Two‐Dimensional Diffusion of a Binary Mixture of Neutral Gases

An expression for the coefficient of twodimensional diffusion of a binary mixture of neutral gases is obtained within the framework of the kinetic theory.     

Calculation of the Outflow of a One‐Velocity Heterogeneous Mixture into Vacuum

The outflow of a waterair mixture (an incompressible fluid) and a mixture of two ideal gases has been studied within the framework of the generalizedequilibrium model of a heterogeneous medium. In the first problem, the solution has been obtained in the form of analytical dependences. In the other, for a complete determination of all the dependent variables both analytical relations and an ordinary differential equation have been integrated numerically. The outflow of a mixture with an arbitrary number of components into vacuum is calculated similarly.     

Synthesis of Cu2 – nSe via Autowave Combustion of an Elemental Powder Mixture

Inorganic Materials - A Cu2 – nSe phase has been prepared by self-propagating high-temperature synthesis in the combustion regime using mixtures of Cu and Se powders. We have carried out...     

Heat Capacity of Atomically Layered 3He –4He Mixture Films

We report preliminary results of the first heat capacity measurements on atomically layered ³ He – ⁴ He mixture films adsorbed on the surface of graphite. The ⁴ He film consists of two solid and two superfluid atomic layers. The heat capacity has been investigated over the range 1 – 70mK as a function of the surface density of ³ He atoms added to the film. At coveragesn₃ < 4nm ^–2 , the ³He forms a uniform two dimensional Fermi system. The coverage dependence of the linear coefficient of the heat capacity, , allows a determination of the hydrodynamic effective mass and . At higher coverages a step-like increase in is observed, interpreted as the formation of a second two dimensional Fermi system.     

Role of Capillary Forces in Filtration of a Gas–Condensate Mixture near a Well

The problem of steadystate flow of a gas–condensate mixture near an operating well is considered. The effect of capillary forces on condensate distribution in a porous medium is studied both analytically and numerically. It is shown that capillary forces can serve to decrease the amount of condensate, with the effect occurring in both cases — wetting and nonwetting liquid phases.     

Diffusion Modes of an Equimolar Methane–Ethane Mixture from Dynamic Light Scattering

The hydrodynamic diffusion modes of an equimolar methane–ethane mixture have been investigated by dynamic light scattering. Measurements were performed over a wide temperature range between the plait critical point at 263.55 K and 310 K along the critical isochore. Two relaxation modes have been observed which are commonly associated with pure mass diffusion and pure thermal diffusion, but in near-critical binary fluid mixtures—according to recent theory—may alternatively be interpreted as two effective diffusivities resulting from a coupling between mass and thermal diffusion. Diffusivity values for the slow mode were obtained with typical standard deviations of 1% over the whole temperature range, whereas the low amplitude of the fast mode only allowed values of this component with a large measurement uncertainty. The results are discussed in connection with literature data available for the thermophysical properties of this binary fluid mixture and regarding the various possibilities of theoretical interpretation.     

Mixture of ε-caprolactone-lactide copolymer and tricalcium phosphate: a histological and immunohistochemical study of tissue reactions

In cranio-maxillofacial surgery, bone transplantation is needed for treatment of bony defects. An autograft, allograft or biomaterial can be used. Autogenous bone grafts are considered to be the best materials available, but there are some disadvantages in their use including donorsite morbidity, need for a second operative site and limited graft supply. A search for new bone-graft materials therefore remains necessary. We prepared a mixture of tricalcium phosphate (TCP), which is a resorbable, non-toxic, osteoconductive ceramic material and -caprolactone-lactide copolymer P(-CL/DL-LA), a resorbable polymer, and placed it in the dermis and in mandibular bone defects in 13 rabbits. Follow-up times were two, three, seven, eight, 12, 15 and 18 weeks, tissue reactions were assessed, histologically and immunohistochemically. Times of resorption of the material from tissues were reported. We found that the mixture caused a mild inflammatory reaction when placed in bone and severe inflammation when placed in dermis. No highly fluorescent layer of tenascin or fibronectin was found surrounding the implant area. The mixture was excellent to handle and very easy to place into bone defects. The results are promising and have led us to continue development of the mixture. © 1999 Kluwer Academic Publishers     

