• Journal of Mechanical Science and Technology
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• 제20권8호
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• pp.1266-1274
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• 2006

A numerical study is performed to investigate the effect of inner surface roughness and micro-particles on adiabatic single phase frictional pressure drop in a perfect square micro channel. With the variation of particles sizes (0.1 to $1{\mu}m$) and occupied volume ratio (0.01 to 10%) by particles, the Eulerian multi-phase model is applied to a $100{\mu}m$ hydraulic diameter perfect square micro channel in laminar flow region. Frictional pressure loss is affected significantly by particle size than occupied volume ratio by particles. The particle properties like density and coefficient of restitution are investigated with various particle materials and the density of particle is found as an influential factor. Roughness effect on pressure drop in the micro channel is investigated with the consideration of roughness height, pitch, and distribution. Additionally, the combination effect by particles and surface roughness are simulated. The pressure loss in microchannel with 2.5% relative roughness surface can be increased more than 20% by the addition of $0.5{\mu}m$ diameter particles.

• 자원리싸이클링
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• 제27권2호
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• pp.24-31
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• 2018

본 연구에서는 폐 ITO 타겟을 염산에 용해시킴으로써 인듐-주석 복합 산 용액을 제조하여 원료용액으로 사용하였다. 이 원료용액으로부터 분무열분해 공정에 의하여 평균입도 30 nm 이하의 ITO 분체를 제조하였다. 또한 본 연구에서는 인듐-주석 산화물(ITO) 형성을 위한 열역학적 수식들을 확립하였다. 반응온도가 $800^{\circ}C$로부터 $900^{\circ}C$로 증가됨에 따라 평균입도 30 nm 이하인 나노입자들이 응집되어 있는 액적 형태의 비율 및 크기는 감소하는 반면 표면 조직은 더욱 치밀해짐을 알 수 있었다. 반응온도가 $800^{\circ}C$인 경우에는 생성된 분체의 평균입도는 약 20 nm이었으며, 현저한 소결 현상은 나타나지 않았다. 한편, 반응온도가 $900^{\circ}C$인 경우에는 노즐에 의하여 미립화되는 액적의 분열 현상은 $800^{\circ}C$의 경우보다 심하게 나타났으며 액적 형태의 비율은 현저하게 감소하였다. 형성된 입자들의 평균 입도는 약 25 nm로서 $800^{\circ}C$의 경우보다 약간 증가하였다. 반응온도에 관계없이 ITO 입자들은 단결정으로 구성되어 있었다. XRD 분석 결과 분무열분해 공정에 의하여 염화물 상은 전혀 존재하지 않았으며 오직 ITO 상만이 형성되었음을 알 수 있었다. 반응온도가 $800^{\circ}C$로부터 $900^{\circ}C$로 증가함에 따라 비표면적은 약 30% 감소하였다.

• 한국전기전자재료학회논문지
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• 제28권2호
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• pp.109-114
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• 2015

We realize a color reflective display without any color filter and sub-pixelation concept, by which the full or single color realization is basically impossible. In this study, we use a 3-electrode on the lower substrate with indium tin oxide (ITO) glass. The width of a rib is $30{\mu}m$, a cell size is $150{\mu}m{\times}150{\mu}m$, and the space of lower electrodes is $10{\mu}m$. To get the single color, we drive this panel by a identical algorithm based on the movement of charged particle in color fluid within a cell with hermetic seal. According to the driving method, the lifetime of panel is different.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
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• pp.224-233
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• 2002

A common YBCO powder has been made from a mixture of Y123 and Y211 that heated at different temperatures, respectively. The synthesis temperature of Y211 is lower than Y123. If Y211 has been heated as a synthesis temperature of Y123, a particle size of it may be very coarse. It exist as one of main defects for superconductor. But We simultaneously synthesize a YBCO(its composition is (Y123+0.4Y211)+$lwt%CeO_2$) using polymeric complex method. In the YBCO, the Y123 is synthesized lower temperature than other methodes, and its crystal structure is orthorombic. For measurement of these superconducting properties, we fabricated a YBCO single crystal. The manufactured YBCO single crystal is measured a magnetic distribution device using 0.5Tesla magnet and trapped magnet fields in it are 0.2Tesla.

• 한국전기전자재료학회논문지
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• 제20권6호
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• pp.550-554
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• 2007

Large and single-grain Y-Ba-Cu-O(YBCO) bulk superconductors have been fabricated by using a seeded infiltration and growth method. $Y_2BaCuO_5$(Y211) precursor pellets and $YBa_2Cu_3O_x$(Y123) liquid source pellets were prepared using commercial powder and were processed by infiltration and growth method to achieve low pore and high trapped field property. The superconductor properties of the single crystal are measured and analyzed in relation with the density and size of the Y211 particle in the Y123 matrix. An optimum processing condition is suggested based on the analyzed results.

