Universität Stuttgart
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Item Open Access 1.3 μm monolithic integrated optoelectronic receiver using InGaAs MSM photodiode and AlGaAs/GaAs HEMTs grown on GaAs(1994) Hurm, Volker; Benz, Willi; Berroth, Manfred; Fink, Thomas; Fritzsche, Daniel; Haupt, Michael; Hofmann, Peter; Köhler, Klaus; Ludwig, Manfred; Mause, Klaus; Raynor, Brian; Rosenzweig, JosefThe first 1.3 μm monolithic integrated optoelectronic receiver using an InGaAs MSM photodiode and AlGaAs/GaAs HEMTs grown on a GaAs substrate has been fabricated. At each differential output the transimpedance is 26.8 kΩ. The bandwidth of 430 MHz implies suitability for transmission rates up to 622 Mbit/s.Item Open Access 10 Gbit/s monolithic integrated Msm-photodiode AlGaAs/GaAs-HEMT optoelectronic receiver(1991) Hurm, Volker; Rosenzweig, Josef; Ludwig, Manfred; Benz, Willi; Osorio, Ricardo; Berroth, Manfred; Hülsmann, Axel; Kaufel, Gudrun; Köhler, Klaus; Raynor, Brian; Schneider, Joachim-Item Open Access 10-20 Gbit/s GaAs/AlGaAs HEMT ICs for high speed data links(1992) Berroth, Manfred; Hurm, Volker; Lang, Manfred; Ludwig, Manfred; Nowotny, Ulrich; Wang, Zhigong; Wennekers, Peter; Hülsmann, Axel; Kaufel, Gudrun; Köhler, Klaus; Raynor, Brian; Schneider, JoachimA set of ICs has been developed for high-speed data links at data rates above 10 Gbit/s. A recessed gate process for double pulse doped quantum well transistors has been used with e-beam written 0.3- μm gates. A 4 bit multiplexer and a laser diode driver for the transmitter as well as a transimpedance amplifier, bit synchronizer, and 4 bit demultiplexer for the receiver have been successfully operated with data rates up to 20 Gbit/s.Item Open Access 15N and 13C spin lattice relaxation in neat liquids at high magnetic fields(1975) Schweitzer, Dieter; Spiess, Hans WolfgangGeneral features of 15N spin lattice relaxation in nitrobenzene, pyridine and triethanolamine are discussed and compared with l3C relaxation mechanisms.Item Open Access 19 GHz monolithic integrated clock recovery using PLL and 0.3 μm gate-length quantum-well HEMTs(1994) Wang, Zhigong; Berroth, Manfred; Seibel, Jörg; Hofmann, Peter; Hülsmann, Axel; Köhler, Klaus; Raynor, Brian; Schneider, JoachimICs for optical data links have been developed for bit rates between 10 and 200 Gb/s. The only exception was the clock recovery (CR) IC at these high bit rates. In fact, the IC realization of CR is generally accepted as the weak point of high-speed system integration. While the bit rates of some ICs reach up to 40 Gb/s, monolithic ICs for a full CR function are limited to 2.5 Gb/s. The monolithic IC described here, for CR with a PLL including a full-balanced VCO, is based on the IC reported by Wang et. al. (1993). Clock frequencies up to 19 GHz are recovered with the IC reported here.Item Open Access 20 Gb/s monolithic integrated clock recovery and data decision(1994) Wang, Zhigong; Berroth, Manfred; Hurm, Volker; Lang, Manfred; Hofmann, Peter; Hülsmann, Axel; Köhler, Klaus; Raynor, Brian; Schneider, JoachimAn IC for 20 Gb/s clock recovery and data decision was realised using 0.3 m gate-length QW-HEMTs. A narrow-band regenerative frequency divider with on-chip resonator filters is used for the clock recovery. The parallel processing concept is accepted for the data decision. The complex IC was tested on wafer using 5 and 10-Gb/s input data. The desired 10-GHz clock signal and regenerated data signals have been obtained. The 2x2 mm 2 IC has a power consumption of about 0.5 W at -3 volt supply voltage.Item Open Access 4 Jahre E-Books an der LMU München - Erfahrungen und Perspektiven(2007) Schallehn, VolkerVorgestellt wird die Präsentation der E-Books in einem eigenen Katalog sowie das Angebot und die Nutzung von Ciando-E-Books in der LMU München.Item Open Access 7.5 Gb/s monolithically integrated clock recovery using PLL and 0.3 μM gate length quantum well HEMTs(1993) Wang, Zhigong; Berroth, Manfred; Nowotny, Ulrich; Hofmann, Peter; Hülsmann, Axel; Köhler, Klaus; Raynor, Brian; Schneider, JoachimA monolithically integrated clock recovery (CR) circuit making use of the phase-locked loop (PLL) circuit technique and enhancement/depletion AlGaAs/GaAs quantum well high electron mobility transistors (QW-HEMTs) with gate lengths of 0.3 μm has been realized. A novel preprocessing circuit was used. In the PLL a fully-balanced varactorless VCO has been introduced. The VCO has a centre oscillating frequency of about 7.5 GHz and a tuning range greater than 500 MHz. A satisfactory clock signal has been obtained at the bit rate of about 7.5 Gb/s. The power consumption is less than 200 mW at the supply voltage of -5 V.Item Open Access β-galactosidase production in two- and threedimensionally cultivated cell cultures(1991) Klünder, Irene; Hülser, Dieter F.In these studies, we demonstrate that the threedimensional arrangement of the cells in