• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.652-658
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• 2016

In practical control systems differences between nominal and real systems arise from internal uncertainties and/or external disturbances. This paper presents a model-based low-order disturbance observer for a sinusoidal disturbance with unknown constant offset. By using the disturbance model of a biased harmonic signal, the proposed method can successfully estimate the biased sinusoidal disturbance with unknown amplitude and phase but known frequency. At the first stage of the observer design, a model-based disturbance observer is designed when all the system states are measurable. Next, a sufficient condition is presented for the proposed observer to estimate the sinusoidal disturbance with a minimal-order additional dynamics using only output measurement. Comparative computer simulations are performed to test the performance of the proposed method. The simulation results show the enhanced performance of the proposed disturbance observer.

• Journal of the Korean Institute of Gas
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• v.25 no.1
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• pp.14-19
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• 2021

The change of the vorticity and the temperature distribution in heat exchanger tube bank were analyzed for the flows with the constant inlet velocity and the sinusoidal inlet velocity. The flow frequency characteristics were examined by analyzing power spectral density of lift and drag at a typical circular tube in the tube bank. Karman vortex street could be seen at the upstream region of tube bank for the case of constant inlet velocity. It could be seen that the Karman vortex street was affected by the change of inlet velocity near the circular tubes for the case with the sinusoidal inlet velocity. It was observed that the unsteady temperature distributions for both inlet velocity conditions had almost the same motion as the flow vorticity behavior. The flow frequency for the case with the constant inlet velocity is 37.25Hz, and that with the sinusoidal inlet velocity, the flow frequency is 18.63Hz, which is equal to the sinusoidal inlet velocity. The mean surface Nusselt number(Nu) for overall heat exchanger tube bank was 1051 for the case with the constant inlet velocity and 1117 for the case with the sinusoidal inlet velocity. From the result of heat transfer analysis, it could be seen that Nu with the sinusoidal inlet velocity showed 6.3% increase than that with the constant inlet velocity.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.570-573
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• 2004

This paper present a distributed RC lines (URCs) oscillator with sinusoidal output. The frequency of oscillator can be controlled and adjustable by varying an one pole amplifier. The circuit incorporated an gain controller loop for amplitude stabilization with low distortion. The realization of simulation and experimental results are in reasonably good agreement with the theoretical , and very low harmonic distortion. In this circuit can be suitable for LSI process fabrication and the circuit application in electronic communications system.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.13-18
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• 2001

This paper deals with finite element analysis for free vibration and forced sine vibration of Ka- and Ku- bend antenna structures using MSC/PATRAN/NASTRAN. The structures are designed to satisfy minimum resonance frequency requirement in order to decouple the dynamic interaction of the satellite with the spacecraft bus structure. From the forced sinusoidal vibration, we have observed output acceleration versus input in X-,Y- and Z- direction, based on base excitation using large mass method. The results of finite elements analysis can be used as the reference data for the experimental test of satellite antenna, resulting in the reduction of cost and time by predicting and complementing experimental data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.687-692
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• 2002

In order to verify the effectiveness of adding visooelastic dampers to full-scale steel frame structure on the reduction of their seismic and wind response a experimental work was carried out. First, The test was conducted on the VE dampers subjected to sinusoidal excitations under a variety of ambient temperatures, frequency, and the damper strain. Results from these tests showed that the viscoelastic dampers have high energy dissipation capacity. Second, The vibration tests was conducted of the full-scale steel frame structure with md without added VE dampers at different temperatures. Viscoelastically damped full-scale structure test result on the effect of ambient temperature show that viscoelastic dampers are very effective in reducing excessive vibration of the structure due to sinusoidal excitation over a wide ringe of ambient temperature.

