• Title, Summary, Keyword: 공진소멸

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A Study on the Optimal Span Length Selection of Conventional Railway Bridges considering Resonance Suppression (공진소멸 현상을 이용한 기존선 철도교량의 지간 최적화를 위한 연구)

  • Kim Sungil;Chung Wonseok;Choi Eunsoo
    • Journal of the Korean Society for Railway
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    • v.8 no.2
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    • pp.137-144
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    • 2005
  • The possibility of resonance exists always in railway bridges unlike highway bridges because railway bridges are loaded repeatedly by specific trains which has equidistant wheel loads. Resonance phenomenon of the bridge can be broken out when exciting frequencies by tram determined from the speed and effective beating internal coincides with natural frequencies of the bridge Excessive fluctuations of dynamic displacements and accelerations by resonance cause unpleasant passenger comfort and instability of railway structures. On the other hand, resonance suppression phenomenon that all the previous loads which pass through the bridge sum to zero can be occurred. In case we apply this resonance suppression properly, design of stable railway bridge from dynamics point of view can be made. In the present study, most dominant beating internal of conventional trams will be find. A(ter that. specific span length of the bridge which derives resonance suppression can be selected for railway bridges which accomplishes superior dynamic behavior.

Resonance Phenomenon according to the relationship between Span Length of the Bridge and Effective Beating Interval of High-Speed Train (교량의 지간장과 고속전철하중 유효타격간격 사이의 관계에 따른 공진현상)

  • 김성일;곽종원;장승필
    • Journal of the Earthquake Engineering Society of Korea
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    • v.3 no.2
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    • pp.67-76
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    • 1999
  • Resonance of the bridge can be occurred with the coincidence between a natural frequency of the bridge and a crossing frequency of moving loads which is determined from the speed and effective beating interval of the vehicle. In case of the railway bridge, the effective beating interval of the vehicle is fixed under the passage of specific trains. In the present study, resonance and cancellation of the bridge subjected to moving high-speed train are analyzed with the variations of span length. A steel-concrete composite railway bridge is idealized by the combinations of plate elements and space frame elements. High-speed train is idealized with moving constant forces and a 3-dimensional full modelling. From analyzing dynamic responses of D.M.F of vertical displacement, maximum vertical acceleration of the slab, and end rotation according to the variations of span length of the bridge, design criteria of span length of the bridge which satisfies dynamic safety is discussed.

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Integrated Photonic Channel Selective Microwave Bandpass Filter Incorporating a 1×2 Switch Based on Tunable Polymeric Ring Resonators (폴리머 링 공진기 기반의 스위치를 이용한 집적광학 채널 선택 마이크로웨이브 대역통과 필터)

  • Kim, Gun-Duk;Lee, Sang-Shin
    • Korean Journal of Optics and Photonics
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    • v.18 no.1
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    • pp.79-83
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    • 2007
  • A reconfigurable photonic microwave (MW) channel selective filter was demonstrated incorporating a $1{\times}2$ switch based on two tunable polymeric resonators with different free spectral ranges. Each resonator, consisting of two cascaded rings with an electrode formed on one of them, plays a role as an on/off switch through the thermooptic effect. The optical signal carrying the MW signal is routed to either port of the switch and detected to show the filtered output at the frequency determined by the free spectral range of the corresponding resonator. When the channel centered at 10 GHz was chosen, the extinction ratio was ${\sim}30dB$, the bandwidth 1 GHz, and the electrical power consumption 4.1 mW. For the other channel located at 20 GHz, we have achieved the extinction ratio of ${\sim}30dB$, the bandwidth of 2 GHz, and the required power of 8.0 mW. Finally the crosstalk between the selected and blocked channels was higher than 24 dB.

Integrated Photonic Microwave Bandpass Filter Incorporating a Polymer Microring Resonator (폴리머 마이크로링 공진기를 이용한 광학적 마이크로웨이브 대역통과 필터)

  • Chin, Won-Jun;Kim, Do-Hwan;Song, Ju-Han;Lee, Sang-Shin
    • Korean Journal of Optics and Photonics
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    • v.16 no.5
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    • pp.469-475
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    • 2005
  • An integrated photonic microwave bandpass filter has been proposed and demonstrated incorporating a coherently coupled microring resonator in low-loss polymers. The proposed device may feature compact site, simple structure, tuning via the thermooptic and electrooptic effect, and flexible integration with other electrical and optical devices. The resonator was designed to have an extremely small bandwidth so that it could be used to selectively pass the optical signal carrying the microwave signal to attain efficient bandpass filtering. We made and tested two resonators with a single ring and double rings, and performed a theoretical fitting of their measured transfer curves to predict the performance of the microwave filters based on them precisely. It was found that as the number of the rings used for the resonator increases, the bandwidth gets smaller, the rolloff sharper, and the band rejection higher. Finally our filter exhibited the center frequency of 10GHz, the 3-dB bandwidth of 1.0GHz, the corresponding quality (Q) factor of 10, and the rejection outside of the passband of more than 25dB.

Polymeric Ring Resonator with Variable Extinction Ratio (소멸비가 가변되는 폴리머 링 레조네이터)

  • Song, Ju-Han;Kim, Do-Hwan;Lee, Sang-Shin
    • Korean Journal of Optics and Photonics
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    • v.17 no.4
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    • pp.342-346
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    • 2006
  • A polymeric ring resonator with electrically variable extinction ratio at resonant wavelengths has been proposed and demonstrated. It consists of a ring waveguide coupled to a straight bus waveguide and a modulating electrode, which is formed in the outer cladding region outside of the ring. When electrical power is applied to the electrode, the refractive index of the polymers underneath the electrode is lowered to strengthen the confinement of the guided mode of the ring and thus the equivalent effective refractive index felt by the mode is decreased. Therefore, the propagation loss of the guided mode is reduced with the applied electrical power Consequently the extinction ratio at resonant wavelengths is varied by the electrical power. For the achieved results, the extinction ratio was changed by about 9 dB for the electrical power of 12 mW, when the propagation loss of the ring was reduced by 80 dB/cm.

