• 분석과학
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• 제35권5호
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• pp.189-196
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• 2022

When cationic basic compounds are chromatographed using hydro-organic mobile phase, the presence of anionic free silanols in the silica-based stationary phases results in broad and asymmetrical peaks. The addition of an ionic reagent to the mobile phase prevents analytes from accessing free silanols, improving peak shape. In this study, the chromatographic behavior of salbutamol sulfate as a basic compound was investigated under various conditions, including the use of different columns, mobile phases, and ion-pair reagents such as triethanolamine (TEA) and sodium heptane sulfonate (SHS). The retention and peak shape of chromatograms were both evaluated. The results show that pre-conditioning the column with TEA and including it in the mobile phase can prevent cationic analytes from accessing anionic silanols, resulting in improved peak shape. Furthermore, buffering the mobile phase is an important factor in keeping the pH constant throughout the process. The chosen method was validated in part. This study could be helpful for researchers and analyst to solve such problems with cationic basic components.

• Korean Chemical Engineering Research
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• 제50권4호
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• pp.729-732
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• 2012

본 논문에서 이온성액체를 이용한 초음파화학을 통해서 칼코젠 나노입자를 in-situ로 합성하여서 다중벽 탄소나노튜브(MWCNT) 위에 도포하였다. 1-Butyl-3-methylimidazolium tetrafluoroborate ($BMimBF_4$) 이온성액체를 이용해서 MWCNT의 표면을 기능화하였다. 합성된 MWCNT/$BMimBF_4$/CdTe, MWCNT/$BMimBF_4$/ZnTe, MWCNT/$BMimBF_4$/ZnSe 나노복합체를 TEM과 EDS를 이용해서 분석하였다. 특히, MWCNT/$BMimBF_4$/CdTe, MWCNT/$BMimBF_4$/ZnTe, and MWCNT/$BMimBF_4$/ZnSe 나노복합체는 각각 요철과 같거나, 거칠거나 부드러운 코어-쉘 형태와 같은 특이한 구조를 보여주었다. 본 연구는 반응속도가 다른 전구체로부터 얻어진 이성분 반도체 나노입자를 합성과 동시에 탄소나노튜브에 도포할 수 있는 새로운 합성법을 제시한다.

• Corrosion Science and Technology
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• 제6권2호
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• pp.50-55
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• 2007

The smaller size and higher integration of advanced electronic package systems result in severe electrochemical reliability issues in microelectronic packaging due to higher electric field under high temperature and humidity conditions. Under these harsh conditions, electronic components respond to applied voltages by electrochemical ionization of metal and the formation of a filament, which leads to short-circuit failure of an electronic component, which is termed electrochemical migration. This work aims to evaluate electrochemical migration susceptibility of the pure Sn, Sn-3.5Ag, Sn-3.0Ag-0.5Cu solder alloys in $Na_{2}SO_{4}$. The water drop test was performed to understand the failure mechanism in a pad patterned solder alloy. The polarization test and anodic dissolution test were performed, and ionic species and concentration were analyzed. Ag and Cu additions increased the time to failure of Pb-free solder in 0.001 wt% $Na_{2}SO_{4}$ solution at room temperature and the dendrite was mainly composed of Sn regardless of the solders. In the case of SnAg solders, when Ag and Cu added to the solders, Ag and Cu improved the passivation behavior and pitting corrosion resistance and formed inert intermetallic compounds and thus the dissolution of Ag and Cu was suppressed; only Sn was dissolved. If ionic species is mainly Sn ion, dissolution content than cathodic deposition efficiency will affect the composition of the dendrite. Therefore, Ag and Cu additions improve the electrochemical migration resistance of SnAg and SnAgCu solders.

• 한국대기환경학회지
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• 제25권1호
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• pp.75-89
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• 2009

The purpose of this study was to identify $PM_{2.5}$ sources and to estimate their contributions to the border of Yongin-Suwon area, based on the analysis of the $PM_{2.5}$ mass concentration and the associated inorganic elements, ions and carbon components. The contribution of $PM_{2.5}$ sources were estimated by using a positive matrix factorization (PMF) model to identify air emission sources. For this study, $PM_{2.5}$ samples were collected from May, 2007 to April, 2008. The inorganic elements were analyzed by an ICP-AES. The ionic components in $PM_{2.5}$ were analyzed by an Ie. The carbon components were also analyzed by DRI/OGC analyzer. After performing PMF modeling, a total of 12 sources were identified and their contributions were quantitatively estimated. The contributions from each emission source were as follows: 11.3% from oil combustion source, 3.4% from bus/highway source, 5.8% from diesel vehicle source, 4.7% from gasoline vehicle source, 8.8% from biomass burning source, 15.1 % from secondary sulfate, 5.2% from secondary nitrate source, 13.4% from industrial related source, 4.1% from Cl-rich source, 19.6% from soil related source, 1.0% from aged sea salt, and 7.4% from coal combustion source, respectively. This study provides basic information on the major sources affecting air quality, and then it will help to effectively control $PM_{2.5}$ in this study area.

