Optimal machining conditions for turning Ti-6AI-4V using response surface methodology     

Satyanarayana Kosaraju  Venu Gopal  Anne 《上海大学学报(英文版)》2013,(4):329-339

Machining titanium is one of ever-increasing magnitude problems due to its characteristics such as low thermal conductivity, modulus of elasticity and work hardening. The efficient titanium alloy machining involves a proper selection of process parameters to minimize the tangential force （Fz） and surface roughness （Ra）. In the present work, the performance of PVD/TiA1N coated carbide inserts was investigated using response surface methodology （RSM） for turning Ti-6A1-4V. The effects of process parameters such as speed （v）, feed （/＇）, depth of cut （d） and back rake angle （Ty） on Fz and Ra were investi- gated. The experimental plan used for four factors and three levels was designed based on face centered, central composite design （CCD）. The experimental results indi- cated that Fz increased with the increase in d, f and decreased with the increase in v and yy, whereas Ra decreased with the increase in v and 7y, and increased with d and v. The goodness of fit of the regression equations and model fits （R2） for Fz and Ra were found to be 0.968 and 0.970, which demonstrated that it was an effective model. A confirmation test was also conducted in order to verify the correctness of the model.  相似文献   

Biomechanical comparison of the double-push technique and the conventional skate skiing technique in cross-country sprint skiing     

Thomas Stöggl  Erich Müller  Stefan Lindinger 《Journal of sports sciences》2013,31(11):1225-1233

Abstract

The aims of the study were to: (1) adapt the “double-push” technique from inline skating to cross-country skiing; (2) compare this new skiing technique with the conventional skate skiing cross-country technique; and (3) test the hypothesis that the double-push technique improves skiing speed in a short sprint. 13 elite skiers performed maximum-speed sprints over 100 m using the double-push skate skiing technique and using the conventional “V2” skate skiing technique. Pole and plantar forces, knee angle, cycle characteristics, and electromyography of nine lower body muscles were analysed. We found that the double-push technique could be successfully transferred to cross-country skiing, and that this new technique is faster than the conventional skate skiing technique. The double-push technique was 2.9 ± 2.2% faster (P < 0.001), which corresponds to a time advantage of 0.41 ± 0.31 s over 100 m. The double-push technique had a longer cycle length and a lower cycle rate, and it was characterized by higher muscle activity, higher knee extension amplitudes and velocities, and higher peak foot forces, especially in the first phase of the push-off. Also, the foot was more loaded laterally in the double-push technique than in the conventional skate skiing technique.  相似文献   

The effect of constant-intensity endurance training and high-intensity interval training on aerobic and anaerobic parameters in youth     

A. Runacres  K.A. Mackintosh  M.A. McNarry 《Journal of sports sciences》2013,31(21):2492-2498

ABSTRACT

Introduction: High-Intensity Interval Training (HIIT) and Constant-Intensity Endurance Training (CIET) improves peak oxygen uptake (V?O₂) similarly in adults; but in children this remains unclear, as does the influence of maturity. Methods: Thirty-seven boys formed three groups: HIIT (football; n = 14; 14.3 ± 3.1 years), CIET (distance runners; n = 12; 13.1 ± 2.5 years) and a control (CON) group (n = 11; 13.7 ± 3.2 years). Peak V?O₂ and gas exchange threshold (GET) were determined from a ramp test and anaerobic performance using a 30 m sprint pre-and-post a three-month training cycle. Results: The HIIT groups peak V?O₂ was significantly higher than the CON group pre (peak V?O₂: 2.54 ± 0.63 l·min^-1 vs 2.03 ± 0.53 l·min^-1, d = 0.88; GET: 1.41 ± 0.26 l·min^-1 vs 1.13 ± 0.29 l·min^-1, d = 1.02) and post-training (peak V?O₂: 2.63 ± 0.73 l·min^-1 vs 2.08 ± 0.64 l·min^-1, d = 0.80; GET: 1.32 ± 0.33 l·min^-1 vs 1.15 ± 0.38 l·min^-1, d = 0.48). All groups showed a similar magnitude of change during the training (p > 0.05). Conclusion: HIIT was not superior to CIET for improving aerobic or anaerobic parameters in adolescents. Secondly, pre- and post-pubertal participants demonstrated similar trainability.  相似文献   

