• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.10a
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• pp.119-120
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• 1999

응집은 입자들간의 상대운동에 의하여 두 입자가 충돌하여 하나의 입자가 되는 것을 말하는데, 상대 운동을 유발하는 원인에 따라 중력응집(gravitational coagulation)을 비롯하여 브라운응집(Brownian coagulation), 난류응집(turbulent coagulation)등으로 나뉜다. 브라운응집 및 난류응집에 비하여 상대적으로 중력응집은 해석적으로 풀기가 어렵고 실험에 대한 연구가 국내외는 물론 외국에서도 전무한 실정이다.(중략)

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.7
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• pp.555-563
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• 2012

In earth orbit, a great number of orbital debris move around in extremely high velocity, and they become serious threats to satellites. In this study, smoothed particle hydrodynamics(SPH) is used to analyze the damage of a low earth orbit satellite due to the hypervelocity impact with orbital debris. The damage of honeycomb sandwich panel(HC/SP) used for walls of a satellite is analyzed with respect to impact velocities. For the additional analysis to examine the safety of interior components of the satellite, an attached electronic box and an offset electronic box are considered. As a result of the analysis considering the orbital debris having a probability of collision more than 2% at altitude of 685km, it is shown that the HC/SP can be perforated but only small craters are formed on both the attached electronic box and the offset electronic box.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.131-131
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• 2010

원자의 여기 및 천이에 의한 플라즈마에서의 빛 방출은 일차적으로 여기를 위한 특정 문턱값 이상의 에너지 공급이 전제 된다. 진공 플라즈마에서 대부분의 에너지 전달 과정은 전자와의 물리적 충돌에 의해 일어나므로 충돌 여기의 결과 발생한 광신호 세기는 전자 에너지 분포에 대한 정보를 내포하고 있다. 전자는 입자들 간의 에너지 전달 매개가 되는 동시에 플라즈마 구성 입자 중 가장 가벼워 빠르게 주변 환경 변화에 응답하여 열평형을 이루므로 EEDF는 플라즈마의 미세한 변동까지도 보여줄 수 있는 인자가 된다. 플라즈마의 열평형 이동에 관한 정보를 광신호로부터 EEDF의 형태로 추출해내기 위해 BEB (Binary - Encounter - Bethe) 모델을 근거로 충돌 반응 단면적을 함수로 나타내어 신호를 분석하였다. EEDF의 꼴을 $f(E)=AEexp(-E^b)$의 임의의 형태로 두고 아르곤의 427nm, 763nm 두 빛의 세기 비를 BEB 모델을 적용하여 전개한 결과 b factor 의 값을 구할 수 있었다. b factor 가 1인 경우는 Maxwellian, 2인 경우는 압력이 높은 조건에서 잦은 충돌에 의한 에너지 손실 때문에 고에너지 전자군이 현격하게 감소된 Druyvesteyn 분포를 의미하므로 광신호에 모델을 적용하여 얻은 b factor의 변화는 EEDF의 형태 자체의 변화가 감지되었음을 보여준다. 실제로 13.56MHz - 1kW ICP 장치에서 아르곤 플라즈마를 발생시켰을 때, 압력이 낮아 Maxwellian 분포가 예상되는 10mTorr 조건에서는 b=1.13, Druyvesteyn 분포에 가까워지는 100mTorr 조건에서는 b=1.502 로 관측되었다.

• Journal of the Korean Vacuum Society
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• v.10 no.3
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• pp.283-288
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• 2001

We have investigated aluminum cluster deposition using a classical molecular dynamics simulations. We studied the variations of the cluster momentum and the impulse force during collisions, and found that the close-packed cluster impact has some of properties of the single particle collision and the linear atomic chain collisions. We also simulated the series of energetic cluster deposition with energy Per atom. When energy Per atom in cluster has some eV rather than very low, the intermixing occurred easily in growth film and we can obtain a good film without subsequent annealing process.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.10a
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• pp.2-2
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• 1999

본 연구에서는 액체 로켓용 추진제 분사기로 많이 활용되는 충돌형 분사기중에서 2중 충돌(F-O-O-F)형 분사기에 대한 미립화 특성을 파악하였다. 액적의 크기를 측정하기 위하여 위상/도플러 입자분석기를 사용하였으며, 모의 추진제로 물을 사용하였다. 모의 추진제의 운동량비와 압력 강하량 변화에 따른 2중 충돌(F-O-O-F)형 분사기의 미립화 특성과 크기분포에 대하여 고찰하였다. 분사기 면으로부터 100mm 떨어진 단면에서 산화제/연료의 운동량비가 MR=1.19에서 MR=6.48까지 증가함에 따라 액적크기(SMD)는 감소하였으며, 액적크기(SMD)가 운동량비(MR)에 대하여 SMD= 193.480+15.687MR-5.036M$R^2$+0.415MR$^3$와 같은 관계식에 근사되었다 또한, 연료와 산화제의 압력강하량이 증가할수록 액적크기(SMD)가 감소하였다. 충돌 분무유동장의 액적크기 분포는 Rosin-Rammler 분포함수와 Upper-limit분포함수 모두에 대하여 잘 일치하고 있다. 본 연구의 결과는 액체 로켓용 충돌형 분사기의 초기 설계단계에서 유용하게 사용될 수 있을 것이다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.7
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• pp.595-600
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• 2014

The characteristics of kinetic energy transfer during a collision between a rigid target particle on a surface and a fragile bullet particle moving at a high velocity were analyzed using molecular dynamics simulation. Bullet particles made of $CO_2$ were considered and their size, temperature, and velocity were varied over a wide range. The fraction of kinetic energy transferred from the bullet particle to the target particle was almost independent of the former's size or velocity; however, it was sensitively dependent on its temperature, which can be attributed to the change in the bullet rigidity with temperature. This fraction was nearly twice as high for $CO_2$ bullets as for Ar bullets. This result explains the reason for the more superior cleaning performance of $CO_2$ bullets than Ar bullets with regard to contaminants in the 10 nm size range.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1802-1812
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• 2001

The purpose of this study is to analyze numerically the movement of particles included in turbulent fluid flow characteristics of metallic surfaces. To describe fluid flew, the incompressible Navier-Stokes equation discretized by the finite volume method were solved on the non-orthogonal coordinates with non-staggered variable arrangement, and the k-$\xi$ turbulence model was adapted. After fluid flow was calculated, particle movement was predicted from the Lagrangian approaches. Non-essential complexities were avoided by assuming that the particles had spherical shapes and the Stoke's drag formula only consisted of external farces acting upon them. In order to validate the numerical calculations, the results were compared with the experimental data reported in literature and agreed well with them. The drag force coefficient equation showed better agreement with the experimental data in the prediction of particle movement than the correction factor equation. Impact velocity and impact angle increased as inlet turbulence intensity decreased, relative jet height was lower. or the Reynolds number was larger.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.1
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• pp.27-31
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• 2015

The degradation of refractories can be caused by erosion, friction of abrasive particles, as well as by corrosion by molten slag in the gasification reactors. There was little knowledge about the erosion of refractories so far. The castable refractories of which the maximum applying temperature of 1300 and $1500^{\circ}C$ were abraded using SiC particles varying the incidence angles. It was revealed that the maximum abrasion was occurred at the incidence angle of $60{\sim}75^{\circ}$ not at $90^{\circ}$ and thought that the porosity of the refractories was the principle factor.

• Bulletin of the Korean Space Science Society
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• 2007.10a
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• pp.74.2-74.2
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• 2007

• Bulletin of the Korean Space Science Society
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• 1999.04a
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• pp.42-42
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• 1999