• Asian Journal of Atmospheric Environment
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• 제7권4호
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• pp.217-226
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• 2013

The collection of TSP and $PM_{2.5}$ aerosols has been made at the Gosan Site of Jeju Island during 2008-2011, and their ionic and elemental species were analyzed, in order to examine the seasonal variation and characteristics of aerosol compositions. The anthropogenic components ($NH_4{^+}$, $nss-SO_4{^{2-}}$, $NO_3{^-}$, S, Zn, Pb) and the soil components ($nss-Ca^{2+}$, Al, Fe, Ca) showed high concentrations in spring as the prevailing westerly wind, but the concentrations of the sea-salt components ($Na^+$, $Cl^-$) were high in winter. In TSP, the neutralization by $NH_3$ increased in summer, but the neutralization by $CaCO_3$ increased in spring and fall seasons. The organic acids ($HCOO^-$, $CH_3COO^-$) contributed to the acidification of the aerosols by only 5.0%, so the acidification could be mostly contributed by the inorganic acids ($SO_4{^{2-}}$, $NO_3{^-}$). From the examination of the source origins by factor analysis, the compositions of TSP were influenced by the order of soil > anthropogenic > marine, on the other hand, those of $PM_{2.5}$ were by the order of anthropogenic > marine > soil. The backward trajectory analyses showed that the concentrations of $NH_4{^+}$, $nss-SO_4{^{2-}}$, $NO_3{^-}$ and $nss-Ca^{2+}$ increased highly when the air masses had moved from China continent into Gosan area of Jeju Island.

• 멤브레인
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• 제29권1호
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• pp.44-50
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• 2019

본 논문에서는 SBS-g-POEM 블록-그래프트 공중합체, 이온성 액체(EMIMTFSI) 및 ZIF-8 나노 입자를 사용하여 $CO_2/N_2$ 기체를 분리하기 위한 혼합 매질 분리막(MMMs)을 개발하였다. SBS-g-POEM은 낮은 비용이 드는 자유 라디칼 중합법을 통해 합성된 유연한 블록-그래프트 공중합체이다. EMIMTFSI는 SBS-g-POEM 매트릭스에 용해시켰으며, 합성된 ZIF-8 나노 입자들 역시 공중합체의 매트릭스에 분산시켰다. 제조된 시료들의 특성은 푸리에 변환 적외 분광법(FT-IR), 시차 주사 열량계(DSC), 주사 전자 현미경(SEM), X선 회절 분석(XRD)을 통해 확인하였으며, 분석 결과 각 성분들은 서로 간의 좋은 혼화성을 나타내었다. 기체 분리 성능은 time-lag measurements를 통해 확인되었으며, 537.0 barrer의 $CO_2$ 투과도와 15.2의 $CO_2/N_2$ 선택도를 나타내었다. 이를 통해 첨가된 EMIMTFSI와 ZIF-8 나노 입자는 $CO_2/N_2$ 선택도를 크게 희생시키지 않고 기체 투과도를 두 배 이상 향상시키는 것으로 확인되었다.

• Korean Chemical Engineering Research
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• 제46권4호
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• pp.799-805
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• 2008

일반적으로 음이온계면활성제와 양이온계면활성제는 수용액상에서 침전하는 불용성복합물을 형성하기 때문에 상용성이 좋지 않다. 하지만 경우에 따라서 일부 음이온계면활성제와 양이온계면활성제의 1:1 molar complex (catanionic surfactant)는물에용해하면서비이온계면활성제와같이행동하기때문에유사비이온계면활성제복합물(pseudo-nonionic surfactant complex)이라고 부른다. 유사비이온계면활성제복합물은 일반적인 이온성계면활성제에 비해 보다 용이하게 계면에 배열되기 때문에 평형 및 동적 표면장력에서 우수한 계면활성효과를 나타낸다. 계면활성제의 친수성 head group에 polyhydroxyl group을 가진 디글리세릴계 양이온계면활성제인 diglyceryl dodecyl dimethyl ammonium chloride(DGDAC)과 음이온계면활성제 sodium dodecyl sulfate(SDS)를 1:1 molar ratio로 수용액상에서 혼합하였을 경우 molecular interaction parameter ${\beta}^M$가 -17.2로 매우 강한 positive synergism을 보였으며. 평형 상거동과 현미경에 의한 실험결과는 이 DGDAC와 SDS의 혼합수용액은 single phase의 vesicle을 형성함을 알 수 있었다.

