TY - CHAP A1 - Dachwald, Bernd T1 - Low-Thrust Mission Analysis and Global Trajectory Optimization Using Evolutionary Neurocontrol: New Results T2 - European Workshop on Space Mission Analysis ESA/ESOC, Darmstadt, Germany 10 { 12 Dec 2007 N2 - Interplanetary trajectories for low-thrust spacecraft are often characterized by multiple revolutions around the sun. Unfortunately, the convergence of traditional trajectory optimizers that are based on numerical optimal control methods depends strongly on an adequate initial guess for the control function (if a direct method is used) or for the starting values of the adjoint vector (if an indirect method is used). Especially when many revolutions around the sun are re- quired, trajectory optimization becomes a very difficult and time-consuming task that involves a lot of experience and expert knowledge in astrodynamics and optimal control theory, because an adequate initial guess is extremely hard to find. Evolutionary neurocontrol (ENC) was proposed as a smart method for low-thrust trajectory optimization that fuses artificial neural networks and evolutionary algorithms to so-called evolutionary neurocontrollers (ENCs) [1]. Inspired by natural archetypes, ENC attacks the trajectoryoptimization problem from the perspective of artificial intelligence and machine learning, a perspective that is quite different from that of optimal control theory. Within the context of ENC, a trajectory is regarded as the result of a spacecraft steering strategy that maps permanently the actual spacecraft state and the actual target state onto the actual spacecraft control vector. This way, the problem of searching the optimal spacecraft trajectory is equivalent to the problem of searching (or "learning") the optimal spacecraft steering strategy. An artificial neural network is used to implement such a spacecraft steering strategy. It can be regarded as a parameterized function (the network function) that is defined by the internal network parameters. Therefore, each distinct set of network parameters defines a different network function and thus a different steering strategy. The problem of searching the optimal steering strategy is now equivalent to the problem of searching the optimal set of network parameters. Evolutionary algorithms that work on a population of (artificial) chromosomes are used to find the optimal network parameters, because the parameters can be easily mapped onto a chromosome. The trajectory optimization problem is solved when the optimal chromosome is found. A comparison of solar sail trajectories that have been published by others [2, 3, 4, 5] with ENC-trajectories has shown that ENCs can be successfully applied for near-globally optimal spacecraft control [1, 6] and that they are able to find trajectories that are closer to the (unknown) global optimum, because they explore the trajectory search space more exhaustively than a human expert can do. The obtained trajectories are fairly accurate with respect to the terminal constraint. If a more accurate trajectory is required, the ENC-solution can be used as an initial guess for a local trajectory optimization method. Using ENC, low-thrust trajectories can be optimized without an initial guess and without expert attendance. Here, new results for nuclear electric spacecraft and for solar sail spacecraft are presented and it will be shown that ENCs find very good trajectories even for very difficult problems. Trajectory optimization results are presented for 1. NASA's Solar Polar Imager Mission, a mission to attain a highly inclined close solar orbit with a solar sail [7] 2. a mission to de ect asteroid Apophis with a solar sail from a retrograde orbit with a very-high velocity impact [8, 9] 3. JPL's \2nd Global Trajectory Optimization Competition", a grand tour to visit four asteroids from different classes with a NEP spacecraft Y1 - 2007 ER - TY - CHAP A1 - Weiss, Alexander A1 - Abanteriba, Sylvester A1 - Esch, Thomas T1 - Investigation of Flow Separation Inside a Conical Rocket Nozzle With the Aid of an Annular Cross Flow T2 - Proceedings of the ASME/JSME 2007 5th Joint Fluids Engineering Conference. Volume 1: Symposia, Parts A and B N2 - Flow separation is a phenomenon