研究者詳細 - 稲垣　哲也

論文 - 稲垣　哲也

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Terahertz time-domain spectroscopy as a novel tool for crystallographic analysis in cellulose: the potentiality of being a new standard for evaluating crystallinity 査読有り

Wang H., Tsuchikawa S., Inagaki T.

Cellulose 28 巻 ( 9 ) 頁： 5293 - 5304 2021年6月

担当区分：最終著者,　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：Cellulose

Given that terahertz (THz) radiation responds to intermolecular forces such as hydrogen bonds, THz time-domain spectroscopy (THz-TDS) has expanded possibilities in cellulose research. In this study, THz-TDS was used to investigate the crystallinity of three types of cellulose-based materials. Microcrystalline cellulose (MCC) and wood were ball milled at different times, and pseudo-wood was a mixture of MCC and lignin of different mass fractions. All the samples showed peaks at 3.04 THz in the THz mass absorption coefficient spectra. Further, the spectra from 2.79 THz to 3.32 THz were cut out and detrended by subtraction from a baseline. The integrated intensity of the detrended spectra showed a correlation with the mass fraction of lignin of the pseudo-wood samples, and ball milling time of the MCC and wood samples. The correlation was similar with the crystallinity index calculated from X-ray powder diffraction. Moreover, the original wood sample without ball milling had an integrated intensity that was about 30% that of the original MCC sample, matching with the cellulose concentration of the wood (about 30% to 40%). We normalized the integrated intensity of 2.79 THz to 3.32 THz into 1 to 0 by a min–max algorithm and proposed a new “index” for evaluating crystallinity.

DOI： 10.1007/s10570-021-03902-x

Demonstration of the applicability of visible and near-infrared spatially resolved spectroscopy for rapid and nondestructive wood classification 査読有り国際共著

Ma T., Inagaki T., Tsuchikawa S.

Holzforschung 75 巻 ( 5 ) 頁： 419 - 427 2021年5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

Although visible and near-infrared (Vis-NIR) spectroscopy can rapidly and nondestructively identify wood species, the conventional spectrometer approach relies on the aggregate light absorption due to the chemical composition of wood and light scattering originating from the physical structure of wood. Hence, much of the work in this area is still limited to further spectral pretreatments, such as baseline correction and standard normal variate to reduce the light scattering effects. However, it should be emphasized that the light scattering rather than absorption inwood is dominant, and thismust be effectively utilized to achieve highly accurate and robust wood classification. Here a novelmethod based on spatially resolved diffuse reflectance (wavelength range: 600-1000 nm) was demonstrated to classify 15 kinds of wood. A portable Vis-NIR spectral measurement system was designed according to previous simulations and experimental results. To simplify spectral data analysis (i.e., against overfitting), support vector machine (SVM) model was constructed for wood sample classification using principal component analysis (PCA) scores. The classification accuracies of 98.6% for five-fold crossvalidation and 91.2%for test set validation were achieved. This study offers enhanced classification accuracy and robustness over other conventional nondestructive approaches for such various kinds of wood and sheds light on utilizing visible and short-wave NIR light scattering for wood classification.

DOI： 10.1515/hf-2020-0074

Rapid and nondestructive evaluation of hygroscopic behavior changes of thermally modified softwood and hardwood samples using near-infrared hyperspectral imaging (NIR-HSI) 査読有り国際共著

Ma T., Schimleck L., Inagaki T., Tsuchikawa S.

Holzforschung 75 巻 ( 4 ) 頁： 345 - 357 2021年4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

The objective of this work was to provide a rapid and nondestructive imaging method for evaluating the hygroscopic behavior of thermally modified lignocellulosic materials (softwood and hardwood). The difference in the hygroscopic behavior was explained by moisture content (MC) mapping results and molecular association characteristics of absorbed water (i.e. weakly, moderately, and strongly hydrogen-bonded water molecules) with wood at various relative humidities (RH). To achieve this goal, near-infrared (NIR) spectral images in the wavelength range 1816-2130 nm (covering the combination of stretching and deformation vibrations for OH) were used to visualize MC distributions over the surface of Japanese cedar and European beech samples which had been thermally treated at different temperatures. A curve fitting method was utilized to explore changes in water-wood structure characteristics based on shifts to longer wavelength in spectral signals caused by increasing MC. The curve fitting results support the recent nuclear magnetic resonance (NMR) studies that different bound water stabilities may pool in different compartments of the wood cell wall. Furthermore, water was firmly bound to wood at low RHs and H-bonds gained mobility as the number of absorbed molecules increased. It is concluded that NIR hyperspectral imaging also has the potential to be a complementary methodology for studying the transient changes of wood-water interactions before equilibrium.

