• Current Optics and Photonics
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• v.2 no.4
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• pp.308-314
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• 2018

Visible light communication (VLC) is considered a strong future candidate for indoor wireless communication. However, its performance seems to be relatively unsatisfactory when compared to wireless local area network (WLAN) communication using millimeter waves. To improve the performance of VLC, numerous technologies have been proposed so far, in both electrical and optical domains. Among the proposals, optical beamforming (OB) is an optical-domain technology that can concentrate light in a specific direction or on a target spot. It can significantly improve VLC performance and can be widely used, because it does not depend on electrical modulation schemes. Therefore, this review discusses the concept, principle, and types of OB, the structure of a VLC system using OB, performance results of OB, and the combination of OB with electrical signal modulation in VLC. OB is expected to be one of the key techniques in future VLC implementations, similar to radio-frequency beamforming in millimeter-wave communication.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.737-741
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• 2001

An illumination system by using sun light is optimally designed. The developing system consists of main controler for sun tracking, Cds sensor module, and light translation system based on optical fiber. A sun tracking algorithm is designed in such away that the illumination system stand with straight angle to the direction of sun within $\pm$2$^{\circ}$as permissible tolerance. To show the validity of the developed system, several experiments will be illustrated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.487-490
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• 1999

The Maxwell displacement current was generated from 4-octyl-4'-(5-carboxyl-pentamethyleneoxy)- azobenzene (denoted as 8A5H) monolayer Langmuir-Blodgett films prepared on Cr/Au-coated glass substrates due to trans-cis photoisomerization of 8A5H by application of alternate irradiation with UV light and Visible light. The displacement current was generated due to the trans-to-CIS photoisomerization by irradiation with ultraviolet light($\lambda_1$=360nm). Whereas the displacement current was generated in the opposite direction due to the cis-to-trans photoisomerization by photoirradiation with visible light($\lambda_2$=450nm). Finally, We concluded that Displacement current change according to power capacity photoirradiation, the more higher generate the more higher power capacity magnitude.

• Journal of Korea Multimedia Society
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• v.20 no.4
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• pp.713-720
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• 2017

We present a non-photo realistic pen-ink drawing method for outlining and shading of the input image. Especially, we focus on the detailed illustration of the image of which stroke's direction is important. The pen-ink renderer is an alternative display models user can generate traditional illustration renderings of their photo realistic image. The previously proposed pen drawing methods produce feasible description in general image but it is difficult to express in detail for the sophisticated images that need to consider the direction of stroke for each image region. In order to overcome the disadvantages of the conventional method, a direction vector is extracted from a tensor field and we determine a stroke's direction in consideration of not only an edge area but also a gradient of a surrounding area in the image. For more detailed description for the sophisticated image, we generate white noises based on the light and shade of the input image and determine the direction and length of the stroke by using the tensor field for each generated white noise. The proposed method works particularly well for traditional architectural images where the direction and detailed description of the pen is important.

• Journal of Bio-Environment Control
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• v.5 no.2
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• pp.152-159
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• 1996

Experiment was performed in a newly developed wind tunnel with light system to determine the aerodynamic resistance and eddy diffusivity above the plug stand under artificial light. Maximum air temperature appeared near the top of the plug stand under artificial light. Since Richardson number was ranged from -0.07 to +0.01, the atmosphere above the plug stand in wind tunnel was in an unstable or near- neutral stability state. The average aerodynamic resistance at rear region of plug stand was 25 % higher than that at middle region. Eddy diffusivity($K_{M}$) linearly increased with the increasing air current speed. $K_{M}$ at air current speed of 0.9 m.$s^{-1}$ was about two times as many as that at air current speed of 0.3 m.$s^{-1}$. And average $K_{M}$ at the rear region was 15% lower than that at the middle region. These results indicated that the diffusion of heat and mass along the direction of air current inside the plug stand was different. It might cause the lack of uniformity in the growth and quality of plug seedlings. The wind tunnel developed in this study would be useful to investigate the effects of air current speed on microclimates and the growth of plug seedlings under artificial light in a semi- closed ecosystem.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.582-588
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• 2014

We study polarization-dependent spontaneous emission (SE) rate and light extraction efficiency (LEE) in localized-surface-plasmon (LSP)-coupled light emitting diodes (LEDs). The closely packed seven $Ag/SiO_2$ core-shell (CS) nanoparticles (NPs) lie on top of the GaN surface for LSP coupling with a radiated dipole. According to the dipole direction, both the SE rate and the LEE are significantly modified by the LSP effect at the $Ag/SiO_2$ CS NPs when the size of Ag, the thickness of $SiO_2$, and the position of the dipole source are varied. The enhancement of the SE rate is related to an induced dipole effect at the Ag, and the high LEE is caused by light scattering with an LSP mode at $Ag/SiO_2$ CS NPs. We suggest the optimum position of the quantum well (QW) in blue InGaN/GaN LEDs with $Ag/SiO_2$ CS NPs for practical application.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.10
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• pp.7-16
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• 2015

