• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.129-137
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• 2000

In the prototype stage of a car developing program, the efficiency of trouble shooting is an important factor to be considered. Structural modifications by the design sensitivity analysis are applied to a steering wheel system for improving the idle vibration of the prototype passenger car. For the design sensitivity analysis, the experimental modal analysis for the steering system attached to a body-in-white is fulfilled and the modal parameters extracted from the experimental data are used to predict the effect of structural modification, The design sensitivity results rank the locations to be reinforced in terms of frequency variation. The modification of steering system according to the sensitivity analysis results shifted the resonant frequency of the system effectively. In addition, the idle test of the car after the structural modifications f steering system shows that the proposed method can reduce vibration of the steering wheel efficiently.

• Korean Journal of Agricultural Science
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• v.43 no.1
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• pp.127-135
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• 2016

Improving farming activity competence of farm households has recently been considered one of the most important factors for increasing farm income. However, few studies examine the relationship between farm income and farming activity competence of farm households directly due to the lack of an available dataset. In this study, we examine the relationship between farm household technical managerial competence and farm household income based on the nearly 30,000 farm households consulting data gathered by the Rural Development Administration, RDA. The major findings of this study are as follows: firstly, statistically significant differences in agricultural and farm household income exist between farm households categorized by farm activity competence levels in terms of technique and management. Secondly, a technically and managerially competent farm household group (high-rank farm household) has 2.2 times higher agricultural income and 1.9 times higher farm household income than the technically and managerially incompetent farm household group (low-rank farm household). Thirdly, farm household technical-managerial competence is one of the major factors that affect agricultural and farm household income. Regarding technical competence, agricultural income and farm household income increased by approximately 1,390,000 won and 1,530,000 won, respectively, as technical points increased by one point. However, with respect to managerial competence, agricultural income and farm household income increased by approximately 1,320,000 won and 2,070,000 won, respectively, as managerial points increased by one point.

• Journal of the Korean Operations Research and Management Science Society
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• v.42 no.3
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• pp.35-49
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• 2017

The main objective of this paper is to empirically analyze the efficiency effects of mergers on Korean pharmaceutical firms and suggests managerial or policy implications for managers or policy makers. This study selects non-merging control firms close to the size of merging firms, as well as a set of merging firms, and measures the effects of mergers on efficiency three years before and after the merger using the non-parametric data envelopment analysis (DEA) method. To compare the differences of efficiency means among several groups, Wilcoxon rank sum test or Wilcoxon signed rank test is used. It showed that the long-term effects after the merger appeared partially. Furthermore, it was observed that there was no difference statistically in the efficiency between merging and non-merging firms. Also, there was no difference statistically in the efficiency between the pre- and post-merger periods. In conclusion, there was not any observed synergy effect through group (or affiliated) mergers between affiliates or related mergers for Korean pharmaceutical firms.

• Asia pacific journal of information systems
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• v.25 no.4
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• pp.686-711
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• 2015

The performance of a novel medical question-answering engine called CliniCluster and existing search engines, such as CQA-1.0, Google, and Google Scholar, was evaluated using known-item searching. Known-item searching is a document that has been critically appraised to be highly relevant to a therapy question. Results show that, using CliniCluster, known-items were retrieved on average at rank 2 ($MRR@10{\approx}0.50$), and most of the known-items could be identified from the top-10 document lists. In response to ill-defined questions, the known-items were ranked lower by CliniCluster and CQA-1.0, whereas for Google and Google Scholar, significant difference in ranking was not found between well- and ill-defined questions. Less than 40% of the known-items could be identified from the top-10 documents retrieved by CQA-1.0, Google, and Google Scholar. An analysis of the top-ranked documents by strength of evidence revealed that CliniCluster outperformed other search engines by providing a higher number of recent publications with the highest study design. In conclusion, the overall results support the use of CliniCluster in answering therapy questions by ranking highly relevant documents in the top positions of the search results.

• Journal of the Korean Society of Combustion
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• v.14 no.3
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• pp.16-23
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• 2009

It is strongly desired for coal-fired power plants to utilize not only low-rank coals with high moisture contents, but also lowering cost with diversifying fuel sources. In this study, combustion characteristics of low rank coal with high moisture, and standard pulverized coals are experimentally investigated using TGA (Thermogravimetric Analysis) and DTF (drop tube furnace). The coals tested are three kinds of coal with moisture content ranging from 8.32 to 26.82%. The results show that under the air combustion condition, the burn-out time at TGA rises as moisture content increases, and standard pulverized coal with 8.32% moisture content showed the lowest activation energy of 55.73 kJ/mol. In case of the high amount of moisture, the combustion efficiency decreases due to evaporation heat loss, and unburned carbon in ash produced at combustion process in DTF increased. Aslo, initial deformation temperature of slag attached in alumina tube of DTF decreased with lowering the crytallinity of anorthite and augite. To improve the combustion reactivity and efficiency, it is effective to upgrade through drying the high moisture coal to moisture level (less than 10%) of standard pulverized coal.

