• Journal of the Korean Geosynthetics Society
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• v.20 no.2
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• pp.23-33
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• 2021

In Korea, many reservoirs have been built for the purpose of solving the food shortage problem and supplying agricultural water. However, the current 75.6% of the reservoirs are in serious aged as more than 50 years have passed since the year of construction. In the case of such an aging reservoir, the stability due to scour and erosion inside the reservoir is very reduced, and if concentrated rainfall due to recent abnormal weather occurs, the aging reservoir may collapse, leading to a lot of damage to property and human life. Accordingly, each agency that manages aging reservoirs uses Ordinary Portland Cement (OPC) as an injection material and applies the grouting method. However, in the case of OPC, it may deteriorate over time and water leakage may occur again. And there are environmental problems such as consumption of natural resources and generation of greenhouse gases. So, there is a need to develop new materials and methods that can replace the OPC. In this study, an laboratory test and analysis were performed on the grout material developed to induce a curing reaction similar to that of OPC by recycling power plant byproduct. In addition, test in the field such as electric resistivity survey, Standard Penetration Test (SPT), and field permeability test were performed to analyzed to reinforcement effect and determine the possibility of using instead of OPC. As a results of the test, in the case of recycled power plant byproduct, the compressive strength was 2.9 to 3.2 times and the deformation modulus was 2.3 to 3.3 times higher, indicating that it is excellent in strength and can be used instead of OPC. And it was analyzed that the N value of the reservoir was increased by 1~2, and the coefficient of permeability (k) decreased to the level of 8.9~42.5%. showing sufficient reinforcing effect in terms of order.

• Economic and Environmental Geology
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• v.55 no.1
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• pp.97-109
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• 2022

This study focused on the physicochemical effects of bottom ash dissolved precipitation on the soil and groundwater environment. The iced column and percolation experiments showed that most of the bottom ash particles were drained as the ash-dissolved solution, while the charcoal powder was filtered through the soil. Ion species of Al, As, Cu, Cd, Cr, Pb, Fe, Mn, Ca, K, Si, F, NO₃, SO₄ were analyzed from the eluates collected during the 24 h column test. In the charcoal powder eluates, a high concentration of K was detected at the beginning of the reaction, but it decreased with time. The concentrations of Al and Ca were observed to increase with time, although they existed in trace amount. In the bottom ash eluates, the concentrations of Ca and SO₄ decreased by 30 mg·L^-1 and 67 mg·L^-1, respectively, over 24 h. It is regarded that the infiltration patterns of the bottom ash and biochar in the unsaturated zone were different owing to their particle sizes and solvent properties. It is expected that a significant amount of the bottom ash will mix with the precipitation and percolate below the water table, especially in the case of thin and highly permeable unsaturated zone. The biochar was filtered through the unsaturated zone. The biochar did not dissolve in the groundwater, although it reached the saturation zone. For these reasons, it is considered that the direct contamination by the bottom ash and biochar are unlikely to occur.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.163-173
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• 2022

Climate change is a key factor that greatly influences changes in the biological seasons and geographical distribution of species. In the ecological field, the BioClimatic predictor (BioClim), which is most related to the physiological characteristics of organisms, is used for vulnerability assessment. However, BioClim values are not provided other than the future period climate average values for each GCM for the Shared Socio-economic Pathways (SSPs) scenario. In this study, BioClim data suitable for domestic conditions was produced using 1 km resolution SSPs scenario detailed data produced by Rural Development Administration, and based on the data, a species distribution model was applied to mainly grow in southern, Gyeongsangbuk-do, Gangwon-do and humid regions. Appropriate habitat distributions were predicted every 30 years for the base years (1981 - 2010) and future years (2011 - 2100) of the Acer pictum subsp. mono. Acer pictum subsp. mono appearance data were collected from a total of 819 points through the national natural environment survey data. In order to improve the performance of the MaxEnt model, the parameters of the model (LQH-1.5) were optimized, and 7 detailed biolicm indices and 5 topographical indices were applied to the MaxEnt model. Drainage, Annual Precipitation (Bio12), and Slope significantly contributed to the distribution of Acer pictum subsp. mono in Korea. As a result of reflecting the growth characteristics that favor moist and fertile soil, the influence of climatic factors was not significant. Accordingly, in the base year, the suitable habitat for a high level of Acer pictum subsp. mono is 3.41% of the area of Korea, and in the near future (2011 - 2040) and far future (2071 - 2100), SSP1-2.6 accounts for 0.01% and 0.02%, gradually decreasing. However, in SSP5-8.5, it was 0.01% and 0.72%, respectively, showing a tendency to decrease in the near future compared to the base year, but to gradually increase toward the far future. This study confirms the future distribution of vegetation that is more easily adapted to climate change, and has significance as a basic study that can be used for future forest restoration of climate change-adapted species.

