• Journal of the Korean Ceramic Society
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• v.17 no.3
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• pp.141-144
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• 1980

Thermal expansion property of $SiO_2-Al_2O_3$ system consisted of Muan clay, Hadong Pink Kaolin and Dangjin Silica was studied. Specimens were heated at the constant rate of 18$0^{\circ}C$/hr to the max. temperatures of 115$0^{\circ}C$ to 130$0^{\circ}C$ with an interval of $25^{\circ}C$, and matured for 3hrs. The result of X-Ray diffraction analysis showed that main crystals formed were $\alpha$-quartz, $\alpha$-cristobalite and mullite. Linear thermal expansion was measured at 90$0^{\circ}C$. The results of the linear thermal expansion were decreased regularly with the increase of the sintering temperature in accordance with the following equation. $y=5$\chi$\perp1100^{\circ}$. Where $\chi$ is amounts of kaolin (wt%), and y is temperature of the changing point of linear thermal expansion.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.19-25
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• 2018

PURPOSES : The purpose of this study is to identify the road-subsidence mechanism in unsaturated sandy soils. METHODS : A series of soil chamber tests were conducted under various conditions. RESULTS : The cavity-expansion characteristics in unsaturated sandy soils due to seepage were affected by the outlet size, seepage intensity, relative density, and fine content. CONCLUSIONS : In unsaturated sandy soils, the cavity-expansion speed was affected by the outlet size, relative density, seepage intensity, and clay content; however, the cavity-expansion shape was very similar. As the outlet size and seepage intensity increased, the cavity-expansion speed increased. As the relative density increased, the cavity-expansion speed increased because of a sudden decrease in shear strength, resulting from the increased saturation (reduction of matric suction). The cavity expanded faster with the increasing clay content, up to a certain threshold. It expanded at a slower rate once it passed the threshold. Finally, it reached a stable state where the cavity did not expand due to seepage.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.85.2-85.2
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• 2011

We investigate the driven magnetohydrodynamic (MHD) turbulence by including the effect of the expansion and collapse of background medium. The main goal is to quantify the evolution and saturation of the strength and characteristic length scales of magnetic fields in expanding and collapsing media. Our findings are as follows. First, with the expansion and collapse of background medium, the time evolution of the magnetic and kinetic energy densities depends on the nature of forcing as well as the rate of expansion and collapse. Second, at scales close to the energy injection (or driving) scale, the slope of magnetic field power spectrum shallows with expansion but steepens with collapse. Third, various characteristic length scales, relative to the energy injection scale, decrease with expansion but increase with collapse. We discuss the astrophysical implications of our results.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.4
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• pp.80-86
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• 2021

Plastics are widely used in mechanical and other fields due to their light weight, design flexibility, and molding processability. In processing plastics, defective products are mixed and reprocessed to improve production efficiency and reduce costs. In this study, an experiment was conducted to confirm the coefficient of thermal expansion of HDPE during this reprocessing. The coefficient of thermal expansion was measured at different measurement directions and heating rates. As a result, we observed that the coefficient of thermal expansion in the direction perpendicular to the injection direction is greater than that in the horizontal direction.

• International Area Studies Review
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• v.13 no.3
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• pp.385-412
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• 2009

This study first analyzes economical environment change (factor) of investment nation Japan and Japanese enterprise at the analysis of Japanese enterprise's over-seas expansion factor and influence. As a result of an analysis of the factor about Japanese enterprise's overseas expansion from 1990 to 1996 and from 1998 to 2006, commonly applied factors were Yen exchange rate, interest rates, wage, enterprise profit, facility investment, and consumption expenditure. Especially, as a result of regression analysis, a sudden change of "low interest rate" was main factor at Japanese enterprise's overseas expansion from 1990 to 1996, and Japan's "Yen ex-change rate" was drawn as an important factor from 1998 to 2006. That is, from 1990 to 1996, a shock by a sudden rise in Yen value could be viewed gradually accumulated and absorbed inside Japanese economy from 1998 to 2006. Whereas it could be said that Japanese enterprise's overseas expansion was accelerated under Japanese government's overseas supporting policy and "low interest rate" together with the factor in the rise of Yen value from 1998 to 2006.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.24-33
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• 2012

The present work has suggested the design methods of the bolt body for making the anti-releasing bolts and provided the changed properties of the bolt body after explosion. To prove this work, two models of the anti-releasing bolts, M10 and M20, are produced and the expansion properties of each model are experimentally obtained. This study verify that the expansion of the bolt body is reproducible and the expansion rate could be controlled by the combination of the design factors and the anti-releasing characteristics could be quantified. It also could provide the data that would be needed to make the bolts with the anti-releasing effect.

• Journal of Korea Multimedia Society
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• v.23 no.11
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• pp.1361-1371
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• 2020

Fonts have developed as a visual element, and their influence has rapidly increased around the world. Research on font automation is actively being conducted mainly in English because Hangul is a combination character and the structure is complicated. In the previous study to solve this problem, the stroke element of the character was automatically extracted by applying the object detection by component. However, the previous research was only for similarity, so it was tested on various print style fonts, but it has not been tested on other characters. In order to extract the stroke elements of all characters and fonts, we performed a performance analysis experiment according to the expansion character in the Hangul stroke element extraction training. The results were all high overall. In particular, in the font expansion type, the extraction success rate was high regardless of having done the training or not. In the character expansion type, the extraction success rate of trained characters was slightly higher than that of untrained characters. In conclusion, for the perfect Hangul stroke element extraction model, we will introduce Semi-Supervised Learning to increase the number of data and strengthen it.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.4
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• pp.380-387
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• 1994

An experimental study was performed to investigate the characteristics of refrigerant flow rate control and superheat in an evaporator with an electronic expansion valve(EEV). The EEV used in this study was devised using a needle valve coupled with a stepping motor controlled by a personal computer. A Pill control equation was used to control the superheat of the evaporator and to set the superheat to $5^{\circ}C$. In order to determine an optimum running condition for the system, Pill parameters were varied for the wide range of values. The running condition of an air conditioning system with a PI control was reasonably stable compared with that of the Pill control. Experimental results for the PI control using parameter values, $K_p=1.5$, $T_i=400(sec)$ and $T_s=6(sec)$ show that the superheat reached its target value. When external disturbances were introduced to the system, the superheat target value was reached within about 3 minutes. When the EEV was applied to the air conditioning system driven by an inverter, room temperature control was excellent.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1031-1036
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• 2009

This study is intended to identify how quick disconnect coupling which connects with refrigerant piping of air-conditioner using R-22 refrigerant has effect on characteristics of flux. in the case where the air-conditioner installs utilizes quick disconnect coupling, COP has an effect on the quantity of cooling load because of changing flow rate and physical properties of refrigerant which flow into an entrance of expansion valve from coupling. Variation of flow rate can be regulated by changing expansion-contraction angle; $\alpha$ of an entrance and an exit of coupling. In this study, quick disconnect coupling is presented flow of coupling by using FLUENT as heat flow program. To have an effect on the expansion entrance valve, and by changing expansion-contraction angle; $\alpha$ of an entrance and an exit

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.1107-1112
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• 2009

Ground anchor should not be used in soft clay, because anchor resistance can not be guaranteed. However, there is a way to increase the capacity of anchors. The pulse powered anchor is an underreamed anchor by using high voltage electrokinetic pulse energy. In this study, a series of field test were carried out in order to find expansion rate related in number of pulse charge. and Anchor pull-out tests were performed at the Geotechnical Experimentation Site at Sungkyunkwan University in Suwon, Korea. Data were analyzed in order to define a relation between expansion rate and ultimate pullout load.