title: Synthesis, Microstructure, and Mechanical Properties of a Novel Ti₂AlC/TiC/Al₂O₃In Situ Composite

authors: Zhang, Deliang

subjects: engineering

abstract: This paper describes a novel process for synthesizing a Ti₂AlC/TiC/Al₂O₃in situ composite. This route utilizes TiO₂, carbon, and Al powders as raw materials, and involves high-energy mechanical milling and powder sintering. The Ti₂AlC/TiC/Al₂O₃ bulk in situ composite produced has a phase composition of Ti₂AlC–20 vol% TiC–35 vol% Al₂O₃ with fine Al₂O₃ particles (size: 0.5–15 μm) embedded in a Ti₂AlC/TiC matrix. The Ti₂AlC grains exhibit a nanometer scale lamellar structure, and most of the Al₂O₃ grains contain fine cubic TiOmC1−m precipitates (size: 10–200 nm). The average hardness and bending strength of the composite are in the ranges of 11–12.5 GPa and 380–440 MPa, respectively. Here we have demonstrated that the mechanical performance (mainly hardness and bending strength) of the composite is directly correlated with the size of the Al2O3 particles present in the as-fabricated in situ composite.

text: Synthesis, Microstructure, and Mechanical Properties of a Novel Ti₂AlC/TiC/Al₂O₃In Situ Composite This paper describes a novel process for synthesizing a Ti₂AlC/TiC/Al₂O₃in situ composite. This route utilizes TiO₂, carbon, and Al powders as raw materials, and involves high-energy mechanical milling and powder sintering. The Ti₂AlC/TiC/Al₂O₃ bulk in situ composite produced has a phase composition of Ti₂AlC–20 vol% TiC–35 vol% Al₂O₃ with fine Al₂O₃ particles (size: 0.5–15 μm) embedded in a Ti₂AlC/TiC matrix. The Ti₂AlC grains exhibit a nanometer scale lamellar structure, and most of the Al₂O₃ grains contain fine cubic TiOmC1−m precipitates (size: 10–200 nm). The average hardness and bending strength of the composite are in the ranges of 11–12.5 GPa and 380–440 MPa, respectively. Here we have demonstrated that the mechanical performance (mainly hardness and bending strength) of the composite is directly correlated with the size of the Al2O3 particles present in the as-fabricated in situ composite.

year: 2006

title: Measuring procrastination: A delay discounting approach within a New Zealand academic domain

authors: Paterson, Karissa

subjects: delay discounting

abstract: Delay discounting is often used to measure impulsiveness and has contributed to the development of interventions within the scopes of gambling, eating disorders, and drug addiction. Procrastination is the opposite of impulsiveness and, therefore, can be measured using delay discounting tools, as shown in previous research on scalloping behaviour. Procrastination is a common issue faced within academia, with research detailing the impacts on student grades and mental wellbeing. I aimed to assess the validity of an academic discounting task (ADT) in measuring procrastination within a cohort of university students while assessing if procrastination impacts students’ grades. Other measures of procrastination were used to analyse the validity of the k values produced by the ADT, such as the latency with which assignments were submitted by students, the number of late submissions, and the level of engagement within the paper. Forty-nine participants enrolled in a 3rd-year university paper completed an online questionnaire on Qualtrics that included the ADT. Additional data on student marks and engagement were collected through Moodle and Panopto. The k values produced from the ADT were not related to student marks or any other measure of procrastination. However, a relationship was identified between student overall marks and measures of procrastination such as latency of submission, number of late submissions and engagement scores, while scallop behaviour was also apparent within the cohort, but varying between tests and assignments. The findings of a relationship between the non-ADT measures of procrastination and overall marks suggests student procrastination behaviour does impact overall marks and therefore the ADT k values were not measuring procrastination and future research is needed with amendments to the ADT to make it a valid measure of procrastination. The variance in scallop behaviour between tests and assignments suggested that the scallop behaviour may not necessarily be always under control by the closeness of the reinforcer and can also be impacted by other variables.

text: Measuring procrastination: A delay discounting approach within a New Zealand academic domain Delay discounting is often used to measure impulsiveness and has contributed to the development of interventions within the scopes of gambling, eating disorders, and drug addiction. Procrastination is the opposite of impulsiveness and, therefore, can be measured using delay discounting tools, as shown in previous research on scalloping behaviour. Procrastination is a common issue faced within academia, with research detailing the impacts on student grades and mental wellbeing. I aimed to assess the validity of an academic discounting task (ADT) in measuring procrastination within a cohort of university students while assessing if procrastination impacts students’ grades. Other measures of procrastination were used to analyse the validity of the k values produced by the ADT, such as the latency with which assignments were submitted by students, the number of late submissions, and the level of engagement within the paper. Forty-nine participants enrolled in a 3rd-year university paper completed an online questionnaire on Qualtrics that included the ADT. Additional data on student marks and engagement were collected through Moodle and Panopto. The k values produced from the ADT were not related to student marks or any other measure of procrastination. However, a relationship was identified between student overall marks and measures of procrastination such as latency of submission, number of late submissions and engagement scores, while scallop behaviour was also apparent within the cohort, but varying between tests and assignments. The findings of a relationship between the non-ADT measures of procrastination and overall marks suggests student procrastination behaviour does impact overall marks and therefore the ADT k values were not measuring procrastination and future research is needed with amendments to the ADT to make it a valid measure of procrastination. The variance in scallop behaviour between tests and assignments suggested that the scallop behaviour may not necessarily be always under control by the closeness of the reinforcer and can also be impacted by other variables.

