• Title/Summary/Keyword: 공진파수

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A Transfer Function Synthesis for Model Approximation with Resonance Peak Value (첨두공진점을 갖는 모델 근사화를 위한 전달함수 합성법)

  • Kim, Jong-Gun;Kim, Ju-Sik;Kim, Hong-Kyu
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.22 no.1
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    • pp.118-123
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    • 2008
  • This paper proposes a frequency transfer function synthesis for approximating a high-order model with resonance to a low-order model in the frequency domain. The presented model approximation method is based on minimizing the error function weighted by the numerator polynomial of approximated models, which is used of the RLS(Recursive Least Square) technique to estimate the coefficient vector of approximated models. The proposed method provides better fitting in a low frequency and peak resonance. And an example is given to illustrate feasibilities of the suggested schemes.

RF Characteristics of TO-can Packaged FP-LD Optical Transceiver Module (TO-can 패키지 레이저 다이오드 모듈의 주파수 특성 개선)

  • 이동수
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.17 no.4
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    • pp.8-12
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    • 2003
  • Characteristics of optical transceiver module in radio frequency(RF) band were investigated with TO-can packaged Fabry-Perot laser diode(FP-LD). R-L-C parameters for equivalent circuit model of the LD were extracted with an impedance analyzer. With this model, impedance matching to the packaged LD could be performed by eliminating inductive components of the leads in the package by using lumped chip capacitors that have opposite reactance, while it shows resonance dip in low frequency band. The resonance dip could be removed using lumped elements for impedance matching by shifting the resonance frequency to the region out of interest.

Estimation of Characteristics Change on Transverse Mode PZT Vibrator Under Space Environment (우주환경하에서 횡진동 모드 PZT진동자의 특성변화 예측)

  • Lee, Sang Hoon;Moon, Guee Won;Yoo, Seong Yeon;Kim, Jung Soon;Kim, Moo Joon
    • The Journal of the Acoustical Society of Korea
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    • v.31 no.8
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    • pp.514-522
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    • 2012
  • The temperature dependence of the characteristics in a PZT-5 piezoelectric ceramic vibrator with the transverse mode was investigated in the range of $-100^{\circ}C$ to $90^{\circ}C$ using a thermal vacuum chamber to utilize the vibrator in aerospace industries. As the results, at room temperature, the resonant and anti-resonant frequencies had the minimum value, whereas, the dielectric constant increased linearly from about 2500 to 7500 in the given temperature range. The mechanical loss decreased linearly from 0.08 to 0.03. Through the regression analysis, the temperature dependence functions of the characteristics were derived to linear and square regression functions. Applying the functions, the input admittance characteristics of the piezoelectric vibrator were calculated, and the results showed good agreement with measured ones. It can be confirmed that this method is useful to estimate the characteristics change of the piezoelectric vibrator caused by the temperature change under the space environment.

A Nonlinear Response Analysis of Tension Leg Platforms in Irregular Waves (불규칙파중의 인장계류식 해양구조물의 비선형 응답 해석)

  • Lee, Chang-Ho;Gu, Ja-Sam;Jo, Hyo-Je;Hong, Bong-Gi
    • Journal of Ocean Engineering and Technology
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    • v.12 no.2 s.28
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    • pp.33-42
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    • 1998
  • In the presence of incident waves with different frequencies, the second order sum and difference frequency waves due to the nonlinearity of the incident waves come into existence. Although the magnitudes of the forces produced on a Tension Leg Platform(TLP) by these nonlinear waves are small, they act on the TLP at sum and difference frequencies away from those of the incident waves. So, the second order sum and difference frequency wave loads produced close to the natural frequencies of TLPs often give greater contributions to high and low frequency resonant responses. The second order wave exciting forces and moments have been obtained by the method based on direct integration of pressure acting on the submerged surface of a TLP. The components of the second order forces which depend on first order quantities have been evaluated using the three dimensional source distribution method. The numerical results of time domain analysis for the nonlinear wave exciting forces in regular waves are compared with the numerical ones of frequency domain analysis. The results of comparison confirmed the validity of the proposed approach.

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An Analysis of Vibration and Frequency Characteristics for Quartz Crystal Using the Finite Element Method (FEM을 이용한 수정진동자의 진동 및 주파수 해석)

  • Park, Jae-Sung;Go, Young-Jun
    • Journal of the Institute of Electronics Engineers of Korea TE
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    • v.42 no.1
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    • pp.7-12
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    • 2005
  • It was analyzed that the vibration and frequency characteristics for quartz crystal using a finite element method, ANSYS. It was investigated that the resonant frequency of quartz crystal by fixing the diameter of quartz crystal for the various its thickness. There were also studied that the resonant frequency value with different electrode thin films of Au, Ag and Al. As the result of this study, the best condition for quartz crystal unit was determined by the finite element method. If the thickness of quartz crystal is smaller than 0.2 mm, the high frequency over 8.102 MHz was obtained. In addition, as to the change of resonant frequency on electrode thin film, Al turned out to be superior to Au or Ag in frequency response.

