Oak Samples Research Articles

Sustainable Lignin Extraction Using a Mild Acidic γ-Valerolactone Process for the Identification of White and Red Oaks.

Current wood identification struggles to differentiate white and red oak (Quercus alba and Quercus rubra) due to highly similar microstructures, as demonstrated by morphological microscope analysis. The present research explores lignin composition as a potential discriminating factor. Here, a rapid and sustainable method for extracting high-quality lignin from oak samples using acidic γ-valerolactone (GVL) under mild conditions is described. As-extracted lignin is thoroughly characterized using various analytical methods, and results reveal a distinct structural difference between the lignin from the two species. White oak lignin possesses a unique "Hibbert ketone" unit detectable by nuclear magnetic resonance spectroscopy (NMR), which is absent in red oak lignin. In addition, infrared spectroscopy differentiates the species based on specific carbonyl groups present in their lignin. These findings suggest that identifying the presence of the Hibbert ketone unit in lignin may offer a highly efficient and reliable method for differentiating white and red oak, opening new avenues for wood identification.

A rapid LAMP assay for the diagnosis of oak wilt with the naked eye

BackgroundOak wilt disease, caused by Bretziella fagacearum is a significant threat to oak (Quercus spp.) tree health in the United States and Eastern Canada. The disease may cause dramatic damage to natural and urban ecosystems without management. Early and accurate diagnosis followed by timely treatment increases the level of disease control success.ResultsA rapid assay based on loop mediated isothermal amplification (LAMP) was first developed with fluorescence detection of B. fagacearum after 30-minute reaction time. Six different primers were designed to specifically bind and amplify the pathogen’s DNA. To simplify the use of this assay in the field, gold nanoparticles (AuNPs) were designed to bind to the DNA amplicon obtained from the LAMP reaction. Upon inducing precipitation, the AuNP-amplicons settle as a red pellet visible to the naked eye, indicative of pathogen presence. Both infected and healthy red oak samples were tested using this visualization method. The assay was found to have high diagnostic sensitivity and specificity for the B. fagacearum isolate studied. Moreover, the developed assay was able to detect the pathogen in crude DNA extracts of diseased oak wood samples, which further reduced the time required to process samples.ConclusionsIn summary, the LAMP assay coupled with oligonucleotide-conjugated gold nanoparticle visualization is a promising method for accurate and rapid molecular-based diagnosis of B. fagacearum in field settings. The new method can be adapted to other forest and plant diseases by simply designing new primers.

Effect of the percentage of MUF adhesive coverage on shear strength when bonding different wood species

Due to climate changes, it is necessary to consider the use of other wood species to replace currently used woods. This work deals with the determination of the shear strength of bonded veneers (eight European wood species: spruce, larch, pine, beech, oak, poplar, birch, and alder) with Silekol® 311 melamine-urea-formaldehyde adhesive (MUF) with a variable coverage on the surface of the samples: 10, 15, 20, 25, 30, 50, 75, and 100%. The Automated Bonding Evaluation System (ABES) was used to evaluate and compare adhesive bond strengths. The larch, beech, and oak samples exhibited greater single-lap shear strength than the control samples from spruce. There was no statistically significant difference in shear strength regarding the adhesive coverage from 100% to 20% on the surface of the samples, for almost all wood species. The results of the project provide basic information about the bonding strengths with different coverage in the adhesive layer, comparing non-commonly used wood species in wood-based composites such as oriented strand board and particleboard.

Effects of Wildland Fuel Composition on Fire Intensity

Assessing the characteristics of fuel flammability during fire is of major significance regarding fire intensity and fire spread control. Under the background of shifting forest composition from heliophytic to mesophytic species in mixed-oak forests, our objective is to determine the impacts of species-driven changes in fuel flammability characteristics and the specific relationships between fuel ignition variations at the species level. Oak and maple fuels were collected from ninety-four plots established in Zaleski State Forest, Ohio. A total of 30 combustion samples were separated (15 oak samples and 15 maple samples), with each combustion sample weighing 20 g to ignite under a laboratory fume hood. Our results determined that oak fuel showed significantly higher flame temperatures than maple fuel, and the fuel consumption and combustion duration time both varied between oak and maple fuel. These findings indicated that the shift from oak forest to mesophytic species could change a fire’s behavior. Combined with the cooler, moister, and less-flammable forest conditions generated by these mesophytic species, fires may not be able to reach their historical fire intensities, suggesting that updated data and new insights are needed for fire management.