Molecular Dynamics Simulation of Pervaporation of an Ethanol–Water Mixture on a Hybrid Silicon Oxide Membrane

A molecular-statistical method for simulating the process of pervaporation on hybrid silicon oxide membranes is proposed. This method is a development of the control volume method. Models of three membrane samples with different densities and pore sizes were obtained. These samples were used for the molecular-dynamics simulation of pervaporation of a 95 mol % aqueous solution of ethanol at a temperature of 343 K. It is shown that the membrane is selective with respect to water; the component flow is found to exponentially depend on the pore size.     

An Improved Computational Method for the Calculation of Mixture Liquid–Vapor Critical Points

Knowledge of critical points is important to determine the phase behavior of a mixture. This work proposes a reliable and accurate method in order to locate the liquid–vapor critical point of a given mixture. The theoretical model is developed from the rigorous definition of critical points, based on the SRK equation of state (SRK EoS) or alternatively, on the PR EoS. In order to solve the resulting system of \(C+2\) nonlinear equations, an improved method is introduced into an existing Newton–Raphson algorithm, which can calculate all the variables simultaneously in each iteration step. The improvements mainly focus on the derivatives of the Jacobian matrix, on the convergence criteria, and on the damping coefficient. As a result, all equations and related conditions required for the computation of the scheme are illustrated in this paper. Finally, experimental data for the critical points of 44 mixtures are adopted in order to validate the method. For the SRK EoS, average absolute errors of the predicted critical-pressure and critical-temperature values are 123.82 kPa and 3.11 K, respectively, whereas the commercial software package Calsep PVTSIM’s prediction errors are 131.02 kPa and 3.24 K. For the PR EoS, the two above mentioned average absolute errors are 129.32 kPa and 2.45 K, while the PVTSIM’s errors are 137.24 kPa and 2.55 K, respectively.     

One-Dimensional Consolidation of Sedimented Stowed Pond Ash and Pond Ash-Lime Mixture Deposits—A Comparative Study

The present study investigates the influence of slaked lime addition on the one-dimensional consolidation properties of sedimented stowed pond ash (Class F category). The effects of step incremental consolidation pressure, lime addition, and curing time on the one-dimensional consolidation characteristics such as rate of settlement, consolidation coefficients, and void ratio, of the sedimented stowed pond ash and pond ash-lime mixture deposits are investigated using a fixed ring consolidometer. The study revealed that the void ratios of both the stowed pond ash and pond ash-lime mixture deposits decrease with the applied pressure. Comparatively, the stowed pond ash-lime mixture deposit demonstrated a higher void ratio than the stowed pond ash deposit. A decrease in coefficient of consolidation (C_v) values with the increase in consolidation pressure and curing time is also observed in the case of both deposits, thereby indicating a decrease in their compressibility. Owing to the addition of lime, an improvement in the consolidation characteristics in terms of increase in C_v values and decrease in final settlement of the sedimented stowed pond ash-lime mixture deposit is generally observed at higher consolidation pressures and longer curing time.     

Theoretical and Experimental Investigations of Identifying the Ingredients of an Oil–Water Mixture Based on a Characteristic Fluid Inverse Problem

To identify the ingredients of an oil–water mixture in petroleum production or petrochemicals process, a method based on a characteristic liquid inverse problem was developed by clarifying its real viscosity and thermal conductivity. A heat transfer and fluid flow model for an oil–water mixture was established for tube flow in this paper. By means of the measured temperature distribution in the tube, the thermal physical properties of the oil–water mixture can be obtained by the governing equations in the model according to their characteristics as a Newtonian or non-Newtonian fluid. The fluid characteristic can be deduced by the rheological properties of the oil–water mixture. Both the Newtonian fluid and non-Newtonian fluid governing equations were established to determine the mixture components. Experiments were also conducted to verify the numerical solutions for the ingredients of the oil–water mixture. The comparison between theoretical solutions and experimental results shows that the maximum error based on the suitable fluid model is 3.11 %, which demonstrated the feasibility of the proposed method for estimating the ingredients of an oil–water mixture.     

