title: A semi-supervised spam mail detector

authors: Pfahringer, Bernhard

subjects: computer science

abstract: This document describes a novel semi-supervised approach to spam classification, which was successful at the ECML/PKDD 2006 spam classification challenge. A local learning method based on lazy projections was successfully combined with a variant of a standard semi-supervised learning algorithm.

text: A semi-supervised spam mail detector This document describes a novel semi-supervised approach to spam classification, which was successful at the ECML/PKDD 2006 spam classification challenge. A local learning method based on lazy projections was successfully combined with a variant of a standard semi-supervised learning algorithm.

year: 2006

title: Microstructure, Thermal Stability and Consolidation of Nanostructured and Ultrafine Structured Cu based Metal Matrix Composite and Alloy Powders Produced by High Energy Mechanical Milling

authors: Mukhtar, Aamir

subjects: high energy mechanical milling

abstract: Ultrafine grained and/or nanostructured Cu and Cu-(2.5-10)vol.%Al2O3 composite balls/granules/powder particles were produced using two high energy mechanical milling (HEMM) routes respectively. The microstructural evolution of the as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles produced using Route 1 (12hours) and Route 2 (Route 1 + 12 hours milling under another condition) of milling was studied using scanning electron microscopy (SEM), transmission electron microcopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray (EDX) mapping. The study confirmed that HEMM can be effectively used to disperse (2.5-10)vol.%Al2O3 nanoparticles into a ultrafine grained or nanocrystalline Cu matrix after both routes of milling.

The as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles were heat treated at 150, 300, 400 and 500 C for 1 hour, respectively, to determine the thermal stability of the microstructure and corresponding microhardness change as a function of annealing temperature. It was found that for Cu and Cu-2.5vol.%Al2O3 composites after heat treatment at 150 C, the Cu grain sizes decreased due to recrystallisation, and increasing the annealing temperature to 300 C causes slight coarsening of the Cu grains. Further increasing the annealing temperature to 500 C caused significant coarsening of the Cu grains and the Al2O3 nanoparticles. With increasing the volume fraction of Al2O3 nanoparticles, (i) the thermal stability of the Cu-Al2O3 composite increases, (ii) the microstructure of the Cu matrix became finer, and (iii) the coarsening of Cu grains in the composite powder particles after annealing at 500 C become less severe.

The average microhardness of the Cu-Al2O3 composites decreased after annealing at 150 C due to decrease of dislocation density, then remained almost unchanged with increasing the annealing temperatures to 300 C and 400 C. Further increasing the annealing temperature to 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Al2O3 composites are thermally stable at temperatures up to 400 C.

Pure copper powder and Cu-Al2O3 composite powders produced using Route 2 were compacted by hot pressing at 350 C followed powder compact forging. Increasing the volume fraction of Al2O3, the average microhardness increased for the forged Cu-Al2O3 composites. A decrease in tensile fracture strength was examined for the Cu-Al2O3 composites with the increase of the volume fraction of Al2O3 as 2.5% to 10%.

Nanostructured Cu-(1-4)at.%Pb alloy powder particles were produced using Route 1 of high energy mechanical milling. The microstructural evolution and thermal stability of microstructure of powder particles as a function of annealing temperature were examined. It was found that heat treatment at 150 C caused slight coarsening of the Cu grains, and increasing the annealing temperatures to 300 and 500 C caused significant coarsening of the Cu grains. The average microhardness of the Cu-Pb alloy powder particles decreased after annealing at 150 C due to decrease of dislocation density, and then remained almost unchanged with increasing the annealing temperature to 300 C. Further increasing the annealing temperatures to 400 C and 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Pb alloy powders are thermally stable at temperatures up to 300 C.

text: Microstructure, Thermal Stability and Consolidation of Nanostructured and Ultrafine Structured Cu based Metal Matrix Composite and Alloy Powders Produced by High Energy Mechanical Milling Ultrafine grained and/or nanostructured Cu and Cu-(2.5-10)vol.%Al2O3 composite balls/granules/powder particles were produced using two high energy mechanical milling (HEMM) routes respectively. The microstructural evolution of the as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles produced using Route 1 (12hours) and Route 2 (Route 1 + 12 hours milling under another condition) of milling was studied using scanning electron microscopy (SEM), transmission electron microcopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray (EDX) mapping. The study confirmed that HEMM can be effectively used to disperse (2.5-10)vol.%Al2O3 nanoparticles into a ultrafine grained or nanocrystalline Cu matrix after both routes of milling.

