• Journal of the Korea Academia-Industrial cooperation Society
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• 제21권1호
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• pp.439-447
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• 2020

Re-coating of the mirror is one of the important things to maintain the performance of a telescope. The metal coated on the mirror reflects light, and if the reflectance decreases, then the telescope's performance decreases, so the mirror must be periodically recoated. It is important to predict re-coating cycles for military telescopes and to develop maintenance plans not only for performance, but also for the telescope's availability for missions and the maintenance costs for long-term use. However, most similar telescopes used for astronomy research determine recoating cycles based on experience and operating conditions, and not for prediction of recoating. Therefore, this study predicts the cleaning cycles and re-coating cycles of a military telescope's mirror by using simulation. First, this study analyzed similar cases of domestic and foreign astronomy research institutes and the study also reviewed the need for re-coating and predicting re-coating cycles. Second, this study developed simulation for predicting cleaning and re-coating cycles according to data analysis and modeling. Finally, the study predicts cleaning cycles and re-coating cycles according to varying reflectance reduction (5%, 10%, 15%, 20%) and cleaning conditions (per 3 months, 6 months, 1 year and 2 years). As a result, this study suggests reference criteria to develop the planning for military telescopes and their maintenance.

• The Journal of the Korea institute of electronic communication sciences
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• 제14권3호
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• pp.497-504
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• 2019

We fabricated $HfO_2$ thin films using RF magnetron sputtering method, and investigated structural and optical properties of $HfO_2$ thin films with RTA temperatures in $N_2$ ambient. $HfO_2$ thin films exhibited polycrystalline structure regardless of annealing process, FWHM of M (-111) showed reduction trend. The surface roughness showed the smallest of 3.454 nm at a annealing temperature of $600^{\circ}C$ in result of AFM. All $HfO_2$ thin films showed the transmittance of about 80% in visible light range. By fitting the refractive index from the transmittance and reflectance to the Sellmeir dispersion relation, we can predict the refractive index of the $HfO_2$ thin film according to the wavelength. The $HfO_2$ thin film annealed at $600^{\circ}C$ exhibited a high refractive index of 2.0223 (${\lambda}=632nm$) and an excellent packing factor of 0.963.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• 제19권6호
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• pp.37-48
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• 2020

Eight colors prescribed by the Enforcement Rules of the Road Traffic Act and the group standard were tested to secure the minimum recursive reflectance performance standards when drying and wetting. The results were calculated to be 260.8 (mcd/㎡·lux) when drying white and 154.6 (mcd/㎡·lux) when wet. Yellow was 67% compared to the white reflective performance when drying. Wet poetry was 79 % and 59 %, respectively. In the case of blue, it was 64% in the case of white versus 72% in the case of white. Wet poetry was 63 % and 72 %, respectively. The range of changes in reflective performance during wetting was higher than when drying, and the absence of glass grains was similar to the previous results. The new colors also have a standard value of more than 50% compared to the white color in red, orange, pink, light green, and green. Based on this, it was estimated that the minimum reflective performance criteria according to the color of the road markings would form the basis for the enforcement rules of the Road Traffic Act.

• Journal of Adhesion and Interface
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• 제24권3호
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• pp.95-99
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• 2023

In this study, LiDAR-detectable black materials are synthesized by coating and reduction of titanium dioxide onto plate-type natural mica, which evaluated practical LiDAR verification. In detail, black TiO₂@Mica materials are fabricated by utilizing a sol-gel reaction to coat titanium dioxide onto natural mica, followed by reduction using sodium tetrahydridoborate. Subsequently, Black TiO₂@Mica materials are dispersed in hydrophilic transparent varnish and sprayed onto the glass substrate to assess applicability as paints. As a result, Black TiO₂@Mica-based paints exhibit true blackness (L^*=12.1) and a higher NIR reflectance (30.2 R%). In addition, it was confirmed that as-synthesized Black TiO₂@Mica materials are successfully recognized by a LiDAR sensor. This phenomenon is attributed to Fresnel's reflection law, in which light reflection occurs at the interface between natural mica and titanium dioxide with different refractive indices. In this regard, the findings of the study are expected to contribute to the potential utilization of LiDAR-detectable materials in various fields such as autonomous vehicles, robotics, and drones.

