• Journal of Power Electronics
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• v.11 no.5
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• pp.621-631
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• 2011

In space qualified DC-DC converters, optimization of the following electrical characteristics is of greater interest in comparison with other specifications; power loss/efficiency, output voltage ripple and volume/weight. The main goal of this paper is to present an appropriate solution for optimizing the above mentioned characteristics. For this purpose, a comprehensive power loss model of a DC-DC converter is fully developed. Proper models are also demonstrated for assessment of the output voltage ripple and the utilized transformer volume as the bulkiest component in a DC-DC converter. In order to provide a test bed for evaluation of the proposed models, a 50W push-pull DC-DC converter is designed and implemented. Finally, a novel cost function with three assigned weight functions is proposed in order to have a trade-off among the power loss, the output voltage ripple and the utilized transformer volume of the converter. The cost function is optimized for applications in which volume has the highest priority in comparison with power loss and ripple. The optimization results show that the transformer volume can be decreased by up to 51% and this result is verified by experimental results. The developed models and algorithms in this paper can be used for other DC-DC converter topologies with some minor modifications.

• The Journal of Korea Robotics Society
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• v.16 no.2
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• pp.147-154
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• 2021

One of the most challenging issues when robots interact with the environment is to establish contact quickly and avoid high impact force at the same time. The proposed method implements the passive suspension system using the redundancy of the torque-controlled robot. Instead of utilizing the actual mechanical compliance, the distal joints near the end-effector are controlled to act as a virtual spring-damper system with low feedback gains. The proximal joints are precisely controlled to push the mid-link, which is defined as the boundary link between the proximal and distal joints, towards the environment with high feedback gains. Compared to the active compliance methods, the contact force measurements or estimates are not required for contact establishment and the control time delay problems do not occur correspondingly. The proposed method was applied to the landing foot control of the 12-DoF biped robot DYROS-RED in the simulations. In the results, the impact force during landing was significantly reduced at the same collision speed.

• Steel and Composite Structures
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• v.36 no.4
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• pp.369-381
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• 2020

Nowadays, in prefabricated composite construction, composite action between steel beam and concrete slab is often achieved with positioning of shear connectors in envisaged openings of concrete slabs. Prefabricated concrete slabs are used for composite steel-concrete buildings and bridges, both for the construction of new structures and for renovation of existing ones, significantly reducing construction time. Development of different types of shear connectors represent alternative solution to the traditionally used headed studs, considering their shear resistance, stiffness and ductility. New types of shear connectors tend to reduce the construction time and overall construction cost. Mechanically fastened shear connectors represent a viable alternative to headed studs, considering their fast installation process and shear resistance. X-HVB shear connectors are attached to the steel beam with two cartridge fired pins. The first step towards extensive implementation of X-HVB shear connectors in composite construction is to understand their behaviour through experimental investigation. Results of the push-out tests, in accordance to Eurocode 4, with X-HVB 110 shear connectors positioned in envisaged openings of prefabricated concrete slabs are presented in this paper. The experimental investigation comprised three different specimen's layout. Group arrangement of X-HVB shear connectors in envisaged openings included specimens with minimal recommended distances and specimens with reduced distances between connectors in both directions. Influence of different installation procedures on overall behaviour of the connection is presented, as well as the orientation of shear connectors relative to the shear force direction. Influence of variations is characterized in terms of failure mechanisms, shear resistance and ductility.

• Journal of the Korea Convergence Society
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• v.11 no.6
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• pp.29-36
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• 2020

As the Ministry of Education adds an item to evaluate whether a university strictly manages class time compliance and student attendance, the number of cases in which universities use electronic attendance systems is increasing. If you use the electronic attendance system, you can manage attendance and record management in real time. In this paper, I would like to suggest a solution to the prevention of cheating, which is a problem with the existing electronic attendance system. In this paper, automatic attendance is possible by automatic or correction. If the electronic attendance is performed manually, the BLE beacon service of the professor's smartphone is activated, and then the student's electronic attendance application is automatically executed using the push message service. When the student clicks the attendance check button and the beacon is found, attendance is processed. In the case of automatic processing, the beacon is automatically searched and attendance is handled even if the student is not involved. The proposed system automatically handles attendance even when the student does not recognize it, and has the advantage of preventing illegal attendance because it can reconfirm attendance at unspecified intervals.

