@article{9759,
  abstract     = {{Among various lead-free piezoelectric materials, (K,Na)NbO$_{3}$ is a very promising candidate. In this study, (K,Na)NbO$_{3}$ ceramics were sintered from mixed (K,Na)NbO$_{3}$ and NaNbO$_{3}$ powders prepared by hydrothermal reaction. These two powders were mixed with distilled water in a KNbO$_{3}$/NaNbO$_{3}$ molar ratio of 1. After sintering the mixed powder, the solid solution of (Na,K)NbO$_{3}$ ceramics was obtained. The electrical properties such as the electromechanical coupling factors k$_{p}$ and k$_{33}$, the mechanical quality factor, Q$_{m}$, and the piezoelectric constant d$_{33}$ of the sintered (K,Na)NbO$_{3}$ ceramics were 0.32, 0.48, 71 (radial mode), 118 ((33)mode), and 107 pC/N, respectively.}},
  author       = {{Maeda, Takafumi and Takiguchi, Norihito and Morita, Takeshi and Ishikawa, Mutsuo and Hemsel, Tobias}},
  issn         = {{1948-5719}},
  journal      = {{Materials Letters}},
  keywords     = {{Lead-free piezoelectric material, (K, Na)NbO$_{3}$ ceramics, Sintering solid solution, Piezoelectric properties}},
  number       = {{2}},
  pages        = {{125--128}},
  title        = {{{(K,Na)NbO3 lead-free piezoelectric ceramics synthesized from hydrothermal powders}}},
  doi          = {{10.1016/j.matlet.2009.10.012}},
  volume       = {{64}},
  year         = {{2010}},
}

@inproceedings{9760,
  abstract     = {{Self-optimizing systems are able to adapt their behavior autonomously according to their current self-determined objectives. Unforeseen influences could lead to dependability-critical behavior of the system. Methods are required which secure self-optimizing systems during operation. These methods to increase the dependability of the system should already be taken into consideration in the design process. This paper presents a guideline for the dependability-oriented design of self-optimizing systems, which integrates established classical methods like failure mode and effects analysis as well as methods based on self-optimization. On the one hand self-optimization is used to increase the dependability of the system by integrating objectives like safety, availability, and reliability to the objectives of the system. On the other hand methods are required to ensure the self-optimization itself. As basis for this guideline serves the principle solution of the system. The six phases of the guideline extend the design process and lead to an enhanced principle solution. Additionally, the guideline illustrates phases to implement and validate the self-optimizing system. The proposed guideline is applied to an innovative rail-bound vehicle, called RailCab, which is equipped with self-optimizing function modules.}},
  author       = {{Sondermann-Wölke, Christoph and Hemsel, Tobias and Sextro, Walter and Gausemeier, Jürgen and Pook, Sebastian}},
  booktitle    = {{Industrial Informatics (INDIN), 2010 8th IEEE International Conference on}},
  keywords     = {{RailCab, dependability-critical behavior, dependability-oriented design, failure mode, rail-bound vehicle, secure self-optimizing systems, self-optimizing function modules, optimisation, railways, self-adjusting systems}},
  pages        = {{739 --744}},
  title        = {{{Guideline for the dependability-oriented design of self-optimizing systems}}},
  doi          = {{10.1109/INDIN.2010.5549490}},
  year         = {{2010}},
}

@article{23230,
  author       = {{Sondermann-Wölke, Christoph and Geisler, Jens and Hirsch, Martin and Hemsel, Tobias}},
  journal      = {{6. Paderborner Workshop: "Entwurf mechatronischer Systeme"}},
  pages        = {{231--243}},
  title        = {{{Verlässlichkeit im aktiven selbstoptimierenden Spurführungsmodul eines schienengebundenen Fahrzeugs}}},
  volume       = {{Band 250}},
  year         = {{2009}},
}

