• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.306-309
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• 2009

Concern for new and renewable energy is growing globally. Biogas is one of the alternative fuels and consists of methane and carbon dioxide. It is difficult to achieve efficient engine operation due to a lower heating value of biogas compared to that of natural gas. In order to improve generating efficiency, finding an optimum point of ignition timing and excess air ratio is important. From this fact, generating efficiency and pollutant emissions of 2300cc gas engine generator operated by biogas as functions of ignition timings and excess air ratios were investigated in this study. As a test result, the generating efficiency of the gas engine generator using biogas was 27.34 % in the condition of the BTDC of $16^{\circ}$ and the excess air ratio of 1.4.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.6
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• pp.617-623
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• 2014

The rapid urbanization in developing countries has caused trasportation problems that need to be solved. For that reason, the study evaluates the potential of cycling in the densely populated part of Kathmandu valley. Slopes and existing roads have been applied as the input cost rasters for finding the shortest cost routes between stations. By taking the average cycling velocity, time to travel from station to destination were compared with the average commuting time in the public transportation. The result comes out as similar time with the public transportation. Although the cycling seems potential replacement for public transportation commuters, in fact, there are some setbacks needed to be supported by the government to make it reality in future.

• The Journal of Information Technology and Database
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• v.4 no.2
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• pp.21-32
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• 1998

A primary concern of physical database design has been efficient retrieval and update of a record because predictable performance of a DBMS is indispensable to time-critical missions. To maintain such phenomenal performance, database manages often spends more than or as much as the goal of an organization can warrant. The motivation of this research stems from the fact that even predictable performance of a physical database can be hampered by stochastic query processing time, physical configurations of a database, and random arrival processes of queries. They all together affect the overall performance of a DBMS. In particular, if there are queuing delays due to limited capacity or during on-peak congestion, this paper suggest to prioritize database services. A surprising finding of this paper is that such a transition from a non-priority system to a corresponding priority-based system can be Pareto-improving in the sense that no users in the system will be worse off after the transition. Thus prioritizing database services can be a viable option for efficient database management.

• KDI Journal of Economic Policy
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• v.40 no.3
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• pp.45-68
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• 2018

We uncover a nexus between actual inflation, inflation perceptions and expectations in Korea through analyzing micro as well as aggregate data from the Consumer Survey. We document two novel findings. First, households' subjective perceptions of inflation exert more impact on expectation formation than actual inflation. Second, inflation perceptions are broadly in line with the trajectory of the inflation trend. This is attributable to the fact that changes in actual inflation have been generated mainly by the consumption items whose price changes are perceived more sensitively as those items are frequently bought or have a larger share in household expenditures. Conducting a cross-country comparison, we find that information rigidity in expectation formation process and the nexus between perceptions and expectations of inflation prove to be stronger in Korea. Additionally, we reconfirm the existing finding that the scope of information utilized for forming inflation expectations is fairly circumscribed.

• Proceedings of the Korean Magnestics Society Conference
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• 2013.12a
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• pp.32-32
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• 2013

Using the Vienna ab initio simulation package (VASP) incorporating van der Waals interaction, we have explored structural, adsorption, and magnetic properties of Ni(111)/BN/Co(111) systems. We have found that both Ni(111) and Co(111) layers shows half metallic state, while the spacer BN layer becomes weak metal for one monolayer (ML) thickness and an insulating barrier for two ML thickness. The half metallic states in both Ni(111) and Co(111) layers are robust because it is unchanged independently on the magnetic coupling of Ni(111) and Co(111). This finding suggests that the Ni(111)/BN/Co(111) systems can be utilized for perfect tunneling magnetoresistance system. Moreover, it can be applied for potential spin injecting into semiconductor in FM/semiconductor system due to the fact that the half metallic state in FM layers at the interface will be unchanged.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.4
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• pp.235-243
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• 2012

The Voronoi diagram of spheres and power diagram have been known as powerful tools to analyze spatial characteristics of weighted points, and these structures have variety range of applications including molecular spatial structure analysis, location based optimization, architectural design, etc. Due to the fact that both diagrams are based on different distance metrics, one has better usability than another depending on application problems. In this paper, we compare these diagrams in various situations from the user's viewpoint, and show the Voronoi diagram of spheres is more effective in the problems based on the Euclidean distance metric such as nearest neighbor search, path bottleneck locating, and internal void finding.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2250-2257
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• 2008

This study examined the existing issues and current status of how to best approach the establishment of railroad asset of the corporation in the long run. It also explored some preventative measures for further problems. Based on the law of state property and related railroad statutes, the research referred to basic plans for railroad management of Korea Rail Network Authority, the outcome of file research, handbook of asset management, guidelines and policy of Ministry of Finance and Economy for state property management, recommendations of the Board of Audit and Inspection and fact-finding research of state property (miscellaneous properties). The findings are making a few suggestions on the service of the Korea Rail Network Authority and Korail.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.4
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• pp.389-395
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• 2008

It is very well known that the natural frequency of an oscillating body on the free surface is determinable only after the added mass is given. However, it is hard to find analytical investigations in which actually the natural frequency is obtained. Difficulties arise from the fact that in order to determine the natural frequency we need to compute the added mass at least for a range of frequencies, and to solve an equation where the frequency is a variable. In this study, first, a formula is obtained for the added mass, and then an equation for finding the natural frequency is defined and solved by Newton's iteration. It is confirmed that the formula shows a good agreement with the results given by Ursell(1949), and the value of natural frequency is reduced by 21.5% compared to the pre-natural frequency, which is obtained without considering the effect of added mass.

• International Journal of Contents
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• v.5 no.3
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• pp.1-7
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• 2009

The importance and the value of call center callers are increasing since they play very crucial roles as representatives of their companies at the closest contact point with customers. However, they have low satisfaction at work and are more likely to leave their jobs due to the fact that they are exhausted from heavy work load; they provide less pay and less chance for promotion than other jobs in the same industry. The high turnover costs companies high expenses on finding and training new callers. In the mean time, customer satisfaction may drop and it can give the customers negative image of the company. Therefore, solutions are required to keep the turnover of call center callers to the minimum. In this study, call center employees in Gwangju area were investigated for their job attitude and turnover intention. Based on the results, several implications are suggested.

• Proceedings of the Ginseng society Conference
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• 1998.06a
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• pp.263-269
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• 1998

It is an established fact that most of the carcinogens implicate bay-region diol epoxides as the ultimate carcinogenic metabolites. These electrophiles react with nucleophilic sites in the cells to form abducts. It is the formation of carcinogenic-DNA adducts that is thought to initiate carcinogenesis. In our previous study we have reported chemopreventive property of Ginseng on 7,12-dimethylbenz (a)anthracene (DMBA) induced skin papillomagenesis in male Swiss albino mice. In this study we have examined the effect on formation of DMBA-DNA adducts in rat hepatocytes pretreated with ginseng. Primary cultures of rat hepatocytes were used. The cells wets treated with ginseng for 24 hrs and then with DMBA (iOn) for 18 hrs. Cells were then harvested, their DNA was isolated and analyzed by P)2 labelling. A significant reduction in the levels of DMBA-DNA adduces (adducts/108 nucleotides) was observed in all cultures pretreated with ginseng. The viability of cells was not affected by pre-treatment with ginseng. Our finding suggests that ginseng block or suppresses the events associated with chemical carcinogenesis by inhibiting metabolic activation of the carcinogens.