• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.133-135
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• 2003

시맨틱 웹은 지식을 구조적으로 표현할 수 있는 수단과, 논리를 기반으로 지식을 처리하는 기술을 주요 요소로 포함하고 있다. 후자에 대한 유력한 기술로 기호 논리를 기반으로 한 연역 추론 기법이 폭넓게 응용되고 있으나 아직 초보적인 단계에 머물러 있다. 본 논문은 시맨틱 웹 환경에서 효과적인 추론 기능을 수행할 수 있는 연역 추론 시스템의 설계 및 구현 내용을 담고 있다. 본 논문에서 제시하는 추론 시스템은 표준 기술 논리(Description Logic)의 상당 부분과 혼 논리(Horn Logic) 기반의 논리 프로그래밍을 아우르는 확장된 표현력을 제공하여, RETE 알고리즘 기반의 생성 시스템을 활용하여 추론한다. 또한, 규칙베이스를 구성하는 단위 지식들을 웹 자원화함으로써 온톨로지로 대표되는 시맨틱 웹의 지식 표현력을 확장하였다. 본 논문이 제시하는 추론 시스템을 이용하면 웹 온톨로지 위에 규칙 및 논리 계층［1］을 효과적으로 구현할 수 있다.

• Journal of the korean Society of Automotive Engineers
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• v.9 no.3
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• pp.16-22
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• 1987

직접분사식 디젤기관의 성능과 배기가스 문제에 여향을 주는 실린더 내에서의 연소형태는 크게 연료분사계와 흡입공기 유동계 두 가지에 의해 결정된다. 즉 분사율, 부사시기, 분무형태와 같은 분사계의 특성과 공기선회, 스퀴시(squish), 난류와 같은 공기 유동 특성에 의하여 연소형태가 결 정된다. 이러한 복잡한 연소형테를 기관 특성에 맞게 조정한다는 것은 대단히 어려운 문제인데 이것은 연료화 공기의 혼합이 연소실형상과 흡기계의 형상에 큰 영향을 받으며 연료가 액체 상 태로 연소실내로 들어와 분무과정을 통하여 증발이 되어야만 연소가 가능하기 때문이다. 특히 흡입공기 유동계에 있어서 현재의 직접 분사식 대젤기관의 흡입구 형상은 흡입공기의 운동에너 지에 모멘트를 가하여 연소실내에서 공기의 선희(swirl)를 발생시켜 줌으로써 연료와 공기의 혼 합기를 형성시키는 Helical type이 많이 이용되고 있다. 그러나 기관 성능과 배기가스 특히 NOx는 상반관계를 이루기 때문에 연소실내로 들어오는 흡입공기의 선희강도(swirl ratio)를 너무 강하게만 한다고 하여 좋은 결과를 얻을 수는 없다. 따라서 설계하고자 하는 각 기관에 있어서 요구되는 성능과 배기가스 문제를 만족하는 흡입공기의 선희강도가 얻어질 수 있도록 흡입구 형상을 설계한다는 것은 많은 연구와 경험이 요구되고 있다. 본 자료에서는 직접분사식 디젤기 관에 있어서 흡입공기의 최적 선희강도에 대한 설정방법과 흡입구 형상 설계를 위한 설계 이론 및 정상류 Rig test상에서의 흡입공기 선희강도의 평가방법을 소개하고자 한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.9 s.112
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• pp.829-835
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• 2006

In this paper, new structure of the Cassegrain reflector antenna whose spill-over is efficiently reduced by modified reflectors is proposed for high power. It can be achieved by designing the geometry of subreflector in Cassegrain system using two hyperbolic curves in order to be suitable a lager beamwidth of feeding pattern without broadening main reflector. Finally, radiation efficiency and side lobe level of the proposed Cassegrain reflector antenna can be improved respectively 9 %, 10 dB than conventional one.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.528-536
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• 2010

A monopulse feeder gives the most important impact upon the radiation pattern characteristics of a multi-function radar or a tracking radar which uses the space feed. It is described that the triple-mode type monopulse feeder which possesses the optimum aperture illumination for three monopulse channels is designed and measured in this paper. The measured results show that the designed feeder has not only the characteristics of the optimum aperture illimination in each channel and also very low return loss over the 10 % of fractional bandwidth at X-band. This means that the feeder provides the antenna system with low sidelobe level and high monopulse slope characteristics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.10
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• pp.935-940
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• 2016

