• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.12A
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• pp.1759-1765
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• 2000

공기 갭을 갖는 일축성 기판위에 마이크로 패치 안테나의 공진 주파수가 full-wave approach와 모멘트 계산법을 이용하여 연구되었다. 일축성 매질내의 구성관계식을 통하여 제안된 구조에서의 파수영역 다이애딕 그린 함수를 유도하였으며 이 결과로부터 전계 적분 방정식을 수식화하였다. 갤러킨 모멘트법을 사용하여 전계 적분 방정식을 이산화 하였으며 기저함수의 선택은 수치 해석적 수렴을 고려하여 패치 위의 실제 전류밀도와 가장 유사한 형태인 정현적 기저함수를 선택하였다. 전사모의 실험 결과의 타당성을 검증하기 위해서 기존의 결과와 비교하여 일치된 결과를 얻었다. 공기 갭의 두께와 패치 길이, 이방성 비의 변화에 따른 공진 주파수가 제시되고 분석되었다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.549-556
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• 2002

주변이 Kinney의 정의에 따른 부분 고정도를 가지고 지지된 직4각형 평판이 부분 분포하중을 받고 있을 때의 안정해석을 유한 요소법으로 수행하였다. 수치해석에서 고려한 변수는 평판의 변장비 (=λ)와 부분 분포하중 작용폭 (=γ) 및 부분 고정도 (=f) 값이다. 여기서 특히 f=0.0 은 주변이 단순지지를 표시하고 f=1.0은 고정지지를 뜻하는데 수치해석에서는 f=0.0, 0.2, …, 1.0으로 변화시켰다. 유한 요소법으로 산정한 판의 좌굴계수 변화는 각각의 변장비에 대하여 나머지 두 개의 매개변수를 변랑으로 하는 대수 함수식으로 표시하였다. 제안한 대수식으로 추정한 임계하중치와 유한 요소법으로 산정한 임계하중치 간의 상관계수는 모든 변장비에 대하여 거의 단위치 (ρ=1.0)에 가까웁다. 따라서 제안한 대수 함수식은 구조 설계자들의 판 설계 및 안정 검토시에 유익한 자료로 이용될 수 있다.

• ETRI Journal
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• v.29 no.1
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• pp.36-44
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• 2007

The wave concept iterative procedure (WCIP) is used to analyze arbitrarily shaped frequency selective surfaces (FSS). The WCIP method is developed from the fast modal transform based on a two-dimensional fast Fourier transform algorithm. Using the proposed procedure, less computing time and memory are needed to calculate the scattering parameters of the FSS structure. The method is applied to the modeling of an FSS structure of a rectangular patch and a comparison with experimental results confirms good agreement.

• Journal of electromagnetic engineering and science
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• v.11 no.3
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• pp.207-212
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• 2011

This paper presents a CPW-fed antenna with three slots. The proposed antenna can operate at 1.9~2.1 GHz and 2.9~3.3 GHz which are generated by the two rectangular slots, and 4.5~11.6 GHz which is generated by the main patch. The semicircle-slot is used as a band-notched filter to stop at a desired band (5.150~5.825 GHz) limited by IEEE 802.11a or HIPERLAN/2 applications. The currents concentrate around corresponding slots at the desired band. The proposed antenna is very small in size, with overall dimensions of $27{\times}32{\times}1\;mm^3$ etched onto an FR4-printed circuit board (PCB).

• Journal of electromagnetic engineering and science
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• v.13 no.4
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• pp.208-213
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• 2013

This paper proposes a tag antenna for radio frequency identification (RFID) food system. The RFID tag antenna is designed and fabricated based on the rectangular loop concept used in the UHF band (Korean and Japanese standards, 916.7-923.5MHz). The proposed tag antenna is composed of a radiation patch, sensor tag chip, temperature sensor, oscillator, and battery. We conjugated matching between the tag antenna and the sensor tag using a U-shaped stub. Details of the proposed tag antenna design and the simulated and measured results are presented and discussed.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.733-738
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• 2002

In this study, contact fatigue in wheel-rail contact is simulated. It is necessary to calculate contact stress and subsurface stresses accurately to predict fatigue behavior. Contact stresses are obtained by contact analysis of semi-infinite solid based on influence function and subsurface stress field obtained by using rectangular patch solutions. Based on these stress values, several multiaxial high-cycle fatigue criteria are used and the critical loads corresponding to fatigue limits are calculated. The simulation results show that the critical load is decreasing rapidly and the site of crack initiation also moves rapidly to the surface from the subsurface when friction coefficient exceeds a specific value for all of three fatigue criteria.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.7
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• pp.282-287
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• 2003

″H″ type resonator has the advantage for the miniaturization of high-T7 superconducting (HTS) microstrip antenna in comparison with the conventional microstrip antenna such as rectangular type or circular type. In this paper we designed miniaturized HTS antennas using this "H"-type resonator and reported the characteristics of our antennas including return loss, bandwidth, radiation patterns, efficiency and so on. To fabricate the "H" type antenna, HTS YBa$_2$Cu$_3$$O_{7-x}$ (YBCO) thin films were deposited on MgO substrates using rf-magnetron sputtering. For comparison between normal conducting antennas and superconducting antennas, the gold antennas with the same dimension were also fabricated. An aperture coupling was used for impedance matching between 50 $\Omega$ feed line and HTS radiating patch. The ″H" type superconducting antenna showed the performance of 1.38 in SWR, 26 % in efficiency, and 13.8 dB in the return loss superior to the normal conducting counterpart.

• Tribology and Lubricants
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• v.21 no.3
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• pp.136-141
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• 2005

Analytical model to calculate the contact fatigue life of rough surface is presented in this paper. The effect of surface roughness can be calculated by this model. Computational method and the theoretical basis are also discussed. Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions; the subsurface stress field is obtained using rectangular patch solutions. Mesoscopic multiaxial fatigue criterion which can yield satisfactory results for non-proportional loading is then applied to predict fatigue damage. Suitable counting method and damage rule were used to calculate the fatigue life of random loading caused by rough surface. As a result of analysis the relationship between the life and the roughness as well as the most probable depth of the crack initiation is calculated.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.2
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• pp.174-180
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• 2002

The subsurface stress field beneath the roller's contacting surface due to the contact pressure in lubricating condition has been calculated. Main purpose of this study in view of engineering is to prove the validity of the numerical profile roller presented by Koo et al. The Love's rectangular patch solution was used to obtain the subsurface stress field. The stress field of the numerical profile roller was compared with the one of the existing dub-off profile roller The analysis results show reduced subsurface stresses for the numerical profile roller.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.1033-1036
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• 2005

The effect of surface roughness on the contact fatigue was investigated in this study. To accomplish this goal, contact analysis based on the influence functions and the rectangular patch solution was performed to obtain the subsurface stress. Mesoscopic multiaxial fatigue criterion is then applied to predict fatigue damage. Suitable counting method and damage rule were used to evaluate the fatigue life of random loading caused by rough surface. As a result of the analysis, relationship between the life and roughness as well as the creack initiation depth was revealed. Below the critical roughness, It is observed that the fatigue life has hardly changed and creack is initiated around the depth at which the maximum shear stress occurs. Different behavior, however, is observed in case that the roughness is above the critical value.