Experimental and theoretical investigations on stiffened and unstiffened composite panels under uniform transverse loading

An experimental investigation on fibre-reinforced stiffened and unstiffened panels under transverse uniform pressure has been carried out. The deflections and strains measured inside the laminate are compared with a finite element analysis. The effect of one or two stiffeners within the panel is small since the stiffener fail at small loads. In contrary to this, the effect of a different lay-up is big, because the angle-ply panels [+45°/−45°]₂ carried higher loads than the cross-ply panels [0°/90°]₂. The failure of the panels near the centre of the long edge at the clamping is correctly predicted by the FEA. In addition, calculated and predicted stresses are close to each other.     

Mechanical,thermomechanical, and creep performance of CNT embedded epoxy at elevated temperatures: An emphasis on the role of carboxyl functionalization

In contrast to polymeric composites, the role of interface/interphase has been widely acknowledged to govern their overall properties and performance. Environmental temperature has substantial effects on the interfacial durability of polymer nanocomposites. In this regard, present investigation has been carried out to study the mechanical performance of pristine (UCNT) and carboxylic functionalized CNT (FCNT) embedded epoxy nanocomposites under different elevated temperatures. Higher flexural strength and modulus of FCNT‐EP nanocomposite were recorded over UCNT‐EP and neat epoxy at room temperature environment. Flexural testing at elevated temperatures revealed a higher rate of strength degradation in polymer nanocomposites over neat epoxy. Postfailure analysis of specimens has been conducted to understand the alteration in failure micro‐mechanisms upon UCNTs and FCNTs addition in epoxy. Variation in viscoelastic properties with temperature has been studied from dynamic mechanical thermal analysis and significant reduction in glass transition temperature (T_g) is observed for nanocomposites. In the studied temperature and stress combinations, FCNT‐EP nanocomposites exhibited better creep resistance over UCNT‐EP and neat epoxy. Room temperature strengthening, elevated temperature strength degradations, improved creep resistance and reduction in T_g in nanocomposites over neat polymer have been discussed in terms of dynamic nature and gradient structure of CNT/epoxy interphase. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44851.     

Modified cuckoo search algorithm in microscopic image segmentation of hippocampus

Microscopic image analysis is one of the challenging tasks due to the presence of weak correlation and different segments of interest that may lead to ambiguity. It is also valuable in foremost meadows of technology and medicine. Identification and counting of cells play a vital role in features extraction to diagnose particular diseases precisely. Different segments should be identified accurately in order to identify and to count cells in a microscope image. Consequently, in the current work, a novel method for cell segmentation and identification has been proposed that incorporated marking cells. Thus, a novel method based on cuckoo search after pre‐processing step is employed. The method is developed and evaluated on light microscope images of rats’ hippocampus which used as a sample for the brain cells. The proposed method can be applied on the color images directly. The proposed approach incorporates the McCulloch's method for lévy flight production in cuckoo search (CS) algorithm. Several objective functions, namely Otsu's method, Kapur entropy and Tsallis entropy are used for segmentation. In the cuckoo search process, the Otsu's between class variance, Kapur's entropy and Tsallis entropy are employed as the objective functions to be optimized. Experimental results are validated by different metrics, namely the peak signal to noise ratio (PSNR), mean square error, feature similarity index and CPU running time for all the test cases. The experimental results established that the Kapur's entropy segmentation method based on the modified CS required the least computational time compared to Otsu's between‐class variance segmentation method and the Tsallis entropy segmentation method. Nevertheless, Tsallis entropy method with optimized multi‐threshold levels achieved superior performance compared to the other two segmentation methods in terms of the PSNR.     