The as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles were heat treated at 150, 300, 400 and 500 C for 1 hour, respectively, to determine the thermal stability of the microstructure and corresponding microhardness change as a function of annealing temperature. It was found that for Cu and Cu-2.5vol.%Al2O3 composites after heat treatment at 150 C, the Cu grain sizes decreased due to recrystallisation, and increasing the annealing temperature to 300 C causes slight coarsening of the Cu grains. Further increasing the annealing temperature to 500 C caused significant coarsening of the Cu grains and the Al2O3 nanoparticles. With increasing the volume fraction of Al2O3 nanoparticles, (i) the thermal stability of the Cu-Al2O3 composite increases, (ii) the microstructure of the Cu matrix became finer, and (iii) the coarsening of Cu grains in the composite powder particles after annealing at 500 C become less severe.

The average microhardness of the Cu-Al2O3 composites decreased after annealing at 150 C due to decrease of dislocation density, then remained almost unchanged with increasing the annealing temperatures to 300 C and 400 C. Further increasing the annealing temperature to 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Al2O3 composites are thermally stable at temperatures up to 400 C.

Pure copper powder and Cu-Al2O3 composite powders produced using Route 2 were compacted by hot pressing at 350 C followed powder compact forging. Increasing the volume fraction of Al2O3, the average microhardness increased for the forged Cu-Al2O3 composites. A decrease in tensile fracture strength was examined for the Cu-Al2O3 composites with the increase of the volume fraction of Al2O3 as 2.5% to 10%.

Nanostructured Cu-(1-4)at.%Pb alloy powder particles were produced using Route 1 of high energy mechanical milling. The microstructural evolution and thermal stability of microstructure of powder particles as a function of annealing temperature were examined. It was found that heat treatment at 150 C caused slight coarsening of the Cu grains, and increasing the annealing temperatures to 300 and 500 C caused significant coarsening of the Cu grains. The average microhardness of the Cu-Pb alloy powder particles decreased after annealing at 150 C due to decrease of dislocation density, and then remained almost unchanged with increasing the annealing temperature to 300 C. Further increasing the annealing temperatures to 400 C and 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Pb alloy powders are thermally stable at temperatures up to 300 C.

year: 2010

title: “Literacy is not a Māori thing": Debunking the deficit discourse

authors: Derby, Melissa

abstract: Literacy has been entrenched in Māori society for more than 200 years, meeting needs that range from serving a political purpose to reading purely for pleasure. Literacy is not solely a Western competency, and Māoristriving for excellence in literacy is not an act of modern-day colonisation. Instead, what the evidence shows is that literacy is a skill at which Māori have excelled, and can excel, without compromising their identity asMāori. I challenge us to be conscious of the discourses underpinning statements related to Māori learners, however well-meaning those statements might be, and reiterate that literacy is indeed “a Māori thing” – both historically and in contemporary times.

text: “Literacy is not a Māori thing": Debunking the deficit discourse Literacy has been entrenched in Māori society for more than 200 years, meeting needs that range from serving a political purpose to reading purely for pleasure. Literacy is not solely a Western competency, and Māoristriving for excellence in literacy is not an act of modern-day colonisation. Instead, what the evidence shows is that literacy is a skill at which Māori have excelled, and can excel, without compromising their identity asMāori. I challenge us to be conscious of the discourses underpinning statements related to Māori learners, however well-meaning those statements might be, and reiterate that literacy is indeed “a Māori thing” – both historically and in contemporary times.

year: 2022-03-22