15 Fakultätsübergreifend / Sonstige Einrichtung

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/16

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    eSciDoc-Anwendungen in der wissenschaftlichen Praxis in der MPG
    (2008) Renn, Jürgen; Voges, Wolfgang
    eSciDoc ist ein gemeinsames Projekt der Max-Planck-Gesellschaft und FIZ Karlsruhe. Entwickelt wird eine integrierte Publikations- und Kommunikationsplattform, die zentrale Facetten der wissenschaftlichen Arbeit unterstützt. - Informationsgewinnung - Aufbereitung und Auswertung - Informationsverbreitung und Speicherung eScidoc berücksichtigt wissenschaftliche Arbeiten sowohl im Labor wie auch am Schreibtisch, durchgeführt von Einzelnen oder in (verteilten) Gruppen, disziplinspezifisch oder interdisziplinär.
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    Strategien und Technologien einer pluralistischen Fern- und Nahwärmeversorgung in einem liberalisierten Energiemarkt unter besonderer Berücksichtigung der Kraft-Wärme-Kopplung und erneuerbarer Energien : Kurzfassung der Studie
    (2000) Besch, H.; Neuffer, Hans; Witterhold, Franz-Georg; Schönberg, Ingo; Jochem, Eberhard; Radgen, Peter; Schmid, Christiane; Mannsbart, Wilhelm; Pfaffenberger, Wolfgang; Schulz, Wolfgang; Voß, Alfred; Blesl, Markus; Fahl, Ulrich; Zschernig, Joachim; Sager, Jörg; Fahlenkamp, Hans; Hölder, Daniel; Dötsch, Christian; AGFW - Arbeitsgemeinschaft Fernwärme e.V. bei der Vereinigung Deutscher Elektrizitätswerke
    Die Zusammenfassung dient zwei Zielen: Zunächst werden die wesentlichen Ergebnisse der Langfassung der o.g. Studie referiert; auf dieser Basis werden dann mögliche Maßnahmen und Strategien diskutiert, die kurzfristig (2000-2001) ergriffen werden könnten. Als Akteure kommen hierbei nicht nur die Bundesregierung, die wichtige Rahmenbedingungen zum Marktgeschehen wird setzen müssen, in den Fokus, sondern auch die Betreiber von Heizkraftwerken und KWK-Anlagen und deren Verbände, aber auch andere Akteure wie z. B. Contracting-Unternehmen und Forschungseinrichtungen. Da die Übergangsphase der Liberalisierung der europäischen Stromwirtschaft in den Jahren 2000-2005 eine besondere Herausforderung für die KWK-Entwicklung darstellt, wird auch ein kurzfristig wirksames Maßnahmenbündel zur Diskussion gestellt. Dem Leser sei zum Verständnis in Erinnerung gerufen, dass diese vorgelegte Analyse im Rahmen einer Vorstudie durchgeführt wurde und langfristig abgesicherte Aussagen auch Analysen mit einschließen müssten, die bis 2010 und 2020 reichen. Weiterführende Arbeiten sollen in einer geplanten Hauptstudie erfolgen.
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    A Bayesian network approach to assess and predict software quality using activity-based quality models
    (2009) Wagner, Stefan
    Assessing and predicting the complex concept of software quality is still challenging in practice as well as research. Activity-based quality models break down this complex concept into more concrete definitions, more precisely facts about the system, process and environment and their impact on activities performed on and with the system. However, these models lack an operationalisation that allows to use them in assessment and prediction of quality. Bayesian Networks (BN) have been shown to be a viable means for assessment and prediction incorporating variables with uncertainty. This paper describes how activity-based quality models can be used to derive BN models for quality assessment and prediction. The proposed approach is demonstrated in a proof of concept using publicly available data.
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    Do code clones matter?
    (2009) Juergens, Elmar; Deißenböck, Florian; Hummel, Benjamin; Wagner, Stefan
    Code cloning is not only assumed to inflate maintenance costs but also considered defect-prone as inconsistent changes to code duplicates can lead to unexpected behavior. Consequently, the identification of duplicated code, clone detection, has been a very active area of research in recent years. Up to now, however, no substantial investigation of the consequences of code cloning on program correctness has been carried out. To remedy this shortcoming, this paper presents the results of a large-scale case study that was undertaken to find out if inconsistent changes to cloned code can indicate faults. For the analyzed commercial and open source systems we not only found that inconsistent changes to clones are very frequent but also identified a significant number of faults induced by such changes. The clone detection tool used in the case study implements a novel algorithm for the detection of inconsistent clones. It is available as open source to enable other researchers to use it as basis for further investigations.
