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表面结构对纳米级气膜稀薄流域分布的影响
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作者 牛荣军 黄平 《润滑与密封》 CAS CSCD 北大核心 2015年第1期9-15,共7页
磁头与磁盘的特征高度目前已经下降到纳米量级,在此微小间隙下,气体表现出明显的稀薄效应特征。建立适用于纳米间隙下的控制方程,并根据方程特点采用特殊处理方法成功对控制方程进行数值求解,采用数值分析和实验方法分析表面结构变化对... 磁头与磁盘的特征高度目前已经下降到纳米量级,在此微小间隙下,气体表现出明显的稀薄效应特征。建立适用于纳米间隙下的控制方程,并根据方程特点采用特殊处理方法成功对控制方程进行数值求解,采用数值分析和实验方法分析表面结构变化对稀薄流域和磁头飞行姿态的影响。研究结果表明:在纳米级气膜润滑间隙下,采用逆Knudsen数来划分稀薄流域比仅从特征膜厚高度方面考虑更合理;负压型磁头的主要工作区间在滑流区和过渡区,且过渡流域所占比例要明显高于滑流区域。稀薄效应最大的区域不是在气膜厚度最薄的磁头尾部,而是在压力突然下降且气膜较薄的阶梯过渡区域;磁头U型气垫、尾端两侧浅台阶和中间台阶结构变化会影响气流流向,从而影响压力分布,使得稀薄流域也跟随发生变化。 展开更多
关键词 气体润滑 稀薄流域 稀薄效应 磁头磁盘系统
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A coin-tap method of composite materials non-destructive testing based on improved grey clustering 被引量:2
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作者 YU Xiaowen XU Liping +1 位作者 LI Jian WANG Wei 《Journal of Measurement Science and Instrumentation》 CAS CSCD 2021年第1期120-126,共7页
Aiming at the problems of low reliability and complex operation of traditional coin-tap test of composite material,this paper introduces the grey system theory and achieves better performance.The response signals of c... Aiming at the problems of low reliability and complex operation of traditional coin-tap test of composite material,this paper introduces the grey system theory and achieves better performance.The response signals of coin-tap are classified through the grey clustering based on relation analysis,and corresponding improvements are made to the calculation method of the relation degree of nearness.First,the time history of acceleration is taken as the system behavior sequence.The improved correlation calculation method is used to solve the relation degree of nearness between the sequences,and the matrix of degree of grey relation is constructed based on this.Then,the sequence groups are summarized through the matrix,and the response signals of coin-tap are qualitatively classified according to the location of the reference sequence.Finally,the defect detection of composite materials is completed without pre-testing.The test results show that the accuracy of the coin-tap test based on improved grey clustering reaches 100%,which simplifies the operation steps while ensuring the reliability of the coin-tap test results. 展开更多
关键词 non-destructive testing coin-tap test grey clustering based on relation analysis composite material
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