Chemical composition dependence of exposure buildup factors for some polymers

Exposure buildup factors for some polymers such as poly-acrylo-nitrile (PAN), poly-methyl-acrylate (PMA), poly-vinyl-chloride (PVC), synthetic rubber (SR), tetra-fluro-ethylene (Teflon) have been computed using the G.P. fitting method in the energy range of 0.015–15.0 MeV, up to the penetration of 40 mean free paths (mfp). The variation of exposure buildup factors for all the selected polymers with incident photon energy at the fixed penetration depths has been studied, mainly emphasizing on chemical composition (equivalent atomic number) of the selected polymers. It has been observed that for the lower penetration depths (below 10 mfp), the exposure buildup factor decreases with the increase in equivalent atomic number of the selected polymers at all the incident photon energies. However, at the penetration depth of 10 mfp and incident photon energy above 3 MeV, the exposure buildup factor becomes almost independent of the equivalent atomic number of the selected polymers. Further, above the fixed penetration depth of 15 mfp of the selected polymers and above the incident photon energy of 3 MeV, reversal in the trend has been observed, i.e., the exposure buildup factor increases with the increase in equivalent atomic number.     

Solvothermal synthesis of Hg1−xCdxTe nanostructures—Their structural and optical properties

This article describes a facile, low-cost, solution-phase approach to the large-scale preparation of Hg_1−xCd_xTe nanostructures of different shapes such as nanorods, quantum dots, hexagonal cubes of different sizes and different compositions at a growth temperature of 180 °C using an air stable Te source by solvothermal technique. The XRD spectrum shows that the crystals are cubic in their basic structure and reveals the variation in lattice constant as a function of composition. The size and morphology of the products were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The formation of irregular shaped particles and few nano-rods in the present synthesis is attributed to the cetyl trimethylammonium bromide (CTAB). The room temperature FTIR absorption and PL studies for a compositon of x = 0.8 gives a band gap of 1.1 eV and a broad emission in NIR region (0.5-0.9 eV) with all bands attributed to surface defects.     

Quantitative characterization of the microstructure of two-phase TiB<Subscript>2</Subscript>+Al<Subscript>2</Subscript>O<Subscript>3</Subscript> ceramics using mean integral curvature

Two-phase TiB₂+Al₂O₃ ceramics with an interconnected or dispersed TiB₂ (minor)-phase microstructure can be produced by variations in processing parameters. A standard method of quantitative characterization of the microstructural bias, i.e., the degree of TiB₂ phase connectivity relative to its dispersion, is necessary to comprehend the mechanism(s) controlling the evolution of microstructure during processing. In this work, techniques derived from stereology were used to quantitatively characterize the microstructural bias on the basis of the connectivity and dispersion of the minor phase (TiB₂), in addition to the size of the TiB₂- and Al₂O₃-phase regions. The mean integral curvature calculated using the area particle-count and area tangent-count methods was determined to quantitatively describe the connectivity of the TiB₂ minor phase around the Al₂O₃ major phase. The results illustrate that, in spite of partial and mixed bias, integral curvature measurements (particularly those based on the area tangent-count method) provide a reliable and reproducible means for quantitative characterization of the two-phase biased microstructure.     

Influence of TCSC on congestion and spot price in electricity market with bilateral contract

This paper presents a quantitative analysis of the effect of TCSC on congestion and spot price in deregulated electricity markets. The paper could also be considered as a comprehensive tutorial on the influence of TCSC in electricity market. A voluntary pool market, where the market participants can trade electricity either via a pool or through bilateral contracts is considered. The electricity market is modeled in an optimal power flow framework with the objective of maximizing the social welfare. In such formulation, the Lagrange operators associated with the equality constraints associated with real power balance give the spot prices of energy at each bus of the system. Studies are carried out with and without TCSC at peak and low loading conditions to capture the influence and to see the effectiveness of TCSC at different loading conditions. The paper further explores the effect of TCSC compensation level on the spot prices and the congestion under varying pool and bilateral loading conditions. A 5-bus test system is used for numerical studies and to showcase the influence of TCSC in an electricity market environment.     

Thermal analysis of buoyancy-motivated Casson fluid flow with time-independent chemical reaction under Lorentz forces

The present research study examines the magneto-hydrodynamic natural convection visco-elastic boundary layer of Casson fluid past a nonlinear stretching sheet with Joule and viscous dissipation effects under the influence of chemical reaction. To differentiate the visco-elastic nature of Casson fluid with Newtonian fluids, an established Casson model is considered. The present physical problem is modeled by utilizing the considered geometry. The resulting system of coupled nonlinear partial differential equations is reduced to a system of nonlinear ordinary differential equations by applying suitable similarity transformations. Numerical solutions of these reduced nondimensional governing flow field equations are obtained by applying the Runge-Kutta integration scheme with the shooting method (RK-4). The physical behavior of different control parameters is described through graphs and tables. The present study describes that the velocity and temperature profiles decreased for increasing values of Casson fluid parameter. Velocity field diminished for the increasing nonlinear parameter whereas velocity profile magnified for increasing free convection parameter. Thermal field enhanced with increasing magnetic parameter in the flow regime. The concentration profile decreased for the rising values of the chemical reaction parameter. The magnitude of the skin-friction coefficient enhanced with increasing magnetic parameter. Increasing Eckert number increases the heat transfer rate and increasing chemical reaction parameter magnifies the mass transfer rate. Finally, the similarity results presented in this article are excellently matched with previously available solutions in the literature.     

Study of Unrecovered Strain and Critical Stresses in One-Way Shape Memory Nitinol

Unique thermomechanical properties of Nitinol known as shape memory and superelasticity make it applicable for different fields such as biomedical, structural, and aerospace engineering. These unique properties are due to the comparatively large recoverable strain, which is being produced in a martensitic phase transformation. However, under certain ranges of stresses and temperatures, Nitinol wires exhibit unrecovered strain. For cyclic applications, it is important to understand the strain behavior of Nitinol wires. In this study, the unrecovered strain of different Nitinol wire diameters was investigated using constant stress experiment. Uniaxial tensile test has been also performed to find the range of critical stresses. It was observed that the unrecovered strain produced in the first loading-unloading cycle affects the total strain in the subsequent cycles. Moreover, a critical range of stress was found beyond which the unrecovered strain was negligible while the wires heated up to the range of 70-80°C, depending on the wire diameters. The unrecovered strain of wire diameters of 0.19 mm and less was found to be sensitive to the critical stress. On the other hand, for wire diameters bigger than 0.19 mm this connection between the unrecovered strain and the critical stress was not observed for the same range of heating temperature.