Anisotropy of Dielectric Constant in Coniferous Wood

Assessment of the dielectric anisotropy in timber using the nondestructive GPR technique

“…The variation in dielectric properties between the longitudinal, radial, and tangential directions is due to the difference in the arrangement of the walls and lumens of wood cells by tree growth and the anisotropy of the chemical components of cell wall substance [26]. The greater dielectric constant in longitudinal direction has been explained in terms of the transition probability of dipole jump to an adjacent site when the field applied to longitudinal direction in contrast to when the electric field was applied in the radial or tangential directions [27].…”

Dielectric and ultrasonic properties of rubber wood. Effect of moisture content grain direction and frequency

“…1-4 that the dielectric constant and dielectric loss factor in parallel to grain direction is greater than in perpendicular to grain direction. The variation of dielectric properties between parallel and perpendicular to grain direction is due to the difference in the arrangement of cell wall and lumen in addition to the anisotropy of cell wall substances (Norimoto et al 1978). The greater dielectric constant in parallel to grain direction may be explained in terms of the transition probability of dipole jump to an adjacent site when the field applied to parallel to grain direction is considerably higher than that when the electric fields were applied in perpendicular to grain (Norimoto and Yamada 1970 Verlustfaktor parallel zur Faser in Abh/ingigkeit yon der Feucht bei Mikrowellenfrequenz mical constituent of wood may also be responsible for the dielectric anisotropy.…”

Heating characteristics of western hemlock (Tsuga heterophylla) in a high frequency field

“…Since the dielectric properties vary with the proportion of latewood (Norimoto et al 1978), oven-dry content of glucose and lignin (Venkateswaran 1972) or even the amount of crystalline regions (Norimoto 1976), individual measurements (twenty) were done for each timber, from high MCs to oven-dry, by placing a rectangular wood sample (116 × 90 × 35 mm 3 ) in the capacitive section of a parallel resonant circuit (Lazarescu and Avramidis 2011). All dielectric coefficients were measured in either radial or tangential Sample plots of the derivative of the imaginary (ε ) and real (ε ) permittivity coefficients and how the MC associated with a change in slope was determined (dotted arrow lines) Abb.…”

“…The residuals that resulted from fitting at MC values over FSP increased in size (conical-shaped) giving a biased estimate of the standard deviation. This effect may be attributed to free water distribution, but could also be a consequence of differences in cellulose content, percentage of latewood or the presence of irregular arrays of cells (Norimoto et al 1971). …”