Search Results (45)

The present study presents the results of an analytical and experimental investigation on the behaviour of Al₂O₃ particles injected into the plasma jet. The dependence of the temperature of the particles and velocity profiles on particle size was estimated by numerically simulating the specific plasma jet in the plasma chemical reactor. The velocity of the particle was investigated experimentally using the ParticleMaster shadowgraphy laser imaging system. The heat flux from the plasma jet to the particles was estimated numerically, and the results were compared with the experimental measurements. Mineral fibre and granules were produced during the plasma spraying process. The studies performed showed that the interaction of the plasma jet and dispersed particles in the reactor mainly depends on the particle’s size, velocity, and temperature of the plasma flow. The modelling and measurements were performed under plasma conditions chosen below the full melting temperature of alumina to avoid particle deposition on the walls while still representative of the reactor environment where finer fractions contribute to melt and fibre formation. The heat flux to the particles inside the reactor increased with the increase in the particle-plasma mass ratio in the reactor. Full article

Artemisia herba-alba Asso. is a medicinal plant rich in phenolic compounds with strong antioxidant and antimicrobial activities. However, these bioactive molecules are highly sensitive to environmental conditions, limiting their stability and potential applications. This study investigated, for the first time, the encapsulation of ethanolic extracts from the aerial parts of A. herba-alba by spray-drying, using maltodextrin (MD) and sodium caseinate (SC) as wall materials. The extract was obtained by ultrasound-assisted extraction, and both free and encapsulated forms were analyzed for phytochemical composition, antioxidant capacity, and antibacterial activity. Spray-dried microcapsules (SDE) were further characterized for encapsulation yield, efficiency, moisture, water activity, hygroscopicity, particle size, and structural integrity (SEM, ATR-FTIR, TGA/DTG). The process resulted in a high encapsulation yield (69.40%) and efficiency (96.39%), producing microcapsules with a small average size (10.05 ± 0.08 µm), low moisture (4.34%), low water activity (0.415), and moderate hygroscopicity (12.67%). Although the encapsulated extract showed lower total phenolic content, antioxidant capacity, and antibacterial activity compared to the free extract, SEM observations confirmed the formation of spherical, crack-free microcapsules, ATR-FTIR analysis revealed non-covalent interactions between wall materials and phenolics, and TGA/DTG demonstrated improved thermal stability. These results highlight spray-drying microencapsulation as an efficient approach to stabilize A. herba-alba phenolic compounds, offering promising applications as natural preservatives in the food industry. Full article

The encapsulation of bioactive compounds using proteins as wall materials has emerged as an effective strategy to enhance their stability, bioavailability, and controlled release. Proteins offer unique functional properties, including amphiphilic behavior, gel-forming ability, and interactions with bioactives, making them ideal candidates for encapsulation. Animal-derived proteins, such as whey and casein, exhibit superior performance in stabilizing lipophilic compounds, whereas plant proteins, including soy and pea protein, demonstrate greater affinity for hydrophilic bioactives. Advances in protein modification and the formation of protein–polysaccharide complexes have further improved encapsulation efficiency, particularly for heat- and pH-sensitive compounds. This review explores the physicochemical characteristics of proteins used in encapsulation, the interactions between proteins and bioactives, and the main encapsulation techniques, including spray drying, complex coacervation, nanoemulsions, and electrospinning. Furthermore, the potential applications of encapsulated bioactives in functional foods, pharmaceuticals, and nutraceuticals are discussed, highlighting the role of emerging technologies in optimizing delivery systems. Understanding the synergy between proteins, bioactives, and encapsulation methods is essential for developing more stable, bioavailable, and sustainable functional products. Full article

