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In optics, the f-number (sometimes called focal ratio, f-ratio, f-stop, or relative aperture) of an optical system is the ratio of the lens’s focal ... more

In materials science fatigue occurs when a material is subjected to repeated loading and unloading. The failure of the material occurs when there are k ... more

Number density is an intensive quantity used to describe the degree of concentration of countable objects. Volume number density is the number of specified ... more

In fluid mechanics, the Rayleigh number (Ra) for a fluid is a dimensionless number associated with buoyancy-driven flow, also known as free convection or ... more

The Rand index or Rand measure (named after William M. Rand) in statistics, and in particular in data clustering, is a measure of the similarity between ... more

In plasma physics, the Lundquist number (denoted by S) is a dimensionless ratio which compares the timescale of an Alfvén wave crossing to the timescale of ... more

A dimensionless empirical expression for the turbulent flow friction factor.

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In statistics and probability theory, the median is the numerical value separating the higher half of a data sample, a population, or a probability ... more

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