• Fibers and Polymers
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• 제5권1호
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• pp.31-38
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• 2004

In the present paper, a variety of fiber reinforcements, for instance, stabilized OXI-PAN fibers, quasi-carbon fibers, commercial carbon fibers, and their woven fabric forms, have been utilized to fabricate pseudo-unidirectional (pseudo-UD) and 2-directional (2D) phenolic matrix composites using a compression molding method. Prior to fabricating quasi-carbon fiber/phenolic (QC/P) composites, stabilized OXI-PAN fibers and fabrics were heat-treated under low temperature carbonization processes to prepare quasi-carbon fibers and fabrics. The thermal conductivity and thermal expansion/contraction behavior of QC/P composites have been investigated and compared with those of carbon fiber/phenolic (C/P) and stabilized fiber/phenolic composites. Also, the chemical compositions of the fibers used have been characterized. The results suggest that use of proper quasi-carbonization process may control effectively not only the chemical compositions of resulting quasi-carbon fibers but also the thermal conductivity and thermal expansion behavior of quasi-carbon fibers/phenolic composites in the intermediate range between stabilized PAN fiber- and carbon fiber-reinforced phenolic composites.

• 한국군사과학기술학회지
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• 제21권6호
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• pp.784-789
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• 2018

Accurate aerodynamic characterization of projectile is crucial for successful development of munition. The aerodynamic characterization of fin stabilized projectile is more difficult than characterization of traditional symmetric ballistic projectile. Instrumented free flight experiments were conducted to quantify rolling behavior of fin stabilized projectile. The instrumented projectiles were launched from a rifled tube and the onboard sensor data were acquired through a telemetry transmitter. Roll rate was measured for fin stabilized projectile by means of an angular rate sensor. And, roll damping coefficients were estimated from onboard sensor data acquired during gun firing and trajectory analysis of mathematical model.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.65-67
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• 2011

The moment-of-fluid (MOF) method is a new volume-tracking method that accurately treats evolving material interfaces. The MOF method uses moment data, namely the material volume fraction, as well as the centroid, for a more accurate representation of the material configuration, interfaces and concomitant volume advection. In this paper, unstructured mesh extension of the MOF method is to be presented. The MOF method is coupled with a stabilized finite element incompressible Navier-Stokes solver for two materials. The effectiveness of the MOF method is demonstrated with a free-surface dam-break problem.

• 전자공학회논문지CI
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• 제41권1호
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• pp.38-46
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• 2004

영상 분할은 영상을 의미 있는 영역들로 분할하기 위한 기법으로 컴퓨터 비전과 영상 처리 분야에서 중요하게 다루어져 왔다. 또한 영상 분할은 MPEG-4 비디오 표준과 같은 객체 기반 동영상 압축 분야에서도 영상에서 객체 영역을 분할하기 위해 많이 사용된다. 보다 정확한 영역 경계를 얻기 위해 Watershed 알고리즘이 많은 분야에서 적용되고 있다. 그러나 Watershed 알고리즘은 영상내의 경계선 잡음에 매우 취약하고 과분할된 결과가 나타난다고 알려져 있다. 이러한 문제를 해결하기 위해 본 논문에서는 안정화된 역 확산 방정식(Stabilized Inverse Diffusion Equation : SIDE)을 사용하여 잡음에 강인한 분할 특성을 가지면서 다중해상도 접근 방식을 통해 효율도 향상시키는 영상 분할 기법을 제안한다. 또한 본 논문에서는 인접 영역의 레이블을 사용한 영역 투영법과 영역 인접 그래프(Region Adjacency Graph : RAG)를 사용한 영역 병합법도 사용하였다. 제안된 기법을 잡음이 포함된 영상의 분할에 적용시킨 결과 과분할을 감소시키고 분할 효율이 개선됨을 확인할 수 있었다.

• Korean Chemical Engineering Research
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• 제43권5호
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• pp.627-631
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• 2005

고온수증기 전기분해의 양극물질로 이용될 수 있는 $(La_{0.8}Sr_{0.2})_{0.95}MnO_3$/yttria-stabilized zirconia(LSM/YSZ) 복합체 전극을 x-ray diffractometry, scanning electron microscopy 그리고 galvanodynamic, galvanostatic polarization method로 연구하였다. 이런 목적으로 perovskite-type의 LSM 물질은 공침법을 이용하여 제조하였으며, 8 mol% YSZ와 몰분율을 달리하여 복합체 전극을 합성하였다. LSM/YSZ 복합체 전극은 평판의 YSZ 전해질에 LSM/YSZ 복합체를 스크린 프린팅 후 $1,100^{\circ}C$에서 열처리 코팅하여 제조하였다. 실험결과로부터 LSM/YSZ 복합체 전극의 전기화학적 특성은 전극을 이루는 삼상계면의 구조와 전기분해 온도에 영향을 받는다는 것을 확인하였다.

