Currently, great attention has been paid to the fast development of high-speed railways all over the world. With an increment of running speed, pantograph arcing has become a significant issue, which can threaten the lifespan and service performance of pantograph strip materials severely. Cu-impregnated carbon strip is one of the most widely used strip materials in high-speed railways, while its arc erosion characteristics and mechanisms are still in absence. In this paper, the arc erosion characteristics of Cu-impregnated carbon materials were experimentally studied. The variations in voltage waveforms between electrodes with time were recorded, and the evolution of the temperature distribution of strip was obtained by a thermal infrared imager. The arc erosion surface was examined using a digital camera, a scanning electron microscopy, and energy dispersive X-ray spectroscopy to assess the macroscopic and microscopic morphologies, as well as elemental distributions in or around the arc erosion crater. An interesting arc crater-centered multicolored subarea on the strip surface was found, which was explained from the aspects of the effect of arc-induced temperature and formation of copper oxide film. The arc erosion crater consisted of several overlapped erosion pits, and the mechanism of the pits was understood from the unique microstructure and physical properties of carbon phase and copper phase in the materials. Finally, the formation of spherical copper particles and cracks was illustrated, and their influences on the sliding wear and friction process were discussed.

The electromagnetic environment safety of the surveillance system at airports plays an important part in ensuring the flight safety in civil aviation. Drone countermeasure equipment is considered as the new active interference source, and when it is used at or around airports, which may cause electromagnetic interference to the surveillance system. In this paper, the radiated field strength of drone countermeasure equipment was measured in an anechoic chamber, and then the stray radiation field strength at frequency bands of the secondary surveillance radar (SSR) and automatic dependent surveillance-broadcast (ADS-B) also were acquired. Meanwhile, test results are compared with protection requirements of electromagnetic environment of the SSR and ADS-B. Moreover, electromagnetic interference effects of drone countermeasure equipment on the SSR and ADS-B were analyzed according to the electromagnetic compatibility theory and protection ratios of the SSR and ADS-B. At last, protective distances of the SSR and ADS-B were proposed separately. The results of this paper can provide some supports for the site selection of drone countermeasure equipment at airports.

We propose a novel phase shifter for beam scanning in phased arrays using a cascaded injection-locked voltage-controlled oscillator (VCO) array with weak reverse coupling. We analyze the phase noise performance of a multi-signal injection-locked oscillator and establish a phase output model for the array, studying the effects of forward and reverse injection ratios on phase and phase noise at each stage. By decoupling and cascade locking VCO array elements through controlled injection ratios, we design a 2.45 GHz one-dimensional linear array of four VCOs that achieves a continuous fixed phase difference between adjacent oscillators from −180${}^{\circ }$ to 180${}^{\circ }$, enabling electronic tuning of phase shift and beam scanning. Finally, the beam scanning of the antenna array is realized by using the VCO array. Our theoretical and experimental results demonstrate the effectiveness of our proposed approach.