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A new method for nondestructive evaluation of solid wood moisture content based on dual-energy X-ray absorptiometry

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Abstract

This paper presents a new method to determine the moisture content of solid wood based on the principle of dual-energy X-ray absorptiometry. The study investigates the theoretical relationship between X-ray wavelength and mass attenuation coefficients of wood, water, and reference substance. In accordance with this relationship, a theoretically obtained equation is proposed to calculate the moisture content in wood. The proposed equation is compared to experimental results using small blocks of sugi wood, which showed that the change in mass attenuation coefficient of wood with X-ray tube voltage increased with increasing moisture content as expected from the theoretical equation. A regression equation for moisture content estimation was determined based on the experimental results, and the standard error of estimate in the 0–120 % dry-basis moisture content range using the regression equation was determined to be 21.9 % with the most appropriate pair of tube voltages, 15 and 40 kVp. The accuracy of the method will be improved by reducing the duration of X-ray radiography and by increasing the disparity between paired tube voltages. This method has the potential to determine moisture content of solid wood using X-ray without oven-drying or assuming oven-dry density.

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Abbreviations

d :

Sample thickness in the X-ray direction, cm

d w :

Thickness of the wood sample in the X-ray direction, cm

d p :

PMMA-equivalent thickness, cm

d p1 :

PMMA-equivalent thickness for a primary X-ray beam, cm

d p2 :

PMMA-equivalent thickness for a secondary X-ray beam, cm

\( \bar{d}_{\text{p}} \) :

Average PMMA-equivalent thickness, cm

\( \bar{d}_{\text{p1}} \) :

Average PMMA-equivalent thickness for a primary X-ray beam, cm

\( \bar{d}_{\text{p2}} \) :

Average PMMA-equivalent thickness for a secondary X-ray beam, cm

e w :

Measurement error in wet-basis moisture content, %

e m :

Measurement error in dry-basis moisture content, %

I :

Transmitted photon intensity of an X-ray beam, s−1

I 0 :

Incident photon intensity of an X-ray beam, s−1

M :

Dry-basis moisture content of a wood sample, %

M e :

Estimated dry-basis moisture content of a wood sample, %

w i :

Proportion of ith element by mass

W :

Wet-basis moisture content of a wood sample, %

W e :

Estimated wet-basis moisture content of a wood sample, %

ρ :

Sample density, g/cm3

ρ w :

Density of a wood sample, g/cm3

ρ p :

Density of the reference wedge made of PMMA, g/cm3

λ :

Linear attenuation coefficient, cm−1

μ :

Mass attenuation coefficient, cm2/g

μ i :

Mass attenuation coefficient of ith element, cm2/g

μ H :

Mass attenuation coefficient of hydrogen, cm2/g

μ C :

Mass attenuation coefficient of carbon, cm2/g

μ O :

Mass attenuation coefficient of oxygen, cm2/g

μ m :

Mass attenuation coefficient of moisture, cm2/g

μ m1 :

Mass attenuation coefficient of moisture for a primary X-ray beam, cm2/g

μ m2 :

Mass attenuation coefficient of moisture for a secondary X-ray beam, cm2/g

μ p :

Mass attenuation coefficient of PMMA, cm2/g

μ p1 :

Mass attenuation coefficient of PMMA for a primary X-ray beam, cm2/g

μ p2 :

Mass attenuation coefficient of PMMA for a secondary X-ray beam, cm2/g

μ s :

Mass attenuation coefficient of wood substance, cm2/g

μ s1 :

Mass attenuation coefficient of wood substance for a primary X-ray beam, cm2/g

μ s2 :

Mass attenuation coefficient of wood substance for a secondary X-ray beam, cm2/g

μ w :

Mass attenuation coefficient of a wood sample, cm2/g

μ w1 :

Mass attenuation coefficient of a wood sample for a primary X-ray beam, cm2/g

μ w2 :

Mass attenuation coefficient of a wood sample for a secondary X-ray beam, cm2/g

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Acknowledgments

This work was supported by JSPS KAKENHI Grant Number 24780170.

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Authors and Affiliations

  1. Graduate School of Agriculture, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8529, Japan

    Takashi Tanaka

  2. Institute of Wood Technology, Akita Prefectural University, Kaieizaka 11-1, Noshiro, Akita, 016-0876, Japan

    Yasuo Kawai

Authors
  1. Takashi Tanaka
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  2. Yasuo Kawai
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Correspondence to Takashi Tanaka.

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Tanaka, T., Kawai, Y. A new method for nondestructive evaluation of solid wood moisture content based on dual-energy X-ray absorptiometry. Wood Sci Technol 47, 1213–1229 (2013). https://doi.org/10.1007/s00226-013-0569-0

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