@inbook{9589, author = {{Beutner, Marc}}, booktitle = {{Lehrerbildung phasenübergreifend denken. Facetten einer bundesweiten Debatte}}, editor = {{Häcker, Th and Bartel, K and Peters, K}}, pages = {{140 -- 158}}, title = {{{Kompetenzbegriff und Evaluation im beruflichen Bildungswesen}}}, year = {{2011}}, } @inbook{9726, author = {{Flotmann, Christina and Tönnies, Merle}}, booktitle = {{Narrative in Drama: CDE Studies 18}}, editor = {{Tönnies, Merle and Flotmann-Scholz, Christina}}, pages = {{9--17}}, publisher = {{WVT}}, title = {{{Introducing Narrative in Drama}}}, volume = {{18}}, year = {{2011}}, } @article{9765, abstract = {{The multi-objective optimal design of a piezoelectric sandwich ultrasonic transducer is studied. The maximum vibration amplitude and the minimum electrical input power are considered as optimization objectives. Design variables involve continuous variables (dimensions of the transducer) and discrete variables (material types). Based on analytical models, the optimal design is formulated as a constrained multi-objective optimization problem. The optimization problem is then solved by using the elitist non-dominated sorting genetic algorithm (NSGA-II) and Pareto-optimal designs are obtained. The optimized results are analyzed and the preferred design is proposed. The optimization procedure presented in this contribution can be applied in multi-objective optimization problems of other piezoelectric transducers.}}, author = {{Hemsel, Tobias and Fu, Bo and Jing, Yi and Fu, Xuan}}, journal = {{Key Engineering Materials}}, pages = {{1808--1812}}, publisher = {{Trans Tech Publ}}, title = {{{Multi-Objective Optimization of a Piezoelectric Sandwich Ultrasonic Transducer by Using Elitist Non-Dominated Sorting Genetic Algorithm}}}, doi = {{10.4028/www.scientific.net/KEM.474-476.1808}}, volume = {{474 - 476}}, year = {{2011}}, } @article{9767, abstract = {{The paper presents the results of numerical and experimental investigation of cylindrical piezoelectric actuator used for achieving independent three degrees of freedom oscillations of the contact point. The design of actuator based on a hollow piezoelectric cylinder mounted on a metal rod. The piezoceramic cylinder has a radial polarization and special configuration of the electrodes that cover inner and outer surface of the cylinder. The main advantage of actuator's design is that solid metallic rod operates as a part of inner electrode of the cylinder and a stator of actuator. The geometry of piezoelectric actuator was adopted to reach resonance of oscillations for the first longitudinal mode and the third flexural mode at same frequency. The actuator is designed to move positioned object through contact point which is located on the top of the rod. The optimal topology of electrodes was found to achieve longitudinal and flexural oscillations of the actuator in two perpendicular planes. Three degrees of freedom of the positioning object can be achieved and control of the system can be implemented by applying different excitation schemes and regimes. The numerical simulation and experimental study of piezoelectric actuator was performed. Impedance of actuator was analyzed under different excitation regimes. The results of numerical modeling and experimental study were compared. Recommendations for the further development of this type of actuator are given.}}, author = {{Lucinskis, Raimundas and Mazeika, Dalius and Hemsel, Tobias and Bansevicius, Ramutis}}, journal = {{AIP Conference Proceedings}}, keywords = {{dielectric polarisation, piezoceramics, piezoelectric actuators}}, number = {{1}}, pages = {{693--696}}, publisher = {{AIP}}, title = {{{Multi-DOF cylindrical piezoelectric actuator with radial polarization}}}, doi = {{10.1063/1.3703277}}, volume = {{1433}}, year = {{2011}}, } @inproceedings{9768, author = {{Lurie, Oleg and Kromov, Ivan and Trächtler, Ansgar and Sondermann-Wölke, Christoph and Sextro, Walter}}, booktitle = {{25. Tagung Technische Zuverlässigkeit (TTZ 2011) - Entwicklung und Betrieb zuverlässiger Produkte}}, pages = {{99--110}}, title = {{{Dependability Analysis of the Degradation Behavior of Mechatronics Systems with Different Operating Strategies}}}, year = {{2011}}, } @article{9769, abstract = {{In this study, we report some improvements in a hydrothermal method for lead-free piezoelectric powders and the performance of the sintered (K$_{0.48}$Na$_{0.52}$)NbO$_{3}$ ceramics. To increase the obtained powder weight per source solution volume, the hydrothermal reaction conditions were modified. This improvement is important for mass production; however, it resulted in a larger particle size dispersion. Therefore, we examined to introduced the ball milling process that is useful for dense (K$_{0.48}$Na$_{0.52}$)NbO$_{3}$ ceramics. When a large amount of powder was obtained, it took a long time to eliminate the residual alkaline ions in the hydrothermal powders by a washing process. Therefore, a neutralization was conducted in the powder washing process. Using this powder, a solid solution of (K,Na)NbO$_{3}$ceramics was synthesized. The relative density was successfully increased. Concerning the electrical properties, the relative permittivity was improved, and the piezoelectric constant d$_{33}$ was also increased from 114 to 130 pC/N.