title: Hybrid polyethylene composites with recycled carbon fibres and hemp fibres produced by rotational moulding

authors: Oliveira, Maria A.S.

subjects: hybrid composites

abstract: This study assessed polyethene composites produced by rotational moulding with hybrid reinforcement using recycled carbon fibre (RCF) and hemp fibre (HF). First, the RCF was treated with nitric acid to introduce hydroxyl groups on the fibres’ surface and was characterised by infrared spectroscopy and microscopy analyses. Although the fibre surface treatment improved the tensile properties of the composites, the use of grafted maleic anhydride polyethylene (MAPE) as a coupling agent was more effective in improving the interfacial bonding between the fibres and the matrix. Alkali-treated hemp fibres were then used in combination with RCF to produce rotationally moulded composites with an overall fibre content of 10 wt.% but with different ratios of HF/RCF, namely, (20/80) and (50/50). The results showed that the addition of RCF increased the composite’s Young’s modulus compared to neat PE, regardless of the fibre treatment. Similarly, the hybrid composites showed superior Young’s moduli than the HF–PE composites through the increase in the RCF content. It was also observed that adding RCF reduced the void size within the final composites compared to the HF–PE composites, which contributed to the greater performance of the hybrid composites compared to their natural counterparts.

text: Hybrid polyethylene composites with recycled carbon fibres and hemp fibres produced by rotational moulding This study assessed polyethene composites produced by rotational moulding with hybrid reinforcement using recycled carbon fibre (RCF) and hemp fibre (HF). First, the RCF was treated with nitric acid to introduce hydroxyl groups on the fibres’ surface and was characterised by infrared spectroscopy and microscopy analyses. Although the fibre surface treatment improved the tensile properties of the composites, the use of grafted maleic anhydride polyethylene (MAPE) as a coupling agent was more effective in improving the interfacial bonding between the fibres and the matrix. Alkali-treated hemp fibres were then used in combination with RCF to produce rotationally moulded composites with an overall fibre content of 10 wt.% but with different ratios of HF/RCF, namely, (20/80) and (50/50). The results showed that the addition of RCF increased the composite’s Young’s modulus compared to neat PE, regardless of the fibre treatment. Similarly, the hybrid composites showed superior Young’s moduli than the HF–PE composites through the increase in the RCF content. It was also observed that adding RCF reduced the void size within the final composites compared to the HF–PE composites, which contributed to the greater performance of the hybrid composites compared to their natural counterparts.

year: 2022

title: Reduced MHD in Astrophysical Applications: Two-dimensional or Three-dimensional?

authors: Oughton, Sean

subjects: Science & Technology

abstract: Originally proposed as an efficient approach to computation of nonlinear dynamics in tokamak fusion research devices, reduced magnetohydrodynamics (RMHD) has subsequently found application in studies of coronal heating, flux tube dynamics, charged particle transport, and, in general, as an approximation to describe plasma turbulence in space physics and astrophysics. Given the diverse set of derivations available in the literature, there has emerged some level of discussion and a lack of consensus regarding the completeness of RMHD as a turbulence model, and its applicability in contexts such as the solar wind. Some of the key issues in this discussion are examined here, emphasizing that RMHD is properly neither 2D nor fully 3D, being rather an incomplete representation that enforces at least one family of extraneous conservation laws.

text: Reduced MHD in Astrophysical Applications: Two-dimensional or Three-dimensional? Originally proposed as an efficient approach to computation of nonlinear dynamics in tokamak fusion research devices, reduced magnetohydrodynamics (RMHD) has subsequently found application in studies of coronal heating, flux tube dynamics, charged particle transport, and, in general, as an approximation to describe plasma turbulence in space physics and astrophysics. Given the diverse set of derivations available in the literature, there has emerged some level of discussion and a lack of consensus regarding the completeness of RMHD as a turbulence model, and its applicability in contexts such as the solar wind. Some of the key issues in this discussion are examined here, emphasizing that RMHD is properly neither 2D nor fully 3D, being rather an incomplete representation that enforces at least one family of extraneous conservation laws.

year: 2017-04-10

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