Kelvin

Abstract: The mathematician and physicist William Thomson, 1st Baron Kelvin, (1824–1907) was one of Britain's most influential scientists, famous for his work on the first and second laws of thermodynamics and for devising the Kelvin scale of absolute temperature. Silvanus P. Thompson (1851–1916) began this biography with the co-operation of Kelvin in 1906, but the project was interrupted by Kelvin's death the following year. Thompson, himself a respected physics lecturer and scientific writer, decided that a more comprehensive biography would be needed and spent several years reading through Kelvin's papers in order to complete these two volumes, published in 1910. Volume 2, beginning in 1871, covers not only Kelvin's mature research, but also more personal aspects of his life, including his love of music and sailing, his experiments with compasses and navigation, and the relationship between his scientific discoveries and his religious beliefs.

Abstract: In this third paper the 1962 He3 Scale of Temperatures is evaluated both as to its precision and its deviations from the thermodynamic Kelvin Scale. Various thermodynamic quantities of He3 consistent with the 1962 He3 Scale are derived and listed. The correction to an observed vapor pressure for small amounts of He4 is discussed and tabulated. A description is given of the method of multiple variable least squares analysis used for deriving the final scale equation and for re-analysis of isotherm data. Finally the present status of the 1962 He3 Scale is discussed along with some considerations for the future.

Abstract: Soil moisture plays an important role in surface energy balances, regional runoff, potential drought and crop yield. Early detection of potential drought or flood is important for the local government and people to take actions to protect their crop. Traditionally measurement of soil moisture is a time-consuming job and only limited samples could be collected. Many problems would be results from extending those point measurements to 2D space, especially for a regional area with heterogeneous soil characteristics. The emergency of remote-sensing technology makes it possible to rapidly monitor soil moisture on a regional scale. Thermal inertia represents the ability of a material to conduct and store heat, and in the context of planetary science, it is a measure of the subsurface's ability to store heat during the day and reradiate it during the night. One major application of thermal inertia is to monitor soil moisture. In this paper, a thermal inertia model was developed to be suitable in situations whether or not the satellite overpass time coincides with the local maximum and minimum temperature time. Besides, the sensibilities of thermal inertia with surface albedo and the surface temperature difference were discussed. It shows that the surface temperature difference has more effects on the thermal inertia than the surface albedo. When the temperature difference is less than 10 Kelvin degrees, 1 Kelvin degree error of temperature difference will lead to a big fluctuation of thermal inertia. When the temperature difference is more than 10 Kelvin degrees, 1 Kelvin degree error of temperature difference will cause a small change of thermal inertia. The temperature difference should be larger than 10 Kelvin degrees when the thermal inertia model is selected to derive soil moisture or other applications. Based on this thermal inertia model, the soil moisture map was obtained for North China Plain. It shows that the averaged difference between the soil moisture values derived from MODIS data and in situ measured soil moisture data is 4.32%. This model is promising for monitoring soil moisture on a large regional scale.

Abstract: The experimental results obtained by several investigators on the magnetic cooling method are investigated in the light of (1) the electric crystalline fields acting on the magnetic ions of the paramagnetic salts used in the experiments, and (2) the magnetic dipole‐dipole coupling between these ions. These two factors produce anomalous specific heats and departures of the magnetic susceptibility from Curie's law at temperatures below 1°K with which the magnetic method is concerned. Thus the empirical Curie temperature, proportional to the reciprocal of the susceptibility, deviates from the true Kelvin temperature in this region. By the methods developed and discussed in the preceding paper by Van Vleck, numerical calculations of the specific heat and susceptibility have been performed for several salts. The experimental specific heat measured on a Curie scale has been corrected to the Kelvin scale and compared with the calculated results. Fairly good quantitative agreement is obtained, although there is some uncertainty as to the effect of (2) on the susceptibility and hence on the relation between the empirical and Kelvin temperature scales.