title: Semi-random model tree ensembles: An effective and scalable regression method

authors: Pfahringer, Bernhard

subjects: computer science

abstract: We present and investigate ensembles of semi-random model trees as a novel regression method. Such ensembles combine the scalability of tree-based methods with predictive performance rivalling the state of the art in numeric prediction. An empirical investigation shows that Semi-Random Model Trees produce predictive performance which is competitive with state-of-the-art methods like Gaussian Processes Regression or Additive Groves of Regression Trees. The training and optimization of Random Model Trees scales better than Gaussian Processes Regression to larger datasets, and enjoys a constant advantage over Additive Groves of the order of one to two orders of magnitude.

text: Semi-random model tree ensembles: An effective and scalable regression method We present and investigate ensembles of semi-random model trees as a novel regression method. Such ensembles combine the scalability of tree-based methods with predictive performance rivalling the state of the art in numeric prediction. An empirical investigation shows that Semi-Random Model Trees produce predictive performance which is competitive with state-of-the-art methods like Gaussian Processes Regression or Additive Groves of Regression Trees. The training and optimization of Random Model Trees scales better than Gaussian Processes Regression to larger datasets, and enjoys a constant advantage over Additive Groves of the order of one to two orders of magnitude.

year: 2011

title: Mobility and emplacement of an ancient, large-volume pyroclastic flow, Ongatiti Ignimbrite, North Island, New Zealand

authors: Zadeh, Elham Yousef

abstract: Pyroclastic flows are the most devastating phenomena of explosive volcanic eruptions. These hazardous fast-moving, hot, concentrated density currents are able to travel several tens of kilometers radially away from their source. Due to an enveloping ash cloud, it is still impossible to directly study pyroclastic flows. However, their deposits (i.e., ignimbrites) provide useful insight into their internal processes of emplacement. This study focuses on the Ongatiti Ignimbrite, which is sourced from Mangakino caldera (i.e., the oldest volcanic centre in the Taupo Volcanic Zone, North Island, New Zealand dated at 1600–950 ka) and offers a unique opportunity to understand the emplacement processes of an ancient and large-volume pyroclastic flow. It is a welded to nonwelded, columnar-jointed, cliff-forming deposit, that has been divided into nine facies based on the variation in pumice and lithic clast abundance, and degree of welding. Our results constrain the minimum deposit volume for the Ongatiti Ignimbrite to ca. 1400 km3, or 1000 km3 dense-rock equivalent. Zircon (U–Th)/He data suggest an eruption age of 1.37 ± 0.04 Ma, which is in good agreement with the previous proposed eruption age. The topographic controls on the spatial distribution of the ignimbrite have been determined to understand pyroclastic flow pathways through valleys and over hills. The ignimbrite covered hills up to ~900 m (about 650 m above the caldera height) to around 40 km from the Mangakino volcanic center (MVC) and, the pyroclastic flow travelled to beyond 90 km from the vent. The Ongatiti Ignimbrite was a landscape-modifying event that covered at least the western North Island and as far away as Auckland and Wellington.

text: Mobility and emplacement of an ancient, large-volume pyroclastic flow, Ongatiti Ignimbrite, North Island, New Zealand Pyroclastic flows are the most devastating phenomena of explosive volcanic eruptions. These hazardous fast-moving, hot, concentrated density currents are able to travel several tens of kilometers radially away from their source. Due to an enveloping ash cloud, it is still impossible to directly study pyroclastic flows. However, their deposits (i.e., ignimbrites) provide useful insight into their internal processes of emplacement. This study focuses on the Ongatiti Ignimbrite, which is sourced from Mangakino caldera (i.e., the oldest volcanic centre in the Taupo Volcanic Zone, North Island, New Zealand dated at 1600–950 ka) and offers a unique opportunity to understand the emplacement processes of an ancient and large-volume pyroclastic flow. It is a welded to nonwelded, columnar-jointed, cliff-forming deposit, that has been divided into nine facies based on the variation in pumice and lithic clast abundance, and degree of welding. Our results constrain the minimum deposit volume for the Ongatiti Ignimbrite to ca. 1400 km3, or 1000 km3 dense-rock equivalent. Zircon (U–Th)/He data suggest an eruption age of 1.37 ± 0.04 Ma, which is in good agreement with the previous proposed eruption age. The topographic controls on the spatial distribution of the ignimbrite have been determined to understand pyroclastic flow pathways through valleys and over hills. The ignimbrite covered hills up to ~900 m (about 650 m above the caldera height) to around 40 km from the Mangakino volcanic center (MVC) and, the pyroclastic flow travelled to beyond 90 km from the vent. The Ongatiti Ignimbrite was a landscape-modifying event that covered at least the western North Island and as far away as Auckland and Wellington.

year: 2023-07-28

title: Tribal guns, tribal gunners : A study of acculturation by Maori of European military technology during the New Zealand inter-tribal musket wars

authors: Bentley, Trevor William

abstract: The Musket Wars were New Zealand’s longest and most costly war. Some 20,000 Maori perished in the raids, battles and sieges that convulsed the tribal societies during the 1820’s and 1830’s. The rise of powerful musket armies set in train forty major hekes or tribal migrations that emptied vast reaches of country by 1840, paving the way for European settlement that proceeded largely unopposed until the 1860’s.

