• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.1011-1019
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• 2015

Insulated-gate bipolar transistors (IGBTs) are the predominantly used power semiconductors for high-current applications, and are used in trains, airplanes, electrical, and hybrid vehicles. IGBT power modules generate a considerable amount of heat from the dissipation of electric power. This heat generation causes several reliability problems and deteriorates the performances of the IGBT devices. Therefore, thermal management is critical for IGBT modules. In particular, realizing a proper thermal design for which the device temperature does not exceed a specified limit has been a key factor in developing IGBT modules. In this study, we investigate the thermal behavior of the 1200 A, 3.3 kV IGBT module package using finite-element numerical simulation. In order to minimize the temperature of IGBT devices, we analyze the effects of various packaging materials and different thickness values on the thermal characteristics of IGBT modules, and we also perform a design-of-experiment (DOE) optimization

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.1
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• pp.27-35
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• 2006

The aim of this study was to identify the sources of benzene detected in airborne of casting workplace where benzene was not used as raw material. We have identified benzene by GC/FID and GC/MSD. In this pilot test, small size iron chamber(diameter 30 cm, height 20 cm) was used. As the raw materials, new sand, recovered sand, and mixed casting sand(new sand + solidifying agent + organic resin + coating material) was tested, respectively. In the new sand benzene was not detected, but in the recovered sand and the mixed casting sand was detected. Xylenesulfonic acid(solidifying agent), one of the mixed casting sand ingredients was thought to product benzene by thermal decomposition above $400^{\circ}$..., but the other raw materials(organic resin and coating material) were thought not to product benzene. In this experiment, the most of benzene by thermal decomposition was produced within 1 hour after pouring the iron solution($1560^{\circ}$...) in small size iron chamber. When the mixed casting sand with coating material was used, the concentration of the produced benzene was average 2.91 ppm(range 1.98~3.72 ppm), and without coating material, benzene concentration was average 0.11 ppm(range 0.08~0.14 ppm).

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.1 no.2
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• pp.136-143
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• 1991

Inorganic mercury in urine and airborne was determined by cold vapor atomic absorption spectrophotometry. Detailed sampling methods and analylical results are as follows : 1. 100~200ml of urine for each person was taken in 250 ml borosilicate bottle and $K_2S_2O_8$ (0.1g/100ml urine) was added to prevent bacterial contamination. About 1001 air of workingplace was absorbed in l0ml of absorbing solution. Urine samples and absorbing solution tubes were stored at $4^{\circ}C$. Dillution solution to prepare standard solution used deionized water (D.W) for urine and absorbing solution (A.S) for air. 2. 1n this procedure deteclion limit was 1ng/ml and mercury contents of blank reagent solution was 1~2ng/ml. 3. Calibration range was $0.02{\sim}0.1{\mu}g/ml$ and in this range r.s.d for each calibration curve in D.W and A.S and ${\pm}7.9%$ and ${\pm}3.7%$, respectively. 4. Repeatability (n=5 times, conc. $0.05{\mu}g/ml$) was ${\pm}5.8%$, in D.W. and ${\pm}4.4%$ in A.S, respectively. 5. Recovery for urine adding spiked concentration ($0.05{\mu}g/ml$) was about 90%. 6. Analytical result of samples was $1{\sim}139{\mu}g/l$ in urine and ${\sim}0.127mg/m^3$ in airborne.

• Journal of Food Hygiene and Safety
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• v.26 no.2
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• pp.150-153
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• 2011

Betulinic acid (BA), a naturally occurring triterpene found in the bark of the white birch tree, has been investigated to induce apoptosis in various cancer cells and animal models. However, there is no report of the chemopreventive effect of BA in cervical cancer cells. Using KB human cervical cancer cells as a model, we currently show that BA decreases cell viability and induces apoptotic cell death. The mechanism of the BA-induced anti-growth response in KB cells is due to the down-regulation of specificity protein 1 (Sp 1) and its downstream targets, myeloid cell leukemia-1(Mcl-1) and survivin. Thus, BA acts as a novel chemopreventive agent through the regulation of Sp1 that is highly expressed in tumors.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1001-1006
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• 2016

As consumption of energy is increasing rapidly, energy saving is emphasized in nowadays. Thermal power plant occupies a large proportion in various type of power plant. Major causes of decreased power generation efficiency on thermal power stations is deposition of fly ash. Soot Blower is a facility to remove the ash which is deposited outside of tube by steam blowing on boiler. Residual stream which caused by lance tube in soot blower cannot be discharged steam effectively in lance tube causes reducing the thickness of lance tube. On the contrary, increasing discharge ratio of steam, lance tube cannot sustain proper pressure to remove ash on tube. This study suggests increasing discharge ratio of steam with proper pressure to remove ash on tube by optimization on shape of lance tube nozzle. To optimize shape of nozzle, discharge ratio and maximum blowing pressure on nozzle is selected as object functions. Diameter of nozzle, distance between nozzles, angle of nozzle and gap between nozzle is selected as design parameters. Then the design of experiment (DOE) with an orthogonal array is performed to analyze the effect of design parameters. And grey relational analysis and analysis of mean (ANOM) is performed to optimize shape of lance tube.

