Science.gov

Sample records for phase equilibria studies

  1. Phase Equilibria Diagrams Database

    National Institute of Standards and Technology Data Gateway

    SRD 31 NIST/ACerS Phase Equilibria Diagrams Database (PC database for purchase)   The Phase Equilibria Diagrams Database contains commentaries and more than 21,000 diagrams for non-organic systems, including those published in all 21 hard-copy volumes produced as part of the ACerS-NIST Phase Equilibria Diagrams Program (formerly titled Phase Diagrams for Ceramists): Volumes I through XIV (blue books); Annuals 91, 92, 93; High Tc Superconductors I & II; Zirconium & Zirconia Systems; and Electronic Ceramics I. Materials covered include oxides as well as non-oxide systems such as chalcogenides and pnictides, phosphates, salt systems, and mixed systems of these classes.

  2. Experimental Studies of Phase Equilibria of Meteorites and Planetary Bodies

    NASA Technical Reports Server (NTRS)

    Stolper, Edward M.

    2005-01-01

    The primary theme of this project was the application of experimental petrology and geochemistry to a variety of problems in meteoritics and planetary geology. The studies were designed to help develop constraints on the histories of primitive meteorites and their components, the environments in which they formed and evolved, and to understand quantitatively the processes involved in the evolution of igneous rocks on the earth and other planetary bodies. We undertook several projects relating to the origin of CAIs and chondrules. Systematics in the thermodynamic properties of CAI-like liquids were investigated and used to elucidate speciation of multi-valent cations and sulfide capacity of silicate melts and to constrain redox conditions and the vapor pressures of volatile species over molten chondrules. We experimentally determined vanadium speciation in meteoritic pyroxenes and in pyroxenes crystallized from CAI-like melts under very reducing conditions. We also found that bulk oxygen isotope compositions of chondrules in the moderately unequilibrated LL chondrites are related to the relative timing of plagioclase crystallization. We completed an experimental study on the vaporization of beta-SiC and SiO2 (glass or cristobalite) in reducing gases and established the conditions under which these presolar grains could have survived in the solar nebula. We expanded our technique for determining the thermodynamic properties of minerals and liquids to iron-bearing systems. We determined activity-composition relationships in Pt-Fe, Pt-Cr and Pt-Fe-Cr alloys. Results were used to determine the thermodynamic properties of chromite-picrochromite spinels including the free energy of formation of end-member FeCr2O4. We also established a new approach for evaluating Pt-Fe saturation experiments. We calculated the T-fO2 relationships in equilibrated ordinary chondrites and thereby constrained the conditions of metamorphism in their parent bodies.

  3. Experimental technique for studying high-temperature phase equilibria in reactive molten metal based systems

    NASA Astrophysics Data System (ADS)

    Ermoline, Alexandre

    The general objective of this work is to develop an experimental technique for studying the high-temperature phase compositions and phase equilibria in molten metal-based binary and ternary systems, such as Zr-O-N, B-N-O, Al-O, and others. A specific material system of Zr-O-N was selected for studying and testing this technique. The information about the high-temperature phase equilibria in reactive metal-based systems is scarce and their studying is difficult because of chemical reactions occurring between samples and essentially any container materials, and causing contamination of the system. Containerless microgravity experiments for studying equilibria in molten metal-gas systems were designed to be conducted onboard of a NASA KC-135 aircraft flying parabolic trajectories. A uniaxial apparatus suitable for acoustic levitation, laser heating, and splat quenching of small samples was developed and equipped with computer-based controller and optical diagnostics. Normal-gravity tests were conducted to determine the most suitable operating parameters of the levitator by direct observations of the levitated samples, as opposed to more traditional pressure mapping of the acoustic field. The size range of samples that could be reliably heated and quenched in this setup was determined to be on the order of 1--3 mm. In microgravity experiments, small spherical specimens (1--2 mm diameter), prepared as pressed, premixed solid components, ZrO2, ZrN, and Zr powders, were acoustically levitated inside an argon-filled chamber at one atmosphere and heated by a CO2 laser. The levitating samples could be continuously laser heated for about 1 sec, resulting in local sample melting. The sample stability in the vertical direction was undisturbed by simultaneous laser heating. Oscillations of the levitating sample in the horizontal direction increased while it was heated, which eventually resulted in the movement of the sample away from its stable levitation position and the laser

  4. Phase Equilibria and Crystallography of Ceramic Oxides

    PubMed Central

    Wong-Ng, W.; Roth, R. S.; Vanderah, T. A.; McMurdie, H. F.

    2001-01-01

    Research in phase equilibria and crystallography has been a tradition in the Ceramics Division at National Bureau of Standards/National Institute of Standatrds and Technology (NBS/NIST) since the early thirties. In the early years, effort was concentrated in areas of Portland cement, ceramic glazes and glasses, instrument bearings, and battery materials. In the past 40 years, a large portion of the work was related to electronic materials, including ferroelectrics, piezoelectrics, ionic conductors, dielectrics, microwave dielectrics, and high-temperature superconductors. As a result of the phase equilibria studies, many new compounds have been discovered. Some of these discoveries have had a significant impact on US industry. Structure determinations of these new phases have often been carried out as a joint effort among NBS/NIST colleagues and also with outside collaborators using both single crystal and neutron and x-ray powder diffraction techniques. All phase equilibria diagrams were included in Phase Diagrams for Ceramists, which are collaborative publications between The American Ceramic Society (ACerS) and NBS/NIST. All x-ray powder diffraction patterns have been included in the Powder Diffraction File (PDF). This article gives a brief account of the history of the development of the phase equilibria and crystallographic research on ceramic oxides in the Ceramics Division. Represented systems, particularly electronic materials, are highlighted. PMID:27500068

  5. Phase Equilibria Studies in the SiO2-K2O-CaO System

    NASA Astrophysics Data System (ADS)

    Chen, Mao; Hou, Xinmei; Chen, Junhong; Zhao, Baojun

    2016-06-01

    Phase equilibria in the SiO2-K2O-CaO system have been experimentally investigated in the SiO2-rich area. High-temperature equilibration, rapid quenching, and electron probe X-ray microanalysis (EPMA) techniques have been used in this study. K2O may vaporize during EPMA measurements causing significant uncertainties. In the present study, optimum EPMA operating conditions have been determined in order to accurately measure K2O concentrations in the quenched samples. The compositions of all phases present in the quenched sample were measured using EPMA with optimum operating parameters. The following primary phase fields were identified in the composition range investigated: SiO2, CaO·SiO2, 2CaO·SiO2, K2O·2CaO·2SiO2, and K2O·6CaO·4SiO2. The isotherms between 1273 K and 1473 K (1000 °C and 1200 °C) in these primary phase fields have been determined. The presence of the compounds K2O·2CaO·2SiO2 and K2O·6CaO·4SiO2 has been confirmed.

  6. An efficient and general approach for implementing thermodynamic phase equilibria information in geophysical and geodynamic studies

    NASA Astrophysics Data System (ADS)

    Afonso, Juan Carlos; Zlotnik, Sergio; Díez, Pedro

    2015-10-01

    We present a flexible, general, and efficient approach for implementing thermodynamic phase equilibria information (in the form of sets of physical parameters) into geophysical and geodynamic studies. The approach is based on Tensor Rank Decomposition methods, which transform the original multidimensional discrete information into a separated representation that contains significantly fewer terms, thus drastically reducing the amount of information to be stored in memory during a numerical simulation or geophysical inversion. Accordingly, the amount and resolution of the thermodynamic information that can be used in a simulation or inversion increases substantially. In addition, the method is independent of the actual software used to obtain the primary thermodynamic information, and therefore, it can be used in conjunction with any thermodynamic modeling program and/or database. Also, the errors associated with the decomposition procedure are readily controlled by the user, depending on her/his actual needs (e.g., preliminary runs versus full resolution runs). We illustrate the benefits, generality, and applicability of our approach with several examples of practical interest for both geodynamic modeling and geophysical inversion/modeling. Our results demonstrate that the proposed method is a competitive and attractive candidate for implementing thermodynamic constraints into a broad range of geophysical and geodynamic studies. MATLAB implementations of the method and examples are provided as supporting information and can be downloaded from the journal's website.

  7. High temperature phase equilibria studies in the Bi-Sr-Ca-Cu-O-Ag system

    SciTech Connect

    Margulies, Lawrence

    1999-11-08

    A variety of experimental techniques were utilized to examine the high temperature phase equilibria in the Bi-Sr-Ca-Cu-O-Ag system. Quenching studies were used to determine the liquid solubility of Ag in the Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (Bi2212) melt and the details of the peritectic decomposition pathway of Bi2212 as a function on Ag content and oxygen partial pressure (PO{sub 2}). A liquid immiscibility region between oxide and Ag liquids in the 8--98 at% range was found above 900 C. Two eutectics were found in the Bi2212-Ag pseudobinary. On the oxide rich side, a eutectic exists at approximately 4 at% Ag. On the Ag rich side, a eutectic exists at approximately 98 at% Ag at a temperature of 15 C below the melting point of pure Ag. Six distinct solid phases were found to be in equilibrium with the partial melt within the Ag content and PO{sub 2} range studied. The stability of these solid phases were found to be highly sensitive to PO{sub 2}, and to a much lesser extent Ag content. High temperature x-ray diffraction (HTXRD) studies of this system are in conflict with these results. It is suggested that these discrepancies are due to experimental artifacts caused by the significant thermal gradients and lack of full bulk sampling which is inherent in conventional HTXRD designs. In part 2, a new furnace design compatible with synchrotron radiation sources is introduced to address these problems. This design allows for full bulk sampling in a low thermal gradient environment using Debye-Scherrer transmission geometry. Sample spinning is also introduced in the design to eliminate preferred orientation and incomplete powder averaging and allow for quantitative phase analysis and structural refinement. Studies on model systems are presented to demonstrate the capabilities for high resolution structural studies (Al{sub 2}O{sub 3}) and time resolved phase transformation studies (SrCO{sub 3}). Finally, the Bi2212 system is examined to confirm the quenching results

  8. Multicomponent three-phase equilibria

    SciTech Connect

    Ho, C.K.

    1995-06-01

    This paper presents the relations that describe thermodynamic equilibrium in a three-phase system. Multiple components, including air, water, and oil components, are considered in three phases: (1) aqueous, (2) oil, and (3) gas. Primary variables are specified for each of seven possible phase combinations. These primary variables are then used to determine the necessary secondary variables to completely describe the system. Criteria are also developed to check the stability of each phase configuration and determine possible transitions from one phase configuration to another phase configuration via phase appearances and disappearances.

  9. Direct phase coexistence molecular dynamics study of the phase equilibria of the ternary methane-carbon dioxide-water hydrate system.

    PubMed

    Michalis, Vasileios K; Tsimpanogiannis, Ioannis N; Stubos, Athanassios K; Economou, Ioannis G

    2016-09-14

    Molecular dynamics simulation is used to predict the phase equilibrium conditions of a ternary hydrate system. In particular, the direct phase coexistence methodology is implemented for the determination of the three-phase coexistence temperature of the methane-carbon dioxide-water hydrate system at elevated pressures. The TIP4P/ice, TraPPE-UA and OPLS-UA forcefields for water, carbon dioxide and methane respectively are used, in line with our previous studies of the phase equilibria of the corresponding binary hydrate systems. The solubility in the aqueous phase of the guest molecules of the respective binary and ternary systems is examined under hydrate-forming conditions, providing insight into the predictive capability of the methodology as well as the combination of these forcefields to accurately describe the phase behavior of the ternary system. The three-phase coexistence temperature is calculated at 400, 1000 and 2000 bar for two compositions of the methane-carbon dioxide mixture. The predicted values are compared with available calculations with satisfactory agreement. An estimation is also provided for the fraction of the guest molecules in the mixed hydrate phase under the conditions examined. PMID:27507133

  10. High-temperature phase equilibria studies in the Bi-Sr- Ca-Cu-O-Ag system

    NASA Astrophysics Data System (ADS)

    Margulies, Lawrence

    A variety of experimental techniques were utilized to examine the high temperature phase equilibria in the Bi- Sr-Ca-Cu-O-Ag system. Quenching studies were used to determine the liquid solubility of Ag in the Bi2Sr 2CaCu2O8 (Bi2212) melt and the details of the peritectic decomposition pathway of Bi2212 as a function on Ag content and oxygen partial pressure (PO2). A liquid immiscibility region between oxide and Ag liquids in the 8-98 at% range was found above 900°C. Two eutectics were found in the Bi2212-Ag pseudo-binary. On the oxide rich side, a eutectic exists at approximately 4 at% Ag. On the Ag rich side, a eutectic exists at approximately 98 at% Ag at a temperature of 15°C below the melting point of pure Ag. Six distinct solid phases were found to be in equilibrium with the partial melt within the Ag content and PO2 range studied. The stability of these solid phases were found to be highly sensitive to PO2, and to a much lesser extent Ag content. High temperature x-ray diffraction (HTXRD) studies of this system are in conflict with these results. It is suggested that these discrepancies are due to experimental artifacts caused by the significant thermal gradients and lack of full bulk sampling which is inherent in conventional HTXRD designs. In part II, a new furnace design compatible with synchrotron radiation sources is introduced to address these problems. This design allows for full bulk sampling in a low thermal gradient environment using Debye- Scherrer transmission geometry. Sample spinning is also introduced in the design to eliminate preferred orientation and incomplete powder averaging and allow for quantitative phase analysis and structural refinement. Studies on model systems are presented to demonstrate the capabilities for high resolution structural studies (Al 2O3) and time resolved phase transformation studies (SrCO 3). Finally, the Bi2212 system is examined to confirm the quenching results of part I, and to demonstrate the degree to which

  11. Phase equilibria for complex fluid mixtures

    SciTech Connect

    Prausnitz, J.M.

    1983-04-01

    After defining complex mixtures, attention is given to the canonical procedure used for the thermodynamics of fluid mixtures: first, we establish a suitable, idealized reference system and then we establish a perturbation (or excess function) which corrects the idealized system for real behavior. For complex mixtures containing identified components (e.g. alcohols, ketones, water) discussion is directed at possible techniques for extending to complex mixtures our conventional experience with reference systems and perturbations for simple mixtures. Possible extensions include generalization of the quasi-chemical approximation (local compositions) and superposition of chemical equilibria (association and solvation) on a physical equation of state. For complex mixtures containing unidentified components (e.g. coal-derived fluids), a possible experimental method is suggested for characterization; conventional procedures can then be used to calculate phase equilibria using the concept of pseudocomponents whose properties are given by the characterization data. Finally, as an alternative to the pseudocomponent method, a brief introduction is given to phase-equilibrium calculations using continuous thermodynamics.

  12. 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.

  13. Crystallization history of lunar picritic basalt sample 12002 - Phase-equilibria and cooling-rate studies

    NASA Technical Reports Server (NTRS)

    Walker, D.; Kirkpatrick, R. J.; Longhi, J.; Hays, J. F.

    1976-01-01

    Experimental crystallization of a lunar picrite composition (sample 12002) at controlled linear cooling rates produces systematic changes in the temperature at which crystalline phases appear, in the texture, and in crystal morphology as a function of cooling rate. Phases crystallize in the order olivine, chromium spinel, pyroxene, plagioclase, and ilmenite during equilibrium crystallization, but ilmenite and plagioclase reverse their order of appearance and silica crystallizes in the groundmass during controlled cooling experiments. The partition of iron and magnesium between olivine and liquid is independent of cooling rate, temperature, and pressure. Comparison of the olivine nucleation densities in the lunar sample and in the experiments indicates that the sample began cooling at about 1 deg C/hr. Pyroxene size, chemistry, and growth instability spacings, as well as groundmass coarseness, all suggest that the cooling rate subsequently decreased by as much as a factor of 10 or more. The porphyritic texture of this sample, then, is produced at a decreasing, rather than a discontinuously increasing, cooling rate.

  14. Electronic structure and phase equilibria in ternary substitutional alloys

    SciTech Connect

    Traiber, A.J.S.; Allen, S.M.; Turchi, P.E.A.; Waterstrat, R.M.

    1996-04-26

    A reliable, consistent scheme to study phase equilibria in ternary substitutional alloys based on the tight-binding approximation is presented. With electronic parameters from linear muffin-tin orbital calculations, the computed density of states and band structures compare well with those from more accurate {ital ab}{ital initio} calculations. Disordered alloys are studied within the tight-binding coherent-potential approximation extended to alloys; energetics of ordered systems are obtained through effective pair interactions computed with the general perturbation method; and partially ordered alloys are studied with a novel simplification of the molecular coherent-potential approximation combined with the general perturbation method. The formalism is applied to bcc-based Zr-Ru-Pd alloys which are promising candidates for medical implant devices. Using energetics obtained from the above scheme, we apply the cluster- variation method to study phase equilibria for particular pseudo- binary alloys and show that results are consistent with observed behavior of electronic specific heat coefficient with composition for Zr{sub 0.5}(Ru, Pd){sub 0.5}.

  15. Phase Equilibria Study of the ZnO-"FeO"-SiO2-Al2O3 System at Po2 10-8 atm

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Phase equilibria studies on ZnO-"FeO"-SiO2-Al2O3 system have been carried out in the temperature range between 1523 K and 1573 K (1250 °C and 1300 °C) at Po2 10-8 atm. Experimental techniques applied in the present study include high temperature equilibration, quenching, and electron probe X-ray microanalysis (EPMA). The compositions of the phases present in the quenched samples were measured by EPMA and used to construct phase diagrams of the pseudo-ternary sections at fixed Al2O3 content. The experimental results show that, spinel, SiO2, and willemite are the major primary phase fields in the composition range investigated. With 2 wt pct Al2O3 content in the liquid phase, the liquidus temperature can be increased by 35 K in the spinel primary phase in comparison with Al2O3-free system. The partitioning of ZnO and Al2O3 between the spinel and liquid phases is also discussed in the paper.

  16. Computational Thermodynamic Study to Predict Complex Phase Equilibria in the Nickel-Base Superalloy Rene N6

    NASA Technical Reports Server (NTRS)

    Copland, Evan H.; Jacobson, Nathan S.; Ritzert, Frank J.

    2001-01-01

    A previous study by Ritzert et al. on the formation and prediction of topologically closed packed (TCP) phases in the nickel-base superalloy Rene' N6 is re-examined with computational thermodynamics. The experimental data on phase distribution in forty-four alloys with a composition within the patent limits of the nickel-base superalloy Rene' N6 provide a good basis for comparison to and validation of a commercial nickel superalloy database used with ThermoCalc. Volume fraction of the phases and partitioning of the elements are determined for the forty-four alloys in this dataset. The baseline heat treatment of 400 h at 1366 K was used. This composition set is particularly interesting since small composition differences lead to dramatic changes in phase composition. In general the calculated values follow the experimental trends. However, the calculations indicated no TCP phase formation when the experimental measurements gave a volume percent of TCP phase less than 2 percent. When TCP phases were predicted, the calculations under-predict the volume percent of TCP phases by a factor of 2 to 8. The calculated compositions of the gamma and gamma' phases show fair agreement with the measurements. However, the calculated compositions of the P Phase do not agree with those measured. This may be due to inaccuracies in the model parameters for P phase and/or issues with the microprobe analyses of these phases. In addition, phase fraction diagrams and sigma and P phase solvus temperatures are calculated for each of the alloys. These calculations indicate that P phase is the primary TCP phase formed for the alloys considered here at 1366 K. Finally, a series of isopleths are calculated for each of the seven alloying elements. These show the effect of each alloying element on creating TCP phases.

  17. Vapor Pressure Plus: An Experiment for Studying Phase Equilibria in Water, with Observation of Supercooling, Spontaneous Freezing, and the Triple Point

    ERIC Educational Resources Information Center

    Tellinghuisen, Joel

    2010-01-01

    Liquid-vapor, solid-vapor, and solid-liquid-vapor equilibria are studied for the pure substance water, using modern equipment that includes specially fabricated glass cells. Samples are evaporatively frozen initially, during which they typically supercool to -5 to -10 [degrees]C before spontaneously freezing. Vacuum pumping lowers the temperature…

  18. New investigation of phase equilibria in the system Al–Cu–Si

    PubMed Central

    Ponweiser, Norbert; Richter, Klaus W.

    2012-01-01

    The phase equilibria and invariant reactions in the system Al–Cu–Si were investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe micro analysis (EPMA). Isothermal phase equilibria were investigated within two isothermal sections. The isothermal section at 500 °C covers the whole ternary composition range and largely confirms the findings of previous phase diagram investigations. The isothermal section at 700 °C describes phase equilibria only in the complex Cu-rich part of the phase diagram. A new ternary compound τ was found in the region between (Al,Cu)-γ1 and (Cu,Si)-γ and its solubility range was determined. The solubility of Al in κ-CuSi was found to be extremely high at 700 °C. In contrast, no ternary solubility in the β-phase of Cu–Al was found, although this phase is supposed to form a complete solid solution according to previous phase diagram assessments. Two isopleths, at 10 and 40 at.% Si, were investigated by means of DTA and a partial ternary reaction scheme (Scheil diagram) was constructed, based on the current work and the latest findings in the binary systems Al–Cu and Cu–Si. The current study shows that the high temperature equilibria in the Cu-rich corner are still poorly understood and additional studies in this area would be favorable. PMID:22287828

  19. PHASE EQUILIBRIA MODIFICATION BY ELECTRIC FIELDS

    EPA Science Inventory

    The primary focus of this program is to obtain a fundamental understanding of the effects of electric fields on polar and nonpolar mixtures in gas and liquid phases, with the ultimate goal of using this understanding in devising novel means to dramatically improve existing enviro...

  20. Phase Equilibria, Morphologies of Microphase Separation, and Interfacial Structures of Polymer Systems Studied by Equations of State

    NASA Astrophysics Data System (ADS)

    Liu, Honglai; Xu, Hui; Chen, Houyang; Peng, Changjun; Hu, Ying

    Polymer blends or copolymers have multiscale complex structures that can be used as templates to prepare various complex materials. To regulate the mesoscale structures of these polymer blends or copolymers, there are three fun damental problems: What is the physical condition of the microphase separation needed to form materials with desired compositions and mesoscale structures in dif ferent domains? How do these compositions and mesoscale structures evolve during the preparation period? How does the morphology change in the interfacial region? Many experimental measurements, computer simulation methods, and theories have been developed. However, most of them are only suitable for individual tasks. In re cent years, we have developed theoretical methods based on equations of state that can be used comprehensively to study the multiscale structure of polymer systems, including the phase diagrams, the morphologies and evolution of microphase sepa ration, the densities and composition profiles in different domains, and the molecular configurations in the interfacial region. The molecular parameters of the equation of state or the Helmholtz function model can be determined from the pressure, volume, temperature, and miscibility data of polymers, which ensures the practical applica bility of the methods.

  1. State-of-the-art review of phase equilibria

    SciTech Connect

    Prausnitz, J.M.

    1980-03-01

    High-pressure phase-equilibrium calculations using an equation of state are more sensitive to the mixing rules than to details in the effect of density or temperature on pressure. Attention must be given to the problem of how to extend equations of state to mixtures. One possible technique is provided by perturbation theory; another by superposition of chemical equilibria. At low or moderate pressures, vapor-phase corrections are often important. When specific intermolecular forces produce formation of molecular aggregates, strong deviations from ideal-gas behavior can be significant even at pressures well below 1 bar. When vapor-liquid equilibrium data are reduced using conventional expressions for the excess Gibbs energy, the resulting binary parameters tend to be partially correlated, it difficult, but no impossible, to calculate ternary liquid-liquid equilibria using binary parameters only. New models for calculating properties of liquid-phase mixtures mist allow for changes in free volume to give consideration to the effect of mixing on changes in rotational and vibrational degrees of freedom. Liquid-phase volumetric effects are also important in describing the solubilities of gases in solvent mixtures. Therefore, future liquid-phase models should incorporate a liquid-phase equation of state, either of the van der Waals type or, perhaps, as given by the direct-correlation function theory of liquids.

  2. Phase equilibria modification by electric fields. 1997 annual progress report

    SciTech Connect

    Tsouris, C.; Shah, V.M.

    1997-09-01

    'In this research program, Oak Ridge National Laboratory is investigating the modification of phase equilibria and interface transport enhancement-caused by electric fields. The majority of environmental and waste treatment processes involve complex chemical separations and reactions. The treatment efficiency in such processes is governed by thermodynamic equilibria and transport. The objective of this project is to use electric fields to favorably manipulate the thermodynamic and transport properties of mixtures so that higher separation efficiencies can be achieved. An understanding of the mechanisms of the underlying phenomena of molecular and fluid interactions with electric fields will lead to the development of efficient remediation methods for contaminated natural environments and wastes. Research Statement The main focus of this project is to understand and quantify the influence of electric fields on thermodynamic equilibria and transport properties of fluid mixtures and to determine the conditions and properties of the systems for which this influence is of practical significance. The specific objectives of the project are discussed.'

  3. Phosphorus Equilibria Among Mafic Silicate Phases

    NASA Technical Reports Server (NTRS)

    Berlin, Jana; Xirouchakis, Dimitris

    2002-01-01

    Phosphorus incorporation in major rock-forming silicate minerals has the following implications: (1) Reactions between phosphorus-hosting major silicates and accessory phosphates, which are also major trace element carriers, may control the stability of the latter and thus may affect the amount of phosphorus and other trace elements released to the coexisting melt or fluid phase. (2) Less of a phosphate mineral is needed to account for the bulk phosphorus of planetaty mantles. (3) During partial melting of mantle mineral assemblages or equilibrium fractional crystallization of basaltic magmas, and in the absence or prior to saturation with a phosphate mineral, silicate melts may become enriched in phosphorus, especially in the geochemically important low melt fraction regime, Although the small differences in the ionic radii of IVp5+, IVSi4+, and IV Al3+ makes phosphoms incorporation into crystalline silicates perhaps unsurprising, isostructural silicate and phosphate crystalline solids do not readily form solutions, e.g., (Fe, Mg)2SiO4 vs. LiMgPO4, SiO)2 VS. AlPO4. Nonetheless, there are reports of, poorly characterized silico-phosphate phases in angrites , 2-4 wt% P2O5 in olivine and pyroxene grains in pallasites and reduced terestrial basalts which are little understood but potentially useful, and up to 17 wt% P2O5 in olivine from ancient slags. However, such enrichments are rare and only underscore the likelihood of phosphoms incorporation in silicate minerals. The mechanisms that allow phosphorus to enter major rock-forming silicate minerals (e.g., Oliv, Px, Gt) remain little understood and the relevant data base is limited. Nonetheless, old and new high-pressure (5-10 GPa) experimental data suggest that P2O5 wt% decreases from silica-poor to silica-rich compositions or from orthosilicate to chain silicate structures (garnet > olivine > orthopyroxene) which implies that phosphorus incorporation in silicates is perhaps more structure-than site-specific. The

  4. Phase equilibria study of {N-hexylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide + aromatic hydrocarbons or an alcohol} binary systems.

    PubMed

    Domańska, Urszula; Zawadzki, Maciej; Tshibangu, M Marc; Ramjugernath, Deresh; Letcher, Trevor M

    2011-04-14

    Isoquinolinium ionic liquid (IL) has been synthesized from N-hexylisoquinolinium bromide as a substrate. Specific basic characterization of the synthesized compound is included, which includes NMR spectra, elementary analysis, and water content. The basic thermal properties of the pure IL, that is, melting and solid-solid transition temperatures, as well as the enthalpy of fusion, or solid-solid transition have been measured using a differential scanning microcalorimetry technique. The density and viscosity as a function of temperature have been measured for the pure IL at temperatures higher than the melting temperature and were extrapolated to T = 298.15 K. The temperature-composition phase diagrams of 8 binary mixtures composed of the IL N-hexylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide, ([HiQuin][NTf(2)]) and an aromatic hydrocarbon (benzene, or toluene, or ethylbenzene, n-propylbenzene) or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol) have been determined from ambient temperature to the boiling-point temperature of the solvent at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from 270 to 330 K. For the binary systems, the eutectic diagrams were observed with immiscibility in the liquid phase with an upper critical solution temperature (UCST). In the case of the mixture {IL + benzene, or alkylbenzene} the eutectic systems with mutual immiscibility in the liquid phase with very high UCSTs were observed. These points were not detectable with our method and were observed at low IL mole fraction. For mixtures with alcohols, it was observed that with an increasing chain length of an alcohol, the solubility decreases and the UCST increases. The coexistence curves corresponding to liquid-liquid phase equilibrium boundaries and the solid-liquid phase equilibrium has been correlated using the well-known nonrandom two-liquid (NRTL) model. PMID:21417475

  5. Phase equilibria in the La-Ba-Co-O system

    SciTech Connect

    Cherepanov, V.A.; Gavrilova, L.Y.; Filonova, E.A.; Trifonova, M.V.; Voronin, V.I.

    1999-04-01

    Phase equilibria in the La-Ba-Co-O system were studied at 1,100 C in air. The existence of oxide phases LaCoO{sub 3}, BaCoO{sub 3{minus}y}, Ba{sub 2}CoO{sub 4}, and La{sub 2}BaO{sub 4} in quasibinary systems in air at 1,100 C was found, in agreement with previous data. Two types of solid solutions were found in the quasiternary system: La{sub 1{minus}x}Ba{sub x}CoO{sub 3{minus}{delta}} and (La{sub 1{minus}z}Ba{sub z}){sub x}CoO{sub 4}. The homogeneity range of La{sub 1{minus}x}Ba{sub x}CoO{sub 3{minus}{delta}} was found to be 0 {le} x {le} 0.8. As the content of alkali-earth metal (x) increased, a rhombohedral distortion of La{sub 1{minus}x}Ba{sub x}CoO{sub 3{minus}{delta}} decreased; La{sub 0.55}Ba{sub 0.45}CoO{sub 3{minus}{delta}} had an ideal cubic structure. The composition of single phase samples of (La{sub 1{minus}z}Ba{sub z}){sub 2}CoO{sub 4} composition was obtained for z = 0.300, 0.325, 0.350, and 0.375. These samples had the tetragonal K{sub 2}NiF{sub 4}-type structure.

  6. Effects of gravity reduction on phase equilibria. Part 1: Unary and binary isostructural solids

    NASA Technical Reports Server (NTRS)

    Larson, D. J., Jr.

    1975-01-01

    Analysis of the Skylab II M553 Experiment samples resulted in the hypothesis that the reduced gravity environment was altering the melting and solidification reactions. A theoretical study was conducted to define the conditions under which such alteration of phase relations is feasible, determine whether it is restricted to space processing, and, if so, ascertain which alloy systems or phase reactions are most likely to demonstrate such effects. Phase equilibria of unary and binary systems with a single solid phase (unary and isomorphous) were considered.

  7. Phase Equilibria and Compressibility of bastnaesite-(La)

    NASA Astrophysics Data System (ADS)

    Rowland, R. L., II; Burnley, P. C.

    2015-12-01

    Bastnaesite (Ce,La,Y)CO3(F,OH) is a rare earth element (REE) bearing ore mineral. REEs are more common in the Earth's crust than precious metals like gold or platinum, but are not commonly concentrated in economically viable ore deposits. For over a decade, China has been the world's leading supplier of REEs. Recent export restrictions from China have necessitated the search for new deposits. Determining basic material properties such as phase equilibria and the equation of state for bastnaesite helps in understanding the processes that form REE ore deposits and thereby assist in locating new deposits. For this study we focus on the lanthanum-fluoride variant of bastnaesite (LaCO3F) since it can be easily synthesized in the laboratory. Previous work by others determined that in both open and closed systems at atmospheric pressure bastnaesite decomposes to lanthanum oxyfluoride and carbon dioxide (LaOF + CO2) above 325°C; at 100 MPa bastnaesite decomposes above 860°C (Hsu, 1992). Using a Griggs-type modified piston cylinder apparatus, we pressurized samples of synthetic bastnaesite-(La) to conditions ranging from 250 MPa to 1.2 GPa, and then subjected each sample to constant temperatures ranging from 700°C to 1050°C for a minimum of five hours. We then analyzed the samples with X-ray powder diffraction to identify phases present and determined that bastnaesite-(La) is stable at 250 MPa up to approximately 800°C and at 1.0 GPa up to approximately 900°C. Reversal experiments are underway. In order to develop an equation of state for bastnaesite-(La), we studied single crystals via monochromatic synchrotron X-ray diffraction in the diamond anvil cell at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. Measurements were made at pressures ranging from ambient to nearly 4 GPa. From these diffraction patterns, we determine the structure of bastnaesite-(La), and the change in unit cell volume as a function of pressure can be fit to a Birch

  8. Phase Equilibria Study in the TeO2-Na2O-SiO2 System in Air Between 723 K (500 °C) and 1473 K (1200 °C)

    NASA Astrophysics Data System (ADS)

    Santoso, Imam; Taskinen, Pekka

    2016-06-01

    Knowledge of phase equilibria in the TeO2-Na2O-SiO2 system at elevated temperatures is important for ceramic and glass industries and for improving the operation of the smelting process of tellurium-containing materials. A review of previous investigations has indicated, however, that there are omissions in the available datasets on the liquidus temperatures of the molten TeO2-Na2O-SiO2 mixtures. The employed experimental method included equilibration of mixtures made from high purity oxides, rapid quenching of the equilibrated samples in water and followed by compositional analysis of the phases using an electron probe X-ray microanalyzer. The liquidus and phase equilibria in the TeO2-SiO2, TeO2-Na2O, and SiO2-TeO2-Na2O systems have been studied for a wide range of compositions between 723 K (500 °C) and 1473 K (1200 °C) at TeO2, SiO2, and Na2SiO3 saturations. New data have been generated in the SiO2-TeO2-Na2O system at SiO2 saturation. The liquidus compositions in the TeO2-Na2O system at TeO2 saturation have been compared with the previous data and an assessed phase diagram.

  9. Phase Equilibria Study in the TeO2-Na2O-SiO2 System in Air Between 723 K (500 °C) and 1473 K (1200 °C)

    NASA Astrophysics Data System (ADS)

    Santoso, Imam; Taskinen, Pekka

    2016-08-01

    Knowledge of phase equilibria in the TeO2-Na2O-SiO2 system at elevated temperatures is important for ceramic and glass industries and for improving the operation of the smelting process of tellurium-containing materials. A review of previous investigations has indicated, however, that there are omissions in the available datasets on the liquidus temperatures of the molten TeO2-Na2O-SiO2 mixtures. The employed experimental method included equilibration of mixtures made from high purity oxides, rapid quenching of the equilibrated samples in water and followed by compositional analysis of the phases using an electron probe X-ray microanalyzer. The liquidus and phase equilibria in the TeO2-SiO2, TeO2-Na2O, and SiO2-TeO2-Na2O systems have been studied for a wide range of compositions between 723 K (500 °C) and 1473 K (1200 °C) at TeO2, SiO2, and Na2SiO3 saturations. New data have been generated in the SiO2-TeO2-Na2O system at SiO2 saturation. The liquidus compositions in the TeO2-Na2O system at TeO2 saturation have been compared with the previous data and an assessed phase diagram.

  10. Modeling phase equilibria in mixtures containing hydrogen fluoride and halocarbons

    SciTech Connect

    Lencka, M. ); Anderko, A. Polish Academy of Sciences, Warszawa )

    1993-03-01

    Recently, much attention has been focused on the production of environmentally acceptable refrigerants, which not only offer desirable physico-chemical properties, but do not deplete the ozone layer and do not cause the greenhouse effect. The production of such refrigerants involves the separation of multicomponent mixtures containing hydrogen fluoride, hydrogen chloride, and various chlorinated and fluorinated hydrocarbons. Therefore, it is indispensable to know the phase behavior of these mixtures. While the phase behavior of refrigerant mixtures can be adequately modeled in the absence of HF using standard thermodynamic techniques, drastically increases the complexity of the mixture because of its unusually strong association. The association of HF manifests itself in its significantly reduced gas-phase compressibility factor and the strong nonideality of mixtures containing HF and hydrocarbons or halocarbons. In this work, the authors develop an accurate, yet simple, association model for HF and compare it with simulation data. The model is combined with a simple equation of state to yield a closed-form expression that is applicable to both pure fluids and mixtures. In addition to representing the pure-component data for HF, the theory accurately predicts phase equilibria in HF + halocarbon systems.

  11. Metamorphism and partial melting of ordinary chondrites: Calculated phase equilibria

    NASA Astrophysics Data System (ADS)

    Johnson, T. E.; Benedix, G. K.; Bland, P. A.

    2016-01-01

    Constraining the metamorphic pressures (P) and temperatures (T) recorded by meteorites is key to understanding the size and thermal history of their asteroid parent bodies. New thermodynamic models calibrated to very low P for minerals and melt in terrestrial mantle peridotite permit quantitative investigation of high-T metamorphism in ordinary chondrites using phase equilibria modelling. Isochemical P-T phase diagrams based on the average composition of H, L and LL chondrite falls and contoured for the composition and abundance of olivine, ortho- and clinopyroxene, plagioclase and chromite provide a good match with values measured in so-called equilibrated (petrologic type 4-6) samples. Some compositional variables, in particular Al in orthopyroxene and Na in clinopyroxene, exhibit a strong pressure dependence when considered over a range of several kilobars, providing a means of recognising meteorites derived from the cores of asteroids with radii of several hundred kilometres, if such bodies existed at that time. At the low pressures (<1 kbar) that typify thermal metamorphism, several compositional variables are good thermometers. Although those based on Fe-Mg exchange are likely to have been reset during slow cooling, those based on coupled substitution, in particular Ca and Al in orthopyroxene and Na in clinopyroxene, are less susceptible to retrograde diffusion and are potentially more faithful recorders of peak conditions. The intersection of isopleths of these variables may allow pressures to be quantified, even at low P, permitting constraints on the minimum size of parent asteroid bodies. The phase diagrams predict the onset of partial melting at 1050-1100 °C by incongruent reactions consuming plagioclase, clinopyroxene and orthopyroxene, whose compositions change abruptly as melting proceeds. These predictions match natural observations well and support the view that type 7 chondrites represent a suprasolidus continuation of the established petrologic

  12. Correlation of three-liquid-phase equilibria involving ionic liquids.

    PubMed

    Rodríguez-Escontrela, I; Arce, A; Soto, A; Marcilla, A; Olaya, M M; Reyes-Labarta, J A

    2016-08-01

    The difficulty in achieving a good thermodynamic description of phase equilibria is finding a model that can be extended to a large variety of chemical families and conditions. This problem worsens in the case of systems containing more than two phases or involving complex compounds such as ionic liquids. However, there are interesting applications that involve multiphasic systems, and the promising features of ionic liquids suggest that they will play an important role in many future processes. In this work, for the first time, the simultaneous correlation of liquid-liquid and liquid-liquid-liquid equilibrium data for ternary systems involving ionic liquids has been carried out. To that end, the phase diagram of the water + [P6 6 6 14][DCA] + hexane system has been determined at 298.15 K and 323.15 K and atmospheric pressure. The importance of this system lies in the possibility of using the surface active ionic liquid to improve surfactant enhanced oil recovery methods. With those and previous measurements, thirteen sets of equilibrium data for water + ionic liquid + oil ternary systems have been correlated. The isoactivity equilibrium condition, using the NRTL model, and some pivotal strategies are proposed to correlate these complex systems. Good agreement has been found between experimental and calculated data in all the regions (one triphasic and two biphasic) of the diagrams. The geometric aspects related to the Gibbs energy of mixing function obtained using the model, together with the minor common tangent plane equilibrium condition, are valuable tools to check the consistency of the obtained correlation results. PMID:27427420

  13. Phase and extraction equilibria in water-polyethyleneglycol ethers of monoethanolamides of synthetic fatty acid-ammonium chloride systems

    NASA Astrophysics Data System (ADS)

    Lesnov, A. E.; Golovkina, A. V.; Kudryashova, O. S.; Denisova, S. A.

    2016-08-01

    Phase equilibria in layering systems of water, polyethyleneglycol ethers of monoethanolamides of synthetic fatty acids (SFAs) (synthamide-5), and ammonium chloride are studied. The possibility of using such systems for the liquid extraction of metal ions is evaluated. The effect the nature of salting-out agents has on the processes of segregation of the systems has been considered.

  14. Phase equilibria in the condensed system n-docosane-cyclododecane- n-decane

    NASA Astrophysics Data System (ADS)

    Shamitov, A. A.; Garkushin, I. K.; Kolyado, A. V.

    2016-07-01

    Phase equilibria in the system n-docosane-cyclododecane-n-decane are studied by means of differential thermal analysis. It is found that the system is of the eutectic type. The temperature of eutectic melting is found to be-34.9°C, the n-docosane content is 3.5 wt %, the n-decane content is 86.5 wt %, and the cyclododecane content is 10.0 wt %. It is concluded that the results can be used to create new optimal heatstorage materials.

  15. Two-dimensional magnetohydrodynamic equilibria with flow and studies of equilibria fluctuations

    SciTech Connect

    Agim, Y.Z.

    1989-08-01

    A set of reduced ideal MHD equations is derived to investigate equilibria of plasmas with mass flow in general two-dimensional geometry. These equations provide a means of investigating the effects of flow on self-consistent equilibria in a number of new two-dimensional configurations such as helically symmetric configurations with helical axis, which are relevant to stellarators, as well as axisymmetric configurations. It is found that as in the axisymmetric case, general two-dimensional flow equilibria are governed by a second-order quasi-linear partial differential equation for a magnetic flux function, which is coupled to a Bernoulli-type equation for the density. The equation for the magnetic flux function becomes hyperbolic at certain critical flow speeds which follow from its characteristic equation. When the equation is hyperbolic, shock phenomena may exist. As a particular example, unidirectional flow along the lines of symmetry is considered. In this case, the equation mentioned above is always elliptic. An exact solution for the case of helically symmetric unidirectional flow is found and studied to determine flow effects on the magnetic topology. In second part of this thesis, magnetic fluctuations due to the thermally excited MHD waves are investigated using fluid and kinetic models to describe stable, uniform, compressible plasma in the range above the drift wave frequency and below the ion cyclotron frequency. It is shown that the fluid model with resistivity yields spectral densities which are roughly Lorentzian, exhibit equipartition with no apparent cutoff in wavenumber space and a Bohm-type diffusion coefficient. Under certain conditions, the ensuing transport may be comparable to classical values. For a phenomenological cutoff imposed on the spectrum, the typical fluctuating-to-equilibrium magnetic field ratio is found to be of the order of 10 {sup {minus}10}.

  16. The Representation of Highly Non-Ideal Phase Equilibria Using Computer Graphics.

    ERIC Educational Resources Information Center

    Charos, Georgios N.; And Others

    1986-01-01

    Previous work focused on use of computer graphics in teaching thermodynamic phase equilibria for classes I and II. Extends this work to include the considerably more non-ideal phase behavior shown by classes III, IV, and V. Student and instructor response has been overwhelmingly positive about the approach. (JN)

  17. Phase equilibria of the magnesium sulfate-water system to 4 kbars

    NASA Technical Reports Server (NTRS)

    Hogenboom, D. L.; Kargel, J. S.; Ganasan, J. P.; Lee, L.

    1993-01-01

    Magnesium sulfate is the most abundant salt in carbonaceous chondrites, and it may be important in the low-temperature igneous evolution and aqueous differentiation of icy satellites and large chondritic asteroids. Accordingly, we are investigating high-pressure phase equilibria in MgSO4-H2O solutions under pressures up to four kbars. An initial report was presented two years ago. This abstract summarizes our results to date including studies of solutions containing 15.3 percent, 17 percent, and 22 percent MgSO4. Briefly, these results demonstrate that increasing pressure causes the eutectic and peritectic compositions to shift to much lower concentrations of magnesium sulfate, and the existence of a new low-density phase of magnesium sulfate hydrate.

  18. Water under-saturated phase equilibria of basaltic andesites from Westdahl volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Rader, E. L.; Larsen, J.

    2008-12-01

    The two most abundant gases released from magmatic systems are typically H2O and CO2, however, most phase equilibria studies examining crystallization applied to natural magmatic systems over the past 200 years have relied on H2O-saturated conditions. We will present the results of new phase equilibria experiments run using natural basaltic andesite starting materials from the 1991-1992 eruption of Westdahl volcano, Alaska, examining both H2O-saturated and undersaturated conditions, using a fixed ratio of XH2O ~0.7 and XCO2 ~0.3 in the total volatile budget. The experiments were conducted at total pressures (PTotal) of 0-200 MPa and 900-1050 °C, and fO2 set to the Ni-NiO buffer. Experiments were loaded into gold and Au75Pd25 capsules, and run in a TZM alloy pressure vessel for 48 hours before rapid quenching while still at pressure. After quenching, samples were polished and examined by microprobe and reflective microscopy. Identified mineral phases include plagioclase, clinopyroxene, Fe-Ti oxides, and minor orthopyroxene in both water-saturated and under- saturated experiments. A ~25 to 50 °C shift in temperature, at similar pressures is observed in the plagioclase and pyroxene stability curves when CO2 is added. Solubility models predict relatively low amounts of CO2 dissolved in the melt at similar conditions. Thus, our experiments indicate a significant effect of CO2 on the crystallization of mafic magmas at crustal pressures in volcanic arcs.

  19. Phase and chemical equilibria in the transesterification reaction of vegetable oils with supercritical lower alcohols

    NASA Astrophysics Data System (ADS)

    Anikeev, V. I.; Stepanov, D. A.; Ermakova, A.

    2011-08-01

    Calculations of thermodynamic data are performed for fatty acid triglycerides, free fatty acids, and fatty acid methyl esters, participants of the transesterification reaction of vegetable oils that occurs in methanol. Using the obtained thermodynamic parameters, the phase diagrams for the reaction mixture are constructed, and the chemical equilibria of the esterification reaction of free fatty acids and the transesterification reaction of fatty acid triglycerides attained upon treatment with supercritical methanol are determined. Relying on our analysis of the obtained equilibria for the esterification reaction of fatty acids and the transesterification reaction of triglycerides attained upon treatment with lower alcohols, we select the optimum conditions for performing the reaction in practice.

  20. Experimental investigation of the phase equilibria in the carbon dioxide-propane-3 M MDEA system

    SciTech Connect

    Jou, F.Y.; Mather, A.E.; Otto, F.D.; Carroll, J.J.

    1995-07-01

    The treating of liquefied petroleum gas (LPG) to remove carbon dioxide and hydrogen sulfide using aqueous alkanolamine solutions is an important aspect of gas processing. One of the amines used in the natural gas industry is methyldiethanolamine (MDEA). Measurements of the phase equilibria in the carbon dioxide-propane-3 M MDEA system have been made at 25 and 40 C at pressures up to 15.5 MPa. Vapor-liquid, liquid-liquid, and vapor-liquid-liquid equilibria were determined. The vapor-liquid equilibrium data were compared with the model of Deshmukh and Mather.

  1. Transport and Phase Equilibria Properties for Steam Flooding of Heavy Oils

    SciTech Connect

    Gabitto, Jorge; Barrufet, Maria

    2001-12-18

    The objectives of this research included experimental determination and rigorous modeling and computation of phase equilibria, volumetric, and transport properties of hydrocarbon/CO2/water mixtures at pressures and temperatures typical of steam injection processes for thermal recovery of heavy oils.

  2. TOWARD A THEORY OF SUSTAINABLE SYSTEMS. FLUID PHASE EQUILIBRIA: JOURNAL ARTICLE

    EPA Science Inventory

    NRMRL/STD JOURNAL NRMRL-CIN-1364 Cabezas*, H., and Fath**, B.D. Toward a Theory of Sustainable Systems. Fluid Phase Equilibria (Nakanishi, K., Yasukiko, A., Miyano, Y. (Ed.), Elsevier Science B.V.) 194-197:3-14 (2002). EPA/600/J-02/186, www.elsevier.com/locate/fluid. 03/2...

  3. Phase equilibria modification by electric fields. 1998 annual progress report

    SciTech Connect

    Tsouris, C.

    1998-06-01

    'The objective of this project is to use electric fields to favorably manipulate the thermodynamic and transport properties of mixtures so that higher separation efficiencies can be achieved. The main focus is to understand and quantify the influence of electric fields on vapor-liquid, liquid-liquid, and solid-liquid systems. It is expected that this program will lead to greater separation efficiency in a wide range of environmental treatment processes, including solvent extraction, sorption, distillation, and stripping. Such processes are widely used by DOE for treatment of wastes and sites contaminated with heavy metals, radionuclides, and organic solvents. Particular examples of applications of vapor-liquid- equilibria modification can be found in the separation of volatile organic compounds by either stripping or distillation. Improvements can also be made in liquid-liquid-extraction processes of TRU, Sr, Tc, and Cs by both thermodynamic and transport enhancements.'

  4. Calculation of liquid water-hydrate-methane vapor phase equilibria from molecular simulations.

    PubMed

    Jensen, Lars; Thomsen, Kaj; von Solms, Nicolas; Wierzchowski, Scott; Walsh, Matthew R; Koh, Carolyn A; Sloan, E Dendy; Wu, David T; Sum, Amadeu K

    2010-05-01

    Monte Carlo simulation methods for determining fluid- and crystal-phase chemical potentials are used for the first time to calculate liquid water-methane hydrate-methane vapor phase equilibria from knowledge of atomistic interaction potentials alone. The water and methane molecules are modeled using the TIP4P/ice potential and a united-atom Lennard-Jones potential, respectively. The equilibrium calculation method for this system has three components, (i) thermodynamic integration from a supercritical ideal gas to obtain the fluid-phase chemical potentials, (ii) calculation of the chemical potential of the zero-occupancy hydrate system using thermodynamic integration from an Einstein crystal reference state, and (iii) thermodynamic integration to obtain the water and guest molecules' chemical potentials as a function of the hydrate occupancy. The three-phase equilibrium curve is calculated for pressures ranging from 20 to 500 bar and is shown to follow the Clapeyron behavior, in agreement with experiment; coexistence temperatures differ from the latter by 4-16 K in the pressure range studied. The enthalpy of dissociation extracted from the calculated P-T curve is within 2% of the experimental value at corresponding conditions. While computationally intensive, simulations such as these are essential to map the thermodynamically stable conditions for hydrate systems. PMID:20392117

  5. Fast Method for Computing Chemical Potentials and Liquid-Liquid Phase Equilibria of Macromolecular Solutions.

    PubMed

    Qin, Sanbo; Zhou, Huan-Xiang

    2016-08-25

    Chemical potential is a fundamental property for determining thermodynamic equilibria involving exchange of molecules, such as between two phases of molecular systems. Previously, we developed the fast Fourier transform (FFT)-based method for Modeling Atomistic Protein-crowder interactions (FMAP) to calculate excess chemical potentials according to the Widom insertion. Intermolecular interaction energies were expressed as correlation functions and evaluated via FFT. Here, we extend this method to calculate liquid-liquid phase equilibria of macromolecular solutions. Chemical potentials are calculated by FMAP over a wide range of molecular densities, and the condition for coexistence of low- and high-density phases is determined by the Maxwell equal-area rule. When benchmarked on Lennard-Jones fluids, our method produces an accurate phase diagram at 18% of the computational cost of the current best method. Importantly, the gain in computational speed increases dramatically as the molecules become more complex, leading to many orders of magnitude in speed up for atomistically represented proteins. We demonstrate the power of FMAP by reporting the first results for the liquid-liquid coexistence curve of γII-crystallin represented at the all-atom level. Our method may thus open the door to accurate determination of phase equilibria for macromolecular mixtures such as protein-protein mixtures and protein-RNA mixtures, that are known to undergo liquid-liquid phase separation, both in vitro and in vivo. PMID:27327881

  6. In situ high temperature X-Ray diffraction study of the phase equilibria in the UO2-PuO2-Pu2O3 system

    NASA Astrophysics Data System (ADS)

    Belin, Renaud C.; Strach, Michal; Truphémus, Thibaut; Guéneau, Christine; Richaud, Jean-Christophe; Rogez, Jacques

    2015-10-01

    The region of the U-Pu-O phase diagram delimited by the compounds UO2-PuO2-Pu2O3 is known to exhibit a miscibility gap at low temperature. Consequently, MOX fuels with a composition entering this region could decompose into two fluorite phases and thus exhibit chemical heterogeneities. The experimental data on this domain found in the literature are scarce and usually provided using DTA that is not suitable for the investigation of such decomposition phenomena. In the present work, new experimental data, i.e. crystallographic phases, lattice parameters, phase fractions and temperature of phase separation, were measured in the composition range 0.14 < Pu/(U + Pu) < 0.62 and 1.85 < O/(U + Pu) < 2 from 298 to 1750 K using a novel in situ high temperature X-ray diffraction apparatus. A very good agreement is found between the temperature of phase separation determined from our results and using the thermodynamic model of the U-Pu-O system based on the CALPHAD method. Also, the combined use of thermodynamic calculations and XRD results refinement proved helpful in the determination of the O/M ratio of the samples during cooling. The methodology used in the current work might be useful to investigate other oxides systems exhibiting a miscibility gap.

  7. Thermodynamic calculations in the system CH4-H2O and methane hydrate phase equilibria

    USGS Publications Warehouse

    Circone, S.; Kirby, S.H.; Stern, L.A.

    2006-01-01

    Using the Gibbs function of reaction, equilibrium pressure, temperature conditions for the formation of methane clathrate hydrate have been calculated from the thermodynamic properties of phases in the system CH4-H 2O. The thermodynamic model accurately reproduces the published phase-equilibria data to within ??2 K of the observed equilibrium boundaries in the range 0.08-117 MPa and 190-307 K. The model also provides an estimate of the third-law entropy of methane hydrate at 273.15 K, 0.1 MPa of 56.2 J mol-1 K-1 for 1/n CH4??H 2O, where n is the hydrate number. Agreement between the calculated and published phase-equilibria data is optimized when the hydrate composition is fixed and independent of the pressure and temperature for the conditions modeled. ?? 2006 American Chemical Society.

  8. Phase equilibria in the neodymium–cadmium binary system

    PubMed Central

    Skołyszewska-Kühberger, Barbara; Reichmann, Thomas L.; Ipser, Herbert

    2014-01-01

    The equilibrium phase diagram of the neodymium–cadmium system has been established by thermal, metallographic and X-ray analysis based on a study of 70 alloys. The system contains three congruently melting intermetallic compounds, i.e. NdCd (1040 °C), NdCd2 (995 °C), Nd11Cd45 (855 °C), and four incongruently melting compounds NdCd3 (860 °C), Nd13Cd58 (740 °C), NdCd6 (655 °C) and NdCd11 (520 °C). Four eutectic reactions are found in this binary system, i.e. at ∼25 at.% Cd and 770 °C, at 58 at.% Cd and 955 °C, at 79 at.% Cd and 850 °C, and very close to pure Cd at 318 °C, as well as one eutectoid reaction at ∼15 at.% Cd and 500 °C. The solid solubility of Nd in Cd is negligible. Dilatometric curves were recorded for three Nd–Cd compositions up to 4 at.% Cd, to accurately determine phase transitions between the solid solutions of Cd in the low- and high-temperature modification of Nd. PMID:25197164

  9. Phase Equilibria in DOPC/DPPC-d62/Cholesterol Mixtures

    PubMed Central

    Davis, James H.; Clair, Jesse James; Juhasz, Janos

    2009-01-01

    Abstract There is broad interest in the question of fluid-fluid phase coexistence in membranes, in particular, whether evidence for liquid-disordered (ld)-liquid-ordered (lo) two-phase regions or membrane “rafts” can be found in natural membranes. In model membrane systems, such phase behavior is observed, and we have used deuterium nuclear magnetic resonance spectroscopy to map the phase boundaries of ternary mixtures containing 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), chain-perdeuterated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC-d62), and cholesterol. For both this ternary model system and the binary DPPC-d62/cholesterol sytem, we present clear evidence for ld-lo two-phase coexistence. We have selected sample compositions to focus on this region of fluid-fluid phase coexistence and to determine its temperature and composition ranges. The deuterium nuclear magnetic resonance spectra for compositions near the ld-lo phase boundary at high cholesterol concentrations show evidence of exchange broadening or critical fluctuations in composition, similar to that reported by Vist and Davis. There appears to be a line of critical compositions ranging from 48°C for a DOPC/DPPC-d62/cholesterol composition of 0:75:25, to ∼−8°C for the composition 57:14:29. At temperatures below this two-phase region, there is a region of three-phase coexistence (ld-lo-gel). These results are collected and presented in terms of a partial ternary phase diagram that is consistent with previously reported results of Vist and Davis. PMID:19167302

  10. Phase equilibria in a system of 'breathing' molecules

    SciTech Connect

    Wu, Jianzhong; Prausnitz, John

    2001-09-30

    It is now well known that details in the intermolecular potential can significantly affect the qualitative features of a phase diagram where temperature is plotted against density for the coexistence curves among fluid and solid phases. While previous calculations of phase diagrams have assumed a time-invariant potential function, this report concerns the phase diagram for ''breathing'' molecules, i.e., molecules whose strength of intermolecular attraction fluctuates in time. Such fluctuations can occur in biomacromolecules where an active site can switch between ''on'' and ''off'' positions. Phase-equilibrium calculations were performed for molecules that have a periodic (breathing) attractive force in addition to the conventional intermolecular forces. The phase diagram for such molecules is as expected when the ''breathing'' properties are independent of density. However, when (more realistically), the ''breathing'' properties are density dependent, the phase diagram exhibits dramatic changes. These calculations may be useful for interpreting experimental data for protein precipitation, for plaque formation in blood vessels and for scaffold-supported tissue formation.

  11. Phase equilibria and crystal chemistry of rubidium niobates and rubidium tantalates

    NASA Technical Reports Server (NTRS)

    Minor, D. B.; Roth, R. S.; Parker, H. S.; Brower, W. S.

    1977-01-01

    The phase equilibria relations and crystal chemistry of portions of the Rb2O-Nb2O5 and Rb2O-Ta2O5 systems were investigated for structures potentially useful as ionic conductors. A hexagonal tungsten bronze-type (HTB) structure was found in both systems as well as three hexagonal phases with mixed HTB-pyrochlore type structures. Ion exchange experiments between various alkali ions are described for several phases. Unit cell dimensions and X-ray diffraction powder patterns are reported.

  12. Postperovskite phase equilibria in the MgSiO3-Al2O3 system.

    PubMed

    Tsuchiya, Jun; Tsuchiya, Taku

    2008-12-01

    We investigate high-P,T phase equilibria of the MgSiO(3)-Al(2)O(3) system by means of the density functional ab initio computation methods with multiconfiguration sampling. Being different from earlier studies based on the static substitution properties with no consideration of Rh(2)O(3)(II) phase, present calculations demonstrate that (i) dissolving Al(2)O(3) tends to decrease the postperovskite transition pressure of MgSiO(3) but the effect is not significant ( approximately -0.2 GPa/mol% Al(2)O(3)); (ii) Al(2)O(3) produces the narrow perovskite+postperovskite coexisting P,T area (approximately 1 GPa) for the pyrolitic concentration (x(Al2O3) approximately 6 mol%), which is sufficiently responsible to the deep-mantle D'' seismic discontinuity; (iii) the transition would be smeared (approximately 4 GPa) for the basaltic Al-rich composition (x(Al2O3) approximately 20 mol%), which is still seismically visible unless iron has significant effects; and last (iv) the perovskite structure spontaneously changes to the Rh(2)O(3)(II) with increasing the Al concentration involving small displacements of the Mg-site cations. PMID:19036928

  13. Phase transitions and connectivity in three-dimensional vortex equilibria

    SciTech Connect

    Akao, J.H.

    1994-05-01

    The statistical mechanics of collections of closed self avoiding vortex loops on a lattice are studied. The system is related to the vortex form of the three dimensional XY model and to lattice vortex equilibrium models of turbulence. The system exhibits vortex connectivity and screening effects, and models in vorticity variables the superfluid transition. The equilibrium states of the system are simulated by a grand canonical Monte Carlo method. A set of geometric transformations for self-avoiding loops is developed. The numerical method employs histogram sampling techniques and utilizes a modification to the Metropolis flow which enhances efficiency. Results are given for a region in the temperature-chemical potential plane, where the chemical potential is related to the vortex fugacity. A line of second order transitions is identified at low temperature. The transition is shown to be a percolation threshold at which connected vortex loops of infinite size appear in the system. The nature of the transition supports the assumption that the lambda transition in bulk superfluid helium is driven by vortices. An asymptotic analysis is performed for the energy and entropy scaling of the system as functions of the system size and the lattice spacing. These estimates indicate that the infinite temperature line is a phase boundary between small scale fractal vortices and large scale smooth vortices. A suggestion is made that quantum vortices have uniform structure on the scale of the lattice spacing and lie in the positive temperature regime, while classical vortices have uniform structure on the scale of the domain and lie in the negative temperature regime.

  14. Phase Equilibria of the Ternary Sn-Zn-Co System at 250°C and 500°C

    NASA Astrophysics Data System (ADS)

    Wang, Chao-hong; Huang, Sheng-en; Huang, Po-yen

    2015-12-01

    The isothermal sections of the ternary Sn-Zn-Co system (<60 at.% Co) at 250°C and 500°C have been experimentally determined. A series of Sn-Zn-Co alloys of various compositions were prepared and annealed at the respective temperatures to reach phase equilibrium. The equilibrium phases in these alloys were examined metallographically and characterized by electron probe microanalysis and x-ray diffraction. In this system, the ternary solubilities of all the binary Sn-Co and Co-Zn intermetallic compounds (IMCs) are very limited. For the phase equilibria at 250°C, two ternary IMCs, T1 and T2, were found, whose compositions were Sn-25 at.%Zn-25 at.%Co and Sn-15 at.%Zn-41 at.%Co, respectively. For the phase equilibria at 500°C, in addition to the T2 phase, another ternary IMC, namely T3 (Sn-18 at.%Zn-37 at.%Co), was also found. Moreover, the phase stability of the T1 and T3 phases was investigated at temperatures of 260°C to 400°C in detail. The equilibrium phase was the T1 phase below 300°C, and changed to the T3 phase at 400°C. The crystal structures of these three ternary IMCs were also studied. The T1 phase has a cubic structure ( Pm3m), and the T2 and T3 phases are orthorhombic in space group Cmcm and Pnma, respectively.

  15. Phase equilibria and modeling of pyridinium-based ionic liquid solutions.

    PubMed

    Domańska, Urszula; Królikowski, Marek; Ramjugernath, Deresh; Letcher, Trevor M; Tumba, Kaniki

    2010-11-25

    The phase diagrams of the ionic liquid (IL) N-butyl-4-methylpyridinium bis{(trifluoromethyl)sulfonyl}imide ([BM(4)Py][NTf(2)]) with water, an alcohol (1-butanol, 1-hexanol, 1-octanol, 1-decanol), an aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene), an alkane (n-hexane, n-heptane, n-octane), or cyclohexane have been measured at atmospheric pressure using a dynamic method. This work includes the characterization of the synthesized compound by water content and also by differential scanning calorimetry. Phase diagrams for the binary systems of [BM(4)Py][NTf(2)] with all solvents reveal eutectic systems with regards to (solid-liquid) phase equilibria and show immiscibility in the liquid phase region with an upper critical solution temperature (UCST) in most of the mixtures. The phase equilibria (solid, or liquid-liquid) for the binary systems containing aliphatic hydrocarbons reported here exhibit the lowest solubility and the highest immiscibility gap, a trend which has been observed for all ILs. The reduction of experimental data has been carried out using the nonrandom two-liquid (NRTL) correlation equation. The phase diagrams reported here have been compared with analogous phase diagrams reported previously for systems containing the IL N-butyl-4-methylpyridinium tosylate and other pyridinium-based ILs. The influence of the anion of the IL on the phase behavior has been discussed. PMID:20964426

  16. Clathrate formation and phase equilibria in the thiourea-bromoform system

    NASA Astrophysics Data System (ADS)

    Chekhova, G. N.; Shubin, Yu. V.; Pinakov, D. V.; Alferova, N. I.

    2008-07-01

    Phase equilibria in the thiourea (host)-bromoform (guest) binary system were studied by physicochemical analysis methods over the temperature range 270 455 K. The stoichiometry and stability region were determined for the channel-type compound CHBr3 · 2.40(2)(NH2)2CS; the compound was observed for the first time. When heated, the clathrate incongruently decomposed at 424.0 ± 0.8 K to rhombic thiourea and the guest component. The solubility isotherm of the thiourea-bromoform-acetic acid system was studied to find that the compound was thermodynamically stable at 293 K over the range of guest component concentrations 100 35 wt %. A decrease in its content in an equilibrium mother liquor resulted in the appearance of X-ray diffraction reflections of the initial host α polymorph. Rhombohedral cell parameters were determined (space group R-3 c, a = 15.89(1) Å, c = 12.40(1) Å, V = 2711(6) Å3, d calcd = 2.000 g/cm3, and d expt = 1.98(2) g/cm3). The mode of packing of bromoform molecules was compared with the organization of the guest subsystem in inclusion compounds formed by the substances studied.

  17. Study of ionic equilibria of indotricarbocyanines in aromatic hydrocarbons

    SciTech Connect

    Dyadyusha, G.G.; Ishchenko, A.A.; Derevyanko, N.A.; Tolmachev, A.I.

    1982-05-01

    Study of the equilibria in nonpolar solvents is very complicated by the poor solubility of the salt-like dyes. Indotricarbocyanines I and II were found to be fairly soluble in aromatic hydrocarbons for solving these problems by means of electronic spectra. In the present work, their absorption spectra were studied in benzene, toluene, and m-xylene (the absorption spectra were measured on the SF-8 spectrophotometer). It was shown that the dyes studied in these solvents have spectral bands of unusual form of polymethine dyes. At the long wave edge of the spectra of indotricarbocyanines, a distinct band appears, whose intensity is very dependent on the nature of the anion. In the case of perchlorate I, it has a lower intensity, and in the case of iodide II, the intensity is higher.

  18. Thermodynamic properties and phase equilibria of selected Heusler compounds

    NASA Astrophysics Data System (ADS)

    Yin, Ming

    Heusler compounds are ternary intermetallics with many promising properties such as spin polarization and magnetic shape memory effect. A better understanding of their thermodynamic properties facilitates future design and development. Therefore, standard enthalpies of formation and heat capacities from room temperature to 1500 K of selected Heusler compounds X2YZ (X = Co, Fe, Ni, Pd, Rh, Ru; Y = Co, Cu, Fe, Hf, Mn, Ni, Ti, V, Zr; Z = Al, Ga, In, Si, Ge, Sn) and half-Heusler compounds XYSn (X = Au, Co, Fe, Ir, Ni, Pd, Pt, Rh; Y = Hf, Mn, Ti, Zr) were measured using high temperature direct reaction calorimetry. The measured standard enthalpies of formation were compared with those predicted from ab initio calculations and the extended semi-empirical Miedema's model. Trends in standard enthalpy of formation with respect to the periodic classification of elements were discussed. The effect of a fourth element (Co, Cu, Fe, Pd; Ti, V; Al, Ga, In, Si, Ge) on the standard enthalpy of formation of Ni2MnSn was also investigated. Lattice parameters of the compounds with an L21 structure were determined using X-ray powder diffraction analysis. Differential scanning calorimetry was used to determine melting points and phase transformation temperatures. Phase relationships were investigated using scanning electron microscopy with an energy dispersive spectrometer. The isothermal section of the Fe-Sn-Ti ternary system at 873 K was established using equilibrated alloys. Three ternary compounds including the Heusler compound Fe2SnTi were observed. A new ternary compound Fe5Sn9Ti 6 was reported and the crystal structure of FeSnTi2 was determined for the first time.

  19. Adiabatic invariants and phase equilibria for first-order orbital resonances. [solar mass change effect on asteroid orbits

    NASA Technical Reports Server (NTRS)

    Heppenheimer, T. A.

    1975-01-01

    In the planar circular restricted three-body problem, the evolution of near-commensurable orbits is studied under change in the mass ratio, mu. The evolution involves preservation of two adiabatic invariants. Transition from circulation to libration may occur; such transitions are of two types. Type I transition occurs when the evolutionary track in phase space passes through near-zero eccentricity; as in the ordinary case (no transition), pre- and post-evolutionary states are linked by solution of a two-point boundary-value problem. Type II transition occurs when the evolutionary track encounters an unstable phase equilibrium or periodic orbit. There is then a discontinuous change in one adiabatic invariant, and pre- and post-evolutionary states are linked by solution of a three-point boundary-value problem. No evolutionary track can encounter a stable phase equilibrium, but the class of all stable phase equilibria is mapped into itself under mu change.

  20. Phase equilibria of H2SO4, HNO3, and HCl hydrates and the composition of polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Wooldridge, Paul J.; Zhang, Renyi; Molina, Mario J.

    1995-01-01

    Thermodynamic properties and phase equilibria behavior for the hydrates and coexisting pairs of hydrates of common acids which exist in the stratosphere are assembled from new laboratory measurements and standard literature data. The analysis focuses upon solid-vapor and solid-solid-vapor equilibria at temperatures around 200 K and includes new calorimetric and vapor pressure data. Calculated partial pressures versus 1/T slopes for the hydrates and coexisting hydrates agree well with experimental data where available.

  1. Phase Equilibria of H2SO4, HNO3, and HCl Hydrates and the Composition of Polar Stratospheric Clouds

    NASA Technical Reports Server (NTRS)

    Wooldridge, Paul J.; Zhang, Renyi; Molina, Mario J.

    1995-01-01

    Thermodynamic properties and phase equilibria behavior for the hydrates and coexisting pairs of hydrates of common acids which exist in the stratosphere are assembled from new laboratory measurements and standard literature data. The analysis focuses upon solid-vapor and solid-solid-vapor equilibria at temperatures around 200 K and includes new calorimetric and vapor pressure data. Calculated partial pressures versus 1/T slopes for the hydrates and coexisting hydrates agree well with experimental data where available.

