• Nuclear Engineering and Technology
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• v.38 no.1
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• pp.99-108
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• 2006

SNU-RCCS is a water pool type RCCS (Reactor Cavity Cooling System) developed for VHTR (Very High Temperature Reactor) application by SNU (Seoul National University). Since radiation heat transfer is the major process of passive heat removal in a RCCS, it is important to determine the precise emissivity of the reactor vessel. Review studies have used a constant emissivity in the passive heat removal analysis, even though the emissivity depends on many factors such as temperature, surface roughness, oxidation level, wavelength, direction, atmosphere conditions, etc. Therefore, information on the emissivity of a given material in a real RCCS is essential in order to properly analyze the radiation heat transfer in a VHTR. The objectives of this study are to develop a method for compensation of the factors affecting the emissivity measurement using an infrared thermometer and to estimate the true emissivity from the measured emissivity via the developed method, especially in the SNU-RCCS environment. From this viewpoint, we investigated factors such as the attenuation effect of the window, filling gas, and the effect of background radiation on the emissivity measurements. The emissivity of the vessel surface of the SNU-RCCS facility was then measured using a sight tube. The background radiation was subsequently removed from the measured emissivity by solving a simultaneous equation. Finally, the calculated emissivity was compared with the measured emissivity in a separate emissivity measurement device, yielding good agreement with the emissivity increase with vessel temperature in a range of 0.82 to 0.88.

• Journal of Welding and Joining
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• v.21 no.7
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• pp.65-70
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• 2003

Thermal emissivity is generally affected by surface situation of material such as roughness. In this study, the effect of surface roughness on measuring thermal emissivity is experimented. And emissivity measurement method and equipment using hemisperical mirror is also reviewed. As the result of this research, thermal emissivity increased as long as increasing surface roughness. So, surface roughness is a essential check point when we measure the emissivity.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.165-168
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• 2005

In this study, emissivity and land surface temperature (LST) were retrieved using the previously developed algorithms and Aqua/MODIS data. And sensitivity of estimated emissivity and LST to the predefined values, such as land cover, normalized difference vegetation index (NOVI) and spectral emissivity were investigated. The methods used for emissivity and LST were vegetation cover method (VCM) and four different split-window algorithms. The spectral emissivity retrieved by VCM was not sensitive to the NOVI error but more sensitive to the land cover error. The comparison of LST showed that the LST was systematically different without regard to the land cover and season. And the LST was very sensitive to the emissivity error excepting the Uliveri et al. This preliminary result indicates that more works are needed for the retrieval of reliable LST from satellite data.

• Carbon letters
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• v.10 no.3
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• pp.225-229
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• 2009

Thermal emissivity of commercial nuclear graphites (IG-110, PCEA, IG-430 and NBG-18) following changes in oxidation degrees were examined. Specimens were oxidized to 0%, 5%, and 10% in air flow of 5l/min at $600^{\circ}C$ using a furnace, and the thermal emissivities were measured using an infrared spectrum analyzer. The measuring temperatures for the thermal emissivity were $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$, $400^{\circ}C$ $500^{\circ}C$. Also density and porosity of the specimens were observed to compare with thermal emissivity. Results showed that emissivity increased with oxidation, and the 10% oxidized NBG-18 showed the highest emissivity (0.890) which value is larger for 24% than the value of as-received specimen. Investigation of factors affecting the emissivity revealed that increases in the surface roughness and porosity due to oxidation were responsible for the increase in emissivity after oxidation.

• Atmosphere
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• v.25 no.4
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• pp.601-610
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• 2015

This study measured the emissivity spectra of 5 major rock-forming minerals using a Fourier Transform Infrared (FT-IR) spectrometer in the spectral region of $650{\sim}1400cm^{-1}$. The mineral samples are quartz, albite, bytownite, anorthite, and sandstone. We compared emissivity spectra measured in this study with spectra provided by Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Arizona State University (ASU). The spectral features of emissivity such as Reststrahlen Band (RB) and Christiansen Feature (CF) locations were compared. Results showed that both CF and RB locations of emissivity spectra measured in this study were similar to those from ASTER and ASU. In the case of quartz, the RB was occurred in the region of $700{\sim}850cm^{-1}$ and $1050{\sim}1250cm^{-1}$. The spectral position of emissivity peak was in good agreement with the location of ASTER and ASU. For plagioclase (albite, bytownite, and anorthite), the spectral location of CF was shifted toward larger wavenumber and the emissivity value was increased in the region of $870{\sim}1200cm^{-1}$ with Ca percentage. The CF of anorthite and bytownite was occurred at $1245.79cm^{-1}$, and that of albite was occurred at $1283.79cm^{-1}$. We also confirmed that emissivity feature of sandstone includes both emissivity features of quartz and calcite. However, there were some differences in the magnitude of emissivity and locations of RB and CF. These were due to the differences in measurement methods, and differences in particle size and temperature of samples.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.1
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• pp.57-62
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• 2024

