• Journal of The Korean Association For Science Education
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• v.23 no.6
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• pp.660-670
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• 2003

This study examined the conceptions of high school students, In-service chemistry teachers, and chemistry teachers related to the electrolysis phenomena by questionnaires and follow-up interviews. High school chemistry II textbooks were analyzed for finding the cause of the misconceptions of the teachers and students. From the analysis, it was found that many teachers represented to students the reduction-oxidation reaction and the electrodes of electrolysis are opposite to the reaction of a chemical cell without explanation of the principles. It means that students would learn the electrolysis phenomena by rote. But the teachers thought that it was not necessary to explain the principles to students because the students could not understand. Also, some of the teacher had misconceptions in electrolysis of solution taking no account of water electrolysis. They only considered the reduction-oxidation reactions of the ions already were contained in solution. They did not considered the ions generated by the electrolysis. This tendency is similar to In-service chemistry teachers and high school students. Also, this tendency can be found in chemistry II textbooks.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.337-337
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• 2014

투명 전도성 산화물(transparent conductive oxide: TCO) 박막은 높은 투과율과 낮은 비저항 덕분에 LCD (liquid crystal display), PDP (plasma display panel), OLED (organic light emitting display) 등 평판 디스플레이에 널리 사용되고 있다. 현재 양산되고 있는 ITO (indium tin oxide)는 90% 이상의 높은 투과율과 우수한 전도성으로 인해 TCO 박막 가운데서 디스플레이 산업에서 가장 널리 쓰이고 있다. 그런데, ITO의 인듐산화물에 의한 간질성 폐렴(interstitial pneumonia)의 유발 위험이 있다든가, 인듐의 매장량이 적어 원자재 가격이 비싼 단점도 가지고 있다. 이에 최근 ITO를 대체할 수 있는 TCO물질로 많은 연구가 이루어지고 있는데, 특히 AZO (aluminum-doped zinc oxide)는 그 중 대표적인 대체물질로서 독성이 없고 가격도 저렴하여 많은 관심이 증폭되고 있다. 현재 AZO는 sol-gel 방법이나 CVD (chemical vapor deposition) 또는 스퍼터링 방법 등으로 증착되고 있다. 본 연구에서는 두 개의 이종타겟(hetero target)을 장착한 대향 타겟 스퍼터링(facing target sputtering: FTS) 장치를 사용하여 AZO 박막을 제작한다. 기존의 여러 증착법과 달리, FTS 장치는 두 타겟 사이에 형성되는 플라즈마 내의 ${\gamma}$-전자를 구속하게 되며, 낮은 가스 압력에서 고밀도 플라즈마가 생성되어 빠른 증착 속도와 안정적인 방전을 유지한 상태에서 박막을 증착할 수가 있다. 또한 기판과 플라즈마가 이격되어 있어 높은 에너지를 갖는 입자들의 기판 충돌을 억제할 수 있는 장점들을 갖는다. 이종 타겟인 ZnO와 Al2O3를 사용하고 각 타겟에 인가되는 파워 변화를 통해 AZO 박막 내 Al2O3의 성분비를 조절하였다. ZnO 타겟의 증착 파워를 100 W로 고정할 경우, Al2O3 타겟의 증착 파워가 (50~90) W으로 실험을 하였으며, Al2O3 타겟의 증착 파워가 70 W일 때 AZO 박막의 Al2O3 성분비는 2.02 wt.%이며 박막의 비저항 값은 $5{\times}10^{-4}{\Omega}{\cdot}cm$로 최소값을 보였다. 이러한 비저항의 변화는 파워에 따른 AZO 박막의 캐리어 이동도(Hall mobility)와 캐리어의 농도(Carrier Concentration)의 변화와 밀접한 관계가 있음을 보여주며, 특히 AZO 박막의 캐리어 농도와 캐리어 이동도는 AZO 박막을 형성하고 있는 결정립의 크기에 의존하는 것이 X-선 회절 패턴과 SEM으로부터 확인되었다. 특히, 본 연구에서는 두 개의 이종 타겟(hetero target) Al2O3와 ZnO를 장착하고 각각의 파워를 변화시켜 도핑 량을 조절할 수는 대향 타겟 스퍼터링(FTS: facing-target sputtering) 방법을 이용하여 제작된 AZO 박막에 대해 전기적, 광학적 및 구조적 특성을 분석하고 ITO의 대체물로서의 가능성을 검토하고자 한다.

