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Sample records for equilibrium phase experimental

  1. Non-equilibrium phase transitions

    SciTech Connect

    Mottola, E.; Cooper, F.M.; Bishop, A.R.; Habib, S.; Kluger, Y.; Jensen, N.G.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Non-equilibrium phase transitions play a central role in a very broad range of scientific areas, ranging from nuclear, particle, and astrophysics to condensed matter physics and the material and biological sciences. The aim of this project was to explore the path to a deeper and more fundamental understanding of the common physical principles underlying the complex real time dynamics of phase transitions. The main emphasis was on the development of general theoretical tools to deal with non-equilibrium processes, and of numerical methods robust enough to capture the time-evolving structures that occur in actual experimental situations. Specific applications to Laboratory multidivisional efforts in relativistic heavy-ion physics (transition to a new phase of nuclear matter consisting of a quark-gluon plasma) and layered high-temperature superconductors (critical currents and flux flow at the National High Magnetic Field Laboratory) were undertaken.

  2. Hierarchical condensation near phase equilibrium

    NASA Astrophysics Data System (ADS)

    Olemskoi, A. I.; Yushchenko, O. V.; Borisyuk, V. N.; Zhilenko, T. I.; Kosminska, Yu. O.; Perekrestov, V. I.

    2012-06-01

    A novel mechanism of new phase formation is studied both experimentally and theoretically in the example of quasi-equilibrium stationary condensation in an ion-plasma sputterer. Copper condensates are obtained to demonstrate that a specific network structure is formed as a result of self-assembly in the course of deposition. The fractal pattern related is inherent in the phenomena of diffusion limited aggregation. Condensate nuclei are shown to form statistical ensemble of hierarchically subordinated objects distributed in ultrametric space. The Langevin equation and the Fokker-Planck equation related are found to describe stationary distribution of thermodynamic potential variations at condensation. Time dependence of the formation probability of branching structures is found to clarify the experimental situation.

  3. Phase coexistence far from equilibrium

    NASA Astrophysics Data System (ADS)

    Dickman, Ronald

    2016-04-01

    Investigation of simple far-from-equilibrium systems exhibiting phase separation leads to the conclusion that phase coexistence is not well defined in this context. This is because the properties of the coexisting nonequilibrium systems depend on how they are placed in contact, as verified in the driven lattice gas with attractive interactions, and in the two-temperature lattice gas, under (a) weak global exchange between uniform systems, and (b) phase-separated (nonuniform) systems. Thus, far from equilibrium, the notions of universality of phase coexistence (i.e., independence of how systems exchange particles and/or energy), and of phases with intrinsic properties (independent of their environment) are lost.

  4. A benchmark study of molecular structure by experimental and theoretical methods: Equilibrium structure of uracil from gas-phase electron diffraction data and coupled-cluster calculations

    NASA Astrophysics Data System (ADS)

    Vogt, Natalja; Khaikin, Leonid S.; Grikina, Olga E.; Rykov, Anatolii N.

    2013-10-01

    The equilibrium structure of uracil, one of the nucleobases, which build nucleic acids, has been determined for the first time by the gas-phase electron diffraction (GED) method. The necessary rovibrational corrections to the experimental internuclear distances have been calculated with quadratic and cubic force constants in the MP2(all)/cc-pVTZ approximation. For the first time, the equilibrium structure has been optimized by the very time-consuming coupled-cluster method with single and double excitations and perturbative treatment of connected triples using the correlation-consistent polarized weighted core-valence triple-zeta basis set with all electrons being correlated (CCSD(T)(all)/cc-pwCVTZ). The optimized structural parameters have been corrected for the diffuse-function effects and extrapolated to the higher basis set (cc-pwCVQZ) using results of MP2 computations (named as best ab initio structure). The GED equilibrium structure remarkably agrees with the best ab initio one as well as with that one derived from microwave (MW) rotational constants by Puzzarini and Barone. Thus, it has been revealed that the precise experiment and coupled-cluster calculations yield the same results when accurate vibrational corrections (including anharmonic ones) are considered in the experimental structural analysis. Moreover, it has been shown that the equilibrium structure derived from the GED data, being in general of one order less accurate than that determined from the MW rotational constants, is still reliable and accurate.

  5. The α +ɛ Two-Phase Equilibrium in the Fe-N-C System: Experimental Investigations and Thermodynamic Calculations

    NASA Astrophysics Data System (ADS)

    Göhring, Holger; Leineweber, Andreas; Mittemeijer, Eric Jan

    2016-09-01

    The present work is dedicated to investigating the occurrence of the α +ɛ equilibrium at temperatures typically applied for nitrocarburizing treatments. To this end, pearlitic Fe-C specimens were treated between 823 K and 863 K (550 °C and 590 °C) in gaseous nitriding and gaseous nitrocarburizing atmospheres, allowing control of the chemical potentials of N and C. Subsequently, the resulting compound-layer microstructures were investigated using light microscopy and X-ray diffraction. Thermodynamic calculations, adopting several models for the Fe-N-C system from the literature, were performed, showing significantly different predictions for both the sequence of the invariant reactions and their temperatures. Comparison of the experimental data and the theoretical calculations led to the conclusion that none of the models from the literature is able to realistically describe the experimentally observed constitution in the Fe-N-C system in the considered temperature range. Values/value ranges for the temperatures of the invariant reactions were obtained.

  6. Non-equilibrium phases and phase diagrams

    SciTech Connect

    Massalski, T.B.; Rizzo, H.F.

    1988-03-01

    In this paper we consider the degree of usefulness of the phase diagram and the related thermodynamics in predicting and understanding the formation of metastable phases during quenching, or during low-temperature solid-state interdiffusion, or during co-deposition. Recent research has demonstrated that many of such metastable phases are formed because the more stable intermediate phases that are favored thermodynamically are nevertheless bypassed kinetically. The kinetic elimination of intermediate phases provides conditions where a metastable equilibrium can be established at low temperatures between the supercooled liquid and the terminal solid solutions, leading to metastable partitioned two-phase regions. Alternatively, the range of the metastable phases may be governed by the T/sub 0/ principle related to the crossover of the respective free energy curves, or may be controlled mainly by kinetic considerations. Which particular thermodynamic conditions apply appears to depend on the initial form of the phase diagram and the specific technique used. The occurrence of massive transformations also is discussed. 34 refs., 10 figs.

  7. Phase Equilibrium Investigations of Planetary Materials

    NASA Technical Reports Server (NTRS)

    Grove, T. L.

    2005-01-01

    This grant provided funds to carry out phase equilibrium studies on the processes of chemical differentiation of the moon and the meteorite parent bodies, during their early evolutionary history. Several experimental studies examined processes that led to the formation of lunar ultramafic glasses. Phase equilibrium studies were carried out on selected low-Ti and high-Ti lunar ultramafic glass compositions to provide constraints on the depth range, temperature and processes of melt generation and/or assimilation. A second set of experiments examined the role of sulfide melts in core formation processes in the earth and terrestrial planets. The major results of each paper are discussed, and copies of the papers are attached as Appendix I.

  8. Thermodynamics of phase equilibrium of binary alloys containing nanprecipitates

    NASA Astrophysics Data System (ADS)

    L'vov, P. E.; Svetukhin, V. V.; Obukhov, A. V.

    2011-02-01

    A model of phase equilibrium in binary alloys has been developed taking into account the formation of phase precipitates of arbitrary (including nanometer) size. It has been shown that the phase composition of alloys substantially depends on the size of phase precipitates and, in the case of the formation of nano-precipitates, the phase composition can differ by a factor of several times from the phase composition of macroscopic precipitates. The proposed model has been used for calculating the dependence of the phase composition of some binary alloys (α-Fe-Cr at the temperature T = 773 K and Zr-Nb at the temperature T = 853-873 K) on the size of precipitates. The results of the calculation agree with experimental data obtained by other authors.

  9. Equilibrium crystal phases of triblock Janus colloids.

    PubMed

    Reinhart, Wesley F; Panagiotopoulos, Athanassios Z

    2016-09-01

    Triblock Janus colloids, which are colloidal spheres decorated with attractive patches at each pole, have recently generated significant interest as potential building blocks for functional materials. Their inherent anisotropy is known to induce self-assembly into open structures at moderate temperatures and pressures, where they are stabilized over close-packed crystals by entropic effects. We present a numerical investigation of the equilibrium phases of triblock Janus particles with many different patch geometries in three dimensions, using Monte Carlo simulations combined with free energy calculations. In all cases, we find that the free energy difference between crystal polymorphs is less than 0.2 kBT per particle. By varying the patch fraction and interaction range, we show that large patches stabilize the formation of structures with four bonds per patch over those with three. This transition occurs abruptly above a patch fraction of 0.30 and has a strong dependence on the interaction range. Furthermore, we find that a short interaction range favors four bonds per patch, with longer range increasingly stabilizing structures with only three bonds per patch. By quantifying the effect of patch geometry on the stability of the equilibrium crystal structures, we provide insights into the fundamental design rules for constructing complex colloidal crystals. PMID:27609002

  10. Experimental studies in non-equilibrium physics

    NASA Astrophysics Data System (ADS)

    Cressman, John Robert, Jr.

    This work is a collection of three experiments aimed at studying different facets of non-equilibrium dynamics. Chapter I concerns strongly compressible turbulence, which turns out to be very different from incompressible turbulence. The focus is on the dispersion of contaminants in such a flow. This type of turbulence can be studied, at very low mach number, by measuring the velocity fields of particles that float on a turbulently stirred body of water. It turns out that in the absence of incompressibility, the turbulence causes particles to cluster rather than to disperse. The implications of the observations are far reaching and include the transport of pollutants on the oceans surface, phytoplankton growth, as well as industrial applications. Chapter II deals with the effects of polymer additives on drag reduction and turbulent suppression, a well-known phenomenon that is not yet understood. In an attempt to simplify the problem, the effects of a polymer additive were investigated in a vortex street formed in a flowing soap film. Measurements suggest that an increase in elongational viscosity is responsible for a substantial reduction in periodic velocity fluctuations. This study also helps to illuminate the mechanism responsible for vortex separation in the wake of a bluff body. Chapter III describes an experiment designed to test a theoretical approach aimed at generalizing the classical fluctuation dissipation theorem (FDT). This theorem applies to systems driven only slightly away from thermal equilibrium, whereas ours, a liquid crystal under-going electroconvection, is so strongly driven, that the FDT does not apply. Both theory and experiment focus on the flux in global power fluctuations. Physical limitations did not permit a direct test of the theory, however it was possible to establish several interesting characteristics of the system: the source of the fluctuations is the transient defect structures that are generated when the system is driven hard

  11. Near-equilibrium polymorphic phase transformations in Praseodymium under dynamic compression

    SciTech Connect

    Bastea, M; Reisman, D

    2007-02-12

    We report the first experimental observation of sequential, multiple polymorphic phase transformations occurring in Praseodymium dynamically compressed using a ramp wave. The experiments also display the signatures of reverse transformations occuring upon pressure release and reveal the presence of small hysteresys loops. The results are in very good agreement with equilibrium hydrodynamic calculations performed using a thermodynamically consistent, multi-phase equation of state for Praseodymium, suggesting a near-equilibrium transformation behavior.

  12. Equilibrium-like phase transition of a dynamic system

    NASA Astrophysics Data System (ADS)

    Han, Ming; Yan, Jing; Granick, Steve; Luijten, Erik

    2014-03-01

    Dynamic systems are considered to be intrinsically different from systems in thermal equilibrium. Despite this fundamental dichotomy, here we demonstrate that a non-equilibrium, fully dynamical system can display behavior that constitutes a complete analogy to thermal equilibrium phase behavior. This dynamical system, consisting of Janus colloids strongly controlled by external fields and over-damped by a viscous solvent, phase separates like a binary fluid mixture, with a coexistence curve separating mixed and demixed regimes and a critical point that we demonstrate to belong to the 2D Ising universality class. Within the coexistence curve, we locate the spinodal curve that separates spinodal decomposition from nucleation and growth.

  13. Experimental approaches for studying non-equilibrium atmospheric plasma jets

    SciTech Connect

    Shashurin, A.; Keidar, M.

    2015-12-15

    This work reviews recent research efforts undertaken in the area non-equilibrium atmospheric plasma jets with special focus on experimental approaches. Physics of small non-equilibrium atmospheric plasma jets operating in kHz frequency range at powers around few Watts will be analyzed, including mechanism of breakdown, process of ionization front propagation, electrical coupling of the ionization front with the discharge electrodes, distributions of excited and ionized species, discharge current spreading, transient dynamics of various plasma parameters, etc. Experimental diagnostic approaches utilized in the field will be considered, including Rayleigh microwave scattering, Thomson laser scattering, electrostatic streamer scatterers, optical emission spectroscopy, fast photographing, etc.

  14. Experimental approaches for studying non-equilibrium atmospheric plasma jets

    NASA Astrophysics Data System (ADS)

    Shashurin, A.; Keidar, M.

    2015-12-01

    This work reviews recent research efforts undertaken in the area non-equilibrium atmospheric plasma jets with special focus on experimental approaches. Physics of small non-equilibrium atmospheric plasma jets operating in kHz frequency range at powers around few Watts will be analyzed, including mechanism of breakdown, process of ionization front propagation, electrical coupling of the ionization front with the discharge electrodes, distributions of excited and ionized species, discharge current spreading, transient dynamics of various plasma parameters, etc. Experimental diagnostic approaches utilized in the field will be considered, including Rayleigh microwave scattering, Thomson laser scattering, electrostatic streamer scatterers, optical emission spectroscopy, fast photographing, etc.

  15. Non-equilibrium phase transitions in a liquid crystal

    NASA Astrophysics Data System (ADS)

    Dan, K.; Roy, M.; Datta, A.

    2015-09-01

    The present manuscript describes kinetic behaviour of the glass transition and non-equilibrium features of the "Nematic-Isotropic" (N-I) phase transition of a well known liquid crystalline material N-(4-methoxybenzylidene)-4-butylaniline from the effects of heating rate and initial temperature on the transitions, through differential scanning calorimetry (DSC), Fourier transform infrared and fluorescence spectroscopy. Around the vicinity of the glass transition temperature (Tg), while only a change in the baseline of the ΔCp vs T curve is observed for heating rate (β) > 5 K min-1, consistent with a glass transition, a clear peak for β ≤ 5 K min-1 and the rapid reduction in the ΔCp value from the former to the latter rate correspond to an order-disorder transition and a transition from ergodic to non-ergodic behaviour. The ln β vs 1000/T curve for the glass transition shows convex Arrhenius behaviour that can be explained very well by a purely entropic activation barrier [Dan et al., Eur. Phys. Lett. 108, 36007 (2014)]. Fourier transform infrared spectroscopy indicates sudden freezing of the out-of-plane distortion vibrations of the benzene rings around the glass transition temperature and a considerable red shift indicating enhanced coplanarity of the benzene rings and, consequently, enhancement in the molecular ordering compared to room temperature. We further provide a direct experimental evidence of the non-equilibrium nature of the N-I transition through the dependence of this transition temperature (TNI) and associated enthalpy change (ΔH) on the initial temperature (at fixed β-values) for the DSC scans. A plausible qualitative explanation based on Mesquita's extension of Landau-deGennes theory [O. N. de Mesquita, Braz. J. Phys. 28, 257 (1998)] has been put forward. The change in the molecular ordering from nematic to isotropic phase has been investigated through fluorescence anisotropy measurements where the order parameter, quantified by the

  16. A Computationally Efficient Algorithm for Aerosol Phase Equilibrium

    SciTech Connect

    Zaveri, Rahul A.; Easter, Richard C.; Peters, Len K.; Wexler, Anthony S.

    2004-10-04

    Three-dimensional models of atmospheric inorganic aerosols need an accurate yet computationally efficient thermodynamic module that is repeatedly used to compute internal aerosol phase state equilibrium. In this paper, we describe the development and evaluation of a computationally efficient numerical solver called MESA (Multicomponent Equilibrium Solver for Aerosols). The unique formulation of MESA allows iteration of all the equilibrium equations simultaneously while maintaining overall mass conservation and electroneutrality in both the solid and liquid phases. MESA is unconditionally stable, shows robust convergence, and typically requires only 10 to 20 single-level iterations (where all activity coefficients and aerosol water content are updated) per internal aerosol phase equilibrium calculation. Accuracy of MESA is comparable to that of the highly accurate Aerosol Inorganics Model (AIM), which uses a rigorous Gibbs free energy minimization approach. Performance evaluation will be presented for a number of complex multicomponent mixtures commonly found in urban and marine tropospheric aerosols.

  17. Experimental Determination of Equilibrium and Non-equilibrium Thermodynamic Propertiesof Natural Porous Media.

    NASA Astrophysics Data System (ADS)

    Peluso, F.; Arienzo, I.

    Experimental investigation of the behavior of porous media is a field of interest of modern non-equilibrium thermodynamics. In the frame of a multi-disciplinary re- search project we are performing in our laboratory experimental tests to measure equilibrium and nonequilibrium thermodynamic properties of natural porous media. Aim of our study is to characterize some stone samples and to verify whether a mass transport due to coupled pressure and temperature gradients (thermo-mechanic) is ap- preciable in this kind of porous medium. We have designed an apparatus that allows to measure the volume flux across a porous sample at various, predefined pressures and temperatures, both in isothermal and non isothermal conditions. A mechanical piston compels a liquid to flow through the sample, previously saturated under vacuum with the same fluid. Knowing the geometrical dimensions of the stone, the volume flux is estimated by measuring the time needed to a known amount of liquid to flow across the sample. Measurements have been performed in isothermal conditions at various temperatures and in non-isothermal conditions. Non-isothermal measurements have been performed both in unsteady and steady-state thermal conditions. Before to be undergone to a measurement cycle, samples are dried and weighted. Then they are sat- urated under vacuum with pure distilled water and weighted once again. By difference between the two measurements, porosity is determined. In all examined samples the volume flux has been found linear with respect to the applied pressure at the various temperatures. The values of volume flux in unsteady thermal conditions are consid- erably higher than the one obtained at the same pressure in isothermal conditions at the higher temperature (T=+45rC). This could be the evidence of a thermo-mechanic effect, pushing the water from hot to cold. Once the steady thermal state is reached, however, this effect disappears. Only measurements performed in unsteady thermal

  18. Equilibrium and non-equilibrium cluster phases in colloids with competing interactions.

    PubMed

    Mani, Ethayaraja; Lechner, Wolfgang; Kegel, Willem K; Bolhuis, Peter G

    2014-07-01

    The phase behavior of colloids that interact via competing interactions - short-range attraction and long-range repulsion - is studied by computer simulation. In particular, for a fixed strength and range of repulsion, the effect of the strength of an attractive interaction (ε) on the phase behavior is investigated at various colloid densities (ρ). A thermodynamically stable equilibrium colloidal cluster phase, consisting of compact crystalline clusters, is found below the fluid-solid coexistence line in the ε-ρ parameter space. The mean cluster size is found to linearly increase with the colloid density. At large ε and low densities, and at small ε and high densities, a non-equilibrium cluster phase, consisting of elongated Bernal spiral-like clusters, is observed. Although gelation can be induced either by increasing ε at constant density or vice versa, the gelation mechanism is different in either route. While in the ρ route gelation occurs via a glass transition of compact clusters, gelation in the ε route is characterized by percolation of elongated clusters. This study both provides the location of equilibrium and non-equilibrium cluster phases with respect to the fluid-solid coexistence, and reveals the dependencies of the gelation mechanism on the preparation route. PMID:24824226

  19. Phase Equilibrium Investigations of Planetary Materials

    NASA Technical Reports Server (NTRS)

    Grove, T. L.

    1997-01-01

    This grant provided funds to carry out experimental studies designed to illuminate the conditions of melting and chemical differentiation that has occurred in planetary interiors. Studies focused on the conditions of mare basalt generation in the moon's interior and on processes that led to core formation in the Shergottite Parent Body (Mars). Studies also examined physical processes that could lead to the segregation of metal-rich sulfide melts in an olivine-rich solid matrix. The major results of each paper are discussed below and copies of the papers are attached as Appendix I.

  20. Microrheology close to an equilibrium phase transition

    SciTech Connect

    Reinhardt, J.; Scacchi, A.; Brader, J. M.

    2014-04-14

    We investigate the microstructural and microrheological response to a tracer particle of a two-dimensional colloidal suspension under thermodynamic conditions close to a liquid-gas phase boundary. On the liquid side of the binodal, increasing the velocity of the (repulsive) tracer leads to the development of a pronounced cavitation bubble, within which the concentration of colloidal particles is strongly depleted. The tendency of the liquid to cavitate is characterized by a dimensionless “colloidal cavitation” number. On the gas side of the binodal, a pulled (attractive) tracer leaves behind it an extended trail of colloidal liquid, arising from downstream advection of a wetting layer on its surface. For both situations the velocity dependent friction is calculated.

  1. Effect of organic matters on CO2 hydrate phase equilibrium conditions in Na-montmorillonite clay

    NASA Astrophysics Data System (ADS)

    Park, T.; Kyung, D.; Lee, W.

    2013-12-01

    Formation of gas hydrates provides an attractive idea for storing greenhouse gases in a long-term stable geological formation. Since the phase equilibrium conditions of gas hydrates indicate the stability of hydrates, estimation of the phase equilibrium conditions of gas hydrates in marine geological conditions is necessary. In this study, we have identified the effects of organic matters (glycine, glucose, and urea) and solid surface (montmorillonite (MMT)) on the three-phase (liquid-hydrate-vapor) equilibrium conditions of CO2 hydrate. CO2 phase equilibrium experiments were conducted using 0.5mol% organic matter solutions with and without 10g soil mineral were experimentally conducted. Addition of organic matters shifted the phase equilibrium conditions of CO2 hydrate to the higher pressure or lower pressure region because of higher competition of water molecules due to the dissolved organic matters. Presence of MMT also leaded to the higher equilibrium pressure due to the interaction of cations with water molecules. By addition of organic matters to the clay suspension, the hydrate phase equilibrium conditions were less inhibited compared to those of MMT and organic matters independently. The diminished magnitudes by addition of organic matters to the clay suspension (MMT > MMT+urea > MMT+glycine > MMT+glucose > DIW) were different to the order of inhibition degree without MMT (Glucose > glycine > urea > DIW). X-ray diffraction (XRD), scanning electron microscope (SEM), and ion chromatography (IC) analysis were conducted to support the hypothesis that the organic matters interact with cations in MMT interlayer space, and leads to the less inhibition of phase equilibrium conditions. The present study provides basic information for the formation and dissociation of CO2 hydrates in the geological formation when sequestering CO2 as a form of CO2 hydrate.

  2. Dynamic equilibrium dissolution of complex nonaqueous phase liquid mixtures into the aqueous phase.

    PubMed

    Schluep, Mathias; Gälli, René; Imboden, Dieter M; Zeyer, Josef

    2002-07-01

    Human health risks posed by hazardous substances seeping from a pool of nonaqueous phase liquids (NAPLs) into groundwater change over time because the more soluble compounds such as benzene, toluene, ethylbenzene, and xylene (BTEX) dissolve faster into the aqueous phase than less soluble compounds such as polycyclic aromatic hydrocarbons (PAH). Long-term dissolution from diesel fuel into the aqueous phase was determined experimentally in a continuous flow-through system using the slow-stirring method. The data obtained are interpreted using a dynamic equilibrium dissolution model based on Raoult's law. The predicted temporal development of aqueous concentrations are in good agreement with the experimental results. When a compound in the NAPL approaches complete depletion, a tailing behavior is observed, which is assigned to nonequilibrium effects, such as mass transfer limitations in the NAPL phase. The model predicted an increase of the mean molar mass of the diesel fuel of 1.5% over the entire experimental period. It should be noted that, if the dissolution process were to proceed further, the change in the mean molar mass could become significant and render the simple model inaccurate. Yet the simple model supports the assessment of initial action after a contamination event as well as the planning of long-term remedial strategies. PMID:12109733

  3. Modeling non-equilibrium phase transitions in isentropically compressed Bi

    SciTech Connect

    Kane, J; Smith, R

    2005-09-19

    We report here on modeling of non-equilibrium phase transitions in Bi samples isentropically compressed to 120 GPa by a ramped drive, which is produced using the Janus laser. In the experiments, the Bi samples are attached to windows of LiF or sapphire, and the velocity history of the sample-window interface is recorded with line VISAR. The 1D response of the targets is modeled using a multiphase Bi EOS, the Andrews-Hayes method for non-equilibrium transitions, and a Boettger-Wallace kinetics model. The pressure drive is deduced by back integration of VISAR data from shots performed with Al samples.

  4. Direct Phase Equilibrium Simulations of NIPAM Oligomers in Water.

    PubMed

    Boţan, Vitalie; Ustach, Vincent; Faller, Roland; Leonhard, Kai

    2016-04-01

    NIPAM (N-isopropylacrylamide)-based polymers in water show many interesting properties in experiments, including a lower critical solution temperature (LCST) at 305 K and a conformational transition of single chains at the same temperature. The results of many simulation studies suggest that standard force fields are able to describe the conformational transition and the phase equilibrium well. We show by performing long molecular dynamics simulations of the direct liquid-liquid phase equilibrium of NIPAM trimers in water that there is no LCST in the expected temperature range for any of the force fields under study. The results show further that the relaxation times of single-chain simulations are considerably longer than anticipated. Conformational transitions of single polymers can therefore not necessarily be used as surrogates for a real phase transition. PMID:26991504

  5. Phase equilibrium behavior of the carbon dioxide + benzophenone binary system

    SciTech Connect

    Tarantino, D.E.; Kohn, J.P.; Brennecke, J.F. . Dept. of Chemical Engineering)

    1994-01-01

    Phase equilibrium behavior of various binary CO[sub 2] + hydrocarbon mixtures has been studied by many researchers, providing data which are useful in the design of economically attractive separation processes using carbon dioxide as a solvent. Pressure, liquid-phase composition, and liquid-phase molar volumes are presented for the binary vapor-liquid system CO[sub 2] + benzophenone at 25, 35, and 50 C. Also, pressure, liquid-phase compositions, and liquid-phase molar volumes on the S[sub 1]-L[sub 1]-V curve and L[sub 1]-L[sub 2]-V curve are presented. The termination points of these loci are located and characterized.

  6. Experimental rovibrational constants and equilibrium structure of phosphorus trifluoride

    NASA Astrophysics Data System (ADS)

    Najib, Hamid

    2014-11-01

    Thanks to recent high-resolution Fourier transform infrared (FTIR) and pure rotational (RF/CM/MMW) measurements, several experimental values of the rotation-vibration parameters of the oblate molecule PF3 have been extracted, contributing thus to the knowledge of the molecular potential of phosphorus trifluoride. The data used are those of the fundamental, overtone and combination bands studied in the 300-1500 cm-1 range. The new values are in good agreement with ones determined at low resolution, but significantly more accurate. The agreement is excellent with the available values determined by ab initio HF-SCF calculations employing the TZP/TZ2P triple-zeta basis. From the recent experimental rovibrational interaction constants αC and αB, new accurate equilibrium rotational constants Ce and Be have been derived for the symmetric top molecule PF3, which were used to derive the equilibrium geometry of this molecule: re(F-P) = 1.560986 (43) Å; θe(FPF) = 97.566657 (64)°.

  7. Equilibrium Phase Behavior of a Continuous-Space Microphase Former

    NASA Astrophysics Data System (ADS)

    Zhuang, Yuan; Zhang, Kai; Charbonneau, Patrick

    2016-03-01

    Periodic microphases universally emerge in systems for which short-range interparticle attraction is frustrated by long-range repulsion. The morphological richness of these phases makes them desirable material targets, but our relatively coarse understanding of even simple models hinders controlling their assembly. We report here the solution of the equilibrium phase behavior of a microscopic microphase former through specialized Monte Carlo simulations. The results for cluster crystal, cylindrical, double gyroid, and lamellar ordering qualitatively agree with a Landau-type free energy description and reveal the nontrivial interplay between cluster, gel, and microphase formation.

  8. Modeling of gamma/gamma-prime phase equilibrium in the nickel-aluminum system

    NASA Technical Reports Server (NTRS)

    Sanchez, J. M.; Barefoot, J. R.; Jarrett, R. N.; Tien, J. K.

    1984-01-01

    A theoretical model is proposed for the determination of phase equilibrium in alloys, taking into consideration dissimilar lattice parameters. Volume-dependent pair interactions are introduced by means of phenomenological Lennard-Jones potentials and the configurational entropy of the system is treated in the tetrahedron approximation of the cluster variation method. The model is applied to the superalloy-relevant, nickel-rich, gamma/gamma-prime phase region of the Ni-Al phase diagram. The model predicts reasonable values for the lattice parameters and the enthalpy of formation as a function of composition, and the calculated phase diagram closely approximates the experimental diagram.

  9. Biological Implications of Dynamical Phases in Non-equilibrium Networks

    NASA Astrophysics Data System (ADS)

    Murugan, Arvind; Vaikuntanathan, Suriyanarayanan

    2016-03-01

    Biology achieves novel functions like error correction, ultra-sensitivity and accurate concentration measurement at the expense of free energy through Maxwell Demon-like mechanisms. The design principles and free energy trade-offs have been studied for a variety of such mechanisms. In this review, we emphasize a perspective based on dynamical phases that can explain commonalities shared by these mechanisms. Dynamical phases are defined by typical trajectories executed by non-equilibrium systems in the space of internal states. We find that coexistence of dynamical phases can have dramatic consequences for function vs free energy cost trade-offs. Dynamical phases can also provide an intuitive picture of the design principles behind such biological Maxwell Demons.

  10. Phase diagram of KHF2 and non-equilibrium effects

    NASA Technical Reports Server (NTRS)

    Hobson, M. C.; Kellner, J. D.

    1978-01-01

    The equilibrium diagram for the KHF2-H2O system was constructed from cooling and heating curves for the compositions between 5 wt% and 40 wt% KHF2 and the results are shown. The phase diagrams shown is typical of that of a two component system with miscible liquid phases and whole solid phases consist of pure components. A eutectic point was found at approximately 15% KHF2 which remains completely liquid down to a temperature of -9.0 C. No hydrate formation was observed and no anomalous behavior such as the occurrence of solid transitions or metastable states was observed. The effect of rapid freezing on the equilibrium diagram did not appear, and cooling curves exhibited only one halt. Also, at rapid freezing rates, the supercooling of the solutions was smaller than those observed at the slow cooling rates. The existence of a eutectic composition and the slow rate of dissolution of the salt are used to interpret heat absorption behavior in practical applications of the KHF2-H2O system.

  11. Optical Properties in Non-equilibrium Phase Transitions

    SciTech Connect

    Ao, T; Ping, Y; Widmann, K; Price, D F; Lee, E; Tam, H; Springer, P T; Ng, A

    2006-01-05

    An open question about the dynamical behavior of materials is how phase transition occurs in highly non-equilibrium systems. One important class of study is the excitation of a solid by an ultrafast, intense laser. The preferential heating of electrons by the laser field gives rise to initial states dominated by hot electrons in a cold lattice. Using a femtosecond laser pump-probe approach, we have followed the temporal evolution of the optical properties of such a system. The results show interesting correlation to non-thermal melting and lattice disordering processes. They also reveal a liquid-plasma transition when the lattice energy density reaches a critical value.

  12. Equilibrium phase diagrams of alloys using nested sampling

    NASA Astrophysics Data System (ADS)

    Bernstein, Noam; Baldock, Robert J. N.; Bartók-Partáy, Livia; Csányi, Gábor

    Temperature-pressure-composition phase diagrams describe the structures of materials in thermal equilibrium, and are an essential tool in understanding material properties. Predicting phase diagrams is challenging, even given a description of the interatomic interactions, because of the need to sample a very large configuration space. Nested sampling (NS) has been shown to be an efficient tool for calculating the partition function, and therefore all thermodynamic properties and ensemble averages, by systematically sampling the configuration space of isolated and periodic systems. Its effectiveness comes from sampling starting from high energy, where barriers are relatively low and equilibration is relatively fast, and iteratively eliminating a fixed fraction of the remaining configuration space. We present an application of NS at constant pressure to the phase diagram of a model binary alloy, CuAu, using an embedded atom method potential. We identify phase transitions indicated by peaks in the calculated specific heat, and the dominant phase at each temperature from ensemble-averaged structural ordering, as represented by quantities such as the radial distribution function. These results demonstrate the power of NS as a method for calculating complete phase diagrams.

  13. Some phase equilibrium systematics of lherzolite melting: I

    NASA Astrophysics Data System (ADS)

    Longhi, John

    2002-03-01

    New piston-cylinder experiments constrain the compositions of a series of synthetic picritic liquids that are in equilibrium with forsteritic olivine, orthopyroxene, clinopyroxene, and garnet or spinel from 2.4 to 3.4 Gpa. Mass balance calculations show that two of the liquid + crystal assemblages are consistent with those expected by 4.4 and 1.6 wt % anhydrous partial melting of a peridotite generally similar in composition to estimates of depleted upper mantle (DPUM). The liquids in these runs contain <=2.0 wt % Na2O. Lherzolitic liquids with higher concentrations of Na2O have negative mass balance coefficients, regardless of Mg', implying that there is a limit of ~2 wt % Na2O in anhydrous partial melts of peridotites with ~0.3 wt % bulk Na2O in the upper garnet-lherzolite stability field. Examination of liquidus equilibria in the NCMAS system demonstrates that coupling of Na2O and SiO2 concentrations in liquids saturated with lherzolite assemblages permits high-Na2O, high-SiO2 melts at pressures ~1.0 GPa, whereas only high-Na2O, low-SiO2 melts are possible in the garnet-lherzolite stability field. Because the bulk partition coefficient for Na2O increases with pressure, the concentration of Na2O in batch melts of the same percent will necessarily decrease with pressure. Calculations of low-degree anhydrous melting of DPUM with a revised melting model, BATCH, indicate that the Na2O concentration decreases with increasing pressure more rapidly than in previous models. Thus, for example, 1% melting of lherzolite with Na2O bulk concentration typical of estimated terrestrial mantle (~0.3 wt %), can produce a liquid with ~6 wt % Na2O at 1.0 GPa but only ~2% Na2O at 3.0 Gpa. In calculated melts of the DPUM and PUM compositions at 1.0 Gpa, the TiO2 concentration decreases between 10 and 1% melting in response to an increase inDTiO2cpx, consistent reported experimental observations. The increase in DTiO2cpx appears to be a response to increasing alkalis in the melt

  14. Eutectic mixed monolayers in equilibrium with phospholipid-bilayers and triolein-liquid phase.

    PubMed Central

    Handa, T; Saito, H; Miyajima, K

    1993-01-01

    Triolein (TO) and phospholipids (egg yolk phosphatidylcholine, egg yolk phosphatidylethanolamine, and bovine brain phosphatidylserine) had low mutual solubilities and separated into the TO-liquid phase and phospholipid-bilayers. Spreading pressures of the TO-phospholipid mixture (i.e., surface pressures of the mixed monolayer in equilibrium with the phase-separating lipid mixture) at the air/saline interface were independent of the lipid composition. On the other hand, collapse pressures of the mixed monolayer of TO and phospholipid (i.e., surface pressures of the mixed monolayer in equilibrium with the TO-liquid phase) at the interface changed with the monolayer composition and were lower than the spreading pressure. The experimental data indicated the spreading and collapse pressures as offering a phase diagram for the presence of equilibrium between the mixed monolayer, the phospholipid-bilayers and the TO-liquid phase. The diagram showed that TO and the phospholipids were miscible in the mixed monolayer, forming an eutectic mixed monolayer. When the mixed monolayer initially had the eutectic composition, no collapse of the monolayer was detected until the surface pressure reached the value of the spreading pressure. No specific complex between TO and the phospholipid is required to explain the stability and collapse of the mixed monolayers. The bulk immiscibility of the lipids elucidated by the spreading pressure-measurements, immediately leads to the phase behaviors observed. PMID:8369406

  15. Off-equilibrium photon production during the chiral phase transition

    SciTech Connect

    Michler, Frank; Hees, Hendrik van; Dietrich, Dennis D.; Leupold, Stefan; Greiner, Carsten

    2013-09-15

    In the early stage of ultrarelativistic heavy-ion collisions chiral symmetry is restored temporarily. During this so-called chiral phase transition, the quark masses change from their constituent to their bare values. This mass shift leads to the spontaneous non-perturbative creation of quark–antiquark pairs, which effectively contributes to the formation of the quark–gluon plasma. We investigate the photon production induced by this creation process. We provide an approach that eliminates possible unphysical contributions from the vacuum polarization and renders the resulting photon spectra integrable in the ultraviolet domain. The off-equilibrium photon numbers are of quadratic order in the perturbative coupling constants while a thermal production is only of quartic order. Quantitatively, we find, however, that for the most physical mass-shift scenarios and for photon momenta larger than 1 GeV the off-equilibrium processes contribute less photons than the thermal processes. -- Highlights: •We investigate first-order photon emission arising from the chiral mass shift. •We provide an ansatz eliminating possible unphysical vacuum contributions. •Our ansatz leads to photon spectra being integrable in the ultraviolet domain.