This study conducted a measurement method of high temeprature conditions using infrared termography. All objects emit infrared light, and this emissivity has a significant impact on the temperature measurements of infrared thermal imaging (IR) cameras. In order to measure the temperature more accurately with the IR camera, correction equations were derived by measuring the emissivity according to the temperature change of combustible metals in a high-temperature environment. Two combustible metals, Mg and Al, were used to measure emissivity with changing temperature. Each metal was heated, the emissivity was measured by comparing the temperature with IR camera and thermocouples so that the correlation between temperature and emissivity could be anslyzed. As a result of the experiment, the emissivity of the metals increases as the temperature increased. This can be interpreted as a result of increased radiation emission as the thermal movement of internal metal molecules increased.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.54-58
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• 2001

The measurement method of the spectral emissivity by using hemispherical mirror which has an inclined observation hole is studied. This method is useful in measuring the spectral emissivity of the solid material both conductor and non-conductor. In this study, the effective reflectivity of the hemispherical mirror is also measured for calculating the spectral emissivity of materials. The effective reflectivity measured is 0.9.

• Journal of the Korean earth science society
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• v.27 no.7
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• pp.787-803
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• 2006

The drought index has been developed, based on a $8.6{\mu}m$ surface emissivity in the $8-12{\mu}m$ MODIS channels over the African Sahel region (10-20 N, 13 W-35 W) and the Seoul Metropolitan Area (SMA: 37.2-37.7 N, 126.6-127.2 E). The emissivity indicates the $SiO_2$ strength and can vary interannually by vegetation, water vapor, and soil moisture, as a potential indicator of drought conditions. In a well-vegetated region close to 10 N of the Sahel, the Normalized Difference Vegetation Index (NDVI) showed high sensitivity, while the emissivity did not. On the other hand, the NDVI experienced negligible variability in a poorly vegetated region near 20 N, while the emissivity reflected sensitively the effects of atmospheric water vapor and soil moisture conditions. Seasonal variations of the emissivity (0.94-0.97) have been examined over the SMA during the 2003-2004 period compared to NDVI (or Enhanced Vegetation Index; EVI). Here, the dryness was more severe in urban area with less vegetation than in suburban area; the two areas corresponded to the north and south of the Han river, respectively. The emissivity exhibiting a significant spatial correlation of ${\sim}0.8$ with the two indices can supplement their information.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.493-501
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• 2013

LED lighting is sensitive because it made by semiconductor. So it has been researched about radiation of heat technologies for a long time. In addition, measurement and assessment a radiation of heat also conducted. It is necessary to get a date of accuracy temperature on the board after LED driven for measuring Junction temperature of the LED Lighting. For this research, we use 5 chip which is 4 W power on top of LED lighting board made by aluminum. Thermal camera effects to emissivity depending on material and property of the surface in LED board because it determines thermal energy which emitted from material surface. it is not only thermal camera has not a standard about emissivity. It has an error of temperature when emissivity was measured by thermal camera. we confirmed that emissivity and reflected temperature depending on color and quality of the surface throughout experiment.

• Journal of the Semiconductor & Display Technology
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• v.12 no.1
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• pp.29-33
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• 2013

We have fabricated transparent polymer composite films with high thermal emissivity, which can be used for heat dissipation of transparent electronics. PMMA (poly(methyl methacrylate)) solution with high transparency and thermal emissivity is mixed with various fillers (carbon nanotubes (CNTs), aluminum nitride (AlN), or silicon carbide (SiC)) with high thermal conductivity. We have achieved the thermal emissivity as high as 0.94 by the addition of CNTs. Compared with the PMMA film on glass, however, the addition of AlN or SiC is shown to rather decrease the thermal emissivity. It is also observed that the thickness of the PMMA film does not affect its thermal emissivity. To avoid any degradation of the thermal conductivity, therefore, the PMMA film thickness is desirable to be $1{\mu}m$. There also exists a tradeoff between the optical transmittance and thermal conductivity on the selection of the amount of fillers.