@article{9541, abstract = {{Piezoelectric transformers are increasingly getting popular in the electrical devices owing to several advantages such as small size, high efficiency, no electromagnetic noise and non-flammable. In addition to the conventional applications such as ballast for back light inverter in notebook computers, camera flash, and fuel ignition several new applications have emerged such as AC/DC converter, battery charger and automobile lighting. These new applications demand high power density and wide range of voltage gain. Currently, the transformer power density is limited to $40 W/cm{^3}$ obtained at low voltage gain. The purpose of this study was to investigate a transformer design that has the potential of providing higher power density and wider range of voltage gain. The new transformer design utilizes radial mode both at the input and output port and has the unidirectional polarization in the ceramics. This design was found to provide 30 W power with an efficiency of 98\% and 30 $\,^{\circ}$C temperature rise from the room temperature. An electro-mechanical equivalent circuit model was developed to describe the characteristics of the piezoelectric transformer. The model was found to successfully predict the characteristics of the transformer. Excellent matching was found between the computed and experimental results. The results of this study will allow to deterministically design unipoled piezoelectric transformers with specified performance. It is expected that in near future the unipoled transformer will gain significant importance in various electrical components.}}, author = {{Hemsel, Tobias and Priya, S}}, issn = {{0041-624X}}, journal = {{Ultrasonics}}, keywords = {{Piezoelectric transformers}}, pages = {{e741 -- e745}}, title = {{{Model based analysis of piezoelectric transformers}}}, doi = {{10.1016/j.ultras.2006.05.086}}, volume = {{44, Supplement}}, year = {{2006}}, } @inproceedings{9542, author = {{Hofmeisterro, Adolf and Sextro, Walter and Röschel, Otto}}, booktitle = {{Proceedings of EUCOMES, the first European Conference on Mechanism Science}}, pages = {{1--12}}, title = {{{Error-Workspace Analysis of Plane Mechanisms}}}, year = {{2006}}, } @article{9543, abstract = {{An improved concept for ultrasonic hyperthermia of tumors is presented. This concept is based on past experience of a German government supported project [1], which ended in 1984. It offers a low cost alternative to common RF- and microwave methods for hyperthermia of tumors with volumes between 1 and 40 ml at treatment times between 30 and 60 min. Our new version of the system considerably improves the temperature suppression in the healthy tissue around the target area and enables the adjustment of the beam width to the actual tumor size and the field geometry to the depth and shape of the tumor. The applicator can be used for moderate hyperthermia with tissue overheating up to 10 K or for ablation therapy with short high temperature pulses. Its central area is free for the integration of a commercial ultrasonic diagnostic sector scanner or a Doppler flow sensor in order to support the adjustment of the transducer and to monitor the whole area during the therapy.}}, author = {{Lierke, E.G. and Hemsel, Tobias}}, issn = {{0041-624X}}, journal = {{Ultrasonics}}, keywords = {{Moderate hyperthermia}}, pages = {{e341 -- e344}}, title = {{{Focusing cross-fire applicator for ultrasonic hyperthermia of tumors}}}, doi = {{10.1016/j.ultras.2006.07.004}}, volume = {{44, Supplement}}, year = {{2006}}, } @inproceedings{9544, author = {{Lierke, Ernst-Günter and Hemsel, Tobias}}, booktitle = {{Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators}}, number = {{Band 180}}, pages = {{215--222}}, title = {{{Focussing Cross-Fire Applicator for Ultrasonic Hyperthermia of Tumors}}}, year = {{2006}}, } @inproceedings{9545, author = {{Mracek, B and Hemsel, Tobias and Mracek, Maik}}, booktitle = {{Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators}}, number = {{Band 180}}, pages = {{177--182}}, title = {{{Powder Transport by Ultrasonic Waves}}}, year = {{2006}}, } @article{9546, abstract = {{Rotary ultrasonic motors have found broad industrial application in camera lens drives and other systems. Linear ultrasonic motors in contrast have only found limited applications. The main reason for the limited range of application of these very attractive devices seems to be their small force and power range. Attempts to build linear ultrasonic motors for high forces and high power applications have not been truly successful yet. To achieve larger force and higher power, multiple miniaturized motors can be combined. This approach, however, is not as simple as it appears at first glance. The electromechanical behaviour of the individual motors differs slightly due to manufacturing and assembly tolerances. The individual motor characteristics are