Advanced Engineering Forum Vol. 59

Abstract: In molten metal flow length tests using a spiral die with a thin gap, a non-filled region of molten metal was observed in the middle of the flow length in some test pieces. The influences of die gap, plunger speed and die temperature on the position and length of the non-filled region were investigated. Both the die gap and molten metal speed significantly affected the occurrence, position and length of non-filled region. The phenomenon of molten metal flow stoppage in the middle of flow length is discussed based on the non-filled regions in the test pieces.

Abstract: Electrohydrodynamic direct-writing (EDW) is widely applied in the field of micro-nano manufacturing due to its advantage of rapid deposition of line structure. However, due to the difficulty of bending-torsion coupled modeling for EDW with large deformation, the mechanism and effective control strategies of EDW still unclear. This study firstly establishes a three-dimensional geometrically exact model for EDW using Euler angles. It contains differential equations for the mass conservation, the jet geometry, the jet kinematics, the jet dynamics, and the electric field and charge. Euler angles are used to exactly describe the jet’s geometric variation. A theoretical electric field description for non-uniform electric field is introduced. The universality of the model is validated by reducing the governing equations system to a two-dimensional steady-state situation. The geometrically exact model established in this study is useful for revealing the mechanism of EDW and exploring its control strategies.

Abstract: Electrohydrodynamic inkjet printing technology can generate femtoliter-scale droplets, which provides significant advantages in additive manufacturing. With these advantages, electrohydrodynamic inkjet printing technology shows broad application prospects in repairing micro/nano-scale complex structures in flexible electronic devices and high-resolution displays. During the repair process, precise control of printed droplet volume is required according to target volume requirements. However, due to the complexity of the printing process, traditional theoretical and simulation methods face challenges in achieving effective volume control. This paper proposes a supervised learning-based electrohydrodynamic droplet volume control method. The algorithm innovatively establishes new strategy samples through historical datasets, which include the deviation between current droplet volume and target volume, current process parameters, and changes in process parameters for the next iteration. Based on a feedforward control strategy, we employ a multilayer perceptron (MLP) supervised algorithm to achieve printing parameter recommendation, significantly improving printing efficiency. Volume control experiments conducted on the established electrohydrodynamic printing platform show that the standard volume filling rate can reach 98%, and the control can be completed within a single control cycle.

Abstract: Effective suppression of vibration is essential for surface quality and tool longevity in machining. This study assesses the viability of Electromechanical Impedance Spectroscopy (EMIS)-based structural health monitoring as a compact alternative to microphone-assisted Fast Fourier Transform (FFT) analysis during the milling of Al-7075-T6. Experiments were conducted with a constant axial depth of cut of 0.5 mm while feed rate (50–70 mm/min) and spindle speed (1200–4300 rpm) were varied. A surface-bonded piezoelectric sensor recorded impedance signatures simultaneously with acoustic data. Dominant modes detected by EMIS lay between 90 Hz and 1.5 kHz and coincided with FFT peaks. The discrepancy between the two methods remained within 1.54–10.78%. The close agreement indicates that a single EMIS sensor can provide reliable, operator-independent vibration diagnostics without the extensive signal-conditioning infrastructure required by microphones. EMIS offers a pathway for real-time, closed-loop vibration control in milling applications.

Abstract: In response to the challenges of low brightness, low contrast, and severe noise in low-light images, this paper proposes a lightweight, multi-scale, frequency- and spatial-domain collaborative low-light image enhancement network—FRT-Net. This method integrates classical Retinex theory with modern deep learning techniques. The Retinex decomposition module explicitly separates reflectance and illumination, providing the network with physical interpretability. A multi-scale feature extraction module is designed to capture global brightness trends and local texture details in parallel. Additionally, a frequency-domain FFT filtering branch is introduced to address spectral deficiencies and suppress noise. The CBAM attention mechanism is embedded to adaptively recalibrate channel and spatial weights, enhancing key feature representation. Finally, a comprehensive loss function is employed to collaboratively optimize brightness enhancement, detail recovery, color fidelity, and noise suppression. Experimental results on three mainstream benchmark datasets—LOLv1, LOLv2_real, and LOLv2_syn—demonstrate that FRT-Net ranks among the top two methods in terms of PSNR, SSIM, and LPIPS metrics, achieving an average PSNR of 22.98 dB, SSIM of 0.866, and LPIPS of only 0.075. The model contains only 0.55 million parameters(M) and requires 32.81 GFLOPs, meeting the real-time application demands of mobile devices. Ablation studies verify the effectiveness of each module. With its excellent performance and lightweight design, FRT-Net provides an efficient and robust visual perception foundation for practical applications such as nighttime autonomous driving and security surveillance.

Abstract: TDM PON technology widely deployed since the early and has evolved with ease to support the increasing bandwidth demands of FTTH. This research work presents the design and performance evaluation of a bidirectional 20 Gbps Time and Wavelength Division Multiplexed Passive Optical Network (TWDM-PON). The system designed by eight channels operating at 2.5 Gbps each and is analyzed using return-to-zero (RZ), non-return-to-zero (NRZ), carrier-suppressed return-to-zero (CSRZ) and duo-binary (DB) modulation formats. Performance metrics such as Q-factor and bit error rate (BER) are evaluated under varying input power conditions. The performance comparison is made in terms of Q factor and BER for varying transmitter powers. It is found that DB modulation format gives best performance when power budget improvement is sought. For low power condition (less than -15 dBm) DB modulation format gives superior performance. High dispersion tolerance in DB makes the system better with low power budget.

Abstract: This paper aims to analyze the behavior of DC corona discharge in wire-to-cylinder electrostatic precipitators. The principal operation of these types of electrostatic precipitators is based on the corona discharge on which their performance depends. In many industrial plants, particulate matter created in the industrial process is carried as dust in the hot exhaust gases. These dust-laden gases pass through an electrostatic filter. The aim of this investigation is to determine the important parameters of the corona discharge influenced by the applied voltage and bias voltage for three cylinders of different diameters. These parameters are done by using the Tassicker’s circular biased probe, which is incorporated at the same level of the surface in the precipitator electrode collector. Current-voltage curves are particularly analyzed. Experimental results show that discharge parameters are strongly affected by the applied voltage, biased voltage, and spacing between the high-voltage electrode and probe for both polarities.

Abstract: This study investigates the seismic response of reinforced concrete (RC) moment-resisting frame structures by analyzing the structural implications of integrating the staircase core. A six-story RC building, regular in plan and elevation, was adopted as the reference configuration (Model A), excluding the staircase. Three alternative models (B, C, and D) incorporated the staircase at varying plan locations to assess its influence. A comprehensive modal and response spectrum was conducted in accordance with RPA99/Version 2003 and BAEL91 design provisions. The introduction of the staircase core resulted in notable reductions in the fundamental period, emergence of torsional modes, particularly in models C and D, and significant redistributions of internal forces in both beams and columns. Short-column effects were observed in members adjacent to the staircase, raising concerns about potential brittle shear failure. The presence of the staircase core increased longitudinal and transverse reinforcement demands in critical columns, with amplification rates reaching up to 60%. These results show that the staircase plays a crucial role in modifying global stiffness, torsional response, and local demand concentrations. Neglecting the staircase core in structural modelling can lead to unconservative seismic assessments and increased vulnerability to damage or collapse under seismic excitations. The study provides an argument for its systematic inclusion in analytical models to ensure resilient and code-compliant design strategies.