• Interaction and multiscale mechanics
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• v.6 no.1
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• pp.15-29
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• 2013

Phononic system composed of periodical elastic structures exhibit band gap phenomenon, and all elastic wave cannot propagate within the band gap. In this article, we consider one-dimensional binary materials which are periodically arranged as a 20-layered medium instead of infinite layered system for phononic system. The layered medium with finite dimension is subjected to a uniformly distributed sinusoidal loading at the upper surface, and the bottom surface is assumed to be traction free. The transient wave propagation in the 20-layered medium is analyzed by Laplace transform technique. The analytical solutions are presented in the transform domain and the numerical Laplace inversion (Durbin's formula) is performed to obtain the transient response in time domain. The numerical results show that when a sinusoidal loading with a specific frequency within band gap is applied, stress response will be significantly decayed if the receiver is away from the source. However, when a sinusoidal force with frequency is out of band gap, the attenuation of the stress response is not obvious as that in the band gap.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.11-16
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• 2002

The differential equations governing free vibrations of the elastic, horizontally curved beams with unsymmetric axis are derived in Cartesian coordinates rather than in polar coordinates, in which the effect of torsional inertia is included. Frequencies are computed numerically for the sinusoidal curved beams with both clamped ends and both hinged ends. Comparisons of natural frequencies between this study and SAP 2000 are made to validate theories and numerical methods developed herein. The convergent efficiency is highly improved under the newly derived differential equations in Cartesian coordinates. The lowest four natural frequency parameters are reported, with and without torsional inertia, as functions of three non-dimensional system parameters: the horizontal rise to chord length ratio, the span length to chord length ratio, and the slenderness ratio.

• Journal of Ocean Engineering and Technology
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• v.7 no.1
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• pp.147-155
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• 1993

The effect of stress waveforms on corrosin fatigue and the role of dissolution mechanism in 3NilCr steel and 20Ni maraging steel have been investigated in aerated 3% NaCl solution and synthetic seawater under sinusoidal, triangular, square, positive sawtooth, negative sawtooth, and trapezoidal stress waveforms with open circuit at frequency of 1Hz and stress ratio of 0.1. The crack growth rates under square waveform were substantially lower than under sinusoidal and triangular waveforms, but the crack growth rates under sinusoidal waveform were slightly higher under triangular waveform. For a given frequency the growth rates under the positive sawtooth waveform are higher than those under the negative sawtooth waveform. The fatigue crack growth rates of most specimens were in good agreement with the values calculated by the model based on the dissoultion mechanism.

• The Journal of the Acoustical Society of Korea
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• v.18 no.2
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• pp.77-82
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• 1999

A sinusoidal model has been widely used in the analysis and synthesis of speech and audio signals, and becomes one of the efficient candidates for high quality low bit rate audio coders. One of the crucial steps in the analysis and synthesis using a sinusoidal model is the detection of tonal components. This paper proposes an efficient method for the analysis and synthesis of audio signals using a sinusoidal model, which uses psychoacoustic criteria such as masking effect, masking index, and JNDf(Just Noticeable Difference in Frequency). Simulation results show that the proposed method reduces the number of sinusoids significantly without degrading the quality of the synthesized audio signals.

• The Journal of the Acoustical Society of Korea
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• v.22 no.4E
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• pp.141-149
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• 2003

As music of digital form has been widely used, many people have been interested in the automatic extraction of natural information of music itself, such as key of a music, chord progression, melody progression, tempo, etc. Although some studies have been tried, consistent and reliable results of musical information extraction had not been achieved. In this paper, we propose a method to extract chord and tempo information from general polyphonic music signals. Chord can be expressed by combination of some musical notes and those notes also consist of some frequency components individually. Thus, it is necessary to analyze the frequency components included in musical signal for the extraction of chord information. In this study, we utilize a sinusoidal modeling, which uses sinusoids corresponding to frequencies of musical tones, and show reliable chord extraction results of sinusoidal modeling. We could also find that the tempo of music, which is the one of remarkable feature of music signal, interactively supports the chord extraction idea, if used together. The proposed scheme of musical feature extraction is able to be used in many application fields, such as digital music services using queries of musical features, the operation of music database, and music players mounting chord displaying function, etc.