• Title/Summary/Keyword: Total luminous flux

Search Result 15, Processing Time 0.02 seconds

Fabrication and analysis of luminous properties of ceramic phosphor plate for high-power LED (High-power LED용 ceramic 형광체 plate 제조 및 발광 특성 분석)

  • Ji, Eun-Kyung;Song, Ye-Lim;Lee, Min-Ji;Song, Young-Hyun;Yoon, Dae-Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.25 no.1
    • /
    • pp.35-38
    • /
    • 2015
  • LEDs are considered to be an alternative for enhancement of energy efficiency, applied for numerous areas such as display, automotive headlight not only lights. Yellow phosphor is generally utilized with blue LEDs to generate WLED, $Y_3Al_{5}O_{12}:Ce^{3+}$ is typically used as the yellow phosphor. The phosphor, mixed with epoxy resin, has been used by being spread and hardened on the blue LED chip. This paste-based packaging gives rise to problems of degradation of phosphor by heat and decrease of luminous efficiency. Although phosphor plate is used instead of the epoxy-phosphor mixture to solve these problems, loss of luminous efficacy by total internal reflection inside the plate also should be solved. In this study, we coated the side of the plate with silver as one of the solution.

LONG-TERM X-RAY VARIABILITIES OF THE SEYFERT GALAXY MCG-2-58-22 : SECULAR FLUX DECREASE AND FLARES

  • CHOI CHUL-SUNG;DOTANI TADAYASU;CHANG HEON- YOUNG;YI INSU
    • Journal of The Korean Astronomical Society
    • /
    • v.35 no.1
    • /
    • pp.1-7
    • /
    • 2002
  • We have studied the long-term X-ray light curve (2-10 keV) of the luminous Seyfert 1 galaxy MCG-2-58-22 by compiling data, from various X-ray satellites, which together cover more than 20 years. We have found two distinct types of time variations in the light curve. One is a gradual and secular decrease of the X-ray flux, and the other is the episodic increase of X-ray flux (or flare) by a factor of 2-4 compared with the level expected from the secular variation. We detected 3 such flares in total; a representative duration for the flares is $\~$2 years, with intervening quiescent intervals lasting $\~$6-8 years. We discuss a few possible origins for these variabilities. Though a standard disk instability theory may explain the displayed time variability in the X-ray light curve, the subsequent accretions of stellar debris, from a tidal disruption event caused by a supermassive black hole in MCG-2-58-22, cannot be ruled out as an alternative explanation.

Discoloration Effects of LEDs on Painting Binder Materials (LED광원에 의한 회화 전색제의 변색 영향 연구)

  • Kim, Ji Won;Lee, Yu Jung;Kim, Kyu Lin;Lee, Hwa Soo;Kang, Dai Ill
    • Journal of Conservation Science
    • /
    • v.34 no.2
    • /
    • pp.77-85
    • /
    • 2018
  • In order to understand the influence of light artifact discoloration, priority must be given to the reaction characteristics of the light the materials constituting the product. In this study, we focus on two representative medium, animal glue and linseed oil which constitute the colored layer of the painting relics. This study is based on an accelerated degradation test using two types of light emitting diods (LEDs) with different wavelength characteristics. In the experiments, discoloration appeared markedly in the animal glue and linseed oil under accelerated aging test conditions using Blue LED. Among the two types of LEDs, the degree of discoloration of the material was much higher with the Blue LED having the total radiation flux (mW). This indicates that the discoloration of painting artifacts such as animal glue and linseed oil is more significantly influenced by the total radiation flux (mW) of the light source than the total luminous flux (lm).

Morphological research on radio loud AGN 4C39.25 using KaVA observation

  • Yoo, Hyemin;Sohn, Bong Won;Yi, Sukyong K.
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.40 no.2
    • /
    • pp.36.3-37
    • /
    • 2015
  • 4C39.25 (0923+392) is a distant radio loud AGN placed at redshift 0.695. The motivation of our work is peculiar properties 4C39.25. Firstly, it has a conspicuous distinction of jet direction between kilo-parsec scale observation made by VLA (Kollgaard et al. 1990) and the parsec scale observation by VLBA (Kellermann et al. 1998). This might indicate episodic-jet activity which recently turned on. This object currently shows two stationary compact parsec-scale components which are bright jet component on east and less luminous core on west. Also, it is known that there have been superluminal jet components which are flowing from the core toward east, and then merging with the bright jet component (Marscher et al. 1991, Alberdi et al. 2000, Lister et al. 2013). Although 4C39.25 seems to be a blazar-like source having broad emission lines (SDSS) and superluminal motion, its property that jet component is brighter than the core is different from ordinary blazars. Furthermore, it has young radio galaxy-like properties such as non-variation in total flux (Alberdi et al. 1997, 2000, MOJAVE database) and high frequency peak at spectral energy distribution (Orienti et al 2007). Such complex properties led us to make recent observations to reveal precise properties and new changes of the source. We used Korean VLBI Network (KVN) and VLBI Exploration of Radio Astronomy (VERA) Array (KaVA) which provide high-frequency (23GHz and 43GHz) and high spatial resolution (1.2mas and 0.6mas). Therefore, this system is suitable for morphological and physical research on parsec scale structure. We present results for several epochs observed during 2013 to 2014, mainly focusing on morphological changes of 4C39.25 using KaVA images.

  • PDF

Improving the Calculation Speed of Ray-tracing Based Simulator for Analyzing an Integrating Sphere with OpenMP Directive and Guaranteeing the Randomness of Monte Carlo Method (광선추적법 기반의 적분구 분석 시뮬레이터에서 OpenMP 지시어를 이용한 속도 향상 및 몬테카를로 방법의 무작위성 보장)

  • Kim, Seung-Yong;Kim, Dae-Chan;O, Beom-Hoan;Park, Se-Geun;Lee, El-Hang;Lee, Seung-Gol
    • Korean Journal of Optics and Photonics
    • /
    • v.22 no.2
    • /
    • pp.83-89
    • /
    • 2011
  • In order to improve the calculation speed of an integrating-sphere simulator based on a ray-tracing method, parallel processing with OpenMP directive was implemented into the simulator and the randomness of Monte Carlo method was guaranteed by utilizing a parallel random number generator. It was confirmed that simulation results obtained with more than $10^7$ rays showed good agreement with theoretical results within the error range of 0.5%, and that the calculation speed improved as the number of threads increased. Finally, the spatial response distribution functions of a real integrating sphere were simulated and compared with previous results.