• Proceedings of the Korea Concrete Institute Conference
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• 1998.10c
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• pp.197-202
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• 1998

The corrosion of steel reinforcements in concrete is of much concern in recent years. The mechanism of corrosion, however, is not clear yet. This study is focused on the corrosion of steel induced by internal chlorides in concrete at early ages. To examine the critical concentration of steel, half-cell potential, chemical composition of expressed pore solutions of mortars and rate of corrosion area were observed with respect to additions of chlorides, types of binders, water-binders ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.455-460
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• 2000

Fly ash can be used as cement replacement material and can also produce the durable concrete. According to the results, the compressive strength of concrete containing fly ash is slightly lower than that of normal concrete at early ages, however, the long-term compressive strength is significantly higher beyond 90 days, and it increases the durability of concrete as well.

• Journal of Oral Medicine and Pain
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• v.6 no.1
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• pp.5-8
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• 1981

The author had sellected stone models of upper premolar teeth from 20 age to 60 ages in male, and studied the attrition pattern of upper premolar teeth having attention to teeth cups on the stone model. All of the attrition patterns were divided (into) 14 forms. The results were as follows : 1. Attrition patterns of upper premolar teeth were divided into 14 forms. 2. Being compared with age group, early attrition pattern (M) showed decreasing tendency and late attrition pattern (A) showed incresing tendency by aging.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.72-77
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• 2000

In order to estimate strength of concrete, many attempts have been made. However, it is difficult to estimate concrete strength with ages. In this study, the factors influencing the strength of concrete such as w/c ratio and curing temperature, were investigated and results predicted by the established strength models were compared to measured strength data. It is found that in general the estimated values are approximate to the test results. In order to accurately predict the concrete strength curing temperature factor should be employed in the strength models.

• Proceedings of the Korean Society of Toxicology Conference
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• 2003.10b
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• pp.185-185
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• 2003

In-vitro expanded CNS precursors provide a potentially unlimited source of dopamine (DA) neurons for the experimental treatment in Parkinson's disease. An efficient dopaminergic differentiation from CNS precursors in vitro is limited to mesencephalic precursors isolated from early embryonic ages (embryonic day 11.5 (E11.5)-E12.5).(omitted)

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.176-177
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• 2019

As a result of the Rietveld analysis to determine the effect of carbon nanotubes on the hydration products of cement composites, the quantitative difference of hydration products according to the addition rate of carbon nanotubes was not significant. Ettringite, an early hydration product, was measured to be slightly higher than the planes with carbon nanotubes over all ages. Therefore, it seems that carbon nanotubes have no effect on the hydration production in cement paste.

• Journal of Family Resource Management and Policy Review
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• v.16 no.1
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• pp.21-39
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• 2012

The purpose of this study is to propose the direction of environmental education for early childhood children based on the environment-friendly life style and to improve the possibility of application of it at home and kindergarten. This study reviewed reflectively the early studies on the concepts of ecocentrism, the emerging process of it, the importance of environmental education for early childhood children based on the ecocentrism, and the practice of these kinds of education at home and kindergarten. The main concepts connected to the environment-friendly life style based on ecocentrism, that is, 'preservation of nature', 'interdepentence', 'wholeness', 'equilibrium' are the foundations of environmental education for early childhood children. When these kinds of concepts are considered, the aims of environmental education for early childhood children should be focused on the life style that attaches great importance to the symbiosis of human being and nature. The educational contents and methods in harmony with ecocentrism are as follows: The educational methods should be connected to the education based on ordinariness, the learning through adults' model, the family-community-centered activities, and ways of thinking of the unity of knowledge and conduct. And educational contents should include all of the life styles in clothes, food, and shelter. And the educational methods also should be connected to the education through joint working of children and teacher, play-centered education, activities considering ages and individual variations, and education connected home. And educational contents should include many different kinds of activities of experiencing nature outside home and kindergarten.

• Korean Journal of Child Studies
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• v.3
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• pp.83-96
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• 1982

TV has a very strong influence on various aspects of children's life and development. In view of this influence, various problems related to the content and production of TV programs for early - childhood deserve a careful study. Recognizant of this significance, this study aims to suggest the direction in which the production of TV programs for early childhood in Korea will steer by defining the concept of TV programs for early childhood and by analyzing the current status and trends of producting TV program for early childhood at abroad. In this study, attempts were made to suggest some strategies for the production of TV programs for early childhood based on an expansive literature review. 1. The running time of TV programs for early-childhood ages of 4-5 year old is suggested to be 15 minutes. 2. In the process of producing the programs, a group of professionals including in-service teachers, researchers specializing in child development, psychology and sociology, idea-creators, script writers, media experts, producers, and monitors should provide concerted efforts throughout the process. 3. The running time of TV programs for early-childhood should be less than 20 minutes and therefore should have simple learning objectives. 4. The contents of programs should be organized in such a way as to enable children to view themselves as well as the environment in more positive ways and to fester desirable values and beliefs in them based on various constructive activities and plays. 5. The programs should adopt various techniques including repetition, to ensure the maximum learning effect in full consideration of children's interest. 6. The programs should be continuously revised and supplemented based on the evaluation of the programs, children's responses and monitor's feedbacks.

