title: Towards industrial Al-Nb-B master alloys for grain refining Al-Si alloys

authors: Bolzoni, Leandro

abstract: It has long been known that foundry Al-Si alloys cannot reliably and consistently be grain refined by means of Ti-containing master alloys due to reaction between Ti and Si. Over the last years we developed and studied new Nb-based grain refiners consistently demonstrating the effectiveness of Nb + B inoculation on foundry alloys studying various Al-Si compositions solidified under different cooling conditions. Most of our studies focused on achieving the finest possible grain size using a lab made Al-2Nb-2B master alloy. This work presents the results, issues, and advancements made from the early stages of development to the first pilot scale trial. Moreover, the results of the present study are a further justification of the choice of the Al-2Nb-2B nominal composition, which was primarily dictated by the poor yield/recovery of Nb and B from their raw materials at lab scale. In the present work, emphasis is put on addressing the unanswered question about the effect of Nb to B ratio considering the inoculation of an Al-10Si alloys via the addition of Al-Nb-B master alloys with different stoichiometries.

text: Towards industrial Al-Nb-B master alloys for grain refining Al-Si alloys It has long been known that foundry Al-Si alloys cannot reliably and consistently be grain refined by means of Ti-containing master alloys due to reaction between Ti and Si. Over the last years we developed and studied new Nb-based grain refiners consistently demonstrating the effectiveness of Nb + B inoculation on foundry alloys studying various Al-Si compositions solidified under different cooling conditions. Most of our studies focused on achieving the finest possible grain size using a lab made Al-2Nb-2B master alloy. This work presents the results, issues, and advancements made from the early stages of development to the first pilot scale trial. Moreover, the results of the present study are a further justification of the choice of the Al-2Nb-2B nominal composition, which was primarily dictated by the poor yield/recovery of Nb and B from their raw materials at lab scale. In the present work, emphasis is put on addressing the unanswered question about the effect of Nb to B ratio considering the inoculation of an Al-10Si alloys via the addition of Al-Nb-B master alloys with different stoichiometries.

year: 2019

title: Supercapacitor assisted LDO (SCALDO) techniquean extra low frequency design approach to high efficiency DC-DC converters and how it compares with the classical switched capacitor converters

authors: Kankanamge, Kosala

abstract: Supercapacitor assisted low dropout regulators (SCALDO) were proposed as an alternative design approach to DC-DC converters, where the supercapacitor circulation frequency (switching frequency) is in the order of few Hz to few 10s of Hz, with an output stage based on a low dropout regulator stage. For converters such as 12–5V, 5–3.3V and 5–1.5V, the technique provides efficiency improvement factors of 2, 1.33 and 3 respectively, in compared to linear converters with same input-output combinations. In a 5–1.5V SCALDO regulator, using thin profile supercapacitors in the range of fractional farads to few farads, this translates to an approximate end to end efficiency of near 90%. However, there were concerns that this patented technique is merely a variation of well-known switched capacitor (charge pump) converters. This paper is aimed at providing a broad overview of the capability of SCALDO technique with generalized theory, indicating its capabilities and limitations, and comparing the practical performance with a typical switched capacitor converter of similar current capability.

text: Supercapacitor assisted LDO (SCALDO) techniquean extra low frequency design approach to high efficiency DC-DC converters and how it compares with the classical switched capacitor converters Supercapacitor assisted low dropout regulators (SCALDO) were proposed as an alternative design approach to DC-DC converters, where the supercapacitor circulation frequency (switching frequency) is in the order of few Hz to few 10s of Hz, with an output stage based on a low dropout regulator stage. For converters such as 12–5V, 5–3.3V and 5–1.5V, the technique provides efficiency improvement factors of 2, 1.33 and 3 respectively, in compared to linear converters with same input-output combinations. In a 5–1.5V SCALDO regulator, using thin profile supercapacitors in the range of fractional farads to few farads, this translates to an approximate end to end efficiency of near 90%. However, there were concerns that this patented technique is merely a variation of well-known switched capacitor (charge pump) converters. This paper is aimed at providing a broad overview of the capability of SCALDO technique with generalized theory, indicating its capabilities and limitations, and comparing the practical performance with a typical switched capacitor converter of similar current capability.

year: 2013

title: Aro mai aro atu: Raising Māori-medium students' academic oral language proficiency

authors: Shandley, Rosina Mary

subjects: Māori-medium

abstract: From the early 1860s, colonial governments worked systematically to eradicate the language and culture of the indigenous people of Aotearoa / New Zealand, and, by the late 1960s, the death of the Māori language was being predicted by leading linguists. Māori leaders responded in the 1980s with language regeneration initiatives that included the birth of Māori-medium education. Today, this uniquely indigenous education system is a significant site of language learning for new generations of Māori children. In Māori-medium education, children are nurtured, educated, and loved as Māori, and they are more likely to attain educational qualifications than their Māori peers who attend English-medium schools. 