• 한국군사과학기술학회지
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• 제21권4호
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• pp.508-519
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• 2018

This paper concerns on stabilization control of a gyro-stabilized 2-axes gimbal system which is mounted on a moving vehicles such as automobiles, armored vehicles, ships, flying vehicles, etc. A target image acquisition system is attached on the inner gimbal, and the gimbal systems are required to retain high stabilization accuracy in the absolute coordinate in order to provide fine target image while vehicle is moving. The stabilization control performance is hardly depended upon disturbance rejection ability of control, and disturbance feedforward compensation is effective because feedforward compensation reduce the amount of disturbance before the disturbance disturbs the systems. This paper suggests an experimental method which can estimate system parameters and disturbance torques by using 3-axes accelerometer mounted on the inner gimbal. Furthermore, a simple disturbance identification method which can be applied to any slanted base conditions has been suggested to identify mass unbalance vector and friction torques of each gimbal simultaneously. By using the estimated parameters, a feedforward compensation has been applied to the gyro-stabilized 2-axes gimbal system. The experimental results showed that the feedforward compensation based on the identification method suggested is effective to improve stabilization performances.

• 한국세라믹학회지
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• 제16권3호
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• pp.155-163
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• 1979

This study was to explore the characteristics of 6 mole% CaO stabilized $ZrO_2$ prepared by wet chemical methods. The results of the experiments were as follows: 1. The powder calcined at 1000$^{\circ}$-110$0^{\circ}C$ was partly agglomerated. The morphology of agglomerate was spherical of 0.5-1$\mu{m}$ in size for Hot Petroleum Drying Method, chain-like of 1-2$\mu{m}$ for Freeze Drying Method, and irreqular of 2-3$\mu{m}$ for Coprecipitation Method. 2. Optimum calcining conditions for powder prepared by wet chemical methods were found: 110$0^{\circ}C$, 2h in air for Hot Petroleum Drying Method and Freeze Drying Method, and 100$0^{\circ}C$, 2h in air for Coprecipitation Method. 3. When specimen was calcined at 1000$^{\circ}$-110$0^{\circ}C$ in air for 2h and then sintered at 1$600^{\circ}C$ in air for 4h, the specimens prepared by wet chemical methods showed a high sintered density (94% of theoretical density) and a low open porosity (<0.8%); however, the sintered density of the specimen prepared by Oxide Wet Mixing Method was 90%. 4. The amount of cubic phase of sintered body prepared by wet chemical methods was observed to be higher than the one prepared by Oxide Wet Mixing Method. 5. It was found that Hot petroleum Drying Method, Freeze Drying Method and Coprecipitation Method were nearly the same in respect of the results of stabilization grade and sintered density of CaO-stabilized $ZrO_2$.

• Korean Journal of Mathematics
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• 제21권2호
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• pp.125-150
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• 2013

The stabilized Gauge-Uzawa method (SGUM), which is a second order projection type algorithm to solve the time-dependent Navier-Stokes equations, has been newly constructed in 2013 Pyo's paper. The accuracy of SGUM has been proved only for time discrete scheme in the same paper, but it is crucial to study for fully discrete scheme, because the numerical errors depend on discretizations for both space and time, and because discrete spaces between velocity and pressure can not be chosen arbitrary. In this paper, we find out properties of the fully discrete SGUM and estimate its errors and stability to solve the evolution Navier-Stokes equations. The main difficulty in this estimation arises from losing some cancellation laws due to failing divergence free condition of the discrete velocity function. This result will be extended to Boussinesq equations in the continuous research (part II) and is essential in the study of part II.

• Korean Journal of Mathematics
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• 제27권1호
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• pp.193-219
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• 2019

The Navier-Stokes equations with variable density are challenging problems in numerical analysis community. We recently built the 2nd order stabilized Gauge-Uzawa method [SGUM] to solve the Navier-Stokes equations with constant density and have estimated theoretically optimal accuracy. Also we proved that SGUM is unconditionally stable. In this paper, we apply SGUM to the Navier-Stokes equations with nonconstant variable density and find out the stability condition of the algorithms. Because the condition is rather strong to apply to real problems, we consider Allen-Cahn scheme to construct unconditionally stable scheme.

• Ocean Systems Engineering
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• 제1권3호
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• pp.207-222
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• 2011

A stabilized incompressible smoothed particles hydrodynamics (ISPH) method is utilized to simulate free falling rigid body into water domain. Both of rigid body and fluid domain are modeled by SPH formulation. The proposed source term in the pressure Poisson equation contains two terms; divergence of velocity and density invariance. The density invariance term is multiplied by a relaxed parameter for stabilization. In addition, large eddy simulation with Smagorinsky model has been introduced to include the eddy viscosity effect. The improved method is applied to simulate both of free falling vessels with different materials and water entry-exit of horizontal circular cylinder. The applicability and efficiency of improved method is tested by the comparisons with reference experimental results.