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This paper describes feature-based techniques for wood knot classification. For automated classification of macroscopic wood knot images, models were established using artificial neural networks with texture and local feature descriptors, and the performances of feature extraction algorithms were compared. Classification models trained with texture descriptors, gray-level co-occurrence matrix and local binary pattern, achieved better performance than those trained with local feature descriptors, scale-invariant feature transform and dense scale-invariant feature transform. Hence, it was confirmed that wood knot classification was more appropriate for texture classification rather than an approach based on morphological classification. The gray-level co-occurrence matrix produced the highest F1 score despite representing images with relatively low-dimensional feature vectors. The scale-invariant feature transform algorithm could not detect a sufficient number of features from the knot images; hence, the histogram of oriented gradients and dense scale-invariant feature transform algorithms that describe the entire image were better for wood knot classification. The artificial neural network model provided better classification performance than the support vector machine and k-nearest neighbor models, which suggests the suitability of the nonlinear classification model for wood knot classification.

Lumber species identification is an important issue for the wood industry. In this study, three types of neural networks (artificial neural network (ANN), deep neural network (DNN), and convolutional neural network (CNN)) were employed for classifying softwood lumber species using NIR spectroscopy. The results show that CNN, which is based on deep learning, was more stable than the other neural networks. In particular, the stability of the training process was remarkably improved in CNN models. During the training procedure, the validation accuracy of the CNN model was 99.3% for the raw spectra, 99.9% for the standard normal variate (SNV) spectra and 100.0% for the Savitzky-Golay second derivative spectra. Interestingly, there was little difference in the validation accuracies among the CNN models depending on mathematical preprocessing. The results showed that CNN is sufficiently adequate to classify the softwood lumber species.

This study aims to evaluate applicability for the continuous drying process using saturated and superheated steam for large-square timber. During drying of the boxed heart square timber, changes in moisture content were examined through the slices of the surface, inner and core layers. The results showed that there was a large moisture content difference between the surface and inner layers during saturated steam drying and between the inner and core layers during superheated steam drying. However, despite the moisture content difference between the layers, no surface check occurred, and an internal check occurred only near the pith or juvenile parts of the wood. The maximum value of the drying stress of the dried larch boxed heart square timber, calculated from the elastic strain of the slice and the tangential elastic modulus of the larch, was 1.30 MPa. The tangential tensile strength of the larch was estimated at 5.21 MPa under temperature and moisture content conditions when drying stress was at a maximum. That is, in the continuous drying process, the saturated and superheated steam did not generate a check in the surface because the drying stress of the wood did not exceed the tangential tensile strength. In further studies, the superheated steam drying conditions will need to be relaxed to suppress the occurrence of internal checks. Such studies would make the continuous drying process using saturated and superheated steam available for the drying of large-square timber.

The development of nanofibrous oil-water separation materials is explosively progressing, but the remarkably low productivity is the main factor hindering their practical application. In this study, biodegradable polybutylene succinate (PBS) nanofibers with excellent productivity (27.0 g/h per nozzle) were successfully fabricated using the solution blow spinning (SBS) process, breaking away from the conventional electrospinning method. The prepared PBS nanofibers exhibited extremely thin fiber diameters (130 nm) with high porosity (97.4%). Without any chemical modification or inorganic/organic hybrid materialization, the PBS nanofibrous membrane showed excellent oil adsorption capacity (minimum: 18.7 g/g and maximum: 38.5 g/g) and separation efficiency; water and oil mixtures (99.4-99.98%) and emulsions (98.1-99.5%) compared to conventional organic polymer-based nanofibers. In terms of disposal after use, this biodegradable nanofibrous membrane was able to return to nature through hydrolysis and biodegradation processes.

Because nanocellulose has a large specific surface area and abundant hydroxyl functional groups due to its unique nanomorphology, interest increases as an eco-friendly water treatment material. However, the distinctive properties of nanocellulose, which exists in a dispersion state, strongly hamper its usage in practical water treatment processes. Additionally, nanocellulose shows low performance in removing anionic pollutants because of its anionic characteristics. In an effort to address this challenge, regenerated cellulose (RC) hydrogel was fabricated through cellulose's dissolution and regeneration process using an eco-friendly aqueous solvent system. Subsequently, a crosslinking process was carried out to introduce the cationic functional groups to the RC surface PEI coating (P/RC). As a result, the PEI surface cationization process improved the mechanical rigidity of RC and showed an excellent Cr(VI) removal capacity of 578 mg/g. In addition, the prepared P/RC maintained more than 90% removal efficiency even after seven reuses.

