TY - JOUR A1 - Volz, Stefan A1 - Storath, Martin A1 - Weinmann, Andreas T1 - Degrees-of-freedom penalized piecewise regression JF - Information and Inference: A Journal of the IMA N2 - Many popular piecewise regression models rely on minimizing a cost function on the model fit with a linear penalty on the number of segments. However, this penalty does not take into account varying complexities of the model functions on the segments potentially leading to overfitting when models with varying complexities, such as polynomials of different degrees, are used. In this work, we enhance on this approach by instead using a penalty on the sum of the degrees of freedom over all segments, called degrees-of-freedom penalized piecewise regression. We show that the solutions of the resulting minimization problem are unique for almost all input data in a least squares setting. We develop a fast algorithm that does not only compute a minimizer but also determines an optimal hyperparameter—in the sense of rolling cross validation with the one standard error rule—exactly. This eliminates manual hyperparameter selection. Our method supports optional user parameters for incorporating domain knowledge. We provide an open-source Python/Rust code for the piecewise polynomial least squares case which can be extended to further models. We demonstrate the practical utility through a simulation study and by applications to real data. A constrained variant of the proposed method gives state-of-the-art results in the Turing benchmark for unsupervised changepoint detection. Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:863-opus-57846 SN - 2049-8772 VL - 14 IS - 1 PB - Oxford University Press ER - TY - JOUR A1 - Gonzalez-Salazar, Miguel A1 - Malcher, Xenia T1 - Strategies for decarbonizing European district heating BT - Evaluation of their effectiveness in Sweden, France, Germany, and Poland JF - Energy N2 - Decarbonizing the EU’s district heating is crucial for meeting climate goals and securing a sustainable energy future. Currently, district heating suffers from inefficiency, high operating temperatures, significant distribution losses, and reliance on fossil fuels. Literature highlights strategies for reducing emissions, including integrating low-carbon heat sources, lowering supply temperatures, and employing efficient technologies like heat pumps and combined heat and power (CHP). However, the individual effectiveness of these strategies in reducing emissions within existing networks remains unassessed. This study addresses the gap by applying a comprehensive model that evaluates energy and emissions across the district heating supply chain, coupled with a derivative-based sensitivity analysis. We apply this methodology to the national-level district heating systems of Sweden, France, Germany, and Poland. Results indicate that the impact of decarbonization strategies on district heating emissions varies significantly by the system’s characteristics, i.e., the energy mix in power and district heating supply and the presence of CHP plants. Primarily, incorporating more low-carbon heat sources emerges as the most effective method for emission reduction across nearly all examined countries. A 1 % increase in the share of low-carbon heat sources can potentially cut emissions by 0.8–1.3 kg CO2e per GJ of heat. In countries like Sweden and France, where the power generation already relies heavily on low-carbon resources, technologies which convert electricity to heat—such as heat pumps and electric boilers—rank as the second most effective approach. In contrast, for countries like Germany and Poland, with their moderate to low use of low-carbon power, reducing distribution losses and decreasing heat demand prove more effective, with emission reductions ranging between 0.8-1.3 and 0.7–1.2 kg CO2e per GJ in these countries, respectively. Additionally, cutting down power generation in fossil fuel-based CHP plants significantly reduces emissions in these regions. While green hydrogen and carbon capture and storage (CCS) also contribute to emission reductions, a 1 % increase in green hydrogen’s share might decrease emissions by just 0.3–0.5 kg CO2e per GJ of heat, highlighting their lower effectiveness compared to the aforementioned strategies. These insights hold value for both district heating operators and for technology suppliers seeking decarbonization pathways. This is also true for policy- makers focused on climate change mitigation, guiding the distribution of subsidies and R&D investments. Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:863-opus-57558 VL - 306 PB - Elsevier ER - TY - JOUR A1 - Chaudhary, Renu A1 - Diethelm, Kai A1 - Hashemishahraki, Safoura T1 - On the separation of solutions to fractional differential equations of order α ∈ (1, 2) JF - Applied Numerical Mathematics N2 - Given a Caputo-type fractional differential equation with order between 1 and 2, we consider two distinct solutions to this equation subject to different sets of initial conditions. In this framework, we discuss nontrivial upper and lower bounds for the difference between these solutions. The main emphasis is on describing how such bounds are related to the differences of the associated initial values. Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:863-opus-57338 VL - 203 SP - Article No. 38 ER - TY - JOUR A1 - Singh, Vikram A1 - Chaudhary, Renu A1 - Kumar, Umesh A1 - Kumar, Sandeep T1 - Approximate Controllability of Fractional Evolution System on Non-Dense Domain JF - Qualitative Theory of Dynamical Systems N2 - This article explores the existence and approximate controllability of integral solutions for Hilfer fractional evolution equations in a non-dense domain. Leveraging the well-known generalized Banach contraction theorem, we establish both the existence and uniqueness of the integral solution. Furthermore, we adopt a sequential approach to derive results related to approximate controllability, without relying on the compactness of semigroups or the uniform boundedness of nonlinear functions. To validate our findings, we present and discuss an illustrative example. Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:863-opus-57760 SN - 1575-5460 VL - 23 IS - S1 PB - Springer ER - TY - JOUR A1 - Diethelm, Kai A1 - Hashemishahraki, Safoura A1 - Thai, Ha Duc A1 - Tuan, Hoang The T1 - A constructive approach for investigating the stability of incommensurate fractional differential systems JF - Journal of Mathematical Analysis and Applications N2 - This paper is devoted to studying the asymptotic behaviour of solutions to generalized incommensurate fractional systems. To this end, we first consider fractional systems with rational orders and introduce a criterion that is necessary and sufficient to ensure the stability of such systems. Next, from the fractional order pseudospectrum definition proposed by Šanca et al., we formulate the concept of a rational approximation for the fractional spectrum of incommensurate fractional systems with general, not necessarily rational, orders. Our first important new contribution is to show the equivalence between the fractional spectrum of a incommensurate linear system and its rational approximation. With this result in hand, we use ideas developed in our earlier work to demonstrate the stability of an equilibrium point to nonlinear systems in arbitrary finite-dimensional spaces. A second novel aspect of our work is the fact that the approach is constructive. It is effective and widely applicable in studying the asymptotic behaviour of solutions to linear incommensurate fractional differential systems with constant coefficient matrices and linearized stability theory for nonlinear incommensurate fractional differential systems. Finally, we give numerical simulations to illustrate the merit of the proposed theoretical results. Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:863-opus-57547 VL - 540 ER - TY - JOUR A1 - Oeser, David A1 - Hein, Thiemo A1 - Ziegler, Andreas A1 - Seefried, Michael A1 - Gielinger, Sebastian A1 - Montesinos-Miracle, Daniel A1 - Bohn, Gunther A1 - Ackva, Ansgar T1 - Age-related development of cell-to-cell variation under various operating conditions in commercial NMC/graphite lithium-ion cells JF - Journal of Energy Storage N2 - In real applications, lithium-ion cells are usually used in individual interconnections, with the worst cell determining capacity, performance and service life. Due to different ageing rates of the assembled cells, cell-to-cell variation changes over lifetime. In literature, cell-to-cell variation is usually investigated near room temperature under one operating condition. Data regarding cell-to-cell variation above and below room temperature under different operating conditions are hard to find. To fill the gap in literature, this study considers cell-to-cell variation as a function of different charge/discharge currents at ambient temperatures between 0 °C and 40 °C on commercial NMC/graphite cells (Samsung SDI ICR18650-26J). The results demonstrate that cell-to-cell variation strongly depends on the selected operating conditions. In particular, operating conditions near the lithium plating boundary at the beginning of the ageing process have a particularly high risk of developing a pronounced variation. Fast charging or charging at lower temperatures should therefore be avoided. Operation at moderate temperatures and currents, on the other hand, only leads to a slight increase in cell-to-cell variation in the tests carried out. A 24-month storage during the testing period at 30% SOC and room temperature of the same cells shows even a slight reduction in cell-to-cell variation. Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:863-opus-57585 VL - 101 PB - Elsevier ER - TY - JOUR A1 - Gläser, Carolin A1 - Bördlein, Christoph T1 - An Application of Behavioral Science to Improve Bicycle Safety: An Innovative Behavioral Prompting Technique JF - Behavior and Social Issues N2 - From a behavioral community perspective, cyclists’ decisions to wear helmets reflect social and cognitive biases rather than purely rational risk assessment. Despite awareness of helmet safety benefits, many cyclists, particularly students, forget helmets due to perceived inconvenience and an underestimation of risk on short trips. In a university-based intervention, we applied a community-driven behavioral prompting technique by distributing stickers featuring the Bavarian Prime Minister wearing a helmet. This simple cue led to a temporary two- to threefold increase in helmet use. However, the effect diminished over time, highlighting the limitations of this student-driven intervention. Future research should explore sustained behavioral change strategies, integrating repeated or varied prompts to reinforce long-term impact within student communities. Y1 - 2025 U6 - https://doi.org/https://doi.org/10.1007/s42822-025-00208-6 SN - 1064-9506 PB - Springer Science and Business Media LLC ER - TY - JOUR A1 - Malcher, Xenia A1 - Tenorio-Rodriguez, Francis Catherine A1 - Finkbeiner, Matthias A1 - Gonzalez-Salazar, Miguel T1 - Decarbonization of district heating: A systematic review of carbon footprint and key mitigation strategies JF - Renewable and Sustainable Energy Reviews Y1 - 2025 U6 - https://doi.org/https://doi.org/10.1016/j.rser.2025.115602 SN - 1364-0321 VL - 215 PB - Elsevier BV ER -