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    Detection of wind evolution and lidar trajectory optimization for lidar-assisted wind turbine control
    (2015) Schlipf, David; Haizmann, Florian; Cosack, Nicolai; Siebers, Tom; Cheng, Po Wen
    In this work a collective pitch feedforward controller for floating wind turbines is presented. The feedforward controller provides a pitch rate update to a conventional feedback controller based on a wind speed preview. The controller is designed similar to the one for onshore turbines, which has proven its capability to improve wind turbine control performance in field tests. In a first design step, perfect wind preview and a calm sea is assumed. Under these assumptions the feedforward controller is able to compensate almost perfectly the effect of changing wind speed to the rotor speed of a full nonlinear model over the entire full load region. In a second step, a nacelle-based lidar is simulated scanning the same wind field which is used also for the aero-hydro-servo-elastic simulation. With model-based wind field reconstruction methods, the rotor effective wind speed is estimated from the raw lidar data and is used in the feedforward controller after filtering out the uncorrelated frequencies. Simulation results show that even with a more realistic wind preview, the feedforward controller is able to significantly reduce rotor speed and power variations. Furthermore, structural loads on the tower, rotor shaft, and blades are decreased. A comparison to a theoretical investigation shows that the reduction in rotor speed regulation is close to the optimum.
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    A model and sensitivity analysis of the quality economics of defect-detection techniques
    (2006) Wagner, Stefan
    One of the main cost factors in software development is the detection and removal of defects. However, the relationships and influencing factors of the costs and revenues of defect-detection techniques are still not well understood. This paper proposes an analytical, stochastic model of the economics of defect detection and removal to improve this understanding. The model is able to incorporate dynamic as well as static techniques in contrast to most other models of that kind. We especially analyse the model with state-ofthe-art sensitivity analysis methods to (1) identify the most relevant factors for model simplification and (2) prioritise the factors to guide further research and measurements.
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    Comparison of Taguchi Method and Robust Design Optimization (RDO) : by application of a functional adaptive simulation model for the robust product-optimization of an adjuster unit
    (2015) Kemmler, Stefan; Fuchs, Alexander; Leopold, Tobias; Bertsche, Bernd
    Current research and development have been trending towards approaches based on simulation and virtual testing. Industrial development processes for complex products employ optimization methods to ensure results are close to reality, simultaneously minimizing required resources. The results of virtual testing are optimized in accordance with requirements using optimization techniques. Robust Design Optimization (RDO) is one established approach to optimization. RDO is based on the identification of an optimal parameter set which includes a small variance of the target value as a constraint. Under most circumstances, this approach does not involve separate optimization of the target value and target variance. However, the basic strategy of the optimization approach developed by Taguchi is to first optimize the parameter sets for the target value and then optimize and minimize the target variance. According to an application example , the benefit of Taguchi's approach (TM) is that it facilitates the identification of an optimal parameter set of nominal values for technical feasibility and possible manufacturing. If an optimal parameter set is determined, the variance can be minimized under consideration of process parameters. This paper examines and discusses the differences between and shared characteristics of the robust optimization methods TM and RDO, and discusses their shortcomings. In order to provide a better illustration, this paper explains and applies both methods using an adjuster unit of a commercial vehicle braking system. A simulation model is developed including an appropriate work ow by applying optiSLang-modules.