The aim of this study is to establish prediction models for the non-destructive evaluation of the carbonization characteristics of lignin-derived hydrochars as a carbon material in real time. Hydrochars are produced via the hydrothermal carbonization of kraft lignins for 1–5 h in the temperature range of 175–250 °C, and as the reaction severity of hydrothermal carbonization increases, the hydrochar is converted to a more carbon-intensive structure. Principal component analysis using near-infrared spectra suggests that the spectral regions at 2132 and 2267 nm assigned to lignins and 1449 nm assigned to phenolic groups of lignins are informative bands that indicate the carbonization degree. Partial least squares regression models trained with near-infrared spectra accurately predicts the carbon content, oxygen/carbon, and hydrogen/carbon ratios with high coefficients of determination and low root mean square errors. The established models demonstrate better prediction than ordinary least squares regression models.

In our previous study, we investigated the use of ensemble models based on LeNet and MiniVGGNet to classify the images of transverse and longitudinal surfaces of five Korean softwoods (cedar, cypress, Korean pine, Korean red pine, and larch). It had accomplished an average F1 score of more than 98%; the classification performance of the longitudinal surface image was still less than that of the transverse surface image. In this study, ensemble methods of two different convolutional neural network models (LeNet3 for smartphone camera images and NIRNet for NIR spectra) were applied to lumber species classification. Experimentally, the best classification performance was obtained by the averaging ensemble method of LeNet3 and NIRNet. The average F1 scores of the individual LeNet3 model and the individual NIRNet model were 91.98% and 85.94%, respectively. By the averaging ensemble method of LeNet3 and NIRNet, an average F1 score was increased to 95.31%.

This study analyzed the effect of organic solvent extractives on the classification of wood species via near-infrared spectroscopy (NIR). In our previous research, five species of Korean softwood were classified into three groups (i.e., Cryptomeria japonica (cedar)/Chamaecyparis obtuse (cypress), Pinus densiflora (red pine)/Pinus koraiensis (Korean pine), and Larix kaempferi (Larch)) using an NIR-based principal component analysis method. Similar tendencies of extractive distribution were observed among the three groups in that study. Therefore, in this study, we qualitatively analyzed extractives extracted by an organic solvent and analyzed the NIR spectra in terms of the extractives’ chemical structure and band assignment to determine their effect in more detail. Cedar/cypress showed a similar NIR spectra patterns by removing the extractives at 1695, 1724, and 2291 nm. D-pinitol, which was detected in cedar, contributed to that wavelength. Red pine/Korean pine showed spectra changes at 1616, 1695, 1681, 1705, 1724, 1731, 1765, 1780, and 2300 nm. Diterpenoids and fatty acid, which have a carboxylic group and an aliphatic double bond, contributed to that wavelength. Larch showed a catechin peak in gas chromatography and mass spectroscopy analysis, but it exhibited very small NIR spectra changes. The aromatic bond in larch seemed to have low sensitivity because of the 1st overtone of the O-H bond of the sawdust cellulose. The three groups sorted via NIR spectroscopy in the previous research showed quite different compositions of extractives, in accordance with the NIR band assignment. Thus, organic solvent extractives are expected to affect the classification of wood species using NIR spectroscopy.

Cross-laminated timber (CLT) is becoming increasingly adopted into wooden construction of South Korea. Due to the lack of standards and protocol for CLT, there are many problems in the production and utilization phases. This study focused on the deformation and defects of CLT due to humidity variations. In this study, small, cross-laminated specimens were manufactured using three layers of laminated larch planks that had various moisture contents. The dimensional changes of these specimens were measured in response to changing internal conditions including side adhesion or moisture content variation and external conditions such as humidity. Shrinkage in width and thickness was less than 1.0% when using dry planks as the cross-laminated specimen. However, high-moisture content (MC) planks were not suitable when used as the surface layer of the CLT, as the shrinkage in width and thickness were greater than 2.0%. When high-MC planks are used in the inner layer, their shrinkage must be less than 2% to prevent splitting caused by a MC difference between the surface and inner planks. For this purpose, laminates with a MC less than 15% should be used for CLT.

