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Karin Hofstetter - One of the best experts on this subject based on the ideXlab platform.
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Theory of transport processes in wood below the fiber Saturation Point. Physical background on the microscale and its macroscopic description
Holzforschung, 2011Co-Authors: Johannes Eitelberger, Staffan Svensson, Karin HofstetterAbstract:The macroscopic formulation of moisture transport in wood below the fiber Saturation Point has motivated many research efforts in the past two decades. Many experiments demonstrated the difference in steady state and transient moisture transport and the inadequacy of models derived for steady state transport when used to describe transient processes. A suitable modeling approach was found by distinguishing between the two phases of water in wood, namely bound water in the cell walls and water vapor in the lumens. Such models are capable of reproducing transient moisture transport processes, but the physical origin of the coupling between the two phases remains unclear. In this paper, the physical background on the microscale is clarified and transformed into a comprehensive macroscopic description, ending up with a dual-scale model comprising three coupled differential equations for bound water, water vapor, and internal energy, as well as a simplified microscale model for determination of the coupling term.
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prediction of transport properties of wood below the fiber Saturation Point a multiscale homogenization approach and its experimental validation part ii steady state moisture diffusion coefficient
Composites Science and Technology, 2011Co-Authors: Johannes Eitelberger, Karin HofstetterAbstract:In this publication a multiscale homogenization model for moisture transport in wood is developed and validated. The model aims at prediction of macroscopic transport properties of clear wood samples from their microstructure and the physical properties of a few microscale constituents. In the first part of this two-part paper, the theoretical background and fundamentals of the model were presented, and its specification for the estimation of macroscopic thermal conductivities was shown. In this second part the model is applied to steady state moisture diffusion below the fiber Saturation Point. The model starts on a scale of about 50 μm, where the wood cells form a honeycomb-like structure. In a first homogenization step the effective moisture transport behavior of the cell structure is determined from moisture diffusion properties of the cell walls and the (moist) air in lumens, respectively. Further homogenization steps account for the larger vessels that exist in hardwood species, the annual rings which are a succession of layers with different densities, and finally wood rays, that form pathways in the radial direction throughout the stem. The model validation rests on experiments as in the case of heat conduction: The macroscopic diffusion coefficients predicted by the multiscale homogenization model for tissue-specific composition data (input data set II) are compared to corresponding experimentally determined tissue-specific diffusion coefficients under steady state conditions (experimental data set). As for thermal conductivity, the good agreement of model predictions and test data underlines the suitability of the presented multiscale model.
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Modeling of Transient Moisture Diffusion in Wood below the Fiber Saturation Point
Defect and Diffusion Forum, 2011Co-Authors: Johannes Eitelberger, Karin HofstetterAbstract:During the last two decades the macroscopic formulation of moisture transport in wood below the fiber Saturation Point has motivated many research efforts. From experiments the difference in steady-state and transient transport processes is well known, but could not be explained in a fully physically motivated manner. In the following article, first the microstructure of wood is depicted, followed by a description of the physical background of steady-state and transient transport processes in wood, and thereon based mathematical formulations. For a correct macroscopic description of transient transport processes, three coupled differential equations have to be solved in parallel, which is done using the finite element method. The validation of the whole model by comparison of model predictions with experimentally derived values is currently in progress and will be published in near future.
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A multi-scale approach for simulation of transient moisture transport processes in wood below the fiber Saturation Point
Composites Science and Technology, 2011Co-Authors: Johannes Eitelberger, Karin Hofstetter, Sergey V. DvinskikhAbstract:Abstract This paper presents a new, physically-based model for transport processes in wood for conditions below the fiber Saturation Point. The macroscopic mathematical description of these processes involves three coupled differential equations: two mass balance laws for the bound water and the water vapor phase, and an energy balance equation. These governing equations and the corresponding boundary conditions are expressed in terms of the state variables bound water concentration, water vapor concentration, and temperature. Macroscopic material properties are estimated based on a multiscale approach in the framework of continuum micromechanics. The phase change between the two water phases and the thus resulting coupling between the differential equations cannot be suitably captured in a purely macroscopic description, therefore a microscale sub-model is presented. Numerical solutions of the model equations are derived by means of the Finite Element Method. Finally, the model is applied to prediction of moisture profiles in a wood sample under transient environmental conditions. Comparing these results with corresponding profiles obtained non-destructively by proton magnetic resonance imaging (MRI) validates the model and confirms suitability of the underlying physical assumptions.
