Abstract: I welcome you to the fourth issue of the IEEE Communications Surveys and Tutorials in 2021. This issue includes 23 papers covering different aspects of communication networks. In particular, ...

The Double Purcell Prusik is an essential knot system for arborists and tree climbers, designed to enhance safety and protect gear during ascents, descents, and complex canopy maneuvers. This tutorial ...

Our weather alerts are colour-coded. The colours tell you what risk the weather is to you. Every type of weather alert—Warnings, Advisories, and Watches—now has a colour when it is issued. The weather ...

Towns and cities across the US are without access to their CodeRED emergency alert system following a cyberattack on vendor Crisis24. Various municipalities have issued near-identical advisories about ...