• Journal of electromagnetic engineering and science
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• 제4권4호
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• pp.150-155
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• 2004

Universal design equations are presented for the H-plane T-junction power divider with a circular conducting post in a rectangular waveguide. For a given operating frequency and power split ratio, the post offset from the T-junction center line, the distance between the post and the waveguide wall, and the post diameter can be adjusted to obtain a minimum reflection at the input waveguide. Optimum values of the post offset are given in terms of the normalized frequency and the power split ratio. Corresponding values of the post diameter and the distance of the post from the waveguide wall are given in terms of the normalized frequency and the post offset.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 춘계학술대회 논문집
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• pp.198-203
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• 1993

In this study, byusing EMAT(Electro Magnetic Acoustic Transducer) the artificial slit is installed on 12B-SUS pipe test piece. By mading 4 cycle SH-bust wave (EMA) incidence to 45 .deg. angle, the signaldata of pulse, which is recevied from EMAT translated intodigital-signal-processing-method SSP and Deconvolution method by using FACOM. Results of these indicated that (1) this method of this study shows exellent result more than Ultrasonic testing method; (2) noise is well removed by SSP using signal dataa and resolving power and S/N ratio are advanced; (3) regradless of Ultrasonic wave, whichhas properties of generalstainless steel is generated into multiscattering and reflection phenomena, the resolving power of more than two times is progressed by being translated into Decon-volution method; and (4) as addition-averaging-processing number is increaing, the resolving power and S/N ratio are improved and the satisfactory signal is obtained.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.598-600
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• 2008

In order to improve the contrast ratio of PDPs in the bright room, we decreased the panel reflection by coating phosphors with pigments. In this work, we investigated the panel reflectance with various sizes of the blue pigments and obtained good results by reducing the size of the pigment properly.

• Journal of Information Display
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• 제1권1호
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• pp.48-51
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• 2000

In this work, we proposed a reflective antiferroelectric liquid crystal display (AFLCD) using a half-wave cell whose inplane tilt angle is $22.5^{\circ}$. To check the validity of our design, we fabricated a reflective half-wave AFLC cell of which inplane tilt angle is $24.9^{\circ}$, and measured VIS reflection spectra, contrast ratio and response time. In the results, the half-wave AFLC cell in the reflective configuration exhibits high brightness, high contrast ratio of 20:1, and fast response time of $700{\mu}s$.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.573-574
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• 2006

This research deals with the wave transmission and dissipation problems for two dimensional regular waves and s vertical circular cylindersr. Using the unsteady mild slope equation, a numerical model has been developed to calculate the reflection and transmission of regular waves from a multiple-row vertical circular cylinders. In addition hydraulic model experiments have been conducted with different values of properties between the cylinders and opening ratio (distances) between the rows of the cylinders. It is found that the transmission coefficients decrease with decreasing the opening ratio and increasing the rows of vertical cylinders. Comparison between hydralic and numerical experiments results shows resonable agreement.

• E2M - 전기 전자와 첨단 소재
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• 제7권3호
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• pp.220-224
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• 1994

In this study, we discussed the optical property to find the optimal condition of Te-based antireflection trilayer(ART) structure for a high density optical recording. It was found that the optical property was improved by suggesting the environmental parameters satisfied the optimum condition. As the results, the optimized(.lambda.=8.000${\AA}$.) thickness of the recording layer is 27${\AA}$, and the 1st and 2nd minimum ART conditions of dielectric layers are 1080${\AA}$, 3820${\AA}$, respectively. And the high SNR, the contrast ratio and the sensitivity are achieved by using the ART conditions.

• Journal of information and communication convergence engineering
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• 제16권4호
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• pp.203-212
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• 2018

In this article, a novel design of patch antenna with wide band characteristics is presented. The proposed antenna is having electrical dimensions of $0.14{\lambda}{\times}0.11{\lambda}$ (at lower initial frequency) and footprints of $150mm^2$. Structural parameters optimization shows 3.1-23.5 GHz frequency range for a (reflection coefficient) $S_{11}{\leq}-10dB$ and simulated gain 6.8 dB is obtained. An equivalent circuit model is proposed to get an insight view of antenna. Advanced Systems Design (ADS) simulation results are obtain which confirm the validity of proposed model. Degenerated foster canonical form has been used to explain the reactance and capacitive behavior idea of simulated proposed antenna's input impedance later on an equivalent circuit model and smith chart is also suggested. HFSS and CST have been used to analyze antenna behavior. The proposed antenna can be further used for microwave image detection applications.

