• 제목/요약/키워드: Coaxial

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시간영역 유한차분법을 이용한 동축선로의 전송특성 및 차폐효과 해석 (Analysis of Coaxial Line Transmission Charactristics and Shielding Effectiveness Using by Finite Difference Time Domain Method)

  • 남상식;윤현보;김정렬;백낙준;우종우
    • 한국전자파학회지:전자파기술
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    • 제6권4호
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    • pp.11-19
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    • 1995
  • 본 논문에서는 시간영역 유한차분법(Finite Difference Time Domain : FDTD) 에 의해서 동축선로의 전달계수와 차폐효과에 대하여 해석하고 그 결과를 모멘트법과 비교하였다. 기존의 여기방법인 TE 나 TM 모드를 대신하여 반사파의 빠른 시간내의 완전흡수를 위하여 TEM 모드로 가정한 Gaussian 펄스를 인가하는 방법을 사용하였다. 또한, 동축선로의 차폐효과를 FDTD를 이용하여 계산 결과와 모멘트법을 이요하여 얻은 결괄와 매우 유사한 결과를 얻었다.

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접지임피던스의 변동이 최소가 되는 동축형 탄소접지전극의 길이의 산정 (Determination of the Length of Coaxial Type Carbon Grounding Electrode to Minimize the Fluctuation of Grounding Impedance)

  • 이강수;김종호;이복희
    • 조명전기설비학회논문지
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    • 제24권12호
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    • pp.164-170
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    • 2010
  • For the surge currents like lightning or ground fault currents containing high frequency components which cause the electromagnetic interferences for the electronic devices and communication equipment, the grounding impedances give the significantly composite characteristics which are dependent on the frequency of surge currents. In this paper, the analytical model and method for determining the optimal length of the newly developed coaxial type carbon ground electrode which has a little fluctuation in grounding impedance with frequency. The length of minimizing the fluctuation of grounding impedance by changing frequency from 100[Hz] to 1[MHz] was determined, and the validity of this proposed method was confirmed by comparing with the simulated and measured data.

동축선회 확산연소기의 1차 및 보조공기유량 변화에 따른 연소배출특성 (Combustion Characteristics in Various Primary and Auxiliary Air Flux Conditions at a Coaxial Swirling Diffusion Combustor)

  • 이용후;오세원;배대석;이도형
    • 동력기계공학회지
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    • 제6권3호
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    • pp.17-23
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    • 2002
  • The purpose of this study is to investigate the combustion emission characteristics changing auxiliary air injection in combustion field of coaxial swirling diffusion combustor. For this purpose, mean temperature, CO, CO2, O2 and HC concentration were measured by changing excess air ratio and auxiliary air injection. As a result of this study, mean temperature, CO2 emission were increased and CO emission decreased by increasing auxiliary air. Therefore, this paper showed the auxiliary air injection effected strongly on flame structure and combustion emission characteristics.

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겹치기 이음부의 레이저용접 동축 모니터링 (Coaxial Monitoring during Laser Lap Welding)

  • 김정학;김철희;김정한;이세헌
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2007년도 춘계학술대회A
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    • pp.1294-1298
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    • 2007
  • Welding process monitoring is advantageous for maintaining weld quality and numerous sensing techniques have been developed for laser welding. Coaxial image monitoring enables direct monitoring of the weld pool shape and keyhole behavior, but requires the complex optical system and the image processing technique. In this study, we coaxially acquired the weld pool images during laser lap welding by using the camera and special illumination. The welding characteristics - pool width and length, keyhole shape, etc - were extracted by using image processing and the relationship between these characteristics and the penetration depth were investigated.

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음파가진에 의한 동축공기 수소 확산화염의 NOx 배출저감연구 (Reduction of NOx Emissions in Turbulent Hydrogen Diffusion Flame using Acoustic Excitation)

  • 김문기;한정재;윤상욱;윤영빈
    • 한국연소학회지
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    • 제10권1호
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    • pp.13-19
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    • 2005
  • Measurements of flame length and NOx emissions have been conducted to investigate the effects of acoustic excitation on flame structure in turbulent hydrogen diffusion flames with coaxial air. When the acoustic excitation of a specific frequency is applied to coaxial air stream, flame length is dramatically reduced, resulting in reduction of flame residence time. Consequently, EINOx could decrease up to 35 % and this shows that acoustic excitation is effective in reducing NOx emissions. Mie scattering technique has been used to visualize the vortex structure induced by acoustic excitation and vortex formation, development and destruction were observed quantitatively. As a result, vortex entrains coflow air into fuel stream and mixing rate between fuel and air is significantly enhanced, which may contribute to reduction of NOx emissions.