To address the high drying temperature, low yield, and low coating rate that characterize traditional chitosan/gum arabic microcapsules, this study used chitosan/sodium tripolyphosphate (STPP) ionic crosslinking to construct a composite wall, combined with optimized emulsifier compounding (T-80/SDBS), to prepare tung oil self-healing microcapsules. Orthogonal testing determined the following optimal parameters: a core-to-wall ratio of 2.0:1.0, a T-80/SDBS ratio of 4.0:6.0 (HLB = 12.383), an STPP concentration of 4%, and a spray-drying temperature of 120 °C. With these parameters, a yield of 42.91% and coating rate of 68.50% were achieved. The microcapsules were spherical (1–6 μm), with chitosan–STPP electrostatic interactions forming a dense wall. Adding 5% microcapsules to the UV topcoat enabled self-healing after 60 s UV curing: the scratch-healing rate reached 25.25% (width decreased from 11.13 μm to 8.32 μm), the elongation at break increased by 110% to 9.31%, the light transmission remained >82.50%, and the color difference (ΔE = 2.16) showed no significant change versus unmodified coating. Full article

To solve the manufacturing problem of the efficient removal of multi-scale surface defects (wrinkles, cracks, scratches, etc.) on the inner wall of MP35N cobalt–chromium alloy vascular stents, this study proposes a collaborative optimization strategy of magnetic abrasive polishing (MAF) based on a new type of magnetic abrasive. In response to the unique requirements for the inner wall processing of high aspect ratio microtubes, metal-based Al₂O₃ magnetic abrasives with superior performance were prepared by the plasma melt powder spraying method. A special MAF system for the inner wall of the bracket was designed and constructed. The four-factor and three-level Box–Behnken response surface method was adopted to analyze the influences and interactions of tube rotational speed, magnetic pole feed rate, abrasive filling amount, and processing clearance on surface roughness (Ra). The significance order of each parameter for Ra is determined as follows: processing clearance > tube rotational speed > abrasive filling amount > magnetic pole feed rate. Using the established model and multiple regression equations, the optimal parameters were determined as follows: a tube rotational speed of 600 r/min, a magnetic pole feed rate of 150 mm/min, an abrasive filling amount of 0.50 g, and a processing clearance of 0.50 mm. The optimized model predicted an Ra value of 0.104 μm, while the average Ra value verified experimentally was 0.107 μm, with the minimum error being 2.9%. Compared with the initial Ra of 0.486 μm, directly measured by the ultra-depth-of-field 3D microscope of model DSX1000, the surface roughness was reduced by 77.98%. MAF effectively eliminates the surface defects and deteriorated layers on the inner wall of MP35N tubes, significantly improving the surface quality, which is of great significance for the subsequent preparation of high-quality vascular stents and their clinical applications. Full article

To enhance Lactobacillus paracei F50 viability during spray drying and long-term storage, this study evaluates whey protein (WP) crosslinked with four polysaccharides (κ-carrageenan (KC), xanthan gum (XG), low-methoxyl pectin (LMP), sodium alginate (SA)) for the first time as protective matrices for L. paracasei F50 during spray drying. The four kinds of crosslinked wall materials were compared by various characterization methods. Among them, the WP-κ-carrageenan (WP-KC) composite exhibited optimal performance, forming a uniform microcapsule with high colloidal stability. After spray drying, WP-KC achieved the highest viable cell density (9.62 lg CFU/g) and survival rate (91.85%). Notably, WP-KC maintained viability above 8.68 lg CFU/g after 120 days of storage at 4 °C, surpassing other formulations. Structural analysis showed that the WP-KC microcapsule was completely encapsulated without breaking or leaking and confirmed the molecular interaction between WP and KC. Under the condition of high temperatures (≤142.63 °C), the wall material of the microcapsule does not undergo any endothermic or exothermic process and is in a state of thermodynamic equilibrium, with excellent stability and good dispersion. Additionally, microcapsules exhibited enhanced resistance to thermal stress (55–75 °C) and UV irradiation, higher than that of free cells. These results highlight WP-KC as an industrially viable encapsulation system for improving probiotic stability in functional foods, offering critical insights into polysaccharide–protein interactions for optimized delivery systems. Full article