• Journal of Periodontal and Implant Science
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• v.25 no.3
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• pp.720-732
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• 1995

The use of transforming growth $factor-{\beta}1$ which functions as a potent biologic mediator regulating numerous activities of wound healing has been suggested for the promotion of periodontal regeneration. The mitogenic effects of transforming growth $factor-{\beta}1$ on human periodontal ligament cells and human gingival fibroblasts were evaluated by determining the incorporation of $[^3H]-thymidine$ into DNA of the cells dose-dependently. Cells were prepared with primary cultured fibroblasts and periodontal ligament cells from humans, and used in experiments were the fourth or sixth subpassage. Cells were seeded with serum free Dulbecco's modified Eagle medium containing 0.1% bovine serum albumine. The added concentrations of transforming growth $factor-{\beta}1$ were 0.25, 0.5, 1, 2.5, 5ng/ml and transforming growth $factor-{\beta}1$ were added to the quiescent cells for 24hours, 48hours, 72hours. They were labeled with lnCi/ml $[^3H]$ thymidine for the last 24hour of the each culture. The results were presented as the mean counts per minute (CPM) per well and S.D. of four determinations. The results were as follows. : The DNA synthetic activity of human gingival fibroblasts was increased dose-dependently by transforming growth $factor-{\beta}1$ at 24 hours, 48 hours and 72 hours. The maximum mitogenic effects were at the 48 hour application of transforming growth $factor-{\beta}1$. The DNA synthetic activity was generally more decreased at the 72 hour application than at the 48 hour the application of transforming growth $factor-{\beta}1$. The DNA synthetic activity of human periodontal ligament cells was increased dose-dependently by transforming growth $factor-{\beta}1$ at 24 hours and 48 hours. But the DNA synthetic activity was decreased at 5ng/ml of the 72 hour application. The maximum mitogenic effects were also at the 48 hour application of transforming growth $factor-{\beta}1$. The DNA synthetic activity of human periodontal ligament cells was generally more decreased at the 72 hour application than at the 48 hour application of transforming growth $factor-{\beta}1$. In the comparision of DNA synthetic activity between the human gingival fibroblasts and human periodontal ligament cells, the human gingival fibroblasts had more activity than the human periodontal ligament cells at all time application with the concentration of transforming growth $factor-{\beta}1$. In conclusion, transforming growth $factor-{\beta}1$ has an important roles in the stimulation of DNA synthesis in human periodontal ligament cells and human gingival fibroblasts, which means an increase in collagen synthesizing cells and thus, may be useful for clinical application in periodontal regenerative procedures.

• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.688-693
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• 2014

For investigating NO reduction activity of an catalytic filter, the catalytic performance was measured under the presence of $SO_2$ and $H_2O$, respectively or simultaneously in the simulation gas composed of NO, $NH_3$, and air. The catalytic filter was prepared by coating $V_2O_5-WO_3/TiO_2$ catalyst on the pore surface of SiC filter element of which the superior performance for the particulate removal was well known. At the temperature below $260^{\circ}C$, the catalytic activities were enormously decreased under the presence of $SO_2$ and $H_2O$, respectively or simultaneously, compared with those under the cases of the absence of $SO_2$ and $H_2O$. However, the presence of $SO_2$ promoted the performance of the catalytic filter above $320^{\circ}C$ with showing the NO conversion better than 99.8% for the NO inlet concentration of 500 ppm and at the face velocity of 2 cm/s. In particular, the presence of water showed high NO conversion higher than 99% up to high temperature of $380^{\circ}C$. This effect of water was explained by the reason that it retarded the ammonia oxidation which is the main step into the formation of $N_2O$. The initial NO reduction activity of the catalytic filter maintained for the duration of 100 hours in the presence of $SO_2$ and $H_2O$. Therefore, it was concluded that the catalytic filter was promisingly useful for the industrial NOx reduction catalyst in order to treat the particulate and NO simultaneously.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.204-208
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• 2012

