• Title/Summary/Keyword: Resonant cavity

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Conductivity Measurement of Soot at Microwave Frequency Using a Cylindrical Cavity (원통형 공진기를 이용한 마이크로파 대역에서 그을음의 도전율 측정)

  • Kim, Jae-Hee;Park, Wee-Sang
    • Proceedings of the IEEK Conference
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    • 2008.06a
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    • pp.341-342
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    • 2008
  • A conductivity of soot at microwave frequency is presented using a novel technique for complex permittivity of materials. The method overcomes limitations of conventional methods which are cavity perturbation and transmission/reflection method. Resonant frequencies and Q factors are measured and simulated for the cylindrical cavity, and they are compared to each other. Similar material property of both real material and simulation material produce similar values of resonant frequency and Q factor. The complex permittivity of material can be determined by simulating the cavity to change material property until the simulation results are nearly the same as the measurement results. Cylindrical cavity has been realized for measurement at 880 MHz, and conductivity of soot is measured. A sample was made by depositing the soot on the glass. The proposed method shows that the conductivity of soot is 11 S/m.

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A Numerical Study on Acoustic Behavior in Combustion Chamber with Acoustic Cavity (음향공이 장착된 로켓엔진 연소실의 음향장 해석)

  • Sohn, Chae-Hoon;Kim, Young-Mog
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.4
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    • pp.28-37
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    • 2002
  • Acoustic behavior in combustion chamber with acoustoc cavity is numerically investigated by adopting linear acoustic analysis. Helmholtz-type resonator is employed as a cavity model to suppress acoustic instability passively. The tuning frequency of acoustic cavity is adjusted by varying the sound speed in acoustic cavity. Through harmonic analysis, acoustic pressure responses of chamber to acoustic oscillating excitation are shown and the resonant acoustic modes are identified. Acoustic damping effect of acoustic cavity is quantified by damping factor. As the tuning frequency approaches the target frequency of the resonant mode to be suppressed, mode split from the original resonant mode to lower and upper modes appears and thereby damping effect is degraded significantly. Considering mode split and damping effect as a function of tuning frequency, it is desirable to make acoustic cavity tuned to maximum frequency of those of the possible splitted upper modes.

Design and Characterization of a Microwave Plasma Source Using a Rectangular Resonant Cavity (마이크로웨이브 공진 공동을 이용한 플라즈마 원의 설계 및 특성)

  • Kim, H.T.;Park, Y.S.;Sung, C.K.;Yi, J.R.;Hwang, Y.S.
    • Journal of the Korean Vacuum Society
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    • v.17 no.5
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    • pp.408-418
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    • 2008
  • The rectangular resonant cavity was designed and characterized as a microwave plasma source for focused ion beam. The optimum cavity was calculated analytically and analyzed in detail by using HFSS(High Frequency Structure Simulator). Since the resonant cavity can be affected by the permittivity of quartz chamber and plasma, the cavity is designed to be changeable in one direction. By observing the microwave input power at which the breakdown begins, the optimum cavity length for breakdown is measured and compared with the calculated one, showing in good agreement with the optimum length reduced by 10cm according to the permittivity change in the presence of quartz chamber. The shape of breakdown power curve as a function of pressure appears to be similar to Paschen-curve. After breakdown, plasma densities increase with microwave power and the reduced effective permittivity in the cavity with plasma results in larger optimum length. However, it is not possible to optimize the cavity condition for high density plasmas with increased input power, because too high input power causes expansion of density cutoff region where microwave cannot penetrate. For more accurate microwave cavity design to generate high density plasma, plasma column inside and outside the density cutoff region needs to be treated as a conductor or dielectric.

Long-term stabilization of optical feedback of a resonant external cavity coupled semiconductor laser (공진형 외부 캐비티 부착 반도체 레이저의 광피드백 장기 안정화)

  • 신철호
    • Korean Journal of Optics and Photonics
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    • v.9 no.2
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    • pp.96-99
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    • 1998
  • In this study, a novel long term stabilization method of optical feedback for the resonant cavity coupled semiconductor lasers is proposed, and its utility was shown experimentally. The proposed method is realized by using the pahse discriminator of optical feedback with high gain. The phase discriminating signal was obtained by the polarization spectroscopic technique using reflection light from the external reflector, which is a confocal Fabry-Perot cavity. Experimental result shows that stable control state can be maintained up to 20 hours. The period can be increased by reducing size of the system and/or fixing position stably of optical parts used, which were arranged on an optical table by using magnetic bases in this experiment. The proposed long-term stabilization method of optical feedack of a resonant external cavity coupled semiconductor laser is very useful for the field of high sensitivity measurement, and for the use in the laboratory level in particular.

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A New Resonance Prediction Method of Fabry-Perot Cavity (FPC) Antennas Enclosed with Metallic Side Walls

  • Kim, Dong-Ho;Yeo, Jun-Ho
    • Journal of electromagnetic engineering and science
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    • v.11 no.3
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    • pp.220-226
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    • 2011
  • We have proposed a new method to accurately predict the resonance of Fabry-Perot Cavity (FPC) antennas enclosed with conducting side walls. When lateral directions of an FPC antenna are not blocked with metallic walls, the conventional technique is accurate enough to predict the resonance of the FPC antenna. However, when the FPC antenna has side walls, especially for case with only a short distance between the walls, the conventional prediction method yields an inaccurate result, inevitably requiring a tedious, time-consuming tuning process to determine the correct resonant height to provide the maximum antenna gain in a target frequency band using three-dimensional full-wave computer simulations. To solve that problem, we have proposed a new resonance prediction method to provide a more accurate resonant height calculation of FPC antennas by using the well-known resonance behavior of a rectangular resonant cavity. For a more physically insightful explanation of the new prediction formula, we have reinvestigated our proposal using a wave propagation characteristic in a hollow rectangular waveguide, which clearly confirms our approach. By applying the proposed technique to an FPC antenna covered with a partially reflecting superstrate consisting of continuously tapered meander loops, we have proved that our method is very accurate and readily applicable to various types of FPC antennas with lateral walls. Experimental result confirms the validness of our approach.

