• International conference on construction engineering and project management
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• 2024.07a
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• pp.894-901
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• 2024

The construction industry has been recognized as one of the most high-risk industries globally, promoting a shift towards enhancing safety culture to mitigate accident rates. With a notable good safety performance in Australia, this study therefore compares its advanced safety culture with the evolving safety culture in China through a systematic review of literature published over the last two decades. The aim of the research is to explore the influence of differing societal cultural contexts on the development of safety culture. The study covers various aspects of safety culture, including leadership and management commitment, regulatory environments, safety communication, workers'involvement, and organizational safety systems. Findings indicate a strong commitment from industry participants in both countries. However, there are notable differences in safety culture conceptualization and implementation. Australia showcases a mature safety culture, deeply integrated with stringent regulations and fostering individual proactive engagement. Conversely, China's safety culture, marked by rapid evolution, emphasizes regulatory compliance, with challenges in achieving broad worker participation. The analysis highlights that Australian construction workers' inclination towards a proactive approach in managing safety, in contrast to Chinese construction workers who tend to focus more on adhering to safety regulations than actively participating in safety initiatives. These findings emphasize the significant role societal culture plays in shaping construction safety cultures. The study's insights are instrumental for practitioners across the global construction industry, advocating for the adoption of nuanced, culturally sensitive safety management strategies to enhance safety outcomes.

• International conference on construction engineering and project management
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• 2024.07a
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• pp.1279-1279
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• 2024

Managing investments in renewable energy (RE) in developing countries is essential for reducing environmental pollution, meeting the growing energy demand, and avoiding the risk of stranded assets. Establishing Public-Private Partnerships (PPPs) is necessary to address budgetary and technical issues in developing countries. PPPs recover investments through long-term operations. Risks from external political, social, and economic environments during both the construction and operational phases of PPP projects affect the stability of investment recovery. Although various support systems are in place to mitigate investment risks for investors, these systems can pose risks to the public sector. Therefore, this study identifies common risks, including construction and operational risks, as well as political, financial, and social risks, for sustainable renewable energy PPP operations. Interpretive Structural Modeling (ISM) and MICMAC (Matrix Impact Cross-Reference Multiplication Applied to a Classification) analyses were conducted to understand the interrelationships among these risks. The ISM and MICMAC analysis results showed that construction phase risks have high dependence power and driving power. In contrast, operational phase risks exhibit low driving power but high dependence power. This indicates that managing construction phase risks is effective for the sustainable operation of renewable energy PPPs. Based on the analyzed ISM and MICMAC results, preventive measures for sustainable operations of renewable energy PPPs were proposed.

• International conference on construction engineering and project management
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• 2024.07a
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• pp.516-523
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• 2024

This study introduces a comprehensive framework for 4D safety analysis in construction site layout planning (CSLP), using a Site Information Model (SIM) environment to enhance spatial hazard identification and effectively integrate it with activity-based safety management. The framework, grounded in a continuous-space layout approach, accurately positions objects to mirror temporary facilities' actual boundaries, incorporating spatial relationships and inherent safety hazards. It also features rasterization to translate layouts into a grid system. Central to this framework are three modules for spatial hazard identification: Visibility Analysis, Spatial Hazard Mapping, and Travel Path Analysis, designed to identify less visible spaces, assess spatial hazards, and simulate optimal travel paths considering safety aspects. By applying this framework to case studies of a residential complex and a commercial office project, the research demonstrates its practical utility in improving visibility and spatial hazard assessment, despite the inherently complex dynamics of construction sites. The study acknowledges challenges, such as the reliance on safety managers' experiential knowledge for setting hazard parameters and the need for further development in integrating these insights with activity-based safety management. It underscores the framework's significant potential to advance construction safety management by offering a method to preemptively recognize and mitigate spatial hazards. The approach promises not only to contribute to accident prevention but also to enhance overall project performance by incorporating spatial and temporal dimensions of safety into CSLP. This research marks a significant step toward a more holistic and integrated approach to construction safety, highlighting the importance of continuous improvement and adaptation in safety practices.

• International conference on construction engineering and project management
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• 2024.07a
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• pp.127-136
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• 2024

Flooding presents a significant threat to infrastructure, and climate change is exacerbating these risks. High-speed rail (HSR) infrastructure, designed based on historical data, may struggle to cope with future extreme flood events. Infrastructure stakeholders require forecasting capabilities to predict the intensity and frequency of future floods so they can develop adaptive strategies to mitigate flood risks and impacts. Floods can cause significant damage to HSR infrastructure networks, disrupting their operations. Traditional network theory-based frameworks are insufficient for analyzing the three-dimensional effects of floods on HSR networks. To address this issue, this study proposes a comprehensive approach to assess flood risk and vulnerability under future climate scenarios for HSR networks. The method consists of three components. (i) Generate flood inundation data by utilizing global climate models, Shared Socioeconomic Pathways(SSPs), and the CaMa-Flood model. (ii) Fit extreme flood depths to the Gumbel distribution to generate flood inundation scenarios. (iii) Overlay flood scenarios on the HSR network and quantitatively assess network vulnerability based on topology network. When applied to the HSR system in mainland China, the results indicate that flood severity does not necessarily increase under higher SSPs, but may worsen over time. The minimum flood return period that causes HSR disruptions is decreasing, with Hubei Province showing a significant increase in HSR segment failure probability. Discontinuous phase transitions in HSR network topology metrics suggest potential nationwide collapses under future infrequent floods. These findings can inform preventive measures for the HSR sector and flood-resistant standards for HSR infrastructure. The method used in this study can be extended to analyze the vulnerability of other transportation systems to natural disasters, serving as a quantitative tool for improving resilience in a changing climate.

