Processes

Automated optical inspection (AOI) technologies are widely used in PCB and semiconductor manufacturing to improve accuracy and reduce human error during quality inspection. While existing AOI systems can perform defect detection, they often rely on pre-defined camera positions and lack flexibility for interactive inspection, especially when the operator needs to visually verify solder pad conditions or examine specific layout regions. This study focuses on the front-end optical positioning and inspection stage of the AOI workflow, providing an automated mechanism to link digitally generated layout reports from EDA layout tools with real PCB inspection tasks. The proposed system operates on component-placement reports exported by EDA layout environments and uses them to automatically guide the camera to the corresponding PCB coordinates. Since PCB design reports may vary in format and structure across EDA tools, this study proposes a vision-based extraction approach that employs Hough transform-based region detection and a CNN-based digit recognizer to recover component coordinates from visually rendered design data. A dual-axis sliding platform is driven through a hierarchical control architecture, where coarse positioning is performed via TB6600 stepper control and Bluetooth-based communication, while fine alignment is achieved through a non-contact, gesture-based interface designed for clean-room operation. A high-resolution autofocus camera subsequently displays the magnified solder pads on a large screen for operator verification. Experimental results show that the proposed platform provides accurate, repeatable, and intuitive optical positioning, improving inspection efficiency while maintaining operator ergonomics and system modularity. Rather than replacing defect-classification AOI systems, this work complements them by serving as a positioning-assisted inspection module for interactive and semi-automated PCB quality evaluation.

Hydrothermal carbonization (HTC) represents a promising thermochemical method for converting wet biomass under moderate aqueous conditions into carbon-rich materials, characterized by specific attributes. Notwithstanding the increasing interest surrounding HTC, the current literature remains fragmented regarding the precise mechanisms by which process parameters influence hydrochar formation, its properties, and sustainable utilization. Consequently, the primary objective of this review is to systematically elucidate the fundamental mechanisms that govern HTC, to identify key parameters impacting hydrochar yield and quality, and to assess the sustainability and prospective contributions of HTC within the context of circular economy principles. This paper elaborates on the reaction pathways of hydrolysis, dehydration, decarboxylation, and aromatization that dictate the structural alterations and carbon densification of hydrochars. It emphasizes the roles of temperature, residence time, solid/liquid ratio, catalysts, and feedstock composition in jointly determining hydrochar yield, elemental composition, aromaticity, porosity, and energy density. Additionally, recent advancements, including microwave-assisted HTC, catalytic modifications, and post-activation techniques, are reviewed to enhance hydrochar functionality for applications in energy, adsorption, catalysis, and soil enhancement. Challenges remain regarding the scale-up of the process, reactor design, standardization of hydrochar properties, and the sustainable management or valorization of process water. This review integrates mechanistic insights with recent technological progress to position HTC as a versatile and sustainable method for producing high-value hydrochars, thereby underscoring its potential role in future biorefineries and circular economy initiatives.

In this study, the thermodynamic and kinetic characteristics of the esterification reaction catalyzed by sol–gel immobilized enzyme in a batch reactor were systematically investigated. Parameters including catalyst particle diameter, stirring speed, initial molar ratio, catalyst dosage, reaction temperature, and catalyst reusability were studied and optimized. Finally, the esterification rate of methyl oleate reached 90.01%. The standard enthalpy change in the reaction was calculated using the Van’t Hoff equation. A pseudo-homogeneous (PH) model was employed to simulate the kinetic process of the reaction, and the simulation results provide a reference for the scale-up of the reaction process.