• 대한가정학회지
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• 제41권11호
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• pp.95-111
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• 2003

The purpose of this study was to investigate the current trend of early education and to examine the relationship between the state of early education and maternal beliefs, stress, and achievement pressure. The subjects were 275 mothers of 4∼6 year-old children in Seoul. The main results were as follows : 1) Most of the subjects' children(87.6%) were involved in early education, especially in the form of home-visit study and study papers. 2) Parental beliefs (about child development and early education) and maternal achievement pressure were significantly related to the degree of actual involvement and perceived necessity of early education. 3) Parental stress regarding child's temperament was significantly related to the starting age of early education. But the other factors of parental stress had no significant relation to the state of early education.

• 영어어문교육
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• 제5호
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• pp.191-218
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• 1999

The purpose of this study is to investigate the actual conditions of preschool English education, and teachers' and parents' recognition of preschool early English education in Cheonan-city. Recently the importance of English education as an essential means for communication in the whole world is emphasized in our society. That atmosphere makes the elementary schools offer English as a subject in their curriculums, and also many preschool education institutes begin to teach English in their education courses. However before we begin to teach English as a subject in the preschool education, we need to survey the actual conditions of preschools and recognition of teachers and parents. The first part of this study is to survey the theoretical foundations of early English education; 1) the definition of early English education. 2) the situation of early foreign language education in foreign countries. 3) the relationship between the language acquisition and the cognitive development. The second part is to analyze the results of the Questionnaire which was distributed among 86 teachers and 103 parents in Cheonan-city preschools. As a conclusion, some suggestions will be given for the development of early English education in the near future.

• 콘크리트학회논문집
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• 제12권6호
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• pp.51-56
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• 2000

Fly ash used as a cement replacement material increases the long term strength and also improves the durability of concrete and mortar. However, the use of fly ash is a little in spite of great benefit. In order to increase the consumption of fly ash, it has to be used as a cement replacement materials in the production of mortar and concrete, and the reduction of early strength development due to the use of fly ash also has to be diminished. In this study, many chemical compounds which accelerate the early strength was investigated. The $Na_2$$SO_4$, $K_2$$SO_4$, Triethanolamine were selected and applied to the production of mortar. It was found that they enhance the early strength development of mortar(1, 3day) and decrease the amount of $Ca(OH)_2$, and also increase the production of ettringite. According to the results of mercury instruction test, the pores ranged from 0.01 $\mu\textrm{m}$ to 5$\mu\textrm{m}$ were decreased and it was also found in the analysis of X ray and SEM that fly ash increases the amount of ettringite at early ages.

• Biotechnology and Bioprocess Engineering:BBE
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• 제5권1호
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• pp.44-47
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• 2000

Cell growth and DNA synthesis were studied from a cultured early- and late- pas- sage mouse aorta smooth muscle cell (MASMC) because the proliferation of vascular smooth muscle cell (VSMC) is a key factor in development of atherosclerosis. In this study, the cells were cultured in fetal bovine serum (FBS) and stimulated by growth factors such as thrombin and platelet-derived growth factor-BB (PDGF-BB). Compared to the number of early-passage MASMC (passage 3 to 9) the number of late-passage MASMC (passage 30 to 40) in a normal serum state was increased 2 fold at Day 1, 3 and 6 in culture, respectively. Incorporation of $[^3H]$ thymidine into DNA induced by serum, PDGF and thrombin in late-passage MASMC was greater than those in early-passage MASMC. We also examined whether intracellular zinc levels would be an aging factor or not. The intracellular zinc level in early- and late-passage MASMC was monitored by using the zinc probe dye N-(6-methoxy-8-quinolyl)-p-toluenesulfonamide. It is interested that late-passage MASMC increased the intracellular fluorescence level of zinc, more than the early passage MASMC did. The alterations of intracellular zinc level occur concurrently with changes in MASMC proliferation rate during aging. This data suggest that the age-associated changes in zinc concentrations may provide a new in vitro model for the study of smooth muscle cell differentiation.

