• Journal of IKEEE
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• v.28 no.3
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• pp.458-464
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• 2024

This study proposes a fault-tolerant caching system to address the issue of caching content imbalance caused by the dynamic departure and participation of cache servers in a heterogeneous cache server network, and validates it in both real and virtual environments. With the increase of large-scale media content requiring various types and resolutions, the necessity of cache servers as key components to reduce response time to user requests and alleviate network load has been growing. In particular, research on heterogeneous cache server networks utilizing edge computing and low-power devices has been actively conducted recently. However, in such environments, the irregular departure and participation of cache servers can occur frequently, leading to content imbalance among the cache servers deployed in the network, which can degrade the performance of the cache server network. The fault-tolerant caching algorithm proposed in this study ensures stable service quality by maintaining balance among media contents even when cache servers depart. Experimental results confirmed that the proposed algorithm effectively maintains content distribution despite the departure of cache servers. Additionally, we built a network composed of seven heterogeneous cache servers to verify the practicality of the proposed caching system and demonstrated its performance and scalability through a large-scale cache server network in a virtual environment.

• Journal of the Korean Institute of Landscape Architecture
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• v.46 no.5
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• pp.59-68
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• 2018

This study deals with post-occupancy evaluation (POE) of 'Kim Gwang-seok Street'as storytelling road for urban regeneration. The evaluation focused on image preference and use satisfaction of visitors. This is the initial project of popular singer-storytelling street as a new attraction, and the results could be used as basic data for the sustainable planning and management of storytelling streets. 200 respondents of visitor group were analyzed. Frequency analysis for demographics, use, behavior, reliability, and means, were evaluated. Factor analysis and multiple regression analysis were conducted for image preference and use satisfaction. Responses showed high frequency of twenties in age, who were typically students. In use motives and activities, strolling, sightseeing, and taking pictures were shown to be the most common. The mean scores of image variables showed symbolic (5.03), familiar (4.84), beautiful (4.71), and bright (4.63), the highest. The result of exploratory factor analysis, led to 3 factors being categorized; the mood of street, the design, and the dynamics. Due to the result of multiple regression analysis, the preference of space image was significantly influenced by 4 image variables; symbolic (${\beta}=.314$), stable (${\beta}=.248$), friendly (${\beta}=.204$), and fresh (${\beta}=.142$). In the use satisfaction analysis, the mean scores were highest concerning facility design (3.81), typical street (3.78), the image of street (3.81), continued use (3.66), and experiential tourism (3.53), respectively. The mean score of parking space (2.56) was the lowest. In factor analysis concerning use satisfaction, 3 factors were categorized; facility management, experience, and image. By the result of multiple regression analysis, the total satisfaction of use was significantly influenced by 4 independent variables; image of street (${\beta}=.296$), management (${\beta}=.277$), continued use (${\beta}=.205$), and typical street (${\beta}=.183$). As storytelling road for urban regeneration, 'Kim Gwang-seok Street' has shown considerable success in significant improvement of image preference and user satisfaction. Therefore, the enhancement of 'placeness' through storytelling of Kim Gwang-seok, and the strengthening of its identity and symbolism, should be the basic focus of development for the street in the future.

• Economic and Environmental Geology
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• v.51 no.2
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• pp.185-201
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• 2018

Nuclear power plants(NPP) are constructed and operated to ensure safety against natural disasters and man-made disasters in all processes including site selection, site survey, design, construction, and operation. This paper will introduce a series of efforts conducted in Korea Hydro and Nuclear Power Co. Ltd., to assure the safety of nuclear power plant against earthquakes and other natural hazards. In particular, the present status of the earthquake, fault, and slope safety monitoring system for nuclear power plants is introduced. A earthquake observatory network for the NPP sites has been built up for nuclear safety and providing adequate seismic design standards for NPP sites by monitoring seismicity in and around NPPs since 1999. The Eupcheon Fault Monitoring System, composed of a strainmeter, seismometer, creepmeter, Global Positioning System, and groundwater meter, was installed to assess the safety of the Wolsung Nuclear Power Plant against earthquakes by monitoring the short- and long-term behavioral characteristics of the Eupcheon fault. Through the analysis of measured data, it was verified that the Eupcheon fault is a relatively stable fault that is not affected by earthquakes occurring around the southeastern part of the Korean peninsula. In addition, it was confirmed that the fault monitoring system could be very useful for seismic safety analysis and earthquake prediction study on the fault. K-SLOPE System for systematic slope monitoring was successfully developed for monitoring of the slope at nuclear power plants. Several kinds of monitoring devices including an inclinometer, tiltmeter, tension-wire, and precipitation gauge were installed on the NPP slope. A macro deformation analysis using terrestrial LiDAR (Light Detection And Ranging) was performed for overall slope deformation evaluation.