• Journal of Sensor Science and Technology
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• 제6권1호
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• pp.24-34
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• 1997

In this study, two different types of complementary electrochromic devices using amorphous $WO_{3}$ films as a working electrode, $V_{2}O_{5}$ film and NiO film as counter electrodes respectively were investigated. For the devices using amorphous and crystalline $V_{2}O_{5}$ films of $100{\sim}150nm$ thickness with $ITO/WO_{3}/LiClO_{4}-PC/V_{2}O_{5}/ITO$ structure, an optical modulation of $50{\sim}60%$ were obtained at a potential range of $1{\sim}2V$. It has been shown that transmittance and reflectance of light could be electrically controlled by low applied voltage. For the devices with $ITO/WO_{3}/LiClO_{4}-PC/NiO/ITO$ structure in which NiO film was deposited by a RF reactive sputtering, the optical modulation in visible light region (${\lambda}=550nm$) and in near infrared light region (${\lambda}=850nm$) were 25% and 30%, respectively.

• Journal of Korean Ophthalmic Optics Society
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• 제8권2호
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• pp.111-117
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• 2003

We collected the domestic and foreign half-mirror coating lens for sunglasses. Their reflectance is measured using Spectrophotometer in order to analysis their optical property and the result which is calculated using Macleod program was compared with measured reflectance. In addition, we designed the new half-mirror coating lens with gold color using TiN material and investigated the optical property of the new half-mirror coating lens. The results obtained from analysis of half-mirror coating lenses are as follow : Two-tone half-mirror coating with silver color is fabricated with [air|$SiO_2$(or $Al_2O_3$)|Cr|glass]. The role of $SiO_2$(or $Al_2O_3$) on Cr improve the hardness of the lens and the thickness of the $Al_2O_3$ with 10 nm is good to show the lens silver color. Incase of color half-mirror coating lens. Blue system is designed by [air|$SiO_2$(66.3)|$TiO_2$(129.0)|$SiO_2$(62.9)|$SiO_2$(26.0)|$TiO_2$(120.3)|$SiO_2$(9.1)|glass], gold system [air|$SiO_2$(60.6)|$TiO_2$(86.2)|$SiO_2$(13.5)|$TiO_2$(86.8)|$SiO_2$(214.38)|glass], green system[air|$SiO_2$(74.3)|$TiO_2$(75.8)|$SiO_2$(44.3)|$TiO_2$(11.6)|$SiO_2$(160.8)|$TiO_2$(12.9)|$SiO_2$(183.3)|$TiO_2$(143.8)|glass], silver system[air|$SiO_2$(21.2)|$TiO_2$(49.7)|$SiO_2$(149.3)|glass]. White half-mirror coating lens has [air|$SiO_2$(17 nm)|$TiO_2$(43 nm)(or $ZrO_2$)|$SiO_2$(87 nm)|polysiloxane($4.46{\mu}m$|glass or CR-19]. It has half-mirror coaling lens which has about 19% reflectance and about 80% transmittance in the range of visible light(400~700nm). we designed the new half-mirror coating lens with gold color, the (x, y) value of the CIE is almost similar to the CIE value of [air|$SiO_2$(170 nm)|TiN(15 nm)|glass].

• Korean Journal of Agricultural and Forest Meteorology
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• 제21권4호
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• pp.317-326
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• 2019

Salinity which is often detected on reclaimed land is a major detrimental factor to crop growth. It would be advantageous to develop an approach for assessment of salinity and drought damages using a non-destructive method in a large landfills area. The objective of this study was to examine applicability of the decision tree classifier using imagery for classifying for spring potatoes (Solanum tuberosum) damaged by salinity or drought at vegetation growth stages. We focused on comparing the accuracies of OA (Overall accuracy) and KC (Kappa coefficient) between the simple reflectance and the band ratios minimizing the effect on the light unevenness. Spectral merging based on the commercial band width with full width at half maximum (FWHM) such as 10 nm, 25 nm, and 50 nm was also considered to invent the multispectral image sensor. In the case of the classification based on original simple reflectance with 5 nm of FWHM, the selected bands ranged from 3-13 bands with the accuracy of less than 66.7% of OA and 40.8% of KC in all FWHMs. The maximum values of OA and KC values were 78.7% and 57.7%, respectively, with 10 nm of FWHM to classify salinity and drought damages of spring potato. When the classifier was built based on the band ratios, the accuracy was more than 95% of OA and KC regardless of growth stages and FWHMs. If the multispectral image sensor is made with the six bands (the ratios of three bands) with 10 nm of FWHM, it is possible to classify the damaged spring potato by salinity or drought using the reflectance of images with 91.3% of OA and 85.0% of KC.

