研究者詳細 - 土川　覚

論文 - 土川　覚

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Simultaneous detection of density, moisture content and fiber direction of wood by THz time-domain spectroscopy 査読有り Open Access

Kashima, M; Tsuchikawa, S; Inagakr, T

JOURNAL OF WOOD SCIENCE 66 巻 ( 1 ) 2020年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Wood Science

In the wood product-manufacturing process, the physical properties of wood must be monitored. The terahertz (THz) radiation has a high potential for sensing and imaging wood with a good spatial resolution. This study demonstrates the simultaneous prediction of the density, moisture content, and fiber direction of wood, which are important in determining the wood quality, using THz time-domain spectroscopy. We measured the spectra of 12 kinds of wood at various moisture contents while rotating the sample against the THz wave polarization. The fiber direction was predicted by observing the birefringence, which is the optical property of a material, in which the refractive index depends on the polarization direction. The density and the moisture content were predicted by multiple linear regression using the refractive indices and absorption coefficients obtained from the THz measurement. In a series of THz measurements, we successfully identified the wood fiber direction with an R2 of 0.90 and a root mean square error (RMSE) of 16.51° (total measured range = 0–170°), the density with an R2 of 0.97 and an RMSE of 0.022 (total measured range = 0.25–0.67 g/cm3), and the moisture content with an R2 of 0.78 and an RMSE of 4.06 (total measured range = 0.00–30.98%).

DOI： 10.1186/s10086-020-01874-3

Steaming-caused chemical changes of sugi (Cryptomeria japonica) wood monitored by NIR spectroscopy 査読有り Open Access

Mahdiyanti S.H., Tsuchikawa S., Mitsui K., Tolvaj L.

Asian Journal of Forestry 4 巻 ( 1 ) 頁： 6 - 9 2020年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Asian Journal of Forestry

Mahdiyanti SH, Tsuchikawa S, Mitsui K, Tolvaj L. 2020. Steaming-caused chemical changes of sugi (Cryptomeria japonica) wood monitored by NIR spectroscopy. Asian J For 4: 6-9. Steaming is a common method to change the color of wood to enhance attractiveness. This study aimed to investigate time-dependence of chemical changes of sugi (Cryptomeria japonica D. Don) wood steamed with temperature of 90 and 110°C and monitored up to 20 days using NIR spectroscopy. The difference spectrum method was applied to find the absorption increases and decreases. Before the subtraction, the spectra were normalized to one unit at 1739 nm to eliminate the parallel shift of the spectra. The results showed that steam-induced chemical changes in the wavelength range of 1300-2100 nm were related to the absorption of water and the absorption of extractives, especially phenolic contents. These chemical changes were suspected to be strongly related to color changes in steamed wood. Longer duration of steaming caused phenolic compounds to change into similar contents in all wood tissues, which cause their color to change more uniformly. Steaming caused a water bounding capacity loss of the cell wall. This change was much faster at 110°C than at 90°C.

DOI： 10.13057/asianjfor/r040102

Cognitive spectroscopy for wood species identification: Near infrared hyperspectral imaging combined with convolutional neural networks

Kanayama H.

Analyst 144 巻 ( 21 ) 頁： 6438 - 6446 2019年11月

Analysis of wood thermal degradation using 2D correlation of near infrared and visible-light spectroscopy 査読有り

Mahdiyanti, SH; Inagaki, T; Tsuchikawa, S

JOURNAL OF NEAR INFRARED SPECTROSCOPY 27 巻 ( 5 ) 頁： 354 - 369 2019年10月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Near Infrared Spectroscopy

Wood changes its properties, especially color, as a result of thermal degradation. In this study, change in wood properties due to thermal degradation have been studied using the nondestructive test methods of near infrared spectroscopy, CIELAB color measurement, visible-light spectroscopy, and Arrhenius time–temperature superposition. Arrhenius time–temperature superposition allowed analysis of near infrared and visible-light spectra, and color parameters to predict thermal degradation and color change of wood at 120–180℃ for 6 min to nine months duration. Two-dimensional correlation spectroscopy for the complementary analysis of near infrared and visible-light spectroscopy was applied to investigate chemical changes during wood thermal degradation that cause the observed color change. Visible-light spectroscopy with CIELAB color measurement was used to obtain information on color changes, and near infrared spectroscopy was applied in the measurement of chemical changes during thermal degradation. Changes in spectral intensities in 2D correlation spectroscopy indicated that different chemical components are responsible for color change during heat treatment and accelerated aging of wood. With dry-thermal treatment, the hemicellulose content decreased following a color change, whereas cellulose and lignin/extractives decreased with hygro-thermal treatment.

