• 지질공학
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• 제27권4호
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• pp.451-462
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• 2017

Physical weathering caused by external forces and chemical weathering caused by the decomposition or alteration of constituent materials are the two factors that dominate the mechanical properties of rocks. In this study, a field investigation was undertaken to identify the physical and chemical weathering characteristics of the biotite granite and granitic weathered soils in Gyeongju, South Korea. Samples were collected according to their grade of weathering and subjected to modal analysis, XRD analysis, XRF analysis, physical property tests, particle size distribution tests, and slake durability tests. Modal and XRD analysis identified these rocks as biotite granite; secondary alteration minerals were not observed. Physical property tests and particle size distribution analyses indicate an average porosity of 41.28% and a sand content of > 90 wt.%. These values are somewhat higher than those of granites in general. The results of the slake durability test and XRF analyses show that the physical and chemical weathering indices of the samples vary with the degree of weathering.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.231-236
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• 2013

Some cytotoxicity studies for the interpretation of the interaction between nanoparticles and cells are non-mechanistic and time-consuming. Therefore, non-biological screening methods, which are faster and simpler than in-vivo and in-vitro methods, are required as alternatives to current cytotoxicity tests. Here, we proposed a simple screening method for the analysis of the interaction between several AgNPs (bare-, citrate-, and polyvinylpyrrolidone-coating) and dye-containing vesicles acting as a biomimetic cell-membrane. The interaction between AgNPs and vesicles could be evaluated readily by UV-vis spectra. Absorbance deviation in UV-vis spectra revealed a large attraction between neighboring particles and vesicles. This was confirmed by (Derjagin, Landau, Verwey, and Overbeek) theory and DMF (dark-field microscopy) analysis. This proposed method might be useful for analyzing the cytotoxicity of nanoparticles with cell-membranes instead of in vitro or in vivo cytotoxicity tests.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.222-232
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• 2009

In this study, the real site test conditions were considered and applied to suggest the improved test method for geosynthetics chemical resistance. For this, index and performance tests were done to specify and regulate the more approached test method. Accelerated model by Arrhenius equation was applied to interpretate the experimental data. Through analysis and comparison the overall experimental results, we could suggest the possibility and setup the advanced chemical resistance test method for geosynthetics.

• Advances in nano research
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• 제2권2호
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• pp.121-133
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• 2014

Polymer nanocomposites are advanced nanomaterials which exhibit dramatic improvements in various mechanical, thermal and barrier properties as compared with the neat polymer. Polystyrene/ alumina nanocomposites were prepared by an ultrasound-assisted solution casting method at filler loadings ranging from 0.2 to 2% and also at different ultrasonic frequencies, viz. 58 kHz, 192/58 kHz, 430 kHz, 470 kHz and 1 MHz. The composites were subjected to mechanical property tests (tensile and impact tests) and cavitation erosion tests to study the enhancement in functional properties. Filler dispersion in the polymer matrix was observed by SEM analysis. The effect of frequency on filler dispersion in the matrix was studied by SEM analysis and functional property enhancement of the composite material. The composites prepared at dual (high/ low) frequency (192/58 kHz) were found to show better property enhancement at low filler loadings as compared with neat polymer and also with composites prepared without ultrasound, thus reinforcing the finding that ultrasound-assisted synthesis is a promising method for the synthesis of nanocomposites.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.213-226
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• 2022

In the present study, the corrosion behavior of aluminum Al-7075 tempered (T-6 condition) alloy was evaluated by immersion testing and electrochemical testing in 1.75% and 3.5% NaCl environment at acidic, neutral and basic pH. The data obtained by both immersion tests and electrochemical corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy tests) present that the corrosion rate of the alloy specimens is minimum for the pH=7 condition of the solution due to the formation of dense and well adherent thin protective oxide layer. Whereas the solutions with acidic and alkaline pH cause shift in the corrosion behavior of aluminum alloy to more active domains aggravated by the constant flux of acidic and alkaline ions (Cl^- and OH^-) in the media which anodically dissolve the Al matrix in comparison to precipitated intermetallic phases (cathodic in nature) formed due to T6 treatment. Consequently, the pitting behavior of the alloy, as observed by cyclic polarization tests, shifts to more active regions when pH of the solutions changes from neutral to alkaline environment due to localized dissolution of the matrix in alkaline environment that ingress by diffusion through the pores in the oxide film. Microscopic analysis also strengthens the results obtained by immersion corrosion testing and electrochemical corrosion testing as the study examines the corrosion behavior of this alloy under a systematic evaluation in marine environment.

