• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.4 s.346
• /
• pp.22-30
• /
• 2006

In this paper, the goal of our proposed algorithm is to reduce link -failure and route failure caused by dead nodes which consume all of the battery life. I propose an algorithm which provides a ability of changing mutes to neighbor nodes before some of intermediate nodes be shutting don to get the stable route maintenance. To achieve this goal, The proposed routing algerian uses additional new messages to check energy status for monitoring energy of neighbor nodes and to change the path to a neighbor node. From extensive simulations, results show that possibility of cut-offs and time-delay cause of packet-loss have been decreased and also the improvement of transmission effectiveness.

• The Journal of the Korea Contents Association
• /
• v.20 no.10
• /
• pp.100-108
• /
• 2020

20th century music has been recognized as disconnected. Some criticized that it is not music. This controversy has been continued over decades in music history. This study applied Darwin's evolutionary theory to John Cage's 4'33", the most popular music in 20th century and tried to prove musical continuity embedded in it. 4'33" has always been a subject of controversy because it has no sound. However, the study found out that 4'33" has the common musical factor, the rest. 4'33" can be interpreted as the variation of the rest in evolutionary view. The rest has undergone a variety of variations in form and meaning since the beginning of the musical notation and was suitable for a new musical environment changed in 20th century. In the evolutionary view, 4'33" is evolved music, not disconnected.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.4B
• /
• pp.270-277
• /
• 2006

In the wireless adaptive modulation and coding(AMC) systems, the modulation type of user's connection can be changed dynamically. and the ongoing connection might fail due to the change of modulation. In this paper, we approach the AMC-induced CAC problem by focusing on the guaranteed connection. Three kinds of calls, new, handoff, and modulation-changed calls, are considered. We propose a modified guard channel CAC scheme that allows the modulation-changed and handoff calls to use the guard channel. Then we analyze a Markov model for the CAC scheme with long-term AMC in mind. According to the simulation results, the proposed approach reduces the call dropping probability for modulation-changed calls, which suggests the threshold of guard channels can be determined based on the proposed approach.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.11A
• /
• pp.1173-1181
• /
• 2007

A number of routing algorithms have been studied for wireless mobile ad-hoc network. Among them, the AODV routing algorithm with on-demand method periodically transmits hello message and monitors link state during data transmission in order to maintain routing paths. When a path is disconnected, a node that senses it transmits a RERR packet to the transmitting node or transmits a RREQ locally so that the path could be repaired. With that, the control packet such as a RREQ is broadcast, which causes the consumption of bandwidth and incurs data latency. This paper proposes a LRRLBP algorithm that locally repairs a path by predicting link state before disconnecting the path based on the AODV routing protocol for solving such problems. Intensive simulations with the results using NS-2 simulator are shown for verifying the proposed protocol.

• Journal of Internet Computing and Services
• /
• v.12 no.2
• /
• pp.75-83
• /
• 2011

Wireless services and devices that use frequency increase more and more because of advancement of the industry. Therefore, the available spectrum band becomes increasingly insufficient. Cognitive Radio, which adaptively utilizes the vacant licensed spectrum band, is considered as an effective way to utilize the spectrum resource shortage. CR user should move from current allocated channel to vacant channel to avoid the interference to the primary user when the primary user appears in the current channel. In this case, CR system undergoes the break off time until handshake is completed. So, in order to guarantee the Quality of Service(QoS) of CR system, fast handshake method is required. In this paper, we propose the embedded control signal transmission technique to reduce the break off time. This method can transmit the control signals in data transmission period as well as the broadcasting period. Proposed method can improve the data throughput and decrease the break off time. Computer based simulation proves that our proposed scheme outperforms conventional one.

