• Journal of the Korean Academy of Esthetic Dentistry
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• v.27 no.2
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• pp.75-81
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• 2018

The aim of this study was to evaluate the biomechanical behavior and long-term safety of high performance polymer PEKK as an intraradicular dental post-core material through comparative finite element analysis (FEA) with other conventional post-core materials. A 3D FEA model of a maxillary central incisor was constructed. A cyclic loading force of 50 N was applied at an angle of $45^{\circ}$ to the longitudinal axis of the tooth at the palatal surface of the crown. For comparison with traditionally used post-core materials, three materials (gold, fiberglass, and PEKK) were simulated to determine their post-core properties. PEKK, with a lower elastic modulus than root dentin, showed comparably high failure resistance and a more favorable stress distribution than conventional post-core material. However, the PEKK post-core system showed a higher probability of debonding and crown failure under long-term cyclic loading than the metal or fiberglass post-core systems.

• Korean Journal of Ecology and Environment
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• v.41 no.3
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• pp.301-310
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• 2008

This study was to analyze characteristics of fish compositions and longitudinal distribution, based on trophic and tolerance guild at 22 sampling sites of Yeongsan River watershed during 2003$\sim$2006, and also to compare before and after the estuary dam construction. The collected fishes, based on catch per unit effort (CPUE), were 44 species in the watershed and dominant fishes were Zacco platypus, Acheilognathus macropeterus, Zacco temminckii and Carassius auratus. According to comparative analysis of fish in the non polluted sites (NPS) vs. polluted sites (PS), the number of species and individuals was lower by 70% in the PS than the NPS, indicating ecological degradations by chemical pollutions or/and habitat modifications. The relative abundance of sensitive and insectivore species decreased as the stream order increases, while tolerant and omnivore species increased with the stream order. In this survey, largemouth bass (Micropterus salmoides), which is a top-carnivore and exotic species, may influence trophic guild system throughout active predations on endemic species, resulting in modifications of ecological functions. The construction of estuary dam on Yeongsan River in 1981 resulted in wider lacustrine zone and desalinated through limitation of seawater input. These physical changes have caused increases of lentic dwelling species and limited fish migrations (i.e., eel). Overall, fish fauna and composition analyses showed that the number of species and individuals in this water body may be reduced due to inputs of pollutants from the watershed, habitat modifications, and increases of exotic species (largemouth bass). For these reasons, effective lake management strategies are required for the ecosystem conservation.

• School Mathematics
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• v.15 no.2
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• pp.315-335
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• 2013

Probability has distinctive characteristics which are different from other areas of school mathematics. The critical change can be noticed in the domain, 'probability and statistics' of 2009 revised national curriculum for elementary school mathematics. This indicates that the concept of chance is supposed to be taught in the 5~6 grade band instead of the definition of probability which is moved to the middle school level. The purpose of this study is to seek desirable methods for teaching the concept of chance which reflect the achievement criteria and the attention point for teaching and learning of the curriculum at the point of time when textbooks haven't yet been developed. To do this, based on theoretical considerations and comparative analysis of the curricula in the longitudinal - latitudinal dimensions respectively, the validity of the latest curriculum change was confirmed and several learning activities were devised. And then two lessons were planned for applying these activities to eight fifth graders and were implemented along the plan. As a result, the relevance of the learning activities was examined and students' difficulties in learning the concept of chance with educational implications were discussed.

• Journal of Nutrition and Health
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• v.40 no.1
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• pp.58-68
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• 2007

The associations between dietary, body composition and sexual maturation were investigated among Korean girls of pubertal age in this study. Dietary intakes were collected by 3 day food records, body compositions were measured by bio-impedence analyzer and sexual maturation stages were determined with a self-administrated questionnaire using Tanner stages in 1,114 girls 9-13 years of age. Girls were divided into early maturation (EM) and late maturation (LM), based on the comparative maturation stages of breast and pubic hair among the same age groups by months. Subjects were excluded if their stage of maturation could not be divided into early and late groups. EM and LM groups consisted of 42.8% and 38.9% of subjects by breast stage and 67.4% and 22.8% by pubic hair stage. Girls in LM group had significantly lower in height, weight and bone mineral contents (p < 0.05). When nutrient densities of average daily intake of the two groups were compared, folate density was significantly higher among the LM group of breast stages (p < 0.01), and Ca, P, K, Vit. $B_1$, Vit. $B_2$ and folate densities were significantly higher among the LM group of pubic hair stages (p < 0.05). These results show that intakes of some micronutrients differ between children with faster and slower sexual maturation velocities at early pubertal stages. More longitudinal studies are needed to confirm whether such differences are consistent throughout the pubertal period.

• Journal of Korean Academy of Nursing
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• v.31 no.2
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• pp.169-179
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• 2001

Recently, there has been an increasing interchange between South Korea and North Korea. Accordingly, there has been active research to understand the society and culture of North Korea, it has been attempted to have comparative study about nursing education to increase understanding between South and North Korea. In the current educational system, 12 years of education is required for entering a nursing college or university in South Korea, but there are only 10 years for entering nursing college in North Korea. After finishing undergraduate studies one can enter graduate school for a masters degree and or a doctoral degree, but there is a longitudinal relation to medical education in North Korea. Regarding the number of nursing educational institutions, there are 50 BSN programs & 61 Diploma programs in South Korea and 11 Diploma programs in North Korea. In regards to curriculum, South Korea has diverse subjects for general education for freshmen, then is subjects to basic specialities sophomore year, and speciality subject and clinical practices from junior year corresponding to the student's intentions. North Korea has minor subjects for general education and basic specialities in freshmen, speciality subjects sophomore year, speciality subjects and clinical practice in the junior year that may not correspond with the student's intentions. The most outstanding difference in the curriculum is North Korea has various subjects for oriental medicine with clinical application. North Korea also does not teach computer science and English is at a very low level. In clinical practice, South Korea has various settings for clinical practice including community health institutions under the nursing professor or clinical instructor. However, North Korea has limited settings for clinical practice (general hospitals) under a doctor's instruction. Also both South and North Korea have a similar licensing system. Therefore, there must be many more studies regarding North Korea, especially in nursing and nursing education in order to decrease differences and confusion between the Koreas and to prepare for a future unification.

