• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.56-62
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• 1995

In this study, the properties of super flowing cocrete containing gly ash were experimentally investigated and compared with those of ordinary concrete. Tests were carried out on five types of super flowing concrete mixes containing fly ash and three types of ordinary concrete mixes without fly ash. Flow test, O-funnel test, box test, Ltype thest and slump test were carried out to obtain the properties for the workability of fresh concrete. Compressime strength, splitting tensile strength, modulus of elasticity. creep and shrinkage test were also obtained as the mechanical properties of hardened concrete. In fresh concrete, it was found that super flowing concrete had excellent workability and flowability compared with ordinary concrete, and the volume ratio of coarse aggregate to concrete volume greatly influenced flowability. Super flowing concrete also had good mechanical properties at both early and late ages with compressive strengths reaching as high as 40 MPa at 28 days. The creep deformation of super flowing concrete investigated were relatively lower than that of ordinary concrete.

• 대한가정학회지
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• 제37권6호
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• pp.97-108
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• 1999

The purpose of this atudy was to identify the influence of demographic characteristics of full-time working mother's family on maternal parenting efficacy as well as child-rearing practices and to examime the relationship between mothers with perceived parenting efficacy and child-rearing practices. The subjects for this study were 100 working mothers of two to six year old children attending employer sponsored child care centers. Descriptive statistics, t-tests, correlation analysis, and step-wise regression were used for data analysis. The major findings of this study were as follows: 1) Full-time working mothers' child-rearing practices were influenced by the ages of mothers and fathers, parental education level and occupation, family income, age of the child, and number of children in the family. 2) The more working mothers perceived parenting efficacy, the more mothers utilized effective child-rearing practices. 3) Age of the child, maternal education level, mothers with levels of perceived parenting efficacy were significant predictors for full-time working mothers' child-rearing practices.

• 천문학논총
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• 제34권3호
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• pp.67-79
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• 2019

We present a semi-analytical method to calculate the global evolution of the ionized state of the intergalactic medium, on the basis of physically motivated star formation histories in the early universe. This method incorporates not only the conventional scenarios in which the star formation rate is proportional to the growth rate of the halo collapse fraction, but also the more sophisticated scenarios in which the star formation is self-regulated. We show that this variance in the star-formation model strongly impacts the resulting reionization history, which bears a prospect for observational discrimination of these models. We discuss how observations of the anisotropic polarization of the cosmic microwave background and the global 21cm signal from the high-redshift universe, most notably by Planck and EDGES, may probe the history of reionization.

• Advances in concrete construction
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• 제4권3호
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• pp.195-206
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• 2016

Today, application of additives to replace cement in order to improve concrete mixes is widely promoted. Micro-silica is among the best pozzolanic additives which can desirably contribute to the concrete characteristics provided it is used properly. In this paper, the effects of AP2RC and P1RB micro-silica gels on strength characteristics of normal concrete are investigated. Obtained results indicated that the application of these additives not only provided proper workability during construction, but also led to increased tensile, compressive and flexural strength values for the concrete during early ages as well as ultimate ones with the resulting reduction in the porosity lowering permeability of the micro-silica concrete. Furthermore, evaluation of microbial contamination of the mentioned gels showed the resultant contamination level to be within the permitted range.

• 자원환경지질
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• 제30권2호
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• pp.143-151
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• 1997

The history of the Palgongsan Fault comprises the growth-fault, the dormant and the strike-slip phases. Dissecting the Palgongsan Granite, the Palgongsan Strike-slip Fault, which is the product of the final phase, sinistrally offset about 5.5 km as shown in the dislocation of the Hasandong Formation. Faulting, sedimentation and igneous activity were inter-related in the early phases of the Palgongsan Fault. Some other faults such as the Dansan Pond Fault and the Hayang Fault have also been discovered, and their some stratigraphic implications and the ages of faulting are discussed. The anomalous development of the Jindong Formation in the study area and the related stratigraphic problems are discussed. It has been confirmed that the Konchonri Formation deposited over the Chaeyaksan Volcanic Formation in spite of the recent doubts on their such stratigraphic relation. The chronological sequence of the volcanisms of the Kyongsang Basin has been summarized.

