Wyniki wyszukiwania - BazTech

1

Laser Ultrasonic Technique for Simultaneous Measurement of Thickness, Slope, and Wave Velocities for Slope Plate in the Thermoelastic Regime

Dung Nguyen Tien, Arai Yoshio

Advances in Science and Technology. Research Journal

|

2024

|

Vol. 18, no 5

EN

This study introduces a reliable method for simultaneously determining the thickness, slope, and ultrasonic velocities of slope plates using laser ultrasonic techniques without any damage in the thermoelastic regime. The method involves solving a system of equations to determine the arrival times of multiple signals displayed on a waveform. Numerical simulations indicate that the velocity of the skimming longitudinal wave remains constant when the Rayleigh wave does not overlap with its signal. Consequently, a prediction model for aluminum alloy has been established, enabling the estimation of the constant ratio between the velocities of skimming longitudinal and bulk longitudinal waves based on the skimming longitudinal velocity obtained by scanning the generating laser along the material's surface. This ratio, approximately 0.950, facilitates the combination of the skimming longitudinal wave with the reflected and mode-converted waves from the specimen's back surface to deduce the desired parameters. The method successfully determined the thickness, slope, and wave velocities of several specimens with slopes ranging from 0% to 1.96% and a maximum thickness of about 10 mm. Evaluating the influence of the size of the disk ultrasound source produced by the unfocused laser beam, we found that the radius of the disk source should be considered when calculating the arrival time of the skimming longitudinal wave. The root mean square deviation in measuring thickness, slope, longitudinal wave velocity, and shear wave velocity were approximately 0.100 mm, 0.10 %, 70 m/s, and 20 m/s, respectively. An assessment of the measured results, based on the root mean square deviation and uncertainty across all specimens, demonstrates the practical feasibility of the proposed method.

2

Simultaneous multi-site measurement system for the assessment of pulse wave delays

Sondej Tadeusz, Sieczkowski Krzysztof, Olszewski Robert, Dobrowolski Andrzej

Biocybernetics and Biomedical Engineering

|

2019

|

Vol. 39, no. 2

488--502

EN

A precise, multi-track system for the simultaneous, real-time measurement of electrocardiographic (ECG) and many photopletysmographic (PPG) signals is described. This system allows the calculation of pulse wave delay parameters such as pulse arrival time (PAT) and pulse transit time (PTT). The measurement system was built on a custom, real-time embedded system with multiple specific analogue-front-end devices. Signals were recorded on-line and data were processed off-line in the Matlab software. Testing of human subjects was carried out on a group of 16 volunteers. The system was capable of taking a measurement of one 24-bit ECG and eight 22-bit PPG tracks with high precision (input-referred noise 1.4 mV for ECG and about 20 pA for PPG). All signals are sampled simultaneously (phase shift between ECG and PPG is only 1.5 ms for 250 Hz frequency sampling). Significant differences in pulse wave delays were found for the 16 subjects studied (e.g. about 100 ms for PAT on a right toe, 40 ms for differential PAT on left-right toes and about 100 ms for PTT calculated for forehead-right toe pulse wave). The proposed system provides a simultaneous and continuous evaluation of pulse wave delays for the entire arterial bed. The proposed measurement methods are comfortable and can be used for a long time. Simultaneous measurements of pulse wave delays at various sites increase the reliability of measurement and create new possibilities for medical diagnosis.

3

Determination of kinetic parameters from simultaneously measured thermally stimulated conductivity and luminescence in diamond

Opanowicz A., Pietrucha P.

Scientific Bulletin. Physics / Lodz University of Technology

|

2002

|

Vol. 22

53-73

EN

Thermally stimulated conductivity (TSC) and luminescence (TSL) are described assuming conventional model of trapping and recombination in an insulator and the quasi-equilibrium approximation. Using these assumptions the method for determination of the relative density of inactive deep traps from the simultaneous TSC-TSL measurement is derived on the basis of the relation between the areas under TSC and TSL curves. The TSC and TSL in insulating diamond simultaneously measured by Chen are analysed with the method and the methods for determination of kinetic parameters known from literature. The electron trap depth, the frequency factor, the density of deep inactive traps, and the recombination and traping coefficients are determined.

PL

W pracy opisano termicznie stymulowane przewodnictwo (TSC) i luminescencję (TSL) za pomocą ogólnie przyjętego modelu pułapkowania i rekombinacji w izolatorze stosując przybliżenie kwazi-równowagi. Opierając się na tych założeniach zaproponowano metodę wyznaczania gęstości głębokich pułapek elektronowych z jednoczesnych pomiarów TSC i TSL wykorzystując relację między powierzchniami pod krzywymi TSC i TSL. Tę metodę oraz metody wyznaczania parametrów kinetycznych znane z literatury zastosowano do pomiarów TSC i TSL wykonanych na diamencie przez Chena. Zostały wyznaczone parametry: głębokość pułapki, parametr częstotliwościowy, gęstość głębokich pułapek, współczynniki rekombinacji i pułapkowania, rząd kinetyki oraz prawdopodobieństwo rekombinacji.