• 한국초전도ㆍ저온공학회논문지
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• 제24권1호
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• pp.8-12
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• 2022

Recently, research on applying composite materials to various industrial fields is being actively conducted. In particular, composite materials fabricated by Fused Deposition Modeling 3D printers have more advantages than existing materials as they have fewer restrictions on manufacturing shape, reduce the time required, weight. With these advantages, it is possible to consider utilizing composite materials in cryogenic environments such as the application of liquid oxygen and liquid hydrogen, which are mainly used in an aerospace and mobility. However, FDM composite materials are not verified in cryogenic environments less than 150K. This study evaluates the characteristics of composite materials such as tensile strength and strain using a UTM (Universal Testing Machine). The specimen is immersed in liquid nitrogen (77 K) to cool down during the test. The specimen is fabricated using 3D print, and can be manufactured by stacking reinforced fibers such as carbon fiber, fiber glass, and aramid fiber (Kevlar) with base material (Onyx). For the experimental method and specimen shape, international standards ASTM D638 and ASTM D3039 for tensile testing of composite materials were referenced.

• 한국기계가공학회지
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• 제20권5호
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• pp.121-127
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• 2021

Reverse offset printing is considering as an emerging technology for printed electronics owing to its environmentally friendliness and cost-effectiveness. In reverse offset printing, selecting the materials for cliché and blanket is critical because of its minimum resolution, registration errors, aspect ratio of reliefs, pattern area, and reusability. Various materials such as silicon, quartz, glass, electroplated nickel plates, and imprinted polymers on rigid substrates can be used for the reverse offset printing of cliché. However, when new structures are designed for specific applications, new clichés need to re-fabricated each time employing multiple time-consuming and costly processes. Therefore, by modifying the blanket materials containing the printing ink, several new structures can be easily created using the same cliché. In this study, we investigated various elastomeric materials and evaluated their applicability for designing a highly stretchable blanket with controlled elastic deformation to implement tunable reverse offset printing.

• Smart Structures and Systems
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• 제21권3호
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• pp.257-262
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• 2018

Vibrational problems in the domestic Small Horizontal Axis Wind Turbines (SHAWT) are due to flap wise vibrations caused by varying wind velocities acting perpendicular to its blade surface. It has been reported that monitoring the structural health of the turbine blades requires special attention as they are key elements of a wind power generation, and account for 15-20% of the total turbine cost. If this vibration problem is taken care, the SHAWT can be made as commercial success. In this work, Shape Memory Alloy (SMA) wires made of Nitinol (Ni-Ti) alloys are embedded into the Glass Fibre Reinforced Polymer (GFRP) wind turbine blade in order to reduce the flapwise vibrations. Experimental study of Nitinol (Ni-Ti) wire characteristics has been done and relationship between different parameters like current, displacement, time and temperature has been established. When the wind turbine blades are subjected to varying wind velocity, flapwise vibration occurs which has to be controlled continuously, otherwise the blade will be damaged due to the resonance. Therefore, in order to control these flapwise vibrations actively, a non-linear current controller unit was developed and fabricated, which provides actuation force required for active vibration control in smart blade. Experimental analysis was performed on conventional GFRP and smart blade, depicted a 20% increase in natural frequency and 20% reduction in amplitude of vibration. With addition of active vibration control unit, the smart blade showed 61% reduction in amplitude of vibration.

• 전기학회논문지P
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• 제66권4호
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• pp.242-246
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• 2017

In this study, it was investigated about optical simulation in high brightness and high uniformity general lighting using glass light guide plate. And we adopt edge-light emission type light plate. Edge-light type lighting has been used LCD application, especially note PC or smart phone backlight unit. Because it had the good properties such as slim shape and light weight. We thought this type was suitable for general lighting application such as wall attached type or ceiling mount type. But many of edge-light type lighting had problems. It called slanted output light rays. That was main key parameter how could control the direction of output light rays. We investigated the solution of this problems, using ray tracing method, we recognized the major fact of the solution relied on the geometric structure of diffusing dot shape. We set the conditions of aspect ratio in diffusing dot shape such as 0.5 to 1. And, at first, we designed diffusing dots shape based on the results of optical simulation and made specimen. as above condition, and acquired good result in confirming dots shape such as the value of the output rays's peak angle was around 75 degrees. And good light distribution characteristics were measured by slated spectro-radiometer. It was shown that the effective ways of designing light distribution characteristics using optical simulation such as ray tracing linear method for making general lighting using glass light guide plate.

