@article{PillingBaehrWunderlich2026, author = {Pilling, Eric and B{\"a}hr, Martin and Wunderlich, Ralf}, title = {Reinforcement learning methods for the stochastic optimal control of an industrial power-to-heat system}, series = {Energies}, volume = {19}, journal = {Energies}, number = {4}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {10.3390/en19041046}, year = {2026}, abstract = {The optimal control of sustainable energy supply systems, including renewable energies and energy storage, takes a central role in the decarbonization of industrial systems. However, the use of fluctuating renewable energies leads to fluctuations in energy generation and requires a suitable control strategy for the complex systems in order to ensure energy supply. In this paper, we consider an electrified power-to-heat system which is designed to supply heat in the form of superheated steam for industrial processes. The system consists of a high-temperature heat pump for heat supply, a wind turbine for power generation, a sensible thermal energy storage for storing excess heat, and a steam generator for providing steam. If the system's energy demand cannot be covered by electricity from the wind turbine, additional electricity must be purchased from the power grid. For this system, we investigate the cost-optimal operation, aiming to minimize the electricity cost from the grid by a suitable system control depending on the available wind power and the amount of stored thermal energy. This is a decision-making problem under uncertainty regarding the future prices for electricity from the grid and the future generation of wind power. The resulting stochastic optimal control problem is treated as finite-horizon Markov decision process for a multi-dimensional controlled state process. We first consider the classical backward recursion technique for solving the associated dynamic programming equation for the value function and compute the optimal decision rule. Since that approach suffers from the curse of dimensionality, we also apply reinforcement learning techniques, namely Q-learning, that are able to provide a good approximate solution to the optimization problem within reasonable time.}, subject = {Stochastic optimal control; Markov decision process; Dynamic programming; Q-learning; Power-to-heat system}, language = {en} } @article{DjoudiAmosseAvironetal.2026, author = {Djoudi, El Aziz and Amoss{\´e}, Ewen and Aviron, St{\´e}phanie and Birkhofer, Klaus and Libereau, Benjamin and Plantegenest, Manuel and P{\´e}tillon, Julien}, title = {Multi‑trophic arthropod communities modulated by local farming system and landscape heterogeneity}, series = {Landscape Ecology}, volume = {41}, journal = {Landscape Ecology}, publisher = {Springer Nature}, address = {Berlin}, issn = {1572-9761}, doi = {10.1007/s10980-026-02298-y}, year = {2026}, abstract = {Organic farming is increasingly used worldwide in recent decades, but the role of this farming system in shaping the trophic structure of arthropod communities remains poorly understood, especially at different spatial scales. Therefore, the contribution of landscape heterogeneity in shaping arthropod's trophic guilds remain understudied. In this study, we assessed how the evenness, the abundance and the taxonomic richness of arthropod trophic groups were shaped by the local farming system, landscape heterogeneity (including the percentage of semi-natural habitats and organic fields), and their interaction. Arthropod's trophic guilds (ground and vegetation-dwelling) were sampled in 20 spatial independent pairs of conventional (CF) and organic (OF) fields located in Brittany (Western France) by using pitfall traps and sweep nets replicated in time and space. A total of 95,822 arthropods belonging to 197 taxonomic groups were sampled. Farming system has a strong overall positive effect on the community structure of both ground- and vegetation-dwelling arthropods. Landscape heterogeneity, alone and in interaction with farming systems, affected positively the diversity and abundance of most trophic groups for both ground- and vegetation-dwelling arthropods. Organic farming therefore affected the trophic composition of arthropod communities not only locally, but also at the landscape scale. Our study highlights the strong positive effect of farming system and the landscape heterogeneity on arthropod communities and more importantly the interconnection between different spatial scales in this process. Taking these aspects into account is therefore crucial in understanding arthropod community dynamics in agroecosystems.