San (letter) San (letter) San (Ϻ) was an archaic letter of the Greek alphabet. Its shape was similar to modern M, or ϡ, or to a modern Greek Sigma (Σ) turned sideways, and it was used as an alternative to Sigma to denote the sound . Unlike Sigma, whose position in the alphabet is between Rho and Tau, San appeared between Pi and Qoppa in alphabetic order. In addition to denoting this separate archaic character, the name "San" was also used as an alternative name to denote the standard letter Sigma. The existence of the two competing letters Sigma and San is
Torque density Torque density Torque density is a measure of the torque-carrying capability of a mechanical component. It is the ratio of torque capability to volume and is expressed in units of torque per volume. Torque density is a system property since it depends on the design of each element of the component being examined and their interconnection. Torque density is useful during the concept evaluation stage of mechanical designs, especially in power train design problems. Typically, it will be one of many factors used to assign potential success measures to each concept. For example, in the upgrade of a drive train