Performance evaluation of minimum quantity lubrication by vege- table oil in terms of cutting force, cutting zone temperature, tool wear, job dimension and surface finish in turning AISI-1060 steel

In all machining processes, tool wear is a natural phenomenon and it leads to tool failure. The growing demands for high productivity of machining need use of high cutting velocity and feed rate. Such machining inherently produces high cutting temperature, which not only reduces tool life but also impairs the product quality. Metal cutting fluid changes the performance of machining operations because of their lubrication, cooling and chip flushing functions, but the use of cutting fluid has become more problematic in terms of both employee health and environmental pollution. The minimization of cutting fluid also leads to economical benefits by way of saving lubricant costs and workpiece/tool/machine cleaning cycle time. The concept of minimum quantity lubrication （MQL） has been suggested since a decade ago as a means of addressing the issues of environmental intrusiveness and occupational hazards associated with the airborne cutting fluid particles on factory shop floors. This paper deals with experimental investigation on the role of MQL by vegetable oil on cutting temperature, tool wear, surface roughness and dimen- sional deviation in turning AISI-1060 steel at industrial speed-feed combinations by uncoated carbide insert. The encouraging results include significant reduction in tool wear rate, dimensional inaccuracy and surface roughness by MQL mainly through reduction in the cutting zone temperature and favorable change in the chip-tool and work-tool interaction.     

Surface treatment of 0Cr19Ni9 stainless steel SMAW joint by plasma melting

Micro-plasma arc surface melting of 0Cr19Ni9 shielded metal arc welding joint with a micro-plasma arc welder produced a thin surface melted layer with a refined microstructure. The surface treatment changed the anodic polarization behavior in 0.5 mol/L H2SO4 solution. The polarization tests showed that for the as-welded joint both the heat-affected zone and the weld metal decreased in resistance to corrosion compared with the as-Received parent material while for the micro-plasma arc surface melted joint the corrosion resistance increased significantly. This increase in corrosion resistance is attributed to the rapid solidification of the melted layer. Rapid solidification of the melted layer refines its microstructure, decreases its microsegregation, and inhibits the precipitation of chromium carbides at the grain boundaries.received parent material while for the micro-plasma arc surface melted joint the corrosion resistance increased significantly. This increase in corrosion resistance is attributed to the rapid solidification of the melted layer. Rapid solidification of the melted layer refines its microstructure, decreases its microsegregation, and inhibits the precipitation of chromium carbides at the grain boundaries.     

The influence of environmental factors on rugby football injuries

The aim of this study was to establish the influence of weather and pitch conditions on the frequency and nature of rugby injuries. Observers at 26 senior rugby clubs in the Borders District of the Scottish Rugby Union reported all injuries to 1169 (96%) registered players at Saturday home and away matches during the 1993-94 season (August 1993 to April 1994). Weather and pitch conditions at 112 grounds were recorded on 605 occasions; 1268 Borders teams played at these grounds,with 344 injury episodes being sustained. Matches were played in dry weather for three-quarters of these occasions. There was a moderate association between weather and the state of the pitch (Spearman's rank correlation, r = -0.46, P ? 0.001), with heavier pitches occurring in wetter weather. Logistic regression revealed that there were significant month-of-season (P = 0.003), wind strength (P = 0.008) and temperature (P = 0.011) effects on the risk of injury. On four of five occasions when matches were played in a downpour of rain, at least one injury episode occurred. Our results show that the month of the season and the weather may influence the occurrence of rugby injuries, but that the state of the pitch does not. Further studies are required to investigate these factors in more detail.     

Adaptive triangular mesh coarsening with centroidal Voronoi tessellations

We present a novel algorithm for adaptive triangular mesh coarsening. The algorithm has two stages. First, the input triangular mesh is refined by iteratively applying the adaptive subdivision operator that performs a so-called red-green split. Second, the refined mesh is simplified by a clustering algorithm based on centroidal Voronoi tessellations （CVTs）. The accuracy and good quality of the output triangular mesh are achieved by combining adaptive subdivision and the CVTs technique. Test results showed the mesh coarsening scheme to be robust and effective. Examples are shown that validate the method.     

论大英教学中汉译英技能的培养

运用乔姆斯基的转换生成语法理论,通过实例分析在大英教学中如何培养学生的汉译英技能,并指出了这种技能的重要性。     

运用表观热惯量遥感地表蒸散——以河北省易县崇陵流域为例

现有遥感地表蒸散的方法是基于地表热量平衡方程,先求出地表净辐射通量、土壤热通量和显热通量,再用余项法求出潜热通量。地表净辐射通量和显热通量的计算需空气温度、风速和地表粗糙度等非遥感参数,并且涉及到空间插值问题,由此增加了估算的复杂性并降低了估算的精度。引入反映地物固有热特性的物理参数一表现热惯量,结合地表辐射温度,充分利用遥感较易获取的这两个参数来估算地表蒸散,可弥补上述不足。利用河北省易县崇陵流域卫星过境同步观测的地面资料,以2007年5月28日过境的LANDSAT／TM作为数据源,尝试利用表现热惯量来遥感地表蒸散的新途径。首先根据像元表现热惯量和地表辐射温度等遥感参数反演出像元的大气下行辐射,进而估算出地表净辐射通量;其次,利用表现热惯量估算出波文比,再根据波文比时地表净辐射通量进行切割,然后代入地表热量平衡方程中,直接估算出地表潜热通量;最后,计算出崇陵流域日地表蒸散量,并获取其空间分布图。这种方法避开了估算显热通量的中闻环节,可操作性更强。     

质子膜表面粗糙化对质子交换膜燃料电池膜电极性能改善研究

通过对Nafion117表面粗糙化和“预先溶胀法”制备技术提高了微型PEM燃料电池膜电极(MEA)的极化性能. 循环伏安(CV)和交流阻抗(EIS)等电化学检测手方法证明, Nafion117表面粗糙化后扩展了催化层/质子膜三相界面区域,增大了电化学反应的催化活性点,降低了界面的接触阻抗.     

梅州市地面水监测优化布点的问题和对策

梅州市地面水监测优化布点工作是在《广东省主要江河水监测优化布点研究大纲》的基础上开展的,本文根据本地的具体实际,提出新的问题和对策,以使地面水监测布点满足代表性、信息量和可操作性原则.     

Si原子在Si(001)表面及其台阶附近扩散的分子动力学模拟

采用Stillinger-Weber势,利用分子动力学方法模拟了Si原子在Si(001)表面和该表面单层台阶附近扩散的动力学过程。(1)给出单个Si原子在Si(001)表面垂直于二聚体排方向扩散的扩散路径和扩散机制。Si原子在Si(001)表面垂直于二聚体排方向扩散能够减弱Si原子在Si(001)表面扩散的各向异性。(2)模拟不仅给出与以往文献中原子从SA台阶下台面扩散到上台面相同的扩散路径而且还给出原子从成键的SB台阶上台面扩散到下台面的一种新的扩散机制:增原子通过与表面原子之间的交换。从而解释实验上观察到的Si(001)表面双层原子台阶形成的机制。无论是单个Si原子在Si(001)表面垂直于二聚体排方向扩散还是在Si(001)表面的单层台阶附近扩散,增原子和表面原子之间的交换机制都起着重要的作用。