  16. Phase equilibrium in coal liquefaction processes. Final report

    SciTech Connect

    Chao, K.C.

    1984-08-01

    Gas-liquid equilibrium data have been determined in simulation of coal liquefaction process conditions in mixtures of light gases + heavy hydrocarbons to add to the accumulated data previously reported in EPRI AP-1593. The mixture systems newly investigated are: methane + 9,10 dihydrophenanthrene; hydrogen + methane + 1-methylnaphthalene; hydrogen + carbon dioxide + tetralin; hydrogen + carbon dioxide + 1-methynaphthalene; hydrogen + carbon dioxide + quinoline; nitrogen + tetralin, + n-hexadecane, + 1-methylnaphthalene, + quinoline, and + m-cresol. Correlations for the solubilities of methane and carbon dioxide have been developed from the data based on the use of solubility parameter. The solubility of hydrogen was correlated in EPRI AP-1593. Two equations of state are developed for the description of both the gas solubility and the vaporization of the heavy oil. The Chain-of-Rotators (COR) equation of state explicitly accounts for the rotational molecular motion contribution to the pressure of a fluid. The Cubic-Chain-of-Rotators (CCOR) equation is obtained upon simplifying the COR equation. Interaction constants in the CCOR equation have been determined for the light gases with the heavy hydrocarbons based on data from this project, and the constants are correlated. Equilibrium flash vaporization has been experimentally determined for three coal liquids and for their mixtures with hydrogen. The data are correlated with the CCOR equation of state. 74 figures, 46 tables.

  17. Solution properties of almandine-pyrope garnet as determined by phase equilibrium experiments

    USGS Publications Warehouse

    Koziol, A.M.; Bohlen, S.R.

    1992-01-01

    The thermodynamic mixing properties of almandine-pyrope garnet were derived from phase equilibrium experiments at temperatures of 900 and 1000??C and pressures from 8 to 14 kbar. Almandine has essentially ideal behavior in almandine-pyrope garnet over the composition range Alm89-Alm61 at the above experimental conditions. In all experimental products a systematic partitioning of Fe and Mg between garnet and ilmenite was seen with ln Kd ??? 1.59 which was not temperature sensitive. The results support the use of garnet mixing models that incorporate ideal or nearly ideal Fe-Mg parameters. -from Authors

  18. Phase-field investigation on the non-equilibrium interface dynamics of rapid alloy solidification

    NASA Astrophysics Data System (ADS)

    Choi, Jeong Yun

    The departure from the equilibrium solid concentration at the solid-liquid interface was often observed during rapid solidification. The energetic associated non-equilibrium solute partitioning has been treated in detail, providing possible ranges of interface concentrations for a given growth condition. For analytical description of specific single-phase dendritic and cellular operating point selection, analytical models for solute partitioning under a given set of growth conditions have been developed and widely utilized in most of the theoretical investigations of rapid solidification. However, these solute trapping models are not rigorously verified due to the difficulty in experimentally measuring under rapid growth conditions. Moreover, since these solute trapping models include kinetic parameters which are difficult to directly measure from experiments, application of the solute trapping models or the associated analytic rapid solidification model is limited. These theoretical models for steady state rapid solidification which incorporate the solute trapping models do not describe the interdependency of solute diffusion, interface kinetics, and alloy thermodynamics. This research program is focused on critical issues that represent conspicuous gaps in current understanding of rapid solidification, limiting our ability to predict and control microstructural evolution at high undercooling, where conditions depart significantly from local equilibrium. Through careful application of phase-field modeling, using appropriate thin-interface and anti-trapping corrections and addressing important details such as transient effects and a velocity-dependent numerics, the current analysis provides a reasonable simulation-based picture of non-equilibrium solute partitioning and the corresponding oscillatory dynamics associated with single-phase rapid solidification and show that this method is a suitable means for a self-consistent simulation of transient behavior and

  19. Protein accumulation in the endoplasmic reticulum as a non-equilibrium phase transition.

    PubMed

    Budrikis, Zoe; Costantini, Giulio; La Porta, Caterina A M; Zapperi, Stefano

    2014-01-01

    Several neurological disorders are associated with the aggregation of aberrant proteins, often localized in intracellular organelles such as the endoplasmic reticulum. Here we study protein aggregation kinetics by mean-field reactions and three dimensional Monte carlo simulations of diffusion-limited aggregation of linear polymers in a confined space, representing the endoplasmic reticulum. By tuning the rates of protein production and degradation, we show that the system undergoes a non-equilibrium phase transition from a physiological phase with little or no polymer accumulation to a pathological phase characterized by persistent polymerization. A combination of external factors accumulating during the lifetime of a patient can thus slightly modify the phase transition control parameters, tipping the balance from a long symptomless lag phase to an accelerated pathological development. The model can be successfully used to interpret experimental data on amyloid-β clearance from the central nervous system. PMID:24722051

  20. Protein accumulation in the endoplasmic reticulum as a non-equilibrium phase transition

    PubMed Central

    Budrikis, Zoe; Costantini, Giulio; La Porta, Caterina A. M.; Zapperi, Stefano

    2014-01-01

    Several neurological disorders are associated with the aggregation of aberrant proteins, often localized in intracellular organelles such as the endoplasmic reticulum. Here we study protein aggregation kinetics by mean-field reactions and three dimensional Monte carlo simulations of diffusion-limited aggregation of linear polymers in a confined space, representing the endoplasmic reticulum. By tuning the rates of protein production and degradation, we show that the system undergoes a non-equilibrium phase transition from a physiological phase with little or no polymer accumulation to a pathological phase characterized by persistent polymerization. A combination of external factors accumulating during the lifetime of a patient can thus slightly modify the phase transition control parameters, tipping the balance from a long symptomless lag phase to an accelerated pathological development. The model can be successfully used to interpret experimental data on amyloid-β clearance from the central nervous system. PMID:24722051

  1. Mechanistic investigation of non-ideal sorption behavior in natural organic matter. 1. Vapor phase equilibrium.

    PubMed

    Bell, Katherine Young; Leboeuf, Eugene J

    2012-06-19

    Results from an experimental and modeling investigation of the influence of thermodynamic properties of highly purified natural organic matter (NOM) on observed equilibrium sorption/desorption behaviors of vapor phase trichloroethylene (TCE) is presented. Identification of glass transition (T(g)) behavior in Leonardite humic acid and Organosolv lignin enabled evaluation of equilibrium and nonequilibrium sorption behavior in glassy and rubbery NOM. Specific differences in vapor phase equilibrium behavior in NOM above and below their T(g) were identified. In the glassy state (below T(g)), sorption of TCE is well-described by micropore models, with enthalpies of sorption characteristic of microporous, glassy macromolecules. Above T(g), sorptive behavior was well-described by Flory-Huggins theory, indicating that the mobility and structural configuration of rubbery NOM materials may be analogous to the characteristic sorption behavior observed in more mobile, rubbery macromolecules, including strong entropic changes during sorption. Results from this work provide further support that, at least for the samples employed in this study, NOM possesses macromolecular characteristics which display sorption behavior similar to synthetic macromolecules-an important assumption in conceptual sorption equilibrium models used in the analysis of the fate and transport of VOCs in the environment. PMID:22642948

  2. Phase equilibrium data for development of correlations for coal fluids

    SciTech Connect

    Robinson, R.L. Jr.; Gasem, K.A.M.; Darwish, N.A.; Raff, A.M.

    1991-02-01

    The overall objective of the authors' work is to develop accurate predictive methods for representations of vapor-liquid equilibria in systems encountered in coal-conversion processes. The objectives pursued in the present project include: (1) Measurements of binary vapor-liquid phase behavior data for selected solute gases (e.g., C{sub 2}H{sub 6}, CH{sub 4}) in a series of paraffinic, naphthenic, and aromatic hydrocarbon solvents to permit evaluations of interaction parameters in models for phase behavior. Solubilities of the gases in the liquid phase have been determined. (2) Evaluation of existing equations of state and other models for representations of phase behavior in systems of the type studied experimentally; development of new correlation frameworks as needed. (3) Generalization of the interaction parameters for the solutes studied to a wide spectrum of heavy solvents; presentation of final results in formats useful in the design/optimization of coal liquefaction processes.

  3. Non-equilibrium model of two-phase porous media flow with phase change

    NASA Astrophysics Data System (ADS)

    Cueto-Felgueroso, L.; Fu, X.; Juanes, R.

    2014-12-01

    The efficient simulation of multi-phase multi-component flow through geologic porous media is challenging and computationally intensive, yet quantitative modeling of these processes is essential in engineering and the geosciences. Multiphase flow with phase change and complex phase behavior arises in numerous applications, including enhanced oil recovery, steam injection in groundwater remediation, geologic CO2 storage and enhanced geothermal energy systems. A challenge of multiphase compositional simulation is that the number of existing phases varies with position and time, and thus the number of state variables in the saturation-based conservation laws is a function of space and time. The tasks of phase-state identification and determination of the composition of the different phases are performed assuming local thermodynamic equilibrium. Here we investigate a thermodynamically consistent formulation for non-isothermal two-phase flow, in systems where the hypothesis of instantaneous local equilibrium does not hold. Non-equilibrium effects are important in coarse-scale simulations where the assumption of complete mixing in each gridblock is not realistic. We apply our model to steam injection in water-saturated porous media.

  4. Phase equilibrium modeling for high temperature metallization on GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Chung, M. A.; Davison, J. E.; Smith, S. R.

    1991-01-01

    Recent trends in performance specifications and functional requirements have brought about the need for high temperature metallization technology to be developed for survivable DOD space systems and to enhance solar cell reliability. The temperature constitution phase diagrams of selected binary and ternary systems were reviewed to determine the temperature and type of phase transformation present in the alloy systems. Of paramount interest are the liquid-solid and solid-solid transformations. Data are being utilized to aid in the selection of electrical contact materials to gallium arsenide solar cells. Published data on the phase diagrams for binary systems is readily available. However, information for ternary systems is limited. A computer model is being developed which will enable the phase equilibrium predictions for ternary systems where experimental data is lacking.

  5. Experimental equilibrium between acid gases and ethanolamine solutions

    SciTech Connect

    Bhairi, A.M.

    1984-01-01

    The general subject area of this study is equilibrium solubility of carbon dioxide and hydrogen sulfide in solutions of some common ethanolamines. The amines studied are most widely used in the area of gas sweetening. They include monoethanolamine, diglycolamine, diethanolamine and methyldiethanolamine. Only limited data are available for some of these amines. The process involved developing simple apparatus and procedure for investigating the equilibrium solubility of carbon dioxide and hydrogen sulfide in aqueous alkanolamine solutions. The procedure uses a single equilibrium cell. No gas chromatograph nor liquid chemical analysis is required. Measurements of the solubility were made in different amine solution concentrations at acid gas partial pressures to 1000 psia and temperatures from 77 to 240{degree}F. The method used was found to be sound as indicated by the consistency and reproducibility of the data.

  6. Relevant Models of Equilibrium Structures in One-Phase Regimes of Microemulsions.

    NASA Astrophysics Data System (ADS)

    Edwards, M. E.

    2000-11-01

    Although several studies have focused on equilibrium structures--domains--in one-phase regimes of dilutive microemulsions, the structures have not been completely determined. Here, we review the relevant continuum-statistical and continuum-mechanical models with the ultimate objective of their extension or modification. Presently, the models describe single droplet domains, two interacting droplets or dimer constructions, and thermal fluctuation description. Also, we present the rudiments of an interaction model which considers the undulations of two ellipsoidal droplets. A satisfactory model of equilibrium structures is essential if we are to further elucidate the behavior of microemulsions in various environments, such as, the case of microemulsions being located in a pulsed, external electric field: the phenomenon of static electro-optical Kerr effect. Currently, variations exist between relevant models and experimental results.

  7. Disposal phase experimental program plan

    SciTech Connect

    1997-01-31

    The Waste Isolation Pilot Plant (WIPP) facility comprises surface and subsurface facilities, including a repository mined in a bedded salt formation at a depth of 2,150 feet. It has been developed to safely and permanently isolate transuranic (TRU) radioactive wastes in a deep geological disposal site. On April 12, 1996, the DOE submitted a revised Resource Conservation and Recovery Act (RCRA) Part B permit application to the New Mexico Environment Department (NMED). The DOE anticipates receiving an operating permit from the NMED; this permit is required prior to the start of disposal operations. On October 29, 1996, the DOE submitted a Compliance Certification Application (CCA) to the US Environmental Protection Agency (EPA) in accordance with the WIPP land Withdrawal Act (LWA) of 1992 (Public Law 102-579) as amended, and the requirements of Title 40 of the Code of Federal Regulations (40 CFR) Parts 191 and 194. The DOE plans to begin disposal operations at the WIPP in November 1997 following receipt of certification by the EPA. The disposal phase is expected to last for 35 years, and will include recertification activities no less than once every five years. This Disposal Phase Experimental Program (DPEP) Plan outlines the experimental program to be conducted during the first 5-year recertification period. It also forms the basis for longer-term activities to be carried out throughout the 35-year disposal phase. Once the WIPP has been shown to be in compliance with regulatory requirements, the disposal phase gives an opportunity to affirm the compliance status of the WIPP, enhance the operations of the WIPP and the national TRU system, and contribute to the resolution of national and international nuclear waste management technical needs. The WIPP is the first facility of its kind in the world. As such, it provides a unique opportunity to advance the technical state of the art for permanent disposal of long-lived radioactive wastes.

  8. Phase equilibrium and intermediate phases in the Eu-Sb system

    SciTech Connect

    Abdusalyamova, M.N.

    2011-10-15

    Rapid heating rate thermal analysis, X-ray diffraction, fluorescence spectrometry, and differential dissolution method were used to study the high-temperature phase equilibrium in the Eu-Sb system within the composition range between 37 and 96 at% Sb. The techniques were effective in determination of the vapor-solid-liquid equilibrium since intermediate phases except Eu{sub 4}Sb{sub 3} evaporated incongruently after melting. A thermal procedure was developed to determine the liquidus and solidus lines of the T-x diagram. Six stable phases were identified: two phases, EuSb{sub 2} and Eu{sub 4}Sb{sub 3}, melt congruently at 1045{+-}10 deg. C and 1600{+-}15 deg. C, the Eu{sub 2}Sb{sub 3}, Eu{sub 11}Sb{sub 10}, Eu{sub 5}Sb{sub 4}, and Eu{sub 5}Sb{sub 3} phases melt incongruently at 850{+-}8 deg. C, 950{+-}10 deg. C, 1350{+-}15 deg. C, and 1445{+-}15 deg. C, respectively. The exact composition shifting of Sb-rich decomposable phases towards Eu{sub 4}Sb{sub 3}, the most refractory compound, was determined. The topology of the Eu-Sb phase diagram was considered together with that of the Yb-Sb system. - Graphical abstract: The high-temperature range of the T-x phase diagram for the Eu-Sb system. Highlights: > The phase relations in the Eu-Sb system were studied over a large composition and temperature scale. > The liquidus and solidus lines of the T-x diagram were well established using effective techniques. > In the system, six binary phases are stable and they melt incongruently except EuSb{sub 2} and Eu{sub 4}Sb{sub 3}. > Incongruent evaporation was found to be typical of all the phases besides Eu{sub 4}Sb{sub 3}.

  9. Trace element partitioning behavior of coal gangue-fired CFB plant: experimental and equilibrium calculation.

    PubMed

    Zhang, Yingyi; Nakano, Jinichiro; Liu, Lili; Wang, Xidong; Zhang, Zuotai

    2015-10-01

    Energy recovery is a promising method for coal gangue utilization, during which the prevention of secondary pollution, especially toxic metal emission, is a significant issue in the development of coal gangue utilization. In the present study, investigation into trace element partitioning behavior from a coal gangue-fired power plant in Shanxi province, China, has been conducted. Besides the experimental analysis, thermodynamic equilibrium calculation was also conducted to help the further understanding on the effect of different parameters. Results showed that Hg, As, Be, and Cd were highly volatile elements in the combustion of coal gangue, which were notably enriched in fly ash and may be emitted into the environment via the gas phase. Cr and Mn were mostly non-volatile and were enriched in the bottom ash. Pb, Co, Zn, Cu, and Ni were semi-volatile elements and were enriched in the fly ash to varying degrees. Equilibrium calculations show that the air/fuel ratio and the presence of Cl highly affect the element volatility. The presence of mineral phases, such as aluminosilicates, depresses the volatility of elements by chemical immobilization and competition in Cl. The coal gangue, fly ash, and bottom ash all passed the toxicity characteristic leaching procedure (TCLP), and their alkalinity buffers the acidity of the solution and contributes to the low solubility of the trace elements. PMID:26006077

  10. Equilibrium and non-equilibrium dynamics of the dilute lamellar phase

    NASA Astrophysics Data System (ADS)

    Ramaswamy, Sriram

    1992-07-01

    A model for the dynamics of the sterically stabilized dilute lamellar phase is constructed and studied. The model consists of a stack of flexible fluid sheets, with excluded volume, separated by macroscopic layers of solvent. The dynamics of small fluctuations of the sheets about their mean positions is found to have two distinct short-wavelength regimes in which the frequency ω depends on the wavenumber q in an unusual manner. One is a single-membrane Zimm mode, ω ≈ - iq3, while the other is a “red-blood-cell mode”, ω ≈ - iq6. These modes give rise to fluctuation corrections for the viscosities of the system, going as ω {-1}/{3} and ω {-2}/{3}, respectively. In addition, it is shown that a sufficiently rapid shear flow with velocity and gradient in the plane of the layers causes a transition into a state where regions of reduced layer spacing co-exist with regions devoid of any layer material. The critical shear-rate for this transition should go as (layer spacing) -3. Possible experimental tests of these predictions are discussed.

  11. Student Understanding of Liquid-Vapor Phase Equilibrium

    ERIC Educational Resources Information Center

    Boudreaux, Andrew; Campbell, Craig

    2012-01-01

    Student understanding of the equilibrium coexistence of a liquid and its vapor was the subject of an extended investigation. Written assessment questions were administered to undergraduates enrolled in introductory physics and chemistry courses. Responses have been analyzed to document conceptual and reasoning difficulties in sufficient detail to…

  12. The non-equilibrium phase diagrams of flow-induced crystallization and melting of polyethylene

    PubMed Central

    Wang, Zhen; Ju, Jianzhu; Yang, Junsheng; Ma, Zhe; Liu, Dong; Cui, Kunpeng; Yang, Haoran; Chang, Jiarui; Huang, Ningdong; Li, Liangbin

    2016-01-01

    Combining extensional rheology with in-situ synchrotron ultrafast x-ray scattering, we studied flow-induced phase behaviors of polyethylene (PE) in a wide temperature range up to 240 °C. Non-equilibrium phase diagrams of crystallization and melting under flow conditions are constructed in stress-temperature space, composing of melt, non-crystalline δ, hexagonal and orthorhombic phases. The non-crystalline δ phase is demonstrated to be either a metastable transient pre-order for crystallization or a thermodynamically stable phase. Based on the non-equilibrium phase diagrams, nearly all observations in flow-induced crystallization (FIC) of PE can be well understood. The interplay of thermodynamic stabilities and kinetic competitions of the four phases creates rich kinetic pathways for FIC and diverse final structures. The non-equilibrium flow phase diagrams provide a detailed roadmap for precisely processing of PE with designed structures and properties. PMID:27609305

  13. The non-equilibrium phase diagrams of flow-induced crystallization and melting of polyethylene.

    PubMed

    Wang, Zhen; Ju, Jianzhu; Yang, Junsheng; Ma, Zhe; Liu, Dong; Cui, Kunpeng; Yang, Haoran; Chang, Jiarui; Huang, Ningdong; Li, Liangbin

    2016-01-01

    Combining extensional rheology with in-situ synchrotron ultrafast x-ray scattering, we studied flow-induced phase behaviors of polyethylene (PE) in a wide temperature range up to 240 °C. Non-equilibrium phase diagrams of crystallization and melting under flow conditions are constructed in stress-temperature space, composing of melt, non-crystalline δ, hexagonal and orthorhombic phases. The non-crystalline δ phase is demonstrated to be either a metastable transient pre-order for crystallization or a thermodynamically stable phase. Based on the non-equilibrium phase diagrams, nearly all observations in flow-induced crystallization (FIC) of PE can be well understood. The interplay of thermodynamic stabilities and kinetic competitions of the four phases creates rich kinetic pathways for FIC and diverse final structures. The non-equilibrium flow phase diagrams provide a detailed roadmap for precisely processing of PE with designed structures and properties. PMID:27609305

  14. Effect of organic matter on CO(2) hydrate phase equilibrium in phyllosilicate suspensions.

    PubMed

    Park, Taehyung; Kyung, Daeseung; Lee, Woojin

    2014-06-17

    In this study, we examined various CO2 hydrate phase equilibria under diverse, heterogeneous conditions, to provide basic knowledge for successful ocean CO2 sequestration in offshore marine sediments. We investigated the effect of geochemical factors on CO2 hydrate phase equilibrium. The three-phase (liquid-hydrate-vapor) equilibrium of CO2 hydrate in the presence of (i) organic matter (glycine, glucose, and urea), (ii) phyllosilicates [illite, kaolinite, and Na-montmorillonite (Na-MMT)], and (iii) mixtures of them was measured in the ranges of 274.5-277.0 K and 14-22 bar. Organic matter inhibited the phase equilibrium of CO2 hydrate by association with water molecules. The inhibition effect decreased in the order: urea < glycine < glucose. Illite and kaolinite (unexpandable clays) barely affected the CO2 hydrate phase equilibrium, while Na-MMT (expandable clay) affected the phase equilibrium because of its interlayer cations. The CO2 hydrate equilibrium conditions, in the illite and kaolinite suspensions with organic matter, were very similar to those in the aqueous organic matter solutions. However, the equilibrium condition in the Na-MMT suspension with organic matter changed because of reduction of its inhibition effect by intercalated organic matter associated with cations in the Na-MMT interlayer. PMID:24844562

  15. Phase-field investigation on the non-equilibrium interface dynamics of rapid alloy solidification

    SciTech Connect

    Choi, Jeong

    2011-01-01

    The research program reported here is focused on critical issues that represent conspicuous gaps in current understanding of rapid solidification, limiting our ability to predict and control microstructural evolution (i.e. morphological dynamics and microsegregation) at high undercooling, where conditions depart significantly from local equilibrium. More specifically, through careful application of phase-field modeling, using appropriate thin-interface and anti-trapping corrections and addressing important details such as transient effects and a velocity-dependent (i.e. adaptive) numerics, the current analysis provides a reasonable simulation-based picture of non-equilibrium solute partitioning and the corresponding oscillatory dynamics associated with single-phase rapid solidification and show that this method is a suitable means for a self-consistent simulation of transient behavior and operating point selection under rapid growth conditions. Moving beyond the limitations of conventional theoretical/analytical treatments of non-equilibrium solute partitioning, these results serve to substantiate recent experimental findings and analytical treatments for single-phase rapid solidification. The departure from the equilibrium solid concentration at the solid-liquid interface was often observed during rapid solidification, and the energetic associated non-equilibrium solute partitioning has been treated in detail, providing possible ranges of interface concentrations for a given growth condition. Use of these treatments for analytical description of specific single-phase dendritic and cellular operating point selection, however, requires a model for solute partitioning under a given set of growth conditions. Therefore, analytical solute trapping models which describe the chemical partitioning as a function of steady state interface velocities have been developed and widely utilized in most of the theoretical investigations of rapid solidification. However, these

  16. Phase Segregation at the Liquid-Air Interface Prior to Liquid-Liquid Equilibrium.

    PubMed

    Bermúdez-Salguero, Carolina; Gracia-Fadrique, Jesús

    2015-08-13

    Binary systems with partial miscibility segregate into two liquid phases when their overall composition lies within the interval defined by the saturation points; out of this interval, there is one single phase, either solvent-rich or solute-rich. In most systems, in the one-phase regions, surface tension decreases with increasing solute concentration due to solute adsorption at the liquid-air interface. Therefore, the solute concentration at the surface is higher than in the bulk, leading to the hypothesis that phase segregation starts at the liquid-air interface with the formation of two surface phases, before the liquid-liquid equilibrium. This phenomenon is called surface segregation and is a step toward understanding liquid segregation at a molecular level and detailing the constitution of fluid interfaces. Surface segregation of aqueous binary systems of alkyl acetates with partial miscibility was theoretically demonstrated by means of a thermodynamic stability test based on energy minimization. Experimentally, the coexistence of two surface regions was verified through Brewster's angle microscopy. The observations were further interpreted with the aid of molecular dynamics simulations, which show the diffusion of the acetates from the bulk toward the liquid-air interface, where acetates aggregate into acetate-rich domains. PMID:26189700

  17. The nuclear liquid-vapor phase transition: Equilibrium between phases or free decay in vacuum?

    SciTech Connect

    Phair, L.; Moretto, L.G.; Elliott, J.B.; Wozniak, G.J.

    2002-11-14

    Recent analyses of multifragmentation in terms of Fisher's model and the related construction of a phase diagram brings forth the problem of the true existence of the vapor phase and the meaning of its associated pressure. Our analysis shows that a thermal emission picture is equivalent to a Fisher-like equilibrium description which avoids the problem of the vapor and explains the recently observed Boltzmann-like distribution of the emission times. In this picture a simple Fermi gas thermometric relation is naturally justified. Low energy compound nucleus emission of intermediate mass fragments is shown to scale according to Fisher's formula and can be simultaneously fit with the much higher energy ISiS multifragmentation data.

  18. An experimental study of trace element partitioning between perovskite, hibonite and melt: Equilibrium values

    NASA Technical Reports Server (NTRS)

    Kennedy, A. K.; Lofgren, G. E.; Wasserburg, G. J.

    1993-01-01

    The presence of perovskite (CATiO3) and hibonite (Ca Al12O19) within different regions of Calcium-, Aluminum-rich Inclusions (CAI) and the trace element concentrations of these minerals in each circumstance, constrain models of precursor formation, nebular condensation, the thermal history of inclusions with relict perovskite and hibonite, and the formation of the Wark-Lovering rim. At present mineral/melt partition coefficient data for hibonite are limited to a few elements in simple experimental systems, or to those derived from hibonite-glass pairs in hibonite/glass microspherules. Similarly, there is only limited data on perovskite D that are applicable to meteorite compositions. Apart from the importance of partitioning studies to meteorite research, D values also are invaluable in the development of thermodynamic models, especially when data is available for a large number of elements that have different ionic charge and radii. In addition, study of the effect of rapid cooling on partitioning is crucial to our understanding of meteorite inclusions. To expand our knowledge of mineral/melt D for perovskite and hibonite, a study was instituted where D values are obtained in both equilibrium and dynamic cooling experiments. As an initial phase of this study mineral/melt D was measured for major elements (Ca, Mg, Al, Ti, and Si), 15 rare earth elements (La-Lu) and 8 other elements (Ba, Sr, U, Th, Nb, Zr, Hf, and Ge) in perovskite and hibonite grown under equilibrium conditions, in bulk compositions that are respectively similar to Compact Type A (CTA) CAI and to a hibonite/glass microspherule. Experimental mixes were doped with REE at 20-50x chondritic (ch) abundances, Ba at 50 ppm, Sr, Hf, Nb, and Zr at 100 ppm and, U and Th at 200 ppm. Trace element abundances were measured with the PANURGE ion microprobe. Major element compositions were obtained by electron microprobe analysis.

  19. Exploiting non-equilibrium phase separation for self-assembly.

    PubMed

    Grünwald, Michael; Tricard, Simon; Whitesides, George M; Geissler, Phillip L

    2016-02-01

    Demixing can occur in systems of two or more particle species that experience different driving forces, e.g., mixtures of self-propelled active particles or of oppositely charged colloids subject to an electric field. Here we show with macroscopic experiments and computer simulations that the forces underlying such non-equilibrium segregation can be used to control the self-assembly of particles that lack attractive interactions. We demonstrate that, depending on the direction, amplitude and frequency of a periodic external force acting on one particle species, the structures formed by a second, undriven species can range from compact clusters to elongated, string-like patterns. PMID:26658789

  20. Thermodynamic Study of the Role of Interface Curvature on Multicomponent Vapor-Liquid Phase Equilibrium.

    PubMed

    Shardt, Nadia; Elliott, Janet A W

    2016-04-14

    The effect of interface curvature on phase equilibrium has been much more studied for single-component than multicomponent systems. We isolate the effect of curvature on multicomponent vapor-liquid equilibrium (VLE) phase envelopes and phase composition diagrams using the ideal system methanol/ethanol and the nonideal system ethanol/water as illustrative examples. An important finding is how nanoscale interface curvature shifts the azeotrope (equal volatility point) of nonideal systems. Understanding of the effect of curvature on VLE can be exploited in future nanoscale prediction and design. PMID:27028744

  1. Phase equilibrium of sodium bis(2-ethylhexyl) phosphate/water/n-heptane/sodium chloride microemulsion

    SciTech Connect

    Shioi, Akihisada; Harada, Makoto; Matsumoto, Keishi )

    1991-09-19

    The microemulsion phase diagram for the sodium bis(2-ethylhexyl) phosphate (SDEHP)/water/n-heptane/sodium chloride system is reported. The salinity effects on the phase diagram are discussed in detail. Cylindrical aggregates were found to exist in the oil-rich region and disklike aggregates in the brine-rich region. The middle-phase microemulsion in equilibrium with both the excess brine and oil phases was concluded to be composed of these microstructures. Sodium bis(2-ethylhexyl) phosphate has a common hydrocarbon tail with sodium bis(2-ethylhexyl) sulfosuccinate (AOT), but the phase equilibrium and the structures of the microemulsion phases in SDEHP system were much different from those in the AOT case. The differences were attributed to those in the shapes of aggregates for the two cases.

  2. Equilibrium lines and barriers to phase transitions: the cubic diamond to beta-tin transition in Si from first principles.

    PubMed

    Qiu, S L; Marcus, P M

    2012-06-01

    The phase transition between the cubic diamond (cd) and beta-tin (β-Sn) phases of Si under pressure and the region of interaction of the two phases are studied by first-principles total energy calculations. For a non-vibrating crystal we determine the pressure of the thermodynamic phase transition p(t) = 96 kbar, the Gibbs free energy barrier at p(t) of ΔG = 19.6 mRyd/atom that stabilizes the phases against a phase transition and the finite pressure range in which both phases are stable. We show that the phases in that pressure range are completely described by three equilibrium lines of states along which the structure, the total energy E, the hydrostatic pressure p that would stabilize the structure and the values of G all vary. Two equilibrium lines describe the two phases (denoted the ph-eq line, ph is cd or β-Sn phase); a third line is a line of saddle points of G with respect to structure (denoted the sp-eq line) that forms a barrier of larger G against instability of the metastable ranges of the phase lines. An important conclusion is that the sp-eq line merges with the two ph-eq lines: one end of the sp-eq line merges with the cd-eq line at high pressure, the other end merges with the β-Sn-eq line at low pressure. The mergers end the barrier protecting the metastable ranges of the two ph-eq lines, hence the lines go unstable beyond the mergers. The mergers thus simplify the phase diagram by providing a natural termination to the stable parts of all metastable ranges of the ph-eq lines. Although 96 kbar is lower than the experimental transition pressure, we note that phonon pressure raises the observed transition pressure. PMID:22551557

  3. Experimental phasing: best practice and pitfalls

    PubMed Central

    McCoy, Airlie J.; Read, Randy J.

    2010-01-01

    Developments in protein crystal structure determination by experimental phasing are reviewed, emphasizing the theoretical continuum between experimental phasing, density modification, model building and refinement. Traditional notions of the composition of the substructure and the best coefficients for map generation are discussed. Pitfalls such as determining the enantiomorph, identifying centrosymmetry (or pseudo-symmetry) in the substructure and crystal twinning are discussed in detail. An appendix introduces com­bined real–imaginary log-likelihood gradient map coefficients for SAD phasing and their use for substructure completion as implemented in the software Phaser. Supplementary material includes animated probabilistic Harker diagrams showing how maximum-likelihood-based phasing methods can be used to refine parameters in the case of SIR and MIR; it is hoped that these will be useful for those teaching best practice in experimental phasing methods. PMID:20382999

  4. The temperature-composition phase diagram of monomyristolein in water: equilibrium and metastability aspects.

    PubMed Central

    Briggs, J; Caffrey, M

    1994-01-01

    The temperature-composition phase diagram of monomyristolein in water was constructed using x-ray diffraction. Low- and wide-angle diffraction patterns were collected from samples of fixed hydration as a function of temperature in the heating direction on x-ray-sensitive film and/or image plates. The phases identified in the system include the lamellar crystalline phase, the lamellar liquid crystalline phase, the fluid isotropic phase, and two inverted cubic phases. Particular attention has been devoted to the issues of phase equilibrium and phase boundary verification. Cubic phase undercooling was examined by adjusting the temperature of several samples in the cubic phase to a value where the lamellar liquid crystalline phase represents equilibrium behavior. Cooling-induced structure and phase changes were monitored continuously over a 30-min period by recording low-angle diffraction patterns from the samples using a streak camera. The cubic-to-lamellar transition rate decreased with increasing sample hydration. Additionally, the transition proceeded more rapidly at an incubation temperature of 25 degrees C compared to that at 0 degrees C. A mechanism is proposed that accounts for the hydration and temperature sensitivity of the phase transition under nonequilibrium conditions. Images FIGURE 1 FIGURE 7 PMID:8011891

  5. Non-equilibrium phase transition in reconstituted acto-myosin cortices

    NASA Astrophysics Data System (ADS)

    Fakhri, Nikta; Abu Shah, Enas; Malik-Garbi, Maya; Mackintosh, Fred C.; Keren, Kinneret; Schmidt, Christoph F.

    2015-03-01

    The cortical actin cytoskeleton is a quasi 2-D active material in which dynamics are dominated by rapid actin turnover and myosin-driven contractility. Here we present a reconstituted model system that emulates these processes in artificial cell-like compartments. By tuning physical and chemical parameters, we induce a non-equilibrium phase transition. We characterize the local dynamics of these reconstituted cortices by tracking embedded single-walled carbon nanotubes (SWNTs). We create high-resolution maps of the contractile actomyosin flows in a homogenous and during transition to an inhomogeneous steady state. We find evidence that connectivity percolation drives the non-equilibrium phase transition.

  6. Phase Equilibria Studies of the Cu-Fe-O-Si System in Equilibrium with Air and with Metallic Copper

    NASA Astrophysics Data System (ADS)

    Hidayat, Taufiq; Henao, Hector M.; Hayes, Peter C.; Jak, Evgueni

    2012-10-01

    Phase equilibria of the Cu-Fe-O-Si system have been investigated in equilibrium: (1) with air atmosphere at temperatures between 1373 K and 1673 K (1100 °C and 1400 °C) and (2) with metallic copper at temperatures between 1373 K and 1573 K (1100 °C and 1300 °C). High-temperature equilibration/quenching/electron-probe X-ray microanalysis (EPMA) techniques have been used to accurately determine the compositions of the phases in equilibrium in the system. The new experimental results are presented in the form of "Cu2O"-"Fe2O3"-SiO2 ternary sections. The relationships between the activity of CuO0.5(l) and the composition of slag in equilibrium with metallic copper are discussed. The phase equilibria information of the Cu-Fe-O-Si system is of practical importance for industrial copper production processes and for the improvement of the existing thermodynamic database of copper-containing slag systems.

  7. The Sulfur-Iodine Cycle: Process Analysis and Design Using Comprehensive Phase Equilibrium Measurements and Modeling

    SciTech Connect

    Thies, Mark C.; O'Connell, J. P.; Gorensek, Maximilian B.

