• Journal of the Korean Chemical Society
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• v.53 no.6
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• pp.717-726
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• 2009

Multivariate models were developed for the simultaneous spectrophotometric determination of copper (II), nickel (II) and zinc (II) in water with 1-(2-thiazolylazo)-2-naphthol as chromogenic reagent in the presence of Triton X-100. To overcome the drawback of spectral interferences, principal component regression (PCR) and partial least square (PLS) multivariate calibration approaches were applied. Performances were validated with several test sets, and their results were then compared. In general, no significant difference in analytical performance between PLS and PCR models. The root mean square error of prediction (RMSEP) using three components for $Cu^{2+}$, $Ni^{2+}$ and $Zn^{2+}$ were 0.018, 0.010, 0.011 ppm, respectively. Figures of merit such as sensitivity, analytical sensitivity, limit of detection (LOD) were also estimated. High reliability was achieved when the proposed procedure was applied to simultaneous determination of $Cu^{2+}$, $Ni^{2+}$ and $Zn^{2+}$ in synthetic mixture and tap water.

• Journal of Environmental Policy
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• v.4 no.1
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• pp.39-67
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• 2005

In order to properly define the terms such as soil, soil contamination, soil contamination site and remediation, which are the key terms under the Soil Environment Conservation Act(SECA) in Korea, we analyzed the legal definitions of the similar key words in legislations of the developed western countries. The selected countries were the United States of America, the United Kingdom, the Netherlands, Germany, and Denmark. The legal definitions of these keywords were very much diversified due to different levels of soil contamination, as well as different industrial, social, and legal backgrounds in each country. However, fair suggestions for definitions of the key terms in SECA were derived from the comparative analyses of these countries. First and foremost, SECA should provide a definition of 'soil' which includes a concept of the natural soil layer produced from soil mineralization processes. Groundwater and sublayer of the groundwater would. be excluded in the boundary of the soil with regards to the Groundwater Act of Korea. Definition of 'soil contamination' of SECA should include a concept of risk assessment(soil contaminants, pathway, and receptors), purpose of land use, and the acquired limitation levels of soil contaminants. Soil contamination activity either industrial or anthropogenic in SECA article2-1, could be substituted for a concept of soil risk assessment. Definition of 'soil contamination site' could derive from amalgamating the concepts of i) soil contamination in conjunction with contaminants, ii) risk assessment, iii) a concept of land use, and iv) knowing limitation of contamination site designation. Definition of 'remediation of contaminated site' should include the objective, intention, action, methodology and limit of the remediation. These suggested definitions would increase the efficacy of soil environment conservation policies, which includes the survey of the potentially contaminated area, remediation, and removal of the site.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.26.2-26.2
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• 2010

최근에는 차세대 조명용 후보광원인 고출력 백색 LED를 개발하기 위한 경쟁이 치열하며, 이를 위해 업체가 고심하고 있는 가장 큰 문제 중의 하나가 칩에서 발생하는 열을 어떻게 관리하는가 하는 방열의 문제이다. 따라서, LED의 가장 큰 특징인 장수명을 손해보지 않기 위해서는 칩에서 발생되고 있는 열을 외부에 확산시키기 위한 기술 개발이 필수적이다. 다양한 방열소재 중 W-Cu 복합재는 W의 낮은 열팽창계수와 Cu의 높은 열전도도로 인해 방열소재로써 유망한 소재로 주목받고 있으나, 우수한 열적 특성을 발현하기 위해서는 고치밀화를 갖는 W-Cu 복합재 제조가 우선적으로 필요하다. W-Cu 복합체는 일반적으로 액상소결법을 통해 균일한 미세조직을 얻을 수 있으나, 열팽창계수를 낮추기 위해 Cu 함량이 적어지게 되면 치밀화가 어려우며 이를 해결하기 위해 나노입자를 갖는 분말을 이용하고자 하는 연구가 많이 진행되고 있다. 본 연구에서는 W과 Cu 산화물을 이용하는 것이 구성성분끼리의 편석이 발생하지 않으며, 소결성도 우수하여 양산화에 가장 접근한 방법으로 알려져 있다. 그러나, 지금까지의 얻어진 W-Cu 복합체의 경우, 분말상태에서의 얻어진 나노입자가 승온시에 마이크로 크기로 과도한 입자성장이 일어나기 때문에 소결 후에도 나노크기를 유지하기 어려울 뿐만 아니라, 구성상끼리의 응집체가 형성된다. 본 연구에서는 액상소결후에 W 입자가 Cu 기지내에 균일하게 분산되는 동시에 나노크기의 입자를 가지는 고분산 W-Cu 소결체를 얻고자 하였다. 이를 위해 금속산화물 분말의 분쇄를 위해 효과적인 방법으로 알려진 습식상태에서의 고에너지 볼밀링을 통하여 혼합된 텅스텐과 구리 산화물 분말의 수소환원공정을 통해 얻어진 100nm 이하의 입자를 가지는 W-20wt%Cu 나노복합분말을 출발분말로 사용하였다. W-20wt%Cu 나노복합분말의 성형체를 $1050^{\circ}C-1250^{\circ}C$의 온도범위에서 소결거동을 조사하였다. 그 결과, $1100^{\circ}C$ 온도에서 이론밀도에 가까운 소결밀도를 나타내었으며, 이는 기존에 비해 $100^{\circ}C$ 정도 치밀화 온도를 낮추는 결과이다. 소결체의 미세구조 관찰결과, 소결 후 약 200nm의 텅스텐 입자가 Cu내에 균일하게 분산되어 있었다. 제조된 W-Cu 시편에 대해서는 LED 응용성을 조사하기 위해 열전도도와 열팽창계수 등을 평가하였다.

