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  • 1
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    Optical and quantum electronics 31 (1999), S. 733-749 
    ISSN: 1572-817X
    Keywords: anisotropy ; Leaky modes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An exact numerical method for analyzing the propagation properties of leaky modes of inhomogeneous channel optical waveguides with a complex uniaxial diagonal permittivity tensor is developed. The method is based on solving the system of integro-differential equations formulated with respect to transversal components of the magnetic field and the longitudinal component of the electric field. Some results of investigation of leaky modes of diffused channel waveguides in LiNbO3 and LiTaO3 crystals are given.
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  • 2
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    Journal of superconductivity 12 (1999), S. 531-534 
    ISSN: 1572-9605
    Keywords: Organic superconductor ; superconductivity ; anisotropy ; Fermi surface
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The electronic states have been studied in the quasi-one-dimensional DMET-TSeF system, which includes several superconductors and nonsuperconductors. The origin of the different ground states has been examined by using the tight-binding band calculation. The type of the superconductivity has been discussed, considering the electronic wave functions that constitute the Fermi surface.
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  • 3
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    Journal of statistical physics 95 (1999), S. 981-996 
    ISSN: 1572-9613
    Keywords: nonequilibrium ; driven diffusive systems ; lattice gas ; kinetic Ising model ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Ising lattice gas, with its well known equilibrium properties, displays a number of surprising phenomena when driven into nonequilibrium steady states. We study such a model with anisotropic interparticle interactions (J ||≠J ⊥), using both Monte Carlo simulations and high temperature series techniques. Under saturation drive, the shift in the transition temperature can be both positive and negative, depending on the ratio J ||/J ⊥! For finite drives, both first- and second-order transitions are observed. Some aspects of the phase diagram can be predicted by investigating the two-point correlation function at the first nontrivial order of a high-temperature series expansion.
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  • 4
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    Journal of statistical physics 95 (1999), S. 1337-1360 
    ISSN: 1572-9613
    Keywords: diffuse interfaces ; hexagonal close packing ; anisotropy ; mean-field theory ; Allen–Cahn equation ; interphase boundaries ; antiphase boundaries ; surface energy ; discrete free energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A multiple-order-parameter mean-field theory of ordering on a binary hexagonal- close-packed (HCP) crystal structure is developed, and adapted to provide a continuum formulation that incorporates the underlying symmetries of the HCP crystal in both the bulk and gradient energy terms of the free energy. The work is an extension of the previous treatment by Braun et al. [Phil. Trans. Roy. Soc. Lond. A 355:1787 (1997)] of order–disorder transitions on a face-centered-cubic crystal (FCC) lattice. The theory is used to compute the orientation dependence of the structure and energy of interphase and antiphase boundaries in ordering to the Cd3Mg and CdMg structures, which are the HCP analogs of Cu3Au and CuAu structures in FCC. As in the corresponding FCC case, the multiple order parameters do not form a vector. Anisotropy is a natural consequence of the underlying crystal symmetries and the multiple-order-parameter continuum formation presented here. The isotropy transverse to the sixfold axis expected for a scalar order parameter is not found.
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  • 5
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    Physics and chemistry of minerals 26 (1999), S. 644-648 
    ISSN: 1432-2021
    Keywords: Key words MnO ; CdO ; rock-salt monoxides ; X-ray diffraction ; equation of state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Room-temperature volume measurements up to 8.1 GPa reveal that rock-salt structured MnO and CdO have identical compressibility in the pressure range studied. In the plot of bulk modulus vs unit-cell volume, CdO plots well above the trend of the 3d transition metal monoxides, a behavior that deviates from empirical predictions of constant K 0 V 0. The present observations are in favor of our earlier suggestion that, for isostructural solids, the empirically predicted bulk modulus-volume relationship may be limited to their subsets that share the same valence electron character (i.e., s vs 3d vs 4d). For cations forming transition metal monoxides, variations of Pauling electronegativity with ionic radius show differences that are qualitatively similar to the observed trends of bulk modulus, suggesting that bond covalency differences may contribute to the different behaviors between the 3d and 4d transition metal monoxides.
