Small-scale experiments are a good means of carrying out explosion and shock wave measurements. Commonly, the shock wave is tracked thanks to pressure sensors and sometimes with a high-speed camera. In the present study, these methods were used to analyze the interaction of a shock wave with an obstacle of simple geometry. The primary aim of the study was to demonstrate the need to correlate these different methods in order to analyze certain phenomena related to the three-dimensional interaction of a shock wave with an object. The correlation between the overpressure and the visualization made it possible to carry out a complex analysis. The visualization was carried out simultaneously on two planes, from the front and top views, thanks to the optical setup. Shock wave characteristics were taken at ground level downstream of the obstacle with pressure gauges. The correlation of the images obtained allows the identification of the waves on the profile and their contribution in intensity.
The aim of this study is to characterize the behaviour and propagation of a shock wave in an obstructed area. The recent literature demonstrates the attenuation of shock wave versus the obstacle shape and matrix arrangement. The paper will present an experimental work conducted at a small scale. The shock wave is created from the detonation of a hemispherical gaseous charge confined in a bubble on a surface. The obstruction zone is obtained by rigid vertical cylinders in an open area. Influences of distribution and areal density of the cylinders as function of the mass of explosive charge are investigated. The blast wave is characterized by using pressure sensors and a high-speed camera. Hence, the pressure sensors acquired overpressure and the arrival time. The propagation and reflexion, diffraction of shock wave, are analysed from the pictures produced during the visualization tests.
ICG (impedance cardiography) is in parallel to ECG (electrocardiography) an important indicator of the functioning of the heart and of the overall cardiovascular system. Adding the ICG to ECG measurement functionality into the wearable devices improves the quality of health monitoring, as the ICG reflects relevant hemodynamic parameters (informative time intervals, but also the stroke volume and cardiac output and their variability). The most challenging task of the ICG signal processing is to extract the key points B, C, X of the cardiac periodstart, peak-location, and value at this point and the end of the LVET (left ventricular ejection time) sub-period in the cardiac cycle. A novel block diagram and analog implementation of it has been proposed, analyzed, and discussed, with discussion of the benefits of the proposed solution. The proposed solution enables developing of relatively simple very power-efficient solutions, monitoring the ICG values of the person with smart and efficient data acquisition and processing.
The aim of this study was to characterize the interaction of a shock wave with a parallelepipedal obstacle. Shock wave properties were quantified downstream of sixty configurations with different obstacle dimensions. With the introduction of new parameters, these experimental measurements were used to write evolution laws for the arrival time and the maximum overpressure downstream of a parallelepipedal obstacle. The accuracy of these laws was satisfactory. Then, the maximum overpressure law was compared with experimental measures from the literature. Despite differences in the obstacle geometry or experimental setup, these experimental data are in good agreement with the maximum overpressure law.
This paper describes the study of an integrated system for the detection of the B-C-X characteristic points of impedance cardiography (ICG) signals, to evaluate the stroke volume of a patient. It compares a discrete-time digital approach and a continuous-time digital architecture, using a level-crossing Analog-to-Digital Conversion (LC-ADC). The results show that the measurement accuracy of the stroke volume, with a relative error between 9% and 13%, is sufficient for practical use and opens the opportunity for future fully integrated circuit solutions. This study also points out that, unlike ECG, the continuous-time digital approach does not bring any improvements for ICG-based systems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.