• 센서학회지
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• 제32권5호
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• pp.320-327
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• 2023

In this study, an FPGA-based sealer inspection system was developed to inspect the sealer applied to install vehicle glass on a car body. The sealer is a liquid or paste-like material that promotes adhesion such as sealing and waterproofing for mounting and assembling vehicle parts to a car body. The system installed in the existing vehicle design parts line does not detect the sealer in the glass rotation section and takes a long time to process. This study developed a line laser camera sensor and an FPGA vision signal processing module to solve this problem. The line laser camera sensor was developed such that the resolution and speed of the camera for data acquisition could be modified according to the irradiation angle of the laser. Furthermore, it was developed considering the mountability of the entire system to prevent interference with the sealer ejection machine. In addition, a vision signal processing module was developed using the Zynq-7020 FPGA chip to improve the processing speed of the algorithm that converted the profile to the sealer shape image acquired from a 2D camera and calculated the width and height of the sealer using the converted profile. The performance of the developed sealer application inspection system was verified by establishing an experimental environment identical to that of an actual automobile production line. The experimental results confirmed the performance of the sealer application inspection at a level that satisfied the requirements of automotive field standards.

• Journal of the Optical Society of Korea
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• 제18권3호
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• pp.256-260
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• 2014

Columnar-structured cesium iodide (CsI) scintillators doped with thallium (Tl) are frequently used as x-ray converters in medical and industrial imaging. In this study we investigated the imaging characteristics of CsI:Tl films with various reflective layers-aluminum (Al), chromium (Cr), and titanium dioxide ($TiO_2$) powder-coated on glass substrates. We used two effusion-cell sources in a thermal evaporator system to fabricate CsI:Tl films on substrates. The scintillators were observed via scanning electron microscopy (SEM), and scintillation characteristics were evaluated on the basis of the emission spectrum, light output, light response to x-ray dose, modulation transfer function (MTF), and x-ray images. Compared to control films without a reflective layer, CsI:Tl films with reflective layers showed better sensitivity and light collection efficiency, and the film with a $TiO_2$ reflective layer showed the best properties.

• 한국산학기술학회논문지
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• 제16권10호
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• pp.7071-7077
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• 2015

최근 스마트폰, 태블릿 PC 및 전자기기 등의 사용이 증가함에 따라 커버글라스의 수요가 증가하고 있는 추세이다. 모바일 기기의 디스플레이가 대형화되면서 접촉이나 낙하 등과 같이 외부에서 힘을 받게 되는 환경에서 높은 강도를 유지하는 것이 요구되고 있다. 커버글라스 제작 공정에서 연마공정은 커버글라스의 표면거칠기 및 충분한 강도를 제공하는 중요한 공정이다. 기존 연삭 숫돌에 의한 가공방법은 커버글라스 가공표면에 스크레치, 칩핑, 노칭 및 마이크로 크랙 등의 가공 문제점이 발생한다. 따라서 본 연구에서는 모바일 커버글라스의 연마를 위해 연마필름을 이용한 폴리싱 시스템을 개발하였다. 구조적 안정성을 평가하기 위해 연마 필름 폴리싱 시스템에 대한 유한요소모델을 생성하였고 다물체 동역학 해석을 수행하였다. 연마 필름 폴리싱 시스템에 대한 응력 및 변위 해석을 통해 특성을 분석하였고 레이저 변위 센서를 이용해 제작된 시스템에 대한 변위를 측정하여 구조적 안정성에 대해 확인하였다.