• 한국식품조리과학회지
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• 제13권4호
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• pp.507-513
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• 1997

두부순물에 함유되어 있는 유용성 물질을 분리·농축하고자 한외여과법을 행하고 그 효율성을 분석하였다. 재생섬유소막과 polysulphone막 모두 pH가 증가할수록 막투과 속도가 감소하였고, pH 3.5에서 한외여과 효율이 가장 높게 나타났다. EDTA를 0.01 M 처리한 두부순물의 경우, 처리하지 않은 것보다 오히려 막투과 속도가 감소하였다. 또한 pH가 증가할수록 두부순물의 이온성 칼슘의 농도가 감소하여 이온성 칼슘의 농도 또한 막투과 속도에 영향을 준다고 생각되었다. Polysulphone막의 경우 용적농축비가 10일 때 COD의 막 제거계수가 79.25%, 단백질 막 제거계수가 98.42%로 나타나 정화효과와 농축액으로의 단백질 농축효과가 컸으며 , 재생섬유소막은 단백질의 막제거 계수는 polysulphone막보다 낮았으나 당을 여과액쪽으로 회수하고자 할 때 더 효율적인 것으로 나타났다. 올리고당을 여과액쪽으로 회수하고자 할 때 라피노오스와 스타키오스의 농도를 상대적으로 높이기 위해서 polysulphone막보다 재생섬유소막이 더 적당하며, 용적농축비는 4배 정도가 적합한 것으로 나타났다.

• 한국대기환경학회지
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• 제34권3호
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• pp.418-429
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• 2018

Measurements of 24-hr size-segregated ambient particles were made at an urban site of Gwangju under high pressure conditions occurred in the Korean Peninsula late in March 2018. The aim of this study was to understand the effect of air stagnation on mass size distributions and formation pathways of water-soluble organic and inorganic components. During the study period, the $NO_3{^-}$, $SO_4{^{2-}}$, $NH_4{^+}$, water-soluble organic carbon (WSOC), and humic-like substances(HULIS) exhibited mostly bi-modal size distributions peaking at 1.0 and $6.2{\mu}m$, with predominant droplet modes. In particular, outstanding droplet mode size distributions were observed on March 25 when a severe haze occurred due to stable air conditions and long range transport of aerosol particles from northeastern regions of China. Air stagnation conditions and high relative humidity during the study period resulted in accumulation of primary aerosol particles from local emission sources and enhanced formation of secondary ionic and organic aerosols through aqueous-phase oxidations of $SO_2$, $NO_2$, $NH_3$, and volatile organic compounds, leading to their dominant droplet mode size distributions at particle size of $1.0{\mu}m$. From the size distribution of $K^+$ in accumulation mode, it can be inferred that in addition to the secondary organic aerosol formations, accumulation mode WSOC and HULIS could be partly attributed to biomass burning emissions.

• 한국전산유체공학회지
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• 제18권3호
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• pp.67-71
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• 2013

Recently, the rapid development of the semiconductor industry induces the prompt technical progress in the area of device integration and the application of large diameter wafers for the price competitiveness. As a result of the usage of large wafers in the semiconductor industry, the silicon carbide components which have layers of silicon carbide on graphite or RBSC substrates is getting widely used due to the advantages of SiC such as high hardness and strength, chemical and ionic resistant to all the environments superior than other ceramic materials. For the uniform and homogeneous deposition of silicon carbide on these huge components, it needs to know about the gas flow in the CVD reactor, not only for the delicate adjustment of the process variables but more essentially for the cost reduction for the shape change of specimens and their holders on the stage of reactor. In this research, the CFD simulation is challenged for the prediction of the inner distribution of the gas velocity. Chemical reaction simulation is used to predict the distribution of concentration of the reacting gas with the rotating velocity of the stage. With the increase of the rotating speed, more uniform distribution of the reacting gas on the surface of the stage was obtained.