TY - JOUR A1 - Blanke, Tobias A1 - Hagenkamp, Markus A1 - Döring, Bernd A1 - Göttsche, Joachim A1 - Reger, Vitali A1 - Kuhnhenne, Markus T1 - Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates JF - Geothermal Energy N2 - Previous studies optimized the dimensions of coaxial heat exchangers using constant mass fow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar fow types. In contrast, in this study, fow conditions in the circular ring are kept constant (a set of fxed Reynolds numbers) during optimization. This approach ensures fxed fow conditions and prevents inappropriately high or low mass fow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic efort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass fow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefcients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy diference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy fux and hydraulic efort. The Reynolds number in the circular ring is instead of the mass fow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar fow and 60% for turbulent fow scenarios. Net-exergetic optimization shows a predominant infuence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the fow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics. Y1 - 2021 U6 - http://dx.doi.org/10.1186/s40517-021-00201-3 SN - 2195-9706 N1 - Corresponding author: Tobias Blanke VL - 9 IS - Article number: 19 PB - Springer CY - Berlin ER - TY - JOUR A1 - Pieper, Martin T1 - Multiobjective optimization with expensive objectives applied to a thermodynamic material design problem JF - Proceedings in applied mathematics and mechanics : PAMM. 11 (2011), H. 1 Y1 - 2011 SN - 1617-7061 SP - 733 EP - 734 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Göttsche, Joachim A1 - Alexopoulos, Spiros A1 - Dümmler, Andreas A1 - Maddineni, S. K. T1 - Multi-Mirror Array Calculations With Optical Error N2 - The optical performance of a 2-axis solar concentrator was simulated with the COMSOL Multiphysics® software. The concentrator consists of a mirror array, which was created using the application builder. The mirror facets are preconfigured to form a focal point. During tracking all mirrors are moved simultaneously in a coupled mode by 2 motors in two axes, in order to keep the system in focus with the moving sun. Optical errors on each reflecting surface were implemented in combination with the solar angular cone of ± 4.65 mrad. As a result, the intercept factor of solar radiation that is available to the receiver was calculated as a function of the transversal and longitudinal angles of incidence. In addition, the intensity distribution on the receiver plane was calculated as a function of the incidence angles. KW - solar process heat KW - concentrating collector KW - raytracing KW - point-focussing system Y1 - 2019 SP - 1 EP - 6 ER - TY - JOUR A1 - Förster, Arnold A1 - Tillmann, K. A1 - Gerthsen, D. T1 - Morphological transformations of MBE-grown In0.6Ga0.4As island on GaAs(001) substrates / K. Tillmann ; D. Gerthsen ; P. Pfundstein ; A. Förster ... JF - Microscopy of semiconducting materials 1995 : proceedings of the Institute of Physics Conference held at Oxford University, 20 - 23 March 1995 / Ed. by A G Cullis ... - (Conference series / Institute of Physics ; 146) Y1 - 1995 SN - 0-7503-0347-6 N1 - MSM <9, 1995, Oxford> ; Institut of Physics SP - 195 EP - ff. PB - Institute of Physics CY - Bristol [u.a.] ER - TY - JOUR A1 - Rossi, Leonardo A1 - Winands, Mark H. M. A1 - Butenweg, Christoph ED - Zhang, Jessica T1 - Monte Carlo Tree Search as an intelligent search tool in structural design problems JF - Engineering with