• Title/Summary/Keyword: 복사특성계수

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Research on the Decolorization of Epoxy Polymer by Accelerated Solar Radiation Test (태양광 복사 가속화 시험을 통한 에폭시 폴리머의 색 변화 특성 연구)

  • Lee, Sang-Bong;Lee, Dong-Geon;Kim, Myung-Jun;Lee, Soo-Yong;Park, Jung-Sun;Kang, Tae-Yeop;Baek, Sang-Hwa
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.44 no.11
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    • pp.949-956
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    • 2016
  • There are a number of effects by solar radiation in many aerospace industrial fields, such as degradation of mechanical properties, sealing effect of sealants or decolorization. Because it takes long time to investigate these effects by using the light of natural state, new methods are developed for accelerating this phenomenon. In this paper, we developed an apparatus to simulate accelerated solar radiation phenomenon selecting irradiation intensity $1,120W/m^2$ as the designed environment. Epoxy polymer as the composite material was chosen and processed by ASTM-D638, a reference for tensile test of polymer and plastic. Total color shift was selected as the test category to evaluate acceleration of the test. We obtained acceleration factors and numerical model from test data and concluded it can shorten test periods by accelerated irradiation intensity of $1,120W/m^2$.

A Study on AESA Antenna Performance Advancement for Seeker (탐색기용 AESA 안테나 성능 고도화 연구)

  • Youngwan Kim;Jong-Kyun Back;Hee-Duck Chae;Ji-Han Joo
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.23 no.5
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    • pp.103-108
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    • 2023
  • In this paper, a performance enhancement study of an AESA antenna that can be applied to a seeker that serves as the eye of a missile was conducted, and the performance of the antenna was verified through actual measurement. When designing an AESA antenna, the optimization of the active reflection coefficient must be considered during transmission due to the mutual coupling between radiators that inevitably occurs, and the selection of a radiator that can overcome the space limitation of the seeker with a small size/light weight is an important design consideration. Accordingly, optimization in terms of electrical performance and low-profile structure is required through research on array antennas for application to the AESA structure. The radiator designed and measured in this paper was designed as an SFN that can satisfy the low-profile structure while enhancing the performance of a general vivaldi antenna. Through this paper, it was confirmed that SFN has the same broadband characteristics as general vivaldi antennas and has optimized characteristics required for AESA antennas. The structure optimized through simulation confirmed the pattern characteristics and active reflection coefficient characteristics through the fabrication of actual proto-type antennas.

Performance Verification of Active Phased Array Broadband Antenna in Ka-Band (Ka대역 능동위상배열 광대역 안테나 성능 검증 )

  • Youngwan Kim;Jong-Kyun-Back;Hee-Duck Chae;Ji-Han Joo
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.24 no.1
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    • pp.23-30
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    • 2024
  • This paper dedcribes the design. verification, and analysis techniques for an advanced phased array antenna. When applying an active phased array antenna to an aircraft or missile, miniaturization of the array antenna and wide-angle beam steering characteristics can be unavoidable antenna design considerations. In particular, the active reflection coefficient characteristics when electronically steering a wide-angle beam is a design parameter that must be minimized in terms of system survival and system performance. As a radiator suitable for broadband characteristics and wide-angle beam steering, this paper designed an array structure using SFN and minimized the active reflection coefficient according to beam steering of up to 40° based on the spherical coordivate system angle. The bandwidth of the radiator was confirmed to be 3GHz based on active reflection in the Ka-band. In addition, the performance of the actually manufactured 8by8 array antenna wsa analyzed by measuring the single pattern of the radiator through a near-field test, mathematically synthesizing it, and predicting the Tx/TRx beam used in the seeker system.

Analysis of a Convective, Radiating Rectangular Fin (대류, 복사 사각 핀의 해석)

  • Kang, Hyung-Suk;Kim, Jong-Ug
    • Journal of Industrial Technology
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    • v.26 no.B
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    • pp.29-34
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    • 2006
  • A convective, radiating rectangular fin is analysed by using the one dimensional analytic method. Instead of constant fin base temperature, heat conduction from the inner wall to the fin base is considered as the fin base boundary condition. Radiation heat transfer is approximately linearized. For different fin tip length, temperature profile along the normalized fin position is shown. The fin tip length for 98% of the maximum heat loss with the variations of fin base length and radiation characteristic number is listed. The maximum heat loss is presented as a function of the fin base length, radiation characteristic number and Biot number.

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A Linear Stability Analysis of Unsteady Combustion of Solid Propellants (고체추진제 비 정상연소의 선형 안정성해석)

  • 이창진;김성인;변영환
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1998.04a
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    • pp.29-29
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    • 1998
  • 고체 추진제 연소불안정에 관한 해석은 준-정상 1차원 해석인 QSHOD(Quasi-Steady Homogcneous One-Dimension)에 의하여 단순화된 지배방정식을 이용하여 응축영역을 해석하는 것이 일반적이다. 이때 외부교란에 대한 기체영역과 표면반응 영역의 응답은 화학반응이 발생하지 않는 고체영역의 응답에 비하여 매우 빠르므로 준-정상적인 거동을 한다. 본 연구에서는 복사열전달에 의한 열속(heat flux)이 고체 추진제의 표면에 존재하며 이 중의 일부가 고체영역에서 흡수될 때 표면에서의 선형교란을 고려한 ZN(Zeldovich-Novozhilov) 방법을 이용하여 연소불안정 현상을 이론적으로 해석하여 연소불안정 현상을 설명할 수 있는 연소 응답함수를 구하였다. 본 연구에서 얻어진 응답함수를 해석함으로써, Zebrowski등$^{(5)}$ 에 의하여 얻어진 복사열 교란에 대한 응답함수가 과소 평가된 응답특성을 나타내고 있음을 알았다. 또한 응답함수의 고유불안정성을 판별하는 민감계수 r과 k의 영역의 해석으로부터 SOn등$^{(6)}$ 에 의하여 밝혀진 안정 경계선의 안정한 영역보다 본 연구에서 구한 안정 경계영역이 줄어드는 경향을 보여주고 있다. 이것은 (6)에서 과소 평가된 복사열전달의 영향을 수정한 결과 때문이다.

