• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.296-304
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• 1998

A design method of an electromagnetic wave absorber with ferrite fins in the second layer, which has very wide band frequency characteristics and is used for single-polarized wave absorption such as TV wave etc, has been designed. To examine the effectiveness of the Equivalent Material Constants Method$(EMCM)^{[1]}$ which is approximate method, the effective complex permittivity calculated by the Hashin-Strikman formulas and the EMCM are compared. Since, furthermore, the reflectivities by the EMCM in space and the FDTD method in an rectangular waveguide agreed well each other, it has been confirmed that the proposed electromagnetic wave absorber has excellent absorption characteristics in the frequency range of 30 MHz to 5830 MHz. Thus, it can be concluded that the EMCM is usefull to design and analyze the electro-magnetic wave absorber proposed here.

• The Journal of the Acoustical Society of Korea
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• v.31 no.6
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• pp.399-409
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• 2012

In this paper we propose a method for measuring the shear modulus of an ultrasound soft tissue phantom using an acoustic radiation force. The proposed method quantitatively determines the shear modulus based on the rise time of a displacement induced by an acoustic radiation force at the focal point of a focused ultrasound beam. The shear wave speed and shear modulus obtained from the proposed method and a shear wave propagation method were compared to verify the validity of the proposed method. In the shear wave propagation method, the shear modulus is first computed by measuring the propagating speed of a shear wave induced in a phantom by a limited-diffraction transmit field, and then was compared to that obtained with the proposed method in an ultrasound data acquisition system calibrated based on the first computed shear modulus. The relative errors between the two methods were found to be 4% for shear wave speed and less than 9% for shear modulus, confirming the usefulness of the proposed method.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.3
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• pp.233-238
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• 2010

In this paper, we have proposed discrete ray tracing method (DRTM) for numerical analysis of characteristics of electromagnetic propagation along 2D random rough surfaces. The point of the present method is to discretize not only rough surface but also ray tracing. The former helps saving computer memories and the latter does simplifying ray searching algorithm resulting in saving computation time. Numerical calculations are carried out for 2D random rough surfaces, and electric field distributions are shown to check the effectiveness of the proposed DRTM.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.637-643
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• 2011

The bond-based peridynamic model is able to capture many of the essential characteristics of dynamic brittle fracture observed in experiments: crack branching, crack-path instability, asymmetries of crack paths, successive branching, secondary cracking at right angles from existing crack surfaces, etc. In this paper we investigate the influence of the stress waves on the crack branching angle and the velocity profile. We observe that crack branching in peridynamics evolves as the phenomenology proposed by the experimental evidence: when a crack reaches a critical stage(macroscopically identified by its stress intensity factor) it splits into two or more branches, each propagating with the same speed as the parent crack, but with a much reduced process zone.

• Journal of the KSME
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• v.34 no.7
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• pp.510-516
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• 1994

탄성파의 속도는 파동 전파 매질의 밀도와 탄선계수에 달려 있으므로, 박막이 입혀진 기판에서 전파하는 표면파에 대해서 기판과 박막의 밀도와 탄성계수 및 박막의 두께 등을 알면 전파 속 도를 계산할 수 있다. 박막의 탄성계수를 모르는 경우에는 표면파 속도를 측정하여 역으로 탄 성계수를 산출할 수 있다. 이러한 역산과정에는 일반적인 비선형 방정식의 curve-fitting에 이용될 수 있는 simplex법이 효율적으로 활용된다. 이 글에서는 표면파 속도를 측정하고 그 데이터로 부터 역산하여 박막의 탄성계수를 구하는 원리와 과정을 설명한다.

