Mechanical properties of a modified acrylic bone cement with etoxytriethyleneglycol monomethacrylate

With the aim of improving some of the disadvantages of the acrylic bone cements, an acrylic bone cement based on polymethyl methacrylate has been modified by substituting different quantities, up to 20%, of the monomer methyl methacrylate (MMA) with the same amount of ethoxytriethyleneglycol monomethacrylate (TEG). The addition of this new monomer decreased noticeably the maximum temperature and increased both setting and working times. Mechanical testing revealed that the introduction of TEG gave rise to a less fragile bone cement by increasing slightly the total deformation without any change in the rest of the tensile parameters.     

Micellization of three-block copolymer poly[styrene-b-(ethene-co-butene)-b-styrene] in mixed solvents of tetrahydrofuran/ethanol

The behaviour of dilute solutions of a three-block copolymer poly[styrene-b-(ethene-co-butene)-b-styrene] in mixtures of tetrahydrofuran (THF)/ethanol was studied using viscometry, osmometry and light scattering. In solutions with a lower ethanol content the copolymer dissolved, but in solutions with a higher ethanol content it became associated, to form spherical micelles with cores composed of middle (aliphatic) blocks. Between the molecular and micellar solutions a region of the so-called anomalous micellization was described. Micelles in mixtures with a higher ethanol content were stabilized by means of fast electrons, isolated and characterized in THF solutions.     

Anisotropic mesh adaptation for finite volume and finite element methods on triangular meshes

The present paper deals with an anisotropic mesh adaptation (AMA) of triangulation which can be employed for the numerical solution various problems of physics. AMA tries to construct an optimal triangulation of the domain of computation in the sense that an “error” of the solution of the problem considered is uniformly distributed over the whole triangulation. First, we describe the main idea of AMA. We define an optimal triangle and an optimal triangulation. Then we describe the process of optimization of the triangulation and the complete multilevel computational process. We apply AMA to a problem of CFD, namely to inviscid compressible flow. The computational results for a channel flow are presented. Received: 11 December 1997 / Accepted: 16 February 1998     

Morphology of coalescence processes: secondary fracture,cracks and spherulites

Summary Similarity in the shapes of fracture curves and spherulite boundaries makes possible to generalize the respective theories to the case of coalescence of two spreading processes of growth, disturbances or excitations. The geometrical shape of a coalescence curve depends on three parametres: the distance of their spreading centres, the relation of spreading velocities and the time delay of the spreading. According to the character of the process, the shielding effect may take place. In this case, the coalescence curve is composed of two parts which are to be described separately.     

Solution of counter-current separation processes—IV. Application of the GPM method to solution of distillation problems

A new non-iterative method for a parametric study of a particular distillation column is devised. The technique takes use of the similarity between difference and differential equations. For solution of nonlinear boundary value problems for difference equations the GPM technique is used. The method is illustrated by calculated examples.     

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