}, subject = {Agroecology; Agricultural geography; Biodiversity; Landscape ecology; Organic farming}, language = {en} } @article{MbuyaPawarJafarietal.2025, author = {Mbuya, Christel Olivier Lenge and Pawar, Kunal and Jafari, Mitra and Shafiee, Parisa and Okoye Chine, Chike George and Tarifa, Pilar and Dorneanu, Bogdan and Arellano-Garcia, Harvey}, title = {Tuning catalyst performance in methane dry reforming via microwave irradiation of nickel-silicon carbide systems}, series = {Journal of CO2 Utilization}, volume = {102}, journal = {Journal of CO2 Utilization}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2212-9820}, doi = {10.1016/j.jcou.2025.103270}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-72832}, year = {2025}, abstract = {The dry reforming of methane (DRM) is a promising route for converting greenhouse gases such as methane (CH4) and carbon dioxide (CO2) into valuable syngas, hydrogen (H2) and carbon monoxide (CO). However, traditional nickel (Ni)-based catalysts suffer from rapid deactivation due to carbon deposition and sintering, especially when supported on low thermal conductivity materials. In this work, a novel post-synthesis microwave irradiation (MIR) treatment is introduced to systematically optimize the performance of Ni - β - SiC and Ni - Ti - Cβ - SiC catalysts for DRM. Unlike previous studies that have used MIR during reaction or with different supports, this approach tunes the metal - support interactions and textural properties of Ni - β - SiC and Ni - Ti - Cβ - SiC catalysts by varying the MIR exposure time after catalyst synthesis. MIR post-treatment (10-25 s) increased the CH4 conversion to 65 \% and the CO2 conversions to 62 \% for Ni-β-SiC catalysts and improved the H₂/CO ratio to 0.80, with stable performance over 20 h. For Ni-Ti-Cβ-SiC, MIR (10-20 s) maintained CH4 conversion up to 60 \% and CO2 conversion to 58 \% over 20 h, while the untreated catalyst, though initially higher, deactivated rapidly. Excessive MIR (30 s) reduced performance for both catalyst types, underscoring the need for optimal exposure time. These findings demonstrate post-synthesis MIR provides a tuneable approach for enhancing both the activity and durability of Ni/SiC - based DRM catalysts through controlled modification of metal - support interactions. This work offers new insights for the design of robust catalysts aimed at greenhouse gas utilization and sustainable syngas production, with activity and stability enhancements linked to controlled changes in metal - support interactions.}, subject = {Carbon dioxide; Dry reforming; Methane; Microwave irradiation; Ni Silicon carbide catalysts}, language = {en} } @article{SharmaRadomskyMathiazhaganetal.2025, author = {Sharma, Dikshant and Radomsky, Lukas and Mathiazhagan, Akilan and Asli, Majid and H{\"o}schler, Klaus and Mallwitz, Regine}, title = {Thermal analysis of metal foam integrated heatsink for electrified aircraft applications}, series = {International Journal of Thermofluids}, volume = {30}, journal = {International Journal of Thermofluids}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2666-2027}, doi = {10.1016/j.ijft.2025.101465}, year = {2025}, abstract = {Metal foams facilitate large heat dissipation in high-power dense systems such as power electronics for electrified propulsion application. This work addresses the cooling of a power semiconductor device with aluminium and copper metal foam integrated hybrid heatsink and its comparative analysis to a conventional finned heatsink using 0D and 3D modelling approach. Two-equation foam model in Fluent is utilized and the numerical approach is validated against experimental dataset. Inlet air velocity is varied such that the Darcy to turbulent regimes of the open-cellular foams are covered. Foam porosities from ∼ 0.85-0.95 with 10-20 PPI are investigated and the thermal performance of the heatsink is found to be independent of the foam material. High porosity (> 0.9), 20 PPI foams are found to aid forced-convection by improving the thermal resistance by more than 10\% against the 10 PPI counterparts. The hybrid heatsink outperforms the foam-based and conventional heatsink by 40\% and 15\% respectively when considering the reduction in junction temperatures, while the hydraulic resistance increases 10 times when compared to the conventional one. The 0D thermal resistance model is robust in predicting the junction temperatures for metal foam heatsinks with only a 5\%-6\% discrepancy for both the 50 W and 100 W heat load scenarios. The key and novel contribution of this study is the integration of detailed 3D simulations of a power electronics cooling environment with the development of a corresponding 0D thermal model. This approach not only eases the physical representation of the system but also enables the model to be extended to diverse heat load conditions.