Investigation of the Thermophysical Properties of Ethyl Alcohol + Water Solutions

The P––Tand P _s–T _sdependences of ethyl alcohol + water solutions are investigated in wide ranges of the parameters of state. The density measurement error is estimated to be 0.05–0.1%. The experimental results are given in tabular form and described by respective equations.     

Study of La1−xMnO3−δ non-stoichiometry and defect structure using ESR and iodometry

The oxidation states of manganese in the La_1–xMnO_3– (x = 0.09–0.11) were investigated by electron spin resonance (ESR) and iodometry. The ESR analysis carried out at room temperature for the samples prepared in air revealed the presence of broad peaks at g = 2.0, considered to be relevant to Mn²⁺. It was also found that the intensity of the peak increased as lanthanum vacancy content increased. The average valence state of manganese, determined by iodometry, was approximately 3.2, and decreased by 1 as the lanthanum vacancy increased by 1. Similar trends were observed with the samples prepared at P _{o 2} = 1×10^–7. The results indicated that Mn²⁺ is stably present in the La_1–xMnO_3– having an average valence number exceeding 3.0. A series of experimental results with respect to the non-stoichiometry of La_1–xMnO_3– can be explained by assuming that Mn²⁺ is stabilized after forming a complex with a lanthanum vacancy and two oxygen vacancies.     

Glass transition temperature of glasses in the SiO2-Na2O-CaO-P2O5-Al2O3-B2O3 system

A total of 24 glasses in or near the bioactive region in the system SiO₂-Na₂O-CaO-P₂O₅-Al₂O₃-B₂O₃ were studied. By differential thermal analysis their glass transition temperatures,T _g, were determined. On basis of an experimental plan for 16 glasses, two phenomenological equations describing the relationship betweenT _g and glass composition were developed. The equations describeT _g within the compositional ranges: SiO₂, 38.0–65.5 Na₂O, 15.0–30.0; CaO, 10.0–25.0; P₂O₅, 0–8.0; B₂O₃, 0–3.0; Al₂O₃, 0–3.0 wt%. The glass transition temperature shows a linear dependence of the Na₂O content. The higher the Na₂O content, the lower theT _g. Compositional alterations not including Na₂O influencesT _g little in comparison with changes in the Na₂O content.     

New equations for enthalpy of vaporization from the triple point to the critical point

Two new equations are proposed for the enthalpy of vaporization from the triple point to the critical point. One of these equations containing four parameters is exceptionally good for fitting the data. The other equation containing three parameters is quite adequate for fitting the data but it is exceptionally suited for interpolation when the data do not cover the entire range. These equations have been tested using the enthalpy of vaporization of water from the triple point to the critical point and are compared with other equations.Nomenclature T _c Critical temperature, K - T _t Triple point, K - T _x Any particular temperature, K - T _r Reduced temperature - P _r Reduced pressure - R Gas constant - P Vapor pressure - X (T _c–T)/T _c - Y (T _c–T)/T - X _x (T _c–T)/(T _c–T _x) - X _t (T _c–T)/(T _c–T _t) - H _vt Enthalpy of vaporization at the triple point, kJ · mol^–1 - H _vx Enthalpy of vaporization at any temperature x, kJ · mol^–1 - Z _v Compressibilty factor of the saturated vapor - Z ₁ Compressibilty factor of the saturated liquid Relative deviation = 100[H_v(obs)–H_v(cal)]/H_v(obsd) Standard deviation = { [H _v(obs)–H _v(cal)]²/(No. points — No. parameters)}^0.5     

Navier-Stokes analysis of vortex flow over a cropped delta wing

Summary The vortex flow over a 65° cropped delta wing with round leading edge, atM =0.85 and Re=2.38×10⁶, has been analyzed for 10°, 20°, and 30° angles of attack. A vertex based finite volume code, JUMBO3D, with an algebraic turbulence model has been used to solve the Reynolds Averaged Navier-Stokes (RANS) equations. An H–O type grid generated by a hybrid elliptic-algebraic method has been used here, and a significant improvement of the results over an O–O type grid has been obtained. The results are compared with available experimental data. The complex physical phenomena due to interactions among the primary, secondary, and tertiary vortices, cross-flow and terminating shocks, and turbulent boundary layer, as visualized from the numerical solutions obtained are presented and discussed here.     

