Interaction of Cu and Ag nanoparticles on MHD water‐based nanofluids past a stretching sheet

The study explores the MHD flow of water‐based nanofluids past a stretching sheet that melts at a constant rate. Cu and Ag nanoparticles are considered to merge into the base fluid to discuss the flow, heat and mass transfer characteristics. Suitable transformation is employed to transform the governing partial differential equations to a system of nonlinear coupled ordinary differential equations (ODEs). A semi‐analytical technique, that is, in particular, the Adomian decomposition method is implemented to tackle this system of ODEs. The influences of characterizing parameters for the flow phenomena are determined via graphs and displayed. Furthermore, the computed values of the quantities of engineering interest are exhibited through tables and discussed. The main findings of the results are laid down as follows: the Cu‐water nanofluid momentum is more pronounced than that of Ag‐water due to the heavier density of the Ag nanoparticles and an increasing melting parameter is favorable to decrease the fluid temperature, which is useful for the cooling of the substances at the final stage of production in industries.     

Biodegradable IPN hydrogel beads of pectin and grafted alginate for controlled delivery of diclofenac sodium

A novel diclofenac sodium (DS) loaded interpenetrating polymer network (IPN) beads of pectin and hydrolyzed polyacrylamide-graft-sodium alginate (PAAm-g-SA) was developed through ionotropic gelation and covalent cross-linking. The graft copolymer was synthesized by free radical polymerization under the nitrogen atmosphere followed by alkaline hydrolysis. The grafting, alkaline hydrolysis, and characterization of beads were confirmed by Fourier transforms infrared spectroscopy. The crystalline structure of drug after encapsulation into IPN beads were evaluated by differential scanning colorimetry and X-ray diffraction analyses. DS encapsulation was up to 96.45 %. The effect of hydrolyzed graft copolymer/pectin ratios and glutaraldehyde concentration on drug release in acidic and phosphate buffer solutions were investigated. The release of drug was significantly increased with increase of pH. The release of drug depends on the extent of cross-linking. The results indicated that IPN beads of hydrolyzed PAAm-g-SA and pectin could be used for sustained release of DS.     

Rapid synthesis of polypyrrole nanospheres by greener mechanochemical route

A simple, rapid and efficient route to prepare polypyrrole nanospheres by template-free method is described. This greener route has advantages in terms of good yield, short reaction time, neat conditions and cost-effectiveness. The resultant polymeric material was characterized by field-emission scanning electron microscopy, X-ray scattering, cyclic voltammetry, chronoamperometry, Fourier transform infrared spectroscopy and UV–visible spectroscopy. From these studies it is confirmed that the as prepared polypyrrole nanospheres possesses good physicochemical properties.     

ROTOR MODELING AND DEVELOPMENT FOR BRUSHLESS DOUBLY-FED MACHINES

ABSTRACT

The basic principles of brushless doubly-fed machine (BDFM) synchronous operation are used to establish the essential components of the rotor configuration and alternative types of construction are examined. Certain forms, which appear to be physically realizable only with wound or fabricated rotors, are dismissed in favor of others which may be fabricated or die-cast in a manner similar to the cage rotors of conventional induction machines.

A detailed simulation model is used to predict the performance of a proof-of-concept laboratory machine in a motoring mode which has been correlated with test data. Various developments and options of the rotor configuration are then examined for relative performance at two different speeds using the modeling techniques. The design features considered include (i) alternative interpretations of the nested-loop configuration requirement, (ii) number of rotor loops per nest, (iii) location (span) of rotor loops, and (iv) conductor section of specific rotor bars and end rings.     

Rheological behavior of chlorosulfonated polyethylene composites: Effect of filler and plasticizer

Thermosets obtained by reacting highly functionalized maleic anhydride-grafted polyethylene and a polyetherdiamine at several NH₂/MA molar ratios were characterized for their gel content, thermal, mechanical, and thermo-mechanical behavior. Gel content varied with composition and a maximum (57%) observed when NH₂/MA molar ratio was 1.5. Two melting transitions were observed for thermosets, representing the semicrystalline polyethylene fraction in the gel and sol part of the material in contrast to a single transition for the starting polyethylene. Overall crosslinking suppressed the crystallinity of the polyethylene in the thermoset. A single T_g observed in the DMA analysis suggested phase mixing between the polyethylene and polyether chains. A shift in the T_g observed was related to the degree of crosslinking in the thermosets. Tensile properties of the thermosets were observed to be a strong function of composition and the degree of crosslinking and the optimum mechanical performance was shown by thermosets when NH₂/MA molar ratio was 1.5 and 2.0. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Modeling of high-tension roll separator for separation of titanium bearing minerals

In this study, a three-level Box-Behnken factorial design combined with response surface methodology (RSM) for modeling and optimizing of process parameters of high-tension roll separator (HTRS), namely feed temperature, feed rate and roll speed for the separation of titanium bearing minerals (ilmenite and rutile) was developed. Second-order response functions were produced for the grade and recovery of the titanium bearing minerals in the conducting fraction. Taking advantage of the quadratic programming, optimized levels of the process variables have been determined as optimum levels to achieve the maximum grade of 98.7%, whereas the maximum level of recovery was 98.4% of titanium bearing minerals in the conducting fraction was predicted. The influence of the process variables of the HTRS on grade and recovery of the titanium bearing minerals in the conducting fraction was presented as 3D response surface graphs.     

