Eldorado - Repositorium der TU Dortmund

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Aktuellste Veröffentlichungen

Land prices and determinants of socio-economic development in Pleiku, Central Highlands, Vietnam
(2026-01-21) Phuong, Tran Trong; Vien, Tran Duc; Loc, Nguyen Duc; Khue, Phan Van; Trung, Nguyen Dinh; Scholz, Wolfgang
The rapid urbanization of Pleiku City, Vietnam, has led to a sharp increase in the demand for and prices of residential land, creating challenges for urban management and land valuation. This study aims to identify and quantify the key factors influencing residential land prices in Pleiku to provide a scientific basis for land use planning and smart urban development. Data were collected through surveys of 30 state officials involved in land valuation and 250 households living along major streets in Pleiku. Cronbach’s alpha was used to test the reliability of the collected data, and exploratory factor analysis (EFA) was used to identify influencing factor groups. The results show that residential land prices are strongly influenced by multiple factors, with location and infrastructure playing the most decisive roles. Market land prices were found to be approximately 1.5–2 times higher than state-regulated prices. Among the identified factor groups, location and infrastructure had the strongest influence, followed by economic, social, legal, and specific land use factors. Price differences between land plots mainly reflect variations in location, street characteristics, accessibility, and commercial potential. The study concludes that location and infrastructure development are the dominant drivers of residential land prices in Pleiku. These findings have important implications for land valuation, urban planning, and the implementation of smart urban construction policies in rapidly developing cities in Vietnam.
Mechanism of the flexible micro-tube plasma and the influence of a metallic target by temporally and spatially resolved spectroscopy and potential measurements in contrast to a corona discharge
(2026) Song, Hao; Kayser, Oliver; Franzke, Joachim
Diese Arbeit untersucht den Entladungsmechanismus typischer flexibler mikro-Tuben Plasmen (FμTP), den Einfluss benachbarter Ziele, die zugrunde liegenden Ionisierungsprozesse sowie die charakteristischen Merkmale, die FμTP von der Koronaentladung unterscheiden. Ziel ist es, die Wechselwirkungen zwischen elektrostatischem Potenzial, dem zeitlichen und räumlichen Verhalten der Plasmaentwicklung und der analytischen Leistungsfähigkeit zu verstehen. Zur Unterscheidung von Edelgas-Ionen und angeregten Spezies wurde eine neue Datenverarbeitungsmethode entwickelt. Mithilfe raum-zeitlich aufgelöster optischer Emissionsmessungen konnten die primären Anregungs- und Ionisierungsprozesse in He-FμTP und Ar-FμTP identifiziert werden. Gleichzeitig wurde der bislang unterschätzte Einfluss eines benachbarten Leiters auf die Plasmadynamik nachgewiesen. In diesem Zusammenhang werden die optischen Evolutionseigenschaften von FμTPs mit drei unterschiedlichen Polaritäten vor einem metallischen Ziel systematisch unter variierenden Abständen untersucht. Aufgrund ähnlicher Entladungsgeometrien wird das FμTP häufig fälschlicherweise als Wechselstrom-Koronaentladung betrachtet. Zur Korrektur dieses Missverständnisses umfasst die vorliegende Studie eine optische Charakterisierung von Gleichstrom- und Wechselstrom-Koronaentladungen. Darüber hinaus werden die elektrostatischen Potenziale im Umfeld von Koronaentladungen und FμTPs analysiert und miteinander verglichen. Ergänzend werden verschiedene Gleichspannungs-Bias in die Ansteuerspannung des FμTP integriert, das mit einem Massenspektrometer (MS) gekoppelt ist, um die Auswirkungen auf die analytische Leistung zu bewerten. Die kombinierte Analyse umfasst optische Emissionsspektren, das Ringpotenzial um die Plasmaregion, die Zündung des Diagnoseplasmas sowie die Signalintensität im MS – jeweils für Koronaentladungen und FμTP. Die zentrale Rolle der Kapillare im FμTP wird hervorgehoben: Sie steuert die Plasmabewegung, verstärkt den Restladungseffekt und isoliert die Sekundärelektronenemission. Diese Eigenschaften machen FμTP zu einer eigenständigen Technologie mit klaren Vorteilen. Auf Basis dieser Experimente wird das FμTP neu definiert – nicht lediglich als Koronaentladung, sondern als geführte Plasmasäule bzw. Plasmajet mit breitem Anwendungspotenzial. Indirekte Hinweise deuten darauf hin, dass FμTP als Ionisierungsquelle effizienter und schonender sein könnte als herkömmliche Koronaentladungen. Diese Erkenntnisse vertiefen das Verständnis der Ionisierungsmechanismen und liefern wertvolle Impulse für die wissenschaftliche Forschung und die ingenieurtechnische Nutzung der Plasmatechnologie.
