In order to explore the influence of wood’s anisotropic characteristics on Acoustic Emission (AE) signals’ propagation, the law of AE signals’ propagation velocity along different directions was studied. First, The center of the specimen’s surface was took as the AE source, then 24 directions were chose one by one every 15º around the center, and 2 AE sensors were arranged in each direction to collect the original AE signals. Second, the wavelet analysis was used to denoise the original AE signals, then the AE signals were reconstructed by Empirical Mode Decomposition (EMD). Finally, time difference location method was utilized to calculate AE signals’ propagation velocity. The results demonstrate that AE signals’ propagation velocity has obvious feature of quadratic function. In the range of 90º, as the angle of propagation direction increases, the propagation velocity of the AE signals presents a downward trend.
The aim of this work was to analyse the relationship between anatomical parameters of spruce tracheids and climatic factors and air pollution load, in the period before, during and after the maximum air pollution load. In this study we used the method of dividing annual rings into a number of equally wide sectors, for which the average values of the tracheid dimensions, i.e., the lumen area and cell wall width, were determined. This method was compared to the classic approach, which works with the average values of parameters for the entire annual ring, or for earlywood and latewood. The study showed that the trees responded to the increased concentration of pollutants by reducing the widths of the annual rings and the values of the anatomical parameters. The higher resolution of data gives us a better insight on the influence of abiotic factors to the wood structure. The ratio of cell wall thicknesses of earlywood to latewood was also shown as a good indicator of stress.
Black locust (Robinia pseudoacacia L.), beech red heartwood (Fagus sylvatica L.) and spruce (Picea abies Karst.) wood samples were treated in saturated steam at 100, 110 and 120°C then irradiated using a UV emitter mercury lamp in order to test their colour stability. Colour change was evaluated and presented in the CIE Lab colour coordinate system. Untreated black locust, beech and spruce specimens as control samples were irradiated using the same mercury lamp. Results revealed that beech produced the greatest colour stability during both steam treatment and the following UV treatment while spruce was the most sensitive species to photodegradation. Steaming reduced the colour change intensity only for black locust during photodegradation. Both redness and yellowness change demonstrate this colour stability increase. Steaming at 120°C resulted in the greatest protection against the colour alteration of black locust caused by photodegradation. The investigated thermal treatments did not change the photodegradation properties of beech and spruce specimens. A considerable increase in colour saturation of the specimens was generated by steaming, and the saturation value further increased during the UV treatment.
The cinnamaldehyde, salicylic acid, stearolic acid and citric acid were plant-derived organic compounds that can be activated to fungi, that could degrade the wood in long term. The compounds with concentrations of 3%, 5% and 7% assisted by different dispersants were impregnated into poplar (Populus nigra L.) specimens by the vacuum-pressure method. After that, weight percentage gain (WPG), decay resistance against white-rot fungi (Trametes versicolor) and brown-rot fungi (Gloeophyllum trabeum), color change, dimensional stability and mechanical properties including modulus of elasticity (MOE) and modulus of rupture (MOR) were measured. The results indicated that cinnamaldehyde impregnated poplar showed antifungi activity against both G. trabeum and T. versicolor, and citric acid impregnated poplar showed antifungi activity against G. trabeum. The color of poplar specimens before and after impregnated cinnamaldehyde and citric acid had a little change, dimensional stability had been improved and mechanical properties especially for MOR increased significantly.
This is a study of the influence of microwave (MW) pre-treatment on the permeability of Norway spruce ripewood (Picea abies L. Karst) as it affects its mechanical properties. Specimens were treated under variable moisture content, MW intensity, and impregnation processes. According to the results, the specimens with an initial moisture content of 45–65% exhibited the highest permeability values compared to reference samples. An insignificant difference was found between MW pre-treatments at 2 and 3 kW. Statistically significant results were found after long-time (24h) vacuum-pressure impregnation (LP). The average retention value following LP was 132 kg.m-3, which is almost three times greater than the MW-treated groups impregnated in a short-time vacuum-pressure process. The average depth of penetration after LP was 2.0 mm and the proportion of the impregnation area following LP was 17.6%. MW pre-treatment had no effect on the impregnability or the mechanical properties of the wood; other MW regimes are open for further examination.
