• Title/Summary/Keyword: emission mask

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Low Power On-channel Repeater for Terrestrial DTV Broadcasting Services(I) : Technical Regulations (지상파방송 난시청 해소를 위한 특정소출력 DTV 중계기(I): 기술기준연구)

  • Kwon, Won-Hyun
    • Journal of IKEEE
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    • v.16 no.3
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    • pp.244-250
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    • 2012
  • In this paper, worldwide standards and regulations on broadcasting services are reviewed to improve the fringe area of terrestrial DTV broadcasting services. Using these results, in-band/out-of-band emission requirements of low power DTV repeater with 10mW/MHz radiating power are proposed, and experimentally evaluated and verified. Using the proposed regulations, compact and cost-effective DTV repeater can be easily implemented to broaden DTV broadcasting coverage and to improve small/medium size DTV fringe areas.

Improvement in LED structure for enhanced light-emission

  • Park, Seong-Ju
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2003.11a
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    • pp.21-21
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    • 2003
  • To increase the light-emission efficiency of LED, we increased the internal and external quantum efficiency by suppressing the defect formation in the quantum well and by increasing the light extraction efficiency in LED, respectively. First, the internal quantum efficiency was improved by investigating the effect of a low temperature (LT) grown p-GaN layer on the In$\sub$0.25/GaN/GaN MQW in green LED. The properties of p-GaN was optimized at a low growth temperature of 900oC. A green LED using the optimized LT p-type GaN clearly showed the elimination of blue-shift which is originated by the MQW damage due to the high temperature growth process. This result was attributed to the suppression of indium inter-diffusion in MQW layer as evidenced by XRD and HR-TEM analysis. Secondly, we improved the light-extraction efficiency of LED. In spite of high internal quantum efficiency of GaN-based LED, the external quantum efficiency is still low due to the total internal reflection of the light at the semiconductor-air interface. To improve the probability of escaping the photons outside from the LED structure, we fabricated nano-sized cavities on a p-GaN surface utilizing Pt self-assembled metal clusters as an etch mask. Electroluminescence measurement showed that the relative optical output power was increased up to 80% compared to that of LED without nano-sized cavities. I-V measurement also showed that the electrical performance was improved. The enhanced LED performance was attributed to the enhancement of light escaping probability and the decrease of resistance due to the increase in contact area.

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Influence of surface geometrical structures on the secondary electron emission coefficient $({\gamma})$ of MgO protective layer

  • Park, W.B.;Lim, J.Y.;Oh, J.S.;Jeong, H.S.;Jeong, J.C.;Kim, S.B.;Cho, I.R.;Cho, J.W.;Kang, S.O.;Choi, E.H.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2003.07a
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    • pp.806-809
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    • 2003
  • Ion-induced secondary electron emission coefficient $({\gamma})$. of the patterned MgO thin film with geometrical structures has been measured by ${\gamma}$ - FIB(focused ion beam) system. The patterned MgO thin film with geometrical structures has been formed by the mask (mesh of ${\sim}$ $10{\mu}m^{2})$ under electron beam evaporation method. It is found that the higher ${\gamma}$. has been achieved by the patterned MgO thin film than the normal ones without patterning.

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Fabrication of Novel Metal Field Emitter Arrays(FEAs) Using Isotropic Silicon Etching and Oxidation

  • Oh, Chang-Woo;Lee, Chun-Gyoo;Park, Byung-Gook;Lee, Jong-Duk;Lee, Jong-Ho
    • Journal of Electrical Engineering and information Science
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    • v.2 no.6
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    • pp.212-216
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    • 1997
  • A new metal tip fabrication process for low voltage operation is reported in this paper. The key element of the fabrication process is that isotropic silicon etching and oxidation process used in silicon tip fabrication is utilized for gate hole size reduction and gate oxide layer. A metal FEA with 625 tips was fabricated in order to demonstrate the validity of the new process and submicron gate apertures were successfully obtained from originally 1.7$\mu\textrm{m}$ diameter mask. The emission current above noise level was observed at the gate bias of 50V. The required gate voltage to obtain the anode current of 0.1${\mu}\textrm{A}$/tip was 74V and the emission current was stable above 2${\mu}\textrm{A}$/tip without any disruption. The local field conversion factor and the emitting area were calculated as 7.981${\times}$10\ulcornercm\ulcorner and 3.2${\times}$10\ulcorner$\textrm{cm}^2$/tip, respectively.

