• Journal of the Korean GEO-environmental Society
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• v.20 no.3
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• pp.39-46
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• 2019

The liquefaction is a phenomenon that the effective stress becomes zero due to the rapidly accumulated excess pore water pressure when a strong load acts on the ground for a short period of time, such as an earthquake or pile driving, resulting in the loss of the shear strength of the ground. Since the Geongju and Pohang earthquake, liquefaction brought increasing domestic attention. This liquefaction can be assessed mainly through the semi-empirical procedures proposed by Seed and Idriss (1982) and the liquefaction risk based on the penetration resistance obtained from borehole DB and SPT. However, the geotechnical information data obtained by the in-situ tests or boring information fundamentally have an issue of the representative of the target area. Therefore, this study sought to construct a ground information database by classifying and reviewing the ground information required for liquefaction assessment, and tried to solve the representative problem of the soil layer that is subject to liquefaction evaluation by performing spatial interpolation using GIS.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.82-96
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• 2019

A semi-submersible structure has been widely used for offshore drilling and production of oil and gas. The small water plane area makes the structure very sensitive to weight increase in terms of payload and stability. Therefore, it is necessary to lighten the substructure from the early design stage. This study aims at an optimization of hull structure based on a sophisticated yield and buckling strength in accordance with classification rules. An in-house strength assessment system is developed to automate the procedure such as a generation of buckling panels, a collection of required panel information, automatic buckling and yield check and so on. The developed system enables an automatic yield and buckling strength check of all panels composing the hull structure at each iteration of the optimization. Design variables are plate thickness and stiffener section profiles. In order to overcome the difficulty of large number of design variables and the computational burden of FE analysis, various methods are proposed. The steepest descent method is selected as the optimization algorithm for an efficient search. For a reduction of the number of design variables and a direct application to practical design, the stiffener section variable is determined by selecting one from a pre-defined standard library. Plate thickness is also discretized at 0.5t interval. The number of FE analysis is reduced by using equations to analytically estimating the stress changes in gradient calculation and line search steps. As an endeavor to robust optimization, the number of design variables to be simultaneously optimized is divided by grouping the scantling variables by the plane. A sequential optimization is performed group by group. As a verification example, a central column of a semi-submersible structure is optimized and compared with a conventional optimization of all design variables at once.

• Korean Journal of Medicinal Crop Science
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• v.27 no.2
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• pp.143-150
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• 2019

Background: Skin is an organ that protects the human body from various environmental stimuli that can induce immune system activation. Skin aging can be largely divided into two categories: physiological aging, which is caused by the a decreased physiological function of the skin and structural changes with aging, and photoaging, which is caused by the chemical stress induced by external stimuli such as ultraviolet (UV) radiation. Methods and Results: The objective of this study was to investigate the anti-wrinkle and UV protective effect of catechin-rich green tea extract (CGTE) in activated keratinocyte (HaCaT cells) and UV-induced skin damage in hairless mice. The results showed that CGTE inhibits the tumor necrosis factor-alpha interferon-gamma ($TNF-{\alpha}+IFN-{\gamma}$)-induced expression of matrix metalloproteinase (MMP)-1 in HaCaT cells. In addition, the CGTE treatment significantly reduced wrinkle formation, epidermal thickness, collagen deposition, and transepidermal water loss in dorsal skin irradiated with UVB. However, the ${\beta}$-glucosidase activity was significantly increased. The CGTE treatment inhibits mRNA expression and enzyme activity of MMP-2 and MMP-9 in the dorsal skin irradiated with UVB. Conclusions: It is expected that CGTE can be effectively used as a functional food and cosmetic ingredient to improve skin moisture retention and reduce wrinkle formation.

• Food Engineering Progress
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• v.21 no.3
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• pp.233-241
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• 2017

Scaffolds of cell substrates are biophysical platforms for cell attachment, proliferation, and differentiation. They ultimately play a leading-edge role in the regeneration of tissues. Recent studies have shown the potential of bioactive scaffolds (i.e., osteo-inductive) through 3D printing. In this study, rice bran-derived biocomposite was fabricated for fused deposition modeling (FDM)-based 3D printing as a potential bone-graft analogue. Rice bran by-product was blended with poly caprolactone (PCL), a synthetic commercial biodegradable polymer. An extruder with extrusion process molding was adopted to manufacture the newly blended "green material." Processing conditions affected the performance of these blends. Bio-filament composite was characterized using field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX). Mechanical characterization of bio-filament composite was carried out to determine stress-strain and compressive strength. Biological behaviors of bio-filament composites were also investigated by assessing cell cytotoxicity and water contact angle. EDX results of bio-filament composites indicated the presence of organic compounds. These bio-filament composites were found to have higher tensile strength than conventional PCL filament. They exhibited positive response in cytotoxicity. Biological analysis revealed better compatibility of r-PCL with rice bran. Such rice bran blended bio-filament composite was found to have higher elongation and strength compared to control PCL.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1119-1126
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• 2021