This study is intending to look into the status of the hitherto established local governments light pollution control ordinance, and to use the ordinance status as basic data of ordinance enactment related to light pollution in time of its establishment and revision in accordance with regional characteristics of each local government for the time to come. This study conducted this research in a total of 3-phase research methods. 1) This study inquired into the direction of the research plan through the theoretical consideration and analysis of the preceding researches after setting up research objectives according to research background and purpose. 2) Targeting 11 local governments which are enforcing the hitherto established ordinance, this study surveyed the status of the light pollution control ordinance. 3) This study carried out the contents analysis of the ordinance in the method of doing a comparative analysis of each provision of the ordinance according to local governments. It's hoped that on the basis of this research, local governments across the nation, which have not yet established the same ordinance, could minimize the damage to natural eco-system due to artificial lighting by promoting the urgent ordinance establishment suited for each region, and create human-oriented light environment by modifying various disorderly lighting environment.

• The Journal of Korean Physical Therapy
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• v.24 no.2
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• pp.134-142
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• 2012

Purpose: This study examined the effect on postural control during the stimulation of haptic touch with fingertip on the stable surface at quiet standing posture, squat flexion stage, 60 degrees squat stage and squat extension stage. Methods: The postural sway was measured on the force platform, while 30 subjects were squatting, under three different haptic touch conditions (No Touch [NT], Light Touch [LT], Heavy Touch [HT]), above the touch pad in front of their body midline. Three different haptic touch conditions were divided into 1) NT condition; squatting as right index fingers held above the touch pad, 2) LT condition (<1N); squatting as the touch pad was in contact with right index fingers pulp with a pressure not exceeding 1N and 3) HT condition; squatting as subjects were allowed to use the touch pad for mechanical support by transmitting onto it with as much force, choosing with their index fingers. Results: There was significant decrease in LT, rather than that of NT (p<0.01), and in HT, rather than that of LT (p<0.01), as the results of the distance and velocity of center of pressure (COP) in mediolateral direction at quiet standing position. In anteroposterior direction, the distance and velocity of COP in LT and HT showed significant decrease, when compared to that of the data of NT (p<0.01). There was no significant difference between the 3 conditions (NT, LT, and HT), with respect to the distance and velocity of COP in mediolateral direction, during dynamic balance (squat flexion stage, squat extension stage) (p>0.05). In anteroposterior direction, the results of the distance and velocity of COP in HT showed significant decrease when compared to that of the data of NT (p<0.05). Conclusion: Light touch, during the task, decreased the postural sway at static balance. The results suggest that haptic touch should be applied, appropriately, because it varies the effects according to different conditions.

• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.429-437
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• 2017

Micro hollow plate type silica with low refraction properties was synthesized and its hollow structure was applied as an optical structure to develop a light diffusion material that simultaneously satisfies the requirements of good light diffusibility, high transmissibility, and high luminance. The developed light diffusion material was applied to a light diffusion film and the film's optical properties were assessed. Hollow silica was synthesized by precipitation method using $Mg(OH)_2$ core particles, sodium silicate, and ammonium sulfate as the silica precursors. The concentration of the silica precursor was adjusted to control hollow silica shell thickness. The total light transmittance of the light diffusion film composed of the hollow silica was 94.55%, which was 4.57% higher than that of the PC film; new film's haze was 71.20%, which was 70.9% higher. Furthermore, the luminance increased by 5.34% compared to that of the light source. The reason for the results is not only that the micro plate type hollow silica, which has a low refractive property, played a role in reducing the difference in refractive index between the medium boundaries, but also that there was a light-concentrating effect due to the changing of light paths to the front direction inside the hollow structure. Optical simulation verified the enhanced optical properties when hollow silica was applied to the light diffusion film.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.6
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• pp.275-286
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• 2014

Light shelf is an efficient system that reduces the energy consumption by bringing the natural light down to the deep spaces inside of a building. However, the existing light shelves have limits in reducing energy usage, because the direction of the light flow is determined by the external environment such as the altitude of the sun and the azimuth. This current study presents a system that increases the efficiency of the light shelf by applying the Location-Awareness technology, in which the efficiency was verified through the performance evaluation. According to the examination of the technology for the Location-Awareness within residential space, 'Zigbee' type appears to be the most appropriate. The Location-Awareness technology operates the light shelf based on both the angle control axis and the light shelf angle control axis through the modularization of the reflector surface which is less affected by the external environment. The results of the performance evaluation showed that the movable light shelf that employs the Location-Awareness technology can reduce the energy consumption for lighting by 98.3% compared to the fixed light shelf and by 97.3% compared to the movable light shelf without Location-Awareness.