    2010-01-10

    Of the 100+ thermochemical hydrogen cycles that have been proposed, the Sulfur-Iodine (S-I) Cycle is a primary target of international interest for the centralized production of hydrogen from nuclear power. However, the cycle involves complex and highly nonideal phase behavior at extreme conditions that is only beginning to be understood and modeled for process simulation. The consequence is that current designs and efficiency projections have large uncertainties, as they are based on incomplete data that must be extrapolated from property models. This situation prevents reliable assessment of the potential viability of the system and, even more, a basis for efficient process design. The goal of this NERI award (05-006) was to generate phase-equilibrium data, property models, and comprehensive process simulations so that an accurate evaluation of the S-I Cycle could be made. Our focus was on Section III of the Cycle, where the hydrogen is produced by decomposition of hydroiodic acid (HI) in the presence of water and iodine (I2) in a reactive distillation (RD) column. The results of this project were to be transferred to the nuclear hydrogen community in the form of reliable flowsheet models for the S-I process. Many of the project objectives were achieved. At Clemson University, a unique, tantalum-based, phase-equilibrium apparatus incorporating a view cell was designed and constructed for measuring fluid-phase equilibria for mixtures of iodine, HI, and water (known as HIx) at temperatures to 350 °C and pressures to 100 bar. Such measurements were of particular interest for developing a working understanding of the expected operation of the RD column in Section III. The view cell allowed for the IR observation and discernment of vapor-liquid (VL), liquid-liquid, and liquid-liquid-vapor (LLVE) equilibria for HIx systems. For the I2-H2O system, liquid-liquid equilibrium (LLE) was discovered to exist at temperatures up to 310-315 °C, in contrast to the models and

  8. Experimental values of the rotational and vibrational constants and equilibrium structure of nitrogen trifluoride

    NASA Astrophysics Data System (ADS)

    Najib, Hamid

    2015-06-01

    Several accurate experimental values of the rovibrational interaction constants αC and αB, the harmonic wave-number parameters ωij, and the anharmonicity xij and gij constants have been extracted from the most recent high-resolution Fourier transform infrared (FTIR), centimeter-wave (CMW) and millimeter-wave (MMW) measurements in the spectra of the oblate symmetric top molecule 14NF3. The data used are those of the four fundamental, the overtone, the combination and the hot bands identified and analyzed in the range between 400 cm-1 and 2000 cm-1. Combining the recent experimental values of the constants αC and αB, with the accurate experimental ground state rotational constants C0 and B0, new equilibrium rotational constants have been evaluated: Ce = 0.1968006 (26) cm-1 and Be = 0.358981442 (43) cm-1 for the pyramidal molecule NF3, from which the following equilibrium structure is obtained: re(F-N) = 1.36757 (58) Å; θe(FNF) = 101.8513 (10)°. This experimental equilibrium geometry is in excellent agreement with the recent structure determined by ab initio calculations at the CCSD(T)/aug-cc-pVQZ level of theory.

  9. On the Effectiveness of Nature-Inspired Metaheuristic Algorithms for Performing Phase Equilibrium Thermodynamic Calculations

    PubMed Central

    Fateen, Seif-Eddeen K.; Bonilla-Petriciolet, Adrian

    2014-01-01

    The search for reliable and efficient global optimization algorithms for solving phase stability and phase equilibrium problems in applied thermodynamics is an ongoing area of research. In this study, we evaluated and compared the reliability and efficiency of eight selected nature-inspired metaheuristic algorithms for solving difficult phase stability and phase equilibrium problems. These algorithms are the cuckoo search (CS), intelligent firefly (IFA), bat (BA), artificial bee colony (ABC), MAKHA, a hybrid between monkey algorithm and krill herd algorithm, covariance matrix adaptation evolution strategy (CMAES), magnetic charged system search (MCSS), and bare bones particle swarm optimization (BBPSO). The results clearly showed that CS is the most reliable of all methods as it successfully solved all thermodynamic problems tested in this study. CS proved to be a promising nature-inspired optimization method to perform applied thermodynamic calculations for process design. PMID:24967430

  10. On the effectiveness of nature-inspired metaheuristic algorithms for performing phase equilibrium thermodynamic calculations.

    PubMed

    Fateen, Seif-Eddeen K; Bonilla-Petriciolet, Adrian

    2014-01-01

    The search for reliable and efficient global optimization algorithms for solving phase stability and phase equilibrium problems in applied thermodynamics is an ongoing area of research. In this study, we evaluated and compared the reliability and efficiency of eight selected nature-inspired metaheuristic algorithms for solving difficult phase stability and phase equilibrium problems. These algorithms are the cuckoo search (CS), intelligent firefly (IFA), bat (BA), artificial bee colony (ABC), MAKHA, a hybrid between monkey algorithm and krill herd algorithm, covariance matrix adaptation evolution strategy (CMAES), magnetic charged system search (MCSS), and bare bones particle swarm optimization (BBPSO). The results clearly showed that CS is the most reliable of all methods as it successfully solved all thermodynamic problems tested in this study. CS proved to be a promising nature-inspired optimization method to perform applied thermodynamic calculations for process design. PMID:24967430

  11. A Simple System for Observing Dynamic Phase Equilibrium via an Inquiry-Based Laboratory or Demonstration

    ERIC Educational Resources Information Center

    Cloonan, Carrie A.; Andrew, Julie A.; Nichol, Carolyn A.; Hutchinson, John S.

    2011-01-01

    This article describes an activity that can be used as an inquiry-based laboratory or demonstration for either high school or undergraduate chemistry students to provide a basis for understanding both vapor pressure and the concept of dynamic phase equilibrium. The activity includes a simple setup to create a closed system of only water liquid and…

  12. Equilibrium Phase Behavior of the Square-Well Linear Microphase-Forming Model.

    PubMed

    Zhuang, Yuan; Charbonneau, Patrick

    2016-07-01

    We have recently developed a simulation approach to calculate the equilibrium phase diagram of particle-based microphase formers. Here, this approach is used to calculate the phase behavior of the square-well linear model for different strengths and ranges of the linear long-range repulsive component. The results are compared with various theoretical predictions for microphase formation. The analysis further allows us to better understand the mechanism for microphase formation in colloidal suspensions. PMID:27117230

  13. Spontaneous Time Symmetry Breaking in System with Mixed Strategy Nash Equilibrium: Evidences in Experimental Economics Data

    NASA Astrophysics Data System (ADS)

    Wang, Zhijian; Xu, Bin; Zhejiang Collaboration

    2011-03-01

    In social science, laboratory experiment with human subjects' interaction is a standard test-bed for studying social processes in micro level. Usually, as in physics, the processes near equilibrium are suggested as stochastic processes with time-reversal symmetry (TRS). To the best of our knowledge, near equilibrium, the breaking time symmetry, as well as the existence of robust time anti-symmetry processes, has not been reported clearly in experimental economics till now. By employing Markov transition method to analysis the data from human subject 2x2 Games with wide parameters and mixed Nash equilibrium, we study the time symmetry of the social interaction process near Nash equilibrium. We find that, the time symmetry is broken, and there exists a robust time anti-symmetry processes. We also report the weight of the time anti-symmetry processes in the total processes of each the games. Evidences in laboratory marketing experiments, at the same time, are provided as one-dimension cases. In these cases, time anti-symmetry cycles can also be captured. The proposition of time anti-symmetry processes is small, but the cycles are distinguishable.

  14. The phase equilibriums in the NH4Cl-CaCl2-H2O system at 50 and 75°C and their Pitzer model representations

    NASA Astrophysics Data System (ADS)

    Zhang, Run-Zhi; Yang, Ji-Min; Zhang, Li; Xu, Chun-Yan

    2014-12-01

    The solubilities and refractive indexes in the NH4Cl-CaCl2-H2O system were measured at 50 and 75°C and the phase diagrams were constructed on the basis of the experimental data. The mixing parameters and equilibrium constant K sp were evaluated using the Pitzer ion-interaction model representations. The results obtained were in good agreement with the experimental data. The mixed parameters of Pitzer ion-interaction model and equilibrium constant obtained in the work can furthermore be applied to solubility predictions of more complicated systems containing NH4Cl and CaCl2.

  15. Experimental study of the hot electron plasma equilibrium in a minimum-B magnetic mirror

    SciTech Connect

    Chen, X.; Lane, B.G.; Smatlak, D.L.; Post, R.S.; Hokin, S.A.

    1989-03-01

    The Constance B mirror (in Plasma Physics and Controlled Nuclear Fusion Research 1984 (IAEA, Vienna, 1985), Vol. II, p. 285) is a single cell quadrupole magnetic mirror in which high-beta (typically 0.3), hot electron plasmas (T/sub e/approx. =400 keV) are created with up to 4 kW of fundamental electron cyclotron resonance heating (ECRH). Details of the plasma equilibrium profile are quantitatively determined by fitting model plasma pressure profiles to the data from four complementary measurements: diamagnetic loops and magnetic probes, x-ray pinhole cameras, visible light TV cameras, and thermocouple probes. The experimental analysis shows that the equilibrium pressure profile of an ECRH generated plasma in a baseball magnetic mirror is hollow and the plasma is concentrated along a baseball-seam-shaped curve. The hollowness of the hot electron density profile is 50% +- 10%. The baseball-seam-shaped equilibrium profile coincides with the drift orbit of deeply trapped electrons in the quadrupole mirror field. Particle drift reversal is predicted to occur for the model pressure profile that best fits the experimental data under the typical operating conditions.

  16. Equilibrium Liquid Crystal Phase Diagrams and Detection of Kinetic Arrest in Cellulose Nanocrystal Suspensions

    NASA Astrophysics Data System (ADS)

    Honorato Rios, Camila; Kuhnhold, Anja; Bruckner, Johanna; Dannert, Rick; Schilling, Tanja; Lagerwall, Jan

    2016-05-01

    The cholesteric liquid crystal self-assembly of water-suspended cellulose nanocrystal (CNC) into a helical arrangement was observed already more than 20 years ago and the phenomenon was used to produce iridescent solid films by evaporating the solvent or via sol-gel processing. Yet it remains challenging to produce optically uniform films and to control the pitch reproducibly, reflecting the complexity of the three-stage drying process that is followed in preparing the films. An equilibrium liquid crystal phase formation stage is followed by a non-equilibrium kinetic arrest, which in turn is followed by structural collapse as the remaining solvent is evaporated. Here we focus on the first of these stages, combining a set of systematic rheology and polarizing optics experiments with computer simulations to establish a detailed phase diagram of aqueous CNC suspensions with two different values of the surface charge, up to the concentration where kinetic arrest sets in. We also study the effect of varying ionic strength of the solvent. Within the cholesteric phase regime, we measure the equilibrium helical pitch as a function of the same parameters. We report a hitherto unnoticed change in character of the isotropic-cholesteric transition at increasing ionic strength, with a continuous weakening of the first-order character up to the point where phase coexistence is difficult to detect macroscopically due to substantial critical fluctuations.

  17. Observation of dynamic equilibrium cluster phase in nanoparticle-polymer system

    NASA Astrophysics Data System (ADS)

    Kumar, Sugam; Mehan, S.; Aswal, V. K.; Schwein, R.

    2016-05-01

    Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) have been used to investigate the existence of a cluster phase in a nanoparticle-polymer system. The nanoparticle-polymer system shows an interesting reentrant phase behavior where the charge stabilized silica nanoparticles undergo particle clustering and back to individual nanoparticles as a function of polymer concentration. This kind of phase behavior is believed to be directed by opposing attractive and repulsive interactions present in the system. The phase behavior shows two narrow regions of polymer concentration immediately before and after the two-phase formation indicating the possibility of the existence of some equilibrium clusters. DLS results show a much higher size of particles than individuals in these two regions which remains unchanged even after dilution. The SANS data show the evolution of attraction with increased volume fraction of the particles supporting the dynamic nature of these clusters.

  18. Studies of the tautomeric equilibrium of 1,3-thiazolidine-2-thione: Theoretical and experimental approaches

    NASA Astrophysics Data System (ADS)

    Abbehausen, Camilla; de Paiva, Raphael E. F.; Formiga, André L. B.; Corbi, Pedro P.

    2012-10-01

    The tautomeric equilibrium of the thione/thiol forms of 1,3-thiazolidine-2-thione was studied by nuclear magnetic resonance, infrared and ultraviolet-visible spectroscopies. Density functional theory was used to support the experimental data and indicates the predominance of the thione tautomer in the solid state, being in agreement with previously reported crystallographic data. In solution, the tautomeric equilibrium was evaluated using 1H NMR at different temperatures in four deuterated solvents acetonitrile, dimethylsulfoxide, chloroform and methanol. The equilibrium constants, K = (thiol)/(thione), and free Gibbs energies were obtained by integration of N bonded hydrogen signals at each temperature for each solvent, excluding methanol. The endothermic tautomerization is entropy-driven and the combined effect of solvent and temperature can be used to achieve almost 50% thiol concentrations in solution. The nature of the electronic transitions was investigated theoretically and the assignment of the bands was made using time-dependent DFT as well as the influence of solvent on the energy of the most important bands of the spectra.

  19. Equilibrium 2H/ 1H fractionations in organic molecules: I. Experimental calibration of ab initio calculations

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Sessions, Alex L.; Nielsen, Robert J.; Goddard, William A., III

    2009-12-01

    Carbon-bound hydrogen in sedimentary organic matter can undergo exchange over geologic timescales, altering its isotopic composition. Studies investigating the natural abundance distribution of 1H and 2H in such molecules must account for this exchange, which in turn requires quantitative knowledge regarding the endpoint of exchange, i.e., the equilibrium isotopic fractionation factor ( α eq). To date, relevant data have been lacking for molecules larger than methane. Here we describe an experimental method to measure α eq for C-bound H positions adjacent to carbonyl group (H α) in ketones. H at these positions equilibrates on a timescale of days as a result of keto-enol tautomerism, allowing equilibrium 2H/ 1H distributions to be indirectly measured. Molecular vibrations for the same ketone molecules are then computed using Density Functional Theory at the B3LYP/6-311G∗∗ level and used to calculate α eq values for H α. Comparison of experimental and computational results for six different straight and branched ketones yields a temperature-dependent linear calibration curve with slope = 1.081-0.00376 T and intercept = 8.404-0.387 T, where T is temperature in degrees Celsius. Since the dominant systematic error in the calculation (omission of anharmonicity) is of the same size for ketones and C-bound H in most other linear compounds, we propose that this calibration can be applied to analogous calculations for a wide variety of organic molecules with linear carbon skeletons for temperatures below 100 °C. In a companion paper ( Wang et al., 2009) we use this new calibration dataset to calculate the temperature-dependent equilibrium isotopic fractionation factors for a range of linear hydrocarbons, alcohols, ethers, ketones, esters and acids.

  20. Gas-phase water-mediated equilibrium between methylglyoxal and its geminal diol

    PubMed Central

    Axson, Jessica L.; Takahashi, Kaito; De Haan, David O.; Vaida, Veronica

    2010-01-01

    In aqueous solution, aldehydes, and to a lesser extent ketones, hydrate to form geminal diols. We investigate the hydration of methylglyoxal (MG) in the gas phase, a process not previously considered to occur in water-restricted environments. In this study, we spectroscopically identified methylglyoxal diol (MGD) and obtained the gas-phase partial pressures of MG and MGD. These results, in conjunction with the relative humidity, were used to obtain the equilibrium constant, KP, for the water-mediated hydration of MG in the gas phase. The Gibbs free energy for this process, ΔG°, obtained as a result, suggests a larger than expected gas-phase diol concentration. This may have significant implications for understanding the role of organics in atmospheric chemistry. PMID:20142510

  1. Experimental study of phase separation in dividing two phase flow

    SciTech Connect

    Qian Yong; Yang Zhilin; Xu Jijun

    1996-12-31

    Experimental study of phase separation of air-water two phase bubbly, slug flow in the horizontal T-junction is carried out. The influences of the inlet mass quality X1, mass extraction rate G3/G1, and fraction of extracted liquid QL3/QL1 on phase separation characteristics are analyzed. For the first time, the authors have found and defined pulsating run effect by the visual experiments, which show that under certain conditions, the down stream flow of the T-junction has strangely affected the phase redistribution of the junction, and firstly point out that the downstream geometric condition is very important to the study of phase separation phenomenon of two-phase flow in a T-junction. This kind of phenomenon has many applications in the field of energy, power, petroleum and chemical industries, such as the loss of coolant accident (LOCA) caused by a small break in a horizontal coolant pipe in nuclear reactor, and the flip-flop effect in the natural gas transportation pipeline system, etc.

  2. Analytical Phase Equilibrium Function for Mixtures Obeying Raoult's and Henry's Laws

    NASA Astrophysics Data System (ADS)

    Hayes, Robert

    When a mixture of two substances exists in both the liquid and gas phase at equilibrium, Raoults and Henry's laws (ideal solution and ideal dilute solution approximations) can be used to estimate the gas and liquid mole fractions at the extremes of either very little solute or solvent. By assuming that a cubic polynomial can reasonably approximate the intermediate values to these extremes as a function of mole fraction, the cubic polynomial is solved and presented. A closed form equation approximating the pressure dependence on mole fraction of the constituents is thereby obtained. As a first approximation, this is a very simple and potentially useful means to estimate gas and liquid mole fractions of equilibrium mixtures. Mixtures with an azeotrope require additional attention if this type of approach is to be utilized. This work supported in part by federal Grant NRC-HQ-84-14-G-0059.

  3. Analytical Phase Equilibrium Function for Mixtures Obeying Raoult's and Henry's Laws

    NASA Astrophysics Data System (ADS)

    Hayes, Robert

    When a mixture of two substances exists in both the liquid and gas phase at equilibrium, Raoults and Henry's laws (ideal solution and ideal dilute solution approximations) can be used to estimate the gas and liquid mole fractions at the extremes of either very little solute or solvent. By assuming that a cubic polynomial can reasonably approximate the intermediate values to these extremes as a function of mole fraction, the cubic polynomial is solved and presented. A closed form equation approximating the pressure dependence on mole fraction of the constituents is thereby obtained. As a first approximation, this is a very simple and potentially useful means to estimate gas and liquid mole fractions of equilibrium mixtures. Mixtures with an azeotrope require additional attention if this type of approach is to be utilized. This work paid for under NRC-HQ-84-14-G-0059.

  4. Calculating Equilibrium Phase Distribution during the Formation of Secondary Organic Aerosol Using COSMOtherm.

    PubMed

    Wang, Chen; Goss, Kai-Uwe; Lei, Ying Duan; Abbatt, Jonathan P D; Wania, Frank

    2015-07-21

    Challenges in the parametrization of compound distribution between the gas and particle phase contribute significantly to the uncertainty in the prediction of secondary organic aerosol (SOA) formation and are rooted in the complexity and variability of atmospheric condensed matter, which includes water, salts, and a multitude of organic oxidation products, often in two separated phases. Here, we explore the use of the commercial quantum-chemistry-based software COSMOtherm to predict equilibrium partitioning and Setchenow coefficients of a suite of oxidation products of α-pinene ozonolysis in an aerosol that is assumed to separate into an organic-enriched phase and an electrolyte-enriched aqueous phase. The predicted coefficients are used to estimate the phase distribution of the organic compounds, water and ammonium sulfate, the resulting phase composition, and the SOA yield. Four scenarios that differ in terms of organic loading, liquid water content, and chemical aging are compared. The organic compounds partition preferentially to the organic phase rather than the aqueous phase for the studied aerosol scenarios, partially due to the salting-out effect. Extremely low volatile organic compounds are predicted to be the dominant species in the organic aerosols at low loadings and an important component at higher loadings. The highest concentration of oxidation products in the condensed phase is predicted for a scenario assuming the presence of non-phase-separated cloud droplets. Partitioning into an organic aerosol phase composed of the oxidation products is predicted to be similar to partitioning into a phase composed of a single organic surrogate molecule, suggesting that the calculation procedure can be simplified without major loss of accuracy. COSMOtherm is shown to produce results that are comparable to those obtained using group contribution methods. COSMOtherm is likely to have a much larger application domain than those group contribution methods because

  5. Infinite-mode squeezed coherent states and non-equilibrium statistical mechanics (phase-space-picture approach)

    NASA Technical Reports Server (NTRS)

    Yeh, Leehwa

    1993-01-01

    The phase-space-picture approach to quantum non-equilibrium statistical mechanics via the characteristic function of infinite-mode squeezed coherent states is introduced. We use quantum Brownian motion as an example to show how this approach provides an interesting geometrical interpretation of quantum non-equilibrium phenomena.

  6. Entropy analysis on non-equilibrium two-phase flow models

    SciTech Connect

    Karwat, H.; Ruan, Y.Q.

    1995-09-01

    A method of entropy analysis according to the second law of thermodynamics is proposed for the assessment of a class of practical non-equilibrium two-phase flow models. Entropy conditions are derived directly from a local instantaneous formulation for an arbitrary control volume of a structural two-phase fluid, which are finally expressed in terms of the averaged thermodynamic independent variables and their time derivatives as well as the boundary conditions for the volume. On the basis of a widely used thermal-hydraulic system code it is demonstrated with practical examples that entropy production rates in control volumes can be numerically quantified by using the data from the output data files. Entropy analysis using the proposed method is useful in identifying some potential problems in two-phase flow models and predictions as well as in studying the effects of some free parameters in closure relationships.

  7. Phase equilibriums, self-assembly and interactions in two-, three- and four medium-chain length component systems.

    PubMed

    Rosenholm, Jarl B

    2014-03-01

    The Scandinavian surface (surfactant) and colloid science owes much of its success to Per Ekwall and Björn Lindman. In this review the main topics shared by their research groups at Åbo Akademi University in Finland and at Lund University in Sweden are described. The nature of surface active substances (cosolvents, co-surfactants and surfactants) and microemulsions are evaluated. It is shown that the properties of medium-chain length surfactants differ dramatically from long-chain surfactants. The phase equilibriums of binary systems are related to the phase equilibriums of ternary and quaternary systems referred to as microemulsions or more recently also as nanoemulsions. A distinction is made between hydrotrope liquids, detergentless microemulsions, surfactant mixture systems and microemulsions. Three component systems are assembled to "true" quaternary microemulsions. An exceptionally comprehensive network of thermodynamic parameters describing molecular site exchange and micelle formation are derived and related mutually. Gibbs free energy, enthalpy, entropy, volume, heat capacity, expansivity and compressibility can be used to illustrate the degree of aggregation cooperativity and to evaluate whether micelle formation is of a first-, second- or intermediate order phase transition. Theoretical simulations and experimental results show that the associate structures of medium-chain length surfactants are quite open and may be deformed due to small aggregation numbers. The self-assembly occurs over a number of distinct steps at a series of experimentally detectable critical concentrations. Despite the low aggregation tendency their phase behavior equals those of long-chain homologs in surfactant mixture and microemulsion systems. A number of models describing the self-assembly are reviewed. Nuclear magnetic resonance (shift, relaxation rate and diffusion), Laser Raman and infrared spectroscopies were chosen as key instruments for molecular interaction

  8. Improving the quality of the experimental reconstructions as the initial equilibrium state for the NIMROD code

    NASA Astrophysics Data System (ADS)

    King, Jacob; Kruger, Scott; NIMROD Team

    2014-10-01

    High quality equilibria are essential for extended-MHD modeling with the initial-value NIMROD code. Typically the spatial resolution requirements for extended-MHD modeling, which must resolve singular-layer physics and highly anisotropic diffusion, are more stringent than the resolution of equilibrium reconstructions from experimental discharges. With the current workflow, reconstructed fields are mapped onto the NIMROD finite-element grid, and the disparity between the coarse resolution reconstruction and the fine resolution FE grid can create artificial small-scale artifacts. Extended-MHD modeling, which contains many high-order differential operators, can be corrupted by the mapping errors. We describe efforts to re-solve the Grad-Shafranov equation with open-flux regions using the NIMEQ solver to generate a new equilibrium while using the mapped results for both an initial guess and to specify the boundary conditions. Effects on computations with and without the re-solving for force balance will be described. Work funded by US DOE.

  9. Unusual dileptions at RHIC a field theoretic approach based on a non-equilibrium chiral phase transition

    SciTech Connect

    Cooper, F.

    1997-09-22

    This paper contains viewgraphs on unusual dileptons at Brookhaven RHIC. A field theory approach is used based on a non-equilibrium chiral phase transformation utilizing the schroedinger and Heisenberg picture.

  10. Experimental clean combustor program, phase 2

    NASA Technical Reports Server (NTRS)

    Gleason, C. C.; Rogers, D. W.; Bahr, D. W.

    1976-01-01

    The primary objectives of this three-phase program are to develop technology for the design of advanced combustors with significantly lower pollutant emission levels than those of current combustors, and to demonstrate these pollutant emission reductions in CF6-50C engine tests. The purpose of the Phase 2 Program was to further develop the two most promising concepts identified in the Phase 1 Program, the double annular combustor and the radial/axial staged combustor, and to design a combustor and breadboard fuel splitter control for CF6-50 engine demonstration testing in the Phase 3 Program. Noise measurement and alternate fuels addendums to the basic program were conducted to obtain additional experimental data. Twenty-one full annular and fifty-two sector combustor configurations were evaluated. Both combustor types demonstrated the capability for significantly reducing pollutant emission levels. The most promising results were obtained with the double annular combustor. Rig test results corrected to CF-50C engine conditions produced EPA emission parameters for CO, HC, and NOX of 3.4, 0.4, and 4.5 respectively. These levels represent CO, HC, and NOX reductions of 69, 90, and 42 percent respectively from current combustor emission levels. The combustor also met smoke emission level requirements and development engine performance and installation requirements.

  11. PHASE-OTI: A pre-equilibrium model code for nuclear reactions calculations

    NASA Astrophysics Data System (ADS)

    Elmaghraby, Elsayed K.

    2009-09-01

    The present work focuses on a pre-equilibrium nuclear reaction code (based on the one, two and infinity hypothesis of pre-equilibrium nuclear reactions). In the PHASE-OTI code, pre-equilibrium decays are assumed to be single nucleon emissions, and the statistical probabilities come from the independence of nuclei decay. The code has proved to be a good tool to provide predictions of energy-differential cross sections. The probability of emission was calculated statistically using bases of hybrid model and exciton model. However, more precise depletion factors were used in the calculations. The present calculations were restricted to nucleon-nucleon interactions and one nucleon emission. Program summaryProgram title: PHASE-OTI Catalogue identifier: AEDN_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDN_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 5858 No. of bytes in distributed program, including test data, etc.: 149 405 Distribution format: tar.gz Programming language: Fortran 77 Computer: Pentium 4 and Centrino Duo Operating system: MS Windows RAM: 128 MB Classification: 17.12 Nature of problem: Calculation of the differential cross section for nucleon induced nuclear reaction in the framework of pre-equilibrium emission model. Solution method: Single neutron emission was treated by assuming occurrence of the reaction in successive steps. Each step is called phase because of the phase transition nature of the theory. The probability of emission was calculated statistically using bases of hybrid model [1] and exciton model [2]. However, more precise depletion factor was used in the calculations. Exciton configuration used in the code is that described in earlier work [3]. Restrictions: The program is restricted to single nucleon emission and nucleon

  12. Canonical deformations of surfaces of equilibrium states in thermodynamic phase space

    PubMed

    Jurkowski

    2000-08-01

    Deformations of submanifolds of thermodynamic equilibrium states introduced by continuous contact maps on a phase-space manifold are considered in terms of the geometrical formulation of thermodynamics. The notion of a contact Hamiltonian is recalled in order to give some possible physical interpretations of such a function in terms of statistical quantities describing initial and deformed systems. Using contact flows we propose a very efficient method for constructing continuous families of thermodynamic systems. A few examples show the possible advantages of using contact Hamiltonians. PMID:11088641

  13. Entropic description of gas hydrate ice/liquid equilibrium via enhanced sampling of coexisting phases

    SciTech Connect

    Malolepsza, Edyta; Kim, Jaegil; Keyes, Tom

    2015-04-28

    Metastable β ice holds small guest molecules in stable gas hydrates, so its solid/liquid equilibrium is of interest. However, aqueous crystal/liquid transitions are very difficult to simulate. A new MD algorithm generates trajectories in a generalized NPT ensemble and equilibrates states of coexisting phases with a selectable enthalpy. Furthermore, with replicas spanning the range between β ice and liquid water we find the statistical temperature from the enthalpy histograms and characterize the transition by the entropy, introducing a general computational procedure for first-order transitions.

  14. Hydrogen and dry ice production through phase equilibrium separation and methane reforming

    NASA Astrophysics Data System (ADS)

    Posada, Alberto; Manousiouthakis, Vasilios

    A clean hydrogen (99.9999%) and dry ice production process is proposed, which is based on phase equilibrium (PE) separation and methane reforming. Heat and power integration studies are carried out for the proposed process, by formulating and solving the minimum hot/cold/electric utility cost problem for the associated heat exchange network. The optimum operating cost of the proposed process is shown to be lower than the corresponding cost of the conventional PSA (pressure swing adsorption) based process, if the produced dry ice is sold for as low as 2 cents kg-dry-ice -1 or if an equivalent CO 2 sequestration credit is conceded.

  15. Entropic Description of Gas Hydrate Ice-Liquid Equilibrium via Enhanced Sampling of Coexisting Phases

    NASA Astrophysics Data System (ADS)

    Małolepsza, Edyta; Kim, Jaegil; Keyes, Tom

    2015-05-01

    Metastable β ice holds small guest molecules in stable gas hydrates, so its solid-liquid equilibrium is of interest. However, aqueous crystal-liquid transitions are very difficult to simulate. A new molecular dynamics algorithm generates trajectories in a generalized N P T ensemble and equilibrates states of coexisting phases with a selectable enthalpy. With replicas spanning the range between β ice and liquid water, we find the statistical temperature from the enthalpy histograms and characterize the transition by the entropy, introducing a general computational procedure for first-order transitions.

  16. Entropic Description of Gas Hydrate Ice-Liquid Equilibrium via Enhanced Sampling of Coexisting Phases.

    PubMed

    Małolepsza, Edyta; Kim, Jaegil; Keyes, Tom

    2015-05-01

    Metastable β ice holds small guest molecules in stable gas hydrates, so its solid-liquid equilibrium is of interest. However, aqueous crystal-liquid transitions are very difficult to simulate. A new molecular dynamics algorithm generates trajectories in a generalized NPT ensemble and equilibrates states of coexisting phases with a selectable enthalpy. With replicas spanning the range between β ice and liquid water, we find the statistical temperature from the enthalpy histograms and characterize the transition by the entropy, introducing a general computational procedure for first-order transitions. PMID:25978217

  17. Equilibrium structure and relative stability of glyceraldehyde conformers: Gas-phase electron diffraction (GED) and quantum-chemical studies

    NASA Astrophysics Data System (ADS)

    Vogt, Natalja; Atavin, Evgenii G.; Rykov, Anatolii N.; Popov, Evgenii V.; Vilkov, Lev V.

    2009-11-01

    For the first time, the five dimensional (5-D) analysis of potential energy surface (PES) from quantum-chemical calculations was carried out to predict reliably the various glyceraldehyde (GLA) conformers. 36 conformers with relative stabilities up to 38 kJ/mol were found in the B3LYP approximation. According to results of MP2/cc-pVQZ calculations, the molecule exists at the experimental temperature of 388 K as a mixture of five conformers in the ratio I:II:III:IV:V = 63:18:4:10:5. Contrary to the theoretical conclusion of Lovas et al., the conformer IV is predicted to be more stable than the conformer III. Our result can explain why the conformer IV could be detected in the microwave (MW) spectroscopic experiment by Lovas et al., whereas the conformer III could not. For the first time, thermal-average and equilibrium structural parameters of GLA (main conformer) have been determined from gas-phase electron diffraction (GED) data. Vibrational corrections to the experimental bond lengths were determined using quadratic and cubic force constants from high-level ab initio calculations (MP2/cc-pVTZ). It was shown that the experimental intensities are sensitive to the contribution of the second conformer (27(15)%). Rotational constants calculated from MP2/cc-pVQZ geometries were found to be in excellent agreement with the experimental rotational constants corrected for anharmonic effects.

  18. Equilibrium phase diagrams and water absorption properties of aqueous mixtures of malonic acid and inorganic salts.

    NASA Astrophysics Data System (ADS)

    Salcedo, D.; Salgado-Olea, G.

    2006-12-01

    Tropospheric aerosols are usually complex mixtures of inorganic and organic components. Although the thermodynamic properties of inorganic aerosols have been widely studied, the effect of organics on such properties is still under discussion. Solubility in water, water activity of aqueous solutions, deliquescence relative humidity (DRH), eutonic composition, and eutonic DRH were determined for bulk mixtures of malonic acid with ammonium sulfate, ammonium bisulfate, and ammonium nitrate at 25oC over the full range of composition (from 0 wt% to the solubility limit of the mixture components). The data was used to construct equilibrium phase diagrams, which show the phase of the mixtures as a function of total composition, dry mixture composition, water content, and ambient relative humidity. Measured water activity of liquid solutions was compared with an extended Zdanovskii-Stokes-Robinson (ZSR) expression, which then was used to predict water absorption of the mixtures.

  19. Tables of phase functions, opacities, albedos, equilibrium temperatures, and radiative accelerations of dust grains in exoplanets

    NASA Astrophysics Data System (ADS)

    Budaj, J.; Kocifaj, M.; Salmeron, R.; Hubeny, I.

    2015-11-01

    There has been growing observational evidence for the presence of condensates in the atmospheres and/or comet-like tails of extrasolar planets. As a result, systematic and homogeneous tables of dust properties are useful in order to facilitate further observational and theoretical studies. In this paper we present calculations and analysis of non-isotropic phase functions, asymmetry parameter (mean cosine of the scattering angle), absorption and scattering opacities, single scattering albedos, equilibrium temperatures, and radiative accelerations of dust grains relevant for extrasolar planets. Our assumptions include spherical grain shape, Deirmendjian particle size distribution, and Mie theory. We consider several species: corundum/alumina, perovskite, olivines with 0 and 50 per cent iron content, pyroxenes with 0, 20, and 60 per cent iron content, pure iron, carbon at two different temperatures, water ice, liquid water, and ammonia. The presented tables cover the wavelength range of 0.2-500 μm and modal particle radii from 0.01 to 100 μm. Equilibrium temperatures and radiative accelerations assume irradiation by a non-blackbody source of light with temperatures from 7000 to 700 K seen at solid angles from 2π to 10-6 sr. The tables are provided to the community together with a simple code which allows for an optional, finite, angular dimension of the source of light (star) in the phase function.

  20. An experimental and thermodynamic equilibrium investigation of the Pb, Zn, Cr, Cu, Mn and Ni partitioning during sewage sludge incineration.

    PubMed

    Liu, Jingyong; Fu, Jiewen; Ning, Xun'an; Sun, Shuiyu; Wang, Yujie; Xie, Wuming; Huang, Shaosong; Zhong, Sheng

    2015-09-01

    The effects of different chlorides and operational conditions on the distribution and speciation of six heavy metals (Pb, Zn, Cr, Cu, Mn and Ni) during sludge incineration were investigated using a simulated laboratory tubular-furnace reactor. A thermodynamic equilibrium investigation using the FactSage software was performed to compare the experimental results. The results indicate that the volatility of the target metals was enhanced as the chlorine concentration increased. Inorganic-Cl influenced the volatilization of heavy metals in the order of Pb>Zn>Cr>Cu>Mn>Ni. However, the effects of organic-Cl on the volatility of Mn, Pb and Cu were greater than the effects on Zn, Cr and Ni. With increasing combustion temperature, the presence of organic-Cl (PVC) and inorganic-Cl (NaCl) improved the transfer of Pb and Zn from bottom ash to fly ash or fuse gas. However, the presence of chloride had no obvious influence on Mn, Cu and Ni. Increased retention time could increase the volatilization rate of heavy metals; however, this effect was insignificant. During the incineration process, Pb readily formed PbSiO4 and remained in the bottom ash. Different Pb compounds, primarily the volatile PbCl2, were found in the gas phase after the addition of NaCl; the dominant Pb compounds in the gas phase after the addition of PVC were PbCl2, Pb(ClO4)2 and PbCl2O4. PMID:26354691

  1. Consideration of a Phase Change Model Based on Apparent Phase Equilibrium

    NASA Astrophysics Data System (ADS)

    Kashiwada, S.; Iga, Y.

    2015-12-01

    It has been known that cavity volume is underestimated and there is a discrepancy between predicted and measured breakdown characteristics for the numerical simulation of unsteady cavitation around a hydrofoil at high angle of attack. Therefore, in this study, in order to predict the cavity volume with high accuracy, the phenomena that gas phase increases even at a pressure higher than saturated vapour pressure which is known as aeration is modelled, and applied to phase change term. It was assumed that the precipitation of dissolved air is promoted by mechanical stimulation such as Reynolds stress in unsteady flow. The effectivity of the proposed model is discussed through the comparison among some kinds of components of the pressure variation.