DOI： 10.1177/0967033519863878

Three-dimensional grain angle measurement of softwood (Hinoki cypress) using near infrared spatially and spectrally resolved imaging (NIR-SSRI) 査読有り

Ma, T; Inagaki, T; Tsuchikawa, S

HOLZFORSCHUNG 73 巻 ( 9 ) 頁： 817 - 826 2019年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Holzforschung

As the strength of wood is greatly affected by its three-dimensional (3D) grain angles (the dive angle and the surface angle), the wood industry today requires automatic, rapid, and robust measurement techniques for measuring them simultaneously. In the present study, a near infrared spatially and spectrally resolved imaging (NIR-SSRI) system was designed in a line scan model, mainly including an NIR hyperspectral imaging camera and a halogen spotlight source (Ø 1 mm). Spatially resolved diffuse reflectance images at three target wavelengths (1002 nm, 1217 nm, and 1413 nm) were obtained from Hinoki cypress [Chamaecyparis obtusa (Siebold & Zucc.) Endl.] samples at various (0°, 3°, 6°, ⋯ 45°) dive angles and surface angles (0°, 3°, 6°, ⋯ 45°). The scattering patterns caused by the "tracheid effect" were almost elliptical. Subsequently, nonlinear least squares fitting was used to determine their eccentricities (e) and rotation angles (θ). The e values at each selected wavelength were highly correlated with the dive angle reference values; and the global identification model developed using Gaussian process regression (GPR) under five-fold cross-validation (CV) reached a determination coefficient (r2) of 0.98 with a root mean square error (RMSE) of 2.2°. On the other hand, local surface angle identification models developed using linear regression analysis achieved determination coefficients higher than 0.90 on r2 and an RMSE of CV lower than 3.8° when the dive angle was lower than 30°.

DOI： 10.1515/hf-2018-0273

Determination of Dielectric Function of Water in THz Region in Wood Cell Wall Result in an Accurate Prediction of Moisture Content 査読有り

Wang, H; Inagaki, T; Hartley, ID; Tsuchikawa, S; Reid, M

JOURNAL OF INFRARED MILLIMETER AND TERAHERTZ WAVES 40 巻 ( 6 ) 頁： 673 - 687 2019年6月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Infrared, Millimeter, and Terahertz Waves

This report follows up previous work that presented a model for the simultaneous detection of moisture content and density of wood using Terahertz time-domain spectroscopy. A significant improvement in the prediction accuracy of the model is demonstrated by including a moisture content-dependent dielectric function for the water within the wood samples. Justification for using the dielectric function is presented, the prediction accuracy is quantified, and the results compared with prior work.

DOI： 10.1007/s10762-019-00594-0

A new approach based on a combination of capacitance and near-infrared spectroscopy for estimating the moisture content of timber 査読有り

Tham, VTH; Inagaki, T; Tsuchikawa, S

WOOD SCIENCE AND TECHNOLOGY 53 巻 ( 3 ) 頁： 579 - 599 2019年5月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Wood Science and Technology

