• Journal of the Korean Society of Safety
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• v.34 no.4
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• pp.32-40
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• 2019

During the manufacturing process of a printed circuit board(PCB), fumes and mists are generated as the ink dries on the PCB surface. The generated fumes and mists are deposited in the dryer wall and the exhaust duct. Deposited fumes and mists may present a fire hazard if the dryer temperature control system fails. In this study, the thermal stability of the fumes and mists deposited in the dryer and ducts has been analyzed by experimental methods such as thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), auto ignition temperature (AIT), and multiple mode calorimetry(MMC). According to the experimental analyses, experimental samples are likely to generate gas at the temperature ($180{\sim}240^{\circ}C$) that deviates from the normal operating temperature ($150{\sim}156^{\circ}C$). It has been shown that the thermal stability is degraded when the temperature is deviated from the normal operating temperature. In the end, engineering and management safety measures of accidental prevention have been suggested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.3
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• pp.632-638
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• 2007

Pyrolysis experiments of HDPE and LDPE were carried out in the stainless steel reactor of internal volume of 40 $cm^3$. Pyrolysis reactions were performed at temperature $410{\sim}460^{\circ}C$ and the pyrolysis products were collected separately as liquid and gas products. The molecular weight distributions(MWDs) and composition of each product were determined by HPLC-GPC and GC analysis. It was represented that the yield and the molecular weight of liquid product were decreased with the increase of reaction temperature and time. The chain-end scission rate parameters, respectively, were determined to be 63.0kcal/mole of HDPE, 45.7kcal/mole of LDPE by the Arrhenius plot.

• Journal of Industrial Technology
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• v.17
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• pp.339-344
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• 1997

DOHC gasoline engine(4-cylinder in line type, 1600cc) is modified for the experiment to develope an alternative fuel. The modified engine is tested with the various combination of gasoline and methanol. Pollutant emissions of CO and HC are measured at the end of exhaust manifold. The concentration of CO and HC in exhaust gas is greatly reduced with the increase of coolant temperature of engine. HC concentration is reduced until methanol content reaches to thirty percent and then increased with the volumetric percentage of methanol in fuel. On the other hand, the concentration of CO is reduced as the methanol centent is increased up to 20 percent and then it becomes constant even though the methanol content is raised. The effect of engine RPM on the HC and CO exhaust is investigated. HC concentration is reduced as the engine RPM is increased but the typical trends of variation are not found in the measured value of CO concentrations.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.4
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• pp.55-65
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• 2020

In this paper, development and acceptance test results of 75-tonf class liquid rocket engine gas generators are described. Up to now, more than 330 times and cumulative time of 7,000 seconds gas generator autonomous tests have been carried out with 44 gas generator models. Through the tests it was verified that 75 tonf gas generator shows very reliable and reproducible characteristics in terms of chamber pressure, combustion efficiency, pressure loss, combustion stability, burnt gas temperature, and etc. 5 gas generators which are the last series of 75 tonf gas generator for the Korea Space Launch Vehicle II, will be manufactured until end of 2019 and their acceptance tests will be executed at the first half of 2020.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.493-501
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• 2013

Taking into account the increasingly stringent legislation on emissions from marine engines, this work aims to analyze several internal engine modifications to reduce $NO_x$ (nitrogen oxides) and other pollutants. To this end, a numerical model was employed to simulate the operation cycle and characterize the exhaust gas composition. After a preliminary validation process was carried out using experimental data from a four-stroke, medium-speed marine engine, the numerical model was employed to study the influence of several internal modifications, such as water addition from 0 to 100% water to fuel ratios, exhaust gas recirculation from 0 to 100% EGR rates, modification of the overlap timing from 60 to $120^{\circ}$, modification of the intake valve closing from 510 to $570^{\circ}$, and modification of the cooling water temperature from 70 to $90^{\circ}C$. $NO_x$ was reduced by nearly 100%. As expected, it was found that, by lowering the combustion temperature, there is a notable reduction in $NO_x$, but an increase in CO (carbon monoxide), HC (hydrocarbons) and consumption.

