• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.111-114
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• 1999

Electroluminescence(EL) devices based on organic thin films have been attracted lots of interests in large-area light-emitting display. In this stuffy, an emissive layer was fabricated using Langmuir-Blodgett(LB) technique in organic light-emitting (OLEDs). This emissive organic material was synthesized and named PECCP[poly(3.6-N-2-ethylhexyl carbazolyl cyanoterephthalidene)] which has a strong electron donor group and an electron acceptor group in main chain repeated unit. This material has good solubility in common organic solvents such as chloroform. THF, etc, and has a good stability in air. The Langmuir-Blodgett(LB) technique has the advantage of precise control of the thickness down to the molecular scale, In particular, by varying the film thickness it is possible to investigate the metal/polymer interface. Optimum conditions for the LB film deposition are usually determined by investigating a relationship between a surface pressure $\pi$ and an effective are A occupied by one molecule on the subphase. The LB films were deposited on an indium-tin-oxide(ITO) glass at a surface pressure of 10 mN/m and dipping speed of 12 mm/min after spreading PECCP solution on distilled water surphase at room temperature, Cell structure was ITO/PECCP LB film/Alq$_3$/Al. We considered PECCP as a hole -transport layer inserted between the emissive layer and ITO. We also used Alq$_3$ as an emissive layer and an electron transport layer. We measured current-voltage(I-V) characteristics, UV/visible absorption, PL spectrum and EL spectrum of the OLEDs.

• 한국광학회지
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• 제9권1호
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• pp.15-19
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• 1998

본 논문에서는 고속 장거리 광전송시스템에서 스펙트럼 저미어진 광섬유 증폭 광원의 분산 패널티를 줄일 수 있는 전 광학적 방법을 새로이 제안하였다. 즉, 수신된 신호의 광 선폭을 확장하므로 잡음광의 2.5 Gb/s 전송에 필요한 송신 채널의 선폭을 0.1 nm까지 줄였다. 선폭 확장은 분산천이 광섬유에서 intra-channel 4광파 혼합현상을 이용하였으며, 그 결과 송신채널의 신호대 잡음비를 개선할 수 있었다. 이 방법을 이용하여 0.1 nm 채널 선폭을 갖는 2.5Gb/s NRZ 변조된 광신호의 분산천이 광섬유 300 km 전송을 성공적으로 수행하였다. 선폭 확대 전에는 비트 에러율이 $1{\times}10^{-5}$이었으나, 선폭 확대 후 비트 에러율이 $1{\times}10^{-10}$ 이하로 개선되었으며, 측정한 전송 패널티는 05. dB 이하였다. 이 결과는 지금까지 보고된 가간섭성이 없는 잡음 광원을 사용한 2.5 Gb/s 전송 실험 중에서 최소의 선폭과 최고의 전송거리 값을 갖는 결과이다.

• 한국운동역학회지
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• 제31권3호
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• pp.162-167
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• 2021

Objective: This study aimed to identify the different wind speed categories and competitive level among windsurfers through GPS variables to provide the useful information on the development of training programs for enhancing windsurfers' performance. Method: Data from 69 female athletes who participated in 27 races during the 2018-2019 windsurfing season were used for the analysis. Average board speed, total race time, total distance, upwind race time, downwind race time, beam reach race time were collected through GPS. Unconfirmed data were excluded along with penalty point data. The wind conditions were classified as light, light to medium, medium, medium to heavy, and heavy wind, the competitive levels were classified as level 1, level 2, and level 3. Results: As for the average board speed, the level 1 or level 2 group showed higher board speed than the level 3 group in all wind conditions except for the light wind. The total race time and upwind race time showed less time in level 1 or level 2 group than level 3 group in all wind conditions. The total distance, downwind race time and beam reach race time showed less distance and time in level1 group than level 3 group under sufficient wind conditions. Conclusion: Our results show that the aerobic capacity to sustain pumping during upwind course in wind conditions below 15 kts effects performance. In wind conditions of 15 kts or more, indicated that the board control for the fast board speed and small distance required during up, down, beam reach courses had an effect on competition performance. This information can be provided to windsurfers and coaching as basic data for training programs to improve performance.

• 반도체디스플레이기술학회지
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• 제21권4호
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• pp.33-38
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• 2022

With an attempt to suppress the moiré phenomenon caused by the interference between the black matrix of a display panel and the metal grid of a camera, we have fabricated an anti-moiré filter using light diffusing particles (LDPs) with the average diameter of 20 ㎛. It is demonstrated that the anti-moiré filter coated on a glass substrate (370 mm × 470 mm) using a table slot-die coater reduces the moiré intensity to a great extent when the area covered by LDPs is 50%. To quantify the intensity of moiré phenomenon, we have measured the lightness ratio and found that it is reduced from 132.12 down to 105.71 by the filter. To find the optimum area covered by LDPs, we have performed ray tracing simulations using Mie scatters as a substitute for LDPs. From the simulated irradiation distribution, we have calculated the standard deviation (SD) and contrast ratio (CR) to evaluate the moiré strength. As expected, the SD and CR values decrease with increasing covered area by LDPs. However, there exists a trade-off between the transmittance of the filter and its capability of reducing the moiré intensity in determining the area covered by LDPs.

