• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1023-1026
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• 2007

Optimal damping layout of the constrained viscoelastic damping layer on beam is identified with temperatures by using a gradient-based numerical search algorithm. An optimal design problem is defined in order to determine the constrained damping layer configuration. A finite element formulation is introduced to model the constrained damping layer beam. The four-parameter fractional derivative model and the Arrhenius shift factor are used to describe dynamic characteristics of viscoelastic material with respect to frequency and temperature. Frequency-dependent complex-valued eigenvalue problems are solved by using a simple resubstitution algorithm in order to obtain the loss factor of each mode and responses of the structure. The results of the numerical example show that the proposed method can reduce frequency responses of beam at peaks only by reconfiguring the layout of constrained damping layer within a limited weight constraint.

• Journal of the Korean Society of Safety
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• v.22 no.2 s.80
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• pp.1-7
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• 2007

A problem of a unsteady time-dependent flow in a channel is of practical importance and widely considered in the design of devices such as heat exchangers, duct, and electronic equipments. The characteristics of fluid flow in channel with oscillating vortex generator was investigated experimentally. The main object of this study was to investigate the effect of the excited frequency, the excited amplitude, and Reynolds numbers on the generated frequency. Flow patterns were visualized using smoke generator and generated frequencies were measured using hot wire anemometer. When the excited frequency is increased, excited amplitude decreased and Reynolds number increased, the strength of PSD of generated frequency is decreased.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.12
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• pp.595-601
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• 2003

For a control of CPS(Contactless Power Supply), the paper deals with the results which are simulated by a equivalent electric circuit on the LIPT(Linear Inductive Power Transmission). In order to control the CPS, the output values is handled with the driving frequency according to the change of a load. The method that controls the driving frequency for adjusting the output power is reasonable to be applied to the controller. But, when the driving frequency meets the resonant frequency and passes, it lead to a serious problem. Therefore, the controlled region of the driving frequency has to be predicted and determined by the simulation of a electric circuit.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2152-2154
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• 2004

A robust bending frequency tracker is proposed to design the adaptive notch filter which removes the time-varying missile structural mode from the sensor measurements. To design the bending frequency tracker, firstly, the signal model is derived from the input-output relationship of Nehorai notch filter structure. Also, the time-varying nature of the bending frequency is modelled as the norm-bounded uncertainty. Based on the uncertain signal model, it is shown that the design problem of robust bending frequency tracker can be casted into that of adaptive robust $H_{\infty}$ filter or equivalently robust LMS filter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.785-790
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• 2000

The resonant frequency of a gas-filled cylindrical Helmholtz resonator in a liquid is obtained analytically. The equation of motion of the resonator is derived by using the condition of equilibrium of forces acting on the mass in the neck of the resonator. The reaction force on the upper side of the cylinder due to the acceleration of external fluid and sound radiation is obtained by using the analytical results for the baffled circular-piston problem. From the frequency response function of the resonator, a formula to predict the resonant frequency of the resonator is derived. It is shown that the resonant frequency of the Helmholtz resonator significantly decreases due to the cushioning effect of gas inside the cavity. Therefore, when a pressure transducer is to be installed in a pin-hole type mounting method, much care should be paid to remove the gas from the cavity.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.58-66
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• 2001

GPC has been reported as a useful self-tuning control algorithm for systems with unknown time-delay and parameters. GPC is easy to understand and implement, and thus has won popularity among many practicing engineers. Despite its success, GPC does not guarantee is nominal stability. So, in this paper, GPC is rederived in frequency domain instead of in the time domain to guarantee its nominal stability. Derivation of GPC in frequency domain involves spectral factorization and Diophantine equation. Frequency domain GPC control law is stable because the zeros of characteristic polynomial are strictly Schur. Recursive least square algorithm is used to identify unknown parameters. To see the effectiveness of the proposed controller, the controller is simulated for a numerical problem that changes in dead-time, in order and in parameters.

• Journal of the Korean Wood Science and Technology
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• v.28 no.4
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• pp.83-93
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• 2000

This study was carried out to improve the physico-mechanical properties of board products by applying the technique of high frequency heating, and find out the optimum conditions of high frequency heating, compared with the technique of hot platen heating. The possibility of isocyanate resin application to board production was also considered to solve the problem of free formaldehyde emission from urea resin which is generally used in wood industry. For this study, 30 mm thick MDP (medium density fiberboard) with isocyanate resin were manufactured by the techniques of hot platen heating, high frequency heating and the combination techniques of both heating methods, and compared in several point of views.

• Journal of Information Processing Systems
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• v.16 no.5
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• pp.1129-1144
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• 2020

The thangka image inpainting method based on wavelet transform is not ideal for contour curves when the high frequency information is repaired. In order to solve the problem, a new image inpainting algorithm is proposed based on edge structural constraints and wavelet transform coefficients. Firstly, a damaged thangka image is decomposed into low frequency subgraphs and high frequency subgraphs with different resolutions using wavelet transform. Then, the improved fast marching method is used to repair the low frequency subgraphs which represent structural information of the image. At the same time, for the high frequency subgraphs which represent textural information of the image, the extracted and repaired edge contour information is used to constrain structure inpainting in the proposed algorithm. Finally, the texture part is repaired using texture synthesis based on the wavelet coefficient characteristic of each subgraph. In this paper, the improved method is compared with the existing three methods. It is found that the improved method is superior to them in inpainting accuracy, especially in the case of contour curve. The experimental results show that the hierarchical method combined with structural constraints has a good effect on the edge damage of thangka images.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.1-6
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• 2007

Two impedance imaging systems of multi-frequency electrical impedance tomography (MFEIT) and magnetic resonance electrical impedance tomography (MREIT) are described. MFEIT utilizes boundary measurements of current-voltage data at multiple frequencies to reconstruct cross-sectional images of a complex conductivity distribution (${\sigma}+i{\omega}{\varepsilon}$) inside the human body. The inverse problem in MFEIT is ill-posed due to the nonlinearity and low sensitivity between the boundary measurement and the complex conductivity. In MFEIT, we therefore focus on time- and frequency-difference imaging with a low spatial resolution and high temporal resolution. Multi-frequency time- and frequency-difference images in the frequency range of 10 Hz to 500 kHz are presented. In MREIT, we use an MRI scanner to measure an internal distribution of induced magnetic flux density subject to an injection current. This internal information enables us to reconstruct cross-sectional images of an internal conductivity distribution with a high spatial resolution. Conductivity image of a postmortem canine brain is presented and it shows a clear contrast between gray and white matters. Clinical applications for imaging the brain, breast, thorax, abdomen, and others are briefly discussed.

• Proceedings of the IEEK Conference
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• summer
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• pp.233-236
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• 2004

This paper proposes new method for the enhancement of nonexistent high frequency spectral contents from low sample rate audio signal. For example, Due to the protocol constraint, the audio bandwidth of MP3 is restricted to 16Khz. Although band-restricted MP3 audio provide savings of storage space and network bandwidth, it suffers a major problem of a loss in high frequency fidelity such as localization, ambient information, and bright nature of audio. This paper provides a new mathematical analysis for the adaptive estimation of the high frequency contents based on the nature of the input low sample rate audio. Proposed method can be worked globally to any kind of audio such as speech and music that are restricted by sampling rate and bandwidth.