• 한국세라믹학회지
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• 제36권11호
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• pp.1150-1155
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• 1999

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 추계학술발표회요약집
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• pp.305.2-305
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• 2002

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2003년도 춘계총회 및 학술발표회
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• pp.23-23
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• 2003

• 한국미생물·생명공학회지
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• 제31권4호
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• pp.400-407
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• 2003

Acidithiobacillus ferrooxidans를 이용한 석탄의 생물학적 탈활공정의 효율에 미치는 여러 조업인자들의 규명하였다. 석탄에 함유된 저해물질이 탈황세균의 활성에 미치는 영향을 평가함으로써 생물탈황기술이 적용 가능한 석탄을 선별할 수 있음을 보였다. 석탄 탈황효율은 석탄 슬러리 농도와 입자크기에 많은 영향을 받았다. 석탄 탈황 효율은 입자크기가 작을수록 증가하였으며, 슬러리 농도가 증가할수록 감소하였다. 탈황효율은 슬러리 농도 20～30% 이상에서는 석탄 입자크기와 슬러리 농도의 영향이 미미하였다. 또한, 석탄 탈황에 적용 가능한 airlift bioreactor에서 석탄 입자와 슬러리농도 변화에 따른 물질전달 특성을 규명하였다. 석탄슬러리에서 물질전달은 석탄입자의 크기와 슬러리 농도에 많은 영향을 받았다. 물질전달 계수는 석탄 입자크기가 175 $\mu\textrm{m}$ 이하의 미분탄인 경우 슬러리 농도의 영향은 미미하였으며, 225 $\mu\textrm{m}$ 이상의 입자크기를 갖는 석탄 슬러리에서는 슬러리 농도가 증가함에 따라 감소하였다. 물질전달 계수는 석탄 입자크기에 많은 영향을 받았다. 물질전달 계수는 미분탄에서 낮았으며 입자크기가 증가함에 따라 증가하여 575 $\mu\textrm{m}$일 때 물질전달이 가장 우수하였으며, 575 $\mu\textrm{m}$ 이상에서는 석탄입자의 침전문제가 발생하여 생물탈황공정에 적용이 어렸다. 물질전달, 탈황효율, 슬러리 농도 등을 조업인자들을 고려할 때 생물탈황에 적용할 최적의 석탄 입자의 크기는 약 500 $\mu\textrm{m}$ 전후인 것으로 평가되었다.

• 한국세라믹학회지
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• 제29권12호
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• pp.956-962
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• 1992

The predominant sintering mechanisms of low firing temperature ceramic substrate which consists of borosilicate glass containing alumina as a filler are the rearrangement of alumina particles and the viscous flow of glass powders. In this system, sintering condition depends on the volume ratio of alumina to glass and on the particle size. When the substrate contains about 35 vol% alumina filler and the average alumina particle size is 4 $\mu\textrm{m}$, the best firing condition is obtained at the temperature range of 900∼1000$^{\circ}C$. The extensive rearrangement behavior occurs at these conditions, and the optimum sintering condition is attained by smaller size of glass particles, too. The formation of cristobalite during sintering causes the difference of thermal expansion coefficient between the substrate and Si chip. This phenomenon degradates the capacity of Si chip. Therefore, the crystallization should be prevented. In the alumina filled borosilicate glass system, the crystallization does not occur. This effect may have some relation with aluminum ions in alumina. For aluminum ions diffuse into glass matrix during sintering, functiong as network former.

• 한국재료학회지
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• 제15권5호
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• pp.340-347
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• 2005

Silver nanoparticles were synthesized by chemical reduction method from aqueous silver nitrate solution ana hydrazine as a reduction agent. The morphology, particle size and shape were dependent on the mixing method, reaction temperature and time, molar ratio of hydrazine and silver nitrate, the kind of surfactant, and the addition of surfactant. The stability of the colloidal silver was achieved by the adsorption of surfactant molecules onto the particle. Silver nanoparticles have a characteristic absorption maximum at 430 nm under UV irradiation. It was found that the colloid was nanometer m size and formed very stable dispersion of silver. The Ag nanoparticles obtained showed the spherical shape with the size range of 10-30 nm.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.81-84
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• 1997

