Equations of State

Hydrodynamic modes for ultracold gases at any general density are considered. By writing the equations for the mode frequencies in a convenient way, we show that it is possible to determine the equation of state of the dense gas from the knowledge of the hydrodynamic frequencies. As an example, we investigate the case of two equal fermionic populations in different hyperfine states with attractive interactions.

The model liquids discussed herein are represented as correlated ensembles of particles, moving around and interacting with strong, short-range forces. A spectrum of local vibrations is introduced for the local, collective movements of particles in such model liquids. The resulting statistics is formally equivalent with that of an ideal gas of bosons in two dimensions, which in turn, as it is well known, leads to a thermodynamics which is equivalent to that of an ideal gas of fermions in two dimensions. The parameters used for describing the statistics of the model are the cohesion energy per particle, the spacing between the energy levels of local vibrations and a constraining volume. The corresponding thermodynamics is derived, with explicit emphasis on both low-and high-temperature regimes. The condensation occurring in the low-temperature limit is discussed.

We investigate a representation of thermodynamic equations-of-state for water and steam using only physical constants and zero ad hoc parameters. Following the reported phase equilibria of a coexisting critical density hiatus and a supercritical mesophase defined by percolation transitions, the state functions density (p,T), and Gibbs energy G(p,T), of pure fluids are seen to exhibit a symmetry characterised by the rigidity,  = (dp/d)T along isotherms from the critical point (Tc) to Boyle temperature (TB), on either side of the supercritical mesophase for T > Tc. We report an analysis of H2O based upon a knowledge of the lower virial coefficients b2 and b3, that describe the gas region (steam) for all T. We show that the same coefficients also describe the supercritical liquid-side range 'water' in an expansion about a rigidity-symmetry (R-S) line defined by (RS)T = RT (R is ideal gas constant) We report further investigation into the Boyle-work line, w = p/(BW)T = RT. A revised Boyle temperature for H2O is reported: TB = 1567+20 K. The BW-line is everywhere linear in fluid regions, and interpolates to a ground state solid-range constant BW(0) at an ice density 82.56 mol/l. Cluster expansions in powers of density truncated at  < b4, equate steam virial coefficients with both BW and RS lines. We find both lines are continuous in all derivatives, and linear within the stable fluid phases. Simple relationships arise from the observation that the higher virial coefficients (bn, n > 4) cancel due to cluster equilibria, or are negligible (0 < T < TB) in the steam regions. All thermodynamic state functions f(p,T) for H2O below TB, are obtainable from the critical ratio of virial coefficients-(b2/b3)Tc determined from the linear Boyle line given only one H2O BW(0) ground-state density physical constant.

This note considers singular systems of nonlinear differential and algebraic equations (DAEs) whose constrained state space depends on the control inputs. A state-space realization of such systems cannot be derived independently of the controller design. An output feedback precompensator is derived, which results in a modified DAE system whose state-space is invariant under any feedback control law and can be used for output feedback controller synthesis. Its application is illustrated by a nonlinear electrical circuit example.

A new equation of state based on the Statistical Associating Fluid Theory (SAFT) is presented to study the phase behavior of associating and non-associating fluids. In the new equation of state, the hard sphere contribution to compressibility factor of the simplified version of the SAFT (SSAFT) is replaced with that proposed by Ghotbi and Vera. The Ghotbi-Vera SSAFT (GV-SSAFT) was also extended to study the phase behavior of associating and non-associating mixtures. The GV-SSAFT like the SSAFT equation of state has three adjustable segment parameters for non-associating fluids and five parameters for associating fluids. The experimental data of liquid densities and vapor pressures for pure fluids studied in this work were used to obtain the best values for the parameters of the GV-SSAFT. The results obtained from the GV-SSAFT for liquid densities and vapor pressures of pure associating and non-associating fluids were compared with those obtained from the SSAFT equation of state. The results showed that the GV-SSAFT similar to the SSAFT can accurately correlate the experimental data of liquid density and vapor pressure for systems studied. On the other hand the results obtained from two SAFT-based equations of state are almost identical. In order to show capability of the GV-SSAFT and SSAFT equations of state, they were used to directly calculate heat of vaporization for a number of pure associating and non-associating fluids. Slightly better results for heat of vaporization comparing to the experimental data were obtained from the GV-SSAFT EOS than those obtained from the SSAFT. The GV-SSAFT was also used to study the VLE phase behavior for a number of binary associating and non-associating mixtures. The results also showed that the GV-SSAFT can be successfully used to study the phase behavior of mixtures studied in this work.

