• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.276-276
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• 2010

Localized surface plasmon resonance (LSPR) has been explored recently as a promising approach to increase energy conversion efficiency in photovoltaic devices, particularly for thin film hydrogenated amorphous silicon (a-Si:H) solar cells. The LSPR is frequently excited via an electromagnetic (EM) radiation in proximate metallic nanostructures and its primary con sequences are selective photon extinction and local EM enhancement which gives rise to improved photogeneration of electron-hole (e-h) pairs, and consequently increases photocurrent. In this work, high-dielectric-constant (k) $ZrO_2$ (refractive index n=2.22, dielectric constant $\varepsilon=4.93$ at the wavelength of 550 nm) is proposed as spacing layer to enhance the LSPR for application to the thin film silicon solar cells. Compared to excitation of the LSPR using $SiO_2$ (n=1.46, $\varepsilon=2.13$ at the wavelength of 546.1 nm) spacing layer with Au nanoparticles of the radius of 45nm, that using $ZrO_2$ dielectric shows the advantages of(i) ~2.5 times greater polarizability, (ii) ~3.5 times larger scattering cross-section and ~1.5 times larger absorption cross-section, (iii) 4.5% higher transmission coefficient of the same thickness and (iv) 7.8% greater transmitted electric filed intensity at the same depth. All those results are calculated by Mie theory and Fresnel equations, and simulated by finite-difference time-domain (FDTD) calculations with proper boundary conditions. Red-shifting of the LSPR wavelength using high-k $ZrO_2$ dielectric is also observed according to location of the peak and this is consistent with the other's report. Finally, our experimental results show that variation of short-circuit current density ($J_{sc}$) of the LSPR enhanced a-Si:H solar cell by using the $ZrO_2$ spacing layer is 45.4% higher than that using the $SiO_2$ spacing layer, supporting our calculation and theory.

• Korean Journal of Remote Sensing
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• v.32 no.5
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• pp.529-538
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• 2016

This study, multispectral and hyperspectral sensors were utilized to use radiometric cross validation for the purpose of radiometric quality evaluation of a 'KOMPSAT-3'. Images of EO-1 Hyperion and Landsat-8 OLI sensors taken in PICS site were used. 2 sections that have 2 different types of ground coverage respectively were selected as the site of cross validation based on aerial hyperspectral sensor and TOA Reflectance. As a result of comparison between the TOA reflectance figures of KOMPSAT-3, EO-1 Hyperion and CASI-1500, the difference was roughly 4%. It is considered that it satisfies the radiological quality standard when the difference of figure of reflectance in a comparison to the other satellites is found within 5%. The difference in Blue, Green, Red band was approximately 3% as a comparison result of TOA reflectance. However the figure was relatively low in NIR band in a comparison to Landsat-8. It is thought that the relatively low reflectance is because there is a difference of band passes in NIR band of 2 sensors and in a case of KOMPSAT-3 sensor, a section of 940nm, which shows the strong absorption through water vapor, is included in band pass resulting in comparatively low reflectance. To overcome these conditions, more detailed analysis with the application of rescale method as Spectral Bandwidth Adjustment Factor (SBAF) is required.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.42-49
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• 2020

This paper is a basic study to improve durability by imparting hydrophobicity to the surface and sphere of cement-based materials. A cement mortar to which a silane/siloxane-based mixed water repellent was added was prepared, and its initial hydration performance, flow performance, and compressive strength were measured. In addition, after the surface was abraded, the water contact angle and water absorption were measured. The flow of cement mortar to which the water repellent was added was found to decrease up to 1.5% in the addition amount of the water repellent agent, and increased at 3.0% in the addition amount. It was found that the setting time of the cement paste was delayed in both the initial setting and the termination when the water repellent was added. It was found that the compressive strength decreased from 3.0% of the maximum added amount of the water repellent to a maximum of 30%. The contact angle was found to increase when the water repellent was added to the cement mortar, and the contact angle after surface polishing was found to be larger than before surface polishing. The addition of the water repellent showed hydrophobicity not only on the surface but also on the surface and cross section damaged by polishing. The water absorption rate was found to decrease when the water repellent was added to the cement mortar, and the water absorption rate after surface polishing was found to be greater than before surface polishing.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.2
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• pp.71-75
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• 2006