The hot deformation behavior of SiCp/AA2024 composites reinforced with different sizes of SiCp reinforcements (1, 8, 15, 36, and 44${\mu}{\textrm}{m}$) was investigated by hot torsion tests. The hot restoration of the composites depending on the SiCp reinforcements particle size was studied from the effective stress - strain curves. Dynamic recrystallization (DRX) was occurred in the SiCp/AA2024 composites during the hot deformation at 320 - 43$0^{\circ}C$ under a strain rate of 1.0/sec. Also, the critical strain for DRX decreased with decreasing the reinforcement size of SiCp from 44 to 8${\mu}{\textrm}{m}$. The composite reinforced with SiCp of 8${\mu}{\textrm}{m}$ showed the highest flow stress (265 MPa) and the work hardening rate at 32$0^{\circ}C$ under a strain rate of 1.0/sec.

• 한국조경학회지
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• 제25권2호
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• pp.94-103
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• 1997

The purpose of this study is to find out the effects of brick paved under-surface soil physical properties which are changed by fixed trampling. Thus, a sandy loam which is known as a profitable soil for plants is used an experimental soil to study the changes of the soil physical properties. It is related to sand bed's thickness & particle size which are settled by experimental variable factors. According to the variation of sand bed's particle size, bulk density and soil hardness at natural dryed soilcondition result in 0.075~2.00mm>2.00~5.00mm>2.00~8.00mm>5.00~8.00mm, and water content at natural dryed soil condition are observed being insensible change rate from the point that sand thickness is 30~40mm and more sand bed's thickness constructed by the variation of sand bed's thickness.

• 열처리공학회지
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• 제36권1호
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• pp.33-39
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• 2023

In this study, the effect of mixing condition of raw material powders possessing various particle size and particle size distribution on thermite reaction efficiency was investigated. When fine raw powders are used, rather the reaction yield tends to decrease due to agglomeration. In contrast, coarse raw powders make deteriorate the contact area between raw material powders containing Al reducing agent. To ensure the optimal thermite reaction efficiency, it is required to optimize a mixture condition of raw material powders prior to thermite reaction. From the current experiment, the maximum thermite reaction efficiency is 77%, which came from Nb₂O₅ + NiO +Al mixtures with size distribution from 9.25 to 22.63 ㎛.

• 천문학회보
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• 제42권2호
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• pp.48.3-49
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• 2017

Interplanetary space of the solar system contains a large number of dust particles, referred to as Interplanetary Dust Particles (IDPs) cloud complex. They are observable through meteors and zodiacal lights. The relative contribution of possible sources to the IDPs cloud complex was an controversial topic, however, recent research (Yang & Ishiguro, 2015 and references therein) suggested a dominance of cometary origin. In this study, we numerically investigated the orbital evolution of cometary dust particles, with special concerns on different evolutionary tracks and its consequences according to initial orbits, size and particle shape. The effect of dust particle density and initial size-frequency distribution (SFD) were not decisive in total cloud complex mass and mass supply rate, when these physical quantities are confined by observed zodiacal light brightness and dust particle SFD at 1 au. We noticed that, if we assume the existence of fluffy aggregates discovered in the Earth's stratosphere and the coma of 67P/Churyumov-Gerasimenko, the required mass supply rate decreases significantly. We also found out that close encounters with planets (mostly Jupiter) are the dominating factor of the orbital evolution of dust particles, as the result, the lifetime of cometary dust particles are shorter than Poynting-Robertson lifetime (around 250 thousand years). As another consequence of severe close encounters, only a small fraction of cometary dust particles can be transferred into the orbit < 1 au. This effect is significant for large size particles of ${\beta}$ < 0.01. The exceptional cases are dust particles ejected from 2P/Encke and active asteroids. Because they rarely encounter with Jupiter, most dust particles ejected from those objects are governed by Poynting-Robertson effect and well transferred into the orbits of small semimajor axis. In consideration of the above effects, we directly estimated probability of mutual collisions between dust particles and concluded that mutual collisions in the IDPs cloud complex is mostly ignorable, except for the case of large sized particles from active asteroids.