• Korean Chemical Engineering Research
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• 제47권1호
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• pp.59-64
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• 2009

본 연구에서는 대기압 플라즈마를 이용하여 polylactic acid(PLA) 필름의 표면 특성 변화를 알아보았다. 극성 용매인 물과 비극성 용매인 Diiodomethane을 사용하여 표면의 접촉각을 측정하고, 이 값을 이용해 표면자유에너지 값을 계산하였다. 또한 대기압 플라즈마의 처리 조건에 따른 PLA 필름의 접촉각과 표면자유에너지 값을 최적화하였다. 그 결과 대기압 플라즈마 처리 시간 30 sec, RF-power 70 W, Ar 가스 유량은 6 lpm, 공기 중의 노출 시간은 5 min이었을 때가 가장 낮은 물 접촉각을 나타내었고, 표면자유에너지는 가장 높은 값을 나타내었다. XPS 분석을 통해서 대기압 플라즈마 처리 전 후 PLA 필름의 화학적 관능기의 변화를 분석하였으며, PLA 표면에 -C=O, -CO, -COO 등의 변화를 관찰하였다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.251-257
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• 2000

A numerical simulation of the temperature rise for sliding surface in dry contact is based on Jaeger's formula combined with a calculated heat input. A gear tooth temperature analysis was performed. The pressure distribution has the Hertzian pressure distribution on the heat source. The heat partition factor is calculated along line of action. A Temperature distribution of tooth surface is calculated about before and after profile modification. A Temperature of addendum and deddendum in modified gear have reduced.

• Journal of Advanced Marine Engineering and Technology
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• 제25권2호
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• pp.331-337
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• 2001

A numerical simulation of the temperature rise for sliding surface in dry contact is based on Jaegers formula combined with a calculated heat input. A gear tooth temperature analysis was performed. The pressure distribution has the Hertzian pressure distribution on the heat source. The heat partition factor is calculated along ling of action. A Temperature distribution of tooth surface is calculated about before and after profile modification. A Temperature of addendum and deddendum in modified gear have reduced.

• Wind and Structures
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• 제2권4호
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• pp.253-266
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• 1999

This paper presents the effects of free-stream turbulence on streamwise surface pressure fluctuations on two-dimensional rectangular cylinders. Particular attention is given to possible effects of turbulence integral scale on fluctuation and peak pressures. The mean, standard deviation, peak pressure coefficients, spectra and cross-correlation of fluctuating pressures were measured to investigate the nature of the separation and reattachment phenomenon in turbulent flows over a wide range of turbulence intensity and integral scale.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.16-16
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• 2014

본 논문에서는 polymer 기판 위에 direct inkjet patterning을 효율적으로 수행하기 위하여 기판 표면의 chemical bonding과 morphology를 in-line system 적용이 가능한 near atmospheric pressure plasma (N-APP)를 이용 하여 기판을 modifying 시켰다. modified substrate 위에 inkjet printing을 이용하여 metal interconnection을 하였다. 그 결과 기존 기판에서의 line width 보다 얇은 선폭을 획득 하였고 adhesion이 향상 되었다.

• Journal of applied mathematics & informatics
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• 제26권1_2호
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• pp.45-60
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• 2008

Here we consider the evaluation of the the dynamic component of the second order force due to wave diffraction by a circular cylinder analytically and numerically. The cylinder is fixed, vertical, surface piercing in water of finite uniform depth. The formulation of the wave-structure interaction is based on the assumption of a homogeneous, ideal, incompressible, and inviscid fluid. The nonlinearity in the wave-structure interaction problem arises from the free surface boundary conditions, namely, dynamic and kinematic free surface boundary conditions. We expand the velocity potential and free surface elevation functions in terms of a small parameter and then consider the second order diffraction problem. After deriving the pressure using Bernoulli's equation, we obtain the analytical expression for the dynamic component of the second order force on the cylinder by integrating the pressure over the wetted surface. The computation of the dynamic force component requires only the first order velocity potential. Numerical results for the dynamic force component are presented.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.297-300
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• 2002

In this study, the deformation of the free surface motion of a magnetic fluid for the change in electromagnetic force is discussed and carried out theoretically and experimentally on the basis of Rosensweig Ferrohydrodynamic Bernoulli Equation. While applied magnetic fields are induced by 4$\times$4 electromagnet located under the magnetic fluid, the surface of the magnetic fluid is formed the balance of surface force, gravity, pressure difference, magnetic normal pressure and magnetic body farce. In case, magnetic fluid in characteristics of fluid adjusted to the opposite direction of the gravity direction. thus, the device of a magnetic fluid proposed the surface actuator. The device of surface deformation as well comparison between numerical simulation and experiments as will be presented.

• Tribology and Lubricants
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• 제19권6호
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• pp.357-364
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• 2003

The sub­surface stress field beneath the gear's contact surface caused by the contact pressure in lubricated condition has been calculated. To evaluate the influence of the clearance shape on the stress field, two kinds of tooth profile models were chosen. One is the conventional cylinder contact model and the other is the new numerical model. Love's rectangular patch solution was used to obtain the sub­surface stress field. The analysis results show that the sub­surface stress is quite dependent on both the contact pressure and the profile model. The maximum effective stress of the new model is lower than that of the old model. The depth where the maximum effective stress occurs in the new model is not proportional to the intensity of the external load.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.970-976
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• 1997

The ultra-precision machining is widely used for final machining process of precision parts, so in this study, mirror surface finishing systems using the micro abrasive film, one of ultra-precision machining method, have to examine mirror surface characteristics of the cylindrical workpiece(SM45) such as surface roughness, workpiece removal and evaluated under the condition varing film feed rate, applied pressure, grinding speed after fixing other condition. It was found that varrious machining condition have significant influences on workpiece removal, surface roughness.

• 한국전산구조공학회논문집
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• 제20권5호
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• pp.551-556
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• 2007

소화시스템에 사용되는 고압의 소화가스 저장용기에는 저장용기의 파손을 막아주는 안전밸브가 있다. 이러한 안전밸브의 내부에는 원형 박판의 파열 판이 들어 있는데, 저장용기의 내압이 위험수준에 도달하면 파열 판이 파손하여 내압을 배출하는 역할을 한다. 안전밸브의 설계인자는 파열 판의 두께, 안전밸브의 유로 직경, 플라스틱 패킹 링의 내부 직경 그리고 파열 판을 고정하는 볼트 안쪽의 필렛 반경이 있다. 이중에서 파열 판의 두께는 0.2mm로 고정을 하였다. 요인배치법을 사용하여 주효과를 결정하였고 회귀방정식을 유도하였다. 이러한 회귀방정식은 추후 안전밸브의 설계에 있어서 기초 설계 자료로서 활용할 수 있도록 실험 결과와 비교하여 검증하였다. 검증실험 및 회귀방정식에 의한 결과의 오차는 약 $2{\sim}5%$ 정도인 것을 확인하였다. 그리고 반응표면법을 사용하여 기밀테스트 압력인 25MPa에서 파열할 수 있는 안전밸브의 최적 모델을 결정하였다.