year: 2024

title: Spat survival of Paphies ventricosa (Toheroa) in an aquaculture setting

authors: Chew, Martyn Andrew

abstract: The toheroa (Papris ventracosta) is a large intertidal surf cam endemic to New Zealand. This species has a long history with the people of New Zealand in both cultural and economic sense. Exploitation and environmental change have greatly diminished the wild stocks of these animals making a sustainable fishery no longer feasible. Aquaculture has been widely discussed as a potentially profitable option for this species due to its large size, esteemed taste and its social and cultural significance. Aquaculture of toheroa could generate many benefits for the people of the toheroa beaches, as aquaculture has done in other regions of New Zealand. However, the suitability of toheroa for aquaculture is largely unknown, with many questions needing to be answered before that can become a reality. The purpose of this research is to gain a better understanding of the environmental conditions which will support the successful cultivation of wild caught toheroa spat in recirculating aquaculture systems (RAS). This is done by answering questions around knowledge gaps in the biology of the animal. Three experiments were conducted on aspects of the animal’s environment and biology. The first experiment sought to identify the presence of microphytobenthos’s within the wild population beds of the toheroa. As evidence suggests from research conducted on other species, microphytobenthos is an essential part of the animal’s ecosystem which might be a necessary component of a successful spat rearing operation. The experiment showed elevated chlorophyll levels (a proxy for microphytobenthos) within toheroa beds relative to other areas of the beach. The second experiment compared survival and growth rates in sediment vs. non-sediment holding systems. The results of this study indicated the benefits of housing spat in sediments, as demonstrated by differences in measured growth and mortality. A third experiment sought to test for size dependent mortality rates within the RAS. Somewhat surprisingly, it was found that smaller toheroa (0-10mm) performed better within a system compared to larger ones (20-30). Larger toheroa tended to eject themselves from the sediment constantly, an act which may have compromised their growth and survivorship. The result of these experiments answered questions and raise many more.  Potentially through understanding these questions we can create tools which industry and conservation can use. This research show that successful toheroa spat can be successfully integrated into an aquaculture system. With mortality settling the animals feeding and showing healthy condition. However, the next stage would be to optimize this. Toheroa aquaculture being in its infancy requires a wide variety of research before considered feasible. However, results and observations made from this research can help in identifying and specializing future research objectives.

text: Spat survival of Paphies ventricosa (Toheroa) in an aquaculture setting The toheroa (Papris ventracosta) is a large intertidal surf cam endemic to New Zealand. This species has a long history with the people of New Zealand in both cultural and economic sense. Exploitation and environmental change have greatly diminished the wild stocks of these animals making a sustainable fishery no longer feasible. Aquaculture has been widely discussed as a potentially profitable option for this species due to its large size, esteemed taste and its social and cultural significance. Aquaculture of toheroa could generate many benefits for the people of the toheroa beaches, as aquaculture has done in other regions of New Zealand. However, the suitability of toheroa for aquaculture is largely unknown, with many questions needing to be answered before that can become a reality. The purpose of this research is to gain a better understanding of the environmental conditions which will support the successful cultivation of wild caught toheroa spat in recirculating aquaculture systems (RAS). This is done by answering questions around knowledge gaps in the biology of the animal. Three experiments were conducted on aspects of the animal’s environment and biology. The first experiment sought to identify the presence of microphytobenthos’s within the wild population beds of the toheroa. As evidence suggests from research conducted on other species, microphytobenthos is an essential part of the animal’s ecosystem which might be a necessary component of a successful spat rearing operation. The experiment showed elevated chlorophyll levels (a proxy for microphytobenthos) within toheroa beds relative to other areas of the beach. The second experiment compared survival and growth rates in sediment vs. non-sediment holding systems. The results of this study indicated the benefits of housing spat in sediments, as demonstrated by differences in measured growth and mortality. A third experiment sought to test for size dependent mortality rates within the RAS. Somewhat surprisingly, it was found that smaller toheroa (0-10mm) performed better within a system compared to larger ones (20-30). Larger toheroa tended to eject themselves from the sediment constantly, an act which may have compromised their growth and survivorship. The result of these experiments answered questions and raise many more.  Potentially through understanding these questions we can create tools which industry and conservation can use. This research show that successful toheroa spat can be successfully integrated into an aquaculture system. With mortality settling the animals feeding and showing healthy condition. However, the next stage would be to optimize this. Toheroa aquaculture being in its infancy requires a wide variety of research before considered feasible. However, results and observations made from this research can help in identifying and specializing future research objectives.

year: 2022