• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.495-500
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• 1997

For hydrogen management in severe accidents with degraded nuclear core of PWR's, several experiments have been performed in the SNU hydrogen mixing facility. The objectives are understanding the extent of hydrogen mixing and analyzing the effects of factors which dominate uniform or non-uniform mixing at compartments in the containment building. The facility represents on a 1/11th linearly scaled model of the YGN unit 3&4, hydrogen was simulated by helium. Because there are the gaps between safety injection tank and compartment layers in the containment, the test facility was constructed in three dimentinal mode for analyzing of mixture behavior through the gaps. From the experimental results we could conclude that overall hydrogen concentration distributed uniformly in the free volume of the test compartment, but fluctuated in the gaps. This paper is focused on experimental result from several experiment.

• Korean Journal of Computational Design and Engineering
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• v.3 no.1
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• pp.48-56
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• 1998

Finite element analysis is very important in the design and analysis of mechanical engineering. The process of FEA encompasses shape modeling, mesh generation, matrix solving and post-processing. Some of these processes can be tightly integrated with the current software architectures and data sharing mode. However, complete integration of all the FEA process itself and the integration to the manufacturing processes is almost impossible in the current practice. The barriers to this problem are inconsistent data format and the enterprise-wise software integration technology. In this research, the information model based on STEP AP209 was chosen for handling finite element analysis data. The international standard for the FEA data can bridge the gap between design, analysis and manufacturing processes. The STEP-based FEA system can be further tightly integrated to the distributed software and database environment using CORBA technology. The prototype FEA system DICESS is implemented to verify the proposed concepts.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.351-353
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• 2018

The compensation characteristics are investigated as a function of the averaged residual dispersion per span (RDPS), which is different in each half transmission section, in dispersion-managed optical transmission links with a randomly distributed single mode fiber lengths and RDPS.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.348-350
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• 2018

In this paper, dispersion-managed optimal link configuration with the repetitively artificial-distributed single mode fiber lengths and residual dispersion per span, in which optical phase conjugator placed at midway, is proposed. It is confirmed that the proposed optical link configuration is suitable for expanding transmission length capable to obtain the good performance.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.109-118
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• 1999

Lifeline system such as oil or gas pipelines and water supply facilities are vulneratble to seismic damages because they are widely exposed to ground failures. Most seismic design criteria of buried pipelines are based on the notion that the longitudinal compressive strain and therefore buckling controls the design. Buckling analysis of buried pipelines subjected to seismic loading is performed by considering the seismic load as the sinusoidally distributed compressive load on the beam on elastic foundation in contrast to existing studies where the buckling load is treated as an end load on the beam column, An approximated analytical solution is obtained by the energy method and its validity is confirmed by the linearized finite element buckling analysis. The results show the beam mode buckling because longitudinal strains at the buckling loads are substantially lower than the strain at the onset of local buckling.

• Journal of Digital Contents Society
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• v.4 no.2
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• pp.139-146
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• 2003

This paper explains the design and implementation of the ERA(Error Recovery Agent). ERA is a system that is suitable for detecting, sharing and recovering software error based on multimedia distance education system. This system consists of an ED, ES, and ER. ED detects an error by hooking techniques. ES is an agent which is an error sharing system for distributed multimedia distance education system. We propose how an error application can be treated and recovered as 'media' in a multimedia collaborative environment.

• Journal of the Optical Society of Korea
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• v.8 no.1
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• pp.13-16
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• 2004

A widely tunable SG-DFB (Sampled Grating Distributed Feedback) laser diode is proposed and its feasibility is confirmed through simulation. The new SG-DFB laser diode is composed of a pair of sampled gratings, some parts of which are gain sections and the other parts of which are phase control sections. It is shown that a few tens of nanometers can be tuned through the adjustment of two currents into the phase control sections. Higher output power is expected compared with a SG-DBR laser diode with similar parameters. The dynamic single mode operation is also observed in the time-domain simulation.

• Journal of Communications and Networks
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• v.15 no.6
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• pp.606-613
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• 2013

This paper proposes a complete solution of a contention-based medium access control in wireless local networks to provide station level quality of service guarantees in both downstream and upstream directions. The solution, based on the mature distributed coordination function protocol, includes a new fixed contention window backoff scheme, a tuning procedure to derive the optimal parameters, a super mode to mitigate the downstream bottleneck at the access point, and a simple admission control algorithm. The proposed system guarantees that the probability of the delay bound violation is below a predefined threshold. In addition, high channel utilization can be achieved at the same time. The numerical results show that the system has advantages over the traditional binary exponential backoff scheme, including efficiency and easy configuration.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.198-199
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• 2017

This paper proposed a new control method for supercapacitor (SC) to compensate the pulse load transient and enhance the power quality of dc microgrid. By coordinating the operation frequency, the supercapacitor is controlled to handle the surge current component while the low-frequency current component is dealt with by remaining sources in the system. Based on the state of charge and dc bus voltage level, the SC unit operation mode is automatically decided. Meanwhile, the dc bus voltage level indicates the power demand of the whole system; by regulating the dc bus voltage, the mismatch of power demand is covered by SC unit. The effectiveness of proposed method is verified by experiment prototype formed by two distributed generation and one supercapacitor unit.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.36-38
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• 2008

본 논문에서는 여러 대의 인버터를 동시에 사용하는 분산전원 환경하에서 Anti-islanding을 효과적으로 할 수 있는 방안을 제안한다. 제안하는 Anti-islanding기법은 SMS(Sliding Mode Frequency Shift)를 근간으로 하면서 공진 Q가 높을 때 검출이 어려운 단점을 해결하는 방법을 제시한다. SMS위상의 변동 값을 판단근거를 사용하지 않고 SMS위상의 적분 값을 판단근거로 사용한다. Run on시간이 0.5초 이내로 국내외 규격을 모두 만족시킨다. 여러 대의 인버터를 병렬로 접속해도 islanding 검출이 탁월하다. 출력전력의 품질 면에 있어서도 다른 Anti-islanding기법에 비해 우수하다. 본 알고리즘의 우수성을 시뮬레이션과 실험을 통해 검증하였다.