Wyniki 1-6 spośród 6 dla zapytania: authorDesc:"MICHAŁ MAJ"


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Podjęto próbę wyznaczenia energii zmagazynowanej na podstawie zależności naprężenie-odkształcenie. Przeprowadzona analiza teoretyczna pokazała, że w ten sposób można wyznaczyć jedynie dolną granicę energii zmagazynowanej. Na pod-stawie uproszczonego modelu materiału polikrystalicznego, podjęto próbę identyfikacji składników energii zmagazynowa-nej. Wykazano, że dolną granicę tej energii można trak[...]


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The subject of the present paper is decomposition of energy storage rate into terms related to different mode of deformation. The stored energy is the change in internal energy due to plastic deformation determined after specimen unloading. Hence, this energy describes the state of the cold-worked material. Whereas, the ratio of the stored energy increment to the appropriate increment of plastic work is the measure of energy conversion process. This ratio is called the energy storage rate. Experimental results show that the energy storage rate is dependent on plastic strain. This dependence is influenced by different microscopic deformation mechanisms. It has been shown that the energy storage rate can be presented as a sum of particular components. Each of them is related to the sep[...]


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Pulsed IR thermography is a non-destructive method that allows detection of subsurface defects in material. In this method the surface of the tested specimen is stimulated by heat pulse and its self-cooling process is analyzed. The temperature decrease rate is different for surface over defect with comparison to that over the sound material. It is caused by difference between values of heat diffusivity of defected zone and sound one. The purpose of this work is to determine the size and depth of the defects in austenitic steel on the basis of thermal contrast analysis. Because the thermal contrast is dependent on both these parameters, two independent experimental methods of defect size and depth determination were proposed. Keywords: pulsed thermography, thermal contrast, defect cha[...]

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

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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

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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[...]

Object detection using radio imaging tomography and tomographic sensors DOI:10.15199/48.2020.01.40

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The goal of the project and articles is to present a comprehensive device (device system) capable of measuring the strength of the received signal for the needs of a radio tomography and being able to act as a "Beacon" device. One of the main tasks of the system is the exchange of information between receivers and transmitters regarding the strength of the radio signal. After polling all devices, a measurement matrix will be created and the image reconstruction will be performed on its basis. The second main task of the system is to provide localization services using small radio transmitters called beacons [1-5]. There are many methods to solve optimization problems and being elements of a specific system [6-16]. In the tomography, deterministic methods and machine learning [17-36] are used to solve the inverse problem. The development of electronics and computing methods, the IoT and the fall in prices of hardware equipment, has created favorable conditions for the development and expansion of existing intelligent building systems. At present, the potential of available technologies is not fully exploited and is usually limited to the ability to control devices using a tablet or smartphone. Technologies related to the accumulation and processing of large amounts of data and computational intelligence are not commonly used in building intelligent systems. The increasing availability of all types of sensors, falling electronic component prices, the growing popularity of Internet technology, and the potential of large data volumes generated by the building's use process, is a developing area that will be heavily exploited in the coming years. The proposed system enables one to adjust the beacon position using data from several receivers using tomographic techniques. Real Time Locating Systems is one of the most dynamically developing branches of ICT. RLTS systems can be divided into systems operating in open spaces and wo[...]

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