• Applied Chemistry for Engineering
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• v.16 no.4
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• pp.533-541
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• 2005

Non-aqueous cleaning agents were formulated with 2,2,2-trifluoroethanol (TFEA) and hydrofluoroether (HFE), and their physical properties and cleaning abilities were examined. TFEA-based aqueous cleaning agents were also formulated with nonionic surfactants, hydrotropes and builders, and their cleaning abilities were compared. Possibilities of these cleaning agents as substitutes for CFC-113 and 1,1,1-TCE were finally evaluated. In this work, fluxes, cutting oils, greases, and fluoric oils were selected as model contaminants for cleaning experiments. These contaminants have different properties of water-solubility or hydrophilicity, and fat-solubility or lypophilicity. Cleaning abilities of TFEA-based cleaning agents were analyzed and compared through the measurement of contaminant weight changes as a function of cleaning time, and their possibilities as alternative cleaning agents were evaluated. As a result, it was shown that TFEA and HFE-based non-aqueous cleaning agents have quite a good cleaning power for fluxes and fluorine soils but low one for greases. And TFEA-based agueous cleaning agents which consisted of nonionic surfactants, hydrotrope, and builders were very effective for cleaning fluxes and greases under certain formulation conditions. Thus, it was revealed that the TFEA-based cleaning agents were very effective for cleaning specific contaminants and can be used as substitutes for CFC-113 and 1,1,1-TCE in some industrial applications.

• Journal of Soil and Groundwater Environment
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• v.19 no.1
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• pp.34-45
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• 2014

A variety of physical, chemical, and microbiological techniques have been developed to deal with soil and groundwater contamination. However, in the presence of the large portion of soil micro-environments, contaminant rebound and/or tailing have been frequently reported. Case study of total petroleum hydrocarbons (TPH) removal by full-scale land farming showed that contaminant rebound and/or tailing occurred in 9 out of total 21 cases and subsequently resulted in problems of a long term operation to satisfy TPH guidelines of contaminated soil and groundwater. The main cause of contaminant rebound and tailing is considered to be the strong interactions between contaminants and micro-environments including micro-particles, micro-pores, and organic matter. Thus, this study reviewed the effects of soil micro-environments of soil and groundwater on the removal efficiency for both heavy metals and petroleum contaminants. In addition, the various methods of sampling, analysis, and assessment of soil micro-environments were evaluated. Thorough understanding of the effects of soil micro-environments on contaminant removal will be essential to achieve a cost-effective and efficient solution to contaminated sites.

• The Journal of Engineering Geology
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• v.24 no.4
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• pp.551-574
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• 2014

The occurrence, distribution, and hydrogeochemical characteristics of uranium and radon in groundwater within different lithologies in Gyeongnam and Gyeongbuk provinces were investigated. A total of 201 groundwater samples from sedimentary rocks taking a large portion of the geology and from igneous rocks taking a small portion of the geology were analyzed and examined using factor analysis. Their radionuclide levels were used to construct detailed concentration maps. The groundwater types, defined using a Piper diagram, are mainly Ca-$HCO_3$ with less Na-$HCO_3$. Among the samples, one site exceeds $30{\mu}g/L$ of uranium (i.e., the maximum contaminant level of the USEPA) and three sites exceed 4,000 pCi/L of radon (i.e., the alternative maximum contaminant level). No samples were found to exceed the 15 pCi/L level of gross alpha or the 5 pCi/L level of radium. The concentration of uranium ranges from 0.02 to $53.7{\mu}g/L$, with a mean of $1.56{\mu}g/L$, a median of $0.47{\mu}g/L$, and a standard deviation of $4.3{\mu}g/L$. The mean concentrations of uranium for the different geological units increase in the following order: Shindong Group, Granites, Hayang Group, Yucheon Group, and Tertiary sedimentary rocks. The concentration of radon ranges from 2 to 8,740 pCi/L, with an mean of 754 pCi/L, a median of 510 pCi/L, and a standard deviation of 907 pCi/L. The mean radon concentrations for the investigated geological units increase in the following order: Granites, Yucheon Group, Tertiary sedimentary rocks, Hayang Group and Shindong Group. According to the factor analysis for each geological unit, uranium and radon behave independently of each other with no specific correlation. However, radionuclides show close relationships with some components. Regional investigations of radionuclides throughout the country require an integrated approach that considers the main lithological units as well as administrative districts.