• 한국식물병리학회지
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• 제14권3호
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• pp.247-252
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• 1998

A series of greenhouse test was conducted to evaluate infection of Calonectria ilicicola on soybean plants of different ages at time of inoculation. Lesion length and number of perithecia were determined on cultivars Braxton, Deltapine 726, and Riverside 699 that were 10∼40 days old and 4-10 days old at time of inoculation. Quadratic and linear relationships were described between plant age at inoculation and lesion length or perithecia production in greenhouse studies. Soybean seedlings exhibited low susceptibility to C. ilicicola regardless of cultivar susceptibility. On 8- or 1-0-days-old Braxton, lesion lenght and perithecia numbers were reduced. Lesion lengths were longest on plants 30 days old whereas perithecia production was greatest on plants 20∼30 days old at time of inoculation. Differences in lesion length and perithecia production that were observed on young plants (4∼10 days old) were similar to relative levels of susceptibility in soybean cultivars in greenhouse and field tests, suggesting that reaction to C. ilicicola in soybean cultivars may be determined early in plant development.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.309-312
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• 2000

Nonuniform temperature distribution due to hydration heat induces thermal stress in mass concrete. At early ages, such thermal stress may induce thermal cracks which can affect on the durability ad safety of the structure. Steel fiber reinforced concrete may be useful when a large amount of energy has to be absorbed, when a high tensile strength and reduced cracking are desirable, of an improvement of thermal conductivity is desirable. In LG IPP Project, the upper part(50cm) of turbine foundation was replaced with steel fiber reinforced concrete to reduce the thermal crack induced by hydration heat. It was shown that the thermal crack control could be successfully achieved by steel fiber reinforced concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.321-326
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• 2003

The nonlinear humidity distribution occurs due to the moisture diffusion when a concrete is exposed to an ambient air. These nonlinear humidity distribution induces shrinkage cracks on surfaces of the concrete. Because shrinkage cracks largely affect the durability and serviceability of concrete structures, the moisture diffusion in concrete must be investigated. The purpose of this paper is to propose a model of the moisture diffusion coefficient that governs moisture diffusion within concrete structures. To propose the model, numerical analysis were performed based on several experiments. Because the moisture diffusion coefficient is changed with aging, especially at early ages, the proposed model includes aging effect by terms of the porosity as well as the humidity of concrete.

• 건축역사연구
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• 제1권2호
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• pp.159-171
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• 1992

Renaissance Age is called the Period of Discovery because of great development of the economy and the science, and is known the Period of scientific analysis of Man and of interest of Nature out of a blind obedience in the Middle ages. Especially in visual art architecture, painting and sculpture, the rational spirit of Renaissance actually and distinctly communicates the meaning of Work through the scientific and mathematical expression after a finding Perspective by Brunelleschi. So the puropse of this study is to clarify the substancial meaning of Renaissance Art by investigating the expression applied Perspective to the works of Brunelleschi's architecture, Donatello's sculpture and Masaccio's painting.

• 한국지구과학회지
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• 제24권2호
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• pp.100-107
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• 2003

The purpose of this study is to assess gifted students' conceptions about nature of science (NOS). Scientifically gifted students who are expected to be professionals in the future should possess an adequate understanding of NOS that if firm foundation for scientific career. 47 volunteers from the 8th grade gifted science program in Seoul National University Gifted Education Center participated to answer questions inquiring NOS conceptions. Their answers were analyzed and compared to different groups such as non-gifted students and younger gifted students. As a result, gifted students' understanding of NOS appeared to surpass that of non-gifted students in many aspects and it seemed that gifted students formed their NOS view in early ages. The relative weakness in their NOS conceptions was found in understanding of scientific enterprise. Their strong misunderstanding about obstacles that minority people would face in scientific enterprise was noticed, too. They admitted that there has been discrimination in scientific enterprise, but they wrongly believed that outstanding scientists cannot be affected by it. Further studies will be required to probe more.