• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.55-59
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• 1998

The water absorption in protective coatings, which may greatly influence the durability of these coatings, was studied using quartz crystal microbalance and electrochemical impedance technique. The water absorption in protective coatings and the change of coating capacitance with concentration of electrolyte were measured. The water absorption in coatings seems to be driven by osmotic pressure, and larger amount of water was absorbed in thinner coatings at initial stage of absorption. The amount of water absorbed in coatings changed with the type and crosslinking density of resin used in coating formulation. When water absorption and desorption of coating occured by exposing the coatings to electrolyte solutions of different concentration, increase in impedance caused by desorption of water was found to be higher in the case of thinner film.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.272-278
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• 2023

In this study, we analyzed the effects of current density and electroosmotic phenomena on the desalination performance of electrodialysis (ED). We conducted ED experiments under constant voltage conditions, changing the concentration of the concentrate solution from 10 to 200 g/L. During the ED operation, we measured the current density and charge supplied to the stack, the concentration of the diluted and concentrated solutions, and the amount of water transported by electroosmosis to analyze desalination performance. As the concentration of the concentrated solution increased, the selectivity of the ion exchange membrane decreased, resulting in a decrease in current efficiency. Moreover, the current efficiency was found to be influenced by the current density supplied. When the current density exceeded 15 mA/cm², back diffusion of ions was suppressed, leading to an increase in current efficiency. We also investigated the specific water transport by electroosmosis during the ED operation. We found that the amount of water transported increased proportionally to the concentration ratio of the concentrated and diluted solutions. When the concentration ratio exceeded 100, the specific water transport rapidly increased due to osmotic pressure, making it challenging to obtain a concentrated solution greater than 200 g/L.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.151-159
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• 2006

A one-dimensional numerical analysis is carried out to investigate the effects of inlet gas humidities, inlet gas pressures, and thicknesses of membrane on the performance of a proton exchange membrane fuel cell. It is found that the relative humidity of inlet gases at anode and cathode sides has a significant effect on the fuel cell performance. Especially, the desirable fuel cell performance occurs at low relative humidity of the cathode side and at high humidity of the anode side. In addition, an increase in the pressure ranging from 1 atm to 4 atm at the cathode side results in a significant improvement in the fuel cell performance due to the convection effect by a pressure gradient toward the anode side, and with decreasing the thickness of membrane, the fuel cell performance is enhanced reasonably.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2010.10a
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• pp.23-23
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• 2010

전북 서해안 새만금 지역에 조성되는 간척지 면적 28,300ha의 30%인 8,400ha 정도가 농업용지로 사용되는 계획이 확정됨에 따라 해당 용지를 효율적으로 사용 할 수 있는 다양한 활용 방안이 요구되고 있다. 대단위 농업지구가 들어설 예정지인 새만금 광활 간척지는 네덜란드와 유사하게 토양의 대부분이 미사질 양토로 이루어져있어 적용 가능한 화훼류를 적절히 선발하고 적합한 재배기술을 도입한다면 대규모 화훼제배 단지로서의 성장 가능성이 충분할 것으로 판단된다. 따라서 전북 농업기술원에서는 2004년부터 7년에 걸쳐 새만금 간척지의 농업적 활용도 제고와 경관농업 육성을 통한 관광자원화 가능성을 확인하기 위하여 72종의 원예작물 적응시험을 실시하였으며 22종의 자생식물과 튤립, 아이리스, 수선화, 히아신스, 참나리 등 5종의 구근 화훼류를 적합 화훼류로 선발하였다. '08~09년에는 내염성과 저온 및 풍해 저항성이 있는 아펠톤, 골든아펠톤, 네그리타, 프랑소와즈, 키스네리스 등을 간척지적용 가능 주요 튤립 품종으로 선발 하였는데 선발된 품종들을 대상으로 높은 염농도 하에서의 체내축적 무기성분을 조사한 결과, K와 Mg은 증가되는 경향이었으나 Ca은 감소되었으며, Cl이온은 현저하게 증가하였다. 또한 튤립체내의 산도 및 전기전도도와 항산화효소의 활성이 증가하였는데 스트레스 반응결과 유해산소가 체내에 축적되고, 이를 중화시키기 위하여 수소이온을 소모함으로써 체내의 산도는 상승된 것으로 추정되며 염분함량이 높을수록 삼투압에 의하여 뿌리에서 흡수는 양분이 적은 반면 잎 줄기의 증산작용은 동일하기 때문에 상대적으로 체내의 농도가 높아져 전기전도도가 상승된 것으로 판단된다. 식물 스트레스의 지표물질로 사용되고 있는 proline 함량도 토양내의 염도가 상승되면서 증가되었으며 엽록소 함량은 감소되는 경향을 보였다.