}}, author = {{Maeda, Takafumi and Hemsel, Tobias and Morita, Takeshi}}, journal = {{Japanese Journal of Applied Physics}}, pages = {{07HC01}}, publisher = {{The Japan Society of Applied Physics}}, title = {{{Improved Process for Hydrothermal Lead-Free Piezoelectric Powders and Performances of Sintered (K0.48Na0.52)NbO3 Ceramics}}}, volume = {{50}}, year = {{2011}}, } @inproceedings{9770, abstract = {{One cannot image today's life without mechatronic systems, which have to be developed in a joint effort by teams of mechanical engineers, electrical engineers, control engineers and software engineers. Often these systems are applied in safety critical environments like in cars or aircrafts. This requires systems that function correctly and do not cause hazardous situations. However, random errors due to wear or external influences cannot be completely excluded. Consequently, we have to perform a hazard analysis for the system. Further, the union of four disciplines in one system requires the development and analysis of the system as a whole. We present a component-based hazard analysis that considers the entire mechatronic system including hardware, i.e. mechanical and electrical components, and software components. Our approach considers the physical properties of different types of flow in mechatronic systems. We have identified reusable patterns for the failure behavior which can be generated automatically. This reduces the effort for the developer. As cycles, e.g. control cycles, are an internal part of every mechatronic system our approach is able to handle cycles. The presented approach has been applied to a real-life case study.}}, author = {{Priesterjahn, Claudia and Sondermann-Wölke, Christoph and Tichy, Mathias and Hölscher, Christian}}, booktitle = {{Proc. of the 2nd IEEE International Workshop MoBE-RTES at the 14th IEEE International Symposium on Object/Component/Service-oriented Real-time Distributed Computing (ISORC)}}, publisher = {{IEEE Computer Society}}, title = {{{Component-based Hazard Analysis for Mechatronic Systems}}}, year = {{2011}}, } @inproceedings{9771, abstract = {{Dieser Beitrag stellt ein Konzept vor, welches die Methode der Mehrzieloptimierung mit einer Online-Bewertung des aktuellen Systemzustands kombiniert. Dieses erlaubt Maßnahmen zur Zuverlässigkeitssteigerung abzuleiten. Das Konzept wird auf ein X-by-wire-Fahrzeug mit Einzelradaktorik angewandt. Dabei steht zunächst die Beeinflussung der Ziele der Mehrzieloptimierung zugunsten der Zuverlässigkeit des Systems im Vordergrund. In Simulationen wird gezeigt, dass über die Wahl und Gewichtung der Zielfunktionen die Quer- und Längskräfte an den Rädern vorteilhaft verteilt werden können. In this contribution a concept is illustrated, which combines the multi-objective optimization technique with an online assessment of the current system state. This allows deriving measures to increase the reliability of the system. The concept is applied to an X-by-wire vehicle with single-wheel actuators. The emphasis is here mostly on the influence of the objectives of the multiobjective optimization for the benefit of the reliability of the system. It is demonstrated in simulations, that the lateral and longitudinal forces at the wheels can be distributed advantageously by the selection of the suitable objective functions and the appropriate weights.}}, author = {{Sondermann-Wölke, Christoph and Sextro, Walter and Reinold, Peter and Trächtler, Ansgar}}, booktitle = {{25. Tagung Technische Zuverlässigkeit (TTZ 2011) - Entwicklung und Betrieb zuverlässiger Produkte}}, pages = {{291--302}}, title = {{{Zuverlässigkeitsorientierte Mehrzieloptimierung zur Aktorrekonfiguration eines X-by-wire-Fahrzeugs}}}, year = {{2011}}, } @article{9772, abstract = {{A profound description of friction in wheel--rail contact plays an essential role for optimization of traction control strategies, as input quantity for railway simulations in general and for the estimation of wear and rolling contact fatigue. A multitude of wheel--rail contact models exists, however, traction--creepage curves obtained from measurements show quantitative and qualitative deviations. There are several phenomena which