Derailleur gears several standards in use, and in each the product of the derailleur's actuation ratio and the length of cable pulled must equal the pitch of the rear sprockets. The following standards exist. Some rear derailleurs, especially for mountain bikes, incorporate a clutch to keep the lower length of chain in sufficient tension to prevent the chain from striking the bottom of the chain stay, called "chain slap", and which can damage the chain stay. Clutches are also helpful in preventing the chain from derailing from the chain ring on systems without a front derailleur. The front derailleur only has to
Word RAM RAM model, and was the original motivation for the model. Dan Willard used y-fast tries to solve this in formula_6 time. Michael Fredman and Willard also solved the problem using fusion trees in formula_7 time. Word RAM In theoretical computer science, the word RAM (word random access machine) model is a model of computation that is a random access machine able to do bitwise operations on a single word of bits. The model was created by Michael Fredman and Dan Willard in 1990 to simulate programming languages like C. The word RAM model is an abstract machine similar to a