@article{MoretAlkemadeUpcraftetal.2020, author = {Moret, J.L.T.M. and Alkemade, J. and Upcraft, T.M. and Paulßen, Elisabeth and Wolterbeek, H.T. and Ommen, J.R. van and Denkova, A.G.}, title = {The application of atomic layer deposition in the production of sorbents for ⁹⁹Mo/⁹⁹ᵐTc generator}, series = {Applied Radiation and Isotopes}, volume = {164}, journal = {Applied Radiation and Isotopes}, number = {109266}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0969-8043}, doi = {10.1016/j.apradiso.2020.109266}, pages = {9}, year = {2020}, abstract = {New production routes for ⁹⁹Mo are steadily gaining importance. However, the obtained specific activity is much lower than currently produced by the fission of U-235. To be able to supply hospitals with ⁹⁹Mo/⁹⁹ᵐTc generators with the desired activity, the adsorption capacity of the column material should be increased. In this paper we have investigated whether the gas phase coating technique Atomic Layer Deposition (ALD), which can deposit ultra-thin layers on high surface area materials, can be used to attain materials with high adsorption capacity for ⁹⁹Mo. For this purpose, ALD was applied on a silica-core sorbent material to coat it with a thin layer of alumina. This sorbent material shows to have a maximum adsorption capacity of 120 mg/g and has a ⁹⁹ᵐTc elution efficiency of 55 ± 2\% based on 3 executive elutions.}, language = {en} } @article{WeberEnglhardArentetal.2019, author = {Weber, Tobias and Englhard, Markus and Arent, Jan-Christoph and Hausmann, Joachim}, title = {An experimental characterization of wrinkling generated during prepreg autoclave manufacturing using caul plates}, series = {Journal of Composite Materials}, volume = {53}, journal = {Journal of Composite Materials}, number = {26-27}, issn = {1530-793X}, doi = {10.1177/0021998319846556}, pages = {3757 -- 3773}, year = {2019}, language = {en} } @article{OttenWeberArent2018, author = {Otten, Dennis and Weber, Tobias and Arent, Jan-Christoph}, title = {Manufacturing Process Simulation - On Its Way to Industrial Application}, series = {International Journal of Aviation, Aeronautics, and Aerospace}, volume = {5}, journal = {International Journal of Aviation, Aeronautics, and Aerospace}, number = {2}, publisher = {Embry-Riddle Aeronautical University}, address = {Daytona Beach, Fla.}, issn = {2374-6793}, doi = {10.15394/ijaaa.2018.1217}, year = {2018}, abstract = {Manufacturing process simulation (MPS) has become more and more important for aviation and the automobile industry. A highly competitive market requires the use of high performance metals and composite materials in combination with reduced manufacturing cost and time as well as a minimization of the time to market for a new product. However, the use of such materials is expensive and requires sophisticated manufacturing processes. An experience based process and tooling design followed by a lengthy trial-and-error optimization is just not contemporary anymore. Instead, a tooling design process aided by simulation is used more often. This paper provides an overview of the capabilities of MPS in the fields of sheet metal forming and prepreg autoclave manufacturing of composite parts summarizing the resulting benefits for tooling design and manufacturing engineering. The simulation technology is explained briefly in order to show several simplification and optimization techniques for developing industrialized simulation approaches. Small case studies provide examples of an efficient application on an industrial scale.}, language = {en} } @article{WeberRuffStahl2017, author = {Weber, Tobias and Ruff-Stahl, Hans-Joachim K.}, title = {Advances in Composite Manufacturing of Helicopter Parts}, series = {International Journal of Aviation, Aeronautics, and Aerospace}, volume = {4}, journal = {International Journal of Aviation, Aeronautics, and Aerospace}, number = {1}, issn = {2374-6793}, doi = {10.15394/ijaaa.2017.1153}, year = {2017}, language = {en} } @article{WeberArentSteffenetal.2017, author = {Weber, Tobias and Arent, Jan-Christoph and Steffen, Lucas and Balvers, Johannes M. and Duhovic, Miro}, title = {Thermal optimization of composite autoclave molds using the shift factor approach for boundary condition estimation}, series = {Journal of Composite Materials}, volume = {51}, journal = {Journal of Composite Materials}, number = {12}, publisher = {Sage}, address = {London}, issn = {1530-793X}, doi = {10.1177/0021998317699868}, pages = {1753 -- 1767}, year = {2017}, language = {en} } @inproceedings{OttenSchmidtWeber2016, author = {Otten, D. and Schmidt, M. and Weber, Tobias}, title = {Advances in Determination of Material Parameters for Functional Simulations Based on Process Simulations}, series = {SAMPE Europe Conference 16 Liege}, booktitle = {SAMPE Europe Conference 16 Liege}, isbn = {978-1-5108-3800-0}, pages = {570 -- 577}, year = {2016}, language = {en} } @inproceedings{WeberTellisDuhovic2016, author = {Weber, Tobias and Tellis, Jane J. and Duhovic, Miro}, title = {Characterization of tool-part-interaction an interlaminar friction for manufacturing process simulation}, series = {ECCM 17, 17th European Conference on Composite Materials, M{\"u}nchen, DE, Jun 26-30, 2016}, booktitle = {ECCM 17, 17th European Conference on Composite Materials, M{\"u}nchen, DE, Jun 26-30, 2016}, isbn = {978-3-00-053387-7}, pages = {1 -- 7}, year = {2016}, language = {en} } @article{WeberArentMuenchetal.2016, author = {Weber, Tobias and Arent, Jan-Christoph and M{\"u}nch, Lukas and Duhovic, Miro and Balvers, Johannes M.}, title = {A fast method for the generation of boundary conditions for thermal autoclave simulation}, series = {Composites Part A}, volume = {88}, journal = {Composites Part A}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1359-835X}, doi = {10.1016/j.compositesa.2016.05.036}, pages = {216 -- 225}, year = {2016}, abstract = {Manufacturing process simulation enables the evaluation and improvement of autoclave mold concepts early in the design phase. To achieve a high part quality at low cycle times, the thermal behavior of the autoclave mold can be investigated by means of simulations. Most challenging for such a simulation is the generation of necessary boundary conditions. Heat-up and temperature distribution in an autoclave mold are governed by flow phenomena, tooling material and shape, position within the autoclave, and the chosen autoclave cycle. This paper identifies and summarizes the most important factors influencing mold heat-up and how they can be introduced into a thermal simulation. Thermal measurements are used to quantify the impact of the various parameters. Finally, the gained knowledge is applied to develop a semi-empirical approach for boundary condition estimation that enables a simple and fast thermal simulation of the autoclave curing process with reasonably high accuracy for tooling optimization.