Most studies assessing the safety of hot bridge wire EEDs employ temperature sensors that directly use the measurements of the temperature measurement device without analyzing the accuracy of the temperature measurement. This study establishes the response function of the exposed bridge and exposed bridge temperature rise system of hot bridge wire EEDs through the Rosenthal’s temperature rise equation and Laplace transformation as well as experimental tests, and through the response function, the response law and numerical characteristics of the two are compared and analyzed under four typical excitations. Under steady current injection and continuous-wave radiation, both exposed bridge and exposed bridge temperature measurement systems can reach thermal equilibrium, and the equilibrium temperature of both are the same. However, under pulse excitation, the temperature rise measurement value is significantly different from the actual value due to the large difference in response time of the exposed bridge (1 ms) and the exposed bridge temperature measurement device (0.82 s). Studies have shown that under steady current injection and continuous-wave radiation, temperature rise measurements can be directly applied to the safety assessment of hot bridge wire EEDs, while under pulsed conditions, temperature rise measurements cannot be directly applied.

When typical radar equipment is subjected to single-frequency electromagnetic radiation, the radar display interface forms a pseudo-signal, resulting in the misjudgment of real targets. Based on the working principle of stepped-frequency radar ranging, the effect mechanism of radar equipment pseudo-signal interference is revealed. Taking a Ku band stepped-frequency ranging radar as the test object, the pseudo-signal interference effect test of single-frequency electromagnetic radiation is carried out in this study. The pseudo-signal level value of 6 dBmV is selected as the sensitive criterion of the pseudo-signal interference effect. Through experiments, the variation curves of the pseudo-signal level values of the sensitive frequency bands and the typical frequency points inside and outside the band with the field strength of the single-frequency interference are obtained. Based on the nonlinear distortion analysis of the receiving circuit, the variation laws of the pseudo-signal level values inside and outside the band are explained, respectively. The experimental results show that there are at least seven pseudo-signal interference-sensitive bands in the tested radar, and the first pseudo-signal strength is only related to the interference signal strength. The essence of the second type of pseudo-signal interference is intermodulation interference, and the pseudo-signal level is related to the interference signal and the useful signal strength.

Hot bridge wire electro explosive device (EED) is widely used as a starting element in aerospace and other fields, its thermal ignition process and safety testing technology have always been the focus of research. In this paper, we constructe the temperature rise model of the hot bridge wire EED by using the law of conservation of energy, then the temperature response of the bridge wire and the reagent is obtained. According to the theoretical and numerical analysis, the sensitive criterion of the hot bridge wire EED is given, and the simulation process of the critical ignition current is designed, based on this process, the law of the influence of bridge wire and reagent parameters on the ignition of hot bridge wire EED was studied. The research results show that the first derivative of the reagent temperature with respect to the radial distance is greater than zero as a sensitive criterion for the ignition of the hot bridge wire EED with high accuracy, and compared with traditional numerical methods, the proposed process makes the acquisition of the critical ignition current more precise and programmed due to the use of sensitive criteria. In addition it is more significant that the critical ignition current increases first squarely as the square root of the bridge wire radius, and then linearly; the square of the critical ignition current increases linearly with the activation energy of the reagent; the rapid exponential decay of the critical ignition current with increasing reagent combustion heat, and the existence of asymptotic values. In engineering use, it is possible to conveniently design the ignition characteristics of the hot bridge wire EED by changing the radius of the bridge wire. This study serves as the foundational work for the safety testing of hot bridge wire EED and can provide theoretical guidance for the safety testing, actual production and use of hot bridge wire EED.

In order to master the position variation rule of radar false alarm signal under continuous wave (CW) electromagnetic interference and reveal the mechanism of CW on radar, taking a certain type of stepping frequency radar as the research object, theoretical analysis of the imaging mechanism of radar CW electromagnetic interference false alarm signals from the perspective of time-frequency decoupling and receiver signal processing. Secondly, electromagnetic interference injection method is used to test the single-frequency and dual-frequency electromagnetic interference effect of the tested equipment. The results show that under the single frequency CW electromagnetic interference, the sensitive bandwidth of false alarm signal is about ±75 MHz, and the position of false alarm signal irregularity changes. Under the in-band dual-frequency CW electromagnetic interference, the position of non-intermodulation false alarm signal is similar to that of single frequency. However, the distance difference of two non-intermodulation false alarm signals is regular. In addition, the positions of the second-order intermodulation false alarm signals of the tested radar are also regular, and its position changes with the change of the second-order intermodulation frequency difference.

This study aims to investigate the hybrid effects of carbon nanotubes (CNTs) and steel fiber (SF) on dynamic mechanical behavior of ultra-high performance concrete (UHPC) under the high-speed dynamic loading effects. The functionalized CNTs content varied from 0.0% to 0.20%, and SF volume content was added from 0.5% to 2.0%. The UHPC specimens were tested at strain rates ranging from about 60 s-1 to 240 s-1 using the split Hopkinson pressure bar. The dynamic behavior of specimens was evaluated in terms of stress–strain relationships, energy absorption capacity and failure patterns. Test results show that dynamic compressive properties of UHPC are strongly sensitive to strain rates. The individual addition of CNTs obviously improves the dynamic performance of plain UHPC, and there exists an optimal CNTs content of about 0.10% to achieve better improvement effects. The dynamic increase factor (DIF) is almost unrelated to CNTs content but closely correlated to strain rate variations, which can be well described by a modified empirical formula. Furthermore, it is found that the hybrid CNTs and SF display more significant reinforcing effects on dynamic properties of UHPC, as the UHPC specimen with 0.10% CNTs and 2.0% SF exhibits the highest dynamic compressive strength and toughness. Meanwhile, UHPC reinforced by hybrid fibers is less sensitive to high strain rates compared to plain UHPC. From microscopic observations, it is reasonably believed CNTs and SF exert synergistic reinforcing effects on UHPC matrix in view of their respective characteristics, which are more significant in improving the interfacial transition zone (ITZ) structure between SF and the surrounding matrix. This work promotes a fundamental understanding for the reinforcing effects of CNTs on UHPC, and provides an effective strategy to reinforce UHPC from multiscale perspectives.