title: Generating spiky solutions of Einstein field equations with the Stephani transformation

authors: Moughal, Muhammad Zubair Ali

subjects: Stephani transformation

abstract: The Geroch/Stephani transformation is a solution-generating transformation, and may generate spiky solutions. The spikes in solutions generated so far are either early-time permanent spikes or transient spikes. We want to generate a solution with a late-time permanent spike. We achieve this by applying the Stephani transformation with the rotational Killing vector field of the locally rotationally symmetric Jacobs solution. The late-time permanent spike occurs along the cylindrical axis. The generated solution also features a rich variety of transient structures. We introduce a new technique to analyse these structures. Our findings lead us to discover a transient behaviour, which we call the overshoot transition.

text: Generating spiky solutions of Einstein field equations with the Stephani transformation The Geroch/Stephani transformation is a solution-generating transformation, and may generate spiky solutions. The spikes in solutions generated so far are either early-time permanent spikes or transient spikes. We want to generate a solution with a late-time permanent spike. We achieve this by applying the Stephani transformation with the rotational Killing vector field of the locally rotationally symmetric Jacobs solution. The late-time permanent spike occurs along the cylindrical axis. The generated solution also features a rich variety of transient structures. We introduce a new technique to analyse these structures. Our findings lead us to discover a transient behaviour, which we call the overshoot transition.

year: 2021

title: Probability calibration trees

authors: Leathart, Tim

subjects: computer science

abstract: Obtaining accurate and well calibrated probability estimates from classifiers is useful in many applications, for example, when minimising the expected cost of classifications. Existing methods of calibrating probability estimates are applied globally, ignoring the potential for improvements by applying a more fine-grained model. We propose probability calibration trees, a modification of logistic model trees that identifies regions of the input space in which different probability calibration models are learned to improve performance. We compare probability calibration trees to two widely used calibration methods—isotonic regression and Platt scaling—and show that our method results in lower root mean squared error on average than both methods, for estimates produced by a variety of base learners.

text: Probability calibration trees Obtaining accurate and well calibrated probability estimates from classifiers is useful in many applications, for example, when minimising the expected cost of classifications. Existing methods of calibrating probability estimates are applied globally, ignoring the potential for improvements by applying a more fine-grained model. We propose probability calibration trees, a modification of logistic model trees that identifies regions of the input space in which different probability calibration models are learned to improve performance. We compare probability calibration trees to two widely used calibration methods—isotonic regression and Platt scaling—and show that our method results in lower root mean squared error on average than both methods, for estimates produced by a variety of base learners.

year: 2017

title: No explanation required: Entrenchment and perception of Māori loanwords in a diachronic newspaper corpus of New Zealand English

authors: Levendis, Katharine Joy

subjects: New Zealand English

abstract: Māori loanwords are uncontestably the most notable feature of New Zealand English (Gordon, 2005; Macalister, 2006b). Although frequencies of Māori loanwords are reported to be increasing in recent years (Macalister, 2006b), and analyses strongly indicate a skew in loanwords across certain topics (Davies & Maclagan, 2006; de Bres, 2006), no studies have yet addressed whether Māori loanword behaviour differs in a corpus restricted to a single topic (with the exception of Calude, Miller, Harper, & Whaanga, Forthcoming). Nor has a thorough diachronic analysis been made on the subject since Davies and Maclagan (2006) and Macalister (2006b). This thesis is concerned with frequency of use and perception of Māori loanwords in a diachronic corpus restricted to a singular theme: te Wiki o te Reo Māori, Māori Language Week. Using a quantitative methodology in a corpus constructed from New Zealand regional and national newspaper articles spanning 2008-2017, average Māori loanword frequencies are found to be almost 5 times that of the most recent comparable diachronic study (Macalister, 2006b), and demonstrate a statistically significant diachronic increase in use. In contrast, the markedness (or translation) of Māori loanwords shows a statistically significant decreasing diachronic trend over the 10-year period. However, practice of marking appears to be affected by user perceptions and intention to educate, and therefore cannot be relied upon as a gauge of loanword entrenchment. Other conventional measures of loanword entrenchment such as frequency, listedness and morphological assimilation are also shown to be unreliable when considered independently from one another, and in cases such as that of New Zealand English where a change from above influenced by social and cultural factors (Māori loanwords functioning as an expression of political attitude and stance) appears to be interfering in loanword use. Measurement of Māori loanword entrenchment cannot be made using the same criteria as loanwords from non-threatened languages, and suggestions are made for the revised criteria for studying loanword entrenchment which takes into account the sociolinguistic context in which the loanwords are used.

text: No explanation required: Entrenchment and perception of Māori loanwords in a diachronic newspaper corpus of New Zealand English Māori loanwords are uncontestably the most notable feature of New Zealand English (Gordon, 2005; Macalister, 2006b). Although frequencies of Māori loanwords are reported to be increasing in recent years (Macalister, 2006b), and analyses strongly indicate a skew in loanwords across certain topics (Davies & Maclagan, 2006; de Bres, 2006), no studies have yet addressed whether Māori loanword behaviour differs in a corpus restricted to a single topic (with the exception of Calude, Miller, Harper, & Whaanga, Forthcoming). Nor has a thorough diachronic analysis been made on the subject since Davies and Maclagan (2006) and Macalister (2006b). This thesis is concerned with frequency of use and perception of Māori loanwords in a diachronic corpus restricted to a singular theme: te Wiki o te Reo Māori, Māori Language Week. Using a quantitative methodology in a corpus constructed from New Zealand regional and national newspaper articles spanning 2008-2017, average Māori loanword frequencies are found to be almost 5 times that of the most recent comparable diachronic study (Macalister, 2006b), and demonstrate a statistically significant diachronic increase in use. In contrast, the markedness (or translation) of Māori loanwords shows a statistically significant decreasing diachronic trend over the 10-year period. However, practice of marking appears to be affected by user perceptions and intention to educate, and therefore cannot be relied upon as a gauge of loanword entrenchment. Other conventional measures of loanword entrenchment such as frequency, listedness and morphological assimilation are also shown to be unreliable when considered independently from one another, and in cases such as that of New Zealand English where a change from above influenced by social and cultural factors (Māori loanwords functioning as an expression of political attitude and stance) appears to be interfering in loanword use. Measurement of Māori loanword entrenchment cannot be made using the same criteria as loanwords from non-threatened languages, and suggestions are made for the revised criteria for studying loanword entrenchment which takes into account the sociolinguistic context in which the loanwords are used.

year: 2018