This paper examines the classification of five coniferous species, including larch (Larix kaempferi), red pine (Pinus densiflora), Korean pine (Pinus koraiensis), cedar (Cryptomeria japonica), and cypress (Chamaecyparis obtusa), using near-infrared (NIR) spectra. Fifty lumber samples were collected for each species. After air-drying the lumber, the NIR spectra (wavelength = 780-2500 nm) were acquired on the wide face of the lumber samples. Soft independent modeling of class analogy (SIMCA) was performed to classify the five species using their NIR spectra. Three types of spectra (raw, standard normal variated, and Savitzky-Golay 2nd derivative) were used to compare the classification reliability of the SIMCA models. The SIMCA model based on Savitzky-Golay 2nd derivatives preprocessing was determined as the best classification model in this study. The accuracy, minimum precision, and minimum recall of the best model (PCA models using Savitzky-Golay 2nd derivative preprocessed spectra) were evaluated as 73.00%, 98.54% (Korean pine), and 67.50% (Korean pine), respectively.

Although nanocellulose is an eco-friendly, high-performance raw material provided by nature, the agglomeration of nanocellulose that occurs during the drying process is the biggest obstacle to its advanced materialization and commercialization. In this study, a facile and simple nanocellulose drying system was designed using lignin, which is self-assembled together with cellulose in natural wood, as an eco-friendly additive. The addition of lignin not only minimized aggregation during the drying and dehydration process of nanocellulose but also ensured excellent redispersion kinetics and stability. In addition, the added lignin could be removed through a simple washing process. Through FTIR, XRD, TGA, tensile and swelling tests, it was confirmed that the addition of lignin enabled the reversible restitution of the nanocellulose physicochemical properties to the level of pristine never-dried nanocellulose in drying, redispersion, and polymer processing processes.

In this study, hot air heat treatments of larch (Larix kaempferi) wood specimens were conducted at various temperatures (160–220 °C) and times (1–12 h) to classify the degree of hot air heat treatment using near-infrared (NIR) spectroscopy. NIR reflectance spectra were acquired from specimen cross-sections and were then preprocessed using the standard normal variate. Hierarchical clustering analysis (HCA) using the complete linkage and squared Euclidean distance was conducted to classify the three degrees of heat treatment. A principal component score plot of the NIR spectra was well grouped by the HCA grouping result, and the first component reflected the cluster analysis grouping well. A partial least squares discriminant analysis was performed to develop the discriminant regression model of the three heat treatment degrees. The R2 and root mean square error of validation were 0.959 and 0.191, respectively. NIR is considered to be a good candidate to routinely measure the degree of hot air treatment for larch wood.

Automatic wood species identification systems have enabled fast and accurate identification of wood species outside of specialized laboratories with well-trained experts on wood species identification. Conventional automatic wood species identification systems consist of two major parts: a feature e...

Cross-laminated timber (CLT) panels – consisting of several cross-wise stacked layers of glued boards – have a high dimensional stability. However, the outer surfaces of CTL are exposed to environmental humidity changes and thus to swelling and shrinking. To improve CLT’s dimensional stability further, the layers of kiln dried (KD) CLT were substituted partly (on the surfaces) and entirely with superheated steam treated (SHST) wood. The effects of SHST wood and the performance of the one-component polyurethane resin (PUR) were tested by block shear and delamination tests after water soaking. Under various conditions, the shear strength ranged from 1.3 MPa to 4.7 MPa and the wood failure percentage (WFP) from 76% to 92%. The optimal parameter were ascertained as pressing time (30–45 min), pressure (0.98 MPa) and adhesive amount (175–200 g m−2). The water soaked delamination of CLT manufactured with SHST wood was approximately 50% lower than that of CLT made of KD wood.

Heat treatment improves the dimensional stability and hydrophobicity of wood, and heat-treated wood is currently attracting attention as a new interior material. However, there are few evaluations where the acoustic properties of heat-treated wood are reported when such wood is used as an interior material. In this study, Larix kaempferi wood, typically used as a building material, was heat-treated at 200, 220, and 240 °C for 9, 12, 15, and 18 h. The sound absorption coefficients of the treated wood samples were measured at 250, 500, 1000, 2000, and 4000 Hz in a reverberation room. The sound absorption coefficient increased with the treatment temperature and the treatment time. The results of this study showed that the high-frequency band range sound absorption coefficient of wood can be increased dramatically by heat treatment.

