• 설비공학논문집
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• 제7권1호
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• pp.89-97
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• 1995

Experimental study was performed for free convection and ice formation around two horizontal circular tubes which were placed vertically. Temperature and velocity distributions were visualized with real time holographic interferometry technique and tracer method. When water was cooled, super cooled region was formed around cooling pipe. It was found that flow induced by free convection always directed downwards when the coolant temperature was low, while it directed upwards when the coolant temperature was comparably high though it directed downwards initially. Flow phenomena with free convection were investigated in detail with varying cooling rate and length between cooling pipes. And growing process of dense ice was also investigated. Dendritic ice is suddenly formed within a supercooled region, and a dense ice layer begins to develop from the cooling wall.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 춘계학술대회 논문집
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• pp.123-126
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• 1994

We discussed the thermal analysis for recording media with the variation of the laser pulse duration and the power and the temperature distribution for the optimized Te-based antireflection structure by using the computer calculations. If the radial diffusion of heat is negligible, we can calculate the maximum temperature at the spot center in recording layer by Simple Method, and the temperature profile considering the specific heat and the latent heat by Numerical Method. As a result, the effect of the heat sinking which acted as a loss for the hole formation can be minimized by introducing the pulse of the hole formation duration( $\tau$ ) shorter than the thermal time constant( $\tau$$\sub$D/) of dielectric layer. This requirments can be satisfied as using the dielectric thickness of the 7nd ART condition or the dielectric materials with low thermal diffusivity.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2004년도 SMICS 2004 International Symposium on Maritime and Communication Sciences
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• pp.96-99
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• 2004

The combination of mechano-chemical activation and Self-propagating High-temperature Synthesis (SHS) has widened the possibilities for both methods. For YBCO systems the investigation showed that a short-term mechano-chemical activation of initial powders before SHS leads to single-phase and ultra-fine products. A new technique for preparation ultra-fine high-temperature superconductors of YBCO composition with a grain size d ＜1 ${\mu}{\textrm}{m}$ is developed. The specific feature of the technique is formation of the YBa$_2$Cu$_3$O$_{7-{\delta}}$ crystalline lattice directly from an X-ray amorphous state arising as a result of mechanical activation of the original oxide mixture. The technique allows the stage of formation of any intermediate reaction products to be ruled out. X-ray and magnetic studies of ultra-fine high temperature superconductors (HTS) are carried out. Dimension effects associated with the microstructure peculiarities are revealed. A considerable enhancement of inter-grain critical currents is found to take place in the ultra-fine samples.fine samples.

• Bulletin of the Korean Chemical Society
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• 제11권5호
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• pp.386-390
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• 1990

Yttrium oxysulfide incoporated with europium has been prepared by direct heating the mixture of $Y_2O_3,\;Eu_2O_3,\;NaOH(or\;Na_2CO_3)$, and S. The reaction of the mixture at low temperatures and treatment at higher temperatures are studied. The formation of $Y_2O_2S$ is completed at lower temperature (ca. 500$^{\circ}C$) and incorporation of $Eu^{3+}$ into $Y_2O_2S$ lattice proceeds at higher temperature (above 1000$^{\circ}C$) along with crystal growth. Small amount of the unknown phase considered to be $Y_2O_2S_2$ is formed along with $Y_2O_2S$ in the temperature range from 400$^{\circ}C$ to 460$^{\circ}C$.

• 한국진공학회지
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• 제16권6호
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• pp.479-482
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• 2007

수소화물 기상 증착법을 이용하여 [0001] 방향에서 $0.3^{\circ}$ 기울어진 사파이어 기판 위에 InN 나노 알갱이를 성장 시켰고, 다양한 성장 조건에 따라 InN 나노 알갱이의 성장이 어떻게 영향 받는지 x-선 산란을 이용하여 연구 하였다. 모든 시료는 암모니아 사전 처리 작업을 한 사파이어 기판 위에 증착하였다. 염화수소 유량, 성장온도, 소스 영역온도에 따라 InN 나노 알갱이의 성장이 영향을 받음을 알 수 있었으며, 갈륨과 인듐을 혼합한 소스를 사용하였음에도 불구하고, 성장 조건에 따라 InN가 성장되지 않는 경우가 있었으며, 이 때는 특히 (001) 방향의 GaN 이외에 (100)및 (101) 방향의 GaN 나노알갱이들이 급격히 많이 생성됨을 확인하였다.

• 한국자원식물학회지
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• 제31권4호
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• pp.372-377
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• 2018

본 연구는 천마의 종자생산을 위한 수확시기별 처리 방법에 따른 자마 생산 효과를 구명하고자 수행하였다. 봄수확 천마는 괴경의 무게를 60-99 g, 100-139 g, 140-179 g, 180 g 이상으로 처리하였고, 가을수확 천마는 $5{\pm}1^{\circ}C$의 저온을 2, 4, 6, 8, 10주 처리하였다. 그 결과, 봄수확 천마는 괴경의 무게가 100 g 이상일 경우, 인공수정률이 90.9%-94.8%, 원괴체 형성률이 3.1%-5.4%, 자마 형성률이 10.1%-15.3%로 나타났다. 가을수확 천마는 4주 이상의 저온처리 시 인공수정률이 70.4%-87.6%, 원괴체 형성률이 2.2%-2.6%, 자마 형성률이 8.7%-9.5%로 나타났다. 따라서, 종자 및 자마 생산을 위해서는 봄수확 천마는 100 g 이상의 괴경을 사용해야 하고, 가을수확 천마는 저온에서 4주 이상의 휴면타파가 필요했다. 가을수확 천마를 이용할 경우 봄수확 천마에 비해 인공수정률, 원괴체 및 자마 형성률이 낮았지만, 자연 발아 상태보다 월등히 높았다. 따라서 일정한 괴경의 무게와 저온처리 휴면타파를 이용하면 천마의 종자와 자마가 확보됨으로써 천마의 연중생산이 가능할 것으로 판단되었다.

