• 자원환경지질
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• 제9권3호
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• pp.127-134
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• 1976

The K-Ar age determined on six granitic rocks samples from the Eonyang- and the northwestern part of Ulsan-quardrangle, Kyeongsang-nam-do, Korea, ranges from $87{\times}10^6$ years to $58{\times}10^6$ years. Three of the samples belong to the upper Cretaceous ($87{\times}10^6-71{\times}10^6years$) and three to the late Cretaceous-early Tertiary ($63{\times}10^6-58{\times}10^6years$) in age. The early Tertiary ages are measured first on the "Younger Granites" in Korea. These two emplacement periods of granitic rocks are representative that the former is correlated to north Kyushu-Seto Inland belt ($95{\times}10^6-75{\times}10^6years$) and the later to Sanin-central Honshu belt ($65{\times}10^6-50{\times}10^6years$), in southwestern Japan.

• 영어어문교육
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• 제6호
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• pp.219-239
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• 2000

There has been a growing enthusiasm in Korea for the early education of English as a foreign language (EFL). The present study examined the validity of the Critical Period Hypothesis in terms of the Universal Grammar (UG), in three different types of learning contexts - first language (L1), second language (SL), and foreign language (FL) learning contexts. While previous research findings in L1 and SL learning contexts suggest that UG principles and parameters are accessible to language learners only for the early years of lifetime, this article argues that their results - and even the methods - cannot be applied to EFL settings and that independent studies on the EFL context are, required. It also proposes the recent UG notion of functional categories as the most appropriate subject in the discussion of Korean EFL learners' access to UG. Findings on foreign language contexts, including the author's own, strongly indicate that UG is not sensitive to learners' starting ages in FL settings. If young children in FL contexts cannot develop their interlanguage grammar based on UG, the existing teaching methods for young children should be revised.

• 콘크리트학회논문집
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• 제17권5호
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• pp.853-856
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• 2005

A low water/cement ratio leads to autogenous shrinkage of cement paste at an early age. This autogenous shrinkage is related to the change of relative humidity in the pore structure that is formed during the hydration process. The relationship between autogenous shrinkage and relative humidity change are relatively well defined today, but the effects of temperature on autogenous shrinkage, relative humidity, and pore structures have been studied less systematically. This study focused on correlating alterations of these properties of cement paste hydrated at constant temperatures of 20, 40, and $60^{\circ}C$. The test results clearly indicate that increasing curing temperature resulted in increased porosity, particularly for pores between 5 to 50 nm as measured by MIP, and increased autogenous shrinkages, as a consequence of a reduction of relative humidity at early ages.

• Computers and Concrete
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• 제16권1호
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• pp.125-140
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• 2015

This paper describes the numerical calculation of elastic properties of a simulated microstructure of cement paste from very early age, when most previous models fail to give accurate results. The development of elastic properties of tricalcium silicate pastes was calculated by discretising a numerical resolution-free 3D vector microstructure to a regular cubic mesh. Due to the connections formed in the microstructure as an artefact of the meshing procedure, the simulated elastic moduli were found to be higher than expected. Furthermore, the percolation of the solids was found to occur even before hydration started. A procedure to remove these artefacts, on the basis of the information available in the vector microstructures was developed. After this correction, a better agreement of the experimental results with calculations was obtained between 20% and 40% hydration. However, percolation threshold was found to be delayed significantly. More realistic estimates of percolation threshold were obtained if either flocculation or a densification of calcium silicate hydrate with hydration was assumed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.95-101
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• 1999

This study was performed to evaluate the characteristics of workability and strength of the concrete containing mineral admixtures such as flyash, blast furnace slag, zeolite powder. As a result, considering their workability and strength, the optimum replacement ratio of them to plain concrete were obtained for each ternary admixture. This increased compressive strength was ascribed to both the closer parkinof fine particles and pozzolan reactivity of powders. This work showed that could be effectively utilized as a blending material without any decrease in the strength of early hydration stage. On the other hand, we found that the compressive strength at early ages ternary ordinary and high strength concrete untill 7 days was small, but that ternary concrete at 28days was highly increased about 31% and 15% extent.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.349-354
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• 1999