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동축확산연소기 화염구조와 NOx 분포에 관한 연구 (A Study on the Flame Structure and NOx Distribution In Coaxial Diffusion Combustor)

  • 김규성;이우섭;강인구;이도형
    • 한국연소학회지
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    • 제4권2호
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    • pp.35-41
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    • 1999
  • The purpose of this study is to establish the flame structure and NOx emission characteristics of the swirl flow coaxial diffusion combustion in the model gas turbine combustor. The mean temperature, ion currents and NOx emission measurement technique showed the effect of equivalence ratio into flame length and flame stability. As a result of this study, NOx emission was increased by increasing the equivalence ratio, and the peak value of the NOx was appeared near the flame front.

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Wedge형 보염기를 장착한 동축형 연소기의 반응 유동장 수치해석 (Numerical Analysis on the Reacting Flow-Field of Coaxial Combustor with a Wedge-Shaped Flame Holder)

  • 고현;성홍계
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2005년도 제25회 추계학술대회논문집
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    • pp.450-454
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    • 2005
  • 축대칭 동축형 램제트 연소기에 대한 반응 유동장 해석을 수행하였다. 2차원 축대칭 Wavier-Stokes 방정식과 낮은 레이놀즈 수 $k-\varepsilon$ 난류 모델을 이용하였고, 유한반응률 화학반응 모델을 적용하였다. 난류 연소 모델인 EDM (Eddy-Dissipation Model)과 층류 반응 모델을 적용한 경우를 서로 비교하였다. 급확대 연소기와 wedge형 보염기를 장착한 동축형 램제트 연소기에 대한 반응 유동장 수치해석을 통해 두 가지 결과를 화염안정 측면에서 서로 비교하였다.

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케로신-산소 로켓 동축 분사기 난류 연소에서 리세스의 영향에 대한 수치해석 (Numerical Study on the Effect Recess on the Turbulent Combustion of Kerosene/LOx Coaxial Rocket Injector)

  • 최정열;신재렬
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2011년도 제37회 추계학술대회논문집
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    • pp.92-95
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    • 2011
  • 케로신-산소 동축 로켓 분사기의 난류 연소를 수치적으로 연구하였다. 이 연구를 위하여 다단 준 총괄 반응 기구를 개발하였다. 이 반응 기구는 가상의 케로신 연료가 수소와 일산화 탄소로 분해된 이후 고온 영역의 상세 산화 반응들로 구성되어 있다. 난류 연소의 LES 해석을 위하여 5차의 WENO 기법을 이용하였다. 반응 및 비 반응 유동의 난류 특성을 살펴 보았으며 리세스의 존재가 난류의 생성과 연소에 미치는 영향을 살펴보는 심화 연구를 수행하였다.

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파이버 레이저를 이용한 순 티타늄 박판의 용접특성 향상을 위한 연구 - 실드가스 노즐변수의 영향 - (The Study for Improving the Weldability of Pure Titanium Sheet by Using Fiber Laser - The Effect of Shielding Gas Nozzle Variable -)

  • 김종도;김지성
    • Journal of Welding and Joining
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    • 제34권5호
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    • pp.6-12
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    • 2016
  • This study was performed bead welding of pure titanium by using fiber laser. Since titanium is very sensitive to oxidation and nitriding during welding, it is important to compose the shielding equipment compared with different material. Thus side and coaxial shield nozzle, rail and chamber type shielding equipment are widely used to protect effectively the weld during welding. Experiments were performed by changing nozzle angle and distance using side and coaxial shield nozzle. The bead colors of gold, brown, blue, purple and yellowish white were obtained by changing variables of shield nozzle, and then its weldability was investigated. As experiment result, sound and not brominated beads were formed when side nozzle angle and distance were respectively $45^{\circ}$ and 10 mm.

Design of Coaxial Magnetic Gear for Improvement of Torque Characteristics

  • Shin, H.M.;Chang, J.H.
    • Journal of Magnetics
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    • 제19권4호
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    • pp.393-398
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    • 2014
  • This paper proposes new types of models that have coaxial magnetic gear (CMG) configurations to increase torque transmission capability. They have flux concentrating structures at the outer low speed rotor, and permanent magnets (PMs) are embedded in the space between stationary pole pieces. The torque performances of the proposed models are compared with those of a basic CMG model. The harmonic torque components due to air gap field harmonics are also analyzed to investigate the torque contribution of each harmonic by using finite element analysis (FEA) and the Maxwell stress tensor. The proposed CMG model is optimized to have high torque density with low torque ripples by response surface methodology (RSM). Compared to the basic CMG model, the proposed model has a huge increase in transmitted torque density, and is very advantageous in term of PM use.