• Journal of the Korean Institute of Gas
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• v.6 no.1 s.17
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• pp.92-97
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• 2002

This paper was studied on corrosion characteristics of gas absorption refrigeration & hot water system using $LiBr-H_2O$ working fluids. In the $62\%$ lithium bromide solution at $60^{\circ}C$, polarization test of Cu, $10\%$ cupronickel($90-10\%$ Cu-Ni) and $30\%$ cupronickel($70-30\%$ Cu-Ni) tube was carried out. And polarization behavior, polarization resistance characteristics, open circuit potential, anodic polarization of heat exchanger tube for gas absorption refrigeration & hot water system were considered. The main results are as following: 1) Polarization resistance of heat exchange tubes appears high in order of $30\%$ cupronickel tube > $10\%$ cupronickel tube > Cu tube. B) Open circuit potential of cupronickel tube is more noble than that of Cu tube, and corrosion current density of cupronickel is controlled than Cu tube. 3) Potential of passive region of $30\%$ cupronickel tube is more wide than that of $10\%$ cupronickel tube, and the passivation critical current of $30\%$ cupronickel tube is lower than that of $10\%$ cupronickel tube.

• Journal of Electrochemical Science and Technology
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• v.13 no.3
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• pp.369-376
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• 2022

In this study, the stability of an anion exchange membrane water electrolyzer (AEMWE) cell was evaluated in an on-off cycling operation with respect to an applied electric bias, i.e., a current density of 500 mA cm^-2, and an open circuit. The ohmic and polarization resistances of the system were monitored during operation (~800 h) using electrochemical impedance spectra. Specific consideration was given to the ohmic resistance of the cell, especially that of the membrane under on-off cycling conditions, by consistently feeding the cell with KOH solution. Owing to an excess feed solution, a momentary increase in the polarization resistance was observed immediately after the open-circuit. The excess feed solution was mostly recovered by subjecting the cell to the applied electric bias. Stability tests on the AEMWE cell under on-off cycling with continuous feeding even under an open circuit can guarantee long-term stability by avoiding an irreversible increase in ohmic and polarization resistances.

• Journal of the Korean Institute of Gas
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• v.28 no.1
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• pp.65-72
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• 2024

Green Hydrogen demonstration complex is under conduction in Jeju island which is rich in renewable energy resources and will produces green hydrogen using a water electrolysis systems. In order to check durability of long-term operation, AST(accelerated stress test) was applied and the power pattern based on Jeju Island's wind power was applied. After 800 hours of repeated application of low current and high current, the performance of the PEM water electrolysis cell was reduced by up to 10% and by about 5.5% in operating conditions. As the result of impedance analysis, it can be seen that the electrode polarization resistance greatly increased than ohmic polarization resistance. In addition, when the durability evaluation was conducted by applying the wind power pattern of Jeju Island, the performance of the PEM water electrolysis cell showed up to 1.6% and a decrease of less than 1% in operating conditions. As a result of the impedance, it can be seen that the change of ohmic resistance and electrode polarization resistance is small.

• Korean Journal of Soil Science and Fertilizer
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• v.46 no.4
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• pp.237-244
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• 2013

Radar remote sensing is appropriate for monitoring rice because the areas where this crop is cultivated are often cloudy and rainy. Especially, Synthetic Aperture Radar (SAR) can acquire remote sensing information with a high temporal resolution in tropical and subtropical regions due to its all-weather capability. This paper analyzes the relationships between backscattering coefficients of rice measured by RADARSAT-2 SAR and growth parameters during a rice growth period. We examined the temporal variations of backscattering coefficients with full polarization. Backscattering coefficients for all polarizations increased until Day Of Year (DOY 222) and then decreased along with Leaf Area Index (LAI), fresh weight, and Vegetation Water Content (VWC). Vertical transmit and Vertical receive polarization (VV)-polarization backscattering coefficients were higher than Horizontal transmit and Horizontal receive polarization (HH)-polarization backscattering coefficients in early rice growth stage and HH-polarization backscattering coefficients were higher than VV-polarization backscattering coefficients after effective tillering stage (DOY 186). Correlation analysis between backscattering coefficients and rice growth parameters revealed that HH-polarization was highly correlated with LAI, fresh weight, and VWC. Based on the observed relationships between backscattering coefficients and variables of cultivation, prediction equations were developed using the HH-polarization backscattering coefficients.

• Journal of the Optical Society of Korea
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• v.17 no.2
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• pp.130-135
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• 2013

Based on the extended Huygens-Fresnel principle and generalized Stokes theory, the evolution of polarization properties of beams generated by quasi-homogenous (QH) sources propagating in clear oceanic water was studied by the use of the oceanic turbulence spatial spectrum function. The results show that the beams have similar polarization self-reconstructed behavior under different turbulence conditions in the far field, but if the propagation distance is not long enough, the degree of polarization (DOP) fluctuates with much more complexity than state of polarization (SOP) of QH beams. The self-reconstructed ability of DOP at the special distance in turbulence would get to the best value if the values of coherence of width were chosen suitably, but for SOP, it has no best value.

