Gas- und Dampfturbinen fuer das Kraftwerk des 21. Jahrhunderts. Teilvorhaben T 1.5: Numerische Simulation instationaerer Stroemung in Turbinenstufen Schlussbericht. Eingehende Darstellung

Das Ziel dieser Arbeiten war die Wahl von numerischen Algorithmen und Parametern, die zuverlaessige Simulationsergebnisse sichern. In dieser Phase wurden auch Computerprogramme zur Bearbeitung der instationaeren Daten entwickelt. Zu Vergleichszwecken wurden zuerst 18 stationaere Rechnungen fuer unterschiedliche Geometrie- und Stroemungskonfigurationen durchgefuehrt. Danach wurden 45 voll instationaere Anordnungen simuliert und die Einfluesse von Mach-Zahl, Reynolds-Zahl, Inzidenzwinkel, Axialspalt, Teilungsverhaeltnis im Stator und Rotor sowie ''Clocking''-Position bei einem Stator-Rotor-Stator Aufbau untersucht. Die Ergebnisse wurden unter Beruecksichtigung der Verluste, des Zu- bzw. Abstroemverhaltens sowie der dynamischen Belastung der Beschaufelung analysiert. Der Hauptaugenmerk lag dabei auf der Betrachtung der Verluste, da zuverlaessige Vergleiche zwischen Wirkungsgraden unterschiedlicher Konfiguration eine sehr hohe Genauigkeit der Ergebnisse und der Auswertungswerkzeuge erforden. Die Verlustbetrachtung stellte bei der vorliegenden Arbeit eine besondere Herausforderung dar. (orig.)The project was to select numeric algorithms and parameters which provide reliable simulation results. This included the development of computer programs for processing the measured data. 18 steady state calculations were carried out for different geometry and flow configurations. After this, 45 fully transient scenarios were simulated, and the influence of the Mach number, Reynolds number, angle of incidence, axial gap, division ratios in the stator and rotor, and 'clocking' position in a stator-rotor-stator set-up were investigated. The results were analyzed in consideration of loss, inflow and outflow characteristics, and dynamic loads on the turbine blades. The emphasis was on loss, as reliable comparisons between the efficiencies of different configurations necessitate very high accuracy of the results and the evaluation tools. The loss calculation was a particular challenge. (orig.)SIGLEAvailable from TIB Hannover: F04B1701 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany)DEGerman

Silicon nanowires reliability and robustness investigation using AFM-based techniques

Silicon nanowires (SiNWs) have undergone intensive research for their application in novel integrated systems such as field effect transistor (FET) biosensors and mass sensing resonators profiting from large surface-to-volume ratios (nano dimensions). Such devices have been shown to have the potential for outstanding performances in terms of high sensitivity, selectivity through surface modification and unprecedented structural characteristics. This paper presents the results of mechanical characterization done for various types of suspended SiNWs arranged in a 3D array. The characterization has been performed using techniques based on atomic force microscopy (AFM). This investigation is a necessary prerequisite for the reliable and robust design of any biosensing system. This paper also describes the applied investigation methodology and reports measurement results aggregated during series of AFM-based tests. © 2013 SPIE

Strain-Tunable Single Photon Sources in WSe2 Monolayers

The appearance of single photon sources in atomically thin semiconductors holds great promises for the development of a flexible and ultracompact quantum technology in which elastic strain engineering can be used to tailor their emission properties. Here, we show a compact and hybrid two-dimensional semiconductor-piezoelectric device that allows for controlling the energy of single photons emitted by quantum emitters localized in wrinkled WSe2 monolayers. We demonstrate that strain fields exerted by the piezoelectric device can be used to tune the energy of localized excitons in WSe2 up to 18 meV in a reversible manner while leaving the single photon purity unaffected over a wide range. Interestingly, we find that the magnitude and, in particular, the sign of the energy shift as a function of stress is emitter dependent. With the help of finite element simulations we suggest a simple model that explains our experimental observations and, furthermore, discloses that the type of strain (tensile or compressive) experienced by the quantum emitters strongly depends on their localization across the wrinkles. Our findings are of strong relevance for the practical implementation of single photon devices based on two-dimensional materials as well as for understanding the effects of strain on their emission properties

Strain-Tunable Single Photon Sources in WSe2 Monolayers

The appearance of single photon sources in atomically thin semiconductors holds great promises for the development of a flexible and ultracompact quantum technology in which elastic strain engineering can be used to tailor their emission properties. Here, we show a compact and hybrid two-dimensional semiconductor-piezoelectric device that allows for controlling the energy of single photons emitted by quantum emitters localized in wrinkled WSe2 monolayers. We demonstrate that strain fields exerted by the piezoelectric device can be used to tune the energy of localized excitons in WSe2 up to 18 meV in a reversible manner while leaving the single photon purity unaffected over a wide range. Interestingly, we find that the magnitude and, in particular, the sign of the energy shift as a function of stress is emitter dependent. With the help of finite element simulations we suggest a simple model that explains our experimental observations and, furthermore, discloses that the type of strain (tensile or compressive) experienced by the quantum emitters strongly depends on their localization across the wrinkles. Our findings are of strong relevance for the practical implementation of single photon devices based on two-dimensional materials as well as for understanding the effects of strain on their emission properties.J.M.-S. acknowledges support through the Cların Programme from the Government of the Principality of Asturias and a Marie Curie-COFUND European grant (PA-18-ACB17-29). J.T.-G. acknowledges support through the Severo Ochoa Program from the Goverment of the Principality of Asturias (PA-18-PF-BP17-126). P.A.-G. acknowledges support from the European Research Council under Starting Grant 715496, 2DNANOPTICA. R.T., D.T., and M.S. acknowledge support by the European Research council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (SPQRel, Grant agreement No. 679183). C.S. acknowledges support by the European Research council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (UnLiMIt-2D, Grant agreement No. 679288). A.R. acknowledges support from the Linz Institute of Technology (LIT). The Würzburg group acknowledges support by the State of Bavaria. S.T. acknowledges support from NSF DMR-1552220, NSF CMMI-1933214 and NSF DMR-1838443.Peer reviewe