• Annual Conference on Human and Language Technology
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• 1996.10a
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• pp.377-385
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• 1996

여러 가지 의미를 갖고 있는 단어의 올바른 해석은 통사론적, 의미론적, 화용론적 지식을 요구하고 있다. 특히 본 논문에서 다루고자 하는 과제는 의미상 연결되어 있는 두 문장의 효과적인 해석을 통해 다의 단어의 애매성을 처리하는 방법에 관한 것이다. 이를 위해서 마커 전파를 근간으로 하는 메모리 기반 파싱에 이완법(relaxation)을 적용하여 양자의 유기적인 결합을 통한 확장된 메모리 기반 파싱 방법을 제안하고자 한다. 이 방법은 마커 전파가 제공하는 효율성을 유지하며, 이완법이 제공하는 효과성을 추구하고 있다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.8
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• pp.805-819
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• 2013

In this paper, we analyze the paradigm shift of radio policy with the development of radio technology. In particular, we propose the definition of spectrum sharing, which is now omitted in the Korean radio law, and analyze the category of spectrum sharing depending on the licensing regime. Also we propose to extend the spectrum usage right, which defines only exclusive usage rights by spectrum auction in the Korean radio law, to all the stations which use radio spectrum and to restructure the Korean radio law.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.73.2-73.2
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• 2011

세계전파통신회의 (WRC; World Radiocommunication Conference)회의는 국제전기통신연합(ITU)에서 발행하는 국제 전파법과 관련된 전파규약을 갱신하거나 새로운 법 제정을 위해, 3-4년 간격으로 개최되는 전파통신 관련 회의라고 할 수 있다. 차기 WRC회의는 2012년 1월23일 - 2월 17일에 개최되며, 따라서 동 회의에서 다룰 의제들의 사전 연구결과에 대한 보고서가 필요하다고 하겠다. 그러므로 WRC 본회의 개최 6개월 전에 상기 기술문서를 의제별로 종합 작성하기 위해 CPM (Conference Preperatory Meeting) 회의를 개최해야 하며, 본 CPM회의에서 작성된 기술보고서의 내용들은 WRC 본회의에서의 여러 가지 국제법의 결정사안에 대한 중요한 정보를 제공하게 된다고 할 수 있다. 2011년 2월 14일-2월 25일에 걸쳐 스위스에서 개최된 CPM-11 2차회의에서는 전파천문업무 보호 및 22 GHz 대역 달탐사, 38 GHz 대역 Space-VLBI운용대역과 관련된 WRC-11 의제 1.6, 1.11, 1.12 등에 대해 활발한 토론이 있었다. 따라서 한국천문연구원에서는 전파천문업무와 관련된 국가기고서를 제출하였으며, 이와 관련된 동 회의의 최종결과 및 향후 WRC-12회의에 대한 대응책에 대해서도 알아보고자 한다.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.4
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• pp.1-7
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• 1997

This paper presents an analysis of the wave propagation in cross-type tunnels using the finite volume time domain (FVTD) method. Because the FVTD method is based on the volume intergrations of themaxwell's equations with respected to arbitrary shaped small polyhedron cells and the fields at every center point of the cells ar eassigned in a average fashion, the method can handle arbitrary boundary problems with inhomogeneous media. In this paper, the wave propagation in cross-type tunnels has been analyzed using the fVTD method with the PML (perfectly matched layer) absorbing bundary conditons, and the numerical results are verified with a set of experimental data.

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.53-59
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• 2000

In this paper, considering configuration of the earth and environment of country, it is classified a radio propagation environment Multipath propagation measuring system based on PN code correlation detection method is built to study a wave propagation characteristics of 1.95GHz. Considering the characteristic artificial structure of country, Cihwa plant superintendent area has been selected for basic and accurate measurement a radio propagation characteristic. The experiments are carried out with respect to the RMS delay Spread and the received power in the two kind of geographical areas, LOS (Line of Sight) and N-LOS (Non Line of Sight). The measurement result of that received power of LOS area is -1.6∼-28.8dBm, RMS delay spread is 0.023㎲∼0.22㎲ and received power of N-LOS area is 16∼36.5dBm and RMS delay spread is 0.068∼0.37㎲.