The effect of molecular weight on slow crack growth in linear polyethylene homopolymers

The rate of initiation and growth of cracks in linear high-density polyethylene with different molecular weights was observed in single-edge-notched tensile specimens under plane strain condition as a function of applied stress, notch depth and temperature. The initial rates of crack initiation all have the form of C ^m a ₀ ⁿ exp (–Q/RT) or AK ^pexp (–Q/RT) where = stress, a ₀ = notch depth and K= stress intensity factor. For the different molecular weights, m, n, P and Q are almost the same where m=5, n=2, P=4.7 and Q=115 kJ mol^–1, but the constants C and A varied as (¯M _w–¯M _c)^–1 where ¯M_c is a limiting molecular weight for sudden fracture. A molecular model based on tie-molecules has been used to explain the dependence on ¯M _w. The effect of ¯M _w on the fast-fracture strength at low temperature and the relationship to tie-molecules have also been investigated. Quantitative relationships between the concentration of tie-molecules and the fracture behaviour have been obtained.     

Preparation and characterization of in1−xGaxAsyP1−y epilayers by liquid-phase epitaxy

In_1–x Ga _x As _y P_1–y epilayers with three different solid compositions of ln_0.73Ga_0.27As_0.60P_1.40, In_0.59Ga_0.41As_0.87P_0.13 and ln_0.53Ga_0.47As were grown on (1 0 0) InP substrate at 623° C by the step cooling technique of liquid-phase epitaxy. From the optical transmission measurements, the corresponding wavelengths of the InGaAsP epilayers were 1.30, 1.55 and 1.69 m, respectively, which are in good agreement with those obtained from the calculations using Vegard's law. The full widths at half maximum of the photoluminescent spectra at 14 K of these layers were as low as 18.6, 22.5 and 7.9meV, respectively. The electron mobility of the InGaAsP epilayers is a function of the solid composition with the ln_0.53Ga_0.47As epilayer having the highest electron mobility. The mobility and concentration of this layer are 8,873cm²V^–1 sec^–1, 9.7×10¹⁵cm^–3 and 22,900 cm²V^–1 sec^–1, 8.5×10¹⁵cm^–3 at 300 and 77 K, respectively. The compensation ratio is between 2 and 5.     

Semi-parametric proportional intensity models robustness for right-censored recurrent failure data

This paper reports the robustness of the four proportional intensity (PI) models: Prentice–Williams–Peterson-gap time (PWP-GT), PWP-total time (PWP-TT), Andersen–Gill (AG), and Wei–Lin–Weissfeld (WLW), for right-censored recurrent failure event data. The results are beneficial to practitioners in anticipating the more favorable engineering application domains and selecting appropriate PI models. The PWP-GT and AG prove to be models of choice over ranges of sample sizes, shape parameters, and censoring severity. At the smaller sample size (U=60), where there are 30 per class for a two-level covariate, the PWP-GT proves to perform well for moderate right-censoring (P_c≤0.8), where 80% of the units have some censoring, and moderately decreasing, constant, and moderately increasing rates of occurrence of failures (power-law NHPP shape parameter in the range of 0.8≤δ≤1.8). For the large sample size (U=180), the PWP-GT performs well for severe right-censoring (0.8<P_c≤1.0), where 100% of the units have some censoring, and moderately decreasing, constant, and moderately increasing rates of occurrence of failures (power-law NHPP shape parameter in the range of 0.8≤δ≤2.0). The AG model proves to outperform the PWP-TT and WLW for stationary processes (HPP) across a wide range of right-censorship (0.0≤P_c≤1.0) and for sample sizes of 60 or more.     

