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Eulerian and Lagrangian descriptions for the vibration analysis of a deploying beam
Sungpil Park,유홍희,정진태 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.9
In this study, the equations of motion derived from the Eulerian and Lagrangian descriptions of the vibration analysis of a deploying beam are compared and discussed. After transforming the equations to their corresponding variational equations, the discretized equations for the two descriptions are derived and their equivalence is verified. The numerical time responses obtained from the equations of both descriptions are the same. We recommend use of the Lagrangian description over the Eulerian one when analyzing the vibration of a deploying beam that includes the entirety of the beam inside and outside a rigid wall.
New cardiac MRI gating method using event-synchronous adaptive digital filter.
Park, Hodong,Park, Youngcheol,Cho, Sungpil,Jang, Bongryoel,Lee, Kyoungjoung Pergamon Press [etc.] 2009 Annals of biomedical engineering Vol.37 No.11
<P>When imaging the heart using MRI, an artefact-free electrocardiograph (ECG) signal is not only important for monitoring the patient's heart activity but also essential for cardiac gating to reduce noise in MR images induced by moving organs. The fundamental problem in conventional ECG is the distortion induced by electromagnetic interference. Here, we propose an adaptive algorithm for the suppression of MR gradient artefacts (MRGAs) in ECG leads of a cardiac MRI gating system. We have modeled MRGAs by assuming a source of strong pulses used for dephasing the MR signal. The modeled MRGAs are rectangular pulse-like signals. We used an event-synchronous adaptive digital filter whose reference signal is synchronous to the gradient peaks of MRI. The event detection processor for the event-synchronous adaptive digital filter was implemented using the phase space method-a sort of topology mapping method-and least-squares acceleration filter. For evaluating the efficiency of the proposed method, the filter was tested using simulation and actual data. The proposed method requires a simple experimental setup that does not require extra hardware connections to obtain the reference signals of adaptive digital filter. The proposed algorithm was more effective than the multichannel approach.</P>
블록식 보강토 옹벽에서 개별 블록간 거동특성을 고려한 수치해석적 연구
황성필 ( Sungpil Hwang ),박병석 ( Byungsuk Park ),우용훈 ( Yong-hoon Woo ),박상기 ( Sangki Park ),김우석 ( Wooseok Kim ) 대한지질공학회 2021 지질공학 Vol.31 No.4
일반 콘크리트 옹벽에 비해 경관성이 우수한 보강토 옹벽이 최근 많이 사용되고 있다. 다양한 재료와 복잡한 현장여건으로 기존 설계 방식만으로는 안정성 확보가 어려운 경우가 발생되고 있다. 이러한 문제를 해결하기 위해 현장여건에 적합한 안정성 분석 방법에 대한 연구를 진행하였다. 본 연구에서는 기존 수치해석과는 다르게 보강토 블록이 개별거동 가능하도록 적용하였으며, 개별 블록거동에 따른 물성치 및 강도 적용을 위하여 블록간 마찰특성과 블록과 보강재의 연결특성에 관한 실규모 시험을 수행하였다. 수치해석을 통해 현장과 동일한 블록조건의 적용 가능성을 확인하였고, 이를 활용하여 다양한 조합의 블록과 보강재의 안정성 검토 및 설계에 활용 가능 할 것으로 판단된다. 또한 외적안정의 범위를 넓혀 안정성을 더욱 확보할 수 있을 것으로 판단된다. Reinforced earth retaining walls have been widely used in recent years, as they are superior from the landscape perspective than normal concrete retaining walls. However, as reinforced earth retaining walls are made of various materials depending on site, existing design methods cannot secure stability, and a variety of problems have occurred. Studies on the design and stability analysis methods, which are different from existing methods, have been conducted to address these problems. This study conducted a stability investigation using numerical analysis, and blocks of reinforced earth retaining walls were individually applied, which is different from pre-existing numerical analyses. To verify the input values of the numerical analysis when applying individual blocks, real-scale experiments of the friction characteristics between the blocks and the connection properties between the blocks and stiffener were conducted. The applicability of the block conditions, which were the same as those of real sites, was verified through numerical analysis, and will be used for the stability review and design of various combinations of blocks and stiffeners.
감속기 내부 기어의 가공정밀도와 구동간 소음의 연관특성에 관한 연구
박성필(Sungpil Park),김우형(Woohung Kim),정진태(Jintai Chung) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
In this paper, we experimentally investigate a noise mechanism related to machining accuracy of reducer at driving state. To calculate and compare the noise, we manufacture a planetary reducer and four types of gears used in the planetary reducer. We use the method of signal analysis to investigate the noise and vibration of the reducer by equally increasing the motor speed from 0 rpm to maximum speed. In addition, we calculate sound level by a sound level meter. Machining accuracy of gears is evaluated by public organizations, Korea Testing Laboratory (ktl), which is based upon the Japanese industrial standard (JIS). We analysis and compare the results with the noise and vibration of the reducer.