The effects of the combined treatment of drying and heat treatment using superheated steam (SHS) were studied relative to the changes of the major chemical components in larch wood. The green lumber was dried and heat-treated in SHS conditions of 250 °C and 0.5 MPa for 18 h, and the relative percentage contents of sugars, lignin, and extractives were investigated and compared with the relative percentage contents in the lumber heat-treated in hot air conditions of 250 °C and atmospheric pressure for 18 h. After both heat treatment methods, the relative percentage contents of xylan, mannan, galactan, and arabinan were greatly decreased, whereas that of the Klason lignin was increased, additionally that of glucan and extractives remained almost unchanged. Lignin may bind with furan compounds decomposed from hemicellulose following heat treatment, thus contributing to the increase in the apparent relative percentage contents of the Klason lignin. In addition, the condensate collected in the condenser after combined drying and heat treatment using SHS was investigated qualitatively and quantitatively by high-performance liquid chromatography (HPLC). A large amount of furfural and acetic acid decomposed from hemicellulose was detected and some sugar components composed of cellulose and hemicellulose were detected in the liquid condensate.

This study compares energy efficiency of a combined drying and heat treatment with that of conventional hot air heat treatment, the theoretical heat consumptions required for each treatment were determined, and the actual heat consumptions for each treatment were measured at a pilot scale. Conventional heat treatment method separately performs kiln-drying and heat treatment for wood with hot air in different equipment. On the contrary, in the combined treatment, the wood is simultaneously dried and heat-treated in the same enclosed space. Because of the time and energy savings, the economic feasibility of combined treatment is much higher than that of conventional heat treatment. Although the theoretical required energy of the combined treatment was similar to that of the two-stage method, the actual energy consumption of combined treatment was less than that of the two-stage method. And, the energy efficiency of the combined treatment was calculated to be two times higher than that of the two-sta...

This study was to establish the interrelation between chemical compositions and near infrared (NIR) spectra for the classification on distinguishability of domestic gymnosperms. Traditional wet chemistry methods and infrared spectral analyses were performed. In chemical compositions of five softwood species including larch (Larix kaempferi), red pine (Pinus densiflora), Korean pine (Pinus koraiensis), cypress (Chamaecyparis obtu-sa), and cedar (Cryptomeria japonica), their extractives and lignin contents provided the major information for distinction between the wood species. However, depending on the production region and purchasing time of woods, chemical compositions were different even though in same species. Especially, red pine harvested from Naju showed the highest extractive content about 16.3%, whereas that from Donghae showed about 5.0%. These results were expected due to different environmental conditions such as sunshine amount, nutrients and moisture contents, and these phenomena were also observed in other species. As a result of the principal component analysis (PCA) using NIR between five species (total 19 samples), the samples were divided into three groups in the score plot based on principal component (PC) 1 and principal component (PC) 2; group 1) red pine and Korean pine, group 2) larch, and group 3) cypress and cedar. Based on the chemical composition results, it was concluded that extractive content was highly relevant to wood class-ification by NIR analysis.

The objective of this study was to separate drying strains into elastic, viscoelastic, and viscous strains using free shrinkage and recovery from the deformation of slices at stress relief. The apparent shrinkage deformation was obtained by measuring the change in width of drying specimens during drying. Using the slice method, elastic and viscoelastic deformation were defined as the instantaneous change in width of a slice right after cutting and the change in the width of a slice with constant moisture content during 48 h, respectively. Viscous deformation, permanent and nonrecoverable deformation of wood, was defined as the difference in deformation between free shrinkage and the sum of the apparent, elastic, and viscoelastic deformations. These elastic, viscoelastic, and viscous strains were applied to a viscoelastic model, and coefficients of viscoelasticity and viscosity were derived. The drying stress and deformation of red pine wood at specific times during the drying process can be predic...

The goal of this study was to predict lamina yield from logs of different diameter for production of cross laminated timber. Log characteristics of red pine (Pinus densiflora) and Japanese cedar (Pryptomeria japonica), including diameter, length, volume, and defects were used for statistical and geometrical analyses, along with the lamina characteristics, including width, thickness, and defects. Based on the data obtained, the strong factors influencing the yield and grade of lamina from the two species were statistically evaluated. A geometrical ap proach was used for analysis of the yield from logs of given diameters. Statistical analysis showed that lamina yield was dependent on target lamina size but the grade of lamina was not related to any of the log characteristics. The suggested yield equations from the geometrical approach indicated an accuracy of less than 20% difference.