• Journal of Life Science
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• v.18 no.2
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• pp.206-212
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• 2008

The quorum sensing (QS) regulatory network has been the subject of extensive studies during recent years and has also attracted a lot of attention because it both positively and negatively regulates various putative virulence factors, although initially considered to be a specialized system of Vibrio fischeri and related species. In this study, to identify the novel materials which inhibit QS system of microorganisms, extracts of eighteen natural products were tested by bioassay using N-(3-oxohexanoyl)-$_L$-homoserine lactone and N-(3-oxooctanoyl)-$_L$-homoserine lactone synthesized in this experiment and an Agrobacterium tumefaciens NT1 biosensor strain containing a traI::lacZ fusion. The result indicated that the extracts of cabbage, leek, and onion exhibited the QS inhibition activity. Thus, materials contained in the extracts were isolated via recycling preparative HPLC and were purified via a JAIGEL-LS255 column. The common fraction corresponding to a peak of the 83 min point of them quenched the quorum sensing of A. tumefaciens NT1 biosensor strain in ABMM containing X-gal and was designated quorum sensing inhibitor-83 min (QSI-83). The QSI-83 exhibited the heat stability and did not inhibit the growth of A. tumefaciens NTl. Furthermore, thin layer chromatography (TLC) results suggested that these novel materials may be antagonists of N-acyl homoserine lactone or may inhibit the QS autoinducer synthesis by Pseudomonas syringae pv. tabaci.

• 한국해양학회지
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• v.29 no.4
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• pp.338-356
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• 1994

Sediment samples from the continental shelf of the South Sea of Korea are analysed to determine the concentration of Al, Fe, Mn, cu, Ni, Zn, Co, Cr and Pb. among these samples, fine-grained sediments were also analysed by a sequential extraction technique to know geochemical forms of the metals in this environments. The total concentration of Al, Fe, Cr, Ni, Cu and Zn in bulk sediments decreased gradually with the increase of distance from the coastal zone. This distribution patterns are well coincide with grain size distribution. However, the patterns of Mn, co and Pb do not follow such and overall distribution. The concentration of Pb, particularly, did not show any features in areal distribution, which may be result from different pathways to the sediments, compared to the other metals. the speculation data show that a considerable amount of Cd, Mn and Co are bounded in the carbonate fraction, accounting for 42.8%, 40.3% and 30.6%, respectively. Cu, Zn, Mn and Fe are largely associated to oxide fraction with proportions of 34.4%, 23.1%, 15.5% and 13.7%, respectively. However, the metals in residual fraction account for more than 50% of the total metal concentration, except for Mn. These observations emphasize that residual fraction in the dominant component controlling the elemental concentration.quartz and glauconite grains.Accordingly,these sediments are interpreted as an extension part of transgressive sand deposit that are widely distributed on the continental shalf floor of southern Yellow Sea.

• Journal of the Korean Institute of Gas
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• v.25 no.2
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• pp.64-71
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• 2021

Research on polymer matrix composites with excellent molding processability and mechanical properties in the automotive field including hydrogen fuel cell electric vehicles is expanding to Computer-Aided Engineering (CAE) to support the design of materials with specific mechanical properties. CAE automation requires the prediction of the mechanical properties and behavior of materials. Unlike single materials, the mechanical properties prediction of polymer matrix composites is difficult to explain with formulas because the mechanical behavior is complicated to be explained only by the relationship between the matrix and the filler. In this study, the stress-strain curve according to the composition of polymer matrix composites, which was difficult to predict due to its sensitivity to large plastic deformation and composition, was predicted based on machine learning of the test data. The developed model finds a complex correlation between matrix and filler types and compositions, and predicts the total stress-strain curve meaningfully even in the absence of learned test data. It is expected that the material design AI system can be completed in the future based on the developed model that predicts the mechanical properties of polymer matrix composites even for the combination and composition that have not been learned.

