• 대한화학회지
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• 제57권2호
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• pp.272-278
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• 2013

Extract of ginger has been evaluated as a green inhibitor for the corrosion of steel in sulfide polluted NaCl solution using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Potentiodynamic polarization measurements showed that this extract acts as a mixed type inhibitor but mainly inhibits the cathodic reaction. The inhibition efficiency was found to increase with inhibitor concentration reaching to approximately 83.9% using 250 ppm of ginger. Nyquist plots show a single capacitive loop in uninhibited and inhibited solutions. From EFM the causality factors are very close to theoretical values which indicate that the measured data are of good quality. The adsorption process of the studied extract on steel surface obeys Temkin adsorption isotherm. The results obtained from the different electrochemical techniques were in good agreement which prove the validity of these tools in measurement of corrosion rate. Ginger extract has no effect on Escherichia Coli and can be applied safely on waste water treatment plants.

• 해양환경안전학회지
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• 제18권6호
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• pp.569-576
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• 2012

일반적으로 중성용액 하에서 알루미늄 합금은 부동태피막($Al_2O_3$나 $Al_2O_3{\cdot}3H_2O$)을 형성한다. 그러나, 해수 환경에서 염소이온이 표면에 생성된 부동태 피막을 파괴하여 부식이 발생하게 된다. 본 연구에서는 해수환경 하에서 부식 문제점을 해결하기 위해 Al-4.5%Mg-0.6%Mn 알루미늄 합금에 대하여 정전위 방식 기술을 적용하였다. 분극실험결과, 개로전위보다 귀한 전위에서는 활성 용해 반응이 나타났으며 개로전위 보다 비한 전위에서는 용존산소 환원에 의한 농도 분극과 활성화 분극이 관찰되었다. 정전위 실험결과, 농도 분극에서 활성화 분극으로 전환되는 전위부터 적용 시간이 증가할수록 전착물이 많이 생성되었으며, 부분적으로 전착물과 모재의 계면사이에서 틈부식이 관찰되었다. 전체적으로 정전위 양극분극실험시, 활성용해반응이 발생하여 정전위 방식 기술을 적용하기 어려운 반면, 정전위 음극분극 실험시 방식 전위인 농도분극 범위내에서 적용 시간을 고려하여 최적 방식 조건을 -1.1 V~-0.75 V로 규명하였다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2020년도 학술발표회
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• pp.166-166
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• 2020

Recently, As the frequency of localized heavy rains increases, the use of high-resolution radar data is increasing. The produced radar rainfall has still gaps of spatial and temporal compared to gauge observation rainfall, and in many studies, various statistical techniques are performed for correct rainfall. In this study, the precipitation correction of the S-band Dual Polarization radar in use in the flood forecast was performed using the ConvAE algorithm, one of the Convolutional Neural Network. The ConvAE model was trained based on radar data sets having a 10-min temporal resolution: radar rainfall data, gauge rainfall data for 790minutes(July 2017 in Cheongju flood event). As a result of the validation of corrected radar rainfall were reduced gaps compared to gauge rainfall and the spatial correction was also performed. Therefore, it is judged that the corrected radar rainfall using ConvAE will increase the reliability of the gridded rainfall data used in various physically-based distributed hydrodynamic models.

• Tribology and Lubricants
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• 제20권2호
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• pp.97-101
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• 2004

This paper reports the studies on the wear-corrosion behavior of Al-Mg alloy in various pH environments. In various pH of sea water, corrosion and wear-corrosion loss of Al-Mg alloy were investigated. Also, the polarization test of Al-Mg alloy using potentiostat/galvanostat was carried out. And the rubbed surface of Al-Mg alloy using scanning electron micrographs after wear-corrosion test was examined in various pH values of sea water. The main results are as following : The polarization resistance of Al-Mg alloy in pH 4 solution is higer than that in pH 6.7 solution, and the corrosion current density in pH 4 is controlled than in pH 6.7 solution. The wear-corrosion loss of Al-Mg alloy with lowering pH becomes sensitive. As the oxide product of Al-Mg alloy appears granular structure and exholiation phenomenon, wear-corrosion loss of Al-Mg alloy increases.

• 한국물환경학회지
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• 제23권2호
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• pp.244-250
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• 2007

This study was carried out to obtain the optimum design factors for an eletrolytric flotation reactor. When the effluent of the leachate treatment facility was treated under the condition of 10 volts, 30 minutes, at the Al-Al electrode system; COD removal efficiency was 45%, and total phosphorus removal efficiency was 98%. The high removal efficiency was caused by the fact that phosphate was removed by leaching $Al^{3+}$ from two electrodes. The leachate containing high ammonium nitrogen concentration was treated by a batch test under the condition of 60 minutes reaction time and added chloride ion; ammonium nitrogen removal efficiency was 89%. This high efficiency was affected by added chloride ion to wastewater. To find the optimum current density and voltage of the leachate containing chloride ion (ratio of $Cl^-/NH_4-N$ is 11) a electrochemical polarization curve was used. These values were found to be $4.5mA/cm^2$ and about 2.1 V, respectively. When C-Al electrode system was used at a batch test, the total nitrogen removal efficiency was increased by 1.8 to 3.3 times, compared to Al-Al electrode system due to high $Cl_2$ gas production.

