传统薄瓣准分子激光原位角膜磨镶术与前弹力层下角膜磨镶术在矫正中高度近视时的疗效对比

目的探讨传统薄瓣准分子激光原位角膜磨镶术与前弹力层下角膜磨镶术在矫正中高度近视时的疗效。方法回顾性分析2009年4月～2010年4月在笔者所在医院行近视矫正手术的患者病历资料。分别对术后1周,1个月和3个月裸眼视力进行比较。结果两组术后1周、1月、3月裸眼视力比较,SBK组裸眼视力优于传统LASIK组,差异有统计学意义(P<0.05)。术后3月,传统LASIK组裸眼视力>1.0,占77.5%,SBK组裸眼视力>1.0,占94.2%;传统LASIK组疗效指数为(0.87±0.15),SBK组为(0.94±0.20),两者比较无统计学意义(P>0.05)。结论前弹力层下角膜磨镶术在矫正中高度近视时能得到更好的视力效果,但两者的疗效指数没有差异。

薄瓣LASIK术后中央角膜厚度的变化分析

目的:探讨薄瓣LASIK术后6mo内中央角膜厚度(central corneal thickness,CCT)及屈光度的变化规律。方法:使用非接触式角膜内皮细胞计追踪观察158例302眼近视眼行LASIK手术患者术前及术后1d;1wk;1,3,6mo时CCT的变化,同时记录患者的年龄,预计激光角膜切削值、术中手术光区的大小,术后预计屈光度以及实际屈光度的改变等。结果:术前平均CCT为531.6±24.3μm。术后第1d平均CCT迅速下降,术后1wk平均CCT继续下降,1mo后角膜厚度开始增厚。术前和术后第1dCCT差值与预计激光角膜切削值呈强相关性(r=0.916,P<0.01)。术后6mo和术后1d时CCT的差值,即6mo内CCT的增厚值与患者年龄、术眼屈光度和术中手术光区均呈显著负相关性(r=-0.180,P=0.026;r=-0.187,P<0.01;r=-0.171,P=0.137)。术后6mo时,实测平均等效球镜与术前预期值接近(术前等效球镜预期值平均为0.34±0.30D)。所有病例随访6mo,无1例发生屈光回退,6mo时裸眼视力均≥0.8,平均视力为1.3±0.2。结论:薄瓣LASIK术后CCT和屈光状态的稳定大约需要6mo时间。术后6mo内CCT增厚值与术前患者年龄、屈光度及术中手术光区大小均呈显著负相关性。术后6mo时实测平均等效球镜值与术前预期值接近。薄瓣LASIK手术治疗近视眼具有良好的预测性和稳定性。

同径异壁厚低合金钢管环焊缝焊接操作技术探析

本文介绍了大口径管道管径相同但壁厚相差较大时,通过对管道内口削薄修磨度数、焊接接头设计和焊接工艺等方面的研究实践,有效地避免了焊缝中的超标缺陷,获得了良好的效果。

Wear of CVD thick film diamond cutter while machining laminated flooring

The wide application of high pressure laminated (HPL) flooring has an insistent need for cutting tools with an excellent performance and fine cutting quality. Chemical vapor deposition (CVD) thick film diamond is a promising material for the machining of HPL flooring. In the present work, CVD thick film diamond tools were used to mill the wear resistance layer of HPL flooring. Wear volumes of flank face were examined by optical microscopy, and micro wear morphologies were observed by scanning electron microscopy (SEM). The experiments revealed that the predominant wear characteristics of CVD diamond tools were transgranular cleavage wear and intergranular peeling of the CVD diamond. Experimental results also showed that twin characteristic, cavity defect, micro crack and grain size of CVD thick film diamond contributed greatly to the wear process of CVD thick film diamond tools. The effects caused by the factors were also analyzed in detail in the paper.

Mechariical and Abrasion Properties of Polyethylene Terephthalate Films Coated with SiO2/Epoxy Hybrid Material

Hybrid materials were prepared using a silane coupling agent, tetraethoxysilane （ TEOS ） as the precursor, dilute hydrochloric acid as the catalyst, and epoxy as the matrices. The films coated with hybrid materials were expected to improve abrasion resistance and mechanical properties. The morphology, mechanical properties, adhesion, and abrasion resistance of the polyethylene terephthalate （PET） films were characterized using an atomic force microscope, a tensile testing machine, a bagger knife, and a reciprocating fabric abrasion tester. The result of research indicated that the modification significantly affected the abrasion resistance and roughness. The-tensile strength and abrasion resistance of the modified PET films increased by 40% and 50% respectively at 3 % TEOS mass fraction.

