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Abstract Traditional piezoelectric materials, such as lead zirconate titanate (PZT), are widely used due to their superior ability to convert mechanical energy into electrical energy. However, these lead-based ceramics are highly toxic and environmentally hazardous. This report explores Rochelle salt as an eco-friendly alternative, despite its brittleness and lower piezoelectric properties compared to PZT. The study investigates methods to enhance the energy capture of Rochelle salt crystals(RS) by varying crystal volume, impact frequency, and force, as well as by incorporating the 3D-printed biomimetic structure inspired by the pomelo fruit peel, which is naturally optimized for absorbing out-of-plane crushing forces. Experimental crystals grown within this structure were compared with those grown without it, focusing on energy capture and durability. Additionally, units with a 64:36 crystal-to-resin ratio were designed to assess the impact of crystal volume on voltage output. The experiments involved varying impact frequencies (120 rpm and 250 rpm) and compression distances (0.034 and 0.068 inches) using a digital oscilloscope and a custom crank slider mechanism. The results indicate that reducing crystal thickness and increasing rpms enhance voltage capture, suggesting that biomimetic structures can significantly improve the mechanical and electrical performance of piezoelectric materials. 

Abstract Shaped by human movement, place connectivity is quantified by the strength of spatial interactions among locations. For decades, spatial scientists have researched place connectivity, applications, and metrics. The growing popularity of social media provides a new data stream where spatial social interaction measures are largely devoid of privacy issues, easily assessable, and harmonized. In this study, we introduced a global multi-scale place connectivity index (PCI) based on spatial interactions among places revealed by geotagged tweets as a spatiotemporal-continuous and easy-to-implement measurement. The multi-scale PCI, demonstrated at the US county level, exhibits a strong positive association with SafeGraph population movement records (10% penetration in the US population) and Facebook’s social connectedness index (SCI), a popular connectivity index based on social networks. We found that PCI has a strong boundary effect and that it generally follows the distance decay, although this force is weaker in more urbanized counties with a denser population. Our investigation further suggests that PCI has great potential in addressing real-world problems that require place connectivity knowledge, exemplified with two applications: (1) modeling the spatial spread of COVID-19 during the early stage of the pandemic and (2) modeling hurricane evacuation destination choice. The methodological and contextual knowledge of PCI, together with the open-sourced PCI datasets at various geographic levels, are expected to support research fields requiring knowledge in human spatial interactions.