• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.5
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• pp.66-72
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• 1999

It is necessary to discuss lightening engine parts and reducing the friction of sliding parts to improve fuel consumption and combustion stability at idling condition. Lean best torque combustion which produce maximum power at a lean air-fuel ratio is effective for the reduction of exhaust gas emission and the improvement of fuel consumption. Accordingly, this study deals with the expansion of lean combustible limitation, the combustion stability and the reduction of idle speed through the analysis of combustion characteristics on the base of the control technique of precise air-fuel ratio because it does not need to maximum power at idling condition. The idle speed is increased proportional to ISC(Idle Speed Control) duty ratio. On the other hand the idle speed decreased by lean air-fuel ratio. The COV in engine speed is stable within maximum two percent up to 17.6 mixture ratio by the control of ISC duty ratio.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.1
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• pp.10-16
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• 2010

Mail centers are essential postal facilities that sort and dispatch postal items, and should be operated efficiently to provide customers high quality postal services. So the efficiency analysis of mail centers should be performed in order to induce better operation. But current performance evaluation system has 95 percent of predetermined and weighted non-quantitative indices. There is need to introduce objective efficiency measurement methodology. The main objectives of this study was to analyze the efficiency of 24 mail centers empirically using cone-ratio DEA and suggest the appropriate cone-ratio method. Consequently, this paper suggests that the cone-ratio DEA model integrating decision-maker's preferences is more desirable for efficiency analysis than that of using transformed data.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2000.11a
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• pp.135-143
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• 2000

This parer is the among educational environment, lighting's role is more important since it improves the visual tasks, capability of work, and it help to build both balanced mind and body. Also, since students need spend most of their time inside rather than outside, students need appropriate illuminance everyday. If optimum illuminance and distribution of luminance is properties controlled, people can decrease the fatigue of eyes, and also, people can maximize their efficiency of work. This present studying class chose of two school measured illuminance using the computer simulation improved ratio of luminance and luminance by distribution of lighting improve the economy and energy saving.

• Journal of Power System Engineering
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• v.18 no.5
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• pp.35-41
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• 2014

The wood pellet, which is one of the woody biomass energy, has very high economic efficiency and combustion efficiency during their combustion. The existing pellet burner have many problems such as low combustion efficiency, flame stabilization, ash problem and ignition time etc. We developed cyclonic wood pellet burner aim to 20,000kcal/hr boiler and measured temperature profiles and exhaust gases in order to investigate the flame stability and optimum combustion condition at any air flow conditions. As results, we confirmed the reappearance and the isotropy of the experimental results in the burner. At the first air flow inlet condition of excess air ratio ${\alpha}=0.02$, second air flow $490{\ell}/min$ had the best combustion condition when pellet supplied 30g. This result means that we need much air supply only for the swirling of second air flow. So we tested various second air flux at first air excess air ratio ${\alpha}=0.7$ condition. At this condition, we could find out that we don't need much second air and total air flux compared to the former condition. We will continuously test this work of air flow distribution, and swirl effect of first air flow, and ash elimination.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.1081-1084
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• 1999

This paper proposes a method of extracting automobile license plate information using color image processing and separation of character regions. The hue and saturation of color information is need for license plate extraction and the specified standard location ratio is need for character region separation. Simulation results show that the proposed algorithm can detect license plates and separate character regions successfully.

• Safety and Health at Work
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• v.13 no.1
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• pp.17-22
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• 2022

Background: This study aimed to identify work-related risk factors, including long working hours and night/shift work, for unmet health care need using data of a representative panel of Korean adults. Methods: Associations between work-related factors and unmet health care need were analyzed using data of 3,440 participants (10,320 observations) from the 2011-2013 Korean Health Panel Study. A generalized estimating equation was used for the analysis of repeated measures. Results: The prevalence of unmet health care was 16.6%. After adjusting sex, age, socioeconomic status, work characteristics, and working more than 60 hours per week (odds ratio [OR]: 1.43, 95% confidence interval [CI]: 1.23-1.65) or 50-59 hours per week (OR: 1.26, 95% CI: 1.08-1.46) instead of 40-49 hours per week and night/shift work (OR: 1.27, 95% CI: 1.06-1.51) were associated with unmet health care need. Conclusion: Long working hours and night/shift work are risk factors for unmet health care need among the Korean working population.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.82-83
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• 2008

In the cases of high speed railway bridge, dynamic behavior analysis is important because of high passing velocity and moving load at the regular intervals, and the damping ratio is a major element in dynamic behavior analysis. In this paper, damping ratios were estimated by two methods and vibration type sections, and relationship between estimated damping ratio and representative value of bridge vibration. At the results, estimated damping ratio using all time of vibration were more stable then using only free vibration section. And in the case of using extended Kalman filter, estimated damping ratio were trend of growth by growth of representative value of bridge vibration. At last, it was shown that study about reliabilities of estimated damping ratios were need.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.210-219
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• 1997

This research which lays emphasis on ready mixed concrete standard 25-210~240kgf/$\textrm{cm}^2$ shows the influence caused by the ratio of ingredients of superplasticized concrete, and the flowing and strength development of mortar and concrete according to the ratio of ingredients. This research shows that flowability, compactability, and segregation resistivity are the best condition under the following ratio of ingredients: fly ash 30%, unit binders 490~510kg/$\textrm{m}^3$, unit weight of water 184~194kg/$\textrm{m}^3$, fine aggregate ratio 49~51%, and superplasticizer 1.1~1.5%. Following this ratio of ingredients, the reinforced concrete structures to need design strength 25-210~240kgf/$\textrm{cm}^2$ can apply to complicated constructions.

• Journal of Ecology and Environment
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• v.30 no.3
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• pp.277-280
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• 2007

Social spiders consistently show highly female-biased sex ratios. However, the sex ratio of subsocial spiders, which have been suggested as an intermediate stage of the evolutionary pathway towards permanent sociality, is generally unknown. We investigated the sex ratio and approximate date of fertilization of the subsocial spider, Amaurobius ferox Walckenaer (Araneae: Amaurobiidae). Investigation over 2 years revealed that sex ratio of A. ferox was consistent across years and averaged 0.49. By early May $(1^{st}{\sim}10^{th})$, 66.6% of female A. ferox observed in the field had already been inseminated, and by late May $(21^{st}{\sim}31^{th})$, 95.4% of females had been inseminated. This result suggests that A. ferox need a long time or cold temperatures to prepare them for reproduction after the developmental attainment of the adult stage.

• Journal of the Korean Society for Railway
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• v.4 no.1
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• pp.23-30
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• 2001

The dynamic characteristics such as natural frequency, mode shape and damping ratio are most important parameters in the high-speed railway bridges rather than general roadway bridges. Also, the need to know the dynamic behavior of bridges greatly increased in recent years. In the early of 1990s, to design the high-speed railway bridges, damping ratio recommended in general code was 2.5～7.5%. However, these values were not applied in all cases. Therefore, obtaining the damping value of specific structures is important to get the correct variable for design of high-speed railway bridges. The purpose of this study is mainly to obtain the damping ratio of high-speed railway bridges. The average damping ratio of high-speed railway bridges evaluated from a field test is about 2.4%.