• 한국광학회지
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• 제5권1호
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• pp.166-172
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• 1994

2.5 Gbps급 장거리 광통신 시스템에 소요되는 단일모우드 광섬유 부착 APD-FET 광수신모듈을 설계 및 제작하였다. 본 논문에서는 광수신모듈 제작시 고려해야 할 광학적, 전기적, 기계적 설계 및 제작 그리고 모듈의 특성평가에 대해 설명하였다. 광학적으로는 GRIN rod 렌즈와 경사 연마된 단일모우드 광섬유를 갖는 단일렌즈계로 구성하였으며 기계적으로는 광부품의 견고한 조립을 위해 레이저 용접법을 도입하였고 전기적으로는 Avalenche Photo Diode로부터의 소신호를 증폭하기 위한 GaAs FET 전치층폭기를 내장 하였다. 모듈 제작후 성능평가에서는 2.5 Gbps 속도에서 223-1의 길이를 갖는 입력광신호에 대해 $10^{-10}$ Bit Error Rate 조건에서 모듈 수신감도가 -30.3dBm으로 측정되어 국제전신전화 자문 위원회의 규격인 -26dBm은 물론 한국통신규격인 상온 -30dBm을 만족시키는 결과를 얻었다. 본 연구에서의 성공적인 모듈제작은 2.5 Gbps 광통신용 광수신모듈ㄹ의 실용화는 물론 앞으로 10 Gbps급 광통신용 광수신모듈 제작에 대한 밝은 전망을 보여주는 것이다.

• KIEAE Journal
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• 제6권4호
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• pp.11-16
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• 2006

This work has carried out some preliminary studies for the utilization of a solar mini-dish system capable of concentrating solar rays to higher densities. A typical mini-dish system considered employs an array of solar mini-dishes where major components are light and compact. It consists of small mini-dishes, optical fiber bundles and diffusers at the end. Each mini-dish (typically has a 20 to 30 cm in diameter) is designed with a simple parabolic profile, concentrating sunlight (after the glass glazing cover to avoid dust deposition on the reflector and facilitate cleaning) onto a centrally-located small mirror which is placed on the bottom side of the transparent glass cover. The focused sunlight is reflected by the mirror surface onto a focal point where the receiving aperture of a homogenizer is located. Optical fibers are used to carry high-density solar rays to the other end where diffusers are mounted for indoor illumination. The proposed high density mini-dish system could make an efficient daylighting system as it excludes large moving parts and expandable if necessary. Each component of the system could be made from the off-the-shelf technology and thus, make the generic unit inexpensive to manufacture. Depending on spatial demand or characteristics, the amount of introducing daylight could be controlled. Preliminary tests have been carried out for a trial system to check any functional problems when in operation. Suggestions are also made to improve the design enhancing its performance and applicability.

• 한국기계가공학회지
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• 제17권4호
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• pp.55-63
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• 2018

In recent years, with the growing interest in electric vehicles, the development of a Neighborhood Electronic Vehicle (NEV) made for urban driving is accelerating. Existing NEVs are set to ~0.3 - 0.35 with more emphasis on performance rather than minimizing air resistance. In this paper, a NEV with a streamlined car body is proposed. The shape of dolphins and sharks was applied to the car body to minimize the air resistance generated when driving. Also, the performance of the vehicle was estimated by calculating the traction force and the roll couple, etc. To check the drag coefficient of the car body, finite element analysis software (COMSOL Multiphysics) was used. The frame of the vehicle is divided into the forward and the rear parts. Carbon pipe is used for the frame by MIG welding. The car body of the vehicle was fabricated by forming carbon fiber. This study confirmed the general possibility of using NEVs through driving experiments.

