• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.6
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• pp.278-285
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• 2006

Coating mixtures of the resin B-H for the application to the desulfurization system of power plant were coated on carbon steels and cured at the temperature of $65^{\circ}C{\sim}80^{\circ}C$. After being contacted with 70wt% $H_2SO_4$ solution of $100^{\circ}C\;and\;120^{\circ}C$ for several hours, their composition, Vicker's hardness and microstructures by SEM were examined. Corrosion resistance of the coating mixtures to $H_2SO_4$ solution was related to the content of $SO_3$ in the coated specimens after corrosion test. The lower curing temperature and the shorter curing time the coated specimens went through, the higher corrosion resistance to acid they showed, but the more cracks were developed at higher temperature. It was realized that the corrosion resistance to sulfaric acid solution was increased on the condition of curing temperature above $65^{\circ}C$ and curing time above 12 hours at least.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.655-662
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• 2012

Gas leakage in an oil refinery causes damage to the environment and unsafe conditions. Therefore, it is necessary to develop a technique that is able to detect the location of the leakage and to filter abnormal gas-leakage signals from normal background noise. In this study, the adaptation filter of the finite impulse response (FIR) least mean squares (LMS) algorithm and a cross-correlation function were used to develop a leakage-predicting program based on LABVIEW. Nitrogen gas at a high pressure of 120 kg/$cm^2$ and the assembled equipment were used to perform experiments in a reverberant chamber. Analysis of the data from the experiments performed with various hole sizes, pressures, distances, and frequencies indicated that the background noise occurred primarily at less than 1 kHz and that the leakage signal appeared in a high-frequency region of around 16 kHz. Measurement of the noise sources in an actual oil refinery revealed that the noise frequencies of pumps and compressors, which are two typical background noise sources in a petrochemical plant, were 2 kHz and 4.5 kHz, respectively. The fact that these two signals were separated clearly made it possible to distinguish leakage signals from background noises and, in addition, to detect the location of the leakage.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.8
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• pp.1199-1208
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• 2005

Abatement of greenhouse gas emitted from ruminants and promotion of biogas energy from animal effluent were comprehensively examined in each anaerobic fermentation reactor and animal experiments. Moreover, the energy conversion efficiency of biomass energy to power generation were evaluated with a gas engine generator or proton exchange membrane fuel cell (PEMFC). To mitigate safely rumen methanogenesis with nutritional manipulation the suppressing effects of some strains of lactic acid bacteria and yeast, bacteriocin, $\beta$1-4 galactooligosaccharide, plant extracts (Yucca schidigera and Quillaja saponarea), L-cysteine and/or nitrate on rumen methane emission were compared with antibiotics. For in vitro trials, cumulative methane production was evaluated using the continuous fermented gas qualification system inoculated with the strained rumen fluid from rumen fistulated Holstein cows. For in vivo, four sequential ventilated head cages equipped with a fully automated gas analyzing system were used to examine the manipulating effects of $\beta$1-4 galactooligosaccharide, lactic acid bacteria (Leuconostoc mesenteroides subsp. mesenteroides), yeast (Trichosporon serticeum), nisin and Yucca schidigera and/or nitrate on rumen methanogenesis. Furthermore, biogas energy recycled from animal effluent was evaluated with anaerobic bioreactors. Utilization of recycled energy as fuel for a co-generator and fuel cell was tested in the thermophilic biogas plant system. From the results of in vitro and in vivo trials, nitrate was shown to be a strong methane suppressor, although nitrate per se is hazardous. L-cysteine could remove this risk. $\beta$1-4 galactooligosaccharide, Candida kefyr, nisin, Yucca schidigera and Quillaja saponarea are thought to possibly control methanogenesis in the rumen. It is possible to simulate the available energy recycled through animal effluent from feed energy resources by making total energy balance sheets of the process from feed energy to recycled energy.

