Yellowing tendency of ozonated cotton fabric and ways to prevent this undesirable side effect

This paper provides a general framework for studying the yellowing tendency of ozonated cotton fabric. Yellowing tendency of ozonated cotton fabric and ways to prevent this situation was examined extensively. For this purpose, five different treatments (hot/cold rinsing, washing, reductive washing, catalase treatment) were performed after ozonation. It was found that performing any kind of treatment was significantly important for preventing yellowing of ozonated cotton fabric during storage.     

Stochastic multiscale analysis in hydrodynamic lubrication

A stochastic multiscale analysis framework is developed for hydrodynamic lubrication problems with random surface roughness. The approach is based on a multi‐resolution computational strategy wherein the deterministic solution of the multiscale problem for each random surface realization is achieved through a coarse‐scale analysis with a local upscaling that is achieved through homogenization theory. The stochastic nature of this solution because of the underlying randomness is then characterized through local and global quantities of interest, accompanied by a detailed discussion regarding suitable choices of the numerical parameters in order to achieve a desired stochastic predictive capability while ensuring numerical efficiency. Finally, models of the stochastic interface response are constructed, and their performance is demonstrated for representative problem settings. Overall, the developed approach offers a computational framework, which can essentially predict the significant influence of interface heterogeneity in the absence of a strict scale separation. Copyright © 2017 John Wiley & Sons, Ltd.     

Artificial neural networks solution to display residual hoop stress field encircling a split-sleeve cold expanded aircraft fastener hole

Cold expansion of holes is a technique, generating intricate three-dimensional residual stresses around fastener holes essentially vital for airplane fatigue resistance. In this work, attention was given to Artificial Neural Networks (ANN) modeling to build up and train simulations of stress topography surrounding a 4% expanded hole. For this, experimental data of recently abridged step drilling-Fourier method was employed. At input layer of ANN; information available for steps through thickness and radial directions, angular variation around the hole, and at output layer, residual hoop stresses were exercised to train and test multilayered, hierarchically connected and directed networks with varying number of hidden layers. It was shown that Levenberg–Marquardt (LM) model with 9 neurons in hidden layer yielded the best of the results, as error percentages were remarkably small both in training and testing sequences. Several results of step drilling-Fourier solution (ATÖzdemir method), diffraction methods and current ANN predictions were overlaid and similarities in residual stress distributions perceived to valid only at regions where strain gradient was not changing precipitously. Nevertheless, best fit to strain data at confusing zones was achieved after ANN modeling.     

Micro-texture design and optimization in hydrodynamic lubrication via two-scale analysis

A novel computational surface engineering framework is developed to design micro-textures which can optimize the macroscopic response of hydrodynamically lubricated interfaces. All macroscopic objectives are formulated and analyzed within a homogenization-based two-scale setting and the micro-texture design is achieved through topology optimization schemes. Two non-standard aspects of this multiscale optimization problem, namely the temporal and spatial variations in the homogenized response of the micro-texture, are individually addressed. Extensive numerical investigations demonstrate the ability of the framework to deliver optimal micro-texture designs as well as the influence of major problem parameters.     

Characterisation and optical vapour sensing properties of PMMA thin films

The present article reports on the characterisation of spin coated thin films of poly (methyl methacrylate) (PMMA) for their use in organic vapour sensing application. Thin film properties of PMMA are studied by UV–visible spectroscopy, atomic force microscopy and surface plasmon resonance (SPR) technique. Results obtained show that homogeneous thin films with thickness in the range between 6 and 15 nm have been successfully prepared when films were spun at speeds between 1000?5000 rpm. Using SPR technique, the sensing properties of the spun films were studied on exposures to several halohydrocarbons including chloroform, dichloromethane and trichloroethylene. Data from measured kinetic response have been used to evaluate the sensitivity of the studied films to the various analyte molecules in terms of normalised response (%) per unit concentration (ppm). The highest PMMA film sensitivity of 0.067 normalised response per ppm was observed for chloroform vapour, for films spun at 1000 rpm. The high film's sensitivity to chloroform vapour was ascribed mainly to its solubility parameter and molar volume values. Effect of film thickness on the vapour sensing properties is also discussed.     

Microstructure–property relationship in textured ZnO-based varistors

The relationship between microstructure texturing and electrical characteristics of a ZnO-based varistor system was investigated in comparison with a varistor system having the same chemical composition but conventional microstructure. Highly textured ZnO-based varistors were produced via the templated grain growth (TGG) technique. Stereological analysis, electron back-scattered diffractometry (EBSD) and X-ray diffractometry (XRD) were conducted to analyze texture development and orientation distribution. The degree of orientation, r, calculated from the (0 0 0 1) EBSD pole figure, was 0.34; the texture fraction, f (Lotgering factor), calculated from the XRD data, was 0.98 for the samples produced via TGG. The threshold voltages were found to be anisotropic, consistent with the observed morphological texture. The non-linear coefficients, α, did not exhibit a significant difference as a function of direction, even in the highly textured samples. However, different types of grain boundary characteristics depending on the direction were identified with 0.42, 0.69 and 1.14 eV Schottky barrier heights.     

Electrocatalytic Performances of Carbon Supported Metallophthalocyanine and Pt/Metallophthalocyanine Catalysts Towards Dioxygen Reduction in Acidic Medium

Electrocatalytic performances of phthalocyanines (Pcs) involving N-benzyl-4-phenyloxyacetamide moieties, dispersed on a high-surface area carbon substrate, Vulcan XC-72 (VC) and Nafion (Nf), towards oxygen reduction in acidic medium were determined and compared. The VC/Nf/CoPc(5) catalyst showed much higher catalytic activity than those of the other Pc(1–4)-based catalysts (H₂Pc 1, ZnPc 2, NiPc 3 and CuPc 4) and that of unsubstituted CoPc-based one. The comparison of the performance of VC/Nf/Pt-5 dual catalyst with that of VC/Nf/Pt one indicated that the former can be a good alternative to the latter as a cathode catalyst both in direct methanol and H₂/O₂ fuel cell applications.     

Microstructural, geochemical and geomechanical properties of caliche deposits from the Adana Basin, Turkey

The 1998 Ceyhan (Adana, Turkey) earthquake caused major damage to construction on caliche formations. Caliche (a heterogenous secondary calcium carbonate deposit formed in arid and semi-arid regions) is widespread in the Adana area. The paper distinguishes three types of caliche: massive, containing vegetation remains and containing gravel. The porosity, water absorption and unconfined compressive strength of these three groups of caliche were determined. The compressive strengths are low compared to caliches in other areas—an important consideration as Adana is the fourth largest city in Turkey.