• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.130-133
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• 2005

An experimental and theoretical study was carried out to estimate the foaming characteristics in the pultrusion process of phenolic foam composite. For the experimental study, a lab-scale pultrusion apparatus was constructed. Methylene chloride(CH2Cl2) was used as a physical blowing agent, glass fiber roving was used as reinforcement and the polymer used was a resol type phenolic resin. Pultruded products were observed to count bubble size by a SEM(Scanning Electron Microscopy). For the theoretical study, a model for bubble growth in a gradually hardening resin was considered and solved for a few foaming conditions.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.472-473
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• 2008

Flow boiling in parallel microchannels has received attention as an effective heat sink mechanism for power-densities encountered in microelectronic equipment. the bubble dynamics coupled with boiling heat transfer in microchannels is still not well understood due to the technological difficulties in obtaining detailed measurements of microscale two-phase flows. In this study, complete numerical simulation is performed to further clarify the dynamics of flow boiling in microchannels. The level set method for tracking the liquid-vapor interface is modified to include the effects of phase change and contact angle. The method is further extended to treat the no-slip and contact angle conditions on the immersed solid. Also, the reverse flow observed during flow boiling in parallel microchannels has been investigated. Based on the numerical results, the effects of channel shape and inlet area restriction on the bubble growth, reverse flow and heat transfer are quantified.

• International Journal of High-Rise Buildings
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• v.12 no.3
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• pp.195-201
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• 2023

This paper reviews the history of the birth and development of the skyscraper in Japan, mainly from the perspective of the legal system, and presents the following points: 1) After 1919, building height was limited to 31 m or less, which continued after the war and defined the skyline of Japan's major cities; 2) The 31-meter height limit became a problem during rapid economic growth. With the development of tall building construction technology, the height limit was eliminated, and skyscrapers were born in Japan in the 1960s; 3) Later, the number of skyscrapers increased more rapidly in the post-bubble period after the collapse of the bubble economy in the 2000s than in the boom years of the 1980s, when the floor-area ratio was relaxed for economic uplift and urban renewal. The number of skyscrapers increased rapidly against the backdrop of the deregulation of the floor-area ratio.

• Korean Journal of Plant Resources
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• v.30 no.6
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• pp.699-706
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• 2017

For rapid production of freesia 'Shiny Gold' shoots by using a bioreactor, several culture conditions were investigated. Young shoots (< 1 cm) obtained from freesia corm section in vitro were used as plant materials for this experiment. As a basic experimental environment, 20 young shoots were inoculated into a 5 L balloon type bubble reactor which contained 1 L 1/2 strength MS medium supplemented with 30 g sucrose (3%), and the aeration was 0.1 vvm (vessel volumes per minute). The bioreactors were placed in a growth room with $23^{\circ}C$ temperature, 60% relative humidity and $60{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ light condition (16 h/8 h, day/night). The concentrations of MS media were set with 1/4, 1/2, 1 strength, medium volume 10, 20, 40%, sucrose concentration 3, 6, 9%, and aeration 0.1, 0.2, 0.4 vvm. After 4 weeks of cultivation, the growth indexes including the fresh and dry weight, and plant height were evaluated. At the same time, the consumption, pH, and EC of medium were estimated 4 weeks after incubating. The best results were achieved when 40 young shoots were incubated in a bioreactor in which 1 L of 1/2 strength MS medium supplemented with 6% sucrose was used for the rapid production of freesia shoots. The shoots were 17 cm in plant height and 1.0 g in fresh weight only 4 weeks after incubation which could be a good plant material suitable for corm enlargement in vitro. No correlation was observed between the growth of freesia shoots and the consumption, pH or EC of medium.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.6
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• pp.484-488
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• 2006

Alteration of illumination with optimum carbon dioxide fixation-based curve in this research successfully enhanced the $CO_{2}-fixation\;(q_CO_{2}$ capability of Chlorella vulgaris Buitenzorg cultivated in a bubble column photo bioreactor. The level of $CO_{2}$ fixation was up to 1.91 times that observed from cultivation with intensification of illumination on an optimum growth-based curve. During 144 h of cultivation, alteration of light intensity on an optimum $CO_{2}-fixation-based$ curve produced a $q_CO_{2}$ of $12.8\;h^{-1}$. Meanwhile, alteration of light intensity with a growth-based curve only produced a $q_CO_{2}$ of $6.68\;h^{-1}$. Increases in light intensity based on a curve of optimum $CO_{2}-fixation$ produced a final cell concentration of about 5.78 g/L. Both cultivation methods were carried out under ambient pressure at a temperature of $29^{\circ}C$ with a superficial gas velocity of $2.4\;m/h(U_{G}$. Cells were grown on Beneck medium in a 1.0 L Bubble Column Photo bioreactor illuminated by a Phillips Halogen Lamp (20 W/12 V/50 Hz). The inlet gas had a carbon dioxide content of 10%.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.351-374
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• 1996

