Freeze/thaw cycle frequency

The conventional use of meteorology will be most important during the construction period at a site. On some projects it may be necessary to furnish climatological data for prospective bidders, seasonal work scheduling, and on information not commonly available, such as freeze-thaw cycle frequency, and annual wet-bulb temperature frequencies and ranges. 

Freeze-Thaw Test. A limited number of mixes were subjected to a series of freeze-thaw cycles in a chest-type freezer at a rate of 6-10 cycles/day. The fundamental transverse frequency at zero cycles, rj, was measured at the beginning of each test. Additional values, rjC, were also measured at 50, 70, 110, and 150 cycles. The fundamental transverse frequency-squared vs. the number of freeze—thaw cycles is plotted in... 

EPR spectra were obtained on a Varian E-9 system equipped with an Air Products liquid helium low temperature dewar and controller. Samples concentrations were 5 X 10 M in MTHF. Samples were prepared in sealed tubes following 3 freeze-pump-thaw cycles. The samples were irradiated with light > 540 nm from a filtered xenon-arc lamp modulated at 500 Hz. The time-resolved EPR signals were detected with a lock-in amplifier. The microwave frequencies given in the figure captions were determined with an HP frequency counter. g-Factors were determined by calibration with weak samples of DPPH. 

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