The PDE framework Peano applied to fluid dynamics: an efficient implementation of a parallel multiscale fluid dynamics solver on octree-like adaptive Cartesian grids

This paper presents the general purpose framework Peano for the solution of partial differential equations (PDE) on adaptive Cartesian grids. The strict structuredness and inherent multilevel property of these grids allows for very low memory requirements, efficient (in terms of hardware performance) implementations of parallel multigrid solvers on dynamically adaptive grids, and arbitrary spatial dimensions. This combination of advantages distinguishes Peano from other PDE frameworks. We describe shortly the underlying octree-like grid type and its most important properties. The main part of the paper shows the framework concept of Peano and the implementation of a Navier–Stokes solver as one of the main currently implemented application examples. Various results ranging from hardware and numerical performance to concrete application scenarios close the contribution.     

Effects of direct electric current and electrode reactions on vinyl chloride degrading microorganisms

The use of electro-bioremediation has gained increasing interest during recent years. In these hybrid technologies bioremediation is stimulated by electrochemical or electrokinetic techniques to increase pollutant biodegradation efficiency. It is a pre-requisite for successful application of the bio-electro-processes that the microorganisms are not negatively affected by the electric fields or electrode reactions.In this study, for the first time microbial activity of aerobic vinyl chloride (VC) degrading microorganisms was assessed after exposure to constant currents ranging from 0.04 to 14 mA cm⁻². Viability and degradation kinetics were monitored during electrolysis for 4 h using two different types of electrodes: stainless steel and dimensionally stable electrodes (DSA). When the mixed microbial culture was exposed in the electrode compartments, inhibiting effects were observed with stainless steel and DSA electrodes beyond doses of 100 and 50 kJ/L, respectively. Incubation of the VC degrading microorganisms in the mineral medium that was pretreated in the electrode compartments with similar doses, resulted in slower VC degradation kinetics thus demonstrating that the inhibition was due to electrochemical reaction products. When electrodes were separated from the microorganisms by bipolar membranes, no inhibition by the electric field was observed.     

Concurrent programming constructs for parallel MPI applications

Concurrency and parallelism have long been viewed as important, but somewhat distinct concepts. While concurrency is extensively used to amortize latency (for example, in web- and database-servers, user interfaces, etc.), parallelism is traditionally used to enhance performance through execution on multiple functional units. Motivated by an evolving application mix and trends in hardware architecture, there has been a push toward integrating traditional programming models for concurrency and parallelism. Use of conventional threads APIs (POSIX, OpenMP) with messaging libraries (MPI), however, leads to significant programmability concerns, owing primarily to their disparate programming models. In this paper, we describe a novel API and associated runtime for concurrent programming, called MPI Threads (MPIT), which provides a portable and reliable abstraction of low-level threading facilities. We describe various design decisions in MPIT, their underlying motivation, and associated semantics. We provide performance measurements for our prototype implementation to quantify overheads associated with various operations. Finally, we discuss two real-world use cases: an asynchronous message queue and a parallel information retrieval system. We demonstrate that MPIT provides a versatile, low overhead programming model that can be leveraged to program large parallel ensembles.     

A Short Way to Switchable Carbenes

A new, one‐step route to N‐heterocyclic oxo‐carbene complexes (NHOCs), representatives of chemo‐switchable NHC complexes, is reported. This simple procedure provides an easy access to gold, palladium and platinum complexes of these ligands.     

Vorbemessung von Aussteifungselementen für Starkbebenbeanspruchungen

Ausgehend von den positiven Erfahrungen mit steifen Gebäuden in Starkbebengebieten wird auf der Basis der türkischen Erdbebennorm ein Vorschlag zur Vorbemessung von Aussteifungselementen für erhöhte seismische Beanspruchungen ausgearbeitet. Die entwickelten Gleichungen beschreiben auf der Basis von wenigen Kenndaten wie Grundbeschleunigung und Betonzugfestigkeit notwendige Wandquerschnittsflächen bzw. Wandlängen in den jeweiligen Geschossen. Ein Beispiel für einen typischen Gewerbebau verdeutlicht den Rechenablauf der Vorbemessung. Preliminary Design of Bracing Elements for Heavy Earthquake Loads Due to the positive experience with stiff buildings in areas of strong earthquakes, a proposition for the preliminary design of the bracing elements will be prepared based on the Turkish earthquake regulation. The developed equations, based on few characteristics like basic acceleration and concrete tensile strength, will describe the necessary cross sectional areas of the wall, respectively the wall length of each level. One example for a typical commercial building will clarify the calculation process of the preliminary design.     

Zur Schadensverteilung des durch Spannungsriss korrosion geschädigten vergüteten Spannstahls bei Brückenbauwerken

Die Aussagekraft der rechnerischen Untersuchung zur Abschätzung des Gefährdungspotentials infolge Spannungsrisskorrosion hängt entscheidend von den Annahmen zu Schädigungsverlauf und —verteilung des Spannstahls ab. Mit systematischer Untersuchung des aus einem Bauwerk entnommenen Spannstahls konnte festgestellt werden, dass die bisher angenommene Schadenskonzentration an einer Stelle, welche zum Ausfall des gesamten Spannglieds führt, sehr wenig wahrscheinlich ist. Viel wahrscheinlicher ist die drahtweise Schädigung mit unbegrenzter Anzahl der Risse über die gesamte Drahtlänge. Weiterhin ist keine Korrelation zwischen chemischer Zusammensetzung des Spannstahls bzw. zwischen Zusammensetzung des Verpressmörtels und der Versprödung des Spannstahls feststellbar. Weitere Untersuchungen zur Bestätigung der gewonnenen Ergebnisse sind wünschenswert. Damage distribution of hardened and tempered prestressing steel dues to stress corrosion in prestressed concrete bridges. The accuracy of the analysis to estimate the hazard potential due to the stress corrosion depends strongly on the assumption of the damage distribution and the damage progress of the prestressing steel in the constructions. Through a systematic test of the prestressing steel, which is taken from an old bridge, it is shown that the traditional assumption of a damage concentration with the breakdown of the whole tendon is less probable. Instead, the damage of single wires over its total length with unlimited number of cracks is considerably more probable. Furthermore, no correlation between the chemical compositions or mixtures of the grout and the brittleness of the prestressing steel is found. More investigations to check these results obtained in this study are preferable.     

The relationship between operating efficiency and service quality: are they compatible?

Transferring and applying manufacturing principles and practices to improve both service efficiency and service quality is an important area of research in service operations. This paper advances this stream of research by examining the compatibility of operating efficiency and service quality. Specifically, our research addresses the following questions: (1) Do operating efficiency and service quality have to be traded off, or can they exist in unison (are they compatible)? and (2) What aspects of service quality have a stronger association with operating efficiency? In disentangling these important issues, we utilise a combination of data envelopment analysis (DEA) and survey-based empirical research methods. Additionally, our focus lies on a novel type of service industry where such research has been sparse. We evaluate the relative operating efficiencies of service driving agencies based on actual transaction data and subsequently analyse differences in service quality dimensions based on efficiencies. Overall, our analyses suggest important strategic decision-making implications for service operations managers and provide novel insights for academic research.