}, language = {en} } @inproceedings{HailerWeberArent2019, author = {Hailer, Benjamin and Weber, Tobias and Arent, Jan-Christoph}, title = {Manufacturing Process Simulation for Autoclave-Produced Sandwich Structures}, series = {Proceedings of SAMPE Europe Conference 2019, Nantes, France}, booktitle = {Proceedings of SAMPE Europe Conference 2019, Nantes, France}, pages = {1 -- 8}, year = {2019}, language = {en} } @inproceedings{WeberEnglhardHaileretal.2019, author = {Weber, Tobias and Englhard, Markus and Hailer, Benjamin and Arent, Jan-Christoph}, title = {Manufacturing Process Simulation for the Prediction of Tool-Part-Interaction and Ply Wrinkling}, series = {Proceedings of SAMPE Europe Conference 2019, Nantes, France}, booktitle = {Proceedings of SAMPE Europe Conference 2019, Nantes, France}, pages = {1 -- 10}, year = {2019}, language = {en} } @inproceedings{WeberEnglhardHaileretal.2015, author = {Weber, Tobias and Englhard, Markus and Hailer, Benjamin and Arent, Jan-Christoph}, title = {Manufacturing Process Simulation for the Prediction of Tool-Part-Interaction and Ply Wrinkling}, series = {Proceedings of SAMPE Europe Conference, Amiens , France}, booktitle = {Proceedings of SAMPE Europe Conference, Amiens , France}, pages = {1 -- 10}, year = {2015}, language = {en} } @inproceedings{Weber2015, author = {Weber, Tobias}, title = {Manufacturing Process Simulation for Tooling Optimization: Reduction of Quality Issues During Autoclave Manufacturing of Composite Parts}, series = {Proceedings of SAMPE Europe Conference 2015, Amiens, France}, booktitle = {Proceedings of SAMPE Europe Conference 2015, Amiens, France}, pages = {1 -- 8}, year = {2015}, language = {en} } @inproceedings{OttenSchmidWeber2015, author = {Otten, D. and Schmid, M. and Weber, Tobias}, title = {Advances In Sheet Metal-Forming: Reduction Of Tooling Cost By Methodical Optimization}, series = {Proceedings of SAMPE Europe Conference, Amiens , France}, booktitle = {Proceedings of SAMPE Europe Conference, Amiens , France}, year = {2015}, language = {en} } @inproceedings{SchmidtsKraftWinkensetal.2020, author = {Schmidts, Oliver and Kraft, Bodo and Winkens, Marvin and Z{\"u}ndorf, Albert}, title = {Catalog integration of low-quality product data by attribute label ranking}, series = {Proceedings of the 9th International Conference on Data Science, Technology and Applications DATA - Volume 1}, booktitle = {Proceedings of the 9th International Conference on Data Science, Technology and Applications DATA - Volume 1}, publisher = {SciTePress}, address = {Set{\´u}bal, Portugal}, isbn = {978-989-758-440-4}, doi = {10.5220/0009831000900101}, pages = {90 -- 101}, year = {2020}, abstract = {The integration of product data from heterogeneous sources and manufacturers into a single catalog is often still a laborious, manual task. Especially small- and medium-sized enterprises face the challenge of timely integrating the data their business relies on to have an up-to-date product catalog, due to format specifications, low quality of data and the requirement of expert knowledge. Additionally, modern approaches to simplify catalog integration demand experience in machine learning, word vectorization, or semantic similarity that such enterprises do not have. Furthermore, most approaches struggle with low-quality data. We propose Attribute Label Ranking (ALR), an easy to understand and simple to adapt learning approach. ALR leverages a model trained on real-world integration data to identify the best possible schema mapping of previously unknown, proprietary, tabular format into a standardized catalog schema. Our approach predicts multiple labels for every attribute of an inpu t column. The whole column is taken into consideration to rank among these labels. We evaluate ALR regarding the correctness of predictions and compare the results on real-world data to state-of-the-art approaches. Additionally, we report findings during experiments and limitations of our approach.}, language = {en} } @article{FrankoDuKallweitetal.2020, author = {Franko, Josef and Du, Shengzhi and Kallweit, Stephan and Duelberg, Enno Sebastian and Engemann, Heiko}, title = {Design of a Multi-Robot System for Wind Turbine Maintenance}, series = {Energies}, volume = {13}, journal = {Energies}, number = {10}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {10.3390/en13102552}, pages = {Article 2552}, year = {2020}, abstract = {The maintenance of wind turbines is of growing importance considering the transition to renewable energy. This paper presents a multi-robot-approach for automated wind turbine maintenance including a novel climbing robot. Currently, wind turbine maintenance remains a manual task, which is monotonous, dangerous, and also physically demanding due to the large scale of wind turbines. Technical climbers are required to work at significant heights, even in bad weather conditions. Furthermore, a skilled labor force with sufficient knowledge in repairing fiber composite material is rare. Autonomous mobile systems enable the digitization of the maintenance process. They can be designed for weather-independent operations. This work contributes to the development and experimental validation of a maintenance system consisting of multiple robotic platforms for a variety of tasks, such as wind turbine tower and rotor blade service. In this work, multicopters with vision and LiDAR sensors for global inspection are used to guide slower climbing robots. Light-weight magnetic climbers with surface contact were used to analyze structure parts with non-destructive inspection methods and to locally repair smaller defects. Localization was enabled by adapting odometry for conical-shaped surfaces considering additional navigation sensors. Magnets were suitable for steel towers to clamp onto the surface. A friction-based climbing ring robot (SMART— Scanning, Monitoring, Analyzing, Repair and Transportation) completed the set-up for higher payload. The maintenance period could be extended by using weather-proofed maintenance robots. The multi-robot-system was running the Robot Operating System (ROS). Additionally, first steps towards machine learning would enable maintenance staff to use pattern classification for fault diagnosis in order to operate safely from the ground in the future.}, language = {en} } @article{KellerRathBruckmannetal.2020, author = {Keller, Johannes and Rath, Volker and Bruckmann, Johanna and Mottaghy, Darius and Clauser, Christoph and Wolf, Andreas and Seidler, Ralf and B{\"u}cker, H. Martin and Klitzsch, Norbert}, title = {SHEMAT-Suite: An open-source code for simulating flow, heat and species transport in porous media}, series = {SoftwareX}, volume = {12}, journal = {SoftwareX}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2352-7110}, doi = {10.1016/j.softx.2020.100533}, pages = {9}, year = {2020}, abstract = {SHEMAT-Suite is a finite-difference open-source code for simulating coupled flow, heat and species transport in porous media. The code, written in Fortran-95, originates from geoscientific research in the fields of geothermics and hydrogeology. It comprises: (1) a versatile handling of input and output, (2) a modular framework for subsurface parameter modeling, (3) a multi-level OpenMP parallelization, (4) parameter estimation and data assimilation by stochastic approaches (Monte Carlo, Ensemble Kalman filter) and by deterministic Bayesian approaches based on automatic differentiation for calculating exact (truncation error-free) derivatives of the forward code.}, language = {en} } @article{NobisSchmittSchemmetal.2020, author = {Nobis, Moritz and Schmitt, Carlo and Schemm, Ralf and Schnettler, Armin}, title = {Pan-European CVAR-constrained stochastic unit commitment in day-ahead and intraday electricity markets}, series = {Energies}, volume = {13}, journal = {Energies}, number = {Art. 2339}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {10.3390/en13092339}, pages = {1 -- 35}, year = {2020}, abstract = {The fundamental modeling of energy systems through individual unit commitment decisions is crucial for energy system planning. However, current large-scale models are not capable of including uncertainties or even risk-averse behavior arising from forecasting errors of variable renewable energies. However, risks associated with uncertain forecasting errors have become increasingly relevant within the process of decarbonization. The intraday market serves to compensate for these forecasting errors. Thus, the uncertainty of forecasting errors results in uncertain intraday prices and quantities. Therefore, this paper proposes a two-stage risk-constrained stochastic optimization approach to fundamentally model unit commitment decisions facing an uncertain intraday market. By the nesting of Lagrangian relaxation and an extended Benders decomposition, this model can be applied to large-scale, e.g., pan-European, power systems. The approach is applied to scenarios for 2023—considering a full nuclear phase-out in Germany—and 2035—considering a full coal phase-out in Germany. First, the influence of the risk factors is evaluated. Furthermore, an evaluation of the market prices shows an increase in price levels as well as an increasing day-ahead-intraday spread in 2023 and in 2035. Finally, it is shown that intraday cross-border trading has a significant influence on trading volumes and prices and ensures a more efficient allocation of resources.