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...     

Bioglass® coated poly(DL‐lactide) foams for tissue engineering scaffolds

The purpose of this study was to prepare poly(DL‐lactic acid) (PDLLA)/Bioglass® composites of foam‐like structure, to measure the degree of bioactivity of the composites by studying the formation of hydroxyapatite (HA) after immersion in simulated body fluid (SBF) and to test the initial attachment of human osteoblasts within the porous network. It was found that crystalline HA formed on the Bioglass® coated PDLLA foams after 7 days of immersion in SBF. HA formed also on the surfaces of non‐coated PDLLA foams, however the rate and amount of HA formation were much lower than in the composites. The rapid formation of HA on the Bioglass®/PDLLA foam surfaces confirmed the high bioactivity of these materials. Osteoblasts attached within the porous network throughout the depth of the foams. Cell density was found to be higher in the PDLLA/Bioglass® composites compared to the pure PDLLA foams. The composite foams developed here exhibit the required bioactivity to be used as scaffolds for bone tissue engineering.     

A suitable model of combined effects of temperature and initial condition on chlorine bulk decay in water distribution systems

Maintaining a chlorine residual is a major disinfection goal in many water distribution systems. A suitable general model of chlorine decay in the transported bulk water is an essential component for efficiently modelling chlorine concentration in distribution systems. The two-reactant model meets basic suitability criteria, including accurate prediction of chlorine residual over hundreds of hours, commencing with chlorine concentration 0-4 mg/L. This model was augmented with an equation that increases the decay coefficients with temperature according to Arrhenius theory. The augmented model was calibrated against decay-test data sets to obtain a single invariant set of parameters for each water. Model estimates of chlorine residuals over time closely matched decay-test data, over the usual operating ranges of initial chlorine concentration (1-4 mg/L) and temperature (3.5-28 °C). When the augmented model was fitted to partial data sets, it also predicted the data reserved for validation very well, suggesting that this model can accurately predict the combined effect of initial chlorine concentration and temperature on chlorine bulk decay in distribution systems, using a single set of invariant parameters for a given source water.     

Microbial mediated dimerization of fattyacids of sunflower oil: An effective role of lipase and biosurfactant

This study emphasizes microbial mediated transformation of sunflower oil to an adhesive product and characterization in detail. Marine bacterial isolates Bacillus (MTCC 5514), when grown in mineral medium, releases both hydrolytic enzymes and surface‐active components during the log phase of growth. When this species was grown in the presence of sunflower oil at an optimized concentration of 5% (w/v) under room temperature, enzymatic hydrolysis of oil proceeds with the release of fatty acids and glycerol. Further, on increasing the incubation period, the presence of surface‐active components, lipase and glycerol, influence the dimerization of the fatty acids, which further, transformed to a polymerized product sunflower oil‐based adhesive product with adhesive nature. Liquid chromatography‐mass spectrometry (electrospray ionization) analysis further authenticates the presence of dimeracids. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40555.     

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.     

Effect of cellulase pretreatment of raw and bleached cotton fibers on properties of hydroentangled nonwoven fabrics

This study was undertaken to investigate the effect of enzymatic pretreatment of cotton (polysaccharides) fibers on the properties of resulting nonwoven fabric. Enzymatic treatment is known to improve the esthetical properties of fabrics but will likely lead to a reduction in strength. In the case of nonwovens the strength loss can be even more drastic as cellulase may attack bonded areas of the fabric. In this work, raw and bleached cotton fibers were treated with enzyme solutions prior to fabric formation to avoid possible damage to the bonded areas and improve strength retention. These fibers were first modified with commercially available whole cellulases and monocomponent endoglucanase enzyme solutions. Then they were formed into a fabric and bonded via hydroentangling. Parameters such as bending modulus, fabric tenacity, fiber strength, length and reducing power were measured for each sample. The pretreatment of cotton fibers prior to fabric formation showed that the resulting nonwovens could be stronger and more drapeable than the same fabric composed of untreated fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

A comprehensive bulk chlorine decay model for simulating residuals in water distribution systems

Chlorine decay models provide efficient ways to develop disinfection strategies for water distribution systems, provided they account separately for bulk and wall decay, and accurately describe decay with a single set of coefficients. The augmented two-reactant (2RA) model is shown to be the simplest model to accurately describe effects of rechlorination dose/timing on bulk chlorine decay, in combination with effects of initial concentration and temperature over long periods. The two-reactant (2R) and variable reaction-coefficient (VRC) models provided predictions of comparable accuracy under higher and successive rechlorination doses at constant temperature. However, the 2RA model provides a more general basis for strategy development, as the VRC model cannot describe the effect of temperature variation. The minimal data-set required for 2RA calibration was similar for all cases considered. The 2RA model is readily applied by incorporation into system modelling software such as the multi-species extension (MSX) to EPANET software.     

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.     

Layered LnBa1−xSrxCoCuO5+δ (Ln = Nd and Gd) perovskite cathodes for intermediate temperature solid oxide fuel cells

The effects of Sr substitution on the crystal chemistry, phase stability, and electrochemical performance as cathodes in intermediate-temperature solid oxide fuel cells (IT-SOFCs) of the layered LnBa_1−xSr_xCoCuO_5+δ (Ln = Nd and Gd) perovskites have been investigated. The LnBa_1−xSr_xCoCuO_5+δ oxides crystallize in tetragonal P4/mmm symmetry for 0 ≤ x ≤ 0.75. The x = 0.75 samples show a significant improvement in electrochemical performance compared to the x = 0 samples for both Ln = Nd and Gd. In an electrolyte (La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.8)-supported single cell configuration (thickness = 0.50 mm), the Ln = Gd series shows an improved maximum power density from 468 mW cm⁻² for the Sr-free (x = 0) sample to 530 mW cm⁻² for the x = 0.75 sample. In the Ln = Nd system, the x = 0.75 sample shows a maximum power density of 562 mW cm⁻². The Sr substitution was found to have negligible effect on the thermal expansion coefficients (TEC) between the x = 0 and x = 0.75 samples in both series.