• Korean Journal of Plant Resources
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• v.32 no.3
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• pp.220-227
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• 2019

Stevia rebaudiana (Asteraceae), a perennial plant, has been used as a low-calorie sweetener and is being developed as a therapeutic agent for diabetes, hypertension, myocardial diseases, and microbial infections. Despite the common use of its leaves and stem, the bioavailability of the components present in S. rebaudiana flowers, when used as ingredients of cosmetics, has not been well investigated. Herein, we investigated the antioxidative and antimelanogenic effects of an aqueous extract of S. rebaudiana flowers (Stevia-F). Total flavonoid and phenolic content in Stevia-F were determined to be $8.64{\pm}0.23mg$ of quercetin equivalents/100 g and $631.5{\pm}2.01mg$ of gallic acid equivalents/100 g, respectively. The $IC_{50}$ values of Stevia-F for reducing power, and 2,2-diphenyl-1-picryl-hydrazyl-hydrate radical, hydrogen peroxide, and nitric oxide scavenging activities were 5541.96, 131.39, 466.34, and $10.44{\mu}g/mL$, respectively. Stevia-F showed inhibitory effects on the tyrosinase ($IC_{50}=134.74{\mu}g/mL$) and ${\alpha}$-glucosidase ($IC_{50}=114.81{\mu}g/mL$) activities. No significant cytotoxicity of Stevia-F was observed in B16F10 cells, treated with up to $100{\mu}g/mL$ of the extract for 24 and 48 h (p > 0.05). Stevia-F ($1-100{\mu}g/mL$) suppressed ${\alpha}$-melanocyte stimulating hormone-induced melanin production in B16F10 cells (p < 0.05) and also inhibited the cellular tyrosinase activity (p < 0.05). Overall, our results show that Stevia-F possesses potential for inhibiting tyrosinase and ${\alpha}$-glucosidase activities and has significant antioxidant capacity. The antimelanogenic potential of Stevia-F should extend the usage of S. rebaudiana flowers in the development of skin-whitening products.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.11a
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• pp.150-152
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• 2019

In this study, the effects of the wave field changes due to the coastal structure on the hydrodynamic performance of the OWC wave energy, converter are analyzed using a three-dimensional numerical wave tank technique (NWT). The OWC device is simulated numerically by introducing a linear pressure drop model, considering the coupling effect between the turbine and the OWC chamber in the time domain. The flow distribution around the chamber is different due to the change of reflection characteristics depending on the consideration of the breakwater model. The wave energy captured from the breakwater is spatially distributed on the plane of the front of the breakwater, and the converted pneumatic power increased when concentrated in front of the chamber. The change of the standing wave distribution is repeated according to the relationship between the incident wavelength and the length of the breakwater, and the difference in energy conversion performance of the OWC was confirmed.

• Korean Journal of Plant Resources
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• v.29 no.1
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• pp.11-19
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• 2016

In this study, we investigated the anti oxidative potential and protective effects of water extract of Leonurus sibiricus L. leaf (LSLW) against ultraviolet B (UVB)-induced oxidative damage in human keratinocytes (HaCaT cells). To evaluate the anti oxidative activity of LSLW, we measured DPPH radical, hydroxyl radical, hydrogen peroxide, superoxide anion scavenging activities, lipid peroxidation inhibition, and reducing power of LSLW. For induction of oxidative stress in HaCaT cells, the cells were irradiated with UVB at 40 mJ/㎠. To investigate the protective effects of LSLW against UVB, we measured cell viability and apoptotic bodies using annexin V staining. LSLW showed anti oxidative activities by scavenging DPPH radical, hydroxyl radical, hydrogen peroxide, superoxide anion and by reducing lipid peroxidation. In addition, LSLW showed high reducing values. The UVB-induced oxidative conditions led to cell apoptosis. However, treatment with LSLW ameliorated oxidative stress conditions, including inhibition of cell death, apoptotic body. Taken together, LSLW exhibited anti oxidative and protective effects against UVB-induced damage in HaCaT cells. Thus, LSLW could be useful for the development of cosmetics for UVB-induced skin aging.

