• Sleep Medicine and Psychophysiology
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• v.1 no.2
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• pp.163-171
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• 1994

Objectives: Symptoms of sleep apnea consisted of insomnia, excessive sleepiness during daytime, impaired cognitive functions and emotional disturbances. It was not so well known how these symptoms are correlated with various parameters of sleep and respiration, and what kind of psychophysiological processes are involved in development of these symptoms. Methods: In sixty patients with sleep apnea, sleep and respiration were studied by polysomnography of one night, also symptoms of sleep apnea were evaluated with the scales of insomnia, daytime sleepiness, emotional disturbance and cognitive impairment We studied correlations between apnea symptoms, and various parameters of sleep and respiration such as sleep efficiency, number severity of apnea, $O_2$ desaturation and number of snoring. Results: The result showing significant correlations are as follows. The patients with better sleep in insomnia scale showed more number of apnea, particularly more central type, and much more snoring in stage 3 sleep and mild desaturation of $O_2$. Excessive sleepiness during daytime correlated significantly with stage 1 sleep and its snoring, but correlated negatively with stage 2 sleep. However, no significant correlation was found with degree of $O_2$ desaturation. Emotional disturbance was more apparent in the patients with severe $O_2$ desaturation and smaller amounts of stage 4 sleep. Cognitive function was more impaired in cases of more REM sleep and less apnea. Conclusions: Symptoms of sleep apnea may occur through different causes and processes. The evaluation of apnea symptoms may be helpful to understand in some degree the condition of sleep and respiration during sleep in clinical setting.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.189-200
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• 2022

In today's digital world, smartphones and web-based applications have gained remarkable importance throughout the globe. These smart applications are playing a very significant role in maintaining a powerful business. As well as, they are helping a lot to expand these businesses via social networks. Social media networks such as Instagram, Facebook, Twitter, and LinkedIn are playing a prominent role to promote the companies. In the hospitality sector, most of the companies are running their hotel booking systems by utilizing mobile applications and a web-based infrastructure, but usability issues still exist. This study has been conducted specifically to tackle the usability issues of hotel booking systems and the best utilization of social networks to promote the business. TripAdvisor was selected as an authentic source for selecting those systems and two international hotels are selected for this study. The first step is to identify different hotel booking systems. In the second step, the user's satisfaction level was measured for the selected systems by performing the System Usability Scale (SUS, Quick & Dirty) approach. Additionally, by which source (social media or personal relations) they found these hotels. It is found that the SUS rating for both systems is below the acceptable level of usability. The Mean SUS for hotel 1 is found at 55.25 and 51.2 for hotel 2. The third step was to identify the user interface (UI) issues, and heuristic evaluation is performed for this. The experts identified the UI issues on the basis of their experience. The major issues were related to the visibility of system status, error prevention, flexibility and efficiency of use. Depending upon the identified issues, an interactive UI (prototype) for the selected web-based applications was proposed. This prototype is mainly based on the user's perspective. This prototype can be used for improving the UI of the selected systems which is based on the user's perspective. During the process of verifying the satisfaction level, it is revealed that the targeted audience is not able to use these systems efficiently and effectively. The reason behind this is the negligence of usability guidelines throughout the process of design and development of these hotel booking systems. Therefore, it is highly recommended that the usability of these systems should be evaluated and redesigned, based on expert opinions. It has also been observed that the reviews/ feedback of customers has spread a negative impact through social networks.

• Journal of Korean Society on Water Environment
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• v.24 no.2
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• pp.147-155
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• 2008

Because of increased nonpoint source runoff potential at highland agricultural fields of Kangwon province, effective agricultural management practices are required to reduce the inflow of sediment and other nonpoint source pollutants into the water bodies. The watershed-scale model, Soil and Water Assessment Tool (SWAT), model has been used worldwide for developing effective watershed management. However, the SWAT model simulated sediment values are significantly affected by the number of subwatershed delineated. This result indicates that the SWAT estimated watershed characteristics from the watershed delineation process affects the soil erosion and sediment behaviors. However, most SWAT users do not spend time and efforts to analyze variations in sediment estimation due to watershed delineation with various threshold value although topography falsification affecting soil erosion process can be caused with watershed delineation processes. The SWAT model estimates the field slope length of Hydrologic Response Unit (HRU) based on average slope of subwatershed within the watershed. Thus the SWAT ArcView GIS Patch, developed by using the regression relationship between average watershed slope and field slope length, was utilized in this study to compare the simulated sediment from various watershed delineation scenarios. Four watershed delineation scenarios were made with various threshold values (700 ha, 300 ha, 100 ha, and 75 ha) and the SWAT estimated flow and sediment values were compared with and without applying the SWAT ArcView GIS Patch. With the SWAT ArcView GIS Patch applied, the simulated flow values are almost same irrespective of the number of subwatershed delineated while the simulated flow values changes to some extent without the SWAT ArcView GIS Patch applied. However when the SWAT ArcView GIS Patch applied, the simulated sediment values vary 9.7% to 29.8% with four watershed delineation scenarios, while the simulated sediment values vary 0.5% to 126.6% without SWAT ArcView GIS applied. As shown, the SWAT estimated flow and sediment values are not affected by the number of watershed delineation significant compared with the estimated flow and sediment value without applying the SWAT ArcView GIS Patch.

