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1
Content available Computer model of acoustic link in a pipe with a flowing gas medium. Part I: Perturbation of ultrasonic transducer directivity pattern
100%
Gudra T. , Opieliński K.
Hydroacoustics
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1997
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tom Vol. 1
299--302
EN
The paper presents an aeroacoustic range equation which makes it possible to elaborate a computer model of ultrasonic link in air for static conditions. The model was made in form of a computer program called KML. Extending the static model, a simulation of uItrasonic wave propagation in a pipeline with flowing air for different profiles of laminar and turbulent flow and different link parameters was performed. The simulation made it possible to work out a computer model of an acoustic link in flowing gas. The model as a computer program can be used to calculate disturbance of ultrasonic beam rays shape and directivity pattem perturbation. Directivity pattem of ultrasonic transmitting transducer, deformed by flowing medium, becomes non-axial symmetric. As a result of the flow, ultrasonic beam rays are curvilinear and the source directivity pattern depends on rectilinearly measured distance.
2
Content available Research and Modeling of Mechanical Crosstalk in Linear Arrays of Ultrasonic Transducers
100%
Celmer M. , Opieliński K.
Archives of Acoustics
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2016
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tom Vol. 41, No. 3
599--612
EN
Linear arrays of ultrasonic transducers are commonly used as ultrasonic probes in medical diagnostics for imaging the interior of a human body in vivo. The crosstalk phenomenon occurs during the operation of transducers in which electrical voltages and mechanical vibrations are transmitted to adjacent components. As a result of such additional excitation of the transducers in the array, the directivity characteristics of the aperture used changes, and consequently there is interference with proper operation of a given array and the emergence of distortions in the obtained ultrasound image that reduce its quality. This paper studies the manner of propagation of mechanical crosstalk in the designed model of a linear array of ultrasonic transducers on the basis of unwanted signals, which appeared on elementary piezoelectric transducers when power is supplied to the selected transducer in the array. The universal model of linear array of ultrasonic transducers, which has been developed, allowed the simulation of mechanical crosstalk, taking into account the cross-coupling phenomenon in all of its structure with the use of finite elements method (FEM) implemented in COMSOL Multiphysics software. The analysis of crosstalk signals showed that they consist of aggregated pulses propagating with different speeds and frequencies. This signifies the formation of different vibration modes transmitted simultaneously via different paths. The paper is an original approach which enables to identify different vibration modes and estimate their participation in the crosstalk signal and their ways of propagation. Conclusions from the research allow predicting specific design changes which are significant due to the minimization of mechanical crosstalk in linear arrays of ultrasonic transducers.
3
Investigation of Biological Structures and Their Phantoms Using Ultrasound Transmission Tomography
100%
Gudra T. , Opieliński K.
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2001
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tom Vol. 22
85-94
EN
The paper contains introductory of investigation of different biological structures and their phantoms carried aut by using the UTT method. The otained images of internal structure cross-sections were compared with images obtained by means of classical ultrasonic reflection methods. The results of tis analysis allow us to conclude that investigations using UTTenable obtaning more information aboute the internal structure of the investigated object than ultrasonic investigations consisting in visualising differences of acoustic impedances. In addition, UTT enables both qualitative and quantitive measurement.
4
Ultrasound Transmission Tomography Image Distortions Caused by the Run-Time Measurement Inacurracy
100%
Opieliński K. , Gudra T.
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1999
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tom Vol. 20
169-179
5
Content available Computer model of acoustic link in a pipe with a flowing gas medium. Part II: Accuracy improvement ot medium flow velocity determination
100%
Gudra T. , Opieliński K.
Hydroacoustics
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1997
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tom Vol. 1
303--306
EN
While constructing medium flow velocity meters with the use of the ultrasonic method, it is assumed, that the deviation of the ultrasonic beam caused by medium flow, is insignificant. The assumption seems to be correct, because the average flow velocity is usually much smaller than the ultrasonic wave velocity in a medium. Basing on the assumption, we can use a known expression, which makes it possible to calculate an average medium flow velocity through run-time measurement from the transmitter to the receiver and in an opposite direction. In the paper, it is shown, that the average flow velocity determined in this way, using the computer model of acoustic link in a pipe with a flowing gas medium, is measured with a significant error. This error depends on the flow pipe diameter, the transducer diameters and the means of placing the transducers in the pipe. Properly modifying the expression for ultrasonic run-time through flowing gas medium and taking into account the means of transducer placing in the pipe, we can eliminate the error related to the measurement geometry and we can find an optimum ultrasonic wave propagation angle.
6
Badania aglomeracji dźwiękowej pęcherzyków gazu w cieczy
80%
Czyż H. , Gudra T. , Opieliński K.
Prace Naukowe Instytutu Telekomunikacji i Akustyki Politechniki Wrocławskiej. Konferencje
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2001
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tom Vol. 83, nr 27
251-256
EN
This paper presents the results of an experiment, which is a continuation of our research series about the sound agglomeration of gas bubbles in the liquid. An idea of the experimental system has been presented so far. The process of gathering the gas bubbles around the equilibrium positions in the ultrasonic standing wave (the loops of the ultrasonic standing wave) was observed. The concentration of the gas bubbles increases around such points and decreases in the regions between the loops and the nodes of the ultrasonic standing wave. The time required to obtain an equilibrium distribution of the gas bubbles near the stable equilibrium points has been measured. The result of the measurement indicates that it's the value of the same order of magnitude as the sound agglomeration times calculated theoretically. The experimental results show that the speed of process of gathering the gas bubbles depends on; the parameters of acoustic field and gas bubbles size. The theoretical results are in good agreement with the experimental data. The measuring method and the method of its analysis were described in the paper.
7
Wstępne wyniki badań fantomów i struktur biologicznych metodą ultradźwiękowej tomografii transmisyjnej
80%
Gudra T. , Opieliński K. , Jeleń M.
Prace Naukowe Instytutu Telekomunikacji i Akustyki Politechniki Wrocławskiej. Konferencje
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2001
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tom Vol. 83, nr 27
329-336
EN
The paper contains introductory results of investigation of different biological structures and their phantoms carded out by using the UTT method. The obtained images of internal structure cross-sections were compared with images obtained by means of classical ultrasonic reflection methods. The results of this analysis allow us to conclude that investigations using UTT enable obtaining more information about the internal structure of the investigated object than ultrasonic investigations consisting in visualising differences of acoustic impedances. In addition, UTT enables both qualitative and quantitative measurement. The results of microscopic histopathological examination of selected fragments of structures have corroborated the occurrence of pathological changes visible in tomographic images in the form of areas of different sound velocity values.
8
Analysis f Possibilities of Biological Structure Phantom Building for Purposes of Ultrasound Transmission Tomography
80%
Gudra T. , Opieliński K. , Zarzycki-Reich A.
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2000
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tom Vol. 21
69-78
9
Content available Ultrasonic Method for Monitoring Environmental Risks Associated with Precipitation
80%
Gudra T. , Banasiak D. , Herman K. , Opieliński K.
Archives of Acoustics
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2013
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tom Vol. 38, No. 1
125--135
EN
This paper presents a solution that utilises ultrasonic technology to allow monitoring snow layer thickness or water level based on measurement from air. It describes the principle of operation of a measurement device using three methods of compensating for changing external factors affecting appliance’s precision. Block diagram of the device is also provided. In order to verify the proposed solutions, the research team tested the device in laboratory and operating conditions. The results obtained this way make it possible to select a configuration of device operation depending on the required measurement precision and limitations associated with installing the system for actual operation.
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