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A comprehensive model for transient moisture transport in wood below the fiber Saturation Point: Physical background, implementation and experimental validation
International Journal of Thermal Sciences, 2011Co-Authors: Johannes Eitelberger, Karin HofstetterAbstract:During the last three decades the macroscopic formulation of moisture transport in wood below the fiber Saturation Point has motivated many research efforts. From experiments the difference in steady-state and transient transport processes is well known, but it could not be explained in a fully physically motivated manner. In this article, we aim at enhancing the current understanding and improving the mathematical description of the moisture transport process in wood. For this purpose, we first present the microstructure of wood and then describe the physical background of steady-state and transient transport processes in wood, based on which we finally derive a suitable mathematical model. For a correct macroscopic description of transient transport processes, three coupled differential equations have to be solved in parallel, which is done using the finite element method. A comparison of model predictions for the sorption behavior of wood specimens with corresponding experimentally derived values yields very promising results and confirms the suitability of the assumptions underlying the model.
Gilles Chaix - One of the best experts on this subject based on the ideXlab platform.
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Rapid prediction of shrinkage and fibre Saturation Point on teak (Tectona grandis) wood based on near-infrared spectroscopy
Annals of Forest Science, 2010Co-Authors: Adzo Dzifa Kokutse, Loïc Brancheriau, Gilles ChaixAbstract:• Dimensional stability, along with the natural durability and colour of the wood, is one of the most important characteristics of teak used as timber. However, it is very time-consuming to take measurements of this kind. For the purposes of selection for the production of improved varieties, the number of samples to be measured rapidly exceeds the capacity of a traditional laboratory. • Near-infrared spectroscopy, based on a set of reference data, is a tool enabling many of the chemical properties of wood to be predicted and the number of laboratory measurements to be reduced exponentially. The issue here is a question of checking the effectiveness of NIRS tool to build models and predict the shrinkage and fibre Saturation Point of teak wood from Togo. • The results show the possible use of NIRS to measure the dimensional stability of teak wood and that it is appropriate to choose the type of wood and type of surface to be measured by NIRS. The best prediction models for radial and tangential shrinkage and fibre Saturation Point give R 2 values of 0.72, 0.83 and 0.87 respectively with ratios of performance deviation of 1.8, 2.4 and 2.8. • Consequently, after verification on other sets of teak samples, which may or may not be included in the prediction model, NIRS can be used to predict shrinkage and fibre Saturation Point values accurately for a large number of samples, making it possible to include these characteristics in the selection criteria for classifying wood and high throughput phenotyping.
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Rapid prediction of shrinkage and fibre Saturation Point on teak (Tectona grandis) wood based on near-infrared spectroscopy
Annals of Forest Science, 2010Co-Authors: Adzo Dzifa Kokutse, Loïc Brancheriau, Gilles ChaixAbstract:• Dimensional stability, along with the natural durability and colour of the wood, is one of the most important characteristics of teak used as timber. However, it is very time-consuming to take measurements of this kind. For the purposes of selection for the production of improved varieties, the number of samples to be measured rapidly exceeds the capacity of a traditional laboratory. • Near-infrared spectroscopy, based on a set of reference data, is a tool enabling many of the chemical properties of wood to be predicted and the number of laboratory measurements to be reduced exponentially. The issue here is a question of checking the effectiveness of NIRS tool to build models and predict the shrinkage and fibre Saturation Point of teak wood from Togo. • The results show the possible use of NIRS to measure the dimensional stability of teak wood and that it is appropriate to choose the type of wood and type of surface to be measured by NIRS. The best prediction models for radial and tangential shrinkage and fibre Saturation Point give R ^2 values of 0.72, 0.83 and 0.87 respectively with ratios of performance deviation of 1.8, 2.4 and 2.8. • Consequently, after verification on other sets of teak samples, which may or may not be included in the prediction model, NIRS can be used to predict shrinkage and fibre Saturation Point values accurately for a large number of samples, making it possible to include these characteristics in the selection criteria for classifying wood and high throughput