• 대한기계학회논문집A
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• 제24권5호
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• pp.1297-1304
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• 2000

The reflective photoelastic experiment can be used more effectively than the transparent type in industrial fields. Therefore the reflective photoelastic experimental hybrid method applied to the fatigue fracture problems is introduced in this research. It is verified that the reflective photoelastic experimental hybrid method is very useful on the determination of crack propagation velocity and stress intensity factor of the fatigue crack and on the separation of stress components in the vicinity of fatigue crack tip etc.

• 한국환경과학회지
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• 제24권1호
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• pp.9-15
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• 2015

Sustainable and eco-friendly polymers, natural polymers, bio-based polymers, and degradable polyesters, are of growing interest because of environmental concerns associated with waste plastics and emissions of carbon dioxide from preparation of petroleum-based polymers. Degradable polymers, poly(butylene adipate-co-terephthalate) (PBAT), poly(propylene carbonate) (PPC), and poly(L-lactic acid) (PLLA), are related to reduction of carbon dioxide in processing. To improve a weak mechanical property of a degradable polymer, a blending method is widely used. This study was forced on the component separation of degradable polymer blends for effective recycling. The melt-mixed blend films in a specific solvent were separated by two layers. Each layer was analysed by FT-IR, DSC, and contact angle measurements. The results showed that each component in the PPC/PLLA and PPC/PBAT blends was successfully separated by a solvent.

• 한국수산과학회지
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• 제15권3호
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• pp.185-190
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• 1982

다획성 어종인 고등어, 정어리, 말쥐치 등을 연제품 기타 식품소재로 이용하기 위해서는 다양처리를 위한 기계처리가 필요하나 적색육조에 많은 혈합육의 분리가 어려워 품질에 문제점이 있다. 기계처리적정에서 보통육과 혈합육을 분리하는 방법으로 당용액의 비중차에 의한 분리유과를 검토한 결과를 요약하면 다음과 같다. (1) 보통육과 혈합육을 분리할 수 있는 유효비중한계는 고등어의 경우 $1.067\sim1.072$, 정어리의 경우$1.02\sim1.070$ 말쥐치의 경우 $1.073\sim1.077$였다. (2) 육립자의 크기에 따른 분리율은 chopper 세공판의 공경이 0.2cm일 때에 $90\%$였고 0.3cm일 때에 $60\%$였다. (3) 육립자의 밀도에 따른 분리효과는 당용액에서의 침강력 높이가 1.8cm정도, 즉 육입자 밀도 $1g/cm^2$일 때 분리율이 $92\%$였고, 즉 $5g/cm^2$일 매에는 $59\%$로 낮았다. (4) 자당용액에서는 부상분리층이 25분 경과하여도 침강하지 않았으나 포도당액에서는 5분후부터 서서히 침강하였다. (5)당용액의 비중이 높아짐에 따라서 유지의 분리율 높았으며 유효비중한계내에서도 $90\%$정도의 지방을 분리할 수 있었다.

• 한국세라믹학회지
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• 제47권6호
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• pp.515-523
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• 2010

Porous SiC candle filter preforms were fabricated by extrusion and ramming process. To fabricate SiC candle filter preform, commercially available F180 mesh ($85\;{\mu}m$) $\alpha$-SiC powder and $44\;{\mu}m$ mullite, $CaCO_3$ powder were used as the starting materials. The candle type preforms were fabricated by vacuum extrusion and ramming process, and sintered at $1400^{\circ}C$ 2 h in air atmosphere. Corrosion test of the sintered candle filter specimens as forming method was performed at $600^{\circ}C$ for 2,400 h in simulated IGCC syngas atmosphere. The effect of forming method on mechanical properties, pore distribution, microstructure and crystalline phase was investigated.

• 멤브레인
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• 제34권4호
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• pp.216-223
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• 2024