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    Comparative sensitivity analysis of muscle activation dynamics
    (2015) Rockenfeller, Robert; Günther, Michael; Schmitt, Syn; Götz, Thomas
    We mathematically compared two models of mammalian striated muscle activation dynamics proposed by Hatze and Zajac. Both models are representative for a broad variety of biomechanical models formulated as ordinary differential equations (ODEs). These models incorporate parameters that directly represent known physiological properties. Other parameters have been introduced to reproduce empirical observations. We used sensitivity analysis to investigate the influence of model parameters on the ODE solutions. In addition, we expanded an existing approach to treating initial conditions as parameters and to calculating second- order sensitivities. Furthermore, we used a global sensitivity analysis approach to include finite ranges of parameter values. Hence, a theoretician striving for model reduction could use the method for identifying particularly low sensitivities to detect superfluous parameters. An experimenter could use it for identifying particularly high sensitivities to improve parameter estimation. Hatze’s nonlinear model incorporates some parameters to which activation dynamics is clearly more sensitive than to any parameter in Zajac’s linear model. Other than Zajac’s model, Hatze’s model can, however, reproduce measured shifts in optimal muscle length with varied muscle activity. Accordingly we extracted a specific parameter set for Hatze’s model that combines best with a particular muscle force-length relation.
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    Hochauflösende Beschleunigungssensoren mit Tunnelstrecke
    (2000) Strobelt, Tilo; Sandmaier, Hermann (Prof. Dr.-Ing.)
    Ziel der Arbeit ist es, alle zur Konstruktion von hochauflösenden Beschleunigungssensoren mit Tunnelstrecke erforderlichen theoretischen Grundlagen zur Verfügung zu stellen und deren Anwendbarkeit an Hand des Entwurfes und der Realisierung eines Sensors nachzuweisen. Wesentliche Themen des theoretischen Teiles der Arbeit sind hierbei: die Beschreibung der Funktion einer Tunnelstrecke sowie die Herleitung der Rauschanteile, welche die Auflösung von Beschleunigungssensoren beschränken. Es wird deutlich, dass die hohe Auflösung des Tunneleffektes den Einsatz einer aktiven Regelung und hochempfindlicher Stellelemente erforderlich macht. Vergleicht man alle in Beschleunigungssensoren auftretenden Rauschquellen, so stellt man fest, daß die Nachweisgrenze hochauflösender Beschleunigungssensoren vom thermische Rauschen des Feder-Masse-Systems bestimmt wird. Auf den hergeleiteten konstruktiven Grundlagen aufbauend, wird anschließend die Entwicklung eines Sensors mit einer Nachweisgrenze von 1E-6 g (g= Erdbeschleunigung) beschrieben. Hierbei wird die mikrotechnischen Konstruktion dargestellt und ausführlich auf die Entwicklung der erforderlichen Sensorelektronik eingegangen. Um die elektronische Regelung geeignet auslegen und optimieren zu können, wurde das dynamische Verhalten des Gesamtsystems analytisch beschrieben. Die geeignete Wahl der Parameter wurde mit Hilfe eines numerischen Modells des Gesamtsystems nochmals überprüft. Im Rahmen dieser Arbeit wurde ferner ein Messplatz entwickelt, auf dem die Beschleunigungssensoren nach ihrer Fertigstellung charakterisiert worden sind. Erstmalig wurde es so möglich, derartige Sensoren direkt an ihrer Auflösungsgrenze zu vermessen. Die dem Rauschen äquivalente Beschleunigung wird mit ca. 2.5E-6 g gemessen, stimmt also mit den theoretischen Vorhersagen gut überein.
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    Design and evaluation of a lidar-based feedforward controller for the INNWIND.EU 10 MW wind turbine
    (2015) Fürst, Holger; Schlipf, David; Iribas Latour, Mikel; Cheng, Po Wen
    For the development of the next generation of multi megawatt wind turbines, advanced control concepts are one of the major tasks. Reduction of fatigue and extreme loading could help to improve the overall design process and make plants more cost effective. This work deals with the application of the promising methodology of feedforward control using nacelle-based lidar sensor measurements on a 10 MW wind turbine concept. After lidar data processing has been described, the feedforward controller is designed such that disturbances from the changing wind speed to the generator speed are compensated by adding an update to the collective pitch rate signal of the normal feedback controller. The evaluation of the feedforward controller is done in two steps: Firstly, simulations using perfect lidar data measurements are applied to check the robustness of the controller against model uncertainties. After that, simulations with realistic lidar measurements are investigated. To improve control performance, the scanning configuration of the used lidar system is optimized. Over all it can be shown that lidar-assisted control leads to significant load reductions, especially in the full load region of the 10 MW turbine.