Selektive Anätzung von Carbiden in Stählen mit Potentiostaten

Versuche zur Einzeldarstellung verschiedener Carbidarten in hochlegierten Eisenwerkstoffen durch potentiostatisches Ätzen. Angabe der günstigsten Ätzbedingungen für die Unterscheidung der Carbidarten MG, M₆C, M₇C₃ und M₂₃C₆, besonders der beiden Eisen-Chrom-Mischcarbide vom Typ M₇C₃ und ₂₃MC₆.     

Three-dimensional harmonic functions near termination or intersection of gradient singularity lines: A general numerical method

The harmonic function u near point 0 from which a single singularity ray emanates is assumed to be dominated by the term r^λρ^ρU where r = distance from point 0, p = known constant and ρ = chosen function of angular spherical coordinates θ, ?, for which a partial differential equation with boundary conditions, especially those at the singularity rays, and a variational principle, are derived. Because grad U is nonsingular, a 1numerical solution is possible, using, e.g. the finite difference or finite element methods. This reduces the problem to finding λ of the smallest real part satisfying the equation Det (A_ij) = 0 where A_ij is a large matrix whose coefficients depend linearly on μ = λ(λ + 1). In general λ and A_ij are complex. Solutions can be obtained either by reduction to a standard matrix eigenvalue problem for μ, or by successive conversions to nonhomogeneous linear equation systems. Computer studies have confirmed the feasibility of the method and have shown that highly accurate results can be obtained. Solutions for cracks and notches ending at a plane or conical surface, and for cracks ending obliquely at a halfspace surface, are presented. In these cases, λ is real and the singularity is always weaker (λ > p) than on the singularity line and may even disappear (λ > 1). Furthermore, elastic stresses under a wedge-shaped rigid sliding stamp or at a corner of a crack edge, and also harmonic functions at three-sided pyramidal notches, have been analyzed. Here λ < p was found to occur. A simple analytical solution for one class of special cases has also been found and used to check some of the numerical results.     

Rendezvous layer protocols for Bluetooth-enabled smart devices

Communication platforms for ubiquitous computing need to be flexible, self-organizing, highly scalable and energy efficient, because in the envisioned scenarios a large number of autonomous entities communicate in potentially unpredictable ways. Short-range wireless technologies form the basis of such communication platforms. In this paper we investigate device discovery in Bluetooth, a candidate wireless technology for ubiquitous computing. Detecting new devices accounts for a significant portion of the total energy consumption in Bluetooth. It is argued that the standard Bluetooth rendezvous protocols for device detection are not well suited for ubiquitous computing scenarios, because they do not scale to a large number of devices, take too long to complete, and consume too much energy. Based on theoretical considerations, practical experiments and simulation results, recommendations for choosing inquiry parameters are given that optimize discovery performance. We propose an adaptive rendezvous protocol that significantly increases the performance of the inquiry procedure by implementing cooperative device discovery. Also higher level methods to optimize discovery performance, specifically the use of sensory data and context information, are considered.     

Large scale implementation of Solar Home Systems in remote,rural areas

Large-scale implementation of Solar Home Systems (SHSs) to provide electricity for people lacking electric power may have several constraints. Some of these are on the input side to realise the potential, and some are on the dismantling side, which are concerned with environmental issues. The questions analysed within this study are: will the industrial production capacity and distributor network grow fast enough to serve market demand and does the flux of lead induced by such a global growth of SHS represent a potential hazard to the environment. Some of the surprising findings are as follows. (i) The photovoltaic (PV) module and other SHS components can be manufactured on time to serve the growing market, even if implementation will take place over 25 years. (ii) The setting up of a distribution network represents a real bottleneck. (iii) Enhancing the average lifetime of SHS batteries from 3 to 5 years, which will result from an improved quality procedure such as implemented by the PV Global Approval Process (PVGAP), has the same effect as improving the recycling rate by 40% and is therefore undoubtedly the most appropriate urgent first step in reducing the impact of lead from SHS on the environment. In addition, recycling rates should be enhanced, and financial agencies and PV distributors may play an important role in stimulating the installation of facilities to undertake the proper recycling of used batteries.     

Preparation and characterization of PbFe12−xGaxO19 single crystals

The single crystals of the magnetoplumbite type of the general formula Pb_12?xGa_xO₁₉ were prepared by the growing from lead oxide flux. The deviations from the ideal compositions are explained by the substitution of S and/or T blocks into the … SRS1R1SR … chains. The structural and magnetic study show on the change of the substitution mechanism of small metallic ions at x = 3. The last member of the serie was found the composition of x = 10.38. The limited mutual substitution of iron and gallium ions is probably caused by an unwillingness of gallium ions to enter into five-fold sites.     

Follicular tumidus retro-auricular lichen planus (author''s transl)

Referring to three comparable cases, a new form of lichen planus is described. This form is characterized by a prominent lesion, violaceus in color or pigmented, with white yellowish specks mimicking milia. The histologic picture of lichen follicularis, the presence of typical papules of lichen distant from the retro-auricular lesion make it possible to consider this clinical aspect as a variety of lichen planus.     

Elastodynamic fields near running cracks by finite elements

A finite element method is developed for the computation of elastodynamic stress intensity factors at a rapidly moving crack tip. The method is restricted to bodies whose surfaces and two-material interfaces are either parallel to the direction of propagation or are sufficiently remote. The crack tip starts to move at the instant that it is struck by an incident wave. The finite element grid moves undeformed with the crack tip. The main result consists in the fact that the method of non-singular calibrated crack tip elements, in which the stress-intensity factor is determined from its statically calibrated ratio to the crack opening displacement in an adjacent node, is extended to dynamic problems with moving cracks, for both in-plane and anti-plane motions. The dependence of the calibration ratio on the crack tip velocity is established from previously developed analytical solutions for the near-tip displacement fields. Numerical results compare favorably with known analytical solutions for cracks moving in an infinite solid. The grid motion causes an apparent asymmetric additional damping matrix.     

Use of patent information at a Czechoslovak research institute

This article describes the patent information services in Czechoslovakia and the use made of patent information in applied research and in patent practice. The various possibilities which exist centrally, regionally and in industry are discussed.