strongly dependent on the driving parameters (frequency, voltage, temperature, pre-stress, etc.) and the driven load and the collective behaviour of the swarm of motors is not just the linear superposition of the individual drive's forces. Thus, the bundle of motors has to be synchronized and controlled appropriately in order to obtain an optimized drive that is not oversized and costly. We have investigated driving and control strategies of a set of linear ultrasonic motors. Our contribution will be divided into three main parts. In part I ultrasonic linear motors will be introduced. In part II driving strategies for a single motor as well as for a bundle of motors will be presented. These concepts will be verified by simulation results and experimental data. In part III a simplified model for the motor's electromechanical behaviour will be given.}}, author = {{Mracek, Maik and Hemsel, Tobias}}, issn = {{0041-624X}}, journal = {{Ultrasonics}}, keywords = {{Ultrasonic linear motor}}, pages = {{e597 -- e602}}, title = {{{Synergetic driving concepts for bundled miniature ultrasonic linear motors}}}, doi = {{10.1016/j.ultras.2006.05.201}}, volume = {{44, Supplement}}, year = {{2006}}, } @article{9547, author = {{Mracek, Maik and Vasiljev, Piotr and Hemsel, Tobias and Wallaschek, Jörg}}, journal = {{Solid State Phenomena}}, pages = {{167--172}}, publisher = {{Trans Tech Publ}}, title = {{{Self configuration of a novel miniature ultrasonic linear motor}}}, volume = {{113}}, year = {{2006}}, } @inproceedings{9548, abstract = {{This paper presents a general model based on the electromechanical circuit theory. The model is set up as a mechanical equivalent model for base excited systems and describes the behaviour of a piezoelectric element around one resonance frequency which is sufficient for most practical applications. The model is extended to obtain the influence of geometrical and material properties. The derivated properties are used to describe the parameters of the general model which is easy to handle. Using this model either the calculation of the output power on a specific electric load or the determination of the design of the used piezoelectric element for a needed electric output power is possible. The paper focuses on the design of the ratio of length and width of a piezoelectric bimorph. The validity of the model is shown by the comparison of computed and experimental results.}}, author = {{Richter, Björn and Twiefel, Jens and Hemsel, Tobias and Wallaschek, Jörg}}, booktitle = {{ASME 2006 International Mechanical Engineering Congress and Exposition}}, keywords = {{Materials properties, Design, Generators}}, title = {{{Model based design of piezoelectric generators utilizing geometrical and material properties}}}, doi = {{doi:10.1115/IMECE2006-14862}}, year = {{2006}}, } @inproceedings{9549, author = {{Schiedeck, Florian and Hemsel, Tobias}}, booktitle = {{Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators}}, number = {{Band 180}}, pages = {{239--242}}, title = {{{Comparison of Piezoelectric and Shape Memory Alloy Based Actuators}}}, year = {{2006}}, } @article{9550, author = {{Schiedeck, Florian and Hemsel, Tobias and Wallaschek, Jörg}}, journal = {{Solid State Phenomena}}, pages = {{195--198}}, publisher = {{Trans Tech Publ}}, title = {{{The use of shape memory alloy wires in actuators}}}, volume = {{113}}, year = {{2006}}, } @inbook{9551, abstract = {{Friction occurs in the contact between tyre and road. The friction of rubber material on dry surfaces is dominated by hysteresis and adhesion effects. Hysterisis friction is characterised by the energy dissipation within the visco-elastic material, which is caused by its deformation while passing the surface roughness. Hysteresis effects are modelled by an extended linear visco-elastic material with several Maxwell elements. The development of a model in the time domain allows to consider nonlinear effects. Additionally temperature effects are taken into account based on the WLF-transformation. Adhesion forces originate from molecular bindings between the contact partners. This effect is simulated by applying a modified model of Achenbach on real surfaces. The temperature distribution within the friction contact region is investigated experimentally as well. Furthermore global stick-slip vibrations of a rubber block element are investigated using a global contact model. Numerical results are compared with experiments performed on a tribometer test rig.