• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.12
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• pp.654-659
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• 2013

This paper presents a numerical optimization of louvered fins to enhance the JF factor in terms of the design parameters, including the fin pitch, the number of louvers, the louver angle, the fin thickness, and the re-direction louver length. We carried out a parametric study to select the three most important parameters affecting the JF factor, which were the fin pitch, number of louvers, and the louver angle. We optimally designed the louvered fin by using 3rd-order full factorial design, the kriging method, and a micro genetic algorithm. Consequently, the JF factor of the optimum model increased by 16% compared to that of the base model. Moreover, the optimum model reduced the pressure drop by 17% with a comparable heat transfer rate.

• Journal of the Korean Chemical Society
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• v.8 no.3
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• pp.98-102
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• 1964

As a practical method to produce the carbonaceous binder, the destructive distillation of coal tar has been studied. The optimum condition on binder in various temp. and cutting time were examined and the compositions of pitch were also examined in connection with ${\alpha},\;{\beta}\;and\;{\gamma}$ by solvent extraction. Coke powder was mixed with binder as treated pitch in the proportions of 77% of coke to 23% of pitch, to give a plastic mix which could then be pressed into molding. The properties of baked body after molding was tested. It was found that cutting of the coal tar at 350${\circ}C$, for 30 min., at 300${\circ}C$. for 1 hr., and at 250${\circ}C$. for 8 hrs. were good condition. Particularly, we found that the cutting of the coal tar obtained by destructive distillation at high temp. and in minimum period of time had shown the best condition for utilization of carbonaceous pitch as binder. The above mentioned cutting condition results in good quality of pitch which is available to be used as binder in carbon industry.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.37 no.3
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• pp.66-73
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• 2005

This study was performed to understand the changes in wood extractives, mainly acetone extracts, in pine woods (Pinus densiflora and Pinus rigida) treated by three blue stain fungi (BSF) such as native BSF in Korea, Leptographium sp., screened Albino strain(BSFcs-1) and commercial Cartapip and fungicide, Wood guard. In addition their pulping and bleaching properties were investigated. BSF treatment has significantly reduced acetone extracts, $25.1{\sim}30.4%$ decreasing in red pine and $22.9{\sim}28.1%$ in pitch pine. Three week aging treatment showed about 20% decreasing in red pine and 19.3% in pitch pine. There were not so significant differences in extracts reduction among native BSF and Albino-type strains (Albino strain, BSFcs-1, and commercial Cartapip). But fungicide, Wood guard, treated wood showed relatively lower decreasing rates of extractives, 14% in red pine and 10.1% in pitch pine. Therefore it is understandable that the fungicide could protect the wood from blue stain fungi attack, but has no effect on its extractive reduction. Concerned to pulping properties of BSF and fungicide treated woods, red pine and pitch pine, optimum pulping condition was 20% active alkali, wood to liquor ratio 1 to 6, $170^{\circ}C$, and 2.5 hr. In the case of BSF woods, optimum pulping condition was same as the sound wood, $43.5{\sim}45%$ of pulp yields and $1.3{\sim}1.45%$ of rejects. Screened pulp yield of fungicide treated wood was lower than those of BSF treated woods. Rejects in pulps were higher in fungicide-treated wood than BSF treated woods. Bleaching pulp yields were ranged of 92 to 93.5%. BSF, Cartapip and fungicide treated woods resulted in lower brightness of $55{\sim}58%$, but Albino-type strain(BSFcs-1) $61.3{\sim}62.3%$, very similar to untreated one. Therefore bleaching chemicals could be saved in the processing of chemical pulping.

• Journal of the Korean Society of Visualization
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• v.9 no.3
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• pp.30-37
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• 2011

The thrust vectoring concept has been used for use in new advanced supersonic aircraft. This study presents the performance characteristics of the thrust vectoring nozzle by visualizing the shock behaviors with Schlieren method. The scaled models were designed and manufactured to see the shock behaviors of the various airflow condition. Also we executed experimental tests to see the geometrical effects of the thrust vector nozzle by changing pitch angle and length of pitch flaps. From this study we could understand the supersonic flow characteristics of the thrust vector nozzle. The total thrust of thrust vector nozzle is diminished by increasing the flap angle. But there is an optimum flap length ratio for attaining the highest thrust level and proper pitch effect.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.175-181
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• 2008

