TY - JOUR A1 - Krause, Gregor A1 - Möller, K. A1 - Meurer, D. T1 - Dielectric phenomena in semicrystalline polymers JF - IEEE Transaction on Electrical Insulation. Vol. 24 (1989), H. No. 2 Y1 - 1989 N1 - Digital Object Identifier 10.1109/14.90276 SP - 215 EP - 222 ER - TY - JOUR A1 - Krause, Gregor A1 - Meurer, D. A1 - Klee, D. T1 - Space Charge Formation Related to the Morphology of Polymers JF - ISE 6 : 6th International symposium on electrets : Papers Y1 - 1988 N1 - International Symposium on Electrets <6, 1988, Oxford> PB - IEEE CY - Piscataway, NY ER - TY - JOUR A1 - Krause, Gregor A1 - Meurer, D. A1 - Klee, D. T1 - Space charge formation related to the morphology of polymers JF - IEEE Transaction on Electrical Insulation. Vol. 24 (1989), H. No. 3 Y1 - 1989 N1 - Digital Object Identifier 10.1109/14.30883 SP - 215 EP - 222 ER - TY - JOUR A1 - Krause, Gregor A1 - Kehle, Uwe T1 - Unterstützung des Motorhochlaufs eines Pumpspeicherkraftwerks durch Mittel der Blindleistungskompensation / Uwe Kehle, Gregor Krause JF - Ertüchtigung von Kraftwerken und Netzen, insbesondere in den neuen Bundesländern. Energietechnische Gesellschaft am 20. und 21. Oktober 1993 in Mannheim Y1 - 1993 SN - 3-8007-1967-3 N1 - ETG-Fachbericht ; 47 SP - 287 EP - 296 PB - VDE-Verl. CY - Berlin [u.a.] ER - TY - JOUR A1 - Krause, Gregor A1 - Göttlich, S. A1 - Möller, K. A1 - Neubert, R. T1 - Dielektrisches Alterungsmodell hochpolymerer Isolierstoffe / S. Göttlich, G. Krause, K. Möller, R. Neubert, R. Pietsch JF - Isoliersysteme der elektrischen Energietechnik. Lebensdauer, Diagnostik und Entwicklungstendenzen ; Vorträge der ETG-Fachtagung am 26. und 27. Mai 1992 in Würzburg Y1 - 1992 SN - 3-8007-1828-6 N1 - ETG-Fachbericht ; 40 SP - 49 EP - 54 PB - vde-Verl. CY - Berlin [u.a.] ER - TY - JOUR A1 - Krause, Gregor A1 - Göttlich, S. A1 - Möller, K. A1 - Meurer, D. T1 - Space Charge Phenomena in Partially Crystalline Polymers: On-Line Measurement of Charge Carrier Motion under High AC-Field Strength / G. Krause, S. Göttlich, K. Möller, D. Meurer JF - Proceedings of the 3rd International Conference on Conduction and Breakdown in Solid Dielectrics : Trondheim, Norway ... 1989 Y1 - 1989 N1 - International Conference on Conduction and Breakdown in Solid Dielectrics <3, 1989, Trondheim> PB - IEEE CY - Piscataway, N.J. ER - TY - JOUR A1 - Krause, Gregor A1 - Fruth, Bernhard A1 - Krause, Gregor A1 - Meurer, D. T1 - Einfluß der Verarbeitungsverfahren und verarbeitungsbedingter Werkstoffzusätze auf die dielektrischen Eigenschaften von Kunststoffen / B. Fruth, G. Krause, D. Meurer, K. Möller Y1 - 1988 N1 - Ergebnisbericht 1986-87-88 Sonderforschungsbereich 106 RWTH Aachen: "Korrelation von Fertigung und Bauteileeigenschaften bei Kunststoffen" CY - Aachen ER - TY - JOUR A1 - Krause, Gregor A1 - Fruth, Bernhard T1 - Dielectric Properties of Polyolefins Stressed by High Electrical Fields. Fruth, B. ; Krause, G. Y1 - 1987 N1 - Fifth International Symposium on High Voltage Engineering : Proceedings; Braunschweig, Stadthalle, August, 24-28, 1987 / International Symposium on High Voltage Engineering <5, 1987, Braunschweig> ER - TY - JOUR A1 - Krause, Gregor A1 - Fruth, B. T1 - Dielectric Properties of Polyolefins Stressed by High Electrical Fields / Fruth, B. ; Krause, G. JF - Plenary lectures and contributions presented at the International Symposium on Polymer Materials : held in San Sebastian (Donostia), Spain, 31 August - 4 