  2. Hydration energies of sodiated amino acids from gas-phase equilibria determinations.

    PubMed

    Wincel, Henryk

    2007-07-01

    The sequential hydration of a number of sodiated amino acids is investigated using a high-pressure mass spectrometer. Ions produced continuously by electrospray are injected into the reaction chamber in the pulsed mode where the hydration equilibria, AANa+(H2O)n-1+H2O=AANa+(H2O)n (AA=Val, Pro, Met, Phe, and Gln), and the temperature dependence of the equilibrium constants are measured in the gas phase at 10 mbar (N2 bath gas and known pressure of H2O). The thermochemical properties, DeltaH degrees n, DeltaS degrees n, and DeltaG degrees n, for the hydrated systems are determined and discussed in conjunction with the structural forms. The results show that the binding energies of water to the AANa+ complexes decrease with the increasing number of water molecules. The present results from equilibrium measurements are compared to those from earlier studies obtained by other techniques. A correlation between the free energy changes for the addition of the first and second water molecules to AANa+, and the corresponding sodium ion affinities, is observed. Generally, the hydration free energy becomes weaker as the AA-Na+ bond strength increases. PMID:17559201

  3. Phase Equilibria Studies in the System ZnO-``FeO''-Al2O3-CaO-SiO2 Relevant to Imperial Smelting Furnace Slags: Part II

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

    The phase equilibria and the liquidus temperatures in the system ZnO-“FeO”-Al2O3-CaO-SiO2 have been determined experimentally in equilibrium with metallic iron. Specifically, the effects of Al2O3 concentrations in Imperial Smelting Furnace slags are identified, and the results are presented in the form of pseudo-ternary sections ZnO-“FeO”-(Al2O3 + CaO + SiO2) in which CaO/SiO2 = 0.93 and (CaO + SiO2)/Al2O3 = 5.0 and 3.5, respectively. It was found that, in the presence of Al2O3, the spinel phase is formed, the spinel primary phase field expands, and the wustite and melilite primary phase fields are reduced in size with an increasing Al2O3 concentration. The implications of the findings to industrial practice are discussed.

  4. Phase Equilibria Studies in the System ZnO-``FeO''-Al2O3-CaO-SiO2 Relevant to Imperial Smelting Furnace Slags: Part I

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

    The phase equilibria and liquidus temperatures in the system ZnO-“FeO”-Al2O3-CaO-SiO2 in equilibrium with metallic iron have been determined experimentally in the temperature range of 1423 K to 1553 K. The experimental conditions were focused on the composition range relevant to Imperial Smelting Furnace slags. The results are presented in the form of a pseudo-ternary section ZnO-“FeO”-(CaO + SiO2 + Al2O3) in which CaO/SiO2 = 0.93 and (CaO + SiO2)/Al2O3 = 7.0. It was found that wustite and spinel are the major primary phases and that zincite and melilite are also present in the composition range investigated. Wustite (Fe2+,Zn)O and spinel (Fe2+,Zn)O (A1,Fe3+)2O3 solid solutions are formed in this system, and the ZnO concentration in the spinel phase is found to be much greater than in the liquid phase.

  5. Diffusion, phase equilibria and partitioning experiments in the Ni-Fe-Ru system

    NASA Technical Reports Server (NTRS)

    Blum, Joel D.; Wasserburg, G. J.; Hutcheon, I. D.; Beckett, J. R.; Stolper, E. M.

    1989-01-01

    Results are presented on thin-film diffusion experiments designed to investigate phase equilibria in systems containing high concentrations of Pt-group elements, such as Ni-Fe-Ru-rich systems containing Pt, at temperatures of 1273, 1073, and 873 K. The rate of Ru diffusion in Ni was determined as a function of temperature, and, in addition, the degree of Pt and Ir partitioning between phases in a Ni-Fe-Ru-rich system and of V between phases in a Ni-Fe-O-rich system at 873 were determined. It was found that Pt preferentially partitions into the (gamma)Ni-Fe phase, whereas Ir prefers the (epsilon)Ru-Fe phase. V partitions strongly into Fe oxides relative to (gamma)Ni-Fe. These results have direct application to the origin and thermal history of the alloys rich in Pt-group elements in meteorites.

  6. Phases, phase equilibria, and phase rules in low-dimensional systems

    SciTech Connect

    Frolov, T.; Mishin, Y.

    2015-07-28

    We present a unified approach to thermodynamic description of one, two, and three dimensional phases and phase transformations among them. The approach is based on a rigorous definition of a phase applicable to thermodynamic systems of any dimensionality. Within this approach, the same thermodynamic formalism can be applied for the description of phase transformations in bulk systems, interfaces, and line defects separating interface phases. For both lines and interfaces, we rigorously derive an adsorption equation, the phase coexistence equations, and other thermodynamic relations expressed in terms of generalized line and interface excess quantities. As a generalization of the Gibbs phase rule for bulk phases, we derive phase rules for lines and interfaces and predict the maximum number of phases than may coexist in systems of the respective dimensionality.

  7. Phases, phase equilibria, and phase rules in low-dimensional systems.

    PubMed

    Frolov, T; Mishin, Y

    2015-07-28

    We present a unified approach to thermodynamic description of one, two, and three dimensional phases and phase transformations among them. The approach is based on a rigorous definition of a phase applicable to thermodynamic systems of any dimensionality. Within this approach, the same thermodynamic formalism can be applied for the description of phase transformations in bulk systems, interfaces, and line defects separating interface phases. For both lines and interfaces, we rigorously derive an adsorption equation, the phase coexistence equations, and other thermodynamic relations expressed in terms of generalized line and interface excess quantities. As a generalization of the Gibbs phase rule for bulk phases, we derive phase rules for lines and interfaces and predict the maximum number of phases than may coexist in systems of the respective dimensionality. PMID:26233156

  8. Calculation of Phase Equilibria in the Y2O3-Yb2O3-ZrO2 System

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Liu, Zi-Kui; Kaufman, Larry; Zhang, Fan

    2001-01-01

    Rare earth oxide stabilized zirconias find a wide range of applications. An understanding of phase equilibria is essential to all applications. In this study, the available phase boundary data and thermodynamic data is collected and assessed. Calphad-type databases are developed to completely describe the Y2O3-ZrO2, Yb2O3-ZrO2, and Y2O3-Yb2O3 systems. The oxide units are treated as components and regular and subregular solution models are used. The resultant calculated phase diagrams show good agreement with the experimental data. Then the binaries are combined to form the database for the Y2O3-Yb2O3-ZrO2 psuedo-ternary.

  9. Phase equilibria in a three-component water-soap-alcohol system. A thermodynamic model

    SciTech Connect

    Joensson, B.; Wennerstroem, H.

    1987-01-15

    A thermodynamic model is presented for ternary systems consisting of ionic surfactant-long-chain alcohol-water. The important contributions to the model free energy are (i) an electrostatic term; (ii) a free energy term; (iii) four entropy terms; (iv) constraints imposed by molecular packing restrictions; and (v) a hydration force. The free energy expressions are developed for (spherical) micellar solutions, normal hexagonal liquid crystals, lamellar liquid crystals, reversed hexagonal liquid crystals, and inverted (spherical) micellar solutions. For all these types of phases the aggregate geometries are optimized and the relative stabilities are determined. The phase equilibria are determined by deriving explicit expressions for the chemical potentials of the three components and using the criterion that they should be equal for phases in equilibrium. The model gives a nearly quantitative description of the equilibria in the test system potassium decanoate-octanol-water. The general conclusions are (i) at high ratios of ionic surfactant to alcohol the dominating factor is the electrostatics, with an additional effect from the fact that the alcohol decreases the free energy of the polar-apolar interface; (ii) the stability of the inverted micellar system is greatly influenced by the entropy of mixing between the palisade layer and the bulk alcohol medium; (iii) at low water contents one has to invoke the occurrence of a hydration force.

  10. On the question of phase equilibria in the succinonitrile-(D)camphor system

    NASA Astrophysics Data System (ADS)

    Witusiewicz, V. T.; Hecht, U.; Rex, S.

    2013-07-01

    Alloys from the succinonitrile-(D)camphor (SCN-DC) system are widely used as model alloys for the in situ investigation of solidification using light optical microscopy, but literature on the binary phase diagram is contradictory with respect to the solubility limit of DC in (SCN). Phase equilibria of the system were therefore revisited experimentally and critically assessed in the present work. The results prove that the maximum solubility of DC in the succinonitrile solid solution (SCN) is far less 1 wt% and the volume fraction of the (DC) phase in the eutectic solid is 23.3%. On this basis and on recently reported experimental data the CALPHAD description of the SCN-DC system was re-optimized.

  11. Phase equilibria of carbon dioxide hydrate system in the presence of sucrose, glucose, and fructose

    SciTech Connect

    Chun, M.K.; Lee, H.

    1999-09-01

    The three-phase (H-L{sub w}-V) equilibria of the carbon dioxide hydrate formation system in aqueous solutions containing sucrose, glucose, and fructose were experimentally determined at pressures ranging from 1.580 to 4.355 MPa and at temperatures between 273.6 and 281.7 K. The upper quadruple points (H-L{sub w}-L{sub CO{sub 2}}-V) were also measured at concentrations of 10, 20, and 30 mass % sucrose, glucose, and fructose. The addition of carbohydrates exhibited a similar inhibition effect as that observed for electrolytes and alcohols. A thermodynamic model predicting the three- and four-phase hydrate equilibria while accounting for the inhibition effect of carbohydrates was developed on the basis of the van der Waals-Platteeuw model and the Redlich-Kwong-Soave equation of state with a modified version of the Huron-Vidal mixing rule. The calculated results were found to be in good agreement with the experimental data.

  12. Liquid-vapor phase equilibria and the thermodynamic properties of 2-methylpropanol- n-alkyl propanoate solutions

    NASA Astrophysics Data System (ADS)

    Suntsov, Yu. K.; Goryunov, V. A.; Chuikov, A. M.; Meshcheryakov, A. V.

    2016-08-01

    The boiling points of solutions of five binary systems are measured via ebulliometry in the pressure range of 2.05-103.3 kPa. Equilibrium vapor phase compositions, the values of the excess Gibbs energies, enthalpies, and entropies of solution of these systems are calculated. Patterns in the changes of phase equilibria and thermodynamic properties of solutions are established, depending on the compositions and temperatures of the systems. Liquid-vapor equilibria in the systems are described using the equations of Wilson and the NRTL (Non-Random Two-Liquid Model).

  13. Planetary phase equilibria - Application to formation of earth, Venus and Mercury

    NASA Astrophysics Data System (ADS)

    Saxena, S. K.

    1981-06-01

    Calculations of phase equilibria in a solar mixture with variable hydrogen abundance show that the major element chemical composition of the earth and Venus can be simply explained by their formation in equilibrium at 800 and 1000 K, respectively, at a pressure of 0.001 atm, provided that there is an iron loss from the region of proto-Venus relative to the solar nebula. The calculated mineralogical chemical compositions of the two planets are in excellent agreement with the available chemical and physical data. Phase equilibrium calculations at 1500 K and 0.001 atm show that nearly 96% of the silicates and 81% of metal must have been lost from the region of proto-Mercury.

  14. Exact calculations of phase and membrane equilibria for complex fluids by Monte Carlo simulation

    SciTech Connect

    Panagiotopoulos, A.Z.

    1990-08-28

    The general objective of this project is the investigation of phase equilibria for complex fluids using a novel methodology, Monte Carlo simulation in the Gibbs ensemble. The methodology enables the direct determination of the properties of two coexisting fluid phases (e.g. a liquid at equilibrium with its vapor) from a single computer experiment, and is applicable to multicomponent systems with arbitrary equilibrium constraints imposed. The specific goals of this work are to adapt the Gibbs technique to (a) highly asymmetric mixtures with large differences in size and potential energies of interaction (b) chain molecules and (c) ionic systems. Significant progress has been made in all three areas. In this paper, we will briefly describe the progress made in each area, using the same numbering scheme for the tasks as in the original proposal.

  15. Planetary phase equilibria - Application to formation of earth, Venus and Mercury

    NASA Technical Reports Server (NTRS)

    Saxena, S. K.

    1981-01-01

    Calculations of phase equilibria in a solar mixture with variable hydrogen abundance show that the major element chemical composition of the earth and Venus can be simply explained by their formation in equilibrium at 800 and 1000 K, respectively, at a pressure of 0.001 atm, provided that there is an iron loss from the region of proto-Venus relative to the solar nebula. The calculated mineralogical chemical compositions of the two planets are in excellent agreement with the available chemical and physical data. Phase equilibrium calculations at 1500 K and 0.001 atm show that nearly 96% of the silicates and 81% of metal must have been lost from the region of proto-Mercury.

  16. Phase liquid-vapor equilibria and thermodynamic properties of solutions of n-propanol-aliphatic ketones

    NASA Astrophysics Data System (ADS)

    Suntsov, Yu. K.; Vlasov, M. V.; Chuikov, A. M.

    2015-06-01

    The boiling points of solutions of five binary systems are measured using the ebulliometric method in the pressure range of 4.4-101.3 kPa. Compositions of the equilibrium vapor phases of systems are calculated, based on the constructed pressure isotherms of saturated vapor. The values of excess Gibbs energy and the enthalpy and entropy of solutions are calculated from the data on the liquid-vapor equilibrium. The patterns of change in the phase equilibria and thermodynamic properties of the solutions are established, based on the composition and temperature of the systems. The liquid-vapor equilibrium of systems is described using the equations of Wilson and the NRTL (Non-Random Two-Liquid model).

  17. Effect of Fluorine on Near-Liquidus Phase Equilibria of Basalts

    NASA Technical Reports Server (NTRS)

    Filiberto, Justin; Wood, Justin; Loan, Le; Dasgupta, Rajdeep; Shimizu, Nobumichi; Treiman, Allan H.

    2010-01-01

    Volatile species such as H2O, CO2, F, and Cl have significant impact in generation and differentiation of basaltic melts. Thus far experimental work has primarily focused on the effect of water and carbon dioxide on basalt crystallization, liquid-line of descent, and mantle melting [e.g., 1, 2] and the effects of halogens have received far less attention [3-4]. However, melts in the planetary interiors can have non-negligible chlorine and fluorine concentrations. Here, we explore the effects of fluorine on near-liquidus phase equilibria of basalt. We have conducted nominally anhydrous piston cylinder experiments using graphite capsules at 0.6 - 1.5 GPa on an Fe-rich model basalt composition. 1.75 wt% fluorine was added to the starting mix in the form of AgF2. Fluorine in the experimental glass was measured by SIMS and major elements of glass and minerals were analyzed by EPMA. Nominally volatile free experiments yield a liquidus temperature from 1330 C at 0.8GPa to 1400 at 1.6GPa and an olivine(Fo72)-pyroxene(En68)-liquid multiple saturation point at 1.25 GPa and 1375 C. The F-bearing experiments yield a liquiudus temperature from 1260 C at 0.6GPa to 1305 at 1.5GPa and an ol(Fo66)-pyx(En64)-MSP at 1 GPa and 1260 C. This shows that F depresses the basalt liquidus, extends the pyroxene stability field to lower pressure, and forces the liquidus phases to be more Fe-rich. KD(Fe-Mg/mineral-melt) calculated for both pyroxenes and olivines show an increase with increasing F content of the melt. Therefore, we infer that F complexes with Mg in the melt and thus increases the melt s silica activity, depressing the liquidus and changing the composition of the crystallizing minerals. Our study demonstrates that on a weight percent basis, the effect of fluorine is similar to the effect of H2O [1] and Cl [3] on freezing point depression of basalts. But on an atomic fraction basis, the effect of F on liquidus depression of basalts is xxxx compared to the effect of H. Future

  18. Solid state phase equilibria and intermetallic compounds of the Al-Cr-Ho system

    SciTech Connect

    Pang, Mingjun; Zhan, Yongzhong; Du, Yong

    2013-02-15

    The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C were experimentally investigated. The phase relations at 500 Degree-Sign C are governed by 14 three-phase regions, 29 two-phase regions and 15 single-phase regions. The existences of 10 binary compounds and 2 ternary phases have been confirmed. Al{sub 11}Cr{sub 2}, Al{sub 11}Cr{sub 4} and Al{sub 17}Ho{sub 2} were not found at 500 Degree-Sign C. Crystal structures of Al{sub 9}Cr{sub 4} and Al{sub 8}Cr{sub 4}Ho were determined by the Rietveld X-ray powder data refinement. Al{sub 9}Cr{sub 4} was found to exhibit cubic structure with space group I4-bar 3m (no. 217) and lattice parameters a=0.9107(5) nm. Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} structure type with space group I4/mmm (no. 139) and lattice parameters a=0.8909(4) nm, c=0.5120(5) nm. It is concluded that the obtained Al{sub 4}Cr phase in this work should be {mu}-Al{sub 4}Cr by comparing with XRD pattern of the hexagonal {mu}-Al{sub 4}Mn compound. - Graphical abstract: The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Al-Cr-Ho system has been investigated. Black-Right-Pointing-Pointer Al{sub 9}Cr{sub 4} has cubic structure with space group I4-bar 3m. Black-Right-Pointing-Pointer Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} type with space group I4/mmm. Black-Right-Pointing-Pointer Al{sub 4}Cr phase is {mu}-type at 500 Degree-Sign C.

  19. The systems Sr-Zn-{l_brace}Si,Ge{r_brace}: Phase equilibria and crystal structure of ternary phases

    SciTech Connect

    Romaka, V.V.; Falmbigl, M.; Grytsiv, A.; Rogl, P.

    2012-02-15

    Phase relations have been established by electron probe microanalysis (EPMA) and X-ray powder diffraction (XPD) for the Sr-poor part of the ternary systems Sr-Zn-Si at 800 Degree-Sign C and Sr-Zn-Ge at 700 Degree-Sign C. In the Sr-Zn-Si system one new ternary compound SrZn{sub 2+x}Si{sub 2-x} (0{<=}x{<=}0.45) with CeAl{sub 2}Ga{sub 2} structure and a statistical mixture of Zn/Si in the 4e site was found. Neither a type-I nor a type-IX clathrate phase was encountered. This system is characterized by formation of two further phases, i.e. SrZn{sub 1-x}Si{sub 1+x} with ZrBeSi-type (0.16{<=}x{<=}0.22) and SrZn{sub 1-x}Si{sub 1+x} with AlB{sub 2}-type (0.35{<=}x{<=}0.65) with a random distribution of Zn/Si atoms in the 2c site. For the Sr-Zn-Ge system, the homogeneity regions of the isotypic phases SrZn{sub 1-x}Ge{sub 1+x} with ZrBeSi-type (0{<=}x{<=}0.17) and AlB{sub 2}-type (0.32{<=}x{<=}0.56), respectively, have been determined. Whereas the germanide SrZn{sub 2+x}Ge{sub 2-x} (CeAl{sub 2}Ga{sub 2}-type) is characterized by a homogeneity region (0{<=}x{<=}0.5), the clathrate type-I phase Sr{sub 8}Zn{sub 8}Ge{sub 38} shows a point composition. - Graphical abstract: Phase equilibria of ternary compounds in the Sr-Zn-Si-system at 800 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Phase equilibria in the Sr-Zn-Si-system are established at 800 Degree-Sign C. Black-Right-Pointing-Pointer Phase equilibria in the Sr-Zn-Ge-system are established at 700 Degree-Sign C. Black-Right-Pointing-Pointer Crystal structures of the ternary compounds were confirmed by X-ray powder diffraction. Black-Right-Pointing-Pointer All ternary compounds except the clathrate-I in the Ge-system are characterized by a homogeneity region.

  20. Heat capacity and phase equilibria of almandine, Fe 3Al 2Si 3O 12

    NASA Astrophysics Data System (ADS)

    Anovitz, L. M.; Essene, E. J.; Metz, G. W.; Bohlen, S. R.; Westrum, E. F., Jr.; Hemingway, B. S.

    1993-09-01

    The heat capacity of a synthetic almandine, Fe 3Al 2Si 3O 12, was measured from 6 to 350 K using equilibrium, intermittent-heating quasi-adiabatic calorimetry and from 420 to 1000 K using differential scanning calorimetry. These measurements yield Cp298 = 342.80 ± 1.4 J/mol · K and S298o = 342.60 J/mol · K. Mössbauer characterizations show the almandine to contain less than 2 ± 1% of the total iron as Fe 3+. X-ray diffraction studies of this synthetic almandine yield a = 11.521 ± 0.001 Å and V298o = 115.11 +- 0.01 cm 3/mol, somewhat smaller than previously reported. The low-temperature Cp data indicate a lambda transition at 8.7 K related to an antiferromagnetic-paramagnetic transition with TN = 7.5 K. Modeling of the lattice contribution to the total entropy suggests the presence of entropy in excess of that attributable to the effects of lattice vibrations and the magnetic transition. This probably arises from a low-temperature electronic transition (Schottky contribution). Combination of the Cp data with existing thermodynamic and phase equilibrium data on almandine yields ΔGf,298 o = -4938.3 kJ/mol and ΔHf,298 o= - 5261.3 kJ/mol for almandine when calculated from the elements. The equilibrium almandine = hercynite + fayalite + quartz limits the upper T/P for almandine and is metastably located at ca. 570°C at P = 1 bar, with a dP/dT of +17 bars/°C. This agrees well with reversed experiments on almandine stability when they are corrected for magnetite and hercynite solid-solutions. In ‖ O2- T space, almandine oxidizes near QFM by the reactions almandine + O2 = magnetite + sillimanite + quartzandalmandine + 02 = hercynite + magnetite + quartz. With suitable correction for reduced activities of solid phases, these equilibria provide useful oxygen barometers for medium- to high-grade metamorphic rocks.

  1. Heat capacity and phase equilibria of almandine, Fe3Al2Si3O12

    USGS Publications Warehouse

    Anovitz, Lawrence M.; Essene, E.J.; Metz, G.W.; Bohlen, S.R.; Westrum, E.F., Jr.; Hemingway, B.S.

    1993-01-01

    The heat capacity of a synthetic almandine, Fe3Al2Si3O12, was measured from 6 to 350 K using equilibrium, intermittent-heating quasi-adiabatic calorimetry and from 420 to 1000 K using differential scanning calorimetry. These measurements yield Cp298 = 342.80 ?? 1.4 J/mol ?? K and S298o = 342.60 J/mol ?? K. Mo??ssbauer characterizations show the almandine to contain less than 2 ?? 1% of the total iron as Fe3+. X-ray diffraction studies of this synthetic almandine yield a = 11.521 ?? 0.001 A?? and V298o = 115.11 +- 0.01 cm3/mol, somewhat smaller than previously reported. The low-temperature Cp data indicate a lambda transition at 8.7 K related to an antiferromagnetic-paramagnetic transition with TN = 7.5 K. Modeling of the lattice contribution to the total entropy suggests the presence of entropy in excess of that attributable to the effects of lattice vibrations and the magnetic transition. This probably arises from a low-temperature electronic transition (Schottky contribution). Combination of the Cp data with existing thermodynamic and phase equilibrium data on almandine yields ??Gf,298o = -4938.3 kJ/mol and ??Hf,298o= -5261.3 kJ/mol for almandine when calculated from the elements. The equilibrium almandine = hercynite + fayalite + quartz limits the upper T P for almandine and is metastably located at ca. 570??C at P = 1 bar, with a dP dT of +17 bars/??C. This agrees well with reversed experiments on almandine stability when they are corrected for magnetite and hercynite solid-solutions. In {norm of matrix}O2-T space, almandine oxidizes near QFM by the reactions almandine + O2 = magnetite + sillimanite + quartz and almandine + 02 = hercynite + magnetite + quartz. With suitable correction for reduced activities of solid phases, these equilibria provide useful oxygen barometers for medium- to high-grade metamorphic rocks. ?? 1993.

  2. Study of improved methods for predicting chemical equilibria. Final technical report, April 1, 1993--August 31, 1997

    SciTech Connect

    Lenz, T.G.; Vaughan, J.D.

    1997-10-01

    A long-standing goal of chemical engineers and chemists has been the development of techniques for accurate prediction of the thermodynamic properties of isolated molecules. The thermochemical functions for an ideal gas then provide a means of computing chemical equilibria, and such computations can be extended to condensed phase chemical equilibria with appropriate physical property data. Such capability for predicting diverse chemical equilibria is important in today`s competitive international economic environment, where bringing new products to market rapidly and efficiently is crucial. The purpose of this project has been to develop such computational methods for predicting chemical equilibria.

  3. Evaluation of phase equilibria in the Nb-rich portion of Nb-B system

    SciTech Connect

    Tang, Zhihong; Kramer, M.; Akinc, M.

    2007-12-19

    The phase equilibria in the Nb-rich portion of Nb-B system have been evaluated experimentally using metallographic analysis, differential thermal analysis (DTA) and X-ray diffraction. It showed that Nb{sub ss} (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L{leftrightarrow}Nb{sub ss}+NbB exists, instead of the generally accepted reaction L{leftrightarrow}Nb{sub ss}+Nb{sub 3}B{sub 2}, as indicated in the Nb-B phase diagram. The Nb{sub 3}B{sub 2} phase, however, forms by the peritectoid reaction Nb{sub ss}+NbB{leftrightarrow}Nb{sub 3}B{sub 2}. DTA tests were conducted on annealed Nb-14B, Nb-16B, Nb-18B and Nb-40B alloys, and temperature and heat of phase transition were determined. The eutectic reaction (L{leftrightarrow}Nb{sub ss}+NbB) temperature was determined to be 2104 {+-} 5 C, and the heat of phase transition was estimated as 22-30 kJ/mol, depending on the method of calibration used. The thermal event associated with peritectoid reactions was not observed in DTA curves due to sluggish solid state transformation, but the thermal annealing experiments show that peritectoid temperature is above 1900 C.

  4. Exploring fluctuations and phase equilibria in fluid mixtures via Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Denton, Alan R.; Schmidt, Michael P.

    2013-03-01

    Monte Carlo simulation provides a powerful tool for understanding and exploring thermodynamic phase equilibria in many-particle interacting systems. Among the most physically intuitive simulation methods is Gibbs ensemble Monte Carlo (GEMC), which allows direct computation of phase coexistence curves of model fluids by assigning each phase to its own simulation cell. When one or both of the phases can be modelled virtually via an analytic free energy function (Mehta and Kofke 1993 Mol. Phys. 79 39), the GEMC method takes on new pedagogical significance as an efficient means of analysing fluctuations and illuminating the statistical foundation of phase behaviour in finite systems. Here we extend this virtual GEMC method to binary fluid mixtures and demonstrate its implementation and instructional value with two applications: (1) a lattice model of simple mixtures and polymer blends and (2) a free-volume model of a complex mixture of colloids and polymers. We present algorithms for performing Monte Carlo trial moves in the virtual Gibbs ensemble, validate the method by computing fluid demixing phase diagrams, and analyse the dependence of fluctuations on system size. Our open-source simulation programs, coded in the platform-independent Java language, are suitable for use in classroom, tutorial, or computational laboratory settings.

  5. Phase equilibria, crystal structure and oxygen content of intermediate phases in the Y-Ba-Co-O system

    NASA Astrophysics Data System (ADS)

    Urusova, A. S.; Cherepanov, V. A.; Aksenova, T. V.; Gavrilova, L. Ya.; Kiselev, E. A.

    2013-06-01

    The phase equilibria in the Y-Ba-Co-O system were systematically studied at 1373 K in air. The intermediate phases formed in the Y-Ba-Co-O system at 1373 K in air were: YBaCo2O5+δ, YBaCo4O7 and BaCo1-yYyO3-δ (0.09≤y≤0.42). It was shown that YBaCo2O5+δ possesses tetragonal structure with the 3ap×3ap×2ap superstructure (sp. gr. P4/mmm). High-temperature X-ray diffraction analysis of the YBaCo2O5+δ in the temperature range from 298 K up to 1073 K under Po2=0.21 аtm has not shown any phase transformations. The value of oxygen content for the YBaCo2O5+δ at room temperature was estimated as 5.40 and at 1323 K it was equal to 5.04. Thermal expansion of sample shows a linear characteristics and the average thermal expansion coefficient (TEC) is about 13.8×10-6, K-1 in the temperature range 298-1273 K. The homogeneity range and crystal structure of the BaCo1-yYyO3-δ (0.09≤y≤0.42) solid solutions were determined by X-ray diffraction of quenched samples. All BaCo1-yYyO3-δ solid solutions were found to have cubic structure (sp. gr. Pm3m). The unit cell parameters were refined using Rietveld full-profile analysis. Oxygen nonstoichiometry of BaCo1-yYyO3-δ solid solutions with 0.1≤y≤0.4 was measured by means of thermogravimetric technique within the temperature range 298-1373 K in air. Thermal expansion of BaCo1-yYyO3-δ (у=0.0; 0.1; 0.2; 0.3) samples was studied within the temperature range 298-1200 K in air. The projection of isothermal-isobaric phase diagram for the Y-Ba-Co-O system to the compositional triangle of metallic components was presented.

  6. Extension of the transferable potentials for phase equilibria force field to dimethylmethyl phosphonate, sarin, and soman.

    PubMed

    Sokkalingam, Nandhini; Kamath, Ganesh; Coscione, Maria; Potoff, Jeffrey J

    2009-07-30

    The transferable potentials for phase equilibria force field is extended to dimethylmethylphosphonate (DMMP), sarin, and soman by introducing a new interaction site representing the phosphorus atom. Parameters for the phosphorus atom are optimized to reproduce the liquid densities at 303 and 373 K and the normal boiling point of DMMP. Calculations for sarin and soman are performed in predictive mode, without further parameter optimization. Vapor-liquid coexistence curves, critical properties, vapor pressures and heats of vaporization are predicted over a wide range of temperatures with histogram reweighting Monte Carlo simulations in the grand canonical ensemble. Excellent agreement with experiment is achieved for all compounds, with unsigned errors of less than 1% for vapor pressures and normal boiling points and under 5% for heats of vaporization and liquid densities at ambient conditions. PMID:19719285

  7. Planet Alsioff - A problem set for students of phase equilibria or metamorphic petrology

    NASA Technical Reports Server (NTRS)

    Burt, Donald M.

    1988-01-01

    This paper presents a problem set that contains questions for students of phase equilibria or metamorphic petrology concerning a hypothetical planet Alsioff, for which incomplete data are given. On this panet, the SiF4 is the major volatile and Al, Si, O, and F are the only elements present. Progressive metamorphism on Alsioff mainly involves devolatilization of fluid SiF4. The problem set includes ten questions. Some of these are concerned with possible chemical reactions that should affect water, wollastonite, or Ca-SiO3 exposed to the atmosphere of Alsioff; the mechanism of controls of the O2 and F2 contents of the Alsioffian atmosphere; and the devolatilization reactions involving SiF4 with progressive thermal metamorphism.

  8. Phase equilibria constraints on the chemistry of hot spring fluids at mid-ocean ridges

    SciTech Connect

    Seyfried, W.E. Jr.; Ding, K.; Berndt, M.E. )

    1991-12-01

    Recent advances in experimental and theoretical geochemistry have made it possible to assess both homogeneous and heterogeneous equilibria involving a wide range of aqueous species at temperatures and pressures appropriate to model hydrothermal alteration processes at mid-ocean ridges. The authors have combined selected aspects of the chemistry of hot spring fluids with constraints imposed by a geologically reasonable assemblage of minerals in the system Na{sub 2}O-K{sub 2}O-CaO-MgO-FeO-Fe{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-SiO{sub 2}-H{sub 2}O-HCl-H{sub 2}S to assess the effect of temperature on the composition of the aqueous phase and the activities of mineral components in plagioclase and epidote solid solutions. Assuming fO{sub 2(g)} and fS{sub 2(g)} controlled by pyrite-pyrrhotite-magnetite equilibria, a constant dissolved Ca concentration, and a dissolved Cl concentration equivalent to that of seawater, increasing temperature from 250 to 400C at 500 bars results in systematic changes in the composition of mineral phases, which in turn constrain pH and the distribution of aqueous species. The model predicts that dissolved concentrations of Fe, SiO{sub 2}, K, H{sub 2}S, and H{sub 2} increase, while Na and pH{sub (25C)} decrease with increasing temperature. That many hot springs vent fluids are characterized by variable degrees of conductive heat loss renders measured temperatures unreliable as indicators of the maximum temperature of subseafloor hydrothermal alteration processes. The implications of this are significant for hot spring fluids which reveal large Cl variations relative to seawater, since likely mechanisms to account for such variability typically require temperatures in excess of those inferred for subseafloor reaction zones by simply correcting measured temperatures for the effects of adiabatic cooling.

  9. Ternary compounds and phase equilibria in Ti-Ge-C and Ti-Ge-B

    SciTech Connect

    Kephart, J.S.; Carim, A.H.

    1998-09-01

    Bulk samples of nearly single-phase Ti{sub 2}GeC and Ti{sub 3}GeC{sub 2} were fabricated using a synthesis process similar to one developed to produce bulk Ti{sub 3}SiC{sub 2}. Elemental powders were stored and mixed under argon and 2 g pellets were uniaxially pressed and encapsulated in quartz under vacuum for annealing. Additional samples were synthesized to establish the isothermal section of the ternary Ti-Ge-C phase diagram at 1200 C. The only ternary compounds present were Ti{sub 3}GeC{sub 2} and Ti{sub 2}GeC, and the equilibria between these and other phases in the system were established for the first time. Attempts at substituting boron for carbon in Ti{sub 3}GeC{sub 2} and Ti{sub 2}GeC by the same technique proved unsuccessful. The phase distributions in Ti-Ge-B samples at 1200 C were consistent with a previously established ternary diagram at 700 C which indicated that no ternary phases of this or any other type are present at equilibrium in the Ti-Ge-B system.

  10. Phase Equilibria of the Fe-Ni-Sn Ternary System at 270°C

    NASA Astrophysics Data System (ADS)

    Huang, Tzu-Ting; Lin, Shih-Wei; Chen, Chih-Ming; Chen, Pei Yu; Yen, Yee-Wen

    2016-07-01

    The Fe-42 wt.% Ni alloy, also known as a 42 invar alloy (Alloy 42), is used as a lead-frame material because its thermal expansion coefficient is much closer to Si substrate than Cu or Ni substrates. In order to enhance the wettability between the substrate and solder, the Sn layer was commonly electroplated onto the Alloy 42 surface. A clear understanding of the phase equilibria of the Fe-Ni-Sn ternary system is necessary to ensure solder-joint reliability between Sn and Fe-Ni alloys. To determine the isothermal section of the Fe-Ni-Sn ternary system at 270°C, 26 Fe-Ni-Sn alloys with different compositions were prepared. The experimental results confirmed the presence of the Fe3Ni and FeNi phases at 270°C. Meanwhile, it observed that the isothermal section of the Fe-Ni-Sn ternary system was composed of 11 single-phase regions, 19 two-phase regions and nine tie-triangles. Moreover, no ternary compounds were found in the Fe-Ni-Sn system at 270°C.

  11. The heat-capacity of ilmenite and phase equilibria in the system Fe-T-O

    USGS Publications Warehouse

    Anovitz, Lawrence M.; Treiman, A.H.; Essene, E.J.; Hemingway, B.S.; Westrum, E.F., Jr.; Wall, V.J.; Burriel, R.; Bohlen, S.R.

    1985-01-01

    Low temperature adiabatic calorimetry and high temperature differential scanning calorimetry have been used to measure the heat-capacity of ilmenite (FeTiO3) from 5 to 1000 K. These measurements yield S2980 = 108.9 J/(mol ?? K). Calculations from published experimental data on the reduction of ilmenite yield ??2980(I1) = -1153.9 kJ/(mol ?? K). These new data, combined with available experimental and thermodynamic data for other phases, have been used to calculate phase equilibria in the system Fe-Ti-O. Calculations for the subsystem Ti-O show that extremely low values of f{hook}O2 are necessary to stabilize TiO, the mineral hongquiite reported from the Tao district in China. This mineral may not be TiO, and it should be re-examined for substitution of other elements such as N or C. Consideration of solid-solution models for phases in the system Fe-Ti-O allows derivation of a new thermometer/oxybarometer for assemblages of ferropseudobrookite-pseudobrookitess and hematite-ilmenitess. Preliminary application of this new thermometer/oxybarometer to lunar and terrestrial lavas gives reasonable estimates of oxygen fugacities, but generally yields subsolidus temperatures, suggesting re-equilibration of one or more phases during cooling. ?? 1985.

  12. The heat-capacity of ilmenite and phase equilibria in the system Fe-T-O

    NASA Astrophysics Data System (ADS)

    Anovitz, Lawrence M.; Treiman, Allan H.; Essene, Eric J.; Hemingway, Bruce S.; Westrum, Edgar F., Jr.; Wall, Victor J.; Burriel, Ramón; Bohlen, Steven R.

    1985-10-01

    Low temperature adiabatic calorimetry and high temperature differential scanning calorimetry have been used to measure the heat-capacity of ilmenite (FeTiO 3) from 5 to 1000 K. These measurements yield S2980 = 108.9 J/( mol · K). Calculations from published experimental data on the reduction of ilmenite yield Δ2980( I1) = -1153.9 kJ/( mol · K). These new data, combined with available experimental and thermodynamic data for other phases, have been used to calculate phase equilibria in the system Fe-Ti-O. Calculations for the subsystem Ti-O show that extremely low values of ƒO 2 are necessary to stabilize TiO, the mineral hongquiite reported from the Tao district in China. This mineral may not be TiO, and it should be re-examined for substitution of other elements such as N or C. Consideration of solid-solution models for phases in the system Fe-Ti-O allows derivation of a new thermometer/oxybarometer for assemblages of ferropseudobrookite-pseudobrookite ss and hematite-ilmenite ss. Preliminary application of this new thermometer/oxybarometer to lunar and terrestrial lavas gives reasonable estimates of oxygen fugacities, but generally yields subsolidus temperatures, suggesting re-equilibration of one or more phases during cooling.

  13. Phase equilibria and liquid phase epitaxy growth of PbSnSeTe lattice matched to PbSe

    NASA Technical Reports Server (NTRS)

    Mccann, Patrick J.; Fonstad, Clifton G.; Fuchs, Jacob; Feit, Ze'ev

    1987-01-01

    The necessary phase diagram data for growing lattice-matched layers of PbSnSeTe on PbSe are presented. Solid compounds of Pb(1-x)Sn(x)Se(1-y)Te(y) lattice-matched to PbSe were grown from liquid melts consisting of (Pb/1-x/Sn/x/)(1-z)(Se/1-y/Te/y/)(z); phase equilibria data were determined together with liquidus data for values of x(liquid) from 0 to 40 percent and y(liquid) from 0 to 40 percent for temperatures between 450 and 540 C. It was found that relatively large amounts of Te must be added to the melt to achieve lattice matching because of its low segregation coefficient relative to Se. A significant lattice-pulling effect was discovered for the 5-percent Sn case, and a similar effect is expected for the 10- and 20-percent Sn cases.

  14. Phase equilibria and structural investigations in the Ni-poor part of the system Al–Ge–Ni

    PubMed Central

    Reichmann, Thomas L.; Duarte, Liliana I.; Effenberger, Herta S.; Leinenbach, Christian; Richter, Klaus W.

    2012-01-01

    The ternary phase diagram Al–Ge–Ni was investigated between 0 and 50 at.% Ni by a combination of differential thermal analysis (DTA), powder- and single-crystal X-ray diffraction (XRD), metallography and electron probe microanalysis (EPMA). Ternary phase equilibria and accurate phase compositions of the equilibrium phases were determined within two partial isothermal sections at 400 and 700 °C, respectively. The two binary intermediate phases AlNi and Al3Ni2 were found to form extended solid solutions with Ge in the ternary. Three new ternary phases were found to exist in the Ni-poor part of the phase diagram which were designated as τ1 (oC24, CoGe2-type), τ2 (at approximately Al67.5Ge18.0Ni14.5) and τ3 (cF12, CaF2-type). The ternary phases show only small homogeneity ranges. While τ1 was investigated by single crystal X-ray diffraction, τ2 and τ3 were identified from their powder diffraction pattern. Ternary phase reactions and melting behaviour were studied by means of DTA. A total number of eleven invariant reactions could be derived from these data, which are one ternary eutectic reaction, six transition reactions, three ternary peritectic reactions and one maximum. Based on the measured DTA values three vertical sections at 10, 20 and 35 at.% Ni were constructed. Additionally, all experimental results were combined to a ternary reaction scheme (Scheil diagram) and a liquidus surface projection. PMID:27087753

  15. Direct molecular dynamics simulation of liquid-solid phase equilibria for a three-component plasma.

    PubMed

    Hughto, J; Horowitz, C J; Schneider, A S; Medin, Zach; Cumming, Andrew; Berry, D K

    2012-12-01

    The neutron-rich isotope ²²Ne may be a significant impurity in carbon and oxygen white dwarfs and could impact how the stars freeze. We perform molecular dynamics simulations to determine the influence of ²²Ne in carbon-oxygen-neon systems on liquid-solid phase equilibria. Both liquid and solid phases are present simultaneously in our simulation volumes. We identify liquid, solid, and interface regions in our simulations using a bond angle metric. In general we find good agreement for the composition of liquid and solid phases between our MD simulations and the semianalytic model of Medin and Cumming. The trace presence of a third component, neon, does not appear to strongly impact the chemical separation found previously for two-component carbon and oxygen systems. This suggests that small amounts of ²²Ne may not qualitatively change how the material in white dwarf stars freezes. However, we do find systematically lower melting temperatures (higher Γ) in our MD simulations compared to the semianalytic model. This difference seems to grow with impurity parameter Q_{imp} and suggests a problem with simple corrections to the linear mixing rule for the free energy of multicomponent solid mixtures that is used in the semianalytic model. PMID:23368065

  16. Direct molecular dynamics simulation of liquid-solid phase equilibria for a three-component plasma

    NASA Astrophysics Data System (ADS)

    Hughto, J.; Horowitz, C. J.; Schneider, A. S.; Medin, Zach; Cumming, Andrew; Berry, D. K.

    2012-12-01

    The neutron-rich isotope 22Ne may be a significant impurity in carbon and oxygen white dwarfs and could impact how the stars freeze. We perform molecular dynamics simulations to determine the influence of 22Ne in carbon-oxygen-neon systems on liquid-solid phase equilibria. Both liquid and solid phases are present simultaneously in our simulation volumes. We identify liquid, solid, and interface regions in our simulations using a bond angle metric. In general we find good agreement for the composition of liquid and solid phases between our MD simulations and the semianalytic model of Medin and Cumming. The trace presence of a third component, neon, does not appear to strongly impact the chemical separation found previously for two-component carbon and oxygen systems. This suggests that small amounts of 22Ne may not qualitatively change how the material in white dwarf stars freezes. However, we do find systematically lower melting temperatures (higher Γ) in our MD simulations compared to the semianalytic model. This difference seems to grow with impurity parameter Qimp and suggests a problem with simple corrections to the linear mixing rule for the free energy of multicomponent solid mixtures that is used in the semianalytic model.

  17. Phase equilibria, crystal structure and oxygen content of intermediate phases in the Y–Ba–Co–O system

    SciTech Connect

    Urusova, A.S.; Cherepanov, V.A. Aksenova, T.V.; Gavrilova, L.Ya.; Kiselev, E.A.

    2013-06-01

    The phase equilibria in the Y–Ba–Co–O system were systematically studied at 1373 K in air. The intermediate phases formed in the Y–Ba–Co–O system at 1373 K in air were: YBaCo₂O5+δ, YBaCo₄O₇ and BaCo1–yYyO3–δ (0.09≤y≤0.42). It was shown that YBaCo₂O5+δ possesses tetragonal structure with the 3aₚ×3aₚ×2aₚ superstructure (sp. gr. P4/mmm). High-temperature X-ray diffraction analysis of the YBaCo₂O5+δ in the temperature range from 298 K up to 1073 K under Po₂=0.21 atm has not shown any phase transformations. The value of oxygen content for the YBaCo₂O5+δ at room temperature was estimated as 5.40 and at 1323 K it was equal to 5.04. Thermal expansion of sample shows a linear characteristics and the average thermal expansion coefficient (TEC) is about 13.8×10⁻⁶, K⁻¹ in the temperature range 298–1273 K. The homogeneity range and crystal structure of the BaCo1–yYyO3–δ (0.09≤y≤0.42) solid solutions were determined by X-ray diffraction of quenched samples. All BaCo1–yYyO3–δ solid solutions were found to have cubic structure (sp. gr. Pm3m). The unit cell parameters were refined using Rietveld full-profile analysis. Oxygen nonstoichiometry of BaCo1–yYyO3–δ solid solutions with 0.1≤y≤0.4 was measured by means of thermogravimetric technique within the temperature range 298–1373 K in air. Thermal expansion of BaCo1–yYyO3–δ (y=0.0; 0.1; 0.2; 0.3) samples was studied within the temperature range 298–1200 K in air. The projection of isothermal–isobaric phase diagram for the Y–Ba–Co–O system to the compositional triangle of metallic components was presented. - Graphical abstract: A projection of isobaric isothermal phase diagram of the Y–Ba–Co–O system to the metallic components

  18. Phase equilibria in the iron oxide-cobalt oxide-phosphorus oxide system

    NASA Technical Reports Server (NTRS)

    De Guire, Mark R.; Prasanna, T. R. S.; Kalonji, Gretchen; O'Handley, Robert C.

    1987-01-01

    Two novel ternary compounds are noted in the present study of 1000 C solid-state equilibria in the Fe-Co-P-O system's Fe2O3-FePO4-Co3(Po4)2-CoO region: CoFe(PO4)O, which undergoes incongruent melting at 1130 C, and Co3Fe4(PO4)6, whose incongruent melting occurs at 1080 C. The liquidus behavior-related consequences of rapidly solidified cobalt ferrite formation from cobalt ferrite-phosphate melts are discussed with a view to spinel formation. It is suggested that quenching from within the spinel-plus-liquid region may furnish an alternative to quenching a homogeneous melt.

  19. Phase equilibria and modeling of ammonium ionic liquid, C2NTf2, solutions.

    PubMed

    Domańska, Urszula; Marciniak, Andrzej; Królikowski, Marek

    2008-01-31

    Novel quaternary ammonium ionic liquid, ethyl(2-hydroxyethyl)dimethylammonium bis(trifluomethylsulfonyl)imide (C2NTf2), has been prepared from N,N-dimethylethanolamine as a substrate. The paper includes a specific basic characterization of the synthesized compound by NMR and the basic thermophysical properties: the melting point, enthalpy of fusion, enthalpy of solid-solid phase transition, glass transition determined by the differential scanning calorimetry (DSC), temperature of decomposition, and water content. The density of the new compound was measured. The solid-liquid or liquid-liquid phase equilibria of binary mixtures containing {C2NTf2+water or an alcohol (propan-1-ol, butan-1-ol, hexan-1-ol, octan-1-ol, decan-1-ol), aromatic hydrocarbons (benzene, toluene), aliphatic hydrocarbons (n-hexane, n-octane), dimethylsulfoxide (DMSO), or tetrahydrofuran (THF)} have been measured by a dynamic method in a wide range of temperatures from 230 to 430 K. These data were correlated by means of the nonrandom two-liquid (NRTL) equation utilizing temperature-dependent parameters derived from the solid-liquid or liquid-liquid equilibrium. From the solubility results, the negative value of the partition coefficient of ionic liquid in binary system octan-1-ol/water (log P) at 298.15 K has been calculated. PMID:18179194

  20. Phase equilibria constraints on the chemical and physical evolution of the campanian ignimbrite

    USGS Publications Warehouse

    Fowler, S.J.; Spera, F.J.; Bohrson, W.A.; Belkin, H.E.; de Vivo, B.

    2007-01-01

    The Campanian Ignimbrite is a > 200 km3 trachyte-phonolite pyroclastic deposit that erupted at 39.3 ?? 0.1 ka within the Campi Flegrei west of Naples, Italy. Here we test the hypothesis that Campanian Ignimbrite magma was derived by isobaric crystal fractionation of a parental basaltic trachyandesitic melt that reacted and came into local equilibrium with small amounts (5-10 wt%) of crustal rock (skarns and foid-syenites) during crystallization. Comparison of observed crystal and magma compositions with results of phase equilibria assimilation-fractionation simulations (MELTS) is generally very good. Oxygen fugacity was approximately buffered along QFM+1 (where QFM is the quartz-fayalite-magnetite buffer) during isobaric fractionation at 0.15 GPa (???6 km depth). The parental melt, reconstructed from melt inclusion and host clinopyroxene compositions, is found to be basaltic trachyandesite liquid (51.1 wt% SiO2, 9.3 wt% MgO, 3 wt% H2O). A significant feature of phase equilibria simulations is the existence of a pseudo-invariant temperature, ???883??C, at which the fraction of melt remaining in the system decreases abruptly from ???0.5 to < 0.1. Crystallization at the pseudo-invariant point leads to abrupt changes in the composition, properties (density, dissolved water content), and physical state (viscosity, volume fraction fluid) of melt and magma. A dramatic decrease in melt viscosity (from 1700 Pa s to ???200 Pa s), coupled with a change in the volume fraction of water in magma (from ??? 0.1 to 0.8) and a dramatic decrease in melt and magma density acted as a destabilizing eruption trigger. Thermal models suggest a timescale of ??? 200 kyr from the beginning of fractionation until eruption, leading to an apparent rate of evolved magma generation of about 10-3 km3/year. In situ crystallization and crystal settling in density-stratified regions, as well as in convectively mixed, less evolved subjacent magma, operate rapidly enough to match this apparent

  1. Phase equilibria in the FeO-Fe2O3-NiO-H2S-H2O-HCl system: An experimental study with implications for the stability of Ni-bearing phases at ultramafic-hosted hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Hoover, R. H.; Foustoukos, D.

    2010-12-01

    Nickel-bearing minerals commonly found in altered abyssal peridotites have been shown to be important catalysts for abiogenic formation of hydrocarbons in ultramafic-hosted hydrothermal systems (e.g. awaruite, pentlandite). Recent theoretical studies on the relative stability of these phases suggest that extremely low f O2 conditions are needed to allow formation of Ni-Fe alloys and sulfides at elevated temperatures and pressures. However, such redox conditions have never been established during hydrothermal experiments involving peridotite alteration, especially at conditions that promote ferric iron partitioning into secondary alteration phases (e.g. brucite, serpentine) and limit the extent of H2(aq) generation through magnetite formation (200°C-400°C). Thus, there is a strong disagreement on the stability of Ni-bearing minerals between petrological observations in altered peridotites and theoretical models. In addition, there is a complete lack of any experimental data on the stability of awaruite (Ni3Fe) coexisting with pentlandite (Fe4.5Ni4.5S8), heazlewoodite (Ni3S2) and magnetite (Fe3O4) at conditions reflecting serpentinization processes in the subseafloor reaction zones of ultramafic-hosted systems. Thus, a series of hydrothermal experiments has been conducted involving, magnetite, heazlewoodite, pentlandite, awaruite and a composite of native Ni, Fe (80:20) coexisting with a 3.2 wt% NaCl aqueous solution at 200°C to 400°C at 500 bars. To establish phase relations as a function of redox conditions, fluid samples were analyzed for dissolved H2(aq) and H2S(aq) by gas chromatography while the chemical composition of final solid products was retrieved by SEM/EDS. Results support formation of awaruite at redox conditions significantly less reducing than those predicted by theoretical phase equilibria models. For example, in experiments conducted at 400°C-500 bars utilizing the Ni:Fe-heazlewoodite-magnetite mineral assemblage, synthesis of awaruite is

  2. On the topological stability of magnetostatic equilibria

    NASA Technical Reports Server (NTRS)

    Tsinganos, K. C.; Rosner, R.; Distler, J.

    1984-01-01

    The topological stability of MHD equilibria is investigated by exploring the formal analogy, in the ideal MHD limit, between the topology of magnetic lines of force in coordinate space and the topology of integral surfaces of one- and two-dimensional Hamiltonian systems in phase space. It is demonstrated that in an astrophysical setting, symmetric magnetostatic equilibria satisfying the ideal MHD equations are exceptional. The principal result of the study is that previous infinitesimal perturbation theory calculations can be generalized to include finite-amplitude and symmetry-breaking effects. The effect of the ergodicity of perturbed symmetric equilibria on heat dispersal in magnetically dominated plasmas is discussed.

  3. Phase equilibria in fullerene-containing systems as a basis for development of manufacture and application processes for nanocarbon materials

    NASA Astrophysics Data System (ADS)

    Semenov, K. N.; Charykov, N. A.; Postnov, V. N.; Sharoyko, V. V.; Murin, I. V.

    2016-01-01

    This review is the first attempt to integrate the available data on all types of phase equilibria (solubility, extraction and sorption) in systems containing light fullerenes (C60 and C70). In the case of solubility diagrams, the following types of phase equilibria are considered: individual fullerene (C60 or C70)-solvent under polythermal and polybaric conditions; C60-C70-solvent, individual fullerene-solvent(1)-solvent(2), as well as multicomponent systems comprising a single fullerene or an industrial mixture of fullerenes and vegetable oils, animal fats or essential oils under polythermal conditions. All published experimental data on the extraction equilibria in C60-C70-liquid phase(1)-liquid phase(2) systems are described systematically and the sorption characteristics of various materials towards light fullerenes are estimated. The possibility of application of these experimental data for development of pre-chromatographic and chromatographic methods for separation of fullerene mixtures and application of fullerenes as nanomodifiers are described. The bibliography includes 87 references.

  4. Phase equilibria in fullerene-containing systems as a basis for development of manufacture and application processes for nanocarbon materials

    NASA Astrophysics Data System (ADS)

    Semenov, K. N.; Charykov, N. A.; Postnov, V. N.; Sharoyko, V. V.; Murin, I. V.

    2016-01-01

    This review is the first attempt to integrate the available data on all types of phase equilibria (solubility, extraction and sorption) in systems containing light fullerenes (C60 and C70). In the case of solubility diagrams, the following types of phase equilibria are considered: individual fullerene (C60 or C70)–solvent under polythermal and polybaric conditions; C60–C70–solvent, individual fullerene–solvent(1)–solvent(2), as well as multicomponent systems comprising a single fullerene or an industrial mixture of fullerenes and vegetable oils, animal fats or essential oils under polythermal conditions. All published experimental data on the extraction equilibria in C60–C70–liquid phase(1)–liquid phase(2) systems are described systematically and the sorption characteristics of various materials towards light fullerenes are estimated. The possibility of application of these experimental data for development of pre-chromatographic and chromatographic methods for separation of fullerene mixtures and application of fullerenes as nanomodifiers are described. The bibliography includes 87 references.

  5. Visual investigation of solid-liquid phase equilibria for nonflammable mixed refrigerant

    NASA Astrophysics Data System (ADS)

    Lee, C.; Yoo, J.; Park, I.; Park, J.; Cha, J.; Jeong, S.

    2015-12-01

    Non-flammable mixed refrigerant (NF-MR) Joule Thomson (J-T) refrigerators have desirable characteristics and wide cooling temperature range compared to those of pure J-T refrigerators. However, the operating challenge due to freezing is a critical issue to construct this refrigerator. In this paper, the solid-liquid phase equilibria (i.e. freezing point) of the NF-MR which is composed of Argon, R14 (CF4), and R218 (C3F8), has been experimentally investigated by a visualized apparatus. Argon, R14 and R218 mixtures are selected to be effectively capable of reaching 100 K in the MR J-T refrigerator system. Freezing points of the mixtures have been measured with the molar compositions from 0.1 to 0.8 for each component. Each test result is simultaneously acquired by a camcorder for visual inspection and temperature measurement during a warming process. Experimental results show that the certain mole fraction of Argon, R14, and R218 mixture can achieve remarkably low freezing temperature even below 77 K. This unusual freezing point depression characteristic of the MR can be a useful information for designing a cryogenic MR J-T refrigerator to reach further down to 77 K.

  6. Petrogenesis of Mt. Baker Basalts and Andesites: Constraints From Mineral Chemistry and Phase Equilibria

    NASA Astrophysics Data System (ADS)

    Mullen, E.; McCallum, I. S.

    2009-12-01

    Basalts in continental arcs are volumetrically subordinate to andesites and this is the case for Mt. Baker in the northern Cascade magmatic arc. However, basalts provide indirect evidence on mantle compositions and processes that produce magmas parental to the abundant andesites and dacites of the stratocones. Basalts at Mt. Baker erupted from monogenetic vents peripheral to the andesitic stratocone. Flows are variable in composition; some samples would more appropriately be classified as basaltic andesites. The “basalts” have relatively low Mg/(Mg+Fe) indicating that they have evolved from their original compositions. Samples studied are Park Butte, Tarn Plateau, Lk. Shannon, Sulphur Cr. basalts, and Cathedral Crag, Hogback, and Rankin Ridge basaltic andesites. Mt. Baker lavas belong to the calc-alkaline basalt suite (CAB) defined by Bacon et al. (1997) and preserve arc geochemical features. High alumina olivine tholeiite (HAOT) are absent. Equilibrium mineral pairs and whole rock compositions were used to calculate pre-eruptive temperatures, water contents, and redox states of the “basalts.” All samples have zoned olivine phenocrysts with Fo68 to Fo87 cores and chromite inclusions. Cpx and zoned plagioclase occur in all flows, but opx occurs only in Cathedral Crag, Rankin Ridge, and Tarn Plateau. Ti-magnetite and ilmenite coexist in all flows except for Sulphur Cr., Lk. Shannon and Hogback, which contain a single Fe-Ti oxide. Liquidus temperatures range from 1080 to 1232°C and are negatively correlated with water contents. Water contents estimated using liquidus depression due to H2O (0.8 to 5.4 wt.%) agree well with plag core-whole rock equilibria estimates (1.2 to 3.9 wt.%). Park Butte, Sulphur Cr. and Lk. Shannon had <1.5 wt.% H2O, and Cathedral Crag is most hydrous. Redox states from ol-chr pairs (QFM +0.1 to +2.8) and Fe-Ti oxide pairs (QFM -0.6 to +1.8) indicate that Park Butte and Sulphur Cr. are most oxidized and Cathedral Crag most reduced

  7. 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.

  8. Postperovskite phase equilibria in the MgSiO3–Al2O3 system

    PubMed Central

    Tsuchiya, Jun; Tsuchiya, Taku

    2008-01-01

    We investigate high-P,T phase equilibria of the MgSiO3–Al2O3 system by means of the density functional ab initio computation methods with multiconfiguration sampling. Being different from earlier studies based on the static substitution properties with no consideration of Rh2O3(II) phase, present calculations demonstrate that (i) dissolving Al2O3 tends to decrease the postperovskite transition pressure of MgSiO3 but the effect is not significant (≈-0.2 GPa/mol% Al2O3); (ii) Al2O3 produces the narrow perovskite+postperovskite coexisting P,T area (≈1 GPa) for the pyrolitic concentration (xAl2O3 ≈6 mol%), which is sufficiently responsible to the deep-mantle D″ seismic discontinuity; (iii) the transition would be smeared (≈4 GPa) for the basaltic Al-rich composition (xAl2O3 ≈20 mol%), which is still seismically visible unless iron has significant effects; and last (iv) the perovskite structure spontaneously changes to the Rh2O3(II) with increasing the Al concentration involving small displacements of the Mg-site cations. PMID:19036928

  9. Phase equilibria and crystal chemistry of the R-Cu-Ti-O systems ( R=lanthanides and Y)

    NASA Astrophysics Data System (ADS)

    Yang, Z.; Wong-Ng, W.; Kaduk, J. A.; Jang, M.; Liu, G.

    2009-05-01

    As part of the study of interaction of the Ba 2RCu 3O 6+z ( R=lanthanides and Y) superconductor with SrTiO 3 buffer, phase equilibria of the subsystem, R2O 3-TiO 2-CuO ( R=Nd, Y, and Yb), have been investigated in air at 960 °C. While the phase relationships of the two phase diagrams with smaller R (Y and Yb) are similar, substantial differences were found in the Nd 2O 3-TiO 2-CuO system, partly due to different phase formation in the binary R2O 3-TiO 2 and R2O 3-CuO systems. R2CuTiO 6 and R2Cu 9Ti 12O 36 were the only ternary phases established in all the three diagrams. R2Cu 9Ti 12O 36 belongs to the perovskite-related [AC 3](B 4)O 12 family which is cubic Im3. Depending on the size of R3+, R2CuTiO 6 crystallizes in two crystal systems: Pnma ( R=La-Gd), and P63cm ( R=Dy-Lu). The structure and crystal chemistry of the Pnma series of R2CuTiO 6 ( R=La, Nd, Sm, Eu, and Gd) are discussed in detail in this paper. Patterns for selected members of R2CuTiO 6 have also been prepared and submitted for inclusion in the Powder Diffraction File (PDF).

  10. Putting Phase Equilibria into Geodynamic Models: An Equation of State Approach (Invited)

    NASA Astrophysics Data System (ADS)

    Connolly, J.

    2009-12-01

    temperature and pressure. Although this formulation is straightforward, the computation of phase equilibria as a function of entropy and volume is challenging because the equations of state for individual phases are usually expressed as a function of temperature and pressure. This challenge can be met by an algorithm in which continuous equations of state are approximated by a series of discrete states; a representation that reduces the phase equilibrium problem to a linear optimization problem that is independent of the functional form used for the equations of state of individual phases and readily solved by successive linear programming. Regardless of the way free energy minimization is implemented and the choice of independent variables, a consistent definition of pressure, and the coupling of equilibrium kinetics to deformation, is only possible if the continuity equation accounts for dilational strain.

  11. Experimental Investigation and Thermodynamic Calculation of the Phase Equilibria in the Mg-Gd-Mn Ternary System

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Hu, Biao; Xu, Honghui; Liu, Shuhong; Zhou, Tao; Jin, Zhanpeng

    2015-10-01

    The phase equilibria of the Mg-Gd-Mn system at 773 K (500 °C) were investigated with sixteen alloys, by means of X-ray diffraction technique and electron probe microanalyses. Eight three-phase equilibria were accurately determined. No ternary compound was observed at 773 K (500 °C). The solubility of the third elements in the binary phases was measured. The isothermal section of the Mg-Gd-Mn system at 773 K (500 °C) was firstly established. It is worth mentioning that the three-phase field GdMg3-GdMg5-( αMn) was experimentally observed and is different from the three-phase field GdMg3-GdMg5-GdMn12 predicted using only the binary interaction parameters. Using the CALPHAD method, a thermodynamic modeling of the Mg-Gd-Mn system has been carried out in order to reasonably describe the experimental observations. The substitutional solution and sublattice models were used to describe the solution phases and intermediate phases. Comprehensive comparison between the calculated and measured isothermal sections shows that the experimental information is satisfactorily accounted for by the present thermodynamic modeling.

  12. Transferable potentials for phase equilibria. 8. United-atom description for thiols, sulfides, disulfides, and thiophene.

    PubMed

    Lubna, Nusrat; Kamath, Ganesh; Potoff, Jeffrey J; Rai, Neeraj; Siepmann, J Ilja

    2005-12-22

    An extension of the transferable potentials for phase equilibria united-atom (TraPPE-UA) force field to thiol, sulfide, and disulfide functionalities and thiophene is presented. In the TraPPE-UA force field, nonbonded interactions are governed by a Lennard-Jones plus fixed point charge functional form. Partial charges are determined through a CHELPG analysis of electrostatic potential energy surfaces derived from ab initio calculations at the HF/6-31g+(d,p) level. The Lennard-Jones well depth and size parameters for four new interaction sites, S (thiols), S(sulfides), S(disulfides), and S(thiophene), were determined by fitting simulation data to pure-component vapor-equilibrium data for methanethiol, dimethyl sulfide, dimethyl disulfide, and thiophene, respectively. Configurational-bias Monte Carlo simulations in the grand canonical ensemble combined with histogram-reweighting methods were used to calculate the vapor-liquid coexistence curves for methanethiol, ethanethiol, 2-methyl-1-propanethiol, 2-methyl-2-propanethiol, 2-butanethiol, pentanethiol, octanethiol, dimethyl sulfide, diethyl sulfide, ethylmethyl sulfide, dimethyl disulfide, diethyl disulfide, and thiophene. Excellent agreement with experiment is achieved, with unsigned errors of less than 1% for saturated liquid densities and less than 3% for critical temperatures. The normal boiling points were predicted to within 1% of experiment in most cases, although for certain molecules (pentanethiol) deviations as large as 5% were found. Additional calculations were performed to determine the pressure-composition behavior of ethanethiol+n-butane at 373.15 K and the temperature-composition behavior of 1-propanethiol+n-hexane at 1.01 bar. In each case, a good reproduction of experimental vapor-liquid equilibrium separation factors is achieved; both of the coexistence curves are somewhat shifted because of overprediction of the pure-component vapor pressures. PMID:16375402

  13. Interpretation of trace element and isotope features of basalts: relevance of field relations, petrology, major element data, phase equilibria, and magma chamber modeling in basalt petrogenesis

    NASA Astrophysics Data System (ADS)

    O'Hara, M. J.; Herzberg, C.

    2002-06-01

    explain the chemical variation between fertile and residual peridotite in natural ultramafic rock suites. The subtleties of magma chamber partial crystallization processes can produce an astounding array of "pseudospidergrams," a small selection of which have been explored here. Major modification of the trace element geochemistry and trace element ratios, even those of the highly incompatible elements, must always be entertained whenever the evidence suggests the possibility of partial crystallization. At one extreme, periodically recharged, periodically tapped magma chambers might undergo partial crystallization by ˜95% consolidation of a succession of small packets of the magma. Refluxing of the 5% residual melts from such a process into the main body of melt would lead to eventual discrimination between highly incompatible elements in that residual liquid comparable with that otherwise achieved by 0.1 to 0.3% liquid extraction in equilibrium partial melting. Great caution needs to be exercised in attempting the reconstruction of more primitive compositions by addition of troctolite, gabbro, and olivine to apparently primitive lava compositions. Special attention is focussed on the phase equilibria involving olivine, plagioclase (i.e., troctolite), and liquid because a high proportion of erupted basalts carry these two phases as phenocrysts, yet the equilibria are restricted to crustal pressures and are only encountered by wide ranges of basaltic compositions at pressures less than 0.5 GPa. The mere presence of plagioclase phenocrysts may be sufficient to disqualify candidate primitive magmas. Determination of the actual contributions of crustal processes to petrogenesis requires a return to detailed field, experimental, and forensic petrologic studies of individual erupted basalt flows; of a multitude of cumulate gabbros and their contacts; and of upper-mantle outcrops.

  14. The Gibbs free energy of nukundamite (Cu3.38Fe0.62S4): A correction and implications for phase equilibria

    USGS Publications Warehouse

    Seal, R.R., II; Inan, E.E.; Hemingway, B.S.

    2001-01-01

    The Gibbs free energy of formation of nukundamite (Cu3.38Fe0.62S4) was calculated from published experimental studies of the reaction 3.25 Cu3.38Fe0.62S4 + S2 = 11 CuS + 2 FeS2 in order to correct an erroneous expression in the published record. The correct expression describing the Gibbs free energy of formation (kJ???mol-1) of nukundamite relative to the elements and ideal S2 gas is ??fG?? nukundamite T(K) = -549.75 + 0.23242 T + 3.1284 T0.5, with an uncertainty of 0.6%. An evaluation of the phase equilibria of nukundamite with associated phases in the system Cu-Fe-S as a function of temperature and sulfur fugacity indicates that nukundamite is stable from 224 to 501??C at high sulfidation states. At its greatest extent, at 434??C, the stability field of nukundamite is only 0.4 log f(S2) units wide, which explains its rarity. Equilibria between nukundamite and bornite, which limit the stability of both phases, involve bornite compositions that deviate significantly from stoichiometric Cu5FeS4. Under equilibrium conditions in the system Cu-Fe-S, nukundamite + chalcopyrite is not a stable assemblage at any temperature.

  15. CRYOCHEM, Thermodynamic Model for Cryogenic Chemical Systems: Solid-Vapor and Solid-Liquid-Vapor Phase Equilibria Toward Applications on Titan and Pluto

    NASA Astrophysics Data System (ADS)

    Tan, S. P.; Kargel, J. S.; Adidharma, H.; Marion, G. M.

    2014-12-01

    Until in-situ measurements can be made regularly on extraterrestrial bodies, thermodynamic models are the only tools to investigate the properties and behavior of chemical systems on those bodies. The resulting findings are often critical in describing physicochemical processes in the atmosphere, surface, and subsurface in planetary geochemistry and climate studies. The extremely cold conditions on Triton, Pluto and other Kuiper Belt Objects, and Titan introduce huge non-ideality that prevents conventional models from performing adequately. At such conditions, atmospheres as a whole—not components individually—are subject to phase equilibria with their equilibrium solid phases or liquid phases or both. A molecular-based thermodynamic model for cryogenic chemical systems, referred to as CRYOCHEM, the development of which is still in progress, was shown to reproduce the vertical composition profile of Titan's atmospheric methane measured by the Huygens probe (Tan et al., Icarus 2013, 222, 53). Recently, the model was also used to describe Titan's global circulation where the calculated composition of liquid in Ligeia Mare is consistent with the bathymetry and microwave absorption analysis of T91 Cassini fly-by data (Tan et al., 2014, submitted). Its capability to deal with equilibria involving solid phases has also been demonstrated (Tan et al., Fluid Phase Equilib. 2013, 360, 320). With all those previous works done, our attention is now shifting to the lower temperatures in Titan's tropopause and on Pluto's surface, where much technical development remains for CRYOCHEM to assure adequate performance at low temperatures. In these conditions, solid-vapor equilibrium (SVE) is the dominant phase behavior that determines the composition of the atmosphere and the existing ices. Another potential application is for the subsurface phase equilibrium, which also involves liquid, thus three-phase equilibrium: solid-liquid-vapor (SLV). This presentation will discuss the

  16. Prediction of the phase equilibria of methane hydrates using the direct phase coexistence methodology

    SciTech Connect

    Michalis, Vasileios K.; Costandy, Joseph; Economou, Ioannis G.; Tsimpanogiannis, Ioannis N.; Stubos, Athanassios K.

    2015-01-28

    The direct phase coexistence method is used for the determination of the three-phase coexistence line of sI methane hydrates. Molecular dynamics (MD) simulations are carried out in the isothermal–isobaric ensemble in order to determine the coexistence temperature (T{sub 3}) at four different pressures, namely, 40, 100, 400, and 600 bar. Methane bubble formation that results in supersaturation of water with methane is generally avoided. The observed stochasticity of the hydrate growth and dissociation processes, which can be misleading in the determination of T{sub 3}, is treated with long simulations in the range of 1000–4000 ns and a relatively large number of independent runs. Statistical averaging of 25 runs per pressure results in T{sub 3} predictions that are found to deviate systematically by approximately 3.5 K from the experimental values. This is in good agreement with the deviation of 3.15 K between the prediction of TIP4P/Ice water force field used and the experimental melting temperature of ice Ih. The current results offer the most consistent and accurate predictions from MD simulation for the determination of T{sub 3} of methane hydrates. Methane solubility values are also calculated at the predicted equilibrium conditions and are found in good agreement with continuum-scale models.