Evaluation of CNC routed surface quality of maple (Acer pseudoplatanus) and oak (Quercus robur L.) with different milling angles as function of grain orientation

The study assessed CNC routing quality on maple and oak samples, using 90º V-Grooving router bits at various milling angles as function of grain orientation: 0°, 15°, 30°, 45°, 60°, 75°, 90°, and feed speeds of 3 and 6 m/min at spindle speed of 15,000 rpm. The routing quality was evaluated by roughness parameters for the V flank surfaces and by visual examination for the flanks’ edges. The change in the feed speed had no significant effect for the flanks surface quality of both species, but roughness values were considerable higher for maple samples at 90º and u=3 m/min (Rk = 23.7 µm compared to along the grain, Rk=9.83 µm for u=6 m/min) due to possible processing vibrations. The milling angle as function of grain orientation was significant in the case of oak, as the processing roughness increased with the cutting angle from 0° (Rk=11 to 13 µm) to 60°(Rk =28 to 30 µm). Fuzziness around the earlywood pores of oak was higher for the 6 m/min feed speed. A substantial increase in waviness coinciding with the annual growth areas was measured for crosscut oak samples (Wa = 34.0 µm, compared with Wa =7 .39 µm along the grain). The surface waviness of maple was not sensitive to the variation in the cutting angle or feed speed (Wa was around 3 to 4 µm). For the flank edges, the best visual option was found for cutting along the wood grain and the worst was for 60º, which caused biggest ruptures and especially for the 3 m/min feed speed, for both species.

Non-destructive Dendrochronology: The Effect of Conservation Agents on Tree-ring Measurements in Archaeological Oak with Micro-computed Tomography

ABSTRACT The effect of different conservation methods on non-destructive dendrochronology with micro-computed tomography (μCT) of waterlogged archaeological wood (WAW) was assessed. To this end, oak samples were conserved with alcohol-ether-resin, Kauramin 800®, lactitol/trehalose, saccharose, silicone oil and different polyethylene glycol (PEG) treatments with subsequent freeze-drying. Tree-ring measurements were compared with respect to the number of rings and the mean ring width using (a) an analog linear measuring table and (b) the digital μCT. Overall, the measurements in the μCT data agreed very well with the corresponding microscopic measurements. It was possible in all cases to recognize the rings in the samples with μCT. A dendrochronological cross dating with regional absolutely dated oak ring width chronologies was successful. However, the varying influence of conservation agents on the quality of the μCT data were also evident. To quantify this influence, the contrast in the μCT data were calculated using gray-scale profiles. An influence on the contrast in the μCT data were detectable for all conservation agents. The contrast is especially reduced due to conservation methods using lactitol/trehalose, PEG, saccharose and silicone oil. Overall, the experiments confirm, though, that μCT is a powerful and accurate tool for dendrochronology of conserved archaeological oak objects.

Impact of biochemical composition on the pyrolysis products of cork oak (Quercus suber) samples

The impact of biochemical composition (cellulose, hemicelluloses, lignin, and suberin) on the products of pyrolysis of lignocellulosic biomass was investigated. A comparative study using double-shot pyrolysis of cork, branches and leaves of cork oak (Quercus suber) was conducted. Differential scanning calorimetry and thermogravimetric analysis (DSC-TGA) demonstrated 350 °C and 550 °C to be the optimal temperatures for the two shots. Leaves and branches released mainly polysaccharide derivatives in the first shot and produced phenols in the second shot, while cork mainly released ketones in the first shot and produced aliphatic hydrocarbons in the second shot. Higher selectivities in high added-value chemicals, such as benzofurans (20.3 %) and ketones (26.5 %) were respectively achieved for leaves and branches at 350 °C whereas aliphatic hydrocarbons (48.8 %) were mainly obtained from cork at 550 °C.