}, language = {en} } @article{EmhardtJarodzkaBrandGruweletal.2020, author = {Emhardt, Selina and Jarodzka, Halszka and Brand-Gruwel, Saskia and Drumm, Christian and Gog, Tamara van}, title = {Introducing eye movement modeling examples for programming education and the role of teacher's didactic guidance}, series = {ETRA '20 Short Papers: ACM Symposium on Eye Tracking Research and Applications}, journal = {ETRA '20 Short Papers: ACM Symposium on Eye Tracking Research and Applications}, number = {Art. 52}, publisher = {ACM}, address = {New York}, doi = {10.1145/3379156.3391978}, pages = {1 -- 4}, year = {2020}, abstract = {In this article, we introduce how eye-tracking technology might become a promising tool to teach programming skills, such as debugging with 'Eye Movement Modeling Examples' (EMME). EMME are tutorial videos that visualize an expert's (e.g., a programming teacher's) eye movements during task performance to guide students' attention, e.g., as a moving dot or circle. We first introduce the general idea behind the EMME method and present studies that showed first promising results regarding the benefits of EMME to support programming education. However, we argue that the instructional design of EMME varies notably across them, as evidence-based guidelines on how to create effective EMME are often lacking. As an example, we present our ongoing research on the effects of different ways to instruct the EMME model prior to video creation. Finally, we highlight open questions for future investigations that could help improving the design of EMME for (programming) education.}, language = {en} } @article{HeinkeKnickerAlbracht2020, author = {Heinke, Lars N. and Knicker, Axel J. and Albracht, Kirsten}, title = {Increased shoulder muscle stretch reflex elicitability in supine subject posture}, series = {Isokinetics and Exercise Science}, volume = {28}, journal = {Isokinetics and Exercise Science}, number = {2}, publisher = {IOS Press}, address = {Amsterdam}, issn = {1878-5913}, doi = {10.3233/IES-192219}, pages = {139 -- 146}, year = {2020}, abstract = {BACKGROUND: Muscle stretch reflexes are widely used to examine neural muscle function. The knowledge of reflex response in muscles crossing the shoulder is limited. OBJECTIVE: To quantify reflex modulation according to various subject postures and different procedures of muscle pre-activation steering. METHODS: Thirteen healthy male participants performed two sets of external shoulder rotation stretches in various positions and with different procedures of muscle pre-activation steering on an isokinetic dynamometer over a range of two different pre-activation levels. All stretches were applied with a dynamometer acceleration of 104∘/s2 and a velocity of 150∘/s. Electromyographical response was measured via sEMG. RESULTS: Consistent reflexive response was observed in all tested muscles in all experimental conditions. The reflex elicitation rate revealed a significant muscle main effect (F (5,288) = 2.358, ρ= 0.040; η2= 0.039; f= 0.637) and a significant test condition main effect (F (1,288) = 5.884, ρ= 0.016; η2= 0.020; f= 0.143). Reflex latency revealed a significant muscle pre-activation level main effect (F (1,274) = 5.008, ρ= 0.026; η2= 0.018; f= 0.469). CONCLUSION: Muscular reflexive response was more consistent in the primary internal rotators of the shoulder. Supine posture in combination with visual feedback of muscle pre-activation level enhanced the reflex elicitation rate.}, language = {en} } @article{SchiedermeierRettnerHeilmannetal.2019, author = {Schiedermeier, Maximilian and Rettner, Cornelius and Heilmann, Marcel and Schneider, Felix and Marz, Martin}, title = {Interference of automotive HV-DC-systems by traction voltage-source-inverters (VSI)}, series = {2019 IEEE Transportation Electrification Conference (ITEC-India)}, journal = {2019 IEEE Transportation Electrification Conference (ITEC-India)}, publisher = {IEEE}, address = {New York}, doi = {10.1109/ITEC-India48457.2019.ITECINDIA2019-37}, pages = {1 -- 6}, year = {2019}, language = {en} } @article{HoevelerBauknechtWolfetal.2020, author = {Hoeveler, B. and Bauknecht, Andr{\´e} and Wolf, C. Christian and Janser, Frank}, title = {Wind-Tunnel Study of a Wing-Embedded Lifting Fan Remaining Open in Cruise Flight}, series = {Journal of Aircraft}, volume = {57}, journal = {Journal of Aircraft}, number = {4}, publisher = {AIAA}, address = {Reston, Va.}, issn = {1533-3868}, doi = {10.2514/1.C035422}, year = {2020}, abstract = {It is investigated whether a nonrotating lifting fan remaining uncovered during cruise flight, as opposed to being covered by a shutter system, can be realized with limited additional drag and loss of lift during cruise flight. A wind-tunnel study of a wing-embedded lifting fan has been conducted at the Side Wind Test Facility G{\"o}ttingen of DLR, German Aerospace Center in G{\"o}ttingen using force, pressure, and stereoscopic particle image velocimetry techniques. The study showed that a step on the lower side of the wing in front of the lifting fan duct increases the lift-to-drag ratio of the whole model by up to 25\% for all positive angles of attack. Different sizes and inclinations of the step had limited influence on the surface pressure distribution. The data indicate that these parameters can be optimized to maximize the lift-to-drag ratio. A doubling of the curvature radius of the lifting fan duct inlet lip on the upper side of the wing affected the lift-to-drag ratio by less than 1\%. The lifting fan duct inlet curvature can therefore be optimized to maximize the vertical fan thrust of the rotating lifting fan during hovering without affecting the cruise flight performance with a nonrotating fan.}, language = {en} } @article{ChoiFelderFelderetal.2020, author = {Choi, Chang-Hoon and Felder, Tim and Felder, J{\"o}rg and Tellmann, Lutz and Hong, Suk-Min and Wegener, Hans-Peter and Shah, N Jon and Ziemons, Karl}, title = {Design, evaluation and comparison of endorectal coils for hybrid MR-PET imaging of the prostate}, series = {Physics in Medicine \& Biology}, volume = {65}, journal = {Physics in Medicine \& Biology}, number = {11}, publisher = {IOP}, address = {Bristol}, issn = {0031-9155}, doi = {10.1088/1361-6560/ab87f8}, year = {2020}, abstract = {Prostate cancer is one of the most common cancers among men and its early detection is critical for its successful treatment. The use of multimodal imaging, such as MR-PET, is most advantageous as it is able to provide detailed information about the prostate. However, as the human prostate is flexible and can move into different positions under external conditions, it is important to localise the focused region-of-interest using both MRI and PET under identical circumstances. In this work, we designed five commonly used linear and quadrature radiofrequency surface coils suitable for hybrid MR-PET use in endorectal applications. Due to the endorectal design and the shielded PET insert, the outer face of the coils investigated was curved and the region to be imaged was outside the volume of the coil. The tilting angles of the coils were varied with respect to the main magnetic field direction. This was done to approximate the various positions from which the prostate could be imaged. The transmit efficiencies and safety excitation efficiencies from simulations, together with the signal-to-noise ratios from the MR images were calculated and analysed. Overall, it was found that the overlapped loops driven in quadrature were superior to the other types of coils we tested. In order to determine the effect of the different coil designs on PET, transmission scans were carried out, and it was observed that the differences between attenuation maps with and without the coils were negligible. The findings of this work can provide useful guidance for the integration of such coil designs into MR-PET hybrid systems in the future.