The possibility of positronium induced free volume cavity expansion in some polymers above the glass transition temperature was investigated using experimental positron annihilation lifetime data from the literature for polydimethylsiloxane, polyisobutylene, and polybutadiene as function of temperature. The results suggest that free volume sites can expand towards an equilibrium size, determine...

The principal effects determining the value of the free energy of mixing of polymer solutions are discussed and compared, namely the combinatorial, energetic and structural effects. The influence of the last on the thermodynamic behaviour of polymer solutions is then dealt with, as revealed in the lower critical solution temperature. and in the effect of pressure on polymer—solvent compatibilit...

the the main objective of this research paper is to present 3-d elasticity solution for free vibration analysis of elastically supported continuously graded carbon nanotube-reinforced (cgcntr) annular plates. the volume fractions of oriented, straight single-walled carbon nanotubes (swcnts) are assumed to be graded in the thickness direction. an equivalent continuum model based on the eshelby-m...

In this research, HMX energy derivatives with different carbon-containing fullerenes in different temperature conditions were studied using density functional theory. For this purpose, the materials were first geometric optimized, then the thermodynamic parameters were calculated for all of them. Then, the process of changing the energy-dependent parameters such as specific heat capacity, entha...

The hypothetical scanning (HS) method is a general approach for calculating the absolute entropy, S, and free energy, F, by analyzing Boltzmann samples obtained by Monte Carlo (MC) or molecular dynamics (MD) techniques. With HS applied to a fluid, each configuration i of the sample is reconstructed by gradually placing the molecules in their positions at i using transition probabilities (TPs). ...

In the current work, free volume concepts, primarily applied to glass formers in the literature, were transferred to ionic liquids (ILs). A series of 1-butyl-3-methylimidazolium ([C4MIM](+)) based ILs was investigated by Positron Annihilation Lifetime Spectroscopy (PALS). The phase transition and dynamic properties of the ILs [C4MIM][X] with [X](-) = [Cl](-), [BF4](-), [PF6](-), [OTf](-), [NTf2...

The free volume holes and light transmission of hydrogel and silicone-hydrogel polymer contact lenses were investigated. As the material, the Proclear family (omafilcon A) of hydrogel contact lenses and the Biofinity family (comfilcon A) of silicone-hydrogel contact lenses were used. Positron annihilation lifetime spectroscopy was used to characterize geometrical sizes and fractions of the free...

This paper introduces a computational strategy to collaboratively develop the Galerkin Finite Volume Method (GFVM) as one of the most straightforward and efficient explicit numerical methods to solve structural problems encountering material nonlinearity in a small limited area, while the remainder of the domain represents a linear elastic behavior. In this regard, the Element Free Galerkin met...

Volume preservation is one of the qualitative characteristics common to many dynamical systems. However, it has been proved by Kang and Shang that e.g. Runge–Kutta (RK) methods can not preserve volume for all linear source-free ODEs (let alone nonlinear ODEs). On the other hand, certain so-called Exponential Runge–Kutta (ERK) methods do preserve volume for all linear source-free ODEs. Do such E...

Mixed convection of Cu-Water nanofluid is studied numerically in a shallow inclined enclosure by applying lattice Boltzmann method. The D2Q9 lattice and internal energy distribution function based on the BGK collision operator are used in order to develop the thermal flow field. The enclosure's hot lid has the constant velocity of U0 while its cold lower wall has no motion. Moreover, sidewalls ...