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The aim of this paper is to carry out a review of radiative heat transfer in dispersed media. Firstly, the solution of the governing equations for radiative transfer in such media as well as the theoretical basis for the modelling of their radiative properties are briefly recalled and discussed. Thereafter, emphasis is placed on practical applications dealing with several types of particulate media which play an important role in a number of industrial processes. Radiative property predictive models as well as studies dealing with property experimental determination are examined and discussed.

The use of dispersed media to synthetize microparticles in “situ” has made considerable progress in the last few years: Reverse micelles[1], Langmuir-Blodgett films[2], zeolites[3], vesicles[4], glass matrices and sol-gel methods[5].Semiconductor nanocrystals present quantum confinement effects, called Q-dots[6]. To control the size and the shape of nanoparticles reverse and normal micelles, bicontinuous and lamellar solutions have been used.

Dynamic Structure of Gaseous Detonation.- The Limits of Stationary Propagation of Gaseous Detonation.- Propagation of Gas Explosion in Channels with Uneven Walls and in Porous Media.- Physical Model of Dynamic Structure of the Surface of Detonation Wave.- Theoretical Description of Direct Initiation of Detonation for One-Step Chemistry.- Group Methods for the Study of Detonation Wave Analysis.- Transition and Structure of Dust Detonations.- On the Detonation of Aluminum Suspensions in Air and in Oxygen.- Non-ideal Detonation in Combustible Gaseous Mixtures with Reactive Solid Particles.- Dust Related Detonations.

WOS: 000229851100004, Multicomponent models containing both substrate and biomass have an advantage over conventional models in seeking better understanding of activated sludge systems. Such models are also useful in the characterization of wastewater. Studies in recent years have shown that most of the soluble organic matter in the effluent of treatment systems consists of soluble microbial products that arise during biological treatment. In order to support experimental studies, mathematical models have also been developed to explain microbial product formation. In connection with the approaches in the literature, a mathematical model for estimating chemical oxygen demand in effluent in dispersed media has been developed in this study. The death-regeneration approach - an approach of multicomponent activated sludge models containing the formation of soluble inert organic matter with together carbon oxidation was used. Because the differential equations developed for dispersed media have no analytical solutions, the system was represented with the in-series reactor approach, with the death-regeneration and hydrolysis concepts advised in the IAWPRC Task Group Model.

Simultaneous measurements of particle size and velocity with different media are important in the experimental study of multiphase flows. Especially, when one of the dispersed media has a relative refractive index close to unity (m? 1.0), the optical configuration requires extra consideration in phase-Doppler anemometry (PDA). Such measurements are often encountered when water flows are composed of air bubbles and glass beads with relative refractive indices of m1 = 0.75 and m2= 1.13, respectively. Large uncertainty in measurements may arise if optical parameters fall into the region of so-called "critical scattering angles.'' Furthermore, the scattering intensities from air bubbles and glass beads in water are found to have two-order-of-magnitude differences at an off-axis angle in between 60 to 85 deg, which narrows the measurable dynamic range and causes bias in the size distribution of different dispersed phases. We use a scheme based on the recently developed combined refraction-reflection model and Mie scattering theory to optimize the off-axis angle to minimize the measurement uncertainty. The variation of the critical scattering angles and scattering intensity ratios of media are quantitatively described. The predictions are validated by conducting experiments to measure glass spheres and vapor bubbles in water.

The theoretical description of the field reconstructed from an in-line hologram of dispersed media is presented. The intensity distribution in the focal plane of a lens placed behind a hologram is analyzed. It is shown that two overlapped patterns are observing in this plane. The first pattern is entirely in accordance with the small-angle spectrum of radiation scattered by the ensemble of particles, and its view does not depend on the distances between the particles, the hologram, and the lens. The second pattern is made of Fresnel's rings and depends on the distance between the particles and the hologram. A statistical interpretation of the distribution of intensity in the focal plane of a lens is proposed. Experimental results and discussion are presented.

