Showing papers on "Binary system published in 1992"

Presupernova Evolution in Massive Interacting Binaries

Abstract: The way in which binary interaction affects the presupernova evolution of massive close binaries and the resulting supernova explosions is investigated systematically by means of a Henyey-type stellar evolution code that was modified to allow its application to binary stellar evolution calculations. The code makes it possible to trace the effects of mass and angular momentum loss from the binary, as well as mass transfer within the binary system. It is found that a large number of binary scenarios can be distinguished, depending on the type of binary interaction and the evolutionary stage of the supernova progenitor at the time of the interaction. Monte Carlo simulations are performed to estimate the frequencies of the occurrence of various scenarios. It is found that, because of a previous binary interaction, 15-30 percent of all massive stars (with initial masses greater than about 8 solar masses) become helium stars, and another 5 percent of all massive stars end their lives as blue supergiants rather than as red supergiants.

Application of molecular simulation to derive phase diagrams of binary mixtures

Abstract: The miscibility behavior of three binary mixtures, solvent with solvent, polymer with solvent, and polymer with polymer, was studied by use of a combination of the Flory-Huggins theory and molecular simulation techniques. Fundamental parameters in the Flory-Huggins theory, including the heat of mixing associated with pairwise interactions (Aw12) and the number of possible interaction partners, i.e., coordination number, z, are calculated from molecular simulations. The pair energies (~11, w22, ~12) are obtained by averaging a large number of confiations generated by a Monte Carlo approach which includes the constraints associated with excluded volume. The temperature dependence of the interaction parameter x is obtained with the formalism developed in this study. In all cases, the calculated upper critical solution temperatures compare favorably with experimental values. This approach provides an opportunity to test the Flory- Huggins theory for a number of model binary systems and to characterize their miscibility behavior. This combined approach also facilitates study of the thermodynamic behavior of a binary mixture without possessing specific knowledge or experimental data of the system under investigation.

A neutron scattering study of the structure of a bimodal colloidal crystal

Abstract: We have studied the freezing of a binary mixture of colloidal poly(methyl methacrylate) spheres of size ratio 0.31 and composition AB4 (here A refers to the larger spheres). When suspended in a suitable liquid these particles interact via a steeply repulsive (approximately hard sphere) potential. The structure of the colloidal crystals formed in this binary system has been established from a combination of small‐angle neutron and light scattering measurements. We find that there is an almost complete size separation on freezing. The crystalline phase contains almost exclusively large spheres while the smaller spheres are excluded from the crystal into a coexisting binary fluid. This observation is in agreement with recent density functional calculations for the freezing of hard sphere mixtures.

Binaries as Tracers of Stellar Formation

Abstract: 1. N-body simulations of primordial binaries and tidal capture in open clusters 2. When and how can binary data test similar models? 3. Statistical analysis of single-lined red giant spectroscopic binaries 4. The formation of binary stars 5. Distribution and evolution of orbital elements for 1 M primaries 6. Tidal circularization of short period binaries 7. Composite-spectrum binaries 8. Orbital elements for field late-type binaries 9. Evidences for interaction among wide binary systems: to Ba or not to Ba? 10. Spectroscopic binaries in the open cluster M67 11. Spectroscopic binaries in the halo 12. Eccentricity evolution of a binary embedded in a disk 13. The eccentricity distribution of pre-main sequence binaries 14. A new algorithm to derive the mass-ratio distribution of spectroscopic binaries in open clusters 15. Are barium dwarfs progenitors of barium giants 16. RZ Eridani as a constraint on synchronization and circularization times 17. Ekman layers and tidal synchronization of binary stars 18. The distribution of mass ration in late-type main-sequence binary systems 19. The dynamical evolution of G-type main sequence binaries 20. Present state of the tidal theory 21. Infrared companions: clues to binary star formation 22. The distribution of cutoff periods with age: an observational constraint on tidal circularization theory.

