• Title/Summary/Keyword: Porous particle

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A Particle Tracking Method for the Lagrangian-Eulerian Finite Element Method in 3-D Subsurface System (3차원 지표하 시스템에서 Lagrangian-Eulerian 유한요소법에 대한 입자추적 알고리즘)

  • Lee, Jae-Young;Kang, Mee-A
    • The Journal of Engineering Geology
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    • v.19 no.2
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    • pp.205-215
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    • 2009
  • The conventional numerical models to analyze flow in subsurface porous media under the transient state usually generate numerical oscillation and unstability due to local flux domain for critical cases such as infiltration into initially dry soil during rainfall period. In this case, it is required refined mesh and small time step, but it decrease efficiency of computation. In this study, numerical unstability in discontinuity domain is removed by applying particle tracking algorithm to simulate unsteady subsurface flow with inflow boundary condition. Finally the hybrid LE FEM improving numerical stability is proposed. The hypothetical domains with unsteady uniform and nonuniform flow field were used to demonstrated algorithm verification. In comparison with analytic solution, we obtained reasonable results and conducted simulation of hypothetical 3-D recharge/pumping area. The proposed algorithm can simulate saturated/unsaturated porous media with more practical problems and will greatly contribute to accuracy and stability of numerical computation.

The Formation Mechanism Synthesizing of $SrTiO_3$Fine Powders by Ultrasonic Spray Pyrolysis (초음파 분무 열분해법에 의한 $SrTiO_3$ 미분말 합성시 그 형성 과정에 관하여)

  • 허화범;이동주;신건철
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.2 no.2
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    • pp.11-19
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    • 1992
  • $SrTiO_3$powders were synthesized from the chloride and the nitrate aqueous solution by spray pyrolysis method using ultrasonic vibrator. The concentration of mother solution was prepared 0.05M and O.lM. The carrier gas flow rate was 0.5cm/sec and 1.5cm/sec, respectively. The formation processing was investigated in the 0.05M and 0.05cm/sec. The $SrTiO_3$powders could not be synthesized from chloride aqueous solution. The prepared powders from nitrate aqueous solution was SrTi03 with cubic structure and nearly sphere particle for all samples. Mean particle size was increased from $0.49{\mu}m$ to $0.67{\mu}m$ by changing the carrier gas flow rate from O.5cm/sec to 1.5cm/sec. Also, mean particle size increased from $0.49{\mu}m$to $0.55{\mu}m$by changing the concentration of mother solution from O.05M to O.1M. Atomizing droplet size was $14.3{\mu}m$. The shape of particles was very porous by evaporation of solvent at the initial step. But through the each step upwards, shape of particles was formed themselves into a nearly roundish.

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Effect of Water Volume and Relaxation Time in the Design of Nano Shock Absorbing Damper Using Silica Particle (실리카 분말을 이용한 나노 충격완화 장치의 설계에서 작동 유체 영향과 복원 시간에 대한 연구)

  • 문병영;김병수
    • Journal of the Korean Ceramic Society
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    • v.40 no.3
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    • pp.286-292
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    • 2003
  • In this study, new shock absorbing system was proposed using silica gel particles according to the nano-technology. For the design and real application of the proposed damper, an experimental investigations are carried out using colloidal damper, which is statically loaded. The porous matrix is composed from silica gel(labyrinth architecture), coated by organo-silicones substances, in order to achieve a hydrophobic surface. Water is considered as associated lyophobic liquid. Reversible colloidal damper static test rig and the measuring technique of the static hysteresis were described. Iufluence of the water volume and particle diameters upon the reversible colloidal damper hysteresis was investigated. Also, influence of the relaxation time on the hysteresis of the damper was investigated. As a result, the proposed new shock absorbing damper is proved as an effective one, which can be replaced for the conventional hydraulic damper.

Fabrication of Porous SiC Ceramics by Partial Sintering and their Properties (부분소결공정에 의한 다공질 탄화규소 세라믹스의 제조 및 특성)

  • 김신한;김영욱;윤중열;김해두
    • Journal of the Korean Ceramic Society
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    • v.41 no.7
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    • pp.541-547
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    • 2004
  • Addition of large particles restrains densification by small particles in mixed particle systems. In the present study, large SiC whiskers or particles were introduced into small particles for restraining densification and the mixtures were sintered using yttrium aluminum garnet (Y$_3$A1$\sub$5/O$\sub$12/, YAG) as a sintering additive. By controlling the content of large SiC whiskers or particles and the applied pressure during sintering, porous SiC ceramics, with a porosity ranging from 0.3% to 39%, were fabricated. Porosity increased with increasing the content of restraining materials. SiC whiskers were more effective than large SiC partcles for restraining densification. Permeability of the porous SiC ceramics increased with increasing the porosity. Flexural strength decreased with increasing porosity. A noticeable increase in strain to failure was observed in the porous ceramics with a porosity ranging from 18% to 39%.

