• 한국정보전자통신기술학회논문지
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• 제9권2호
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• pp.155-161
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• 2016

본 논문은 광 도움 전기화학적 식각으로 나노갭 트렌치 구조를 형성하고 이를 이용해서 정전 용량형 가속도 센서를 설계하고 제작한 것에 대한 연구이다. 정전 용량형 가속도 센서의 감도를 증가시키기 위해 스프링에 연결된 관성질량과 연결된 전극과 감지전극 사이의 간격을 좁혀 커패시턴스의 변화량을 증가시키고 있다. 이를 실현시키기 위해 광-도움 전기화학적 식각을 이용하였고 ANSYS 프로그램을 이용하여 구조해석을 실시하여 $1mm{\times}mm$ 크기의 초소형 정전 용량형 가속도 센서를 설계하였다. 광-도움 전기화학적 식각의 실험 변수인 빛의 세기, dc 전압, 용액의 조성, 피치 등을 고려하여 가속도 센서는 제작 되었다. 최적 공정 조건은 dc전압 2V, Blue LED 20mA, 49wt%HF:DMF:D.I.Water=1:20:10, 피치 $20{\mu}m$이며, 폭 344nm, 깊이 $11.627{\mu}m$의 나노갭 트렌치가 형성되었다.

• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.8-22
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• 2020

In this study, we investigated the deactivation characteristics of Ni-Zn-Fe electrodes due to intermittent operation in alkaline water electrolysis. To find suitable method to accelerate deactivation of electrode, the accelerated stress-test (AST) which repeated on/off step was performed with constant current/voltage control. The AST under constant voltage control is suitable to deactivate electrode so it were selected to investigate deactivation of electrode. The AST which repeated on/off step in range of -1.3 V and 0 V was performed and the relationship between oxidation current and electrode deactivation in the off step was investigate. As results, it was confirmed that the nickel and zinc on electrode surface were oxidized due to anodic current which occurred at off step.

• 유기물자원화
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• 제15권1호
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• pp.178-184
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• 2007

분변토 처리의 기계화 및 자동화 공정 개발을 위하여, 본 연구에서는 슬러지 침출액을 이용한 지렁이 퇴비화 지표에 대하여 고찰하였다. 이 연구에서는 회분식 및 연속식 실험을 위하여 현장 하수 슬러지가 사용되었다. 슬러지 처리방버버에 따른, 발생되는 침출수의 이화학적 특성 변화는 거의 유사함을 나타내었다. 그러나, 산화환원전위, pH, 전기전도도, $NH_3-N$ 항목에서는 퇴비화 전후, 분명한 차이를 보였다. 또한, 지렁이 퇴비화 지표 설정에 가장 적합한 변수들은 ORP과EC임을 알 수 있었다. 이러한 연구 결과들은 실제적으로 분변토 처리가 이루어지는 지렁이 퇴비하 기술로 사용될 수 있을 것이다.

• 한국대기환경학회지
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• 제20권5호
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• pp.593-601
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• 2004

In this study, we are going to compare the chemical composition of the precipitation that falls in the Dangjin and Anmyon-do areas by analyzing the water soluble components (anion and cation). We also examined the effects of seasonal change and regional difference in those data sets. The [$NO_3\;^- \;+\;SO_4\;^{2-}$] at 49.2${\mu}$eq/l is 67% of the total anion of 73.1${\mu}$eq/l, while that of [$NH_4\;^+\;+\;Ca^{2+}$] at 37.7${\mu}$eq/l is 62% of the cation in Dangjin area. Also, the [$NO_3\;^-\;+\;SO_4\;^{2-}$] concentration of 151.8 (${\mu}$eq/l) is 62% for the total anion of 143.5 (${\mu}$eq/l), and the [$NH_4\;^+\;+\;Ca^{2+}$] concentration of 119.7 (${\mu}$eq/l) is 47% for the cation of 254.3 (${\mu}$eq/l) in Anmyon-do area. The ion composition ratio is shown for the order by 22% of $SO_4\;^{2-}$, 20.8% of $NH_4\;^+$ and 15.4% of $Cl^-$ that is the sum of 58.7% for the total ion composition in Dangjin area, and is the order by 33.8% of $NH_4\;^+$, 16.3% of $SO_4\;^{2-}$ and 11.1% of $Cl^-$ in Anmyon-do area. Furthermore, We predicted that even areas which were previously clean will get acid rain if there is large scale construction there or nearby.