The thermal conductivity of propane

This paper presents thermal conductivity measurements of propane over the temperature range of 192–320 K, at pressures to 70 MPa, and densities to 15 mol · L^–1, using a transient line-source instrument. The precision and reproducibility of the instrument are within ±0.5%. The measurements are estimated to be accurate to ±1.5%. A correlation of the present data, together with other available data in the range 110–580 K up to 70 MPa, including the anomalous critical region, is presented. This correlation of the over 800 data points is estimated to be accurate within ±7.5%.Nomenclature a _n, b_ij, b_n, c_n Parameters of regression model - C Euler's constant (=1.781) - P Pressure, MPa (kPa) - P _cr Critical pressure, MPa - Q ₁ Heat flux per unit length, W · m^–1 - t time, s - T Temperature, K - T _cr Critical temperature, K - T ₀ Equilibrium temperature, K - T _re Reference temperature, K - T _r Reduced temperature = T/T _cr - T _TP Triple-point temperature, K Greek symbols Thermal diffusivity, m² · s^–1 - T _i Temperature corrections, K - T Temperature difference, K - T _w Temperature rise of wire between time t ₁ and time t ₂, K - T ^* Reduced temperature difference (T–T _cr)/T_cr - _corr Thermal conductivity value from correlation, W · m^–1 · K^–1 - _cr Thermal conductivity anomaly, W · m^–1 · K^–1 - _e Excess thermal conductivity, W · m^–1 · K^–1 - ^* Reduced density difference - Thermal conductivity, W^–1 · m^–1 · K^–1, mW · m^–1 · K^–1 - _bg Background thermal conductivity, W · m^–1 · K^–1 - ₀ Zero-density thermal conductivity, W · m^–1 · K^–1 - Density, mol · L^–1 - _cr Critical density, mol · L^–1 - _re Reference density, mol · L^–1 - _r Reduced density Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Anisotropic scattering of conduction electrons on dilute Cu impurities in aluminum

The transverse magnetoresistivity /₀ and the low-field Hall coefficient R ₀ were measured in aluminum containing dilutely concentrated Cu impurities. It is found that the low-field Hall coefficient R ₀ is positive, in contrast to the isotropic value, which is negative. The large and positive values of R ₀ are due to the conduction electrons of aluminum that suffer an anisotropic scattering on the copper impurities. The simultaneous low-field magnetoresistance and Hall coefficient measurements, combined with the simple equations derived by Kesternich, permitted us to determine the anisotropy of the electronic scattering in terms of the mean free path ratios 1 ₊₊/1 _– and 1 _––/1 _–.     

Sur une formulation rigoureuse du problème de la convection libre atmosphérique

Summary The method of matched asymptotic expansions is used here to analyse unsteady free convection of a fluid in the vicinity of a flat wall induced by a temperature difference between the wall and the fluid.This analysis allows one to obtain in a rational manner an asymptotic model for the free convection in the atmosphere.We start from the complete Navier-Stokes equations for a heavy, compressible viscous fluid in rotation, and the corresponding initial and boundary conditions.With a proper choice of non-dimensional quantities, the Navier-Stokes equations depend, in particular, on the Grashof (Gr), Strouhal (S) and Rossby (Ro) numbers. The boundary condition for the temperature on the wall include the parameter ₀ (similar to the Eckert number). It is assumed that ₀ and ₀ Gr ^–1/2 are simultaneously very small (as indeed is the case for atmospheric problems) and satisfy the similarity relation ₀= ₀ , with > 0 a real number to be determined. Two types of inner degeneracies occur corresponding to the values=1 and=2/5; the former yield linear equations and the latter, under the assumptionsS= _{0 0} ^1/5 andRo= _{0 0} ^–1/5, yield non linear equations. The two outer degeneracies give the trivial zero solution which determine the behaviour of the inner asymptotic representations far from the wall.It is of interest to note that this method allows one to determine the exact form of the inner and outer asymptotic representations and leaves the opportunity, if necessary, of going beyond the limiting equations obtained here.Lastly, the asymptotic theory presented here, permits one, to obtain not only the classical free atmospheric convection equations but also to define the limits of validity of the approximations through which the equations are obtained.     