Evaluation of Tribological Properties of Sulfur- and Phosphorous-Free Quinolinium Salts and Their Correlation with Quantum Chemical Parameters

For developing antiwear additives with high efficiency but with low sulfated ash, phosphorous, and sulfur (SAPS), N-substituted quinolinium halides, [DIP-Q]⁺Br^? [DIP-Q=1-(3-(1,3-dioxoisoindolin-2-yl)propyl)quinolon-1-ium], [DIE-Q]⁺Br^? [DIE-Q=1-(3-(1,3-dioxoisoindolin-2-yl)ethyl)quinolon-1-ium], [P-Q]⁺I^? [P-Q=propylquinolon-1-ium], and [M-Q]⁺I^? [M-Q=methylquinolon-1-ium] have been prepared and characterized by ¹H- and ¹³C-NMR spectroscopic techniques. The tribological performance of these quinolone-based quaternary salts as antiwear additives in paraffin oil has been assessed on a four-ball test rig. The observed results have been compared with those of zinc dialkyldithiophosphate (ZDDP), a high SAPS additive. The tribotesting of these additives has been performed using 1% w/v additives concentration at different loads and times. The potential of these compounds as antiwear additives is evident from their observed tribological data: mean wear scar diameter (MWD), friction coefficient (µ), mean wear volume (MWV), and wear rates. All of the quinolinium derivatives prove to be better antiwear additives than ZDDP. Among the tested synthesized compounds, [DIP-Q]⁺Br^? exhibits the best tribological behavior followed by [DIE-Q]⁺Br^?, [P-Q]⁺I^?, and [M-Q]⁺I^?. The surface topography of worn surface studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that surface roughness is reduced to a greater extent in case of quinolinium derivatives than lubrication with ZDDP or base oil alone. Energy-dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analysis of worn surfaces in the presence of quinolinium additives shows that the tribofilm is composed of FeBr₃, Fe₃O₄, and organic compounds containing carbonyl and imine bonds. Theoretical investigations using quantum chemical calculations are indicative of significant chemical interactions of these quinolinium additives with metal surfaces, which is strongly supported by the observed experimental data.     

Study of magnetorheological fluids towards smart energy absorption of composite structures for crashworthiness

A study of magnetorheological fluids energy absorption capability towards development of composite retrofit technologies for aged helicopters is presented in this article. Design parameters that influence the performance of magnetorheological dampers were identified and evaluated based on the damping force as a measure of compatibility to energy absorption. Tensile, compression, and cyclic loading tests were also conducted experimentally to validate the numerical investigation. An extensive parametric study conveyed that the piston head radius plays a major role in achieving higher damping force. The fundamental behaviors and results of the damping force in the numerical studies were also in a good agreement with the experimental results. The novel parametric numerical analysis framework validated in this article will allow for efficient design and optimization of future dampers.

Received 2 August 2013 Accepted 9 January 2015     

Polypropylene oxide/polyethylene oxide-cellulose hybrid nanocomposite hydrogels as drug delivery vehicle

This article deals with the synthesis of hybrid nanocomposite hydrogels through the combination of cellulose (C), polypropylene oxide/poly ethylene oxide (PPO/PEO), and silver nanoparticles (AgNPs) by in situ polymerization technique for the in vitro release of ornidazole drugs. The structure of the resulted materials is identified using SEM, XRD, FTIR, XPS, and TGA spectroscopic techniques. The resulting structure, morphology, thermo responsive property, water retention, and swelling behavior of hydrogels are investigated. The rheological measurement is studied to establish the enhancement of the viscoelasticity and stiffness of hydrogels. The antibacterial activity of the biodegradable silver hybrid nanocomposite hydrogel is investigated by inhibition zone method against gram positive and negative bacteria. Maximum drug release of 96.4% is recorded at 7.4 pH in 5 h. The biocompatibility and cytotoxicity of the hybrid nanocomposite hydrogel are verified using mouse fibroblast cell line L-929 (ATCC CCL-1) cells for their possible use as controlled drug delivery vehicles. The nontoxic nature makes the materials more biocompatible and suitable to apply in the biological systems. Therefore, nontoxic and biocompatible natures of present materials with improved thermal and rheological properties support for their possible uses as drug delivery vehicles.     

