Reliability approach for vehicle safety components

Owing to ‘producer's liability for defective products’ the safety-related components of vehicles have to be designed, tested and manufactured in an appropriate way. Some considerations are presented about useful procedures in design and testing of safety parts which may help to reach the required high reliability and minimize risks. Problem areas are indicated which need more research. In future the reliability approach in automotive industries will come closer to the standards in aeronautics. This trend is accelerated by the rapid use of electronics in automobiles.     

Polarization stability of phase-locked arrays of vertical-cavitysurface-emitting lasers

The polarization stability of the fundamental lasing super-mode obtained from coherently coupled arrays of vertical-cavity surface-emitting lasers has been investigated. Various devices have been analyzed and none showed the abrupt change of the polarization direction (flip) often observed in solitary devices. This polarization stability is due to a current independent dichroism of 0.5 GHz     

Long-term spectral stability of singlemode VCSELs

The long-term spectral stability of 780 nm AlGaAs-based vertical-cavity surface-emitting lasers has been investigated. The 28 devices from two different wafers show a thermally induced averaged total spectral shift of 75±9 and 47±7 GHz, respectively     

Autonomic and Decentralized Management of Wireless Access Networks

In this article, we apply autonomic and distributed management principles to wireless access networks. Most interesting is the application of autonomic properties and behaviors including adaptive, aware, and automatic operation in a decentralized setting. In particular, we present a generic and autonomic management architecture for decentralized management of wireless access networks, such as GERAN/UTRAN, E-UTRAN, WiMAX or WLAN. For evaluation purposes, we apply this architecture to the management of a Wireless LAN network, and we evaluate the architecture and some of the autonomic management functions through simulations, a prototype implementation and the setup of a real-world testbed for experimentation with the proposed management approach.     

Focused ion beam (FIB) etching to investigate aluminium-coated polymer laminates subjected to heat and moisture loads

Multilayered aluminium-coated polymer laminates are the common barrier envelopes of vacuum insulation panels used as high performance thermal insulation in building applications. These laminates are made of up to ten distinct layers including three aluminium barrier layers applied by vacuum web coating. During their expected lifetime, which is required to last longer than 20 years, they will be subjected to heat and moisture loads induced by internal and external climatic conditions. This paper investigates the deteriorations of the barrier function of two different laminates commonly used for the production of vacuum insulation panels. These were subjected to well defined exterior heat and moisture loads and investigated by means of focused ion beam etching. Delamination of the polyurethane adhesive layers and stress induced relaxation in them are made visible. Oxidised aluminium layers are also detected by this method.     

Polypropylene-graphite nanocomposites made by solid-state shear pulverization: Effects of significantly exfoliated, unmodified graphite content on physical, mechanical and electrical properties

Nanocomposites made from polypropylene and as-received graphite were prepared by solid-state shear pulverization (SSSP) as a function of graphite loading (0.3-8.4 wt%). X-ray diffraction indicates that SSSP employing harsh pulverization conditions yields substantial graphite exfoliation at 0.3-2.7 wt% graphite content with less exfoliation being achieved at higher graphite content. With increasing graphite content, thermal degradation temperature and non-isothermal onset crystallization temperature increase substantially (by as much as 35 and 23 °C relative to neat polypropylene) while isothermal crystallization half-time decreases dramatically. In contrast, Young’s modulus and tensile yield strength exhibit maxima (∼100% and ∼60% increases, respectively, relative to neat polypropylene) at 2.7 wt% graphite content, with all nanocomposites retaining high elongation at break values except at the highest filler loading. Electrical conductivity measurements indicate percolation of graphite at 2.7 wt% and higher graphite content, consistent with rheology measurements showing the presence of a solid-like response of melt-state shear storage modulus as a function of frequency. Significant tunability of graphite exfoliation and property enhancements is demonstrated as a function of SSSP processing.     

Gas transport through ceramic membranes under super-critical conditions

In order to select and to apply a porous membrane under supercritical conditions, it is necessary to understand the transport mechanism affecting the permeation behaviour.This paper describes the investigation of gas transport through micro porous ceramic membranes consisting of several layers. The separation layer is made from TiO² with a nominal pore size diameter of 0.9 nm. Single gas permeation of helium, nitrogen, argon, methane, and carbon dioxide was measured in the temperature range of 293-443 K and in the pressure range of 1-10 MPa.Observation of the permeability of these membranes revealed that the transport of non?adsorbing gases under these conditions is governed by Knudsen diffusion and viscous flow.     

Regelungstechnik für die Schnittholztrocknung heute

After explaining the requirements which must be fulfilled by modern microprocessor- or computer-operated control units for kiln dryers, four control methods are compared. Concerning these methods, the initial moisture content of the wood as well as the constantly changing moisture content play very different roles depending on whether it is above, below or within the so-called range of fibre saturation of the wood. The most highly developed method No. IV includes the distribution of moisture content over the cross section of the board as a comparative figure in the control data processed by the computer, with the aim of optimizing the drying time and guaranteeing a high drying quality.