• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2001년도 춘계학술발표회 초록집
• /
• pp.21-22
• /
• 2001

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2015년도 추계학술대회 논문집
• /
• pp.322-322
• /
• 2015

• 한국환경과학회지
• /
• 제11권4호
• /
• pp.319-325
• /
• 2002

This experiment was carried out to investigate the effects of heavy metals (copper, cadmium, lead and chrome) on the growth of plant and seed germination of Arabidopsis thaliana treated with various concentrations of heavy metals. Cadmium and chrome among the 4 heavy metals had no effect on the growth of stem even in the concentration fifty times higher than the official standard concentration of pollutant exhaust notified by the Ministry of Environment. The official standard concentration of cadmium, however, stimulated the growth of stem in general, increasing leaf size and surface area, although it had no effect on the length of stem. But the growth of stem was decreased about 18% in the official standard concentration of pollutant exhaust of lead and copper. There was no growth of root in the concentration of lead and copper ten times higher than the official standard concentration. Cadmium and chrome had no effect on the seed germination, but lead and copper decreased the rate of seed germination. Seeds were not germinated in the concentration of copper ten times higher than the official standard concentration and in the concentration of lead fifty times higher than the official standard concentration. From this research three peculiar results were obtained. Chrome in the soil did not have much effect on the plant growth and seed germination of Arabidopsis thaliana. Cadmium stimulated the stem growth in an optimum concentration. But lead and copper reduced the plant growth and seed germination even in a small concentration, especially copper had the worse effect.

• Tribology and Lubricants
• /
• 제21권6호
• /
• pp.302-305
• /
• 2005

Various carbon nanotubes (CNTs) are added into the epoxy matrix as reinforcements to investigate the effect on the wear behavior. Effects to the tribological properties of different loading concentrations and types of surface modification are investigated by using a linear reciprocal wear tester. As increasing the concentration of CNTs shows the reduction of the wear loss. Moreover, surface modified CNTs give better tribological property than as produced CNTs. It is due that the functional groups on the surface of CNTs increase the interfacial bonding between CNTs and epoxy matrix through chemical bonding. Changes in worn surface morphology are observed by optical microscope and SEM to investigate the wear behavior. CNTs in the epoxy matrix near the surface are exposed and it becomes the lubricating working film on the worn surface. It reduces the friction and results in the lower surface roughness morphology in the epoxy matrix as increasing the contents of the CNTs.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
• /
• 제4권3호
• /
• pp.127-137
• /
• 2000

This study presents an analysis of the characteristics of vertical ozone distribution near the surface using ozonesonde data(l995 to 1998), plus surface ozone and meteorological data from the Pohang region. These features were examined in detail using three case studies. The first related to episodes of high surface ozone concentrations during the Spring season when the frontogenesis between the high and low pressure associated with the upper-level jet stream was found to be located near the surface. The second was a 5-day winter period(l3 -17 December, 1997) in the Pohang province when the hourly concentrations exceeded 90 ppb on several occasions owing to low-level jets(LLJs) induced by a nocturnal stable layer. Accordingly, this explains why the high surface ozone concentrations occurred at night as the ozone was transported across the zone by a strong wind speed( over 12.5 ms .1). The third case study was ozone enhancement due to photochemical reactions. In this case, the maximum concentration of ozone exceeded 60 ppb in the summer(23 -28 August, 1997). When an ozone peak appeared within the boundary layer, the occurrence frequency of a low-level jet due to the nocturnal stable layer was about 77%, similarly the occurrence frequency of a near-surface ozone peak relative to the appearance of an LLJ was about 76%. Accordingly, there is clearly a close correlation between the occurrence of LLJs and near-surface ozone peaks.

• 한국염색가공학회지
• /
• 제26권4호
• /
• pp.297-304
• /
• 2014

In this study, we investigated the relationship between the adsorption property of Methyl violet or Tartrazine dye onto silica sol surface and surface charge density of the sol. The adsorption ratio of Methyl violet dye on silica sol decreased to 74% and 92% for the 68nm and 94nm silica sol, respectively, at dye concentration of $175{\mu}g/m^2$. However, the adsorption ratio of Tartrazine dye on 68nm and 94nm silica sol was about 0% for both of them. The surface charge density is $-0.40C/m^2$, $-0.26C/m^2$ for 68nm and 94nm silica sol, respectively. The amount of Methyl violet dye adsorbed on silica sol increased with an increase of surface charge density of particle at the same concentration of the dye. The adsorbed amount of the silica having high surface charge density is larger at high pH domain. But adsorbed amount of the silica having low surface charge density is larger at low pH domain.

• 한국레이저가공학회지
• /
• 제3권1호
• /
• pp.29-37
• /
• 2000

For a development purpose of thick metal / metal Graded-Boundary Materials(GBM), a basic research on the fabrication of Ni-Cr/steel GBM was carried out by a laser beam and its mechanical properties and thermal characteristics were investigated. In order to produce a compositionally graded boundary region between substrate steel and added Ni-Cr alloy, a series of surface alloying treatments was performed with a high power CO$_2$ laser beam. Ni-Cr sheet was placed on a low carbon steel plate(0.18%C), and then a CO$_2$ laser beam was irradiated on the surface to produce a homogeneous alloyed layer. On this first surface-alloyed layer, another Ni-Cr sheet was placed and then the CO$_2$ laser beam was irradiated again to produce second surface-alloyed layer. Sequential repetitions of laser surface alloying treatment 4 times resulted in a graded-boundary region with the thickness of about 1.4mm. Simultaneous concentration profiles of different kinds of alloying elements(Ni and Cr) showed from 42%Ni, 45%Cr and 13%Fe on surface region to 0%Ni, 0%Cr and 99%Fe in substrate region. Also a thermal conductivity gradient resulted in graded-region and its value changed from 0.03㎈/cm s$\^{C}$ in surface region to 0.1㎈/cm s$\^{C}$ in substrate region. Microstructural observation showed that any visible root porosities and solidification shrinkage cracks were not formed in graded region between alloyed layer and substrate region during rapid cooling.

