Massive transformation and absolute stability

Under carefully chosen conditions, solidification theory may be applied to solid-state transformations, and this has been done here for composition-invariant diffusion transformations. The predictions of the modeling are compared with isovelocity experiments in two iron systems, Fe-7.29 wt pct Cr and Fe-3.1 wt pct Ni. The ferrite to austenite phase transformation is used to demonstrate that stabilization of a planar transformation front at absolute stability is the natural lower velocity limit for a composition-invariant (massive) transformation. The results of the model, which includes nonequilibrium effects, clearly show that steady-state plane-front growth leading to composition invariance can be obtained at various temperatures depending on the growth velocity. In the lower velocity range, at the limit of absolute stability (of the order of 10 μm/s in the systems studied), the transformation interface moves under conditions of local equilibrium, and the temperature corresponds to the lower solvus temperature. At higher velocity (of the order of the interface diffusion rate, which in these systems is of the order of cm/s), the transformation is predicted to proceed at temperatures close to T ₀. At even higher rates, atom attachment kinetic undercooling will decrease the transformation temperature with respect to T ₀. In some cases, this temperature might even drop below the lower solvus. This article is based on a presentation made at the symposium entitled “The Mechanisms of the Massive Transformation,” a part of the Fall 2000 TMS Meeting held October 16–19, 2000, in St. Louis, Missouri, under the auspices of the ASM Phase Transformations Committee.     

Zur Verantwortung des Informatikers-Militärische Anwendungen der Informatik

Ohne Zusammenfassung     

Continued fraction for formal laurent series and the lattice structure of sequences

Besides equidistribution properties and statistical independence the lattice profile, a generalized version of Marsaglia's lattice test, provides another quality measure for pseudorandom sequences over a (finite) field. It turned out that the lattice profile is closely related with the linear complexity profile. In this article we give a survey of several features of the linear complexity profile and the lattice profile, and we utilize relationships to completely describe the lattice profile of a sequence over a finite field in terms of the continued fraction expansion of its generating function. Finally we describe and construct sequences with a certain lattice profile, and introduce a further complexity measure.     

Chinongruppenhaltige Polymere als Träger zur Immobilisierung von Enzymen

Crosslinked poly(4-styrenesulfonic acid chloride) was reacted with 3-amino-4-hydroxyphenyl benzoate to give a reactive carrier after saponification and oxidation. Its binding ability was tested with α-chymotrypsin. The binding ability as well as the enzyme activity could be increased by introduction of spacers, e.g. ethylenediamine and hexamethylenediamine between the poly(styrene)-matrix and p-benzoquinone. Also crosslinked poly(vinyl alcohol) was reacted with p-benzoquinone to give a reactive carrier, which could also immobilize α-chymotrypsin. Some properties of the immobilized α-chymotrypsin as activity, pH-optimum and storage stability were investigated.     

Evaluating meeting support tools

Many attempts are underway for developing meeting support tools, but less attention is paid to the evaluation of meetingware. This article describes the development and testing of an instrument for evaluating meeting tools. First, we specified the object of evaluation—meetings—by means of a set of input, process, and outcome factors. Then, we designed the process of evaluation, consisting of, first, the generation of meeting behavior in the form of a controlled series of meetings within the context of a project and, second, the measurement of the identified meeting factors. To measure these factors, a rating scale, questionnaires, and information flow analysis were used. Next, the instrument was tested, and the factors for successful meetings were determined in 13 projects in which four participants had to meet four times. The evaluation instrument proved to be a reliable and useful aid for the development and improvement of meeting tools.     

On mind &; Turing’s machines

Turing’s notion of human computability is exactly right not only for obtaining a negative solution of Hilbert’s Entscheidungsproblem that is conclusive, but also for achieving a precise characterization of formal systems that is needed for the general formulation of the incompleteness theorems. The broad intellectual context reaches back to Leibniz and requires a focus on mechanical procedures; these procedures are to be carried out by human computers without invoking higher cognitive capacities. The question whether there are strictly broader notions of effectiveness has of course been asked for both cognitive and physical processes. I address this question not in any general way, but rather by focusing on aspects of mathematical reasoning that transcend mechanical procedures.Section 1 discusses Gödel’s perspective on mechanical computability as articulated in his [193?], where he drew a dramatic conclusion from the undecidability of certain Diophantine propositions, namely, that mathematicians cannot be replaced by machines. That theme is taken up in the Gibbs Lecture of 1951; Gödel argues there in greater detail that the human mind infinitely surpasses the powers of any finite machine. An analysis of the argument is presented in Section 2 under the heading Beyond calculation. Section 3 is entitled Beyond discipline and gives Turing’s view of intelligent machinery; it is devoted to the seemingly sharp conflict between Gödel’s and Turing’s views on mind. Their deeper disagreement really concerns the nature of machines, and I’ll end with some brief remarks on (supra-) mechanical devices in Section 4.     

Effective stiffness and microscopic deformation of an orthotropic plate containing arbitrary holes

Many engineering materials and structures, such as cellular structures, sandwich core structures and laminated plates with holes, can be modeled by an inclusion problem with anisotropic matrix. The paper studies the effective properties and the microscopic deformation of anisotropic plates with periodic holes by using direct and mathematical homogenization. The effective stiffnesses are calculated by different homogenization methods and the microscopic deformation of a RVE is modeled by the finite element method for the plate with arbitrarily shaped holes. All of the effective stiffness coefficients, especially stretching-shear coupling coefficients are evaluated.