• Tunnel and Underground Space
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• v.31 no.6
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• pp.610-622
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• 2021

The DECOVALEX project is one of the representative international cooperative projects to enhance the understanding of the complex Thermo-Hydro-Mechanical-Chemical(THMC) coupled behavior in the high-level radioactive waste disposal system based on the numerical simulation. DECOVALEX-2023 is the current phase consisting of 7 tasks, and Task C aims to model the THM coupled behavior in the disposal system based on the Full-scale Emplacement (FE) experiment at the Mont-Terri underground rock laboratory. This study performs the numerical simulation based on the OGS-FLAC developed for the current study. In the numerical model, we emplaced the heater with constant power horizontally based on the FE experiment and monitored the pressure development, temperature increase, and mechanical deformation at the specific monitoring points. We monitored the capillary pressure as the primary effect inducing the flow in the buffer system, and thermal stress and pressurization were dominant in the surrounding rocks' area. The results will also be compared and validated with the other participating groups and the experimental data further.

• Korean Journal of Culture and Social Issue
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• v.19 no.4
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• pp.553-576
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• 2013

The purpose of this study was to investigate the impact of retirement stress, character strengths and marital dissatisfaction on depression. Additionally this study examined direct effects and indirect effects of character strengths and marital dissatisfaction. The participant group was composed of 197 retired men living in Daegu and Gyongsangbuk-do. The Retirement Stress Scale (RSS), Character Strengths Test (CST), Korean Marital Satisfaction Inventory (K-MSI), and Center for Epistemology Studies Depression scale (CES-D) were administered to participants. Structural Equation Modeling (SEM) with AMOS was used for the purpose of analysis. The results of the study were as follows. First, an increase in retirement stress was associated with higher levels of depression. Second, hierarchical regression analysis indicated that higher levels of optimism significantly predicted higher depression. Also hierarchical regression analysis indicated that lower levels of appreciation of beauty and excellence without optimism significantly predicted higher depression. Furthermore, increases in marital dissatisfaction were associated with higher levels of depression. Third, the constructed model including both direct effects and indirect effects appeared to fit better than alternative model in explaining relationships between retirement stress and depression. In other words, character strengths and marital dissatisfaction appeared to affect the depression levels of retired men directly and indirectly. To sum up, this study demonstrated that the factors which had an effect on depression in retired men, character strengths and harmonious marital relationships appeared to act as a buffer against depression in retired men. The current results might serve as basic data for psychological well-being programs for retired men. Finally, the limitations and implications of the current study were discussed.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.137-148
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• 2008

There have been many cases of using wetlands as an alternative in controlling stormwater, treating mining leachate, and agricultural discharge, and so on, recently. The reality is, however, that the wetlands are not properly applicable because of the lack of enough longterm data for wetlands due to the difficulty of long-term monitoring. Therefore, this study tries to analyze the storage of Upo, Mokpo, Sajipo, and Jjokjibeul in Topyeong watershed using SWAT(Soil and Water Assessment Tool) model, one of the long-term runoff hydrologic model, for the purpose of generating the long-term data and analyzing the hydrologic behavior of wetlands based on the generated data. Also, the changes in runoff at the outlet are analyzed after applying the simulation of constructing washland in Topyeong watershed and the storage in Upo is analyzed. The result shows that the runoff at the outlet of the watershed is decreased in rainy season from July to August and increased in dry season from December to February. In addition, the analysis of Upo storage concludes that Upo can be influenced by the construction of the washland. The duration curve of washland is then analyzed in order to evaluate the wetland's sustainability in terms of washland and it appears that the runoff of washland is simulated to be less than that of the existing wetland. Moreover, runoffs of some washlands are simulated to be less even in wet season. These results lead to the fact that there should be further hydrologic management for constructed washland. Then, the changes in loads (TN and TP) because of constructing washland are analyzed. The result shows that the loads are reduced because of the construction. Also, the changes in loads due to the construction of buffer strips are analyzed to compare the load reductions caused by a washland. Finally, REMM model, a riparian management model, is applied to overcome the hydrologic ambiguousness of SWAT model, and then, the SWAT model results are compared to those of REMM.

