In multi-extended target tracking, each target may generate more than one observation. The traditional probability hypothesis density (PHD)-based methods are no longer effective in such scenarios. Recently, the Gaussian mixture PHD approach for the extended target tracking (ET-GM-PHD) has been presented to solve such a problem. The tracking performance of this approach has been restricted by the following disadvantages. First, it only focuses on the linear models. When targets are moving with nonlinear models, it may lead to great tracking errors. Second, the birth intensities are commonly assumed as a prior. In practice, these intensities are always unknown. In order to improve the tracking performance of the traditional ET-GM-PHD approach, a novel extended target tracking approach, namely the ET-cubature information GM-PHD (ET-CIGM-PHD) approach, has been proposed in this paper. To be more specific, we, first, utilize the cubature information filter (CIF) and gating methods to predict and update the Gaussian mixture components of the ET-GM-PHD approach. In the merit of high estimating accuracy of the CIF method, the tracking accuracy of the traditional ET-GM-PHD approach can be significantly improved. Due to the gating method, only part of cells can be used to construct the observation set in the update stage. Thus, the computational load of our approach can be significantly reduced. Then, we propose an adaptive initiating method for the birth intensity initiating. In our method, we utilize the estimated target set to select the most possible partition. Then, we remove cells associated with the estimated targets from the selected partition. The left cells are used to initiate the birth intensity. With the help of the above implementations, the birth intensity can be adaptively initiated. Using such a method, our approach can solve the cases that the prior information of birth intensity is rather little. The simulation results demonstrate the effectiveness of our approach.

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 missiles 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.

The humanitarian damage caused by the unexploded submunitions is one of the hot issues of concern to the international community at present. A portion of the submunition that did not explode was caused by a break at the connection between the ribbon riveting and the fuze. According to the physical structure of the submunition and the trajectory into which it was ejected, we analyzed the forces of the submunition in flight, deduced the related mathematical models, and clarify the key elements of the mechanics. In this paper, the commercial simulation software was used to calculate the mechanical properties of the ribbon. And the variation regularity between drop velocity and straightening force of ribbon are revealed. And the response characteristics of different material ribbon with different sizes of riveting holes and riveting joints under tensile action were simulated. The simulation results show that, in the trajectory environment with 30 m/s~55 m/s typical stream speed, the tensile force of the ribbon is less than 300 N, and the application concentration of the connecting parts of the riveting joint and the ribbon will not cause the failure of the kevlar ribbon, but it will cause the failure of the nylon ribbon. In order to verify the variation of the tension of kevlar ribbons in different trajectory environments, we designed the experimental scheme of tension test of the ribbon straightening section of submunition and conducted experiments. Experimental results and numerical simulation results revealed the same law. This paper provides effective technical support for solving the problem of unexploded submunitions.