In this work, we propose a computational strategy and methods for the automated calculation of complete loci of homogeneous azeotropy of binary mixtures and the related Pxy and Txy diagrams for models of the equation-of-state (EOS) type. The strategy consists of first finding the system's azeotropic end points (AEPs). These can exist on vapor-liquid (VL) critical lines (CAEPs), on liquid-liquid-vapor (LLV) lines (HAEPs), and on pure-compound vapor pressure lines (PAEPs). Next, for the chosen binary system, we generate one or two azeotropic lines. Each of these lines has, as its starting point, one of the previously identified AEPs. We calculate the azeotropic lines using a numerical continuation method that solves the nonlinear azeotropic system of equations under a range of conditions and efficiently tracks entire azeotropic curves. We have integrated our strategy for calculating azeotropic lines into a general algorithm for the single-run computation of binary global phase equilibrium diagrams (GPEDs). GPEDs are defined by pure-compound, critical, LLV, and azeotropic lines. We implemented this general algorithm in the computer program GPEC (Global Phase Equilibrium Calculations), which makes it possible to evaluate, at a glance, the behavior of a given model-parameter values combination, for a chosen model and binary system.

Midbrain dopamine (DA) neurons are not homogeneous but differ in their molecular properties and responses to external stimuli. We examined whether the modulation of excitatory synapses on DA neurons by rewarding or aversive stimuli depends on the brain area to which these DA neurons project. We identified DA neuron subpopulations in slices after injection of ''Retrobeads'' into single target areas of adult mice and found differences in basal synaptic properties. Administration of cocaine selectively modified excitatory synapses on DA cells projecting to nucleus accumbens (NAc) medial shell while an aversive stimulus selectively modified synapses on DA cells projecting to medial prefrontal cortex. In contrast, synapses on DA neurons projecting to NAc lateral shell were modified by both rewarding and aversive stimuli, which presumably reflects saliency. These results suggest that the mesocorticolimbic DA system may be comprised of three anatomically distinct circuits, each modified by distinct aspects of motivationally relevant stimuli.

In this work, we propose a computational strategy and methods for the automated calculation of complete loci of homogeneous azeotropy of binary mixtures and the related Pxy and Txy diagrams for models of the equation-of-state (EOS) type. The strategy consists of first finding the system's azeotropic end points (AEPs). These can exist on vapor-liquid (VL) critical lines (CAEPs), on liquid-liquid-vapor (LLV) lines (HAEPs), and on pure-compound vapor pressure lines (PAEPs). Next, for the chosen binary system, we generate one or two azeotropic lines. Each of these lines has, as its starting point, one of the previously identified AEPs. We calculate the azeotropic lines using a numerical continuation method that solves the nonlinear azeotropic system of equations under a range of conditions and efficiently tracks entire azeotropic curves. We have integrated our strategy for calculating azeotropic lines into a general algorithm for the single-run computation of binary global phase equilibrium diagrams (GPEDs). GPEDs are defined by pure-compound, critical, LLV, and azeotropic lines. We implemented this general algorithm in the computer program GPEC (Global Phase Equilibrium Calculations), which makes it possible to evaluate, at a glance, the behavior of a given model-parameter values combination, for a chosen model and binary system.

We study the influence of Nb doping on the TiO 2 anatase-to-rutile phase transition, using combined transmission electron microscopy, Raman spectroscopy, x-ray diffraction and selected area electron diffraction analysis. This approach enabled anatase-to-rutile phase transition hindering to be clearly observed for low Nb-doped TiO 2 samples. Moreover, there was clear grain growth inhibition in the samples containing Nb. The use of high resolution transmission electron microscopy with our samples provides an innovative perspective compared with previous research on this issue. Our analysis shows that niobium is segregated from the anatase structure before and during the phase transformation, leading to the formation of NbO nanoclusters on the surface of the TiO 2 rutile nanoparticles.

