In contemporary educational environments, supporting not only academic achievement but also social interaction and community experience has become increasingly important. The conventional classroom-centered structure has limitations in meeting these needs, underscoring the need for spatial concepts that foster communication and engagement. This study applies Ray Oldenburg's "Third Place" theory to examine the role of homebase spaces in high schools and to derive universal spatial conditions that enhance students' daily school lives. By reviewing the Third Place concept and its eight core characteristics, and comparing them with previous research on homebase spaces, three analytical criteria-openness, multifunctionality, and connectivity - were identified. Four newly built high schools in Gyeonggi-do and Incheon, completed after 2020, were selected as case studies. Field investigations, including on-site observations, photographic documentation, and architectural drawings, were conducted to evaluate how design intentions were implemented and to identify discrepancies between planned and realized spaces. The analysis revealed common spatial features: minimizing columns and walls and using transparent facades to enhance openness: introducing mobile furniture and flexible layouts to enable user-driven reconfiguration: and positioning the homebase at the center of circulation to encourage frequent encounters and casual interactions. The findings demonstrate that the homebase operates as an active social hub rather than a transitional space, embodying the characteristics of a Third Place. The three criteria-openness, multifunctionality, and connectivity - are proposed as universal design principles for future educational facility planning. By framing the homebase as a space that supports both academic activities and social relationships, the study highlights its educational potential and offers practical strategies for fostering students' holistic development.

This study analyzed underground cavities along 73.75 km of water pipeline routes in Incheon and Gimpo using Ground Penetrating Radar (GPR). The first survey detected 41 anomalies; subsequent verification confirmed 28 cavities, classified as 61% critical and 39% priority. Most cavities were located directly beneath pavement, posing severe sinkhole risks. Dimensions averaged 0.85 m longitudinally, 0.79 m transversely, and 0.24 m in thickness. Rapid restoration was applied to 26 sites, with 23 completed and 3 unresolved. Findings demonstrate GPR's effectiveness and emphasize proactive maintenance strategies and advanced technologies for urban infrastructure safety.

This study examines the often-overlooked influence of unsaturated soils on the corrosion of buried metal pipes. We analyze capillary rise behaviors using physical modeling across different soil types and confirm that the magnitude of capillary rise varies significantly with particle size distribution and pore structure. A central finding is that degree of saturation, which has been largely absent from traditional corrosion-prediction frameworks, plays a critical role in defining soil corrosivity. In particular, unsaturated sandy soils with large, well-connected pores facilitate higher oxygen ingress, enhancing chemical activity and thereby accelerating corrosion. These results highlight the substantial impact of real-world unsaturated conditions on corrosion mechanisms and underscore the need to explicitly incorporate saturation effects into future corrosion assessment and predictive models.

This study aims to evaluate the flexural behavior of a STKM450 high-strength corrosion-resistant steel pipe, and to propose an allowable compressive flexural stress criterion applicable to port and offshore structures. Various domestic design standards were first investigated for this study, and finite element analysis was performed to evaluate the proposed allowable stress criterion. The comparison of design standards revealed that the criteria (0.6 × yield strength) is basically used as an allowable flexural compressive stress. Therefore, it may be appropriate to set the allowable stress (270 MPa) for the STKM450 steel pipe, similar to other steel types that have the same yield strength. Finite element analysis was also performed to evaluate the applicability of the proposed allowable flexural stress. As a result of nonlinear bending analysis applying STKM450 D609×12t and D1200×11t steel pipe sections, the maximum moment value derived from the analysis exceeded the theoretical nominal plastic moment, which indicates the validity of the proposed allowable stress criterion.

본 연구는 사질토의 한계상태선(Critical State Line, CSL)의 유일성에 대한 기존 문헌을 검토하고, 서로 상충되는 실험 결과의 원인을 규명하고자 하였다. 문헌 분석 결과, 삼축 압축(Triaxial Compression)과 삼축 인장(Triaxial Extension) 시험에서 도출된 CSL의 차이는 흙 시료 내부의 비균질 변형, 특히 Shear Band의 형성으로 인해 발생하는 것으로 나타났다. 개별요소법(D티VI) 모사 결과 또한 시료 평균 응력-간극비와 Shear Band 응력-간극비 간의 괴리를 확인하였다. 따라서 기존 삼축시험으로부터 산정된 CSL은 실제 한계상태를 완전히 대표하지 못하며, 유일성 논쟁은 시험방법상의 한계로 해석될 수 있다. 본 연구는 균질 변형 조건을 구현할 수 있는 실험적 접근의 필요성을 제시하며, 이를 통해 CSL의 유일성을 명확히 규명할 수 있는 방향을 제안하였다.