@article{23249,
  author       = {{Sondermann-Wölke, Christoph and Geisler, Jens and Hirsch, Martin and Hemsel, Tobias}},
  journal      = {{6. Paderborner Workshop: "Entwurf mechatronischer Systeme"}},
  pages        = {{231--243}},
  title        = {{{Verlässlichkeit im aktiven selbstoptimierenden Spurführungsmodul eines schienengebundenen Fahrzeugs}}},
  volume       = {{Band 250}},
  year         = {{2009}},
}

@inproceedings{9735,
  abstract     = {{Die Entwicklung piezoelektrischer Tr{\"a}gheitsmotoren basiert derzeit auf Erfahrungswissen und Prototypenbau. Es existiert kein allgemeines Modell und keine Methodik f{\"u}r die systematische Entwicklung dieser Motoren. In diesem Beitrag stellen wir einen Ansatz zur Entwicklung einer solchen Methodik und den von uns aufgebauten Versuchsmotor vor. Der Motor ist modular aufgebaut; er besteht im Wesentlichen aus einer piezoelektrischen Antriebseinheit, einem Antriebsstab und dem zu bewegenden Schlitten. Eine wesentliche Aufgabe bei der modellbasierten Entwicklung von Tr{\"a}gheitsmotoren ist die hinreichende Beschreibung des dynamischen Verhaltens der Antriebseinheit. Um ein geeignetes Modell zu finden, bzw. um nachzuweisen, dass einfache parametrische Modelle gen{\"u}gen, wird die Antriebseinheit des Motors detailliert untersucht. Es zeigt sich, dass der derzeitige Aufbau eine Reihe von Nachteilen aufweist, die durch eine teilweise Neukonstruktion der Antriebseinheit beseitigt oder zumindest entsch{\"a}rft werden k{\"o}nnen.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias}},
  booktitle    = {{6. Paderborner Workshop Entwurf mechatronischer Systeme}},
  editor       = {{Gausemeier, Jürgen and Rammig, Franz and  Schäfer,  Wilhelm and Trächtler, Ansgar}},
  issn         = {{1948-5719}},
  keywords     = {{Piezoelektrischer Tr{\}},
  pages        = {{85--96}},
  publisher    = {{Heinz Nixdorf Institut, Universität Paderborn}},
  title        = {{{Modellbasierte Entwicklung piezoelektrischer Trägheitsmotoren}}},
  volume       = {{250}},
  year         = {{2009}},
}

@inproceedings{9740,
  abstract     = {{Die Integration von Selbstoptimierung in mechatronische Systeme beinhaltet sowohl Risiken als auch Potenziale für die Verlässlichkeit. Die Risiken entstehen durch die Selbstoptimierung in den komplexen Systemen, da das Systemverhalten nur begrenzt im Voraus vorhersehbar ist. Daher wurde innerhalb des Sonderforschungsbereichs 614 ''Selbstoptimierende Systeme des Maschinenbaus" ein mehrstufiges Verlässlichkeitskonzept entworfen, welches das Ziel Verlässlichkeit stärker im Zielsystem verankert. In diesem Beitrag wird zum einen das erarbeitete Verlässlichkeitskonzept und zum anderen die Anwendung dieses Konzepts innerhalb des aktiven Spurführungsmoduls eines schienengebundenen Fahrzeugs vorgestellt. Um Programmierfehler auszuschließen wurde das Verlässlichkeitskonzept modelliert und über Model Checking verifiziert. Anhand von Simulationsergebnissen wird gezeigt, wie durch das mehrstufige Verlässlichkeitskonzept auf einen Ausfall eines Wirbelstromsensors des aktiven Spurführungsmoduls reagiert werden kann.}},
  author       = {{Sondermann-Wölke, Christoph and Geisler, Jens and Hirsch, Martin and Hemsel, Tobias}},
  booktitle    = {{Entwurf mechatronischer Systeme}},
  editor       = {{Gausemeier, Jürgen and Rammig, Franz Josef and Trächtler, Ansger}},
  keywords     = {{Verlässigkeit}},
  pages        = {{231 -- 242}},
  title        = {{{Verlässlichkeit im aktiven selbstoptimierenden Spurführungsmodul eines schienengebundenen Fahrzeugs}}},
  volume       = {{250}},
  year         = {{2009}},
}

