• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.311-314
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• 2010

본 논문에서는 밀리미터파 대역 전파특성 분석용 샘플홀더 제작을 위하여 전파의 도파이론을 정립하고 밀리미터파 W-bnad(75 GHz ~ 110 GHz) 주파수 대역에 알맞은 도파관형 샘플홀더를 설계 및 실 제작하였다. 그리고 제작된 샘플홀더를 테스트하기 위하여 샘플시료를 제작하여 재료정수 및 전파흡수능을 측정하고 분석하였다. 분석결과 샘플시료 특성을 정확하게 측정할 수 있음을 확인하였으며, 향후 이 측정 샘플홀더는 밀리미터파 대역 전파특성 분석을 위해 매우 유용하게 쓰일 수 있을 것이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.108-113
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• 2002

Short range communications between road-side equipments and on-board equipment is very important for ITS(intelligent Transport System). Roadside communication is for short range communication, and needs performance of high data bit rate and should support the function for very short term communication. In addition to it, a radio propagation characteristics is very different according to a road environment. In this paper, for reliable roadside communication, the radio multi-path propagation profile at roadside is measured and the characteristics is analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1329-1334
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• 2003

We prepared EM wave absorbers by using recycled Ba ferrite far GHz frequency, and investigated the effects of carbon additions and preparation temperatures on their EM wave absorption properties. We clarified that it is very important to consider carbon amounts in Ba ferrite and preparation temperature for Ba ferrite EM wave absorbers with high quality.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.2
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• pp.23-32
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• 2001

Rock masses are usually discontinuous in nature, as a result of various geological processes they have underdone and they contain rock joints and bridges. Crack propagation and coalescence processes mainly cause rock failures in tunnels. In this study, we focused on the crack initiation, propagation and coalescence process of rock materials containing two pre-existing open cracks arranged in different geometries. During uniaxial compression, wing crack initiation stress, wing crack propagation angle, and crack coalescence stress of Diastone gypsum and Yeosan Marble specimens were examined. And crack initiation, propagation, and coalescence processes were observed. Shear, tensile and mixed (shear+tensile) types of crack coalescence occurred. To compare the experimental results with Ashby & Hallam model, crack coalescence stress was normalized and it generally agreed with the experimental results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1633-1639
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• 1993

In spark ignition engine, EGR of lean mixture operation has advantage in emission, but disadvantages in power output and combustion flame propagation. Fast burn system is known to be a useful method to solve these disadvantages. This paper presents the characteristics of in-cylinder flow for different combustion chamber geometries, and the correlation between the in-cylinder flow and the combustion flame speed using an ion current method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.3
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• pp.500-506
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• 2015

In this paper, we designed and fabricated the EM wave absorber consisted of Sendust for suppressing EM wave noise PCB in ISM (Industrial, Scientific and Medical) band of 2.4 GHz. We fabricated several samples with different composition ratios of some kinds of Sendust to CPE (Chlorinated Ploy-ethylene) as a binder, and it was confirmed that the optimum composition ratio of absorbing materials was Flaked Sendust : CPE = 72.5 : 27.5 wt.%.. The absorbing abilities were simulated by changing the thickness and the measured material constants of EM wave absorber. The measured absorption abilities were analyzed and compared with the simulated ones. As a result, the simulated results agree well with the measured ones, and the developed EM wave absorber with extremely thin thickness of 0.6 mm has absorption ability of 5.4 dB at 2.4 GHz is excellent one. The thin type EM wave absorber can be applied for suppressing and absorbing electromagnetic noises from information and communication equipments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.1
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• pp.57-63
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• 1991

In this paper, propagation characteristics of W-type single mode fiber with dual shape core is investigeted theoretically. Design parameters of DSC(dual shape core) W-type single mode fiber with very low dispersion over a wide wavelength range are computed using scalar approximation. The results have larger core radius and stronger confinement for mode field distribution in core than conventional W-type fiber with single shape core.

• Journal of Energy Engineering
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• v.4 no.1
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• pp.85-94
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• 1995

본 연구에서는 최근 차량용 대체연료로서 주목받고 있는 천연가스의 연소특성을 규명하기 위해 밀폐된 정적연소실을 이용, 당량비, 초기압력 및 점화위치 변화에 따른 연소실험을 행하였으며, 그 결과 다음과 같은 결론을 얻었다. 메탄-공기 예혼합기의 화염전파과정은 이론혼합기 부근에서 구면형으로 진행되는데 반해, 과농 또는 과박 혼합기 그리고 점화위치가 연소실 벽면에 가까울수록 타원형으로 진행되며, 초기압력이 증가함에 따라 화염전파는 느려진다. 화염전파속도와 연소 속도는 초기압력이 낮고 점화위치가 연소실 중심에 가까울수록 빠르며, 당량비 1.0∼1.1 사이에서 최대치를 보인다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1994.11a
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• pp.17-22
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• 1994

오류역전파 신경망을 인산형 연료전지의 조업변수인 산소 및 수소 유량, 작동온도에 대하여 학습시켜 연료전지 모델을 구성하였다. 또한 구성된 모델을 이용하여 다양한 조업조건에서의 단위전지 성능을 예측하여 이를 실험결과와 비교하였으며, 학습된 신경망을 ASPEN PLUS의 단위공정으로 도입하여 50kW 출력의 연료전지 공정을 구성한 후 조업변수에 대한 영향을 살펴보았다. 3개의 층으로 구성된 오류역전파 신경망은 학습단계상수와 모멘텀이 각각 0.7 및 0.9인 경우 단위전지 성능곡선을 가장 정확히 학습하였으며, 이에 의하여 구성된 신경망 모델은 수소 및 산소의 유량, 온도의 변화에 따른 단위전지 성능곡선의 변화를 정확히 예측하였다. 연료전지 전체공정의 모사에서는 개질기의 경우 $600^{\circ}C$의 상압에서 수증기/탄화수소 비율이 2.6일 때, 연료전지의 경우 작동온도가 190~20$0^{\circ}C$일 때 연료전지의 출력이 최대값을 나타내었으며, 단위전지의 전기화학적 효율은 약 45%, 수소이용률은 약 61%, 발전시스템 전체의 효율은 18%이었다.

• 한국지구물리탐사학회:학술대회논문집
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• 2011.10a
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• pp.49-53
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• 2011