• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.4
• /
• pp.342-347
• /
• 2016

This paper dealt with the economic analysis on the application of shipboard LED (Light Emitting Diode) luminaires to replace incandescent and fluorescent lamps, which account for over 80 % of light source on a training or naval vessel. The rates of savings achieved in the power consumption, initial investment, maintenance cost, and fuel cost were analyzed. The break-even points and the $CO_2$ emissions were also calculated. For the training vessel, the initial investment was increased by 3.8 times, while the maintenance cost over five years was reduced by 51 %. When 40 %, 50 %, and 60 % of luminaires were turned on, the calculated break-even points were 11 months, 9 months, and 7 months, respectively. On the other hand, the initial investment was increased by 3.5 times while the maintenance cost over five years was saved by 55 % for the naval vessel. The break-even points were calculated as 15 months, 12 months, and 10 months, respectively. Moreover, the $CO_2$ emissions of the training and the naval vessels were reduced by 69 % and 65 %, respectively. From the results, it was revealed that the maintenance cost can be reduced by more than 50 %, and that the power consumption, fuel cost, and $CO_2$ emissions can be reduced by more than 60 % if LED luminaires are used on two types of vessels.

• The Korean Journal of Mycology
• /
• v.51 no.2
• /
• pp.69-80
• /
• 2023

The cultivation conditions of shiitake mushrooms (Lentinula edodes) influence the production and quality of fruiting bodies. We conducted this study to improve the productivity and quality of shiitake mushrooms by modifying the cultivation conditions. Two types of spawns (sawdust and liquid spawn) were used, and corn flour was used as a nutritional source for the sawdust medium. A blue light-emitting diode (LED; 300 lux) was also used instead of a white LED during the incubation period. Sanbaekhyang was used as the experimental variety. When using corn flour, the mycelial growth rate increased 1.1 to 2.7 times the growth rate of the control up to 21 days of incubation, and the weight loss rate of the media was also higher. Mushroom productivity increased 1.2 times when the liquid spawn was used compared to when the sawdust spawn was used, and the blue LED also increased fruiting body production by 1.1 times compared to the white LED. Mushroom productivity increased when the liquid spawn was used, and the blue LED also increased fruiting body production. Fruiting body weight and the size of the cap were greater when sawdust spawn was used. The fruiting body weight and the stipe diameter were greater when the blue LED was used. Taste analysis showed that the saltiness increased when corn flour was used, and the sourness increased when the blue LED was used.

• Journal of Technologic Dentistry
• /
• v.42 no.4
• /
• pp.355-361
• /
• 2020

Purpose: In this study, we added two kinds of photoinitiators (CQ and TPO) to prepare two kinds of denture base resins (Bis-GMA series and UDMA series) for three-dimensional (3D) printing to compare and analyze their mechanical and biological properties and to find the optimal composition. Methods: Control specimens were made using the mold made of polyvinyl siloxane of the same size. Light curing was performed twice for 20 seconds on both the upper and lower surfaces with LED (light emitting diode) light-curing unit (n=10). Experimental 3D printing dental resins were prepared, to which two photoinitiators were added. Digital light processing type 3D printer (EMBER, Autodesk, CA, USA) was used for 3D printing. The specimen size was 64 mm×10 mm×3.3 mm according to ISO 20795-1. The final specimens were tested for flexural strength and flexural modulus, and MTT test was performed. Furthermore, one-way analysis of variance was performed, and the post-test was analyzed by Duncan's test at α=0.05. Results: The flexural strength of both Bis-GMA+CQ (97.12±6.47 MPa) and UDMA+TPO (97.40±3.75 MPa) was significantly higher (p<0.05) in the experimental group. The flexural modulus in the experimental group of UDMA+TPO (2.56±0.06 GPa) was the highest (p<0.05). MTT test revealed that all the experimental groups showed more than 70% cell activity. Conclusion: The composition of UDMA+TPO showed excellent results in flexural strength, flexural modulus, and biocompatibility.

• Korean Journal of Clinical Laboratory Science
• /
• v.49 no.2
• /
• pp.150-160
• /
• 2017

