• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.66-76
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• 2005

In this study, star visibility analysis of a star tracker is performed by using a statistical apprach. The probability of the Sun and the Earth proximity, the solar array masking probability, and the solar array blinding probability by the Sun light are obtained from the arbitrary chosen satellite positions as a function of a line of sight vector of the star tracker in several satellite attitude modes. This analysis demonstrates that the optimized star tracker accomodations can be determined to be an elevation angle -40o and two azimuth angles $-35^{circ}$ and $-150^{circ}$.

• Journal of Photoscience
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• v.9 no.2
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• pp.436-438
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• 2002

Since solar radiation contains wavelength essential for photosynthesis accompanying with near-UV light, UV-B effects on biological parameters and acclimation mechanisms are influenced by photosynthetically active radiation (PAR). Therefore, to elucidate near-UV shielding mechanism in higher plants, we cultivated cauliflower under usual solar radiation and increased UV-B from fluorescent lamps, two- or three-fold excess over continuously estimated UV-B dose in PAR during daytime, using computer regulated systems. Increased UV-B radiation had little effect on growth expressed as fresh weigh and leaf area. Water soluble low molecular weight compounds showing absorption in near UV region were enhanced according to the irradiated UV-B dose. One of compounds in cauliflower leaves was identified as chlorogenic acid. This was found to have no near-UV photosenSitizerable activity and is known to have an ability to scavenge a wide species of active oxygen. Another pro-oxidant compound that generates superoxide anion radical under near-UV irradiation was not induced by increased UV-B during cultivation, and identified as lumazine, a degradation product from folic acid.

• Journal of the Korean Solar Energy Society
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• v.32 no.spc3
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• pp.199-206
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• 2012

The purpose of this study is to understand the change of impression by comparing the uniformity lighting with the compound lighting. In previous study, we proposed a light controlling method to harmonize daylight from a window and artificial lights from a ceiling and obtained the results to support our method. We referred this method as the Adjusted Compound-Lighting Model (AC Model). The experiment is carried out with the scaled-models and mock-up spaces that were supposed to be an office space. One is lit by the uniform lighting and the other by the compound lighting in each experimental space. In order to present varying illuminance distributions, the two variables were used in this study. Subjects were asked to evaluate the point of difference by semantic differential rating on their overall impression after comparing with two rooms. The results showed that the impressions of compound lighting were more positive score than that of uniformity lighting on the items of 'dim-bright', 'dislike-like', 'artificial-natural' and 'closed-open', and that there was no significant difference in impressions between two spaces on other items.

• Korean Journal of Remote Sensing
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• v.30 no.3
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• pp.383-397
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• 2014

Information technology advances are allowing conventional surveillance systems to be combined with mobile communication technologies, creating ubiquitous monitoring systems. This paper proposes monitoring system that uses smart camera technology. We discuss the dependence of interior orientation parameters on calibration target sheets and compare the accuracy of a three-dimensional monitoring system with camera location calculated by space resectioning using a Digital Surface Model (DSM) generated from stereo images. A monitoring housing is designed to protect a camera from various weather conditions and to provide the camera for power generated from solar panel. A smart camera is installed in the monitoring housing. The smart camera is operated and controlled through an Android application. At last the accuracy of a three-dimensional monitoring system is evaluated using a DSM. The proposed system was then tested against a DSM created from ground control points determined by Global Positioning Systems (GPSs) and light detection and ranging data. The standard deviation of the differences between DSMs are less than 0.12 m. Therefore the monitoring system is appropriate for extracting the information of objects' position and deformation as well as monitoring them. Through incorporation of components, such as camera housing, a solar power supply, the smart camera the system can be used as a ubiquitous monitoring system.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.61.3-62
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• 2015

