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Zusammenfassung  Diese Arbeit stellt ein Modell und ein System zur Steuerung von Exoskeletten mit Hilfe von elektrischen Signalen vor, die an den Muskeln des Benutzers gemessen werden. Anhand dieser Signale wird der eigene Drehmomentbeitrag des Benutzer zur gewünschten Bewegung abgesch?tzt, und ein einstellbarer Faktor bestimmt das vom Exoskelett hinzugefügte Drehmoment in Bezug auf den Beitrag des Benutzers. Die Signale werden durch ein komplexes biomechanisches Modell ausgewertet. CR subject classification  J.3 ; J.7 ; I.6.5  相似文献   
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Over the last decade, researchers have developed sophisticated online learning environments to support students engaging in dialogic argumentation. This review examines five categories of analytic frameworks for measuring participant interactions within these environments focusing on (1) formal argumentation structure, (2) conceptual quality, (3) nature and function of contributions within the dialogue, (4) epistemic nature of reasoning, and (5) argumentation sequences and interaction patterns. Ultimately, the review underscores the diversity of theoretical perspectives represented within this research, the nature of dialogic interaction within these environments, the importance of clearly specifying theoretical and environmental commitments throughout the process of developing or adopting an analytic framework, and the role of analytic frameworks in the future development of online learning environments for argumentation.
Douglas B. ClarkEmail:
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A few years ago, publishing companies started to sell digital copies of their magazines. This study investigates a consequence of this change: the increasing online trade with illegal copies. We collected data on almost 10,000 issues of German magazines that are illegally offered online. The files are distributed in a three-sided market, in which a small number of platforms bring suppliers of illegal copies, consumers, and advertisers together. The market has been growing rapidly—between 2009 and 2012 by a factor of 10. In contrast to the legal magazine market, the illegal trade mostly concerns IT and consumer electronics magazines.  相似文献   
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This paper discusses the problem of the fuzzy sliding mode control for a class of disturbed systems. First, a fuzzy auxiliary controller is constructed based on a feedback signal not only to estimate the unknown control term, but also participates in the sliding mode control due to the fuzzy rule employed. Then, we extend our theory into the cases, where some kind of system information can not be obtained, for better use of our theoretical results in real engineering. Finally, some typical numerical examples are included to demonstrate the effectiveness and advantage of the designed sliding mode controller.  相似文献   
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This paper deals with the problem of adaptive output feedback neural network controller design for a SISO non-affine nonlinear system. Since in practice all system states are not available in output measurement, an observer is designed to estimate these states. In comparison with the existing approaches, the current method does not require any information about the sign of control gain. In order to handle the unknown sign of the control direction, the Nussbaum-type function is utilized. In order to approximate the unknown nonlinear function, neural network is firstly exploited, and then to compensate the approximation error and external disturbance a robustifying term is employed. The proposed controller is designed based on strict-positive-real (SPR) Lyapunov stability theory to ensure the asymptotic stability of the closed-loop system. Finally, two simulation studies are presented to demonstrate the effectiveness of the developed scheme.  相似文献   
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Educational Studies in Mathematics - It is widely assumed that teachers play a key role in providing high-quality learning opportunities to students and fostering students’ learning. Yet it...  相似文献   
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Constituting a metacognitive strategy, system competence or systems thinking can only assume its assigned key function as a basic concept for the school subject of geography in Germany after a theoretical and empirical foundation has been established. A measurement instrument is required which is suitable both for supporting students and for the evaluation of methodical‐didactic measures. Such a tool is theoretically anchored in an empirically validated geography‐didactic and cognition‐psychological competence model, providing a differentiated representation of both the internal structure of a competency and the proficiency levels. The starting point of this foundation was the development of a normative‐theoretically derived model of geographic system competence. Its empirical validation was performed in different phases aimed at operationalising the competence model by means of test problems. In order to analyse the factor structure of the theoretical model, various item response models were estimated. The item levels of difficulty expected in the competence model were related to the empirical levels of difficulty and predicted by means of ordinary least squares regression to verify the model for proficiency levels. The two‐dimensional competence model – with the two dimensions ‘system organisation and behaviour’ and ‘system‐adequate intention to act’ – exhibits a better fit in reference to the model fit criteria than the one‐dimensional and three‐dimensional models. The correlations between the expected and empirical item difficulties are positive. Items that should be more difficult according to the competence model are actually shown to be more difficult. These findings suggest the reliability and validity of this new measurement instrument for diagnosing and promoting geographical system competence. It has to be implemented in practice as the next step.  相似文献   
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Armin Gretler 《Prospects》1999,29(3):379-392
Summary This article is divided into three parts. It begins with an overview of the historical background of educational research as a scientific discipline which emerged in Europe towards the end of the nineteenth century and gives two definitions: the first characterizes educational research as to its content, the second as to its functions. The second part deals, one by one, with the national and international structures of educational research and development. The article ends with a series of views on the prospects for educational research, deliberately looking beyond the European framework. Original language: French Armin Gretler Graduated in sociology at the University of Geneva and took post-graduate courses at the Bologna Centre of the Johns Hopkins University, the Paul H. Nitze School of Advanced International Studies and at Pittsburgh State University. Vocational education researcher at the International Labour Office (ILO) from 1963 to 1968. Independent researcher from 1968 to 1971. Director of the Swiss Co-ordination Centre for Research in Education (CSRE) in Aarau since 1971. Member of Parliament for the Canton of Aargau from 1979 to 1993, member of that canton's Education Council from 1977 to 1989. Founding member of the Société suisse de recherche en éducation and of the European educational Research Association (EERA). He has published several books and many articles on educational research.  相似文献   
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