• 대한기계학회논문집B
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• 제29권1호
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• pp.151-158
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• 2005

A characteristic of discharge for a foam spray nozzle with various parameters was investigated. The discharge patterns from a fire foam spray nozzle are important to evenly spray over a maximum possible floor area. Two parameters of a foam spray nozzle were chosen, and compared with those from the standard one. Also, in order to evaluate the performance of discharged foam agents used to protect structures from heat and fire damages, the thermal characteristics of fire-protection foams were experimentally investigated. A simple repeatable test for fire-protection foams subjected to fire radiation was developed. This test involves foam generation equipment, a fire source for heat generation, and data acquisition techniques. Results show that the bubble size of foam is increased by large inside diameter of orifice or closed air hole, but phenomenon of discharge angle and expansion ratio is opposite. For the case of the open air hole, liquid film of a circular cone discharges with formation, growth, split and fine grain. In case of the closed air hole, a pillar of foam solution discharges with that. Though the temperature gradient in the foam increases with increased foam expansion ratio. it is not change with increased intensity of heat flux.

• 한국컴퓨터그래픽스학회논문지
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• 제23권2호
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• pp.29-39
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• 2017

본 논문에서는 효율적이고 사실적으로 수면거품과 웨이브거품을 표현할 수 있는 통합된 프레임워크를 제안한다. 이 프레임워크는 거품입자가 생성되어야 하는 곳을 결정할 때 발생하는 계산 복잡도를 줄이기 위해 3차원 공간의 물 입자들을 2차원 스크린 공간으로 투영하도록 설계되었다. 거품효과는 빠르고 복잡한 물의 흐름에서 생성되기 때문에, 가속도와 곡률 값을 분석하여 복잡한 유체의 흐름 패턴을 갖는 영역을 2차원에서 찾고 이를 3차공간으로 변환한다. 변환된 3차원 영역에서 거품입자가 방출되고, 각 거품입자는 속도가 따라 분류되며, 그 종류에 따라 다르게 이류됨으로써 웨이브거품의 본질적인 특징을 잘 포착해 낸다. 우리는 거품입자들을 두 가지 유형인 수면 거품과 웨이브거품으로 분류하여 결과적으로 거품의 사실감을 향상시킨다. 웨이브거품은 급류와 같은 부분에서 날카로운 웨이브패턴이 표현되는 특징이 있고, 수면거품은 느린 유속에서 뿌연 거품형태로 표현되는 특징이 있다. 이러한 특징을 표현하기 위해 거품입자의 속도와 위치를 올바르게 가이드해주는 기법을 제안한다. 또한 스크린공간의 밀도를 이용한 커널함수를 제안한다. 이 함수를 이용하여 거품입자의 속도와 위치를 올바르게 조정하여 불필요한 거품입자들을 효율적으로 제거하며, 결과적으로, 거품효과의 시각적인 손실없이 전반적인 메모리 효율성을 향상시켰다. 우리는 신빙성있는 실험결과를 보여주며 제안된 접근법은고품질의 결과를 제공하는 동시에 사용하기 쉽다는 장점이 있다.

• 대한기계학회논문집A
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• 제27권5호
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• pp.772-778
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• 2003

Polystyrene foam is easily melted and vapoured by heat, has a proper quality in the pattern manufacturing and has a low price. The objective of this study is to develop a rapid prototyping method fur polystyrene foam pattern manufacuring to use the eliminative pattern casting (EPC). Applying fur the rapid prototyping concept reversely, the unnecessary part of section is vapored away by heat source of laser beam. In order to examine the applicability between laser beam process and polystyrene foam material, the basic experiments such as hole, line, plane and contour process are carried out. With these results, various three-dimensional shape patterns are made and this rapid prototyping tool for polystyrene foam manufacturing.

• 한국전산유체공학회지
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• 제18권2호
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• pp.49-55
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• 2013

The goal of the research is to evaluate the open source code of OpenFOAM for the use of nuclear plant flow simulation objectively. Of the various incompressible flow solvers, simpleFoam, pimpelFoam are then tested under three validated cases (backward facing step, flow over circular cylinder and turbulent round jet flow). For the evaluation of steady state incompressible laminar flow simulation, low reynolds number of backward facing step flow was solved by simpleFoam. The resultant of the reattached lengths turned out to be similar with the other experimental and simulation results. For transient flow simulation, flow over circular cylinder and turbulent round jet flow were solved by pimpleFoam. The simulation accuracy was evaluated by comparing the resultant flow patterns with the description of the characteristics of the flow over the circular cylinder. The quantitative accuracy was evaluated for no more than 85% by comparing it to the decaying constants of the turbulent round jet velocity.

• Steel and Composite Structures
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• 제23권1호
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• pp.107-114
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• 2017

Design of stepwise foam claddings subjected to air-blast is performed based on random Voronoialgorithm. FE models are constructed using the random Voronoialgorithm, and numerical analysis is carried out to simulate deformation mode and energy absorption of the cladding by the ABAQUS/Explicit software. The FE model is validated by test result, and good agreement is achieved. The deformation patterns are presented to give an insight into the influences of distribution on deformation mechanisms. The energy absorbed by the stepwise foam cladding is examined, and the parameter effects, including layer number, gradient, and blast loading, are discussed. Results indicate that the energy absorption capacity increases with the number of layer, gradient degree, and blast pressure increasing.

