Wood species identification based on an ensemble of deep convolution neural networks

Our paper proposed an ensemble framework of combining three deep convolution neural networks (CNN). This method was inspired by network in network. Transfer learning used to accelerate training and deeper layers of network. Nine different CNN architectures were trained and evaluated in two wood macroscopic images datasets. After two times of 30 epochs training, our proposed network obtained 100% test rate in our dataset, which including 8 kinds of wood species and 918 images. The proposed method achieved 98.81% test recognition rate after three times training with 30 epochs in other dataset, which including 41 kinds of wood species and 11,984 images. Results showed that magnification macroscopic images can be instead of microscopic images in wood species identification, and our proposed ensemble of deep CNN can be used for wood species identification.

Thermogravimetric analysis, differential scanning calorimetry and time-to-ignition of wood materials treated with water glass flame retardants

The paper investigates efficiency of silicate flame retardants on wooden fibres (used for production of medium-density fibreboards) and spruce boards. A simultaneous thermal analysis and cone calorimetry were used for the assessment. Specimens were treated with three different types of silicate water glass: sodium silicate, potassium silicate and modified silicate. Along with these, one sample of untreated fibres was tested in order to provide a baseline sample. As a result of the simultaneous thermal analysis, the ability of the treatments to increase the residual amount of biological char in samples during pyrolysis and ability of the flame retardant to be retained in these wood fibres was used to assess the efficiency of each flame retardant on the wood fibres.

Experimental and numerical studies on mechanical behaviors of beech wood under compressive and tensile states

Effect of loading type (compression and tension) on mechanical properties, including elastic constants, yield strength and ultimate strength of beech (Fagus orientalis) wood were studied based on experimental and numerical methods. The mechanical behaviors of beech wood in compressive and tensile states were simulated by finite element method (FEM) using mechanical parameters measured in an experiment. The results showed that the effect of loading types on mechanical properties of beech was statistically significant. The elastic moduli measured in tension were all bigger than those in compression, but the Poisson’s ratios determined in compression were bigger than those in tension. In compressive state, the yield and ultimate strengths of beech in longitudinal grain orientation were all smaller than those measured in tensile state, while the yield and ultimate strengths of beech in radial and tangential directions were higher than those of longitudinal direction. The results of the FEM in compression and tension were all well consistent with those measured by experiments respectively, and the average errors were all within 13.69%. As a result, the finite element models proposed in this study can predict the mechanical behaviors of wood in tensile and compressive states.

The concentration of selected heavy metals in poplar wood biomass and liquid fraction obtained after high temperature pretreatment

The concentration of selected heavy metals: chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu) and zinc (Zn) in 5-year-old wood of Populus trichocarpa before and after steam explosion (SE) and liquid hot water (LHW) pretreatments was studied. The concentration of the above heavy metals in the liquid fraction obtained after pretreatments was also studied. The studied problem of heavy metals in lignocellulosic biomass is an interesting and important issue in the context of bioethanol production technology. An X-ray fluorescence spectrometer (XRF) was used to analyse the concentration of heavy metals. The change of concentration of the tested elements in wood biomass after pretreatment was small (except for iron). On the other hand, the average concentration of iron in wood biomass of a 5-year-old Populus trichocarpa, after SE and LHW with duration of the pretreatments 15 and 60 min, increased about 24-fold to 28-fold, comparing to its average concentration in native wood. During the pretreatment process, wood biomass absorbed the iron that at high temperatures passed from the pretreatment equipment to the solution. The average concentration of the elements under research in liquid fraction obtained during SE and LHW of wood biomass with duration of the pretreatments 15 and 60 min was at a low level.

Study on the structure and properties of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)/ rubber wood fiber composites modified with titanate coupling agent

In this study, the biodegradable composites were prepared from rubber wood fibers (Hevea brasiliensis) and biopolymer poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) via hot pressing process, using the titanate as the coupling agent. The morphological, chemical structure, mechanical properties and water absorption (WA) of the composites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), mechanical properties and WA analysis. Results showed that a new absorption peak of Ti-O-C was formed due to the addition of titanate, indicating that it was successfully grafted on the surface of wood fibers. In addition, the mechanical properties of the composites first increased and then decreased with the increasing of the titanate content. The obvious improvement of WA of composites was attributed to the inclusion of P34HB by titanate modified wood fiber. Moreover, it was also found that the optimal condition of the titanate coupling agent content was 1 wt%.