  2. Phase transformations in the system Cu-Zn-Al under conditions far from equilibrium

    NASA Astrophysics Data System (ADS)

    Klopotov, Anatolii; Ivanov, Yuri; Vlasov, Viktor; Dedov, Nikolai; Loskutov, Oleg

    2016-01-01

    It is shown that the alloy Cu-Zn-Al is a multiphase material. Under equilibrium conditions this alloy can form an α-phase (FCC crystalline lattice) and a β-phase (simple cubic crystalline lattice) based on copper. The possibility of formation of a γ-phase due to a three-component alloy composition is revealed. It is established that different chemical composition of the copper-based solid solution (alloys with zinc or alloys with aluminum), different concentration of the second element in a solid solution leads to the fact that within the same type of the crystalline lattice there is a certain amount of α- and γ-phases, differing in the parameter value of the crystalline lattice. The possibility of formation of powder alloys with an x-ray amorphous and a nanocrystalline structure using the plasma chemical synthesis methods is demonstrated. A wide variety of binary phases, each with different concentrations of zinc and aluminum in a solid copper-based solution is revealed. These results indicate that plasma-chemical synthesis of metal alloy powders is accompanied by separation of elements. Powders of the ternary composition are not detected.

  3. Activity mediated phase separation: Can we understand phase behavior of the nonequilibrium problem from an equilibrium approach?

    PubMed

    Trefz, Benjamin; Das, Subir K; Egorov, Sergei A; Virnau, Peter; Binder, Kurt

    2016-04-14

    We present results for structure and dynamics of mixtures of active and passive particles, from molecular dynamics (MD) simulations and integral equation theory (IET) calculations, for a physically motivated model. The perfectly passive limit of the model corresponds to the phase-separating Asakura-Oosawa model for colloid-polymer mixtures in which, for the present study, the colloids are made self-propelling by introducing activity in accordance with the well known Vicsek model. Such activity facilitates phase separation further, as confirmed by our MD simulations and IET calculations. Depending upon the composition of active and passive particles, the diffusive motion of the active species can only be realized at large time scales. Despite this, we have been able to construct an equilibrium approach to obtain the structural properties of such inherently out-of-equilibrium systems. In this method, effective inter-particle potentials were constructed via IET by taking structural inputs from the MD simulations of the active system. These potentials in turn were used in passive MD simulations, results from which are observed to be in fair agreement with the original ones. PMID:27083747

  4. Activity mediated phase separation: Can we understand phase behavior of the nonequilibrium problem from an equilibrium approach?

    NASA Astrophysics Data System (ADS)

    Trefz, Benjamin; Das, Subir K.; Egorov, Sergei A.; Virnau, Peter; Binder, Kurt

    2016-04-01

    We present results for structure and dynamics of mixtures of active and passive particles, from molecular dynamics (MD) simulations and integral equation theory (IET) calculations, for a physically motivated model. The perfectly passive limit of the model corresponds to the phase-separating Asakura-Oosawa model for colloid-polymer mixtures in which, for the present study, the colloids are made self-propelling by introducing activity in accordance with the well known Vicsek model. Such activity facilitates phase separation further, as confirmed by our MD simulations and IET calculations. Depending upon the composition of active and passive particles, the diffusive motion of the active species can only be realized at large time scales. Despite this, we have been able to construct an equilibrium approach to obtain the structural properties of such inherently out-of-equilibrium systems. In this method, effective inter-particle potentials were constructed via IET by taking structural inputs from the MD simulations of the active system. These potentials in turn were used in passive MD simulations, results from which are observed to be in fair agreement with the original ones.

  5. Immunodominance: a new hypothesis to explain parasite escape and host/parasite equilibrium leading to the chronic phase of Chagas' disease?

    PubMed

    Rodrigues, M M; Alencar, B C G de; Claser, C; Tzelepis, F

    2009-03-01

    Intense immune responses are observed during human or experimental infection with the digenetic protozoan parasite Trypanosoma cruzi. The reasons why such immune responses are unable to completely eliminate the parasites are unknown. The survival of the parasite leads to a parasite-host equilibrium found during the chronic phase of chagasic infection in most individuals. Parasite persistence is recognized as the most likely cause of the chagasic chronic pathologies. Therefore, a key question in Chagas' disease is to understand how this equilibrium is established and maintained for a long period. Understanding the basis for this equilibrium may lead to new approaches to interventions that could help millions of individuals at risk for infection or who are already infected with T. cruzi. Here, we propose that the phenomenon of immunodominance may be significant in terms of regulating the host-parasite equilibrium observed in Chagas' disease. T. cruzi infection restricts the repertoire of specific T cells generating, in some cases, an intense immunodominant phenotype and in others causing a dramatic interference in the response to distinct epitopes. This immune response is sufficiently strong to maintain the host alive during the acute phase carrying them to the chronic phase where transmission usually occurs. At the same time, immunodominance interferes with the development of a higher and broader immune response that could be able to completely eliminate the parasite. Based on this, we discuss how we can interfere with or take advantage of immunodominance in order to provide an immunotherapeutic alternative for chagasic individuals. PMID:19287899

  6. Out-of-equilibrium phase re-entrance(s) in long-range interacting systems

    SciTech Connect

    Staniscia, F.; Chavanis, P. H.; De Ninno, G.; Fanelli, D.

    2009-08-15

    Systems with long-range interactions display a short-time relaxation toward quasistationary states (QSSs) whose lifetime increases with system size. The application of Lynden-Bell's theory of 'violent relaxation' to the Hamiltonian Mean Field model leads to the prediction of out-of-equilibrium first- and second-order phase transitions between homogeneous (zero magnetization) and inhomogeneous (nonzero magnetization) QSSs, as well as an interesting phenomenon of phase re-entrances. We compare these theoretical predictions with direct N-body numerical simulations. We confirm the existence of phase re-entrance in the typical parameter range predicted from Lynden-Bell's theory, but also show that the picture is more complicated than initially thought. In particular, we exhibit the existence of secondary re-entrant phases: we find unmagnetized states in the theoretically magnetized region as well as persisting magnetized states in the theoretically unmagnetized region. We also report the existence of a region with negative specific heats for QSSs both in the numerical and analytical caloric curves.

  7. Discontinuous non-equilibrium phase transition in a threshold Schloegl model for autocatalysis: Generic two-phase coexistence and metastability

    SciTech Connect

    Wang, Chi -Jen; Liu, Da -Jiang; Evans, James W.

    2015-04-28

    Threshold versions of Schloegl’s model on a lattice, which involve autocatalytic creation and spontaneous annihilation of particles, can provide a simple prototype for discontinuous non-equilibrium phase transitions. These models are equivalent to so-called threshold contact processes. A discontinuous transition between populated and vacuum states can occur selecting a threshold of N ≥ 2 for the minimum number, N, of neighboring particles enabling autocatalytic creation at an empty site. Fundamental open questions remain given the lack of a thermodynamic framework for analysis. For a square lattice with N = 2, we show that phase coexistence occurs not at a unique value but for a finite range of particle annihilation rate (the natural control parameter). This generic two-phase coexistence also persists when perturbing the model to allow spontaneous particle creation. Such behavior contrasts both the Gibbs phase rule for thermodynamic systems and also previous analysis for this model. We find metastability near the transition corresponding to a non-zero effective line tension, also contrasting previously suggested critical behavior. As a result, mean-field type analysis, extended to treat spatially heterogeneous states, further elucidates model behavior.

  8. Discontinuous non-equilibrium phase transition in a threshold Schloegl model for autocatalysis: Generic two-phase coexistence and metastability

    DOE PAGESBeta

    Wang, Chi -Jen; Liu, Da -Jiang; Evans, James W.

    2015-04-28

    Threshold versions of Schloegl’s model on a lattice, which involve autocatalytic creation and spontaneous annihilation of particles, can provide a simple prototype for discontinuous non-equilibrium phase transitions. These models are equivalent to so-called threshold contact processes. A discontinuous transition between populated and vacuum states can occur selecting a threshold of N ≥ 2 for the minimum number, N, of neighboring particles enabling autocatalytic creation at an empty site. Fundamental open questions remain given the lack of a thermodynamic framework for analysis. For a square lattice with N = 2, we show that phase coexistence occurs not at a unique valuemore » but for a finite range of particle annihilation rate (the natural control parameter). This generic two-phase coexistence also persists when perturbing the model to allow spontaneous particle creation. Such behavior contrasts both the Gibbs phase rule for thermodynamic systems and also previous analysis for this model. We find metastability near the transition corresponding to a non-zero effective line tension, also contrasting previously suggested critical behavior. As a result, mean-field type analysis, extended to treat spatially heterogeneous states, further elucidates model behavior.« less

  9. Discontinuous non-equilibrium phase transition in a threshold Schloegl model for autocatalysis: Generic two-phase coexistence and metastability

    SciTech Connect

    Wang, Chi-Jen; Liu, Da-Jiang; Evans, James W.

    2015-04-28

    Threshold versions of Schloegl’s model on a lattice, which involve autocatalytic creation and spontaneous annihilation of particles, can provide a simple prototype for discontinuous non-equilibrium phase transitions. These models are equivalent to so-called threshold contact processes. A discontinuous transition between populated and vacuum states can occur selecting a threshold of N ≥ 2 for the minimum number, N, of neighboring particles enabling autocatalytic creation at an empty site. Fundamental open questions remain given the lack of a thermodynamic framework for analysis. For a square lattice with N = 2, we show that phase coexistence occurs not at a unique value but for a finite range of particle annihilation rate (the natural control parameter). This generic two-phase coexistence also persists when perturbing the model to allow spontaneous particle creation. Such behavior contrasts both the Gibbs phase rule for thermodynamic systems and also previous analysis for this model. We find metastability near the transition corresponding to a non-zero effective line tension, also contrasting previously suggested critical behavior. Mean-field type analysis, extended to treat spatially heterogeneous states, further elucidates model behavior.

  10. Solid-liquid phase equilibrium for binary Lennard-Jones mixtures

    NASA Astrophysics Data System (ADS)

    Hitchcock, Monica R.; Hall, Carol K.

    1999-06-01

    Solid-liquid phase diagrams are calculated for binary mixtures of Lennard-Jones spheres using Monte Carlo simulation and the Gibbs-Duhem integration technique of Kofke. We calculate solid-liquid phase diagrams for the model Lennard-Jones mixtures: argon-methane, krypton-methane, and argon-krypton, and compare our simulation results with experimental data and with Cottin and Monson's recent cell theory predictions. The Lennard-Jones model simulation results and the cell theory predictions show qualitative agreement with the experimental phase diagrams. One of the mixtures, argon-krypton, has a different phase diagram than its hard-sphere counterpart, suggesting that attractive interactions are an important consideration in determining solid-liquid phase behavior. We then systematically explore Lennard-Jones parameter space to investigate how solid-liquid phase diagrams change as a function of the Lennard-Jones diameter ratio, σ11/σ22, and well-depth ratio, ɛ11/ɛ22. This culminates in an estimate of the boundaries separating the regions of solid solution, azeotrope, and eutectic solid-liquid phase behavior in the space spanned by σ11/σ22 and ɛ11/ɛ22 for the case σ11/σ22<0.85.

  11. Equilibrium thermodynamics of radiation defect clusters in δ-phase Pu-Ga alloys

    NASA Astrophysics Data System (ADS)

    Karavaev, A. V.; Dremov, V. V.; Ionov, G. V.

    2016-01-01

    The paper presents a theoretical investigation into the response of δ-phase Pu-Ga alloys to self-irradiation. Using classical molecular dynamics we investigate the long-term behavior of primary radiation defects (vacancies) in the face-centered cubic lattice of the alloys under ambient conditions. High diffusive migration energy barriers and the corresponding low mobility of vacancies do not allow us to track their dynamics in the lattice by direct molecular dynamics simulations. Instead, we use the Helmholtz free energy to investigate the equilibrium thermodynamics of metastable microconfigurations of Pu-Ga crystals with artificially introduced vacancy clusters in various regular and random configurations. The Helmholtz free energy of the microconfigurations are calculated with the thermodynamic integration method. Based on the free energy evaluation we draw conclusions about the relative thermodynamic stability of various microconfigurations under ambient conditions. The equilibrium parameters of vacancy clusters in the bulk of the lattice and in the presence of edge dislocations are estimated.

  12. Rare Earth Element - Humic Acid Interaction: Experimental Evidence for Kinetic and Equilibrium Fractionation in Aqueous Systems.

    NASA Astrophysics Data System (ADS)

    Sonke, J. E.; Salters, V. J.; Benedetti, M. F.

    2003-12-01

    Dissolved organic matter (DOM) is well known for it's strong binding capacity for trace metals. In order to better predict the role of DOM in the speciation and transport of trace metals in the environment we coupled capillary electrophoresis (CE), a molecular separation technique, to a Sector Field Inductively Coupled Plasma Mass Spectrometer (SF-ICP-MS). The combination of these two techniques allows for the study of non-labile metal speciation in aquatic samples. By separating Rare Earth Element (REE) complexes with EDTA and Humic Acid's (i.e. ligand competition) we have been able to determine conditional equilibrium binding constants (Kc) and kinetic rate constants for all 14 REE's with Humic (HA) and Fulvic Acids (FA) as a function of pH (6-9) and ionic strength (IS, 0.01-0.1 mol/L). Assuming a 1:1 binding mechanism, logKc values for REE-FA varied from 9.0 (La) to 10.5 (Lu) at pH 6, 0.1 mol/L IS, and 11.7 (La) to 14.6 (Lu) at pH 9, 0.1 mol/L IS. LogKc values for REE-HA were 10.6 (La) to 12.2 (Lu) at pH 6, 0.1 mol/L IS and 13.2 (La) to 16.5 (Lu) at pH 9, 0.1 mol/L IS. Slightly higher values for Kc were obtained at 0.01 mol/L IS. The general observations of stronger REE-HA binding compared to REE-FA, and stronger binding with increasing pH and decreasing IS correlate with our current understanding of metal-DOM interactions (1). Both Kc's as well as kinetic rate constants increase with increasing REE mass number (decreasing ionic radius); a reflection of the well-known lanthanide contraction. This is the first comprehensive metal binding dataset between REE and DOM, and the first experimental evidence for differential equilibrium and kinetic binding behavior between REE's and DOM. The 30-1000 fold increase in binding strength of heavy REE's with DOM provides for a an equilibrium fractionation mechanism that may explain features of the global geochemical REE cycle such as fractionation related to weathering, estuarine mixing, and REE scavenging in the deep ocean

  13. Experimental realization of atomtronic circuit elements in non-equilibrium ultracold atomic systems

    NASA Astrophysics Data System (ADS)

    Caliga, Seth C.

    Research in the field of atomtronics aims to develop a new paradigm for the use of ultracold atomic systems in a manner that mimics the functionality of electronic circuits and devices. Given the ubiquity of the electronic transistor and its application to a vast array of signal processing tasks, the development of its atomtronic counterpart is of significant interest. This dissertation presents the experimental studies of two atomtronic circuit elements: a battery and transistor. Experiments are conducted in an atom-chip-based apparatus utilizing hybrid magnetic and optical trapping techniques that enable one to ``pattern" atomtronic circuit elements. An atomtronic battery is realized in a double-well trapping potential in which a finite-temperature Bose-Einstein condensate is prepared in a non-equilibrium state to generate thermodynamic gradients that drive atom current flow. Powered by the atomtronic battery, a triple-well atomtronic transistor is demonstrated, and quasi-steady-state behavior of the device is characterized. Results are found to be in agreement with a semiclassical model of the transistor that is also used to study the active properties of the device, including current gain. Based on these results, future directions regarding signal processing operations are proposed.

  14. Statistical enhancement of a dynamic equilibrium-based damage identification strategy: Theory and experimental validation

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Lu, Bo; Su, Zhongqing; Cheng, Li

    2015-09-01

    A previously developed damage identification strategy, named Pseudo-Excitation (PE), was enhanced using a statistical processing approach. In terms of the local dynamic equilibrium of the structural component under inspection, the distribution of its vibration displacements, which are of necessity to construct the damage index in the PE, was re-defined using sole dynamic strains based on the statistical method. On top of those advantages inheriting from the original PE compared with traditional vibration-based damage detection including the independence of baseline signals and pre-developed benchmark structures, the enhanced PE (EPE) possesses improved immunity to the interference of measurement noise. Moreover, the EPE can facilitate practical implementation of online structural health monitoring, benefiting from the use of sole strain information. Proof-of-concept numerical study was conducted to examine the feasibility and accuracy of the EPE, and the effectiveness of the proposed statistical enhancement in re-constructing the vibration displacements was evaluated under noise influence; experimental validation was followed up by characterizing multi-cracks in a beam-like structure, in which the dynamic strains were measured using Lead zirconium titanate (PZT) sensors. For comparison, the original PE, the Gapped Smoothing Method (GSM), and the EPE were respectively used to evaluate the cracks. It was observed from the damage identification results that both the GSM and EPE were able to achieve higher identification accuracy than the original PE, and the robustness of the EPE in damage identification was proven to be superior than that of the GSM.

  15. Damage of Honeybee Colonies and Non-Equilibrium Percolation Phase Transition

    NASA Astrophysics Data System (ADS)

    Zhang, Peipei; Su, Beibei; He, Da-Ren

    Recently the mechanism of the damage caused by invasion of Apis mellifera capensis honeybee into the normal A. M. Scutellata colonies became interesting for scientists due to the fact that the mechanism may resemble those of cancer vicious hyperplasia, spreading of some epidemic, and turbulence of society induced by some bad society groups. We suggest a new guess that losing control of self-reproduction disturbs and throws information structure of the society into confuse. We simulate the damage process with a cellular automata based on the guess. The simulation shows that the process is equivalent to a non-equilibrium percolation phase transition. This discussion remind us that the management and monitor on the information network between society members may be a more effective way for avoiding the overflow of the destructor sub-colonies.

  16. Chemicals loading in acetylated bamboo assisted by supercritical CO2 based on phase equilibrium data

    NASA Astrophysics Data System (ADS)

    Silviana, Petermann, M.

    2015-12-01

    Indonesia has a large tropical forest. However, the deforestation still appears annually and vastly. This reason drives a use of bamboo as wood alternative. Recently, there are many modifications of bamboo in order to prolong the shelf life. Unfortunately, the processes need more chemicals and time. Based on wood modification, esterifying of bamboo was undertaken in present of a dense gas, i.e. supercritical CO2. Calculation of chemicals loading referred to ASTM D1413-99 by using the phase equilibrium data at optimum condition by a statistical design. The results showed that the acetylation of bamboo assisted by supercritical CO2 required 14.73 kg acetic anhydride/m3 of bamboo for a treatment of one hour.

  17. Impurity-tuned non-equilibrium phase transition in a bacterial carpet

    NASA Astrophysics Data System (ADS)

    Hsiao, Yi-Teng; Wu, Kuan-Ting; Uchida, Nariya; Woon, Wei-Yen

    2016-05-01

    The effects of impurity on the non-equilibrium phase transition in Vibrio alginolyticus bacterial carpets are investigated through a position-sensitive-diode implemented optical tweezers-microsphere assay. The collective flow increases abruptly as we increase the rotation rate of flagella via Na+ concentration. The effects of impurities on the transition behavior are examined by mixing cells of a wild type strain (VIO5) with cells of a mutant strain (NMB136) in different swimming patterns. For dilute impurities, the transition point is shifted toward higher Na+ concentration. Increasing the impurities' ratio to over 0.25 leads to a significant drop in the collective force, suggesting a partial orientational order with a smaller correlation length.

  18. Entropic screening preserves non-equilibrium nature of nematic phase while enthalpic screening destroys it.

    PubMed

    Dan, K; Roy, M; Datta, A

    2016-02-14

    The present manuscript describes the role of entropic and enthalpic forces mediated by organic non-polar (hexane) and polar (methanol) solvents on the bulk and microscopic phase transition of a well known nematic liquid crystalline material MBBA (N-(4-methoxybenzylidene)-4-butylaniline) through Differential Scanning calorimetry (DSC), UV-Visible (UV-Vis), and Fourier Transform Infrared (FTIR) spectroscopy. DSC study indicates continuous linear decreases in both nematic-isotropic (N-I) phase transition temperature and enthalpy of MBBA in presence of hexane while both these parameters show a saturation after an initial decay in methanol. These distinct transitional behaviours were explained in terms of the "depletion force" model for entropic screening in hexane and "screening-self-screening" model for methanol. Heating rate dependent DSC studies find that non-Arrhenius behaviour, characteristic of pristine MBBA and a manifestation of non-equilibrium nature [Dan et al., J. Chem. Phys. 143, 094501 (2015)], is preserved in presence of entropic screening in the hexane solution, while it changes to Arrhenius behaviour (signifying equilibrium behaviour) in presence of enthalpic screening in methanol solution. FTIR spectra show similar dependence on the solvent induced screening in the intensities of the imine (-C = N) stretch and the out-of-plane distortion vibrations of the benzene rings of MBBA with hexane and methanol as in DSC, further establishing our entropic and enthalpic screening models. UV-Vis spectra of the electronic transitions in MBBA as a function of temperature also exhibit different dependences of intensities on the solvent induced screening, and an exponential decrease is observed in presence of hexane while methanol completely changes the nature of interaction to follow a linear dependence. PMID:26874498

  19. Entropic screening preserves non-equilibrium nature of nematic phase while enthalpic screening destroys it

    NASA Astrophysics Data System (ADS)

    Dan, K.; Roy, M.; Datta, A.

    2016-02-01

    The present manuscript describes the role of entropic and enthalpic forces mediated by organic non-polar (hexane) and polar (methanol) solvents on the bulk and microscopic phase transition of a well known nematic liquid crystalline material MBBA (N-(4-methoxybenzylidene)-4-butylaniline) through Differential Scanning calorimetry (DSC), UV-Visible (UV-Vis), and Fourier Transform Infrared (FTIR) spectroscopy. DSC study indicates continuous linear decreases in both nematic-isotropic (N-I) phase transition temperature and enthalpy of MBBA in presence of hexane while both these parameters show a saturation after an initial decay in methanol. These distinct transitional behaviours were explained in terms of the "depletion force" model for entropic screening in hexane and "screening-self-screening" model for methanol. Heating rate dependent DSC studies find that non-Arrhenius behaviour, characteristic of pristine MBBA and a manifestation of non-equilibrium nature [Dan et al., J. Chem. Phys. 143, 094501 (2015)], is preserved in presence of entropic screening in the hexane solution, while it changes to Arrhenius behaviour (signifying equilibrium behaviour) in presence of enthalpic screening in methanol solution. FTIR spectra show similar dependence on the solvent induced screening in the intensities of the imine (—C = N) stretch and the out-of-plane distortion vibrations of the benzene rings of MBBA with hexane and methanol as in DSC, further establishing our entropic and enthalpic screening models. UV-Vis spectra of the electronic transitions in MBBA as a function of temperature also exhibit different dependences of intensities on the solvent induced screening, and an exponential decrease is observed in presence of hexane while methanol completely changes the nature of interaction to follow a linear dependence.

  20. Equilibrium phase boundary between hcp-cobalt and fcc-cobalt

    NASA Astrophysics Data System (ADS)

    Cynn, Hyunchae; Lipp, Magnus J.; Evans, William J.; Baer, Bruce J.

    In 2000 (Yoo et al., PRL), fcc-cobalt was reported as a new high pressure phase transforming from ambient hcp-cobalt starting at around 105 GPa and 300 K. Both cobalts coexist up to 150 GPa and thereafter only fcc-cobalt was found to be the only stable phase to 200 GPa. Our recent synchrotron x-ray diffraction data on cobalt are at odds with the previous interpretation. We will present our new finding and elaborate on our understanding in terms of the equilibrium phase boundary of cobalt. We will also compare our previous work on xenon (Cynn et al., 2001, PRL) with our new results on cobalt. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Portions of this work were performed at HPCAT (Sector 16), APS, Argonne National Laboratory. HPCAT operations are supported by DOE-NNSA under Award No. DENA0001974 and DOE-BES under Award No. DE-FG02-99ER45775. The Advanced Photon Source is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

  1. A two-phase restricted equilibrium model for combustion of metalized solid propellants

    NASA Technical Reports Server (NTRS)

    Sabnis, J. S.; Dejong, F. J.; Gibeling, H. J.

    1992-01-01

    An Eulerian-Lagrangian two-phase approach was adopted to model the multi-phase reacting internal flow in a solid rocket with a metalized propellant. An Eulerian description was used to analyze the motion of the continuous phase which includes the gas as well as the small (micron-sized) particulates, while a Lagrangian description is used for the analysis of the discrete phase which consists of the larger particulates in the motor chamber. The particulates consist of Al and Al2O3 such that the particulate composition is 100 percent Al at injection from the propellant surface with Al2O3 fraction increasing due to combustion along the particle trajectory. An empirical model is used to compute the combustion rate for agglomerates while the continuous phase chemistry is treated using chemical equilibrium. The computer code was used to simulate the reacting flow in a solid rocket motor with an AP/HTPB/Al propellant. The computed results show the existence of an extended combustion zone in the chamber rather than a thin reaction region. The presence of the extended combustion zone results in the chamber flow field and chemical being far from isothermal (as would be predicted by a surface combustion assumption). The temperature in the chamber increases from about 2600 K at the propellant surface to about 3350 K in the core. Similarly the chemical composition and the density of the propellant gas also show spatially non-uniform distribution in the chamber. The analysis developed under the present effort provides a more sophisticated tool for solid rocket internal flow predictions than is presently available, and can be useful in studying apparent anomalies and improving the simple correlations currently in use. The code can be used in the analysis of combustion efficiency, thermal load in the internal insulation, plume radiation, etc.

  2. Carbon dioxide hydrate phase equilibrium and cage occupancy calculations using ab initio intermolecular potentials.

    PubMed

    Velaga, Srinath C; Anderson, Brian J

    2014-01-16

    Gas hydrate deposits are receiving increased attention as potential locations for CO2 sequestration, with CO2 replacing the methane that is recovered as an energy source. In this scenario, it is very important to correctly characterize the cage occupancies of CO2 to correctly assess the sequestration potential as well as the methane recoverability. In order to predict accurate cage occupancies, the guest–host interaction potential must be represented properly. Earlier, these potential parameters were obtained by fitting to experimental equilibrium data and these fitted parameters do not match with those obtained by second virial coefficient or gas viscosity data. Ab initio quantum mechanical calculations provide an independent means to directly obtain accurate intermolecular potentials. A potential energy surface (PES) between H2O and CO2 was computed at the MP2/aug-cc-pVTZ level and corrected for basis set superposition error (BSSE), an error caused due to the lower basis set, by using the half counterpoise method. Intermolecular potentials were obtained by fitting Exponential-6 and Lennard-Jones 6-12 models to the ab initio PES, correcting for many-body interactions. We denoted this model as the “VAS” model. Reference parameters for structure I carbon dioxide hydrate were calculated using the VAS model (site–site ab initio intermolecular potentials) as Δμ(w)(0) = 1206 ± 2 J/mol and ΔH(w)(0) = 1260 ± 12 J/mol. With these reference parameters and the VAS model, pure CO2 hydrate equilibrium pressure was predicted with an average absolute deviation of less than 3.2% from the experimental data. Predictions of the small cage occupancy ranged from 32 to 51%, and the large cage is more than 98% occupied. The intermolecular potentials were also tested by calculating the pure CO2 density and diffusion of CO2 in water using molecular dynamics simulations. PMID:24328234

  3. Fourier phase analysis on equilibrium gated radionuclide ventriculography: Range of phase spread and cut-off limits in normal individuals

    PubMed Central

    Ramaiah, Vijayaraghavan L; Harish, B; Sunil, HV; Selvakumar, Job; Ravi, Kishore AG; Nair, Gopinathan

    2011-01-01

    Aim: To define the range of phase spread on equilibrium gated radionuclide ventriculography (ERNV) in normal individuals and derive the cut-off limit for the parameters to detect cardiac dyssynchrony. Materials and Methods: ERNV was carried out in 30 individuals (age 53±23 years, 25 males and 5 females) who had no history of cardiovascular disease. They all had normal left ventricular ejection fraction (LVEF 55–70%) as determined by echocardiography, were in sinus rhythm, with normal QRS duration (≤120 msec) and normal coronary angiography. First harmonic phase analysis was performed on scintigraphic data acquired in best septal view. Left and right ventricular standard deviation (LVSD and RVSD, respectively) and interventricular mechanical delay (IVMD), the absolute difference of mean phase angles of right and left ventricle, were computed and expressed in milliseconds. Mean + 3 standard deviation (SD) was used to derive the cut-off limits. Results: Average LVEF and duration of cardiac cycle in the study group were 62.5%±5.44% and 868.9±114.5 msec, respectively. The observations of LVSD, RVSD and right and left ventricular mean phase angles were shown to be normally distributed by Shapiro–Wilk test. Cut-off limits for LVSD, RVSD and IVMD were calculated to be 80 msec, 85 msec and 75 msec, respectively. Conclusion: Fourier phase analysis on ERNV is an effective tool for the evaluation of synchronicity of cardiac contraction. The cut-off limits of parameters of dyssynchrony can be used to separate heart failure patients with cardiac dyssynchrony from those without. ERNV can be used to select patients for cardiac resynchronization therapy. PMID:23326063

  4. Sorption equilibrium of a wide spectrum of organic vapors in Leonardite humic acid: experimental setup and experimental data.

    PubMed

    Niederer, Christian; Goss, Kai-Uwe; Schwarzenbach, René P

    2006-09-01

    The environmental fate of volatile and semivolatile organic compounds is determined by their partitioning between air and soil constituents, in particular soil organic matter (SOM). While there are many studies on the partitioning of nonpolar compounds between water and SOM, data on sorption of polar compounds and data for sorption from the gas phase are rather limited. In this study, Leonardite humic acid/air partition coefficients for 188 polar and nonpolar organic compounds at temperatures between 5 and 75 degrees C and relative humidities between < 0.01% and 98% have been determined using a dynamic flow-through technique. To the best of our knowledge, this is by far the largest and most diverse and consistent data set for sorption into humic material published so far. The major results are as follows: the relative humidity affected the experimental partition coefficients by up to a factor of 3; polar compounds generally sorbed more strongly than nonpolar compounds due to H-bonding (electron donor/ acceptor interactions) with the humic acid; no glass transitions in the range of 5-75 degrees C that would be relevant with respect to the sorption behavior of hydrated Leonardite humic acid were observed; our experimental data agree well with experimental partition coefficients from various literature sources. PMID:16999112

  5. Sorption equilibrium of a wide spectrum of organic vapors in Leonardite humic acid: experimental setup and experimental data

    SciTech Connect

    Christian Niederer; Kai-Uwe Goss; Rene P. Schwarzenbach

    2006-09-01

    The environmental fate of volatile and semivolatile organic compounds is determined by their partitioning between air and soil constituents, in particular soil organic matter (SOM). While there are many studies on the partitioning of nonpolar compounds between water and SOM, data on sorption of polar compounds and data for sorption from the gas phase are rather limited. In this study, Leonardite humic acid/air partition coefficients for 188 polar and nonpolar organic compounds at temperatures between 5 and 75{sup o}C and relative humidities between {lt}0.01% and 98% have been determined using a dynamic flow-through technique. The Leonardite used is a standard humic acid produced by the natural oxidation of expose lignite originating from the Gascoyne Mine in North Dakota. To the best of our knowledge, this is by far the largest and most diverse and consistent data set for sorption into humic material published so far. The major results are as follows: the relative humidity affected the experimental partition coefficients by up to a factor of 3; polar compounds generally sorbed more strongly than nonpolar compounds due to H-bonding (electron donor/acceptor interactions) with the humic acid; no glass transitions in the range of 5-75{sup o}C that would be relevant with respect to the sorption behavior of hydrated Leonardite humic acid were observed; our experimental data agree well with experimental partition coefficients from various literature sources. 42 refs., 2 figs., 2 tabs.

  6. Theoretical Aspects of Differential Scanning Calorimetry as a Tool for the Studies of Equilibrium Thermodynamics in Pharmaceutical Solid Phase Transitions.

    PubMed

    Faroongsarng, Damrongsak

    2016-06-01

    Although differential scanning calorimetry (DSC) is a non-equilibrium technique, it has been used to gain energetic information that involves phase equilibria. DSC has been widely used to characterize the equilibrium melting parameters of small organic pharmaceutical compounds. An understanding of how DSC measures an equilibrium event could make for a better interpretation of the results. The aim of this mini-review was to provide a theoretical insight into the DSC measurement to obtain the equilibrium thermodynamics of a phase transition especially the melting process. It was demonstrated that the heat quantity obtained from the DSC thermogram (ΔH) was related to the thermodynamic enthalpy of the phase transition (ΔH (P) ) via: ΔH = ΔH (P) /(1 + K (- 1)) where K was the equilibrium constant. In melting, the solid and liquefied phases presumably coexist resulting in a null Gibbs free energy that produces an infinitely larger K. Thus, ΔH could be interpreted as ΔH (P). Issues of DSC investigations on melting behavior of crystalline solids including polymorphism, degradation impurity due to heating in situ, and eutectic melting were discussed. In addition, DSC has been a tool for determination of the impurity based on an ideal solution of the melt that is one of the official methods used to establish the reference standard. PMID:27091667

  7. The role of equilibrium volume and magnetism on the stability of iron phases at high pressures.

    PubMed

    Alnemrat, S; Hooper, J P; Vasiliev, I; Kiefer, B

    2014-01-29

    The present study provides new insights into the pressure dependence of magnetism by tracking the hybridization between crystal orbitals for pressures up to 600 GPa in the known hcp, bcc and fcc iron. The Birch-Murnaghan equation of state parameters are; bcc: V0 = 11.759 A(3)/atom, K0 = 177.72 GPa; hcp: V0 = 10.525 A(3)/atom, K0 = 295.16 GPa; and fcc: V0 = 10.682 A(3)/atom, K0 = 274.57 GPa. These parameters compare favorably with previous studies. Consistent with previous studies we find that the close-packed hcp and fcc phases are non-magnetic at pressures above 50 GPa and 60 GPa, respectively. The principal features of magnetism in iron are predicted to be invariant, at least up to ∼6% overextension of the equilibrium volume. Our results predict that magnetism for overextended fcc iron disappears via an intermediate spin state. This feature suggests that overextended lattices can be used to stabilize particular magnetic states. The analysis of the orbital hybridization shows that the magnetic bcc structure at high pressures is stabilized by splitting the majority and minority spin bands. The bcc phase is found to be magnetic at least up to 600 GPa; however, magnetism is insufficient to stabilize the bcc phase itself, at least at low temperatures. Finally, the analysis of the orbital contributions to the total energy provides evidence that non-magnetic hcp and fcc phases are likely more stable than bcc at core earth pressures. PMID:24355938

  8. m-Plane Homoepitaxy and Equilibrium Crystal Shapes of Gallium Nitride by Hydride Vapor Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Bryant, Benjamin Nathaniel

    Nonpolar and semipolar growth of GaN has been shown to offer a promising path for high performance devices. These non-basal plane orientations allow for minimization of the polarization effects seen in c-plane GaN which cause spatial separation of the electron and hole wavefunctions (Quantum Confined Stark Effect). Yet despite the advantages these planes present, there remains consistent problems in both their growth and the lack of substrates. This dissertation focuses on the growth of these nonpolar and semipolar planes, in particular the homoepitaxy of m-plane GaN. The equilibrium crystal shape of GaN and its stable facets were also investigated. It is hoped that with this work, progress is made towards low defect large area nonpolar and semipolar substrates and their improved vapor phase growth. Work was initially done on m-plane regrowth by hydride vapor phase epitaxy. Extended defect generation, in particular basal plane stacking faults (BPSF), and poor morphology control are consistent problems in m-plane growth. These issues have prevented the expansion and multiplication of m-plane GaN substrates. In this work the effects of carrier gas were investigated on m-plane regrowth. Hydrogen carrier gas was shown to create highly faceted 3D nucleation. These islands had exposed N-face facets which lead to BPSF generation. In contrast, nitrogen carrier gas lead to 2D growth and thus minimized BPSF generation. These stacking faults were then characterized by both reciprocal space mapping and cathodolumienscence where type I1 and I2 faults were observed in the regrown GaN. Further work was done in exploring the equilibrium crystal shapes of GaN under varying growth conditions. Selective area growth experiments were done on high quality bulk m-plane GaN substrates where GaN facets were exposed to show the stable polar, semipolar and nonpolar planes. From these facets the kinetic Wulff plots for GaN were constructed. This work highlights the stable growth conditions

  9. An experimental verification of a criterion for forming metastable phases in containerless solidification

    NASA Astrophysics Data System (ADS)

    Kuribayashi, K.; Kato, H.; Nagayama, K.; Inatomi, Y.; Kumar, M. S. Vijaya

    2015-04-01

    On the thermodynamic condition for forming a metastable phase from undercooled melt in a containerless state, we had proposed a criterion that crystals will preferentially form if they have a smaller entropy of fusion than the entropy of fusion of equilibrium crystals (Kuribayashi et al., Mater. Sci. Eng., A 449-451, 675 (2007)). This criterion is proposed for being applied to materials that exhibit a faceted interface, such as semiconductors and oxides. However, no experimental data that support this criterion have been obtained. From this point, we used an aerodynamic levitator as a tool for forming metastable phases from undercooled melt and verified the above-mentioned criterion using LnFeO3 (Ln: lanthanide and Y) as the model material. In addition, the condition for double recalescence, which corresponds to forming metastable phases and stable phases, was discussed in terms of competitive 2D isomorphic nucleation of the metastable phase and 3D polymorphic nucleation of the stable phase.