Refractive index measurements on bismuth tellurium oxide (Bi2TeO5) single crystal

The refractive indices of the biaxial Bi₂TeO₅ single crystal have been measured for the first time at seven wavelengths in the range of 457.9–632.8 nm at room temperature with an error of about 0.0003 (at λ=632.8 nm, n₁=2.3203, n₂=2.3678 and n₃=2.4022). The optical plane was found to be the (010) plane and the crystal is shown to be optically negative. The crossing angle of the optical axes was found to be between 79° and 86°. The parameters of Sellmeier's one- and two-term dispersion equations have been determined by the least squares method. Resonance wavelengths λ₁=219 nm for the first and λ₁=182 nm and λ₂=318 nm for the second one were found. The conditions of phase-matched SHG are discussed.     

The critical constants of long-chain normal paraffins

Because of the recent availability of the critical constants of normal alkanes up to octadecane, some modifications in the estimation procedures for the critical constants have become necessary. It has been shown that the equation of Ambrose for the critical temperature of normal alkanes leads to the result that as n , the limiting value for the critical temperature is equal to the limiting value for the normal boiling point and the limiting value for the critical pressure is 1 atm. Currently, the CH₂ increment for the critical volume is considered constant. The recent data of Teja have shown that the CH₂ increment increases indefinitely in a homologous series until the critical volume reaches its limiting value. This has made the current procedure for estimating the critical volume obsolete. Taking into account the new measurements of Teja, we have now developed new equations for estimating the critical constants. The limiting values for an infinitely long alkyl chain for T _b, T _c, P _c, and V _c have been found to be 1021 K, 1021 K, 1.01325 bar, and 18618 cm³ · mol^–1, respectively. These new concepts have been applied to the estimation of various properties other than the critical constants.Nomenclature M Molar mass, kg·mol ^–1 - V _c Critical volume, cm³·mol^–1 - V ₁ Saturated liquid volume, cm³·mol^–1 - P _c Critical Pressure, bar - T _c Critical temperature, K - T _b Normal boiling point, K - T _B Boyle temperature, K - T _A Temperature at which the third virial coefficient is zero, K - V _c Limiting value of critical volume = 18,618 cm³ · mol^–1 - P _c Limiting value of critical pressure=1.01325 bar - T _c Limiting value of critical temperature = 1021 K - T _b Limiting value of normal boiling point = 1021 K - P _b Pressure at the normal boiling point, 1 atm - Z _c Critical compressibility factor - Z _c Limiting value for the critical compressibility factor = 0.22222 - R Gas constant, 83.1448×10^–6m³ · bar · K^–1 · mol^–1 - Acentric factor - X (T _c–T _b)/T _c - X ₁ (T _c–T)/T _c - X ₂ 1–(T _B/T)^5/4 - X ₃ 1–(T _A/T)^5/2 - Y P _c/RT _c - Surface tension, mN · m^–1 - B Second virial coefficient, cm³ · mol^–1 - B Limiting value for the second virial coefficient = –30,463 cm³ · mol^–1 - C Third virial coefficient, cm⁶ · mol^–2 - C _b Third virial coefficient at the normal boiling point, cm⁶ · mol^–2 - C _c Third virial coefficient at the critical temperature, cm⁶ · mol^–2 - C _B Third virial coefficient at the Boyle temperature, cm⁶ · mol^–2 - H _vb Enthalpy of vaporization at the normal boiling point, kJ · mol^–1 - n Number of carbon atoms in a homologous series - p Platt number, number of C-C-C-C structural elements - a, b, c, d, e, etc Constants associated with the specific equation - T _c ^* , T _b ^* , P _c ^* , V _c ^* , etc. Dimensionless variables     