September, 1987 / symposium ed. G. M. Guzmán ; A. Santamaria Y1 - 1988 SN - 3-85739-220-7 N1 - International Symposium on Polymer Materials <1987, San Sebastián, Golfo de Vizcaya> PB - Huethig & Wepf CY - Basel ER - TY - JOUR A1 - Krause, Gregor A1 - Forsyth, Paul A. A1 - Peter, Till T1 - Robuste Filter in der Energieversorgung / Paul A. Forsyth, Gregor Krause, Till Peter JF - ETZ. 114 (1993), H. 22 Y1 - 1993 N1 - Printausgabe: Aachen Eupener Str.: 23 Z 133; Jülich: 63 ZS 035 SP - 1382 EP - 1385 ER - TY - JOUR A1 - Krause, Gregor T1 - Verhandeln statt Energiesparen? Über den Umgang mit Preisnachlässen im Energiebereich JF - extrACT: Das Magazin der Fachhochschule Aachen (2001) Y1 - 2001 SP - 22 EP - 23 ER - TY - JOUR A1 - Krause, Gregor T1 - High Field Phenomena of Polymeric Insulation Investigated at PE Needle-Plane Specimen JF - Seventh International Symposium on High Voltage Engineering : Dresden, August 26 - 30, 1991 / Technische Universität Dresden Y1 - 1991 N1 - International Symposium on High Voltage Engineering ; (7, 1991, Dresden); International Symposium on High Voltage Engineering (ISH) ; (7 : ; 1991.08.26-30 : ; Dresden) PB - TU Dresden CY - Dresden ER - TY - BOOK A1 - Krause, Gregor T1 - Leitungsmechanismen und Raumladungsphänomene in Polyolefinen bei Hochfeldbeanspruchung Y1 - 1991 SN - 3-925038-97-3 N1 - Zugl.: Aachen, Techn. Hochsch., Diss., 1991 PB - Verl. d. Augustinus-Buchh. CY - Aachen ER - TY - CHAP A1 - Krause, Gregor T1 - Brenchmarking elektrischer Energie in Zweckbauten - Aussagefähigkeit von Energiekennzahlen T2 - Betriebliches Energiemanagement : Tagung Cottbus, 6. und 7. März 2001. (VDI-Berichte ; 1593) Y1 - 2001 SN - 3180915935 SP - 413 EP - 422 PB - VDI-Verlag CY - Düsseldorf ER - TY - CHAP A1 - Krause, Gregor T1 - Energiemanagement in Gebäuden T2 - Energiemanagement in Gebäuden : 24. April 2002 : Tagung und Ausstellung Y1 - 2002 SP - 1 EP - 10 PB - Fachhochschule Aachen CY - Aachen ER - TY - JOUR A1 - Kraff, Oliver A1 - Wrede, Karsten H. A1 - Schoemberg, Tobias A1 - Dammann, Philipp A1 - Noureddine, Yacine A1 - Orzada, Stephan A1 - Ladd, Mark E. A1 - Bitz, Andreas T1 - MR safety assessment of potential RF heating from cranial fixation plates at 7 T JF - Medical Physics Y1 - 2013 U6 - http://dx.doi.org/10.1118/1.4795347 SN - 2473-4209 VL - 40 IS - 4 SP - 042302-1 EP - 042302-10 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Kraff, Oliver A1 - Bitz, Andreas A1 - Kruszona, Stefan A1 - Orzada, Stephan A1 - Schaefer, Lena C. A1 - Theysohn, Jens M. A1 - Maderwald, Stefan A1 - Ladd, Mark E. A1 - Quick, Harald H. T1 - An eight-channel phased array RF coil for spine MR imaging at 7 T JF - Investigative Radiology Y1 - 2009 U6 - http://dx.doi.org/10.1097/RLI.0b013e3181b24ab7 SN - 1536-0210 VL - 44 IS - 11 SP - 734 EP - 740 PB - Lippincott Williams & Wilkins ER - TY - JOUR A1 - Kraff, Oliver A1 - Bitz, Andreas A1 - Dammann, Philipp A1 - Ladd, Susanne C. A1 - Ladd, Mark E. A1 - Quick, Harald H. T1 - An eight-channel transmit/receive multipurpose coil for musculoskeletal MR imaging at 7 T JF - Medical Physics N2 - Purpose: MRI plays a leading diagnostic role in assessing the musculoskeletal (MSK) system and is well established for most questions at clinically used field strengths (up to 3 T). However, there are still limitations in imaging early stages of cartilage degeneration, very fine tendons and ligaments, or in locating nerve lesions, for example. 