  10. An experimental verification of a criterion for forming metastable phases in containerless solidification

    SciTech Connect

    Kuribayashi, K.; Inatomi, Y.; Kumar, M. S. Vijaya

    2015-04-21

    On the thermodynamic condition for forming a metastable phase from undercooled melt in a containerless state, we had proposed a criterion that crystals will preferentially form if they have a smaller entropy of fusion than the entropy of fusion of equilibrium crystals (Kuribayashi et al., Mater. Sci. Eng., A 449–451, 675 (2007)). This criterion is proposed for being applied to materials that exhibit a faceted interface, such as semiconductors and oxides. However, no experimental data that support this criterion have been obtained. From this point, we used an aerodynamic levitator as a tool for forming metastable phases from undercooled melt and verified the above-mentioned criterion using LnFeO{sub 3} (Ln: lanthanide and Y) as the model material. In addition, the condition for double recalescence, which corresponds to forming metastable phases and stable phases, was discussed in terms of competitive 2D isomorphic nucleation of the metastable phase and 3D polymorphic nucleation of the stable phase.

  11. Non-local equilibrium two-phase flow model with phase change in porous media and its application to reflooding of a severely damaged reactor core

    NASA Astrophysics Data System (ADS)

    Bachrata, A.; Fichot, F.; Quintard, M.; Repetto, G.; Fleurot, J.

    2012-05-01

    A generalized non local-equilibrium, three-equation model was developed for the macroscopic description of two-phase flow heat and mass transfer in porous media subjected to phase change. Six pore-scale closure problems were proposed to determine all the effective transport coefficients for representative unit cells. An improved model is presented in this paper with the perspective of application to intense boiling phenomena. The objective of this paper is to present application of this model to the simulation of reflooding of severely damaged nuclear reactor cores. In case of accident at a nuclear power plant, water sources may not be available for a long period of time and the core heats up due to the residual power. Any attempt to inject water during core degradation can lead to quenching and further fragmentation of the core material. The fragmentation of fuel rods and melting of reactor core materials may result in the formation of a "debris bed". The typical particle size in a debris bed might reach few millimeters (characteristic length-scale: 1 to 5 mm), which corresponds to a high permeability porous medium. The proposed two-phase flow model is implemented in the ICARECATHARE code, developed by IRSN to study severe accident scenarios in pressurized water reactors. Currently, the French IRSN has set up two experimental facilities to study debris bed reflooding, PEARL and PRELUDE, with the objective to validate safety models. The PRELUDE program studies the complex two phase flow of water and steam in a porous medium (diameter 180 mm, height 200 mm), initially heated to a high temperature (400°C or 700°C). The series of PRELUDE experiments achieved in 2010 constitute a significant complement to the database of high temperature bottom reflood experimental data. They provide relevant data to understand the progression of the quench front and the intensity of heat transfer. Modeling accurately these experiments required improvements to the reflooding model

  12. Non-local equilibrium two-phase flow model with phase change in porous media and its application to reflooding of a severely damaged reactor core

    SciTech Connect

    Bachrata, A.; Fichot, F.; Quintard, M.; Repetto, G.; Fleurot, J.

    2012-05-15

    A generalized non local-equilibrium, three-equation model was developed for the macroscopic description of two-phase flow heat and mass transfer in porous media subjected to phase change. Six pore-scale closure problems were proposed to determine all the effective transport coefficients for representative unit cells. An improved model is presented in this paper with the perspective of application to intense boiling phenomena. The objective of this paper is to present application of this model to the simulation of reflooding of severely damaged nuclear reactor cores. In case of accident at a nuclear power plant, water sources may not be available for a long period of time and the core heats up due to the residual power. Any attempt to inject water during core degradation can lead to quenching and further fragmentation of the core material. The fragmentation of fuel rods and melting of reactor core materials may result in the formation of a {sup d}ebris bed{sup .} The typical particle size in a debris bed might reach few millimeters (characteristic length-scale: 1 to 5 mm), which corresponds to a high permeability porous medium. The proposed two-phase flow model is implemented in the ICARECATHARE code, developed by IRSN to study severe accident scenarios in pressurized water reactors. Currently, the French IRSN has set up two experimental facilities to study debris bed reflooding, PEARL and PRELUDE, with the objective to validate safety models. The PRELUDE program studies the complex two phase flow of water and steam in a porous medium (diameter 180 mm, height 200 mm), initially heated to a high temperature (400 deg. C or 700 deg. C). The series of PRELUDE experiments achieved in 2010 constitute a significant complement to the database of high temperature bottom reflood experimental data. They provide relevant data to understand the progression of the quench front and the intensity of heat transfer. Modeling accurately these experiments required improvements to the

  13. Experimental validation of free-energy-landscape reconstruction from non-equilibrium single-molecule force spectroscopy measurements

    NASA Astrophysics Data System (ADS)

    Gupta, Amar Nath; Vincent, Abhilash; Neupane, Krishna; Yu, Hao; Wang, Feng; Woodside, Michael T.

    2011-08-01

    Free-energy-landscape formalisms provide the fundamental conceptual framework for physical descriptions of how proteins and nucleic acids fold into specific three-dimensional structures. Although folding landscapes are difficult to measure experimentally, recent theoretical work by Hummer and Szabo has shown that landscape profiles can be reconstructed from non-equilibrium single-molecule force spectroscopy measurements using an extension of the Jarzynski equality. This method has been applied to simulations and experiments but never validated experimentally. We tested it using force-extension measurements on DNA hairpins with distinct, sequence-dependent folding landscapes. Quantitative agreement was found between the landscape profiles obtained from the non-equilibrium reconstruction and those from equilibrium probability distributions. We also tested the method on a riboswitch aptamer with three partially folded intermediate states, successfully reconstructing the landscape but finding some states difficult to resolve owing to low occupancy or overlap of the potential wells. These measurements validate the landscape-reconstruction method and provide a new test of non-equilibrium work relations.

  14. Non-equilibrium phase transitions in the two-temperature Ising model with Kawasaki dynamics. Phase diagram from position space renormalization group transformation

    NASA Astrophysics Data System (ADS)

    Renklioglu, B.; Yalabik, M. C.

    2012-12-01

    Phase transitions of the two-finite temperature Ising model on a square lattice are investigated by using a position space renormalization group (PSRG) transformation. Different finite temperatures, T x and T y , and also different time-scale constants, α x and α y for spin exchanges in the x and y directions define the dynamics of the non-equilibrium system. The critical surface of the system is determined by RG flows as a function of these exchange parameters. The Onsager critical point (when the two temperatures are equal) and the critical temperature for the limit when the other temperature is infinite, previously studied by the Monte Carlo method, are obtained. In addition, two steady-state fixed points which correspond to the non-equilibrium phase transition are presented. These fixed points yield the different universality class properties of the non-equilibrium phase transitions.

  15. Phases, periphases, and interphases equilibrium by molecular modeling. I. Mass equilibrium by the semianalytical stochastic perturbations method and application to a solution between (120) gypsum faces

    NASA Astrophysics Data System (ADS)

    Pedesseau, Laurent; Jouanna, Paul

    2004-12-01

    The SASP (semianalytical stochastic perturbations) method is an original mixed macro-nano-approach dedicated to the mass equilibrium of multispecies phases, periphases, and interphases. This general method, applied here to the reflexive relation Ck⇔μk between the concentrations Ck and the chemical potentials μk of k species within a fluid in equilibrium, leads to the distribution of the particles at the atomic scale. The macroaspects of the method, based on analytical Taylor's developments of chemical potentials, are intimately mixed with the nanoaspects of molecular mechanics computations on stochastically perturbed states. This numerical approach, directly linked to definitions, is universal by comparison with current approaches, DLVO Derjaguin-Landau-Verwey-Overbeek, grand canonical Monte Carlo, etc., without any restriction on the number of species, concentrations, or boundary conditions. The determination of the relation Ck⇔μk implies in fact two problems: a direct problem Ck⇒μk and an inverse problem μk⇒Ck. Validation of the method is demonstrated in case studies A and B which treat, respectively, a direct problem and an inverse problem within a free saturated gypsum solution. The flexibility of the method is illustrated in case study C dealing with an inverse problem within a solution interphase, confined between two (120) gypsum faces, remaining in connection with a reference solution. This last inverse problem leads to the mass equilibrium of ions and water molecules within a 3 Å thick gypsum interface. The major unexpected observation is the repulsion of SO42- ions towards the reference solution and the attraction of Ca2+ ions from the reference solution, the concentration being 50 times higher within the interphase as compared to the free solution. The SASP method is today the unique approach able to tackle the simulation of the number and distribution of ions plus water molecules in such extreme confined conditions. This result is of prime

  16. Experimental and calculated phases in two as-cast and annealed Mg-Zn-Y alloys

    SciTech Connect

    Farzadfar, S.A.; Sanjari, M.; Jung, I.-H.; Essadiqi, E.; Yue, S.

    2012-01-15

    The CALPHAD (Calculation of Phase Diagram) method was used to select ternary alloys from Mg-Zn-Y system, aimed at determining the role of precipitates in the microstructure and texture evolution of Mg during and after deformation. The selected alloys are Mg-6Zn-1.2Y and Mg-5Zn-2Y. The constituent phases in the as-cast Mg-6Zn-1.2Y alloy are {alpha}-Mg solid solution phase and I (Mg{sub 3}YZn{sub 6}) intermetallic phase. The as-cast Mg-5Zn-2Y alloy is composed of {alpha}-Mg, I and W (Mg{sub 3}Y{sub 2}Zn{sub 3}) phases. The intermetallics in the two alloys form by eutectic reaction, which in Mg-5Zn-2Y alloy results in initially W-phase formation and ultimately I-phase formation during solidification. After heat treatment, the Mg-6Zn-1.2Y and Mg-5Zn-2Y alloys contain nearly the same amount of ternary intermetallics (I and W phases, respectively) in equilibrium with {alpha}-Mg solid solution phase. The main solute in {alpha}-Mg phase is Zn with the same amount in the two alloys. The type and quantity of the phases obtained experimentally disagree with the results obtained from the thermodynamic database. One important discrepancy is that, in Mg-6Zn-1.2Y alloy, the I phase is not stable at the temperature of 430 Degree-Sign C, and that the W phase is the stable phase at this temperature. The differences in the experimental and calculated data indicate that the Mg-Zn-Y system requires to be reassessed with more experimental data. - Highlights: Black-Right-Pointing-Pointer Mg-6Zn-1.2Y and Mg-5Zn-2Y alloys were selected by FactSage Trade-Mark-Sign Thermodynamic software. Black-Right-Pointing-Pointer The I and W intermetallics in the two alloys form by eutectic reaction. Black-Right-Pointing-Pointer The alloys contain similar amounts of different intermetallics in equilibrium with {alpha}-Mg. Black-Right-Pointing-Pointer In Mg-6Zn-1.2Y, the I phase is not stable at the temperature of 430 Degree-Sign C. Black-Right-Pointing-Pointer The hardness of W phase is determined to be

  17. Two-phase quasi-equilibrium in β-type Ti-based bulk metallic glass composites

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Pauly, S.; Tang, M. Q.; Eckert, J.; Zhang, H. F.

    2016-01-01

    The microstructural evolution of cast Ti/Zr-based bulk metallic glass composites (BMGCs) containing β-Ti still remains ambiguous. This is why to date the strategies and alloys suitable for producing such BMGCs with precisely controllable volume fractions and crystallite sizes are still rather limited. In this work, a Ti-based BMGC containing β-Ti was developed in the Ti-Zr-Cu-Co-Be system. The glassy matrix of this BMGC possesses an exceptional glass-forming ability and as a consequence, the volume fractions as well as the composition of the β-Ti dendrites remain constant over a wide range of cooling rates. This finding can be explained in terms of a two-phase quasi-equilibrium between the supercooled liquid and β-Ti, which the system attains on cooling. The two-phase quasi-equilibrium allows predicting the crystalline and glassy volume fractions by means of the lever rule and we succeeded in reproducing these values by slight variations in the alloy composition at a fixed cooling rate. The two-phase quasi-equilibrium could be of critical importance for understanding and designing the microstructures of BMGCs containing the β-phase. Its implications on the nucleation and growth of the crystalline phase are elaborated.

  18. Two-phase quasi-equilibrium in β-type Ti-based bulk metallic glass composites

    PubMed Central

    Zhang, L.; Pauly, S.; Tang, M. Q.; Eckert, J.; Zhang, H. F.

    2016-01-01

    The microstructural evolution of cast Ti/Zr-based bulk metallic glass composites (BMGCs) containing β-Ti still remains ambiguous. This is why to date the strategies and alloys suitable for producing such BMGCs with precisely controllable volume fractions and crystallite sizes are still rather limited. In this work, a Ti-based BMGC containing β-Ti was developed in the Ti-Zr-Cu-Co-Be system. The glassy matrix of this BMGC possesses an exceptional glass-forming ability and as a consequence, the volume fractions as well as the composition of the β-Ti dendrites remain constant over a wide range of cooling rates. This finding can be explained in terms of a two-phase quasi-equilibrium between the supercooled liquid and β-Ti, which the system attains on cooling. The two-phase quasi-equilibrium allows predicting the crystalline and glassy volume fractions by means of the lever rule and we succeeded in reproducing these values by slight variations in the alloy composition at a fixed cooling rate. The two-phase quasi-equilibrium could be of critical importance for understanding and designing the microstructures of BMGCs containing the β-phase. Its implications on the nucleation and growth of the crystalline phase are elaborated. PMID:26754315

  19. Two-phase quasi-equilibrium in β-type Ti-based bulk metallic glass composites.

    PubMed

    Zhang, L; Pauly, S; Tang, M Q; Eckert, J; Zhang, H F

    2016-01-01

    The microstructural evolution of cast Ti/Zr-based bulk metallic glass composites (BMGCs) containing β-Ti still remains ambiguous. This is why to date the strategies and alloys suitable for producing such BMGCs with precisely controllable volume fractions and crystallite sizes are still rather limited. In this work, a Ti-based BMGC containing β-Ti was developed in the Ti-Zr-Cu-Co-Be system. The glassy matrix of this BMGC possesses an exceptional glass-forming ability and as a consequence, the volume fractions as well as the composition of the β-Ti dendrites remain constant over a wide range of cooling rates. This finding can be explained in terms of a two-phase quasi-equilibrium between the supercooled liquid and β-Ti, which the system attains on cooling. The two-phase quasi-equilibrium allows predicting the crystalline and glassy volume fractions by means of the lever rule and we succeeded in reproducing these values by slight variations in the alloy composition at a fixed cooling rate. The two-phase quasi-equilibrium could be of critical importance for understanding and designing the microstructures of BMGCs containing the β-phase. Its implications on the nucleation and growth of the crystalline phase are elaborated. PMID:26754315

  20. KEMOD: A mixed chemical kinetic and equilibrium model of aqueous and solid phase geochemical reactions

    SciTech Connect

    Yeh, G.T.; Iskra, G.A.; Szecsody, J.E.; Zachara, J.M.; Streile, G.P.

    1995-01-01

    This report presents the development of a mixed chemical Kinetic and Equilibrium MODel in which every chemical species can be treated either as a equilibrium-controlled or as a kinetically controlled reaction. The reaction processes include aqueous complexation, adsorption/desorption, ion exchange, precipitation/dissolution, oxidation/reduction, and acid/base reactions. Further development and modification of KEMOD can be made in: (1) inclusion of species switching solution algorithms, (2) incorporation of the effect of temperature and pressure on equilibrium and rate constants, and (3) extension to high ionic strength.

  1. Integrated tokamak modelling taskforce: Validation of the equilibrium reconstruction from experimental data

    SciTech Connect

    Zwingmann, W.; Airaj, M.; Eriksson, L.-G.; Guillerminet, B.; Huysmans, G. T. A.; Imbeaux, F.; Moreau, Ph.; McCarthy, P.; Strand, P.

    2008-03-19

    The Integrated tokamak modelling taskforce was set up to provide the European scientific community with simulation tools for preparing and analysing discharges of fusion experiments. We will report on recent progress made on the taskforce project on equilibrium and linear stability. A generic data structure has been devised to describe the geometry of a machine and physical processes in the discharge. This data structure is used to interface all individual analysis program within the taskforce. One of the analysis tools, the equilibrium code EFIT-ITM, based on the EFIT code written by L. L. Lao, has been completely rewritten in order to make it suitable for the ITM. It has algorithm enhancements to increase execution speed, and the ability to treat anisotropic pressure and deviation from axisymmetry. The reconstruction code is now completely independent of the machine description. First results on veriflcation and validation of the new tool are presented.

  2. Equilibrium phase diagrams of aqueous mixtures of malonic acid and sulfate/ammonium salts.

    PubMed

    Salcedo, Dara

    2006-11-01

    Tropospheric aerosols are usually complex mixtures of inorganic and organic components. Although the thermodynamic properties of inorganic aerosols have been widely studied, the effect of organics on such properties is still under discussion. In this study, solubility in water, water activity (a(w)) of aqueous solutions, deliquescence relative humidity (DRH), eutonic composition, and eutonic DRH were determined for bulk mixtures of malonic acid (MA) with ammonium sulfate (AS) and ammonium bisulfate (ABS) at 25 degrees C over the full range of composition (from 0 wt % to the solubility limit of the mixture components). The data were used to construct equilibrium phase diagrams, which show the phase of the mixtures as a function of total composition, dry mixture composition, water content, and ambient relative humidity (RH). This work complements previous reports on the thermodynamic properties of AS/MA mixtures because the range of concentrations investigated is larger than in any other published single study. On the other hand, this is the first report on the a(w), deliquescence, and water absorption of ABS/MA mixtures. The eutonic composition for AS/MA mixtures was found to be 66.8 MA dry wt % (MA dry wt % = MA mass x 100/(AS mass + MA mass) with a DRH of 0.437. The eutonic composition for the ABS/MA mixtures was lower than for the AS/MA mixtures: 20.9 MA dry wt % with a DRH of 0.327. Measured a(w) of liquid AS/MA and ABS/MA solutions is compared with an extended Zdanovskii-Stokes-Robinson expression, obtaining a good agreement (error < 5-6%). The expression was used to predict water uptake of mixtures and might be useful to interpret particle hygroscopic growth experiments. Comparison of the AS/MA and ABS/MA systems indicates that ABS reduces the DRH and enhances water uptake, relative to mixtures with AS. The results confirm that ambient particles containing sulfate and water-soluble organic compounds can remain liquid or partially liquid at very low ambient RH

  3. Compact Phase-Conjugating Correlator: Simulation and Experimental Analysis

    NASA Astrophysics Data System (ADS)

    Sharp, James H.; Budgett, David M.; Slack, Tim G.; Scott, Brian F.

    1998-07-01

    A simulation and experimental investigation of a recently proposed, compact, phase-conjugating correlator is undertaken. The effects of noise and other distortions in the input image and in the correlator filter plane are considered. As with other phase-only designs, the phase-conjugating correlator is sensitive to distortion of the input image while being robust in the presence of filter-plane distortions; this robustness is enhanced by the phase-conjugating property of the design.

  4. Experimental phasing using zinc anomalous scattering

    SciTech Connect

    Cha, Sun-Shin; An, Young Jun; Jeong, Chang-Sook; Kim, Min-Kyu; Lee, Sung-Gyu; Lee, Kwang-Hoon; Oh, Byung-Ha

    2012-09-01

    The surface of proteins can be charged with zinc ions and the anomalous signals from these zinc ions can be used for structure determination of proteins. Zinc is a suitable metal for anomalous dispersion phasing methods in protein crystallography. Structure determination using zinc anomalous scattering has been almost exclusively limited to proteins with intrinsically bound zinc(s). Here, it is reported that multiple zinc ions can easily be charged onto the surface of proteins with no intrinsic zinc-binding site by using zinc-containing solutions. Zn derivatization of protein surfaces appears to be a largely unnoticed but promising method of protein structure determination.

  5. Reflection of no equilibrium two Phase Processes of Filtration in heterogeneous Media in the active seism acoustic borehole monitoring Data

    NASA Astrophysics Data System (ADS)

    Hachay, Olga; Dryagin, Veniamin; Igolkina, Galina; Khachay, Oleg

    2013-04-01

    It is provided a comparison of no equilibrium effects by independent hydro dynamical and seism acoustic influence on an oil layer. It is known, that by drainage and steeps the hysteresis effect on curves of the relative phase permeability in dependence from porous medium water saturation by some cycles of influence: drainage-steep-drainage is observed. In earlier papers the analysis of the seism acoustic monitoring data in regimes of phone radiation, response on the first influence of given frequency and on the second influence is developed. For the analysis of seism acoustic response in time on fixed intervals along the borehole an algorithm of phase diagrams of the state of many phase medium is suggested In that paper on the base of developed algorithm a new algorithm of analyze of space, but integral in time for equal observation periods changing by the method of phase diagram state of many phase medium in the oil layer is developed. The paper was supported by the Program of Presidium UB RAS 2012-2014. Key words: Oil and gas deposits, seism acoustic borehole monitoring data, new method of processing, reflection of no equilibrium two phase processes, heterogeneous media.

  6. Information performances and illative sequences: Sequential organization of explanations of chemical phase equilibrium

    NASA Astrophysics Data System (ADS)

    Brown, Nathaniel James Swanton

    While there is consensus that conceptual change is surprisingly difficult, many competing theories of conceptual change co-exist in the literature. This dissertation argues that this discord is partly the result of an inadequate account of the unwritten rules of human social interaction that underlie the field's preferred methodology---semi-structured interviewing. To better understand the contributions of interaction during explanations, I analyze eight undergraduate general chemistry students as they attempt to explain to various people, for various reasons, why phenomena involving chemical phase equilibrium occur. Using the methods of interaction analysis, I characterize the unwritten, but systematic, rules that these participants follow as they explain. The result is a description of the contributions of interaction to explaining. Each step in each explanation is a jointly performed expression of a subject-predicate relation, an interactive accomplishment I call an information performance (in-form, for short). Unlike clauses, in-forms need not have a coherent grammatical structure. Unlike speaker turns, in-forms have the clear function of expressing information. Unlike both clauses and speaker turns, in-forms are a co-construction, jointly performed by both the primary speaker and the other interlocutor. The other interlocutor strongly affects the form and content of each explanation by giving or withholding feedback at the end of each in-form, moments I call feedback-relevant places. While in-forms are the bricks out of which the explanation is constructed, they are secured by a series of inferential links I call an illative sequence. Illative sequences are forward-searching, starting with a remembered fact or observation and following a chain of inferences in the hope it leads to the target phenomenon. The participants treat an explanation as a success if the illative sequence generates an in-form that describes the phenomenon. If the illative sequence does

  7. Experimental clean combustor program, phase 2

    NASA Technical Reports Server (NTRS)

    Roberts, R.; Peduzzi, A.; Vitti, G. E.

    1976-01-01

    The alternate fuels investigation objective was to experimentally determine the impacts, if any, on exhaust emissions, performance, and durability characteristics of the hybrid and vorbix low pollution combustor concepts when operated on test fuels which simulate composition and property changes which might result from future broadened aviation turbine fuel specifications or use of synthetically derived crude feedstocks. Results of the program indicate a significant increase in CO and small NOX increase in emissions at idle for both combustor concepts, and an increase in THC for the vorbix concept. Minimal impact was observed on gaseous emissions at high power. The vorbix concept exhibited significant increase in exhaust smoke with increasing fuel aromatic content. Altitude stability was not affected for the vorbix combustor, but was substantially reduced for the hybrid concept. Severe carbon deposition was observed in both combustors following limited endurance testing with No. 2 home heat fuel. Liner temperature levels were insensitive to variations in aromatic content over the range of conditions investigated.

  8. Numerical analysis of unsteady cavitating flow by using a modification based on an assumption of apparent phase equilibrium

    NASA Astrophysics Data System (ADS)

    Iga, Y.

    2014-03-01

    The prediction accuracy of cavitation by CFD is still not so high even in a simplest flow field around a single hydrofoil especially in transient condition at higher angle of attack, which is common problem in both commercial software and in-house solvers. In the transient condition, unsteady cavitation occurs, in which sheet cavity breaks off and cloud cavity sheds downstream periodically. At that time, the sheet cavity length tends to be underestimated in usual CFD. In the present study, modification for the phase change model is suggested, which is based on an idea of apparent phase equilibrium on gas-liquid interface with unsteady and disturbed flow. At first, a preliminary experiment has been done for evaporation on two gas- liquid interfaces with and without flow, the result contributes the evidence of the idea of apparent phase equilibrium with flow. In the result, the pressure around gas-liquid interface with flow was higher than that without flow on the occasion of evaporation, it means flow accelerates evaporation. I treat the gap of the pressure as a gap of phase equilibrium pressure macroscopically. Then, numerical simulation of cavitating flow around a hydrofoil is performed with a modification of phase change model in the transient condition at higher angle of attack which is most difficult to predict by the present solvers. In the modification, the gap of the pressure with and without flow is taken into account according to a value of a local variation of velocity in the cavitating flow filed. The formulation is similar to the PDF model for phase change model in cavitation by Singhal. The numerical results by the present modification are compared among few pressure variation components which are assumed to accelerate the evaporation in transient cavitation.

  9. Experimental determination of equilibrium magnesium isotope fractionation between spinel, forsterite, and magnesite by the three-isotope method at 700 °C and 1 GPa

    NASA Astrophysics Data System (ADS)

    Macris, C. A.; Young, E. D.; Manning, C. E.; Schauble, E. A.

    2011-12-01

    Magnesium isotopes are potentially powerful tools for high-temperature geochemistry if relevant fractionation factors are known. However, experimental data for Mg isotope fractionation are lacking at high temperatures. We performed piston-cylinder experiments at 700 °C and 1 GPa to establish the equilibrium magnesium isotope partitioning between forsterite (Mg2SiO4) and magnesite (MgCO3), and between spinel (MgAl2O4) and magnesite, making use of the well-established advantages of using carbonates as an isotope exchange medium (e.g. Clayton et al., 1989). Our results provide the first experimental calibration of the equilibrium 26Mg/24Mg fractionation between minerals at high temperature. For these experiments we used a high-pressure piston cylinder apparatus and a three-isotope spike technique. The present study extends the applicability of the three-isotope method to experiments involving simple isotope exchange rather than exchange by heterogeneous reaction (Shahar et al., 2008). In these experiments we used magnesite as the exchange medium (and exchange partner) to overcome the sluggish diffusion-limited exchange between spinel and forsterite alone. The carbonate media facilitates chemical and isotopic exchange by promoting annealing and re-crystallization of minerals during the experiment. The combination of a three-isotope method with the use of carbonate as exchange media, used for the first time in this study, allows the experimentalist to determine the partitioning of Mg isotopes between two solid phases without requiring heterogeneous reaction. Results show that at 700 °C and 1 GPa 26ΔFo-Mgs = -0.16 ± 0.13% and 26ΔSp-Mgs = 0.93 ± 0.28%. From these two experimentally-determined equilibrium fractionation values, we can derive the equilibrium fractionation between spinel and forsterite by difference, yielding 26ΔSp-Fo = 1.09 ± 0.31%. This agrees within error with a first- principles estimate of equilibrium magnesium isotope fractionation of 26

  10. Phase-equilibrium modelling of blueschists from the Vestgötabreen Complex (SW Svalbard)

    NASA Astrophysics Data System (ADS)

    Kośmińska, Karolina; Majka, Jarosław; Manecki, Maciej; Lorenz, Henning; Kozub, Gabriela

    2014-05-01

    In Svalbard Archipelago, blueschists are known from Motalafjella area (Oscar II Land). They belong to the Vestgötabreen Complex, which is divided into a Lower (LU) and Upper Unit (UU). The former is composed of high pressure-low temperature (HP-LT) metasediments. The latter consists mainly of blueschists and eclogites. Various radiometric dating yielded an age of c. 470 Ma for the HP-LT metamorphism in the Motalafjella area. The pressure-temperature (P-T) conditions for carpholite-bearing schists from LU have been estimated to c. 16 kbar and 330-450°C (Agard et al., 2005), whereas eclogites from UU indicate peak conditions of 18-24 kbar and 580-640°C (Hirajima et al., 1988). During the fieldwork in 2011, blueschists were also discovered at the western coast of Nordenskiöld Land. They form isolated bodies enclosed within metasedimentary units, but their tectonic position is still under debate. Preliminary P-T estimates indicate peak pressure conditions of c. 17 kbar and 480°C (Kośmińska et al., in revision). The age of metamorphism is unknown, however P-T conditions as well as metamorphic assemblage suggest that the blueschists from Nordenskiöld Land may be an equivalent of these in the Vestgötabreen Complex. Samples of blueschists from UU have been collected on Skipperryggen. They consist mainly of glaucophane, garnet, white micas (phengite and paragonite), rutile, lawsonite and chlorite. The garnet typically forms euhedral to subhedral porphyroblasts which contain voluminous inclusions. Its composition varies from Alm63Prp13Grs22Sps2 in the cores to Alm60Prp19Grs20Sps1 in the rims. The change in chemical zoning is rather gradual. The garnet shows bowl-shaped pyrope profiles and opposite almandine trends. The P-T conditions were estimated using phase equilibrium modeling. Preliminary modeling in the NCKFMMnASHTO system yields peak pressure conditions at c. 20 kbar and 520°C. The estimated P-T conditions for the blueschists from Skipperryggen are in

  11. Improving experimental phases for strong reflections prior to density modification

    DOE PAGESBeta

    Uervirojnangkoorn, Monarin; Hilgenfeld, Rolf; Terwilliger, Thomas C.; Read, Randy J.

    2013-09-20

    Experimental phasing of diffraction data from macromolecular crystals involves deriving phase probability distributions. These distributions are often bimodal, making their weighted average, the centroid phase, improbable, so that electron-density maps computed using centroid phases are often non-interpretable. Density modification brings in information about the characteristics of electron density in protein crystals. In successful cases, this allows a choice between the modes in the phase probability distributions, and the maps can cross the borderline between non-interpretable and interpretable. Based on the suggestions by Vekhter [Vekhter (2005), Acta Cryst. D61, 899–902], the impact of identifying optimized phases for a small number ofmore » strong reflections prior to the density-modification process was investigated while using the centroid phase as a starting point for the remaining reflections. A genetic algorithm was developed that optimizes the quality of such phases using the skewness of the density map as a target function. Phases optimized in this way are then used in density modification. In most of the tests, the resulting maps were of higher quality than maps generated from the original centroid phases. In one of the test cases, the new method sufficiently improved a marginal set of experimental SAD phases to enable successful map interpretation. Lastly, a computer program,SISA, has been developed to apply this method for phase improvement in macromolecular crystallography.« less

  12. Improving experimental phases for strong reflections prior to density modification

    SciTech Connect

    Uervirojnangkoorn, Monarin; Hilgenfeld, Rolf; Terwilliger, Thomas C.; Read, Randy J.

    2013-09-20

    Experimental phasing of diffraction data from macromolecular crystals involves deriving phase probability distributions. These distributions are often bimodal, making their weighted average, the centroid phase, improbable, so that electron-density maps computed using centroid phases are often non-interpretable. Density modification brings in information about the characteristics of electron density in protein crystals. In successful cases, this allows a choice between the modes in the phase probability distributions, and the maps can cross the borderline between non-interpretable and interpretable. Based on the suggestions by Vekhter [Vekhter (2005), Acta Cryst. D61, 899–902], the impact of identifying optimized phases for a small number of strong reflections prior to the density-modification process was investigated while using the centroid phase as a starting point for the remaining reflections. A genetic algorithm was developed that optimizes the quality of such phases using the skewness of the density map as a target function. Phases optimized in this way are then used in density modification. In most of the tests, the resulting maps were of higher quality than maps generated from the original centroid phases. In one of the test cases, the new method sufficiently improved a marginal set of experimental SAD phases to enable successful map interpretation. Lastly, a computer program,SISA, has been developed to apply this method for phase improvement in macromolecular crystallography.

  13. Constrained dynamics of localized excitations causes a non-equilibrium phase transition in an atomistic model of glass formers.

    PubMed

    Speck, Thomas; Chandler, David

    2012-05-14

    Recent progress has demonstrated that trajectory space for both kinetically constrained lattice models and atomistic models can be partitioned into a liquid-like and an inactive basin with a non-equilibrium phase transition separating these behaviors. Recent work has also established that excitations in atomistic models have statistics and dynamics like those in a specific class of kinetically constrained models. But it has not been known whether the non-equilibrium phase transitions occurring in the two classes of models have similar origins. Here, we show that the origin is indeed similar. In particular, we show that the number of excitations identified in an atomistic model serves as the order parameter for the inactive-active phase transition for that model. In this way, we show that the mechanism by which excitations are correlated in an atomistic model - by dynamical facilitation - is the mechanism from which the active-inactive phase transition emerges. We study properties of the inactive phase and show that it is amorphous lacking long-range order. We also discuss the choice of dynamical order parameters. PMID:22583302

  14. Experimental observation of the hot-electron equilibrium in a minimum-B mirror plasma

    SciTech Connect

    Smatlak, D.L.; Chen, X.; Lane, B.G.; Hokin, S.A.; Post, R.S.

    1987-05-04

    Measurements of the hot-electron (T = 450 keV, n = 2 x 10/sup 11/ cm/sup -3/) equilibrium in the Constance B minimum-B magnetic mirror show that the pressure profile is peaked off the axis and is shaped like the seam on a baseball. This curve is the drift surface of the deeply trapped electrons and the location of the strongest microwave heating. The configuration is stable and decays quiescently on the hot-electron collisional time scale (1--2 s) after the microwave power is turned off. According to 1D pressure-weighted ..integral.. dl/B analysis this plasma configuration is expected to be unstable.

  15. Clusters in sedimentation equilibrium for an experimental hard-sphere-plus-dipolar Brownian colloidal system

    PubMed Central

    Newman, Hugh D.; Yethiraj, Anand

    2015-01-01

    In this work, we use structure and dynamics in sedimentation equilibrium, in the presence of gravity, to examine, via confocal microscopy, a Brownian colloidal system in the presence of an external electric field. The zero field equation of state (EOS) is hard sphere without any re-scaling of particle size, and the hydrodynamic corrections to the long-time self-diffusion coefficient are quantitatively consistent with the expected value for hard spheres. Care is taken to ensure that both the dimensionless gravitational energy, which is equivalent to a Peclet number Peg, and dipolar strength Λ are of order unity. In the presence of an external electric field, anisotropic chain-chain clusters form; this cluster formation manifests itself with the appearance of a plateau in the diffusion coefficient when the dimensionless dipolar strength Λ ~ 1. The structure and dynamics of this chain-chain cluster state is examined for a monodisperse system for two particle sizes. PMID:26323363

  16. Clusters in sedimentation equilibrium for an experimental hard-sphere-plus-dipolar Brownian colloidal system.

    PubMed

    Newman, Hugh D; Yethiraj, Anand

    2015-01-01

    In this work, we use structure and dynamics in sedimentation equilibrium, in the presence of gravity, to examine, via confocal microscopy, a Brownian colloidal system in the presence of an external electric field. The zero field equation of state (EOS) is hard sphere without any re-scaling of particle size, and the hydrodynamic corrections to the long-time self-diffusion coefficient are quantitatively consistent with the expected value for hard spheres. Care is taken to ensure that both the dimensionless gravitational energy, which is equivalent to a Peclet number Peg, and dipolar strength Λ are of order unity. In the presence of an external electric field, anisotropic chain-chain clusters form; this cluster formation manifests itself with the appearance of a plateau in the diffusion coefficient when the dimensionless dipolar strength Λ ~ 1. The structure and dynamics of this chain-chain cluster state is examined for a monodisperse system for two particle sizes. PMID:26323363

  17. Effect of aircraft noise on the equilibrium of airport residents: Longitudinal study around Roissy, phase 3

    NASA Technical Reports Server (NTRS)

    Francois, J.

