Space-time modulation systems have garnered significant attention due to their resemblance to moving-matter systems and promising applications. Unlike conventional movingmatter systems, modulation systems do not involve net motion of matter, and are therefore easier to implement and not restricted to subluminal velocities. However, canonical wavemedium interaction aspects, such as scattering and energymomentum relations, have remained largely unexplored. In this paper, we address the aforementioned issues for three dynamic systems: moving-matter blocs, moving-perturbation interfaces and moving-perturbation periodic structures, and provide corresponding general formulations along with comparisons. Our investigation reveals the significant roles played by the "catchup" effect between waves and interfaces. Even more interestingly, it reveals different energy and momentum exchanges between moving media and homogenized moving-perturbation structures as a result of conventional and reverse Fresnel-Fizeau drag effects.
High-voltage power cables can be subjected to thermomechanical forces during operation due to the rising cable temperature or drastic ambient temperature changes, which threaten the operational safety of the cables. In this paper, first of all, the thermal expansion, serpentine arc displacement and serpentine arc axial force of the cable in the limit operation state are analyzed theoretically. The serpentine arc displacement and serpentine arc axial force under different serpentine laying parameters are compared and the optimal laying method is derived. Then the theoretical optimal solution is simulated using finite element analysis method to prove the correctness of the theoretical results. Finally, the recommended laying parameters of the serpentine laying method are given.
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