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Seoyeon Ahn,남찬혁,최성진,안대권,Ingi Kim,Kyungsoo Seo,Chang Hyun Sohn 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.5
In this paper, to help reduce the squeal noise produced during the braking of urban railway vehicles, the shape of the disc brake pad was investigated to relieve contact stress. To analyze the disc brake system to identify the source of the squeal noise, a finite element model of the disc brake system was used, including the peripheral brake parts to increase accuracy. A complex eigenvalue analysis was performed to predict squeal noise generation. Verification was carried out using domestic urban railway field test results to confirm the accuracy of the analysis model. A pad shape that relieves contact stress is proposed to reduce squeal noise produced by nonuniform contact between the disc and pad. The results of this study can be utilized for future studies on squeal noise reduction.
Seoyeon Ahn,손창현,Sung-Jin Choi,남찬혁 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5
The present study was conducted on the disc brake systems of urban railway vehicles to investigate the effects of braking temperature on squeal noise. A finite element method-based analytical model was constructed to predict the generation of squeal noise through the analysis of complex eigenvalues. The reliability of the analytical model was confirmed by verification with experimental results obtained from a test vehicle on an urban railway track in Korea. The braking temperature of the brake system was applied to the analytical model to analyze the effects of braking temperature on squeal noise. This article proposes a brake pad shape to reduce the impact of squeal noise caused by nonuniform contact between the brake disc and the brake pad due to braking temperature. The results from the present study can be used to reduce squeal noise further.
안서연(Ahn, Seoyeon),조미라(Cho, Mira) 한국인구학회 2018 한국인구학 Vol.41 No.3
한국사회에서는 장시간노동 문제가 부각되면서 이를 해결하기 위해 다양한 사회적 노력을 기울이고 있다. 그러나 노동시간의 평균양으로만 노동시간의 조건들을 살펴보는 것은 충분치 않으며, 노동시간의 집단간 차이와 불평등 그리고 측정단위를 다양하게 하여 파악할 필요가 있다. 이에 본 연구는 한국노동패널의 25-65세 개인과 부부를 대상으로, 2001년부터 2015년의 노동시간의 변화와 불평등에 관하여 개인 및 부부단위로 분석하고자 하였다. 특히 법정노동시간의 단축과 같은 주요한 정책적 개입이 있었던 연도(2003, 2011, 2015년)를 중심으로, 노동시간의 불평등의 요인들을 하위그룹 분해(subgroup decomposition)를 적용하여 분석하였다. 분석결과 2001-2015년간 개인 및 부부단위의 노동시간과 노동시간의 불평등은 지속적으로 감소한 것으로 나타났다. 개인단위의 불평등 요인 분해 결과, 노동시장 관련 변수의 영향력이 크게 나타났으며, 부부단위에서는 동질혼 변수의 집단구성의 변화가 노동시간 불평등에 미치는 영향이 크게 나타났다. 또한 자녀보육을 필요로 하지 않는 부부 비중의 증가와 저소득가구의 노동시간의 급격한 감소가 노동시간 불평등을 강화시키는 것으로 나타났다. 법정노동시간에 대한 제도적 개입이 노동시간 단축의 동인이 된 것으로 보이며, 이는 앞으로도 적극적인 제도 도입과 추진이 장시간노동에서 벗어날 수 있는 추동력이 될 수 있음을 시사한다. 전반적으로 노동시간 불평등은 감소하였으나, 동질혼의 강화나 저출산 등 현재의 변화추세가 지속될 경우, 노동시간 불평등은 감소가 아니라 증가할 가능성도 높아 보인다. This study aims to estimate changes in trends in working hours and its inequality using the individual and couple as units of analysis over fifteen years (2001-2015). In addition, we use Mookherjee and Shorrocks’ (1982) technique to decompose working hours inequality by individual characteristics, labour market factors, assortative mating, and household characteristics for the years 2003, 2011, and 2015 which saw policy interventions in the form of 40-hour workweek. Data is obtained from the Korea Labour and Income Panel Study. Results show that the amount of working hours and its inequality among individuals and couples have decreased from 2001 to 2015. Decline in inequality of working hours within subgroups explains a large part of individual and couple level inequality. Changes in labour market structure in terms of industry, occupation, and work status contribute to a more equitable distribution of working hours at the individual level. Educational and occupational assortative mating in the upper class lead to rising inequality in working hours, but these effects have been offset by decreasing educational and occupational assortative mating in the lower class. If these trends of assortative mating in the upper class continue, inequality of working hours would increase dramatically.