Microstructure and abrasive wear behaviour of anodizing composite films containing Si C nanoparticles on Ti6Al4V alloy

Anodized composite films containing Si C nanoparticles were synthesized on Ti6Al4 V alloy by anodic oxidation procedure in C4O6H4Na2 electrolyte. Scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray photoelectron spectroscopy(XPS) were employed to characterize the morphology and composition of the films fabricated in the electrolytes with and without addition of Si C nanoparticles. Results show that Si C particles can be successfully incorporated into the oxide film during the anodizing process and preferentially concentrate within internal cavities and micro-cracks. The ball-on-disk sliding tests indicate that Si C-containing oxide films register much lower wear rate than the oxide films without Si C under dry sliding condition. Si C particles are likely to melt and then are oxidized by frictional heat during sliding tests. Potentiodynamic polarization behavior reveals that the anodized alloy with Si C nanoparticles results in a reduction in passive current density to about 1.54×10-8 A/cm2, which is more than two times lower than that of the Ti O2 film(3.73×10-8 A/cm2). The synthesized composite film has good anti-wear and anti-corrosion properties and the growth mechanism of nanocomposite film is also discussed.

An Experimental Study on Slotting of Inconel 718 Thin Sheet

Many difficult-to-cut materials such as Ni-base super alloy, titanium alloy, and austenite stainless steel which are used extensively in aerospace generally have high strength-to-weight ratios, high corrosion resistance, high strength retention ability at elevated temperatures, and low thermal conductivity. These characteristics can result in uneven tool wear and chatter vibration. Therefore, determining the appropriate end-milling conditions is more difficult for difficult-to-cut materials than for other materials. There has been much research on the high-speed milling of difficult-to-cut materials, and effective end-milling conditions, end-mill tool shapes, and processing methods have been reported. In addition, irregular pitch and lead end-mills with different helix angles have been developed by tool maker＇s to reduce chatter vibration, making it easier to perform high-speed milling. However, there have been few reports of slotting information useful for determining appropriate end-milling conditions and processing methods for Ni-base super alloy. The aim of this study is to derive end-milling condition with high efficiency grooving process for Ni-base super alloy （Inconel 718） sheet. Effects of cutting parameters were examined from the view point of cutting resistance, ＂tool tip maximum temperature and tool flank wear width. As a result from experiments, if the grooving process condition of axial depth of cut is smaller than other conditions on the same material removable rate value, it has been found that it is possible to reduce the tool tip maximum temperature and prolong the tool life.

为母亲补鞋

母亲尽管年事已高,可远不是那种朝不虑夕的老人,凡事总要未雨绸缪,从长计议。比如,我不久前回老家探望她时,正赶上老人家脱去冬衣,她拎着那双毡鞋左看右看,说:“鞋后跟磨薄了,鞋帮子也开裂了,得赶在下一个冬天来临前修补好。”母亲是“半解放脚”,市面上卖的鞋子不是大,便是小,总不合脚。所以老人家一辈子只穿家做鞋。视力好时,母亲自己做着穿;后来是姨妈给做着穿。可如今姨妈也卧床不起了,而儿媳、孙女又没有做手工鞋的能耐,于是,母亲穿鞋就成了不大不小的问题。

Lubricating properties of oil-in-water emulsion with low oil concentration:Competitive wetting effect

Oil-in-water （O/W） emulsions are widely used in metal working such as hot rolling and cutting. Three kinds of O/W emulsions with low oil concentration were prepared which include conventional emulsion （CE）, miniemulsion （MNE） and microemulsion （ME）. The lubricating properties of O/W emulsions with low oil concentration were investigated using the tribological testers and the thin film interferometry based on the relative optical interference intensity method. The tribological test results under boundary lubrication show that the friction coefficient and the total losing weight can be clearly seen： CE 〈 MNE 〈 ME. The lubricating film thicknesses under elastohydrodynarnic lubrication and thin film lubrication show that a relationship of the film formation abilities： CE 〉 MNE 〉 ME. Competitive wetting behavior of water and oil on solid surface was confirmed to play an important role in the film formation and tribological behaviors of O/W emulsion.