Computers : An International Journal for Simulation-Based Engineering N2 - Monte Carlo Tree Search (MCTS) is a search technique that in the last decade emerged as a major breakthrough for Artificial Intelligence applications regarding board- and video-games. In 2016, AlphaGo, an MCTS-based software agent, outperformed the human world champion of the board game Go. This game was for long considered almost infeasible for machines, due to its immense search space and the need for a long-term strategy. Since this historical success, MCTS is considered as an effective new approach for many other scientific and technical problems. Interestingly, civil structural engineering, as a discipline, offers many tasks whose solution may benefit from intelligent search and in particular from adopting MCTS as a search tool. In this work, we show how MCTS can be adapted to search for suitable solutions of a structural engineering design problem. The problem consists of choosing the load-bearing elements in a reference reinforced concrete structure, so to achieve a set of specific dynamic characteristics. In the paper, we report the results obtained by applying both a plain and a hybrid version of single-agent MCTS. The hybrid approach consists of an integration of both MCTS and classic Genetic Algorithm (GA), the latter also serving as a term of comparison for the results. The study’s outcomes may open new perspectives for the adoption of MCTS as a design tool for civil engineers. KW - Monte Carlo Tree Search KW - Structural design KW - Artificial intelligence KW - Civil engineering KW - Genetic algorithm Y1 - 2022 U6 - http://dx.doi.org/10.1007/s00366-021-01338-2 SN - 1435-5663 SN - 0177-0667 VL - 38 IS - 4 SP - 3219 EP - 3236 PB - Springer Nature CY - Cham ER - TY - JOUR A1 - Förster, Arnold A1 - Zettler, J.-T. A1 - Mikkelsen, H. A1 - Leo, K. T1 - Modulated ellipsometric measurements and transfer-matrix calculation of the field-dependent dielectric function of a multiple quantum well / J.-Th. Zettler ; H. Mikkelsen ; K. Leo ... A. Förster JF - Physical Review B . 46 (1992), H. 24 Y1 - 1992 SN - 0163-1829 N1 - 2. ISSN: 1098-0121 ; ISSN der E-Ausg.: 1095-3795 SP - 15955 EP - 15962 ER - TY - JOUR A1 - Mistler, Michael A1 - Butenweg, Christoph A1 - Meskouris, Konstantin T1 - Modelling methods of historic masonry buildings under seismic excitation JF - Journal of seismology Y1 - 2006 U6 - http://dx.doi.org/10.1007/s10950-006-9033-z SN - 1383-4649 (Print) ; 1573-157X (E-Journal) VL - Volume 10 IS - No. 4 SP - 497 EP - 510 ER - TY - JOUR A1 - Vogt, Christian A1 - Iwanowski-Strahser, Katha A1 - Marquart, Gabriele A1 - Arnold, Juliane A1 - Mottaghy, Darius A1 - Pechnig, Renate A1 - Gnjezda, Daniel A1 - Clauser, Christoph T1 - Modeling contribution to risk assessment of thermal production power for geothermal reservoirs JF - Renewable Energy Y1 - 2013 U6 - http://dx.doi.org/10.1016/j.renene.2012.11.026 SN - 0960-1481 VL - 53 SP - 230 EP - 241 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Rieke, Christian A1 - Stollenwerk, Dominik A1 - Dahmen, Markus A1 - Pieper, Martin T1 - Modeling and optimization of a biogas plant for a demand-driven energy supply JF - Energy N2 - Due to the Renewable Energy Act, in Germany it is planned to increase the amount of renewable energy carriers up to 60%. One of the main problems is the fluctuating supply of wind and solar energy. Here biogas plants provide a solution, because a demand-driven supply is possible. Before running such a plant, it is necessary to simulate and optimize the process. This paper provides a new model of a biogas plant, which is as accurate as the standard ADM1 model. The