Noninvasive online measurement of particle size and concentration in liquid–particle mixture by estimating equivalent circuit of electrical double layer

ABSTRACT

Three electrical elements (i.e., resistance, capacitance, and relaxation frequency) of electrical double layer (EDL) formed around particles have been extracted by a measuring–fitting combination for a novel noninvasive online measurement technique of particle size and concentration in a liquid–particle mixture. The measuring–fitting combination means measuring the impedances with electrical-impedance spectroscopy (EIS) method, and fitting the equivalent circuit with Levenberg–Marquardt method. The liquid–particle mixture in the impedance measurement is made of sodium chloride solution and stainless particles; the equivalent circuit is established corresponding to the contents in the liquid–particle mixture. As a result, the influence of the particle size and concentration on the electrical elements in the EDL which are the resistance, capacitance, and relaxation frequency in the EDL are clarified and discussed. This method is useful for determination of the particle size and concentration in liquid–particle mixture.     

Relaxation of the composition of combustion products in cylindrical channels

The results of an experimental study and numerical simulation of the relaxation of the composition of the flow of high-temperature combustion products in cylindrical channels with cooled and uncooled walls are presented. Primary attention is given to the effect of parameters such as the channel radius, the oxidizer excess coefficient in the initial mixture, and the wall temperature on the relaxation of carbon monoxide CO and on the level of its concentration at the channel outlet.     

Acoustic instability in a two-phase mixture with temperature relaxation of particles

Theoretical calculation of acoustic instability in a two-phase mixture with temperature relaxation of particles is performed. Particles are assumed to be spherical and monodisperse, while their mass fraction does not exceed 50%. The formula for calculation of the acoustic oscillation frequency and increment, as well as the approximate formula for oscillation-amplitude calculation, are derived in this work. The heat exchange between the particles and the gas mixture is taken into consideration explicitly in these formulas.     

Stresses in mixture theory

The foundations of mixture theory are formulated using a geometrical approach. In order to model diffusion, configurations of mixtures are allowed in which the various constituents may occupy different regions in space in addition to the usual relaxation of the impenetrability axiom. Forces on a mixture are defined as continuous linear functional on the space of virtual displacements of the mixture. This implies the existence of partial stresses without any further assumptions. The notions of the total force and the total stress are critically reviewed and introduced through the definition of a simple body model of a mixture. Some examples of such models are given.     

Phonon-Impuriton Relaxation and Transport in 3He-4He Superfluid Solutions

No Heading The measurements of the effective thermal conductivity coefficient of a superfluid³He-⁴He mixture with initial concentration of 9.8% ³He are carried out in the temperature range 70 – 500 mK. The results obtained and the other experimental data available on effective thermal conductivity, shear viscosity, and spin diffusion are interpreted within the kinetic theory of phonon - impuriton system of superfluid solutions. It is shown that all experimental data can be explained by taking into account the following relaxation processes: longitudinal phonon relaxation, phonon scattering by impuriton, phonon absorption and emission by impuriton, and impuriton - impuriton interaction. The last process is characterized by different relaxation times for each transport phenomenon: transfer of mass, momentum, and nucleus spin. The impuriton - impuriton and phonon - impuriton relaxation times are estimated and the hierarchy of relaxation times in such system is established. The phonon longitudinal relaxation time in phonon diffusion process should be taken into account. The phonon and impuriton contributions to thermal conductivity, viscosity, and mass diffusion are estimated.PACS numbers: 66.20.+d, 67.60–g, 64.75+g, 67.40.Pm, 66.60+a, 66.30.Xj     

Analysis of molecular dynamics of moist wood components by applying the stretched-exponential function

On the basis of the molecular dynamics of wood components, the effects of adsorption water molecules on the change of relaxation behavior were examined for wood specimens with various moisture contents using the low of mixture and stretched-exponential function (so-called the Kohlrausch–Williams–Watts (KWW) function). The KWW function has two parameters: the characteristic relaxation time and a parameter related to the dispersion of the relaxation time. Both parameters and the relaxation modulus at time 10 s, E(10), could be separated into three regions corresponding to moisture contents of 0–0.05, 0.05–0.10, and greater than 0.10. Experimental results provided a consistent explanation for the relationships between the isotherm curve analysis of wood, the dielectric relaxation behavior of adsorption water molecules, and the mechanical relaxation behavior of wood.     

