• Applied Science and Convergence Technology
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• v.23 no.5
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• pp.254-260
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• 2014

Organic solar cells have attracted extensive attention as a promising approach for cost-effective photovoltaic devices. However, organic solar cell has disadvantage of low power conversion efficiency in comparison with other type of solar cell, due to the recombination ratio of hole and electron is too large in the active layer. Thus we have change the surface structure of PEDOT:PSS layers to improve the current density by colloidal lithography method using various-size of polystyrene sphere. The two types of coating method were applied to fabricate the different pattern shape and height, such as spin coating and drop casting. Using the organic solvent, we easily eliminate the PS sphere and could make the varied pattern shapes by controlling the wet etching time. Also we have measured the electrical properties of patterned PEDOT:PSS film to check whether it is suitable for organic photovoltaics.

• Conservation Science in Museum
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• v.5
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• pp.49-57
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• 2004

The Divine Bell of King Seongdeok was completed in 771 A.D. It is a true masterpiece both grand in its size and style (height 3.66 m, diameter 2.23 m, thickness 20.3 cm, weight 18.9 ton), illustrating the essence of the Korean bronze culture. However, there are no remaining records about its casting: where the raw material came from, how the materials were mixed and how the bell was casted. The absence of such records has limited the understanding of the bell. This article contains analysis of three samples collected from a protruding part inside of the bell during a safety test for the bell by the Gyeongju National Museum. The main issues are the element composition of the bell, microstructure on the casting time and the source where the raw material came from.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.29-38
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• 2009

Statement of problem: A casting connection technique is widely used for repair, correction and addition to base metal framework. However, a casting connection technique may increase the risk of failure in clinical situations when high stresses exist. Purpose: The purpose of this study was to investigate the mechanical retentive groove design comparatively to increase the joint strength by using the three-dimensional finite element analysis model of a 3-unit fixed partial denture. Material and methods: Ten finite element models were constructed. (Model A: One retentive groove, Model B: Two retentive grooves, Model C: Three retentive grooves, Model D: Four retentive grooves, Model E: One horizontal groove and two vertical grooves, Model F: Two horizontal grooves and one vertical groove, Model G: One groove with the enlarged dimension, Model H: Two grooves with the enlarged dimension, Model I: One groove with the increased height, Model J: One groove with the increased width of base). The vertical force was applied to the mesial and the distal fossa to the casting connection of mandibular first molar. Results: The main factors, affecting joint strength of casting connection were both the retention between the primary cast and the secondary cast and the thickness of the primary cast remaining after preparing retentive groove. The increase of retentive force, according to the numbers and the dimension of retentive groove had an effect on distributing stress. However, in some cases, the increase of retentive force resulted in the increase of stress by reducing thickness of the primary cast in the connection area. Conclusion: The design of retentive groove that limits number of retentive groove for metal thickness and increases the depth of retentive groove for retention is highly recommended.

• Journal of The Korean Society of Grassland and Forage Science
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• v.23 no.2
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• pp.77-80
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• 2003

This study was conducted to determine the optimum organic fertilizer rate (0, 100, 200, 300, 400, 500, 600kg/10a) of worm casting on growth response and yield of Ieol´ radish in Jeiu island. The results obtained were summarized as follows; plant height was getting bigger as organic fertilizer increased from 0 to 500kg/10a and then became smaller at 600kg/10a. But was no significance from 200 to 600kg/10a. Number of leaves, leaf width and root diameter were the same trend with plant height response. Root length was not significantly affected by organic fertilizers. SPAD reading value of leaves increased as increasing of organic fertilizers. Fresh matter yield (top+root) increased significantly 2,949∼4,561kg/10a as fertilizer rate increased from 0 to 200kg/10a, increased 5.096∼5,707kg/10a from 300 to 500kg/10a of fertilizer rate and decreased to 4,873kg/10a at 600kg/10a. Top and root weight were the same trend with fresh matter yield.

• Journal of Korea Game Society
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• v.7 no.4
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• pp.71-80
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• 2007

In this paper, we introduce an efficient GPU-based real-time rendering technique applicable to every kind of game. Our method, without an extra geometry, can represent terrain just with a height map. It makes it possible to freely go around in the air or on the surface, so we can directly apply it to any computer games as well as a virtual reality. Since our method is not based on any geometrical structure, it doesn't need special LOD policy and the precision of geometrical representation and visual quality absolutely depend on the resolution of height map and color map. Moreover, GPU-only technique allows the general CPU to be dedicated to more general work, and as a result, enhances the overall performance of the computer. To date, there have been many researches related to the terrain representation, but most of them rely on CPU or confmed its applications to flight simulation, Improving existing displacement mapping techniques and applying it to our terrain rendering, we completely ruled out the problems, such as cracking, poping etc, which cause in polygon-based techniques, The most important contributions are to efficiently deal with arbitrary LOS(Line Of Sight) and dramatically improve visual quality during walk-through by reconstructing a height field with curved patches. We suggest a simple and useful method for calculating ray-patch intersections. We implemented all these on GPU 100%, and got tens to hundreds of framerates with height maps a variety of resolutions$(256{\times}256\;to\;4096{\times}4096)$.

