Thermodynamics of the displacive mechanism of alpha(1) transformation in a beta

Thermodynamics of the displacive mechanism of plate-shaped phase alpha(1) was analyzed in beta'Cu-Zn alloys. It was proposed that the displacive transformation of the alpha(1) plate took place in the solute-depleted region formed in the parent phase during the incubation period. The thermodynamic analysis indicated that the driving force of alpha(1) transformation, Delta G, increased with the reduction of x(d), the solute concentration of the depleted region. And, Delta G could overcome-the transformation barrier with solute depletion to a certain degree. In addition, x(d) was higher than the equilibrium concentration in the phase diagram. Therefore, the shear formation of alpha(1) plate in the solute-depleted region was thermodynamically supported.

Molecular/Cluster Statistical Thermodynamics Methods To Simulate Quasi-Static Deformations At Finite Temperature

The rapid evolution of nanotechnology appeals for the understanding of global response of nanoscale systems based on atomic interactions, hence necessitates novel, sophisticated, and physically based approaches to bridge the gaps between various length and time scales. In this paper, we propose a group of statistical thermodynamics methods for the simulations of nanoscale systems under quasi-static loading at finite temperature, that is, molecular statistical thermodynamics (MST) method, cluster statistical thermodynamics (CST) method, and the hybrid molecular/cluster statistical thermodynamics (HMCST) method. These methods, by treating atoms as oscillators and particles simultaneously, as well as clusters, comprise different spatial and temporal scales in a unified framework. One appealing feature of these methods is their "seamlessness" or consistency in the same underlying atomistic model in all regions consisting of atoms and clusters, and hence can avoid the ghost force in the simulation. On the other hand, compared with conventional MD simulations, their high computational efficiency appears very attractive, as manifested by the simulations of uniaxial compression and nanoindenation. (C) 2008 Elsevier Ltd. All rights reserved.

Numerical-simulation of ac plasma-arc thermodynamics

A mathematical model and approximate analysis for the energy distribution of an ac plasma arc with a moving boundary is developed. A simplified electrical conductivity function is assumed so that the dynamic behavior of the arc may be determined, independent of the gas type. The model leads to a reduced set of non-linear partial differential equations which governs the quasi-steady ac arc. This system is solved numerically and it is found that convection plays an important role, not only in the temperature distribution, but also in arc disruptions. Moreover, disruptions are found to be influenced by convection only for a limited frequency range. The results of the present studies are applicable to the frequency range of 10-10(2) Hz which includes most industry ac arc frequencies. (C) 1994 Academic Press, Inc.

Temperature transformation in relativistic thermodynamics

This paper reviews conflicting results on relativistic transformation formula for tem-perature obtained by different authors in the last half century, discusses the proper expres-sion for elementary work done under reversible processes, and presents a correct derivationof the transformation formula, rather similar in spirit to that of Einstein. It is pointed outthat the point of view adopted by Eddington, Ott, Mφller and Landsberg are erroneous,and that by correctly carrying out detailed analysis for Mφller's working model, which wasoriginally proposed to disprove Planck-Einstein result, we have arrived instead at a result incomplete agreement with that of Planck-Einstein. Thercupon this long standing controversyover the temperature transformation dilemma for relativistic thermodynamics is clarified.

Thermodynamics and kinetics analysis of in-situ synthesizing AlN

AIN powders were prepared by in-situ synthesis technique. It is a reaction of binary molten Al-Mg alloys with highly pure nitrogen. It was confirmed through thermodynamics calculation that Mg element in Al-Mg alloys can decrease oxygen content in the reacting system. Thus, nitridation reaction can be performed to form AIN. Moreover, an analysis of kinetics shows that the nitridation reaction of Al-Mg alloys can be accelerated and transferred rapidly with the increment of Mg content.

The generalized second law of thermodynamics in generalized gravity theories

We investigate the generalized second law of thermodynamics (GSL) in generalized theories of gravity. We examine the total entropy evolution with time including the horizon entropy, the non-equilibrium entropy production, and the entropy of all matter, field and energy components. We derive a universal condition to protect the generalized second law and study its validity in different gravity theories. In Einstein gravity (even in the phantom-dominated universe with a Schwarzschild black hole), Lovelock gravity and braneworld gravity, we show that the condition to keep the GSL can always be satisfied. In f ( R) gravity and scalar-tensor gravity, the condition to protect the GSL can also hold because the temperature should be positive, gravity is always attractive and the effective Newton constant should be an approximate constant satisfying the experimental bounds.

Dynamical horizon entropy and equilibrium thermodynamics of generalized gravity theories

We study the relation between the thermodynamics and field equations of generalized gravity theories on the dynamical trapping horizon with sphere symmetry. We assume the entropy of a dynamical horizon as the Noether charge associated with the Kodama vector and point out that it satisfies the second law when a Gibbs equation holds. We generalize two kinds of Gibbs equations to Gauss-Bonnet gravity on any trapping horizon. Based on the quasilocal gravitational energy found recently for f(R) gravity and scalar-tensor gravity in some special cases, we also build up the Gibbs equations, where the nonequilibrium entropy production, which is usually invoked to balance the energy conservation, is just absorbed into the modified Wald entropy in the Friedmann-Robertson-Walker spacetime with slowly varying horizon. Moreover, the equilibrium thermodynamic identity remains valid for f(R) gravity in a static spacetime. Our work provides an alternative treatment to reinterpret the nonequilibrium correction and supports the idea that the horizon thermodynamics is universal for generalized gravity theories.