• Journal of Soil and Groundwater Environment
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• v.13 no.5
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• pp.57-73
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• 2008

Nitrate concentrations were measured up to 49 mg/L (as $NO_3$-N) and 22% of the samples exceeded drinking water standard in shallow and bedrock groundwater of the northern Nonsan area. Nitrate concentrations showed a significant difference among land use groups. To predict nitrate concentration in groundwater, multiple regression analysis was carried out using hydrogeologic parameters of soil media, topography and land use which were categorized as several groups, well depth and altitude, and field parameters of temperature, pH, DO and EC. Hydrogeologic parameters were quantified as area proportions of each category within circular buffers centering at wells. Regression was performed to all the combination of variables and the most relevant model was selected based on adjusted coefficient of determination (Adj. $R^2$). Regression using hydrogelogic parameters with varying buffer radii show highest Adj. $R^2$ at 50m and 300m for shallow and bedrock groundwater, respectively. Shallow groundwater has higher Adj. $R^2$ than bedrock groundwater indicating higher susceptibility to hydrogeologic properties of surface environment near the well. Land use and soil media was major explanatory variables for shallow and bedrock groundwater, respectively and residential area was a major variable in both shallow and bedrock groundwater. Regression involving hydrogeologic parameters and field parameters showed that EC, paddy and pH were major variables in shallow groundwater whereas DO, EC and natural area were in bedrock groundwater. Field parameters have much higher explanatory power over the hydrogeologic parameters suggesting field parameters which are routinely measured can provide important information on each well in assessment of nitrate contamination. The most relevant buffer radii can be applied to estimation of travel time of contaminants in surface environment to wells.

• Korean Journal of Food Science and Technology
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• v.26 no.3
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• pp.213-220
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• 1994

Gastrodia (G) Rhizoma has been used clinically as an oriental herbal medicine with sedative, anticonvulsive, and depressor effects. The present study tested effects of G. Rhizoma extracts on the coronary circulation and myocardial oxygen consumption in perfused rat hearts. Sprague Dawley rats (SD) and spontaneously hypertensive rats (SHR) were employed as experimental animals and nonworking Langendorff heart perfusion technique introduced for heart experiments. G. Rhizoma extracts were prepared from grinding G. Rhizoma into powder, extracting in water and 50% ethanol for 4 or 16 hr and diluting with Krebs-Henseleit bicarbonate perfusion buffer to be 70%. Hearts were perfused with bicarbonate buffer oxygenated with 95% $O_{2}:$ 5% $CO_{2}$ at constant coronary perfusion pressure of $90cmH_{2}O$. The diluted extracts were infused into coronary arteries in a concentration of $1{\sim}5\;{\mu}M$ for $7{\sim}8 min. While in SD water- or ethanol-extracts of G. Rhizoma extracted for 16 hr increased coronary perfusate flow (CPF) and decreased coronary vascular resistance (CVR), ethanol-extracts in SHR produced coronary vasoconstriction associated with enhanced CVR. G. Rhizoma extracts-induced increase in CPF reduced myocardial oxygen extraction, and thus myocardial oxygen consumption ($MVO_{2}$) remained at that observed prior to infusion of extracts. In SD and SHR 16 hr-water-extracts markedly altered coronary venous effluent pH and $Pco_{2}$ and evoked metabolic acidosis, which could be a coronary vasodilator mechanism decreasing CVR. In this study, the extracts decreasing CVR in SD and SHR did not augment the lactate production. Therefore, although the effects of the extracts on cardiac function and coronary circulation depended on solvents and duration for extraction, the 16hr-water-extracts, at least, exhibited coronary vasodilation in SD and SHR. Conversely, ethanol-extracts constricted coronary arteries in SHR. G. Rhizoma extracts-induced vasodilation might be due to the metabolic acidosis rather than due to the increased lactate production. The results indicate that G. Rhizoma extracts obtained from proper extracting procedures can be used as a safe and clinically applicable herbal medicine in the cardiovascular diseases such as coronary artery disease and hypertension for vasodilatory and antihypertensive actions.

• Journal of the Korean Ceramic Society
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• v.49 no.5
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• pp.404-411
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• 2012

The reliability of solid oxide fuel cells (SOFCs) particularly depends on the high quality of solid oxide electrolytes. The application of thinner electrolytes and multi electrolyte layers requires a more reliable characterization method. Most of the investigations on thin film solid electrolytes have been made for the parallel transport along the interface, which is not however directly related to the fuel cell performance of those electrolytes. In this work an array of ion-blocking metallic Ti/Au microelectrodes with about a $160{\mu}m$ diameter was applied on top of an ultrathin ($1{\mu}m$) yttria-stabilized-zirconia/gadolinium-doped-ceria (YSZ/GDC) heterolayer solid electrolyte in a micro-SOFC prepared by PLD as well as an 8-${\mu}m$ thick YSZ layer by screen printing, to study the transport characteristics in the perpendicular direction relevant for fuel cell operation. While the capacitance variation in the electrode area supported the working principle of the measurement technique, other local variations could be related to the quality of the electrolyte layers and deposited electrode points. While the small electrode size and low temperature measurements increaseed the electrolyte resistances enough for the reliable estimation, the impedance spectra appeared to consist of only a large electrode polarization. Modulus representation distinguished two high frequency responses with resistance magnitude differing by orders of magnitude, which can be ascribed to the gadolinium-doped ceria buffer electrolyte layer with a 200 nm thickness and yttria-stabilized zirconia layer of about $1{\mu}m$. The major impedance response was attributed to the resistance due to electron hole conduction in GDC due to the ion-blocking top electrodes with activation energy of 0.7 eV. The respective conductivity values were obtained by model analysis using empirical Havriliak-Negami elements and by temperature adjustments with respect to the conductivity of the YSZ layers.