We apply the chiral SU (3) quark mean field model to study the properties of strange hadronic matter at finite temperature. The liquid-gas phase transition is studied as a function of the strangeness fraction. The pressure of the system cannot remain constant during the phase transition, since there are two independent conserved charges (baryon and strangeness number). In a range of temperatures around 15 MeV (precise values depending on the model used) the equation of state exhibits multiple bifurcates. The difference in the strangeness fraction f s between the liquid and gas phases is small when they coexist. The critical temperature of strange matter turns out to be a non-trivial function of the strangeness fraction.

In this study, the process of capturing CO2 by using an aqueous MDEA solution under the operating conditions of the concentration range of 10-98 wt% of MDEA, temperature range of 303-323K and atmospheric pressure is investigated. Most researchers have measured the effect of pressure changes on the loading, but in this work, we have investigated the effect of changing the concentration of amine on the loading. We employed the apparatus introduced by Pahlavanzadeh et al. to evaluate the solubility of carbon dioxide in the aqueous solutions of N-methyldiethanolamine (MDEA). The results indicate that the maximum absorption of CO2 takes place in concentration of between 40-50 wt% of MDEA. Subsequently, the Cubic-Two-State Equation of State (CTS EoS) was improved and used to describe the solubility of CO2 in aqueous MDEA solutions in a wide range of concentrations and temperatures. This equation, referred to as CTSDH, includes three terms relating to the different intermolecular interactions happening in electrolyte solutions. The same EoS was used for vapor and liquid phases. Model parameters were adjusted according to the experimental results of this work and other researches. Using the adjustable parameters from this work, the model successfully approximated CO2 loading under a wide range of functional conditions. The evaluation of model results with experimental data showed the average absolute percent deviation (AAD%) to be 7.05%, indicating a satisfactory alignment between model predictions and Measured results.

We analyze the effect that peculiar velocities have on the cosmological inferences we make using luminosity distance indicators, such as Type Ia supernovae. In particular we study the corrections required to account for (1) our own motion, (2) correlations in galaxy motions, and (3) a possible local under-or overdensity. For all of these effects we present a case study showing the impact on the cosmology derived by the Sloan Digital Sky Survey-II Supernova Survey (SDSS-II SN Survey). Correcting supernova (SN) redshifts for the cosmic microwave background (CMB) dipole slightly overcorrects nearby SNe that share some of our local motion. We show that while neglecting the CMB dipole would cause a shift in the derived equation of state of Δw ∼ 0.04 (at fixed Ω m ), the additional local-motion correction is currently negligible (Δw 0.01). We then demonstrate a covariance-matrix approach to statistically account for correlated peculiar velocities. This down-weights nearby SNe and effectively acts as a graduated version of the usual sharp low-redshift cut. Neglecting coherent velocities in the current sample causes a systematic shift of Δw ∼ 0.02. This will therefore have to be considered carefully when future surveys aim for percent-level accuracy and we recommend our statistical approach to down-weighting peculiar velocities as a more robust option than a sharp low-redshift cut.

Small-scale detonability testing: We developed the capability to perform small-scale detonation performance testing, using as little as 10 g of material. Normally, detonation performance tests require several kilograms of material, making it very resource-intensive to obtain data with the necessary breadth to parametrize models. We started with a microwave interferometer that could provide a nearcontinuous shock front position history. We have also performed testing with systems not amenable to microwave using high-speed imaging. • Model development and calibration: Reliable models are required for the Department of Homeland Security (DHS) to be able to perform accurate threat assessments. We have demonstrated the ability to use data from small-scale detonation failure experiments to calibrate computational models. Through this work, we have determined the small-scale experimental configuration that would be most amenable to computational modeling.

Small scale characterization experiments using only 1–5 g of a baseline ammonium nitrate plus fuel oil (ANFO) explosive are discussed and simulated using an ignition and growth reactive flow model. There exists a strong need for the small scale characterization of non-ideal explosives in order to adequately survey the wide parameter space in sample composition, density, and microstructure of these materials. However, it is largely unknown in the scientific community whether any useful or meaningful result may be obtained from detonation failure, and whether a minimum sample size or level of confinement exists for the experiments. In this work, it is shown that the parameters of an ignition and growth rate law may be calibrated using the small scale data, which is obtained from a 35 GHz microwave interferometer. Calibration is feasible when the samples are heavily confined and overdriven; this conclusion is supported with detailed simulation output, including pressure and reaction co...