Thermodynamic calculation of the ternary TiAlNb system

Abstract: Phase equilibria of the ternary TiAlNb system are dominated by the large range of homogeneity of (β-Ti,Nb), the binary intermetallic compounds of the NbAl and TiAl systems and the formation of two ternary compounds. The available ternary experimental data, together with a thermodynamic extrapolation of the ternary system from the binary systems, have been used to calculate the ternary phase diagram. The model descriptions of the Gibbs energies of most of these compounds are given by the existing calculations of the binary systems. In order to model a phase which is present in only one binary system, but has a ternary homogeneity range, a hypothetical phase with the same structure was analytically described for each binary system. Such a phase would, of course, be metastable in the other binary systems. Constraints on the Gibbs energies of formation were derived from the crystal structures of the corresponding ordered compounds. These same constraints were employed for the corresponding phases in the ternary system. In a final optimization step, ternary parameters were introduced and adjusted to the available experimental data. The as-derived description of the ternary TiAlNb system can be used to estimate single or multiphase fields and thermodynamic quantities where no experimental data are yet available. It is also useful as an indicator of problem areas for which additional experimental data are required.

Coalescing binary systems of compact objects to (post)5/2-Newtonian order. II. Higher-order wave forms and radiation recoil.

Abstract: Using formulas developed by Blanchet, Damour, and Iyer, we obtain a symmetric trace-free multipolar expansion of the gravitational radiation from a coalescing binary system which is sufficiently accurate to allow a post-Newtonian calculation of the linear momentum carried off by the gravitational radiation prior to a binary coalescence. We briefly examine the structure of the post-quadrupole corrections to the wave form for an orbiting binary system near coalescence. The post-Newtonian correction to the momentum ejection allows a more accurate calculation of the system recoil velocity (radiation rocket effect). We find that the higher-order correction actually reduces the net momentum ejection. Furthermore, the post-Newtonian correction to the momentum flux has only a weak dependence on the mass ratio of the objects in the binary, suggesting that previous test mass calculations may be quite accurate. We estimate an upper bound of the center-of-mass velocity of 1 km ${\mathrm{s}}^{\ensuremath{-}1}$ for neutron star binaries very near coalescence. In an appendix we give a self-contained (albeit less rigorous) derivation of the gravitational wave form using the Epstein-Wagoner formalism.

Surface tension of binary and ternary aluminium alloys of the systems Al-Si-Mg and Al-Zn-Mg

Abstract: The surface tension and density of liquid binary and ternary aluminium alloys of the systems Al-Si-Mg and Al-Zn-Mg (Si, Mg and Zn contents less than 19, 8 and 20 wt %, respectively) have been measured by means of the maximum bubble pressure method. A semi-empirical theory, which relates the surface tension to bulk thermodynamic properties, is used to calculate the surface tension of the binary alloys and discuss the experimental data. For the ternary alloys, the present results indicate that in the range of compositions explored here, the properties of the ternaries can be obtained from those of the binaries. Comparison with results previously reported by other authors is made.

Intermediate liquid crystalline phases in the binary system C16TACl-H2O: an NMR and low-angle x-ray diffraction study

Abstract: The liquid crystalline phases formed in the concentration range between the hexagonal and the lamellar phase in the binary system C 16 TACl-H 2 O have been studied by 2 H, 14 N, and 35 Cl NMR, low-angle X-ray diffraction and optical microscopy. A cubic phase and three anisotropic so-called intermediate phases have been found. At 45 o C the hexagonal phase is stable up to 75 wt % C 16 TACl. Between 75% and 79%, a biaxial phase (Int-1) built up by long rods with noncircular cross sections is formed

Solubility of methane in hexane, decane, and dodecane at temperatures from 311 to 423 K and pressures to 10.4 MPa

Abstract: The solubilities of methane in the normal paraffins hexane, decane, and dodecane were measured using a static equilibrium cell over the temperature range from 311 to 423 K and pressures to 10.4 MPa. The new solubility measurements are believed to have uncertaities of 0.002 in mole fraction, and they compare favorably with available literature data. The data were analyzed using the Soave-Redlich-Kwong and Peng-Robinson equations of state. In general, the two equations represent the experimenal data well over the complete temperature range when two interaction parameters are used for each binary system

Phase equilibria of oleic acid, methyl oleate, and anhydrous milk fat in supercritical carbon dioxide