}, subject = {Electric propulsion; Electronics thermal management; Metal foam heatsink; Porous media; Forced convection}, language = {en} } @article{YangHenkeMoehlenkamp2025, author = {Yang, Yinghui and Henke, Markus and M{\"o}hlenkamp, Georg}, title = {Analytical investigation of short-circuit protection and post-fault operation in dual three-phase PMSMs for hybrid electric counter-rotating compressor applications}, series = {IEEE Access}, volume = {14}, journal = {IEEE Access}, publisher = {IEEE}, address = {New York}, issn = {2169-3536}, doi = {10.1109/ACCESS.2026.3658195}, pages = {17303 -- 17323}, year = {2025}, abstract = {The hybrid electric counter-rotating compressor (CRC) has the potential to improve power-specific fuel consumption in aircraft engines. However, due to its cascaded structure, a reduction or loss of driving power in a single compressor stage can significantly degrade the overall compressor performance. A short-circuit fault is a typical electrical failure in an electric motor that can lead to a complete loss of driving power. One innovative post-fault operation strategy is to utilize the braking capability of the failed motor at low speed to lock its corresponding compressor stage. In this way, the failed stage can function as a stator stage, still providing degraded flow-guiding capability and preventing reverse rotation. This article investigates the short-circuit protection strategy and post-fault operation of dual three-phase permanent magnet synchronous motors (DTP-PMSMs) for hybrid electric CRC applications. Analytical models are developed to characterize the post-fault behavior of the DTP-PMSM. Key design factors are defined, and their influence on post-fault performance is analyzed. Critical post-fault operating points are identified to evaluate and compare different protection strategies. Based on these results, an optimized shortcircuit protection strategy is proposed for DTP-PMSMs in CRC applications. Finally, the analytical findings and the proposed strategy are validated through simulation.}, subject = {Windings; Circuit faults; Rotors; Torque; Protection}, language = {en} } @article{JuliaJuliaTobias2025, author = {Julia, Zscherneck and Julia, Binder and Tobias, Mettenberger}, title = {Rural network assemblages : disentangling egocentric networks of digital pioneers in peripheral German regions}, series = {Regional studies, regional science}, volume = {12}, journal = {Regional studies, regional science}, number = {1}, publisher = {Routledge}, address = {London}, issn = {2168-1376}, doi = {10.1080/21681376.2025.2594312}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-72787}, pages = {996 -- 1012}, year = {2025}, abstract = {Digital solutions are seen as promising ways of addressing current challenges in rural regions. Individual or group key actors accessing resources foster these developments through networks. In light of regional clustering and agglomeration effects on the one hand and increased virtual mobility on the other hand, assumptions about the spatiality of such networks are highly controversial. Our paper takes this as a point of departure, asking how spatiality is constructed in the networks of so-called 'digital pioneers' (DPs). The sampling process took place in two German rural regions with different preconditions for digital technology adoption, where we conducted egocentric network analysis and qualitative interviews. Employing the assemblage perspective, we analysed networks of 30 individuals in terms of the analytical categories of territoriality, stability and connectivity. Our findings distinguish between three important roles of network contacts: (1) multipliers in social networking, (2) users of the DP's products and services, as well as (3) close family members that are important in professional contexts. Although DPs are often deeply embedded in and feel attached to their region, networks vary significantly in their territorial radius, also including highly functional problem-solving contacts to distant places. Consequently, our evidence challenges static territorial models of innovation processes, advocating for processual and multidimensional perspectives that consider social networks and individual agency. Likewise, our study complements current research on rural governance by shifting the focus from key institutions and formal networks to less formally integrated actors and problem-solving networks.