& Key message A fully automated algorithm allowed knot detection and positioning on computed tomography (CT) images of Douglas-fir logs. The detection of knot diameter and status could benefit from further improvements, i.e., testing other configurations and implementing texture measures. Manual measurement on CT images allows for tridimensional assessment and greater attainable sampling, while manual measurement on discs provides additional color and texture information. & Context Computed tomography (CT) is a very successful tool to non-destructively acquire the internal knot structure of a log. To enable large-scale applications, an algorithm that automatically detects knots is required. The accuracy of such algorithms depends heavily on the species and image resolution. & Aim This study validates a knot detection algorithm (Johansson et al. in Comput Electron Agric 96:238-45, 2013) on fresh Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) logs. & Methods In this study, 282 knots were sampled from 15 logs, selected from six 78-year-old trees in southwest Germany. The validation of the algorithm's knot detection was performed via comparison against two manual methods: on physical samples and on CT images. & Results The saturated sapwood negatively influences the overall knot detection, which causes underestimation of knot diameter in this area or incomplete detection. The algorithm tended to overestimate knot diameter, longitudinal position, and knot length. & Conclusion The algorithm provides the knot position with satisfactory accuracy. Other settings on contrast and considered volume around a knot can be tested within the algorithm, as well as new development and implementation of texture measures in the image analysis to improve the accuracy results for Douglas-fir in future investigations.

O objetivo foi produzir painéis OSB com partículas de E. benthamii e mix de Pinus taeda e Pinus elliottii. O delineamento experimental envolveu cinco tratamentos compostos por painéis com três camadas de partículas e densidade nominal de 0,65 g/cm3. Foram aplicados 6% de resina fenol formaldeído e 1% de emulsão de parafina. O ciclo de prensagem foi de 8 minutos, temperatura de 180 ºC e pressão específica de 40 kgf/cm2. Os ensaios foram realizados de acordo com a norma ASTM D1037 (1993) e a DIN 52362 (1982), sendo os resultados avaliados por meio da Análise de Variância e Teste de Scott-Knott. Como resultados, observou-se que as melhores composições foram obtidas no tratamento composto exclusivamente por partículas de Pinus spp e no tratamento com partículas de Pinus spp na camada central e E. benthamii nas camadas externas. Foi verificado potencial do Eucalyptus benthamii  para a produção de painéis OSB quando misturada com partículas de P. taeda e P. eliiottii, tendo em vista que em painéis puros apresentou resultados insatisfatórios.AbstractUse of Eucalyptus benthamii wood in the production of Oriented Strand Boards (OSB). This research aimed to produce OSB with particles of E. benthamii and mix of Pinus taeda and Pinus elliottii. The experimental plan involved five treatments composed of panels with three layers of particles and nominal density of 0,65 g/cm3. The resin phenol formaldehyde and the wax sizing were applied in the amount of 6% and 1%, respectively. The pressing cycle was 8 minutes, temperature of 180 ºC and specific pressure of 40 kgf/cm2. The assays were performed according to standard ASTM D1037 (1993) and DIN 52362 (1982) and the results were evaluated by Analysis of Variance and Scott-Knott Test. As result, it was observed that the best compositions are obtained in the treatment composed exclusively of Pinus spp particles and in the treatment with particles of Pinus spp in the core layer and the E. benthamii in the outer layers. It was verified potential of Eucalyptus benthamii for the production of OSB when mixed with particles of P. taeda and P. eliiottii, considering that in pure panels it showed unsatisfactory results.Keywords: Wood panels; OSB; Eucalyptus sp and Pinus spp; Technological properties.

O objetivo do presente estudo foi caracterizar tecnologicamente painéis particulados produzidos com resíduo de beneficiamento de cinco espécies tropicais comerciais: angelim (Hymenolobium sp. / Andira sp.), cambará (Qualea sp.), canelão (Nectandra sp. / Ocotea sp.), cedro (Cedrelinga cateniformis) e itaúba (Mezilaurus itauba). Foram confeccionados três painéis de cada espécie, além de três painéis com a mistura das cinco espécies em iguais proporções (mix), totalizando 18 painéis com massa específica nominal de 0,65 g/cm³. Os painéis foram compostos por 12% de resina ureia formaldeído e 1% de emulsão de parafina. O ciclo de prensa utilizado foi de 160°C de temperatura, pressão de 40 kgf/cm² durante 8 minutos. Os dados foram submetidos à análise de variância e teste de Tukey a 95% de confiabilidade. Todas as madeiras, exceto o cedro, apresentaram massas específicas maiores e razões de compactação menores que o intervalo proposto pela literatura, o que refletiu em valores baixos de resistência e rigidez. Todos os painéis apresentaram resultados satisfatórios quanto à estabilidade dimensional dos painéis. As madeiras de angelim, cambará e canelão apresentaram resultados promissores. O cedro, apesar de resultar na maior razão de compactação, não apresentou resultados mecânicos na mesma magnitude, exceto para ligação interna. Recomenda-se a incorporação de espécies com menor massa específica básica, bem como o controle da granulometria das partículas e o aumento da massa específica nominal dos painéis. Palavras-chave: espécies alternativas, uso de resíduos, painéis de média densidade.