phenotyping. • La stabilité dimensionnelle avec la durabilité naturelle et la couleur du bois, est l’une des plus importantes caractéristiques pour le teck utilisé en bois d’œuvre. Néanmoins, les mesures de ce caractère sont longues et coûteuses en temps. Pour les besoins de la sélection pour la production de variétés améliorées, le nombre d’échantillons à mesurer devient vite supérieur aux capacités d’un laboratoire traditionnel. • La spectroscopie proche infrarouge, sur la base d’un jeu de données de références, est un outil qui permet de prédire de nombreuses propriétés chimiques du bois et de réduire le nombre de mesures de laboratoire de façon exponentielle. La question ici est de vérifier l’efficacité de l’outil NIRS pour construire des modèles et prédire les retraits et le Point de Saturation des fibres du bois de teck provenant de plantations du Togo. • Les résultats démontrent la possible utilisation de la SPIR pour mesurer la stabilité dimensionnelle du bois de teck et qu’il a y lieu de choisir le type de bois et le type de face que l’on mesure par SPIR. Les modèles de prédiction pour les retraits radial et tangentiel et le Point de Saturation des fibres montrent des R^2 de 0,72, 0,83, 0,87 respectivement avec des rapports d’efficacité de 1,8, 2,4 et 2,8. • En conséquence, et après vérification sur d’autres jeux d’échantillons de teck, qu’il conviendra ou non d’intégrer dans le modèle de prédiction, la SPIR permet de prédire des valeurs de retrait et de PSF avec efficacité pour un grand nombre d’échantillons rendant possible l’intégration de ces caractères dans les critères de sélection pour le classement des bois et pour le phénotypage à grande échelle.
Johannes Eitelberger - One of the best experts on this subject based on the ideXlab platform.
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Theory of transport processes in wood below the fiber Saturation Point. Physical background on the microscale and its macroscopic description
Holzforschung, 2011Co-Authors: Johannes Eitelberger, Staffan Svensson, Karin HofstetterAbstract:The macroscopic formulation of moisture transport in wood below the fiber Saturation Point has motivated many research efforts in the past two decades. Many experiments demonstrated the difference in steady state and transient moisture transport and the inadequacy of models derived for steady state transport when used to describe transient processes. A suitable modeling approach was found by distinguishing between the two phases of water in wood, namely bound water in the cell walls and water vapor in the lumens. Such models are capable of reproducing transient moisture transport processes, but the physical origin of the coupling between the two phases remains unclear. In this paper, the physical background on the microscale is clarified and transformed into a comprehensive macroscopic description, ending up with a dual-scale model comprising three coupled differential equations for bound water, water vapor, and internal energy, as well as a simplified microscale model for determination of the coupling term.
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prediction of transport properties of wood below the fiber Saturation Point a multiscale homogenization approach and its experimental validation part ii steady state moisture diffusion coefficient
Composites Science and Technology, 2011Co-Authors: Johannes Eitelberger, Karin HofstetterAbstract:In this publication a multiscale homogenization model for moisture transport in wood is developed and validated. The model aims at prediction of macroscopic transport properties of clear wood samples from their microstructure and the physical properties of a few microscale constituents. In the first part of this two-part paper, the theoretical background and fundamentals of the model were presented, and its specification for the estimation of macroscopic thermal conductivities was shown. In this second part the model is applied to steady state moisture diffusion below the fiber Saturation Point. The model starts on a scale of about 50 μm, where the wood cells form a honeycomb-like structure. In a first homogenization step the effective moisture transport behavior of the cell structure is determined from moisture diffusion properties of the cell walls and the (moist) air in lumens, respectively. Further homogenization steps account for the larger vessels that exist in hardwood species, the annual rings which are a succession of layers with different densities, and finally wood rays, that form pathways in the radial direction throughout the stem. The model validation rests on experiments as in the case of heat conduction: The macroscopic diffusion coefficients predicted by the multiscale homogenization model for tissue-specific composition data (input data set II) are compared to corresponding experimentally determined tissue-specific diffusion coefficients under steady state conditions (experimental data set). As for thermal conductivity, the good agreement of model predictions and test data underlines the suitability of the presented multiscale model.
