• Journal of the Korean Society for Railway
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• v.8 no.2
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• pp.137-144
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• 2005

The possibility of resonance exists always in railway bridges unlike highway bridges because railway bridges are loaded repeatedly by specific trains which has equidistant wheel loads. Resonance phenomenon of the bridge can be broken out when exciting frequencies by tram determined from the speed and effective beating internal coincides with natural frequencies of the bridge Excessive fluctuations of dynamic displacements and accelerations by resonance cause unpleasant passenger comfort and instability of railway structures. On the other hand, resonance suppression phenomenon that all the previous loads which pass through the bridge sum to zero can be occurred. In case we apply this resonance suppression properly, design of stable railway bridge from dynamics point of view can be made. In the present study, most dominant beating internal of conventional trams will be find. A(ter that. specific span length of the bridge which derives resonance suppression can be selected for railway bridges which accomplishes superior dynamic behavior.

• Advances in aircraft and spacecraft science
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• v.3 no.3
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• pp.271-298
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• 2016

In this paper, we study a problem of passive suppression of helicopter Ground Resonance (GR) using a single degree freedom Nonlinear Energy Sink (NES), GR is a dynamic instability involving the coupling of the blades motion in the rotational plane (i.e. the lag motion) and the helicopter fuselage motion. A reduced linear system reproducing GR instability is used. It is obtained using successively Coleman transformation and binormal transformation. The analysis of the steadystate responses of this model is performed when a NES is attached on the helicopter fuselage. The NES involves an essential cubic restoring force and a linear damping force. The analysis is achieved applying complexification-averaging method. The resulting slow-flow model is finally analyzed using multiple scale approach. Four steady-state responses corresponding to complete suppression, partial suppression through strongly modulated response, partial suppression through periodic response and no suppression of the GR are highlighted. An algorithm based on simple criterions is developed to predict these steady-state response regimes. Numerical simulations of the complete system confirm this analysis of the slow-flow dynamics. A parametric analysis of the influence of the NES damping coefficient and the rotor speed on the response regime is finally proposed.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1908-1916
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• 2018

This paper proposes a controller design method for suppressing the resonance generated in the slave motor in the middle and low speed operation range, according to the load and parameter differences between two motors, during parallel operation using the master and slave method that controls two surface permanent magnet synchronous motors connected in parallel by a single inverter. The proposed resonance suppression controller is directly obtained by analyzing the resonance characteristics, using the lead controller method. Therefore, it is possible to fundamentally reduce trial and error to set the controller gain. In addition, because the proposed resonance suppression controller was designed as a lead controller, the stability region of the system increased owing to the added zero point, making the system robust with respect to parametric variations. Simulations and experiments confirmed the usefulness of the proposed method and the system's robustness with respect to parametric variations.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.5
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• pp.540-549
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• 1999

In this paper, the vibration suppression scheme based on a model referece approach is proposed. The vibration results from the coupling of the system and its frequency are given by the mechanical factors. In the proposed scheme, a low frequency vibration mode is transferred to high one. And also its damping ratio can be increased without any mechanical redesign. Therefore, bandwidth and open loop gain of the plant are increased and the performance of the system can be improved. This paper analyzes the proposed vibration suppression scheme, which is compared with the conventional control scheme for mechanical resonance suppression. For proving the realistic validity, we apply the proposed scheme to a LOS(Line Of Sight) stabilization system which has vibration effect. Finally, the proposed scheme is verified through simulations and experiments.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.9
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• pp.679-691
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• 2003

The band-width of disk drive servo system is rapidly increasing for the robustness to external disturbance as the track density is increasing. The increase of the band-width may cause mechanical resonance of an actuator. In disk drive servo system, a notch filter is usually used to suppress the mechanical resonance of the actuator. However, the resonance frequency differs from drive to drive because of manufacturing tolerance and varies with temperature even within a single drive. The variation of resonance frequency degrades the suppression performance of the notch filter. In this paper, we present an adaptive digital notch filter that identifies the resonance frequency of the disk drive servo actutaor precisely and adjusts automatically its center frequency. For this, we design an adaptive FIR digital filter for the estimation of the resonance frequency. The estimation filter identifies the resonance frequency adaptively using the output signal generated from the servo system, which is excited with an excitation signal including all the expected resonance frequency components. We prove mathematically the convergence of the resonance frequency estimation filter. Furthermore, in order to demonstrate the practical use of our work, we present some experimental results using a commercially available disk drive.

• Proceedings of the KSMRM Conference
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• 1999.04a
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• pp.26-33
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• 1999

이 강의의 목적은 fat suppresion 과 water suppression에 관계되는 수소자기공명영상법의 기본 원리를 포괄적으로 이해하는데 있다. 임상적으로 이런 Technique의 수행이 필요한 가장 간단한 이유는 다른 병소의 신호와 구별을 하고 불필요한 artifact을 제거하기 위함이다.

• Proceedings of the Korean Magnetic Resonance Society Conference
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• 2002.08a
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• pp.73-73
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• 2002

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.967-970
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• 2003

A new modified singular value decomposition method, piecewise polynomial truncated SVD (PPTSVD), which was originally developed to identify discontinuity of the earth's radial density function, has been used for large solvent peak suppression and noise elimination in nuclear magnetic resonance (NMR) signal processing. PPTSVD consists of two algorithms of truncated SVD (TSVD) and L₁ problems. In TSVD, some unwanted large solvent peaks and noise are suppressed with a certain soft threshold value, whereas signal and noise in raw data are resolved and eliminated in L₁ problems. These two algorithms were systematically programmed to produce high quality of NMR spectra, including a better solvent peak suppression with good spectral line shapes and better noise suppression with a higher signal to noise ratio value up to 27% spectral enhancement, which is applicable to multidimensional NMR data processing.

• Journal of the Korean Magnetic Resonance Society
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• v.5 no.2
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• pp.66-72
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• 2001

The noise suppression of time domain NMR data by discrete wavelet transform with high order Daubechies wavelet coefficients exhibits severe peak distortion and incomplete noise suppression near real signal. However, the fact that even a shift averaged Harr wavelet transform with a set of Daubechies wavelet coefficients (1/2, -l/2) can be used as a new and excellent tool to distinguish real peaks from the noise contaminated NMR signal is introduced. New algorithms of shift averaged Harr wavelet were developed and quantitatively evaluated in terms of threshold and signal to noise ratio (SNR).

• ETRI Journal
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• v.31 no.2
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• pp.201-208
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• 2009

This paper proposes a spiral-shaped power island structure that can effectively suppress simultaneous switching noise (SSN) when the power plane drives high-speed integrated circuits in a small area. In addition, a new technique is presented which greatly improves the resonance peaks in a stopband by utilizing ${\lambda}$/4 open stubs on a conventional periodic electromagnetic bandgap (EBG) power plane. Both proposed structures are simulated numerically and experimentally verified using commercially available 3D electromagnetic field simulation software. The results demonstrate that they achieve better SSN suppression performance than conventional periodic EBG structures.