Directed energy weapon enables to radiate the concentrated energy so as to result in distraction and overload of the target electronics. Analysis on effectiveness of weapon system can be important consideration in order to determine performance and design weapon system. In this paper, air defense weapon system, which is one of directed energy weapon system is studied. In order to analyze the effectiveness, the reflector antenna with high power circularly polarized horn antenna is designed, and power density in axial effective area is simulated and calculated using Friis formula. Through the study, the validity of antenna system is verified, and the effectiveness of directed energy weapon system on the target is evaluated.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.4 s.346
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• pp.58-66
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• 2006

This paper proposes an FSS(Frequency Selective Surface) design system that automatically derives design parameters minimally specified by engineers. The proposed system derives optimal design parameters through theory of electromagnetic scattering on FSS, database implemented from real data obtained from practically manufactured FSS, and GA(Genetic Algorithm) for optimizing design parameters. The system, at the first step, searches the best matching FSS within preconstructed DB with given characteristics specified by operators, and then sets initial genes from the searched FSS parameters. GA iterates the optimization process until the system finds the FSS design parameters that matches the characteristics specified by operators. The theory for the electromagnetic scattering on FSS is verified by comparing the simulation results with real data obtained by measuring system composed of horn antenna and receiver. The process for manufacturing the FSS is also included in the paper.

• Journal of Satellite, Information and Communications
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• v.11 no.3
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• pp.80-85
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• 2016

In this paper, by comparatively analyzing horn type speaker and line array type speaker developed based on line sound source theory and point sound source theory, we research whether theory is adaptable or not in real. Academically, point sound source is attenuated as much as 6dB in accordance with double distance and line sound source is attenuated as much as 3dB in accordance with double distance. Line array speaker system developed based on line sound source is analyzed by theory of line sound source about occurring small sound pressure attenuation and it is propose of research that array composition of right speaker is selected in accordance with use purpose and environment. For this purpose, we analyze theory of point sound source and line sound source. we analyze parameter value by simulating designed horn type speaker and line array speaker based on theory.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2B
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• pp.175-185
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• 2011

This study investigates tsunami force acting on a group of onshore structures numerically by using three-dimensional one-field model for immiscible multi-phase flows, which is based on Navier-Stokes solver. In particular, we studied on the characteristics of tsunami with respect to the arrangement of onshore structures and the distance from seawall trough numerical experiments. For validation of the numerical method used in this study to calculate tsunami force, numerical results for tsunami force on the structures in coastal area are compared with available experimental data. Furthermore, a detail study on the efficiency of the numerical method is performed for the estimation of tsunami force based on the hydrostatic and hydrodynamic methods in which the numerical results are used. The obtained results are compared to the previous experimental one and design criteria. Considering both experimental results and numerical analysis results, semi-empirical formula by regression analysis is proposed. As a result, it was confirmed that the numerical analysis is effective to estimate on tsunami force acting on onshore structures.

• Journal of IKEEE
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• v.7 no.1 s.12
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• pp.88-96
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• 2003

In this paper, We designed and implemented a linear high-power amplifier which can be used for the commercial service in band of $1.9GHz(1.93{\sim}1.99GHz)$ at U.S.A. The output power of the implemented linear high power amplifier is 25W. In order to satisfy IMD characters decided by FCC, the Feedforward linearization techniques has been used. The used feedforward method has improved the IMD characteristics from 10.51dBc to 19.01dBc in each power level from 1W(30dBm) to 25W(44dBm). The IMD level of the final output shows from minimum 64.84dBc to maximum 68.17dBc. Because this good characteristics of IMD, the LPA is expected to use as a commercial product of PCS base station.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.806-812
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• 2000

In this paper, we theoretically studied on the large antenna array whose element had wider than one wavelength. And we also verified the adaptedness through the experiments. Using grating lobes, we could make antenna have sharp HPBW. Not only HPBW but also SLL could be controlled by giving optimal space for antenna array. In order to verify this method, we designed 4 horn antenna array and measured the radiation patterns at 9 GHz. Each horn antenna has the dimension of 64.3$\times$82.5$\textrm{mm}^2$ and HPBW of 27$^{\circ}$. The space between antennas is longer than one wavelength so that it may have the grating lobes in visible region. As a result of experiments, we could get HPBW of 4.3$^{\circ}$, 3.3$^{\circ}$ and 1.7$^{\circ}$when giving 2.5λ, 2.7λ and 3.0λ of the spacing respectively. We concluded this could be useful making the antenna with narrow HPBW.