Research Articles

The effects of varying the laser power output, from 5.6 to 8 W, and the scanning speed, from 100 to 500 mm/s of a CO2 laser beam on the surface quality of Norway maple (Acer platanoides) were investigated. The results showed that the roughness parameters (Ra, Rsk, Rt, Rk, Rpk, and Rvk) increased with increased laser power and decreased with decreased laser scanning speed. The roughness parameters had a linear trend with the laser power and a logarithmic correlation with the laser scanning speed. The best correlation was found for the composed parameter Rk + Rpk + Rvk, which may be the best descriptor of the laser action on wood, closely followed by Ra, Rk, and Rt. Rpk was the most affected parameter by the laser action on wood. The roughness parameters correlated best with the laser power for a laser scanning speed of 300 mm/s. An ablation effect on wood combined with protruding latewood bands visible as surface ridges was more pronounced with an increase in the laser power and with a decrease in scanning speed. The high laser powers (7.2, 7.6, and 8 W) combined with the lowest scanning speed, 100 mm/s, burned and visibly degraded the surface.

Fiber quality greatly influences the performance of medium-density fiberboard (MDF). To evaluate the fiber quality more accurately during refining, a novel quantitative parameter-property relationship model was developed based on the support vector machine (SVM) algorithm. Based on the mill production conditions, a total data set of 1173 experimental fiber quality data points under a wide range of five refining parameters was employed to train and verify the model. By comparing the effectiveness between the model using nonlinear SVM and the model based on multiple linear regression (MLR), the values of mean absolute error (MAE), mean relative error (MRE), root mean square error (RMSE), and Theil’s inequality coefficient (TIC) were reduced 92.19%, 92.36%, 87.29%, and 87.21%, respectively. The results showed that the performance of the predictive model developed using SVM was superior to the MLR model. Furthermore, the variations of the percentage of qualified fibers with each production parameter were predicted using the established model. The prediction model that resulted can be applied to predict the fiber quality during the refining process in an MDF production mill.

Development of cost-effective process technologies to produce biofuels and enzymes from lignocellulosic materials has gained importance. However, few studies have considered high pressure processing (HPP) as an emerging technology for the bioconversion of lignocellulosic biomass. This study aimed to determine and optimize the effect of HPP combined with dilute acid and enzymatic saccharification on the production of fermentable sugars from hazelnut shells. Optimization via response surface methodology was carried out for acid concentration of 1 to 3% (w/v) for a pretreatment time of 10 to 30 min at a pressure range of 200 to 500 MPa. The combined HPP processes were evaluated in terms of the production of total reducing sugars. The optimized total reducing sugar production was estimated at 473.4 mg/g, with production of 88.4% fermentable sugars under 2.9% H2SO4 for 10 min at 350 MPa. The results implied a 2.4 fold increase in fermentable sugar production under the optimized conditions using combined HPP. The combined HPP process appeared to significantly lower costs due to the decreases in pressure requirement, liquid consumption, and pretreatment time.

A co-culture consisting of Clostridium thermocellum ATCC 27405 and Thermoanaerobacterium thermosaccharolyticum DSM 571 was employed to improve the ethanol yield from microcrystalline cellulose (MCC) and corn straw substrates. An ethanol concentration of 1.29 g/L (26.1% ethanol yield) was obtained with 98.6% cellulose degradation when MCC was used as substrate in fermenter tanks. The ethanol yield obtained in fermenter tanks was 13.9% higher than that obtained via an anaerobic process performed in bottles. An ethanol concentration of 0.45 g/L, corresponding to 55.6% cellulose degradation and 11.2% ethanol yield, was achieved with corn straw as substrate in fermenter tanks. This ethanol yield was 28.2% higher than that formed in anaerobic bottles. Surprisingly, a 40.7% hemicellulose degradation was achieved via fermentation tanks, which was 127% higher than that obtained from anaerobic bottles.

Indoor environment quality in wooden family houses was compared to bricked houses or concrete slab apartments. Based on measurements, the influence of selected systems of forced ventilation without heat recovery and with efficient heat recovery were compared in selected houses in consideration of monitored parameters of CO2 and relative humidity in the course of 24 hours. Auxiliary parameters such as temperature and absolute pressure were also measured. The CO2 and relative humidity parameters had demonstrable effects in all the houses. The differences of CO2 values while using recuperation or not in wooden houses reached 21.2%, 44.7%, and 31.6%. The relative humidity value differences reached 6.6%, 2.8%, and 2.9%. More significant differences in values were reached in the course of measuring in a brick building – 73.1% CO2 and 39.4% of relative humidity. In the concrete slab apartment, the value differences reached 46.1% CO2 and 1.8% at relative humidity. The permitted limit of 1,500 ppm of CO2 was exceeded in all the objects without active heat recovery. In the case of efficient heat recovery, the values oscillated around the recommended value of 1,000 ppm of CO2.

