• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.7
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• pp.1039-1046
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• 2002

Co-flow axisymmetric laminar premixed flame of methane was used to study the influence of air temperature and $N_2$ addition on the flame structure, temperature field and emission characteristics. OH 2-D images and temperatures along the centerline were measured experimentally by PLIF and CARS techniques respectively to observe the influences of dilution and thermal effects of $N_2$ in the gas mixture. Also, the concentration of NOx was measured at each condition by gas analyser to see the suppression effect of N2 addition on NOx emissions. It was found that OH concentrations distribute widely as air temperature goes higher, while the effect of $N_2$ addition is not significant. But $N_2$ addition highly contributes to the flame front and NOx emissions which was argued to be due to the reduction of flame temperature. In accordance with experimental study, numerical simulation using CHEMKlN code was carried out to compare the temperature results with those acquired by CARS measurement, and we could find that there is good agreement between those results.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.810-813
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• 1995

Coherent anti-Stokes Raman scattering (CARS) spectra of HCl, N2, and the ν1 fundamental of C2H2 have been measured in the gas phase. The measured spectra show rotational structures which originate from the Q-branch transitions. The spectra have successfully been simulated with proper selection rules, line positions, and relative intensities from room temperature Boltzmann population distributions. The vibration-rotation interaction constant α of HCl in the ground electronic state has been measured from the rotationally resolved CARS spectra which is α=0.3076 cm-1. Possibilities of optical pumping and of measuring state specific energy distributions of molecules are discussed.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.185-191
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• 2002

The influence of N2 addition on soot formation, flame temperature and NOx emissions is investigated experimentally with methane fuel co-flow diffusion flames. The motivation of the present investigation is the differences in NOx reduction reported between fuel-side and oxidizer-side introduction of N2. To determine the influence of dilution alone, fuel was diluted with nitrogen while keeping the adiabatic flame temperature fixed by changing the temperature of the reactants. And to see the thermal effect only, air was supplied at different temperature without N2 addition. N2 addition into fuel side suppressed the soot formation than the case of oxidizer-side, while flame temperature enhanced the soot formation almost linearly. These results reveals the relative influences of the thermal, concentration effects of N2 additives on soot formation In accordance with experimental study, numerical simulation using CHEMKIN code was carried out to compare the temperature results with those acquired by CARS measurement, and we could find that there is good agreement between those results. Emission test revealed that NOx emissions were affected by not only flame temperature but also N2 addition.

• 재활복지
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• v.20 no.4
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• pp.135-156
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• 2016

The purpose of this study was to investigate item goodness-of-fit of Childhood Autism Rating Scale(CARS), Rasch rating scale model was applied to 15 items of the CARS in a sample of pervasive development disorder(n=238). An assumption to test Rasch Model, which is satisfaction of unidimensionality, is regarded through PCAR analysis, and jMetrik 4.03 program is used to test the goodness-of-fit of items. The results of this study were: First, 5-point rating scale was appropriate for the CARS rather than 7-point original rating scale. Second, the result of examining the CARS questions goodness-of-fit, there was a overfitting or misfitting items according to the classified groups. Only in particular Q11 item in diagnosis subject of integration population of autism has become inappropriate. Therefore, it is necessary to provide education for the CARS more systematically. Thirdly, the result of comparing the personal attributes score and difficulty of a CARS question, Q2, Q3, Q10, Q11 items are necessary to distinguish conceptually defined in more detail. Fourth, the results of investigating the difficulty of CARS question, it was found to exhibit a verbal communication is most serious problem for the population of autism.

• 한국연소학회:학술대회논문집
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• 2000.12a
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• pp.160-167
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• 2000

We investigated a uniform temperature zone, produced by double flame structure of a coflow CH4/air partially premixed flame, to be used as a temperature calibration source for laser diagnostics. A broadband N2 CARS(coherent anti-Stokes Raman spectroscopy) system with a modeless laser was used for temperature measurement. When the stoichiometric ratio was 1.5, we found the uniform temperature zone in radial direction of the flame of which the averaged temperature was 2110 K with standard deviation 24 K. In the stoichiometric ratio range between 2.0 and 2.5, we found very stable temperature-varying zones in vertical direction at the center of the flame. The size of the zone was approximately 15 mm and it covered a temperature range from 300 K to 1900 K. We also suggest that this zone can be used as a calibration source for 2-D PLIF(planar laser induced flurescence) temperature measurement.

