Monitoring of moisture content and basic specific gravity in black spruce logs using a hand-held MEMS-based near-infrared spectrometer

Abstract

Our study presents results of a test of a hand-held micro-electro-mechanical system (MEMS)-based near-infrared (NIR) spectrometer to estimate moisture content and basic specific gravity of black spruce frozen and unfrozen logs. The spectra were acquired on sapwood and heartwood as well as on tangential and transversal log sections. Partial least square regression was used to develop and validate the models that relate NIR spectral data to the log properties. Models were developed for the frozen and unfrozen logs separately (temperature-specific models) and for both kinds of logs together (generalized model). Both model types gave similar prediction accuracy and there were no temperature condition effects on the PLS model, for both moisture content and basic specific gravity estimation. This implies that the NIR spectrometer can be used whatever the log temperature conditions, even under freezing conditions. Keywords: near-infrared spectroscopy, black spruce, partial least square regression, moisture content, basic specific gravity, hand-held near-infrared spectrometer, MEMS, log, sapwood, heartwood résumé Notre étude présente le test d'un spectromètre proche infra-rouge portable basé sur un système micro-électro-mécanique (SMEM) pour mesurer la teneur en eau et la densité basale de grumes gelées et non gelées. Les spectres ont été acquis sur l'aubier et sur le duramen ainsi que sur les sections tangentielles et transversales de la grume. La régression des moindres carrés partiels (PLS) est utilisée pour calibrer et valider les modèles d' estimation des propriétés de la grume à partir des données proche infra-rouge. Des modèles ont été développés pour les grumes gelées et non gelées, séparément (modèles spécifiques à une température donnée) ainsi que pour les deux types de grumes ensemble (modèles généralisés). Les deux types de modèles ont donné des précisions d' estimation semblables et il n'y a pas eu d' effets des conditions de température sur les prédictions des modèles PLS. Ceci implique que les mesures du spectromètre proche infra-rouge portable peuvent être utilisées quel que soient les conditions de température des grumes, même avec des températures en-dessous du point de congélation.Mots-clés : spectroscopie proche infra-rouge, épinette noire, régression PLS, teneur en eau, densité basale, spectromètre portable, MEMS, grume, aubier, duramen

Determination of moisture content and basic specific gravity ofPopulus tremuloides(Michx.) andPopulus balsamifera(L.) logs using a portable near-infrared spectrometer

“…Indeed, temperature variations produce changes in band shapes by changing the weaker inter-and intra-molecular forces (Wulfert et al 2000).The average shift of the maximum absorbance peak (around 1450 nm) in our data is 8.6 nm for the sapwood and 25.8 nm for the heartwood. Hans et al (2013) reported an opposite tendency for the shift between thawed and frozen wood spectra of black spruce sapwood and heartwood with values of 17.2 and 8.6 nm, respectively. Using FT-NIR spectra acquired from Norway spruce (Picea abies (L.) H. Karst) planed square samples, Thygesen and Lundqvist (2000a) reported a shift of 39 nm for the sapwood and 19 nm for the heartwood when the temperature decreased from 20a°C to −15°C.…”

Challenges in the use of Near Infrared Spectroscopy for improving wood quality: A review

“…They showed MC predictions for conditioned samples within 2-3% of measured values in the 0-30% MC range. Hans et al (2012) applied NIR spectroscopy for estimating MC of frozen and unfrozen black spruce logs. They acquired spectra on sapwood and heartwood as well on tangential and transversal log sections and developed predictive models for the frozen and unfrozen logs separately (temperature-specific models) and for both kinds of logs together (generalized model).…”

“…Their study demonstrated that the wavelength range and resolution of the portable instruments are adequate showing promising results and pointing out that the properties (wavelength range and resolution) of the portable instruments are suitable for the prediction of Kraft pulp yield and cellulose content. Hans et al (2012) tested a hand-held microelectro-mechanical system (MEMS) based on NIR spectrometer to estimate moisture content and basic specific gravity of frozen and unfrozen black spruce logs. They stated that this type of spectrometer apparatus can be used independently of temperature and freezing conditions.…”

A review of near-infrared spectroscopy for monitoring moisture content and density of solid wood

“…Knots present a higher density than normal wood. Depending on the studies and methods used, knots can be included in the models (Mora et al 2011a) or not (Hans et al 2012). Decay is a major matter of concern in the wood industry because it reduces wood strength and is particularly difficult to detect.…”

“…The second solution is to build a generalized model based on spectra collected for all the temperatures. Hans et al (2012) reported that PLS models developed for predicting moisture content and density for frozen and unfrozen logs of black spruce (Picea mariana [Mill.] BSP) using NIR spectra gave similar prediction accuracy with R 2 of 0.91, 0.84 and 0.89, respectively, for unfrozen, frozen logs and both types of logs.…”