• Journal of Pharmaceutical Investigation
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• v.34 no.6
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• pp.491-497
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• 2004

We investigated some important factors which affect the transdermal flux of ketoprofen, a nonsteroidal anti-inflammatory agent, as a first step to provide some basic knowledge for the development of a iontophoretic transdermal patch system. Factors such as current density, polarity, buffer (HEPES) and electrolyte concentration and pH were studied using hairless mouse skin. The effect of poly(L-lysin), which is known to affect the electro-osmotic flow through skin, on flux was also studied. Passive flux was about $20\;{\mu}g/cm^2hr$ at pH 4.0, but was negligible at pH 7.4 where all ketoprofen molecules dissolved are ionized (ketoprofen pKa=5.94). At pH 4.0, application of anodal current increased the flux further above the passive level, however anodal flux at pH 7.4 was much smaller than passive flux at pH 4.0. The application of cathodal current at pH 4.0 increased the average flux to $30-40\;{\mu}g/cm^2hr$, depending on the current density applied. At pH 7.4, cathodal flux was only about $5\;{\mu}g/cm^2hr$. Decrease in buffer and electrolyte concentration increased this cathodal flux about 10 fold. However decrease in HEPES buffer concentration 100 fold did not affect the flux. Anodal flux of acetaminophen was much larger than cathodal flux, indicating that electroosmotic flow can be playing an important role in the flux. Poly(L-lysin) increased the cathodal flux at pH 7.4. These results provide some important insights into the mechanism of transdermal flux of ketoprofen and the role of electroosmotic flow.

• Journal of the Korean Geotechnical Society
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• v.39 no.8
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• pp.41-48
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• 2023

Microbially induced calcite precipitation(MICP) is a novel cementation method meant to enhance soil engineering properties through the use of microorganisms. This study investigates the effect of different MICP concentrations on plant growth. Tall fescue seeds are grown in plant columns filled with Jumunjin sand. Following plant growth, the soil samples are treated with MICP via spraying method. The results indicate that the MICP-treated plants exhibit hampered growth compared with the untreated plants. pH and electrical conductivity(EC) tests are performed to analyze the changes in soil properties by MICP. The MICP-treated soils exhibit a pH = 7, similar to the untreated soil. However, the EC dramatically increases with the increase in the MICP concentration, which leads to an increase in the osmotic pressure of the soil surrounding the plant roots. Eventually, the higher osmotic pressure in MICP-treated soil hinders the absorption of water and nutrients in plant roots, thus inhibiting plant growth.

• Membrane Journal
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• v.8 no.3
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• pp.148-156
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• 1998

Diffusion dialysis is a membrane process driven by concentration difference using ion-exchange membranes and has been employed for many years for the acid recovery from acidic waste generated in steel, metal-refining and dectro-plating industries. Theoretically acid flux increases in propomon to the acid concentration difference. At acid concentrations higher than 3 N HCl, however, the acid flux had not increased linearly with the concentration difference. In this paper the effects of acid concentrations on diffusion dialysis for hydrochloric acid recovery and the acid transport mechanism in an anion exchange membrane were studied by membrane sorption tests and diffusion clialysis cell tests. The experimental results showed that the molecular diffusion was a major transport mechanism in a low acid concentration range and the proton leakage through an anion exchange membrane played an important role at higher acid concentrations. Also osmotic water transport and membrane dehydration retarded the transport of protons and caused the permeate flux to decrease.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.414-414
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• 2019

