• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.181-184
• /
• 2007

This paper deals with the method of vibration measurement of a gun barrel structure using mechanical filter. When a bullet with high speed is moving within a gun barrel type structure with low bending vibration frequencies, it is difficult to measure the bending vibration signals of the structure. For example, noncontact type sensors such as displacement or velocity sensor are not appropriate for the measurement of vibrational signals because of the movement effect of the equipment frame through the moving structures or effect of the ground vibration. One of contact type sensors such as accelerometer is profitable for measurement of vibrational signals because of its wide measurement ranges. In the case of a gun barrel structure including high vibrational signals like shock waves, however, it is necessary to propose vibration measurement method filtering high frequencies. The purpose of the paper is to propose the proper vibrational measurement technique filtering high frequencies of a gun barrel type structure.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.1
• /
• pp.119-126
• /
• 2005

The geometrical parameters, vibrational frequencies, and relative energies of H$_2$(A$_{n+1}$X$_{2n}$)H$_2$ (A=C or Si, X=O or S, n = 1-2) oligomers have been investigated using high level ab initio quantum mechanical techniques with large basis sets. The equilibrium geometries have been optimized at the self-consistent field (SCF), the coupled cluster with single and double excitation (CCSD), and the CCSD with connected triple excitations [CCSD(T)] levels of theory. The highest level of theory employed in this study is cc-pVTZ CCSD(T). Harmonic vibrational frequencies and IR intensities are also determined at the SCF level of theory with various basis sets and confirm that all the optimized geometries are true minima. Also zero-point vibrational energies have been considered to predict the dimerization and the relative energies.

• Journal of the Korea Society for Simulation
• /
• v.7 no.2
• /
• pp.105-114
• /
• 1998

Using finite elements, a simulation is prformed for the pipe systems to investigate free vibrational characteristics, that is natural frequencies, considering the intial tension due to the velocity and the pressure of the inside fluid flow. To confirm the program developed in this study, the results are compared with the results of commercial software ANSYS. When the initial tension is neglected in curved pipes, the natural frequencies are reduced as flow velocity increases, and the rapid decreases of the natural frequencies took place. However, when the initial tension is taken into account, the natural frequencies are not changed with the change of the flow velocity. In free vibrational simulation of pipe systems, it is necessary to calculate the initial state force due to the velocity and the pressure of the fluid flow from the equilibrium first, then the force should be included in the equation of motion of the systems to get more accurate natural frequencies.

• Journal of the Korean Chemical Society
• /
• v.50 no.1
• /
• pp.7-13
• /
• 2006

infrared(IR) absorption spectra were calculated for the ethyl ester of p-tert-butylcalix[4]arene (1) in the cone conformer and its alkali-metal-ion complex. The vibrational spectra were obtained by restricted Hartree-Fock (RHF) calculations with the 6-31G basis set. The characteristic vibrational frequencies of various C-O and C=O stretching motions of the complexes show that the structure of 1+K+ complex is almost of C4v symmetry compared to 1+Na+ (C2v) analogue. The theoretical results for the host molecule 1 and complex (1+Na+) were compared with the experimental results, and the calculated vibrational frequencies agree well with the features of the experimental spectra.

• The Journal of the Acoustical Society of Korea
• /
• v.16 no.1
• /
• pp.16-23
• /
• 1997

As analysis of the forced dynamic response and vibrational mode for the cantilevered beam is described. Experimental results are compared with the natural frequencies and vibrational modes for the cantilevered beam using the theory of Bernoulli-Euler and finite element method. We have found 1st and 2nd resonance frequency of the cantilevered beam by means of the various external frequencies, $1{\sim}70Hz$, using magnetic transducer. And we have studied the vibrational displacement at obtained resonance frequency of the cantilevered beam. The experimental results for the nodes of cantilevered beam were 0 in 1st mode and 0,0.786 in 2nd mode. close agreement between the theoretically predicted results and experimental result was obtained for the vibrational mode.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.971-977
• /
• 2005

