• 대한토목학회논문집
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• 제28권1A호
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• pp.125-133
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• 2008

사장교의 장대화로 주탑 및 보강형과 더불어 사장 케이블의 동적 안정화에 많은 노력이 요구된다. 사장 케이블에서 동적 불안정은 주로 대칭 1모드와 역대칭 1모드에서 발생되며 대칭 1모드는 역대칭 1모드와 다르게 새그의 영향이 명확하게 나타나므로 기본진동수는 팽팽한 스트링으로부터 얻은 것과 상이한 결과를 제공하게 된다. 이러한 현상에 관해 Irvine, Triantafyllou, 안상섭 등은 해석적 기법을 통해 동적거동 분석을 수행하였다. 이들의 연구는 광범위한 영역의 Irvine Parameter에 대해 중요한 결과를 제시하였으나 특성점(Cross-Over Point 혹은 복합모드 형성점) 이후 영역에 대해서는 상이한 결과를 제시하였고 진동수방정식의 높은 비선형성으로 인해 해가 매우 민감한 난점이 있다. 본 연구는 사장 케이블 동적안정 문제에 주요한 모드들 중 새그의 영향이 가장 높은 대칭 1모드의 기본진동수에 초점을 맞추었으며 일반화된 역학적에너지에 경계조건을 만족시키는 진동형상을 적용하고 Rayleigh-Ritz 방법으로 해석적인 해를 제시하였다. 선행연구들과 다르게 본 연구는 선형적인 해를 제공하며 이에 따른 오차는 특성점 이내에서 3% 미만의 오차를 보였다. 또한, 사장 케이블이나 이에 준한 케이블은 특성점을 넘지 않으므로 공학적으로 충분한 가치를 갖는다고 볼 수 있다. 더불어 대칭 1모드에서 발생되는 갤로핑과 Parametric 공진대역을 분석하여 연구의 활용성을 확인하였다.

• 비파괴검사학회지
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• 제32권1호
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• pp.34-40
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• 2012

본 연구에서는 FRP 보강판 부착 콘크리트에서의 유도초음파 기본 모드의 전파 특성에 부착제인 epoxy의 두께와 물성이 미치는 영향을 알아보고자 하였으며, 이를 위해 FRP-epoxy-concrete로 구성된 다층 유도초음파 시스템을 모델링하고 모드 해석을 수행하였다. Epoxy 층의 두께와 탄성계수를 변수로 하여 해석을 수행한 결과, A0 모드에 비해 S0 모드가 epoxy 층의 두께와 탄성계수 변화에 큰 영향을 받으며, 이로부터 경계층인 Epoxy 층의 상태 평가에는 A0 모드에 비해 S0 모드가 유효하리라는 결론을 얻었다.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3771-3776
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• 2010

The dynamics of the $CN^-$-ligated ferric cytochrome c (CytcCN) in $D_2O$ at 283 K following Q-band photoexcitation at 575 nm was observed using femtosecond time-resolved vibrational spectroscopy. The equilibrium vibrational spectrum of the CN stretching mode of CytcCN shows two overlapping bands: one main band (82%) at $2122\;cm^{-1}$ with $23\;cm^{-1}$ full width at half maximum (fwhm) and the other band (18%) at $2116\;cm^{-1}$ with $7\;cm^{-1}$ fwhm. The time-resolved spectra show bleaching of the CN fundamental mode of CytcCN and two absorption features at lower energies. The bleach signal and both absorption features are all formed within the time resolution of the experiment (< 200 fs) and decay with a life time of 1.9 ps. One transient absorption feature, appearing immediately red to the bleach signal, results from the thermal excitation of low-frequency modes of the heme that anharmonically couple to the CN fundamental mode, thereby shifting the CN mode to lower energies. The shift of the CN mode decays with a lifetime of 2 ps, equivalent to the time scale for vibrational cooling of the low-frequency heme modes. The other transient absorption feature, which is 3.3 times weaker than the bleach signal and shifted $27\;cm^{-1}$ toward lower energies, is attributed to the CN mode in an electronically excited state where the CN bond is weakened with a lowered extinction coefficient. These observations suggest that photoexcited CytcCN mainly undergoes ultrafast radiationless relaxation, causing photo-deligation of $CN^-$ from CytcCN highly inefficient. As also observed in $CN^-$-ligated myoglobin, inefficient ligand photodissociation might be a general property of $CN^-$-ligated ferric hemes.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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• pp.194-200
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• 1999

