• 한국가스학회지
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• 제6권1호
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• pp.92-97
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• 2002

가스흡수식 냉온수기의 작동매체로 사용되고 있는 LiBr 수용액 중에서 열교환기 세관용 재료인 동 세관 및 동합금재인 큐프로니켈 세관의 부식특성에 관한 연두를 하기 위하여 $62\%$ LiBr 수용액 중에서 각 재료에 대한 전기화학적 분극실험을 실시하여 부식특성을 고찰한 결과 다음과 같은 결론을 얻었다 1) 열교환기 세관재의 분극저항은 $30\%$ 큐프로니켈 세관 > $10\%$ 큐프로니켈 세관 > 동 세관의 순으로 높게 나타난다 2) 큐프로니켈 세관의 개로전위는 동 세관보다 귀전위화되면서 부식전류밑도는 더 억제된다 3) $30\%$ 큐프로니켈 세관의 부동태 영역은 $10\%$ 큐프로니켈 세관보다 전위구간이 더 크게. 나타나면서 부동태유지 전류밀도는 더 낮아진다.

• Journal of Electrochemical Science and Technology
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• 제13권3호
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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.

• 한국가스학회지
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• 제28권1호
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• pp.65-72
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• 2024

재생에너지 자원이 풍부한 제주도에서 수전해 시스템을 활용하여 그린수소를 생산하는 실증단지를 준비 중이며, 수전해 시스템의 장기 운영시 상황을 검토하기 위하여, PEM 수전해 셀을 가속시험평가 하여 수전해 셀의 내구성을 검토하였고, 제주도 풍력기반의 전력패턴을 적용하였을 때 수전해 셀의 내구성을 검토하였다. 가속시험평가 (저전류-고전류 반복 인가)를 800시간 진행한 후, PEM 수전해 셀의 성능이 최대 10%, 운전조건에서 5.5% 감소되었으며, 임피던스 분석결과 PEM 수전해 셀의 Ohmic 저항보다 전극의 분극저항이 크게 증가한 것을 확인할 수 있다. 그리고 제주도의 풍력패턴을 적용하여 내구성평가를 진행한 경우, PEM 수전해 셀의 성능이 최대 1.6%, 운전 조건에서 1% 미만의 성능감소를 보여주었으며, 임피던스 결과 Ohmic 저항 및 전극의 분극저항의 변화가 작은 것을 알 수 있다.

• 한국토양비료학회지
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• 제46권4호
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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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• 제17권2호
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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.

• 동의생리병리학회지
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• 제38권1호
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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.

• 한국표면공학회지
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• 제36권4호
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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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• 제4권3호
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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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• 제28권2호
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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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• 제10권5호
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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.