• Korean Journal of Agricultural and Forest Meteorology
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• v.8 no.2
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• pp.61-67
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• 2006

We examined seedlings of two species (Ilex rotunda and Illicium anisatum) which have a different level of shade tolerance and raised them under different light regimes (full sunlight and 50% shading). After 12 months, we investigated chlorophyll content (Chl. a, Chl. b and Chl. a+b), photosynthetic systems (photosynthetic rate, light compensation point, dark respiration rate and quantum yield), intercellular $CO_2$ concentration and water use efficiency to show acclimation reaction to different light conditions. Seedlings grown under full sunlight showed lower chlorophyll content than those in the shading regime. There was a significant difference between the full sunlight and shade treatments in I. anisatum (shade tolerance species). I. rotunda (intermediate species) showed high photosynthetic rate and water use efficiency over PPFD $1000\;{\mu}mol\;m^{-2}s^{-1}$ to full sunlight. Also, I. anisatum grown under full sunlight showed lower photosynthetic rate and water use efficiency over a range of all PPFD. This result showed that I. rotunda has a more flexible reaction system than that of I. anisatum.

• Journal of the Korean Solar Energy Society
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• v.32 no.5
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• pp.41-51
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• 2012

Heliostat field is the most important subsystem in the tower type solar thermal power plant since its optical performance affects the total system efficiency most significantly while the construction cost of it is the major part of total construction cost in such a power plant. Thus a well designed heliostat field to maximize the optical efficiency as well as to minimize the land usage is very important. This work presents methodology, procedures and result of heliostat filed design for 200kW solar thermal power plant built recently in Daegu, Korea. A $2{\times}2(m)$ rectangular shaped receiver located at 43(m) high and tilted $28^{\circ}$ toward heliostat field, 450 of heliostats of which the reflective surface is formed by 4 of $1{\times}1(m)$ flat plate mirror facet, and the land area having about $140{\times}120(m)$ size are used to form the heliostat field. A procedure to deploy 450 heliostats in radial staggered nonblocking formation is developed. Also the procedures to compute the cosine effect, intercept ratio, blocking and shading ratio in the field are developed. Finally the heliostat filed is designed by finding the optimal radial distance and azimuthal spacing in radial staggered nonblocking formation such that the designed heliostat field optical efficiency could be maximized. The designed heliostat field has 77% of annual average optical efficiency, which is obtained by annually averaging the optical efficiencies computed between the time of where sun elevation angle becomes $10^{\circ}$ after sunrise and the time of where sun elevation angle becomes $10^{\circ}$ before sunset in each day.

• Journal of Power Electronics
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• v.17 no.2
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• pp.476-489
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• 2017

Under partial shading conditions (PSCs), multiple maximums may be exhibited on the P-U curve of string inverter photovoltaic (PV) systems. Under such conditions, heuristic methods are invalid for extracting a global maximum power point (GMPP); intelligent algorithms are time-consuming; and model-based methods are complex and costly. To overcome these shortcomings, a novel hybrid MPPT (MPF-IP&O) based on a model-based peak forecasting (MPF) method and an improved perturbation and observation (IP&O) method is proposed. The MPF considers the influence of temperature and does not require solar radiation measurements. In addition, it can forecast all of the peak values of the PV string without complex computation under PSCs, and it can determine the candidate GMPP after a comparison. Hence, the MPF narrows the searching range tremendously and accelerates the convergence to the GMPP. Additionally, the IP&O with a successive approximation strategy searches for the real GMPP in the neighborhood of the candidate one, which can significantly enhance the tracking efficiency. Finally, simulation and experiment results show that the proposed method has a higher tracking speed and accuracy than the perturbation and observation (P&O) and particle swarm optimization (PSO) methods under PSCs.

• The Journal of the Korea Contents Association
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• v.10 no.8
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• pp.119-129
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• 2010

Recently, development of mobile service and increased demand for mobile device make mobile environment noticeable in computer graphics. Especially demand for 3D graphic services in mobile devices is steadily increased. However up to the present non-photorealistic rendering is mainly studied in desktop platform. In the result, existing research were designed for desktop computers and are not well-suited for mobile devices. Thus, there is a growing needs for processing techniques that provide the ability to render 3D non-photorealistic graphics through mobile devices. In this paper, we discuss processing techniques for non-photorealistic rendering that are especially cartoon shading and rendering in mobile devices. Through the result of this research, it is expected that silhouette edge rendering for mobile display environment and preprocessing file technique for shading. The efficiency of 3D mobile graphic service like 3D model in cartoon style is increased by using proposed preprocessing file and rendering pipeline. Our work can provide mobile cartoon rendering results and various mobile contents to users.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.26-34
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• 2008

The purpose of this study is to analyze daylight distribution and characteristics of light on the Korean traditional paper and to investigate a possibility as the shading systems. First of all, daylight distribution through the Korean traditional paper windows and doors of the Traditional House is analyzed at Genjaegotaek of the Asan Oeam Traditional Village. After making a model, the characteristics of light on the Korean traditional paper and Roller Shade fabric are analyzed Korean traditional paper has a good efficiency to diffuse the light and is less glare than Roller Shade fabric. In the present office buildings and apartmant houses, daylight characteristics of the Korean traditional paper windows and doors could be used as preliminary data to develop a window system which makes greatest performance of daylight.