}, language = {en} } @article{KhayyamJamaliBabHadiasharetal.2020, author = {Khayyam, Hamid and Jamali, Ali and Bab-Hadiashar, Alireza and Esch, Thomas and Ramakrishna, Seeram and Jalili, Mahdi and Naebe, Minoo}, title = {A Novel Hybrid Machine Learning Algorithm for Limited and Big Data Modeling with Application in Industry 4.0}, series = {IEEE Access}, volume = {8}, journal = {IEEE Access}, number = {Art. 9108222}, publisher = {IEEE}, address = {New York, NY}, issn = {2169-3536}, doi = {10.1109/ACCESS.2020.2999898}, pages = {111381 -- 111393}, year = {2020}, abstract = {To meet the challenges of manufacturing smart products, the manufacturing plants have been radically changed to become smart factories underpinned by industry 4.0 technologies. The transformation is assisted by employment of machine learning techniques that can deal with modeling both big or limited data. This manuscript reviews these concepts and present a case study that demonstrates the use of a novel intelligent hybrid algorithms for Industry 4.0 applications with limited data. In particular, an intelligent algorithm is proposed for robust data modeling of nonlinear systems based on input-output data. In our approach, a novel hybrid data-driven combining the Group-Method of Data-Handling and Singular-Value Decomposition is adapted to find an offline deterministic model combined with Pareto multi-objective optimization to overcome the overfitting issue. An Unscented-Kalman-Filter is also incorporated to update the coefficient of the deterministic model and increase its robustness against data uncertainties. The effectiveness of the proposed method is examined on a set of real industrial measurements.}, language = {en} } @inproceedings{BraunChengDoweyetal.2020, author = {Braun, Sebastian and Cheng, Chi-Tsun and Dowey, Steve and Wollert, J{\"o}rg}, title = {Survey on Security Concepts to Adapt Flexible Manufacturing and Operations Management based upon Multi-Agent Systems}, series = {2020 IEEE 29th International Symposium on Industrial Electronics (ISIE), Proceedings}, booktitle = {2020 IEEE 29th International Symposium on Industrial Electronics (ISIE), Proceedings}, publisher = {IEEE}, address = {New York, NY}, doi = {10.1109/ISIE45063.2020.9152210}, pages = {5 Seiten}, year = {2020}, abstract = {The increasing digitalization brings new opportunities but also puts new challenges to modern industrial systems. Software agents are one of the key technologies towards self-optimizing factories and are currently used to address the needs of cyber-physical production systems (CPPS). However their interplay in industrial settings needs to be understood better.This paper focusses on securing a cloud infrastructure for multi-agent systems for industrial sites. An industrial site contains multiple production processes that need to communicate with each other and each physical resource is abstracted with a software agent. This volatile architecture needs to be managed and protected from manipulation. The proposed infrastructure presents a security concept for TCP/IP communication between agents, machines, and external networks. It is based on open-source software and tested on a three-node edge cloud controlling a model-plant.}, language = {en} } @article{SvaneborgKarimiVarzanehHojdisetal.2016, author = {Svaneborg, Carsten and Karimi-Varzaneh, Hossein Ali and Hojdis, Nils and Fleck, Franz and Everaers, Ralf}, title = {Multiscale approach to equilibrating model polymer melts}, series = {Physical Review E}, volume = {94}, journal = {Physical Review E}, number = {032502}, publisher = {AIP Publishing}, address = {Melville, NY}, issn = {2470-0053}, doi = {10.1103/PhysRevE.94.032502}, year = {2016}, abstract = {We present an effective and simple multiscale method for equilibrating Kremer Grest model polymer melts of varying stiffness. In our approach, we progressively equilibrate the melt structure above the tube scale, inside the tube and finally at the monomeric scale. We make use of models designed to be computationally effective at each scale. Density fluctuations in the melt structure above the tube scale are minimized through a Monte Carlo simulated annealing of a lattice polymer model. Subsequently the melt structure below the tube scale is equilibrated via the Rouse dynamics of a force-capped Kremer-Grest model that allows chains to partially interpenetrate. Finally the Kremer-Grest force field is introduced to freeze the topological state and enforce correct monomer packing. We generate 15 melts of 500 chains of 10.000 beads for varying chain stiffness as well as a number of melts with 1.000 chains of 15.000 monomers. To validate the equilibration process we study the time evolution of bulk, collective, and single-chain observables at the monomeric, mesoscopic, and macroscopic length scales. Extension of the present method to longer, branched, or polydisperse chains, and/or larger system sizes is straightforward.}, language = {en} } @article{SchwabHojdisLacayoetal.2016, author = {Schwab, Lukas and Hojdis, Nils and Lacayo, Jorge and Wilhelm, Manfred}, title = {Fourier-Transform Rheology of Unvulcanized, Carbon Black Filled Styrene Butadiene Rubber}, series = {Macromolecular Materials and Engineering}, volume = {301}, journal = {Macromolecular Materials and Engineering}, number = {4}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-2054}, doi = {10.1002/mame.201500356}, pages = {457 -- 468}, year = {2016}, abstract = {Rubber materials filled with reinforcing fillers display nonlinear rheological behavior at small strain amplitudes below γ0 < 0.1. Nevertheless, rheological data are analyzed mostly in terms of linear parameters, such as shear moduli (G′, G″), which loose their physical meaning in the nonlinear regime. In this work styrene butadiene rubber filled with carbon black (CB) under large amplitude oscillatory shear (LAOS) is analyzed in terms of the nonlinear parameter I3/1. Three different CB grades are used and the filler load is varied between 0 and 70 phr. It is found that I3/1(φ) is most sensitive to changes of the total accessible filler surface area at low strain amplitudes (γ0 = 0.32). The addition of up to 70 phr CB leads to an increase of I3/1(φ) by a factor of more than ten. The influence of the measurement temperature on I3/1 is pronounced for CB levels above the percolation threshold.