}, subject = {Qualitative network analysis; Assemblage; Bridging and bonding ties; Peripheral regions Germany}, language = {en} } @article{MalkRiedelHinzetal.2025, author = {Malk, Konrad and Riedel, Ramona and Hinz, Christoph and Fischer, Thomas and Martienssen, Marion}, title = {Adsorption of phosphonates to iron- or aluminum-based flocculants in wastewater treatment}, series = {Water}, volume = {18}, journal = {Water}, number = {1}, publisher = {MDPI}, address = {Basel}, issn = {2073-4441}, doi = {10.3390/w18010116}, year = {2025}, abstract = {In this study, we investigated the impact of varying iron (Fe) and aluminum (Al) contents on the adsorption of phosphonates to activated sludge. Phosphonates originating from household applications account for up to 40\% of the non-reactive dissolved phosphorus in domestic sewage treatment plants and thus can contribute to the eutrophication of water bodies. Although these substances are not readily degradable, substantial quantities, ranging from 40\% to more than 90\%, are removed by sludge adsorption. The results demonstrate a strong correlation between the adsorption of aminophosphonates and the Fe3+ content of the sludge. The maximum phosphonate loadings were 5.94 mmol g-1 Fe3+ for ATMP, 4.94 mmol g-1 Fe3+ for EDTMP, 4.74 mmol g-1 Fe3+ for DTPMP, and 2.25 mmol g-1 Fe3+ for glyphosate. In contrast to pure ferric hydride flocs, the adsorption of phosphonates was approximately threefold higher when the hydroxides were located within activated sludge flocs. It is concluded that native sludge flocs provide larger iron surfaces than ferric hydroxide alone. Based on the weight of the adsorbents, aluminum salts were four times less efficient than ferric salts. In sludge without ferric or aluminum hydroxides, phosphonate adsorption was negligible.}, subject = {Adsorption; Activated sludge; Ferrous oxide; Phosphonates; Wastewater treatment}, language = {en} } @article{SenguelReiterLotfietal.2025, author = {Seng{\"u}l, Akant and Reiter, Sebastian and Lotfi, Zahra and Efremenko, Julia and Laroussi, Arwa and Corley-Wiciak, Agnieszka Anna and Ratzke, Markus and Mirsky, Vladimir M. and Wenger, Christian and Fischer, Inga Anita}, title = {Titanium nitride plasmonic nanohole arrays with polymer coating : optical properties and their humidity-induced modifications}, series = {Optical Materials Express}, volume = {16}, journal = {Optical Materials Express}, number = {2}, publisher = {Optica Publishing Group}, address = {Washington D.C.}, issn = {2159-3930}, doi = {10.1364/OME.578871}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-72739}, pages = {184 -- 196}, year = {2025}, abstract = {The use of titanium nitride (TiN) for the fabrication of plasmonic structures such as nanohole arrays (NHAs) can enable their integration into optoelectronic devices on the silicon (Si) platform, for example, for the realization of on-chip chemical sensors and biosensors based on refractometric transduction. With a corresponding functionalization of the TiN nanohole arrays, these ultra-compact devices can be utilized in the development of various affinity sensors and sensor systems, such as cost-effective electronic noses for the early detection of gases in the food industry or agriculture. In this work, we focus on two types of coating for functionalization of TiN nanohole arrays: electrochemically synthesized poly-N-methylaniline and layer-by-layer deposited polyacrylic-acid/poly-allylamine (PAA/PAH). Our investigation comprises the experimental characterization of the optical properties of TiN nanhole arrays coated with polymer layers of different thicknesses as well as a comparison with simulation results. We demonstrate the potential of our setup sensing applications by measuring changes in optical properties of TiN nanohole arrays coated with PAA/PAH upon exposure to air of different humidity.