Diesel–methanol dual-fuel (DMDF) mode holds significant potential for achieving highly efficient and clean combustion in modern marine engines. However, issues such as low methanol substitution rate and high pollutant emissions persist, and the underlying mechanisms are not fully understood. This study numerically investigated the combustion and emissions of a heavy-duty marine engine operating in DMDF mode. Multi-cycle simulations, incorporating diesel and methanol dual-fuel chemical mechanisms, were carried out to explore engine performance across various key parameters, including valve phasing, injection pressure, injection phasing, and nozzle diameter. The results indicate that valve phasing can greatly affect the indicated thermal efficiency, particularly at large valve overlap angles. This is primarily attributed to the variations of methanol film mass and thereby overall combustion efficiency. The optimized valve phasing increases the indicated thermal efficiency by 2.4%. By optimizing injection parameters, the formation of methanol film is effectively reduced, facilitating the improvement in the indicated thermal efficiency. The optimal injection pressure and nozzle diameter are 20 bar and 0.3 mm, respectively, resulting in increases in indicated thermal efficiency of 1.28% and 1.07%, compared to the values before optimization. Advancing injection timing and increasing nozzle diameter markedly decrease methanol film mass because some methanol remains undisturbed by the intake flow, while large droplet sizes tend to enhance the resistance to airflow. As injection pressure rises from 20 bar to 50 bar, the spray–wall interaction region expands, droplet size diminishes, and methanol film formation increases. Consequently, the combustible methanol in the cylinder is reduced, undermining the indicated thermal efficiency. Additionally, there exists a trade-off relationship between NO_x and soot emissions, and the high heat release rate results in increased NO_x but decreased soot emissions for diesel–methanol dual-fuel engines. Full article

The limited mechanical properties of composite materials, including stiffness, strength, and biocompatibility, restrict their effectiveness in biomedical applications. This research enhanced the mechanical properties and biocompatibility of polylactic acid and carbon fiber-reinforced composites (PLA/CFRCs) by incorporating multi-walled carbon nanotube (MWCNT) fillers. The methodology involved synthesizing MWCNTs and integrating them into PLA/CFRC laminates using fusion-blending, dispersion, and interlaminar spray-coating. Raman spectroscopy confirmed the presence of MWCNTs, with characteristic D and G band peaks and an I_D/I_G of 1.44 ± 0.089. SEM revealed MWCNTs in the PLA/CFRC matrix and allowed size determination, with an outer diameter range of 125–150 nm and a length of 14,407 ± 2869 nm. FTIR identified interactions between the matrix and the MWCNTs, evidenced by band shifts. TGA/DSC analysis showed thermal stability above 338 °C for all composites. The tensile tests revealed that all composites had values greater than 19 GPa for the elastic modulus and 232 MPa for the ultimate strength. Cytotoxicity assays confirmed biocompatibility, and all samples maintained a cell growth rate greater than 80%. This study highlighted the potential of nanotechnology to optimize the mechanical behavior of polymer-based composites, expanding their applicability in biomedical fields. Full article

‘Liuyuezao’ pummelo is highly prone to cracking, which seriously affects its quality. The aim of this study was to illustrate the effect of foliar sprays of calcium (Ca) and boron (B) and their combined treatments on the fruit cracking and quality of ‘Liuyuezao’ pummelos during the fruit expansion period (40–55 days after flowering). Analysis of 12 mineral elements of the pericarp by ICP-MS revealed that the three treatments significantly increased the content of calcium and boron in the corresponding pericarp. These treatments effectively reduced the enzyme activities of pectin methylesterase (PME), polygalacturonase (PG), pectin lyase (PL), β-galactosidase (β-Gal), and cellulase (Cx) in the peel and down-regulated the expression of corresponding cell wall-degrading enzyme genes. Calcium, boron, and their combination treatments reduced water-soluble pectin (WSP) in the peel. Simultaneously, they inhibited the degradation of CDTA-soluble pectin (CSP) and Na₂CO₃-soluble pectin (NSP), thereby stabilizing the cell wall structure. Additionally, these treatments enhanced fruit skin break force (Bf) and elasticity (Ela), ultimately decreasing the fruit cracking rate. Diversification analysis showed that Ca and B elements significantly increased the sugar and vitamin C (Vc) content of ‘Liuyuezao’ pummelo fruits and reduced their organic acid content, thus improving fruit quality. The study provides new ideas on the use of fertilizer interactions to control fruit cracking and improve the quality of the pummelo fruit. Full article

