• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.67-74
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• 2000

The usage of nondestructive testing on early-aged concrete leads to enhacned safty and allows effective scheduling of construction, thus making it possible to maximize the time and cost efficiencies. In this study, a reliable nondestructive strength evaluation method for early-aged concrete using the longitudinal wave velocity is proposed. Compression tests were performed to examine factors influencing the velocity-strength relationship of concrete, such as water-cement (w/c) ratio, fine aggregate ratio, curing temperature, and curing condition. The test results show that a change in the w/c ratio and curing temperature has minor effect on the velocity-strength relationship/ However, curing condition significantly influences the velocity-strength relationship of early-aged concrete. Moreover, the longitudinal wave velocity increases with decreasing fine aggregate ratio. It is concluded from this study that the strength evaluation of early-age concrete can be achieved by a nonlinear equation which considers the effects of curing condition and fine aggregate ratio.

• Clinical and Experimental Reproductive Medicine
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• v.38 no.2
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• pp.75-81
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• 2011

Objective: Bisphenol A (BPA) is a chemical used extensively to manufacture plastics and epoxy resin liners for food and beverage cans. BPA, with properties similar to estrogen, has endocrine-disrupting effects. In the present study, we examined the effects of early prepubertal BPA exposure on the onset of puberty and reproductive parameters such as estrous cycle and reproductive organ weights in female mice. Methods: Female mice were injected subcutaneously at postnatal day (PND) 8 with BPA (0.1, 1, 10, 100 mg/kg) in sesame oil or with sesame oil alone. Body weight was measured from PND 10 to 70. Vaginal opening and estrous cycle were monitored from PND 20 to 29. Animals were sacrificed at PND 25, 30, and 70, and the ovary and uterus weights were measured. Results: Early prepubertal exposure to BPA (10 and 100 mg/kg) significantly decreased body weight from PND 18 to 30. BPA treated mice at testing dose levels showed early opening of the vagina compared to the control group. The number of estrous cycle and days of estrus were significantly decreased in high dose (100 mg/kg) BPA treated mice. The ovary weight at PND 25 and 30 was significantly decreased in all BPA treatment groups. Conclusion: Early prepubertal exposure to BPA accelerated the onset of puberty but decreased reproductive parameters in female mice.

• Human Ecology Research
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• v.59 no.2
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• pp.233-243
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• 2021

This study examined the longitudinal effects of media usage by early school-age children and of maternal parenting stress on children's school adjustment. The study focused on the mediating effect of executive function difficulty. Longitudinal data to examine the hypothetical model were drawn from the eighth (2015) through tenth (2017) waves of the Panel Study of Korean Children (PSKC) collected by the Korea Institute of Child Care and Education (KICCE). A total of 581 children (293 boys and 288 girls) and their mothers were included. Confirmatory factor analysis, structural equation model, and bootstrapping analysis were applied using SPSS 25.0 and Amos 26.0. The results are as follows. First, no significant correlation was found between early school-age children's media usage and maternal parenting stress. Second, neither media usage by early school-age children nor maternal parenting stress were found to directly affect children's school adjustment. Third, media usage by early school-age children and maternal parenting stress were shown to indirectly affect children's school adjustment via executive function difficulties. In other words, higher levels of media usage by early school-age children and maternal parenting stress during the first grade lead to greater executive function difficulties after a year, which, in turn, lead to a lower level of school adjustment in the third grade. This study indicates the need to develop practical support for the psychological wellbeing of mothers while they are performing their role as a parent and for children in maintaining suitable levels of media usage during early childhood.

• Journal of Applied Biological Chemistry
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• v.62 no.3
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• pp.247-250
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• 2019

Wheat is one of the most important grains. Its consumption is increasing globally. Many countries are making efforts to increase the extent of wheat harvest. It is known that plant growth promoting rhizobacteria (PGPRs) have beneficial effects on various plants. Two PGPRs including Paenibacillus pabuli strain P7S (PP7S) and Pseudomonas nitroreducens strain IHB (PnIHB) were employed to investigate effects of PGPRs on early growth of three wheat cultivars (Koso, Seakumkang, and Jokyung). While PP7S had adverse effects on Seakumkang and Jokyung, PP7S had positive effects on Koso except root length compared to control group having no treatment of PP7S. However, all treatments with PnIHB had adverse effects on germination rate, root/shoot lengths, vigor index, and dry root/shoot weights of all three wheat cultivars. These positive effects with PP7S on Koso might be related to the earlier emergence of wheat seed above soil which is known to be an indicator of increased yield. Results of the present study suggest that if proper PGPR strains are selected, they could have positive effects on early growth rate of a wheat cultivar.

