https://scholar.korea.ac.kr/handle/2021.sw.korea/353 Wed, 08 Apr 2026 04:28:07 GMT 2026-04-08T04:28:07Z https://scholar.korea.ac.kr/handle/2021.sw.korea/270704 Title: Ultrastrong and ductile martensitic low-density steel achieved by local strain partitioning into ferrite and delayed TRIP effect Authors: Chung, Hyun; Lee, Sangwon; Ko, Seokwoo; Hwang, Sun Uk; Zargaran, Alireza; Sohn, Seok Su Abstract: Martensitic-based microstructures in low-density steels offer high strength and improved specific strength, combined with the lightweight effect of aluminum (Al). However, while Al effectively reduces density, it simultaneously promotes the formation of coarse ferrite and expands the two-phase (α + γ) intercritical temperature range. Thus, increasing the Al content for higher weight reduction inevitably leads to ferrite formation and impedes further strengthening. To achieve both high strength and ductility while incorporating ferrite, it is crucial to elucidate the effects of ferrite fraction, size, and distribution on mechanical properties and deformation behavior, particularly in relation to phase interactions. In this study, three model steels were developed through controlled annealing temperatures, producing distinct triplex microstructures comprising ferrite, martensite, and retained austenite (RA). The role of each phase in strain partitioning was investigated using ex-situ microscopic digital image correlation and electron back-scattered diffraction analysis. Key findings reveal that the martensitic matrix ensures an ultrahigh strength level (1758 MPa), while a moderate fraction (∼17 %) and homogeneous distribution of intercritical-ferrite (IC-ferrite) enable sustainable strain-hardening behavior by delaying the transformation-induced plasticity (TRIP) effect. Strain partitioning into IC-ferrite reduces local strains in the martensitic matrix, preventing early exhaustion of the TRIP effect and facilitating ductile fracture behavior. This strategy leverages the presence of ferrite, offering significant advantages for applications requiring both ultrahigh strength and ductility. © 2025 Wed, 10 Dec 2025 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/270704 2025-12-10T00:00:00Z https://scholar.korea.ac.kr/handle/2021.sw.korea/268525 Title: Exploration of deep learning leak detection model across multiple smart water distribution systems: Detectable leak sizes with AMI meters Authors: Jun, Sanghoon; Jung, Donghwi Abstract: Numerous deep learning (DL) models have been developed for leak detection in water distribution systems (WDSs). However, significant lack of knowledge still remains concerning their detectability and the smallest detectable leak sizes across various WDSs. To address these research gaps, this study explores the performance of a DL leak detection model across eleven smart WDSs. A convolutional neural network (CNN) is employed to identify leaks using the spatially distributed pressure response images derived from the difference between advanced metering infrastructure (AMI) measurements and predictions from a well-calibrated hydraulic model (i.e., digital twin). Ten leak magnitudes are evaluated for each WDS, and three performance metrics (recall, precision, and F1 score) are calculated to assess the detectability and the detectable leak sizes of the CNN. The analysis reveals that the DL model's detection ability is highly impacted by WDS type, whether transmission- or distribution-oriented. The former networks exhibit low accuracy in identifying leaks due to the indistinguishability of pressure response images between normal and leak conditions. On the other hand, the latter networks generally achieve higher precision and recall results and can detect smaller leaks. Moreover, the smallest detectable leak sizes are more sensitive to WDS structural parameters (pipe diameter and length) than system hydraulics (system demand). Examining pipe characteristics along the leakage flow path provides most useful information in determining the detectability of leaks. Mon, 01 Dec 2025 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/268525 2025-12-01T00:00:00Z https://scholar.korea.ac.kr/handle/2021.sw.korea/267336 Title: Aligned Ion Conduction Pathway of Polyrotaxane-Based Electrolyte with Dispersed Hydrophobic Chains for Solid-State Lithium-Oxygen Batteries Authors: Kim, Bitgaram; Sung, Myeong-Chang; Lee, Gwang-Hee; Hwang, Byoungjoon; Seo, Sojung; Seo, Ji-Hun; Kim, Dong-Wan Abstract: Strategic materials design of polyrotaxane-based electrolytes was suggested by aligning the ion conduction pathways and dispersing hydrophobic chains for solid-state Li-O2 batteries.Owing to intentional design, solid-state Li-O2 battery resulted in stable potential over 300 cycles at 25 degrees C. A critical challenge hindering the practical application of lithium-oxygen batteries (LOBs) is the inevitable problems associated with liquid electrolytes, such as evaporation and safety problems. Our study addresses these problems by proposing a modified polyrotaxane (mPR)-based solid polymer electrolyte (SPE) design that simultaneously mitigates solvent-related problems and improves conductivity. mPR-SPE exhibits high ion conductivity (2.8 x 10-3 S cm-1 at 25 degrees C) through aligned ion conduction pathways and provides electrode protection ability through hydrophobic chain dispersion. Integrating this mPR-SPE into solid-state LOBs resulted in stable potentials over 300 cycles. In situ Raman spectroscopy reveals the presence of an LiO2 intermediate alongside Li2O2 during oxygen reactions. Ex situ X-ray diffraction confirm the ability of the SPE to hinder the permeation of oxygen and moisture, as demonstrated by the air permeability tests. The present study suggests that maintaining a low residual solvent while achieving high ionic conductivity is crucial for restricting the sub-reactions of solid-state LOBs. Mon, 01 Dec 2025 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/267336 2025-12-01T00:00:00Z https://scholar.korea.ac.kr/handle/2021.sw.korea/270790 Title: Direct air capture-assisted sustainable fuel solution in maritime sector: a carbon footprint perspective Authors: Li, Shuangjun; Du, Zhenyu; Wang, Junyao; Wang, Hao; Cao, Xiangkun Elvis; Chen, Runkai; Pang, Yujia; Deng, Shuai; Mašek, Ondřej; Yuan, Xiangzhou; Lee, Ki Bong Abstract: Carbon emissions reduction within the maritime sector is pivotal for realizing zero-carbon goals and mitigating climate impacts. Adopting renewable carbon fuels presents a potent strategy. It is necessary to have a comprehensive understanding of its negative carbon attributes and enduring contributions to future development based on carbon footprint assessment. By using the CO2 captured through direct air capture (DAC) technology and the H2 obtained via water electrolysis as feedstock, electro-methanol (e-methanol) can be produced under renewable energy-driven conditions. Owing to the environmental benefits and economic feasibility of e-methanol, we highlight its potential as a practical alternative to traditional fossil fuel-based technical scenarios. A quantitative analysis of this integrated system from a carbon footprint perspective allows for an environmental sustainability assessment. According to predictions, scaled-up usage of the system can reduce the maritime sector's contribution to global carbon emissions by half by 2050. © The Author(s) 2025. Mon, 01 Dec 2025 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/270790 2025-12-01T00:00:00Z