• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.462-469
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• 2003

This paper presents an experimental study on the potential durability enhancement of infrastructures repaired by a sprayed high ductile fiber-reinforced cementitious composite (ECC). For this study, a PVA-ECC which exhibits sprayable properties in the fresh state and tensile strain-hardening behavior in hardened state was sprayed and tested. The experimental results show that the sprayed ECC exhibits mechanical properties with strain capacity comparable to the cast ECC with the same mix design. During loading, the crack widths of ECC are tightly controlled with an average of 30${\mu}m$. It is also revealed that when sprayed ECC is used as a repair material, ductility represented by deformation capacity at peak load of repaired beams in flexure are obviously increased in comparison to those of commercial prepackaged mortar (PM) repaired beams. In addition to high delamination resistance, the significant enhancement of energy absorption capacity and crack width control in ECC repair system suggest that sprayed ECC can be effective in extending the service life of rehabilitated infrastructures.

• Journal of Korean Medicine for Obesity Research
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• v.5 no.1
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• pp.121-131
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• 2005

During last few decades dietary guidelines for the weight management mainly have focused on a low-fat, high carbohydrate diet. Carbohydrate was supposed to be low-dense, highly satiating as well as it affects little on the lipogenesis. Although low-fat diet has significant weight-reducing effect, the loss was modest and usually regained after cessation of the diet. Furthermore, low-fat, modest-carbohydrate diet did not impact on the ever increasing rates of overweight and obesity. Alternative approaches include low-carbohydrate diet, high-carbohydrate diet and low-glycemic index diet. Although none of above mentioned diet have sufficient evidence for standard weight management diet, short-term efficacy and safety are being approved continuously. Low-carbohydrate diet contains less than 45% of carbohydrate in daily energy consumption, it is claimed to have more satiating effect and to improve metabolism. However, low compliance due to the limitation of food choice should be considered on prescribing the diet. High-carbohydrate which contains 90% of carbohydrate in total daily energy consumption, is effective in providing satiety and lowering total calorie intake and cholesterol. On the other hand, nutritional unbalance should be took into account. Low-glycemic index diet is based on the theory that contemporary diet contains significantly less fiber and unrefined carbohydrate, therefore insulin secretion is disturbed. Because low glycemic index food slowly increase blood glucose and insulin level, it induces much satiating effect and may decrease calorie ultimate intake. However, poor standardization of glycemic index is one of the main obstacle for the diet to be applied in the clinic. Meanwhile, high fructose food and beverage should be discouraged because it has little satiating effect and may cause insulin resistance. High fiber food is another recommendation for healthy, lean diet.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.167-170
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• 2001

The stochiometric mix of evaporating materials for the CdGa$_2$Se$_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, CdGa$_2$Se$_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were 630$^{\circ}C$ and 420$^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of CdGa$_2$Se$_4$ single crystal thin films measured from Hall erect by van der Pauw method are 8.27x10$\^$17/ cm$\^$-3/, 345 $\textrm{cm}^2$/V$.$s at 293 K, respectively. From the Photocurrent spectrum by illumination of perpendicular light on the c-axis of the CuInSe$_2$ single crystal thin film, we have found that the values of spin orbit splitting ΔSo and the crystal field splitting ΔCr were 106.5 meV and 418.9 meV at 10 K, respectively. From the photoluminescence measurement on CdGa$_2$Se$_4$ single crystal thin film, we observed free excition (E$\_$X/) existing only high quality crystal and neutral bound exiciton (D$\^$0/,X) having very strong peak intensity. Then, the full-width-at-half-maximum(FWHM) and binding energy of neutral donor bound excision were 8 meV and 13.7 meV, respectivity. By Haynes rule, an activation energy of impurity was 137 meV,

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.167-170
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• 2004