• Steel and Composite Structures
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• 제46권5호
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• pp.649-658
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• 2023

Although some scholars have studied the thermal post-buckling of graphene platelets strengthened metal foams (GPLRMFs) plates, they have not considered the influence of initial geometrical imperfection. Inspired by this fact, the present paper studies the thermal post-buckling characteristics of GPLRMFs plates with initial geometrical imperfection. Three kinds of graphene platelets (GPLs) distribution patterns including three patterns have been considered. The governing equations are derived according to the first-order plate theory and solved with the help of the Galerkin method. According to the comparison with published paper, the accuracy and correctness of the present research are verified. In the end, the effects of material properties and initial geometrical imperfection on the thermal post-buckling response of the GPLRMFs plates are examined. It can be found that the presence of initial geometrical imperfection reduces the thermal post-buckling strength. In addition, the present study indicates that GPL-A pattern is best way to improve thermal post-buckling strength for GPLRMFs plates, and the presence of foams can improve the thermal post-buckling strength of GPLRMFs plates, the Foam- II and Foam- I patterns have the lowest and highest thermal post-buckling strength. Our research can provide guidance for the thermal stability analysis of GPLRMFs plates.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.198-201
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• 2004

This paper aims to investigate the micro-mechanical behaviour of tow geometry with forming pressures and densities of foams during the curing process of plain weave carbon fibre fabric prepregs onto polymer foams. In order to find out and compare deformation patterns between different forming conditions, tow parameters such as amplitude and crimp angle etc. are investigated. From the observation results, geometric difference in the tow architecture with respect to forming conditions and foam characteristics were found. To observe the micro-deformation of the fabric structure, appropriate specimens from carbon fibre-foam sandwich structures are sectioned and observed under the microscope.

• 한국재료학회지
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• 제23권1호
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• pp.24-30
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• 2013

Today, the modification of carbon foam for high performance remains a major issue in the environment and energy industries. One promising way to solve this problem is the optimization of the pore structure for desired properties as well as for efficient performance. In this study, using a sol-gel process followed by carbonization in an inert atmosphere, hollow spherical carbon foam was prepared using resorcinol and formaldehyde precursors catalyzed by 4-aminobenzoic acid; the effect of carbonization temperature and re-immersion treatment on the pore structure and characteristics of the hollow spherical carbon foam was investigated. As the carbonization temperature increased, the porosity and average pore diameter were found to decrease but the compression strength and electrical conductivity dramatically increased in the temperature range of this study ($700^{\circ}C$ to $850^{\circ}C$). The significant differences of X-ray diffraction patterns obtained from the carbon foams carbonized under different temperatures implied that the degree of crystallinity greatly affects the characteristics of the carbon form. Also, the number of re-impregnations of carbon form in the resorcinol-formaldehyde resin was varied from 1 to 10 times, followed by re-carbonization at $800^{\circ}C$ for 2 hours under argon gas flow. As the number of re-immersion treatments increased, the porosity decreased while the compression strength improved by about four times when re-impregnation was repeated 10 times. These results imply the possibility of customizing the characteristics of carbon foam by controlling the carbonization and re-immersion conditions.

• Composites Research
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• 제17권2호
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• pp.34-39
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• 2004

본 연구에서는 폐쇄형 발포금속의 인장 특성을 이해하기 위하여 수정된 단위모델을 제시하였다. 또한 발포금속의 밀도는 가우스 분포에 의거하여 확률적으로 분포한다고 가정하고 본 연구에서 제시된 수정 단위 모델을 조합하여 유한요소 모델을 제안하였다. 이 모델은 실제 인장 시험과 유사한 변형거동을 보이는 것을 확인하였고, 적절한 밀도 분포와 내부 기공을 고려하게 되면, 해석에서 구해진 최대 인장 강도가 근사적으로 실험결과와 일치하는 것을 볼 수 있었다. 또한, 발포 알루미늄의 최대 인장 강도는 밀도 분포의 표준편차보다는 내부 기공 부피분율에 더 민감하게 변하는 것으로 밝혀졌다.

• 한국정보통신학회논문지
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• 제7권8호
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• pp.1598-1603
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• 2003

위성방송 수신용 마이크로스트립 안테나를 설계하고 이를 제작하여 안테나 성능을 측정하였다. 마이크로스트립 패치 모양은 Sierpinski 프랙탈 구조를 가지는 정삼각형 패치를 이용하였고 안테나 구조는 다층의 SSFIP(slot­strip­foam­inverted patch) 구조를 이용하였다. Sierpinski 프랙탈 구조가 가지는 특징을 이용하여 원형 편파 발생을 위한 sequential 회전 기법을 적용하였으며, 이를 기본 안테나로 하여 8${\times}$2 배열 안테나로 확장하였다. 제작된 안테나의 반사계수와 방사패턴의 측정 결과 시뮬레이션 결과와 비슷한 결과를 얻었다.