The identification of weak vital signs has always been one of the difficulties in the field of life detection. In this paper, a novel vital sign detection and extraction method with high efficiency, high precision, high sensitivity and high signal-to-noise ratio is proposed. Based on the NVA6100 pulse radar system, the radar matrix which contains several radar pulse detection signals is received. According to the characteristics of vital signs and radar matrices, the Singular Value Decomposition (SVD) is adopted to perform signal denoising and decomposition after preprocessing, and the temporal and spatial eigenvectors of each principal component are obtained. Through the energy proportion screening, the Wavelet Transform decomposition and linear trend suppression, relatively pure vital signs in each principal component, are obtained. The human location is detected by the Energy Entropy of spatial eigenvectors, and the respiratory signal and heartbeat signal are restored through a Butterworth Filter and an MTI harmonic canceller. Finally, through an analysis of the performance of the algorithm, it is proved to have the properties of efficiency and accuracy.

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A water jet with an air ring protective layer is a promising rock-breaking and cutting rate improvement method in submerged environment, such as oil-gas drilling. The jet flow field characteristic determines the jet impinge performance and is affected by nozzle structure parameters. In this study, the water jet flow with air ring under submerged environment was numerically simulated. The jet flow field structure with air ring was obtained by analyzing the distributions of jet velocity and air content at different cross sections. The effects of several critical nozzle structure parameters on jet isokinetic core length and axial velocity were investigated by adopting the orthogonal design method. The results show that the jet flow field structure with air ring in radial direction includes a high-speed water jet zone, air ring protective layer, and air-water mixed zone, having the advantages of concentrated energy in axis region, long core section length, and lowvelocity attenuation. The influence degrees of nozzle structure parameters on jet core section length and axial velocity at X = 0.3 m are: length-diameter ratio > outlet diameter > conic angle > air nozzle diameter > water-air nozzle spacing and outlet diameter > length-diameter ratio > conic angle > water-air nozzle spacing > air nozzle diameter, respectively. The jet core section length and axial velocity both increase exponentially with the increasing outlet diameter, both first increase rapidly and then slowly decreases with the increase of conic angle and water-air nozzle spacing. There is the optimal conic angle of 15°and appropriate water-air nozzle spacing of 3-5 mm. With the increase of length-diameter ratio, they both first decrease rapidly and then slow down, indicating that conical nozzle is more suitable for water jet with air ring. And 0.9-1.2 mm is proper for the air nozzle diameter.

Previously conducted studies have established that as a disaster-bearing body, a coal mine is vulnerable to flood disasters and their consequent impacts. The purpose of this study is to put forward a quantitative evaluation method of the risk of coal mine flood disaster. Based on the scientific theory of disaster risk, a risk assessment model and index system for coal mine flood disaster was constructed, and a risk assessment method was proposed based on the projection pursuit and fuzzy cluster analysis. The results show that the risk of coal mine flood disaster was mainly determined by the hazard of disaster-causing factors, the stability of the disaster-prone environment, and the vulnerability of disaster-bearing bodies. Further research shows that the maximum daily rainfall had the greatest impact the risk of coal mine flood disaster. Therefore, the early warning mechanism should be established between the coal mine and the meteorological department to improve the fortification level. A risk assessment method of coal mine flood disaster was proposed in this study, which is of great significance for energy sustainability.