Unusual types of gramophone records Unusual types of gramophone records The overwhelming majority of records manufactured have been of certain sizes (7, 10, or 12 inches), playback speeds (33, 45, or 78 RPM), and appearance (round black discs). However, since the commercial adoption of the gramophone record (called a phonograph record in the U.S., where both cylinder records and disc records were invented), a wide variety of records have also been produced that do not fall into these categories, and they have served a variety of purposes. The most common diameter sizes for gramophone records are 12-inch, 10-inch, and 7-inch. Early American shellac records were
Hydraulic diameter also used in calculation of heat transfer in internal-flow problems. For a fully filled duct or pipe whose cross-section is a regular polygon, the hydraulic diameter is equivalent to the diameter of a circle inscribed within the wetted perimeter. Hydraulic diameter The hydraulic diameter, , is a commonly used term when handling flow in non-circular tubes and channels. Using this term, one can calculate many things in the same way as for a round tube. It is defined as where More intuitively, the hydraulic diameter can be understood as a function of the hydraulic radius , which is defined as