Selective laser melting is an advanced additive manufacturing technology to use laser beams to melt metal powder and fabricate parts layer by layer. To understand the involved multi-physics, a ...validated mathematical model is employed in this work to assess effect of material properties such as powder melting and solidification coefficients and mushy zone constant. The results show that large pores are produced by the gas bubble coalesce and elongated narrow pores are generated from the gas bubble compression by the melt pool flow at the low melting coefficient. Two freeze modes, the pasty freeze mode and full freeze mode, can be observed, depending on the magnitude of the solidification coefficient. The results indicate that a large solidification rate is preferred to avoid the pore defect and surface cavity. A low mushy zone constant provides a high velocity of molten liquid resulting in large pores and severe surface concave cavities.
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•Melt pool dynamics and pore formation in SLM are studied numerically.•Large and elongated pores are generated at a low melting coefficient.•Large solidification coefficient can reduce pore defect and surface cavity.•Low mushy zone constant leads to large pores and severe surface concave cavities.
Duck short beak and dwarfism syndrome (SBDS) is a viral infectious disease caused by novel goose parvovirus (NGPV), which has been responsible for serious economic losses to the Chinese duck industry ...in recent years. Currently, there is no effective vaccine against this disease. In this study, we developed an inactivated virus vaccine candidate for SBDS based on NGPV strain DS15 isolated from a duck in China. Immune efficacy was evaluated in 112 ducks, which were randomly divided into vaccination, challenge-control, vaccination-challenge, and blank control groups (28 per group). Clinical characteristics, antibodies, virus excretion, viremia, and pathological changes were monitored. No morbidity or death was observed in the immunized ducks, which showed normal weight and a good mental state. High levels of serum antibodies (optical density at 450 nm of ~ 0.63) were detected in ducks immunized with the inactivated vaccine at 7 days post-vaccination (dpv), and the titer of virus-neutralizing antibodies increased from 1:2
3
to 1:2
8.5
from 7 to 42 dpv. Measurement of the viral load in anal swab, serum, and tissue samples showed that vaccination significantly inhibited the replication of NGPV in immunized ducks. Moreover, NGPV could not be isolated from the spleens of immunized or vaccinated and challenged ducks. Collectively, these results demonstrate that the newly developed inactivated NGPV vaccine, administered in an oil emulsion adjuvant, possesses good immunogenicity and represents a potentially powerful tool for SBDS prevention and control.
High-speed precision seed metering device is the key to achieve efficient and precise seed planting in agricultural industry. In this work, a novel quantitative seed feeding system containing a ...feeding device and a venturi feeding tube is investigated using the coupled CFD and DEM approach. The flow behavior of seed particles and airflow field in this system are analyzed in detail, and the effects of different variables related to venturi tube and operations are examined. The results show that as the nozzle convergence angle increases, the pressure at the nozzle gradually decreases and the pressure gradient extends. As a result, particle movement mobility is enhanced and particle accumulation is reduced. With the increase of the feeding angle, seed particles tend to deposit and collide with the bottom wall. The results also show that when wind pressure reaches above 10 kPa, the spacing between two adjacent seed particles is more consistent, and seed particles are more uniformly discharged from the venturi tube. The results demonstrate that for a better design of the quantitative seed feeding system, the proper nozzle convergence angle is roughly at 70°, and the feeding angle is at around 45°
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•CFD-DEM is used to optimize a novel seed feeding system parameters.•Seed particles can flow evenly in a grid groove seed supply wheel.•Feeding convergence angle of 70° shows relatively uniform gas and particle flow.•Feeding angle at 45° gives more smooth entry of particles to nozzle.•Wind pressure affects discharged particle positions and uniformity significantly.
