Zur Frage der Elastizität,der Beanspruchung und der Festigkeit warmbetriebener Rohrleitungen

Zusammenfassung Die Entwicklung der Dampfkraftanlagen zu immer h?heren Temperaturen, Drücken und Leistungen zwingt den Rohrleitungsbauer, sich noch eingehender als bisher mit den Fragen der Elastizit?t, der Beanspruchung und der Festigkeit der Rohrleitung zu besch?ftigen. Zu einigen der wesentlichen Fragen werden im folgenden rechnerische und experimentelle Beitr?ge mitgeteilt. VDI     

State/event fault trees—A safety analysis model for software-controlled systems

Safety models for software-controlled systems should be intuitive, compositional and have the expressive power to model both software and hardware behaviour. Moreover, they should provide quantitative results for failure or hazard probabilities. Fault trees are an accepted and intuitive model for safety analysis, but they are incapable of expressing state dependencies or temporal order of events. We propose to combine fault trees with an explicit State/Event semantics, using a graphical notation that is similar to Statecharts. Our new model, named State/Event Fault Trees (SEFTs), subsumes both deterministic state machines suited to describe software behaviour, and Markov chains that model probabilistic failures, while keeping the visualisation of causal chains known from fault trees. We allow exponentially distributed probabilistic events, deterministic delays, and triggered events. The model provides a component concept, where components are connected by typed ports. Quantitative evaluation is achieved by translating the component models to Deterministic and Stochastic Petri Nets (DSPNs) and using an existing tool for analysis or simulation. This paper, which is an extended version of [Kaiser B, Gramlich C. State-Event-Fault-Trees—a safety analysis model for software controlled systems. Computer safety, reliability, and security. Proceedings of the 23rd international conference, SAFECOMP 2004, Potsdam, Germany, September 21st–24th. Lecture Notes in Computer Science, vol. 3219, 2004.p. 195–209], revisits the model elements and the analysis procedure and provides a small case study of a fire alarm system, completed by an outlook on our tool project ESSaRel.     

Prediction of pyrolysis of pistachio shells based on its components hemicellulose, cellulose and lignin

The objective of this contribution is to describe thermal degradation of pistachio shells by a detailed reaction mechanism. Pistachio shells are assumed to be composed of hemicellulose, cellulose and lignin of which degradation is described by relevant kinetics based on experimental data. The mechanism yields a detailed composition of product gases, and therefore, is well-suited to predict evolution of both thermal decomposition and products. Thermal degradation is described by a system of coupled differential conservation equations for mass, momentum, species, and energy for a pistachio shell particle. The relevant conservation equations are discretised by the Finite Volume Method (FVM) and solved within the conversion module of the Discrete Particle Method (DPM). A comparison between experimental data and predicted results yielded good agreement.     

Determination of hemin-binding characteristics of proteins by a combinatorial peptide library approach

Studies of the binding of heme/hemin to proteins or peptides have recently intensified as it became evident that heme serves not only as a prosthetic group, but also as a regulator and effector molecule interacting with transmembrane and cytoplasmic proteins. The iron‐ion‐containing heme group can associate with these proteins in different ways, with the amino acids Cys, His, and Tyr allowing individual modes of binding. Strong coordinate‐covalent binding, such as in cytochrome c, is known, and reversible attachment is also discussed. Ligands for both types of binding have been reported independently, though sometimes with different affinities for similar sequences. We applied a combinatorial approach using the library (X)₄(C/H/Y)(X)₄ to characterize peptide ligands with considerable hemin binding capacities. Some of the library‐selected peptides were comparable in terms of hemin association independently of whether or not a cysteine residue was present in the sequence. Indeed, a preference for His‐based (≈39 %) and Tyr‐based (≈40 %) sequences over Cys‐based ones (≈21 %) was detected. The binding affinities for the library‐selected peptides, as determined by UV/Vis spectroscopy, were in the nanomolar range. Moreover, selected representatives efficiently competed for hemin binding with the human BK channel hSlo1, which is known to be regulated by heme through binding to its heme‐binding domain.     

Kinetics of nucleation and crystallization in poly(?-caprolactone) (PCL)

The recently developed differential fast scanning calorimetry (DFSC) is used for a new look at the crystal growth of poly(?-caprolactone) (PCL) from 185 K, below the glass transition temperature, to 330 K, close to the equilibrium melting temperature. The DFSC allows temperature control of the sample and determination of its heat capacity using heating rates from 50 to 50,000 K/s. The crystal nucleation and crystallization halftimes were determined simultaneously. The obtained halftimes cover a range from 3 × 10⁻² s (nucleation at 215 K) to 3 × 10⁹ s (crystallization at 185 K). After attempting to analyze the experiments with the classical nucleation and growth model, developed for systems consisting of small molecules, a new methodology is described which addresses the specific problems of crystallization of flexible linear macromolecules. The key problems which are attempted to be resolved concern the differences between the structures of the various entities identified and their specific role in the mechanism of growth. The structures range from configurations having practically unmeasurable latent heats of ordering (nuclei) to being clearly-recognizable, ordered species with rather sharp disordering endotherms in the temperature range from the glass transition to equilibrium melting for increasingly perfect and larger crystals. The mechanisms and kinetics of growth involve also a detailed understanding of the interaction with the surrounding rigid-amorphous fraction (RAF) in dependence of crystal size and perfection.