In this paper, two modified Ricci models are considered as the candidates of unified dark matter-dark energy. In model one, the energy density is given by ρ MR = 3M pl (αH 2 + βḢ), whereas, in model two, by ρ MR = 3M pl (α 6 R + γḦ H −1). We find that they can explain both dark matter and dark energy successfully. A constant equation of state of dark energy is obtained in model one, which means that it gives the same background evolution as the wCDM model, while model two can give an evolutionary equation of state of dark energy with the phantom divide line crossing in the near past.

We present a comparison of experimentally and theoretically determined osmotic pressures for various colloidal dispersions. Experimental data is collected from several different silica and polystyrene dispersions. The theoretical pressure determinations are based on the Primitive Model combined with the Cell Model and the physical quantities are calculated exactly using Monte Carlo simulations in the canonical and grand canonical ensemble. The input to the simulations in terms of colloidal particle size, surface charge density etc are taken directly from experiments and the approach does not contain any adjustable parameters. The agreement between theory and experiment is excellent without any fitting parameters showing that the simplifications behind the primitive model and the cell model are physically sound. For one of the silica dispersions we have also investigated how various monovalent counterions influence the swelling properties. Within experimental errors, we are unable to detect any ion specificity, which is another support for the theoretical models used.

Quasi-hydrostatic compression of aluminum carbide, Al 4 C 3 has been studied to 6 GPa at room temperature using energydispersive X-ray powder diffraction with synchrotron radiation. A fit of the experimental p-V data to the Birch equation of state yields the values of the bulk modulus, B 0 , of 130(5) GPa and the first pressure derivative of the bulk modulus, B 0 0 , of 4.6(9). The compression is found to be anisotropic, with the a-axis being more compressible than the c-axis.

Quasi-hydrostatic compression of rhombohedral boron subnitride has been studied up to 30 GPa at room temperature using angle-dispersive X-ray diffraction with synchrotron radiation. The α-rhombohedral boron type R3m structure of B 13 N 2 is stable in the whole pressure range under study. A fit of the experimental p-V data to the Birch equation of state yields the values of the bulk modulus, B 0 , of 200(15) GPa with fixed first pressure derivative of the bulk modulus, B 0 , of 4.0. The compression is found to be slightly anisotropic with higher compressibility along c-axis.

We present the first principles calculations of the thermodynamical properties of magnesium hydride (MgH 2 ) over a temperature range of 0-1000 K. The phonon dispersions are determined within the density functional framework and are used to calculate the free energy of MgH 2 within the quasiharmonic approximation (QHA) at each cell volume and temperature T. Using the free energies the thermal equation of state (EOS) is derived at several temperatures. From the thermal EOS structural parameters such as the equilibrium cell volume (V 0 ) and elastic properties, namely, bulk modulus (K 0 ) and its pressure derivative ðK 0 0 Þ are computed. The free energies are also used to calculate various thermodynamical properties within QHA. These include internal energy E, entropy S, specific heat capacity at constant pressure C P , thermal pressure P thermal (V, T) and volume thermal expansion DV/V (%). The good agreement of calculated values of S and C P with experimental data exhibits that QHA can be used as a tool for calculating the thermodynamical properties of MgH 2 over a wide temperature range. P thermal (V,T) increases strongly with T at all the volumes but it is a slowly varying function of volume for T = 298-500 K. According to Karki [B.B. Karki, Am. Miner. 85 (2000) 1447] such volume based variations can be neglected and so it is possible to estimate the thermal EOS only with the knowledge of the measured P thermal (V, T) versus temperature at ambient pressure and isothermal compression data at ambient temperature. Temperature dependence of DV/V(%) shows that V 0 increased with increase in temperature. However, the percentage decrease in K 0 superseded this percentage increase in V 0 even at temperatures moderately higher than 298 K. Therefore, we suggest application of temperature (T > 298 K) as an approach to enhance the hydrogen storage capacity of MgH 2 because of its better compressibility at these temperatures.

