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Mechanical Behaviour of Wood Compressed in Radial Direction:Part II. Influence of Temperature and Moisture Content

  • Corresponding author: Chen Huang, chen.huang@unb.ca
  • Received Date: 2020-04-30
    Accepted Date: 2020-06-04
    Fund Project:

  • This study investigated the influence of pressing temperature and moisture content on the mechanical properties of wood compressed in radial direction. Jack pine (Pinus banksiana) and balsam poplar (Populus balsamifera) specimens were tested under a combination of pressing temperature (20℃, 55℃, 90℃, and 125℃) and wood moisture content (2%, 7%, 12%, and 17%). The yield stress (σy) and modulus of elasticity (MOE) of the specimens were determined from the stress-strain response. It was found that an increase in either pressing temperature or moisture content of wood generally caused a decrease in the mechanical properties for both species. The t-test results revealed that jack pine specimens are more sensitive to changes in pressing temperature and wood moisture content than balsam poplar. For jack pine specimens, at any of the pressing temperatures, the moisture content of 12% was found to be a crucial level to start a significant decrease in σy and MOE, while at any of the moisture content, a change in temperature from 55℃ to 90℃ exhibited a significant change in σy and MOE. The regression models developed can be used to predict σy and MOE as a function of temperature and moisture content.
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Mechanical Behaviour of Wood Compressed in Radial Direction:Part II. Influence of Temperature and Moisture Content

    Corresponding author: Chen Huang, chen.huang@unb.ca
  • a. Wood Science & Technology Centre, University of New Brunswick, Fredericton, NB, E3C 2G6, Canada
  • b. Department of Civil & Environmental Engineering, University of Alberta, Edmonton, AB, T6G 1H9, Canada
  • c. Faculty of Forestry & Environmental Management, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada
Fund Project: 

Abstract: This study investigated the influence of pressing temperature and moisture content on the mechanical properties of wood compressed in radial direction. Jack pine (Pinus banksiana) and balsam poplar (Populus balsamifera) specimens were tested under a combination of pressing temperature (20℃, 55℃, 90℃, and 125℃) and wood moisture content (2%, 7%, 12%, and 17%). The yield stress (σy) and modulus of elasticity (MOE) of the specimens were determined from the stress-strain response. It was found that an increase in either pressing temperature or moisture content of wood generally caused a decrease in the mechanical properties for both species. The t-test results revealed that jack pine specimens are more sensitive to changes in pressing temperature and wood moisture content than balsam poplar. For jack pine specimens, at any of the pressing temperatures, the moisture content of 12% was found to be a crucial level to start a significant decrease in σy and MOE, while at any of the moisture content, a change in temperature from 55℃ to 90℃ exhibited a significant change in σy and MOE. The regression models developed can be used to predict σy and MOE as a function of temperature and moisture content.

1.   Introduction
  • Wood is a porous material, and thus the compression load applied in transverse direction can be used to densify wood by the reduction of the amount of void space. The strength and stiffness of wood is believed to be closely related to density (Wolcott et al., 1989). The relationship between the mechanical behaviour of wood and the structural changes of wood cells during different compressive stages can be reflected by the stress-strain curve, as illustrated in Fig. 1 (Bodig, 1963; 1965; 1966; Easterling et al., 1982; Gibson and Ashby, 1988; Dai and Steiner, 1993; Wolcott et al. 1994; Ando and Onda, 1999; Tabarsa and Chui, 2000; 2001). As shown in Fig. 1, wood deforms in a linear elastic manner before a yield point (at the onset of cellular collapse). After yield point, wood enters into the second part of compression stage, which is known as the plateau region. For softwoods compressed into the plateau region, the larger cells in the earlywood layers collapse first and then the smaller cells in the latewood layers collapse with increasing stress. For ring-porous hardwoods, the larger vessels in ring-porous hardwoods begin to collapse in plateau region. When a majority of the cells collapse, the third region (densification stage) begins.

