TY - CHAP A1 - Wollert, Jörg T1 - Windows und Echtzeit? - Ein kritischer Blick auf Windows NT als Echtzeitbetriebssystem T2 - Tagungsband / 8. Int. Fachmesse und Kongress für Speicherprogrammierbare Steuerungen, Industrie-PCs und Elektrische Antriebstechnik, Nürnberg, 25. - 27. Nov. 1997; SPS IPC Drives Y1 - 1997 SN - 3-7785-2683-9 SP - 250 EP - 260 PB - Hüthig CY - Heidelberg ER - TY - CHAP A1 - Vedral, Andreas A1 - Wollert, Jörg T1 - Praktische Untersuchungen zum zeitlichen Übertragungs- und Bündelfehlerverhalten der IEEE 802.15.4 T2 - ZigBee & Co. - drahtlose Nahbereichsnetzwerke : 04. April 2006, München Y1 - 2006 PB - Design&Elektronik CY - Poing ER - TY - JOUR A1 - Wollert, Jörg T1 - Zeitsprung : Grundlagen und Marktübersicht zu Echtzeit-Betriebssystemen JF - ELRAD : Magazin für Elektronik und technische Rechneranwendungen Y1 - 1995 SN - 0170-1827 IS - H. 6 SP - 48 EP - 59 ER - TY - RPRT A1 - Wollert, Jörg T1 - MAUS - Mobile Ad-hoc Netzwerke für Userspezifische Systeme : Abschlussbericht (BMBF-Forschungsbericht) Y1 - 2010 PB - BMBF CY - Berlin ER - TY - CHAP A1 - Weingart, Daniel A1 - Schneider, Ulf A1 - Wollert, Jörg T1 - Doppelt gekoppelt - Kabellose und dynamische Anbindung von CANopen an Profinet IO T2 - Elektrische Automatisierung - Systeme und Komponenten: SPS-IPC-Drives 2009, Fachmesse & Kongress, 24. - 26. Nov. 2009, Nürnberg ; [Tagungsband] Y1 - 2009 SN - 978-3-8007-3184-8 SP - 147 EP - 154 PB - VDE-Verl. CY - Berlin [u.a.] ER - TY - RPRT A1 - Wollert, Jörg T1 - DANA - Dynamische Ad-hoc Netzwerke in der Automatisierungstechnik. Schlussbericht. Laufzeit: 01.09.2004 - 30.06.2008 (BMBF-Forschungsbericht; Förderkennzeichen 1714X04) Y1 - 2008 PB - BMBF CY - Berlin ER - TY - CHAP A1 - Buda, Aurel A1 - Vredal, Andreas A1 - Wollert, Jörg ED - Wollert, Jörg T1 - Einfache Integration von funkgestützten Kommunikationssystemen in der Automation T2 - Wireless Technologies : 9. Kongress, 18. - 19. September 2007, Stuttgart ; von der Technologie zur Anwendung Y1 - 2007 SN - 978-3-89838-084-3 SP - 189 EP - 198 PB - Aka CY - Berlin ER - TY - CHAP A1 - Wollert, Jörg T1 - Sicherheit in kabellosen Netzwerken T2 - SPS/IPC/DRIVES 2004 : SPS/IPC/DRIVES, Elektrische Automatisierung - Systeme und Komponenten, Fachmesse & Kongress, 23. - 25. Nov. 2004, Nürnberg Y1 - 2004 SN - 3-7723-6709-7 SP - 335 EP - 341 PB - Poing CY - Franzis ER - TY - JOUR A1 - Wollert, Jörg A1 - Fiedler, J. A1 - Stockmann, T. T1 - Automatisieren mit dem PC : was der Personal Computer kann und wo er passen muss JF - Elektronik : Fachmedium für industrielle Anwender und Entwickler Y1 - 1994 SN - 0013-5658 IS - Nr. 6 SP - 76 EP - 82 ER - TY - JOUR A1 - Wollert, Jörg T1 - Euros - 166 - Echtzeitentwicklungskit für den 80C166 JF - ELRAD : Magazin für Elektronik und technische Rechneranwendungen Y1 - 1995 SN - 0170-1827 IS - H. 8 SP - 32 EP - 34 ER - TY - JOUR A1 - Wollert, Jörg T1 - Bluetooth aktuell - Technik und Anwendungen ; 4: Der Bluetooth Protokoll-Stack JF - Elektronik : Fachmedium für industrielle Anwender und Entwickler Y1 - 2001 SN - 0013-5658 VL - Jg. 50 IS - Nr. 20 SP - 76 EP - 81 ER - TY - JOUR A1 - Barth, Heiko A1 - Wollert, Jörg T1 - SMARTes Konzept - von Produkt zur Fabrik JF - Facility-Management : Integration, Planung, Gebäudemanagement Y1 - 1998 SN - 0948-0048 VL - Bd. 4 IS - H. August SP - 30 EP - 35 ER - TY - CHAP A1 - Wollert, Jörg T1 - Bluetooth, WLAN und ZigBee für die Automatisierungstechnik T2 - Jahrbuch Elektrotechnik 2006 Y1 - 2005 SN - 