• Korean Journal of Child Studies
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• v.26 no.3
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• pp.61-76
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• 2005

Using ethnographic methods, this study identified the meaning of paternal experience through 1 to 2 hours of individual interviews with the fathers of preschool children. The interviewees were 33 middle-class fathers from 28 to 41 years of age, Twenty had infants under 36 months of age the others had preschool children 37 months of age and older. Results were summed up with two statements : The first is that paternal experience with the under 36-month-old infants can be called "the stage of adjustment". The other statement is that paternal experience with 37-months and older preschool children can be called "the stage of model-building as a father".

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.30-31
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• 2021

The construction industry is an industry in which skilled construction workers should be secured and trained because of the quality and productivity of buildings, but the negative image makes it difficult to supply and demand skilled construction workers. In response, this study derived the factors influencing the intention of transferring construction workers to other occupations and investigated ways to improve the prevention of leaving other occupations by age of construction workers. The factors influencing the turnover of construction workers have also been derived, and work overload, salary, workplace stability, and employment competitiveness have a significant impact on the intention of new employees to change jobs. According to a survey on ways to improve the prevention of leaving other jobs, those in their 20s and 30s are "improving working conditions, such as providing holidays, paying overtime, compliance with working hours," and those in their 50s and 60s.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.11a
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• pp.13-16
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• 2003

There is no study that application of the maturity using H.B.C and H.S.C. Also activation energy has different values according to the cement, admixture and water-cement ratio. Therefore to make accurate explanation for the effect of temperature on concrete strength development properties, it is necessary that activation energy value according to the kind of cement is reviewed. This study compares and estimates equivalent age using activation energy value obtained by this experiment and Freiesleben activation energy value with compressive strength of concrete. As the result of this study, activation energy value obtained by this study has more accurate explanation of temperature's influence on concrete strength development than Freiesleben activation energy value.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.13.1-16
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• 2003

There is no study that application of the maturity using H.S.C and H.S.C. Also activation energy has different values according to the cement, admixture and water-cement ratio. Therefore to make accurate explanation for the effect of temperature on concrete strength development properties, it is necessary that activation energy value according to the kind of cement is reviewed. This study compares and estimates equivalent age using activation energy value obtained by this experiment and Freiesleben activation energy value with compressive strength of concrete. As the result of this study, activation energy value obtained by this study has more accurate explanation of temperature's influence on concrete strength development than Freiesleben activation energy value.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.115-116
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• 2013

Property of the compressive strength of high strength concrete was investigated in adiabatic temperature history considering hot-weather conditions. As a result, compressive strength of specimens subjected to high temperature history showed more than 120% at 3days of age compare to standard cured specimens. But, at 91days of age showed the incidence of strength less than 100%.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.134-135
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• 2020

In this study, optimum time of drilling for injection of repair material was determined through surface stripping and cracking investigation by drilling from the 1 days to the 3 days of the age for the specimens with ∅100 mm. No surface stripping and cracking occurred on the third day of age, and the compressive strength value was above 14 MPa, which resulted in the appropriate time for drilling on the third day of age.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.55-56
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• 2023

Recently, large and high-rise buildings are increasing, and accordingly, concrete weight reduction is required. Lightweight aggregate concrete can provide economic feasibility and large space, but safety can be reduced due to problems such as low strength and poor durability. Since the development of such low strength of concrete is important in the early construction stage, it is necessary to evaluate the vertical formwork demolding period at the early age. The correlation was analyzed by measuring the compressive strength and ultrasonic pulse velocity. As a result, the ultrasonic pulse rates of normal and lightweight aggregate concrete at the time of 5 MPa expression, which is the time of vertical mold deformation, were 3.07 km/s and 2.77 km/s for W/B 41, and 2.89 km/s and 2.73 km/s for W/B 33.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.103-104
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• 2021

This study attempted to confirm the possibility of estimating condensation time and initial compressive strength with five types of estimation needles in the existing Durometer D type. In order to determine the surface finishing operation time and develop a method for estimating the initial age compression strength, an estimation needle capable of complexly measuring the estimation time and the initial age compression strength based on the Durometer D type was derived as 1.5, 2.0mm.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.61-62
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• 2021

Because of the problem of increasing self-weight due to the enlargement and high-rise of buildings using normal aggregate concrete, the need for structural lightweight aggregate concrete increases. However, early strength prediction is required when placing structural lightweight aggregate concrete, but research is insufficient. In this study, the ultrasonic pulse velocity of normal aggregate concrete and lightweight aggregate concrete was measured at early age. As a result, the ultrasonic pulse velocity of lightweight aggregate concrete was lower than normal aggregate concrete according to elapsed time at early age.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.228-229
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• 2017

MOCK-UP TEST was conducted in the extreme region of the cement which was researched and developed by using the reducing slag Experimental results show that the basic properties (air volume, slump) are improved compared with the specimens using Mongolian cement. The compressive strength achieved the target strength (target strength: age 3day: 7MPa, age 7day 14MPa) and the hydration heat was about 8 ℃ higher than that of Mongolian cement products. Therefore, it is considered that the cement powders developed by our company showed the strength of concrete due to high hydration heat even at extreme temperatures.