    Figure 1.  A generalized stress-strain curve of wood under transverse compression

    Wood is made from three major polymers: cellulose, hemicelluloses, and lignin, which have viscos and elastic behavior. Similar to other synthetic polymers, heat and moisture can be used to manipulate the mechanical behavior of wood by the thermal-softening effect on wood in the densification process. The degree of the densification of wood can be modified by the compressive pressures applied at various combinations of heat and moisture conditions. The thermal compression of solid wood can generally be considered as analogous to the hot-pressing operation of wood based composites, such as particleboard, medium density fiberboard and oriented strand board (OSB), except without bonding effect of resins. The density distribution through the thickness of OSB typically shows surface layers with higher density and core layers with lower density. The density profile is influenced by the combination of effects from temperature, moisture, compaction pressure, resin curing and other processing variables during hot-pressing and affects the mechanical and physical properties of the products (Kamke and Casey, 1988; Wang and Winistorfer, 2000).

    Some investigations have been done on the formation and the permanent fixation of wood compression set (Iida et al., 1984; Norimoto, 1993; Inoue et al., 1996; Inoue et al., 2007). The compression methods included not only lumber compression and lumber surface compression (Gong et al., 2006; Lamason and Gong, 2007; Skyba et al., 2009; Gong et al., 2010), but also log compression (Inoue et al., 1990). Other studies were conducted to explore the mechanical behaviour of wood influenced by wood anatomical structure and the processing variables in the hot-pressing operation (Kelley et al., 1987; Kamke and Casey, 1988; Wolcott et al., 1989; Inoue et al., 1990; Wolcott et al., 1990; Kawai et al., 1992; Wolcott et al., 1994; Lenth and Kamke, 2001; Ellis and Steiner, 2002). The findings of these investigations confirmed that the applied pressure, temperature and moisture content of wood can dramatically impact on not only the mechanical behavior of wood during compression, but the properties of wood after compression. More recently, much research work has performed to utilize available fast-growing and low-density wood species for producing the densified wood products by using the thermo-hydro-mechanical densification technology (Bao et al., 2017; Kiaei et al., 2018; Chu et al., 2019; Pelit and Yorulmaz, 2019; Sözbir et al., 2019; Mania et al., 2020; Kubovský et al., 2020). The research results indicated that the mechanical properties for the densified wood products, such as strength, stiffness, abrasive resistance, surface hardness, recoverability and dimensional stability, can be either increased or decreased, depending on the processing parameters and conditions during compression operations.

    The studies cited above, however, were mainly on the mechanical behavior of wood compressed to a high compression strain level (over the plastic region or in the densification region, as illustrated in Fig. 1). From the viewpoint of materials science, an increase of the wood density without the damage of its structural materials—wood cell walls, could be achieved by the application of mechanical compression on wood beyond its yield point but before permanent structural damage would occur. In designing the hot-press or equipment to produce the densified-wood products with improved mechanical properties, knowledge of yield point and modulus of elasticity (MOE), and how they are influenced by temperature and moisture content is desirable. The knowledge allows for the estimation of force required to achieve a certain compression level during the hot-pressing process.

    This investigation was intent to explore the effect of two major parameters (pressing temperature and moisture content of wood) on yield point and MOE for one softwood and one hardwood species under compression in radial direction. This paper is the second part report in a series on mechanical behaviour of wood compressed in radial direction. The first report (Part I) covered new method of determining the yield stress of wood from the stress-strain curve (Huang et al., 2020).

2.   Materials and Methods
  • Jack pine (Pinus banksiana) and balsam poplar (Populus balsamifera) were chosen because jack pine is a commercially important softwood species for dimensional lumber production, while balsam poplar is another commercially important species used in the production of oriented strand board and laminated veneer lumber. The structure of a softwood is relatively simple. The axial or vertical system is composed mostly of axial tracheids, and the radial or horizontal system is the rays, which are composed mostly of ray parenchyma cells. However, the structure of a hardwood is much more complicated than that of a softwood. The axial system consists of fibrous elements of various kinds, vessel elements in various sizes and arrangements, and axial parenchyma in various patterns and abundance (Panshin and de Zeeuw, 1980).