}, language = {en} } @article{HarishWriggersJungketal.2016, author = {Harish, Ajay B. and Wriggers, Peter and Jungk, Juliane and Hojdis, Nils and Recker, Carla}, title = {Mesoscale Constitutive Modeling of Non-Crystallizing Filled Elastomers}, series = {Computational Mechanics}, volume = {57}, journal = {Computational Mechanics}, publisher = {Springer}, address = {Berlin}, issn = {1432-0924}, doi = {10.1007/s00466-015-1251-1}, pages = {653 -- 677}, year = {2016}, abstract = {Elastomers are exceptional materials owing to their ability to undergo large deformations before failure. However, due to their very low stiffness, they are not always suitable for industrial applications. Addition of filler particles provides reinforcing effects and thus enhances the material properties that render them more versatile for applications like tyres etc. However, deformation behavior of filled polymers is accompanied by several nonlinear effects like Mullins and Payne effect. To this day, the physical and chemical changes resulting in such nonlinear effect remain an active area of research. In this work, we develop a heterogeneous (or multiphase) constitutive model at the mesoscale explicitly considering filler particle aggregates, elastomeric matrix and their mechanical interaction through an approximate interface layer. The developed constitutive model is used to demonstrate cluster breakage, also, as one of the possible sources for Mullins effect observed in non-crystallizing filled elastomers.}, language = {en} } @article{HentschkeHagerHojdis2014, author = {Hentschke, Reinhard and Hager, Jonathan and Hojdis, Nils}, title = {Molecular Modeling Approach to the Prediction of Mechanical Properties of Silica-Reinforced Rubbers}, series = {Journal of Applied Polymer Science}, volume = {131}, journal = {Journal of Applied Polymer Science}, number = {18}, publisher = {Wiley}, address = {New York, NY}, issn = {1097-4628}, doi = {10.1002/app.40806}, pages = {1 -- 9}, year = {2014}, abstract = {Recently, we have suggested a nanomechanical model for dissipative loss in filled elastomer networks in the context of the Payne effect. The mechanism is based on a total interfiller particle force exhibiting an intermittent loop, due to the combination of short-range repulsion and dispersion forces with a long-range elastic attraction. The sum of these forces leads, under external strain, to a spontaneous instability of "bonds" between the aggregates in a filler network and attendant energy dissipation. Here, we use molecular dynamics simulations to obtain chemically realistic forces between surface modified silica particles. The latter are combined with the above model to estimate the loss modulus and the low strain storage modulus in elastomers containing the aforementioned filler-compatibilizer systems. The model is compared to experimental dynamic moduli of silica filled rubbers. We find good agreement between the model predictions and the experiments as function of the compatibilizer's molecular structure and its bulk concentration.}, language = {en} } @article{KuhnhenneRegerPyschnyetal.2020, author = {Kuhnhenne, Markus and Reger, Vitali and Pyschny, Dominik and D{\"o}ring, Bernd}, title = {Influence of airtightness of steel sandwich panel joints on heat losses}, series = {E3S Web of Conferences 12th Nordic Symposium on Building Physics (NSB 2020)}, volume = {172}, journal = {E3S Web of Conferences 12th Nordic Symposium on Building Physics (NSB 2020)}, number = {Art. 05008}, publisher = {EDP Sciences}, address = {Les Ulis}, doi = {10.1051/e3sconf/202017205008}, pages = {6}, year = {2020}, abstract = {Energy saving ordinances requires that buildings must be designed in such a way that the heat transfer surface including the joints is permanently air impermeable. The prefabricated roof and wall panels in lightweight steel constructions are airtight in the area of the steel covering layers. The sealing of the panel joints contributes to fulfil the comprehensive requirements for an airtight building envelope. To improve the airtightness of steel sandwich panels, additional sealing tapes can be installed in the panel joint. The influence of these sealing tapes was evaluated by measurements carried out by the RWTH Aachen University - Sustainable Metal Building Envelopes. Different installation situations were evaluated by carrying out airtightness tests for different joint distances. In addition, the influence on the heat transfer coefficient was also evaluated using the Finite Element Method (FEM). The combination of obtained air volume flow and transmission losses enables to create an "effective heat transfer coefficient" due to transmission and infiltration. This summarizes both effects in one value and is particularly helpful for approximate calculations on energy efficiency.}, language = {en} } @article{KunkelGebhardtMpofuetal.2019, author = {Kunkel, Maximilian Hugo and Gebhardt, Andreas and Mpofu, Khumbulani and Kallweit, Stephan}, title = {Quality assurance in metal powder bed fusion via deep-learning-based image classification}, series = {Rapid Prototyping Journal}, volume = {26}, journal = {Rapid Prototyping Journal}, number = {2}, issn = {1355-2546}, doi = {10.1108/RPJ-03-2019-0066}, pages = {259 -- 266}, year = {2019}, language = {en} } @article{MaurischatPerkins2020, author = {Maurischat, Andreas and Perkins, Rudolph}, title = {Taylor coefficients of Anderson generating functions and Drinfeld torsion extensions}, number = {Vol. 18, No. 01}, publisher = {World Scientific}, address = {Singapur}, doi = {10.1142/S1793042122500099}, pages = {113 -- 130}, year = {2020}, abstract = {We generalize our work on Carlitz prime power torsion extension to torsion extensions of Drinfeld modules of arbitrary rank. As in the Carlitz case, we give a description of these extensions in terms of evaluations of Anderson generating functions and their hyperderivatives at roots of unity. We also give a direct proof that the image of the Galois representation attached to the p-adic Tate module lies in the p-adic points of the motivic Galois group. This is a generalization of the corresponding result of Chang and Papanikolas for the t-adic case.}, language = {en} } @article{ElMoussaouiTalbiAtmaneetal.2020, author = {El Moussaoui, Noureddine and Talbi, Sofian and Atmane, Ilyas and Kassmi, Khalil and Schwarzer, Klemens and Chayeb, Hamid and Bachiri, Najib}, title = {Feasibility of a new design of a Parabolic Trough Solar Thermal Cooker (PSTC)}, series = {Solar Energy}, volume = {201}, journal = {Solar Energy}, number = {Vol. 201 (May 2020)}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0038-092X}, doi = {10.1016/j.solener.2020.03.079}, pages = {866 -- 871}, year = {2020}, abstract = {In this article, we describe the structure, the functioning, and the tests of parabolic trough solar thermal cooker (PSTC). This oven is designed to meet the needs of rural residents, including Urban, which requires stable cooking temperatures above 200 °C. The cooking by this cooker is based on the concentration of the sun's rays on a glass vacuum tube and heating of the oil circulate in a big tube, located inside the glass tube. Through two small tubes, associated with large tube, the heated oil, rise and heats the pot of cooking pot containing the food to be cooked (capacity of 5 kg). This cooker is designed in Germany and extensively tested in Morocco for use by the inhabitants who use wood from forests. During a sunny day, having a maximum solar radiation around 720 W/m2 and temperature ambient around 26 °C, maximum temperatures recorded of the small tube, the large tube and the center of the pot are respectively: 370 °C, 270 °C and 260 °C. The cooking process with food at high (fries, ..), we show that the cooking oil temperature rises to 200 °C, after 1 h of heating, the cooking is done at a temperature of 120 °C for 20 min. These temperatures are practically stable following variations and decreases in the intensity of irradiance during the day. The comparison of these results with those of the literature shows an improvement of 30-50 \% on the maximum value of the temperature with a heat storage that could reach 60 min of autonomy. All the results obtained show the good functioning of the PSTC and the feasibility of cooking food at high temperature (>200 °C).