WTO《补贴协议》中关于搜集严重侵害信息程序之探析——以三个相关经典案例为中心     

王永杰 《华东师范大学学报(哲学社会科学版)》2012,(2):76-81,154,155

WTO《补贴协议》附件5规定了搜集严重侵害信息的程序。该程序由申诉方提出请求,DSB做出决定,指定代表负责实施。指定代表需要确定附件5程序的工作步骤和进程;制订保护商业机密信息程序;完成调查问卷以及向专家组提交报告。所有这些工作都是在与当事方协商的情况下完成的。附件5程序搜集的信息可以适用于严重侵害的诉讼请求,专家组裁定该信息也可以适用于禁止性补贴的诉讼请求。通过对现有的三个涉及WTO《补贴协议》附件5程序的经典案例的分析,可以进一步了解附件5程序的运作特点、存在问题及注意事项,从而为完善附件程序5以及我国在WTO框架内的补贴争诉提供可资借鉴之处。  相似文献   

基于语料库的中国大学生口语中高频动词“V n”类联接研究     

龙桃先 《福建师大福清分校学报》2009,(6):86-89

本研究采用语料库证据支持的中介语对比分析方法,基于《中国学习者英语口语语料库》、《中国学生英语口笔语语料库》口语部分和《英国国家语料库》口语部分,重点考察中国英专与非英专学生口语中四个高频动词DO,GET,MAKE和TAKE＋名词（Vn）类联接的使用特征,并对出现的使用特征给予可能的解释。  相似文献   

道是“无根”却有根——奈保尔的后殖民文化身份之思考     

洪春梅 《江西广播电视大学学报》2009,(1)

关于奈保尔的文化身份的论述,始终是奈保尔研究的一个热点与焦点.通过创作,奈保尔建构了自己的文化身份.奈保尔在后殖民文学界因"无根性"(roodess ness)而闻名,然而"无根性"是评论界对其写作边缘性质的概括,具有混合文化身份的他文化之根是在西方.  相似文献   

魏晋六朝完成貌句式语法属性研究述评     

吴茂刚 《安徽教育学院学报》2009,(2):36-39

不能简单地依据语义来判断魏晋六朝时期的两种完成貌句法格式的语法属性;文章倾向于将“V1＋O＋V”格式及大部分“V1＋V完”格式看作主谓结构;同时认为“V＋已”此期应该可以视为动结式。  相似文献   

“V上”结构的语义分析   总被引：2，自引：0，他引：2  

常海星 《贵州教育学院学报》2009,25(4):67-71

“V上”结构是现代汉语中一个使用频率比较高的结构,结构所表示的意义丰富多样,这些意义不但与结构中动词的意义密切相关,也与“上”的意义及其发展演变有千丝万缕的联系,不论是对结构整体意义的分析还是对“上”的虚化过程的探索都是很有意义的。  相似文献   

"V不下"与"V不了"句法语义语用对比探析     

季艳 《常熟理工学院学报》2005,19(3):70-73

“V不下”与“V不了”虽然都属于可能补语类型,但是它们在具体运用的时候,又存在着交叉和不交叉的地方。通过研究发现它们在句法、语义、语用方面都存在一些不对等的方面。  相似文献   

2008-2017年国内BIM技术研究热点与演进趋势     

崔庆宏  王广斌  刘潇  曹冬平  路浩 《科技管理研究》2019,39(4)

以2008~2017年间CNKI数据库中10本代表性期刊作为数据源,将发表在上述期刊的698篇BIM技术学术论文作为样本,基于文献计量的研究方法并且采用VOSviewer和CiteSpace V两种软件工具进行研究热点与演进趋势分析。研究结果表明信息化、项目管理、深化设计与高层建筑等是国内BIM技术研究的主要热点,演进趋势则沿着管理、功能与应用领域、技术集成3条主线,以期为该领域的后续理论研究与实践应用提供参考和借鉴。  相似文献