title: The influence of educational context on science learning: a cross-national analysis of PISA

authors: Coll, Richard K.

subjects: PISA

abstract: The literature is replete with studies about the importance of context in relation to teaching and learning. Major international studies such as PISA, among others, attempt to develop an understanding of achievement in science learning in a variety of educational contexts. Here we explore the influence of educational context itself on science learning as measured by PISA. Comparison is made between two countries: one developed or 'western' nation, New Zealand, and one non-western developing nation from southeast Asia, Thailand. In this work the authors seek to establish links between the nature of the educational context (based on Lave's notion of situated cognition) and achievement in the PISA science evaluation exercise.

text: The influence of educational context on science learning: a cross-national analysis of PISA The literature is replete with studies about the importance of context in relation to teaching and learning. Major international studies such as PISA, among others, attempt to develop an understanding of achievement in science learning in a variety of educational contexts. Here we explore the influence of educational context itself on science learning as measured by PISA. Comparison is made between two countries: one developed or 'western' nation, New Zealand, and one non-western developing nation from southeast Asia, Thailand. In this work the authors seek to establish links between the nature of the educational context (based on Lave's notion of situated cognition) and achievement in the PISA science evaluation exercise.

year: 2010

title: Efficiency enhancements to a linear AC voltage regulator: Multi-transformer  and multi-winding designs

authors: Wijesooriya, Priyanwada Nimesha

subjects: Linear AC voltage regulator

abstract: Utility companies are expected to distribute electricity that conforms with international or national standards related to RMS voltage fluctuations. However, RMS voltage variations sometimes exceed acceptable limits and this demands consumer-end voltage regulators. Commercial AC regulators such as (i) servo-driven variacs, (ii) ferro-resonant, (iii) transformer tap changers, (iv) solid-state types, have their own advantages and limitations. Common issues include (a) slow response time, (b) low efficiency and flattened-output waveform, (c) tap dancing and related switching issues, (d) harmonics and RFI/EMI at the output, respectively.

The linear RMS AC voltage regulator is a patented technique developed in the late 1980s to address most of the above issues. It is a solid-state, single-phase system that employs a line-frequency transformer with its primary connected in series with an AC-operable variable impedance based on power transistors. The secondary winding is placed in series with the varying AC input, so that the induced secondary voltage acts as a correction signal to maintain the output at the desired value. A feedback circuit varies the effective impedance of the transistor-array, thus, manipulate the induced secondary voltage to regulate the output.

This is a linear technique that allows seamless transition between boost to buck mode. However, this comes at the cost of lower efficiency at high AC input, particularly when line voltage goes beyond the nominal value.  

Commercial partner, Thor Technologies, Australia, wanted the team to modify their servo-driven AC regulator (PS-10), based on our technique with efficiency in the range of 90-95% and the response time improved by about 10 times.

During development of a commercial prototype, the author implemented two potential solutions: (i) multi-transformer and (ii) multi-winding transformer based techniques to overcome the reduced efficiency during buck-mode operation, an issue inherent to the basic linear AC technique. 

Thesis was aimed at improving the power stage of the linear technique while maintaining the already developed analog control loop with true RMS regulation capability. thesis presents two alternative transformer solutions to reach efficiencies in the range of $90-95\%$ on a laboratory prototype of 500VA. Experimental results were validated by constructing a theoretical model for the two transformer configurations, supported by an equivalent circuit analysis using MATLAB and LTSpice software.

text: Efficiency enhancements to a linear AC voltage regulator: Multi-transformer  and multi-winding designs Utility companies are expected to distribute electricity that conforms with international or national standards related to RMS voltage fluctuations. However, RMS voltage variations sometimes exceed acceptable limits and this demands consumer-end voltage regulators. Commercial AC regulators such as (i) servo-driven variacs, (ii) ferro-resonant, (iii) transformer tap changers, (iv) solid-state types, have their own advantages and limitations. Common issues include (a) slow response time, (b) low efficiency and flattened-output waveform, (c) tap dancing and related switching issues, (d) harmonics and RFI/EMI at the output, respectively.