advantage compared to ADM1 is that it is based on only four parameters compared to 28. Applying this model, an optimization was installed, which allows a demand-driven supply by biogas plants. Finally the results are confirmed by several experiments and measurements with a real test plant. Y1 - 2018 U6 - http://dx.doi.org/10.1016/j.energy.2017.12.073 SN - 0360-5442 VL - 145 SP - 657 EP - 664 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Förster, Arnold A1 - Zamdmer, N. A1 - Hu, Qing A1 - Verghese, S. T1 - Mode-Discriminating Photoconductor and Coplanar Wave-Guide Circuits for Picosecond Sampling. Zamdmer, N.; Hu, Qing ; Verghese, S. ; Förster, A. JF - Applied Physics Letters. 74 (1999), H. 7 Y1 - 1999 SN - 1077-3118 SP - 1039 EP - 1041 ER - TY - JOUR A1 - Förster, Arnold A1 - Dieker, C. A1 - Gerthsen, D. T1 - Microstructure of the AlAs/GaAs and AlAs/InGaAs resonant tunneling diodes and its correlation with the electrical properties / C. Dieker ; D. Gerthsen ; A. Förster ... JF - Microscopy of semiconducting materials 1993 : proceedings of the Royal Microscopical Society Conference held at Oxford University, 5 - 8 April 1993 / ed. by A. G. Cullis ... - (Conference series / Institute of Physics ; 134) Y1 - 1993 SN - 0-7503-0290-9 N1 - Royal Microscopical Society Conference on Microscopy of Semiconducting Materials <8, 1993, Oxford> ; MSM <8, 1993, Oxford> SP - 253 EP - ff. PB - Institute of Physics CY - Bristol [u.a.] ER - TY - JOUR A1 - Hoyler, Friedrich T1 - Microscopic and semimicroscopic analysis of the reaction 27al- (p,#ga)24mg in the energy range between 20 and 45 mev JF - Physical review / C, nuclear physics. 31 (1985), H. 1 Y1 - 1985 SN - 0556-2813 SP - 17 ER - TY - JOUR A1 - Schmidt, R. A1 - Tonnesmann, A. A1 - Förster, Arnold A1 - Grimm, M. A1 - Kordos, P. A1 - Lüth, H. T1 - Metamorphic InAlAs/InGaAs HEMT's on GaAs substrates using an InP buffer layer JF - 8th IEEE International Symposium on High Performance Electron Devices for Microwave and Optoelectronic Applications : EDMO 2000 ; [13 - 14 November 2000, University of Glasgow] / organised by Department of Electronics and Electrical Engineering, University of Glasgow, Glasgow Scotland. MTT/ED/AP/LEO Societies Joint Chapter, United Kingdom and Republic of Ireland Section. With technical co-sponsorship from IEEE Electron Device Society Y1 - 2000 SN - 0-7803-6550-X N1 - EDMO <8, 2000, Glasgow> ; University / Department of Electronics and Electrical Engineering ; IEEE catalog number 00TH8534 SP - 95 EP - 98 PB - IEEE Operations Center CY - Piscataway, NJ ER - TY - JOUR A1 - Kern, Alexander A1 - Zischank, Wolfgang J. T1 - Melting effects on metal sheets and air termination wires caused by direct lightning strikes JF - Conference proceedings : Graz, Österreich, 25. - 29. April 1988 / Gesamtorganisation: Österr. Verb. für Elektrotechnik (ÖVE), Fachausschuß Blitzschutz ... [Red.: G. Diendorfer ...] Y1 - 1988 SN - 3-85133-001-3 N1 - International Conference on Lightning Protection >19, 1988, Graz> ; ICLP <19, 1988, Graz> ; Österreichischer Verband für Elektrotechnik / Fachausschuss Blitzschutz PB - Eigenverl. des ÖVE CY - Wien ER - TY - JOUR A1 - Helsper, Christoph T1 - Measurement Techniques For Ultrafine Particles JF - Ultrafine aerosols. Properties and behaviour. Proceedings of the 1. International Workshop on Ultrafine Aerosols of the Sonderforschungsbereich 209 'Stoff- und Energietransport in Aerosolen' -'Mass and energy transfer in aerosols'-, held at the Univ. of Duisburg on Sept. 29, 1986 Y1 - 1986 N1 - International Workshop on Ultrafine Aerosols ; (01) CY - Duisburg ER - TY - JOUR A1 - Butenweg, Christoph A1 - Marinkovic, Marko