influence the traction--creepage characteristics: Mechanisms resulting from surface roughness, frictional heating or the presence of interfacial fluids can have a dominating influence on friction. In this paper, a new wheel--rail contact model, accounting for these influential parameters, will be presented. The presented model accounts for the interaction of an interfacial fluid model for combined boundary and mixed lubrication of rough surfaces with a wheel--rail contact model that additionally accounts for frictional heating. A quantitative comparison with measurements found in the literature is not conducted, since the exact conditions of the measurements are mostly unknown and parameters can easily be adjusted to fit the measurements. Emphasis is placed on the qualitative behavior of the model with respect to the measurements and good agreement is found. The dependence of the maximum traction coefficient on rolling velocity, surface roughness and normal load is studied under dry and water lubricated conditions.}}, author = {{Tomberger, Christoph and Dietmaier, Peter and Sextro, Walter and Six, Klaus}}, issn = {{0043-1648}}, journal = {{Wear}}, keywords = {{Wheel--rail contact, Rolling contact, Friction, Interfacial fluid, Lubrication, Surface roughness, Contact temperature}}, pages = {{2 -- 12}}, title = {{{Friction in wheel--rail contact: A model comprising interfacial fluids, surface roughness and temperature}}}, doi = {{10.1016/j.wear.2010.10.025}}, volume = {{271}}, year = {{2011}}, } @article{9877, author = {{Isobe, Gaku and Bornmann, Peter and Hemsel, Tobias and Morita, Takeshi}}, journal = {{Proceedings of Symposium on Ultrasonic Electronics}}, pages = {{19--20}}, publisher = {{Trans Tech Publ}}, title = {{{High temperature tolerant transducer for Ultrasonic Assisted Hydrothermal Method}}}, volume = {{32}}, year = {{2011}}, } @book{9918, editor = {{Tönnies, Merle and Flotmann, Christina}}, publisher = {{WVT}}, title = {{{Narrative in Drama}}}, year = {{2011}}, } @article{4140, abstract = {{In this paper we report on the successful reduction of tensile strain in a thin strained ion-beam synthesized 3C-SiC(1 1 1) layer on silicon. The creation of a near-interface defect structure consisting of nanometric voids and stacking fault type defects by He ion implantation and subsequent annealing yields significant relaxation in the top SiC film. The microstructure of the defect layer is studied by transmission electron microscopy, and the strain state of the 3C-SiC layer was studied by high-resolution X-ray diffraction in a parallel beam configuration. Typical process conditions for the growth of GaN films on the SiC layer were emulated by high temperature treatments in a rapid thermal annealer or a quartz tube furnace. It is found that prolonged annealing at high temperatures leads to ripening of the voids and to a weaker reduction of the tensile strain. It is shown that this problem can be overcome by the co-implantation of oxygen ions to form highly thermally stable void/extended defect structures.}}, author = {{Häberlen, M. and Murphy, B. and Stritzker, B. and Lindner, Jörg}}, issn = {{0168-583X}}, journal = {{Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms}}, pages = {{322--325}}, publisher = {{Elsevier BV}}, title = {{{Relaxation of a strained 3C-SiC(111) thin film on silicon by He+ and O+ ion beam defect engineering}}}, doi = {{10.1016/j.nimb.2011.01.092}}, volume = {{272}}, year = {{2011}}, } @article{4142, abstract = {{This paper reports the successful reduction of tensile strain in a thin ion-beam-synthesized 3C-SiC(111) layer on silicon. Significant relaxation is achieved by creating a near-interface defect structure containing nanometric voids and dislocation loops by the implantation of He ions and subsequent thermal annealing. The structural features of this defect microstructure are investigated by transmission electron microscopy. High-resolution X-ray diffraction in a parallel beam configuration is used to quantify the strain state of the top SiC layer. Further annealing experiments were carried out in order to emulate typical process conditions for the growth of wide-bandgap semiconductors like, for example GaN. It is found that prolonged annealing at elevated temperatures leads to coarsening of the voids and to a much less efficient strain reduction. We show that this issue can be resolved by the co-implantation of oxygen to form highly thermally stable cavity/extended defect structures. The technique presented here may be useful for a variety of other thermally mismatched bulk/thin film couples as well.