Effect of fuzzy C means technique in failure mode discrimination of glass/epoxy laminates using acoustic emission monitoring

Acoustic emission is one of the powerful techniques that can be used for in situ structural health monitoring of composite laminates. One of the main issues of AE is to characterize the different damage mechanisms from the detected AE signals. Unsupervised Pattern recognition has been one of the techniques used for the identification of a specific failure mode in composites from Acoustic emission data. Cross ply composite laminate of size 300 × 300 mm is fabricated using Vacuum bag molding. ASTM D3039 Standard tensile specimens are cut from the laminate and these specimens are subjected to uni axial tensile test under Acoustic Emission monitoring. Fast Fourier transform analysis (FFT) and Short Time Fast Fourier Transform (STFFT) analysis are performed on the Wave forms of the AE hit data obtained during the conduct of tensile test to characterize the failure modes in crossply specimens. Fast Fourier Transform enabled calculating the frequency content of each damage mechanism. In this paper Fuzzy C Mean clustering is performed for the AE parameters obtained from the test and the efficiency of this technique is being investigated using FFT AND STFFT analysis.     

Electrochemical performance of Nd0.6Sr0.4Co0.5Fe0.5O3−δ–Ag composite cathodes in intermediate temperature solid oxide fuel cells

The electrochemical performances of Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ–Ag composite cathodes have been investigated in intermediate temperature solid oxide fuel cells. The Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ–Ag cathodes prepared by ball milling followed by firing at 920 °C show the maximum performance (power density: 0.15 W cm⁻² at 800 °C) at 3 wt.% Ag. On the other hand, the Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ–Ag composite cathodes with 0.1 mg cm⁻² (0.5 wt.%) Ag that were prepared by an impregnation of Ag into Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ followed by firing at 700 °C (but the electrolyte–Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ assembly was prepared first by firing at 1100 °C) exhibit much better performance (power density: 0.27 W cm⁻² at 800 °C) than the composite cathodes prepared by ball milling, despite a much smaller amount of Ag due to a better dispersion and an enhanced adhesion. AC impedance analysis indicates that the Ag catalysts dispersed in the porous Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ cathode reduce the ohmic and the polarization resistances due to an increased electronic conductivity and enhanced electrocatalytic activity.     

Investigation on the Nonlinear Excitation in an Array of Spin Valve Pillars During the propagation of Electromagnetic Wave

We have investigated the nonlinear excitations in an array of spin valve pillars during the propagation of an electromagnetic wave. The flowing electrons exhibit spins transportation effect due to the torque experienced by the spin magnetization. From the Hamiltonian which models the spin interaction in a spin valve array, we have studied the effect of perturbation using multiple scale expansion and Reduction Perturbation method. The Landau–Lifshitz–Gilbert equation of magnetization, which models the evolution of magnetization of the ferromagnetic layer, is studied along with Maxwell’s equation for the electromagnetic waves. It is found that the system of equations reduce to the celebrated modified KdV equation. The solution of the spin excitations are localized solitons. The physically interesting solitons can be harnessed to the increase in density of memory devices.     

Synthesis of gold nanoparticles: an ecofriendly approach using Hansenula anomala

This work describes a bioassisted approach for the preparation of metal nanoparticles using yeast species Hansenula anomala. Gold nanoparticles were prepared using gold salt as the precursor, amine-terminated polyamidoamine dendrimer as the stabilizer, and the extracellular material from H. anomala as the bioreductant. It could also be demonstrated that, using our approach, small molecules such as cysteine can act as stabilizers as well. This synthetic approach offers a greener alternative route to the preparation of gold sols that are devoid of cellular and toxic chemical components. The ability of as-synthesized gold sol to function as biological ink for producing patterns for the analysis of fingerprints and to act as an antimicrobial reagent is evaluated. The generality of this toxin-free synthetic approach to other metals was assessed using palladium and silver.     

Crystal chemistry and properties of mixed ionic-electronic conductors

Oxides exhibiting mixed oxide-ion and electronic conducting (MIEC) properties have been attracting great interest in recent years due to their technological applications in solid-state electrochemical devices such as solid oxide fuel cells (SOFC), oxygen separation membranes, and electrochemical sensors. This article provides an overview of the composition-structure–property-performance relationships of several mixed conducting oxides: disordered ABO₃ perovskite oxides, A-site ordered layered LnBaCo₂O_5+δ (Ln = lanthanide) perovskite oxides, Ruddlesden-Popper series of perovskite-based (La,Sr)_n+1M_nO_3n+1 (n = 1–3 and M = Fe, Co, and Ni) intergrowth oxides, and hexagonal RBa(Co_1-yM_y)₄O₇ (R = rare earth or alkaline earth and M = Zn) oxides. Based on the available data, the role of chemical composition, crystal chemistry, and chemical bonding on the electrical and ionic transport, thermal, and electrochemical properties is discussed.     

Effect of Process Parameters on Microstructure and Mechanical Properties of Al-11.5%Si-1%Mg/bimodal SiC(m–n)composites

Silicon - Bimodal size SiC particles reinforced Al-Si alloy composites were fabricated by powder metallurgy route. Three different bimodal reinforcements with various volume fractions of micro and...     

Nonfragile control design for consensus of semi-Markov jumping multiagent systems with disturbances

The consensus problem for multiagent systems (MASs) with semi-Markov jumping parameters under the influence of disturbances is investigated in this article. In the first part of this article, an extended dissipative approach is used for the consensus of MASs with semi-Markovian jumping parameters and external disturbances via nonfragile controller with randomly occurring gain fluctuations. Besides, in the second part of the article, the consensus of stochastic semi-Markovian jumping MASs via nonfragile controller subject to probabilistic time-varying delay is discussed. The primary motive of this article is to develop a robust controller such that the considered MASs with semi-Markov jumping parameters achieve consensus in the presence of external disturbances. For this, the chosen problems are first converted to stabilization problems then by using Lyapunov stability theory and linear matrix inequality approach, the stabilization criterion have been established. At last, two numerical examples are worked out to illustrate the efficiency of the proposed control methodologies.