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.     

The fit between capabilities and priorities and its impact on performance improvement: revisiting and extending the theory of production competence

This paper revisits and extends the theory of production competence, which has received wide attention in the operations and production management literature. As such, considering the aspects of quality, delivery, flexibility, and cost, we develop two novel measures that assess the concept of production competence, which is conceptualised as the fit between production and operations management (POM) capabilities and production and operations management priorities. Inherent to both measures is their multi-dimensional conceptualisation of POM capabilities. We then investigate the influence of the production competence measures on the improvement in plant productivity and plant responsiveness, which are more immediate outcomes compared with what had been utilised in prior production competence research. Furthermore, we investigate a range of control variables, an omission in most extant production competence research. We assess the relationship based on data collected recently in a large-scale, multi-national survey encompassing a multitude of industries. Results consistently confirm the impact of the production competence measures on plant-productivity improvement, and partially support the relationship to the improvement in plant responsiveness. The importance of this research is emphasised by the fundamental nature of the theory of production competence to the field of production research, and by limitations in prior studies examining this concept. Most notably, the current research contributes to the theory of production competence by its investigation with two novel measures among a dataset that is much more recent and global in scope compared with prior studies. Our investigation thus contributes to the generalizability of the theory of production competence. Implications for practitioners and academics studying production research are provided.     

Host reaction to poly(2-hydroxyethyl methacrylate) scaffolds in a small spinal cord injury model

Tissue engineered scaffolds and matrices have been investigated over the past decade for their potential in spinal cord repair. They provide a 3-D substrate that can be permissive for nerve regeneration yet have other roles including neuroprotection, altering the inflammatory cascade and mechanically stabilizing spinal cord tissue after injury. In this study we investigated very small lesions (approx. 0.25 μL in volume) of the dorsal column into which a phase-separated poly(2-hydroxyethyl methacrylate) hydrogel scaffold is implanted. Using fluorescent immunohistochemistry to quantify glial scarring, the poly(2-hydroxyethyl methacrylate) scaffold group showed reduced intensity compared to lesion controls for GFAP and the chondroitin sulfate proteoglycan neurocan after 6 days. However, the scaffold and tissue was also pushed dorsally after 6 days while the scaffold was not integrated into the spinal cord after 28 days. Overall, this small-lesion spinal cord injury model provided information on the host tissue reaction of a TE scaffold while reducing animal discomfort and care.     

Modularity in small machine tools

Up to now, machine tools in micro production hardly feature modularity and hence offer only few opportunities to reconfigure or individualize a manufacturing process. This article gives a summary of concepts, how modularity in small micro machine tools can be designed and implemented. A size-adaptable machine frame is the basis for various possible process layouts. Adapters, a feed module with replaceable drive and kinematics, equipped with appropriate interfaces as well as a supply concept are introduced to allow further configuration. The combination of those concepts characterizes a small modular machine tool system. Technical solutions and fully functional prototypes will be shown and discussed in the following paper.     

IFMIF test cell design: Current status and key components

The IFMIF (International Fusion Material Irradiation Facility) test cell design has been further developed and optimized based on the existing modular test cell concept. Key features of the current test cell include actively cooled surrounding shielding walls with coverage of internal surfaces with stainless steel liner, independent two layer top shielding plugs for protecting the access cell from neutron and gamma radiation from the test cell, optimized piping and cabling plugs for accommodating pipe and cable penetrations and for minimizing neutron streaming, rearranged lithium quench tank to outside of the test cell, etc. According to preliminary neutronic calculation results, limited access to the quench tank area for maintenance after beam shut-off can be expected with the current arrangement. Maintenance of the lithium inlet and outlet pipes as well as the two beam ducts are also possible by introducing removable shielding plugs which can be removed and replaced in case of failure.     

Role of cation exchange processes on the sorption influenced transport of cationic β-blockers in aquifer sediments

The influence of cation exchange processes on the transport behavior of the cationic β-blockers atenolol and metoprolol was investigated by applying saturated laboratory column experiments. Breakthrough curves using natural sediments under different competitive conditions were generated and resulting sorption coefficients were compared. For the cationic species of atenolol (at pH = 8), the existence and dominating role of cation exchange processes were demonstrated by varying calcium concentrations. No effect of atenolol concentration on its retardation was observed within a wide concentration range. The breakthrough curve comparison of atenolol and the more hydrophobic metoprolol under constant conditions showed a significantly stronger retardation for metoprolol than for atenolol. However, additional non-polar interactions cannot explain the observed differences as they are determined to be negligible for both compounds. Due to the dominating role of cation exchange processes for the cationic species on overall sorption, a simple prediction of β-blocker transport in the subsurface by using K_OC values derived from log K_OW-log K_OC correlations is not feasible.