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  • 6
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    Acta mechanica Sinica 15 (1999), S. 355-365 
    ISSN: 1614-3116
    Keywords: dentin ; dentin tubules ; anisotropy ; inhomogeneity ; stress-strain relations ; strength criterion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract As known, there is a large number of dentin tubules in dentin. These tubules have varying radii and are shaped into radially parallel pattern. The anisotropy of microstructure of dentin shows that dentin should be treated as a material of varying transverse isotropy. In this Part, the elastic stress-strain relations and the quadratic strength criterion are established in the form of having varying transverse isotropy, in the framework of micromechanics to take into account of the effect of the microstructures-dentin tubules. Simplified forms for isotropic and homogeneous cases, as well as the corresponding plane stress form of the stress-strain relations are also given. These theoretical models are very well supported by the experiments shown later in the continued paper (Part II).
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  • 7
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    Journal of superconductivity 12 (1999), S. 511-514 
    ISSN: 1572-9605
    Keywords: Organic superconductors ; BETS ; superconductivity ; critical field ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The upper critical field B c2 of the organic superconductor λ-(BETS)2GaCl4 has been determined from resistance measurements for orientation of the magnetic field along three perpendicular crystallographic directions. The Ginzburg–Landau coherence length was estimated from the slope of B c2(T) curve near T c as 12.5 nm, 1.6 nm, and 12.5 nm for the a*-, b*-, and c-directions. Angular dependence of the critical field within highly conducting ac plane at 1.5 K was shown to possess two-fold symmetry, which can be related to the band structure anisotropy.
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  • 8
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    Journal of statistical physics 95 (1999), S. 1245-1280 
    ISSN: 1572-9613
    Keywords: anisotropy ; surface energy ; diffuse interface model ; phase-field model ; stress tensor ; equilibrium shapes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper we review two important theoretical areas to which J. W. Cahn has made major contributions: (i) The theory of the ξ-vector developed by Hoffman and Cahn, which provides an elegant setting for the description of the equilibrium shapes of sharp interfaces in the presence of anisotropic surface energy. (ii) Diffuse interface theories of phase transitions. We describe recent work which connects these two complementary facets of models of interfaces by the development of a generalized ξ-vector for diffuse interface models with anisotropic surface energy. We show that the generalized ξ-vector plays a central role in both the mathematical and physical aspects of a wide range of diffuse interface theories of interfaces with either anisotropic surface energy or attachment kinetics.
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  • 9
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    Journal of statistical physics 96 (1999), S. 1163-1330 
    ISSN: 1572-9613
    Keywords: Coulomb ; plasma ; Saha ; screening ; Debye–Hückel ; virial ; equation of state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results on the correlations of low-density classical and quantum Coulomb systems at equilibrium in three dimensions are reviewed. The exponential decay of particle correlations in the classical Coulomb system, Debye–Hückel screening, is compared and contrasted with the quantum case, where strong arguments are presented for the absence of exponential screening. Results and techniques for detailed calculations that determine the asymptotic decay of correlations for quantum systems are discussed. Theorems on the existence of molecules in the Saha regime are reviewed. Finally, new combinatoric formulas for the coefficients of Mayer expansions are presented and their role in proofs of results on Debye–Hückel screening is discussed.
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  • 10
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    International journal of thermophysics 20 (1999), S. 1547-1555 
    ISSN: 1572-9567
    Keywords: cohesive energy ; equation of state ; non-polar fluids ; refrigerants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this work, we apply an equation of state based on statistical–mechanical perturbation theory to liquid refrigerants and their mixtures. Three temperature-dependent parameters are needed to use the equation of state: the second virial coefficient, B 2(T), an effective van der Waals covolume, b(T), and a scaling factor, α(T). The second virial coefficients are calculated from a correlation based on the heat of vaporization, ΔH vap, and the liquid density at the freezing point, ρfp. α(T) and b(T) can also be calculated from the second virial coefficient by a scaling rule. Based on the theory, these two temperature-dependent parameters depend only on the repulsive branch of the potential function, and therefore, by our procedure, can be found from ΔH vap and ρfp. The theory has considerable predictive power, since it permits the construction of the p–v–T surface from the heat of vaporization plus the triple-point density. The equation of state is tested for pure, two- and three-component liquid refrigerant mixtures.
