Safety analysis of the height control system for the Elbtunnel

A new tunnel tube crossing the river Elbe has been built in Hamburg until the end of 2002. Therefore, a new height control system was required. A computer examines the signals from light barriers and overhead sensors to detect vehicles, which try to drive into a tube with insufficient height. If necessary, it raises an alarm that blocks the road. This paper describes the application of two safety analysis techniques on this embedded system: model checking has been used to prove functional correctness with respect to a formal model. Fault tree analysis has validated the model and considered technical defects. Their combination uncovered a safety flaw, led to a precise requirement specification for the software, and showed various ways to improve system safety.     

Sensorforschung in Österreich – Optische Sensorik

Ohne Zusammenfassung     

Thermo-hydro-chemical couplings considered in safety assessment of shallow tunnels subjected to fire load

Fire loading of concrete tunnel linings is characterized by various physical, chemical, and mechanical processes, resulting in spalling of near-surface concrete layers and degradation of strength and stiffness of the remaining tunnel lining. In this paper, the governing transport processes taking place in concrete at elevated temperatures are considered within a recently published fire-safety assessment tool [Savov K, Lackner R, Mang HA. Stability assessment of shallow tunnels subjected to fire load. Fire Safety J 2005; 40: 745–763] for underground structures. In contrast to consideration of heat transport only [Savov et al.], a coupled thermo-hydro-chemical analysis, simulating the heat and mass transport in concrete under fire loading, is performed, giving access to more realistic temperature distributions as well as gas-pressure distributions within the tunnel lining. These data serve as input for the structural safety assessment tool considering, in addition to the temperature dependence of mechanical properties, the effect of the gas pressure on the strength properties of the heated lining concrete. The combination of the two analysis tools (coupled analysis of governing transport processes and structural safety assessment) is illustrated by the fire-safety assessment of a cross-section of the Lainzer tunnel (Austria) characterized by low overburden (shallow tunnel).     

Formation of tyramine byLactobacillus curvatus LTH 972

The effect of food-related environmental factors on the formation of tyramine byLactobacillus curvatus LTH 972 was investigated in liquid culture supplemented with tyrosine. The highest concentrations of tyramine (up to 201 mg/l) were formed at 30 °C, pH 5.2 and at a water activity (a_w) of 0.97. At lower temperatures and at higher pH- and a_w values the reaction slowed down but was still clearly detectable. Glucose, nitrate and nitrite had no effect at concentrations applied in sausage fermentations. The strain was able to form tyramine from tyrosine-containing di- and tripeptides in phosphate buffer. Therefore, in proteinaceous substrates an increased formation of tyramine cannot be excluded when ongoing proteolysis creates precursors, as is the case in the presence of proteolytic micro-organisms.

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Die Bildung von Tyramin durchLactobacillus curvatus LTH 972

Zusammenfassung Der Einfluß von Lebensmittel kennzeichnenden ökologischen Faktoren auf die Bildung von Tyramin durchLactobacillus curvatus LTH 972 wurde in Flüssigkultur mit Tyrosinzusatz untersucht. Höchste Konzentrationen an Tyramin (bis zu 201 mg/l) wurden bei 30 °C, pH 5,2 und a_w 0,97 gebildet. Bei niedrigeren Temperaturen (15 °C) sowie höheren pH- und a_w-Werten wurde eine verlangsamte, aber dennoch deutliche Tyraminbildung beobachtet. Glucose, Nitrat und Nitrit hatten in Konzentrationen, wie sie bei der Rohwurstherstellung üblich sind, keinen Einfluß. Eine Tyraminbildung aus Di- und Tripeptiden mit Tyrosylresten wurde in Phosphatpuffer beobachtet. In proteinreichen Substraten ist daher eine verstärkte Tyraminbildung nicht auszuschließen, wenn bei ablaufender Proteolyse Präkursoren gebildet werden, wie es z. B. bei Anwesenheit proteolytischer Mikroorganismen möglich ist.

     

Comments on: “the heat capacity of poly(oxymethylene) as a function of crystallinity”

Summary It is shown that the heat capacities of semicrystalline poly(oxymethylene)s (POM) measured recently by Illers and published in this journal support, rather than refute, the existence of a rigid, amorphous fraction. The former was suggested by Illers, the latter was our proposal (Suzuki et al.).     

Modified shape functions for the three-node plate bending element passing the patch test

A polynomial displacement basis for the three-node plate bending element (Zienkiewicz-triangle) is developed from a relaxed C¹-continuity requirement called the interpolation test. The test provides a general convergence criterion for non-conforming shape functions and a practical guideline to select a proper displacement basis. The resulting simple displacement type element passes the patch test. Several reduced numerical integration schemes are discussed and numerical testing provides a comparison with the standard element formulated by Zienkiewicz.     

A discrete-time min-max certainty equivalence principle

We extend a result of (Bernhard, submitted) to a setup comparable to that provided in (Bernhard and Rapaport, submitted) for the continuous-time case, thus obtaining the most comprehensive certainty equivalence principle for the discrete-time problem to date.     

Grain-Size Dependence of Fracture Energy in Ceramics

A simple model incorporating thermal elastic anisotropy stresses is used to calculate the microcrack zone size around cracks in Al₂O₃. It is found that the ratio of microcrack zone size to grain size is almost constant for notched beam tests, but increases with grain size for double cantilever beam data. It is suggested that notched-beam ratios of fracture toughness are related to crack initiation, whereas double cantilever beam values are related to propagation and reflect R-curve behavior of the material.