Impact behavior of aminosilane functionalized nanosilica based shear thickening fluid impregnated Kevlar fabrics

In the present work, two types of shear thickening fluids have been synthesized by using neat and aminosilane functionalized silica nanoparticles and their viscosity curves have been obtained by the rheometer. Based on the values of peak viscosity of synthesized shear thickening fluids, the surface functionalized nanosilica based shear thickening fluid has been chosen as a best candidate due to the high viscosity for impregnation into the neat Kevlar of different layers viz. four (04) and eight (08) layers for velocity impact study. The experimental investigations reveal high energy absorption of shear thickening fluid impregnated Kevlar as compared to the neat Kevlar. The maximum energy absorption 62 J is achieved corresponding to the initial velocity 154 m∙s⁻¹ for 08 layers shear thickening fluid impregnated Kevlar specimen. The data have also been analytically determined and validated with the experimental data. The experimental data have good agreement with the analytical data within the accuracy of around 15 to 20%. The present findings can have significant inferences towards the fabrication of shear thickening fluids using nanomaterials for numerous applications such as soft armors, dampers, nanofinishing and so forth.     

Incremental maintenance of aggregate and outerjoin expressions

Views stored in a data warehouse need to be kept current. As recomputing the views is very expensive, incremental maintenance algorithms are required. Over recent years, several incremental maintenance algorithms have been proposed. None of the proposed algorithms handle the general case of relational expressions involving aggregate and outerjoin operators efficiently.     

Studies on the dielectric and relaxor behavior of sol-gel derived barium strontium zirconate titanate thin films

The dielectric behavior of sol-gel derived Ba_0.80Sr_0.20(Zr_xTi_1−x)O₃ (0.0 ≤ x ≤ 0.50) thin films is studied. A relaxor behavior is observed for x ≥ 0.35. The degree of relaxation increases with Zr content. The frequency dependence of the polar regions follows Vogel-Fulcher relation with a characteristic cooperative freezing at freezing temperature (T_f). Below T_f, a long range polarization ordering is likely to take place. The plausible mechanism of the relaxor behavior of BSZT thin films with Zr contents ≥ 0.35 has been proposed based on the measured temperature as well as frequency dependent dielectric data. The solid solution system is visualized as a mixture of Ti^+ 4 rich polar regions and Zr^+ 4 rich regions; with the increase in Zr content the volume fraction of the polar regions is progressively reduced. At and above 35.0 at.% Zr substitution the polar regions exhibit typical relaxor behavior.     

An Authentication Based Approach for Prevention of Spectrum Sensing Data Falsification Attacks in Cognitive Radio Network

Wireless Personal Communications - This is the era of Intelligent Cognitive Radio Network (CRN) technology that provides the available spectrum with efficient utilization. Cognitive Radio (CR)...     

Introducing robustness in multi-objective optimization

In optimization studies including multi-objective optimization, the main focus is placed on finding the global optimum or global Pareto-optimal solutions, representing the best possible objective values. However, in practice, users may not always be interested in finding the so-called global best solutions, particularly when these solutions are quite sensitive to the variable perturbations which cannot be avoided in practice. In such cases, practitioners are interested in finding the robust solutions which are less sensitive to small perturbations in variables. Although robust optimization is dealt with in detail in single-objective evolutionary optimization studies, in this paper, we present two different robust multi-objective optimization procedures, where the emphasis is to find a robust frontier, instead of the global Pareto-optimal frontier in a problem. The first procedure is a straightforward extension of a technique used for single-objective optimization and the second procedure is a more practical approach enabling a user to set the extent of robustness desired in a problem. To demonstrate the differences between global and robust multi-objective optimization principles and the differences between the two robust optimization procedures suggested here, we develop a number of constrained and unconstrained test problems having two and three objectives and show simulation results using an evolutionary multi-objective optimization (EMO) algorithm. Finally, we also apply both robust optimization methodologies to an engineering design problem.     

Hydrogen from empty cotton boll agro-waste via thermochemical route and feasibility study of operating an IC engine in continuous mode

