Effect of surface lay in the surface roughness evaluation using machine vision

This work explores the influence of orientation of surface lay pattern of the machined components, while quantifying the surface roughness using machine vision approach. The surface images are captured from milled low carbon steel specimens with different roughness values using a vision system with coaxial lighting arrangement at different angular orientations of the work pieces (0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, and 180°). The captured images are subjected to preprocessing in order to retain the frequency components that attribute to roughness using a Gaussian filter by adapting the filtering procedures specified in ISO 4288. Numerous image based parameters such as gray level average (G_a), gray level co-occurrence matrix based image quantification parameters namely contrast, correlation, energy or uniformity, maximum probability and differential box courting based fractal dimension are computed from the surface images captured at different angular positions of the work piece. The computed vision based parameters are compared and correlated with the roughness average (R_a) obtained using a stylus instrument and the results are analyzed. The results clearly indicated that it is important to consider the orientation of the work piece when the machine vision approach is used to quantify the surface texture parameters.     

The study of fractal correlation method in the displacement measurement and its application

The classical digital speckle, or digital image, correlation method of deformation measurement is based on gray level correlation between unformed and deformed digital images. The pattern of artificial random speckles and the natural textures on some object's surfaces have fractal characteristics, and their fractal dimensions represent both gray and morph information. Furthermore, the fractal dimensions are stable feature parameters of the patterns. The digitized images of the patterns are confirmed to be also fractals. By this fact, a new method of displacement measurement is developed in the paper, based on the fractal dimensions correlation. The in-plane displacement fields of a body can be acquired. In order to verify the validity of the new method, an experiment has been designed and the results have been compared with those obtained from the classical digital image correlation method. The validity of the new method is not less than that of classical method. Further discussions about the traits and the developing vista of the method are given at the end.     

Electrochemical behavior of Al2O3/Al composite coated Al electrodes through surface mechanical alloying in alkaline media

The behavior of $A{l}_2{O}_3/Al$ composite coated Al electrodes fabricated by surface mechanical alloying ‘SMA’ was studied. The work was accomplished using Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques in alkaline media $2MKOH$ were done at room temperature. Results show hydroxyl ions accumulate on the surface due to Al deformation micro cavities filling with $A{l}_2{O}_3$ until full charge blockage reached. A barrier cover layer development causing an increase of both resistance and capacitance as it becomes more stable and thinner with exposure time increase. Migrating hydroxyl ion inside micro cavity changed its composition from Al₂O₃ to stable tetrahedral $Al{\left(OH\right)}_4^{?}$ aluminate ions. Therefore future benefits could be reached by developing such surfaces having charge accumulation that enables environmental interaction.     

Fractal analysis and atomic force microscopy measurements of surface roughness for Hastelloy C276 substrates and amorphous alumina buffer layers in coated conductors

In coated conductors, surface roughness of metallic substrates and buffer layers could significantly affect the texture of subsequently deposited buffer layers and the critical current density of superconductor layer. Atomic force microscopy (AFM) is usually utilized to measure surface roughness. However, the roughness values are actually relevant to scan scale. Fractal geometry could be exerted to analyze the scaling performance of surface roughness. In this study, four samples were prepared, which were electro polished Hastelloy C276 substrate, mechanically polished Hastelloy C276 substrate and the amorphous alumina buffer layers deposited on both the substrates by ion beam deposition. The surface roughness, described by root mean squared (RMS) and arithmetic average (R_a) values, was analyzed considering the scan scale of AFM measurements. The surfaces of amorphous alumina layers were found to be fractal in nature because of the scaling performance of roughness, while the surfaces of Hastelloy substrates were not. The flatten modification of AFM images was discussed. And the calculation of surface roughness in smaller parts divided from the whole AFM images was studied, compared with the results of actual AFM measurements of the same scan scales.     

On the relation between correlation dimension,approximate entropy and sample entropy parameters,and a fast algorithm for their calculation

We explore the relation between correlation dimension, approximate entropy and sample entropy parameters, which are commonly used in nonlinear systems analysis. Using theoretical considerations we identify the points which are shared by all these complexity algorithms and show explicitly that the above parameters are intimately connected and mutually interdependent. A new geometrical interpretation of sample entropy and correlation dimension is provided and the consequences for the interpretation of sample entropy, its relative consistency and some of the algorithms for parameter selection for this quantity are discussed. To get an exact algorithmic relation between the three parameters we construct a very fast algorithm for simultaneous calculations of the above, which uses the full time series as the source of templates, rather than the usual 10%. This algorithm can be used in medical applications of complexity theory, as it can calculate all three parameters for a realistic recording of 10⁴${10}^4$ points within minutes with the use of an average notebook computer.     

