Application of the morphological alpha shape method to the extraction of topographical features from engineering surfaces

In contrast to the mean-line based filters, morphological filters are function oriented and more suitable for the functional prediction of component performance. This paper presents a novel morphological method based on the alpha shape for the extraction of topographical features from engineering surfaces. Compared to the traditional implementation of morphological filters, the alpha shape method is more efficient in performance for large structuring elements. The resulting envelope follows the form of the surface all over such that the distortions caused the end effects are avoided. A series of measured surfaces from the automotive cylinder liner and the bioengineering artificial femoral heads are analyzed using the morphological alpha shape method. The topographical features are successfully extracted, enabling further physical and tribological analysis to the components.     

基于冗余提升形态小波的非对称表面特征提取研究

针对提升小波提取非对称表面形貌特征时存在平移变动性和较差的方向选择性,将具有平移不变性和良好的方向选择性的冗余提升形态Haar小波应用到非对称表面的特征提取中。开展了该形态小波对具有显著特征的非对称平顶珩磨的缸套内表面进行特征提取的分析;同时结合仿真的方法,研究了该形态Haar小波对一个模拟的具有一定长度沟槽特征的空间表面进行特征提取的效果。研究结果表明,冗余提升形态Haar小波对非对称表面形貌进行形态特征提取时,在各尺度重构的信号沿特征边缘几乎没有变动且无畸变,可实现准确提取。     

Application of the lifting wavelet to rough surfaces

This paper proposes a lifting wavelet model for enhancement of accuracy of surface roughness characterisation. In this work, the theory and fast algorithm of the lifting wavelet are briefly introduced and a lifting wavelet model for extraction of roughness of surfaces has been developed. The rough surface recovered has good refinement accuracy in contrast to the least squares polynomial fitting. Applications are conducted by using a series of typical surfaces, planes and curves, measured by contact (stylus) and non-contact (phase-shifting interferometry) instruments, to demonstrate the feasibility and applicability of using the lifting wavelet model in the analysis of these surfaces.     

表面微缺陷形态小波提取方法研究

为了解决小波由于不具有平移不变性而在处理信号时出现畸变效应的问题,在提升小波变换的基础上,结合形态小波和冗余变换的优点,构造了冗余提升形态小波,解决了提升小波变换在信号处理过程中的畸变效应;并选用极大值冗余提升形态Haar小波,使用模拟数据进行了数据处理实验。数据处理试验结果表明,冗余提升形态小波具有平移不变性的特点。     

小波变换在粗糙表面几何形貌表征中的应用

粗糙表面几何形貌对于表面特性如摩擦、磨损、润滑、腐蚀疲劳等具有重大的影响,表面几何形貌能否及时准确地被表征具有重要的工程意义．简要叙述小波变换的特点,重点介绍目前小波变换在表面粗糙度评定、表面形貌分离与重构以及表面形貌分形维数提取等方面的应用,提出了目前小波变换在表面几何形貌表征中存在的不足,以及今后小波技术在表面形貌中发展的新趋势．     

Topography-related effects on the lubrication of nanostructured hard surfaces

This study reports the effect of nanoscaled surface structure of some hard coatings on the (micro-) frictional behaviour of systems under minimum lubrication conditions with modest contact pressures and low sliding speeds (below 1 mm/s). For this purpose, Cr-N coatings with a randomly crater-like topography and with varying dimensions of surface features as well as a smooth Cr-N surface were tested with a microtribometer. The friction on the samples was measured as a function of the viscosity of the applied mineral base oil and the sliding velocity. For all tests, the structured surfaces exhibited lower friction than the smooth surface. Furthermore, it was possible to detect variations in the lubrication-promoting effect of the structures depending on the oil viscosity and the sliding speed. Indications for the existence of an optimum topographic scale for this type of surface structure were found.     

A simulated investigation on the machining instability and dynamic surface generation

In this paper, the authors propose the generic concept of machining instability based on the analysis of all kinds of machining instable behaviours and their features. The investigation covers all aspects of the machining process, including the machine tool structural response, cutting process variables, tooling geometry and workpiece material property in a full dynamic scenario. The paper presents a novel approach for coping with the sophisticated machining instability and enabling better understanding of its affect on the surface generation through a combination of the numerical method with the characteristic equations and using block diagrams/functions to represent implicit equations and non-linear factors. It therefore avoids the lengthy algebraic manipulations in deriving the outcome and the solution scheme is thus simple, robust and intuitive. Several machining case studies and their simulation results demonstrate the proposed approach is feasible for shop floor CNC machining optimisation in particular. The results also indicate the proposed approach is useful to monitor the machining instability and surface topography and to be potentially applied in adaptive control of the instability in real time.     

