• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 추계종합학술대회
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• pp.853-855
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• 2003

기존의 마이크로파 대역의 전송 용량이 포화상태가 됨에 따라, 더 넓은 주파수 대역의 초 광대역에 대한 시스템의 요구가 커져가고 있다. 따라서, UWB(Ultra Wide Bnd)를 이용한 기술은, 향후 무선 통신망에서의 멀티미디어 통신을 가능하게 할 광대역 무선 통신 시스템의 기술로 발전하고 있다. 이러한 UWB 기술과 fiber-optic 기술과의 접속은, 더 넓은 주파수 대역의 제공, 다 많은 전소 용량 및 저잔송 손실이라는 측면에서 큰 장점을 가지고 있다. 그래서, Radio-on-fiber 시스템을 위한 연구가 많이 진행되고 있는 추세이다. 최근들어, 음성, 데이터, 영상을 포함한 멀티미디어 통신에 대한 요구가 증가되고 있다. 이러한 요구에 부응하기 위한 방법이 광대역 통신인데, 광통신이 하나의 방법으로 대두되고 있으며, 기존의 마이크로파 대역의 전송량이포화 상태로 됨에 따라, 더 넓은 주파수 대역의 UWB 대역의 시스템에 대한 요구가 커져가고 있다. 따라서, HS 논문에서는 이러한 UWB의 신호 생성을 위한 광 주입 방법을 제안하고 시스템의 평가를 위해 전송거리에 대한 CNR(Carrier-to-Noise Ratio)에 대한 페널티를 분석하였다.

• 한국통신학회논문지
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• 제17권8호
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• pp.816-822
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• 1992

본 논문에서는 중심코어가 사다리꼴분포를 갖는 segmented core 단일모드 광섬유의 전파특성을 \ulcorner=1.55um에서 영분산을 만족하는 조건하에서 상대 굴절율차비의 변화에 대해 이론적으로 조사하였다. 기존의 광섬유(삼각형 굴정율, 이중형 코어)와 곡률손실을 비교한 결과 크게 감소함을 확인하였다. 그리고 코어내의 모드필드의 집속효과가 기존의 사다리꼴 굴절율 광섬유보다 28% 더 향상되었다. 기존의 삼각형 분포를 갖는 segmented core 광섬유와 비교하여 여러 장점들을 제시 하였다.

• Structural Engineering and Mechanics
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• 제82권6호
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• pp.691-699
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• 2022

This paper is devoted to the presentation of a numerical study on vibration behavior of composite panels reinforced by glass fibres and carbon nanotubes (CNTs) subjected to thermal environments. The effect of temperature variation has been included as thermal load acting on in-plane direction of the panel. To model the composite material, a micromechanical model which contains random dispersion of nanotubes and single-direction fibers has been selected. The geometry of the panel has been considered to have a single curveture along its width. Based on the above assumptions, the governing equations have been derived by using thin shell theory capturing the panel curveture and also nonlinear deflections. Finally, the panel dependence on various factors such as the curveture, nanotube amount, fiber volume, fiber direction and temperature variation has been researched.

• 폴리머
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• 제27권4호
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• pp.307-312
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• 2003

고밀도 폴리에틸렌 (HDPE)과 초고분자량 폴리에틸렌 (UHMWPE)을 혼합하여 중공사막을 제조하고, 이의 형태구조와 물성 변화를 조사하였다. 분자량 측정과 FT-IR을 이용한 분석 결과, 상품화된 중공사막(Sterapore)은 고분자량의 HDPE로 제조되었으며, 표면은 친수성 고분자인 비닐 알코올/비닐 아세테이트 공중합체로 코팅되어 높은 수투과도를 갖는 이유를 규명하였다. HDPE/UHMWPE 블렌드에서 UHMWPE의 혼합 한계 조성비는 10 wt% 이하이며, UHMWPE의 분산성을 높이기 위하여 혼합과정에서 광유를 도입하여야 할 것으로 판단되었다. 제조된 HDPE/UHMWPE 블렌드 중공사의 기계적 물성과 막 구조는 Sterapore와 유사하였다.

• 한국생산제조학회지
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• 제21권4호
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• pp.619-624
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• 2012

In this study, MMT/fiber/polymer composites were fabricated by impregnating chopped strand glass mat into a vinylester resin mixed with clay. Tensile tests has been performed by using a universal testing machine to determine the effect of MMT addition on the tensile properties of MMT/chopped strand glass fiber/vinylester composites. And some pictures which are magnified cross section of breaking parts are has been taken by using a FE-SEM to confirm the behavior at breaking. The contents ratio of MMT applied in the composites were 0.5, 1.0, 1.5, and 2.0 wt% respectively. It has been found that the tensile strength and elastic modulus of MMT/chopped strand glass fiber/vinylester composites were improved at a proper content of MMT. Tensile strength and elastic modulus were maximized at a content of 1.0 wt% due to most effective dispersion of MMT. On the contrary, the failure strain was increased as MMT content was increased.

