TY  - JOUR
A1  - Hirschfeld, Julian A.
A1  - Lustfeld, Hans
A1  - Reißel, Martin
A1  - Steffen, Bernhard
T1  - Tomographic diagnostics of current distributions in a fuel cell stack
JF  - International Journal of Energy Research
N2  - A novel tomographic scheme for analysing the state of any single membrane electrode assembly (MEA) in a stack is suggested. Plates of very high conductivity placed between every fuel cell and slitted in an appropriate manner cause surface currents at well-defined locations of the stack. We show that knowing these surface currents, information about anomalies of the currents in a MEA can be obtained using the methods of tomography. The results are mathematically not unique. However, when assuming plausible defect structures, one can exclude improbable deficiencies by applying a special form of simulated annealing. We present numerical calculations of typical examples demonstrating that the essential defects of the MEA in any single cell of the stack can be detected and their extent can be determined.
Y1  - 2010
U6  - https://doi.org/10.1002/er.1634
SN  - 0363-907X
VL  - 34
IS  - 3
SP  - 284
EP  - 292
PB  - Wiley
CY  - London
ER  - 
TY  - JOUR
A1  - Heinrichs, U.
A1  - Pietrzyk, Uwe
A1  - Ziemons, Karl
T1  - Design optimization of the PMT-ClearPET prototypes based on simulation studies with GEANT3
JF  - IEEE Transactions on Nuclear Science
N2  - Within the Crystal Clear Collaboration (CCC), four centers are developing second generation high performance small animal positron emission tomography (PET) scanners for different kinds of animals and medical applications. The first prototypes are photomultiplier tube (PMT)-based systems including depth of interaction (DOI) detection by using a phoswich layer of lutetium oxyorthosilicate (LSO) and lutetium yttrium aluminum perovskite (LuYAP). The aim of these simulation studies is to optimize sensitivity and spatial resolution of given designs, which vary in fields of view (FOVs) caused by different detector configurations (ring/octagon) and sizes. For this purpose the simulation tool GEANT3 (CERN, Geneva, Switzerland) was used.
Y1  - 2003
SN  - 0018-9499
VL  - 50
IS  - 5
SP  - 1428
EP  - 1432
ER  - 
TY  - THES
A1  - Emonts, Jessica
T1  - Searching for many defective edges in hypergraphs
Y1  - 2013
N1  - Ist auch als Online-Ausgabe erschienen: Emonts, Jessica: Searching for many defective edges in hypergraphs
PB  - Rheinisch-Westfälischen Technischen Hochschule Aachen
CY  - Aachen
ER  - 
TY  - JOUR
A1  - Müller, Martin
A1  - Hirschfeld, Julian A.
A1  - Lambertz, Rita
A1  - Schulze Lohoff, Andreas
A1  - Lustfeld, Hans
A1  - Pfeifer, Heinz
A1  - Reißel, Martin
T1  - Validation of a novel method for detecting and stabilizing malfunctioning areas in fuel cell stacks
JF  - Journal of power sources
N2  - In this paper a setup for detecting malfunctioning areas of MEAs in fuel cell stacks is described. Malfunctioning areas generate electric cross currents inside bipolar plates. To exploit this we suggest bipolar plates consisting not of two but of three layers. The third one is a highly conducting layer and segmented such that the cross currents move along the segments to the surface of the stack where they can be measured by an inductive sensor. With this information a realistic model can be used to detect the malfunctioning area. Furthermore the third layer will prevent any current inhomogeneity of a malfunctioning cell to spread to neighbouring cells in the stack. In this work the results of measurements in a realistic cell setup will be compared with the results obtained in simulation studies with the same configuration. The basis for the comparison is the reliable characterisation of the electrical properties of the cell components and the implication of these results into the simulation model. The experimental studies will also show the limits in the maximum number of segments, which can be used for a reliable detection of cross currents.
Y1  - 2014
U6  - https://doi.org/10.1016/j.jpowsour.2014.08.045
SN  - 1873-2755 (E-Journal); 0378-7753 (Print)
VL  - 272
SP  - 225
EP  - 232
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Mang, Thomas
A1  - Hodenius, Michael A. J.
A1  - Schmitz-Rode, Thomas
A1  - Baumann, Martin
A1  - Ivanova, Gergana
A1  - Wong, John Erik
A1  - Haulena, Friedhelm
A1  - Soenen, Stefaan J. H.
