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Pulse tube cryocooler(or refrigerator) can be made without moving parts in the low temperature part of the device, making the cooler suitable for a wide ... more

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

Pressure altitude within the atmosphere is the altitude in the International Standard Atmosphere with the same pressure as the part of the atmosphere in ... more

Pressure altitude within the atmosphere is the altitude in the International Standard Atmosphere with the same pressure as the part of the atmosphere in ... more

In fluid flow, friction loss (or skin friction) is the loss of pressure or “head” that occurs in pipe or duct flow due to the effect of the fluid’s ... more

Electromotive force, abbreviated emf (denoted ℰ and measured in volts) is the electrical intensity or “pressure” developed by a source of ... more

In fluid flow, friction loss (or skin friction) is the loss of pressure or “head” that occurs in pipe or duct flow due to the effect of the fluid’s ... more

Permeability is a measure of the ability of a porous material a rock or unconsolidated material, to allow fluids to pass through it.
Permeability is ... more

Components of an electrical circuit or electronic circuit can be connected in many different ways. The two simplest of these are called series and parallel ... more

The highest angular resolutions can be achieved by arrays of telescopes called astronomical interferometers: These instruments can achieve angular ... more