The luminescence of dispersed media during light generation in spherical microresonators has been investigated theoretically. The effect that is predicted for the first time to our knowledge is a drastic increase of the dispersed-medium luminescence intensity in the case of an inverted population of the metastable-molecule energy levels.

An analogy is established between phase transitions of the second kind and processes of thixotropic structure-formation in dispersed media.

We consider statements of inverse problems of radiative and coupled heat and mass-transfer in dispersed media. We review some of the recent papers and discuss the algorithm of the method of inverse dynamical systems.

We obtain formulas for determining the principal values of the thermal-conductivity and electrical-conductivity tensors of materials obtained by the pressing of a powder consisting of anisotropic grains.

The article explains an algorithm for determining the thermophysical characteristics of dispersed media with phase transitions based on the method of solving inverse problems of heat conduction.

A generalization of the kinetic theory of gases to non-uniform and non-equilibrium systems is given, and this is used to construct a kinetic theory of dispersed media.

The effective viscosity and heat conductivity coefficients of dispersed media with spherically symmetric particles are calculated for various shapes of the binary distribution function.

A system of heat-mass-transfer equations describing filtration of a vapor in dispersed media is presented. The cases of “local thermal equilibrium” and temperature difference between the filtering agent and medium particles are considered.

On the basis of a two-zone heat-transfer model, a universal form of the dependence of the maximal magnitude of the conductive component of the external heat transfer on governing factors is set up.

The positive influence of vibropacking before isostatic pressing is caused by the effects of vibration breaking of the structural “arched” formations in dispersed media and is revealed in obtaining blanks of uniform and high density. These phenomena are used most rationally in vibropacking powders in vacuum. For this it is necessary to use a design of container vibrating with harmonic oscillations with an inertia-free overload. A method of isostatic pressing with preliminary vibrovacuum packing and a hydraulic over load has been developed. A feature of the method is pouring of the material into the mold with vibration and then repeated vibropacking of the evacuated powder with the use of an overload. The method makes it possible to obtain large high-quality refractory parts of complex configuration.

In this paper the continuum and noncontinuum (discrete) theories for radiative properties and radiative transfer models in dispersed particulate, porous and cellular media capable of absorbing, emitting, and scattering thermal radiation are reviewed. The governing equations for the radiative transfer are presented. Different models for the radiative properties of dispersed media are discussed. The methods for solving the inverse radiation problems to determine the spectral and total properties of homogeneous and nonhomogeneous radiatively participating dispersed media and other relevant parameters are also reviewed.

