• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.8
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• pp.7-17
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• 2015

Changes in melatonin concentration levels by differences in CCT of white LED light focused on Spectral Power Distribution (SPD) differences compared to the same CCT of conventional fluorescent light were analyzed. For this, melatonin concentration levels in saliva samples were taken over four different experiments at seven-day intervals. In 71.4% of participants, it was confirmed that melatonin concentration is suppressed by exposure to light, and a slight difference was observed by different CCTs. In addition, Experiment II with a high CCT was relatively high in terms of the melatonin suppression rate compared to Experiment III. A key finding was the possibility that different SPDs under a particular CCT of white LED light compared to the same CCT of conventional fluorescent light could have the same effect on the melatonin suppression.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.6 no.5
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• pp.19-26
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• 1992

A computer program to calculate the illumination distributions of a room interior was made. The room has a light source with arbitrary intensity distribution. The program follows the paths of the particles from the light sources, and the illumination distribution is calculated by repeating this following to many particles. Monte Carlo method is applied to the decision of the direction of the particle from light source, and the new direction of the reflected particles. Making simulation program on this basis, illumination distributions were measured for various light sources and wall surfaces tocertify the calculated results. As a results, it is known that the calculated distribution would be correct if the size of the light source is sufficiently smaller than the size of the room.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.8
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• pp.395-401
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• 2015

Recently, many research studies have been carried out on the efficiency of light-shelf daylighting systems, especially comparing performance improvements and the limitations of reflective surfaces and their lighting performance. In this study, a crystal face reflective surface is proposed. The objective of the study is to evaluate the lighting performance of a crystal face light-shelf through a performance study. The performance study was carried out in a full scale test-bed in order to calculate the light distribution and energy consumption utilizing the standard indoor illumination as an index. The conclusions of the performance study are as follows. 1) The optimal angle of incidence for daylighting for both the operable flat type light-shelf and the crystal face light-shelf are taken in the natural environment on the dates of the winter and summer solstices, as well as the autumn and spring equinoxes. 2) The application and installation of the crystal face light-shelf can produce a 29.9%~34.3% increase of light distribution within the indoor space. However, the increase of light distribution can also lead to a decrease in the uniformity ratio, a design challenge that should be considered when applying a crystal face light-shelf. 3) It is possible to achieve a 7.98%~13.3% greater reduction in energy consumption when applying a crystal face light-shelf than when applying a flat type light-shelf. The increase in the number of crystal faces should concur with the analysis of the energy reduction. A limitation of the study is that only one predetermined pattern was performance tested for a crystal face light-shelf. In order to carry out further research on crystal face light-shelves, additional performance studies are needed based on alternative patterns and designs.

• Korean Journal of Optics and Photonics
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• v.29 no.6
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• pp.253-261
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• 2018

In this paper, we study a method of designing a reflector for LED light sources with an asymmetric light distribution. In a sports game, lighting with a symmetric distribution makes the athlete and spectators look directly at the light source, so it can cause glare. We derive the optimal tilt angle and design a reflector with asymmetric light distribution to solve these problems. Afterward, performance is analyzed according to the tennis-court lighting standard, and is confirmed to meet the class 1 European standard.

• Tribology and Lubricants
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• v.17 no.6
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• pp.482-489
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• 2001

Changes in light transmission characteristics caused by various types of oil contaminations were experimentally measured with a built-in type wear monitoring device. Three kinds of iron powders of different size distribution, carbon duct, two kinds of solutions and grease were used for the test contaminants in this work. Light intensity of the transmitted light was measured with the contamination level. Results showed that the transmitted light intensity decreased linearly with the contamination concentration in the oil and the slope was affected by the size distribution. Light attenuation was also caused greatly by carbon dust, water contamination and poly-meric fibers in terms of the light absorption. As a result, it was proved that the optical measurement device could be applicable effectively for detecting any significant change in lubricating oils.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.287-298
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• 2001

