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.
Field observations of shallow freeze and thaw processes using high‐frequency ground‐penetrating radar
We have used reflection profiles and common‐midpoint (CMP) soundings with 900 MHz ground‐penetrating radar (GPR) to monitor freezing and thawing processes during winter seasonal periods at two separate sites located in Ontario, Canada. GPR responds to the large contrast in dielectric permittivity between liquid water and ice. The profiles reveal the long‐term development of a very shallow (<0·5 m) soil frost zone overlying unfrozen wet substratum. During the course of the winter season, long‐term travel time analysis yielded physical properties of the frozen and unfrozen layers as well as the spatial distribution of the base of the soil frost zone. Short‐term shallow thawing events overlying frozen substratum formed a dispersive waveguide for both the CMP and reflection profile surveys. Inversion of the dispersive wavefields for the CMP data yielded physical property estimates for the thawed and frozen soils and thawed layer thickness. We have shown that GPR can be used to monitor very shallow freezing and thawing events by responding to changes in the relative dielectric permittivity of the soil water phase (e.g. liquid water vs ice). The non‐invasive collection of such data permits interpretation of dynamic temporal and spatial freeze–thaw events, which are important for characterizing a range of hydrological processes. Copyright © 2010 John Wiley & Sons, Ltd.
Pig Vocalizations Under Selected Husbandry Practices
Acoustical characteristics of vocalizations of sows, piglets, and nursery pigs under selected husbandry practices were analyzed with a digital signal processing system. The duration (D) and major energy-resonance frequency (P) for each call were determined as follows: a) processing of piglets (D = 0.81 s and f* = 3 700 Hz); b) food anticipation of breeding-gest ation sows (2.50 s and 3 000 Hz); c) isolation of piglet (0.34 s and 500, 3 500 Hz); d) startling of nursery pigs (0.29 s and 900 Hz); e) sows in heat (3.07 s and 1 375 Hz); f) farrowing (0.10 s and 3 000 Hz); g) sow nursing (0.15 s and 1 000 Hz); and h) mate greeting of sow (0.13 s and 1 000 Hz). Calls a) to d) are responses to human generated stressors, and calls e) through h) responses to social and physiological states of the pigs. Thus, vocalizations can be segmented for different pig production situations.