• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.485-496
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• 2013

In recent years, frequent terror or military attacks by explosion or impact accidents have occurred. Examplary case of these attacks were World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. These attacks of the civil infrastructure have induced numerous casualties and property damage, which raised public concerns and anxiety of potential terrorist attacks. However, a existing design procedure for civil infrastructures do not consider a protective design for extreme loading scenario. Also, the extreme loading researches of prestressed concrete (PSC) member, which widely used for nuclear containment vessel, gas tank, bridges, and tunnel, are insufficient due to experimental limitations of loading characteristics. To protect concrete structures against extreme loading such as explosion and impact with high strain rate, understanding of the effect, characteristic, and propagation mechanism of extreme loadings on structures is needed. Therefore, in this paper, to evaluate the impact resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, impact tests were carried out on $1400mm{\times}1000mm{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PS), prestressed concrete with rebar (PSR, general PSC) specimens. According to test site conditions, impact tests were performed with 14 kN impactor with drop height of 10 m, 5 m, 4 m for preliminary tests and 3.5 m for main tests. Also, in this study, the procedure, layout, and measurement system of impact tests were established. The impact resistance capacity was measured using crack patterns, damage rates, measuring value such as displacement, acceleration, and residual structural strength. The results can be used as basic research references for related research areas, which include protective design and impact numerical simulation under impact loading.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.382-393
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• 2020

The engineered barrier system of high-level radioactive waste disposal must maintain its performance in the long term, because it must play a role in slowing the rate of leakage to the surrounding rock mass even if a radionuclide leak occurs from the canister. In particular, it is very important to clarify gas dilation flow phenomenon clearly, that occurs only in a medium containing a large amount of clay material such as a bentonite buffer, which can affect the long-term performance of the bentonite buffer. Accordingly, DECOVALEX-2019 Task A was conducted to identify the hydraulic-mechanical mechanism for the dilation flow, and to develop and verify a new numerical analysis technique for quantitative evaluation of gas migration phenomena. In this study, based on the conventional two-phase flow and mechanical behavior with effective stresses in the porous medium, the hydraulic-mechanical model was developed considering the concept of damage to simulate the formation of micro-cracks and expansion of the medium and the corresponding change in the hydraulic properties. Model verification and validation were conducted through comparison with the results of 1D and 3D gas injection tests. As a result of the numerical analysis, it was possible to model the sudden increase in pore water pressure, stress, gas inflow and outflow rate due to the dilation flow induced by gas pressure, however, the influence of the hydraulic-mechanical interaction was underestimated. Nevertheless, this study can provide a preliminary model for the dilation flow and a basis for developing an advanced model. It is believed that it can be used not only for analyzing data from laboratory and field tests, but also for long-term performance evaluation of the high-level radioactive waste disposal system.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.3 s.47
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• pp.393-397
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• 2004

L-Carnitine $({\beta}-hydroxy-{\gamma}-trimethyl-ammoniumbutyric{\;}acid)$ is a small water-soluble molecule important in mammalian fat metabolism. It is essential for the normal oxidation of fatty acids by the mitochondria, and is involved in the trans-esterification and excretion of acyl-CoA esters. In this paper, to investigate the relationship between aging and L-carnitine, we investigated the effects of in vitro matrix-metalloproteinase (MMP) inhibition and activity and expression of UYA-induced MMPs in human skin fibroblasts. Also, we studied to develop as anti-aging cosmetics with L-carnitine. Fluorometric assays of the proteolytic activities of MMP-1 (collagenase) were performed using fluorescent collagen substrates. ELISA (enzyme linked immune sorbent assay), gelatin-substrate zymography, RT-PCR ELISA techniques were used for the effects of L-carnitine on MMP expression, activity, and MMP mRNA expression in UVA irradiated fibroblast $(5\;J/cm^2)$, respectively. In addition, we performed clinical study with L-carnitine cream. L-carnitine inhibited the activities of MMP-1 in a dose-dependent manner and the $IC_{50}$ values calculated from semi-log plots were 2.45 mM, and L-carnitine showed strong inhibition on MMP-2 (gelatinase) activity in UVA irradiated fibroblast by zymography. Also, UVA induced MMP-1, 2 expression was reduced $43\%,\;53\%$ by treated with L-carnitine at 1.25 mM, and MMP-1 mRNA expression was reduced dose-dependent manner. Therefore L-carnitine was able to significantly inhibit the MMP activity, and regulate MMP expression in protein and mRNA level. The results of clinical study showed that $1.0\%$ L-carnitine treated group reduced wrinkle significantly compared with placebo treated group (P<0.05). All these results suggest that L-carnitine may be useful as new anti-aging cosmetics for protection against UVA induced Mm expression and activity.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.715-728
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• 2023