• Journal of Power System Engineering
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• v.19 no.1
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• pp.56-63
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• 2015

In this study, the exhaust characteristics of the diesel engine for the change of the mixing ratio of biodiesel fuel were quantitatively analyzed by using the numerical analysis method. As the fuel used in the experiment, the diesel and biodiesel(waste oil, soybean oil), the mixed fuel BD2(Diesel only), BD3, BD5, BD20, BD50 and BD100 were used. The injection pressure($p_{inj}$) was set to 400bar, 600bar, 800bar, 1000bar and 1200bar as the experimental variable. Also the concept of the standard deviation, Pearson's correlation coefficient and Spearman rank-order correlation coefficient based on the statistics was introduced in order to analyze the exhaust characteristics of the quantitative NOx and Soot according to the injection pressure and the mixing ratio variation of biodiesel blending fuel. It is considered that as a result of studies, for the waste oil, NOx and Soot can be simultaneously reduced through control of the mixing ratio at the regions of $p_{inj}=400bar$ and $p_{inj}=600bar$, and the Soot can be reduced without affecting on the emission of NOx at more than $p_{inj}=800bar$. For the soybean oil, NOx and Soot can be simultaneously reduced at $p_{inj}=400bar$ and the Soot can be reduced without affecting on the emission of NOx at $p_{inj}=600bar$.

• Journal of the Korean Society of Costume
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• v.64 no.7
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• pp.143-155
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• 2014

This study focuses on Yusam, a military raincoat that was worn during the Joseon Dynasty. The purpose of this study is to review the types and management system of Yusam. Documentary records, paintings and relics were used as research materials. Yusam was recorded as either Yusam(油衫) or Yu-ui(油衣) in writing. It usually looked like a skirt and was worn like a cape, but there were differences in length. Some of them took the form of a short coat with half-sleeves and side slits. Research analysis results of Silrok, Ilseongrok and the archives of the military camp in the later Joseon are as follows: First, Mokyusam and Jiyusam coexisted as military raincoats. Mokyusam was made with cotton and perilla oil, while Jiyusam was made with traditional Korean paper, a cotton edging and perilla oil. Second, the differences between general Yusam and military Yusam include the material of the clothing, the materials for waterproofing, the color, and the manufacturer. Third, each military camp supplied soldiers with hundreds to thousands of Yusam. Military officers and King's guards wore Mokyusam because Mokyusam was higher than Jiyusam. Fourth, soldiers Yusam together with Yujeongeon, Chorip, Galmo, or Hwihang as a hat. Fifth, the higher the rank, the higher the price of Yusam and the longer the term of usage. On the other hand, as the rank got higher, the cost of the supplementary oil rose, while the duration of usage got shorter.

• IE interfaces
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• v.24 no.3
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• pp.220-230
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• 2011

The multi-reservoir operation problem for efficient utilization of water resources involves conflicting objectives, and the problem can be solved by varying weight coefficient on objective functions. Accordingly, decision makers need to choose appropriate weight coefficients balancing the trade-offs among multiple objectives. Although the appropriateness of the weight coefficients may depend on the total amount of water inflow, reservoir operating policy may not be changed to a certain degree for different hydrological conditions on inflow. Therefore, we propose to use fuzzy Data Envelopment Analysis (DEA) to rank the weight coefficients in consideration of the inflow variation. In this approach, we generate a set of Paretooptimal solutions by applying different weight coefficients on Coordinated Multi-reservoir Operating Model. Then, we rank the Pareto-optimal solutions or the corresponding weight coefficients by using Fuzzy DEA model. With the proposed approach, we can suggest the best weight coefficients that can produce the appropriate Pareto-optimal solution considering the uncertainty of inflow, whereas the general DEA model cannot pinpoint the best weight coefficients.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.790-805
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• 1988

Static strength and fatigue life scattering of glass fiber reinforced epoxy composite materials has been studied. Normal, lognormal, two-parameter and three-parameter Weibull distribution functions are used for strength and one-stress fatigue life distribution. The value of mean fatigue life is analysed using mean fatigue life, mean log fatigue life and expected value of 2 and 3-parameter Weibull distribution functions. Modification on non-statistical cumulative damage models is made in order to interpret the result of two-stress level fatigue life scattering. The comparison results show that 3-parameter Weibull distribution has better predictions in static strength and one-stress level fatigue life distributions. However, no advantage of 3-parameter Weibll distribution is found over 2-parameter Weibull distribution in two-stress level fatigue life predictions. It is found that two-stress level fatigue life prediction by the expanded equal rank assumption is close to the experimental data.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.3
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• pp.357-365
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• 2004

Effect of artificial circulation on amelioration of water quality in Yeoncho Lake was analyzed using summer data between 1991-2002. Two sites, intake tower area where aeration systems are concentrated in and near the inlet of reservoir were selected for comparison in this study. Summer averages between may and september Showed that aeration system might be beneficial in the improvement of water quality of BOD5, COD, and TN while Chl-a concentration and transparency did show opposite pattems. Wilcoxon's singed rank test for matched pair indicated slight increase of BOD5 and COD concentrations in the vicinity of intake tower while other variables did not show any significant differences from data of inlet of reservoir. During the study, it was found that the following subjects need to be investigated for more detailed analysis. 1) Dynamic pollutant loading from outside and inside the lake, 2) Biological, Chemical and Physical lake data when aeration systems are in and not in operation and 3) Radius of influence of aeration system.