There is little known about the nature of Maori warfare in this period for the Musket Wars have yet to receive the same kind of intense study currently being given by New Zealand historians to the Northern and New Zealand Wars. While other nations have conducted exhaustive research into the military history of their indigenous people, the Musket Wars remain New Zealand’s least known war.

The paucity of information on inter-tribal; warfare in this period is sourced in the fact that native warfare was actively discouraged by the missionaries, judged barbaric by most early visitors and regarded as an inferior form of warfare by settlers and English military men. Later nineteenth century writers perpetuated a distorted view of the Musket Wars as chaotic inter-tribal conflicts in which Maori fought and destroyed Maori. This distorted view has its origins in the two widely divergent systems of values that operated in nineteenth century New Zealand and in the dominance of Victorian ideas about race and colonialism.

This thesis is revisionist only in its attempt to demolish the entrenched colonial view of Maori musket warfare as disordered and exclusively Maori. It endeavours to fill specific gaps that exist in the research on this period by examining the role and purpose of the European gun trading enterprise in New Zealand and the extent of European involvement in Maori warfare. The thesis explores the deployment and effectiveness of European guns during the three phases of Maori warfare that characterise the period; predatory raiding, the great rakau-musket battles and the musket to musket conflicts of the 1830’s. The thesis also develops the theme that while the Musket Wars were shaped by non-Maori influences they were distinctly Maori in style.
While the bulk of evidence is provided by contemporary European observers and nineteenth century historians, every attempt has been made to provide a more balanced picture of Maori warfare by reporting Maori experiences wherever possible. The thesis consequently draws on current Maori oral testimony, the evidence of contemporary Maori eyewitness and the substantial and well developed body of written tribal history currently available.

The Musket Wars represent a fascinating but largely forgotten military age in New Zealand where Maori armies of unprecedented size employed powerful armaments of flintlock guns and ships cannon on long distance campaigns against remote enemies. This period has provided a unique opportunity to research the ways an indigenous warrior society acculturated European firearms technology in established tribal rituals and in warfare, independent of European military influences and in a purely Maori context. Most importantly the Musket Wars have provided the opportunity to examine Maori tactical developments through the critical stage between classical Maori warfare and the clashes with British and Colonial forces during the Northern war of 1845 and New Zealand wars of the 1860’s.

text: Tribal guns, tribal gunners : A study of acculturation by Maori of European military technology during the New Zealand inter-tribal musket wars The Musket Wars were New Zealand’s longest and most costly war. Some 20,000 Maori perished in the raids, battles and sieges that convulsed the tribal societies during the 1820’s and 1830’s. The rise of powerful musket armies set in train forty major hekes or tribal migrations that emptied vast reaches of country by 1840, paving the way for European settlement that proceeded largely unopposed until the 1860’s.

There is little known about the nature of Maori warfare in this period for the Musket Wars have yet to receive the same kind of intense study currently being given by New Zealand historians to the Northern and New Zealand Wars. While other nations have conducted exhaustive research into the military history of their indigenous people, the Musket Wars remain New Zealand’s least known war.

The paucity of information on inter-tribal; warfare in this period is sourced in the fact that native warfare was actively discouraged by the missionaries, judged barbaric by most early visitors and regarded as an inferior form of warfare by settlers and English military men. Later nineteenth century writers perpetuated a distorted view of the Musket Wars as chaotic inter-tribal conflicts in which Maori fought and destroyed Maori. This distorted view has its origins in the two widely divergent systems of values that operated in nineteenth century New Zealand and in the dominance of Victorian ideas about race and colonialism.

This thesis is revisionist only in its attempt to demolish the entrenched colonial view of Maori musket warfare as disordered and exclusively Maori. It endeavours to fill specific gaps that exist in the research on this period by examining the role and purpose of the European gun trading enterprise in New Zealand and the extent of European involvement in Maori warfare. The thesis explores the deployment and effectiveness of European guns during the three phases of Maori warfare that characterise the period; predatory raiding, the great rakau-musket battles and the musket to musket conflicts of the 1830’s. The thesis also develops the theme that while the Musket Wars were shaped by non-Maori influences they were distinctly Maori in style.
While the bulk of evidence is provided by contemporary European observers and nineteenth century historians, every attempt has been made to provide a more balanced picture of Maori warfare by reporting Maori experiences wherever possible. The thesis consequently draws on current Maori oral testimony, the evidence of contemporary Maori eyewitness and the substantial and well developed body of written tribal history currently available.

The Musket Wars represent a fascinating but largely forgotten military age in New Zealand where Maori armies of unprecedented size employed powerful armaments of flintlock guns and ships cannon on long distance campaigns against remote enemies. This period has provided a unique opportunity to research the ways an indigenous warrior society acculturated European firearms technology in established tribal rituals and in warfare, independent of European military influences and in a purely Maori context. Most importantly the Musket Wars have provided the opportunity to examine Maori tactical developments through the critical stage between classical Maori warfare and the clashes with British and Colonial forces during the Northern war of 1845 and New Zealand wars of the 1860’s.

year: 1997