Specialty cellulose fibers processed for the reinforcement of concrete offer relatively high levels of elastic modulus and bond strength. The hydrophilic surfaces of specialty cellulose fibers facilitate their dispersion and bonding in concrete. Specialty cellulose fibers have small effective diameters which are comparable to the cement particle size, and thus promote close packing and development of dense bulk and interface microstructure in the matrix. The relatively high surface area and the close spacing of specialty cellulose fibers when combined with their desirable mechanical characteristic make them quite effective in the suppression and stabilization of microcracks in the concrete matrix. The properties of fresh mixed specialty cellulose fiber reinforced concrete and the contribution of specialty cellulose fiber to the restrained shrinkage crack reduction potential of cement composites at early age and theirs evaluation are presented in this paper. Results indicated that specialty cellulose fiber reinforcement showed an ability to reduce the total area significantly (as compared to plain concrete and polypropylene fiber reinforced concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.309-312
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• 2003

Quasi-instanteneously performed creep loading is probably one way to seperate the viscous and the plastic creep from the elastic deformation. For mature concrete no differences seem to exist depending on whether the loading is rapidly applied or not. At early age the plastic deformations probably dominate the deformation. A series of test have been done to measure the quasi-instanteneous deformation in concrete specimens according to loading durations and concrete ages. The present study indicates that even very short-term loading contains creep deformation. As concrete is younger and load duration is longer, the proportion of creep deformation in quasi-instanteneous deformation is increased.

• 천문학회보
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• 제42권2호
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• pp.40.1-40.1
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• 2017

Massive early-type galaxies (ETG) have been spectroscopically confirmed up to z>3 which, together with their ages and abundances at z>1.5, implies that their progenitors must have converted gas into stars on short timescales. The termination of star formation in these galaxies can occur through several channels, but they remain largely conjectural, in part due to the current lack of direct measurements of the amount of residual gas in high redshift ETGs. Here I will present constraints on the star formation rate and dust/gas content of z=1.4-2.5 ETGs. These galaxies, close to their epoch of quenching, contained more than 2 orders of magnitude more dust than their local counterparts, which suggests the presence of substantial amounts of gas and a low star formation efficiency.

• Journal of Genetic Medicine
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• 제10권1호
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• pp.7-12
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• 2013

Familial Juvenile hyperuricemic nephropathy (FJHN) is a rare autosomal dominant disorder, characterized by early onset of hyperuricemia, gout and progressive kidney disease. Hyperuricemia prior to renal impairment and decreased fractional excretion of uric acid are hallmarks of FJHN. Renal dysfunction gradually appears early in life and results in end-stage renal disease usually between the ages of 20 and 70 years. FJHN is mostly caused by mutations in the uromodulin gene located at 16p12. The course of FJHN is highly variable. Treatment includes management for hyperuricemia, gout and progressive kidney disease. Individuals with gout have been usually treated with allopurinol. But controversy exists as to whether uric acid lowering therapy prevents the progression of chronic kidney disease.

• Journal of Chest Surgery
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• 제29권2호
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• pp.164-170
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• 1996

From January 1986 to June 1993, 12 patients Aad required reoperation: 9 had undergone mitral and 3 aortic valve replacement. Five were male and 7 female, and ages ranged from 29 to 61 years. Replacement of the prosthetic heart valve was performed at a mean interval of 98 $\pm$ 1 months after the Hrst operation. In aortic valve replacement patients the mean interval was 115 $\pm$ 2 months and in mitral valve replacement patients 98 $\pm$ 4 months. Primary tissue failure was the most frequent reason of replacement (10 patients) followed by valve thrombosis (1 patient) and prophylactic replacement (1 patient) in order. The most pronounced pathology of the failed prosthetic heart valves seen in the primary tissue failure group was calcification, perforation, shrinkage and tearing of the cusps. There was one early operative death (8.3%) due to intractable low cardiac output and acute renal failure. Eleven early survivors had successful operative results and there was no late death.