• Journal of Korean Society of Transportation
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• v.22 no.7 s.78
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• pp.131-137
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• 2004

Conventional traffic signal optimization models assume that green intervals for pedestrian crossings are given as exogenous inputs such as minimum green intervals for straight-ahead movements. As the result, in reality, the green intervals of traffic movements may not distribute adequately by the volume/saturation-flow of them. In this paper, we proposed signal optimization models formulated in BMILP to integrate pedestrian crossings into traffic movements under under-saturated traffic flow. The model simultaneously optimizes traffic and pedestrian movements to minimize weighted queues of primary queues during red interval and secondary queues during queue clearance time. A set of linear objective function and constraints set up to ensure the conditions with respect to pedestrian and traffic maneuvers. Numerical examples are given by pedestrian green intervals and the number of pedestrian crossings located at an arm. Optimization results illustrated that pedestrian green intervals using proposed models are greater than those using TRANSYT-7F, but opposite in the ratios of pedestrian green intervals to the cycle lengths. The simulation results show that proposed models are superior to TRANSYT-7F in reducing delay, where the longer the pedestrian green interval the greater the effect.

• Journal of Food Hygiene and Safety
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• v.16 no.4
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• pp.308-314
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• 2001

This study was conducted to determine the content of heavy metals in canned foods and soft drinks available on the Korean markets. Trace metals (Pb, Cr, Cd, and Sn) were detected in 24 kinds, 120 samples by Atomic Absorption Spectrophotometer. The average concentration of heavy metals in canned foods was in the order of Sn (6.930 ppm)>Cr (0.050 ppm)>Pb (0.030 ppm)>Cd (0.008 ppm), which was the same order in soft drinks as Sn (3.519 ppm)>Cr (0.080 ppm)>Pb (0.024 ppm)>Cd (0.001 ppm). The total contents of heavy metals in canned fruits and fruit juices were relatively higher than those in cans and drinks made of vegetable and fish. It can be supposed that the high acidity owing to the organic acid of fruit itself promotes to extract metals from can materials, and although fish usually contains more heavy metals than vegetables, canned fish revealed low level because internal organs and most of skin which had more heavy metals than meat were removed throughout canning process. Because processed foods such as canned foods and soft drinks are very popular with the children and adolescence according to the change of life style and eating habit, and the possibility of exposure to heavy metals by the habitual intake of these is increasing simultaneously, it is suggested that more practical study about the process of exposure and the amount in each step is needed fur the assessment of safety.

• Journal of Life Science
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• v.19 no.10
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• pp.1337-1345
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• 2009

This study investigated the effect of exercise training and garlic powder ingestion on blood lipids and antioxidants activity in rats. Twenty-eight male Sprague Dawley rats were fed a high-fat diet with or without garlic powder (500 mg/kg) for four weeks as grouped in control (CON), exercise (EXE), garlic (GAR), and garlic + exercise training (GAREXE), respectively. EXE and GAREXE were trained on the treadmill for the same periods. Weight of fats (mesentery, perirenal, and epididymal) were weighed and blood glucose, triglycerides (TG), total cholesterol (TC), and high density lipoprotein- cholesterol (HDL-C) were analyzed and low density lipoprotein-cholesterol (LDL-C) was calculated. Malondialdehyde (MDA) and superoxide dismutase (SOD) for lipid peroxidation were analyzed in liver tissue. Body weight in GAREXE was significantly lower in the statistics than that in other groups (p<0.05), and the volume of fat in GAR and GAREXE was also much lower (p<0.05). Blood glucose was significantly lower in EXE and GAR (p<0.05), however, there was no effect of exercise training. Blood TG was lower in GAR and GAREXE (p<0.05), however, there was no effect of exercise training. HDL-C was significantly improved in EXE and GAR compared to CON (p<0.05), and GAREXE was higher than EXE (p<0.05). MDA content was considerably lower in GAREXE compared to EXE (p<0.05), and SOD activity was much higher in other groups compared to CON (p<0.05). In addition, GAREXE was significantly higher than EXE and GAR, thus there was significant increase when a garlic diet was carried out together with exercise (p<0.05). These results suggested that garlic powder ingestion during the training periods had a beneficial effect of lowering glucose and enhancing blood lipids profiles. Moreover, it also has antioxidant effects, which means that it could possibly suppress aging. It is necessary to inspect various effects of garlic with a variety of research methods regarding sampling process, production process, intake method, etc.