• Journal of Korean Elementary Science Education
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• v.23 no.1
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• pp.27-36
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• 2004

This paper aims to examine how well university students, who are going to be primary school teachers, understand the International System of Units (SI), focusing on seven basic units such as 'm', '㎏', '㏖', 'A', 'K', 's', 'cd'. This study specifically investigates whether the students know the seven units and understand their uses and how they read and learn them. The subjects were 1030 students from the University of Education in Jinju, Geongsangnamdo. Data was collected through a questionnaire which was designed by this researcher and checked by an authority, and the frequency and percentage of reponses to each question were obtained and analysed. Findings show all the students knew very well that 'm' and '㎏' are included in the seven units, compared to the others which low percentage of the students considered as the elements. In terms of understanding of use, the units of the length 'm', the mass '㎏', and the time 's' are well understood, presumably, because they are often used in ordinary life and school, while the amount of substance '㏖', the electric current 'A', the thermodynamic temperature 'K', and the luminous intensity 'cd' are not as well understood. It is probably because 'A', 'cd', and 'K' are hardly used in everyday life. With respect to reading the units, the subjects read 'm', '㎏', '㏖', and's' much better than the others. As for the source of learning them, most students answered they learned them in schools, which implies school education is very important. From these results it is concluded that school education should be accompanied with use in everyday life for understanding and using the units. SI Base Units understanding was investigated by an academic year. According to this investigation, generally the right answer rate differed 4<2<3<1 by an academic year in order. For the Senior, Sophomore appeared the right answer rate more high. because, they learned before in deepening or elementary course on chemistry and physics related with SI Base Units. On the other hand, for the junior answered low rate by this reason that they couldn't remember about SI Base Units that learned before. For the Freshman appeared low rate by this reason that they were not learned or graduated from the department of liberal art in high school.

• Korean Journal of Optics and Photonics
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• v.25 no.2
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• pp.78-84
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• 2014

In this paper secondary optics for an LED lamp with a narrow beam angle of $15^{\circ}$ were optimized by using a two-reflector system, to reduce both its size and the occurrence of satellite rings. The conic constant and the curvature of the primary reflector were determined by considering the relation of the source size to the beam angle, and the optimal position and radius of the secondary reflector were found for reducing the occurrence of satellite rings. Luminous flux efficiency was about 80%.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.36.1-36.1
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• 2020

The progenitor of Type Ia supernovae (SNe Ia) is mainly believed to be a carbon/oxygen white dwarf (WD) with non-degenerate (single degenerate) or another WD companion (double degenerate). However, there is little observational evidence of their progenitor system. Recent studies suggest that shock-breakout cooling emission after the explosion can constrain the size of the progenitor system. To do so, we obtained a optical/Near-IR light curve of SN 2019ein, a normal but slightly sub-luminous type Ia supernova, from the very early phase using our high-cadence observation of Intensive Monitoring Survey of Nearby Galaxies (IMSNG). Assuming the expanding fireball model, the simple power-law fitting of the early part of the light curve gives power indices of 1.91 (B) and 2.09 (R) implying radioactive decay of 56Ni is the dominant energy source. By comparison with the expected light curve of the cooling emission, the early observation provides us an upper limit of the companion size of R∗≤1R⊙. This result suggests that we can exclude a large companion such as red giants, which is consistent with the previous study.

• Journal of Fashion Business
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• v.13 no.6
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• pp.61-75
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• 2009

