Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"Michał GOŁĄBEK"

Image reconstruction in ultrasound transmission tomography using the Fermat’s Principle DOI:10.15199/48.2020.01.41

Czytaj za darmo! »

The construction of a physical model of an ultrasonic tomograph is highly problematic due to the complexity of the acoustic phenomena necessary for modeling in the case of a heterogeneous environment of propagation of acoustic waves in small limited spaces [1]. The radial propagation model commonly used in transmission tomography turns out to be sufficient for effective detection of disturbances in the interior of objects and is used in commercial solutions, for example for non-invasive examination of the state of trees. The lack of the correct physical model does not allow us to fully understand phenomena occurring during imaging with the help of acoustic waves. Problems such as [2-14] are used to solve optimization problems. In tomography, methods [15-25] are used to solve the inverse problem. This work is a collection of numerical experiments that use the Fermat principle, originally used in optics, to better understand the process of acoustic wave propagation during tomographic measurements using ultrasound [26-40] to create a more precise solver for problems with ultrasound tomography. Algorithm Classical approach to modeling the ultrasonic tomographical system is to approximate the behavior of the system by the model of straight rays of propagation between two ultrasonic sensors. There are many works confirming the effectiveness of such a solutions in the terms of reliable ability of imaging positions of inclusions along the domain of tomographical system. The effectiveness of that types of models can be also confirmed by practical analysis of a measurement data from tomographical device. As the example Figure 2 shows the sensitivity visualization of the tomographical system. Presented visualization is made for one pair of sensor and is created on the basis of real measurement data with one air inclusion with water background. One can see that higher sensitivity is concentrated approximately along the line between [...]

Ultrasound tomography measuring system for acquisition and analysis data DOI:10.15199/48.2019.03.26

Czytaj za darmo! »

The main purpose of this work is to design a system for data acquisition and data analysis. Control methods include issues related to the processing of data obtained from various sensors located in nodes. Monitoring takes place as part of data processing and parameters obtained and processed (Fig. 1). The device has been designed for tomographic measurements of the properties of processes occurring in reservoirs. Fig. 1 Principle of ultrasonic measurement using the transmission method Measurement technologies are still being built and improved. There is a clear tendency in the industry to implement more optimal related functions with an emphasis on active inspection and monitoring [24-26,18-22]. There are many optimization methods [1,8-15], but to solve the inverse problem in the ultrasound tomography can use [2- 7,16,17,23]. Measurement system One of the active probes sends an ultrasonic signal (the number of sent signal periods will depend on the type / size of the tested object, in the case of the container being tested, 4 periods were sufficient), the rest of the probes are in the listening mode. Active probes measure the time individually from the moment the signal is sent until it is picked up by individual transducers. We assume that this is the time in which ultrasounds overcome the distance between the probes. Fig.2 Signal waveforms in the measurement probe Fig.3. Measurement time of one measuring frame After receiving the signal by all sensors, one measuring frame is terminated, the signal from the next probe is transmitted, the remaining probes receive the signal again. The sequence repeats until each probe gives a signal and all times are collected. Figure 2 shows the signal waveform for one pair of transducers. The signal is fed into a rectangular signal fed to the ultrasound transducer in order 112 PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 95 NR 3/2019 to force transmission (probe). The obtained signa[...]

 Strona 1