In an assault on a military fortress, the attacking side often attacks the fortress through the use of underground mining, so that the defensive side cannot be prepared. The existing monitoring methods make it difficult to monitor such underground excavation. One effective way to monitor for tunneling activity is to detect and identify seismic signals generated by underground excavation. However, the main problem facing the practical application of this technology is that many behaviors on the ground may generate seismic signals, and the monitoring system cannot identify whether a signal is generated by underground excavation or by someone walking on the ground, resulting in a high false alarm rate. To effectively identify underground excavation signals, we propose an approach for estimating speed based on a double point synchronization measurement. In our approach, we first formulate mathematical models of the velocities of underground and ground-level objects. Then, signals acquired by different seismic detectors are used to estimate the velocities of underground and ground-level objects. By analyzing the differences between velocities, signals due to human movement and underground excavation are effectively identified. Lastly, simulations and a field test are performed. It is found that the proposed approach can effectively distinguish between signals generated by a human moving at ground-level and underground excavation. Our approach can be helpful for reducing the false alarm rate of a monitoring system.
The paper aimed to analyze the dynamic response of a new type penetrating missile in rotary attacking warship. The dynamic response characteristics of the penetrator become more complex when attacking the ship target due to the special materials of the deck such as stiffeners. Therefore, different from attacking other targets, the article reveals the design rules of precession penetration ammunition and fuze. A physical model of the missile target is established to study the numerical simulation of the penetration process of rotating projectile into a stiffened target based on finite element analysis (FEA) software. We studied the dynamic response characteristics of different projectile positions, rotational speeds, and positions that act in precession penetration. As experimental results show, the residual velocity of the precession penetrator decreases with the distance between the projectile point and stiffener. When the projectile penetrates the second target plate, the acceleration is greater than that in the first layer. It is proved that the deflection angle of the shell body is affected by comprehensive factors. The rotational speed in the projectile has less contribution to precession penetration ammunition. In addition, the change of acceleration in the missile’s central section can be significantly perceived in the direction perpendicular to the penetration direction.
In this study, we propose effective monitoring equipment intended for monitoring the underground tunnel of illegal excavation (such as theft, jailbreak, and smuggling). It mainly detects the microseismic information produced by underground excavation in a short distance to detect the status of underground excavation. Based on the arrival time difference principle, the positioning mathematical models of the 5-1-1 layout method, 4-3 layout method, and 7-0-0 layout method are established, respectively. In the research process, the measurement and the placement error caused by the installation of a seismic detector are joined into the detectors. Simulation results show that the relative error and its average value are obtained when mining outside the monitoring area. The experiment results demonstrate that, first, the depth positioning error is positively affected by the number of seismic detectors. Then, the relative error of plane positioning can be reduced when the installation distance among detectors is increased. Finally, the main causes of location error include time measurement error, propagation velocity difference caused by terrain, and the performance of detector hardware. The array of a ground motion detector has a weak influence on it. These emerging trends will have profound impacts on application of an underground excavation system.
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.