TY - CONF AB - Die Integration von Selbstoptimierung in mechatronische Systeme beinhaltet sowohl Risiken als auch Potenziale für die Verlässlichkeit. Die Risiken entstehen durch die Selbstoptimierung in den komplexen Systemen, da das Systemverhalten nur begrenzt im Voraus vorhersehbar ist. Daher wurde innerhalb des Sonderforschungsbereichs 614 ''Selbstoptimierende Systeme des Maschinenbaus" ein mehrstufiges Verlässlichkeitskonzept entworfen, welches das Ziel Verlässlichkeit stärker im Zielsystem verankert. In diesem Beitrag wird zum einen das erarbeitete Verlässlichkeitskonzept und zum anderen die Anwendung dieses Konzepts innerhalb des aktiven Spurführungsmoduls eines schienengebundenen Fahrzeugs vorgestellt. Um Programmierfehler auszuschließen wurde das Verlässlichkeitskonzept modelliert und über Model Checking verifiziert. Anhand von Simulationsergebnissen wird gezeigt, wie durch das mehrstufige Verlässlichkeitskonzept auf einen Ausfall eines Wirbelstromsensors des aktiven Spurführungsmoduls reagiert werden kann. AU - Sondermann-Wölke, Christoph AU - Geisler, Jens AU - Hirsch, Martin AU - Hemsel, Tobias ED - Gausemeier, Jürgen ED - Rammig, Franz Josef ED - Trächtler, Ansger ID - 9740 KW - Verlässigkeit T2 - Entwurf mechatronischer Systeme TI - Verlässlichkeit im aktiven selbstoptimierenden Spurführungsmodul eines schienengebundenen Fahrzeugs VL - 250 ER - TY - CONF AU - Sondermann-Wölke, Christoph AU - Hesse, Tobias AU - Sattel, Thomas AU - Hemsel, Tobias ID - 9741 T2 - 24. Tagung Technische Zuverlässigkeit (TTZ 2009) - Entwicklung und Betrieb zuverlässiger Produkte, Leonberg TI - Menschliche Unzuverlässigkeit als Grundlage für den Entwurf von Kollisionsvermeidungssystemen. VL - 2065 ER - TY - CONF AB - New mechatronic systems, called self-optimizing systems, are able to adapt their behavior according to environmental, user and system specific influences. Self-optimizing systems are complex and due to their non-deterministic behavior comprise hidden risks, which cannot be foreseen in the design phase of the system. Therefore, this paper presents modifications of the current condition monitoring policy, to be able to cope with this new kind of systems. Beside avoiding critical situations evoked by self-optimization, the proposed concept uses self-optimization to increase the dependability of the system. In this case, the concept is applied to the active guidance module of an innovative rail-bound vehicle. AU - Sondermann-Wölke, Christoph AU - Sextro, Walter ID - 9742 KW - condition monitoring KW - mechatronic systems KW - rail bound vehicle KW - rail guidance module KW - self-optimization KW - self-optimizing function modules KW - condition monitoring KW - mechatronics KW - railway rolling stock KW - self-adjusting systems T2 - Future Computing, Service Computation, Cognitive, Adaptive, Content, Patterns, 2009. COMPUTATIONWORLD '09. Computation World: TI - Towards the Integration of Condition Monitoring in Self-Optimizing Function Modules ER - TY - JOUR AB - A novel technique to form periodically nanostructured Si surface morphologies based on nanosphere lithography (NSL) and He ion implantation induced swelling is studied in detail. It is shown that by implantation of keV He ions through the nanometric openings of NSL masks regular arrays of hillocks and rings can be created on silicon surfaces. The shape and size of these surface features can be easily controlled by adjusting the ion dose and energy as well as the mask size. Feature heights of more than 100 nm can be obtained, while feature distances are typically 1.15 or 2 (hillock or ring) nanosphere radii, which are chosen to be between 100 and 500 nm in this study. Atomic force and scanning electron microscopy measurements of the surface morphology are supplemented by cross-sectional transmission electron microscopy, revealing the inner structure of hillocks to consist of a central cavity surrounded by a hierarchical arrangement of smaller voids. The surface morphologies developed here have the potential to be useful for fixing and separating nano-objects on a silicon surface. AU - Fischer, Frederic J.C. AU - Weinl, Michael AU - Lindner, Jörg AU - Stritzker, Bernd ID - 4152 JF - MRS Proceedings SN - 1946-4274 TI - Nanoscale Surface Patterning of Silicon Using Local Swelling Induced by He Implantation through NSL-Masks VL - 1181 ER - TY - CONF AB - We show that an optically driven carrier spin undergoes indirect dephasing even in the absence of spin-reservoir coupling and illustrate it for phonon-induced decoherence during optical spin rotation in a single quantum dot. AU - Grodecka, Anna AU - Machnikowski, Pawel AU - Förstner, Jens ID - 4180 KW - tet_topic_qd SN - 9781557528735 T2 - Advances in Optical Sciences Congress TI - Indirect Dephasing Channel for Optically Controlled Spin in a Single Quantum Dot ER - TY - JOUR AB - We demonstrate that an optically driven spin of a carrier in a quantum dot undergoes indirect dephasing via conditional optically induced charge evolution even in the absence of any direct interaction between the spin and its