This work focused on the shrinkage and drying stress of red pine (Pinus densiflora) wood during kiln drying and investigated transverse shrinkage and moisture changes in thin specimens using digital image analysis and near-infrared spectroscopy, respectively. The effect of specimen thickness, which ranged from 1 to 10 mm on shrinkage, was analyzed under drying conditions with restrained stresses. The shrinkage due to moisture content was presented in the form of an exponential function and a linear function above and below the fiber saturation point, respectively. A shorter existence of the moisture gradient increased the transverse shrinkage. The tangential and radial shrinkage at the tissue level in 30-µm (longitudinal) thick slices was measured and compared with the shrinkage of above specimens with difference thicknesses. The transverse shrinkage of 1-mm-thick specimen is similar to the shrinkage measured using 30-µm-thick slice.

In this study, various ethanol organosolv pretreatment factors including reaction temperature, time, and concentration of acid catalyst were evaluated for effective decomposition of lignocellulosic biomass. The different pretreatment conditions had the same combined severity factor (1.16). With an increase in reaction temperature and pH, the water-insoluble residue recovery and amount of lignin in the solid residue decreased from 52.6% to 42.4% and from 10.4% to 5.5%, respectively, whereas enzymatic digestibility increased up to 97.9%. After pretreatment, ethanol organosolv lignin (EOL) recovered from the liquid hydrolyzate was subjected to nitrobenzene oxidation, gel permeation chromatography, and supercritical ethanol treatment for evaluation of the lignin structural properties. At a higher reaction temperature and pH, the proportion of ether linkages and the polydispersity of EOL decreased from 15.7% to 10.9% and from 3.1 to 1.9, respectively, while the amount of phenolic monomers ranged from 16.7 mg/g to 27.9 mg/g.

The objective of this study was to evaluate the effect of lamina distortion control on the production yield of cross-laminated timber (CLT) using domestic larch (Larix kaempferi) wood. The measured production yield of CLT was 27 %. The yields based on log volume of sawing, planing, cross-cutting, and finish planing of CLT were 49, 66, 96, and 86 %, respectively. The yield of sawing and planing can be improved by controlling distortion during drying. Using an experimental enforced-loading apparatus, the cup and twist of laminas were reduced by 50 and 90 %, respectively. To analyze the effect of a reduction in sawing dimensions on the final production yield of CLT, an analysis of a geometrically applied sawing pattern of logs was used to predict the sawing yield and the number of laminas after sawing. The geometrical analysis showed that a change in the sawing dimensions affected the production yield of CLT. If the width and thickness of the sawing dimensions can be reduced by 5 mm by decreasing the distortion of lamina during drying, the sawing yield was unchanged (49 %), but it was expected that the number of laminas after sawing would increase from 278 to 303. It was also predicted that the production yield of CLT would increase from 27 to 32 %.

The objective of this research was to investigate the effect of freeze storage on the efficiency of hemicellulose degradation and enzymatic hydrolysis by dilute-acid pretreatment of Mongolian oak. The freeze storage of Mongolian oak was conducted depending on several factors (freezing time, solid to freezing solution ratio, and freezing solution type) before dilute-acid pretreatment process of constant condition. The results showed that the major contents of reducing sugars and their degradation products in the liquid hydrolysates were slightly increased until a freezing time of 120 min. The xylose content was the highest (18.22 g/100 g initial input) at a specific solid to freezing solution ratio of 5:3 (w/v), while the sugar degradation product contents were not remarkably increased at these points. Based on these conditions, when distilled water was used as the freezing solution, glucose yield was maximized (36.20% of initial input (conversion rate of 87.92%)) after enzymatic hydrolysis to a greater degree than control.