• 한국작물학회지
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• 제37권1호
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• pp.59-67
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• 1992

벼 기계이앙을 위한 어린모 육묘에 이앙 가능한 최단기 육묘일수와 맷트형성기간을 구명하기 위하여 육묘온도와 깔판재료를 달리하여 그 효과를 조사하였던 바 다음과 같은 결과를 얻었다. 1. 육모온도가 높을수록, 또 육묘기간이 길어질수록 어린모의 맷트형성이 양호하였으며, Metalaxyl(25% 수화제, 1,000 배액) 종자침종처리는 무처리에 비하여 맷트형성 기간이 단축되었다. 2. Metalaxyl 침종처리는 무처리에 비하여 어린모의 초장신장 효과가 있었고, 경엽중과 근중도 무거웠으며, 입고병과 뜸묘의 발생을 방지하였다. 3. 어린모의 맷트형성 촉진 보조재로서 흡수지깔판(키친타올 1컵)의 효과가 인정되었으며, ＆apos;Metalaxyl 침종＋비닐＋흡수지＆apos;처리는 다른 처리에 비하여 맷트형성 기간을 1～2일 단축시켰다. 4. 어린모의 최소 육묘일수는 파종 후 5일이였다. 육묘조건은 종자를 Metalaxyl 1,000배액에 24시간 침종한 후 비닐＋흡수지 깔판에 파종하여 30/2$0^{\circ}C$(획 / 야) 온도에서 육묘한다. 5. 일반농가 비닐하우스에서 어린모 육묘시(중부지방)에는 5월의 하우스내 온도를 야간 11～16$^{\circ}C$, 획간 28～32$^{\circ}C$ 정도로 볼 때, 산파상자를 사용할 경우에는 ＆apos;Metalaxyl 침종＋비닐깔판＆apos;처리로, 또 어린모 전용 육묘상자를 사용할 경우에는 ＆apos;Metalaxyl 침종＆apos;처리로 육묘하면 파종 후 6일에 안전 이앙이 가능한 것으로 판단된다.

• 대한화학회지
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• 제59권3호
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• pp.238-245
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• 2015

The crystallization and morphology change of amorphous titanias by hydrothermal treatment have been investigated. The amorphous titanias were prepared by pure water hydrolysis of two different precursors, titanium tetraisopropoxide (TTIP) and TTIP modified with acetic acid (HOAc) and characterized prior to hydrothermal treatment. In order to avoid complicate situation, the hydrothermal treatment was performed in a single solvent water with and without strong acids at various temperatures. The effects of strong acid, temperature and time were systematically investigated on the transformation of amorphous titania to crystalline TiO₂ under simple hydrothermal condition. Without strong acid the titanias were transformed into only anatase phase nanoparticle regardless of precursor type, temperature and time herein used (up to 250 ℃ and 48 hours). The treatment temperature and time effected only on the crystalline size, not on the crystal phase et al. However, it was clearly revealed that the strong acids such as HNO₃ and HCl catalyzed the formation of rutile phase depending on temperature. HCl was slightly better than HNO₃ in this catalytic activity. The morphology of rutile TiO₂ formed was also a little affected by the type of acid. The precursor modifier, HOAc slightly reduced the catalytic activity of the strong acids in rutile phase formation.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.100-106
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• 1998

The wide open throttle performance and piston temperatures were measured by the change of fuel : gasoline and liquefied petroleum gas(LPG). Bench test method was developed and experimented to study the effect of temperature on the formation of carbon deposit. The bench test results were confirmed by measuring the piston temperature and observing the deposit production rate at an actual engine running condition. Results show that if the fuel of spark ignition engine is changed from gasoline to LPG, the output power decreases about 10% and the piston temperatures increase about 40~55$^{\circ}C$. In actual engine tests, because of this temperature increase, it was observed that the quantity of carbon deposit in the top ring groove increased in a big degree. Consuquently, it is known that the fing sticking may occur if the gasoline engine was rebuilt to LPG fuelled engine. Therefore, in order to preserve the durability of LPG fuelled engine, it is necessary to lower the piston temperature by hardware modificationor to reduce the carbon deposit by the improvement of engine oil.

• Nuclear Engineering and Technology
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• 제28권4호
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• pp.366-372
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• 1996

The simulated spent PWR fuel pellet which is corresponding to the turnup of 33,000 MWD/MTU is prepared by adding 11 fission-product elements to UO$_2$. The simulated spent fuel pellet is treated at 40$0^{\circ}C$ in air (oxidation), at 110$0^{\circ}C$ in air (high-temperature treatment), and at $600^{\circ}C$ in hydrogen (reduction). The product is treated through additional addition and reduction up to 3 cycles. Pellets are completely pulverized by the first oxidation, and the high-temperature treatment causes particle and crystallite to grow and surface to be smooth, and thus particle size significantly increases and surface area decreases. The reduction following the high-temperature treatment decreases much the particle size by means of the formation of intercrystalline cracks. The particle size decreases a little during the second oxidation and reduction cycle and then remains nearly constant during the third and fourth cycles. Surface area of pounder increases progressively with the repetition of oxidation and reduction cycles, mainly due to the formation of Surface cracks. The degradation of surface area resulting from high-temperature treatment is restored by too subsequent resulting oxidation and reduction cycles.