• Earthquakes and Structures
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• v.17 no.2
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• pp.233-244
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• 2019

In this work, we have studied the effects of different soil thicknesses, haunch heights, reinforcement forms and construction technologies on the seismic performance of a composite precast fabricated utility tunnel by pseudo-static tests. Five concrete specimens were designed and fabricated for low-cycle reciprocating load tests. The hysteretic behavior of composite precast fabricated utility tunnel under simulated seismic waves and the strain law of steel bars were analyzed. Test results showed that composite precast fabricated utility tunnel met the requirements of current codes and had good anti-seismic performance. The use of a closed integral arrangement of steel bars inside utility tunnel structure as well as diagonal reinforcement bars at its haunches improved the integrity of the whole structure and increased the bearing capacity of the structure by about 1.5%. Increasing the thickness of covering soil within a certain range was beneficial to the earthquake resistance of the structure, and the energy consumption was increased by 10%. Increasing haunch height within a certain range increased the bearing capacity of the structure by up to about 19% and energy consumption by up to 30%. The specimen with the lowest haunch height showed strong structural deformation with ductility coefficient of 4.93. It was found that the interfaces of haunches, post-casting self-compacting concrete, and prefabricated parts were the weak points of utility tunnel structures. Combining the failure phenomena of test structures with their related codes, we proposed improvement measures for construction technology, which could provide a reference for the construction and design of practical projects.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.4
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• pp.159-165
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• 2013

One of the leading causes of night time automobile accidents is the darkness of surroundings. Headlamps play a critical role in casting light and providing drivers with visibility. Headlamp design and new technology have been developed recently as research has been actively carried out to increase headlamp recognition. This study statistically analyzes irradiation distance using computer simulation by categorizing headlamps applied in domestic automobiles in the last decade by year, light source, form, vehicle type, and height of installation. After analyzing results of irradiation distance, it appears irradiation distance has been increased by approximately 10m in the last decade. This increase in irradiation distance is predicted to decrease night time accidents by allowing more time to recognize potential causes of accidents.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1003-1006
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• 2003

We have investigated the effect of hole-injection buffer layer and cathodes in organic light-emitting diodes u sing poly (3,4-ethylenedioxythiophene) : poly (stylenesulfonate) (PEDOT: PSS) in a device structure of $ITO/PEDOT:PSS/TPD/Alq_3/Cathode$. Polymer PEDOT:PSS buffer layer was made using spin casting method. Current-voltage, luminance-voltage characteristics and efficiency of device were measured at room temperature with a variation of cathode materials. The device with LiF/Al cathode shows an improvement of external quantum efficiency approximately by a factor of ten compared to that of Al cathode only device. Our observation shows that the energy barrier-height in cathode side is important in improving the efficiency of the organic light-emitting diodes.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.566-571
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• 2010

Dispersion behavior of the slurries consisted of bimodal-type AlN powders was examined in non-aqueous solvent system. Azotropic solvent system and copolymer acidic dispersant were applied to the slurries. Measurements of the sedimentation height and the viscosity of the each slurry, and the test of particle size distribution of the each powder sample were conducted as examinations for the dispersion behavior at the various dispersant contents. The bimodal-type particle size distribution was continued after addition of the dispersant and small particle portions were increased as the dispersant content increases. The density of the green sheet was also increased as the dispersant content increases and a green density of $2.114\;g/cm^3$ was obtained at the sample prepared from 2.4 wt% dispersant content. The increase of large particle portions resulted in the surface defects of the green sheets.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.9
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• pp.166-171
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• 2002

The objective of this paper is to investigate the effect of clearance and the configuration of die system on burr formation by FEM analysis and experimental tests. Compared with casting, forging and machining, shearing has been known, especially in heavy or mass-production industries, as a very economical and fast way to obtain the desired shape Recently, the shearing process becomes widely used in the small and light electronic component manufacturing industries. When shearing a part of sheet metal, the burr formed on the cutting edge is usually unavoidable. The burr would not only degrade the precision of products but also causes additional cost for the deburring process. In this paper, the influence of shearing parameters such as clearance and configurations of the lower pad (ejector) on burr formation is investigated by using the experimental and numerical approach. From the experimental results, it has been shown that the more narrow clearance gives the smaller burr height and the higher shearing forces. The removal of lower holder also makes the sheared surface integrity and the dimensional accuracy become worse. The FEM results (using DEFORM-2D) show good agreement with the experimental results.