RESUMO
Fractures are ubiquitous and can lead to the catastrophic material failure of materials. Although fracturing in a two-dimensional plane is well understood, all fractures are extended in and propagate through three-dimensional space. Moreover, their behaviour is complex. Here we show that the forward propagation of a fracture front occurs through an initial rupture, nucleated at some localized position, followed by a very rapid transverse expansion at velocities as high as the Rayleigh-wave speed. We study fracturing in a circular geometry that achieves an uninterrupted extended fracture front and use a fluid to control the loading conditions that determine the amplitude of the forward jump. We find that this amplitude correlates with the transverse velocity. Dynamic rupture simulations capture the observations for only a high transverse velocity. These results highlight the importance of transverse dynamics in the forward propagation of an extended fracture.
RESUMO
The 2019-20 Australian wildfires caused extreme haze events across New South Wales (NSW), which reduced photovoltaic (PV) power output. We analyze 30-min energy data from 160 geographically separated residential PV systems in NSW with a total capacity of 312 kW from 6 Nov 2019-15 Jan 2020. The observed mean power reduction rate for PV energy generation as a function of the fine particulate matter (PM2.5) concentration is 13 ± 2% per 100 µg/m3 of PM2.5. The resulting energy loss for residential and utility PV systems is estimated at 175 ± 35 GWh, equating to a worst-case financial loss of 19 ± 4 million USD. We found the relative impact to be most significant in the mornings and evenings, which may necessitate the installation of additional energy storage. As PV systems are sensitive to smoke and become ubiquitous, we propose employing them to support wildfire detection and monitoring.
RESUMO
Phase Change Materials (PCMs) have demonstrated tremendous potential as a platform for achieving diverse functionalities in active and reconfigurable micro-nanophotonic devices across the electromagnetic spectrum, ranging from terahertz to visible frequencies. This comprehensive roadmap reviews the material and device aspects of PCMs, and their diverse applications in active and reconfigurable micro-nanophotonic devices across the electromagnetic spectrum. It discusses various device configurations and optimization techniques, including deep learning-based metasurface design. The integration of PCMs with Photonic Integrated Circuits and advanced electric-driven PCMs are explored. PCMs hold great promise for multifunctional device development, including applications in non-volatile memory, optical data storage, photonics, energy harvesting, biomedical technology, neuromorphic computing, thermal management, and flexible electronics.
RESUMO
Polymer-ceramic composites are commonly used as flexoelectric films. In existing studies, the flexoelectric effect of composites are generally improved by adjusting the material structures or adding ferroelectric materials. Further improvement of flexoelectric response has encountered a bottleneck. Considering from a new perspective, this study innovatively proposes to prepare the uniformly dispersed BT-PVDF composite films with giant flexoelectric response by surfactant SDS-assisted treatment. According to the engineering applications, tilt sensors have been fabricated with the SDS/BT-PVDF composite films. The prepared tilt sensors can accurately sense the tilt change in a small-angle range (0-10°) between the coaxial connecting parts, the response signal changes significantly (49.25-72.35 mV/°), and the response speed can reach 0.166 s. The research provides a new idea for improving the flexoelectric response and also paves a way for developing tilt sensors through a low-cost, facile, and reliable method, showing potential applications including bending sensing and structural health monitoring.