• Journal of the Korean Society of Combustion
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• v.8 no.2
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• pp.17-26
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• 2003

The objective of present study is to understand the interaction of burning droplets in air stream for various droplet arrangement. The unsteady combustion of linearly arranged droplets with a convective flow has been studied numerically. The droplets with spacing of $5R_0\;to\;40R_0$ horizontally and with spacing of $4R_0\;to\;16R_0$ vertically are studied. The effects of Reynolds number, horizontal spacing, and vertical spacing on the interaction of burning droplets are examined. The results indicate that the droplet burning behavior is influenced by Reynolds number and relative location of droplets in the array. The interaction of droplets is increased for arrays with smaller droplet spacing. The vaporization of droplets in the array is varied with both horizontal and vertical spacing exponentially.

• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.132-137
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• 2005

The burning characteristics of interacting spherical droplet in a turbulent flow are numerically investigated. The transient combustion of 3-dimensionally arranged droplets, both the fixed streamwise droplet distances of 3 radii and 10 radii and different turbulence intensities, is studied. The results obtained from the present numerical analysis show that droplet vaporization rate for heptane droplet is insensitive to turbulence intensity, and that the transient flame configuration and retardation of droplet surface temperature augmentation with streamwise droplet spacing substantially influence vaporization process of interacting droplets. Single flame mode in which individual flames are merged into single flame, with decreasing streamwise droplet spacing, becomes faster. Therefore, vaporization rate of the second droplet with decreasing streamwise droplet spacing decreases remarkably with flame movement.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.47-53
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• 2007

The laminar combustion characteristics of interacting coal particles in a convective flow are numerically investigated at particle arrangement and size difference. The numerical simulations, which use the two-step global reaction model to account for the surrounding gas effect, show the detailed interaction among the inter-space particles, undergoing devolatilization and subsequent char burning. Several parametric studies, which include the effect of the gas temperature (1700 K), high pressure(10 atm) and variation in geometrical arrangement of the particle diameter on the volatile release rate and the char combustion rate, have been carried out. The comparison indicates that the shift to the multiple particle arrangement resulted in the substantial change of the combustion characteristics and that the volatile release rate of the interacting coal particles exhibits a strong dependency on the particle spacing and size difference.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.194-195
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• 2006

미래의 전력 시스템은 환경과 기술적인 이유로 인해 더욱더 많은 분산전원을 이용하게 될 것이다. 분산전원은 서로 다른 특징을 가지고 있고 또한 배전계통에서 기존의 계통운영과는 다른 형태로 운전될 것이다. 이런 관점에서 다수의 분산전원을 모아 하나의 가상의 발전소로 운영하는 개념이 등장하게 되었는데, 이를 Virtual Power Plant(VPP)라고 한다. VPP는 매니지먼트 시스템이 관리하는 여러 클러스터들로 이루어져 있으며 이들 클러스터들은 각각 여러 종류의 분산전원으로 구성되어 있다. 본 논문에서는 클러스터를 이루는 분산전원을 어떻게 운영하는 것이 최적의 경제적 효율을 지닐 수 있을 지에 대해 논의하게 될 것이다. 디젤 발전기의 출력의 경우 그 소유자에 의해 제어가 가능하지만, 태양광 발전 시스템의 경우 기상 상태에 따라 그 출력이 결정된다. 따라서 이러한 각각의 특성을 고려하여 본 논문에서는 디젤, CHP(Combined Heat and Power), 보일러, 태양광발전으로 구성된 복합 시스템에서 각 시간별로 수용가의 전력 및 열 수요와 분산전원의 에너지 생산을 비교하여 VPP 최적 운영 계획을 구성하였다.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1308-1311
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• 1996

