• Nuclear Engineering and Technology
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• 제52권2호
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• pp.373-380
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• 2020

This study was carried out to convert the hydrophobic characteristics of PVDF to hydrophilic. Poly(-vinylidene fluorine) (PVDF) was grafted by electron beam irradiation and sulfonated. The grafting degree of modified PVDF increased with the monomer concentration, but not the conversion degree. From the results of FTIR and XPS, it was shown that the amount of converted sulfur increased with the grafting degree. The radiation-induced graft polymerization led to decrease fluorine from 35.7% to 21.3%. Meanwhile, the oxygen and sulfur content increased up to 8.1% and 3.2%. The pore size of modified membranes was shrunken and the roughness sharply decreased after irradiation. The ion exchange capacity and contact angle were investigated to show the characteristics of PVDF. The enhanced ion exchange capacity and lower contact angle of modified PVDF showed that the hydrophilicity played a role in determining membrane fouling. Electron beam irradiation successfully modified the hydrophobic characteristics of PVDF to hydrophilic.

• Computers and Concrete
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• 제19권2호
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• pp.127-131
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• 2017

This paper presents a generalized formulation for optimizing the design of concrete beam reinforced with glass fiber reinforced polymer bar. The optimization method is formulated to find the design variables leading to the minimum weight of concrete beam with constraints imposed based on ACI code provisions. A simple genetic algorithm is utilized to solve the optimization task. The weights of concrete and glass fiber reinforced polymer bar are included in the formulation of the objective function. The ultimate limit states and the serviceability limit states are included in formulation of constraints. The results of illustrated example demonstrate the efficiency of the proposed method to reduce the weight of beam as well as to satisfy the above requirement. The application of the optimization based on the most economical design concept have led to significant savings in the amount of the component materials to be used in comparison to classical design solutions.

• Journal of Korean Vacuum Science & Technology
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• 제5권2호
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• pp.38-42
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• 2001

We investigated physical properties of ion-beam mixed Fe/si multilayerd films(MLF) prepared by rf sputtering onto glass substrates at room temperature. Such an ion-beam treatment has led to noticeable changes in the structural and physical properties of the MLF: the formation of a new phase which is characterized by a crystalline silicide with a low coercivity and Tc = 550 K. In contrast to the as-prepared state, the ion-beam mixed MLF contains two magnetic phases. One of them is a very soft (Hc < 2 Oe), but microscopically homogeneous one with M$\sub$eff/=6.7 kG.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.167-168
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• 2023

Construction of reinforced concrete structures required massive amounts of concrete and steel rebar. The current procedure to estimate the quantity of rebar requires tedious and time-consuming manual labor. Consequently, this circumstance made the engineers vulnerable to error and mistake, which led to the rebar waste. No system that is capable of automatically calculating rebar length has yet been developed Thus, this study proposes a preliminary investigation of automatic rebar length estimation of beam element by using BIM-based shape codes drawn in Revit. Beam is chosen due to its complexity in the rebar arrangement. In addition, the development of this study could assist engineers on the construction site and effectively contribute to the minimization of rebar waste in the future.

• Journal of the Optical Society of Korea
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• 제20권4호
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• pp.488-499
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• 2016

We present a design and optical simulation of a cost-effective hybrid daylighting/LED system composed of mixing sunlight and light-emitting diode (LED) illumination powered by renewable solar energy for indoor lighting. In this approach, the sunlight collected by the concentrator is split into visible and non-visible rays by a beam splitter. The proposed sunlight collector consists of a Fresnel lens array. The non-visible rays are absorbed by the solar photovoltaic devices to provide electrical power for the LEDs. The visible rays passing through the beam splitters are coupled to a stepped thickness waveguide (STW) by tilted mirrors and confined by total internal reflection (TIR). LEDs are integrated at the end of the STW to improve the lighting quality. LEDs’ light and sunlight are mixed in the waveguide and they are coupled into an optical fiber bundle for indoor illumination. An optical sensor and lighting control system are used to control the LED light flow to ensure that the total output flux for indoor lighting is a fixed value when the sunlight is inadequate. The daylighting capacity was modeled and simulated with a commercial ray tracing software (Lighttools^TM). Results show that the system can achieve 63.8% optical efficiency at geometrical concentration ratio of 630. A required accuracy of sun tracking system achieved more than ±0.5^o . Therefore, our results provide an important breakthrough for the commercialization of large scale optical fiber daylighting systems that are faced with challenges related to high costs.

