钛对活塞铝硅合金组织性能的影响

针对国内外含Ｔｉ活塞Ａｌ－Ｓｉ合金的应用和发展程度存在较大的差距，在探讨Ｔｉ对ＡＬ－Ｓｉ合金作用机理的基础上，着重讨论Ｔｉ对活塞Ａｌ－Ｓｉ合金组织、性能的影响。分析结果认为，活塞Ａｌ－Ｓｉ合金中加入０．０８％￣０．３５％的微量Ｔｉ元素，可显著提高活塞的耐热性和耐磨性；燕可通过采取更接近工作温度的时效处理工艺，改善活塞的体积稳定性，从而提高活塞的综合性能。     

Preservation of the NBUCA Class of Life Distributions

Introduction As is well known, lifetime distributions can beclassified by stochastic ordering. Recently, Ahmad etal.[1]defined a new aging class, namely, NBUCA(new better than used in increasing convex average),based upon the increasing convex average order. Inthe theory of economics, this order is known as weakthird-order stochastic dominance[2]. Under the as-sumption that the elements are independent andidentically distributed (i.i.d.), the preservationproperties of this class under convo…