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Feasibility study of improved median filtering in PET/MR fusion images with parallel imaging using generalized autocalibrating partially parallel acquisition

  • Chanrok Park;Jae-Young Kim;Chang-Hyeon An;Youngjin Lee
    • Nuclear Engineering and Technology
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    • v.55 no.1
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    • pp.222-228
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    • 2023
  • This study aimed to analyze the applicability of the improved median filter in positron emission tomography (PET)/magnetic resonance (MR) fusion images based on parallel imaging using generalized autocalibrating partially parallel acquisition (GRAPPA). In this study, a PET/MR fusion imaging system based on a 3.0T magnetic field and 18F radioisotope were used. An improved median filter that can set a mask of the median value more efficiently than before was modeled and applied to the acquired image. As quantitative evaluation parameters of the noise level, the contrast to noise ratio (CNR) and coefficient of variation (COV) were calculated. Additionally, no-reference-based evaluation parameters were used to analyze the overall image quality. We confirmed that the CNR and COV values of the PET/MR fusion images to which the improved median filter was applied improved by approximately 3.32 and 2.19 times on average, respectively, compared to the noisy image. In addition, the no-reference-based evaluation results showed a similar trend for the noise-level results. In conclusion, we demonstrated that it can be supplemented by using an improved median filter, which suggests the problem of image quality degradation of PET/MR fusion images that shortens scan time using GRAPPA.

Variable-color Light-emitting Diodes Using GaN Microdonut Arrays

  • Tchoe, Youngbin;Jo, Janghyun;Kim, Miyoung;Heo, Jaehyuk;Yoo, Geonwook;Sone, Cheolsoo;Yi, Gyu-Chul
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.280-280
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    • 2014
  • We report the fabrication and electroluminescent characteristics of GaN/InxGa1-xN microdonut-shaped light-emitting diode (LED) microarrays as variable-color emitters. The diameter, width, height, and period of the GaN microdonuts were controlled by their growth parameters and the geometrical factors of the growth mask patterns. For the fabrication of microdonut LEDs, p-GaN/p-AlxGa1-xN/u-GaN/u-InxGa1-xN heteroepitaxial layers were coated on the entire surface of n-GaN microdonuts. The microdonut LED arrays showed strong light emission, which could be seen with the unaided eye under normal room illumination. Additionally, magnified optical images of microdonut LED arrays exhibited microdonut-shaped light emissions having spatially resolved blue and green colors. Their electroluminescence spectra had two dominant peaks at 460 and 560 nm. With increasing applied voltage, the intensity of the blue emission peak increased much faster than that of the green emission peak, indicating that the color of the LEDs is tunable. We also demonstrated that EL spectra of the devices could be controlled by changing the size of microdonut LEDs. What we want to emphasize here with the microdonut LEDs is that they have additional inner sidewall facets which did not exist for other typical three-dimensional structures including nanopyramids and nanorods, and that InxGa1-xN single quantum well formed on the inner sidewall facets had unique thickness and chemical composition, which generated additional EL color. The origin of the electroluminescence peaks was investigated by structural characterizations and chemical analyses.