Hot Corrosion of Iron in the Presence of Salt Mixture Deposit Containing NaCl and V_2O_5 at 600℃

Iron suffered low temperature hot corrosion (LTHC) in the presence of salt deposits of Na2SO4,Na2SO4 mixed with NaCl and Na2SO4 mixed with V2O5 in a combustion gas at 600℃. The additions of NaCl to Na2SO4 and of V2O5 to Na2SO4 changed the corrosion kinetics significantly and modified the scale structure markedly It is proposed that trivalent iron ions were more favored than divalent ions in the eutectic responsible for the occurrence of LTHC when NaCl was present, while the reaction between Na2SO4 mixed with V2O5 and the gas formed (Na2O)xV2O4(V2O5)6-x providing directly the liquid required by LTHC. The suphide formation in the inner FeO larer was related to the sites of the reduction step wher SO2 was released.     

Structure of the Intermetallic Compound Ni_3Al Synthesized under Compression of the Powder Mixture of Pure Elements Part Ⅰ: Phase Composition and Microstructure of Main Phase

1.IotroductionIntermetalliccompoundsofAlwithNiarebasisofmodernNibasesuperalloysforthehightemperaturepurpose.Thehightemperaturesynthesisundercompressionofthepowdermixtureofptireelemelltsispromisingasatechniqueforproducingtheseal-loys.Thehighrateofthesynthesisoftheintermetal-licalloysinalargedegreedefinesthecharacteristicfeatureofthestructure,phasecompoundandfinally,thestrengthofintermetallicalloysathightemperature.Therearetwotypesofwell-knownworksinthisdirection,investigationsofthephasecompou…     

Two‐Dimensional Calculation of the Parameters of a Steam‐Air Mixture in a Film‐Type Heat and Mass Exchanger

A mathematical model for twodimensional calculation of the temperature and density of the steam in a steamair mixture which rises between two water films flowing down adiabatic shields has been proposed. The parameters of the films have been calculated in a onedimensional approximation. The results of calculating the parameters of air according to the onedimensional and twodimensional models of the processes of heat and mass transfer have been compared. The range of applicability of the former to a filmtype heat and mass exchanger has been determined.     

Melting and Boiling Points of an Equimolar Mixture in the KCl–MnCl2–CeCl3System

The melting point of the equimolar mixture of KCl, MnCl₂, and CeCl₃was determined by thermal analysis: T _m= 683 ± 1 K. Using the additivity rule, the melting enthalpy was evaluated from the melting entropies of the constituent chlorides: _m H= 26200 ± 1200 J/mol. The vapor pressure over the mixture was measured between 1274 and 1510 K. From the temperature-dependent vapor-pressure data, the enthalpy of vaporization was determined to be 144400 J/mol, and the boiling point at normal pressure was determined to be 1073 K. The estimated vapor pressure at the melting point is 0.24 Pa, which indicates that the mixture studied is low-volatile and is potentially attractive as a thermal energy storage composition.     

Phase Diagram of a ^6Li–^{40}K Mixture in a Square Lattice

We calculate the mean-field phase diagram for an attractive interacting Fermi mixture of Lithium-6 ( \(^6Li\) ) and Potassium-40 ( \(^{40}K\) ) atoms in a two-dimensional optical lattice at finite temperatures. The polarization versus temperature diagrams show that there are three phases: the Sarma phase (in which the condensed pairs have zero net momentum), the Fulde–Ferrell (FF) phase (in which the pairs have non-zero net momentum), and the normal phase (in which the Helmholtz free energy is minimized for gapless phase). The zero polarization line is the conventional Bardeen–Cooper–Schrieffer state. The phase diagram contains a Lifshitz point. When the interaction strength is increased, the Lifshitz point moves toward the higher temperatures and larger polarizations. Moreover, contrary to the phase diagram of population-imbalanced \(^6Li\) Fermi gas, where the phase separation appears for low polarizations, we found the existence of a polarization window for the FF phase. This means that as soon as the system is polarized it goes into the FF phase if the temperature is low enough. This polarization window is larger for a majority of \(^{40}K\) atoms compared to the majority of \(^6Li\) atoms. We also find that the largest polarization that the system can support before it becomes a normal fluid is larger for majority of \(^6Li\) atoms.     

