A scheme to measure temperature distribution inside a gain medium of a diode-pumped solid-state laser is proposed based on the fluorescence intensity ratio technique. By recording the temperature-dependent upconversion fluorescence related to the H2→I4 and S4→I4 transitions of Er, the real-time temperature distribution inside an Er:Yb:LuAl(BO) crystal end-pumped by a 976 nm diode laser can be measured while a 1.55 μm laser is operating. Influences of pump power, output power, and output mirror transmissivity on the temperature distribution inside the gain medium are investigated. This scheme can conveniently and accurately measure the temperature distribution along the laser path in a rare-earth-doped gain medium in real time.
Driven by recent technological breakthroughs, the electric vertical take-off and landing (eVTOL) aircraft has gained considerable attention. The widespread demand for eVTOL aircraft can be attributed to their potential use in the commercialisation of urban air mobility (UAM) in low-altitude urban airspaces. However, the urban low-altitude airspace environment is complex. UAM has a high traffic density and the eVTOL aircraft specifications are not uniform. Particularly in commercial scenarios, controlling eVTOL aircraft and ensuring safety in UAMs are the two major problems that should be addressed in future studies. The design of reasonable traffic rules is a potential solution; hence, we organised a UAM traffic rule system and proposed several alternative UAM traffic rules from three perspectives: a single eVTOL aircraft, a certain route, and key control areas. In addition, we validated these traffic rules using multi-rotor and fixed-wing eVTOL aircraft. The results show that designing reasonable traffic rules can facilitate attaining the primary objectives of commercialisation of UAM.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.