• KSBB Journal
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• v.22 no.5
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• pp.297-304
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• 2007

For large and rapid screening of high-yielding mutants of lovastatin produced by filamentous fungal cells of Aspergillus terreus, one of the most important stage is to test as large amounts of mutated strains as possible. For this purpose, we intended to develop a miniaturized cultivation method using $7m{\ell}$ culture tube instead of traditional $250m{\ell}$ flask (working volume $50m{\ell}$). For obtaining large amounts of conidiospores to be used as inoculums for miniaturized cultures, 4 components i.e., glucose, sucrose, yeast extract and $KH_2PO_4$ were intensively investigated, which had been observed to show positive effect on enhancement of spore production through Plackett-Burman design experimet. When optimum concentrations of these components that were determined through application of response surface method (RSM) based on central composite design (CCD) were used, maximum spore numbers amounting to $1.9\times10^{10}$ spores/plate were obtained, resulting in approximately 190 fold increase as compared to the commonly used PDA sporulation medium. Using the miniaturized cultures, intensive strain development programs were carried out for screening of lovastatin high-yielding as well as highly reproducible mutants. It was observed that, for maximum production of lovastatin, the producers should be activated through 'PaB' adaptation process during the early solid culture stage. In addition, they should be proliferated in condensed filamentous forms in miniaturized growth cultures, so that optimum amounts of highly active cells could be transferred to the production culture-tube as reproducible inoculums. Under these highly controlled fermentation conditions, compact-pelleted morphology of optimum size (less than 1 mm in diameter) was successfully induced in the miniaturized production cultures, which proved essential for maximal utilization of the producers' physiology leading to significantly enhanced production of lovastatin. As a result of continuous screening in the miniaturized cultures, lovastatin production levels of the 81% of the daughter cells derived from the high-yielding producers turned out to be in the range of 80%$\sim$120% of the lovastatin production level of the parallel flask cultures. These results demonstrate that the miniaturized cultivation method developed in this study is efficient high throughput system for large and rapid screening of highly stable and productive strains.

• Cartoon and Animation Studies
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• s.48
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• pp.359-383
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• 2017

3,000 years ago, since the first poster of humanity appeared in Egypt, the invention of printing technique and the development of civilization have accelerated the poster production technology. In keeping with this, the expression of poster has also been developed as an attempt to express artistic sensibility in a simple arrangement of characters, and now it has become an art form that has become a domain of professional designers. However, the technological development in the expression of poster is keep staying in two-dimensional, and is dependent on printing only that it is irrelevant to the change of ICT environment based on modern multimedia. Especially, among the many kinds of posters, the style of movie posters, which are the only objects for video, are still printed on paper, and many attempts have been made so far, but the movie industry still does not consider ICT integration at all. This study started with the feature that the object of the movie poster dealt with the video and attempted to introduce the augmented reality to apply the dynamic image of the movie to the static poster. In the graduation work of the media design major of a university in Korea, the poster of each works for promoting the visual work of the students was designed and printed in the form of a commercial film poster. Among them, 6 artworks that are considered to be suitable for augmented reality were selected and augmented reality was introduced and exhibited. Content that appears matched to the poster through the mobile device is reproduced on a poster of a scene of the video, but the text informations of the original poster are kept as they are, so that is able to build a moving poster looked like a wanted from the movie "Harry Potter". In order to produce this augmented reality poster, we applied augmented reality to posters of existing commercial films produced in two different formats, and found a way to increase the characteristics of AR contents. Through this, we were able to understand poster design suitable for AR representation, and technical expression for stable operation of augmented reality can be summarized in the matching process of augmented reality contents production.

• Korean Journal of Ecology and Environment
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• v.46 no.1
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• pp.33-40
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• 2013

From March 2012 to January 2013, this study was conducted as a part of the project for making a precise electronic ecological zoning map of vegetation on a highly reduced scale of 1 to 5,000 with a view to improving management efficiency of national parks and enlarging the availability of the data produced from the basic research monitoring the resources of national parks. For the research accuracy and rapidity, a vegetation map was specially created for the on-the-site-vegetation research. To make the map more meticulous, we categorized the vegetation database into five groups: broadleaved forest, coniferous forest, mixed forest, rock vegetation and miscellaneous one. After comparing the results of the data built for the vegetation research and the actual research findings, it was made clear that vegetation of both categories was almost the same in case of broad-leaved forest with 72.20% and 78.45% respectively, and also equivalent in other groups like, for example, coniferous forest (16.70%, 13.41%), mixed forest (9.50%, 7.49%) and rock vegetation (0.60%, 0.15%). According to the precise vegetation map produced from the research, the deciduous broad-leaved forest was the most widely prevalent type in the correlated hierarchical classification of vegetation, occupying 65.78% of the overall vegetation. It was followed by mountain valley forest (15.17%), coniferous forest (10.90%), and plantation forest (7.00%) in order. It is particularly noteworthy that Mt. Deogyusan national park has retained a very stable and versatile forest vegetation in the outstanding state since approximately 20% of the mountain turns out to belong to the I grade vegetation conservation classification which contains climax forests, unique vegetation, subalpine vegetation, matured stands which are older than 50 years and etc.

