Article
Refine
Year of publication
- 2024 (39)
- 2023 (76)
- 2022 (91)
- 2021 (109)
- 2020 (132)
- 2019 (120)
- 2018 (125)
- 2017 (108)
- 2016 (116)
- 2015 (126)
- 2014 (142)
- 2013 (139)
- 2012 (130)
- 2011 (182)
- 2010 (178)
- 2009 (199)
- 2008 (180)
- 2007 (176)
- 2006 (180)
- 2005 (188)
- 2004 (214)
- 2003 (154)
- 2002 (167)
- 2001 (157)
- 2000 (173)
- 1999 (153)
- 1998 (165)
- 1997 (154)
- 1996 (140)
- 1995 (147)
- 1994 (135)
- 1993 (107)
- 1992 (102)
- 1991 (74)
- 1990 (82)
- 1989 (79)
- 1988 (80)
- 1987 (77)
- 1986 (65)
- 1985 (59)
- 1984 (56)
- 1983 (47)
- 1982 (38)
- 1981 (39)
- 1980 (50)
- 1979 (43)
- 1978 (41)
- 1977 (22)
- 1976 (25)
- 1975 (18)
- 1974 (13)
- 1973 (6)
- 1972 (15)
- 1971 (7)
- 1970 (2)
- 1968 (2)
- 1967 (1)
Institute
- Fachbereich Medizintechnik und Technomathematik (1592)
- Fachbereich Wirtschaftswissenschaften (705)
- Fachbereich Elektrotechnik und Informationstechnik (638)
- Fachbereich Energietechnik (609)
- Fachbereich Chemie und Biotechnologie (602)
- INB - Institut für Nano- und Biotechnologien (542)
- Fachbereich Maschinenbau und Mechatronik (484)
- IfB - Institut für Bioengineering (450)
- Fachbereich Luft- und Raumfahrttechnik (379)
- Fachbereich Bauingenieurwesen (333)
Language
Document Type
- Article (5645) (remove)
Keywords
- Einspielen <Werkstoff> (7)
- Multimediamarkt (6)
- Rapid prototyping (5)
- avalanche (5)
- Earthquake (4)
- FEM (4)
- Finite-Elemente-Methode (4)
- LAPS (4)
- Rapid Prototyping (4)
- biosensors (4)
The Dry Low NOx (DLN) Micromix combustion principle with increased energy density is adapted for the industrial gas turbine APU GTCP 36-300 using hydrogen and hydrogen-rich syngas with a composition of 90%-Vol. hydrogen (H₂) and 10%-Vol. carbon-monoxide (CO). Experimental and numerical studies of several combustor geometries for hydrogen and syngas show the successful advance of the DLN Micromix combustion from pure hydrogen to hydrogen-rich syngas. The impact of the different fuel properties on the combustion principle and aerodynamic flame stabilization design laws, flow field, flame structure and emission characteristics is investigated by numerical analysis using a hybrid Eddy Break Up combustion model and validated against experimental results.
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.
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.
An overview on dry low NOx micromix combustor development for hydrogen-rich gas turbine applications
(2019)
Flexible fuel operation of a Dry-Low-NOx Micromix Combustor with Variable Hydrogen Methane Mixture
(2022)
The role of hydrogen (H2) as a carbon-free energy carrier is discussed since decades for reducing greenhouse gas emissions. As bridge technology towards a hydrogen-based energy supply, fuel mixtures of natural gas or methane (CH4) and hydrogen are possible.
The paper presents the first test results of a low-emission Micromix combustor designed for flexible-fuel operation with variable H2/CH4 mixtures. The numerical and experimental approach for considering variable fuel mixtures instead of recently investigated pure hydrogen is described.
In the experimental studies, a first generation FuelFlex Micromix combustor geometry is tested at atmospheric pressure at gas turbine operating conditions corresponding to part- and full-load. The H2/CH4 fuel mixture composition is varied between 57 and 100 vol.% hydrogen content.
