• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.561-566
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• 2014

Our Korean traditional cultural inheritance Bangpae Kite has the stable rectangular shield shape decorated with artistic paint or poem and a good flight performance due to the central wind hole. In this paper, to analyse the wind hole effect to kite performance we performed the wind tunnel testing of the various design factor of kite model and air flow visualization passing through the wind hole. As the result of aerodynamic analysis, we knew that the wind hole of kite displays similar function of slot system for the wing high lift device. This fact demonstrates that our ancestor understood the function of slot system and applied effectively to the development of kite flight performance.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.87-91
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• 1997

Ecological stability of the Lake Shihwa, artificially made by the construction of the Shihwa Dike, was evaluated by the species composition and variation in biomass of zooplankton. Species composition and seasonal variation in biomass in the seaside stations were similar to those observed in nearby bays and coastal zone. However, those in the lake sites showed very different patterns. The brackish water copepod, Sinocaianus tenellus, held the first rank in every season (with more than 66% in spring, 98% in summer and fall, and 80% in winter). The species composition was very simple and the biomass (in terms of total individuals $m^{-3}$) varied markedly with season up to the order of $10^4$ magnitude. These results imply that the lake ecosystem made by the construction of Sihwa dike is in very unstable stage probably due to the input of industrial wastes as well as unpredictable variation in salt content caused by irregular control of the watergate of the dike and resultant irregular flow direction of the water through the gate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.11
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• pp.1599-1607
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• 2022

The data mainly used for the model are as follows: the personal information, the information of insurance product, etc. With the data, we suggest three types of models: content-based filtering model, collaborative filtering model and classification models-based model. The content-based filtering model finds the cosine of the angle between the users and items, and recommends items based on the cosine similarity; however, before finding the cosine similarity, we divide into several groups by their features. Segmentation is executed by K-means clustering algorithm and manually operated algorithm. The collaborative filtering model uses interactions that users have with items. The classification models-based model uses decision tree and random forest classifier to recommend items. According to the results of the research, the contents-based filtering model provides the best result. Since the model recommends the item based on the demographic and user features, it indicates that demographic and user features are keys to offer more appropriate items.

• The Korean Journal of Food And Nutrition
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• v.30 no.2
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• pp.218-225
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• 2017

This study was carried out to compare the cooked and antioxidant characteristics with of cooked mixed grain rice with an addition rate (0, 5, 10, 15 and 20%) of proso millet and various cooking methods. Mixed grain rice with added proso millet was cooked by general and high pressure cooking methods with and without fermented alcohol. All pasting characteristics, except for breakdown viscosity, decreased with increasing the amounts of proso millet. Water binding capacity and swelling power significantly decreased when increasing the amounts of proso millet, however the water solubility index significantly increased. The palatability characteristics of rice with added proso millet showed similar results to rice without proso millet. Total polyphenol contents of rice with 20% proso millet and fermented alcohol added, cooked by general and high pressure cooking methods, were $184.33{\pm}2.69$ and $179.80{\pm}5.22{\mu}g\;GAE/g$, respectively. Total flavonoid contents increased as amounts of proso millet increased. DPPH radical scavenging activities with and without proso millet added were 4.20~7.50 and 2.97~5.19 mg TE/100 g, respectively. ABTS radical scavenging activities with and without proso millet added were 14.36~27.92 and 14.07~15.83 mg TE/100 g, respectively. In this study, cooked and antioxidant characteristics of cooked mixed grain rice with added proso millet were expected to be used as basic data for manufactured processed products.

• The korean journal of orthodontics
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• v.29 no.2 s.73
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• pp.267-276
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• 1999

Distributions trends were examined in 9159 malocclusion patients who had been examined and diagnosed at Department of Orthodontics, College of Dentistry Yonsei University over a 6 year-period from 1992 to 1997. The results were as follows ; 1. The total number of orthodontic patients in 1997 increased in comparing with that of 1992(86%) and after 1995, the number of annual patients showed an increase. 2. Age distribution had shown over-19 year-old group being the largest(39.9%) but percentages of pre-adolescent patients had been decreasing while that of adult patient had gradually increased. 3. Distributions in the types of malocclusion, the Angle's Classification had shown : 33.3% for Class I, 28.6% for Class II and the largest 38.1% for Class III. 4. Among Class I patients, crowding showed the largest(32.6%) and protrusion group had gradually increased to 33.9% in 1996. Otherwise openbite and crossbite groups tend to decrease, annually. 5. Geographic distribution showed a majority of patients from Seoul(above 70%). Among the patients from Seoul, group within the distance 3-6Km from Yonsei dental hospital was the largest(32.3%) and group within 9Km showed 69% of total patients.

