Research Articles

Selective Laser Sintering (SLS) is an advanced additive manufacturing technology that is widely used in multiple fields. This study investigated the effects of laser power and scanning speed on the SLS melt pool using FLOW-3D numerical simulations and experimental validation. The raw material was a mixture of walnut shell powder and copolyester (co-PES) hot melt adhesive powder. Experimental temperature measurements confirmed the numerical model’s accuracy, revealing a deviation of less than 10% between the simulated and actual center temperatures of the melt pool. The results demonstrated that a stable, continuous single-track melt pool was achieved under optimal parameters of 10 W laser power and 1400 mm/s scanning speed. Conversely, increasing the scanning speed to 1600 to 2200 mm/s at a constant 10 W power substantially reduced thermal energy input. This reduction induced a transition to metastable melt pools, ultimately leading to the formation of semi-melted particles. These insights can provide a basis for optimization of SLS manufacturing parameters.

Improving the performance of laminated veneer lumber can be a key to expanding the value-added use of renewable, fast-growing, low-density poplar raw material. This study evaluated the impact of a commercial neat pMDI (polymeric methylene diphenyl diisocyanate) and a pMDI formulation containing 5% polyol (pMDI +5%P) on the physical, mechanical, and bonding properties of laminated veneer lumber (LVL) prepared from poplar (Populus × euramericana I-214) veneers. Physical properties including the moisture content (9.03% and 8.75%), air-dry density (0.54 g/cm³ and 0.56 g/cm³), thickness (11.1% and 11.3%), and volumetric swelling (after 72 h) (19.9% and 18.9%), were found to be similar to 15-layered LVLs produced from pMDI and pMDI +5%P, respectively. However, mechanical test results showed that bonding quality (4.44 to 5.92 N/mm²) and correspondingly modulus of elasticity (MOE, 7880 to 9410 N/mm²), bending strength (MOR, 73.4 to 90.5 N/mm²), and screw withdrawal capacity (22.6 to 30.6 N/mm²) significantly (at 95% confidence level) increased on the LVLs produced from pMDI +5%P. Additionally, hardness on the surface (3460 to 4000 N), longitudinal (2950 to 3600 N), and parallel hardness (4570 to 5600 N) values of LVLs were increased. However, impact strength decreased from 4.50 to 3.80 kJ/m² with polyol addition. It can be said that this situation stems from an increase in adhesion brittleness upon the addition of polyol.

This study evaluated the influence of the cutting position (terminal, middle, and basal) and the growth medium [soil only; soil + biochar (BC); soil + phosphorus solubilizing bacteria (PSB); soil + arbuscular mycorrhizal fungi (AMF); soil + BC + PSB + AMF] on vegetative growth attributes and root morphology, soil microbial carbon and respiration, available phosphorus, and the rate of its absorption in fig trees (Ficus carica L.). The results demonstrated that using soil + BC + PSB + AMF as a growth medium for the medium cutting gave the highest plant height, shoot fresh weight, shoot dry weight, root fresh weight, root dry weight, root length, and root surface area, as well as the absorbed phosphorus by cuttings compared to the other growth media used. Besides, the vegetative growth attributes and root morphology of middle cuttings were better than those of terminal or basal cuttings. Besides, using soil + BC + PSB + AMF as a cultivation medium increased phosphorus availability in the soil for medium, terminal, and basal cuttings.

This study’s main goal is to investigate the guqin’s frequency spectrum and the time frequency analysis. Its non-fret-based pitch system yields measurable polynomial connections between the partial frequency and the harmonic number for all strings. The tuning, harmonic content changes across the strings provide fresh perspectives on the instrument’s acoustic character and artistic versatility. Although the sound of the lowest to the highest pitch was perceived as: C2, D2, F2, G2, A2, C3 and D3, the results from the picoscope showed: C3, D3, F3, G3, A3, C3, and D4. The 1^st harmonic on the open 7^thstring occur at C3. The 2^nd, 3^rd, 4^th, 5^th, 6^th and 8^th harmonic occur at half the string length i.e. hui 7 is C4, at one and two third the string length i.e. hui 5 and hui 9 are G3, at one and three fourth the string length i.e. hui 4 and hui 10 are C4, at one and four fifth the string length i.e. hui 3, 6, 8 and 11 are E4, at one and five sixth the string length i.e. hui 2 and hui 12 are G4 and one and seven eight the string length i.e. hui 1 and 13 are C5.