• International Journal of Ocean System Engineering
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• 제2권3호
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• pp.185-194
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• 2012

A Macroscopic combination of two or more distinct materials is commonly referred to as a "Composite Material", having been designed mechanically and chemically superior in function and characteristic than its individual constituent materials. Composite materials are used not only for aerospace and military, but also heavily used in boat/ship building and general composite industries which we are seeing increasingly more. Regardless of the various applications for composite materials, the industry is still limited and requires better fabrication technology and methodology in order to expand and grow. An example of this is that the majority of fabrication facilities nearby still use an antiquated wet lay-up process where fabrication still requires manual hand labor in a 3D environment impeding productivity of composite product design advancement. As an expert in the advanced composites field, I have developed fabrication skills with the use of machinery based on my past composite experience. In autumn 2011, the Korea government confirmed to fund my project. It is the development of a composite sanding machine. I began development of this semi-robotic prototype beginning in 2009. It has possibilities of replacing or augmenting the exhaustive and difficult jobs performed by human hands, such as sanding, grinding, blasting, and polishing in most often, very awkward conditions, and is also will boost productivity, improve surface quality, cut abrasive costs, eliminate vibration injuries, and protect workers from exposure to dust and airborne contamination. Ease of control and operation of the equipment in or outside of the sanding room is a key benefit to end-users. It will prove to be much more economical than normal robotics and minimize errors that commonly occur in factories. The key components and their technologies are a 360 degree rotational shoulder and a wrist that is controlled under PLC controller and joystick manual mode. Development on both of the key modules is complete and are now operational. The Korean government fund boosted my development and I expect to complete full scale development no later than 3rd quarter 2012. Even with the advantages of composite materials, there is still the need to repair or to maintain composite products with a higher level of technology. I have learned many composite repair skills on composite airframe since many composite fabrication skills including repair, requires training for non aerospace applications. The wind energy market is now requiring much larger blades in order to generate more electrical energy for wind farms. One single blade is commonly 50 meters or longer now. When a wind blade becomes damaged from external forces, on-site repair is required on the columns even under strong wind and freezing temperature conditions. In order to correctly obtain polymerization, the repair must be performed on the damaged area within a very limited time. The use of pre-impregnated glass fabric and heating silicone pad and a hot bonder acting precise heating control are surely required.

• Structural Engineering and Mechanics
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• 제77권2호
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• pp.167-177
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• 2021

Due to various benefits such as unlimited degrees of freedom, environment adaptability, and safety for humans, engineers have used soft materials with hyperelastic behavior in various industrial, medical, rescue, and other sectors. One of the applications of these materials in the fabrication of bending soft actuators (SA) is that they have eliminated many problems in the actuators such as production cost, mechanical complexity, and design algorithm. However, SA has complexities, such as predicting and monitoring behavior despite the many benefits. The first part of this paper deals with the prediction of SA behavior through mathematical models such as Ogden and Darijani, and its comparison with the results of experiments. At first, by examining different geometric models, the cubic structure was selected as the optimal structure in the investigated models. This geometrical structure at the same pressure showed the most significant bending in the simulation. The simulation results were then compared with experimental, and the final gripper model was designed and manufactured using a 3D printer with silicone rubber as for the polymer part. This geometrical structure is capable of bending up to a 90-degree angle at 70 kPa in less than 2 seconds. The second section is dedicated to monitoring the bending behavior created by the strain sensors with different sensitivity and stretchability. In the fabrication of the sensors, silicon is used as a soft material with hyperelastic behavior and carbon fiber as a conductive material in the soft material substrate. The SA designed in this paper is capable of deforming up to 1000 cycles without changing its characteristics and capable of moving objects weigh up to 1200 g. This SA has the capability of being used in soft robots and artificial hand making for high-speed objects harvesting.

• 천문학회보
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• 제40권1호
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• pp.52.3-53
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• 2015

The GMT-Consortium Large Earth Finder (G-CLEF) is a fiber-fed, optical band high dispersion echelle spectrograph that selected as the first light instrument for the Giant Magellan Telescope (GMT). This G-CLEF has been designed to be a general- purpose echelle spectrograph with the precisional radial velocity (PRV) capability of 10 cm/sec as a goal. The preliminary design review (PDR) was held on April 8 to 10, 2015 and the scientific observations will be started in 2022 with four mirrors installed on GMT. We have been participating in this preliminary design study in flexure control camera (slit monitoring system), calibration lamp sources, dichroic assembly and the fabrication of the proto-Mangin Mirror. We present the design concept on the parts KASI undertaken, introducing the specifications and capabilities of G-CLEF.

