• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.403-406
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• 2006

An ejector is designed for the purpose of engine bay cooling. The primary flow of the ejector is the exhaust gas of the PW206C turboshaft engine. The mass flow of secondary flow is calculated by using the approximate analytic equation. For the purpose of verification of approximate analytic method, comparison is made with the results of Navier-Stokes turbulent flow solution. According to the results of CFD, the mixing of two flows is incomplete due to the short length of mixing duct.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2006.05a
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• pp.420-424
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• 2006

본 논문에서는 외란을 갖는 불확실한 비선형 시스템을 제어하기 위하여 $H^{\infty}$ 제어를 이용한 강인 간접 적응 퍼지 관측기를 설계하여 상태변수를 관측하고 외란관측기를 설계하여 시스템의 외란을 제거하는 강인한 제어기를 구성한다. 제안된 외란관측기는 시스템과 외란의 대역폭보다 큰 궤환 이득을 가짐으로써 기존의 역플랜트 모델 또는 퍼지 기반의 외란관측기 보다 간단한 구조를 가지고 외란과 시스템 모델링 오차의 합을 관측해 낼 수 있다. 본 논문에서는 도립진자 시스템의 모의실험을 통하여 관측기, 외란관측기와 제어기의 성능을 평가한다.

• Journal of the Korean Ceramic Society
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• v.35 no.7
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• pp.699-705
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• 1998

This paper is about design of optimal structure of microstrip dielectric ceramic antenna with rectangular electrode patches in accordance with the cavity model and fabrication of its prototype sample operating at the frequency of 900 MHz. Results of this work can be employed as a useful too to develop and diversify ceramic antenna having superior performance and omni-directivity to that of current helical antenna.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.519-522
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• 2006

Experimental and computational studies on an turbopump inducer with and without a bearing strut were performed to evaluate the effects of a strut on the performance of an inducer. Global performance data such as head rise and efficiency, and detailed flow characteristics such as surface static pressures were measured and compared with computational results. Generally a good agreement is observed between experimental and computational results, but some discrepancies are observed due to complex flow features such as backflows at the inlet and strut/inducer interactions. For the flow rates where the backflow region is large, installing a strut enhanced the hydraulic performance of the inducer by diminishing the size of the backflows. The results also show that the strut has negligible effect on the suction performance of the inducer.

• Journal of the Korean Solar Energy Society
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• v.24 no.4
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• pp.77-87
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• 2004

BIPV or double skin applied to the surface of the building, power and thermal load cannot both be increased. In the case of BIPV, because it is applied to the facade, incident solar energy decreases and efficiency drops off. The system in this paper complements these disadvantages and aims to decrease the heating & cooling load by transforming solar energy to electronic and thermal energy. The research in this paper is about the applicability of the clear PV attached double-skin system. And the PV electronic generation and the factors that affect the heating & cooling load such as the daily radiation, sun shading ratio, heating & cooling load, daylight luminance and glare distributions in the building are simulated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1735-1740
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• 2000

The aim of this study is to analyze the sound insulation performance of windows depending on the sound source types and to propose the noise control method in the apartment house. The regions where apartment houses are constructed are varied in the dominant noise sources such as aircraft noise, railway noise and road traffic noise. For the experiment, nine noise sources including pink noise were selected and recorded, which was used in the experiment by reproducing. As a result of this study, the sound insulation performance of window was found that when the frequency contents of the noise were high level in all frequency bands the difference of sound insulation performance was negligible, but when the frequency contents were low level at particular frequency band the difference of sound insulation performance was shown very differently.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.5
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• pp.867-871
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• 2013

In this paper, a major factor in determining voice quality that corresponds to the jitter and jitter buffer algorithm for removing jitter will be described. We analyze various jitter buffer algorithms and suggest ways to improve performance of jitter buffer algorithm.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.691-693
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• 1999

이동 컴퓨팅 환경은 유선망에 비하여 대역폭이 낮고, 호스트의 성능이 낮으며, 사용자의 이동에 따른 여러 가지 문제점이 나타난다. 이러한 이동 컴퓨팅 환경에서 멀티미디어 서비스를 제공하기 위해서는 무엇보다 QoS 제어가 중요하다. 따라서 본 논문에서는 이동 멀티미디어 컴퓨팅 환경의 동적 변화에 적응하고, 효율적으로 QoS를 제어하기 위하여 동적 우선순위를 기반으로 한 QoS 제어 기법을 제시한다. 동적 우선순위는 최초 연결성정 시에 결정되는 정적 우선순위와 보상을 기반으로 한 대역폭 변화값에 따라 결정되며, QoS 제어를 위한 기준으로 사용된다. 이러한 동적 우선순위는 낮은 QoS를 제공받은 MH(Mobile Host)가 핸드오프를 수행하여 새로운 셀로 이동한 경우에도 지속적으로 낮은 QoS를 제공받는 문제를 해결함으로써 공평하게 대역폭을 할당하는 장점이 있다.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.37-37
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• 2000

This paper introduces the Performance Monitoring System(PMS) in a thermal power plant. The purpose of the PMS is to offer the operator current performance information of plant which could be an index of plant status or information to improve plant efficiency. The PMS of Bukcheju thermal power plant unit ＃2&3 is implemented under the SIEMENS DCS which supplies about 150 function blocks for performance calculation and all measured signals. The performance of unit, boiler, turbines, feedwater heaters, condenser, airpreheaters, feedwater pumps will be monitored and updated for every 5 minutes in PMS of Bukcheju TPP.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.421-421
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• 2000

In this paper, robust two-degree-of-freedom controller for satellite antenna system which tracks reference signal is designed. Two-degree-of-freedom controller consists of a prefilter and a feedback controller to solve trade-off between robust stability and command response. The feedback controller is designed from specifications like stability, disturbance rejection and robustness via H$_{\infty}$ design technique. In the sequel, H$_2$ optimal prefilter is introduced to improve the command response. This suggests a two-step design, with different types of performance specifications at each stage. In practical problems, this may easily lead to a prefilter of unacceptably high order. In order to avoid high order prefilter we use a particular structure in which both the prefilter and the feedback controller share the same dynamics. H$_2$-prefilter technique proposed in this paper is verified by simulation.