• Journal of the Korean Institute of Landscape Architecture
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• v.39 no.1
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• pp.11-21
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• 2011

In this paper, in order to select specialist butterfly species that inhabit Haneul and Noeul Parks, previously landfill areas, we verified the reciprocal relationships between nectar plants and butterflies. While we will design the butterfly habitats, this paper will provide the foundation data for selecting the plants. The completed survey indicated that there were a total of 5 families, 23 species and 1,129 individuals. Butterflies of the main action were feeding on nectar, and such behavior was 36% of the total actions. Therefore, these parks play an important role in butterflies feeding on nectar. The correlation between butterflies and the nectar plants' color was not significant; Therefore, it is not necessary to consider flower color when choosing plants to attract the butterflies. In addition, butterflies prefer naturalized plants for feeding on nectar. Thus, when creating butterfly habitats, there is no use in attracting the butterflies by classifying the naturalized plants and native plants. However, if some areas that are need to plant native plants such as Inkigofera pseudo-tinctoria, Lespedeza bicolor, Aster koraiensis make use it, there could be taken an advantage to attract the butterflies. According to the algebraic curve model of curve estimation regression analysis, we were able to classify the generalist species and specialist species by regression analysis. As a result, Colias erate, Artogeia rapae and Parnara guttata were classified as generalist species, where as Rapala caerulea, Pieris melete, Zizera maha and Celastrina argiolus were classified as specialist species. Rapala caerulea prefers hills and forest for its habitat; therefore, it is clearly distinct from Pieris melete, Zizera maha and Celastrina argiolus which prefer grassland for habitats. These results show that Rapala caerulea is high conservation value in a landfill area where is developing ecological succession from grasslands to wood lands. In conclusion, these research are able to contribute to select the target species and suitable species that consider a singularity between butterflies and nectar plants, when we are creating the butterfly habitats, moreover these research will contribute to maintain a stable habitats.

• Journal of the Korean Society of Floral Art and Design
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• no.44
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• pp.33-51
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• 2021

This thesis analyzes the formal characteristics of Dutch flower still life from the 17th century to the early 18th century and looks into the relevance with the Dutch art market from a macro perspective. The 17th Flower Still Life is to represent social hierarchy in that as the imported exotic, recherch items, the flowers were classified in the terms of their rarity and expensiveness. For this intriguing research, the subject is circumscribed to a vase of flowers, which is the quintessence of In the form of various Dutch Flower Still Life. Dutch society in the early 17th century was centered on the civilian class engaged in trade and commerce, which allowed them to purchase art works to show off their wealth, economic benefits and satisfaction of aesthetic tastes. Among them, the popularity of flower still life was related to the concentrated demand for rare flowers from the new continent. Accordingly, exact depiction and sense of the three dimensional manner were highly regarded in the early flower still life. For the tastes of the wealthy citizens who succeeded in business, the identity of flowers and the actual screen were considered as important. However, after the mid 17th century, economic growth in the Netherlands put an end, and the art market was also on a downward path. The demand class of flower still life has gotten farther away from the spirit of businessmen and has changed into city aristocrats who were stable rentiers. Their tastes laid emphasis on subjective sensibility, which meant that aristocratic, asymmetric, and dramatic chiaroscuro were preferred rather than being realistic. Furthermore, in the 18th century illusionistic realism was abandoned as an expression method of the planar characteristics and a new era in the floral still life was ushered with the reinforcement of decorative effect. From this perspective, it is not an exaggeration to say that romanticism, which is thought of as the beginning of Contemporary Art, originated from the aesthetic taste of Dutch civic culture.

• Journal of Intelligence and Information Systems
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• v.26 no.2
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• pp.105-129
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• 2020