• Journal of Chest Surgery
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• v.27 no.6
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• pp.427-434
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• 1994

A clinical study was designed to evaluate myocardial metabolism during continuous cold blood cardioplegia [Group A, n=10] in comparison with continuous warm blood cardioplegia [Group B, n=10], in a prospective randomized manner. Myocardial metabolism was assessed in two ways: either by collecting blood from coronary sinus before and after cardiopulmonary bypass or by collecting blood from cardioplegic affluent and effluent simultaneously at the beginning and at the end of cardioplegia. The former samples were assayed for gas analysis, lactic acid and cardiac enzyme [CK, LDH, SGOT] and the latter for gas analysis and lactic acid as a maker of anaerobic metabolism. The results were as follows. 1] Myocardial metabolism was shown to be continued in the state of cardioplegia at lower temperature as evidenced by high oxygen extraction of cardioplegic solution in Group A. 2] Anaerobic metabolism occurring at lower temperature in spite of continuous cold blood cardioplegia can be significantly reduced by continuous perfusion of normothermic blood cardioplegics as evidenced by significant reduction of lactate production in Group B [p〈0.05]. 3] Better myocardial protection can be achieved by employing continuous warm blood cardioplegia as evidenced by less cardiac enzyme release in Group B after cardiopulmonary bypass.

• Journal of the Korean Vacuum Society
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• v.18 no.1
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• pp.44-48
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• 2009

The effect of temperature gradient between the substrate and ambient gas on the structural characteristics of GaN nanorods grown on r-plane sapphire substrates by hydride vapor phase epitaxy was investigated. The density, diameter, and length strongly depended on the tempearture gradient. In addition, the cross-sectional shape of the nanorrods at the end of growth was found to be more dependedent on the temperature of a substrate itself than the temperature gradient.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1241-1248
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• 2010

In large-scale production of hydrogen, a PHE (Process Heat Exchanger) is a key component because the heat required to carry out the Sulfur-Iodine chemical reaction that yields hydrogen is transferred from a VHTR (Very High Temperature Reactor) by the PHE. Korea Atomic Energy Research Institute established a helium gas loop for conducting performance test of components that are used in the VHTR. In this study, as a part of high-temperature structural-integrity evaluation of a designed PHE prototype that is scheduled to be tested in the helium gas loop, we carried out high-temperature structural-analysis modeling, thermal analysis, and thermal-expansion analysis for the designed PHE prototype. An appropriate constraint condition is proposed at the end of the in-flow and out-flow pipelines of the primary and secondary coolants and the proposed constraint condition will be applied to the design of the performance-test loop setup for the designed PHE prototype.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.696-701
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• 2018

The nitrogen oxides generated during combustion reactions have a great influence on the generation of acid rain and fine dust. As an NOx reduction method, exhaust gas recirculation combustion using Coanda nozzles capable of recirculating a large amount of exhaust gas with a small amount of air has recently been utilized. In this study, for the burner outlet with dual end opening, the use of a recirculation burner was investigated for the distribution of the pressure, streamline, temperature, combustion reaction rate and nitrogen oxides using computational fluid analysis. The gas mixed with the combustion air and the recirculated exhaust gas flow in the tangential direction of the circular cylinder burner, so that there is a region with low pressure in the vicinity of the fuel nozzle exit. As a result, a reverse flow is formed in the central portion of the burner near the center of the circular cylinder burner and the exhaust gas is discharged to the outside region of the circular cylinder burner. The combustion reaction occurs on the right side of the burner and the temperature and NOx distribution are relatively higher than those on the left side of the burner. It was found that the average NOx production decreased from an air flow ratio of 1.0 to 1.5. When the air flow ratio is 1.8, the NOx production increases abruptly. It is considered that the NOx production reaction increases exponentially with temperature when the air ratio is more than 1.5 and the NOx production reaction rate increases rapidly on the right-hand side of the burner.

• Journal of Environmental Science International
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• v.22 no.2
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• pp.235-242
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• 2013

The purpose of this article is analyzing the impacts of climate change on winter chinese cabbage yield in Korea, with employing a panel data regression model. Our results show that there is a negative impacts of high temperature and precipitation amount on winter chinese cabbage yields. Especially high temperature and rainfall in September cause serious damage to winter chinese cabbage yield. According to the reduction schedule on greenhouse gas emission(RCP 4.5 scenario.), winter chinese cabbage yield would be 7.7% lower than it is, for reasons of high temperature and rainfall damages by the end of 21st century.