The moisture content (MC) of wood influences its material properties. Determination of MC is essential in both the research and manufacturing fields. This study examined a nondestructive method for estimating MC rapidly and effectively. A capacitance sensor and a near-infrared (NIR) spectrometer were used to measure the MC of Japanese cedar and Japanese cypress timber. High-frequency capacitance (20 MHz) and NIR spectral absorption (908–1676 nm) data were collected for cross section and tangential section, as well as for the whole-sample average, in two MC ranges: from the green to the fiber saturation point (FSP) and from FSP to air-dried state. The results indicated that when standard error of prediction (SEP) is compared, the performance in [FSP to air-dried state] was better; when coefficient of determination in cross-validation (Rval2) and residual predictive deviation in cross-validation (RPD val ) were compared, the performance in [Green to FSP] was better. Statistical analysis was performed using multiple linear regression and partial least squares. Combining capacitance and NIR absorbance at two wavelengths (Capacitance + NIR-MLR calibration) from the green to FSP was the best calibration yielding the most promising results: Rval2 = 0.96, SEP = 5.20% and RPD val = 4.97 on the cross section of samples. The results were higher than those of other calibrations in R 2 and SEP and RPD values. The NIR-PLS calibration performed better than others with quite good R 2 , lower SEP and higher RPD in the MC range from FSP to air-dried state. The first calibration using only capacitance of wood was good in the first range of MC, but it is not good in the second range (R 2 under 0.5). Depending on the MC range, the performance of each calibration was different. In both MC ranges, the results on the cross section were higher than on the tangential section due to the anisotropic characteristics of wood material. From Capacitance + NIR-MLR calibration, the predicted models were developed using multiple linear regression and logarithmic regression. Results suggest the possibility of developing a new portable device combining a capacitance sensor and NIR spectroscopy to accurately predict the MC of wood.

DOI： 10.1007/s00226-019-01077-0

Rapid identification of wood species by near-infrared spatially resolved spectroscopy (NIR-SRS) based on hyperspectral imaging (HSI) 査読有り

Ma T.

Holzforschung 73 巻 ( 4 ) 頁： 323 - 330 2019年4月

Near infrared estimation of concentration of ginsenosides in Asian ginseng 査読有り

Inagaki, T; Katayama, N; Cho, RK; Chen, XJ; Tsuchikawa, S

JOURNAL OF NEAR INFRARED SPECTROSCOPY 27 巻 ( 2 ) 頁： 115 - 122 2019年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Near Infrared Spectroscopy

In this study, the feasibility of near infrared reflectance spectroscopy for the quality evaluation of the main bioactive compounds, ginsenosides, in Panax ginseng was examined. Second derivative NIR spectra of standard reagents of ginsenoside Rg1, Re, Rb1, Rc, Rb2 and Rd were used for analysis. Characteristic bands were observed at around 5250 cm−1 in the spectra of ginsenoside Rg1 group (including Rg1 and Re); however, this was not to be observed on the spectra of ginsenoside Rb1 group (including Rb1, Rc, Rb2 and Rd). PLS regression models were constructed of air-dry ginseng powder samples and ginsenoside content in ginsengs was determined by HPLC methods. The calibration models covered various types of ginseng (white ginseng, red ginseng and bleached ginseng) from various cultivated areas (Japan, China and Korea) and were well established for each kind of ginsenoside. It was shown that NIR spectroscopy can be used for the accurate prediction of ginsenoside.

DOI： 10.1177/0967033518814851

Effect of knots and holes on the modulus of elasticity prediction and mapping of sugi (<i>Cryptomeria japonica</i>) veneer using near-infrared hyperspectral imaging (NIR-HSI) 査読有り Open Access

Sofianto, IA; Inagaki, T; Ma, T; Tsuchikawa, S

HOLZFORSCHUNG 73 巻 ( 3 ) 頁： 259 - 268 2019年3月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Holzforschung

Naturally occurring knots reduce the mechanical strength of wood. Veneers from sugi (Cryptomeria japonica) served as research material to study the effect of knots and holes. Veneer samples were first subjected to a three-point bending test to obtain measured modulus of elasticity (MOE) values. Then, near-infrared (NIR) hyperspectral imaging (HSI) was used to construct a prediction model and map the predicted MOE values. This is the first attempt for MOE prediction from the entire veneer surface based on NIR-HSI technology, while the mathematical part relies on chemometrics and cross-validation partial least squares regression (CV-PLSR). Maps of MOE prediction values could distinguish between latewood (LW) and earlywood (EW), as well as between a sound knot and a dead knot.

