Publications
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Members of TU Berlin can publish different kinds of (text) publications on DepositOnce:
- publications with academic content such as monographs and collected editions, journal articles and book chapters, conference proceedings and conference papers, research reports,
- publications that must be made public in connection with examination regulations (doctoral theses and post-doctoral theses),
- theses of TU Berlin students if the thesis has received the grade "very good" and the publication is endorsed by the supervisor or referee.
The following publication types can be selected: Doctoral thesis, Habilitation, Master thesis, Bachelor thesis, Book, Conference Proceedings, Periodical Part, Preprint, Report, Research Paper, Article, Book Part, Conference Object
For further information on requirements and workflows see Checklists and Hints for Publishing.
Contact:- Dissertation Office (theses): [email protected]
- University Press: [email protected]
- Other text publications (reports, open access self-archiving for journal articles, etc.): [email protected]
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- 2025Doctoral Thesis
Evaluating the potential of life on superhabitable exoplanets in the habitable zones around K dwarf stars
Earth may be our only example of a life-bearing world, but it might not be the optimal habitat for life. Superhabitable planets—those with conditions even more favorable than Earth’s—could provide richer, more stable environments that enhance the chances for complex life to emerge and thrive. A superhabitable planet would likely be slightly larger and more massive than Earth, with a denser atmosphere, warmer surface temperatures, and a balanced distribution of land and water to support diverse ecosystems. Such planets might orbit long-lived, stable stars like K dwarfs, which are cooler and less active than our Sun but more favorable than the smaller and often volatile M dwarf stars. Despite the promise of these worlds, there remain significant gaps in our understanding of the specific conditions that enhance habitability and the signs of life that might be detectable on these planets. To address these gaps, this dissertation explores the potential of superhabitable planets around K dwarf stars through three interconnected studies. The first study examines Earth’s Phanerozoic Eon to identify key periods of enhanced habitability, revealing how changes in oxygen and carbon dioxide levels, temperature, and water availability have historically impacted the biosphere. This analysis shows that periods with higher oxygen and stable, warmer and wetter climates supported greater biodiversity and biomass, providing a comparative framework for assessing potential biospheres on exoplanets. The second study experimentally investigates photosynthetic responses of garden cress Lepidium sativum and the cyanobacterium Chroococcidiopsis sp. CCMEE 029 under simulated K dwarf star illumination. We find that while garden cress grows comparably to Earth conditions, cyanobacteria exhibit a significant increase in photosynthetic efficiency, indicating that life under K dwarf illumination could be highly productive. The third study uses atmospheric modeling tools to simulate the environments of superhabitable planets around K dwarfs and assesses their observability with the James Webb Space Telescope (JWST). The results suggest that planets located at the center of the habitable zones around K dwarf stars may not be as habitable or observable as previously believed. Instead, the optimal position for habitability appears to be midway between the inner edge and the center of the star’s habitable zone. Furthermore, such planets could have enhanced atmospheric biosignatures–such as elevated levels of oxygen and nitrous oxide–and larger transit depths, making them significantly more detectable than Earth-like planets around Sun-like stars. Upcoming telescopes and space missions, such as the Extremely Large Telescope (ELT) and NASA’s Habitable Worlds Observatory (HWO), have the potential to considerably cut down observation times needed for detecting such habitable conditions. By integrating geological, biological, and simulated observational data, these findings collectively advance our understanding of what makes a planet superhabitable and demonstrate the unique potential of planets around K dwarf stars as candidates in the search for extraterrestrial life. Future research should aim to refine atmospheric modeling and broaden laboratory experiments to confirm the environmental conditions that could support life, ultimately enhancing our ability to identify truly habitable exoplanets. - 2022-04-01Article
A new class of double phase variable exponent problems: Existence and uniqueness
In this paper we introduce a new class of quasilinear elliptic equations driven by the so-called double phase operator with variable exponents. We prove certain properties of the corresponding Musielak-Orlicz Sobolev spaces (an equivalent norm, uniform convexity, Radon-Riesz property with respect to the modular) and the properties of the new double phase operator (continuity, strict monotonicity, (S+)-property). In contrast to the known constant exponent case we are able to weaken the assumptions on the data. Finally we show the existence and uniqueness of corresponding elliptic equations with right-hand sides that have gradient dependence (so-called convection terms) under very general assumptions on the data. As a result of independent interest, we also show the density of smooth functions in the new Musielak-Orlicz Sobolev space even when the domain is unbounded. - 2024Article
Monotonicity formulas and (S_+)-property: Old and new