• The Journal of the Korea Contents Association
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• v.20 no.7
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• pp.594-601
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• 2020

This study focuses on the changes in the national innovation system between Korea and China since the 1990s, and studies how to benchmark the limitations of the current national innovation system in Korea from successful national innovation systems in China and apply it to Korean cultural contents. As a result of the review, the current cultural content of Korea is a time when it is necessary to drive sustainable growth in a rapidly changing era, and as a result of applying it from the successful cases of China's national innovation system, it is necessary to change the production of Korean cultural content of the Push strategy into a Pull strategy. In other words, it is necessary to produce cultural contents that fit the paradigm of market change. In addition, the existing technology should lead to the creation of new added value from each element composed of Korean cultural contents, K-pop, K-beauty, Korean food, and above all, it is necessary to institutional innovation of the country in distribution abroad.

• The Journal of Korean Institute for Practical Engineering Education
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• v.2 no.1
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• pp.1-7
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• 2010

Recently, interest in u-learning to pursue effective learning by using ubiquitous environment in teaching and learning activities. In u-learning environment, learners should be able to push necessary information at the right time and the right place. Also calm technology oriented to, and this means that it can recognize learners' terminal information and to provide adaptive interface. In u-learning environment, main learning terminals would be mobile terminals which support mobility. However, learning in the existing PC environment should not be excluded. Thus, by providing adaptive interface according to various learners' terminal in LMS for u-learning, learners are able to learn through consistent and natural learning interface with any computer or any network at any place and at any time. The purpose of this study is to propose the interface adaptation based on terminal information focusing on the layout transformation process in the development environment.

• Journal of the Society of Disaster Information
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• v.9 no.4
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• pp.400-412
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• 2013

For the composite behavior of steel tube and inner concrete, the shear connectors should be applied to the CFT structures. However, the present design codes don't provide the design criteria that can be applied on shear connectors in the CFT structures typically filled with plain concrete. This study has been carried out to propose design criteria (shear strength and resistance factor) for the stud shear connectors in CFT structures. Experimental tests using the push-out specimens with the plain concrete blocks and finite element analysis were conducted for the purpose of verifying the main failure mode to propose the shear strength of studs in CFT structures. From the results of this study, the main failure mode of studs in CFT structures is splitting crack of concrete and this failure mode reduces shear strength of studs in CFT structures relatively to those embedded in RC blocks.

• Journal of the Korea Convergence Society
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• v.11 no.3
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• pp.61-66
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• 2020

Modern society is developing rapidly due to the convergence of industry and IT technology. In that case, the role of construction work that provides basic infrastructure can be very large. Recently, as construction work becomes more complicated, larger, and more advanced, the importance of management, such as system improvement for quality improvement, has become even more important. However, when a quality control problem occurs at a construction site, much time is required to solve the problem. In order for a construction project to be successful, various systems need to be organically connected and able to manage optimal decisions. In this paper, provide a quality control model using GCM push alarm service based on RESTful_API. The proposed model is a model that can be used by construction company quality control rooms and project managers for decision making. When applied to construction site project management, it is expected that more efficient and safe construction management will be possible.

• The KIPS Transactions:PartB
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• v.12B no.2 s.98
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• pp.137-142
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• 2005

Since wireless communication cost is relatively expensive, the mobile games using cellular phones or PDAs are mostly played after being downloaded unlike more updated types of phone-to-phone or online games. In particular, the upbringing games, in which garners foster virtual companion animals or vegetables as their avata, have been spotlighted. It is essential to supply variety of items for upbringing avatas. However, due to diverse tastes for avatas and limited storage of mobile terminals, game manias must download their desired items from homepages. In addition, game developers must inform users through SMS messages whenever a new item is created. To do so, they must link WEB server and WAP server to Call Back URL or ARS. This paper proposed a linkage method suitable for JAVA-based mobile phone operating system. The proposed method will consequently increase life cycle of a game and reinforce profitability.

• Journal of Korea Society of Industrial Information Systems
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• v.23 no.6
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• pp.59-66
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• 2018

In this paper, we experimented how long distance voice communication is possible After implemented PTT(Push to talk) Bi-directional radio using open source project Codec 2, which is a low speed voice codec for digital amateur radio and 900MHz FSK transceiver. In case of a general digital radio, the AMBE+2 codec, which is regarded as an industry standard in terms of performance, is expensive and has the monopoly of technology. Using the 400MHz band in terms of frequency, narrow bandwidth of DMR(12.5kHz) and DPMR(6.25kHz) is used, so the data rate is low. In the 900MHz bandwidth can be extended, which is advantageous in terms of data transmission. As a result of the voice quality and distance field test, we could find that the communication takes place within about 500m. In this paper, only voice communication is reviewed. if a review of data transmission such as a simple image is added, this solution can be used in various fields as a low cost IOT radio.