• Journal of Korean Society of Environmental Engineers
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• 제33권12호
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• pp.907-912
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• 2011

Development of visible light responsive photocatalysts is a promising research area to facilitate utilization of solar energy for hydrogen production via photocatalytic water splitting. In this study two groups of samples, nitrogen (N)-doped niobium pentoxide ($Nb_2O_5$) and titanium dioxide ($TiO_2$) ($Nb_2O_5-N$, $HNb_3O_8-N$, $TiO_2-N$) and N-undoped ones ($Nb_2O_5$ and $TiO_2$) were tested. In order to utilize visible light, nitrogen atoms were doped in selected photocatalysts by using urea. A shift of the absorption edges of the Ndoped samples in the visible light region was observed. Under visible light irradiation, N-doped samples were more prominent photocatalytic activities than the N-undoped samples. Specifically, 99.7% of rhodamine B (RhB) was degraded after 60 minutes of visible light irradiation with $TiO_2-N$. Since $TiO_2-N$ shows the highest activity of RhB degradation, it was supposed to generate the highest current response. However, $HNb_3O_8-N$ showed the highest current response ($63.7mA/cm^2$) than $TiO_2-N$. More interestingly, when we compare the hydrogen production, $Nb_2O_5-N$ produced $19.4{\mu}mol/h$ of hydrogen.

• Asian-Australasian Journal of Animal Sciences
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• 제13권1호
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• pp.68-76
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• 2000

A total of 290 pork loins were selected to include a wide variation of quality to investigate the quality categories into which most pork falls, selection criteria for these categories and methods to objectively assess ultimate pork quality. They were probed at 24 h postmortem (PM) for the following: A) light reflectance by Danish Meat Quality Marbling (MQM), Hennessy Grading Probe (HGP) and Sensoptic Invasive Probe (SIP); B) electrical properties by NWK LT-K21 conductivity (NLT) and Sensoptic Resistance Probe (SRP): and C) pH by NWK pH-K21 (NpH). Also, measurements of % drip loss (PDL) and filter paper wetness (FPW), color brightness (L*), ultimate pH (pHu), lipid content, subjective color (SC), firmness/wetness (SF) and marbling scores (SM) were assessed. Each loin was categorized as either pale, soft and exudative (PSE), reddish-pink, soft and exudative (RSE), reddish-pink, firm and non-exudative (RFN) or dark, firm and dry (DFD). Statistically comparing coefficients of determination (CD), the results indicated that overall, the HGP predicted quality groups slightly better than MQM (CD=71 and 62% respectively), NpH and SRP were less effective (CD= 56 and 44% respectively), and SIP and NLT had the lowest values (CD=36 and 5% respectively). Combining various independent variable did not greatly improve the variation accounted for. When the data was sorted into marbling groups based on lipid content, this was not accurately predicted by any of the probe measurements. The MQM probe remained the best predictor for marbling class and accounted for about 25% of the lipid content variation. This was slightly improved to 33% when pHu was combined with MQM.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.408.2-409
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• 2016

Theoretically, the dye-sensitized solar cells (DSSCs) are high efficiency solar cells. However DSSCs have low power conversion efficiency (PCE) than silicon based solar cells. In this study, we use the phosphor materials, such as $Y_2O_3:Eu$ (Red), $Zn_2SiO_4:Mn$ (Green), $BaMgAl_{14}O_{23}:Eu$ (Blue), to enhance the PCE of DSSCs. Three phosphors were prepared and used as an effective scattering layer on the transparent $TiO_2$ with doctor blade method. We confirmed that the three scattering layers improve the PCE and Jsc due to the light harvesting enhancement via increased the scattering and absorbance in visible range. Under the sun illumination AM 1.5 conditions, the PCE of the mesoporous $TiO_2$ based DSSCs is 5.18 %. The PCE of the DSSCs with Y2O3:Eu, $Zn_2SiO_4:Mn$ and $BaMgAl_{14}O_{23}:Eu$ as scattering layer were enhanced to 5.66 %, 5.72% and 5.82%, respectably. In order to compare the optical properties change, DSSCs were measured by EQE, reflectance and PCE. At the same time, FE-SEM and XRD were used to confirm the structural changes of each layer.