Atopic dermatitis (AD) is a chronic inflammatory skin disease. It is characterized by eczematous lesions, skin dryness, and pruritus. The existing treatment drugs for AD have side effects, especially if the drugs are taken for extended periods. Therefore, new alternative therapies are necessary. The aim of this study was to investigate the combined effects of curcumin administration and LED irradiation on AD. AD-like lesions were induced in BALB/c mice by repeated application of 1-chloro-2,4-dinitrobenzene (DNCB) to the shaved skin of the ear and neck. Thirty male BALB/c mice were divided into five groups: vehicle, DNCB, curcumin, LED, and curcumin+LED groups. Curcumin (0.1 g/kg/day) was administrated repeatedly during a period of 14 days (experimental period) and 630 nm LED irradiation ($5J/cm^2/day$) was performed in the acryl box once a day for 10 days, after inducing AD-like lesions via DNCB application. The severity of AD-like lesions was evaluated during the experimental period, using a modified SCORAD index. Both ear and neck skin tissues were examined histologically for epidermal thickness, mast cell, eosinophil counting, and dermal collagen density. Epidermal cell proliferation and apoptosis were detected using immunohistochemistry and TUNEL, respectively. These were all reduced in SCORAD index, epidermal thickness, collagen density, number of mast cell and eosinophil in dermis, and number of proliferating cell and apoptotic cell in epidermis by curcumin administration and 630 nm LED irradiation. Moreover, all parameters were significantly lower in the curcumin+LED group compared with the curcumin group and LED group. These results suggest that the combined therapy of curcumin and LED is more effective than a single treatment. We recommend that this can be a feasible alternative therapy to manage AD.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.104-104
• /
• 2011

ZnO는 3.37 eV의 넓은 에너지 밴드갭을 갖는 투명 전도성 반도체이며 우수한 전기적, 광학적 특성으로 인해 광원소자 개발을 위한 새로운 물질로 많은 주목을 받아왔다. 더욱이, ZnO는 쉽게 나노구조 형성이 가능하기 때문에 이를 응용한 가스센서, 염료감응태양전지, 광검출기 등의 소자 개발이 활발히 이루어지고 있다. 최근에는 GaN 기반 발광다이오드 (light emitting diode, LED)의 광추출 효율을 향상시키기 위한 ZnO 나노구조 응용에 관한 연구가 보고되고 있다. GaN 기반 LED의 경우 반도체 물질과 공기 사이의 높은 굴절률 차이로 인하여 낮은 광추출 효율을 나타낸다. 이를 해결하기 위한 방법으로 표면 roughening, texturing 등 에칭공정을 이용해 광추출 효율을 개선하려는 연구들이 보고되고 있으나, 복잡한 공정과정을 필요로 하고 에칭공정에 의한 소자 표면 손상으로 전기적 특성이 나빠질 수 있다. 반면 전기화학증착법으로 성장된 ZnO 나노구조를 이용할 때, 보다 간단한 방법으로 쉽고 빠르게 나노구조를 형성할 수 있고 낮은 공정온도를 가지기 때문에 소자의 전기적 특성에 큰 영향을 주지 않는다. 수직방향으로 잘 정렬된 ZnO 나노구조를 갖는 LED의 경우 내부 Fresnel 반사 손실을 효과적으로 줄여 발광 효율을 크게 향상시킬 수 있다. 따라서, ZnO 나노구조의 성장제어 및 성장특성을 분석하는 것은 매우 중요하다. 본 연구에서는 ITO glass 위에 ZnO 나노구조를 성장하고 그 특성을 분석하였다. ITO glass 기판 위에 RF magnetron 스퍼터를 사용하여 Al 도핑된 ZnO (AZO)를 얇게 증착한 후 전기화학증착법으로 ZnO 나노구조를 성장하였다. 농도, 인가전압, 공정시간 등 다양한 공정조건을 변화시키면서 성장 메커니즘을 분석하였고, scanning electron microscope (SEM) 및 X-ray diffraction (XRD)을 통하여 구조 및 결정성 등을 분석하였다. 또한, UV-Visible-NIR spectrophotometer를 사용하여 투과율을 실험적으로 측정하여 ZnO 나노구조의 광학적 특성을 분석하였고, rigorous coupled wave analysis (RCWA) 방법을 사용하여 계면에서 발생하는 내부 반사율을 계산함으로써 나노구조의 효과를 이론적으로 분석하였다.

• Journal of Sensor Science and Technology
• /
• v.28 no.5
• /
• pp.311-317
• /
• 2019

Rotating devices are commonly installed in power plants and factories. This study proposes a self-powered sensor node that is powered by converting the vibration energy of a rotating device into electrical energy. The self-powered sensor consists of a piezoelectric harvester for self-power generation, a rectifier circuit to rectify the AC signal, a sensor unit for measuring the vibration frequency, and a circuit to control the light emitting diode (LED) lighting. The frequency of the vibration source was measured using a piezoelectric-cantilever-type vibration frequency sensor. A green LED was illuminated when the measured frequency was within the normal range. The power generated by the piezoelectric harvester was determined, and the LED operation was assessed in terms of the vibration frequency. The piezoelectric harvester was found to generate a power of 3.061 mW or greater at a vibration acceleration of 1.2 g ($1g=9.8m/s^2$) and vibration frequencies between 117 and 123 Hz. Notably, the power generated was 4.099 mW at 122 Hz. As such, our self-powered sensor node can be used as a module for monitoring rotating devices, because it can convert vibration energy into electrical energy when installed on rotating devices such as air compressors.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.500-500
• /
• 2013

