Requirements for thermodynamic

The Gibbs Ensemble MC simulation methodology [17-19] enables direct simulations of phase equilibria in fluids. A schematic diagram of the technique is shown in Fig. 10.1. Let us consider a macroscopic system with two phases coexisting at equilibrium. Gibbs ensemble simulations are performed in two separate microscopic regions, each within periodic boundary conditions (denoted by the dashed lines in Fig. 10.1). The thermodynamic requirements for phase coexistence are that each... 

Charge transfer reactions on semiconductor electrodes proceed under the condition of anodic and cathodic polarization in which the Fermi level epfsc) is different either from the Fermi level Eputicox) of redox electron transfer reactions or from the equivalent Fermi level ep,ioN) of ion transfer reactions. For redox electron transfer reactions, thermodynamic requirement for the anodic and cathodic reactions to proceed is given by the following inequalities ... 

Similarly, the thermodynamic requirement for the transfer of anodic holes to proceed from the valence band to reductant particles is given by Eqn. 10-8 ... 

Thermodynamic calculations presented here are based on Gibbs free energy minimization and were carried out using HSC Chemistry. The equilibrium amount of each species that is formed is normalized on the basis of one mole of n-Ci6, a model compound for diesel fuel, fed to the reactor. Carbon formation is a function of both the S/C ratio and reforming temperature. Figure 17 shows the minimum amount of S/C ratio thermodynamically required for carbon-free SR of n-Ci6 at a given temperature. Carbon-free operation of n-Cig is thermodynamically possible above the curve. Higher temperatures and S/C ratios inhibit carbon formation. 

From the perspective of the design engineer, the advantage of this approach is that the expressions for the adsorbed-phase concentrations are simple and explicit. However, the expressions do not reduce to Henry s law in the low-concentration limit, which is a thermodynamic requirement for physical adsorption. They therefore suffer from the disadvantage of any purely empirical equations, and they do not provide a reliable basis for extrapolation outside the range of experimental study. 

An important thermodynamic requirement for the homogeneous distribution of the organic gas phase in the close coupled showerhead is temperature uniformity, which also guarantees no unintended condensation of the organic material. Figure 9.3 depicts the temperature simulation of an Gen 2 OVPD showerhead suitable for substrate sizes of 400 mm x 400 mm. The showerhead is uniformly heated to 300 °C, whereas the chiller actively cools the substrate and the mask to 2 °C and to 3 °C, respectively, across the whole area. Both the mask and the substrate are in close contact and thereby actively cooled down across the whole area. 

We examine, as an example, the exergy vector diagram for methanol synthesis to estimate the minimum exergy loss thermodynamically required for the synthesis reaction of methanol from methane [Ref. 16.]. First, we consider a direct (single step) synthesis of methanol from methane through a coupled-and-coupling reaction consisting of the oxidation of methane (objective reaction) and the dissociation of water molecule (coupled reaction) shown, respectively, as follows ... 

The thermodynamic requirements for efficient photoelectrolysis may be described in isolation from the kinetic requirements if factors (3)-(8) are ignored and this simplest case scenario will be considered in the next section. The remainder of Section 9.3 will discuss the modifications that... 

Interface — In chemistry and physics interface means the two-dimensional plane separating two phases. The general thermodynamic requirement for the stability of an interface between two phases is a positive Gibbs energy of formation, because otherwise the interface... 

Noteworthy exanples are sensitizers such as Ru(bipy)j (29). porphyrins derivatives (30) and acridine dyes, e.g., proflavin (31). Among the electron relay compounds investigated it is worth mentioning the viologens (32) Eu , and their respective salicylate complexes ( ), Ru(bipy)j (3U) and cobalt complexes (35). Thus, at present a considerable choice of sensitizer/relay pairs is available that fulfill the photochemiical and thermodynamic requirements for water decomposition. 

The positive curvature is not realized in actual systems from the thermodynamic requirement for the stability of a system, that is, the second derivative of the excess Gibbs energy, AG = y, with respect to Aq 0 variable be negative, at T and P constant ... 

From the perspective of band positions, among the semiconductors represented in Figure 10, those that fulfil the thermodynamic requirements for overall water splitting are KTaOa, SrTiOa, Ti02, ZnS, CdS, and SiC. However, it is important to stress that the potential of the band structure... 

The mechanism underlying the threshold requirement is not clear. It could reflect a simple thermodynamic requirement for a transmembrane electrochemical gradient of a sufficient magnitude so that three protons traversing the ATP syn-... 

Given the postulated thermodynamic requirement for low hydrogen pressures and the possible heterotrophic carbon requirement for synthesis... 

For constant temperature and pressure, dG = 0 defines the condition of an equilibrium state. The second law of thermodynamics requires for spontaneous processes that... 

The main difference arises in the thermodynamic requirements for polymerization. In the case of the polymerization of a vinyl monomer, there is a large enthalpic difference between the monomer and polymer that overcomes the loss in entropy that accompanies the constraining of the monomer to form a linear chain. In the case of conversion of a cyclic molecule to a polymer, there is little change in the enthalpy per repeat unit between the monomer and the polymer, just a loss of the ring stmin energy. 

It is generally assumed that the same transition-state describes the reaction in the reverse direction and that this is a thermodynamic requirement for a process at equilibrium [as is written Eq. (3)]. 

The thermodynamic requirement for any type of phase equilibrium is that the composition of each species in each phase in which it appears be such that the equilibrium criterion... 

When the melt of a crystalline polymer is cooled to a temperature between the glass-transition and the equilibrium melting point, the thermodynamic requirement for crystallization is fulfilled. 

The thermodynamic requirement for crystallization in a miscible blend is that the blend exhibits a free energy on crystallization that is more negative than the free energy of the liquid-liquid mixture. A liquid-solid phase separation can occur when the miscible melt is cooled to a temperature between the glass-transition of the blend and the equilibrium melting point of the crystallizable component(s) (section 3.3.1). 

Consider a system in equilibrium that contains two liquid layers, two liquid phases. Let one of these liquid layers consist of pure liquid A, the other layer is a saturated solution of A in liquid B. The thermodynamic requirement for equilibrium is that the chemical potential of A in the solution, be equal to that in the pure liquid, p. So P = or... 

Spanos, T.J.T., Dusseault, M.B. Udey, N. 2003. Fundamental thermodynamics requirements for porous media description. Proc. GeoProc 2003 Conference, Stockholm, Sweden, 6 pages. 

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