-
Modeling of Transient Moisture Diffusion in Wood below the Fiber Saturation Point
Defect and Diffusion Forum, 2011Co-Authors: Johannes Eitelberger, Karin HofstetterAbstract:During the last two decades the macroscopic formulation of moisture transport in wood below the fiber Saturation Point has motivated many research efforts. From experiments the difference in steady-state and transient transport processes is well known, but could not be explained in a fully physically motivated manner. In the following article, first the microstructure of wood is depicted, followed by a description of the physical background of steady-state and transient transport processes in wood, and thereon based mathematical formulations. For a correct macroscopic description of transient transport processes, three coupled differential equations have to be solved in parallel, which is done using the finite element method. The validation of the whole model by comparison of model predictions with experimentally derived values is currently in progress and will be published in near future.
-
A multi-scale approach for simulation of transient moisture transport processes in wood below the fiber Saturation Point
Composites Science and Technology, 2011Co-Authors: Johannes Eitelberger, Karin Hofstetter, Sergey V. DvinskikhAbstract:Abstract This paper presents a new, physically-based model for transport processes in wood for conditions below the fiber Saturation Point. The macroscopic mathematical description of these processes involves three coupled differential equations: two mass balance laws for the bound water and the water vapor phase, and an energy balance equation. These governing equations and the corresponding boundary conditions are expressed in terms of the state variables bound water concentration, water vapor concentration, and temperature. Macroscopic material properties are estimated based on a multiscale approach in the framework of continuum micromechanics. The phase change between the two water phases and the thus resulting coupling between the differential equations cannot be suitably captured in a purely macroscopic description, therefore a microscale sub-model is presented. Numerical solutions of the model equations are derived by means of the Finite Element Method. Finally, the model is applied to prediction of moisture profiles in a wood sample under transient environmental conditions. Comparing these results with corresponding profiles obtained non-destructively by proton magnetic resonance imaging (MRI) validates the model and confirms suitability of the underlying physical assumptions.
-
A comprehensive model for transient moisture transport in wood below the fiber Saturation Point: Physical background, implementation and experimental validation
International Journal of Thermal Sciences, 2011Co-Authors: Johannes Eitelberger, Karin HofstetterAbstract:During the last three decades the macroscopic formulation of moisture transport in wood below the fiber Saturation Point has motivated many research efforts. From experiments the difference in steady-state and transient transport processes is well known, but it could not be explained in a fully physically motivated manner. In this article, we aim at enhancing the current understanding and improving the mathematical description of the moisture transport process in wood. For this purpose, we first present the microstructure of wood and then describe the physical background of steady-state and transient transport processes in wood, based on which we finally derive a suitable mathematical model. For a correct macroscopic description of transient transport processes, three coupled differential equations have to be solved in parallel, which is done using the finite element method. A comparison of model predictions for the sorption behavior of wood specimens with corresponding experimentally derived values yields very promising results and confirms the suitability of the assumptions underlying the model.
Adzo Dzifa Kokutse - One of the best experts on this subject based on the ideXlab platform.
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Rapid prediction of shrinkage and fibre Saturation Point on teak (Tectona grandis) wood based on near-infrared spectroscopy
Annals of Forest Science, 2010Co-Authors: Adzo Dzifa Kokutse, Loïc Brancheriau, Gilles ChaixAbstract:• Dimensional stability, along with the natural durability and colour of the wood, is one of the most important characteristics of teak used as timber. However, it is very time-consuming to take measurements of this kind. For the purposes of selection for the production of improved varieties, the number of samples to be measured rapidly exceeds the capacity of a traditional laboratory. • Near-infrared spectroscopy, based on a set of reference data, is a tool enabling many of the chemical properties of wood to be predicted and the number of laboratory measurements to be reduced exponentially. The issue here is a question of checking the effectiveness of NIRS tool to build models and predict the shrinkage and fibre Saturation Point of teak wood from Togo. • The results show the possible use of NIRS to measure the dimensional stability of teak wood and that it is appropriate to choose the type of wood and type of surface to be measured by NIRS. The best prediction models for radial and tangential shrinkage and fibre Saturation Point give R 2 values of 0.72, 0.83 and 0.87 respectively with ratios of performance deviation of 1.8, 2.4 and 2.8. • Consequently, after verification on other sets of teak samples, which may or may not be included in the prediction model, NIRS can be used to predict shrinkage and fibre Saturation Point values accurately for a large number of samples, making it possible to include these characteristics in the selection criteria for classifying wood and high throughput phenotyping.
