| Radial Compressor: A compressor belonging to the group of dynamic compressors. Characterized by radial flow. |
| Radiance Temperature: The temperature of a black body which has a radiance equal to the radiance of the object at a particular wavelength or wavelength band.
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| Radiant Energy: The electromagnetic energy emitted by an object due to its temperature. |
| Radioactivity: Spontaneous decay of some isotopes in nuclei.
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| Radiography: Nondestructive method of internal examination in which metal objects are exposed to a beam of X-ray or gamma radiation; differences in thickness, density, or absorption caused by internal defects or inclusions are apparent in the shadow image produced on a fluorescent screen or photographic film placed behind the object.
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| Radionuclide: any radioactive isotope.
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| Rankine Cycle: The thermodynamic cycle that is an ideal standard for comparing performance of heat-engines, steam power plants, steam turbines, and heat pump systems that use a condensable vapor as the working fluid; efficiency is measured as work done divided by sensible heat supplied.
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| Rankine or R: The absolute temperature scale related to Fahrenheit in the equivalent manner Kelvin is to Celsius. R = 1.8 x K, or also R = F 459.67. |
| Reagent: A substance or solution used in a chemical reaction, especially those used in laboratory work to detect, measure, or produce other substances |
| Reciprocating Compressors: Machines in which the compressing element is a piston having a reciprocating motion in a cylinder. |
| Reduced Instruction Set Computer (RISC): A computer architecture that has reduced chip complexity by using simpler processing instructions. It is faster than its more complex counterparts, thanks to its simplicity, and is also designed and built more economically.
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| Reflectance That ratio of power reflected to the incident power at a connector junction or other or other component or device.
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| Reflectance: The ratio of the radiant energy reflected from a surface to that incident on the surface.
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| Reflected Energy Compensation: A variable used to achieve greater accuracy by compensating for background IR energy that is reflected off the target into the instrument. If the temperature of the background is known, the instrument reading can be corrected. |
| Refrigeration Dryer: A device consisting of a heat transfer system, a moisture elimination system and a refrigeration system designed to improve the quality of the air and reduce the temperature of the air. |
| Relief Valve: A spring loaded pressure relief valve actuated by the static pressure upstream of the valve. The valve opens normally in proportion to the pressure increase over the opening pressure. |
| Resilience: The tendency of a material to return to its original shape after the removal of a stress that has produced elastic strain.
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| Resin : An organic polymer that crosslinks to form a thermosetting plastic when mixed with a curing agent.
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| Resolution: The smallest signal increment that can be detected by a measurement system, expressed in bits, proportions, or as percentage of full scale reading; resolution in a video system is the amount of detail in a graphic image. |
| Reverse Osmosis: A method of separating water from dissolved salts by passing feedwater through a semipermeable membrane at a pressure greater than the osmotic pressure caused by the dissolved salts.
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| Reynolds Number : A dimensionless flow parameter, ( Jnr/m), in which J is a significant dimension, often a diameter, n is the fluid velocity, r is mass density, and m is dynamic viscosity, all in consistent units |
| RFC -- (Request For Comments) The name of the result and the process for creating a standard on the Internet. New standards are proposed and published on the Internet, as a Request For Comments. The proposal is reviewed by the Internet Engineering Task Force (http://www.ietf.org/), a consensus-building body that facilitates discussion, and eventually a new standard is established, but the reference number/name for the standard retains the acronym RFC, e.g. the official standard for e-mail message formats is RFC 822.
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| Rheology: Study of flow characteristics.
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| Roentgen: A unit of gamma radiation measured by the amount of ionization in air. In non-bony biological tissue 1 roentgen delivers a dose approximately equal to 1 rad.
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| Rotameter: A flow measurement device for liquids and gases that uses a flow tube and specialized float. The float device is supported by the flowing fluid in the clear glass or plastic flow tube. The vertical scaled flow tube is calibrated for the desired flow volumes/time.
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| Rotary Compressors: A compressor belonging to the group of displacement rotary compressors, a type of valve less displacement machine. Also referred to as "Roots blower". |
| Router A special-purpose computer (or software package) that handles the connection between 2 or more Packet-Switched networks. Routers spend all their time looking at the source and destination addresses of the packets passing through them and deciding which route to send them on. |
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