• 한국환경과학회지
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• 제8권3호
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• pp.411-417
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• 1999

The interfacial chemical behavior, lattice exchange and dissolution, of $FeS_{(S)}$ as one of the important sulfide minerals was studied. Emphases were made on the surface characterization of hydrous $FeS_{(S)}$, the lattice exchange of Cu(II) and $FeS_{(S)}$, and its effect on the dissolution of $FeS_{(S)}$, and also affect some organic ligands on that of both Cu(II) and $FeS_{(S)}$. Cu(II) which has lower sulfide solubility in water than $FeS_{(S)}$ undergoes the lattice exchange reaction when Cu(II) ion contacts $FeS_{(S)}$ in the aqueous phase. For heavy metals which have higher sulfide solubilities in water than $FeS_{(S)}$, these metal ions were adsorbed on the surface of $FeS_{(S)}$. Such a reaction was interpreted by the solid solution formation theory. Phthalic acid(a weak chelate agent) and EDTA(a strong chelate agent) were used to demonstrate the effect of organic lignads on the lattice exchange reaction between Cu(II) and $FeS_{(S)}$. The $pH_{zpc}$ of $FeS_{(S)}$ is 7 and the effect of ionic strength is not showed. It can be expected that phthalic acid has little effect on the lattice exchange reaction between Cu(II) and $FeS_{(S)}$. whereas EDTA has very decreased the removal of Cu(II) and $FeS_{(S)}$. This study shows that stability of sulfide sediments was predicted by its solubility. The pH control of the alkaline-neutralization process to treat heavy metal in wastewater treatment process did not needed. Thereby, it was regarded as an optimal process which could apply to examine a long term stability of marshland closely in the treatment of heavy metal in wastewater released from a disussed mine.

• 공업화학
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• 제9권1호
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• pp.58-65
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• 1998

에폭시계 분체도료에 사용되고 있는 경화제로는 치환 dicyandiamide(Sub-DICY), 촉진 dicyandiamide(Acc-DICY), trimellitic anhydride(TMA), pyromellitic dianhydride(PMDA), Phenolic curing agent(Ph.C.A.)등이 사용되고 있다. 본 연구는 상기 5가지의 에폭시 경화제를 사용해서 제조한 에폭시 분체도료를 적합한 경화조건에서 완전히 경화시킨 뒤 여러 가지 실험기기 및 분석기기를 이용해서 경화된 도막 $T_g$, 인장강도, 파단신율, 경도, 내마모성등의 기계적 물성을 측정하였다. 그리고 흡수율, 내산성, 내알카리성등의 화학적물성, 전기적특성, 방식성등을 측정함으로써 경화제의 종류에 따른 에폭시 도막의 화학구조가 도막의 물성에 미치는 영향을 비교하였다. 그 결과 Phenolic curing agent는 toughness가 우수하지만 온도에 따른 색상 변화가 크고 산무수물 경화제는 전기절연성과 온도에 따른 색상안정성이 우수하지만 toughness와 부착성이 부족하고 DICY계는 흡수율과 온도에 따른 색상변화가 큰 특성을 나타내었다.

• Journal of Korean Society for Atmospheric Environment
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• 제15권E호
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• pp.17-28
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• 1999

Gas-liquid contact tests above a perforated-plate were conducted with air and water at flooding gas-flow conditions in order to study two-phase flow characteristics in a limestone-gypsum SO2 absorber. Gas layers were in the form of air pockets and confined to the limited areas around each duct pipe, while the remaining tary area were in the wet condition. The liquid above the tray was always in the flooded and even fluidized conditions at gas flows over the range studied, although vigorous bubbly or churn-turbulent two-phase regime was only observed in the immediate vicinity of the gas hole exit at low gas loads. The froth zone was extremely active to provide intimate contact between gas and liquid so that the necessary mass transfer operation can take place, which is the primary purpose of high-performance SO2 absorbers. Howefer, the absorber $\Delta$P was 250mmH2O for the initial water level at 150mm, which is an important issue to be resolved for economical operation of the SO2 absorber. It was seen in the liquid level-and gas flow-transient tests that changes in the absorber liquid inventory were much more pronounced for intimate gas-liquid contact than changes in the gas flow. Based on the 4- and 8-duct pipe test results, grouping the duct pipes near the center of the test tray seemed to promote better recirulation of liquid from gas-liquid contact zone back to the reaction tank so that the absorbed SO2 can be neutralized.