The objective of this research is to the enhance the color function of work clothing : to research and analyze the hue and tone of work clothing colors to be used for machinery and heavy industries in national industrial complexes, Through this research, the color using problems which related with safety workers will be revealed. For this project, total 42 sets of work suits were sampled from 12 different companies in the machinery and construction industries in the national industrial complexes of Gyeongsang Namdo Province and 16 sets of work suits currently being sold in the market. The collected work suits samples were classified according to item types and design. Color measurements were taken thus: After calibration according to ASTM D1729 specifications of standardized configuration settings to match standardized luminous source D65(Daylight 6500K) in color cabinet BOTECK SuperLight-VI, the RGB values of the work suits were calculated using PANTONE Color Cue TX. The RGB values of the colors thus derived were converted into V/C values using the Munsell Conversion 9.0.6 and analyzed with Munsell's 10-color system and PCCS. The results were presented according to Munsell's color wheel and color and brightness distributions were expressed in table form, as well as presented as a tone map. Following analysis, color hue distribution was found to be concentrated around PB, and brightness distribution toward the low end and mid range of the scale. Saturation values were distributed mostly around the low end of the scale. Following color tone analysis according to PCCS, it became apparent that colors were mainly distributed around dkg, ltg, and g, at low- and mid-brightness and low-saturation. Therefore, it may be concluded that colors used in work suits in the machinery and heavy industries are mainly cool colors, at low- and mid-brightness and low saturation. It is conjectured that such colors were applied uniformly in the workplace in order to serve certain functions, such as concealment of stains and contamination. Therefore, it follows that the utilization of colors, among other functions served by working clothings, must be taken into consideration in order to enhance safety and efficiency.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.231-238
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• 2011

Variable message signs(VMS) in use are being displaying with the LED device as the luminous source, and it is a recent trend to be changed from the Lamp type to the Surface-Mount Devices(SMD) type. The LED device leads to get VMS display brightly and clearly, leading to have visibility and legibility better than the existing VMS. However, the lights which display off the road, the unnecessary energy, might have negative effect on ecosystem. This study developed the way of getting the lights be displayed only to drivers without the unnecessary energy and estimated the energy efficiency of the development by the optical testing. As a result, this study showed that the energy consumption of the developed display device appeared to decrease by about 36.1% compared to the existing device. Also the upward and downward angle of the lights changed from an angle of $24^{\circ}C$ to $0^{\circ}C$and from an angle of $-24^{\circ}C$ to $-11^{\circ}C$, respectively. Therefore, it anticipates that the developed device would benefit highway safety due to an improvement in visibility and legibility compared to the existing VMS and the energy consumption would be less lower than the existing VMS.

• Journal of Radiation Protection and Research
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• v.37 no.1
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• pp.10-15
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• 2012

Design and performance test results of a newly developed optically stimulated luminescence (OSL) measurement system are presented in this paper. Generally, different types of optical filters are used in OSL reader system to minimize the interference of the stimulation light in the OSL signal. For optically stimulation of $Al_2O_3:C$, we have arrived at an optimal combination of the filters, i.e., GG420 filter for filtering the stimulating light source, and a combined UG11 and BG39 filter at the detecting window (PMT). By using a high luminance blue LED (Luxeon V), sufficient luminous intensity could be obtained for optically stimulation. By using various control boards, the OSL reader device was successfully interfaced with a personal computer. A software was developed to deliver required commands to operate the OSL reader by using the LabView program (National Instruments, Inc.). In order to evaluate the reliability and the reproducibility of newly designed-OSL reader. Performance testing of the OSL reader was carried out for OSL efficiency, OSL decay curve and signal to noise ratio of the standard $Al_2O_3:C$ OSL material. It was found to be comparable with that of commercial Riso reader system.

• Journal of The Korean Astronomical Society
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• v.47 no.6
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• pp.235-253
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• 2014