• Journal of Korean Society on Water Environment
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• v.24 no.1
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• pp.54-62
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• 2008

It is often believed that a more complex water quality model is better able to simulate reality. The more complex a model, however, the more parameters are involved thus increases the cost and uncertainty of modeling processes. The objective of this study was to compare the performance of two steady-state river water quality models, QUAL2E and QUAL-NIER, that have different complexity. QUAL-NIER is recently developed by National Institute of Environmental Research aiming to enhance the simulation capability of QUAL2E for eutrophic rivers. It is a carbon based model that considers different forms, such as dissolved versus particulate and labile versus refractory, of carbon and nutrients, and the contribution of autochthonous loading due to algal metabolism. The models were simultaneously applied to Nakdong River and their performance was evaluated by statistical verification with field data. Both models showed similar performance and satisfactorily replicated the longitudinal variations of BOD, T-N, T-P, Chl.a concentrations along the river. The algal blooms occurred at the stagnant reaches of downstream were also reasonably captured by the models. Although QUAL-NIER somewhat reduced the magnitude of errors, the hypothesis tests revealed no statistical evidence to justify its better performance. The contribution of autochthonous carbon and nutrient load by algal metabolism was insignificant because the hydraulic retention time is relatively short compare to the time scale of kinetic reactions. The results imply that the kinetic processes included in QUAL-NIER are too complex for the nature and scale of the real processes involved, thus needs to be optimized for improving the modeling efficiency.

• Journal of Elementary Mathematics Education in Korea
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• v.21 no.1
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• pp.135-160
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• 2017

Since mathematics textbooks for 6th graders based on the 2009 revised national curriculum were applied to the site, there has been a note pointing out that the unit of 'ratio and rate' causes some learning difficulties. This implies the necessity of search for desirable methods of organizing the unit of ratio and rate in mathematics textbooks. This study analyzed and compared Korean and foreign mathematics textbooks on ratio and rate longitudinally and horizontally, respectively. For longitudinal analysis, we selected the mathematics textbooks according to the national curriculum since the 5th one. For horizontal analysis, we took the mathematics textbooks of Japan, Singapore, Hong Kong, and Finland. In each textbook, the contents and the order in relation to ratio and rate, the definitions of terminology, and the methods for introducing related concepts are set as the analysis framework. The results of analysis revealed many characteristics and the differences in ways of dealing contents about ratio and rate. Based on these results, we suggested some implications for writing the unit of ratio and rate in elementary mathematics textbooks.

• School Mathematics
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• v.19 no.3
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• pp.513-531
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• 2017

This study aims to analyze and compare Korean mathematics textbooks on time and to induce its educational implications. Concretely, the mathematics textbooks from the 1st to the 2009 national revised curriculum were selected for the longitudinal analysis. In each textbook, the contents such as clock reading, units of time, and calculation of elapsed time among various contents about time were chosen. The learning elements and their teaching sequence, the teaching method (the introducing ways of each concept and principle), and the didactical representations are set as an analysis framework. The results of analysis revealed many characteristics and differences in ways of dealing contents about time. Based on these results, we suggested several implications for writing the unit of time in elementary mathematics textbooks and teaching about time in classrooms.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.6
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• pp.731-738
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• 2017

Twin-hulls frequently incur structural damage at connecting members between the hull and deck induced by pitching motions during voyages. so, reasonable reinforcement is necessary around vulnerable spots such as corner knuckle, the chine bottom and inner hull. Since guidelines for structural design are not clear, engineers often respond by reinforcing plate thickness, changing stiffener sizes and reducing frame spacing, etc. These members constitute about 85 % of the longitudinal dimensions of the ship, so it is necessary to locally reinforce certain points to minimize weight stress, and also solve construction cost problems while securing the freeboard margin. Therefore, we developed a new program by analyzing the structural design procedures for the twin car-ferries based on Korean Register of Shipping (KR) High Speed Craft Rules, identifying items that need to be added. In order to ensure the reliability of buckling estimations for procedures and design programs, we conducted a comparative study with other standards and confirmed that differences were minimal.

• Korean Journal of Social Welfare Studies
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• v.42 no.4
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• pp.61-102
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• 2011

The purpose of this article is to anatomize the political dynamics of South Korea's healthcare policymaking through the integrative analytical framework combining the policy network perspective and the advocacy coalition theory. This framework is expected to be advantageous to the analysis of Korea's turbulent healthcare policy change from a systematic and process-driven point of view. A target of analysis is the two decades of turbulence to transform the health insurance system into a single payer system. Through the analysis, this article tries to illuminate the dynamics of Korea's healthcare policymaking, by connecting environmental context, policy networks, advocacy coalitions, and policy outputs. For a case study, this article classifies the debates to inaugurate a single payer system into four sub-phases and conducts longitudinal comparative research.