Powder bed fusion additive manufacturing has been applied to the fabrication of functionally graded materials. A new design that allows the material composition to change along the direction ...perpendicular to the powder spreading has been reported in the literature. Based on this design, this work examines the quality of the graded spread powder layer with two powders, which have a large difference of density. The results reveal that during the spreading of graded powders, the volume of particles on the heavy powder side is deposited less than that on the light powder side, indicating that heavy particles diffuse to the light powder side. This diffusion is affected by the spreading speed, but not much by the layer gap. Large spreading speed causes more significant deviation. The results also show that particle size affects diffusion, indicating that decreasing the particle size of the heavy powder may be a solution to reduce diffusion.
The formation of pores can severely deteriorate the quality of parts fabricated by laser powder bed fusion (LPBF) technology. However, how the pores formation relates to melt pool and gas bubble ...dynamics is still not well understood. Here, through the modeling of the metal powder melting and the subsequent solidification under the conduction mode, it was found that the molten liquid near the gas-liquid interface flows centrifugally and vortices including a clockwise and an anticlockwise vortex are produced. The anticlockwise vortex dominates the molten liquid when laser turns off. The motion of gas bubbles originating from the powder bed voids follows the melt pool flow synchronously, where bubbles can coalesce, and some escape from the top and sides of the melt pool, and some remain as pores in the solidified part. For the positive value of surface tension gradient, the centripetal Marangoni convection drives the melt pool to flow in the dual clockwise circulation and obstructs the escaping orbit of bubbles, leading to higher porosity and surface humping. The present study enhances the further understanding of multi-physics in LPBF process.
Melt pool dynamics (top); gas bubbles formation (middle); bubble trajectories (left bottom); and average bubble velocity (right bottom). Display omitted
•Melt pool and gas bubble dynamics in LPBF are studied mathematically.•Two vortices are captured within the melt pool which controls bubble dynamics.•Bubbles escaping from the melt pool or remaining as pores are quantified.•The positive surface tension gradient has the higher porosity and humping surface.
In this work, a covalent organic framework (TADM-COF) with high crystallinity and large specific surface area (2597 m
g
) has been successfully synthesized using 1,3,5-(4-aminophenyl) benzene (TAPB) ...and 2,5-dimethoxy-p-phenyldiformaldehyde (DMTP). The COF was grown in situ on oxide particles to form core-shell nanocomposites (SiO
@TADM COF, Fe
O
@TADM COF and Co
O
@TADM COF) to realize its function as a shell material. Among them, the Co
O
@TADM COF with the highest electrochemical response to purine bases was further cross-linked with multi-walled carbon nanotubes (MWCNT) to construct a novel electrochemical sensor (Co
O
@TADM COF/MWCNT/GCE) for detection of purine bases. In this nanocomposite, Co
O
possesses rich catalytic active sites, MWCNT ensures superior electrical conductivity and COF provides a stable environment for electrocatalytic reactions as the shell. At the same time, regular pore structure of the COFs also offers smooth channels for the transfer of analytes to the catalytic site. The synergistic effect among the three components showed remarkable sensing performance for the simultaneous detection of guanine (G) and adenine (A) with a wide linear range of 0.6-180 μM and low limits of detection (LODs) of 0.020 μM for G and 0.024 μM for A (S/N = 3), respectively. The developed sensor platform was also successfully applied in the detection of purine bases in thermally denatured herring DNA extract. The work provided a general strategy for amplifying signal of COF and its composite in the electrochemical sensing.
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•DEM is used to optimize performance of a novel seed metering device with ground speed at 14 km/h.•Seed inlet speed of 3 m/s shows relatively stable seed filling performance.•The ...number of seeds in metering device significantly affects seeding performance.•Feeding rate maintained at 14 seeds/s shows best seeding performance.•Angle of seed cleaning element at 30° gives more smooth particles backflow and better performance.
