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2 results on '"LEROUX, ANDREW"'

1. Problem solving difficulty from unrecognized equivalency

Author

Leroux, Andrew L., NC DOCKS at The University of North Carolina at Greensboro, Leroux, Andrew L., and NC DOCKS at The University of North Carolina at Greensboro

Abstract

Equivalency occurs in problem solving when a single state can be represented by multiple configurations. If unrecognized, multiple equivalent states can be perceived as new, unique states. This confusion can hinder problem solving. Three experiments used two river crossing problems to explain changes in difficulty through changes in the external representation. The order in which objects were selected, the appearance of objects, and the spatial location of objects were manipulated to affect the difficulty of recognizing equivalent problem states. Blocking equivalency by fixing the selection order was the most reliable effect, helping participants solve the problems in fewer moves.

Published
2011

2. Annealing of -decay damage in zircon: a Raman spectroscopic study

Author

Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK Laboratoire de Structure et Propri??t??s de l'Etat Solide, B??timent C6, Universit?? Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq, France Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK Mineralogisches Museum, Mineralogisch-Petrographisches Institut, Universit??t Hamburg, Grindelallee 48, D-20146 Hamburg, Germany Department of Nuclear Engineering and Radiological Sciences Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109-2104, USA M Zhang Ming Zhang, Ekhard K H Salje, Gian Carlo Capitani, Hugues Leroux, Andrew M Clark, Jochen Schl??ter and Rodney C Ewing, Department of Nuclear Engineering and Radiological Sciences Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109-2104, USA, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK, Laboratoire de Structure et Propri??t??s de l'Etat Solide, B??timent C6, Universit?? Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq, France, Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK, Ann Arbor, Zhang, Ming, Salje, Ekhard K. H., Capitani, Gian Carlo, Leroux, Hugues, Clark, Andrew M., Schl??ter, Jochen, Ewing, Rodney C, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK Laboratoire de Structure et Propri??t??s de l'Etat Solide, B??timent C6, Universit?? Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq, France Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK Mineralogisches Museum, Mineralogisch-Petrographisches Institut, Universit??t Hamburg, Grindelallee 48, D-20146 Hamburg, Germany Department of Nuclear Engineering and Radiological Sciences Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109-2104, USA M Zhang Ming Zhang, Ekhard K H Salje, Gian Carlo Capitani, Hugues Leroux, Andrew M Clark, Jochen Schl??ter and Rodney C Ewing, Department of Nuclear Engineering and Radiological Sciences Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109-2104, USA, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK, Laboratoire de Structure et Propri??t??s de l'Etat Solide, B??timent C6, Universit?? Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq, France, Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK, Ann Arbor, Zhang, Ming, Salje, Ekhard K. H., Capitani, Gian Carlo, Leroux, Hugues, Clark, Andrew M., Schl??ter, Jochen, and Ewing, Rodney C

Abstract

Recrystallization and structural recovery in -decay damage in zircon samples have been studied using Raman spectroscopy. Fifteen zircon samples with different degrees of radiation damage have been thermally annealed between 600 K and 1800 K for up to 28 days and 8 hours. The experimental results from this study reveal that recrystallization in the damaged zircon samples is a multi-stage process that depends on the degree of initial damage of the samples. In partially damaged samples the lattice recovery of damaged crystalline ZrSiO4 takes place at temperatures as low as about 700 K, as shown by a remarkable band-sharpening and a significant increase in the frequencies of 1 and 3 Si-O stretching vibrations together with the external band near 357 cm-1 with increasing temperature. A dramatic increase of Raman scattering intensity of ZrSiO4 occurs in partially damaged samples near 1000 K due to a recrystallization process involving epitaxial growth. Heavily damaged samples tend to decompose into ZrO2 and SiO2 at high temperatures. Tetragonal ZrO2 has been observed under annealing between 1125 K and about 1600 K in heavily damaged samples while monoclinic ZrO2 appears above 1600 K. Weak signals from ZrSiO4 were detected at 1125 K in highly metamict zircon although the main recrystallization appears to occur near 1500 K accompanied by a decrease of the volumes of ZrO2 as well as SiO2 . This suggests that this recrystallization is associated with the reaction of ZrO2 with SiO2 to form ZrSiO4 . A possible intermediate phase has been observed, for the first time, by Raman spectroscopy in damaged zircons annealed at temperatures between 800 K and 1400 K. This phase is characterized by strong, broad Raman signals near 670, 798 and 1175 cm-1 . Prolonged isothermal annealing at 1050 K results in a decrease of these characteristic bands and eventually the disappearance of this intermediate phase.

Published
2006

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