Change in light transmission characteristics caused by various types of oil contaminations was experimentally measured with a built-in type wear monitoring device. Three kinds of iron powders of different size distribution, carbon dust, two kinds of solutions and grease were used for the lest contaminants in this work. Light intensity of the transmitted light was treasured with the contamination level. Results showed that the transmitted light intensity decreased linearly with the contamination concentration in the oil and the slope was affected by the size distribution. Light attenuation was also caused greatly by carbon dust, water contamination and polymeric fibers mainly due to the light absorption. As a result, it was proved that the optical measurement device could be applicable effectively for detecting any significant change iii lubricating oils.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.48.2-48.2
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• 2019

Light from universe is absorbed, scattered, and re-released by interstellar dust before it reaches us. Therefore, accurate correction of the observed light requires not only spatial distribution of interstellar dust, but also information on absorption and scattering for each wavelength. Far-ultraviolet (FUV) light is mainly produced by bright, young O-type and some B-type stars, but it is also observed in interstellar space without these stars. Called FUV Galactic light (DGL), these lights are mostly known as starlight scattered by interstellar dust. With the recent release of GAIA DR2, not only accurate distance information of stars in our Galaxy, but also accurate three-dimensional distribution maps of interstellar dust of our Galaxy were produced. Based on this, we performed 3-dimensional Monte Carlo dust scattering radiative transfer simulations for FUV light to obtain dust scattered FUV images and compared them with the observed FUV image obtained by FIMS and GALEX. From this, we find the scattering properties of interstellar dust in our Galaxy and suggest the intensity of extragalactic background light. These results are expected to aid in the study of chemical composition, size distribution, shape, and alignment of interstellar dust in our Galaxy.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.149-153
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• 2001

A study on the particle growth in $TEOS/O_2$ plasma was performed, and particle size and its distribution was measured by the electrical aerosol analyzer (EAA), light scattering particle size analyzer and the particle size was also determined by SEM. The effects of process variables such as total gas flow rate, reactor pressure, supplied power and initial reactant concentration on the particle growth were investigated. From the EAA results, the particle size distribution is divided into three groups of the cluster size and the small and large size particles. The particle size distribution measured by the light scattering particle size analyzer becomes bimodal, because the cluster size particles smaller than 20 nm in diameter cannot be detected by the light scattering particle size analyzer. The size of particles measured by the light scattering particle size analyzer is in good agreements with those by the SEM. Also we could understand that the particle formation is very sensitive to the changes of reactor pressure and reactant concentration. As the total gas flow rate increases, the particle size decreases because of the shorter residence time. As the reactor pressure, or the reactant concentration increases, the particle concentration increases and the particles grow more quickly by the faster coagulation between particles.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.5
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• pp.303-309
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• 2017

In this study, the characteristics of the temperature generated by light irradiation, on the surface of a biological tissue with an abnormal tissue part (paraffin) and at the surroundings of the abnormal tissue were studied by numerical and experimental methods. The temperature in the tissue was solved using the computational heat transfer and was compared with the temperature measured with thermocouples. The effects of the light wavelength and the irradiation time on the temperature distribution were analyzed. As a result, the temperature distribution from the irradiation of light in the biological tissue was different when there was an abnormal tissue part. The temperature in the biological tissue with the abnormal tissue part was higher than in a normal tissue.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.10 no.4
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• pp.53-61
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• 1996

A distribution photometer was constructed to measure the angular distribution of luminous intensity of light sources and the reflected luminance of retroreflectors. This system incorporates a goniometer to rotate test light source(360 degree in yaw rotation and $\pm$30 degree in pictch rotation), a photomultiplier tube as light detector, light projector for retroreflection measurements, and the control and display unit. The ranges of luminous Intensity measurements and observation angles are 0.01~199900 cd and 0.2~1.5 degree respectively. The uncertainty of luminous intensity measurements is $\pm$3%. This paper describes the construction of the distribution photometer and the performance characteristics.