Remote-sensing observation is one of the observation methods that provide valuable information, such as composition and surface physical conditions of solar system objects. The Hayabusa spacecraft succeeded in the first sample returning from a near-Earth asteroid, (25143) Itokawa. It has established a ground truth technique to connect between ordinary chondrite meteorites and S-type asteroids. One of the scientific observation instruments that Hayabusa carried, Asteroid Multi-band Imaging Camera(AMICA) has seven optical-near infrared filters (ul, b, v, w, x, p, and zs), taking more than 1400 images of Itokawa during the rendezvous phase. The reflectance of planetary body can provide valuable information of the surface properties, such as the optical aspect of asteroid surface at near zero phase angle (i.e. Sun-asteroid-observer's angle is nearly zero), light scattering on the surface, and surface roughness. However, only little information of the phase angle dependences of the reflectance of the asteroid is known so far. In this study, we investigated the phase angle dependences of Itokawa's surface to understand the surface properties in the solar phase angle of $0^{\circ}-40^{\circ}$ using AMICA images. About 700 images at the Hayabusa rendezvous phase were used for this study. In addition, we compared our result with those of several photometry models, Minnaert model, Lommel-Seeliger model, and Hapke model. At this conference, we focus on the AMICA's v-band data to compare with previous ground-based observation researches.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.28-35
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• 2016

Forging operations are non-stationary processes occurring because of indirect pressure, generally, under conditions of three-dimensional stress and deformation. Furthermore, due to friction and the constraints of die geometry, deformation is not homogeneous. Material flow and deformation are largely determined by the shape of the tools. It is well known that net-shape forging can improve the mechanical strength of the final product as well as reduce material waste. Oxygen-free copper that is used for electrical and electronic components has excellent electrical and thermal conductivity. Oxygen-free copper parts have a low productivity in cutting process. Thus, the forging process is performed in order to improve the low productivity in cutting process. The forging of oxygen-free copper for electrode body parts was modeled using finite element simulation and forging experiments that were conducted for producing electrode body parts at room temperature. In order to reduce the cost of cutting products, the forging was performed in a closed cavity to obtain near-net or net-shape parts.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.5
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• pp.345-348
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• 2012

The optical losses associated with the reflectance of incident radiation are among the most important factors limiting the efficiency of a solar cell. Therefore, photovoltaic cells normally require special surface structures or materials, which can reduce reflectance. In this study, nano-scale textured structures with anti-reflection properties were successfully formed on silicon. The surface of sicon wafer was etched by the inductively coupled plasma process using the gaseous mixture of $SF_6+O_2$. We demonstrate that the reflection characteristic has significantly reduced by ~0% compared with the flat surface. As a result, the power efficiency $P_{max}$ of the nano-scale textured silicon solar cell were enhanced up to 20%, which can be ascribed primarily to the improved light trapping in the proposed nano-scale texturing.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1485_1486
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• 2009

Transparent conductive metal oxide films of $In_{2-x}Sn_xO_3$ (ITiO) and $In_{2-x}Sn_xO_3$ (ITO) were deposited by RF magnetron sputtering at relatively low substrate temperature (~$300^{\circ}C$) and at high rate (~10nm/min). Electrical and optical properties of the films were investigated as well as film structure and morphology, as it is compared with the commercial F:$SnO_2$ (FTO) glass. Near infrared ray transmittance of ITiO is the highest for wavelengths over 1000nm, which can increase dye sensitized compared to ITiO and FTO. Dye-sensitized solar cells (DSCs) were fabricated using the ITiO, ITO and FTO. Photoconversion efficiency ($\eta$) of DSC using ITiO is 5.5%, whereas 5.0% is obtained from DSC with ITO, both at 100mW/$cm^2$ light intensity.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.180-182
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• 2009

Two different wet etching solutions, NaOH 40% and Acid, were used for etching in tri-crystalline Silicon(Tri-Si) solar cell fabrication. The wafers etched in NaOH40% solution showed higher reflectance compared to the wafers etched in Acid solution after $SiN_x$ deposition. In light current-voltage results, the cells etched in Acid solution exhibited higher short circuit current and open circuit voltage than those of the cells etched in NaOH 40% solution. We have obtained 16.70% conversion efficiency in large area($156cm^2$) Tri-Si solar cells etched in Acid solution.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.269-274
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• 2008

Nowaday, The Sustainable Development about global environment is the most important subject. In urban environment, a variety of the nature energy utilization such as the solar energy are the most efficient solution to solve this issue. One of these efficient, solutions, a photovoltaic system using sunlight has been introduced to the building with an advantage such as cost-effective, safe for using and good for environment friendly in light with energy utilization. Recently, many of the apartment housings are built in domestic country. The apartment buildings have been constructed since early of 1970's. now apartment is taking over 50% out of entire housing in korea. The apartment housing applying to a photovoltaic system has been extensively studied in the foreign country but our county runs short. So, It was necessary to technical development of PV application which is suitable in Korean house culture. The objective of this study is to develop the building integrated PV application method for apartment building.