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The edoc server is the Open Access publication server and institutional repository of the Humboldt-Universität zu Berlin. It is available to university members for the publication of academic work as a first or second publication. In addition to text publications, research data can also be published via the edoc server. These publications are available to the general public worldwide, free of charge and for the long term.

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Recent Submissions

Publication
2023-05-16Zeitschriftenartikel
Balanced-Viscosity Solutions to Infinite-Dimensional Multi-Rate Systems
(Mathematisch-Naturwissenschaftliche Fakultät) Mielke, Alexander; Rossi, Riccarda
We consider generalized gradient systems with rate-independent and rate-dependent dissipation potentials. We provide a general framework for performing a vanishing-viscosity limit leading to the notion of parametrized and true Balanced-Viscosity solutions that include a precise description of the jump behavior developing in this limit. Distinguishing an elastic variable u having a viscous damping with relaxation time εαand an internal variable z with relaxation time εwe obtain different limits for the three cases α∈(0,1), α=1and α>1. An application to a delamination problem shows that the theory is general enough to treat nontrivial models in continuum mechanics.
Publication
2022-06-22Zeitschriftenartikel
Political Theory of the Digital Constellation
(Kultur-, Sozial- und Bildungswissenschaftliche Fakultät) Berg, Sebastian; Staemmler, Daniel; Thiel, Thorsten
The introductory contribution to this special issue on “Political Theory of the Digital Constellation” addresses the conditions and possibilities of political theory’s engagement with digital developments. The motivation for this inquiry is the growing interest in questions of political theory arising from the digital transformation, as well as the acknowledgement that digitalisation not only changes politics, but conversely that politics also shapes digitalisation. The article identifies three pitfalls of previous engagement: The narrowing of the subject of “digitalisation” to the topic of the “internet” and, thereby, to the aspect of communication, the disregard for the technicality of the digital, and the insufficient recognition that (digital) technology is political. To avoid these pitfalls, the research perspective of the digital constellation is presented. The digital constellation serves as an epistemological guide that helps to structure theoretical reflection on the interrelationship between digitalisation and political questions. Ultimately, the outlines of the political theory in the digital constellation become clear in the fourteen contributions of the special volume, which are presented in conclusion.
Publication
2022-02-23Zeitschriftenartikel
Traveling Fronts in a Reaction–Diffusion Equation with a Memory Term
(Mathematisch-Naturwissenschaftliche Fakultät) Mielke, Alexander; Reichelt, Sina
Based on a recent work on traveling waves in spatially nonlocal reaction–diffusion equations, we investigate the existence of traveling fronts in reaction–diffusion equations with a memory term. We will explain how such memory terms can arise from reduction of reaction–diffusion systems if the diffusion constants of the other species can be neglected. In particular, we show that two-scale homogenization of spatially periodic systems can induce spatially homogeneous systems with temporal memory. The existence of fronts is proved using comparison principles as well as a reformulation trick involving an auxiliary speed that allows us to transform memory terms into spatially nonlocal terms. Deriving explicit bounds and monotonicity properties of the wave speed of the arising traveling front, we are able to establish the existence of true traveling fronts for the original problem with memory. Our results are supplemented by numerical simulations.
Publication
2023-12-07Zeitschriftenartikel
Time-domain modeling of interband transitions in plasmonic systems
(Mathematisch-Naturwissenschaftliche Fakultät) Pfeifer, Max; Huynh, Dan-Nha; Wegner, Gino; Intravaia, Francesco; Peschel, Ulf; Busch, Kurt
Efficient modeling of dispersive materials via time-domain simulations of the Maxwell equations relies on the technique of auxiliary differential equations. In this approach, a material’s frequency-dependent permittivity is represented via a sum of rational functions, e.g., Lorentz poles, and the associated free parameters are determined by fitting to experimental data. In the present work, we present a modified approach for plasmonic materials that requires considerably fewer fit parameters than traditional approaches. Specifically, we consider the underlying microscopic theory and, in the frequency domain, separate the hydrodynamic contributions of the quasi-free electrons in partially filled bands from the interband transitions. As an illustration, we apply our approach to gold and demonstrate how to treat the interband transitions within the effective model via connecting to the underlying electronic band structure, thereby assigning physical meaning to the remaining fit parameters. Finally, we show how to utilize this approach within the technique of auxiliary differential equations. Our approach can be extended to other plasmonic materials and leads to efficient time-domain simulations of plasmonic structures for frequency ranges where interband transitions have to be considered.
Publication
2023-06-10Zeitschriftenartikel
Field path optimization to reduce headland and turning maneuvers at regional scales: automated detection of cultivation direction in the state of Brandenburg, Germany
(Lebenswissenschaftliche Fakultät) Donat, Marco; Geistert, Jonas; Grahmann, Kathrin; Bellingrath-Kimura, Sonoko D.
Path planning for optimized field-work pattern is an important task within precision farming. The decision on a particular direction and path to cultivate and manage the field is complex and can significantly affect working time, energy consumption, soil compaction and yield. This study proposed a new method for automated detection of the current cultivation direction of several thousands of agricultural fields and compared the current cultivation direction with an optimized cultivation direction generated from a path planning algorithm. Airborne imagery from 2019 was analyzed using a modified Gabor filter. The identification takes place on a sub-plot level and can therefore detect small-scale differences in cultivation direction within fields. The method for identification of current cultivation direction had a high success rate of 87.5%. Fields with a high potential to save turning maneuvers and to reduce the area of headland were identified. From 3410 fields, a total of 58162 turning maneuvers and 507 ha headland were saved. This corresponds to 14.1% of all turning maneuvers and 7.6% of the total headland area for all analyzed fields in Brandenburg. A high optimization potential was demonstrated for field paths when efficient processing directions are taken into account. The method can be extended to the analysis of satellite imagery and thus offers the possibility of identifying current cultivation directions with a high spatial and temporal resolution. In future, this knowledge can be embedded within decision support systems for real-time optimization of field machinery path planning to support sustainable cropping practices.