Acceleration waves in condensing gases

Summary The flow of a condensing gas is treated as a two-phase-flow, in which the size of the condensate-droplets may vary due to transfer of mass, momentum, and heat; the formation of new droplets is disregarded. An ordinary differential equation for the temporal variation of the amplitude of a one-dimensional acceleration wave is deduced, which holds along the path of the wave. Especially, if the wave propagates into a mixture at rest with spatial variation of the volume fraction of the droplets, the variation of the amplitude is given by the sum of three terms, one of which is quadratic in the amplitude and the others are linear. The quadratic term is solely determined by nonlinear effects in the pure gas and leads to a growth. The first linear term is given by the dissipative effect of the velocity relaxation; this term is the same as for the flow of a mixture of a gas and small solid particles. The second linear term is determined by the combined dissipative effects of the temperature relaxation and the mass transfer; both linear terms lead to a decay. Further, conditions are discussed, on which shock waves are formed.With 6 Figures     

One-velocity model of a multicomponent heat-conducting medium

A model of a one-velocity heat-conducting heterogeneous medium with the Fourier relaxation law of heat transfer has been constructed. It is shown that the model’s equations are of hyperbolic type. The results of numerical experiments for a three-component mixture of ideal gases carried out with the use of the Courant–Isaacson–Rees scheme are presented.     

Dielectric losses in materials with limited range of relaxation times

Features of the spectra of dielectric materials with the range of relaxation times limited from below have been studied. It is established that the dielectric losses (and conductivity) exhibit relaxation at an average frequency that is significantly (up to several orders of magnitude) greater than the permittivity relaxation frequency. These effects are characteristic of both homogeneous materials with non-Debye spectra and inhomogeneous materials of the statistical mixture type near the percolation threshold. A giant enhancement of the permittivity and conductivity in these statistical mixtures takes place at various concentrations of components corresponding to the dielectric-conductor and conductor-dielectric phase transitions.     

Stability and compatibility testing using a microcalorimetric method

A microcalorimetric method is used for compatibility and stability studies. The high sensitivity of the instrument permits measurements at 60°C or even lower, i.e. under more realistic conditions than offered by conventional techniques like DTA and vacuum stability tests. The instrument consists of four independent calorimeters with a short thermal relaxation time, high sensitivity and excellent baseline stability. The calorimeters are placed in a common, precisely thermostated water bath.In compatibility studies, heat flow curves are recorded for the pure components and a mixture of these. A theoretical curve is constructed, which simulates a non-interacting system. The difference between the theoretical and the experimental curve for the mixture reflects the degree of interaction between the materials. A number of compatibility problems are discussed, including interactions in mixtures of TNT with amine/amide type polymers, polycarbonate — double base propellant interactions under various conditions and the influence of an anaerobic sealant on a high explosive and a propellant. Some results from stability measurements on an igniting compound are also presented.     

Predicting the tensile relaxation modulus of asphalt mixes based on the mix design and environmental factors

The main objective of this study was to predict the tensile relaxation modulus of asphalt mixes, without having to perform the common relaxation modulus tests, by developing a predictive model based on the mix characteristics, ageing condition, temperature and loading time. To this end, cylindrical asphalt mixture specimens containing crushed stone aggregates with 60/70 penetration asphalt binder were fabricated using two aggregate gradations, two binder contents, two air void levels and three ageing conditions with four replicates. Uniaxial tensile relaxation modulus tests were conducted on the specimens at four temperatures using the trapezoidal loading pattern at a low level of strain. Tensile relaxation modulus master curves of all the experimental combinations were constructed by the sigmoidal model. Statistical analysis of variance and regression analysis was performed on the test data and a predictive model was developed. Finally, the predictive model was verified using a group of measured values other than those used for the development of the model, and it was found that the predicted values correlated well with the measured ones.     

The Use of Stress Relaxation Trials to Characterize Tablet Capping

Abstract

A new method is described for estimating capping risks due to the entrapment of air during compression.

For this, the curves obtained during a stress relaxation test were analysed using a WISCHERT model.

Two processing modes of computation from experimental data made it possible to characterize the stress relaxation of each product or mixture of products by a sum of two or three exponentials.

The first exponential represents a more or less rapid structure relaxation. When the quantity of fines particles is too great, the structure relaxation is slowed down by the entrapped air as soon as constant deformation is applied.     

Improvement of response times in electrochromic switchable nematic emulsions

Electrochromic nematic emulsion can be obtained by fast cooling of isotropic mixtures of electrochromic mixture, nematic liquid crystal and monomers. Films obtained with this procedure show very low saturation fields but rather long relaxation times. In this paper we have doped nematic electrochromic emulsions with surfactant agents, in order to obtain a good compromise between low saturation fields and fast relaxation times. The decay time decreases in a significant way and the saturation field is slightly affected by the addition of small amounts of surfactant.     

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.     

Dynamic equation of state of a gas mixture containing solid particles

A dynamic equation of state is derived, describing the relationship between the pressure and volume of a thermal-nonequilibrium gas mixture. The methods of nonequilibrium thermodynamics are used to calculate the relaxation time.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 34, No. 5, pp. 833–838, May, 1978.     