that occurs in all kinds of supersonic nozzles sometimes during run-up and shut-down operations. Especially in expansion nozzles of rocket engines with large area ratio, flow separation can trigger strong side loads that can damage the structure of the nozzle. The investigation presented in this paper seeks to establish measures that may be applied to alter the point of flow separation. In order to achieve this, a supersonic nozzle was placed at the exit plane of the conical nozzle. This resulted in the generation of cross flow surrounding the core jet flow from the conical nozzle. Due to the entrainment of the gas stream from the conical nozzle the pressure in its exit plane was found to be lower than that of the ambient. A Cold gas instead of hot combustion gases was used as the working fluid. A mathematical simulation of the concept was validated by experiment. Measurements confirmed the simulation results that due to the introduction of a second nozzle the pressure in the separated region of the conical nozzle was significantly reduced. It was also established that the boundary layer separation inside the conical nozzle was delayed thus allowing an increased degree of overexpansion. The condition established by the pressure measurements was also demonstrated qualitatively using transparent nozzle configurations. Y1 - 2007 SN - 0-7918-4288-6 U6 - https://doi.org/10.1115/FEDSM2007-37387 N1 - Proceedings of the ASME/JSME 2007 5th Joint Fluids Engineering Conference. Volume 1: Symposia, Parts A and B. San Diego, California, USA. July 30–August 2, 2007 SP - 1861 EP - 1871 PB - American Society of Mechanical Engineers (ASME) CY - New York ER - TY - CHAP A1 - Köllensperger, P. A1 - Bragard, Michael A1 - Plum, T. A1 - De Doncker, R. W. T1 - The dual GCT : a new high-power device using optimized GCT technology T2 - Conference record of the 2007 IEEE Industry Applications Conference : 42. IAS annual meeting ; September 23 - 27, 2007, New Orleans, Louisiana, USA Y1 - 2007 SN - 978-1-4244-1260-0 (Online) SN - 978-1-4244-1259-4 (Print) U6 - https://doi.org/10.1109/07IAS.2007.76 SP - 358 EP - 365 PB - IEEE Operations Center CY - Piscataway, NJ ER - TY - CHAP A1 - Jacobs, Stephan ED - Bleek, Wolf-Gideon T1 - Towards integration driven design : experience report T2 - Software Engineering 2007 : Beiträge zu den Workshops ; Fachtagung des GI-Fachbereichs Softwaretechnik ; 27. - 30.03.2007 in Hamburg. - (GI-Edition : Proceedings ; 106) Y1 - 2007 SN - 978-3-88579-200-0 SP - 143 EP - 150 PB - Ges. für Informatik CY - Bonn ER - TY - CHAP A1 - Hagebeuker, Bianca A1 - Ringbeck, Thorsten A1 - Frydlewicz, Paul A1 - Jesorsky, Oliver A1 - Sünkel, Thomas ED - Grote, Caspar T1 - PMD-Sensoren als Schlüsselkomponenten für die mehrdimensionale Umfelderfassung des Fahrzeuginnenraums T2 - Begleittexte zum Entwicklerforum KFZ-Elektronik & FlexRay Solution Day : 15.Mai 2007, Ludwigsburg Y1 - 2007 N1 - Entwicklerforum Kfz-Elektronik <2007, Ludwigsburg> ; FlexRay Solution Day <2007, Ludwigsburg> SP - 287 EP - 296 PB - WEKA-Fachzeitschr.-Verl. CY - Poing ER - TY - CHAP A1 - Tippkötter, Nils A1 - Stückmann, H. A1 - Winkelmann, G. A1 - Noack, U. A1 - Beutel, S. A1 - Scheper, T. A1 - Ulber, Roland T1 - Optimisation of antibody-labelling of gold colloids for their application in an immunchromatographic assay for microcystin-LR T2 - European BioPerspectives : celebrating the 25th DECHEMA annual convention of biotechnologists ; 30 May - 1 June 2007, Cologne, Germany ; book of abstracts ; abstracts, poster programme Y1 - 2007 SP - 126 PB - Dechema CY - Frankfurt am Main ER - TY - CHAP A1 - Wellmer, Georg A1 - Chen, B.