The increasing interest in sustainability has driven research into the utilization of food by-products. Onion by-products, rich in bioactive compounds, represent a valuable resource for developing functional ingredients; however, they are prone to degradation due to environmental factors such as light, heat, and oxygen, leading to reduced efficacy and increased spoilage. Microencapsulation represents an effective approach to meet important goals in the formulation of food products such as the protection against degradation or the control of interactions with other ingredients that may modify and impair their functionality. This study explores the microencapsulation of flavonoid-rich onion by-product extract through spray drying, employing various wall materials (maltodextrin and a mixture of maltodextrin/trehalose and maltodextrin/trehalose/inulin) and their effect on the chemical and physical properties of the powders such as encapsulation efficiency, total flavonoids content, moisture content, water activity, bulk density, and bulk tapped density. The storage stability was further evaluated. This research supports waste reduction and suggests strategies for developing functional ingredients with extended shelf life and controlled release properties. Full article

Peptide aggregation inevitably occurs during hydrolysis, and insoluble peptide aggregates (ISPA) are used as feed for animals due to their poor water solubility and unpleasant bitter flavor. Ultrasound was used to fabricate soy peptide nanoparticles by reassembling ISPA, followed by spray-drying encapsulation to develop low-bitterness peptide microcapsules with soluble soybean polysaccharide (SSPS) and stevioside (STE) as wall materials. Powder properties, bitter taste, and the morphology of the microcapsules were evaluated. The formation of soluble peptide nanoparticles (<200 nm) was observed after ultrasound due to the reassembly of ISPA through the disruption of non-covalent intermolecular interactions. A gradual reduction in bitter taste was observed with increasing ultrasonic time. Moreover, spray-drying encapsulation with STE could effectively improve the flowability and wettability of the microcapsule powder owing to the rapid migration of surface-active STE to the atomized droplet surface, as evidenced by the lower angle of repose and wettability time. Peptide microcapsules with STE (spherical particles with smooth surfaces) exhibited lower density and reduced bitterness because STE (0–0.1%, w/w) exhibited an excellent bitter-masking effect. With high STE concentrations (>0.5%, w/w), microcapsules exhibited a higher bitter taste than unencapsulated peptides due to the increased surface distribution of STE on the microcapsules. These results provide an effective technique to improve the physicochemical properties of ISPA. Full article

This paper aims to reveal the motion law and collision behaviors of shotcrete particle flow jets. A physical model of the jet flow field composed of a nozzle structure and jet area was constructed and meshes with various sizes were used to mesh the nozzle and jet area. With the basic contact parameters and contact model parameters of the particles set, the CFD-DEM-coupling simulation method was adopted to perform the numerical simulation of concrete-particle-flow-jet impingement. The variation laws of the continuous-phase velocity and pressure drop of the shotcrete, coarse-aggregate motion characteristics, and particle collision behavior under the interaction of the continuous and discrete phases were obtained. The results showed that the velocity field and pressure-drop field of the continuous phase had an ideal symmetry in the XY plane in the stable injection stage, the continuous-phase velocity gradually increased inside the nozzle and gradually decreased after entering the jet area, the continuous-phase pressure drop was the maximum at the nozzle inlet, and the pressure value at the nozzle outlet became atmospheric pressure. The central axis of the particle flow jet was displaced by 0.15 m in the negative direction of the Y-axis under the action of gravity, the diffusion angle of the small particles that exited the nozzle and entered the jet area was larger than that of the large particles, and the large-particle jets were more concentrated and easier to spray into the designated spraying areas. The particle flow reached a stable jet state about 0.3 s after the jet began, and the peak velocity of the 4 mm particles in the flow reached 25 m/s, while the peak velocity of the 12 mm particles was only 19 m/s. The acceleration time for particles of different sizes to reach the peak velocity also varied, and the large particles took longer to reach the maximum velocity: small particles reached their peak within 0.4 m–8 m of the jet area, and large particles reached their peak within 0.8 m–1.2 m of the jet area. The particle velocity peaked within 0.6 m–1 m of the jet area. Particle collision took three forms: particle collision with the inner wall of the nozzle, interparticle collision, and particle collision with the sprayed wall. The collision between the particles and the sprayed wall was the main form leading to the rebound of the wet shotcrete, and the rebound angle after particle collision was uncertain. Full article