• Environmental Analysis Health and Toxicology
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• v.20 no.1
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• pp.13-21
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• 2005

The purpose of this study was to determine the effects of bisphenol A (BPA), which is known to have estrogenic activity, on the early development of medaka fish (Oryzias latipes). The fertilized eggs of medaka were treated with BPA at different concentrations for 3 weeks. Embryonic growth, deformation, hatching success, and gonadal differentiation were determined to observe the effects of this chemical. Also we tried to measure the estrogenic activity of bisphenol A using ELISA and RT-PCR methods. By using this techniques, we evaluated the induction of vitellogenin, an estrogen-regulated gene from the whole body-homogenates of larvae. At results, a reduced blood circulation was seen in embryos and peritoneal edema and hindrance of yolk-sac absorption were observed in larvae of treated group. However, BPA at the concentrations tested (2～200 ㎍/L) did not have severe adverse effects on the early life-stages. According to the observation of gonadal histology, inter-sex or sex -reversal was not found in all test fish. After the exposure was ended, vitellogenin mRNA and protein levels were measured in larvae and then their levels were found to be increased in treated group with 200㎍/L. These results indicate that BPA can induce the expression of vitellogenin in early life-stages as well as in adult male fish.

• Journal of Digital Convergence
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• v.15 no.2
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• pp.393-403
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• 2017

The purpose of this study was to investigate the correlation on the relationship between economic level, self-esteem and teaching efficacy first, and then to investigate the mediating effects of self-esteem on the relationship between economic level and teaching efficacy. The subjects of this study were 457 students who attend two collages in Incheon and all of them were majoring in early childhood education. The collected data were analyzed through SPSS Window program. Correlation analysis and Multiple regression analysis were conducted. Results showed the there were correlation among economic level, self-esteem and teaching efficacy. Also there were mediating effects of self-esteem on the relationship between economic level and personal teaching efficacy. As a whole the result of this study showed the teaching efficacy of early childhood preservice teacher were more influenced by self-esteem than by economic level. The implication of the result were discussed with the necessity of curriculum development to improve the student's self-esteem.

• Journal of the Korea Concrete Institute
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• v.13 no.4
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• pp.362-370
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• 2001

The internal or external restraint of thermal and dry shrinkage movements could thus generate tensile stresses in concrete pavement for early traffic opening. Restrained shrinkage and thermal stresses could produce microcracks in concrete which increase its permeability and accelerate its long-term deterioration under weathering and load effects. Fiber reinforced concrete is an effective approach to the control of microcrack and crack development under tensile stresses. This study aims at evaluation of the durability of high early strength concrete for early traffic opening and increase of service life. Three different types of regulated-set cement which recently has been used much in Korea were adopted. Fibers were added and their mixtures were compared with plain high early strength concrete mixture. The use of fibers increased durability performance of high early strength concrete using regulated-set cement than the corresponding plain mixtures.

• Journal of the Korean Home Economics Association
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• v.49 no.3
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• pp.55-66
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• 2011

The purpose of this study was to examine the effects of We Start home visiting intervention program on the positive changes of infants and their low-income families. The subjects were 171 18~36-month olds and their mothers living in We Start and non We Start areas. The instruments used were Developmental Profile, Cleminshaw-Guidubaldi Parent Satisfaction Scale(CGPSS) and Home Observation for Measurement of the Environment(HOME). The results were as follows: First, the result of Developmental Profile showed positive changes in all domains(physical development, self-help skills, social development, cognitive development, and communication ability). Second, the result of CGPSS showed positive effects on parent-child relationships. Third, the result of HOME showed positive effects on mothers' emotional and language responses. In conclusion, We Start home visiting program for infants from low-income families is an effective early intervention program to end intergenerational transition of poverty in Korea.

• Journal of Nutrition and Health
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• v.26 no.3
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• pp.347-356
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• 1993

Plasma concentrations of zinc and copper were measured in 59 non-pregnant women and 105 pregnant women(12 ; early pregant, 93 ; late pregnant) to estimate and compare both groups and to detect the effects of iron supplementation on the plasma zinc and copper concentrations in the pregant women. The mean plasma zinc concentration of the early pregnant group was not significantly different with those of the non-pregnant group. But in contrast, the mean plasma zinc concentration of the late pregnant group was significantly lower than those of the non-pregnant and early pregnant group. Mean plasma copper concentration were significantly elevated in ealry pregnant group and doubled in late pregnant compared to non-pregnant. In Fe supplemented group, mean plasma zinc concentrations were lower and mean plasma copper higher than those of Fe non-supplemented group. It appeared that Fe supplementation had effects on the decrease of plasma zinc concentrations in pregnancy.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.806-809
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• 2004

The early-age cracks have bad effects on the diffusion movement of chloride ions and oxygen. In this study, a corrosion analysis algorithm for cracked concrete is proposed to examine the influence of early-age cracks on corrosion of RC structures. For different environmental exposure conditions of RC structures, a corrosion model is combined with models for activation polarization and concentration polarization. From the finite element corrosion analysis using the proposed algorithm and the models, the effects of early-age cracks to the corrosion is simulated.