A1 - Kubalski, Thomas A1 - Klinkel, Sven T1 - Masonry infilled reinforced concrete frames under horizontal loading T1 - Stahlbetonrahmen mit Ausfachungen aus Mauerwerk unter horizontalen Belastungen JF - Mauerwerk N2 - The behaviour of infilled reinforced concrete frames under horizontal load has been widely investigated, both experimentally and numerically. Since experimental tests represent large investments, numerical simulations offer an efficient approach for a more comprehensive analysis. When RC frames with masonry infill walls are subjected to horizontal loading, their behaviour is highly non-linear after a certain limit, which makes their analysis quite difficult. The non-linear behaviour results from the complex inelastic material properties of the concrete, infill wall and conditions at the wall-frame interface. In order to investigate this non-linear behaviour in detail, a finite element model using a micro modelling approach is developed, which is able to predict the complex non-linear behaviour resulting from the different materials and their interaction. Concrete and bricks are represented by a non-linear material model, while each reinforcement bar is represented as an individual part installed in the concrete part and behaving elasto-plastically. Each brick is modelled individually and connected taking into account the non-linearity of a brick mortar interface. The same approach is followed using two finite element software packages and the results are compared with the experimental results. The numerical models show a good agreement with the experiments in predicting the overall behaviour, but also very good matching for strength capacity and drift. The results emphasize the quality and the valuable contribution of the numerical models for use in parametric studies, which are needed for the derivation of design recommendations for infilled frame structures. Y1 - 2016 U6 - http://dx.doi.org/10.1002/dama.201600703 SN - 1437-1022 VL - 20 IS - 4 SP - 305 EP - 312 PB - Ernst & Sohn CY - Berlin ER - TY - JOUR A1 - Hellmanns, Mark A1 - Böhm, Stefan A1 - Dilger, Klaus T1 - Manual applications of adhesives JF - Journal of adhesion and interface Y1 - 2006 VL - Vol. 7 IS - No. 4 SP - 24 EP - 27 ER - TY - JOUR A1 - Bechstedt, U. A1 - Haas, H. A1 - Hacker, U. A1 - Hardt, Arno A1 - Henn, K. A1 - Martin, S. A1 - Wimmer, J. T1 - Magnets for the German Spallation Source SNQ JF - IEEE transactions on nuclear science. Vol. 32, iss. 5 Y1 - 1985 SN - 1558-1578 (E-Journal); 0018-9499 (Print) SP - 3631 EP - 3633 ER - TY - JOUR A1 - Förster, Arnold A1 - Betko, J. A1 - Morvic, M. A1 - Novak, J. T1 - Magnetoresistance in low-temperature grown molecular-beam epitaxial GaAs. Betko, J.; Morvic, M.; Novak, J.; Förster, A.; Kordos, P. JF - Journal of Applied Physics. 86 (1999), H. 11 Y1 - 1999 SN - 1089-7550 SP - 6243 EP - 6248 ER - TY - JOUR A1 - Förster, Arnold A1 - Mikulics, M. A1 - Marso, M. A1 - Adam, R. T1 - Low-temperature-grown MBE GaAs for terahertz photomixers. Mikulics, M.; Marso, M.; Adam, R.; Fox, A.; Buca, D.; Förster, A.; Kordos, P.; Xu, Y.; Sobolewski, R. JF - 2001 Symposium on Electron Devices for Microwave and Optoelectronic Applications ; [Vienna University of Technology, Institute of Electrical Measurements and Circuit Design, 15 - 16 November 2001, Vienna, Austria ; proceedings] / EDMO 2001. Organised by: Institute of Electrical Measurements and Circuit Design, Vienna University of Technology, Austria. With technical co-sponsorship from IEEE Electron Devices Society Y1 - 2001 SN - 078037049X N1 - IEEE catalog number: 01TH8567 SP - 155 EP - 155 PB - IEEE Operations Center CY - Piscataway, NJ ER -