7 T MRI of the knee has already received increasing attention in the current published literature, but there is a strong need to develop new radiofrequency (RF) coils to assess more regions of the MSK system. In this work, an eight-channel transmit/receive RF array was built as a multipurpose coil for imaging some of the thus far neglected regions. An extensive coil characterization protocol and first in vivo results of the human wrist, shoulder, elbow, knee, and ankle imaged at 7 T will be presented. Methods: Eight surface loop coils with a dimension ofurn:x-wiley:00942405:media:mp7176:mp7176-math-0001 were machined from FR4 circuit board material. To facilitate easy positioning, two coil clusters, each with four loop elements, were combined to one RF transmit/receive array. An overlapped and shifted arrangement of the coil elements was chosen to reduce the mutual inductance between neighboring coils. A phantom made of body-simulating liquid was used for tuning and matching on the bench. Afterward, the S-parameters were verified on a human wrist, elbow, and shoulder. For safety validation, a detailed compliance test was performed including full wave simulations of the RF field distribution and the corresponding specific absorption rate (SAR) for all joints. In vivo images of four volunteers were assessed with gradient echo and spin echo sequences modified to obtain optimal image contrast, full anatomic coverage, and the highest spatial resolution within a reasonable acquisition time. The performance of the RF coil was additionally evaluated by in vivo B1 mapping. Results: A comparison of B1 per unit power, flip angle distribution, and anatomic images showed a fairly homogeneous excitation for the smaller joints (elbow, wrist, and ankle), while for the larger joints, the shoulder and especially the knee, B1 inhomogeneities and limited penetration depth were more pronounced. However, the greater part of the shoulder joint could be imaged.In vivo images rendered very fine anatomic details such as fascicles of the median nerve and the branching of the nerve bundles. High-resolution images of cartilage, labrum, and tendons could be acquired. Additionally, turbo spin echo (TSE) and inversion recovery sequences performed very well. Conclusions: This study demonstrates that the concept of two four-channel transmit/receive RF arrays can be used as a multipurpose coil for high-resolutionin vivo MR imaging of the musculoskeletal system at 7 T. Not only gradient echo but also typical clinical and SAR-intensive sequences such as STIR and TSE performed well. Imaging of small structures and peripheral nerves could in particular benefit from this technique. Y1 - 2010 U6 - http://dx.doi.org/10.1118/1.3517176 SN - 2473-4209 VL - 37 IS - 12 SP - 6368 EP - 6376 PB - Wiley CY - Hoboken, NJ ER - TY - JOUR A1 - Kraff, Oliver A1 - Bitz, Andreas A1 - Breyer, Tobias A1 - Kruszona, Stefan A1 - Maderwald, Stefan A1 - Brote, Irina A1 - Gizewski, Elke R. A1 - Ladd, Mark E. A1 - Quick, Harald H. T1 - A transmit/receive radiofrequency array for imaging the carotid arteries at 7 Tesla: coil design and first in vivo results JF - Investigative Radiology N2 - Objective: To develop a transmit/receive radiofrequency (RF) array for magnetic resonance imaging (MRI) of the carotid arteries at 7 T. The prototype is characterized in numerical simulations and bench measurements, and the feasibility of plaque imaging at 7 T