Universal relationship between crystallinity and irreversibility field of MgB2

The relationship between irreversibility field, Hirr, and crystallinity of MgB2 bulks including carbon substituted samples was studied. The Hirr was found to increase with an increase of FWHM of MgB2 (110) peak, which corresponds to distortion of honeycomb boron sheet, and their universal correlation was discovered even including carbon substituted samples. Excellent Jc characteristics under high magnetic fields were observed in samples with large FWHM of (110) due to the enhanced intraband scattering and strengthened grain boundary flux pinning. The relationship between crystallinity and Hirr can explain the large variation of Hirr for MgB2 bulks, tapes, single crystals and thin films.Comment: 3 pages, 4 figures, to be published in Appl. Phys. Lett. (in press

An ‘ideal’ form of decaying two-dimensional turbulence

In decaying two-dimensional Navier-Stokes turbulence, Batchelor's similarity hypothesis fails due to the existence of coherent vortices. However, it is shown that decaying two-dimensional turbulence governed by the Harney-Hasegawa-Mima (CHM) equation ∂/∂t (V^2 φ-λ^2 φ)+J(φ,∇^2 φ)=D where D is a damping, is described well by Batchelor's similarity hypothesis for wave numbers k ≪ λ (the so-called AM regime). It is argued that CHM turbulence in the AM regime is a more `ideal' form of two-dimensional turbulence than is Navier-Stokes turbulence itself

小学校教師の影響を起点とする学習意欲の内在化過程 : (1)分析方法の検討

本研究は，社会化エージェントとしての小学校教師の多様なはたらきかけが，子どもたちの学習に対する価値や興味に対してどのような影響を与えているか，そしてそれらの影響を子どもたちはどのように内在化しているかを検討するものである。大学4年生および大学院生を対象とした構造化面接にもとづき，彼らの回想した様々なエピソードが収集された。これらのエピソードにもとづいて，小学校教師からの影響によって喚起された子どもたちの学習への動機づけが，中学校・高校・大学へと時間が経過するのにともなってどのように内在化されていくか，という長期的な視点に立って分析が行われた。本報告では，その分析のための方法の有効性について検討が加えられた。ここでは，鹿毛（1996）の分析方法を基盤として，いくつかの改善を加えた方法が用いられた。まず教師のはたらきかけに関して3カテゴリー，子どもの学習動機に関して5カテゴリー（うち1カテゴリーは両者に共通）の7つのカテゴリーを設定し，エピソードの中の個々の事象ごとに，いずれかのカテゴリーに分類した。次に，このカテゴリーを横軸，時間経過を縦軸とした2次元平面上に個人の全エピソードを位置づけ，それらを矢印で結んで影響の連鎖を示した。このマップ化による方法は，多様な影響過程を整理していくのに有効であることが示唆された。しかし一方では，各カテゴリーへの分類の信頼性については，今後さらに高めていく必要性が指摘された。In this study, we examined how elementary-school teachers\u27 behaviors and attitudes affect pupil\u27s motivation to learn, and how pupils internalize them. Using a structured interview approach, 160 undergraduate (fourth grade) and graduate students were asked to recall their elementary-school teacher\u27s behaviors and attitudes that developed or undermined their motivation to learn. They were also interviewed about how those motivations changed as they went into upper schools. These episodes were classified into one of 7 categories, three for children\u27s motivations, and five for teacher\u27s influences (One category is common for both). Then, they were plotted on a map and were connected each other by arrows. This mapping method is expected to provide an effective way to analyze the long-term internalization process of children\u27s motivation