978-3-8007-2895-4 SP - 27 EP - 41 PB - VDE Verl. CY - Berlin [u.a.] ER - TY - JOUR A1 - Wollert, Jörg T1 - Wieviel Echtzeit kann Windows? JF - IEE : elektrische Automatisierung und Antriebstechnik Y1 - 1997 SN - 1434-2898 VL - Jg. 42 IS - Nr. 9 SP - 30 EP - 37 ER - TY - JOUR A1 - Wollert, Jörg T1 - Zeitgemäß : Echtzeit-Zusatz für Windows 3.11 und Windows 95 JF - ELRAD : Magazin für Elektronik und technische Rechneranwendungen Y1 - 1996 SN - 0170-1827 IS - H. 9 SP - 96 EP - 99 ER - TY - CHAP A1 - Wollert, Jörg A1 - Vedral, Andreas T1 - Einsatz von Opensource-Software für Evaluationsprototypen : Anwendungsempfehlungen und Einsatzbeispiele T2 - Vorträge und Begleittexte zum Entwicklerforum Wireless 2002 : Technologien und Grundlagen ; 16. Mai 2002 Y1 - 2002 SP - 37 EP - 46 PB - Design & Elektronik CY - Poing ER - TY - JOUR A1 - Wollert, Jörg T1 - Bluetooth in der Klemme JF - Computer & Automation : Fachmedium der Automatisierungstechnik Y1 - 2008 SN - 1615-8512 IS - H. 10 SP - 62 EP - 67 ER - TY - JOUR A1 - Wollert, Jörg T1 - Funk-Suche : Lokalisierung und Ortsbestimmungs-Verfahren für mobile Systeme JF - Elektronik : Fachmedium für industrielle Anwender und Entwickler ; Sonderh. Wireless : Fachmedium für Entwicklungen funkbasierter Systeme Y1 - 2009 IS - H. 2 SP - 24 EP - 27 PB - Weka Fachmedien GmbH CY - Haar ER - TY - JOUR A1 - Wollert, Jörg T1 - Bluetooth: Funk für alle(s)? : 10 Jahre Bluetooth: ein Technologie-Über- und -Ausblick JF - Elektronik : Fachmedium für industrielle Anwender und Entwickler ; Sonderh. Wireless : Fachmedium für Entwicklungen funkbasierter Systeme Y1 - 2008 IS - Okt. SP - 36 EP - 43 ER - TY - JOUR A1 - Wollert, Jörg T1 - Wireless in industriellen Anwendungen JF - Elektronik : Fachmedium für industrielle Anwender und Entwickler ; Sonderh. Scout : Leitfaden für Elektronik-Entwickler Y1 - 2007 SN - 1863-3420 SP - 40 EP - 46 ER - TY - CHAP A1 - Buda, Aurel A1 - Jozenfini, B. A1 - Wollert, Jörg T1 - Mobile ad-hoc Network for home automation based on ZigBee application framework T2 - 1st European ZigBee Developer's Conference : June 18 - 20, 2007, Munich, Germany Y1 - 2007 SP - 1 EP - 5 PB - Design & Elektronik CY - Poing ER - TY - CHAP A1 - Kallweit, Stephan A1 - Gottschalk, Michael A1 - Walenta, Robert T1 - ROS based safety concept for collaborative robots in industrial applications T2 - Advances in robot design and intelligent control : proceedings of the 24th International Conference on Robotics in Alpe-Adria-Danube Region (RAAD). (Advances in intelligent systems and computing ; 371) N2 - The production and assembly of customized products increases the demand for flexible automation systems. One approach is to remove the safety fences that separate human and industrial robot to combine their skills. This collaboration possesses a certain risk for the human co-worker, leading to numerous safety concepts to protect him. The human needs to be monitored and tracked by a safety system using different sensors. The proposed system consists of a RGBD camera for surveillance of the common working area, an array of optical distance sensors to compensate shadowing effects of the RGBD camera and a laser range finder to detect the co-worker when approaching the work cell. The software for collision detection, path planning, robot control and predicting the behaviour of the co-worker is based on the Robot Operating System (ROS). A first prototype of the work cell shows that with advanced algorithms from the field of mobile