• 한국농공학회논문집
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• 제55권3호
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• pp.113-121
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• 2013

Recently, it has been studied for the application of nano-materials in the concrete. Applied a small amount of nano-materials can achieve the goal of high strength, high performance and high durability. The small addition of nano clay improves strength, thermal stability, and durability of concrete because of the excellent dispersion. The present study has investigated the effectiveness, when varying with the contents of nano clay, influencing the pull-out behavior of macro synthetic fibers in nano materials cement mortar. Pullout tests conducted in accordance with the Japan Concrete Institute (JCI) SF-8 standard for fiber-reinforced concrete test methods were used to evaluate the pullout performance of the different nano clay. Nano clay was added to the 0, 1, 2, 3, 4 and 5 % of cement weight. The experimental results demonstrated that the addition of nano clay led to improve the pull-out properties as of the load-displacement curve in the precracked and debonded zone. Also, the compressive strength, flexural strength and pullout performance and of Mix No. 1 and No. 2 increased up to the point when nano clay used increased by 2 and 3 % contents, respectively, but decreased when the exceeded 3 and 4 %, respectively. It was proved by verifying increase of the scratching phenomenon in macro synthetic fiber surface through the microstructure analysis on the surface of macro synthetic fiber.

• 한국주조공학회지
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• 제13권6호
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• pp.547-554
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• 1993

Aluminum alloy matrix composites reinforced with various amounts of $Al_2O_3$ short fibers have been produced by rheo-compocasting accompanied by hot pressing. When composites reinforced with fibers are produced by rheo-compocasting, S-L process is the most effective method for homogeneous dispersion of fibers. A sound composites with the improved orientation(3 dimension${\rightarrow}$2 dimension) of the fibers and increased volume fraction of them have been fabricated through the hot pressing of the casted composites. Fibers are broken down when rheo-compocasting, hot pressing, and $T_6$ treating. Among them fibers are broken down most heavily in the hot pressing. And even in the case of the composite reinforced with 30 vol% fibers, which showed the hardest fiber break down, aspect ratio(11.6) is higher than critical aspect ratio(10.7). The fiber strengthening effect in the composites has showed upto 573K. As the test temperature increases to the range of 573K, the effect has been higher. The fracture of composites is controlled by fiber from room temperature to 473K, but the fracture of composites is controlled by interface between fiber and matrix alloy above 473K.

• Current Optics and Photonics
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• 제2권3호
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• pp.233-240
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• 2018

We proposed a two-mode fiber (TMF) design that can effectively reduce the mode overlap between $LP_{01}$ and $LP_{11}$ modes by using a W-shaped index profile core structure, which is a primary concern in uncoupled mode division multiplexing (MDM). TMF has a three-layered core structure; central circular core, inner cladding, and outer ring core. We confirmed that in an optimal structure the $LP_{01}$ mode was highly confined to the central core while the $LP_{11}$ mode was guided along the outer ring core to result in a minimum overlap integral. We used a full-vectorial finite element method to estimate effective index, differential group delay (DGD), confinement loss, chromatic dispersion, and mode overlap controlling the parameters of the W-shaped structure. The optimized W-profile fiber provided optical characteristics within the ITU-T recommended standards over the entire C+L band.

• 한국염색가공학회지
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• 제32권1호
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• pp.65-71
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• 2020

Electrical energy is used for heating and cooling because electric cars do not have engines and cooling water. The downside is that when the heating and cooling system is applied to electric vehicles, about 40 percent of the energy is spent on heating and cooling, which is less efficient in winter. This has increased demand for electric vehicle battery efficiency. In this study, the condensation and dispersion of carbon nanotubes were controlled, and carbon fibers and composite slurry were manufactured without binders to manufacture paper. Manufactured by content showed the highest heat generation characteristic at 143℃ with a carbon fiber content ratio of 20wt% and confirmed that the heat temperature rises with increasing pressure. The plane heaters made through this study can be applied to a variety of products other than electric vehicles because they can be simplified by process and high temperature.

• 콘크리트학회논문집
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• 제20권6호
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• pp.731-739
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• 2008

이 연구에서는 강섬유 보강 초고강도 콘크리트의 타설방법에 따라 섬유의 방향성이 인장강도에 미치는 영향을 파악하고자 섬유의 방향성을 정량적으로 평가할 수 있는 이미지 프로세싱 기법을 개발하였으며, 개발한 기법을 적용하여 섬유의 방향성을 평가하였다. 또한 휨인장실험을 수행하여 섬유의 방향성이 균열발생강도 및 휨인장강도에 미치는 영향을 파악하였다. 이 연구에서 개발한 이미지 프로세싱 기법은 섬유 방향성 이외에 분산성 계수, 단위면적당 섬유의 개수 등, 분포 특성을 정량적으로 평가하고 있으며, 타설방법에 따라 섬유 분포 특성에 상당한 차이가 있음을 확인할 수 있었다. 그리고 섬유의 방향 분포특성은 강섬유 보강 초고강도 콘크리트의 균열발생강도에는 크게 영향을 미치지 않으나, 휨인장강도에 미치는 영향은 아주 큰 것으로 나타났으며, 이론적인 휨강도 모델식에 실제 섬유 방향성을 적용하여 예측한 결과, 실험 결과와 잘 일치하는 것으로 나타났다.