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RISS 인기검색어
- 검색키워드
- 저자 : M. Farhat (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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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.
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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.
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Johnson Ryan M.,Young Michael,Guglielmi Gina N.,Farhat Hamad 대한뇌혈관외과학회 2021 Journal of Cerebrovascular and Endovascular Neuros Vol.23 No.2
Iatrogenic vessel perforation from endovascular intervention is a devastating complication that commonly is treated with vessel sacrifice. We present a unique case of an iatrogenic proximal basilar artery perforation after submaximal angioplasty in a 67-year-old male presenting with an acute basilar artery occlusion with underlying intracranial atherosclerotic disease. Telescoping flow-diverting stents were then deployed to reconstruct the vessel wall with resulting active hemorrhage resolution. Our case documents a successful deployment of flow-diverting stents with resolution of active hemorrhage after an iatrogenic basilar artery perforation.
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Estimation of Denominators- a New Approach for Calculating of Various Rates in Cancer Registries
Haroon, A.S.,Gupta, S.M.,Tyagi, B.B.,Farhat, J. Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.7
In this study, cancer incidence data were assessed to provide various rates of five year age groups for a given year, lying between two census years. The individual exponential growth rate method is most useful in both population-based and non-population cased cancer registries in India to estimate the population by five yearly age groups and also find the rates of crude rates, age standard rates and cumulative rates. This method has been shown to endure from bias and often results sacrificing the overall growth rate and correction factor must be needful in five year age group population to maintain it. A second method, the difference distribution method is also able to maintain the overall growth rate and overcome the bias in estimation of five yearly age group populations. From this point of view these methods serving a new technique for population estimation by five yearly age groups for inter census years.
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