Dielectric anisotropy of oven- and air-dried wood evaluated using a free space millimeter wave
Dielectric anisotropy of oven- and air-dried wood evaluated using a free space millimeter wave
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DOI：
10.1007/s10086-013-1341-7
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发表时间：
2013-04
影响因子：
2.9
通讯作者：
Soichi Tanaka;Y. Fujiwara;Y. Fujii;S. Okumura;H. Togo;N. Kukutsu;S. Mochizuki
中科院分区：
文献类型：
--
作者：
Soichi Tanaka;Y. Fujiwara;Y. Fujii;S. Okumura;H. Togo;N. Kukutsu;S. Mochizuki
为了评估在100 GHz的毫米波频率下由木材结构引起的介电各向异性，使用自由空间方法测量了9种木材在0和11%含水率（MC）下的平锯试样的介电参数，该方法被设计用于减少在平行于木材的纵向和切向方向的毫米波电场下的多次反射，而径向上的那些是使用常规近似理论估计的。在切向和径向方向的介电参数几乎是相同的，并不断小于那些在纵向方向。所有的介电参数都随木材密度的增加而增加，并且在11%MC时大于0%MC。在纵向和横向方向上的介电参数和它们之间的介电各向异性很好地拟合回归线的基础上的介电混合物模型由孔隙和介电各向同性木材物质，并采用并联电容器和Lichtenecker的指数公式来表示的混合物的介电参数的纵向和横向方向上，分别。得出的结论是，在100 GHz的介电各向异性是由孔隙排列和介电参数几乎不受解剖结构，如射线。同时也证实了自由空间法测量平锯试样介电参数的有效性。
To evaluate the dielectric anisotropy caused by wood structure at a millimeter wave frequency of 100 GHz, the dielectric parameters for flat-sawn specimens of nine wood species at 0 and 11 % moisture content (MC) were measured using a free space method devised for reducing the multiple reflections under an electric field of millimeter waves parallel to longitudinal and tangential directions of wood, and those in radial direction were estimated using a conventional approximation theory. The dielectric parameters in the tangential and radial directions were almost identical and constantly smaller than those in the longitudinal direction. All the dielectric parameters increased with wood density and were larger at 11 than 0 % MC. The dielectric parameters in the longitudinal and transverse directions and the dielectric anisotropy between them were well fitted to the regression lines based on a dielectric mixture model composed of pores and dielectric isotropic wood substance, and a parallel capacitor and Lichtenecker’s exponential formulas were employed to represent the dielectric parameters of the mixture in the longitudinal and transverse directions, respectively. It was concluded that the dielectric anisotropy at 100 GHz is caused by the pore alignment and that the dielectric parameters are almost unaffected by anatomical structures, such as the rays. It was also confirmed that the free space method was effective for the measurement of the dielectric parameters for the flat-sawn specimens.