• Journal of the Economic Geographical Society of Korea
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• v.24 no.3
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• pp.313-329
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• 2021

This study analyzed the characteristics of the management crisis, the level of resilience, and the alternatives based on the companies' self-evaluation of the game industry in Daegu. The Daegu game industry, which started spontaneously in the late 1990s, grew rapidly until the late 2000s with the support of the government and supporting organizations. However, from the mid-2010s, it has entered a period of recession due to the number of companies that failed to respond to the saturation of the mobile game market and fierce competition at home and abroad. In response, some game companies turned the crisis into an opportunity to strengthen their competitiveness by pursuing challenging strategies for product differentiation and pioneering new markets. On the other hand, companies that were passive in responding to the crisis have not get out of the management crisis. In addition, in terms of the resilience level of game companies in Daegu, the level of immediate response to shock(rapidity) and replacement of the damaged part(redundancy) was low, but the level of mobilizing sufficient resources internally(resourcefulness) was high. However, as the Daegu game industry is facing more complex multi-spatial-scale environmental changes than in the past, its resilience should be strengthened through strategies that can compensate for weaknesses in terms of the game industry ecosystem beyond individual company-level efforts.

• Journal of the Korean Geotechnical Society
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• v.21 no.4
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• pp.99-114
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• 2005

In Part I of this paper, a conceptual approach of the stress path method was newly proposed for a rational estimation of settlements of saturated clay deposits. A detailed procedure for effective evaluation and use of settlement-related characteristic deformation behaviors was developed in order to provide practicality to the new approach. In this Part II, on the basis of the results of Part 1, the concept of the new approach was embodied in the form of a detailed settlement estimation procedure. The applicability and usefulness of the new procedure were strongly supported by various application examples. In addition, possible errors of other conventional settlement estimation methods were investigated by comparing with the new procedure. Because of its flexible applicability for wide range of field conditions, the new procedure will have great usefulness in the practical side. For example, a reasonable foundation design based on allowable settlement criteria can be easily performed and modification of design factors can be readily reflected even during the subsequent construction stage. Especially, the new procedure will be of great use for preliminary work in a large scale construction site where various structures are planned to be constructed on a nearly identical ground condition.

• Journal of the Economic Geographical Society of Korea
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• v.6 no.2
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• pp.403-419
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• 2003

Busan Port, Korea, is a region that must take integrated measures against problems such as the excessive handling of cargo volume, the intensification of port congestion, and the construction of a new port to improve port competitive power. In particular, if a great deal of function in the existing area of Busan Port transfers to a new port, then the problems of port redevelopment will occur as shown in the cases of port developed countries explained hereafter. For Korean ports, port redevelopment in a port zone is implemented for improving the port productivity that targets a local area, but the entire and systematic port redevelopment is not accounted for. Focused on this point, the paper is to present the directions for full-scale port redevelopment of the existing zone of Busan Port. The findings are as follows: First, the region of Busan is divided according to a regional classification that is necessary for port redevelopment. Thereby, 4 zones, total 26 regions of redevelopment were selected. Second, overseas case studies were considered for port redevelopment. From these same studies, appropriate types of port development in Korea were extracted and presented. Third, the status and problems of the selected redevelopment regions were analyzed, and types of port redevelopment were assigned. This study was not applied to the strict evaluation technique by quantitative analysis, but the concept and directions for unprecedented port redevelopment were first defined and established. It is significant to select target areas for redevelopment by regional classification and present directions for developing each region by choosing Busan Port as a real case study. This initiation will greatly contribute to the succeeding study.

