International Journal of Precision Engineering and Manufacturing-Green Technology最新文献

Methanol–water electrolysis technology, which electrochemically produces hydrogen using methanol instead of water, has received significant attention given that the substantial amount of power required by conventional water electrolysis can be drastically reduced when using it. This study investigates the electrochemical performance and microstructural characteristics of methanol–water electrolyzers according to the ionomer-to-carbon (I/C) ratio range of 0.5–2.0 in electrode catalyst layers. The lowest voltage at the same current density is observed at an I/C ratio of 1.5 at the anode. When the I/C ratio was 2.0, the voltage was observed to be approximately 25% higher than that at an I/C ratio of 1.5. A microstructural analysis shows a decrease of the specific surface area due to catalyst agglomeration at I/C ratios higher than 1.5. The results of the BET analysis showed a decrease in the surface area with an increase in the I/C ratio. Furthermore, when the I/C ratio exceeds 1.5, separated layers of excessive amounts of ionomer are observed, possibly blocking the electron conduction pathways in the electrode catalyst layer. The energy conversion efficiency of the developed methanol–water electrolyzer was assessed in an current density range of 0.08–0.80 A cm⁻², demonstrating values between 81.4% and 92.4%.

The manufacturing industry is currently confronted with global challenges such as customization demands, climate change, and energy scarcity. To address these challenges and improve efficiency, the industry is exploring the integration of Industry 4.0 and smart manufacturing. One promising approach for incorporating smart factory technology into urban manufacturing is the Urban Smart Factory (USF), which aims to create a sustainable, resilient, and human-centric environment. However, existing Industry 4.0 maturity models are insufficient for evaluating the diverse aspects of the USF. To bridge this gap, this study proposes a novel maturity model specifically designed to assess the integration of smart manufacturing principles and technologies within the USF, with a focus on achieving sustainability, resilience, and human-centricity. The practicality of this model is demonstrated through two case studies from different sectors, showcasing its applicability for evaluating the readiness of manufacturing firms to adopt the USF. Additionally, this research presents potential directions for future academic investigations interested in this topic.

Robotic automation has emerged as a leading solution for replacing human workers in dirty, dangerous, and demanding industries to ensure the safety of human workers. However, practical implementation of this technology remains limited, requiring substantial effort and costs. This study addresses the challenges specific to nuclear power plants, characterized by hazardous environments and physically demanding tasks such as nozzle dam replacement in confined workspaces. We propose a digital twin and deep-reinforcement-learning-driven robotic automation system with an autonomous mobile manipulator. The study follows a four-step process. First, we establish a simplified testbed for a nozzle dam replacement task and implement a high-fidelity digital twin model of the real-world testbed. Second, we employ a hybrid visual perception system that combines deep object pose estimation and an iterative closest point algorithm to enhance the accuracy of the six-dimensional pose estimation. Third, we use a deep-reinforcement-learning method, particularly the proximal policy optimization algorithm with inverse reachability map, and a centroidal waypoint strategy, to improve the controllability of an autonomous mobile manipulator. Finally, we conduct pre-performed simulations of the nozzle dam replacement in the digital twin and evaluate the system on a robot in the real-world testbed. The nozzle dam replacement with precise object pose estimation, navigation, target object grasping, and collision-free motion generation was successful. The robotic automation system achieved a (92.0%) success rate in the digital twin. Our proposed method can improve the efficiency and reliability of robotic automation systems for extreme workspaces and other perilous environments.

Abstract

Advances in nanotechnology have enabled solid oxide fuel cells to perform high-efficiency energy conversion at lower operating temperatures than before. In particular, the thin film electrolyte can effectively offset the drop in ion conductivity at a low operating temperature due to a reduced ion path. In this study, the performance difference of solid oxide fuel cells according to the thickness of these thin film electrolytes was compared. Thin film solid oxide fuel cells were fabricated with YSZ electrolytes of 3.3 μm, 4.0 μm, and 4.7 μm thickness using different sputtering deposition times. First, the thickness of the electrolyte affected the gas tightness. The OCV of the cell using the 3.3 μm, 4.0 μm, and 4.7 μm thick electrolyte showed 1.01 V, 1.03 V and 1.05 V respectively. As the sputter deposition time increased, the surface grain size of the YSZ electrolyte also increased, affecting both the electrolyte's ohmic and the electrode's polarization resistance. Therefore, the difference in the thickness of the electrolyte showed a dramatic difference in performance. The cells with 3.3 μm, 4.0 μm, and 4.7 μm thick electrolytes showed performances of 193 mW/cm², 99 mW/cm², and 57 mW/cm², respectively at 500 °C.

Multi-material tubular components have found versatile applications in various products and machine parts because of their ability to offer simultaneous advantages of the constituent materials, such as corrosion-resistance, lightweight, higher strength, and electrical conductivity in one single component. However, creating such components using traditional joining methods possess a lot of challenges due to differences in the properties of joining materials resulting in defects such as hot cracking, embrittlement and intermetallic formation. Therefore, solid-state cold processes like electromagnetic forming can be of great use in joining such multi-material components, referred to as electromagnetic joining (EMJ). This article presents a comprehensive review that considers almost all the major aspects of the subject. This article presents a thorough detailed review of the EMJ processes. It begins by providing a broad overview of the process, tracing its history and development up to the present day, and highlighting its prevalent usage in industry. Following this, an in-depth analysis of the current state of the art in EMJ is given. The working principle is then explained, along with a comprehensive examination of the different stages of the EMJ process. The various factors that influence the quality of the joint and their effects are also discussed in detail. In the end, detailed conclusions are drawn, and future research insights are highlighted.