    Wood is an anisotropic material and many of its properties vary with the direction of measurement. Three principal reference directions are recognized: the grain direction, the radial direction, and the tangential direction. The grain direction is parallel to the length of the stem. A line drawn in the direction of the radius of the circular cress-section of a tree would be in the radial direction. A line drawn tangent to the circular cross-section of the tree stem would be perpendicular to the two other reference directions and would be in the tangential direction. Five logs with approximately 50 cm in length were cut at breast height from jack pine and balsam poplar trees respectively. Each log was then cut into 15 mm thick disks. From each disk, wood blocks with nominal dimensions 10 mm (longitudinal) × 18 mm (tangential) × one complete annual ring with one more latewood section (radial) were cut from the clear sapwood sections. All the blocks were cut from the same annual growth ring along the tangential direction to minimize variations in the cellular structure. Figure 2 shows the process of preparing a wood block from a 15 mm- thick log disk. Only those wood blocks, whose density fell within a range of 0.41–0.42 g/cm3 for jack pine wood, and 0.39–0.40 g/cm3 for balsam poplar wood, were used. This small density range was selected to minimize any influence that the variation of density might have on the results.

    Microtest tensile/compression stage (Deben research, 2003), originally designed for performing mechanical test on small specimen within the confined space of a Scanning Electron Microscopy chamber, was modified and adopted as a compression test module, which was shown in Fig. 2, in the first study on new method of determining the yield stress of wood on the stress- strain curve (Huang et al., 2020). The 5 kN compression load and a load speed of 1.5 mm/min were selected in this study. A computer-based data acquisition system was used to record load data and to control the compression module. A full factorial experimental design was employed with two different variables: pressing temperature (20 ℃, 55 ℃, 90 ℃, and 125 ℃) and moisture content of wood (2%, 7%, 12%, and 17%), and five replications of each treatment combination, for two species, respectively.

    Figure 2.  Preparation of a wood block from a log disk

    Compression test specimens of nominal dimensions: 7 mm (longitudinal) × 14 mm (tangential) × one complete annual ring with one more latewood section (radial) under the same density-range for each testing species, were cut from the conditioned wood blocks, as shown in Fig. 3. Thickness of each specimen varied since it was cut to ensure there was at least one full growth ring. Subsequent measurement of compression deformation would be confined to one growth ring. To allow high quality images of the microscopic deformation to be visually examined and recorded by using a digital camera during compression test, one end surface of each specimen was cut and finished with a microtome. This surface was one exposed to a light microscope to be observed.

    Figure 3.  A schematic representation of the enlarged compression specimen

    All test specimens were preconditioned in a conditioning chamber at a temperature of (20 ± 1) ℃ and 65% relative humidity (RH) for two months to achieve the equilibrium moisture content (EMC) of approximately 12%. In order to obtain various moisture levels designed for various specimens, different saturated salt solutions were used in a desiccator for conditioning the specimens under various relative humidity at 20 ℃ until the target EMC was reached (Greenspan, 1977). To achieve the EMC of 2%, the preconditioned specimens were oven-dried for one week, and then returned to the conditioning chamber that was set at (20 ± 1) ℃ and 33% RH with the saturated MgCl2 for six hours. After the EMC reached approximately 2%, specimens were sealed in a zipper plastic bag until tested. For the specimens with initial EMC of 7%, the preconditioned specimens were oven- dried for one week. The oven-dried specimens were conditioned in a desiccator containing saturated MgCl2 under moisture adsorption condition of 33% RH at (20 ± 1) ℃ for two weeks. To achieve the specimens with EMC of 12%, the saturated NaNO3 solution with 66% RH at (20 ± 1) ℃ was used to condition the specimens in a desiccator. Likewise, to achieve the specimens with an initial EMC of 17%, the preconditioned specimens were placed directly in a desiccator containing saturated KCl under moisture adsorption condition of 85% RH at (20 ± 1) ℃ for two weeks. The EMC of each specimen was obtained by the weighing-drying-weighing (20 ± 1) ℃ method at the end of the sorption cycle. The weight of each conditioned specimen was measured by the balance Mettler Toledo XS 105 with an accuracy of ± 0.01 mg. Figure 4 shows a desiccator used for conditioning the specimens to a designed EMC level with a certain saturated salt solution.

    Figure 4.  Specimens in a desiccator containing saturated salt solution

    The method developed in the study on new method of determining the yield stress of wood on the stress-strain curve (Huang et al., 2020), was used to determine the yield point. Compared with traditional way of locating the yield point on the stress-strain curve visually and manually, this method was found to be more reasonable in determining the yield stress, particularly when no pronounced morphological turning point is visible on the elastic and plastic transition zone of the stress-strain curve. The MOE of a compressed specimen was then determined by the computation of the slope of a linear part of line below the yield point on the stress-strain curve, which was indicated in Fig. 1.