In this article we consider the solution of the compound problem of a parabolic equation with coefficients which have a discontinuity along a movable line which is not given beforehand. Problems of this kind (see [1]) arise in hydraulic construction in the arrangement of anti-filtration screens, when the ground rock and the shore adjoining dams are injected with cement, clay, silica and other solutions to fill up to pores and cracks in the rock and make it impenetrable to water. The injection of solutions which can harden into the rock (cementation) also serves to increase the mechanical strength of the foundations of hydrotechnical constructions and to reduce water influx in mine workings and foundation areas. Finally, we can give as an example the pumping of liquid into a porous medium when there is extra-contour flooding of petroleum deposits and secondary extraction of oil. If the pumping is done simultaneously from a number of boreholes lying in a straight line, and at equal, sufficiently small, distances from one another, then in order to determine the pressure u1(x, t) of the pumped liquid and the pressure u2(x, t) of the displaced liquid moving in a porous medium without mixing (where x = h(t) is the line of separation) we have the following mathematical problem (which we shall refer to as Verigin's problem), rather similar to Stefan's problem of freezing (see [3], pp. 263–264), but with essential differences. It is required to find three functions u1(x, t), u2(x, t) and h(t) satisfying the system of parabolic equations: ∂u i t6t = ∂ t6x [a i (x, t) ∂u i t6x ], 0 (0.1) where 0 ∂u i (c i , t) t6x = ϑ i (t), c 1 = 0, c 2 =l; i =1,2; 0 ⩽ t ⩽ T, (0.3) and the continuity conditions on the unknown line x = h(t): u1 (h (t), t) = u2 (h (t), t), 0 ⩽ t ⩽ T, (0.4) α 1 (h(t),t) ∂ 1 (h (t), t) ∂x = α 2 (h(t),t) ∂ 2 (h (t), t) ∂x , 0 ⩽t ⩽ T, (0.5) dh (t) dt = − β(h (t), t) ∂u 1 (h (t), t) t6x , 0 ⩽ t ⩽ T, (0.6) where B > 0 is a constant. The coefficients ai(x, t) and B depend on the compressibility and viscosity of the liquids, and also on the penetrability and porosity of the medium (for more detail see [1]). It is clear from (0.1)–(0.6) that, as in Stefan's problem, u1 and u2 satisfy different parabolic equations (0.1), the differential relation of Stefan's condition (0.6) being satisfied on the previously unknown line of separation, but the second condition of Stefan (viz. that u1 and u2 take a fixed value on the line of separation which is equal to zero for the problem of freezing) is replaced in Verigin's problem by basically different conditions — the condition for equality of pressures (0.4) and of flow (0.5) on the line of separation of the phases. Verigin's problem has been studied for constant values of ai(x, t) (i = 1, 2) in [1] and [2]. In this paper we consider the case of variable ai(x, t) which corresponds more exactly to the physical picture of the phenomena described by Verigin's problem. In fact, when rocks are cemented during the injection there can occur a gradual hardening and setting of the solution. When there is argillization and silification during pumping, there occurs partial coagulation of the dispersed media. These two processes change both the penetrability of the rock and the viscosity of the solutions and so naturally ai(x, t) which depend on these physical characteristics become variables. Our aim in this paper is to prove the existence of a solution of the problem (0.1)–(0.6) given sufficiently broad smoothness conditions for the coefficients of equation (0.1) and for the initial and boundary functions of (0.2) and (0.3). We shall use the system of heat potentials, the results of Gevrey [4] for linear parabolic equations, and the results of the author in [5], [6] in the theory of boundary problems for parabolic equations with discontinuous coefficients. The work consists of three sections. In § 1 we state the Verigin problem more exactly and indicate conditions for the data of the problem for which we shall prove the existence of a solution. After deriving the basic non-linear integral equation to find h(t) we formulate an auxiliary boundary problem for a parabolic equation with discontinuous coefficients, the analogue of which is discussed in [5], and using the solution of this problem we construct a non-linear operator S which we shall need later. In § 2 we study the properties of the operator S on the basis of which, using Schauder's fixed point method, we prove the existence of a solution of the integral equation for h(t). An essential part of the argument is the continuous dependence of the solution of the boundary problems for a parabolic equation with discontinuous coefficients on the boundary of the region, as the author proved in [6]. At the end of § 2 we give the proof of the existence of a solution of Verigin's problem. In § 3 we give the formally cumbersome proofs of a number of auxiliary propositions used in § 2, which are based on certain properties of heat potentials. The results of the paper were briefly quoted in the author's note [7].

A solution is given for a system of differential equations for heat and mass transfer in a dispersed medium in the presence of phase conversions (the evaporation of liquid or steam condensation). The mass transfer is thought to occur under the effect of mass transfer potential gradient ▽θ, a temperature gradient ▽t and a total pressure gradient ▽p. Solutions are obtained for the heat and mass transfer potentials (t, θ, p) applicable to a one-dimensional problem (an infinite plate and a sphere with boundary conditions of the third order. The solutions are given in the criterion form using heat and mass transfer similarity criteria. An analysis is given of the effect of the separate similarity criteria (Biq, Bim, Pn, Lup) on the fields of heat and mass transfer potentials. The effect of molar (filtration) transfer on heat and mass transfer is shown.

