Research Articles

The box frame is a common structure in modern furniture, especially for cabinets. Accordingly, the joint contact force of the frame is important in evaluating the stability of classified furniture. In this study, a new type of keyed joint was proposed to alter the dovetail joint used in box frame structures. The tensile strength of the dovetail joint and the keyed joint in the frame were evaluated, and the contact forces and failure modes of these two joints were compared. Three levels (T1, T2, and T3) were proposed for the ratio of groove depth (D) to inclined contact surface height (H), under the condition of the same joint spacing and inclination angle considering the effects of keyed joint size on the contact force. Meanwhile, experimental analysis was performed on both sides (S1 and S2) of the dovetail joint. Results showed that the contact force of the joint under the gluing condition decreased in the order of S2 > T2 > T3 > S1 > T1. In terms of failure modes, the keyed joint could be maintained in good condition, whereas failure of the dovetail joint always occurred at the root of the tenon in the S1 direction.

Saline-alkali soils of northern China are prone to waterlogging after degradation caused by overuse. The effects of biochar (40 t/ha) were tested relative to the physico-chemical properties of maize rhizosphere soil, the composition and function of the soil bacterial community, and its response to sudden waterlogging. Biochar treatment decreased the pH and bulk density of the soil and increased soil organic carbon (SOC), available nitrogen (AN), and available phosphorus (AP). The relative abundance of bacteria (Proteobacteria, Actinobacteria, Bacteroidetes, and Nitrospirae) also increased, along with the activities of soil enzymes, such as dehydrogenase, β-glucosidase, and alkaline phosphomonoester. The response of soil microbial enzymes to biochar addition was induced by changes in the soil physical properties (pH, soil moisture content, and soil respiration (BR)). Changes in the bacterial community structure were driven by soil nutrients and physical characteristics (AN, AP, SOC, pH, moisture, water-stable aggregate stability rate, BR, and bulk density). After waterlogging, soil with biochar demonstrated high water permeability and improved soil respiration. The relative abundance of soil bacteria and enzyme activities remained higher in the biochar plot than in the no-biochar plot. Biochar maintained the growth and vitality of maize roots in unfavorable environmental conditions, thus ensuring high yields.

Sintering behaviour of ash specimens from blends of Jincheng (JC) coal and pine sawdust (PS) was investigated using a pressure-drop sintering device combined with scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD) analysis, and FactSage modeling. The sintering temperatures consistently displayed a decreased trend when the PS was added into JC. In addition, the ashing temperature had an important influence on the sintering temperature of ash. The SEM analysis revealed a fine, irregular, and fibrous texture in the ash specimens from the lower ashing temperature. Regular block-shape particles were present in the ash from the higher ashing temperature. The EDS results showed that more Ca and Fe appeared with the increase of ashing temperature and more K and Na appeared, while Ca and Fe decreased with the addition of PS. The XRD analysis revealed that low-temperature minerals melted or co-fused with 10% PS addition into coal, while the high-temperature minerals formed with increased ashing temperature. The FactSage calculation indicated that the alkali and alkali earth metal species mainly existed in the forms of aluminosilicates and silicates. Calcium, magnesium, and potassium played a vital role during the sintering of the blends with PS.

In a simulation model of the process of corn straw crushing, its physical parameters and the model itself influence the accuracy of the numerical calculations of the discrete element method. This study attempts to improve the simulation accuracy of the crushing process and to find the optimal combination of parameters. Based on the Hertz-Mindlin with Bonding contact model, multiple particle replacement and bonding programs written using Visual Studio were imported through the application programming interface (API) of a discrete element method (DEM) model to establish three particle-bonding materials for a numerical simulation of the crushing process. Using results of mechanical corn stalk tests, DEM simulations of impact fracture, compression fracture, and bending fracture were conducted to determine the optimal combination of parameters. The resultant DEM-parameter combination led to simulation errors of 3.83%, 5.95%, and 7.86% in numerical simulations of impact fracture, bending fracture, and compression fracture of corn stalks, respectively. The performance of the corn stalk DEM using the proposed optimal parameter combination was validated using a 9RS-60 corn stalk crusher, revealing that the numerical simulation error was 8.77%. This study can improve the accuracy of the discrete element method in the simulation of the corn straw breaking process.

This study reports the feasibility of using deep convolutional neural networks (CNN), for automatically detecting knots on the surface of wood with high speed and accuracy. A limited dataset of 921 images were photographed in different contexts and divided into 80:20 ratio for training and validation, respectively. The “You only look once” (YoloV3) CNN-based architecture was adopted for training the neural network. The Adam gradient descent optimizer algorithm was used to iteratively minimize the generalized intersection-over-union loss function. Knots on the surface of wood were manually annotated. Images and annotations were analyzed by a stack of convolutional and fully connected layers with skipped connections. After training, model checkpoint was created and inferences on the validation set were made. The quality of results was assessed by several metrics: precision, recall, F1-score, average precision, and precision x recall curve. Results indicated that YoloV3 provided knot detection time of approximately 0.0102 s per knot with a relatively low false positive and false negative ratios. Precision, recall, f1-score metrics reached 0.77, 0.79, and 0.78, respectively. The average precision was 80%. With an adequate number of images, it is possible to improve this tool for use within sawmills in the forms of both workstation and mobile device applications.

