• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.6
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• pp.1054-1061
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• 2007

In this paper, the comparison between UPML and Liao's absorbing boundary condition in the FDTD(Finite-Difference Time-Domain) method was performed for the analysis of the 2D cylindrical coordinate system. Generally, it is known as the absorbing characteristics of the UPML is bro than Liao's absorbing boundary condition in the 2D rectangular coordinate. The simulation results in this paper showed that Liao's original absorbing boundary condition is better than other two absorbing boundary conditions, Liao's modified condition and UPML. We concluded that more numerical, theoretical studies, simulations and verifications for various absorbing boundary conditions will be needed to get more accurate results for the design of useful 2D cylindrical microwave circuits.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.118-120
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• 2003

현재 웹의 패러다임은 정적인 웹 페이지들의 모임에서부터 기업이 비즈니스를 더 신속하고 효율적으로 수행할 수 있게 하는 웹 서비스라는 동적인 웹으로 변화하고 있다. 이를 위하여 XML을 기반으로 하는 SOAP WSDL, UDDI, WSFL, XLANG, BPML. WSCL, WSCI 및 BPEL4WS 등과 같은 다양한 표준들과 더 불어 시맨틱 웹과 온톨로지를 기반으로 하는 컴퓨터에 의해서 자동으로 이해될 수 있는 방법으로 웹 서비스를 언급하는 UPML. WSMF 및 DAML-S와 같은 연구들이 최근에 대두되고 있다. 우리는 이 논문에서 시맨틱 웹을 기반으로 하는 지능형 웹 서비스를 가능하게 하기 위하여 새로운 시맨틱 웹 서비스 마크업 언어를 설계하기 위한 전략들을 제시한다. 이를 위하여 먼저 지능형 웹 서비스를 위한 서비스 마크업 언어의 요구사항들을 분석하고, 기존 웹 서비스를 위한 표준들과 연구들을 비교하고 분석한다. 그리고 효과적인 지능형 웹 서비스를 위한 새로운 마크업 언어의 설계를 위한 방법론을 제시한다. 이 논문의 연구결과들은 시맨틱 웹을 기반으로 하는 지능형 웹 서비스를 위한 마크업 언어의 필요성 및 기존 노력들의 문제점들을 지적함으로써 보다 개선된 웹 서비스를 위한 근간으로 사용될 수 있다. 뿐만 아니라 기존 연구들이 추후 보완해나가야 할 사항들을 언급함으로써 보다 향상된 지능형 웹 서비스의 실현을 가능하게 한다.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.2
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• pp.19-27
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• 2012

In railway tunnel environment, the reliability of a high-data-rate and real-time train-to-wayside communication should be maintained especially when high-speed train moves along the track. In China and Europe, the communication frequency around 900 MHz is widely used for railway applications. At this carrier frequency band, both of the solutions based on continuously laid leaky coaxial cable (LCX) and discretely installed base-station antennas (BSAs), are applied in tunnel radio coverage. Many available works have concentrated on the radio-wave propagation in tunnels by different kinds of prediction models. Most of them solve this problem as natural propagation in a relatively large hollow waveguide, by neglecting the transmitting/receiving (Tx/Rx) components. However, within such confined areas like railway tunnels especially loaded with train, the complex communication environment becomes an important factor that would affect the quality of the signal transmission. This paper will apply a full-wave numerical method to this case, for considering the BSA or LCX, train antennas and their interacted environments, such as the locomotive body, overhead line for power supply, locomotive pantograph, steel rails, ballastless track, tunnel walls, etc.. Involving finite-difference time-domain (FDTD) method and uni-axial anisotropic perfectly matched layer (UPML) technique, the entire wireless RF downlinks of BSA and LCX to tunnel space to train antenna are precisely modeled (so-called integrative modeling technique, IMT). When exciting the BSA and LCX separately, the field distributions of some cross-sections in a rectangular tunnel are presented. It can be found that the influence of the locomotive body and other tunnel environments is very significant. The field coverage on the locomotive roof plane where the train antennas mounted, seems more homogenous when the side-laying position of the BSA or LCX is much higher. Also, much smoother field coverage solution is achieved by choosing LCX for its characteristic of more homogenous electromagnetic wave radiation.