This study evaluates the potential of rice husk biochar as a sustainable admixture to mitigate the strength degradation of calcium aluminate cement (CAC) caused by the inherent conversion phenomenon. To enhance the surface characteristics of the biochar, it was subjected to acid (nitric acid), alkali (sodium hydroxide), and sequential acid-alkali treatments. Four types of biochar (untreated, acid-treated, alkali-treated, and acid-alkali treated) were incorporated into CAC mortar as a partial replacement for sand at 2, 4, and 6 wt.%. The mechanical properties were analyzed by measuring the compressive strength at early ages (3 and 7 days) and after an accelerated conversion process induced at 60℃ (14 and 28 days). The results indicated that the acid-alkali treated biochar significantly promoted early hydration, increasing the 3-day compressive strength by up to 20.3% compared to the reference specimen. Most notably, while the reference specimen exhibited a strength loss of approximately 59.3% due to conversion, the specimen containing 6% acid-alkali treated biochar retained a residual strength 41.1% higher than the reference, effectively suppressing the detrimental effects of conversion. This improvement is attributed to the nucleation effect of the modified biochar surface and the internal stress-buffering role of its porous structure. These findings suggest that properly surface-treated rice husk biochar has high potential as a high-performance, eco-friendly admixture for simultaneously enhancing both the early strength and long-term durability of CAC.

This study is based on the seventh pilot experiment conducted in the unsaturated zone of the EIT (Environmental Impact Evaluation test Facility on Seepage of Geological Stored CO₂ ) and aims to elucidate CO₂ leakage behavior through multilevel monitoring. The unsaturated zone is the primary pathway where leaked CO₂ from geological storage is first detected, making precise monitoring crucial for early detection and environmental impact assessment. However, conventional single-depth wells are limited in their ability to simultaneously capture depth-dependent responses and spatial dispersion characteristics. To overcome these limitations, an inclined well was constructed to simulate diverse leakage pathways under field conditions, and the CMT 403 multilevel system was applied to analyze both vertical and horizontal dispersion characteristics.The experiment involved the artificial injection of gaseous CO₂ into the unsaturated zone, with gas concentrations measured at multiple depths using a GA5000 portable gas analyzer. Additionally, SF₆ was injected as an independent tracer to validate plume migration patterns and to compare concentration responses across depths. Results from the CMT system clearly showed depth-specific and spatially heterogeneous variations in CO₂ and SF₆ concentrations, confirming the presence of preferential flow pathways governed by small-scale heterogeneity in the pore structure. Importantly, the multilevel dataset revealed distinct time-lag patterns, anisotropic plume spreading, and nonlinear attenuation behavior - phenomena that cannot be captured through single-depth monitoring. These findings demonstrate that the multilevel approach enables a more realistic representation of CO₂ leakage behavior, improving the reliability of leakage detection and the interpretation of early-warning signals. Overall, this study highlights that a multilevel monitoring system provides a robust framework for characterizing CO₂ migration dynamics in the unsaturated zone. The approach offers a significant advancement in monitoring technologies for CCS sites by (1) enabling simultaneous multi-depth detection, (2) reducing uncertainty in leakage interpretation, and (3) supporting the development of site-specific early-warning protocols. These contributions suggest that multilevel monitoring can serve as a key technology for ensuring environmental safety and strengthening risk management strategies at CCS pilot sites and large-scale geological storage facilities.

This study proposes a deep learning framework for detecting urban walking barriers using only smartphone accelerometer data. The proposed model integrates Multi-layer Long Short-Term Memory (MLSTM) and Fully Convolutional Networks (FCN) in a hybrid parallel architecture, enhanced with Squeeze-and-Excitation (SE) blocks and a Multi-Head Attention mechanism. These modules enable the model to simultaneously capture long-term temporal dependencies and channel-wise spatial importance from tri-axial acceleration sequences. To validate the framework, a simulation-based walking dataset representing both elderly and adult pedestrians was constructed, including diverse urban environmental conditions such as uneven pavements, curbs, and surface irregularities over a 2 km walking path. The model was trained using AdamW optimizer and focal loss with multiple signal augmentations, achieving an F1-score of 0.88 and PR-AUC of 0.90, outperforming baseline models such as CNN, Bi-LSTM, and standard LSTM-FCN. Visualization through attention-weight maps confirmed that the model selectively focuses on acceleration perturbations associated with environmental barriers. This research demonstrates the feasibility of smartphone-based urban walkability assessment, offering a scalable and non-invasive approach to identifying hazardous walking environments for elderly pedestrians and informing urban accessibility improvements.