As a random process, the temperature microstructure in water exhibits both time and spatial correlation characteristics. Thus, acoustic signals propagated along diverging or converging paths should indicate some degree of cross correlation due to the temperature microstructure. This dependence is investigated in a water tank with a controlled temperature microstructure. The angular separation between paths is varied and cross-correlation functions are computed for the various separations. The measurements were made using pulsed signals at 500 kHz. The correlation between the received signals decreases as the angular separation between the paths is increased.
NMR spin—lattice and spin—spin relaxation times have been measured in the associated liquids 1,3-butanediol, 2-methyl-2,4-pentanediol, glycerol, and 1,2,6-hexanetriol at resonant frequencies of 10 and 20 Mc/sec and over the temperature range —40° to +40°C using ``spin echo'' techniques. These data were translated into average correlation times using the Kubo—Tomita model of the NMR relaxation process. By using a log Gaussian type of distribution it was possible in all four liquids to reconcile the average correlation times derived from both relaxation times and at both resonant frequencies. The rigid lattice limiting value of T2 and the variation of the distribution width with temperature were also determined.
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