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  • 11
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    International journal of thermophysics 20 (1999), S. 1575-1585 
    ISSN: 1572-9567
    Keywords: alkali metal alloys ; cohesive energy ; equation of state ; statistical mechanics ; surface tension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Calculated results of the liquid density of binary molten alloys of Na–K and K–Cs over the whole range of concentrations and that of a ternary molten eutectic of Na–K–Cs from the freezing point up to several hundred degrees above the boiling point are presented. The calculations were performed with the analytical equation of state proposed by Ihm, Song, and Mason, which is based on statistical-mechanical perturbation theory. The second virial coefficients were calculated from the corresponding-states correlation of Mehdipour and Boushehri. Calculation of the other two temperature-dependent parameters was carried out by scaling. The calculated results cover a much wider range of temperatures and are more accurate than those presented in our previous work.
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  • 12
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    International journal of thermophysics 20 (1999), S. 217-228 
    ISSN: 1572-9567
    Keywords: air ; equation of state ; fundamental equation ; high pressure ; high temperature ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A thermodynamic property formulation for standard dry air based upon experimental P–ρ–T, heat capacity, and speed of sound data and predicted values, which extends the range of prior formulations to higher pressures and temperatures, is presented. This formulation is valid for temperatures from the solidification temperature at the bubble point curve (59.75 K) to 2000 K at pressures up to 2000 MPa. In the absence of experimental air data above 873 K and 70 MPa, air properties were predicted from nitrogen data. These values were included in the fit to extend the range of the fundamental equation. Experimental shock tube measurements ensure reasonable extrapolated properties up to temperatures and pressures of 5000 K and 28 GPa. In the range from the solidification point to 873 K at pressures to 70 MPa, the estimated uncertainty of density values calculated with the fundamental equation for the vapor is ±0.1%. The uncertainty in calculated liquid densities is ±0.2%. The estimated uncertainty of calculated heat capacities is ±1% and that for calculated speed of sound values is ±0.2%. At temperatures above 873 K and 70 MPa, the estimated uncertainty of calculated density values is ±0.5%, increasing to ±1% at 2000 K and 2000 MPa.
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  • 13
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    International journal of thermophysics 20 (1999), S. 455-484 
    ISSN: 1572-9567
    Keywords: CF4 ; C2F6 ; equation of state ; hexafluoroethane ; speed of sound ; tetrafluoromethane ; thermodynamic properties ; virial coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A cylindrical resonator was employed to measure the sound speeds in gaseous CF4 and C2F6. The CF4 measurements span the temperature range 300 to 475 K, while the C2F6 measurements range from 210 to 475 K. For both gases, the pressure range was 0.1 MPa to the lesser of 1.5 MPa or 80% of the sample’s vapor pressure. Typically, the speeds of sound have a relative uncertainty of less than 0.01 % and the ideal-gas heat capacities derived from them have a relative uncertainty of less than 0.1%. The heat capacities agree with those determined from spectroscopic data. The sound speeds were fitted with the virial equation of state to obtain the temperature-dependent density virial coefficients. Two models for the virial coefficients were employed, one based on square-well potentials and the second based on a Kihara spherical-core potential. The resulting virial equations reproduce the sound-speed measurements to within 0.005 % and yield densities with relative uncertainties of 0.1% or less. The viscosity calculated from the Kihara potential is 2 to 11% less than the measured viscosity.
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  • 14
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    International journal of thermophysics 20 (1999), S. 1629-1638 
    ISSN: 1572-9567
    Keywords: equation of state ; mixtures ; R-32 ; R-125 ; R-134a ; R-152a ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A mixture model explicit in Helmholtz energy has been developed that is capable of predicting thermodynamic properties of refrigerant mixtures containing R-32, R-125, R-134a, and R-152a. The Helmholtz energy of the mixture is the sum of the ideal gas contribution, the compressibility (or real gas) contribution, and the contribution from mixing. The contribution from mixing is given by a single equation that is applied to all mixtures used in this work. The independent variables are the density, temperature, and composition. The model may be used to calculate thermodynamic properties of mixtures, including dew and bubble point properties and critical points, generally within the experimental uncertainties of the available measured properties. It incorporates the most accurate published equation of state for each pure fluid. The estimated uncertainties of calculated properties are ±0.25% in density, ±0.5% in the speed of sound, and ±1% in heat capacities. Calculated bubble point pressures are generally accurate to within ±1%.
