ANKA – a synchrotron light source for X-ray based micromachining

ANKA (Angströmquelle Karlsruhe) is a state-of-the-art synchrotron radiation facility currently under construction at the Forschungszentrum Karlsruhe. Based on a 2.5?GeV electron storage ring it delivers photons from the infrared through to the hard X-rays. Operation of ANKA is scheduled for September 2000. Synchrotron radiation related services in the fields of microfabrication and analytical services will be available from ANKA GmbH to industrial clients and scientific users.     

A transparent online memory test for simultaneous detection of functional faults and soft errors in memories

The Transparent Online Memory Test (TOMT) introduced here has been specifically developed for online testing of word-oriented memories with parity or Hamming protection. Careful interleaving of a word-oriented and a bit-oriented test facilitates a fault coverage and a test duration comparable to the widely used March C- algorithm. Unlike similar methods TOMT actively exercises all bit cells in memory within one test period. Hence it not only detects soft errors but also functional faults and reliably prevents fault accumulation. Different variants of the basic TOMT algorithm are investigated in terms of fault coverage and test time. A prototype implementation for SRAM is introduced which-integrated into a standard processor/memory interface-autonomously performs the transparent online memory test. The trade-offs in terms of hardware overhead and memory access delay caused by this system integration are explored.     

Dealing with dormant faults in an embedded fault-tolerant computer system

Accumulation of dormant faults is a potential threat in a fault tolerant system, especially because most often fault tolerance is based on the single-fault assumption. We investigate this threat by the example of an automotive steer-by-wire application based on the Time-Triggered Architecture (TTA). By means of a Markov model we illustrate that the effect of fault dormancy can degrade the MTTF of a system by several orders of magnitude. We study potential remedies, of which transparent online testing proves to be the most powerful one, while taking a hot spare offline temporarily to test it provides a more feasible solution, though with tight constraints regarding the test duration.     

Ergotamine-induced rectal stenosis in a patient with long-term migraine

A 36 year old woman was admitted to our hospital for treatment of a high-grade rectal stenosis of unknown origin. She had a history of migraine going back 10 years. On intensive questioning she admitted using up to 5 ergotamine-containing suppositories a day. On the basis of history and clinical investigations the rectal stenosis must be connected with the abuse of ergotamine-containing suppositories. This case demonstrates that patients with an unexplained rectal syndrome should be asked for analgetics-containing suppositories specifically. Only discontinuation of treatment in time can preserve the patient from development of a rectal stenosis. In case of a rectal stenosis surgical treatment can be avoided by means of endoscopic controlled dilatation.     

Subpixel forest cover in central Africa from multisensor, multitemporal data

Seven Landsat Multispectral Scanner (MSS) scenes in central Africa were coregistered with 8 km resolution data from the 1987 AVHRR Pathfinder Land data set. Percent forest cover in each 8 km grid cell was derived from the classified MSS scenes. Linear relationships between percent forest cover and 30 multitemporal metrics derived from all AVHRR optical and thermal channels were determined. Correlations were strongest for the mean annual normalized difference vegetation index (NDVI) and mean annual brightness temperature (AVHRR Channel 3) and weakest for those metrics, besides NDVI, based on near-infrared reflectances (AVHRR Channel 2). The relationships were used to estimate percent forest cover in various locations in the study area using multiple linear regression and regression trees. Overall, the multiple linear regression provided more accurate results. Predicted percent forest cover estimates were within 20% of the “actual” percent forest cover (derived from the MSS data) for approximately 90% of the grid cells. The RMS error for the prediction was 12% forest cover. RMS errors above 18% forest cover were obtained when using AVHRR data from a single month to derive predictive relationships. The results demonstrate that multitemporal data reflecting vegetation phenology can be used to estimate subpixel forest cover at coarse spatial resolutions.     

Micromechanical processes and failure phenomena in reactively compatibilized blends of polyamide 6 and styrenic polymers. I. Polyamide 6/acrylonitrile– butadiene–styrene copolymer blends

In this work, in situ investigations of the micromechanical properties of reactively compatibilized blends of polyamide 6 (PA6) and an acrylonitrile–butadiene–styrene copolymer (ABS) were performed with transmission electron microscopy. Three PA6/ABS blends were prepared with a disperse morphology (inclusions of PA6 or ABS) and with a cocontinuous structure. The objective of this work was to study the deformation of the inclusions and the interface between the PA6 phase and the ABS phase. Our transmission electron microscopy investigations revealed that the morphology of the blends was strongly influenced by the asymmetric nature of the interface between PA6 and ABS. In the blends with a PA6 matrix, the interface between PA6 and the ABS inclusions was deformed in tensile deformation under uniaxial loading. A strong influence of the PA6 water content on the (micro)mechanical behavior was observed. Although the “dry” blends behaved in a brittle fashion, the “wet” blends behaved in a ductile fashion with the formation of deformation bands in the matrix (PA6 or ABS), which were initiated by stress concentration at the particles (ABS or PA6, respectively). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Vom Lenkrad zum Joystick

Embedded computer systems are increasingly being entrusted with vital control tasks in safety critical applications. Due to their immense versatility they are replacing conventional relay- and mechanical control systems as well as pneumatic systems. The high complexity inherent to computer control systems, however, makes the assessment and proof of their reliability more difficult. While conventional failure mode analysis has proven effective for mechanical and relay control, embedded systems rather require probabilistic and metrological approaches. In this context our paper will concentrate on some aspects of fail-silent architectures as an alternative to TMR systems, system level reliability modelling and fault injection for the assessment of fault tolerance. The implications of this approach will be demonstrated for an automotive steer-by-wire system.     

FEM supported optimization of bending processes for vibration damping steel sheets

An FE-model has been developed that allows large relative sheet displacement and sheet splitting as well, in order to obtain more information for the bending process of vibration damping steel sheets. In addition to the evaluation of the material data for the visco-elastic resin core the main process parameters for the die bending are optimized. Best results are realized by using higher forming temperatures in combination with a large die width and different flange length. The variation of the punch force and the punch radius can be used to regulate the spring back and the possible splitting of the sheets.