• Macromolecular Research
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• 제17권12호
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• pp.943-949
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• 2009

A highly dispersed W/O emulsion of silicone oil (cyclomethicone)/water system was prepared with a nonionic surfactant. The surface and interfacial tension between the oil and water were characterized in terms of the droplet size distribution and viscosity change of the emulsion. When the dispersed phase concentration was relatively high, the viscosity of the emulsion was rapidly increased and the droplet size of the emulsion was decreased. The rheological behavior of the emulsion system showed non-Newtonian and shear thinning phenomena depending upon the content of the dispersed phase. The droplet size of the emulsion was decreased with increasing surfactant content and water concentration. The relative viscosity of the emulsion was better predicted with the Choi-Schowalter model than with the Taylor model. The value of the complex modulus increased with increasing surfactant concentration. The linear viscoelastic region was expanded with a dispersed phase concentration. According to the change in the viscosity, the behavior was classified into three distinct regions: [I] linear viscoelastic, [II] partially viscoelastic, and [III] viscous. The creep/recovery behaviors in each region were characterized.

• 한국세라믹학회지
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• 제48권6호
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• pp.549-558
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• 2011

Application of a generalized equivalent circuit including the electrode condition for the Hebb-Wagner polarization in the frequency domain proposed by Jamnik and Maier can provide a consistent set of material parameters, such as the geometric capacitance, partial conductivities, chemical capacitance or diffusivity, as well as electrode characteristics. Generalization of the shunt capacitors for the chemical capacitance by the constant phase elements (CPEs) was applied to a model mixed conducting system, $Ag_2S$, with electron-blocking AgI electrodes and ion-blocking Pt electrodes. While little difference resulted for the electron-blocking cell with almost ideal Warburg behavior, severely non-ideal behavior in the case of Pt electrodes not only necessitates a generalized transmission line model with shunt CPEs but also requires modelling of the leakage in the cell approximately proportional to the cell conductance, which then leads to partial conductivity values consistent with the electron-blocking case. Chemical capacitance was found to be closer to the true material property in the electron-blocking cell while excessively high chemical capacitance without expected silver activity dependence resulted in the electron-blocking cell. A chemical storage effect at internal boundaries is suggested to explain the anomalies in the respective blocking configurations.

• 한국기후변화학회지
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• 제6권2호
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• pp.121-131
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• 2015

As the temperature has changed by climate change, changes in its own characteristic values of the chemical substance or the movement and distribution of chemicals take place in accordance with the changes of hydrological and meteorological phenomena. Depending on the impact of climate change on the chemical behavior, it is necessary to understand and predict quantitative changes in the dynamics of the environment of pollutants due to climate change in order to predict in advance the occurrence of environmental disasters, and minimize the impact on the life and the environment after the incident. In this study, we have analysed and compared chemical fate models validated by previous studies in terms of model configuration, application size and input/output factors. The potential models applicable to municipal and industrial areas were selected on the basis of characteristic of each model, availability of input parameters and consideration for climate change, identified the problems, and then presented an approach to improve applicability.

• 대한화학회지
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• 제61권3호
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• pp.112-121
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• 2017

본 연구는 수압 공식을 이용한 설명 대신, 밀도와 중력의 개념을 연결한 설명이 뜨거나 가라앉는 현상에 대한 학생들의 대안 개념에 어떠한 영향을 미치는가를 알아보고자 하였다. 연구 대상은 강원도에 위치한 한 고등학교 2학년 4개반, 140명의 학생들이었으며, 이들을 실험집단과 비교집단의 두 집단으로 나누었다. 실험집단에는 밀도와 중력 개념을 연계한 설명을 도입한 수업을, 비교집단은 교과서에 제시된 수압 공식을 이용한 설명을 도입한 수업을 각각 실시하였다. 사전검사 결과를 공변수로 하여 공변량분석(ANCOVA)을 한 결과, 물질의 특성과 관련된 3 문항 중 2개 문항은 두 집단 간 차이가 통계적으로 유의하지 않았으나, 1개 문항은 수업의 작은 효과크기(Hedges' g=0.327)를 보였다. 그리고 대안개념 변화 추이에서도 두 집단 사이에 유의미한 차이가 없었다. 반면, 물과 물체와의 상대적 무게 관계와 관련된 문항에서는 3개 문항 모두 두 집단 간 차이가 통계적으로 유의미한 효과크기(0.286~0.502)를 나타내었다. 뿐만 아니라 사후에 실험집단의 압력과 관련된 대안개념의 빈도수가 비교집단에 비해 상당히 감소하였다. 따라서 이 연구에서 제안한 무게와 밀도를 연계한 설명 방식은 뜨고 가라앉는 현상에 대한 학생들의 대안개념을 제거하고 과학적 개념을 형성하는데 효과적임을 알 수 있다.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3433-3436
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• 2011

Some of metal nanoparticles have the potential for use as colorimetric assays for estimating solution properties, such as pH and temperature due to localized surface plasmon (LSP) phenomena. This report describes the use of silver nanoparticles (AgNP) conjugated with cytochrome c (Cyt c) for the colorimetric determination of solution pHs. When the pH of a solution decreases, the Cyt c immobilized on the AgNP undergoes a conformational change, leading to a decrease in the interparticle distance between Cyt c-AgNP probes and consequent red-shift in LSP. As a result, the color of the Cyt c-AgNP probe solution changes from yellow to red and finally to a grayish blue in the pH range from 11 to 3. This gradual color change can be used to determine the pH of a solution over a wide pH range, compared to other colorimetric methods that use gold nanoparticles.

• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2207-2212
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• 2012

Dimethylaluminum isopropoxide (DMAI, $(CH_3)_2AlO^iPr$) as a single precursor, which contains one aluminum and one oxygen atom, has been adopted to deposit non-stoichiometric aluminum oxide ($AlO_x$) films by low pressure metal organic chemical vapor deposition without an additional oxygen source. The atomic concentration of Al and O in the deposited $AlO_x$ film was measured to be Al:O = ~1:1.1 and any serious interfacial oxide layer between the film and Si substrate was not observed. Gaseous by-products monitored by quadruple mass spectrometry show that ${\beta}$-hydrogen elimination mechanism is mainly contributed to the $AlO_x$ CVD process of DMAI precursor. The current-voltage characteristics of the $AlO_x$ film in Au/$AlO_x$/Ir metalinsulator-metal (MIM) capacitor structure show high ON/OFF ratio larger than ${\sim}10^6$ with SET and RESET voltages of 2.7 and 0.8 V, respectively. Impedance spectra indicate that the switching and memory phenomena are based on the bulk-based origins, presumably the formation and rupture of filaments.

• 보존과학회지
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• 제5권1호
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• pp.20-40
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• 1996

For obtaining the basic data for establishing plan on the conservation of the Gameunsa 3-story and Naweonri 5-story Pagodas located at the Kyeongju city, the characteristics of the rock and weathering phenomena have been investigated. The former consists of quartz-rlch granite containing small amount of biotite, and the latter of alkali granite with abundant perthite, These rock phases are nearly identical to the marginal phase of medium-grained hornblende-biotite granodiorite and alkali granite respectively, which are distributed around the Kyeongju city. The rock weathering may be governed mainly by chemical weathering of feldspar following physical segregation of quartz grains and pervasive moss. The feldspar easily dissolve In the solution with pH<7 to precipitate clay mineral such as a kaolinite as a secondary phase on the feldspar surface. However, the chemical weathering of feldspar may continue when the surface is washed by the rain according to removal of the reprecipitated phase. On forwarding, the weathering may be greatly Influenced by the acid rain. Exfoliation and weathering along igneous lineation resulting in exfoliating along the structural line are the characteristic weathering phenomena. Also the secondary small cracks are irregularly developed on the rocks due to different strain on places by the overall structural unbalance of the pagodas. Along these cracks, the rain water intrudes deeply into the rocks and weathering occurs intensively compared to other parts. Weathering may be artificially promoted by the grinding or sculpturing when the pagodas were made. Because it may influence on the physical properties of the rocks as well as destruct the surface of the feldspar crystals, the major constituents of the rocks, it results in providing the environment of easy chemical weathering along time. For conservation, the pagodas must be structurally balanced by compacting the soil basement and supplementing rocks on the destroyed part. On the exfoliated part it is better not to be artifically treated as using cementing material. But the cracks may be filled up by cementing material to avoid the intrusion of acidic water. To supplement the rocks on the destroyed part, it may be better to use similar rock phases from identical biotite granite and alkali granite masses around the Kyeongju city.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.49-50
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• 2002

Rapid advancements in analytical instrumentations and techniques in the last several decades offer an unprecedented opportunity to analyze the complex chemistry and probe the surfaces for chemical evidence. Recent developments in nanotechnology provide further ability to examine phenomena and mechanisms at the nanometer level. As a result of these advances, our understanding of the complex lubrication system has improved significantly. This paper will attempt to provide a molecular basis of how lubricant and additives function in lubrication.

• 한국응용과학기술학회지
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• 제23권1호
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• pp.54-62
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• 2006

Kelvin equation is revisited, which accounts for important phenomena observed frequently in nano-dispersion systems. They include vapor pressure increase for curved interfaces, nucleation, capillary condensation, Ostwald ripening and so on. The smaller the radius of curvature is, the more significant Kelvin equation becomes. Therefore, its meaning, curvature effect, and importance are examined and discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1407-1409
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• 1998

It was investigated that space charge characteristics and Breakdown characteristics of XLPE/EPDM laminates as a function of interfacial condition. When the chemical A was pasted in laminate interface, there was little space charge in XLPE/EPDM interface and it was shown that breakdown strength of XLPE/EPDM laminate was influenced by laminate condition.