The Brazilian standard ABNT 7190 (1997) establishes the strength classes C20, C30, C40 and C60 for the proper framework of the different wood types in the group of hardwoods. Associated with the strength class, which is based on the compressive strength characteristic value parallel to the fibers (fc0,k), the standard stipulates the respective values representing the stiffness (Ec0), with 19500 MPa being the reference value for the class C40, essential variables in structural design. For being the C40 class is the one with the greatest amplitude (20 MPa), it is possible that the value 19500 MPa is not the best representation of stiffness. This work aimed to verify the representativeness the stiffness value established by the Brazilian standard for C40 wood. The result obtained from the average confidence interval indicates the value of 14110 MPa as being the most representative, which may imply structures that are supposedly more rigid than they really are.
Trace element investigation and its corresponding concentration level in selected tropical woods from western Nigeria was done using PIXE-particle induced X-ray emission methods. Fifteen selected tropical woods were analyzed and twenty-seven trace elements were identified and quantified. The identified trace elements are Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Br, Rb, Sr, Y, Zr, Ba, Pb and Bi. Calcium concentration were 2835, 3195, 4923, 5608, 7770, 5110, 2743, 5092 and 3451 ppm in samples 2, 5, 6, 10, 11, 12, 13, 14 and 15, respectively. Potassium recorded 2838, 4811, 3184, and 2021ppm in samples 1, 3, 8 and 9, respectively. Silicon recorded 5206 ppm for sample 4 and 5253 ppm for sample 7. Calcium and potassium were observed to have concentration level that is greater than 1000 ppm in all the studied samples, hence it can be said that calcium and potassium are major trace element of wood. The concentrations of the elements identified have no immediate health concern on environment and human, therefore the studied tropical woods safe for use as fuel and other purposes.
The purpose of this research was to analyze the performance (wear resistance, surface roughness, chip formation, and noise level) of AlCrN, TiN, and TiAlN coated tungsten carbides in cutting composite boards. The composite boards of wood plastic composite, laminated veneer lumber, and oriented strand board were cut by the coated tungsten carbide tools in a computer numerical control router. The results show that the differences in structure among the composite boards resulted in the difference in clearance wear, chip formation, surface roughness, and noise level phenomenon. The abrasive materials in wood plastic composite generated the highest clearance wear on the coated carbide tools tested. TiAlN coated carbide tool provided better wear resistance, smoother composite boards surfaces, and lower noise levels.
In this study, effects of heat treatment on bending strength, compression strength, chemical compound and solubility of Black pine wood (Pinus nigra J.F. var. seneriana) was examined. For this purpose, Black pine wood samples were kept in temperature of 250°C for 2 hours. Test results of heat-treated Black pine wood and control samples indicated that mechanical characteristics including compression strength and bending strength were affected negatively with heat treatment. Bending strength of heat treated and non-treated test samples were 129 and 76 N.mm-2, respectively. Compression strength of heat treated and non-treated test samples were 53 and 43 N.mm-2, resp. In addition, level of extractives, cellulose and hemicellulose decreased while lignin content increased with percentage of 40%. Significant decreases occurred in all chemical solubility values.
The publication is focused on the effect of ultra low and high temperature on enzymatic pretreatment of beech wood (Fagus sylvatica L.). Two fractions < 0.7 mm and 1.0 – 2.5 mm of disintegrated branches sawdust were used for experiments. Glucose and xylose yields were measured after 24, 48, and 72 hours of enzymatic hydrolysis with 15 % load of the enzyme measured to total cellulose content. The influence of freezing under -80°C and boiling under pressure at +160°C on samples before enzymatic hydrolysis was observed. Mutual combination of boiling under pressure to obtain the maximum water uptake and subsequent freezing was used to better understand the process of cell destruction. The results show that the boiling pretreatment has a positive influence on the total monosaccharide yields and the subsequent freezing may slightly increase these yields even further. The maximum monosaccharide conversion (73.24%) was achieved using the fraction < 0.7 mm.