Nuclear spin-lattice relaxation times of metallic antimony at low temperatures

We have used pulsed Nuclear Quadrupole Resonance (NQR) techniques to measure the nuclear spin-lattice relaxation times in antimony at low temperatures. High quality echoes with strong signal/noise ratios were only observed for finely powdered samples of high purity (99.9999%). The samples were carefully annealed and diluted with fine silica to below the percolation limit to minimize RF heating. The powder mixture was immersed in liquid³He to ensure good thermal contact to a sintered silver heat exchanger attached to a copper nuclear demagnetization refrigerator. We report the temperature dependence of the nuclear spin-lattice relaxation times for the multiple level nuclear spin system.     

Deuterium nuclear magnetic resonance spectroscopy as a probe for reversed-phase liquid chromatographic bonded-phase solvation. 3. Tetrahydrofuran and water binary systems

Deuterium nuclear magnetic resonance ((2)H NMR) spectroscopy is a useful tool in probing molecular association between components in a binary hydro-organic mixture, such as tetrahydrofuran (THF) and water. Measurements of (2)H longitudinal relaxation times (T(1)) for deuterated analogs of THF and water provide this type of information, since the magnitude of T(1) is indicative of molecular association and mobility. This technique is also useful in determining the interactions between the mobile phase and reversed-phase stationary phase. T(1) measurements of slurry samples, consisting of both mobile- and stationary-phase components, allow for changes in the longitudinal relaxation time of mobile-phase components upon contact with the stationary phase (ΔT(1)) to be monitored. These ΔT(1) values are indicative of the degree of association of the THF-water mobile-phase components with the stationary phase.     

Effect of Critical State Model on Magnetic Relaxation in Type-II Superconductors

Based on the theoretical model in which magnetic relaxation was considered, exact equations are derived for the relaxation rate, normalized relaxation rate and relaxation time. The relations between the theory on relaxation rate and experimental data are compared, as well as the relaxation time. The valid ranges of several models are specified and the magnitude of relaxation time is estimated. The results indicate that different models are suitable for different temperature regions and the effect of relaxation time on the experimental measurements could not be neglected.     

Targeted profiling: quantitative analysis of 1H NMR metabolomics data

Extracting meaningful information from complex spectroscopic data of metabolite mixtures is an area of active research in the emerging field of "metabolomics", which combines metabolism, spectroscopy, and multivariate statistical analysis (pattern recognition) methods. Chemometric analysis and comparison of 1H NMR1 spectra is commonly hampered by intersample peak position and line width variation due to matrix effects (pH, ionic strength, etc.). Here a novel method for mixture analysis is presented, defined as "targeted profiling". Individual NMR resonances of interest are mathematically modeled from pure compound spectra. This database is then interrogated to identify and quantify metabolites in complex spectra of mixtures, such as biofluids. The technique is validated against a traditional "spectral binning" analysis on the basis of sensitivity to water suppression (presaturation, NOESY-presaturation, WET, and CPMG), relaxation effects, and NMR spectral acquisition times (3, 4, 5, and 6 s/scan) using PCA pattern recognition analysis. In addition, a quantitative validation is performed against various metabolites at physiological concentrations (9 microM-8 mM). "Targeted profiling" is highly stable in PCA-based pattern recognition, insensitive to water suppression, relaxation times (within the ranges examined), and scaling factors; hence, direct comparison of data acquired under varying conditions is made possible. In particular, analysis of metabolites at low concentration and overlapping regions are well suited to this analysis. We discuss how targeted profiling can be applied for mixture analysis and examine the effect of various acquisition parameters on the accuracy of quantification.     

Temperature and Concentration Relaxation in Phase-separated Superfluid 3He–4He Mixtures

The kinetics of the temperature and concentration variations in the superfluid ³He–⁴He mixtures with initial concentration of 9.8% ³He, and heated from below, was studied experimentally under the pressure of 0.38 bar over a temperature range of 150–400 mK. It is found that in contrast to homogeneous liquids, the temperature and concentration relaxation in phase-separated mixtures can be described by a superposition of two exponential processes in which the time constants of temperature and concentration variations coincide. If the initial mixture was homogeneous and phase separation was triggered by a heat flow, the temperature and concentration vary non-monotonically and exhibit anomalous features at the moment of phase separation. In this case the phase transition starts in the metastable superfluid, formed out of a quite supersaturated mixture where the nucleation of the new phase may be caused by quantized vortices. The results are analyzed in terms of two possible mechanisms of relaxation–the acoustic mechanism with the second sound velocity and the diffusive one connected with dissipative flows of impurity and thermal excitations. It is shown that the measured relaxation times agree with a prediction of the theory.