Research Articles

Understanding and mastering the color change of wood during heat treatment is essential in the wood working industry because it saves time and reduces energy costs. An artificial neural network (ANN) was employed in this study to establish the relationship between the process parameters of heat treatment and the color change of wood. Three important parameters: temperature (180 °C, 190 °C, 200 °C, 210 °C, and 220 °C), treatment time (2 h, 4 h, 6 h, and 8 h), and wood species (larch and poplar) were considered as inputs to the neural network. There were four neurons in the hidden layer that were used, and an output layer as wood color. According to the results, the mean absolute percentage errors were determined as 0.53%, 0.65%, and 0.31% in the prediction of color change color (ΔE) values for training, validation, and testing data sets, respectively. Determination coefficients (R2) greater than 0.99 were obtained for all data sets with the proposed ANN models. These results showed that ANN models can be used successfully for predicting the color changes in wood during heat treatment.

Wood is a renewable and environmental friendly material, but its low dimensional stability characteristics limit its applications. In this study, wax mixed with dimethyl silicone oil was used to enhance the dimensional stability under heat treatment. Samples were heated at 120 °C under 3 impregnation conditions (wax, wax + 20% dimethyl silicone oil, and wax + 40% dimethyl silicone oil) for 3 and 6 h respectively. After treatment the effects of combination pretreatment on wood weight gain percentage (WPG), tangential, radial and volume swelling coefficients (TS, RS, VS), distribution of impregnation liquid, and the types of functional groups of African Padauk (Pterocarpus soyauxii) were evaluated. The results showed that impregnation improved the dimensional stability of wood to a certain extent; moreover, the addition of dimethyl silicone oil improved the modification effect. Furthermore, the VS reduced to 0.66 (±0.28)% in the treatment of wax + 20% dimethyl silicone oil for 6 h. The impregnation liquid mainly adhered to the walls of vessels and ray cells. The hydroxyl absorption intensity of the impregnated groups was lower than that of the control group.

During the last decade, the Slovak and Croatian furniture industry markets have experienced changes that have made these markets more interesting for domestic and foreign investors. Furniture manufacturers and retailers are still trying to determine the best ways to adjust to customer demands, and understanding the furniture preferences of customers would provide beneficial information to the furniture industry. The purpose of this study, which was conducted in 2016, was to improve the knowledge regarding differences in the preferences of customers for furniture materials, attributes, and styles when purchasing furniture in Slovakia and Croatia. The findings showed that Slovak and Croatian respondents differ in their preferences for furniture materials, as well as the factors that influence their purchasing decisions when buying interior and exterior furniture. Overall, it was found that wood as the furniture material, compared with the surveyed substitutes, was widely preferred among the Croatian and Slovak respondents.

Current approaches to human resource management are focused on the sustainable development of small and medium-sized enterprises (SMEs). Career strategies of employees are its integral part. The aim of this paper is to determine the changes in professional priorities of employees in small and medium-sized wood-processing enterprises in the area of motivation relating to career aspiration throughout the course of life. The research outcomes show significant correlation between age, gender, and motivation factors relating to career aspiration. Slovak women working in SMEs prefer motivation factors relating to finances, mutual relationships, work, and career aspiration. Motivation factors selected by men are almost the same. In terms of age, motivation factors relating to career aspiration are preferred mainly by women aged 30 to 40 years old. Mentioned factors become less important for respondents of older age groups. Men working in SMEs prefer the motivation factors relating to career aspiration at the age of 30 and subsequently they become less important as well. Following the outcomes of this research, managers of SMEs should motivate career-oriented employees especially according to their needs. In the long-term perspectives, managers can encourage employees to stay focused on their careers.

Chitosan-cellulose film is found in food processing and biotechnology because of its biocompatibility, biodegradability, and antibacterial property. Despite the excellent properties, the presence of intramolecular and intermolecular hydrogen bonds cause cellulose and chitosan to be insoluble in common solvents, resulting in limited mechanical strength. Graphene oxide has heavy oxygen-containing functional groups with excellent mechanical properties, which makes it an ideal filler for reinforcing polymers. In this work, blends of graphene oxide and chitosan-cellulose were successfully produced using 1-ally-3-methylimidazolium chloride ([Amim]Cl) and dimethyl sulfoxide (DMSO) as solvent media. Films were prepared by phase-transfer method and investigated by Fourier transform infrared analysis, scanning electron microscopy, atomic force microscopy, X-ray diffraction, thermogravimetric analysis, and mechanical tests. The absence of the bands corresponding to C=O stretching in graphene oxide and the -NH bending of amides and amines in chitosan, the absence of the diffraction peak at 2θ =11.3° in graphene oxide (XRD), and the improvement of thermal stability and mechanical property provided evidence for the interaction between graphene oxide and chitosan-cellulose.