Interaction of (-)-epigallocatechin gallate with lysozyme-conjugated silver nanoparticles

The interaction of lysozyme (Lyz)-conjugated silver (Ag) nanoparticles with (-)-epigallocatechin gallate (EGCG), one of the major components of green tea, has been investigated. Interaction of a protein with ligand/drug molecules perturbs the conformation of secondary and tertiary structures of the protein. We have demonstrated the conformational changes in the tertiary structures of the Lyz molecules on EGCG binding using surface-enhanced Raman scattering (SERS) and circular dichroism (CD) spectroscopic measurements. From the analysis of the amide I band of Lyz in SERS and CD spectra, the site of interaction of EGCG with protein molecules in Lyz-conjugated Ag particles has been identified. Spectroscopic evidence for the conformational response of Trp62 and Trp63, in the β-domain of the protein, to the binding of EGCG has been discussed.     

Conductive carbon black-filled ethylene acrylic elastomer vulcanizates: physico-mechanical,thermal, and electrical properties

The effect of conductive carbon black (CCB) on the physico-mechanical, thermal, and electrical properties have been investigated by various characterization techniques. Physico-mechanical properties of the vulcanizates were studied with variation of filler loading, which revealed that the tensile strength increased up to 20 phr (parts per hundred rubber) CCB loading, whereas at higher filler loading it decreased marginally. Furthermore, tensile modulus, tear strength, and hardness gradually increased with increase in filler loading. The compression set and abrasion loss decreased with increasing CCB loading. The bound rubber content (Bdr) of unvulcanized rubber was found to increase significantly with increasing CCB content. The crosslink density increased, whereas the swelling decreased with CCB loading. The thermal stability of the vulcanizates evaluated by thermogravimetric analysis (TGA) showed a minor increment with increase in CCB content. It is observed from the dynamic mechanical thermal analysis (DMTA) that the storage modulus (E′), loss modulus (E″), and glass transition temperature (T _g) of ethylene acrylic elastomer (AEM) matrix increased by incorporation of CCB. The dielectric relaxation characteristics of AEM vulcanizates such as dielectric permittivity (ε′), electrical conductivity (σ _ac), and electric moduli (M′ and M″) have been studied as a function of frequency (10¹ to 10⁶ Hz) at different filler loading. The variation of ε′ with frequency and filler loading was explained based on the interfacial polarization of the fillers within a heterogeneous system. The ε′ increased with increasing the CCB loading and it decreased with applied frequency. The frequency dependency of σ _ac was investigated using conduction path theory and percolation threshold limit. The σ _ac increased with increase in both CCB concentration and applied frequency. The M′ increased with applied frequency, however, it decreased above 30 phr filler. The M″ peak shifted towards higher frequency region and above 20 phr filler loading the peaks were not observed within the tested frequency region. The electromagnetic interference shielding effectiveness (EMISE) was studied in the X-band frequency region (8–12 GHz), which significantly improved with increase in CCB loading.     

Psychophysical measures of auditory nonlinearities as a function of frequency in individuals with normal hearing

In order to gain a better understanding of how auditory nonlinear phenomena vary as a function of location along the cochlea, several psychophysical measures of nonlinearity were examined as a function of signal frequency. Six normal-hearing individuals completed three experiments, each designed to measure one aspect of nonlinear behavior: (1) the effects of level on frequency selectivity in simultaneous masking, measured using notched-noise maskers at spectrum levels of 30 and 50 dB, (2) two-tone suppression, measured using forward maskers at the signal frequency (fs) and suppressor tones above fs, and (3) growth of masking, measured using forward maskers below fs at a signal/masker frequency ratio of 1.44. Four signal frequencies (375, 750, 1500, and 3000 Hz) were tested to sample the nonlinear behavior at different locations along the basilar membrane, in order to test the hypothesis that the apical (low-frequency) region of the cochlea behaves more linearly than the basal (high-frequency) region. In general, all three measures revealed a progressive increase in nonlinear behavior as signal frequency increased, with little or no nonlinearity at the lowest frequency, consistent with the hypothesis.