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Effects of surface radiation on the insulation for mechanical system (표면복사특성이 단열성능에 미치는 영향)

  • Oh, Dong-Eun;Park, Jong-Il;Lee, Min-Woo;Hong, Jin-Kwan;Kang, Byung-Ha;Kim, Suk-Hyun
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.1006-1011
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    • 2006
  • In this study, a rational procedures for estimation of insulation thickness for condensation control or personnel protection has been investigated. Both horizontal pipe and vertical wall configuration are included. Design parameters are pipe diameter or, height of the wall, thermal conductivity, emissivity, and operating temperatures. The results Indicated that the surface emissivity plays a very important role in the design of insulation for the purpose of surface temperature control, especially in natural convection situation. radiation heat transfer coefficients for some new insulation material surface, such as elastomers, estimated to be more than 90% of the total surface heat transfer coefficient. Adequate revision of specifications or standards has been also suggested.

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Radiator Design Method considering Wide-Angle Beam Steering Characteristics of AESA Radar (AESA 레이더 광각 빔조향 특성을 고려한 복사소자 설계 기법)

  • Kim, Young-Wan;Chae, Hee-Duck;An, Se-Hwan;Joo, Ji-Han
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.22 no.5
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    • pp.87-92
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    • 2022
  • In this paper, a study was conducted on the design of an array element that can be applied to the AESA radar for seeker. An antenna for application to AESA radar should choose an optimal radiation element to be applied to an array antenna in order to secure electronical beam steering characteristics, and consider beam steering characteristics when designing. In particular, in order to satisfy the wide-angle beam steering characteristics, the wide-angle impedance matching technique should be used to minimize the scan blindness region that may occur during wide-angle steering. As such, securing the stability of system operation is becoming an important design consideration for AESA radar. In this paper, WAIM is applied to the end of the radiation element to improve the characteristics of the radiation element applied to the AESA radar antenna device, and the change in the performance of the active reflection coefficient, which is a stable operation index of the system, is reviewed. The final performance result verified the validity of the proposed method by mathematically synthesizing the simulation data.

The Design of a Wideband E-plane Phased Array Antenna using W/G Simulator (도파관 시뮬레이터를 이용한 광대역 E-평면 넛치 위상 배열 안테나 설계)

  • 김준연;소준호;임중수
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.2
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    • pp.111-118
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    • 2003
  • Notch Antenna is a travelling wave type antenna and can provide multioctave operation in phased arrays that scan over wide angle. In this paper, we designed a wideband E-plane phased array antenna using E-plane waveguide simulator which has a bandwidth of 3 : 1 and a scan volume of $\pm$45$^{\circ}$ in E-plane. We compared impedance of single antenna and infinite array antenna using equivalent circuit modeling. We analyzed full structure of 1$\times$9 phased array antenna and we evaluated active reflection coefficient with variation of beam scan angle through mutual coupling coefficient acquired from simulation and investigated the variation of antenna gain with variation of active element pattern as beam scan angle is varied.

Unsteady Heat Transfer in Radiatively Active Spherical Medium (구형 복사 매질에서의 비정상 열전달 특성에 관한 연구)

  • 한상헌;백승욱;안국영
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.10
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    • pp.2582-2589
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    • 1993
  • Transient heat transfer characteristics of cooling of a spherical body were investigated in the radiatively active spherical medium. Initially the spherical body and the medium were maintained at their constant temperatures. Then heat transfer begins from spherical body t medium. The heat transfer mode inside the spherical body is just conduction. But heat is transferred by both conduction and radiation inside the medium. All thermodynamic properties were held constant in time. Spherical symmetry is assumed. DOM was adopted to solve RTE. The effect of characteries-tic optical thickness, conduction to radiation parameters, and solid surface emissivity has been studied.

Observation of Aerosol Optical Properties using Multi-Channel LIDAR System (다중채널 라이다를 이용한 에어로졸의 광학적 특성 관측)

  • 최성철;노영민;김영준
    • Proceedings of the Optical Society of Korea Conference
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    • 2003.02a
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    • pp.212-213
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    • 2003
  • 대기 중에 존재하는 에어로졸은 지구 복사수지에 영향을 줄뿐 만 아니라 기상학적으로 구름의 응결 핵으로 작용하는 것으로 알려져 있다. 그러므로 이에 대한 보다 정확한 물리·화학적 정보를 얻기 위해 많은 연구가들이 측정을 수행하고 있지만, 기존의 측정 시스템은 에어로졸의 시·공간적 변화를 정확하게 측정하기에는 많은 문제점을 가지고 있다. 라이다 시스템을 이러한 문제를 해결하는데 유용한 장비로써 대기중에 존재하는 에어로졸의 광학적 특성(후방산란계수, 편광소멸도, 라이다 비 등)을 보다 정확하게 측정할 수 있는 장비로 알려져 있다. (중략)

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