robotics a very flexible safety concept can be realized: the robot not simply stops its movement when detecting a collision, but plans and executes an alternative path around the obstacle. KW - Collaborative robot KW - Human-Robot interaction KW - Safety concept KW - Workspace monitoring KW - Path planning Y1 - 2016 SN - 978-3-319-21289-0 (Print) ; 978-3-319-21290-6 (E-Book) U6 - http://dx.doi.org/10.1007/978-3-319-21290-6_3 SP - 27 EP - 35 PB - Springer CY - Cham ER - TY - BOOK A1 - Dobischat, Rolf A1 - Witt, Gerd A1 - Eich, Dieter A1 - Marschall, Herbert A1 - Thurn, Laura A1 - Kunkel, Maximilian A1 - Richter, Alina A1 - Gebhardt, Andreas T1 - 3D-Drucken in Deutschland : Entwicklungsstand, Potentiale, Herausforderungen, Auswirkungen und Perspektiven Y1 - 2015 SN - 978-3-8440-3479-0 N1 - Andreas Gebhardt: Hrsg. PB - Shaker-Verl. CY - Aachen ER - TY - JOUR A1 - Fateri, Miranda A1 - Gebhardt, Andreas T1 - Additive manufactured mechanical disentanglement lock JF - RTejournal - Forum für Rapid Technologie Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0009-2-42147 SN - 1614-0923 VL - 12 PB - Fachhochschule Aachen CY - Aachen ER - TY - CHAP A1 - Großmann, Agnes A1 - Gabrielli, Roland Antonius A1 - Herdrich, Georg A1 - Fasoulas, Stefanos A1 - Schnauffer, Peter A1 - Middendorf, Peter A1 - Fateri, Miranda A1 - Gebhardt, Andreas T1 - Overview of the MultiRob 3D Lunar Industrial Development Project T2 - Conference Contribution for the 30th ISTS, Kobe, Japan, 04.07.-10.07.2015 Y1 - 2015 ER - TY - CHAP A1 - Ferrein, Alexander A1 - Kallweit, Stephan A1 - Scholl, Ingrid A1 - Reichert, Walter T1 - Learning to Program Mobile Robots in the ROS Summer School Series T2 - Proceedings 6th International Conference on Robotics in Education (RiE 15) N2 - The main objective of our ROS Summer School series is to introduce MA level students to program mobile robots with the Robot Operating System (ROS). ROS is a robot middleware that is used my many research institutions world-wide. Therefore, many state-of-the-art algorithms of mobile robotics are available in ROS and can be deployed very easily. As a basic robot platform we deploy a 1/10 RC cart that is wquipped with an Arduino micro-controller to control the servo motors, and an embedded PC that runs ROS. In two weeks, participants get to learn the basics of mobile robotics hands-on. We describe our teaching concepts and our curriculum and report on the learning success of our students. Y1 - 2015 ER - TY - CHAP A1 - Gregorio, Fabrizio de A1 - Fatigati, Giovanni A1 - Kallweit, Stephan T1 - Tiltrotor airframe flow field characterization by SPIV T2 - 11th International Symposium on Partivle Image Velocimetry - PIV15 , Santa Barbara, California, Sept 14-16, 2015 Y1 - 2015 ER - TY - CHAP A1 - Gabrielli, Roland Antonius A1 - Seelmann, Jürgen A1 - Großmann, Agnes A1 - Herdrich, Georg A1 - Fasoulas, Stefanos A1 - Middendorf, Peter A1 - Fateri, Miranda A1 - Gebhardt, Andreas T1 - System Architecture of a Lunar Industry Plant Using Regolith T2 - Conference Contribution for the 30th ISTS, Kobe, Japan, 04.07.-10.07.2015 Y1 - 2015 ER - TY - CHAP A1 - Alhwarin, Faraj A1 - Ferrein, Alexander A1 - Gebhardt, Andreas A1 - Kallweit, Stephan A1 - Scholl, Ingrid A1 - Tedjasukmana, Osmond Sanjaya T1 - Improving additive manufacturing by image processing and robotic milling T2 - 2015 IEEE International Conference on Automation Science and Engineering (CASE), Aug 24-28, 2015 Gothenburg, Sweden Y1 - 2015 U6 - http://dx.doi.org/10.1109/CoASE.2015.7294217 SP - 924 EP - 929 ER - TY - CHAP A1 - Wiezik, P. A1 - Hötter, Jan-Steffen A1 - Gebhardt, Andreas T1 - Integration des Laserpolierens in den SLM-Prozess T2 - DVS Congress 2015, Große Schweißtechnische Tagung, DVS-Studentenkongress, Fügen von faserverstärkten Kunststoffen, Anwendungsnahe Schweißsimulation, Vorträge der Veranstaltungen, Nürnberg, DE, 15.