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A pound lock has a chamber with gates at both ends that control the level of water in the pound. In contrast, an earlier design with a single gate was known as a flash lock. [4] Pound locks were first used in China during the Song dynasty (960–1279 CE), having been pioneered by the Song politician and naval engineer Qiao Weiyue in 984. [5]
The Pound–Drever–Hall (PDH) technique is a widely used and powerful approach for stabilizing the frequency of light emitted by a laser by means of locking to a stable cavity. The PDH technique has a broad range of applications including interferometric gravitational wave detectors , atomic physics , and time measurement standards , many of ...
A short pound on the Chesterfield Canal in England, United Kingdom. A canal pound (from impound), [1] reach, or level (American usage), is the stretch of level water impounded between two canal locks. Canal pounds can vary in length from the non-existent, where two or more immediately adjacent locks form a lock staircase, to many kilometres/miles.
There are 40 multiple-choice questions per session. Several disciplines require a common morning breadth exam which broadly covers the discipline and then a more detailed afternoon depth exam where the test taker selects a more detailed area of the discipline. Other disciplines essentially have morning and afternoon breadth exams. [4]
All three sets of locks are paired; that is, there are two parallel flights of locks at each of the three lock sites. This, in principle, allows ships to pass in opposite directions simultaneously; however, large ships cannot cross safely at speed in the Culebra Cut, so in practice ships pass in one direction for a time, then in the other ...
Metrology is a wide reaching field, but can be summarized through three basic activities: the definition of internationally accepted units of measurement, the realisation of these units of measurement in practice, and the application of chains of traceability (linking measurements to reference standards).
A canal lock system in modern-day France which uses the pound lock system developed during the Song dynasty. In ancient China, the sluice gate, the canal lock, and flash lock had been known since at least the 1st century BCE (as sources then alluded that they were not new innovations), during the ancient Han dynasty (202 BCE–220 CE). [67]
He built locks 72 feet 7 inches (22.12 m) long by 15 feet (4.6 m) wide when he extended the Bridgewater Canal to Runcorn, where the canal's only locks lowered boats to the River Mersey. The narrow locks on the Trent and Mersey limited the width (beam) of the boats (which came to be called narrowboats ), and thus limited the quantity of the ...