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Transit-oriented development (TOD) has long been recognized as a significant model for prospering urban vibrancy. However, most studies on TOD and urban vibrancy do not consider temporal differences or the nonlinear effects involved. This study applies the gradient boosting decision tree (GBDT) model to metro station areas in Wuhan to explore the nonlinear and synergistic effects of the built-environment features on urban vibrancy during different times. The results show that (1) the effects of the built-environment features on the vibrancy around metro stations differ over time; (2) the most critical features affecting vibrancy are leisure facilities, floor area ratio, commercial facilities, and enterprises; (3) there are approximately linear or complex nonlinear relationships between the built-environment features and the vibrancy; and (4) the synergistic effects suggest that multimodal is more effective at leisure-dominated stations, high-density development is more effective at commercial-dominated stations, and mixed development is more effective at employment-oriented stations. The findings suggest improved planning recommendations for the organization of rail transport to improve the vibrancy of metro station areas.

To suppress dielectric loss while still harvesting high dielectric constant (k) and thermal conductivity in polymer composites, core–shell structured fillers are synthesized via controlled calcination under air, where the conductive copper (Cu) particles are encapsulated by a thin insulating oxidation layer (CuO). The dielectric constant can be substantially improved in the poly(vinylidene fluoride) PVDF composites filled with Cu@CuO fillers, and the dielectric loss is strongly restrained even at high filler loadings. The improved dielectric performance can be ascribed to the insulating CuO shell, which promotes the multiple interfacial polarization and meanwhile impedes the long-range electron migration. Additionally, the Cu@CuO/PVDF composites exhibit higher thermal conductivity (TC) than the unfilled polymer and the Cu/PVDF, owing to the reduced interfacial thermal resistance between the fillers and the matrix. Composites with high TC and k but low loss are promising materials for potential applications in microelectronic, electrical and energy storage devices.