• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.10
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• pp.2529-2547
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• 2012

In this paper, we use a quadrotor-based mobile sink to gather sensor data from the terrestrial deployed wireless sensor network. By analyzing the flight features of the mobile sink node, we theoretically study the flight constraints of height, velocity, and trajectory of the mobile sink node so as to communicate with the terrestrial wireless sensor network. Moreover, we analyze the data amount which the mobile sink can send when it satisfies these flight constraints. Based on these analysis results, we propose a data acquisition approach for the mobile sink node, which is discussed detailed in terms of network performance such as the transmission delay, packet loss rate, sojourning time and mobile trajectory when given the flying speed and height of the mobile sink node. Extensive simulation results validate the efficiency of the proposed scheme.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.8
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• pp.51-61
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• 2007

For provisioning reliable data transmission, the 3GPP RLC specification adopted a selective-repeat ARQ scheme assisted by a window-based admission control scheme. In the 3GPP ARQ, which is a member of the selective-repeat ARQ clan, inheres the reordering problem A long and irregular reordering time results in the degradation of throughput and delay performance, and may incur the overflow of the reordering buffer. Furthermore, the reordering time must be regulated to meet the requirements of some services which are loss-sensitive and delay-sensitive as well. Perceiving the reordering hazard, we propose an alternative, identified as snowball scheme, to the original admission control scheme of the 3GPP ARQ with aiming at deflating the occupancy of the reordering buffer. A unique feature of the snowball scheme is to reject a new DATA PDU if it is non-adjacent to any DATA PDU sojourning at the reordering buffer. Such an intentional rejection apparently reduces the occupancy of the reordering buffer while it may deteriorate the throughput and delay performance. Developing an analytical approximation method, we investigate the effect of snowball scheme on the saturated occupancy and throughput. Also, we, using a simulation method, evaluate the peak occupancy, normalized throughput and average delay in the practical environment. From the simulation results, we reveal that the snowball scheme is able to enhance occupancy performance as well as throughput performance compared with the original admission control scheme of the 3GPP ARQ.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.12 s.138
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• pp.1644-1654
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• 2004

As globalization has been accelerating in recent years, more people have opportunities to live abroad for an extended period of time, which is known to have strong influence on consumers. The main purposes of this study were to examine if and how sojourning experience could bring changes to people in general and in clothing styles with focus on Korean adults. The researchers conducted in-depth interviews on a total of thirty-six women and twenty-one men who lived in foreign countries more than two years and have been back in Korea longer than one year. The major results indicated that in addition to personalities, age, length of stay, activities during stay, gender, and cultural distances played important roles in bringing long-term changes on people. Re-established self-identity, changes in values, and openness toward diversity were major common changes observed in the interviewees. In addition, they became educated consumers with good knowledge of diverse brands and prices, and emphasized value as opposed to price. Changes in clothing styles were noted mainly among women. They placed high importance on having their own style, coordination and appropriateness, which were consistent with the general changes. Influences of different cultures were also noted.