• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.2
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• pp.156-164
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• 2019

In this paper, we propose an efficient dynamic slot re-assignment scheme for swarming drone networks in which networks members merged and split frequently. The leader drone of each network recognizes the slot allocation information of neighbor networks by periodic information exchange among between the drones. Using the information, the leader drone makes a decision how to reallocate the slots between members in case of network merge. The non-competitive method in the proposed scheme can re-assign the slots without any slot collision and shows always superior performance than competitive scheme. The competitive method in the proposed scheme reduces the number of slots that should be re-assigned in case of network merge. The experimental performance analysis shows that the proposed scheme performs better or at least equal to the performance of the competitive scheme in a swarming drone network.

• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.47-51
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• 2015

In the study, a new non-open cut tunnel steel pipe method using slot hole has been developed. As is overcomes shortcomings of conventional methods, it is applied to the field. The main concept of the new method is the steel pipe pumping system with slot holes which, by means of formation slot holes between each steel pipe, applied to the magnitude of the relaxed earth pressure caused by excavation to the ground to prevent ground displacement. The stability of the support members and effect of displacement control of the new method were verified through several ways as numerical analysis and site test. The new method was applied to the construction of a 11.5m wide, 7.4m high and 50m long section that passes side subway and large buildings in inner city. By applying the new method, tunnel construction was successfully completed in 6 months. It decreases the construction period to 30% compared to that of conventional methods, and ground was almost negligible.

• Journal of Korean Association for Spatial Structures
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• v.20 no.4
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• pp.123-130
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• 2020

Generally the non-bearing walls in apartment buildings in Korea are not considered as a lateral force resisting members for the design consideration. This engineering practice caused large crack damages and brittle fractures of the non-bearing walls when subjected to Pohang earthquakes in 2017 since those have not been designed for seismic loading. In this study, finite element analysis was conducted for slot type non-bearing wall connection system to reduce damages and concentrate damages to the designated damping device through separation from the structural wall members. Steel plate and dowel bar systems designed for the dissipation of seismic energies were modeled and analyzed to investigate the damage reductions. Finally, the test result and the analysis result were compared and verified.

• Journal of electromagnetic engineering and science
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• v.12 no.1
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• pp.1-7
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• 2012

In this paper, we investigated the throughput of a cognitive radio network where two primary frequency channels (PCs) are sensed and opportunistically accessed by N secondary users. The sharing sensing member (SSM) protocol is introduced to sense both PCs simultaneously. According to the SSM protocol, N SUs (Secondary User) are divided into two groups, which allows for the simultaneous sensing of two PCs. With a frame structure, after determining whether the PCs are idle or active during a sensing slot, the SUs may use the remaining time to transmit their own data. The throughput of the network is formulated as a convex optimization problem. We then evaluated an iterative algorithm to allocate the optimal sensing time, fusion rule and the number of members in each group. The computer simulation and numerical results show that the proposed optimal allocation improves the throughput of the SU under a misdetection constraint to protect the PCs. If not, its initial date of receipt shall be nullified.

• Journal of Korean Association for Spatial Structures
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• v.14 no.3
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• pp.101-108
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• 2014

Recently, natural disasters such as earthquake, tsunami, typhoon and tornado are increasing, and cause huge economical loses and victim. Thus, when the disaster occurs, it is important to prepare emergency evacuation shelters for fast and easy construction compared to general building system. And, deployable structures will provide a great help for such aim. Deployable structures have the great advantage of being faster and easier to erect and dismantle compared to conventional building forms. In this study, we confirm the possibility of deployment for shelter structures using scissor structure system. First, Basic model was performed to recognize the appllicability of the deployable systems of the dome-shaped structure. Second, Advanced model that more improved inner space and deployment mechanism was confirmed.

• Korean Journal of Comparative Education
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• v.26 no.3
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• pp.103-132
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• 2016

This study aims to suggest ways of improving the quality of confirmation hearings for the Secretary of Education in South Korea by: 1) comparing the confirmation process by the presidents in South Korea and the United States; and 2) contrasting procedures and contents of hearings for Education Secretary nominee in South Korea and the United States. As the process of selecting a nominee to be the Secretary of Education started, the Blue House Office of Secretary conducted an investigation on the nominee's personal details, family matters, and etc within a week. The investigation, with very limited time frame, led the selection process to be a mere verification on the nominee's morality. On the other hand, the White House Office of Presidential Personnel carried out a thorough investigation on the nominee collectively with the White House Council, Federal Bureau of Investigation (FBI), and Internal Revenue Service, taking from two to three months. In terms of contents of the hearings, the members of the ruling party mainly asked the nominee for clarification, and his ideas on certain policies, whereas the opposition party focused mostly on verifying his morality. In addition, the committee members led the hearing whilst strongly expressing their own political ideologies. However, in the case of the hearings in the United States, the committee members did not ask any questions to verify the nominee's morality but questions that could help them to get an understanding of the nominee's experience, professionalism, and perspective on nation- wide issues regarding education and federal education policy. As for the procedural characteristics of South Korean hearings, the Committee on Education conducted the hearing with a week of advanced preparation. However, submission of required reports by the nominee, performing confirmation hearings, and reports on the hearing were not mandatory in order to appoint the nominee as the Secretary of Education. On the contrary, in the United States, the members of the Committee on Health, Education, Labor, and Pension spent about a month preparing for the confirmation hearing. For the nominee to be appointed, submission of reports and the committee's approval on the President's nomination were required. Based on the results, this research suggests that it is important to develop a policy that can strengthen the substantiality of the nomination process, to establish a professional agency for personnel investigation, to make a mandatory submission of personal reports before hearings, to extend the time frame for hearing preparation, to secure enough time slot for nominees to respond, and to increase the member's autonomy.