Tracksite of pterosaurs, birds, and dinosaurs in Chungmugong-dong in Jinju was designated as a natural monument in 2011 and is known as the world's largest in terms of the number and density of pterosaur footprints. This site has been managed by installing protection buildings to conserve in 2018. About 17% of the footprints of pterosaur, theropod, and ornithopod in this site under management in the 2nd protection building are of great academic value, but observation of footprints has difficulties due to continuous physical and chemical damage. In particular, the accumulation of milk-white contaminants is formed by the gypsum and air pollutant complex. Gypsum remains evaporated with a plate or columnar shape in the process of water circulation around the 2nd protection building, and the dust is from through the inflow of the gallery windows. The aqueous solution of gypsum, consisting of calcium from the lower bed and sulfur from grass growth, is catchmented into the groundwater from the area behind the protection building. Pollen and a few minerals other constituents of contaminants, go through the gallery window, which makes it difficult to expel dust. To conserve the fossil-bearing beds from two contaminants of different origins, controlling the water and atmospheric circulation of the 2nd protection building and removing the contaminants continuously is necessary. When cleaning contaminants, the steam cleaning method is sufficiently effective for powder-shaped milk-white contaminants. The fossil-bearing bed consists of dark gray shale with high laser absorption power; the laser cleaning method accompanies physical loss to fossils and sedimentary structures; therefore, avoiding it as much as possible is desirable.

• The Journal of Engineering Geology
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• v.35 no.4
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• pp.799-809
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• 2025

Recent intense convective rainfall events have triggered an increasing number of slope disasters, underscoring the critical need to enhance the structural integrity of unreinforced concrete (URC) buildings located in mountainous regions. In this study, focusing on unreinforced masonry buildings, we utilized NDMI's steep-slope simulator to assess impact pressures generated when sliding soil masses, moving at an approximate velocity of 4.6 m/s, collided with the structures. The impact forces were measured using load cells installed at the foundation, central wall, and side walls of the building models. The experimental results revealed that structural failure initiated at the lower portion (0.2-0.4 m) of the central wall under an impact pressure of approximately 67 kPa, subsequently propagating to the side walls and roof, exhibiting a progressive collapse behavior. In contrast, the foundation exhibited no structural damage even under a high impact pressure of 162 kPa, while a peak impact pressure of approximately 207 kPa was recorded at a height of 0.6 m on the side wall following the collapse of the central wall. These results provide empirical evidence that the structural vulnerability at the lower section of the central wall in unreinforced masonry buildings serves as a critical trigger for progressive collapse. This underscores the importance of prioritizing structural resistance reinforcement at the lower wall segments in future strengthening and design strategies. Based on these findings, this study established reinforcement design conditions intended for use as protective measures for buildings located in areas without check dams or in regions prone to debris-related disasters. Two reinforcement methods were proposed: a reinforced masonry attachment wall method designed to enhance structural resistance against landslides and steep-slope failures, and a debris-deflecting bentwall system designed to reduce impact forces and redirect debris during debris-flow events. The results of this study are expected to serve as fundamental data for developing a road map of structural countermeasures focusing on disaster resilience and for formulating detailed design criteria in future research.

• Journal of the Korean GEO-environmental Society
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• v.26 no.11
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• pp.27-41
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• 2025

Land reclamation projects inevitably induce consolidation of soft ground due to filling and embankment loading, which may lead to residual settlement and subsequent structural distress after construction. To ensure construction quality and evaluate long-term serviceability, the Interferometric Synthetic Aperture Radar (InSAR) technique has emerged as a promising tool for continuous, wide-area monitoring of ground deformation. This study investigates the applicability of satellite-based InSAR techniques for settlement monitoring in reclaimed land. A Persistent Scatterer InSAR (PS-InSAR) analysis was first performed using Sentinel-1 C-band SAR images acquired between 2017 and 2025 over the western container terminal site of the Busan New Port, Republic of Korea, to identify stable reference ground control points. Based on this reference points, three time-series InSAR algorithms (SBAS; Small Baseline Subset, E-SBAS; Enhanced SBAS, E-PS; Enhanced PS-InSAR) were applied with varying temporal configurations to assess their monitoring applicability. During the construction periods, rapid surface deformation caused severe coherence loss and phase discontinuities, preventing stable interferometric observations. Although the E-PS technique yielded lower spatial density of observations, it provided a clearer settlement trend and stronger agreement with ground-based measurements compared with SBAS and E-SBAS. After construction, the coherence and observation density markedly improved across all methods, even the E-PS results exhibited consistent coverage throughout the site. These findings confirm that PS-based InSAR techniques are more effective than DS-based approaches for reliably capturing long-term settlement behavior in reclaimed areas. For accurate interpretation of InSAR monitoring, however, a prior knowledge of construction methods, schedules, subsurface conditions, and underlying deformation mechanisms remains essential.