spheroids influences the β-galactosidase activity of transfected ltk--cells. In contrast to cells grown in monolayer culture cells growing as spheroids lost their β-galactosidase activity within few days. The reduction of β-galactosidase activity in cells grown as spheroids was not caused by a lost of the lacZ-gene as can be seen from the recovery of the β-galactosidase production when cells were retransferred in monolayer culture. As we showed in cells cultivated as monolayer, β-galactosidase activity seems to be not impaired by gradients of nutrient supply or cell cycle. These measurements are confirmed by histological sections, where the highest β-galactosidase activity was found in the viable center of the spheroids.Item Open Access Der Abbau von Modellstrukturen der Kohle: Stoffwechselweg des Dibenzofuran- und Fluorenabbaus(1991) Engesser, Karl-Heinrich; Strubel, Volker; Trenz, Stefan Peter; Rothe, Bernd; Schmid, Andreas; Knackmuss, Hans-JoachimSeveral microorganisms have been isolated degrading structural elements of coal like dibenzofuran. fluorene and biphenyl. Extensive investigation of the degradation pathways revealed a common mechanism of initial attack. Although catalyzed by different enzymes, all three substrates are converted to 3-phenyl-substituted catechols, which, after meta-cleavage are transformed to simple aromatic structures like salicylate, phthalate and benzoate. This ring cleaving enzymes have been cloned and are further analyzed after subcloning. Two different initial dioxygenases seem to be present in some strains cataIyzing ether cleavage of dibenzofuran and oxygenation of biphenyl respectively. Attempts are presently made to clone the first enzyme in order to produce higher yields of its optically active products. Some of these compounds have been characterized and may be of commercial value as fine chemicals.Item Open Access Abbildung von Frames auf neuere Datenmodelle(1987) Härder, Theo; Mattos, Nelson Mendonca; Mitschang, BernhardEs wird die Abbildung von Frames mit ihren Modellierungskonzepten und charakteristischen Operationen auf objektorientierte Datenmodelle untersucht, um Wissensrepräsentation in sogenannten Non-Standard-Datenbanksystemen - beispielsweise für Expertensystem-Anwendungen - unterstützen zu können. Nach einem Vergleich der Eigenschaften von Relationenmodell, NF 2-Modell und MAD-Modell für diese Aufgabe wird eine Bewertung der verschiedenen Ansätze vorgenommen, um ihre Tauglichkeit für die Frame-Modellierung deutlicher herauszukristallisieren.Item Open Access Abschaltung von dezentralen Erzeugungsanlagen infolge von Unterspannungen im Kontext von LFSM-O(2022) Schöll, Christian; Lehner, Joachim; Weidner, Johannes; Lens, HendrikBei einer Überfrequenz jenseits von 50,2 Hz müssen sämtliche Erzeugungsanlagen ihre in das Netz eingespeiste Wirkleistung reduzieren. In den zumeist resistiv geprägten Verteilungsnetzen der Mittel- und Niederspannung führt diese überfrequenzbedingte Leistungsreduktion zu einer lokalen Absenkung des Spannungsprofils. Unterschreiten die Spannungen die Vorgaben aus den Netzanschlussbedingungen, unter denen dezentrale Erzeugungsanlagen die Verbindung zum Netz aufrechterhalten müssen, kann es zu unterspannungsbedingten Schutzabschaltungen kommen. Theoretisch könnten diese bei großflächigem Auftreten zu einer Umkehr des ursprünglichen Überfrequenzereignisses in ein Unterfrequenzereignis führen. Anhand von simulationsbasierten Untersuchungen wird in diesem Beitrag jedoch aufgezeigt, dass unter realitätsnahen Annahmen und unter Berücksichtigung der nationalen Richtlinien sowie der zugehörigen netzplanerischen Leitplanken kein besonderes Risiko hinsichtlich der Anregung der beschriebenen Wirkungskette vorliegt.Item Open Access Abschätzverfahren für die Kontakttemperatur bei Radial-Wellendichtungen(2016) Feldmeth, Simon; Bauer, Frank; Haas, WernerItem Open Access Abtragung von Knorpel- und Knochengewebe mittels fasergeführtem Excimerlaserstrahl(1992) Neu, Walter; Dressel, Martin; Jahn, Renate; Grzesik, UlrichBei der Ablation von Gewebe mit kurzgepulsten Excimerlasern erfolgt die Materialabtragung nicht mehr ausschließlich durch photothermische Wirkung, sondern indem auch molekulare Bindungen aufgrund der hohen Photonenenergie des Lasers aufgebrochen werden. Die entstehenden gasförmigen Ablationsprodukte und Materialtrümmer werden dabei explosionsartig aus dem Bestrahlungsvolumen herausgeschleudert. Bei diesem Abtragungsmechanismus treten nur sehr geringe thermische Nebenwirkungen auf, da die Laserwellenlänge stark absorbiert, damit verbunden nur eine geringe Eindringtiefe erreicht wird und zusätzlich die Bestrahlungsdauer aufgrund des kurzen Laserpulses im Vergleich zu thermischen Diffusionszeiten klein ist.Item Open Access Accident simulations of a novel restraint safety concept for motorcyclists(2023) Maier, Steffen; Fehr, JörgItem Open Access Acoustic and seismic emissions