• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1559-1566
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• 1994

Using the finite element method, the contact force, contact band width and temperature distribution of lip seals analyzed for the interference including some nonlinearities such as material nonlinearity, geometrical nonlinearity and nonlinear contact boundary condition. The calculated results showed that the contact stress concentrated on the contact zone between the garter spring and the rubber toward the flex side, the contact edge of lip seals. The high contact forces due to the increased interference separate the sealing gap between the lip edge and the rotating shaft. This may lead to leak the sealed oil.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.377-379
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• 2001

Contamination flashover is responsible for insulator electrical failures. Particularly, in Korea, with its perennially dry spring, the first spring rain often cause serious line outages by forming a conductive liquid film on the insulator surface. Rainwater and fog are not normally conductive but unfortunately atmospheric dust deposited on the insulator surface contains soluble salts which may lead to bad condition of insulation by combining watery and salts. Transmission design engineers have used a contamination map drawn on the traditional paper map. But it is not convenient because it does not include the information of Geographic Information accurately. This paper explains the newly developed salt contamination map program using Geographic Information System, which provide accurate geographic information. The program is designed to use four parts of datum, salt contamination levels, 345kV & 154 kV transmission lines, power plants & substations and background map. The digital background map is composed of raster files, the others are done by vector map.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2003.10a
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• pp.39-43
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• 2003

• Journal of Aerospace System Engineering
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• v.2 no.2
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• pp.46-50
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• 2008

Aerodynamic characteristics, such as drag and lift, play an important role in automobile design under certain speed conditions. Such characteristics are essential to design an automobile since they are directly related to automobile's performance such as passenger safety and fuel consumption. There is a huge demand for the automobile to have safe performance at high speed. Reduction in drag is also important and it could lead to the solution of air flow induced noise and dust problems. The objective of this research is to find out the aerodynamic differences between conventional side mirror and a modified one using CFD. Although drag generated around a side mirror is only about 7% of the total drag when a car runs, it is very closely related to driver's field of vision and noise generation. CFD simulation of the flowfield around a car side-view mirror was performed using a commercial code; Gambit and FLUENT.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.253-256
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• 2005

This paper is to investigate the mixture proportion, compressive strength and drying. shrinkage of concrete depending on mineral admixtures such as fly ash (FA), blast furnace slag (BS) and cement kiln dust (CKD) under various contents of admixtures. The use of CKD had little effect on strength development at 3 days, while the use of FA and BS lead to similar compressive strength compared with that of control concrete. Concrete with CKD exhibited a reduction of compressive strength at 91 days, meanwhile concrete with FA and BS had a increase compared with that of control concrete. Drying shrinkage of concrete depending on CKD and BS increase compared with that of control concrete about $10\∼20\%$, while the use of FA exhibited reduce compared with that of control concrete about $10\∼15\%$.

• Journal of Microbiology and Biotechnology
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• v.18 no.2
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• pp.314-321
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• 2008

Acaricidal effects of materials derived from Diospyros kaki roots against Dermatophagoides farinae and D. pteronyssinus were assessed using impregnated fabric disk bioassay and compared with that of the commercial benzyl benzoate. The observed responses varied according to dosage and mite species. The $LD_{50}$ values of the chloroform extract of Diospyros kaki roots were 1.66 and $0.96{\mu}g/cm^2$ against D. farinae and D. pteronyssinus. The chloroform extract of Diospyros kaki roots was approximately 15.2 more toxic than benzyl benzoate against D. farinae, and 7.6 times more toxic against D. pteronyssinus. Purification of the biologically active constituent from D. kaki roots was done by using silica gel chromatography and high-performance liquid chromatography. The structure of the acaricidal component was analyzed by GC-MS, $^1H-NMR,\;^{13}C-NMR,\;^1H-^{13}C$ COSY-NMR, and DEPT-NMR spectra, and identified as plumbagin. The acaricidal activity of plumbagin and its derivatives (naphthazarin, dichlon, 2,3-dibromo-1,4-naphthoquinone, and 2-bromo-1,4-naphthoquinone) was examined. On the basis of $LD_{50}$ values, the most toxic compound against D. farinae was naphthazarin $(0.011{\mu}g/cm^2)$ followed by plumbagin $(0.019{\mu}g/cm^2),$ 2-bromo-1,4-naphthoquinone $(0.079{\mu}g/cm^2)$, dichlon $(0.422{\mu}g/cm^2)$, and benzyl benzoate $(9.14{\mu}g/cm^2)$. Additionally, the skin color of the dust mites was changed from colorless-transparent to dark brown-black by the treatment of plumbagin. Similar results have been exhibited in its derivatives (naphthazarin, dichlon, and 2-bromo-1,4-naphthoquinone). In contrast, little or no discoloration was observed for benzyl benzoate. From this point of view, plumbagin and its derivatives can be very useful for the potential control agents, lead compounds, and indicator of house dust mites.

• Environmental Engineering Research
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• v.14 no.4
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• pp.212-219
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• 2009

Emission characteristics of air pollutants from three commercially operating cement kilns co-burning waste were investigated. The major heavy metals emitted were mercury (Hg), zinc (Zn), nickel (Ni), chromium (Cr), lead (Pb), cadmium (Cd), and arsenic (As) Removal efficiency of the bag filter was above 98.5% for heavy metals (except Hg), and above 60% for Hg. Higher fractions of heavy metals entering the bag filter were speciated to cement kiln dust. On average, 3.3% of the -heavy metals of medium and low toxicity (Pb, Ni, and Cr) entering the bag filter were released into the atmosphere. Among highly toxic heavy metals, 0.14% of Cd, 0.01% of As, and 40% of Hg entering the bag filter were released into the atmosphere. In passing through the bag filter, the proportion of oxidized Hg in all cases increased. Emission variations of hazardous air pollutants in cement kilns tested were related to raw materials, fuel, waste feed and operating conditions. Volatile organic compounds detected in gas emissions were toluene, acrylonitrile benzene, styrene, 1,3-butadiene, and methylene chloride. Although hazardous air pollutants in emissions from cement kilns co-burning waste were within the existing emission limit, efforts are required to minimize their levels.

