ICA – POSTER 406 Acoustics and Dielectric properties of Borassus Flabellifier ‘ BF ’ with frequency at 308 K .
Dielectric properties of Borassus Flabellifier ‘BF’ wood were carried out by authors with frequency at room temperature 308K. The wood section is taken from ma le BF tree and female BF tree from where the natura l j ice is collected over night. A large variation occurs at f requencies less than 10 Hz. at room temperature 308 K.The dielectric constant decreased as frequency increase d from 1 Hz to 4.0 x10 Hz. The minimum peak value of the dielectric loss tangents shifted towards higher fre quencies at room temperature 308K. Very low dielect ric conductivity has been observed. Characterization of the samples was made by scanning electron microsco pe (SEM) Model JEOL JSM5400. Results shows that the dielectr ic properties are slight different in male and fema le BF wood considerably. The variation of the dielectric const a t in different wood structures is correlated at r oom temperature with the frequency variations in a way the received signal strength. Acoustics measurement were carrie d out in our laboratory using Ultrasonic Interferometer by NDT t echnique and the dielectric measuring device used i n this study at UGC-DAE Consortium for Scientific Research Centr Indore (M.P.) India. In this study the drying of wood done by microwave energy using a continuous microwave dr i r was compared to that by conventional method.
Effects of Ultrasonic Detection Modes on the Longitudinal Ultrasonic Wave Transmission in Domestic Plantation Lumber
The performances of different ultrasonic detection applications on the longitudinal wave propagation in Japanese cedar (Cryptomeria japonica) and China fir (Cunninghamia lanceolata var. lanceolata) lumber were evaluated in the study. Results showed that insignificant differences among longitudinal ultrasonic wave velocities measured by transducers from 40 to 1000 kHz were found using the direct transmission method. The average wave velocities were 5074 and 6003 m s^(-1) for Japanese cedar and China fir, respectively. The longitudinal ultrasonic wave velocity obviously decreased with both the surface transmission method and semi-direct transmission method under 500-and 1000-kHz conditions. Good correlations, i.e., R^2 values of between 0.92 and 0.94, among the measured longitudinal ultrasonic wave velocities in the 3 detection methods with a 40-kHz transducer were obtained. Longitudinal ultrasonic wave velocities of wood measured with the different-shaped transducers and coupling methods also had good correlations, with R^2 values of between 0.95 and 0.99. The velocity measured with the flat transducer was 8.8~11.1% higher than that with the tapered transducer. The modulus of elasticity of wood can be estimated using longitudinal ultrasonic wave velocities measured by the 3 different detection methods with R^2 values of between 0.79 and 0.85 for Japanese cedar and China fir. It is expected that ultrasonic detection can be applied to the derivation of allowable strengths of structural lumber from Taiwanese plantations and for field inspections.
Dielectric Properties of Wood from 2 to 3 GHz
Many applications of microwave energy to wooden materials have been developed in the lastfew decades, both for treatment and for diagnostic purposes. All these applications require a reliable estimation of the permittivity of the wood species of interest, which is the physical parameter ofcrucial importance in the absorption of electromagnetic energy. This paper presents results obtained in the dielectric characterization of five wood species in the frequency range from 2 to 3 including the ISM frequency of 2.45 GHz. Permittivity was measured by an open-ended coaxial-line probe of new design on wood samples conditioned at several moisture levels. The influence of the natural variability of wood characteristics on the measured pennittivity was also investigated by a suitable experimental setup consisting of a poplar table including both sapwood and heartwood regions. Finally, a theoretical discussion on the meaning of a scalar measurement on anisotropic dielectrics is conducted in terms of an isotropic-equivalent permittivity, which is related to the permittivity tensor of the dielectric material.