This paper deals with heat and mass transfer inside a moist capillary porous body under conditions of an intensive heating process. It was found by the experiments that in the capillaries of a body a pressure of gas and vapour mixture occurs exceeding that of the surrounding air (barometric pressure). One of the main reasons stimulating moisture transfer inside a body in the process of drying is a decrease of this excessive pressure. The coefficients of moisture content are calculated and in analysis the mechanism of drying is given on the basis of the differential equation for heat and mass transfer in dispersed media.

The mechanisms contributing to current transfer under alternating and steady voltage conditions through fixed arrays of particles dispersed in a continuous electrolyte medium are discussed. Lumped parameter expressions for the effective conductivity of the dispersed phase incorporating the intraparticle and double layer resistances are proposed which can be substituted in equations of the Maxwell type to predict the conductivity of dispersed media. Experimental measurements of the conductivity of arrays of copper cylinders in acid copper sulphate electrolyte over a range of void fractions and potential gradients under both dc and ac conditions are compared with the conductivities predicted by the model equations. Satisfactory agreement is taken to confirm the broad theoretical approach in predicting the effects of void fraction, phase geometry, interfacial resistance, and intra phase resistance on static two phase media conductivity.

Results of mathematical statistics about the covering of a plane by circles are used for a quantitative description of transparency fluctuations. It is shown from a comparison of the theoretical and experimental results for the dispersion of fluctuations of passing radiation that statistical screening is the governing reason for the fluctuations of passing radiation in dispersed media. An empirical formula permitting the approximate computation of the dispersion with an accuracy sufficient for practical purposes is proposed for large optical depths.

Scientific and industrial interest in the chemical modification of polymers has obviously increased since the middle of the last century. Some important discoveries include the vulcanization of natural rubbers (by Goodyear in 1839) and cellulose nitration (by Braconnot in 1833). This latter modified natural polymer was used as a substitute for ivory, by Hyatt in 1870, after plasticizing by camphor and lead to the first easily processable material: celluloid. Besides these examples based on chemically modified natural macromolecules, it is worthwhile noticing how many possibilities exist for chemically modifying synthetic polymers, as indicated in the exhaustive review published by Fettes.1 Generally, the use of solvents or dispersed media facilitates the control and adjustment of reactivity between polymers and other components of the system. The rate of conversion as well as the final structure of the modified polymer depend to a large extent on the reaction scheme and on the process parameters, including the nature of the continuous phase (solvent or dispersing agent) and such processing parameters as temperature and pressure. It is important to point out that the low concentration of polymer (around 10%) and the related separation and purification processes, which have a great influence on the final costs of modified polymers, are among the main disadvantages of reactions conducted in solvent media. Another approach is to perform these modifications of thermoplastic polymers, leading mainly to grafting and crosslinking reactions, by reactive processing in a discontinuous or continuous mixing equipment, which will be the chemical reactor, involving problems of high temperature, viscosity, risks of corrosion, etc. The main medium is the molten polymer, with an associated polarity related to its chemical composition, and the corresponding reaction and processing parameters are very different from those in solution. Adjustment of the reactivity requires specific basic research on the kinetic behaviour under these conditions, even if the main reaction is well known in classical organic or polymer chemistry.2

Systems in the form of a gas containing suspended dispersed particles suffering the effect of strong nonuniform electric fields rather often occur in nature and in human activities. The transfer of energy, mass, and impulses in such systems greatly depends on the characteristics of the electric field, viz., the degree of non-uniformity, field strength, volume charge content, etc. These factors influence, in particular, atmospheric and hence, weather conditions, electrization of aerospace vehicles, and some technological processes.

This chapter discusses the basic properties of capillary-porous bodies. The presence of water in a material affects in different ways its principal properties and, first of all, its mechanical properties. This phenomenon is determined by the type of bonding between water and the capillary-porous body. The only correct method of evaluating and classifying the types of water bond is the method depending on the evaluation of the bond energy, that is, the free energy of the dehydration process. The chapter also discusses the hygrothermic equilibrium state of capillary-porous bodies. The investigation of the equilibrium state of a capillary-porous body with the surrounding air is of interest, not only in the study of the problem of the bonding of water with dispersed media, but it also has practical importance in the technology of the production of building materials. The equilibrium-moisture content of a body depends on the temperature, the humidity of the surrounding air, and on the method of reaching equilibrium.