  17. Phase equilibria of carbon dioxide and methane gas-hydrates predicted with the modified analytical S-L-V equation of state

    NASA Astrophysics Data System (ADS)

    Vinš, Václav; Jäger, Andreas; Hrubý, Jan; Span, Roland

    2012-04-01

    Gas-hydrates (clathrates) are non-stoichiometric crystallized solutions of gas molecules in the metastable water lattice. Two or more components are associated without ordinary chemical union but through complete enclosure of gas molecules in a framework of water molecules linked together by hydrogen bonds. The clathrates are important in the following applications: the pipeline blockage in natural gas industry, potential energy source in the form of natural hydrates present in ocean bottom, and the CO2 separation and storage. In this study, we have modified an analytical solid-liquid-vapor equation of state (EoS) [A. Yokozeki, Fluid Phase Equil. 222-223 (2004)] to improve its ability for modeling the phase equilibria of clathrates. The EoS can predict the formation conditions for CO2- and CH4-hydrates. It will be used as an initial estimate for a more complicated hydrate model based on the fundamental EoSs for fluid phases.

  18. Polarization effects and phase equilibria in high-energy-density polyvinylidene-fluoride-based polymers.

    SciTech Connect

    Ranjan, V.; Yu, L.; Nakhmanson, S.; Bernholc, J.; Nardelli, M. B.; Materials Science Division; North Carolina State Univ.; ORNL

    2010-01-01

    Using first-principles calculations, the phase diagrams of polyvinylidene fluoride (PVDF) and its copolymers under an applied electric field are studied and phase transitions between their nonpolar {alpha} and polar {beta} phases are discussed. The results show that the degree of copolymerization is a crucial parameter controlling the structural phase transition. In particular, for tetrafluoroethylene (TeFE) concentration above 12%, PVDF-TeFE is stabilized in the {beta} phase, whereas the {alpha} phase is stable for lower concentrations. As larger electric fields are applied, domains with smaller concentrations ({le} 12%) undergo a transition from the {alpha} to the {beta} phase until a breakdown field of {approx}600 MV m{sup -1} is reached. These structural phase transitions can be exploited for efficient storage of electrical energy.

  19. New apparatus for simultaneous determination of phase equilibria and rheological properties of fluids at high pressures: Its application to coal pastes studies up to 773 K and 30 MPa

    NASA Astrophysics Data System (ADS)

    Cohen, Albert; Richon, Dominique

    1986-06-01

    In this article, we present a new apparatus based on a static method to simultaneously measure rheological properties of a dense (liquid or liquid+solid) medium and sample phases (dense and gaseous) for analysis purposes. It was especially designed to study coal pastes in the working conditions of hydroliquefaction processes. It can also be used to study other mediums such as asphalts and polymers. The rheometer part of the apparatus was already tested and results published in a previous paper. The ability of the new apparatus to get reliable vapor-liquid equilibrium data in the range of thermal stability of chemical materials is shown as a result of measurements on the nitrogen-n-heptane system at 497.1 K and the methane-n-hexadecane system at 623.1 K and comparison to literature's data. Reproducibility tests have displayed very small data dispersion.

  20. DEVELOPMENT OF A HIGH-TEMPERATURE CERAMIC BRAZE: ANALYSIS OF PHASE EQUILIBRIA IN THE Pd-Ag-CuOx SYSTEM

    SciTech Connect

    Weil, K. Scott; Darsell, Jens T.

    2006-01-18

    This paper describes the effects of small palladium additions on the phase equilibria in the Ag-CuOx system. Below a concentration of 5 mol%, palladium was found to increase the temperature of the eutectic reaction present in the pseudobinary system, but have little effect on a higher temperature monotectic reaction. However once enough palladium was added to increase the pseudoternary solidus temperature to that of the lower boundary for this three-phase field (~970°C), the lower boundary begins to increase in temperature as well. The addition of palladium also causes the original eutectic point to move to lower silver concentrations, which also causes a convergence of the two new three-phase fields, CuOx + L1 + L2 and CuOx + α + L1. This suggests that with higher palladium concentrations, a peritectic reaction, α + L1 + L2 → CuOx, may eventually be observed in the system.

  1. Phase and extraction equilibria in the water-ammonium chloride-Sintamid-5 system

    NASA Astrophysics Data System (ADS)

    Lesnov, A. E.; Kudryashova, O. S.; Denisova, S. A.; Chepkasova, A. V.

    2008-06-01

    The solubility isotherm of the H2O-NH4Cl-Sintamid-5 ternary system at 298 K was constructed on the basis of refractometer measurements. It was found that the region of two-phase liquid equilibrium existed over a wide pH range at inorganic acid concentrations from 10 to 2 mol/l. The distribution of some metal ions between the phases was studied. Conditions for quantitative extraction of thallium(III) and gallium were determined.

  2. An analytical equation of state for describing isotropic-nematic phase equilibria of Lennard-Jones chain fluids with variable degree of molecular flexibility

    NASA Astrophysics Data System (ADS)

    van Westen, Thijs; Oyarzún, Bernardo; Vlugt, Thijs J. H.; Gross, Joachim

    2015-06-01

    We develop an equation of state (EoS) for describing isotropic-nematic (IN) phase equilibria of Lennard-Jones (LJ) chain fluids. The EoS is developed by applying a second order Barker-Henderson perturbation theory to a reference fluid of hard chain molecules. The chain molecules consist of tangentially bonded spherical segments and are allowed to be fully flexible, partially flexible (rod-coil), or rigid linear. The hard-chain reference contribution to the EoS is obtained from a Vega-Lago rescaled Onsager theory. For the description of the (attractive) dispersion interactions between molecules, we adopt a segment-segment approach. We show that the perturbation contribution for describing these interactions can be divided into an "isotropic" part, which depends only implicitly on orientational ordering of molecules (through density), and an "anisotropic" part, for which an explicit dependence on orientational ordering is included (through an expansion in the nematic order parameter). The perturbation theory is used to study the effect of chain length, molecular flexibility, and attractive interactions on IN phase equilibria of pure LJ chain fluids. Theoretical results for the IN phase equilibrium of rigid linear LJ 10-mers are compared to results obtained from Monte Carlo simulations in the isobaric-isothermal (NPT) ensemble, and an expanded formulation of the Gibbs-ensemble. Our results show that the anisotropic contribution to the dispersion attractions is irrelevant for LJ chain fluids. Using the isotropic (density-dependent) contribution only (i.e., using a zeroth order expansion of the attractive Helmholtz energy contribution in the nematic order parameter), excellent agreement between theory and simulations is observed. These results suggest that an EoS contribution for describing the attractive part of the dispersion interactions in real LCs can be obtained from conventional theoretical approaches designed for isotropic fluids, such as a Perturbed

  3. Direct molecular dynamics simulation of liquid-solid phase equilibria for two-component plasmas.

    PubMed

    Schneider, A S; Hughto, J; Horowitz, C J; Berry, D K

    2012-06-01

    We determine the liquid-solid phase diagram for carbon-oxygen and oxygen-selenium plasma mixtures using two-phase molecular dynamics simulations. We identify liquid, solid, and interface regions using a bond angle metric. To study finite-size effects, we perform 27,648- and 55,296-ion simulations. To help monitor nonequilibrium effects, we calculate diffusion constants D(i). For the carbon-oxygen system we find that D(O) for oxygen ions in the solid is much smaller than D(C) for carbon ions and that both diffusion constants are 80 or more times smaller than diffusion constants in the liquid phase. There is excellent agreement between our carbon-oxygen phase diagram and that predicted by Medin and Cumming. This suggests that errors from finite-size and nonequilibrium effects are small and that the carbon-oxygen phase diagram is now accurately known. The oxygen-selenium system is a simple two-component model for more complex rapid proton capture nucleosynthesis ash compositions for an accreting neutron star. Diffusion of oxygen, in a predominantly selenium crystal, is remarkably fast, comparable to diffusion in the liquid phase. We find a somewhat lower melting temperature for the oxygen-selenium system than that predicted by Medin and Cumming. This is probably because of electron screening effects. PMID:23005226

  4. Direct molecular dynamics simulation of liquid-solid phase equilibria for two-component plasmas

    NASA Astrophysics Data System (ADS)

    Schneider, A. S.; Hughto, J.; Horowitz, C. J.; Berry, D. K.

    2012-06-01

    We determine the liquid-solid phase diagram for carbon-oxygen and oxygen-selenium plasma mixtures using two-phase molecular dynamics simulations. We identify liquid, solid, and interface regions using a bond angle metric. To study finite-size effects, we perform 27 648- and 55 296-ion simulations. To help monitor nonequilibrium effects, we calculate diffusion constants Di. For the carbon-oxygen system we find that DO for oxygen ions in the solid is much smaller than DC for carbon ions and that both diffusion constants are 80 or more times smaller than diffusion constants in the liquid phase. There is excellent agreement between our carbon-oxygen phase diagram and that predicted by Medin and Cumming. This suggests that errors from finite-size and nonequilibrium effects are small and that the carbon-oxygen phase diagram is now accurately known. The oxygen-selenium system is a simple two-component model for more complex rapid proton capture nucleosynthesis ash compositions for an accreting neutron star. Diffusion of oxygen, in a predominantly selenium crystal, is remarkably fast, comparable to diffusion in the liquid phase. We find a somewhat lower melting temperature for the oxygen-selenium system than that predicted by Medin and Cumming. This is probably because of electron screening effects.

  5. Tales from supereruptions: Combining pumice and mineral textures with phase equilibria to constrain the evolution of giant silicic magma bodies in the crust

    NASA Astrophysics Data System (ADS)

    Gualda, G. A. R.; Pamukcu, A. S.; Wright, K. A.; Ghiorso, M. S.; Miller, C. F.

    2014-12-01

    Supereruption deposits demonstrate that giant magma bodies sporadically exist within the Earth's crust. We rely on study of such deposits to better understand the underlying magma bodies and their eruptions. We are studying several deposits: Bishop Tuff (BT, CA USA), Peach Spring Tuff (PST, SW USA), and Oruanui Tuff (OT, NZ). We combine quantitative textural characterization in 3D via x-ray tomography (XRT), focusing particularly on CSDs of major and accessory minerals; characterization of mineral zoning, particularly of Ti and CL in quartz, including inferences from diffusion chronometry; documentation of glass inclusion textures in 3D via XRT, with implications to crystallization timescales; and phase equilibria modeling (rhyolite-MELTS), including glass (inclusion and matrix) composition geobarometry, to constrain crystallization conditions. CSDs ubiquitously record a growth-dominated regime, characterized by limited nucleation, consistent with pre-eruptive crystallization under low supersaturation. Phenocryst interiors are largely unzoned, consistent with phase equilibria predictions of nearly invariant, effectively isothermal crystallization. Glass compositions record storage over a large spread of depths (~125-250 MPa) for early and late-erupted BT, while the OT represents multiple magma batches evacuated from different depths. Diffusion chronometry and melt inclusion faceting suggest pre-eruptive crystallization over centennial timescales. CSDs and mineral textures also record syn-eruptive crystallization, which results in huge numbers of small crystals, revealing extensive nucleation prior to eruption. Crystal rims develop on pre-existing phenocrysts, and they can be obvious if compositionally distinct from interiors (BT and PST). In PST, evidence for rim crystallization from hotter magma is very strong. BT contrasts with PST in many ways; evidence for heating is ambiguous, and pumice properties are difficult to reconcile with magma mixing, while the

  6. Experimental Determination of Phase Equilibria in the Silver-Copper Oxide System at High Temperature

    SciTech Connect

    Darsell, Jens T.; Weil, K. Scott

    2007-06-01

    The phase diagram of silver-copper oxide was studied using thermal, microstructural and compositional analysis of quenched samples. The eutectic and monotectic temperature were found and compared to previous data. The miscibility gap was analyzed at higher temperatures than previous experimental work. The profile of the miscibility gap was found to extend from the monotectic composition and extend further into the copper rich portion than previously experimental work had show, which verifies a previous computational study.

  7. Priming Silicic Giant Magma Bodies: Finding Evidence for Internal Forcing Versus External Triggering of Supereruptions by Phase Equilibria Modeling.

    NASA Astrophysics Data System (ADS)

    Tramontano, S.; Gualda, G. A. R.; Ghiorso, M. S.; Kennedy, B.

    2015-12-01

    It is important to understand what triggers silicic eruptions because of the implications for modern-day systems. The goal of this project is to use phase equilibria modeling (i.e. rhyolite-MELTS) to determine to what extent magmas within the crust are induced to erupt due to external triggers (e.g. earthquakes; new magma injection; neighboring eruptions) and to what extent they naturally evolve to a point where eruption is inevitable (e.g. by fluid exsolution and decrease in magma strength and density). Whole-rock compositions from four rhyolite tuffs across the globe associated with large or supereruptions (Mamaku Tuff, New Zealand; Peach Spring Tuff, SW USA; early and late-erupted Bishop Tuff, California; and Toba Tuff, Indonesia) are studied using rhyolite-MELTS modeling. Key physical properties of magma are strongly affected by the initial volatile content due to fluid exsolution. By running simulations with varying water contents, we can track the evolution of fluid exsolution during crystallization. Isobaric (constrained temperature change at constant pressure) and isochoric (constrained temperature change at constant volume) models were run for the four compositions. In constrained-pressure scenarios, fluid is free to exsolve as crystallization proceeds, and the total system volume can increase or decrease accordingly; this would require deformation of the surrounding crust to accommodate the magma volume change. In constrained-volume scenarios, bubble exsolution is limited to the volume change due to crystallization; in this case, pressure can decrease or increase (if bubbles are absent or present). For fixed-pressure scenarios, fluid exsolution is more extensive and leads to internal triggering, at least for fluid-saturated conditions; external triggering is more likely in fluid-undersaturated conditions. For fixed-volume scenarios, none of the systems cross a fragmentation threshold for the crystal contents typically observed in natural pumice. If

  8. Phase equilibria and NaCu 2O 2 crystal growth in the Na-Cu-O system

    NASA Astrophysics Data System (ADS)

    Maljuk, A. N.; Kulakov, A. B.; Sofin, M.; Capogna, L.; Lin, C. T.; Jansen, M.; Keimer, B.

    2005-02-01

    The phase equilibria in the Cu-rich part of the Na-Cu-O phase diagram have been investigated by DTA-TG and powder X-ray diffraction (XRD) methods at different oxygen pressures. Part of the preliminary Na-Cu-O phase diagram has been built up, and the low-stability-limit of the NaCu 2O 2 phase was established. Based on these data single crystals of NaCu 2O 2 compound were obtained for the first time by the self-flux technique. Powder and single crystal XRD measurements verify the high quality of prepared crystals. All crystals have the orthorhombic structure: a=6.2087(1) Å, b=2.9343(1) Å and c=13.0648(3) Å. The magnetic susceptibility and heat capacity measurements carried out on the NaCu 2O 2 single crystals in the temperature range 2-325 K showed clear evidence of antiferromagnetism at T=12.25 K.

  9. NIMROD studies of RWM stability and non-linear evolution for NSTX equilibria

    NASA Astrophysics Data System (ADS)

    Becerra, A. L.; Hegna, C. C.; Sovinec, C. R.; Kruger, S. E.; King, J. R.; Sabbagh, S. A.

    2015-11-01

    We make use of the generalized thin resistive wall boundary condition recently implemented in NIMROD to study the linear and nonlinear RWM stability properties of a series of reconstructed NSTX equilibria. The boundary condition operates by matching the magnetic field inside the computational domain with external fields found using the Green's function method in the GRIN vacuum-field solver at the wall, and is valid for toroidal geometries with poloidal asymmetry as well as for cylindrical geometries. Time series of NSTX equilibrium reconstructions from two shots whose normalized betas span the no-wall limit are studied. The critical beta for RWM onset found by NIMROD is compared with the stability limit predicted by ideal MHD code DCON. Scans with varying wall parameters are also performed to demonstrate the approximately linear relationship between growth rate and wall resistivity, and to test the performance limits of the boundary condition. The stability of these equilibria for n>1 is also examined, with both linear and non-linear runs in preparation for examining the non-linear effects due to toroidal rotation. Research supported by U. S. DoE under grant no. DE-FG02-86ER53218.

  10. Calculations of phase equilibria for mixtures of triglycerides, fatty acids, and their esters in lower alcohols

    NASA Astrophysics Data System (ADS)

    Stepanov, D. A.; Ermakova, A.; Anikeev, V. I.

    2011-01-01

    The objects of study were mixtures containing triglycerides and lower alcohols and also the products of the transesterification of triglycerides, glycerol and fatty acid esters. The Redlich-Kwong-Soave equation of state was used as a thermodynamic model for the phase state of the selected mixtures over wide temperature, pressure, and composition ranges. Group methods were applied to determine the critical parameters of pure substances and their acentric factors. The parameters obtained were used to calculate the phase diagrams and critical parameters of mixtures containing triglycerides and lower alcohols and the products of the transesterification of triglycerides, glycerol and fatty acid esters, at various alcohol/oil ratios. The conditions of triglyceride transesterification in various lower alcohols providing the supercritical state of reaction mixtures were selected.

  11. A New Internally Consistent Thermodynamic Model for Calculating Hornblende-Bearing Phase Equilibria With Rhyolite-MELTS

    NASA Astrophysics Data System (ADS)

    Brooks, C. E.; Ghiorso, M. S.; Gualda, G. A.

    2011-12-01

    Hornblendes are the most widespread and compositionally variable hydrous minerals in igneous rocks, and provide important constraints on magmatic T-, P-conditions, volatile contents, and redox state. Despite their importance, the stability of hornblende is not currently modeled in the MELTS software package, due principally to the lack of an internally consistent thermodynamic model for the phase. This work represents a first attempt to rectify this deficiency. A database of phase compositions from hornblende-liquid equilibrium experiments was compiled from relevant studies in LEPR (Library of Experimental Phase Relations, Hirschmann et al. 2008) and supplemented with additional literature sources. We analyzed the compositional space of these compiled amphibole data using Principal Component Analysis (PCA) and selected eight component end-members to represent the major degrees of variance. A thermodynamic model was formulated under the assumption of ideal-site mixing on A, M4, M13, M2, and T1 sites, and a strictly regular solution to describe the excess Gibbs free energy of mixing. The model is calibrated from liquid-hornblende exchange equilibria with end-member properties (H, S, V) optimized along with excess mixing terms. The eight end-members selected, K-Hastingsite ( KCa2Mg4Fe3+Si6Al2O22(OH)2 ), Hastingsite ( NaCa2Mg4Fe3+Si6Al2O22(OH)2 ), Pargasite ( NaCa2Mg4AlSi6Al2O22(OH)2 ), Fe-Pargasite ( NaCa2Fe4AlSi6Al2O22(OH)2 ), Hornblende ( []Ca2Mg4AlSi7AlO22(OH)2 ), Kaersutite ( NaCa2Mg4TiSi6Al2O22OOH ), Edenite ( NaCa2Mg5AlSi7AlO22(OH)2 ), and Barroisite ( []NaCaMg3Al2Si7AlO22(OH)2 ), together with reciprocal exchange reactions, describe the general compositional variation of most volcanic amphiboles found in rocks spanning from basalt to rhyolite. The compiled database represents a liquid bulk compositional range from 40 to 73 wt. % SiO2. Preliminary modeling of natural and experimental whole rock data suggests hornblende compositions produced using this model in

  12. Phase equilibria in the oxide system Nd 2O 3-K 2O-P 2O 5

    NASA Astrophysics Data System (ADS)

    Szczygieł, Irena; Znamierowska, Teresa; Mizer, Dagmara

    2010-07-01

    A phase equilibria diagram of the partial system NdPO 4-K 3PO 4-KPO 3 has been developed as part of the research aimed at determining the phase equilibrium relationships in the oxide system Nd 2O 3-K 2O-P 2O 5. The investigations were conducted using thermoanalytical techniques, X-ray powder diffraction analysis and reflected-light microscopy. Three isopleths existing between: K 3Nd(PO 4) 2-K 4P 2O 7, NdPO 4-K 5P 3O 10 and NdPO 4-K 4P 2O 7 have been identified in the partial NdPO 4-K 3PO 4-KPO 3 system. Previously unknown potassium-neodymium phosphate "K 4Nd 2P 4O 15" has been discovered in the latter isopleth section. This phosphate exists in the solid phase up to a temperature of 890 °C at which it decomposes into the parent phosphates NdPO 4 and K 4P 2O 7. Four invariant points: two quasi-ternary eutectics, E 1 (1057 °C) and E 2 (580 °C) and two quasi-ternary peritectics, P 1 (1078 °C) and P 2 (610 °C), occur in the NdPO 4-K 3PO 4-KPO 3 region.

  13. Effect of Slag Basicity on Phase Equilibria and Selenium and Tellurium Distribution in Magnesia-Saturated Calcium Iron Silicate Slags

    NASA Astrophysics Data System (ADS)

    Johnston, M. D.; Jahanshahi, S.; Zhang, L.; Lincoln, F. J.

    2010-06-01

    New measurements have been made on the phase equilibria of magnesia-saturated CaO-FeOx-SiO2 slags at 1573 K (1300 °C) and an oxygen partial pressure of 10-9 atm. The thermodynamic behavior of selenium (Se) and tellurium (Te) in the slag and the stability of oxide mineral phases within the slag were examined as a function of slag composition. The measured equilibrium distribution of Se and Te between the slag and the copper showed nonlinear dependence on the slag basicity, reaching maxima at CaO/(CaO + SiO2) ratios of about 0.2 and 1 and a minimum at a ratio of about 0.5. The solubility of the copper oxide in the bulk slag also passed through a minimum value at a ratio of about 0.5. Results from drop-quench experiments confirmed the stability of various oxide solid solution phases at 1573 K (1300 °C) that had virtually no solubility for Se and Te. The deduced capacity of the liquid slag for Se was found to be independent of basicity in relatively basic slags, and decreased sharply as SiO2 replaced CaO in relatively acidic slags.

  14. Phase equilibria and PVT data for the methane-methanol system to 300 MPa and 240/sup 0/C

    SciTech Connect

    Francesconi, A.Z.; Lentz, H.; Franck, E.U.

    1981-10-29

    The apparatus and experimental procedure are described, which permit the determination of phase equilibria and PVT data of fluid binary systems to high temperatures and pressures. Visual observation through a sapphire window is combined with pT measurements at constant volumes. The boundary surface of the two-phase region of the methane-methanol system is determined by pT curves of nine compositions (isopleths) from 8 to 90 mol % CH/sub 3/OH. The critical curve is of the interrupted type and extends from the critical point of methanol (239/sup 0/C, 8.1 MPa) to 33.0/sup 0/C and 300 MPa with a critical volume of 31.2 cm/sup 3/ mol/sup -1/. At 150/sup 0/C molar volume data for the one-phase region to 300 MPa are given. For pressures to 30 MPa the critical curve could be calculated by a semiempirical method. New experimentally determined data for the molar volumes of methane are presented from 50 to 450/sup 0/C and from 30 to 300 MPa.

  15. Applications of Wang-Landau sampling to determine phase equilibria in complex fluids

    NASA Astrophysics Data System (ADS)

    Ganzenmüller, Georg; Camp, Philip J.

    2007-10-01

    Applications of the Wang-Landau algorithm for simulating phase coexistence at fixed temperature are presented. The number density is sampled using either volume scaling or particle insertion/deletion. The resulting algorithms, while being conceptually easy, are of comparable efficiency to existing multicanonical methods but with the advantage that neither the chemical potential nor the pressure at phase coexistence has to be estimated in advance of the simulation. First, we benchmark the algorithm against literature results for the vapor-liquid transition in the Lennard-Jones fluid. We then demonstrate the general applicability of the algorithm by studying vapor-liquid coexistence in two examples of complex fluids: charged soft spheres, which exhibit a transition similar to that in the restricted primitive model of ionic fluids, being characterized by strong ion pairing in the vapor phase; and Stockmayer fluids with high dipole strengths, in which the constituent particles aggregate to form chains, and for which the very existence of a transition has been widely debated. Finally, we show that the algorithm can be used to locate a weak isotropic-nematic transition in a fluid of Gay-Berne mesogens.

  16. Applications of Wang-Landau sampling to determine phase equilibria in complex fluids.

    PubMed

    Ganzenmüller, Georg; Camp, Philip J

    2007-10-21

    Applications of the Wang-Landau algorithm for simulating phase coexistence at fixed temperature are presented. The number density is sampled using either volume scaling or particle insertion/deletion. The resulting algorithms, while being conceptually easy, are of comparable efficiency to existing multicanonical methods but with the advantage that neither the chemical potential nor the pressure at phase coexistence has to be estimated in advance of the simulation. First, we benchmark the algorithm against literature results for the vapor-liquid transition in the Lennard-Jones fluid. We then demonstrate the general applicability of the algorithm by studying vapor-liquid coexistence in two examples of complex fluids: charged soft spheres, which exhibit a transition similar to that in the restricted primitive model of ionic fluids, being characterized by strong ion pairing in the vapor phase; and Stockmayer fluids with high dipole strengths, in which the constituent particles aggregate to form chains, and for which the very existence of a transition has been widely debated. Finally, we show that the algorithm can be used to locate a weak isotropic-nematic transition in a fluid of Gay-Berne mesogens. PMID:17949170

  17. Volumetric Properties and Fluid Phase Equilibria of CO2 + H2O

    SciTech Connect

    Capobianco, Ryan; Gruszkiewicz, Miroslaw {Mirek} S; Wesolowski, David J; Cole, David R; Bodnar, Robert

    2013-01-01

    The need for accurate modeling of fluid-mineral processes over wide ranges of temperature, pressure and composition highlighted considerable uncertainties of available property data and equations of state, even for the CO2 + H2O binary system. In particular, the solubility, activity, and ionic dissociation equilibrium data for the CO2-rich phase, which are essential for understanding dissolution/precipitation, fluid-matrix reactions, and solute transport, are uncertain or missing. In this paper we report the results of a new experimental study of volumetric and phase equilibrium properties of CO2 + H2O, to be followed by measurements for bulk and confined multicomponent fluid mixtures. Mixture densities were measured by vibrating tube densimetry (VTD) over the entire composition range at T = 200 and 250 C and P = 20, 40, 60, and 80 MPa. Initial analysis of the mutual solubilities, determined from volumetric data, shows good agreement with earlier results for the aqueous phase, but finds that the data of Takenouchi and Kennedy (1964) significantly overestimated the solubility of water in supercritical CO2 (by a factor of more than two at 200 C). Resolving this well-known discrepancy will have a direct impact on the accuracy of predictive modeling of CO2 injection in geothermal reservoirs and geological carbon sequestration through improved equations of state, needed for calibration of predictive molecular-scale models and large-scale reactive transport simulations.

  18. Phase equilibria in a system of aqueous arginine with an octane solution of sulfonic acid

    NASA Astrophysics Data System (ADS)

    Kuvaeva, Z. I.; Koval'chuk, I. V.; Vodop'yanova, L. A.; Soldatov, V. S.

    2013-05-01

    The extraction of arginine (Arg) from aqueous salt (0.1 M NaCl) solutions with a sulfo extractant in a wide range of pH values and amino acid concentrations was studied. The 0.1 M solution of dinonylnaphthalenesulfonic acid (HD) in octane was used as an extractant. The degree of extraction was found to be high at pH 0.8-9.0. This can be explained by the effect of additional intermolecular interactions in the extractant phase involving the guanidine group of Arg.

  19. Phase equilibria and crystal structure of the complex oxides in the Ln-Ba-Co-O (Ln=Nd, Sm) systems

    SciTech Connect

    Gavrilova, L.Ya.; Aksenova, T.V.; Volkova, N.E.; Podzorova, A.S.; Cherepanov, V.A.

    2011-08-15

    The phase equilibria in the Ln-Ba-Co-O (Ln=Nd, Sm) systems were systematically studied at 1100 deg. C in air. The homogeneity ranges and crystal structure of the solid solutions: Ln{sub 2-x}Ba{sub x}O{sub 3-{delta}} (0phase diagrams for the Ln-Ba-Co-O (Ln=Nd, Sm) systems to the compositional triangle of metallic components were presented. - Graphical Abstract: Projections of isobaric isothermal phase diagrams of the Nd-Ba-Co-O system and Sm-Ba-Co-O system. Highlights: > Phase equilibria in the Ln-Ba-Co-O systems (Ln=Nd, Sm). > The homogeneity range for Nd{sub 2-x}Ba{sub x}O{sub 3-{delta}} solid solutions at studied conditions 0 The homogeneity range for Sm{sub 2-x}Ba{sub x}O{sub 3-{delta}} solid solutions at studied conditions 0 Nd{sub 3-y}Ba{sub y}Co{sub 2}O{sub 7} solid solutions within the range 0.7{<=}y{<=}0.8. > BaCo{sub 1-z}Sm{sub z}O{sub 3-{delta}} solid solutions within the range 0.1{<=}z{<=}0.2.

  20. Three-dimensional stellarator equilibria by iteration

    SciTech Connect

    Boozer, A.H.

    1983-02-01

    The iterative method of evaluating plasma equilibria is especially simple in a magnetic coordinate representation. This method is particularly useful for clarifying the subtle constraints of three-dimensional equilibria and studying magnetic surface breakup at high plasma beta.

  1. Experimental phase equilibria of a Mount St. Helens rhyodacite: a framework for interpreting crystallization paths in degassing silicic magmas

    NASA Astrophysics Data System (ADS)

    Riker, Jenny M.; Blundy, Jonathan D.; Rust, Alison C.; Botcharnikov, Roman E.; Humphreys, Madeleine C. S.

    2015-07-01

    We present isothermal (885 °C) phase equilibrium experiments for a rhyodacite from Mount St. Helens (USA) at variable total pressure (25-457 MPa) and fluid composition (XH2Ofl = 0.6-1.0) under relatively oxidizing conditions (NNO to NNO + 3). Run products were characterized by SEM, electron microprobe, and SIMS. Experimental phase assemblages and phase chemistry are consistent with those of natural samples from Mount St. Helens from the last 4000 years. Our results emphasize the importance of pressure and melt H2O content in controlling phase proportions and compositions, showing how significant textural and compositional variability may be generated in the absence of mixing, cooling, or even decompression. Rather, variations in the bulk volatile content of magmas, and the potential for fluid migration relative to surrounding melts, mean that magmas may take varied trajectories through pressure-fluid composition space during storage, transport, and eruption. We introduce a novel method for projecting isothermal phase equilibria into CO2-H2O space (as conventionally done for melt inclusions) and use this projection to interpret petrological data from Mount St. Helens dacites. By fitting the experimental data as empirical functions of melt water content, we show how different scenarios of isothermal magma degassing (e.g., water-saturated ascent, vapor-buffered ascent, and vapor fluxing) can have quite different textural and chemical consequences. We explore how petrological data might be used to infer degassing paths of natural magmas and conclude that melt CO2 content is a much more useful parameter in this regard than melt H2O.

  2. Transferable potentials for phase equilibria-united atom description of five- and six-membered cyclic alkanes and ethers.

    PubMed

    Keasler, Samuel J; Charan, Sophia M; Wick, Collin D; Economou, Ioannis G; Siepmann, J Ilja

    2012-09-13

    While the transferable potentials for phase equilibria-united atom (TraPPE-UA) force field has generally been successful at providing parameters that are highly transferable between different molecules, the polarity and polarizability of a given functional group can be significantly perturbed in small cyclic structures, which limits the transferability of parameters obtained for linear molecules. This has motivated us to develop a version of the TraPPE-UA force field specifically for five- and six-membered cyclic alkanes and ethers. The Lennard-Jones parameters for the methylene group obtained from cyclic alkanes are transferred to the ethers for each ring size, and those for the oxygen atom are common to all compounds for a given ring size. However, the partial charges are molecule specific and parametrized using liquid-phase dielectric constants. This model yields accurate saturated liquid densities and vapor pressures, critical temperatures and densities, normal boiling points, heat capacities, and isothermal compressibilities for the following molecules: cyclopentane, tetrahydrofuran, 1,3-dioxolane, cyclohexane, oxane, 1,4-dioxane, 1,3-dioxane, and 1,3,5-trioxane. The azeotropic behavior and separation factor for the binary mixtures of 1,3-dioxolane/cyclohexane and ethanol/1,4-dioxane are qualitively reproduced. PMID:22900670

  3. Phase equilibria, fluid structure, and diffusivity of a discotic liquid crystal.

    PubMed

    Cienega-Cacerez, Octavio; Moreno-Razo, José Antonio; Díaz-Herrera, Enrique; Sambriski, Edward John

    2014-05-14

    Molecular Dynamics simulations were performed for the Gay-Berne discotic fluid parameterized by GB(0.345, 0.2, 1.0, 2.0). The volumetric phase diagram exhibits isotropic (IL), nematic (ND), and two columnar phases characterized by radial distribution functions: the transversal fluid structure varies between a hexagonal columnar (CD) phase (at higher temperatures and pressures) and a rectangular columnar (CO) phase (at lower temperatures and pressures). The slab-wise analysis of fluid dynamics suggests the formation of grain-boundary defects in the CO phase. Longitudinal fluid structure is highly periodic with narrow peaks for the CO phase, suggestive of a near-crystalline (yet diffusive) system, but is only short-ranged for the CD phase. The IL phase does not exhibit anisotropic diffusion. Transversal diffusion is more favorable in the ND phase at all times, but only favorable at short times for the columnar phases. In the columnar phases, a crossover occurs where longitudinal diffusion is favored over transversal diffusion at intermediate-to-long timescales. The anomalous diffusivity is pronounced in both columnar phases, with three identifiable contributions: (a) the rattling of discogens within a transient "interdigitation" cage, (b) the hopping of discogens across columns, and (c) the drifting motion of discogens along the orientation of the director. PMID:24718439

  4. Phase equilibria in DOPC/DPPC: Conversion from gel to subgel in two component mixtures.

    PubMed

    Schmidt, Miranda L; Ziani, Latifa; Boudreau, Michelle; Davis, James H

    2009-11-01

    Biological membranes contain a mixture of phospholipids with varying degrees of hydrocarbon chain unsaturation. Mixtures of long chain saturated and unsaturated lipids with cholesterol have attracted a lot of attention because of the formation of two coexisting fluid bilayer phases in such systems over a broad range of temperature and composition. Interpretation of the phase behavior of such ternary mixtures must be based on a thorough understanding of the phase behavior of the binary mixtures formed with the same components. This article describes the phase behavior of mixtures of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with 1,2-di-d(31)-palmitoyl-sn-glycero-3-phosphocholine (DPPC) between -20 and 50 degrees C. Particular attention has been paid to the phase coexistence below about 16 degrees C where the subgel phase appears. The changes in the shape of the spectrum (and its spectral moments) during the slow transformation process leads to the conclusion that below 16 degrees C the gel phase is metastable and the gel component of the two-phase mixture slowly transforms to the subgel phase with a slightly different composition. This results in a line of three-phase coexistence near 16 degrees C. Analysis of the transformation of the metastable gel domains into the subgel phase using the nucleation and growth model shows that the subgel domain growth is a two dimensional process. PMID:19895044

  5. Phase equilibria and trace element partitioning in a magma ocean to 260 kilobars

    NASA Technical Reports Server (NTRS)

    Herzberg, Claude

    1992-01-01

    A magma ocean can solidify in a way that is intermediate between perfect equilibrium and perfect fractional crystallization. In order to model quantitatively any fractional crystallization scenario, it is necessary to understand the geochemical characteristics of the phases that crystallize from a magma ocean, and how they vary with pressure. The crystallizing phase is called the liquidus phase, and their identities were determined by numerous experiments utilizing the multianvil apparatus. For chondritic compositions the liquidus phases are as follows: olivine at 1 atmosphere to 100 kilobars; garnet from 100 to about 260 kilobars; silicate perovskite from 260 kilobars to possibly the core-mantle boundary in the Earth.

  6. Phase Equilibria of a S- and C-Poor Lunar Core

    NASA Technical Reports Server (NTRS)

    Righter, K.; Pando, K.; Go, B. M.; Danielson, L. R.; Habermann, M.

    2016-01-01

    The composition of the lunar core can have a large impact on its thermal evolution, possible early dynamo creation, and physical state. Geochemical measurements have placed better constraints on the S and C content of the lunar mantle. In this study we have carried out phase equilibrium studies of geochemically plausible S- and C-poor lunar core compositions in the Fe-Ni-S-C system, and apply them to the early history of the Moon. We chose two bulk core compositions, with differing S and C content based on geochemical analyses of S and C trapped melts in Apollo samples, and on the partitioning of S and C between metal and silicate. This approach allowed calculation of core S and C contents - 90% Fe, 9% Ni, 0.5% C, and 0.375% S by weight; a second composition contained 1% each of S and C. Experiments were carried out from 1473K to 1973K and 1 GPa to 5 GPa, in piston cylinder and multi- anvil apparatuses. Combination of the thermal model of with our results, shows that a solid inner core (and therefore initiation of a dynamo) may have been possible in the earliest history of the Moon (approximately 4.2 Ga ago), in agreement with. Thus a volatile poor lunar core may explain the thermal and magnetic history of the Moon.

  7. Prediction of fluid phase equilibria and interfacial tension of triangle-well fluids using transition matrix Monte Carlo

    NASA Astrophysics Data System (ADS)

    Sengupta, Angan; Adhikari, Jhumpa

    2016-05-01

    The triangle-well (TW) potential is a simple model which is able to capture the essence of the intermolecular attraction in real molecules. Transition matrix Monte Carlo simulations in the grand canonical ensemble (GC-TMMC) are performed to investigate the role of the range of attraction on the features of fluid phase equilibria. As the TW potential range increases, the vapour-liquid coexistence curves shift towards a higher temperature range with the critical temperature and pressure increasing, and the critical density values decreasing. These GC-TMMC results are in excellent agreement with the predictions of Gibbs ensemble Monte Carlo and replica exchange Monte Carlo (REMC) simulations reported in literature. Using the GC-TMMC method, the vapour pressures are also computed directly from the particle number probability distributions (PNPDs). It has been noted in literature that the surface tension values are computationally more expensive and difficult to determine than other coexistence properties using molecular simulations. The PNPDs from GC-TMMC simulations along with Binder's formalism allow for the calculation of the interfacial tension with relative ease. Also, our simulation generated results for the interfacial tension are in good agreement with the literature data obtained using REMC (via the virial route) and the plots of our interfacial tension values as a function of temperature are smooth unlike the literature data.

  8. Thermal analysis, phase equilibria, and superconducting properties in magnesium boride and carbon doped magnesium boride

    NASA Astrophysics Data System (ADS)

    Bohnenstiehl, Scot David

    In this work, the low temperature synthesis of MgB2 from Mg/B and MgH2/B powder mixtures was studied using Differential Scanning Calorimetry (DSC). For the Mg/B powder mixture, two exothermic reaction events were observed and the first reaction event was initiated by the decomposition of Mg(OH)2 on the surface of the magnesium powder. For the MgH 2/B powder mixture, there was an endothermic event at ˜375 °C (the decomposition of MgH2 into H2 and Mg) and an exothermic event ˜600 °C (the reaction of Mg and B). The Kissinger analysis method was used to estimate the apparent activation energy of the Mg and B reaction using DSC data with different furnace ramp rates. The limitations of MgB2 low temperature synthesis led to the development of a high pressure induction furnace that was constructed using a pressure vessel and an induction heating power supply. The purpose was to not only synthesize more homogeneous MgB2 samples, but also to determine whether MgB2 melts congruently or incongruently. A custom implementation of the Smith Thermal Analysis method was developed and tested on aluminum and AlB2, the closest analogue to MgB2. Measurements on MgB2 powder and a high purity Mg/B elemental mixture confirmed that MgB2 melts incongruently and decomposes into a liquid and MgB4 at ˜1445 °C at 10 MPa via peritectic decomposition. Another measurement using a Mg/B elemental mixture with impure boron suggested that ˜0.7 wt% carbon impurity in the boron raised the incongruent melting temperature to ˜1490-1500 °C. Lastly, the solubility limit for carbon in MgB2 was studied by making samples from B4C and Mg at 1530 °C, 1600 °C and 1700 °C in the high pressure furnace. All three samples had three phases: Mg, MgB2C2, and carbon doped MgB2. The MgB 2C2 and carbon doped MgB2 grain size increased with temperature and the 1700 °C sample had needle-like grains for both phases. The presence of the ternary phase, MgB2C2, suggested that the maximum doping limit for carbon in

  9. Phase Equilibria, Microstructure, and High-Temperature Strength of TiC-Added Mo-Si-B Alloys

    NASA Astrophysics Data System (ADS)

    Miyamoto, Shimpei; Yoshimi, Kyosuke; Ha, Seong-Ho; Kaneko, Takahiro; Nakamura, Junya; Sato, Tetsuya; Maruyama, Kouichi; Tu, Rong; Goto, Takashi

    2013-05-01

    TiC was added to Mo-Si-B alloys using a conventional Ar arc-melting technique, and the phase equilibria, microstructure evolution, and high-temperature strength at 1673 K (1400 °C) were investigated. The primary phase changed to Mo solid solution (Moss), Mo5SiB2 (T2), or TiC depending on the composition. Following the primary phase solidification, a Moss + TiC, Moss + T2, or Moss + T2 + TiC + Mo2C eutectic reaction took place as the secondary solidification step. In some alloys, Moss + T2 + TiC and Moss + T2 + Mo2C eutectic reactions were present as higher-order solidification steps. After annealing at 2073 K (1800 °C) for 24 hours, Moss, T2, TiC, and Mo2C coexisted stably with microstructural coarsening. The coarsening rate was much faster in an alloy with no TiC dispersion, suggesting that TiC has a strong pinning effect on the grain boundary and interface migration. Compression tests conducted at 1673 K (1400 °C) revealed strength properties of almost all the alloys that were better than those of the Mo-Hf-C alloy (MHC). Alloy densities were 9 g/cm3 or less, which is lighter than pure Mo and MHC (≥10 g/cm3) and competitive with Ni-base superalloys. TiC-added Mo-Si-B alloys are promising candidates for ultrahigh-temperature materials beyond Ni-base superalloys.

  10. Phase equilibria, leaching characteristics and ceramic processing of SYNROC D formulations for US defense wastes

    SciTech Connect

    Newkirk, H.; Ryerson, F.; Coles, D.; Hoenig, C.; Rozsa, R.; Rossington, C.; Bazan, F.; Tewhey, J.

    1980-01-01

    The assemblage of coexisting phases in SYNROC D is perovskite, zirconolite, nepheline and spinel. Cesium from the supernate is to be immobilized in hollandite. In the current processing scheme, presynthesized granules of hollandite are added to calcined SYNROC D powders prior to hot procesing or sintering. The disposition of inert and radwaste components of Savannah River Plant (SRP) wastes in SYNROC D formulations has been determined by means of optical microscopy, XRD, XRF, SEM, STEM, electron microprobe analysis and autoradiography. A summary of results is presented. Leaching studies of SYNROC D have been done by means of static, high temperature experiments and continuous-flow experiments. The data reported are from high-temperature experiments (distilled water, powdered sample, 150/sup 0/C, one day). The elements reported are the only ones observed in the leachate. Analysis was done by means of XRF. The flowsheet which depicts the current experimental methods that are being employed at LLNL to produce SYNROC D samples containing presynthesized Cs-bearing hollandite is presented. The starting material for SYNROC D (high Fe, high Al and composite compositions) is simulated sludge obtained in 55 gallon quantities from Southwestern Chemical Corporation. Hot pressing temperatures for SYNROC D are 1000 to 1150/sup 0/C. Hot pressing temperatures for hollandite are 1200 to 1400/sup 0/C.

  11. Magnesium sulfate-water to 400 MPa using a novel piezometer: Densities, phase equilibria, and planetological implications.

    NASA Astrophysics Data System (ADS)

    Hogenboom, D. L.; Kargel, J. S.; Ganasan, J. P.; Lee, L.

    1995-06-01

    Carbonaceons chondrites commonly contain 10-20% water-soluble salts by mass, the products of low-temperature aqueous alteration under oxidizing conditions. About 75% (by mass) of chondrite salts typically consists of magnesium sulfate hydrates. Conditions similar to those that affected carbonaceous chondrites may have prevailed within some asteroids and icy satellites, resulting in the formation of similar salt-rich rock (plus ice). These salts would be important in determining the physical and chemical characteristics of cryomagmatic brines. Frozen eutectic mixtures of MgSO 4-rich brines could constitute a large fraction of the mass and volume of differentiated salty icy satellites, and widespread volcanic ice plains on some icy satellites may consist of frozen MgSO 4-rich brines. The nature of brine magmatism depends in part on phase equilibria and volumetric relations of solid and liquid phases under the pertinent conditions of temperature, pressure, and other physical parameters. Accordingly, we have investigated densities and phase equilibria in the system MgSO 4-H 2O under pressures ranging from ˜0.1 MPa to ˜400 MPa, temperatures from 230 K to 300 K, and compositions up to 22% (by mass) MgSO 4 using a novel high-pressure apparatus, described here for the first time in detail. We have found no evidence for a transition of MgSO 4 hydrates to high-pressure polymorphs, although we have seen the expected transitions in water ice and we have found some evidence of a possible new magnesium sulfate hydrate. The graph of the eutectic melting point vs pressure approximately parallels the melting curve of water ice, except that the freezing-point depression increases slightly with pressure. Brine flows on icy satellites and chondritic asteroids mostly should correspond to eutectic and peritectic compositions (˜17 and ˜21% MgSO 4, respectively, if modeled in the pure system H 2O-MgSO 4; compositions vary somewhat with pressure). Ice phases I and III, MgSO 4 hydrates

  12. Equilibria in Chemical Systems

    Energy Science and Technology Software Center (ESTSC)

    1992-01-01

    SOLGASMIX-PV calculates equilibrium relationships in complex chemical systems. Chemical equilibrium calculations involve finding the system composition, within certain constraints, which contains the minimum free energy. The constraints are the preservation of the masses of each element present and either constant pressure or volume. SOLGASMIX-PV can calculate equilibria in systems containing a gaseous phase, condensed phase solutions, and condensed phases of invariant and variable stoichiometry. Either a constant total gas volume or a constant total pressuremore » can be assumed. Unit activities for condensed phases and ideality for solutions are assumed, although nonideal systems can be handled provided activity coefficient relationships are available.« less

  13. Transport and Phase Equilibria Properties for Steam Flooding of Heavy Oils

    SciTech Connect

    Gabitto, Jorge; Barrufet, Maria

    2002-11-20

    The objectives of this research included experimental determination and rigorous modeling and computation of phase equilibrium diagrams, volumetric, and transport properties of hydrocarbon/CO2/water mixtures at pressures and temperatures typical of steam injection processes for thermal recovery of heavy oils.

  14. A Classroom Experiment on Phase Equilibria Involving Orientational Disordering in Crystals.

    ERIC Educational Resources Information Center

    Mjojo, C. C.

    1985-01-01

    Background information, procedures used, and results obtained are provided for an experiment in which a phase diagram is determined using a differential scanning calorimeter. Commercial samples of D-camphoric anhydride (Eastman Kodak) and D,L-camphoric anhydride (Aldrich) were used in the experiment. (JN)

  15. The system Ta-V-Si: Crystal structure and phase equilibria

    SciTech Connect

    Khan, A.U.; Broz, P.; Bursik, J.; Grytsiv, A.; Chen, X.-Q.; Giester, G.; Rogl, P.

    2012-03-15

    Phase relations have been evaluated for the Ta-V-Si system at 1500 and 1200 Degree-Sign C. Three ternary phases were found: {tau}{sub 1}-(Ta,V){sub 5}Si{sub 3} (Mn{sub 5}Si{sub 3}-type), {tau}{sub 2}-Ta(Ta,V,Si){sub 2} (MgZn{sub 2}-type) and {tau}{sub 3}-Ta(Ta,V,Si){sub 2} (MgCu{sub 2}-type). The crystal structure of {tau}{sub 2}-Ta(Ta,V,Si){sub 2} was solved by X-ray single crystal diffraction (space group P6{sub 3}/mmc). Atom order in the crystal structures of {tau}{sub 1}-(Ta,V){sub 5}Si{sub 3} (Mn{sub 5}Si{sub 3} type) and {tau}{sub 3}-Ta(Ta,V,Si){sub 2} was derived from X-ray powder diffraction data. A large homogeneity range was found for {tau}{sub 1}-(Ta{sub x}V{sub 1-x}){sub 5}Si{sub 3} revealing random exchange of Ta and V at a constant Si content. At 1500 Degree-Sign C, the end points of the {tau}{sub 1}-phase solution (0.082{<=}x{<=}0.624) are in equilibrium with the solutions (Ta{sub 1-x}V{sub x}){sub 5}Si{sub 3} (Cr{sub 5}B{sub 3} type, 0{<=}x{<=}0.128) and (Ta{sub x}V{sub 1-x}){sub 5}Si{sub 3} (W{sub 5}Si{sub 3} type, 0{<=}x{<=}0.048). - Graphical abstract: Phase relations have been evaluated for the Ta-V-Si system at 1500 and 1200 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Phase relations have been evaluated for the Ta-V-Si system at 1500 and 1200 Degree-Sign C. Black-Right-Pointing-Pointer Three ternary phases were found at 1500 Degree-Sign C. Black-Right-Pointing-Pointer At 1500 Degree-Sign C, {tau}{sub 1}-phase has large homogeneity region (0.064{<=}x{<=}0.624).

  16. Phase equilibria and self-organizing behavior of side-chain liquid crystalline polymer mixtures

    NASA Astrophysics Data System (ADS)

    Chiu, Hao-Wen

    1998-12-01

    Phenomenological models for elucidating phase diagrams of binary smectic-A mixtures, polymer/smectic-A mixtures, induced smectic in nematic mixtures, and nematic/smectic mixtures have been proposed on the basis of the combination of the Flory-Huggins (FH) free energy of isotropic mixing and Maier-Saupe-McMillan (MSM) free energy for nematic/smectic ordering. The nematic and smectic order parameters have been coupled through the normalized partition and the orientation distribution functions. Flory-Huggins interaction parameter (chi) for isotropic mixing and the coupling term involving the nematic interaction parameter (nu) and the McMillan smectic interaction parameter (alpha) for phase transitions of liquid crystals have been incorporated in the calculation. The predictive capability of the combined FH/MSM theory has been demonstrated by testing with reported phase diagrams. Dynamics of phase separation and morphology development in mixtures of a nematic liquid crystal and a polymer due to thermal quenching have been investigated theoretically in comparison with experimental results. In the proposed model, the combined free energy densities of Flory-Huggins theory for isotropic mixing and Maier-Saupe (MS) theory for nematic ordering have been incorporated into the time-dependent Ginzburg-Landau equation (TDGL, type C). The temporal evolution of the structure factor and the emergence of phase separated liquid crystal (LC) domains have been simulated on the basis of an explicit central difference method based on a square lattice with a periodic boundary condition. Of particular interest is the observed plateau (or inflection) region in the growth dynamic curve, which may be attributed to the breakdown of the interconnected domains caused by the nematic ordering. The emergence of LC domains during polymerization induced phase separation in a polymer dispersed liquid crystal (PDLC) has been solved numerically by incorporating the reaction kinetics into the TDGL

  17. Integrating crystallographic data and phase equilibria to quantify P-T-X evolution during reaction texture formation

    NASA Astrophysics Data System (ADS)

    Goergen, E. T.

    2008-12-01

    Coronal symplectitic reaction textures occur as a result of changes in intensive variables. This variation can arise as a result of changes in pressure and/or temperature or result from modification of bulk composition due to an influx of fluids. These processes lead to development of chemical potential gradients that drive diffusion and are responsible for the vermicular nature of symplectitic reaction textures. Deducing the P-T conditions of reaction and the P-T-X path responsible for texture formation is a difficult but critical step in interpreting the crystallization history of symplectites as well as providing appropriate boundary conditions for modeling texture development. Symplectite textures in gedrite-cordierite rocks from Thor-Odin gneiss dome in British Columbia, Canada preserve spl+crd, an+crd, and crn+crd two-phase assemblages after sillimanite porphyroblasts. These two-phase assemblages are not present as a consistent progression of layers as in other examples of symplectitic textures, but occur in a variety of locations with respect to the central sillimanite porphyroblast that are also unrelated to adjacent matrix mineral assemblages. This suggests that the chemical potential gradients responsible for symplectite formation are not consistent around the texture. The two-phase symplectitic assemblages are encased by a rim of polygonal cordierite. These inconsistent relationships make proper interpretation of the relative timing of symplectite and cordierite rim growth, as well as establishing the P-T-X conditions and kinetics of reaction difficult using traditional methods. The integration of mineral chemistry, phase-equilibria, crystallographic analysis and image analysis has provided a method of determining the P-T conditions at which symplectite formation began as well as providing information on how the size and nature of the chemical system evolved during reaction and growth. EBSD data from cordierite rims and the sillimanite porphyroblasts

  18. TRANSPORT AND PHASE EQUILIBRIA PROPERITIES FOR STEAM FLOODING OF HEAVY OILS

    SciTech Connect

    Jorge Gabitto; Maria Barrufet

    2002-09-01

    Hydrocarbon/water and CO{sub 2} systems are frequently found in petroleum recovery processes, petroleum refining, and gasification of coals, lignites and tar sands. Techniques to estimate the phase volume and phase composition are indispensable to design and improve oil recovery processes such as steam, hot water, or CO{sub 2}/steam combinations of flooding techniques typically used for heavy oils. An interdisciplinary research program to quantify transport, PVT, and equilibrium properties of selected oil/CO{sub 2}/water mixtures at pressures up to 10,000 psia and at temperatures up to 500 F has been put in place. The objectives of this research include experimental determination and rigorous modeling and computation of phase equilibrium diagrams, and volumetric properties of hydrocarbon/CO{sub 2}/water mixtures at pressures and temperatures typical of steam injection processes for thermal recovery of heavy oils. Highlighting the importance of phase behavior, researchers ([1], and [2]) insist on obtaining truly representative reservoir fluids samples for experimental analysis. The prevailing sampling techniques used for compositional analysis of the fluids have potential for a large source of error. These techniques bring the sample to atmospheric conditions and collect the liquid and vapor portion of the samples for further analysis. We developed a new experimental technique to determine phase volumes, compositions and equilibrium K-values at reservoir conditions. The new methodology is able to measure phase volume and composition at reservoir like temperatures and pressures. We use a mercury free PVT system in conjunction with a Hewlett Packard gas chromatograph capable of measuring compositions on line at high pressures and temperatures. This is made possible by an essentially negligible disturbance of the temperature and pressure equilibrium during phase volume and composition measurements. In addition, not many samples are withdrawn for compositional analysis

  19. Using nanogranitoids and phase equilibria modeling to unravel anatexis in the crustal footwall of the Ronda peridotites (Betic Cordillera, S Spain)

    NASA Astrophysics Data System (ADS)

    Bartoli, Omar; Acosta-Vigil, Antonio; Tajčmanová, Lucie; Cesare, Bernardo; Bodnar, Robert J.

    2016-07-01

    Anatexis in the crustal footwall of Ronda peridotites (Betic Cordillera, S Spain) is apparently related to the hot emplacement of this mantle slab over metasedimentary rocks. In this study, we combine the analysis of melt inclusions (MI) and phase equilibria calculations on quartzo-feldspathic mylonites (former migmatites) occurring at the contact with the mantle rocks, in the region of Sierra Alpujata (Ojén unit). The goal is to better characterize anatexis in these rocks and to provide new constraints on the geodynamic evolution of the crustal footwall. Such data are important for understanding the mechanisms of crustal emplacement of the mantle slice. The quartzo-feldspathic mylonites are characterized by the mineral assemblage Qtz + Pl + Kfs + Sil + Grt + Ilm + Bt ± Ap ± Gr. Clusters of MI are observed both at the core and toward the rim of peritectic garnet. In each cluster, MI range from totally glassy to nanogranitoids, consisting of Qtz + Kfs + Bt + Ms + Pl aggregates. The trapped melt is leucogranitic and peraluminous with variable Na2O/K2O values and low H2O contents (≈ 2-4 wt%). Phase equilibria modeling in the MnO-Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2-TiO2-O2-C (MnNCaKFMASHTOC) system with graphite-saturated fluid constrains the P-T conditions of melting at ≈ 6 kbar, ≈ 820 °C. MI data support the fluid-absent character of melting. The investigated MI represent the primary anatectic melts produced during prograde anatexis of the host rocks via biotite dehydration melting. Field, compositional, and textural observations indicate that mylonitic migmatites represent strongly deformed former diatexites. The comparison between the new data and some recently published information on migmatites located further from the contact with the peridotites and toward the bottom of the crustal footwall, raises some important issues which question the previously proposed geodynamic models for this region. Among them, (i) the crustal footwall at Sierra Alpujata

  20. The role of intermolecular interactions in the prediction of the phase equilibria of carbon dioxide hydrates

    NASA Astrophysics Data System (ADS)

    Costandy, Joseph; Michalis, Vasileios K.; Tsimpanogiannis, Ioannis N.; Stubos, Athanassios K.; Economou, Ioannis G.

    2015-09-01

    The direct phase coexistence methodology was used to predict the three-phase equilibrium conditions of carbon dioxide hydrates. Molecular dynamics simulations were performed in the isobaric-isothermal ensemble for the determination of the three-phase coexistence temperature (T3) of the carbon dioxide-water system, at pressures in the range of 200-5000 bar. The relative importance of the water-water and water-guest interactions in the prediction of T3 is investigated. The water-water interactions were modeled through the use of TIP4P/Ice and TIP4P/2005 force fields. The TraPPE force field was used for carbon dioxide, and the water-guest interactions were probed through the modification of the cross-interaction Lennard-Jones energy parameter between the oxygens of the unlike molecules. It was found that when using the classic Lorentz-Berthelot combining rules, both models fail to predict T3 accurately. In order to rectify this problem, the water-guest interaction parameters were optimized, based on the solubility of carbon dioxide in water. In this case, it is shown that the prediction of T3 is limited only by the accuracy of the water model in predicting the melting temperature of ice.

  1. Reentrant radio-frequency resonator for automated phase-equilibria and dielectric measurements in fluids

    SciTech Connect

    Goodwin, A.R.; Mehl, J.B.; Moldover, M.R.

    1996-12-01

    A reentrant rf cavity resonator has been developed for automated detection of phase separation of fluid mixtures contained within the cavity. Successful operation was demonstrated by redetermining the phase boundaries of a CO{sub 2}+C{sub 2}H{sub 6} mixture in the vicinity of its critical point. We developed an accurate electrical model for the resonator and used helium to determine the deformation of the resonator under pressure. With the model and pressure compensation, the resonator was capable of very accurate dielectric measurements. We confirmed this by remeasuring the molar dielectric polarizability {ital A}{sub {epsilon}} of argon and obtained the result {ital A}{sub {epsilon}}=(4.140{plus_minus}0.006) cm{sup 3}/mol (standard uncertainty) in excellent agreement with published values. We exploited the capability for accurate dielectric measurements to determine the densities of the CO{sub 2}+C{sub 2}H{sub 6} mixture at the phase boundaries and to determine the dipole moment of 1,1,1,2,3,3-hexafluoropropane, a candidate replacement refrigerant. Near the operating frequency of 375 MHz the capacitor in the resonator has an impedance near 14 {Omega}. This low impedance is more tolerant of electrical conductivity within the test fluid and in parallel paths in the support structures than comparable capacitors operating at audio frequencies. This will be an advantage for operation at high temperatures where some conductivity must be expected in all fluids. Of further value for high-temperature applications, the present rf resonator has only two metal{endash}insulator joints. These joints seal coaxial cables; neither joint is subjected to large mechanical stresses and neither joint is required to maintain precise dimensional tolerances. The resonator is rugged and may be operated with inexpensive electronics.

  2. Phase equilibria of Fe-C binary alloys in a magnetic field

    NASA Astrophysics Data System (ADS)

    England, Roger Dale

    The deployment of high flux magnetic processing in industry requires the ability to model the expected results of a proposed processing, and the current assumptions in the literature did not reflect the actual outcome in measurements of ductile iron. Simple binary iron-carbon alloys of less than one weight percent carbon were thermo-magnetically processed and then compared with Gibbs free energy phase transformation predictions. The data was used to quantify the change in the Gibbs free energy associated with the addition of a static high flux magnetic field, which is complicated by the change in magnetic response as the iron carbon alloys pass through the Curie point. A current common practice is to modify Gibbs free energy by -12J per mole per Tesla applied, as has been reported in the literature. This current prediction practice was employed in initial experiments for this work and the experimental data did not agree with these predicted values. This work suggests two specific influences that affect the model, chemistry and magnetic dipole changes. First, that the influence of alloying elements in the original chemistry, as the samples in the literature were a manganese alloy with 0.45 weight percent carbon, as well as not being precisely controlled for tramp elements that commonly occur in recycled material, created a change that was not predicted and therefore the temperatures were incorrect. Also, the phase transformation in a high flux magnetic field was measured to have a different response under warming versus cooling than the normal hysteresis under ambient magnetism. The change in Gibbs free energy for the binary alloys was calculated as -3J per mole per Tesla in warming, and -8J per mole per tesla in cooling. The change from these values to the -12J per mole per Tesla previously reported is attributed to the change in chemistry. This work attributes the published increase in physical properties to the Hall-Petch relation as a result of the finer product

  3. Phase equilibria in the system H{sub 2}O-NaCl-KCl-MgCl{sub 2} relevant to salt cake processing

    SciTech Connect

    Bodnar, R.J.; Vityk, M.O.; Hryn, J.N.; Mavrogenes, J.

    1997-02-01

    One waste product in recycling of Al is salt cake, a mixture of Al, salts, and residue oxides. Several methods have been proposed to recycle salt cake, one involving high-temperature leaching of salts from the salt cake. The salt composition can be approximated as a mixture predominantly of NaCl and KCl salts, with lesser amounts of Mg chloride. In order to better assess the feasibility of recycling salt cake, an experimental study was conducted of phase equilibria in the system H{sub 2}O-NaCl-KCl-MgCl{sub 2} at pressure (P), temperature (T), and composition conditions appropriate for high- temperature salt cake recycling. These experiments were designed to evaluate the effect of small amounts (2-10 wt%) of MgCl{sub 2} on solubilities of halite (NaCl) and sylvite (KCl) in saturated solutions (30-50 wt% NaCl+KCl; NaCl:KCl = 1:1 and 3:1) at elevated P and T.

  4. Application of the cell potential method to predict phase equilibria of multicomponent gas hydrate systems.

    PubMed

    Anderson, Brian J; Bazant, Martin Z; Tester, Jefferson W; Trout, Bernhardt L

    2005-04-28

    We present the application of a mathematical method reported earlier by which the van der Waals-Platteeuw statistical mechanical model with the Lennard-Jones and Devonshire approximation can be posed as an integral equation with the unknown function being the intermolecular potential between the guest molecules and the host molecules. This method allows us to solve for the potential directly for hydrates for which the Langmuir constants are computed, either from experimental data or from ab initio data. Given the assumptions made in the van der Waals-Platteeuw model with the spherical-cell approximation, there are an infinite number of solutions; however, the only solution without cusps is a unique central-well solution in which the potential is at a finite minimum at the center to the cage. From this central-well solution, we have found the potential well depths and volumes of negative energy for 16 single-component hydrate systems: ethane (C2H6), cyclopropane (C3H6), methane (CH4), argon (Ar), and chlorodifluoromethane (R-22) in structure I; and ethane (C2H6), cyclopropane (C3H6), propane (C3H8), isobutane (C4H10), methane (CH4), argon (Ar), trichlorofluoromethane (R-11), dichlorodifluoromethane (R-12), bromotrifluoromethane (R-13B1), chloroform (CHCl3), and 1,1,1,2-tetrafluoroethane (R-134a) in structure II. This method and the calculated cell potentials were validated by predicting existing mixed hydrate phase equilibrium data without any fitting parameters and calculating mixture phase diagrams for methane, ethane, isobutane, and cyclopropane mixtures. Several structural transitions that have been determined experimentally as well as some structural transitions that have not been examined experimentally were also predicted. In the methane-cyclopropane hydrate system, a structural transition from structure I to structure II and back to structure I is predicted to occur outside of the known structure II range for the cyclopropane hydrate. Quintuple (L

  5. Experimental constraints on the Qitianling granite in south China: phase equilibria and petrogenetic implications

    NASA Astrophysics Data System (ADS)

    Huang, Fangfang; Scaillet, Bruno; Wang, Rucheng; Erdmann, Saskia; Chen, Yan; Faure, Michel; Liu, Hongsheng; Xie, Lei; Wang, Bo; Zhu, Jinchu

    2016-04-01

    In South China, the huge distribution of the Mesozoic metallogenic province reflects the abundant magmatism and associated mineralizations which occurred during that period. Building up the phase equilibrium diagrams of representative Mesozoic granites allows us to better understand Mesozoic magmatic events, an approach so far little applied to granites of South China. The Qitianling ganite is a representative Jurassic A-type metaluminous pluton which is associated with tin mineralization in South China. The dominant rock-types are hornblende-biotite monzonitic granites, biotite±hornblende bearing granites and fine-grained biotite-bearing granites. Three metaluminous granite samples (QTL38C, QTL14A and QTL13), of varying mafic character but all bearing hornblende, were chosen for constraining crystallization and magma generation conditions of the Qitianling composite batholith. Crystallization experiments were performed in the 100-700 MPa range, albeit mainly at 200 MPa, at an fO2 at NNO-1 or NNO +2.5, in a temperature range 700°C to 900°C. At 200 MPa, the water content in melt varies between 3 wt% and 6.5 wt% (water-saturated). Experimental results show that under H2O-saturated conditions and at NNO-1, ilmenite, magnetite and pyroxene are the liquidus phases, followed by hornblende, biotite and plagioclase. Hornblende is present only in the most mafic sample (QTL38C), below 900°C and above 5 wt% H2O. In contrast, for H2O-saturated conditions and at NNO+2.5, magnetite, pyroxene crystallize first, followed by biotite while ilmenite is rarely observed. Petrographic observations of natural samples show that magnetite and ilmenite coexist, whereas pyroxene is never observed. The Fe# value (Fe/Mg+Fe) of natural amphibole goes up to 0.69, being on average at 0.67. Experiments indicate that the crystallization of pyroxene occurs at early magmatic stages, but it breaks down to hornblende and biotite at low temperatures, explaining its absence in natural assemblages

  6. Simulation studies of non-neutral plasma equilibria in an electrostatic trap with a magnetic mirror

    SciTech Connect

    Gomberoff, K; Fajans, J; Wurtele, J; Friedman, A; Grote, D P; Cohen, R H; Vay, J

    2006-06-05

    The equilibrium of an infinitely long, strongly magnetized, non-neutral plasma confined in a Penning-Malmberg trap with an additional mirror coil has been solved analytically [J. Fajans, Phys. Plasmas 10, 1209 (2003)] and shown to exhibit unusual features. Particles not only reflect near the mirror in the low field region, but also may be weakly trapped in part of in the high field region. The plasma satisfies a Boltzmann distribution along field lines; however, the density and the potential vary along field lines. Some other simplifying assumptions were employed in order to analytically characterize the equilibrium; for example the interface region between the low and high field regions was not considered. The earlier results are confirmed in the present study, where two-dimensional particle-in-cell simulations are performed with the Warp code in a more realistic configuration with an arbitrary (but physical) density profile, realistic trap geometry and magnetic field. A range of temperatures and radial plasma sizes are considered. Particle tracking is used to identify populations of trapped and untrapped particles. The present study also shows that it is possible to obtain local equilibria of non-neutral plasmas using a collisionless PIC code, by a scheme that uses the inherent numerical collisionality as a proxy for physical collisions.

  7. Simulation studies of non-neutral plasma equilibria in anelectrostatic trap with magnetic mirror

    SciTech Connect

    Gomberoff, K.; Fajans, J.; Wurtele, J.; Friedman, A.; Grote,D.P.; Cohen, R.H.; Vay, J-L.

    2006-06-01

    The equilibrium of an infinitely long, strongly magnetized, non-neutral plasma confined in a Penning-Malmberg trap with an additional mirror coil has been solved analytically [J. Fajans, Phys. Plasmas 10, 1209 (2003)] and shown to exhibit unusual features. Particles not only reflect near the mirror in the low field region, but also may be weakly trapped in part of in the high field region. The plasma satisfies a Boltzmann distribution along field lines; however, the density and the potential vary along field lines. Some other simplifying assumptions were employed in order to analytically characterize the equilibrium; for example the interface region between the low and high field regions was not considered. The earlier results are confirmed in the present study, where two-dimensional particle-in-cell simulations are performed with the Warp code in a more realistic configuration with an arbitrary (but physical) density profile, realistic trap geometry and magnetic field. A range of temperatures and radial plasma sizes are considered. Particle tracking is used to identify populations of trapped and untrapped particles. The present study also shows that it is possible to obtain local equilibria of non-neutral plasmas using a collisionless PIC code, by a scheme that uses the inherent numerical collisionality as a proxy for physical collisions.

  8. Experimental Determinations of the Activity-Composition Relations and Phase Equilibria of H{sub 2}O-CO{sub 2}-NaCl Fluids

    SciTech Connect

    Anovitz, L.M.; Labotka, T.C.; Blencoe, J.G.; Singh, J.; Horita, J.

    1999-09-12

    An understanding of activity-composition (a/X) relations and phase equilibria for halite-bearing, mixed-species supercritical fluids is critically important in many geological and industrial applications. The authors have performed experiments on the a/X relations and phase equilibria of H{sub 2}O-CO{sub 2}-NaCl fluids at 5OO C, 500 bars, to obtain highly accurate and precise data for this ternary system. H{sub 2}O-CO{sub 2}-NaCl samples were reacted at a (H{sub 2}O) = 0.350, 0.425, 0.437, 0.448, 0.560, 0.606, 0.678, 0.798, and 0.841. Results indicate that fluids with these activities lie in the vapor-NaCl two-phase region, and that a fluid with the last value has a composition close to the three-phase (vapor + brine + halite) field. Data from these experiments and NaCl solubility runs also suggest that the vapor comer of the three-phase field lies near X(H{sub 2}O) = 0.760, X(NaCl) = 0.065, which is a significantly more water-rich composition than suggested by the model of [1].

