Triple-objective optimization of a double-tube heat exchanger with elliptic cross section in the presence TiO2 nanofluid

Journal of Thermal Analysis and Calorimetry - The present paper deals with numerical simulation and triple-objective optimization of a double-tube heat exchanger equipped with an elliptic cross...     

Zwitterionic Functionalizable Scaffolds with Gyroid Pore Architecture for Tissue Engineering

Stereolithography‐assisted fabrication of hydrogels of carboxybetaine methacrylamide (CBMAA) and a α,ω‐methacrylate poly(d,l ‐lactide‐block‐ethylene glycol‐block‐ d,l ‐lactide) (MA‐PDLLA‐PEG‐PDLLA‐MA) telechelic triblock macromer is presented. This technique allows printing complex structures with gyroid interconnected porosity possessing extremely high specific area. Hydrogels are characterized by infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and laser scanning confocal microscopy (LSCM). The copolymerization with zwitterionic comonomer leads hydrogels with high equilibrium water content (EWC), up to 700% while maintaining mechanical robustness. The introduction of carboxybetaine yields excellent resistance to nonspecific protein adsorption while providing a facile way for specific biofunctionalization with a model protein, fluorescein isothiocyanate labeled bovine serum albumin (BSA). The homogeneous protein immobilization across the hydrogel pores prove the accessibility to the innermost pore volumes. The remarkably low protein adsorption combined with the interconnected nature of the porosity allowing fast diffusion of nutrient and waste product and the mimicry of bone trabecular, makes the hydrogels presented here highly attractive for tissue engineering.     

Comparison of photocatalysis degradation of 4-nitrophenol using N,S co-doped TiO2 nanoparticles synthesized by two different routes

The photocatalytic degradation of 4-nitrophenol as pollutant in aqueous solutions was investigated under visible light irradiation over two different N?CS-codoped anatase TiO₂ catalysts prepared by sol?Cgel methods using titanium isopropoxide and titanium tetrachloride as two different precursors. The catalysts were characterized by XRD, SEM, DRS, EDAX and FT-IR. The effects of various operating parameters including the initial concentration of 4-nitrophenol (2?C14?ppm), solution pH (5?C8) and kinetic reactions were studied. The optimum solution pH was at around 6. For comparison purpose, the photodegradation activity of the commercial Degussa P-25 TiO₂ catalyst has also been studied. The results indicated that photocatalytic activity of N?CS-codoped TiO₂ with titanium isopropoxide as precursor was higher than N?CS-codoped TiO₂ with titanium tetrachloride as precursor and Degussa P-25.     

Dominating Sets of Some Graphs Associated to Commutative Rings

Let G = (V, E) be a graph. A set S ? V is a dominating set of G if every vertex in V is either in S or is adjacent to a vertex in S. The domination number γ(G) of G is the minimum cardinality among the dominating sets of G. The main object of this article is to study and characterize the dominating sets of the zero-divisor graph Γ(R) and ideal-based zero-divisor graph Γ _I (R) of a commutative ring R.     

Large-amplitude free vibrations of functionally graded beams by means of a finite element formulation

The large-amplitude free vibration analysis of functionally graded beams is investigated by means of a finite element formulation. The Von-Karman type nonlinear strain–displacement relationships are employed where the ends of the beam are constrained to move axially. The effects of the transverse shear deformation and rotary inertia are included based upon the Timoshenko beam theory. The material properties are assumed to be graded in the thickness direction according to the power-law distribution. A statically exact beam element which devoid the shear locking effect with displacement fields based on the first order shear deformation theory is used to study the geometric nonlinear effects on the vibrational characteristics of functionally graded beams. The finite element method is employed to discretize the nonlinear governing equations, which are then solved by the direct numerical integration technique in order to obtain the nonlinear vibration frequencies of functionally graded beams with different boundary conditions. The influences of power-law exponent, vibration amplitude, beam geometrical parameters and end supports on the free vibration frequencies are studied. The present numerical results compare very well with the results available from the literature where possible. Some new results for the nonlinear natural frequencies are presented in both tabular and graphical forms which can be used for future references.     

Effect of hydrophilicity of room temperature ionic liquids on the electrochemical and electrocatalytic behaviour of choline oxidase

In the present report, six different nano-composites contaning the same amine functionalized multi-walled carbon nanotubes (NH(2)-MWCNTs) but different room temperature ionic liquids (RTILs) were prepared. Then, the efficiency of these nano-composites as supporting materials for studying the electrochemistry and electrocatalysis of choline oxidase (ChOx) as a model enzyme were compared. The corresponding cyclic voltammetric and amperometric data showed that the electrocatalytic activity and the electroanalytical performance of immobilized ChOx depends on the degree of hydrophilicity of RTILs used in the applied nano-composite. The higher stability (180 days), higher enzyme loading (6.56 mol cm(-2)), lower detection limit (3.85 μM) and wider linear range (0.005-0.8 mM) was obtained for the most hydrophilic RTIL (1-allyl-3-methylimidazolium bromide).     

On local metric pressure of dynamical systems

In this paper, a local version of the topological pressure of dynamical systems is presented. It is a function defined on the product space which does not depend on any measure. It is shown that, for any invariant measure, integration of the introduced function with respect to its corresponding diagonal measure results in the metric pressure of the dynamical system.

     

Correlation of viscosity in nanofluids using genetic algorithm-neural network (GA-NN)

An accurate and efficient artificial neural network based on genetic algorithm (GA) is developed for predicting of nanofluids viscosity. The genetic algorithm (GA) is used to optimize the neural network parameters. The experimental viscosity in eight nanofluids in the range 238.15–343.15 K with the nanoparticle volume fraction up to 9.4% was used. The obtained results show that the GA-NN model has a good agreement with the experimental data with absolute deviation 2.48% and high correlation coefficient (R ≥ 0.98). The Results also reveals that GA-NN model outperforms to the conventional neural nets in predicting the viscosity of nanofluids with the overall percentage improvement of 39%. Furthermore, the results have also been compared with Einstein, Batchelor and Masoumi et al. models. The findings demonstrate that this model is an efficient method and have better accuracy.     

An iterative solver for the finite‐difference frequency‐domain (FDFD) method for the simulation of materials with negative permittivity

A stable iterative solver for the simulation of optical waves in metals using finite difference frequency domain (FDFD) method is presented. The corresponding discretization of Maxwell's equations enables simulating electromagnetic waves in structures when materials with negative permittivity are involved. Convergence of the iterative solver is proved for positive and negative permittivities. Numerical results are presented for a thin‐film silicon solar cell structure containing silver back contact. Copyright © 2010 John Wiley & Sons, Ltd.