Wood and Fiber Science (E-Journal)
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Identification of Log Characteristics in Computed Tomography Images Using Back-Propagation Neural Networks with the Resilient Back-Propagation Training Algorithm and Textural Analysis: Preliminary Results
Get PDFThis research addressed the feasibility of identifying internal log characteristics in computed tomography (CT) images of sugar maple and black spruce logs by means of back-propagation (BP) neural networks with a resilient BP training algorithm. Five CT images were randomly sampled from each log. Three of the images were used to develop the corresponding classifier, and the remaining two images were used for validation. The image features that were used in the classifier were gray-level values, textual, and distance features. The important part of the classifier topology, ie the hidden node number, was determined based on the performance indicators: overall accuracy, mean square error, training iteration number, and training time. For the training images, the classifiers produced class accuracies for heartwood, sapwood, bark, and knots of 99.3, 100, 96.7, and 97.9%, respectively, for the sugar maple log; and 99.7, 95.3, 98.4, and 93.2%, respectively, for the black spruce log. Overall accuracies were 98.5% for sugar maple and 96.6% for black spruce, respectively. High overall accuracies were also achieved with the validation images of both species. The results also suggest that using textural information as the inputs can improve the classification accuracy. Moreover, the resilient BP training algorithm made BP artificial neural networks converge faster compared with the steepest gradient descent with momentum algorithm. This study indicates that the developed BP neural networks may be applicable to identify the internal log characteristics in the CT images of sugar maple and black spruce logs
Comparison of the Mechanical Properties of Branch and Stem Wood for Three Species
Get PDFBranch wood could be used in new added-value products as an alternative to stem wood provided that its characteristics are known and understood. This article compares the modulus of elasticity (MOE), modulus of rupture (MOR), and compression strength of maple (Acer spp.) and Scots pine (Pinus sylvestris L.) and the compression strength of beech (Fagus sylvatica L.) branch wood with stem wood. The mechanical tests showed that the MOE and compression strength of maple branch wood were slightly lower than those of stem wood, maple MOR was slightly higher for branch wood, and beech compression strength was similar for branch and stem wood. However, the MOR and compression strength of Scots pine branch wood were approximately one-half of those of stem wood, whereas the MOE was approximately one-third. Branch wood had a higher density than corresponding stem wood, except for Scots pine. No correlation was observed between branch density and mechanical strength except for MOR
Moisture in Untreated, Acetylated, and Furfurylated Norway Spruce Studied During Drying Using Time Domain NMR1
Get PDFUsing time domain NMR, the moisture in Norway spruce (Picea abies (L.) Karst.) sapwood subjected to four different treatments (never-dried, dried and remoistened, acetylated, and furfurylated) was studied during drying at 40°C, at sample average moisture contents above fiber saturation. Spin-spin relaxation time distributions were derived from CPMG relaxation curves using multiexponential fitting (CONTIN), and the resulting water populations were assigned according to the literature and their behavior during drying. It was found that both acetylation and furfurylation increased the average spin-spin relaxation time of the lumen water in earlywood tracheids from about 80-100 ms to 200 and 300 ms, respectively. The average spin-spin relaxation time of the cell wall water was reduced from about 1.4 to 0.65 ms by furfurylation, while acetylation had less effect on this water. The relaxation times of both the earlywood lumen water and of the cell wall water were slightly longer for the never-dried samples than for the dried and remoistened samples
Investigation of OSB Thickness-Swell Based on a 3-D Density Distribution. Part II. Variations in Thickness-Swell and Internal Stresses
Get PDFA recently developed finite element (FE) model was used to examine the thickness-swell, density changes, and internal stresses in oriented strandboard (OSB) panels under moisture loading. The model accounts for the nonlinear mechanical behavior of OSB and for the moisture transport through the specimen. The FE model is based on the 3-D density variation of the board. The density variation, resulting from manufacturing processes, affects the uniformity of thickness-swell in OSB and is often exacerbated by continuous sorption of moisture, which leads to potentially damaging internal stresses in the panel. The model was validated through comparison of experimental results. The use of the model is illustrated by quantifying the effects of resin content changes on thickness swell, and the examination of internal stresses and bond failures in an OSB specimen
Predicting Internal Yellow-Poplar Log Defect Features Using Surface Indicators
Get PDFDetermining the defects that are located within the log is crucial to understanding the tree/log resource for efficient processing. However, existing means of doing this non-destructively requires the use of expensive X-ray/CT, MRI, or microwave technology. These methods do not lend themselves to fast, efficient, and cost-effective analysis of logs and tree stems in the mill. This study quantified the relationship between external defect indicators and internal defect characteristics for yellow-poplar logs. A series of models were developed to predict internal features using visible external features, log diameter, indicator width, length, and rise. Good correlations and small prediction errors were observed with sound (sawn), overgrown, and unsound knot defects. For less severe defects such as adventitious buds/clusters and distortion type defects weaker correlations were observed, but the magnitude of prediction errors was small and acceptable
Effects of Selected Wood Species and Moisture Content on PMDI Resin Application and Panel Properties