    Minitab statistical software was used to conduct the statistical analyses on test results after compression tests. The effects of two fixed factors: pressing temperature (Temp) and wood moisture content (MC) on response variables: yield stress (σy) and MOE, were evaluated for the species studied.

3.   Results and Discussion
  • Table 1 shows the statistical analysis results based on the data tested from both jack pine and balsam poplar specimens. As shown in Table 1, it was found that for jack pine specimens, the pressing temperature statistically significantly influenced yield stress (P < 0.001) and the wood moisture content had marginally effect (P < 0.05) at a significance level of 0.05. However, both pressing temperature and wood moisture content had significantly influence on MOE at a significance level of 0.05. For balsam poplar specimens, both pressing temperature and wood moisture content significantly influenced yield stress at a significance level of 0.001, while pressing temperature (P < 0.01), more than moisture content (P < 0.05), significantly influenced the MOE. In addition, the factorial experimental results indicated that the interaction between pressing temperature and wood moisture content had no significant effect on either yield stress or MOE for both species at a significance level of 0.05.

    Species Response variable Experimental variable
    Temp MC Temp × MC Temp × Temp MC × MC
    Jack pine σy *** * NS NS *
    MOE *** *** NS NS *
    Balsam poplar σy * * NS NS *
    MOE ** * NS NS **
    Notes: *, P < 0.05; **, P < 0.01; ***, P < 0.001; NS, not significant (P > 0.05). σy, yield stress; MOE, modulus of elasticity; Temp, pressing temperature; MC, wood moisture content.

    Table 1.  Effects between each experimental variable on response variable

    The main effect plots of factorial variables (pressing temperature and moisture content) on response variables (σy and MOE) for both species are plotted in Figs 5, 7, 9, and 11, respectively. Based on the t-test results, a double header arrowed line between two consecutive points along the same axial direction was added into each of the Figs 6, 8, 10 and 12, indicating that the change in two consecutive levels of one factorial variable under the other factorial level fixed resulted in a significant difference in mean values of the given response variable at a significance level of 0.05.

    Figure 5.  Main effect plots of pressing temperature and moisture content on yield stress for jack pine

    Figure 6.  Effects of pressing temperature and moisture content on yield stress for jack pine (A double header arrowed line indicates a significant difference in means between two levels along arrow direction)

    Figure 7.  Main effect plots of pressing temperature and moisture content on yield stress for balsam poplar

    Figure 8.  Effects of pressing temperature and moisture content on yield stress for balsam poplar (A double header arrowed line indicates a significant difference in means between two levels along arrow direction)

    Figure 9.  Main effect plots of pressing temperature and moisture content on MOE for jack pine

    Figure 10.  Effects of pressing temperature and moisture content on MOE for jack pine (A double header arrowed line indicates a significant difference in means between two levels along arrow direction)

    Figure 11.  Main effect plots of pressing temperature and moisture content on MOE for balsam poplar

    Figure 12.  Effects of pressing temperature and moisture content on MOE for balsam poplar (A double header arrowed line indicates a significant difference in means between two levels along arrow direction)

  • In general, the magnitude of yield stress was found to be decreased with the increase of pressing temperature level at a fixed wood moisture content level (i.e., means of yield stress at pressing temperature of 20 ℃, 55 ℃, 90 ℃, and 125 ℃, under moisture content of 12%, were 4.212 MPa, 3.816 MPa, 3.278 MPa, and 2.839 MPa, respectively), or with increasing the moisture content level at a fixed pressing temperature level (i.e., means of yield stress at moisture content of 2%, 7%, 12%, and 17%, under pressing temperature of 20 ℃, were 5.006 MPa, 4.740 MPa, 4.212 MPa, and 3.299 MPa, respectively), which are shown in Fig. 5.

    The t-test results showed that a change in two consecutive moisture content levels at any of the pressing temperature level, or vice versa, resulting in significant differences in mean value of yield stress for most of the jack pine combinations, as illustrated by the double header arrowed lines in Fig. 6. At any pressing temperature level, a change in moisture content between each of the following consecutive levels: 7%, 12% and 17%, caused a significant difference in mean value of yield stress.

