Elastic Modulus-Porosity Relation in Polycrystalline Rare-Earth Oxides

Many equations have been previously proposed to describe the elastic modulus-porosity relation of brittle solids. The equations arc not applicable to all materials over a wide range of porosity. A new equation representing elastic modulus-porosity relation of brittle solids has been proposed. It has been shown that the proposed equation describes best the Young's modulus-porosity data of six rare-earth oxides over a wide range of porosity reported by previous investigators. The equation suggests that there was some kind of ordered packing in all the oxides.     

Anomalous roughness of fracture surfaces in 2D fuse models

We study anomalous scaling and multiscaling of two-dimensional crack profiles in the random fuse model using both periodic and open boundary conditions. Our large scale and extensively sampled numerical results reveal the importance of crack branching and coalescence of microcracks, which induce jumps in the solid-on-solid crack profiles. Removal of overhangs (jumps) in the crack profiles eliminates the multiscaling observed in earlier studies and reduces anomalous scaling. We find that the probability density distribution ${p(\Delta h(\ell))}$ of the height differences ${\Delta h(\ell) = [h(x+\ell) - h(x)]}$ of the crack profile obtained after removing the jumps in the profiles has the scaling form ${p(\Delta h(\ell)) = \langle\Delta h^2(\ell)\rangle^{-1/2} ~f\left(\frac{\Delta h(\ell)}{\langle\Delta h^2(\ell)\rangle^{1/2}}\right)}$ , and follows a Gaussian distribution even for small bin sizes ?. The anomalous scaling can be summarized with the scaling relation ${\left[\frac{\langle\Delta h^2(\ell)\rangle^{1/2}}{\langle\Delta h^2(L/2)\rangle^{1/2}}\right]^{1/\zeta_{loc}} + \frac{(\ell-L/2)^2}{(L/2)^2} = 1}$ , where ${\langle\Delta h^2(L/2)\rangle^{1/2}\sim L^{\zeta}}$ and L is the system size.     

On the Constraint Factor and Tabor Coefficient Pertinent to Spherical Indentation

Measuring the uniaxial stress–strain response from indentation testing has been of great interest to the materials community ever since the seminal work on spherical indentation by David Tabor. In this regard, spherical indentation is the primary choice due to the ability to access a wide range of strains in a single test. While indentation testing is fairly simple to perform, the conversion factors required to calculate the uniaxial flow stress from hardness, which is commonly referred to as constraint factor and uniaxial strain from indentation contact radius and ball radius, which is called the Tabor coefficient, are not necessarily constant and most of the prior work involves assumptions about one of these conversion factors to calculate the other. In this work, we present a finite element analysis-based approach to independently determine the constraint factor and Tabor coefficient in the fully plastic indentation regime which is a pre-requisite for this analysis. The criteria to determine whether fully plastic indentation regime is satisfied has also been presented. The proposed approach has been validated by comparing the uniaxial stress–strain response from spherical indentation tests on OFHC copper and the data obtained by conventional uniaxial testing. Excellent agreement has been found between the two approaches which can be readily applied for measuring the uniaxial stress–strain response of coatings which is otherwise difficult to determine.     

Structural topology synthesis with dynamics and nonlinearities using equivalent linear systems

Topology optimization for nonlinear and dynamic problems is expensive because of the necessity to solve the equations of motion at every optimization iteration in order to evaluate the objective function and constraints. In this work, an iterative methodology is developed using the concept of an equivalent linear system for the topology synthesis of structures undergoing nonlinear and dynamic response, using minimal nonlinear response evaluations. The approach uses equivalent loads obtained from nonlinear dynamic analysis to perform optimization iterations, during the course of which the nonlinear and dynamic system is continuously approximated. In this process, the optimization is decoupled from the nonlinear dynamic analysis. Results are presented for various kinds of nonlinear and dynamic problems showing the effectiveness of the developed approach.     