  9. Numerical and experimental studies of attractors in memristor-based Chua's oscillator with a line of equilibria. Noise-induced effects

    NASA Astrophysics Data System (ADS)

    Semenov, V.; Korneev, I.; Arinushkin, P.; Strelkova, G.; Vadivasova, T.; Anishchenko, V.

    2015-07-01

    The intrinsic features of systems with a line of equilibria are analyzed by studying of memristor-based Chua's oscillator. The analog modeling of the system is carried out together with its numerical simulation. The characteristics of stochastic oscillations in the system under study are explored in the presence of noise. The issues concerning the physical realization of a system with a line of equilibria are also considered.

  10. Two-dimensional magnetohydrodynamic equilibria with flow and studies of equilibrium fluctuations

    SciTech Connect

    Agim, Y.Z.

    1989-01-01

    A set of reduced ideal MHD (magnetohydrodynamic) equations is derived to investigate equilibria of plasmas with mass flow in general two-dimensional geometry. These equations provide a means of investigating the effects of flow on self-consistent equilibria in a number of new two-dimensional configurations such as helically symmetric configurations with helical axis, which are relevant to stellarators, as well as axisymmetric configurations. In the second part, magnetic fluctuations due to the thermally excited MHD waves are investigated using fluid and kinetic models to describe a stable, uniform, compressible plasma in the range above the drift wave frequency and below the ion cyclotron frequency.

  11. Re-investigation of phase equilibria in the system Al–Cu and structural analysis of the high-temperature phase η1-Al1−δCu

    PubMed Central

    Ponweiser, Norbert; Lengauer, Christian L.; Richter, Klaus W.

    2011-01-01

    The phase equilibria and reaction temperatures in the system Al–Cu were re-investigated by a combination of optical microscopy, powder X-ray diffraction (XRD) at ambient and elevated temperature, differential thermal analysis (DTA) and scanning electron microscopy (SEM). A full description of the phase diagram is given. The phase equilibria and invariant reactions in the Cu-poor part of the phase diagram could be confirmed. The Cu-rich part shows some differences in phase equilibria and invariant reactions compared to the known phase diagram. A two phase field was found between the high temperature phase η1 and the low temperature phase η2 thus indicating a first order transition. In the ζ1/ζ2 region of the phase diagram recent findings on the thermal stability could be widely confirmed. Contrary to previous results, the two phase field between δ and γ1 is very narrow. The results of the current work indicate the absence of the high temperature β0 phase as well as the absence of a two phase field between γ1 and γ0 suggesting a higher order transition between γ1 and γ0. The structure of γ0 (I-43m, Cu5Zn8-type) was confirmed by means of high-temperature XRD. Powder XRD was also used to determine the structure of the high temperature phase η1-Al1−δCu. The phase is orthorhombic (space group Cmmm) and the lattice parameters are a = 4.1450(1) Å, b = 12.3004(4) Å and c = 8.720(1) Å; atomic coordinates are given. PMID:27103761

  12. Phase relations in the system NaCl-KCl-H2O: V. Thermodynamic-PTX analysis of solid-liquid equilibria at high temperatures and pressures

    USGS Publications Warehouse

    Sterner, S.M.; Chou, I.-Ming; Downs, R.T.; Pitzer, Kenneth S.

    1992-01-01

    The Gibbs energies of mixing for NaCl-KCl binary solids and liquids and solid-saturated NaCl-KCl-H2O ternary liquids were modeled using asymmetric Margules treatments. The coefficients of the expressions were calibrated using an extensive array of binary solvus and solidus data, and both binary and ternary liquidus data. Over the PTX range considered, the system exhibits complete liquid miscibility among all three components and extensive solid solution along the anhydrous binary. Solid-liquid and solid-solid phase equilibria were calculated by using the resulting equations and invoking the equality of chemical potentials of NaCl and KCl between appropriate phases at equilibrium. The equations reproduce the ternary liquidus and predict activity coefficients for NaCl and KCl components in the aqueous liquid under solid-saturation conditions between 673 and 1200 K from vapor saturation up to 5 kbar. In the NaCl-KCl anhydrous binary system, the equations describe phase equilibria and predict activity coefficients of the salt components for all stable compositions of solid and liquid phases between room temperature and 1200 K and from 1 bar to 5 kbar. ?? 1992.

  13. Phase equilibria of a fluorine-rich leucogranite from the St. Austell pluton, Cornwall

    SciTech Connect

    Weidner, J.R.; Martin, R.F.

    1987-06-01

    Highly evolved leucogranitic rocks in the St. Austell pluton, Cornwall, of Hercynian age, contain accessory muscovite, topaz and fluorite. The authors have studied the H/sub 2/O-saturated melting behavior of one representative sample. Its solidus and liquidus pass through the points 663 and 725/sup 0/C, respectively, at 1 kbar, 640 and 665/sup 0/C at 2 kbar, 610 and 717/sup 0/C at 4 kbar, and 608 and 700+/sup 0/C at 8 kbar. Plagioclase is on the liquidus at low pressure, and topaz is on the liquidus at 4 kbar. The fluorite is consumed in the formation of the first-formed liquid. Calcium can partition into an evolved granitic melt if complexed by fluorine. The fluorite appears to be largely primary in fresh fluorite granite at St. Austell, and not to reflect the albitization of oligoclase in the surrounding biotite granite. Such fluorine-rich leucogranites can be expected to be of subsolvus character.

  14. Storage conditions and evolution of andesitic magma prior to the 1991 95 eruption of Unzen volcano: Constraints from natural samples and phase equilibria experiments

    NASA Astrophysics Data System (ADS)

    Botcharnikov, Roman E.; Holtz, Francois; Almeev, Renat R.; Sato, Hiroaki; Behrens, Harald

    2008-07-01

    -temperature silicic magma. The combination of data from melt inclusions and phase equilibria experiments indicates that the mafic end-member magma at Unzen was already partially crystallized and contained significant proportions (20 to 40 wt.%) of Pl and orthopyroxene (Opx) when melt inclusions started to form. Since clinopyroxene (Cpx) and magnetite (Mt) crystallize after Pl and Opx, the temperatures derived for the mafic end-member magma from coexisting Opx-Cpx and Ilm-Mt pairs do not represent temperatures near to the liquidus. Assuming that the injected mafic magma was nearly aphyric, its initial temperature might have been higher than estimated in previous studies.

  15. Two-population replicator dynamics and number of Nash equilibria in matrix games

    NASA Astrophysics Data System (ADS)

    Galla, T.

    2007-04-01

    We study the connection between the evolutionary replicator dynamics and the number of Nash equilibria in large random bi-matrix games. Using techniques of disordered systems theory we compute the statistical properties of both, the fixed points of the dynamics and the Nash equilibria. Except for the special case of zero-sum games, one finds a transition as a function of the so-called co-operation pressure between a phase in which there is a unique stable fixed point of the dynamics coinciding with a unique Nash equilibrium, and an unstable phase in which there are exponentially many Nash equilibria with statistical properties different from the stationary state of the replicator equations. Our analytical results are confirmed by numerical simulations of the replicator dynamics, and by explicit enumeration of Nash equilibria.

  16. Experimental determination and prediction of (solid+liquid) phase equilibria for binary mixtures of heavy alkanes and fatty acids

    NASA Astrophysics Data System (ADS)

    Benziane, Mokhtar; Khimeche, Kamel; Dahmani, Abdellah; Nezar, Sawsen; Trache, Djalal

    2012-06-01

    Solid-liquid equilibria for three binary mixtures, n-Eicosane (1) + Lauric acid (2), n-Tetracosane (1) + Stearic acid (2), and n-Octacosane (1) + Palmitic acid (2), were measured using a differential scanning calorimeter. Simple eutectic behaviour was observed for these systems. The experimental results were correlated by means of the modified UNIFAC (Larsen and Gmehling versions), UNIQUAC and ideal models. The root-mean-square deviations of the solubility temperatures for all measured data vary from 0.26 to 3.15 K and depend on the particular model used. The best solubility correlation was obtained with the UNIQUAC model.

  17. Phase equilibria, formation, crystal and electronic structure of ternary compounds in Ti-Ni-Sn and Ti-Ni-Sb ternary systems

    SciTech Connect

    Romaka, V.V.; Rogl, P.; Romaka, L.; Stadnyk, Yu.; Melnychenko, N.; Grytsiv, A.; Falmbigl, M.; Skryabina, N.

    2013-01-15

    The phase equilibria of the Ti-Ni-Sn and Ti-Ni-Sb ternary systems have been studied in the whole concentration range by means of X-ray and EPM analyses at 1073 K and 873 K, respectively. Four ternary intermetallic compounds TiNiSn (MgAgAs-type), TiNi{sub 2-x}Sn (MnCu{sub 2}Al-type), Ti{sub 2}Ni{sub 2}Sn (U{sub 2}Pt{sub 2}Sn-type), and Ti{sub 5}NiSn{sub 3} (Hf{sub 5}CuSn{sub 3}-type) are formed in Ti-Ni-Sn system at 1073 K. The TiNi{sub 2}Sn stannide is characterized by homogeneity in the range of 50-47 at% of Ni. The Ti-Ni-Sb ternary system at 873 K is characterized by formation of three ternary intermetallic compounds, Ti{sub 0.8}NiSb (MgAgAs-type), Ti{sub 5}Ni{sub 0.45}Sb{sub 2.55} (W{sub 5}Si{sub 3}-type), and Ti{sub 5}NiSb{sub 3} (Hf{sub 5}CuSn{sub 3}-type). The solubility of Ni in Ti{sub 0.8}NiSb decreases number of vacancies in Ti site up to Ti{sub 0.91}Ni{sub 1.1}Sb composition. - Graphical abstract: Isothermal section of the Ti-Ni-Sn phase diagram and DOS distribution in hypothetical TiNi{sub 1+x}Sn solid solution. Highlights: Black-Right-Pointing-Pointer Ti-Ni-Sn phase diagram was constructed at 1073 K. Black-Right-Pointing-Pointer Four ternary compounds are formed: TiNiSn, TiNi{sub 2-x}Sn, Ti{sub 2}Ni{sub 2}Sn, and Ti{sub 5}NiSn{sub 3}. Black-Right-Pointing-Pointer Three ternary compounds exist in Ti-Ni-Sb system at 873 K. Black-Right-Pointing-Pointer The TiNi{sub 2}Sb compound is absent.

  18. Transferable potentials for phase equilibria. 9. Explicit hydrogen description of benzene and five-membered and six-membered heterocyclic aromatic compounds.

    PubMed

    Rai, Neeraj; Siepmann, J Ilja

    2007-09-13

    The explicit hydrogen version of the transferable potentials for phase equilibria (TraPPE-EH) force field is extended to benzene, pyridine, pyrimidine, pyrazine, pyridazine, thiophene, furan, pyrrole, thiazole, oxazole, isoxazole, imidazole, and pyrazole. While the Lennard-Jones parameters for carbon, hydrogen (two types), nitrogen (two types), oxygen, and sulfur are transferable for all 13 compounds, the partial charges are specific for each compound. The benzene dimer energies for sandwich, T-shape, and parallel-displaced configurations obtained for the TraPPE-EH force field compare favorably with high-level electronic structure calculations. Gibbs ensemble Monte Carlo simulations were carried out to compute the single-component vapor-liquid equilibria for benzene, pyridine, three diazenes, and eight five-membered heterocycles. The agreement with experimental data is excellent with the liquid densities and vapor pressures reproduced within 1 and 5%, respectively. The critical temperatures and normal boiling points are predicted with mean deviations of 0.8 and 1.6%, respectively. PMID:17713943

  19. Effects of volatiles on phase equilibria of a basalt from Piton de la Fournaise (Réunion island): experimental results and comparison with natural products.

    NASA Astrophysics Data System (ADS)

    Brugier, Yann-Aurélien; Pichavant, Michel; di Muro, Andréa; Bourdier, Jean-Louis

    2015-04-01

    The eruptive activity of the Piton de la Fournaise (PdF) hotspot volcano is monitored by geophysical, geochemical and petrological approaches. Nevertheless, the structure of the feeding system and magma reservoirs is still debated. 4 different lava groups occur at PdF: (1) Steady State Basalts (SSB), the dominant group in the recent activity, (2) the Differentiated Lavas group, typical of the early activity, (3) the Picrites group with olivine-rich lavas (oceanites) characteristic of La Réunion volcanism and (4) the Abnormal Group (AbG) that contains lavas with mixed geochemical characteristics. To understand the petrogenetic relations between the 4 groups of lavas, constrain the structure of the feeding system and the magma storage conditions, experimental phase equilibria have been determined under fluid-present conditions, with either H2O or H2O+CO2 added, for a SSB lava from the 2009 eruption. Experiments have been performed both at high pressures (HP) and 1atm. The HP experiments were carried out in an IHPV, pressurized with Ar-H2 mixtures, at 50MPa and 400MPa. The 1atm experiments used a vertical CO-CO2 gas mixing furnace. Experimental products were analyzed by SEM, EMPA and µ-FTIR Spectroscopy. Results at 50 MPa lead to a crystallization sequence in the order olivine (ol, + spinel), clinopyroxene (cpx), plagioclase (plag). Volatile concentrations in experimental glasses range from 0.5 to 1 wt% for H2O and 30 to 180 ppm for CO2, within the range of glass inclusions in olivine phenocrysts. Fo contents in ol, Mg# in cpx and An contents in plag are in agreement with compositions of natural phenocrysts, suggesting that our experiments closely approach the shallow magmatic evolution at PdF. Preliminary experiments at 400 MPa indicate a change in the crystallization sequence, olivine being replaced by cpx as the liquidus phase. Our data are in marked contrast with previous experimental results under volatile-free conditions. Experiments at 1 atm are in progress

  20. DFT Study of Solvent Effects on Conformational Equilibria and Vibrational Spectra of 4-(1-PYRROLIDINYL)PIPERAZINE

    NASA Astrophysics Data System (ADS)

    Baglayan, O.; Kesan, G.; Parlak, C.; Senyel, M.

    2012-06-01

    The optimized structural parameters (bond lengths, bond and dihedral angles), conformational equilibria and normal mode frequencies and corresponding vibrational assignments of 4-(1-Pyrrolidinyl)piperazine (4-pypp) have been examined by means of B3LYP hybrid density functional theory (DFT) method with 6-31++G(d,p) basis set. Furthermore, reliable vibrational assignments have made on the basis of potential energy distribution (PED) calculated and the thermodynamics functions, highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of 4-pypp (C_8H17N_3) have been predicted. Calculations are employed for different conformations of 4-pypp both in gas phase and in solution. Solvent effects are investigated using chloroform and dimethylsulfoxide. Results from the theoretical values are showed that the structural parameters, mole fractions of stable conformers, vibrational frequencies, IR intensities and Raman activities of 4-pypp are solvent dependent. {Keywords}: 4-(1-Pyrrolidinyl)piperazine, vibrational spectra, solvent effect, DFT.

  1. Thermodynamics and phase equilibria of the silicate-fluoride-water systems: Implications for fluorine-bearing granites

    NASA Astrophysics Data System (ADS)

    Dolejs, David

    The progressive enrichment in volatiles and light incompatible elements observed during upper-crustal differentiation of granitic and rhyolitic magmas leads to significant changes in melt physical-chemical properties and has important implications for ore deposition and volcanic devolatization. Thermodynamic calculations and experimental studies of melting equilibria in the Na 2O-K2O-Al2O3-SiO2-F 2O-1-H2O system are used to evaluate mineral stabilities, fluid compositions, the extent of fluoride-silicate liquid-liquid immiscibility, fluorine and water solubility limits and differentiation paths of natural fluorine-bearing silicic magmas. The interaction of fluorine with rock-forming aluminosilicates corresponds to progressive fluorination by the thermodynamic component F2O-1. Formation of fluorine-bearing minerals first occurs in peralkaline and silica-undersaturated systems that buffer fluorine concentrations at very low levels (villiaumite, fluorite). The highest concentrations of fluorine are achieved in peraluminous silica-oversaturated systems, saturated with fluorite or topaz. Thermodynamic models of fluorosilicate melts indicate clustering of silicate tetrahedra in the Na2O-SiO 2-F2O-1 system, whereas initial NaAl-F short-range order evolves into partial O-F disorder in the albite-cryolite system. Experiments performed at 520-1100°C and 0.1-100 MPa completely describe liquidus relations and differentiation paths of fluorine-bearing felsic magmas. Coordination differences and short-range order effects between [NaAl]-F, Na-F vs. Si-O lead to the fluoride-silicate liquid immiscibility, which extends from the silica-cryolite binary through the peralkaline albite-silica-cryolite ternary and closes in multicomponent, topaz-bearing systems owing to the destabilizing effect of increasing peraluminosity. Liquidus relations indicate that fluoride-silicate liquid-liquid immiscibility is inaccessible to quartz-feldspar-saturated granitic melts. Differentiation paths of

  2. Subseafloor phase equilibria in high-temperature hydrothermal fluids of the Lucky Strike Seamount (Mid-Atlantic Ridge, 37°17‧N)

    NASA Astrophysics Data System (ADS)

    Pester, Nicholas J.; Reeves, Eoghan P.; Rough, Mikaella E.; Ding, Kang; Seewald, Jeffrey S.; Seyfried, William E.

    2012-08-01

    As part of an integrated study conducted at the Lucky Strike Seamount (Mid-Atlantic Ridge, 37°17'N) in 2008, gas-tight sampling devices were used to collect high-temperature (˜300 °C) hydrothermal fluids issuing from sulfide structures distributed throughout the vent field located in the summit depression. Compared with previous observations from 1993 to 1997, the most substantial changes in vent fluid compositions are dramatically increased CO2 concentrations (˜5×, up to 133 mmol/L) and the observation of vent fluids enriched in dissolved chloride relative to seawater. Combined with an increase in δ13C values by ˜4‰ in 2008, the elevated CO2 indicates replenishment of the magmatic heat source and may be indicative of a recent magmatic event. The additional supporting fluid chemistry is, however, similar to that of the previous sampling intervals, necessitating a reassessment of the subseafloor controls on vent fluid chemistry at Lucky Strike in the context of recently obtained geophysical data that provides the depth/extent of a steady-state magma chamber. Two-phase behavior is indicated by the chloride variability in the vent fluids; and comparison with experimental data for the associated chloride-dependent partitioning of minor/trace elements suggests the possibility of a similar source fluid for all the vent structures, while limiting the likelihood of shallow phase separation and subseafloor mixing for the hydrothermal end-members. A recently calibrated Fe/Mn geothermometer indicates minimum subseafloor equilibration temperatures of 350-385 °C. However, constraints imposed by dissolved Si/Cl in conjunction with geophysical observations are consistent with peak reaction conditions at temperatures of 430-475 °C and pressures near the top of the axial magma chamber (˜410-480 bars), where magmatic CO2 becomes entrained in the circulating fluids. The distance between the magma chamber and the seafloor at Lucky Strike is substantially greater than at

  3. Determination of epsomite-hexahydrite equilibria by the humidity-buffer technique at 0.1 MPa with implications for phase equilibria in the system MgSO4-H2O.

    USGS Publications Warehouse

    Chou, I.-Ming; Seal, R.R., 2nd.

    2003-01-01

    Epsomite (MgSO(4).7H(2)O) and hexahydrite (MgSO(4).6H(2)O) are common minerals found in marine evaporite deposits, in saline lakes as precipitates, in weathering zones of coal and metallic deposits, in some soils and their efflorescences, and possibly on the surface of Europa as evaporite deposits. Thermodynamic properties of these two minerals reported in the literature are in poor agreement. In this study, epsomite-hexahydrite equilibria were determined along four humidity-buffer curves at 0.1 MPa and between 25 and 45 degrees C. Results obtained for the reaction epsomite = hexahydrite + H(2)O, as demonstrated by very tight reversals along each humidity buffer, can be represented by ln K(+/- 0.012) = 20.001 - 7182.07/T, where K is the equilibrium constant, and T is temperature in Kelvin. The derived standard Gibbs free energy of reaction is 10.13 +/- 0.07 kJ/mol, which is essentially the same value as that calculated from vapor pressure measurements reported in the literature. However, this value is at least 0.8 kJ/mol lower than those calculated from the data derived mostly from calorimetric measurements.

  4. Optimized Mie potentials for phase equilibria: Application to noble gases and their mixtures with n-alkanes

    NASA Astrophysics Data System (ADS)

    Mick, Jason R.; Soroush Barhaghi, Mohammad; Jackman, Brock; Rushaidat, Kamel; Schwiebert, Loren; Potoff, Jeffrey J.

    2015-09-01

    Transferrable force fields, based on n-6 Mie potentials, are presented for noble gases. By tuning the repulsive exponent, ni, it is possible to simultaneously reproduce experimental saturated liquid densities and vapor pressures with high accuracy, from the normal boiling point to the critical point. Vapor-liquid coexistence curves for pure fluids are calculated using histogram reweighting Monte Carlo simulations in the grand canonical ensemble. For all noble gases, saturated liquid densities and vapor pressures are reproduced to within 1% and 4% of experiment, respectively. Radial distribution functions, extracted from NVT and NPT Monte Carlo simulations, are in similarly excellent agreement with experimental data. The transferability of the optimized force fields is assessed through calculations of binary mixture vapor-liquid equilibria. These mixtures include argon + krypton, krypton + xenon, methane + krypton, methane + xenon, krypton + ethane, and xenon + ethane. For all mixtures, excellent agreement with experiment is achieved without the introduction of any binary interaction parameters or multi-body interactions.

  5. Optimized Mie potentials for phase equilibria: Application to noble gases and their mixtures with n-alkanes.

    PubMed

    Mick, Jason R; Soroush Barhaghi, Mohammad; Jackman, Brock; Rushaidat, Kamel; Schwiebert, Loren; Potoff, Jeffrey J

    2015-09-21

    Transferrable force fields, based on n-6 Mie potentials, are presented for noble gases. By tuning the repulsive exponent, ni, it is possible to simultaneously reproduce experimental saturated liquid densities and vapor pressures with high accuracy, from the normal boiling point to the critical point. Vapor-liquid coexistence curves for pure fluids are calculated using histogram reweighting Monte Carlo simulations in the grand canonical ensemble. For all noble gases, saturated liquid densities and vapor pressures are reproduced to within 1% and 4% of experiment, respectively. Radial distribution functions, extracted from NVT and NPT Monte Carlo simulations, are in similarly excellent agreement with experimental data. The transferability of the optimized force fields is assessed through calculations of binary mixture vapor-liquid equilibria. These mixtures include argon + krypton, krypton + xenon, methane + krypton, methane + xenon, krypton + ethane, and xenon + ethane. For all mixtures, excellent agreement with experiment is achieved without the introduction of any binary interaction parameters or multi-body interactions. PMID:26395716

  6. Electronic absorption study on acid-base equilibria for some pyrimidine derivatives containing semi- and thiosemicarbazone moiety

    NASA Astrophysics Data System (ADS)

    Kılıç, H.

    2010-02-01

    The UV-vis spectra of recently synthesized 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-one, ( I), and 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-thione, ( II) were studied in aqueous methanol (5%, v/v methanol). The nature of the electronic transitions and the roles of carbonyl oxygen of I and thiocarbonyl sulfur of II on the behavior of UV-vis spectra were discussed. Acid-base equilibria of the compounds against varying pH and p Ka values related equilibria were determined at an ionic strength of 0.10 M by using the Henderson-Haselbalch equation. The mean acidity constants for the protonated forms of the compounds were determined as p Ka1 = 5.121, p Ka2 = 7.929 and p Ka3 = 11.130 for I and p Ka1 = 4.684, p Ka2 = 7.245 and p Ka3 = 10.630 for II. The preferred dissociation mechanisms were discussed based on UV-vis data and a mechanism was proposed for each compound.

  7. Phase equilibria among the superconductors in the Y[sub 2]O[sub 3][endash]BaO[endash]Cu[endash]O system

    SciTech Connect

    Zhou, Z.; Navrotsky, A. )

    1999-09-01

    The enthalpy of formation of Y[sub 2]Ba[sub 4]Cu[sub 7]O[sub 14.864] at room temperature has been determined by using high-temperature reaction calorimetry. The standard enthalpy of formation of the 247 phase is [Delta]H[sup o][sub f]=[minus]5463[plus minus]18 hthinsp;kJ hthinsp;mol[sup [minus]1]. Phase relationships among the superconductors, namely, the 123, 124, and 247, are assessed. It is intrinsic that impurity phases, such as Y[sub 2]Cu[sub 2]O[sub 5], BaCuO[sub 2], CuO, etc., coexist with the superconductors at equilibrium. Equilibria among the superconductor phases in the Y[sub 2]O[sub 3][endash]BaO[endash]Cu[endash]O system have been determined. The results show that, at the 124 bulk composition, the 247 phase coexists with the excess CuO in a narrow area of p[sub O[sub 2

  8. Phase equilibria and distribution constants of metal ions in diantipyryl alkane-organic acid-hydrochloric acid-water systems

    NASA Astrophysics Data System (ADS)

    Degtev, M. I.; Popova, O. N.; Yuminova, A. A.

    2014-08-01

    The ability of antipyrine and its derivatives (diantipyryl alkanes) to form separating systems in the presence of salicylic (sulfosalicylic) acid and hydrochloric acid and water is studied. The optimum volume of the organic phase, the composition of complexes, and the mechanism for the distribution of metal ions are determined, depending on the concentrations of the main components and the salting-out agent. The complex distribution and extraction constants are calculated.

  9. The heat capacity of a natural monticellite and phase equilibria in the system CaO-MgO-SiO2-CO2

    USGS Publications Warehouse

    Sharp, Z.D.; Essene, E.J.; Anovitz, Lawrence M.; Metz, G.W.; Westrum, E.F., Jr.; Hemingway, B.S.; Valley, J.W.

    1986-01-01

    The heat capacity of a natural monticellite (Ca1.00Mg.09Fe.91Mn.01Si0.99O3.99) measured between 9.6 and 343 K using intermittent-heating, adiabatic calorimetry yields Cp0(298) and S2980 of 123.64 ?? 0.18 and 109.44 ?? 0.16 J ?? mol-1 K-1 respectively. Extrapolation of this entropy value to end-member monticellite results in an S0298 = 108.1 ?? 0.2 J ?? mol-1 K-1. High-temperature heat-capacity data were measured between 340-1000 K with a differential scanning calorimeter. The high-temperature data were combined with the 290-350 K adiabatic values, extrapolated to 1700 K, and integrated to yield the following entropy equation for end-member monticellite (298-1700 K): ST0(J ?? mol-1 K-1) = S2980 + 164.79 In T + 15.337 ?? 10-3 T + 22.791 ?? 105 T-2 - 968.94. Phase equilibria in the CaO-MgO-SiO2 system were calculated from 973 to 1673 K and 0 to 12 kbar with these new data combined with existing data for akermanite (Ak), diopside (Di), forsterite (Fo), merwinite (Me) and wollastonite (Wo). The location of the calculated reactions involving the phases Mo and Fo is affected by their mutual solid solution. A best fit of the thermodynamically generated curves to all experiments is made when the S0298 of Me is 250.2 J ?? mol-1 K-1 less than the measured value of 253.2 J ?? mol-1 K-1. A best fit to the reversals for the solid-solid and decarbonation reactions in the CaO-MgO-SiO2-CO2 system was obtained with the ??G0298 (kJ ?? mole-1) for the phases Ak(-3667), Di(-3025), Fo(-2051), Me(-4317) and Mo(-2133). The two invariant points - Wo and -Fo for the solid-solid reactions are located at 1008 ?? 5 K and 6.3 ?? 0.1 kbar, and 1361 ?? 10 K and 10.2 ?? 0.2 kbar respectively. The location of the thermodynamically generated curves is in excellent agreement with most experimental data on decarbonation equilibria involving these phases. ?? 1986.

  10. An Introduction to Multivariate Curve Resolution-Alternating Least Squares: Spectrophotometric Study of the Acid-Base Equilibria of 8-Hydroxyquinoline-5-Sulfonic Acid

    ERIC Educational Resources Information Center

    Rodriguez-Rodriguez, Cristina; Amigo, Jose Manuel; Coello, Jordi; Maspoch, Santiago

    2007-01-01

    A spectrophotometric study of the acid-base equilibria of 8-hydroxyquinoline-5-sulfonic acid to describe the multivariate curve resolution-alternating least squares algorithm (MCR-ALS) is described. The algorithm provides a lot of information and hence is of great importance for the chemometrics research.

  11. Extension of Toth function from gas-solid to liquid-solid equilibria and application to reversed-phase liquid chromatography systems

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2006-03-01

    The extension of the {Psi} function developed by Toth from equilibria taking place at gas-solid interfaces to those taking place at liquid-solid interfaces was investigated. The results were applied to conventional liquid-solid systems used in reversed-phase liquid chromatography (RPLC). The adsorbents in these systems are made of porous silica having a hydrophobic solid surface obtained by chemically bonding C{sub 18} alkyl chains to a porous silica gel then endcapping the surface with trimethylsilyl groups. The liquid is an aqueous solution of an organic solvent, most often methanol or acetonitrile. The probe compound used here is phenol. Adsorption data of phenol were measured using the dynamic frontal analysis (FA) method. The excess adsorption of the organic solvent was measured using the minor disturbance (MD) method. Activity coefficients in the bulk were estimated through the UNIFAC group contributions. The results show that the {Psi} function predicts 90% of the total free energy of immersion, {Delta}F, of the solid when the concentration of phenol is moderate (typically less than 10 g/L). At higher concentrations, the nonideal behavior of the bulk liquid phase becomes significant and it may contribute up to about 30% of {Delta}F. The high concentration of adsorbed molecules of phenol at the interface decreases the interfacial tension, {sigma}, by about 18 mN/m, independently of the structure of the adsorbed phase and of the nature of the organic solvent.

  12. Kinetic Study of Radiation-Reaction-Limited Particle Acceleration During the Relaxation of Force-Free Equilibria

    NASA Astrophysics Data System (ADS)

    Yuan, Yajie; Nalewajko, Krzysztof; Blandford, Roger D.; East, William E.; Zrake, Jonathan

    2016-01-01

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over short time scales. This might be due to prodigal dissipation in a highly magnetized outflow. In order to understand the generic behavior of relativistic plasma with high magnetization, we consider a class of prototypical force-free equilibria which are shown to be unstable to ideal modes (East et al 2015 PRL 115, 095002). Kinetic simulations are carried out to follow the evolution of the instability and to study the basic mechanisms of particle acceleration, especially in the radiation-reaction-limited regime. We find that the instability naturally produces current layers and these are sites for efficient particle acceleration. Detailed calculations of the gamma ray spectrum, the evolution of the particle distribution function and the dynamical consequences of radiation reaction will be presented.

  13. Phase equilibria and elements partitioning in zirconolite-rich region of Ca-Zr-Ti-Al-Gd-Si-O system

    SciTech Connect

    Knyazev, O.A.; Stefanovsky, S.V.; Ioudintsev, S.V.; Nikonov, B.S.; Omelianenko, B.I.; Mokhov, A.V.; Yakushev, A.I.

    1997-12-31

    Zirconolite-rich ceramics were produced by the cold crucible melting technique in an air atmosphere, at 1550 {+-} 50 C and 1 atm. Four samples with overall composition (in wt.%): 4.9-14.3 CaO; 19.0-41.3 ZrO{sub 2}; 24.1-42.6 TiO{sub 2}; 1.3-11.3 Al{sub 2}O{sub 3}; 6.8-30.0 Gd{sub 2}O{sub 3}; and 1.1-8.5 SiO{sub 2} have been studied. Total phases in the ceramics consist of major zirconolite and minor rutile, perovskite, zirconia, aluminium titanate, and glass. The Gd{sub 2}O{sub 3} content in zirconolite reaches up to 31.4 wt.% corresponding to the formula: (Ca{sub 0.4},Gd{sub 0.7})Zr{sub 1.0}(Ti{sub 1.4},Al{sub 0.5})O{sub 7.0}. The data on the phase composition agree well with coupled Gd incorporation into the mineral structure: Ca(II) + Ti(IV) = Gd(III) + Al(III), and 2Gd(III) = Ca(II) + Zr(IV). The highest Gd contents observed in the other phases are 25.4% for zirconia, 12.6% in glass, 8.8% in perovskite, and 1.4% for rutile. The rest of the elements` distribution in the samples are analyzed.

  14. Phase Equilibria of the Ternary Sn-Pb-Co System at 250°C and Interfacial Reactions of Co with Sn-Pb Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Chao-hong; Kuo, Chun-yi; Yang, Nian-cih

    2015-11-01

    The isothermal section of the ternary Sn-Pb-Co system at 250°C was experimentally determined through a series of the equilibrated Sn-Pb-Co alloys of various compositions. The equilibrium phases were identified on the basis of compositional analysis. For the Sn-Co intermetallic compounds (IMCs), CoSn3, CoSn2, CoSn and Co3Sn2, the Pb solubility was very limited. There exist five tie-triangle regions. The Co-Pb system involves one monotectic reaction, so the phase separation of liquid alloys near the Co-Pb side occurred prior to solidification. The immiscibility field was also determined. Additionally, interfacial reactions between Co and Sn-Pb alloys were conducted. The reaction phase for the Sn-48 at.%Pb and Sn-58 at.%Pb at 250°C was CoSn3 and CoSn2, respectively. Both of them were simultaneously formed in the Sn-53 at.%Pb/Co. The formed IMCs were closely associated to the phase equilibria relationship of the liquid-CoSn3-CoSn2 tie-triangle. Furthermore, with increasing temperatures, the phase formed in equilibrium with Sn-37 wt.%Pb was found to transit from CoSn3 to CoSn2 at 275°C. We propose a simple method of examining the phase transition temperature in the interfacial reactions to determine the boundaries of the liquid-CoSn3-CoSn2 tie-triangles at different temperatures.

  15. Equilibria in Quantitative Reachability Games

    NASA Astrophysics Data System (ADS)

    Brihaye, Thomas; Bruyère, Véronique; de Pril, Julie

    In this paper, we study turn-based quantitative multiplayer non zero-sum games played on finite graphs with reachability objectives. In this framework each player aims at reaching his own goal as soon as possible. We prove existence of finite-memory Nash (resp. secure) equilibria in multiplayer (resp. two-player) games.

  16. Study of the kinetics and equilibria of the oligomerization reactions of 2-methylglyceric acid

    NASA Astrophysics Data System (ADS)

    Birdsall, A. W.; Zentner, C. A.; Elrod, M. J.

    2012-11-01

    The presence of a variety of chemical species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA) has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has demonstrated that 2-methylglyceric acid (2-MG) is an important isoprene-derived ambient SOA component and atmospheric chamber experiments have suggested that 2-MG may exist in oligomeric form (as oligoesters) under conditions of low SOA water content. In order to better understand the thermodynamic and kinetic parameters of such oligomerization reactions, nuclear magnetic resonance techniques were used to study the bulk phase acid-catalyzed aqueous reactions (Fischer esterification) of 2-MG. While the present results indicate that 2-MG oligoesters are formed in the bulk phase with similar water content equilibrium dependences as observed in atmospheric chamber SOA experiments, the acid-catalyzed rate of the Fischer esterification mechanism may be too slow to rationalize the 2-MG oligoester production timescales observed in the atmospheric chamber experiments. Furthermore, it appears that unrealistically high ambient SOA acidities would also be required for significant 2-MG oligoester content to arise via Fischer esterification. Therefore, the present results suggest that other, more kinetically facile, esterification mechanisms may be necessary to rationalize the existence of 2-MG oligomers in atmospheric chamber-generated and ambient SOA.

  17. Study of the kinetics and equilibria of the oligomerization reactions of 2-methylglyceric acid

    NASA Astrophysics Data System (ADS)

    Birdsall, A. W.; Zentner, C. A.; Elrod, M. J.

    2013-03-01

    The presence of a variety of chemical species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA) has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has demonstrated that 2-methylglyceric acid (2-MG) is an important isoprene-derived ambient SOA component and atmospheric chamber experiments have suggested that 2-MG may exist in oligomeric form (as oligoesters) under conditions of low SOA water content. In order to better understand the thermodynamic and kinetic parameters of such oligomerization reactions, nuclear magnetic resonance techniques were used to study the bulk phase acid-catalyzed aqueous reactions (Fischer esterification) of 2-MG. While the present results indicate that 2-MG oligoesters are formed in the bulk phase with similar water content equilibrium dependences as observed in atmospheric chamber SOA experiments, the acid-catalyzed rate of the Fischer esterification mechanism may be too slow to rationalize the 2-MG oligoester production timescales observed in the atmospheric chamber experiments. Furthermore, it appears that unrealistically high ambient SOA acidities would also be required for significant 2-MG oligoester content to arise via Fischer esterification. Therefore, the present results suggest that other, more kinetically facile, esterification mechanisms may be necessary to rationalize the existence of 2-MG oligomers in atmospheric chamber-generated and ambient SOA.

  18. Computation of liquid-liquid equilibria and phase stabilities: implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Marcolli, C.; Peter, T.; Seinfeld, J. H.

    2010-05-01

    Semivolatile organic and inorganic aerosol species partition between the gas and aerosol particle phases to maintain thermodynamic equilibrium. Liquid-liquid phase separation into an organic-rich and an aqueous electrolyte phase can occur in the aerosol as a result of the salting-out effect. Such liquid-liquid equilibria (LLE) affect the gas/particle partitioning of the different semivolatile compounds and might significantly alter both particle mass and composition as compared to a one-phase particle. We present a new liquid-liquid equilibrium and gas/particle partitioning model, using as a basis the group-contribution model AIOMFAC (Zuend et al., 2008). This model allows the reliable computation of the liquid-liquid coexistence curve (binodal), corresponding tie-lines, the limit of stability/metastability (spinodal), and further thermodynamic properties of the phase diagram. Calculations for ternary and multicomponent alcohol/polyol-water-salt mixtures suggest that LLE are a prevalent feature of organic-inorganic aerosol systems. A six-component polyol-water-ammonium sulphate system is used to simulate effects of relative humidity (RH) and the presence of liquid-liquid phase separation on the gas/particle partitioning. RH, salt concentration, and hydrophilicity (water-solubility) are identified as key features in defining the region of a miscibility gap and govern the extent to which compound partitioning is affected by changes in RH. The model predicts that liquid-liquid phase separation can lead to either an increase or decrease in total particulate mass, depending on the overall composition of a system and the particle water content, which is related to the hydrophilicity of the different organic and inorganic compounds. Neglecting non-ideality and liquid-liquid phase separations by assuming an ideal mixture leads to an overestimation of the total particulate mass by up to 30% for the composition and RH range considered in the six-component system simulation

  19. Phase Equilibria, Crystal Structure and Hydriding/Dehydriding Mechanism of Nd4Mg80Ni8 Compound

    NASA Astrophysics Data System (ADS)

    Luo, Qun; Gu, Qin-Fen; Zhang, Jie-Yu; Chen, Shuang-Lin; Chou, Kuo-Chih; Li, Qian

    2015-10-01

    In order to find out the optimal composition of novel Nd-Mg-Ni alloys for hydrogen storage, the isothermal section of Nd-Mg-Ni system at 400 °C is established by examining the equilibrated alloys. A new ternary compound Nd4Mg80Ni8 is discovered in the Mg-rich corner. It has the crystal structure of space group I41/amd with lattice parameters of a = b = 11.2743(1) Å and c = 15.9170(2) Å, characterized by the synchrotron powder X-ray diffraction (SR-PXRD). High-resolution transmission electron microscopy (HR-TEM) is used to investigate the microstructure of Nd4Mg80Ni8 and its hydrogen-induced microstructure evolution. The hydrogenation leads to Nd4Mg80Ni8 decomposing into NdH2.61-MgH2-Mg2NiH0.3 nanocomposites, where the high density phase boundaries provide a great deal of hydrogen atoms diffusion channels and nucleation sites of hydrides, which greatly enhances the hydriding/dehydriding (H/D) properties. The Nd4Mg80Ni8 exhibits a good cycle ability. The kinetic mechanisms of H/D reactions are studied by Real Physical Picture (RPP) model. The rate controlling steps are diffusion for hydriding reaction in the temperature range of 100 ~ 350 °C and surface penetration for dehydriding reaction at 291 ~ 347 °C. In-situ SR-PXRD results reveal the phase transformations of Mg to MgH2 and Mg2Ni to Mg2NiH4 as functions of hydrogen pressure and hydriding time.

  20. Phase Equilibria, Crystal Structure and Hydriding/Dehydriding Mechanism of Nd4Mg80Ni8 Compound

    PubMed Central

    Luo, Qun; Gu, Qin-Fen; Zhang, Jie-Yu; Chen, Shuang-Lin; Chou, Kuo-Chih; Li, Qian

    2015-01-01

    In order to find out the optimal composition of novel Nd-Mg-Ni alloys for hydrogen storage, the isothermal section of Nd-Mg-Ni system at 400 °C is established by examining the equilibrated alloys. A new ternary compound Nd4Mg80Ni8 is discovered in the Mg-rich corner. It has the crystal structure of space group I41/amd with lattice parameters of a = b = 11.2743(1) Å and c = 15.9170(2) Å, characterized by the synchrotron powder X-ray diffraction (SR-PXRD). High-resolution transmission electron microscopy (HR-TEM) is used to investigate the microstructure of Nd4Mg80Ni8 and its hydrogen-induced microstructure evolution. The hydrogenation leads to Nd4Mg80Ni8 decomposing into NdH2.61-MgH2-Mg2NiH0.3 nanocomposites, where the high density phase boundaries provide a great deal of hydrogen atoms diffusion channels and nucleation sites of hydrides, which greatly enhances the hydriding/dehydriding (H/D) properties. The Nd4Mg80Ni8 exhibits a good cycle ability. The kinetic mechanisms of H/D reactions are studied by Real Physical Picture (RPP) model. The rate controlling steps are diffusion for hydriding reaction in the temperature range of 100 ~ 350 °C and surface penetration for dehydriding reaction at 291 ~ 347 °C. In-situ SR-PXRD results reveal the phase transformations of Mg to MgH2 and Mg2Ni to Mg2NiH4 as functions of hydrogen pressure and hydriding time. PMID:26471964

  1. Computation of liquid-liquid equilibria and phase stabilities: implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Marcolli, C.; Peter, T.; Seinfeld, J. H.

    2010-08-01

    Semivolatile organic and inorganic aerosol species partition between the gas and aerosol particle phases to maintain thermodynamic equilibrium. Liquid-liquid phase separation into an organic-rich and an aqueous electrolyte phase can occur in the aerosol as a result of the salting-out effect. Such liquid-liquid equilibria (LLE) affect the gas/particle partitioning of the different semivolatile compounds and might significantly alter both particle mass and composition as compared to a one-phase particle. We present a new liquid-liquid equilibrium and gas/particle partitioning model, using as a basis the group-contribution model AIOMFAC (Zuend et al., 2008). This model allows the reliable computation of the liquid-liquid coexistence curve (binodal), corresponding tie-lines, the limit of stability/metastability (spinodal), and further thermodynamic properties of multicomponent systems. Calculations for ternary and multicomponent alcohol/polyol-water-salt mixtures suggest that LLE are a prevalent feature of organic-inorganic aerosol systems. A six-component polyol-water-ammonium sulphate system is used to simulate effects of relative humidity (RH) and the presence of liquid-liquid phase separation on the gas/particle partitioning. RH, salt concentration, and hydrophilicity (water-solubility) are identified as key features in defining the region of a miscibility gap and govern the extent to which compound partitioning is affected by changes in RH. The model predicts that liquid-liquid phase separation can lead to either an increase or decrease in total particulate mass, depending on the overall composition of a system and the particle water content, which is related to the hydrophilicity of the different organic and inorganic compounds. Neglecting non-ideality and liquid-liquid phase separations by assuming an ideal mixture leads to an overestimation of the total particulate mass by up to 30% for the composition and RH range considered in the six-component system

  2. Phase equilibria in the Fe-rich corner of the Nd-Fe-Ti ternary alloy system at 1100 C

    NASA Astrophysics Data System (ADS)

    Margarian, A.; Dunlop, J. B.; Day, R. K.; Kalceff, W.

    1994-11-01

    High-temperature phase relations in the Fe-rich corner of the Nd-Fe-Ti ternary alloy system have been investigated and an equilibrium phase diagram has been constructed at 1100 C. Arc-melted and annealed alloys of systematically varying compositions were characterized utilizing scanning electron microscopy, and energy dispersive x-ray microanalysis system (EDS), x-ray diffraction, and optical metallography. Three major phases have been idenfified, the well known Nd(Fe,Ti)12 '1:12' (ThMn12-type structure) and Nd2(Fe,Ti)17 '2:17' (Th2Zn17-type structure compounds, and a phase with approximate composition Nd2(Fe,Ti)19 '2:19.' The crystal structure of the latter phase has very recently been solved, and the 'ideal' composition shown to be Nd3(Fe,Ti)29 '3:29.' Quantitative EDS data has been used to identify the compositional limits for the three major phases. Annealing the '1:12' and '3:29' ternary phases at 900 C results in a slow decomposition into Nd2(Fe,Ti)17, Fe2Ti, and alpha-Fe(Ti).

  3. Self-association equilibria of Escherichia coli UvrD helicase studied by analytical ultracentrifugation.

    PubMed

    Maluf, Nasib K; Lohman, Timothy M

    2003-01-31

    The Escherichia coli UvrD protein (helicase II) is an SF1 superfamily helicase required for methyl-directed mismatch repair and nucleotide excision repair of DNA. We have characterized quantitatively the self-assembly equilibria of the UvrD protein as a function of [NaCl], [glycerol], and temperature (5-35 degrees C; pH 8.3) using analytical sedimentation velocity and equilibrium techniques, and find that UvrD self-associates into dimeric and tetrameric species over a range of solution conditions (t

  4. Phase equilibria in four-component system consisting of water, a nonionic surfactant mixture, and oleic acid

    SciTech Connect

    Matveenko, V.N.; Drovetskii, B.Yu.; Kirasanov, E.A.

    1994-05-01

    The phase diagram of the system consisting of water, Tween 20, Span 80, and oleic acid has been obtained; the coexisting phases have been identified; and the character of the equilibrium of microemulsion, liquid crystal, and molecular solution has been described. In the water-Tween 20-oleic acid system, the ratio of the water volume to the surfactant volume is identical in all of the coexisting phases; this proves the existence of a corresponding field variable in a system with a nonionic surfactant.

  5. Spontaneous Decay of Periodic Magnetostatic Equilibria.

    PubMed

    East, William E; Zrake, Jonathan; Yuan, Yajie; Blandford, Roger D

    2015-08-28

    In order to understand the conditions that lead to a highly magnetized, relativistic plasma becoming unstable, and in such cases how the plasma evolves, we study a prototypical class of magnetostatic equilibria in which the magnetic field satisfies ∇×B=αB, where α is spatially uniform, on a periodic domain. Using numerical solutions, we show that generic examples of such equilibria are unstable to ideal modes (including incompressible ones), which are marked by exponential growth in the linear phase. We characterize the unstable mode, showing how it can be understood in terms of merging magnetic and current structures, and explicitly demonstrate its instability using the energy principle. Following the nonlinear evolution of these solutions, we find that they rapidly develop regions with relativistic velocities and electric fields of comparable magnitude to the magnetic field, liberating magnetic energy on dynamical time scales and eventually settling into a configuration with the largest allowable wavelength. These properties make such solutions a promising setting for exploring the mechanisms behind extreme cosmic sources of gamma rays. PMID:26371660

  6. Theoretical study on the vibrational spectra of methoxy- and formyl-dihydroxy- trans-stilbenes and their hydrolytic equilibria

    NASA Astrophysics Data System (ADS)

    Molnár, Viktor; Billes, Ferenc; Tyihák, Ernő; Mikosch, Hans

    2008-02-01

    Compounds formed by exchanging one of the resveratrol hydroxy groups to methoxy or formyl groups are biologically important. Quantum chemical DFT calculations were applied for the simulation of some of their properties. Their optimized structures and charge distributions were computed. Based on the calculated vibrational force constants and optimized molecular structure infrared and Raman spectra were calculated. The characteristics of the vibrational modes were determined by normal coordinate analysis. Applying the calculated thermodynamic functions also for resveratrol, methanol, formaldehyde and water, thermodynamic equilibria were calculated for the equilibria between resveratrol and its methyl and formyl substituted derivatives, respectively.

  7. Chemometric investigation of complex equilibria in solution phase II: Sensitivity of chemical models for the interaction of AADH and FAH with Ni(II) in aqueous medium.

    PubMed

    Babu, A R; Krishna, D M; Rao, R S

    1993-12-01

    A detailed study of the species formed in the complex equilibria involving adipic acid dihydrazide (AADH)/2-furoic acid hydrazide (FAH) with Ni(II) using pH titration with glass electrode is performed. The results of modeling studies and effect of errors on the equilibrium constants of AADH/FAH with Ni(II) refined by the non-linear least squares program MINIQUAD75 are reported. Based on the expert system approach developed in our laboratory for the species formed from secondary formation data (n and n (H)), several preliminary chemical models were tested. For the four species identified (MLH, ML, ML(2)H, ML(2)), an exhaustive search of a different combination of models (15) was performed. Then other suspected minor species (ML(2)H(2), ML(3) and ML(3)H) were tested. The final best fit chemical model was found to contain ML(3)H to an extent of 3% along with the other four major species. In order to ascertain the accuracy of the stability constants and consequently distribution of the species, a detailed error analysis is attempted. As the existing least squares procedures cannot suppress the systematic errors, three-dimensional plots of the simultaneous effects of pH and TLO:TMO (1.5:1 to 5:1) on the percentage of species are drawn which are of immense use in arriving at optimum conditions for the preparation of a complex of definite stoichiometry. PMID:18965865

  8. Phase equilibria between iron and slag in carbon monoxide/carbon dioxide/water atmospheres relevant to a novel flash ironmaking technology

    NASA Astrophysics Data System (ADS)

    Mohassab Ahmed, Mohassab Yousef

    In an effort to develop a novel flash ironmaking process, to be called the Sohn process in this dissertation, with the potential of steelmaking in a single continuous process, the phase equilibria involved and the chemistry of selected slag systems were investigated. The Sohn process is an ecofriendly flash ironmaking process for producing iron from iron oxide concentrates in a flash reactor using fuels and reductants that help reduce energy consumption and minimize greenhouse gas emissions. Amongst the proposed reductants and fuels are H2, natural gas, and coal gas. The molten bath (iron-slag bath) is expected to equilibrate with gas atmospheres of mainly H2/H 2O, CO/CO2/H2/H2O, and CO/CO2 corresponding to H2, natural gas/coal gas (NG/CG), and coke/coal (blast furnace, BF), respectively. The latter was investigated to allow comparison with the blast-furnace conditions. The slag composition was selected to resemble that of the blast furnace, which consisted of the CaO-MgO-SiO2-Al 2O2-FeO-MnO-P2O5 system with CaO/SiO 2 in the range 0.8 to 1.4. The temperature range was 1550 to 1650°C encompassing a wide range of expected ironmaking temperatures for the Sohn process. The oxygen partial pressure was maintained in the reducing range 10-10 to 10-9 atm in the three gas atmospheres. It was found that H2O dramatically affects the chemistry of the slag and strongly affects the phase equilibria in the slag as well as the equilibrium distribution of elements between slag and molten metal. It was found that the slags under H2O-containing (H2 and NG/CG) atmospheres had a moderately higher degree of polymerization as compared to that under the blast furnace conditions. H2O in the gas atmosphere also increased the activity coefficient of FeO in the slag and accordingly lowered the FeO content. The FeO content in the slag of H 2 (FeO wt% = 10) and NG/CG (11) was significantly less than under the BF (16) conditions. On the other hand, the average MgO solubility (22 wt%) under the

  9. Density functional models of the interfacial tensions near the critical endpoints and tricritical point of three-phase equilibria

    NASA Astrophysics Data System (ADS)

    Koga, K.; Widom, B.

    2016-06-01

    We treat two different density-functional models of the structures and tensions of the interfaces between phases on approach to the tricritical point of three-phase equilibrium. The major objective is to account for some of the results of earlier experimental measurements of these tensions. The thermodynamic background is first reviewed, including representations of the properties near the critical endpoints and tricritical point and of the wetting transitions that may occur on approach to those critical points. The first of the models treated is analytically soluble. Its properties are illuminating but at the price of some artificiality paid for its analytical solubility. The second model, called model T, is in a class of those treated in the past and analyzed numerically. Some of its properties are obtained with sufficient precision to allow one to conclude with near certainty what the analytically exact results would be. This model, too, illuminates the experimental measurements. It is noted where its properties are in accord with those of the analytically soluble model and where the two differ.

  10. Density functional models of the interfacial tensions near the critical endpoints and tricritical point of three-phase equilibria.

    PubMed

    Koga, K; Widom, B

    2016-06-22

    We treat two different density-functional models of the structures and tensions of the interfaces between phases on approach to the tricritical point of three-phase equilibrium. The major objective is to account for some of the results of earlier experimental measurements of these tensions. The thermodynamic background is first reviewed, including representations of the properties near the critical endpoints and tricritical point and of the wetting transitions that may occur on approach to those critical points. The first of the models treated is analytically soluble. Its properties are illuminating but at the price of some artificiality paid for its analytical solubility. The second model, called model T, is in a class of those treated in the past and analyzed numerically. Some of its properties are obtained with sufficient precision to allow one to conclude with near certainty what the analytically exact results would be. This model, too, illuminates the experimental measurements. It is noted where its properties are in accord with those of the analytically soluble model and where the two differ. PMID:27116351

  11. Spin Equilibria in Monomeric Manganocenes: Solid State Magnetic and EXAFS Studies

    SciTech Connect

    Walter, M. D.; Sofield, C. D.; Booth, C. H.; Andersen, R. A.

    2009-02-09

    Magnetic susceptibility measurements and X-ray data confirm that tert-butyl-substituted manganocenes [(Me{sub 3}C){sub n}C{sub 5}H{sub 5?n}]{sub 2}Mn (n = 1, 2) follow the trend previously observed with the methylated manganocenes; that is, electron-donating groups attached to the Cp ring stabilize the low-spin (LS) electronic ground state relative to Cp{sub 2}Mn and exhibit higher spin-crossover (SCO) temperatures. However, introducing three CMe{sub 3} groups on each ring gives a temperature-invariant high-spin (HS) state manganocene. The origin of the high-spin state in [1,2,4-(Me{sub 3}C){sub 3}C{sub 5}H{sub 2}]{sub 2}Mn is due to the significant bulk of the [1,2,4-(Me{sub 3}C){sub 3}C{sub 5}H{sub 2}]{sup -} ligand, which is sufficient to generate severe inter-ring steric strain that prevents the realization of the low-spin state. Interestingly, the spin transition in [1,3-(Me{sub 3}C){sub 2}C{sub 5}H{sub 3}]{sub 2}Mn is accompanied by a phase transition resulting in a significant irreversible hysteresis ({Delta}T{sub c} = 16 K). This structural transition was also observed by extended X-ray absorption fine-structure (EXAFS) measurements. Magnetic susceptibility studies and X-ray diffraction data on SiMe{sub 3}-substituted manganocenes [(Me{sub 3}Si){sub n}C{sub 5}H{sub 5-n}]{sub 2}Mn (n = 1, 2, 3) show high-spin configurations in these cases. Although tetra- and hexasubstituted manganocenes are high-spin at all accessible temperatures, the disubstituted manganocenes exhibit a small low-spin admixture at low temperature. In this respect it behaves similarly to [(Me{sub 3}C)(Me{sub 3}Si)C{sub 5}H{sub 3}]{sub 2}Mn, which has a constant low-spin admixture up to 90 K and then gradually converts to high-spin. Thermal spin-trapping can be observed for [(Me{sub 3}C)(Me{sub 3}Si)C{sub 5}H{sub 3}]{sub 2}Mn on rapid cooling.

  12. Phase equilibria in systems Ce-M-Sb (M=Si, Ge, Sn) and superstructure Ce{sub 12}Ge{sub 9-x}Sb{sub 23+x} (x=3.8+-0.1)

    SciTech Connect

    Nasir, Navida; Grytsiv, Andriy; Rogl, Peter; Saccone, Adriana; Giester, Gerald

    2009-04-15

    Phase relations in the ternary systems Ce-M-Sb (M=Si, Ge, Sn) in composition regions CeSb{sub 2}-Sb-M were studied by optical and electron microscopy, X-ray diffraction, and electron probe microanalysis on arc-melted alloys and specimens annealed in the temperature region from 850 to 200 deg. C. The results, in combination with an assessment of all literature data available, were used to construct solidus surfaces and a series of isothermal sections. No ternary compounds were found to form in the Ce-Si-Sb system whilst Ce{sub 12}Ge{sub 9-x}Sb{sub 23+x} (3.3phase equilibria in the composition region investigated. Crystallographic parameters for the ternary compound Ce{sub 12}Ge{sub 9-x}Sb{sub 23+x} (x=3.8+-0.1) were determined from X-ray single crystal and powder diffraction. For the binary system Ge-Sb a eutectic was defined Lreversible(Ge)+(Sb) at 591.6 deg. C and 22.5 at%. Ge EPMA revealed a maximal solubility of 6.3 at% Ge in (Sb) at the eutectic temperature. - Graphical abstract: Phase relations in the ternary systems Ce-M-Sb (M=Si, Ge, Sn) in composition regions CeSb{sub 2}-Sb-M have been studied by optical and electron microscopy, XRD and EPMA on as cast alloys and specimens annealed in the temperature region 200-850 deg. C.

  13. Phase-equilibria for design of coal-gasification processes: dew points of hot gases containing condensible tars. Final report

    SciTech Connect

    Prausnitz, J.M.

    1980-05-01

    This research is concerned with the fundamental physical chemistry and thermodynamics of condensation of tars (dew points) from the vapor phase at advanced temperatures and pressures. Fundamental quantitative understanding of dew points is important for rational design of heat exchangers to recover sensible heat from hot, tar-containing gases that are produced in coal gasification. This report includes essentially six contributions toward establishing the desired understanding: (1) Characterization of Coal Tars for Dew-Point Calculations; (2) Fugacity Coefficients for Dew-Point Calculations in Coal-Gasification Process Design; (3) Vapor Pressures of High-Molecular-Weight Hydrocarbons; (4) Estimation of Vapor Pressures of High-Boiling Fractions in Liquefied Fossil Fuels Containing Heteroatoms Nitrogen or Sulfur; and (5) Vapor Pressures of Heavy Liquid Hydrocarbons by a Group-Contribution Method.

  14. Sorption equilibria of vapor-phase organic pollutants on unsaturated soils and soil minerals. Final report, Mar 85-Mar 89

    SciTech Connect

    Lion, L.W.; Ong, S.K.; Linder, S.R.; Swager, J.L.; Schwager, S.J.

    1990-04-01

    Most groundwater pollutants are volatile organic compounds; however, there is relatively little understanding of the sorption reactions that control the transport and fate of organic vapors in the vadose zone. This investigation identified the physical/chemical properties of the soil matrix and organic vapors which control vapor-solid phase distribution. The dominant property which regulates vapor sorption in the unsaturated zone is the moisture content of the soil. Under very dry conditions, soil mineral/vapor interactions are regulated by specific surface area, indicating the dominance of a relatively non-specific physical adsorption process. However, at moisture contents exceeding an average surface coverage of four to eight layers of water, vapor uptake is controlled by partitioning reactions into soil moisture and soil organic matter.

  15. Deep Recycling of Sedimentary Lithologies in Subduction Zones: Geochemical and Physical Constraints from Phase Equilibria and Synchrotron-Based Multi-Anvil Experiments at 15-25 GPa

    NASA Astrophysics Data System (ADS)

    Rapp, R. P.; Nishiyama, N.; Irifune, T.; Inoue, T.; Yamasaki, D.

    2003-12-01

    Ocean island basalts (OIBs) provide geochemical evidence for the presence of crustally-derived sedimentary material in the deep mantle plume source region for EM-type OIBs, and global seismic tomography provides us with dramatic images of subducted slabs, presumably carrying a sediment component, penetrating through the transition zone and into the lower mantle, in some cases to the core-mantle boundary. In an effort to better constrain the geochemical effects of deeply recycled sedimentary material in subduction zones, and their role in the petrogenesis of EM-type OIBs, we have undertaken a series of phase equlibria experiments in the multi-anvil apparatus at 10-25 GPa, using natural sediment lithologies as starting materials. The goal of these experiments is to identify the dominant phases in deeply subducted sediments, constrain their P-T stability limits, and to assess their role in crustal recycling and element redistribution in the deep mantle during subduction. The phase equilibria experiments were performed in a 2000-ton Kawai-type apparatus, using tungsten carbide cubes with 3 mm TEL and Cr-doped MgO and zirconia pressure media. A cylindrical lanthanum chromite heater was used, along with short (< 1 mm), thick-walled, pressure-welded gold capsules to minimize thermal gradients and to retain the small amounts of water (< 1 wt%) present in the starting material, and long run-durations (12-48 hours) in order to facilitate future analyses of the dominant phases for key trace elements using the ion microprobe. Our preliminary results at 10-25 GPa indicate that K-hollandite (KalSi3O3) and stishovite are the primary high-pressure phases in the sediment composition, with subordinate garnet and an as-yet-unidentified (possibly hydrous) Al-silicate phase present as well. These results suggest that K-hollandite is the primary repository for incompatible elements (e.g., La, Ce, Sr, Ba, Rb, etc., and the heat-producing elements K, U and Th) in sedimentary material

  16. Phase equilibria investigations and thermodynamic modeling of the system Bi2O3-Al2O3

    NASA Astrophysics Data System (ADS)

    Oudich, F.; David, N.; Mathieu, S.; Vilasi, M.

    2015-02-01

    The system Bi2O3-Al2O3 has been experimentally investigated above 600 °C by DTA, XRD and EPMA under air and low oxygen pressure. Only two compounds were found to exist in equilibrium, which are Bi2Al4O9(1Bi2O3:2Al2O3) and Bi25AlO39(25:1). The latter exhibits a sillenite structure and does not contain pentavalent bismuth. A peritectoid decomposition of (25:1) and a peritectic melting of (1:2) occur at 775 °C and 1075 °C respectively, while an eutectic transformation was observed at 815 °C for 97 mol% Bi2O3. On the basis of the results obtained within the present work as well as experimental data provided from literature, a thermodynamic modeling where the liquid phase is described by the two-sublattice ionic liquid model was performed according to the Calphad approach. The resulting thermodynamic optimization yielded good agreement with experimental results in the investigated region.

  17. (Sulfide-oxide-silicate phase equilibria and associated fluid inclusion properties in the Salton Sea geothermal system, California)

    SciTech Connect

    McKibben, M.A.

    1988-06-01

    Our studies involved petrographic, fluid inclusion, geochemical and stable isotopic studies of drillcores and fluids from the Salton Sea geothermal system. Our initial studies revealed the presence of previously-unrecognized evaporitic anhydrite at depth throughout the geothermal system. The high salinity of the Salton Sea geothermal brines previously had been attributed to low-temperature dissolution of surficial evaporitic deposits by meteoric waters. Our microthermometric studies of halite--containing fluid inclusions in the meta-evaporites indicated that the high salinity of the geothermal brines is derived in part from the hydrothermal metamorphism of relatively deeply-buried salt and evaporites. In addition, our research concentrated on mineralized fractures in drillcores.

  18. Phase-space transport in cuspy triaxial potentials: can they be used to construct self-consistent equilibria?

    NASA Astrophysics Data System (ADS)

    Siopis, Christos; Kandrup, Henry E.

    2000-11-01

    This paper focuses on the statistical properties of chaotic orbit ensembles evolved in triaxial generalizations of the Dehnen potential which have been proposed recently to model realistic ellipticals that have a strong density cusp and manifest significant deviations from axisymmetry. Allowance is made for a possible supermassive black hole, as well as low-amplitude friction, noise, and periodic driving which can mimic irregularities associated with discreteness effects and/or an external environment. The chaos exhibited by these potentials is quantified by determining (1) how the relative number of chaotic orbits depends on the steepness of the cusp, as probed by γ, the power-law exponent with which density diverges, and MBH, the black hole mass, (2) how the size of the largest Lyapunov exponent varies with γ and MBH, and (3) the extent to which Arnold webs significantly impede phase-space transport, both with and without perturbations. The most important conclusions dynamically are (1) that, in the absence of irregularities, chaotic orbits tend to be extremely `sticky', so that different pieces of the same chaotic orbit can behave very differently for times ~10000tD or more, but (2) that even very low-amplitude perturbations can prove efficient in erasing many - albeit not all - of these differences. The implications of these facts are discussed both for the structure and evolution of real galaxies and for the possibility of constructing approximate near-equilibrium models using Schwarzschild's method. For example, when trying to use Schwarzschild's method to construct model galaxies containing significant numbers of chaotic orbits, it seems advantageous to build libraries with chaotic orbits evolved in the presence of low-amplitude friction and noise, since such noisy orbits are more likely to represent reasonable approximations to time-independent building blocks. Much of the observed qualitative behaviour can be reproduced with a toy potential given as the

  19. Kinetic Study of Radiation-reaction-limited Particle Acceleration During the Relaxation of Unstable Force-free Equilibria

    NASA Astrophysics Data System (ADS)

    Yuan, Yajie; Nalewajko, Krzysztof; Zrake, Jonathan; East, William E.; Blandford, Roger D.

    2016-09-01

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focus on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The “flares” are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model. Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. Higher magnetization studies are promising and will be carried out in the future.

  20. Two-step solvent gradients in simulated moving bed chromatography. Numerical study for linear equilibria.

    PubMed

    Antos, Dorota; Seidel-Morgenstern, Andreas

    2002-01-25

    The application of gradients in simulated moving bed (SMB) chromatography has recently attracted interest as a method for further improving the performance of this continuous separation process. One possible implementation of gradients consists in setting the solvent strength in the desorbent stream higher than that in the feed stream. As a result, the components to be separated are more retained in the zones upstream of the feed position and more easily eluted in the zones downstream of the feed position. If a liquid mobile phase is used, gradients can be created by dosing different solvents into the feed and desorbent ports. In a closed-loop gradient SMB arrangement the solvent strength within the unit will depend on the two feed compositions and on the characteristic flow-rates of the process. In this work an equilibrium stage model describing a true moving bed process is used to analyze numerically the main features of a two-step gradient SMB process. The adsorption isotherms are assumed to be always linear under isocratic conditions. The relevant Henry constants depend in a nonlinear manner on the composition of the solvent. Based on numerical simulations the impact of the two inlet solvent compositions is demonstrated in terms of the size and shape of regions of applicable flow-rates. Different strategies of designing the process are discussed and compared with respect to maximizing productivities and minimizing desorbent requirements. PMID:11831766

  1. Effect of trans-cis photoisomerization on phase equilibria and phase transition of liquid-crystalline azobenzene chromophore and its blends with reactive mesogenic diacrylate.

    PubMed

    Kim, Namil; Li, Quan; Kyu, Thein

    2011-03-01

    Photoisomerization-induced phase transition of neat liquid-crystalline azobenzene chromophore (LCAC) and its effect on phase diagrams of its mixtures with reactive mesogenic diacrylate monomer (RM257) have been investigated experimentally and theoretically. Upon irradiation with ultraviolet light, the nematic phase of LCAC transformed to isotropic, while the crystal phase showed corrugated textures on the surface (i.e., ripples). The phase-transition temperatures and corresponding morphologies of the blends have been investigated by means of differential scanning calorimetry and optical microscopy. A theoretical phase diagram of a binary nematic and crystalline system was constructed by self-consistently solving the combined free energies of Flory-Huggins, Maier-Saupe, and phase-field theory. The calculation revealed various coexistence regions such as nematic + liquid (N₁ + L₂), crystal + liquid (Cr₁ + L₂), crystal + nematic (Cr₁ + N₂), and crystal + crystal (Cr₁ + Cr₂) over a broad range of compositions including the single-phase nematic (N₁, N₂) of the corresponding constituents. The calculated liquidus lines were in good accord with the depressed mesophase-isotropic transition points. The present paper demonstrates the effect of trans-cis photoisomerization on the mesophase transitions of neat LCAC and the phase diagram of LCAC-RM257 as well as on the ripple formation (i.e., periodic undulation) on the azobenzene crystals. PMID:21517513

  2. Phase Equilibria of the Cu-Ti-Er System at 773 K (500 °C) and Stability of the CuTi3 Phase

    NASA Astrophysics Data System (ADS)

    Zhan, Yongzhong; Peng, Dan; She, Jia

    2012-11-01

    The phase relationships of the Cu-Ti-Er ternary phase diagram at 773 K (500 °C) were investigated mainly by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and differential thermal analysis (DTA). It is confirmed in this work that the binary compounds Cu9Er2 and Cu7Er2 exist in the Cu-Er binary system at 773 K (500 °C). The stability of the CuTi3 phase is confirmed in the Cu-Ti system. After heat treatment at 1023 K (750 °C) for 90 hours, the phase CuTi3 is observed in the microstructure of the alloy 25Cu75Ti. The temperature of the eutectoid transformation, namely, β-Ti ↔ α-Ti + CuTi3, is determined to be 1078 K (805 °C) in this work. The 773 K (500 °C) isothermal section consists of 14 single-phase regions, 25 two-phase regions, and 12 three-phase regions. None of the phases in this system reveals a remarkable homogeneity range at 773 K (500 °C).

  3. Development of a free-boundary tokamak equilibrium solver for advanced study of tokamak equilibria

    NASA Astrophysics Data System (ADS)

    Jeon, Young Mu

    2015-09-01

    A free-boundary Tokamak equilibrium solver (TES), developed for advanced study of tokamak equilibra, is described with two distinctive features. One is a generalized method to resolve the intrinsic axisymmetric instability, which is encountered in all equilibrium calculations with a freeboundary condition. The other is an extension to deal with a new divertor geometry such as snowflake or X divertors. For validations, the uniqueness of a solution is confirmed by the independence of variations in the computational domain, the mathematical correctness and accuracy of equilibrium profiles are checked by using a direct comparison with an analytic equilibrium known as a generalized Solov'ev equilibrium, and the governing force balance relation is tested by examining the intrinsic axisymmetric instabilities. As an application of an advanced equilibrium study, a snow-flake divertor configuration that requires a second-order zero of the poloidal magnetic flux is discussed in the circumstance of the Korea superconducting tokamak advanced research (KSTAR) coil system.

