Thermomechanical processing of aluminium-based particulate composites

Thermomechanical processing of aluminium-based particulate composites containing dispersions of various soft and hard particles such as graphite, zircon, glass, alumina and mica in aluminium alloy matrices, with a view to improving strength and ductility for structural applications, has been discussed. The existing literature on the subject has been critically reviewed and analysed, and broad guidelines for optimum thermomechanical processing have been presented. Considerable improvements in strength and ductility of these composite materials have been reported after rolling, forging and extrusion due to fragmentation/fibrization of particles together with the refinement of matrix microstructure, annihilation of defects such as porosity, and texture hardening, etc. The influence of process variables, and of volume fraction, size and morphology of the particles on the strengthening mechanisms, fracture toughness and work-hardening behaviour of worked composites has been discussed.     

In situ generated diphenylsiloxane‐polyimide adduct‐based nanocomposites

Arylsiloxane was incorporated into polyimide (PI) via electronic interaction with polyamic acid (PAA)/PI, and a wide spectrum of properties were evaluated for different compositions. The samples prepared with relatively low concentrations (0.0001–0.1%) of oligomers showed unusual synergism, which is attributed to the generation of nanostructures dispersed in the continuous PI matrix. The incorporation of siloxane with bulky phenyl groups contributed to enhanced thermal stability as determined by thermogravimetric analysis. Water uptake and methanol absorption by these composites were evaluated and correlated with the underlying micro‐ and nanostructures. Fourier Transform Infrared (FTIR) spectroscopy was used to elucidate the probable reaction mechanism (including in situ polymerization of arylsilanol), and to study the synthetic aspects associated with the molecular composites and nanocomposites formation. POLYM. ENG. SCI., 45:142–152, 2005. © 2004 Society of Plastics Engineers     

Lateral crushing of square and rectangular tubes by non-orthogonally placed narrow width indenters

A study of the collapse behaviour of square or rectangular tubes subjected to transverse loading by narrow width indenters, placed in orthogonal and non-orthogonal positions is presented. Experiments were conducted on as-received aluminium tubes, wherein the tubes were compressed in an unsymmetrical and a symmetric arrangement. Typical load-compression curves and histories of the deforming specimens are presented. Based on experimental observations, an analysis which considers the energy absorbed in stationary and rolling plastic hinges is developed for typical cases of the two modes of tube collapse. Computed results of the hinge locations, deforming tube geometry and load-compression curves are presented in each case. These results show good agreement with the experimental observations.     

Magnetic and electrical properties of Al3+-substituted MgFe2O4

The structural, magnetic and electrical properties of the Al³⁺-substituted disordered spinel system Mg(Fe_2–x Al _x )O₄ have been investigated by X-ray diffraction, magnetization, a.c. susceptibility and electrical resistivity measurements. The cation distribution derived from the X-ray diffractometry data was found to agree very well with the cation distribution obtained through Mössbauer spectroscopy. The variation of saturation magnetization per formula unit as a function of aluminium context, x, has been satisfactorily explained on the basis of Neel's collinear spin model and the slight discrepancy between the observed and calculated n _B values can be explained in terms of a random canting model. The Néel temperatures calculated theoretically by applying molecular field theory agreed well with the experimentally determined values from thermal variation of susceptibility and electrical resistivity. An unusual metal-like thermo-electric behaviour was found for the compositions with x 0.3 which was attributed to the decrease in the Fe-Fe separation distance arising from aluminium substitution.     

Group II-VI semiconductor quantum dot heterojunction photodiode for mid wave infrared detection

In this article we report the development of 10×10 photodiode array by realizing heterojunction between mercury cadmium telluride (HgCdTe) quantum dot (diameter ~14 nm) and silicon responsive in mid wave infrared (MWIR) range (l=3—5 μm) at room temperature. Performance of this optical sensor has been evaluated experimentally and Detectivity of 1.6×108 cm /W has been achieved at spectral wavelength of 3.5 μm at 300 K. This work ascertains the compatibility of chemically synthesized HgCdTe quantum dots with commercially available direct injection type readout integrated circuits (ROIC) for the development of low cost large format MWIR focal plane array (FPA).     

Concurrence and three-tangle of the graph

In this article, we study the entanglement properties of two-qubit quantum states based on concurrence using the graph-theoretic approach. Entanglement properties of a density operator are obtained from the combinatorial Laplacian matrix which is constructed for a given graph. In the study of entanglement, we found that measure of entanglement is either \( \frac{1}{ |{E}| } \) or zero for simple graphs. We further propose a simple method to evaluate the three-tangle and analyze inequivalent classes belonging to three-qubit pure states using graph-theoretic perspective. Our results allow a clear distinction between three-qubit separable states, genuinely entangled Greenberger–Horne–Zeilinger and W states, purely based on graphical interpretations.     

A synergistic approach of adapalene-loaded nanostructured lipid carriers,and vitamin C co-administration for treating acne

Abstract

The present study documents the fabrication and characterization of a topically applicable gel loaded with nanostructured lipid carriers (NLCs) of adapalene (ADA) and vitamin C (ascorbyl-6-palmitate [AP]). The NLCs were prepared by high pressure homogenization (HPH) method followed by incorporation into AP loaded gel. The fabricated system was characterized for size, poly dispersity index, entrapment efficiency (EE) and in vitro drug release properties, and was further investigated for skin compliance, skin transport characteristics (skin permeation and bio-distribution), rheological behavior, texture profile analysis and anti-acne therapeutic potential against testosterone-induced acne in male Wistar rats. The NLC-based formulation improved targeting of the skin epidermal layer and reducing systemic penetration. The co-administration of vitamin C led to an adjunct effect in acne therapy in physiological conditions. In brief, the present results suggest the potential of NLCs as a novel carrier for the dermal delivery of ADA and also the synergistic effect of vitamin C in topical therapeutics.     

Investigation of structural and some physical properties of Cr substituted polycrystalline Eu<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>Mn<Subscript>1−x</Subscript>Cr<Subscript>x</Subscript>O<Subscript>3</Subscript> (0 ≤ x ≤ 0.1) manganites

The polycrystalline samples with nominal composition Eu_0.5Sr_0.5Mn_1?x Cr _x O₃ (0 ≤ x ≤ 0.1) were prepared by the conventional solid state reaction method and characterized by X-ray diffraction, scanning electron microscopy and electrical resistivity behavior without and with magnetic field. The structural parameters obtained by using Rietveld refinement of X-ray diffraction data showed that all samples crystallize with orthorhombic perovskite type symmetry with Pbnm space group. The scanning electron micrograph images reveal that the increase in Cr substitution hinders grain growth and grain connectivity. The temperature dependence of electrical resistivity show the semiconducting nature of these compounds and support the small polaron hoping model and variable range hopping conduction model. The calculated hopping distance and activation energy decreased as rate of Cr content increased whereas density of states at Fermi level increased. A large negative magnetoresistance is also present in the sample at the lowest temperature of measurements.     

Performance optimization in delay tolerant networks using backtracking algorithm for fully credits distribution to contrast selfish nodes

The Journal of Supercomputing - Delay Tolerant Network (DTN) can be characterized as a heterogeneous network of nodes in which nodes mobility is high and resources are limited to transmit messages....