농업으로부터의 비점오염은 지표수와 지하수 모두의 수질에 영향을 미친다. 특히, 비료, 퇴비, 농약 등의 인공적 질소가 살포된 토양은 강우시 화학 침출로 인한 수질오염이 발생되고 있다. 강우시 강우유출수와 함께 지표 수역으로 흘러들어오는 영양물질(질소, 인)은 저수지로 유입되어 침수시 작물이 죽게 되어 저수지의 부영양화 등의 수질 오염문제를 야기시킨다. 국내에서는 홍수조절용지에서의 영농활동의 전면 금지하고 있는 실정이지만, 불법적으로 경작활동이 진행되고 있다. 따라서, 본 연구에서는 다목적댐 홍수조절지 내 경작지 토양 및 양분 특성 평가를 수행하였다. 홍수조절지 내 경작지 토양 특성 및 양분 조사를 위하여 경작이 집중적으로 이루어지고 있는 대청호 지역을 모니터링 지점으로 선정하였다. 모니터링은 경작지 내 토양 시료 및 주변 토양을 채취하여 분석을 수행하였다. 채취한 토양은 토양표준분석법(농촌진흥청, 2012) 및 농업토양분석방법(국립산림과학원, 2014) 기준을 바탕으로 물리 화학적 분석을 수행하였다. 모니터링은 2018년 5월부터 수행되었으며 현재까지 월 1회씩 모니터링을 진행하고 있다. 연구 결과, 밭 경작지 토양은 논에 비해 실트질 함량이 절반으로 침투성이 높은 토양으로 분석되었으며, 영양염류의 침투를 통한 이동 가능(기저유출)이 높게 나타나는 것으로 조사되었다. 이는 중간유출 및 기저유출 저감방안 도입이 필요한 것으로 평가되었다. 작물별 토양 양분분석 결과 고추, 마늘, 담배 경작지에서 화학비료사용량이 타 작물에 비해 높은 것을 분석되었으며, 경작지에 화학비료 및 퇴비의 과다 사용으로 염류농도가 증가할 경우 전기전도도가 높아지며 토양의 삼투압을 증가시켜 물의 흡수와 각종 양분 흡수를 방해하는 것으로 평가되었다. 인의 존재 형태별 비교시 대부분의 경작지에서 높은 값을 보였으며, 특히 경작지 토양의 Residual-P의 농도가 원지반 보다 2~5배 정도 높게 나타났다. 이러한 원인은 퇴비의 사용으로 인한 Residual-P의 누적으로 평가되며, 환경변화에 따라 수층으로 인의 용출이 쉽게 발생하므로 향후 수질에 미치는 영향이 더 클 것으로 사료된다.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.9-14
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• 2023

In this work, we developed a Nafion polymer-coated impedance sensor with two gold electrode configurations to measure the ion concentration in solution samples. The gold electrodes were fabricated through the sputtering process, followed by surface modification using Nafion polymer. The resulting sensors enable the prevention of the polarization phenomenon on the electrode surface, resulting in stable measurement of electrochemical signals. Spectroscopy and scanning electron microscopy measurements revealed that the thin film of Nafion was coated uniformly onto the surface of the gold electrode. The Nafion-coated sensor exhibited more stable impedance signals than the conventional gold electrode. It showed a highly reliable calibration curve (R² = 0.983) of the impedance sensor using a standard sodium chloride solution. In addition, a comparison experiment between the impedance sensor and a commercial conductivity sensor was performed to measure the ion concentration of artificial tears, showing similar results for the two sensors.

• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.493-500
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• 2023

In this study, we developed an impedance sensor capable of controlling electrode polarization by coating iridium oxide (IrO_x) on the surface of the screen-printed carbon electrode. IrO_x was deposited on the surface of carbon electrodes according to the number of cycles (0~50 cycles) by cyclic voltammetry. Observation of scanning electron microscope images revealed that the size and number of IrO_x particles increased as the number of cycles increased. The changes in impedance responses as a function of the NaCl concentration of the as-obtained sensors were investigated using electrochemical impedance spectroscopy. The sensors manufactured in 50 cycles exhibited the best coefficient of determination and reproducibility, attributed to the well-controlled electrode polarization. We further demonstrated the usefulness of the IrO_x-based sensor as a diagnosis sensor for dry eye syndrome by comparing the results of the commercially available osmometer and our sensor using actual solution samples.