  4. Nickel biosorption from aqueous systems: Studies on single and multimetal equilibria, kinetics, and recovery

    SciTech Connect

    Suhasini, I.P.; Sriram, G.; Asolekar, S.R.; Sureshkumar, G.K.

    1999-10-01

    This paper reports studies on the removal of toxic trace metals (nickel separately, and simultaneously with cobalt) from aqueous solutions by employing fungal biosorbents, PFB1 and PFB2, which were developed in the authors' laboratory. The observed maximum equilibrium uptake of nickel on the biosorbent was 214 mg/g (PFB1) and 110 mg/g (PFB2). The average efficiency for nickel removal was 84.5% (PFB1) and 60.8% (PFB2). The equilibrium uptake of nickel followed first-order Langmuir kinetics in the case of PFB1 and second-order Langmuir kinetics in the case of PFB2. Studies on simultaneous removal of cobalt and nickel indicated that the extent of secondary interactions between cobalt and nickel can be quantified by the change in Langmuir equilibrium constants for both metals. A mathematical model based on Fick's law of diffusion and Langmuir adsorption was developed to simulate the kinetics of nickel removal. The model was able to predict the experimentally observed kinetics well. From the simulations, the diffusivity of nickel in PFB1 was found to be 1.6 x 10{sup {minus}8} m{sup 2}/s. Desorption studies indicated that it was possible to reuse the biosorbent over three sorption-desorption cycles, and that acidic solutions desorbed better than basic or salt solutions. Among the desorbents studied, HCl and CaCl{sub 2}, with desorption efficiencies equal to 73.2 and 74.1%, respectively, for PFB1 and 70.0 and 63.1%, respectively, for PFB2 at the end of three cycles, were found to be the best desorbents.

  5. A scanning calorimetric study of unfolding equilibria in homodimeric chicken gizzard tropomyosins.

    PubMed Central

    O'Brien, R; Sturtevant, J M; Wrabl, J; Holtzer, M E; Holtzer, A

    1996-01-01

    Using both circular dichroism (CD) and differential scanning calorimetry (DSC), several laboratories find that the thermal unfolding transitions of alpha alpha and beta beta homodimeric coiled coils of rabbit tropomyosin are multistate and display an overall unfolding enthalpy of near 300 kcal (mol dimer)(-1). In contrast, an extant CD study of beta beta and gamma gamma species of chicken gizzard tropomyosin concludes that their unfolding transitions are simple two-state transitions, with much smaller overall enthalpies (98 kcal mol(-1) for beta beta and 162 kcal mol(-1) for gamma gamma). However, these smaller enthalpies have been questioned, because they imply a concentration dependence of the melting temperatures that is far larger than observed by CD. We report here DSC studies of the unfolding of both beta beta and gamma gamma chicken gizzard homodimers. The results show that these transitions are very similar to those in rabbit tropomyosins in that 1) the overall unfolding enthalpy is near 300 kcal mol(-1); 2) the overall delta C(rho) values are significantly positive; 3) the various transitions are multistate, requiring at least two and as many as four domains to fit the DSC data. DSC studies are also reported on these homodimeric species of chicken gizzard tropomyosin with a single interchain disulfide cross-link. These results are also generally similar to those for the correspondingly cross-linked rabbit tropomyosins. PMID:9172766

  6. Binary metal sorption by pine bark: Study of equilibria and mechanisms

    SciTech Connect

    Al-Asheh, S.; Duvnjak, Z.

    1998-06-01

    Pine bark was able to sorb cadmium, copper, and nickel ions from aqueous solutions. Binary equilibrium data from the combination of these metals were collected in this work using the sorbent. These data were modeled using three types of binary component equilibrium isotherms, all of which resulted in good fitting of the experimental data, with the Langmuir-Freundlich model resulting in their best representation. In general, the capacity of bark for each metal in the binary system was lower than in the single metal systems. The study also examined the mechanisms of metal biosorption by bark. Scanning electron microscopy (SEM) and energy-dispersive c-ray (EDX) microanalyses revealed that metal ions were sorbed mainly at the cell wall of the bark and only a small amount of ions diffused into the cytoplasm. Both the EDX analysis and the atomic absorption spectrophotometry (AAS) measurements showed that ion exchange was an important mechanism in this sorption process. Electron spin resonance (ESR) tests demonstrated that free radicals from the sorbent also have a significant role in the sorption processes.

  7. Options Study - Phase II

    SciTech Connect

    R. Wigeland; T. Taiwo; M. Todosow; W. Halsey; J. Gehin

    2010-09-01

    The Options Study has been conducted for the purpose of evaluating the potential of alternative integrated nuclear fuel cycle options to favorably address the issues associated with a continuing or expanding use of nuclear power in the United States. The study produced information that can be used to inform decisions identifying potential directions for research and development on such fuel cycle options. An integrated nuclear fuel cycle option is defined in this study as including all aspects of the entire nuclear fuel cycle, from obtaining natural resources for fuel to the ultimate disposal of used nuclear fuel (UNF) or radioactive wastes. Issues such as nuclear waste management, especially the increasing inventory of used nuclear fuel, the current uncertainty about used fuel disposal, and the risk of nuclear weapons proliferation have contributed to the reluctance to expand the use of nuclear power, even though it is recognized that nuclear power is a safe and reliable method of producing electricity. In this Options Study, current, evolutionary, and revolutionary nuclear energy options were all considered, including the use of uranium and thorium, and both once-through and recycle approaches. Available information has been collected and reviewed in order to evaluate the ability of an option to clearly address the challenges associated with the current implementation and potential expansion of commercial nuclear power in the United States. This Options Study is a comprehensive consideration and review of fuel cycle and technology options, including those for disposal, and is not constrained by any limitations that may be imposed by economics, technical maturity, past policy, or speculated future conditions. This Phase II report is intended to be used in conjunction with the Phase I report, and much information in that report is not repeated here, although some information has been updated to reflect recent developments. The focus in this Options Study was to

  8. Phase equilibria of CFC alternative refrigerant mixtures: Binary systems of isobutane + 1,1,1,2-tetrafluoroethane, + 1,1-difluoroethane, and + difluoromethane

    SciTech Connect

    Lim, J.S.; Park, J.Y.; Lee, B.G.; Lee, Y.W.; Kim, J.D.

    1999-12-01

    Isothermal vapor-liquid equilibria were measured in the binary systems 1,1,1,2-tetrafluoroethane + isobutane at 303.2 and 323.2 K, 1,1-difluoroethane + isobutane at 303.2, 313.2, 323.2, and 333.2 K, and difluoromethane + isobutane at 301.8 and 321.8 K in a circulation-type equilibrium apparatus. The experimental data were well correlated with the Peng-Robinson equation of state using the Wong and Sandler mixing rules.

  9. Structure of alloys and diagram of phase equilibria of the Zr-Ru-Ir system. II. Solidification pattern of alloys of the partial system Ru-ZrRu-ZrIr-Ir

    SciTech Connect

    Eremenko, V.N.; Khoruzhaya, V.G.; Shtepa, T.D.

    1985-10-01

    The authors constructed the solidification diagram of alloys of the partial system Ru-ZrRu-ZrIr-Ir using data on the structure of alloys in the as-cast condition, yielded from metallographic examinations, microhardness determinations, and x-ray phase analyses together with results of an investigation of the solidus surface of the system. No ternary compounds were detected in the system. In accordance with the four three-phase regions found on the solidus surface, in the Ru-ZrRu-ZrIr-Ir system there are four invariant equilibria involving the participation of liquid, each of which is an equilibrium of the peritectic type. Their temperatures fall toward the Zr-Ru side of the composition triangle.

  10. Signaling equilibria in sensorimotor interactions.

    PubMed

    Leibfried, Felix; Grau-Moya, Jordi; Braun, Daniel A

    2015-08-01

    Although complex forms of communication like human language are often assumed to have evolved out of more simple forms of sensorimotor signaling, less attention has been devoted to investigate the latter. Here, we study communicative sensorimotor behavior of humans in a two-person joint motor task where each player controls one dimension of a planar motion. We designed this joint task as a game where one player (the sender) possesses private information about a hidden target the other player (the receiver) wants to know about, and where the sender's actions are costly signals that influence the receiver's control strategy. We developed a game-theoretic model within the framework of signaling games to investigate whether subjects' behavior could be adequately described by the corresponding equilibrium solutions. The model predicts both separating and pooling equilibria, in which signaling does and does not occur respectively. We observed both kinds of equilibria in subjects and found that, in line with model predictions, the propensity of signaling decreased with increasing signaling costs and decreasing uncertainty on the part of the receiver. Our study demonstrates that signaling games, which have previously been applied to economic decision-making and animal communication, provide a framework for human signaling behavior arising during sensorimotor interactions in continuous and dynamic environments. PMID:25935748

  11. Equilibria with incompressible flows from symmetry analysis

    SciTech Connect

    Kuiroukidis, Ap E-mail: gthroum@cc.uoi.gr; Throumoulopoulos, G. N. E-mail: gthroum@cc.uoi.gr

    2015-08-15

    We identify and study new nonlinear axisymmetric equilibria with incompressible flow of arbitrary direction satisfying a generalized Grad Shafranov equation by extending the symmetry analysis presented by Cicogna and Pegoraro [Phys. Plasmas 22, 022520 (2015)]. In particular, we construct a typical tokamak D-shaped equilibrium with peaked toroidal current density, monotonically varying safety factor, and sheared electric field.

  12. Phase equilibria in the Ti-Al-O system at 945 C and analysis of Ti/Al{sub 2}O{sub 3} reactions

    SciTech Connect

    Kelkar, G.P.; Carim, A.H.

    1995-03-01

    Phase relations in the Ti-Al-O system were evaluated experimentally at 945 C. The tie lines were established using equilibrated samples with phase compositions determined by electron probe microanalysis. The phase relations were in agreement with previous estimates but the phase fields of {alpha}-Ti[O,Al] and Ti{sub 3}Al[O] were significantly different. The Ti{sub 3}Al[O] phase has a maximum solubility of 22 at.% O, corresponding to a nominal stoichiometry of Ti{sub 3}AlO, whereas the {alpha}-Ti[O,Al] phase, at a maximum O solubility of 33.33 at.%, has a negligible amount of Al in solution. The disagreement between these results and previous studies was attributed to the differences in experimental techniques for sample preparation and analysis. The reported layer sequences at the Ti/Al{sub 2}O{sub 3} interface were evaluated based on the ternary section and the corresponding O activity diagram. The layered interfaces were found to be stable, with the evolution of the reaction products governed by the thickness of the initial Ti layer and the partial pressure in the ambient.

  13. Illite equilibria in solutions: 1. Phase relationships in the system K sub 2 O-Al sub 2 O sub 3 -SiO sub 2 -H sub 2 O between 25 and 250C

    SciTech Connect

    Aja, S.U.; Rosenberg, P.E.; Kittrick, J.A. )

    1991-05-01

    Natural illite from Marblehead, Wisconsin (MH), USA, has been equilibrated with 0.2 and 2.0M KCl/KOH and KCl/HCl solutions in the presence of excess kaolinite or microcline and quartz or amorphous silica at temperatures between 25 and 250C and P{sub v} = P{sub H2O}. Reversibility of univariant equilibria was demonstrated by approach from high and low a{sub K{sup +}}/a{sub H{sup +}} vs. log a{sub SiO{sub 2,aq}} diagrams have been constructed defining possible stability fields for kaolinite, microcline, gibbsite (or boehmite or diaspore), muscovite, and four illitic phases. Assuming an R{sup +2}-free stoichiometry, K-content per half cell, estimated from the slopes of univariant lines, are 0.29, 0.50, 0.69, and 0.85 K; these phases are compositional analogs of smectite (S), mixed-layer illite I/S (i.e., IS, ISII) and illite (I), respectively. Illitization reactions are strongly affected by temperature and porewater chemistry. At quartz saturation, direct conversion of smectite or kaolinite to endmember illite can occur at high pH; at low pH, these reactions are unlikely inasmuch as K{sup +} requirements exceed concentrations observed in most natural pore waters. In silica-supersaturated solutions, illitization reactions proceed through crystallization of intermediated phases with compositions between smectite and endmember illite (I).

  14. Phase equilibria and the thermodynamic properties of saturated solid solutions of BiTeI, Bi2TeI, and Bi4TeI1.25 compounds of the AgI-Bi-Bi2Te3-BiTeI system

    NASA Astrophysics Data System (ADS)

    Moroz, M. V.; Prokhorenko, M. V.

    2016-07-01

    The phase equilibria of the Ag-Bi-Te-I system in the part AgI-Bi-Bi2Te3-BiTeI is studied in the interval of 500-540 K by means of physicochemical analysis. Thermodynamic properties of phases are determined via EMF. Potential-forming processes occur in electrochemical cells (ECCs) of the C|Ag|glass Ag3GeS3I|D|C structure (where C denotes inert (graphite) electrodes; Ag, D denotes ECC electrodes; D denotes four-phase alloys of the AgI-Bi-Bi2Te3-BiTeI system; and Ag3GeS3I glass is the selective Ag+ conducting membrane). Linear dependences of the EMFs of cells E(T) in the interval of 505-535 K are used to calculate the values of the thermodynamic functions of BiTeI, Bi2TeI, and Bi4TeI1.25 phases saturated over silver.

  15. Thermodynamic assessment of hydrothermal alkali feldspar-mica-aluminosilicate equilibria

    USGS Publications Warehouse

    Sverjensky, D.A.; Hemley, J.J.; d'Angelo, W. M.

    1991-01-01

    The thermodynamic properties of minerals retrieved from consideration of solid-solid and dehydration equilibria with calorimetric reference values, and those of aqueous species derived from studies of electrolytes, are not consistent with experimentally measured high-temperature solubilities in the systems K2O- and Na2O-Al2O3-SiO2-H2O-HCl (e.g., K-fs - Ms - Qtz - K+ - H+). This introduces major inaccuracies into the computation of ionic activity ratios and the acidities of diagenetic, metamorphic, and magmatic hydrothermal fluids buffered by alkali silicate-bearing assemblages. We report a thermodynamic analysis of revised solubility equilibria in these systems that integrates the thermodynamic properties of minerals obtained from phase equilibria studies (Berman, 1988) with the properties of aqueous species calculated from a calibrated equation of state (Shock and Helgeson, 1988). This was achieved in two separate steps. First, new values of the free energies and enthalpies of formation at 25??C and 1 bar for the alkali silicates muscovite and albite were retrieved from the experimental solubility equilibria at 300??C and Psat. Because the latter have stoichiometric reaction coefficients different from those for solid-solid and dehydration equilibria, our procedure preserves exactly the relative thermodynamic properties of the alkali-bearing silicates (Berman, 1988). Only simple arithmetic adjustments of -1,600 and -1,626 (??500) cal/mol to all the K- and Na-bearing silicates, respectively, in Berman (1988) are required. In all cases, the revised values are within ??0.2% of calorimetric values. Similar adjustments were derived for the properties of minerals from Helgeson et al. (1978). Second, new values of the dissociation constant of HCl were retrieved from the solubility equilibria at temperatures and pressures from 300-600??C and 0.5-2.0 kbars using a simple model for aqueous speciation. The results agree well with the conductance-derived dissociation

  16. Jump conditions in transonic equilibria

    SciTech Connect

    Guazzotto, L.; Betti, R.; Jardin, S. C.

    2013-04-15

    In the present paper, the numerical calculation of transonic equilibria, first introduced with the FLOW code in Guazzotto et al.[Phys. Plasmas 11, 604 (2004)], is critically reviewed. In particular, the necessity and effect of imposing explicit jump conditions at the transonic discontinuity are investigated. It is found that 'standard' (low-{beta}, large aspect ratio) transonic equilibria satisfy the correct jump condition with very good approximation even if the jump condition is not explicitly imposed. On the other hand, it is also found that high-{beta}, low aspect ratio equilibria require the correct jump condition to be explicitly imposed. Various numerical approaches are described to modify FLOW to include the jump condition. It is proved that the new methods converge to the correct solution even in extreme cases of very large {beta}, while they agree with the results obtained with the old implementation of FLOW in lower-{beta} equilibria.

  17. Distributed phased array architecture study

    NASA Technical Reports Server (NTRS)

    Bourgeois, Brian

    1987-01-01

    Variations in amplifiers and phase shifters can cause degraded antenna performance, depending also on the environmental conditions and antenna array architecture. The implementation of distributed phased array hardware was studied with the aid of the DISTAR computer program as a simulation tool. This simulation provides guidance in hardware simulation. Both hard and soft failures of the amplifiers in the T/R modules are modeled. Hard failures are catastrophic: no power is transmitted to the antenna elements. Noncatastrophic or soft failures are modeled as a modified Gaussian distribution. The resulting amplitude characteristics then determine the array excitation coefficients. The phase characteristics take on a uniform distribution. Pattern characteristics such as antenna gain, half power beamwidth, mainbeam phase errors, sidelobe levels, and beam pointing errors were studied as functions of amplifier and phase shifter variations. General specifications for amplifier and phase shifter tolerances in various architecture configurations for C band and S band were determined.

  18. Code System to Model Aqueous Geochemical Equilibria.

    Energy Science and Technology Software Center (ESTSC)

    2001-08-23

    Version: 00 MINTEQ is a geochemical program to model aqueous solutions and the interactions of aqueous solutions with hypothesized assemblages of solid phases. It was developed for the Environmental Protection Agency to perform the calculations necessary to simulate the contact of waste solutions with heterogeneous sediments or the interaction of ground water with solidified wastes. MINTEQ can calculate ion speciation/solubility, adsorption, oxidation-reduction, gas phase equilibria, and precipitation/dissolution ofsolid phases. MINTEQ can accept a finite massmore » for any solid considered for dissolution and will dissolve the specified solid phase only until its initial mass is exhausted. This ability enables MINTEQ to model flow-through systems. In these systems the masses of solid phases that precipitate at earlier pore volumes can be dissolved at later pore volumes according to thermodynamic constraints imposed by the solution composition and solid phases present. The ability to model these systems permits evaluation of the geochemistry of dissolved traced metals, such as low-level waste in shallow land burial sites. MINTEQ was designed to solve geochemical equilibria for systems composed of one kilogram of water, various amounts of material dissolved in solution, and any solid materials that are present. Systems modeled using MINTEQ can exchange energy and material (open systems) or just energy (closed systems) with the surrounding environment. Each system is composed of a number of phases. Every phase is a region with distinct composition and physically definable boundaries. All of the material in the aqueous solution forms one phase. The gas phase is composed of any gaseous material present, and each compositionally and structurally distinct solid forms a separate phase.« less

  19. Solid state equilibria in the Ba-Cu-O system

    SciTech Connect

    Voronin, G.F.; Degterov, S.A. )

    1994-05-01

    Thermodynamic modeling is performed for the Ba-Cu-O system, which is essential to a good understanding of phase and chemical equilibria in the Y-Ba-Cu-O and some other oxide systems containing high-temperature superconductors. A self-consistent set of thermodynamic functions of the phases BaO[sub 2], BaCu[sub 2]O[sub 2], BaCuO[sub 2], Ba[sub 2]Cu[sub 3]O[sub 5+y], and Ba[sub 2]CuO[sub 3+q] is obtained. A variety of phase equilibria in the Ba-Cu-O system are calculated for a wide range of oxygen pressures and temperatures. The present thermodynamic data can be readily used for computing the phase equilibria and conditions for thermodynamic stability of oxide superconductors. It is detected that both BaCuO[sub 2] and Ba[sub 2]CuO[sub 3+q] have two stability boundaries, one at low temperatures and low oxygen pressures. Critical analysis of phase equilibria in the Ba-Cu-O system makes it possible to explain a number of conflicting results encountered in the literature. These contradictions arise from solid state reactions between phases, which may be very slow due to kinetic problems.

  20. Free boundary skin current MHD (magnetohydrodynamic) equilibria

    SciTech Connect

    Reusch, M.F.

    1988-02-01

    Function theoretic methods in the complex plane are used to develop simple parametric hodograph formulae which generate sharp boundary equilibria of arbitrary shape. The related method of Gorenflo and Merkel is discussed. A numerical technique for the construction of solutions, based on one of the methods is presented. A study is made of the bifurcations of an equilibrium of general form. 28 refs., 9 figs.

  1. Phase equilibria in the Bi/sub 2/Se/sub 3/-Bi/sub 2/Te/sub 3/-Te-Se system

    SciTech Connect

    Abrikosov, N.Kh.; Poretskaya, L.V.

    1988-04-01

    The authors studied and constructed the phase diagram of polythermal cuts passing from their ternary delta-solid solution corresponding to the formula Bi/sub 2/Te/sub 2.85/Se/sub 0.15/ to tellurium, a mixture of tellurium and selenium used in the ratio of Te:Se = 1:1, and selenium, by methods of physicochemical analysis for the first time. The parts of the radial cut of the Bi-Te-Se ternary system originating from the angle corresponding to bismuth, within the boundaries of 0-40 atom % Bi, are quasi-binary and of the eutectic type below the temperatures of the end of crystallization. Doping of solid solutions of the Bi/sub 2/Se/sub 3/-Bi/sub 2/Te/sub 3/ system with a chalcogen in a ratio different from the starting melt results in a change in not only the composition of the initially separated delta-solid solutions but also the compositions of the delta- and ..beta..-phases at the end of crystallization.

  2. Experimental determination of phase equilibria of a basalt from Piton de la Fournaise (La Réunion island): 1 atm data and high pressure results in presence of volatiles.

    NASA Astrophysics Data System (ADS)

    Brugier, Yann-Aurélien; Pichavant, Michel; di Muro, Andréa

    2015-04-01

    To understand the petrogenetic relations between the 4 groups of lavas erupted at Piton de la Fournaise (PdF), constrain the structure of the feeding system and the magma storage conditions, experimental phase equilibria have been determined, both at 1 atm and high pressures (HP), on a lava representative of Steady State Basalts (SSB). The lava (SiO2=49.2 wt%, MgO=7.8 wt%, CaO/Al2O3= 0.81) was fused at 1400°C, 1 atm in air. The resulting glass was crushed and the powder directly used as starting material. The 1atm experiments were performed with the wire-loop method in a vertical CO-CO2 gas mixing furnace. To minimize Fe-loss from the charge, experiments were repeated under constant T-fO2 conditions to progressively saturate the suspension wire with Fe. Intermediate charges were dissolved in HF and the charge from the last cycle retained for detailed study. Analyses of experimental products are in progress. The HP experiments were carried out in an internally heated pressure vessel, at 50MPa and 400MPa, between 1100-1200°C and under fluid-present conditions. Glass (30-50 mg) plus 10% in mass of volatiles (H2O or H2O+CO2) were loaded in Au80Pd20 capsules. Distilled water and Ag2C2O4 (CO2 source) were weighted to give charges with xH2O initial (molar H2O / (H2O+CO2)) ranging from 1 to 0. Run durations lasted for 2-14h. Redox conditions were controlled by loading a given proportion of H2 gas in the vessel (3 bar H2 for 50MPa, 5 bar H2 for 400MPa). Experimental fH2 were determined by solid Pd-Co sensors, leading to fO2 conditions approaching NNO-1. All experiments were rapidly drop quenched and products analyzed by SEM, EMPA and µ-FTIR Spectroscopy. To overcome Fe-loss, both capsule Fe pre-saturation and charge Fe pre-enrichment were tested. The first method was shown to be time-consuming and fraught with difficulties while the second is still being developed. Consequently, the experimental data presented here were obtained with no attempt to circumvent Fe loss

  3. Illite equilibria in solutions: 2. Phase relationships in the system K sub 2 O-MgO-Al sub 2 O sub 3 -SiO sub 2 -H sub 2 O

    SciTech Connect

    Aja, S.U.; Rosenberg, P.E.; Kittrick, J.A. )

    1991-05-01

    The stability of the Marblehead illite has been investigated in the five-component system K{sub 2}O-MgO-Al{sub 2}O{sub 3}-SiO{sub 2}-H{sub 2}O in the presence of kaolinite and microcline. The mica-like solubility-controlling phases (K{sub x}(Mg{sub y}Al{sub 2{minus}y})(Al{sub x{minus}y}Si{sub 4{minus}(x{minus}y)}) O{sub 10}(OH){sub 2}) identified include (1) smectite x = 0.29 {plus minus} 0.04, y = 0.26 {plus minus} 0.02; (2) illite x = 0.50 {plus minus} 0.05, y = 0.22 {plus minus} 0.14; (3) illite x = 0.69 {plus minus} 0.08, y = 0.16 {plus minus} 0.03; (4) illite x = 0.85 {plus minus} 0.05, y = 0.12 {plus minus} 0.04; and (5) muscovite. Possible stability regions have been defined for these solubility-controlling phases using isothermal isobaric log a{sub Mg{sup +2}}{sup {1/2}}/a{sub H{sup +}} vs. log a{sub K{sup +}}/a{sub H{sup +}} diagrams. When illite stability is referred to the quaternary system K{sub 2}O-Al{sub 2}O{sub 3}-SiO{sub 2}-H{sub 2}O, the effect of (R{sup +2}){sup VI} substitution is neglected. The error inherent in this simplification has been estimated. Inasmuch as a four-fold increase in a{sub Mg{sup 2+}} shifts the illite-smectite-kaolinite-solution invariant point by less than 0.3 log units, stability relationships in the quaternary system provide an adequate representation of illite solution equilibria, to a first approximation, However, the error caused by neglecting Mg{sup 2+} is close to or within experimental error. Thus, a more precise determination of the effect of Mg{sup +2} on illite solution equilibria may not be possible using the solution equilibration method.

  4. Chemical equilibria of rare earth oxides in glow-discharge mass spectrometry

    SciTech Connect

    Mei, Y.

    1992-01-01

    This research centers around method development and fundamental exploration of the rare earth elements (REE) in glow discharge mass spectrometry (GDMS). The capability of GDMS to analyze directly solids materials eliminates the sample dissolution and preconcentration steps required by many other methods. The simplicity of sample preparation and instrumental operation makes GDMS a promising analytical technique for the field of earth science. Initial studies were dedicated to improving the detection sensitivity of GDMS in analyzing the REE. This was accomplished by eliminating water contamination, a factor that was found to prevent the conversion of the rare earth oxidized to their atomic form in the glow discharge plasma. Methods experimented for water elimination included the uses of both a cryogenic cooling device and getter reagents. When used to determine the REE concentrations in a standard rock sample, the chemical elimination approach yielded comparable results to that obtained by other analytical methods. Further studies focused on probing the chemical reactions involving the REE and other plasma constituents in the glow discharge. It is proposed that the availability of the atomic REE in the glow discharge is strongly influenced by the oxidant and reductant contents in the plasma. Species that contain oxygen tend to shift the redox equilibria of REE toward the formation of their oxides, whereas species that compete for oxygen help reduce the oxidant content in the plasma, and shift the REE redox equilibria toward the formation of the REE atoms. Factors that govern the reaction processes of the REE equilibria were investigated by means of plasma reagent introduction and time-resolved discharge operation. Results indicate that while redox equilibria between the elemental REE and their monoxides exist on the cathode surface and in the gas phase, interactions occurring in the gas phase are probably the main paths for this equilibration in the glow discharge.

  5. Two phase detonation studies

    NASA Technical Reports Server (NTRS)

    Nicholls, J. A.; Pierce, T. H.; Miyajima, H.; Oza, R.; Patil, P.

    1974-01-01

    An experimental study of the passage of a shock wave over a burning fuel drop is described. This includes high speed framing photographs of the interaction taken at 500,000 frames per second. A theoretical prediction of the ignition of a fuel drop by a shock wave is presented and the results compared with earlier experimental work. Experimental attempts to generate a detonation in a liquid fuel drop (kerosene)-liquid oxidizer drop (hydrogen peroxide)-inert gas-environment are described. An appendix is included which gives the analytical prediction of power requirements for the drop generator to produce certain size drops at a certain mass rate. A bibliography is also included which lists all of the publications resulting from this research grant.

  6. Numerical Studies of Topological phases

    NASA Astrophysics Data System (ADS)

    Geraedts, Scott

    The topological phases of matter have been a major part of condensed matter physics research since the discovery of the quantum Hall effect in the 1980s. Recently, much of this research has focused on the study of systems of free fermions, such as the integer quantum Hall effect, quantum spin Hall effect, and topological insulator. Though these free fermion systems can play host to a variety of interesting phenomena, the physics of interacting topological phases is even richer. Unfortunately, there is a shortage of theoretical tools that can be used to approach interacting problems. In this thesis I will discuss progress in using two different numerical techniques to study topological phases. Recently much research in topological phases has focused on phases made up of bosons. Unlike fermions, free bosons form a condensate and so interactions are vital if the bosons are to realize a topological phase. Since these phases are difficult to study, much of our understanding comes from exactly solvable models, such as Kitaev's toric code, as well as Levin-Wen and Walker-Wang models. We may want to study systems for which such exactly solvable models are not available. In this thesis I present a series of models which are not solvable exactly, but which can be studied in sign-free Monte Carlo simulations. The models work by binding charges to point topological defects. They can be used to realize bosonic interacting versions of the quantum Hall effect in 2D and topological insulator in 3D. Effective field theories of ''integer'' (non-fractionalized) versions of these phases were available in the literature, but our models also allow for the construction of fractional phases. We can measure a number of properties of the bulk and surface of these phases. Few interacting topological phases have been realized experimentally, but there is one very important exception: the fractional quantum Hall effect (FQHE). Though the fractional quantum Hall effect we discovered over 30

  7. NHEXAS PHASE I MARYLAND STUDY

    EPA Science Inventory

    The National Human Exposure Assessment Survey (NHEXAS) is a federal interagency research effort coordinated by the Environmental Protection Agency (EPA), Office of Research and Development (ORD). Phase I consists of demonstration/scoping studies using probability-based sampling ...

  8. NHEXAS PHASE I ARIZONA STUDY

    EPA Science Inventory

    The National Human Exposure Assessment Survey (NHEXAS) is a federal interagency research effort coordinated by the Environmental Protection Agency (EPA), Office of Research and Development (ORD). The objective of the NHEXAS Phase I Arizona study was to determine the distribution...

  9. Wavelength resolved specific optical rotations and homochiral equilibria.

    PubMed

    Polavarapu, P L; Covington, C L

    2015-09-01

    The fundamental expressions governing specific optical rotations (SORs) of homochiral systems exhibiting monomer-dimer equilibria are presented. These equations are then utilized with the experimental measurements of wavelength resolved circular birefringence for (R)-(-)-α-hydroxy-β,β-dimethyl-γ-butyrolactone, to determine the wavelength resolved SORs of monomer and dimer components for the first time. Density functional theory predictions on the corresponding dispersion properties of monomer and dimer are found to match with experimentally determined quantities within a factor of ∼2. The wavelength resolved circular birefringence in the liquid solution phase thus provides a powerful means to investigate the molecular properties involved in homochiral equilibria. PMID:26227210

  10. 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.

  11. Outlook on the phase equilibria of the innovative system of "protected glycerol": 1,4-dioxaspiro[4.5]decane-2-methanol and alternative solvents.

    PubMed

    Melo, Catarina I; Rodrigues, Ana I; Bogel-Łukasik, Rafał; Bogel-Łukasik, Ewa

    2012-02-23

    Fundamental data on 1,4-dioxaspiro[4.5]decane-2-methanol are scarce. This work presents the foremost systematic data on the solubility of 1,4-dioxaspiro[4.5]decane-2-methanol in sustainable solvents such as water and ionic liquids accompanied by the interpretation of interactions occurring in such binary systems. 1,4-Dioxaspiro[4.5]decane-2-methanol, here called protected glycerol, has been synthesized in order to protect the two hydroxyl groups of glycerol, thus avoiding the formation of side products in a specific process. A series of imidazolium salts accompanied by pyridinium, phosphonium, and ammonium ones with various types of counterions were used in this study. The liquid-liquid and solid-liquid equilibrium measurements in binary systems were carried out by using a dynamic method at atmospheric pressure over the temperature range from 273.00 to 378.30 K or below the boiling point of the solvent. Among all tested sustainable solvents, protected glycerol exhibited limited solubility, with only a few of them in the temperature range studied. The majority of the examined ionic liquids, either hydrophilic or hydrophobic, showed complete miscibility with this monohydroxyol. The Fourier-transform infrared (FTIR) spectroscopy studies of solute and solvents showing a miscibility gap and of their mixtures were performed to obtain insight into major inter- and intramolecular interactions in the investigated systems. Furthermore, the differential scanning calorimetry was used for the first time to determine the melting point, the enthalpy of melting, and the temperature and enthalpy of the solid-solid phase transition of 1-allyl-3-methylimidazolium chloride [Amim][Cl]. The results for the solubility of protected glycerol in sustainable solvents can be used to design future alternative reactions, such as telomerization with protected glycerol in ionic liquids for more specific building blocks and extraction/or separation that involves these mixtures. PMID:22236350

  12. Vent fluid chemistry of the Rainbow hydrothermal system (36°N, MAR): Phase equilibria and in situ pH controls on subseafloor alteration processes

    NASA Astrophysics Data System (ADS)

    Seyfried, W. E., Jr.; Pester, Nicholas J.; Ding, Kang; Rough, Mikaella

    2011-03-01

    -fluid equilibria. Indeed, the predicted correlation between dissolved silica and H 2 defines a trend that is in good agreement with vent fluid data from Rainbow and other high-temperature ultramafic-hosted hydrothermal systems. We speculate that the moderate concentrations of dissolved silica in vent fluids from these systems result from hydrothermal alteration of plagioclase and olivine in the form of subsurface gabbroic intrusions, which, in turn are variably replaced by chlorite + magnetite + talc ± tremolite, with important implications for pH lowering, dissolved sulfide concentrations, and metal mobility.

  13. Scapolite phase equilibria and carbon isotope variations in high grade rocks: Tests of the CO sub 2 -flooding hypothesis of granulite gneiss

    SciTech Connect

    Moecher, D.P.

    1988-01-01

    Scapolite decarbonation reactions and carbon isotope analysis of CO{sub 2} extracted from scapolite are used to determine the presence, composition, and source of fluid components in high grade rocks. Scapolite-plagioclase-garnet-quartz assemblages, common to many lithologies in high grade terranes, monitors CO{sub 2} activity (aCO{sub 2}) by the reaction 2 Meionite + Quarts = 5 Anorthite + Grossular + 2 CO{sub 2}. The P-T-X location of this reaction was calculated using an internally consistent thermodynamic data set for meionite and phases in the CASCH system. Activity-composition relations for meionite in scapolite were calculated from the thermodynamic data set and compositional data on natural scapolite-plagioclase-calcite assemblages. Equilibration pressures of scapolite assemblages were calculated from clinopyroxene-garnet-plagioclass-quartz barometers calibrated for this study. The aCO{sub 2} was calculated for a variety of high grade gneisses from the southwestern Grenville Province and other terranes. Granulites typically yield low to moderate values of aCO{sub 2} (less than 0.5). Calc-silicates and meta-anorthosite yield moderate aCO{sub 2}. Deep crustal xenoliths yield a range of aCO{sub 2}.

  14. Stable and Metastable Equilibria in the Pb-Cd System

    NASA Astrophysics Data System (ADS)

    Chuang, Ying-Yu; Paik, J.-S.; Zhang, C.; Perepezko, J. H.; Chang, Y. A.

    2013-07-01

    Thermodynamic and phase diagram data in the Pb-Cd system are reevaluated. A substitutional solution model is used for the liquid and fcc and hcp phases. The stable and metastable equilibria of this system are calculated using the thermodynamic equations derived from equilibrium data. Besides the well-established eutectic reaction at 521 K (248 °C), one stable monotectic reaction at 548 K (275 °C) is found due to the existence of a stable liquid miscibility gap. The stable monotectic reaction has been missed in all previous evaluations. Experimental verifications of the stable and metastable phase equilibria are provided using droplet samples and undercooled liquid alloys. A differential thermal analysis (DTA) method is applied to determine the phase reaction temperatures using both traditional heating and cooling processes and a specially designed cycling process. Additional microstructural evidence is used to elucidate the nature of the phase reactions. The refined thermodynamic descriptions are based upon both the thermochemical and phase diagram stable and metastable data. The agreement between the calculated and experimental data is good. All experimental stable and metastable results are well explained by the new Pb-Cd phase diagram calculations within the experimental accuracy limits. Combined experimental and thermodynamic modeling procedures developed for determining the stable and metastable phase equilibria yield a highly reliable overall phase diagram assessment and a quantitative basis for the interpretation of non-equilibrium solidification processing.

  15. Solution equilibria of deferoxamine amides.

    PubMed

    Ihnat, Peter M; Vennerstrom, Jonathan L; Robinson, Dennis H

    2002-07-01

    The physico-chemical solution properties of deferoxamine were modified by acylating the terminal amino group with short-chain aliphatic, succinic, and methylsulphonic moieties. The analog iron(III)-binding constants and stabilities under physiological conditions were determined to confirm that the iron binding ability of the parent molecule was retained following modification. The proton dissociation constants of the lipophilic deferoxamine analogs were determined by potentiometric titration and nonlinear least-squares analysis. However, because the iron(III) binding complex is fully formed below pH 2, the metal-ligand equilibria could not be studied using potentiometric methods. The iron binding constants of the deferoxamine analogs were determined by spectrophotometrically following the proton-dependent exchange of iron with EDTA in the pH range of 4.0 to 6.5 and solving mass balance equations. The proton-dissociation constants and the iron binding constants of the lipophilic deferoxamine analogs were comparable to those of deferoxamine. However, at physiological conditions, the iron-binding complex of the most lipophilic butylamide derivative was slightly less stable and the succinamide derivative complex was slightly more stable. Like deferoxamine, the hydroxamate groups of the analogs were unhindered and free to form a 1:1 coordination complex with iron(III). Consequently, changes in aqueous solvation, conformation, and steric interference, imparted by the modifications at the terminal amino group of deferoxamine, may have affected the stabilities of the iron(III) complex and the efficiency of iron binding. PMID:12115836

  16. Correct Representation of Conformational Equilibria.

    ERIC Educational Resources Information Center

    Fulop, F.; And Others

    1983-01-01

    In representing conformational equilibria of compounds having only one chiral center, erroneous formulas showing different antipodes on the two sides of the equilibrium are rare. In contrast, with compounds having two or more chiral centers especially with saturated heterocycles, this erroneous representation occurs frequently in the chemical…

  17. A new equation of state of a flexible-chain polyelectrolyte solution: Phase equilibria and osmotic pressure in the salt-free case

    NASA Astrophysics Data System (ADS)

    Budkov, Yu. A.; Kolesnikov, A. L.; Georgi, N.; Nogovitsyn, E. A.; Kiselev, M. G.

    2015-05-01

    We develop a first-principle equation of state of salt-free polyelectrolyte solution in the limit of infinitely long flexible polymer chains in the framework of a field-theoretical formalism beyond the linear Debye-Hueckel theory and predict a liquid-liquid phase separation induced by a strong correlation attraction. As a reference system, we choose a set of two subsystems—charged macromolecules immersed in a structureless oppositely charged background created by counterions (polymer one component plasma) and counterions immersed in oppositely charged background created by polymer chains (hard-core one component plasma). We calculate the excess free energy of polymer one component plasma in the framework of modified random phase approximation, whereas a contribution of charge densities' fluctuations of neutralizing backgrounds we evaluate at the level of Gaussian approximation. We show that our theory is in a very good agreement with the results of Monte Carlo and MD simulations for critical parameters of liquid-liquid phase separation and osmotic pressure in a wide range of monomer concentration above the critical point, respectively.

  18. Investigations on the phase equilibria of some hydride ion conducting electrolyte systems and their application for hydrogen monitoring in sodium coolant

    NASA Astrophysics Data System (ADS)

    Joseph, Kitheri; Sujatha, K.; Nagaraj, S.; Mahendran, K. H.; Sridharan, R.; Periaswami, G.; Gnanasekaran, T.

    2005-09-01

    Electrochemical meters for measuring hydrogen levels in liquid sodium need thermodynamically stable hydride ion conducting electrolytes. In order to identify electrolytes that have high hydride ion conductivity, phase diagram of systems consisting of low melting compounds such as CaCl 2-LiCl, SrBr 2-LiBr, SrBr 2-SrHBr and CaBr 2-CaHBr were investigated by differential scanning calorimetry and their phase diagrams established. Using these information and supplementary information on effects of addition of alkaline earth hydride to these systems, potential electrolytes were tested for their use in electrochemical meters. Meters were constructed using electrolytes with (i) 22mol%SrCl 2-12.2mol%CaCl 2-54.5mol%LiCl-11.3mol%CaHCl, (ii) 70mol%LiCl-16mol%CaHCl-14mol%CaCl 2 and (iii) 40mol%CaHBr-60mol%CaBr 2 compositions. Output of meters that had Li ions in liquid phase electrolyte showed non-linearity at low hydrogen levels. Output of meters using CaBr 2-40mol%CaHBr solid showed linearity in the concentration range of 50-250 ppb in sodium.

  19. EQUILGAS: Program to estimate temperatures and in situ two-phase conditions in geothermal reservoirs using three combined FT-HSH gas equilibria models

    NASA Astrophysics Data System (ADS)

    Barragán, Rosa María; Núñez, José; Arellano, Víctor Manuel; Nieva, David

    2016-03-01

    Exploration and exploitation of geothermal resources require the estimation of important physical characteristics of reservoirs including temperatures, pressures and in situ two-phase conditions, in order to evaluate possible uses and/or investigate changes due to exploitation. As at relatively high temperatures (>150 °C) reservoir fluids usually attain chemical equilibrium in contact with hot rocks, different models based on the chemistry of fluids have been developed that allow deep conditions to be estimated. Currently either in water-dominated or steam-dominated reservoirs the chemistry of steam has been useful for working out reservoir conditions. In this context, three methods based on the Fischer-Tropsch (FT) and combined H2S-H2 (HSH) mineral-gas reactions have been developed for estimating temperatures and the quality of the in situ two-phase mixture prevailing in the reservoir. For these methods the mineral buffers considered to be controlling H2S-H2 composition of fluids are as follows. The pyrite-magnetite buffer (FT-HSH1); the pyrite-hematite buffer (FT-HSH2) and the pyrite-pyrrhotite buffer (FT-HSH3). Currently from such models the estimations of both, temperature and steam fraction in the two-phase fluid are obtained graphically by using a blank diagram with a background theoretical solution as reference. Thus large errors are involved since the isotherms are highly nonlinear functions while reservoir steam fractions are taken from a logarithmic scale. In order to facilitate the use of the three FT-HSH methods and minimize visual interpolation errors, the EQUILGAS program that numerically solves the equations of the FT-HSH methods was developed. In this work the FT-HSH methods and the EQUILGAS program are described. Illustrative examples for Mexican fields are also given in order to help the users in deciding which method could be more suitable for every specific data set.

  20. Pyrochlore-rich titanate ceramics for the immobilization of plutonium: redox effects on phase equilibria in cerium- and thorium- substituted analogs

    SciTech Connect

    Ryerson, F J; Ebbinghaus, B

    2000-05-25

    Three compositions representing plutonium-free analogs of a proposed Ca-Ti-Gd-Hf-U-PU oxide ceramic for the immobilization of plutonium were equilibrated at 1 atm, 1350 C over a range of oxygen fugacities between air and that equivalent to the iron-wuestite buffer. The cerium analog replaces Pu on a mole-per-mole basic with Ce; the thorium analog replaces Pu with Th. A third material has 10 wt% Al{sub 2}O{sub 3} added to the cerium analog to encourage the formation of a Hf-analog of, CaHfTi{sub 2}O{sub 7}, zirconolite, which is referred to as hafnolite. The predominant phase produced in each formulation under all conditions is pyrochlore, A{sub 2}T{sub 2}O{sub 7}, where the T site is filled by Ti, and Ca, the lanthanides, Hf, U and Pu are accommodated on the A-site. Other lanthanide and uranium-bearing phases encountered include brannerite (UTi{sub 2}O{sub 6}), hafnolite (CaHfTi{sub 2}O{sub 7}), perovskite (CaTiO{sub 3}) and a calcium-lanthanide aluminotitanate with nominal stoichiometry (Ca,Ln)Ti{sub 2}Al{sub 9}O{sub 19}, where Ln is a lanthanide. The phase compositions show progressive shifts with decreasing oxygen fugacity. All of the phases observed have previously been identified in titanate-based high-level radioactive waste ceramics and demonstrate the flexibility of these ceramics to variations in processing parameters. The main variation is an increase in the uranium concentrations of pyrochlore and brannerite which must be accommodated by variations in modal abundance. Pyrochlore compositions are consistent with existing spectroscopic data suggesting that uranium is predominantly pentavalent in samples synthesized in air. A simple model based on ideal stoichiometry suggests the U{sup +4}/{Sigma}U varies linearly with log fO{sub 2} and that all of the uranium is quadravalent at the iron-wuestite buffer.

  1. Stability and bifurcations of relative equilibria of a pendulum suspended on the equator

    NASA Astrophysics Data System (ADS)

    Burov, A. A.; Kosenko, I. I.

    2013-05-01

    The problem of equilibria of a pendulum suspended at an equatorial point relative to the rotating Earth is considered. An altitude is determined at which the degree of instability of the inverted pendulum changes from two to unity. Relative equilibria are investigated that bifurcate from the radial one when its degree of instability changes. Their stability properties are studied.

  2. Phase equilibria and solid solution relationships in the La 2O 3-TiO 2-ZrO 2 system

    NASA Astrophysics Data System (ADS)

    Škapin, S. D.; Kolar, D.; Suvorov, D.

    1999-07-01

    In the ternary La 2O 3-TiO 2-ZrO 2 system the subsolidus phase relations at 1350 °C were determined using X-ray diffraction, scanning electron microscopy end energy dispersive X-ray analysis. The collected results are presented in the form of a phase diagram. In the equilibrium state there are 7 ternary and 5 binary compatible subsystems. In the system TiO 2ss, ZrO 2ss, ZrTiO 4ss, La 2Zr 2O 7ss and La 2O 3ss solid solutions were confirmed and La 4Ti 9O 2ss and La 2Ti 2O 7ss solid solutions were identified. The addition of ZrO 2 does not stabilize the La 2/3TiO 3 perovskite compound, nor the addition of TiO 2 a highly temperature stable compound La 2/3ZrO 3.

  3. The clathrate Ba{sub 8}Cu{sub x}Ge{sub 46-x-y}square{sub y}: Phase equilibria and crystal structure

    SciTech Connect

    Melnychenko-Koblyuk, Nataliya; Grytsiv, Andriy; Rogl, Peter; Schmid, Harald; Giester, Gerald

    2009-07-15

    Phase relations at 700 deg. C, 800 deg. C and solidus temperatures have been derived for the clathrate system Ba{sub 8}Cu{sub x}Ge{sub 46-x-y}square{sub y} via X-ray single crystal and powder diffractometry combined with electron probe micro analysis and differential thermal analysis. The ternary clathrate phase derives from binary Ba{sub 8}Ge{sub 43}square{sub 3} and extends up to x=6. Structure investigations define cubic primitive symmetry with the space group type Pm3-barn consistent with a clathrate type I structure throughout the entire homogeneity region 0=5.5. - Graphical Abstract: Cages and atom thermal displacement parameters in clathrate Ba{sub 8}Cu{sub x}Ge{sub 46-x-y}square{sub y} for Ba{sub 8}Cu{sub 2}Ge{sub 42}square{sub 2} and Ba{sub 8}Cu{sub 6}Ge{sub 40}.

  4. Investigation of the phase equilibria and phase transformations associated with the Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} superconductor

    SciTech Connect

    Holesinger, T.

    1993-12-09

    The solid solution region and reaction kinetics of the Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (2212) superconductor were examined as a function of temperature and oxygen partial pressure. Crystallization studies from the glassy and molten states were undertaken to determine the phase transformation and kinetics associated with the formation of 2212 and other competing phases. Crystallization of nominal 2212 glasses was found to proceed in two steps with the formation of Bi{sub 2}Sr{sub 2{minus}x}Ca{sub x}CuO{sub y} (2201) and Cu{sub 2}O followed by Bi{sub 2}Sr{sub 3{minus}x}Ca{sub x}O{sub y}, CaO, and SrO. The 2212 phase converts from the 2201 phase with increasing temperatures. However, its formation below 800 C was kinetically limited. At 800 C and above, a nearly full conversion to the 2212 phase was achieved after only one minute although considerably longer anneal times were necessary for the system to reach equilibrium. In low oxygen partial pressures, the solidus is reduced to approximately 750 C. Solidification studies revealed an eutectic structure separating the incongruently melting 2212/2201 phases at high oxygen partial pressures from the congruently melting Bi{sub 2}Sr{sub 3{minus}x}Ca{sub x}O{sub y} (23x) and Bi{sub 2}Sr{sub 2{minus}x}Ca{sub x}O{sub y} (22x) phases present at low oxygen partial pressures. During solidification in various oxygen partial pressures, the separation of CaO in the melt and the initial crystallization of alkaline-earth cuprates leaves behind a Bi-rich liquid from which it is impossible to form single-phase 2212. Hence, significant amounts of 2201 were also present in these samples. These problems could be reduced by melt processing in inert atmospheres. Bulk 2212 material produced in this manner was found to possess high transition temperatures, high intergranular critical current densities below 20K, and modest critical current densities at 77K.

  5. Metal biosorption equilibria in a ternary system

    SciTech Connect

    Chong, K.H.; Volesky, B.

    1996-03-20

    Equilibrium metal uptake performance of a biosorbent prepared from Ascophyllum nodosum seaweed biomass was studied using aqueous solutions containing copper, cadmium, and zinc ions in binary and ternary mixtures. Triangular equilibrium diagrams can graphically represent all the ternary equilibrium sorption data. Application of the multicomponent Langmuir model to describe the three-metal system revealed its nonideal characteristics, whereby the value of apparent dissociation constants for the respective metals differed for each system. This restricted the prediction of the ternary equilibria from the binary systems. However, some predictions of the ternary system behavior from the model were consistent with experimental data and with conclusions postulated from the three possible binary subsystems.

  6. Crystal chemistry and phase equilibria of the CaO-½Eu2O3-CoOz system at 885 °C

    NASA Astrophysics Data System (ADS)

    Wong-Ng, W.; Laws, W.; Kaduk, J. A.

    2016-08-01

    The CaO-½Eu2O3-CoOz system prepared at 885 °C in air consists of two calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca3-xEux)Co4O9-z (0 ≤ x ≤ 0.5) which has a misfit layered structure, and the 1D Ca3Co2O6 compound which consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a point compound without the substitution of Eu on the Ca site when prepared at 885 °C. A solid solution region of distorted perovskite, (Eu1-xCax)CoO3-z (0 ≤ x ≤ 0.22, space group Pnma) was established. The (Eu0.91(1)Ca0.09(1))CoO3-z perovskite member has a distorted structure with tilt angles θ (17.37°), ϕ (8.20°), and ω (19.16°) which represent rotations of an octahedron about the pseudo-cubic perovskite [110]p, [001]p and [111]p axes. The reported Eu2CoO4 phase was not observed at 885 °C, but a ternary Ca-doped oxide, (Eu1+xCa1-x)CoO4-z (Bmab) where 0 ≤ x ≤ 0.10 was found to be stable at this temperature. In the peripheral binary systems, Eu was not present in the Ca site of CaO, while a small solid solution region was identified for (Eu1-xCax)O(3-z)/2 (0 ≤ x ≤ 0.05). Seven solid solution tie-line regions and six three-phase regions were determined in the CaO-½Eu2O3-CoOz system in air.

  7. Complete thermodynamic characterization of the multiple protonation equilibria of the aminoglycoside antibiotic paromomycin: a calorimetric and natural abundance 15N NMR study.

    PubMed

    Barbieri, Christopher M; Pilch, Daniel S

    2006-02-15

    The binding of aminoglycoside antibiotics to a broad range of macromolecular targets is coupled to protonation of one or more of the amino groups that typify this class of drugs. Determining how and to what extent this linkage influences the energetics of the aminoglycoside-macromolecule binding reaction requires a detailed understanding of the thermodynamics associated with the protonation equilibria of the aminoglycoside amino groups. In recognition of this need, a calorimetric- and NMR-based approach for obtaining the requisite thermodynamic information is presented using paromomycin as the model aminoglycoside. Temperature- and pH-dependent 15N NMR studies provide pK(a) values for the five paromomycin amino groups, as well as the temperature dependence of these pK(a) values. These studies also indicate that the observed pK(a) values associated with the free base form of paromomycin are lower in magnitude than the corresponding values associated with the sulfate salt form of the drug. This difference in pK(a) is due to drug interactions with the sulfate counterions at the high drug concentrations (> or = 812 mM) used in the 15N NMR studies. Isothermal titration calorimetry studies conducted at drug concentrations < or = 45 microM reveal that the extent of paromomycin protonation linked to the binding of the drug to its pharmacologically relevant target, the 16 S rRNA A-site, is consistent with the pK(a) values of the free base and not the sulfate salt form of the drug. Temperature- and pH-dependent isothermal titration calorimetry studies yield exothermic enthalpy changes (deltaH) for protonation of the five paromomycin amino groups, as well as positive heat capacity changes (deltaC(p)) for three of the five amino groups. Regarded as a whole, the results presented here represent an important first step toward establishing a thermodynamic database that can be used to predict how aminoglycoside-macromolecule binding energetics will be influenced by conditions such

  8. Phase equilibria in the Tb-Mg-Co system at 500 °C, crystal structure and hydrogenation properties of selected compounds

    NASA Astrophysics Data System (ADS)

    Shtender, V. V.; Denys, R. V.; Zavaliy, I. Yu.; Zelinska, O. Ya.; Paul-Boncour, V.; Pavlyuk, V. V.

    2015-12-01

    The isothermal section of the Tb-Mg-Co phase diagram at 500 °C has been built on the basis of XRD analysis of forty samples prepared by powder metallurgy. The existence of two ternary compounds Tb4Mg3Co2 and Tb4MgCo was confirmed. The formation of two solid solutions, Tb1-xMgxCo3 (0≤x≤0.4) and Tb1--xMgxCo2 (0≤x≤0.6), was found for the first time. It is shown that Tb5Mg24 also dissolves a small amount of Co. Other binary compounds do not dissolve the third component. The Tb4MgCo and TbMgCo4 compounds form hydrides (12.7 and 5.3 at.H/f.u. capacity, respectively) that retain the original structure of metallic matrices. Upon thermal desorption the Tb4MgCoH12.7 hydride was stable up to 300 °C and disproportionated at higher temperature. Two other hydrides, Tb4Mg3Co2H∼4 and Tb2MgCo9H12, are unstable in air and decompose into the initial compounds.

  9. ZBLAN Fiber Phase B Study

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Smith, Guy A.

    1997-01-01

    A Phase B feasibility study will be performed for the study of the effects of microgravity on the preform processing and fiber pulling of ZBLAN optical glass. Continuing from the positive results achieved in the fiber annealing experiments in 20 second intervals at 0.001 g on the KC-135 and the 5 minute experiments on the SPAR rocket, experiments will continue to work towards design of a fiber sting to initiate fiber pulling operations in space. Anticipated results include less homogeneous nucleation than ground-based annealed fibers. Infrared Fiber Systems and Galileo are the participating industrial investigators.

  10. An electronic spectral study of the coupled effect on the tautomeric equilibria of some α-hydroxy azo compounds

    NASA Astrophysics Data System (ADS)

    Ahmed, Z. A.; Arta, F. M.; Abd Alla, M. A.; Abd El-Monem, M. E.; Metwally, S. A.

    1989-01-01

    The spectral behaviour of six a-hydroxy azo compounds has been investigated in solution. The bands appearing in the u.v. and visible regions are assigned to possible electronic transitions. Azo compounds containing pyrazolone and acetyl or ester moieties are found to exist mainly in the hydrazo form in solution, while those containing the naphthol moiety exist in the azo-hydrazone tautomeric equilibrium. The solvatochromic behaviour of the compounds is investigated by studying their spectra in organic solvents of different polarities. The acidity constants are determined from the spectra of the compounds in aqueous ethanolic solutions of varying pH values.

  11. Reduced and mutant lysozyme refolding with lipid vesicles. Model study of disulfide impact on equilibria and dynamics.

    PubMed

    Zhu, Weiying; Silvers, Robert; Schwalbe, Harald; Keiderling, Timothy A

    2016-09-01

    The recovery of secondary structure in disordered, disulfide-reduced hen egg white lysozyme (HEWL) upon interaction with lipid vesicles was studied using circular dichroism (CD), fluorescence and infrared (IR) spectroscopic techniques. Lipid vesicles having negative head groups, such as DMPG, interact with reduced HEWL to induce formation of more helical structure than in native HEWL, but no stable tertiary structure was evident. Changes in tertiary structure, as evidenced by local environment of the tryptophan residues, were monitored by fluorescence. Spectra for oxidized HEWL, reduced HEWL and mutants with no or just one disulfide bond developed variable degrees of increased helicity when added to negatively charged lipid vesicles, mostly depending on packing of tails. When mixed with zwitterionic lipid vesicles, reduced HEWL developed β-sheet structure with no change in helicity, indicating an altered interaction mechanism. Stopped flow CD and fluorescence dynamics, were fit to multi-exponential forms, consistent with refolding to metastable intermediates of increasing helicity for HEWL interacting with lipid vesicles. Formation of an intermediate after rapid interaction of the lipid vesicles and the protein is supported by the correlation of faster steps in CD and fluorescence kinetics, and largely appears driven by electrostatic interaction. In subsequent slower steps, the partially refolded intermediate further alters structure, gaining helicity and modifying tryptophan packing, as driven by hydrophobic interactions. PMID:27240304

  12. Decomposition reactions of magnesium sulfate hydrates and phase equilibria in the MgSO 4-H 2O and Na +-Mg 2+-Cl --SO 42--H 2O systems with implications for Mars

    NASA Astrophysics Data System (ADS)

    Steiger, Michael; Linnow, Kirsten; Ehrhardt, Dorothee; Rohde, Mandy

    2011-06-01

    We report new measurements of equilibrium relative humidities for stable and metastable hydration-dehydration equilibria involving several magnesium sulfates in the MgSO 4· nH 2O series. We also report a comprehensive thermodynamic treatment of the system including solution properties and experimental data from the published literature, i.e. solubilities, heat capacities and additional decomposition humidities. While for some magnesium sulfate hydrates solubility data in the binary system MgSO 4-H 2O are sparse, there is a reasonable database of solubility measurements of these hydrates in the ternary MgCl 2-MgSO 4-H 2O and the quaternary reciprocal Na +-Mg 2+-Cl --SO 42--H 2O systems. To make these data suitable for the determination of solubility products, we parameterized a Pitzer ion interaction model for the calculation of activity coefficients and water activities in mixed solutions of these systems and report the ion interaction parameters for the Na +-Mg 2+-Cl --SO 42--H 2O system. The model predicted solubilities in the reciprocal system are in very good agreement with experimental data. Using all available experimental data and the solution model an updated phase diagram of the MgSO 4-H 2O system covering the whole temperature range from about 170 to 473 K is established. This treatment includes MgSO 4·H 2O (kieserite), MgSO 4·4H 2O (starkeyite), MgSO 4·5H 2O (pentahydrite), MgSO 4·6H 2O (hexahydrite), MgSO 4·7H 2O (epsomite) and MgSO 4·11H 2O (meridianiite). It is shown that only kieserite, hexahydrite, epsomite and meridianiite show fields of stable existence while starkeyite and pentahydrite are always metastable. Due to sluggish kinetics of kieserite formation, however, there is a rather extended field of metastable existence of starkeyite which makes this solid a major product in dehydration reactions. The model predicted behavior of the magnesium sulfates is in excellent agreement with observations reported in the literature under terrestrial

  13. Study of diatoms/aqueous solution interface. I. Acid-base equilibria and spectroscopic observation of freshwater and marine species

    NASA Astrophysics Data System (ADS)

    Gélabert, A.; Pokrovsky, O. S.; Schott, J.; Boudou, A.; Feurtet-Mazel, A.; Mielczarski, J.; Mielczarski, E.; Mesmer-Dudons, N.; Spalla, O.

    2004-10-01

    This work reports on a concerted study of diatom-water interfaces for two marine planktonic ( Thalassiosira weissflogii= TW, Skeletonema costatum= SC) and two freshwater periphytic species ( Achnanthidium minutissimum= AMIN, Navicula minima= NMIN). Proton surface adsorption was measured at 25°C, pH of 3 to 11 and ionic strength of 0.001 to 1.0 M via potentiometric titration using a limited residence time reactor. Electrophoretic mobility of living cells and their frustules was measured as a function of pH and ionic strength. Information on the chemical composition and molecular structure of diatoms surfaces was obtained using FT-IR (in situ attenuated total reflectance) and X-ray Photoelectron Spectroscopy (XPS). The surface area of living cells and their frustules in aqueous solutions was quantified using Small Angle X-ray Scattering Spectroscopy (SAXS). These observations allowed us to identify the nature and to determine the concentration of the major surface functional groups (carboxyl, amine and silanol) responsible for the amphoteric behavior of cell surfaces in aqueous solutions. Taking into account the relative proportion of surface sites inferred from XPS and FT-IR measurements, a surface complexation model of diatom-solution interfaces was generated on the basis of surface titration results. The cell-normalized ratios of the three major surface sites {>COOH}: {>NH 3}: {>SiOH} are 1:1:0.1, 1:10:0, 1:1:0.4 and 1:1:0.3 for TW, SC, AMIN and NMIN, respectively. The total amount of proton/hydroxyl active surface sites for investigated species ranges from 1 (NMIN) to 9 (SC) mmol/g dry weight. Normalization of these site densities to the area of siliceous skeleton yields values between 0.3 (NMIN) and 0.9 mmol/m 2 (SC) which are an order of magnitude higher than corresponding values for organic-free frustules or amorphous silica. This suggests that the amphoteric properties and possibly the affinity for metal adsorption of diatom cultures are essentially

  14. Eutectic equilibria in the quaternary system Fe-Cr-Mn-C

    NASA Technical Reports Server (NTRS)

    Nowotny, H.; Wayne, S.; Schuster, J. C.

    1982-01-01

    The constitution of the quaternary system, Fe-Cr-Mn-C and to a lesser extent of the quinary system, Fe-Cr-Mn-Al-C were examined for in situ composite alloy candidates. Multivariant eutectic compositions were determined from phase equilibria studies wherein M7C3 carbides (approximately 30% by volume) formed from the melt within gamma iron. An extended field of the hexagonal carbide, (Cr, Fe, Mn)7 C3, was found without undergoing transformation to the orthorhombic structure. Increasing stability for this carbide was found for higher ratios of Cr/Fe(+) Cr + Mn. Aluminum additions promoted a ferritic matrix while manganese favored the desired gamma austenitic matrix. In coexistence with the matrix phase, chromium enters preferentially the carbide phase while manganese distributes equally between the gamma matrix and the M7C3 carbide. The composition and lattice parameters of the carbide and matrix phases were determined to establish their respective stabilities.

  15. The effect of sub-solidus water loss on the melt fertility of crustal source rocks: constraints from phase equilibria modelling

    NASA Astrophysics Data System (ADS)

    Webb, Gordon; Powell, Roger; McLaren, Sandra

    2014-05-01

    produced via the sub-solidus breakdown of hydrous minerals (e.g. micas) in starting materials that were effectively 'dry' at ambient conditions. An exception to this behavior was a natural tonalite starting composition that yielded similar melt fractions when compared to the corresponding phase equilibrium models. This result can be explained by the expulsion of water from the tonalitic melt as it crystallised, thereby minimising the water content of bulk rock at the solidus. These results indicate that under typical conditions of crustal melting lower melt fractions may be attainable than previously thought and will have important implications for our understanding of the overall melt - fertility of the crust and the volumes of granitic melt that can be produced during anatexis. Furthermore, the increase in temperature of the MCT will have a significant impact on the strength of crustal rocks during the onset of melting.

  16. Heat capacity and phase equilibria of almandine, Fe[sub 3]Al[sub 2]Si[sub 3]O[sub 12

    SciTech Connect

    Anovitz, L.M. ); Essene, E.J.; Metz, G.W.; Westrum, E.F. Jr. ); Bohlen, S.R. ); Hemingway, B.S. )

    1993-09-01

    The heat capacity of a synthetic almandine, Fe[sub 3]Al[sub 2]Si[sub 3]O[sub 12], was measured from 6 to 350 K using equilibrium, intermittent-heating quasi-adiabatic calorimetry and from 420 to 1000 K using differential scanning calorimetry. These measurements yield Cp[sub 298] = 342.80 [+-] 1.4 J/mol[center dot]K and S[degrees][sub 298] = 342.60 J/mol[center dot]K. Moessbauer characterizations show the almandine to contain less than 2 [+-] 1% of the total iron as Fe[sup 3+]. X-ray diffraction studies of this synthetic almandine yield a = 11.521 [+-] 0.001 [angstrom] and V[degrees][sub 298] = 115.11 [+-] 0.01 cm[sup 3]/mol, somewhat smaller than previously reported. The low-temperature Cp data indicate a lambda transition at 8.7 K related to an antiferromagnetic-paramagnetic transition with T[sub N] = 7.5 K. Modeling of the lattice contribution to the total entropy suggests the presence of entropy in excess of that attributable to the effects of lattice vibrations and the magnetic transition. This probably arises from a low-temperature electronic transition (Schottky contribution).

  17. Syneruptive deep magma transfer and shallow magma remobilization during the 2011 eruption of Shinmoe-dake, Japan—Constraints from melt inclusions and phase equilibria experiments

    NASA Astrophysics Data System (ADS)

    Suzuki, Yuki; Yasuda, Atsushi; Hokanishi, Natsumi; Kaneko, Takayuki; Nakada, Setsuya; Fujii, Toshitsugu

    2013-05-01

    The 2011 Shinmoe-dake eruption started with a phreatomagmatic eruption (Jan 19), followed by climax sub-Plinian events and subsequent explosions (Jan 26-28), lava accumulation in the crater (end of January), and vulcanian eruptions (February-April). We have studied a suite of ejecta to investigate the magmatic system beneath the volcano and remobilization processes in the silicic magma mush. Most of the ejecta, including brown and gray colored pumice clasts (Jan 26-28), ballistically ejected dense lava (Feb 1), and juvenile particles in ash from the phreatomagmatic and vulcanian events are magma mixing products (SiO2 = 57-58 wt.%; 960-980 °C). Mixing occurred between silicic andesite (SA) and basaltic andesite (BA) magmas at a fixed ratio (40%-30% SA and 60%-70% BA). The SA magma had SiO2 = 62-63 wt.% and a temperature of 870 °C, and contains 43 vol.% phenocrysts of pyroxene, plagioclase, and Fe-Ti oxide. The BA magma had SiO2 = 55 wt.% and a temperature of 1030 °C, and contains 9 vol.% phenocrysts of olivine and plagioclase. The SA magma partly erupted without mixing as white parts of pumices and juvenile particles. The two magmatic end-members crystallized at different depths, requiring the presence of two separate magma reservoirs; shallower SA reservoir and deeper BA reservoir. An experimental study reveals that the SA magma had been stored at a pressure of 125 MPa, corresponding to a depth of 5 km. The textures and forms of phenocrysts from the BA magma indicate rapid crystallization directly related to the 2011 eruptive activity. The wide range of H2O contents of olivine melt inclusions (5.5-1.6 wt.%) indicates that rapid crystallization was induced by decompression, with olivine crystallization first (≤ 250 MPa), followed by plagioclase addition. The limited occurrence of olivine melt inclusions trapped at depths of < 5 km is consistent with the proposed magma system model, because olivine crystallization ceased after magma mixing. Our petrological

  18. Imaging phased telescope array study

    NASA Technical Reports Server (NTRS)

    Harvey, James E.

    1989-01-01

    The problems encountered in obtaining a wide field-of-view with large, space-based direct imaging phased telescope arrays were considered. After defining some of the critical systems issues, previous relevant work in the literature was reviewed and summarized. An extensive list was made of potential error sources and the error sources were categorized in the form of an error budget tree including optical design errors, optical fabrication errors, assembly and alignment errors, and environmental errors. After choosing a top level image quality requirment as a goal, a preliminary tops-down error budget allocation was performed; then, based upon engineering experience, detailed analysis, or data from the literature, a bottoms-up error budget reallocation was performed in an attempt to achieve an equitable distribution of difficulty in satisfying the various allocations. This exercise provided a realistic allocation for residual off-axis optical design errors in the presence of state-of-the-art optical fabrication and alignment errors. Three different computational techniques were developed for computing the image degradation of phased telescope arrays due to aberrations of the individual telescopes. Parametric studies and sensitivity analyses were then performed for a variety of subaperture configurations and telescope design parameters in an attempt to determine how the off-axis performance of a phased telescope array varies as the telescopes are scaled up in size. The Air Force Weapons Laboratory (AFWL) multipurpose telescope testbed (MMTT) configuration was analyzed in detail with regard to image degradation due to field curvature and distortion of the individual telescopes as they are scaled up in size.

  19. Phase equilibria of chlorofluorocarbon alternative refrigerant mixtures

    SciTech Connect

    Lee, B.G.; Park, J.Y.; Lim, J.S.; Cho, S.Y.; Park, K.Y.

    1999-03-01

    Isothermal vapor-liquid equilibrium data were determined for binary systems of difluoromethane/1,1,1,2-tetrafluoroethane (HFC-32/HFC-134a), difluoromethane/pentafluoroethane (HFC-32/HFC-125), difluoromethane/1,1,1-trifluoroethane (HFC-32/HFC-143A), and difluoromethane/1,1-difluoroethane (HFC-32/HFC-152a). The vapor and liquid compositions and pressures were measured in a circulation-type apparatus at 303.15 K and 323.15 K. The experimental data were compared with literature results and correlated with the Canahan-Starling-De Santis equation of state within the uncertainty of {+-}1.0%.

  20. Predictive thermochemistry and phase equilibria of slags

    NASA Astrophysics Data System (ADS)

    Barry, Thomas I.; Dinsdale, Alan T.; Gisby, John A.