An Analysis in Optimum Coupling Method of Cylindrical Dielectric Resonator Filter Designed by Non-decaying Mode Analysis (Non-decaying 모드 해석을 이용해서 설계한 원통형 유전체 공진기 여파기의 최적 결합 방법에 대한 분석)

  • Lee, Won-Hui;Park, Chang-Won;Kim, Tai-Shin;Hur, Jung;Lee, Sang-Young
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.38 no.7
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    • pp.14-21
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    • 2001
  • In this paper, we designed and fabricated C-band bandpass filter using dielectric resonators. From waveguide cutoff frequency which applied the region between adjacent dielectric resonators, the height of cavity is determined. The cavity's diameter is determined to the twice of dielectric resonator? diameter considering the conductor loss. The resonant frequency of the DR cavity is calculated with non decaying mode analysis. Conventionally, cylindrical dielectric resonator is analysed by Cohn's model which use the decaying mode in the region between dielectric resonator wall and circular cavity wall, which is an approximated method. The external quality factor, $Q_{ex}$ has found with simulation result using Ansoft's Maxwell simulation tool. The designed filter using dielectric resonators with dielectric constant of 45 has the passband center at 5.065GHz. The bandpass filter using dielectric resonators has about 1dB insertion loss, 20MHz bandwidth and more than 30dB attenuation at $f_0+15MHz$.

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Wind Pressure Reducing Soundproof Wall Which Has Many Holes on the Surface and Selectable Stop-Frequency Ranges (표면에 다수의 구멍을 뚫고 차단 주파수 영역의 선택이 가능한 풍압저감형 방음벽)

  • Kim, Sang-Hoon;Lee, Donchool
    • Journal of The Korean Society of Civil Engineers
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    • v.36 no.2
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    • pp.191-196
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    • 2016
  • Applying diffraction of waves and muffler principle, the theory of macroscopic air ventilation with soundproofing was explained. Soundproofing frequency range can be selected by this method. The sound wave was attenuated at the resonator located between double-layered walls. A soundproof plate was designed and the experiment was processed. There are two air holes of diameter of 5cm and thickness of 8cm on the surfaces per each soundproofing cell. There was a transmission loss of about 25dB and it is more than at least 10dB compared with that of the Comnex technology of wave cancellation by air holes in Japan. Furthermore, there was no soundproof frequency selection in the Comnex technology.

Self-starting phase conjugate laser in population inverted Nd:YAG (밀도 반전된 Nd:YAG에서의 자체 발진 위상공액 레이저)

  • ;M.J.Damzen
    • Korean Journal of Optics and Photonics
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    • v.8 no.5
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    • pp.357-361
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    • 1997
  • We report the operation of a self-starting phase conjugate laser(PCL) oscillator which compensates intracavity phase distortion. The self-starting PCL in the population inverted Nd:YAG gain media produced an output energy of 200 mJ in a 20 ns single-longitudinal-mode pulse at 10Hz. And it showed well-defined Gaussian spatial profile.

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LARGE EDDY SIMULATION OF THE COMPRESSIBLE FLOW OVER A OPEN CAVITY (큰에디모사기법을 이용한 공동 주위의 압축성유동 해석)

  • 오건제
    • Journal of the Korean Society of Propulsion Engineers
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    • v.7 no.1
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    • pp.40-48
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    • 2003
  • Large eddy simulation is used to investigate the compressible flow over a open cavity, The sub-grid scale stresses are modeled using the dynamic model. The compressible Navier-Stokes equations are solved with the sixth order accurate compact finite difference scheme in the space and the 4th order Runge-Kutta scheme in the time. The results show a typical flow pattern of the shear layer mode of oscillation over the cavity. The votical disturbances, the roll-up of vorticity, and impingement and scattering of vorticity at the downstream cavity edge can be seen in the shear layer. Predicted acoustic resonant frequency is in good agreement with that of the empirical formula. The mean flow streamlines are nearly horizontal along the mouth of the cavity. The pressure has its minimum value in the vortex core inside the cavity.

Photonic K-Band Microwave Bandpass Filter with Electrically Controllable Transfer Characteristics Based on a Polymeric Ring Resonator (전기적으로 가변되는 전달특성을 갖는 폴리머 링 광공진기를 이용한 마이크로웨이브 대역통과 필터)

  • Kim, Gun-Duk;Lee, Sang-Shin
    • Korean Journal of Optics and Photonics
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    • v.17 no.5
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    • pp.475-479
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    • 2006
  • An integrated photonic K-band microwave bandpass filter has been proposed and demonstrated by incorporating a polymeric ring resonator. Its transfer characteristics were adjusted by shilling the resonance wavelength of the ring resonator via the thermooptic effect. The achieved performance of the filter includes the center frequency of 20 GHz, the attenuation of ${\sim}15dB$, the bandwidth of 2 GHz, and the corresponding quality factor of 10. The microwave output power within the passband of the device was adjusted at the rate of about 6.7 dB/mW in the range of 27 dB. This kind of device with electrically controllable transfer characteristics can be applied to implement microwave switches and other devices.