Localized damage to a structure affects its dynamic properties, and much work has been undertaken investigating the variation of natural frequencies, damping ratios and mode shapes. This paper presents a technique based on wavelet transform to detect the existences and locations of structural damages. The procedure operates solely on the mode shape from the damaged structure, and does not require a priori knowledge of the undamaged structure. The procedure is developed using a 32-story shear building model. Applying wavelet transform to the mode shape successfully identifies the location of damage. The procedure is best suited to the mode shape obtained from the fundamental natural frequency. The wavelet coefficients from the higher mode shapes can be used to verify the location of damage, but they are not as sensitive as the wavelet coefficients of the lower mode shapes.

• 대한기계학회논문집A
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• 제21권2호
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• pp.232-244
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• 1997

In this paper weight function theory is extended to the determination of the stress intensity factors for the mode I in elliptic crack. For the calculation of the fundamental fields Poisson's theorem and Ferrers's method were employed. Fundamental fields are constructed by single layer potentials with surface density of crack harmonic fundamental polynimials. Crack harmonic fundamental polynimials up to order four were given explicitly. As an example of the application of the weight function theory the stress intensity factors along crack tips in nearly penny-shaped elliptic crack are calculated.

• 한국전자파학회논문지
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• 제24권11호
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• pp.1047-1054
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• 2013

본 논문은 다중 대역 레이더 수신기의 소형화를 위한 이중 모드 주파수 혼합기를 구현하였다. 제안한 혼합기는 역병렬 다이오드(anti-parallel diode)를 이용하였고, 제어 전압 유무에 따라 기본파 혼합기 또는 부고조파 혼합기로 동작한다. 제어 전압을 인가하여 기본파 혼합기로 동작하는 경우, X-대역에서 -10 dB 변환 손실, 2.0 dBm P1dB 특성을 나타내었고, 제어 전압을 인가하지 않은 부고조파 혼합기로 동작하는 경우 K-대역에서 -10 dB 변환 손실, 2.0 dBm P1dB 특성을 나타내었다.

• 동력기계공학회지
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• 제17권2호
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• pp.56-62
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• 2013

A technique is presented that uses a circular waveguide for the measurement of the bulk shear (S-wave) velocities of unconsolidated, saturated media, with particular application to near surface soils. The technique requires the measurement of the attenuation characteristics of the fundamental torsional mode that propagate along an embedded pipe, from which the acoustic properties of the surrounding medium are inferred. From the dispersion curve analysis, the feasibility of using fundamental torsional mode which is non-dispersive and have constant attenuation over all frequency range is discussed. The principles behind the technique are discussed and the results of an experimental laboratory validation are presented. The experimental data are best fitted for the different depths of wetted sand and the shear velocities are evaluated as a function of depths. Also the characteristics of the reflected signal from the defects are examined and the reflection coefficients are calculated for identifying the relation between defect sizes and the magnitude of the reflected signal.

• 한국자동차공학회논문집
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• 제8권3호
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• pp.171-180
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• 2000

This paper deals with the whole-body vibration and ride quality evaluation in the vertical direction. The responses of the floor, hip, back, and head in four subjects were measured for various seats when the floor was excited by random vibration with r.m.s of 1.2m/s2 in the vertical direction. In the transmissibility between the hip and floor, the fundamental mode is observed at 4.4 Hz. In the transmissibility between the head and floor, the fundamental mode at 4.4Hz and the second mode at 7.6Hz are observed. It is shown that the head motion is 41% larger than the hip motion and the response of female subject is larger than that of male subject. The response without backrest also was compared with that with backrest. From these human responses ride quality of five seats were evaluated by the ride value such as transfer ration having frequency weighting function is the statistical sense. It is observed that the seat having high damping property can reduce the most acceleration exposed to hip in the statistical sense for all ride valves, while the seat having different seat spring doesn't show statistical difference.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.271.1-271.1
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• 2008

• Journal of Advanced Marine Engineering and Technology
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• 제28권7호
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• pp.1165-1171
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• 2004

The free vibration analyses of the isotropic and CFRP laminated composite rectangular plates with point supports at the fix edge is performed by FEM. We showed optimal position and mode shape of point supports that maximized fundamental natural frequency of the isotropic and CFRP laminated composite rectangular plates by each aspect ratio and the number of point supports.