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Calculation of coupled added mass of multibody system immersed in fluids
이진행,Jae-Hun Cho,김성균 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9
The natural frequencies of structures submerged in a fluid are significantly influenced by fluid properties and adjacent structures, which can be expressed by added mass. Some finite element software can effectively determine the added mass matrix of arbitrary structures immersed in viscous fluids, provided the structure lengths are relatively long;however, the added mass specified in a second-order tensor cannot be used as is. Herein, we propose methods to calculate the coupled added mass as a single value for each structure using the MassInFlu code. When the x- and y-directional components of the coupled added mass are unequal, an effective added mass can be determined by rotating the structures or coordinate axes. Various examples considering different scenarios show that the coupled natural frequencies obtained using the coupled or effective added mass coincide with those obtained from fluid-structure interaction analyses.
RC교각을 이용한 실시간 하이브리드 실험 시스템의 적용성 연구
이진행,박민석,김철영,채윤병 한국지진공학회 2018 한국지진공학회논문집 Vol.22 No.4
Structure behaviors resulting from an earthquake are experimentally simulated mainly through a shaking table test. As for large-scale structures, however, size effects over a miniature may make it difficult to assess actual behaviors properly. To address this problem, research on the hybrid simulation is being conducted actively. This method is to implement numerical analysis on framework members that affect the general behavior of the structure dominantly through an actual scale experiment and on the rest parts by applying the substructuring technique. However, existing studies on hybrid simulation focus mainly on Slow experimental methods, which are disadvantageous in that it is unable to assess behaviors close to the actual level if material properties change depending on the speed or the influence of inertial force is significant. The present study aims to establish a Real-time hybrid simulation system capable of excitation based on the actual time history and to verify its performance and applicability. The hybrid simulation system built up in this study utilizes the ATS Compensator system, CR integrator, etc. in order to make the target displacement the same with the measured displacement on the basis of MATLAB/Simulink. The target structure was a 2-span bridge and an RC pier to support it was produced as an experimental model in order for the shaking table test and Slow and Real-time hybrid simulations. Behaviors that result from the earthquake of El Centro were examined, and the results were analyzed comparatively. In comparison with the results of the shaking table test, the Real-time hybrid simulation produced more similar maximum displacement and vibration behaviors than the Slow hybrid simulation. Hence, it is thought that the Real-time hybrid simulation proposed in this study can be utilized usefully in seismic capacity assessment of structural systems such as RC pier that are highly non-linear and time-dependent.
이진행,송현교,강민구 한국정보통신학회 1999 한국정보통신학회논문지 Vol.3 No.2
본 연구는 스캐너로 입력한 사진을 법의학을 응용한 안면삼각법(facial triangle)과 사진분석법을 이용하여 수직각, 수평각 등을 측정한 각도에서 CCD 카메라로 두개골 영상을 입력받아 중첩시키기 위한 슈퍼임포즈 개인식별 영상시스템의 성능향상과 다양한 영상처리 응용 프로그램을 활용함으로서 자동식별을 위한 개인식별 능력을 향상하였다. In this progressed super-impose individual recognition system, the photograph of a skull was caught by CCD-camcoder with the MPEG, and an ante-mortem photograph was read by scanner. These two images were processed and superimposed using horizontal angle and vertical angle of face using the forensic dental medicine theory. The enhancement of super-impose individual recognition by anatomical references was performed on the two superimposed images of the same angle using the facial triangle and histogram analysis scheme.
이진행,강민지,전혜영 한국기상학회 2019 Asia-Pacific Journal of Atmospheric Sciences Vol.55 No.3
Differences in convective activities in the tropical region (30°S–30°N, 180°E–180°W) during different phases of the quasibiennial oscillation (QBO) are investigated over 32 years (1979–2010) using five metrics representing tropical convection: (i) precipitation and (ii) outgoing longwave radiation from observations and (iii) convective available potential energy (CAPE), (iv) deep convective heating rate, and (v) convective cloud top pressure from reanalysis data. The easterly (QBOE) and westerly (QBOW) phases of the QBO are defined using the zonal wind anomaly from the monthly climatology at 50 hPa. During the QBOE (QBOW), the convective activities are intensified (weakened) over the Maritime Continent and weakened (intensified) over the equatorial eastern and central Pacific. Therefore, the zonal mean values of the five metrics averaged over chronically convective regions show stronger convective activities during the QBOE than during the QBOW, while the opposite is true for the whole tropical region. Composite analyses are also performed during the neutral, El Niño, and La Niña periods. In the neutral period, the convective activities during QBOE are stronger than during QBOWexcept in the equatorial region (10°S–10°N). The convective activities over the Maritime Continent (central and eastern Pacific) are enhanced when La Niña and the QBOE (El Niño and the QBOW) occur simultaneously. All metrics show similar pattern to one another, implying that the metrics from reanalysis data represent the variations in the convective activities with respect to the QBO reasonably well. Among the five metrics, the CAPE is most sensitive to the QBO phase, likely because the virtual temperature in the upper troposphere is modulated by anomalous meridional circulations induced by different QBO phases.