@inbook{8457, author = {{Kremer, H.-Hugo}}, booktitle = {{Sozialökonomische Theorie - sozialökonomisches Handeln. Konturen und Perspektiven der Wirtschafts- und Sozialpädagogik}}, editor = {{Euler, D. and Jongebloed, H.-C. and Sloane, P.F.E.}}, title = {{{Didaktische Theorie implementieren - Innovationen gestalten}}}, year = {{2000}}, } @article{8458, author = {{Hasenbank, T. and Kremer, H.-Hugo and Sloane, Peter F. E.}}, journal = {{Wirtschaft und Erziehung}}, number = {{11}}, title = {{{Running into practice - Theorie-Praxis-Seminar zum Lernfeldkonzept}}}, year = {{2000}}, } @article{8914, abstract = {{Piezoelectric ultrasonic motors have been investigated for several years and have already found their first practical applications. Their key feature is that they are able to produce a high thrust force related to their volume. Beside rotary drives like the travelling wave motor, linear drives have also been developed, but only a few are presently commercially available. In the present paper, we first describe the state of the art of linear piezoelectric motors. The motors are characterized with respect to their no-load velocity, maximum thrust force, efficiency and other technical properties. In the second part, we present a new motor, which is judged to be capable of surpassing the characteristics of other piezoelectric motors because of its unique design which allows the piezoelectric drive elements to be pre-stressed in the direction of their polarization. The piezoelectric elements convert energy using the longitudinal d33 effect which allows an improved reliability, large vibration amplitudes and excellent piezoelectric coupling. Energy loss by vibration damping is minimized, and the efficiency can be improved significantly. Experimental results show that the motor characteristics can be optimized for a particular task by choosing the appropriate operating parameters such as exciting voltage, exciting frequency and normal force. }}, author = {{Hemsel, Tobias and Wallaschek, Jörg}}, issn = {{0041-624X}}, journal = {{Ultrasonics}}, keywords = {{Linear motor}}, pages = {{37 -- 40}}, title = {{{Survey of the present state of the art of piezoelectric linear motors}}}, doi = {{10.1016/S0041-624X(99)00143-2}}, volume = {{38}}, year = {{2000}}, } @inproceedings{8915, abstract = {{Ultrasonic linear motors have now been investigated for several years. Their key features are high thrust forces related to their volume and good position-accuracy. This contribution consists of two main parts. In the first part we describe the state-of-the-art of linear piezoelectric motors. Characteristics like no-load velocity, maximum thrust force and other technical properties of commercially available devices will be reported as well as those of prototypes. In the second part we report an ongoing research and development project aiming at a linear piezoelectric motor, which is capable of surpassing some of the shortcomings of other piezoelectric motors}}, author = {{Hemsel, Tobias and Wallaschek, Jörg}}, booktitle = {{Ultrasonics Symposium, 2000 IEEE}}, issn = {{1051-0117}}, keywords = {{linear motors, ultrasonic motors, linear piezoelectric motor, maximum thrust force, no-load velocity, ultrasonic linear motor, Electromagnetic devices, Electromagnetic fields, Frequency, Friction, Gears, Materials science and technology, Piezoelectric materials, Research and development, Vibrations, Wheels}}, pages = {{663--666 vol.1}}, title = {{{State of the art and development trends of ultrasonic linear motors}}}, doi = {{10.1109/ULTSYM.2000.922635}}, volume = {{1}}, year = {{2000}}, } @inproceedings{8916, author = {{Hemsel, Tobias and Wallaschek, Jörg}}, booktitle = {{Tagungsband der ACTUATOR}}, pages = {{250--253}}, title = {{{Piezoelectic linear motors}}}, year = {{2000}}, } @inproceedings{8917, abstract = {{Piezoelektrische Schwingungsantriebe sind Kleinmotoren, deren Funktionsprinzip darin besteht, dass elektrische Energie mit Hilfe von Piezokeramiken in mechanische Schwingungsenergie gewandelt und diese dann durch hochfrequente Kontaktvorgänge auf den anzutreibenden Teil übertragen wird. Der Stand der Technik auf dem Gebiet piezoelektrischer Linearantriebe zeigt, dass viele piezoelektrische Linearantriebe bereits zufriedenstellende Leistungsmerkmale aufweisen. Gleichzeitig ist zu erwarten, dass die Leistungen dieser Antriebe noch deutlich verbessert werden können. Ein Ansatz, insbesondere den Wirkungsgrad und die mechanische Leistung zu erhöhen, wird anhand eines Motors aufgezeigt, der am Heinz Nixdorf Institut entwickelt wurde. Eine Übersicht der in ausgewählten Einsatzgebieten geforderten Leistungsdaten führt auf Entwicklungsziele für bestehende und neuartige piezoelektrische Linearantriebe.