U wie Un

Article for general public (2012)

The U.S.–China Supply Competition for Rare Earth Elements: A Dynamic Game View

in Environmental Modeling and Assessment (2022)

Rare earth elements govern today’s high-tech world and are deemed to be essential for the attainment of sustainable development goals. Since the 1990s, these elements have been predominantly supplied by ... [more ▼]

Rare earth elements govern today’s high-tech world and are deemed to be essential for the attainment of sustainable development goals. Since the 1990s, these elements have been predominantly supplied by one single actor, China. However, due to the increasing relevance of their availability, the United States, who imports 80% of its rare earths from China, recently announced its plan to (re-)enter the rare earths supply market. This paper analyzes the strategic interactions among these two countries in open-loop and Markovian strategy spaces. Particular interest is devoted to the impact of heterogeneous supply concepts on (1) the theoretical optimal timing for the U.S. to enter the non-renewable resource market, (2) China’s optimal supply reaction to the U.S.’ entry announcement, (3) the central planner outcome, and (4) the profitability of the suppliers’ extraction behavior. By setting up a continuous-time differential game model, we show that in the absence of arbitrage opportunity, (1) the U.S. should always postpone the production launch until its rare earths reserves coincide with those of China, (2) China’s monopolistic supply is not shaped by the selected strategy, (3) while the duopolistic Markovian behavior is initially more lucrative than open-loop commitment, the opposite situation emerges as the competition proceeds, and (4) on balance, both countries are financially better off when committing to an open-loop supply path. [less ▲]

UAS See-and-Avoid using two different approaches of Fuzzy Control

in 2012 International Conference on Unmanned Aircraft Systems (ICUAS'12) (2012)

This work presents two UAS See and Avoid approaches using Fuzzy Control. We compare the performance of each controller when a Cross-Entropy method is applied to optimase the parameters for one of the ... [more ▼]

This work presents two UAS See and Avoid approaches using Fuzzy Control. We compare the performance of each controller when a Cross-Entropy method is applied to optimase the parameters for one of the controllers. Each controller receive information from an image processing frontend that detect and track targets in the environment. Visual information is then used under a visual servoing approach to perform autonomous avoidance. Experimental flight trials using a small quadrotor were performed to validate and compare the behaviour of both controllers. [less ▲]

UAV fleet area coverage with network connectivity constraint

in Proceedings of the 11th ACM International Symposium on Mobility Management and Wireless Access (MobiWac'13) (2013)

UAV Multilevel Swarms for Situation Management

in Proceedings of the 2Nd Workshop on Micro Aerial Vehicle Networks, Systems, and Applications for Civilian Use (2016)

The development and usage of Unmanned Aerial Vehicles (UAVs) quickly increased in the last decades, mainly for military purposes. Nowadays, this type of technology is used in non-military contexts mainly ... [more ▼]

The development and usage of Unmanned Aerial Vehicles (UAVs) quickly increased in the last decades, mainly for military purposes. Nowadays, this type of technology is used in non-military contexts mainly for civil and environment protection: search & rescue teams, fire fighters, police officers, environmental scientific studies, etc. Although the technology for operating a single UAV is now mature, additional efforts are still necessary for using UAVs in fleets (or swarms). This position paper presents the ASIMUT project (Aid to SItuation Management based on MUltimodal, MUltiUAVs, MUltilevel acquisition Techniques). The challenges of this project consist of handling several fleets of UAVs (swarms) including communication, networking and positioning aspects. This motivates the development of novel multilevel cooperation algorithms which is an area that has not been widely explored, especially when autonomy is an additional challenge. Moreover, we will provide techniques to optimize communications for multilevel swarms. Finally, we will develop distributed and localized mobility management algorithms that will cope with conflicting objectives such as connectivity maintenance and geographical area coverage. [less ▲]

UAV Relay-Assisted Emergency Communications in IoT Networks: Resource Allocation and Trajectory Optimization

E-print/Working paper (2020)

Unmanned aerial vehicle (UAV) communication has emerged as a prominent technology for emergency communications (e.g., natural disaster) in Internet of Things (IoT) networks to enhance the ability of ... [more ▼]