-17. Sep, 2015 Y1 - 2015 SN - 978-3-945023-46-4 VL - 315 SP - 117 EP - 120 PB - Verl. für Schweißen und verwandte Verfahren, DVS-Verl. CY - Düsseldorf ER - TY - JOUR A1 - Wollert, Jörg T1 - IO-Link – für smarte Sensoren JF - elektroniknet.de Y1 - 2015 ER - TY - JOUR A1 - Wollert, Jörg T1 - Echtzeit-Ethernet : Protokoll-Reigen JF - elektroniknet.de Y1 - 2015 ER - TY - JOUR A1 - Kessler, Julia A1 - Balc, Nicolae A1 - Gebhardt, Andreas A1 - Abbas, Karim T1 - Basic Research on Lattice Structures Focused on the Tensile Strength JF - Applied Mechanics and Materials Y1 - 2015 U6 - http://dx.doi.org/10.4028/www.scientific.net/AMM.808.193 SN - 1662-7482 N1 - MTeM ; October 14-16, 2015, Cluj-Napoca, Romania VL - Vol. 808 SP - 193 EP - 198 PB - Trans Tech Publications CY - Bäch ER - TY - CHAP A1 - Fateri, Miranda A1 - Gebhardt, Andreas A1 - Gabrielli, Roland Antonius A1 - Herdrich, Georg A1 - Fasoulas, Stefanos A1 - Großmann, Agnes A1 - Schnauffer, Peter A1 - Middendorf, Peter T1 - Additive Manufacturing of Lunar Regolith for Extra-terrestrial Industry Plant T2 - International Symposium on Space Technology and Science (ICTS). July 2015, Kobe, Japan Y1 - 2015 ER - TY - CHAP A1 - Gabrielli, Roland Antonius A1 - Mathies, Johannes A1 - Großmann, Agnes A1 - Herdrich, Georg A1 - Fasoulas, Stefanos A1 - Middendorf, Peter A1 - Fateri, Miranda A1 - Gebhardt, Andreas T1 - Space Propulsion Considerations for a Lunar Take Off Industry Based on Regolith T2 - International Symposium on Space Technology and Science (ISTS). July 2015, Kobe, Japan Y1 - 2015 ER - TY - CHAP A1 - Fateri, Miranda A1 - Gebhardt, Andreas A1 - Renftle, Georg T1 - Additive Manufacturing of Drainage Segments for Cooling System of Crucibles Melting Furnaces T2 - International Conference and Expo on Advanced Ceramics and Composites, (ICACC). January 2015, Florida, USA N2 - The cooling process in induction based crucible melting furnaces for Industrial applications is one of the important and challenging factors in production and safety engineering. Accordingly, proper implementation of the cooling system of the furnace using optimum cooling guides and fail-safe features are critical in order to improve the safety of the process. Regarding this, manufacturing of porous material with high electrical isolation for the drainage segments of the cooling channels is examined in this study. Consequently, various geometries with different porosities using glass and ceramic powder are fabricated using Selective Laser Sintering (SLS) process. The manufactured parts are examined in a prototype furnace testing and the feasibility of the SLS manufacturing of parts for this application is discussed. Y1 - 2015 ER - TY - JOUR A1 - Pfaff, Raphael T1 - Praxisnahe Ausbildung im Fach Schienenfahrzeugtechnik JF - Deine Bahn Y1 - 2015 SN - 0172-4479 IS - 8 SP - 52 EP - 55 PB - Eisenbahn-Fachverlag CY - Mainz ER - TY - JOUR A1 - Pfaff, Raphael A1 - Schmidt, Bernd A1 - Pinders, Udo T1 - Energieeffizienz steigern durch Rekuperationseinrichtungen JF - Deine Bahn Y1 - 2015 SN - 0172-4479 IS - 5 SP - 50 EP - 53 PB - Eisenbahn-Fachverlag