Effect of Abrasive Grain Size on the Abrasion Volume Loss of Subfossil and Recent Oak Wood in Three Characteristic Sections

Subfossil wood is a valuable and rare material often used for production of expensive furniture and decorative artistic items of unique beauty. Its mechanical and tribological properties are still being studied and are considered specific due to the particular conditions of its long-lasting formation in aqueous sediment sludge. Various elements that have been impregnated into the wood tissue over many years make the machining and grinding of this type of wood rather difficult compared to normal recent wood. The main objective of this study was to determine the influence of the abrasive grain size of sandpaper on the abrasion volume loss of recent and two subfossil oak samples in three characteristic sections (cross, radial, and tangential). The results showed that the average size of abrasive grains and the orientation of the wood structure have an influence on the abrasion volume loss of all three samples. The phenomenon of the critical size of abrasive grains was observed in all samples and on all sections. As the size of abrasive grains increased to the critical size, the abrasive volume loss of the sample increased simultaneously. The lowest abrasion volume loss was observed on recent oak. In all samples, the lowest volume loss was measured on the cross sections, and the tangential and radial sections had mutually equal values. It was also found that the increase in the size of abrasive grains to a critical value resulted in the increasing value of the absolute difference between the abrasion volume loss of the cross, radial, and tangential section samples, while the relative relations between the abrasive volume loss values of three different sections (C/R, C/T, R/T) within the same grit of sandpaper remained quite similar.

Proof of the Elongation Reserve of Longitudinally Compressed Wood by Tensile Tests

This paper deals with the proof of the theory of elongation reserve remaining in wood after compression parallel to the grain. After compression, the wood becomes much more pliable and the force required for bending is reduced. At the end of the 1-minute fixation following 20% compression, the compressive stress in the beech samples was reduced to an average of 72.3%, while the oak samples showed a 65.6% change. The remaining shortening at this time was 3-5%. At the end of the 3-hours fixation, the compressive stress had decreased to 37.1% for beech and 27.9% for oak, resulting in a residual shortening of 12-18%. An average maximum tensile force of 1.76 kN was required for untreated beech samples, which resulted in a 1.55 mm increase in size parallel to the grain. For specimens fixated for a short-time, a tensile force of 1.06 kN caused a 3.66 mm increase in size, while for specimens fixated for a long-time, a force of 0.85 kN caused an 8.79 mm increase in size. The trends were similar for oaks. The higher moisture content provided a significantly larger increase in size during the tensile tests. The existence of the elongation reserve was clearly confirmed.

Enhancement of Biogas Production from Sawdust through Sustainable Alkaline and Biological Pretreatment Methods

This study aims to enhance biogas production from sawdust fibers Quercus genus (oak) using sustainable pretreatment methods. Sawdust and poultry dung (substrates) were obtained in Ogbomoso and delignification of oak samples was carried out through gravimetric method on 5, 10, and 15 days before and after digestion. Physico-chemical parameters were analyzed according to American Public Health Association (APHA) (2018) standard. Anaerobic digestion on substrates was performed through alkaline and biological pretreatment processes, biogas samples were collected and analyzed using gas chromatograph mass spectrometer. Pretreatment results for delignification of raw sawdust, alkaline and biological pretreated at 5, 10 and 15 days were; 13.5, 2.0, 1.5, 1.0 and 1.0 in mg/l. Physico-chemical results of substrates before and after digestion respectively were; pH (7.38, 8.12); alkalinity (350, 475); Nitrogen (25.5, 38.2); Phosphorus (2.67, 2.43); Carbon (192.8, 342.1); Potassium (4.1, 3.5); Phosphate (56.0, 128); Sulphate (74.0; 69.0), Calcium (12, 44); Magnesium (65, 36); Manganese (0.010, 0.031), Iron (5.2, 6.1); Zinc (25.0, 17.4); Aluminium (0.35, 0.34); Copper (2.5, 2.5); Biochemical Oxygen Demand (110, 175); Chemical Oxygen Demand (964, 1440); Carbon/Nitrogen ratio (8:1, 9:1); Volatile Solids (1216, 4560); Moisture Content (25.8%, 63.1); Total Solids (66.2%, 17.8%) and Volume of Solids (58.2%, 77.7%) in mg/l. Biogas samples composition from biological and alkaline pretreatments were: Methane (65.05%, 62.27%); and Carbon Dioxide (17.51%, 13.28%). Both pretreatment methods produced enough methane percentages, but biological pretreatment performed better. This work is applicable in sustainable biogas production for environmental protection.