• Asian-Australasian Journal of Animal Sciences
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• v.9 no.5
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• pp.597-601
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• 1996

Twelve Philippine does of 3.5-5.0 years old were used in this study. They were divided into three groups, $T_1$, $T_2$ and $T_3$. Four animals were randomly allocated to each group. Before infection, they were dewormed and housed in individual pens with concrete floors. They were provided with a uniform management. They were infected orally with a single dose of three levels (0, 15,000 and 30,000) of infective Haemonchus contortus larvae. Blood samples were collected from the jugular vein of each animal at fortnightly intervals for 17 fortnights. Hemoglobin (Hb) concentration was determined using hemoglobinometer and packed cell volume (PCV) by microhematocrit methods. Animals in infected groups showed significantly (p < 0.05) lower hemoglobin values than the control except during fortnight 1 for group 2 and fortnights 1, 2, 5, 6 and 7 for group 3. Hemoglobin concentration did not significantly (p > 0.05) differ between the animals in infected groups throughout the sampling period except fortnight 2. The PCV values of animals in infected groups were significantly (p < 0.05) lower than the control for most of the sampling periods. The PCV values of animals in group 2 did not significantly (p > 0.05) differ from group 3.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.173-178
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• 2012

Currently, active research is being performed on printing of electronic devices such as RFID devices, flexible displays, solar cells, and e-paper. This technique has several advantages over existing technologies such as lithography and etching. In particular, RFID devices, flexible displays, solar cells, and e-paper require flexibility and a mass production system. Thus, attention is being focused on the roll-to-roll process. High quality should be guaranteed in the roll-to-roll printed electronics systems, and good thickness and roughness qualities must be ensured. Experimental design was applied to this problem to analyze the main effects and interaction effects of various factors. Matching technology between the nip roll characteristics and the quality of the print pattern in roll-to-roll printed electronics systems was proposed to improve the printing quality.

• Microbiology and Biotechnology Letters
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• v.16 no.4
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• pp.327-333
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• 1988

For optimal production of recombinant human interleukin-2 (IL-2) in E. coli the effect of fermentation conditions on cell growth, IL-2 production, and stability of recombinant cells were investigated. Among the complex nutrients tested in this work, yeast extract, peptone and corn steep liquor were found to be effective for recombinant cell growth. The recombinant cells were maintained stably under repression condition (3$0^{\circ}C$), but the stability of recombinant cells were drastically reduced upon induction of IL-2 expression (42$^{\circ}C$) even under the selection pressure. Addition of antibiotics to the culture medium resulted in the cell growth inhibition without significant improvement in recombinant stability. When the expression of IL-2 gene was induced at different growth phases, highest IL-2 production was achieved by the induction of IL-2 at the middle-exponential growth phase. It was found that the production of IL-2 significantly inhibited the cell growth and the ex-pression of other genes in the plasmid.

• Journal of Navigation and Port Research
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• v.26 no.4
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• pp.465-472
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• 2002

The waterfront has distinct climate characteristics different from urban or inland area. These may create not only the rise of energy and maintenance costs for facilities located at waterfront areas, but also the negative effects on the climate of the nearby inland area, unless these are treated with particular care. For the present study, the climate characteristics of waterfront were examined with climate data of 10 observation points carefully selected in Busan area. Each weather observation point was classified into either waterfront area of inland area, based on the distance from the coastal line. Special considerations were given to the climate data gathered at the Dae-Yeon weather station because it shows the climate characteristics similar to those of inland area, although it is located very near the waterfront area. Results indicates that this peculiar climate condition attributes, at least in part, to the reclamation of frontal coastal area.

• Journal of Navigation and Port Research
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• v.26 no.1
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• pp.85-94
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• 2002

The purpose of this study is to propose new systems for improvement of coastal landscape management in Busan area. The coastal landscape management systems in Busan are divided into urban planning sector, coastal management sector and environmental preservation sector without any comprehensive lay or integrated management system. These findings indicate that the coastal landscape is in need of integrated management in the form of coastal management rather than urban planning because coastal landscape os different from urban landscape by nature. The coastal landcape management ordinance which is based on the Coastal Management Ant should be established and the special zoning system for costal landscape management is to be set up under this ordinance. Then the comprehensive landscape plan for Busan coastal area and the design guidelines for each zone are mandatory. Also Busan city government and the district office must have a responsible department, experts and coastal landscape review committees.