• The Journal of the Petrological Society of Korea
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• v.12 no.2
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• pp.79-99
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• 2003

Muscovite and biotite from 52 metasediments and 5 granites in the Hwasan area, the southwest of the Okcheon metamorphic belt and the Miwon-Jeungpyeong area, central Okcheon metamorphic belt were dated by the K-Ar and $^{40}$ Ar/$^{39}$ Ar methods. Muscovite and biotite ages from metapelitic and psammitic rocks (metasediments) of the Boeun and Pibanryeong units in the Hwasan area are concentrated in the mid-Jurassic (149-180 Ma). K-Ar and $^{40}$ Ar/$^{39}$ Ar ages for metapelitic and psammitic rocks of the Boeun and Pibanryeong units in the Miwon-Jeungpyeong area show complicated age distribution. Muscovite and biotite ages are classified by three groups, 142-194 Ma, 216-234 Ma, and 241-277 Ma. Younger (Cretaceous) ages occur only in metasediments close to Cretaceous granitic rocks in the southeastern region and the older ages of 216-277 Ma are restricted to the middle Part of the Jeungpyeong area. Most ages in the other area of the central Okcheon metamorphic belt fall between 142-194 Ma (Jurassic). K-Ar and $^{40}$ Ar/$^{39}$ Ar ages for granite from the northern part in the both the southwest and central Okcheon metamorphic belt also gave middle Jurassic ages (156-168 Ma). The similar ages from both metasediments and granites in the study areas indicate simultaneous cooling of both rocks to 300-350$^{\circ}C$ during the middle Jurassic. The state of graphitization of carbonaceous material of all metasediments in the study areas Indicates fully ordered graphite falling within a small range, from 3.353 to 3.359 ${\AA}$, which indicate amphibolite facies regional metamorphism. In the southern sector of the Boeun unit from the Hwasan area, metamorphic grade indicated by mineral paragenesis during regional intermediate-P/T metamorphism is greenschist facies. Whereas, the $d_{002}$ values for carbonaceous materials in the same sector show fully ordered graphite (ca. 500$^{\circ}C$) indicating amphibolite facies. This result with the concentration of mica ages of metasediments into the middle Jurassic, the presence of low-P/T thermal metamorphic zone (>500$^{\circ}C$) in the metasediments close to the Jurassic granite and the regional intrusion of Jurassic granites and their middle Jurassic intrusion and cooling ages may indicate the low-P/T regional thermal event during the early(\ulcorner)-middle Jurassic after main intermediate-P/T metamorphism which formed main mineral assemblage regionally in the study area. The regional thermal event failed, however, to reset the mineral assemblage of regional intermediate-P/T metamorphism except for narrow aureole (1-2 km) around Jurassic granite because e duration of thermal effect was relatively short by repid cooling of the Jurassic granite. In the middle part of the Jeungpyeong area, central Ogcheon metamorphic belt, muscovite and biotite K-Ar ages from 5 samples are 263-277 Ma and 241-249 Ma, respectively. An intermediate-P/T metamorphism is currently accepted to have occurred between 280 and 300 Ma. Therefore, the muscovite and biotite ages can be interpreted as cooling ages after Ml metamorphism indicating rapid cooling to ca 350$^{\circ}C$ between 280-300 Ma and 263-271 Ma, and biotite ages indicate slower cooling to ca. 300$^{\circ}C$ between 263-277 Ma and 241-249 Ma. However, more detail study is needed to confirm why the Permian to Triassic ages occur only in the middle Part of the Jeungpyeong area.a.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.253-261
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• 2016

This study discusses the effective management of mixed-ages classes in kindergarten. For the study, 300 kindergarten teachers in charge of mixed classes for regular courses completed a self-reported questionnaire through a web survey. The data were analyzed by chi-square test and presented by frequency and percentage. Mixed-ages classes had relatively fewer children than one-age classes and they were prevalent in public kindergartens and rural areas. The results were as follows. First, mixed-ages classes were induced by the small number of young children. Second, teachers managed their classes with difficulty due to the lack of supporting staff and few chances for additional teaching training. Third, teachers needed supporting human resources for their teaching and administration assistances. About 23.0% of kindergartens received assistance such as additional training, financial assistance, and consulting supervision from related institutions. The study results suggested the challenges in regulations of age ratio in mixed-ages class, additional teaching training for teachers in mixed-ages classes and replacement of mixed-ages class to same age class as the long-term plan.