The connection between monotonicity formulas and the (S_+)-property is that, for some popular differential operators, the former is used to prove the latter. The purpose of this paper is to explore this connection, remark how in the past both the monotonicity formulas and the (S_+)-property were focused on power-law growth, and prove the same type of results for a more general class of operators. - 2025-01Book
Texte, Blätter, Verzweigungen. Handbuch der zeitgenössischen deutschsprachigen Literatur
55 deutschsprachige Autorinnen und Autoren 2005-2020: Diskursfelder, Beschreibung, Transformationen, Kritik. Dies ist eine Übersicht über zeitgenössische deutschsprachige Erzählliteratur mit einer Einführung zum Erzählen und zu den Beschreibungsinstrumenten für einen erzählenden Text. Das Buch enthält Fotografiekunst von Sandra Ratkovic. - 2021-04-10Article
Computational analysis and experimental calibration of cold isostatic compaction of Mg-SiC nanocomposite powders
The consolidation process and density distribution of Mg-SiC nanocomposite powder were studied using computational finite element modeling (FEM) and experimental approaches. Cold isostatic pressing (CIP) was employed for producing fully dense Mg-SiC nanocomposites with a homogeneous distribution of SiC nanoparticles. The elastoplastic modified Drucker-Prager Cap (DPC) model was applied to predict SiC nanoparticle density distribution effects on the milled powder compressibility after the CIP. The FEM results revealed that increasing SiC nanoparticles from 1% (M1Sn) to 10% (M10Sn) volume leads to harder compressibility, increasing the maximum equivalent pressure stress value 717.2 to 737.1 MPa, and decreasing the relative density value 94.63% to 88.67%. The maximum element volume (EVOL) for pure Mg (MM), M1Sn, and M10Sn powders was estimated as 21.69, 20.13, and 15, respectively. The model is validated by comparing finite element simulations with experimental results of relatve density and reduction of volume under 700 MPa cold isostatic pressure for MM, M1Sn, and M10Sn powders. The finite element modeling results of samples after the CIP process were consistent with the experimental results. These results indicate the effectiveness of the modified DPC model and confirmed compaction behavior and relative density of Mg-SiC nanocomposite powders. - 2024-05-22Article
Unprivileged groups are less served by green cooling services in major European urban areas
Heat stress is the leading climate-related cause of premature deaths in Europe. Major heatwaves have struck Europe recently and are expected to increase in magnitude and length. Large cities are particularly threatened due to the urban morphology and imperviousness. Green spaces mitigate heat, providing cooling services through shade provision and evapotranspiration. However, the distribution of green cooling and the population most affected are often unknown. Here we reveal environmental injustice regarding green cooling in 14 major European urban areas. Vulnerable residents in Europe are not concentrated in the suburbs but in run-down central areas that coincide with low-cooling regions. In all studied areas, lower-income residents, tenants, immigrants and unemployed citizens receive below-average green cooling, while upper-income residents, nationals and homeowners experience above-average cooling provision. The fatality risk during extreme heatwaves may increase as vulnerable residents are unable to afford passive or active cooling mitigation. - 2024Doctoral Thesis
Potential and challenges of open source hardware development
Open source hardware (OSH) is a practical phenomenon transferring the idea of open source from software to physical objects. It thus requires theoretical founding with regard to epistemic knowledge in engineering science. This thesis investigates how the advancement of open source product development processes, openness and cultivation of company collaboration in OSH development for mechanical and mechatronic products can be better supported conceptually through the investigation of collaborative capacity, integration of quality tools, development of assessment schemes, and investigation of the concept of company-community collaboration. It responds to this question by delivering the following cumulative work: empirical research of open source product development processes and integration of classical quality tools; development of OSH assessment schemes for product marking and design reuse; and comparing and contrasting of the concept of company-community collaboration and its key enablers for collaboration between companies and OSH communities for enriching OSH development and mutual benefit. The thesis follows an industrial-engineering-based design science research framework guiding the development and refinement of conceptual models, methods and tools for providing guidance and reinforcing of principles of OSH for the benefit of all involved actors specifically, including OSH practitioners, businesses and civil society. - 2024Doctoral Thesis
Revealing challenges and opportunities in cycling safety through crowdsourcing