The success of Māori-medium education is achieved in the face of a raft of ongoing challenges that teachers and students confront on a daily basis. Years of language marginalisation, including the disruption to intergenerational transfer, mean Māori-medium students are required to learn the curriculum through their second and less-developed language. They have limited opportunities to hear or use the Māori language outside of the school, and this places huge pressure on teachers who are often their most significant language models. The challenge is compounded by the limited education that has been made available to teachers in relation to second-language pedagogies specifically designed for Māori-medium classrooms. The resulting situation is that Māori-medium teachers are often left struggling to find ways that they can develop students’ Māori language proficiency at the same time as their curriculum achievement so that one is not sacrificed for the other. 

This study designed and trialled pedagogies to support Māori-medium students to develop their academic oral language proficiency at the same time as their curriculum achievement. It was a mixed methods study grounded in a kaupapa Māori approach, and involved three teachers and 24 students across three separate Māori-medium schools. An Anga Putanga Ako (Curriculum Outcomes Matrix) was developed to support the students to understand what they needed to learn to progress through the writing curriculum. Teachers then learnt to share explicit learning outcomes from the Anga Putanga Ako with students before lessons and to allow them time to discuss their achievement of those outcomes in pairs at the conclusion of those lessons. Linguistic scaffolds were developed to support students’ learning conversations, including the self and peer assessment of the learning outcomes, and decisions about their curriculum achievement levels and next learning steps.

The quantitative and qualitative results of the study revealed that the confluence of the self and peer assessment practices, supported by the Anga Putanga Ako and linguistic scaffolds, improved the students’ academic oral language and accelerated their reading and writing achievement significantly beyond what is usually expected in a Māori-medium classroom in 14 weeks. The study also found that, through implementing the self and peer assessment pedagogies, teachers were able to identify ways they could develop their students’ academic language and curriculum achievement simultaneously and how these approaches could be applied across the curriculum.

It was clear from the research results that pedagogies that support second-language development and curriculum learning, such as the self and peer assessment pedagogies demonstrated in this study, need to be explicitly taught with consistency across initial and in-service teacher education programmes. This development is necessary to help ensure Māori-medium students are supported with the thinking and linguistic skills needed to contribute to the creation of new knowledge, to support or challenge the current social order as they see fit, and to continue to transfer the Māori language to new generations of mokopuna.

text: Aro mai aro atu: Raising Māori-medium students' academic oral language proficiency From the early 1860s, colonial governments worked systematically to eradicate the language and culture of the indigenous people of Aotearoa / New Zealand, and, by the late 1960s, the death of the Māori language was being predicted by leading linguists. Māori leaders responded in the 1980s with language regeneration initiatives that included the birth of Māori-medium education. Today, this uniquely indigenous education system is a significant site of language learning for new generations of Māori children. In Māori-medium education, children are nurtured, educated, and loved as Māori, and they are more likely to attain educational qualifications than their Māori peers who attend English-medium schools. 

The success of Māori-medium education is achieved in the face of a raft of ongoing challenges that teachers and students confront on a daily basis. Years of language marginalisation, including the disruption to intergenerational transfer, mean Māori-medium students are required to learn the curriculum through their second and less-developed language. They have limited opportunities to hear or use the Māori language outside of the school, and this places huge pressure on teachers who are often their most significant language models. The challenge is compounded by the limited education that has been made available to teachers in relation to second-language pedagogies specifically designed for Māori-medium classrooms. The resulting situation is that Māori-medium teachers are often left struggling to find ways that they can develop students’ Māori language proficiency at the same time as their curriculum achievement so that one is not sacrificed for the other. 

This study designed and trialled pedagogies to support Māori-medium students to develop their academic oral language proficiency at the same time as their curriculum achievement. It was a mixed methods study grounded in a kaupapa Māori approach, and involved three teachers and 24 students across three separate Māori-medium schools. An Anga Putanga Ako (Curriculum Outcomes Matrix) was developed to support the students to understand what they needed to learn to progress through the writing curriculum. Teachers then learnt to share explicit learning outcomes from the Anga Putanga Ako with students before lessons and to allow them time to discuss their achievement of those outcomes in pairs at the conclusion of those lessons. Linguistic scaffolds were developed to support students’ learning conversations, including the self and peer assessment of the learning outcomes, and decisions about their curriculum achievement levels and next learning steps.

The quantitative and qualitative results of the study revealed that the confluence of the self and peer assessment practices, supported by the Anga Putanga Ako and linguistic scaffolds, improved the students’ academic oral language and accelerated their reading and writing achievement significantly beyond what is usually expected in a Māori-medium classroom in 14 weeks. The study also found that, through implementing the self and peer assessment pedagogies, teachers were able to identify ways they could develop their students’ academic language and curriculum achievement simultaneously and how these approaches could be applied across the curriculum.

It was clear from the research results that pedagogies that support second-language development and curriculum learning, such as the self and peer assessment pedagogies demonstrated in this study, need to be explicitly taught with consistency across initial and in-service teacher education programmes. This development is necessary to help ensure Māori-medium students are supported with the thinking and linguistic skills needed to contribute to the creation of new knowledge, to support or challenge the current social order as they see fit, and to continue to transfer the Māori language to new generations of mokopuna.

year: 2022