Water repellency which affects infiltration, evaporation, erosion and other water transfer mechanisms through soil has been observed under several natural conditions. Water repellency is thought to be caused by hydrophobic organic compounds, which are present as coatings on soil particles or as an interstitial matter between soil particles. This study was conducted to evaluate the characteristics of the water repellent soil and transport characteristics of trace elements within this soil. Capillary height of the water repellent soil was measured. Batch and column studies were accompanied to identify sorption and transport mechanism of trace elements such as $Cu^{2+}$, $Mn^{2+}$, $Fe^{2+}$, $Zn^{2+}$ and $Mo^{5+}$. Difference of sorption capacity between common and repellent soils was observed depended on the degree of repellency. In the column study, the desorption of trace elements and the spatial concentration distribution as a function of time were evaluated. The capillary height was in the repellency order of 0% > 15% > 40% > 70% > 100%. No water was absorbed in soil indicating >70% repellency. Using trace elements, $Fe^{2+}$ and $Mo^{5+}$ showed higher sorption capacity in the repellent soil than in non-repellent soil. The sorption performance of $Fe^{2+}$ was found to be in the repellency order of 40% > 15% > 0%. Our results found that transfer of $Mo^{5+}$ had similar sorption tendency in soils having 0%, 15% and 40% repellency at the beginning, however, the higher desorption capacity was observed as time passes in the repellent soil compared to in non-repellent soils.

• The Korean Journal of Air & Space Law and Policy
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• v.27 no.2
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• pp.67-106
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• 2012

Today air traffic at the airport is complicated including a significant increase in the volume of air transport, so aviation accidents are constantly occurring. Therefore, we should newly recognize importance of the Air Traffic Safety, the core values of the Air Traffic. The location of airport that is the basic infrastructure of the air traffic and the security of safety for facilities and equipments are more important than what you can. From this dimension, I analyze the step-by-step safety factors that are taken into account in the airport development projects from the construction or improvement of the airport within the current laws and institutions and give my opinion on the enhancement of safety in the design and construction of airport. The safety of air traffic, as well as airport, depends on location, development, design, construction, inspection and management of the airport including airport facilities because we have to carry out the national responsibility that prevents the risk of large social overhead capital for many and unspecified persons in modern society through legislation regarding intervention of specialists and locational criteria for aviation safety from the planning stage of airport development. In addition, well-defined installation standards of airports and air navigation facilities, the key points of the airport development phase, can ensure the safety of the airport and airport facilities. Of course, the installation standards of airport and air navigation facilities are based on the global standard due to the nature of air traffic. However, to prevent the chaos for the safety standards in design, construction, inspection of them and to ensure the aviation safety, the safety standards must be further subdivided in the course of domestic legislation. The criteria for installation of the Air Navigation facilities is regulated most specifically. However, to ensure the safety of the operation for Air Navigation Facilities, performance system proved suitable for the Safety of Air Navigation Facilities must change over from arbitrary restrictions to mandatory restrictions and be applied for foreign producers as well as domestic producers. Of course, negligence of pilots and defective aircraft maintenance lead to a large portion of the aviation accidents. However, I think that air traffic accidents can be reduced if the airport or airport facility is perfect enough to ensure the safety. Therefore, legal and institutional supplement to prioritize the aviation safety from the stage of airport development may be necessary.

• Journal of Intelligence and Information Systems
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• v.22 no.3
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• pp.113-127
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• 2016