Spacer grid with mixing vane had been widely used in nuclear reactor core. One of the main feather of spacer grid with mixing vane was that strong swirl flow was formed after the spacer grid. The swirl flow not only changed the bubble generation in the near wall field, but also affected the bubble behaviors in the center region of the subchannel. The interaction between bubble and the swirl flow was one of the basic phenomena for the two phase flow modeling in fuel assembly. To obatin better understanding on the bubble behaviors in swirl flow, full three dimension numerical simulations were conducted in the present paper. The swirl flow was assumed in the cylindral calculation domain. The bubble interface was captured by Volume Of Fluid (VOF) method. The properties of saturated water and steam at different pressure were applied in the simulation. The bubble trajectory, motion, shape and force were obtained based on the bubble parameters captured by VOF. The simulation cases in the present study included single bubble with different size, at different angular velocity conditions and at different pressure conditions. The results indicated that bubble migrated to the center in swirl flow with spiral motion type. The lateral migration was mainly related to shear stress magnitude and bubble size. The bubble moved toward the center with high velocity when the swirl magnitude was high. The largest bubble had the highest lateral migration velocity in the present study range. The effect of pressure was small when bubble size was the same. The prelimenery simulation result would be beneficial for better understanding complex two phase flow phenomena in fuel assembly with spacer grid.

• Biomedical Science Letters
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• v.27 no.3
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• pp.142-153
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• 2021

Liver fibrosis is a wound-healing response to chronic liver injury, which is caused by the continuous and excess deposition of extracellular matrix (ECM). The aim of this study is to investigate whether Uncaria rhynchophylla water extract (UR) can ameliorate thioacetamide (TAA)-induced liver fibrosis. The liver fibrosis model was induced on C57BL/6 mice by intraperitoneal injection with TAA three times a week for 8 weeks. UR (200 mg/kg) or silymarin (50 mg/kg) was administered orally daily for 8 weeks. Biochemical analyses including AST, ALT, MPO, and Ammonia levels were measured in serum. In the mice liver tissues, western blot and histological staining were analyzed. As a result, UR dramatically reduced the levels in serum AST, ALT, MPO, and Ammonia levels. UR treatment regulated NADPH oxidase factors expression, and antioxidant enzymes except for GPx-1/2 were significantly increased via Nrf2 activation. Furthermore, pro-inflammatory mediators, such as COX-2 and iNOS were markedly suppressed through the inhibition of NF-κB activation. Expressions of ECM-related protein including α-SMA and Collagen I were noticeably decreased. The additional histological evaluation confirmed that hepatocyte damage and collagenous fiber accumulation were attenuated. Taken together, these data suggest that UR possessed hepatoprotective effects in TAA-induced liver fibrosis via the NF-κB inactivation and Nrf2 activation. Therefore, UR may act as a potential therapeutic drug against liver fibrosis.

• Journal of Ginseng Research
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• v.43 no.4
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• pp.517-526
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• 2019

Background: The root of Panax ginseng, a member of Araliaceae family, has been used as herbal medicine and functional food in Asia for thousands of years. According to Traditional Chinese medicine, ginseng is the most widely used "Qi-invigorating" herbs, which provides tonic and preventive effects by resisting oxidative stress, influencing energy metabolism, and improving mitochondrial function. Very few reports have systematically measured cell mitochondrial bioenergetics after ginseng treatment. Methods: Here, H9C2 cell line, a rat cardiomyoblast, was treated with ginseng extracts having extracted using solvents of different polarity, i.e., water, 50% ethanol, and 90% ethanol, and subsequently, the oxygen consumption rate in healthy and tert-butyl hydroperoxideetreated live cultures was determined by Seahorse extracellular flux analyzer. Results: The 90% ethanol extracts of ginseng possessed the strongest antioxidative and tonic activities to mitochondrial respiration and therefore provided the best protective effects to H9C2 cardiomyocytes. By increasing the spare respiratory capacity of stressed H9C2 cells up to three-folds of that of healthy cells, the 90% ethanol extracts of ginseng greatly improved the tolerance of myocardial cells to oxidative damage. Conclusion: These results demonstrated that the low polarity extracts of ginseng could be the best extract, as compared with others, in regulating the oxygen consumption rate of cultured cardiomyocytes during mitochondrial respiration.

