@article{15346,
  author       = {{Henning, Bernd and Rautenberg, Jens}},
  journal      = {{Ultrasonics}},
  number       = {{44}},
  pages        = {{e1395--e1399}},
  title        = {{{Process monitoring using ultrasonic sensor systems}}},
  year         = {{2006}},
}

@misc{15352,
  abstract     = {{Impulsbasierte Ultraschallsensorsysteme zur Messung von Füllstand, Durchfluss und Konzentration sind heutzutage aufgrund ihrer Robustheit und Wartungsfreundlichkeit weit verbreitet. Probleme treten immer dann auf, wenn sich Gasblasen im Medium befinden. Diese verändern das empfangene Signal derart, dass eine exakte Messung der Schallgeschwindigkeit des flüssigen Mediums nicht mehr möglich ist. Dieser Beitrag behandelt eine neue Art der Signalauswertung, die eine zuverlässige Bestimmung der Schallgeschwindigkeit auch in diesem Fall gewährleistet. Darüber hinaus können auch Rückschlüsse auf den Gasanteil innerhalb des flüssigen Mediums gewonnen werden.}},
  author       = {{Gulsch, Michael and Henning, Bernd}},
  title        = {{{Bestimmung des Anteils ungelöster Gase in flüssigen Medien}}},
  year         = {{2005}},
}

@inproceedings{15353,
  abstract     = {{Currently there are pulse based ultrasonic sensor systems used to measure flow, liquid level, concentration or in process monitoring. In several processes the investigated media are a mixture of liquid and solid ingredients (emulsions, suspensions). The use of ultrasonic sensor systems will be very complicated if gas bubbles appear at the measurement place caused by chemical reactions, high temperature or fast flow that means by typical process conditions. Firstly, the appearance of gas bubbles falsifies the measured absorption. Secondly, the measured velocity is influenced by gas bubbles. In figure 1 is visible that a volume fraction of 0.1 ppm of undissolved air decreases the sound velocity by 1.4 m s-1}},
  author       = {{Gulsch, Michael and Henning, Bernd}},
  booktitle    = {{2005 IEEE Ultrasonics Symposium}},
  pages        = {{780--782}},
  title        = {{{Bubble detection and gas volume measurement in bubble loaded liquids with pulse driven measurement devices}}},
  year         = {{2005}},
}

@inproceedings{15354,
  abstract     = {{In vielen verfahrenstechnischen Prozessen ist die kontinuierliche Regelung von Prozessgrößen für einen stabilen und sicheren Betrieb eine wichtige Vorraussetzung. Die Erfassung der Zielgrößen geschieht aufgrund von hoher Robustheit und Wartungsfreundlichkeit zunehmend mit akustischen Messverfahren. Besonders impulsbasierte Messsysteme werden häufig zur Messung von Durchfluss, Füllstand und in der Flüssigkeitsanalytik auch zur Konzentrationsmessung benutzt. Dabei führen am Messort auftretende Gasblasen zu großen messtechnischen Problemen. Sie verändern die gemessenen akustischen Stoffkenngrößen, wodurch es zur fehlerhaften Regelung bestimmter Prozesszielgrößen kommt.}},
  author       = {{Gulsch, Michael and Henning, Bernd}},
  booktitle    = {{Fortschritte der Akustik - DAGA '05}},
  editor       = {{Fastl, Hugo and Fruhmann, Markus}},
  isbn         = {{3-9808659-1-6}},
  pages        = {{587--588}},
  publisher    = {{Deutsche Gesellsch. f. Akustik}},
  title        = {{{Gasvolumenmessung in blasenbeladenen Flüssigkeiten}}},
  year         = {{2005}},
}

@inproceedings{15355,
  abstract     = {{Today headlights are built with transparent polycarbonate front windows. If the air moisture inside the headlight is high and the outside temperature decreases below the dew-point, the air moisture condensates inside and the inner surface of the polycarbonate front window (PCFW) becomes nontransparent (figure 1). To the costumer this appears as an optical defect.In order to avoid the condensation and to speed up the evaporation of the condensed water (condensate) on the PCFW a Computational-Fluid-Dynamic-simulation is used. The simulation results are proceeded to optimise the airflow and the arrangement of the breather holes. An important problem is the validation of the simulated results with the reality. It was necessary to build a non-invasive measurement system for the continuous characterisation of condensated areas without affecting the material properties, the airflow and the light distribution inside the headlight.}},
  author       = {{Gulsch, Michael and Unverzagt, Carsten and Henning, Bernd and Nolte, Sascha}},
  location     = {{Nürnberg}},
  pages        = {{455--460}},
  title        = {{{Visualisation and Measurement of Condensed Water in Automobile Headlights}}},
  year         = {{2005}},
}

