TY - JOUR A1 - Becker, Meike A1 - Frauenrath, Tobias A1 - Hezel, Fabian A1 - Krombach, Gabriele A. A1 - Kremer, Ute A1 - Koppers, Benedikt A1 - Butenweg, Christoph A1 - Goemmel, Andreas A1 - Utting, Jane F. A1 - Schulz-Menger, Jeanette A1 - Niendorf, Thoralf T1 - Comparison of left ventricular function assessment using phonocardiogram- and electrocardiogram-triggered 2D SSFP CINE MR imaging at 1.5 T and 3.0 T JF - European Radiology N2 - Objective: As high-field cardiac MRI (CMR) becomes more widespread the propensity of ECG to interference from electromagnetic fields (EMF) and to magneto-hydrodynamic (MHD) effects increases and with it the motivation for a CMR triggering alternative. This study explores the suitability of acoustic cardiac triggering (ACT) for left ventricular (LV) function assessment in healthy subjects (n=14). Methods: Quantitative analysis of 2D CINE steady-state free precession (SSFP) images was conducted to compare ACT’s performance with vector ECG (VCG). Endocardial border sharpness (EBS) was examined paralleled by quantitative LV function assessment. Results: Unlike VCG, ACT provided signal traces free of interference from EMF or MHD effects. In the case of correct Rwave recognition, VCG-triggered 2D CINE SSFP was immune to cardiac motion effects—even at 3.0 T. However, VCG-triggered 2D SSFP CINE imaging was prone to cardiac motion and EBS degradation if R-wave misregistration occurred. ACT-triggered acquisitions yielded LV parameters (end-diastolic volume (EDV), endsystolic volume (ESV), stroke volume (SV), ejection fraction (EF) and left ventricular mass (LVM)) comparable with those derived fromVCG-triggered acquisitions (1.5 T: ESVVCG=(56± 17) ml, EDVVCG=(151±32)ml, LVMVCG=(97±27) g, SVVCG=(94± 19)ml, EFVCG=(63±5)% cf. ESVACT= (56±18) ml, EDVACT=(147±36) ml, LVMACT=(102±29) g, SVACT=(91± 22) ml, EFACT=(62±6)%; 3.0 T: ESVVCG=(55±21) ml, EDVVCG=(151±32) ml, LVMVCG=(101±27) g, SVVCG=(96±15) ml, EFVCG=(65±7)% cf. ESVACT=(54±20) ml, EDVACT=(146±35) ml, LVMACT= (101±30) g, SVACT=(92±17) ml, EFACT=(64±6)%). Conclusions: ACT’s intrinsic insensitivity to interference from electromagnetic fields renders KW - Magnetic resonance imaging (MRI) KW - MR-stethoscope KW - Magnetic field strength KW - Left ventriular function KW - Cardiovascular MRI Y1 - 2010 U6 - http://dx.doi.org/10.1007/s00330-009-1676-z SN - 1432-1084 (Onlineausgabe) SN - 0938-7994 (Druckausgabe) VL - 20 SP - 1344 EP - 1355 PB - Springer CY - Berlin ER - TY - JOUR A1 - Funke, Harald A1 - Beckmann, Nils A1 - Keinz, Jan A1 - Abanteriba, Sylvester T1 - Comparison of Numerical Combustion Models for Hydrogen and Hydrogen-Rich Syngas Applied for Dry-Low-NOx-Micromix-Combustion JF - ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition Volume 4A: Combustion, Fuels and Emissions Seoul, South Korea, June 13–17, 2016 N2 - The Dry-Low-NOₓ (DLN) Micromix combustion technology has been developed as low emission combustion principle for industrial gas turbines fueled with hydrogen or syngas. The combustion process is based on the phenomenon of jet-in-crossflow-mixing. Fuel is injected perpendicular into the air-cross-flow and burned in a multitude of miniaturized, diffusion-like flames. The miniaturization of the flames leads to a significant reduction of NOₓ emissions due to the very short residence time of reactants in the flame. In the Micromix research approach, CFD analyses are validated towards experimental results. The combination of numerical and experimental methods allows an efficient design and optimization of DLN Micromix combustors concerning combustion stability and low NOₓ emissions. The paper presents a comparison of several numerical combustion models for hydrogen and hydrogen-rich syngas. They differ in the complexity of the underlying reaction mechanism and the associated computational effort. For pure hydrogen combustion a one-step global reaction is applied using a hybrid Eddy-Break-up