The influence of diode laser cutting parameters—feed rate, laser power, and cutting angle—was investigated relative to the kerf width and heat-affected zone (HAZ) in 2.5-mm-thick oak and walnut veneers. Utilizing a 445 nm diode laser, experimental data were analyzed via analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests to quantify the thermo-mechanical responses of these anisotropic hardwood species. Results demonstrated that in ring-porous oak, kerf geometry is primarily dictated by the cutting angle (p < 0.05), whereas the HAZ expansion is significantly governed by energy input variables, specifically laser power and feed rate. Conversely, semi-ring-porous walnut exhibited pronounced thermal stability against feed rate fluctuations; its kerf width remained dependent on the cutting angle, while HAZ dimensions were strictly correlated with laser power. The findings establish a clear dichotomy where mechanical removal efficiency (kerf) is regulated by beam-angle interactions, while thermal degradation (HAZ) is modulated by thermal energy deposition. Overall, kerf width increased up to 0.226 mm in oak at 60° cutting angle, while HAZ values reached 0.104 mm under high power and low feed rates, confirming species-specific optimization requirements. These species-specific thermodynamic insights provide a foundation for optimizing industrial diode laser processing and developing predictive models for lignocellulosic materials.

Urea-formaldehyde (UF) resin is widely used in wood-based panels due to low cost and fast curing, but its high brittleness, low wet strength, and formaldehyde emissions restrict outdoor and high-humidity applications. Traditional biomass modifiers (starch, cellulose, or lignin) rely on hydrogen bonding or simple condensation with UF, offering limited improvement in wet‑state bonding strength and stress distribution. This study used industrial-grade whole wheat flour to prepare hydrolysate (WWFH) via acid-catalyzed hydrolysis and optimized the co-condensation with UF resin by response surface methodology. The optimized wheat flour–based UF (WFUF) showed wet shear strength of 1.30 MPa (54.8% higher than 0.84 MPa for neat UF) and dry shear strength of 1.66 MPa. Formaldehyde emission was 0.59 mg/L, meeting the E1 standard. Characterization indicated that WWFH reducing sugars, protein degradation products, and pentosans crosslinked into the cured network through hydroxymethylation, urea linkages, and ether bonds. WFUF exhibited lower crystallinity, higher crosslinking density, and better thermal stability than neat UF. This work supports value-added use of low-cost whole wheat flour and development of high-performance biomass-modified UF resins.

The objective of this work was to prepare functional food by microbial conversion using agricultural biomass. The nutrient and bioactive properties of cashew apple (CA) juice extracted from the seven CA varieties were analyzed. The VRI-3 variety CA juice presented a low pH value (3.19 ± 0.02), high titratable acidity (0.24 ± 0.03%), and total suspended solids (13.9 ± 0.2 Brix). The reducing sugar and total phenolic compounds were maximum in VRI-3 (12.5 ± 0.3% and 192 ± 1.3 mg GAE/100 mL) compared to other varieties. Due to rich phenolic compounds in the VRI-3 CA juice, it was used as the source of phenolic compounds; and the extraction procedure was optimized by statistical approach. A central composite design (CCD) was used to optimize the extraction procedure, and the model was significant (F value 163.8; P value < 0.0001). CCD mediated optimized procedure improved phenolic compounds in the extract and presented high antioxidant activity. In order to utilize the CA waste (bagasse) of VRI-3, it was pretreated and used as the culture medium for lactic acid bacterial fermentation. The cashew apple bagasse fermented with lactic acid bacteria exhibited a significant amount of α-glucosidase inhibitory activity.