DOI： 10.1515/hf-2018-0060

DETERMINATION OF CAROTENOIDS AND DOBI CONTENT IN CRUDE PALM OIL BY SPECTROSCOPY TECHNIQUES: COMPARISON OF RAMAN AND FT-NIR SPECTROSCOPY 査読有り Open Access

Nokkaew Rayakorn, Punsuvon Vittaya, Inagaki Tetsuya, Tsuchikawa Satoru

INTERNATIONAL JOURNAL OF GEOMATE 16 巻 ( 55 ) 頁： 92 - 98 2019年3月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：International Journal of GEOMATE

Crude palm oil (CPO) is a rich source of carotenoids which are a precursor of vitamin A as an important antioxidant. Carotenoids and Deterioration Of Bleachability Index (DOBI) are important factors to indicated quality of CPO. The conventional method for DOBI and carotenoids determination use UV-Vis spectrophotometry and HPLC, respectively which methods use solvents and spend time for analysis. This research interests Raman and FT-NIR spectroscopy for carotenoids and DOBI determination due to those techniques are an alternative technique for rapid measurement, non-destruction of material, and environmental suitability. The results indicated that Raman is better for determination than FT-NIR spectrometry. In Raman analysis, multiplicative scatter correction (MSC) and standard normal variate (SNV) treated methods were the best models for carotenoids and DOBI, respectively. The bands of carotenoids were at 1,100 and 1,500 cm-1 wavenumber. Validation on carotenoids produced 0.94 of correlation coefficient (R), 0.88 of coefficient of determination (R2), 40.65 ppm of root mean square error of prediction (RMSEP) and 3.25 of the ratio of standard error of prediction to standard deviation (RPD). The validation of DOBI produced 0.76 of R, 0.57 of R2, 0.31 of RMSEP, 1.92 of RPD of 1.92. The limitation of carotenoids and DOBI determination using FT-NIR is having sufficient concentration of carotenoids for analysis. In addition, data for various samples regarding location, season, and oil palm species are important to build models for precise prediction.

DOI： 10.21660/2019.55.4813

Non-destructive evaluation of wood stiffness and fiber coarseness, derived from SilviScan data, via near infrared hyperspectral imaging 査読有り

Ma, T; Inagaki, T; Tsuchikawa, S

JOURNAL OF NEAR INFRARED SPECTROSCOPY 26 巻 ( 6 ) 頁： 398 - 405 2018年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Near Infrared Spectroscopy

Near infrared hyperspectral imaging combined with partial least squares regression analysis was used to evaluate wood stiffness (modulus of elasticity) and fiber coarseness. Five samples with normal wood and compression wood collected from two Japanese Cedar (Cryptomeria japonica) trees were analyzed. To achieve high reliability of the prediction values, a SilviScan system (X-ray densitometry, X-ray diffractometry, and optical microscopy) with the high spatial resolution was used for measuring reference data. The measurement interval for modulus of elasticity and fiber coarseness was 1µm and 25 µmm, respectively. After spectral pre-treatment and key wavelengths selection, partial least squares analysis was applied to calibrate near infrared data to reference values. The determination coefficient (RCV2) of modulus of elasticity was 0.66 with a root mean square error of cross validation (RMSECV) of 1.80 GPa. For the constructed fiber coarseness calibration model, RCV2 and RMSECV were 0.62 and 35.02 µmm/g, respectively. Finally, modulus of elasticity and fiber coarseness mapping results show detailed information (156 µmm/pixel) at the grown ring level. The differences among earlywood, latewood, and compression wood were all well identifiable.

DOI： 10.1177/0967033518808053

NIR estimation of concentration of ginsenosides in Asian ginseng 査読有り

Inagaki, T.; Katayama, N.; Cho, R.; Chen, X.; Tsuchikawa S.

Journal of Near Infrared Spectroscopy 2018年12月

Inspection of Microfibril Angle of Sugi Wood by THz-TDS 査読有り

Wang H, Tsuchikawa S, Inagaki T

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2018-September 巻 2018年10月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz

Wood as a biological material has large differences in individual properties, and terahertz time-domain spectroscopy (THz-TDS) provide a new possibility for the wood products industry since THz exhibits high transparency to wood with big birefringence and diattenuation. By using the complex refractive index and absorption coefficient, THz is excepted to estimate important properties such as fiber orientation, microfibril angle (MFA) etc. simultaneously. In this study, sugi was used as sample because of its simple structure. Density and moisture content were predicted by using the real part of complex refractive index combined with absorption coefficient and showed a high correlation between measured and predicted values, prediction of MFA is still an ongoing mission.

