Torsional Models of Two - ply Yarn

In this paper,the vector equation of a generaliseddoubly wound helix was derived.Treloar's pliedyarn geometry could be obtained as a special case ofthe generalised doubly wound helix.The shortest fi-bre length around the surface of a helical tube(formed by fibre helices)was determined by apply-ing variational principles.The fibre length as calcu-lated by using Treloar's geometry was compared in-directly with the shortest possible fibre length at dif-ferent levels of yarn deformation when some of Tre-loar's rigid geometrical constraints were relaxed.Anew idea based on non-concentric circles was intro-duced to approximate the fibre helix movement in atwo-ply yarn.A torsional model of two-ply yarnwas developed and the theoretical predictions werecompared with some preliminary experimental re-sults.     

基于GM—ARMA组合模型的全球年平均气温预测

针对全球年平均气温历史数据既有趋势性又有波动性的特点，提出用灰色系统理论与时间序列分析相结合的方法建立GM—ARMA组合模型来预测全球年平均气温。基于这个模型采用等维递补的预测方法预测出了过去十年内的全球年平均气温，通过与实际数据相比较发现该模型具有较高的预测精度。最后采用该组合模型预测出了未来十年内的全球年平均气温。