Historic Wooden Shipwrecks Influence Dispersal of Deep-Sea Biofilms

Wood arrives on the seabed from natural and anthropogenic sources (e.g., wood falls and wooden shipwrecks, respectively) and creates seafloor habitats for macro-, meio- and microbiota. The way these habitats shape microbial communities and their biogeographic patterns in the deep sea requires study. The objective of this work was to investigate how historic wooden-hulled shipwrecks impact the dispersal of wood-colonizing microbial biofilms. The study addressed how proximity to wooden shipwrecks shapes diversity, richness, and community composition in the surrounding environment. Study sites included two historic shipwrecks in the northern Gulf of Mexico identified as wooden-hulled sailing vessels dating to the late 19th century. Two experimental microbial recruitment arrays containing pine and oak samples were deployed by remotely operated vehicle proximate (0–200 m) to each shipwreck and used to establish new wooden habitat features to be colonized by biofilms. The experiments remained in place for approximately 4 months, were subsequently recovered, and biofilms were analyzed using 16S rRNA gene amplification and sequencing for bacteria and archaea and ITS2 region amplification and sequencing for fungi to determine alpha diversity metrics and community composition. The work examined the influence of wood type, proximity to shipwrecks, and environmental context on the biofilms formed on the surfaces. Wood type was the most significant feature shaping bacterial composition, but not archaeal or fungal composition. Proximity to shipwrecks was also a significant influence on bacterial and archaeal composition and alpha diversity, but not on fungal communities. In all 3 domains, a peak in alpha diversity and richness was observed on pine and oak samples placed ~125 m from the shipwrecks. This peak may be evidence of an ecotone, or convergence zone, between the shipwreck influenced seabed and the surrounding seafloor. This study provides evidence that historic wooden shipwrecks influence microbial biofilm dispersal in the deep sea.

Оценка изменений генетической структуры субпопуляций дуба черешчатого и сосны обыкновенной в условиях длительного воздействия малых доз радиации

The probability of population significant changes as a result of prolonged exposure to increased radiation in the habitat of the main forest-forming species is considered. The amount of contamination at stationary sites is correlated with the level of heterozygosity of pine and oak samples.

Regional Drought Conditions Control Quercus brantii Lindl. Growth within Contrasting Forest Stands in the Central Zagros Mountains, Iran

The magnitude and duration of ongoing global warming affects tree growth, especially in semi-arid forest landscapes, which are typically dominated by a few adapted tree species. We investigated the effect of climatic control on the tree growth of Persian oak (Quercus brantii Lindl.), which is a dominant species in the Central Zagros Mountains of western Iran. A total of 48 stem discs was analyzed from trees at three sites, differing in local site and stand conditions (1326 to 1704 m a.s.l.), as well as the level and type of human impact (high human intervention for the silvopastoral site, moderate for the agroforestry site, and low for the forest site). We used principal component analysis (PCA) to investigate the common climatic signals of precipitation, air temperature, and drought (represented by SPEI 1 to 48 months) across the site chronologies. PC1 explains 83% of the total variance, indicating a dominant common growth response to regional climatic conditions that is independent of the local environmental conditions (i.e., forest stand density and land-use type). Growth–climate response analyses revealed that the radial growth of Q. brantii is positively affected by water availability during the growing season (r = 0.39, p < 0.01). Precipitation during April and May has played an ever-important role in oak growth in recent decades. Our study provides evidence that hydroclimatic conditions control tree-ring formation in this region, dominating the effects of topography and human impact. This finding highlights the great potential for combining historical oak samples and living trees from different forest stands in order to generate multi-centennial tree-ring-based hydroclimate reconstructions.

Diagonal Tension Performance of Impregnated Woodworking Corner Joints

In this study, the effects were examined of wood species, processing types and processing time on diagonal tension performance of woodworking corner joint with double tenon and mortise. Test samples were prepared by using Scots pine (Pinus sylvestris Lipsky), sessile oak (Quercus petreae Lipsky) and black locust (Robinia pseudoacacia L.). Poly vinyl acetate (PVAc) adhesive was used to join the tenon and mortise corner joints. The samples were impregnated by using the method of immersion for 20 and 40 min with a mixture of wax / linseed oil (3 % paraffin, 10 % linseed oil, 87 % white spirit) and Imersol-Aqua. The test of diagonal compression was used to test 120 samples. In this study, the minimum strength decrease of around 68 % was obtained for Scots pine impregnated with Imersol-Aqua for 40 min and the highest strength increase of around 10 % was obtained for sessile oak samples impregnated with Imersol-Aqua for 40 min. The highest diagonal tension performance of 879.734 N·m was obtained for oak samples impregnated with Imersol-Aqua for 40 min., the lowest diagonal tension performance of 189.111 N·m was obtained for Scots pine samples impregnated with Imersol-Aqua for 40 min.

