@misc{MauererRamsauerKoelbl, author = {Mauerer, Wolfgang and Ramsauer, Ralf and K{\"o}lbl, Andreas}, title = {The Many Approaches to Real-Time and Safety-Critical Linux}, series = {Open Source Summit Japan 2017}, journal = {Open Source Summit Japan 2017}, language = {en} } @inproceedings{StadtlerNitaDuennweber, author = {Stadtler, Timo and Nita, Spyro and D{\"u}nnweber, Jan}, title = {A Parallel Hybrid Genetic Search for the Capacitated VRP with Pickup and Delivery}, series = {34th International Workshop, LCPC 2021, Newark, DE, USA, October 13-14, 2021}, booktitle = {34th International Workshop, LCPC 2021, Newark, DE, USA, October 13-14, 2021}, doi = {10.35096/othr/pub-6985}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-69854}, abstract = {In the realm of parallel computing, optimization plays a pivotal role in achieving efficient and scalable solutions. In this work, we present the parallelization of a hybrid genetic search for solving the Capacitated Vehicle Routing Problem with Pickup and Delivery (CVRPPD).It leverages the synergy between genetic algorithms and parallel computing to address the complex optimization problem. This hybrid algorithm combines a customized version of local search with a genetic algorithm to compute an effective solution. Our implementation makes use of the Message Passing Interface (MPI) for data distribution and parallel execution. In addition, we run multi-threaded processes on NVIDIA graphical processors using the CUDA technology, which further increases the computation speed and consequently minimizes the runtime. Parallelization also allows the best-improvement strategy to be used instead of the rst-improvement strategy while maintaining the same runtime. We store the resulting routes in a bus route database which we created as the basis of an extensive library of optimal routes for our specifc use case of optimizing bus routes in a rural area. The experimental results on real road data show that the parallel implementation of the Hybrid Genetic Search (HGS) achieves significant improvements in runtime over the sequential implementation above a certain problem size. We believe that our implementation of the parallel hybrid genetic search method can have a great in influence on optimization strategies in parallel computing and can also be applied to other subproblems of the VRP.}, language = {en} } @incollection{Weber, author = {Weber, Karsten}, title = {Kommunikation und Zivilgesellschaft: Hoffnungen und Realit{\"a}t}, series = {Kommunikation und Medien zwischen Kulturindustrie, Lebenswelt und Politik}, booktitle = {Kommunikation und Medien zwischen Kulturindustrie, Lebenswelt und Politik}, editor = {Dr{\"u}eke, Ricarda and Gmainer-Pranzl, Franz}, publisher = {Peter Lang}, address = {Frankfurt a.M.}, isbn = {978-3-631-88308-2}, pages = {15 -- 31}, subject = {Zivilgesellschaft}, language = {de} } @inproceedings{SchiekBaronio, author = {Schiek, Roland and Baronio, Fabio}, title = {Spatial Akhmediev Breathers in Slab Waveguides}, series = {2019 Conference on Lasers and Electro-Optics Europe European Quantum Electronics Conference (CLEO/Europe-EQEC), 23-27 June 2019, Munich, Germany}, booktitle = {2019 Conference on Lasers and Electro-Optics Europe European Quantum Electronics Conference (CLEO/Europe-EQEC), 23-27 June 2019, Munich, Germany}, doi = {10.1109/CLEOE-EQEC.2019.8872896}, abstract = {Summary form only given. The analytical breather-solutions of the Nonlinear Schr{\"o}dinger Equation (NLS) [1] have been intensively studied and verified experimentally in the time-space system of optical pulse propagation in fibers [2]. In space-space systems, i.e. in optical beam propagation breathers in ultra-fast nonlinear media have not been observed due to the breather's infinite background and a resulting extremely large power. In a lithium niobate slab waveguide with two second-harmonic (SH) resonances the resulting quasi-cubic cascaded quadratic nonlinearity provided together with the intrinsic cubic susceptibility enough nonlinearity for breather excitation at experimentally reachable powers. We could characterize the fi rst ultra -fast spatial -spatial optical breathers in a 5 -cm -long titanium indiffused lithium niobate slab waveguide at power levels down to tens of kW. The guided fundamental wave (FW) TM° fi lm mode at A = 1.32μm is phase -matched for type -I SH generation to TE 0 and TEi SH modes at temperatures near 295 and 344C. With temperature tuning the phase -mismatch and