Elastic properties of porous polycrystalline thoria—A relook

Elastic constant–porosity relation for polycrystalline thoria reported by previous researchers has been reanalyzed on the basis of the Mori–Tanaka mean field approach and a power law dependence of moduli with porosity. It indicates that the shear modulus dependence on Young's modulus is possibly related to the sintering characteristics of the material rather than pore morphology. A new method has been suggested for predicting variations of elastic properties and porosity with the progress in sintering of thoria based on experimental data at a single porosity only. The predicted values agree with the experimental data quite well.     

Sulfosuccination of Methyl Ricinoleate and Methyl 12-Hydroxy Stearate Derived from Renewable Castor Oil and Evaluation of Their Surface Properties

Sulfosuccination of castor oil-derived methyl ricinoleate and methyl 12-hydroxy stearate have been carried out in the present work. Synthesis involves malenization of secondary alcohol of methyl ricinoleate/methyl 12-hydroxy stearate followed by sulfonation of maleic monoester to generate double-headed dianionic surfactant with carboxylate and sulfosuccinate functionalities in the head group region. Various reaction conditions were optimized for maximum production of these two sulfosuccinates. Both compounds were evaluated for surface and detergency properties. The surface tension study indicated that the critical micelle concentration of sulfosuccinated methyl ricinoleate and methyl 12-hydroxy stearate is 0.26 and 0.11 mM, respectively. The detergency property of these two surfactants indicated that they were excellent in wetting time emulsification and Ca-tolerance. However, these two surfactants exhibited very poor foam height and foam stability.     

Chemical Synthesis of PEDOT–Au Nanocomposite

In this work, gold-incorporated polyethylenedioxythiophene nanocomposite material has been synthesized chemically, employing reverse emulsion polymerization method. Infrared and Raman spectroscopic studies revealed that the polymerization of ethylenedioxythiophene leads to the formation of polymer polyethylenedioxythiophene incorporating gold nanoparticles. Scanning electron microscope studies showed the formation of polymer nanorods of 50–100 nm diameter and the X-ray diffraction analysis clearly indicates the presence of gold nanoparticles of 50 nm in size.     

A Novel Method of Predicting Ultrasonic and Elastic Properties of Isotropic Ceramic Materials after Sintering from the Properties of Partially Sintered or Green Compacts

A novel method for predicting the porosity dependence of ultrasonic and elastic properties of isotropic ceramics after sintering based on the properties of green or partially sintered compacts has been proposed. The method is based on the observation that the ratio of ultrasonic shear wave to longitudinal wave velocity is a function of porosity only and varies linearly with the longitudinal wave velocity. It is also shown that the predicted trend of variation of Poisson's ratio with porosity agrees with the predictions of the Mori–Tanaka mean field approach. The method can be used as a quality control tool during the preparation of ceramic materials.     

Novel low-temperature growth of SnO2 nanowires and their gas-sensing properties

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Compact UWB flexible elliptical CPW‐fed antenna with triple notch bands for wireless communications

A coplanar waveguide (CPW)‐fed flexible elliptical antenna with triple band notched characteristics is presented in this article. The designed antenna consists of an elliptical patch and slots incorporated CPW feed line to cover the bandwidth requirements for ultra‐wideband (UWB) applications. The designed UWB antenna has a fractional bandwidth of about 166.19% (1.20‐13 GHz) with a center frequency of 7.1 GHz in simulation and about 170.10% (1.05‐13 GHz) with a center frequency of 7.025 GHz in measurement. The overall dimension of the proposed flexible antenna is 45 × 35 × 0.6 mm³. The triple notched bands are realized by designing with circular shaped split‐ring‐resonators (SRRs) and defected ground structure (DGS). According to the measurement, first notched band (2.0? 2.70 GHz) is generated for rejecting 2.4 GHz WLAN by introducing a single circular ST‐SRR on the radiating patch. The second notch (3.45‐3.80 GHz) is obtained by embedding another circular ST‐SRR on the patch to mitigate the interference of 3.5 GHz Wi‐MAX system. Finally, due to presence of DGS, third notch (5.15‐6.20 GHz) is produced which suppresses the interference from 5.5 GHz Wi‐MAX and 5.2/5.8 GHz WLAN systems. The proposed antenna offers excellent performance in different flexible conditions that confirm its applicability on curved surfaces for UWB systems.