• 생물환경조절학회지
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• 제30권4호
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• pp.278-286
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• 2021

본 연구에서는 단면설계 및 열 교환 장치 위치 변경을 통해 온실의 구조 변경을 진행하였으며, 선행연구를 통해 개발된 모델을 근간으로 하여 개선 여부에 따른 온실 내부 환경을 예측하였다. 단면형상과 열 교환 장치의 개선 후 유속 변화에 따른 시뮬레이션 분석을 진행하였으며, 이 때 온도와 균일도는 각각 평균 0.65℃, 0.75%p 상승함을 확인하였다. 해석대상 온실과 같은 소규모 온실의 경우 방열관의 난방성능 개선보다 FCU에 의해 형성되는 공기 유동이 균일한 환경 조성에 더 큰 영향을 미치는 것으로 판단된다. 개선 전·후 온실에 환기시스템 적용 시 공기 유동 특성 분석을 위해 시뮬레이션 분석을 진행하였다. 공기 유동과 공기령은 유사한 분포를 보였으며, 개선 후 온실의 공기령이 개선 전 온실 대비 18초낮게 나타났다. 개선 전·후 온실 시뮬레이션 분석 결과 전체적으로 개선된 온실에서의 평균온도 및 온도 균일도 상승, 최대편차 감소 등 내부 환경의 균일성이 향상됨을 확인하였다. 선행연구로 개발된 모델은 형상 변경, 열 교환 장치 위치 변경 등에 따라 변화하는 온실 내부 환경을 예측할 수 있음을 확인하였으며, 온실 설계, 온실 내 난방시스템 설계 등의 분야에 적용 가능할 것으로 판단된다.

• Smart Structures and Systems
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• 제10권6호
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• pp.501-515
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• 2012

We design and test a shape memory alloy (SMA)-based actuation system that can be used to propel a fish robot. The actuator in the system is composed of a 0.1 mm diameter SMA wire, a 0.5 mm-thick glass/epoxy composite strip, and a fixture frame. The SMA wire is installed in a pre-bent composite strip that provides initial tension to the SMA wire. The actuator can produce a blocking force of about 200 gram force (gf) and displacement of 3.5 mm at the center of the glass/epoxy strip for an 8 V application. The bending motion of the actuator is converted into the tail-beat motion of a fish robot through a linkage system. The fish robot is evaluated by measuring the tail-beat angle, swimming speed, and thrust produced by the tail-beat motion. The tail-beat angle is about $20^{\circ}$, the maximum swimming speed is about 1.6 cm/s, and the measured average thrust is about 0.4 gf when the fish robot is operated at 0.9 Hz.

• 한국결정성장학회지
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• 제6권3호
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• pp.439-448
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• 1996

광투과성 BK10 glass fiber/PMMA 복합재료의 합성조건을 변화시켜 복합재료가 온도와 파장을 감지하는 센서로서의 응용 가능성이 있는지를 연구하였다. 유리섬유 제조시 뽑아내는 속도와 온도등의 공정조건에 따른 유리섬유의 직경 및 굴저율을 측정하였고 유리섬유에 코팅되는 coupling agent의 용매 및 코팅방법에 대하여 연구하였다. 복합재료의 최대광투과도를 나타내는 온도($T_{max%}$)는 복합재료에 강화되는 유리섬유의 크기(굴정율), 유리섬유 vol%, PMMA의 분자량등을 변화시키면 $13~50^{\circ}C$ 범위에서 조정될 수 있었으며, 측정파장을 변화시킬 경우 $T_{max%}$ 값이 $35~55^{\circ}C$ 범위가 되도록 합성하는 것이 가능하였다. 한편 복합재료를 파장의 함수로서 광투과도를 측정하였을 때 최대광투과도가 나타나는 파장($\lamda_{max%}$)은 나타나지 않았다.