| Section D | D index | 261-269 of 573 terms |
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diffuse reflectorAny surface with irregularities so large compared to the wavelength of the incident radiation that the reflected rays are sent back in multiple directions; the opposite of a specular reflector, such as a mirror. Most natural surfaces act more like diffuse reflectors than specular reflectors. Exceptions are calm water and some ice surfaces. To be distinguished from a perfectly diffuse reflector.
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diffuse solar radiationDownward scattered and reflected solar radiation coming from the whole hemisphere of the sky with the exception of the solid angle subtended by the sun's disk.
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diffusion denuder techniqueA technique for stripping a certain molecule or class of molecules from an airstream. The molecules of interest diffuse to the walls of a flow-through reactor, and are deposited there, while particulate matter passes through the reactor unchanged. The reactors are usually cylindrical or annular tubes, to maximize the surface area for a given volume, and the inner walls can be coated with chemicals to remove the molecules of interest, for example, citric or oxalic acid for ammonia removal. At the end of a given time the chemicals of interest are removed from inside the denuder for quantitative chemical analysis.
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diffusion hygrometerA hygrometer based upon the diffusion of water vapor through a porous membrane. In its simplest form, it consists of a closed chamber having porous walls and containing a hygroscopic compound. The absorption of water vapor by the hygroscopic compound causes a pressure drop within the chamber that is measured by a manometer.
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diffusion modelA set of mathematical equations that simulates the diffusion of material released in the atmosphere (or ocean). Usually in the form of computer codes, diffusion models simulate diffusion in a variety of physical processes.
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