Effects of Imperfect Fixing at the Active End of Spring-top Resonant Column Apparatus (주동단에 반력으프링이 부착된 공진우 시험기에서 우동단 불완전 고정의 영향)

  • 민덕기
    • Geotechnical Engineering
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    • v.6 no.1
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    • pp.7-14
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    • 1990
  • The two degree of freedom model is proposed to study the effects of imperfect fixing at the active end of spring-top resonant column apparatus. A computer program using the SYMPHONY spreadsheet is developed to calculate the dimensionless frequency, F, from which modulug can be determined. It is found that the effect of reaction mass through the parameter Tr on dimensionless frequency, F, can not be ignored if Tr$\leq$20. As To increases, the variation of F increases. But for Tr$\geq$ 20, the effect of To becomes small. It is recommended that T. be greater than 20 if single degree of freedom model is rosed to determine modulus of soil. It also is found that damping ratios of specimen and apparatus do not strongly affect the dimensionless frequency, F.

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Measurement of angular velocity using the self-mixing effect of semiconductor laser (되먹임 효과를 이용한 회전체의 속도측정)

  • 이병욱
    • Korean Journal of Optics and Photonics
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    • v.11 no.4
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    • pp.250-254
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    • 2000
  • We have constructed laser Doppler velocimetry system using self-mixing effect with a semiconductor laser. This technology is based on the frequency mixing phenomena which occurs when light scattered back from the moving object into the laser cavity interferes with light inside the laser. We have compared the value of Doppler shifted frequency with the velocity variation of the wheel. Frequency dependence on the angle between the moving direction of rotating aluminum wheel and the incident beam also have been proved. As an illustration of the performance of the velocimeter, velocity measurements of a rotating disk are described. Doppler signal shows a good linear relationship with velocity of rotating disk.

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Sound absorption of micro-perforated thin plates in a duct (덕트내 미세천공 박판의 흡음)

  • Kim, Hyun-Sil;Kim, Bong-Ki;Kim, Sang-Ryul;Seo, Yun-Ho;Ma, Pyung-Sik
    • The Journal of the Acoustical Society of Korea
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    • v.36 no.5
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    • pp.305-313
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    • 2017
  • In this paper, sound absorption of thin elastic plates installed in a rigid duct is discussed using an analytic method. The number of plates can be one or two, and each plate might have micro-perforation. Vibration of the plates and sound pressure fields inside the duct and air cavity are expressed in terms of an infinite series of modal functions. Under the plane wave assumption, a low frequency approximation is derived by including the first few plate modes. It is found that the sound absorption coefficient of the plates without micro-perforation shows sharp peaks at resonance frequencies, and due to the interaction between the plates and air cavity, the resonance frequencies move as the cavity depth changes. For the case of micro-perforated plates, it is found that the sound absorption is mainly affected by the perforation ratio. When the perforation ratio is order of few percent, the sound absorption is almost independent of plate vibration.

Transmitted Noise Reduction of Piezoelectric Smart Panels using Passive/Active Method in Wide Range frequency (수동/능동적 방법을 혼용한 압전지능패널의 광대역 전달 소음저감성능)

  • 이중근;박우철
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.2 no.2
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    • pp.73-79
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    • 2001
  • In this paper, the transmitted noise reduction performance of piezoelectric smart panels is experimentally studied. The proposed piezoelectric smart panels are comprised of plate structure on which piezoelectric sensor/actuators are bonded and sound absorbing material is provided. It is a combination of passive and active approaches utilizing a passive effect at high frequencies and an active effect at low frequencies. To prove the concept of piezoelectric smart panels, an acoustic measurement experiment is performed. An acoustic tunnel is designed and its acoustic characteristics are tested. Below 800Hz, the tunnel exhibits a plane wave guide characteristics. When an absorbing material is bonded on a single plate, a remarkable transmitted noise reduction in mid frequency range is observed except the first resonance frequency. By enabling the active control of single smart panel with negative feedback control. about 10dB noise reduction is achieved at the resonance frequencies. The double smart panel got 4dB at the first resonance frequency and has more potential to reduce the transmitted noise in a wide range frequency. Piezoelectric smart panels incorporating passive absorbing material and active piezoelectric devices is a promising technology for noise reduction in a wide range frequency.

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Frequency and power stabilization of radio frequency excited CO2 laser using photoacoustic effect (광음향 효과에 의한 고주파 여기식 CO2 레이저의 주파수 및 출력 안정화)

  • Choi, Jong-Woon;Yu, Moon-Jong;Woo, Sam-Yong;Suh, Ho-Suhng
    • Korean Journal of Optics and Photonics
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    • v.15 no.6
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    • pp.569-574
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    • 2004
  • We stabilized the frequency and power of a CW radio-frequency-excited $CO_2$ laser on the peak of the Doppler broadened gain curve using the photoacoustic effect generated from the laser itself. The condenser microphone is installed in the radio frequency discharge chamber to detect a photoacoustic signal. The photoacoustic signal is fed to a lock-in stabilizer as a reference signal for stabilization. The frequency stability is estimated to be better then 5.4${\times}$10$^{-8}$ at the P(20) line. The stabilized output variation was reduced 9.3%, compared to 100% for a free running laser.