Red luminescence of spherical CuxZn1−xS semiconductor nanoparticles using 2-mercaptoethanol as capping agent

Cu²⁺-doped (0–2 at%) ZnS nanoparticles stabilized by 2-mercaptoethanol (2-ME) were successfully prepared using wet precipitation route in aqueous solution. The structural and optical characteristics were studied by various techniques. XRD pattern showed zinc blende cubic structure of Cu²⁺-doped ZnS with grain size of 4±0.5 nm. Spherical shape and well distribution of particles is confirmed by TEM, SEM and STM microscopy. Copper doping were identified by elemental dispersive (EDS) spectrometry. UV–vis spectroscopy revealed strong confinement effect due to blue shift in absorption shoulder peak as compared to bulk ZnS. Red luminescence band at～657 nm on Cu²⁺ doping may be arising from recombination of electrons at sulfur vacancies (V_s) and Cu(t₂) states formed at ZnS band gap. Optimum concentration of 0.25 at% (red band) of Cu²⁺ doping was selected by the observed enhanced PL emission.     

A Unified Approach to Similarity Measures Between Intuitionistic Fuzzy Sets

Two general classes of similarity measures between intuitionistic fuzzy sets (hereafter IFSs) are introduced. Some properties of these measures are investigated with respect to some well‐known reasonable axioms. It is shown that several similarity measures between IFSs introduced elsewhere can be expressed by these definitions as special cases. Some illustrative and practical examples from the areas of pattern recognition, fuzzy clustering analysis, and decision making will be used to investigate the performance of the proposed measures with respect to some common measures. The results indicate that these measures can provide a useful way for measuring the degree of similarity between IFSs and that the proposed approach performs well in pattern recognition, fuzzy clustering, and decision making.     

Microstructure, property and processing relation in gradient porous cathode of solid oxide fuel cells using statistical continuum mechanics

This paper investigates the relation between microstructure, macroscopic transport properties, and fabrication processing for a gradient porous cathode of solid oxide fuel cells (SOFCs). Functionally graded porous cathode with smooth variations in pore size is composed of lanthanum strontium manganite (LSM) fabricated on yttria stabilized zirconia (YSZ) electrolyte substrate using a multi-step spray pyrolysis (SP) technique at various deposition conditions. Two-dimensional (2D) serial-sections of the gradient porous microstructure obtained by FIB-SEM are fully characterized using statistical correlation functions. Results of statistical analysis of the microstructures revealed that the SP processing technique is capable of generating statistically identical and homogeneous microstructures with smooth gradient in pore size resulting from changing the processing parameters. Strong contrast statistical approach is also used to predict the in-plane temperature dependent effective electrical conductivity of the gradient porous cathode and the results are compared to the experimental data.     

No-chatter model-free sliding mode control for synchronization of chaotic fractional-order systems with application in image encryption

Multimedia Tools and Applications - Synchronization of different Chaotic dynamical systems is one of the main issues in engineering which has a lot of applications in applied sciences like secure...     

Experimental Investigation Into the Fatigue of Welded Stiffened 350WT Steel Plates Using Neutron Diffraction Method

Abstract: The propagation of fatigue cracks under constant amplitude cyclic loading was studied in welded stiffened steel plates. The residual stresses in the stiffened plates were measured using the neutron diffraction strain‐scanning technique. The neutron diffraction measurements indicated that, in general, the residual stresses were tensile near the welded stiffeners and compressive between the stiffeners and ahead of the starter notch tips. Fatigue testing indicated that the fatigue crack growth rates of the stiffened plates were, in general, lower than that of a corresponding unstiffened plate, especially near the notch tips, where compressive residual stresses existed. An analytical method, using Green's function, was developed to predict the fatigue crack growth rates. Reasonable accuracy was obtained.     

Ductile crack growth and constraint in pipelines subject to combined loadings

An important failure mode of offshore pipelines is ductile fracture of the pipe wall triggered by a hypothetical welding defect. In this study, pipelines having an external part-through semi-circumferential crack of various sizes, subject to combined internal pressure and inelastic bending are considered. This is done to assess the response of pipelines during both their installation and operational conditions. Detailed 3D nonlinear finite element (FE) models of pipelines are developed. A row of elements ahead of the initial crack front are modeled using a voided plasticity material model, which enables simulation of crack growth and the subsequent fracture failure mode (denoted by the critical curvature, κ_crit). After discussing the typical response characteristics of such pipelines, the FE model is used to parametrically investigate the influence of varying pipe and crack dimensions, and also the internal pressure levels, on κ_crit. In the second part of this paper, the crack tip constraint ahead of a growing crack in such pipes is evaluated and systematically compared to the crack tip constraint of both the traditionally used deeply cracked Single Edge Notch Bend (SENB) specimens and the constraint-matched Single Edge Notch Tensile (SENT) specimens. This is achieved by comparing the crack resistance curves (R-curves) along with stress triaxiality and equivalent plastic strain fields evaluated ahead of a growing crack of the three systems. The results present grounds for justification of usage of SENT specimens in fracture assessment of such pipes as an alternative to the traditional overly conservative SENB specimens.     

Hot tensile properties and microstructural evolution of as cast NiTi and NiTiCu shape memory alloys

Hot tensile properties of as cast NiTi and NiTiCu shape memory alloys were investigated by hot tensile test at temperature range of 700–1100 °C using the strain rate of 0.1 s⁻¹. The NiTi alloy exhibited a maximum hot ductility at temperature range of 750–1000 °C, while the NiTiCu alloy showed it at temperature range of 800–1000 °C. It was found that at temperatures less than 750 °C, diffusion-assisted deformation mechanism was inactive leading to semi-brittle type of failure and limited ductility in both alloys. Also it was found that at temperature range of 800–1000 °C, dynamic recrystallization is dominant leading to high ductility. Likewise, the fracture surface of the specimens presenting the maximum hot ductility showed an ideal type of ductile rupture in which they gradually pulled out to a fine point. On the other hand, the decline in ductility occurred at the temperatures above 1000 °C was attributed to the liquid phase formation leading to interdendritic and intergranular type of fracture.     

In situ synthesis of hydroxyapatite-grafted titanium nanotube composite

ABSTRACT

The present study is an investigation to demonstrate the effectiveness of in situ approach in the synthesis of hydroxyapatite-grafted titanium nanotube composite (HA-TNT). This method involves combining the process of HA sol–gel and rapid breakdown anodisation of titanium in a novel solution consisting of NaCl and N₃PO₄. This new synthesis approach produced a uniform dispersion of Anatase and Rutile phases of TiO₂ nanotubes with minimal agglomeration in the matrix of crystalline HA. The characterisation of homogenised HA-TNT composite was investigated via field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM) and X-ray diffraction (XRD). FESEM and TEM images indicated the nanostructure of composite with TiO₂ nanotube diameter of approximately 10 nm. XRD and EDS analyses confirmed the formation of HA crystalline with the Ca/P ratio of 1.58 and formation of Anatase and Rutile phase of TiO₂ nanotubes.