DOI： 10.1109/IRMMW-THz.2018.8510303

Quality Evaluation of Engineered Wood by THz-TDS 査読有り

Kashima M, Tsuchikawa S, Inagaki T

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2018-September 巻 2018年10月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz

This study attempts simultaneous prediction of grain angle, density and moisture content by THz time domain spectroscopy (THz-TDS) which has sufficient spatial resolution and transparency for wood. Terahertz waves transmitted through wood contain information on moisture content, density, grain angle and crystallinity of the sample. In this study, we measured spectra of 14 kinds of wood (5 soft wood, 9 hard woods) at various moisture contents and air-dried douglas fir while rotating the sample against the polarization of the terahertz wave. It was shown that the fiber orientation, density and moisture content of wood can be predicted simultaneously from the calculated complex permittivity.

DOI： 10.1109/IRMMW-THz.2018.8510155

Optical characteristics of Douglas fir at various densities, grain directions and thicknesses investigated by near-infrared spatially resolved spectroscopy (NIR-SRS) 査読有り

Ma, T; Schajer, G; Inagaki, T; Pirouz, Z; Tsuchikawa, S

HOLZFORSCHUNG 72 巻 ( 9 ) 頁： 789 - 796 2018年9月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Holzforschung

A near-infrared spatially resolved spectroscopy (NIR-SRS) system, also called the hyperspectral imaging system, was applied in a line scanning model combined with a concentrated halogen light source (Ø 1 mm), and spatially resolved reflectance images of Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] wood were obtained. The samples with various densities, grain directions and thicknesses were observed in the NIR range of 1000-1600 nm. Then, a nonlinear curve-fitting algorithm was applied based on the steady-state diffusion theory model to estimate the absorption coefficient (μa), and reduced scattering coefficients (μ′s μ) both parallel and perpendicular to the grain direction at each measurement position. The absorption scattering coefficients at 1457 nm and two kinds of reduced scattering coefficients at 1002 nm were highly correlated with wood densities measured by an X-ray densitometer. The correlation coefficients were 0.953 and 0.987 for 3 mm and 5 mm samples, respectively, while three optical profiles were combined. It can be concluded that NIR-SRS is a fast and simple method for measuring the optical characteristics of softwood, although it has a non-homogeneous cellular structure. Sub-surface density and grain direction could be predicted with satisfactory accuracy based on a few key wavelengths without relying on multivariate statistical analysis.

DOI： 10.1515/hf-2017-0213

Determination of physical and chemical properties and degradation of archeological Japanese cypress wood from the Tohyamago area using near-infrared spectroscopy 査読有り Open Access

Inagaki, T; Yonenobu, H; Asanuma, Y; Tsuchikawa, S

JOURNAL OF WOOD SCIENCE 64 巻 ( 4 ) 頁： 347 - 355 2018年8月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Wood Science

Here, we evaluated the application of near-infrared (NIR) spectroscopy for estimating the degradation level of archeological wood samples from the Tohyamago area, the dendrochronological ages of which were also determined. The wood samples were radially cut from three logs obtained from the Tohyamago area. NIR reflectance spectra were measured from the tangential faces of air- and oven-dried wood samples using a Fourier transform NIR spectrophotometer. The second derivative spectra within the wavenumber range of 6400–5200 cm−1, in which the effect of moisture content in wood is suspected to be insignificant, showed a characteristic behavior with age. By comparing the second derivative spectral change in our wood samples with that in wood degraded by aging, thermal treatment, fungal attack, and lightning reported in the literature, we found that the second derivative spectra of wood samples from one log was similar to those of wood degraded by hygro-thermal treatment, whereas those of wood samples from another log was similar to those of wood degraded by brown-rot fungi. The physical and chemical properties of archeological wood were well predicted using a combination of partial least square regression analysis and NIR spectroscopy.