Despite the challenges flexible-fuel operation poses onto the design of a combustion system, the evaluated FuelFlex Micromix prototype shows a significant low NOx performance
Absatzkanäle kaum verknüpft
(2011)
Two single-incision mini-slings used for treating urinary incontinence in women are compared with respect to the stresses they produce in their surrounding tissue. In an earlier paper we experimentally observed that these implants produce considerably different stress distributions in a muscle tissue equivalent. Here we perform 2D finite element analyses to compare the shear stresses and normal stresses in the tissue equivalent for the two meshes and to investigate their failure behavior. The results clearly show that the Gynecare TVT fails for increasing loads in a zipper-like manner because it gradually debonds from the surrounding tissue. Contrary to that, the tissue at the ends of the DynaMesh-SIS direct may rupture but only at higher loads. The simulation results are in good agreement with the experimental observations thus the computational model helps to interpret the experimental results and provides a tool for qualitative evaluation of mesh implants.
We present an electromechanically coupled computational model for the investigation of a thin cardiac tissue construct consisting of human-induced pluripotent stem cell-derived atrial, ventricular and sinoatrial cardiomyocytes. The mechanical and electrophysiological parts of the finite element model, as well as their coupling are explained in detail. The model is implemented in the open source finite element code Code_Aster and is employed for the simulation of a thin circular membrane deflected by a monolayer of autonomously beating, circular, thin cardiac tissue. Two cardio-active drugs, S-Bay K8644 and veratridine, are applied in experiments and simulations and are investigated with respect to their chronotropic effects on the tissue. These results demonstrate the potential of coupled micro- and macroscopic electromechanical models of cardiac tissue to be adapted to experimental results at the cellular level. Further model improvements are discussed taking into account experimentally measurable quantities that can easily be extracted from the obtained experimental results. The goal is to estimate the potential to adapt the presented model to sample specific cell cultures.
Thermodynamic relations between component activities and gas solubilities in binary metallic systems
(1985)
Experimentelle Ergebnisse zum Lösungsverhalten von Sauerstoff in den Systemen Cu-O-Bi und Cu-O-Pb
(1986)
Anwendung des Haustürgeschäftewiderrufsgesetzes unter Angehörigen (BGH, Urteil vom 17.09.1996)
(1997)
Das Fernabsatzgesetz
(2000)
Das Verbraucherkreditgesetz
(2001)
Mit Gesetz vom 29.7.2009 (BGBl 2009 I S. 2355) hat der deutsche Gesetzgeber die EU-Verbraucherkreditrichtlinie 2008/48/EG vom 23.4.2008 NWB PAAAD-28762 in nationales Recht umgesetzt. In diesem Gesetz ist auch der Immobiliardarlehensvertrag neu geregelt worden. Auf diese besondere Kreditform sind grds. die Vorschriften zum Verbraucherkredit anzuwenden, so dass der Darlehensgeber auch im Fall einer Immobilienfinanzierung zu vorvertraglicher Information des Verbrauchers verpflichtet ist. Beim finanzierten Immobilienerwerb werden Veräußerer und kreditgebende Bank häufig in Abstimmung und Zusammenarbeit tätig, so dass für die Bank besondere Aufklärungspflichten gegenüber dem Verbraucher entstehen. Im Fall der Verletzung dieser Pflichten drohen ihr Schadensersatzansprüche oder ein Widerrufsrecht des Verbrauchers.
Der Deutsche Bundestag und Bundesrat haben am 2.3.2012 bzw. 30.3.2012 das Gesetz gegen Kostenfallen im Internet verabschiedet, das am 1.8.2012 in Kraft treten wird. Hiermit hat der deutsche Gesetzgeber einen ersten Schritt getan, um die neue EU-Verbraucherrechterichtlinie vom 25.10.2011 (2011/83/EU, ABl L 304/64) in nationales Recht umzusetzen. Mit dieser Umsetzung ist das drängendste Problem der Kosten- und Abo-Fallen im elektronischen Geschäftsverkehr aus dem Gesamtpaket der Verbraucherrechterichtlinie herausgelöst und in dem neugefassten § 312g BGB behandelt worden. Eile bei der Umsetzung war hier geboten, weil unseriöse Unternehmen im elektronischen Rechtsverkehr zunehmend und in großem Umfang gegenüber ihren Kunden durch irreführende Gestaltungen ihrer Internetseiten verschleiern, dass die angebotenen Leistungen entgeltpflichtig sind.
