title: Statistical properties of solar wind discontinuities, intermittent turbulence, and rapid emergence of non-Gaussian distributions

authors: Greco, A.

subjects: turbulence

abstract: Recent studies have compared properties of the magnetic field in simulations of Hall MHD turbulence with spacecraft data, focusing on methods used to identify classical discontinuities and intermittency statistics. Comparison of ACE solar wind data and simulations of 2D and 3D turbulence shows good agreement in waiting‐time analysis of magnetic discontinuities, and in the related distribution of magnetic field increments. This supports the idea that the magnetic structures in the solar wind may emerge fast and locally from nonlinear dynamics that can be understood in the framework of nonlinear MHD theory. The analysis suggests that small scale current sheets form spontaneously and rapidly enough that some of the observed solar wind discontinuities may be locally generated, representing boundaries between interacting flux tubes.

text: Statistical properties of solar wind discontinuities, intermittent turbulence, and rapid emergence of non-Gaussian distributions Recent studies have compared properties of the magnetic field in simulations of Hall MHD turbulence with spacecraft data, focusing on methods used to identify classical discontinuities and intermittency statistics. Comparison of ACE solar wind data and simulations of 2D and 3D turbulence shows good agreement in waiting‐time analysis of magnetic discontinuities, and in the related distribution of magnetic field increments. This supports the idea that the magnetic structures in the solar wind may emerge fast and locally from nonlinear dynamics that can be understood in the framework of nonlinear MHD theory. The analysis suggests that small scale current sheets form spontaneously and rapidly enough that some of the observed solar wind discontinuities may be locally generated, representing boundaries between interacting flux tubes.

year: 2010

title: Interfacial microstructure and shear strength of Ti-6Al-4V/TiAl laminate composite sheet fabricated by hot packed rolling

authors: Kong, Fantao

subjects: Intermetallics

abstract: A two layer Ti-6Al-4V(wt%)/Ti-43Al-9V-Y(at%) laminate composite sheet with a uniform interfacial microstructure and no discernible defects at the interfaces has been prepared by hot-pack rolling, and its interfacial microstructure and shear strength were characterized. Characterization of the interfacial microstructure shows that there was an interfacial region of uniform thickness of about 250 μm which consisted of two layers: Layer I on the TiAl side which was 80 μm thick and Layer II on the Ti-6Al-4V side which was 170 μm thick. The microstructure of Layer I consisted of massive γ phases, needlelike γ phases and B2 phase matrix, while the microstructure of Layer II consisted of α₂ phase. The microstructure of the interfacial region is the result of the interdiffusion of Ti element from Ti-6Al-4V alloy layer into the TiAl alloy layer and Al element from the TiAl alloy layer into the Ti-6Al-4V alloy layer. The shear strength measurement demonstrated that the bonding strength between the TiAl alloy and Ti-6Al-4V alloy layers in the laminate composite sheet was very high. This means that the quality of the interfacial bonding between the two layers achieved by the multi-path rolling is high, and the interface between the layers is very effective in transferring loading, causing significantly improved toughness and plasticity of the TiAl/Ti-6Al-4V laminate composite sheet.

text: Interfacial microstructure and shear strength of Ti-6Al-4V/TiAl laminate composite sheet fabricated by hot packed rolling A two layer Ti-6Al-4V(wt%)/Ti-43Al-9V-Y(at%) laminate composite sheet with a uniform interfacial microstructure and no discernible defects at the interfaces has been prepared by hot-pack rolling, and its interfacial microstructure and shear strength were characterized. Characterization of the interfacial microstructure shows that there was an interfacial region of uniform thickness of about 250 μm which consisted of two layers: Layer I on the TiAl side which was 80 μm thick and Layer II on the Ti-6Al-4V side which was 170 μm thick. The microstructure of Layer I consisted of massive γ phases, needlelike γ phases and B2 phase matrix, while the microstructure of Layer II consisted of α₂ phase. The microstructure of the interfacial region is the result of the interdiffusion of Ti element from Ti-6Al-4V alloy layer into the TiAl alloy layer and Al element from the TiAl alloy layer into the Ti-6Al-4V alloy layer. The shear strength measurement demonstrated that the bonding strength between the TiAl alloy and Ti-6Al-4V alloy layers in the laminate composite sheet was very high. This means that the quality of the interfacial bonding between the two layers achieved by the multi-path rolling is high, and the interface between the layers is very effective in transferring loading, causing significantly improved toughness and plasticity of the TiAl/Ti-6Al-4V laminate composite sheet.

year: 2011

title: New Zealand’s Performance Based Research Funding (PBRF) model undermines Maori research

authors: Roa, Tom

subjects: Performance Based Research Funding

abstract: The Performance Based Research Funding (PBRF) model was instigated in 2002 to increase “the quality of research through peer assessment and performance indicators” in New Zealand (Ministry of Education 2002: 17). It is used to allocate funding between universities, departments and researchers according to the putative quality and quantity of their research outputs over the preceding 6 years. PBRF is expected to incentivise improved research excellence and efficiency, and allow government to invest research funds where greatest returns will result. This is potentially a huge gain for Māori. However, “by changing the conditions of knowledge production, research assessment exercises may also alter the shape and direction of disciplines by diverting and channelling researchers’ intellectual attention and political engagement, influencing what they study, how they do it, and how they report and write” (Middleton 2009: 194). Indeed, universities repeatedly encourage researchers to focus on activities that will improve their PBRF rankings. We believe that an unintended consequence of PBRF is the creation of significant barriers to increasing the volume, scope and quality of environmental research for Māori.

text: New Zealand’s Performance Based Research Funding (PBRF) model undermines Maori research The Performance Based Research Funding (PBRF) model was instigated in 2002 to increase “the quality of research through peer assessment and performance indicators” in New Zealand (Ministry of Education 2002: 17). It is used to allocate funding between universities, departments and researchers according to the putative quality and quantity of their research outputs over the preceding 6 years. PBRF is expected to incentivise improved research excellence and efficiency, and allow government to invest research funds where greatest returns will result. This is potentially a huge gain for Māori. However, “by changing the conditions of knowledge production, research assessment exercises may also alter the shape and direction of disciplines by diverting and channelling researchers’ intellectual attention and political engagement, influencing what they study, how they do it, and how they report and write” (Middleton 2009: 194). Indeed, universities repeatedly encourage researchers to focus on activities that will improve their PBRF rankings. We believe that an unintended consequence of PBRF is the creation of significant barriers to increasing the volume, scope and quality of environmental research for Māori.

year: 2009