Geometrical encapsulation

Svabik, Samsonkova, and Perdikoulias [45] proposed another explanation for the interface distortion in coextrusion of fluids with equal viscosity. They performed three-dimensional flow analysis of coextrusion flow and found that even in coextrusion with Newtonian fluids with equal viscosity layer distortion takes place. Obviously, this type of distortion cannot be caused by normal stress differences since these do not occur in Newtonian fluids. Also, with the viscosities being equal the distortion cannot be caused by viscosity differences. The predicted layer distortion is schematically illustrated in Fig. 9.43. The authors call the distortion resulting from purely viscous flow geometrical encapsulation. 

Initial layer configuration Figure 9.43 Illustration of geometrical encapsulation... 

Geometric encapsulation is caused by the parabolic velocity profiles in the die flow channel. Because the velocities are highest in the center region of the channel the layer thickness increases in this part of the channel, while the thickness of the outside layers reduces in the center region of the channel. At the side walls the inner layer thickness reduces while the outside layer thickness increases. The distortion caused by geometric encapsulation becomes more severe as the fluid becomes shear thinning. 

It appears that there are several mechanisms for interface distortion. One is distortion caused by viscosity differences (viscous encapsulation), another is caused by normal stress differences in the fluid (elastic encapsulation), and a third is caused by normal velocity differences within the fluid (geometrical encapsulation). Obviously, the distortion will increase when viscosity differences are large and when normal stress differences play a significant role. 

Use sealing (encapsulating or enveloping type with shrinkable plastic) on bimetallic joints if geometrical arrangements prohibit access to such joints for replacement. 

It can be concluded that polymeric carbon can be successfully generated inside the channels of the MCM-41 from l,4-diiodo-l,3-butadiyne and l-iodo-l,3,5-hexatriyne and was found to be protected by its host. The changes in the porous structure due to this encapsulation were assessed using the geometrical model of the MCM-41. 

The template encapsulation has recently been extended still further to the cobalt(III) complex of the vicinal tridentate l,l,l-tris(aminomethyl)ethane but leads to a surprising set of products, which in retrospect shows the geometrical influence of the original tridentate ligand (Scheme 52) 228 Although mixtures of products are formed in rather modest yields, the individual compounds can be separated by chromatography. 

These doubly encapsulated strips are the building blocks for assembling plaques or other geometrical forms that are the gamma energy-emitting sources of food irradiators. Figure 5 illustrates one such plaque. 

A metal ion encapsulated in the three-dimensional ligand cavity must be an acceptor bonded to the donor groups of all macrocycles forming the cage framework. This is time either when the metal ion size corresponds to the ligand cavity size or when the cavity can be transformed under the influence of the metal ion so that the distance between the central ion and the donor atoms of the cage is not over the sum of their ionic or covalent radii. In addition to the geometric parameters, the thermodynamic and kinetic stability of... 

Previous studies of aligned and oriented gas-phase reactions had relied on the use of laboratory-based fields (lasers, hexapoles, etc.) to fix reactants relative to the lab system, thereby introducing geometric bias into the reaction [11-20]. However, referring to Figure 1, when a weakly bonded complex is used as a precursor, one of the reactants is encapsulated within one... 

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