Among the techniques for recommendation, collaborative filtering (CF) is commonly recognized to be the most effective for implementing recommender systems. Until now, CF has been popularly studied and adopted in both academic and real-world applications. The basic idea of CF is to create recommendation results by finding correlations between users of a recommendation system. CF system compares users based on how similar they are, and recommend products to users by using other like-minded people's results of evaluation for each product. Thus, it is very important to compute evaluation similarities among users in CF because the recommendation quality depends on it. Typical CF uses user's explicit numeric ratings of items (i.e. quantitative information) when computing the similarities among users in CF. In other words, user's numeric ratings have been a sole source of user preference information in traditional CF. However, user ratings are unable to fully reflect user's actual preferences from time to time. According to several studies, users may more actively accommodate recommendation of reliable others when purchasing goods. Thus, trust relationship can be regarded as the informative source for identifying user's preference with accuracy. Under this background, we propose a new hybrid recommender system that fuses CF and social network analysis (SNA). The proposed system adopts the recommendation algorithm that additionally reflect the result analyzed by SNA. In detail, our proposed system is based on conventional memory-based CF, but it is designed to use both user's numeric ratings and trust relationship information between users when calculating user similarities. For this, our system creates and uses not only user-item rating matrix, but also user-to-user trust network. As the methods for calculating user similarity between users, we proposed two alternatives - one is algorithm calculating the degree of similarity between users by utilizing in-degree and out-degree centrality, which are the indices representing the central location in the social network. We named these approaches as 'Trust CF - All' and 'Trust CF - Conditional'. The other alternative is the algorithm reflecting a neighbor's score higher when a target user trusts the neighbor directly or indirectly. The direct or indirect trust relationship can be identified by searching trust network of users. In this study, we call this approach 'Trust CF - Search'. To validate the applicability of the proposed system, we used experimental data provided by LibRec that crawled from the entire FilmTrust website. It consists of ratings of movies and trust relationship network indicating who to trust between users. The experimental system was implemented using Microsoft Visual Basic for Applications (VBA) and UCINET 6. To examine the effectiveness of the proposed system, we compared the performance of our proposed method with one of conventional CF system. The performances of recommender system were evaluated by using average MAE (mean absolute error). The analysis results confirmed that in case of applying without conditions the in-degree centrality index of trusted network of users(i.e. Trust CF - All), the accuracy (MAE = 0.565134) was lower than conventional CF (MAE = 0.564966). And, in case of applying the in-degree centrality index only to the users with the out-degree centrality above a certain threshold value(i.e. Trust CF - Conditional), the proposed system improved the accuracy a little (MAE = 0.564909) compared to traditional CF. However, the algorithm searching based on the trusted network of users (i.e. Trust CF - Search) was found to show the best performance (MAE = 0.564846). And the result from paired samples t-test presented that Trust CF - Search outperformed conventional CF with 10% statistical significance level. Our study sheds a light on the application of user's trust relationship network information for facilitating electronic commerce by recommending proper items to users.

• Journal of the Korean Society of Radiology
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• v.11 no.5
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• pp.297-302
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• 2017

Recently, building materials and air purification filters with eco-friendly charcoal are actively studying to reduce the concentration of radon gas in indoor air. In this study, radon reduction performance was assessed by designing and producing new panel-type activated carbon filter that can be handled more efficiently than conventional charcoal filters, which can reduce radon gas. For the fabrication of our panel-type activated carbon filter, first the pressed molding product after mixing activated carbon powder and polyurethane. Then, through diamond cutting, the activated carbon filter of 2 mm, 4 mm and 6 mm thickness were fabricated. To investigate the physical characteristics of the fabricated activated carbon filter, a surface area and flexural strength measurement was performed. In addition, to evaluate the reduction performance of radon gas in indoor, the radon concentration of before and after the filter passes from a constant amount of air flow using three acrylic chambers was measured, respectively. As a result, the surface area of the fabricated activated carbon was approximately $1,008m^2/g$ showing similar value to conventional products. Also, the flexural load was found to have three times higher value than the gypsum board with 435 N. Finally, the radon reduction efficiency from indoor gas improved as the thickness of the activated carbon increases, resulting in an excellent radon removal rate of more than 90 % in the 6 mm thick filter. From the experimental results, the panel-type activated carbon is considered to be available as an eco-friendly building material to reduce radon gas in an enclosed indoor environment.

• Journal of Korea Game Society
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• v.4 no.4
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• pp.11-18
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• 2004

The on-line games in the past were played by only two persons exchanging data based on one-to-one connections, whereas recent ones (e.g. MMORPG: Massively Multi-player Online Role-playings Game) enable tens of thousands of people to be connected simultaneously. Specifically, Korea has established an excellent network infrastructure that can't be found anywhere in the world. Almost every household has a high-speed Internet access. What made this possible was, in part, high density of population that has accelerated the formation of good Internet infrastructure. However, this rapid increase in the use of on-line games may lead to surging traffics exceeding the limited Internet communication capacity so that the connection to the games is unstable or the server fails. expanding the servers though this measure is very costly could solve this problem. To deal with this problem, the present study proposes the load distribution technology that connects in the form of local clustering the game servers divided by their contents used in each on-line game reduces the loads of specific servers using the load balancer, and enhances performance of sewer for their efficient operation. In this paper, a cluster system is proposed where each Game server in the system has different contents service and loads are distributed efficiently using the game server resource information such as CPU utilization. Game sewers having different contents are mutually connected and managed with a network file system to maintain information consistency required to support resource information updates, deletions, and additions. Simulation studies show that our method performs better than other traditional methods. In terms of response time, our method shows shorter latency than RR (Round Robin) and LC (Least Connection) by about 12%, 10% respectively.