The technologies of mold design, manufacturing, injection molding process and computer aided engineering(CAE) are developed rapidly with the growth of plastic product market. Injection molding process optimum design can not be easily determined. This study was determined factors and levels which carried out to analyze an influence of narrow pitch BGA socket warpage and performed investigating the main effect and interaction effect between factors using design of experiment. The result of this paper is injection time and packing pressure are affect on narrow pitch BGA socket warpage at injection molding.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.2
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• pp.116-126
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• 2002

A three dimensional numerical analysis of the corrugated louver fin for a vehicle heat exchanger was performed. The heat transfer rate and the air pressure drop of the corrugated louver fins for a slim heater were compared with experimental results at the same operating conditions. As for the slim heater fin, we found an optimum fin pitch at certain operating conditions. As the fin pitch increased, the air pressure drop decreased. The vertical or flat top fin was superior to the common declined fin in the aspect of heat transfer performance. As the louver length increased, both the heat transfer rate and the air pressure drop increased.

• Journal of the Korean Solar Energy Society
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• v.30 no.3
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• pp.55-64
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• 2010

The study has conducted a research on the main shape of domestic multi-family residential buildings. The four arrangements were selected after the research and each of them was analyzed for daylight, view and natural ventilation according to the different pitch of buildings. Based on the results from the analysis, the optimum pitch of buildings for each of the arrangements are as follows. With looking at the outcomes from the analysis on changes in residential environment by the pitch of building buildings in the four arrangements, it was figured out that it would be the best if the distance is more than 1.0H for Case_1. For Case_2, it should be more than 0.9H and for Case_3, it has to be 1.0H or more. Last but not least, it seems to be superb if the distance is more than 0.9H for Case_4.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.213-216
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• 2006

This paper was a study about noise reduction through flow stabilization in duct using experimental method and numerical analysis at the same time. To determine the fan's type three kinds of fans(axial fan, centrifugal fan, and axial fan with centrifugal type blades) was examined to investigate the suitability for in-line duct. As a result, under the equal number of rotation 2000 RPM, performance of an axial fan with centrifugal type blades was the most superior by 55dBA at 4.3CMM among other fans. After this, analyzed the results of the numerical analysis to find out the optimum design of pitch angle such as $0^{\circ}$, $10^{\circ}$, $15^{\circ}$ and $20^{\circ}$. The intensity of turbulence was low when pitch angle was $15^{\circ}$ and air volume became peak by 5.08 CMM. It was observed that axis component of velocity increased gradually when pitch angle increased from $0^{\circ}$ to $20^{\circ}$, and embodied noise reduction and improvement of air flow rate through flow stabilization.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.84-93
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• 2013

Stealthy, high maneuverability and super cruise abilities are required for the next generation fighter and unmanned aircraft. Thrust vector control technique currently come into use to meet these requirements. In this experimental study, axial and pitch thrust were measured and Schlieren visualization were carried out using the scaled two dimensional thrust vector nozzles under various pitch deflection angle, pitch flap length and height. From the study, we could get the supersonic flow characteristics and draw an optimum geometric configuration of the two dimensional thrust vector nozzle.

• Korean Chemical Engineering Research
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• v.43 no.6
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• pp.745-750
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• 2005

Naphtha cracking bottoms(NCB) oil was reformed by varying the heat treatment temperature, treatment time, and nitrogen flow rate in preparation of precursor pitch for isotropic pitch-based carbon fibers and activated carbon fibers. The reformed pitches were investigated in the yield, softening point, elementary analysis, and molecular weight distribution, and then the precursors reformed were melt spun to certify the optimum reforming conditions. The optimum precursor pitch was prepared when the NCB oil was reformed at $380^{\circ}C$, 3 h and 1.25 vvm $N_2$, and it's the softening point was around $240^{\circ}C$. The reforming resulted in product yield of 21 wt％. The C/H mole ratio of the precursor pitch increased from 1.07 to 1.34, the aromaticity increased from 0.85 to 0.88. The insolubles in benzene and quinoline were 30.0 wt％ and 1.5 wt％, respectively. The spinning temperature was about $50^{\circ}C$ higher than the softening point. The molecular weights of the precursor components were distributed from 250 to 1250, and 80％ of them were in the range of 250 to 700.