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  • 15
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    International journal of thermophysics 20 (1999), S. 1639-1651 
    ISSN: 1572-9567
    Keywords: alternative refrigerant ; equation of state ; Helmholtz energy ; R-143a ; 1,1,1-trifluoroethane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A fundamental equation of state has been developed for 1,1,1-trifluoroethane (R-143a) using the dimensionless Helmholtz energy. The experimental thermodynamic property data, which cover temperatures from the triple point (161 K) to 433 K and pressures up to 35 MPa, are used to develop the present equation. These data are represented by the present equation within their reported experimental uncertainties: ±0.1% in density for both vapor and liquid phase P–ρ–T data, ±1% in isochoric specific heat capacities, and ±0.02% in the vapor phase speed-of-sound data. The extended range of validity of the present model covers temperatures from 160 to 650 K and pressures up to 50 MPa as verified by the thermodynamic behavior of the isobaric heat-capacity values over the entire fluid phase.
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  • 16
    ISSN: 1572-9567
    Keywords: alternative refrigerant ; equation of state ; hydrofluorocarbon ; R-32 ; R-125 ; second virial coefficient ; speed of sound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The second virial coefficients, B, for difluoromethane (R-32, CH2F2) and pentafluoroethane (R-125, CF3CHF2) are derived from speed-of-sound data measured at temperatures from 273 to 343 K with an experimental uncertainty of ±0.0072%. Equations for the second virial coefficients were established, which are valid in the extensive temperature ranges from 200 to 400 K and from 240 to 440 K for R-32 and R-125, respectively. The equations were compared with theoretically derived second virial coefficient values by Yokozeki. A truncated virial equation of state was developed using the determined equation for the virial coefficients. The virial equation of state represents our speed-of-sound data and most of the vapor PρT data measured by deVries and Tillner-Roth within ±0.01 and ±0.1%, respectively.
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  • 17
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    International journal of thermophysics 20 (1999), S. 1721-1735 
    ISSN: 1572-9567
    Keywords: corresponding states ; density ; equation of state ; Lee–Kesler ; natural gas mixtures ; n-heptane ; n-pentane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The accurate description of mixtures includes both single-phase (bulk) properties and the location of phase equilibrium boundaries, e.g., properties that depend upon partial molar properties. In order to estimate these properties, many variants of corresponding-states theory have been developed, especially for nonpolar mixtures such as those found in natural gas systems, In this work we have developed two new, modified BWR equations of state for two natural gas components (n-pentane and n-heptane) and used these equations in a reformulated (Teja-like) Lee–Kesler model. The reformulated model has been tested on bulk-phase properties of hydrocarbon systems, in both the pure and the mixed states. Results have been obtained using the original Lee–Kesler model, the extended corresponding-states theory, and the multifluid corresponding-states principle using several combinations of reference fluids chosen from this and previous equation of state studies. Details of the new equations of state and theoretical comparisons are reported.
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  • 18
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    International journal of thermophysics 20 (1999), S. 1557-1574 
    ISSN: 1572-9567
    Keywords: binary mixtures ; critical properties ; critical volume ; equation of state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The predictive capability of the Peng–Robinson–Stryjek–Vera (PRSV-2) equation of state (1986) for critical properties of binary mixtures was investigated. The procedure adopted by Heidemann and Khalil (1980) and discussed by Abu-Eishah et al. (1998) was followed. An optimized value for the binary interaction parameter based on minimization of error between experimental and predicted critical temperatures was used. The standard and the average of the absolute relative deviations in critical properties are included. The predicted critical temperature and pressure for several nonpolar and polar systems agree well with experimental data and are always better than those predicted by the group-contribution method. A correction is introduced here to modify the predicted critical volume by the PRSV-2 equation of state, which makes the average deviations between predicted and experimental values very close to or even better than those predicted by the group-contribution method.
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  • 19
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    International journal of thermophysics 20 (1999), S. 1689-1697 
    ISSN: 1572-9567
    Keywords: equation of state ; experimental method ; phase equilibrium parameters ; refrigerant ; speed of sound
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    Topics: Physics
    Notes: Abstract The speed of sound in the liquid phase of the binary blend of R134a and R152a and its components has been studied. The speed of sound was measured by means of the impulse method at a frequency of 2.1 MHz. The temperature range was 230 to 350 K at pressures up to 16 MPa. The values of speed of sound were measured with a standard error of not more than 0.25%. The results obtained for both components of the blend are represented with expressions based on a physical model. The standard deviation (versus the model) of the measured data is 0.09%, On the basis of the results obtained, the Redlich–Kister correlation has been used over the entire ranges of composition, temperature, and pressure to determine the speed of sound in the liquid phase and at the bubble point of the blend investigated.
