![]() These delays are used in all practical applications: it does not take very long for a system of pulses (representing dots and dashes, for instance) to be attenuated and forgotten, when sent along an electric cable, but this short time interval is long enough for transmission even over a long distance, and makes telecommunications possible.Ī system capable of retaining information for some time can be used as a memory device in a computing machine. The examples discussed in the preceding section are not only interesting from a theoretical point of view, but they also show how to attack a practical problem. #Brillouin science and information theory how to In information theory and statistics, negentropy is used as a measure of distance to normality. Let us consider, for instance, the problems of diffusion and spin distribution. The concept and phrase 'negative entropy' was introduced by Erwin Schrdinger in his 1944 popular-science book What is Life 1 Later, Lon Brillouin shortened the phrase to negentropy. ![]() The information stored in this system corresponds to a decrease in entropy. Our discussion shows how this situation is progressively destroyed by diffusion and collisions that increase the entropy and erase the information.Įntropy is usually described as measuring the amount of disorder in a physical system. A more precise statement is that entropy measures the lack of information about the actual structure of the system. This lack of information introduces the possibility of a great variety of microscopically distinct structures, which we are, in practice, unable to distinguish from one another. Since any one of these different microstructures can actually be realized at any given time, the lack of information corresponds to actual disorder in the hidden degrees of freedom. ![]() This picture is clearly illustrated in the case of the ideal gas. When we specify the total number n of atoms, their mass m, their degeneracy factor g, and the total energy E., we do not state the positions and velocities of each individual atom.Since we do not specify the positions and velocities of the atoms, we are unable to distinguish between two different samples of the gas, when the difference consists only in different positions and velocities for the atoms. #Brillouin science and information theory free. ![]() #Brillouin science and information theory how to. ![]()
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