Five different softwoods were used to investigate fast methods for predicting quantitative chemical information via near-infrared (NIR) spectroscopy. In biomass-related industries, fast collection of chemical information from a feedstock is needed. Prior to predicting quantitative information, a principal component analysis (PCA) using NIR spectra was conducted to evaluate the possibility of discriminating the softwoods. As a result of PCA, the five species were divided into three groups. This result indicated that the extractive compounds were key factors because the powder samples were separated by species having a similar extractive content. The partial least square (PLS) method was applied to develop a calibration model for predicting chemical composition. This model showed good performance in predicting the extractive and lignin content of all species. The calibration results of the extractive and lignin content for all species were indicated as R2 = 0.99. The cross-validation of the components for all species also showed an excellent value of R2 = 0.98 and 0.97, respectively. Based on our results, it was possible to suggest a useful tool for providing rapid information about wood used in the bioenergy and pulp production fields.

본 연구에서는 국산 소경 신갈나무를 이용하여 약산 전처리를 실시하고, 당으로부터 변환된 푸르푸랄 및 레불린산의 함량 변화를 평가하였다. 약산 전처리는 반응온도(140-180℃), 반응시간(10-30분), 황산 촉매 농도(0-2%, w/w)에 따라 수행하였고, 전처리 후 액상 내 글루코오스, XMG (자일로오스 + 만노오스 + 갈락토오스), 푸르푸랄, 레불린산의 함량을 측정/분석하였다. 글루코오스는 반응온도의 상승, 반응시간과 황산 촉매 농도의 증가에 의해 그 함량이 높아져최대 16.02%까지 나타났으나, 황산 촉매 농도 2% (반응온도 170℃ 이상, 반응시간 20분 이상)에서 함량이 감소하였다. 한편, XMG 함량은 반응온도의 영향을 크게 받았고, 반응온도와 황산 촉매 농도의 증가에 따라 1.63%까지 감소하였으며, 반응시간의 증가에 의한 함량변화는 적었다. 푸르푸랄 함량은 반응온도, 반응시간, 황산 촉매 농도 증가에 따라 높아져 초기시료 중량 대비 최대 7.61% (반응온도 180℃, 반응시간 20분, 1% 황산 촉매 농도)로 나타났으나, 전처리 조건이 최대 푸르푸랄 함량 조건보다 가혹해지면서 감소하는 경향이 발생하였다. 레불린산 함량은 반응온도, 반응시간, 황산 촉매 농도가 증가함에 따라 높아졌고, 특히 반응온도 170℃ 이상에서 급격한 함량 증가를 확인하였으며, 최대 10.98% (반응온도 180℃, 반응시간 30분, 2% 황산 촉매 농도)로 나타났다. 반면 황산 촉매를 투입하지 않았을 경우 모든 반응온도, 반응시간 조건에서 푸르푸랄 및 레불린산 함량은 1% 미만으로 나타났다.

This study is aiming at the simulation of wood compression (C) at a macroscopic level by means of a three-dimensional finite element analysis (3D-FEA) of solid wood and evaluation of the capability and limitations of this approach. C-Tests were carried out on Douglas fir according to ASTM D 143. The specimens included the 25×25×100 mm3 cuboid bars for longitudinal (L), radial (R) and tangential (T) directions and the conventional 50×50×150 mm3 blocks for the perpendicular to grain (⊥) direction. Two sets of wood parameters were developed and the 3D-FEA was implemented for the two types of specimens. The 3D-FEA worked successfully provided that the stress state coming from the total wood C was uniform. However, in case of the dominance of local compressive behaviour such as bearing, crushing and fibre shear, a microscopic-level modelling technique is needed for correction of the material parameters. More details on the limitations and difficulties of 3D-FE implementation for wood were discussed.

We investigated the optimization of the organosolv pretreatment of yellow poplar for bioethanol production. Response surface methodology was used to determine the optimal conditions of three independent variables (reaction temperature, reaction time, and sulfuric acid (SA) concentration). Reaction temperature is the most significant variable in the degradation of xylan and lignin in the presence of an acid catalyst, and ethanol production increased with a decrease in the lignin content. The highest ethanol concentration (42.80 g/l) and theoretical ethanol yield (98.76%) were obtained at 152℃ (2.5 bar) with 1.6% SA for 16 min. However, because of excessive degradation of the raw material, the overall ethanol yield was less than under other pretreatment conditions which has approximately 50% of WIS recovery rate after pretreatment. The optimal conditions for the maximum overall ethanol yield (146℃ with 1.22% SA for 15.9 min) were determined with a predicted yield of 17.11%, and the experimental values were very close (17.15%). Therefore, the quadratic model is reliable.