Get PDFThis study investigated the effect of selected species and moisture conditions on resin distribution and composite panel properties. Flakeboard composites were made from aspen, pine, or poplar flakes that were equilibrated to 4, 8, or 12% moisture content (MC). Resin droplet size (resin "footprint") was measured, as was the percentage of the flake surface that was covered by resin. Aspen flakes showed higher resin coverage and also larger resin droplet sizes. Conversely, pine and poplar flakes had smaller resin droplets and lower resin coverage per flake surface, suggesting greater pMDI penetration. Internal bond (IB) testing revealed optimal performance for aspen flakes at 12% precure MC, and poplar and pine flakes at 8% precure MC. Modulus of rupture and modulus of elasticity results correlated with IB results. Aspen panels bonded at 8 and 12% MC had minimal thickness swell
FTIR-ATR Spectroscopic Analysis of Changes in Fiber Properties During Insulating Fiberboard Manufacture of Beech Wood
Get PDFFourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy was applied to trace changes in chemical fiber properties during the production process of insulating fiber mats. In combination with cluster analysis, FTIR spectra were used to interpret the homogeneity of the products. Beech wood (Fagus sylvatica L.) was used as a novel sustainable material for fiberboard production. The insulating fiberboards were either processed without binder or with potato pulp or potato starch as renewable binders and dried in a dryer or a microwave. FTIR spectral analyses revealed chemical modifications at the O-H association band of carbohydrates that distinguished the two different drying methods. Additions of plant-based renewable binders diminished the absorbance of the resulting products at characteristic wavenumbers in the IR. These decreases were closely correlated with the amount of added binder and thus have the potential to quantify binder additions to the fiberboards. Cluster analysis grouped FTIR spectra of samples from different production steps or processes correctly and therefore is an effective and simple technique for quality control of insulating fiberboards from renewable resources
Thermal Modification of Color in Red Alder Veneer. Part II. Effects of Season, Log Storage Time, and Location of Wood in Stems
Get PDFThe value of red alder lumber is diminished by discoloration caused by the enzyme-mediated polymerization of the diarylheptanoid xyloside, Oregonin that results in the formation of red-colored chromophores in freshly felled wood. This discoloration can be reduced by pre-steaming wood prior to kiln drying of lumber or veneer slicing, but in practice, there is still variation in the color of heat-treated wood, particularly in veneer sliced from heat-treated cants processed at different times of the year. There is seasonal variation in the concentration of Oregonin that is involved in the discoloration of red alder wood and it is hypothesized here that heat-treated red alder wood will be redder and darker when the wood is obtained from logs harvested during spring when the concentration of Oregonin is known to be higher than in other seasons. The aim of this research was to test this hypothesis, and also examine the effects of log storage time and location of wood in stems on the color of heat-treated red alder wood. The color of red alder wood subjected to an isothermal heat treatment at 70°C was strongly influenced by the season in which parent trees were harvested and the length of time that logs were stored prior to heat treatment of wood. In particular, wood harvested in spring and stored for 2 wk prior to heat treatment was significantly darker than similarly treated wood obtained from logs harvested in other seasons, and redder than wood harvested in summer and winter. If the storage time of logs harvested in spring and summer was extended to 4 wk, however, the heat-treated wood became lighter and less red. Heat-treated wood from the inner part of the logs was redder and darker than heat-treated wood from the outer part of the logs except occasionally, when the outer sapwood was obtained from logs harvested in spring or summer. Careful control of log storage time, heating temperature, and duration of heat treatment could be used to minimize seasonal variation in the color of veneer sliced from heated red alder cants
Preferences for Pressure-Treated Wooden Deck Materials
Get PDFEnvironmental regulations and restrictions have increased the need for new treatments of wood for outdoor residential use. Further, new tastes and the growing importance of do-it-yourself retailing have initiated a need for more knowledge in the industry about end-consumer preferences for outdoor wooden products. In this study consumer preferences for different types of outdoor decking were analyzed using the conjoint analysis approach. The results indicate that environmental certification is an important product attribute for many customers, together with price and type of treatment. Service and ready-to-assemble products are of low importance. Significant preference differences between customer subgroups were identified. Conjoint part-worth values were also used to distinguish three consumer segments. Finally, the utilization of the conjoint results for simulation of market shares dynamics for hypothetical products is demonstrated
Dynamic Viscoelastic Properties of Wood Treated by three Drying Methods Measured at High-Temperature Range
Get PDFThe heartwood of Chinese fir was dried by high-temperature drying (HTD), low-temperature drying (LTD), and freeze-vacuum drying (FVD), respectively. The dynamic viscoelastic properties were investigated at a temperature range from 30 to 280°C at frequencies of 0.5-10 Hz using the technique of Dynamic Mechanical Analysis (DMA). The results showed that two relaxations labeled as α and β were detected in the order of the decreasing temperatures at which they occurred, attributed to the micro-Brownian motion of the amorphous cell-wall polymers and the molecular motion of lignin, respectively. The loss peak temperature in β relaxation of HTD wood was the lowest, probably because of the degradation of hemicellulose in the amorphous region. The highest apparent activation energy (ΔE) of HTD wood suggested that more bonds among molecular chains were broken in its segmental motion