Abstract: A static recirculation method was developed and used to measure phase equilibria of binary, ternary, and multicomponent systems in supercritical carbon dioxide (SC-CO 2 ). Binary fluid-liquid equilibria of oleic acid + SCCO 2 were experimentally determined at 313.15 and 333.15 K and at pressures between 3 and 31 MPa. Fluid-liquid equilibria of the binary system methyl oleate + SCCO 2 were also measured at 313.15 and 333.15 K and at pressures between 2 and 14 MPa. Finally, the phase equilibria of anhydrous milk fat (AMF) in SC-CO 2 were determined at 313.15 and 333.15 K and at pressures between 2 and 31 MPa. The data were correlated using the Peng-Robinson equation-of-state with the Panagiotopoulos and Reid mixing rule.

The Mass-Ratio Distribution of Spectroscopic Binary Stars

Abstract: In order to determine the mass-ratio distribution of spectroscopic binary stars, the selection effects that govern the observations of this class of binary systems are investigated. The selection effects are modelled numerically and analytically. The results of the models are compared to the data inThe Eighth Catalogue of the Orbital Elements of Spectroscopic Binary Stars (DAO8) compiled by Battenet al. (1989). The investigations involve binary systems with Main-Sequence primary components only, in order to avoid confusion of evolutionary and selection effects.

The equilibrium phase properties of the propane‐methanol and n‐Butane‐methanol binary systems

Abstract: Vapor and liquid equilibrium phase compositions were determined at 310.7, 352.2, 393.0 and 474.3 K for the propane-methanol system and at 469.9 K for the n-butane–methanol system. Measurements were made at pressures from the vapor pressure of the less volatile component to the maximum pressure where two phases coexisted either as an azeo-trope or at the critical condition, depending on the system. Azeotropic behavior was observed at 310.7 and 352.2 K for the propane-methanol system. Equilibrium ratios were calculated at each temperature from the phase composition data. The temperature dependence of the azeotrope pressure and of the corresponding azeotrope composition was expressed analytically.

29Si MAS-NMR Study of the Short-Range Order in Lithium Borosilicate Glasses

Abstract: 29Si MAS-NMR measurements have been made on a series of lithium borosilicate glasses of general composition RLi2O.B2O3·KSiO2. At low alkali contents (R < 1), the 29Si resonance envelope is broadened and indicates a distribution of Si sites. As R increases above 1, the FWHM of the 29Si resonance narrows considerably to that representative of a single chemical site. Simultaneously, the average chemical shift of the resonance shifts upfield in agreement with the trends found in the binary lithium silicate glass system. Using the chemical shifts for the individual Q species in the binary system it was found that very good agreement between the chemical shifts of the binary glasses and the ternary glasses examined here could be achieved if a model of proportional sharing of the added oxygen (from lithia) between silicate and borate units was used. In contrast to the 11B NMR studies of these same glasses, the 29Si NMR data are quantitatively best-fit if it is assumed that the proportional sharing of the oxygen from the added lithia begins at R= 0. Models of sharing developed from the 11B NMR studies of these glasses, where proportional sharing above a certain fixed (independent of K) or variable (dependent on K) minimum R0, have been reexamined and were quantitatively shown through residual analysis to give consistently poorer fits to our data. At present the reasons for the discrepancy between the two sets of NMR data are unknown.

Connectivity of critical lines around the van Laar point in T, X projections

Abstract: It is shown that the SPHCT equation of state describes qualitatively the same types of binary phase behavior around the van Laar point as the van der Waals and the Redlich–Kwong equation of state. A continuous transition is possible from a binary system with a van Laar point into binary systems that show type II, III, IV and IV* phase behavior. The global phase diagram turns out to be a helpful tool in the exploration of these different types of phase behavior. Special attention is paid to the link between moving across the global phase diagram and the resulting changes in the phase behavior of the corresponding binary mixtures. We will focus on the temperature‐composition behavior of the critical lines in the binary mixtures. This temperature‐composition behavior is very important if one wants to make an experimental verification of the van Laar point or type IV* phase behavior.