Antioxidant activity of Swietenia macrophylla king bark extracts

This study investigated the antioxidant activity from the methanol (MeOH) soluble extract of the inner and outer bark of Swietenia macrophylla. The MeOH soluble extracts were fractionated into ethyl acetate (EtOAc) soluble and insoluble. The antioxidant activity was conducted by DPPH (1,1-diphenyl-2-picrylhydrazyl) method and the phenolic compounds were detected by GC-MS. The levels of total phenolic content of soluble and insoluble fraction of EtOAc of outer bark were higher than in inner bark, while total flavonoid content showed opposite results. The crude methanol extract and its EtOAc soluble fraction of outer bark showed a higher level of antioxidant activity. The GC-MS analysis detected higher levels of fatty acids and alcohols of 87.12% than phenolic compounds of 12.17% in the inner bark, while the outer bark showed the opposite pattern with phenolic compounds of 82.65% than fatty acids of 8.43%. A strong correlation was demonstrated between total phenolic content and antioxidant activity.

Comparison of thermal transfer and inkjet printing of UHF RFID tag antennas on paper substrates

UHF RFID printed antennas on conventional and experimentally coated papers by thermal transfer and inkjet technique were not conductive due to high surface roughness. Reducing the surface roughness of paper and hence the electrical resistance of the antennas printed by thermal transfer and inkjet printing was achieved by coating and subsequent calendering process. Papers for thermal transfer and inkjet printed of aluminum and silver antennas were prepared by coating with top functional coating, whose main component was pigment – precipitated calcium carbonate with addition of polyvinyl alcohol, cationic polymer PDADMAC and glyoxal. The desired quality of inkjet-printed silver antennas was achieved by using coated paper with a polyvinyl alcohol barrier layer and a top functional hydrophilic layer. Silver nanoparticles of inkjet ink require a sintering process to obtain a conductive printed trace. The microstructure and thickness of antennas printed by thermal transfer and inkjet technique were compared. Thermal transfer printing created a more homogeneous antenna with greater sharpness of drawing compared to inkjet printing.

Effect of silica on alkaline bagasse cellulose and softwood cellulose

This study investigates the effect of silica on sugarcane bagasse (SCB) and softwood (SW) cellulose. Cellulose was extracted from raw SCB and SW chips using a three-step process, namely thermal pre-treatment, alkaline treatment and bleaching treatment. Alkali treated cellulose was then subjected to silica surface modification using the solvent exchange method. The effect of silica modification on SCB and SW cellulos was investigated using X-ray diffractions analysis (XRD), Fourier transform infrared (FTIR) spectroscopy and optical microscope (OPM) techniques. Both the FTIR and XRD results confirm successful extraction of cellulose from both raw fibers and addition of silane functional groups in the cellulose surface. XRD patterns of all samples revealed typical spectra for natural fibers corresponding to crystalline peaks of cellulose and undissolved amorphous hemicellulose respectively. SCB and SW showed similar increasing patterns of crystallinity with nanosilica surface modification. The surface morphology results showed that both SCB and SW cellulose modified with silica were swollen and displayed small particles agglomerating on the surface of the fibers. The solvent exchange method proved to be a successful method for modifying SCB and SW cellulose with nanosilica. It also proved to be cost-efficient and time-efficient.

Effects of light thermal treatments on the color, hygroscopity and dimensional stability of wood

Ailanthus wood (Ailanthus desf.) was thermally treated at three different low temperatures (140, 160, 180°C) for 2 and 4 h in order to investigate the effects on wood color, hygroscopity and dimensional stability. Results indicate that mass loss increased following the treatments, while equilibrium moisture content decreased from 11.86% to 9.88% for the 180°C and 4 h treatment. Moreover, improvements in the dimension stability were observed for post-treatment samples. The thermal treatment induced color changes in the Ailanthus wood, with a significant reduction in the lightness, yet the redness and yellowness exhibited minimal changes. FITR spectra of the thermally treated wood suggest that the heat treatment resulted in the deacetylation of hemicellulose. These results help to conclude that thermal treating temperature under 160°C can improve wood dimensional stability and maintain original color.

Cross-correlation of color and acidity of wet beech wood in the process of thermal treatment with saturated steam

The paper presents changes in the color and acidity of Fagus sylvatica L. in the process of heat treatment of wood with saturated water steam in the temperature range t = 105 – 135°C during τ = 3 to 12 hours. The light white-gray color of beech wood with a yellow tint changes on the pale pink, red-brown to a brown-red color in the heat treatment process. The color changes of beech wood expressed in the form of the total color difference are in the range of values ΔE* = 1.97 – 26.85. Due to the hydrolysis of hemicelluloses, the acidity changes in the process of thermal treatment of wet beech wood. Decrease in acidity of beech wood in the range of temperatures t = 105 – 135 °C and time τ = 3 – 12 hours is in the range of pH values = 4.9 to 3.4. The dependence of the total color difference ΔE* on the change in acidity of beech wood is described by the polynomial of function II. degree. The above knowledge is a suitable tool for evaluating the degree of change in beech wood color in the technological process based on the change in pH of wood.