• 한국분무공학회지
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• 제26권4호
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• pp.182-188
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• 2021

In this paper, using a transfer function-based analytical model, major factors influencing the acoustics and combustion instability in a two-stage duct system composed of a nozzle and a combustor were derived and their quantitative effects were evaluated. From the acoustic analysis, it was confirmed that the change in reflection coefficient and mean flow could have a great influence on the instability growth rate, and the area ratio and speed of sound ratio between the nozzle and the combustor are also key parameters to determine combustion instability as well as flame transfer functions.

• Earthquakes and Structures
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• 제22권4호
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• pp.373-386
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• 2022

The development of performance-based design methodologies requires a reasonable definition of a displacement-response spectrum. Although ground motions are known to be significantly affected by the resonant-like amplification behavior caused by multiple wave reflections within the surface soil, such a soil-resonance effect is seldom explicitly considered in current-displacement spectral models. In this study, an analytical approach is developed for the construction of displacement-response spectra by considering the soil-resonance effect. For this purpose, a simple and rational equation is proposed for the response spectral ratio at the site fundamental period (SRTg) to represent the soil-resonance effect based on wave multiple reflection theory. In addition, a bilinear model is adopted to construct the soil displacement-response spectra. The proposed model is verified by comparing its results with those obtained from actual observations and SHAKE analyses. The results show that the proposed model can lead to very good estimations of SRTg for harmonic incident seismic waves and lead to reasonable estimations of SRTg and soil displacement-response spectra for earthquakes with a relatively large magnitude, which are generally considered for seismic design, particularly in high-seismicity regions.

• 지구물리와물리탐사
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• 제11권3호
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• pp.242-249
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• 2008

AVO 분석은 지하의 가스 존재에 대한 직접적인 지시자로서 최근 탄성파 지하구조 단면도와 함께 석유탐사에 널리 이용되어져 왔다. 동해가스전과 같이 해저면 심부에 위치한 저류층의 경우 때때로 중합단면도 상에서 명점은 보이나 CMP 단면도 상에서 AVO 반응을 관찰하기가 어려운 경우가 종종 발생한다. 심부저류층의 경우 고결성이 증가하기 때문에 매질의 공극유체가 가스로 치환되더라도 매질의 P파 속도가 크게 감소하지 않으며 이로 인해 AVO 반응을 나타내는 주요 요소인 상부층과의 포아송비 차이도 크게 증가하지 않는다. 본 연구에서는 상 하부층의 포아송비를 달리하면서 포아송비의 차이가 AVO 반응에 미치는 영향을 분석하였다. 이를 통해 상 하부층의 포아송비 차이가 작아질수록 입사각에 따른 반사진폭의 변화량이 작아져 AVO 반응이 미미해짐을 관찰할 수 있었다. 이 결과를 이용하여 동해가스전의 AVO 반응의 한계점을 고찰하기 위해 탄성파 자료와 물리검층 자료를 이용하여 고래 V구조를 모사한 속도모델을 만들고 합성탄성파 탐사자료를 생성하였다. 매질의 성질을 이용하여 이론적으로 계산한 AVO 반응과 실제 합성탄성파 자료를 처리하여 얻은 AVO 반응을 비교한 결과, 상 하부층의 포하송비의 차이가 작을 경우 입사각에 따른 반사진폭 변화가 매우 작으며 잡음이나 전처리 과정 중에서 발생하는 진폭 왜곡에 의해 AVO 반응 특성이 가려짐을 확인할 수 있었다. 이러한 심부저류층의 AVO 분석의 한계점을 극복하기 위해서는 자료취득 단계부터 정확한 반사파 진폭을 획득해야 하며 자료처리 과정에서도 반사파 진폭을 보존할 수 있는 기술이 필요하다.