Successful continuous fiber-reinforced composite filament 3D printing hinges on the synergistic relationship between the printing nozzle and precisely controlled process parameters. This research uses a simulation model to investigate how printing temperature, printing speed, and nozzle length affect the prepreg filament’s molten state during 3D printing. We employed the Box–Behnken response surface methodology to optimize these key parameters. Using continuous fiber-reinforced composite filament polylactic acid (CFRCF/PLA) as an example, and a printing nozzle with a 1 mm diameter and an 8 mm length of heating zone were designed. The optimal printing parameters were determined to be as follows: printing temperature of 220 °C, printing speed of 300 mm/min, and printing layer height of 0.2 mm. Experimental validation using the optimized nozzle and parameters demonstrated enhanced stability in continuous fiber prepreg filament printing.

Backward-facing step (BFS) flow is a benchmark case study in fluid mechanics. Its control by means of electromagnetic actuation has attracted great interest in recent years. This paper focuses on the effects of a uniform stationary magnetic field on the laminar ferrofluid BFS flows for the Reynolds number range $0.1≤Re≤400$ and different expansion ratios. The coupled ferrohydrodynamic equations, including the microscopically derived magnetization equation, for a two-dimensional domain are solved numerically by an openfoam solver after validation and a test of accuracy. The application of a magnetic field causes the corner vortices in the concave corner behind the step to be retracted compared with their positions in the absence of a magnetic field. The maximum percentage of the normalized decrease in length of these eddies reaches 41.23% in our simulations. For small Reynolds numbers (<10), the flow separation points on the convex corner are lowered in the presence of a magnetic field. Furthermore, the dimensionless total pressure drop between the channel inlet and outlet decreases almost linearly with Reynolds number $Re$⁠, but the drop is greater when a magnetic field is applied. On the whole, the normalized recirculation length of the corner vortex increases nonlinearly with increasing magnetic Reynolds number $Rem$ and Brownian Péclet number $Pe$⁠, but it tends to constant values in the limits $Rem≪1$ and $Rem≫1$⁠.

Accurate prediction of Electro-Discharge Machining (EDM) results is crucial for industrial applications, aiming to achieve high-performance and cost-efficient machining. However, both the current physical model and the standard Artificial Neural Network (ANN) model exhibit inherent limitations, failing to fully meet the accurate requirements for predicting EDM machining results. In addition, Micro-EDM Drilling can lead to the distortion of the macroscopic shape of machining pits under different input conditions, rendering the use of only the volume of machining pits as the evaluation index insufficient to express the complete morphological information. In this study, we propose a novel hybrid prediction model that combines the strengths of both physical and data-driven models to simultaneously predict Material Removal Rate (MRR) and shape parameters. Our experiment demonstrates that the hybrid model achieves a maximum prediction error of 4.92% for MRR and 5.28% for shape parameters, showcasing excellent prediction accuracy and stability compared to the physical model and the standard ANN model.

It is necessary to recognize the spatial distribution of ion density and temperature in some practical applications. While numerical modeling is a useful method to fulfill this task, a self-consistent numerical model based on the first few moments of the Boltzmann transport equation coupled to Poisson's equation was built using COMSOL Multiphysics to simulate the dc discharge of a needle-to-plane geometry in atmospheric pressure. Simulation of the discharge was carried out for an actual geometry in aerosol sensors when only the main compositions of air and the main collisional populating and depopulating processes were considered. The simulation results demonstrated that the space occupied by the positive ions with a density of sufficiently charging aerosol particles was very limited. In the meanwhile, the electron temperature in the vicinity of the entire plane electrode was higher than the melting point of most metals. Experiments of measuring the current inducted by charged particles with a diameter of 95 nm using devices with narrowed channels showed that the specific current increased to nearly five times when the width of the channel in the charging stage decreases from 5 to 2 mm. Furthermore, the ablation of the plane electrode used in the experiments occurred on almost the entire surface, which was agreed with the prediction by simulation.