• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.25-31
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• 2004

In order to prepare for the large power diesel vehicle, the current trend of advanced nations is to shift from the aluminum alloy piston to the steel piston. In this research, a steel forging piston which replaces the aluminum alloy piston is developed to improve the power performance of the diesel engine. The three dimensional flow and combustion analysis of the target engine is conducted. Using the result of the analysis, the piston is optimized, and a prototype of the articulated steel forging piston is built. The reliability of the piston has been evaluated through durability test using a Hydropuls Test Machine for 300,000 km.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.1
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• pp.61-68
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• 1991

The purpose of this study is to investigate the heat transfer characteristics and the flow structure in the case of rectangular air jet impinging vertically on the flat heating surface. The maximum value of Nusselt number at stagnation point is observed at H/B=10. It is found that this trend has been caused by the effect of stretching of large scale vortex in the stagnation region. For potential core region the Nusselt number distribution in the downstream of the stagnation point decreases gradually and begins to increase at about X/B=3. From the flow visualization it could be seen that small eddy produced from the nozzle edge grows in large scale and that large scale eddy disturbed the thermal boundary layer on the heating plate. The local average Nusselt number becomes maximum at X/B=0.5 regardless of H/B variation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.3
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• pp.186-196
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• 1991

Numerical analysis has been performed to investigate the effects of the turbulence intensity and Prandtl number on the local heat transfer around a circular cylinder in crossflow. The governing equations were reformulated in a non-orthogonal coordinate system with Cartesian velocity components and discretised by the finite volume method with a non-staggered variable arrangement. For laminar flow, the calculations were performed for the Reynolds numbers 26 and 200. The results showed good agreement with the experimental results. For turbulent flow of the Reynolds number $1{\times}10^5$ and $2{\times}10^6$, the results showed that with an increase in the turbulent intensity in the main stream, the local Nusselt number increases in the front region of the circular cylinder. But the effect of turbulent intensity on the local Nusselt number diminishes in the wake region. The influence of Prandtl numbers show similar trend to that of turbulent intensity.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2047-2052
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• 2004

Inconel-600 alloy has been used as steam generator tube material for current pressurized water reactors (PWRs). The long-term operation of steam generators showed that the use of this material induced localized corrosion damages and increased tube wear of steam generator. To protect these problems, steam generator tube material is being changed to Inconel-690 alloy. Based on the current trend, we have chosen Inconel 690 as the Advanced Power Reactor 1400 (APR1400) steam generator(SG) tube material and performed the design optimization of preventive measure against tube fretting wear for the APR1400 steam generator. In this paper, we examined the technical consideration in this modification : the selection of material, wear characteristics, effect of the Egg-crate Flow Distribution Plate installation, and effect analysis of vertical strip installation.

• Journal of the Semiconductor & Display Technology
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• v.15 no.1
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• pp.52-55
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• 2016

GZO film was prepared on p-type Si wafer and then annealed at various temperatures in an air conditions to research the bonding structures in accordance with the annealing processes. GZO film annealed in an atmosphere showed the various bonding structure depending on annealing temperatures and oxygen gas flow rate during the deposition. The difference of bonding structures of GZO films made by oxygen gas flows between 18 sccm and 22 sccm was so great. The bonding structures of GZO films made by oxygen gas flow of 18 sccm were showed the crystal structure, but that of 22 sccm were showed the amorphous structure in spite of after annealing processes. The bonding structure of GZO as oxide-semiconductor was observed the trend of becoming amorphous structures at the temperature of $200^{\circ}C$. Therefore, the characteristics of oxide semiconductor are needed to research the variation near the annealing at $200^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.5
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• pp.423-427
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• 2005

In this paper, the lateral displacement of soft soil was measured in pier structure. The result was compared and investigated with the result of numerical analysis. The lateral displacement of soft soil was affected by lateral flow of soft soil due to embankment rather than settlement, and rapidly occurred at the embankment and preloading phases. The measurement and the numerical analysis showed very similar trend of lateral displacement but the magnitude was larger in numerical analysis than in measurement.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.22 no.4
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• pp.217-239
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• 2018