CY - Mainz ER - TY - CHAP A1 - Nakagawa, Masaki A1 - Michaux, Frank A1 - Kallweit, Stephan A1 - Maeda, Kazuhiro T1 - Unsteady flow measurements in the wake behind a wind-tunnel car model by using high-speed planar PIV T2 - 11TH International Symposium on Particle Image Velocimetry – PIV15 Santa Barbara, California, September 14-16, 2015 N2 - This study investigates unsteady characteristics of the wake behind a 28%-scale car model in a wind tunnel using highspeed planar particle image velocimetry (PIV). The car model is based on a hatchback passenger car that is known to have relatively high fluctuations in its aerodynamic loads. This study primarily focuses on the lateral motion of the flow on the horizontal plane to determine the effect of the flow motion on the straight-line stability and the initial steering response of the actual car on a track. This paper first compares the flow fields in the wake behind the above mentioned model obtained using conventional and high-speed planar PIV, with sampling frequencies of 8 Hz and 1 kHz, respectively. Large asymmetrically coherent flow structures, which fluctuate at frequencies below 2 Hz, are observed in the results of highspeed PIV measurements, whereas conventional PIV is unable to capture these features of the flow owing to aliasing. This flow pattern with a laterally swaying motion is represented by opposite signs of cross-correlation coefficients of streamwise velocity fluctuations for the two sides of the car model. Effects of two aerodynamic devices that are known to reduce the fluctuation levels of the aerodynamic loads are then extensively investigated. The correlation analyses reveal that these devices indeed reduce the fluctuation levels of the flow and the correlation values around the rear combination-lamp, but it is found that the effects of these devices are different around the c-pillar. Y1 - 2015 ER - TY - JOUR A1 - Gebhardt, Andreas T1 - 3D-Druck ist überall. Modische Accessoires, Kleidung, Medikamente, Nahrungsmittel, Autos, Häuser, Waffen, Büsten, Musikinstrumente - alles geht JF - Kunststoffe Y1 - 2015 SN - 0023-5563 VL - 105 IS - 10 SP - 62 EP - 70 PB - Hanser CY - München ER - TY - CHAP A1 - Kilic, S. A. A1 - Raatschen, Hans-Jürgen A1 - Astaneh-Asl, A. A1 - Apaydin, N. M. T1 - Finite element modeling of the Fatih Sultan Mehmet Suspension Bridge T2 - Multi-Span Large Bridges - Proceedings of the International Conference on Multi-Span Large Bridges Y1 - 2015 SN - 9781138027572 SP - 1169 EP - 1173 PB - CRC Press CY - Leiden ER - TY - CHAP A1 - Wollert, Jörg T1 - Industrie 4.0 - warten bis die Revolution vorbei ist? T2 - Automatisierung im Fokus von Industrie 4.0 : Tagungsband AALE 2016 ; 13. Fachkonferenz, Lübeck Y1 - 2016 SN - 978-3-8356-7312-0 N1 - AALE-Konferenz <13., 2016, Lübeck> SP - 127 EP - 136 PB - DIV Deutscher Industrieverlag GmbH CY - München ER - TY - CHAP A1 - Kallweit, Stephan A1 - Schleupen, Josef A1 - Dahmann, Peter A1 - Bagheri, Mohsen A1 - Engemann, Heiko T1 - Entwicklung eines Kletterroboters zur Diagnose und Instandsetzung von Windenergieanlagen (SMART) T2 - Automatisierung im Fokus von Industrie 4.0 : Tagungsband AALE 2016 ; 13. Fachkonferenz, Lübeck Y1 - 2016 SN - 978-3-8356-7312-0 N1 - AALE-Konferenz <13., 2016, Lübeck> SP - 207 EP - 212 PB - DIV Deutscher Industrieverlag GmbH CY - München ER - TY - CHAP A1 - Wollert, Jörg T1 - Wireless systems for machinery safety : Requirements and solutions for wireless real time systems T2 - 16th