• Polymer(Korea)
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• v.29 no.4
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• pp.350-356
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• 2005

Poly(methyl methauylate)/montmorillonite nanocomposites were incorporated into acrylic bone cement in order to improve the mechanical properties and reduce the exotherm of acrylic bone cement. The nanocomposites were prepared using a suspension polymerization and characterized by scanning electron microscopy, X-ray diffraction, trans-mission electron microscopy, gel permeation chromatography, particle size analyzer and electron dispersive spectroscopy. The acrylic bone cements with poly (methyl methacrylate)/nanocomposite s were prepared and their thermal and mechanical properties were characterized. The prepared polymeric beads were composed of polymer-intercalated nanocomposites with partially exfoliated MMT layers, and the mean diameter of them was $50\~60$ fm with the spherical shape. The maximum setting temperature of the acrylic bone cements decreased from 98 to $81\~87^{circ}C$. The mechanical strengths and moduli of the acrylic bone cement with 0.1 $wt\%$ MMT were increased. compared to that without MMT. However, the mechanical properties were generally decreased with increasing incorporated MMT amounts. It is presumably due to the bubbles in nanocomposite beads generated during polymerization.

• Journal of the Mineralogical Society of Korea
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• v.22 no.2
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• pp.163-176
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• 2009

The pyrophyllite deposits located in Jinhae area have been studied through field observations and laboratory works including the X-ray diffraction (XRD), X-ray fluorescence (XRF), Electron probe microanalyzer (EPMA) and Inductively Coupled Plasma (ICP). The pyrophyllite deposits consist of mainly illite, dickite, pyrophyllite, diaspore, chlorite, pyrite and copiapite. According to the mineral assemblages, geological occurrences and alteration modes, the altered rocks can be classified into four types: Type A; quartz with silicifictaion, Type B; quartz + illite with illitization, Type C; quartz + dickite + illite with kaolin alteration, Type D; pyrophyllite + illite + dickite + diaspore with pyrophyllite alteraion. Rocks in Type A, which is generated by silicifictaion, have high $SiO_2$ contents more than 90 wt% and distinctive equigranular textures with microcrtstalline quartz. The pyrophyllites from the study area belong to 2M polytype. The host rocks of the pyrophyllite ore in this mine are rhyolitic rock, andecitic tuff and volcanic breccia. The alteration products seem to be controlled by the different lithology of the host rocks. The hydrothermal solution formed the deposits would be inferred to the acidic and have relatively high ionic activity of hydrogen and silica judging from alteration mineral assemblage. Pyrophyllite alteraion zone is generated by highest temperature condition of all alteration zone.

• Korean Journal of Materials Research
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• v.10 no.7
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• pp.499-504
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• 2000

Recently there have been many investigations on the synthesis and properties of transition metal trialuminides based on Ti, Zr, V, Nb and Ta for use aircraft structure materials in an elevated environment. The effect of Zr additions on the formation behaviour of Al-Nb alloy was investigated. Al-1.3at.%(Nb+Zr) alloys with different Nb to Zr atomic 1:3, 1:1 and 3:1 were prepared by mechanical alloying(MA). The morphological changes and microstructural evolution of Al-Nb-Zr powders during MA were investigated by SEM, XRD and TEM. The intermetallic compound phase of $Nb_2Al\; and\; Al_3Zr_4$ was identified by X-ray diffraction. The intemetallic compound of $Al_3Zr,\; Al_3Nb$ and $Al_3Zr_4$ were formed by heat treatment for 1 hour at $500^{\circ}C$. The size of intermetallic compounds observed by TEM were approximately below 100nm, when they were heat treated after mechanically alloying for 30 hours.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.445-450
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• 2012

From 2015, PM2.5 standards will be added to Korean national ambient air quality standards. To characterize PM2.5 levels in Cheonan, annual PM2.5 concentrations along with PM10 concentrations were investigated between February 2010 and January 2011 using a dust monitor. The annual PM2.5 concentration was $40.45{\mu}g/m^3$ and over the standards($25{\mu}g/m^3$). The daily average PM2.5 concentrations ranged from 2.43 to $178.84{\mu}g/m^3$, and 26% days exceeded the daily PM2.5 standard($50{\mu}g/m^3$). During the same periods, only 11% days exceeded the daily PM10 standard, showing that PM2.5 were more concerning levels than PM10. Seasonal variations showed the highest concentrations in spring and winter, and lowest concentration in summer due to heavy rain fall. Changes in PM2.5 concentrations during the day were remarkable and showed the highest concentrations in commuting periods. The results indicated that the concentrations of PM2.5 in Cheonan were at the concerning level, and mainly from the mobile sources.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.113-113
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• 2017