DOI： 10.1515/hf-2019-0298

Non-destructive and fast method of mapping the distribution of the soluble solids content and pH in kiwifruit using object rotation near-infrared hyperspectral imaging approach 査読有り

Ma T., Xia Y., Inagaki T., Tsuchikawa S.

Postharvest Biology and Technology 174 巻 2021年4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：Postharvest Biology and Technology

This work aimed to offer a non-destructive and fast approach to visualizing the soluble solids content (SSC) and acidity (pH) of the whole kiwifruit. Most of the visible-near-infrared spectral imaging techniques used in postharvest fruit and vegetables assessment exhibit issues related to the identification of the quality spatial distribution within intact samples, mainly due to sampling surface curvature effects. Here, a push-broom-type NIR hyperspectral imaging camera and a sample rotation stage were combined to scan entire kiwifruit surfaces. Then, key wavelengths in the range of 1002–2300 nm were extracted for constructing SSC and pH calibration models by partial least squares regression analysis. The resulting SSC prediction accuracy was sufficiently high: the coefficient of determination (R2cv) and the root mean square error (RMSEcv) of cross-validation set were 0.74 and 0.7 %, respectively. For pH, the R2cv and RMSEcv were 0.64 and 0.14, respectively. Finally, the SSC and pH 360˚mapping results surpassed earlier works in this area that they showed a distinct spatial distribution within each intact sample. It was concluded that the proposed object rotation hyperspectral imaging approach is promising for the non-destructive prediction mapping of SSC and pH in kiwifruit or other cylindrical-shaped samples.

DOI： 10.1016/j.postharvbio.2020.111440

Rapid and nondestructive evaluation of soluble solids content (SSC) and firmness in apple using Vis–NIR spatially resolved spectroscopy 査読有り国際共著

Ma T., Xia Y., Inagaki T., Tsuchikawa S.

Postharvest Biology and Technology 173 巻 2021年3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：Postharvest Biology and Technology

Visible–near infrared (Vis–NIR) spectroscopy is a rapid and nondestructive method used to characterize organic compounds in postharvest fruit and vegetable assessment. However, developing robust calibration models is a challenge as conventional spectrometers collect only the cumulative effects of light absorption and scattering. In this study, a multifiber-based Vis–NIR spatially resolved spectra measurement system was designed for simultaneous evaluation of soluble solid content (SSC) and firmness in apple. Thirty silica fibers separated into five groups at 1, 2, 3, 4, and 5 mm away from the light illumination point and connected to a cost-effective Vis–NIR hyperspectral imaging camera were used to acquire spectral data with an improved signal-to-noise ratio (S/N) by a two-step signal averaging process (i.e., 30 camera pixels per fiber and six optical fibers per group). Reflectance ratio spectra were then calculated by dividing the diffusely reflected light intensity detected at distance d +△ by that detected at distance d to realize a light reference-free approach. Finally, the useful explanatory variables were selected by competitive adaptive reweighted sampling (CARS) to construct individual calibration models for various regions. The coefficients of determination (Rcal2) and the root mean square errors (RMSEcal) of the best-performing calibration models were approximately 0.97 and 0.20 % for SSC and 0.96 and 0.37 N for firmness, respectively. Furthermore, the predicted results were 0.92 and 0.35 % for SSC and 0.87 and 0.71 N for firmness. Our method offers low-cost and portable detection of SSC and firmness for postharvest fruit evaluation.

DOI： 10.1016/jpostharvbio.2020.111417

Non-destructive and fast method of mapping the distribution of the soluble solids content and pH in kiwifruit using object rotation near-infrared hyperspectral imaging approach 査読有り国際共著

T. Ma, Y. Xia, T. Inagaki, S. Tsuchikawa

Post Harvest Biology and Technology 174 巻頁： 111440 2021年2月

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

Kashima M., Tsuchikawa S., Inagaki T.

Journal of Wood Science 66 巻 ( 1 ) 2020年12月

担当区分：最終著者,　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 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

Wooden Material and Environmental Sciences 査読有り

Ma T., Tsuchikawa S., Inagaki T.

Near-Infrared Spectroscopy: Theory, Spectral Analysis, Instrumentation, and Applications 頁： 361 - 379 2020年11月

担当区分：最終著者掲載種別：論文集(書籍)内論文出版者・発行元：Near-Infrared Spectroscopy: Theory, Spectral Analysis, Instrumentation, and Applications

Near-infrared spectroscopy (NIRS) is suitable for both the qualification and quantification of organic properties associated with C-H, O-H, or N-H groups. There have been considerable efforts made toward proposing and developing various technologies and devices for the rapid and nondestructive measurement of various samples related to natural materials and environmental sciences. In this chapter, the utilizations of NIRS in the fields of wood material, soil, sediment, waste liquid, atmospheric gas detection, and archeological science will be explained through some representative studies.