the two effective cascaded nonlinearities were adjusted. For breather observation, we aimed for a large phase -mismatch with low SH levels such that the cascaded nonlinearity is quasi -cubic and the propagation is well approximated by the NLS and its breather solutions. A frequency -doubled Nd:YAG-pumped OPA with CW-seeding delivered 5-ps long pulses with up to 200kW peak power in the waveguide. With a cylindrical telescope the beam was transformed into a very wide elliptical beam to approximate the breather background. The beam was end -fire coupled into the FW TM () mode. A variable few \% of the beam were separated and coupled with a tilt and good overlap to the main beam into the waveguide to produce a spatial modulation of the input with adjustable period and modulation depth. A beam width of 1.5mm was large enough in the compromise between available beam power and infinite beam width. A beam with a transverse modulation with periods between 130 to 300μm approximates a constant background with modulation well enough to trigger modulation instability that develops eventually into the breather.}, language = {en} } @article{Frikel, author = {Frikel, J{\"u}rgen}, title = {A measurement-based model for image reconstruction in MPI using a FFL}, series = {Proceedings of the 20th International Conference of Numerical Analysis and Applied Mathematics (ICNAAM-2022), 2022, Heraklion (Crete, Greece)}, journal = {Proceedings of the 20th International Conference of Numerical Analysis and Applied Mathematics (ICNAAM-2022), 2022, Heraklion (Crete, Greece)}, publisher = {AIP Publishing}, abstract = {Most of the common model-based reconstruction schemes in magnetic particle imaging (MPI) use idealized assumptions, e.g., of an ideal field-free-line (FFL) topology. However, the magnetic fields that are generated in real MPI scanners have distortions and, therefore, model-based approaches often lead to inaccurate reconstructions and may contain artifacts. In order to improve the reconstruction quality in MPI, more realistic MPI models need to be derived. In the present work, we address this problem and present a hybrid model for MPI that allows us to incorporates real measurements of the applied magnetic fields. We will explain that the measurements, that are needed to setup a model for the magnetic fields, can be obtained in a novel calibration procedure that is independent of the resolution and which is much less time-consuming than the one employed in measurement-based MPI reconstructions.We will also present a discretization strategy for this model, that can be used in context of algebraic reconstructions. The presented approach was validated on simulated data in [1], however, its evaluation on real data is a topic for future research.}, language = {en} } @article{GoeppelFrikelHaltmeier, author = {G{\"o}ppel, Simon and Frikel, J{\"u}rgen and Haltmeier, Markus}, title = {Regularization of Inverse Problems with Translation Invariant Frames}, series = {Proceedings of the 20th International Conference of Numerical Analysis and Applied Mathematics (ICNAAM-2022), 2022, Heraklion (Crete, Greece)}, journal = {Proceedings of the 20th International Conference of Numerical Analysis and Applied Mathematics (ICNAAM-2022), 2022, Heraklion (Crete, Greece)}, publisher = {AIP Publishing}, abstract = {In various fields of applications, inverse problems are characterized by their sensitivity to data perturbations which can cause severe reconstruction errors. Hence, regularization procedures are employed in order to ensure stability and reconstruction quality. To overcome limitations of classical approaches such as the filtered singular value decomposition (SVD), frame based diagonalization methods have been studied in the recent years, e.g., wavelet-vagulette (WVD) decomposition. While these methods can be well adapted to the problem at hand, it is well-known, that the lack of translation invariance in multiscale systems can cause specific artifacts in the recovered object. Thus, to overcome these drawbacks we use the translation invariant diagonal frame decomposition (TI-DFD) of linear operators. For illustration, we construct a TI-WVD for one-dimensional integration operator, and confirm our theoretical findings by numerical simulations.