• Journal of Korea Multimedia Society
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• v.20 no.12
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• pp.1940-1950
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• 2017

The security threat types in underwater communication networks environment are almost the same as the terrestrial, but the security of mechanisms the terrestrial RF-based networks environment can not be directly applied due to not only the limited resources of each node but also unsafe channel such as low propagation delay, high bit error rate etc. Nevertheless there has not been much research on the security of underwater acoustic communication networks. Therefore, in this paper analyzes the differences between the terrestrial communication networks and underwater acoustic communication networks, and identifies issues that are the starting points of underwater communication networks security research.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.4
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• pp.2196-2218
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• 2017

Multicast communication has been widely used in the Internet. However, multicast communication is vulnerable to DoS attack due to static router configuration. In this paper, HMC, a hopping multicast communication method based on SDN, is proposed to tackle this problem. HMC changes the multicast tree periodically and makes it difficult for the attackers to launch an accurate attack. It also decreases the probability of multicast communication being attacked by DoS and in the meanwhile, the QoS constrains are not violated. In this research, the routing problem of HMC is proven to be NP-complete and a heuristic algorithm is proposed to solve it. Experiments show that HMC has the ability to resist DoS attack on multicast route effectively. Theoretically, the multicast compromised probability can drop more than 0.6 when HMC is adopt. In addition, experiments demonstrate that HMC achieves shorter average multicast delay and better robustness compared with traditional method, and more importantly, it better defends DoS attack.

• Journal of information and communication convergence engineering
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• v.4 no.2
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• pp.62-66
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• 2006

The objective of this thesis is to measure the limit of the real space where wireless Local Area Network (LAN) is used, and to apply this result as reference to set up a real Wireless LAN environment. The organized circumference was composed of Wireless LAN based on IEEE 802.11b of the American standard, and the examination is carried out on the campus. On the real condition of office environment and open space, the ratio of available distance to a signal at each distance was measured and this result was studied as data to embody wireless LAN on the campus. The measurement under an indoor environment was executed under circumstance having two walls and open space, however, was executed respectively under three circumstances: Where no obstacle, where one wall exists, and where two or more walls exist.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3276-3292
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• 2015

Relay-assisted D2D communication extends the communication range of the D2D pairs and helps users to form D2D pairs effectively. However, due to the introduction of the multi-hop relaying, the D2D communication has to occupy extra transmission time, which may decrease the efficiency of the communication system. In this paper, we propose a scheme to make node receive D2D signal and BS signal at overlapping time to improve the spectrum efficiency according to ZigZag decoding and successive-interference-cancellation (SIC). In this way, more data can be delivered during the same duration, thus the network throughput can be further improved. Numerical results verify the performance improvement of the proposed scheme when compared with a baseline scheme. Moreover, we expand the proposed scheme from one-hop relay scenario to multi-hop relay scenario.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.9
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• pp.4541-4554
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• 2019

This paper proposes a planar projection DV-hop location algorithm (PTCDV-hop) based on the LED semi-angle at half power (SAHP, which accounts for LED SAHP characteristics in visible light communication (VLC)) and uses the DV-hop algorithm for range-free localization. Distances between source nodes and nodes positioned in three-dimensional indoor space are projected onto a two-dimensional plane to reduce complexity. Circles are structured by assigning source nodes (projected onto the horizontal plane of the assigned nodes) to be centers and the projection distances as radii. The proposed PTCDV-hop algorithm then determines the position of node location coordinates using the trilateral-weighted-centroid algorithm. Simulation results show localization errors of the proposed algorithm are on the order of magnitude of a millimeter when three sources are used. The PTCDV-hop algorithm has higher positioning accuracy and stronger dominance than the traditional DV-hop algorithm.