• Journal of the Korea Convergence Society
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• v.9 no.4
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• pp.251-259
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• 2018

The purpose of this study is to investigate of mental health professionals regarding job burnout, emotional labor and mental health by verifying the moderating effect of resilience. Results from analyzing 1,020 mental health professionals(certified people with 1st, 2nd grade licence in nursing, social welfare, and psychology) collected in the academic service studies by the National Mental Health Education Research Center in 2014 showed that job burnouts and emotional labor both had negative correlation with mental health, but in cases of analyzing moderating effects in resilience, only job burnout presented significant results. Accordingly, the results indicated that resilience could buffer the danger of mental health of mental health workers from job burnouts and emotional laboring. This study shows that it is important to care about the mental health of not only the people who receive mental health care services, but also the mental health care professionals who provide services. It also shows that the research has to be conducted with convergence considering both sides. Measures regarding the mental health care of mental health professionals were further discussed based on the results of this study.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.443-453
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• 2011

This research aims at suggesting the mitigation measures of decreasing pollution by analyzing land cover characteristics according to subwatershed, and non-pollutant load characteristics occurring in each subwatershed. Mushim-cheon is selected as a research area, and HyGIS-SWAT is used as a water quality model. This research analyzed outflow load characteristics by classifying land cover, which has over 50% classified items, into a city area, a farmland area and a forest area. The result shows that the yearly occurrence load quantity represents a farmland area, a forest area and a city area in order. In subwatershed-2, occurrence load quantity is analyzed by setting up a buffer zone in the center of stream, and by changing a farmland area into a natural grass land. Therefore, a farmland area in a subwatershed changes 36.6% into 27.9% and 15.3% comparing to previous land cover change. In the analysis of sediment loads occurrence quantity and nutritive salt load occurrence quantity in subwatershed-2, sediment loads occurrence quantity decreases 52% to about 47%, and nutritive salt load decreases 49% and 34% in compare with previous change. Hereafter, this research will set up the mitigation measures scenario, and find out which is more effective for the mitigation measures.

• Journal of KIISE:Information Networking
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• v.35 no.3
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• pp.173-182
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• 2008

Promoting quality of streaming service in wireless networks has attracted intensive research over the years. Instable wireless channel condition causes high transmission delay and packet loss, due to fading and interference. Therefore, they lead to degrade quality of video streaming service. The IEEE 802.11 Working Group is currently working on a new standard called IEEE 802.11e to support quality of service in WLANs. And several schemes were proposed in order to guarantee QoS. However, they are not adaptable to network condition. Accordingly, they suffered video quality degradation, due to buffer overflow or packet loss. In this paper, to promote quality of video streaming service in WLANs, we propose a cross-layer architecture based on IEEE 802.11e EDCA model. Our cross-layer architecture provides differentiated transmission mechanism of IEEE 802.11e EDCA based on priority of MPEG-4 video frames and adaptively controls the transmission rate by dropping video frames through the efficient bandwidth estimation based on distinction of each AC. Through the simulation, proposed scheme is shown to be able to improve end-to-end qualify for video streaming service in WLANs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.843-850
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• 2020

The purpose of this study is to evaluate the structural risk and weakness of a railway tank car through nonlinear collision analysis according to overseas collision safety standards. The goal is to propose a crash safety design guideline for railway tank cars for transporting dangerous goods in Korea. We analyzed the buffer impact test procedure of railway freight cars prescribed in EN 12663-2 and the tank puncture test criteria prescribed in 49CFR179. A nonlinear finite element model according to each standard was modeled using LS-DYNA, a commercial finite element analysis solver. As a result of the buffing impact test simulation, it was predicted that plastic deformation would not occur at a collision speed of 6 km/h or less. However, plastic deformation was detected at the rear of the center sill and at the tank center supporting the structure at a collision speed of 8 km/h or more. As a result of a head-on test simulation of tank puncture, the outer tank shell was destroyed at the corner of the tank head when 4% of the kinetic energy of the impacter was absorbed. The tank shell was destroyed in the area of contact with the impacter in the test mode analysis of tank shell puncture when the kinetic energy of the moving vehicle was reduced by 30%. Therefore, the simulation results of the puncture test show that fracture at the tank shell and leakage of the internal material is expected. Consequently, protection and structural design reinforcement are required on railway tank cars in Korea.