최근 많은 산업의 발전으로 인해 환경오염을 유발시키는 폐수가 다량으로 배출되고 있으며, 이러한 폐수 속에는 유기용매, 고분자 물질 및 각종 염 등의 난분해성 물질들이 다량으로 함유되어 있다. 이런 물질들을 분해시키기 위해 물리적, 생물학적 수처리 방법이 많이 이용되고 있지만 이 방법들은 각각 운전비용과 처리비용이 고가인 단점이 있다. 따라서 비용과 효율 측면에서 효과적인 폐수처리를 위해서 전기화학적 폐수처리 방법이 많이 사용되고 있다. 물리적, 생물학적 처리 방법에 비해 비용이 적게 들고, 처리 후 잔류물이 남지 않으며, 독성을 띄는 산화제의 첨가 없이도 높은 폐수처리 능력을 보이기 때문에 친환경적이므로, 전기화학적 폐수산화 처리에 사용되는 불용성 전극에 대한 연구가 많이 진행되어져 오고 있다. 그 중 BDD(Boron-doped diamond) 전극은 표면에서 강력한 산화제인 수산화 라디칼의 높은 발생량으로 인해 뛰어난 폐수처리 능력을 보이므로 불용성 전극 분야에서 활발한 연구가 진행 중이다. 그러나 기존에 BDD 전극의 기판 모재로 이용되던 Si, W, Pb등은 모두 기계적 강도, 폐수처리 능력 및 독성 문제로 인해 한계가 있었고, 특히 Nb기판 위에 형성시킨 BDD 전극은 뛰어난 폐수처리 능력에도 불구하고 비싼 모재 원가로 인해 상용화가 힘든 실정이다. 이런 문제점을 해결하기 위해 높은 기계적 강도와 전기화학적 안정성을 가진 Ti 기판을 사용한 BDD 전극에 대한 연구가 보고되고 있다. 그러나 BDD와 Ti 간의 lattice mismatch, BDD층 형성을 위한 고온 공정시 탄소의 확산으로 인한 기판 표면에서의 TiC층 형성으로 인해 접착력이 감소하여 박리가 생기는 문제점이 있다. BDD와 Ti의 접착력을 향상시키기 위해 융점이 높고, 전기전도성이 우수한 TiN을 diffusion barrier layer로 삽입하면 탄소 확산에 의한 TiC층의 생성을 억제하여, 내부응력에 기인한 접착력 감소를 방지할 수 있다. 또 하나의 방법으로 Ti 기판의 전처리를 통해 BDD층의 접착력을 향상 시킬 수 있다. Sanding과 etching을 통해 기판 표면의 물리, 화학적인 표면조도를 부여하고, seeding을 통해 diamond 결정 성장에 도움을 주는 seed 입자를 분포시킴으로써, 중간층과 BDD층의 접착력을 향상시키고, BDD 결정핵 성장을 촉진시켜 고품질의 BDD박막 증착이 가능하다. 본 연구에서는 기존 Si, Nb 등의 기판 모재를 Ti로 대체함으로써 제조원가를 절감시키고, TiN 중간층을 삽입하여 접착력을 향상 시킴으로써 기존의 BDD 전극과 동등한 수준의 물성 및 수처리 특성을 가진 BDD전극 제작을 목표로 하였다. $25{\times}25mm$의 Ti 기판위에 TiN 중간층을 DC magnetron sputtering을 이용하여 증착 후, BDD 전극 층을 HFCVD로 증착하였다. 전처리를 진행한 기판과 중간층 및 BDD층의 미세구조를 XRD로 분석하였고, 표면 형상을 SEM으로 확인하였다. BDD전극의 접착력 분석을 통해 TiN 중간층의 최적 조성을 도출하고, 최종적으로 BDD/TiN/Ti 전극의 CV특성과 가폐수의 COD분해능력 및 축산폐수, 선박평형수 등의 실제 폐수 처리 능력을 BDD/Si, BDD/Nb 전극과 비교 검토할 것이다.