@inproceedings{9741,
  author       = {{Sondermann-Wölke, Christoph and Hesse, Tobias and Sattel, Thomas and Hemsel, Tobias}},
  booktitle    = {{24. Tagung Technische Zuverlässigkeit (TTZ 2009) - Entwicklung und Betrieb zuverlässiger Produkte, Leonberg}},
  pages        = {{335 -- 340}},
  title        = {{{Menschliche Unzuverlässigkeit als Grundlage für den Entwurf von Kollisionsvermeidungssystemen.}}},
  volume       = {{2065}},
  year         = {{2009}},
}

@inproceedings{9568,
  abstract     = {{A simple pre-stress estimate method of Langevin transducers is studied. The measurement setup consists of a capacitor, an impedance converter and a voltmeter. Based on the piezoelectric equation and the basic circuit theory, the mathematical expression between the pre-stress and the voltage across the capacitor is derived. The pre-stress level can then be calculated out of the measurement of the capacitor voltage. In order to evaluate the precision of this method, a force washer is used to measure the pre-stress of the Langevin transducer. The result shows the pre-stress level obtained from this method is 30-40\% higher than the pre-stress level measured by the force washer. This method is simple and can be used to estimate the pre-stress of various Langevin transducers. The precision of this method can be raised if d33 is identified under different pre-stress levels.}},
  author       = {{Bo, Fu and Ting, Li and Hemsel, Tobias}},
  booktitle    = {{Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium on}},
  keywords     = {{capacitors, impedance convertors, piezoelectric transducers, stress analysis, Langevin transducers, basic circuit theory, capacitor, impedance converter, piezoelectric equation, pre-stress estimating method, voltmeter, Capacitors, Educational institutions, Equations, Force measurement, Impedance measurement, Manufacturing, Mechatronics, Piezoelectric transducers, Voltage, Voltmeters, Langevin transducer, capacitor, piezoelectric element, pre-stress}},
  pages        = {{324--327}},
  title        = {{{A simple pre-stress estimating method of langevin transducers}}},
  doi          = {{10.1109/SPAWDA.2008.4775801}},
  year         = {{2008}},
}

@article{9569,
  abstract     = {{Ultrasonic hyperthermia and thermo-ablation are two promising alternatives for local overheating of deep-seated human tumours. After a short characterisation of the two techniques and the identification of the main parameters, results of an analytical theory of local heat up, cooling, and heat diffusion are presented. The theory is based on a spherical model for hyperthermia with a critical thermal dose and on a cylinder-symmetrical model for thermo-ablation with a critical temperature threshold for thermal toxicity and cell death through coagulative necrosis. Two representative hard ware concepts are discussed. The hyperthermia applicator consists of a MHz transducer, which rotates concentrically in a water filled capsule with acoustically transparent window, and radiates collimated or focussed ultrasound under 45$\,^{\circ}$ into a concentric target area of nearly spherical symmetry. The applicator for thermo-ablation is a MHz transducer which radiates high intensity focussed ultrasound (HIFU) into "cigar shaped" target areas at the focal zone. Typical therapy diagrams for both techniques are presented. They show therapeutic target volumes as functions of the therapy time with the peak temperature or the radiated acoustic power as parameters. These diagrams are discussed under consideration of power requirement, maximal sound intensity, and power efficiency at close to optimized frequency conditions.}},
  author       = {{Lierke, Ernst-Günter and Hemsel, Tobias}},
  journal      = {{Acta Acustica united with Acustica}},
  number       = {{3}},
  pages        = {{369--381}},
  title        = {{{Local Ultrasonic Hyperthermia and Thermo-ablation: A Description and Theoretical Evaluation of Two Alternative Concepts for the Heat Therapy of Tumours}}},
  doi          = {{10.3813/AAA.918044}},
  volume       = {{94}},
  year         = {{2008}},
}