}, language = {en} } @inproceedings{DuennweberStadlerWeikletal., author = {D{\"u}nnweber, Jan and Stadler, Timo and Weikl, Sandra and Sch{\"a}fer, Andreas and Georg, Peter and Wein, Simon}, title = {Bus Route Classification for Rural Areas using Graph Convolutional Networks}, series = {Proceedings of the 22th International Conference on Artificial Intelligence and Soft Computing, Zakopane, Poland}, booktitle = {Proceedings of the 22th International Conference on Artificial Intelligence and Soft Computing, Zakopane, Poland}, pages = {15}, abstract = {In this paper, we present a new approach to determine the estimated time of arrival (ETA) for bus routes using (Deep) Graph Convolutional Networks (DGCNs). In addition we use the same DGCN to detect detours within a route. In our application, a classification of routes and their underlying graph structure is performed using Graph Learning. Our model leads to a fast prediction and avoids solving the vehicle routing problem (VRP) through expensive computations. Moreover, we describe how to predict travel time for all routes using the same DGCN Model. This method makes it possible not to use a more computationally intensive approximation algorithm when determining long travel times with many intermediate stops, but to use our network for an early estimate of the quality of a route. Long travel times, in our case result from the use of a call-bus system, which must distribute many passengers among several vehicles and can take them to places without a regular stop. For a case study, the rural town of Roding in Bavaria is used. Our training data for this area results from an approximation algorithm that we implemented to optimize routes, and to generate an archive of routes of varying quality simultaneously.}, language = {en} } @inproceedings{ThelenEderMelzeretal., author = {Thelen, Simon and Eder, Friedrich and Melzer, Matthias and Nunes, Danilo Weber and Stadler, Michael and Rechenauer, Christian and Obergrießer, Mathias and Jubeh, Ruben and Volbert, Klaus and D{\"u}nnweber, Jan}, title = {A Slim Digital Twin For A Smart City And Its Residents}, series = {SOICT '23: Proceedings of the 12th International Symposium on Information and Communication Technology, 2023, Hi Chi Minh, Vietnam}, booktitle = {SOICT '23: Proceedings of the 12th International Symposium on Information and Communication Technology, 2023, Hi Chi Minh, Vietnam}, publisher = {ACM}, isbn = {979-8-4007-0891-6}, doi = {10.1145/3628797.3628936}, pages = {8 -- 15}, abstract = {In the engineering domain, representing real-world objects using a body of data, called a digital twin, which is frequently updated by "live" measurements, has shown various advantages over tradi- tional modelling and simulation techniques. Consequently, urban planners have a strong interest in digital twin technology, since it provides them with a laboratory for experimenting with data before making far-reaching decisions. Realizing these decisions involves the work of professionals in the architecture, engineering and construction (AEC) domain who nowadays collaborate via the methodology of building information modeling (BIM). At the same time, the citizen plays an integral role both in the data acquisition phase, while also being a beneficiary of the improved resource management strategies. In this paper, we present a prototype for a "digital energy twin" platform we designed in cooperation with the city of Regensburg. We show how our extensible platform de- sign can satisfy the various requirements of multiple user groups through a series of data processing solutions and visualizations, in- dicating valuable design and implementation guidelines for future projects. In particular, we focus on two example use cases concern- ing building electricity monitoring and BIM. By implementing a flexible data processing architecture we can involve citizens in the data acquisition process, meeting the demands of modern users regarding maximum transparency in the handling of their data.}, language = {en} } @article{RathsBauerKuettneretal., author = {Raths, Max and Bauer, Lukas and Kuettner, Andreas and Fischer, Samuel and Laumer, Tobias}, title = {Gradual error detection technique for non-destructive assessment of density and tensile strength in fused filament fabrication processes}, series = {The International Journal of Advanced Manufacturing Technology}, journal = {The International Journal of Advanced Manufacturing Technology}, number = {131}, publisher = {Springer}, address = {London}, issn = {1433-3015}, doi = {10.1007/s00170-024-13280-w}, pages = {4149 -- 4163}, abstract = {Fused filament fabrication (FFF) is a widely used additive manufacturing process