Evaluation of the wavelet transform method for machined surface topography 2: fractal characteristic analysis

In this paper, a new method based on wavelet transform is proposed as a means for studying the fractal characteristics of rough surfaces. Through estimation of normal mathematical curves with known fractal dimensions, generated by the Weierstrass-Mandelbrot function, Majumdar-Bhushan function, Fractal Brownian motion (including three methods: the Midpoint FBm, the Additions FBm, the Interpolated FBm) and Interposed method (Kiesswetter curve), it is validated that the wavelet transform method can accurately calculate the fractal dimension. These fractal functions have been used to simulate some surface profiles. The results indicate that the Wavelet transform method is the most precise in its calculation of the fractal dimensions of the curves. It obtains more accurate results than seven other methods, named the Box counting method, the Yardstick method, the Co-variation method, the Structure function method, the Variation method, the Power Spectrum method and the Rescaled range analysis method. Precisely calculating the fractal dimensions of the curves is the first step in characterising machined surface topography. In addition, this paper aims to further develop the evaluation procedure for the fractal characteristics of machined surface topography.     

Theoretical and experimental investigation of surface generation in swing precess bonnet polishing of complex three-dimensional structured surfaces

Three-dimensional structured surfaces (3D-structured surfaces) possessing specially designed functional textures are widely used in the development of advanced products. This paper presents a novel swing precess bonnet polishing (SPBP) method for generating complex 3D-structured surfaces which is accomplished by the combination of specific polishing tool orientation and tool path. The SPBP method is a sub-aperture finishing process in which the polishing spindle is swung around the normal direction of the target surface within the scope of swing angle while moving around the center of the bonnet. This is quite different from the ‘single precess’ and ‘continuous precessing’ polishing regime, in which the precess angle is constant. The technological merits of the SPBP were realized through a series of polishing experiments. The results show that the generation of complex 3D-structured surfaces is affected by many factors which include point spacing, track spacing, swing speed, swing angle, head speed, tool pressure, tool radius, feed rate, polishing depth, polishing cloth, polishing strategies, polishing slurry, etc. To better understand and determine the surface generation of complex 3D-structured surfaces by the SPBP method, a multi-scale material removal model and hence a surface generation model have been built for characterizing the tool influence function and predicting the 3D-structured surface generation in SPBP based on the study of contact mechanics, kinematics theory, abrasive wear mechanism, and the convolution of the tool influence function and dwell time map along the swing precess polishing tool path. The predicted results agree reasonably well with the experimental results.     

微纳制造技术文献计量分析

对微纳制造技术领域2000-2010年时间段的SCI和EI文献计量分析,结果显示,近年来该领域的研究呈现出增长趋势,美国在微纳制造领域的研究处于绝对领先的地位.SCI文献分析表明,纳米尺度的制造技术、微米尺度的制造技术、微机电系统、微流体、微加工等是近年来研究的热点领域;EI分析则显示,光刻技术、微加工、微机电器件、纳米结构材料、扫描电子显微镜等是研究的热点.     

Tribological characteristics of one-process and two-process cylinder liner honed surfaces under reciprocating sliding conditions

This paper reports an experimental study of the effect of surface texture on cylinder liner wear. This research is important because the conjunction between piston rings and cylinder liner is one of the major sources to frictional losses in internal combustion engines. Experiments were conducted on a reciprocating tester. Specimens were cut from cylinder liners honed or plateau honed made of grey cast iron of hardness 218 HB. The honing operation was performed in order to obtain very similar values of the Sq parameter of one-process and two-process surfaces. In addition, one-process specimens characterised by different Sq parameter values were tested. Counter-specimens were made from chromium-coated steel C45. It was found that wear of two-process surfaces was lower than that of one-process surfaces characterized by the same Sq parameter. Linear wear of specimens was proportional to initial Sq parameter value. The effect of additional oil pockets created by the burnishing technique on cylinder liner wear was negligible.     

双正交提升小波在非对称表面形貌分析中的应用

由平顶珩磨获得的表面形貌是非对称的、多尺度的,而传统滤波函数处理这类表面形貌时存在畸变效应.利用双正交小波的优点,使用提升方案,采用边界对称延拓策略,解决了传统滤波函数在突变处和边界处的畸变效应,并以缸套内表面为例,选用bior4.4双正交小波,证明了提升双正交小波在表面形貌分析中的改善作用.     

