40 research outputs found

    Robot Control based on Motor Primitives -- A Comparison of Two Approaches

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    Motor primitives are fundamental building blocks of a controller which enable dynamic robot behavior with minimal high-level intervention. By treating motor primitives as basic "modules," different modules can be sequenced or superimposed to generate a rich repertoire of motor behavior. In robotics, two distinct approaches have been proposed: Dynamic Movement Primitives (DMPs) and Elementary Dynamic Actions (EDAs). While both approaches instantiate similar ideas, significant differences also exist. This paper attempts to clarify the distinction and provide a unifying view by delineating the similarities and differences between DMPs and EDAs. We provide eight robot control examples, including sequencing or superimposing movements, managing kinematic redundancy and singularity, obstacle avoidance, and managing physical interaction. We show that the two approaches clearly diverge in their implementation. We also discuss how DMPs and EDAs might be combined to get the best of both approaches. With this detailed comparison, we enable researchers to make informed decisions to select the most suitable approach for specific robot tasks and applications.Comment: 22 pages, 11 figure

    Exp[licit]-A Robot modeling Software based on Exponential Maps

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    Deriving a robot's equation of motion typically requires placing multiple coordinate frames, commonly using the Denavit-Hartenberg convention to express the kinematic and dynamic relationships between segments. This paper presents an alternative using the differential geometric method of Exponential Maps, which reduces the number of coordinate frame choices to two. The traditional and differential geometric methods are compared, and the conceptual and practical differences are detailed. The open-source software, Exp[licit], based on the differential geometric method, is introduced. It is intended for use by researchers and engineers with basic knowledge of geometry and robotics. Code snippets and an example application are provided to demonstrate the benefits of the differential geometric method and assist users to get started with the software.Comment: 8 pages, 5 figure

    Detection of 135Cs & 137Cs in environmental samples by AMS

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    The detection of low abundances of 135Cs in environmental samples is of significant interest in different fields of environmental sciences, especially in combination with its shorter-lived sister isotope 137Cs. The method of Ion–Laser InterAction Mass Spectrometry (ILIAMS) for barium separation at the Vienna Environmental Research Accelerator (VERA) was investigated and further improved for low abundance cesium detection. The difluorides BaF2- and CsF2- differ in their electron detachment energies and make isobar suppression with ILIAMS by more than 7 orders of magnitude possible. By this method, samples with ratios down to the order of 135,137Cs/133Cs ˜10-11 are measurable and the 135Cs/137Cs ratios of first environmental samples were determined by AMS

    Developing Accelerator Mass Spectrometry Capabilities for Anthropogenic Radionuclide Analysis to Extend the Set of Oceanographic Tracers

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    Recent major advances in Accelerator Mass Spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA) regarding detection efficiency and isobar suppression have opened possibilities for the analysis of additional long-lived radionuclides at ultra-low environmental concentrations. These radionuclides, including 233^{233}U, 135^{135}Cs, 99^{99}Tc, and 90^{90}Sr, will become important for oceanographic tracer application due to their generally conservative behavior in ocean water. In particular, the isotope ratios 233^{233}U/236^{236}U and 137^{137}Cs/135^{135}Cs have proven to be powerful fingerprints for emission source identification as they are not affected by elemental fractionation. Improved detection efficiencies allowed us to analyze all major long-lived actinides, i.e., 236^{236}U, 237^{237}Np, 239,240^{239,240}Pu, 241^{241}Am as well as the very rare 233^{233}U, in the same 10 L water samples of a depth profile from the northwest Pacific Ocean. For this purpose, a simplified and very flexible chemical purification procedure based on extraction chromatography (a single UTEVA® column) was implemented which can be extended by a DGA® column for Am purification. The procedure was validated with the reference materials IAEA-381/385. With the additional increase in ionization efficiency expected for the extraction of actinides as fluoride molecules from the AMS ion source, a further reduction of chemical processing may become possible. This method was successfully applied to an exemplary set of air filter samples. In order to determine the quantitative 237^{237}Np concentration reliably, a 236^{236}Np spike material is being developed in collaboration with the University of Tsukuba, Japan. Ion-Laser Interaction Mass Spectrometry (ILIAMS), a novel technique for the efficient suppression of stable isobaric background, has been developed at VERA and provides unprecedented detection sensitivity for the fission fragments 135^{135}Cs, 99^{99}Tc, and 90^{90}Sr. The corresponding setup is fully operational now and the isobar suppression factors of >105^{5} achieved, in principle, allow for the detection of the mentioned radionuclides in the environment. Especially for 90^{90}Sr analysis, this new approach has already been validated for selected reference materials (e.g., IAEA-A-12) and is ready for application in oceanographic studies. We estimate that a sample volume of only (1-3) L ocean water is sufficient for 90^{90}Sr as well as for 135^{135}Cs analysis, respectively

    Challenges for continuing teacher training in relation to digital transformation : perspectives of adult and further education

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    Angesichts der digitalen Transformation schulischer Kontexte ergeben sich neue Anforderungen an die berufliche Handlungskompetenz von Lehrkräften. Dies führt zu einem erhöhten Handlungsbedarf im Bereich der Lehrkräftefortbildung. Diese befindet sich als eine spezifische Form beruflicher Fortbildung an der Schnittstelle zwischen Lehrkräftebildung und Erwachsenen- und Weiterbildung, so dass eine Betrachtung dieser Lernkontexte aus dieser Perspektive subdisziplinübergreifende Impulse für die Umsetzung und Gestaltung von Lehrkräftefortbildung geben kann. Im Beitrag werden daher aktuelle Herausforderungen der Lehrkräftefortbildung vor dem Hintergrund der digitalen Transformation anhand des Mehrebenensystems der Erwachsenen- und Weiterbildung aufgezeigt und mit Blick auf die Erkenntnisse und Konzepte der Erwachsenen- und Weiterbildung diskutiert.publishe