@article{15356,
  author       = {{Handel, Peter and Tournier, Adam and Henning, Bernd}},
  journal      = {{IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control}},
  number       = {{9}},
  pages        = {{1461--1467}},
  title        = {{{Quantum 1/f Effect in Resonant Biochemical Piezoelectric and MEMS Sensors}}},
  volume       = {{52}},
  year         = {{2005}},
}

@inproceedings{15358,
  abstract     = {{In the 1950's many investigations have been made in measuring the Young's and the shear modus of isotropic materials with acoustic waves. Therefore both the longitudinal and transversal sound velocities have been determined with only one specimen, that had to be large in comparison to the wavelength (Brown, Reynolds, Dunegan). Therewith the method was suited only for low absorbing materials. In the 1990's further developments led to mono mode rods to describe viscoelastic properties. Their diameters had to be very small for high frequencies, thus giving practical values up to 65 kHz (Benatar). This contribution is about a tubular multi mode specimen and its application for the simultaneous measurement of the abovementioned acoustic properties at high frequencies.}},
  author       = {{Rautenberg, Jens and Henning, Bernd}},
  location     = {{Beijing, China}},
  title        = {{{Acoustic properties of highly attenuating isotropic media}}},
  year         = {{2005}},
}

@inproceedings{15359,
  abstract     = {{In den bekannten grundlegenden Ausf¨uhrungen zur Erzeugung hörbaren Schalls durch Eigendemodulation amplitudenmodulierten
Leistungsultraschalls (siehe u.a. Westervelt, Berktay) wird von zwei räumlich übereinander
liegenden Wellen unterschiedlicher Frequenz im nichtlinearen Medium ausgegangen, so dass neben ihren
Harmonischen auch Summen- und Differenzfrequenzen entstehen. Die perfekte räumliche Ueberdeckung
der Wellen im Freifeld kann mit herkömmlichen Schallwandlern allerdings nur unzul¨anglich erreicht werden.
Trotzdem sind in der Vergangenheit einige so genannte parametrische Lautsprecher entwickelt worden. Um
annähernd die erwähnten Voraussetzungen zu gewährleisten, sind gängige Systeme mit einem Durchmesser
von ca. 30 cm relativ groß. Dies soll auch dem angestrebten Sekundärschalldruck Rechnung tragen, der linear
mit der effektiv abstrahlenden Fl¨ache wächst. Zum Aufbau dieser großen Flächen werden teilweise viele
kleine Ultraschallwandler zu einem Array zusammengesetzt. Der hohe Preis einzelner Wandler aber auch
die notwendige Sortierung beispielsweise bezüglich ihrer Mittenfrequenz macht den Aufbau solcher Systeme
aufwändig. Erst am vollständig aufgebauten Array werden schließlich Frequenzgang und Richtcharakteristik
des Sekundärschalls ermittelt. Im Sinne kürzerer Entwicklungszeiten und -kosten wäre es wünschenswert,
bereits vor dem Aufbau des Arrays allein durch Untersuchung des einzelnen Ultraschallwandlers eine Prognose
über die zu erwartenden Eigenschaften des Gesamtsystems vornehmen zu können. In diesem Beitrag
wird ein Versuchsaufbau vorgestellt, der unter strenger Beachtung der anfangs erwähnten Voraussetzungen
die parametrische Schallerzeugung mit nur einem Ultraschallwandler kleiner Baugröße erlaubt. Die Frequenzg
änge des Sekundärschalls von Einzelelement und Array werden bei entsprechender Distanz gegen¨ubergestellt.
Vorzüge des neuen Messaufbaus, beispielsweise die Möglichkeit zur Variation von Druck, Temperatur
oder Luftfeuchtigkeit, um atmosphärische Einflüsse auf die parametrische Schallerzeugung zu untersuchen,
werden skizziert}},
  author       = {{Rautenberg, Jens and Henning, Bernd}},
  booktitle    = {{Fortschritte der Akustik - DAGA '05}},
  editor       = {{Fastl, Hugo and Fruhmann, Markus}},
  isbn         = {{3-9808659-1-6}},
  pages        = {{491--492}},
  publisher    = {{Deutsche Gesellsch. f. Akustik}},
  title        = {{{Charakterisierung einzelner Ultraschallwandler für den Aufbau eines mehrelementigen parametrischen Lautsprechers}}},
  year         = {{2005}},
}

@inproceedings{15360,
  abstract     = {{One method to generate focused sound is to transmit amplitude modulated ultrasound of high energy in a nonlinear medium, so that sum and difference frequencies develop. Practically wide arrays of many small ultrasonic transducers are used, but the generation of very low frequencies is always weak. This contribution is about the experimental investigation of the {\textquotedbl}generation zone{\textquotedbl} -- that is the distance between the ultrasonic loudspeaker and the listener -- and the decrease of the lower frequency bound of the audible sound beam with distance. The main focus is on the experimental setup, which permits the parametric sound generation with only one ultrasonic transducer and a waveguide. In addition, the new measurement setup enables to show an additional effect: The de-coherence of the primary ultrasound wave which may be caused by saturation of air. This is why the lower frequency bound decreases as well if we approach the ultrasonic transducer.}},
  author       = {{Rautenberg, Jens and Henning, Bernd}},
  location     = {{Paderborn}},
  title        = {{{Lower Frequency Bound of Parametric Arrays}}},
  year         = {{2005}},
}