Influence of Ageing on Abrasion Volume Loss, Density, and Structural Components of Subfossil Oak

Subfossil oak wood has spent centuries or millennia in the aquatic medium (rivers, lakes, bogs, etc.) and, due to water anoxic conditions, its decomposition is very slow. As a result of its long residing in specific conditions, its chemical composition, appearance, as well as mechanical and tribological properties have changed. Because of its aesthetic and mechanical properties, subfossil wood is very attractive and often used to produce valuable objects. The main objective of this study was to test how abrasion wear resistance of subfossil oak is affected by ageing. The effects of ageing on wood density and on the structure of lignin and cellulose were tested, as well as the loss of volume during abrasion in correlation with these changes. A study was conducted on samples of recent (regular) pedunculate oak wood and on six subfossil pedunculate oak samples in the age range of 890 and nearly 6000 years. Abrasion wear resistance was expressed through the loss of volume recorded using the Taber abraser. The smallest abrasion volume loss was measured for the recent oak specimens. Linear regression analyses showed that there was a very strong negative linear relationship between the age of subfossil oak and its abrasion volume loss. There was also a strong, but positive and significant linear correlation between subfossil oak age and density. Ageing also affected the structural composition of wood. Results obtained by Fourier Transform Infrared spectroscopy indicated a reduction of the relative crystalline fraction of subfossil wood in recent oak. The degradation of lignin in subfossil oak samples progressed more slowly over time than cellulose degradation. There was a negative correlation between age and the ratio of cellulose and lignin degradation; however, that relationship was found statistically insignificant. Similar results were obtained for the relationship between abrasion wear resistance and changes in the structural composition of the studied samples of subfossil oak wood.

Chemo-sensory characterization of aroma active compounds of native oak wood in relation to their geographical origins

Oak wood contains aroma-active compounds that contribute significantly to the chemical structure, olfactory and gustatory qualities of alcoholic beverages and vinegars as by-products that have been either fermented and/or aged in oak barrels. The chemical composition of cooperage oak is highly variable, depending on the degree of toasting and natural seasoning. However, it is unclear whether the odor of oak varies according to different geographical regions and pedoclimatic conditions. Especially in view of the actual challenges in forestry in relation to climate change, the present study aimed at elucidating the odorous constituents of nine natural oak samples from Germany, Austria and Hungary with respect to these influencing parameters. The odor profiles of the oaks were compared, the potent odorants were determined, and selected odorants were quantified using stable isotope dilution assays (SIDA). The majority of the identified odorants in all samples were fatty acid degradation products, followed by a series of odorants with terpenoic structure and others resulting from the degradation of lignin. Several different odorants including 2-propenoic acid and cinnamaldehyde are reported here for the first time in oaks from different growth regions. Odor activity values (OAVs), calculated based on odor thresholds (OTs) in water, revealed hexanal, (E)-2-nonenal, (Z)-3-hexenal, eugenol, vanillin, and whiskey lactone as potent odorants for the oak odor. Principal component analysis of the data obtained from sensory evaluation, comparative aroma extract dilution analysis (cAEDA) and their corresponding quantified odorants showed that the highest separation rate was obtained for Hungarian oak, whereas Austrian and Bavarian oak samples were more similar. Recombination experiments by mixing the dominant odorants in their naturally occurring concentrations revealed a good agreement of the smell properties of the model mixture with the smell of the respective original sample. These findings aimat evaluating and establishing a better understanding of the distinctive smell of oak wood and demonstrated the prospects of new oak sources.