• 상하수도학회지
• /
• 제37권4호
• /
• pp.177-186
• /
• 2023

Perfluorooctanoic acid(PFOA) was one of widely used per- and poly substances(PFAS) in the industrial field and its concentration in the surface and groundwater was found with relatively high concentration compared to other PFAS. Since various processes have been introduced to remove the PFOA, adsorption using GAC is well known as a useful and effective process in water and wastewater treatment. Surface modification for GAC was carried out using Cu and Fe to enhance the adsorption capacity and four different adsorbents, such as GAC-Cu, GAC-Fe, GAC-Cu(OH)₂, GAC-Fe(OH)₃ were prepared and compared with GAC. According to SEM-EDS, the increase of Cu or Fe was confirmed after surface modification and higher weight was observed for Cu and Fe hydroxide(GAC-Cu(OH)₂ and GAC-Fe(OH)₃, respectively). BET analysis showed that the surface modification reduced specific surface area and total pore volumes. The highest removal efficiency(71.4%) was obtained in GAC-Cu which is improved by 17.9% whereas the use of Fe showed lower removal efficiency compared to GAC. PFOA removal was decreased with increase of solution pH indicating electrostatic interaction governs at low pH and its effect was decreased when the point of zero charges(pzc) was negatively increased with an increase of pH. The enhanced removal of PFOA was clearly observed in solution pH 7, confirming the Cu in the surface of GAC plays a role on the PFOA adsorption. The maximum uptake was calculated as 257 and 345 ㎍/g for GAC and GAC-Cu using Langmuir isotherm. 40% and 80% of removal were accomplished within 1 h and 48 h. According to R², only the linear pseudo-second-order(pso) kinetic model showed 0.98 whereas the others obtained less than 0.870.

• Korean Chemical Engineering Research
• /
• 제48권1호
• /
• pp.33-38
• /
• 2010

구리 이온 농도를 측정하기 위하여 생체재료를 사용하여 마이크로플루이딕 시스템을 제작하였다. 은 전극에 세포막을 모방한 이중층 지질막(bilayer lipid membrane; BLM)을 피복하여 제2 구리 이온 농도를 감지하도록 하였다. 은 전극에 지지된 BLM은 그 안정성이 증대되었다. 은에 지지된 이중층 지질막(s-BLM)은 은 전선을 지질 (phosphatidylcholine; PC) 용액에 담갔다가 KCl 용액에 담글 때 자기조립 특성에 의하여 용이하게 형성할 수 있다. 이 지지된 이중층 지질막(s-BLM)은 $Cu^{2+}$의 농도와 s-BLM을 통과하는 전류 간의 상관 관계를 결정하기 위하여 사용되었다. 얻어진 상관관계는 선형을 보였으며 높은 재현성을 가졌다. $Cu^{2+}$ 농도가 $10{\sim}130{\mu}M$인 범위에서 $Cu^{2+}$ 농도와 전류의 상관관계를 나타내기 위하여 보정 곡선을 구축하였다. 이 보정 곡선을 미지 시료의 $Cu^{2+}$ 농도 측정에 사용하였다. 지지된 이중층 지질막이 구비된 마이크로플루이딕 시스템은 PDMS(polydimethyl siloxane)를 사용하여 전형적인 연질 포토리소그라피와 몰딩 기법으로 제작하였다. 집적된 마이크로플루이딕 시스템은 은 전선을 절단하지 않고도 은 표면을 활성화시키는 기능, 은 표면에 이중층 지질막을 피복하는 기능, KCl 완충 용액을 주입하는 기능, $Cu^{2+}$를 포함한 시료를 주입하는 기능, 시료 중의 $Cu^{2+}$ 농도를 측정하는 기능 등 다중 기능을 가지도록 하였다.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제7권3호
• /
• pp.71-77
• /
• 2002

본 연구는 비교적 인위적 오염의 개연성이 있다고 판단되는 난지도 주변 지역 토양을 대상으로 2001년 4월부터 5월까지 표토에서 깊이 3m까지 표토, 표토 1m깊이, 표토 2m깊이, 표토 3m깊이로 하여 중금속 오염농도를 조사 분석하였다. 조사대상 중금속은 Cd, Cu, Pb, As, $Cr^{+6}$ Hg의 6개 항목이였으며 농도 정량은 원자흡광광도 방법을 사용하였다. 결과로는 난지도 주변지역에서 중금속 평균도가 Cd 0.229mg/kg. Cu는 8.349mg/kg, Pb 11.083mg/kg, As 0.298mg/kg, $Cr^{+6}$ 0.124mg/kg, Hg 0.134mg/kg로 나타났다. 표토 평균농도는 Cd 0.305mg/kg, Cu 8.464mg/kg, Pb 11.383mg/kg, As 0.128mg/kg, $Cr^{+}$60.153mg/kg, and Hg 0.092mg/kg로 나타났다. 이는 Cd 과 $Cr^{+6}$가 조사대상 전체 평균농도의 80%수준으로 나타났다. Hg과 As는 전체 평균농도와 비슷한 수준으로 나타났다. 조사대상을 중심으로 살펴본 난지도 주변 지역의 중금속 농도조사에서 깊이별 변화 추이의 일관성은 찾을 수 없었으나 C지점과 D지점에서의 금속 수준은 오염된 향동천의 영향과 매립된 폐기물에 영향을 받은 것으로 생각되었다.