• Journal of Life Science
• /
• v.22 no.11
• /
• pp.1435-1443
• /
• 2012

The changes of plant communities at Angol valley and Baetgol valley in Geoje-do were studied. Both ${\alpha}$-diversity and ${\gamma}$-diversity decreased with the sizes and degrees of habitat fragmentations. The mean number of winner species decreased with habitat fragmentation. All Quercus species, including Quercus acutissima, significantly declined in importance, while the many introduced species, including Trifolium pretense, all increased in importance. As the proportional change in adult survival rate increased, the absolute value of the bias in the elasticity prediction also increased from 2003 to 2011 at undisturbed forests. However, the bias was low for decreases in disturbed populations. Moran's I values showed overall decreases for habitat fragmentation and for the periods of habitat conversion. Eventually, plant communities, due to urbanization in Goeje-do, might have led to decreased chances of common species when the environment was disturbed.

• The Journal of the Korea Contents Association
• /
• v.15 no.5
• /
• pp.475-487
• /
• 2015

This study measures the managerial efficiency of Korea's 14 public enterprises using bootstrap DEA in 2013. In addition, it examines the factors that affect on the bootstrap bias-corrected efficiency using truncated regression analysis. The results and implications of this study are as follows. First, using bootstrap DEA model analysis, the results showed that the mean technical efficiency was 0.3182, the mean pure technical efficiency was 0.4994 and the mean scale efficiency was 0.6585. The main cause of technical inefficiency was due to pure technical inefficiency. Second, rank test between technical efficiency of general DEA model and bootstrap DEA model was no significant difference under CRS and VRS assumption. Third, the main cause of the inefficiency in 11 DMUs among 14 DMUs were mainly due to the pure technology and three DMUs were because of the scale efficiency. Finally, in the truncated regression analysis, cost of labor, profit, sales, return of equity, and the number of employees appeared as factors affecting the scale efficiency at the 10% significance level.

• Journal of Digital Convergence
• /
• v.11 no.10
• /
• pp.379-385
• /
• 2013

MANET is not suitable to be applied to vehicle environments because of frequent path loss and path re-routing. To solve these problem, It is known that location-based routing protocol VANET is efficient. But, the VANET algorithm does not consider urban environments due to frequent vehicle movement and jamming by tall building. In this paper, we propose an efficient routing protocol to improve transfer efficiency and reduce transfer hop count. in urban networks.

• Korea journal of population studies
• /
• v.20 no.2
• /
• pp.5-42
• /
• 1997

This study contributes to understanding women's labor market behavior by focusing on a particular set of labor force transitions - labor force withdrawal and entry during the period surrounding the first birth of a child. In particular, this study provides a dynamic analyses, using longitudinal data and event history analysis, to conceptualize labor force behaviors in a straightforward way. The main research question addresses which factors increase or decrease the hazard rates of leaving and entering the labor market. This study used piecewise Gompertz model, following the guide of the non-parametric analysis on the hazard rates, which allowed relatively detailed description on the distribution of timing of leave and entry to the labor market as parameters of interest. The results show that preferences and structural variables, as well as economic considerations, are very important factors to explain the labor market behavior of women in the period surrounding childbirth.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.12B
• /
• pp.1075-1082
• /
• 2008

A greedy forwarding algorithm is one of the most suitable solutions for routing in vehicular ad-hoc networks. Compared to conventional routing protocols for mobile ad-hoc networks, greedy forwarding based routing protocols maintain only local information of neighbors instead of per-destination routing entries, and thus they show better performance in highly-mobile vehicular ad-hoc networks. With greedy forwarding, each node learns its geographical position and periodically broadcasts a beacon message including its position information. Based on the position information, each node selects a neighbor node located closest to the destination node as the next forwarder. One of the most serious problems in greedy forwarding is the lost link problem due to the mobility of nodes. In this paper, we propose a new algorithm to reduce the lost link problem. The proposed algorithm aims to find an efficient and stable routing path by taking account of the position of neighbors and the last beacon reception time. Our simulation results show that the proposed algorithm outperforms the legacy greedy algorithm and its variants.