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.338-349
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• 2010

This study compared the instruction effectiveness between experiments of precipitation and a ball & stick model related to the 'Law of Definite Proportions' of 9th grade science in this study. The subjects were 250 students in the 9th grade. They were divided into two groups, an experimental group and a model group. The results showed that the ratio of thought in which the elements were divided in the solutions and the ratio of thought in which a new compound was created when the two solutions were mixed were higher in the precipitation experiment group than in the model group. The two groups were not different in terms of the ratio of thought related to the reason for the creation of the precipitate. The ratio of thought pertaining to incorrect answers was high, implying that the two strategies were not effective in correcting students' thoughts. However, the ratio of finding patterns from the measuring data in the model group was higher than in the experimental group. However, the ratios of 'definite proportions' inference in the bonding of the reactants were similar in the two groups. From these data, we concluded that the inference of the 'Law of definite proportion' from experiments or models was not suitable for middle school students.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.255-263
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• 2016

This study conducted empirical tests on contemporary finance theories for corporate cash holdings, such as trade-off, pecking order, and agency theory. There is ongoing debate on the possibility of excess cash savings by domestic firms, including chaebols in the Korean capital markets. Thus, it may be worthy to identify any financial characteristics based on each aforementioned theory as an extension of previous studies on similar subjects. Two primary hypotheses were postulated and tested, and the following empirical results were obtained. First, principal component analysis (PCA) provides evidence that nine out of the twenty explanatory variables showed a significant influence on the level of corporate cash holdings, such as cash conversion cycle in trade-off theory and leverage in pecking order theory. Second, the chaebol firms that decreased cash holdings after global financial turmoil may be affected by financial factors that include investment opportunities and foreign ownership according to the PCA. The results may reinforce the outcomes derived from previous research on corporate cash holdings. Based on the robust results, large firms in advanced or emerging capital markets could approach the optimal level of the cash reserves.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1132-1141
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• 1996

Heterogeneous cation exchange membrane(HCEM) was prepared with LLDPE(Linear Low Density Poly-ethylene) as binder, powdered cation exchange resins($diameter{\leq}149{\mu}m$) as ion-exchange material and glycerol as additive for electrodialysis and electrodeionization system. The weight ratio of (binder/ion exchange)/glycerol was (60%/40%)/5%, (55%/45%)/5%, (50%/50%)/5% and (40%/60%)/5%. The characterization of prepared HCEM was evaluated on mechanical, electrochemical, morphology and ion permeable properties. It was compared with commercial membrane. Electrochemical properties of HCEM of (50%/50% )/5% were very similar to value of IONPURE(commercial membrane), in which ion exchange capacity, ion transfer number and membrane resistance were to be 1.733meq/g, 0.96 and $16.08{\Omega}/cm^2$, respectively. Ion permeability of the membrane was better than that of IONPURE membrane. Compared with IONPURE membrane, the HCEM had a higher tensile strength and lower elongation and modulus, in which HCEM had tensile strength of $62.33kg/cm^2$, elongation of 87.42% and modulus of $658.53kg/cm^2$. The HCEM of (50%/50% )15% was optimum combination.

• Journal of the Korean School Mathematics Society
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• v.25 no.2
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• pp.125-148
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• 2022

This study aimed to compare and analyze the number and characteristics of modeling problems in chapters related to function contents in International Baccalaureate Diploma Program (IBDP) mathematics textbooks and Korean high school mathematics textbooks. This study implies how the textbooks contributed to the improvement of students' modeling competency. In this study, three textbooks from IBDP and all nine textbooks from the Korean 2015 revised curriculum were selected. All the problems in textbooks were classified into real-world problems and non-real-world problems. Problems classified as real-world problems were once again divided into word problems and modeling problems according to the need to set up mathematical models. Modeling problems were further categorized into standard applications and good modeling problems depending on whether all the necessary information was included in the problem-solving process. Among the 12 textbooks, the textbook with the most modeling problems was the IBDP textbook, 'Math: Applications and Interpretation', which accounted for 50.41% of modeling problems to the total number of problems. This textbook provided learners with significantly higher modeling opportunities than other IBDP and Korean textbooks, which had 2% and 9% modeling problem ratios. In all 12 textbooks, all problems classified as modeling problems appeared as standard applications, and there were no proper modeling problems. Among the six sub-competencies of mathematical modeling, 'mathematical analysis' and 'interpretation and evaluation of results' sub-competencies appeared the most with very similar number of modeling problems, followed by the 'mathematization'. It is expected that the results of this study will help compare the number and ratio of modeling problems in each textbook and provide a better understanding of which modeling sub-competencies appear to what extent in the modeling problems.

• Journal of Korean Society of Forest Science
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• v.105 no.4
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• pp.414-421
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• 2016

Fourteen Acer pseudosieboldianum populations in South Korea were used to estimate genetic diversity, genetic differentiation and genetic relationships using seven AFLP primer combinations. The average of effective alleles ($A_e$), the proportion of polymorphic loci (%P) and Shannon's diversity index (I) was 1.4, 82.2% and 0.358, respectively. The expected heterozygosity ($H_e$) under Hardy-Weinberg equilibrium was 0.231 and the expected heterozygosity (Hj) from Bayesian inference was 0.253. The level of genetic diversity was moderate compared to those of Genus Acer and lower than those of other species having similar ecological niche and life history. The inbreeding coefficient within populations ($F_{IS}$) from Bayesian method was 0.712 and it could be influenced by selfing or biparental inbreeding to induce homozygote excess. The level of genetic differentiation was 0.107 from AMOVA (${\Phi}_{ST}$) and 0.110 from Bayesian method (${\Phi}^{II}$). The genetic differentiation was lower than those of other species having similar ecological niche and life history. Ulleungdo population had the lowest level of genetic diversity and was genetically the most distinct population from others in the study. We consider that founder effect and genetic drift might be occurred to reduce genetic diversity and then the geographical isolation might interrupt gene flow to aggravate it.