An increased modal share of bicycle traffic is a key mechanism to reduce emissions and solve traffic-related problems. However, a lack of comfort and (perceived) safety keeps people from using their bicycles more frequently. To improve comfort and safety in bicycle traffic, city planners need (a), an overview of accidents, near miss incidents, and bike routes, (b), an overview of the cycling infrastructure's maintenance state, and (c), a way to study the effect of potential changes in the cycling infrastructure before implementing them in the real life. However, these needs, which are also of interest to cyclists and policy makers, are currently not being met satisfactorily. In this thesis, we present three main contributions to solve these problems. First, we show SimRa, a crowdsourcing-based citizen science project to record cycling trips and near miss incidents. As part of this contribution, we also present CycleSense, an approach based on Deep Learning to automatically detect near miss incidents from recorded cycling trip data. Knowing the hazardous bicycle traffic hotspots, policy makers and city planners can approve and implement safety improvements for cyclists. Cyclists, on the other hand, can use this information to circumvent these spots. Second, we describe an approach for deriving the road surface quality from cycling trip data. Our approach uses data produced by the inertial measurement unit of the smartphone to calculate the smoothness of the road surface from the vibrations caused by traversing on the road with a bicycle. We then show how our approach can easily be integrated into a cycling trip recording app with SimRa as a case study. This contribution also contains a visualization of the cycling infrastructure's smoothness and helps policy makers, city planners and cyclists in the same way as our first contribution. Third, we improve the cyclist simulation model of the urban traffic simulation software SUMO. For this, we first show that the default cyclist model of SUMO is not realistic by comparing it to cyclist behavior in the SimRa dataset. We then split the cycling trips in the SimRa dataset into three parts for slow, medium, and fast cyclists and implement our findings as a plugin that can be added to SUMO for a more realistic cyclist simulation. This new cyclist simulation can provide a strong tool for city planners to better to study effects of potential changes in the traffic infrastructure. - 2024Doctoral Thesis
Agility at the front end of innovation – rapid validity testing as a way for mid-sized firms to improve innovation performance
The focus is on decision-making during the early stages of innovation, where high levels of uncertainty and ambiguity are prevalent. Previous findings underscore that early validation of ideas is crucial for the success of innovation processes, leading to the adoption of methodologies such as lean innovation (Ries, 2011), prototyping (Bogers and Horst, 2014), design thinking (Carlgren, Rauth, and Elmquist, 2016), and pretotyping (Savoia, 2019). Despite their growing popularity, empirical evidence supporting these approaches remains sparse, highlighting the need for strategies that accelerate formal responses while preserving flexibility. Rapid validity testing (RVT) (Peña Häufler, Globocnik, Landaeta Saldías, and Salomo, 2021) is introduced as a concept that synthesizes aspects of these existing methods to enable the swift testing of new ideas' assumptions. The success of RVT in enhancing innovation performance is influenced by factors such as organizational culture and technological turbulence. A quantitative empirical approach involving data from 1,625 respondents across 232 firms in Europe and Latin America was employed. The findings reveal that technological turbulence, risk aversion, and long-term orientation moderate the positive impact of RVT on innovation performance. The insights gained provide a deeper understanding of the complexities involved in the front-end of innovation (FEI) and offer practical guidance for managers navigating uncertainty and error management in early innovation stages. Furthermore, the study identifies effective patterns for improving firm competitiveness in various contexts. - 2024Doctoral Thesis
Relative and systematic methods in computational alchemy
The prediction of properties is among the central pursuits of computational chemistry, condensed matter, and materials design. However, the mathematical and computational difficulties associated with solving the underlying Schrödinger equation, and the impossibility of encyclopedic approaches due to the sheer scaling of chemical compound space, are often reasons to resort to relative and approximate methods, the latter being preferably systematic, i.e. generalizable and equipped with an error estimate. In this thesis, we contribute two such relative and systematic approaches: firstly, we establish the Alchemical Integral Transform (AIT) based on thermodynamic integration of electronic energies along an alchemical path lambda between two iso-electronic systems A and B. In its essence, the AIT allows its user to transfer the lambda-dependency inherent to a general electron density to a parametrization of coordinates in the initial electron density. We examine rigorous and approximate parametrizations for different systems. The parametrization allows a natural inclusion of external constrains, e.g. a known electric dipole moment. However, these constraints also limit the possible compounds under consideration which might be a worthwhile endeavor in the context of machine learning (ML) models---either for the purpose of efficient data selection or when informing ML architectures. Secondly, we employ a novel alchemical and harmonic Ansatz in lambda (AHA) combined with a new, electronic interatomic potential to describe the energy of all neutral iso-electronic diatomics with one calibration calculation. This is used as a baseline model in Delta-ML using kernel ridge regression to evaluate its systematic qualities. Through learning curves, we obtain sought after information about generalizability and scalability. In doing so, we find a clear example why a systematic baseline model is crucial for the accuracy of Delta-ML, as numerical proximity to reference data alone is shown to be a poor indicator for the quality of a model. So far, the AHA is limited to iso-electronic diatomics but with possible extensions to larger molecules, a matching number of valence electrons or multi-level learning.