openHSU – Research Showcase

4462
Research outputs
779
People
140
Organizational Units
108
Projects
31
Conferences
17
Journals
Recent Additions
  • Publication
    Open Access
    Untersuchung zu modularen Hochspannungsschaltern in Sonderanwendungen der Leistungselektronik
    (UB HSU, 2024-05-17)
    Kemper, Johannes
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    Helmut-Schmidt-Universität / Universität der Bundeswehr Hamburg
    ;
    Die vorliegende Arbeit befasst sich mit der Aufgabe, einen Hochspannungsschalter zu entwickeln. Zu den Herausforderungen der Aufgabenstellung gehörten das wiederholte, schnelle Schalten einer unterschiedlich hohen Spannung mit der Möglichkeit eines kontrollierten bidirektionalen Stromflusses. Der realisierte Schalter erweitert den Stand der Technik dahingehend, dass er einen Leistungshalbleiter im linearen Bereich ansteuert, um die Spannungssymmetrie in einer Reihenschaltung zu ermöglichen. Das Gesamtsystem aus Schalter und Ansteuerung kann hinsichtlich der Spannungsfestigkeit zu jedem Zeitpunkt skalierbar werden. Die Treiberschaltungen beziehen ihre Energie aus dem Lastkreis parasitär und besitzen eine Stromaufnahme von weniger als 1mA im statischen Zustand. Für die Ansteuerung wird eine analoge Schaltung verwendet, die durch den Einsatz von diskreten Standardkomponenten eine hohe Verfügbarkeit der Bauteile sicherstellt.
  • Publication
    Open Access
    Diversity and (in)equality in organizations
    (UB HSU, 2024-05-08) ; ;
    Helmut-Schmidt-Universität / Universität der Bundeswehr Hamburg
    ;
    Rastetter, Daniela
    Despite extensive legal and organizational measures to promote diversity, inequalities in organizations, e.g. based on gender, class, or sexual orientation, persist or are (re)produced. This cumulative dissertation comprises six manuscripts that examine issues of diversity and inequality in organizations from a critical perspective. What are differences and inequalities and how are they maintained and (re)produced in daily work practices? The focus is on different aspects of doing difference and diversity as well as on specific contexts of work, management and organization, such as equal participation through e-voice in a digital alternative organization, intersections of gender and class in service work in the luxury segment, barriers and success factors for women’s entrepreneurship in the hospitality and tourism industry, and gay leaders in management. In the dissertation’s frame, the studies’ research perspectives and their critical, politicizing aim are reflected in order to position them within the research field of Critical Management Studies with a focus on diversity and (in)equality as well as in the field of Critical Diversity Studies with a focus on management and organizations.
  • Publication
    Open Access
    Advances in High-Power Electromagnetics: A Mechanical Perspective on Sources, Systems, Detection and Protection Techniques
    (UB HSU, 2024)
    AlMansoori, Mae
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    Helmut-Schmidt-Universität / Universität der Bundeswehr Hamburg
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    Rachidi-Haeri, Farhad
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    Kasmi, Chaouki
    This dissertation explores innovative advancements within the high-power electromagnetics (HPEM) domain, focusing on the optimization of electromagnetic sources, the development of compact and mechanically efficient systems, the rapid prototyping of advanced sensing techniques, and the conceptualization of effective protection methodologies. It adeptly bridges mechanical engineering and electromagnetics, enhancing conventional approaches and addressing existing challenges in the HPEM field. Key research methods span both computational and experimental modalities. First, a detailed stochastic analysis is conducted to optimize the design of Virtual Cathode Oscillators (Vircator), a type of HPEM source, with findings indicating a 30% increase in peak power output, accompanied by a minor frequency shift. A novel portable, cost-effective, and easily maintained switched oscillator (SWO) system is devised for susceptibility and vulnerability testing, employing mechanical integration and experimental validation. Furthermore, the dissertation employs additive manufacturing techniques to create a compact Luneburg lens, facilitating the design and validation of a portable direction-of-arrival estimation system. This innovative solution is not only more affordable than traditional counterparts, but its manufacturing process is streamlined and efficient. The research concludes with the prototyping of radar absorbing materials for stealth applications, utilizing intelligent rapid prototyping methodologies. This approach allows for enhanced production efficiency, thereby contributing to the field of protection techniques in HPEM. The implications of this thesis span the broad field of HPEM, encompassing electromagnetic sources, sensing, and protection techniques. The findings illuminate potential pathways for improving HPEM applications, integrating mechanical engineering insights, and emphasizing the importance of rapid prototyping methodologies.