@inproceedings{9570,
  abstract     = {{EN: Although the use of new actuator technologies is quite enthusiastic, the realization of innovative systems based on these principles fails because of doubts in dependability. Until now, new working principles for actuators have not been systematically investigated in the means of dependability. Therefore we developed a proceeding for a dependability-oriented evaluation of technologies. This is shown in the case of shape memory alloy actuators. 
DE: Die Realisierung von Systemen mittels innovativer Aktortechnologien scheitert oftmals an der Skepsis gegenüber der Verlässlichkeit (Vertrauen in die zuverlässige und sichere Funktionalität der Technologie). Diese liegt darin begründet, dass neue Aktortechnologien bzw. die Integration von innovativen physikalischen Wirkprinzipen innerhalb neuer Aktorkonzepte bisher noch nicht systematisch im Kontext der Verlässlichkeit untersucht werden. Daher haben wir ein Vorgehen zur verlässlichkeitsorientierten Technologiebewertung entwickelt. Neben der detaillierten Darstellung des Vorgehensmodells wird es exemplarisch anhand von Formgedächtnislegierungen zur Entwicklung innovativer Antriebslösungen angewendet.}},
  author       = {{Müller, Thomas and Schiedeck, Florian and Hemsel, Tobias}},
  booktitle    = {{2. Tagung des DVM -- Arbeitskreis Zuverlässigkeit mechatronischer und adaptronischer Systeme: Absicherung der Systemzuverlässigkeit, Koblenz}},
  keywords     = {{EN: Dependability, Reliability, Evaluation of Technology, Actuators, Shape Memory Alloys DE: Verl{\}},
  title        = {{{Verlässlichkeitorientierte Technologiebewertung innovativer Aktortechnologien am Beispiel von Formgedächtnislegierungen}}},
  year         = {{2008}},
}

@article{9571,
  abstract     = {{Several positioning tasks demand translatory drive instead of rotary motion. To achieve drives that are capable, e.g., to drive the sunroof of a car or to lift a car's window, multiple miniaturized motors can be combined. But in this case many other questions arise: The electromechanical behavior of the individual motors differs slightly, the motor characteristics are strongly dependent on the driving parameters and the driven load, many applications need some extra power for special cases like overcoming higher forces periodically. Thus, the bundle of motors has to act well-organized and at last controlled to get an optimized drive that is not oversized and costly.}},
  author       = {{Mracek, Maik and Hemsel, Tobias and Sattel, Thomas and Vasiljev, Piotr and Wallaschek, Jörg}},
  issn         = {{1385-3449}},
  journal      = {{Journal of Electroceramics}},
  keywords     = {{Ultrasonic linear motor, High power, Control, Modeling, Characteristics}},
  number       = {{3-4}},
  pages        = {{153--158}},
  publisher    = {{Springer US}},
  title        = {{{Driving concepts for bundled ultrasonic linear motors}}},
  doi          = {{10.1007/s10832-007-9123-5}},
  volume       = {{20}},
  year         = {{2008}},
}

@article{9574,
  abstract     = {{For devices having non-linear contact, load plays a fundamental role. Variations in the characteristics of the load cause change in eigenfrequency and amplitude of the vibration. In most technical applications, this unwanted behaviour is cancelled by the use of control algorithms. However, multiple applications, like bond quality monitoring or chemical and pressure sensors, have found that the load may be characterised by interpreting the change in characteristics of a resonant vibrating device used as a sensor. Surgical resection of tumours is a very difficult task. After localising the tumour by the use of imaging techniques, the resection demands the surgeon to decide where and what to resect based on visual and tactile differentiation of tumour and healthy tissue. Exactness of this process could be enhanced if we can provide the surgeon with a device capable of evaluating mechanical characteristics of the tissue much more accurately than the surgeon himself can do. As the mechanical characteristics of tumour and healthy tissue differ but slightly, the task is to design a system with high sensitivity. Therefore, we have developed a resonant actuator-sensor that allows the differentiation among distinct media that have similar mechanical characteristics to tumour and healthy tissue using a piezoelectric bimorph. The design is based on the detection and evaluation of frequency shift and amplitude variation of the fundamental and higher harmonics using one layer for the resonant excitation of vibration and the other one as the sensing element.}},
  author       = {{Stroop, Ralf and Uribe, David Oliva and Martinez, Melisa Orta and Brökelmann, Michael and Hemsel, Tobias and Wallaschek, Jörg}},
  issn         = {{1385-3449}},
  journal      = {{Journal of Electroceramics}},
  keywords     = {{Piezo ceramics, Bimorph, Tactile sensor, Tumour tissue}},
  number       = {{3-4}},
  pages        = {{237--241}},
  publisher    = {{Springer US}},
  title        = {{{Tactile tissue characterisation by piezoelectric systems}}},
  doi          = {{10.1007/s10832-007-9183-6}},
  volume       = {{20}},
  year         = {{2008}},
}

