Corneal surfaces in eyes with regular astigmatism are thought to be toroidal surfaces . based on mathematical models for corneal surfaces before and after treatment , a corneal ablation model is given for such refractive errors as spherical myopia , compound myopic astigmatism , and simple myopic astigmatism . a similar corneal ablation model is also given for such refractive errors as hyperopia , compound hyperopic astigmatism , and simple hyperopic astigmatism 采用超环面( toroidalsurface )建立起规则散光下的角膜曲面模型方程;定量研究了手术光学区屈光不正两种通用的矫正模型,一种模型适用于单纯近视、复性近视散光、单纯近视散光的矫正,另一种模型适用于单纯远视、复性远视散光、单纯远视散光的矫正;另外,作为影响手术效果的重要因素,提出了一种用于光学区直径和过渡区宽度均可调节时过渡区角膜切削量的计算模型。
Some respects of self - compacting high - strength concrete ( schsc ) made of fujian province ' s local material have been studied in this thesis as follows : 1 . studies on microstructure of the schsc . three different mixed schsc and one normal high - strength concrete ( nhsc ) were observed by the scanning electron microscope at different sites and different ages of 1 day , 3 days , 7 days , 28 days and 60 days . from the test , the effects due to no vibrating and admixture on the microstructure of schsc were studied 通过四组强度等级相当，分别为普通混凝土、两组不掺膨胀剂的自密实混凝土（其粉煤灰的掺量不同）和掺有膨胀剂的自密实混凝土，在同一养护龄期的条件下（ 1天、 3天、 7天、 28天和60天） ，分别选择粗骨料过渡区、细骨料过渡区、水泥石和砂坑作为观测点，采用sem进行细观扫描对比实验，以研究自密实混凝土因免振捣的特性及掺合料对其骨料界面和水泥石结构的影响。
An ophthalmic excimer laser system used to correct wavefront aberration is presented . the conception and zernike representation of wavefront aberration of human eyes recommended by osa are introduced . the connection of wavefront aberration and ablation profile is analyzed and a model for calculating ablation profile to correct wavefront aberration is presented . because the ablation depth on the boundary is nonzero and irregular , we present a model for calculating ablation profile in a transition zone 深入研究了准分子激光像差矫正系统,采用美国光学大会推荐的像差的定义、像差的zernike多项式表示方法,定量分析zernike多项式表示的像差与角膜切削量的关系,采用主观式人眼像差仪测量像差,得出了像差矫正的角膜切削模型,并提出了一种采用过渡函数进行边界切削的方法,用于可调的过渡区切削量的计算,为人眼单色像差的矫正提供了理论基础。
The particles distributed hi the matrix of grey cast iron , but some contact each other . the composite layer extend gradually into the substrate . when volume fraction of wc is 36 wt % and 27 wt % , the matrix of the composite is high chromium cast iron , consist of white carbide bars and the austenite . wc particles distributed uniformly , retaining approximately quondam granular form in the composite layer which has an evident interface area with the substrate , with good bonding strength 对不同碳化钨体积分数的灰铁和低铬铸铁基复合材料的微观组织结构分析表明：碳化钨体积分数为52时，复合层内基体为灰口铸铁组织，颗粒直接分布在灰铁基体上，部分碳化钨颗粒有相互接触的现象，基材与复合层之间没有明显的过渡；碳化钨体积分数为36 、 27时，复合层内基体为高铬铸铁，由面块状的奥氏体和白条状碳化物组成，碳化钨颗粒表面固溶于基体组织中，粒形基本保持完整，分布均匀，与基体构成冶金结合，基材与复合层之间存在一个明显的平缓过渡区。