Characterization and Electrochemical Studies of LiMn2O4 Cathode Materials Prepared by Combustion Method

A combustion method using urea as a fuel has been developed for the synthesis of the spinel LiMn₂O₄ around 500°C. Physical features of the products were identified by X-ray photoelectron spectroscopy, X-ray diffractometry, Raman scattering and FTIR spectroscopy. Cells were fabricated with Li//LiMn₂O₄ and C//LiMn₂O₄ in nonaqueous organic electrolyte and their performances were studied. A kinetic profile for diffusion of Li ions in the composite matrix was developed and tested.     

Ozonation of tannery effluent for removal of cod and color

Ozonation of leather dye effluent for removal of color and COD reduction covering wide range in operating parameters forms the scope of the present work. The influence of parameters such as influent pH, ozone flow rate and initial effluent concentration on ozonation efficiency has been critically examined. It has been observed from the present investigation that a maximum of COD removal efficiency of 92% has been achieved under optimum operating conditions. Further the biodegradability index of the tannery effluent has increased from an initial value of 0.18 to 0.49 during ozonation indicating favorable adaptation of ozonation as a primer to the biochemical technique to enhance the efficiency of biochemical treatment.     

Dimethylammonium iodide stabilized bismuth halide perovskite photocatalyst for hydrogen evolution

Metal halide perovskites have emerged as novel and promising photocatalysts for hydrogen generation.Currently,their stability in water is a vital and urgent research question.In this paper a novel approach to stabilize a bismuth halide perovskite[(CH₃)₂NH₂]₃[Bil₆](DA₃Bil₆)in water using dimethylammonium iodide(DAI)without the assistance of acids or coatings is reported.The DA3Bil6 powder exhibits good stability in DAI solutions for at least two weeks.The concentration of DAI is found as a critical parameter,where the I^-ions play the key role in the stabilization.The stability of DA3Bil6 in water is realized via a surface dissolution-recrystallization process.Stabilized DA3Bil6 demonstrates constant photocatalytic properties for visible light-induced photo-oxidation of I^-ions and with PtCI4 as a co-catalyst(Pt-DA₃Bil₆),photocatalytic H2 evolution with a rate of 5.7μmol·h^-1from HI in DAI solution,obtaining an apparent quantum efficiency of 0.83%at 535 nm.This study provides new insights on the stabilization of metal halide perovskites for photocatalysis in aqueous solution.     

Textile dye degradation by bacterial consortium and subsequent toxicological analysis of dye and dye metabolites using cytotoxicity, genotoxicity and oxidative stress studies

The present study aims to evaluate Red HE3B degrading potential of developed microbial consortium SDS using two bacterial cultures viz. Providencia sp. SDS (PS) and Pseudomonas aeuroginosa strain BCH (PA) originally isolated from dye contaminated soil. Consortium was found to be much faster for decolorization and degradation of Red HE3B compared to the individual bacterial strain. The intensive metabolic activity of these strains led to 100% decolorization of Red HE3B (50 mg l(-1)) with in 1h. Significant induction of various dye decolorizing enzymes viz. veratryl alcohol oxidase, laccase, azoreductase and DCIP reductase compared to control, point out towards their involvement in overall decolorization and degradation process. Analytical studies like HPLC, FTIR and GC-MS were used to scrutinize the biodegradation process. Toxicological studies before and after microbial treatment was studied with respect to cytotoxicity, genotoxicity, oxidative stress, antioxidant enzyme status, protein oxidation and lipid peroxidation analysis using root cells of Allium cepa. Toxicity analysis with A. cepa signifies that dye Red HE3B exerts oxidative stress and subsequently toxic effect on the root cells where as biodegradation metabolites of the dye are relatively less toxic in nature. Phytotoxicity studies also indicated that microbial treatment favors detoxification of Red HE3B.