  • Publication
    Open Access
    Der Einfluss der Rechtsform auf die Mitarbeiterbeteiligung
    (UB HSU, 2024-05-06)
    Roggan, Michael
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    ; ; ;
    Helmut-Schmidt-Universität / Universität der Bundeswehr Hamburg
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    Royer, Susanne
  • Publication
    Unknown
    Entwicklung eines semi-probabilistischen Bemessungskonzepts zur Optimierung der Füllung einer Binnenschifffahrtsschleuse
    (Helmut-Schmidt-Universität / Universität der Bundeswehr Hamburg, Bibliothek, 2024-04-25)
    Belzner, Fabian
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    ;
    Helmut-Schmidt-Universität / Universität der Bundeswehr Hamburg
    ;
    Schlenkhoff, Andreas
    Diese Dissertation beschäftigt sich mit der Vertäuung von Binnenschiffen in Schleusen. Ziel der Arbeit ist die Entwicklung einer Methodik zur Bestimmung der Seilkräfte der Vertäuung in Abhängigkeit von der Schiffskraft. Die Seilkräfte müssen begrenzt werden, um ein Versagen der Trossen zu verhindern. Im Fall eines Trossenrisses wird die Spannenergie schlagartig frei und es besteht Lebensgefahr durch zurückschnellende Trossenenden. Diese Forschungsarbeit leistet damit einen Beitrag zur notwendigen Überarbeitung der Kriterien für die während einer Schleusung zulässigen Schiffskräfte. Von der wirkenden Schiffskraft kann nicht direkt auf die wirkende Trossenkraft geschlossen werden, da letztere unter anderem von unbekannten Parametern wie Trossenlänge, Trossenmaterial und der Vorspannung abhängt. Aus diesem Grund werden Trossen und Schiffskräfte in einem statistischen Zusammenhang betrachtet. Damit wird das Verhältnis von Trossen- zu Schiffskraft durch einen Verstärkungsfaktor und eine korrespondierende Überschreitungswahrscheinlichkeit ausgedrückt, was eine direkte Bestimmung der zulässigen Schiffskräfte in Abhängigkeit von einem festzulegenden Risiko ermöglicht. Hierfür werden zunächst mit Monte-Carlo-Simulationen auf Basis eines stark abstrahierten Modells die wirkenden Trossenkräfte bestimmt. Der erzeugte Datensatz wird zur statistischen Beschreibung der Verstärkungsfaktoren genutzt. Die Zulässigkeit der Abstraktion wird durch einen Vergleich mit den Ergebnissen eines hierfür erstellten 3D-hydronumerischen Modells auf Basis des Strömungslösers OpenFOAM® nachgewiesen. Weiterhin wurde der hydronumerische Ansatz durch einen Vergleich mit einem gegenständlichen Labormodell des Systems validiert.
  • Publication
    Open Access
  • Publication
    Metadata only
    Knowledge discovery meets linked APIs
    (RWTH, 2013)
    Hoxha, Julia
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    ;
    Korevaar, Peter
    Knowledge Discovery and Data Mining (KDD) is a very wellestablished research field with useful techniques that explore patterns and regularities in large relational, structured and unstructured datasets. Theoretical and practical development in this field have led to useful and scalable solutions for the tasks of pattern mining, clustering, graph mining, and predictions. In this paper, we demonstrate that these approaches represent great potential to solve a series of problems and make further optimizations in the setting of Web APIs, which have been significantly increasing recently. In particular, approaches integrating Web APIs and Linked Data, also referred to as Linked APIs, provide novel opportunities for the application of synergy approaches with KDD methods. We give insights on several aspects that can be covered through such synergy approach, then focus, specifically, on the problem of API usage mining via statistical relational learning.We propose a Hidden Relational Model, which explores the usage of Web APIs to enable analysis and prediction. The benefit of such model lies on its ability to capture the relational structure of API requests. This approach might help not only to gain insights about the usage of the APIs, but most importantly to make active predictions on which APIs to link together for creating useful mashups, or facilitating API composition.