}, language = {en} } @article{MuellerJungAhammer2017, author = {M{\"u}ller, Wolfram and Jung, Alexander and Ahammer, Helmut}, title = {Advantages and problems of nonlinear methods applied to analyze physiological time signals: human balance control as an example}, series = {Scientific Reports}, volume = {7}, journal = {Scientific Reports}, number = {Article number 2464}, publisher = {Springer Nature}, address = {Cham}, isbn = {2045-2322}, doi = {10.1038/s41598-017-02665-5}, pages = {1 -- 11}, year = {2017}, language = {en} } @article{OrzadaFiedlerBitzetal.2020, author = {Orzada, Stephan and Fiedler, Thomas M. and Bitz, Andreas and Ladd, Mark E. and Quick, Harald H.}, title = {Local SAR compression with overestimation control to reduce maximum relative SAR overestimation and improve multi-channel RF array performance}, series = {Magnetic Resonance Materials in Physics, Biology and Medicine}, journal = {Magnetic Resonance Materials in Physics, Biology and Medicine}, number = {34 (2021)}, publisher = {Springer}, address = {Heidelberg}, isbn = {1352-8661}, doi = {10.1007/s10334-020-00890-0}, pages = {153 -- 164}, year = {2020}, abstract = {Objective In local SAR compression algorithms, the overestimation is generally not linearly dependent on actual local SAR. This can lead to large relative overestimation at low actual SAR values, unnecessarily constraining transmit array performance. Method Two strategies are proposed to reduce maximum relative overestimation for a given number of VOPs. The first strategy uses an overestimation matrix that roughly approximates actual local SAR; the second strategy uses a small set of pre-calculated VOPs as the overestimation term for the compression. Result Comparison with a previous method shows that for a given maximum relative overestimation the number of VOPs can be reduced by around 20\% at the cost of a higher absolute overestimation at high actual local SAR values. Conclusion The proposed strategies outperform a previously published strategy and can improve the SAR compression where maximum relative overestimation constrains the performance of parallel transmission.}, language = {en} } @article{UlmerBraunChengetal.2020, author = {Ulmer, Jessica and Braun, Sebastian and Cheng, Chi-Tsun and Dowey, Steve and Wollert, J{\"o}rg}, title = {Human-Centered Gamification Framework for Manufacturing Systems}, series = {Procedia CIRP}, volume = {93}, journal = {Procedia CIRP}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2212-8271}, doi = {10.1016/j.procir.2020.04.076}, pages = {670 -- 675}, year = {2020}, abstract = {While bringing new opportunities, the Industry 4.0 movement also imposes new challenges to the manufacturing industry and all its stakeholders. In this competitive environment, a skilled and engaged workforce is a key to success. Gamification can generate valuable feedbacks for improving employees' engagement and performance. Currently, Gamification in workspaces focuses on computer-based assignments and training, while tasks that require manual labor are rarely considered. This research provides an overview of Enterprise Gamification approaches and evaluates the challenges. Based on that, a skill-based Gamification framework for manual tasks is proposed, and a case study in the Industry 4.0 model factory is shown.}, language = {en} } @inproceedings{JockwerKleiberUibel2018, author = {Jockwer, R. and Kleiber, M. and Uibel, Thomas}, title = {Criteria for Evaluating the Simplification of Design Rules for Dowel-type Fasteners}, series = {International Network on Timber Engineering Research, INTER : proceedings, meeting 51, 10 - 13 August 2016, Tallinn, Estonia}, booktitle = {International Network on Timber Engineering Research, INTER : proceedings, meeting 51, 10 - 13 August 2016, Tallinn, Estonia}, editor = {G{\"o}rlacher, Rainer}, publisher = {Timber Scientific Publishing, KIT Holzbau und Baukonstruktionen}, address = {Karlsruhe}, pages = {461 -- 466}, year = {2018}, language = {en} } @article{EveraersKarimiVarzanehFlecketal.2020, author = {Everaers, Ralf and Karimi-Varzaneh, Hossein Ali and Fleck, Franz and Hojdis, Nils and Svaneborg, Carsten}, title = {Kremer-Grest Models for Commodity Polymer Melts: Linking Theory, Experiment, and Simulation at the Kuhn Scale}, series = {Macromolecules}, volume = {53}, journal = {Macromolecules}, number = {6}, publisher = {ACS Publications}, address = {Washington, DC}, issn = {1520-5835}, doi = {10.1021/acs.macromol.9b02428}, pages = {1901 -- 1916}, year = {2020}, abstract = {The Kremer-Grest (KG) polymer model is a standard model for studying generic polymer properties in molecular dynamics simulations. It owes its popularity to its simplicity and computational efficiency, rather than its ability to represent specific polymers species and conditions. Here we show that by tuning the chain stiffness it is possible to adapt the KG model to model melts of real polymers. In particular, we provide mapping relations from KG to SI units for a wide range of commodity polymers. The connection between the experimental and the KG melts is made at the Kuhn scale, i.e., at the crossover from the chemistry-specific small scale to the universal large scale behavior. We expect Kuhn scale-mapped KG models to faithfully represent universal properties dominated by the large scale conformational statistics and dynamics of flexible polymers. In particular, we observe very good agreement between entanglement moduli of our KG models and the experimental moduli of the target polymers.}, language = {en} } @article{MeyerHentschkeHageretal.2017, author = {Meyer, Jan and Hentschke, Reinhard and Hager, Jonathan and Hojdis, Nils and Karimi-Varzaneh, Hossein Ali}, title = {Molecular Simulation of Viscous Dissipation due to Cyclic Deformation of a Silica-Silica Contact in Filled Rubber}, series = {Macromolecules}, volume = {50}, journal = {Macromolecules}, number = {17}, issn = {1520-5835}, doi = {10.1021/acs.macromol.7b00947}, pages = {6679 -- 6689}, year = {2017}, language = {en} } @article{HagerHentschkeHojdisetal.2015, author = {Hager, Jonathan and Hentschke, Reinhard and Hojdis, Nils and Karimi-Varzaneh, Hossein Ali}, title = {Computer Simulation of Particle-Particle Interaction in a Model Polymer Nanocomposite}, series = {Macromolecules}, volume = {48}, journal = {Macromolecules}, number = {24}, issn = {1520-5835}, doi = {10.1021/acs.macromol.5b01864}, pages = {9039 -- 9049}, year = {2015}, language = {en} } @article{WallerBraunHojdisetal.2007, author = {Waller, Mark P. and Braun, Heiko and Hojdis, Nils and B{\"u}hl, Michael}, title = {Geometries of Second-Row Transition-Metal Complexes from Density-Functional Theory}, series = {Journal of Chemical Theory and Computation}, volume = {3}, journal = {Journal of Chemical Theory and Computation}, number = {6}, issn = {1549-9626}, doi = {10.1021/ct700178y}, pages = {2234 -- 2242}, year = {2007}, language = {en} } @article{SvaneborgKarimiVarzanehHojdisetal.2018, author = {Svaneborg, Carsten and Karimi-Varzaneh, Hossein Ali and Hojdis, Nils and Fleck, Franz and Everaers, Ralf}, title = {Kremer-Grest Models for Universal Properties of Specific Common Polymer Species}, series = {Soft Condensed Matter}, journal = {Soft Condensed Matter}, number = {1606.05008}, year = {2018}, abstract = {The Kremer-Grest (KG) bead-spring model is a near standard in Molecular Dynamic simulations of generic polymer properties. It owes its popularity to its computational efficiency, rather than its ability to represent specific polymer species and conditions. Here we investigate how to adapt the model to match the universal properties of a wide range of chemical polymers species. For this purpose we vary a single parameter originally introduced by Faller and M{\"u}ller-Plathe, the chain stiffness. Examples include polystyrene, polyethylene, polypropylene, cis-polyisoprene, polydimethylsiloxane, polyethyleneoxide and styrene-butadiene rubber. We do this by matching the number of Kuhn segments per chain and the number of Kuhn segments per cubic Kuhn volume for the polymer species and for the Kremer-Grest model. We also derive mapping relations for converting KG model units back to physical units, in particular we obtain the entanglement time for the KG model as function of stiffness allowing for a time mapping. To test these relations, we generate large equilibrated well entangled polymer melts, and measure the entanglement moduli using a static primitive-path analysis of the entangled melt structure as well as by simulations of step-strain deformation of the model melts. The obtained moduli for our model polymer melts are in good agreement with the experimentally expected moduli.