Accelerating clustering algorithms with tree data structures
(2025) Lang, Andreas Roland; Schubert, Erich; Züfle, Andreas
Clustering is a central task in unsupervised learning, enabling the discovery of structure in data without prior labels. It supports a wide range of applications, from image recognition and anomaly detection to customer analytics and text mining. Despite decades of research, classical methods such as Hierarchical Agglomerative Clustering (HAC) and k-means remain popular due to their simplicity and interpretability, yet scaling them to large datasets is challenging. One of the most influential approaches for scalability is BIRCH, which introduced the Cluster Feature tree (CF-Tree) as a compact data representation. However, BIRCH suffers from numerical instability due to problematic variance computations, which can lead to catastrophic cancellation and unreliable results. This thesis presents BETULA, a refinement of BIRCH that replaces unstable variance formulas with robust running-statistics computations, preserving the efficiency of CF-Trees while ensuring numerical stability. For HAC, BETULA enables efficient and stable approximations of common linkage methods, making exploratory analysis feasible on much larger datasets. It also extends cluster features to support Gaussian Mixture Models, where (co-)variance-aware summaries allow scalable and stable optimization with high approximation quality. For k-means, we leverage variance information in cluster features to introduce new initialization strategies (tree, trunk, leaves) that approximate k-means++ and improve convergence speed over existing solutions. We show that the BETULA approximation for k-means delivers comparable results to standard k-means while being more efficient. For applications where approximation is not suitable, we present Cover-means, which accelerates exact k-means by integrating a Cover Tree index to prune redundant distance calculations, achieving superior runtime in a range of experimental settings. Finally, we highlight the crucial role of good initialization and its importance, directly influencing clustering quality.
Quantum resource theory of lasers
(2026-02-13) Brune, Yannik; Cizauskas, Marius; Assmann, Marc
Lasers serve as the fundamental workhorses of photonic quantum technologies, with perfectly coherent light fields being essential for many protocols that generate nonclassical light, implement coherent control schemes, and initialize qubits. However, no laser is absolutely ideal and the implications of deviations from perfect coherence in quantum technological tasks remain unclear. In this study, we theoretically and experimentally explore the quantum coherence properties of lasers from a resourcetheory perspective, establishing a significant connection between photonics, quantum optics, and quantum information science. We demonstrate that the maximum achievable quantum coherence for laser light is constrained by spontaneous emission and the purity of the dephased laser field state. As a critical example application in quantum information protocols, we show that the quantum coherence of a laser field with a given mean photon number directly governs the maximum purity attainable when initializing a qubit in a superposition state through resonant driving. Our findings are highly relevant for bridging applied physics and engineering with integrated photonic quantum technologies and resource theories, paving the way for reliable benchmarking of various coherent light sources for applications in photonics and quantum protocols.
Co-production of privately owned public space: who, why, when, and how?
(2024-01-29) Lee, Dahae; Scholten, Nele
The term ‘co-production’ has been used in various fields, including planning, as collaborative forms of public goods and service delivery gain significance. Co-production has two sides—the ‘co’ side refers to actors and their motivations, while the ‘production’ side refers to phases and instruments. This paper examines privately owned public space/s (POPS) based on the two sides of co-production. Thereby, it addresses two research gaps. First, less has been written to date on the involvement of actors other than local authorities and developers. Second, little attention has been paid to the phase through which POPS are co-produced. The paper fills these research gaps by presenting the empirical work undertaken in HafenCity, Hamburg. It reveals a wide range of actors engaged in four different phases through various instruments. This paper also identifies challenges of co-production of POPS, and makes recommendations.