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Rapid prediction of shrinkage and fibre Saturation Point on teak (Tectona grandis) wood based on near-infrared spectroscopy
Annals of Forest Science, 2010Co-Authors: Adzo Dzifa Kokutse, Loïc Brancheriau, Gilles ChaixAbstract:• Dimensional stability, along with the natural durability and colour of the wood, is one of the most important characteristics of teak used as timber. However, it is very time-consuming to take measurements of this kind. For the purposes of selection for the production of improved varieties, the number of samples to be measured rapidly exceeds the capacity of a traditional laboratory. • Near-infrared spectroscopy, based on a set of reference data, is a tool enabling many of the chemical properties of wood to be predicted and the number of laboratory measurements to be reduced exponentially. The issue here is a question of checking the effectiveness of NIRS tool to build models and predict the shrinkage and fibre Saturation Point of teak wood from Togo. • The results show the possible use of NIRS to measure the dimensional stability of teak wood and that it is appropriate to choose the type of wood and type of surface to be measured by NIRS. The best prediction models for radial and tangential shrinkage and fibre Saturation Point give R ^2 values of 0.72, 0.83 and 0.87 respectively with ratios of performance deviation of 1.8, 2.4 and 2.8. • Consequently, after verification on other sets of teak samples, which may or may not be included in the prediction model, NIRS can be used to predict shrinkage and fibre Saturation Point values accurately for a large number of samples, making it possible to include these characteristics in the selection criteria for classifying wood and high throughput phenotyping. • La stabilité dimensionnelle avec la durabilité naturelle et la couleur du bois, est l’une des plus importantes caractéristiques pour le teck utilisé en bois d’œuvre. Néanmoins, les mesures de ce caractère sont longues et coûteuses en temps. Pour les besoins de la sélection pour la production de variétés améliorées, le nombre d’échantillons à mesurer devient vite supérieur aux capacités d’un laboratoire traditionnel. • La spectroscopie proche infrarouge, sur la base d’un jeu de données de références, est un outil qui permet de prédire de nombreuses propriétés chimiques du bois et de réduire le nombre de mesures de laboratoire de façon exponentielle. La question ici est de vérifier l’efficacité de l’outil NIRS pour construire des modèles et prédire les retraits et le Point de Saturation des fibres du bois de teck provenant de plantations du Togo. • Les résultats démontrent la possible utilisation de la SPIR pour mesurer la stabilité dimensionnelle du bois de teck et qu’il a y lieu de choisir le type de bois et le type de face que l’on mesure par SPIR. Les modèles de prédiction pour les retraits radial et tangentiel et le Point de Saturation des fibres montrent des R^2 de 0,72, 0,83, 0,87 respectivement avec des rapports d’efficacité de 1,8, 2,4 et 2,8. • En conséquence, et après vérification sur d’autres jeux d’échantillons de teck, qu’il conviendra ou non d’intégrer dans le modèle de prédiction, la SPIR permet de prédire des valeurs de retrait et de PSF avec efficacité pour un grand nombre d’échantillons rendant possible l’intégration de ces caractères dans les critères de sélection pour le classement des bois et pour le phénotypage à grande échelle.
Loïc Brancheriau - One of the best experts on this subject based on the ideXlab platform.