-H. A1 - Braun, Carsten A1 - Ballmann, Josef T1 - Numerical prediction of aeroelastic effects on twin-sting-rig mounted models for rear fuselage and empennage flow investigation in transonic windtunnel T2 - Proceedings / IFASD 2007, CEAS/AIAA/KTH International Forum on Aeroelasticity and Structural Dynamics, June 18 - 21, 2007, Stockholm, Sweden Y1 - 2007 PB - KTH CY - Stockholm ER - TY - CHAP A1 - Ringbeck, Thorsten A1 - Hagebeuker, Bianca ED - Grün, Armin T1 - A 3D time of flight camera of object detection T2 - Optical 3-D measurement techniques VIII : applications in GIS, mapping, manufacturing, quality control, robotics, navigation, mobile mapping, medical imaging, cultural heritage, VR generation and animation; papers presented to the conference organized at ETH Zurich, Switzerland, July 9 - 12, 2007. - Vol. 1 Y1 - 2007 SN - 3-906467-67-8 (Gesamtwerk) N1 - Conference on Optical 3-D Measurement Techniques <8, 2007, Zürich> SP - 1 EP - 16 PB - ETH CY - Zürich ER - TY - CHAP A1 - Fredebeul-Krein, Markus T1 - Time for revision: The regulation of Germany's next generation networks in the light of new economic and technological challenges on telecom markets : Presentation for the 18th Biennial conference of the International Telecommunications Society, June 24–27, 2008 Montreal, Canada N2 - On 1st January 1998, the German telecom market was fully liberalised. Since then genuine competition between market participants has developed, based on a comprehensive legal and regulatory framework that provides for safeguards against unfair competition and market power by Deutsche Telekom. Today, about 10 years after the liberalisation of the telecommunications sector a revision of this regulatory approach has become necessary because at least on three dimensions the situation is quite different from the one 10 years ago: First, with numerous established alternative operators in the market monopolies have been successfully challenged and competition introduced. Second, not only is Cable TV becoming in large parts of Germany a viable alternative for the provision of broadband services but also mobile services are becoming increasingly a substitute for fixed services. Last but not least there are important technological changes under way, requiring huge investments in infrastructure upgrades for next generation networks. In the light of these new developments the question is to which extent the current regulatory approach of severe ex-ante regulatory intervention is still appropriate. Is any part of the network of the former incumbent still a bottleneck? A more light handed regulatory approach might be the right response to this new situation. The paper is organised as follows: The first section will briefly examine the economic rationale for regulating network access. Based on the assumption that regulation is always necessary when bottlenecks exist regulatory principles for an efficient network access regime will be derived. The second section compares the situation of the German market in early 1998 with the one of today. Thereby three dimensions will be considered: the degree of competition, the potential for substitution and technological developments. The third section will define some requirements for the future regulation of telecom markets. Proposals will be elaborated how to ensure competitive telecom markets in the light of new economic and technological challenges. KW - Telekommunikationsmarkt KW - Telekommunikationsmarkt Y1 - 2008 ER - TY - CHAP A1 - Fredebeul-Krein, Markus A1 - Haunert, Martina T1 - Assessing the effectiveness of price cap regimes for the regulation of fixed telephony markets: has it been successful in achieving competition? : preliminary draft / by Markus Fredebeul-Krein and Martina Haunert. 19th European Regional ITS Conference of the International Telecommunications Society, September 17–19, 2008 Rome, Italy N2 - 1. Introduction 2. Tariff regulation, rebalancing and price caps 3. Price cap regimes in selected European countries 4. Has price cap regulation been successful? 5. Regulatory implications for other countries KW - Telekommunikationsmarkt KW - Telekommunikationsmarkt Y1 - 2008 ER - TY - CHAP A1 - Christen, Marc A1 - Bartelt, Perry A1 - Kowalski, Julia A1 - Stoffel, Lukus T1 - Calculation of dense snow avalanches in three-dimensional terrain with the numerical simulation programm RAMMS T2 - Proceedings ISSW 2008 ; International Snow Science Workshop. Whistler 2008 N2 - Numerical models have become an essential part of snow avalanche engineering. Recent advances in understanding the rheology of flowing snow and the mechanics of entrainment and deposition have made numerical models more reliable. Coupled with field observations and historical records, they are especially helpful in understanding avalanche flow in complex terrain. However, the