Characterization of bis‐(phenoxy)phosphazene polymers using radio frequency glow discharge mass spectrometry

A radio frequency glow discharge mass spectrometry (rf‐GDMS) source is evaluated for future applications in the “fingerprint” characterization of polyphosphazene membranes. The rf‐GDMS spectra of a series of bis(phenoxy)phosphazene polymers contain ions that originate from both the phosphazene backbone and the phenoxy moiety, resulting in signature ions of the polymer family. “Fingerprint” ions from the substituted R‐group on the phenoxy moiety of the different derivatives allows the individual polymers to be distinguished from one another. The ability of the rf‐GDMS source to characterize these materials directly in the solid state will be useful for the continued application of these polymers as separation membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 954–961, 2000     

Theory and numerics of three‐dimensional beams with elastoplastic material behaviour

A theory of space curved beams with arbitrary cross‐sections and an associated finite element formulation is presented. Within the present beam theory the reference point, the centroid, the centre of shear and the loading point are arbitrary points of the cross‐section. The beam strains are based on a kinematic assumption where torsion‐warping deformation is included. Each node of the derived finite element possesses seven degrees of freedom. The update of the rotational parameters at the finite element nodes is achieved in an additive way. Applying the isoparametric concept the kinematic quantities are approximated using Lagrangian interpolation functions. Since the reference curve lies arbitrarily with respect to the centroid the developed element can be used to discretize eccentric stiffener of shells. Due to the implemented constitutive equations for elastoplastic material behaviour the element can be used to evaluate the load‐carrying capacity of beam structures. Copyright © 2000 John Wiley & Sons, Ltd.     

Application of essential boundary conditions in mesh‐free methods: a corrected collocation method

Collocation methods for applying essential boundary conditions are defined as those methods in which conditions are enforced exactly at a discrete set of boundary nodes. In mesh‐free methods, this is usually accomplished by replacing rows of the matrix equations which result from discretization of the weak form with equations which ensure the enforcement of boundary conditions. In this paper, an inconsistency in this method is pointed out, and a correction is derived. Numerical test are done on one‐ and two‐dimensional equations; it is shown that convergence rates decrease with the use of the invalid traditional collocation and are restored with the corrected method. Copyright © 2000 John Wiley & Sons, Ltd.     

CFD in der chemischen Verfahrenstechnik aus industrieller Sicht

Computational fluid dynamics (CFD) is increasingly becoming established as a tool for analysis and design in the chemical industry. Several projects from various areas are introduced as examples of CFD projects from the perspective of the CFD user in chemical industry. The areas chosen are based on those in a process chain: transportation, mixing, reaction, and separation of materials. The most important steps and decisions in the use of CFD are presented from the perspective of the process engineer. This paper attempts to convey an appreciation for the possibilities and opportunities, but also for the limits of computational fluid dynamics.