• Journal of Broadcast Engineering
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• v.19 no.3
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• pp.316-328
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• 2014

In this paper, we parallelize the popular feature detection algorithms, i.e. SIFT and SURF, and its application to fast panoramic image generation on the latest embedded GPU. Parallelized algorithms are implemented using recently developed OpenCL as the embedded GPGPU software platform. We compare the implementation efficiency and speed performance of conventional OpenGL Shading Language and OpenCL. Experimental result shows that implementation on OpenCL has comparable performance with GLSL. Compared with the performance on the embedded CPU in the same application processor, the embedded GPU runs 3~4 times faster. As an example of using feature extraction, panorama image synthesis is performed on embedded GPU by applying image matching using detected features.

• Current Photovoltaic Research
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• v.9 no.1
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• pp.6-10
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• 2021

The mesh mask screen, which is generally used for screen printing metallization of silicon solar cell, requires high squeegee pressure and low printing speed. These requirements are acting as a limiting factor in production yield in photovoltaic industries. In order to improve the productivity, a metal mask, which has high durability and high printing speed, has been researched. In this paper, the characteristics of each solar cell, in which electrodes were formed by using a metal mask and a mesh mask, were analyzed through recombination current density. In particular, the metal-induced recombination current density (Jom) representing the recombination of the emitter-metal interface was calculated using the shading method, and the resulting efficiency and open-circuit voltage were analyzed through the diode equation. As a result of analyzing the proportion of the metal-induced recombination current density to the total emitter recombination current density, it was analyzed that the reduction of the metal-induced recombination current density through the metal mask is an important factor in reducing the total recombination current density of the solar cell.

• Journal of Microbiology and Biotechnology
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• v.10 no.6
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• pp.817-822
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• 2000

A proper flashing light is expected to enhance microalgal biomass productivity and photosynthetic efficiency. The effect of flashing light on high-density Chlorella kessleri (UTEX 398) cultures was studied using light-emitting diodes. A frequency modulator was designed to flash LEDs, and the device successfully provided wide range of frequencies and various duty cycles of flashing. A relatively high frequencies of 10, 20 and 50 kHz were used in this study. These frequencies have very short flashing time ($2-50{\mu}s$), which corresponded to the time constant of the light reaction of photosynthesis. The specific oxygen production rates of photosynthesis under flashing light were compared with those under an equivalent continuous light in specially designed illumination cuvette. The specific oxygen production rates under flashing light were 5-25% higher than those under the continuous light. A range of cell concentration was discovered, where the benefit of flashing light was maximized. The photosynthetic efficiency was also higher under flashing light with frequencies of over 1 kHz, which was a clear indication of flashing light effect and the degree of mutual shading could by overcome by flashing lights, particularly at high-density algal cultures.

• Journal of Microbiology and Biotechnology
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• v.14 no.3
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• pp.442-449
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• 2004

Improving the light utilization efficiency of photosynthetic cells in photobioreactors (PBRs) is a major topic in algal biotechnology. Accordingly, in the current study we investigated the effect and suitability of photosynthetic pigment reduction for improving light utilization efficiency. The light-harvesting complex II (LH-II) genes of Rhodobacter sphaeroides were removed to construct a mutant strain with less pigment content. The mutant strain exhibited a slower growth rate than the wild-type under a low light intensity, while the mutant grew faster under a high light intensity. In addition, the specific absorption coefficient was lower in the mutant due to its reduced pigment content, thus it seemed that light penetrated deeper into its culture broth. However, the distance (light penetration depth) from the surface of the PBR to the compensation point did not increase, due to an increase in the compensation irradiance of the mutant strain. Experimental data showed that a reduced photosynthetic pigment content, which lessened the photoinhibition under high-intensity light, helped the volumetric productivity of photosynthetic microorganisms.

• Journal of IKEEE
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• v.18 no.1
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• pp.159-164
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• 2014

This paper targets the development of micro-converter such as a power converter for photovoltaic module. In corresponding to the poor performance of centralized PV system under partial shading, the power converter for single PV module to maximize the energy harvest from PV module. The power converter is constantly tracking the maximum power point of photovoltaic system and increases energy output power. To minimize the quantity of devices and switchs, 320W solar micro-converter is developed using synchronous rectifier. From the basis of these results, through simulations and experiments were verified efficiency.