• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.327-328
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• 2010

In this paper, was determined optimal mixture proportion of segregation reducing type superplasticizer, and it was used to analyze the characteristics of the concrete. As a result, organic acid type and organic synthesis containing complex flow concrete with KASS 5T-401 are satisfied with the quality standards.

• Journal of the Economic Geographical Society of Korea
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• v.11 no.4
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• pp.661-667
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• 2008

We examine the major factors governing the travel time for commuters in the Seoul metropolitan area. To identify the determinants of the commuting time for residents with jobs in the city centre, a multiple regression analysis is performed using household survey data. The results reveal that commuters in Seoul place higher value on time than on living space. Thus, we may conclude that recent trends in income segregation in Seoul are not the result of increased housing demand but of dispersed jobs and better amenities offered in the suburbs.

• Journal of Korea Foundry Society
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• v.17 no.2
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• pp.180-187
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• 1997

The influence of solidification condition on the segregation of SiC particles in the $Al-xSi/6wt%SiC_p$(x: 6, 10, 14, 18${\cdot}$wt%) composites was investigated in the study. The results are as follows: 1) During the counter-gravity unidirectional solidification of $Al-Si/SiC_p$ composites melt, most of the SiC particles are pushed to the top of the casting. 2) The SiC particles pushing in the $Al-Si/SiC_p$ composite melts are not observed, when the interface velocity of melts increases more than 1.41 ${\mu}m/sec$. 3) The SiC particles are entrapped in the interdendrite regions, when the sizes of SiC particles in the $Al-Si/SiC_p$ composites are large than ${\varphi}22{\mu}m$.

• Journal of Magnetics
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• v.6 no.1
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• pp.19-22
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• 2001

Change of magnetic properties in CoCrPt/Ti perpendicular media with varying CoCrPt film thickness has been studied. As the CoCrPt film thickness increases from 25 nm, the Ms (saturation magnetization) increases rapidly at first and then more gradually. This Ms behavior is associated primarily with the formation of an "amorphous-like"reacted layer created by intermixing of CoCrPt and Ti at the CoCrPt/Ti interface and secondarily with a change of the Cr segregation mode with varying CoCrPt film thickness. Magnetic domain structure distinctively changes with increasing CsCrPt magnetic layer (ML) thickness. Also the strength of exchange coupling measured from the slope in the demagnetizing region of the M-H loop changes with ML thickness. The expansion of lattice parameters a and c at smaller film thickness suggests that the Cr segregation mode may be connected with the residual stress of the films. Finally, the negative nucleation field (Hn) shows a unique behavior with the change of strength of the exchange interaction.teraction.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.76-82
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• 1997

Recently as the development of a large-scale ocean structure or ocean is in progress, the importance of underwater concrete construction came to the fore. However, a problem with this underwater concrete construction is the segregation of cement and aggregate occurs when concrete is poured into the underwater. However, recently as an adhesiveness of the constituents of fresh concrete is increased even in our country, antiwashout concrete admixture were developed. The antiwashout concrete admixture can reduce the segregation significantly. Although this antiwashout underwater concrete is superior to the traditional underwater concrete in terms of durability, watertightness, stability, etc. But it is still unsatisfied due to the lack of criterion or construction experiences. Furthermore, because of an insufficiency of natural aggregate, the development of replacing aggregate came to be necessary. Accordingly, the purpose of this study is to investigate the feasibility of sea sand as a replacing aggregate and the characteristic change of antiwashout underwater concrete using river sand, sea sand, and blended sand (river sand:sea sand=3:7) through experimental researches.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.385-390
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• 1997

In the mixing proportion of high flowing concrete we have to use quantity of power such as cement and superplasticizer, and increase the proportion of fine aggregate more than that of plain concrete to increase flowability and segregation resistance. Therefore, the fresh state of high flowing concrete is largely affected by superplasticizer and change of grade the percentage of surface water. This study aims at development of self-filling up high flowing concrete without compaction, in case of using the fine aggregate of standard grade range, by examination on the influence of fresh state of high flowing concrete, and by understanding influence on various fluidity such as flowability, reinforcement passibility, fillingability, segregation resistance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.15-18
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• 1996

The elemental segregation in the sputter-deposited AgInSbTe recording thin films was studied by means of Auger electron spectroscopy and ESCA for the specimens of as-deposited and as heat-treated conditions. Auger electron spectroscopy and ESCA revealed an extremely thin layer of elemental inhomogeneity, especially for the silver, even in as-deposited condition. The chemical analysis results obtained in this alloy system are discussed in terms of process parameters and target microstructure.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.152-155
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• 2004

In the semi-solid die casting process, the important thing is the flow behaviors of semi-solid material. The flow patterns of semi-solid material can make the defects during die filling. To control of the flow patterns, is very important and difficult. In this paper, the flow behaviors of the semi-solid A356 alloy material during die filling at various die gate shapes has been observed with the grain size controlled material. The effects of the gate shape on the die filling characteristics were investigated. The filling tests in each plunger strokes were experimented, also simulated on the semi-solid material die casting process by MAGMAsofi. According to the filling tests and computer simulation, the effect of the gate shape on liquid segregation had been investigated.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.6
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• pp.139-144
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• 1998

In Semi-Solid Forging, it is necessary to control the forming variables accurately in order to make near-net-shape products. Generally, the defects of products may occur due to liquid segregation which can be caused by the degree of deformation and strain rate, and condition of friction in Semi-Solid Forging, where the segregation is to be predicted by flow analysis. This paper presents the feasibility of theoretical analysis model using the new yield function for compressible P/M materials which is proposed by Doraivelu et at. to the flow analysis of the semi-solid dendritic Sn-15％Pb alloys instead of adopting the yield criterion of Shima and Oyane which is used by Charreyron and Flemings. The simple compression process is taken into consideration as the model to confirm the usefulness of the adopted yield function. The distribution of the liquid fraction at various strains and strain rates in radial direction, and the influence of friction are estimated by upper-bound method.

• Journal of Korea Foundry Society
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• v.15 no.5
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• pp.507-513
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• 1995

The effect of forced convention on the solute redistribution of the Al ingot was studied quantitatively in an effort to fabricate high purity aluminum using a segregation method. Based on the experimental results, the solute concentration in the solid phase tended to decrease at the early state of solidification, and then increased gradually as solidification proceeded. Fe and Si concentrations decreased as growth rate decreased and as revolution speed increased. The solute redistribution obtained from the BPS model incorporated with the tangential flow component as well as the axial flow component within the melt, agreed well with the measurements.