With the increase of low-powered electronic devices, there is growing social interest in environmentally friendly energy sources capable of replacing batteries. In this study, a flutter-driven piezoelectric nanogenerator (FD-PENG) using electrospun PVDF nanofiber was fabricated to create a wind-energy harvesting device. The FD-PENG was composed of a PVDF nanofiber mat (active layer) and Al foil (electrodes), with these components encapsulated by polyethylene terephthalate (PET) film using an ordinary coating machine. The short-circuit current generated from the FD-PENG during a bending test was significantly enhanced by optimizing the electrospinning process and with the proper alignment of the PVDF nanofibers. The dynamic behavior of the FD-PENG with respect to various wind speeds was systematically analyzed by categorizing its motion into four distinct modes. The flapping mode, in which the FD-PENG displays the largest amplitude of oscillation, was induced when wind speed was in the range of (3-4~mathrm{ m}/{text{s}}). The FD-PENG generated open-circuit voltage of approximately 10 V at a wind speed of (4~mathrm{ m}/{text{s}}) and exhibited excellent durability over 10,000 cycles. Using a single FD-PENG, maximum power approaching 14.66 μW was achieved under an external load of 1.1 MΩ. Furthermore, the wind speed inducing the flapping mode was modulated by the shape of the FD-PENG. The results here show that the wind energy harvester can be applied at a wide range of wind speeds by modifying the shape of the FD-PENG.

Direct Energy Deposition (DED) 3D printing has gained significant importance in various industries due to its ability to fabricate complex and functional parts with reduced material waste, and to repair existing components. Titanium alloys, known for their exceptional mechanical properties and biocompatibility, are widely used in DED 3D printing applications, where they offer benefits such as lightweight design possibilities and high strength-to-weight ratio. However, given the high material cost of titanium alloys, certain applications can benefit from the coating capabilities of DED to achieve the advantages of titanium on a distinct material substrate. Nevertheless, challenges related to material incompatibility and the development of unwanted brittle phases still affect the successful deposition of titanium alloys on steel substrates with DED 3D printing. This paper investigates the processing challenges and reviews delamination prevention methods, specifically targeting titanium-steel interfaces. In particular, the formation of unwanted brittle Ti–Fe intermetallics and methods to circumvent their formation are explored. The findings of this research contribute to a deeper understanding of the processing challenges and delamination prevention methods in DED 3D printing.

This paper outlines an innovative biaxial segment blade test methodology for large wind turbine rotor blades. Today, as a blade size is getting bigger, not only it is hard to find the test facility incorporating blade over 100 m, but also a blade test time and test cost required for certification according to IEC 6140023 are also increased, which could cause the delay of product entrance to wind energy market. The proposed biaxial segment test method mainly aims at improving the efficiency of the fatigue test because fatigue test takes up more than 70% of total test time and 60% of total test time approximately and is also intended to utilize existing test facilities through the segmentation of a large blade. For the feasibility assessment of the novel methodology, the virtual test model of the fatigue test configuration was constructed including virtual mass element, spring element, damping element, blade beam element, and kinematic lever-arm mechanism. Through the optimization process, it was found out that the proposed test methodology has a significant time saving up to 36% compared to conventional blade test method for 90 m blade test, which is even 17% further saving compared to uniaxial segment test. Also, the proposed methodology could save cost by 17% compared to traditional method. Among categories constituting the total cost calculated from 90 m blade case, electricity cost category related to hydraulic pumps necessary to maintain high forces was increased by 7% while labor and material costs reduced by 3% and 3% respectively compared to traditional test approach. The current study also showed that the biaxial segment test method is even more effective for a supersized wind blade. For the 115 m blade, the cost reduction rate was even higher by 5% than one of 90 m blade in addition to the utilization of the existing test facility.

In recent years, flexible electronics has emerged as a promising field that has attracted significant attention as a potential industry of the future. To realize full potential of flexible electronics, flexible power sources are essential. Polymer electrolyte membrane fuel cells (PEMFCs) are well-suited for this purpose, but the high cost of the catalyst, specifically platinum (Pt), is a major hurdle. This study sought to determine the optimal Pt loading for flexible PEMFCs, to reduce waste of catalyst and find a cost-effective solution. The optimal catalyst loading for flexible fuel cells varies depending on the operating environment and conditions. In environments requiring the generation of high power regardless of operating voltage, the optimal Pt loading is 0.1 mg_Pt cm⁻². In contrast, in environments where higher voltage is required with a minimum stacking, the optimal Pt loading is between 0.3 and 0.4 mg_Pt cm⁻². These results demonstrate optimal catalyst loading for flexible fuel cells in consideration of the operating environment and conditions. These results contribute valuable insight into the optimal catalyst loading for various applications, reducing the cost of flexible fuel cells, and paving the way for wider adoption of flexible electronics.

We demonstrate the facile fabrication of flexible and transparent heating structures via the soft-contact printing and patterning (SCOP) of an ionic metal solution layer, a process generally applicable to flat, flexible, and curved surfaces with scalable sizes. The SCOP process involves the conformal contact of a soft micropattern mold onto an ionic metal solution and mild thermal annealing under controlled temperature and pressure conditions to reduce metal ions into a micropatterned metallic structure. Through parametric optimization of the SCOP pressure and annealing temperature, multilayering with sequential SCOP processes, and airbrush coating of a carbon nanotube solution, a printable metallic micropattern can be tailored to a high-performance transparent heater capable of achieving the temperature up to ~ 125 °C at 8 V and optical transmittance of 80% (achievable > 250 °C at 5 V when multilayered and CNT-reinforced). The scalability and solution processability of the developed process pave the way for the high-throughput eco-friendly fabrication of flexible and transparent heaters on arbitrary surfaces as well as many practical devices, including but not limited to printable electronic and photonic components and wearable sensors as well as warm-up gear.