• Earthquakes and Structures
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• 제18권1호
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• pp.57-72
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• 2020

This paper presents the results of a monodirectional shaking table test on a full-scale unreinforced masonry cross vault characterized by asymmetric boundary conditions. The specimen represents a vault of the mosque of Dey in Algiers (Algeria), reproducing in detail the mechanical characteristics of masonry, and the constructive details including the presence of some peculiar wooden logs placed within the vault's abutments. The vault was tested with and without the presence of two steel bars which connect two opposite sides of the vault. The dynamic behaviour of both the vault's configurations were studied by using an incremental dynamic analysis up to the collapse of the vault without the steel bars. The use of an innovative high-resolution 3D optical system allowed measure displacement data of the cross vault during the shake table tests. The experimental results were analysed in terms of evolution of damage mechanisms, and in-plane and out-of-plane deformations. Moreover, the dynamic properties of the structure were investigated by means of an experimental modal analysis.

• Korean Chemical Engineering Research
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• 제48권6호
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• pp.695-699
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• 2010

추진제 KM10은 니트로셀룰로오스를 주원료로 제조된 단기추진제로서 장기저장 시자연분해현상을 일으키는 것으로 알려져 있다. 따라서 본 연구에서는 고온가속노화시험과 저장분석시험을 이용하여 추진제의 저장수명을 추정하였다. 고온가속 노화시험을 이용한 저장수명추정은 Arrhenius 식과 Berthelot 식을 사용하였으며, 저장분석시험을 이용한 저장수명 예측은 1차 회귀직선식을 이용하였다. 본 연구 결과에 따르면 고온가속 노화시험의 Arrhenius 식과 Berthelot식을 이용하여 추정한 추진제 KM10의 저장수명은 43.72년, 16.53년으로 큰 차이를 보였으며, 저장분석시험으로 이용한 저장수명은 42.94년으로 나타났다. 이것을 E. R. Bixon의 연구결과와 비교할 때 Arrhenius 식을 이용하여 추정한 값이 타당한 것으로 판단되었다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 춘계학술대회
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• pp.690-693
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• 2022

본 연구는 와인 데이터를 활용하여 와인 품질에 영향을 미치는 요인에 대해 상관관계 분석을 실시하였고, 그 결과를 토대로 와인 품질의 기준을 예측 하였다. 본 연구에서 사용된 데이터셋은 포르투갈의 비뉴베르드(Vinho verde)에서 생산된 레드와인의 1599개, 화이트와인 4898개의 관측지의 데이터로 총 6497개를 사용하였다. 변수 항목은 물리적, 화학적 분석 테스트를 통해 와인 성분을 나타내는 12가지 성분 변수, 총 1599개의 관측치, 세계 와인 3대 생산지국가(프랑스, 이탈리아, 스페인)들의 대표와인 한 개씩 총 3개를 추가하였고, 그 국가들의 기후변화 데이터를 적용하여 분석하였다.

• 대한화학회지
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• 제54권6호
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• pp.818-828
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• 2010

대학수학능력시험(수능)이 1994학년도에 처음 시행된 이후 17년이 지나고 여러 번의 모의평가 출제로 인해 문항의 패턴화, 지식 중심의 출제라는 비판이 제기되고 있다. 이러한 문제에 대한 시사점을 얻기 위해 한국과 마찬가지로 국가 중심 교육과정이며 국가 수준에서 이루어지는 선다형 시험 유형을 가진 일본의 대학입시센터시험(센터시험) 문항을 분석하였다. 이 연구에서는 2009년 1월에 시행한 센터시험의 이과시험에서 화학 문항을 수능과 관련하여 내용 요소 및 행동 영역에 따라 분석하고, 문항 유형과 특이 사항을 분석하였다. 또한 한국 수험생의 관점에서 예상 정답률을 추정하여 수능의 화학 문항 출제에 주는 시사점을 도출하였다.

• Bulletin of the Korean Chemical Society
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• 제29권5호
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• pp.1038-1042
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• 2008

Mono and multilayer TiO2(Fe, $PEG_{600}$) films were deposited by the dip-coating on $SiO_2$/glass substrate using sol-gel method. In an attempt to improve the antibacterial properties of doped $TiO_2$ films, the influence of the iron oxides and polyethilenglycol ($PEG_{600}$) on the morphological, optical, surface chemical composition and biological properties of nanostructured layers was studied. Complementary measurements were performed including Spectroscopic Ellipsometry (SE), Scanning Electron Microscopy (SEM) coupled with the fractal analysis, X-Ray Photoelectron Spectroscopy (XPS) and antibacterial tests. It was found that different concentrations of Fe and $PEG_{600}$ added to coating solution strongly influence the porosity and morphology at nanometric scale related to fractal behaviour and the elemental and chemical states of the surfaces as well. The thermal treatment under oxidative atmosphere leads to films densification and oxides phase stabilization. The antibacterial activity of coatings against Escherichia Coli bacteria was examined by specific antibacterial tests.