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The detection of cavitation in hydraulic machines by use of ultrasonic signal analysis
Gruber, P.,Farhat, M.,Odermatt, P.,Etterlin, M.,Lerch, T.,Frei, M. Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.4
This presentation describes an experimental approach for the detection of cavitation in hydraulic machines by use of ultrasonic signal analysis. Instead of using the high frequency pulses (typically 1MHz) only for transit time measurement different other signal characteristics are extracted from the individual signals and its correlation function with reference signals in order to gain knowledge of the water conditions. As the pulse repetition rate is high (typically 100Hz), statistical parameters can be extracted of the signals. The idea is to find patterns in the parameters by a classifier that can distinguish between the different water states. This classification scheme has been applied to different cavitation sections: a sphere in a water flow in circular tube at the HSLU in Lucerne, a NACA profile in a cavitation tunnel and two Francis model test turbines all at LMH in Lausanne. From the signal raw data several statistical parameters in the time and frequency domain as well as from the correlation function with reference signals have been determined. As classifiers two methods were used: neural feed forward networks and decision trees. For both classification methods realizations with lowest complexity as possible are of special interest. It is shown that two to three signal characteristics, two from the signal itself and one from the correlation function are in many cases sufficient for the detection capability. The final goal is to combine these results with operating point, vibration, acoustic emission and dynamic pressure information such that a distinction between dangerous and not dangerous cavitation is possible.
GRUBER, HARALD 한국국제경제학회 1993 International Economic Journal Vol.7 No.3
The model investigates the possible relationships between market structure, product innovation and trade policy. It is shown that the speed of product innovation is most rapid with a more fragmented market structure and in a free trade regime. Under free trade the origin of the leader in product innovation is indeterminate. If a country unilaterally restricts access to its home market without incurring retaliation, then it increases profits compared to free trade and it ensures also leadership in product innovation. [F13]
Novel Bearingless Segment Motor Design with Axial Magnetized Rotor Magnets
W. Gruber,J. Passenbrunner,G. Bramerdorfer,W. Amrhein 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
Bearingless motors and active magnetic bearings work completely contact- and wearless. With these properties, hermetically sealed and lubricant free rotating systems for various applications can be designed. It is possible to stabilize three degrees of freedom by reluctance forces, when a permanent magnet excited rotor disc is used. This constructional design is called bearingless slice motor. The bearingless segment motor is a subtype of the slice motor, featuring a segmented stator composition. This paper comprises the design process of a novel bearingless segment motor with axial magnetized rotor magnets, five stator elements and concentrated windings. Finite-element-simulations are applied to maximize the bearing forces and the motor torque per ampere and minimize the reluctance forces. However, the mathematical model of the system is nonlinear, so an appropriate nonlinear control scheme has to be applied to put the system into operation. The introduction of a prototype together with measurements completes the paper.
The detection of cavitation in hydraulic machines by use of ultrasonic signal analysis
P. Gruber,M. Farhat,P. Odermatt,M. Etterlin,T. Lerch,M. Frei 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.4
This presentation describes an experimental approach for the detection of cavitation in hydraulic machines by use of ultrasonic signal analysis. Instead of using the high frequency pulses (typically 1MHz) only for transit time measurement different other signal characteristics are extracted from the individual signals and its correlation function with reference signals in order to gain knowledge of the water conditions. As the pulse repetition rate is high (typically 100Hz), statistical parameters can be extracted of the signals. The idea is to find patterns in the parameters by a classifier that can distinguish between the different water states. This classification scheme has been applied to different cavitation sections: a sphere in a water flow in circular tube at the HSLU in Lucerne, a NACA profile in a cavitation tunnel and two Francis model test turbines all at LMH in Lausanne. From the signal raw data several statistical parameters in the time and frequency domain as well as from the correlation function with reference signals have been determined. As classifiers two methods were used: neural feed forward networks and decision trees. For both classification methods realizations with lowest complexity as possible are of special interest. It is shown that two to three signal characteristics, two from the signal itself and one from the correlation function are in many cases sufficient for the detection capability. The final goal is to combine these results with operating point, vibration, acoustic emission and dynamic pressure information such that a distinction between dangerous and not dangerous cavitation is possible.
Tatjana Gruber-Rouh,Clara Lee,Jan Bolck,Nagy N.N. Naguib,Boris Schulz,Katrin Eichler,Rene Aschenbach,,Julian L. Wichmann,Thomas. J. Vogl,Stephan Zangos 대한영상의학회 2015 Korean Journal of Radiology Vol.16 No.4
To investigate the accuracy, efficiency and radiation dose of a novel laser navigation system (LNS) compared to those of free-handed punctures on computed tomography (CT). Sixty punctures were performed using a phantom body to compare accuracy, timely effort, and radiation dose of the conventional free-handed procedure to those of the LNS-guided method. An additional 20 LNS-guided interventions were performed on another phantom to confirm accuracy. Ten patients subsequently underwent LNS-guided punctures. The phantom 1-LNS group showed a target point accuracy of 4.0 ± 2.7 mm (freehand, 6.3 ± 3.6 mm; p = 0.008), entrance point accuracy of 0.8 ± 0.6 mm (freehand, 6.1 ± 4.7 mm), needle angulation accuracy of 1.3 ± 0.9° (freehand, 3.4 ± 3.1°; p < 0.001), intervention time of 7.03 ± 5.18 minutes (freehand, 8.38 ± 4.09 minutes; p = 0.006), and 4.2 ± 3.6 CT images (freehand, 7.9 ± 5.1; p < 0.001). These results show significant improvement in 60 punctures compared to freehand. The phantom 2-LNS group showed a target point accuracy of 3.6 ± 2.5 mm, entrance point accuracy of 1.4 ± 2.0 mm, needle angulation accuracy of 1.0 ± 1.2°, intervention time of 1.44 ± 0.22 minutes, and 3.4 ± 1.7 CT images. The LNS group achieved target point accuracy of 5.0 ± 1.2 mm, entrance point accuracy of 2.0 ± 1.5 mm, needle angulation accuracy of 1.5 ± 0.3°, intervention time of 12.08 ± 3.07 minutes, and used 5.7 ± 1.6 CT-images for the first experience with patients. Laser navigation system improved accuracy, duration of intervention, and radiation dose of CT-guided interventions.