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  • 20
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    International journal of thermophysics 20 (1999), S. 129-140 
    ISSN: 1572-9567
    Keywords: correlation ; equation of state ; R-125 ; R-134a ; R-143a ; R-404A ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An 18-coefficient modified Benedict–Webb–Rubin equation of state has been developed for R-404A, a ternary mixture of 44% by mass of pentafluoroethane (R-125), 52% by mass of 1,1,1-trifluoroethane (R-143a), and 4% by mass of 1,1,1,2-tetrafluoroethane (R-134a). Correlations of bubble point pressures, dew point pressures, saturated liquid densities, and saturated vapor densities are also presented. This equation of state has been developed based on the reported experimental data of PVT properties, saturation properties, and isochoric heat capacities by using least-squares fitting. These correlations are valid in the temperature range from 250 K to the critical temperature. This equation of state is valid at pressures up to 19 MPa, densities to 1300 kg·m−3, and temperatures from 250 to 400 K. The thermodynamic properties except for the saturation pressures are calculated from this equation of state.
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  • 21
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    International journal of thermophysics 20 (1999), S. 519-530 
    ISSN: 1572-9567
    Keywords: activity coefficients ; binary interaction parameters ; equation of state ; fugacity coefficients ; HFC-32/134a mixture ; HFC-125/134a mixture ; thermodynamic consistency ; vapor–liquid equilibrium
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    Topics: Physics
    Notes: Abstract A vapor-liquid equilibrium apparatus has been developed and used to obtain data for the binary HFC-32/134a and HFC-125/134a systems. Twenty-two equilibrium data are obtained for the HFC-32/134a system over the temperature range from 258.15 to 283.15 K at 5 K intervals and the composition range from 0.2 to 0.8 liquid mole fraction. Twenty-five equilibrium data are obtained for the HFC-125/134a system over the temperature range from 263.15 to 303.15 K at 10 K intervals and the composition range from 0.18 to 0.81 liquid mole friction. These data have been tested and found to be thermodynamically consistent. Based upon the present data, the binary interaction parameters of the Carnahan-Starling-De Santis (CSD) and Redlich–Kwong–Soave (RKS) equations of state are calculated for five isotherms for the HFC-125/134a mixture and six isotherms for the HFC-32/134a mixture. The calculated results from the CSD equation are compared with data in the open literature.
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  • 22
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    International journal of thermophysics 20 (1999), S. 601-610 
    ISSN: 1572-9567
    Keywords: complex liquid mixtures ; corresponding states ; equation of state ; surface tension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The present work shows a successful extension of previous studies to molecular liquids for which the second virial coefficients are not known. Recent advances in the statistical mechanical theory of equilibrium fluids can be used to obtain an equation of state (EOS) for compressed normal liquids and molten alkali metals. Three temperature-dependent quantities are needed to use the EOS: the second virial coefficient, B(T), an effective van der Waals covolume, b(T), and a scaling factor, α(T). The second virial coefficients are calculated from a correlation that uses the surface tension, γtr, and the liquid density at the triple point. Calculation of α(T) and b(T) follows by scaling. Thus, thermodynamic consistency is achieved by use of two scaling parameters (γtr, ρtr). The correlations embrace the temperature range T tr〈T〈T c and can be used in a predictive mode. The remaining constant parameter is best found empirically from ρtr data for pure dense liquids. The equation of state is tested on 42 liquid mixtures The results indicate that the liquid density at any pressure and temperature can be predicted within about 5%, over the range from T tr to T c.
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  • 23
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    International journal of thermophysics 20 (1999), S. 825-835 
    ISSN: 1572-9567
    Keywords: cryogens ; equation of state ; hydrocarbons ; mixtures ; refrigerants ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A mixture model explicit in Helmholtz energy has been developed which is capable of predicting thermodynamic properties of mixtures containing nitrogen, argon, oxygen, carbon dioxide, methane, ethane, propane, n-butane, i-butane, R-32, R-125, R-134a, and R-152a within the estimated accuracy of available experimental data. The Helmholtz energy of the mixture is the sum of the ideal gas contribution, the compressibility (or real gas) contribution, and the contribution from mixing. The contribution from mixing is given by a single generalized equation which is applied to all mixtures studied in this work. The independent variables are the density, temperature, and composition. The model may be used to calculate the thermodynamic properties of mixtures at various compositions including dew and bubble point properties and critical points. It incorporates accurate published equations of state for each pure fluid. The estimated accuracy of calculated properties is ±0.2% in density, ±0.1 % in the speed of sound at pressures below 10 MPa, ±0.5% in the speed of sound for pressures above 10 MPa, and ±1% in heat capacities. In the region from 250 to 350 K at pressures up to 30 MPa, calculated densities are within ±0.1 % for most gaseous phase mixtures. For binary mixtures where the critical point temperatures of the pure fluid constituents are within 100 K of each other, calculated bubble point pressures are generally accurate to within ±1 to 2%. For mixtures with critical points further apart, calculated bubble point pressures are generally accurate to within ±5 to 10%.
