Intake charge temperature effect on performance characteristics of direct injection low-temperature combustion engines

Journal of Thermal Analysis and Calorimetry - The low-temperature combustion (LTC) concept presents solutions for simultaneous reduction in pollution and fuel consumption of internal combustion...     

Exp-Function Based Solution of Nonlinear Radhakrishnan,Kundu and Laskshmanan (RKL) Equation

In this work, we implement a relatively new analytical technique, Exp-Function method, for solving special form of generalized nonlinear Radhakrishnan, Kundu and Laskshmanan equation (RKL), which may contain highly nonlinear terms. This method can be used as an alternative to obtain analytic and approximate solutions of different types of differential equations applied in engineering mathematics. Some numerical examples are presented to illustrate the efficiency and reliability of Exp-Function method. It is predicted that Exp-Function method can be found widely applicable in engineering problems.     

Application of homotopy-perturbation and variational iteration methods to nonlinear heat transfer and porous media equations

Perturbation methods depend on a small parameter which is difficult to be found for real-life nonlinear problems. To overcome this shortcoming, two new but powerful analytical methods are introduced to solve nonlinear heat transfer problems in this article; one is He's variational iteration method (VIM) and the other is the homotopy-perturbation method (HPM). The VIM is to construct correction functionals using general Lagrange multipliers identified optimally via the variational theory, and the initial approximations can be freely chosen with unknown constants. The HPM deforms a difficult problem into a simple problem which can be easily solved. Nonlinear convective–radiative cooling equation, nonlinear heat equation (porous media equation) and nonlinear heat equation with cubic nonlinearity are used as examples to illustrate the simple solution procedures. Comparison of the applied methods with exact solutions reveals that both methods are tremendously effective.     

Vapor phase acylation of phenol over Hβ, CeHβ and SO42-/ZrO2a

Phenol acylation on Hβ, CeHβ and SO₄ ^2-/ZrO₂ using acetic acid and acetic anhydride as acylating agents is compared in the temperature range 250-400°C. Acetic acid formed phenyl acetate (PA) and o-hydroxy acetophenone (o-HAP) and acetic anhydride formed p-hydroxyacetophenone (p-HAP ) along with PA and o-HAP. The formation of o-HAP and p-HAP, the products of C-acylation of phenol using acetic acid is proposed by studying phenyl acetate conversion on Hb, CeHβ and SO₄ ^2-/ZrO₂. Our studies show that for phenol acylation the most suitable acid site is available on CeHβ. This revised version was published online in June 2006 with corrections to the Cover Date.     

Solvent bar microextraction combined with high‐performance liquid chromatography for preconcentration and determination of pramipexole in biological samples

A simple, rapid and sensitive analytical method for preconcentration and determination of pramipexole in different biological samples has been developed using solvent bar microextraction (SBME) combined with HPLC‐UV. The target drugs were extracted from 10 mL of basic aqueous sample solution into an organic extracting solvent located inside the pores of a polypropylene hollow fiber, then back‐extracted into an acidified aqueous solution in the lumen of the hollow fiber. In order to obtain high extraction efficiency, the effect of different variables on the extraction efficiency was studied simultaneously using an experimental design. The experimental parameters of SBME were optimized using a Box–Behnken design after a Plackett–Burman screening design. Under the optimized conditions, an enrichment factor up to 96 was achieved and the relative standard deviation of the method was 4.64% (n = 5). The linear range was 0.05–2000 µg/L with a correlation coefficient (r) of 0.987. Finally, the applicability of the proposed method was evaluated by extraction and determination of pramipexole in plasma and urine samples. The results indicated that SBME method has excellent clean‐up and high preconcentration factor and can serve as a simple and sensitive method for analysis of pramipexole in biological samples. Copyright © 2013 John Wiley & Sons, Ltd.     

On the solution of time-fractional dynamical model of Brusselator reaction-diffusion system arising in chemical reactions

Fractional Brusselator reaction-diffusion system (BRDS) is used for modeling of specific chemical reaction-diffusion processes. It may be noted that numerous models in nonlinear science are defined by fractional differential equations (FDEs) in which an unknown function appears under the operation of a fractional-order derivative. Even though many researchers have studied the applicability and practicality of this model, the analytical approach of this model is rarely found in the literature. In this investigation, a novel semi-analytical technique called fractional reduced differential transform method (FRDTM) has been applied to solve the present model, which is characterized by the time-fractional derivative (FD). Obtained outcomes are compared with the solution of other existing methods for a particular case. Also, the convergence analysis of this model has been studied here.     

Computational design of multi-states monomolecular device using molecular hydrogen and C<Subscript>20</Subscript> isomers

We perform detailed calculations for the interaction of molecular hydrogen with C₂₀isomers in the framework of density functional theory method. The adsorption of H₂ outside the C₂₀-e isomer with parallel orientation with respect to the plane of the hexagon is found to be the most stable adsorption configuration. Thus this might have potential for the hydrogen storing. We have also investigated the number and the position of adsorption sites in the pentagon for the parallel configurations of the H₂/C₂₀ systems. We find two stable configurations of the molecule for the C₂₀-bowl isomer that have a small difference in energy. Thus, surprisingly, despite their apparent simplicity these H₂/C₂₀-bowl systems are shown to exhibit the flip-flop motion by a small current pulse. Hence, it might be a candidate for multi-states monomolecular device. Convenient experimental techniques such as field emission microscopy are proposed to test these predictions.