    1993-04-01

    It is well understood that the efficient recovery of values by pyrometallurgical processing of ores requires control of the slag chemistry. In an effort to improve the understanding of slags, a thermodynamic database on subsystems of the CaO-MgO-Fe-O-Al2O3-SiO2 system has been generated through critical assessment of the literature. Data for connecting systems of specific industrial interest are being added. The data can be combined using well-established thermodynamic principles to make calculations on the multicomponent systems of practical interest. Following a description of the calculations, this article illustrates specific applications of thermodynamic modeling to the extraction of copper, nickel, and precious metals; zinc extraction; purification of pig iron; meltdown in nuclear reactors; hot corrosion; and pollution control.

  1. Estimation of Fluid Properties and Phase Equilibria.

    ERIC Educational Resources Information Center

    Herskowitz, M.

    1985-01-01

    Describes a course (given to junior/senior students with strong background in thermodynamics and transport phenomena) that covers the theoretical and practical aspects of properties estimation. An outline for the course is included. (JN)

  2. Grain boundary phase equilibria in metallic systems

    NASA Astrophysics Data System (ADS)

    Deymier, P.; Campos, V.; Evans, H.

    1987-08-01

    One of the primary objectives of this joint experimental/computational research program on grain boundaries in metals is to reconcile experiments and calculations. Both areas have been so often conducted separately for facility's sake that loss of coherency is the recurrent characteristic of research on internal interfaces. Progress has been made consistent with the original objectives of the proposal both in the theoretical and experimental areas. On the theoretical side, analytical expressions to generate density dependent interatomic potentials in simple metals have been elaborated. Extension of the constant stress molecular dynamics technique to these volume dependent potentials is under way. The molecular dynamics code has been revised to improve its performances on vectorial processors. On the experimental side, an Electron Beam Float-Zone Refiner has been designed and built. The floating zone method has been selected for the preparation of highly pure Al bicrystals as well as bicrystals doped with Mg. The apparatus is currently under testing. Actual simulation of bulk and defected metallic systems and preparation of Al bicrystals of controlled misorientation is anticipated for the near future.

  3. Reflectivity method for geomechanical equilibria

    NASA Astrophysics Data System (ADS)

    Kuvshinov, Boris N.

    2007-08-01

    It is shown that the block LU decomposition of the transfer and scattering matrix convert these matrices into each other. This allows to introduce a generalization of the Kennett reflectivity method, which is applicable to arbitrary systems of linear differential equations. The introduced method is convenient to analyse equilibria, where the governing matrix is degenerate. The resulting algorithm is compact and numerically stable. To illustrate the concept, we consider elastic equilibrium of a layered medium. We also derive closed-form expressions for a quasi-stationary poroelastic case taking into account solid-fluid and electrokinetic coupling.

  4. Steady State Tokamak Equilibria without Current Drive

    SciTech Connect

    Shaing, K.C.; Aydemir, A.Y.; Lin-Liu, Y.R.; Miller, R.L.

    1997-11-01

    Steady state tokamak equilibria without current drive are found. This is made possible by including the potato bootstrap current close to the magnetic axis. Tokamaks with this class of equilibria do not need seed current or current drive, and are intrinsically steady state. {copyright} {ital 1997} {ital The American Physical Society}

  5. Recent developments in Bayesian inference of tokamak plasma equilibria and high-dimensional stochastic quadratures

    NASA Astrophysics Data System (ADS)

    von Nessi, G. T.; Hole, M. J.; The MAST Team

    2014-11-01

    We present recent results and technical breakthroughs for the Bayesian inference of tokamak equilibria using force-balance as a prior constraint. Issues surrounding model parameter representation and posterior analysis are discussed and addressed. These points motivate the recent advancements embodied in the Bayesian Equilibrium Analysis and Simulation Tool (BEAST) software being presently utilized to study equilibria on the Mega-Ampere Spherical Tokamak (MAST) experiment in the UK (von Nessi et al 2012 J. Phys. A 46 185501). State-of-the-art results of using BEAST to study MAST equilibria are reviewed, with recent code advancements being systematically presented though out the manuscript.

  6. Current Sheet Formation, Equilibria and Heating in the Closed Corona

    NASA Astrophysics Data System (ADS)

    Rappazzo, A. F.

    2014-12-01

    Parker model for coronal heating is investigated within theframework of reduced magnetohydrodynamics (RMHD) in cartesian geometry. A popular hypothesis is that in response to slow photospheric motionsthe magnetic field evolves quasi-statically through a seriesof unstable equilibria. Instabilities, e.g., kink modes or else,allow the release of energy while the field relaxes to a new equilibrium.On the other hand it has long been suggested that the dynamics relevant to the basic heating of coronal loops may not entaila quasi-static evolution (Parker 1972, 1994), and recently it has beenshown that the relaxation of an initial configuration out of equilibriumdevelops current sheets without accessing intermediate equilibria (Rappazzo & Parker 2013).The properties of the equilibria are therefore key in understanding thedynamics of coronal heating both in the case of low-frequency photospheric motions (DC) and for propagating waves (AC).Equilibria and nonlinear dynamics are studied numerically and theoretically,explaining why dynamics are inhibited below a critical twist, while for highervalues of the fluctuations nonlinear dynamics lead to the formation of current sheets (and magnetic reconnection in the non ideal case), whose thickness istracked with the analiticity strip method and shown to decrease at least exponentiallydown to dissipative lenght-scales on fast ideal Alfvenic timescales. The impact onthe heating of solar and stellar coronae will be discussed.

  7. Helical relativistic electron beam Vlasov equilibria

    NASA Astrophysics Data System (ADS)

    Lai, H. M.

    1980-08-01

    Three existing helical relativistic electron beam models are discussed and compared. Both Yoshikawa's and Lawson's models are shown to be derivable from appropriate Vlasov equilibria. A new helical Vlasov equilibrium with energy spread is presented and studied. Unlike Auer's axial current model in which the allowance of an energy spread limits the total current in the relativistic beam case, the present model, with the addition of an azimuthal current, permits solutions with arbitrarily large current. On the other hand, like the model studied by Kan and Lai, the present model leads to nonhollowed-out beam solutions in which, the larger the beam current, the more force-free is the magnetic field configuration.

  8. Investigation of Liquidus Temperatures and Phase Equilibria of Copper Smelting Slags in the FeO-Fe2O3-SiO2-CaO-MgO-Al2O3 System at PO2 10-8 atm

    NASA Astrophysics Data System (ADS)

    Henao, Hector M.; Nexhip, Colin; George-Kennedy, David P.; Hayes, P. C.; Jak, E.

    2010-08-01

    Copper concentrates and fluxes can contain variable levels of SiO2, CaO, and MgO in addition to main components Cu, Fe, and S. Metal recovery, slag tapping, and furnace wall integrity all are dependent on phase equilibria and other properties of the phases and are functions of slag composition and operational temperature. Optimal control of the slag chemistry in the copper smelting, therefore, is essential for high recovery and productivity; this, in turn, requires detailed knowledge of the slag phase equilibria. The present work provides new phase equilibrium experimental data in the FeO-Fe2O3-SiO2-CaO-MgO-Al2O3 system at oxygen partial pressure of 10-8 atm within the range of temperatures and compositions directly relevant to copper smelting. For the range of conditions relevant to the Kennecott Utah Copper (South Magna, UT) smelting furnace, it was confirmed experimentally that increasing concentrations of MgO or CaO resulted in significant decreases of the tridymite liquidus temperature and in changes in the position of the tridymite liquidus in the direction of higher silica concentration; in contrast, the spinel liquidus temperatures increase significantly with the increase of MgO or CaO. Olivine and clinopyroxene precipitates appeared at high MgO concentrations in the liquid slag. The liquidus temperature in the spinel primary phase field was expressed as a linear function of 1/(wt pctFe/wt pctSiO2), wt pctCaO, wt pctMgO, and wt pctAl2O3. The positions of each of the liquidus points (wt pctFe)/(wt pctSiO2) at a fixed temperatures in the tridymite primary phase field were expressed as linear functions of wt pctCaO, wt pctMgO, and wt pctAl2O3.

  9. Relative equilibria of vortices in two dimensions.

    PubMed

    Palmore, J I

    1982-01-01

    An old problem of the evolution of finitely many interacting point vortices in the plane is shown to be amenable to investigation by critical point theory in a way that is identical to the study of the planar n-body problem of celestial mechanics. For any choice of positive circulations of the vortices it is shown by critical point theory applied to Kirchhoff's function that there are many relative equilibria configurations. Each of these configurations gives rise to a stationary configuration of the vortices in a suitably chosen rotating coordinate system. A sharp lower bound on the number of stationary vortex configurations for the problem of point vortices interacting in the plane is given. The problem of point vortices in a circular disk is defined and it is shown that these estimates hold for stationary configurations of small size. PMID:16593155

  10. Multiple Reaction Equilibria--With Pencil and Paper: A Class Problem on Coal Methanation.

    ERIC Educational Resources Information Center

    Helfferich, Friedrich G.

    1989-01-01

    Points out a different and much simpler approach for the study of equilibria of multiple and heterogeneous chemical reactions. A simulation on coal methanation is used to teach the technique. An example and the methodology used are provided. (MVL)

  11. Vapor-Liquid Equilibria Using the Gibbs Energy and the Common Tangent Plane Criterion

    ERIC Educational Resources Information Center

    Olaya, Maria del Mar; Reyes-Labarta, Juan A.; Serrano, Maria Dolores; Marcilla, Antonio

    2010-01-01

    Phase thermodynamics is often perceived as a difficult subject with which many students never become fully comfortable. The Gibbsian geometrical framework can help students to gain a better understanding of phase equilibria. An exercise to interpret the vapor-liquid equilibrium of a binary azeotropic mixture, using the equilibrium condition based…

  12. Phase formation and chemical phase equilibria in aqueous-based systems pertinent to waste-management: calcium oxide-alluminum oxide-borate-water, calcium oxide-lead oxide-phosphate-water and calcium oxide-arsenate-water

    NASA Astrophysics Data System (ADS)

    Bothe, James Vincent, Jr.

    -ettringite and 28.51 for 4CaO{*}Alsb2Osb3{*}1/2Bsb2Osb3{*}12Hsb2O. The formation of a solid-solution series between the two apatites, Casb{10}(POsb4)sb6(OH)sb2 and Pbsb{10}(POsb4)sb6(OH)sb2, under ambient conditions and using only oxide starting materials was studied. It was observed that under those conditions, a very limited range of miscibility occurred resulting in the formation of the quaternary apatite, Pbsb{x}Casb{10-x}(POsb4)sb6(OH)sb2 where 5≤ x<6. The ternary system, CaO-Assb2Osb5-Hsb2O, was also studied under ambient conditions in order to identify a potential host compound suitable for the stabilization of soluble arsenic. Analyses of the solid precipitates and their saturated solutions have revealed the following compounds along with their solubility products (pKsp = -logKsp): Casb4(OH)sb2(AsOsb4)sb2{*}4Hsb2O (29.20), Casb5(AsOsb4)sb3OH (38.04), Casb3(AsOsb4)sb2{*}3{2/3}Hsb2O (21.00), Casb3(AsOsb4)sb2{*}4{1/4}Hsb2O (21.00), Casb5Hsb2(AsOsb4)sb4{*}9Hsb2O-ferrarisite (31.49), Casb5Hsb2(AsOsb4)sb4{*}9Hsb2O-guerinite (30.69), and CaHAsOsb4{*}Hsb2O (4.79). The conditions under which the hydrates Casb4(OH)sb2(AsOsb4)sb2{*}4Hsb2O and Casb5(AsOsb4)sb3OH (arsenate-apatite) precipitated were determined to be best in terms of immobilizing soluble arsenic. Both are highly insoluble and are associated with the lowest concentrations of dissolved arsenic under equilibrium conditions. However, the conditions under which they preferentially form are slightly different. Casb4(OH)sb2(AsOsb4)sb2{*}4Hsb2O was observed to form consistently in the presence of magnesium impurity, whereas the arsenate-apatite formed phase-pure only in the absence of magnesium impurity. This can be advantageous in the sense that the arsenate ion is assured to be stabilized via the precipitation of either one or the other, making the presence of magnesium impurity inconsequential under those conditions which precipitate these two stable hydrates.

  13. 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.

  14. Centrifuge workers study. Phase II, completion report

    SciTech Connect

    Wooten, H.D.

    1994-09-01

    Phase II of the Centrifuge Workers Study was a follow-up to the Phase I efforts. The Phase I results had indicated a higher risk than expected among centrifuge workers for developing bladder cancer when compared with the risk in the general population for developing this same type of cancer. However, no specific agent could be identified as the causative agent for these bladder cancers. As the Phase II Report states, Phase I had been limited to workers who had the greatest potential for exposure to substances used in the centrifuge process. Phase II was designed to expand the survey to evaluate the health of all employees who had ever worked in Centrifuge Program Departments 1330-1339 but who had not been interviewed in Phase I. Employees in analytical laboratories and maintenance departments who provided support services for the Centrifuge Program were also included in Phase II. In December 1989, the Oak Ridge Associated Universities (ORAU), now known as Oak Ridge Institute for Science and Education (ORISE), was contracted to conduct a follow-up study (Phase II). Phase H of the Centrifuge Workers Study expanded the survey to include all former centrifuge workers who were not included in Phase I. ORISE was chosen because they had performed the Phase I tasks and summarized the corresponding survey data therefrom.

  15. TDRSS telecommunications study, phase 2

    NASA Technical Reports Server (NTRS)

    Cahn, C. R.

    1974-01-01

    Providing an extension to parametric analysis of the telecommunications support capability of the Tracking and Data Relay Satellite System (TDRSS), this phase considers candidate modulation waveforms which could meet the shuttle telecommunications requirements and also be compatible with the TDRSS single access S-band service. In addition, it considers the feasibility of modifying a single access S-band user transponder for operation with conventional STDN signals emanating from remotely located ground stations.

  16. Approximation of stochastic equilibria for dynamic systems with colored noise

    SciTech Connect

    Bashkirtseva, Irina

    2015-03-10

    We consider nonlinear dynamic systems forced by colored noise. Using first approximation systems, we study dynamics of deviations of stochastic solutions from stable deterministic equilibria. Equations for the stationary second moments of deviations of random states are derived. An application of the elaborated theory to Van der Pol system driven by colored noise is given. A dependence of the dispersion on the time correlation of the colored noise is studied.

  17. Symmetry transforms for ideal magnetohydrodynamics equilibria.

    PubMed

    Bogoyavlenskij, Oleg I

    2002-11-01

    A method for constructing ideal magnetohydrodynamics (MHD) equilibria is introduced. The method consists of the application of symmetry transforms to any known MHD equilibrium [ O. I. Bogoyavlenskij, Phys. Rev. E. 62, 8616, (2000)]. The transforms break the geometrical symmetries of the field-aligned solutions and produce continuous families of the nonsymmetric MHD equilibria. The method of symmetry transforms also allows to obtain MHD equilibria with current sheets and exact solutions with noncollinear vector fields B and V. A model of the nonsymmetric astrophysical jets outside of their accretion disks is developed. The total magnetic and kinetic energy of the jet is finite in any layer c(1)equilibria that model ball lightning with dynamics of plasma inside the fireball. PMID:12513610

  18. Braided magnetic fields: equilibria, relaxation and heating

    NASA Astrophysics Data System (ADS)

    Pontin, D. I.; Candelaresi, S.; Russell, A. J. B.; Hornig, G.

    2016-05-01

    We examine the dynamics of magnetic flux tubes containing non-trivial field line braiding (or linkage), using mathematical and computational modelling, in the context of testable predictions for the laboratory and their significance for solar coronal heating. We investigate the existence of braided force-free equilibria, and demonstrate that for a field anchored at perfectly-conducting plates, these equilibria exist and contain current sheets whose thickness scales inversely with the braid complexity—as measured for example by the topological entropy. By contrast, for a periodic domain braided exact equilibria typically do not exist, while approximate equilibria contain thin current sheets. In the presence of resistivity, reconnection is triggered at the current sheets and a turbulent relaxation ensues. We finish by discussing the properties of the turbulent relaxation and the existence of constraints that may mean that the final state is not the linear force-free field predicted by Taylor’s hypothesis.

  19. Studies of two phase flow

    NASA Technical Reports Server (NTRS)

    Witte, Larry C.

    1994-01-01

    The development of instrumentation for the support of research in two-phase flow in simulated microgravity conditions was performed. The funds were expended in the development of a technique for characterizing the motion and size distribution of small liquid droplets dispersed in a flowing gas. Phenomena like this occur in both microgravity and normal earth gravity situations inside of conduits that are carrying liquid-vapor mixtures at high flow rates. Some effort to develop a conductance probe for the measurement of liquid film thickness was also expended.

  20. Calculation of multicomponent chemical equilibria in gas-solid- liquid systems: calculation methods, thermochemical data, and applications to studies of high-temperature volcanic gases with examples from Mount St. Helens

    USGS Publications Warehouse

    Symonds, R.B.; Reed, M.H.

    1993-01-01

    This paper documents the numerical formulations, thermochemical data base, and possible applications of computer programs, SOLVGAS and GASWORKS, for calculating multicomponent chemical equilibria in gas-solid-liquid systems. SOLVGAS and GASWORKS compute simultaneous equilibria by solving simultaneously a set of mass balance and mass action equations written for all gas species and for all gas-solid or gas-liquid equilibria. Examples of gas-evaporation-from-magma and precipitation-with-cooling calculations for volcanic gases collected from Mount St. Helens are shown. -from Authors

  1. Beltrami–Bernoulli equilibria in plasmas with degenerate electrons

    SciTech Connect

    Berezhiani, V. I.; Shatashvili, N. L.; Mahajan, S. M.

    2015-02-15

    A new class of Double Beltrami–Bernoulli equilibria, sustained by electron degeneracy pressure, is investigated. It is shown that due to electron degeneracy, a nontrivial Beltrami–Bernoulli equilibrium state is possible even for a zero temperature plasma. These states are, conceptually, studied to show the existence of new energy transformation pathways converting, for instance, the degeneracy energy into fluid kinetic energy. Such states may be of relevance to compact astrophysical objects like white dwarfs, neutron stars, etc.

  2. Dynamic equilibria in an epidemic model with voluntary vaccinations.

    PubMed

    Chen, Frederick H; Cottrell, Allin

    2009-07-01

    The dynamics of an epidemic model with voluntary vaccinations are studied. Individual vaccination decisions are modelled using an economic/game-theoretic approach: agents in the model decide whether to vaccinate or not by weighing the cost and benefit of vaccination and choose the action that maximizes their net benefit. It is shown that, when vaccine efficacy is low, there are parameter values for which multiple steady-state equilibria and periodic equilibria coexist. When multiplicity of steady states is obtained, which one the population reaches in some cases depends entirely on agents' expectations concerning the future course of an epidemic and not on the initial conditions of the model. (†)Comments and suggestions from anonymous referees of the journal are gratefully acknowledged. This paper is dedicated to the loving memory of Lucy Hauser. PMID:22876938

  3. Speculative equilibria and asymptotic dominance in a market with adaptive CRRA traders (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Anufriev, Mikhail; Bottazzi, Giulio; Pancotto, Francesca

    2005-05-01

    We consider a simple pure exchange economy with two assets, one riskless, yielding a constant return on investment, and one risky, paying a stochastic dividend. Trading takes place in discrete time and in each trading period the price of the risky asset is fixed through the market clearing condition. Individual demands are expressed as fractions of traders wealth and depend on traders forecasts about future price movement. Under these assumptions, we derive the stochastic dynamical system that describes the evolution of price and wealth. We study the cases in which one or two agents operate in the market, identifying the possible equilibria and discussing their stability conditions. The main novelty of this paper rests in the abstraction from the precise characterization of agents' beliefs and preferences. In this respect our results generalize several previous contributions in the field. In particular, we show that, irrespectively of agents' behavior, the system can only possess isolated generic equilibria where a single agent dominates the market and continuous manifolds of non-generic equilibria where heterogeneous agents hold finite shares of the aggregate wealth. Moreover, we show that all possible equilibria belong to a one dimensional "Equilibria Market Line". Finally we discuss the role of different parameters for the stability of equilibria and the selection principle governing market dynamics.

  4. Phase II Study Proposal Briefs.

    ERIC Educational Resources Information Center

    National Center for the Study of Postsecondary Educational Supports, Honolulu, HI.

    This document collects 23 study proposal briefs presented to the National Center for the Study of Postsecondary Educational Supports. The proposals address the following topics concerned with postsecondary services for students with disabilities: cultural empowerment, longitudinal analysis of postsecondary students' experience, effective models of…

  5. School Safety Study: Phase I.

    ERIC Educational Resources Information Center

    Arora, Alka

    This report summarizes findings from a study concerned with Arizona school safety. The survey component highlights safety-related policy information across 300 schools; the interview component highlights school-safety perceptions of 64 staff across 16 schools. Various policies and programs that respond to internal and external threats to school…

  6. PARALLEL ASSAY OF OXYGEN EQUILIBRIA OF HEMOGLOBIN

    PubMed Central

    Lilly, Laura E.; Blinebry, Sara K.; Viscardi, Chelsea M.; Perez, Luis; Bonaventura, Joe; McMahon, Tim J.

    2013-01-01

    Methods to systematically analyze in parallel the function of multiple protein or cell samples in vivo or ex vivo (i.e. functional proteomics) in a controlled gaseous environment have thus far been limited. Here we describe an apparatus and procedure that enables, for the first time, parallel assay of oxygen equilibria in multiple samples. Using this apparatus, numerous simultaneous oxygen equilibrium curves (OECs) can be obtained under truly identical conditions from blood cell samples or purified hemoglobins (Hbs). We suggest that the ability to obtain these parallel datasets under identical conditions can be of immense value, both to biomedical researchers and clinicians who wish to monitor blood health, and to physiologists studying non-human organisms and the effects of climate change on these organisms. Parallel monitoring techniques are essential in order to better understand the functions of critical cellular proteins. The procedure can be applied to human studies, wherein an OEC can be analyzed in light of an individual’s entire genome. Here, we analyzed intraerythrocytic Hb, a protein that operates at the organism’s environmental interface and then comes into close contact with virtually all of the organism’s cells. The apparatus is theoretically scalable, and establishes a functional proteomic screen that can be correlated with genomic information on the same individuals. This new method is expected to accelerate our general understanding of protein function, an increasingly challenging objective as advances in proteomic and genomic throughput outpace the ability to study proteins’ functional properties. PMID:23827235

  7. Relative Equilibria of Identical Point Vortices

    NASA Astrophysics Data System (ADS)

    Aref, Hassan

    2006-11-01

    The problem of finding relative equilibria of identical point vortices is classical and was considered by Kelvin and J. J. Thomson almost immediately after the model had been introduced by Helmholtz in 1858. At the time relative equilibria of vortices were proposed as models of atoms. Apart from the intrinsic interest of the problem, and its mathematical challenge, such equilibria have been used as models for stationary states of distributed vortices, and have been observed in rotating superfluids, most recently in spectacular images of BECs. Simple equilibria such as regular polygons (both open and centered) were found and analyzed in the 19th century. Double rings and more recently triple rings have been found analytically. However, the numerically known relative equilibria continue to greatly outnumber those that are analytically known. A major numerical exploration was undertaken by Campell & Ziff in 1978 resulting in what is known as the Los Alamos Catalog. We will explore the results in this catalog and what we have learned since then, and present details on the quest for an analytical understanding of these intriguing states.

  8. NHEXAS PHASE I REGION 5 STUDY

    EPA Science Inventory

    The National Human Exposure Assessment Survey (NHEXAS) is a federal interagency research effort coordinated by the Environmental Protection Agency (EPA), Office of Research and Development (ORD). Phase I consists of demonstration/scoping studies using probability-based sampling d...

  9. Calculation of pH and mineral equilibria in hydrothermal waters with application to geothermometry and studies of boiling and dilution

    NASA Astrophysics Data System (ADS)

    Reed, Mark; Spycher, Nicolas

    1984-07-01

    Using chemical analyses and 25° pH measurements of quenched high-temperature waters, we calculate in situ pH and distribution of aqueous species at high temperature. This is accomplished by solving simultaneous mass action equations for complexes and redox equilibria and mass balance equations, on all components, including a H + equation with as many as 60 terms (depending on water composition). This calculation provides accurate values for the activities of aqueous ions in a given water at high temperature, which are used to calculate an ion activity product ( Q) for each of more than 100 minerals. The value of log( Q/ K) for each mineral, where K is the equilibrium constant, provides a measure of proximity of the aqueous solution to equilibrium with the mineral. By plotting log Q/ Kvs. T for natural waters, it is possible to determine: a) whether the water was in equilibrium with a host rock mineral assemblage, b) probable minerals in the equilibrium assemblage and c) the temperature of equilibrium. In cases where the fluid departs from equilibrium with a host rock assemblage, it is possible to determine whether this may result from boiling or dilution, and an estimate of amount of lost gas or diluting water can be determined. The calculation is illustrated by application to geothermal waters from Iceland, Broadlands, and Sulphur Bank, hot spring waters from Jemez, Yellowstone and Blackfoot Reservoir (Idaho) and fluid inclusions from the Sunnyside Mine, Colorado. It is shown that most geothermal waters approach equilibrium with a subsurface mineral assemblage at a temperature close to measured temperatures and that some hot springs also approach equilibrium with the host rock at temperatures above outlet temperatures but commonly below the Na-K-Ca temperatures. The log Q/ K plots show that some discrepancies between Na-K-Ca temperatures on spring waters and actual temperatures result from a failure of alkali feldspars to equilibrate with the fluid and with each

  10. On Nash equilibria in Eisert-Lewenstein-Wilkens game

    NASA Astrophysics Data System (ADS)

    Bolonek-Lasoń, Katarzyna; Kosiński, Piotr

    2015-12-01

    Landsburg method of classifying mixed Nash equilibria for maximally entangled Eisert-Lewenstein-Wilkens (ELW) game is analyzed with special emphasis on symmetries inherent to the problem. Nash equilibria for the original ELW game are determined.

  11. Tokamak Equilibria with Reversed Current Density

    NASA Astrophysics Data System (ADS)

    Martynov, A. A.; Medvedev, S. Yu.; Villard, L.

    2003-08-01

    Observations of nearly zero toroidal current in the central region of tokamaks (the “current hole”) raises the question of the existence of toroidal equilibria with very low or reversed current in the core. The solutions of the Grad-Shafranov equilibrium equation with hollow toroidal current density profile including negative current density in the plasma center are investigated. Solutions of the corresponding eigenvalue problem provide simple examples of such equilibrium configurations. More realistic equilibria with toroidal current density reversal are computed using a new equilibrium problem formu­lation and computational algorithm which do not assume nested magnetic surfaces.

  12. Two phase detonation studies conducted in 1971

    NASA Technical Reports Server (NTRS)

    Nicholls, J. A.

    1972-01-01

    A report is presented describing the research conducted on five phases: (1) ignition of fuel drops by a shock wave and passage of a shock wave over a burning drop, (2) the energy release pattern of a two-phase detonation with controlled drop sizes, (3) the attenuation of shock and detonation waves passing over an acoustic liner, (4) experimental and theoretical studies of film detonations, and (5) a simplified analytical model of a rotating two-phase detonation wave in a rocket motor.

  13. Study Of Phase Separation In Glass

    NASA Technical Reports Server (NTRS)

    Neilson, George F.; Weinberg, Michael C.; Smith, Gary L.

    1989-01-01

    Report describes an experimental study of effect of hydroxide content on phase separation in soda/silica glasses. Ordinary and gel glasses melted at 1,565 degree C, and melts stirred periodically. "Wet" glasses produced by passing bubbles of N2 saturated with water through melts; "dry" glasses prepared in similar manner, except N2 dried before passage through melts. Analyses of compositions of glasses performed by atomic-absorption and index-of-refraction measurements. Authors conclude hydroxide speeds up phase separation, regardless of method (gel or ordinary) by which glass prepared. Eventually helps material scientists to find ways to control morphology of phase separation.

  14. Water-Nafion equilibria. absence of Schroeder's paradox.

    PubMed

    Onishi, Lisa M; Prausnitz, John M; Newman, John

    2007-08-30

    Water-Nafion phase equilibria and proton conductivities were measured in two ways. First, Nafion was in contact with saturated water vapor. Second, Nafion was in contact with liquid water at the same temperature. At 29 degrees C, for preboiled, vapor-equilibrated Nafion exposed to water with an activity = 1 and air pressures ranging from 0 to 0.96 bar, the water content was lambda = 23 +/- 1 mol H(2)O/mol SO3-. For the preboiled, liquid-equilibrated membrane, lambda = 24 +/- 2. At 100% relative humidity (RH), the water content of preboiled Nafion decreased as the temperature rose from 30 to 80 degrees C but did not recover its initial water content when the temperature returned to 30 degrees C. The water content of predried Nafion at 1 atm and 30 degrees C was lambda = 13.7 +/- 0.2 when vapor-equilibrated and lambda = 13.1 +/- 0.5 when liquid-equilibrated. A Nafion membrane originally boiled in water had much higher liquid- and 100% RH vapor-equilibrated proton conductivities than the same membrane originally dried at 110 degrees C with a RH less than 2%. The liquid-equilibrated and 100% RH vapor-equilibrated membrane conductivities were the same when the membrane had the same thermal history. The conductivity data was fit to a model, and the water content was determined at different temperatures. The predried membrane water content increased with temperature, and the preboiled membrane's water content changed slightly with temperature. Both water sorption and proton-conductivity data do not exhibit Schroeder's paradox. These studies and previous results suggest that Schroeder's paradox is resolved when attention is given to the thermal history of the absorbing polymer. PMID:17685645

  15. Instability of magnetic equilibria in barotropic stars

    NASA Astrophysics Data System (ADS)

    Mitchell, J. P.; Braithwaite, J.; Reisenegger, A.; Spruit, H.; Valdivia, J. A.; Langer, N.

    2015-02-01

    In stably stratified stars, numerical magnetohydrodynamics simulations have shown that arbitrary initial magnetic fields evolve into stable equilibrium configurations, usually containing nearly axisymmetric, linked poloidal and toroidal fields that stabilize each other. In this work, we test the hypothesis that stable stratification is a requirement for the existence of such stable equilibria. For this purpose, we follow numerically the evolution of magnetic fields in barotropic (and thus neutrally stable) stars, starting from two different types of initial conditions, namely random disordered magnetic fields, as well as linked poloidal-toroidal configurations resembling the previously found equilibria. With many trials, we always find a decay of the magnetic field over a few Alfvén times, never a stable equilibrium. This strongly suggests that there are no stable equilibria in barotropic stars, thus clearly invalidating the assumption of barotropic equations of state often imposed on the search of magnetic equilibria. It also supports the hypothesis that, as dissipative processes erode the stable stratification, they might destabilize previously stable magnetic field configurations, leading to their decay.

  16. Equilibrator: Modeling Chemical Equilibria with Excel

    ERIC Educational Resources Information Center

    Vander Griend, Douglas A.

    2011-01-01

    Equilibrator is a Microsoft Excel program for learning about chemical equilibria through modeling, similar in function to EQS4WIN, which is no longer supported and does not work well with newer Windows operating systems. Similar to EQS4WIN, Equilibrator allows the user to define a system with temperature, initial moles, and then either total…

  17. Anomeric and tautomeric equilibria in D-2-glucosamine Schiff bases

    NASA Astrophysics Data System (ADS)

    Kołodziej, B.; Grech, E.; Schilf, W.; Kamieński, B.; Makowski, M.; Rozwadowski, Z.; Dziembowska, T.

    2007-11-01

    The structure of some glucosamine Schiff bases has been studied by means of ab initio RHF and DFT calculation and CP/MAS 13C and 15N NMR measurements. The anomeric and tautomeric equilibria in a DMSO solution have been studied by 1H, 13C and 15N NMR spectroscopy. The anomeric composition of D-2-glucosamine Schiff bases in the solid state and in DMSO solution has been shown to depends on the tautomeric form of Schiff bases and electronic properties of substituents on the aromatic ring.

  18. Phased array-fed antenna configuration study

    NASA Technical Reports Server (NTRS)

    Crosswell, W. F.; Ball, D. E.; Taylor, R. C.

    1983-01-01

    The scope of this contract entails a configuration study for a phased array fed transmit antenna operating in the frequency band of 17.7 to 20.2 GHz. This initial contract provides a basis for understanding the design limitations and advantages of advanced phased array and cluster feeds (both utilizing intergral MMIC modules) illuminating folded reflector optics (both near field and focused types). Design parametric analyses are performed utilizing as constraints the objective secondary performance requirements of the Advanced Communications Technology Satellite (Table 1.0). The output of the study provides design information which serves as a data base for future active phased array fed antenna studies such as detailed designs required to support the development of a ground tested breadboard. In general, this study is significant because it provides the antenna community with an understanding of the basic principles which govern near field phased scanned feed effects on secondary reflector system performance. Although several articles have been written on analysis procedures and results for these systems, the authors of this report have observed phenomenon of near field antenna systems not previously documented. Because the physical justification for the exhibited performance is provided herein, the findings of this study add a new dimension to the available knowledge of the subject matter.

  19. Bilinear relative equilibria of identical point vortices

    NASA Astrophysics Data System (ADS)

    Aref, Hassan; Beelen, Peter; Brøns, Morten

    2011-11-01

    A new class of bilinear relative equilibria of identical point vortices in which the vortices are constrained to be on two perpendicular lines, taken to be the x- and y-axes of a cartesian coordinate system, is introduced and studied. In general we have m vortices on the y-axis and n on the x- axis. We define generating polynomials q (z) and p (z) , respectively, for each set of vortices. A second order, linear ODE for p (z) given q (z) is derived. Several results relating the general solution of the ODE to relative equilibrium configurations are established. Our strongest result, obtained using Sturm's comparison theorem, is that if p (z) satisfies the ODE for a given q (z) with its imaginary zeros symmetric relative to the x-axis, then it must have at least n - m + 2 simple, real zeros. For m = 2 this provides a complete characterization of all zeros, and we study this case in some detail. In particular, we show that given q (z) =z2 +η2 , where η is real, there is a unique p (z) of degree n, and a unique value of η2 =An , such that the zeros of q (z) and p (z) form a relative equilibrium of n + 2 point vortices. We show that An ~2/3 n +1/2 , as n --> ∞ , where the coefficient of n is determined analytically, the next order term numerically. Supported in part by the Danish National Research Foundation through a Niels Bohr visiting professorship.

  20. Calorimetric Study of Phase Stability and Phase Transformation in U- xZr ( x = 2, 5, 10 wt pct) Alloys

    NASA Astrophysics Data System (ADS)

    Rai, Arun Kumar; Subramanian, Raju; Hajra, Raj Narayan; Tripathy, Haraprasanna; Rengachari, Mythili; Saibaba, Saroja

    2015-11-01

    A comprehensive calorimetric study of high-temperature phase equilibria and phase transformation characteristics in U- xZr ( x = 2, 5, 10 wt pct) alloys has been undertaken, as a function of heating and cooling rates. It is found that the following sequence of phase transformation takes place upon slow heating in annealed U-2 wt pct Zr alloy: α + α' + δ-UZr2 → α + γ 2 → β + γ 2 → β + γ 1 → γ. For alloys of 5 and 10 wt pct Zr, the additional presence of a miscibility gap ( γ 1 U-rich bcc + γ 2 Zr-rich bcc) in the high-temperature γ(bcc) phase region resulted in the following transformation sequence: α + α' + δ-UZr2 → α + γ 2 → β + γ 2 → γ 1 + γ 2 → γ. Further, it has been demonstrated that depending on the nature of starting microstructure, namely whether it is α eq + δ-UZr2, or a mix of α' + α eq + δ-UZr2 phases, the relative extents of two possible co-occurring modes of the first on-heating phase transformation step differ. In case of starting microstructure having mixture of three phases α' + α eq + δ-UZr2, it is found that α'-martensite relaxation via α' + α eq + δ-UZr2 → α eq + δ-UZr2 constitutes the first on-heating thermal response. The α'-martensitic relaxation is very closely followed by the dissolution of δ-UZr2. The co-occurrence of these two events gives rise to a composite thermal arrest in a normal dynamic calorimetry profile. However, if the starting microstructure is the one having the equilibrium mix of α eq and δ-UZr2, then only the peritectoidal dissolution of δ-UZr2 is found in the calorimetry profile. Unless, a very slow cooling rate of the order of 0.1 K min-1 is adopted from high-temperature γ(bcc) phase, it is not possible to obtain 100 pct of α eq phase along with equilibrium amount of δ-UZr2. At normal and high cooling rates, it is possible to suppress the diffusional decomposition of γ to varying extents. The direct γ → α'-martensite transformation has been observed at

  1. LST phase A design update study

    NASA Technical Reports Server (NTRS)

    1973-01-01

    An update is presented of the Phase A study of the Large Space Telescope (LST), based on changes in guidelines and new data developed subsequent to the Phase A study. The study defines an LST concept based on the broad mission guidelines provided by the Office of Space Science (OSS), the scientific requirements developed by OSS with the scientific community, and an understanding of long range NASA planning current at the time the study was performed. A low cost design approach was followed. This resulted in the use of standard spacecraft hardware, the provision for maintenance at the black box level, growth potential in systems designs, and sharing of shuttle maintenance flights with other payloads (See N73-18449 through N73-18453)

  2. Computation of Multi-region Relaxed Magnetohydrodynamic Equilibria

    SciTech Connect

    Hudson, S. R.; Dewar, R. L.; Dennis, G.; Hole, M. J.; McGann, M.; von Nessi, G.; Lazerson, S.

    2013-03-29

    We describe the construction of stepped-pressure equilibria as extrema of a multi-region, relaxed magnetohydrodynamic (MHD) energy functional that combines elements of ideal MHD and Taylor relaxation, and which we call MRXMHD. The model is compatible with Hamiltonian chaos theory and allows the three-dimensional MHD equilibrium problem to be formulated in a well-posed manner suitable for computation. The energy-functional is discretized using a mixed finite-element, Fourier representation for the magnetic vector potential and the equilibrium geometry; and numerical solutions are constructed using the stepped-pressure equilibrium code, SPEC. Convergence studies with respect to radial and Fourier resolution are presented.

  3. TDRSS telecommunications study. Phase 1: Final report

    NASA Technical Reports Server (NTRS)

    Cahn, C. R.; Cnossen, R. S.

    1974-01-01

    A parametric analysis of the telecommunications support capability of the Tracking and Data Relay Satellite System (TDRSS) was performed. Emphasis was placed on maximizing support capability provided to the user while minimizing impact on the user spacecraft. This study evaluates the present TDRSS configuration as presented in the TDRSS Definition Phase Study Report, December 1973 to determine potential changes for improving the overall performance. In addition, it provides specifications of the user transponder equipment to be used in the TDRSS.

  4. MHD Stability Trends from Perturbed Equilibria: Possible Limitations with Toroidal Geometry

    NASA Astrophysics Data System (ADS)

    Comer, K. J.; Callen, J. D.; Hegna, C. C.; Turnbull, A. D.; Cowley, S.

    2003-10-01

    The effects of equilibrium changes on ideal MHD properties are usually studied using numerical parameter scans. Previously, we introduced a new technique to explore these dependencies: changes in the potential energy δ W due to equilibrium changes are found with an expansion of the energy principle, rather than an eigenvalue-solver code. Validation of the approach in toroidal geometry attempted to use GATO (an ideal MHD stability code) and DIII-D shot 87009. The approach should succeed with the global modes of 87009; however, ˜ 0.1% changes to qo predicted δ W rapidly increasing. Perturbing β of other toroidal equilibria resulted in similar behavior. We first review results for a cylindrical equilibrium and for 87009. Between the cylindrical case and 87009 lie several other equilibria, which should produce intermediate results. We examine several of these intermediate equilibria, starting with the cylindrical case and changing aspect ratio, shape and profiles until ending at 87009.

  5. Prediction of thermodynamic properties, including solubility equilibria and vapor pressures, for mixed aqueous electrolytes to high temperatures

    SciTech Connect

    Pabalan, R.T.; Pitzer, K.S.

    1988-01-01

    A number of different models have been proposed in the literature that treat the thermodynamic properties of electrolyte solutions. The most frequently used at present is the ion-interaction or virial coefficient approach, which was initially developed by Pitzer (1973) and Pitzer and Kim (1974) for aqueous solutions near room temperature. Since the model is based on a general equation for the excess Gibbs energy of the aqueous fluid, any thermodynamic property can be obtained from the appropriate derivatives. Thus the model has been used to describe osmotic and activity coefficients, as well as volumetric and thermal properties (e.g., heat capacity and enthalpy) of aqueous electrolytes. Success of this model when applied to complex and concentrated electrolyte mixtures was initially demonstrated for calculations of equilibria at room temperature between a brine phase and one or more solids by Harvie and Weare (1980). In this study we show that the same success holds over a wider range of temperature conditions. The model is applied to calculations of solubility equilibria, as well as to calculations of vapor pressures of electrolyte mixtures to high temperatures. 32 refs., 8 figs., 2 tabs.

  6. Phase Equilibria of the Sn-Ni-V System: The 980°C Isothermal Section and the Sn-Rich Corner at 600°C and 300°C

    NASA Astrophysics Data System (ADS)

    Wu, Changjun; Su, Xuping; Peng, Haoping; Liu, Ya; Tu, Hao; Wang, Jianhua

    2015-10-01

    Ternary Sn-Ni-V alloys were prepared and annealed at 980°C, 600°C, and 300°C for 15, 60 and 60 days, respectively. The annealed alloys were metallographically examined and the equilibrium phases formed were identified on the basis of determination of composition and x-ray diffraction analysis. The isothermal region of the ternary Sn-Ni-V system at 980°C was studied. Nine three-phase regions and more than 20 conjugate lines were detected at 980°C. The range of composition of VNi2Sn at 980°C spans 24.5-59.2 at.% V, 52.1-25.5 at.% Ni, and 15.3-23.4 at.% Sn. Its lattice constant increases with increasing V content. A sharp increase near 40.4 at.% V is indicative of a second-order transition. It is believed that atomic site occupation changed when the V content was >40.4 at.%. The maximum solubility of V in Ni3Sn2 can reach 23.3 at.%; that in Ni3Sn is below 0.6 at.%. Up to 3.4 at.% Ni dissolves in V3Sn. The Sn-rich corner of the Sn-Ni-V system at 600°C and 300°C was also investigated experimentally. The solubility of Ni in VSn2 and V in Ni3Sn4 at 600°C and 300°C are both less than 0.5 at.%.

  7. Swollen lamellar phases confined in capillarylike pores

    NASA Astrophysics Data System (ADS)

    Tasinkevych, M.; Ciach, A.

    2005-12-01

    Structure and mechanical properties of swollen lamellar phases confined in square-base pipes are studied in a mesoscopic lattice model for oil-water-surfactant mixtures. Structure depends crucially on a thermodynamic state and is quite different far and close to the coexistence with a uniform phase. Lamellar domains with different orientations of lamellas are formed in most cases, and the mechanics is determined mainly by domain-wall energies. Shift of phase equilibria in square-base pipes compared to the bulk is just opposite to the shift in slits. We find capillary delamellarization for short-period and for swollen phases, for hydrophilic and for neutral external surfaces.

  8. Phase stability in processing of high temperature intermetallic alloys

    SciTech Connect

    Perepezko, J.H.; Nunes, C.A.; Yi, S.H.; Thoma, D.J.

    1997-12-31

    In the development of high temperature intermetallics involving various aluminides, silicides and Laves phases, it has become evident that it is essential to consider the strong influence of materials processing throughout all stages. The underlying basis for alloy synthesis, processing and the assessment of thermal stability is established by the relevant phase equilibria, the characteristic diffusivities and the possible solidification reaction pathways. In almost all cases the microstructures of the most useful metallic alloys are multiphase assemblies in which the relative phase fractions, compositions and morphologies play key roles in optimizing the performance under high temperature conditions. The microstructure designs are usually tailored for strength, toughness, creep resistance and environmental stability and involve a balance of features derived from mixtures of a ductile phase and intermetallic phases. There is a clear experience that the level of materials processing can only be as sophisticated as the level of knowledge of the phase equilibria and the underlying kinetics. In many of the contemporary intermetallic alloys the phase stability must be considered in terms of multicomponent equilibria and non-stoichiometric intermetallic compositions. Recent developments in several important intermetallic alloy classes illustrate the guidance into alloy design and processing options provided by systematic studies of phase stability. 58 refs., 7 figs.

  9. Exotic equilibria of Harary graphs and a new minimum degree lower bound for synchronization

    SciTech Connect

    Canale, Eduardo A.; Monzón, Pablo

    2015-02-15

    This work is concerned with stability of equilibria in the homogeneous (equal frequencies) Kuramoto model of weakly coupled oscillators. In 2012 [R. Taylor, J. Phys. A: Math. Theor. 45, 1–15 (2012)], a sufficient condition for almost global synchronization was found in terms of the minimum degree–order ratio of the graph. In this work, a new lower bound for this ratio is given. The improvement is achieved by a concrete infinite sequence of regular graphs. Besides, non standard unstable equilibria of the graphs studied in Wiley et al. [Chaos 16, 015103 (2006)] are shown to exist as conjectured in that work.

  10. Simulation studies of GST phase change alloys

    NASA Astrophysics Data System (ADS)

    Martyna, Glenn

    2008-03-01

    In order to help drive post-Moore's Law technology development, switching processes involving novel materials, in particular, GeSbTe (GST) alloys are being investigated for use in memory and eFuse applications. An anneal/quench thermal process crystallizes/amorphosizes a GST alloy which then has a low/high resistance and thereby forms a readable/writeable bit; for example, a ``one'' might be the low resistance, conducting crystalline state and a ``zero'' might be the high resistance, glassy state. There are many open questions about the precise nature of the structural transitions and the coupling to electronic structure changes. Computational and experimental studies of the effect of pressure on the GST materials were initiated in order to probe the physics behind the thermal switching process. A new pathway to reversible phase change involving pressure-induced structural metal insulator transitions was discovered. In a binary GS system, a room-temperature, direct, pressure-induced transformation from the high resistance amorphous phase to the low resistance crystalline phase was observed experimentally while the reverse process under tensile load was demonstrated via ab initio MD simulations performed on IBM's Blue Gene/L enabled by massively parallel software. Pressure induced transformations of the ternary material GST-225 (Ge2Sb2Te5) were, also, examined In the talk, the behavior of the two systems will be compared and insight into the nature of the phase change given.

  11. Vapor-liquid phase separator studies

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Hepler, W. A.; Frederking, T. H. K.

    1985-01-01

    A study of porous plug use for vapor-liquid phase seperation in spaceborne cryogenic systems was conducted. The three main topics addressed were: (1) the usefulness of porous media in designs that call for variable areas and flow rates; (2) the possibility of prediction of main parameters of porous plugs for a given material; and (3) prediction of all parameters of the plug, including secondary parameters.

  12. Symmetry breaking of quasihelical stellarator equilibria

    SciTech Connect

    Weening, R.H. )

    1993-04-01

    A mean-field Ohm's law is used to determine the effects of the bootstrap current on quasihelically symmetric stellarator equilibria. The Ohm's law leads to the conclusion that the effects of the bootstrap current break the quasihelical stellarator symmetry at second order in an inverse aspect ratio expansion of the magnetic field strength. The level of symmetry breaking suggests that good approximations to quasihelical stellarator fusion reactors may not be attainable.

  13. Magnetohydrodynamic equilibria with incompressible flows: Symmetry approach

    SciTech Connect

    Cicogna, G.; Pegoraro, F.

    2015-02-15

    We identify and discuss a family of azimuthally symmetric, incompressible, magnetohydrodynamic plasma equilibria with poloidal and toroidal flows in terms of solutions of the Generalized Grad Shafranov (GGS) equation. These solutions are derived by exploiting the incompressibility assumption, in order to rewrite the GGS equation in terms of a different dependent variable, and the continuous Lie symmetry properties of the resulting equation and, in particular, a special type of “weak” symmetries.

  14. Fixed boundary toroidal plasma equilibria with toroidal flows

    NASA Astrophysics Data System (ADS)

    Hu, Yanqiang; Hu, Yemin; Xiang, Nong

    2016-04-01

    The fixed boundary toroidal plasma equilibria with toroidal flows are investigated by solving the modified Grad-Shafranov equation numerically in the cylindrical coordinate system. For normal equilibrium configurations with geometry and profiles similar to usual tokamaks with no flow, it is found that the effect of flow is to lead to an outward shift of the magnetic flux surfaces, together with the profiles of pressure, and mass and current densities. The shifts could become significant when the toroidal flow Mach number exceeds 0.5. For non-conventional current profiles, even for the usual tokamak geometry, novel current reversal equilibrium configurations may result, sometimes with changed topology in the poloidal flux function. This change in the topology of plasma equilibrium can be attributed to the large toroidal flow. The computed results may correspond to situations of intense tangential injection during the low toroidal current phase in expected experimental situations.

  15. Equilibria near asteroids for solar sails with reflection control devices

    NASA Astrophysics Data System (ADS)

    Gong, Shengping; Li, Junfeng

    2015-02-01

    Solar sails are well-suited for long-term, multiple-asteroid missions. The dynamics of solar sails near an asteroid have not yet been studied in detail. In this paper, out-of-plane artificial equilibria in a Sun-asteroid rotating frame and hovering points in a body-fixed rotating frame are studied (using a solar sail equipped with reflection control devices). First, the dynamics and the stability of out-of-plane artificial equilibria are studied as an elliptical restricted three body problem. Next, the body-fixed hovering problem is discussed as a two-body problem. Hovering flight is only possible for certain values of the latitude of the asteroid's orbit. In addition, the feasible range of latitudes is determined for each landmark on the asteroid's surface. The influence of the sail lightness number on the feasible range is also illustrated. Several special families of hovering points are discussed. These points include points above the equator and poles and points with an altitude equal to the radius of the synchronous orbit. In both of these types of problems, the solar sail (equipped with reflection control devices) can equilibrate over a large range of locations.

  16. Close relative equilibria of identical point vortices

    NASA Astrophysics Data System (ADS)

    Dirksen, Tobias; Aref, Hassan

    2011-11-01

    Via numerical solution of the classical problem of relative equilibria for identical point vortices on the unbounded plane we have found configurations that are very close to the analytically known, centered, symmetrically arranged, nested equilateral triangles. Numerical solutions of this kind were found for 3 n + 1 vortices, where n = 2 , 3 , ... , 30 . A sufficient, although apparently not necessary, condition for this phenomenon of close solutions is that the ``core'' of the configuration is marginally stable, as occurs for a central vortex surrounded by an equilateral triangle. The open, regular heptagon also has this property, and new relative equilibria close to the nested, symmetrically arranged, regular heptagons have been found. The centered regular nonagon is also marginally stable. Again, a new family of close relative equilibria has been found. The closest relative equilibrium pairs occur, however, for symmetrically nested equilateral triangles. The numerical evidence is surveyed and related recent work mentioned. A Letter in Physics of Fluids 23 (2011) 051706 is available. Supported in part by the Danish National Research Foundation through a Niels Bohr visiting professorship.

  17. Four motional invariants in axisymmetric tori equilibria

    SciTech Connect

    A ring gren, O.; Moiseenko, V.E.

    2006-05-15

    In addition to the standard set ({epsilon},{mu},p{sub {phi}}) of three invariants in axisymmetric tori, there exists a fourth independent radial drift invariant I{sub r}. For confined particles, the net radial drift has to be zero, whereby the drift orbit average I{sub r}= of the gyro center radial Clebsch coordinate is constant. To lowest order in the banana width, the radial invariant is the gyro center radial coordinate r{sub 0}(x,v), and to this order the gyro center moves on a magnetic flux surface. The gyro center orbit projected on the (r,z) plane determines the radial invariant and first order banana width corrections to I{sub r} are calculated. The radial drift invariant exists for trapped as well as passing particles. The new invariant is applied to construct Vlasov equilibria, where the magnetic field satisfies a generalized Grad-Shafranov equation with a poloidal plasma current and a bridge to ideal magnetohydrodynamic equilibria is found. For equilibria with sufficiently small banana widths and radial drift excursions, the approximation I{sub r}{approx_equal}r{sub 0}(x,v) can be used for the equilibrium state.

  18. Quantum Nash Equilibria and Quantum Computing

    NASA Astrophysics Data System (ADS)

    Fellman, Philip Vos; Post, Jonathan Vos

    In 2004, At the Fifth International Conference on Complex Systems, we drew attention to some remarkable findings by researchers at the Santa Fe Institute (Sato, Farmer and Akiyama, 2001) about hitherto unsuspected complexity in the Nash Equilibrium. As we progressed from these findings about heteroclinic Hamiltonians and chaotic transients hidden within the learning patterns of the simple rock-paper-scissors game to some related findings on the theory of quantum computing, one of the arguments we put forward was just as in the late 1990's a number of new Nash equilibria were discovered in simple bi-matrix games (Shubik and Quint, 1996; Von Stengel, 1997, 2000; and McLennan and Park, 1999) we would begin to see new Nash equilibria discovered as the result of quantum computation. While actual quantum computers remain rather primitive (Toibman, 2004), and the theory of quantum computation seems to be advancing perhaps a bit more slowly than originally expected, there have, nonetheless, been a number of advances in computation and some more radical advances in an allied field, quantum game theory (Huberman and Hogg, 2004) which are quite significant. In the course of this paper we will review a few of these discoveries and illustrate some of the characteristics of these new "Quantum Nash Equilibria". The full text of this research can be found at http://necsi.org/events/iccs6/viewpaper.php?id-234

  19. Extended MHD Stabiliy Calculations of Spheromak Equilibria

    NASA Astrophysics Data System (ADS)

    Howell, E. C.; Sovinec, C. R.

    2013-10-01

    Linear extended MHD calculations of spheromak equilibria in a cylindrical flux conserver are performed using the NIMROD code (Sovinec et al., JCP 195, 2004). A series of Grad-Sharfranov equilibria are generated with β ranging from 0 . 4 % to 4 . 2 % , corresponding to peak electron temperatures ranging 50 to 300 eV. These equilibria use a λ profile representative of SSPX shot 14590, which measured a peak electron temperature of 325 eV (McLean et al., POP 13, 2006). Resistive MHD calculations find that the β = 0 . 4 % case is unstable to resonant resistive interchange modes with γτA <= 2 . 3 % . These modes transition to ideal interchange as the equilibrium pressure is increased. Growth rates as large as γτA = 20 % are calculated for the 4 . 2 % β case. Calculations including ion-gyroviscosity show a minimal reduction of growth rate. Effects from including the Hall and Electron pressure terms in Ohm's Law and the cross-field diamagnetic heat flux are investigated. Results of related nonlinear simulations are also presented. Work Supported by US DOE.

  20. Fluid-solid equilibria of flexible and linear rigid tangent chains from Wertheim's thermodynamic perturbation theory

    NASA Astrophysics Data System (ADS)

    Blas, Felipe J.; Sanz, Eduardo; Vega, Carlos; Galindo, Amparo

    2003-11-01

    An extension of Wertheim's first-order thermodynamic perturbation theory is proposed to describe the global phase behavior of linear rigid tangent hard sphere chains. The extension is based on a scaling proposed recently by Vega and McBride [Phys. Rev. E 65, 052501 (2002)] for the equation of state of linear chains in the solid phase. We have used the Einstein-crystal methodology, the Rahman-Parrinello technique, and the thermodynamic integration method for calculating the free energy and equation of state of linear rigid hard sphere chains with different chain lengths, including the solid-fluid phase equilibria. Agreement between the simulation data and theoretical predictions is excellent in all cases. Once it is confirmed that the proposed theory can be used to describe correctly the equation of state, free energy, and solid-fluid phase transitions of linear rigid molecules, a simple mean-field approximation at the level of van der Waals is included to account for segment-segment attractive interactions. The approach is used to determine the global phase behavior of fully flexible and linear rigid chains of varying chain lengths. The main effect of increasing the chain length in the case of linear rigid chains is to decrease the fluid densities at freezing, so that the triple-point temperatures increase. As a consequence, the range of temperatures where vapor-liquid equilibria exist decreases considerably with chain length. This behavior is a direct result of the stabilization of the solid phase with respect to the liquid phase as the chain length is increased. The vapor-liquid equilibria are seen to disappear for linear rigid chains formed by more than 11 hard sphere segments that interact through an attractive van der Waals mean-field contribution; in other words, long linear rigid chains exhibit solid-vapor phase behavior only. In the case of flexible chains, the fluid-solid equilibrium is hardly affected by the chain length, so that the triple

  1. FETAX interlaboratory validation study: Phase 2 testing

    SciTech Connect

    Bantle, J.A. . Dept. of Zoology); Burton, D.T. ); Dawson, D.A. . Dept. of Biology and Toxicology)

    1994-10-01

    The Frog Embryo Teratogenesis Assay-Xenopus (FETAX) is a 96-h whole embryo developmental toxicity screening assay that can be used in ecotoxicology and in detecting mammalian developmental toxicants when an in vitro metabolic activation system is employed. A standardized American Society for Testing and Materials (ASTM) guide for the conduct of FETAX has been published along with a companion atlas that helps in embryo staging and identifying malformations. As part of the ASTM process, an interlaboratory validation study was undertaken to evaluate the repeatability and reliability of FETAX. Six different laboratories participated in the study. Each laboratory utilized one technician with the exception of one laboratory, which utilized two independent technicians. In Phase 1, FETAX proved to be more repeatable and reliable than many other bioassays. However, some excessive variation was observed in a few laboratories. Some of this variation may have been due to an initial lack of experience with the assay by some technicians. Phase 2, which is reported here, showed far less intralaboratory and interlaboratory variability than did Phase 1. Nonteratogens such as saccharin and sodium cyclamate showed the most consistent results, whereas more variability was observed for the teratogens caffeine and 5-fluorouracil. Interlaboratory coefficient of variation values for all FETAX end points ranged from 7.3 to 54.7%. The minimum concentration to inhibit growth proved to be the most variable end point for three of the four test chemicals, whereas the LC50 and EC50 (malformation) proved to be less variable.

  2. The Growth and Characterization of Germanium-Carbon Alloy Thin Films and Solid Phase Equilibria for Metal-Silicon - Ternary Systems: Magnesium, Calcium, Strontium, Barium, Scandium, Yttrium, Lanthanum, Titanium, Zirconium and Hafnium

    NASA Astrophysics Data System (ADS)

    Yuan, Haojie

    1992-09-01

    Thin films of pure germanium-carbon alloys (Ge _{rm x}C _{rm 1-x} with 0 <=q x <=q 1) have been grown on Si and Al_2O_3 substrates by pulsed laser ablation in a high vacuum chamber. The films were analyzed by x-ray 0-20 diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), conductivity measurements and optical absorption spectroscopy. The analyses of these new materials showed that films of all compositions were amorphous, free of contamination and uniform in composition. By changing the film composition, the optical band gap of these semiconducting films was varied from 0.00 eV to 0.85 eV for x = 0.0 to 1.0 respectively. According to the AES results, the carbon atoms in the Ge-C alloy thin film samples have a bonding structure that is a mixture of sp^2 and sp^3 hybridizations. The presence of the sp^2 C is apparently what causes the bandgap of amorphous Ge-C alloys to decrease with increasing carbon concentration. The solidus portion of the ternary phase diagrams of the type M-Si-O, where M = Mg, Ca, Sr, Ba, Sc, Y, La, Ti, Zr and Hf have been derived at 298K and 1 atm oxygen partial pressure by investigating the bulk reactions possible in these systems. These phase diagrams, which have been determined by experiments and by calculations using thermodynamic data available, can be used to predict the occurrence of the reaction products or the stability of the phases present at the interfaces between different solid materials. Hence, they provide guides in designing thin film structures and in selecting candidate materials to form chemically stable interfaces. A research effort has been made on the investigation of the growth of diamond thin films from a carbon containing solid-CI_4, using laser ablation technique. The film grown by laser ablation from CI _4 is mainly composed of carbon with very small amount of oxygen and iodine as indicated by x-ray photoelectron spectroscopy data. The Auger electron spectroscopy result shows

  3. Conducting Phase IV clinical studies: a moral imperative?

    PubMed Central

    Hill, TP

    2012-01-01

    The answer to this question lies in knowing the moral standing of Phase IV studies and whether we ought to conduct them. And to know this, in part, we need to compare them to studies in Phases I, II, and III and then determine where Phase IV studies stand in relation to Phase I–III studies scientifically and commercially.

  4. A Magnetic Diagnostic Code for 3D Fusion Equilibria

    SciTech Connect

    Samuel Aaron Lazerson

    2012-07-27

    A synthetic magnetic diagnostics code for fusion equilibria is presented. This code calculates the response of various magnetic diagnostics to the equilibria produced by the VMEC and PIES codes. This allows for treatment of equilibria with both good nested flux surfaces and those with stochastic regions. DIAGNO v2.0 builds upon previous codes through the implementation of a virtual casing principle. The codes is validated against a vacuum shot on the Large Helical Device where the vertical field was ramped. As an exercise of the code, the diagnostic response for various equilibria are calculated on the Large Helical Device (LHD).

  5. A Magnetic Diagnostic Code for 3D Fusion Equilibria

    SciTech Connect

    Samuel A. Lazerson, S. Sakakibara and Y. Suzuki

    2013-03-12

    A synthetic magnetic diagnostics code for fusion equilibria is presented. This code calculates the response of various magnetic diagnostics to the equilibria produced by the VMEC and PIES codes. This allows for treatment of equilibria with both good nested flux surfaces and those with stochastic regions. DIAGNO v2.0 builds upon previous codes through the implementation of a virtual casing principle. The code is validated against a vacuum shot on the Large Helical Device (LHD) where the vertical field was ramped. As an exercise of the code, the diagnostic response for various equilibria are calculated on the LHD.

  6. Tokamak equilibria with toroidal current reversal: properties and computational issues

    SciTech Connect

    Rodrigues, Paulo; Bizarro, Joao P. S.

    2006-11-30

    Several properties of axisymmetric plasma equilibria with toroidal-current reversal (TCR) are discussed using some unifying concepts from catastrophe theory. Namely, those of structural stability of functions near critical points, singularity unfolding by small perturbations, and model parameter-space division by bifurcation sets are found to be of particular usefulness. Magnetic configurations displaying, simultaneously, TCR and nested flux surfaces are thence shown to be necessarily degenerate and structurally unstable, meaning that they are easily transformed into non-nested ones by small perturbations in the model parameter set. This should lead to a new paradigm when discussing TCR equilibria, as most of present knowledge relies mainly on the properties of nested solutions, which is expected to favor the study of the broader class of non-nested configurations that recently attracted a considerable discussion in the fusion community. In addition, it is also shown how TCR imposes some constraints on plasma profiles, and how these may be dealt with computationally while keeping the ability to manipulate the shape of the inner island system.

  7. Stability of Hall equilibria in neutron star crusts

    SciTech Connect

    Marchant, Pablo; Reisenegger, Andreas; Valdivia, Juan Alejandro; Hoyos, Jaime H.

    2014-12-01

    In the solid crusts of neutron stars, the advection of the magnetic field by the current-carrying electrons, an effect known as Hall drift, should play a very important role as the ions remain essentially fixed (as long as the solid does not break). Although Hall drift preserves the magnetic field energy, it has been argued that it may drive a turbulent cascade to scales at which ohmic dissipation becomes effective, allowing a much faster decay in objects with very strong fields. On the other hand, it has been found that there are 'Hall equilibria', i.e., field configurations that are unaffected by Hall drift. Here we address the crucial question of the stability of these equilibria through axially symmetric (two-dimensional (2D)) numerical simulations of Hall drift and ohmic diffusion, with the simplifying assumption of uniform electron density and conductivity. We demonstrate the 2D stability of a purely poloidal equilibrium, for which ohmic dissipation makes the field evolve toward an attractor state through adjacent stable configurations, around which damped oscillations occur. For this field, the decay scales with the ohmic timescale. We also study the case of an unstable equilibrium consisting of both poloidal and toroidal field components that are confined within the crust. This field evolves into a stable configuration, which undergoes damped oscillations superimposed on a slow evolution toward an attractor, just as the purely poloidal one.

  8. Protolytic equilibria on the surface of carboxyl-containing silica

    SciTech Connect

    Mil'chenko, D.V.; Kudryavtsev, G.V.; Lisichkin, G.V.

    1986-09-01

    Potentiometric titration has been used to study the protolytic equilibria on the surface of carboxyl-containing silica (CS) prepared by the reaction of silica (Silokhrom S-80, S /SUB sp/ = 80 m2/g) with C1/sub 3/SiCH/sub 2/CH/sub 2/COOCH/sub 3/, followed by hydrolysis with 30% sulfuric acid. The titration curve of the vacuum-dried sample is irreversible. The titration curve of its Na+ form with hydrochloric acid proceeds lower than the titration curve of its H+ form and coincides with the titration curve of the air-dried sample (the last curve is reversible). The titration curve of CS coincides with the titration curve of butyric acid at pH < 6. At pH > 6 the titration curve of CS passes below the titration curve of butyric acid; this is due to the participation of silanol groups on the silica surface in the protolytic equilibria. The pK /SUB a/ of the grafted CS groups is equal to 4.80 which is close to the pK /SUB a/ value of butyric acid (4.78). A method has been proposed for the determination of the amount of weak acid groups grafted to the silica. It has been shown that in the titration of CS the equilibrium is established much faster than in the case of the unmodified silica.

  9. Spacelab data management subsystem phase B study

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The Spacelab data management system is described. The data management subsystem (DMS) integrates the avionics equipment into an operational system by providing the computations, logic, signal flow, and interfaces needed to effectively command, control, monitor, and check out the experiment and subsystem hardware. Also, the DMS collects/retrieves experiment data and other information by recording and by command of the data relay link to ground. The major elements of the DMS are the computer subsystem, data acquisition and distribution subsystem, controls and display subsystem, onboard checkout subsystem, and software. The results of the DMS portion of the Spacelab Phase B Concept Definition Study are analyzed.

  10. A Computer Algebra Approach to Solving Chemical Equilibria in General Chemistry

    ERIC Educational Resources Information Center

    Kalainoff, Melinda; Lachance, Russ; Riegner, Dawn; Biaglow, Andrew

    2012-01-01

    In this article, we report on a semester-long study of the incorporation into our general chemistry course, of advanced algebraic and computer algebra techniques for solving chemical equilibrium problems. The method presented here is an alternative to the commonly used concentration table method for describing chemical equilibria in general…

  11. On the existence of a high-temperature polymorph of Na2Ca6Si4O15—implications for the phase equilibria in the system Na2O-CaO-SiO2

    NASA Astrophysics Data System (ADS)

    Kahlenberg, Volker; Maier, Matthias

    2016-06-01

    Singe crystals of a new high-temperature polymorph of Na2Ca6Si4O15 have been obtained from solid state reactions performed at 1300 °C. The basic crystallographic data of this so-called β-phase at ambient conditions are as follows: space group P1c1, a = 9.0112(5) Å, b = 7.3171(5) Å, c = 10.9723(6) Å, β = 107.720(14)°, V = 689.14(7) Å3, Z = 2. The crystals showed twinning by reticular merohedry (mimicking an orthorhombic C-centred unit cell) which was accounted for during data processing and structure solution. Structure determination was accomplished by direct methods. Least-squares refinements resulted in a residual of R(|F|) = 0.043 for 5811 observed reflections with I > 2σ(I). From a structural point of view β-Na2Ca6Si4O15 can be attributed to the group of mixed-anion silicates containing [Si2O7]-dimers as well as isolated [SiO4]-tetrahedra in the ratio 1:2, i.e. more precisely the formula can be written as Na2Ca6[SiO4]2[Si2O7]. The tetrahedral groups are arranged in layers parallel to (100). Sodium and calcium cations are located between the silicate anions for charge compensation and are coordinated by six to eight nearest oxygen ligands. Alternatively, the structure can be described as a mixed tetrahedral-octahedral framework based on kröhnkite-type [Ca(SiO4)2O2]-chains in which the CaO6-octahedra are corner-linked to bridging SiO4-tetrahedra. The infinite chains are running parallel to [001] and are concentrated in layers parallel to (010). Adjacent layers are shifted relative to each other by an amount of +δ or -δ along a*. Consequently, a …ABABAB… stacking sequence is created. A detailed comparison with related structures such as α-Na2Ca6Si4O15 and other A2B6Si4O15 representatives including topological as well as group theoretical aspects is presented. There are strong indications that monoclinic Na2Ca3Si2O8 mentioned in earlier studies is actually misinterpreted β-Na2Ca6Si4O15. In addition to the detailed crystallographic analysis of the

  12. Intelligent Robotic Systems Study (IRSS), phase 4

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Under the Intelligent Robotics Systems Study (IRSS), a generalized robotic control architecture was developed for use with the ProtoFlight Manipulator Arm (PFMA). Based upon the NASREM system design concept, the controller built for the PFMA provides localized position based force control, teleoperation, and advanced path recording and playback capabilities. The PFMA has six computer controllable degrees of freedom (DOF) plus a 7th manually indexable DOF, making the manipulator a pseudo 7 DOF mechanism. Joints on the PFMA are driven via 7 pulse width modulated amplifiers. Digital control of the PFMA is implemented using a variety of single board computers. There were two major activities under the IRSS phase 4 study: (1) enhancement of the PFMA control system software functionality; and (2) evaluation of operating modes via a teleoperation performance study. These activities are described and results are given.

  13. Aluminum Deoxidation Equilibria in Liquid Iron: Part II. Thermodynamic Modeling

    NASA Astrophysics Data System (ADS)

    Paek, Min-Kyu; Pak, Jong-Jin; Kang, Youn-Bae

    2015-10-01

    Al deoxidation equilibria in liquid iron over the whole composition range from very low Al ([pct Al] = 0.0027) to almost pure liquid Al were thermodynamically modeled for the first time using the Modified Quasichemical Model in the pair approximation for the liquid phase. The present modeling is distinguished from previous approaches in many ways. First, very strong attractions between metallic components, Fe and Al, and non-metallic component, O, were taken into account explicitly in terms of Short-Range Ordering. Second, the present thermodynamic modeling does not distinguish solvent and solutes among metallic components, and the model calculation can be applied from pure liquid Fe to pure liquid Al. Therefore, this approach is thermodynamically self-consistent, contrary to the previous approaches using interaction parameter formalism. Third, the present thermodynamic modeling describes an integral Gibbs energy of the liquid alloy in the framework of CALPHAD; therefore, it can be further used to develop a multicomponent thermodynamic database for liquid steel. Fourth, only a small temperature-independent parameter for ternary liquid was enough to account for the Al deoxidation over wide concentration (0.0027 < [pct Al] < 100) and wide temperature range [1823 K to 2139 K (1550 °C to 1866 °C)]. Gibbs energies of Fe-O and Al-O binary liquid solutions at metal-rich region (up to oxide saturation) were modeled, and relevant model parameters were optimized. By merging these Gibbs energy descriptions with that of Fe-Al binary liquid modeled by the same modeling approach, the Gibbs energy of ternary Fe-Al-O solution at metal-rich region was obtained along with one small ternary parameter. It was shown that the present model successfully reproduced all available experimental data for the Al deoxidation equilibria. Limit of previously used interaction parameter formalism at high Al concentration is discussed.