• 말소리와 음성과학
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• 제7권2호
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• pp.63-73
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• 2015

This study investigated longitudinally early vocalization and phonological developments of typically developing children. Ten typically developing children participated in the study from 9 months to 18 months of age. Spontaneous utterance samples were collected at 9, 12, 15, 18 months of age and phonetically transcribed and analyzed. Utterance samples were classified into 5 levels using Stark Assessment of Early Vocal Development-Revised(SAEVD-R). The data analysis focused on 4 and 5 levels of vocalizations classified by SAEVD-R and word productions. The percentage of each vocalization level, vocalization length, syllable structures, and consonant inventory were obtained. The results showed that the percentages of level 4 and 5 vocalizations and word significantly increased with age and the production of syllable structures containing consonants significantly increased around 12 and 15 months of age. On average, the children produced 4 types of syllable structure and 5.4 consonants at 9 months and they produced 5 types of syllable structure and 9.8 consonants at 18 months. The phonological development patterns in this study were consistent with those analyzed from children's meaningful utterances in previous studies. The results support the perspective on the continuity between babbling and early speech. This study has clinical implications in early identification and speech-language intervention for young children with speech delays or at risk.

• KIEAE Journal
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• 제12권3호
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• pp.115-122
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• 2012

Based on previous research and existing literature, this study examines the development of admixture, which increases the early concrete strength (1 and 3 day) by mixing blast furnace slag cement and concrete stimulant. The research on early strength development of concrete is necessary in dealing with the drawbacks of slow early strength concrete on site and to shorten the construction time. The study confirmed that when a high alkaline mortar mixture is mixed with blast furnace slag, the early strength of admixture exceeds that of ordinary portland cement (OPC). The use of calcium chloride ($CaCl_2$) promotes hydration of cement at low temperature and show similar strength as the blast furnace slag admixture. Although calcium chloride seems economically advantageous, it causes steel corrosion and its use in concrete should be further studied in-depth.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.641-646
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• 2001

In early-age concrete, volumetric deformations due to thermal expansion and moisture transfer are restrained by various boundary conditions, and then restraint stresses occur in proportion to developed stiffness. With increase of the age, these stresses are gradually relieved by significant relaxation behavior of early-age concrete. Therefore, it is necessary to consider the stress relaxation in order to analyze the behavior of early-age concrete more accurately. In this paper, we propose a unified algorithm which combines a relaxation model with hydration model, heat conduction model, micropore structure formation model, moisture diffusion model and mechanical properties development model and develop a finite element program based on the algorithm. The program is applied to evaluate stress development if a temperature-stress test machine (TSTM) specimen and a massive concrete structure, and then validity of the program is discussed and evaluated.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.668-671
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• 2004

Recently, the concern for mechanical properties at early age concrete are increasing because of the importance of the thermal stress and the determination of removal time of form work and prestressing work. In this study, an estimation for the development of compressive strength and elastic modulus with age in concretes isothermally cured $(10^{\circ}C,\;20^{\circ}C)$ and having W/C ratio of 30, 40, and $50\%$ were investigated. According to experiment results, the development of compressive strength and elastic modulus shows higher values at early ages as the W/C ratio decreases and curing temperature increases. When the maturity concept, for estimation of the strength, is adopted, a modification for W/C ratio is required at early ages.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.97-103
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• 2006

A modified one-sided measurement technique is proposed for Rayleigh wave (R-wave) velocity measurement in concrete. The scattering from heterogeneity may affect the waveforms of R-waves in concrete, which may make the R-waves dispersive. Conventional one-sided techniques do not consider the scattering dispersion of R-waves in concrete. In this study, the maximum energy arrival concept is adopted to determine the wave velocity by employing its continuous wavelet transform. Experimental study was performed to show the effectiveness of the proposed method. The present method is applied to monitor the strength development of early-age concrete. A series of experiments were performed on early-age concrete specimens with various curing conditions. Results reveal that the proposed method can be effectively used to measure the R-wave velocity in concrete structures and to monitor the strength development of early-age concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.741-744
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• 2003

In this study, the influence of chemical admixture on early strength development of concrete is discussed. According to the results, fluidity with variation of kinds of chemical admixture is lower in the case of acceleration type than in the case of normal type. Setting time of naphthalene acceleration type is shortened by I hour, and that of melamine is nearly same, but that of polycarbonic acid is somewhat retarded in comparison with that of naphthalene normal type. Early compressive strength gains 5MPa in about 18hours regardless of the kinds of chemical admixture. But as time elapses, compressive strength is higher in order of polycarbonic acid, naphthalene and melamine type. The relativity between compressive strength and the rebound value of P-type schmidt hammer is also favorable at early age, and compressive strength of 5MPa is estimated at the rebound value of 22.