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시변동이 있는 근거리 음향신호의 시간영역 지음향학적 역산
Park, Cheolsoo,Seong, Woojae,Gerstoft, Peter,Hodgkiss, William S. 한국음향학회 2013 韓國音響學會誌 Vol.32 No.4
2006년 여름 New Jersey 대륙붕 근해에서 일련의 해상실험(Shallow Water 2006, SW06)이 수행되었다. 이 때 수직선배열에서 계측된 근거리 chirp 신호(1100~2900 Hz)에서 직접도달파와 해수면 반사파의 강한 시변동이 관찰되었다. 본 논문은 시변동성이 있는 근거리 음향신호의 지음향학적 역산기법과 실험 데이터에 대한 역산결과를 제시한다. 불규칙한 해수면 반사파가 역산에 미치는 영향을 최소화하기 위해 수직선배열에서 음원의 위치로 직접도달 경로와 해저면 반사경로를 통해 역전파된 신호의 에너지로써 목적함수를 정의하였다. 또한 VFSR(Very Fast Simulated Reannealing) 최적화기법을 활용한 다단계 역산기법을 실험데이터에 적용하였다. 역산 결과 음원은 주기적인 수직운동을 한 것으로 파악되었고 그 주기는 수면파의 주기와 일치하였다. 해저면의 음속은 1645 m/s로 추정되었고 이는 동일 해역의 다른 연구결과와 유사한 것으로 파악되었다. A set of experiments (Shallow Water 2006, SW06) was carried out in shallow water near the New Jersey shelf break in summer 2006. Significant fluctuations in direct and surface reflected arrivals were observed from the chirp data (1100~2900 Hz) measured on a vertical line array. This paper presents a geoacoustic inverssion technique for short-range acoustic data with fluctuating arrivals and inversion results of experimental data. In order to reduce effects of random sea surface on the inversion, the acoustic energy back-propagated from the array to the source through direct and bottom-reflected paths is defined as the objective function. A multi-step inversion scheme is applied to the data using VFSR (Very Fast Simulated Reannealing) optimization technique. The inversion results show a source depth oscillation period equal to the measured ocean surface wave period. The inverted bottom sound speed is 1645 m/s and is similar to that estimated by other work at the same site.
Fluctuating arrivals of short-range acoustic data.
Park, Cheolsoo,Seong, Woojae,Gerstoft, Peter,Hodgkiss, William S American Institute of Physics for the Acoustical S 2011 JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA - Vol.129 No.1
<P>Geoacoustic inversion using fluctuating signal observations can be challenging. The origin of these fluctuations needs to be understood so the signals can be used appropriately. A set of experiments [Tang et al., Oceanogr. 20(4), 156-167 (2007)] was carried out in shallow water near the New Jersey shelf break in summer 2006. Significant fluctuations in the direct path and surface-reflected arrivals of short-range chirp transmissions (1.1-2.9 kHz) were observed on a vertical line array. This paper explains the origin of these signal fluctuations through analysis of the arrival amplitudes. It is shown that the strong thermocline combined with an oscillating source motion due to ocean surface waves results in the signal fluctuations.</P>
Park, CheolSoo,Kim, KoKeun,Choi, JongMin,Park, KwangSuk IOP Pub 2007 Physiological measurement Vol.28 No.5
<P>In order to detect minute amounts of glucose in diluted urine, we applied the Raman spectroscopy method. To simulate abnormal diluted urine in a toilet bowl, we diluted normal urine ten-fold with water and added glucose up to 8 mg dl<SUP>−1</SUP>. Data were collected using a low-resolution Raman spectrometer that was preprocessed with the optimizing kernel method. We also applied the neural network algorithm to classify abnormal and normal urine samples according to their glucose concentrations. The kernel optimizing method was very effective in the classification of the tested subjects as it increased the accuracy of classification by 92%. This method suggests the possibility of caring for patients by daily monitoring their urine components in a manner non-invasive to ordinary life.</P>
Review of Data-Driven Multivariate and Multiscale Methods
Park, Cheolsoo The Institute of Electronics and Information Engin 2015 IEIE Transactions on Smart Processing & Computing Vol.4 No.2
In this paper, time-frequency analysis algorithms, empirical mode decomposition and local mean decomposition, are reviewed and their applications to nonlinear and nonstationary real-world data are discussed. In addition, their generic extensions to complex domain are addressed for the analysis of multichannel data. Simulations of these algorithms on synthetic data illustrate the fundamental structure of the algorithms and how they are designed for the analysis of nonlinear and nonstationary data. Applications of the complex version of the algorithms to the synthetic data also demonstrate the benefit of the algorithms for the accurate frequency decomposition of multichannel data.
Vector Fitting기법을 이용한 필터링 전도체 비발디 안테나의 등가회로 구현
이철수(Cheolsoo Lee),유홍균(Hongkyun Ryu),박범준(Beomjun Park),김인선(Inseon Kim),박주래(Joorae Park) 대한전자공학회 2023 대한전자공학회 학술대회 Vol.2023 No.6
An equivalent circuit model is demonstrated of the wideband metallic Vivaldi array antenna with band notched performance using vector fitting technique (VFT). The metal post placed in the resonator for broadband impedance matching is achieved band stop function. A numerical S11 characteristic of the filtering Vivaldi antenna is calculated using CSTMWS and the rational terms are driven using ‘rational’ function of MATLAB. The results of the reflection of the equivalent circuit using ADS, the frequency response of rational terms of VFT and CST-MWS are agreed well each other.