@article{9575,
  abstract     = {{Many ultrasonic processes are based on the mechanical contact of oscillating parts. Within ultrasonic machining (drilling, milling, grinding) micro impacts lead to abrasion at the processed workpiece and hopefully do not damage the tool. In ultrasonic motors ideally neither part gets worn. Thus the appropriate design of contact partners as well as their kinematics is a substantial task during the development of such devices. A first step to optimize contact mechanics is to understand their behavior and dependencies on parameter variations, such as vibration amplitude and pre-stress of the impacting parts. For a detailed understanding models validated with convincing experimental data from measurements are absolutely essential. This paper focuses on simple vibro-impact experiments which can be used as benchmark data for future models. The setup of the experiment and first experimental investigations are described in detail.}},
  author       = {{Twiefel, Jens and Potthast, Christian and Mracek, Maik and Hemsel, Tobias and Sattel, Thomas and Wallaschek, Jörg}},
  issn         = {{1385-3449}},
  journal      = {{Journal of Electroceramics}},
  keywords     = {{Contact measurements, Vibro-impact, Ultrasonic application}},
  number       = {{3-4}},
  pages        = {{209--214}},
  publisher    = {{Springer US}},
  title        = {{{Fundamental experiments as benchmark problems for modeling ultrasonic micro-impact processes}}},
  doi          = {{10.1007/s10832-007-9169-4}},
  volume       = {{20}},
  year         = {{2008}},
}

@inproceedings{9576,
  abstract     = {{In neurosurgery, delineation of tumor boundaries during resection of brain tumors is of substantial relevance. During operation distinction between tumor and healthy tissue rely on the abilities of the surgeon based on visual and tactile differentiation. In this paper a high sensitivity actuator-sensor system using a piezoelectric bimorph is presented. Frequency shift and transfer function of the bimorphpsilas voltages are detected and evaluated. Sensorpsilas sensitivity is evaluated using two frequency controls strategies: A phase-locked loop (PLL) and a self-oscillating circuit. Results of measurements conducted on gel-phantoms are presented and discussed.}},
  author       = {{Uribe, David Oliva and Stroop, Ralf and Hemsel, Tobias and Wallaschek, Jörg}},
  booktitle    = {{Frequency Control Symposium, 2008 IEEE International}},
  issn         = {{1075-6787}},
  keywords     = {{biomedical measurement, brain, cancer, neurophysiology, phantoms, phase locked loops, piezoelectric actuators, surgery, tactile sensors, transfer functions, tumours, PLL, biomedical tissue differentiation system, brain tumor resection, frequency control, frequency shift, gel-phantom, high sensitivity actuator-sensor system, neurosurgery, phase-locked loop, piezoelectric actuators, piezoelectric bimorph, self-oscillating circuit, sensor sensitivity, tactile differentiation, tactile sensor system, transfer function, tumor boundary, visual differentiation, Biomedical measurements, Circuits, Frequency control, Neoplasms, Neurosurgery, Phase locked loops, Piezoelectric actuators, Surges, Transfer functions, Voltage}},
  pages        = {{91--94}},
  title        = {{{Development of a biomedical tissue differentiation system using piezoelectric actuators}}},
  doi          = {{10.1109/FREQ.2008.4622963}},
  year         = {{2008}},
}