The stochiometric mix of evaporating materials for the $CuGaT_2$ single crystal thin films was prepared from horizontal furnance. Using extrapolation method of X-ray diffraction patterns for the $CuGaTe_2$ polycrystal, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were 6.025 ${\AA}$ and 11.931 ${\AA}$, respectively. To obtain the single crystal thin films, $CuGaTe_2$ mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $670^{\circ}C$ and $410^{\circ}C$ respectively, and the thickness of the single crystal thin films is $2.1{\mu}m$. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). From the photocurrent spectrum by illumination of perpendicular light on the c - axis of the $CuGaTe_2$ single crystal thin film, we have found that the values of spin orbit coupling ${\Delta}s.o$ and the crystal field splitting ${\Delta}cr$ were $0.079\underline{1}eV$ and $0.246\underline{3}eV$ at 10 K, respectively. From the PL spectra at 10K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be $0.047\underline{0}eV$ and the dissipation energy of the donor-bound exciton and acceptor-bound exciton to be $0.049\underline{0}eV$, $0.055\underline{8}eV$, respectively.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.51-57
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• 2021

The quality of the ceramic sintered coating on a metal surface through laser surface treatment is affected by the laser irradiation pattern. Depending on the laser irradiation pattern, the amount of residual stress and heat applied or accumulated on the surface increases or decreases, affecting the thickness attained in the ceramic sintering area. When the heat energy accumulated in the sintering area is high, the ceramic and the metal alloy melt and sufficiently mix to form a homogeneous and thick bonding interface. In this study, the thermal energy accumulation in the region sintered with zirconia was controlled using four types of laser processing patterns. The thickness of the diffusion region is analyzed by laser-induced breakdown spectroscopy of Mg-ZrO2 generated by laser sintering zirconia powder on the magnesium alloy surface. On the basis of the analysis of the Mg and Zr present in the sintered region through LIBS, the effect of the irradiation pattern on the sintering quality is confirmed by comparing and analyzing the heat and mass transfer tendency of the diffusion layer and the degree of diffusion according to the irradiation pattern. The derived diffusion coefficients differed by up to 9.8 times for each laser scanning pattern.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.83-83
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• 2003

The stochiometric mix of evaporating materials for the CuInSe$_2$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, CuInSe$_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were 62$0^{\circ}C$ and 41$0^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of CuInSe$_2$ single crystal thin films measured from Hall effect by van der Pauw method are 9.62$\times$10$^{16}$ cm$^{-3}$ , 296 $\textrm{cm}^2$/V.s at 293 K, respectively From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the CuInSe$_2$ single crystal thin film, we have found that the values of spin orbit splitting ΔSo and the crystal field splitting ΔCr were 6.1 meV and 175.2 meV at 10 K, respectively. From the photoluminescence measurement on CuInSe$_2$ single crystal thin film, we observed free excition (Ex) existing only high quality crystal and neutral bound exiciton (D$^{\circ}$,X) having very strong peak intensity. Then, the full-width-at -half-maximum(FWHM) and binding energy of neutral donor bound excition were 7 meV and 5.9 meV, respectivity. By Haynes rule, an activation energy of impurity was 59 meV.

• Computers and Concrete
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• v.31 no.5
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• pp.433-442
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• 2023

This study presents the visually observed behavior of fibers embedded in concrete samples that were subjected to a flexural bending test. Three types of fibers such as macro polypropylene, macro polyethylene, and the hybrid of steel and polyvinyl alcohol were mixed with cement by a designated mix ratio to prepare a total of nine specimens of each. The bending test was conducted by following ASTM C1609 with a net deflection of 2, 4, and 7 mm. The X-ray computed tomography (XCT) was carried out for 7 mm-deflection specimens. The original XCT images were post-processed to denoise the beam-hardening effect. Then, fiber, crack, and void were semi-manually segmented. The hybrid specimen showed the highest toughness compared to the other two types. Debonding based on 2D XCT sliced images was commonly observed for all three groups. The cement matrix near the crack surface often involved partially localized breakage in conjunction with debonding. The pullout was predominant for steel fibers that were partially slipped toward the crack. Crack bridging and rupture were not found presumably due to the image resolution and the level of energy dissipation for poly-fibers, while the XCT imaging was advantageous in evaluating the distribution and behavior of various fibers upon bending for fiber-reinforced concrete beam elements.