The aggregates made of clay, carbon and $Fe_2O_3$ were prepared to investigate the mechanism of black core formation and the property differences at various sintering atmospheres. The aggregates were sintered at oxidized, neutralized and reduced atmospheres. The specific gravity, absorption rate, percent of black core area were measured at various compositions and sintering atmospheres. The aggregates sintered at oxidized atmosphere showed clear border between shell and black core area. Hence, the aggregates sintered at reduced and neutralized atmospheres showed only black core area in the cross-section of the aggregates. The specific gravity of the aggregates sintered at reduced atmosphere increased with increasing carbon contents and that was the lowest of all aggregates sintered at various atmospheres. Adsorption rate increased with increasing carbon contents at all atmospheres.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.3
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• pp.339-347
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• 2014

In this paper, the authors present a new design for a broad-band metamaterial(MTM) absorber that utilizes flexible substrate. The proposed MTM unit cell is constructed by a electric-inducive-capacitive(ELC) resonator and a cut-wire on the same side of the flexible polyimide substrate. To reduce the radar cross section at frequencies other than the targeted frequency bands, the metallic pattern layer of the proposed structure is placed facing toward the incident wave propagation direction. A prototype absorber was fabricated with a planar array of $33{\times}45$ unit cells. Our experiments showed that the proposed absorber exhibits a peak absorption rate of 92 % and 93 % at 9.06 GHz and 15.0 GHz, respectively, and 75 % of the full-width at half-maximum(FWHM) bandwidth is achieved. The proposed backplane-less MTM structure can be used for a broad-band microwave absorber and irregular surface applications.

• Nuclear Engineering and Technology
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• v.23 no.3
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• pp.352-362
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• 1991

Recent popular trends in pressurized water reactor(PWR) fuel management are to extend the cycle length and to employ the low-leakage core designs for the optimal utilization of the uranium resources. In control strategy incorporated with the fuel management, turnable absorbers are required to control the power peaking and to ensure a negative moderator temperature coefficient during reactor operation. In this study, the nuclear characteristics and the optimal allocation of gadolinium-poisoned rods within the fuel assembly are considered using KWU SAV 79 A Code Package. First, analyses are carried out to compare the nuclear characteristics of the fuel assemblies contain-ing WABA(Wet Annular Burnable Absorber) and Gadolinium burnable absorbers respectively. The analyses show that the gadolinium-bearing fuel assembly has peculiar depletion characteristics ensuing from the very large thermal neutron absorption cross section. Peculiar characteristics of gadolinium provide basis for the optimal allocation of Gd rods in fuel assembly. Second, the methodology of an optimal allocation of gadolinium-poisoned rods within the fuel assembly is developed and applied to some nuclear designs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.420-423
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• 2003

[ $TiO_2$ ] thin films were fabricated by DC magnetron sputtering system at by controlling deposition times, ratios of $Ar:O_2$ partial presser ratio and substrate conditions. And the surface, cross-section morphology, microstructure, and composition ratio of the films were analyzed by FE-SEM, TEM and XPS. Besides, the optical absorption and transmittance of the $TiO_2$ films were measured by a UV-VIS-NIR Spectrophotometer, and photocatalytic properties were studied by G C Analyzer & Data Analysis system. As the result, when $TiO_2$ thin film was made at deposition time of 120[min] and $Ar:O_2$ ratio of 60:40, the best structural and optical properties among many thin films could be accepted. The best results of properties were as follows: thickness; $360{\sim}370[nm]$, grain size; 40[m], gap between two peak binding energy, $5.8{\pm}0.05[eV]$ ($2p_{3/2}$ peak and $2p_{1/2}$ peak of Ti was show at $458.3{\pm}0.05[eV]$ and $464.1{\pm}0.05[eV]$ respectively), binding energy; $530{\pm}0.05\;[eV]$, opticalenergy band gap; 3.4[eV].

