title: Characterisation and modelling of loudspeaker cone resonance

authors: Taberner, Andrew James

abstract: Loudspeaker cone resonance (“cone break-up”) is a fundamental cause of ripple in the electrical impedance and sound pressure responses of electrodynamic loudspeakers. In this thesis, the dependence of the characteristics of loudspeaker cone resonances on the material properties and thickness profile of the cone is extensively determined by creating 2D and 3D finite element models of a 6½-inch polypropylene-cone loudspeaker. Techniques for adjusting the resonant characteristics of loudspeaker cones by varying the material properties and thickness profile of the cone are explored and summarised.

The effect of cutting narrow slots through the surface of a loudspeaker cone is determined using 3D finite element modelling techniques, and cone slots are shown to have a large influence on the characteristics of the loudspeaker cone. A slotted loudspeaker cone with desirable impedance and sound pressure response characteristics is modelled and constructed. The measured response of the slotted loudspeaker is demonstrated to be a significant improvement over the characteristics of an unslotted loudspeaker.

text: Characterisation and modelling of loudspeaker cone resonance Loudspeaker cone resonance (“cone break-up”) is a fundamental cause of ripple in the electrical impedance and sound pressure responses of electrodynamic loudspeakers. In this thesis, the dependence of the characteristics of loudspeaker cone resonances on the material properties and thickness profile of the cone is extensively determined by creating 2D and 3D finite element models of a 6½-inch polypropylene-cone loudspeaker. Techniques for adjusting the resonant characteristics of loudspeaker cones by varying the material properties and thickness profile of the cone are explored and summarised.

The effect of cutting narrow slots through the surface of a loudspeaker cone is determined using 3D finite element modelling techniques, and cone slots are shown to have a large influence on the characteristics of the loudspeaker cone. A slotted loudspeaker cone with desirable impedance and sound pressure response characteristics is modelled and constructed. The measured response of the slotted loudspeaker is demonstrated to be a significant improvement over the characteristics of an unslotted loudspeaker.

year: 1998

title: Grid edge system simulation and evaluation tool (GESSO): Development of a tool for the modelling and design of distributed cooperating microgrids

authors: Kelly, Nathan Bryan

abstract: As advancements are made in the availability of small renewable generation power storage technologies, nations are starting to see a trend towards more distributed power and generation. As times change, changes must also be made to the ways in which we consume and distribute power. Distributed microgrids represent the ability for communities to cooperate in the distribution of power within neighborhoods.

This thesis explores the structure of neighborhood scale distributed microgrids, defining the features and components needed to provide for accurate simulation. Techniques are developed for the integration of non-homogeneous microgrid systems to allow for smart grid-edge trading between units and microgrids. Exploration is conducted on the features required for an interactive system allowing the design and modelling of individual microgrid components and of neighborhood-scale microgrids, including the design of per-unit smart control schemes, and a proof of concept implementation is created allowing for simulation of non-homogeneous neighborhood scale fractal microgrids with arbitrary complexity. Sample cases are presented in order to demonstrate the effectiveness of the tool. The presented sample cases serve to demonstrate the effectiveness of small non-homogeneous microgrids, including those involving third party storage leasing services, and analysis is performed on the expected economic impacts of these types of systems.

text: Grid edge system simulation and evaluation tool (GESSO): Development of a tool for the modelling and design of distributed cooperating microgrids As advancements are made in the availability of small renewable generation power storage technologies, nations are starting to see a trend towards more distributed power and generation. As times change, changes must also be made to the ways in which we consume and distribute power. Distributed microgrids represent the ability for communities to cooperate in the distribution of power within neighborhoods.

This thesis explores the structure of neighborhood scale distributed microgrids, defining the features and components needed to provide for accurate simulation. Techniques are developed for the integration of non-homogeneous microgrid systems to allow for smart grid-edge trading between units and microgrids. Exploration is conducted on the features required for an interactive system allowing the design and modelling of individual microgrid components and of neighborhood-scale microgrids, including the design of per-unit smart control schemes, and a proof of concept implementation is created allowing for simulation of non-homogeneous neighborhood scale fractal microgrids with arbitrary complexity. Sample cases are presented in order to demonstrate the effectiveness of the tool. The presented sample cases serve to demonstrate the effectiveness of small non-homogeneous microgrids, including those involving third party storage leasing services, and analysis is performed on the expected economic impacts of these types of systems.

year: 2020

title: Colouring in the White Spaces: Reclaiming Cultural Identity in Whitestream Schools

authors: Milne, Beverley Ann

subjects: Maori education

abstract: If we look at a child’s colouring book, before it has any colour added to it, we think of the page as blank.  It’s actually not blank, it’s white.  That white background is just “there” and we don’t think much about it.  Not only is the background uniformly white, the lines are already in place and they dictate where the colour is allowed to go.  When children are young, they don’t care where they put the colours, but as they get older they colour in more and more cautiously. They learn about the place of colour and the importance of staying within the pre-determined boundaries and expectations. 

This thesis argues that this is the setting for our mainstream, or what I have called, whitestream New Zealand schools — that white background is the norm.   When we talk about multiculturalism and diversity what we are really referring to is the colour of the children, or their difference from that white norm, and how they don’t fit perfectly inside our lines.  If the colour of the space doesn’t change schools are still in the business of assimilation, relegating non-white children to the margins, no matter how many school reform initiatives, new curricula, strategic plans, or mandated standards we implement.  What the schools in this study have tried to do is change the colour of the space – so that the space fits the children and they don’t have to constantly adjust to fit in.  

