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Chulhee Lee 서울대학교 경제연구소 2000 Seoul journal of economics Vol.13 No.1
The labor force participation of older males in the United States started to decline in the late nineteenth century, long before the development of major public welfare programs for the elderly. Some scholars have attributed this phenomenon to the expansion of the Union army pension programs. This note suggests that the veterans' pension is of secondary importance in explaining the trend toward declining labor market activity of older males. This result implies that the labor force participation of older males would have declined over the last century even without the rise of public welfare and social insurance programs.
Changing Industrial Structure and Economic Activity of Older Males in Korea: 1980-2000
Chulhee Lee 서울대학교 경제연구소 2004 Seoul journal of economics Vol.17 No.2
This article examines how long-term changes in the industrial structure in Korea affected the economic activity of older males. The structural shift in industry between 1980 and 2000 greatly lowered the average labor market survival rate, a measure of employment stability, for male workers aged 55 and older. In particular, the relative decline of the agricultural sector fully explains the observed impact of the sectoral shift on the employment of the elderly. The labor force participation rate of older men would have been much higher if the percentage of the labor force employed in agriculture had remained unchanged since 1980. It is estimated that the shrinkage of agriculture explains 84% of the actual decline in the labor force participation rate of men aged 55 to 69 between 1985 and 2000. These results suggest that changing industrial structure, especially the decline in agriculture, could produce a further decline in the labor market activity of older men in the near future. It also points out the limitations of the recent government labor-market policies to boost the employment of older workers, because it is highly difficult, and sometimes undesirable, to alter the course of long-term structural economic changes that diminish the economic activity of the elderly.
Reliability estimation for ultrasonic transducer by voltage accelerated life test
Chulhee Kim,Bochul Kang,Byeongsuk Song 대한전자공학회 2008 ICEIC:International Conference on Electronics, Inf Vol.1 No.1
As the income level was improved, the demand of humidifiers is increased. So the reliability of ultrasonic transducer which is the main part of humidifiers is very important too. To verify the reliability of ultrasonic transducers which were made of two kinds of material (TiN anodizing and Cr plating), voltage accelerated life test was performed . According to the data of failure time, PDF(Probability Density Function) and B10 life time were derived. As a result, TiN Anodizing material has better reliability than Cr plating material. Also failure analysis was performed using optical microscope and SEM. By the proper implementation, it is assumed that the same failure in field will be not occurred
Chulhee Jang,Jae Hong Lee IEEE 2012 IEEE Transactions on Vehicular Technology VT Vol.61 No.9
<P>In this paper, we propose a novel class of a decode-and-forward-based (DF) multi-hop transmission system where the relays forward the source data simultaneously and derive a closed-form expression of the outage probability. In addition, we provide an optimization method and a complexity-reduced optimization method. Monte Carlo simulations verify the validity of our theoretical analysis, compare the performance of two optimization methods, and compare the outage probabilities of the proposed multi-hop system with those of the conventional multi-hop system and the direct transmission system.</P>
Analytical Approach of Proxy-LMA Mobility System in Heterogeneous IP-based Mobile Networks
Chulhee Cho,Jae-Young Choi,Jongpil Jeong 한국인터넷방송통신학회 2015 Journal of Advanced Smart Convergence Vol.4 No.1
Mobile users want to be provided with undisrupted network services when they navigate on the Next-Generation (NG) wireless networks. For that, interlocking with a heterogeneous network is important, but there have been few studies on the method for guaranteeing global mobility. Thus, this paper proposes the Proxy-LMA technique, the mobile IP-based global inter-networking system, to enhance global mobility and interoperability within the Next-Generation (NG) network environment. The purpose of the proposed Proxy-LMA system is to expand the boundary of the mobility with regards to the existing mobility management protocol (PMIPv6 and MIPv6) in order to guarantee global mobility and interoperability within the heterogeneous network environment. The results of the performance evaluation showed that the proposed Proxy-LMA system was more efficient than other methods from the standpoint of signaling cost and delay in the heterogeneous network environment.