International Conference on Research and Education in Mechatronics (REM), 2015 Y1 - 2015 SN - 978-3-945728-01-7 U6 - http://dx.doi.org/10.1109/REM.2015.7380377 SP - 88 EP - 91 ER - TY - CHAP A1 - Nakagawa, Masaki A1 - Kallweit, Stephan A1 - Michaux, Frank A1 - Hojo, Teppei T1 - Typical Velocity Fields and Vortical Structures around a Formula One Car, based on Experimental Investigations using Particle Image Velocimetry T2 - SAE International Journal of Passenger Cars - Mechanical Systems Y1 - 2016 U6 - http://dx.doi.org/10.4271/2016-01-1611 SN - 1946-4002 ER - TY - JOUR A1 - Wollert, Jörg T1 - Rapid Application Development JF - Design & Elektronik N2 - Das IoT ist ohne eingebettete Systeme undenkbar. Erst kleine und kleinste Mikrocontroller mit intelligenten Kommunikationsschnittstellen und Anbindung ans Internet ermöglichen sinnvolles und flächendeckendes Einsammeln von Daten. Doch wie kompliziert ist der Einstieg in die Embedded-Welt? Dieser Artikel gibt Einblick, wie die »Arduino-Plattform« die Einstiegshürden für eingebettete Systeme dramatisch reduzieren kann. Y1 - 2016 SN - 0933-8667 IS - 4 SP - 8 EP - 11 PB - WEKA-Fachmedien CY - München ER - TY - JOUR A1 - Wollert, Jörg T1 - Industrial Internet of Things : Seifenblase oder Revolution JF - Elektronik Y1 - 2016 SN - 0013-5658 N1 - gedruckt in der Bereichsbibliothek Eupener Str. unter der Signatur Z 263 IS - 7 SP - 39 EP - 45 PB - WEKA-Fachmedien CY - München ER - TY - BOOK A1 - Gebhardt, Andreas A1 - Hötter, Jan-Steffen T1 - Additive manufacturing : 3D printing for prototyping and manufacturing Y1 - 2016 SN - 978-1-56990-582-1 ; 978-1-56990-583-8 PB - Hanser Publishers CY - Munich ER - TY - BOOK A1 - Gebhardt, Andreas A1 - Kessler, Julia A1 - Thurn, Laura T1 - 3D-Drucken: Grundlagen und Anwendungen des additive manufacturing (AM) Y1 - 2016 SN - 978-3-446-44672-4 U6 - http://dx.doi.org/10.3139/9783446448452 PB - Hanser CY - München ET - 2., neu bearbeitete und erweiterte Auflage ER - TY - JOUR A1 - Koster, Arie A1 - Scheidweiler, Robert A1 - Tieves, Martin T1 - A flow based pruning scheme for enumerative equitable coloring algorithms JF - A flow based pruning scheme for enumerative equitable coloring algorithms N2 - An equitable graph coloring is a proper vertex coloring of a graph G where the sizes of the color classes differ by at most one. The equitable chromatic number is the smallest number k such that G admits such equitable k-coloring. We focus on enumerative algorithms for the computation of the equitable coloring number and propose a general scheme to derive pruning rules for them: We show how the extendability of a partial coloring into an equitable coloring can be modeled via network flows. Thus, we obtain pruning rules which can be checked via flow algorithms. Computational experiments show that the search tree of enumerative algorithms can be significantly reduced in size by these rules and, in most instances, such naive approach even yields a faster algorithm. Moreover, the stability, i.e., the number of solved instances within a given time limit, is greatly improved. Since the execution of flow algorithms at each node of a search tree is time consuming, we derive arithmetic pruning rules (generalized Hall-conditions) from the network model. Adding these rules to an enumerative algorithm yields an even larger runtime improvement. Y1 - 2016 U6 - http://dx.doi.org/10.48550/arXiv.1607.08754 N1 - Lehrstuhl II für Mathematik, RWTH Aachen University SP - 1 EP - 30 ER -