  14. Discovering the Thermodynamics of Simultaneous Equilibria: An Entropy Analysis Activity Involving Consecutive Equilibria

    ERIC Educational Resources Information Center

    Bindel, Thomas H.

    2007-01-01

    An activity is presented in which the thermodynamics of simultaneous, consecutive equilibria are explored. The activity is appropriate for second-year high school or AP chemistry. Students discover that a reactant-favored (entropy-diminishing or endergonic) reaction can be caused to happen if it is coupled with a product-favored reaction of…

  15. Spectrometric study of tautomeric and protonation equilibria of o-vanillin Schiff base derivatives and their complexes with Cu(II)

    NASA Astrophysics Data System (ADS)

    Galić, Nives; Cimerman, Zvjezdana; Tomišić, Vladislav

    2008-12-01

    Electronic absorption and emission properties of a series of Schiff bases derived from 2-hydroxy-3-methoxybenzaldehyde and 2-aminopyridine, 2,3-diaminopyridine, 2,6-diaminopyridine, or 3-aminomethylpyridine were studied in solvents of different polarities. The interconversion of the enolimine to the ketoamine tautomeric form was observed for compound 1, 6-methoxy-2-(3-pyridylmethyliminomethyl)phenol, and the corresponding equilibrium constant was estimated in several solvents. Protonation constants of all the investigated compounds were determined spectrophotometrically in the methanol/water 1/4 system. The effect of copper(II) ions on absorption and on the emission spectra of these ligands was examined in the buffered dioxane/water 1/1 system (pH 5.8). Strong complexation of Cu(II) and formation of a 1:1 complex were observed for the bis-Schiff base derived from 2,3-diaminopyridine. The complex of copper(II) with compound 1 was isolated and characterized by elemental analysis, magnetic susceptibility measurement, UV-vis and IR spectrometry.

  16. Ultraviolet-visible study on acid-base equilibria of aporphine alkaloids with antiplasmodial and antioxidant activities from Alseodaphne corneri and Dehaasia longipedicellata

    PubMed Central

    Zahari, Azeana; Ablat, Abdulwali; Omer, Noridayu; Nafiah, Mohd Azlan; Sivasothy, Yasodha; Mohamad, Jamaludin; Khan, Mohammad Niyaz; Awang, Khalijah

    2016-01-01

    The UV-vis spectra of isocorydine 1, norisocorydine 2 and boldine 3 were studied in 2% v/v acetonitrile, at constant ionic strength (0.1 M NaCl, 35 degree Celsius). The pKa values of isocorydine 1 and norisocorydine 2 were 11.75 and 12.07, respectively. Boldine 3 gave a pKa value of 9.16 and 10.44. All of the alkaloids 1–3 were stable at physiological pH; thereby all of them will not ionize, thus permitting the basic nitrogen to be protonated and accumulated within the acidic food vacuole of Plasmodium via pH trapping. Subsequently, acidic food vacuoles that have been neutralized by alkaloids would result in enhancement of the antiplasmodial activity. The alkaloids showed antiplasmodial activity against Plasmodium falciparum and antioxidant activities; DPPH radical scavenging, metal chelating and ferric reducing power. The antioxidant properties of the alkaloids under investigation revealed that in addition to the antiplasmodial activity, the alkaloids can also prevent oxidative damage. It can be prevented by binding free heme and neutralizing the electrons produced during the Plasmodium falciparum mediated haemoglobin destruction in the host. Slightly basic properties of the aforementioned alkaloids, along with their antioxidant activities, are advantageous in improving the suppression of malaria infection that cause less damage to the host. PMID:26898753

  17. Ultraviolet-visible study on acid-base equilibria of aporphine alkaloids with antiplasmodial and antioxidant activities from Alseodaphne corneri and Dehaasia longipedicellata

    NASA Astrophysics Data System (ADS)

    Zahari, Azeana; Ablat, Abdulwali; Omer, Noridayu; Nafiah, Mohd Azlan; Sivasothy, Yasodha; Mohamad, Jamaludin; Khan, Mohammad Niyaz; Awang, Khalijah

    2016-02-01

    The UV-vis spectra of isocorydine 1, norisocorydine 2 and boldine 3 were studied in 2% v/v acetonitrile, at constant ionic strength (0.1 M NaCl, 35 degree Celsius). The pKa values of isocorydine 1 and norisocorydine 2 were 11.75 and 12.07, respectively. Boldine 3 gave a pKa value of 9.16 and 10.44. All of the alkaloids 1-3 were stable at physiological pH; thereby all of them will not ionize, thus permitting the basic nitrogen to be protonated and accumulated within the acidic food vacuole of Plasmodium via pH trapping. Subsequently, acidic food vacuoles that have been neutralized by alkaloids would result in enhancement of the antiplasmodial activity. The alkaloids showed antiplasmodial activity against Plasmodium falciparum and antioxidant activities; DPPH radical scavenging, metal chelating and ferric reducing power. The antioxidant properties of the alkaloids under investigation revealed that in addition to the antiplasmodial activity, the alkaloids can also prevent oxidative damage. It can be prevented by binding free heme and neutralizing the electrons produced during the Plasmodium falciparum mediated haemoglobin destruction in the host. Slightly basic properties of the aforementioned alkaloids, along with their antioxidant activities, are advantageous in improving the suppression of malaria infection that cause less damage to the host.

  18. Acid-base and Electrochemical Properties of Manganese meso(ortho- and meta-ethylpyridyl)porphyrins: Potentiometric, Spectrophotometric and Spectroelectrochemical Study of Protolytic and Redox Equilibria

    PubMed Central

    Weitner, Tin; Budimir, Ana; Batinić-Haberle, Ines

    2013-01-01

    The difference in electrostatics and reduction potentials between manganese ortho-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP) and manganese meta-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-3-PyP) is a challenging topic, particularly because of the high likelihood for their clinical development. Hence, a detailed study of the protolytic and electrochemical speciation of MnII–IVTE-2-PyP and MnII-IVTE-3-PyP in a broad pH range has been performed using the combined spectrophotometric and potentiometric methods. The results reveal that in aqueous solutions within the pH range ~2–13 the following species exist: (H2O)MnIITE-m-PyP4+, (HO)MnIITE-m-PyP3+, (H2O)2MnIIITE-m-PyP5+, (H2O)(HO)MnIIITE-m-PyP4+, (H2O)(O=)MnIIITE-m-PyP3+, (H2O)(O=)MnIVTE-m-PyP4+ and (HO)(O=)MnIVTE-m-PyP3+ (m = 2, 3). All the protolytic equilibrium constants that include the accessible species as well as the thermodynamic parameters for each particular protolytic equilibrium have been determined. The corresponding formal reduction potentials related to the reduction of the above species and the thermodynamic parameters describing the accessible reduction couples were calculated as well. PMID:21052598

  19. Study of improved methods for predicting chemical equilibria: Technical progress report for the period July 1, 1986 to September 1, 1987

    SciTech Connect

    Lenz, T.G.; Vaughan, J.D.

    1987-01-01

    We carried out a detailed study of the capabilities and limitations of two force field models (MMP2 and MOLBD3) for calculating thermodynamic properties of -diene and -ene hydrocarbons. New force field parameters were introduced for the MOLBD3 program for unsaturated five-member rings and for methylene-bridged compounds. We investigated the Diels-Alder condensation of 1,3-cyclopentadiene in the temperature range 273 to 500K by use of MOLBD3. Equilibrium constants, standard enthalpies of reaction, and standard entropies of reaction were calculated. The calculated results were compared with experimental data reported in the literature. Anthracene derivatives, maleic anhydride derivatives, and Diels-Alder adducts were synthesized and purified in preparation for future experimental determination of equilibrium constants for various Diels-Alder reactions. The structure of the 9-phenylanthracene-maleic anhydride adduct was determined by x-ray crystallography. Equilibrium constants for the Diels-Alder reaction of 9-phenylanthracene and maleic anhydride in 1,2,4-trichlorobenzene were determined for seven temperatures between 124 and 175/sup 0/C. 27 refs., 1 fig., 13 tabs.

  20. Measurements and Modeling To Determine the Reduction Potential of Uncomplexed Bi(III) in Nitrate Solutions for Application in Bi(III)-Ligand Equilibria Studies by Voltammetry.

    PubMed

    Billing, Caren; Cukrowski, Ignacy

    2016-05-12

    The free metal ion potential, E(M), is a critical parameter in the calculation of formation constants when using voltammetry. When studying complex formation of Bi(III), however, E(Bi) cannot be directly measured. In this work a nitrate background electrolyte was employed to obtain reversible reduction waves. To determine E(Bi), measurements have to be made below pH ∼ 2 before the bismuth-oxy-nitrate species precipitates and thus corrections for the diffusion junction potential (monitored using Tl(I) as an internal reference ion) must be made. Additionally shifts in potential due to both Bi(III) hydrolysis and Bi(III) nitrate formation must also be compensated for before E(Bi) can be evaluated. The value of E(Bi) was determined relative to E(Tl) so that in an experiments where ligand is added to determine formation constants, E(Bi) can be determined as accurately as possible (since E(Tl) can generally still be measured). The value of E(Bi) - E(Tl) was found to be 495.6 ± 1.4 mV for the conditions employed. PMID:27088843

  1. Study of the solid-liquid equilibria in the LiPO{sub 3}-Y(PO{sub 3}){sub 3} binary system

    SciTech Connect

    Jouini, Anis; Ferid, Mokhtar; Trabelsi-Ayadi, Malika

    2003-02-20

    The LiPO{sub 3}-Y(PO{sub 3}){sub 3} system has been studied for the first time. Microdifferential thermal analysis ({mu}-DTA), infrared spectroscopy (IR) and X-ray diffraction were used to investigate the liquidus and solidus relations. The only new compound observed within this system is LiY(PO{sub 3}){sub 4}, melting incongruently at 1104 K. An eutectic appears at 4{+-}1 mol% Y(PO{sub 3}){sub 3} at 933 K. LiY(PO{sub 3}){sub 4} crystallizes in the monoclinic system C{sub 2/c} with a unit cell: a=16.201(4) A, b=7.013(2) A, c=9.573(2) A, {beta}=125.589(9) deg. , Z=4 and V=884.5 A{sup 3}, which is isostructural to LiNd(PO{sub 3}){sub 4}. The infrared absorption spectrum indicates that this salt is a chain polyphosphate.

  2. Space shuttle phase B study plan

    NASA Technical Reports Server (NTRS)

    Hello, B.

    1971-01-01

    Phase B emphasis was directed toward development of data which would facilitate selection of the booster concept, and main propulsion system for the orbiter. A shuttle system is also defined which will form the baseline for Phase C program activities.

  3. Acid-base and electrochemical properties of manganese meso(ortho- and meta-N-ethylpyridyl)porphyrins: potentiometric, spectrophotometric and spectroelectrochemical study of protolytic and redox equilibria.

    PubMed

    Weitner, Tin; Budimir, Ana; Kos, Ivan; Batinić-Haberle, Ines; Biruš, Mladen

    2010-12-28

    The difference in electrostatics and reduction potentials between manganese ortho-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP) and manganese meta-tetrakis(N-ethylpyridinium-3-yl)porphyrin (MnTE-3-PyP) is a challenging topic, particularly because of the high likelihood for their clinical development. Hence, a detailed study of the protolytic and electrochemical speciation of Mn(II-IV)TE-2-PyP and Mn(II-IV)TE-3-PyP in a broad pH range has been performed using the combined spectrophotometric and potentiometric methods. The results reveal that in aqueous solutions within the pH range ∼2-13 the following species exist: (H(2)O)Mn(II)TE-m-PyP(4+), (HO)Mn(II)TE-m-PyP(3+), (H(2)O)(2)Mn(III)TE-m-PyP(5+), (HO)(H(2)O)Mn(III)TE-m-PyP(4+), (O)(H(2)O)Mn(III)TE-m-PyP(3+), (O)(H(2)O)Mn(IV)TE-m-PyP(4+) and (O)(HO)Mn(IV)TE-m-PyP(3+) (m = 2, 3). All the protolytic equilibrium constants that include the accessible species as well as the thermodynamic parameters for each particular protolytic equilibrium have been determined. The corresponding formal reduction potentials related to the reduction of the above species and the thermodynamic parameters describing the accessible reduction couples were calculated as well. PMID:21052598

  4. Solid-liquid phase equilibria at 50 and 75°C in the NaCl + MgCl2 + H2O system and the pitzer model representations

    NASA Astrophysics Data System (ADS)

    Yang, Ji-min; Zhang, Rui-zhi; Liu, Hong; Ma, Si-hong

    2013-12-01

    The solubilities in the NaCl-MgCl2-H2O system were determined at 50 and 75°C and the phase diagrams were constructed on the base of experimental data. One invariant point, two univariant curves, and two crystallization zones, corresponding to sodium chloride and dihydrate (MgCl2 · 6H2O) showed up in the phase diagrams of the ternary system, The mixing parameters θNa,Mg and ΨNa,Mg, Cl and equilibrium constant K sp were evaluated in NaCl-MgCl2-H2O system by least-squares optimization procedure, in which the single-salt Pitzer parameters of NaCl and MgCl2β(0), β(1), and C φ were directly calculated from the literature. The results obtained were in good agreement with the experimental data.

  5. Relativistic thermal plasmas - Pair processes and equilibria

    NASA Technical Reports Server (NTRS)

    Lightman, A. P.

    1982-01-01

    The work of Bisnovatyi-Kogan, Zel'dovich and Sunyaev (1971) is extended and generalized, through the inclusion of pair-producing photon processes and effects due to the finite size of the plasma, in an investigation of the equilibria of relativistic thermal plasmas which takes into account electron-positron creation and annihilation and photons produced within the plasma. It is shown that the bridge between an effectively thin plasma and an effectively thick plasma occurs in the transrelativistic region, where the dimensionless temperature value is between 0.1 and 1.0 and the temperature remains in this region over a great luminosity range.

  6. Erratum: "A new equation of state of a flexible-chain polyelectrolyte solution: Phase equilibria and osmotic pressure in the salt-free case" [J. Chem. Phys. 142, 174901 (2015)

    NASA Astrophysics Data System (ADS)

    Budkov, Yu. A.; Kolesnikov, A. L.; Georgi, N.; Nogovitsyn, E. A.; Kiselev, M. G.

    2015-11-01

    We develop a first-principle equation of state of salt-free polyelectrolyte solution in the limit of infinitely long flexible polymer chains in the framework of a field-theoretical formalism beyond the linear Debye-Hueckel theory and predict a liquid-liquid phase separation induced by a strong correlation attraction. As a reference system we choose a set of two subsystems - charged macromolecules immersed in a structureless oppositely charged background created by counterions (polymer one component plasma) and counterions immersed in oppositely charged background created by polymer chains (hard-core one component plasma). We calculate the excess free energy of polymer one component plasma in the framework of Modified Random Phase Approximation, whereas a contribution of charge densities fluctuations of neutralizing backgrounds we evaluate at the level of Gaussian approximation. We show that our theory is in a very good agreement with the results of Monte-Carlo and MD simulations for critical parameters of liquid-liquid phase separation and osmotic pressure in a wide range of monomer concentration above the critical point, respectively.

  7. Phase equilibria and crystal chemistry of the CaO–1/2 Nd{sub 2}O{sub 3}–CoO{sub z} system at 885 °C in air

    SciTech Connect

    Wong-Ng, W.; Laws, W.; Talley, K.R.; Huang, Q.; Yan, Y.; Martin, J.; Kaduk, J.A.

    2014-07-01

    The phase diagram of the CaO–1/2 Nd{sub 2}O{sub 3}–CoO{sub z} system at 885 °C in air has been determined. The system consists of two calcium cobaltate compounds that have promising thermoelectric properties, namely, the 2D thermoelectric oxide solid solution, (Ca{sub 3−x}Nd{sub x})Co{sub 4}O{sub 9−z} (0≤x≤0.5), which has a misfit layered structure, and Ca{sub 3}Co{sub 2}O{sub 6} which consists of 1D chains of alternating CoO{sub 6} trigonal prisms and CoO{sub 6} octahedra. Ca{sub 3}Co{sub 2}O{sub 6} was found to be a point compound without the substitution of Nd on the Ca site. The reported Nd{sub 2}CoO{sub 4} phase was not observed at 885 °C. A ternary (Ca{sub 1−x}Nd{sub 1+x})CoO{sub 4−z} (x=0) phase, or (CaNdCo)O{sub 4−z}, was found to be stable at this temperature. A solid solution region of distorted perovskite (Nd{sub 1−x}Ca{sub x})CoO{sub 3−z} (0≤x≤0.25, space group Pnma) was established. In the peripheral binary systems, while a solid solution region was identified for (Nd{sub 1−x}Ca{sub x}){sub 2}O{sub 3−z} (0≤x≤0.2), Nd was not found to substitute in the Ca site of CaO. Six solid solution tie-line regions and six three-phase regions were determined in the CaO–Nd{sub 2}O{sub 3}–CoO{sub z} system in air. - Graphical abstract: Phase diagram of the 1/2 Nd{sub 2}O{sub 3}–CaO–CoO{sub x} system at 885 °C, showing the limits of various solid solutions, and the tie-line relationships of various phases. - Highlights: • Phase diagram of the CaO–1/2 Nd{sub 2}O{sub 3}–CoO{sub z} system constructed. • System consists of thermoelectric oxide (Ca{sub 3−x}Nd{sub x})Co{sub 4}O{sub 9−z} (0≤x≤0.5). • Structures of (Nd{sub 1−x}Ca{sub x})CoO{sub 3−z} and (CaNdCo)O{sub 4−z} determined.

  8. On Learning Algorithms for Nash Equilibria

    NASA Astrophysics Data System (ADS)

    Daskalakis, Constantinos; Frongillo, Rafael; Papadimitriou, Christos H.; Pierrakos, George; Valiant, Gregory

    Can learning algorithms find a Nash equilibrium? This is a natural question for several reasons. Learning algorithms resemble the behavior of players in many naturally arising games, and thus results on the convergence or non-convergence properties of such dynamics may inform our understanding of the applicability of Nash equilibria as a plausible solution concept in some settings. A second reason for asking this question is in the hope of being able to prove an impossibility result, not dependent on complexity assumptions, for computing Nash equilibria via a restricted class of reasonable algorithms. In this work, we begin to answer this question by considering the dynamics of the standard multiplicative weights update learning algorithms (which are known to converge to a Nash equilibrium for zero-sum games). We revisit a 3×3 game defined by Shapley [10] in the 1950s in order to establish that fictitious play does not converge in general games. For this simple game, we show via a potential function argument that in a variety of settings the multiplicative updates algorithm impressively fails to find the unique Nash equilibrium, in that the cumulative distributions of players produced by learning dynamics actually drift away from the equilibrium.

  9. Fluorite solubility equilibria in selected geothermal waters

    USGS Publications Warehouse

    Nordstrom, D.K.; Jenne, E.A.

    1977-01-01

    Calculation of chemical equilibria in 351 hot springs and surface waters from selected geothermal areas in the western United States indicate that the solubility of the mineral fluorite, CaF2, provides an equilibrium control on dissolved fluoride activity. Waters that are undersaturated have undergone dilution by non-thermal waters as shown by decreased conductivity and temperature values, and only 2% of the samples are supersaturated by more than the expected error. Calculations also demonstrate that simultaneous chemical equilibria between the thermal waters and calcite as well as fluorite minerals exist under a variety of conditions. Testing for fluorite solubility required a critical review of the thermodynamic data for fluorite. By applying multiple regression of a mathematical model to selected published data we have obtained revised estimates of the pK (10,96), ??Gof (-280.08 kcal/mole), ??Hof (-292.59 kcal/mole), S?? (16.39 cal/deg/mole) and CoP (16.16 cal/deg/mole) for CaF2 at 25??C and 1 atm. Association constants and reaction enthalpies for fluoride complexes with boron, calcium and iron are included in this review. The excellent agreement between the computer-based activity products and the revised pK suggests that the chemistry of geothermal waters may also be a guide to evaluating mineral solubility data where major discrepancies are evident. ?? 1977.

  10. Calculation of multicomponent chemical equilibria in gas-solid-liquid systems: Calculation methods, thermochemical data, and applications to studies of high-temperature volcanic gases with examples from Mt. St. Helens

    SciTech Connect

    Symonds, R.B. ); Reed, M.H. )

    1993-10-01

    This paper documents the numerical formulations, thermochemical data base, and possible applications of computer programs, SOLVGAS and GASWORKS, for calculating multicomponent chemical equilibria in gas-solid-liquid systems. SOLVGAS and GASWORKS compute simultaneous equilibria by solving simultaneously a set of mass balance and mass action equations written for all gas species and for all gas-solid or gas-liquid equilibria. The programs interface with a thermo-chemical data base, GASTHERM, which contains coefficients for retrieval of the equilibrium constants from 25[degrees] to 1200[degrees]C. The programs and data base model dynamic chemical processes in 30- to 40-component volcanic-gas systems. The authors can model gas evaporation from magma, mixing of magmatic and hydrothermal gases, precipitation of minerals during pressure and temperature decrease, mixing of volcanic gas with air, and reaction of gases with wall rock. Examples are given of the gas-evaporation-from-magma and precipitation-with-cooling calculations for volcanic gases collected from Mt. St. Helens in September 1981. The authors predict: (1) the amounts of trace elements volatilized from shallow magma, deep magma, and wall rock, and (2) the solids that precipitate from the gas upon cooling. The predictions are tested by comparing them with the measured trace-element concentrations in gases and the observed sublimate sequence. This leads to the following conclusions: (1) most of the trace elements in the Mt. St. Helens gases are volatilized from shallow magma as simple chlorides; (2) some elements (for example, Al, Ca) exist dominantly in rock aerosols, not gases, in the gas stream; (3) near-surface cooling of the gases triggers precipitation of oxides, sulfides, halides, tungstates, and native elements; and (4) equilibrium cooling of the gases to 100[degrees]C causes most trace elements, except for Hg, Sb, and Se, to precipitate from the gas. 94 refs., 30 figs., 7 tabs.

  11. The space transportation main engine phase A' study

    NASA Technical Reports Server (NTRS)

    1987-01-01

    The Space Transportation Main Engine Phase A prime study was conducted over a 7 month period as an extension to the Phase A study. The Phase A prime program was designed to expand the study effort completed in Phase A, focusing on the baseline engine configuration selected. Analysis and trade studies were conducted to further optimize some of the major engine subsystems. These changes resulted in improvements to the baseline engine. Several options were evaluated for consideration by vehicle contractors.

  12. Studying Three-Phase Supply in School

    ERIC Educational Resources Information Center

    Singhal, Amit Kumar; Arun, P.

    2009-01-01

    The power distributions of nearly all major countries have accepted three-phase distribution as a standard. With increasing power requirements of instrumentation today even a small physics laboratory requires a three-phase supply. While physics students are given an introduction to this in passing, no experimental work is done with three-phase…

  13. 21 CFR 312.85 - Phase 4 studies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 5 2010-04-01 2010-04-01 false Phase 4 studies. 312.85 Section 312.85 Food and...-debilitating Illnesses § 312.85 Phase 4 studies. Concurrent with marketing approval, FDA may seek agreement from the sponsor to conduct certain postmarketing (phase 4) studies to delineate additional...

  14. 21 CFR 312.85 - Phase 4 studies.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 5 2011-04-01 2011-04-01 false Phase 4 studies. 312.85 Section 312.85 Food and...-debilitating Illnesses § 312.85 Phase 4 studies. Concurrent with marketing approval, FDA may seek agreement from the sponsor to conduct certain postmarketing (phase 4) studies to delineate additional...

  15. Three-dimensional equilibria in axially symmetric tokamaks.

    PubMed

    Garabedian, Paul R

    2006-12-19

    The NSTAB and TRAN computer codes have been developed to study equilibrium, stability, and transport in fusion plasmas with three-dimensional (3D) geometry. The numerical method that is applied calculates islands in tokamaks like the Doublet III-D at General Atomic and the International Thermonuclear Experimental Reactor. When bifurcated 3D solutions are used in Monte Carlo computations of the energy confinement time, a realistic simulation of transport is obtained. The significance of finding many 3D magnetohydrodynamic equilibria in axially symmetric tokamaks needs attention because their cumulative effect may contribute to the prompt loss of alpha particles or to crashes and disruptions that are observed. The 3D theory predicts good performance for stellarators. PMID:17159158

  16. Three-dimensional equilibria in axially symmetric tokamaks

    PubMed Central

    Garabedian, Paul R.

    2006-01-01

    The NSTAB and TRAN computer codes have been developed to study equilibrium, stability, and transport in fusion plasmas with three-dimensional (3D) geometry. The numerical method that is applied calculates islands in tokamaks like the Doublet III-D at General Atomic and the International Thermonuclear Experimental Reactor. When bifurcated 3D solutions are used in Monte Carlo computations of the energy confinement time, a realistic simulation of transport is obtained. The significance of finding many 3D magnetohydrodynamic equilibria in axially symmetric tokamaks needs attention because their cumulative effect may contribute to the prompt loss of α particles or to crashes and disruptions that are observed. The 3D theory predicts good performance for stellarators. PMID:17159158

  17. Efficiently Finding Trends in Macroscopic MHD Stability Using Perturbed Equilibria

    NASA Astrophysics Data System (ADS)

    Comer, K. J.; Callen, J. D.; Hegna, C. C.; Turnbull, A. D.; Cowley, S. C.

    2001-10-01

    The effects of equilibrium shaping and profiles on long wavelength ideal MHD instabilities in toroidal plasmas are traditionally studied using numerical parameter scans. Previously, we introduced a new perturbative technique to explore these dependencies: assuming small equilibrium variations, new stability properties are found using a perturbation of the energy principle rather than with a traditional stability code. With this approach, stability dependencies can be efficiently examined without numerically generating complete MHD stability results for every set of parameters (which can be time-intensive for accurate representations of several configurations). Here, we briefly expand on previous successful perturbed stability analyses for screw pinch equilibria by discussing cases where the approach fails. Next, we extend the approach to toroidal geometry using the GATO and TOQ codes, and present cases that both validate the approach and suggest caution in its application.

  18. Multi-rotor internal rotations and conformational equilibria in oxiraneethanol and assignment of its vibrational spectra

    NASA Astrophysics Data System (ADS)

    Badawi, Hassan M.; Ali, Shaikh A.

    2009-09-01

    The complex internal rotations and conformational equilibria in oxiraneethanol were investigated at the DFT-B3LYP/6-311G** level of theory. Four minima were predicted in the CCOH potential energy scans of the molecule to have relative energies of about 2 kcal/mol or less and all were calculated to have real frequencies upon full optimization of structural parameters and the calculation of the Gibb's free-energies at the DFT level of calculation. At the DFT-B3LYP, the MP2 and the MP4(SDQ) levels of theory, the G1gg1 conformation, predicted to be the lowest energy conformation for oxiraneethanol, was in excellent agreement with the rotational microwave study. The equilibrium mixture was calculated to be about 47% G1gg1, 32% Cg1g, 15% Gg1t and 6% G1g1g at the B3LYP/6-311G** level of theory at 298.15 K. Solvent study corroborated the presence of the high energy Cg1g form in the liquid phase of oxiraneethanol. The vibrational frequencies of oxiraneethanol in its two stable forms were computed at the B3LYP level and vibrational assignments were made for the two lowest energy G1gg1 and Cg1g forms on the basis of calculated and experimental data of the molecule.

  19. A molecular-thermodynamic framework for asphaltene-oil equilibria

    SciTech Connect

    Wu, J.; Prausnitz, J.M. |; Firoozabadi, A.

    1997-02-01

    Asphaltene precipitation is a perennial problem in production and refinery of crude oils. To avoid precipitation, it is useful to predict the solubility of asphaltenes in petroleum liquids as a function of temperature, pressure and liquid-phase composition. In the molecular-thermodynamic model presented here, both asphaltenes and resins are represented by pseudo-pure components, and all other components in the solution are represented by a continuous medium which affects interactions among asphaltene and resin particles. The effect of the medium on asphaltene-asphaltene, resin-asphaltene, resin-resin pair interactions is taken into account through its density and molecular-dispersion properties. To obtain expressions for the chemical potential of asphaltene and for the osmotic pressure of an asphaltene-containing solution, the authors use the integral theory of fluids coupled with the SAFT model to allow for asphaltene aggregation and for adsorption of resin on asphaltene particles. With these expressions, a variety of experimental observations can be explained including the effects of temperature, pressure and composition on the phase behavior of asphaltene-containing fluids. For engineering application, the molecular parameters in this model must be correlated to some macroproperties of oil such as density and molecular weight. When such correlations are established, it will be possible to calculate asphaltene-precipitation equilibria at a variety of conditions for realistic systems.

  20. Effect of long-range interactions on ion equilibria in liquid-liquid extraction

    NASA Astrophysics Data System (ADS)

    Dufrêche, J.-F.; Zemb, Th.

    2015-02-01

    We demonstrate here that equilibria of electrolytes between a water phase and an (organic) solvent phase containing amphiphilic extractants depend not only on complexation toward nearest neighbors but also on long range supramolecular interactions (LRI). Taking into account bulk, polarization and chain reorganization terms, we show that the net free energy difference associated with one metal ion transfer from water results from a strong inhibition (>25 kBT/ metal ion) due to colloidal long range interactions competing with differences in complexation considered in surpramolecular chemistry (≈-30 kBT/ metal ion). LRI also influence selectivity.

  1. TOKAMAK EQUILIBRIA WITH CENTRAL CURRENT HOLES AND NEGATIVE CURRENT DRIVE

    SciTech Connect

    CHU, M.S.; PARKS, P.B.

    2002-06-01

    OAK B202 TOKAMAK EQUILIBRIA WITH CENTRAL CURRENT HOLES AND NEGATIVE CURRENT DRIVE. Several tokamak experiments have reported the development of a central region with vanishing currents (the current hole). Straightforward application of results from the work of Greene, Johnson and Weimer [Phys. Fluids, 3, 67 (1971)] on tokamak equilibrium to these plasmas leads to apparent singularities in several physical quantities including the Shafranov shift and casts doubts on the existence of this type of equilibria. In this paper, the above quoted equilibrium theory is re-examined and extended to include equilibria with a current hole. It is shown that singularities can be circumvented and that equilibria with a central current hole do satisfy the magnetohydrodynamic equilibrium condition with regular behavior for all the physical quantities and do not lead to infinitely large Shafranov shifts. Isolated equilibria with negative current in the central region could exist. But equilibria with negative currents in general do not have neighboring equilibria and thus cannot have experimental realization, i.e. no negative currents can be driven in the central region.

  2. Subsolidus phase equilibria and properties in the system Bi{sub 2}O{sub 3}:Mn{sub 2}O{sub 3+}/-{sub x}:Nb{sub 2}O{sub 5}

    SciTech Connect

    Vanderah, T.A. . E-mail: terrell.vanderah@nist.gov; Lufaso, M.W.; Adler, A.U.; Levin, I.; Nino, J.C.; Provenzano, V.; Schenck, P.K.

    2006-11-15

    Subsolidus phase relations have been determined for the Bi-Mn-Nb-O system in air (750-900deg. C). Phases containing Mn{sup 2+}, Mn{sup 3+}, and Mn{sup 4+} were all observed. Ternary compound formation was limited to pyrochlore (A{sub 2}B{sub 2}O{sub 6}O'), which formed a substantial solid solution region at Bi-deficient stoichiometries (relative to Bi{sub 2}(Mn,Nb){sub 2}O{sub 7}) suggesting that {approx}14-30% of the A-sites are occupied by Mn (likely Mn{sup 2+}). X-ray powder diffraction data confirmed that all Bi-Mn-Nb-O pyrochlores form with structural displacements, as found for the analogous pyrochlores with Mn replaced by Zn, Fe, or Co. A structural refinement of the pyrochlore 0.4000:0.3000:0.3000 Bi{sub 2}O{sub 3}:Mn{sub 2}O{sub 3+}/-{sub x}:Nb{sub 2}O{sub 5} using neutron powder diffraction data is reported with the A and O' atoms displaced (0.36 and 0.33A, respectively) from ideal positions to 96g sites, and with Mn{sup 2+} on A-sites and Mn{sup 3+} on B-sites (Bi{sub 1.6}Mn{sup 2+}{sub 0.4}(Mn{sup 3+}{sub 0.8}Nb{sub 1.2})O{sub 7}, Fd3-bar m (-bar 227), a=10.478(1)A); evidence of A or O' vacancies was not found. The displacive disorder is crystallographically analogous to that reported for Bi{sub 1.5}Zn{sub 0.92}Nb{sub 1.5}O{sub 6.92}, which has a similar concentration of small B-type ions on the A-sites. EELS spectra for this pyrochlore were consistent with an Mn oxidation between 2+ and 3+. Bi-Mn-Nb-O pyrochlores exhibited overall paramagnetic behavior with negative Curie-Weiss temperature intercepts, slight superparamagnetic effects, and depressed observed moments compared to high-spin, spin-only values. At 300K and 1MHz the relative dielectric permittivity of Bi{sub 1.600}Mn{sub 1.200}Nb{sub 1.200}O{sub 7} was {approx}128 with tan {delta}=0.05; however, at lower frequencies the sample was conductive which is consistent with the presence of mixed-valent Mn. Low-temperature dielectric relaxation such as that observed for Bi{sub 1.5}Zn{sub 0.92}Nb{sub 1

  3. Intelligent Robotic Systems Study (IRSS), phase 3

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This phase of the Intelligent Robotic Systems Study (IRSS) examines some basic dynamics and control issues for a space manipulator attached to its worksite through a compliant base. One example of this scenario is depicted, which is a simplified, planar representation of the Flight Telerobotic Servicer (FTS) Development Test Flight 2 (DTF-2) experiment. The system consists of 4 major components: (1) dual FTS arms to perform dextrous tasks; (2) the main body to house power and electronics; (3) an Attachment Stabilization and Positioning Subsystem (ASPS) to provide coarse positioning and stabilization of the arms, and (4) the Worksite Attachment Mechanism (WAM) which anchors the system to its worksite, such as a Space Station truss node or Shuttle bay platform. The analysis is limited to the DTF-2 scenario. The goal is to understand the basic interaction dynamics between the arm, the positioner and/or stabilizer, and the worksite. The dynamics and controls simulation model are described. Analysis and simulation results are presented.

  4. Vapor-liquid equilibria for the systems difluoromethane + hydrogen fluoride, dichlorodifluoromethane + hydrogen fluoride, and chlorine + hydrogen fluoride

    SciTech Connect

    Kang, Y.W.

    1998-01-01

    Isothermal vapor-liquid equilibria for difluoromethane + hydrogen fluoride, dichlorodifluoromethane + hydrogen fluoride, and chlorine + hydrogen fluoride have been measured. The experimental data for the binary systems are correlated with the NRTL equation with the vapor-phase association model for the mixtures containing hydrogen fluoride, and the relevant parameters are presented. The binary system difluoromethane + hydrogen fluoride forms a homogeneous liquid phase, and the others form minimum boiling heterogeneous azeotropes at the experimental conditions.

  5. Two-phase flow studies. Final report

    SciTech Connect

    Kestin, J.; Maeder, P.F.

    1980-08-01

    Progress on the following is reported: literature survey, design of two-phase flow testing facility, design of nozzle loop, thermophysical properties, design manual, and advanced energy conversion systems. (MHR)

  6. Vapor-liquid phase separator studies

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Lee, J. M.; Kim, Y. I.; Hepler, W. A.; Frederking, T. H. K.

    1983-01-01

    Porous plugs serve as both entropy rejection devices and phase separation components separating the vapor phase on the downstream side from liquid Helium 2 upstream. The liquid upstream is the cryo-reservoir fluid needed for equipment cooling by means of Helium 2, i.e Helium-4 below its lambda temperature in near-saturated states. The topics outlined are characteristic lengths, transport equations and plug results.

  7. Formalism for multi-fluid equilibria with flow

    SciTech Connect

    Steinhauer, L.C.

    1999-07-01

    A formalism is developed for flowing multifluid equilibria. In the standard reduced case (massless electrons, quasineutrality) this system simplifies to a pair of second-order partial differential equations for the magnetic and ion flow stream functions plus a Bernoulli equation giving the density. Each species has its own characteristic surfaces, which are the drift surfaces, and three arbitrary surface functions associated with each species. In the case of minimum energy equilibria, the surface functions are no longer arbitrary. The flowing equilibrium system is a generalization of the familiar Grad{endash}Shafranov system for magnetostatic equilibria. {copyright} {ital 1999 American Institute of Physics.}

  8. Following the equilibria of slender elastic rods

    NASA Astrophysics Data System (ADS)

    Lazarus, Arnaud; Miller, James; Reis, Pedro

    2012-02-01

    We present a novel continuation method to characterize and quantify the equilibria of elastic rods under large geometrically nonlinear displacements and rotations. To describe the kinematics we exploit the synthetic power and computational efficiency of quaternions. The energetics of bending, stretching and torsion are all taken into account to derive the equilibrium equations which we solve using an asymptotic numerical continuation method. This provides access to the full set of analytical equilibrium branches (stable and unstable), a.k.a bifurcation diagrams. This is in contrast with the individual solution points attained by classic energy minimization or predictor-corrector techniques. We challenge our numerics for the specific problem of an extremely twisted naturally curved rod and perform a detailed comparison against a precision desktop-scale experiments. The quantification of the underlying 3D buckling instabilities and the characterization of the resulting complex configurations are in excellent agreement between numerics and experiments.

  9. Magnetic equilibria for X-Diverted plasmas

    NASA Astrophysics Data System (ADS)

    Pekker, M.; Valanju, P.; Kotschenreuther, M.; Wiley, J.; Mahajan, S.

    2006-10-01

    The X-divertor has been proposed to solve heat exhaust problems for reactors beyond ITER. By generating an extra X-point downstream from the main X-point, the X-divertor greatly expands magnetic flux at the divertor plates. As a result, the heat is distributed over a larger area and the line length is greatly increased. We have developed coil sets for X-diverted magnetic equilibria for many devices (NSTX, PEGASUS, EAST, HL-2A, CREST, and a CTF). These demonstrate that the XD configuration can be created for highly shaped plasmas using moderate coil currents. For reactors, all coils can be placed behind 1 m of shielding. We have also shown that XD configurations are robust to modest plasma perturbations and VDEs; this is in contrast to the sensitivity of highly tilted divertor plates.

  10. Two-Phase Calorimetry. II. Studies on the Thermodynamics of Cesium and Strontium Extraction by Mixtures of H+CCD- and PEG-400 in FS-13

    SciTech Connect

    Zalupski, Peter R.; Herbst, R. S.; Delmau, Laetitia Helene; Martin, L. R.; Peterman, D. R.; Nash, Ken L

    2010-01-01

    Thermochemical characterization of the partitioning of cesium and strontium from nitric acid solutions into mixtures of the acid form of chlorinated cobalt dicarbollide (H+CCD-) and polyethylene glycol (PEG-400) in FS-13 diluent has been completed using isothermal titration microcalorimetry and radiotracer distribution methods. The phase transfer reaction for Cs+ is a straightforward (H+ for Cs+) cation exchange reaction. In contrast, the extraction of Sr2+ does not proceed in the absence of the co-solvent molecule PEG-400. This molecule is believed to facilitate the dehydration of the Sr2+ aquo cation to overcome its resistance to partitioning. The phase transfer reactions for both Cs+ and Sr2+ are enthalpy driven (exothermic), but partially compensated by an unfavorable entropy. The results of the calorimetry studies suggest that the PEG-400 functions as a stoichiometric phase transfer reagent rather than acting simply as a phase transfer catalyst or phase modifier. The calorimetry results also demonstrate that the extraction of Sr2+ is complex, including evidence for both the partitioning of Sr(NO3)+ and endothermic ion pairing interactions in the organic phase that contribute to the net enthalpic effect. The thermodynamics of the liquid-liquid distribution equilibria are discussed mainly considering the basic features of the ion solvation thermochemistry.

  11. Conceptual design study for a teleoperator visual system, phase 1

    NASA Technical Reports Server (NTRS)

    Adams, D.; Grant, C.; Johnson, C.; Meirick, R.; Polhemus, C.; Ray, A.; Rittenhouse, D.; Skidmore, R.

    1972-01-01

    Results are reported for work performed during the first phase of the conceptual design study for a teleoperator visual system. This phase consists of four tasks: General requirements, concept development, subsystem requirements and analysis, and concept evaluation.

  12. Vapor-liquid equilibria for alcohol + alcohol + sodium iodide at 298.15 K

    SciTech Connect

    Yamamoto, H.; Fukase, K.; Shibata, J.

    1996-09-01

    Estimation and correlation of phase equilibria data in chemical engineering are indispensable for the design of equilibrium separation processes. If a salt, being completely nonvolatile, is added to the solvent mixture, the relative volatility generally changes; this is known as the salting-in or -out effect on vapor-liquid equilibria. Vapor-liquid equilibria for methanol + propan-1-ol + NaI, methanol + propan-2-ol + NaI, ethanol + propan-1-ol + NaI, and ethanol + propan-2-ol + NaI systems were measured at 298.15 K using a static method. The apparatus was tested by comparing results for ethanol + water and ethanol + water + CaCl{sub 2} with literature results. Results were tested for thermodynamic consistency by Herinton`s area test and point test. NaI exerted a salting-in effect on all binary alcohol solutions and the order of the salt effect of NaI was methanol + ethanol < ethanol + propan-1-ol < ethanol + propan-2-ol < methanol + propan-1-ol < methanol + propan-2-ol. Hala`s model was applied for the correlation of four alcohol + alcohol + salt systems using observed data. Calculated {beta} values in Hala`s equation were between 2.8 and 3.9 for the four alcohol + alcohol + NaI systems.

  13. DETERMINATION OF SOLID-LIQUID EQUILIBRIA DATA FOR MIXTURES OF HEAVY HYDROCARBONS IN A LIGHT SOLVENT

    SciTech Connect

    F.V. Hanson; J.V. Fletcher; Karthik R.

    2003-06-01

    A methodology was developed using an FT-IR spectroscopic technique to obtain solid-liquid equilibria (SLE) data for mixtures of heavy hydrocarbons in significantly lighter hydrocarbon diluents. SLE was examined in multiple Model Oils that were assembled to simulate waxes. The various Model oils were comprised of C-30 to C-44 hydrocarbons in decane. The FT-IR technique was used to identify the wax precipitation temperature (WPT). The DSC technique was also used in the identification of the onset of the two-phase equilibrium in this work. An additional Model oil made up of C-20 to C-30 hydrocarbons in decane was studied using the DSC experiment. The weight percent solid below the WPT was calculated using the FT-IR experimental results. The WPT and the weight percent solid below the WPT were predicted using an activity coefficient based thermodynamic model. The FT-IR spectroscopy method is found to successfully provide SLE data and also has several advantages over other laboratory-based methods.

  14. Recent advances in the study of the UO2-PuO2 phase diagram at high temperatures

    NASA Astrophysics Data System (ADS)

    Böhler, R.; Welland, M. J.; Prieur, D.; Cakir, P.; Vitova, T.; Pruessmann, T.; Pidchenko, I.; Hennig, C.; Guéneau, C.; Konings, R. J. M.; Manara, D.

    2014-05-01

    Recently, novel container-less laser heating experimental data have been published on the melting behaviour of pure PuO2 and PuO2-rich compositions in the uranium dioxide-plutonium dioxide system. Such data showed that previous data obtained by more traditional furnace heating techniques were affected by extensive interaction between the sample and its containment. It is therefore paramount to check whether data so far used by nuclear engineers for the uranium-rich side of the pseudo-binary dioxide system can be confirmed or not. In the present work, new data are presented both in the UO2-rich part of the phase diagram, most interesting for the uranium-plutonium dioxide based nuclear fuel safety, and in the PuO2 side. The new results confirm earlier furnace heating data in the uranium-dioxide rich part of the phase diagram, and more recent laser-heating data in the plutonium-dioxide side of the system. As a consequence, it is also confirmed that a minimum melting point must exist in the UO2-PuO2 system, at a composition between x(PuO2) = 0.4 and x(PuO2) = 0.7 and 2900 K ⩽ T ⩽ 3000 K. Taking into account that, especially at high temperature, oxygen chemistry has an effect on the reported phase boundary uncertainties, the current results should be projected in the ternary U-Pu-O system. This aspect has been extensively studied here by X-ray diffraction and X-ray absorption spectroscopy. The current results suggest that uncertainty bands related to oxygen behaviour in the equilibria between condensed phases and gas should not significantly affect the qualitative trend of the current solid-liquid phase boundaries.

  15. Integrated design of electrical distribution systems: Phase balancing and phase prediction case studies

    NASA Astrophysics Data System (ADS)

    Dilek, Murat

    Distribution system analysis and design has experienced a gradual development over the past three decades. The once loosely assembled and largely ad hoc procedures have been progressing toward being well-organized. The increasing power of computers now allows for managing the large volumes of data and other obstacles inherent to distribution system studies. A variety of sophisticated optimization methods, which were impossible to conduct in the past, have been developed and successfully applied to distribution systems. Among the many procedures that deal with making decisions about the state and better operation of a distribution system, two decision support procedures will be addressed in this study: phase balancing and phase prediction. The former recommends re-phasing of single- and double-phase laterals in a radial distribution system in order to improve circuit loss while also maintaining/improving imbalances at various balance point locations. Phase balancing calculations are based on circuit loss information and current magnitudes that are calculated from a power flow solution. The phase balancing algorithm is designed to handle time-varying loads when evaluating phase moves that will result in improved circuit losses over all load points. Applied to radial distribution systems, the phase prediction algorithm attempts to predict the phases of single- and/or double phase laterals that have no phasing information previously recorded by the electric utility. In such an attempt, it uses available customer data and kW/kVar measurements taken at various locations in the system. It is shown that phase balancing is a special case of phase prediction. Building on the phase balancing and phase prediction design studies, this work introduces the concept of integrated design, an approach for coordinating the effects of various design calculations. Integrated design considers using results of multiple design applications rather than employing a single application for a

  16. Phase structure of a single urban intersection: a simulation study

    NASA Astrophysics Data System (ADS)

    Ebrahim Foulaadvand, M.; Fukui, M.; Belbasi, S.

    2010-07-01

    We study the phase structure of a cellular automata model proposed by Belbasi and Foulaadvand to describe the vehicular traffic flow at the intersection of two perpendicular streets. A set of traffic lights operating in a fixed-time scheme controls the traffic flow. A closed boundary condition is applied to the streets, each of which conducts a unidirectional flow. Streets are single-lane and cars cannot turn upon reaching the intersection. Via extensive Monte Carlo simulations it is shown that the model phase diagram consists of ten phases. The flow characteristics in each phase are investigated and the types of phase transitions between phases are specified.

  17. EPA GAS PHASE CHEMISTRY CHAMBER STUDIES

    EPA Science Inventory

    Gas-phase smog chamber experiments are being performed at EPA in order to evaluate a number of current chemical mechanisms for inclusion in EPA regulatory and research models. The smog chambers are 9000 L in volume and constructed of 2-mil teflon film. One of the chambers is co...

  18. Quaternary liquid/liquid equilibria of sodium sulfate, sodium sulfite and water with two solvents: Acetone and 2-propanol

    SciTech Connect

    Schiozer, A.L.

    1994-03-01

    Aqueous solutions of sodium sulfate and sodium sulfite are produced from sodium carbonate in flue-gas scrubbers; recovery of these salts often requires multi-effect evaporators; however, a new energy-efficient unit operation called extractive crystallization has been shown to have reduced energy costs. In this process, an organic solvent is added to the aqueous salt solution to precipitate salt. Acetone is a suitable solvent for this process, better than 2-propanol. Liquid/liquid/solid equilibria for ternary systems containing a salt, water, and an organic solvent were measured. Systems investigated were sodium sulfite/water/acetone and sodium sulfite/water/2-propanol. Experiments were conducted at salt saturation covering a temperature range between the lower consolute temperature and 48.6{degrees}C. In the attempt to improve the extractive crystallization process for recovery of sodium sulfate from flue-gas scrubbers, attention was given to a feed containing a mixture of sodium sulfite and sodium sulfate. Liquid-liquid equilibria for quaternary systems containing two salts, water, and an organic solvent were experimentally determined at 35{degrees}C. The systems investigated were sodium sulfate/sodium sulfite/water/acetone and sodium sulfate/sodium sulfite/water/2propanol. The systems were studied at three salt ratios. For each salt ratio, experiments were conducted starting at saturation, water was then added until the one-phase region was reached. Mixtures of the two salts proved to have a small disadvantage relative to the 100 % sulfate feed process. Therefore, a sulfate-based extractive crystallization process is recommended.

  19. The freedom to choose neutron star magnetic field equilibria

    NASA Astrophysics Data System (ADS)

    Glampedakis, Kostas; Lasky, Paul D.

    2016-08-01

    Our ability to interpret and glean useful information from the large body of observations of strongly magnetised neutron stars rests largely on our theoretical understanding of magnetic field equilibria. We answer the following question: is one free to arbitrarily prescribe magnetic equilibria such that fluid degrees of freedom can balance the equilibrium equations? We examine this question for various models for neutron star matter; from the simplest single-fluid barotrope to more realistic non-barotropic multifluid models with superfluid/superconducting components, muons and entropy. We do this for both axi- and non-axisymmetric equilibria, and in Newtonian gravity and general relativity. We show that, in axisymmetry, the most realistic model allows complete freedom in choosing a magnetic field equilibrium whereas non-axisymmetric equilibria are never completely arbitrary.

  20. Molecular equilibria and condensation sequences in carbon rich gases

    NASA Technical Reports Server (NTRS)

    Sharp, C. M.; Wasserburg, G. J.

    1993-01-01

    Chemical equilibria in stellar atmospheres have been investigated by many authors. Lattimer, Schramm, and Grossman presented calculations in both O rich and C rich environments and predicted possible presolar condensates. A recent paper by Cherchneff and Barker considered a C rich composition with PAH's included in the calculations. However, the condensation sequences of C bearing species have not been investigated in detail. In a carbon rich gas surrounding an AGB star, it is often assumed that graphite (or diamond) condenses out before TiC and SiC. However, Lattimer et al. found some conditions under which TiC condenses before graphite. We have performed molecular equilibrium calculations to establish the stability fields of C(s), TiC(s), and SiC(s) and other high temperature phases under conditions of different pressures and C/O. The preserved presolar interstellar dust grains so far discovered in meteorites are graphite, diamond, SiC, TiC, and possibly Al2O3.

  1. Building Enclosure Hygrothermal Performance Study, Phase 1

    SciTech Connect

    Karagiozis, A.N.

    2002-08-08

    The moisture performance of three different classes of wall systems has been investigated in the context of the preliminary hygrothermal analysis of walls in Seattle. The results reported in this phase specifically address the moisture performance of walls designed with loads that have some unintentional water penetration. The results have been developed in a manner to present the relative performance of the walls in the same climate with similar water penetration effects. The analysis was performed with the best available input data. Several limitations should be recognized within the context of this study. Results showed that selection of wooden sheathing boards on interior vapor-tight assemblies does not significantly influence the performance of stucco-clad walls. A larger effect was observed when the interior vapor control is made vapor open. When continuous cavity ventilation is employed, the effect of the selection of the type of sheathing board on the hygrothermal performance of the wall was found to be negligible. When comparing oriented strand board sheathing performance against the performance of exterior grade gypsum, the differences are very significant in terms of the amount of moisture content present in the walls. Moisture content alone does not indicate their respective durability as durability is directly related to the combination of relative humidity and temperature, mechanical, chemical, and biological properties of the substrates. This study did not investigate the durability performance of either sheathing. In terms of interior vapor control, inhabitant behavior must be considered during the wall hygrothermal design stage. If interior relative humidity is maintained below 60%, then a latex primer and paint may perform better than the use of PVA or even a polyethylene sheet. When the interior environment is maintained at a higher relative humidity, then stricter vapor control is needed. Multilayered building paper was experimentally shown to

  2. MOLECULAR SIMULATION OF PHASE EQUILIBRIA FOR COMPLEX FLUIDS

    SciTech Connect

    Athanassios Z. Panagiotopoulos

    2009-09-09

    The general area of this project was the development and application of novel molecular simulation methods for prediction of thermodynamic and structural properties of complex polymeric, surfactant and ionic fluids. Over this project period, we have made considerable progress in developing novel algorithms to meet the computational challenges presented by the strong or long-range interactions in these systems and have generated data for well-defined mod-els that can be used to test theories and compare to experimental data. Overall, 42 archival papers and many invited and contributed presentations and lectures have been based on work supported by this project. 6 PhD, 1 M.S. and 2 postdoctoral students have been associated with this work, as listed in the body of the report.

  3. Phase equilibria in systems of formates with isobutyl alcohol

    SciTech Connect

    Seselkin, I.V.; Garber, Y.N.; Mironenko, V.F.

    1985-09-01

    The borate method, based on esterification with boric acid, was proposed for isolation of isobutyl alchohol. The method inv olves formation and hydrolysis of alkyl borate esters; in particular, formation and hydrolysis of triisobutyl borate. Esterification of isobutyl alcohol with boric acid is a reversible equilibrium reaction, and therefore in order to obtain high yields the water formed in the reaction must be removed. The presence of other organic compounds, which do not react with boric acid, in the mixture does not affect esterification of the alcohol. The reaction proceeds at 95-100/sup 0/ under atmospheric pressure. It was found that up to 97% of the isobutyl alcohol combines with boric acid. The resultant triisobutyl borate is isolated by ordinary distillation and then hydrolyzed to form boric acid and isobutyl alcohol.

  4. A phase-field model for the solidification of multicomponent and multiphase alloys

    NASA Astrophysics Data System (ADS)

    Qin, R. S.; Wallach, E. R.; Thomson, R. C.

    2005-05-01

    A phase-field model for the simulation of solidification of a multicomponent and multiphase systems has been developed, which is based on an earlier developed multiphase field model for binary alloys and a phase-field multicomponent model for single-solid-phase systems. After incorporation with alloy thermodynamics and commercial software for the calculation of phase equilibria, the model has been implemented to study the microstructural evolution of an Al-11.5 mol% Si-0.9 mol% Cu-0.4 mol% Fe alloy. Numerical results for the morphological evolution of primary aluminium, silicon and AlFeSi intermetallic phases agree with experimental observations very well.

  5. Linear Stability of Equilibria of a Fluid that is a Nonconductor of Heat

    NASA Astrophysics Data System (ADS)

    Yudovich, V. I.

    1995-02-01

    Convective stability is studied in the linear approximation of equilibria of a strongly viscous fluid that is a nonconductor of heat where the fluid fills a bounded domain in a gravitational field. The corresponding system consists of the heat equation with transport in a velocity field and the steady-state Stokes system for the velocity and pressure. The latter includes an Archimedean force proportional to the temperature.It is proved that equilibria for which the temperature strictly increases upward are stable in L_2 with respect to the temperature and in W_2^2 with respect to the velocity. Here, however, perturbations may die out arbitrarily slowly (Banach-Steinhaus stability). Under rough violation of the condition of monotonicity of the temperature the equilibrium is unstable.Some critical cases of stability are also considered.Bibliography: 13 titles.

  6. Equilibria, stability and Hamiltonian Hopf bifurcation of a gyrostat in an incompressible ideal fluid

    NASA Astrophysics Data System (ADS)

    Guirao, Juan L. G.; Vera, Juan A.

    2012-10-01

    For a gyrostat in a incompressible ideal fluid, by writing Kirchhoff’s equations as a Lie-Poisson system and using a non-canonical Hamiltonian formulation, we provide the expressions of the equilibria when the gyrostatic momentum is constant with the form l=(0,0,l) and present necessary and sufficient conditions for the stability of some of them via the energy-Casimir method and the study of the linearized equations of the motion. Finally, using a recent geometric method introduced by Hanssmann and Van der Meer, we give a sufficient condition for the existence of a non-degenerate Hamiltonian Hopf bifurcation at those equilibria when the gyrostat is symmetric.

  7. Phase stability in the Cd-Mg system

    SciTech Connect

    Asta, M.; McCormack, R.; de Fontaine, D.

    1993-12-31

    This paper reports on results of a theoretical study of solid-state phase equilibria and short-range order in Cd-Mg alloys. Results of first-principles linear muffin-tin orbital method total-energy calculations for seven hcp-based superstructures have been combined with cluster-variation-method calculations of thermodynamic properties in order to compute the Cd-Mg phase diagram. Effect on the calculated phase diagram of contributions to the alloy free energy arising from atomic vibrations and structural relaxations are assessed using available experimental information for ordered and disordered alloys in the Cd-Mg system.

  8. Tokamak equilibria and edge stability when non-axisymmetric fields are applied

    NASA Astrophysics Data System (ADS)

    Ham, C. J.; Chapman, I. T.; Simpson, J.; Suzuki, Y.

    2015-05-01

    Tokamaks are traditionally viewed as axisymmetric devices. However this is not always true, for example in the presence of saturated instabilities, error fields, or resonant magnetic perturbations (RMPs) applied for edge localized mode (ELM) control. We use the VMEC code (Hirshman and Whitson 1983 Phys. Fluids 26 3553) to calculate three dimensional equilibria by energy minimization for tokamak plasmas. MAST free boundary equilibria have been calculated with profiles for plasma pressure and current derived from two dimensional reconstruction. It is well known that ELMs will need to be controlled in ITER to prevent damage that may limit the lifetime of the machine (Loarte et al 2003 Plasma Phys. Control. Fusion 45 1549). ELM control has been demonstrated on several tokamaks including MAST (Kirk et al 2013 Nucl. Fusion 53 043007). However the application of RMPs causes the plasma to gain a displacement or corrugation (Liu et al 2011 Nucl. Fusion 51 083002). Previous work has shown that the phase and size of these corrugations is in agreement with experiment (Chapman et al 2012 Plasma Phys. Control. Fusion 54 105013). The interaction of these corrugations with the plasma control system (PCS) may cause high heat loads at certain toroidal locations if care is not taken (Chapman et al 2014 Plasma Phys. Control. Fusion 56 075004). VMEC assumes nested flux surfaces but this assumption has been relaxed in other stellarator codes. These codes allow equilibria where magnetic islands and stochastic regions can form. We show some initial results using the HINT2 code (Suzuki et al 2006 Nucl. Fusion 46 L19). The Mercier stability of VMEC equilibria with RMPs applied is calculated. The geodesic curvature contribution can be strongly influenced by helical Pfirsch-Schlüter currents driven by the applied RMPs. ELM mitigation is not fully understood but one of the factors that influences peeling-ballooning stability, which is linked to ELMs, is a three dimensional corrugation of the

  9. Phase relations in the system NaCl-KCl-H2O: IV. Differential thermal analysis of the sylvite liquidus in the KCl-H2O binary, the liquidus in the NaCl-KCl-H2O ternary, and the solidus in the NaCl-KCl binary to 2 kb pressure, and a summary of experimental data for thermodynamic-PTX analysis of solid-liquid equilibria at elevated P-T conditions

    USGS Publications Warehouse

    Chou, I.-Ming; Sterner, S.M.; Pitzer, Kenneth S.

    1992-01-01

    The sylvite liquidus in the binary system KCl-H2O and the liquidus in the ternary system NaCl-KCl-H2O were determined by using isobaric differential thermal analysis (DTA) cooling scans at pressures up to 2 kbars. Sylvite solubilities along the three-phase curve in the binary system KCl-H2O were obtained by the intersection of sylvite-liquidus isopleths with the three-phase curve in a P-T plot. These solubility data can be represented by the equation Wt.% KCl (??0.2) = 12.19 + 0.1557T - 5.4071 ?? 10-5 T2, where 400 ??? T ??? 770??C. These data are consistent with previous experimental observations. The solidus in the binary system NaCl-KCl was determined by using isobaric DTA heating scans at pressures up to 2 kbars. Using these liquidus and solidus data and other published information, a thermodynamic-PTX analysis of solid-liquid equilibria at high pressures and temperatures for the ternary system has been performed and is presented in an accompanying paper (Part V of this series). However, all experimental liquidus, solidus, and solvus data used in this analysis are summarized in this report (Part IV) and they are compared with the calculated values based on the analysis. ?? 1992.

  10. Kinetic equilibria of very high- β plasmas

    NASA Astrophysics Data System (ADS)

    Steinhauer, Loren; TAE Team

    2015-11-01

    Plasma equilibria with many large ion orbits, such as an advanced beam-driven field-reversed configuration, are neither static (Grad-Shafranov) nor describable as a flowing, multi-fluid. A fully-kinetic treatment of the ions is essential for such high- β plasmas. A kinetic equilibrium is needed to properly support realistic stability and transport analyses, both of which are strongly affected by large-orbit ions. A hybrid equilibrium model has been developed with a fully-kinetic treatment of both thermal ions and a rapidly-rotating ``beam-ion'' component, such as produced by neutral beam injection, relevant to the C-2U experiments at TAE. It employs analytic Vlasov solutions in that the distribution depends only on the two constants of motion, the Hamiltonian (H) and the canonical angular momentum (Pθ) . Electrons are treated as a pressure-bearing fluid. Since realistic forms of f (H ,Pθ) are affected by collisions, f is limited to solutions of a simplified Fokker-Planck equation. Importantly, a kinetic end-loss condition applies to unconfined ions, using a particle sink at a rate consistent with Monte-Carlo-like simulations of end loss accounting for a strong end mirror.

  11. Tearing Mode Stability of Evolving Toroidal Equilibria

    NASA Astrophysics Data System (ADS)

    Pletzer, A.; McCune, D.; Manickam, J.; Jardin, S. C.

    2000-10-01

    There are a number of toroidal equilibrium (such as JSOLVER, ESC, EFIT, and VMEC) and transport codes (such as TRANSP, BALDUR, and TSC) in our community that utilize differing equilibrium representations. There are also many heating and current drive (LSC and TORRAY), and stability (PEST1-3, GATO, NOVA, MARS, DCON, M3D) codes that require this equilibrium information. In an effort to provide seamless compatibility between the codes that produce and need these equilibria, we have developed two Fortran 90 modules, MEQ and XPLASMA, that serve as common interfaces between these two classes of codes. XPLASMA provides a common equilibrium representation for the heating and current drive applications while MEQ provides common equilibrium and associated metric information needed by MHD stability codes. We illustrate the utility of this approach by presenting results of PEST-3 tearing stability calculations of an NSTX discharge performed on profiles provided by the TRANSP code. Using the MEQ module, the TRANSP equilibrium data are stored in a Fortran 90 derived type and passed to PEST3 as a subroutine argument. All calculations are performed on the fly, as the profiles evolve.

  12. Free-boundary magnetohydrodynamic equilibria with flow

    SciTech Connect

    Schmitt, R. F.; Park, G. Y.; Guazzotto, L.; Strauss, H.; Chang, C.-S.

    2011-02-15

    The finite-element M3D code [W. Park et al., Phys. Plasmas 6, 1796 (1999)] has been modified to include a free-boundary equilibrium solver with arbitrary toroidal and poloidal flows. With this modification, the M3D code now has the capability to self-consistently model two essential ingredients necessary for equilibrium calculations in the edge region, namely, free-boundary and arbitrary flow. As a free-boundary code, M3D includes the separatrix and scrape-off layer regions in the equilibrium calculation. Poloidal flows in the subsonic, supersonic, and transonic regimes can be calculated with the new version of the M3D code. Calculation results show that the presence of equilibrium flows, in particular those next to the plasma boundary, can considerably influence the position of the X-point and magnetic separatrix shape/location and hence the position of the strike point on the divertor plates. Moreover, it is shown that poloidal flow is not a rigid-body rotation, with the fastest flows occurring on the inboard side of the plasma. A numerical confirmation of the ''de Laval nozzle'' model of Betti and Freidberg [R. Betti and J. P. Freidberg, Phys. Plasmas 7, 2439 (2000)] for free-boundary equilibrium calculations is obtained, with the formation of the predicted discontinuities between regions of subsonic and supersonic flows (with respect to the poloidal sound speed). Finally, a detailed comparison between isentropic and isothermal equilibria is presented, showing qualitative analogies and quantitative differences.

  13. Mathematics Achievement, Comparative Study Phase IV IGE Evaluation Project. Phase IV, Project Paper 80-9.

    ERIC Educational Resources Information Center

    Webb, Norman L.; Nerenz, Anne G.

    This is one of a series of reports which provide definitions of and descriptive data on the variables used in the Comparative Study of Phase IV of the Individually Guided Education (IEG) Evaluation Project. Phase IV investigated three curriculum programs specifically designed to be compatible with instructional programming for the individual…

  14. Mechanistic study of organometallic vapor phase epitaxy

    SciTech Connect

    Stringfellow, G.B.

    1990-12-31

    Only AsH{sub 3} and PH{sub 3} have been used as the group V source molecules for organometallic vapor phase epitaxy (OMVPE) of III/V semiconductors until recently, since they have been the only precursors yielding device quality materials. This paper reviews recent work on the pyrolysis of individual organometallic molecules, with emphasis on the group V sources, including: (1) the methylarsines, di- and tri-methylarsine, (2) the ethylarsines, mono-, di-, and tri-ethylarsine, and (3) the singly substituted tertiarybutyl arsine and phosphine molecules. The pyrolysis and growth reactions occurring when both group III and group V precursors are present simultaneously, i.e., the reactions occuring during OMVPE growth of several III/V semiconductors, are also briefly reviewed.

  15. Mechanistic study of organometallic vapor phase epitaxy

    SciTech Connect

    Stringfellow, G.B.

    1990-01-01

    Only AsH{sub 3} and PH{sub 3} have been used as the group V source molecules for organometallic vapor phase epitaxy (OMVPE) of III/V semiconductors until recently, since they have been the only precursors yielding device quality materials. This paper reviews recent work on the pyrolysis of individual organometallic molecules, with emphasis on the group V sources, including: (1) the methylarsines, di- and tri-methylarsine, (2) the ethylarsines, mono-, di-, and tri-ethylarsine, and (3) the singly substituted tertiarybutyl arsine and phosphine molecules. The pyrolysis and growth reactions occurring when both group III and group V precursors are present simultaneously, i.e., the reactions occuring during OMVPE growth of several III/V semiconductors, are also briefly reviewed.

  16. 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.

  17. Analysis of Complexation Equilibria of Polyacrylic Acid by a Donnan-Based Concept

    PubMed

    Miyajima; Mori; Ishiguro

    1997-03-01

    Complexation equilibria of uni- and divalent metal ions (Ag+, Ca2+, Cu2+, and Pb2+) with polyacrylic acid (PAA) have been studied at various degrees of dissociation (alpha) of PAA under different sodium salt concentration levels at 25°C. Both pH and pM(MZ+ = Ag+, Ca2+, Cu2+, and Pb2+) of equilibrium mixture solutions of MZ+/PAA/Na+ (excess) have been determined concurrently by a potentiometric titration method. The electrostatic effect inherent in the polyion-metal ion binding equilibria has been evaluated by a Donnan-based concept and is corrected for by the use of a nonideality term of acid dissociation equilibria of the polyacid as a probe. For Ag+-PAA and Ca2+-PAA bindings, only monodentate ligand complexes, (MA)(Z-1), have proven to be formed, whereas for Cu2+ and Pb2+ ion bindings, formation of both monodentate and bidentate ligand complexes have been observed. For both Cu2+-PAA and Pb2+-PAA systems, bidentate carboxylate complex formation is predominant at alpha > ca. 0.3, whereas at alpha < ca. 0.3, formation of monodentate carboxylate complexes becomes appreciable as alpha decreases. Stability constants of these complexes together with the intra-molecular complexation equilibrium constants expressed by the ratio of the concentrations of bidentate complexes to monodentate complexes have successfully been evaluated and are compared with each other in order to discuss the multidentate complexation properties of the polycarboxylic acid. PMID:9245334

  18. Lattice melting and rotation in perpetually pulsating equilibria

    SciTech Connect

    Pichon, C.; Lynden-Bell, D.; Pichon, J.; Lynden-Bell, R.

    2007-01-15

    Systems whose potential energies consists of pieces that scale as r{sup -2} together with pieces that scale as r{sup 2}, show no violent relaxation to Virial equilibrium but may pulsate at considerable amplitude forever. Despite this pulsation these systems form lattices when the nonpulsational ''energy'' is low, and these disintegrate as that energy is increased. The ''specific heats'' show the expected halving as the ''solid'' is gradually replaced by the ''fluid'' of independent particles. The forms of the lattices are described here for N{<=}18 and they become hexagonal close packed for large N. In the larger N limit, a shell structure is formed. Their large N behavior is analogous to a {gamma}=5/3 polytropic fluid with a quasigravity such that every element of fluid attracts every other in proportion to their separation. For such a fluid, we study the ''rotating pulsating equilibria'' and their relaxation back to uniform but pulsating rotation. We also compare the rotating pulsating fluid to its discrete counterpart, and study the rate at which the rotating crystal redistributes angular momentum and mixes as a function of extra heat content.

  19. Raman study of thermochromic phase transition in tungsten trioxide nanowires

    NASA Astrophysics Data System (ADS)

    Lu, Dong Yu; Chen, Jian; Chen, Huan Jun; Gong, Li; Deng, Shao Zhi; Xu, Ning Sheng; Liu, Yu Long

    2007-01-01

    Tungsten trioxide (WO3) nanowires were synthesized by thermal evaporation of tungsten powder in two steps: tungsten suboxide (WO3-x) nanowires were synthesized, and then oxidized in O2 ambient and transformed into WO3 nanowires. Raman spectroscopy was applied to study the thermochromic phase transition of one-dimensional WO3 nanowires. From the temperature dependence of the characteristic mode at 33cm-1 in WO3, the phase transition temperature was determined. It was found that the phase transition of WO3 nanowires was reversible and the phase transition temperatures were even lower than that of WO3 nanopowder.