• Journal of Magnetics
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• 제18권1호
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• pp.21-25
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• 2013

Nickel substituted manganese ferrites, $Mn_{1-x}Ni_xFe_2O_4$ ($0.0{\leq}x{\leq}0.6$), were fabricated by sol-gel method. The effects of sintering and substitution on their crystallographic and magnetic properties were studied. X-ray diffractometry of $Mn_{0.6}Ni_{0.4}Fe_2O_4$ ferrite sintered above 523 K indicated a spinel structure; particles increased in size with hotter sintering. The M$\ddot{o}$ssbauer spectrum of this ferrite sintered at 523 K could be fitted as a single quadrupole doublet, indicative of a superparamagnetic phase. Sintering at 573 K led to spectrum fitted as the superposition of two Zeeman sextets and a single quadrupole doublet, indicating both ferrimagnetic and paramagnetic phase. Sintering at 673 K and at 773 K led to spectra fitted as two Zeeman sextets due to a ferrimagnetic phase. The saturation magnetization and the coercivity of $Mn_{0.6}Ni_{0.4}Fe_2O_4$ ferrite sintered at 773 K were 53.05 emu/g and 142.08 Oe. In $Mn_{1-x}Ni_xFe_2O_4$ ($0.0{\leq}x{\leq}0.6$) ferrites, sintering of any composition at 773 K led to a single spinel structure. Increased Ni substitution decreased the ferrites' lattice constants and increased their particle sizes. The M$\ddot{o}$ssbauer spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and the octahedral sites of the $Fe^{3+}$ ions. The variations of saturation magnetization and coercivity with changing Ni content could be explained using the changes of particle size.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.75-81
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• 2001

This paper presents the atomization characteristics of single hole injector in the direct injection type diesel engine. The spray characteristics of fuel injector such as the droplet size and velocity were measured by phase Doppler particle analyzer. In this paper, the atomization characteristics of fuel spray are investigated for the experimental analysis of the measuring data by the results of mean diameter and mean velocity of droplet. The effect of fuel injection pressure on the droplet size shows that the higher injection pressure results in the decrease of mean droplet diameter in the fuel spray. The minimum size of fuel spray droplet appears on the location of 40mm axial distance from nozzle exit of diesel injector. Based on the experimental results, the correlation between the droplet diameter and mean velocity of the diesel spray due to the change of axial and radial distance from the nozzle tip were investigated.

• 한국세라믹학회지
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• 제35권4호
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• pp.406-412
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• 1998

The reaction bonded alumina ceramics was prepared through the addition of each SiC and ZrO2 powder to the mixture of Al metal powder and Al2O3 The mono sized (3mm) and biodal sized (3mm+5mm) balls were used in attrition milling of Al and starting powders. The milling efficiency of both cases was compared by the analysis of particle size and X-ray diffraction. After the forming and sintering of each powder batchs the weight gains dimensional changes and densities were determined. The specimens were investigated by X-ray diffraction analysis and scanning electron microscope. Bimodal sized balls had better milling effect than single ball size in the milling of Al powder. However in the milling which ceramic powders mono sized the green body during the reaction sintering at 1$600^{\circ}C$ for 5 hour was about 10% The densities attained the values of 92-98% theoretical. The SiC added specimen that was milled with 3mm ball media had 96% theoretical density and dense microstructure.

• 한국자기학회지
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• 제21권5호
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• pp.157-162
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• 2011

황산제일철/황산제이철의 몰비와 침전제 종류(NaOH, $NH_4OH$)를 변화시켜 공침법으로 $Fe_3O_4$를 합성하였다. 합성한 분말의 특성을 평가한 결과 모든 실험조건(황산제일철/황산제이철의 몰비와 침전제의 종류)에서 단일상의 나노 크기 $Fe_3O_4$가 생성 되었다. NaOH를 침전제로 사용한 경우에 $NH_4OH$를 침전제로 사용한 경우보다 입자크기가 작고, 좁은 입도분포를 나타내었다. 동일한 침전제를 사용할 경우에는 혼합 황산철(황산제일철/황산제이철)의 몰비가 증가할수록 입자크기와 결정자 크기가 증가하였으며 입도 분포는 넓어졌다. 모든 실험조건에서 합성된 $Fe_3O_4$ 분말은 초상자성을 나타내었으며 침전제로 $NH_4OH$를 사용하고 혼합 황산철의 몰비를 2.5로 하였을 때 가장 높은 포화자화 값 72 emu/g을 갖는 $Fe_3O_4$를 합성할 수 있었다.

• 센서학회지
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• 제31권3호
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• pp.175-179
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• 2022

The physical properties of biomaterials are important for their isolation and separation from body fluids. In particular, the precise evaluation of the multi-physical properties of single biomolecules is essential in that the correlation between physical and biological properties of specific biomolecule. However, the majority of scientific equipment, can only determine specific-physical properties of single nanoparticles, making the evaluation of the multi-physical properties difficult. The improvement of analytical techniques for the evaluation of multi-physical properties is therefore required in various research fields. In this study, we developed a motion-tracking algorithm to evaluate the multi-physical properties of single-nanoparticles by analyzing their behavior. We observed the Brownian motion and electric-field-induced drift of fluorescent nanoparticles injected in a microfluidic chip with two electrodes using confocal microscopy. The proposed algorithm is able to determine the size of the nanoparticles by i) removing the background noise from images, ii) tracking the motion of nanoparticles using the circular-Hough transform, iii) extracting the mean squared displacement (MSD) of the tracked nanoparticles, and iv) applying the MSD to the Stokes-Einstein equation. We compared the evaluated size of the nanoparticles with the size measured by SEM. We also determined the zeta-potential and surface-charge density of the nanoparticles using the extracted electrophoretic velocity and the Helmholtz-Smoluchowski equation. The proposed motion-tracking algorithm could be employed in various fields related to biomaterial analysis, such as exosome analysis.