This paper examined the MHD and thermal behavior of unsteady mixed convection flow of a rotating fluid in a porous parallel plate channel in the presence of Hall current and heat source. The exact solutions of the concentration, energy and momentum equations are obtained. The influence of each governing parameter on non dimensional velocity, temperature, concentration, skin friction coefficient, rate of heat transfer and rate of mass transfer at the porous parallel plate channel surfaces is discussed. During the course of numerical computation, it is observed that as Hall current parameter and Soret number at the porous channel surfaces increases, the primary and secondary velocity profiles are increases while the primary and secondary skin friction coefficients are increases at the cold wall and decreases at the heated wall. In particular, it is noticed that a reverse trend in case of heat source parameter.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_3
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• pp.1333-1339
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• 2023

To produce activated carbon fibers, the process is carried out through either physical activation method or chemical activation method. In this study, we present the results regarding the characteristics of activated carbon fibers manufactured under various conditions through the quantitative control of steam. The yield after activation indicates a decreasing trend with the increase in steam quantity and activation time. Additionally, specific surface area characteristics exhibit variations based on activation time and steam flow rate. The SEM analysis results reveal that higher steam flow rates lead to the presence of both mesopores and macropores on the surface of activated carbon fibers (ACF).

• Journal of Korean Society on Water Environment
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• v.27 no.6
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• pp.905-913
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• 2011

This study was conducted to characterize the discharge feature of pollutant load from the upper and lower watershed influencing on the water quality of South Han River using the empirical equation and Factor Analysis. The results of regression analysis between flow rate and pollutant load were as follows. In the streams of the upper watershed of South Han river, $BOD_5$ and $COD_{Mn}$ were increased as the flow rate was increased. Also, steep increases in SS and TP were observed with positive correlation with the flow rate while change in TN was slightly shown. On the other hand, in the streams of the lower watershed of South Han river, $BOD_5$ was negatively correlated with the flow rate, being decreased with the increase in the flow rate. However, changes in $COD_{Mn}$, TN, SS, and TP showed a similar trend with those observed in the upper watershed. With Factor Analysis of the water quality and various components, it was appeared that the flow rate, SS, and TP were significantly correlated each other and they were indicated as the principal component influencing on water quality in the streams of the upper watershed. In contrast, $BOD_5$, $COD_{Mn}$ and TOC were significantly correlated each other and they were included as the principal pollution component of the streams in the lower watershed. From these results, it was conclusive that the upper watershed of South Han River was mainly affected by non point source pollutants while the lower watershed was influenced by point source pollutants from the developed areas.

• Bulletin of the Korean Chemical Society
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• v.24 no.8
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• pp.1172-1176
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• 2003

This study aims to investigate the applicability of Sd/StFFF and to develop a method for size characterization of urban airborne particles, focusing primarily on particles larger than about 1 mm. It was found that the airborne concentration vary with time, although no particular seasonal trend was observed. When averaged over time, the airborne concentration was the lowest in the park areas with 99 ㎍/m³. The apartment, industrial, and central city area showed similar levels of the airborne concentrations with 166, 170, and 171 ㎍/m³, respectively. The housing area showed the highest airborne concentration with 201 μg/m³ among all tested areas. A power-programmed Sd/StFFF was used for size analysis of airborne particles with the initial field strength of 300 rpm, $t_a$ = 4, $t_i$ = -16, p = 8, and the flow rate of 7 mL/min. It was found that urban airborne samples were mostly populated by particles having diameters between about 5 to 20 ㎛, although all have broad size distributions ranging up to about 50 ㎛. Under the Sd/StFFF condition used in this study, no significant differences were found in size distributions among the airborne particles collected at different urban sites, and also among those collected at different times.