DOI： 10.1007/978-981-15-8648-4_16

Time-of-Flight Spectroscopy 査読有り

Inagaki T., Tsuchikawa S.

Near-Infrared Spectroscopy: Theory, Spectral Analysis, Instrumentation, and Applications 頁： 265 - 275 2020年11月

担当区分：筆頭著者掲載種別：論文集(書籍)内論文出版者・発行元：Near-Infrared Spectroscopy: Theory, Spectral Analysis, Instrumentation, and Applications

This chapter summarizes the principle and application of time-of-flight (TOF) NIR spectroscopy, which can evaluate the contribution of scattering and absorption of light in samples simultaneously. In order to construct robust calibrations for organic materials by NIR spectroscopy, it is important to evaluate and understand the spectral contribution from light absorption (absorption resulting from harmonics or overtones of the fundamental absorptions of molecular vibrations) and light scattering (mainly due to the cellular structure). In this chapter,we introduce the principle of TOF-NIR spectroscopy and some applications to agricultural, medical area, and forest products.

DOI： 10.1007/978-981-15-8648-4_11

Terahertz time-domain spectroscopy as a novel tool for crystallographic analysis in cellulose 査読有り

Wang H., Horikawa Y., Tsuchikawa S., Inagaki T.

Cellulose 27 巻 ( 17 ) 頁： 9767 - 9777 2020年11月

担当区分：最終著者,　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：Cellulose

Terahertz (THz) radiation is responsive to optical phonons in crystal lattices; therefore, THz time-domain spectroscopy (THz-TDS) has potential utility in crystallographic analysis. In this study, THz-TDS was used to investigate cellulose samples extracted from different sources with varying ratios of Iα and Iβ fractions. This is the first study to report that the absorption coefficient in the THz region of cellulose Iα and Iβ presents different characteristic absorption peaks around 2 THz. This can be used to distinguish the cellulose I allomorph, which exhibits differences in its crystalline structure. The absorption coefficient at 2.11 and 2.38 THz showed a considerable linear correlation with the Iα fraction of the cellulose samples. The absorption coefficient spectra of 1.88–3.40 THz were further detrended and separated into three Gaussian peaks. The correlations between the parameters of these separated peaks (integrated intensities, peak positions) and the crystalline structural values (d-spacing, crystalline size, crystallinity index) that calculated from the X-ray diffraction (XRD) pattern were investigated.

DOI： 10.1007/s10570-020-03508-9

Rapid and non-destructive seed viability prediction using near-infrared hyperspectral imaging coupled with a deep learning approach 査読有り

Ma T., Tsuchikawa S., Inagaki T.

Computers and Electronics in Agriculture 177 巻 2020年10月

担当区分：最終著者,　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：Computers and Electronics in Agriculture

Seeds are the basis of the agricultural food industry, greater insights into seed viability before sowing could improve storage management and field performance. In the present study, we aimed to address this issue by using highly cost-efficient near-infrared hyperspectral imaging (NIR-HSI) and a convolutional neural network (CNN) deep learning approach. An NIR-HSI camera was used because it can recognize both molecular vibration information (i.e. chemical component differences) and its spatial distribution in each seed sample; this camera is much more informative than a regular RGB digital camera. Using this technology, the emphasis of this study was firstly to provide a methodology for enhancing the interpretability of viable and non-viable seeds via principal component analysis (PCA) and support vector machine (SVM) viability classification analysis of NIR-HSI data. A CNN was then constructed to“cognize” the differences in viable and non-inviable seeds and classify them automatically. Experimental results indicate that the methodology produces a ~90% classification accuracy for both a five-fold cross-validation set and a test set of naturally aged Japanese mustard spinach seeds. Therefore, this study provides a new strategy for effective and practical seed viability prediction.

DOI： 10.1016/j.compag.2020.105683

Physical and mechanical properties of fast growing polyploid acacia hybrids (A. auriculiformis x A. mangium) from Vietnam 査読有り国際共著

Viet D.D., Ma T., Inagaki T., Kim N.T., Chi N.Q., Tsuchikawa S.