@inproceedings{15362,
  abstract     = {{In der industriellen Messtechnik werden optische, chemische und akustische Messverfahren zur Ermittlung von Prozessgrößen eingesetzt. Dabei haben die akustischen Messverfahren aufgrund ihrer Robustheit und Wartungsfreundlichkeit ein sehr großes Einsatzgebiet. Impulsbasierte Ultraschallmesssysteme werden unter anderem zur Messung von Durchfluss und Füllstand eingesetzt. Zunehmend werden sie aber auch in der Flüssigkeitsanalytik zur Konzentrationsmessung und Stoffanalyse herangezogen. Dabei führen Gasblasen in den zu untersuchenden flüssigen Medien immer wieder zu Problemen, da bei Anwesenheit von Gasblasen die akustischen Stoffkenngrößen verändert werden. Diese Probleme können ihre Ursache auch in der Signalverarbeitung haben. Dieser Beitrag soll zeigen, welche Methoden zur Signalverarbeitung geeignet sind um dieses Problem zu lösen.
}},
  author       = {{Gulsch, Michael and Henning, Bernd}},
  location     = {{ Ludwigsburg}},
  pages        = {{31}},
  title        = {{{Neue Methoden der Signalauswertung für Ultraschall-Messsysteme}}},
  year         = {{2004}},
}

@inproceedings{15363,
  abstract     = {{The classical forms of noise present in the frequency of MEMS resonators have been recently investigated and described in detail. The present paper extends this investigation to 1/f noise. That is of fundamental nature in microelectromechanical systems (MEMS) resonators, and is given by the universal quantum 1/f effect. In recent years new piezoelectric and compound semiconductor materials have been developed along with advanced manufacturing technologies for MEMS including them. These technologies enable the deposition of thin compound semiconductor, or PZT films and their integration into MEMS devices.}},
  author       = {{Handel, Peter and Henning, Bernd}},
  isbn         = {{80-2272050-X}},
  location     = {{Smolenice, Slovakia}},
  pages        = {{88--89}},
  title        = {{{1/f-Frequency Fluctations and Phase Noise in MEMS Resonators}}},
  year         = {{2004}},
}

@article{15364,
  author       = {{Henning, Bernd}},
  journal      = {{Technisches Messen}},
  number       = {{9}},
  pages        = {{492--500}},
  title        = {{{Die akustische Impedanz als Messgröße zur Charakterisierung flüssiger Stoffsysteme}}},
  volume       = {{71}},
  year         = {{2004}},
}

@inproceedings{15365,
  abstract     = {{The appliance of time-reversal acoustics to classical trans-ducer design, medical, technical or audible range applica-tions brings forward new ideas whenever we need both, focusing acoustical energy in time and space. Unfortunately, the spatiotemporal focusing is limited through the amount of applied transducer elements as well as the ergodicity and randomness of the cavity [1]. This paper will show how the simulated annealing technique, a multi-objec¬tive optimiza-tion algorithm [2], is used to increase the nar¬rowness of the refocused spot by breaking up randomness for the benefit of ergodicity in a predetermined cavity.}},
  author       = {{Rautenberg, Jens and Olszewski, Dirk and Henning, Bernd}},
  booktitle    = {{Proceedings of the Joint Congress CFA/DAGA 2004}},
  isbn         = {{2-9521105-2-2}},
  pages        = {{1021--1022}},
  publisher    = {{DEGA}},
  title        = {{{A Space Optimization Method for Time-Reversal Super-Focusing}}},
  year         = {{2004}},
}

@misc{15380,
  author       = {{Auge, Jörg and Dierks, Karsten and Henning, Bernd and Prange, Stefan}},
  title        = {{{Vorrichtung zur Bestimmung des Volumens, der Oberflächenspannung und der Viskosität von Flüssigkeitstropfen}}},
  year         = {{2003}},
}

