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An autoblock (or autobloc or "third hand") is a rope device used in climbing and caving for both rappelling (downward) and ascending (upward). [1] [2]While rappelling, it slides freely down the rope when pushed downward by the hand, allowing a controlled descent, but jams in the event of a sudden drop or loss of control, stopping the descent.
Automatic block signaling (ABS), spelled automatic block signalling or called track circuit block (TCB [1]) in the UK, is a railroad communications system that consists of a series of signals that divide a railway line into a series of sections, called blocks. The system controls the movement of trains between the blocks using automatic signals.
Placer mining (/ ˈ p l æ s ər /) [1] is the mining of stream bed deposits for minerals. [2] This may be done by open-pit mining or by various surface excavating equipment or tunneling equipment.
Automatic block signaling uses a series of automated signals, normally lights or flags, that change their display, or aspect, based on the movement of trains past a sensor. This is by far the most common type of block system as of 2018, used in almost every type of railway from rapid transit systems to railway mainlines. There is a wide variety ...
Placer mining is an important source of gold, and was the main technique used in the early years of many gold rushes, including the California Gold Rush. Types of placer deposits include alluvium, eluvium, beach placers, aeolian placers and paleo-placers. [2] Placer materials must be both dense and resistant to weathering processes. To ...
Terraced paddy fields are used widely in rice, wheat and barley farming in east, south, southwest, and southeast Asia, as well as the Mediterranean Basin, Africa, and South America. Drier-climate terrace farming is common throughout the Mediterranean Basin, where they are used for vineyards, olive trees, cork oak, and other crops. [citation needed]
Here, placer gold has been industrially extracted by sluices and mechanical devices. Great volumes of material have been washed along this river, the traces can still been seen on this aerial image, Prospecting for placer gold is normally done with a gold pan or similar instrument to wash free gold particles from loose surface sediment. [1]
The U.S. Federal Trade Commission moved to block the proposed acquisition of Activision Blizzard by Microsoft. [65] The Game Awards 2022, honoring the best video games of the year, took place at the Microsoft Theater in Los Angeles. [66] 16 John Carmack announced his departure from Meta as its CTO. [67]