One of the most important factors affecting underground cable ampacity is the thermal resistivity of the soil. It is well known that thermal resistivity of the soil will vary with moisture content. It is also well known that the heat generated by cables can cause soil drying thus affecting the soil thermal resistivity. The ability of the soil to maintain its thermal resistivity in the presence of a heat source is known as thermal stability. Soil will increase in resistivity due to drying caused by heating from underground sources. This phenomenon makes it challenging for the design engineer to decide how to account for the drying effect in cable ampacity calculations. This paper will examine the information available from standard soil tests and the information these tests may provide relating to the migration of moisture in soil and the resulting changes in soil resistivity. Furthermore a method is suggested for including this information in underground cable ampacity calculations.

Quantitative analysis of gas mixtures from sources external to a mass spectrometer (MS) requires vacuum hardware that systematically introduces the gas to the ionization region of the MS and calibration procedures that reflect the MS response to time dependent partial pressures in the gas source. Formalism for describing the gas flow, fractionation processes, and the ionization process is presented. Long-term sensitivity data for D2 is presented for three types of mass spectrometers: a quadrupole, a cycloid, and a magnetic sector mass spectrometer. The use of appropriate standard gas mixtures to monitor the accuracy of the MS calibration by control chart is advocated. Bias data from control charts can be used as the basis for minor calibration adjustments rather than total recalibration.

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Thermal diffusion factors for the 4He-2 0Ne system have been measured in a low temperature region previously unexplored (down to 31 K) using a trennschaukel. Both quantum and classical transport collision integrals were evaluated for a recently proposed helium-neon intermolecular potential of the Hartree-Fock dispersion (HFD) type which has been shown to correlate cross section and transport property data quite well. The present data agree extremely well with the quantum mechanically calculated thermal diffusion factors. The classically calculated values fall considerably lower.

Mutual diffusion coefficients of the He–Ar, Ne–Ar, and Xe–Ar systems were measured in the temperature range from approximately 350 to 1300 K. These results agree within the mutual uncertainty with the Marrero and Mason correlations derived from diffusion and molecular beam data. Viscosity and thermal diffusion derived data were found to be mutually consistent with diffusion to within ∼5% at high temperatures and probably better than ∼2 1/2% at the lower temperatures. A comparison with theoretical diffusion coefficients calculated from recently proposed intermolecular potentials is made.