Role of MgO nanoparticles on zirconia-toughened alumina-5 wt-% CeO2 ceramics mechanical properties

The poor hardness of zirconia-toughened alumina (ZTA) with 5?wt-% CeO₂ (ZTA5CeO₂) ceramic has limited its applications as a cutting insert. Therefore, in this work, the possibility of MgO nanoparticles (20?nm) as reinforcement to ZTA5CeO₂ ceramics was investigated. Mgo nanoparticles with different weight percentages (0-2?wt-%) were added to ZTA5CeO₂ ceramics. ZTA5CeO₂ with 0.5?wt-%MgO showed the highest fracture toughness of 9.14?MPa.√m. The addition of 0.5?wt-%MgO nanoparticles showed the excellent role of MgAl₁₁CeO₁₉ grains as a crack deflector, which consequently produced a reasonable hardness value of 1591?HV and lowered the wear areas to 0.0528?mm².     

Development of bridge tooling for fabricating mold inserts of aspheric optical lens

A bridge tooling is developed for fabricating the temporary mold inserts of aspheric lens using silicone rubber materials. Prototype material of the aspheric lens is not recommended as quartz due to low successful rate in the fabrication process. This technology provides a fast, low cost, and high successful rate for fabricating the epoxy‐based composites mold inserts of plastic aspheric optical lens.     

Ophthalmic delivery of ciprofloxacin hydrochloride from different polymer formulations: in vitro and in vivo studies

Reservoir-type ocular inserts were fabricated using sodium alginate containing ciprofloxacin hydrochloride as the core (drug reservoir) that was sandwiched between the Eudragit and/or polyvinylacetate films. Ocular inserts were packaged in aluminium foil and sterilized by gamma radiation. These were tested for sterility as per British Pharmacopoeia (BP). Ocular inserts were evaluated for in vitro release rate studies, microbial efficacy, in vivo release studies, efficacy against induced bacterial conjunctivitis in rabbit's eyes, concentration in the aqueous humor, and stability studies as per the International Conference on Harmonization (ICH) guidelines. Ocular inserts passed the test for sterility. They showed zero-order release of the drug in the in vitro and in vivo release studies over a period of 120 hr. The drug was found to be active against selected microorganisms as was proved by microbial efficacy studies. A high correlation coefficient was found between in vitro and in vivo release rate studies. Better improvement was observed in artificially induced bacterial conjunctivitis in rabbit's eyes, compared with marketed eye drops and placebo. Drug concentration in the aqueous humor was found above Minimum Inhibitory Concentration (MIC-90) against selected microorganisms. Shelf-life of the product was found to be more than 2 years.     

Substrate treatments/modifications to improve the adhesion of diamond-coated cutting inserts

In this paper we first describe the basic idea of adhesion and various methods for measuring adhesion. We then discuss the various state-of-the-art techniques for the improvement of the adhesion between diamond films and substrates. The techniques discussed are categorized into two main types: (a) those which reduce internal stress and (b) those which increase the ideal or basic adhesion itself. Techniques in category (a) include forming a composition gradient layer on top of an insert substrate surface to reduce the detrimental effect caused by the difference in thermal expansion with diamond, and/or the use of insert substrates themselves having a smaller difference in thermal expansion with diamond. Techniques in category (b) include modification of cemented carbide substrates so as to reduce the detrimental effect caused by Co and the increase of the mechanical interlocking effect using a special etching process.     

Effect of polymer molecular weight and of polymer blends on the properties of rapidly gelling nasal inserts

The objective was to investigate the potential of polymer molecular weight (MW) and polymer blends for the control of drug release from in situ gelling nasal inserts prepared by lyophilization of solutions of model drugs (oxymetazoline HCl, diprophyllin) and polymers. Drug release, polymer solution viscosity, water uptake and mass loss, mechanical properties, and bioadhesion potential were measured. Sonication was effective to reduce the viscosity/polymer MW of carrageenan solutions. Nasal inserts prepared from sonicated carrageenan showed an insignificant reduction in water uptake with sonication time and no disintegration of the gel matrix. In contrast, inserts of different MW Na-alginates revealed a reduced water uptake and an increased mass loss with lower MW. Inserts prepared from carrageenan/low MW Na-alginate blends took up more water at a higher low MW Na-alginate content. Sonicated carrageenan inserts released oxymetazoline HCl independent of the sonication time and diprophyllin with only a slight reduction in the release rate. Release of both drugs from Na-alginate inserts was slow from high MW inserts because no insert dissolution occurred. Increasing the Na-alginate content of inserts prepared from polymer blends accelerated the drug release enabling release rates over a broad range. The bioadhesion potential of Na-alginate inserts was strongly reduced for the low MW grades because of dissolution of the inserts. Xanthan gum and Carbopol 971 blended with Na-alginate formed inserts with poor bioadhesion. The use of polymer blends to control the drug release from nasal inserts was superior to the use of polymers of different MW.     

可转位球头立铣刀最大进给量算法

基于可转位球头立铣刀的几何造形 ,建立了最大进给量计算的数字模型。该模型可容易地计算出使用该种刀具加工时的最大进给量 ,从而避免了刀具的损坏 ,并保证了被加工件的表面质量     

高温环境下蜂窝夹层结构埋件拉脱性能研究

介绍了常温环境下和高温环境下蜂窝夹层结构埋件拉脱性能的试验和结果,对比分析了高温环境对埋件拉脱性能的影响。结果发现,埋件在受法向拉脱力时,高温环境中承载力下降为常温的8%左右,且失效模式也发生了变化,由常温的蜂窝芯剪切破坏变为面板与蜂窝芯脱粘破坏;埋件在受面内拉脱力时,常温环境和高温环境下埋件分别呈现出了两种典型的失效模式,常温环境中失效模式为面板压缩破坏,高温环境中失效模式为面板皱褶失稳破坏,且拉脱力降为常温的28%左右。     

输电线路钢管斜插式基础安装工艺的质量控制

本文主要就钢管斜插式基础安装工艺的重点和难点并结合笔者的实际施工经验,阐述了如何做好钢管斜插式基础安装及调整控制工作,以便为输电线路杆塔的组立提供坚实的基础保障。     

数控磨削可转位刀片的几何建模及其仿真

构建了可转位刀片数控磨削成形的几何模型,借助虚拟仿真技术对刀片的磨削加工进行了仿真。该方法对可转位刀片的实际加工具有指导作用,提高了刀片工艺制造的效率和可靠性。     

宏程序在复杂曲线曲面加工中的应用

二次及多次曲线、曲面的加工在一些特殊零件的制造中经常会出现,而在一般的数控机床的指令系统中,往往只有普通的直线与圆弧插补指令,在一些高级的数控系统中也仅包含一些简单的二次曲线插补指令(如抛物线插补),但是这些指令并不能直接用来编制复杂曲线与曲面的加工程序。这里针对宏指令的多样性与灵活性,对数控系统的指令系统进行二次开发,为解决复杂曲线、曲面的加工难题提供了一种可行的途径。