• Journal of Mechanical Science and Technology
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• v.15 no.5
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• pp.630-638
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• 2001

The electrical resistivity of sinter dusts generated from the steel industry and coal fly ash from the coal power plant has been investigated using the high voltage conductivity cell based on JIS B 9915 as a function of temperature and water content. Dust characterization such as the chemical composition, size distribution, atomic concentration, and surface structure has been conducted. Major constituents of sinter dusts were Fe$_2$O$_3$(40∼74.5%), CaO (6.4∼8.2%), SiO$_2$(4.1∼6.0%), and unburned carbon (7.0∼14.7%), while the coal fly ash consisted of mainly SiO$_2$(51.4%), Al$_2$O$_3$(24.1%), and Fe$_2$O$_3$(10.5%). Size distributions of the sinter dusts were bi-modal in shape and the mass median diameters (MMD) were in the range of 24.7∼137㎛, whereas the coal fly ash also displayed bi-modal distribution and the MMD of the coal fly ash was 35.71㎛. Factors affecting resistivity of dusts were chemical composition, moisture content, particle size, gas temperature, and surface structure of dust. The resistivity of sinter dusts was so high as 10(sup)15 ohm$.$cm at 150$\^{C}$ that sinter dust would not precipitate well. The resistivity of the coal fly ash was measured 1012 ohm$.$cm at about 150$\^{C}$. Increased water contents of the ambient air lowered the dust resistivity because current conduction was more activated for absorption of water vapor on the surface layer of the dust.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.16 no.1
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• pp.74-83
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• 2020

A number of so-called 'Type IV' cracking was reported to occur at the welded joints of the P91 steel or P92 steel reheat steam piping systems in Korean supercritical thermal power plants. The reheat steam piping systems are subjected to severe thermal and pressure loading conditions of coolant higher than 570℃ and 4MPa, respectively. In this study, piping analyses and design evaluations were conducted for the piping system of a specific thermal plant in Korea and suggestions were made how structural integrity could be improved so that type IV cracks at the welded joints could be prevented. Integrity evaluations were conducted as per ASME B31.1 code with implicit consideration of creep effects which was used in original design of the piping system and as per nuclear-grade RCC-MRx code with explicit consideration of creep effects. Comparisons were made between the evaluation results from the two design rules. Another approach with modification or reduction of the redundant supports in the piping systems was investigated as a tool to mitigate thermal stresses which should essentially contribute to prevention of Type IV cracking without major modification of the existing piping systems. In addition, a post weld heat treatment method and repair weld method which could improve integrity of the welded joint of P91 steel were investigated.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.184-187
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• 2006

The heat transfer characteristics of solar tower receivers are experimentally investigated with receiver shapes. Generally the heat transfer characteristics become different according to the shapes and materials of the volumetric air receiver. In order to study these effects, The experimental apparatus adopting laminated mesh and honeycombs as the volumetric air receiver is proposed. The receiver consists of laminated mesh (diameter; 100mm, thickness; 1mm), honeycombs (diameter; 100mm, thickness; 30 mm) inserted out the heat transfer characteristics of the laminated mesh the air temperatures are obtained by installing 3 thermocouples on each layer, dividing ceramic tube into 4 layers. Also, a radiative shield is installed to measure the only air temperature. The data for laminated mesh and honeycomb thickness of 30, 60, 90mm are obtained. The results show that the temperature of layer 3 is higher than those of layer 2 and layer 1.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.251-252
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• 2012

ITER(국제핵융합실험로) 제어시스템은 중앙제어와 Plant System으로 구성되며 CODAC, Central Interlock, Central Safety System으로 구분된다. 초전도자석에 전류를 공급하는 AC/DC 컨버터 시스템은 2상한, 4상한 구조의 전원 장치, 초기 플라즈마 발생에 필요한 Switching Network Unit, 코일에 저장된 에너지의 급속 방전을 위한 Fast Discharge Unit 및 무효 전력 보상장치로 구성된다. 4상한 전원장치는 1, 2, 4, 6대의 전원 장치가 직렬 접속되어 무효전력 발생이 최소로 하도록 제어된다. 대용량의 무효전력이 급격히 변화는 환경에서 계통 전압을 유지하기위해 무효전력보상장치는 각 전원 장치가 예측한 무효전력 값을 이용하여 제어한다. 본 논문은 ITER 전원 장치를 운전하기 위한 제어시스템의 개요와 예비설계 결과이다.