    On the other hand, it was found that at a given moisture content, changes of pressing temperature from 55 ℃ to 90 ℃, led to a markedly change in mean yield stress for jack pine specimens in radial compression. Irvine (1984) reported that the glass transition temperature (Tg) of native lignin occurred when heated to the temperature ranging from 60 ℃ to 90 ℃, and the softening of water saturated wood was mainly dependent on the behavior of its amorphous polymer, i.e., lignin. As lignin constitutes about 30%–40% of the wood volume, this could explain the sensitivity of yield strength of wood to pressing temperature in the range of 55 ℃–90 ℃.

    Moreover, the statistical analysis results suggested that, unlike MC2, the second-order temperature parameter, Temp2, had no significant effects on the response variable: σy (due to P > 0.05), hence it was not considered for the developed regression model below.

    As shown in Equation (1), yield stress (σy) is highly correlated to the first order of MC and Temp, the second order of MC2 (due to R2 = 0.90). Therefore, this regression model can be applied to effectively predict the yield stress for jack pine wood under radial compression based on the knowledge of moisture content and pressing temperature.

  • In general, the magnitude of yield stress for balsam poplar specimens was found to be decreased with the increase of pressing temperature level at a fixed wood moisture content level (i.e., means of yield stress at pressing temperature of 20 ℃, 55 ℃, 90 ℃, and 125 ℃, under moisture content of 12%, were 5.281 MPa, 4.801 MPa, 4.181 MPa, and 3.717 MPa, respectively), or with increasing the moisture content level at a fixed pressing temperature level (i.e., means of yield stress at moisture content of 2%, 7%, 12%, and 17%, under pressing temperature of 20 ℃, were 5.929 MPa, 5.568 MPa, 5.281 MPa, and 4.459 MPa, respectively), as shown in Fig. 7. These findings were similar to those for jack pine wood.

    However, unlike jack pine, the results of t-test showed that only in a few cases illustrated by the double header arrow lines in Fig. 8, which the differences between mean yield stresses at consecutive levels exhibit statistical significance. The elemental constituents of wood are combined into a number of organic polymers: cellulose, hemicellulose and lignin. The approximate percent of dry weight of hemicellulose and lignin in hardwood and softwood are different (Kollman and Côté, 1968). The proportion of lignin varies between hardwoods (18%–25%), and softwoods (25%–35%) could be the reason to explain different sensitivity to thermal and moisture softening occurring in cell walls in balsam poplar and jack pine specimens.

    According to Fig. 8, the few cases where sensitivity is significant for balsam poplar specimens are: changes in pressing temperature levels of 55 ℃–90 ℃ and 90 ℃–125 ℃ at 2% MC, and changes in pressing temperature levels between 90 ℃ and 125 ℃ at 7% MC. This would indicate that the dry balsam poplar wood is, at 90 ℃ degree or above, more sensitive to temperature than moisture content as for moisture sensitivity above 7% MC, only cases with medium pressing temperatures, i.e., between 55 ℃ and 90 ℃, seemed to be significant.

    As before, the statistical analysis results suggested that the second-order parameter (Temp2) had no significant effects on the response variable (σy) (due to P > 0.05), which was not considered into the developed regression model. Therefore, the developed regression model to describe the yield stress (σy) as a function of MC and Temp, is presented in Equation (2):

    The above regression model can be applied to estimate the yield stress in radial compression under a condition that is within the range of parameters studied. However, with a relatively low coefficient of determination (R2 = 0.78), the prediction accuracy with this model is not as good as the model developed for jack pine specimens.

  • It was found that the magnitude of the MOE decreased with an increase in pressing temperature level at a fixed wood moisture content level (i.e., means of MOE at pressing temperature of 20 ℃, 55 ℃, 90 ℃, and 125 ℃, under moisture content of 12%, were 64.474 MPa, 57.225 MPa, 47.432 MPa, and 42.205 MPa, respectively), or with increasing the moisture content level at a fixed pressing temperature level (i.e., means of MOE at moisture content of 2%, 7%, 12%, and 17%, under pressing temperature of 20 ℃, were 77.412 MPa, 72.105 MPa, 64.474 MPa, and 57.480 MPa, respectively), as shown in Fig. 9.