• Journal of Korean Society of Transportation
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• v.21 no.5
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• pp.7-18
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• 2003

Due to the changes of shipping and logistic environment, Asian ports today face severe competition. To be a mega-hub port, Asian ports have achieved a big scale development. For these reasons, it has been widely recognized as an important study to analyze and evaluate characteristics of Asian ports, from the standpoint of Korea where Busan Port is located. Although some previous studies have been reported, most of them have been beyond the scope of Asian ports and analyzed the world's major ports; moreover, the studied ports have been about the ports which are well known from the previous research and reports. So, most studies is unlikely to be used as substantial indicators from the perspective of Busan Port. In addition. most of the existing studies have used hierarchical evaluation algorithm for port ranking, such as AHP (analytical hierarchy process) and clustering analysis. However, these two methods have fundamental weaknesses from the algorithm perspective. The aim of this study is to classify major Asian ports based on competitiveness level. Especially. in order to overcome serious problem of the existing studies, major Asian ports were analyzed by using objective indicators. and Fuzzy C-Means algorithm, which alleviates the weakness of the clustering method. It was found that 10 ports of 16 major Asian ports have their own phases and were classified into 4 port groups. This result implies that some ports have higher potential as ports to lead some zones in Asia. Based on those results. present status and future direction of Busan port were discussed as well.

• Journal of the Korean Geotechnical Society
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• v.29 no.1
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• pp.93-107
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• 2013

Thermal conduction of the particulate composites or granular materials can be widely used in porous materials and geotechnical engineering. And it has continued to develop "effective thermal conductivity" of medium by modeling energy relationship among particles in medium. This study focuses on the development of the effective thermal conductivity at the unsaturated conditions of soils using the modified network model approach assisted by synthetic 3D random packed systems (DEM method, Discrete Element Method) at the particle scale. To verify the network model, three kinds of glass beads and the Jumunjin sand are used to obtain experimental values at various unsaturated conditions. The PPE (Pressure Plate Extractor) test is then performed to obtain SWCC (Soil-Water Characteristic Curve) of soil samples. In the modified network model, SWCC is used to adjust the equivalent radius of thermal cylinder at contact area between particles. And cutoff range parameter to define the effective zone is also adjusted according to the SWCC at given conditions. From a series of laboratory tests and the proposed network model, the modified network model which adopts a SWCC shows a good agreement in modeling thermal conductivity of granular soils at given conditions. And an empirical correlation between the fraction of the mean radius (${\chi}$) and thermal conductivity at given saturated condition is provided, which can be used to expect thermal conductivity of the granular soils, to estimate thermal conductivity of granular soils.

• Fire Science and Engineering
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• v.32 no.1
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• pp.89-98
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• 2018

Fire accidents in foreign countries, like the accident in a thermal power plant in Beijing, the accidents in domestic power plants, including Boryeong Power Plant in 2012 and Taean Power Plant in 2016, a disaster in a nuclear power plant in Fukushima in 2011 or the large-scale power failure in California in 2001 are safety accidents related to electric power, which caused losses in the people's stable lives and the countries. Electricity has an absolute impact on the people's life and the economy, so we can easily expect the serious situation affecting economic growth as well as direct damage to the protection of the people's lives and the losses of properties, if there are fire or explosion accidents or radioactive leak because of negligence in safety management, or problems because of natural disasters like an earthquake in power plants that generate electricity. In this study, it was drawn the improvement of the organizations exclusively in charge of firefighting, the operation of a program for the improvement of professional competency, the development of a customized firefighting management system for plants for systematic firefighting safety management and the improvement of the earthquake-proof correspondence system, which has recently become an issue, as measures for improvements through a survey of the actual conditions concerning the necessity of the construction of a firefighting safety management system for power plants with five power generation companies, including Korea Southern Power Co., Ltd., and the persons in charge of firefighting safety Korea Hydro & Nuclear Power Co., Ltd.

• Korean Journal of Environment and Ecology
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• v.27 no.5
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• pp.642-649
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• 2013

This study evaluated the efficacy of information and self-interpretive media that provide information on park environment using self-administered visitor survey to the Dadohaehaesang National Park, Korea. Excluding missing and unreliable responses, 205 valid responses were used for the analysis. Socioeconomic status and visiting behavior of the visitors to the Dadohaehaesang National Park were similar to those to other Korean national parks. Results showed that, of the self-interpretive media, 'Information board of park use and resources' were most frequently used (87.7%), followed by 'Interpretive label of woody plant,' and 'Bulletin boards for information and enlightenment.' 'Guided interpretation' was used less than 40% of the visitors. Visitors also highly rated the importance of the media (higher than 4.0 on average out of 5 point Liker scale question). The average performance rate was 3.82, suggesting that visitors were satisfied on the self-interpretive media. Visitors responded that 'Information board of park use and resources' and 'Bulletin boards for information and enlightenment' were not useful and, therefore, should be amended and managed to improve the self-interpretability of the media.