• Journal of Environmental Policy
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• v.2 no.1
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• pp.87-105
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• 2003

토양오염기준은 토지이용별 또는 오염노출경로별 오염토양의 조사, 평가 및 복구를 위한 유용한 지침으로 이용될 수 있다. 이 연구에서는 한국을 포함한 몇몇 국가의 토양오염기준을 특히 중금속에 주안점을 두고 검토하였다. 또한 국내 일부 폐광산 지역의 환경오염 조사결과를 토양오염기준과 비교하며 평가하였다. 영국, 네덜란드, 독일, 캐나다, 일본 등의 국가에서는 복구우선순위 선정과 인체건강 및 생태계 보전을 위한 오염토양의 선별수단으로 토양오염기준을 개발하여 왔다. 국내에서는 1996년 토양환경보전법(시행규칙)의 시행에 따라 토양 오염기준 설정과 특정토양오염유발시설의 관리, 정기적 토양오염도 조사를 실시하고 있으며 이후 2001년 보완 개정되어 토양오염물질의 확대적용과 토양오염 조사, 관리 및 복원 방법의 보완이 이루어진 바 있다. 그럼에도 불구하고 현 중금속(Cd, Cu 및 Pb)의 오염기준을 적용할때 폐광산 지역의 폐기물과 이에 오염된 토양의 경우 다량의 중금속을 함유하고 있지만 오염지역으로 규정되지 않을 수도 있다. 이 연구 결과, 0.1N 염산용출법은 중금속의 토양 내 화학적 형태 중 일부 교환성 및 환원성 형태만을 추출하며 황화물 형태를 충분히 용출하지 못하고 있는 것으로 나타났다. 또한 장기적인 환경조건 변화에 따른 토양 내 중금속의 용출성 변화를 평가하기 위해서는 강산추출법이 요구되어진다. 따라서 폐광산지 역의 중금속에 의한 토양오염의 타당한 환경평가 결정을 위해 현 분석기법 외에 총함량 분석방법의 병행적용과 이에 따른 새로운 오염기준 설정 등이 필요한 것으로 제시되었다.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.348-351
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• 2011

In this research, we developed a sensor system which can easily detect several chelating agents using polydiacetylene(PDA) vesicles. In comparison to other sensors, PDA based sensor has several advantages. First, detection method is much simpler and faster because it does not require any labeling step in the experiment procedure. Second, significant color-transition from blue to red based upon external stimulus allows us the detection by naked eyes. Finally, it is also possible to perform quantitative analysis of the concentration of the chelating agent by measuring the colorimetric response. In this paper, five types of chelating agents were used, including EDTA, EGTA, NTA, DCTA and DTPA. Among them, EDTA and DCTA triggered especially strong color-transition. In conclusion, this study has led to a successful development of a color transition-based PDA sensor system for easy and rapid detection of chelating agents.

• Korean Chemical Engineering Research
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• v.48 no.1
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• pp.1-9
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• 2010

Since carbon dioxide, $CO_2$, was revealed as a major greenhouse gas, techniques for its separation, capture, and storage have received increasing interest in recent years. Aqueous amines are the most widely accepted $CO_2$ absorbents, but they cause the problems such as high regeneration energy, thermal degradation, and loss of absorbents due to their volatility. Ionic liquids having high thermal stability, extremely low vapor pressure, and capability of selectively absorbing specific gases have been proposed as new $CO_2$ capturing solvents which may potentially replace aqueous amines. By reviewing the ionic liquids having capability to absorb $CO_2$ reported in previous papers, we seek to develop a comprehensive understanding on the factors that influence the $CO_2$ solubility in ionic liquids such as their structures, absorption temperature, pressure, water content, etc., and to estimate the potential of ionic liquids as $CO_2$ separating media.

• The Journal of Korean Institute for Practical Engineering Education
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• v.2 no.1
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• pp.35-41
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• 2010

An enzyme-catalized reaction is usually characterized by a very large increase in the rate and high specificity. Kinetics of simple enzyme-catalized reactions are often referred to as Michelis-Menten kinetics. A chemical that interferes with an enzyme's activity is called inhibitor. There are two types of enzyme inhibitions (viz. reversible and irreversible). If an inhibitor attaches to the enzyme with weak bonds, such as hydrogen bonds, the inhibition is usually reversible. Many enzyme reactions are also inhibited reversibly by their corresponding products. The rate of substrate disappearance together with the rate of product formation may be written by nonlinear differential equations. In the present study, numerical analyses of simple enzyme kinetics and inhibited enzyme kinetics are reported for the purpose of undergraduate education in engineering.