Theory for incongruent crystallization: Application to a ZBLAN glass

Equations which describe incongruent nucleation and subsequent crystal growth have been derived. A ZrF₄-BaF₂-LaF₃-AlF₃-NaF glass was used to test the validity of these equations. Nucleation rate measurements were fitted to theory and some growth rate measurements were found in reasonable agreement with theoretical predictions. Both nucleation theory and crystal growth theory were used for computer simulations of the crystallization behaviour during heat treatments. Some heat treatments were performed in a differential scanning calorimeter to verify the theories. The experimental results were in good agreement with the numerical data. Using these theoretical results it is possible to estimate fibre scattering losses due to crystallization. Depending on drawing temperature, estimated losses can vary from 0.014 (310 °C) to 25 (320 °C) or more dB km^–1.Nomenclature a _s the chemical activity of component A in solution referred to the activity of the component in crystalline form - c _c ^A the concentration of A in the crystalline form (mol m^–3) - c _r ^A the concentration of A in the liquid at the interface (mol m^–3) - c ₁ ^A the concentration of A far from the interface in the bulk (mol m^–3) - c _e ^A the equilibrium concentration of A (mol m^–3) - D the diffusion coefficient (m²s^–1) - G the free energy difference between the liquid and the crystal, equal to the molar Gibbs' free enthalpy of component A in solution minus the molar Gibbs' enthalpy of the crystalline form of A (J mol^–1). - -G free energy difference between crystal A and pure liquid A (J mol^–1) - G _a activation energy for growth (J mol^–1) - G _r free energy difference between the liquid (of composition c _r ^A ) at the interface and the pure liquid A - G ₁ free energy difference between the liquid (of compositionc ₁ ^A ) far from the interface and the pure liquid A - H _f heat of fusion of the pure component A (J mol^–1) - I the nucleation frequency (1 m^–3 s^–1) - k Boltzmann constant (J K^–1) - K a constant of the order 10³²–10³³ Pa m^–3 K^–1 - r the radius of the spherical crystal - R gas constant (J mol^–1 K^–1) - t time (s) - T temperature (K) - T T ₁ - T the undercooling of the melt of compositionx ^A (T ₁ is the liquidus of the melt and depends onx _A). - T ₁ liquidus temperature (K) - T _m melting temperature of pure component A (K) - T _p temperature at the top of the DSC peak (K) - u crystal growth rate (ms^–1) - V _m molar volume of the crystallizing phase (mol m^–3) - x _A molar fraction of the precipitating component A in the melt (for an example: see Appendix) - viscosity (Pa s) - jump distance of the order of molecular dimensions (m) - ₀ frequency of vibration (s^–1) - surface tension of the crystal-liquid interface (J m^–2) - the thickness of the diffusion layer     

Crystal Structure of (Ti,Mo)12P7and Refined Phase Equilibria in the Ti–Mo–P System

A new ternary compound of composition Ti_3.8Mo_8.2P_7.0 was identified, and its structure was determined by single-crystal x-ray diffraction: sp. gr. P6¯, a= 1.67821(6) nm, c= 0.33196(2) nm; R _F = 0.073 and R _w = 0.078 for 1359 independent reflections with F _hkl > 4(F _hkl). The phase equilibria in the Ti–Mo–P system were refined in the region 0–25 mol % Ti and 33–40 mol % P.     

On the uniform vorticity in a high Reynolds number flow

A method is proposed for determining the value of the uniform vorticity (₀) in the inviscid region of a high Reynolds number (Re) flow with closed streamlines. An asymptotic treatment of the area integral of the Navier-Stokes equations over the enclosed region leads to a constraint involving the core vorticity; this requires the solution of the momentum equations at O(1) and O(Re ^{–% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGymaiaac+% cacaaIYaaaaa!3816!\[1/2\]}) both in the core and in the surrounding boundary layers, although we are subsequently able to show that, under the assumption that the core vorticity at O() is also constant, the value of ₀ depends only on the flow at O(1). The analysis is verified numerically for the case where the boundary is an ellipse, and is also shown to be in agreement with the only case for which an analytic solution is available, namely when the enclosing boundary is circular. The validity of the above-mentioned assumption is also discussed.     