@inproceedings{15381,
  abstract     = {{Currently there are ultrasonic sensors to measure flow, liquid level, concentrations or to monitor the process course. In several processes the investigated media is a mixture of liquid and solid ingredients. The use of ultrasonic sensor systems will become very complicated if gas bubbles appear at the measurement place caused by chemical reactions, high temperature or fast flow this means under typical process conditions. The appearance of gas bubbles falsifies the measured absorption and also the velocity. The sound propagation in liquid mixtures is influenced in a complex manner for instance by solid particles, rapid changes of temperature, and liquid droplets of other density in the measured liquid simultaneously. For the detailed investigation of the influence of bubbles on sound propagation, an experimental setup was build. This setup permits the comprehensive processing of transmitted and scattered signals. Using a smart signal processing it is possible to find a reliable indication for gas bubbles.}},
  author       = {{Gulsch, Michael and Henning, Bernd and Prange, Stefan and Auge, Jörg}},
  editor       = {{Cassereau, Didier}},
  location     = {{Paris, France}},
  pages        = {{243--246}},
  title        = {{{Approach of continuous characterisation of liquid multi-component mixtures}}},
  year         = {{2003}},
}

@inproceedings{15382,
  abstract     = {{Today there are many different ultrasonic sensors to measure flow, liquid level and concentrations or viscosity in several processes. One of the biggest problems by doing the measurement using ultrasonic sensors is the appearance of bubbles at the measurement place caused by chemical reactions, high temperature or fast flow. These bubbles falsify the received signal and the measurement becomes erroneous. Therefore, it is useful to know if there are gas bubbles or not. It is important to obtain the information about bubbles in real-time, how ever the detection of the signal amplitude is not reliable to detect gas bubbles. The amplitude is influenced by solid particles, rapid changes of temperature and liquid droplets of other densities in the measured liquid. These arguments are the motivation to find new possibilities to detect the appearance of gas bubbles in liquids independent of the transparency and rheological properties of liquid.}},
  author       = {{Gulsch, Michael and Henning, Bernd and Prange, Stefan and Auge, Jörg}},
  location     = {{Nuremberg}},
  pages        = {{199--203}},
  title        = {{{Ultrasonic Detection of Gas Bubbles in Liquids}}},
  year         = {{2003}},
}

@misc{15383,
  abstract     = {{Die elektrische Impedanzmessung ist heute in einem weiten Frequenzbereich technisch möglich und wird vielfach zur Materialcharakterisierung eingesetzt. Neben den elektrischen und optischen Messverfahren verfügen aber auch gerade die akustischen Messverfahren über vorteilhafte Applikationseigenschaften wie Robustheit und geringe Wartungsanforderungen. Die zuverlässige Bestimmung der Schallkennimpedanz als eine der drei akustischen Stoffkenngrößen erweist sich aber noch heute als sehr diffizil, wie im Folgenden gezeigt wird.}},
  author       = {{Henning, Bernd}},
  title        = {{{Ultraschall-Impedanz-Spektrometrie zur Erfassung von Stoff- und Strukturgrößen}}},
  year         = {{2003}},
}

@misc{15384,
  author       = {{Auge, Jörg and Dierks, Karsten and Henning, Bernd and Prange, Stefan}},
  title        = {{{Vorrichtung zur Bestimmung des Volumens, der Oberflächenspannung und der Viskosität von Flüssigkeitstropfen}}},
  year         = {{2003}},
}

@inproceedings{15385,
  abstract     = {{One of the most widely spread measuring tasks in chemistry or food technology is the continuous determination of fill levels in liquid tanks. The aim of this paper is to present a new contactless and noninvasive measuring method based on ultrasonic time-reversal and correlation techniques. The novel method enables asserted fill levels to be identified and small deviations of them to be calculated even if the direct path from the sensor to the liquid surface is obstructed. This article will present the structure and principle of the measuring system as well as the procedure of signal processing. A simulative approach is used to demonstrate the excitation of a virtual sound source in the liquid and to show both the advantages and limits of the new technique. In addition a simplified model is developed where the solutions of the simulations are applied to.}},
  author       = {{Henning, Bernd and Rautenberg, Jens and Gulsch, Michael and Klüppel, Stefan}},
  booktitle    = {{SENSOR~Proceedings}},
  publisher    = {{AMA Service GmbH}},
  title        = {{{The Use of Time-Reversal Technology for Level Measurement in Liquid Tanks}}},
  year         = {{2003}},
}

@inproceedings{15361,
  abstract     = {{The determination of small liquid volumes and their changes over a period of time is a measuring problem with increasing importance considering the growing market of micro-systems. In this paper, experimental investigations are described which aim to observe the growth of droplets at the end of a micro channel, such as a cannula or capillary. The main focus of the work lies on the calculation of flow rates below 1 millilitre per hour. Furthermore, the potential of the measuring equipment for liquid level and surface tension measurement is described.}},
  author       = {{Auge, Jörg and Dierks, Karsten and Prange, Stefan and Henning, Bernd}},
  location     = {{Prag}},
  pages        = {{375--378}},
  title        = {{{Monitoring of droplet growth with nano-litre resolution for liquid flow rate, level or surface tension measurement}}},
  volume       = {{5-12}},
  year         = {{2002}},
}