• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.12
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• pp.994-1001
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• 2007

Numerical analysis has been carried out to investigate air-side convective heat transfer characteristics in a compact heat exchanger with circular tubes and continuous plate fins. Simulation results such as air velocity and temperature distributions are presented, and heat transfer coefficients are compared with previous experimental correlations. Three models of standard and RNG $k-{\varepsilon}$, and Reynolds stress are applied for turbulence model applicability. Predicted heat transfer coefficient from the models of standard and RNG $k-{\varepsilon}$ are very close to those of the heat transfer correlations while there are relatively large difference, more than 17 percentage in the result from the Reynolds stress model. From the calculated results a correlation for Colburn j factor in the compact heat exchanger system is suggested.

• Journal of Navigation and Port Research
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• v.26 no.2
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• pp.199-207
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• 2002

Radar Cross Sections(RCS) for the radar targets are measured and their performance characteristics are analyzed through computer simulation. In addition, constructional features for the commercial radar reflectors are investigated. Then, the optimum design condition of a passive-type radar reflector was chosen. The results show that the octahedral-type radar reflector with 10$\lambda$ sized circular plates has best performance in X-band($\lambda$=3.2cm). However, to comply with newly adopted 2000 SOLAS regulations, larger sized circular plate is required to provide at both X-band and S-band.

• Korean Journal of Microbiology
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• v.27 no.2
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• pp.98-107
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• 1989

Intraspecific fusants, produced by protoplast fusion of auxotrophic mutants from Trichoderma koningii ATCC 26113, were segregated into various strains including parental types, non-parental auxotrophic hybrids, and prototrophic hybrids on complete plate. Interestingly, some of non-parental prototrophic hybrids revealed to have enhanced cellulolytic activity incomparison with other strains of parents or hybrids derived thereafter. It was also evident that prototrophic hybrids of aneuploid could be constructed after the spontaneous segregation of complementing fusants produced through the protoplast fusion.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1979-1989
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• 1992

An experimental study has been performed to investigate the horseshoe vortex system formed around cylindrical obstacles mounted vertically on the surface over which a boundary layer is formed. To measure the mean velocity of the flow field, a five-hole Pitot tube has been used. In addition, surface static pressure measurements and surface flow visualization were also performed. From the five-hole probe measurements, vorticity distribution was deduced numerically and the streamwise velocity distribution was also examined. To consider the effect of the leading-edge shape on the formation of the horseshoe vortex, a qualitative comparison was made between the three-dimensional flows around a circular cylinder and a wedge-type cylinder. The five-hole probe measurements showed a single primary vortex which exists immediately upstream of the obstacles, and endwall flow visualization showed the existence of a corner vortex. As the vortex passes around the obstacle, the vortex strength is reduced and the vortex core moves radially outward. Due to this horseshoe vortex, the fluid momentum is found to decrease along the streamwise direction. Since the horseshoe vortex formed around a wedge-type cylinder has weaker strength and is confined to a narrower region than that around a circular, the possibility that the secondary flow loss due to the horseshoe vortex can be reduced through a change of the leading- edge shape is proposed.

• Microbiology and Biotechnology Letters
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• v.15 no.2
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• pp.89-94
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• 1987

The optimal conditions for the protoplast formation and regeneration of Streptomyces mitakaensis have been investigated. S. mitakaensis cells were converted to protoplast by treating with 0.1 mg/$m\ell$ of lysozyme in phosphate-tris buffer (pH 7.2) to the cells grown at the late logarithmic growth phase in the GBYN medium (gycerol 20g, beef extract 5g, yeast extract 5g, NaCl 5g in 1 liter of distilled water) contained 0.5% glycine. Cell regeneration from protoplast was accomplished in 10 days post inoculation on the R2 regeneration agar medium and at 3 days post inoculation on the H2 regeneration liquid medium. The efficiency of the regeneration was 0.l% in 3 days at 35$^{\circ}C$.

• Journal of Energy Engineering
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• v.18 no.2
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• pp.108-113
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• 2009

An experimental study of jet impingement on aluminum foam mounted on the surface with constant heat flux is conducted with the presentation of the heat transfer rate measured when jet impinges normally to a flat plate. Effects of pore density, foam thickness and Reynolds number on the heat transfer are analyzed. Experimental results show that the significant enhancement in Nu is obtained when the aluminum foam is mounted on the heated plate and that the increase in the heat transfer due to the porous material insertion is dominated by both the increase in the heat transfer area and the decrease in the momentum flux resulted from the pressure drop.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.4
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• pp.300-306
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• 2019

Transmission cross section(TCS) is described analytically as $2G{\lambda}^2/4{\pi}$ irrespective of the aperture shapes for various transmission resonant apertures, such as small ridged circular or H-shaped, U-shaped, or Jerusalem cross-shaped apertures in an infinite thin conducting plane. The proposed expression is validated by comparison with the numerical results obtained from the method of moments(MOM). The TCS characteristics of the transmission resonant cavity structure in a thick conducting plane are also studied and the equivalence between the two small aperture structures is reported from the viewpoint of transmission efficiency.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.3
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• pp.60-66
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• 1991

In this paper, circula and rectangular apertures arranged with triangular and rectangular lattices and having a certain thickness are considered for eddective electromagnctic wave shielding when the plane wave is incident normally to the perfectly conductingmaterrial. The shielding effectiveness is represented by the transmitted power which can be obtained by reflection and transmission coefficients using Floquet mode representation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1169-1177
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• 2002

A study of fee vibration of circular Mindlin plates is presented. The analysis is based on the pseudospctral method, which uses Chebyshev polynomials and Fourier series as basis functions. It Is demonstrated that rapid convergence and accuracy as well as the conceptual simplicity could be achieved when the pseudospectral method was apt)lied to the solution of eigenvalue problems. Numerical examples of circular Mindlin plates with clamped and simply supported boundary conditions are provided for various thickness-to-radius ratios.

• Journal of Dairy Science and Biotechnology
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• v.12 no.1
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• pp.20-27
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• 1994

건강한 성인의 분변으로 부터 호기적인 평판배지에서의 생육이 가능한 비피더스균을 선별 분리하는 조건과 상기 분리주의 특성을 규명한 결과는 다음과 같다. 1.5%의 탈섬유소 말혈액을 첨가한 BLB Agar Medium에 인체 분변을 호기적으로 표면 배양하여 내산소성 비피더스균 변이주를 분리하였다. 상기 분리주는 BLB Agar Medium 평판배지에 호기적으로 배양 했을때 $1.1\;{\times}\;10^9$ cfu/ml 이상의 높은 균수를 유지하였다. 2. 상기의 내산소성 비피더스균 분리주를 BLB Agar Medium 에 호기적으로 배양했을때 0.5mm, 연유갈색, 원형, 융기상의 윤택한 집락을 형성하였으며 현미경 검경 결과 Y 자형 분지상과 V자형 만곡간균상, 팽윤상 등의 전형적인 비피더스균 형상으로 나타냈다. 3. 탄수화물 발표실험 결과 상기의 내산소성 비피더스균 분리주는 Bif. adolescentis 로 동정되었으며 F6PPK GKA효소 활성 함께 매우 높은 ${\alpha}$-Galactosidase, $\beta$ - Galactosidase, ${\alpha}$-Galactosidase, 효소 활성을 나타냈다. 한편 아무것도 첨가하지 않은 순수한 우유 중에서의 발효성 및 호기적인 생육능이 매우 양호하였다.