煤岩破裂微震信号的小波特征能谱系数分析法

煤岩破裂微震信号是一种时变非平稳信号,具有不可预知性和突发瞬态性,为了提取能够表征微震源信息的有效特征,基于小波理论,选取了适合微震信号的小波基函数,并根据采样定理及Mallat算法确定了小波分解最大尺度,提出了用小波特征能谱系数分析煤岩破裂微震信号波形的状态分析方法。实验结果表明,微震信号与噪声信号有明显不同的小波特征能谱系数分布特征,而且可利用提取的能谱系数作为特征向量表示信号特征。这对于抑制微震信号的不稳定性和同频段的干扰信号,以及后续的特征编码非常有利,为实现煤岩破裂微震信号实时的模式识别打下了重要基础。     

正常角膜和圆锥角膜的特征提取

基于角膜测量仪器Corvis ST采集的图像视频,提出提取新特征参数以便准确区分正常角膜和圆锥角膜。首先对图像进行滤波、分割等预处理,检测角膜上下边界,并计算前角膜曲率值;用小波变换分析角膜曲率变化,获取与角膜运动趋势相关的特征,包括角膜运动的整体趋势和角膜振动的范数和标准差。然后,基于均方误差最小化法,提取特征参数,构建最优参数。最后,用支持向量机(SVM)对正常角膜和圆锥角膜进行分类。从频率的角度实施的实验显示角膜在基本运动趋势上存在着振动过程。此外,提出的参数优于形变幅度(DA)、峰值距离(PD)等传统参数,使准确度、灵敏度和特异性分别提高了10.2%,5.7%和6.9%。受试者工作特征曲线(ROC)下面积为0.948,接近于1。结果显示本文方法自动提取的特征参数可提高正常角膜和圆锥角膜区分的准确性,对临床诊断有辅助作用。     

A dynamic surface topography model for the prediction of nano-surface generation in ultra-precision machining

Materials induced vibration has its origin in the variation of micro-cutting forces caused by the changing crystallographic orientation of the material being cut. It is a kind of self-excited vibration which is inherent in a cutting system for crystalline materials. The captioned vibration results in a local variation of surface roughness of a diamond turned surface. In this paper, a dynamic surface topography model is proposed to predict the materials induced vibration and its effect on the surface generation in ultra-precision machining. The model takes into account the effect of machining parameters, the tool geometry, the relative tool–work motion as well as the crystallographic orientation of the materials being cut. A series of cutting experiments was performed to verify the performance of the model and good correlation has been found between the experimental and simulation results.     

基于二代小波变换和PCNN的高光谱图像融合算法

采用信息融合技术可以降低高光谱遥感图像的分析难度。本文提出一种基于二代小波变换和脉冲耦合神经网络(PCNN)的融合算法。在利用自适应子空间分解技术将高光谱图像的数据空间划分为数个子空间后,对各子空间内的每一波段图像进行二代提升小波分解。对低频系数部分进行方差加权融合的同时利用PCNN的脉冲同步和全局耦合特性对高频系数部分进行选取,最后用二代小波逆变换得到各子空间的融合图像.其仿真实验结果显示:所提算法有效降低了高光谱图像维数,很好保留了原图像的信息,效果优于单一的一代小波和二代小波融合算法。     

基于小波变换和时域能量熵的 P300特征提取算法

针对P300信号特征提取和分类过程中训练及测试速度相对较慢的不足,提出了一种基于P300带内带外特征的脑电信号特征提取方法,将时域能量熵和离散小波变换相结合,克服了P300信号识别中对电极数量和脑电信号叠加次数的苛刻要求.试验采用支持向量机作为分类器,在BCI Competition 2003和BCI Competition 2005的P300试验数据集上进行验证,结果表明,提出的方法只需对一导数据进行处理,只有2次叠加平均,就能得到很好的分类效果及较短的分类系统运算时间.     

Study of morphological and mechanical features of multinuclear and mononuclear SW480 cells by atomic force microscopy

This article studies the morphological and mechanical features of multinuclear and mononuclear SW480 colon cancer cells by atomic force microscopy to understand their drug‐resistance. The SW480 cells were incubated with the fullerenol concentrations of 1 mg/ml and 2 mg/ml. Morphological and mechanical features including the height, length, width, roughness, adhesion force and Young's modulus of three multinuclear cell groups and three mononuclear cell groups were imaged and analyzed. It was observed that the features of multinuclear cancer cells and mononuclear cancer cells were significantly different after the treatment with fullerenol. The experiment results indicated that the mononuclear SW480 cells were more sensitive to fullerenol than the multinuclear SW480 cells, and the multinuclear SW480 cells exhibited a stronger drug‐resistance than the mononuclear SW480 cells. This work provides a guideline for the treatments of multinuclear and mononuclear cancer cells with drugs.     

基于共振解调和小波分析方法的轴承故障特征提取研究

首先研究了共振解调和小波分析的基础理论,并结合两者应用于对轴承外圈和滚子的故障特征提取。该方法先从振动信号频谱中判断系统固有高频成分的大致范围,然后利用小波分解取出固有高频信号成分,再利用Hilbert变换做包络检波,最后对包络信号进行傅里叶频谱分析得出故障信号特征频率。对实际轴承故障数据的分析表明,该方法能有效地提取轴承的外圈故障特征,有一定的应用价值。但该方法不能清晰地提取出滚子故障特征,探讨了其内在原因,并提出了可能改进的措施。