简介：WehavecarefullyreadDr.Yuandhiscolleagues'~1reviewonthemechanismofhamstringmusclestraininjuryinsprinting.Thereisnodoubtthattheyhavedonealotworkinthisfield.Theirviewsarebasedon3piecesofevidence.First,observationsfrominsituanimalmodelssuggestthatmusclestraininjuriesarehighlyassociatedwitheccentriccontractions.Second,themagnitudeofmusclestrain,ratherthantheforce,is

简介：WehavecarefullyreadthedescriptionoftheproposedmechanismsofhamstringmusclestraininjurybyLiuetal.1andnoticedthattheysuggestthathamstringstraininjuriesmaybeassociatedwithextensivemuscleforceandoccurduringtheearlystancephaseofsprintingwhenthehamstringsarethoughttoworkconcentrically.Wedidnotfindanyevidenceinourextensiveliteraturereviewtosupportthisparticular

简介：采用粉末冶金技术制备了Ti-15V-10Al合金.利用金相显微镜、扫描电子显微镜和电子探针对合金的组织与成分进行了表征,并测试了各组织的显微硬度.结果表明,粉末冶金法制备Ti-15V-10Al合金的最佳烧结温度为1450℃.该合金主要由Ti3Al的基体相和TU0.2析出相组成.随着烧结温度的升高,析出相呈先细化后粗大、总含量逐渐增加的趋势,合金的密度逐渐增加,显微硬度先增加后减小,在1450℃时达到峰值451.6HV.