• Geomechanics and Engineering
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• v.35 no.4
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• pp.367-383
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• 2023

The present paper examines the natural frequency responses of the bi-directional (n_x-n_y, n_y-n_z and n_z-n_x) and multidirectional (n_x-n_y-n_z) functionally graded (FG) plate and curved structures with and without porosity. The even and uneven kind of porosity pattern are considered to observe the influence of porosity type and porosity index. The numerical findings have been obtained using a higher order shear deformation theory (HSDT) based isometric finite element (FE) approach generated in a MATLAB platform. According to the convergence and validation investigation, the proposed HSDT based FE model is adequate to predict free vibrational responses of multidirectional porous FG plates and curved structures. Further a parametric analysis is carried out by taking various design parameters into account. The free vibrational behavior of bidirectional (2D) and multidirectional (3D) perfect-imperfect FGM structure is examined against various power law index, support conditions, aspect, and thickness ratio, and for the curvature of curved structures. The results indicate that the maximum non-dimensional fundamental frequency (NFF) value is observed in perfect FGM plates and curved structures compared to porous FGM plates and curved structures and it is maximum for FGM plates and curved structures with uneven kind of porosity than even porosity.

• Journal of the Korea Furniture Society
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• v.16 no.1
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• pp.17-23
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• 2005

European maple is famous for the optimum solid wood for making bridge which is the most important part in violin acoustics. This study was carried out to investigate the variation of main features, i. e. annual ring width and cutting direction of costly imported violin bridge blanks and to examine the effect of these features of the blanks on the vibrational characteristics of bridge blanks. Imported violin bridge blanks had somewhat large variation in major macroscopical and physical properties and there was little relationship between annual ring density and weight of maple blanks. Resonant frequency of violin bridge blanks had some positive correlation with weight, however, damping having negative relationship with frequency was seldom affected by any physical properties of the maple blanks. Deviation from the radial cutting of tail side(ray direction from top toward feet on the edge of bridge blank) lowered the resonant frequency. Consequently, weight and ray direction should be taken for the critical quality decisive factors(QDF) of incoming bridge blanks by not only inspectors also luthiers who tune the bridge by shaping and are responsible for the final timbre quality of this complicate instrument.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.151-154
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• 1997

An open loop vibrational control of underactuated mechanical systems with amplitude and frequency modulations is investigated. The underactuated systems considered in the paper are assumed to have free joints with no brake. The active joints are positioned first by a linearizing control, and then periodic oscillatory inputs are applied to them to move the remaining free joints to their desired states. A systematic way of obtaining averaged systems for the underactuated systems with oscillatory vibrations is developed. A complete solution to the open loop control strategy in terms of determining amplitudes and frequencies for general system is still under investigation. However, a specific control design for 2R manipulator which is obtained the averaging system is demonstrated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1197-1202
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• 2007

The paper deals with the structural analysis and vibration test for the scaffolding system of LNG cargo containment. The eight-stories scaffolding system has telescopic area, working area, coner area and storage area in real system. In the structural analysis, the maximum displacement and stress of the each floor for the scaffolding system are investigated by finite element method. In the vibrational analysis, the natural frequencies and mode shapes for 8-stories scaffolding system of the LNG cargo containment are investigated. In order to compare theoretical natural frequencies with experimental ones, small size of 2-step scaffolding structure is used, and the theoretical results for natural frequency have a good agreement with experimental ones.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.534-537
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• 1995

An open loop vibrational control of underactuated mechanical system with amplitude and frequency modulations is investigated. The underactuated systems sonsidered in the paper are assumed to have free joints with no brake. The active joints are positioned first by a linearizing control, and then periodic oscillatory input are applied to them to move the remaining free joints to their desired states. A systematic way of obtaining averaged systems for the underactuated systems with oscillatory vibration is developed. A complete solution to the open loop control strateegy in terms of determining amplitudes and frequencies for general system is still under investigation. However, a specific control design for 2R manipulator which is obtained through the averaged system is demonstrated.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.3
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• pp.110-116
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• 2002

Here are shown on stress and vibration evaluations and application of piping system in petrochemical plant with and actual example. While stress evaluation by thermal growth has no argument on the calculated results, vibrational evaluations have some different results in accordance with the evaluation methods. In case of the static stress evaluation the ASME B3l.3 code defines 7000 cycles of fatigue lift: in operating the piping system with a design condition. However, the method of vibrational evaluation on piping systems in petrochemical plants has not been established clearly, yet. In this stuffy, it is purposed to present the requirement of a vibrational evaluation method for petrochemical plant piping system, with an actual application.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1855-1858
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• 2004

Molecular geometries for the cationic and neutral species of OXO (X=Cl, Br, and I) are optimized using the Hartree-Fock (HF) theory, the second order Moller-Plesset perturbation theory (MP2), the density functional theory with the B3LYP hybrid functional (B3LYP), and the coupled cluster theory using single and double excitation with a perturbational treatment of triplet excitation (CCSD[T]) methods, with two basis sets of triple zeta plus polarization quality. The single point calculations for these species are performed at the CCSD(T,Full) level. The harmonic vibrational frequencies for these species are calculated at the HF, MP2, B3LYP and CCSD(T) levels. The adiabatic ionization potential for OIO is calculated to be 936.7 kJ/mol at the CCSD(T,Full) level and the correct value is estimated to be around 945.4 kJ/mol.

• Journal of Sensor Science and Technology
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• v.24 no.2
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• pp.93-95
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• 2015

We present an optical detection method for the fundamental vibrational mode of a tuning fork crystal oscillator in air. A focused He/Ne laser beam is directed onto the edge of one vibrating tine of the tuning fork; its vibrating motion chops the incoming laser beam and modulates the intensity. The beam with modulated intensity is then detected and converted to an electrical signal by a high-speed photo-detector. This electrical signal is a sinusoid at the resonant frequency of the tuning fork vibration, which is 32.76 kHz. Our scheme is robust enough that the sinusoidal signal is detectable at up to $40^{\circ}$ of rotation of the tuning fork.

• Bulletin of the Korean Chemical Society
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• v.19 no.2
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• pp.202-206
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• 1998

The p-fluorotoluene was vibronically excited in a jet with a buffer gas He in a corona excited supersonic expansion. The vibronic emission spectrum of the jet cooled p-fluorotoluene in the transition of S1 → S0 has been recorded with a Fourier transform spectrometer in the uv region. The spectrum observed was analyzed to obtain accurate vibrational frequencies in the ground electronic state by comparing with those reported previously. The origin of the low frequency sequence bands observed in this work was discussed. Also, the absence of significant intensity of hot band resulting from the excited vibrational states in the spectrum suggests extensive vibrational cooling in the source.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.339-348
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• 1990

Techniques which are able to predict and control dynamic characteristics, not affecting the vibrational characteristics on the modification of structural design, are being studied. As one of these techniques, experimental modal analysis is widely applied by many researchers. In this study, modal analysis is performed using transfer matrix method by a macro computer. The developed program would estimate the structural modal parameters precisely, and the validity of this program is certified by comparing with the experimental results of .GAMMA A. structure. Estimated modal parameters(natural frequency, vibrational mode, equivalent mass, etc.) are in accord with the experimental results. Also, the optimal location of the additive mass is determined by the evaluation of the vibrational mode and the equivalent mass. The relation between the additive mass and the equivalent mass is specified, and we come to know that the ratio of equivalent mass to additive mass alter linearly within the range of 20%.