@article{Pieper2009, author = {Pieper, Martin}, title = {Vector hyperinterpolation on the sphere}, series = {Journal of approximation theory. 156 (2009), H. 2}, journal = {Journal of approximation theory. 156 (2009), H. 2}, isbn = {0021-9045}, pages = {173 -- 186}, year = {2009}, language = {en} } @article{PieperKlein2011, author = {Pieper, Martin and Klein, Peter}, title = {A simple and accurate numerical network flow model for bionic micro heat exchangers}, series = {Heat mass transfer}, volume = {47}, journal = {Heat mass transfer}, number = {5}, publisher = {Springer}, address = {Berlin}, isbn = {0947-7411}, pages = {491 -- 503}, year = {2011}, language = {en} } @article{PieperKlein2012, author = {Pieper, Martin and Klein, Peter}, title = {Application of simple, periodic homogenization techniques to non-linear heat conduction problems in non-periodic, porous media}, series = {Heat mass transfer}, volume = {48}, journal = {Heat mass transfer}, number = {2}, publisher = {Springer}, address = {Berlin}, issn = {0947-7411}, doi = {10.1007/s00231-011-0879-4}, pages = {291 -- 300}, year = {2012}, abstract = {Often, detailed simulations of heat conduction in complicated, porous media have large runtimes. Then homogenization is a powerful tool to speed up the calculations by preserving accurate solutions at the same time. Unfortunately real structures are generally non-periodic, which requires unpractical, complicated homogenization techniques. We demonstrate in this paper, that the application of simple, periodic techniques to realistic media, that are just close to periodic, gives accurate, approximative solutions. In order to obtain effective parameters for the homogenized heat equation, we have to solve a so called "cell problem". In contrast to periodic structures it is not trivial to determine a suitable unit cell, which represents a non-periodic media. To overcome this problem, we give a rule of thumb on how to choose a good cell. Finally we demonstrate the efficiency of our method for virtually generated foams as well as real foams and compare these results to periodic structures.}, language = {en} } @article{Pieper2008, author = {Pieper, Martin}, title = {Nonlinear integral equations for an inverse electromagnetic scattering problem}, series = {Journal of Physics Conference Series. 124 (2008)}, journal = {Journal of Physics Conference Series. 124 (2008)}, isbn = {1742-6596}, year = {2008}, language = {en} } @article{PieperIvanyshyn2008, author = {Pieper, Martin and Ivanyshyn, Olha}, title = {Nonlinear integral equations for a 3D inverse acoustic scattering problem : abstract / O. Ivanyshyn and M. Pieper}, year = {2008}, language = {en} } @article{EweKleinPieperetal.2009, author = {Ewe, Hendrik and Klein, Peter and Pieper, Martin and F{\"u}ldner, G.}, title = {Heat conductivity in sintered aluminium fibers}, series = {Cellular metals for structural and functional applications : CELLMET 2008 ; proceedings of the International Symposium on Cellular Metals for Structural and Functional Applications held October 8 - 10, 2008 in Dresden, Germany / ed. by G{\"u}nter Stephani}, journal = {Cellular metals for structural and functional applications : CELLMET 2008 ; proceedings of the International Symposium on Cellular Metals for Structural and Functional Applications held October 8 - 10, 2008 in Dresden, Germany / ed. by G{\"u}nter Stephani}, publisher = {Fraunhofer IFAM}, address = {Dresden}, pages = {187 -- 193}, year = {2009}, language = {en} } @article{Pieper2011, author = {Pieper, Martin}, title = {Multiobjective optimization with expensive objectives applied to a thermodynamic material design problem}, series = {Proceedings in applied mathematics and mechanics : PAMM. 11 (2011), H. 1}, journal = {Proceedings in applied mathematics and mechanics : PAMM. 11 (2011), H. 1}, publisher = {Wiley}, address = {Weinheim}, isbn = {1617-7061}, pages = {733 -- 734}, year = {2011}, language = {en} } @article{AlebouyehSamamiPieperBreitbachetal.2014, author = {Alebouyeh Samami, Behzad and Pieper, Martin and Breitbach, Gerd and Hodapp, Josef}, title = {Heat production in the windings of the stators of electric machines under stationary condition}, series = {Heat and mass transfer}, volume = {50}, journal = {Heat and mass transfer}, publisher = {Springer}, address = {Heidelberg}, issn = {0947-7411 (Print) ; 1432-1181 (E-Journal)}, doi = {10.1007/s00231-014-1371-8}, pages = {1707 -- 1716}, year = {2014}, abstract = {In electric machines due to high currents and resistive losses (joule heating) heat is produced. To avoid damages by overheating the design of effective cooling systems is required. Therefore the knowledge of heat sources and heat transfer processes is necessary. The purpose of this paper is to illustrate a good and effective calculation method for the temperature analysis based on homogenization techniques. These methods have been applied for the stator windings in a slot of an electric machine consisting of copper wires and resin. The key quantity here is an effective thermal conductivity, which characterizes the heterogeneous wire resin-arrangement inside the stator slot. To illustrate the applicability of the method, the analysis of a simplified, homogenized model is compared with the detailed analysis of temperature behavior inside a slot of an electric machine according to the heat generation. We considered here only the stationary situation. The achieved numerical results are accurate and show that the applied homogenization technique works in practice. Finally the results of simulations for the two cases, the original model of the slot and the homogenized model chosen for the slot (unit cell), are compared to experimental results.}, language = {en} } @inproceedings{PieperSchulz2014, author = {Pieper, Martin and Schulz, Silvia}, title = {Teaching Simulation Methods with COMSOL Multiphysics}, organization = {COMSOL Conference <2014, Cambridge>}, pages = {7}, year = {2014}, abstract = {This paper describes two courses on simulation methods for graduate students: "Simulation Methods" and "Simulation and Optimization in Virtual Engineering" The courses were planned to teach young engineers how to work with simulation software as well as to understand the necessary mathematical background. As simulation software COMSOL is used. The main philosophy was to combine theory and praxis in a way that motivates the students. In addition "soft skills" should be improved. This was achieved by project work as final examination. As underlying didactical principle the ideas of Bloom's revised taxonomy were followed. The paper basically focusses on educational aspects, e.g. how to structure the course, plan the exercises, organize the project work and include practical COMSOL examples.}, language = {en} } @article{JildehWagnerSchoeningetal.2015, author = {Jildeh, Zaid B. and Wagner, Torsten and Sch{\"o}ning, Michael Josef and Pieper, Martin}, title = {Simulating the electromagnetic-thermal treatment of thin aluminium layers for adhesion improvement}, series = {Physica status solidi (a)}, volume = {Vol. 212}, journal = {Physica status solidi (a)}, number = {6}, publisher = {Wiley}, address = {Weinheim}, issn = {1862-6319}, doi = {10.1002/pssa.201431893}, pages = {1234 -- 1241}, year = {2015}, abstract = {A composite layer material used in packaging industry is made from joining layers of different materials using an adhesive. An important processing step in the production of aluminium-containing composites is the surface treatment and consequent coating of adhesive material on the aluminium surface. To increase adhesion strength between aluminium layer and the adhesive material, the foil is heat treated. For efficient heating, induction heating was considered as state-of-the-art treatment process. Due to the complexity of the heating process and the unpredictable nature of the heating source, the control of the process is not yet optimised. In this work, a finite element analysis of the process was established and various process parameters were studied. The process was simplified and modelled in 3D. The numerical model contains an air domain, an aluminium layer and a copper coil fitted with a magnetic field concentrating material. The effect of changing the speed of the aluminium foil (or rolling speed) was studied with the change of the coil current. Statistical analysis was used for generating a general control equation of coil current with changing rolling speed.}, language = {en} }