This paper presents a hybrid way mixing time and frequency domain for transmission lines modelling. The proposed methodology handles steady fundamental signal mixed with fast and slow transients, including impulsive and oscillatory behaviour. A transmission line model is developed based on lumped elements representation and state-space techniques. The proposed methodology represents an easy and practical procedure to model a three-phase transmission line directly in time domain, without the explicit use of inverse transforms. The proposed methodology takes into account the frequency-dependent parameters of the line, considering the soil and skin effects. In order to include this effect in the state matrices, a fitting method is applied. Furthermore the accuracy of proposed the developed model is verified, in frequency domain, by a simple methodology based on line distributed parameters and transfer function related to the input/output signals of the lumped parameters representation. In addition, this article proposes the use of a fast and robust analytic integration procedure to solve the state equations, enabling transient and steady-state simulations. The results are compared with those obtained by the commercial software Microtran (EMTP), taking into account a three-phase transmission line, typical in the Brazilian transmission system.

The viscosity of pure hydrocarbons was correlated using a simple function based on the fluid density. The correlation has three adjustable parameters, a compressed state density, F s °, an empirical parameter, c 2 , that scales the viscosity response to fluid expansion, and another empirical parameter, c 3 , used to tune at pressures above 10 MPa. The inputs to the correlation are the fluid density, pressure, and low-pressure gas viscosity. The correlation fit experimental viscosities for 39 pure hydrocarbons including n-alkanes, branched alkanes, alkenes, cyclics, and aromatics, within experimental error over a broad range of temperatures and pressures. Heavy hydrocarbons such as mineral oils were also fit with an AAPRD of 2.7%. Binary mixture viscosities were predicted to within 10% using simple volumetric mixing rules. The method provides a single framework for liquid and vapor phases, is simple to implement, and is very fast computationally, making it ideal for incorporation into process and reservoir simulators.

A practical method has been developed for determining parameters for the statistical associating fluid theory (SAFT) equation of state. Critical temperature, pressure, and density as well as normal boiling point are used to determine parameters for associating compounds, especially sugars. The method has been verified by the description of sugar solubilities in water and in mixed solvents. The predicted and correlated results are in good agreement with the experimental data of systems containing D-fructose, D-glucose, and sucrose. The SAFT model has been further applied to a sugar-containing system in modeling of the recovery of chemicals, such as the sugars levoglucosan and hydroxyacetaldehyde, from a pyrolysis liquid produced from biomass fast pyrolysis. At high temperatures, the two sugars are instable. The modeling of separation of the sugars has been carried out at temperatures 50 • C and 60 • C and in a pressure range of 0.01-0.03 bar. Under these conditions, the effect of pressure on the separation is larger than that of temperature. A lower pressure and a higher water content of the pyrolysis liquid are favourable for the separation. With pressure decreasing, the effect of water content on the separation is becoming less significant.

A practical method has been developed for determining parameters for the statistical associating fluid theory (SAFT) equation of state. Critical temperature, pressure, and density as well as normal boiling point are used to determine parameters for associating compounds, especially sugars. The method has been verified by the description of sugar solubilities in water and in mixed solvents. The predicted and correlated results are in good agreement with the experimental data of systems containing D-fructose, D-glucose, and sucrose. The SAFT model has been further applied to a sugar-containing system in modeling of the recovery of chemicals, such as the sugars levoglucosan and hydroxyacetaldehyde, from a pyrolysis liquid produced from biomass fast pyrolysis. At high temperatures, the two sugars are instable. The modeling of separation of the sugars has been carried out at temperatures 50 • C and 60 • C and in a pressure range of 0.01-0.03 bar. Under these conditions, the effect of pressure on the separation is larger than that of temperature. A lower pressure and a higher water content of the pyrolysis liquid are favourable for the separation. With pressure decreasing, the effect of water content on the separation is becoming less significant.

There are now many known exoplanets with M sin i within a factor of two of Neptune's, including the transiting planets GJ436b and HAT-P-11b. Planets in this mass-range are different from their more massive cousins in several ways that are relevant to their radiative properties and thermal structures. By analogy with Neptune and Uranus, they are likely to have metal abundances that are an order of magnitude or more greater than those of larger, more massive planets. This increases their opacity, decreases Rayleigh scattering, and changes their equation of state. Furthermore, their smaller radii mean that fluxes from these planets are roughly an order of magnitude lower than those of otherwise identical gas giant planets. Here, we compute a range of plausible radiative equilibrium models of GJ436b and HAT-P-11b. In addition, we explore the dependence of generic Neptune-mass planets on a range of physical properties, including their distance from their host stars, their metallicity, the spectral type of their stars, the redistribution of heat in their atmospheres, and the possible presence of additional optical opacity in their upper atmospheres.