NH4Cl was used to optimize the pretreatment conditions for biomass pretreatment to improve enzymatic saccharification and hemicellulose degradation of eucalyptus chips. After pretreatment, the solid substrate (SS) and pretreatment liquor (PL) were characterized, and the SS was enzymatically hydrolyzed to detect the conversion yield of cellulose (CYC). For the pretreatment using NH4Cl, the removal rate of hemicellulose reached up to 100% in some cases, but a great proportion of cellulose remained in the SS. The optimized conditions for pretreatment using NH4Cl were 0.3 M NH4Cl at 200 °C for 25 min. A comprehensive evaluation found that the most suitable severity parameter for pretreatment and enzymatic saccharification was 4.5, although a higher severity parameter could increase the CYC. XRD and FTIR analysis showed that the pretreatment had little influence on the cellulose crystalline region, and the lignin was well-retained in the pretreatment process.

The performance of short pineapple leaf fiber (PALF) reinforced tapioca biopolymer (TBP) composites were investigated, specifically the effect of fiber length and fiber composition on mechanical properties (tensile properties, flexural strength, and impact strength). Composite samples with different fiber lengths (< 0.50 mm, 0.51 mm to 1.00 mm, and 1.01 mm to 2.00 mm) and different fiber compositions (10%, 20%, 30%, and 40%) were prepared through crushing, sieving, internal mixing, compression molding, and machining processes. The combination of PALF and TBP enhanced the mechanical properties of composites with 30% as the optimum fiber content. However, the influence of different fiber lengths up to 2.00 mm provided no significant effect on producing maximum tensile properties. Good interfacial adhesion between PALF and TBP was evident from scanning electron microscopy analysis. Therefore, the combination of PALF and TBP has great potential as a renewable and biodegradable polymer. Moreover, PALF-TBP composites are expected to become alternatives to petroleum-based polymers.

Carbon black (CB) was used to fill the shell of wood high-density polyethylene (HDPE) composite to improve its antistatic properties and simultaneously maintain its mechanical properties. The conductivity analysis revealed that the percolation threshold of the CB in coextruded WPC was between 15% and 20%, and the surface resistivity of the sample containing 20% CB (CW-20) achieved the floor antistatic requirements of an electronic information system room and its support area according to GB/T 50174 (2017). The addition of CB into the shell of the coextruded WPC inhibited its crystallization. The mechanical properties of coextruded WPC were increased when the CB content was increased. The flexural strength, flexural modulus, and impact strength of the CW-20 sample were increased by 21.6%, 10.8%, and 26.1%, respectively. In addition, the dosage of CB in regular WPCs was 6.71 times as much as that of coextruded WPCs, which achieved similar antistatic and mechanical properties of the two structural WPCs. These results demonstrated that the low CB filled shell of HDPE composite exhibited a large reduction in its surface resistivity and a significant enhancement in its mechanical properties, which expands the application of coextruded WPCs in flammable and explosive uses while also improving the antistatic and mechanical properties.

Pine oleoresin is an important industrial resource, used widely in pharmaceuticals, cosmetics, and insecticides. To reveal the function of 1-deoxy-D-xylulose 5-phosphate synthase (DXS) in oleoresin biosynthesis in Simao pine, three complete cDNAs of DXS genes were obtained, of lengths 2223 bp (PkDXS1), 2217 bp (PkDXS2), and 2142 bp (PkDXS3). Phylogenetic analysis showed that PkDXS1 belonged to DXS type 1, and both PkDXS2 and PkDXS3 belonged to DXS type 2. Functional complementation experiments indicated that the three PkDXS genes had DXS protein function. Real-time PCR detection showed that physical wounding slightly influenced the gene expression of PkDXS1 and strongly influenced the gene expression of PkDXS2 and PkDXS3. The gene expressions of PkDXS3 in high-oleoresin-yield individuals were higher than their gene expressions in low-oleoresin-yield individuals. This result implied that the gene expressions of DXS regulated the oleoresin yields in different individuals of Simao pine. These results will provide information to help reveal the mechanisms of high-oleoresin-yield of Simao pine in the future.

Correlations were determined between the thermal degradation behaviors of ball-milled Miscanthus plants and their enzymatic digestibilities. Overall, thermal degradation temperatures of Miscanthus giganteus were higher than those of M. sinensis. The differential thermogravimetric (DTG) curve of M. giganteus had a characteristic shoulder peak near 292 °C as opposed to that of M. sinensis. The thermal degradation temperatures of both ball-milled samples decreased with increased ball-milling time, although the composition was not changed by ball milling. Remarkable changes in the DTG curves of M. sinensis and M. giganteus occurred with ball milling for more than 60 min and 120 min, respectively. These thermal degradation results were similar to the results for physicochemical pretreatments and enzymatic digestibilities. The thermal decomposition temperatures of both ball-milled samples at 20% weight loss were most negatively correlated with the enzymatic digestibilities with a value of approximately -1.0.