Thin lamellae, corresponding to the layer components of structural glued members, i.e. 2-ply or 3-ply glued parquet, can be manufactured in re-sawing operations of kiln-dried wood blocks. These must be prepared with high dimensional accuracy and adequate surface quality following specific technical requirements for lamellae thickness variations, especially in the upper layers of the glued composite parquet. The accuracy of oak lamellae thickness was examined here for a re-sawing process performed on the sash gang saw. A series of cutting tests were carried out in sawmill production conditions. The overall objective for these observations was to determine an effect of both the cumulative time of sawing (progress of the tool wear) and the lamella position (distribution of lateral forces) on the dimensional accuracy of production. Lamellae size control was conducted following the Brown methodology. Detailed within-board, between-board, and total sawing standard deviations for the examined lamellae positions in the gang were determined. The obtained results revealed that outermost lamellae are more subjected to dimensional inaccuracy than lamellae from the centre of the sawn block or frieze.

Water-based flexographic-printed ink has attracted much attention due to the reduced emission of volatile organic compounds in the printing process. However, it is difficult to remove water-based ink particles with small particle size and high hydrophilicity because they are easily reabsorbed onto cellulosic fibers during wastepaper recycling. In this paper, the absorption mechanism of water-based ink particles onto fibers was studied by using isotherm models and adsorption dynamic kinetics models at different temperatures. The adsorption process was fitted to the Freundlich isotherm, and the adsorption behavior was spontaneous and exothermic processes with an increase of entropy. It fitted well with the pseudo-second-order rate model, and the equilibrium adsorption amounts at three temperature conditions were 2.55, 2.34, and 2.21 mg/g, respectively. The B value was 9.20 g·mg−1·min−1, and the Ea value was 15.6 kJ·mol−1. The results showed that it was easier to remove the water-based ink particles from cellulosic fibers under shorter contact time and higher operation temperature during wastepaper recycling. It would be helpful to optimize the wastepaper recycling operation and to develop a novel deinking process.

Rice straw bales and fresh pig manure were used as feedstock, and added microbial fortification agent and stepwise spraying methods were used to investigate the effect on the gas yield characteristics and fermentation properties of garage-type anaerobic solid-state fermentation at ambient temperature. The test results showed that the added microbial fortification agent advanced the arrival time of the peak temperature by one day and increased the average fermentation temperature by 8.28%. The microbial fortification agent can increase gas production and the time of first yield peak and shorten the start-up time. The maximum gas yield of the enhanced groups was 13.01% higher than the ordinary groups, and the methane concentration increased 16.98%. After the second gas yield peak, the reduction of spraying frequency had almost no effect on the gas yield. The stepwise spraying method was helpful to improve the moisture distribution and the degradation rate of the middle layer. This study provides a basis for evaluating and improving the operating efficiency of the anaerobic solid-state fermentation systems.

Tannins and lignins, which are natural phenolic compounds, are gaining substantial interest in biobased wood adhesive research. In this study, several different biobased tannin-lignin-hexamine adhesive mixtures were prepared and compared in a lap-joint shear strength test. In the first part, the suitability of different types of kraft and organosolv lignins as part of the mixture used in the production of biobased adhesives (in combination with pine tannins) were observed. It was found that biobased adhesive mixtures containing kraft lignins performed significantly better than those that contained organosolv lignins. In the second part, unmodified kraft lignins were mixed with pine tannin in different proportions, ranging from 0% to 100%. The pressing parameters were set to 150 °C for 15 min after performing oscillatory tests with a rheometer. Pure tannin adhesives performed the best, but no significant differences or a trend line were observed among adhesives containing different proportions of tannins and lignins.

The current study aimed to optimize Cd(II) removal from aqueous solutions by a composite adsorbent (BCB) prepared from Alternanthera philoxeroides (AP) biochar (BC) and bentonite (BE) using response surface methodology (RSM). The results showed that the loading of BE did not significantly change the microstructure of BC but increased the number of functional groups. The X-ray diffraction (XRD) analysis showed that precipitation was the primary mechanism of Cd(II) adsorption. The adsorption behavior for Cd(II) fitted the Freundlich model. The pH, adsorbent dosage, and initial Cd(II) concentration were the main influencing factors affecting Cd(II) adsorption. There were significant interactions between pH and adsorbent dosage, adsorbent dosage, and initial concentration. The optimum adsorption conditions for Cd(II) with the maximum adsorption level of 89.4% were: 6.55 pH, 0.04 g adsorbent dosage, and 68.7 mg∙L-1 initial concentration. Overall, the BCB exhibited great potential as an efficient sorbent for the Cd(II) removal from aqueous solutions.