    1981-01-01

    The effects of airplane noise on the mental equilibrium of residents living near airports are discussed, and based on population sample surveys involving health questionnaires and self-administered personality tests. Progressive changes were observed on the part of residents living near a large airport.

  18. Experimental investigation of a steady-state dynamical phase transition in a Jaynes-Cummings dimer

    NASA Astrophysics Data System (ADS)

    Raftery, James; Sadri, Darius; Mandt, Stephan; Tureci, Hakan; Houck, Andrew

    Experimental progress in circuit-QED has made it possible to study non-equilibrium many-body physics using strongly correlated photons. Such open and driven systems can display new types of dynamical phase transitions. A steady state transition has also been predicted for a Jaynes-Cummings dimer where the photon current between the two cavities acts as an order parameter. Here, we discuss the theory and report measurements of the steady-state behavior of a circuit-QED dimer with in situ tunable inter-cavity coupling and on-site photon-photon interaction. Recently deceased.

  19. Phase Equilibrium Study of ZnO-"FeO"-SiO2 System at Fixed Po2 10-8 atm

    NASA Astrophysics Data System (ADS)

    Liu, Hongquan; Cui, Zhixiang; Chen, Mao; Zhao, Baojun

    2016-02-01

    Experimental studies of phase equilibria and liquidus temperatures have been carried out in the systems "FeO"-SiO2 and ZnO-"FeO"-SiO2 at Po2 10-8 atm. Research techniques have been developed to enable the ZnO-containing system to be investigated under reducing conditions controlled by CO-CO2 gas mixture. The experimental approach includes master slag preparation, high-temperature equilibration, quench, and electron probe X-ray microanalysis (EPMA). Phase compositions in the quenched samples were measured by EPMA and used for construction of phase diagram. It was found that the isotherms of the system ZnO-"FeO"-SiO2 at Po2 10-8 atm are significantly different from those in equilibrium with metallic iron and those predicted by FactSage. The presence of ZnO in copper smelting slag significantly increases the liquidus temperature in spinel primary phase field. Partitioning of ZnO in liquid and spinel is also discussed in this paper.

  20. Experimental verification of phase retrieval of microbeads in high-speed phase imaging using digital holography

    NASA Astrophysics Data System (ADS)

    Matoba, Osamu; Xia, Peng; Quan, Xiangyu; Nagahama, Naoya; Tanimoto, Shunsuke; Nitta, Kouichi; Awatsuji, Yasuhiro

    2016-06-01

    One of fast measurement systems of μm-size phase objects based on digital holographic microscope with transmission geometry is presented. For building a 3D inspection system of the phase objects, the improvement of recovered phase image is discussed. Under the CW laser illumination, the movement afterimage of phase object was observed. The phase object is recovered by deconvolution filter. Experimental and numerical evaluation are presented.

  1. Statistical Thermodynamics of an "Open" Hard Sphere System on the Equilibrium Fluid Isotherm: Study of Properties of the Freezing Transition Without Direct Involvement of the Equilibrium Solid Phase

    NASA Astrophysics Data System (ADS)

    Reiss, Howard; Manzanares, José A.

    2016-09-01

    Using several theoretical toolsldots (i) the nucleation theorem, (ii) an equivalent cavity, (iii) the reversible work of adding a cavity to an open hard sphere system, and (iv) the theory of "stability"... the authors estimated the density at which the hard sphere freezing transition occurs. No direct involvement of the equilibrium solid phase is involved. The reduced density \\uppi a^3ρ _f/6 (where a is the hard sphere diameter and ρ _f is the actual density at which freezing occurs) is found to be 0.4937 while the value obtained by computer simulation is 0.494. The agreement is good, but the new method still contains some approximation. However, the approximation is based on the idea that at a density just below ρ _f the fluid adopts a distorted structure resembling the solid, but different enough so that long-range order vanishes. Initial loss of stability may not be involved in every fluid-solid transition, but it may be an early step in the hard sphere and related systems.

  2. Experimental investigation and application of the equilibrium rutile + orthopyroxene = quartz + ilmenite

    USGS Publications Warehouse

    Hayob, J.L.; Bohlen, S.R.; Essene, E.J.

    1993-01-01

    Equilibria in the Sirf (Silica-Ilmenite-Rutile-Ferrosilite) system: {Mathematical expression} have been calibrated in the range 800-1100?? C and 12-26 kbar using a piston-cylinder apparatus to assess the potential of the equilibria for geobarometry in granulite facies assemblages that lack garnet. Thermodynamic calculations indicate that the two end-member equilibria involving quartz + geikielite = rutile + enstatite, and quartz + ilmenite = rutile + ferrosilite, are metastable. We therefore reversed equilibria over the compositional range Fs40-70, using Ag80Pd20 capsules with {Mathematical expression} buffered at or near iron-wu??stite. Ilmenite compositions coexisting with orthopyroxene are {Mathematical expression} of 0.06 to 0.15 and {Mathematical expression} of 0.00 to 0.01, corresponding to KD values of 13.3, 10.2, 9.0 and 8.0 (??0.5) at 800, 900, 1000 and 1100?? C, respectively, where KD=(XMg/XFe)Opx/(XMg/XFe)Ilm. Pressures have been calculated using equilibria in the Sirf system for granulites from the Grenville Province of Ontario and for granulite facies xenoliths from central Mexico. Pressures are consistent with other well-calibrated geobarometers for orthopyroxeneilmenite pairs from two Mexican samples in which oxide textures appear to represent equilibrium. Geologically unreasonable pressures are obtained, however, where oxide textures are complex. Application of data from this study on the equilibrium distribution of iron and magnesium between ilmenite and orthopyroxene suggests that some ilmenite in deep crustal xenoliths is not equilibrated with coexisting pyroxene, while assemblages from exposed granulite terranes have reequilibrated during retrogression. The Sirf equilibria are sensitive to small changes in composition and may be used for determination of activity/composition (a/X) relations of orthopyroxene if an ilmenite model is specified. A symmetric regular solution model has been used for orthopyroxene in conjunction with activity models

  3. Numerical and experimental exploration of phase control of chaos.

    PubMed

    Zambrano, Samuel; Allaria, Enrico; Brugioni, Stefano; Leyva, Immaculada; Meucci, Riccardo; Sanjuán, Miguel A F; Arecchi, Fortunato T

    2006-03-01

    A well-known method to suppress chaos in a periodically forced chaotic system is to add a harmonic perturbation. The phase control of chaos scheme uses the phase difference between a small added harmonic perturbation and the main driving to suppress chaos, leading the system to different periodic orbits. Using the Duffing oscillator as a paradigm, we present here an in-depth study of this technique. A thorough numerical exploration has been made focused in the important role played by the phase, from which new interesting patterns in parameter space have appeared. On the other hand, our novel experimental implementation of phase control in an electronic circuit confirms both the well-known features of this method and the new ones detected numerically. All this may help in future implementations of phase control of chaos, which is globally confirmed here to be robust and easy to implement experimentally. PMID:16599742

  4. THE EFFECT OF METASTABLE EQUILIBRIUM STATES ON THE PARTITIONING OF NITRATE BETWEEN THE GAS AND AEROSOL PHASES. (R826371C005)

    EPA Science Inventory

    With the aid of three atmospheric aerosol equilibrium models, we quantify the effect of metastable equilibrium states (efflorescence branch) in comparison to stable (deliquescence branch) on the partitioning of total nitrate between the gas and aerosol phases. On average, effl...

  5. Experimental phase-advance in woven textile metasurface

    NASA Astrophysics Data System (ADS)

    Burgnies, L.; Cochrane, C.; Rault, F.; Sadaune, V.; Lheurette, É.; Koncar, V.; Lippens, D.

    2015-11-01

    Transmission with phase advance is experimentally evidenced in a woven metasurface made of metallic wires and dielectric yarns. Similar to the negative refraction in metamaterials, phase advance is analyzed with a retrieval procedure of effective medium parameters. It is shown that a quasi-unitary transmission level can be achieved below the magnetic plasma frequency with a phase advance in a propagation regime for which both effective permittivity and permeability exhibit negative values. By stacking two metasurfaces with metallic wires woven in orthogonal directions, the phase advance is maintained and a polarization insensitive woven metamaterial is achieved.

  6. Improving experimental phases for strong reflections prior to density modification

    SciTech Connect

    Uervirojnangkoorn, Monarin; Hilgenfeld, Rolf; Terwilliger, Thomas C.; Read, Randy J.

    2013-10-01

    A genetic algorithm has been developed to optimize the phases of the strongest reflections in SIR/SAD data. This is shown to facilitate density modification and model building in several test cases. Experimental phasing of diffraction data from macromolecular crystals involves deriving phase probability distributions. These distributions are often bimodal, making their weighted average, the centroid phase, improbable, so that electron-density maps computed using centroid phases are often non-interpretable. Density modification brings in information about the characteristics of electron density in protein crystals. In successful cases, this allows a choice between the modes in the phase probability distributions, and the maps can cross the borderline between non-interpretable and interpretable. Based on the suggestions by Vekhter [Vekhter (2005 ▶), Acta Cryst. D61, 899–902], the impact of identifying optimized phases for a small number of strong reflections prior to the density-modification process was investigated while using the centroid phase as a starting point for the remaining reflections. A genetic algorithm was developed that optimizes the quality of such phases using the skewness of the density map as a target function. Phases optimized in this way are then used in density modification. In most of the tests, the resulting maps were of higher quality than maps generated from the original centroid phases. In one of the test cases, the new method sufficiently improved a marginal set of experimental SAD phases to enable successful map interpretation. A computer program, SISA, has been developed to apply this method for phase improvement in macromolecular crystallography.

  7. Experimental Investigation of the Cd-Pr Phase Diagram

    PubMed Central

    Reichmann, Thomas L.; Effenberger, Herta S.; Ipser, Herbert

    2014-01-01

    The complete Cd-Pr equilibrium phase diagram was investigated with a combination of powder-XRD, SEM and DTA. All intermetallic compounds within this system, already reported in literature, could be confirmed: CdPr, Cd2Pr, Cd3Pr, Cd45Pr11, Cd58Pr13, Cd6Pr and Cd11Pr. The corresponding phase boundaries were determined at distinct temperatures. The homogeneity range of the high-temperature allotropic modification of Pr could be determined precisely and a limited solubility of 22.1 at.% Cd was derived. Additionally, single-crystal X-ray diffraction was employed to investigate structural details of Cd2Pr; it is isotypic to the AlB2-type structure with a z value of the Cd site of 0.5. DTA results of alloys located in the adjacent two-phase fields of Cd2Pr suggested a phase transformation between 893 and 930°C. For the phase Cd3Pr it was found that the lattice parameter a changes linearly with increasing Cd content, following Vegard’s rule. The corresponding defect mechanism could be evaluated from structural data collected with single-crystal XRD. Introduction of a significant amount of vacancies on the Pr site and the reduction in symmetry of one Cd position (8c to 32f) resulted in a noticeable decrease of all R-values. PMID:24718502

  8. Experimental investigation of the Cd-Pr phase diagram.

    PubMed

    Reichmann, Thomas L; Effenberger, Herta S; Ipser, Herbert

    2014-01-01

    The complete Cd-Pr equilibrium phase diagram was investigated with a combination of powder-XRD, SEM and DTA. All intermetallic compounds within this system, already reported in literature, could be confirmed: CdPr, Cd2Pr, Cd3Pr, Cd45Pr11, Cd58Pr13, Cd6Pr and Cd11Pr. The corresponding phase boundaries were determined at distinct temperatures. The homogeneity range of the high-temperature allotropic modification of Pr could be determined precisely and a limited solubility of 22.1 at.% Cd was derived. Additionally, single-crystal X-ray diffraction was employed to investigate structural details of Cd2Pr; it is isotypic to the AlB2-type structure with a z value of the Cd site of 0.5. DTA results of alloys located in the adjacent two-phase fields of Cd2Pr suggested a phase transformation between 893 and 930°C. For the phase Cd3Pr it was found that the lattice parameter a changes linearly with increasing Cd content, following Vegard's rule. The corresponding defect mechanism could be evaluated from structural data collected with single-crystal XRD. Introduction of a significant amount of vacancies on the Pr site and the reduction in symmetry of one Cd position (8c to 32f) resulted in a noticeable decrease of all R-values. PMID:24718502

  9. An interactive computer code for calculation of gas-phase chemical equilibrium (EQLBRM)

    NASA Technical Reports Server (NTRS)

    Pratt, B. S.; Pratt, D. T.

    1984-01-01

    A user friendly, menu driven, interactive computer program known as EQLBRM which calculates the adiabatic equilibrium temperature and product composition resulting from the combustion of hydrocarbon fuels with air, at specified constant pressure and enthalpy is discussed. The program is developed primarily as an instructional tool to be run on small computers to allow the user to economically and efficiency explore the effects of varying fuel type, air/fuel ratio, inlet air and/or fuel temperature, and operating pressure on the performance of continuous combustion devices such as gas turbine combustors, Stirling engine burners, and power generation furnaces.

  10. Experimental implementation of phase locking in a nonlinear interferometer

    SciTech Connect

    Wang, Hailong; Jing, Jietai; Marino, A. M.

    2015-09-21

    Based upon two cascade four-wave mixing processes in two identical hot rubidium vapor cells, a nonlinear interferometer has been experimentally realized [Jing et al., Appl. Phys. Lett. 99, 011110 (2011); Hudelist et al., Nat. Commun. 5, 3049 (2014)]. It has a higher degree of phase sensitivity than a traditional linear interferometer and has many potential applications in quantum metrology. Phase locking of the nonlinear interferometer is needed before it can find its way into applications. In this letter, we investigate the experimental implementation of phase locking of the relative phase between the three beams at different frequencies involved in such a nonlinear interferometer. We have utilized two different methods, namely, beat note locking and coherent modulation locking. We find that coherent modulation locking can achieve much better phase stability than beat note locking in our system. Our results pave the way for real applications of a nonlinear interferometer in precision measurement and quantum manipulation, for example, phase control in phase-sensitive N-wave mixing process, N-port nonlinear interferometer and quantum-enhanced real-time phase tracking.

  11. Experimental Investigation of the Instability of the Mechanical Equilibrium of a Four-Component Mixture with Ballast Gases

    NASA Astrophysics Data System (ADS)

    Moldabekova, M. S.; Asembaeva, M. K.; Akzholova, A. A.

    2016-03-01

    The instability of the mechanical equilibrium of the diffusion mixing of a four-component mixture with ballast gases by the two-flask method was investigated experimentally. The main gases helium and methane were diluted with nitrous oxide and propane, respectively. An analysis of the evolution of the diffusion mixing of these gases with time has shown that, in the case where the diffusion proceeding in a system with a ballast gas is unstable, in it there arises circulation of the gas-diluent by the diffusion channel from one flask to the other of a diffusion apparatus. It was established that the circulation of the ballast gas by the diffusion channel makes it possible to sustain the unsteady multicomponent diffusion during a long time and, in so doing, to decelerate the change of this regime to the regime of stable mass transfer.

  12. A two phase Mach number description of the equilibrium flow of nitrogen in ducts

    NASA Technical Reports Server (NTRS)

    Bursik, J. W.; Hall, R. M.; Adcock, J. B.

    1979-01-01

    Some additional thermodynamic properties of the usual two-phase form which is linear in the moisture fraction are derived which are useful in the analysis of many kinds of duct flow. The method used is based on knowledge of the vapor pressure and Gibbs function as functions of temperature. With these, additional two-phase functions linear in moisture fraction are generated, which ultimately reveal that the squared ratio of mixture specific volume to mixture sound speed depends on liquid mass fraction and temperature in the same manner as do many weighted mean two-phase properties. This leads to a simple method of calculating two-phase Mach numbers for various duct flows. The matching of one- and two-phase flows at a saturated vapor point with discontinuous Mach number is also discussed.

  13. Experimental verification of electro-refractive phase modulation in graphene

    NASA Astrophysics Data System (ADS)

    Mohsin, Muhammad; Neumaier, Daniel; Schall, Daniel; Otto, Martin; Matheisen, Christopher; Lena Giesecke, Anna; Sagade, Abhay A.; Kurz, Heinrich

    2015-06-01

    Graphene has been considered as a promising material for opto-electronic devices, because of its tunable and wideband optical properties. In this work, we demonstrate electro-refractive phase modulation in graphene at wavelengths from 1530 to 1570 nm. By integrating a gated graphene layer in a silicon-waveguide based Mach-Zehnder interferometer, the key parameters of a phase modulator like change in effective refractive index, insertion loss and absorption change are extracted. These experimentally obtained values are well reproduced by simulations and design guidelines are provided to make graphene devices competitive to contemporary silicon based phase modulators for on-chip applications.

  14. Experimental verification of electro-refractive phase modulation in graphene

    PubMed Central

    Mohsin, Muhammad; Neumaier, Daniel; Schall, Daniel; Otto, Martin; Matheisen, Christopher; Lena Giesecke, Anna; Sagade, Abhay A.; Kurz, Heinrich

    2015-01-01

    Graphene has been considered as a promising material for opto-electronic devices, because of its tunable and wideband optical properties. In this work, we demonstrate electro-refractive phase modulation in graphene at wavelengths from 1530 to 1570 nm. By integrating a gated graphene layer in a silicon-waveguide based Mach-Zehnder interferometer, the key parameters of a phase modulator like change in effective refractive index, insertion loss and absorption change are extracted. These experimentally obtained values are well reproduced by simulations and design guidelines are provided to make graphene devices competitive to contemporary silicon based phase modulators for on-chip applications. PMID:26061415

  15. Analytical and experimental study of high phase order induction motors

    NASA Astrophysics Data System (ADS)

    Klingshirn, Eugene A.

    1989-08-01

    Induction motors having more than three phases were investigated to determine their suitability for electric vehicle applications. The objective was to have a motor with a current rating lower than that of a three-phase motor. The name chosen for these is high phase order (HPO) motors. Motors having six phases and nine phases were given the most attention. It was found that HPO motors are quite suitable for electric vehicles, and for many other applications as well. They have characteristics which are as good as or better than three-phase motors for practically all applications where polyphase induction motors are appropriate. Some of the analysis methods are presented, and several of the equivalent circuits which facilitate the determination of harmonic currents and losses, or currents with unbalanced sources, are included. The sometimes large stator currents due to harmonics in the source voltages are pointed out. Filters which can limit these currents were developed. An analysis and description of these filters is included. Experimental results which confirm and illustrate much of the theory are also included. These include locked rotor test results and full-load performance with an open phase. Also shown are oscillograms which display the reduction in harmonic currents when a filter is used with the experimental motor supplied by a non-sinusoidal source.

  16. Analytical and experimental study of high phase order induction motors

    NASA Technical Reports Server (NTRS)

    Klingshirn, Eugene A.

    1989-01-01

    Induction motors having more than three phases were investigated to determine their suitability for electric vehicle applications. The objective was to have a motor with a current rating lower than that of a three-phase motor. The name chosen for these is high phase order (HPO) motors. Motors having six phases and nine phases were given the most attention. It was found that HPO motors are quite suitable for electric vehicles, and for many other applications as well. They have characteristics which are as good as or better than three-phase motors for practically all applications where polyphase induction motors are appropriate. Some of the analysis methods are presented, and several of the equivalent circuits which facilitate the determination of harmonic currents and losses, or currents with unbalanced sources, are included. The sometimes large stator currents due to harmonics in the source voltages are pointed out. Filters which can limit these currents were developed. An analysis and description of these filters is included. Experimental results which confirm and illustrate much of the theory are also included. These include locked rotor test results and full-load performance with an open phase. Also shown are oscillograms which display the reduction in harmonic currents when a filter is used with the experimental motor supplied by a non-sinusoidal source.

  17. Significance of vapor phase chemical reactions on CVD rates predicted by chemically frozen and local thermochemical equilibrium boundary layer theories

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.

    1988-01-01

    This paper investigates the role played by vapor-phase chemical reactions on CVD rates by comparing the results of two extreme theories developed to predict CVD mass transport rates in the absence of interfacial kinetic barrier: one based on chemically frozen boundary layer and the other based on local thermochemical equilibrium. Both theories consider laminar convective-diffusion boundary layers at high Reynolds numbers and include thermal (Soret) diffusion and variable property effects. As an example, Na2SO4 deposition was studied. It was found that gas phase reactions have no important role on Na2SO4 deposition rates and on the predictions of the theories. The implications of the predictions of the two theories to other CVD systems are discussed.

  18. Signature of a continuous quantum phase transition in non-equilibrium energy absorption: Footprints of criticality on higher excited states

    PubMed Central

    Bhattacharyya, Sirshendu; Dasgupta, Subinay; Das, Arnab

    2015-01-01

    Understanding phase transitions in quantum matters constitutes a significant part of present day condensed matter physics. Quantum phase transitions concern ground state properties of many-body systems, and hence their signatures are expected to be pronounced in low-energy states. Here we report signature of a quantum critical point manifested in strongly out-of-equilibrium states with finite energy density with respect to the ground state and extensive (subsystem) entanglement entropy, generated by an external pulse. These non-equilibrium states are evidently completely disordered (e.g., paramagnetic in case of a magnetic ordering transition). The pulse is applied by switching a coupling of the Hamiltonian from an initial value (λI) to a final value (λF) for sufficiently long time and back again. The signature appears as non-analyticities (kinks) in the energy absorbed by the system from the pulse as a function of λF at critical-points (i.e., at values of λF corresponding to static critical-points of the system). As one excites higher and higher eigenstates of the final Hamiltonian H(λF) by increasing the pulse height , the non-analyticity grows stronger monotonically with it. This implies adding contributions from higher eigenstates help magnifying the non-analyticity, indicating strong imprint of the critical-point on them. Our findings are grounded on exact analytical results derived for Ising and XY chains in transverse field. PMID:26568306

  19. Phase Equilibrium Studies of Savannah River Tanks and Feed Streams for the Salt Waste Processing Facility

    SciTech Connect

    Weber, C.F.

    2001-06-19

    A chemical equilibrium model is developed and used to evaluate supersaturation of tanks and proposed feed streams to the Salt Waste Processing Facility. The model uses Pitzer's model for activity coefficients and is validated by comparison with a variety of thermodynamic data. The model assesses the supersaturation of 13 tanks at the Savannah River Site (SRS), indicating that small amounts of gibbsite and or aluminosilicate may form. The model is also used to evaluate proposed feed streams to the Salt Waste Processing Facility for 13 years of operation. Results indicate that dilutions using 3-4 M NaOH (about 0.3-0.4 L caustic per kg feed solution) should avoid precipitation and reduce the Na{sup +} ion concentration to 5.6 M.

  20. Liquid-vapor phase equilibrium in a tin-selenium system

    NASA Astrophysics Data System (ADS)

    Volodin, V. N.; Burabaeva, N. M.; Trebukhov, S. A.

    2014-12-01

    Based on the pressure of the saturated vapor and components over liquid alloys in a tin-selenium system, determined using the boiling points approach (isothermal variant), its boiling point and corresponding vapor phase composition are calculated in the region of liquid solutions. The phase diagram is supple-mented with the liquid-vapor phase transition under atmospheric pressure and in vacuums of 100 and 10 Pa with the boundaries of the region in which the regions of liquid and vapor coexist being determined.

  1. Vacuum-assisted headspace solid phase microextraction: improved extraction of semivolatiles by non-equilibrium headspace sampling under reduced pressure conditions.

    PubMed

    Psillakis, Elefteria; Yiantzi, Evangelia; Sanchez-Prado, Lucia; Kalogerakis, Nicolas

    2012-09-12

    A new headspace solid-phase microextraction (HSSPME) procedure carried out under vacuum conditions is proposed here where sample volumes commonly used in HSSPME (9 mL) were introduced into pre-evacuated commercially available large sampling chambers (1000 mL) prior to HSSPME sampling. The proposed procedure ensured reproducible conditions for HSSPME and excluded the possibility of analyte losses. A theoretical model was formulated demonstrating for the first time the pressure dependence of HSSPME sampling procedure under non equilibrium conditions. Although reduced pressure conditions during HSSPME sampling are not expected to increase the amount of analytes extracted at equilibrium, they greatly increase extraction rates compared to HSSPME under atmospheric pressure due to the enhancement of evaporation rates in the presence of an air-evacuated headspace. The effect is larger for semivolatiles whose evaporation rates are controlled by mass transfer resistance in the thin gas film adjacent to the sample/headspace interface. Parameters that affect HSSPME extraction were investigated under both vacuum and atmospheric conditions and the experimental data obtained were used to discuss and verify the theory. The use of an excessively large headspace volume was also considered. The applicability of Vac-HSSPME was assessed using chlorophenols as model compounds yielding linearities better than 0.9915 and detection limits in the low-ppt level. The repeatability was found to vary from 3.1 to 8.6%. PMID:22884204

  2. Equilibrium aluminium hydroxo-oxalate phases during initial clay formation; H +-Al 3+-oxalic acid-Na + system

    NASA Astrophysics Data System (ADS)

    Bilinski, Halka; Horvath, Laszlo; Ingri, Nils; Sjöberg, Staffan

    1986-09-01

    The conditions necessary for initial clay formation have been studied in different model systems comprising different organic acids besides Si and Al. In the present paper the solid phases and the precipitation boundary characterizing the subsystem H +-Al 3+-oxalic acid (H 2L) are discussed. pH and tyndallometric measurements were performed in an ionic medium of 0.6 M Na(Cl) at 25 °C. The two phases Al 3(OH) 7(C 2O 4) · 3H 2O (phase I) and NaAl(OH) 2(C 2O 4) · 3H 2O (phase II) determine the precipitation boundary. The following formation constants for the two phases were deduced: lgβ1 = lg([ Al3+] -3[ H2C2O4] -1[ H+] 9 = -21.87 ± 0.08 and lgβ11 = lg([ Al3+] -1[ H2C2O4] -1[ H+] 4 = -5.61 ± 0.06. Phase I exists in the range [ Al] tot≥ 10 -4.4moldm-3,[ H2C2O4] tot ≥ 10 -4.9moldm-3 and at pH < 6.8, thus being a possible precipitate in oxalic-rich natural waters. The more soluble sodium phase is unlikely to exist in natural waters. The two phases are metastable relative to crystalline gibbsite and may be considered as the first precipitation step in the transition from aqueous Al oxalates down to stable Al hydroxide. Model calculations illustrating these competing hydrolysis-complexation reactions are discussed in terms of predominance and speciation diagrams. The solid phases have been characterized by X-ray analysis of powders, TGA and IR spectra, and tentative structures are proposed. Phase I seems to be an octahedral layer structure, in which 3/5 of the octahedral sites between two close packed oxygen sheets are occupied by Al 3+ and the oxalate ion acts as a bridge ligand between two aluminium atoms. Phase II forms a more open sheet structure and has ion exchange properties. Powder data for a phase crystallized from the studied solution after a year are also presented. This phase, Na 4Al 2(OH) 2(C 2O 4) 4 · 10H 2O, supports the results from the equilibrium analysis of recent solution data by SJöBERG and ÖHMAN (1985), who have found the dinuclear

  3. Advanced Crystallographic Data Collection Protocols for Experimental Phasing.

    PubMed

    Finke, Aaron D; Panepucci, Ezequiel; Vonrhein, Clemens; Wang, Meitian; Bricogne, Gérard; Oliéric, Vincent

    2016-01-01

    Experimental phasing by single- or multi-wavelength anomalous dispersion (SAD or MAD) has become the most popular method of de novo macromolecular structure determination. Continuous advances at third-generation synchrotron sources have enabled the deployment of rapid data collection protocols that are capable of recording SAD or MAD data sets. However, procedural simplifications driven by the pursuit of high throughput have led to a loss of sophistication in data collection strategies, adversely affecting measurement accuracy from the viewpoint of anomalous phasing. In this chapter, we detail optimized strategies for collecting high-quality data for experimental phasing, with particular emphasis on minimizing errors from radiation damage as well as from the instrument. This chapter also emphasizes data processing for "on-the-fly" decision-making during data collection, a critical process when data quality depends directly on information gathered while at the synchrotron. PMID:26227043

  4. Experimental determination of equilibrium magnesium isotope fractionation between spinel, forsterite, and magnesite from 600 °C to 800 °C

    NASA Astrophysics Data System (ADS)

    Macris, C. A.; Young, E. D.; Manning, C. E.

    2012-12-01

    Magnesium isotopes are potentially powerful tools for high-temperature geochemistry if relevant fractionation factors are known. However, experimental data for Mg isotope fractionation are lacking at high temperatures. We performed piston-cylinder experiments at 600, 700, and 800 °C at 1 GPa to establish the equilibrium magnesium isotope partitioning between forsterite (Mg2SiO4) and magnesite (MgCO3) and between spinel (MgAl2O4) and magnesite, making use of the well-established advantages of using carbonates as an isotope exchange medium (e.g. Clayton et al., 1989). In these experiments we implemented the three-isotope method with forsterite and magnesite, and with spinel and magnesite, at three different temperatures in high-pressure piston cylinder apparatus for varying lengths of time. The present study extends the applicability of the three-isotope method to experiments involving simple isotope exchange rather than exchange by heterogeneous reaction (Shahar et al., 2008). We used magnesite as the exchange medium (and exchange partner) to overcome the sluggish diffusion-limited exchange between spinel and forsterite alone. The carbonate medium evidently facilitates chemical and isotopic exchange by promoting annealing and re-crystallization of minerals during the experiment. Results are as follows: 600 °C and 1 GPa 26ΔSp-Mgs = 1.73 ± 0.38‰ and 26ΔFo-Mgs = 0.44 ± 0.10‰; 700 °C 26ΔSp-Mgs = 1.10 ± 0.27‰ and 26ΔFo-Mgs = -0.13 ± 0.13‰; 800 °C 26ΔSp-Mgs = 0.90 ± 0.28‰ and 26ΔFo-Mgs = 0.04 ± 0.04‰. From these experimentally determined equilibrium fractionation values, we derive the temperature-dependent equilibrium fractionation between spinel and forsterite by difference, yielding 26ΔSp-Fo = 1.29 ± 0.39‰, 26ΔSp-Fo = 1.22 ± 0.30‰, and 26ΔSp-Fo = 0.86 ± 0.29‰ for 600, 700, and 800 °C respectively. These results agree within error with first- principles estimates of equilibrium magnesium isotope fractionation between spinel and

  5. Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS

    NASA Astrophysics Data System (ADS)

    Gualda, G. A.; Ghiorso, M. S.; Begue, F.; Pamukcu, A. S.; Gravley, D. M.

    2013-12-01

    Constraining the pressure of crystallization of magmas is an important but elusive task. We propose here a method to derive crystallization pressures for rocks that preserve glass compositions (either glass inclusions or matrix glass) representative of equilibration between melt, quartz, and 1 or 2 feldspars. The method relies on the shift of the quartz-feldspar saturation surface towards higher silica with decreasing pressure. The critical realization is that melt, quartz and feldspars need to be in equilibrium at the liquidus for the melt composition of interest. Thus, this method consists of calculating the saturation surfaces for quartz and feldspars using rhyolite-MELTS over a range of pressures, and searching for the pressure at which the expected assemblage (quartz+1 feldspar or quartz+2 feldspars) is found at the liquidus. We evaluate errors resulting from uncertainties in glass composition using Monte Carlo simulations, which reveal errors of ~20-45 MPa for the quartz+2 feldspars constraint and of ~25-100 MPa for the quartz+1 feldspar constraint; actual errors are likely closer to the lower bounds of these ranges. We demonstrate that the effect of fluid-saturation is more important at higher pressures (~300 MPa) than at lower pressures (~100 MPa), but reasonable pressure estimates can be derived irrespective of fluid saturation for geologically relevant H2O concentrations (>3 wt. %). And, we show that pressures calculated using the rhyolite-MELTS geobarometer compare well with those resulting from H2O-CO2 glass inclusion barometry and Al-in-hornblende barometry for an array of natural systems for which data has been compiled from the literature. We apply the rhyolite-MELTS barometer to three systems we are currently studying in detail: (1) For the Bishop Tuff (CA, USA), we find that quartz-hosted glass inclusion compositions yield indistinguishable crystallization pressures for early-erupted and late-erupted pumice, consistent with the Bishop Tuff having

  6. Phase equilibrium for surfactant Ls-54 in liquid CO2 with water and solubility estimation using the Peng-Robinson equation of state

    PubMed Central

    Tarafa, Pedro J.; Matthews, Michael A.

    2010-01-01

    It is known that the commercial surfactant Dehypon® Ls-54 is soluble in supercritical CO2 and that it enables formation of water-in-CO2 microemulsions. In this work we observed phase equilibrium for the Ls-54/CO2 and Ls-54/water/CO2 systems in the liquid CO2 region, from 278.15 - 298.15 K. In addition, the Peng-Robinson equation of state (PREOS) was used to model the phase behavior of Ls-54/CO2 binary system as well as to estimate water solubilities in CO2. Ls-54 in CO2 can have solubilities as high as 0.086 M at 278.15 K and 15.2 MPa. The stability of the microemulsion decreases with increasing concentration of water, and lower temperatures favor increased solubility of water into the one-phase microemulsion. The PREOS model showed satisfactory agreement with the experimental data for both Ls-54/CO2 and water/CO2 systems. PMID:21037962

  7. A general unified non-equilibrium model for predicting saturated and subcooled critical two-phase flow rates through short and long tubes

    SciTech Connect

    Fraser, D.W.H.; Abdelmessih, A.H.

    1995-09-01

    A general unified model is developed to predict one-component critical two-phase pipe flow. Modelling of the two-phase flow is accomplished by describing the evolution of the flow between the location of flashing inception and the exit (critical) plane. The model approximates the nonequilibrium phase change process via thermodynamic equilibrium paths. Included are the relative effects of varying the location of flashing inception, pipe geometry, fluid properties and length to diameter ratio. The model predicts that a range of critical mass fluxes exist and is bound by a maximum and minimum value for a given thermodynamic state. This range is more pronounced at lower subcooled stagnation states and can be attributed to the variation in the location of flashing inception. The model is based on the results of an experimental study of the critical two-phase flow of saturated and subcooled water through long tubes. In that study, the location of flashing inception was accurately controlled and adjusted through the use of a new device. The data obtained revealed that for fixed stagnation conditions, the maximum critical mass flux occurred with flashing inception located near the pipe exit; while minimum critical mass fluxes occurred with the flashing front located further upstream. Available data since 1970 for both short and long tubes over a wide range of conditions are compared with the model predictions. This includes test section L/D ratios from 25 to 300 and covers a temperature and pressure range of 110 to 280{degrees}C and 0.16 to 6.9 MPa. respectively. The predicted maximum and minimum critical mass fluxes show an excellent agreement with the range observed in the experimental data.

  8. A meniscus where three phases coexist at equilibrium: Microscopic derivation of the Herring relations

    SciTech Connect

    De Coninck, J.; de Gottal, P.; Menu, F. )

    1989-07-01

    The geometrical characteristics of a meniscus between 2 phases are studied. In particular, the behavior of the contact angles as a function of the temperature is derived for SOS-type models. A microscopic derivation of the Herring relations is given within a continuous Gaussian model.

  9. Phase equilibrium in the formation of silicon carbide by topochemical conversion of silicon

    NASA Astrophysics Data System (ADS)

    Kukushkin, S. A.; Osipov, A. V.

    2016-04-01

    Methods of linear algebra were used to find a basis of independent chemical reactions in the topochemical conversion of silicon into silicon carbide by the reaction with carbon monoxide. The pressure-flow phase diagram was calculated from this basis, describing the composition of the solid phase for a particular design of vacuum furnace. It was demonstrated that to grow pure silicon carbide, it is necessary to ensure the pressure of carbon monoxide less than a certain value and its flow more than a certain value, depending on the temperature of the process. The elastic fields around vacancies formed were considered for the first time in calculating the topochemical reaction. It was shown that the anisotropy of these fields in a cubic crystal increases the constant of the main reaction approximately fourfold.