@misc{9572,
  author       = {{Rischmueller, Volker and Wallaschek, Jörg and Froehlich, Peter and Haussecker, Walter and Rieger, Vincent and Twiefel, Jens and Guenther, Dirk and Hemsel, Tobias}},
  title        = {{{Patent EP2156480: Piezoelektrische Antriebsvorrichtung / Piezoelectric Drive Unit}}},
  year         = {{2008}},
}

@inproceedings{9562,
  abstract     = {{Penetration tests (Magness-Taylor, force/deformation, Kramer multiblade shear) applied directly over the peel of the fruit are the most acceptable methods for measuring firmness and turgidity of fruits and vegetables [1, 2]. To replace these destructive and mechanical penetration methods by non-destructive ultrasonic measurements implies a great advance in order to obtain fast studies about the state of the fruit at the time of harvest, during storage, and in the distribution points. Moreover, there are other advantages since this technique can be fast, non-destructive, fully automated, and performed on-line [1]. Within this context, the objective of this study was to examine the relationship between physico-mechanical characteristics (oil-gland break stress, thickness and dehydration) and ultrasonic characteristics in the ``Salustiana'' orange peel during the complete dehydration process of the orange at ambient conditions. After a description of the measurement system [3], the fruit selection procedure and the measurement protocol, we analyze the results of the change of physico-mechanical and ultrasonic properties in the orange peel and their change with storage time.}},
  author       = {{Camarena Gandia, Francisco and Hemsel, Tobias and Espinosa, Victor and Twiefel, Jens and Ardid, Miquel and Martinez-Mora, Joan and Gandia, Joan Babtiste}},
  booktitle    = {{Proceedings of 19th international congress on Acoustics, Madrid}},
  title        = {{{Non-destructive ultrasonic test of orange dehydration}}},
  year         = {{2007}},
}

@article{9564,
  abstract     = {{Surgical resection of brain tumours is a difficult task. To enhance surgery results, a tactile sensor is wanted that gives better resolution and sensitivity than the human tactile sense. The characteristics of resonant vibrating piezoelectric elements change with varying load. This allows for calculation of mechanical load parameters by measuring electrical quantities. Different setups of piezoelectric sensors have been used to investigate soft materials. Finally, a piezoelectric bimorph sensor gave good results for distinguishing tissue mimicking gel-phantoms with different gelatine concentrations. }},
  author       = {{Hemsel, Tobias and Stroop, Ralf and Oliva Uribe, David and Wallaschek, Jörg}},
  issn         = {{0022-460X}},
  journal      = {{Journal of Sound and Vibration}},
  pages        = {{441 -- 446}},
  title        = {{{Resonant vibrating sensors for tactile tissue differentiation}}},
  doi          = {{10.1016/j.jsv.2007.03.063}},
  volume       = {{308}},
  year         = {{2007}},
}

@inproceedings{9565,
  author       = {{Lierke, Ernst-Günter and Hemsel, Tobias}},
  booktitle    = {{Proceedings of 19th international congress on Acoustics, Madrid}},
  title        = {{{Perspectives of Tumour Therapy by Local Ultrasonic Hyperthermia and Thermal Ablation}}},
  year         = {{2007}},
}

@article{9566,
  author       = {{Shigematsu , Takashi and Morita, Takeshi and Hemsel, Tobias}},
  journal      = {{Proceedings of Symposium on Ultrasonic Electronics}},
  pages        = {{439 -- 440}},
  title        = {{{Fundamental Study on A Thickness-Shear Transformer using X-Cut Lithium Niobate}}},
  volume       = {{28}},
  year         = {{2007}},
}

@inproceedings{9532,
  author       = {{Becker, C and Wedman, S and Hemsel, Tobias}},
  booktitle    = {{Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators}},
  number       = {{Band 180}},
  pages        = {{481}},
  title        = {{{Design and Construction of a 3D-Scanning-Laservibrometer}}},
  year         = {{2006}},
}