Das Wohnungsrecht : Ausübungshindernis, Sozialhilferegress und Fremdvermietung bei Übergabeverträgen
(2009)
Haftung im Vereinsrecht
(2008)
Next Generation Access Networks: Why is there a higher risk of investment and how to deal with it?
(2009)
The case for a more binding WTO agreement on regulatory principles in telecommunication markets
(1999)
Veränderte Anforderungen an eine europäische Standardisierungspolitik in der Telekommunikation
(1997)
Im Jahr 2015 wurden in Deutschland über drei Millionen Benzinautos und lediglich 12.363 Elektroautos neu zugelassen. Das ursprünglich von der Bundesregierung vorgegebene Ziel, dass bis 2020 eine Million E-Autos auf deutschen Straßen fahren (und bis 2030 sechs Millionen), rückt damit in immer weitere Ferne. Um das Ziel dennoch zu erreichen, plant die Bundesregierung nun eine staatliche Prämie für den Kauf von Elektroautos: Umwelt-, Verkehrs- und Wirtschaftsministerium haben gemeinsam ein Konzept entworfen, dem zufolge private Käufer zukünftig einen Zuschuss von 5.000 Euro beim Erwerb eines Elektroautos bekommen sollen. 40 Prozent dieses Zuschusses soll von den Autoherstellern getragen werden. Das Programm, das weitere ausgabenwirksame öffentliche Maßnahmen vorsieht, würde Kosten in Milliardenhöhe verursachen. Die beabsichtigte Subventionierung wirft die Frage auf, ob diese wirtschaftlich sinnvoll sind.
Magnetic Resonance Imaging (MRI) of moving organs requires synchronization with physiological motion or flow, which dictate the viable window for data acquisition. To meet this challenge, this study proposes an acoustic gating device (ACG) that employs acquisition and processing of acoustic signals for synchronization while providing MRI compatibility, immunity to interferences with electro-magnetic and acoustic fields and suitability for MRI at high magnetic field strengths. The applicability and robustness of the acoustic gating approach is examined in a pilot study, where it substitutes conventional ECG-gating for cardiovascular MR. The merits and limitations of the ACG approach are discussed. Implications for MR imaging in the presence of physiological motion are considered including synchronization with other structure- or motion borne sounds.
Background
To demonstrate the applicability of acoustic cardiac triggering (ACT) for imaging of the heart at ultrahigh magnetic fields (7.0 T) by comparing phonocardiogram, conventional vector electrocardiogram (ECG) and traditional pulse oximetry (POX) triggered 2D CINE acquisitions together with (i) a qualitative image quality analysis, (ii) an assessment of the left ventricular function parameter and (iii) an examination of trigger reliability and trigger detection variance derived from the signal waveforms.
Results
ECG was susceptible to severe distortions at 7.0 T. POX and ACT provided waveforms free of interferences from electromagnetic fields or from magneto-hydrodynamic effects. Frequent R-wave mis-registration occurred in ECG-triggered acquisitions with a failure rate of up to 30% resulting in cardiac motion induced artifacts. ACT and POX triggering produced images free of cardiac motion artefacts. ECG showed a severe jitter in the R-wave detection. POX also showed a trigger jitter of approximately Δt = 72 ms which is equivalent to two cardiac phases. ACT showed a jitter of approximately Δt = 5 ms only. ECG waveforms revealed a standard deviation for the cardiac trigger offset larger than that observed for ACT or POX waveforms.
Image quality assessment showed that ACT substantially improved image quality as compared to ECG (image quality score at end-diastole: ECG = 1.7 ± 0.5, ACT = 2.4 ± 0.5, p = 0.04) while the comparison between ECG vs. POX gated acquisitions showed no significant differences in image quality (image quality score: ECG = 1.7 ± 0.5, POX = 2.0 ± 0.5, p = 0.34).
Conclusions
The applicability of acoustic triggering for cardiac CINE imaging at 7.0 T was demonstrated. ACT's trigger reliability and fidelity are superior to that of ECG and POX. ACT promises to be beneficial for cardiovascular magnetic resonance at ultra-high field strengths including 7.0 T.