Dual Entwining Structures and Dual Entwined Modules

In this note we introduce and investigate the concepts of dual entwining structures and dual entwined modules. This generalizes the concepts of dual Doi–Koppinen structures and dual Doi–Koppinen modules introduced (in the infinite case over rings) by the author in his dissertation. Presented by A. VerschorenMathematics Subject Classifications (2000) 16W30, 18E15.Jawad Y. Abuhlail: Current address: Department of Mathematical Sciences, P.O. Box 5046, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Saudi Arabia.     

Validation of CFD‐CSD coupling interface methodology using commercial codes

Coupling interface between computational fluid dynamics (CFD) and computational structural dynamics (CSD) is required to provide exchange of information for the simulation of fluid–structure interaction (FSI) phenomena. Accuracy and consistency of information exchanged through coupling interface between the independent CFD and CSD solvers plays a central role in the simulation and prediction of FSI phenomenon, like flutter. In this paper validation of an implemented coupling interface methodology is presented for subsonic, transonic and near supersonic mach regime. The test case chosen for this purpose is the flutter of AGARD445.6 standard I‐wing weakened model configuration for subsonic to near transonic flow regime. Gambit^® and Fluent^® are used for CFD grid generation and solution of fluid dynamic equations, respectively. CSD modeling and simulation are provided by numerical time integration of modal dynamic equations derived through the finite element modeling in ANSYS^® environment. Copyright © 2009 John Wiley & Sons, Ltd.     

Second representable modules over commutative rings*

Let R be a commutative ring. We investigate R-modules which can be written as finite sums of second R-submodules (we call them second representable). The class of second representable modules lies between the class of finitely generated semisimple modules and the class of representable modules; moreover, we give examples to show that these inclusions are strict even for Abelian groups. We provide sufficient conditions for an R-module M to be have a (minimal) second presentation, in particular within the class of lifting modules. Moreover, we investigate the class of (main) second attached prime ideals related to a module with such a presentation.     

Electrical Properties of Polymethylmethacrylate Polymer Dispersed Liquid Crystals*

The effect on the electrical properties of polymethylmethacrylate polymer containing liquid crystal as dispersed molecules is investigated in the temperature range 30-100°C and the frequency ange from 100 Hz to 10 kHz. It is found that increasing the liquid crystal content enhances the ac-impedance, decreases the ac-loss conductivity and decreases the value of the dielectric constant. The decrease in the ac-impedance with increasing frequency is associated with a dramatic increase in the ac-loss conductivity at frequencies higher than 1 kHz. The decrease in the ac-conductivity with increasing the dispersed liquid crystal phase is attributed to the reduction of the mobility of the charge carriers. Thus, the dielectric property of the system improves.     

Tilting modules over almost perfect domains

We provide a complete classification of all tilting modules and tilting classes over almost perfect domains, which generalizes the classifications of tilting modules and tilting classes over Dedekind and 1-Gorenstein domains. Assuming the APD is Noetherian, a complete classification of all cotilting modules is obtained (as duals of the tilting ones).     

Semicorings and Semicomodules

In this paper, we introduce and investigate semicorings over associative semirings and their categories of semicomodules. Our results generalize old and recent ones on corings over rings and their categories of comodules. The generalization is not straightforward and even subtle at several places due to the nature of the base category of commutative monoids which is neither Abelian (not even additive) nor homological, and has no nonzero injective objects. To overcome these and other difficulties, a combination of methods and techniques from categorical, homological and universal algebra is used including a new notion of exact sequences of semimodules over semirings.     

Nonlinear Axisymmetric Deformation Model for Structures of Revolution

An axisymmetric formulation for modeling three-dimensional deformation of structures of revolution is presented. The axisymmetric deformation model is described using the cylindrical coordinate system. Large displacement effects and material nonlinearities and anisotropy are accommodated by the formulation. Mathematical derivation of the formulation is given, and an example is presented to demonstrate the capabilities and efficiency of the technique compared to the full three-dimensional model.     

Reconstruction of Scalar Field Dark Energy Models in Kaluza-Klein Universe

This paper is devoted to study the modified holographic dark energy model by taking its different aspects in the flat Kaluza-Klein universe. We construct the equation of state parameter which evolutes the universe from quintessence region towards the vacuum. It is found that the modified holographic model exhibits instability against small perturbations in the early epoch of the universe but becomes stable in the later times. We also develop its correspondence with some scalar field dark energy models. It is interesting to mention here that all the results are consistent with the present observations.