model that incorporates finite rate kinetics. The model is evaluated and compared to a detailed hydrogen combustion mechanism derived by Li et al. including 9 species and 19 reversible elementary reactions. Based on this mechanism, reduction of the computational effort is achieved by applying the Flamelet Generated Manifolds (FGM) method while the accuracy of the detailed reaction scheme is maintained. For hydrogen-rich syngas combustion (H₂-CO) numerical analyses based on a skeletal H₂/CO reaction mechanism derived by Hawkes et al. and a detailed reaction mechanism provided by Ranzi et al. are performed. The comparison between combustion models and the validation of numerical results is based on exhaust gas compositions available from experimental investigation on DLN Micromix combustors. The conducted evaluation confirms that the applied detailed combustion mechanisms are able to predict the general physics of the DLN-Micromix combustion process accurately. The Flamelet Generated Manifolds method proved to be generally suitable to reduce the computational effort while maintaining the accuracy of detailed chemistry. Especially for reaction mechanisms with a high number of species accuracy and computational effort can be balanced using the FGM model. Y1 - 2016 SN - 978-0-7918-4975-0 U6 - http://dx.doi.org/10.1115/GT2016-56430 PB - ASME CY - New York, NY ER - TY - JOUR A1 - Funke, Harald A1 - Beckmann, Nils A1 - Keinz, Jan A1 - Abanteriba, Sylvester T1 - Comparison of Numerical Combustion Models for Hydrogen and Hydrogen-Rich Syngas Applied for Dry-Low-Nox-Micromix-Combustion JF - Journal of Engineering for Gas Turbines and Power N2 - The Dry-Low-NOx (DLN) Micromix combustion technology has been developed as low emission combustion principle for industrial gas turbines fueled with hydrogen or syngas. The combustion process is based on the phenomenon of jet-in-crossflow-mixing (JICF). Fuel is injected perpendicular into the air-cross-flow and burned in a multitude of miniaturized, diffusion-like flames. The miniaturization of the flames leads to a significant reduction of NOx emissions due to the very short residence time of reactants in the flame. In the Micromix research approach, computational fluid dynamics (CFD) analyses are validated toward experimental results. The combination of numerical and experimental methods allows an efficient design and optimization of DLN Micromix combustors concerning combustion stability and low NOx emissions. The paper presents a comparison of several numerical combustion models for hydrogen and hydrogen-rich syngas. They differ in the complexity of the underlying reaction mechanism and the associated computational effort. The performance of a hybrid eddy-break-up (EBU) model with a one-step global reaction is compared to a complex chemistry model and a flamelet generated manifolds (FGM) model, both using detailed reaction schemes for hydrogen or syngas combustion. Validation of numerical results is based on exhaust gas compositions available from experimental investigation on DLN Micromix combustors. The conducted evaluation confirms that the applied detailed combustion mechanisms are able to predict the general physics of the DLN-Micromix combustion process accurately. The FGM method proved to be generally suitable to reduce the computational effort while maintaining the accuracy of detailed chemistry. Y1 - 2018 U6 - http://dx.doi.org/10.1115/1.4038882 SN - 0742-4795 N1 - Article number 081504; Paper No: GTP-17-1567 VL - 140 IS - 8 PB - ASME CY - New York, NY ER - TY - CHAP A1 - Leise, Philipp A1 - Simon, Nicolai A1 - Altherr, Lena T1 - Comparison of Piecewise Linearization Techniques to Model Electric Motor Efficiency Maps: A Computational Study T2 - Operations Research Proceedings 2019 N2 - To maximize the travel distances of battery electric vehicles such as cars or buses for a given amount of stored energy, their powertrains are