  • Publication
    Metadata only
    iService: Human Computation through Semantic Web Services
    (RWTH, 2008) ;
    Komazec, Srdjan
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    Grasic, Bostjan
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    Denaux, Ronald
    This paper presents iService, a platform which addresses the inferiority of computing technology in certain problem domains (like identifying objects in photos or videos or researching data details), by enabling a simple, scalable and on-demand access to human intelligence in the form of Semantic Web Services by using the Web as a platform and common mobile devices as user interface.
  • Publication
    Open Access
    Selektive Adsorption von Nickel(II)- und Cobalt(II)-Ionen aus sauren Prozesslösungen
    (Helmut-Schmidt-Universität / Universität der Bundeswehr Hamburg, 2024)
    Kriese, Friederike Karolin
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    Niemeyer, Bernd
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    Helmut-Schmidt-Universität / Universität der Bundeswehr Hamburg
    ;
    The demand for raw materials such as nickel, cobalt and lithium has risen due to the grow¬ing demand for batteries. In order to meet this high demand, the use of efficient recycling processes is becoming important. Adsorption as a basic process engineering operation is an efficient separation process, since e.g. a high selectivity can be set. In this work, a functionalized silica-based adsorbent for the selective separation of nickel(II) cations in the presence of cobalt(II) cations was identified and characterized with the aim of using it in battery recycling or in the electroplating of components with gold. On the one hand, it was challenging to find selectively binding ligands, as the two target substances have similar physical-chemical properties. On the other hand, acidic pH values and in¬creased temperatures are unfavorable process conditions for adsorptive bonding. In the course of the screening process for the adsorbent, it was identified that despite the initial acidic pH value, the pH value was shifted to the basic environment during adsorption by some of the functionalized adsorbents, so that separation took place by metal hydroxide precipi¬tation instead of adsorption. This was not considered in previous studies in the literature. The control of the pH value in the equilibrium state in discontinuous adsorption experiments was therefore established as the first screening criterion. The adsorbent HSU331, finally favored for the application, enabled the separation of nickel(II) and cobalt(II) by chelate complexation under the given process conditions. The complex nickel(II)/HSU331 always produced higher equilibrium constants in direct compari¬son to cobalt(II)/HSU331. Thus, the energetic effect was exploited as a selectivity mech¬anism. Consequently, high integral selectivities for nickel(II) up to S_(Nickel(II)/L,L) = 0.98 could be quantified. A requirement for the occurrence of selectivity was that the total initial ad¬sorptive amount corresponded approximately to the amount of substance of the binding sites present. The selectivity with respect to nickel(II) (up to S_(Nickel(II)/L,L) = 0.97) remained comparable when the model system nickel(II)/cobalt(II) was extended by lithium(I) or a gold electrolyte solution. Kinetical investigations showed that the equilibrium loadings were reached after 5 to 10 min, so that short residence times can be set for a later con¬tinuous operation of the adsorption. Desorption tests confirmed the difference in equilibrium state between nickel(II)/HSU331 and cobalt(II)/HSU331. Cobalt(II) was already completely desorbed by a diluted nitric acid solution with pH = 1.0, whereas nickel(II) was only desorbed at pH = 0.5.
  • Publication
    Open Access
    Durability of hybrid salt concretes for sealing structures for nuclear waste repositories in contact with saline solutions
    (Helmut-Schmidt-Universität / Universität der Bundeswehr Hamburg, 2024)
    Henning, Ricky
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    Helmut-Schmidt-Universität / Universität der Bundeswehr Hamburg
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    Götz-Neunhoeffer, Friedlinde