Hydrogen can be cited as prospective source of clean power. In this work hydrogen rich syn-gas generated from the agro-waste, empty cotton bolls was injected into an IC engine in continuous mode along with gasoline. At the air-fuel ratio of 23.40, specific fuel consumption of 0.35 kg kWh^?1, the engine could be operated with higher efficiency than with gasoline alone. A distinct reduction in emission characteristics could also be seen. Empty cotton bolls derived after removal of cotton from the flower in field, was first studied for fuel properties. The reasonably high heating value (HHV) of 17.54 MJ kg^?1 suggested that it could be a precursor to hydrogen via two stepped thermo-chemical process. The first step involved slow pyrolysis of the biomass at 500 °C for 60 min at a heating rate of 10 °C min^?1 yielding 39.71% bio-char by weight. The C, H, N, S and O contents of the produced bio-char was 59.91, 2.91, 0.72, 0.47 and 35.99% respectively and its HHV was 26.7 MJ kg^?1. Steam gasification of this bio-char, at 700 °C and water flowrate of 7 mL min^?1 exhibited maximum hydrogen yield of 67.42% (v/v) in the syn-gas mixture. Subsequent enrichment of the gas using ethanolamine/ethylene diamine and KMnO₄ solutions resulted in more than 90% (v/v) hydrogen in the combustible gas mixture and the test engine could be effectively operated.     

Automatic synthesis of quaternary quantum circuits

Quaternary encoded binary circuits are more compact than their binary counterpart. Although quaternary reversible circuits are realizable, design of such circuits is still in its infancy. This work proposes a new, enhanced method of quaternary Galois field sum of products (QGFSOP) synthesis for quaternary quantum circuits. To reduce QGFSOP product terms, the algorithm makes use of 11 newly defined quaternary Galois field (QGF) expansions (for a total of 21 QGF expansions). This algorithm achieves QGFSOP minimization with the assistance of a pseudo-Kronecker Galois field decision diagram (QGFDD). This is a novel approach for QGFSOP synthesis. Finally, QGFSOP expressions are translated into quantum cost optimized quaternary quantum circuits using: (1) newly developed quaternary quantum gate realizations of controlled Feynman and Toffoli gate that are optimized in terms of quantum cost, (2) use of composite literals consisting of 1 digit and M–S gates. Performance evaluation against existing works in the literature determined that our proposed method achieves an average QGFSOP expression product term savings of 32.66 %. Also, the synthesized QGFSOP circuits were evaluated in terms of quantum cost.     

WO3 nano-ribbons: their phase transformation from tungstite (WO3·H2O) to tungsten oxide (WO3)

Tungsten oxide (WO₃) nano-ribbons (NRs) were obtained by annealing tungstite (WO₃·H₂O) NRs. The latter was synthesized below room temperature using a simple, environmentally benign, and low cost aging treatment of precursors made by adding hydrochloric acid to diluted sodium tungstate solutions (Na₂WO₄·2H₂O). WO₃ generates significant interests and is being used in a growing variety of applications. It is therefore important to identify suitable methods of production and better understand its properties. The phase transformation was observed to be initiated between 200 and 300 ^°C, and the crystallographic structure of the NRs changed from orthorhombic WO₃·H₂O to monoclinic WO₃. It was rigorously studied by annealing a series of samples ex situ in ambient air up to 800 ^°C and characterizing them afterward. A temperature-dependent Raman spectroscopy study was performed on tungstite NRs between minus 180 and 700 ^°C. Also, in situ heating experiments in the transmission electron microscope allowed for the direct observation of the phase transformation. Powder X-ray diffraction, electron diffraction, electron energy-loss spectroscopy, and X-ray photoelectron spectroscopy were employed to characterize precisely this transformation.     

One‐Pot Lipase Entrapment Within Silica Particles to Prepare a Stable and Reusable Biocatalyst for Transesterification

In order to enhance the reusability, Rhizomucor miehei lipase was entrapped in a single step within silica particles having an oleic acid core (RML@SiO₂). Characterization of RML@SiO₂ by scanning and transmission electron microscopy and Fourier transform infrared studies supported the lipase immobilization within silica particles. The immobilized enzyme was employed for transesterification of cottonseed oil with methanol and ethanol. Under the optimum reaction conditions of a methanol‐to‐oil molar ratio of 12:1 or ethanol‐to‐oil molar ratio of 15:1, stirring speed of 250 revolutions/min (flask radius = 3 cm), reaction temperature of 40 °C, and biocatalyst concentration of 5 wt% (with respect to oil), more than 98 % alkyl ester yield was achieved in 16 and 24 h of reaction duration in case of methanolysis and ethanolysis, respectively. The immobilized enzyme did not require any buffer solution or organic solvent for optimum activity; hence, the produced biodiesel and glycerol were free from metal ion or organic molecule contamination. The activation energies for the immobilized enzyme‐catalyzed ethanolysis and methanolysis were found to be 34.9 ± 1.6 and 19.7 ± 1.8 kJ mol^?1, respectively. The immobilized enzyme was recovered from the reaction mixture and reused in 12 successive runs without significant loss of activity. Additionally, RML@SiO₂ demonstrated better reusability as well as stability in comparison to the native enzyme as the former did not lose the activity even upon storage at room temperature (25–30 °C) over an 8‐month period.