• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.721-724
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• 2008

The present study was to develop a dry PFB method similar to the existing gypsum board construction method in order to apply the existing wet PFB method that uses fire.resistant adhesive. It was found that the existing wet method can produce concrete compressive strength of 80MPa and fire resistance of 3 hours with 30mm PF boards. The goal of development in this study was fire resistance of 3 hours through dry construction of 15mm fire resistant boards. The results of fire resistance test showed an increase in thermal durability and thermal strain. It is believed that inorganic fiber reduces thermal strain, and lowers heat insulation performance by 15% or less. This suggests that heat insulation performance was improved by the change in the inner composition of PF board resulting from the adjustment of Al:Si mol ratio, high temperature molding, and dry curing. According to the results of fire resistance test, when the dry PF method was applied, the temperature of the main reinforcing bar was 116$^\circ$C in 15mm, 103.8$^\circ$C in 20mm, and 94$^\circ$C in 25mm, and these results satisfied the current standards for fire resistance control presented by the Ministry of Land, Transport and Maritime Affairs. When a 3 hour fire resistance test was performed and the external properties of the specimen were examined, the outermost gypsum board hardly remained and internal PF board maintained its form without thermal strain.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.262-266
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• 2010

ZnO nanostructures were grown on an Au seed layer by a hydrothermal method. The Au seed layer was deposited by ion sputter on a Si (100) substrate, and then the ZnO nanostructures were grown with different precursor concentrations ranging from 0.01 M to 0.3M at $150^{\circ}C$ and different growth temperatures ranging from $100^{\circ}C$ to $250^{\circ}C$ with 0.3 M of precursor concentration. FE-SEM (field-emission scanning electron microscopy), XRD (X-ray diffraction), and PL (photoluminescence) were carried out to investigate the structural and optical properties of the ZnO nanostructures. The different morphologies are shown with different growth conditions by FE-SEM images. The density of the ZnO nanostructures changed significantly as the growth conditions changed. The density increased as the precursor concentration increased. The ZnO nanostructures are barely grown at $100^{\circ}C$ and the ZnO nanostructure grown at $150^{\circ}C$ has the highest density. The XRD pattern shows the ZnO (100), ZnO (002), ZnO (101) peaks, which indicated the ZnO structure has a wurtzite structure. The higher intensity and lower FWHM (full width at half maximum) of the ZnO peaks were observed at a growth temperature of $150^{\circ}C$, which indicated higher crystal quality. A near band edge emission (NBE) and a deep level emission (DLE) were observed at the PL spectra and the intensity of the DLE increased as the density of the ZnO nanostructures increased.

• Fire Science and Engineering
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• v.29 no.6
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• pp.40-44
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• 2015

National and international standards for curtain wall glass are focused on wind pressure and insulation performance, but disasters such as fires and earthquakes are not considered. Failure of curtain wall glass during a fire in a skyscraper increases the loss of lives and property due to the spread of fire. Therefore, the fire resistance of curtain wall glass should be investigated, and technology to prevent glass failure should be developed to prevent fire damage due to spreading fire. It is important to predict the starting point of cracks and the cause of glass failure to prevent it effectively using the limited water in a skyscraper. In this study, double glazed glass was exposed to a radiator in an experiment performed to analyze the thermal characteristics. The results show that glass that was not directly exposed to high temperature and pressure was broken. To identify this failure case, numerical analysis was performed. Three glass specimens were installed in an ISO 9705 room and exposed to radiation using a radiator, and a thermocouple was used to measure the temperature on the surface of the glass. Widely used double glazed glass was analyzed for weakness to fire.

• Journal of the Korean Geotechnical Society
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• v.31 no.3
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• pp.39-50
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• 2015

The installation of the expansion joints in a tunnel concrete lining and duct would minimize the cracking at the location of structural shape and stiffness change, differential settlement, big temperature change, and so on. However, it is difficult to determine the required spacing of the expansion joint in a tunnel concrete lining and duct quantitatively because the spacing is influenced by temperature change, structure construction condition, ground-structure interaction, and etc. Nevertheless, a highway specification (Korea Expressway Corporation, 2012) or a road design manual (Ministry of Land, Transport and Maritime Affairs, 2010) specifies that the expansion joint spacing in a tunnel concrete lining should be installed uniformly smaller than 25 m from the tunnel portals to 50 m inside of a tunnel and elsewhre 20-60 m in a tunnel (because there is no specifcation for a duct it is assumed that a duct follows the specfication of lining). This specification results in several construction and economic problems in relation with a tunnel construction. Accordingly, in order to minimize the problems, this study analyzed both domestic and foreign design standards and specifications. In addition, field test, theoretical and numerical analyses were carried out in relation to the expansion joint in a tunnel lining and duct. The purpose of this study is to reestabilish a criterion for installing the expansion joint in a tunnel concrete lining and duct.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.12
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• pp.733-740
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• 2017

'The facilities standards of water supply' issued by the Ministry of Environment in 2004 indicates that expansion joints cannot be used in welding water supply steel pipes. However, their reason is not clear and it is difficult to confirm the stability of the steel pipe for a water supply pipeline. The purpose of this study is to determine whether or not an expansion joint is necessary to improve the stability of water supply in steel pipe through a displacement analysis of the pipework. The test results are as follows. Firstly, it was found that expansion and contraction of the water supply steel pipe (D 2,400 mm) occur repeatedly in 4 cycles per year, and the maximum expansion and contraction amount of the pipe is 13.03 mm in 1.24 km pipelines. Secondly, the thermal stress caused by expansion and contraction of the steel pipe is $13.7{\sim}36.1kgf/cm^2$ according to the burial depth (0~4 m). The main comparison factors to determine the stability of the steel pipe (STWW 400) were the allowable tensile strength and the fatigue limit, which were computed to be $4,100kgf/cm^2$ and $1,840kgf/cm^2$, respectively. Finally, the thermal stress of the steel pipe is very small compared to the allowable tensile stress and fatigue stress. Therefore, thermal stress does not affect the stability of the steel pipe, although the expansion and contraction of the steel pipe occurs by temperature changes. In conclusion, the study demonstrated that expansion joints are not required in water supply steel pipelines.