특정한 유기 물질에 전류를 인가했을 때 발광을 하는 특성을 이용한 Organic Light Emitting Diode (OLED)는 뛰어난 색재현성, 적은 전력소모, 간단한 제조공정, 넓은 시야각 등으로 인해 PDP, LCD, LED에 이은 차세대 디스플레이 소자로 많은 관심을 받고 있다. 하지만 OLED는 각기 다른 굴절률을 가지는 다층구조로 되어있어 실질적으로 소자 밖으로 나오는 빛은 원래 생성된 빛의 20% 정도 밖에 되지 않는다. 이러한 광 손실을 줄이기 위해 Photonic Crystal (PC)이나 마이크로 렌즈 어레이(MLA) 부착 등과 같이 특정한 크기를 갖는 주기적인 나노 구조물을 이용한 광추출 효율 상승 방법은 특정 파장의 빛에서만 효과가 있는 한계가 있었으며 고가의 공정과정을 거쳐야 했으므로 OLED 소자의 가격 향상에 일조하였다. 이의 해결을 위해 본 연구는 유리기판 위에 랜덤한 분포를 가지는 나노 구조물 제작 공정법을 제안한다. 먼저 유리기판 위에 스퍼터로 금속 박막을 입혀 이를 Rapid thermal annealing (RTA) 공정을 이용하여 랜덤한 분포의 Island를 가지는 마스크를 제작하였다. 그 후 플라즈마 식각을 이용하여 유리기판에 나노 구조물을 형성하였고 기판 위에 남아있는 마스크는 Ultrasonic cleaning을 이용하여 제거하였다. 제작된나노구조물은 200~300 nm의 높이와 약 200 nm 폭을 가지고 있다. 제작된 유리기판의 OLED 소자로의 적용가능성을 알아보기 위한 광학특성 조사결과는 300~900 nm의 파장영역에서 맨유리와 거의 비슷한 수직 투과율을 보이면서 최대 50%정도의 Diffusion 비율을 나타내고 있고 임계각(41도) 이상의각도에서 인가된 빛의 투과율에 대해서도 향상된 결과를 보여주고 있다. 제안된 공정의 전체과정 기존의 PC, MLA 등의 공정에 비해 난이도가 쉽고 저가로 진행이 가능하며 추후 OLED 소자에 적용될 시 대량생산에 적합한 후보로 보고 있다.

• Journal of the Korean Applied Science and Technology
• /
• v.17 no.3
• /
• pp.174-177
• /
• 2000

The effect of a-sexithiophene(${\alpha}-6T$) layers on the light emitting diode (LED) were studied. The ${\alpha}-6T$ was used for a buffer layer in electroluminescent (EL) devices. Enhanced carrier (hole) injection and improved emission efficiency were observed. Carrier injection characteristics were investigated as a function of ${\alpha}-6T$ later thickness. The efficiency of the electroluminescence was proportional to the thickness of ${\alpha}-6T$ layer. The highest efficiency was observed 600A of ${\alpha}-6T$ later, which was about 1.5 times higher than that of device without ${\alpha}-6T$ later. The device with a-6T showed an operation voltage lowered by 2V. The ${\alpha}-6T$ layer can substitute hole blocking layer, and control charge injection properties.

• ETRI Journal
• /
• v.34 no.4
• /
• pp.542-552
• /
• 2012

In this paper, a gaze estimation method is proposed for use with a large-sized display at a distance. Our research has the following four novelties: this is the first study on gaze-tracking for large-sized displays and large Z (viewing) distances; our gaze-tracking accuracy is not affected by head movements since the proposed method tracks the head by using a near infrared camera and an infrared light-emitting diode; the threshold for local binarization of the pupil area is adaptively determined by using a p-tile method based on circular edge detection irrespective of the eyelid or eyelash shadows; and accurate gaze position is calculated by using two support vector regressions without complicated calibrations for the camera, display, and user's eyes, in which the gaze positions and head movements are used as feature values. The root mean square error of gaze detection is calculated as $0.79^{\circ}$ for a 30-inch screen.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.11
• /
• pp.70-76
• /
• 2009

Web tension control system recently have been applied to OLED(Organic Light-Emitting Diode), RFID of flexible material, e-Paper and PLED(Polymeric LED) and various web control algorithms have being developed for higher productivity and product quality These system need an accuracy model to design and implement controller. In this paper, the web tension control system with dancer roll is mathematically modeled. Mathematical model consists of 8 subsystems and each subsystems can be described as impedance structure which connected by velocity and tension. Mathematical model is different from the estimated model at high frequency range because of structure dynamics which is ignored on mathematical model. The estimated model is derived using ARMAX model. The controller is designed using the estimated model. The step response of the estimated model are compared with that of physical model for a validation of estimated model. The experimental results show a good match between them.