높은 내화학성과 소수성 특성을 갖는 polymethylpentene (PMP) 소재는 polypropylene 소재 대비 결정성이 낮아 dense skin층을 갖는 비대칭 분리막을 제조하기 수월하지만 녹는점이 높아 가공이 용이하지 않다. 본 연구에서는 비용매 유도상분리법(NIPS)과 열유도 상분리법(TIPS)을 혼합한 N-TIPS 법을 활용하여 polymethylpentene (PMP) 고분자 분리막을 제조하고 성능과 특성을 평가하였다. Cyclohexane을 용매로 사용하여 PMP 도프용액을 제조하였으며, 상전이조로 물, EtOH, IPA를 사용하였다. Cyclohexane과 섞이지 않는 물을 비용매로 상전이한 분리막은 TIPS 영향으로 인해 큰 기공과 높은 기체 투과도를 보였으나, 표면이 거칠고 구조가 불안정한 특성을 보였다. 반면, cyclohexane과 혼합될 수 있는 알코올류(ethanol, isopropanol)를 상전이조로 사용한 경우 NIPS 효과로 인해 dense skin층이 형성됨을 확인하며, 높은 기계적 강도를 보였다. 추가적인 기공형성을 위해 polyethylene glycol (PEG)를 첨가한 경우 기체투과도가 높아지는 결과를 얻을 수 있었다.

• Journal of Mechanical Science and Technology
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• 제14권4호
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• pp.448-455
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• 2000

The bow wave breaking and the viscous interaction of stern wave are studied by simulating the free-surface flows. The Navier-Stokes equation is solved by a finite difference method in which the body-fitted coordinate system, the wall function and the triple-grid system are invoked. After validation, the calculations are extended to turbulent flows. The wave elevation at the Reynolds number of $10^4$ is much less than that at $10^6$ although the Froude number is the same. The numerical appearance of the sub-breaking waves is qualitatively supported by experimental observation. They are also applied to study the stern flow of S-103 for which extensive experimental data are available. Although the interaction between separation and the stern wave generation are not yet clear, the effects of the bow wave on the development of the boundary layer flows are concluded to be significant.

• International Journal of Fluid Machinery and Systems
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• 제9권1호
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• pp.95-106
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• 2016

A method of optimization design for the blade profile of a centrifugal impeller by controlling velocity distribution is presented, and a plenum fan is successfully designed. This method is based on the inner flow calculation inside the centrifugal impeller, and is related to the distribution of relative velocity. The results show that after optimization, the boundary layer separation on the suction surface has been inhibited and the stability of plenum fan is improved. The flow at the impeller outlet is also studied, and the jet-wake pattern at the impeller outlet is improved obviously by optimization. The calculation result shows that the static pressure and static pressure efficiency can be increased by 15.4% and 21.4% respectively.

• 대한기계학회논문집
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• 제14권3호
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• pp.725-733
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• 1990

본 연구에서는 Raju등의 연구의 확장으로 일정한 온도로 유지되는 경사진 평 판에 대하여 혼합대류 전 영역에 유효한 부력계수(.xi.)로서 (1+Gr$^{2}$$_{x}$cos.gamma./ Re$^{4}$$_{x}$)$_{-1}$를 적용하여 비상사 경계층 방정식을 유도하였다. 또한 적분 형 경계조건을 가진 편미분 경계층방정식을 유한차분법으로 Keller와 Cebeci의 Box scheme을 6차로 적용하여 수치해석하였다. 부력계수가 큰 영역에서 Mucoglu등의 해 석적 연구결과는 일정한 온도와 45˚의 경사를 유지하는 평판에 대한 Ramachandran의 실험적 연구결과와 약 10%정도 벗어난다. 이에 Ramachandran의 실험적 연구를 해석 적으로 재고찰하였다.하였다.

• Structural Engineering and Mechanics
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• 제35권2호
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• pp.217-240
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• 2010

A semi-analytical method is presented for accurately prediction of the free vibration behavior of generally laminated composite plates with arbitrary boundary conditions. The method employs the technique of separation of spatial variables within Hamilton's principle to obtain the equations of motion, including two systems of coupled ordinary homogeneous differential equations. Subsequently, by applying the laminate constitutive relations into the resulting equations two sets of coupled ordinary differential equations with constant coefficients, in terms of displacements, are achieved. The obtained differential equations are solved for the natural frequencies and corresponding mode shapes, with the use of the exact state-space approach. The formulation is exploited in the framework of the first-order shear deformation theory to incorporate the effects of transverse shear deformation and rotary inertia. The efficiency and accuracy of the present method are demonstrated by obtaining solutions to a wide range of problems and comparing them with finite element analysis and previously published results.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.407-410
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• 2006

This study describes a simulation of two-dimensional bubble forming and motion by the Lattice Boltzmann Method with the phase field equation. The free energy model is used to treat the interfacial force and deformation of binary fluids system, drawn into a T-junction the micro channel. A numerical simulation of a binary flow in a cross-junction channel is carried out by using the parallel computation method. The aim in this investigation is to examine the applicability of LBM to numerical analysis of binary fluid separation and motion in the micro channel.