• Applied Microscopy
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• v.31 no.2
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• pp.207-214
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• 2001

Anatomy and ultrastructure of the modifeid Krana pattern have been studied in succulent Salsola collina Pall. Cylindrical leaves exhibited the Salsoloid Kranz type containing two layers of peripheral chlorenchyma that surrounded the water storage cells and vascular tissues. Small veins were also peripherally arranged, but mostly embedded in the vicinity of the inner chlorenchma without the orderly arrangement of the concentric layering of bundle sheath and mesophyll cells. The current study mainly focused on the chlorenchyma tissue abutting such minor veins. The outer columnar layer exhibited features similar to the characteristics of palisade mesophyll cells, while the inner cuboid layer to the bundle sheath cells of a typical $C_4$ Kranz pattern. Cellular components of the inner chlorenchyma were centripetal and numerous, but starch-laden chloroplasts were rudimentary in the thylakoidal system. The outer chlorenchyma demonstrated normally developed chloroplasts having well-stacked thylakoids and plastoglobuli. Branched and complicated plasmodesmata frequently occurred in thick interfaces of the two layers, implying the active movement of the photosynthates between them. The present data were mostly congruent with one of the structural features of the C4 subtypes , NADP-ME type, reported in the $C_4$ pattern. The Kranz pattern encountered in this Salsola probably has been directly related to the structural modification that occurred during a functional adaptation to the $C_4$ photosynthesis.

• Journal of Veterinary Clinics
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• v.32 no.3
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• pp.224-230
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• 2015

This study was designed in the fabricated poly (L-Lactic-co-${\varepsilon}$-Caprolactone) (PLCL) scaffold using chitosan-alginate hydrogel, which would be more suitable to maintain the biological and physiological functions continuing three dimensional spatial organizations for chondrocytes. As a scaffold, hydrogels alone is weak at endure complex loading within the body. In this study, we made cell hybrid scaffold constructs with poly (L-Lactic-co-${\varepsilon}$-Caprolactone) (PLCL) scaffold and hydrogels to make a three-dimensional composition of cells and extracellular matrix, which would be a mimic of a native cartilage. Using a particle leaching technique with NaCl, we fabricated a highly-elastic scaffold from PLCL with 85% porosity and $300-500{\mu}m$ pore size. A mixture of bovine chondrocytes and chitosan-alginate gel was seeded and compared with alginate as a control on the PLCL scaffold. The cell maturation, proliferation, extracellular matrix synthesis, glycosaminoglycans (sGAG) production and collagen type-II expressions were better in chondrocytes seeded in chitosan-alginate hydrogel than in alginate only. These results indicate that chondrocytes with chitosan-alginate gel on PLCL scaffolds provide an appropriate biomimetic environment for cell proliferation and matrix synthesis, which could successfully be used for cartilage repair and regeneration.

• 한국해양학회지
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• v.30 no.4
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• pp.341-354
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• 1995

Fluorescence characteristic and amino acids composition of organic matter were determined from extracted seawater samples at eight stations in the East Sea of Korea. Organic compounds have been extracted onto C-18 Sep-Pak cartridges. Three dimensional excitation/emission fluorescence contouring of extracts showed two markedly distinct characterized fluoroscopies representing protein-like biomacromolecule and humic-like geomacromolecule. Protein-like biomacromolecule showing fluorescence maxima at 280 nm/330 nm (excitation/emission) were abundant in the surface mixed layer and then apparently decreased below the thermocline at most stations. It suggests that source of biomacromolecule is comely related with vigorous biological synthetic activity in the surface layer and bacteria decompose its biologically labile components near the thermocline and in the deeper layer. On the other hand, humiliate geomacromolecule showing fluorescence maxima at 330 nm/430 nm (excitation/emission) were low in the surface mixed layer implying photochemical oxidation and then increased below the thermocline at most stations. It suggests that geomacromolecule might be transformed by condensation of bio-refractoryorganic fraction after decomposition of biomacromolecule and particulate organic carbon derived from the surface mixed layer. HPLC measurements of amino acids showed similar composition between seawater and extracted organic macromolecule after hydrolysis. Glycine, serine and alanine were predominant, accounting for more than 50% of total amino acids. Dissolved free amino acids of seawater were more abundant in the surface layer(0.7∼1.8 uM) than the deeper layer (0.2∼0.4 uM). D/L racemic ratio of alanine of extracted organic matter showed lower value in the surface layer than the deeper layer. It suggests that biomacromolecule predominant in the surface layer is relatively young, rapidly recycling and biologically labile.