Wood properties comparation of Cedrela odorata from trees in agroforestry and in pure plantation

The aim of this work was to compare the general, physical, mechanical, chemical and energy properties of the wood from Cedrela odorata trees growing in two agroforestry condition (tree-agroforestry) with Theobroma cacao (9 and 10 years old), with a ten-year-old C. odorata tree growing in pure plantation (tree-plantation). The results showed that there growing in agroforestry presented higher heartwood diameter (6.7 to 7.6 cm) and heartwood (approx. 17%) and lower bark (12-13%) and sapwood (69-70%) percentages than trees in pure plantation. In addition, this tendency was observed through different heights of the tree. Moreover, wood from 9-tree-agroforestry presented highest specific gravity and volume shrinkage. Then wood from this growing condition presented highest strength in axial hardness and flexure relative, and extractives in cold water and ethanol-toluene. No differences were observed between the energy properties. In general, wood from trees in agroforestry present better properties than the trees growing in pure plantation. According with these results, the potential of agroforestry systems relative to pure plantations, as regards to differences in tree growth produced by crop fertilization, pruning and other management measures to which the agricultural crop is subjected, which can give the wood qualities different from those found at earlier ages.

Effect of hot pressing modification on surface properties of rubberwood (Hevea brasiliensis)

This research aims to investigate the effect of thermal modification by hot pressing on surface characteristics of rubberwood. For this purpose, rubberwood specimens were thermally modified by hot pressing in an open system at three different temperatures (170, 185, and 200°C) for two different durations (1.5 or 3 h). Based on the results, the values of chromatic aberration (ΔE), contact angle and glossiness increased, and roughness decreased with increasing temperature and enlarging duration further. Although the contact angle had increased, it was still less than 90°. This aesthetic surface of rubberwood could be retained by using transparent organic coatings. The thermally modified rubberwood with excellent performance could be used as a material for solid wood flooring, wallboard, and furniture applications.

Study on lamb wave propagation characteristics along the grain of thin wood sheet

Through the time-frequency analysis of the propagation waveform of the acoustic emission (AE) signal propagating in the thin sheet of Pinus sylvestris var. mongolica, the propagation characteristics of the stress wave when propagating as a lamb wave was studied. An AE source was generated on the surface of the specimen, the discrete wavelet transform method was used to achieve AE signal de-noising and reconstruct the waveform of the AE signal. On this basis, the time difference positioning method was used to calculate the propagation velocity of lamb waves, and compared with the propagation characteristics of lamb waves in the metal specimen. The results show that the high-frequency mode of lamb waves attenuated sharply as they propagate in the thin wood sheet, indicating that the microstructure of wood has a significant low-pass characteristic for lamb waves. The average attenuation rates of lamb waves in metal and thin wood sheet were 87.1% and 75.7%, and the velocity was 4447.0 m.s-1 and 1186.3 m.s-1, respectively. This shows that AE signals can travel longer distances in the thin wood sheet, but the propagation velocity is significantly reduced.

Analysis of cutting force in the process of chipless felling wood

This study compared the magnitude of the value of the cutting force using different tools with different thickness for different wood species with the same size. Measurements were made on wooden samples of spruce, aspen, and beech wood with dimensions 30 × 30 × 200 mm (w × d × h). The tearing machine pushed knives with dimension 150 × 100 mm and thicknesses of 4, 6, 8, and 10 mm with a 30° angle of cutting edge into the wood samples in a direction perpendicular to the fiber growth. Research shows that this angle of cutting edge is most effective for chipless cutting. The results were analysed by the Statistica 12 software. From the measurement results, for chipless wood felling is most preferred the 10 mm cutting knife thickness.

Synthesis and characterization of resol type phenol-formaldehyde resin improved by SiO2-Np

In this work, resol type phenol–formaldehyde (RPF) resin was modified with silicon dioxide nanoparticles (SiO2-Np). SiO2-Np was added at varying ratios from 1 to 4 wt.% to improve the bonding performance of the RPF resins. The physical characteristics of the nano-modified RPF (nano-RPF) resins were examined. The effects of modification were studied by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The results of FT-IR revealed that the nano-RPF resins were successfully produced by phenol, formaldehyde, and SiO2-Np. The nano-RPF resins demonstrated high thermal stability at temperatures above 500°C. The adhesive performance of the nano-RPF resins was investigated under dry and wet conditions. The nano-RPF resins indicated better adhesive performance than unmodified RPF resin. The RPF resin could be improved by SiO2-Np.