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In-vivo Mapping of Human Skin Anisotropy Using Multi-directional Ultrasonic Probe
Tokar, Daniel ; Hradilová, Jana ; Převorovský, Zdeněk
In this paper, investigation of anisotropic behavior of forearm and back skin tissue is presented. Knowledge in this research field is of great interest mainly in dermatology, plastic surgery and regenerative therapies. Anisotropy characteristics of the skin are determined by ultrasonic wave propagation velocity using special multi-directional flexible ultrasonic probe, which enables local investigation of skin anisotropy in vivo. Assessing data, obtained from local measurements of human back, enables visualization of anisotropy map of the back skin tissue. Findings in current state of human skin anisotropy using the multi-directional ultrasonic probe provide an easy method to evaluate the local anisotropy of inter-individual skin tissue.
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Multilevel Analysis of Continuous Acoustic Emission Records
Chlada, Milan ; Převorovský, Zdeněk
The latest acoustic emission (AE) systems provide continuous recording of high-frequency signals registered during longtime monitoring of various processes in materials. Recorded data represent extremely large amount of information to analyze, however, it reflects the health of the structure. Therefore, in the last years the attention is paid to the diagnostic method of continuous AE also as a part of Structural Health Monitoring (SHM) systems. For example it can disclose the early damage phases (cracks) or certain imperfections in rotating gearboxes, the leakage of liquids from pressure vessels and many other material defects. This method requires new signal processing and analysis approaches, which are different from the burst AE. The paper deals with the analysis of continuous AE, recorded during the test of renovated gearbox at different flight modes. As an alternative to classical spectrogram, so-called multilevel countogram based on the signal wavelet decomposition is proposed and discussed.
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Utilising of position profiles for location of continuous acoustic emission sources
Chlada, Milan ; Převorovský, Zdeněk ; Sladký, Petr
By detecting of continuous acoustic emission (AE) sources it is possible to precede potential emergencies as e.g. leaks of the media from pressure vessels, pipelines etc. Present location methods using attenuation characteristics of elastic waves have certain application restrictions. These disadvantages can be solved by introduction of so called position profiles. In this way, the attenuation dependencies of AE wave amplitude and the distance from emission source are converted to the dependencies between position profiles and Root Mean Square (RMS) of captured voltage signals of continuous AE. Proper location of real AE source is done by comparing of position profiles corresponding to model virtual sources with the position profile computed for a real source, while it is possible to apply optimization comparative methods or artificial neural networks. The paper presents detailed derivation and description of the new method, which is a subject of patent pending.
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Location of acoustic emission sources in geometrically sparce structures
Chlada, Milan ; Převorovský, Zdeněk
In recent years, the importance of modern philosophy of Structural Health Monitoring (SHM) is increasing. SHM systems are gradually integrated into, e.g., aircraft or bridge structures and also become newly a part of certain modern buildings, where the break down would cause significant material or human losses. One of the effective prewarning methods is the detection of acoustic emission (AE). The paper yields the discussion about the utilization of artificial neural networks in comparison with the segment location based on the chronology of signal arrivals to selected groups of AE sensors for “geometrically sparse” structures. Both methods and their results are demonstrated in case of experiment with gradual loading of a part of a roof construction until the final breakdown.
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