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  • 24
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    International journal of thermophysics 20 (1999), S. 563-588 
    ISSN: 1572-9567
    Keywords: binary mixtures ; critical region ; D2O ; equation of state ; H2O ; phase behavior ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A parametric crossover model is adapted to represent the thermodynamic properties of pure D2O in the extended critical region. The crossover equation of state for D2O incorporates scaling laws asymptotically close to the critical point and is transformed into a regular classical expansion far from the critical point. An isomorphic generalization of the law of corresponding states is applied to the prediction of thermodynamic properties and the phase behavior of D2O + H2O mixtures over a wide region around the locus of vapor-liquid critical points. A comparison is made with experimental data for pure D2O and for the D2O + H2O mixture. The equation of state yields a good representation of thermodynamic property data in the range of temperatures 0.8T c(x)≤T≤1.5T c(x) and densities 0.35ρc(x)≤ρ≤1.65ρc(x).
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  • 25
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    International journal of thermophysics 20 (1999), S. 611-629 
    ISSN: 1572-9567
    Keywords: equation of state ; fluorine ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An analytical equation of state is applied to calculate the compressed and saturation thermodynamic properties of fluorine. The equation of state is that of Song and Mason. It is based on a statistical–mechanical perturbation theory of hard convex bodies and is a fifth-order polynomial in the density. There exist three temperature-dependent parameters: the second virial coefficient, an effective molecular volume, and a scaling factor for the average contact pair distribution function of hard convex bodies. The temperature-dependent parameters can be calculated if the intermolecular pair potential is known. However, the equation is usable with much less input than the full intermolecular potential, since the scaling factor and effective volume are nearly universal functions when expressed in suitable reduced units. The equation of state has been applied to calculate thermodynamic parameters including the critical constants, the vapor pressure curve, the compressibility factor, the fugacity coefficient, the enthalpy, the entropy, the heat capacity at constant pressure, the ratio of heat capacities, the Joule–Thomson coefficient, the Joule–Thomson inversion curve, and the speed of sound for fluorine. The agreement with experiment is good.
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  • 26
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    Hyperfine interactions 120-121 (1999), S. 23-30 
    ISSN: 1572-9540
    Keywords: NMR ; Co/Cu ; multilayers ; anisotropy ; 59Co
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 59Co NMR studies of multilayers are able to give three direct pieces of information: (i) the crystal phase of Co, fcc (217.4 MHz), hcp (220–228 MHz) and in exotic cases bcc (198 MHz) for films measured at T= 4.2 K, (ii) the nature of the interfaces from low frequency satellite lines, and (iii) the strain state deduced from small changes in the line positions. Extensive studies of Co/Cu multilayer interfacial structures as a function of deposition technique, layer thickness, substrate/buffer layer structure and annealing temperature have been undertaken. This work has shed new light on the relationship between interfacial structure and magnetoresistance and in particular has demonstrated that flat, atomic scale, interfaces lead to greater magnetoresistance. The difference between the Co and Cu lattice constant results in an extensive, tensile in-plane strain developing in Co layers provided that some epitaxial registry is present. Information on strain effects can be obtained from the position and width of the NMR lines. The magnetic anisotropy field can be determined by measuring the field dependence of the enhancement effect due to electronic magnetisation. This provides unique insight into the distribution of magnetic anisotropy within the Co layers, as the enhancement can be investigated independently for each NMR line and, hence, provides environment specific information on magnetic anisotropy at the interfaces and in the interior of the layers.