• Korean Journal of Materials Research
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• v.23 no.5
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• pp.260-265
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• 2013

Silicon nanoparticle is a promising material for electronic devices, photovoltaics, and biological applications. Here, we synthesize silicon nanoparticles via $CO_2$ laser pyrolysis and study the hydrogen flow effects on the characteristics of silicon nanoparticles using high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-Vis-NIR spectrophotometry. In $CO_2$ laser pyrolysis, used to synthesize the silicon nanoparticles, the wavelength of the $CO_2$ laser matches the absorption cross section of silane. Silane absorbs the $CO_2$ laser energy at a wavelength of $10.6{\mu}m$. Therefore, the laser excites silane, dissociating it to Si radical. Finally, nucleation and growth of the Si radicals generates various silicon nanoparticle. In addition, researchers can introduce hydrogen gas into silane to control the characteristics of silicon nanoparticles. Changing the hydrogen flow rate affects the nanoparticle size and crystallinity of silicon nanoparticles. Specifically, a high hydrogen flow rate produces small silicon nanoparticles and induces low crystallinity. We attribute these characteristics to the low density of the Si precursor, high hydrogen passivation probability on the surface of the silicon nanoparticles, and low reaction temperature during the synthesis.

• Journal of the Korean Society of Food Culture
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• v.29 no.5
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• pp.428-436
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• 2014

This study was conducted to investigate the use of sugar alcohols (sorbitol, erythritol, and xylitol) as alternative sweeteners for replacing sucrose in Yukwa (traditional Korean oil-puffed rice snack). The moisture contents of Bandegi (dried Yukwa dough) and Yukwa containing sugar alcohols were higher than that of control (containing only sucrose). The microstructures of control and Bandegi containing sugar alcohols showed uniformly and finely distributed air holes. Expansion ratio and oil absorption of Yukwa containing sorbitol and 30% erythritol were higher than those of control. Appearance and cross section of control and Yukwa containing sorbitol, 30% erythritol, and 30% xylitol showed a good shape. The lightness (L) of control was significantly lower than Yukwa containing sugar alcohols, whereas redness (a) and yellowness (b) were higher than those in Yukwa containing sugar alcohols. Hardness of Yukwa containing sugar alcohols was significantly lower than that of control, and that of Yukwa containing sorbitol was the lowest. Peak number of Yukwa containing sugar alcohols was significantly lower than that of control, and that of Yukwa containing 60% erythritol and 60% xylitol was the lowest among all samples. In the sensory evaluation, color of control was deepest, whereas that of Yukwa containing 60% xylitol was lightest. Volume and air hole uniformity of Yukwa containing 60% erythritol and 60% xylitol were inferior than those of other samples. Sweetness of Yukwa containing sugar alcohols was lower than that of control, whereas oily flavor was stronger. Hardness of Yukwa containing sugar alcohols was lower than that of control, and Yukwa containing xylitol showed the lowest hardness among the samples. Crispness of Yukwa containing sugar alcohols was lower than that of control. There were no significant differences in overall acceptability between control and Yukwa containing 30% sorbitol and 30% erythritol. Overall, sorbitol and erythritol were appropriate as a 30% replacement for sucrose when preparing Yukwa.

• Journal of Korean Medicine Rehabilitation
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• v.26 no.1
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• pp.1-11
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• 2016

Objectives The purpose of this study was to investigate the effect of Hyulboochucke-tang on the collagenase induced intracerebral hemorrhage in white rats. Methods To identify the effect of the Hyulboochucke-tang on intracerebral hemorrhage, intracerebral hemorrhage was induced in the right caudate nuclei of white rats. For normal group (n=12) and comparative group (n=12), saline was dosed, and vaccum evaporated Hyulboochucke-tang extract was dosed to treatment group (n=12), 3 and 10 days after the collagenase injection, the body weight, the brain weight, the size of hematoma, the size of the area of malacia, the number of apoptotic cell and the change in pathological histology were observed. Results 3 days after the injection, the brain weight(g) was considerably decreased in treatment group (n=12) compared to comparative group (n=12). The brain weight after 10 days of the injection was also considerably decreased in treatment group (n=6) against comparative group (n=6). The cross section(mm) of cerebral malacia after 10 days of the injection was considerably decreased in treatment group (n=6) compared to comparative group (n=6). The number of apoptotic cell in normal intracerebral around the area of malacia did not show considerable change between treatment group and comparative group. 12 days after the injection, the multiplication of gitter cells, astrocyte and newly formed capillaries around the area of malacia was distinct. Conclusions On the basis of these results, We sugggest that Hyulboochucke-tang controls swelling caused by hemorrhage and contributes to absorption of hematoma by multiplication of newly formed capillaries and recovery of damaged cerebral tissue by multiplication of gitter cells and astrocyte.