Various types of garnet compounds were synthsized by iso-and aliovalent substitutions and sintering method. Among them, fiber shapes of garnet crystals were grown from the $Ca_3Li_xNb_{(1.5+x)}Ga_{(3.5-2x)}O_{12}$ melt where x = 0 ~ 0.5 by modified micro-pulling down method in air using Pt crucibles. The measured lattice constants as a function of solidification fraction of grown fiber crystals are about $12.54\;{\AA}$ irrespective of x. It was found that the $Ca_3Li_{0.275}Nb_{1.775}Ga_{2.95}O_{12}$ garnet melts congruently at about $1450\;^{\circ}C$ based on the purities of garnet phase and variations of lattice parameter. Transparent and bubble-free crystals of x = 0.25 and 0.275 were grown by Czochralski techniques in air using Pt crucibles. An absorption spectrum is also reported.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.143-144
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• 2003

The growth characteristics of Spirulina Platensis was carried out in photo bubble bioreactor at different nitrogen soucres and concentration. The result showed that S. Platensis grew well at sodium nitrate source rather than urea source in relatively high concentration region.

• Transactions of the Korean Society of Mechanical Engineers
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• v.4 no.3
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• pp.96-104
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• 1980

유압이 변화할 때 증기기포의 크기를 구하는 공식을 제시하였다. 이 공식은 변화하는 유압하에서 기포의 크기를 상한과 하한으로 표시한 Hopper, Faucher 및 Eidlitz가 제시한 공식과, Plesset과 Zwick이 해결한 일정유압하에서 성립하는 기포에 관한 간단한 asymptotic 공식을 모두 대체 하기 위한 것이다. 여기에 제시한 새로운 공식의 정확성을 검토하기 위하여 Hooper, Faucher 및 Eidlitz가 보고한 실험결과와 이론적으로 얻은 결과와를 비교하여 보았다.

• Journal of the Korean Ceramic Society
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• v.25 no.1
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• pp.78-82
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• 1988

Good quality LiNbO3 single crystals which can be applied to SAW devices, were grown by Czochralski method. It was observed that the gas-bubbles were concentrated in ring shape at the outer part of grown crystals, and this anomaly was illustrated by modeling the mechanism of gas-bubble entrapment according to the melt flow pattern in the crucible. And this mechanism was also encertained by observation of solid-liquid interface shape of grown crystals. The optimal condition for good quality crystals was known that the solid-liquid interface shape was slightly concave.

• Land and Housing Review
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• v.2 no.3
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• pp.227-238
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• 2011

There are similarities between Korea and Japan in terms of national planning and development system and housing policies. Japan has suffered from great shifts of social and economic systems due to skyrocketing land prices for three times and the collapse of the bubble economy after the Second World War. The study reviews historically important changes in the national territory and housing policies for last 60 years in Japan. It also investigates changing trends and characteristics of many socioeconomic indicators with regard to population, housing and other fields in response to these policies. First of all, Japan has experienced significant economic growth before and after the 1960's, and the era of national rebuilding projects in the 1970's. After then, the period of the bubble economy has emerged since 1980; however, it suffered from skyrocketing land values between the late 1980's and the early 1990's, and the collapse of Japanese bubble economy in the early 1990's. In response, many urban regeneration policies and projects were proposed to recover the national economy since 2000. It is found that these national territory development and housing supply policies throughout the country have been influenced by the changing characteristics of social and economic conditions. Since the housing supply ratio in 1968 reached up to around 100% on average, Japan has been focusing attention to improving the residential and living quality for existing housing stock rather than supplying new housing units through large-scale new town projects. These experiences are full of helpful suggestions for our future housing and urban regeneration policies as we reach to more than 100% of housing supply ratio on average.