Acoustic Characteristics of the Haegeum Body (해금 몸체의 음향학적 특성에 관한 연구)

  • Noh, Jung-Uk;Park, Sang-Ha;Sung, Koeng-Mo
    • The Journal of the Acoustical Society of Korea
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    • v.26 no.7
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    • pp.317-322
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    • 2007
  • This paper is the first step to study on the acoustic characteristics of the Haegeum, a Korean traditional bowed-string instrument. We measured acoustic transfer functions of a Haegeum body using impulse response method. All the measurements are performed in anechoic chamber, INMC, SNU. We examined resonant characteristics of the Haegeum body with obtained transfer functions. Then we performed additional studies which are the Chladni pattern experiments and calculations of air cavity resonances to verify relations between the resonant peaks on the transfer functions and the resonances of each component, such as top plate, air cavity and so on. As a result, we can explain the acoustic characteristics of a Haegeum body and its components.

Equivalent Circuit Parameters of S-band 1.5 Cell RF Gun Cavity

  • Kim, Ki-Young;Kang, Heung-Sik;Tae, Heung-Sik
    • Journal of electromagnetic engineering and science
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    • v.4 no.1
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    • pp.30-36
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    • 2004
  • We determined equivalent circuit parameters of a 1.5 cell S-band RF gun cavity from the resonant characteristics of its decoupled cavities(half cell and full cell) using the code SUPERFISH. Equivalent circuit parameters of the 1.5 cell RF gun cavity resonated in the 0-mode were obtained easily from the circuit parameters of each decoupled cavities. In order to obtain equivalent circuit parameters for the $\pi$ -mode cavity, we calculated the differences of the resonant frequencies and the equivalent resistances between the 0- and $\pi$ -modes with slight variations of the radius and thickness of the coupling iris. From those differences, we obtained R/Q value and equivalent resistance of the $\pi$ -mode, which are directly related to the equivalent circuit parameters of the coupled cavity. Using calculated R/Q value, we can express equivalent inductance, capacitance and resistances of the RF gun cavity resonated in the $\pi$ -mode, which can be useful for analyzing coupled cavities in a steady state.

A Numerical Analysis of Acoustic Behavior in Combustion Chamber with Acoustic Cavity (음향공이 장착된 로켓엔진 연소실의 음향장 수치해석)

  • 손채훈;김영목
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2003.05a
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    • pp.249-252
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    • 2003
  • Acoustic behavior in combustion chamber with acoustic cavity is numerically investigated by adopting linear acoustic analysis. Helmholtz-type resonator is employed as a cavity model to suppress acoustic instability. The tuning frequency of acoustic cavity is adjusted by varying the sound speed in acoustic cavity. Acoustic pressure responses of chamber to acoustic oscillating excitation are shown md acoustic damping effect of acoustic cavity is quantified by damping factor. As the tuning frequency approaches the target frequency of the resonant mode, mode split from the original resonant mode to lower and upper modes appears and thereby damping effect is degraded. Considering mode split and damping effect as a function of tuning frequency, it is desirable to make acoustic cavity tuned to maximum frequency of those of the possible splitted upper modes.

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A TWO CAVITY MODEL FOR UMBRAL OSCILLATIONS

  • Lee, Jeong-Woo;Yun, Hong-Sik
    • Journal of The Korean Astronomical Society
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    • v.20 no.1
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    • pp.27-47
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    • 1987
  • In the present study a two-mode, separately concurring resonant cavity model is proposed for theoretical interpretation of the 3 minute umbral oscillation. The proposed model has been investigated by calculating the transmission coefficients of the waves propagating through the umbral photosphere (photospheric weak-field cavity) and chromosphere (chromospheric strong-field cavity) into the corona, for 3 different umbral model atmospheres by Staude (1982), Beebe et al. (1982) and Avrett (1981). In computing the transmission coefficients we made use of multi-layer approximation by representing the umbra] atmosphere by a number of separate layers with (1) temperature varying linearly with depth and (2) temperature constant within each layer. The medium is assumed to be compressible, non-viscous, perfectly conducting under gravity. The computed resonant periods, transmission spectra, phase spectra, and kinetic energy density of the waves associated with the oscillations are presented in comparison with the observations and their model dependent characteristics are discussed.

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Resonant Transmission through Slits in a Cavity inside a Thin Conducting Plane

  • Lee, Jong-Ig;Cho, Young-Ki
    • Journal of electromagnetic engineering and science
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    • v.10 no.3
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    • pp.127-131
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    • 2010
  • In this paper, the problem of electromagnetic transmission via slits in a cavity inside a conducting screen of finite thickness has been considered in the case that the transverse electric(to the slit axis) polarized plane wave is incident on a slit. The problem is solved numerically by the method of moments and the results are compared with those obtained from an equivalent circuit suitable for a case in which the slit width is infinite and the structure is modified to the two partially overlapped conducting planes. It is observed that when the cavity is resonated, the effective slit width reaches its maximum value of $1/\pi$ wavelengths, irrespective of the actual slit width and the incidence angle. When the thickness of the conducting plane is much smaller than the wavelength, the numerical results for the effective slit width(or transmission width) agree well with those obtained from the equivalent circuit, even though the slit is as narrow as the thickness of the conducting plane.