We propose a new linearized model which can be used very efficiently for the design and analysis of the autopilot of aerodynamically controlled skid-to-turn missiles. Proposed model is based on the linearized equations of the missile dynamics derived in the aerodynamic frame where xz plane contains the missile longitudinal axis and velocity vector. However, to take the effect due to the small perturbation of the missile body into consideration, we introduce a new frame which is identical to the aerodynamic frame in the trim state but after small perturbation it moves fixed with the missile body, and finally, the proposed model is set up in this frame. It is shown by nonlinear simulations and stability analysis of a numerical example that the new model describes the missile motion better than the conventional one linearized in the body frame with a certain amount of simplification.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.7
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• pp.245-252
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• 1996

$\lambda$/4 phase-shifted DFB lasers with nonideal grating structure have been studied by using an effective-index transfer matrix method where material dispersion, vwaveguide dispersion and waveguide-structuredependent loss are taken into consideration. Nonideal grating structure in the center phase-shift region does not incur serous degradation of laser characteristics. Phase-shift error from the ideal shift of $\pi$ causes a decrease in the threshold gain difference and lasing wavelength shift and should be less than $\pi$/4 when residual facet reflectivity is 0.7%. also, positional error of the phase-shift should be less than 9% of the cavity length in order for the threshold gain difference to be decreased less than 10%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.257-265
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• 2009

The present study deals with the leading edge shape on a wing-body junction to decrease a horseshoe vortex, one of the main factors to generate the secondary flow losses. The shape of leading-edge is optimized with design variables form the leading-edge shape. Approximate optimization design method is used for the optimization. The study is investigated using $FLUENT^{TM}$ and $iSIGHT^{TM}$. As the result, total pressure coefficient of the optimized design case was decreased about 9.79% compare to the baseline case.

• Review of KIISC
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• v.30 no.2
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• pp.5-9
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• 2020

널리 알려진 바와 같이 드론산업은 4차 산업혁명을 견인하는 13대 혁신성장 동력 산업 중 하나이다. 드론은 조종사가 탑승하지 않는 무인/원격조종 비행장치로 영상촬영, 감시, 조사, 물품배송 등의 서비스에 활용되고 있다. 드론을 이용한 서비스가 안전하게 상용화되기 위해서는 필수적으로 드론 자체 및 드론 기반 서비스를 보호하는 드론 보안기술이 적용되어야 한다. 드론은 피해자임과 동시에 가해자가 될 수 있는 양면성을 지니고 있기 때문에 이러한 특성을 고려한 보안기술이 필요하다. 최근 드론 보안의 양면성을 고려한 핵심요소로 드론식별모듈(DIM)이 개발되고 있다. 본 논문에서는 드론식별모듈 개념을 정의하고, 주요 기능 소개 및 국제표준화 추진 현황을 설명한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1047-1049
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• 2003

Stibenequinone(SQ) derivative which was electronic transportation materials in Poly(N-vinylcarbazole) (PVK)-based on organic EL and an optical characteristic of organic EL which is mentioned previously was investigated. The Photoluminescence highest pick with blending TBSQ with PVK was shifted from 439nm to 517nm. This result indicates that an energy gap of a PVK/TBSQ blended sample is less than an energy gap of PVK. According to the electrochemistry characteristic, the ionization energy(Ip) and the electro affinity(Ea) decreased from 5.79eV to 5.63eV and 2.23eV to 2.63eV, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.21-24
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• 2000

Properties of thermoelectric power in PbS thin films by chemical bath deposition were investigated The qualified PbS thin film was gained with the amounts of Thiourea($4-8ml/{\ell}$ ), Triethanolamine (1-2ml) and NaOH(l0ml). The molecular ratio of Pb and S was 3 : 7. Satisfied crystallization rate and deposition rate of PbS were greater at $50^{\circ}C$ than at $30^{\circ}C$. The constant of thermoelectric power in PbS was nearly $ 500uv/^{\circ}k$. The PbS thin film was changed from p-type to n-type semiconductor at around $200^{\circ}C$. In case of heat treatment at $300^{\circ}C$, the sample kept the characteristic of p-type semiconductors up to $250^{\circ}C$.