• The Journal of Advanced Prosthodontics
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• 제15권5호
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• pp.248-258
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• 2023

PURPOSE. This study aims to evaluate the effects of exposure energy on the lateral resolution and mechanical strength of dental zirconia manufactured using digital light processing (DLP). MATERIALS AND METHODS. A zirconia suspension and a custom top-down DLP printer were used for in-office manufacturing. The viscosity of the suspension and uniformity of the exposed light intensity were controlled. Based on the exposure energy dose delivered to each layer, the specimens were classified into three groups: low-energy (LE), medium-energy (ME), and high-energy (HE). For each energy group, a simplified molar cube was used to measure the widths of the outline (X_o and Y_o) and isthmus (X_i and Y_i), and a bar-shaped specimen of the sintered body was tested. A Kruskal-Wallis test for the lateral resolution and one-way analysis of variance for the mechanical strength were performed (α = .05). RESULTS. The zirconia green bodies of the ME group showed better lateral resolution than those of the LE and HE groups (both P < .001). Regarding the flexural strength of the sintered bodies, the ME group had the highest mean value, whereas the LE group had the lowest mean value (both P < .05). The ME group exhibited fewer agglomerates than the LE group, with no distinctive interlayer pores or surface defects. CONCLUSION. Based on these findings, the lateral resolution of the green body and flexural strength of the sintered body of dental zirconia could be affected by the exposure energy dose during DLP. The exposure energy should be optimized when fabricating DLP-based dental zirconia.

• 한국항만학회지
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• 제13권1호
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• pp.79-86
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• 1999

This paper deals with the evaluation problem of complex systems by introducing a fuzzy approach. The authors are functionally supposing a hierarchical structure model of a complex system and give light on the following problems. First for the purpose of clarifying the characteristics of measures the property and differences between two method such as linear and fuzzy viewpoint are discussed through two level-down evaluation process. Second the integrated evaluation process which keeps reversibility between hierarchical levels is discussed and obtained some necessary conditions for reversibility of fuzzy evaluation. From these results it is expected that the fuzzy approach overcomes partly the limitation of reductionism at the hierarchical evaluation of complex systems.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 봄 학술발표회 논문집
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• pp.17-20
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• 2003

Step index POFs(SIPOF) are composed of core polymers and cladding polymers. Poly(methyl methacrylate) (PMMA) and polystyrene (PS) are normally used as core materials. The refractive index of cladding materials should be less than 2-5 % that of the core material. PMMA and fluorinated polymers are used as cladding materials on PS and PMMA core, respectively$^1$. Cladding materials which have lower refractive index than core materials reflect light at less than critical angle, which is transmitted down the core. (omitted)

• 한국신뢰성학회지:신뢰성응용연구
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• 제7권4호
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• pp.173-181
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• 2007

Out door exposure to daylight and weather climate conditions can cause adverse effect on the properties of automotive plastic materials. The effects of sunlight exposure, especially ultra violet (UV) radiation, can break down the chemical bonds in a polymeric material. This degradation process is called photo-degradation and ultimately leads to color changes, cracking, chalking, the loss of physical properties and deterioration of other properties. To explore the effect of sunlight exposure on the automotive materials, this study investigated photo-oxidation degree and surface property change of molding parts by analytical methods. For the further study, accelerated weathering test methods are proposed, which can correlate with out door weathering, to predict long term performance of automotive plastic materials.

• 한국전자거래학회지
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• 제4권3호
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• pp.43-62
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• 1999

This paper is to analyze business activities of approval/permission (A/P) and to describe its problems. To conduct the A/P business activities currently, there are many problems such as complex business process and different business policies among the each organization. In order to solve the problems, this paper suggests the A/P system of highway construction CALS (Commerce at Light Speed). CALS, a top down vision of complete computing integration, promises to support electronic data exchange. The A/P system is designed to classified documents based on CALS standard and store them to database. The data register to the A/P system by the Internet, and each construction company can use the A/P system by Internet also. Benefits of the A/P system is reduction in junk documents for approval/permission actives, improvement in conduct and services life cycle support.

• 소성∙가공
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• 제14권4호
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• pp.360-367
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• 2005

The injection-molded plastic parts have many surface defects: warpage, weldline, flowmark, zetting, scratching, shading and so on. As weldline was one of the major surface defects in the case of desktop monitor, warpage and surface shrinkage are the bigger problems of LCD monitor in the pursuit of light weight and thinner thickness of parts. Some measures to improve these defects were introduced in this paper. Based on these, the laboratory work to find out the optimum processing conditions and to get the best parts was repeated injection moulding try-out after reflecting these improvements. The defects of warpage and surface shrinkage was significantly improved after the improvements in the case of the 20.1 inch even if in the 15 and 17inch case the warpage size was a lttle over the allowed specification because of not taking the measure for parts design within the allowable limits from the required specification in the cause of cost down.