• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.470-473
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• 2002

Most networks for automation are tuned to an expected traffic at their design stage. During their actual operations, however, the networks experience considerable changes in traffic from time to time. These traffic changes caused by common events like machine failure and production schedule change may adversely affect the network performance and, in turn, the performance of the connected devices. This paper presents communication delay model for Profibus token passing protocol, and introduces TTR selection methods to maintain a uniform level of network performance at all stations under changing network traffic.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2006.06a
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• pp.329-333
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• 2006

New computing paradigm in ubiquitous computing environments is revolutionizing the way people interact with computers, services and the surrounding physical spaces. In order to provide stronger authentication, MIST proposed an authentication framework for ubiquitous computing environments and assigned confidence values to some authentication methods to facility the combining. However, the assigned confidence values lack sufficient evidence. In this paper reliable confidence values for each authentication method used in MIST is proposed. These confidence values can combine multiple confidence values in some manner, producing a more accurate net confidence value. Authentication entities with confidence values allows the authentication framework to blond nicely into ubiquitous computing environments.

• ETRI Journal
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• v.33 no.1
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• pp.18-26
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• 2011

The necessity for services of emergency communication systems to be uninterrupted and reliable has brought forward strict requirements for express software upgrades of base stations. Based on reconfigurability technology, this paper presents a protocol reconfiguration scheme for emergency communication base stations. By introducing the concept of 'local safe state,' the proposed scheme could make the updating and replacement of the protocol software flexible and maintain interactions during the updating procedure to achieve seamless system upgrades. Further, taking TETRA protocol stack and VxWorks operating system as an example, specific processes and realization methods of reconfiguration are proposed in this paper, along with the measurements of the factors impacting on the system performance. Simulation results show that, compared with traditional technology, the method proposed significantly improves the system efficiency and does not interrupt system services.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.641-642
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• 2018

LED-based visible light communication requires separate transmission and reception equipment and is capable of communication only in the range of the light source. Also, there is an advantage that it can be used in a frequency sensitive area using a visible light band. Research is needed to apply these advantages and characteristics to various fields. In this paper, we implemented and verified the functions of the visible light communication system using broadcast methods.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.77-78
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• 2012

본 논문에서는 고효율 중대용량 컨버터에 적용되는 트랜스포머의 권선법에 따른 성능 및 특성을 분석한다. 누설 인덕턴스 및 EMI를 저감하는 권선법, 고주파 스위칭 트랜스포머의 최적 적층법, 공극과 권선의 위치에 따른 영향 등을 분석하였다. 또한 트랜스포머의 기생성분 계산법을 설명한다.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.173-174
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• 2012

본 논문에서는 전기자동차용 부하 직렬 공진형 컨버터(Series-loaded Resonant Converter, SRC)타입의 탑재형 충전기 (On-Board Charger, OBC)의 추가 회로 없이 경부하 효율을 향상시키기 위한 스위칭 방법들을 비교 분석한다. 시스템에 적용할 스위칭 제어 방법은 Asymmetrical Duty Cycle Control (ADC)과 Asymmetrical Voltage-Cancellation Control (AVC) 방법이다. 각 제어 방법을 기존의 3.3kW SRC-OBC의 적용하여 경부하 영역에서의 효율을 확인하고 각 제어 방법의 타당성을 검증한다.

• Journal of Contemporary Eastern Asia
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• v.12 no.1
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• pp.65-79
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• 2013

This paper examines communication patterns of key Twitter users by considering the socially and politically controversial Sejong City issue in South Korea. The network and message data were drawn from twtkr.com. Social network-based indicators and visualization methods were used to analyze political discourse among key Twitter users over time and illustrate various types of Tweets by these users and the interconnection between these key users. In addition, the study examines general Twitter users' participation in the discussion on the issue. The results indicate that some Twitter profiles of media outlets tend to be very dominant in terms of their message output, whereas their Tweets are not likely to be circulated by other users. Noteworthy is that Twitter profiles of individuals who are geographically affiliated with the issue are likely to play an important role in the flow of communication.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.9
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• pp.1700-1709
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• 2006

In this raper we researched on the development methods and design of the B-ISDN protocol embedded IP-PBX System with the computers interconnected by the Internet for the previous telephone exchange and communication. We designed the structure of the user terminal and exchange sewer of the IP-PBX System, defined message and data structure for call control, and designed call control state transition and call control message flows for user's communication. And we researched on the message flows for supplementary services and the call control for multiple calls.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.68.4-68
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• 2001

In the area of factory automation (FA), a lot of researches are being executed about intelligent system using network. Conventional industry controllers are implemented the connection with other controllers by using asynchronous serial communications. These methods of communication have an advantage of easy implementation but have disadvantages of lack of real-time characteristics needed in motion control, slow baud rate too low to exchange required data sufficiently and low integrity because of different communication protocol. Serial real-time communication system (SERCOS) provides international standard communication specifications (IEC 61491) for interfacing between control units and drives from different manufacturers, has real-time ...

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.312-315
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• 2003

The paper presents a small. unmanned remote controlled probing ship that can reduce the cost for acquiring data of marine and coastal environments. The control system is composed of three microprocessors. one is for overall mission control. another for control of propulsion motors. and the other for sensor operation. For communication system, we adopt direct and indirect methods based on the wireless modem of commercial cellular telephone. The former is a direct communication between the modems of the ship and the server. and the latter is an indirect communication via internet between the ship and the server. The system is equipped with a digital compass and a GPS system for position estimation, and extended Kalman filter is used for the data association. The performance of the ship is demonstrated with the results produced by sets of experiments.