is demonstrated in first in vivo images. Materials and Methods: The RF phased array coil consists of 8 surface loop coils. To allow imaging of both sides of the neck, the RF array is divided into 2 coil clusters, each with 4 overlapping loop elements. For safety validation, numerical computations of the RF field distribution and the corresponding specific absorption rate were performed on the basis of a heterogeneous human body model. To validate the coil model, maps of the transmit B1+ field were compared between simulation and measurement. In vivo images of a healthy volunteer and a patient (ulcerating plaque and a 50% stenosis of the right internal carotid artery) were acquired using a 3-dimensional FLASH sequence with a high isotropic spatial resolution of 0.54 mm as well as using pulse-triggered proton density (PD)/T2-weighted turbo spin echo sequences. Results: Measurements of the S-parameters yielded a reflection and isolation of the coil elements of better than −18 and −13 dB, respectively. Measurements of the g-factor indicated good image quality for parallel imaging acceleration factors up to 2.4. A similar distribution and a very good match of the absolute values were found between the measured and simulated B1+ transmit RF field for the validation of the coil model. In vivo images revealed good signal excitation of both sides of the neck and a high vessel-to-background image contrast for the noncontrast-enhanced 3-dimensional FLASH sequence. Imaging at 7 T could depict the extent of stenosis, and revealed the disruption and ulcer of the plaque. Conclusions: This study demonstrates that 2 four-channel transmit/receive RF arrays for each side of the neck is a suitable concept for in vivo MRI of the carotid arteries at 7 Tesla. Further studies are needed to explore and exploit the full potential of 7 T high-field MRI for carotid atherosclerotic plaque imaging. Y1 - 2011 U6 - http://dx.doi.org/10.1097/RLI.0b013e318206cee4 SN - 1536-0210 VL - 46 IS - 4 SP - 246 EP - 254 PB - Wolters Kluwer CY - Köln ER - TY - JOUR A1 - Kowalewski, Paul A1 - Bragard, Michael A1 - Hüning, Felix A1 - De Doncker, Rik W. T1 - An inexpensive Wiegand-sensor-based rotary encoder without rotating magnets for use in electrical drives JF - IEEE Transactions on Instrumentation and Measurement N2 - This paper introduces an inexpensive Wiegand-sensor-based rotary encoder that avoids rotating magnets and is suitable for electrical-drive applications. So far, Wiegand-sensor-based encoders usually include a magnetic pole wheel with rotating permanent magnets. These encoders combine the disadvantages of an increased magnet demand and a limited maximal speed due to the centripetal force acting on the rotating magnets. The proposed approach reduces the total demand of permanent magnets drastically. Moreover, the rotating part is manufacturable from a single piece of steel, which makes it very robust and cheap. This work presents the theoretical operating principle of the proposed approach and validates its benefits on a hardware prototype. The presented proof-of-concept prototype achieves a mechanical resolution of 4.5 ° by using only 4 permanent magnets, 2Wiegand sensors and a rotating steel gear wheel with 20 teeth. KW - Rotary encoder KW - Wiegand sensor Y1 - 2023 U6 - http://dx.doi.org/10.1109/TIM.2023.3326166 SN - 0018-9456 (Print) SN - 1557-9662 (Online) N1 - Early Access SP - 10 Seiten PB - IEEE ER -