• Journal of Korean Vacuum Science & Technology
• /
• v.6 no.2
• /
• pp.67-70
• /
• 2002

Multi-period low-emissivity (low-e) filters based on [TiO$_2$｜Ti｜Ag｜TiO$_2$] layer structure were designed and fabricated by a RF magnetron sputtering method. Optical, structural, chemical, and electrical properties were investigated with various analytical tools. Interface layers consisting of Ag, Ti, and O were observed next to Ag layers by Rutherford backscattering spectrometry (RBS) analysis. The results show that Ti layers of ~ 1.8 nm protect the Ag layers from oxidation better than those of ~ 1 nm and the optical spectra of the filter with thicker Ti layers are in agreement with the simulated one. The average transmittance of a low-e filter with thicker Ti layers is reduced and the sheet resistance is slightly increased due to the increased Ti thickness.

• Journal of the Society of Naval Architects of Korea
• /
• v.44 no.1 s.151
• /
• pp.40-47
• /
• 2007

This study is focused on developing a software that predicts the temperature distribution and infrared Emission from 30 objects considering the solar radiation through the atmosphere. The solar radiation through the atmosphere is modeled by using the well-known LOWTRAN7 code. Surface temperature information is essential for generating the infrared scene of the object. Predictions of the transient surface temperature and the infrared emission from a naval ship by using the software developed here show fairly good results by representing the typical temperature and emitted radiance distributions expected for the naval ship considered in mid latitude. Emissivity of each material is appeared to be an important parameter for recognizing the target in Infrared band region. The numerical results also show that the low emissivity surface on the heat source can be helpful in reducing the IR image contrast as compared to the background sea.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.25 no.3
• /
• pp.251-258
• /
• 2022

Infrared stealth technology used in aircraft is applied to reduce the infrared signal by controlling surface temperature and emissivity using internal heat sink, low emissivity material or metamaterial. However, there is one part of the aircraft where the use of this technology is limited, and that is the radome. Especially, radome should have transmittance for the specific radio frequency, therefore, common stealth technology such as emissivity control surfaces cannot be applied to radome surface. In this study, we developed metal nano-coating for infrared stealth which is applicable to radome surface. We designed slot-type pattern for frequency selective transmission in X-band, and also controlled thickness of metal nano-coating for long wavelength infrared emissivity control. As a result, our infrared stealth surface for radome has 93.2 % transmittance in X-band and various infrared emissivities from 0.17 to 0.57 according to nano-coatings thickness. Also, we analyzed infrared signature of radome through numerical simulation, and finally reduced contrast radiant intensity by 97.57 % compared to polyurethane surface.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.10
• /
• pp.3371-3380
• /
• 1996

Low resolution spectral modeling of water vapor is carried out by applying the weighted-sum-of-gray-gases model (WSGGM) to a narrow band. For a given narrow band, focus is placed on proper modeling of gray gas absorption coefficients vs. temeprature relation used for any solution methods for the Radiative Transfer Equation(RTE). Comparison between the modeled emissivity and the "true" emissivity obtained from a high temperatue statistical narrow band parameters is made ofr the total spectrum as well as for a few typical narrow bands. Application of the model to nonuniform gas layers is also made. Low resolution spectral intensities at the boundary are obtained for uniform, parabolic and boundary layer type temeprature profiles using the obtained for uniform, parabolic and boundary layer type temperature profiles using the obtained WSGGM's with 9 gray gases. The results are compared with the narrow band spectral intensities as obtained by a narrow band model-based code with the Curtis-Godson approximation. Good agreement is found between them. Local heat source strength and total wall heat flux are also compared for the cases of Kim et al, which again gives promising agreement.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.5
• /
• pp.347-350
• /
• 2013

By inserting a very thin metal layer of Ag between two outer oxide layers of amorphous silicon indium zinc oxide (SIZO), we fabricated a highly transparent SIZO/Ag/SIZO multilayer on a glass substrate. In order to find the optimized thickness of Ag layers, we investigated the variation of optical properties depending on Ag thickness. It was found that the transition of Ag layer from island formation to a continuous film occurred at a critical thickness. Continuity of the Ag film is very important for optical properties in SIZO/Ag/SIZO multilayer. With about 15 nm thick Ag layer, the multilayer showed a high optical transmittance of 80% at 550 nm and low emissivity in IR.

• Korean Journal of Materials Research
• /
• v.23 no.4
• /
• pp.215-218
• /
• 2013