Experimental study of the heat pipe phenomenon in porous media heated from above (상부가열인 다공물질내의 열파이프 현상에 관한 실험적 연구)

  • 이진호;김홍제;함윤영;남궁규완
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.4
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    • pp.825-832
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    • 1988
  • An experiment was performed to study the heat pipe phenomenon of porous media heated above at one-dimensional steady state for the range of heat flux, 300 W/ $m^{2}$ ~ 2000w/ $m^{2}$. Glass beads, sand, and copper particles were used as porous media and distilled water was used as a working fluid. Result of experiment shows that the length of the two-phase zone increases with the decreasing particle size for the same heat flux. At relatively lower heat flux the length of the two-phase zone increases with the increasing heat flux, which contradicts the result of earlier work. However, its length remains nearly constant when the heat flux increases above a certain value. The length of the two-phase zone is proportional to the product of the heat flux by the hydrostatic capillary height under the limited value on heat flux, that is, $l_{t}$ = A(q. $l_{cap}$)+B, q.leg.1/A(C+B/ $l_{cap}$) where A is 1.7*10$^{-4}$ $m^{2}$/w, B is 1.9*10$^{-2}$ m, and C is 0.43 for copper particles and 0.31 for glass beads and sand.d.d.d.

PEALD과 ALD을 이용한 다공성 기판의 증착 특성 비교

  • Gang, Go-Ru;Cha, Deok-Jun;Kim, Jin-Tae;Yun, Ju-Yeong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.155.2-155.2
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    • 2014
  • Plasma Enhanced Atomic Layer Deposition(PEALD)와 Atomic Layer Deposition(ALD) Techniques는 '정확한 두께 조절' 및 '우수한 균일도'를 가지는 신뢰할 수 있는 진공 기술이다. 본 연구에서는 다공성 구조를 가지는 기판을 대상으로 PEALD와 ALD Techniques을 이용한 $Al_2O_3$ 형성 공정의 증착 특성을 비교하였다. 각 공정은 공통적으로 Tris-Methyl-Aluminium(TMA)을 첫번째 전구체로 사용하였고 purge gas로는 Nitrogen를 사용하였다. 그리고 두번째 전구체로 PEALD 공정에서는 Oxygen Plasma를 사용하였고 ALD 공정에서는 Water를 사용하였다. 복잡한 다공성 구조를 가지는 기판은 $TiO_2$ Nano-Particle paste과 colloidal Silver paste를 소결시켜 제작하여 사용하였다. 각 공정의 차이점을 비교하기 위해서 배기단에 Capacitor Diaphram Gauge(CDG)와 Residual Gas Analyzer(RGA)를 통해서 압력과 잔류 가스를 모니터하였다. 그리고 각 공정을 통해서 porous한 Nano-Particles Network에 형성된 $Al_2O_3$막의 특성을 비교하기 위해서 FE-SEM과 EDX를 통해서 관찰하였다. 또한 좀 더 자세한 비교 분석을 위해서 $Al_2O_3$ 막이 형성된 porous한 Nano-Particles Networks의 각 각의 particles들을 분산시켜 TEM과 AFM를 통해서 관찰하였다. 나아가 전기적 물성의 차이점을 비교하기 위해서 IV 및 CV를 측정하였다. 위의 일련의 비교 실험을 통해서 'PEALD과 ALD을 이용한 다공성 기판의 증착 특성'에 대하여 고찰하였다.

