• Land and Housing Review
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• v.14 no.1
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• pp.115-122
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• 2023

Modular construction is popular as a smart building system because it can shorten the construction period. This study proposed a precast concrete (PC) core system that can further shorten modular construction time. The system was developed and its structural performance was verified through computational analysis. The proposed PC core system is a complete PC construction method using dry bonding. The results of the study indicated that the proposed PC core system has structural stability and performance suitable for modular housing.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.15-19
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• 2008

The use of Precast Concrete (PC) stairways is increasing to replace existing Reinforced Concrete (RC) stairways for the faster construction and the better quality control. Among several already developed PC stairway construction methods, RC Core Sequential Construction Method by Using PC Stairways (COSEC) has advantages of 1) allowing core of a building to be built prior to PC stairways so that two different procedures will not interfere with each other, and 2) having a newly developed joint connection with the core so that the RC core and PC stairways can be easily put together. In this paper, cases of several construction sites with the PC stairways method are analyzed. The elements of the developed method are described for further application and improvement.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.425-430
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• 1996

The purpose of this study is to investigate the behavior of the bearing precast concrete (pc) wall structure with hollow core based on experimental tests. In order to evaluate the cyclic performance of the pc walls. Too one story pc walls and ond one reinforced concrete wall are made. The experimental results of pc walls were compared with those values of reinforced concrete (rc) wall. The structural behaviors of pc wall structure with hollow core are similar to those of reinforced concrete bearing wall structure. This study shows that the pc wall with hollow core could be treated as rc wall when designs the pc wall structure against lateral loads

• The Korean Journal of Quaternary Research
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• v.25 no.2
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• pp.17-24
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• 2011

We investigated the variation of $CaCO_3$ contents in cores PC1 and PC2 recovered from the continental slope area of the Ulleung Basin in the East Sea. $CaCO_3$ contents of cores PC1 and PC2 varied between 0.6 and 17.2% and between 0.3 and 43.0%, respectively. $CaCO_3$ contents in the upper part of core PC1 corresponding to MIS 1 are less than 5%, whereas those in the lower part of MIS 2 are more than 10%. Such variation of $CaCO_3$ contents in core PC1 confirms the previous results of $CaCO_3$ studies in the East Sea. In core PC2, $CaCO_3$ contents of the upper part are similar to those of core PC1. However, $CaCO_3$ contents in the lower part of core PC2 are more than 40%. According to XRD operation and SEM examination, the high $CaCO_3$ contents in the lower part of core PC2 are more attributable to the authigenic carbonate minerals rather than the biogenic carbonate composition. Such abundant authigenic carbonate minerals are closely related to the dissociation of methan hydrates which were observed in the Ulleung Basin.

• Textile Coloration and Finishing
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• v.5 no.1
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• pp.19-25
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• 1993

Plastic optical fibers(POFs) composed of poly(methylmethacrylate) (PMMA), polystyrene (PS), or polycarbonate(PC) as a core materials, and of fluorinated polymer or PMMA as a cladding were fabricated and their properties were investigated in this study. The attenuation loss of PMAA core POF was about 1,700 dB/Km at 660 nm, the loss of PS core POF was 1,800 dB/Km at 560 nm, and the loss of PC core POF was 2,200 dB/Km at 780 nm. These attenuation losses of POFs prepared ill this study were higher than those of commerically available POFs. Compared to PMMA and PS core POFs, PC core POF has excellent characteristics, including high thermal stability, high flexibility, and high impact strength.