Forests 11 巻 ( 7 ) 2020年7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：Forests

Acacia plants are globally important resources in the wood industry, but particularly in Southeast Asian countries. In the present study, we compared the physical and mechanical properties of polyploid Acacia (3x and 4x) clones with those of diploid (2x) clones grown in Vietnam. We randomly selected 29 trees aged 3.8 years from different taxa for investigation. BV10 and BV16 clones represented the diploid controls; X101 and X102 were the triploid clones; and AA-4x, AM-4x, and AH-4x represented neo-tetraploid families of Acacia auriculiformis, Acacia mangium, and their hybrid clones. The following metrics were measured in each plant: stem height levels, basic density, air-dry equilibrium moisture content, modulus of rupture (MOR), modulus of elasticity (MOE), compression strength, and Young's modulus. We found that the equilibrium moisture content significantly differed among clones, and basic density varied from pith-to-bark and in an axial direction. In addition, the basic density of AA-4x was significantly higher than that of the control clones. Furthermore, the MOR of AM-4x was considerably lower than the control clones, whereas the MOE of X101 was significantly higher than the control values. The compression strength of AM-4x was significantly lower than that of the control clones, but AH-4x had a significantly higher Young's modulus. Our results suggest that polyploid Acacia hybrids have the potential to be alternative species for providing wood with improved properties to the forestry sector of Vietnam. Furthermore, the significant differences among the clones indicate that opportunities exist for selection and the improvement of wood quality via selective breeding for specific properties.

DOI： 10.3390/f11070717

Rapidly visualizing the dynamic state of free, weakly, and strongly hydrogen-bonded water with lignocellulosic material during drying by near-infrared hyperspectral imaging 査読有り

Ma T., Inagaki T., Tsuchikawa S.

Cellulose 27 巻 ( 9 ) 頁： 4857 - 4869 2020年6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：Cellulose

Real-time monitoring of the dynamic state of water molecular structure in lignocellulosic material is challenging, but important for both theoretical studies and industrial applications. In the present study, three typical wood samples which have a fundamental difference in the anatomical structure were scanned in the near-infrared spectral range, and images were acquired from wavelengths of 1002–1847 nm during drying. Then, partial least squares regression was used to determine the water content by mass, and principal component analysis was utilized to characterize the variance of NIR difference spectral data between 1340 and 1610 nm after baseline correlation for showing the distribution changing from free water to bound water during air drying. It was clarified that the PC1 loading mainly correlates with simple water content by mass, whereas the PC2 loading contains information about water–wood hydrogen structure interactions. The three loading curve peaks of PC2 could be correlated with free, weakly bound, and strongly bound water based on longer wavelength shifting. Finally, PC1 and PC2 scores were comprehensively applied to show the distribution changing from free water to bound water in each wood sample with a 62.5 μm/pixel high spatial resolution.

DOI： 10.1007/s10570-020-03117-6

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

M. Kashima, S. Tsuchikawa, T. Inagaki

Journal of Wood Science 66 巻頁： 27 2020年4月

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

Kanayama H., Ma T., Tsuchikawa S., Inagaki T.

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

担当区分：最終著者,　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：Analyst

From the viewpoint of combating illegal logging and examining wood properties, there is a contemporary demand for a wood species identification system. Several nondestructive automatic identification systems have been developed, but there is room for improvement to construct a highly reliable model. The present study proposes cognitive spectroscopy that combines near infrared hyperspectral imaging (NIR-HSI) with a deep convolutional neural network approach. We defined "cognitive spectroscopy" as a protocol that extracts features from complex spectroscopic data and presents the best results without human intervention. Overall, 120 samples representing 38 hardwood species were scanned using an NIR-HSI camera. A deep learning prediction model was built based on the principal component (PC) images obtained from the PC scores of hyperspectral images (wavelength range: 1000-2200 nm at approximately 6.2 nm interval). The results showed that the accuracy of wood species identification based on 6PC (PC1-PC6) images was 90.5%, which was considerably higher than the accuracy of 56.0% obtained with conventional visible images.

DOI： 10.1039/c9an01180c

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

Mahdiyanti S., Inagaki T., Tsuchikawa S.

Journal of Near Infrared Spectroscopy 27 巻 ( 5 ) 頁： 354 - 369 2019年10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

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

Electrode polarization effects on interfacial kinetics of ionic liquid at graphite surface: An extended lagrangian-based constant potential molecular dynamics simulation study 査読有り

Inagaki Taichi, Nagaoka Masataka

JOURNAL OF COMPUTATIONAL CHEMISTRY 40 巻 ( 24 ) 頁： 2131 - 2145 2019年9月

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 I., Tsuchikawa S., Reid M.

Journal of Infrared, Millimeter, and Terahertz Waves 40 巻 ( 6 ) 頁： 673 - 687 2019年6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 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 V.T.H., Inagaki T., Tsuchikawa S.

Wood Science and Technology 53 巻 ( 3 ) 頁： 579 - 599 2019年5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：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 (R2val) and residual predictive deviation in cross-validation (RPDval) were compared, the performance in [Green to FSP] was better. val 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: R2val= 0.96, SEP = 5.20% and RPDval = 4.97 on the cross section of samples. The results were higher than those of other calibrations in R2 and SEP and RPD values. The NIR-PLS calibration performed better than others with quite good R2, lower SEP and higher RPD in the MC range from FSP to airdried 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 (R2 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

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