• 한국대기환경학회지
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• 제31권1호
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• pp.15-27
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• 2015

The collection of fine particulate matter samples was made at Gosan site of Jeju Island, one of the background sites of Korea, during a year of 2013, and their water-soluble ionic species were analyzed in order to examine the chemical compositions and pollution characteristics. The concentrations of $nss-SO_4{^{2-}}$, $NH_4{^{+}}$, $NO_3{^{-}}$, and $K^+$ had occupied 66.0% of water-soluble ionic species in $PM_{10}$, especially 94.3% in $PM_{2.5}$ fine mode, however the $nss-Ca^{2+}$ and $Na^+$ showed high concentrations in $PM_{10-2.5}$ coarse mode. $NO_3{^-}/nss-SO_4{^{2-}}$ concentration ratios in $PM_{10}$ and $PM_{10-2.5}$ were 0.30 and 0.13, showing less significant effect from automobile and local pollution sources. The sulfate and nitrate compounds were presumed to be long-range transported to Gosan area by the relatively high SOR and NOR values. The trajectory cluster analysis showed the higher concentrations of the major secondary pollutants ($nss-SO_4{^{2-}}$, $NO_3{^{-}}$, $NH_4{^{+}}$) and $nss-Ca^{2+}$ when the air masses had moved from China continent and Korean peninsula into Gosan area.

• Tribology and Lubricants
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• 제22권5호
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• pp.260-268
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• 2006

The dielectric constants of used gasoline engine oils were obtained at a few temperatures and a frequency. Through analyzing the characteristics of dielectric constant, the related correlation between the changes in dielectric constants of oil and the degree of oil deterioration is going to be found. The dielectric constant was calculated using cross capacitances measured by a sensor tube. As results of the measurement of the fresh engine oil's dielectric constant, it was found that the value of dielectric constant was set down below $60^{\circ}C$ regardless changing frequency. Further, above 6 kHz, the dielectric constant was set down even if temperature was above $100^{\circ}C$ Therefore, for the measurement of used oils, it was selected the frequency of 6 kHz,,and the temperature of $80^{\circ}C$ preventing a certain ionic-conduction effects on the measured dielectric constant and the evaporation of a certain fluid mixed with engine oil. Specially, the effects of the mixing fluid like coolant, water and fuel on the fresh engine oil's dielectric constant were studied. It was found that the oil mixed with coolant showed the highest value, next water, and the lowest fuel. As results of the measurement of the used engine oil's dielectric constant, it was found that the possible changed rate of the used engine oil's dielectric constant based on the warning limit for engine oil in service was below 4% for gasoline engine oil.

• Tribology and Lubricants
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• 제22권5호
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• pp.290-300
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• 2006

The dielectric constants of used diesel engine oils were obtained at a few temperatures and a frequency. Through analyzing the characteristics of dielectric constant, the related correlation between the changes in dielectric constants of oil and the degree of oil deterioration is going to be found. The dielectric constant was calculated using cross capacitances measured by a sensor tube. As results of the measurement of the fresh engine oil's dielectric constant, it was found that the value of dielectric constant was set down below $60^{\circ}C$ regardless changing frequency. Further, above 6 kHz, the dielectric constant was set down even if temperature was above $100^{\circ}C$. Therefore, for the measurement of used oils, it was selected the frequency of 6 kHz, and the temperature of $80^{\circ}C$ preventing a certain ionic-conduction effects on the measured dielectric constant and the evaporation of a certain fluid mixed with engine oil. Specially, the effects of the mixing fluid like coolant, water and fuel on the fresh engine oil's dielectric constant were studied. It was found that the oil mixed with coolant showed the highest value, next water, and the lowest fuel. As results of the measurement of the used engine oil's dielectric constant, it was found that the possible changed rate of the used engine oil's dielectric constant based on the warning limit for engine oil in service was below 10% for diesel engine oil.