• Journal of the korean society of oceanography
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• v.33 no.4
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• pp.185-195
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• 1998

Two piston cores (94PC-2 and 95PC-4) taken from the East Sea (Sea of Japan) are studied to evaluate the paleoceanographic changes and its interaction with climatic variation. The bulk geochemistry of the non-biogenic fractions of 54 sediment samples is determined using X-ray fluorescence. Four geochemical stratigraphic units at both core sediments are recognized based on the variations in major element concentration. These chemical stratigraphic units correspond well with the sedimentological and paleontological facies. Source materials are considered as basic and/or intermediate rocks judging from silica content. A distinctive boundary around 11 kyr may correspond to Younger Dryas event. The switch of most major elements at this level and the distinctive changes in concentration of typical terrigenous elements (TiO$_2$ and Al$_2$O$_3$) are the strong evidence for the difference in sources of terrigenous materials. The weathering indices exhibit high degree in Core 94PC-2 and low degree in Core 95PC-4. The changes in weathering degree can be distinguished by the lowest value occurred at 11 kyr in Core 94PC-2 and by a gradual decrease from top to bottom in Core 95PC-4. The profiles of potassium and sodium exhibit specific excursions between the Holocene and the late Pleistocene. This implies that sediments of the two cores originating from different sources with different weathering degrees. The distinct two-group distributions in K$_2$O/CaO vs. Na$_2$O/K$_2$O also support the difference in provenance of aluminosilicate materials at the boundary of 11 kyr. Thus, supply patterns of terrigenous materials are stable in Holocene and more complicated in the last glacial period.

• Journal of The Korean Astronomical Society
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• v.35 no.2
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• pp.105-110
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• 2002

We present the results of VLA $NH_3$ (1,1) and (2,2) line observations of the young-stellar object (YSO) IRAS 19550+3248. The integrated intensity map of the $NH_3$ (1,1) line shows that there are two ammonia cores in this region; core A which is associated with the YSO, and core B which is diffuse and located at the northeast of core A. Core A is compact and elongated along the east-west direction (0.07 pc$\times$0.05 pc) roughly perpendicular to the molecular outflow axis. Core B is diffuse and extended (0.18 pc$\times$0.07 pc). $NH_3$ (2,2) line is detected only toward core A, which indicates that it is hotter (~ 15 K), presumably due to the heating by the YSO. The $NH_3$ (1,1) line toward core A is wide (${\Delta}v{\ge} 3 km s^{-l}$) and appears to have an anomalous intensity ratio of the inner satellite hyperfine lines. The large line width may be attributed to the embedded YSO, but the hyperfine anomaly is difficult to explain. We compare the results of $NH_3$ observations with those of previous CS observations and find that the CS emission is detected only toward core A and is much more extended than the $NH_3$ emission.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.123-126
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• 2005

The purpose of this study is to evaluate a effect of core reinforcement ratio to PC wide girder-column joint. Three half scale subassemblies were representing a portion of a protype structure were design, constructed, and tested to failure. From the test result, girder-column width ratio play an important role in the improvement of strength and ductility.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.587-598
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• 2004

In this study, an experiment was conducted on the Slim Floor system, using a hollow core PC slab, which could reduce the over-all depth of a composite beam. The Slim Floor system is a method used in steel frame multi-story building construction, in which the structural depth of each floor is minimized after incorporating the steel floor beams within the depth of the concrete floor slab. This experimental study focused on the flexural behavior of the partially connected Slim Floor system with asymmetric steel beams encased in hollow core PC slabs. Ten full-scale specimens were constructed and tested in this study, with different steel beam heights, hollow core PC slabs, slab widths, and PC slab bearings. Observations made in line with the experiments indicated that the degree of shear connection without additional shear connection was 0.48-0.98 times more than that of the full shear connection, due to inherent mechanical and chemical bond stress.

• Journal of the Korea Institute of Building Construction
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• v.14 no.6
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• pp.571-581
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• 2014

In the present study, hollow precast concrete wall (PC Double Wall) for staircase construction was developed. Comparing the conventional walls, the PC Double Wall can be reduced the lift weight using hollow core and improves the integrity between the PC members. The cross-section and re-bar details of the PC Double Wall were developed considering precast concrete manufacturing, constructability, and the structural safety. Particularly, a form system was developed to manufacture thin and hollow core PC wall efficiently. A mock-up test for a staircase using the PC Double wall was performed to verify the constructability and integrity of the PC walls. The test result verified that joint deformation and cracking did not occur as showing good constructability.