Intensity interferometry, based on the Hanbury Brown-Twiss effect, is a simple and inexpensive method for optical interferometry at microarcsecond angular resolutions; its use in astronomy was abandoned in the 1970s because of low sensitivity. Motivated by recent technical developments, we argue that the sensitivity of large modern intensity interferometers can be improved by factors up to approximately 25 000, corresponding to 11 photometric magnitudes, compared to the pioneering Narrabri Stellar Interferometer. This is made possible by (i) using avalanche photodiodes (APD) as light detectors, (ii) distributing the light received from the source over multiple independent spectral channels, and (iii) use of arrays composed of multiple large light collectors. Our approach permits the construction of large (with baselines ranging from few kilometers to intercontinental distances) optical interferometers at the cost of (very) long-baseline radio interferometers. Realistic intensity interferometer designs are able to achieve limiting R-band magnitudes as good as $m_R{\approx}14$, sufficient for spatially resolved observations of main-sequence O-type stars in the Magellanic Clouds. Multi-channel intensity interferometers can address a wide variety of science cases: (i) linear radii, effective temperatures, and luminosities of stars, via direct measurements of stellar angular sizes; (ii) mass-radius relationships of compact stellar remnants, via direct measurements of the angular sizes of white dwarfs; (iii) stellar rotation, via observations of rotation flattening and surface gravity darkening; (iv) stellar convection and the interaction of stellar photospheres and magnetic fields, via observations of dark and bright starspots; (v) the structure and evolution of multiple stars, via mapping of the companion stars and of accretion flows in interacting binaries; (vi) direct measurements of interstellar distances, derived from angular diameters of stars or via the interferometric Baade-Wesselink method; (vii) the physics of gas accretion onto supermassive black holes, via resolved observations of the central engines of luminous active galactic nuclei; and (viii) calibration of amplitude interferometers by providing a sample of calibrator stars.

• Journal of Digital Convergence
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• v.14 no.4
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• pp.419-424
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• 2016

In this paper, we studied a light distribution for the LED chips arrangement using an optical design software. The structures of the edge type LED luminaires are reflector plane, LGP(lighting guide plane) and diffuse plane. The reflector plane is on the middle of the overall structure. We had simulation that placing LED chips on the reflector center of the reflector edge by changing the position of LED chips above the reflector center at 1mm, 2mm, and 3mm respectively. In the case, when LED chips are on the center of the reflector, it shows the light distribution of the general diffuse illumination, the semi-direct distribution with 0.56 efficiency and the direct distribution with 0.31 efficiency. And the wedge type LGP shows more efficiency than the flat type. Gradually increasing shape of semi-spherical type by 0.015mm has power of 1.02W, efficiency of 0.25, and maximum luminous intensity of 0.104W/sr, it also and shows the better optical characteristics than the reflector plane that have no patterns. This semi-spherical type shows the better optical characteristics than the reflector plane that have no patterns.

• Journal of Radiation Protection and Research
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• v.40 no.1
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• pp.46-54
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• 2015

The thermoluminescence (TL) and optically stimulated luminescence (OSL) are commonly used to measure and record the expose of individuals to ionization radiation. Design and performance test results of a newly developed TL and OSL measurement system are presented in this paper. For this purpose, the temperature of the TL material can be controlled precisely in the range of $1{\sim}1.5^{\circ}C$ by using high-frequency (35 kHz) heating system. This high-frequency power supply was made of transformer with ferrite core. For optical stimulation, we have completed an optimal combination of the filters with the arrangement of GG420 filter for filtering the stimulating light source and a UG11 filter at the detecting window (PMT). By using a high luminance blue LED (Luxeon V), sufficient luminous intensity could be obtained for optical stimulation. By using various control boards, the TL/OSL reader device was successfully interfaced with a personal computer. A software based on LabView program (National Instruments, Inc.) was also developed to control the TL/OSL reader system. In this study, a multi-functional TL/OSL dosimeter was developed and the performance testing of the system was carried out to confirm its reliability and reproducibility.

• Journal of IKEEE
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• v.21 no.4
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• pp.368-374
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• 2017

In this Paper, we developed a low power type LED security light using LED lighting that substitutes a 220[V] commercial power source for a solar cell module instead of a halogen or a sodium lamp. in addition, a PWM type drive control circuit is designed to minimize the heat generation problem and the drive current of the LED drive controller. in developed system, The light efficiency measurement value is 93.6[lm/W], and a high precision temperature sensor is used inside the controller to control the heat generation of the LED lamp. In order to eliminate the high heat generated from the LED lamp, it is designed to disperse quickly into the atmosphere through the metal insertion type heat sink. The heat control range of LED lighting was $50-55[^{\circ}C]$. The luminous flux and the lighting speed of the LED security lamp were 0.5[s], and the beam diffusion angle of the LED lamp was about $110[^{\circ}C]$ by the light distribution curve based on the height of 6[m].