A1  - de Cuyper, Marcel
T1  - Absorption of 10-hydroxycamptothecin into the coat of magnetoliposomes / Hodenius, M. A. J. ; Schmitz-Rode, T. ; Baumann, M. ; Ivoanova, G. ; Wong, J. E. ; Mang, T. ; Haulena, F. ; Soenen, S. J. H. ; De Cuyper, M.
JF  - Colloids and Surfaces A: Physicochemical and Engineering Aspects. 343 (2009), H. 1-3
Y1  - 2009
SN  - 0927-7757
N1  - Colloid and Surface Science for Nanotechnology
SP  - 20
EP  - 23
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Reißel, Martin
A1  - Lustfeld, Hans
A1  - Hirschfeld, Julian A.
A1  - Steffen, Bernhard
T1  - Uniqueness of magnetotomography for fuel cells and fuel cell stacks / Lustfeld, H. ; Hirschfeld, J. ; Reißel, M ; Steffen, B.
JF  - Journal of Physics A: Mathematical and Theoretical. 42 (2009), H.  495205
Y1  - 2009
SN  - 0022-3689
SP  - 9 S.
ER  - 
TY  - JOUR
A1  - Reißel, Martin
A1  - Lustfeld, Hans
A1  - Steffen, Bernhard
A1  - Schmidt, U.
T1  - Reconstruction of Electric Currents in a Fuel Cell by Magnetic Field Measurements / Lustfeld, H. ; Reißel, M. ; Steffen, B. ; Schmidt, U.
JF  - Journal of fuel cell science and technology
Y1  - 2009
SN  - 1550-624X
VL  - Vol. 6
IS  - Iss. 2
SP  - 021012-1
EP  - 021012-8
ER  - 
TY  - JOUR
A1  - Reißel, Martin
A1  - Hirschfeld, Julian A.
A1  - Lustfeld, Hans
A1  - Steffen, Bernhard
T1  - Magnetotomography and Electric Currents in a Fuel Cell / Lustfeld, H. ; Reißel, M. ; Steffen, B.
JF  - Fuel Cells. 9 (2009), H. 4
Y1  - 2009
SN  - 1615-6854
SP  - 474
EP  - 481
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Lustfeld, Hans
A1  - Hirschfeld, Julian A.
A1  - Reißel, Martin
A1  - Steffen, Bernhard
T1  - Enhancement of precision and reduction of measuring points in tomographic reconstructions
JF  - Physics Letters A
Y1  - 2011
SN  - 0375-9601
VL  - 375
IS  - 8
SP  - 1167
EP  - 1171
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Heinrichs, U.
A1  - Pietrzyk, Uwe
A1  - Ziemons, Karl
T1  - Design optimization of the PMT-ClearPET prototypes based on simulation studies with GEANT3
JF  - 2002 IEEE Nuclear Science Symposium Conference Record, Vol. 3
N2  - Within the Crystal Clear Collaboration four centres are developing 2nd generation high performance small animal PET scanners for different kinds of animals and medical applications. The first prototypes are PMT-based systems including depth of interaction (DOI) detection by using a phoswich layer of LSO and LuYAP. The aim of these simulation studies is to optimize sensitivity and spatial resolution of given designs, which vary in FOVs caused by different detector configurations (ring/octagon) and sizes. For this purpose the simulation tool GEANT3 (CERN) was used. The simulations have shown that all PMT designs with one-to-one coupling of crystals have a very nonlinear axial sensitivity profile. By shifting every other PMT 1/4 of a PMT length in axial direction the sampling of the FOVs became more homogeneous. At an energy threshold of 350keV the regression coefficient increases from 0.818 for the non-shifted to 0.993 for the shifted design. Simulations of a point source centred in the FOV (threshold: 350keV) resulted in sensitivities of 4.2% for a 4×20PMT (LSO/LuYAP a 10mm) and 3.8% for a 4×16PMT (LSO/LuYAP a 8mm) ring design. The 3D-MLEM reconstruction of a point source shows the enormous improvement of resolution using a crystal double layer with DOI (3.1mm at 40mm from CFOV) instead of a 20mm single layer (11.9mm).
Y1  - 2003
SN  - 1082-3654
SP  - 682
EP  - 686
ER  -