| Section S | S index | 181-189 of 1376 terms |
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sechard—A dry, warm foehn wind over Lake Geneva in Switzerland.
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second-foot day—The volume of water represented by a flow of 1 cubic foot per second for 24 hours; equal to 86 400 cubic feet. This is used extensively as a unit of runoff volume or reservoir capacity and is closely equivalent to 2 acre-feet.
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second-foot—A unit of water measure equal to 1 cubic foot per second, or about 449 gallons per minute. It is the unit of stream discharge commonly used in the United States.
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second law of thermodynamics—An inequality that is fundamentally different from the first law because it specifies the direction in which a natural process will evolve rather than merely requiring that certain quantities are conserved. As formulated by Planck, the second law asserts that a thermodynamic state function, S, known as entropy, exists for all physical systems. For the universe and for a system isolated from its surroundings,  Equality prevails only for reversible processes or when the system is in a steady state. When the universe of a system is a maximum, no further evolution of the system is possible. The second law is often asserted in other forms, including the following. | When two bodies at different temperatures interact, the temperature of the hotter body can only decrease and that of the colder body can only increase unless work is done. |
| No device can continuously deliver mechanical work and produce no effect other than cooling a reservoir. |
| In the neighborhood of every state that can be reached reversibly, there exist states that cannot be reached by a reversible, adiabatic process, or, in other words, that can be reached only irreversibly or cannot be reached at all. |
Dutton, J. A., 1995: Dynamics of Atmospheric Motion, Dover Press, 45–51, 406–410.
Sommerfeld, A., 1964: Thermodynamics and Statistical Mechanics, Academic Press, 26–36, 39.
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second-order climatological station—A station at which observations of atmospheric pressure, temperature, humidity, winds, clouds, and weather are made at least twice daily at fixed hours, and at which the daily maximum and minimum of temperature, the daily amount of precipitation, and the duration of bright sunshine are observed. Compare second-order station; see also first-order climatological station, third-order climatological station, climatological substation, precipitation station.
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second-order reaction—A chemical reaction for which the rate of disappearance of reactants or the rate of appearance of the reaction product(s) is proportional to the product of the concentration of two reacting species, which may be the same. The constant of proportionality is the second-order rate coefficient for the chemical reaction and has the units of inverse concentration multiplied by inverse time.
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