}}, author = {{Häberlen, Maik and Murphy, Brian and Stritzker, Bernd and Lindner, Jörg}}, issn = {{1862-6351}}, journal = {{physica status solidi (c)}}, number = {{3}}, pages = {{944--947}}, publisher = {{Wiley}}, title = {{{Decoupling of a strained 3C-SiC(111) thin film on silicon by He+ and O+ ion implantation}}}, doi = {{10.1002/pssc.201000342}}, volume = {{8}}, year = {{2011}}, } @article{4148, abstract = {{Photoluminescence spectra of Sm^(2+)-doped BaBr^2 have been measured under hydrostatic pressures up to 17 GPa at room temperature. In the low pressure range a red-shift of the broad 5d–4f transition of -145 cm^(-1)/GPa is observed. From 5 to 8 GPa a phase mixtureof the initial orthorhombic phase and the high-pressure monoclinic phase gives rise to two 5d–4f bands, which are strongly overlapping. Above 8 GPa the crystalis completely transformed to its high-pressure phase where two different Sm2^(2+) sites exist, but only one broad 5d–4f transition is detected. It exhibits are d-shift of -36 cm^(-1)/GPa. In addition,the line shifts of the (_^5)D_0→(_^7)F_J (J=0,1,2) transitions are investigated. Linear shifts of -19cm^(-1)/GPa for J=0,2 and of -13cm^(-1)/GPa for J01 are observed in the pressure range from 0 to 5 GPa.}}, author = {{Wiegand, Marie Christin and Sievers, Werner and Lindner, Jörg and Tröster, Th. and Schweizer, S.}}, issn = {{0022-2313}}, journal = {{Journal of Luminescence}}, number = {{11}}, pages = {{2400--2403}}, publisher = {{Elsevier BV}}, title = {{{Photoluminescence properties of Sm2+-doped BaBr2 under hydrostatic pressure}}}, doi = {{10.1016/j.jlumin.2011.05.035}}, volume = {{131}}, year = {{2011}}, } @article{4150, abstract = {{Atomistic simulations on the silicon carbide precipitation in bulk silicon employing both, classical potential and first-principlesmethods are presented. The calculations aim at a comprehensive,microscopic understanding of the precipitation mechanism in the context of controversial discussions in the literature. For the quantum-mechanical treatment, basic processes assumed in the precipitation process are calculated in feasible systems of small size. The migration mechanism of a carbon 100 interstitial and silicon 11 0 self-interstitial in otherwise defect-free silicon are investigated using density functional theory calculations. The influence of a nearby vacancy, another carbon interstitial and a substitutional defect as well as a silicon self-interstitial has been investigated systematically. Interactions of various combinations of defects have been characterized including a couple of selected migration pathways within these configurations. Most of the investigated pairs of defects tend to agglomerate allowing for a reduction in strain. The formation of structures involving strong carbon–carbon bonds turns out to be very unlikely. In contrast, substitutional carbon occurs in all probability. A long range capture radius has been observed for pairs of interstitial carbon as well as interstitial carbon and vacancies. A rather small capture radius is predicted for substitutional carbon and silicon self-interstitials. Initial assumptions regarding the precipitation mechanism of silicon carbide in bulk silicon are established and conformability to experimental findings is discussed. Furthermore, results of the accurate first-principles calculations on defects and carbon diffusion in silicon are compared to results of classical potential simulations revealing significant limitations of the latter method. An approach to work around this problem is proposed. Finally, results of the classical potential molecular dynamics simulations of large systems are examined, which reinforce previous assumptions and give further insight into basic processes involved in the silicon carbide transition.}}, author = {{Zirkelbach, F. and Stritzker, B. and Nordlund, K. and Lindner, Jörg and Schmidt, W. G. and Rauls, E.}}, issn = {{1098-0121}}, journal = {{Physical Review B}}, number = {{6}}, publisher = {{American Physical Society (APS)}}, title = {{{Combinedab initioand classical potential simulation study on silicon carbide precipitation in silicon}}}, doi = {{10.1103/physrevb.84.064126}}, volume = {{84}}, year = {{2011}}, } @article{4157, author = {{Hehenkamp, Burkhard and Kaarboe, Oddvar}}, issn = {{0313-5926}}, journal = {{Economic Analysis and Policy}}, number = {{1}}, pages = {{49--70}}, publisher = {{Elsevier BV}}, title = {{{Paying for Performance in Hospitals}}}, doi = {{10.1016/s0313-5926(11)50004-9}}, volume = {{41}}, year = {{2011}}, } @misc{4171, abstract = {{The method involves exciting a quantum system with photons in a polarization state. Two states of the quantum system are excited with linear horizontal and vertical polarizations that are orthogonal to each other, where the states exhibit an energetic gap smaller than energetic bandwidth of photons. The states are assigned based on the polarizations, where the quantum system is arranged in a superposition state. The quantum system is formed by a quantum bit that is formed as a two-level system.