The objective of this study was to evaluate the technical feasibility of producing particleboard from oversize resin fibers in a reduced proportion of adhesive. It was used as raw material, oversize resin fibers discarded from the MDF (Medium Density Fiberboard) production process, flake particles of Pinus spp. derived from an MDP (Medium Density Particleboard) company’s chipper and adhesive formed by the urea-formaldehyde resin and paraffin emulsion. The experiment consisted of five treatments, mixing particles and fibers in different proportions (100: 0%; 75: 25%; 50: 50%; 25: 75%; 0: 100%). Three panels were produced per treatment, with nominal density of 650 kg.m-3, 8% resin and pressing cycle of 160ºC, 40 kgf.cm-2 for 8 minutes. The properties of the panels were evaluated by the procedures described in ASTM D-1047 (1993), DIN 53362 (1982) and ABNT / NBR 14810 (2013). The results showed that oversize resin fibers have potential for use in the sector, especially in quantities above 75%, a fact that was evidenced by the values found for dimensional stability and strength/stiffness. For internal adhesion, the increase in the number of fibers above 25% was not significant.

Branches are not only of vital importance to tree physiology and growth but are also one of the most influential features in wood quality. To improve the availability of data throughout the forest-to-industry production, information on internal quality (e.g. knots) of both felled and standing trees in the forest would be desirable. This study presents models for predicting the internal knot diameter of Douglas-fir logs based on characteristics measured in the field. The data were composed of 87 trees (aged from 32 to 78 years), collected from six trial sites in southwest Germany, and cut into 4–5 m logs on-site. The internal knot diameter was obtained by applying a knot detection algorithm to the CT images of the logs. Applying the Random Forest (RF) technique, two models were developed: (1) MBD: to predict the branch diameter (BD) at different radial positions within the stem, and (2) MBDmax: to predict the maximum internal branch diameter (BDmax). Both models presented a good performance, predicting BD with an RMSE of 4.26 mm (R2 = 0.84) and BDmax with an RMSE of 5.65 mm (R2 = 0.78). In this context, the innovative combination of CT technology and RF modelling technique showed promising potential to be used in future investigations, as it provided a good performance while being flexible in terms of input data structure and also allowing the inclusion of otherwise underexplored databases. This study showed a possibility to predict the internal diameter of branches from field measurements, introducing an advance towards connecting forest and sawmill.

Branches are as essential for tree growth as knots are detrimental from the wood quality point of view. To bridge the gap between tree growth and the quality toward end-use, this study aims to establish a relationship between internal and external diameters of Douglas-fir whorl branches. The data comprised 102 trees of a wide age range (30–80 years old) from nine study sites in Southwest Germany. External branch measurements were performed in the field following an established protocol. Logs were scanned on a MiCROTEC CT.LOG, and knots were detected by applying an automated algorithm. Obvious detection artefacts by the CT algorithm were excluded to reveal the relationship between inner-outer branch diameters as clear as possible. Results showed a significant mean difference of 13.8 (± 10.0) mm between the methods (external diameter being larger), with a model indicating an offset of 9.75 mm and angular shift of 0.53 (RMSE = 7.12 mm; R2 = 0.57) between the methods. Separate calculations of sound and dead datasets did not reveal a statistically significant difference. By linking the internal knot structure to external branch measurements, the findings of this study constitute a first step toward the incorporation of CT data into growth models, providing a meaningful prediction of the maximum internal knot diameter at an early stage in the wood supply chain.

RESUMOO setor madeireiro é caracterizado por ser uma grande fonte de geração de desperdícios. Assim, o efetivo controle das atividades produtivas é condição indispensável para que qualquer empresa possa competir no mercado. O objetivo do estudo foi avaliar o rendimento da matéria-prima em termos percentuais e financeiros de uma indústria de Clear Blocks, com intuito de definir as melhores variáveis para fornecedor, bitola e destopadeira. A metodologia envolveu a seleção das variáveis de interesse: fornecedor (interno e externo); bitola (67 e 92 mm) e destopadeira (corte de baixo para cima e de cima para baixo); a determinação do rendimento percentual total e por classe de qualidade através do balanço de material, e o financeiro através do custo da matéria-prima, custo de produção e preço de venda. A análise dos resultados foi realizada através da análise de variância multifatorial e teste de Tukey. O rendimento de matéria-prima em termos percentuais encontrado no estudo demonstrou a superioridade da bitola 92 mm frente a 67 mm, em virtude do maior aproveitamento das peças. Quanto ao fornecedor, observou-se melhor desempenho do externo frente ao interno devido à qualidade da madeira, entretanto, em termos financeiros, esta situação foi inversa em função do menor custo da matéria-prima do fornecedor Interno. Para a forma de processamento da destopadeira, não foi verificado diferença estatística entre os dois sistemas de corte. Palavras-chave: beneficiamento da madeira; fornecedores de matéria-prima; plaina e destopadeira. ABSTRACTWood sector is characterized by a great source of waste generation. This way, the effective control of the productive activities is an essential condition for any company to compete in the market. The objective of the study was to evaluate the yield of raw material in percentage and financial terms of a clear blocks industry, in order to define the best variables for supplier, size and edger. The method involved the selection of variables of interest, edgers (up-down and down-up cuts), size (67 mm and 92 mm) and supplier (internal and external); the determination of the total percent yield and quality grade through the material balance and the financial means of the cost of raw materials, production costs and selling price. The analysis was performed by multifactorial analysis of variance and Tukey's test. The yield of raw materials in percentage terms found in the study demonstrated the superiority of the size 92 mm front and 67 mm, because of the increased use of parts. Concerning to the supplier, it was observed a better performance of the sternum against internal due to the quality of the wood, however, in financial terms, this situation was reversed due to the lower cost of raw material for domestic supplier. To the form of processing in the edger, unverified