application of numerical models poses several new challenges to avalanche engineers. A detailed understanding of the avalanche phenomena is required to specify initial conditions (release zone dimensions and snowcover entrainment rates) as well as the friction parameters, which are no longer based on empirical back-calculations, rather terrain roughness, vegetation and snow properties. In this paper we discuss these problems by presenting the computer model RAMMS, which was specially designed by the SLF as a practical tool for avalanche engineers. RAMMS solves the depth-averaged equations governing avalanche flow with first and second-order numerical solution schemes. A tremendous effort has been invested in the implementation of advanced input and output features. Simulation results are therefore clearly and easily visualized to simplify their interpretation. More importantly, RAMMS has been applied to a series of well-documented avalanches to gauge model performance. In this paper we present the governing differential equations, highlight some of the input and output features of RAMMS and then discuss the simulation of the Gatschiefer avalanche that occurred in April 2008, near Klosters/Monbiel, Switzerland. KW - snow KW - avalanche Y1 - 2008 SP - 709 EP - 716 ER - TY - CHAP A1 - Kowalski, Julia A1 - McElwaine, J. T1 - Two-phase debris flow modeling T2 - Geophysical Research Abstracts Y1 - 2008 N1 - A-01048 ER - TY - CHAP A1 - Müller, Karsten A1 - Hüben, Susanne T1 - From rehabilitation strategy up to formation of lots : implementation of a computer-aided decision support system T2 - 11th International Conference on Urban Drainage, Edinburgh, Scotland, UK, 31st August to 5th September 2008 Y1 - 2008 ER - TY - CHAP A1 - Schwarzer, Klemens A1 - Kroker, Jan A1 - Rusack, Markus T1 - Technical improvement of a small modular parabolic trough collector T2 - EuroSun 2008 : 1st International Conference on Solar Heating, Cooling and Buildings ; 7th - 10th October 2008, Lisbon, Portugal : key lectures / ISES, International Solar Energy Society. Vol. 1 Y1 - 2008 SN - 978-1-61782-228-5 SP - 1395 EP - 1402 PB - Sociedade Portuguesa De Energia Solar (SPES) CY - Lissabon ER - TY - CHAP A1 - Schwarzer, Klemens T1 - Desalination systems with renewable energies T2 - DME Seminar Desalination and Renewable Energies : June 19 and 20 2008, Solar Institut Jülich / Deutsche Meerwasserentsalzung e.V. Y1 - 2008 SN - 978-3-86861-017-8 PB - DME CY - Duisburg ER - TY - CHAP A1 - Hoffschmidt, Bernhard T1 - Solar tower power plants T2 - DME Seminar Desalination and Renewable Energies : June 19 and 20 2008, Solar Institut Jülich / Deutsche Meerwasserentsalzung e.V. Y1 - 2008 SN - 978-3-86861-017-8 PB - DME CY - Duisbrug ER - TY - CHAP A1 - Hellmanns, Mark A1 - Böhm, Stefan A1 - Dilger, Klaus T1 - Weight and noise reduction in power transmissions through epoxy resin foams T2 - Proceedings of the 31st annual meeting of the Adhesion Society : 17. - 20.2.2008, Austin, Texas Y1 - 2008 SP - 291 EP - 293 PB - Adhesion Society CY - Blacksburg ER - TY - CHAP A1 - Döring, Bernd A1 - Feldmann, Markus A1 - Kuhnhenne, Markus A1 - Hellberg, Jan T1 - Implementing a thermal activation system into a light-weight steel deck element T2 - Eurosteel 2008 : 5th European Conference on Steel and Composite Structures ; research, practice, new materials ; 3rd to 5th September 2008, Graz, Austria / ed. by Robert Ofner ... Y1 - 2008 SN - 92-0147-000-90 SP - 941 EP - 946 PB - ECCS, European Convention for Construction Steelwork CY - Brussels ER - TY - CHAP A1 - Schürmann, Volker A1 - Buda, Aurel A1 - Wollert, Jörg T1 - XML-based Middleware approach for industrial wireless communication systems T2 - IEEE International Conference on Emerging Technologies and Factory Automation, 2008 : ETFA 2008 ; 15 - 18 Sept., 2008, Hamburg, Germany Y1 - 2008 SN - 978-1-4244-1505-2 U6 - https://doi.org/10.1109/ETFA.2008.4638463 SP - 632 EP - 639 PB - IEEE CY - Piscataway, NJ ER - TY - CHAP T1 - B-AMC — broadband aeronautical multi-carrier communications T2 - Integrated Communications, Navigation and Surveillance Conference : [ICNS 2008] ; Bethesda, Md., 5 - 7 May 2008 Y1 - 2008 SN - 978-1-4244-2303-3 ; 978-1-4244-2304-0 SP - 1 EP - 12 ER -