}, language = {en} } @article{MayerHentschkeHageretal.2017, author = {Mayer, Jan and Hentschke, Reinhard and Hager, Jonathan and Hojdis, Nils and Karimi-Varnaneh, Hossein Ali}, title = {A Nano-Mechanical Instability as Primary Contribution to Rolling Resistance}, series = {Scientific Reports}, volume = {7}, journal = {Scientific Reports}, number = {Article number 11275}, publisher = {Springer}, address = {Berlin}, issn = {2045-2322}, year = {2017}, language = {en} } @inproceedings{WiegnerVolkerMainzetal.2022, author = {Wiegner, Jonas and Volker, Hanno and Mainz, Fabian and Backes, Andreas and L{\"o}ken, Michael and H{\"u}ning, Felix}, title = {Wiegand-effect-powered wireless IoT sensor node}, series = {ITG-Fb. 303: Sensoren und Messsysteme}, booktitle = {ITG-Fb. 303: Sensoren und Messsysteme}, publisher = {VDE Verlag GmbH}, address = {Berlin}, isbn = {978-3-8007-5835-7}, pages = {255 -- 260}, year = {2022}, abstract = {In this article we describe an Internet-of-Things sensing device with a wireless interface which is powered by the oftenoverlooked harvesting method of the Wiegand effect. The sensor can determine position, temperature or other resistively measurable quantities and can transmit the data via an ultra-low power ultra-wideband (UWB) data transmitter. With this approach we can energy-self-sufficiently acquire, process, and wirelessly transmit data in a pulsed operation. A proof-of-concept system was built up to prove the feasibility of the approach. The energy consumption of the system is analyzed and traced back in detail to the individual components, compared to the generated energy and processed to identify further optimization options. Based on the proof-of-concept, an application demonstrator was developed. Finally, we point out possible use cases.}, language = {en} } @article{UlmerBraunChengetal.2022, author = {Ulmer, Jessica and Braun, Sebastian and Cheng, Chi-Tsun and Dowey, Steve and Wollert, J{\"o}rg}, title = {Gamification of virtual reality assembly training: Effects of a combined point and level system on motivation and training results}, series = {International Journal of Human-Computer Studies}, volume = {165}, journal = {International Journal of Human-Computer Studies}, number = {Art. No. 102854}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1071-5819}, doi = {10.1016/j.ijhcs.2022.102854}, year = {2022}, abstract = {Virtual Reality (VR) offers novel possibilities for remote training regardless of the availability of the actual equipment, the presence of specialists, and the training locations. Research shows that training environments that adapt to users' preferences and performance can promote more effective learning. However, the observed results can hardly be traced back to specific adaptive measures but the whole new training approach. This study analyzes the effects of a combined point and leveling VR-based gamification system on assembly training targeting specific training outcomes and users' motivations. The Gamified-VR-Group with 26 subjects received the gamified training, and the Non-Gamified-VR-Group with 27 subjects received the alternative without gamified elements. Both groups conducted their VR training at least three times before assembling the actual structure. The study found that a level system that gradually increases the difficulty and error probability in VR can significantly lower real-world error rates, self-corrections, and support usages. According to our study, a high error occurrence at the highest training level reduced the Gamified-VR-Group's feeling of competence compared to the Non-Gamified-VR-Group, but at the same time also led to lower error probabilities in real-life. It is concluded that a level system with a variable task difficulty should be combined with carefully balanced positive and negative feedback messages. This way, better learning results, and an improved self-evaluation can be achieved while not causing significant impacts on the participants' feeling of competence.}, language = {en} } @inproceedings{KronigerHorikawaFunkeetal.2021, author = {Kroniger, Daniel and Horikawa, Atsushi and Funke, Harald and Pf{\"a}ffle, Franziska}, title = {Numerical investigation of micromix hydrogen flames at different combustor pressure levels}, series = {The Proceedings of the International Conference on Power Engineering (ICOPE)}, booktitle = {The Proceedings of the International Conference on Power Engineering (ICOPE)}, doi = {10.1299/jsmeicope.2021.15.2021-0237}, pages = {4 Seiten}, year = {2021}, abstract = {This study investigates the influence of pressure on the temperature distribution of the micromix (MMX) hydrogen flame and the NOx emissions. A steady computational fluid dynamic (CFD) analysis is performed by simulating a reactive flow with a detailed chemical reaction model. The numerical analysis is validated based on experimental investigations. A quantitative correlation is parametrized based on the numerical results. We find, that the flame initiation point shifts with increasing pressure from anchoring behind a downstream located bluff body towards anchoring upstream at the hydrogen jet. The numerical NOx emissions trend regarding to a variation of pressure is in good agreement with the experimental results. The pressure has an impact on both, the residence time within the maximum temperature region and on the peak temperature itself. In conclusion, the numerical model proved to be adequate for future prototype design exploration studies targeting on improving the operating range.}, language = {en} } @inproceedings{HorikawaOkadaYamaguchietal.2021, author = {Horikawa, Atsushi and Okada, Kunio and Yamaguchi, Masato and Aoki, Shigeki and Wirsum, Manfred and Funke, Harald and Kusterer, Karsten}, title = {Combustor development and engine demonstration of micro-mix hydrogen combustion applied to M1A-17 gas turbine}, series = {Conference Proceedings Turbo Expo: Power for Land, Sea and Air, Volume 3B: Combustion, Fuels, and Emissions}, booktitle = {Conference Proceedings Turbo Expo: Power for Land, Sea and Air, Volume 3B: Combustion, Fuels, and Emissions}, doi = {10.1115/GT2021-59666}, pages = {13 Seiten}, year = {2021}, abstract = {Kawasaki Heavy Industries, LTD. (KHI) has research and development projects for a future hydrogen society. These projects comprise the complete hydrogen cycle, including the production of hydrogen gas, the refinement and liquefaction for transportation and storage, and finally the utilization in a gas turbine for electricity and heat supply. Within the development of the hydrogen gas turbine, the key technology is stable and low NOx hydrogen combustion, namely the Dry Low NOx (DLN) hydrogen combustion. KHI, Aachen University of Applied Science, and B\&B-AGEMA have investigated the possibility of low NOx micro-mix hydrogen combustion and its application to an industrial gas turbine combustor. From 2014 to 2018, KHI developed a DLN hydrogen combustor for a 2MW class industrial gas turbine with the micro-mix technology. Thereby, the ignition performance, the flame stability for equivalent rotational speed, and higher load conditions were investigated. NOx emission values were kept about half of the Air Pollution Control Law in Japan: 84ppm (O2-15\%). Hereby, the elementary combustor development was completed. From May 2020, KHI started the engine demonstration operation by using an M1A-17 gas turbine with a co-generation system located in the hydrogen-fueled power generation plant in Kobe City, Japan. During the first engine demonstration tests, adjustments of engine starting and load control with fuel staging were investigated. On 21st May, the electrical power output reached 1,635 kW, which corresponds to 100\% load (ambient temperature 20 °C), and thereby NOx emissions of 65 ppm (O2-15, 60 RH\%) were verified. Here, for the first time, a DLN hydrogen-fueled gas turbine successfully generated power and heat.