• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.553-557
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• 2013

The stretching vibration of OH of ice Ih is studied by Car-Parrinello molecular dynamics in regarding the effect of mixed H/D contamination while the vibrational spectrum is considered by velocity-velocity autocorrelations of the sampled ensemble. When hydrogen atoms are immersed randomly into the deuterated ice, a typical vibrational frequency of OH stretching mode is observed to be similar to that from the pure $H_2O$ ice. When focusing on the correlation of isolated neighboring OH stretching, a narrower and blue shifted peak is observed at the high frequency range as a result of the screening from the complex many body correlations by $D_2O$ environment. It is also specifically related to the symmetric intermolecular correlations between neighboring OH stretching modes. More enhanced high frequency range can be explained by the expansion of such two body correlations to collective many body correlations among all possible OH stretching modes. This contribution becomes important when it involves in chemical interactions via excitation of such vibrational states.

• Nuclear Engineering and Technology
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• 제30권1호
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• pp.8-16
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• 1998

In this work a method to detect the vibrational peak and to decide the vibrational mode of detected peak for core internal vibration monitoring system which is particularly concerned on the core support barrel (CSB) and fuel assemblies is developed. Flow induced vibration and aging process in the reactor internals cause unsoundness of the internal structure. In order to monitor the vibrational status of core internal, signals from the ex-core neutron detectors are transformed into frequency domain. By analyzing transformed frequency domain signal, an analyst can acquire the information on the vibrational characteristics of the structures, i.e., vibration frequencies of each component, vibrational level, modes of vibration, and the causes of the abnormal vibration, if any. This study is focused on the development of the automated monitoring system. Several methods are surveyed to define the peaks in power spectrum and fuzzy theory is used to automatic detection of the vibrational peaks. Fuzzy algorithm is adopted to define the modes of vibration using the peak values from fuzzy peak recognition, phase spectrum, and coherence spectrum.

• Bulletin of the Korean Chemical Society
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• 제6권4호
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• pp.183-186
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• 1985

The lattice vibrational calculation of orthorhombic hydrogen chloride is performed using physically realistic potential function which can reproduce the X-ray structure and heat of sublimation of the low temperature phase. The polar coordinates representation is introduced in order to describe the intermolecular interactions in a molecular crystal. The splitting in internal modes is calculated as 49 $cm^{-1}$ and the other modes are in good agreement with experimental results.

• 대한기계학회논문집A
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• 제21권6호
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• pp.896-906
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• 1997

The effect of duplicate flexible disks on the vibrational modes of a flexible rotor system is investigated by using an anlytical method based on the assumed modes method. The rotor model to be analyzed consists of duplicate disks on a flexible shaft. In modeling the system, centrifugal stiffening and disk flexibility effects are taken into account. To demonstrate the effectiveness of the method, a hard disk drive spindle system commonly used in personal computers and a simple flexible rotor system with two disks are selected as examples. In particular, the dynamic coupling between the vibrational modes of the shaft and the duplicate disks is investigated with the shaft rotational speed varied.

• Bulletin of the Korean Chemical Society
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• 제24권6호
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• pp.717-722
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• 2003

The structure, force field and vibrational spectra of triphenylene are studied by $B3LYP/6-31G^*$(5d) level of theory. The results are compared to those of the related system, phenanthrene. The scale factors in nonredundant local coordinates obtained after fitting the DFT frequencies to the experimental numbers of phenanthrene-$d_0 and -d_{10}$ are transferred to predict the spectra and assignment of triphenylene for in-plane modes. The frequencies based on scaling methodology due to Lee et al. are also obtained. These frequencies are compared with the predicted numbers based on scale factors from phenanthrene. Probable assignment for out-of-plane modes is proposed based on simple scaling of Scott and Radom (scale factor 0.9614) as well as by scaling methodology by Lee et al.

• Bulletin of the Korean Chemical Society
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• 제15권3호
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• pp.228-236
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• 1994

The effect of the vibration mode coupling induced by the vibration-rotation interaction on total energy was investigated for the states with zero total angular momentum(J=0) in a quasilinear symmetric triatomic molecule of $AB_2$ type using a model potential function with a slight potential barrier to linearity. It is found that the coupling energy becomes larger for the levels of bend and asymmetric stretch modes and smaller for symmetric stretch mode as the excitation of the vibrational modes occurs. The results for the real molecule of $CH_2^+$, which is quasilinear, generally agree with the results for the model potential function in that common mode selective dependence of coupling energy is exhibited in both cases. The differences between the results for the model and real potential function in H-C-H system are analyzed and explained in terms of heavy mixing of the symmetric stretch and bend mode in excited vibrational states of the real molecule of $CH_2^+$. It is shown that the vibrational mode coupling in the potential energy function is primarily responsible for the broken nodal structure and chaotic behavior in highly excited levels of $CH_2^+$ for J= 0.

• 한국통신학회:학술대회논문집
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• 한국통신학회 1986년도 춘계학술발표회 논문집
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• pp.202-205
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• 1986

In this paper, real-time vibration measurement using system is described. Modes getting from different vibrational frequencies of come vibrational plates are rectified and filtered by digitizer and recorded 488 dots(abscissa) printer. PZT and mechanical chopper is placed in front of cw laser for better resolving power. Rayleigh`s mode theory and mode pattern are compared with experimental results.

• Bulletin of the Korean Chemical Society
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• 제24권8호
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• pp.1061-1068
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• 2003

The correlation between the water and N-methylacetamide (NMA) intramolecular vibrational frequencies and the hydrogen-bond length in a variety of NMA-H₂O and NMA-D₂O complexes was investigated by carrying out ab initio calculations. As the hydrogen-bond length decreases, the frequencies of bending and stretching modes of the hydrogen-bonding water increases and decreases, respectively, and the amide I and II (III) mode frequencies of the NMA decreases and increases, respectively. In this paper, correlation maps among the amide (I, II, and III) modes of NMA and three intramolecular water modes are thus established, which in turn can be used as guidelines for interpreting two-dimensional vibrational spectra of aqueous NMA solutions.

• 소음진동
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• 제9권3호
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• pp.509-516
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• 1999

The ESPI (Electronic Speckle Pattern Interferometry) algorithm has been simulated to calculate vibrational modes of a thin right-angled STS304 plate. The phase transformation of the reference wave of the ESPI is carried out only one time during vibration in order to clarify ESPI speckle patterns. Two dimensional vibrational modes are calculated from one ESPI pattern before vibration onset and two ESPI patterns during vibrations but with and without the phase transformation. The ESPI harmonic results are compared with those derived from the finite element method (FEM), and they agree very well. Additionally a phase unwrapping algorithm has been newly developed to derive a displacement map from an ESPI phase map.

• 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.