• Transactions of Materials Processing
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• v.25 no.2
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• pp.124-129
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• 2016

Recently, global railway car makers are competing desperately in developing high-speed railway vehicles. Ensuring passenger safety during a crash is essential. The design and the manufacturing of energy absorbing components are becoming more and more important. A deformation tube is a typical passive energy absorbing component for railway cars. In the current study the slab method was used to predict the energy absorbing capability of a deformation tube during the early design stage. The usefulness of the prediction method is verified through the comparisons between the results of FE simulations and those of the prediction method.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.5
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• pp.518-526
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• 2012

The objective of this research was to develop fugitive emission models of HFC-134a (Hydrofluorocarbon-134a) at the operation and disposal stages of passenger cars. It is essential to estimate the emission of HFC-134a from mobile air conditioner (MAC) due to its high Global Warming Potential (GWP) and extensive use as a refrigerant in MAC. The first-order emission model was introduced and the emission rate constant was assumed to be unvaried with time. A commercial recovery station of refrigerants was used to recover the HFC-134a from the MAC. Average emission rate constant and annual emission rate during the operation period of vehicle are estimated to be $0.0538{\pm}0.0092$ (n=21) $yr^{-1}$ and $5.2{\pm}0.6%$, respectively within a confidence interval of 95%. According to the model results, about 50% of HFC-134a would be emitted from the MAC during the 10 years operation of passenger cars. On the other hand, average remaining portion of HFC-134a in the MACs of scrap cars is $58.2{\pm}4.8%$ (n=50) within a confidence interval of 95%, suggesting that over 40% of the initially charged amount could be released fugitively after disposal provided that the HFC-134a would not be properly treated or recycled.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.11 no.6
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• pp.1-9
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• 2016

In this study, we investigate the announcement effects of M&As with a start-up as a target firm on shareholder wealth of an acquiring firm. We use M&A events in KOSPI or KOSDAQ market between 2002 and 2014 after the financial crisis. Among the total 1436 mergers and acquisitions that took place domestically during this period, 1383 cases were selected as cases to be studied, excluding 53 cases where acquiring firms were unlisted firms. The results of the analysis are as follows: First, as a result of a comparison between the acquiring firms' CARs of the whole sample group(n=1383) occurred during the (-2, +1), (-5, +2), (-10, +5) periods of M&A announcement date(t=0) and the sub-sample group(n=468) where the target firms are start-ups which were established within five years, the acquiring firms of the whole sample group do not show significat CARs, while the acquiring firms of the sub-sample group show the significantly positive CARs. This suggests that M&A with start-ups have a positive effect on firm value of acquiring firms. Second, when merging unlisted start-ups, the acquiring firms show positive CARs, showing that there exists a listing effect in the merger of start-up. Third, merging the start-ups belonging to the high-tech industry shows the higher CARs than the case of merging the start-ups belonging to the non-high-tech industry. This study has great significance as the first in Korea to investigate the effect of M&A announcement with a start-up.

• Journal of the Korean Society of Combustion
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• v.5 no.1
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• pp.91-98
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• 2000

We investigated a uniform temperature zone, produced by double flame structure of a co flow CH4/air partially premixed flame, to be used as a temperature calibration source for laser diagnostics. A broadband N2 CARS(coherent anti-Stokes Raman spectroscopy) system with a modeless laser was used for temperature measurement. When the stoichiometric ratio was 1.5, we found the uniform temperature zone in radial direction of the flame of which the averaged temperature was 2110 K with standard deviation 24 K. In the stoichiometric ratio range between 2.0 and 2.5, we found very stable temperature-varying zones in vertical direction at the center of the flame. The size of the zone was approximately 15 mm and it covered a temperature range from 300 K to 1900 K. We also suggest that this zone can be used as a calibration source for 2-D PLIF(planar laser induced flurescence) temperature measurement.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.357-358
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• 2014

Coherent anti-Stokes Raman spectroscopy is one of the best tools to measure temperature distributions in the flame. Since it does not disturb the flow field, it could be used to study anchoring mechanism especially in the lifted flame. However, the length of probe volume is, normally, much greater than flame thickness. This weak point was overcome with lens combination in this study. It was found out that no peculiar temperature changes was happened near tribrachial point and heat transfer to the upstream was minimal near the flame anchoring position.