A recovery system for an automatic spraying robot to conduct the spraying operation outdoors for ships is designed in this paper, which addresses the pollution problem of volatile organic compounds (VOCs) by employing the vacuum recovery method. The recovery system consists of the recovery hood, nozzle, and vacuum tubes. The recovery hood is the critical part of the recovery system and is designed with internal and external cavities, as well as four vacuum tubes for recycling VOCs. Based on the computational fluid dynamics (CFD) method, simulation in the time domain of the gas–liquid interaction, droplet evaporation, and wall impingement is conducted. To identify the better recovery performance, three vacuum recovery-hood schemes are designed, and their performance is compared. The numerical results show that the distance between the vacuum tubes and the intake gap has a significant impact on the VOCs’ recovery effect. One of the main reasons for the escape of VOCs is that the swirling airflows in the baffle plane act as vortices which may capture VOCs, causing the accumulation of VOCs beyond the capacity of the external cavity. Dividing the external cavity into four chambers with deflectors (with each chamber equipped with one vacuum tube only) can significantly reduce the leakage rate of the recovery system. The recovery system provides a theoretical solution for implementing the prevention and control of VOCs in shipyards as soon as possible. Full article

The purpose of this paper is to provide a numerical simulation, taking into account the collisional interactions of droplets in an airless rotary spray coating process. The hydrodynamics of gas and droplets are simulated using the CFD-discrete element method (DEM) with the JKR contact model in an airless rotary spray coating process of a horizontal square duct. The surface energy parameter used in the JKR model is calibrated using a virtual accumulation angle test in the funnel device. Based on the distribution of accumulation angles, a suitable surface energy for wall droplets is proposed. A rational gas RNG k-ε model is suggested in accordance with the comparisons of velocities, standard deviations, and the skewness of droplet number fractions from three turbulence models. The simulations of droplet film thicknesses agree with measurements from the literature regarding the film thickness along a vertical panel. The correlations of the exit gas and droplet velocities of sprayer holes are proposed with a discharge coefficient of 0.85 for gas and 5.87 for droplets. A number index of droplets is introduced in order to measure the uniformity of droplet distributions. A low droplet number index is found at low rotational speeds, representing a more uniform distribution of droplets as the rotation speeds reduce within the square duct. The normal force between the droplet and the wall is approximately an order of magnitude larger than the droplet–wall tangential force of collisions. Full article

Spray impacts can be found in several technical applications and consist of many single droplets, which impact under different trajectories on wetted walls. This study investigates the asymmetric crown morphology resulting from an oblique impact ($\alpha =$ 60°) of a single droplet on a horizontal and quiescent wall film of the same liquid. A droplet generator with an accelerated needle releases the droplets ($D=$ 1.5 mm) in a controlled trajectory on a thin film ($h_f/D=$ 0.2). The impact process is recorded from two perspectives with two synchronized high-speed cameras. Varying the Weber number within the splashing regime reveals distinct crown morphologies, which are described in detail. For $We<$ 500, a single central finger develops at the front of the crown, with subsequent detachments of secondary droplets. At higher $We$ (>500), a collision of the crown with the wall film shortly after impact introduces disturbances into the rim, leading to two fingers in the middle of the front crown. A further increase in $We$ (>600) intensifies the crown–film interaction, resulting in an early ejection of tiny droplets and a complete breakup of the front rim. The influence of $We$ on the crown morphology during an oblique impact is also compared to the normal impact (90°). This study paves the way for a classification of impact regimes and a comprehensive picture of the oblique impact process, which deserve more investigation. Full article