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  • 27
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    Journal of elasticity 57 (1999), S. 133-155 
    ISSN: 1573-2681
    Keywords: uncoupling of displacements ; elasticity ; anisotropy ; Green's function ; dislocation ; elliptic inclusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract It was shown in an earlier paper that, under a two-dimensional deformation, there are anisotropic elastic materials for which the antiplane displacement u 3 and the inplane displacements u 1, u 2 are uncoupled but the antiplane stresses σ31, σ32 and the inplane stresses σ11, σ12, σ22 remain coupled. The conditions for this to be possible were derived, but they have a complicated expression. In this paper new and simpler conditions are obtained, and a general anisotropic elastic material that satisfies the conditions is presented. For this material, and for certain monoclinic materials with the symmetry plane at x 3 = 0, we show that the unnormalized Stroh eigenvectors a k for k = 1, 2, 3 are all real. The matrix A =[a 1, a 2, a 3] is a unit matrix when the material has a symmetry plane at x 2 = 0. Thus any one of the u 1, u 2, u 3 can be the only nonzero displacement, and the solution is a one-displacement field. Application to the Green's function due to a line of concentrated force f and a line dislocation with Burgers vector v in the infinite space, the half-space with a rigid boundary, and the infinite space with an elliptic rigid inclusion shows that one can indeed have a one-displacement field u 1, u 2 or u 3. One can also have a two-displacement field polarized on a plane other than the (x 1, x 2)-plane. The material that uncouples u 1, u 2, u 3 is not as restrictive as one might have thought. It can be triclinic, monoclinic, orthotropic, tetragonal, transversely isotropic, or cubic. However, it cannot be isotropic.
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  • 28
    ISSN: 1573-2681
    Keywords: elasticity ; anisotropy ; inclusion ; crack ; Peach-Koehler force
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Orlov and Indenbom [1] have shown that the net (integrated) interaction force F between two skew dislocations with Burgers vectors $$\hat b,b$$ separated by a distance h in an infinite anisotropic elastic medium is independent of h. Nix [2] computed numerically the net interaction force F between two skew dislocations that are parallel to the traction-free surface X2=0 of an isotropic elastic half-space. His numerical results showed that F was independent of h; a partial result of what Barnett [3] called Nix"s theorem. The separation-independence portion of Nix"s theorem has been proved to hold for a general anisotropic elastic half-space with a traction-free, rigid, or slippery surface, and for bimaterials [3-5]. In this paper, we show that the net interaction force $$F\left( {on \hat b} \right)$$ is independent of the presence of inclusions. We will consider the case in which the line dislocation b is a more general line singularity which can include a coincident line force with strength f per unit length of the line singularity. An inclusion is an infinitely long dissimilar anisotropic elastic cylinder of an arbitrary cross-section whose axis is parallel to the line singularity (f, b). The (skew) line dislocation $$\hat b$$ does not intersect the inclusion. The special cases of an inclusion are a void, crack, or rigid inclusion. There can be more than one inclusion of different cross sections and different materials. The line singularity (f, b) can be outside the inclusions or inside one of the inclusions. The inclusions and the matrix need not have a perfect bonding. One can have a debonding with or without friction.
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  • 29
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    Journal of elasticity 57 (1999), S. 1-24 
    ISSN: 1573-2681
    Keywords: elasticity ; anisotropy ; bounds ; elasticity tensor ; compliance tensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Hill [12] showed that it was possible to construct bounds on the effective isotropic elastic coefficients of a material with triclinic or greater symmetry. Hill noted that the triclinic symmetry coefficients appearing in the bounds could be specialized to those of a greater symmetry, yielding the effective isotropic elastic coefficients for a material with any elastic symmetry. It is shown here that it is possible to construct bounds on the effective elastic constants of a material with any anisotropic elastic symmetry in terms of triclinic symmetry elastic coefficients. Similarly, it is then possible to specialize the triclinic symmetry coefficients appearing in the bounds to those of a greater symmetry. Specific bounds are given for the effective elastic coefficients of cubic, hexagonal, tetragonal and trigonal symmetries in terms of the elastic coefficients of triclinic symmetry. These results are obtained by combining the approach of Hill [12] with a representation of the stress-strain relations due, in principle, to Kelvin [25,26] but recast in the structure of contemporary linear algebra.
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  • 30
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    Journal of elasticity 55 (1999), S. 99-109 
    ISSN: 1573-2681
    Keywords: anisotropy ; nonlinear elasticity ; membranes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The existence and uniqueness of a relaxed energy function for anisotropic elastic membranes is established. It is shown that the extra strains during wrinkling abide by a normality rule akin to that of metal plasticity, and that throughout such wrinkling processes both the strain energy and the Piola-Kirchhoff stresses remain constant.
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