  10. Decoding the pair correlations and properties of equilibrium microscopic cluster phases

    NASA Astrophysics Data System (ADS)

    Bollinger, Jonathan; Jadrich, Ryan; Truskett, Thomas

    Due to competing interactions acting between particles, dispersed colloidal suspensions can reversibly transition to phases comprising aggregate clusters. Cluster phases have been reported for both 'model' colloidal particles and complex monomers (e.g., proteins); however, many questions remain regarding how to detect and characterize cluster phases given only pair structural correlations (the information most accessible across diverse systems) and how to relate clustering susceptibility and behavior to underlying monomer-monomer interactions. Using molecular simulations and liquid-state theory across a wide survey of conditions, we decode the widely-observed intermediate range order pre-peak in the structure factor by: (1) validating a physically-intuitive rule for detecting clustering based on the pre-peak thermal correlation length; and (2) relating pre-peak position to cluster size and bulk monomer density. We further demonstrate how clustering transitions and resultant properties relate to monomer interactions along coordinates tunable in experiments. These trends are suitable for comparing against clustering systems that can be directly visualized (via, e.g., confocal microscopy), which should aid in assessing the realism of commonly-adopted monomer interaction potentials.

  11. Non-equilibrium Simulation of CO­2-hydrate Phase Transitions from Mixtures of CO2 and N2 Gases

    NASA Astrophysics Data System (ADS)

    Qorbani Nashaqi, K.

    2015-12-01

    Storage of CO2 in aquifers is one of several options for reducing the emissions of CO2 to the atmosphere. Generally this option requires sealing integrity through layers of clay or shale. Many reservoirs have regions of temperature and pressure inside hydrate formation conditions. Whether hydrate formation can provide long term extra sealing still remains unverified in view of all co-existing phases that affect hydrate stability. Yet another storage option for CO2 is in the form of hydrate through exchange of in situ CH4 hydrate. Injection of CO2 into hydrate filled sediments is challenging due to the partial filling of pores with hydrate which results in low porosity and low permeability. Formation of new hydrate from injected CO2 will enhance these problems, Mixing N2 gas with the CO2 will increase permeability and will reduce driving forces for formation of new hydrate from pore water and injection gas. Hydrate can generally not reach thermodynamic equilibrium due to Gibbs' phase rule and the combined first and second laws of thermodynamics. These thermodynamic constraints on distribution of masses over co-existing phases are dynamically coupled to local mass- and heat-transport. Reservoir simulations are one possible method for investigation of possible scenarios related to injection of CO2 with N2 into aquifers containing CH4 hydrate. In this work we have developed prevoiusly modified RetrasoCodeBrite (RCB) simulator to handle injection of CO2/N2 gas mixtures. Hydrate formation and dissociation were determined by investigating Gibbs free energy differences between hydrate and hydrate formers. Gibbs free energy differences were calculated from changes in chemical potentials, which were obtained using non-equilibrium thermodynamic approach. Further extension of RCB has been implemented in this work through adding on-the-fly thermodynamic calculations. Correspondingly, hydrate phase transitions are calculated directly inside the code as a result of super

  12. Impact of Associated Gases on Equilibrium and Transport Properties of a Stream: Molecular Simulation and Experimental Studies

    NASA Astrophysics Data System (ADS)

    Creton, Benoit; de Bruin, Theodorus; Le Roux, Dominique; Duchet-Suchaux, Pierre; Lachet, Véronique

    2014-02-01

    During the various carbon dioxide capture and storage (CCS) stages, an accurate knowledge of thermodynamic properties of streams is required for the correct sizing of plant units. The injected streams are not pure and often contain small amounts of associated gaseous components such as , , noble gases, etc. In this work, the thermodynamic behavior and transport properties of some -rich mixtures have been investigated using both experimental approaches and molecular simulation techniques such as Monte Carlo and molecular dynamics simulations. Using force fields available in the literature, we have validated the capability of molecular simulation techniques in predicting properties for pure compounds, binary mixtures, as well as multicomponent mixtures. These validations were performed on the basis of experimental data taken from the literature and the acquisition of new experimental data. As experimental data and simulation results were in good agreement, we proposed the use of simulation techniques to generate new pseudo-experimental data and to study the impact of associated gases on the properties of streams. For instance, for a mixture containing 92.0 mol% of , 4.0 mol% of , 3.7 mol% of Ar, and 0.3 mol% of , we have shown that the presence of associated gases leads to a decrease of 14 % and 21 % of the dense phase density and viscosity, respectively, as compared to pure properties.

  13. Characterization of sodium carboxymethylcellulose-gelatin complex coacervation by chemical analysis of the coacervate and equilibrium fluid phases.

    PubMed

    Koh, G L; Tucker, I G

    1988-05-01

    The complex coacervation of sodium carboxymethylcellulose (SCMC) and gelatin has been characterized by chemical analyses of the coacervate and equilibrium fluid phases. The phenol-sulphuric acid (for SCMC) and Lowry (for gelatin) assays were used. Chemically analysed coacervate yield was used to predict optimum coacervation conditions, which occurred at a SCMC-gelatin mixing ratio of 3:7 at pH 3.5. The effects of pH, colloid mixing ratio and total colloid concentration on coacervate yield and composition were studied. The colloid mixing ratio, at which the peak coacervate yields occurred varied with coacervation pH. Increase in the total colloid concentration suppressed coacervation, resulting in a coacervate of higher water content. A similar coacervation mechanism was seen for two viscosity grades SCMC. However, because of the different degree of substitution of these two grades the SCMC-gelatin coacervates had different SCMC contents. PMID:2899623

  14. A history of experimental phasing in macromolecular crystallography

    PubMed Central

    Isaacs, Neil

    2016-01-01

    It was just over a century ago that W. L. Bragg published a paper describing the first crystal structures to be determined using X-ray diffraction data. These structures were obtained from considerations of X-ray diffraction (Bragg equation), crystallography (crystal lattices and symmetry) and the scattering power of different atoms. Although W. H. Bragg proposed soon afterwards, in 1915, that the periodic electron density in crystals could be analysed using Fourier transforms, it took some decades before experimental phasing methods were developed. Many scientists contributed to this development and this paper presents the author’s own perspective on this history. There will be other perspectives, so what follows is a history, rather than the history, of experimental phasing. PMID:26960116

  15. Cosmological QCD phase transition in steady non-equilibrium dissipative Hořava-Lifshitz early universe

    NASA Astrophysics Data System (ADS)

    Khodadi, M.; Sepangi, H. R.

    2014-07-01

    We study the phase transition from quark-gluon plasma to hadrons in the early universe in the context of non-equilibrium thermodynamics. According to the standard model of cosmology, a phase transition associated with chiral symmetry breaking after the electro-weak transition has occurred when the universe was about 1-10 μs old. We focus attention on such a phase transition in the presence of a viscous relativistic cosmological background fluid in the framework of non-detailed balance Hořava-Lifshitz cosmology within an effective model of QCD. We consider a flat Friedmann-Robertson-Walker universe filled with a non-causal and a causal bulk viscous cosmological fluid respectively and investigate the effects of the running coupling constants of Hořava-Lifshitz gravity, λ, on the evolution of the physical quantities relevant to a description of the early universe, namely, the temperature T, scale factor a, deceleration parameter q and dimensionless ratio of the bulk viscosity coefficient to entropy density ξ/s. We assume that the bulk viscosity cosmological background fluid obeys the evolution equation of the steady truncated (Eckart) and full version of the Israel-Stewart fluid, respectively.

  16. Experimental Studies of the Vibrational Entropies of Alloy Phases

    SciTech Connect

    Prof. Brent Fultz

    2001-02-18

    This is the annual progress report for the Grant DE-FG03-96ER45572. This research is on the entropy of materials, particularly alloy phases. It is an experimental effort utilizing inelastic neutron scattering facilities at two DOE facilities: Oak Ridge National Laboratory (HFIR) and Argonne National Laboratory (IPNS), and the NIST Center for Neutron Research. It includes an overview of completed research in 2000, a list of publications, and personnel supported under this grant.

  17. Experimental First Order Pairing Phase Transition in Atomic Nuclei

    NASA Astrophysics Data System (ADS)

    Moretto, L. G.; Larsen, A. C.; Giacoppo, F.; Guttormsen, M.; Siem, S.

    2015-02-01

    The natural log of experimental nuclear level densities at low energy is linear with energy. This can be interpreted in terms of a nearly 1st order phase transition from a superfluid to an ideal gas of quasi particles. The transition temperature coincides with the BCS critical temperature and yields gap parameters in good agreement with the values extracted from even- odd mass differences from rotational states. This converging evidence supports the relevance of the BCS theory to atomic nuclei.

  18. Investigation of the phase equilibrium of alloys of the ternary system Ti-Al-Nb

    SciTech Connect

    Nartova, T.T.; Sopochkin, G.G.

    1987-09-09

    This investigation of the constitution diagram of the ternary system titanium-aluminum-niobium is limited to the specific system Ti-Ti3A1-Nb in order to establish the regions of the alpha and beta solid solutions of titanium, the solid solutions based on aluminide Ti3A1, and the phases conjugated with them. The constitution diagram of the systems Ti-A1 and Ti-Nb obtained from the data were used as the basis for constructing the constitution diagram of the ternary system. The methods of microstructural, thermal and X ray phase analysis were used in the study. The X ray pictures were taken in copper emission from powders that had been preliminarily annealed in a vacuum at 600 for 30 min. Iodic titanium, aluminum brand AV-000 and fillet niobium were used as the source materials. The alloys were remelted five times in an electric-arc furnace with a nonconsumable tungsten electrode in an argon atmosphere, and then by crucibleless melting in the suspended state. The constancy of the chemical composition of the alloys was monitored by their weight after smelting in an electric arc furnace.

  19. Experimental assessment of phased-array heating of neck tumours.

    PubMed

    Gross, E J; Cetas, T C; Stauffer, P R; Liu, R L; Lumori, M L

    1990-01-01

    An investigation of phased-array microwave systems (PAMS) for non-invasively inducing hyperthermia, primarily in neck lesions, has been done with implications for applications at other sites such as lung and pelvis. Our general approach was to combine numerical and analytical approaches with parallel experimental studies. In this paper we will concentrate only on the experimental aspects. The object, such as a homogeneous cylindrical phantom or a neck phantom, was encircled with several standard applicators driven by a single source, but with relative phase and amplitude control over each applicator. The relative phases of the applicators were adjusted by using an implanted monopole antenna connected to an HP network analyser. Power was applied and the specific absorption rate (SAR) was determined by using split phantoms and thermography or by measuring temperature transients dT/dt, recorded by implanted thermometer probes. We found that at 915 MHz for our applicators (SMA Co.) the centre of an 11 cm diameter muscle-like phantom heated to about 33% of the value at the surface in front of the applicator. Similarly, we were able to show significant SAR at the centre of realistically sized neck phantoms using four phased apertures of 915 MHz. Furthermore, substantial improvement was observed if the frequency was lowered to about 400 MHz. PMID:2324581

  20. Equilibrium properties and phase diagram of two-dimensional Yukawa systems

    NASA Astrophysics Data System (ADS)

    Hartmann, P.; Kalman, G. J.; Donkó, Z.; Kutasi, K.

    2005-08-01

    Properties of two-dimensional strongly coupled Yukawa systems are explored through molecular dynamics simulations. An effective coupling coefficient Γ* for the liquid phase is introduced on the basis of the constancy of the first peak amplitude of the pair-correlation functions. Thermodynamic quantities are calculated from the pair-correlation function. The solid-liquid transition of the system is investigated through the analysis of the bond-angular order parameter. The static structure function satisfies consistency relation, attesting to the reliability of the computational method. The response is shown to be governed by the correlational part of the inverse compressibility. An analysis of the velocity autocorrelation demonstrates that this latter also exhibits a universal behavior.

  1. Equilibrium properties and phase diagram of two-dimensional Yukawa systems

    SciTech Connect

    Hartmann, P.; Donko, Z.; Kutasi, K.; Kalman, G.J.

    2005-08-01

    Properties of two-dimensional strongly coupled Yukawa systems are explored through molecular dynamics simulations. An effective coupling coefficient {gamma}{sup *} for the liquid phase is introduced on the basis of the constancy of the first peak amplitude of the pair-correlation functions. Thermodynamic quantities are calculated from the pair-correlation function. The solid-liquid transition of the system is investigated through the analysis of the bond-angular order parameter. The static structure function satisfies consistency relation, attesting to the reliability of the computational method. The response is shown to be governed by the correlational part of the inverse compressibility. An analysis of the velocity autocorrelation demonstrates that this latter also exhibits a universal behavior.

  2. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model.

    PubMed

    Butlitsky, M A; Zelener, B B; Zelener, B V

    2014-07-14

    A two-component plasma model, which we called a "shelf Coulomb" model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The "shelf Coulomb" model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ɛ parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ɛ and γ = βe(2)n(1/3) (where β = 1/kBT, n is the particle's density, kB is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ɛ and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ɛ(crit) ≈ 13(T(*)(crit) ≈ 0.076), γ(crit) ≈ 1.8(v(*)(crit) ≈ 0.17), P(*)(crit) ≈ 0.39, where specific volume v* = 1/γ(3) and reduced temperature T(*) = ɛ(-1). PMID:25028031

  3. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model

    SciTech Connect

    Butlitsky, M. A.; Zelener, B. V.

    2014-07-14

    A two-component plasma model, which we called a “shelf Coulomb” model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The “shelf Coulomb” model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ε parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ε and γ = βe{sup 2}n{sup 1/3} (where β = 1/k{sub B}T, n is the particle's density, k{sub B} is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ε and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ε{sub crit}≈13(T{sub crit}{sup *}≈0.076),γ{sub crit}≈1.8(v{sub crit}{sup *}≈0.17),P{sub crit}{sup *}≈0.39, where specific volume v* = 1/γ{sup 3} and reduced temperature T{sup *} = ε{sup −1}.

  4. Cosmological QCD phase transition in steady non-equilibrium dissipative Hořava–Lifshitz early universe

    SciTech Connect

    Khodadi, M. Sepangi, H.R.

    2014-07-15

    We study the phase transition from quark–gluon plasma to hadrons in the early universe in the context of non-equilibrium thermodynamics. According to the standard model of cosmology, a phase transition associated with chiral symmetry breaking after the electro-weak transition has occurred when the universe was about 1–10 μs old. We focus attention on such a phase transition in the presence of a viscous relativistic cosmological background fluid in the framework of non-detailed balance Hořava–Lifshitz cosmology within an effective model of QCD. We consider a flat Friedmann–Robertson–Walker universe filled with a non-causal and a causal bulk viscous cosmological fluid respectively and investigate the effects of the running coupling constants of Hořava–Lifshitz gravity, λ, on the evolution of the physical quantities relevant to a description of the early universe, namely, the temperature T, scale factor a, deceleration parameter q and dimensionless ratio of the bulk viscosity coefficient to entropy density (ξ)/s . We assume that the bulk viscosity cosmological background fluid obeys the evolution equation of the steady truncated (Eckart) and full version of the Israel–Stewart fluid, respectively. -- Highlights: •In this paper we have studied quark–hadron phase transition in the early universe in the context of the Hořava–Lifshitz model. •We use a flat FRW universe with the bulk viscosity cosmological background fluid obeying the evolution equation of the steady truncated (Eckart) and full version of the Israel–Stewart fluid, respectively.

  5. Femtosecond structural transformation of phase-change materials far from equilibrium monitored by coherent phonons.

    PubMed

    Hase, Muneaki; Fons, Paul; Mitrofanov, Kirill; Kolobov, Alexander V; Tominaga, Junji

    2015-01-01

    Multicomponent chalcogenides, such as quasi-binary GeTe-Sb2Te3 alloys, are widely used in optical data storage media in the form of rewritable optical discs. Ge2Sb2Te5 (GST) in particular has proven to be one of the best-performing materials, whose reliability allows more than 10(6) write-erase cycles. Despite these industrial applications, the fundamental kinetics of rapid phase change in GST remain controversial, and active debate continues over the ultimate speed limit. Here we explore ultrafast structural transformation in a photoexcited GST superlattice, where GeTe and Sb2Te3 are spatially separated, using coherent phonon spectroscopy with pump-pump-probe sequences. By analysing the coherent phonon spectra in different time regions, complex structural dynamics upon excitation are observed in the GST superlattice (but not in GST alloys), which can be described as the mixing of Ge sites from two different coordination environments. Our results suggest the possible applicability of GST superlattices for ultrafast switching devices. PMID:26403198

  6. Femtosecond structural transformation of phase-change materials far from equilibrium monitored by coherent phonons

    NASA Astrophysics Data System (ADS)

    Hase, Muneaki; Fons, Paul; Mitrofanov, Kirill; Kolobov, Alexander V.; Tominaga, Junji

    2015-09-01

    Multicomponent chalcogenides, such as quasi-binary GeTe-Sb2Te3 alloys, are widely used in optical data storage media in the form of rewritable optical discs. Ge2Sb2Te5 (GST) in particular has proven to be one of the best-performing materials, whose reliability allows more than 106 write-erase cycles. Despite these industrial applications, the fundamental kinetics of rapid phase change in GST remain controversial, and active debate continues over the ultimate speed limit. Here we explore ultrafast structural transformation in a photoexcited GST superlattice, where GeTe and Sb2Te3 are spatially separated, using coherent phonon spectroscopy with pump-pump-probe sequences. By analysing the coherent phonon spectra in different time regions, complex structural dynamics upon excitation are observed in the GST superlattice (but not in GST alloys), which can be described as the mixing of Ge sites from two different coordination environments. Our results suggest the possible applicability of GST superlattices for ultrafast switching devices.

  7. Femtosecond structural transformation of phase-change materials far from equilibrium monitored by coherent phonons

    PubMed Central

    Hase, Muneaki; Fons, Paul; Mitrofanov, Kirill; Kolobov, Alexander V.; Tominaga, Junji

    2015-01-01

    Multicomponent chalcogenides, such as quasi-binary GeTe–Sb2Te3 alloys, are widely used in optical data storage media in the form of rewritable optical discs. Ge2Sb2Te5 (GST) in particular has proven to be one of the best-performing materials, whose reliability allows more than 106 write–erase cycles. Despite these industrial applications, the fundamental kinetics of rapid phase change in GST remain controversial, and active debate continues over the ultimate speed limit. Here we explore ultrafast structural transformation in a photoexcited GST superlattice, where GeTe and Sb2Te3 are spatially separated, using coherent phonon spectroscopy with pump–pump–probe sequences. By analysing the coherent phonon spectra in different time regions, complex structural dynamics upon excitation are observed in the GST superlattice (but not in GST alloys), which can be described as the mixing of Ge sites from two different coordination environments. Our results suggest the possible applicability of GST superlattices for ultrafast switching devices. PMID:26403198

  8. Non-equilibrium phase transition in a two-species driven-diffusive model of classical particles

    NASA Astrophysics Data System (ADS)

    Ghadermazi, Mohammad; Jafarpour, Farhad H.

    2016-09-01

    A two-species driven-diffusive model of classical particles is introduced on a lattice with periodic boundary condition. The model consists of a finite number of first class particles in the presence of a second class particle. While the first class particles can only hop forward, the second class particle is able to hop both forward and backward with specific rates. We have shown that the partition function of this model can be calculated exactly. The model undergoes a non-equilibrium phase transition when a condensation of the first class particles occurs behind the second class particle. The phase transition point and the spatial correlations between the first class particles are calculated exactly. On the other hand, we have shown that this model can be mapped onto a two-dimensional walk model. The random walker can only move on the first quarter of a two-dimensional plane and that it takes the paths which can start at any height and end at any height upper than the height of the starting point. The initial vertex (starting point) and the final vertex (end point) of each lattice path are weighted. The weight of the outset point depends on the height of that point while the weight of the end point depends on the height of both the outset point and the end point of each path. The partition function of this walk model is calculated using a transfer matrix method.

  9. Non-equilibrium phase transition in a two-species driven-diffusive model of classical particles

    NASA Astrophysics Data System (ADS)

    Ghadermazi, Mohammad; Jafarpour, Farhad H.

    2016-06-01

    A two-species driven-diffusive model of classical particles is introduced on a lattice with periodic boundary condition. The model consists of a finite number of first class particles in the presence of a second class particle. While the first class particles can only hop forward, the second class particle is able to hop both forward and backward with specific rates. We have shown that the partition function of this model can be calculated exactly. The model undergoes a non-equilibrium phase transition when a condensation of the first class particles occurs behind the second class particle. The phase transition point and the spatial correlations between the first class particles are calculated exactly. On the other hand, we have shown that this model can be mapped onto a two-dimensional walk model. The random walker can only move on the first quarter of a two-dimensional plane and that it takes the paths which can start at any height and end at any height upper than the height of the starting point. The initial vertex (starting point) and the final vertex (end point) of each lattice path are weighted. The weight of the outset point depends on the height of that point while the weight of the end point depends on the height of both the outset point and the end point of each path. The partition function of this walk model is calculated using a transfer matrix method.

  10. An experimental investigation of two-phase liquid oxygen pumping

    NASA Technical Reports Server (NTRS)

    Gross, L. A.

    1973-01-01

    The results of an experimental program to explore the feasibility of pumping two-phase oxygen (liquid and gas) at the pump inlet are reported. Twenty-one cavitation tests were run on a standard J-2 oxygen pump at the MSFC Components Test Laboratory. All tests were run with liquid oxygen 5 to 10 K above the normal boiling point temperature. During ten tests run at approximately at the pump inlet were noted before complete pump performance 50 percent of the nominal operating speed, two phase conditions were achieved. Vapor volumes of 40 to 50 percent at the pump inlet were noted before complete pump performance loss. The experimental results compared to predictions. Nine cavitation tests run at the nominal pump speed over a 5 K temperature range showed progressively lower net positive suction head (NPSH) requirements as temperature was increased. Two-phase operation was not achieved. The temperature varying NPSH data were used to calculate thermodynamic effects on NPSH, and the results were compared to existing data.

  11. Correlation Between Experimental and Calculated Phase Fractions in Aged 20Cr32Ni1Nb Austenitic Stainless Steels Containing Nitrogen

    NASA Astrophysics Data System (ADS)

    Dewar, Matthew P.; Gerlich, Adrian P.

    2013-02-01

    A centrifugally cast 20Cr32Ni1Nb stainless steel manifold in service for 16 years at temperatures ranging from 1073 K to 1123 K (800 °C to 850 °C) has been characterized using scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), auger electron spectroscopy (AES), and X-ray diffraction (XRD). Nb(C,N), M23C6, and the silicide G-phases (Ni16Nb6Si7) were all identified in a conventional SEM, while the nitride Z-phase (CrNbN) was observed only in AES. M23C6, Z-phase and G-phase were characterized in XRD. Thermodynamic equilibrium calculations using ThermoCalc Version S, with the TCS Steel and Fe-alloys Database (TCFE6), and Thermotech Ni-based Superalloys Database (TTNI8) were validated by comparing experimental phase fraction results obtained from both EPMA and AES. A computational study looking at variations in the chemical composition of the alloy, and how they affect phase equilibria, was investigated. Increasing the nitrogen concentration is shown to decrease G-phase formation, where it is replaced by other intermetallic phases such as Z-phase and π-phase that do not experience liquation during pre-weld annealing treatments. Suppressing G-phase formation was ultimately determined to be a function of minimizing silicon content, and understabilizing the Nb/(C + 6/7N) ratio.

  12. Sorption equilibrium of a wide spectrum of organic vapors in Leonardite humic acid: modeling of experimental data.

    PubMed

    Niederer, Christian; Goss, Kai-Uwe; Schwarzenbach, Renè P

    2006-09-01

    In a recent publication we presented experimental Leonardite humic acid/air partition coefficients for 188 polar and nonpolar organic compounds measured with one consistent method. In this paper these experimental data are evaluated with various model predictions. For the PcKocWIN model some major shortcomings become apparent. The octanol-based Karickhoff-model exhibits a good performance for the nonpolar compounds but not for the polar ones. A good description of the whole data set is achieved with a polyparameter linear free energy relationship (pp-LFER) that explicitly accounts for the nonpolar (van der Waals and cavity formation) and polar (electron donor/acceptor) interactions between the sorbate molecule and the sorbent phase. With this pp-LFER model, most of the humic acid/air partition coefficients could be predicted within a factor of 2. The pp-LFER model also successfully predicts organic-C/water partition coefficients (K(ioc)) collected from the literature when it is combined with a pp-LFER for air/water partition coefficients. This supports our earlier conclusion that the thermodynamic cycle is applicable in the humic acid/water/air system. Based on our experimental data, we present a pp-LFER-model for humic acid/air and humic acid/water partitioning at any ambient temperatures. PMID:16999113

  13. Recent advances in the CRANK software suite for experimental phasing

    SciTech Connect

    Pannu, Navraj S. Waterreus, Willem-Jan; Skubák, Pavol; Sikharulidze, Irakli; Abrahams, Jan Pieter; Graaff, Rudolf A. G. de

    2011-04-01

    Recent developments in the CRANK software suite for experimental phasing have led to many more structures being built automatically. For its first release in 2004, CRANK was shown to effectively detect and phase anomalous scatterers from single-wavelength anomalous diffraction data. Since then, CRANK has been significantly improved and many more structures can be built automatically with single- or multiple-wavelength anomalous diffraction or single isomorphous replacement with anomalous scattering data. Here, the new algorithms that have been developed that have led to these substantial improvements are discussed and CRANK’s performance on over 100 real data sets is shown. The latest version of CRANK is freely available for download at http://www.bfsc.leidenuniv.nl/software/crank/ and from CCP4 (http://www.ccp4.ac.uk/)

  14. Experimental demonstration of microring quadrature phase-shift keying modulators.

    PubMed

    Dong, Po; Xie, Chongjin; Chen, Long; Fontaine, Nicolas K; Chen, Young-kai

    2012-04-01

    Advanced optical modulation formats are a key technology to increase the capacity of optical communication networks. Mach-Zehnder modulators are typically used to generate various modulation formats. Here, we report the first experimental demonstration of quadrature phase-shift keying (QPSK) modulation using compact microring modulators. Generation of 20 Gb/s QPSK signals is demonstrated with 30 μm radius silicon ring modulators with drive voltages of ~6 V. These compact QPSK modulators may be used in miniature optical transponders for high-capacity optical data links. PMID:22466187

  15. Water-saturated phase-equilibrium experiments on rhyolite and dacite obsidians: the effect of variable melt water concentration on the composition of phenocrysts

    NASA Astrophysics Data System (ADS)

    Waters, L.; Lange, R. A.; Andrews, B. J.

    2012-12-01

    Results of water-saturated phase equilibrium experiments on three obsidians ranging in composition from dacite to rhyolite (67-74 wt% SiO2) are presented and demonstrate the effect of changing melt water concentrations on the composition of plagioclase and orthopyroxene phenocrysts. Experiments were conducted in a cold-seal Ni-rich pressure vessel (Waspaloy) with Ni filler rod, so that experiments were buffered at ΔNNO +1 (± 0.5) (Gershwind & Rutherford, 1992) and pressurized with H2O (where Ptotal= PH2O). Temperatures ranged from 750-900°C and pressures ranged from 100-300 MPa. Prior to the experiments, detailed petrologic studies were first conducted on the three obsidian samples, which are from Cascade and Mexican arcs. Overall phenocryst abundances in all three samples are low (<2.3%), with little to no microlite crystallization. Despite low phenocryst abundances, the obsidians are saturated in five to seven mineral phases: plagioclase + orthopyroxene + ilmenite + magnetite + apatite ± clinopyroxene ± biotite. Eruptive temperatures (±1σ), on the basis of Fe-Ti two oxide thermometry (Ghiorso & Evans, 2008), range from 760 ± 18°C to 943 ± 20°C; corresponding ΔNNO values (±1σ) range from -0.9 ± 0.1 and 0.7 ± 0.1. Plagioclase compositions span a wide range in each sample (e.g., 9-40 and 30-54 mol% An), despite low phenocryst abundances. Orthopyroxene compositions also span a wide range (≤ 15 mol% En), which correspond to Fe-MgKD(opx-liq) values that range from 0.18-0.46. Given the low crystallinity, absence of evidence for mixing of magmas, and no apparent change in oxygen fugacity recorded by iron oxides, the progressive loss of water from a melt, through degassing during rapid magma ascent, is a plausible hypothesis to explain the observed variation in phenocryst compositions. This hypothesis is evaluated with the run products from the water-saturated phase equilibrium experiments on the three obsidian samples. The experimental results indicate

  16. Swelling equilibrium of dentin adhesive polymers formed on the water-adhesive phase boundary: Experiments and micromechanical model

    PubMed Central

    Misra, Anil; Parthasarathy, Ranganathan; Ye, Qiang; Singh, Viraj; Spencer, Paulette

    2013-01-01

    During their application to the wet, oral environment, dentin adhesives can experience phase separation and composition change which can compromise the quality of the hybrid layer formed at the dentin-adhesive interface. The chemical composition of polymer phases formed in the hybrid layer can be represented using a ternary water-adhesive phase diagram. In this paper, these polymer phases have been characterized using a suite of mechanical tests and swelling experiments. The experimental results were evaluated using granular micromechanics based model that incorporates poro-mechanical effects and polymer-solvent thermodynamics. The variation of the model parameters and model-predicted polymer properties has been studied as a function of composition along the phase boundary. The resulting structure-property correlations provide insight into interactions occurring at the molecular level in the saturated polymer system. These correlations can be used for modeling the mechanical behavior of hybrid layer, and are expected to aid in the design and improvement of water-compatible dentin adhesive polymers. PMID:24076070

  17. Swelling equilibrium of dentin adhesive polymers formed on the water-adhesive phase boundary: experiments and micromechanical model.

    PubMed

    Misra, A; Parthasarathy, R; Ye, Q; Singh, V; Spencer, P

    2014-01-01

    During their application to the wet, oral environment, dentin adhesives can experience phase separation and composition change, which can compromise the quality of the hybrid layer formed at the dentin-adhesive interface. The chemical composition of polymer phases formed in the hybrid layer can be represented using a ternary water-adhesive phase diagram. In this paper, these polymer phases are characterized using a suite of mechanical tests and swelling experiments. The experimental results were evaluated using a granular micromechanics-based model incorporating poro-mechanical effects and polymer-solvent thermodynamics. The variation in the model parameters and model-predicted polymer properties was studied as a function of composition along the phase boundary. The resulting structure-property correlations provide insight into interactions occurring at the molecular level in the saturated polymer system. These correlations can be used for modeling the mechanical behavior of the hybrid layer, and are expected to aid in the design and improvement of water-compatible dentin adhesive polymers. PMID:24076070

  18. Experimental study of a two-phase surface jet

    NASA Astrophysics Data System (ADS)

    Perret, Matias; Esmaeilpour, Mehdi; Politano, Marcela S.; Carrica, Pablo M.

    2013-04-01

    Results of an experimental study of a two-phase jet are presented, with the jet issued near and below a free surface, parallel to it. The jet under study is isothermal and in fresh water, with air injectors that allow variation of the inlet air volume fraction between 0 and 13 %. Measurements of water velocity have been performed using LDV, and the jet exit conditions measured with PIV. Air volume fraction, bubble velocity and chord length distributions were measured with sapphire optical local phase detection probes. The mean free surface elevation and RMS fluctuations were obtained using local phase detection probes as well. Visualization was performed with laser-induced fluorescence. Measurements reveal that the mean free surface elevation and turbulent fluctuations significantly increase with the injection of air. The water normal Reynolds stresses are damped by the presence of bubbles in the bulk of the liquid, but very close to the free surface the effect is reversed and the normal Reynolds stresses increase slightly for the bubbly flow. The Reynolds shear stresses < {u^' } w^' } } rangle decrease when bubbles are injected, indicating turbulence attenuation, and are negative at deeper locations, as turbulent eddies shed downward carry high axial momentum deeper into the flow. Flow visualization reveals that the two-phase jet is lifted with the presence of bubbles and reaches the free surface sooner. Significant bubble coalescence is observed, leading to an increase in mean bubble size as the jet develops. The coalescence near the free surface is particularly strong, due to the time it takes the bubbles to pierce the free surface, resulting in a considerable increase in the local air volume fraction. In addition to first explore a bubbly surface jet, the comprehensive dataset reported herein can be used to validate two-phase flow models and computational tools.

  19. Reaction of plutonium with water kinetic and equilibrium behavior of binary and ternary phases in the Pu + O + H system

    SciTech Connect

    Haschke, J.M.; Hodges, A.E. III; Bixby, G.E.; Lucas, R.L.

    1983-02-03

    The kinetic and equilibrium behavior of the Pu + O + H system has been studied by measuring the production of hydrogen gas formed by a sequence of hydrolysis reactions. The kinetic dependence of the Pu + H/sub 2/O reaction on salt concentration and temperature has been defined. The metal is quantitatively converted to a fine black powder which has been identified as plutonium monoxide monohydride, PuOH. Other hydrolysis products formed in aqueous media include a second oxide hydride, Pu/sub 7/O/sub 9/H/sub 3/, and the oxides Pu/sub 2/O/sub 3/, Pu/sub 7/O/sub 12/, Pu/sub 9/O/sub 16/, Pu/sub 10/O/sub 18/, Pu/sub 12/O/sub 22/, and PuO/sub 2/. Thermal decomposition products of PuOH include Pu/sub 2/O/sub 2/H and PuO. A tentative phase diagram for Pu + O + H is presented and structural relationships of the oxide hydrides and oxides are discussed. 10 figures, 5 tables.

  20. Phase equilibrium modeling, fluid inclusions and origin of charnockites in the Datian region of the northeastern Cathaysia Block, South China

    NASA Astrophysics Data System (ADS)

    Yang, Xiao-Qiang; Li, Zi-Long; Yu, Sheng-Qiang

    2016-08-01

    Charnockites in the Datian region of the northeastern Cathaysia Block, South China have an assemblage of garnet, clinopyroxene, orthopyroxene, plagioclase, anti-perthite, K-feldspar, biotite, quartz and ilmenite. Phase equilibrium modeling indicates that the Datian charnockite was formed at T = 845-855 °C and P = 8.2-8.4 kbar with corresponding water activity lower than 0.50. Fluid inclusions in the Datian charnockite are dominated by N2 and CO2 with minor CH4. The fluids homogenized to liquid at -153.0 to -138.8 °C and 18.3-21.6 °C, respectively, showing a low-density nature. The low-density fluids could be attributed to selective leakage of water due to the affinity of water to melt and decompression-dominated retrograde process. Combined with previous studies, a two-stage formation model is proposed to interpret the petrogenesis of the Datian charnockite, viz emplaced at the Paleoproterozoic and underwent the granulite-facies metamorphism during the Phanerozoic tectonic event.

  1. Experimental measurements within a phase change metallurgical reactor

    NASA Astrophysics Data System (ADS)

    Bertrand, C.; Désilets, M.; Soucy, G.

    2011-12-01

    The measurement of solidification front evolution is essential for the optimization and control of many important metallurgical processes. However, this measurement is tedious, imprecise, and time consuming. More generally, industry needs reliable instruments for the thermal characterization of phase change reactors. This paper enables researchers with means and instruments to study the thermal behavior of processes involving the transformation of phase change materials up to 1000 °C. In this work, an original experimental setup is described to analyze the behavior of two high temperature phase change materials: zinc and molten salts. In particular, it is possible to evaluate the 2D solid solidification front evolution with time. The measurements done with zinc show the presence of two thermal regimes. A solidification rate of 20 mm h-1 is measured with two different approaches: thermocouples and a mechanical probe. Finally, an infrared camera is also used to make the link between the external thermal behavior and the solidification front evolution inside the reactor. When implemented within an inverse numerical method, the use of this instrument as a new external sensor looks promising.

  2. Transmission and phase balancing of alternating phase-shifting masks (5x): theoretical and experimental results

    NASA Astrophysics Data System (ADS)

    Griesinger, Uwe A.; Pforr, Rainer; Knobloch, Juergen; Friedrich, Christoph M.

    1999-12-01

    Dual trench alternating phase shifting masks with an optimized value of the so-called shallow trench depth represents an interesting approach to overcome aerial image imbalances. In order to get a better understanding of the possibilities and limits of this approach, especially for 5X reduction, theoretical and experimental investigations were accomplished. In this paper experimental data obtained from 5X dual trench type alternating PSMs, using DUV-lithography are introduced and compared with 3D-mask simulations. The masks were fabricated with different etch depths and contain parts of typical DRAM patterns. Besides the transmission balancing also the phase balancing has an important influence on the effective process window of an alternating PSM. The effective phase error can be measured with an AIMS-system (MSM100). The comparison with simulated data allows the determination of the phase error. In a second step the influence of different balancing methods on phase and transmission were investigated with the TEMPEST mask simulator for unpolarized light. The optimization of the balancing with respect to the CD-bias, undercut and etch depth will be shown and a first approach of a sensitivity analysis will be presented.