}}, author = {{Förstner, Jens and Mantei, D. and de Vasconcellos, S. Michaelis and Zrenner, Artur}}, keywords = {{tet_topic_qd}}, title = {{{Method for transmission of information about polarization state of photons to stationary system}}}, year = {{2011}}, } @article{4377, abstract = {{Confocal Raman spectroscopy was performed as an archetype imaging method to study the ferroelectric domain structure of periodically poled lithium niobate. More precisely, the linkage out of spatial resolution and spectral information proved itself as very useful. Here a specific modulation of the Raman lines by the local variation of polarity and a non-symmetric measuring-signal across the domain structure were found, which allows for imaging of domain boundaries as well as oppositely orientated domains. The high potential of this method is demonstrated by the visualization of the ferroelectric domain structures based on various phonon modes.}}, author = {{Berth, Gerhard and Hahn, Wjatscheslaw and Wiedemeier, Volker and Zrenner, Artur and Sanna, Simone and Schmidt, Wolf Gero}}, issn = {{0015-0193}}, journal = {{Ferroelectrics}}, keywords = {{Raman spectroscopy, ferroelectric domains, LiNbO3, confocal imaging}}, number = {{1}}, pages = {{44--48}}, publisher = {{Informa UK Limited}}, title = {{{Imaging of the Ferroelectric Domain Structures by Confocal Raman Spectroscopy}}}, doi = {{10.1080/00150193.2011.594774}}, volume = {{420}}, year = {{2011}}, } @article{4378, abstract = {{Using a combined all-ultra-high-vacuum process employing lateral patterning with focused ion beams and molecular beam epitaxy, site-selective growth of single (In,Ga)As quantum dots is achieved. We have embedded such a layer of intentionally positioned quantum dots in the intrinsic region of a p-i-n junction so that the quantum dots can be driven electrically. In this contribution, we will present our results on the morphological properties of the ion-beam modified surface on which the quantum dot nucleation occurs together with a characterization of the electrical and optoelectronic properties. We will demonstrate that a single, individual quantum dot can directly be electrically addressed.}}, author = {{Mehta, Minisha and Reuter, Dirk and Wieck, Andreas D. and Michaelis de Vasconcellos, Steffen and Zrenner, Artur and Meier, Cedrik}}, issn = {{1862-6351}}, journal = {{physica status solidi (c)}}, keywords = {{molecular beam epitaxy, quantum dot, site control, electroluminescence}}, number = {{4}}, pages = {{1182--1185}}, publisher = {{Wiley}}, title = {{{Electrically driven intentionally positioned single quantum dot}}}, doi = {{10.1002/pssc.201000828}}, volume = {{8}}, year = {{2011}}, } @article{4379, abstract = {{Uniform mesoporous Si double layers are formed on 4 inch p-type < 100> wafers with an off orientation of 6º towards < 111> by means of electrochemical etching in ethanoic-based HF electrolytes. These substrates are of interest for the epitaxial growth of III–V compound semiconductor stacks on their top for the production of multi-junction solar cells and very thin electronic devices. We demonstrate transfer of porous layers after an annealing process in hydrogen atmosphere. Electron Back-Scatter Diffraction analysis confirms that the substrate orientation is conserved during the etching and annealing steps. Confocal μ-Raman spectroscopy analysis shows a decrease in the Raman signal intensity after etching and a subsequent increase after annealing while no shift is observed. By means of Atomic Force Microscopy, analysis the surface appearance after the etching and annealing steps can be visualized. The mean surface roughness varies during the process from 0.55 nm for the unprocessed wafers to 0.27 nm after etching and 0.78 nm after annealing. The decrease of average roughness after etching is caused by an electropolishing step prior to porous formation. Despite of slight increase of mean surface roughness after annealing the samples are still appropriate for high quality epitaxial growth and subsequent lift-off.}}, author = {{Garralaga Rojas, E. and Terheiden, B. and Plagwitz, H. and Hensen, J. and Wiedemeier, V. and Berth, Gerhard and Zrenner, Artur and Brendel, R.}}, issn = {{0040-6090}}, journal = {{Thin Solid Films}}, keywords = {{Porous Si, Layer transfer, Thin-film, Photovoltaics}}, number = {{1}}, pages = {{606--609}}, publisher = {{Elsevier BV}}, title = {{{Lift-off of mesoporous layers by electrochemical etching on Si (100) substrates with miscut of 6° off towards (111)}}}, doi = {{10.1016/j.tsf.2011.07.063}}, volume = {{520}}, year = {{2011}}, }