In the work of N. Martys et al. [Nicos S. Martys, Xiaowen Shan, Hudong Chen, Phys. Rev. E, Vol. 58, Num.5, 1998 ], a self-consistent force term to any order in the Boltzmann-BKG equation is derived by the Hermite basis with raw velocity. As an extension, in the present work, the force term is expanded by the Hermite basis with the relative velocity in the comoving coordinate and the Hermite basis with the relative velocity scaled by the local temperature. It is found that the force scheme proposed by He et al. [Xiaoyi He, Xiaowen Shan, Gary D. Doolen, Phys. Rev. E, Vol. 57, Num.1,1998] can be derived by the Hermite basis with the relative velocity. Furthermore, another new force scheme in which the velocity is scaled by the local temperature is obtained.

We identify the global symmetries of SU(2) lattice gauge theory with N flavors of staggered fermion in the presence of a quark chemical potential µ, for fermions in both fundamental and adjoint representations, and anticipate likely patterns of symmetry breaking at both low and high densities. Results from numerical simulations of the model with N = 1 adjoint flavor on a 4 3 × 8 lattice are presented, using both hybrid Monte Carlo and Two-Step Multi-Boson algorithms. It is shown that the sign of the fermion determinant starts to fluctuate once the model enters a phase with non-zero baryon charge density. HMC simulations are not ergodic in this regime, but TSMB simulations retain ergodicity even in the dense phase, and in addition appear to show superior decorrelation. The HMC results for the equation of state and the pion mass show good quantitative agreement with the predictions of chiral perturbation theory, which should hold only for N ≥ 2. The TSMB results incorporating the sign of the determinant support a delayed onset transition, consistent with the pattern of symmetry breaking expected for N = 1.

The combustion and detonation characteristics of CL20 can be improved if it is formed into nanoparticles of uniform size. A new, promising process for particulation of materials utilizes environmentally benign compressed gases as either solvents or anti-solvents. Predictive models are required to describe the solubility and phase behavior of supercritical solutions of CL20 and supercritical carbon dioxide and for process simulation and development. Here, the solubility of CL20 in supercritical carbon dioxide was evaluated using the Peng-Robinson cubic equation of state. Critical properties, vapor pressure, and other required thermodynamic properties were estimated using a variety of available estimation techniques, including the group contribution methods of Lydersen and of Joback. A Fortran program to predict the solubility of CL20 was developed during the course of this project. The program was validated using available literature data for the solubility of naphthalene and of biphenyl in supercritical carbon dioxide. The applicability of the estimation techniques employed for the critical properties for CL20 was established using these same techniques to estimate the critical properties of comparable compounds, including RDX and HMX. Solubility data for RDX in supercritical carbon dioxide reported in the literature were also used to establish the validity of the estimation approach. Solubility was predicted over the temperature range of 305.15 to 368.15 K and over the pressure range of 74 to 150 atm. In general, as the temperature increases, the solubility decreases, while as the pressure increases, the solubility increases. For CL20, the estimated vapor pressures are extremely small, on the order of 10-18 at ambient temperature, increasing to 10-13 at 368.15 K. Thus, the predicted solubilities are also small (range of 10-13 to 10-6), with the highest solubility predicted for 308.15 K (35°C) and 150 atm. In the region of temperature nearest the critical point of carbon dioxide, the influence of the supercritical fluid is stronger. It would be most desirable to operate in this region if one is interested in maximizing the solubility of the solute, CL20, in the carbon dioxide.

CL20, a high-energy explosive compound, is a polyazapolycyclic caged polynitramine (2,4,6,8,10,12- Hexanitro- 2,4,5,8,10,12-hexaazaisowurtzitane). The combustion and detonation characteristics of CL20 can be improved if it is formed into nanoparticles of uniform size. A new, promising process for particulation of materials utilizes environmentally benign compressed gases as either solvents or anti-solvents. Predictive models are required to describe the solubility and phase behavior of supercritical solutions of CL20 and supercritical carbon dioxide and for process simulation and development. Here, the solubility of CL20 in supercritical carbon dioxide was evaluated using the Peng-Robinson cubic equation of state. Critical properties, vapor pressure, and other required thermodynamic properties were estimated using a variety of available estimation techniques. A Fortran program to predict the solubility of CL20 was developed during the course of this project. The program was validate...

