Numerical investigations on the rubbing process in labyrinth seals for full flight mission

Labyrinth seals are a commonly used sealing technology to prevent and control leakage flows at rotor-stator interfaces in turbo machinery. Small clearances required by higher pressure ratios and the economical use of cooling air lead to potential rubbing events. These may cause detrimental heat input into the rotating structure and can lead to severe damages. Honeycomb liners on the stator part tolerate rubbing events to a certain extent and therefore allow for smaller gap widths, which lead to minimal leakage. A unique and independently developed one-dimensional numerical model is used to investigate critical rubbing conditions in a typical aircraft flight mission. It considers kinematic contact conditions, friction, heat conduction and abrasive and plastic wear. This model allows the calculation of the loads, such as the contact pressures and temperatures on the components. First experimental investigations for an idealized contact between a metal foil, representing the honeycomb part, and a rotating seal fin are used to validate the model. Then, predictions of engine performance calculations are additionally used to calculate input parameters for the one-dimensional model. These are the relative contact velocity and the casing temperature of the honeycomb. Finally, the results of the one-dimensional rubbing model such as rub forces, temperatures and wear of the seal fin or the honeycomb liner are compared for five different operating points of the flight mission: Ground idle, Takeoff, Cruise, Approach, Re-slam. Based on these results, damaging effects on the sealing system are evaluated and the most critical operating point, in this case the Re-slam, could be identified

Abstract Performance Modelling for SLA-compliant but cost-effective IT-Service Provisioning

Modern enterprises make use of distributed service-based IT infrastructures to handle their day-to-day business. To remain competitive, basic IT-services have to be performed of high-quality but cost-effective. However, today’s productive large-scale system environments suffer an enormous complexity due to the sheer component size and their highly dynamic and compositional nature what makes capacity planning a challenge. In this article we present a performance methodology for optimized, SLA-compliant but costeffective service provisioning. Based on a real-world data set of our industry partner, we show the practical application of our methodology and present early results

Prolyl isomerase PIN1 regulates DNA double-strand break repair by Counteracting DNA end resection

The regulation of DNA double-strand break (DSB) repair by phosphorylation-dependent signaling pathways is crucial for the maintenance of genome stability; however, remarkably little is known about the molecular mechanisms by which phosphorylation controls DSB repair. Here, we show that PIN1, a phosphorylation-specific prolyl isomerase, interacts with key DSB repair factors and affects the relative contributions of homologous recombination (HR) and nonhomologous end-joining (NHEJ) to DSB repair. We find that PIN1-deficient cells display reduced NHEJ due to increased DNA end resection, whereas resection and HR are compromised in PIN1-overexpressing cells. Moreover, we identify CtIP as a substrate of PIN1 and show that DSBs become hyperresected in cells expressing a CtIP mutant refractory to PIN1 recognition. Mechanistically, we provide evidence that PIN1 impinges on CtIP stability by promoting its ubiquitylation and subsequent proteasomal degradation. Collectively, these data uncover PIN1-mediated isomerization as a regulatory mechanism coordinating DSB repair

Adaptive Zugriffskontrollverfahren : Ein Entscheidungsmodell für die Kontrolle des Zugriffs auf gemeinsam genutzte IT-Infrastrukturen

Der Artikel stellt ein Entscheidungsmodell für die Zugriffskontrolle von Diensten vor, die auf einer gemeinsam genutzten IT-Infrastruktur (shared infrastructure) erbracht werden. Ziel ist hierbei die Maximierung des Ertrags eines IT-Dienstleisters bzw. die effiziente Erfüllung von Dienstleistungsverträgen durch dynamische Priorisierung von Diensten in Phasen von Ressourcenengpässen. * Opportunitätskostenüberlegungen dienen als Kriterium zur Entscheidung über direkte Annahme, Pufferung oder Ablehnung einer Dienstanfrage. * Das Modell berücksichtigt kombinatorische Effekte, die sich aufgrund der Belegung mehrerer Ressourcen durch Dienstausführungen und deren Interdependenzen ergeben. * Das darauf aufbauende Zugriffskontrollverfahren antizipiert zukünftige Nachfrage nach Diensten und korrespondierenden Ressourcenanforderungen und optimiert daher vorausschauend. * Die Evaluierung des Verfahrens mittels Simulationen realitätsnaher Szenarien eines Anbieters von Media-On-Demand-Diensten zeigt eine wesentliche Verbesserung des erzielten Ertrags gegenüber Standardverfahren