Refine
Year of publication
- 2024 (14)
- 2023 (29)
- 2022 (19)
- 2021 (27)
- 2020 (29)
- 2019 (44)
- 2018 (44)
- 2017 (37)
- 2016 (35)
- 2015 (36)
- 2014 (43)
- 2013 (43)
- 2012 (41)
- 2011 (40)
- 2010 (36)
- 2009 (38)
- 2008 (41)
- 2007 (39)
- 2006 (27)
- 2005 (25)
- 2004 (35)
- 2003 (33)
- 2002 (29)
- 2001 (33)
- 2000 (34)
- 1999 (31)
- 1998 (28)
- 1997 (34)
- 1996 (25)
- 1995 (22)
- 1994 (21)
- 1993 (18)
- 1992 (13)
- 1991 (14)
- 1990 (9)
- 1989 (17)
- 1988 (11)
- 1987 (8)
- 1986 (9)
- 1985 (9)
- 1984 (3)
- 1983 (7)
- 1982 (4)
- 1981 (3)
- 1980 (12)
- 1979 (6)
- 1978 (7)
- 1977 (1)
- 1976 (7)
- 1975 (3)
- 1974 (4)
- 1973 (1)
- 1972 (3)
- 1971 (2)
- 1970 (1)
Institute
- Fachbereich Elektrotechnik und Informationstechnik (1184) (remove)
Language
- English (719)
- German (464)
- Multiple languages (1)
Document Type
- Article (637)
- Conference Proceeding (302)
- Book (114)
- Part of a Book (64)
- Patent (17)
- Report (9)
- Other (8)
- Conference: Meeting Abstract (6)
- Contribution to a Periodical (6)
- Course Material (6)
Keywords
- Multimediamarkt (7)
- Enterprise Architecture (5)
- MINLP (5)
- Engineering optimization (4)
- Gamification (4)
- Serious Game (4)
- Auslenkung (3)
- Digitale Transformation (3)
- Digitalisierung (3)
- Education (3)
This paper covers the use of the magnetic Wiegand effect to design an innovative incremental encoder. First, a theoretical design is given, followed by an estimation of the achievable accuracy and an optimization in open-loop operation.
Finally, a successful experimental verification is presented. For this purpose, a permanent magnet synchronous machine is controlled in a field-oriented manner, using the angle information of the prototype.
As the field strength and, therefore, the operational frequency in MRI is increased, the wavelength approaches the size of the human head/body, resulting in wave effects, which cause signal decreases and dropouts. Several multichannel approaches have been proposed to try to tackle these problems, including RF shimming, where each element in an array is driven by its own amplifier and modulated with a certain (constant) amplitude and phase relative to the other elements, and Transmit SENSE, where spatially tailored RF pulses are used. In this article, a relatively inexpensive and easy to use imaging scheme for 7 Tesla imaging is proposed to mitigate signal voids due to B1 field inhomogeneity. Two time-interleaved images are acquired using a different excitation mode for each. By forming virtual receive elements, both images are reconstructed together using GRAPPA to achieve a more homogeneous image, with only small SNR and SAR penalty in head and body imaging at 7 Tesla.
Purpose
To calculate local specific absorption rate (SAR) correctly, both the amplitude and phase of the signal in each transmit channel have to be known. In this work, we propose a method to derive a conservative upper bound for the local SAR, with a reasonable safety margin without knowledge of the transmit phases of the channels.
Methods
The proposed method uses virtual observation points (VOPs). Correction factors are calculated for each set of VOPs that prevent underestimation of local SAR when the VOPs are applied with the correct amplitudes but fixed phases.
Results
The proposed method proved to be superior to the worst-case calculation based on the maximum eigenvalue of the VOPs. The mean overestimation for six coil setups could be reduced, whereas no underestimation of the maximum local SAR occurred. In the best investigated case, the overestimation could be reduced from a factor of 3.3 to a factor of 1.7.
Conclusion
The upper bound for the local SAR calculated with the proposed method allows a fast estimation of the local SAR based on power measurements in the transmit channels and facilitates SAR monitoring in systems that do not have the capability to monitor transmit phases