The equilibrium solubility of anthracene (as a model of coke precursor) in sub-and supercritical propane has been measured using a static viewcell at temperatures from (298 to 405) K and pressures from (4.7 to 11.3) MPa. The values of the mole fraction of anthracene in propane were from 1.4 • 10-4 to 6.6 • 10-3 over the experimental conditions studied. These values are two orders of magnitude higher than those reported in the literature for anthracene in CO 2 and are indicative of the excellent solvent properties of propane for the extraction of polyaromatics, compared to supercritical CO 2. The experimental solubility data have been correlated by the Peng-Robinson equation of state using different mixing rules for the calculation of parameters a and b. The mathematical model proposed provides a good agreement between the experimental and the calculated solubility, with a standard deviation of 6 • 10-4 of the model predictions.

Two different types of problems are approached by connecting simplified molecular models with equations Ž. of state EOS. For aqueous-organic solutions of gases chemically reacting with solvent, special techniques to handle electrostatic and nonelectrostatic interaction contributions in the calculation of liquid composition and fugacity coefficients are applied for modeling VLE. A modified hole model and the Soave-Redlich-Kwong Ž. Ž. SRK EOS are utilized to describe solubility of gases in water-alkanolamine-acid gas CO , H S mixtures. A 2 2 polydisperse version of a thermodynamic micellization model proposed earlier is formulated and applied to describe asphaltene phase drop-out from crude oils.

Two different types of problems are approached by connecting simplified molecular models with equations Ž. of state EOS. For aqueous-organic solutions of gases chemically reacting with solvent, special techniques to handle electrostatic and nonelectrostatic interaction contributions in the calculation of liquid composition and fugacity coefficients are applied for modeling VLE. A modified hole model and the Soave-Redlich-Kwong Ž. Ž. SRK EOS are utilized to describe solubility of gases in water-alkanolamine-acid gas CO , H S mixtures. A 2 2 polydisperse version of a thermodynamic micellization model proposed earlier is formulated and applied to describe asphaltene phase drop-out from crude oils.

Perturbation theory of equation of state due to Barker and Henderson is reformulated. This new formulation makes it possible to calculate the Helmholtz free energy of a fluid system analytically by perturbation relations of Barker and Henderson, without use of any approximation or need of any numerical table for the hard-sphere reference system other than the original Percus-Yevick approximations. The results are compared with the calculation of Barker and Henderson, and it is shown that the two agree with each other at all the temperatures which are compared, while the present method produces compressibilities slightly closer to the experimental and machine-calculated data. The results of the present method, based on average Percus-Yevick hard-sphere compressibilities, are also compared with the result of other theories of equation of state of simple fluids, molecular dynamics, and Monte Carlo calculations.

Isothermal vapour-liquid equilibrium (VLE) of the R-1234yf + R-245cb binary system were measured using a "static-analytic" apparatus at temperatures from 283.39 to 343.27 K. The data measured were compared with literature data for conformity checking. Albeit both VLE measurement sets are in good accordance, an unexpected behaviour was observed for the relative volatility calculated on the basis of the literature data. The thermodynamic model used for the calculations reproduces very well R-1234yf + R-245cb VLE data, and is based on a 3-parameter cubic equation of state (denoted by NEoS). This cubic equation of state was associated with the Mathias-Copeman alpha function and van der Waals mixing rules. Comparisons were also done with Peng Robinson EoS with similar alpha function and mixing rules.

Isothermal vapor-liquid equilibrium data for the Difluoromethane (R32) + Propane binary system are presented at 278.10, 294.83, 303.23, 313.26 and 343.26 K and pressures up to 5.4 MPa. The experimental method is the static-analytic type. It takes advantage of mobile pneumatic capillary samplers (Rolsi™, Armines' patent) developed in our laboratory. At a fixed temperature the azeotrope vapor pressure is larger then those of the pure component. The particularity of R32-Propane azeotropic binary system is to present in two critical point over the critical temperature if the azeotrope. This particular behavior has been proved and even shown visually by means of two supplementary experiments with equipment based on the static-synthetic method involving a variable volume cell. Data along the five isotherms have been represented with the Soave-Redlich-Kwong (SRK) equation of state and MHV1 mixing rules involving the NRTL model. We have calculated the location of the azeotrope using the equality of Equation of State attractive parameter between the two phases.

