Improved Permittivity Calibration Method for Wideband In Situ Permittivity Probe
This letter discusses about an improved permittivity probe calibration method for calculating the complex permittivity of soils from reflection data over a very wide bandwidth. The accuracy of this method is demonstrated using reflection data collected from a unique wideband (10-1000 MHz) permittivity probe specifically designed for quick in situ permittivity measurements of soils at different depths. The improved calibration method is based on the traditional capacitance model, which suffers from errors caused by the assumption that the capacitance is independent of the frequency and the permittivity of the ambient medium under test. The improved capacitance model is introduced here to account for the frequency- and permittivity-dependent effects. Thus, it produces more accurate permittivity estimation over a much wider frequency and permittivity ranges. This letter will discuss about the accuracy of this improved permittivity probe calibration method and a wideband in situ soil probe design.
In Situ Measurement of Electromagnetic Properties of Welded Tuff Under Compression
The high-frequency electromagnetic permittivity and attenuation rate were measured in situ in a block of densely welded ash flow tuff compressed uniaxially. For stress changes up to 800 psi, the electromagnetic properties were found to be independent of stress, except where the water content of fractures may have been controlled by aperture changes induced by the compressional loading.
AXIOMATISABILITY OF WEAKLY FLAT, FLAT, AND PROJECTIVE S-ACTS
ABSTRACT This paper gives necessary and sufficient conditions on a monoid S that the class of flat left S-acts be (first order) axiomatisable. It presents also a streamlined version of the result of Stepanova that the class of projective left S-acts is axiomatisable if and only if the strongly flat left S-acts are axiomatisable and S is left perfect.