Volume 13 Issue 4

The relationship between the thermal conductivity and some mechanical properties of Uludağ fir and black poplar specimens were determined based on related standards. It was hypothesized that thermal conductivity can be used as a predictor for wood properties. The hot plate test method was used as a thermal conductivity testing method. The density, compression strength, modulus of rupture, and modulus of elasticity values were also measured. Pearson’s correlation coefficient was determined and both linear and multiple regression analyses were performed to estimate the relationship between the parameters. The correlation between the thermal conductivity and density values was strong, which was consistent with past findings. Also, there was a strong correlation between the thermal conductivity, modulus of rupture, and modulus of elasticity, while the compression strength and thermal conductivity had a moderate correlation. The regression equations and test graphs were also determined and shown. Overall, it can be claimed that the thermal conductivity could be used for predicting the density and mechanical properties of wooden materials.

Increasing environmental concern in developed countries has supported the search for greener building materials. In this regard, using materials from renewable resources is of great interest, including the case of wood-plastic composites in replacement of fiberglass-reinforced composites.  Since in the Mediterranean regions annual plants are more abundant than wood forests, in the present work, agroforestry wastes were used as reinforcing elements in composites. Specifically, rapeseed wastes were used to produce polypropylene copolymer based composites. The mechanical behavior of the resulting composites was studied, as well as the influence of a coupling agent in the formulation. From the results, rapeseed sawdust exhibited reinforcing capacity and was considered a plausible substitute for wood-plastic composites in certain uses. The stiffness of the composites was affected by the coupling agent, as the Young’s Moduli progressed from 3.2 to 4 GPa for the formulation containing 50wt% of rapeseed sawdust. Micromechanical analysis was used to identify the contribution of each phase by means of a modified rule of mixtures and Halpin-Tsai equations. The micromechanical study confirmed the competitive stiffening capability of rapeseed sawdust in composite materials.

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.