TY  - JOUR
A1  - Kirchner, Patrick
A1  - Oberländer, Jan
A1  - Suso, Henri-Pierre
A1  - Rysstad, Gunnar
A1  - Keusgen, Michael
A1  - Schöning, Michael Josef
T1  - Towards a wireless sensor system for real-time H2O2 monitoring in aseptic food processes
JF  - Physica status solidi (a)
N2  - A wireless sensor system based on the industrial ZigBee standard for low-rate wireless networking was developed that enables real-time monitoring of gaseous H2O2 during the package sterilization in aseptic food processes. The sensor system consists of a remote unit connected to a calorimetric gas sensor, which was already established in former works, and an external base unit connected to a laptop computer. The remote unit was built up by an XBee radio frequency (RF) module for data communication and a programmable system-on-chip controller to read out the sensor signal and process the sensor data, whereas the base unit is a second XBee RF module. For the rapid H2O2 detection on various locations inside the package that has to be sterilized, a novel read-out strategy of the calorimetric gas sensor was established, wherein the sensor response is measured within the short sterilization time and correlated with the present H2O2 concentration. In an exemplary measurement application in an aseptic filling machinery, the suitability of the new, wireless sensor system was demonstrated, wherein the influence of the gas velocity on the H2O2 distribution inside a package was determined and verified with microbiological tests.
KW  - calorimetric gas sensor;hydrogen peroxide;wireless sensor system
Y1  - 2013
U6  - https://doi.org/10.1002/pssa.201200920
SN  - 1862-6319
VL  - 210
IS  - 5
SP  - 877
EP  - 883
PB  - Wiley
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Kirchner, Patrick
A1  - Reisert, Steffen
A1  - Pütz, Patrick
A1  - Keusgen, Michael
A1  - Schöning, Michael Josef
T1  - Characterisation of polymeric materials as passivation layer for calorimetric H2O2 gas sensors
JF  - Physica Status Solidi (a)
N2  - Calorimetric gas sensors for monitoring the H₂O₂ concentration at elevated temperatures in industrial sterilisation processes have been presented in previous works. These sensors are built up in form of a differential set-up of a catalytically active and passive temperature-sensitive structure. Although, various types of catalytically active dispersions have been studied, the passivation layer has to be established and therefore, chemically as well as physically characterised. In the present work, fluorinated ethylene propylene (FEP), perfluoralkoxy (PFA) and epoxy-based SU-8 photoresist as temperature-stable polymeric materials have been investigated for sensor passivation in terms of their chemical inertness against H₂O₂, their hygroscopic properties as well as their morphology. The polymeric materials were deposited via spin-coating on the temperature-sensitive structure, wherein spin-coated FEP and PFA show slight agglomerates. However, they possess a low absorption of humidity due to their hydrophobic surface, whereas the SU-8 layer has a closed surface but shows a slightly higher absorption of water. All of them were inert against gaseous H₂O₂ during the characterisation in H₂O₂ atmosphere that demonstrates their suitability as passivation layer for calorimetric H₂O₂ gas sensors.
Y1  - 2012
U6  - https://doi.org/10.1002/pssa.201100773
SN  - 1862-6319
VL  - 209
IS  - 5
SP  - 859
EP  - 863
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Kirchner, Patrick
A1  - Spelthahn, H.
A1  - Schöning, Michael Josef
A1  - Henkel, H.
A1  - Schneider, A.
A1  - Friedrich, P.
A1  - Kolstad, J.
A1  - Berger, J.
T1  - Realisierung eines Polyimid-basierten kalorimetrischen Gassensors zur Inline-Überwachung der H2O2-Konzentration in aseptischen Abfüllanlagen
JF  - Sensoren und Messsysteme 2010 [Elektronische Ressource] : Vorträge der 15. ITG/GMA-Fachtagung vom 18. bis 19. Mai 2010 in Nürnberg / Informationstechnische Gesellschaft im VDE (ITG); VDI/VDE-Gesellschaft Mess- und Automatisierungstechnik (GMA)
Y1  - 2010
SN  - 978-3-8007-3260-9
N1  - Fachtagung Sensoren und Messsysteme 15, 2010, Nürnberg ; Gesellschaft Mess- und Automatisierungstechnik
SP  - 607
EP  - 612
PB  - VDE Verlag
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Kleefeld, Andreas
T1  - The hot spots conjecture can be false: some numerical examples
JF  - Advances in Computational Mathematics
N2  - The hot spots conjecture is only known to be true for special geometries. This paper shows numerically that the hot spots conjecture can fail to be true for easy to construct bounded domains with one hole. The underlying eigenvalue problem for the Laplace equation with Neumann boundary condition is solved with boundary integral equations yielding a non-linear eigenvalue problem. Its discretization via the boundary element collocation method in combination with the algorithm by Beyn yields highly accurate results both for the first non-zero eigenvalue and its corresponding eigenfunction which is due to superconvergence. Additionally, it can be shown numerically that the ratio between the maximal/minimal value inside the domain and its maximal/minimal value on the boundary can be larger than 1 + 10− 3. Finally, numerical examples for easy to construct domains with up to five holes are provided which fail the hot spots conjecture as well.
