A new approach to solving Poisson system for free surface nonhydrostatic flow simulations

A nonhydrostatic finite volume model is presented to simulate free surface flow in a two‐dimensional vertical plane. The algorithm is based on a projection method including the solution of the pressure Poisson equation (PPE). The model is developed in a Cartesian grid in which the size of all the cells in the computational domain, excluding those of the top layer, is constant in time. To simulate the variable water surface, the heights of the top layer cells are variable and proportional to the local water elevation. Taking the layout of the grid system into consideration, a new method is proposed to solve the PPE derived in Cartesian coordinates. In this method, the system of pressure equations is divided into two subsystems, namely a subsystem for the upper layer cells and another for the remaining cells. The coefficient matrix of the former is variable with respect to time, whereas that of the latter remains constant. Therefore, the coefficient matrix of the latter subsystem can be inversed once and saved throughout the simulation. The application of this procedure reduces the computational cost compared with other PPE solvers in certain conditions. The model is applied to simulate a series of numerical tests including strong vertical accelerations and is verified against analytical and experimental results, demonstrating satisfactory performance. Copyright © 2011 John Wiley & Sons, Ltd.     

Non-Newtonian ink transfer in gravure-offset printing

The inks used in gravure-offset printing are non-Newtonian fluids with higher viscosities and lower surface tensions than Newtonian fluids. This paper examines the transfer of a non-Newtonian ink between a flat plate and a groove when the plate is moved upward with a constant velocity while the groove is held fixed. Numerical simulations were carried out with the Carreau model to explore the behavior of this non-Newtonian ink in gravure-offset printing. The volume of fluid (VOF) method was implemented to capture the interface during the ink transfer process. The effects of varying the contact angle of the ink on the flat plate and groove walls and geometrical parameters such as the groove angle and the groove depth on the breakup time of the liquid filament that forms between the plate and the groove and the ink transfer ratio were determined. Our results indicate that increasing the groove contact angle and decreasing the flat plate contact angle enhance the ink transfer ratio and the breakup time. However, increasing the groove depth and the groove angle decreases the transfer ratio and the breakup time. By optimizing these parameters, it is possible to achieve an ink transfer from the groove to the flat plate of approximately 92%. Moreover, the initial width and the vertical velocity of the neck of the ink filament have significant influences on the ink transfer ratio and the breakup time.     

Pd(II) salen complex covalently anchored to multi‐walled carbon nanotubes as a heterogeneous and reusable precatalyst for Mizoroki–Heck and Hiyama cross‐coupling reactions

A Pd(II) salen complex anchored to multi‐walled carbon nanotubes showed excellent catalytic activity and stability for the Mizoroki–Heck and Hiyama cross‐couplings of aryl halides with olefins and phenylsiloxanes. Furthermore, the heterogeneous catalyst could be reused up to four times with the catalytic activity being recovered easily after simple manipulations. Copyright © 2014 John Wiley & Sons, Ltd.     

Density functional theory study of nitrogen‐14 nuclear quadrupole coupling parameters of L‐histidine: hydrogen‐bonded system

The calculations of nitrogen‐14 nuclear quadrupole parameters, nuclear quadrupole coupling constant, χ, and asymmetry parameter, η, of L‐His were done in two distinct environments: one as a free fully optimized molecule, an isolated molecule with the geometrical parameters taken from X‐ray, and the other in the orthorhombic and monoclinic solid states. The most probable interacting molecules with the central molecule in the crystalline phase were considered in the hexameric clusters to include hydrogen‐bonding effects in the calculations. The computations were performed with PW91P86/6‐31++G** and B3LYP6‐31++G** methods using the Gaussian 98 program. The good agreement between the nitrogen‐14 quadrupole parameters of the free His and imidazole molecules with their microwave available data demonstrates that the applied level of theory and the 6‐31++G** basis set are suitable to obtain reliable electric field gradient values. In the solid state, the shifts of quadrupole coupling parameters from the monomer to the solid phase are reasonably well reproduced for the amino and imino sites of imidazole ring in a hexameric cluster. That implies the fact that the hexameric cluster worked effectively to generate the results which are compatible with the experiment. The quadrupole coupling constant values of –N⁺H₃ group are in fair agreement with the experiment. This discrepancy is due to the absences of vibrational effects and the rotation of –N⁺H₃ group around N–C(α) bond. Copyright © 2012 John Wiley & Sons, Ltd.     

An efficient Stille cross‐coupling reaction catalyzed by ortho‐palladated complex of tribenzylamine under microwave irradiation

The catalytic activity of [Pd{C₆H₄(CH₂N(CH₂Ph)₂)}(μ‐Br)]₂ complex as an efficient, stable and catalyst that is non‐sensitive to air and moisture was investigated in the Stille cross‐coupling reaction of various aryl halides with phenyltributyltins under microwave irradiation. The substituted biaryls were produced in excellent yield in short reaction times using a catalytic amount of this complex in DMF at 100 C. The combination of dimeric complex as homogeneous catalyst and microwave irradiation and also DMF as microwave‐active polar solvent gave higher yields in shorter reaction times. Copyright © 2011 John Wiley & Sons, Ltd.     

One-Pot Green Synthesis of Novel Polysubstituted 1,2-Dihydronaphtho[2,1-b]furans

A simple and highly efficient one-pot protocol for the synthesis of novel polysubstituted 1,2-dihydronaphtho[2,1-b] furans has been developed by three-component coupling reaction of 2-aminopyridines, naphthols, and glyoxal in the presence of guanidinium chloride as a polyfunctional organocatalyst under solvent-free conditions. The protocol avoids the use of expensive catalysts, toxic solvents, and chromatographic separation and provides a wide range of novel dihydronaphthofurans in good to excellent yields.     

H6P2W18O62-18H2O,a Green and Reusable Catalyst for the Three-Component,One-Pot Synthesis of 4,6-Diarylpyrimidin-2(1H)-ones Under Solvent-Free Conditions

Three-component, one-pot synthesis of 4,6-diarylpyrimidin-2(1H)-ones and 9-phenyl-8-oxa-10,12-diaza-tricyclo[7.3.1.0^2,7]trideca-2(7),3,5-trien-11-one by condensing acetophenone derivatives, aldehydes, and urea in the presence of trimethylsilyl chloride using a catalytic amount of H₆P₂W₁₈O₆₂-18H₂O under solvent-free conditions is reported.