optimized energetically. One key part within optimization models for electric powertrains is the efficiency map of the electric motor. The underlying function is usually highly nonlinear and nonconvex and leads to major challenges within a global optimization process. To enable faster solution times, one possibility is the usage of piecewise linearization techniques to approximate the nonlinear efficiency map with linear constraints. Therefore, we evaluate the influence of different piecewise linearization modeling techniques on the overall solution process and compare the solution time and accuracy for methods with and without explicitly used binary variables. KW - MINLP KW - Powertrain KW - Piecewise linearization KW - Efficiency optimization Y1 - 2020 SN - 978-3-030-48439-2 SN - 978-3-030-48438-5 U6 - http://dx.doi.org/10.1007/978-3-030-48439-2_55 N1 - Annual International Conference of the German Operations Research Society (GOR), Dresden, Germany, September 4-6, 2019 SP - 457 EP - 463 PB - Springer CY - Cham ER - TY - CHAP A1 - Latzke, Markus A1 - Alexopoulos, Spiros A1 - Kronhardt, Valentina A1 - Rendón, Carlos A1 - Sattler, Johannes, Christoph T1 - Comparison of Potential Sites in China for Erecting a Hybrid Solar Tower Power Plant with Air Receiver T2 - Energy Procedia Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.egypro.2015.03.142 SN - 1876-6102 N1 - International Conference on Concentrating Solar Power and Chemical Energy Systems, SolarPACES 2014, Beijing, China SP - 1327 EP - 1334 ER - TY - JOUR A1 - Kern, Alexander A1 - Thomsen, M. T1 - Comparison of single point and equipotential bonding for I&C systems of large-area industrial sites JF - Volume of proceedings : Budapest, Hungary, September 19-23, 1994 / organized by: Technical University of Budapest Y1 - 1994 N1 - International Conference on Lightning Protection <22, 1994, Budapest> ; ICLP <22, 1994, Budapest> ; Budapesti Műszaki Egyetem PB - Techn. Univ. CY - Budapest ER - TY - JOUR A1 - Späte, Frank A1 - Faber, Christian A1 - Schwarzer, Klemens A1 - Hartz, Thomas T1 - Comparison of solar hot water systems in solar settlements - decentralized or centralized systems? JF - Proceedings / organised by: ISES Europe ... [Ed.: Deutsche Gesellschaft für Sonnenenergie e.V. - DGS, Munich ; PSE GmbH - Forschung Entwicklung Marketing, Freiburg]. - Vol. 1 Y1 - 2004 SN - 3-9809656-1-9 N1 - EuroSun <5, 2004, Freiburg, Breisgau> ; Internationales Sonnenforum <14, 2004, Freiburg, Breisgau> ; Deutsche Gesellschaft für Sonnenenergie SP - 1-666-1-671 PB - PSE CY - Freiburg [Breisgau] ER - TY - CHAP A1 - Alexopoulos, Spiros A1 - Hoffschmidt, Bernhard A1 - Rau, Christoph T1 - Comparison of steady-state and transient simulations for solar tower power plants with open-volumetric receiver T2 - SolarPACES 2011 : concentrating solar power and chemical energy systems : 20 - 23 September, 2011, Granada, Spain Y1 - 2011 CY - Granada ER - TY - JOUR A1 - Kern, Alexander A1 - Roth, J. A1 - Wiedmann, J. T1 - Comparison of the damage for various types of fibre reinforced composites due to different lightning test standards (MIL-STD 1757 A, German military VG-standard 96903) JF - Proceedings of the 1992 International Aerospace and Ground Conference on Lightning and Static Electricity : October 6-8, 1992, Trump Taj Mahal, Atlantic City, NJ. Y1 - 1992 N1 - International Conference on Lightning and Static Electricity <1992, Atlantic City, NJ> PB - U.S. Dept. of Transportation, Federal Aviation Administration CY - [Atlantic City, N.J.] ER - TY - JOUR A1 - Kaminsky, Randolph A1 - Weber, Hans-Joachim A1 - Simons, Antoine A1 - Kallweit, Stephan A1 - Kramm, K. A1 - Verdonck, Pascale T1 - Comparison of the flow downstream two prototypes of a new monoleaflet artificial aortic heart valve by means of PIV visualization JF - Computer methods in biomechanics and biomedical engineering. 8 (2005), H. 4, Suppl. 1 Y1 - 2005 SN - 1476-8259 SP - 159 EP - 160 ER -