for producing functional components and prototypes. The FFF process involves depositing melted material layer-by-layer to build up 3D physical parts. The quality of the final product depends on several factors, including the component density and tensile strength, which are typically determined through destructive testing methods. X-ray microtomography (XCT) can be used to investigate the pore sizes and distribution. These approaches are time-consuming, costly, and wasteful, making it unsuitable for high-volume manufacturing. In this paper, a new method for non-destructive determination of component density and estimation of the tensile strength in FFF processes is proposed. This method involves the use of gradual error detection by sensors and convolutional neural networks. To validate this approach, a series of experiments has been conducted. Component density and tensile strength of the printed specimens with varying extrusion factor were measured using traditional destructive testing methods and XCT. The cumulative error detection method was used to predict the same properties without destroying the specimens. The predicted values were then compared with the measured values, and it was observed that the method accurately predicted the component density and tensile strength of the tested parts. This approach has several advantages over traditional destructive testing methods. The method is faster, cheaper, and more environmentally friendly since it does not require the destruction of the product. Moreover, it facilitates the testing of each individual part instead of assuming the same properties for components from one series. Additionally, it can provide real-time feedback on the quality of the product during the manufacturing process, allowing for adjustments to be made as needed. The advancement of this approach points toward a future trend in non-destructive testing methodologies, potentially revolutionizing quality assurance processes not only for consumer goods but various industries such as electronics or automotive industry. Moreover, its broader applications extend beyond FFF to encompass other additive manufacturing techniques such as selective laser sintering (SLS), or electron beam melting (EBM). A comparison between the old destructive testing methods and this innovative non-destructive approach underscores the possible fundamental change toward more efficient and sustainable manufacturing practices. This approach has the potential to significantly reduce the time and cost associated with traditional destructive testing methods while ensuring the quality of FFF-manufactured products.}, language = {en} } @inproceedings{HauerSchultzHaugetal., author = {Hauer, Franziska and Schultz, Maximilian and Haug, Sonja and Weber, Karsten}, title = {Acceptance and Usage of AI Applications in Health-Focused NGOs}, series = {dHealth 2025, Proceedings of the 19th Health Informatics Meets Digital Health Conference}, booktitle = {dHealth 2025, Proceedings of the 19th Health Informatics Meets Digital Health Conference}, editor = {Baumgartner, Martin and Hayn, Dieter and Pfeifer, Bernhard and Schreier, G{\"u}nter}, publisher = {IOS Press}, address = {Wien}, isbn = {978-1-64368-592-2}, doi = {10.3233/SHTI250172}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-80613}, pages = {123 -- 128}, abstract = {Background: AI applications promise to be a valuable tool for healthfocused NGOs. While often operating with limited resources, these organizations recognize the potential of AI to streamline processes and support workflows through automation. However, challenges such as data privacy concerns—especially regarding personal medical data—and the low prioritization of implementation hinder progress. Objectives: This study examines the extent to which German health-focused NGOs can currently benefit from the application of AI. It evaluates demands, available resources, and use cases. Methods: A health-focused subset of data from project KINiro was analyzed. This research utilized a mixed-methods approach, combining two rounds of qualitative interviews with a quantitative survey. Results: The study revealed that while health-focused NGOs are in the early stages of AI implementation, there are hurdles such as ethical concerns and a lack of resources. Conclusion: AI has the potential to support health-focused NGOs in their work, if the challenges like resources, ethics, and data privacy are effectively addressed.}, language = {en} }