Abstract The moisture diffusion process in balsa wood was monitored using the terahertz time-domain spectroscopy (THz-TDS) technique. The reflective THz signals were measured during the drying and the absorption phase of the moisture in the balsa wood. Measurements were conducted along the direction of the wood grain (longitudinal) and perpendicular to the direction of the wood grain (tangential). From the results, the relationship between the pulse intensity of the THz signal and moisture content was quantitatively investigated. Further, an image of the moisture concentration gradient was constructed through the THz intensity analysis. From the study, it was possible to monitor the variation of diffusion coefficient depending on the moisture content gradient from the THz measurement. Moreover, using the measured concentration gradient, the moisture diffusion coefficient could be derived regardless of complicated boundary conditions of diffusion. Consequently, the degree of moisture diffusion can be successfully measured using the THz-TDS technique. This can then be utilized for the determination of the moisture diffusion coefficient in various industrial structures.

中文翻译：

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太赫兹时域光谱对木材水分扩散过程的原位监测

摘要 使用太赫兹时域光谱 (THz-TDS) 技术监测轻木中的水分扩散过程。反射太赫兹信号是在轻木中水分的干燥和吸收阶段测量的。沿着木纹方向（纵向）和垂直于木纹方向（切线）进行测量。从结果中，定量研究了太赫兹信号的脉冲强度与水分含量之间的关系。此外，通过太赫兹强度分析构建了水分浓度梯度的图像。从研究中，可以根据太赫兹测量的水分含量梯度监测扩散系数的变化。此外，使用测量的浓度梯度，无论扩散的复杂边界条件如何，都可以导出水分扩散系数。因此，可以使用 THz-TDS 技术成功测量水分扩散程度。然后可以将其用于确定各种工业结构中的水分扩散系数。