}}, author = {{Hemsel, Tobias and Wallaschek, Jörg}}, pages = {{147--166}}, title = {{{Stand der Technik und Entwicklungsperspektiven linearer piezoelektrischer Schwingungsantriebe}}}, volume = {{1533}}, year = {{2000}}, } @article{8918, abstract = {{The paper deals with cyclic periodic structures modelling bladed disk assemblies of blades with friction elements for vibration damping. These elements placed between adjacent blades reduce the vibration amplitudes by means of dry friction resulting from centrifugal forces acting on the elements and relative displacements of the blades. However, the application of these friction elements results in an additional dynamical coupling which together with mistuning of some system parameters (e.g., blade eigenfrequency or contact parameters) may cause localization of vibration. In the present paper a linear approximation of such a system is investigated. The structure composed of cyclic periodic cells modelled each as a clamped-free beam interacting with each other by means of viscoelastic elements of complex stiffness is applied for dynamic system analysis. In case of free vibrations as well as in case of steady-state dynamic response to a harmonic pressure field, a perfect periodic structure and the structures with periodically mistuned parameters (blade eigenfrequencies and contact parameters) are studied. Some regularities in the dynamic response of the systems with mistuning have been noticed. Despite the fact that only a linear approximation has been used, the results and conclusions can be applied for models which describe the blade interaction in a nonlinear way.}}, author = {{Krzyzynski, Tomasz and Popp, Karl and Sextro, Walter}}, issn = {{0960-0779}}, journal = {{Chaos, Solitons \& Fractals}}, number = {{10}}, pages = {{1597 -- 1609}}, title = {{{On some regularities in dynamic response of cyclic periodic structures}}}, doi = {{10.1016/S0960-0779(99)00080-6}}, volume = {{11}}, year = {{2000}}, } @inproceedings{8919, abstract = {{the vibration amplitudes of bladed disk assemblies can be reduced significantly by means of friction damping devices such as shrouds, damping wires and interblade Friction dampers. in practice, interblade Friction dampers are applied in rotating arrangements with various geometries showing curved or flat surfaces like so-called wedge-shaped dampers. this paper is focusing on a computation method to predict the dynamical behaviour of turbine blades with Friction dampers including both, curved and wedge-shaped dampers with hertzian and non-herutian contact conditions, respectively. the presented computation method uses a 3d contact model to calculate the contact forces, including normal and tangential stiffnesses, roughness and microslip effects. the relative displacements in the contact area can be expressed by means of 6 dof of the blade platforms and 6 rigid body dof of the damper including translational and rotational displacements. the relative displacement of the Friction damper with respect to the adjacent blades can be derived from the contact kinematics of the blade-damper-blade system and the equations of motion of the Friction damper. thus, the model can be applied to investigate spatial motions of the bladed disk assembly including bending and torsional vibrations. a comparison of different Friction damper designs with respect to an optimal damper geometry and damper mass is presented. the advantages and disadvantages of each design will be discussed. experimental results are shown to validate the developed computation method.}}, author = {{Panning, Lars and Sextro, Walter and Popp, Karl}}, booktitle = {{International Gas Turbine \& Aeroengine Congress \& Exhibition, ASME}}, pages = {{1--8}}, title = {{{Optimization of Interblade Friction Damper}}}, year = {{2000}}, } @inproceedings{8920, author = {{Sextro, Walter}}, booktitle = {{International Gas Turbine \& Aeroengine Congress \& Exhibition, ASME}}, pages = {{1--8}}, title = {{{The Calculation of the Forced Response of Shrouded Blades with Friction Contacts and Its Experimental Verification}}}, year = {{2000}}, } @misc{9665, author = {{Tönnies, Merle}}, booktitle = {{Journal for the Study of British Cultures}}, number = {{1}}, pages = {{80--83}}, title = {{{Lewis, J.E.: Mary Queen of Scots. Romance and Nation, 1998}}}, volume = {{7}}, year = {{2000}}, } @article{6507, author = {{Platzner, Marco}}, issn = {{0018-9162}}, journal = {{Computer}}, number = {{4}}, pages = {{58--60}}, publisher = {{Institute of Electrical and Electronics Engineers (IEEE)}}, title = {{{Reconfigurable accelerators for combinatorial problems}}}, doi = {{10.1109/2.839322}}, volume = {{33}}, year = {{2000}}, } @inproceedings{6690, author = {{Bendfeld, Jörg and Gruffke, Michael and Ortjohann, Egon and Peters, T. and Voss, Jürgen}}, booktitle = {{Proceedings of the 16th European Photovoltaic Solar Energy Congress and Exhibition, 1-5 May 2000, Glasgow United Kingdom}}, title = {{{FULL AREA COVERAGE MEASURING NETWORK FOR RECORDING THE DISTRIBUTION OF INCIDENT SOLAR RADIATION}}}, year = {{2000}}, } @inproceedings{6691, author = {{Bendfeld, Jörg and Bettenwort, Gerd and Drilling, Carsten and Gruffke, Michael and Ortjohann, Egon and Rump, S. and Voß, Jürgen}}, booktitle = {{Proceedings of the 16th European Photovoltaic Solar Energy Congress and Exhibition, 1-5 May 2000, Glasgow United Kingdom}}, title = {{{MODEL FOR EVALUATING MPP METHODS FOR GRID-CONNECTED PV PLANTS}}}, year = {{2000}}, } @article{6692, author = {{Bendfeld, Jörg and Gruffke, Michael and Ortjohann, Egon and Voss, Jürgen}}, journal = {{Bundes Bau Blatt}}, publisher = {{Ministerium für Verkehr, Bau- und Wohnungswesen}}, title = {{{Der Solar-Igel Neue Möglichkeiten der Steuerung solarstrahlungsabhängiger Anlagen und Geräte}}}, volume = {{3}}, year = {{2000}}, } @book{6762, editor = {{Tönnies, Merle and Stratmann, Gerd and Viol, Claus-Ulrich}}, publisher = {{Winter}}, title = {{{Youth Identities. Teens and Twens in British Culture}}}, year = {{2000}}, } @inproceedings{16495, author = {{Meyer auf der Heide, Friedhelm and Räcke, Harald and Westermann, Matthias}}, booktitle = {{Proceedings of the twelfth annual ACM symposium on Parallel algorithms and architectures - SPAA '00}}, isbn = {{1581131852}}, title = {{{Data management in hierarchical bus networks}}}, doi = {{10.1145/341800.341814}}, year = {{2000}}, } @inproceedings{16496, abstract = {{We present a general framework for the development of on-line algorithms for data management in networks with limited memory capacities. These algorithms dynamically create and delete copies of shared data objects that can be read and written by the nodes in the network. Our algorithms aim to minimize the congestion, i.e., the maximum communication load over all network resources, so that that none of these resources become a communication bottleneck. We give several examples of networks for which our framework yields efficient algorithms, including meshes, fat-trees, hypercubic networks, and complete networks. For example, our framework yields an $O(d cdot log n)$-competitive caching algorithm for $d$-dimensional meshes of size $n$ with respect to the congestion on the communication links, and an $O(1)$-competitive algorithms for complete networks with respect to the congestion at the memory modules due to remote accesses. Previous work on data management in networks either neglects memory capacity constraints or minimizes only the total communication load, i.e., the sum of the communication load over all resources, which may produce congestion as some of the links become bottlenecks.}}, author = {{Meyer auf der Heide, Friedhelm and Vöcking, Berthold and Westermann, Matthias}}, booktitle = {{SODA '00: Proceedings of the eleventh annual ACM-SIAM symposium on Discrete algorithms}}, isbn = {{0898714532}}, pages = {{430–439}}, title = {{{Caching in networks}}}, year = {{2000}}, } @inbook{16497, author = {{Meyer auf der Heide, Friedhelm and Kutyłowski, Mirosław and Ragde, Prabhakar}}, booktitle = {{Euro-Par 2000 Parallel Processing}}, isbn = {{9783540679561}}, issn = {{0302-9743}}, title = {{{Complexity Theory and Algorithms}}}, doi = {{10.1007/3-540-44520-x_59}}, year = {{2000}}, } @inbook{16513, author = {{Aston, P. J. and Dellnitz, M.}}, booktitle = {{Equadiff 99}}, isbn = {{9789810243593}}, title = {{{The Computation of Lyapunov Exponents via Spatial Integration Using Vector Norms}}}, doi = {{10.1142/9789812792617_0196}}, year = {{2000}}, } @inbook{16553, author = {{Dellnitz, Michael and Froyland, Gary and Sertl, Stefan}}, booktitle = {{Equadiff 99}}, isbn = {{9789810243593}}, title = {{{A Conjecture on the Existence of Isolated Eigenvalues of the Perron-Frobenius Operator}}}, doi = {{10.1142/9789812792617_0199}}, year = {{2000}}, }