    The t-test results showed that a change in two consecutive moisture content levels at any pressing temperature level, or vice versa, resulted in the significant differences in mean values of the MOE for most of the jack pine groups, as illustrated by the double header arrow lines in Fig. 10. At any pressing temperature level, changes in moisture content level from 7% to 12%, led to the significant difference in mean value of the MOE. In addition, at a pressing temperature level (except for 90 ℃), changes in moisture content from 12% to 17%, led to significant difference in mean MOE. The MOE of jack pine is also found to be sensitive to changes in pressing temperature from 55 ℃ to 90 ℃ at all moisture content levels. This can be explained by the softening of lignin as was discussed above (Irvine, 1984). Above 90 ℃ pressing temperature, the MOE did not change obviously.

    The statistical analysis results suggested that the Temp2 term was again found not to be significant, and was therefore ignored on the developed regression model. Similar to yield stress, the following regression model was developed to describe the MOE as a function of MC and Temp:

    As shown in Equation (3), the R2 is 0.91, indicating a correlation between the MOE of jack pine wood under radial compression and moisture content and pressing temperature.

  • Similar to the findings for jack pine specimens, the magnitude of the MOE for balsam poplar specimens was found to be decreased with the increase of pressing temperature level at a fixed moisture content level (i.e., means of yield stress at pressing temperature of 20 ℃, 55 ℃, 90 ℃, and 125 ℃, under moisture content of 12%, were 75.574 MPa, 67.874 MPa, 60.487 MPa, and 55.760 MPa, respectively), or with increasing the moisture content level at a fixed pressing temperature level (i.e., means of yield stress at moisture content of 2%, 7%, 12%, and 17%, under pressing temperature of 20 ℃, were 86.591 MPa, 81.102 MPa, 75.574 MPa, and 69.105 MPa, respectively), as shown in Fig. 11.

    Unlike jack pine specimens, as can be seen from Fig. 12, the results of t-test showed that in most cases, the mean MOE for balsam poplar specimens did not show statistically significant difference when pressing temperature or MC was changed from one level to another. The few cases of statistical significance seemed to be at the low moisture content and temperature regions, as shown in Fig. 12. This would indicate that influence of pressing temperature and moisture content were less significant at high temperature and moisture content regions.

    The statistical analysis results suggested that the second-order parameter (Temp2) had no significant effects on the response variable (MOE) (due to P > 0.05), which was not considered into the developed regression model. Therefore, the developed second- order two variable regression model to describe the MOE as a function of MC and Temp, is presented as follows:

    As shown in Equation (4), it can be noted that the MOE is correlated to the first order of MC and Temp, the second order of MC2. The above regression model can be applied to predict the MOE in radial compression under a condition that is within the range of parameters studied. However, with a lower coefficient of determination of R2 = 0.77, the prediction capability of this model is not as reliable as the model developed for jack pine specimens.

4.   Conclusions
  • The following conclusions can be drawn from this study on pressing temperature and moisture content of wood affecting jack pine and balsam poplar compression in radial direction:

    For jack pine specimens, pressing temperature was found to be a more significant factor affecting yield stress than moisture content, and both pressing temperature and moisture content exhibited a highly significant influence on modulus of elasticity, while for balsam poplar specimens, both pressing temperature and moisture content had highly significant influence on yield stress. Therefore, pressing temperature was found to be a more significant factor affecting yield stress than moisture content.

    In general, both yield stress and module of elasticity decreased noticeably with any increase in pressing temperature and wood moisture content for both species tested. A change in two consecutive levels of pressing temperature at a given moisture content, or a change in two consecutive levels of moisture content at a given pressing temperature, resulted in a significant change in yield stress and modulus of elasticity in most cases for jack pine specimens, but only in limited cases for balsam poplar specimens.

    At a given wood moisture content, changes in pressing temperature levels from 55 ℃ to 90 ℃, caused a significant change in yield stress and modulus of elasticity for jack pine specimens. This could be attributed to the occurrence to the softening of wood cell walls.

    The developed regression models demonstrated that the response variables (yield stress and modulus of elasticity) can be efficiently related to the experimental factors (pressing temperature and moisture content of wood) for both species. In general the models developed for jack pine appeared to have more precise modelling capability, as indicated by the higher coefficient of determination.

Conflict of Interest
  • There are no conflicts to declare.

Acknowledgements
  • This work was founded by a grant from the Natural Sciences and Engineering Research Council of Canada and New Brunswick Innovation Foundation. Their support is acknowledged greatly.

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