Vanadium dioxide ($VO_2$) is an attractive material for smart window applications where the transmittance of light can be automatically modulated from a transparent state to an opaque state at the critical temperature of ${\sim}68^{\circ}C$. Meanwhile, F : $SnO_2$ (F-doped $SnO_2$, FTO) glass is a transparent conductive oxide material that is widely used in solar-energy-related applications because of its excellent optical and electrical properties. Relatively high transmittance and low emissivity have been obtained for FTO-coated glasses. Tunable transmittance corresponding to ambient temperature and low emissivity can be expected from $VO_2$ films deposited onto FTO glasses. In this study, FTO glasses were applied for the deposition of $VO_2$ thin films by pulsed DC magnetron sputtering. $VO_2$ thin films were also deposited on a Pyrex substrate for comparison. To decrease the phase transition temperature of $VO_2$, tungsten-doped $VO_2$ films were also deposited onto FTO glasses. The visible transmittance of $VO_2$/FTO was higher than that of $VO_2$/pyrex due to the increased crystallinity of the $VO_2$ thin film deposited on FTO and decreased interface reflection. Although the solar transmittance modulation of $VO_2$/FTO was lower than that of $VO_2$/pyrex, room temperature solar transmittance of $VO_2$/FTO was lower than that of $VO_2$/pyrex, which is advantageous for reflecting solar heat energy in summer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.28 no.9
• /
• pp.350-354
• /
• 2016

Although fibrous insulations are generally used with resistive insulation type, metallic insulation is proper matter to satisfy low head-loss and equipment life when considering the specific condition, especially for Nuclear power plant. Common insulation is resistance insulation with a low thermal conductivity. but RMI is made of sheet plate with low emissivity and closed air space. Thermal radiation is blocked by stainless steel with low emissivity. Thermal conductivity and thermal convection are blocked by closed air space. This study shows the changes and effects of the heat loss according to shape and method of stacking sheet plates inserted into the insulation and analyzed the most optimized way for thermal insulation performance. The result shows that using sheet plate structure through raised and protruding shape processing was the appropriate model to optimize thermal performance. Additionally, insulating performance of RMI improved by placing the sheet plate in a high temperature region intensively.

• Korean Journal of Remote Sensing
• /
• v.30 no.1
• /
• pp.109-126
• /
• 2014

We improved the Land Surface Emissivity (LSE) data (Kongju National University LSE v.2: KNULSE_v2) over the Communication, Ocean and Meteorological Satellite (COMS) observation region using recent(2009-2012) Moderate Resolution Imaging Spectroradiometer (MODIS) data. The surface emissivity was derived using the Vegetation Cover Method (VCM) based on the assumption that the pixel is only composed of ground and vegetation. The main issues addressed in this study are as follows: 1) the impacts of snow cover are included using Normalized Difference Snow Index (NDSI) data, 2) the number of channels is extended from two (11, 12 ${\mu}m$) to four channels (3.7, 8.7, 11, 12 ${\mu}m$), 3) the land cover map data is also updated using the optimized remapping of the five state-of-the-art land cover maps, and 4) the latest look-up table for the emissivity of land surface according to the land cover is used. The updated emissivity data showed a strong seasonal variation with high and low values for the summer and winter, respectively. However, the surface emissivity over the desert or evergreen tree areas showed a relatively weak seasonal variation irrespective of the channels. The snow cover generally increases the emissivity of 3.7, 8.7, and 11 ${\mu}m$ but decreases that of 12 ${\mu}m$. As the results show, the pattern correlation between the updated emissivity data and the MODIS LSE data is clearly increased for the winter season, in particular, the 11 ${\mu}m$. However, the differences between the two emissivity data are slightly increased with a maximum increase in the 3.7 ${\mu}m$. The emissivity data updated in this study can be used for the improvement of accuracy of land surface temperature derived from the infrared channel data of COMS.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.8 no.4
• /
• pp.561-575
• /
• 1996

The interaction of turbulent mixed convection and surface radiation in a three-dimensional channel with the heated blocks is analyzed numerically. Two blocks are maintained at high temperature and the other bottom and horizontal walls are insulated. S-4 method is employed to calculate the effect of the radiative heat transfer. The low Reynolds number k-$\varepsilon$ model proposed by Launder and Sharma is used to estimate the turbulent influence on the heat transfer enhancement. From above modeling, the effects of various channel specifications on the flow and heat transfer characteristics are investigated. The variables used for the present study are Reynolds number, block spacing, the channel height spacing for block and the emissivity. Average Nusselt numbers along the block surfaces are correlated and presented in terms of Reynolds number, emissivity and dimensionless geometric parameters. For the range of conditions in this study, average Nusselt numbers along the block surfaces are strongly influenced by the Reynolds numbers and channel height spacing for block but weakly influenced by the block spacing and the emissivity of the adiabatic walls.

• Journal of the Korean Solar Energy Society
• /
• v.37 no.6
• /
• pp.103-114
• /
• 2017

Radiation energy budget was analyzed using observation data from the Weather Information Service Engine (WISE) energy flux tower on the Seoul metropolitan area. Among observation data from the 13 energy flux towers, we used meteorological variables, radiation data (upward and downward short wave, upward and downward long wave, net short wave, net long wave and net radiation), albedo and emissivity for 15 months from July 2016 to September 2017. Although Gajwa (205) and Ttuksumm (216) sites located in urban, the albedo was relatively high due to the surround environment by glass wall buildings and the Han river around the sites. And Bucheon (209) site located in the suburb represented generally low emissivity. As a result, the albedo decreased and the emissivity increased in the city center. In the Seoul metropolitan area, the net radiation energy is $73.9W/m^2$ that the radiation budget of the surface is absorbed into the atmosphere. According to WISE observation data, it can be seen that observation at each sites are influenced by the surrounding environment.