KW  - Numerics
KW  - Boundary integral equations
KW  - Potential theory
KW  - Helmholtz equation
KW  - Interior Neumann eigenvalues
Y1  - 2021
U6  - https://doi.org/10.1007/s10444-021-09911-5
SN  - 1019-7168
VL  - 47
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - CHAP
A1  - Kleefeld, Andreas
ED  - Constanda, Christian
T1  - Numerical calculation of interior transmission eigenvalues with mixed boundary conditions
T2  - Computational and Analytic Methods in Science and Engineering
N2  - Interior transmission eigenvalue problems for the Helmholtz equation play an important role in inverse wave scattering. Some distribution properties of those eigenvalues in the complex plane are reviewed. Further, a new scattering model for the interior transmission eigenvalue problem with mixed boundary conditions is described and an efficient algorithm for computing the interior transmission eigenvalues is proposed. Finally, extensive numerical results for a variety of two-dimensional scatterers are presented to show the validity of the proposed scheme.
Y1  - 2020
SN  - 978-3-030-48185-8 (Hardcover)
U6  - https://doi.org/10.1007/978-3-030-48186-5_9
SP  - 173
EP  - 195
PB  - Birkhäuser
CY  - Cham
ER  - 
TY  - JOUR
A1  - Kleefeld, Andreas
A1  - Pieronek, J.
T1  - Elastic transmission eigenvalues and their computation via the method of fundamental solutions
JF  - Applicable Analysis
N2  - A stabilized version of the fundamental solution method to catch ill-conditioning effects is investigated with focus on the computation of complex-valued elastic interior transmission eigenvalues in two dimensions for homogeneous and isotropic media. Its algorithm can be implemented very shortly and adopts to many similar partial differential equation-based eigenproblems as long as the underlying fundamental solution function can be easily generated. We develop a corroborative approximation analysis which also implicates new basic results for transmission eigenfunctions and present some numerical examples which together prove successful feasibility of our eigenvalue recovery approach.
KW  - elastic scattering
KW  - method of fundamental solutions
KW  - Interior transmission eigenvalues
Y1  - 2020
U6  - https://doi.org/10.1080/00036811.2020.1721473
SN  - 1563-504X
VL  - 100
IS  - 16
SP  - 3445
EP  - 3462
PB  - Taylore & Francis
CY  - London
ER  - 
TY  - JOUR
A1  - Kleefeld, Andreas
A1  - Reißel, Martin
T1  - The Levenberg–Marquardt method applied to a parameter estimation problem arising from electrical resistivity tomography
JF  - Applied Mathematics and Computation
Y1  - 2011
SN  - 0096-3003
VL  - 217
IS  - 9
SP  - 4490
EP  - 4501
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Kleefeld, Andreas
A1  - Zimmermann, M.
ED  - Constanda, Christian
ED  - Bodmann, Bardo E.J.
ED  - Harris, Paul J.
T1  - Computing Elastic Interior Transmission Eigenvalues
JF  - Integral Methods in Science and Engineering
N2  - An alternative method is presented to numerically compute interior elastic transmission eigenvalues for various domains in two dimensions. This is achieved by discretizing the resulting system of boundary integral equations in combination with a nonlinear eigenvalue solver. Numerical results are given to show that this new approach can provide better results than the finite element method when dealing with general domains.
Y1  - 2022
SN  - 978-3-031-07171-3
U6  - https://doi.org/10.1007/978-3-031-07171-3_10
N1  - Corresponding author: Andreas Kleefeld
SP  - 139
EP  - 155
PB  - Birkhäuser
CY  - Cham
ER  - 
TY  - JOUR
A1  - Kleines, H.
A1  - Erki, I.
A1  - Ziemons, Karl
A1  - Zwoll, K.
ED  - Lehmann, Thomas
T1  - ATM- und Multimedia Pilotsystem im Rahmen des Projektes M-FIBRe Aufbau und Erfahrungen
JF  - Bildverarbeitung für die Medizin : Algorithmen - Systeme - Anwendungen
Y1  - 1997
SN  - 3-86073-519-5
N1  - Proceedings des Aachener Workshops am 8. u. 9. November 1996 ; PP_001 Posterpräsentation
SP  - 241
EP  - 248
PB  - Verl. der. Augustinus-Buchh.
CY  - Aachen
ER  - 
TY  - JOUR
A1  - Kloock, Joachim P.
A1  - Moreno, Lia
A1  - Bratov, A.
A1  - Huachupoma, S.
A1  - Xu, J.
A1  - Wagner, Torsten
A1  - Yoshinobu, T.
A1  - Ermolenko, Y.
A1  - Vlasov, Y. G.
A1  - Schöning, Michael Josef
T1  - PLD-prepared cadmium sensors based on chalcogenide glasses —ISFET, LAPS and μISE semiconductor structures
JF  - Sensors and Actuators B: Chemical. 118 (2006), H. 1-2
Y1  - 2006
SN  - 0925-4005
N1  - Eurosensors XIX - Eurosensors XIX - The 19th European Conference on Solid-State Transducers
SP  - 149
EP  - 155
ER  -