The mechanisms contributing to current transfer under alternating and steady voltage conditions through fixed arrays of particles dispersed in a continuous electrolyte medium are discussed. Lumped parameter expressions for the effective conductivity of the dispersed phase incorporating the intraparticle and double layer resistances are proposed which can be substituted in equations of the Maxwell type to predict the conductivity of dispersed media. Experimental measurements of the conductivity of arrays of copper cylinders in acid copper sulphate electrolyte over a range of void fractions and potential gradients under both dc and ac conditions are compared with the conductivities predicted by the model equations. Satisfactory agreement is taken to confirm the broad theoretical approach in predicting the effects of void fraction, phase geometry, interfacial resistance, and intra phase resistance on static two phase media conductivity.

Controlled release systems are attracting increasing interest because of their potential application in biomedical field. Indeed, such systems should enable to lower toxicity of medicines by targeting the therapeutic action and by limiting the concentration of drugs in the organism. In this research project, new nanoparticles have been developed for a thermosensitive control of drugs' delivery. These particles consist of a polynorbornene core and a polyethylene oxide shell and are developed by dispersion ring opening metathesis polymerization. As a model drug, salicylic acid has been encapsulated in those core-shell materials. This multidisciplinary project is original for two reasons. On the one hand, the nature of the particle which enables to release the drug from 35-45°C. On the other hand, the encapsulation technique that has been chosen is the impregnation under supercritical carbon dioxide., La délivrance contrôlée de médicaments constitue un enjeu thérapeutique de première importance pour le milieu médical. Elle doit, en effet, permettre de diminuer la toxicité du médicament en limitant sa concentration dans l'organisme et en ciblant son lieu de délivrance. Ce projet de recherche a conduit à la réalisation de nouveaux nano-vecteurs particulaires utilisables pour la délivrance de médicaments par hyperthermie locale. Ces objets sont constitués d'un cœur de polynorbornène et d'une écorce de poly (oxyde d'éthylène) et sont synthétisés par polymérisation par ouverture de cycle de type métathèse (ROMP) en dispersion. L'acide salicylique est encapsulé dans ces particules en tant que molécule modèle. L'originalité de ce sujet pluridisciplinaire réside : dans la nature de la particule, qui permet une libération du principe actif à partir de 35-45°C et dans la technique d'imprégnation des particules par la voie fluide supercritique.

The classical treatments of thermal-explosion theory for isolated reactant masses are extended to cover an aggregate of reactant particles embedded in a chemically inert matrix. In this model the heat released by one particle influences the heat-release rates in the others. The critical conditions for thermal runaway can be cast in terms of the classical dimensionless groups ψ or δ, which contain only known thermochemical parameters appropriate to the given reactant. The numerical values of ψ or δ at criticality are determined by a second parameter ω, β or Ω. These parameters compare the resistances to heat transfer of the reactant and the matrix material, and again contain only known or measurable physical quantities. These three different groups are each appropriate to different boundary conditions. We study the following cases: (i) systems where the resistances to heat transfer are concentrated at the reactant and matrix surfaces (low surface heat-transfer coefficients), (ii) systems where the resistance to heat transfer from the matrix is concentrated at the surface, but where there is an internal resistance to heat transfer in the reactant (low reactant thermal conductivity), and (iii) systems where there are internal resistances in both reactant and matrix. Case (i) gives rise to a uniform temperature throughout the matrix and a (higher) uniform temperature throughout each reactant. Case (ii) leads to uniform matrix temperatures but an internal temperature distribution throughout the particles. Case (iii) allows for temperature distributions throughout both matrix and reactant.