Evaluation of an alternative biotreatment for the extraction of harmful iron and sulfur species from waterlogged wood

An innovative bioextraction method was tested and compared to common chemical extraction for the preservation of waterlogged archeological wood (WAW) artifacts. During burial, WAW artifacts accumulate iron and sulfur species forming iron sulfides. These compounds are harmless in the burial environment, where the oxygen content is low. But upon excavation, the WAW undergoes the oxidation of these compounds, and thus, irreversible physical and chemical damages occur. Fresh and archeological oak and pine samples were selected as representative species of WAW artifacts. Fresh samples were previously artificially contaminated to ascertain the presence of iron and sulfur. Thiobacillus denitrificans and natural iron chelators, called siderophores, were investigated to extract iron and sulfur as a 2-step biological treatment (BT) and compared to sodium persulfate–EDTA as chemical treatment (CT). Consolidation and freeze-drying were performed on the samples after BT and CT as traditional conservation protocols. BT and CT efficiency was evaluated through Raman, inductively coupled plasma–optical emission (ICP-OES), and Fourier transformed infrared (FTIR) spectroscopies. Raman and ICP showed that most of the iron and sulfur was extracted after BT, while some sulfur species remained present on CT samples. None of the extraction methods resulted in a degradation of the wood, as ascertained by FTIR analyses. Yet, all samples presented visual modifications after conservation. Pine samples treated with BT illustrated the oxidation of the species. Present principal component analysis (PCA) and analysis of variance (ANOVA) which were selected as statistical approaches and validated BT as a promising alternative extraction method, with encouraging extraction rates and less alteration of the sample appearance.

On the basic chemical composition of selected biomass types from four regions of Mexico, for bioenergetic purposes

The chemical composition of hardwoods sawdust and citrus residues from four states of the Mexican Republic (Quintana Roo, Durango, Veracruz, and Sonora) were determined. The results ranged as follows: total extractives from 8.2% (Quercus spp.) to 35.0% (lime leaves), holocellulose from 45.4% (lime leaves) to 70.6% (Lysiloma latisiliquum), lignin from 3.9% (lemon peels) at 25.4% (Caesalpinia platyloba), ash from 0.4% (orange branches) to 6.3% (lemon peels), pH from 5.1 (Swartzia cubensis) to 7.3 (orange branches), and calorific value of 19.8 MJ/kg (Lysiloma latisiliquum and Quercus spp.) to 21.7 MJ/kg (Olneya tesota). With the exception of the oak samples, in all the biomass samples the extractives content is relatively high (10.1% for Lysiloma latisiliquum to 35% for Persian lime leaves), and could represent a potential for future study and applications in the field of antioxidants. Due to the chemical properties and calorific value, the biomass samples studied present potential for local use as densified biofuels (pellets or briquettes).

Improvement of technology of application of wood as a floor covering

The analysis of wood flooring has been made and it has been found that the manufacture of wood flooring poses certain difficulties in ensuring resistance to destruction. Thermally modified wood is one of the promising uses of flooring. Therefore, knowledge of the physico-mechanical featutes of wood composites, their quality indicators, adhesion with organic adhesives, allows to make a choice taking into account economic indicators, duration and safety of application. Experimental studies have found out that a floor covering with an upper layer of thermally modified oak wood is less resistant to abrasion. The additional moisture effect showed a better result for the thermally modified oak samples than for the ash and oak samples. The test pieces with an upper layer of thermally modified oak are found to have the lowest measure of power. The results of the research will enable the further development of new composites of thermally modified wood and the conditions under which they are operated at different sites.

INFLUENCE OF DIFFERENT MACHINING ON THE ROUGHNESS OF OAK WOOD

The paper presents research on the differences the in total roughness and the impact of parameters during different kinds of machining processes of oak samples. Oak wood samples were planed referring to a radial surface structure of wood. The planing machine was Weinig Unimat 500 and the planing head had two blades. The planing was conducted at a feed speed of 10, 15, 20, 25, and 30 m·min-1. The cutting depth of the machining grip was 1.00 mm and the rake angle of the tool blade was bio γ = 15°, at 6000°/min. The diameter of the cutting blade was Φ = 125 mm. Sanding was performed on a Viet Opera V contact sanding machine in combination heads with pre-planing knives and a roller with sanding belt. Roughness was measured along the grain in the latewood area of the annual growth using the electro mechanical profiler Mitutoyo SJ-500. The samples which were machined at a feed speed of 10 m·min-1 had the lowest roughness. The highest value of the roughness had samples which were machined at a feed speed of 30 m·min-1. After comparing roughness obtained during sanding and planing it was determined that the surface roughness obtained on a sanding machine approximately corresponds to the roughness obtained by planing at a feed speed of 20 and 25 m·min-1.