Unmanned aerial vehicle (UAV) communication has emerged as a prominent technology for emergency communications (e.g., natural disaster) in Internet of Things (IoT) networks to enhance the ability of disaster prediction, damage assessment, and rescue operations promptly. In this paper, a UAV is deployed as a flying base station (BS) to collect data from time-constrained IoT devices and then transfer the data to a ground gateway (GW). In general, the latency constraint at IoT users and the limited storage capacity of UAV highly hinder practical applications of UAV-assisted IoT networks. In this paper, full-duplex (FD) technique is adopted at the UAV to overcome these challenges. In addition, half-duplex (HD) scheme for UAV-based relaying is also considered to provide a comparative study between two modes (viz., FD and HD). Herein, a device is successfully served iff its data is collected by UAV and conveyed to GW within the flight time. In this context, we aim at maximizing the number of served IoT devices by jointly optimizing bandwidth and power allocation, as well as the UAV trajectory, while satisfying the requested timeout (RT) requirement of each device and the UAV’s limited storage capacity. The formulated optimization problem is troublesome to solve due to its non-convexity and combinatorial nature. Toward appealing applications, we first relax binary variables into continuous values and transform the original problem into a more computationally tractable form. By leveraging inner approximation framework, we derive newly approximated functions for non-convex parts and then develop a simple yet efficient iterative algorithm for its solutions. Next, we attempt to maximize the total throughput subject to the number of served IoT devices. Finally, numerical results show that the proposed algorithms significantly outperform benchmark approaches in terms of the number of served IoT devices and the amount of collected data. [less ▲]

UAV-UGV-UMV Multi-Swarms for Cooperative Surveillance

in Frontiers in Robotics and AI (2021), 8

In this paper we present a surveillance system for early detection of escapers from a restricted area based on a new swarming mobility model called CROMM-MS (Chaotic Rössler Mobility Model for Multi ... [more ▼]

In this paper we present a surveillance system for early detection of escapers from a restricted area based on a new swarming mobility model called CROMM-MS (Chaotic Rössler Mobility Model for Multi-Swarms). CROMM-MS is designed for controlling the trajectories of heterogeneous multi-swarms of aerial, ground and marine unmanned vehicles with important features such as prioritising early detections and success rate. A new Competitive Coevolutionary Genetic Algorithm (CompCGA) is proposed to optimise the vehicles’ parameters and escapers’ evasion ability using a predator-prey approach. Our results show that CROMM-MS is not only viable for surveillance tasks but also that its results are competitive in regard to the state-of-the-art approaches. [less ▲]

Über Bildungskategorien in der „Community Music“. Überlegungen zur Ausbildung in der Blasmusik

Presentation (2019, April 28)

Während das Konzept des formalen, nicht-formalen und informellen Lernens in seinen allgemeinen Orientierungen als bekannt vorausgesetzt werden kann, gilt dies weniger für die Musikpädagogik. Die ... [more ▼]

Während das Konzept des formalen, nicht-formalen und informellen Lernens in seinen allgemeinen Orientierungen als bekannt vorausgesetzt werden kann, gilt dies weniger für die Musikpädagogik. Die Sichtweise auf die Kategorien des Lernens im Allgemeinen, auf die Musikpädagogik und auf die Musikausübung von Amateuren im Besonderen wird Gegenstand der folgenden Zeilen sein. Darüber hinaus wird das Konzept der „community music“ (CM), für das sich in der deutschen Sprache keine geeignete Übersetzung findet, vorgestellt werden. Der Begriff „community music“ ist nicht an einer einzigen Definition festzumachen. Zunächst scheint es, als wäre er komplett losgelöst von traditionellen Methoden des Lernens formaler und nicht-formaler Art aufzufassen und eher der Kategorie informellen Lernens zuzuordnen. In neueren Ansätzen wird CM als Teil der Inklusion und Partizipation in einem assoziativen Umfeld gesehen und als Mittel, die Barriere zwischen traditioneller Musikpädagogik und den Anforderungen der musizierenden Menschen zu überwinden. Auf der anderen Seite versteht sich CM als Gegenentwurf zur musikalischen Hochkultur Das Konzept von CM eignet sich in besonderem Maße, um den Prozess der musikalischen Ausbildung junger Menschen darzustellen. Einerseits beginnt dieser oft mit einer Amateurphase, um später, für die talentiertesten, zum Berufsleben zu führen. Andererseits beschreibt CM die Ausbildung und den Weg junger Musiker hin zu Laienmusikorganisationen. Schließlich zeichnet CM das lebenslange Wirken von Amateurmusikern nach. In meinem Beitrag werde ich Definitionen für die drei Kategorien von Bildung in Bezug auf die Musikpädagogik anbieten. (Dabei kann nicht ignoriert werden, dass es im wissenschaftlichen Diskurs für den Aspekt der non-formalen Bildung im Zusammenhang mit Musik keinen Konsens gibt.) Schließlich wird, mithilfe der in Europa gängigen künstlerischen Praxis des Blasmusikwesens, die Verbindung der beiden Konzepte – Bildungskategorien und CM – exemplifiziert. [less ▲]

Über das Potenzial von Aufgabenbearbeitungszeiten beim komplexen Problemlösen: Vorhersage von schulischen Leistungen und Zusammenhang mit Selbstkonzept

Scientific Conference (2015, March)

Über den Einsatz eines Windschutzes bei gravimetrischen Messungen

Scientific Conference (2010, October)