Volume 79, Issue 4-5

The identification of wood species is critical for effective forest management and conservation. However, existing methods frequently neglect the potential benefits of integrating multiple spectral properties. Current research often relies on uniform feature selection and modelling methods, despite the fact that each spectral technique has its own optimal recognition model. This study aims to address the gap in THz, NIR, and HSI data, systematically comparing these techniques to derive the best recognition models. This study employed the SNV transformation to preprocess the spectral data of four coniferous and one broad-leaved species. Subsequently, relevant frequency features were filtered using competitive adaptive weighting (CARS), uninformative variable elimination (UVE), and successive projections algorithm (SPA) to reduce dimensionality and enhance recognition efficacy. A comparative analysis of five algorithms – extreme learning machines (ELM), support vector machines (SVM), random forests (RF), long short-term memory networks (LSTM), and convolutional neural networks (CNN) – was conducted to identify the optimal recognition models. The results demonstrated impressive accuracy rates: 96.7 % for NIR (UVE + CARS + ELM), 96.7 % for HSI (CARS + LSTM), and 98.3 % for THz (SPA + RF). This analysis identifies the most effective models for each spectral type, advancing the field of spectral wood identification.

Solutions for species discrimination are important for monitoring native timber harvesting. Near-infrared (NIR) spectroscopy has shown promise for identifying wood species in real time. The influence of moisture content on the model’s performance for classifying wood is not well known. The objective was to evaluate the effect of wood moisture on the predictive capacity of the models for species discrimination based on NIR spectra using a benchtop and a portable spectrometer. First, NIR signatures were collected on the radial face of wood specimens at equilibrium moisture content (EMC) of 11 native species from Amazonia using both equipments. After saturation, new spectra were collected at the maximum moisture condition and subsequently at every 10 % of the water mass loss during drying. Partial least squares discriminant analysis (PLS-DA) was developed to discriminate the timber species according to their spectral signatures. Principal component analysis of the spectral data obtained in EMC was able to discriminate the species depending on the density gradient of the specimens. Moisture had no significant impact on the spectral signal. The PLS-DA models successfully classified unknown wood samples by species with over 91 % accuracy, regardless of moisture content. Both NIR devices show strong potential for use in forest inspections.

This study was aimed to efficiently produce vanillin and its analogues (vanillins) from kraft or soda lignin in a system that is ready for practical installation owing to its possible operation in already-established mill equipment. This readiness is absent from most previous studies on the same topic. The knowledge accumulated in previous studies by the authors’ group on lignin oxidation resulted in a conclusion that the highly alkaline hydrogen peroxide treatment (HA–H 2 O 2 –Tr) can be the best method. Another authors’ recent study showed the efficient production of vanillins in HA–H 2 O 2 –Tr of a lignin model compound. In this study, kraft or soda lignin was treated in HA–H 2 O 2 –Tr to examine optimal conditions for the efficient production of vanillins. The highest yields of vanillins, 7.5 and 8.5 %, were obtained using HA–H 2 O 2 –Tr of kraft and soda lignin, respectively, under the following conditions: NaOH, FeCl 3 , and d -mannitol concentrations of 3.0 mol/L, 1.08 mmol/L, and 3.92 mmol/L, respectively; H 2 O 2 solution (0.245 mol/L) addition rate and period of 80 μL/min and 100 min, respectively; temperature of 90 °C. The highest yields were no lower than those in previous studies on the production of vanillins from kraft or soda lignin.

This article investigates the mechanical properties of linden green wood, setting out the results of three approaches to assessing tree stability and strength aimed at improving the safety evaluation of living trees. Due to the high moisture content (MC) of green wood and its significant impact on its mechanical properties, data from dried specimens cannot be used to model green wood behaviour. The research was carried out on wood samples with both 40 % and 60 % MC. A non-destructive test (NDT) assessed specimens and measured their vibro-acoustic material properties. Subsequently, destructive static tests were conducted along the three main orthotropic axes of the wood samples. The resulting data led to the development of a bilinear orthotropic model and a comprehensive dataset covering both elastic and plastic material properties. Next, the material properties were optimised to compute and validate a numerical model using the finite element method (FEM). By refining the material properties, the FEM predictions closely matched the experimental results, with a maximum error of 5 %. This information on the wood’s experimental, FEM and NDT-derived properties offers an excellent basis for evaluating linden green wood for many applications.

Free shrinkage is a natural characteristic of wood during drying, occurring when the moisture content (MC) drops below the fiber saturation point (FSP). However, achieving complete free shrinkage in practical processes is challenging due to drying stresses from varying rates between the surface and core layers. Eucalyptus wood is particularly prone to collapse above the FSP, complicating the free shrinkage process. This study investigates the free shrinkage characteristics of 2-mm thick Eucalyptus urophylla  ×  E . grandis specimens, both sliced along the fiber direction and split tangentially (layered). The findings are as follows: Layered specimens exhibited significant shrinkage ratios (5.7–6.7 %) and equilibrium moisture content (EMC) values (19.0–22.7 %), which can be attributed to the differing anatomical structures across layers. In contrast, sliced specimens did not display a MC gradient during drying, but their shrinkage was somewhat constrained by adjacent layers. Consequently, layered specimens had fewer radial and tangential restrictions, allowing more pronounced unrestricted shrinkage. Also, the slight collapse in smaller sliced specimens had a negligible impact on free shrinkage. To achieve free shrinkage without collapse, it is essential to use small-sized specimens in both fiber and radial directions while maintaining low temperatures and high relative humidity (RH) conditions.

Electromagnetic waves are used in wood inspection and treatment. Three important parameters need to be considered in the application of this method, including moisture content (MC), porosity, and dielectric constant ( ε ), which affect the effectiveness of application of electromagnetic waves, and these parameters can interact with each other. This study’ elucidated the effect of porosity on the ε of wood at different MCs (absolute dry to saturated) in the frequency ( f ) range of 1 Hz–10 7  Hz. The results indicated that the porosity on the ε needs to consider both f and MC. Relationships between porosity and ε of absolute dry wood shows opposite patterns in different f bands. When f  ≤ 200 Hz, the porosity was positively correlated with ε . When f  > 200 Hz, the porosity was negatively correlated with ε . However, the effect of f on ε with the increased of MC was complicated., Correlations with MC, porosity and ε was not significant when f was low. As f increased, the relationship between MC and ε became linear. The results of this study provide a reference for use of ε to detect wood pore characteristics and MC.

This study assessed marine borer damage to various wood species along Korea’s coast, severe damage was found in 6 Korean and a tropical (Dillenia) species, other tropical (Apitong and Ipe) and modified woods showed resistance to marine borers even after exposure for up to six months. Molecular identification of organisms from wood samples revealed 12 species, including key marine borers Bankia carinata , Teredo navalis , and Limnoria sp. The results of this study are expected to provide useful information on marine borers and marine durability as preliminary data for the use of wood in the marine environment of Korea.