title: Lagrangian relaxation schemes for calculating force-free magnetic fields, and their limitations

authors: Pontin, D.I.

subjects: magnetic fields

abstract: Force-free magnetic fields are important in many astrophysical settings. Determining the properties of such force-free fields—especially smoothness and stability properties—is crucial to understanding many key phenomena in astrophysical plasmas, for example, energy release processes that heat the plasma and lead to dynamic or explosive events. In the present work we discuss a serious limitation on the computation of force-free fields, within the context of a Lagrangian relaxation scheme that conserves magnetic flux and ∇ • B identically. This issue has the potential to invalidate the results produced by numerical force-free field solvers even for cases in which they appear to converge (at fixed grid resolution) to an equilibrium magnetic field. Error estimates are introduced to assess the quality of the calculated equilibrium. We go on to present an algorithm, based on rewriting the curl operation via Stokes' theorem, for calculating the current which holds great promise for improving dramatically the accuracy of the Lagrangian relaxation procedure.

text: Lagrangian relaxation schemes for calculating force-free magnetic fields, and their limitations Force-free magnetic fields are important in many astrophysical settings. Determining the properties of such force-free fields—especially smoothness and stability properties—is crucial to understanding many key phenomena in astrophysical plasmas, for example, energy release processes that heat the plasma and lead to dynamic or explosive events. In the present work we discuss a serious limitation on the computation of force-free fields, within the context of a Lagrangian relaxation scheme that conserves magnetic flux and ∇ • B identically. This issue has the potential to invalidate the results produced by numerical force-free field solvers even for cases in which they appear to converge (at fixed grid resolution) to an equilibrium magnetic field. Error estimates are introduced to assess the quality of the calculated equilibrium. We go on to present an algorithm, based on rewriting the curl operation via Stokes' theorem, for calculating the current which holds great promise for improving dramatically the accuracy of the Lagrangian relaxation procedure.

year: 2009

title: Weka: A machine learning workbench for data mining

authors: Frank, Eibe

subjects: computer science

abstract: The Weka workbench is an organized collection of state-of-the-art machine learning algorithms and data preprocessing tools. The basic way of interacting with these methods is by invoking them from the command line. However, convenient interactive graphical user interfaces are provided for data exploration, for setting up large-scale experiments on distributed computing platforms, and for designing configurations for streamed data processing. These interfaces constitute an advanced environment for experimental data mining. The system is written in Java and distributed under the terms of the GNU General Public License.

text: Weka: A machine learning workbench for data mining The Weka workbench is an organized collection of state-of-the-art machine learning algorithms and data preprocessing tools. The basic way of interacting with these methods is by invoking them from the command line. However, convenient interactive graphical user interfaces are provided for data exploration, for setting up large-scale experiments on distributed computing platforms, and for designing configurations for streamed data processing. These interfaces constitute an advanced environment for experimental data mining. The system is written in Java and distributed under the terms of the GNU General Public License.

year: 2005

title: Taku Ara, Taku Mahara: Pākehā Family Experiences of Kaupapa Māori and Bilingual Education

authors: Barnes, Alexander Louis

subjects: Kaupapa Maori

abstract: Kaupapa Māori (indigenous Māori-centred philosophies) initiatives have transformed various social, cultural and public projects in the domains of governance and constitutional issues, health, education, the environment, community development and research in Aotearoa – New Zealand. As a Pākehā graduate of te kōhanga reo and kura kaupapa Māori (Māori language immersion pre-school and primary school), this research is concerned with exploring the impact of kaupapa Māori and bilingual educational initiatives on my life and the lives of two other Pākehā families who share similar educational backgrounds. This foundational study utilises qualitative narrative inquiry methods as a means of understanding and analysing the implications for Pākehā as a result of their participation in kaupapa Māori and bilingual education. An intergenerational family approach is used in this research whereby the individual voices and experiences of young adults are heard equally alongside their parents’. Collectively understood, the themes represented in this research offer a unique means of understanding why Päkehä families decided to be involved in Māori immersion settings, and what these experiences mean to them now. One of the principle aims of this study is that it be used as a platform for dialogue amongst Pākehā, non-Māori and Māori about the future direction of bicultural education in Aotearoa – New Zealand.

text: Taku Ara, Taku Mahara: Pākehā Family Experiences of Kaupapa Māori and Bilingual Education Kaupapa Māori (indigenous Māori-centred philosophies) initiatives have transformed various social, cultural and public projects in the domains of governance and constitutional issues, health, education, the environment, community development and research in Aotearoa – New Zealand. As a Pākehā graduate of te kōhanga reo and kura kaupapa Māori (Māori language immersion pre-school and primary school), this research is concerned with exploring the impact of kaupapa Māori and bilingual educational initiatives on my life and the lives of two other Pākehā families who share similar educational backgrounds. This foundational study utilises qualitative narrative inquiry methods as a means of understanding and analysing the implications for Pākehā as a result of their participation in kaupapa Māori and bilingual education. An intergenerational family approach is used in this research whereby the individual voices and experiences of young adults are heard equally alongside their parents’. Collectively understood, the themes represented in this research offer a unique means of understanding why Päkehä families decided to be involved in Māori immersion settings, and what these experiences mean to them now. One of the principle aims of this study is that it be used as a platform for dialogue amongst Pākehā, non-Māori and Māori about the future direction of bicultural education in Aotearoa – New Zealand.

year: 2006