Phase uniformity

The rubber phase particles are formed in the first reactor and their average size is also largely determined by conditions existing there. The Ruffing et al patent (27)implies that the first reactor operates significantly backmixed at temperatures between 85 and 130°C with sufficient agitation to maintain the rubber phase uniformly dispersed with a 2-to 25-micron particle... 

For analytical purposes, the fiber composites are conveniently modeled using axisymmetric three-phase (i.e. fiber-interlayer-matrix), four-phase (i.e. fiber-interlayer-matrix-composite medium) cylindrical composites, or in rare cases multi-layer composites (Zhang, 1993). These models are schematically presented in Fig. 7.9. The three-phase uniform interphase model is typified by the work of Nairn (1985) and Beneveniste et al. (1989), while Mitaka and Taya (1985a, b, 1986) were the pioneers in developing four-phase models with interlayer/interphase of varying stiffness and CTE values to characterize the stress fields due to thermo-mechanical loading. The four phase composite models contain another cylinder at the outermost surface as an equivalent composite (Christensen, 1979 Theocaris and Demakos, 1992 Lhotellier and Brinson, 1988). 

For steady-state, isothermal, single-phase, uniform, fully developed newtonian flow in straight pipes, the velocity is greatest at the center of the channel and symmetric about the axis of the pipe. Of those flowmeters that are dependent on the velocity profile, they are usually calibrated for this type of flow. Thus any disturbances in flow conditions can affect flowmeter readings. 

In this model, instead of the uniform and interpenetrating continuous phases of the gas and the solids, a distinct heterogeneous structure is assumed. The elemental volume in the flow field, which has displayed observable heterogeneity, is partitioned into fractions occupied by the gas-rich, dilute phase (denoted by subscript "f") and the particle-rich, dense phase (denoted by subscript "c"), respectively. Within each "phase," uniformity is assumed, and the dense "phase" is assumed to occur as spherical clusters. That is, the dense phase is discrete, surrounded by the continuous dilute phase. In this way, eight variables... 

Colloids are similar to solutions in that they consist of one phase uniformly dispersed in a second phase. There are many common examples of colloids, including milk, blood, paint, and jelly. However, colloids are not true solutions because the particles in the dispersed phase are not the size of molecules or ions. The particles in a colloid range in size from 10 to 200 nm. The dispersed particles might be supersized molecules (e.g., proteins) or aggregates of ions. While these particles are typically too small to be discerned, even by a microscope, they are much larger than, say, a sodium ion, which has a diameter of about 0.1 nm. 

The possibility of fracture on impact can be reduced by dispersing an elastomeric phase uniformly through the rigid material, as it is done in polyblends or better in grafting vinyl monomer upon rubber. H. Bartl and D. Hardt describe the manufacture of a tough rigid PVC by grafting vinyl chloride upon an elastomeric ethylene—vinyl acetate copolymer. 

The synthesis of rare earth orthophosphate nanomaterials involves obtaining pure phase, uniform morphology, as well as the surface structures, in order to fulfill the requirement for applications such as phosphors. The rare earth orthophosphate NCs could be obtained through precipitation in aqueous or nonaqueous solutions and dry methods. 

In the case of lipid fractionation, however, a different crystal size distribution is desired. As the fat crystals are to be separated from the liquid phase, uniform crystals of distinct size and shape are needed for the most efficient separation. For the most efficient separation by filtration, reasonably large (200 to 300 pm) crystals of fairly uniform size (narrow distribution of sizes) are needed. Fractionation technologies carefully control nucleation and growth to produce this uniform distribution of crystals to enhance filtration and separation of the high-melting stearin phase from the low-melting olein phase. 

For automotive exhaust gas treatment. Oh [42] presented a transient, one-dimensional single-channel model that predicts the temperature and species concentrations as a function of axial position and time in both solid and gas phase. Uniform flow distribution was... 

In bubble columns, gas is dispersed in a continuous liquid phase. Uniform bubble size and bubble concentration characterize the homogeneous regime, particularly in the traverse direction indicating the absence of bulk liquid circulation. In contrast, the heterogeneous regime is characterized by a nonuniform bubble concentration, especially in the traverse direction, because of liquid circulation. 

In this section we consider what happens when two miscible liquids are contacted and mixed in a flow. The equilibrium for such a case is simply that of one phase uniformly distributed throughout the second, so any phenomena of interest are unsteady ones. The process whereby one phase is distributed in the second is termed miscible dispersion. In a laminar flow both convection and molecular diffusion will contribute to this dispersion. Other factors can also enter, including the geometry and any forced unsteadiness. 

The single-phase uniformly crosslinked open network can be stressed in two opposite ways, on shrinkage and extension. As was discussed earlier, stresses of shrinkage appear in the dry hypercrosslinked material as a result of confrontation between the network rigidity and the attraction forces... 

For instance, V.N. Ozyabkin (1995) subdivides them depending on the complexity and dimension of the forecast object. J.Rubin (1983), W. Kinzelbach (1992), S.R. Kraynov et al. (2004) base the classification on phase uniformity of the medium and velocity of chemical processes. In this connection they distinguish thermodynamical, transport and kinetic models. In Europe and the USA are broadly used classifications based on typization of local problems (Chen Zhu, Anderson G., 2002, Bethke C. M., 2008, etc.). In connection with this all hydrogeochemical models are subdivided there into three groups speciation-solubility models or batch models, reaction path modelsor mass transfer models reactive transport models or couplet mass transport models. In the second group of this classification is non-uniquely identified the role of mass transfer kinetics. 

Density. This property was found to be useful for a first selection of the polysulfide crystals. In each of the Nd, Pr and Sm systems 20-30 crystals selected randomly showed identical density, giving a good proof of phase uniformity of all these crystals. For the Dy crystals there was considerable scatter in density values, and only a histogram based on 100 measurements with well-defined maxinoa allowed the polysulfides with different density and hence with different compositions to be observed. At least two polysulfide phases were identified according to this histogram. The scatter still persists between the... 

The oldest description of CVD uses the boundary-layer model, which assumes that between the bulk gas phase (uniform in composition) and the substrate there is a stagnant boundary layer in which gradients develop in temperature (cold wall reactors) and in the partial pressures of the reactants and the gaseous reaction products. The boundary-layer model presents some difficulties. Stagnant gas layers have a variable thickness in the reactor as long as unmodified bulk gas concentrations exist, if they exist at all. Moreover the flow is always laminar. Conceptually, however, the model has its advantages.The boundary-layer thickness is an effective parameter by which to characterize the deposition regime. This model will be used here for a simple overview of reaction conditions. 

Cubic phase, uniform, and crack-free films with much lower grain... 

Cases (c) and (d) both represent truly ferroelectric behavior, which can be found in smectic C phases of chiral molecules only if the helix is suppressed by the boundary conditions at the liquid crystal glass interfaces. Because it is nearly impossible to align columnar phases uniformly with rubbed or otherwise anisotropic polymer surfaces (the switching is generally studied in polydomain or sheared samples), and because the ferroelectric behavior remains present in thick cells, surface induction of ferroelectricity can be excluded. It must be assumed that the two-dimensional column lattice suppresses helix formation in these materials. 

The cholesteric phases could be identified by their fingerprint textures in the polarization microscope, which are characteristic for non-oriented cholesteric phases. Uniformly oriented cholesteric phases show characteristic stripe textures. Both textures are presented in Figs. 11.29 a and 11.29 b. From the distance of the stripes the pitch of the phase can be cal-... 

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