Beiträge zur galvanisierung von polymeren, 11. Metallisierung von mischungen aus epoxidharzen und acrylnitril-butadien-copolymeren

The metallization of mixtures containing epoxy resins and acrylonitrile-butadiene copolymers depends on taking the suitable ratio of components and on the hardener, which was brought to reaction with the epoxy prepolymer in presence of the copolymer. Using triethylenetetramine as curing agent the highest values of peel strength have been reached and have been increased up to 150 N/25 mm by short-time-treatment with ozone. Longer ozonization times lead to lower values of peel strength and impairment of the material. Caverns occur only in mixtures which are rich on epoxy resin, and increase in size with increasing time of ozone treatment. These samples have relatively low values of peel strength.     

Pattern evocation and geometric phases in mechanical systems with symmetry

This paper is concerned with the relation between the dynamics of a given Hamiltonian system with a given symmetry group and its reduced dynamics. We illustrate the process of visualization of reduced orbits using the double spherical pendulum. In this process of visualization, one sees certain patterns when the dynamics is viewed relative to rotating frames with certain critical angular velocities. By using the reduced dynamics, we also explain these patterns. We show that if the motion on the phase space reduced by a continuous symmetry group at a given momentum level is periodic, then there is a uniformly rotating frame, that is, a one-parameter group motion, relative to which the unreduced trajectory is periodic with the same period. If the continuous symmetry group of the system is Abelian, which corresponds to the system having cyclic variables, we derive an explicit expression for the required angular velocity in terms of the dynamic phase (an average of the mechanical connection) and the geometric phase (the holonomy of the mechanical connection). We show that one can also find such a frame if the reduced orbit is quasi-periodic and a KAM (Kolmogorov-Arnold-Moser) condition is satisfied The almost periodic case is also discussed. An important aspect of this procedure is how to use it in the presence of discrete symmetries. We show that, under appropriate conditions, the visualized orbit has, relative to a suitable uniformly rotating frame, the same temporal behavior and discrete symmetries as the reduced orbit. Since these spatio-temporal patterns are not apparent with repect to most frames, we call the phenomenon pattern evocation     

Reliability indicators

This is a review paper. It describes the state-of-the-art of the research on reliability indicators for either electronic or mechanical components. Typical component failure patterns are presented and discussed. The concept of component screening using reliability indicators is then outlined. The paper sketches a theoretical approach to the problem of detecting flaws in components. The approach is based on an old concept of energy imbalance in flawed objects.     

Comparison of kernel estimators,perceptrons and radial-basis functions for OCR and speech classification

We compare kernel estimators, single and multi-layered perceptrons and radial-basis functions for the problems of classification of handwritten digits and speech phonemes. By taking two different applications and employing many techniques, we report here a two-dimensional study whereby a domain-independent assessment of these learning methods can be possible. We consider a feed-forward network with one hidden layer. As examples of the local methods, we use kernel estimators like k-nearest neighbour (k-nn), Parzen windows, generalised k-nn, and Grow and Learn (Condensed Nearest Neighbour). We have also considered fuzzy k-nn due to its similarity. As distributed networks, we use linear perceptron, pairwise separating linear perceptron and multi-layer perceptrons with sigmoidal hidden units. We also tested the radial-basis function network, which is a combination of local and distributed networks. Four criteria are taken for comparison: correct classification of the test set; network size; learning time; and the operational complexity. We found that perceptrons, when the architecture is suitable, generalise better than local, memory-based kernel estimators, but require a longer training and more precise computation. Local networks are simple, leant very quickly and acceptably, but use more memory.     

Cadmium in Blaumohn und Mohnerzeugnissen

Zusammenfassung Blaumohnsamen, blaumohnhaltige Halberzeugnisse und blaumohnhaltige Bäckereier-zeugnisse werden mittels AAS (Atomabsorptions-spektralphotometrie) auf ihren Cadmiumgehalt untersucht. Die Mittelwerte lagen bei 0,739 mg/kg (Median 0,654 mg/kg) für Blaumohn, 0,317 mg/kg (Median 0,366 mg/kg) für Halberzeugnisse und 0,107 mg/kg (Median 0,088 mg/kg) für Mohngebäck. Damit muß Blaumohn zu den am stärksten mit Cadmium kontaminierten Lebensmitteln gezählt werden. Für Verbraucher, insbesondere Kinder, sollten Verzehrsempfehlungen erstellt werden.

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Cadmium in blue poppy seeds and in poppy seed containing products

Summary Blue poppy seeds, semi finished products and finished baked goods with poppy seeds, were analyzed for cadmium by atomic-absorption spectrometry. The average content was 0.739 mg/kg (median 0.654 mg/kg) for poppy seeds, 0.317 mg/kg (median 0.366 mg/kg) for semi finished products and 0.107 mg/kg (median 0.088 mg/kg) for baked goods. Poppy seeds therefore must be considered as one of the most cadmium contaminated foods. For consumers, especially children, recommendations for consumption should be established.

     

Using sneak circuit analysis in aerospace product assurance

In this paper sneak circuit analysis is introduced. Sneak circuit analysis is a method that detects functional deficiencies that can usually not be detected by other reliability methods. Sneak path analysis as a special technique is presented. The method is applied to a pneumatic system.     

Numerical results for a parallel linearly-implicit Runge-Kutta method

For the parallelization of implicit Runge-Kutta methods for stiff ODE’s a parallel computation of the stages is obvious. In this paper we consider the parallelization of the stages of linearly-implicit Runge-Kutta methods. The construction and implementation of a parallel linearly-implicit Runge-Kutta method is described. The numerical results are compared with the code PSODE of van der Houwen/Sommeijer [6] and a straightforward parallelization of RADAU5 [5]. All methods are based on the 3-stage implicit Radau-IIA method.     

Auftragschweißungen mit Hastelloy alloy B-42

Hastelloy alloy B-42 weld overlay welding Alloy NiMo 28, Mat. No. 2.4617 (HASTELLOY alloy B-2), is known for its excellent corrosion resistance in hydrochloric and sulfuric acids over a wide range of concentrations and temperatures. Under critical conditions, however, severe corrosion can occur in welds (weld deposit and HAZ). This is attributed to molybdenum depletion of the microstructure. The properties of a filler material were investigated which contained an excessive amount of molybdenum over the parent alloy. This filler is called HASTELLOY alloy B-42, a nickel alloy having about 42% molybdenum. The much less ductile HASTELLOY alloy B-42 weld deposit is more corrosion resistant in hydrochloric and sulfuric acids than wrought HASTELLOY alloy B-2 and Hastelloyalloy B-2 filler. It can therefore be applied as weld overlay of HASTELLOY alloy B-2 welds subject to critical corrosion conditions. In field testing promising results were obtained. Currently only TIG rod having a diameter of not less than 4.76 mm (0.187”?) are available which are causing handling problems. Tube wire with a diameter of 2.5 mm (0.098”?) is under development and will be available shortly.     

Exception handling—A static approach

This paper presents a static approach to exception handling. The static approach is proposed as a consequence of an examination of existing language constructs for exception handling in which several trouble spots have been revealed. The static approach consists basically of one concept, namely the sequel concept. Although the sequel concept is sufficient to specify exception handling within a program, one additional concept is introduced, namely the derived definition concept that is introduced as a generalization of the derived type and generic concepts from Ada. The main advantages of the static approach are first that it is truly static as opposed to the existing language constructs in which dynamic association is used in some way or another; and, secondly, the language constructs for exception handling are simple, easy to implement and based on familiar concepts.