• Journal of Physiology & Pathology in Korean Medicine
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• v.38 no.1
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• pp.32-37
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• 2024

The aim of this study was to investigate the role of Daesiho-tang (Da Chai Hu-Tang) water extract (DSTE) in regulating chronic stress-induced cancer progression, focusing on its activity in modulating tumor-associated macrophages (TAMs). Different stimuli can polarize TAMs into immune-stimulating M1 macrophages or immunosuppressive M2 macrophages. During cancer progression, M2 phenotype increases and supports tumor growth, angiogenesis and metastasis. Notably, chronic stress-induced catecholamines promote M2 macrophage polarization. In this study, we investigated whether DSTE regulates norepinephrine (NE)-induced M2 macrophage polarization in RAW 264.7 mouse macrophage cells. Even though NE itself did not increase the expression of M2 markers, the conditioned media of NE-treated 4T1 mouse breast cancer cells (NE CM) significantly up-regulated M2 markers in RAW 264.7 cells, suggesting that NE-regulated cancer cell secretome stimulated M2 polarization. However, such increase was abrogated by DSTE. NE CM also induced phosphorylation of signal transducer and activator of transcription 6 (STAT6) in RAW 264.7 cells, which was clearly reversed by pretreatment with DSTE, demonstrating that DSTE inhibited M2 polarization by inactivating STAT6. Finally, M2-polarized RAW264.7 cells by NE CM markedly increased the migration of 4T1 cells. However, such increase was completely reversed by co-treating RAW264.7 cells with NE CM and DSTE, indicating that DSTE attenuated cancer cell migration by blocking M2 polarization. Taken together, our results suggest a probable use of DSTE for cancer patients under chronic stress by regulating M2 macrophage polarization.

• Journal of the Korean institute of surface engineering
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• v.36 no.4
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• pp.324-328
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• 2003

This study was made on the crevice corrosion behavior of chromium plating in fresh water. Under the various crevice, the electrochemical polarization test of chromium plating was carried out. Results are discussed In terms of corrosion potential, polarization resistance, corrosion current density and cathodic control of chromium plating.

• Corrosion Science and Technology
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• v.4 no.3
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• pp.95-99
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• 2005

Wheel test and potentiodynamic polarization methods were used to evaluate the relative effectiveness of some hydrogen sulfide corrosion inhibitors for the wet gas pipeline API 5L grade X 65 steel. Five commercially corrosion inhibitors have been studied in the deoxygenated produced water solutions containing 10 ppm and 100 ppm of hydrogen sulfide. Based on the experiment results the steel corrosion inhibition mechanism in discussed and two most effective corrosion inhibitors are selected.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.332-337
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• 2004

The use of gas absorption refrigeration machine has considerably increased because of the shortage of the electric power in the summer and the regulation of freon refrigerant. Gas absorption refrigeration machine consists of a condenser, a heat exchanger. supplying pipes, a radiator etc, This system is likely to be corroded by acid. dissolved oxygen and gases, Cavitation erosion-corrosion by flow velocity of cooling water may happen in absorption refrigeration machine. In these cases. erosion and corrosion occur simultaneously. Then, it makes a serious damage with synergy effect. Therefore, this paper was studied on the cavitation damage of cupronickel(70/30) tube for gas absorption refrigeration machine, In the $30^{\circ}C$ tap water, linear polarization test and anodic polarization test were carried out for copper(C1220T-OL) and cupronickel(70/30) tube. Also, cavitation erosion-corrosion behavior of cupronickel (70/30) tube was considered, The main results are as following: (1) In the linear test, the corrosion current density of cupronickel(70/30) is higher than that of copper. (2) The erosion-corrosion rate of cupronickel(70/30) displayed later tendency than that of copper by vibratory cavitation in cooling water. (3) In cooling water, the progress mechanism of erosion-corrosion rate of copper and cupronickel(70/30) follows a pattern of incubation, acceleration, attenuation and a steady state period.

• Membrane and Water Treatment
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• v.10 no.5
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• pp.387-394
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• 2019

Membrane distillation (MD) is one of the water treatment processes which involves the momentum, heat and mass transfer through channels and membrane. In this study, CFD modeling has been used to simulate the heat and mass transfer in the direct contact membrane distillation (DCMD). Also, the effect of operating parameters on the water flux is investigated. The result shows a good agreement with the experimental result. Results indicated that, while feed temperature is increasing in the feed side, water flux improves in the permeate side. Since higher velocity leads to the higher mixing and turbulence in the feed channel, water flux rises due to this increase in the feed velocity. Moreover, results revealed that temperature polarization coefficient is rising as flow rate (velocity) increases and it is decreasing while the feed temperature increases. Lastly, the thermal efficiency of direct contact membrane distillation is defined, and results confirm that thermal efficiency improves while feed temperature increases. Also, flow rate increment results in enhancement of thermal efficiency.