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박우재(Woojae Park),김승호(Seungho Kim),김상부(Sangboo Kim) 한국경영과학회 2016 한국경영과학회 학술대회논문집 Vol.2016 No.4
국내에 가장 많이 설치되어 사용되는 엘리베이터는 로프식 엘리베이터이다. 로프식 엘리베이터의 경우 와이어로프가 엘리베이터의 하중을 견디기 때문에 와이어로프의 수명을 정확히 추정하는 것이 엘리베이터 고장의 사전 예방을 포함한 정비 활동의 중요한 요소가 된다. 지금까지 엘리베이터 와이어로프의 수명을 추정하기 위해 많은 연구들이 이루어져 왔으며, 대부분의 연구는 시험 데이터에 근거하여 통계적 회귀모형을 구하는 방법을 취하고 있다. 이 연구에서는 실제 엘리베이터 와이어로프의 수명 시험 결과를 이용하여, 엘리베이터 와이어로프의 수명을 추정하는 서로 다른 5가지 방법들 간의 비교 분석을 수행하였다.
박우재(Woojae Park),김승호(Seungho Kim),김상부(Sangboo Kim) 대한산업공학회 2016 대한산업공학회 춘계학술대회논문집 Vol.2016 No.4
국내에 가장 많이 설치되어 사용되는 엘리베이터는 로프식 엘리베이터이다. 로프식 엘리베이터의 경우 와이어로프가 엘리베이터의 하중을 견디기 때문에 와이어로프의 수명을 정확히 추정하는 것이 엘리베이터 고장의 사전 예방을 포함한 정비 활동의 중요한 요소가 된다. 지금까지 엘리베이터 와이어로프의 수명을 추정하기 위해 많은 연구들이 이루어져 왔으며, 대부분의 연구는 시험 데이터에 근거하여 통계적 회귀모형을 구하는 방법을 취하고 있다. 이 연구에서는 실제 엘리베이터 와이어로프의 수명 시험 결과를 이용하여, 엘리베이터 와이어로프의 수명을 추정하는 서로 다른 5가지 방법들 간의 비교 분석을 수행하였다.
Park, Kyu Hyung,Kim, Pyosang,Kim, Woojae,Shimizu, Hideyuki,Han, Minwoo,Sim, Eunji,Iyoda, Masahiko,Kim, Dongho WILEY‐VCH Verlag 2015 Angewandte Chemie Vol.127 No.43
<P><B>Abstract</B></P><P>Excited‐state dynamic planarization processes play a crucial role in determining exciton size in cyclic systems, as reported for π‐conjugated linear oligomers. Herein, we report time‐resolved fluorescence spectra and molecular dynamics simulations of π‐conjugated cyclic oligothiophenes in which the number of subunits was chosen to show the size‐dependent dynamic planarization in the vicinity of a ring‐to‐linear behavioral turning point. Analyses on the evolution of the total fluorescence intensity and the ratio between 0–1 to 0–0 vibronic bands suggest that excitons formed in a cyclic oligothiophene composed of six subunits fully delocalize over the cyclic carbon backbone, whereas those formed in larger systems fail to achieve complete delocalization. With the aid of molecular dynamics simulations, it is shown that distorted structures unfavorable for efficient exciton delocalization are more easily populated as the size of the cyclic system increases.</P>
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>
Woojae Han,Minki Hong,Taeoh Kim,Sihun Park 한국청각언어재활학회 2020 Audiology and Speech Research Vol.16 No.2
Purpose: The purpose of this study was to compare change in the perception of hearing impairment before and after the handicap experience and to qualitatively analyze accepting attitude and change toward the impairment in college students. Methods: Twenty college students were asked to wear personalized earplugs on their ears to experience the handicap of hearing loss for five days. They reported 12-items questionnaire before and after the experience and had also 1:1 individual interview using a structured format with open questions. Results: Although the negative attitude toward the hearing impairment (78.30%) was high enough before the handicap experience, the positive attitude (78.02%) was prominent after the experience. Further, the participants had expressed negative feeling such as guilt and avoidance toward the hearing impairment before the experience, while showing discrepancies between their cognition and behaviors. However, their perception and attitude were changed with positive recognition after the experience. Conclusion: Although it was a short period of the experience, the present results confirmed that the non-disabled students had an internal understanding and distracted negative attitudes toward the hearing impairment. The systematic and detailed handicap experiences might be expected to maintain a positive attitude toward the students with disabilities for a while.
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.
Array tilt effect induced by tidal currents in the northeastern East China Sea
Park, Jungyong,Seong, Woojae,Yang, Haesang,Nam, SungHyun,Lee, Seung-Woo Elsevier 2019 Ocean engineering Vol.194 No.-
<P><B>Abstract</B></P> <P>The relation between the tidal current and the acoustic signal measured at vertical line arrays (VLAs) is investigated from data of the shallow-water acoustic variability experiment 2015 performed in the northeastern East China Sea. From the channel impulse response, the arrival structure measured on the VLA was observed to vary with semidiurnal tidal period. To explain this phenomenon, the direction of the array tilt is assumed to be consistent with the current flow direction. The modeling results based on ray tracing prove the relation between the variation of the arrival structure and array tilt angle in a time-varying form, yielding an estimation of tidal currents in the region. We compared the projected time series of horizontal currents to the acoustic paths with the curvature variation in the arrival structure to validate our results and confirmed that they are consistent with each other.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The curvature variation of the acoustic arrival structure varies with the semidiurnal period, which was recorded with vertical line array using in the SAVEX-15 which performed in the northern East China Sea. </LI> <LI> The modeling result using ray theory shows that tilting of vertical line array induces the curvature variation in the arrival structure. </LI> <LI> The trend of measured tidal current data is consistent with that of curvature variation of acoustic arrival structure. </LI> </UL> </P>