}, language = {en} } @inproceedings{KronigerHorikawaFunkeetal.2021, author = {Kroniger, Daniel and Horikawa, Atsushi and Funke, Harald and Pf{\"a}ffle, Franziska and Kishimoto, Tsuyoshi and Okada, Koichi}, title = {Experimental and numerical investigation on the effect of pressure on micromix hydrogen combustion}, series = {Conference Proceedings Turbo Expo: Power for Land, Sea and Air, Volume 3A: Combustion, Fuels, and Emissions}, booktitle = {Conference Proceedings Turbo Expo: Power for Land, Sea and Air, Volume 3A: Combustion, Fuels, and Emissions}, publisher = {ASME}, address = {New York, NY}, doi = {10.1115/GT2021-58926}, pages = {11 Seiten}, year = {2021}, abstract = {The micromix (MMX) combustion concept is a DLN gas turbine combustion technology designed for high hydrogen content fuels. Multiple non-premixed miniaturized flames based on jet in cross-flow (JICF) are inherently safe against flashback and ensure a stable operation in various operative conditions. The objective of this paper is to investigate the influence of pressure on the micromix flame with focus on the flame initiation point and the NOx emissions. A numerical model based on a steady RANS approach and the Complex Chemistry model with relevant reactions of the GRI 3.0 mechanism is used to predict the reactive flow and NOx emissions at various pressure conditions. Regarding the turbulence-chemical interaction, the Laminar Flame Concept (LFC) and the Eddy Dissipation Concept (EDC) are compared. The numerical results are validated against experimental results that have been acquired at a high pressure test facility for industrial can-type gas turbine combustors with regard to flame initiation and NOx emissions. The numerical approach is adequate to predict the flame initiation point and NOx emission trends. Interestingly, the flame shifts its initiation point during the pressure increase in upstream direction, whereby the flame attachment shifts from anchoring behind a downstream located bluff body towards anchoring directly at the hydrogen jet. The LFC predicts this change and the NOx emissions more accurately than the EDC. The resulting NOx correlation regarding the pressure is similar to a non-premixed type combustion configuration.}, language = {en} } @inproceedings{LorenzAltherrPelz2020, author = {Lorenz, Imke-Sophie and Altherr, Lena and Pelz, Peter F.}, title = {Assessing and Optimizing the Resilience of Water Distribution Systems Using Graph-Theoretical Metrics}, series = {Operations Research Proceedings 2019}, booktitle = {Operations Research Proceedings 2019}, editor = {Neufeld, Janis S. and Buscher, Udo and Lasch, Rainer and M{\"o}st, Dominik and Sch{\"o}nberger, J{\"o}rn}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-48439-2}, doi = {10.1007/978-3-030-48439-2_63}, pages = {521 -- 527}, year = {2020}, abstract = {Water distribution systems are an essential supply infrastructure for cities. Given that climatic and demographic influences will pose further challenges for these infrastructures in the future, the resilience of water supply systems, i.e. their ability to withstand and recover from disruptions, has recently become a subject of research. To assess the resilience of a WDS, different graph-theoretical approaches exist. Next to general metrics characterizing the network topology, also hydraulic and technical restrictions have to be taken into account. In this work, the resilience of an exemplary water distribution network of a major German city is assessed, and a Mixed-Integer Program is presented which allows to assess the impact of capacity adaptations on its resilience.}, language = {en} } @inproceedings{LeiseSimonAltherr2020, author = {Leise, Philipp and Simon, Nicolai and Altherr, Lena}, title = {Comparison of Piecewise Linearization Techniques to Model Electric Motor Efficiency Maps: A Computational Study}, series = {Operations Research Proceedings 2019}, booktitle = {Operations Research Proceedings 2019}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-48439-2}, doi = {10.1007/978-3-030-48439-2_55}, pages = {457 -- 463}, year = {2020}, abstract = {To maximize the travel distances of battery electric vehicles such as cars or buses for a given amount of stored energy, their powertrains are optimized energetically. One key part within optimization models for electric powertrains is the efficiency map of the electric motor. The underlying function is usually highly nonlinear and nonconvex and leads to major challenges within a global optimization process. To enable faster solution times, one possibility is the usage of piecewise linearization techniques to approximate the nonlinear efficiency map with linear constraints. Therefore, we evaluate the influence of different piecewise linearization modeling techniques on the overall solution process and compare the solution time and accuracy for methods with and without explicitly used binary variables.}, language = {en} } @inproceedings{MuellerSchmittLeiseetal.2021, author = {M{\"u}ller, Tim M. and Schmitt, Andreas and Leise, Philipp and Meck, Tobias and Altherr, Lena and Pelz, Peter F. and Pfetsch, Marc E.}, title = {Validation of an optimized resilient water supply system}, series = {Uncertainty in Mechanical Engineering}, booktitle = {Uncertainty in Mechanical Engineering}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-77255-0}, doi = {10.1007/978-3-030-77256-7_7}, pages = {70 -- 80}, year = {2021}, abstract = {Component failures within water supply systems can lead to significant performance losses. One way to address these losses is the explicit anticipation of failures within the design process. We consider a water supply system for high-rise buildings, where pump failures are the most likely failure scenarios. We explicitly consider these failures within an early design stage which leads to a more resilient system, i.e., a system which is able to operate under a predefined number of arbitrary pump failures. We use a mathematical optimization approach to compute such a resilient design. This is based on a multi-stage model for topology optimization, which can be described by a system of nonlinear inequalities and integrality constraints. Such a model has to be both computationally tractable and to represent the real-world system accurately. We therefore validate the algorithmic solutions using experiments on a scaled test rig for high-rise buildings. The test rig allows for an arbitrary connection of pumps to reproduce scaled versions of booster station designs for high-rise buildings. We experimentally verify the applicability of the presented optimization model and that the proposed resilience properties are also fulfilled in real systems.}, language = {en} }