• 한국통신학회논문지
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• 제38B권9호
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• pp.715-721
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• 2013

RF소자의 소형화 기법으로는 헤리컬 구조를 적용하는 방법, Meta Material을 사용하는 방법 및 적층구조를 적용하는 방법 등 여러 방법들이 적용되고 있다. 그러나 헤리컬 구조는 한 번의 원주의 회전이 있을 때 마다 공진주파수가 생김에 따라 단일 공진주파수 특성을 가지는 RF회로의 소형화 기법에는 맞지 않으며, Meta Material과 적층구조를 적용하는 방법들은 구조가 복잡하며 비용이 많이 드는 단점이 있다. 또한, 3차원 구조의 기본적인 뫼비우스 스트립을 활용한 논문과 뫼비우스 스트립의 특성을 활용한 평판형 구조의 논문이 제안되었으나 완전한 평판형구조가 아니고, 선로결합효과(coupling effect) 현상의 문제점이 있었다. 따라서 본 논문은 기존 M$\ddot{o}$bius Strip과 위상동형인 Quasi M$\ddot{o}$bius Strip과 via hole구조를 응용함으로써, RF회로의 소형화와 선로결합효과를 완화한 안테나를 제시하였다. 본 논문의 시뮬레이션 결과에 의하면, 2.4GHz의 공진주파수 일 때, 기존의 링 안테나와 대비하여 물리적 원주의 길이는 1/3배로 소형화 되었다. 그리고 기존의 헤리컬 안테나의 다중공진특성이 아니라 단일 주파수에서의 공진특성을 보인다. 또한, 2.4GHz의 공진주파수 근처에서 선로결합 효과 현상이 거의 발생하지 않았다.

• Journal of Mechanical Science and Technology
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• 제16권12호
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• pp.1652-1663
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• 2002

It is desirable to perform nondestructive evaluation to assess material properties and part homogeneity because manufacturing of carbon/carbon (C/C) composites requires complicated and costly processes. In this work several ultrasonic techniques were applied to carbon/carbon composites for the evaluation of spatial variations in material properties that are attributable to the manufacturing process. In a large carbon/carbon composite manufactured by chemical vapor infiltration (CVI) method, the spatial variation of ultrasonic velocity was measured and found to be consistent with the densification behavior in CVI process in order to increase the density of C/C composites. Ultrasonic velocity and attenuation depend on a density variation of materials. Low frequency through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the material property inhomogeneity These results were compared with that obtained by dry-coupling ultrasonics. Pulse-echo C-scans was used to image near-surface material property anomalies such as the placement of spacers between disks during CVI. Also, optical micrograph had been examined on the surface of C/C composites using a destructive way.

• 한국정밀공학회지
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• 제30권5호
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• pp.537-543
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• 2013

In this paper, a novel radial beam coupling model was proposed and the design parameters were studied for the efficient transmission of torque. To develop a high performance radial beam coupling, an analytical way to predict the performance in design phase is required. One of the best ways to estimate the performance of the coupling without manufacturing is to evaluate the stress and torsional stiffness by building a finite element model with a special attention to the radial beam cutting part. For the best results of FEA, the material properties were obtained through testing. To verify the reliability of finite element model, the results of FEA were compared with the experiments. The main design parameters of radial beam cutting width, radial beam cutting depth, and radial beam cutting direction were considered for the performance of radial beam coupling.

• Elastomers and Composites
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• 제25권4호
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• pp.280-290
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• 1990

The effect of surface treatment of kaolinite with silane coupling agent on the reinforcement of SBR was investigated. The possibility of the practical use of kaolinite as an organic filler was also scrutinized and it was found that the reinforcement of SBR was improved by modifying surface of the cheap inactive inorganic filler with organic silane coupling agents. 3-Chloropropyltrimethoxysilane(C-series), 3-mercaptopropyltrimethoxysilane(M-series) and 3-aminopropyltriethoxysilane(A-series) were used as coupling agents. To test the material properties of vulcanized and unvulcanized SBR, Mooney viscosity, modulus, elongation and fractured surface measurements by SEM were carried out by changing the amount of silane coupling agents. Torqe of the unvulcanized SBR following the measurement of the degree of vulcanization was to be increased as the amount of silane was increasing, and Mooney viscosity of M-series and A-series was also increased.

• 대한의용생체공학회:의공학회지
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• 제29권4호
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• pp.267-271
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• 2008

The RF shimming technique has been used to improve the transmit RF field homogeneity in highfield MRI. In the RF shimming technique, the amplitude and phase of the driving currents in each coil element are optimized to get homogenous flip angle or uniform image intensity. The inductive and capacitive coupling between the coil elements may degrade the RF field homogeneity if not taken into account in the optimization procedure. In this paper, we have analyzed the coupling effects on the RF shimming using a sixteen-element TEM RF coil model operating at 300 MHz. We have found that the coupling effects on the RF shimming can be reduced by putting high dielectric material between the active rung and the shield.

• E2M - 전기 전자와 첨단 소재
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• 제9권6호
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• pp.584-592
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• 1996

Coupling optical modulator which on the $LiTaO_3$ substrate is fabricated by using proton exchange method and self-aligned method. Proton exchange of proton diffusion method was applied to pattern a waveguide on $LiTaO_3$ substrate. The annealing at >$400^{\circ}C$ was carded out to control waveguide width and depth. The depths of the two annealed optical waveguides, which were measured by using .alpha.-step, were 1.435 K.angs. and 1.380 K.angs. Using .alpha.-step facility, we examined that the width of waveguides is increased from 5.mu.m to 6.45 .mu.m and 6.3.mu.m due to the annealing effects. The process of proton exchange was done at 150.deg. C for 120 min, >$200^{\circ}C$ for 60 min and annealing process was done at >$400^{\circ}C$ for 90 min, >$400^{\circ}C$ for 60 min. The high speed coupling optical modulator has very good figures of merits; the measured high frequency power were achieved.

• 대한전기학회논문지
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• 제41권6호
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• pp.640-651
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• 1992

This paper describes the electric properties of mica reinforced silicone composites with the parameter of curing condition of silicone resin, application amount of silane coupling agent to the mica paper and the mica wt% to the composite. Heat-resistant silicone resin and mica paper made of mica flakes are used to prepared the mica/silicone composite as matrix and filler, respectively. To improve the dielectric properties and interfacial adhesion between matrix and filler, silane coupling agent is applied on the mica paper. As for matrix, tan$\delta$ value of 30$0^{\circ}C$ heat-treated silicone resin is the lowest under 1%. The optimal wt% of coupling agent is 0.3% to the weight of mica paper. 80 wt% of mica as filler to the mica/silicone composite shows the best electric properties. And the mica reinforced silicone composite shows good high-frequency and mechanical tensile stress properties.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 somma/kms meeting
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• pp.89-89
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• 2003

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2004년도 동계학술연구발표회 논문개요집
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• pp.72-72
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• 2004

• 한국잠사학회:학술대회논문집
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• 한국잠사학회 2004년도 제47회 춘계 학술연구 발표회
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• pp.35-35
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• 2004