The influence of stand density on the resin duct morphological structure and terpene components of Pinus massoniana were studied. The resin duct morphological characteristics and the relative content of the terpene components were investigated by microscopy and gas chromatography-mass spectroscopy, respectively. The experimental results revealed that there was a specific correlation between the stand density and resin duct area, resin duct diameter, and the relative contents of main terpene components in the turpentine extracts. Additionally, the relative contents of β-pinene and (+)-camphene were positively correlated with stand density, with correlation coefficients of 0.8208 and 0.5539, respectively. In contrast, the relative contents of (+)-longifolene and (+)-longicyclene were negatively correlated with stand density, with correlation coefficients of -0.5750 and -0.7726, respectively, and α-pinene, β-caryophyllene, and (+)-α-longipinene had no correlation with stand density. The relative content of (+)-α-pinene was negatively correlated with the relative contents of both (+)-longifolene and (+)-longicyclene, with correlation coefficients of -0.8770 and -0.8914, respectively. There were positive correlations between the relative contents of (+)-longifolene and (+)-longicyclene with correlation coefficient of 0.9718, (+)-longifolene and (+)-α-longipinene with correlation coefficient of 0.8399, β-caryophyllene and (+)-α-longipinene with correlation coefficient of 0.9360, and (+)-longicyclene and (+)-α-longipinene with correlation coefficient of 0.8626.
Grifola frondosa HAI 1232 was tested for ligninolytic enzyme activities and for lignin, cellulose and hemicellulose degradation during cultivation on eight common agro-forestry residues in Serbia. Wheat straw was favorable lignocellulosic for the production of Mn-dependent and Mn-independent peroxidases (2513.89 and 354.17 U L-1, respectively), while selected residues inhibited the synthesis of laccases. The highest lignin removal was observed during fermentation of blackberry sawdust (36.75%), while the highest selectivity index was recorded on oak sawdust (4.34). The dry matter loss varied between 8.17% in corn stalks and 14.16% in apple sawdust. According to the presented results, it can be concluded that G. frondosa HAI 1232 could be an important participant in various biotechnological processes due to its high capacity to selectively degrade different agro-forestry residues.
Four solvents including distilled water, acetone, ethyl acetate and petroleum ether were used to extract xylem of C. camphora. The differences in chemical compounds of xylem of C. camphora were analyzed by gas chromatography/mass spectrometry (GC/MS) and the anti-fungal activity of C. camphora extractives on Coriolus versicolor (CV), Trametes versicolor (TV), Poria vaporaria (PP) and Gloeophyllum trabeum (GT) were tested. The result showed that the chemical composition and relative content of the four different solvent extracts were different. A large number of chemical compounds in the C. camphora extractives had a variety of biological activity and certain application value. The growth inhibitory rates of ethyl acetate extracts of C. camphora on PP, CV, TV and GT were 52.24%, 52.51%, 43.26%, and 54.63%, respectively. According to the concentration for 50% of maximal effect, the inhibitory order on test fungus were GT > PP > CV > TV.
Given the carcinogenicity of hardwood dust, the aim of this study was to determine the effectiveness of the photometric method for different types of woodworking machines and its application in determining the mass concentration of inhalable dust for raw and dry hardwoods. In addition to the optical part of the device, the input part of the measuring device contains the Institute of Occupational Medicine (IOM) inhalable dust filter holder. This correlation of gravimetric and photometric methods in determining the dust mass concentration showed that photometry underestimates the mass concentration measured gravimetrically. The results of this study recommend the application of a correction factor 2 for a timber band saw and a correction factor 3 for circular saws in determining the mass concentration of hardwood dust by the photometric method. It was showed that photometry can be used if the correction factor of the optical device has been previously tested for specific wood processing place.
The paper aims to use the residue of sunflower seed hulls to obtain organic briquettes and to improve their properties by using larch shavings obtained in the process of solid wood planning. The physical-mechanical properties of briquettes made on a hydraulic machine, calorific value, ash content and volatile content were evaluated. The obtain results highlighted the briquettes obtained from larch waste, but also the acceptable characteristics of the briquettes obtained from sunflower seed husks. The main conclusions of this study is that briquettes obtained from unprocessed sunflower seed husks are acceptable in terms of physical-mechanical and calorific characteristics, even if they do not reach the level of briquettes obtained from larch shavings.