The present study introduEs a generalized correlation for the interaction coefficients of N,(i)/hydrocarbon( j) binary systems as a function of the reduced temperature of nitrogen (T,J and the acentric factor of the hydrocarbon (LI)/). It is applicable to the translated-modified Peng-Robinson equation of state (t-mPR EoS) and the original PR as well. The prediction results for N,/n-alkanc binary systems are satisfactory with an average absolute error in bubble-point pressure below 6%. Equally good results are obtained for the binaries of N, with naphthenes, iso-alkanes and aromatics. Use of temperature independent interaction c&ficients is recommended for the N,/alkene systems. The proposed correlation is limited to pressures lower than 500 bar, and gives better prediction than those reported previously.

The present study introduEs a generalized correlation for the interaction coefficients of N,(i)/hydrocarbon(j) binary systems as a function of the reduced temperature of nitrogen (T,J and the acentric factor of the hydrocarbon (LI)/). It is applicable to the translated-modified Peng-Robinson equation of state (t-mPR EoS) and the original PR as well. The prediction results for N,/n-alkanc binary systems are satisfactory with an average absolute error in bubble-point pressure below 6%. Equally good results are obtained for the binaries of N, with naphthenes, iso-alkanes and aromatics. Use of temperature independent interaction c&ficients is recommended for the N,/alkene systems. The proposed correlation is limited to pressures lower than 500 bar, and gives better prediction than those reported previously.

Remarkable differences in the shape of the nematic-smectic-B interface in a quasi-two-dimensional geometry have been experimentally observed in three liquid crystals of very similar molecular structure, i.e., neighboring members of a homologous series. In the thermal equilibrium of the two mesophases a faceted rectanglelike shape was observed with considerably different shape anisotropies for the three homologs. Various morphologies such as dendritic, dendriticlike, and faceted shapes of the rapidly growing smectic-B germ were also observed for the three substances. Experimental results were compared with computer simulations based on the phase field model. The pattern forming behavior of a binary mixture of two homologs was also studied. ͓S1063-651X͑96͒04208-0͔

En esta tesis se ha profundizado en la construcción del tensor para dos ansatz: placas y tubos, de materia hadrónica a partir del modelo de Skyrme. Las ecuaciones del movimiento, la densidad de la carga bariónica y el tensor energía-momentum dan a conocer que ciertas estructuras, denominadas pastas nucleares, se manifiestan con estos ansatz correctos en la teoría de Skyrme. Se ha efectuado una descripción exhaustiva para cada una de las componentes del tensor energía-momentum general y diagonal para el caso placas y tubos que
permiten un acercamiento a la materia bariónica en altas densidades.

STEP (the Satellite Test of the Equivalence Principle) will advance experimental limits on violations of Einstein's equivalence principle (EP) from their present sensitivity of 2 parts in 10 13 to 1 part in 10 18 through multiple comparison of the motions of four pairs of test masses of different compositions in an earth-orbiting drag-free satellite. Dimensional arguments suggest that violations, if they exist, should be found in this range, and they are also suggested by leading attempts at unified theories of fundamental interactions (e.g. string theory) and cosmological theories involving dynamical dark energy. Discovery of a violation would constitute the discovery of a new force of nature and provide a critical signpost toward unification. A null result would be just as profound, because it would close off any possibility of a natural-strength coupling between standard-model fields and the new light degrees of freedom that such theories generically predict (e.g., dilatons, moduli, quintessence). STEP should thus be seen as the intermediate-scale component of an integrated strategy for fundamental physics experiments that already includes particle acclerators (at the smallest scales) and supernova probes (at the largest). The former may find indirect evidence for new fields via their missing-energy signatures, and the latter may produce direct evidence through changes in cosmological equation of state-but only a gravitational experiment like STEP can go further and reveal how or whether such a field couples to the rest of the standard model. It is at once complementary to the other two kinds of tests, and a uniquely powerful probe of fundamental physics in its own right.