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Rapid prediction of shrinkage and fibre Saturation Point on teak (Tectona grandis) wood based on near-infrared spectroscopy
Annals of Forest Science, 2010Co-Authors: Adzo Dzifa Kokutse, Loïc Brancheriau, Gilles ChaixAbstract:• Dimensional stability, along with the natural durability and colour of the wood, is one of the most important characteristics of teak used as timber. However, it is very time-consuming to take measurements of this kind. For the purposes of selection for the production of improved varieties, the number of samples to be measured rapidly exceeds the capacity of a traditional laboratory. • Near-infrared spectroscopy, based on a set of reference data, is a tool enabling many of the chemical properties of wood to be predicted and the number of laboratory measurements to be reduced exponentially. The issue here is a question of checking the effectiveness of NIRS tool to build models and predict the shrinkage and fibre Saturation Point of teak wood from Togo. • The results show the possible use of NIRS to measure the dimensional stability of teak wood and that it is appropriate to choose the type of wood and type of surface to be measured by NIRS. The best prediction models for radial and tangential shrinkage and fibre Saturation Point give R 2 values of 0.72, 0.83 and 0.87 respectively with ratios of performance deviation of 1.8, 2.4 and 2.8. • Consequently, after verification on other sets of teak samples, which may or may not be included in the prediction model, NIRS can be used to predict shrinkage and fibre Saturation Point values accurately for a large number of samples, making it possible to include these characteristics in the selection criteria for classifying wood and high throughput phenotyping.
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Rapid prediction of shrinkage and fibre Saturation Point on teak (Tectona grandis) wood based on near-infrared spectroscopy
Annals of Forest Science, 2010Co-Authors: Adzo Dzifa Kokutse, Loïc Brancheriau, Gilles ChaixAbstract:• Dimensional stability, along with the natural durability and colour of the wood, is one of the most important characteristics of teak used as timber. However, it is very time-consuming to take measurements of this kind. For the purposes of selection for the production of improved varieties, the number of samples to be measured rapidly exceeds the capacity of a traditional laboratory. • Near-infrared spectroscopy, based on a set of reference data, is a tool enabling many of the chemical properties of wood to be predicted and the number of laboratory measurements to be reduced exponentially. The issue here is a question of checking the effectiveness of NIRS tool to build models and predict the shrinkage and fibre Saturation Point of teak wood from Togo. • The results show the possible use of NIRS to measure the dimensional stability of teak wood and that it is appropriate to choose the type of wood and type of surface to be measured by NIRS. The best prediction models for radial and tangential shrinkage and fibre Saturation Point give R ^2 values of 0.72, 0.83 and 0.87 respectively with ratios of performance deviation of 1.8, 2.4 and 2.8. • Consequently, after verification on other sets of teak samples, which may or may not be included in the prediction model, NIRS can be used to predict shrinkage and fibre Saturation Point values accurately for a large number of samples, making it possible to include these characteristics in the selection criteria for classifying wood and high throughput phenotyping. • La stabilité dimensionnelle avec la durabilité naturelle et la couleur du bois, est l’une des plus importantes caractéristiques pour le teck utilisé en bois d’œuvre. Néanmoins, les mesures de ce caractère sont longues et coûteuses en temps. Pour les besoins de la sélection pour la production de variétés améliorées, le nombre d’échantillons à mesurer devient vite supérieur aux capacités d’un laboratoire traditionnel. • La spectroscopie proche infrarouge, sur la base d’un jeu de données de références, est un outil qui permet de prédire de nombreuses propriétés chimiques du bois et de réduire le nombre de mesures de laboratoire de façon exponentielle. La question ici est de vérifier l’efficacité de l’outil NIRS pour construire des modèles et prédire les retraits et le Point de Saturation des fibres du bois de teck provenant de plantations du Togo. • Les résultats démontrent la possible utilisation de la SPIR pour mesurer la stabilité dimensionnelle du bois de teck et qu’il a y lieu de choisir le type de bois et le type de face que l’on mesure par SPIR. Les modèles de prédiction pour les retraits radial et tangentiel et le Point de Saturation des fibres montrent des R^2 de 0,72, 0,83, 0,87 respectivement avec des rapports d’efficacité de 1,8, 2,4 et 2,8. • En conséquence, et après vérification sur d’autres jeux d’échantillons de teck, qu’il conviendra ou non d’intégrer dans le modèle de prédiction, la SPIR permet de prédire des valeurs de retrait et de PSF avec efficacité pour un grand nombre d’échantillons rendant possible l’intégration de ces caractères dans les critères de sélection pour le classement des bois et pour le phénotypage à grande échelle.
