of Māori potential by explicitly shifting from deficit- focused frameworks to a focus on systemic factors that influenced Māori wellbeing. Highlights were that whānau (participants) who were connected with friends, partners and family were motivated to achieve wellness and to stay well.

text: Reconnecting whānau: Pathways to recovery for Māori with bipolar disorder While Māori are known to experience a higher burden of mental health and addiction problems compared to non-Māori (Baxter, 2008), little exploratory research has been conducted into Māori experiences of bipolar affective disorder. Bipolar disorder is at times regarded as a “life sentence”, with little hope of recovery. The recovery- focused mental health literature, however, argues wellness is achievable for even the most intractable conditions (Lapsley, Nikora, & Black, 2002; Mental Health Commission, 2001). The aim of this research was to gather information about the experiences of Māori who were diagnosed with bipolar affective disorder. Interviews were conducted with 22 Māori wāhine (women) and tāne (men), and using thematic analyses, themes relevant to their life stories were uncovered. This research sought to contribute to the realisation of Māori potential by explicitly shifting from deficit- focused frameworks to a focus on systemic factors that influenced Māori wellbeing. Highlights were that whānau (participants) who were connected with friends, partners and family were motivated to achieve wellness and to stay well.

year: 2015