from wind turbines(2017) Calarco, Francesca; Cheng, Po Wen; Zieger, Toni; Ritter, JoachimWith regards to the interdisciplinary “TremAc” Project funded by the German Federal Ministry for Economic Affairs and Energy, this paper examines acoustic and seismic emissions generated by wind turbines with the aim of identifying a better understanding of their interaction. Measurement campaigns will be carried out in the field around a single wind turbine plant and results in terms of acoustic and seismic signals will be correlated and then evaluated in relation to environmental factors such as wind speed, wind direction and temperature as well as to data related to the wind turbines-specifications (e.g. rotation speed).Item Open Access Active versus passive control of vehicle suspensions - hardware in the loop experiments(1994) Rieger, Karl-Josef; Schiehlen, WernerHardware-in-the-loop simulation is shown to be a valuable tool for designing and testing controllers for active vehicle suspensions. The vehicle is modeled as a multibody system, whereas the electronic and hydraulic parts of the suspension are actuated on a test bed. A comparison between an active and a passive suspension shows higher performance of the active suspension with respect to low frequency excitation.Item Open Access Ada compiler validation(1986) Plödereder, ErhardThis paper discusses Ada Compiler Validation from the viewpoint of both the compiler supplier and the compiler user. The objectives of the requirement for validation and the resulting benefits, as well as the limitations of validation are presented. The process of Ada compiler validation is detailed along with the various problems as well as issues relating to validation and the use of validated compilers. Solutions to these problems and issues are explained, as they are proposed in a recent AJPO draft of a revised validation policy.Item Open Access An adaptive data processing technique for lidar-assisted control to bridge the gap between lidar systems and wind turbines(2015) Schlipf, David; Fleming, Paul; Raach, Steffen; Scholbrock, Andrew; Haizmann, Florian; Krishnamurthy, Raghu; Boquet, Matthieu; Cheng, Po WenThis paper presents first steps toward an adaptive lidar data processing technique crucial for lidar-assisted control in wind turbines. The prediction time and the quality of the wind preview from lidar measurements depend on several factors and are not constant. If the data processing is not continually adjusted, the benefit of lidar-assisted control cannot be fully exploited or can even result in harmful control action. An online analysis of the lidar and turbine data is necessary to continually reassess the prediction time and lidar data quality. In this work, a structured process to develop an analysis tool for the prediction time and a new hardware setup for lidar-assisted control are presented. The tool consists of an online estimation of the rotor effective wind speed from lidar and turbine data and the implementation of an online cross-correlation to determine the time shift between both signals. Further, we present initial results from an ongoing campaign in which this system was employed for providing lidar preview for feedforward pitch control.Item Open Access Advances on reduced-order modeling of floating offshore wind turbines(2021) Lemmer, Frank; Yu, Wei; Steinacker, Heiner; Skandali, Danai; Raach, SteffenAero-hydro-servo-elastic modeling of Floating Offshore Wind Turbines (FOWTs) is a key component in the design process of various components of the system. Different approaches to order reduction have been investigated with the aim of improving structural design, manufacturing, transport and installation, but also the dynamic behavior, which is largely affected by the blade pitch controller. The present work builds on previous works on the SLOW (Simplified Low-Order Wind Turbine) code, which has already been used for the above purposes, including controller design. While the previous rigid rotor model gives good controllers in most cases, we investigate in the present work the question if aero-elastic effects in the design model can improve advanced controllers. The SLOW model is extended for the flapwise bending and coupled to NREL's AeroDyn, linearized and verified with the OlavOlsen OO-Star Wind Floater Semi 10MW public FOWT model. The results show that the nonlinear and linear reduced-order SLOW models agree well against OpenFAST. The state-feedback Linear Quadratic Regulator (LQR) applied with the same weight functions to both models, the old actuator disk, and the new aero-elastic model shows that the LQR becomes more sensitive to nonlinear excitation and that the state feedback matrix is significantly different, which has an effect on the performance and potentially also on the robustness. Thus modeling uncertainties might even be more critical for the LQR of the higher-fidelity model.