}}, author = {{Sextro, Walter and Moldenhauer, Patrick and Wangenheim, M and Lindner, Markus and Kröger, Matthias}}, booktitle = {{Analysis and Simulation of Contact Problems}}, editor = {{Wriggers, Peter and Nackenhorst, Udo}}, isbn = {{978-3-540-31760-9}}, pages = {{243--252}}, publisher = {{Springer Berlin Heidelberg}}, title = {{{Contact behaviour of a sliding rubber element}}}, doi = {{10.1007/3-540-31761-9_27}}, volume = {{27}}, year = {{2006}}, } @inproceedings{9552, author = {{Twiefel, Jens and Hemsel, Tobias and Kauczor, Christopher}}, booktitle = {{Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators}}, number = {{Band 180}}, pages = {{207--212}}, title = {{{Energy harvesting with piezoelectric Elements}}}, year = {{2006}}, } @proceedings{9553, abstract = {{In the design process of energy harvesting systems based on piezoelectric elements, achievable energy output is the most interesting factor. To estimate this amount a priori manufacturing of prototypes a mathematical model is very helpful. Within this contribution we will introduce a model based on electro-mechanical circuit theory. Its parameters are identified by measurements and the model is validated by comparison to experimental results. The model is designed to support the development-engineer in the dimensioning of energy harvesting units to specific application demands. Two main challenges in device design are investigated with the mathematical model: influence of the ambient excitation frequency, and influence of the load impedance. Typically, the equivalent model approach delivers models for piezoelectric elements that are driven in resonance by electrical excitation. In the case of energy harvesting the piezoelectric elements are excited mechanically and most often non-resonant. Thus, we first set up a mechanical equivalent model for base excited systems. In first approximation it represents an energy harvesting unit around one resonance frequency. The model is expandable for a wider frequency range using the superpositioning of multiple circuits. From the viewpoint of optimum energy transformation between mechanical and electrical energy it is favorable to drive piezoelectric elements at resonance or anti-resonance. Thus, an energy harvesting system should be tuned to the excitation frequency.}}, editor = {{Twiefel, Jens and Richter, Björn and Hemsel, Tobias and Wallaschek, Jörg}}, pages = {{616909--616909--10}}, title = {{{Model-based design of piezoelectric energy harvesting systems}}}, doi = {{10.1117/12.658623}}, volume = {{6169}}, year = {{2006}}, } @inproceedings{9558, author = {{Wilmanns, S and Nakamura, K and Mracek, Maik and Hemsel, Tobias}}, booktitle = {{Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators}}, pages = {{205}}, title = {{{Non-resonant piezoelectric motors driven in audible frequency range}}}, volume = {{Band 180}}, year = {{2006}}, } @inproceedings{9559, author = {{Zhou, W and Fu, Bo and Hemsel, Tobias and Wallaschek, Jörg}}, booktitle = {{Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators}}, pages = {{213}}, title = {{{Piezoelectrics in dental tools}}}, volume = {{Band 180}}, year = {{2006}}, } @proceedings{7780, editor = {{Pleuß, Andreas and Van den Bergh, Jan and Hußmann, Heinrich and Sauer, Stefan and Bödcher, Alexander}}, publisher = {{CEUR-WS.org}}, title = {{{Proceedings of the Workshop on Model Driven Development of Advanced User Interfaces, satellite of the MoDELS 2006 conference}}}, volume = {{214}}, year = {{2006}}, } @inproceedings{7947, author = {{Loeser, Christoph and Schomaker, Gunnar and Schubert, Matthias and Schattkowsky, Tim}}, booktitle = {{Proceedings of the 5th International Conference on Networking (ICN 2006), Morne (Mauritius)}}, pages = {{105}}, publisher = {{IEEE Computer Society}}, title = {{{Fairness Considerations in Replication and Placement Strategies for large Documents in heterogeneous Content Delivery Networks}}}, doi = {{http://dx.doi.org/10.1109/ICNICONSMCL.2006.96}}, year = {{2006}}, } @inproceedings{7948, author = {{Schattkowsky, Tim and Förster, Alexander and Loeser, Christoph}}, booktitle = {{Proceedings of the 5th International Conference on Networking (ICN 2006), Morne (Mauritius)}}, pages = {{86}}, publisher = {{IEEE Computer Society}}, title = {{{Secure Storage for Physically Exposed Web- and Application Servers}}}, year = {{2006}}, } @inproceedings{7949, author = {{Schattkowsky, Tim and Hendrik Hausmann, Jan and Engels, Gregor}}, booktitle = {{Proceedings of the International Conference on Model Driven Engineering Languages and Systems (MoDELS 2006), Genova (Italy)}}, pages = {{737--752}}, publisher = {{Springer}}, title = {{{Using UML Activities for System-on-Chip Design and Synthesis}}}, doi = {{dx.doi.org/10.1007/11880240_51}}, volume = {{4199/2006}}, year = {{2006}}, } @inproceedings{7950, author = {{Pleuß, Andreas and Van den Bergh, Jan and Sauer, Stefan and Hußmann, Heinrich}}, booktitle = {{Satellite Events at the MoDELS 2005 Conference, MoDELS 2005 International Workshops, Doctoral Symposium, Educators Symposium, Revised Selected Papers, Montego Bay (Jamaica)}}, pages = {{182--190}}, publisher = {{Springer}}, title = {{{Workshop Report: Model Driven Development of Advanced User Interfaces (MDDAUI)}}}, doi = {{dx.doi.org/10.1007/11663430_19}}, volume = {{3844}}, year = {{2006}}, }