DOI： 10.1007/s10086-018-1718-8

Noncontact evaluation of soluble solids content in apples by near-infrared hyperspectral imaging 査読有り

Ma, T; Li, XZ; Inagaki, T; Yang, HY; Tsuchikawa, S

JOURNAL OF FOOD ENGINEERING 224 巻頁： 53 - 61 2018年5月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Food Engineering

Near-infrared (NIR) hyperspectral imaging was used to evaluate soluble solids content (SSC) in ‘Fuji’ apples [Malus sylvestris (L.) Mill. var. domestica (Borkh. Mansf.)]. Eighty ‘Fuji’ apples were analyzed by collecting four small block samples from each one (approximately 2.0 cm × 2.0 cm × 1.5 cm). Partial least squares (PLS) regression analysis was performed to determine the relation between SSC reference data and NIR spectral data measured from each sample. The cross-validation coefficient of determination (r2) between predicted and measured SSC values is 0.89 with a root mean squared error of cross-validation (RMSECV) of 0.55%. Then, we successfully mapped SSC at a high spatial resolution (375 μm per pixel). In addition, the absorption and reduced scattering coefficients of the measured samples were determined based on a diffusion theory model. The absorption coefficients are positively correlated to the SSC values (chemical information), whereas water cored tissue content (physical information) causes a characteristic change in light scattering coefficients. The fitting results were validated by Monte Carlo simulation, and the light penetration depth in ‘Fuji’ apples was estimated to be around 0.33 cm at 1198 nm and 0.17 cm at 1450 nm, respectively.

DOI： 10.1016/j.jfoodeng.2017.12.028

Effect of cellular structure on the optical properties of wood 査読有り Open Access

Ban, M; Inagaki, T; Ma, T; Tsuchikawa, S

JOURNAL OF NEAR INFRARED SPECTROSCOPY 26 巻 ( 1 ) 頁： 53 - 60 2018年2月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Near Infrared Spectroscopy

To construct robust calibrations of wood properties by near infrared spectroscopy, one must independently evaluate the spectral contributions of light absorption and light scattering. However, the light propagation in wooden cellular structures is difficult to interpret because these structures are complex, heterogeneous, and anisotropic. This study investigates the reduced scattering coefficients of softwood and hardwood (with ring-porous or diffuse-porous vessels) at 846 nm by time-resolved spectroscopy. It also evaluates the effect of wooden cellular structure and air-dry density on the light propagation. After determining the reduced scattering coefficients, we observed cross-sectional microscopic images of the wood samples. Eighty-five percent of the variation in the reduced scattering coefficients was explainable by the air-dry density, area ratio of the cell wall, and the median pore area. Monte Carlo simulations of the light propagation through wood revealed that most of the photon transport occurs in the cell-wall substance.

DOI： 10.1177/0967033518757233

Selective assessment of duplex heat-treated wood by near-infrared spectroscopy with principal component and kinetic analyses 査読有り Open Access

Inagaki, T; Asanuma, Y; Tsuchikawa, S

JOURNAL OF WOOD SCIENCE 64 巻 ( 1 ) 頁： 6 - 15 2018年2月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Wood Science

We selectively assessed the thermal and hygrothermal treatment times of duplex heat-treated samples from the softwood hinoki cypress (Chamaecyparis obtusa) and the hardwood Japanese zelkova (Zelkova serrata) using near-infrared (NIR) spectroscopy with principal component analysis (PCA) and spectral-kinetic analysis. Wood samples from each species were thermally or hygrothermally treated at 120, 130, 150, and 180 °C, and the second-derivative spectra of these samples in the 6300–5450 cm−1 range, where moisture content has the smallest effect, were then subjected to PCA. The master curve that was calculated by kinetic analysis successfully explained changes in the first principal component (PC1) scores with thermal treatment time for all temperatures. The angles between the PC1 loadings that explained the spectral variation due to thermal and hygrothermal treatment were 79° for hinoki and 80° for zelkova. Thus, calculation of the inner product between the second-derivative spectra of duplex heat-treated wood and a loading vector that explained the spectral variation due to thermal or hygrothermal treatment allowed us to selectively assess the thermal and hygrothermal treatment times.

DOI： 10.1007/s10086-017-1670-z

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