Power Flow Analysis (PFA) is developed for the effective predictions of frequency-averaged vibrational response in medium-to-high frequency ranges. In PFA, the power coefficients of semi-infinite structure and for-field energy density are used to predict the vibrational responses of structures. Generally, at high frequencies, PFA can predict narrow-band frequency-averaged vibrational responses of built-up structures. However, in low- to medium frequency ranges, the dynamic responses obtained by PFA represent broad-band frequency-averaged vibrational energy densities. For the prediction of vibrational response variance in Power Flow Finite Element Method (PFFEM), the variances of input power and joint element matrix describing structural coupling relationship are derived. Finally, for the validity of developed formulation, numerical examples for two co-planer plates are performed and the vibrational response variance of the structure are compared with the results of classical and PFFEM solutions.

• Journal of the Korean Institute of Gas
• /
• v.20 no.6
• /
• pp.58-64
• /
• 2016

Vibrational characteristics of curved pipe structures are investigated with respect to the change of inside flow velocities. Based upon the Hamilton's principle, the equations of motions are derived, and the finite element equation is constructed to solve the frequency equation for curved pipe structures. When the initial tension is neglected in cured pipes, the natural frequencies are reduced as flow velocity increases, and the rapid decreases of the natural frequencies take place. However, when the initial tension is taken into account, the natural frequencies are not changed with the change of the flow velocity. In free vibrational simulation of pipe systems, it is necessary to calculate the initial force due to the velocity and the pressure of the fluid flow from the equilibrium. The force should be included in the equation of motion of the systems to get more accurate natural frequencies. The mechanical properties like stiffness or the location of pipe support need to be changed to avoid resonance. The natural frequencies are to be isolated from the frequency range of dominant vibration modes. The angles of elbows do not affect the change of the fundamental natural frequency, but affect the change of the third or higher natural frequencies.

• Journal of the Korean Chemical Society
• /
• v.47 no.4
• /
• pp.325-333
• /
• 2003

The geometrical parameters, vibrational frequencies, and relative energies for 1,2-, 1,3-dioxetanes, and 1,3-cyclodisiloxane have been investigated using high level ab initio quantum mechanical techniques with large basis sets. The geometries have been optimized at the self-consistent field(SCF), the single and double excitation configuration interaction(CISD), the coupled cluster with single and double excitation(CCSD), and the CCSD with connected triple excitations[CCSD(T)] levels of theory. The highest level of theory employed in this study is TZ2P CCSD(T). Harmonic vibrational frequencies and IR intensities are also determined at the SCF level of theory with various basis sets and confirm that all the optimized geometries are true minima. Also zero-point vibrational energies have been considered to predict the dimerization energies for 1,2- and 1,3-isomers.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.9
• /
• pp.3017-3024
• /
• 2012

The geometrical parameters, vibrational frequencies, and binding energies for $(H_2O_3)_n$ (n = 1-5) have been investigated using various quantum mechanical techniques. The possible structures of the clusters (n = 2-5) are fully optimized and the binding energies are predicted using energy differences at each optimized geometry. The harmonic vibrational frequencies are also determined and zero-point vibrational energies (ZPVEs) are considered for the better prediction of the binding energy. The best estimation of the binding energy for the dimer is 8.65 kcal/mol. For n = 2 and 3, linear structures with all trans forms of the HOOOH monomers are predicted to be the lowest conformations in energy, while the cyclic structures with all cis-HOOOH monomers are preferable structures for n = 4 and 5.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.9
• /
• pp.2699-2703
• /
• 2014

We solve the Klein-Gordon equation with the modified Rosen-Morse potential energy model. The bound state energy equation has been obtained by using the supersymmetric shape invariance approach. The relativistic vibrational transition frequencies for the $6^1{\Pi}_u$ state of the $^7Li_2$ molecule have been computed by using the modified Rosen-Morse potential model. The calculated relativistic vibrational transition frequencies are in good agreement with the experimental RKR values.