This study uses corporate data from 2012 to 2018 when K-IFRS was applied in earnest to predict default risks. The data used in the analysis totaled 10,545 rows, consisting of 160 columns including 38 in the statement of financial position, 26 in the statement of comprehensive income, 11 in the statement of cash flows, and 76 in the index of financial ratios. Unlike most previous prior studies used the default event as the basis for learning about default risk, this study calculated default risk using the market capitalization and stock price volatility of each company based on the Merton model. Through this, it was able to solve the problem of data imbalance due to the scarcity of default events, which had been pointed out as the limitation of the existing methodology, and the problem of reflecting the difference in default risk that exists within ordinary companies. Because learning was conducted only by using corporate information available to unlisted companies, default risks of unlisted companies without stock price information can be appropriately derived. Through this, it can provide stable default risk assessment services to unlisted companies that are difficult to determine proper default risk with traditional credit rating models such as small and medium-sized companies and startups. Although there has been an active study of predicting corporate default risks using machine learning recently, model bias issues exist because most studies are making predictions based on a single model. Stable and reliable valuation methodology is required for the calculation of default risk, given that the entity's default risk information is very widely utilized in the market and the sensitivity to the difference in default risk is high. Also, Strict standards are also required for methods of calculation. The credit rating method stipulated by the Financial Services Commission in the Financial Investment Regulations calls for the preparation of evaluation methods, including verification of the adequacy of evaluation methods, in consideration of past statistical data and experiences on credit ratings and changes in future market conditions. This study allowed the reduction of individual models' bias by utilizing stacking ensemble techniques that synthesize various machine learning models. This allows us to capture complex nonlinear relationships between default risk and various corporate information and maximize the advantages of machine learning-based default risk prediction models that take less time to calculate. To calculate forecasts by sub model to be used as input data for the Stacking Ensemble model, training data were divided into seven pieces, and sub-models were trained in a divided set to produce forecasts. To compare the predictive power of the Stacking Ensemble model, Random Forest, MLP, and CNN models were trained with full training data, then the predictive power of each model was verified on the test set. The analysis showed that the Stacking Ensemble model exceeded the predictive power of the Random Forest model, which had the best performance on a single model. Next, to check for statistically significant differences between the Stacking Ensemble model and the forecasts for each individual model, the Pair between the Stacking Ensemble model and each individual model was constructed. Because the results of the Shapiro-wilk normality test also showed that all Pair did not follow normality, Using the nonparametric method wilcoxon rank sum test, we checked whether the two model forecasts that make up the Pair showed statistically significant differences. The analysis showed that the forecasts of the Staging Ensemble model showed statistically significant differences from those of the MLP model and CNN model. In addition, this study can provide a methodology that allows existing credit rating agencies to apply machine learning-based bankruptcy risk prediction methodologies, given that traditional credit rating models can also be reflected as sub-models to calculate the final default probability. Also, the Stacking Ensemble techniques proposed in this study can help design to meet the requirements of the Financial Investment Business Regulations through the combination of various sub-models. We hope that this research will be used as a resource to increase practical use by overcoming and improving the limitations of existing machine learning-based models.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.1-12
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• 2008

The purpose of this study is to characterize the hydrogeochemical characteristics of hot spring waters and to interpret the source of noble gases and the geochemical environment of the hot spring waters distributed along the eastern area of the Korean peninsula. For this purpose, We carried out the chemical, stable isotopic and noble gas isotopic analyses for eleven hot spring water and fourteen hot spring gas samples collected from six hot spring sites. The hot spring waters except the Osaek hot spring water show the pH range of 7.0 to 9.1. However, the Osaek $CO_2$-rich hot spring water shows a weak acid of pH 5.7. The temperature of hot spring waters in the study area ranges from $25.7^{\circ}C$ to $68.3^{\circ}C$. Electrical conductivity of hot spring waters varies widely from 202 to $7,130{\mu}S/cm$. High electrical conductivity (av., $3,890{\mu}S/sm$) by high Na and Cl contents of the Haeundae and the Dongrae hot spring waters indicates that the hot spring waters were mixed with seawater in the subsurface thermal system. The type of hot springs in the viewpoint of dissolved components can be grouped into three types: (1) alkaline Na-$HCO_3$ type including sulfur gas of the Osaek, Baekam, Dukgu and Chuksan hot springs, and (2) saline Na-Cl type of the Haeundae and Dongrae hot springs, and (3) weak acid $CO_2$-rich Na-$HCO_3$ type of Osaek hot spring. Tritium ratios of the Haeundae and the Dongrae hot springs indicate different residence time in their aquifers of older water of $0.0{\sim}0.3$ TU and younger water of $5.9{\sim}8.8$ TU. The ${\delta}^{18}O$ and ${\delta}D$ values of hot spring waters indicate that they originate from the meteoric water, and that the values also reflect a latitude effect according to their locations. $^3He/^4He$ ratios of the hot spring waters except Osaek $CO_2$-rich hot spring water range from $0.1{\times}10^{-6}$ to $1.1{\times}10^{-6}$ which are plotted above the mixing line between air and crustal components. It means that the He gas in hot spring waters was originated mainly from atmosphere and crust sources, and partly from mantle sources. The Osaek $CO_2$-rich hot spring water shows $3.3{\times}10^{-6}$ in $^3He/^4He$ ratio that is 2.4 times higher than those of atmosphere. It provides clearly a helium source from the deep mantle. $^{40}Ar/^{36}Ar$ ratios of hot spring water are in the range of an atmosphere source.