• Journal of Biosystems Engineering
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• 제25권2호
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• pp.131-140
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• 2000

Spraying operation is one of the most essential in an orchard management and it is also hazardous to human body. for automatic and unmanned spraying , an autonomous travelling vehicle is demanded. In this study, a telemeter was developed using infrared beam which could detect trunks and obstacles measure distance and direction from the vehicle travelling in the orchard. The telemeter system was composed of two infrared LED transmitters and receivers, a beam scanning device for continuous object detection , two rotary encoders for angle detector, and a beam level controller for uneven soil surface. The detected distance and direction signal s were sent to personal computer which made for the system display the angular and distance measurements through I/O board. According to a field test in an apple farm, the system detected up to 10m distance under 12 V of transmitted beam intensity, however, it was recommended that the proper beam transmit intensity be 7 v at the 10 m distance, because of the negative effect to human body at 12 V. The error rate of this system was 0.92 % when the actual distance was compared to measured one. The system was feasible at the small error rate. The developed telemeter system was an important part for autonomous travelling vehicle provided the real time object recognition . A direction control system could be constructed suing the system. It is expected that the system could greatly contribute to the development of autonomous farm vehicle.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.593-593
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• 2013

나노패턴 제작은 차세대 초고밀도 반도체 메모리기술과 바이오칩 등 나노기술의 핵심 분야로, 나노패턴 구조를 나노-바이오 전자소자 및 반도체 산업분야에 적용할 경우 시장 선점 및 막대한 부가가치 창출 등을 통해 국가경쟁력 강화에 크게 기여할 것으로 기대된다. 하지만 대면적 패턴형성이 어려워 뿐만 아니라 $300^{\circ}$ 이상의 열처리 과정에 의한 생산성이 떨어진다. 또한 나노구조가 잘 이루어진 차원, 표면상태, 결정성, 화학적 조성을 갖도록 하는 합성 및 제조상의 어려움 때문이다. 이에 반해 자기정렬 ITO Dot 형성은 상기 기술한 1차원 나노구조형성을 하는 것에 비하여, 나노구조를 제작하기 위하여 공정이 단순하며, 비용 및 생산성 측면에서 유리 할 것으로 생각된다. 이에 본 연구는 E-beam을 이용하여 형성된 ITO 박막에 HCl solution을 이용하여 자기정렬 ITO Dot 형성 후 n-AlGaInP Vertical LED[VLED] 표면에 nano pillar의 두께에 각기 다르게 형성하였으며, 최종적으로 제작된 VLED의 전기적, 광학적 특성을 조사하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.42-42
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• 2010

Deep-trenched photonic crystals passing through InGaN/GaN quantum well structural layer have been fabricated on the surface of GaN-based light emitting diode(LED) using by electron beam nanolithography. The lattice constant and hole diameter of the photonic crystals are 230nm and 140nm, respectively. The structural and electro-optical properties have been investigated by scanning electron microscope(SEM) and power-current-voltage(L-I-V). Electroluminescence from GaN-based LED with deep-trenched photonic crystal shows the higher intensity than that without photonic crystal.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 추계학술대회
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• pp.139-140
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• 2010

This paper presents an indoor prototype for wireless digital signal transmission using Visible Light Communications (VLC) in which high power Light Emitting Diode (LED) is used. Using low cost and off-the-shelf components, the transmitter module is constructed using an AVR Atmega128 microcontroller and commercial white beam LEDs. Modulating the light intensity of the LED enables digital signals to be transmitted across the optical link. The receiver module employs a high speed PIN photodetector for optical signal detection and a recovery circuit for optical-electro signal conversion. By sending digitalized data via VLC technology, many applications can be realized in the areas of consumer advertising, traffic safety information and disaster control.

• 전기전자학회논문지
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• 제21권4호
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• pp.368-374
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• 2017

본 연구에서는 220[V] 상용전원을 대체한 태양전지 모듈을 응용하고 등 기구는 할로겐 등이나 나트륨 등을 대체한 LED 조명을 이용한 저전력형 LED 보안등을 개발하였다. 또한 LED 구동제어기의 발열문제와 구동전류를 최소화할 수 있는 PWM형 구동제어회로를 설계하였다. 개발된 시스템에서, 광 효율에 대한 측정값은 93.6 [lm/Ｗ] 이고, LED 램프의 발열 제어를 위하여 제어기 내부에 고 정밀 온도센서(TC1047A)를 사용하였다. LED 조명등에서 발생하는 고열을 제거하기 위하여 금속 삽입형 방열 장치를 통하여 대기 속으로 신속하게 다중분산 시키도록 설계하였다. LED 조명등의 발열제어 온도 범위는 $50{\sim}55[^{\circ}C]$였다. LED 보안등의 광속 및 점등 속도는 0.5[sec] 이고 LED 램프의 빔 확산 각도는 높이 6[m]를 기준으로 하는 배광곡선에 의해 약 $110[^{\circ}]$의 빔 각도를 얻었다.