Dielectric and magnetic properties of DyMnO3 ceramics

This paper reports the dielectric and magnetic properties of DyMnO₃ (DMO) ceramics sintered at 1,100 and 1,350 °C temperature for 10 h. Sample sintered at 1,100 °C showed presence of secondary phases of Dy₂O₃ whereas the monophasic orthorhombic structure of DyMnO₃ sample is synthesized only at sintering temperature of 1,350 °C. The dielectric properties of the sintered sample of DMO were investigated as a function of temperature (T ≥ 300 K) and frequency (10 kHz–1 MHz). Both the sintered samples showed frequency independent dielectric anomaly at 313 K. These samples exhibited ferroelectric behavior at room temperature which was evidenced from the polarization hysteresis loop measurement. No magnetic transition has been observed at room temperature. However, magnetic field dependent magnetization and temperature dependent magnetization showed the paramagnetic behavior of the DyMnO₃ samples.     

Adaptive Kalman filter and neural network based high impedance fault detection in power distribution networks

This paper presents an intelligent approach for high impedance fault (HIF) detection in power distribution feeders using combined Adaptive Extended Kalman Filter (AEKF) and probabilistic neural network (PNN). The AEKF is used to estimate the different harmonic components in HIF and NF (no-fault) current signals accurately under non-linear loading condition. The estimated harmonic components are used as features to train and test PNN for accurate classification of HIF from NF. Also a performance comparison is made between the results from feed forward neural network (FNN) and PNN for the same features extracted using AEKF. Thus a qualitative comparison is made for HIF detection and classification using the above techniques with FNN and PNN, separately. The testing results in noisy environment ensure the robustness of the proposed technique for HIF detection in distribution network.     

Constitutive analysis to predict high-temperature flow stress in modified 9Cr–1Mo (P91) steel

Constitutive analysis for hot working of modified 9Cr–1Mo (P91) ferritic steel was carried out employing experimental stress–strain data from isothermal hot compression tests, in a wide range of temperatures (1123–1373 K), strains (0.1–0.5) and strain rates (10⁻³–10² s⁻¹). The effects of temperature and strain rate on deformation behaviour were represented by Zener–Hollomon parameter in an exponent-type equation. The influence of strain was incorporated in the constitutive equation by considering the effect of strain on different material constants. Activation energy was found to vary with strain in the range 369–391 kJ mol⁻¹. The developed constitutive equation (considering the compensation of strain) could predict flow stress of modified 9Cr–1Mo steel over the specified hot working domain with very good correlation and generalization.     

Studies of structural,dielectric and impedance properties of Bi<Subscript>9</Subscript>Fe<Subscript>5</Subscript>Ti<Subscript>3</Subscript>O<Subscript>27</Subscript> ceramics

Bi₉Fe₅Ti₃O₂₇ is an eight-layered material belonging to the family of bismuth layered structured ferroelectromagnets. The polycrystalline sample of this compound was prepared by a standard solid-state reaction technique. The formation of the compound in an orthorhombic crystal structure was confirmed by an X-ray diffraction (XRD) technique (lattice parameters: a?=?5.5045[27] Å, b?=?5.6104[27] Å, c?=?76.3727[27] Å). Detailed studies of surface morphology of the compound using scanning electron microscopy (SEM) exhibit that the compound has domains of plate shaped grains. Studies of dielectric and electric properties in a wide temperature range (30–500 °C) at different frequencies (100 Hz–1 MHz) exhibit an anomaly at 291?±?2 °C, which is related to ferroelectric to paraelectric phase transition as suggested by hysteresis loop at room temperature. The values and nature of temperature variation of dc conductivity exhibit the NTCR behavior of the compound.     

Optimization of quality characteristics parameters in a pulsed metal inert gas welding process using grey-based Taguchi method

Optimization of a manufacturing process has to take into accounts all of the factors that influence the product quality and productivity. Optimization of welding process parameters is considerably complex because welding is a multi-variable process, which is influenced by a lot of process uncertainties. In this paper, a grey-based Taguchi method has been adopted to optimize the pulsed metal inert gas welding process parameters. Many quality characteristic parameters are combined into one integrated quality parameter by using grey relational grade or rank. The welding process parameters considered in this analysis are pulse voltage, background voltage, pulse frequency, pulse duty factor, wire feed rate, and table feed rate. The quality parameters considered are the tensile strength, bead geometry, transverse shrinkage, angular distortion, and deposition efficiency. Analysis of variance has been performed to find out the impact of individual process parameter on the quality parameters. If the tensile strength as the most important quality parameter is assigned a higher weight, then the pulse voltage was found to be the most influential process parameter. Experiments with the optimized parameter settings, which have been obtained from the analysis, are given to validate the results.     

X-ray study of crystallinity and disorder in ramie fiber

The degree of crystallinity and the disorder parameter in ramie fibers treated with various concentrations of aqueous NaOH solutions at room temperature (～ 30°C) and at 0°C, respectively, have been analyzed by the wide-angle x-ray diffraction method of Ruland and Vonk.^9–11 The results appear to suggest the presence of highly distorted crystalline regions that are first affected by lower concentrations of alkali. At higher concentrations of mercerizing strength it is observed that the lattice conversion to cellulose II is accompanied by a decrease in the degree of crystallinity and an increase in the disorder parameter values. The tensile properties of the fibers corroborate the results. © 1994 John Wiley & Sons, Inc.     

Development of a compliant legged quadruped robot

This paper presents the detailed steps for design and development of a compliant legged fault tolerant quadruped robot where each leg has two links and two motorized revolute joints for locomotion. The body and upper links of legs are rigid whereas the lower link of each leg is compliant. Amble gait is demonstrated on the developed robot. Safety and reliability are the most critical issues for the quadruped robot. During the failure of any joint, performance of quadruped robot is affected. In this paper, locked joint failure is also discussed. Strategies for fault tolerant control of the quadruped are developed and experimentally validated. The developed robot can be used for various hardware-in-the-loop controller prototyping such as reconfiguration, fault tolerant control, and posture control, etc. pertaining to quadruped robots.