New Zealand’s education system has been largely silent on the topic of whiteness and the Eurocentric nature of our schooling policy and practice. However, when I talk to senior Māori and Pasifika ‘warrior-scholars” in Te Whānau o Tupuranga and Clover Park Middle School about “white spaces” they have encountered in their schooling experience they can identify them all too easily.  “White spaces,” they explain, are anything you accept as “normal” for Māori – when it’s really not,  any situation that prevents, or works against you “being Māori” or who you are, and that requires you to “be” someone else and leave your beliefs behind. White spaces are spaces that allow you to require less of yourself and that reinforce stereotypes and negative ideas about Māori.  Most telling of all was the comment from a Māori student that goes straight to the root of the problem, “White spaces are everywhere,” she said, “even in your head.”

This thesis describes the 25 year journey of two schools and their community’s determination to resist and reject alienating school environments in favour of a relevant culturally-located, bilingual learning model based in a secure cultural identity, stable positive relationships, and aroha (authentic caring and love).  While the research design is a case study, in terms of western, “white space” academic tradition, it is also a story in terms of kaupapa Māori and critical race methodology. More importantly, it is a counter-story that chronicles the efforts of these two schools to step outside education’s “white spaces” to create new space.  This counter-story is juxtaposed against pervasive, deficit-driven whitestream explanations of “achievement gaps” and the “long tail” of Māori and Pasifika “under-achievement” in New Zealand schools.  In the process of this research the focus shifted from how could Māori and Pasifika learners develop secure cultural identities in mainstream schools, to examining what barriers exist in schools that prevent this from happening already?  As these issues became clear the language of the thesis shifted accordingly; “developing” a cultural identity was reframed as a reclamation of educational sovereignty — the absolute right to “be Māori” or “be Pasifika” in school — and “mainstream” schooling became better understood as the “whitestream.” 

The study hopes to contribute to the journey other schools might take to identify and name their own white spaces, and to make learning equitable for indigenous and minoritised learners.

text: Colouring in the White Spaces: Reclaiming Cultural Identity in Whitestream Schools If we look at a child’s colouring book, before it has any colour added to it, we think of the page as blank.  It’s actually not blank, it’s white.  That white background is just “there” and we don’t think much about it.  Not only is the background uniformly white, the lines are already in place and they dictate where the colour is allowed to go.  When children are young, they don’t care where they put the colours, but as they get older they colour in more and more cautiously. They learn about the place of colour and the importance of staying within the pre-determined boundaries and expectations. 

This thesis argues that this is the setting for our mainstream, or what I have called, whitestream New Zealand schools — that white background is the norm.   When we talk about multiculturalism and diversity what we are really referring to is the colour of the children, or their difference from that white norm, and how they don’t fit perfectly inside our lines.  If the colour of the space doesn’t change schools are still in the business of assimilation, relegating non-white children to the margins, no matter how many school reform initiatives, new curricula, strategic plans, or mandated standards we implement.  What the schools in this study have tried to do is change the colour of the space – so that the space fits the children and they don’t have to constantly adjust to fit in.  

New Zealand’s education system has been largely silent on the topic of whiteness and the Eurocentric nature of our schooling policy and practice. However, when I talk to senior Māori and Pasifika ‘warrior-scholars” in Te Whānau o Tupuranga and Clover Park Middle School about “white spaces” they have encountered in their schooling experience they can identify them all too easily.  “White spaces,” they explain, are anything you accept as “normal” for Māori – when it’s really not,  any situation that prevents, or works against you “being Māori” or who you are, and that requires you to “be” someone else and leave your beliefs behind. White spaces are spaces that allow you to require less of yourself and that reinforce stereotypes and negative ideas about Māori.  Most telling of all was the comment from a Māori student that goes straight to the root of the problem, “White spaces are everywhere,” she said, “even in your head.”

This thesis describes the 25 year journey of two schools and their community’s determination to resist and reject alienating school environments in favour of a relevant culturally-located, bilingual learning model based in a secure cultural identity, stable positive relationships, and aroha (authentic caring and love).  While the research design is a case study, in terms of western, “white space” academic tradition, it is also a story in terms of kaupapa Māori and critical race methodology. More importantly, it is a counter-story that chronicles the efforts of these two schools to step outside education’s “white spaces” to create new space.  This counter-story is juxtaposed against pervasive, deficit-driven whitestream explanations of “achievement gaps” and the “long tail” of Māori and Pasifika “under-achievement” in New Zealand schools.  In the process of this research the focus shifted from how could Māori and Pasifika learners develop secure cultural identities in mainstream schools, to examining what barriers exist in schools that prevent this from happening already?  As these issues became clear the language of the thesis shifted accordingly; “developing” a cultural identity was reframed as a reclamation of educational sovereignty — the absolute right to “be Māori” or “be Pasifika” in school — and “mainstream” schooling became better understood as the “whitestream.” 

The study hopes to contribute to the journey other schools might take to identify and name their own white spaces, and to make learning equitable for indigenous and minoritised learners.

year: 2013