The Effect of Different Polishing Sequences on the Adhesion of Streptococcus mutans to Feldspathic Porcelain

The aim of this research was to determine whether extra-oral surface treatments on feldspathic porcelain surfaces influence initial adhesion of Streptococcus mutans. Ninety-six porcelain specimen discs were fabricated and divided into six equal groups according to surface treatment: fine-grit diamond polishing (Group 1); self-glazing (Group 2); overglazing (Group 3); overglazing followed by a finishing procedure and then overglazing (Group 4); Pearl Surface polishing (Group 5); and Diamond Twist SCL^TM polishing (Group 6). Surface roughness and hydrophobicity were assessed. An S. mutans suspension was incubated on each specimen group and evaluated. A one-way analysis of variance, post-hoc Tukey honestly significantly different test, Friedman test, and t-test were used for statistical analysis. Group 1 showed the highest surface roughness (p < 0.001) and bacterial adhesion (p < 0.05). Groups 5 and 6 specimen surfaces presented significantly higher contact angles (p < 0.05). Group 1 had the highest S. mutans adhesion, followed by Groups 3, 5, 6, 2, and 4 (p < 0.05). Reglazing after grinding may therefore decrease bacterial adhesion beneficially.     

Analysis of the benefit generated by using fuzzy numbers in a TOPSIS model developed for machine tool selection problems

Selection of the appropriate machine tools for a manufacturing company is a very important but at the same time a complex and difficult problem because of the availability of wide-ranging alternatives and similarities among machine tools. In the literature, various machine tool selection procedures are developed. The developed procedures mainly use Multi Criteria Decision Making (MCDM) methods. In the literature, fuzzy MCDM models, in which fuzzy numbers are used instead of crisp values, are proposed to deal with the vagueness and imprecision inherent in the machine tool selection problem. Although, the available studies in the literature developed various fuzzy models, they do not propose any approaches to measure the benefit generated by incorporating fuzziness in their selection models. This paper aims to fill this gap by trying to quantify the level of benefit provided by employing the fuzzy numbers in the MCDM models. Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is used as the MCDM approach to rank the machine tools in this paper. In the paper, by increasing the fuzziness level steadily in the fuzzy numbers, the obtained machine tool rankings are compared with the ranking obtained with the crisp values. The statistical significance of the differences between the ranks is calculated using Spearman's rank-correlation coefficient. It can be observed from the results that as the vagueness and imprecison increases, fuzzy numbers instead of crisp numbers should be used. On the other hand, in sitiuations where there is a low level of fuzziness or the average value of the fuzzy number can be guessed, using crisp numbers will be more than adequate.     

Torsional dynamics of coaxial nanotubes with different lengths in viscoelastic medium

Microsystem Technologies - Torsional vibration analysis of double-walled carbon nanotube system embedded in viscoelastic medium is carried out in the present work. Hamilton’s Principle is...     

Synthesis,Characterization, and Thermoelectric Properties of Electrospun Boron-Doped Barium-Stabilized Bismuth-Cobalt Oxide Nanoceramics

In this study, the boron-doped barium-stabilized bismuth cobalt oxide thermoelectric nanocrystalline ceramic powders were produced by the polymeric precursor technique. The powders were characterized by X-ray diffraction, scanning electron microscopy, and the physical properties measurement system. The X-ray diffraction results showed that these patterns have mixture of two phases as face-centered cubic and body-centered cubic. Values of the crystallite size, the dislocation density, and the microstrain were calculated by the Scherrer equation. According to these values, the crystallite size decreased from 60 to 51 nm with the boron addition in the boron-undoped and boron-doped samples, respectively. The scanning electron microscope results showed that nanograins are rarely seen in the boron-undoped samples, but nanograins turn into needle-like and layered structures with boron addition. The diameters distribution of nanofibers was calculated. The average diameter of the boron-doped sample is smaller than the boron-undoped sample. The physical properties measurement system values showed that the electrical and thermal conductivity, the Seebeck coefficient, and the figure of merit increased with the temperature rise for both samples. The boron-doping effect increased the electrical and thermal conductivity, decreased the Seebeck coefficient, and decreased the figure of merit.     

Structural and Magnetic Properties of (Al/Mg) Co-doped Nano ZnO

The doped ZnO systems Zn_1?x?y Mg _x Al _y O (ZMAO) (x=0, 0.05, 0.1 and y=0, 0.05 and 0.1) were prepared as polycrystalline nanoparticle by a simple sol–gel process. Structural and microstructural analyses were carried out applying X-ray diffraction (XRD) and Rietveld method. Analysis showed that Mg²⁺ and Al³⁺ replace Zn²⁺ substitutionally yielding ZMAO single phase. Replacing Zn⁺² affects the lattice parameters in opposite ways, the parameter c decreases while a increases with an overall decrease in the ratio c/a, which deviates the ZMAO lattice gradually from the wurtzite hexagonal structure. The magnetization versus temperature was measured with zero-field cooled (ZFC) and field cooled (FC) at different applied fields. Also, measurement of magnetization versus applied field was carried out at different temperatures. The system exhibits ferromagnetic properties at room temperature. The saturation magnetization increases as Al doped amount increases.     

Development of a quick credibility scoring decision support system using fuzzy TOPSIS

In this study, a quick credibility scoring decision support system is developed for the banks to determine the credibility of manufacturing firms in Turkey. The proposed decision support system is expected to be used by the banks when they want to determine whether an applicant firm is worth a detailed credit check or not. Using such a quick credit scoring decision model reduces the banks’ workload. The proposed credit scoring model is based on the financial ratios and fuzzy TOPSIS approach. It obtains two separate scores which reflect the attractiveness of manufacturing industries within the overall economy and manufacturing firms’ performance with respect to its competitors belonging to the same industry. These two scores are then used to determine the credibility of applicant manufacturing firms. The developed decision support system is tested with various real cases and satisfactory results are obtained. An application is also provided in the paper for illustrative purposes.     

Effect of the ozonation process on the dyeability of mohair fibres

This work has focused on the use of ozonation in order to improve the dyeability of mohair fibres. The study was carried out using a known concentration of ozone and involved process parameters such as wet pick‐up, level of pH and treatment time. The effect of fibre ozonation was assessed in terms of colour, and test samples were also evaluated using scanning electron microscopy and Fourier transform–infrared spectroscopy. The optimum conditions of the ozonation process were determined as 60% wet pick‐up, pH 7 and 30 min. According to the experimental results, it can be concluded that ozonated mohair fibres can be dyed both at 90 and 80 °C with all dye classes without causing any decrease in colour yield. Dyeing kinetics and thermodynamics were also studied and it was demonstrated that the rate constant and the standard affinity of the ozonated sample increased.