• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.4
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• pp.82-87
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• 1999

The Asynchronous Transfer Mode(ATM) networks are being adopted as backbones over various parts of Internet. TCP is one of the most widespread transport protocols and can be used with ATM. But, TCP shows poor end-to-end performance on ATM networks. Effective throughput of TCP over ATM can be quite low when cells are dropped at the congested ATM switch. As congested link transmits cells from corrupted packets, it wastes bandwidth and throughput becomes low. This paper examines the behavior of TCP over ATM-UBR using EPD switch in a broadband environment. As threshold value closes to the buffer size, the buffer can be used more efficiently, but more drops and retransmission occur. If the threshold value is much less than buffer size, efficiency becomes low, but few drops can be happen. Therefore, the decision of threshold value becomes important factor.

• Journal of Korean Institute of Industrial Engineers
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• v.19 no.1
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• pp.47-59
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• 1993

Recently, Broadband ISDN(B-ISDN) has received increased attention as a communication architecture which can support multimedia applications. Also, Asynchronous Transfer Mode(ATM) is considered as a promising technique to transfer and switch various kinds of media, such as telephone speech, data and motion video. Comparisons among a variety of ATM switching systems which have already been proposed will provide quite useful information for the new ATM switching system design. To facilitate the comparison, we introduce the design requirements and classification criteria for the ATM switch, and propose a performance analysis model for the Banyan network which is the basic switching fabric of most multi-stage ATM switching systems. The model is based on the standard discrete-time Markov chain analysis and can be conveniently used for extensive Banyan network analysis. The computational results are also presented.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.635-638
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• 2002

In this paper, the connection device of RS232C and TCP/IP implementation using ARM processor and LINUX is proposed. Data interaction flash memory the multiple serial ports are transferred to ARM processor and the data are processed and formed into data packet for transfer via internet protocol. Packet flash memory Internet is decoded to extract the serial port data. The serial ports supports RS232C asynchronous protocol communication and control program is developed in GNU-C and installed in the on-board memory for packet conversion and control. The research result can be applied to terminal server, printer server and multiple serial ports equipments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2249-2257
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• 1998

In this paper, we propose the enhanced priority control algorithm that adaptively controls the cell service ratio according to the relative cell occupancy ratio of buffer. The asynchronous transfer mode (ATM) provides the means to support various multimedia services in broadband networks. To support multimedia services, various data traffics of different priorities should be controlled effectively. And also it needs congestion control functions required in the netowrk to carry out the control operation. To accomplish this in a flexible and effective manner, priority classes for the different services ar ecommonly used. The proposed enhanced priority control mechanism have two service calsses of the delay sensitive class and the loss sensitive class. The simulation results show that te proposed control mechanism improves the QoS, the charateristics of cell loss probability and mean cell delay time, by selecting propeor relativ ecell occupancy ratio of buffer and the average arrival rate.

• ETRI Journal
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• v.26 no.2
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• pp.149-160
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• 2004

In this paper, we present an interactive data broadcasting system compliant with the Advanced Television Systems Committee (ATSC) standards. The proposed system provides users not only with various data broadcasting services but also remote interactive services. For various data broadcasting services, we have adopted a synchronized data injector that calculates the transmission time of synchronized data accurately and multiplexes synchronized data with the data of an MPEG-2 audio-visual program according to the calculated transmission time. To support remote interactive services, we designed and implemented a return channel server connected on a bi-directional interaction channel. Test results show that the proposed system provides both an asynchronous and synchronized data broadcasting service and remote interactive service appropriately.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.50.1-50.1
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• 2016

The incorporation of radiation from massive stars is essential for modeling the dynamics and chemistry of star-forming clouds, yet it is a computationally demanding task for three-dimensional problems. We describe the implementation and tests of radiative transfer module due to point sources on a three-dimensional Cartesian grid in the Eulerian MHD code Athena. To solve the integral form of the radiation transfer equation, we adopt a widely-used long characteristics method with spatially adaptive ray tracing in which rays are split when sampling of cells becomes coarse. We use a completely asynchronous communication pattern between processors to accelerate transport of rays through a computational domain, a major source of performance bottleneck. The results of strong and weak scaling tests show that our code performs well with a large number of processors. We apply our radiation hydrodynamics code to some test problems involving dynamical expansion of HII regions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.709-712
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• 2001

본 논문은 광대역 무선통신 채널환경에서 3GPP 표준안에 기반한 비동기식 IMT-2000 시스템의 송수신기를 구성하여 수신단의 기지국 수신성능을 분석한다. 다중 경로 페이딩 모델로는 ITU-R M.1225에서 제시된 모델을 적용하였으며, 이동국과 기지국의 Uplink 채널환경을 고려하였다. 성능개선 기법으로 어레이 안테나를 채용하였고, 동일채널 간섭제거기와 레이크 수신기를 혼합하여 기존의 레이크 수신기에서 제거할 수 없었던 자기 간섭(Auto Interference)을 제거하는 새로운 레이크 수신기를 제안하였다. 성능 분석 결과, 제안된 레이크 수신기는 자기 간섭 제거로 인한 성능개선 효과를 얻을 수 있었으며 또한, 어레이 안테나를 채용하여 다중접속간섭으로 인한 성능열화를 보상할 수 있었다.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.961-963
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• 1998

Power telecommunication networks, being used to support the operation and management of power utility services, exhibits different characteristics from those of public domain networks. KEPCO is planning to evolve its own power network infrastructure to exploit ATM (Asynchronous Transfer Mode) technology. The ATM network to be developed needs to effectively utilize existing network of KEPCO and to fully support new and emerging power-utility-services. This paper summarizes the features of power communication services and the characteristics of Power telecommunication networks, and reports our evolution methodology for KEPCO network.

• English Language & Literature Teaching
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• v.10 no.1
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• pp.127-152
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• 2004

The purpose of this study is to elaborate design strategies for a Web-based self-directed cooperative distance language learning community. Research was done regarding the theoretical foundations for self-directed cooperative language learning and Web-based learning communities. The components of a Web-based community for self-directed cooperative language learning system are also investigated. As a result of this study, design strategies for Web-based communities are suggested. There are performance and supporting environments(synchronous/asynchronous) for self- directed cooperative language learning. There are also cultural experiences and communication factors in the performance field. Furthermore, matching communicators, finding and offering information, language learning content and other supporting agents are important in the supporting environment.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.458-458
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• 2004