• Corrosion Science and Technology
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• 제20권6호
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• pp.391-402
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• 2021

In this investigation, the electrochemical characteristics of superaustenitic and general austenitic stainless steels were compared by conducting potentiodynamic polarization experiment with varying temperatures in natural seawater solution. From the result of the potentiodynamic polarization experiment, the corrosion rate of UNS S31603 was found to be 17 times faster than that of UNS N08367 under the most severe corrosion conditions. The relationship between the corrosion rate by maximum damage depth and the corrosion rate by the corrosion current density was expressed as α value for each stainless steel. The α value of UNS S31603 under all temperature conditions was higher than that of UNS N08367 under similar conditions. This means that UNS S31603 is more prone to localized corrosion than UNS N08367. UNS S31603 expressed pitting type damages under all temperature conditions as shown by SEM analysis results. The pitting damage rapidly grew at the relatively poor grain boundaries. Damage on UNS N08367 was not clearly represented at 30 ℃ and 60 ℃, and slight intergranular corrosion damage was observed on the entire surface at 90 ℃.

• 한국지반공학회논문집
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• 제21권2호
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• pp.93-103
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• 2005

본 연구에서는 저주파수 영역에서 유전상수 측정시 발생할 수 있는 왜곡효과를 규명하고, 함수비에 따른 사질토의 유전상수 변화를 실수부와 허수부를 구분하여 조사하였다. 축전기 형태의 셀에서 유전상수를 측정하는 경우 100kHz 이하의 주파수 영역에서 전극분극효과에 의하여 실제 매질의 유전상수보다 크게 측정되었기 때문에 전극 분극효과에 의한 영향을 배제하기 위해서는 100kHz 이상의 주파수에서 유전상수가 평가되어야 하는 것으로 판단되었다. 함수비에 따른 사질토의 유전상수를 평가한 결과 체적함수비 증가에 따라 연속적인 증가경향을 나타내었다. 이는 유전상수 실수부의 경우에는 사질토에서 발생하는 분극이 단위체적당 쌍극자 모멘트에 비례하기 때문이며, 유전상수 허수부의 경우에는 함수비 증가에 따른 전도손실량이 증가하기 때문이다. 그러나 유전상수 실수부에서의 체적함수비에 따른 증가경향은 공간전하분극의 영향이 크지 많은 1MHz 이상의 주파수 영역에서 유효한 것으로 나타났다.

• 한국어병학회지
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• 제19권1호
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• pp.83-86
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• 2006

Effect of iron on the extracellular proteolytic activity of live Uronema marium was determined by fluorescence polarization (FP) method. Supplementation of 0.5 and 5.0 μM iron significantly increased caseinolytic activity of live U. marinum. In contrast, supplementation of 50 μM iron showed no significant differences in FP values compared to the control. The present result suggests that iron in cultured water or skin tissue of olive flounder may influence on the penetration and establishment of U. marinum, correlating with modulation of extracellular protease activity of the ciliates.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 춘계학술대회 논문집
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• pp.180-184
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• 2008

Preliminary results are reported on ship detection using coherence images computed from crosscorrelating images of multi-look-processed dual-polarization data (HH and HV) of ENVISAT ASAR. The traditional techniques of ship detection by radars such as CFAR (Constant False Alarm Rate) rely on the amplitude data, and therefore the detection tends to become difficult when the amplitudes of ships images are at similar level as the mean amplitude of surrounding sea clutter. The proposed method utilizes the property that the multi-look images of ships are correlated with each other. Because the inter-look images of sea surface are covered by uncorrelated speckle, crosscorrelation of multi-look images yields the different degrees of coherence between the images and water. The polarimetric information of ships, land and intertidal zone are first compared based on the cross-correlation between HH and HV. In the next step, we examine the technique when the dual-polarization data are split into two multi-look images.

• 한국자기공명학회논문지
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• 제22권2호
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• pp.34-39
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• 2018

The Nuclear Magnetic Resonance (NMR) technique using Dynamic Nuclear Polarization (DNP) procedures is one of the promising techniques that enable overcoming low sensitivity problems in NMR spectroscopy. We constructed an ODNP-NMR system using a commercial benchtop EPR spectrometer. The $^1H$ NMR peak area of water in aqueous solutions of 4-hydroxy-TEMPO was enhanced more than 95 times in the ODNP-NMR experiments. Our signal enhancement results were about 55% of the previously reported result. This could be due to non-uniform microwave power over a sample and unwanted sample heating by microwave. However, this portable ODNP-NMR spectrometer will be eventually useful for site-specific detection with nano-scale spatial resolutions and molecular dynamics studies with significantly improved signal sensitivity.