Dense high voltage power transmission lines limit human living space and affect the natural landscape and environment. Concerns about the environment in the corridor of high voltage power transmission lines and the occupied land area need to be addressed. Trees are a dissipative medium that can affect polarization in electric fields, leading to excitation of the induced electric field and shielding the impact of electric fields. A mathematical model for the electric field calculation of trees was established by selecting, mapping, and calculating the larch tree species in an experimental forest field at Northeast Forestry University, Heilongjiang Province, China. This study used the finite element method of equivalent excitation sources and the equivalent tree model to estimate the electric field shielding effectiveness of trees. The shielding effect of trees on the electric field of high voltage transmission lines was obvious. Planting trees reduced the transmission lines corridor width by 50.7%, and the maximum electric field in the ground decreased by 95.9%. Thus, planting trees to reduce the electric field of power transmission lines was more effective than the currently widely used method of erecting wires.

Effects of ethylene oxide (EO) treatment on library and museum furniture were investigated. Three treatments (accelerated ageing, EO treatment, and EO treatment followed by accelerated ageing) were applied to understand the effects on physical and mechanical properties of the common furniture woods. The Buchholz indentation test/micro-hardness (MH), color and gloss, Brinell hardness/macro-hardness (BH), and surface roughness were tested. The MH of oak and beech samples was not noticeably affected by any of the treatments, whereas elm samples showed some effects. For all types of wood, color was affected by EO treatments, but not considerably affected by ageing. Gloss significantly decreased with EO and accelerated ageing treatments for all samples. In BH measurements, ageing caused a decrease in hardness for both the control and EO treated samples, although this affect was not marked in beech samples. The EO treatment caused a decrease in hardness for beech and elm samples, but no major effect was observed in oak samples. There was a significant effect on the R_a values (arithmetic average of the absolute values of the roughness profile ordinates) in the aged groups of beech and oak samples, as well as oak samples that received both EO treatment and ageing.

Machinability is one of the most important technological properties in the machining process. The machinability index is a numerical value that shows the degree of difficulty or ease with which a material can be machined. The research described herein consisted of drilling blind holes in a medium density fibreboard (MDF) using a cemented carbide tool. Different cutting speeds (vc) and feeds (fn) were used in the tests. The goal was to determine the value of the axial force (Ff), the cutting torque (Mc), and the chip thickness. To analyse signals involving axial force and cutting torque, a methodology for determining the average values of these signals was proposed to avoid random changes in signal values. The results obtained were used to determine the MDF machinability index in the drilling process based on the measurement of the axial force, cutting moment, and shear angle of the chips. The results obtained showed that the machinability index based on the adopted criteria is constant for a given workpiece and does not depend on the cutting parameters.

Soluble products from oil palm frond hydrolysate (OPFH) were incorporated as the fermentation substrate for succinic acid (SA) production. To construct a reliable kinetic model for the production of SA from OPFH, the inhibitory effects during fermentation involving glucose were evaluated based on the modified Gompertz model. The application of the modified Gompertz model was found to fit well with the experimental data for characterizing the SA fermentation profile and could predict the maximum potential of the metabolite formation in the form of concentrations, production rates, and initial lag times. The maximum potential of the SA production was determined to be 38.0 g/L, which was yielded from 61.3 g/L glucose in anaerobic batch cultivation after 30 h. The inhibitory effects on the cell growth and SA production became more apparent at higher substrate concentrations, which coincided with the substrate inhibition constant of 78.7 g/L. The model also helped in estimating the OPFH fermentation baseline, which consequently led to a SA concentration of 36.5 g/L and productivity of 1.95 g/Lh. The results suggested that OPFH as an inexpensive and renewable source of lignocellulosic syrup is advantageous for the economic production of SA.

The adhesion strength was evaluated for polyvinyl chloride (PVC) and Eastern beech (Fagus orientalis L.) veneers glued onto specially produced fiberboards using urea-formaldehyde (UF), polyvinyl acetate (PVAc), and polyurethane (PU) adhesives. Inorganic fillers including rock salt (NaCl), calcite (CaCO3), borax pentahydrate (Na2B44O7•5H2O), or talc (3MgO•4SiO2•H2O) were incorporated into the fiberboards at levels of 3%, 6%, and 9%. The adhesion strength of the samples was determined in accordance to Turkish Standard TS EN 311 (2005). Scanning electron microscopy (SEM) was employed to determine the structural morphology at the bonding interface of the veneers and the modified fiberboards. The results of this study indicated that veneer adhesion strength was reduced by the addition of inorganic fillers to the fiberboard. The highest adhesion strength was obtained with Eastern beech veneer that was glued using UF adhesive on the control samples without inorganic fillers. It was concluded that UF and PVAc adhesives are not suitable for bonding PVC veneers onto fiberboard surfaces.