• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.130-137
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• 2018

In long freight trains, there is a brake time delay in the neighboring freight cars that causes damage and fractures of couplers, especially the knuckle of them. If there is a problem for couplers in the cars, this could cause a derailment and lead to damage of human life and property damage. In this study, maximum forces on the couplers are studied when a long freight car brakes, with brake delay time and coupler gap. We have made a dynamic model of 50 freight cars and couplers, applying contact between couplers and a characteristic curve for expressing force and displacement of buffers with SIMPACK, a multi-body dynamics program. We use EN 14531-2 from the British Standards Institution, a standard of freight car brakes for the verification of the dynamic model. We also use a simplified method to analyze the dynamic model of 50 freight cars. With changing coupler gap and brake delay time, we do comparative analysis with AAR M-201 from the Association of American Railroads, a standard of AAR couplers. From this result, we find that the standard on fatigue limit is satisfied, such that the brake delay time is within 0.06 second if the coupler gap of the AAR coupler is within 20 millimeters.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.2
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• pp.65-72
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• 2019

In long freight trains, there is a brake time delay in neighboring freight cars, which causes damage and fractures in the couplers, especially at their knuckle. A problem in the couplers of the cars can cause derailment and damages of human life and property. In this study, maximum forces on the couplers are studied when a long freight car brakes with the brake delay time and coupler gap. We make a dynamic model of 50 freight cars and couplers, applying contact between the couplers and a characteristic curve to express the force and displacement of the buffers using SIMPACK, which is a multi-body dynamics program. We use EN 14531-2, which is a standard of freight car brakes, to verify the dynamic model. Then, we compare the analyzed impact force with the coupler knuckle standard after applying the two carriages of a locomotive in the model based on the dispersed double head control system. The result shows that all coupler gap conditions satisfy the infinite lifetime of the material when the brake delay time is 0.1 second.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.05a
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• pp.113-116
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• 1993

A guided - wave electro - optical modulatored directional coupler $2{\times}2$ was fabricated on X-cut $LiNbO_3$ by proton exchange wi th self-aligned method. The Electode pattern was formed by the four extra gap electrode separtion within self-aligned electrode mask. Initial cross over state turned that by controlling the anneal ing process and self-aligned electrodes are used in fabricating the electro-optical modulatored directional coupler $2{\times}2$. The modulatored directional coupler $2{\times}2$ has very good figures of merits: the measured crosstalk was -28.2 dB and the modulating valtage of 3.2[V].

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.7
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• pp.25-31
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• 1998

Modal transmission-line is utilized to analyze the power coupling of optical directional coupler composed by two parallel guiding slabs. By defining a coupling efficiency .eta. amenable to rigorous supermodes and boundary conditions of modal functions, we evaluate the power transfer for TE mode of gainy coupler. The results reveal that optimized power exchange occurs at a novel wavelength .lambda.$_{op}$ , which is generally different from minimum gap .lambda.$_{min}$ between rigorous modes and phase-matching condition .lambda.$_{ph}$ .

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.688-693
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• 1999

This paper presents a very simple coupled line structure for MMIC which uses stacked microstrip line and does not employ any dielectric process step. For the analysis and optimization of these coupled line structure, HP-Momentum was used. The measured performance of 3 dB coupler shows 23 to 45 GHz broadband characteristics. Additionally, a balanced 2-stage Ka-Band power amplifier which uses the proposed 3 dB coupler, was also fabricated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.6
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• pp.548-553
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• 2004

In this paper, single, two, and three-section microstrip directional couplers are implemented for realizing the high directivity characteristics. The achievement of the high directivity with microstrip configuration is carried out by the distributed capacitor to decrease the even and odd mode phase difference. Capacitive compensation is performed by gap coupling of open stub formed in sub-coupled line. Therefore, insertion loss and power handling capability are not affected by the gap coupling. The proposed structure is easy to fabricate and incorporate another microwave device due to the planner microstrip. We designed and fabricated single, two, and three-section directional coupler with 20 ㏈ coupling. In spite of microstrip structure, the capacitive compensation structure shows 30 ㏈, 27 ㏈, and 25 ㏈ of directivity in single, two, and three-section directional couplers, respectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.6 s.348
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• pp.46-52
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• 2006

We report on a high performance 94 GHz MMIC resistive mixer using 70-nm metamorphic high electron mobility transistor (MHEMT) and micro-machined W-band ring coupler. A novel 3-dimensional structure of resistive mixer was proposed in this work, and the ring coupler with the surface micro-machined dielectric-supported air-gap microstrip line (DAMLs) structure was used for high LO-RF isolation. The fabricated mixer showed an excellent LO-RF isolation of -29.3 dB and a low conversion loss of 8.9 dB at 94 GHz. To our knowledge, compared to previously reported W-band mixers, the proposed MHEMT-based resistive mixer using micro-machined ring coupler has shown superior LO-RF isolation as well as similar conversion loss.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.5
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• pp.175-180
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• 2019

The optical characteristics and power transfers between guiding channels of blazed grating-assisted directional coupler (B-GADC) are evaluated in detail by using novel and rigorous modal transmission-line theory (MTLT) based on eigenvalue problem. To evaluate the coupling efficiency of B-GADC, the dispersion curves as a function of the grating period and wavelength are analyzed numerically for quasi-TE and quasi-TM modes. Furthermore, symmetric, sawtooth and asymmetric grating profiles are considered to know the effect of blazing characteristics on power transfer of GADC. The numerical results show that the grating period for minimum-gap condition to obtain maximum power transfer decreases gradually as the blazed structure changes from symmetric to asymmetric profile. On the other hand, the coupling length increases reversely.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.966-969
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• 1999

Using modal transmission-line theory (MTLT), we evaluate the power coupling of optical directional coupler composed by two parallel guiding slabs. The numerical results reveal that maximum power transfer occurs at a novel wavelength λ$_{opt}$, in which the excitation ratio of supermodes at input boundary is equal to each other, and it is generally different from minimum gap λ$_{min}$.in/.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.272-273
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• 2005

전력선 통신을 위한 커플러용 자심재료의 열처리 온도증가에 따라 결정이 성장하여 인덕턴스는 증가 하였고, $550^{\circ}C$ 이상에서는 포화점을 나타내었다. 커플러는 자심재료의 투자율이 높을수록 커플러의 저주파 대역의 신호전승 특성이 우수하게 나타났지만, 주파수 증가에 따라 급격히 저하하는 불안정한 특성을 나타내었다. 그리고 절단면 사이의 Air gap 증가에 따라 10 MHz이하의 주파수 대역에서 신호전승특성이 급격히 감소하였고, 허용전류는 직선적으로 증가하였으며 Air gap이 $600{\mu}m$이상일 때 300A의 전류에서 특성을 발휘하였다.