@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} } @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} } @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} } @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} }