This paper presents a numerical study on the motions of seed particles in a novel high-speed seed metering device based on the discrete element method. The effects of key parameters, including inlet velocity of particles, feeding rates and the angle of seed cleaning element, are investigated by a series of controlled numerical experiments. The results show that in the seed filling area of the device, a better match of particle velocity and the tangential linear velocity of the seeding plate can improve the seed filling performance. The number of particles remaining in the metering device is an important factor that affects the device performance. A large number of particles in the device results in more multiple seeding, and a small number causes more leakage seeding. Under the conditions of the seeding plate rotational speed at 194.5 rpm (corresponding to the high ground speed of 14 km/h), feeding rate at ~14 seeds/s can ensure that around 24 seed particles are maintained in the device which generates minimum leakage and multiple seeding. The studies of the effect of the seed cleaning element angle show that an appropriate angle (e.g., 30°) can effectively enhance the clearing ability, increase the uniform stability of particles backflow, and improve the seeding performance.
Previous hydrocyclone optimization often neglected interactions among key performance objectives, which limits hydrocyclone wide applications to meet increasingly diverse industry demands. This study ...proposes an optimization framework to identify the most suitable hydrocyclone design and operating conditions with conflicting key performance objectives. An advanced multi-objective evolutionary algorithm (PICEA-g) is employed to generate Pareto-optimal solutions that capture trade-offs among multiple conflicting objectives. A novel data-driven predictive algorithm, INFO-ELM, is introduced to establish nonlinear relationships between key variables and performance objectives, thereby accelerating the search for Pareto-optimal solutions by PICEA-g. Furthermore, a multi-criteria decision-making method (TOPSIS) is utilized to determine the optimal solution based on decision-makers' preferences, ensuring consistency between preference information and decision outcomes. The framework's effectiveness is validated across various separation scenarios using two decision-making strategies. This study offers a comprehensive approach to address trade-offs in hydrocyclone optimization, widening its application in diverse separation scenarios.
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•A framework optimizing four key performance objectives in hydrocyclones is proposed.•The framework identifies the most suitable solution for various separation scenarios.•The novel INFO-ELM method improves the predictive accuracy and reliability of BP-ANN.•PICEA-g outperforms other advanced MOEAs in terms of convergence and diversity.
Multibody dynamics (MBD) simulation is a useful tool to analyse the kinematic function of multibody systems, while discrete element method (DEM) is widely used to simulate particle flows in various ...types of equipment at the individual particle scale and as an overall process. A combination of MBD and DEM methods, such as functional mock-up interface (FMI) based co-simulation, could capture both updated material behaviour and equipment behaviour and predict the equipment performance. In this work, MBD and FMI co-simulations are based on the commercial software Dymola. MBD models have been developed for hydraulic excavator system. GPU-based DEM models have also been developed for excavator digging cycles. Finally, MBD-DEM FMI co-simulation results show that solid materials can significantly affect the movement of excavators.
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•MBD model for a simplified excavator is developed based on Dymola.•MBD dig cycles can be flexibly adjusted.•GPU-based DEM model is developed with dynamic computational domain.•MBD-DEM FMI co-simulation models have been developed.•Co-simulation results show the mutual effect of solid materials and excavator.
Modelling of machine-material interaction system is challenging. Many efforts have been made in the past to predict machine-material interactions through analytical and numerical models. However, few ...studies have focused on the dynamic response of machine to materials in automated machine operations. In this work, the co-simulation of multibody dynamics for excavators and discrete element method for granular materials is employed to evaluate the excavator performance. The results show that the full working cycle of excavators can be well captured by the co-simulation method, and the variations of the hydraulic pressure and flow rate and the power consumption with cylinder positions can be obtained. The results also demonstrate that with the material density increasing, the bucket payload experiences small changes. The complex bucket-particle interactions mainly occur in the process of the digging, loading, and lifting, while the significant hydraulic power consumption and intense particle-to-bucket interactions take place in the digging process.
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•Excavator performance is evaluated by MBD-DEM co-simulation.•Bucket payload experiences small changes with the increase of material density.•Larger material density results in more hydraulic power consumption.•Bucket-particle interaction forces increase with the material density increasing.•Severe wear on the bucket occurs primarily during the digging process.