• Applied Microscopy
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• v.34 no.1
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• pp.61-69
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• 2004

The microwave dielectric properties and microstructures of the Complex Perovskite (1-x)$(Li_{1/2}Sm_{1/2})TiO_3-x (Na_{1/2}Sm_{1/2})TiO_3$(LNST) system were investigated using the X-ray diffraction (XRD) and scanning electron microscopy (SEM). LNST had not only the antiphase tilting of oxygen octahedron but also the inphase tilting of oxygen octahedron and the antiparallel shift of cations. Also, when $0.0{\leq}x{\leq}0.4$, LNST had the vacancy ordering of A-sites because of the evaporation of Li ions. From the observation of the microstructure, abnormal grain growth phenomena were observed over the whole range of x. The temperature coefficient of resonant frequency ($T_{cf}$) of the $({Li_{1/2}}^{+1}{Sm_{1/2}}^{+3})TiO_3$(LST) system has a large negative value ($-220ppm/^{\circ}C$) but the $({Na_{1/2}}^{+1}{Sm_{1/2}}^{+3})TiO_3$(NST) system which substituted $Na^{+1}$ has a large positive value ($+173ppm/^{\circ}C$). The dielectric properties of ${\varepsilon}_r=103,\;Q*f_{0}=3,700GHz$ and $T_{cf}=+50ppm/^{\circ}C$ at 4GHz were obtained when x =0.4.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1182-1189
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• 1998

High quality $TiN/TiSi_2$-bilayers were formed on the Si(100) substrate at room temperature and at $600^{\circ}C$ first by coevaporation of stoichiometric Si and Ti(Si:Ti = 2:1) fellowed by Ti reactive deposition in N, gas ambient, and in situ annealing in ultrahigh vacuum. Stoichiometric $Ti_{0.}N_{0.5}$, films with (111) texture and $C54-TiSi_2$ films were grown by annealing at temperatures above $700^{\circ}C$. $TiN/C54-TiSi_2$/Si(100) interface was clear and flat without agglomoration, and $CS4-TiSi_2$ film was epitxailly grown. The sheet resistance of the $TiN/TiSi_2$- bilayer decreased as the annealing temperature increased and about $2.5\omega/\textrm{cm}^2$ was obtained from the sample annealed over $700^{\circ}C$.

• Journal of Bio-Environment Control
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• v.27 no.3
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• pp.269-275
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• 2018

In order to establish the criterion for analyzing outdoor weather conditions in the greenhouse heating and cooling system design, we analyzed heating and cooling design outdoor temperatures by the annual percentile method and compared with design outdoor temperatures by the existing seasonal percentile method. In the annual percentile method, 0.4%, 1% and 2% of the total 8,760 hours per year are presented as cooling design outdoor temperatures and 99.6% and 99% as heating design outdoor temperatures. When the annual percentile method was adopted, heating design outdoor temperatures increased by 6.7 to 9.6% compared with the seasonal percentile method, and cooling design outdoor temperatures decreased by 0.6 to 1.1%. The maximum heating load in the same greenhouse condition decreased by 3.0 to 3.6% when the annual percentile method was adopted, but the effect on the maximum cooling load was insignificant. Therefore, it is necessary to consider the change of heating design outdoor temperatures to the annual percentile method, but it is not necessary to change the cooling design outdoor temperatures since there is little difference between the two methods.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.1
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• pp.29-37
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• 2008

With the rapid development of display technology as well as the diversity of display, image quality assessment plays an important role in display color reproduction. The image quality has described by objective evaluation based on the physical measured data, such as contrast ratio, color reproduction range, color temperature, and gamma characteristics, etc., however, the final judgement is achieved by perceptual quality assessment of observers. Therefore, it is necessary to investigate the relationship between physical performance of display and perceptual image quality. Thus, in order to evaluate objectively the color reproduction characteristics of two mobile displays, TFT-LCD and AMOLED, we measured the darkroom contrast ratio of full screen, luminance and color temperature of full-screen white, full-screen gray and color linearity, tone reproduction of color scales for each RGB primary, and color reproduction range. Then the pair-wise comparison is implemented for image experts and naive observers not only to judge their preference on principal evaluation attributes but also to subjectively describe perceived image quality. Through two evaluation processes, we derived the objective bases that can prove the results of subjective image quality assessment by interconnecting physical factors that have influence on observers' preference judgements. Finally, this paper provided important information for improving the image quality and increasing preference from an observer's point of view.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.1
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• pp.63-66
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• 2008

Sunscreen is usually used by people when they are at the beach or outdoor swimming pools. Since the existing methods of and standards for measuring the effects of blocking ultra violet rays do not employ water resistance test methods, the establishment of a water resistance SPF test method is required. In this study, to standardize the SPF evaluation methods for a water resistant sunscreen, proposed measurement methods in this study were compared with those of foreign countries. Selected water resistance SPF experiments confirmed the product's suitability and a verification test was then conducted by establishing the variables of water resistance SPF measurement methods. In the comparative experiment on water resistance SPF given a water temperature of $23{\sim}32$ degrees centigrade showed that temperature did not have any statistically significant effect on water resistance SPF. The changing water flow also did not have any statistically significant effect on the water resistance SPF. Therefore, continuous 20 min water circulation is deemed appropriate as an alternative to the subject's usual activity.