environment. A generic model for the indirect dephasing with a three-component system with spin, charge, and reservoir is proposed. This indirect decoherence channel is studied for the optical spin manipulation in a quantum dot with a microscopic description of the charge-phonon interaction taking into account its non-Markovian nature. AU - Grodecka, A. AU - Machnikowski, P. AU - Förstner, Jens ID - 4182 IS - 4 JF - Physical Review A KW - tet_topic_qd SN - 1050-2947 TI - Indirect spin dephasing via charge-state decoherence in optical control schemes in quantum dots VL - 79 ER - TY - JOUR AB - Buried ion beam synthesized 3C-SiC layers were revealed to the surface of silicon wafers to provide lattice matched substrates for GaN thin film epitaxy. Both epitaxial SiC/Si(1 1 1) and SiC/Si(0 0 1) growth surfaces with either six- or four-fold crystal symmetry, respectively, were formed. GaN thin film growth was achieved by ion beam assisted molecular beam epitaxy (IBA–MBE) which – owing to the energy and momentum transfer of the ions – allows to deposit epitaxial thin films at particularly low growth temperatures where both the stable hexagonal and the metastable cubic polytype of GaN can be formed. It is shown by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM) that using appropriate fluxes of Ga atoms both purely hexagonal and purely cubic GaN films can be grown epitaxially on SiC/Si(1 1 1) and SiC/Si(0 0 1), respectively. Thereby Ga rich growth conditions seem to stabilize the formation of the cubic polytype. It is obvious from XTEM studies that the high density of crystal defects in the SiC layer is not transferred onto the growing GaN films and that the crystalline quality of GaN films improves with increasing film thickness. The influence of surface roughness and wettability, interfacial cavities and the nucleation of twin-type defects at the GaN/SiC interface on the crystalline quality of the GaN thin films is discussed. AU - Häberlen, M. AU - Gerlach, J.W. AU - Murphy, B. AU - Lindner, Jörg AU - Stritzker, B. ID - 4192 IS - 6 JF - Journal of Crystal Growth SN - 0022-0248 TI - Structural characterization of cubic and hexagonal GaN thin films grown by IBA–MBE on SiC/Si VL - 312 ER - TY - JOUR AB - The growth of cubic group III-nitrides is a direct way to eliminate polarization effects, which inherently limit the fabrication of normally-off heterojunction field-effect transistors (HFETs) in GaN technology. HFET structures were fabricated of non-polar cubic AlGaN/GaN hetero layers grown by plasma assisted molecular beam epitaxy (MBE) on free standing 3C-SiC (001). The electrical insulation of 3C-SiC was realised by Ar+ implantation before c-AlGaN/GaN MBE. The structural properties of the epilayers were studied by highresolution x-ray diffraction (HRXRD). HFETs with normally off and normally-on characteristics were fabricated of cubic AlGaN/GaN. Capacitance-voltage (CV) characteristics of thegate contact were performed to detect the electron channel at the c-AlGaN/GaN hetero interface. AU - Tschumak, Elena AU - Lindner, Jörg AU - Bürger, M. AU - Lischka, K. AU - Nagasawa, H. AU - Abe, M. AU - As, Donald ID - 4196 IS - 1 JF - physica status solidi (c) SN - 1862-6351 TI - Non-polar cubic AlGaN/GaN HFETs grown by MBE on Ar+implanted 3C-SiC (001) VL - 7 ER - TY - JOUR AB - Three-dimensional (3D) photonic crystal exhibit direction-selective transmission with respect to the center frequency of the stop gap. As a model system, the stop gap of a 3D fcc inverted-opal photonic crystal is studied in the microwave regime in detail using 3D polyamide models. The difference in the direction-selective transmittance between crystals grown in two different high symmetry directions is experimentally shown and compared to numerical simulations. AU - Üpping, J. AU - Miclea, P.T. AU - Wehrspohn, R.B. AU - Baumgarten, T. AU - Greulich-Weber, Siegmund ID - 4198 IS - 2 JF - Photonics and Nanostructures - Fundamentals and Applications SN - 1569-4410 TI - Direction-selective optical transmission of 3D fcc photonic crystals in the microwave regime VL - 8 ER - TY - JOUR AB - The solar cell concept presented here is based on 3C-SiC nano- or microwires and conju¬gated polymers. Therefore the silicon carbide wires are fabricated by a sol-gel route including a car-bothermal reduction step, allowing growth with predetermined uniform diameters between 0.1 and 2μm and lengths up to several centimetres. The design of our photovoltaic device is therein based on a p-i-n structure, well known e.g. from silicon photovoltaics, involving an intrinsic semiconduc¬tor as the central photoactive layer, sandwiched between two complementary doped wide-bandgap semiconductors giving the driving force for charge separation. In our case the 3C-SiC microwires act as the electron acceptor and simultaneously as carrier material for all involved components of the photovoltaic element. AU - Greulich-Weber, Siegmund AU - Zöller, M. AU - Friedel, B. ID - 4219 JF - Materials Science Forum SN - 1662-9752 TI - Textile Solar Cells Based on SiC Microwires VL - 615-617 ER -