NIR PLSR results obtained by calibration with noisy, low-precision reference values: Are the results acceptable?
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José Rodrigues
Abstract
Both spectral noise and reference method noise affect the accuracy and the precision NIR predicted values. The reference noise is often neglected, and the few reports dealing with it only consider random noise artificially added to the original sound reference data. A calibration for lignin content of maritime pine (Pinus pinaster Ait.) wood meal was developed, but due to low precision and accuracy in the reference data set, NIR partial least-squares regression (PLSR) yielded a slope of 0.51 and an intercept at 14% Klason lignin. We demonstrate with an independent data set for external validation, obtained with higher precision and accuracy, that the NIR PLSR model based on the noisy reference data led to better results. The slope of the correlation between predicted and reference values was 0.89 and the intercept was 3.9. Thus, the model performed much better than expected from the cross-validation results. The predictability can be explained by the facts that the loadings of the first principal component (PC) of the calibration and test samples are very similar and dominated by lignin-related bands, and that most of the variation in the test set can be explained by the first PC. This only explains why the Klason lignin content could be predicted with the model without giving many spectral outliers, but not the good result of the external validation. We show that the latter can be explained by the inverse calibration used for PLSR and that predicted values can be more accurate and precise than the reference values used for calibration.
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©2006 by Walter de Gruyter Berlin New York
Articles in the same Issue
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Articles in the same Issue
- Upgrading of paper-grade pulps to dissolving pulps by nitren extraction: Optimisation of extraction parameters and application to different pulps
- De-esterification and sulfonation in spruce CTMP: Effects on pulp and paper properties
- The nature of chromophores in high-extractives mechanical pulps: Western red cedar (Thuja plicata Donn) chemithermomechanical pulp (CTMP)
- On the relationship between fibre length, cellulose chain length and pulp viscosity of a softwood sulfite pulp
- The formation of aromatic end group structures in O-alkyl substituted celluloses under alkaline pulping conditions
- Kraft pulp from budworm-infested Jack pine
- Elucidation of the structure of cellulolytic enzyme lignin
- Effect of acetyl groups on enzymatic hydrolysis of cellulosic substrates
- NIR PLSR results obtained by calibration with noisy, low-precision reference values: Are the results acceptable?
- The hydration of paper studied with solid-state magnetisation-exchange 1H NMR spectroscopy
- Impact of drying temperature and pressing time factor on VOC emissions from OSB made of Scots pine
- Factors influencing timber gluability with one-part polyurethanes – studied with nine Australian timber species
- Mechanical characterisation of wood-adhesive interphase cell walls by nanoindentation
- Parameters of wood welding: A study with infrared thermography
- Polycarboxylic acids as non-formaldehyde anti-swelling agents for wood
- Influence of variation in modulus of elasticity on creep of wood during changing process of moisture
- Permeability changes in heartwood of Picea abies and Abies alba induced by incubation with Physisporinus vitreus
- Combined effect of boron compounds and heat treatments on wood properties: Boron release and decay and termite resistance
- Antioxidant activity of extracts from the bark of Chamaecyparis lawsoniana (A. Murray) Parl.
- Obituary Carlton W. Dence (1926–2006)
- Characteristics of NAEM salt-catalyzed alcohol organosolv pulping as a biorefinery