Cosmological equations and thermodynamics on apparent horizon in thick braneworld

We derive the generalized Friedmann equation governing the cosmological evolution inside the thick brane model in the presence of two curvature correction terms: a four-dimensional scalar curvature from induced gravity on the brane, and a five-dimensional Gauss-Bonnet curvature term. We find two effective four-dimensional reductions of the generalized Friedmann equation in some limits and demonstrate that the reductions but not the generalized Friedmann equation can be rewritten as the first law of equilibrium thermodynamics on the apparent horizon of thick braneworld.

The research of rheology and thermodynamics of organic-inorganic hybrid membrane during the membrane formation

To clarify the mechanism of organic-inorganic hybrid membrane formation by phase-inversion method, the thermodynamical and theological properties of PSF/TiO2 casting solution were investigated by the viscosity measurement and the triangle phase diagram, respectively. TiO2 introduction decreased the non-solvent tolerance of casting solution with non-solvent 20% ethanol aqueous solution, which caused thermodynamic enhancement of phase separation, and also resulted in the change of theological properties from Newtonian fluid to non-Newtonian fluid and the viscosity increase of casting solution, which induced rheological hindrance in demixing process

Biophysical studies on the full-length human cyclin A(2): Protein stability and folding/unfolding thermodynamics

Human cyclin A(2) participates in cell cycle regulation, DNA replication, and transcription. Its overexpression has been implicated in the development and progression of a variety of human cancers. However, cyclin A(2) or its truncated form is very unstable in the absence of binding partner, which makes it difficult to get a deep insight of structural basis of the interactions. Therefore, biophysical studies of the full-length human cyclin A, would provide important information regarding protein stability and folding/unfolding process.

Pressure effects on thermodynamics of phase behavior in polystyrene/methylcyclohexane solutions

The calculations presented in this paper are based on the Sanchez-Lacombe (SL) lattice fluid theory. The interaction energy parameter, g*(12)/k, required in this approach was obtained by fitting the cloud points of polystyrene (PS) /methyleyclohexane (MCH) polymer solutions under pressure. The SL lattice fluid theory was used to calculate the spinodals, the binodals, and the Flory-Huggins (FH) interaction parameter of the solutions. The calculated results show that the SL lattice fluid theory can describe the dependences of thermodynamics of PS/MCH solutions on temperature and pressure very well. However, the calculated enthalpy and the excess volume changes indicate that the Clausius-Clapeyron equation cannot be suitable to describe pressure effect on PS/MCH solutions. Further analysis on the thermodynamics of this system under pressure shows that the role of entropy is more important than the excess volume in the present case.

Pressure effects on the thermodynamics of trans-decahydronaphthalene/polystyrene polymer solutions: Application of the Sanchez-Lacombe lattice fluid theory

The cloud-point temperatures (T-cl's) of trans-decahydronaphthalene(TD)/polystyrene (PS, (M) over bar (w) = 270 000) solutions were determined by light scattering measurements over a range of temperatures (1-16degreesC), pressures (100-900 bar), and compositions (4.2-21.6 vol.-% polymer). The system phase separates upon cooling and T-cl was found to increase with rising pressure for constant composition. In the absence of special effects, this finding indicates positive excess volume for the mixing. Special attention was paid to the demixing temperatures as a function of pressure for different polymer solutions and the plots in the T-phi plane (where phi signifies volume fractions). The cloud-point curves of polymer solutions under different pressures were observed for different compositions, which demonstrated that pressure has a greater effect on the TD/PS solutions when far from the critical point as opposed to near the critical point. The Sanchez-Lacombe lattice fluid theory (SLLFT) was used to calculate the spinodals, the binodals, the Flory-Huggins (FH) interaction parameter, the enthalpy of mixing, and the volume changes of mixing. The calculated results show that modified PS scaling parameters can describe the thermodynamics of the TD/PS system well. Moreover the SLLFT describes the experimental results well.

Thermodynamics of phase behavior in PEO/P(EO-b-DMS) homopolymer and block co-oligomer mixtures under pressure

The cloud-point temperatures (T-cl's) of poly(ethylene oxide) (PEO) and poly(ethylene oxide)-block-polydimethylsiloxane (P(EO-b-DMS)) homopolymer and block-oligomer mixtures were determined by turbidity measurements over a range of temperatures (105 to 130degrees), pressures (1 to 800 bar), and compositions (10-40 wt.-% PEO). The system phase separates upon cooling and T-cl was found to decrease with an increase in pressure for a constant composition. In the absence of special effects, this finding indicates negative excess volumes. Special attention was paid to the demixing temperatures as a function of the pressure for the different polymer mixtures and the plots in the T-phi plane (where phi signifies volume fractions). The cloud-point curves of the polymer mixture under pressures were observed for different compositions. The Sanchez-Lacombe (SL) lattice fluid theory was used to calculate the spinodals, the binodals, the Flory-Huggins (FH) interaction parameter, the enthalphy of mixing, and the volume changes of mixing. The calculated results show that modified P(EO-b-DMS) scaling parameters with the new combining rules can describe the thermodynamics of the PEO/P(EO-b-DMS) system well with the SL theory.