• Journal of Microbiology and Biotechnology
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• v.16 no.10
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• pp.1591-1596
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• 2006

Acaricidal effects of materials derived from Caesalpinia sappan heartwoods against Dermatophagoides farinae and D. pteronyssinus were assessed and compared with those evidenced by commercial benzyl benzoate and DEET. The observed responses varied according to dosage and mite species. The $LD_{50}$ values of the methanol extracts derived from C. sappan heartwoods were 6.13 and $5.44{\mu}g/cm^3$ against D. farinae and D. pteronyssinus, respectively. Furthermore, the ethyl acetate fraction derived from the methanol extract was approximately 8.71 more toxic than DEET against D. farinae, and 4.73 times more toxic against D. pteronyssinus. The biologically active constituent from the ethyl acetate fraction of C. sappan heartwood extract was purified via silica gel chromatography and high-performance liquid chromatography. The structure of the acaricidal component was analyzed by $GC-MS,\;^1H-NMR,\;^{13}C-NMR,\;^1H-^{13}C\;COSY-NMR$, and DEPT-NMR spectroscopy, and identified as juglone (5-hydroxy-l,4-naphthoquinone). Based on the $LD_{50}$ values of juglone and its derivatives, the most toxic compound against D. farinae was juglone ($0.076{\mu}g/cm^3$), followed by benzyl benzoate ($9.143{\mu}g/cm^3$) and 2methyl-l,4-naphthoquinone ($40.0{\mu}g/cm^3$). These results indicate that the acaricidal activity of C. sappan heartwoods is likely to be the result of the effects of juglone. Additionally, juglone treatment was shown to effect a change in the color of the cuticles of house dust mites, from colorless-transparent to dark brownish-black. Accordingly, as a naturally occurring acaricidal agent, C. sappan heartwood-derived juglone should prove to be quite 'useful as a potential control agent, lead compound, and house dust mite indicator.

• Resources Recycling
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• v.4 no.4
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• pp.59-69
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• 1995

Distillation oI the dust generated during waste tue pyrolysis was perIomerl to rccover valuable metal sucll as zlnc. lead and iron. Pemcahilily and carnprcssivc tests were pursucd to ahlain the basic dala for cslraclian of zinc from the slntering propcrtp ol stccl making dusts and distilled carhon of waste tires as wcll as wastc pulp sludge mixlure hr~quet were investigated at various sinlcring lempcraturcs. Permeablllly rncieased with increastng amount of waste pulp in specil~cd istilled carhon due tn the fnrmat~ono f porusily in lhe sample TIE co~npress~vsctr ength showed the vanous values wlth different amDunl of dislilled-carhon adrlit~nilsa nd at diIIerenl sinlering tcmpcralures. X-ray diffifraction anvlyscs oI a hnquet rn~rhtre of steelmaking dusts(20Q didilled carhon and 10% waste pulp sblered ;>I SOOT) showcd thal the briquet consisted ot ZnO and Fc,O.,, hut was not found at the hriguet rintered at over 10OO'C. Crude zinc oxide sintered a1 IOOOC contained OZA Zn.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.1 no.1
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• pp.89-99
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• 1991

The metal concentrations in lungs from 12 coal workers' pneumoconiosis(CWP) patients and 6 controls, who were not exposed occupationally to coal mine dust and metals during their life time, were analyzed by atomic absorption spectrophotometry. 1. Copper, lead, nickel, magnesium, manganese, zinc and iron concentrations in lungs of CWP patients were $1.10{\pm}0.088$, $1.12{\pm}0.068$, $0.22{\pm}0.020$, $113.7{\pm}1.31$, $0.19{\pm}0.012$, $10.2{\pm}1.54$, $426.7{\pm}2.63{\mu}g/g$ wet weight. 2. Copper, lead, nickel, magnesium, manganese, zinc and iron concentrations in lungs of controls were $1.10{\pm}0.013$, $0.85{\pm}0.007$, $0.10{\pm}0.008$, $87.6{\pm}1.29$, $0.18{\pm}0.005$, $10.6{\pm}1.44$, $164.9{\pm}3.29{\mu}g/g$ wet weight. 3. The ratios of concentrations for copper, lead, nickel, magnesium, manganese, zinc, and iron in lungs for CWP patients and controls were 1 : 1, 1.32 : 1, 2.20 : 1, 1.30 : 1, 1.06 : 1, 0.92 : 1, 2.58 : 1, respectively. There were significant differences in concentrations of lead, nickel, magnesium, iron by group(p<0.05). 4. There was no significant difference in metal concentrations of right upper lobe, right lower lobe, left upper lobe and left lower lobe for both CWP patients and controls (p>0.05, p>0.05). 5. In CWP patients lead was well correlated with nickel showing a rank correlation coefficient of 0.533, and zinc was correlated with copper showing a rank correlation coefficient of 0.476. 6. The concentrations of copper, nickel, maganese, and zinc in Korean CWP patients were lower than those in foreign CWP patients.