• Advances in concrete construction
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• v.15 no.4
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• pp.251-267
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• 2023

In this paper, an experimental investigation is carried out to assess the inherent self-compacting properties of geopolymer mortar and its impact on flexural strength of thin-walled ferro-geopolymer box beam. The inherent self-compacting properties of the optimal mix of normal geopolymer mortar was studied and compared with self-compacting cement mortar. To assess the flexural strength of box beams, a total of 3 box beams of size 1500 mm × 200 mm × 150 mm consisting of one ferro-cement box beam having a wall thickness of 40 mm utilizing self-compacting cement mortar and two ferro-geopolymer box beams with geopolymer mortar by varying the wall thickness between 40 mm and 50 mm were moulded. The ferro-cement box beam was cured in water and ferro-geopolymer box beams were cured in heat chamber at 75℃ - 80℃ for 24 hours. After curing, the specimens are subjected to flexural testing by applying load at one-third points. The result shows that the ultimate load carrying capacity of ferro-geopolymer and ferro-cement box beams are almost equal. In addition, the stiffness of the ferro-geoploymer box beam is reduced by 18.50% when compared to ferro-cement box beam. Simultaneously, the ductility index and energy absorption capacity are increased by 88.24% and 30.15%, respectively. It is also observed that the load carrying capacity and stiffness of ferro-geopolymer box beams decreases when the wall thickness is increased. At the same time, the ductility and energy absorption capacity increased by 17.50% and 8.25%, respectively. Moreover, all of the examined beams displayed a shear failure pattern.

• Environmental and Resource Economics Review
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• v.31 no.2
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• pp.165-204
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• 2022

This study organized data from 2000 to 2014 for 20 grid-connected countries in Europe and analyzed the determinants of carbon emissions through the panel GLS method considering the problem of heteroscedasticity and autocorrelation. At the same time, the effect of introducing ETS was considered by dividing the sample period as of 2005 when the European emission trading system was introduced. Carbon emissions from individual countries were used as dependent variables, and proportion of generation by each source, power self-sufficiency ratio of neighboring countries, power production from resource-holding countries, concentration of power sources, total energy consumption per capita in the industrial sector, tax of electricity, net electricity export per capita, and size of national territory per capita. According to the estimation results, the proportion of nuclear power and renewable energy generation, concentration of power sources, and size of the national territory area per capita had a negative (-) effect on carbon emissions both before and after 2005. On the other hand, the proportion of coal power generation, the power supply and demand rate of neighboring countries, the power production of resource-holding countries, and the total energy consumption per capita in the industrial sector were found to have a positive (+) effect on carbon emissions. In addition, the proportion of gas generation had a negative (-) effect on carbon emissions, and tax of electricity were found to have a positive (+) effect. However, all of these were only significant before 2005. It was found that net electricity export per capita had a negative (-) effect on carbon emissions only after 2005. The results of this study suggest macroscopic strategies to reduce carbon emissions to green growth, suggesting mid- to long-term power mix optimization measures considering the electricity trade market and their role.

• Journal of Energy Engineering
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• v.16 no.2
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• pp.83-92
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• 2007

In view of stringent environment regulations to control the emission of green house gases and also depleting fossil fuel reserves, it is high quality desirable to develop alternative technologies to produce high quality fuels. To this end Biomass to Liquid (BTL) technology has received much attention in recent years. BTL process generally consists of gasification of biomass to produce bio-syngas, cleaning and control of $H_{2}/CO$ mole ratio of bio-syngas and Fischer-Tropsch synthesis & upgrading systems. Choren, Germany has first developed the commercial BTL process using unique gasification system i.e., Carbo-V. A new technology to remove tars and BTX has been developed by ECN in Netherlands employing a gasification system combined with OLGA technology. Several other countries including USA and Japan are showing great interest in BTL technology. Thus in view of our national energy security and also the environmental regulations, it is essential to develop alternative technologies like BTL in order to meet the increasing demand of energy though our insufficient biomass resources. In this paper we present an overview and development status of BTL-diesel technology.