• Nanomaterials
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• v.12 no.7
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• pp.1158-1168
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• 2022

Commercial lithium-ion batteries using liquid electrolytes are still a safety hazard due to their poor chemical stability and other severe problems, such as electrolyte leakage and low thermal stability. To mitigate these critical issues, solid electrolytes are introduced. However, solid electrolytes have low ionic conductivity and inferior power density. This study reports the optimization of the synthesis of sodium superionic conductor-type Li_1.5Al_0.3Si_0.2Ti_1.7P_2.8O₁₂ (LASTP) solid electrolyte. The as-prepared powder was calcined at 650 ℃, 700 ℃, 750 ℃, and 800 ℃ to optimize the synthesis conditions and yield high-quality LASTP powders. Later, LASTP was sintered at 950 ℃, 1000 ℃, 1050 ℃, and 1100 ℃ to study the dependence of the relative density and ionic conductivity on the sintering temperature. Morphological changes were analyzed using field-emission scanning electron microscopy (FE-SEM), and structural changes were characterized using X-ray diffraction (XRD). Further, the ionic conductivity was measured using electrochemical impedance spectroscopy (EIS). Sintering at 1050 ℃ resulted in a high relative density and the highest ionic conductivity (9.455 × 10^-4 S cm^-1). These findings corroborate with the activation energies that are calculated using the Arrhenius plot. Therefore, the as-synthesized superionic LASTP solid electrolytes can be used to design high-performance and safe all-solid-state batteries.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.6
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• pp.657-661
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• 2024

Gallium oxide (Ga₂O₃) is emerging as a next-generation power semiconductor material due to its excellent electrical properties, including an ultra-wide bandgap of approximately 4.8 eV and a breakdown electric field of about 7 MV/cm. However, its low thermal conductivity of around 0.13 W/cmK presents significant challenges to the performance and reliability of Ga₂O₃-based devices. In this study, we employed the Silvaco TCAD simulator to analyze the thermal and electrical characteristics of Ga₂O₃ Schottky barrier diodes (SBDs) with heat sinks of varying thermal conductivities. The results demonstrate that heat sinks with higher thermal conductivity effectively mitigate the temperature rise in the device, leading to an increase in current density. The limitation in heat dissipation due to parasitic on-state resistance not only affects device performance but also impacts long-term reliability. Therefore, this study contributes to the development of effective thermal management strategies for Ga₂O₃-based power semiconductors.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.5
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• pp.799-808
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• 2024

In this paper, a method (phase weighting) is presented to achieve high-gain radiation performance and dual-beamforming functionality based on a reflectarray antenna system. The proposed method aims to mitigate the beam overlap phenomenon by implementing split dual-beamforming, using phase weighting that induces differential electric field strength between sub-arrays. To validate the proposed method, a numerical model for analyzing the radiation characteristics of the reflectarray antenna was developed, and a comparative analysis was conducted with a conventional sub-array-based dual-beamforming method. Simulation results under various conditions confirmed that the proposed method not only improves the beam overlap phenomenon but also efficiently forms split dual beams across a range of required beam steering angles.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.5
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• pp.435-448
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• 2024

Liquefaction of the ground caused by earthquakes results in significant damage to underground structures such as tunnels, pipelines, manholes, and underground tanks. The uplift of underground structures due to liquefaction has been identified as a major cause of this damage. However, current design practices have not adequately considered the upward displacement of underground structures. This paper proposes an analytical solution based on the limit equilibrium method for cut-and-cover tunnels. Using this solution, a sensitivity analysis was performed on soil cover height, liquefaction depth, ground improvement, and ledge. It was confirmed that the contribution of each factor to the safety factor can be reasonably derived through changes in the safety factor. Although there are still many assumptions and uncertainties that need to be reviewed for their appropriateness, a conservative approach appears to mitigate a significant portion of these uncertainties. This study is meaningful as a stability evaluation method considering the uplift behavior characteristics of underground structures.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.3
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• pp.99-104
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• 2024

With the advancement of power electronics technology and the increasing demand for high-efficiency power semiconductors, silicon carbide (SiC) devices have gained attention as an alternative to overcome the limitations of traditional silicon (Si) semiconductors. SiC devices enable excellent switching efficiency due to their high switching speed. However, parasitic inductance within the power module can cause voltage oscillations and overshoot phenomena, potentially leading to issues with electrical reliability and efficiency. To address these challenges, two approaches were proposed and validated. The first approach involved applying an RC snubber circuit to mitigate the effects of parasitic inductance, thereby improving electrical stability. The second approach focused on optimizing the lead-frame design to reduce parasitic inductance. Both methods were verified through simulations and experiments, demonstrating that the electrical reliability and efficiency of SiC power modules can be simultaneously improved.

• Journal of IKEEE
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• v.28 no.3
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• pp.419-425
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• 2024

As the variability of renewable energy output increases, there is a growing emphasis on flexible resources that facilitate effective output control to maintain the stability of the power grid. In the absence of such flexible resources, grid instability, including large-scale blackouts, may occur. Therefore, methods for assessing flexibility are essential for the effective utilization of flexible resources that mitigate variability. This study proposes a performance-based assessment method to accurately evaluate the effectiveness of flexible resources, considering both grid stability and efficiency. The validity of this method was verified through a case study that accounted for potential errors during actual operations.