• The Korean Journal of Community Living Science
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• v.20 no.1
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• pp.91-102
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• 2009

The purpose of this study was to analyze the effect of home related variables like socio-demographic variables, parent-child communication, and concern for children's education on children's school adjustment. The data was collected from 287 elementary school children living in Gyunggido. Measurement scales included the children's school adjustment inventory, the questionnaire of the socio-demographic variables, the parent-child communication index, and the parent's concern about children's education index. Results showed that children's school adjustment was significantly effected with regard to: father's age, father's education, mother's education, income, and mother's job. Correlation analysis indicated that parent-child open communication was positively correlated to children's school adjustment; that is the relationships with teachers and with friends, study at school, and rule of school. As well, parent-child problematic communication was negatively correlated to all of the school adjustment variables. Parent's concern about children's education indicated positive correlations with all of the school adjustment variables. It was also found that: parent's concern about children's education, parent-child open communication, parent-child problematic communication, mother's education, and income were significant predictors of the children's school adjustment.

• Journal of Korean Association for Spatial Structures
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• v.17 no.4
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• pp.93-102
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• 2017

Wireless MEMS sensors have common features such as wireless communication, data measurement, embedded processing, battery-based self-power, and low cost, and increased measurement effectiveness. Wireless MEMS sensors enable efficient SHM without interfering with location because there is no requirement for triboelectric noise and cumbersome cables. However, there is little research on the communication distance with sensors and data. For instance, existing researches have limited communication distance experiments in civil engineering bridges. It is also necessary to investigate the characteristics of dynamic behavior and the communication distance of architectural structures with different wireless transmission/reception environments. Therefore, in a building structure with walls and slabs instead of open spaces, MEMS sensors and data loggers were used as distance experiments where communication disturbance between the vertical slab and the horizontal wall could actually be communicated.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.675-678
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• 2007

In organic light emitting diodes (OLEDs), the electrons and holes need to be injected efficiently to obtain the best device performance. This means that a small injection barrier height at the ITO/organic interface is required. In this study, the surface of the ITO anode was treated with an Aluminum oxynitride (AlON).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.2
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• pp.287-312
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• 2011

Internet chat programs and instant messaging services are becoming increasingly popular among Internet users. One of the crucial issues with Internet chat is how to manage the corresponding pairs of questions and answers in a sequence of conversations. Although many novel methodologies have been introduced to cope with this problem, most are poor in managing interruptions, organizing turn-taking, and conveying comprehension. The Internet environment is recently evolving into a 3D environment, but the problems with managing chat dialogues with the standard 2D text-based chat have remained. Therefore, we propose a more realistic communication model for chat agents in 3D virtual space in this paper. First, we propose a new method to measure the capacity of communication between chat agents and a novel visualization method to depict the hierarchical structure of chat dialogues. In addition, we are concerned with communication networks for virtual people (avatars) living in virtual worlds. In this paper we consider a microscopic aspect of a social network in a relatively short period of time. Our experiments show that our model is highly effective in a virtual chat environment, and the communication network based on our model greatly facilitates investigation of a very large and complicated communication network.

• Journal of The Korean Association For Science Education
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• v.28 no.2
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• pp.159-168
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• 2008

The purpose of this study was to apply the coteaching to the teaching practice of the student-teachers and identify the distinctive characteristics of the communication processes appeared in coteaching. We developed the semiotic analyzing-frame and observed 7 classes of middle schools where the student-teachers cotaught one or two units. Then we analyzed the communication processes on the view of semiotics. We found three patterns of the communication processes. First, when there was a discontinuous communication between the student-teacher and the students, the communication was restarted by the other student-teacher leading to the complete meaning making. Second, when an insufficient communication took place by the student-teacher using inadequate interpretant, the other student-teacher modified the communication by selecting another interpretant including sufficient meaning towards the object. With this new interpretant, students could refine the imperfect private meanings and eventually establish the more objective meanings. Third, the communication was pre-planned between coteachers to help students understand the contents through the successful translation of interpretants. Coteaching provided positive implications to improve the communication processes in science lesson.