An improved progressive preconditioning method for steady non‐cavitating and sheet‐cavitating flows

An improved progressive preconditioning method for analyzing steady inviscid and laminar flows around fully wetted and sheet‐cavitating hydrofoils is presented. The preconditioning matrix is adapted automatically from the pressure and/or velocity flow‐field by a power‐law relation. The cavitating calculations are based on a single fluid approach. In this approach, the liquid/vapour mixture is treated as a homogeneous fluid whose density is controlled by a barotropic state law. This physical model is integrated with a numerical resolution derived from the cell‐centered Jameson's finite volume algorithm. The stabilization is achieved via the second‐and fourth‐order artificial dissipation scheme. Explicit four‐step Runge–Kutta time integration is applied to achieve the steady‐state condition. Results presented in the paper focus on the pressure distribution on hydrofoils wall, velocity profiles, lift and drag forces, length of sheet cavitation, and effect of the power‐law preconditioning method on convergence speed. The results show satisfactory agreement with numerical and experimental works of others. The scheme has a progressive effect on the convergence speed. The results indicate that using the power‐law preconditioner improves the convergence rate, significantly. Copyright © 2010 John Wiley & Sons, Ltd.     

Investigation of magnetic field effect on surface and finite-site free energy in one-dimensional Ising model of nanosystems

We investigate a one-dimensional (1-D) Ising model for finite-site systems. The finite-site free energy and the surface free energy are calculated via the transfer matrix method. We show that, at high magnetic fields, the surface free energy has an asymptotic limit. The absolute surface energy increases when the value of f (the ratio of magnetic field to nearest-neighbor interactions) increases, and for f?≥?10 approaches a constant value. For the values of f?≥?0.2, the finite-site free energy also increases, but slowly. The thermodynamic limit in which physical properties approach the bulk value is also explored.     

Synthesis of ZnO Nanoparticles Based on Zn Complex Achieved from L‐leucine

In the present study, ZnO nanoparticle preparation in a water‐base medium without using toxic chemicals was investigated. Zinc (II) acetate dehydrate, L? leucine and 5? sulfosalicylaldehyde sodium salt were utilized as the starting materials. X? ray diffraction analyses proved that ZnO was achieved as a unique phase. The highest value of crystallinity was obtained at 600 °C and the minimum values of crystallite size and lattice strain were reported at 400 and 500 °C, respectively. The photoluminescence spectroscopy showed that firing at 500 °C leads to decrease the point defects in ZnO structure. SEM and TEM images confirmed the relation between the firing temperature, the degree of crystallinity and the crystallite size. Firing at 400 °C leads to form ZnO nanoparticles with a size distribution ranging from 15 to 50 nm with cubic, circle and hexagonal shapes. By increasing the temperature to 500 °C, the nanoparticles dimensions increase to 30–60 nm. The particle size of sample ‘c’ is more than 50 nm. The optimum temperature to achieve the goal of this research, namely a high crystallinity and low structure defects, was found to be 500 °C.     

Buckling and postbuckling of size-dependent cracked microbeams based on a modified couple stress theory

The elastic buckling analysis and the static postbuckling response of the Euler–Bernoulli microbeams containing an open edge crack are studied based on a modified couple stress theory. The cracked section is modeled by a massless elastic rotational spring. This model contains a material length scale parameter and can capture the size effect. The von Kármán nonlinearity is applied to display the postbuckling behavior. Analytical solutions of a critical buckling load and the postbuckling response are presented for simply supported cracked microbeams. This parametric study indicates the effects of the crack location, crack severity, and length scale parameter on the buckling and postbuckling behaviors of cracked microbeams.     

A Novel and Efficient One‐Pot Synthesis of 2‐Aminopyrimidinones and Their Self‐Assembly

A three‐component reaction of benzaldehyde derivatives, methyl cyanoacetate, and guanidinium carbonate affords 2‐amino‐4‐aryl‐1,6‐dihydro‐6‐oxopyrimidine‐5‐carbonitriles and the four‐component reaction of benzaldehyde derivatives, methyl cyanoacetate, and guanidinium hydrochloride in the presence of piperidine leads to piperidinium salts of pyrimidinones. X‐ray crystallography data confirm self‐assembly and H‐bonding in these compounds.     

A simple synthesis of ferrocenyl bis-amides by a Ugi four-component reaction

An efficient and simple synthesis of ferrocenyl bis-amides by the Ugi four-component reaction of ferrocenecarboxaldehyde, carboxylic acids, isocyanides and amines in methanol at room temperature is reported.