δ-FeO(OH) and its solid solutions

-FeO(OH)-type solid solutions have been synthesized with compositions Fe_1–x M _x O_1–x (OH)_1+x ranging up tox=0.10 for M=Ca,x=0.35 for M=Mg or Cd andx=0.40 for M=Zn. The phases are characterized by X-ray diffraction and transmission electron microscope studies. A structural model giving satisfactory intensity agreement is postulated for Fe_1–x Zn _x O_1–x (OH)_1+x . In this model, Zn²⁺ ions are situated in the 0 0 0 octahedral sites of space group D _3d ³ -P¯3ml while the Fe³⁺ ions are almost equally distributed among both octahedral sites (0 0 0 and 0 0 1/2).     

Phase Equilibria and Structure of Solid Solutions in the La–Co–Fe–O System at 1100°C

Phase equilibria in the La–Co–Fe–O system are studied at 1100°C in air using samples prepared by the citrate, nitrate, and conventional ceramic routes. The stability regions and structures of solid solutions in the La–Co–Fe–O system are determined by x-ray powder diffraction: LaCo_{1 – y} Fe _y O_{3 –} (0 < y 0.25, sp. gr. R c; 0.775 y< 1, sp. gr. Pbnm), Co_{1 – y} Fe _y O (0 < y 0.13, NaCl-type structure, sp. gr. Fm3m), and Fe_{3 – x} Co _x O₄ (0.84 x 1.38, sp. gr. Fd3m). The structural parameters of phase-pure solid solutions are determined by the Rietveld method. The composition dependences of lattice parameters are presented for LaCo_{1 – y} Fe _y O_{3 –} (0 < y 0.25) and Fe_{3 – x} Co _x O₄ (0.84 x 1.38). The 1100°C isotherm of the pseudoternary system La₂O₃–CoO–Fe₂O₃ in air is constructed.     

Description of two-dimensional spallation in pure copper

A new ductile dynamic failure model, based on a porous element consisting of a single spherical void of radius a in a sphere of radius b subject to internal pressure P_g and external stress _r = – P + ( – 1) P_g is developed in the present work. Work-hardening behavior, rate-dependent contribution and inertial effects are taken into account in the model. Stress controlling mechanism is adopted while considering the contribution of void nucleation to rate of porosity . The mathematical model presented here is incorporated in a hydrodynamic two-dimensional finite-difference computer code, to simulate two-dimensional spallation of pure copper. Comparison of numerical calculation with experimental results shows that the model described the process of spall experiment successfully. The future improvements of the model are discussed.     

FTIR Spectroscopy of Solid Parahydrogen in the NIR/VIS Region

We report the results of FTIR measurements of solid parahydrogen at 12.5 K in the spectral region 9 000 – 16 500 cm ^–1 using an internal multireflection cell with 14 cm optical path length. We find several new ro–vibrational transitions such as the single transition W ₂(0) at 10241.07 cm ^–1 and double transitions among which we consider the most interesting ones to be Q ₂ (0) + Q ₁ (0), due to its unexplained induction mechanism, and Q ₂ (0) + S ₁ (0) due to its fine structure, revealing non–resonant hopping of rotational excitations. Furthermore we find absorption features at 8650–8670 cm ^–1 and at 8980–9000 cm ^–1 which we interpret as the triple transitions Q ₁ (0) + Q ₁ (0) + S ₀ (0) and S ₁ (0) + Q ₁ (0) + S ₀ (0), which acquire intensity from nearby double transitions. At 12 788 cm ^–1 we find the triple transition S ₁ (0) + Q ₁ (0) + Q ₁ (0).