• Journal of Ginseng Research
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• v.45 no.1
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• pp.108-118
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• 2021

Background: Korean ginseng (Panax ginseng Meyer) contains a variety of ginsenosides that can be metabolized to a biologically active substance, compound K. Previous research showed that compound K could be enriched in the red ginseng extract (RGE) after hydrolysis by pectinase. The current study investigated whether the enzymatically hydrolyzed red ginseng extract (HRGE) containing a notable level of compound K has cognitive improving and neuroprotective effects. Methods: A scopolamine-induced hypomnesic mouse model was subjected to behavioral tasks, such as the Y-maze, passive avoidance, and the Morris water maze tests. After sacrificing the mice, the brains were collected, histologically examined (hematoxylin and eosin staining), and the expressions of antioxidant proteins analyzed by western blot. Results: Behavioral assessment indicated that the oral administration of HRGE at a dosage of 300 mg/kg body weight reversed scopolamine-induced learning and memory deficits. Histological examination demonstrated that the hippocampal damage observed in scopolamine-treated mouse brains was reduced by HRGE administration. In addition, HRGE administration increased the expression of nuclear-factor-E2-related factor 2 and its downstream antioxidant enzymes NAD(P)H:quinone oxidoreductase and heme oxygenase-1 in hippocampal tissue homogenates. An in vitro assay using HT22 mouse hippocampal neuronal cells demonstrated that HRGE treatment attenuated glutamate-induced cytotoxicity by decreasing the intracellular levels of reactive oxygen species. Conclusion: These findings suggest that HRGE administration can effectively alleviate hippocampus-mediated cognitive impairment, possibly through cytoprotective mechanisms, preventing oxidative-stress-induced neuronal cell death via the upregulation of phase 2 antioxidant molecules.

• Geomechanics and Engineering
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• v.24 no.2
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• pp.179-191
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• 2021

In this study, the strength and failure mechanism of red sandstones with combined defects were investigated by uniaxial compression tests on red sandstones with different crack angles using two-dimensional particle flow code numerical software, and their mechanical parameters and failure process were studied and analyzed. The results showed that the mechanical characteristics such as peak strength, peak strain, and elastic modulus of the samples with prefabricated combined defects were significantly inferior than those of the intact samples. With increasing crack angle from 15° to 60°, the weakening area of cracks increased, elastic modulus, peak strength, and peak strain gradually reduced, the total number of cracks increased, and more strain energy was released. In addition, the samples underwent initial brittle failure to plastic failure stage, and the failure form was more significant, leading to peeling phenomenon. However, with increasing crack angle from 75° to 90°, the crack-hole combination shared the stress concentration at the tip of the crack-crack combination, resulted in a gradual increase in elastic modulus, peak strain and peak strength, but a decrease in the number of total cracks, the release of strain energy reduced, the plastic failure state weakened, and the spalling phenomenon slowed down. On this basis, the samples with 30° and 45° crack-crack combination were selected for further experimental investigation. Through comparative analysis between the experimental and simulation results, the failure strength and final failure mode with cracks propagation of samples were found to be relatively similar.

• International Journal of Industrial Entomology and Biomaterials
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• v.41 no.2
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• pp.36-44
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• 2020

Mulberry root bark is one of potential plant sources for antioxidant materials which can be used for the relief of oxidative stress. To explore the effects of solvent type and temperature on the structural characteristics and antioxidant activity of the root bark extracts, we prepared various extracts of mulberry root bark (Morus alba L.) using 0 - 100 % ethanol (EtOH) at RT - 100℃. EtOH concentration and temperature critically affected the extraction yields, the content of bioactive components, and antioxidant activity of the extracts. Use of high content of EtOH solvent and low temperature resulted in the low extraction yield. Meanwhile, it was revealed that the extract prepared using absolute EtOH at room temperature contained polyphenols and flavonoids with the highest contents among other extracts. Interestingly, the temperature differently affected the polyphenol and flavonoid contents according to the solvent types. In the case of 30% EtOH solvent, polyphenol and flavonoid contents increased with an increase in temperature, whereas in the case of 70 and 100 % EtOH, these contents decreased. Using the radical scavenging assay, it was confirmed that the 100% EtOH extracts had higher antioxidant activity compared to distilled water (DW) extracts regardless of temperature. Also, heating might extract more antioxidant components from the root bark. Especially, the extract prepared using 30% EtOH solvent at 100℃ showed the highest antioxidant activity. Taken together, these experimental results imply that the extraction parameters should be designed carefully considering the productivity, the extracted bioactive components, and antioxidant activity.