The linear RMS AC voltage regulator is a patented technique developed in the late 1980s to address most of the above issues. It is a solid-state, single-phase system that employs a line-frequency transformer with its primary connected in series with an AC-operable variable impedance based on power transistors. The secondary winding is placed in series with the varying AC input, so that the induced secondary voltage acts as a correction signal to maintain the output at the desired value. A feedback circuit varies the effective impedance of the transistor-array, thus, manipulate the induced secondary voltage to regulate the output.

This is a linear technique that allows seamless transition between boost to buck mode. However, this comes at the cost of lower efficiency at high AC input, particularly when line voltage goes beyond the nominal value.  

Commercial partner, Thor Technologies, Australia, wanted the team to modify their servo-driven AC regulator (PS-10), based on our technique with efficiency in the range of 90-95% and the response time improved by about 10 times.

During development of a commercial prototype, the author implemented two potential solutions: (i) multi-transformer and (ii) multi-winding transformer based techniques to overcome the reduced efficiency during buck-mode operation, an issue inherent to the basic linear AC technique. 

Thesis was aimed at improving the power stage of the linear technique while maintaining the already developed analog control loop with true RMS regulation capability. thesis presents two alternative transformer solutions to reach efficiencies in the range of $90-95\%$ on a laboratory prototype of 500VA. Experimental results were validated by constructing a theoretical model for the two transformer configurations, supported by an equivalent circuit analysis using MATLAB and LTSpice software.

year: 2020

title: Ka hao te rangatahi: Exploring school and work pathways for rangatahi Māori / Youth  growing up within gang space in Aotearoa

authors: Maihi, Bonnie

subjects: Rangatahi

abstract: This thesis explores the experiences of rangatahi Māori growing up in gang environments in Aotearoa, focusing on their educational and employment journeys. The research aims to elevate the rangatahi narratives without reducing them to mere statistics or stereotypes, highlighting their resilience and insights in contexts often characterized by stigma and judgement. Employing principles of Kaupapa Māori, Critical Pedagogy, and a Waka navigation framework, this study challenges deficit-based perspectives that typically dominate discussions about gangs. 

On a practical level, it advocates for trust-based partnerships with gang whānau, emphasizing the importance of honesty and respect to foster collaboration. Existing Whānau -led initiatives illustrate the possibilities of merging cultural knowledge with everyday survival, showcasing resilience as a lived reality. Theoretically, the research offers an insider perspective, positioning myself as researcher to honor lived experiences and mitigate traditional negative framings of gang spaces, instead framing them as complex sites of identity and resilience. 

Ultimately, this thesis posits that rangatahi Māori in gang settings are not merely problems to be solved but are agents of hope and strength, rooted in their heritage. Their futures should be shaped by their identities rather than deficits, affirming their tino rangatiratanga and capacities for meaningful contributions within their communities.

text: Ka hao te rangatahi: Exploring school and work pathways for rangatahi Māori / Youth  growing up within gang space in Aotearoa This thesis explores the experiences of rangatahi Māori growing up in gang environments in Aotearoa, focusing on their educational and employment journeys. The research aims to elevate the rangatahi narratives without reducing them to mere statistics or stereotypes, highlighting their resilience and insights in contexts often characterized by stigma and judgement. Employing principles of Kaupapa Māori, Critical Pedagogy, and a Waka navigation framework, this study challenges deficit-based perspectives that typically dominate discussions about gangs. 

On a practical level, it advocates for trust-based partnerships with gang whānau, emphasizing the importance of honesty and respect to foster collaboration. Existing Whānau -led initiatives illustrate the possibilities of merging cultural knowledge with everyday survival, showcasing resilience as a lived reality. Theoretically, the research offers an insider perspective, positioning myself as researcher to honor lived experiences and mitigate traditional negative framings of gang spaces, instead framing them as complex sites of identity and resilience. 

Ultimately, this thesis posits that rangatahi Māori in gang settings are not merely problems to be solved but are agents of hope and strength, rooted in their heritage. Their futures should be shaped by their identities rather than deficits, affirming their tino rangatiratanga and capacities for meaningful contributions within their communities.

year: 2025