  3. An experimental study of trace element partitioning between olivine, orthopyroxene and melt in chondrules - Equilibrium values and kinetic effects

    NASA Technical Reports Server (NTRS)

    Kennedy, A. K.; Lofgren, G. E.; Wasserburg, G. J.

    1993-01-01

    Mineral/melt partition coefficients were measured using an ion microprobe for 32 elements in orthopyroxene and olivine in equilibrium and dynamic crystallization experiments on compositions corresponding to chondrules. The mineral/melt partition coefficients calculated from the measured concentrations for both olivine and orthopyroxene show very little change between equilibrium experiments and dynamic experiments with cooling rates of up to 100 C/h. The results provide a self-consistent set of partition coefficients that can be used in thermodynamic models of equilibrium and kinetic partitioning between olivine, orthopyroxene, and melt. These data can be used in models of partial melting and crystal fractionation in olivine- and orthopyroxene-rich systems, such as chondrules. The results may also be applicable to mantle peridotites, komatiitic and picritic lavas, and ultramafic intrusions.

  4. Experimental and Theoretical Studies on Two-Phase Flows.

    NASA Astrophysics Data System (ADS)

    Koh, Christopher James

    This thesis, comprised of two parts, deals with the flow of suspensions. Part I concerns specifically with the stability of a single drop translating through a quiescent, unbounded suspending fluid at low Reynolds number. The evolution of the shape of an initially nonspherical drop as it translates is studied numerically and experimentally. For finite capillary numbers, it is shown that the drop reverts to a sphere provided that the initial deformation is small enough. However, beyond certain critical initial deformation, the drop deforms continuously. For initially prolate shapes, the drop elongates with the formation of a tail; for initially oblate shapes, the drop flattens with the formation of a cavity at its rear. Experiments extend the numerical results. It is found that initially unstable prolate drops break up into multiple droplets, while initially unstable oblate drops deform in double-emulsion drops. Part II of this thesis considers the flow of high concentration solid suspensions through a rectangular channel. By adapting the well-known Laser Doppler Anemometry, an experimental technique is developed to measure the velocity as well as particle volume fraction of the suspension. A crucial element in these experiments is the reduction of the optical turbidity of the suspension. To accomplish this goal, a systematic method based on refractive-index-matching of the two phases is employed. Experimental results show that the velocity profile is blunted while the concentration profile has a maximum near the center. The qualitative features of the experimental data compare reasonably well with theoretical predictions based on the shear-induced particle migration theory.

  5. Catalytic supercritical water gasification of primary paper sludge using a homogeneous and heterogeneous catalyst: Experimental vs thermodynamic equilibrium results.

    PubMed

    Louw, Jeanne; Schwarz, Cara E; Burger, Andries J

    2016-02-01

    H2, CH4, CO and CO2 yields were measured during supercritical water gasification (SCWG) of primary paper waste sludge (PWS) at 450°C. Comparing these yields with calculated thermodynamic equilibrium values offer an improved understanding of conditions required to produce near-equilibrium yields. Experiments were conducted at different catalyst loads (0-1g/gPWS) and different reaction times (15-120min) in a batch reactor, using either K2CO3 or Ni/Al2O3-SiO2 as catalyst. K2CO3 up to 1g/gPWS increased the H2 yield significantly to 7.5mol/kgPWS. However, these yields and composition were far from equilibrium values, with carbon efficiency (CE) and energy recovery (ER) of only 29% and 20%, respectively. Addition of 0.5-1g/gPWS Ni/Al2O3-SiO2 resulted in high H2 and CH4 yields (6.8 and 14.8mol/kgPWS), CE of 84-90%, ER of 83% and a gas composition relatively close to the equilibrium values (at hold times of 60-120min). PMID:26638140

  6. Replacement of barite by a (Ba,Ra)SO4 solid solution at close-to-equilibrium conditions: A combined experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Brandt, F.; Curti, E.; Klinkenberg, M.; Rozov, K.; Bosbach, D.

    2015-04-01

    Solid solution formation between RaSO4 and BaSO4 has long been recognized as a process which potentially controls the Ra concentration in the environment. Here, we have systematically studied the replacement of pure barite by a (Ba,Ra)SO4 solid solution in 0.1 M NaCl through batch experiments extending up to 883 days at close-to-equilibrium (CTE) conditions, which are relevant to disposal of nuclear waste in a deep geological repository. Kinetic and thermodynamic models were applied to support the interpretation of the experiments, which were carried out at room temperature and at two distinct solid/liquid ratio (0.5 or 5 g/L). Different stages of recrystallization were observed, based on the rate of removal of Ra from aqueous solution. After a first slow kinetic step, a change in the slope of the aqueous Ra concentration vs. time is observed, suggesting nucleation of a new (Ba,Ra)SO4 phase from supersaturation. If this stage was considered to reflect equilibrium between aqueous and solid solution, one would infer ideality or even negative interaction parameters (a0 ⩽ 0). After this fast nucleation step, in the 0.5 g/L experiments the Ra concentrations in the aqueous solution slowly increase, approaching a concentration close to that required for equilibrium with a regular (Ba,Ra)SO4 solid solution with an interaction parameter a0 = 1.0. Therefore, these data suggest a non-equilibrium Ra entrapment during the nucleation phase of the replacement, followed by slow recrystallization toward true thermodynamic solid solution equilibrium. Moreover, an interaction parameter value of a0 = 1.0 was inferred from our experiments, which is in good agreement with theoretical predictions from atomistic simulations. A key result from this study is that aqueous solution and binary (Ba,Ra)SO4 approach full thermodynamic equilibrium within laboratory time scales (2.5 years). This justifies assuming complete thermodynamic equilibrium for this system in geochemical calculations of

  7. Non-aqueous-phase fluids in heterogeneous aquifers -- experimental study

    SciTech Connect

    Illangasekare, T.H.; Yates, D.N.; Armbruster, E.J. III.

    1995-08-01

    Understanding of flow and entrapment of non-aqueous-phase liquids (NAPLs) in aquifers contaminated with organic chemicals is important in the effective design of recovery and remediation schemes. Soil heterogeneities play a significant role in the physical behavior of these chemicals. An experimental facility consisting of a large soil tank (lysimeter) and a dual-gamma spectroscopy system for fluid saturation measurements was developed to simulate and monitor plume migration in water-table aquifers after chemical spills. Experimental techniques and results form a preliminary set of experiments conducted in unsaturated and saturated soils under homogeneous and heterogeneous conditions are presented. the effects of the layered homogeneities were pronounced in modifying the migration pattern and velocity of the plume. Pockets of coarse sand placed across the path of the plume resulted in the soil acting as a light NAPL trap. A fine-sand pocket acted as a barrier. Qualitative and quantitative data generated in the type of experiments presented in this paper can be used to validate multiphase flow models.

  8. Phase Equilibria of ``Cu2O''-``FeO''-CaO-MgO-Al2O3 Slags at PO2 of 10-8.5 atm in Equilibrium with Metallic Copper for a Copper Slag Cleaning Production

    NASA Astrophysics Data System (ADS)

    Henao, Hector M.; Pizarro, Claudio; Font, Jonkion; Moyano, Alex; Hayes, Peter C.; Jak, Evgueni

    2010-12-01

    Limited data are available on phase equilibria of the multicomponent slag system at the oxygen partial pressures used in the copper smelting, converting, and slag-cleaning processes. Recently, experimental procedures have been developed and have been applied successfully to characterize several complex industrial slags. The experimental procedures involve high-temperature equilibration on a substrate and quenching followed by electron probe X-ray microanalysis. This technique has been used to construct the liquidus for the “Cu2O”-“FeO”-SiO2-based slags with 2 wt pct of CaO, 0.5 wt pct of MgO, and 4.0 wt pct of Al2O3 at controlled oxygen partial pressures in equilibrium with metallic copper. The selected ranges of compositions and temperatures are directly relevant to the copper slag-cleaning processes. The new experimental equilibrium results are presented in the form of ternary sections and as a liquidus temperature vs Fe/SiO2 weight ratio diagram. The experimental results are compared with the FactSage thermodynamic model calculations.

  9. Phase equilibrium data for coal-derived liquids: mixture of model compounds. Subcontracted R and D final report

    SciTech Connect

    Mehta, D.C.; Craft, S.; Ho, C.

    1984-05-01

    ICRC initiated a test program to develop VLE and enthalpy data on selected model compounds and on well-defined coal liquids. The results obtained from the model compounds would be used to improve existing correlations in their application to coal liquefaction equipment design. The data on the coal liquids would be helpful in optimizing the design and operation of the corresponding equipment in the SRC-I Demonstration Plant. The overall test program was divided into four tasks: (1) Sample Acquisition and Preparation, (2) VLE Measurements, (3) Enthalpy Measurements, and (4) Analytical Characterization. Tasks 1 and 4 were performed by Air Products and Chemicals, Inc. (APCI). Task 2 was contracted to Chromaspec Corp., and Task 3 was performed by Colorado School of Mines (CSM). The ICRC work at Chromaspec was divided into two phases: the first phase covered VLE measurements of model compounds and coal liquids in the presence of hydrogen-rich gas at demonstration plant operating conditions; the second phase reported herein, covers VLE measurements on mixtures of polar model compounds. The results of the VLE measurements on mixtures of model compounds are presented in the attached Chromaspec report. The timing of the availability of results from Chromaspec did not permit incorporating them in the correlation development work at APCI. In spite of the schedule, the work at Chromaspec was continued so that the experimental setup could be fully utilized to develop all the necessary VLE data on the coal liquids and model compounds. 4 references.

  10. Dynamic Phase Relations in Ascending Silicic Magmas: Insights from Experimental Decompression of Mount St. Helens Rhyodacite

    NASA Astrophysics Data System (ADS)

    Riker, J. M.; Blundy, J. D.; Rust, A.

    2011-12-01

    Ascent-driven degassing and crystallization play a major role in modulating the chemical and physical properties of erupting magmas. Previous experimental studies of ascent-driven crystallization have focused on instantaneous or stepped decompression, measuring a response to discrete imposed undercoolings. More recently, technical advances have enabled the study of magmas undergoing slow decompression at controlled rates. In these instances, undercooling is a variable, not a constant. Time-dependent changes in effective undercooling may generate complex textural or compositional variations as the relevant liquidus shifts and kinetically-favored phases compete for components. The challenge is to extract meaningful information from rocks that have experienced a time-integrated history of crystallization and vesiculation. To address this problem, we have performed a series of dynamic decompression experiments on a hydrous Mount St. Helens rhyodacite. Each sample was first equilibrated at conditions inferred for the shallow 1980 magma chamber (200 MPa and 880-900 °C), then isothermally decompressed at a constant rate (1-1000 MPa/hr). Charges quenched at different pressures yield syn-eruptive 'snapshots' of the decompressing system. We use these snapshots to assess how kinetics governs the stabilities of multiple phases (plagioclase, amphibole, orthopyroxene, and Fe-Ti oxides) as a function of depth and decompression rate. Our results can be qualitatively summarized by 'dynamic phase diagrams' that define the crystallizing phases in quench pressure-decompression rate space. Such diagrams are useful for two reasons: (1) they provide a means of relating observed rock textures to quench pressures and decompression rates for the simple case of continuous ascent, and (2) they identify the dominant crystallizing phases across a range of conditions. Our initial results show that, as in other silicic systems, plagioclase is often the principal crystallizing phase; however

  11. Shape characteristics of equilibrium and non-equilibrium fractal clusters

    NASA Astrophysics Data System (ADS)

    Mansfield, Marc L.; Douglas, Jack F.

    2013-07-01

    It is often difficult in practice to discriminate between equilibrium and non-equilibrium nanoparticle or colloidal-particle clusters that form through aggregation in gas or solution phases. Scattering studies often permit the determination of an apparent fractal dimension, but both equilibrium and non-equilibrium clusters in three dimensions frequently have fractal dimensions near 2, so that it is often not possible to discriminate on the basis of this geometrical property. A survey of the anisotropy of a wide variety of polymeric structures (linear and ring random and self-avoiding random walks, percolation clusters, lattice animals, diffusion-limited aggregates, and Eden clusters) based on the principal components of both the radius of gyration and electric polarizability tensor indicates, perhaps counter-intuitively, that self-similar equilibrium clusters tend to be intrinsically anisotropic at all sizes, while non-equilibrium processes such as diffusion-limited aggregation or Eden growth tend to be isotropic in the large-mass limit, providing a potential means of discriminating these clusters experimentally if anisotropy could be determined along with the fractal dimension. Equilibrium polymer structures, such as flexible polymer chains, are normally self-similar due to the existence of only a single relevant length scale, and are thus anisotropic at all length scales, while non-equilibrium polymer structures that grow irreversibly in time eventually become isotropic if there is no difference in the average growth rates in different directions. There is apparently no proof of these general trends and little theoretical insight into what controls the universal anisotropy in equilibrium polymer structures of various kinds. This is an obvious topic of theoretical investigation, as well as a matter of practical interest. To address this general problem, we consider two experimentally accessible ratios, one between the hydrodynamic and gyration radii, the other

  12. Shape characteristics of equilibrium and non-equilibrium fractal clusters.

    PubMed

    Mansfield, Marc L; Douglas, Jack F

    2013-07-28

    It is often difficult in practice to discriminate between equilibrium and non-equilibrium nanoparticle or colloidal-particle clusters that form through aggregation in gas or solution phases. Scattering studies often permit the determination of an apparent fractal dimension, but both equilibrium and non-equilibrium clusters in three dimensions frequently have fractal dimensions near 2, so that it is often not possible to discriminate on the basis of this geometrical property. A survey of the anisotropy of a wide variety of polymeric structures (linear and ring random and self-avoiding random walks, percolation clusters, lattice animals, diffusion-limited aggregates, and Eden clusters) based on the principal components of both the radius of gyration and electric polarizability tensor indicates, perhaps counter-intuitively, that self-similar equilibrium clusters tend to be intrinsically anisotropic at all sizes, while non-equilibrium processes such as diffusion-limited aggregation or Eden growth tend to be isotropic in the large-mass limit, providing a potential means of discriminating these clusters experimentally if anisotropy could be determined along with the fractal dimension. Equilibrium polymer structures, such as flexible polymer chains, are normally self-similar due to the existence of only a single relevant length scale, and are thus anisotropic at all length scales, while non-equilibrium polymer structures that grow irreversibly in time eventually become isotropic if there is no difference in the average growth rates in different directions. There is apparently no proof of these general trends and little theoretical insight into what controls the universal anisotropy in equilibrium polymer structures of various kinds. This is an obvious topic of theoretical investigation, as well as a matter of practical interest. To address this general problem, we consider two experimentally accessible ratios, one between the hydrodynamic and gyration radii, the other

  13. Using the chemical equilibrium partitioning space to explore factors influencing the phase distribution of compounds involved in secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Wania, F.; Lei, Y. D.; Wang, C.; Abbatt, J. P. D.; Goss, K.-U.

    2015-03-01

    Many atmospheric and chemical variables influence the partitioning equilibrium between gas phase and condensed phases of compounds implicated in the formation of secondary organic aerosol (SOA). The large number of factors and their interaction makes it often difficult to assess their relative importance and concerted impact. Here we introduce a two-dimensional space which maps regions of dominant atmospheric phase distribution within a coordinate system defined by equilibrium partition coefficients between the gas phase, an aqueous phase and a water-insoluble organic matter (WIOM) phase. Placing compounds formed from the oxidation of n-alkanes, terpenes and mono-aromatic hydrocarbons on the maps based on their predicted partitioning properties allows for a simple graphical assessment of their equilibrium phase distribution behaviour. Specifically, it allows for the simultaneous visualisation and quantitative comparison of the impact on phase distribution of changes in atmospheric parameters (such as temperature, salinity, WIOM-phase polarity, organic aerosol load, and liquid water content) and chemical properties (such as oxidation state, molecular size, functionalisation, and dimerisation). The graphical analysis reveals that the addition of hydroxyl, carbonyl and carboxyl groups increases the affinity of aliphatic, alicyclic and aromatic hydrocarbons for the aqueous phase more rapidly than their affinity for WIOM, suggesting that the aqueous phase may often be relevant even for substances that are considerably larger than the C2 and C3 compounds that are typically believed to be associated with aqueous SOA. In particular, the maps identify some compounds that contribute to SOA formation if partitioning to both WIOM and aqueous phase is considered but would remain in the gas phase if either condensed phase were neglected. For example, many semi-volatile α-pinene oxidation products will contribute to aqueous SOA under the conditions of high liquid water content

  14. Using the chemical equilibrium partitioning space to explore factors influencing the phase distribution of compounds involved in secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Wania, F.; Lei, Y. D.; Wang, C.; Abbatt, J. P. D.; Goss, K.-U.

    2014-10-01

    Many atmospheric and chemical variables influence the partitioning equilibrium between gas phase and condensed phases of compounds implicated in the formation of secondary organic aerosol (SOA). The large number of factors and their interaction makes it often difficult to assess their relative importance and concerted impact. Here we introduce a two-dimensional space, which maps regions of dominant atmospheric phase distribution within a coordinate system defined by equilibrium partitioning coefficients between the gas phase, an aqueous phase and a water insoluble organic matter (WIOM) phase. Placing compounds formed from the oxidation of n-alkanes, terpenes and mono-aromatic hydrocarbons on the maps based on their predicted partitioning properties allows for a simple graphical assessment of their equilibrium phase distribution behaviour. Specifically, it allows for the simultaneous visualization and quantitative comparison of the impact on phase distribution of changes in atmospheric parameters (such as temperature, salinity, WIOM phase polarity, organic aerosol load, and liquid water content), and chemical properties (such as oxidation state, molecular size, functionalization, and dimerisation). The graphical analysis reveals that the addition of hydroxyl, carbonyl and carboxyl groups increases the affinity of aliphatic, alicyclic and aromatic hydrocarbons for the aqueous phase more rapidly than their affinity for WIOM, suggesting that the aqueous phase may often be relevant even for substances that are considerably larger than the C2 and C3 compounds that are typically believed to be associated with aqueous SOA. In particular, the maps identify some compounds that contribute to SOA formation if partitioning to both WIOM and aqueous phase is considered, but would remain in the gas phase if either condensed phase were neglected. For example, many semi-volatile α-pinene oxidation products will contribute to aqueous SOA under the high liquid water content

  15. Application of Molecular Interaction Volume Model for Phase Equilibrium of Sn-Based Binary System in Vacuum Distillation

    NASA Astrophysics Data System (ADS)

    Kong, Lingxin; Yang, Bin; Xu, Baoqiang; Li, Yifu

    2014-09-01

    Based on the molecular interaction volume model (MIVM), the activities of components of Sn-Sb, Sb-Bi, Sn-Zn, Sn-Cu, and Sn-Ag alloys were predicted. The predicted values are in good agreement with the experimental data, which indicate that the MIVM is of better stability and reliability due to its good physical basis. A significant advantage of the MIVM lies in its ability to predict the thermodynamic properties of liquid alloys using only two parameters. The phase equilibria of Sn-Sb and Sn-Bi alloys were calculated based on the properties of pure components and the activity coefficients, which indicates that Sn-Sb and Sn-Bi alloys can be separated thoroughly by vacuum distillation. This study extends previous investigations and provides an effective and convenient model on which to base refining simulations for Sn-based alloys.

  16. Experimental investigation of bioethanol liquid phase dehydration using natural clinoptilolite.

    PubMed

    Karimi, Samira; Ghobadian, Barat; Omidkhah, Mohammad-Reza; Towfighi, Jafar; Tavakkoli Yaraki, Mohammad

    2016-05-01

    An experimental study of bioethanol adsorption on natural Iranian clinoptilolite was carried out. Dynamic breakthrough curves were used to investigate the best adsorption conditions in bioethanol liquid phase. A laboratory setup was designed and fabricated for this purpose. In order to find the best operating conditions, the effect of liquid pressure, temperature and flow rate on breakthrough curves and consequently, maximum ethanol uptake by adsorbent were studied. The effects of different variables on final bioethanol concentration were investigated using Response Surface Methodology (RSM). The results showed that by working at optimum condition, feed with 96% (v/v) initial ethanol concentration could be purified up to 99.9% (v/v). In addition, the process was modeled using Box-Behnken model and optimum operational conditions to reach 99.9% for final ethanol concentration were found equal to 10.7 °C, 4.9 bar and 8 mL/min for liquid temperature, pressure and flow rate, respectively. Therefore, the selected natural Iranian clinoptilolite was found to be a promising adsorbent material for bioethanol dehydration process. PMID:27222748

  17. Experimental Investigation of Ice Phase Change Material Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.; Stephan, Ryan A.

    2012-01-01

    Phase change materials (PCM) may be useful for spacecraft thermal control systems that involve cyclical heat loads or cyclical thermal environments. Thermal energy can be stored in the PCM during peak heat loads or in adverse thermal environments. The stored thermal energy can then be released later during minimum heat loads or in more favorable thermal environments. This can result in a decreased turndown ratio for the radiator and a reduced system mass. The use of water as a PCM rather than the more traditional paraffin wax has the potential for significant mass reduction since the latent heat of formation of water is approximately 70% greater than that of wax. One of the potential drawbacks of using ice as a PCM is its potential to rupture its container as water expands upon freezing. In order to develop a space qualified ice PCM heat exchanger, failure mechanisms must first be understood. Therefore, a methodical experimental investigation has been undertaken to demonstrate and document specific failure mechanisms due to ice expansion in the PCM. A number of ice PCM heat exchangers were fabricated and tested. Additionally, methods for controlling void location in order to reduce the risk of damage due to ice expansion were investigated. This paper presents an overview of the results of this investigation from the past three years.

  18. Experimental investigation of bioethanol liquid phase dehydration using natural clinoptilolite

    PubMed Central

    Karimi, Samira; Ghobadian, Barat; Omidkhah, Mohammad-Reza; Towfighi, Jafar; Tavakkoli Yaraki, Mohammad

    2016-01-01

    An experimental study of bioethanol adsorption on natural Iranian clinoptilolite was carried out. Dynamic breakthrough curves were used to investigate the best adsorption conditions in bioethanol liquid phase. A laboratory setup was designed and fabricated for this purpose. In order to find the best operating conditions, the effect of liquid pressure, temperature and flow rate on breakthrough curves and consequently, maximum ethanol uptake by adsorbent were studied. The effects of different variables on final bioethanol concentration were investigated using Response Surface Methodology (RSM). The results showed that by working at optimum condition, feed with 96% (v/v) initial ethanol concentration could be purified up to 99.9% (v/v). In addition, the process was modeled using Box–Behnken model and optimum operational conditions to reach 99.9% for final ethanol concentration were found equal to 10.7 °C, 4.9 bar and 8 mL/min for liquid temperature, pressure and flow rate, respectively. Therefore, the selected natural Iranian clinoptilolite was found to be a promising adsorbent material for bioethanol dehydration process. PMID:27222748

  19. Experimental Investigation of Ice Phase Change Material Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.; Stephan, Ryan A.

    2011-01-01

    Phase change materials (PCM) may be useful for spacecraft thermal control systems that involve cyclical heat loads or cyclical thermal environments. Thermal energy can be stored in the PCM during peak heat loads or in adverse thermal environments. The stored thermal energy can then be released later during minimum heat loads or in more favorable thermal environments. This can result in a decreased turndown ratio for the radiator and a reduced system mass. The use of water as a PCM rather than the more traditional paraffin wax has the potential for significant mass reduction since the latent heat of formation of water is approximately 70% greater than that of wax. One of the potential drawbacks of using ice as a PCM is its potential to rupture its container as water expands upon freezing. In order to develop a space qualified ice PCM heat exchanger, failure mechanisms must first be understood. Therefore, a methodical experimental investigation has been undertaken to demonstrate and document specific failure mechanisms due to ice expansion in the PCM. A number of ice PCM heat exchangers were fabricated and tested. Additionally, methods for controlling void location in order to reduce the risk of damage due to ice expansion were investigated. This paper presents an overview of the results of this investigation from the past three years.

  20. Experimental verification of equilibrium para-hydrogen levels in hydrogen moderators irradiated by spallation neutrons at J-PARC

    NASA Astrophysics Data System (ADS)

    Teshigawara, M.; Harada, M.; Tatsumoto, H.; Aso, T.; Ohtsu, K.; Takada, H.; Futakawa, M.; Ikeda, Y.

    2016-02-01

    By sampling gaseous hydrogen from a circulating liquid hydrogen loop for Laser Raman spectroscopy, we measured the para-/ortho-hydrogen fractions in liquid hydrogen under neutron irradiation for the first time to identify whether irradiated hydrogen has an elevated ortho-hydrogen fraction. This measurement indicates that para-hydrogen equilibrium persists at 300 kW proton power in the presence of an iron(III) oxide hydroxide [Fe(OH)3] catalyst. The measurements will be repeated as the power at the Japan Proton Accelerator Research Complex (J-PARC) increases to the MW level.

  1. Determination of methane concentrations in water in equilibrium with sI methane hydrate in the absence of a vapor phase by in situ Raman spectroscopy

    USGS Publications Warehouse

    Lu, W.; Chou, I.-Ming; Burruss, R.C.

    2008-01-01

    Most submarine gas hydrates are located within the two-phase equilibrium region of hydrate and interstitial water with pressures (P) ranging from 8 to 60 MPa and temperatures (T) from 275 to 293 K. However, current measurements of solubilities of methane in equilibrium with hydrate in the absence of a vapor phase are limited below 20 MPa and 283.15 K, and the differences among these data are up to 30%. When these data were extrapolated to other P-T conditions, it leads to large and poorly known uncertainties. In this study, in situ Raman spectroscopy was used to measure methane concentrations in pure water in equilibrium with sI (structure one) methane hydrate, in the absence of a vapor phase, at temperatures from 276.6 to 294.6 (??0.3) K and pressures at 10, 20, 30 and 40 (??0.4%) MPa. The relationship among concentration of methane in water in equilibrium with hydrate, in mole fraction [X(CH4)], the temperature in K, and pressure in MPa was derived as: X(CH4) = exp [11.0464 + 0.023267 P - (4886.0 + 8.0158 P)/T]. Both the standard enthalpy and entropy of hydrate dissolution at the studied T-P conditions increase slightly with increasing pressure, ranging from 41.29 to 43.29 kJ/mol and from 0.1272 to 0.1330 kJ/K ?? mol, respectively. When compared with traditional sampling and analytical methods, the advantages of our method include: (1) the use of in situ Raman signals for methane concentration measurements eliminates possible uncertainty caused by sampling and ex situ analysis, (2) it is simple and efficient, and (3) high-pressure data can be obtained safely. ?? 2007 Elsevier Ltd. All rights reserved.

  2. Phase equilibrium in argon films stabilized by homogeneous surfaces and thermodynamics of two-stage melting transition

    SciTech Connect

    Ustinov, E. A.

    2014-02-21

    Freezing of gases adsorbed on open surfaces (e.g., graphite) and in narrow pores is a widespread phenomenon which is a subject of a large number of publications. Modeling of the gas/liquid–solid transition is usually accomplished with a molecular simulation technique. However, quantitative analysis of the gas/liquid–solid coexistence and thermodynamic properties of the solid layer still encounters serious difficulties. This is mainly due to the effect of simulation box size on the lattice constant. Since the lattice constant is a function of loading and temperature, once the ordering transition has occurred, the simulation box size must be corrected in the course of simulation according to the Gibbs–Duhem equation. A significant problem is also associated with accurate prediction of the two-dimensional liquid–solid coexistence because of a small difference in densities of coexisting phases. The aim of this study is thermodynamic analysis of the two-dimensional phase coexistence in systems involving crystal-like free of defects layers in narrow slit pores. A special attention was paid to the determination of triple point temperatures. It is shown that intrinsic properties of argon monolayer adsorbed on the graphite surface are similar to those of isolated monolayer accommodated in the slit pore having width of two argon collision diameters. Analysis of the latter system is shown to be clearer and less time-consuming than the former one, which has allowed for explanation of the experimentally observed two-stage melting transition of argon monolayer on graphite without invoking the periodic surface potential modulation and orientational transition.

  3. Phase equilibrium in argon films stabilized by homogeneous surfaces and thermodynamics of two-stage melting transition.

    PubMed

    Ustinov, E A

    2014-02-21

    Freezing of gases adsorbed on open surfaces (e.g., graphite) and in narrow pores is a widespread phenomenon which is a subject of a large number of publications. Modeling of the gas/liquid-solid transition is usually accomplished with a molecular simulation technique. However, quantitative analysis of the gas/liquid-solid coexistence and thermodynamic properties of the solid layer still encounters serious difficulties. This is mainly due to the effect of simulation box size on the lattice constant. Since the lattice constant is a function of loading and temperature, once the ordering transition has occurred, the simulation box size must be corrected in the course of simulation according to the Gibbs-Duhem equation. A significant problem is also associated with accurate prediction of the two-dimensional liquid-solid coexistence because of a small difference in densities of coexisting phases. The aim of this study is thermodynamic analysis of the two-dimensional phase coexistence in systems involving crystal-like free of defects layers in narrow slit pores. A special attention was paid to the determination of triple point temperatures. It is shown that intrinsic properties of argon monolayer adsorbed on the graphite surface are similar to those of isolated monolayer accommodated in the slit pore having width of two argon collision diameters. Analysis of the latter system is shown to be clearer and less time-consuming than the former one, which has allowed for explanation of the experimentally observed two-stage melting transition of argon monolayer on graphite without invoking the periodic surface potential modulation and orientational transition. PMID:24559359

  4. Effects of Al2O3 and CaO/SiO2 Ratio on Phase Equilbria in the ZnO-"FeO"-Al2O3-CaO-SiO2 System in Equilibrium with Metallic Iron

    NASA Astrophysics Data System (ADS)

    Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

    2011-02-01

    The phase equilibria and liquidus temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2 system in equilibrium with metallic iron have been determined experimentally in the temperature range 1383 K to 1573 K (1150 °C to 1300 °C). The experimental conditions were selected to characterize lead blast furnace and imperial smelting furnace slags. The results are presented in a form of pseudoternary sections ZnO-"FeO"-(Al2O3 + CaO + SiO2) with fixed CaO/SiO2 and (CaO + SiO2)/Al2O3 ratios. It was found that wustite and spinel are the major primary phases in the composition range investigated. Effects of Al2O3 concentration as well as the CaO/SiO2 ratio on the primary phase field, the liquidus temperature, and the partitioning of ZnO between liquid and solid phases have been discussed for zinc-containing slags.

  5. Phase Distribution Phenomena for Simulated Microgravity Conditions: Experimental Work

    NASA Technical Reports Server (NTRS)

    Singhal, Maneesh; Bonetto, Fabian J.; Lahey, R. T., Jr.

    1996-01-01

    This report summarizes the work accomplished at Rensselaer to study phase distribution phenomenon under simulated microgravity conditions. Our group at Rensselaer has been able to develop sophisticated analytical models to predict phase distribution in two-phase flows under a variety of conditions. These models are based on physics and data obtained from carefully controlled experiments that are being conducted here. These experiments also serve to verify the models developed.

  6. Phase Distribution Phenomena for Simulated Microgravity Conditions: Experimental Work

    NASA Technical Reports Server (NTRS)

    Singhal, Maneesh; Bonetto, Fabian J.; Lahey, R. T., Jr.

    1996-01-01

    This report summarizes the work accomplished at Rensselaer to study phase distribution phenomenon under simulated microgravity conditions. Our group at Rensselaer has been able to develop sophisticated analytical models to predict phase distribution in two-phase flows under variety of conditions. These models are based on physics and data obtained from carefully controlled experiments that are being conducted here. These experiments also serve to verify the models developed.

  7. Condensed-phase versus gas-phase ozonolysis of catechol: A combined experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Barnum, Timothy J.; Medeiros, Nicholas; Hinrichs, Ryan Z.

    2012-08-01

    Anthropogenic emissions of volatile aromatic compounds contribute to the formation of secondary organic aerosols (SOA), especially in urban environments. Aromatic SOA precursors typically require oxidation by hydroxyl radicals, although recent work suggests that ozonolysis of 1,2-benzenediols produces SOA in high yields. We employed attenuated total reflectance and transmission infrared spectroscopy to investigate the heterogeneous ozonolysis of catechol thin films. Formation of the dominant condensed-phase product muconic acid was highly dependent on relative humidity (RH) with few products detected below 40% RH and a maximum reactive uptake coefficient of γ = (5.6 ± 0.5) × 10-5 measured at 81.2% RH. We also performed quantum chemical calculations mapping out several reaction pathways for the homogeneous ozonolysis of gaseous catechol. 1,3-cycloaddition transition states were rate limiting with the most favorable activation energies at 45.4 and 47.1 kJ mol-1 [CCSD(T)/6-311++G(d,p)] corresponding to addition across and adjacent to the diol Cdbnd C, respectively. Gas-phase rate constants, calculated using transition state theory, were six orders of magnitude slower than experimental values. In contrast, a calculated activation energy was lower for the ozonolysis of a catechol•H2O complex, which serves as a first-approximation for modeling the ozonolysis of condensed-phase catechol. These combined results suggests that homogeneous ozonolysis of catechol may not be important for the formation of secondary organic aerosols but that ozonolysis of surface-adsorbed catechol may contribute to SOA growth.

  8. Aerothermal modeling, phase 1. Volume 2: Experimental data

    NASA Technical Reports Server (NTRS)

    Kenworthy, M. J.; Correa, S. M.; Burrus, D. L.

    1983-01-01

    The experimental test effort is discussed. The test data are presented. The compilation is divided into sets representing each of the 18 experimental configurations tested. A detailed description of each configuration, and plots of the temperature difference ratio parameter or pattern factor parameter calculated from the test data are also provided.

  9. Partition Equilibrium

    NASA Astrophysics Data System (ADS)

    Feldman, Michal; Tennenholtz, Moshe

    We introduce partition equilibrium and study its existence in resource selection games (RSG). In partition equilibrium the agents are partitioned into coalitions, and only deviations by the prescribed coalitions are considered. This is in difference to the classical concept of strong equilibrium according to which any subset of the agents may deviate. In resource selection games, each agent selects a resource from a set of resources, and its payoff is an increasing (or non-decreasing) function of the number of agents selecting its resource. While it has been shown that strong equilibrium exists in resource selection games, these games do not possess super-strong equilibrium, in which a fruitful deviation benefits at least one deviator without hurting any other deviator, even in the case of two identical resources with increasing cost functions. Similarly, strong equilibrium does not exist for that restricted two identical resources setting when the game is played repeatedly. We prove that for any given partition there exists a super-strong equilibrium for resource selection games of identical resources with increasing cost functions; we also show similar existence results for a variety of other classes of resource selection games. For the case of repeated games we identify partitions that guarantee the existence of strong equilibrium. Together, our work introduces a natural concept, which turns out to lead to positive and applicable results in one of the basic domains studied in the literature.

  10. Phase Equilibria in Ferrous Calcium Silicate Slags: Part II. Evaluation of Experimental Data and Computer Thermodynamic Models

    NASA Astrophysics Data System (ADS)

    Nikolic, Stanko; Henao, Hector; Hayes, Peter C.; Jak, Evgueni

    2008-04-01

    Ferrous calcium silicate slags (described by the FeO-Fe2O3-CaO-SiO2 system) are the basis for a number of slag systems used in nonferrous smelting. Characterization of this slag system is necessary to improve the design and optimization parameters of new processes, including fluxing and operating temperatures. Particularly of interest are the phase relations at intermediate oxygen partial pressures relevant to processes such as copper converting. Experimental data on the phase equilibria of these slags at controlled oxygen partial pressures in the temperature range between 1200 °C and 1350 °C are discussed, differences between various data sources are analyzed, and discrepancies are resolved. An evaluation of two thermodynamic computer models is undertaken to verify the computer-aided predictions using the experimental data. New experimental data for this system are reported for the temperature condition of 1300 °C, defined using the equilibration/rapid-quenching/electron probe microanalysis (EPMA) with wavelength dispersive detectors technique. This new information, combined with results from the previous study, has enabled the equilibrium liquidus compositions to be defined over a wide range of temperatures and oxygen partial pressures.