The disposal of olive mill wastewater (OMW) poses significant environmental challenges because of its high organic load and phytotoxic compounds. This study focused on treating OMW from a modern oil mill using a filtration-percolation technique and evaluated its impact on the germination of barley and fenugreek seeds. Filters were prepared using lime and charcoal derived from the mill’s pomace. Four distinct treatments were applied: (1) raw OMW (T0), (2) a lime layer (1.0 cm) sandwiched between two layers of sand (T1), (3) an activated charcoal layer (1.0 cm) derived from pomace sandwiched between two layers of sand (T2), and (4) a combination of lime and activated charcoal derived from pomace, sandwiched between two layers of sand (T3). Extensive physicochemical analyses, including pH, electrical conductivity (EC), total suspended solids (TSS), moisture content (MC), dry matter (DM), total Kjeldahl nitrogen (TKN), biochemical oxygen demand (BOD₅), phosphorus (P), polyphenol (PP), and exchangeable cation content (Ca, Na, and K) were performed. The results revealed significant differences between treatments, with substantial reductions in polyphenols, EC, organic matter (OM), total organic carbon (TOC), and BOD₅. Treatments T2 and T3 were the most effective depollution of OMW, and T3 exhibited the highest germination rate. These findings highlight the potential of this filtration technique for treating OMW and promoting its reuse in sustainable agriculture.

Wear characteristics were evaluated for 3D-printed polylactic acid (PLA) composites reinforced with wood particles and carbon fiber. The goal was enhanced robustness and wear resistance. Specimens were fabricated by fused deposition modelling and tested on a pin-on-disc tribometer in agreement with ASTM G99-23. Load, sliding speed, and sliding distance were considered as three primary factors with three-level Box–Behnken design. Analysis of variance (ANOVA) confirmed statistically significant regression models for both composites (F = 32.48, PLA-wood; F = 16.38, PLA-carbon fiber; p ≤ 0.003). Applied load was the dominant factor influencing wear rate, contributing 44.1% for PLA-carbon fiber and 44.9% for PLA-wood, followed by sliding velocity (12.6% and 21.0%, respectively) and sliding distance (5.60% and 9.35%, respectively). Wear rate increased with load (10 to 30 N) and sliding velocity (2.19 to 3.76 m/s) but stabilized at longer sliding distances (up to 2871 m) due to tribofilm creation. PLA/carbon fiber composites showed lower wear than PLA/wood particle composites, which was ascribed to higher hardness, improved load-bearing capacity, and development of a stable transfer layer. Scanning electron microscopy indicated severe fiber pull-out, voids, and delamination in PLA/wood specimens, whereas PLA/carbon fiber specimens established a protective tribofilm with minimal damage of carbon fiber.

Thermally modified Scots pine (Pinus sylvestris var. mongolica Litv.) was used as the substrate, while Scots pine and birch (Pinus sylvestris var. mongolica Litv.) were used as dowel materials. Infrared thermography, SEM, GC-MS, and FTIR were employed to investigate the relationships among process parameters, interfacial temperature, and welding performance in rotary friction welding of wood. The interfacial temperature exhibited a three-stage evolution pattern of rapid heating, stabilisation, and cooling-solidification. Rotational speed, feed rate, and dowel-to-hole diameter ratio regulated the interfacial temperature by affecting frictional heat generation efficiency and interaction duration, with each parameter exhibiting an optimal range. An appropriate temperature range (360 to 380 °C) promoted hemicellulose degradation, lignin softening, and flow, and the formation of a dense welded zone after cooling. Birch dowels generated higher interfacial temperatures and bonding strength than Scots pine dowels. The findings indicate that rotary friction welding of wood is a temperature-dominated thermo-mechanical-chemical coupled process, and that optimising process parameters to precisely control interfacial temperature is essential for achieving high-performance adhesive-free joints.