@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}},
}

@inproceedings{15386,
  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}},
}

@article{13889,
  author       = {{Puttmer, A. and Hauptmann, P. and Henning, Bernd}},
  issn         = {{0885-3010}},
  journal      = {{IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control}},
  pages        = {{85--92}},
  title        = {{{Ultrasonic density sensor for liquids}}},
  doi          = {{10.1109/58.818751}},
  year         = {{2002}},
}

@article{13890,
  author       = {{Püttmer, A and Hoppe, N and Henning, Bernd and Hauptmann, P}},
  issn         = {{0924-4247}},
  journal      = {{Sensors and Actuators A: Physical}},
  pages        = {{122--126}},
  title        = {{{Ultrasonic density sensor - analysis of errors due to thin layers of deposits on the sensor surface}}},
  doi          = {{10.1016/s0924-4247(98)00365-3}},
  year         = {{2002}},
}

@article{13812,
  author       = {{Püttmer, A. and Lucklum, R. and Henning, Bernd and Hauptmann, P.}},
  issn         = {{0924-4247}},
  journal      = {{Sensors and Actuators A: Physical}},
  pages        = {{8--12}},
  title        = {{{Improved ultrasonic density sensor with reduced diffraction influence}}},
  doi          = {{10.1016/s0924-4247(97)01720-2}},
  year         = {{2002}},
}

@inproceedings{15387,
  abstract     = {{In diesem Beitrag werden Messungen und Auswertungen der Ultraschallgeschwindigkeitsmessung zur Überwachung von Hefekultivierungen vorgestellt. Die Ultraschallgeschwindigkeit ist abhängig von Biomasse-, Glukose- und Ethanolkonzentration, aber auch von anderen Bioprozessvariablen. Um den Einfluss von Blasen auf das Signal zu reduzieren, wurde der Ultraschallsensor in einem Bypass-System eingesetzt. Es wurden Messungen sowohl im Flow- als auch Stop-Flow-Betrieb durchgeführt. Um die richtigen Informationen aus diesem unspezifischen Signal zu erhalten, wurde ein multilineares Regressionsmodell berechnet, wobei die Biomasse-, Glukose- und Ethanolkonzentration als unabhängige Variablen dienten. Ein Beispiel der Ergebnisse ist in Abbildung eins gezeigt. Es sind die Biomasse-, Glukose- und Ethanolkonzentration während einer Saccharomyces cerevisiae Kultivierung dargestellt. Die Parameter des multilinearen Regressionsmodells wurden durch Verwendung der Daten aus der dargestellten Kultivierung identifiziert. Wird dieses Modell zur Auswertung auf die Signale anderer Prozesse übertragen, ist das Ergebnis ähnlich, jedoch vergrößert sich der Fehler der Schätzung. Die Ergebnisse sowie Erfahrungen werden ausführlich in dem Beitrag diskutiert.}},
  author       = {{Cha, Y. L. and Hitzmann, Bernd and Bellgardt, Karl-Heinz and Daur, Peter-Christoph and Henning, Bernd}},
  location     = {{Leipzig}},
  pages        = {{226}},
  title        = {{{Ultraschallgeschwindigkeitsmessung zum Bioprozessmonitoring}}},
  year         = {{2001}},
}

@inproceedings{15388,
  abstract     = {{Nowadays the use of ultrasonic sensors for process control for flow, level or concentration measurement is wide spread. In this application there are high demands for a defined and stable quality of the properties of such ultrasonic sensors. For the detailed investigation and characterization of ultrasonic sensor properties an efficient PC-controlled measuring system has been developed at ifak. In this report this new high performance approach will be presented to make the vibrating ultrasonic sensor surface and also the sound field in front of acoustic sensors in liquids visible.}},
  author       = {{Henning, Bernd and Prange, Stefan and Dierks, Karsten and Daur, Peter-Christoph}},
  location     = {{Nürnberg}},
  title        = {{{Quality inspection and characterisation of ultrasonic sensor properties using a PC-controlled scanning measuring system}}},
  volume       = {{A8.2}},
  year         = {{2001}},
}

@article{15389,
  abstract     = {{Recently there has been increased demand for chemicaJ sensors measuring in-line the concentration of selected substances in complex liquids in order to guarantee a high product quality in the process industry. At present there is a great interest in acoustic sensor systems for concentration measurements. This article presents a new ultrasonic sensor system consisting of a miniaturized multi-sensor arrangement for the comprehensive acoustic characterization of liquid mixtures. The sensor system measures sound velocity, impedance coefficient, attenuation coefficient an9 temperature.}},
  author       = {{Henning, Bernd and Daur, Peter-Christoph and Prange, Stefan and Dierks, Karsten and Hauptmann, Peter}},
  journal      = {{Ultrasonics}},
  pages        = {{799--803}},
  title        = {{{In-line concentration measurement in complex liquids using ultrasonic sensors}}},
  doi          = {{10.1016/s0041-624x(99)00190-0}},
  year         = {{2000}},
}

@misc{15390,
  author       = {{Henning, Bernd and Daur, Peter-Christoph and Prange, Stefan and Dierks, Karsten}},
  pages        = {{165--172}},
  title        = {{{In-Line-Flüssigkeitsanalysator für verfahrenstechnische Prozesse}}},
  year         = {{1998}},
}