Segmental models

N. Ashgriz and J.Y. Poo, FLAIR Flux Line-Segment Model for Advection and Interface Reconstruction, J. Comput. Phys. 93 (1991). 

Tobolsky, A. V. and DuPre, D. B. Macromolecular Relaxation in the Damped Torsional Oscillator and Statistical Segment Models. Vol. 6, pp. 103 — 127. 

Polarization of the Emission. We have sought support for the weakly interacting chain segment model from measurements of room temperature fluorescence polarization (19) on dilute solutions of 1 in 3-methylpentane. An independent preliminary report of similar measurements on a dilute glassy solution at 77K and on a neat polymer has also appeared (21). In the latter case, the analysis is complicated by inter-chain energy transfer. 

Structural effects on dienes and polyenes 2. The segmental model... 

The most important parts of creating a segment model are the application of the physical boundary conditions and the positioning of the internals to allow for the symmetry and periodic boundary conditions. Without properly applying boundary conditions the simulation results cannot be compared to full-bed results, both as a concept and as a validation, since the segment now is not really a part of a continuous geometry. Our approach was to apply symmetry boundaries on the side planes parallel to the main flow direction, thereby mimicking the circumferential continuation of the bed, and translational periodic boundaries on the axial planes, as was done in the full-bed model. 

When simulations are done in a WS model, the results need to be validated against a full-bed model. The main reason for this is not only to see if the WS model results are representative for a full bed but also to check that the symmetry boundaries, which are relatively close to all parts of the segment model, do not influence the solution. 

To extend these calculations to cylinders is more complicated, as both the position and orientation of a cylinder must be obtained. To do that we followed the sequence of operations used to position each cylinder, as shown in Fig. 32a, for particle 1, the lower front particle in the wall segment (note that wire frames of the previous positions are retained in each sketch for comparison). Similar sequences were available for each of the other particles in the wall segment model. 

Fig. 8.9 Two spherical-segment model of an indented fluid particle.

We have alluded to the fact that MDI produces stiffer polymers than TDI, based on the hard-and-soft segment model of polymer design. In the experiment cited below, the concentration of MDI in a formulation was increased and the resultant polymer analyzed. 

Clark, M.B., Zimm,B.H. A linearized chain model for dielectric loss in polymers. ACS Polymer Preprints 12, 116-120 (1971). See also Tobolsky,A.V., DuPre,D.B. Macromolecular relaxation in the damped torsional oscillator and statistical segment models. Advan. Polymer Sci. 6,103-127 (1969). 

Macromolecular Relaxation in the Damped Torsional Oscillator and Statistical Segment Models... 

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