  20. URe{sub 2}-A compressibility study of allotropic phases

    SciTech Connect

    Shukla, B. Shekar, N. V. Chandra Sahu, P. Ch.

    2014-04-24

    URe{sub 2} compound exists in two phases- orthorhombic and hexagonal. The hexagonal phase has been prepared using arc melting and annealingat 500°C for one week, whereas the orthorhombic phase was achieved by annealing the arc melted sample at a temperature 150°C for the same period. High pressure x-ray diffraction studies on these two allotropic forms of URe{sub 2} have been carried out up to ∼15GPa using a diamond anvil cell. Normal compression was observed without any kind of phase transformation; although there is a probability of transformation from the metastable hexagonal to itsstable orthorhombicphase under pressure.

  1. Small modular biopower initiative Phase 1 feasibility studies executive summaries

    SciTech Connect

    Bain, R.

    2000-03-06

    The Phase 1 objective is a feasibility study that includes a market assessment, resource assessment, preliminary system design, and assessment of relevant environmental and safety considerations, and evaluation of financial and cost issues, and a preliminary business plan and commercialization strategy. Each participating company will share at least 20% of the cost of the first phase.

  2. Higher-order equilibria of temporal soliton molecules in dispersion-managed fibers

    NASA Astrophysics Data System (ADS)

    Hause, A.; Mitschke, F.

    2013-12-01

    Bound states of two or three solitons in dispersion-managed fibers (soliton molecules) were experimentally demonstrated recently. We investigate with a modified perturbation analysis whether the binding mechanism creates a unique stable equilibrium of the relative positions of the solitons in the molecule. Indeed, we find a multitude of equilibrium states, alternatingly stable and unstable. This holds for either case: nearest neighbor solitons having the same or the opposite phase. The number of equilibria are limited by the level of the radiation background. The state with the smallest separation and the highest binding energy ("ground state") always occurs for opposite-phase pulses; the lowest-order state for in-phase pulses is always unstable. Stable long-chain molecules can be built with a mixture of different nearest-neighbor equilibrium separations. Our results agree with our numerical simulations and experimental results, and connect well with certain results in the literature.

  3. Three-dimensional force-free looplike magnetohydrodynamic equilibria

    NASA Technical Reports Server (NTRS)

    Finn, John M.; Guzdar, Parvez N.; Usikov, Daniel

    1994-01-01

    Computations of three-dimensional force-free magnetohydrodynamic (MHD) equilibria, del x B = lambdaB with lambda = lambda(sub 0), a constant are presented. These equilibria are determined by boundary conditions on a surface corresponding to the solar photosphere. The specific boundary conditions used correspond to looplike magnetic fields in the corona. It is found that as lambda(sub 0) is increased, the loops of flux become kinked, and for sufficiently large lambda(sub 0), develop knots. The relationship between the kinking and knotting properties of these equilibria and the presence of a kink instability and related loss of equilibrium is explored. Clearly, magnetic reconnection must be involved for an unknotted loop equilibrium to become knotted, and speculations are made about the creation of a closed hyperbolic field line (X-line) about which this reconnection creating knotted field lines is centered.

  4. Extended fluid models: Pressure tensor effects and equilibria

    SciTech Connect

    Cerri, S. S.; Henri, P.; Califano, F.; Pegoraro, F.; Del Sarto, D.; Faganello, M.

    2013-11-15

    We consider the use of “extended fluid models” as a viable alternative to computationally demanding kinetic simulations in order to manage the global large scale evolution of a collisionless plasma while accounting for the main effects that come into play when spatial micro-scales of the order of the ion inertial scale d{sub i} and of the thermal ion Larmor radius ρ{sub i} are formed. We present an extended two-fluid model that retains finite Larmor radius (FLR) corrections to the ion pressure tensor while electron inertia terms and heat fluxes are neglected. Within this model we calculate analytic FLR plasma equilibria in the presence of a shear flow and elucidate the role of the magnetic field asymmetry. Using a Hybrid Vlasov code, we show that these analytic equilibria offer a significant improvement with respect to conventional magnetohydrodynamic shear-flow equilibria when initializing kinetic simulations.

  5. Multi-path transportation futures study: Results from Phase 1

    SciTech Connect

    Patterson, Phil; Singh, Margaret; Plotkin, Steve; Moore, Jim

    2007-03-09

    This PowerPoint briefing provides documentation and details for Phase 1 of the Multi-Path Transportation Futures Study, which compares alternative ways to make significant reductions in oil use and carbon emissions from U.S. light vehicles to 2050. Phase I, completed in 2006, was a scoping study, aimed at identifying key analytic issues and constructing a study design. The Phase 1 analysis included an evaluation of several pathways and scenarios; however, these analyses were limited in number and scope and were designed to be preliminary.

  6. Oak Ridge Health Studies phase 1 report, Volume 1: Oak Ridge Phase 1 overview

    SciTech Connect

    Yarbrough, M.I.; Van Cleave, M.L.; Turri, P.; Daniel, J.

    1993-09-01

    In July 1991, the State of Tennessee initiated the Health Studies Agreement with the United States Department of Energy to carry out independent studies of possible adverse health effects in people living in the vicinity of the Oak Ridge Reservation. The health studies focus on those effects that could have resulted or could result from exposures to chemicals and radioactivity released at the Reservation since 1942. The major focus of the first phase was to complete a Dose Reconstruction Feasibility Study. This study was designed to find out if enough data exist about chemical and radionuclide releases from the Oak Ridge Reservation to conduct a second phase. The second phase will lead to estimates of the actual amounts or the ``doses`` of various contaminants received by people as a result of off-site releases. Once the doses of various contaminants have been estimated, scientists and physicians will be better able to evaluate whether adverse health effects could have resulted from the releases.

  7. Singular Isothermal Disks. Paper 2; Nonaxiymmetric Bifurcations and Equilibria

    NASA Technical Reports Server (NTRS)

    Galli, Danielle; Shu, Frank H.; Laughlin, Gregory; Lizano, Susana

    2000-01-01

    We review the difficulties of the classical fission and fragmentation hypotheses for the formation of binary and multiple stars. A crucial missing ingredient in previous theoretical studies is the inclusion of dynamically important levels of magnetic fields. As a minimal model for a candidate presursor to the formation of binary and multiple stars, we therefore formulate and solve the problem of the equilibria of isopedically magnetized, singular isothermal disks, without the assumption of axial symmetry. Considerable analytical progress can be made if we restrict our attention to models that are scale-free, i.e., that have surface densities that vary inversely with distance omega from the rotation axis of the system. In agreement with earlier analysis by Syer and Tremaine, we find that lopsided (M = 1) configurations exist at any dimensionless rotation rate, including zero. Multiple-lobed (M = 2, 3, 4, ...) configurations bifurcate from an underlying axisymmetric sequence at progressively higher dimensionless rates of rotation, but such nonaxisymmetric sequences always terminate in shockwaves before they have a chance to fission into M = 2, 3, 4, ... separate bodies. On the basis of our experience in this paper, we advance the hypothesis that binary and multiple star-formation from smooth (i.e., not highly turbulent) starting states that are supercritical but in unstable mechanical balance requires the rapid (i.e., dynamical) loss of magnetic flux at some stage of the ensuing gravitational collapse.

  8. Fluctuation theory of molecular association and conformational equilibria

    PubMed Central

    Jiao, Yuanfang; Smith, Paul E.

    2011-01-01

    General expressions relating the effects of pressure, temperature, and composition on solute association and conformational equilibria using the fluctuation theory of solutions are provided. The expressions are exact and can be used to interpret experimental or computer simulation data for any multicomponent mixture involving molecules of any size and character at any composition. The relationships involve particle-particle, particle-energy, and energy-energy correlations within local regions in the vicinity of each species involved in the equilibrium. In particular, it is demonstrated that the results can be used to study peptide and protein association or aggregation, protein denaturation, and protein-ligand binding. Exactly how the relevant fluctuating properties may be obtained from experimental or computer simulation data are also outlined. It is shown that the enthalpy, heat capacity, and compressibility differences associated with the equilibrium process can, in principle, be obtained from a single simulation. Fluctuation based expressions for partial molar heat capacities, thermal expansions, and isothermal compressibilities are also provided. PMID:21744905

  9. Advanced supersonic propulsion study, phase 4

    NASA Technical Reports Server (NTRS)

    Howlett, R. A.

    1977-01-01

    Installation characteristics for a Variable Stream Control Engine (VSCE) were studied for three advanced supersonic airplane designs. Sensitivity of the VSCE concept to change in technology projections was evaluated in terms of impact on overall installed performance. Based on these sensitivity results, critical technology requirements were reviewed, resulting in the reaffirmation of the following requirements: low-noise nozzle system; a high performance, low emissions duct burner and main burner; hot section technology; variable geometry components; and propulsion integration features, including an integrated electronic control system.

  10. A model of vapor-liquid equilibria for acid gas-alkanolamine-water systems

    SciTech Connect

    Austgen, D.M. Jr.

    1989-01-01

    A physico-chemical model was developed for representing liquid phase chemical equilibria and vapor-liquid (phase) equilibria of H{sub 2}SCO{sub 2}-alkanolamine-water systems. The equilibrium composition of the liquid phase is determined by minimization of the Gibbs free energy. Activity coefficients are represented with the Electrolyte-NRTL equation treating both long-range electrostatic interactions and short-range binary interactions between liquid phase species. Vapor phase fugacity coefficients are calculated using the Redlich-Kwong-Soave Equation of State. Adjustable parameters of the model, binary interaction parameters and carbamate stability constants, were fitted on published binary system alkanolamine-water and ternary system (H{sub 2}S-alkanolamine-water, CO{sub 2}-alkanolamine-water) VLE data. The Data Regression System of ASPEN PLUS, based upon the Maximum Likelihood Principle, was used to estimate adjustable parameters. Ternary system measurements used in parameter estimation ranged in temperature from 25 to 120{degree}C in alkanolamine concentration from 1 to 5 M, in acid gas loading from 0 to 1.5 moles per mole alkanolamine, and in acid gas partial pressure from 0.1 to 1,000 kPa. Maximum likelihood estimates of ternary system H{sub 2} or CO{sub 2} equilibrium partial pressures and liquid phase concentrations were found to be in good agreement with measurements for aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), diglycolamine (DGA), and methyldiethanolamine (MDEA) indicating that the model successfully represents ternary system data. The model was extended to represent CO{sub 2} solubility in aqueous mixtures of MDEA with MEA or DEA. The solubility was measured at 40 and 80{degree}C over a wide range of CO{sub 2} partial pressures. These measurements were used to estimate additional binary parameters of the mixed solvent systems.

  11. External fuel vaporization study, phase 1

    NASA Technical Reports Server (NTRS)

    Szetela, E. J.; Chiappetta, L.

    1980-01-01

    A conceptual design study was conducted to devise and evaluate techniques for the external vaporization of fuel for use in an aircraft gas turbine with characteristics similar to the Energy Efficient Engine (E(3)). Three vaporizer concepts were selected and they were analyzed from the standpoint of fuel thermal stability, integration of the vaporizer system into the aircraft engine, engine and vaporizer dynamic response, startup and altitude restart, engine performance, control requirements, safety, and maintenance. One of the concepts was found to improve the performance of the baseline E(3) engine without seriously compromising engine startup and power change response. Increased maintenance is required because of the need for frequent pyrolytic cleaning of the surfaces in contact with hot fuel.

  12. Vlasov versus reduced kinetic theories for helically symmetric equilibria

    SciTech Connect

    Tasso, H.; Throumoulopoulos, G. N.

    2013-04-15

    A new constant of motion for helically symmetric equilibria in the vicinity of the magnetic axis is obtained in the framework of Vlasov theory. In view of this constant of motion the Vlasov theory is compared with drift kinetic and gyrokinetic theories near axis. It turns out that as in the case of axisymmetric equilibria [H. Tasso and G. N. Throumoulopoulos, Phys. Plasmas 18, 064507 (2011)] the Vlasov current density thereon can differ appreciably from the drift kinetic and gyrokinetic current densities. This indicates some limitation on the implications of reduced kinetic theories, in particular, as concerns the physics of energetic particles in the central region of magnetically confined plasmas.

  13. A method of computational magnetohydrodynamics defining stable Scyllac equilibria

    PubMed Central

    Betancourt, Octavio; Garabedian, Paul

    1977-01-01

    A computer code has been developed for the numerical calculation of sharp boundary equilibria of a toroidal plasma with diffuse pressure profile. This generalizes earlier work that was done separately on the sharp boundary and diffuse models, and it allows for large amplitude distortions of the plasma in three-dimensional space. By running the code, equilibria that are stable to the so-called m = 1, k = 0 mode have been found for Scyllac, which is a high beta toroidal confinement device of very large aspect ratio. PMID:16592383

  14. Ideal MHD beta-limits of poloidally asymmetric equilibria

    SciTech Connect

    Todd, A.M.M.; Miller, A.E.; Grimm, R.C.; Okabayashi, M.; Dalhed, H.E. Jr.

    1981-05-01

    The ideal MHD stability of poloidally asymmetric equilibria, which are typical of a tokamak reactor design with a single-null poloidal divertor is examined. As with symmetric equilibria, stability to non-axisymmetric modes improves with increasing triangularity and ellipticity, and with lower edge safety factor. Pressure profiles optimized with respect to ballooning stability are obtained for an asymmetric shape, resulting in ..beta../sub critical/ approx. = 5.7%. The corresponding value for an equivalent symmetric shape is ..beta../sub critical/ approx. = 6.5%.

  15. External fuel vaporization study, phase 2

    NASA Technical Reports Server (NTRS)

    Szetela, E. J.; Chiappetta, L.

    1981-01-01

    An analytical study was conducted to evaluate the effect of variations in fuel properties on the design of an external fuel vaporizaton system. The fuel properties that were considered included thermal stability, critical temperature, enthalpy a critical conditions, volatility, and viscosity. The design parameters that were evaluated included vaporizer weight and the impact on engine requirement such as maintenance, transient response, performance, and altitude relight. The baseline fuel properties were those of Jet A. The variation in thermal stability was taken as the thermal stability variation for Experimental Referee Broad Specification (ERBS) fuel. The results of the analysis indicate that a change in thermal stability equivalent to that of ERBS would increase the vaporization system weight by 20 percent, decrease oprating time between cleaning by 40 percent and make altitude relight more difficult. An increase in fuel critical temperature of 39 K would require a 40 percent increase in vaporization system weight. The assumed increase in enthalpy and volatility would also increase vaporizer weight by 40 percent and make altitude relight extremely difficult. The variation in fuel viscosity would have a negligible effect on the design parameters.

  16. Space transfer vehicle concepts and requirements study, phase 2

    NASA Technical Reports Server (NTRS)

    Cannon, Jeffrey H.; Vinopal, Tim; Andrews, Dana; Richards, Bill; Weber, Gary; Paddock, Greg; Maricich, Peter; Bouton, Bruce; Hagen, Jim; Kolesar, Richard

    1992-01-01

    This final report is a compilation of the Phase 1 and Phase 2 study findings and is intended as a Space Transfer Vehicle (STV) 'users guide' rather than an exhaustive explanation of STV design details. It provides a database for design choices in the general areas of basing, reusability, propulsion, and staging; with selection criteria based on cost, performance, available infrastructure, risk, and technology. The report is organized into the following three parts: (1) design guide; (2) STV Phase 1 Concepts and Requirements Study Summary; and (3) STV Phase 2 Concepts and Requirements Study Summary. The overall objectives of the STV study were to: (1) define preferred STV concepts capable of accommodating future exploration missions in a cost-effective manner; (2) determine the level of technology development required to perform these missions in the most cost effective manner; and (3) develop a decision database of programmatic approaches for the development of an STV concept.

  17. Western Wind and Solar Integration Study: Phase 2 (Presentation)

    SciTech Connect

    Lew, D.; Brinkman, G.; Ibanez, E.; Lefton, S.; Kumar, N.; Venkataraman, S.; Jordan, G.

    2013-09-01

    This presentation summarizes the scope and results of the Western Wind and Solar Integration Study Phase 2, which examined operational impacts of high penetrations of variable renewable generation in the West.

  18. Phase A design study of microgravity fluoride fiber puller

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Smith, Guy A.; Kosten, Susan

    1994-01-01

    Improved transmission properties for fluoride fibers due to space processing has great potential for commercial benefits. Phase A design study will determine conceptual feasibility and provide initial definition of the technical requirements and design issues for space.

  19. Western Wind and Solar Integration Study Phase 2 (Fact Sheet)

    SciTech Connect

    Not Available

    2013-09-01

    This is one-page, two-sided fact sheet presents high-level summary results of the Western Wind and Solar Integration Study Phase 2, which examined operational impacts of high penetrations of variable renewable generation in the West.

  20. Intelligent Robotic Systems Study (IRSS), phase 2

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Under the Intelligent Robotics System Study (IRSS) contract, a generalized robotic control architecture was developed for use with the ProtoFlight Manipulator Arm (PFMA). The controller built for the PFMA provides localized position based force control, teleoperation and advanced path recording and playback capabilities. Various hand controllers can be used with the system in conjunction with a synthetic time delay capability to provide a realistic test bed for typical satellite servicing tasks. The configuration of the IRSS system is illustrated and discussed. The PFMA has six computer controllable degrees of freedom (DOF) plus a seventh manually indexable DOF, making the manipulator a pseudo 7 DOF mechanism. Because the PFMA was not developed to operate in a gravity field, but rather in space, it is counter balanced at the shoulder, elbow and wrist and a spring counterbalance has been added near the wrist to provide additional support. Built with long slender intra-joint linkages, the PFMA has a workspace nearly 2 meters deep and possesses sufficient dexterity to perform numerous satellite servicing tasks. The manipulator is arranged in a shoulder-yaw, pitch, elbow-pitch, and wrist-pitch, yaw, roll configuration, with an indexable shoulder roll joint. Digital control of the PFMA is implemented using a variety of single board computers developed by Heurikon Corporation and other manufacturers. The IRSS controller is designed to be a multi-rate, multi-tasking system. Independent joint servos run at a 134 Hz rate and position based impedance control functions at 67 Hz. Autonomous path generation and hand controller inputs are processed at a 33 Hz.

  1. Phase diagrams of diphenyl- n-dodecane and diphenyl-diphenyl oxide- n-dodecane systems

    NASA Astrophysics Data System (ADS)

    Garkushin, I. K.; Kolyado, A. V.; Yakovlev, I. G.

    2016-08-01

    The phase equilibria in the binary diphenyl- n-dodecane and ternary diphenyl-diphenyl oxide- n-dodecane systems was studied by differential scanning calorimetry. The melting temperatures and eutectic compositions were determined. The physicochemical characteristics of eutectic alloys such as the flash point, density, and enthalpy of fusion were given. The kinematic viscosity of eutectic alloys was determined in the temperature range 25-50°C.

  2. Dynamic Particle Growth Testing - Phase I Studies

    SciTech Connect

    Hu, M.Z-C.

    2001-05-17

    , particle growth in the bulk would still affect scale formation by consuming a portion of the scale-forming precursor materials. In either case, solid-particle-formation data must be obtained to understand the problem. Previous and ongoing testing based on the measurement of [Al] and [Si] consumption kinetics have indicated that the format of aluminosilicate may be rapid under evaporator conditions. However, the kinetics of particle formation (both in bulk solution and on surfaces) has not been studied. Conditions that cause extremely rapid particle formation are of particular interest, because in that case the solids-formation reactions in the evaporator would be sensitively dependent on process conditions such as chemical composition, temperature, fluid flow, and heat transfer.

  3. Acid/base equilibria in clusters and their role in proton exchange membranes: Computational insight

    SciTech Connect

    Glezakou, Vanda A; Dupuis, Michel; Mundy, Christopher J

    2007-10-24

    We describe molecular orbital theory and ab initio molecular dynamics studies of acid/base equilibria of clusters AH:(H2O)n↔A-:H+(H2O)n in low hydration regime (n = 1-4), where AH is a model of perfluorinated sulfonic acids, RSO3H (R = CF3CF2), encountered in polymeric electrolyte membranes of fuel cells. Free energy calculations on the neutral and ion pair structures for n = 3 indicate that the two configurations are close in energy and are accessible in the fluctuation dynamics of proton transport. For n = 1,2 the only relevant configuration is the neutral form. This was verified through ab initio metadynamics simulations. These findings suggest that bases are directly involved in the proton transport at low hydration levels. In addition, the gas phase proton affinity of the model sulfonic acid RSO3H was found to be comparable to the proton affinity of water. Thus, protonated acids can also play a role in proton transport under low hydration conditions and under high concentration of protons. This work was supported by the Division of Chemical Science, Office of Basic Energy Sciences, US Department of Energy (DOE under Contract DE-AC05-76RL)1830. Computations were performed on computers of the Molecular Interactions and Transformations (MI&T) group and MSCF facility of EMSL, sponsored by US DOE and OBER located at PNNL. This work was benefited from resource of the National Energy Research Scientific Computing Centre, supported by the Office of Science of the US DOE, under Contract No. DE-AC03-76SF00098.

  4. Pseudocapacitive Properties of Two-Dimensional Surface Vanadia Phases Formed Spontaneously on Titania.

    PubMed

    Samiee, Mojtaba; Luo, Jian

    2016-05-25

    Pseudocapacitive properties of V2O5-based adsorbates supported on TiO2 nanoparticles, which form spontaneously as two-dimensional (2-D) nonautonomous surface phases (complexions) at thermodynamic equilibria, have been systematically measured. Surprisingly, surface amorphous films (SAFs), which form naturally at thermodynamic equilibria at 550-600 °C with self-regulating or "equilibrium" thicknesses on the order of 1 nm, exhibit superior electrochemical performance at moderate and high scan rates (20-500 mV/s) that are of prime importance for supercapacitor applications, as compared with submonolayer and monolayer adsorbates formed at lower equilibration temperatures. This study suggests a new direction to design and fabricate a novel class of supercapacitors and other functional devices via utilizing 2-D interfacial phases that can form spontaneously via facile, cost-effective, and highly scalable synthesis routes. PMID:27144457

  5. Integrated thermal treatment system study -- Phase 2 results. Revision 1

    SciTech Connect

    Feizollahi, F.; Quapp, W.J.

    1996-02-01

    This report presents the second phase of a study on thermal treatment technologies. The study consists of a systematic assessment of nineteen thermal treatment alternatives for the contact-handled mixed low-level waste (MLLW) currently stored in the US Department of Energy complex. The treatment alternatives consist of widely varying technologies for safely destroying the hazardous organic components, reducing the volume, and preparing for final disposal of the MLLW. The alternatives considered in Phase 2 were innovative thermal treatments with nine types of primary processing units. Other variations in the study examined the effect of combustion gas, air pollution control system design, and stabilization technology for the treatment residues. The Phase 1 study examined ten initial thermal treatment alternatives. The Phase 2 systems were evaluated in essentially the same manner as the Phase 1 systems. The alternatives evaluated were: rotary kiln, slagging kiln, plasma furnace, plasma gasification, molten salt oxidation, molten metal waste destruction, steam gasification, Joule-heated vitrification, thermal desorption and mediated electrochemical oxidation, and thermal desorption and supercritical water oxidation. The quantities, and physical and chemical compositions, of the input waste used in the Phase 2 systems differ from those in the Phase 1 systems, which were based on a preliminary waste input database developed at the onset of the Integrated Thermal Treatment System study. The inventory database used in the Phase 2 study incorporates the latest US Department of Energy information. All systems, both primary treatment systems and subsystem inputs, have now been evaluated using the same waste input (2,927 lb/hr). 28 refs., 88 figs., 41 tabs.

  6. Wave Tank Studies of Phase Velocities of Short Wind Waves

    NASA Astrophysics Data System (ADS)

    Ermakov, S.; Sergievskaya, I.; Shchegolkov, Yu.

    Wave tank studies of phase velocities of short wind waves have been carried out using Ka-band radar and an Optical Spectrum Analyser. The phase velocities were retrieved from measured radar and optical Doppler shifts, taking into account measurements of surface drift velocities. The dispersion relationship was studied in centimetre (cm)- and millimetre(mm)-scale wavelength ranges at different fetches and wind speeds, both for a clean water surface and for water covered with surfactant films. It is ob- tained that the phase velocities do not follow the dispersion relation of linear capillary- gravity waves, increasing with fetch and, therefore, depending on phase velocities of dominant decimetre (dm)-centimetre-scale wind waves. One thus can conclude that nonlinear cm-mm-scale harmonics bound to the dominant wind waves and propagat- ing with the phase velocities of the decimetric waves are present in the wind wave spectrum. The resulting phase velocities of short wind waves are determined by re- lation between free and bound waves. The relative intensity of the bound waves in the spectrum of short wind waves is estimated. It is shown that this relation depends strongly on the surfactant concentration, because the damping effect due to films is different for free and bound waves; this results to changes of phase velocities of wind waves in the presence of surfactant films. This work was supported by MOD, UK via DERA Winfrith (Project ISTC 1774P) and by RFBR (Project 02-05-65102).

  7. The Design of the IGE Evaluation Project Phase IV Comparative Studies. Comparative Study of Phase IV IGE Evaluation Project. Phase IV, Project Paper 80-2.

    ERIC Educational Resources Information Center

    Romberg, Thomas A.; And Others

    This paper outlines the design of two Comparative Studies of Phase IV of the Individually Guided Education (IGE) Evaluation Project. More than 2,000 elementary schools in 25 states use the IGE system. The Evaluation Project was designed to gain a comprehensive view of the system's operation and effectiveness. Phase IV investigated pupil outcomes,…

  8. Solid phases of spatially nanoconfined oxygen: A neutron scattering study

    SciTech Connect

    Kojda, Danny; Wallacher, Dirk; Hofmann, Tommy; Baudoin, Simon; Hansen, Thomas; Huber, Patrick

    2014-01-14

    We present a comprehensive neutron scattering study on solid oxygen spatially confined in 12 nm wide alumina nanochannels. Elastic scattering experiments reveal a structural phase sequence known from bulk oxygen. With decreasing temperature cubic γ-, orthorhombic β- and monoclinic α-phases are unambiguously identified in confinement. Weak antiferromagnetic ordering is observed in the confined monoclinic α-phase. Rocking scans reveal that oxygen nanocrystals inside the tubular channels do not form an isotropic powder. Rather, they exhibit preferred orientations depending on thermal history and the very mechanisms, which guide the structural transitions.

  9. Solid phases of spatially nanoconfined oxygen: a neutron scattering study.

    PubMed

    Kojda, Danny; Wallacher, Dirk; Baudoin, Simon; Hansen, Thomas; Huber, Patrick; Hofmann, Tommy

    2014-01-14

    We present a comprehensive neutron scattering study on solid oxygen spatially confined in 12 nm wide alumina nanochannels. Elastic scattering experiments reveal a structural phase sequence known from bulk oxygen. With decreasing temperature cubic γ-, orthorhombic β- and monoclinic α-phases are unambiguously identified in confinement. Weak antiferromagnetic ordering is observed in the confined monoclinic α-phase. Rocking scans reveal that oxygen nanocrystals inside the tubular channels do not form an isotropic powder. Rather, they exhibit preferred orientations depending on thermal history and the very mechanisms, which guide the structural transitions. PMID:24437900

  10. Graphic Representation of Carbon Dioxide Equilibria in Biological Systems.

    ERIC Educational Resources Information Center

    Kindig, Neal B.; Filley, Giles F.

    1983-01-01

    The log C-pH diagram is a useful means of displaying quantitatively the many variables (including temperature) that determine acid-base equilibria in biological systems. Presents the diagram as extended to open/closed biological systems and derives a new water-ion balance method for determining equilibrium pH. (JN)

  11. Chaotic magnetic fields in Vlasov-Maxwell equilibria

    SciTech Connect

    Ghosh, Abhijit; Janaki, M. S.; Dasgupta, Brahmananda; Bandyopadhyay, Alak

    2014-03-15

    Stationary solutions of Vlasov-Maxwell equations are obtained by exploiting the invariants of single particle motion leading to linear or nonlinear functional relations between current and vector potential. For a specific combination of invariants, it is shown that Vlasov-Maxwell equilibria have an associated Hamiltonian that exhibits chaos.

  12. Calculation of complex equilibria involving vaporization into vacuum

    NASA Technical Reports Server (NTRS)

    Paule, R. C.

    1974-01-01

    A simplified, direct approach is presented to the description of complex equilibria involving vaporization into vacuum. Emphasis is on the basic problem-solving process and on modification of existing techniques. Sequential solutions are presented to problems involving purification of a melt by vaporization into vacuum. The effects of concentration of melt and oxygen partial pressures on vaporization rates are demonstrated.

  13. Acid-Base and Precipitation Equilibria in Wine

    ERIC Educational Resources Information Center

    Palma, Miguel; Barroso, Carmelo G.

    2004-01-01

    Experiments are performed to establish the changes of pH during the precipitation of potassium hydrogen tartrate, with its unfavorable impact on the stability of wine. Students, thus, obtain a clearer understanding of the interplay between a variety of chemical equilibria within a single medium.

  14. Kinetic axisymmetric gravitational equilibria in collisionless accretion disk plasmas

    SciTech Connect

    Cremaschini, Claudio; Miller, John C.; Tessarotto, Massimo

    2010-07-15

    A theoretical treatment is presented of kinetic equilibria in accretion disks (AD) around compact objects, for cases where the plasma can be considered as collisionless. The plasma is assumed to be axisymmetric and to be acted on by gravitational and electromagnetic fields; in this paper, the particular case is considered where the magnetic field admits a family of toroidal magnetic surfaces, which are locally mutually nested and closed. It is pointed out that there exist asymptotic kinetic equilibria represented by generalized bi-Maxwellian distribution functions and characterized by primarily toroidal differential rotation and temperature anisotropy. It is conjectured that kinetic equilibria of this type can exist which are able to sustain both toroidal and poloidal electric current densities, the latter being produced via finite Larmor-radius effects associated with the temperature anisotropy. This leads to the possibility of existence of a new kinetic effect - referred to here as a 'kinetic dynamo effect - resulting in the self-generation of toroidal magnetic field even by a stationary plasma, without any net radial accretion flow being required. The conditions for these equilibria to occur, their basic theoretical features, and their physical properties are all discussed in detail.

  15. Model Checking Coalition Nash Equilibria in MAD Distributed Systems

    NASA Astrophysics Data System (ADS)

    Mari, Federico; Melatti, Igor; Salvo, Ivano; Tronci, Enrico; Alvisi, Lorenzo; Clement, Allen; Li, Harry

    We present two OBDD based model checking algorithms for the verification of Nash equilibria in finite state mechanisms modeling Multiple Administrative Domains (MAD) distributed systems with possibly colluding agents (coalitions) and with possibly faulty or malicious nodes (Byzantine agents). Given a finite state mechanism, a proposed protocol for each agent and the maximum sizes f for Byzantine agents and q for agents collusions, our model checkers return PASS if the proposed protocol is an ɛ-f-q-Nash equilibrium, i.e. no coalition of size up to q may have an interest greater than ɛ in deviating from the proposed protocol when up to f Byzantine agents are present, FAIL otherwise. We implemented our model checking algorithms within the NuSMV model checker: the first one explicitly checks equilibria for each coalition, while the second represents symbolically all coalitions. We present experimental results showing their effectiveness for moderate size mechanisms. For example, we can verify coalition Nash equilibria for mechanisms which corresponding normal form games would have more than 5 ×1021 entries. Moreover, we compare the two approaches, and the explicit algorithm turns out to outperform the symbolic one. To the best of our knowledge, no model checking algorithm for verification of Nash equilibria of mechanisms with coalitions has been previously published.

  16. MINTEQ--A COMPUTER PROGRAM FOR CALCULATING AQUEOUS GEOCHEMICAL EQUILIBRIA

    EPA Science Inventory

    MINTEQ is a computer program for computation of geochemical equilibria. MINTEQ was developed for incorporation into the Metals Exposure Analysis Modeling System (MEXAMS), a modeling system for the assessment of the fate and migration of selected priority pollutant metals in aquat...

  17. Substituent Effects on Keto-Enol Equilibria Using NMR Spectroscopy

    ERIC Educational Resources Information Center

    Manbeck, Kimberly A.; Boaz, Nicholas C.; Bair, Nathaniel C.; Sanders, Allix M. S.; Marsh, Anderson L.

    2011-01-01

    In this extension to a classic physical chemistry experiment, students record the proton nuclear magnetic resonance spectra of the [beta]-diketones 2,4-pentanedione, 3-methyl-2,4-pentanedione, and 3-chloro-2,4-pentanedione to investigate the effect of substituents on keto-enol tautomerization equilibria. From the integrated intensities of keto and…

  18. A Simple Chaotic Flow with a Plane of Equilibria

    NASA Astrophysics Data System (ADS)

    Jafari, Sajad; Sprott, J. C.; Molaie, Malihe

    2016-06-01

    Using a systematic computer search, a simple four-dimensional chaotic flow was found that has the unusual feature of having a plane of equilibria. Such a system belongs to a newly introduced category of chaotic systems with hidden attractors that are important and potentially problematic in engineering applications.

  19. Antenna evaluation study for the shuttle multispectral radar, phase 2

    NASA Technical Reports Server (NTRS)

    Coffey, E. L., III; Carver, K. R.

    1977-01-01

    The results of the second phase of the Antenna Evaluation Study for the Shuttle Imaging Radar are presented. The objectives of Phase II were (1) to complete the specifications for the subarray test panels, (2) to begin a study of the effects of electrical and mechanical tolerance variations on overall SIRA performance, (3) to initiate the development of a mathematical model which adequately described the array performance and (4) to begin the development of a comprehensive computer program which will eventually simulate the performance characteristics of the antenna in a spaceborne environment. Items (2), (3), and (4) were begun in Phase I (ahead of schedule), and because of this, it has been possible to accelerate the Phase II modeling/simulation objectives to the point where simulations of expected mechanical/electrical errors have already been produced.

  20. Comparative study viruses with computer-aided phase microscope AIRYSCAN

    NASA Astrophysics Data System (ADS)

    Tychinsky, Vladimir P.; Koufal, Georgy E.; Perevedentseva, Elena V.; Vyshenskaia, Tatiana V.

    1996-12-01

    Traditionally viruses are studied with scanning electron microscopy (SEM) after complicated procedure of sample preparation without the possibility to study it under natural conditions. We obtained images of viruses (Vaccinia virus, Rotavirus) and rickettsias (Rickettsia provazekii, Coxiella burnetti) in native state with computer-aided phase microscope airyscan -- the interference microscope of Linnik layout with phase modulation of the reference wave with dissector image tube as coordinate-sensitive photodetector and computer processing of phase image. A light source was the He-Ne laser. The main result is coincidence of dimensions and shape of phase images with available information concerning their morphology obtained with SEM and other methods. The fine structure of surface and nuclei is observed. This method may be applied for virus recognition and express identification, investigation of virus structure and the analysis of cell-virus interaction.

  1. PLCO Ovarian Phase III Validation Study — EDRN Public Portal

    Cancer.gov

    Our preliminary data indicate that the performance of CA 125 as a screening test for ovarian cancer can be improved upon by additional biomarkers. With completion of one additional validation step, we will be ready to test the performance of a consensus marker panel in a phase III validation study. Given the original aims of the PLCO trial, we believe that the PLCO represents an ideal longitudinal cohort offering specimens for phase III validation of ovarian cancer biomarkers.

  2. Study of expansion tube problems with phase transition

    NASA Astrophysics Data System (ADS)

    Goncalves, E.; Zeidan, D.

    2012-09-01

    In this work, a compressible multiphase one-fluid Euler solver has been developed to study one-dimensional expansion problems with cavitation process. A new model for the mass transfer between phases is proposed, and its efficiency in predicting phase transition is evaluated. Numerical simulations are compared with reference solutions computed with the two-fluid models type. The results suggest that the present model exhibits good robustness and accuracy.

  3. Molecular dynamics studies on liquid-phase dynamics and structures of four different fluoropropenes and their binary mixtures with R-32 and CO2.

    PubMed

    Raabe, Gabriele

    2014-01-01

    Fluoropropenes such as R-1234yf or R-1234ze(E) have attracted attention as low GWP (global warming potential) refrigerants, both as pure compounds but also to an increasing extent as components in refrigerant blends. In our earlier work [Raabe, G.; Maginn, E. J. J. Phys. Chem. B 2010, 114, 10133-10142 and Raabe, G. J. Phys. Chem. B 2012, 116, 5744-5751], we have introduced a transferable force field for different fluoropropene compounds. This molecular model has already been applied for predictive molecular simulation studies on the vapor-liquid phase equilibria in binary mixtures of the tetrafluoropropenes R-1234yf or R-1234ze(E) with the difluoromethane R-32 and CO2. In this work we present molecular dynamics simulations on the liquid phase properties of the pure fluoropropenes R-1234yf, R-1234ze, R-1234ze(E), and R-1216 and their binary mixtures with CO2 and R-32. Our study covers temperatures from 273 to 313 K, pressures up to 3.5 MPa, and different mixture compositions. We provide predictions on the densities and transport properties of the pure compounds and the binary mixtures to complement experimental data. Additionally, we have analyzed radial and spatial distribution functions in the systems to gain insight into their microscopic structures and preferred interaction sites. PMID:24328116

  4. Numerical investigation of bifurcations of equilibria and Hopf bifurcations in disease transmission models

    NASA Astrophysics Data System (ADS)

    Maglevanny, I. I.; Meletlidou, E.; Stagika, G.

    2011-01-01

    One of the general SIRS disease transmission model is considered under the assumptions that the size of the population varies, the incidence rate is nonlinear, and the recovered (removed) class may also be directly reinfected. A combination of analytical and numerical techniques is used to show that (for some parameters) the bifurcations of equilibria can occur and also asymptotically orbitally stable periodic solutions with asymptotic phase can arise through Hopf bifurcations. The investigation is based on computer simulation of bifurcation manifolds in the parameter space. Hopf bifurcations are investigated on the base of center manifold theory by the computation of bifurcation parameters and the approximation of Hopf-bifurcating cycles by bifurcation formulas. This method finds the limit cycle to a good approximation and also its stability. For computer simulations the necessary computer oriented algorithms were developed and encoded by C++. Some results of computer simulations are presented and numerical evidence of existence of bifurcations of equilibria and Hopf bifurcations for the considered model is provided.

  5. Solid-liquid equilibria in the NaCl-SrCl2-H2O system at 288.15 K

    NASA Astrophysics Data System (ADS)

    Li, Dan; Meng, Qing-fen; Meng, Ling-zong; Fan, Xiu-xiu

    2016-02-01

    The phase equilibria in the ternary system NaCl-SrCl2-H2O at 288.15 K were studied with the isothermal equilibrium solution method. The phase diagram and refractive index diagram were plotted for this system at 288.15 K. The phase diagram contains one invariant solubility point, two univariant solubility curves, and two crystallization fields of NaCl and SrCl2 · 6H2O. The refractive indices of the equilibrium solution change regularly with w(NaCl) increase. The calculated refractive index data are in good agreement with the experimental data. Combining the experimental solubility data of the ternary system, the Pitzer binary parameters for NaCl at 288.15 K and SrCl2 at 298.15 K, the Pitzer mixing parameters θNa, Sr, ΨNa, Sr, Cl and the solubility equilibrium constants Ksp of solid phases existing in the ternary system at 288.15 K were fitted using the Pitzer and Harvie-Weare (HW) models. The mean activity coefficients of sodium chloride and strontium chloride, and the solubilities for the ternary system at 288.15 K were presented. A comparison between the calculated and measured solubilities shows that the predicted data agree well with the experimental results.

  6. A study of two phase flow in fracture networks

    SciTech Connect

    Karasaki, K.; Pruess, K.; Vomvoris, S.; Segan, S.

    1994-12-31

    Accurate characterization of the two-phase flow behavior of the fractured rock mass is vital to the safety of a potential high level nuclear waste repository in the unsaturated, fractured welded tuff at Yucca Mountain, NV. A tool for studying the two-phase flow properties of a fracture networks was developed. It is based on a simple mechanistic model in which the capillary pressure of a fracture is a unique function of the aperture. Whether a particular fracture element is occupied by wetting fluid or non-wetting fluid is determined by allowability and accessibility criteria. Relative permeability characteristics of a simulated fracture network were investigated using the model. Different assumptions are examined regarding the interactions between phases. In all cases, strong phase interference was observed. Hysteresis effects and irreducible saturation were also explained based on the model.

  7. Intensity and phase fields behind Phase Shifting Masks studied with High Resolution Interference Microscopy

    NASA Astrophysics Data System (ADS)

    Puthankovilakam, Krishnaparvathy; Scharf, Toralf; Herzig, Hans Peter; Weichelt, Tina; Zeitner, Uwe; Vogler, Uwe; Voelkel, Reinhard

    2015-03-01

    The proximity printing industry is in real need of high resolution results and it can be done using Phase Shift Mask (PSM) or by applying Optical Proximity Correction (OPC). In our research we are trying to find out details of how light fields behind the structures of photo masks develop in order to determine the best conditions and designs for proximity printing. We focus here on parameters that are used in real situation with gaps up to 50 μm and structure sizes down to 2 μm. The light field evolution behind the structures is studied and delivers insight in to precisions and tolerances that need to be respected. It is the first time that an experimental analysis of light propagation through mask is presented in detail, which includes information on intensity and phase. The instrument we use is known as High Resolution Interference Microscopy (HRIM). HRIM is a Mach-Zehnder interferometer which is capable of recording three dimensional distributions of intensity and phase with diffraction limited resolution. Our characterization technique allows plotting the evolution of the desired light field and therefore printable structure till the desired proximity gap. In this paper we discuss in detail the evolution of intensity and phase fields of elbow or corner structure at different position behind a phase mask and interpret the main parameters. Of particular interest are tolerances against proximity gap variation and the resolution in printed structures.

  8. Illite equilibria in solutions: III. A re-interpretation of the data of Sass et al. (1987)

    SciTech Connect

    Aja, S.U. )

    1991-11-01

    In a recent solubility study of Goose Lake and Beavers Bend illite, SASS et al. (1987) inferred the existence of three components of natural illites (K{sub 0.24}/O{sub 10}(OH){sub 2}), (K{sub 0.67}/O{sub 10}(OH){sub 2}), and (K{sub 0.90}/O{sub 10}(OH){sub 2}) which were interpreted to be smectite, illite, and K-mica, respectively. They also speculated that illite-smectite equilibrium is metastable under diagenetic conditions except between 90 and 110C where it is stabilized by an ordering transition. A re-interpretation of the data of SASS et al. (1987) indicates that the solubility-controlling phases have the following K atoms per half cell: 0.29, 0.52, 0.69, 0.084, and 1.0. Furthermore, solution equilibration investigations of kaolinite-microcline mixtures have shown that these two minerals do not coexist stably. Thus, the question of an ordering transition whose main effect is to stabilize illite-smectite equilibria relative to kaolinite-microcline assemblage does not arise.

  9. A MATLAB GUI to study Ising model phase transition

    NASA Astrophysics Data System (ADS)

    Thornton, Curtislee; Datta, Trinanjan

    We have created a MATLAB based graphical user interface (GUI) that simulates the single spin flip Metropolis Monte Carlo algorithm. The GUI has the capability to study temperature and external magnetic field dependence of magnetization, susceptibility, and equilibration behavior of the nearest-neighbor square lattice Ising model. Since the Ising model is a canonical system to study phase transition, the GUI can be used both for teaching and research purposes. The presence of a Monte Carlo code in a GUI format allows easy visualization of the simulation in real time and provides an attractive way to teach the concept of thermal phase transition and critical phenomena. We will also discuss the GUI implementation to study phase transition in a classical spin ice model on the pyrochlore lattice.

  10. Western Wind and Solar Integration Study Phase 2 (Presentation)

    SciTech Connect

    Lew, D.; Brinkman, G.; Ibanez, E.; Kumar, N.; Lefton, S.; Jordan, G.; Venkataraman, S.; King, J.

    2013-06-01

    This presentation accompanies Phase 2 of the Western Wind and Solar Integration Study, a follow-on to Phase 1, which examined the operational impacts of high penetrations of variable renewable generation on the electric power system in the West and was one of the largest variable generation studies to date. High penetrations of variable generation can induce cycling of fossil-fueled generators. Cycling leads to wear-and-tear costs and changes in emissions. Phase 2 calculated these costs and emissions, and simulated grid operations for a year to investigate the detailed impact of variable generation on the fossil-fueled fleet. The presentation highlights the scope of the study and results.

  11. Dynamics of phase slips in systems with time-periodic modulation

    NASA Astrophysics Data System (ADS)

    Gandhi, Punit; Knobloch, Edgar; Beaume, Cédric

    2015-12-01

    The Adler equation with time-periodic frequency modulation is studied. A series of resonances between the period of the frequency modulation and the time scale for the generation of a phase slip is identified. The resulting parameter space structure is determined using a combination of numerical continuation, time simulations, and asymptotic methods. Regions with an integer number of phase slips per period are separated by regions with noninteger numbers of phase slips and include canard trajectories that drift along unstable equilibria. Both high- and low-frequency modulation is considered. An adiabatic description of the low-frequency modulation regime is found to be accurate over a large range of modulation periods.

  12. Nash Equilibria and the Price of Anarchy for Flows over Time

    NASA Astrophysics Data System (ADS)

    Koch, Ronald; Skutella, Martin

    We study Nash equilibria in the context of flows over time. Many results on static routing games have been obtained over the last ten years. In flows over time (also called dynamic flows), flow travels through a network over time and, as a consequence, flow values on edges are time-dependent. This more realistic setting has not been tackled from the viewpoint of algorithmic game theory yet; but there is a rich literature on game theoretic aspects of flows over time in the traffic community.

  13. Isobaric vapor-liquid equilibria in the system methyl propanoate + n-butyl alcohol

    SciTech Connect

    Susial, P.; Ortega, J. . Lab. de Termodinamica y Fisicoquimica)

    1993-10-01

    Isobaric vapor-liquid equilibria were determined at 74.66, 101.32, and 127.99 kPa for binary mixtures containing methyl propanoate + n-butyl alcohol by using a dynamic still with vapor and liquid circulation. No azeotrope was detected. The data were found to be thermodynamically consistent according to the point to point test. Application of the group-contribution models ASOG, UNIFAC, and modified UNIFAC to the activity coefficients at the three pressures studied gives average errors of less than 10%, 11%, and 3%, respectively.

  14. Scaling-law equilibria for calcium in canopy-type models of the solar chromosphere

    NASA Technical Reports Server (NTRS)

    Jones, H. P.

    1982-01-01

    Scaling laws for resonance line formation are used to obtain approximate excitation and ionization equilibria for a three-level model of singly ionized calcium. The method has been developed for and is applied to the study of magnetograph response in the 8542 A infrared triplet line to magnetostatic canopies which schematically model diffuse, nearly horizontal fields in the low solar chromosphere. For this application, the method is shown to be efficient and semi-quantitative, and the results indicate the type and range of effects on calcium-line radiation which result from reduced gas pressure inside the magnetic regions.

  15. Two Equilibria of (N-Methyl-3-pyridinium)chlorocarbene, a Cationic Carbene.

    PubMed

    Cang, Hui; Moss, Robert A; Krogh-Jespersen, Karsten

    2016-02-11

    Equilibrium constants and the associated thermodynamic parameters are reported for the equilibria established between the cationic carbene (N-methyl-3-pyridinium)chlorocarbene tetrafluoroborate (MePyr(+)CCl BF4(-), 3) and 1,3,5-trimethoxybenzene (TMB) to form a carbene-TMB complex, as well as between carbene 3 and chloride ion to form the zwitterion, N-methyl-3-pyridinium dichloromethide (10). These equilibrium constants and thermodynamic parameters are contrasted with analogous data for several related carbenes, and the influence of the pyridinium unit in carbene 3 is thereby highlighted. Computational studies augment and elucidate the experimental results. PMID:26830199

  16. Study of two-phase flows in reduced gravity

    NASA Astrophysics Data System (ADS)

    Roy, Tirthankar

    Study of gas-liquid two-phase flows under reduced gravity conditions is extremely important. One of the major applications of gas-liquid two-phase flows under reduced gravity conditions is in the design of active thermal control systems for future space applications. Previous space crafts were characterized by low heat generation within the spacecraft which needed to be redistributed within the craft or rejected to space. This task could easily have been accomplished by pumped single-phase loops or passive systems such as heat pipes and so on. However with increase in heat generation within the space craft as predicted for future missions, pumped boiling two-phase flows are being considered. This is because of higher heat transfer co-efficients associated with boiling heat transfer among other advantages. Two-phase flows under reduced gravity conditions also find important applications in space propulsion as in space nuclear power reactors as well as in many other life support systems of space crafts. Two-fluid model along with Interfacial Area Transport Equation (IATE) is a useful tool available to predict the behavior of gas-liquid two-phase flows under reduced gravity conditions. It should be noted that considerable differences exist between two-phase flows under reduced and normal gravity conditions especially for low inertia flows. This is because due to suppression of the gravity field the gas-liquid two-phase flows take a considerable time to develop under reduced gravity conditions as compared to normal gravity conditions. Hence other common methods of analysis applicable for fully developed gas-liquid two-phase flows under normal gravity conditions, like flow regimes and flow regime transition criteria, will not be applicable to gas-liquid two-phase flows under reduced gravity conditions. However the two-fluid model and the IATE need to be evaluated first against detailed experimental data obtained under reduced gravity conditions. Although lot of studies

  17. Electrostatic levitation studies of supercooled liquids and metastable solid phases

    NASA Astrophysics Data System (ADS)

    Rustan, Gustav Errol

    been carried out to study the metastable phase formation in an Fe83B17 near eutectic alloy. Initial supercooling measurements using the ISU-ESL identified the formation of three metastable phases: a precipitate phase that shows stable coexistence with the deeply supercooled liquid, and two distinct bulk solidification phases. To identify the structure of the metastable phases, the Washington University Beamline ESL (WU-BESL) has been used to perform in-situ high energy x-ray diffraction measurements of the metastable phases. Based on the x-ray results, the precipitate phase has been identified as bcc-Fe, and the more commonly occurring bulk solidification product has been found to be a two-phase mixture of Fe23B6 plus fcc-Fe, which appears, upon cooling, to transform into a three phase mixture of Fe23B6, bcc-Fe, and an as-yet unidentified phase, with the transformation occurring at approximately the expected fcc-to-bcc transformation temperature of pure Fe. To further characterize the multi-phase metastable alloy, the ISU-ESL has been used to perform measurements of volume thermal expansion via the videographic technique, as well as RF susceptibility via the TDO technique. The results of the thermal expansion and susceptibility data have been found to be sensitive indicators of additional structural changes that may be occurring in the metastable solid at temperatures below 1000 K, and the susceptibility data has revealed that three distinct ferromagnetic phase transitions take place within the multi-phase mixture. Based on these results, it has been hypothesized that there may be an additional transformation taking place that leads to the formation of either bct- or o-Fe3B in addition to the Fe23B6 phase, although further work is required to test this hypothesis.

  18. Engineering study for the phase 1 privatization facilities electrical power

    SciTech Connect

    Singh, G., Westinghouse Hanford

    1996-07-18

    This engineering study evaluates the availability of electric power from the existing 13.8 kV substation, BPA 115 kV system,and RL 230 kV transmission line; for supporting the Privatization Phase I Facilities. 230 kV system is a preferable alternative.

  19. Bullying during the Intermediate School Phase: A South African Study

    ERIC Educational Resources Information Center

    Greeff, P.; Grobler, A. A.

    2008-01-01

    Bullying in the intermediate school phase was studied, using the Revised Olweus Bully/Victim Questionnaire (R-OBVQ). The total sample comprised 360 grade 4 to 6 pupils from English-medium, single-sex schools in Bloemfontein, South Africa. To ensure a more homogeneous sample, the grade (grades 4 to 6) and race (black and white) of the participants…

  20. Western Wind and Solar Integration Study Phase 3: Technical Overview

    SciTech Connect

    2015-11-01

    Technical fact sheet outlining the key findings of Phase 3 of the Western Wind and Solar Integration Study (WWSIS-3). NREL and GE find that with good system planning, sound engineering practices, and commercially available technologies, the Western grid can maintain reliability and stability during the crucial first minute after grid disturbances with high penetrations of wind and solar power.

  1. Numerical studies of gravity effects in two-phase reservoirs

    SciTech Connect

    Bodvarsson, G.S.; Cox, B.L.

    1986-06-01

    Numerical studies are performed to investigate the effects of localized feed zones on the pressure transients in two-phase reservoirs. It is shown that gravity effects can significantly affect the pressure transients, because of the large difference in the density of liquid water and vapor. Pressure transients for shallow and deep feed zones and the resulting fluid flow patterns are discussed.

  2. SOURCE ASSESSMENT: TEXTILE PLANT WASTEWATER TOXICS STUDY--PHASE I

    EPA Science Inventory

    The report gives results of the first phase of a study to provide chemical and toxicological baseline data on wastewater samples collected from textile plants in the U.S. Raw waste and secondary effluent wastewater samples were analyzed for 129 consent decree priority pollutants,...

  3. Ab initio study of energetics and magnetism of sigma phase in Co-Mo and Fe-Mo systems

    NASA Astrophysics Data System (ADS)

    Pavlů, J.; Vřešťál, J.; Šob, M.

    2016-02-01

    We analyse, from first-principles, the energetics and magnetic ordering of sigma phases in Co-Mo and Fe-Mo systems. Total energy differences between the sigma phase and Standard Element Reference (SER) structures are calculated in the whole concentration range at equilibrium volumes by means of the linear muffin-tin orbitals method in the atomic-sphere approximation (LMTO-ASA), the full-potential linearised augmented-plane waves (FLAPW) method and the pseudopotential approach. They are compared with the enthalpy of formation of sigma phase obtained from the phase equilibria calculations at higher temperature based on the semiempirical CALPHAD (CALculation of PHAse Diagram) method. It turns out that the binary sigma phases are more stable than the weighted average of the sigma phase of elemental constituents and that this stability for Fe-Mo is higher than for Co-Mo. On the other hand it was found that the binary sigma phases do not exhibit any stability with respect to the weighted average of the SER structures. The magnetic configurations in all systems are investigated and the stabilizing effect of magnetic order in sigma phase at 0 K is presented. It turns out that the atomic magnetic moment strongly depends on the type of occupied sublattice and total composition of the alloy.

  4. Alternating-phase focusing: A model to study nonlinear dynamics

    SciTech Connect

    Sagalovsky, L.; Delayen, J.R.

    1992-01-01

    We discuss a new model to study alternating-phase focusing (APF). Our approach is based on representing the accelerating electric field with a continuous phase modulated traveling wave. The resulting nonlinear equations of motion can be solved analytically to predict the regions of stable APF motion. We also identify the key parameters which adequately describe the physics of APF. The model is believed to be applicable to low-{beta} ion linacs with short independently-controlled superconducting cavities being developed at ANL.

  5. Alternating-phase focusing: A model to study nonlinear dynamics

    SciTech Connect

    Sagalovsky, L.; Delayen, J.R.

    1992-09-01

    We discuss a new model to study alternating-phase focusing (APF). Our approach is based on representing the accelerating electric field with a continuous phase modulated traveling wave. The resulting nonlinear equations of motion can be solved analytically to predict the regions of stable APF motion. We also identify the key parameters which adequately describe the physics of APF. The model is believed to be applicable to low-{beta} ion linacs with short independently-controlled superconducting cavities being developed at ANL.

  6. A solvable many-body problem, its equilibria, and a second-order ordinary differential equation whose general solution is polynomial

    NASA Astrophysics Data System (ADS)

    Calogero, Francesco

    2013-01-01

    Some properties of a solvable N-body problem featuring several free parameters ("coupling constants") are investigated. Restrictions on its parameters are reported which guarantee that all its solutions are completely periodic with a fixed period independent of the initial data (isochrony). The restrictions on its parameters which guarantee the existence of equilibria are also identified. In this connection a remarkable second-order ODE—generally not of hypergeometric type, hence not reducible to those characterizing the classical polynomials—is studied: if its parameters satisfy a Diophantine condition, its general solution is a polynomial of degree N, the N zeros of which identify the equilibria of the N-body system.

  7. Vlasov tokamak equilibria with shearad toroidal flow and anisotropic pressure

    NASA Astrophysics Data System (ADS)

    Throumoulopoulos, George; Kuiroukidis, Apostolos; Tasso, Henri

    2015-11-01

    By choosing appropriate deformed Maxwellian ion and electron distribution functions depending on the two particle constants of motion, i.e. the energy and toroidal angular momentum, we reduce the Vlasov axisymmetric equilibrium problem for quasineutral plasmas to a transcendental Grad-Shafranov-like equation. This equation is then solved numerically under the Dirichlet boundary condition for an analytically prescribed boundary possessing a lower X-point to construct tokamak equilibria with toroidal sheared ion flow and anisotropic pressure. Depending on the deformation of the distribution functions these steady states can have toroidal current densities either peaked on the magnetic axis or hollow. These two kinds of equilibria may be regarded as a bifurcation in connection with symmetry properties of the distribution functions on the magnetic axis. This work has received funding from (a) the National Programme for the Controlled Thermonuclear Fusion, Hellenic Republic, (b) Euratom research and training programme 2014-2018 under grant agreement No 633053.

  8. Topology of tokamak plasma equilibria with toroidal current reversal

    SciTech Connect

    Rodrigues, Paulo; Bizarro, Joao P. S.

    2012-01-15

    Some general principles about scalar functions with critical points are used to rigorously ascertain that magnetic equilibria with both toroidal current reversal and nested magnetic surfaces are atypical solutions and highly unstable to arbitrary perturbations of boundary conditions and other parameters. The cause for such is shown to lie in the condition of nested magnetic surfaces and not in the possibility of current reversal and consequent vanishing of the poloidal field inside the plasma. Rather than supporting the claim that instability against experimentally driven perturbations forbids configurations with toroidal current reversal, it is argued that these can be attained if an axisymmetric island system is allowed for in order to break the condition of nested magnetic surfaces. A number of results previously reported in the literature are discussed and reinterpreted under the proposed framework, providing some physical insight on the nature of equilibria with toroidal current reversal.

  9. Sloshing-ion equilibria in the TARA endplugs

    SciTech Connect

    Hokin, S.; Kesner, J.

    1983-11-01

    We have employed a modified version of the LLNL Bounce-average Fokker-Planck code to model neutral beam-produced sloshing-ion equilibria in the TARA endplugs. The questions we have addressed concern the effect of deuterium beam operation as opposed to hydrogen operation, and the advantage of using full-energy beams rather than the usual three-component beams. We find that, for the expected base case TARA operating parameters, a 40% savings in required beam power is attained by using deuterium beams rather than hydrogen beams, and that the use of full-energy beams results in an additional 26% power savings for these parameters. For higher plasma temperatures the use of full-energy beams becomes significantly advantagous. We have also investigated the equilibria of two possible alternate mirror configurations for the TARA endplugs, believed to be more stable to trapped particle modes, and report those results here.

  10. Vlasov tokamak equilibria with sheared toroidal flow and anisotropic pressure

    SciTech Connect

    Kuiroukidis, Ap; Throumoulopoulos, G. N.; Tasso, H.

    2015-08-15

    By choosing appropriate deformed Maxwellian ion and electron distribution functions depending on the two particle constants of motion, i.e., the energy and toroidal angular momentum, we reduce the Vlasov axisymmetric equilibrium problem for quasineutral plasmas to a transcendental Grad-Shafranov-like equation. This equation is then solved numerically under the Dirichlet boundary condition for an analytically prescribed boundary possessing a lower X-point to construct tokamak equilibria with toroidal sheared ion flow and anisotropic pressure. Depending on the deformation of the distribution functions, these steady states can have toroidal current densities either peaked on the magnetic axis or hollow. These two kinds of equilibria may be regarded as a bifurcation in connection with symmetry properties of the distribution functions on the magnetic axis.

  11. Braided coronal loops: equilibria, heating, and observational signatures

    NASA Astrophysics Data System (ADS)

    Pontin, David Iain; Hornig, Gunnar; Candelaresi, Simon

    2016-05-01

    We examine the dynamics of coronal loops containing non-trivial magnetic field line braiding. We discuss the existence of braided force-free equilibria, and demonstrate that these equilibria must contain current layers whose thickness becomes increasingly small for increasing field complexity. In practical terms, the implication is that if one considers a line-tied coronal loop that is driven by photospheric motions, then the eventual onset of reconnection and energy release is inevitable. Once the initial reconnection event is triggered a turbulent relaxation ensues. We discuss the relation with Parker’s braiding mechanism for coronal heating, and go on to describe the expected observational signatures of energy release in such a braided coronal loop.

  12. Finding Bounded Rational Equilibria. Part 1; Iterative Focusing

    NASA Technical Reports Server (NTRS)

    Wolpert, David H.

    2004-01-01

    A long-running difficulty with conventional game theory has been how to modify it to accommodate the bounded rationality characterizing all real-world players. A recurring issue in statistical physics is how best to approximate joint probability distributions with decoupled (and therefore far more tractable) distributions. It has recently been shown that the same information theoretic mathematical structure, known as Probability Collectives (PC) underlies both issues. This relationship between statistical physics and game theory allows techniques and insights from the one field to be applied to the other. In particular, PC provides a formal model-independent definition of the degree of rationality of a player and of bounded rationality equilibria. This pair of papers extends previous work on PC by introducing new computational approaches to effectively find bounded rationality equilibria of common-interest (team) games.

  13. Bifurcation Analysis of Equilibria in Competitive Logistic Networks with Adaptation

    NASA Astrophysics Data System (ADS)

    Raimondi, A.; Tebaldi, C.

    2008-04-01

    A general n-node network is considered for which, in absence of interactions, each node is governed by a logistic equation. Interactions among the nodes take place in the form of competition, which also includes adaptive abilities through a (short term) memory effect. As a consequence the dynamics of the network is governed by a system of n2 nonlinear ordinary differential equations. As a first step, equilibria and their stability are investigated analytically for the general network in dependence of the relevant parameters, namely the strength of competition, the adaptation rate and the network size. The existence of classes of invariant subspaces, related to symmetries, allows the introduction of a reduced model, four dimensional, where n appears as a parameter, which give full account of existence and stability for the equilibria in the network.

  14. A study of geometric phase topology using Fourier transform method

    NASA Astrophysics Data System (ADS)

    Samlan, C. T.; Naik, Dinesh N.; Viswanathan, Nirmal K.

    2016-07-01

    Topological aspect of the geometric phase (GP) due to pure polarization projection is studied using the 2D Fourier transform (2D-FT) method. Projection of orthogonal polarization state results in a phase singularity in the 2D parameter space of ellipticity and orientation of polarization ellipse. Projection of its surrounding states results in an accumulation of GP in different amount that form a spiral structure. A half wave plate–quarter wave plate combination is used to generate different polarization states which are projected using a polarizer. The accumulated phase for each orientation of the wave plate is extracted from 2D-FT of the interferogram, obtained by interfering it with a reference beam in a Mach–Zehnder like interferometer.

  15. Preliminary Exploratory Study of Different Phase II Collimators

    SciTech Connect

    Lari, L.; Assmann, R.W.; Bertarelli, A.; Bracco, C.; Brugger, M.; Cerutti, F.; Dallocchio, A.; Ferrari, A.; Mauri, M.; Roesler, S.; Sarchiapone, L.; Vlachoudis, Vasilis; Doyle, J.E.; Keller, L.; Lundgren, S.A.; Markiewicz, Thomas W.; Smith, J.C.; Lari, L.; /LPHE, Lausanne

    2011-11-02

    The Large Hadron Collider (LHC) collimation system is installed and commissioned in different phases, following the natural evolution of the LHC performance. To improve cleaning efficiency towards the end of the low beta squeeze at 7TeV, and in stable physics conditions, it is foreseen to complement the 30 highly robust Phase I secondary collimators with low impedance Phase II collimators. At this stage, their design is not yet finalized. Possible options include metallic collimators, graphite jaws with a movable metallic foil, or collimators with metallic rotating jaws. As part of the evaluation of the different designs, the FLUKA Monte Carlo code is extensively used for calculating energy deposition and studying material damage and activation. This report outlines the simulation approach and defines the critical quantities involved.

  16. A 220 GHz reflection-type phased array concept study

    NASA Astrophysics Data System (ADS)

    Hedden, Abigail S.; Dietlein, Charles R.; Wikner, David A.

    2011-05-01

    The goal of this project is to enable light-weight, durable, and portable systems capable of performing standoff detection of person-borne improvised explosive devices (PB-IEDs) through the development of millimeter-wave reflection-type phased arrays. Electronic beam steering eliminates the need for complex mechanical scanners that are commonly implemented with millimeter-wave imaging systems and would reduce overall system size and weight. We present a concept study of a 220 GHz reflection-type phased array for the purpose of performing beam scanning of a confocal reflector system. Requirements for effective imaging of the desired target region are established, including spatial resolution, total scan angle, and number of image pixels achievable. We examine the effects of array architecture on beam characteristics as it is scanned off broadside, including Gaussicity and encircled energy. Benchmark requirements are determined and compared with the capabilities of several potential phase shifter technologies, including MEMS-based variable capacitor phase shifters, switches, and varactor diode-based phase shifters.

  17. a Comprehensive DFT Study of Zinc Oxide in Different Phases

    NASA Astrophysics Data System (ADS)

    Ul Haq, Bakhtiar; Afaq, A.; Ahmed, R.; Naseem, S.

    2012-06-01

    A density functional study for structural and electronic properties of Zinc Oxide (ZnO), in wurtzite, rock salt and zinc-blende phases has been performed using full potential-linearized augmented plane wave/linearized augmented plane wave plus local ideal orbital (FP-LAPW/L(APW+lo) approach as realized in WIEN2k code. To approximate exchange correlation energy and corresponding potential, a special GGA parameterized by Wu-Cohen has been implemented. Our results of lattice constants, bulk moduli as well as for internal parameter with GGA-WC are found to be more reliable. This study reveals that value of internal parameter decreases with increasing volume whereas computed electronic band structure confirms the direct band gap behavior of ZnO in B4 and B3 phases while indirect band gap behavior in B1 phase. Moreover, two fold degeneracy at the maxima of valence band for B4 and B1 phases whereas three fold for B3 is observed. A detailed comparison with experimental and other first principles studies is also made.

  18. A Chaotic System with Different Shapes of Equilibria

    NASA Astrophysics Data System (ADS)

    Pham, Viet-Thanh; Jafari, Sajad; Wang, Xiong; Ma, Jun

    Although many chaotic systems have been introduced in the literature, a few of them possess uncountably infinite equilibrium points. The aim of our short work is to widen the current knowledge of the chaotic systems with an infinite number of equilibria. A three-dimensional system with special properties, for example, exhibiting chaotic attractor with circular equilibrium, chaotic attractor with ellipse equilibrium, chaotic attractor with square-shaped equilibrium, and chaotic attractor with rectangle-shaped equilibrium, is proposed.

  19. Chemical equilibria involved in the oxygen-releasing step of manganese ferrite water-splitting thermochemical cycle

    SciTech Connect

    Seralessandri, L.; Bellusci, M.; Alvani, C.; La Barbera, A.; Padella, F.; Varsano, F.

    2008-08-15

    Sodium ferrimanganite carbonatation reaction was investigated at different temperatures/carbon dioxide partial pressures to evaluate the feasibility of the thermochemical water-splitting cycle based on the MnFe{sub 2}O{sub 4}/Na{sub 2}CO{sub 3}/Na(Mn{sub 1/3}Fe{sub 2/3})O{sub 2} system. After thermal treatments in selected experimental conditions, the obtained powder samples were investigated by using the X-ray diffraction (XRD) technique and Rietveld analysis. Two different lamellar Na{sub 1-x}Mn{sub 1/3}Fe{sub 2/3}O{sub 2-{delta}} phases were observed together with the expected MnFe{sub 2}O{sub 4}/Na{sub 2}CO{sub 3} mixture. Different equilibrium regions among sodium-depleted lamellar phases, manganese ferrite and sodium carbonate were found as a function of the different reaction conditions. A hypothesis concerning the regeneration mechanism of the initial compounds is proposed. Chemical equilibrium between stoichiometric and sub-stoichiometric forms of sodium ferrimanganite and sodium carbonate formation/dissociation appears to be essential factors governing the oxygen-releasing step of the manganese ferrite thermochemical cycle. - Graphical abstract: Na(Mn{sub 1/3}Fe{sub 2/3})O{sub 2} disproportion reaction in the presence of CO{sub 2} was studied. Chemical equilibria among Na{sub 1-x}(Mn{sub 1/3}Fe{sub 2/3})O{sub 2}, MnFe{sub 2}O{sub 4} and Na{sub 2}CO{sub 3} compounds were evidenced and studied by means of Rietveld analysis performed on XRD patterns. Two different sodium-depleted lamellar structures were identified. The role of sodium carbonate formation/dissociation equilibrium in the oxygen-releasing step of the manganese ferrite thermochemical cycle has been highlighted.

  20. A binary phase field crystal study for liquid phase heteroepitaxial growth

    NASA Astrophysics Data System (ADS)

    Lu, Yanli; Peng, Yingying; Chen, Zheng

    2016-09-01

    The liquid phase heteroepitaxial growth on predefined crystalline substrate is studied with binary phase field crystal (PFC) model. The purpose of this paper focuses on changes of the morphology of epitaxial films, influences of substrate vicinal angles on epitaxial growth, characteristics of islands growth on both sides of the substrate as well. It is found that the morphology of epitaxial films undergoes the following transitions: layer-by-layer growth, islands formation, mismatch dislocations nucleation and climb towards the film-substrate interface. Meanwhile, the density of steps and islands has obviously direct ratio relations with the vicinal angles. Also, preferential regions are found when islands grow on both sides of the substrate. For thinner substrate, the arrangement of islands is more orderly and the appearance of preferential growth is more obvious than that of thicker substrate. Also, the existing of preferential regions is much more valid for small substrate vicinal angles in contrast for big substrate vicinal angles.