介质pH对银基上4-甲基-4H-3-巯基-1,2,4-三氮唑成膜结构和缓蚀性能影响的SERS和电化学研究

在不同pH介质中,缓蚀试剂4-甲基-4H-3-巯基-1,2,4-三氮唑(4-MTTL)都能在银基底上形成自组装膜。SERS光谱表明:当pH=3时,4-MTTL分子是以硫醇式,通过两个氮原子为吸附位点,以较平躺方式在银表面构筑自组装膜;当介质为pH=7和pH=11时,4-MTTL以硫醇式,通过氮和硫原子为吸附位点倾斜或垂直方式作用于银表面。由于后者的吸附方式比前者更为垂直于表面,所以形成的膜中分子排列更为致密。电化学极化实验也表明,在pH=3的条件下,形成的4-MTTL单层有更正的腐蚀电位;在pH=11时,构筑的膜缓蚀能力强于pH=7的。并由电化学交流阻抗数据解析了相应的缓蚀机理。     

Electrochemical, morphological and microstructural characterization of carbon film resistor electrodes for application in electrochemical sensors

The electrochemical and microstructural properties of carbon film electrodes made from carbon film electrical resistors of 1.5, 15, 140 Ω and 2.0 kΩ nominal resistance have been investigated before and after electrochemical pre-treatment at +0.9 V vs SCE, in order to assess the potential use of these carbon film electrodes as electrochemical sensors and as substrates for sensors and biosensors. The results obtained are compared with those at electrodes made from previously investigated 2 Ω carbon film resistors. Cyclic voltammetry was performed in acetate buffer and phosphate buffer saline electrolytes and the kinetic parameters of the model redox system Fe(CN)₆^3−/4− obtained. The 1.5 Ω resistor electrodes show the best properties for sensor development with wide potential windows, similar electrochemical behaviour to those of 2 Ω and close-to-reversible kinetic parameters after electrochemical pre-treatment. The 15 and 140 Ω resistor electrodes show wide potential windows although with slower kinetics, whereas the 2.0 kΩ resistor electrodes show poor cyclic voltammetric profiles even after pre-treatment. Electrochemical impedance spectroscopy related these findings to the interfacial properties of the electrodes. Microstructural and morphological studies were carried out using contact mode Atomic Force Microscopy (AFM), Confocal Raman spectroscopy and X-ray diffraction. AFM showed more homogeneity of the films with lower nominal resistances, related to better electrochemical characteristics. X-ray diffraction and Confocal Raman spectroscopy indicate the existence of a graphitic structure in the carbon films.     

The interplay between molecular orientation, film morphology and luminescence properties of tetracene thin films on epitaxial AlOx/Ni3Al(1 1 1)

We report a systematic study of the interplay between molecular orientation, film morphology and luminescence properties of tetracene thin films on epitaxial alumina films on Ni₃Al(1 1 1), employing high resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), and photoluminescence spectroscopy (PL). If deposited at low temperatures, tetracene forms laterally disordered and compact films in which at least the first monolayer is oriented parallel to the substrate. For thicknesses in the range of 10 Å or below, these as-deposited films show no luminescence, while thicker films exhibit weak luminescence from higher layers. On annealing to 210 K, tetracene films dewet the AlO_x/Ni₃Al(1 1 1) surface and transform into an island morphology. At the same time, molecules tend to re-orient into a more upright configuration. In this island configuration, even thin films show luminescence. We can thus conclude that in spite of the insulating nature of the surface, the interaction of flat-lying tetracene molecules with AlO_x/Ni₃Al(1 1 1) is strong enough to provide at least one efficient non-radiative decay channel.     

Photoelectron spectroscopy study of the K-covered ZnO(1 0 1̄ 0) surface; annealing-induced changes in the electronic structure and the chemical composition

The electronic structure and the chemical composition of the K-covered ZnO(1 0 1̄ 0) surface at temperatures between 300 and 1200 K are investigated by X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Adsorption of K on ZnO(1 0 1̄ 0) at room temperature results in the formation of a two-dimensional disordered K overlayer and induces 0.2 eV downward bending of the substrate’s bands going from the bulk to the surface. Upon annealing the K-covered surface, initial downward bending turns to upward bending with maximum bending of 0.5 eV at 700-800 K. The thermally induced migration of the bulk O atoms and the resultant increase in the number of the O atoms on the surface is responsible for upward bending on the annealed surface. The accumulated O atoms interact with the predeposited K atoms on the surface to form non-stoichiometric K-O complexes with the O/K atomic ratio being 1.6-1.8 in the temperature range between 600 and 1000 K.     

Study of the interactions between the overlayer and the substrate in the early stages of palladium growth on TiO2(1 1 0)

The interaction between palladium and the (1 1 0) surface of a TiO₂ single crystal and the electronic properties of the system were studied by means of photoelectron spectroscopy (core levels and valence band) and resonant photoemission for Pd coverage in the sub- and monolayer range. We performed the metal depositions at room temperature. Similarly to copper, platinum and rhodium, palladium does not reduce titanium, has metallic character already from a quite early deposition, grows with a 3D-island mode and the interactions between palladium and TiO₂ are very weak. Annealing treatments at 400 °C provoke a change in the morphology of the palladium clusters and the formation of islands characterized by a higher ratio between volume and area in contact with the substrate.