• 복식문화연구
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• 제17권6호
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• pp.1034-1046
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• 2009

Based upon literature survey, this research aims to analyze western children's clothing and characteristics over centuries. It was not until the 18th century that children were given serious consideration and that fabrication of clothing began to be designed only for children. The very first clothes which revolutionized children's wear was 'a la matelot' in the 18th century which freed children from physical restriction, recognized gender difference, and sailor suit became popular among all sexes and adopted as school uniform. And then children's clothing was shortened in length and adopted tubular silhouette, which allowed greater comfort and movement. The 20th century saw children's wear reform to be carried out after the World War II due to invention of synthetic fiber, easy care dress material, mass production system and sophistication of marketing methods. Further evidence of improvement of children's social status can be found in contemporary designs: for example, 'casualized' wear, 'character design' which reflects children's psychology and 'family look' which is designed to be worn with mothers. This evolution of children's clothing within western dressing support the view that children's clothing is not a miniature of adult wear but it reflects idiosyncrasies of the era and exerts children's dignity.

• Advances in nano research
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• 제1권4호
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• pp.183-192
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• 2013

One-dimensional multiferroic nanostructured composites have drawn increasing interest as they show tremendous potential for multifunctional devices and applications. Herein, we report the synthesis, structural and dielectric characterization of barium titanate ($BaTiO_3$)-bismuth ferrite ($BiFeO_3$) composite fibers that were obtained using a novel sol-gel based electrospinning technique. The microstructure of the fibers was investigated using scanning electron microscopy and transmission electron microscopy. The fibers had an average diameter of 120 nm and were composed of nanoparticles. X-ray diffraction (XRD) study of the composite fibers demonstrated that the fibers are composed of perovskite cubic $BaTiO_3$-$BiFeO_3$ crystallites. The magnetic hysteresis loops of the resultant fibers demonstrated that the fibers were ferromagnetic with magnetic coercivity of 1500 Oe and saturation magnetization of 1.55 emu/g at room temperature (300 K). Additionally, the dielectric response of the composite fibers was characterized as a function of frequency. Their dielectric permittivity was found to be 140 and their dielectric loss was low in the frequency range from 1000 Hz to $10^7$ Hz.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.165-168
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• 2008

본 연구에서는 철근콘크리트 구조물의 보강에 이용되는 유리섬유강화 복합재료(Glass Fiber Reinforced Polymer, GFRP) 형상에 관한 연구로서 콘크리트의 피복두께 및 FRP 보강재의 형상(Plate, Box)을 실험 변수로 하여 FRP 보강 철근콘크리트 보의 거동 평가 관한 연구를 수행하였다. 이를 위하여 본 연구에서는 T. J. Teng 등이 제안한 설계식을 이용하여 보강량을 결정하였고 기존의 FRP Plate 보강재의 성능개선을 위하여 FRP Sandwich box 보강재를 설계, 적용하여 보았다. 연구의 결과 예상과 달리 FRP Plate 보강재가 Sandwich box 보강재보다 보강효과가 우수한 것으로 조사되었으며, 이는 보강재 제작상의 한계점 및 core 재료가 너무 약하여 Sandwich box 보강재의 Top Plate와 Bottom Plate가 일체화 거동을 하지 못하여 나타난 결과로 사료된다.

• 대한기계학회논문집A
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• 제41권7호
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• pp.613-620
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• 2017

금속이 코팅된 FBG(fiber Bragg grating) 센서는 구조물이 과거에 겪은 최대 변형률을 기억하는 기억효과(memory effect)를 가진다. 본 연구에서는 무전해 도금법과 전해 도금법을 이용하여 약 $43{\mu}m$의 두께를 가지는 니켈(nickel)이 코팅된 FBG 센서를 제작하였다. 니켈 코팅된 FBG 센서의 잔류 변형률 생성 성능, 즉, 기억효과를 검증하기 위해 반복하중 실험(잔류 변형률 생성실험)을 수행하였다. 인가한 최대 변형률의 크기가 증가함에 따라 잔류 변형률이 증가함을 확인함으로써 기억효과를 검증하였다. 본 연구에서 수행한 니켈이 코팅된 FBG 센서의 제작 기법과 센서에 대한 반복하중 실험결과는 향후 광섬유 센서를 이용한 구조물 건전성 감시(SHM, structural health monitoring)기법 개발에 기본 데이터로서 활용될 것이다.