The Experts below are selected from a list of 7368 Experts worldwide ranked by ideXlab platform
Jurgen Hennig - One of the best experts on this subject based on the ideXlab platform.
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magnetization preparation during the steady state fat saturated 3d truefisp
Magnetic Resonance in Medicine, 2001Co-Authors: K Scheffler, Oliver Heid, Jurgen HennigAbstract:A novel fat Saturation scheme is proposed which combines spectral fat Saturation with a steady-state 3D true Fast Imaging with Steady Precesson (TrueFISP) sequence. Fat Saturation consisted of a conventional frequency-selective excitation pulse surrounded by spoiler gradients. This Saturation Block was periodically repeated within a continuously running TrueFISP sequence. Except for the fat signals, the steady-state signal formation and the resulting image contrast of TrueFISP was not modified by the periodically inserted fat Saturation Block. This was achieved by a α/2 flip-back pulse before the fat Saturation Block, which stores the established steady-state transverse magnetization as pure longitudinal magnetization. After fat Saturation this longitudinal magnetization was excited by a α/2 preparation pulse to continue the TrueFISP acquisition. The resulting images show contrast identical to conventional TrueFISP images, but without the usually very bright fat signals. The short repetition time allows acquisition of a 3D data set of the abdomen within a single breath-hold. Magn Reson Med 45:1075–1080, 2001. © 2001 Wiley-Liss, Inc.
Al-turki Y.a. - One of the best experts on this subject based on the ideXlab platform.
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New sogi-fll grid frequency monitoring with a finite state machine approach for better response in the face of voltage sag and swell faults
'MDPI AG', 2020Co-Authors: Abdali Nejad Sajad, Matas Alcalá José, Martín Cañadas, María Elena, Jordi De La ,hoz Casas, Al-turki Y.a.Abstract:The SOGI-FLL (Second-Order Generalized Integrator–Frequency-Locked Loop) is a well-known and simple adaptive filter that allows for estimating the parameters of grid voltage with a small computational burden. However, the SOGI-FLL has been shown to be especially sensitive to voltage sags and voltage swells, which deeply distort the estimated parameters, especially the frequency. This problem can be alleviated by simply using a Saturation Block at the Frequency-Locked Loop (FLL) output to limit the impact of distortion on the estimated frequency. Improving upon this straightforward approach, in this paper we propose the use of a finite state machine (FSM) for the definition of the different states of the SOGI-FLL frequency response during a voltage sag or swell fault. The FSM approach allows for applying different gains during the fault, enhancing the SOGI-FLL transient response. The performance of the FSM-based SOGI-FLL is evaluated by using simulation results, which show a better and faster response to these kinds of faultsPeer ReviewedPostprint (published version
K Scheffler - One of the best experts on this subject based on the ideXlab platform.
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magnetization preparation during the steady state fat saturated 3d truefisp
Magnetic Resonance in Medicine, 2001Co-Authors: K Scheffler, Oliver Heid, Jurgen HennigAbstract:A novel fat Saturation scheme is proposed which combines spectral fat Saturation with a steady-state 3D true Fast Imaging with Steady Precesson (TrueFISP) sequence. Fat Saturation consisted of a conventional frequency-selective excitation pulse surrounded by spoiler gradients. This Saturation Block was periodically repeated within a continuously running TrueFISP sequence. Except for the fat signals, the steady-state signal formation and the resulting image contrast of TrueFISP was not modified by the periodically inserted fat Saturation Block. This was achieved by a α/2 flip-back pulse before the fat Saturation Block, which stores the established steady-state transverse magnetization as pure longitudinal magnetization. After fat Saturation this longitudinal magnetization was excited by a α/2 preparation pulse to continue the TrueFISP acquisition. The resulting images show contrast identical to conventional TrueFISP images, but without the usually very bright fat signals. The short repetition time allows acquisition of a 3D data set of the abdomen within a single breath-hold. Magn Reson Med 45:1075–1080, 2001. © 2001 Wiley-Liss, Inc.
Fariborz Lohrabi Pour - One of the best experts on this subject based on the ideXlab platform.
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indirect dc advanced vector control based on anti Saturation Block and voltage limitation
Iranian Conference on Electrical Engineering, 2014Co-Authors: Behzad Salmani, Mohammad Bagher Bana Sharifian, Fariborz Lohrabi PourAbstract:This paper investigates an indirect DC vector control based on anti-Saturation current controller and voltage limitation considering to voltage limitation. We investigate a novel method based on anti-Saturation Block that combined with the advanced vector control to improve problems of the PMSM (Permanent magnet synchronous machine) control methods. Also it is used to avoid Saturation of the stator current and the inverter voltage controller that don't allow these controllers to going to Saturation at high speeds. And it can eliminate the error between the input and the output. Generating the references voltages from the obtained references current causes the lack of proper coupling between the d-axis and q-axis. Control in a wide range of speed, increase the speed due to use the voltage limitation, no need to the high speed estimator opposite of the direct vector controller, avoid Saturation of the controllers and reduce costs by remove the estimator and control the current ripple in appropriate value are advantages of the indirect vector control, also this method makes independent and proper control of the flux and torque. To assess and confirm the performance of the proposed system, the system is simulated by MATLAB / SIMULINK.
Abdali Nejad Sajad - One of the best experts on this subject based on the ideXlab platform.
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New sogi-fll grid frequency monitoring with a finite state machine approach for better response in the face of voltage sag and swell faults
'MDPI AG', 2020Co-Authors: Abdali Nejad Sajad, Matas Alcalá José, Martín Cañadas, María Elena, Jordi De La ,hoz Casas, Al-turki Y.a.Abstract:The SOGI-FLL (Second-Order Generalized Integrator–Frequency-Locked Loop) is a well-known and simple adaptive filter that allows for estimating the parameters of grid voltage with a small computational burden. However, the SOGI-FLL has been shown to be especially sensitive to voltage sags and voltage swells, which deeply distort the estimated parameters, especially the frequency. This problem can be alleviated by simply using a Saturation Block at the Frequency-Locked Loop (FLL) output to limit the impact of distortion on the estimated frequency. Improving upon this straightforward approach, in this paper we propose the use of a finite state machine (FSM) for the definition of the different states of the SOGI-FLL frequency response during a voltage sag or swell fault. The FSM approach allows for applying different gains during the fault, enhancing the SOGI-FLL transient response. The performance of the FSM-based SOGI-FLL is evaluated by using simulation results, which show a better and faster response to these kinds of faultsPeer ReviewedPostprint (published version