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Monitoring the failure mechanisms of a reinforced concrete beam strengthened by textile reinforced cement using acoustic emission and digital image correlation

  • Aggelis, Dimitrios G.;Verbruggen, Svetlana;Tsangouri, Eleni;Tysmans, Tine;Van Hemelrijck, Danny
    • Smart Structures and Systems
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    • v.17 no.1
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    • pp.91-105
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    • 2016
  • One of the most commonly used techniques to strengthen steel reinforced concrete structures is the application of externally bonded patches in the form of carbon fiber reinforced polymers (CFRP) or recently, textile reinforced cements (TRC). These external patches undertake the tensile stress of bending constraining concrete cracking. Development of full-field inspection methodologies for fracture monitoring are important since the reinforcing layers are not transparent, hindering visual observation of the material condition underneath. In the present study acoustic emission (AE) and digital image correlation (DIC) are applied during four-point bending tests of large beams to follow the damage accumulation. AE helps to determine the onset of fracture as well as the different damage mechanisms through the registered shifts in AE rate, location of active sources and change in waveform parameters. The effect of wave propagation distance, which in large components and in-situ can well mask the original information as emitted by the fracture incidents is also discussed. Simultaneously, crucial information is supplied by DIC concerning the moments of stress release of the patches due to debonding, benchmarking the trends monitored by AE. From the point of view of mechanics, conclusions on the reinforcing contribution of the different repair methodologies are also drawn.

Characterization and Preparation of the Hydrogel has Excellent Release Effect of the Active Ingredients Using a Radiation Cross-linking Technology (방사선 가교 기술을 이용한 유효성분 방출력이 우수한 하이드로겔 제조 및 특성 분석)

  • Hwang, Seung-Hyun;Ahn, Sung-Jun;Park, Jong-Seok;Jeong, Sung In;Gwon, Hui-Jeong;Lee, Dong Yun;Lim, Youn-Mook
    • Journal of Radiation Industry
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    • v.9 no.4
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    • pp.199-207
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    • 2015
  • Typical radiation cross-linked hydrogels has the characteristic that high water content, but low emission efficiency of active ingredients. Therefore, the hydrogel was prepared by the addition to collagen, which is closely related to the formation of skin wrinkles in biocompatibility and highly water-soluble carboxymethyl cellulose sodium salt (CMC) in order to preparation of hydrogels has excellent emission efficiency of active ingredients. Hydrogels were prepared by dissolving CMC and collagen each of 0.5%, 10% concentration in deionized water. Then, prepared hydrogels are performed by gamma-radiation at 1, 3, 5 kGy irradiation dose. The results showed that the gel fraction of after irradiated 3 kGy hydrogel was higher than before irradiated gelation as long as the 55.3%. The swelling rate of irradiated 3 kGy hydrogel was lower than the non-irradiated sample. The compressive strength of 3 kGy irradiated hydrogel was the highest. The visco-elastic did not show any significant differences, even after irradiation. The CMC hydrogel in this study suggested a potential use as a material for the mask pack for improved emission efficiency of the active ingredient and anti-wrinkles.

System Co-existence Analysis Using Monte-Carlo Method (몬테-카를로(Monte-Carlo) 방법을 적용한 시스템 양립성 분석)

  • KIm, Young-Hwan;Eo, Pill-Seon;Yang, Hoon-Gee;Park, Seung-Keun;Cho, Pyung-Dong
    • Proceedings of the IEEK Conference
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    • 2005.11a
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    • pp.193-196
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    • 2005
  • This paper presents a Monte-Carlo based method to obtain a probability of interference among systems. We show an efficient algorithm to calculate not only in-band interference for a given emission mask, but out-of-band interference, which depends on the blocking performance of a victim receiver filter. Applying the proposed method to an arbitrary system, we show the simulation results by Matlab and compare them with those by a SEAMCAT software

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Non-ideal filter interference calculation algorithm (Non-ideal 필터에 수신된 간섭전력 계산 방법)

  • Kim, Young-Hwan;Eo, Pil-Seon;Yang, Hoon-Gee;Shin, Hyun-Chol;Yang, Sung-Hyun
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.5 no.2 s.10
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    • pp.11-18
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    • 2006
  • In this paper, we present the algorithm for calculating the interference of the received Non-ideal receiver filter and present the method for calculating the interference faster than that of the conventional method. The algorithm is simulated by Matlab and the simulation procedure is described by the flow-chart. The algorithm is verified by comparing the simulated results by Matlab with the result by calculator.

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