Preliminary Measurement of the Critical Casimir Effect near the Tricritical Point in 3He–4He Mixture Films

We report a preliminary measurement of the critical Casimir effect in ³ He- ⁴ He mixture films near the tricritical point. Whereas we had found that the pure ⁴ He film adsorbed on Cu substrates thins due to the critical Casimir force near the lambda transition, in our present experiments we find that the adsorbed mixture film thickens near the tricritical point. This difference in behavior most likely reflects the difference in the universality class of these two phase transitions and the difference in boundary conditions that the order parameter must satisfy at liquid-substrate and liquid-vapor interfaces.     

In-situ Formed AIN Particulates and TiN Whiskers Mixture Reinforced Al Composite

The TiNw-AINp/Al composite has been successfully fabricated by gas-liquid reaction method in an intensive electromagnetic mixing and casting in an appropriate cooling condition. The as-cast samples of the composite exhibit a homogeneous distribution of TiNw and AINp, and the in situ formed TiN whisker has a mean diameter of 0.5 μm and mean aspect ratio of 5.8~7.5, and the diameter of the AIN particulates is less than 5 μm. TEM observation indicates that there exist some submicron and nanometer sized in situ formed TiNw-AINp in α-Al matrix. The formation mechanism of in situ formed TiNw and AINp is also discussed     

Gas Sensing Based on a Nonlinear Response: Discrimination between Hydrocarbons and Quantification of Individual Components in a Gas Mixture

A novel sensing system is proposed based on the multidimensional information contained in a dynamic nonlinear response. A sinusoidal temperature change was applied to a SnO(2) semiconductor gas sensor, and the resulting output conductance of the sensor was analyzed by fast Fourier transformation (FFT). The higher harmonics of the FFT characterized the nonlinear properties of the response. The amplitudes of the higher harmonics of the FFT exhibit characteristic changes which depend on the chemical structure, concentration, and the kinetics of adsorption and the reaction of hydrocarbon gases and aromatic vapors on the sensor surface. In addition, it is possible to distinguish between gases in a gaseous mixture with a single detector using this dynamic nonlinear response. Nonlinear responses are discussed in relation to the kinetics of the reaction at the sensor surface and the temperature-dependent barrier potential of the semiconductor.     

An Attempt at Bringing to Light a “Phase Inversion” in a Binary Mixture of Two Dimensional Rounded Particles

Abstract

It has been demonstrated previously in our Laboratory that the disintegrant concentration corresponding to an interparticular network between drug or diluent particles in tablets may be calculated.

When the disintegrant concentration increases little by little, for a critical concentration, a sudden modification of the physical properties of the powder mixture and of the resulting tablets can be observed.

A new structure is set up in the tablet: in a way, a “phase inversion” is produced.

This experimental critical concentration is the same as the calculated critical concentration for more or less rounded particles.

An investigation into the physical properties of binary powder mixtures and of resulting tablets is carried out when increasing, little by little, the quantity of disintegrant particles: Starches and their derivatives, cross linked PVP, are more particularly studied.

The authors study:

• – The flowing properties of powder mixtures

• – The compressibility (Hardness/Compression forces, transmission forces through the powder mixture during compression, compression cycles…)

• – The physical properties of tablets (hardness, structure hydrophilicity, disintegration time and drug dissolution).

Several formulations were studied. The results point out the setting up of the continuous network of the small particles between the larger particles for the calculated critical concentration. The same theory may be applied to the hydrophilization of powders in hard gelatin capsules and to all the more o r less rounded two dimensional particles in a mixture.