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Collection Characteristics of Wet-type Multi-layered and Multi-staged Porous Plate System (습식 다층 다단 다공성 플레이트 시스템의 집진특성)

  • Yoa, Seok-Jun;Kim, Joo-Yeon
    • Journal of Power System Engineering
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    • v.18 no.3
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    • pp.42-50
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    • 2014
  • The main object of this study is to investigate the collection characteristics of wet-type multi-layered and multi-staged porous plate system experimentally. The experiment is carried out to analyze the characteristics of pressure drop and collection efficiency for the present system with the experimental parameters such as water spray, inlet velocity, stage number and inlet particle concentration, etc. In results, for the present system of wet-type, the pressure drop represents 158 $mmH_2O$ higher 3% than that in dry-type at 5 stage and $v_{in}$=3.53 m/s. In case of 5 stage, $v_{in}$=3.53 m/s and water spray 250 ml/min, the collection efficiency of the present system becomes significantly higher as 99.7% comparing to that of the conventional wet-type scrubber. Additionally, for 5 stage and 250 ml/min, $SO_2$ removal efficiencies decrease with the increment of inlet velocity representing 75.0, 62.5, 50.0%, at $v_{in}$=2.12, 2.82, 3.53 m/s, respectively.

Preparation and Characterization of Monodisperse Porous Poly(acrylonitrile-ethylene glycol dimethacrylate) Microgels (단분산성 다공의 폴리아크릴로니트릴-에틸렌 글리콜 디메타크릴레이트 마이크로 겔의 제조 및 특성)

  • Kim, Kong-Soo;Kang, Seog-Ho;Kim, Young-Sik
    • Applied Chemistry for Engineering
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    • v.7 no.4
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    • pp.777-786
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    • 1996
  • Uniform sized-porous poly(acrylonitrile-ethylene glycol dimethacrylate) (PAN) microgels were synthesized by seed polymerization using monodisperse polystyrene seed particles. The effect of weight ratios of monomer/seed (M/S) and diluent/monomer (DIM), concentration of crosslinking agent and the type of diluent was investigated on the formation of PAN microgels. The particle size distribution of PAN microgels was found to be monodisperse in that the weight ratio of M/S is less than 50. More porous microgels were formed and the interstices between small sized interior microspheres present inside of PAN microgels were also smaller with increasing crosslinking agent concentration. Well-developed pore structure was found to be in that weight ratio of D/M is 1 and toluene is used as a diluent.

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Fabrication of Composite Filler Metal by Melt Infiltration (용탕 침투법을 이용한 복합 삽입 금속의 제조)

  • Park, Heung-Il;Kim, Ji-Tae;Kim, Woo-Yeol
    • Journal of Korea Foundry Society
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    • v.23 no.5
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    • pp.244-250
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    • 2003
  • The aim of this study is fabricating of composite filler metal (CFM) by a combination of selective laser sintering (SLS) of stainless steel powders (RapidSteel $2.0^{TM}$ and liquid phase infiltration of Ag-28 wt.%Cu alloy. Porous stainless steel body with inter-connected pore channels was fabricated by SLS, binder decomposing and densification processes. By the direct contact infiltration, the narrow inter-particle channels of the porous body were completely filled with the Ag-28 wt.%Cu alloy infiltrant. During infiltration, the dissolved elements of Fe, Ni and Cr from the porous body were solved into copper solid solution phases, which consist of eutectic structure of composite metal matrix. The S10C/CFM/S10C joints, which have narrow clearance gaps between them up to 10 micrometers, were joined successfully by self-feeding of filler metal from the matrix of CFM. The CFM kept its original thickness and microstructure after brazing. The tensile strength of brazed specimen was higher than 30 kgf/$mm^2$ and showed a typical ductile fracture mode in the CFM.

Low Temperature Processing and Properties of Porous Frit-Bonded SiC Ceramics (프릿을 이용한 다공질 SiC 세라믹스의 저온 제조 공정 및 물성)

  • Chae, Su-Ho;Kim, Young-Wook;Song, In-Hyuck;Kim, Hai-Doo;Bae, Ji-Soo;Na, Sang-Moon;Kim, Seung-Il
    • Journal of the Korean Ceramic Society
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    • v.46 no.5
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    • pp.488-492
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    • 2009
  • Porous frit-bonded SiC ceramics were successfully prepared at a temperature as low as $800^{\circ}C$ from SiC, frit, and microbeads (glass or polymer). The effects of SiC starting particle size and microbead addition on microstructure, porosity, and flexural strength were investigated. The addition of hollow glass microbead improved the strength of frit-bonded SiC ceramics without the loss of porosity by acting additional binder phase between SiC grains. The 65 ${\mu}m$-sized SiC resulted in lower porosity and higher strength than 50 ${\mu}m$-sized SiC because of higher packing density. Typical flexural strengths of frit-bonded SiC were 23 MPa at 46% porosity and 19 MPa at 49% porosity.