}, subject = {Chemical sensors; Extraordinary optical transmission; Localized surface plasmon resonance; Optical coatings; Optical properties; Refractive index}, language = {en} } @article{OleynikRyzhakSchlipfetal.2025, author = {Oleynik, Paul and Ryzhak, Diana and Schlipf, Jon and Alvarado Chavarin, Carlos and Yamamoto, Yuji and Berkmann, Fritz and Ratzke, Markus and Fischer, Inga Anita}, title = {Influence of illumination conditions on photoluminescence enhancement in an Al/Si/Ge metasurface}, series = {Optics Express}, volume = {34}, journal = {Optics Express}, number = {1}, publisher = {Optica Publishing Group}, address = {Washington D.C.}, issn = {1094-4087}, doi = {10.1364/OE.577751}, pages = {78 -- 86}, year = {2025}, abstract = {Strong field enhancement supported by metasurfaces at resonance can be used to control and enhance the spontaneous emission rate of emitters. This is particularly relevant for emitters with comparatively low quantum yield such as germanium. Here, we investigate the µ-photoluminescence response obtained from a hybrid metasurface comprising a square lattice of Al/Si/Ge pillars. We explore how variations in excitation energy, excitation intensity and number of excited meta-atoms affect the spectral dependence of the photoluminescence signal and, in particular, the contribution of the metasurface to it. Our metasurface exhibits a magnetic dipole collective lattice resonance, whose contribution to the photoluminescence signal increases with increasing number of excited meta-atoms. Measuring only one metasurface under different illumination conditions can potentially be an alternative approach to probe the transition between finite-size effects and collective effects.}, subject = {Field enhancement; Germanium; Light emitting diodes; Photonic crystals; Quantum light sources; Scanning electron microscop}, language = {en} } @article{KimGerstbergerAslietal.2025, author = {Kim, Dongsuk and Gerstberger, Ulf and Asli, Majid and H{\"o}schler, Klaus}, title = {U-Net Driven Semantic Segmentation for Detection and Quantification of Cracks on Gas Turbine Blade Tips}, series = {Results in Engineering}, volume = {29}, journal = {Results in Engineering}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2590-1230}, doi = {10.1016/j.rineng.2025.108864}, year = {2025}, abstract = {Crack detection and quantification on gas turbine blades is crucial for component validation during the development phase and for operational efficiency in service, as unexpected cracks can compromise blade integrity and lead to early engine removals. Gas turbine blades operate under extreme thermal and mechanical stresses, making them particularly susceptible to crack formation. At the same time deterministic predictions of crack formation are subject to high uncertainty in material data and actual loading conditions. Accurate detection and quantification of cracks, therefore, is essential for the validation and calibration of life predictions in order to prevent in-service failures, to extend component lifespan, and to reduce maintenance costs. This study introduces a U-Net based semantic segmentation model designed to automate crack detection on turbine blade tips. The model was trained on a dataset of 210 surface images with and without evidence of cracks, each divided into 128  ×  128 pixel patches. Data augmentation techniques were applied to address the class imbalance between cracked and non-cracked pixels. The U-Net architecture, optimized with a Dice loss function, achieved a validation IoU of 0.7557, along with approximately 85\% recall and precision in identifying cracked pixels. The pixel-based accuracy of the model primarily affects the quantification of cracks rather than their identification. A sliding window pipeline was implemented to extend the model's applicability, enabling segmentation of entire blade tip images for comprehensive crack localization. While the model may occasionally miss low-contrast cracks, it holds potential as a supplementary tool for manual inspection as part of the life prediction validation. By providing automated crack localization and quantification, the model can assist in analyzing crack characteristics relative to engine operating conditions.}, subject = {Crack detection; Semantic segmentation; Gas turbine blade; U-Net; Deep learning; Convolutional neural network}, language = {en} }