• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.1
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• pp.7-11
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• 2010

The reduction of optical losses in mono-crystalline silicon solar cell by surface texturing is a critical step to improve the overall cell efficiency. In this study, we have changed the sub-micrometer structure on the micrometer pyramidal structure by 2-step texturing. The Ag particles were coated on the micrometer pyramid surface in $AgNO_3$ solution, and then the etching with hydrogen fluoride and hydrogen peroxide created even smaller nano-pyramids in these pyramids. As a result, we observed that the changes of size and thickness of nano structure on pyramidal surface were determined by $AgNO_3$ concentration and etching time. Using 2-step texturing, the surface of wafers is etched to resemble the rough surface of a lotus leaf. Lotus surface can reduce average reflectance from 10% to below 3%. This reflectance is less than conventional textured wafer including anti-reflection coating.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.1
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• pp.98-105
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• 2013

This paper presents a finite-difference time-domain(FDTD) simulation and a data processing technique for radar sensing of the internal structure of a wall using an ultra-wide band antenna. We first designed an ultra-wide band anti-podal vivaldi antenna with a frequency range of 0.3~7 GHz which is chosen to be relatively low after considering the characteristics of wave attenuation, wall penetration, and range resolution. In this study the two-dimensional FDTD technique was used to simulate a wall-penetration-radar experiment under practical conditions. The next, the measured radiation pattern of the practical antenna is considered as an equivalent source in the FDTD simulation, and the reflection data of a concrete wall and targets are obtained by using the simulation. Then, a data processing technique has been applied to the FDTD reflection data to get a radar image for remote sensing of the internal structure of the wall. We compared the two different source excitations in the FDTD simulation; (1) commonly-used isotropic point sources and (2) polynomial curve fitting sources of the measured radiation pattern. As a result, when we apply the measured antenna pattern into the FDTD simulation, we could obtain about 2.5 dB higher signal to noise level than using a plane wave incidence with isotropic sources.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.11
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• pp.2075-2082
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• 2006

This paper presents modeling and optimization techniques for hish efficiency solar cell process on single-crystalline float zone (FZ) wafers. Among a sequence of multiple steps of fabrication, the followings are the most sensitive steps for the contact formation: 1) Emitter formation by diffusion; 2) Anti-reflection-coating (ARC) with silicon nitride using plasma-enhanced chemical vapor deposition (PECVD); 3) Screen-printing for front and back metalization; and 4) Contact formation by firing. In order to increase the performance of solar cells in terms of efficiency, the contact formation process is modeled and optimized using neural networks and genetic algorithms, respectively. This paper utilizes the design of experiments (DOE) in contact formation to reduce process time and fabrication costs. The experiments were designed by using central composite design which consists of 24 factorial design augmented by 8 axial points with three center points. After contact formation process, the efficiency of the fabricated solar cell is modeled using neural networks. Established efficiency model is then used for the analysis of the process characteristics and process optimization for more efficient solar cell fabrication.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.3
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• pp.237-245
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• 2011

Purpose: The present study was conducted to investigate whether certain repeated physical and/or chemical stimuli added on ophthalmic lenses might induce any changes of the functions of lens coatings. Methods: The changes in lens surface, light transmittance, foggy duration, durability of ophthalmic lenses were determined after the application of tearing-off with tape, rubbing with acetone, soaking in acetone or distilled water of ophthalmic lens (CR-39 material) as physical and/or chemical stimuli. Results: The change of ophthalmic lens surface was detected after soaking in acetone for longer than 30 minutes by observing the lens surface to figure out the functional change of hard coating. The ophthalmic lens soaked in distilled water for 180 minutes showed little functional change of anti-reflection coating as 1% by measuring light transmittance of lens. However, the function of anti-reflection coating was almost disappeared after the ophthalmic lens was soaked in acetone for 60 minutes. The foggy duration of ophthalmic lens soaked in acetone was increased by estimating foggy duration of lens. The lens coating was shown to be defected when the pre-damaged ophthalmic lenses were torn off with tape, rubbed with acetone and soaked in distilled water or acetone by observing pre-damaged lens surface to evaluate its durability. Conclusions: The careful management during ophthalmic lens dispensing or usual eyeglass wearing is needed since the change in ophthalmic lens coatings was shown by repeated physical and/or chemical stimuli.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.10-15
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• 2020

Ultraviolet rays, which have wavelengths smaller than 400 nm, are very harmful to the eyes. Recently, high-energy visible light was also revealed to be harmful to retinal cells. Therefore, polymer eyeglass lenses that can block UV and high-energy visible light are needed for eye health. In this study, high-refractive-index polymer eyeglass lens, n=1.67, were manufactured using the injection-mold method with the m-xylene diisocyanate monomer, 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol monomer, benzotriazole UV absorber, release of alkyl phosphoric ester, dye mixture of CI solvent violet 13, and catalyst of dibutyltin dichloride mixture. A multi-layer anti-reflection coating was applied to manufactured polymer eyeglass lenses for both sides using an E-beam evaporation system. The optical properties of the manufactured lenses with the UV and high-energy visible light-blocking function were analyzed by UV-visible spectrophotometry. As a result, the polymer eyeglass lens with a UV absorber of 0.5 wt. % blocked 99% of UV and high-energy visible light shorter than 411 nm. The average transmittance of the polymer eyeglass lens with a UV absorber of 0.5wt.% was 97.9% in the range of 460 ~ 660 nm for photopic eye sensitivity higher than 10%. Therefore, clear image acquisition in photopic vision is possible.

• Journal of the Korea Fashion and Costume Design Association
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• v.7 no.2
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• pp.101-110
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• 2005

Vivienne Westwood could be placed in a unique position in the contemporary fashion design. She has never belonged in a core group of mainstream fashion designer but not been always in an outsider position. She got from mainstream fashion designer circles enormous appreciation, even established fashion industry was influenced by her fashion design. She began her fashion design with rebellious T-shirts like 'destroy' T-shirt, chicken-bone T-shirt, and nipple-zipper T-shirt, all of which revealed her disgust against establishment. All these T-shirts testify her total negation tendency in her youth. However, she did not continue to keep such a kind of total negation attitude against establishment In 1980s she changed her political attitude towards establishment, and this change also found a reflection in her fashion design. In her pirate-collection the dark image of her fashion in the 1970s changed into a totally different bright image with full of gold colour. Although this collection had radiated brightness, it contained still outsider character from mainstream fashion design. The following fashion design in 1980s and 1990s evolved further on the line of Pirate-collection, but they continued to contain certain outsider characteristics. Vivienne Westwood kept some kind of anti-establishment attitude, and this attitude more or little came to the surface of her design. She was always political and critical to the establishment. In 2005, in her 64, she designed a liberty T-shirt, which showed her political attitude and her engagement in social issues. Also it showed the change from the early total negation to the constructive critical affirmation. In this paper the relation between the fashion design of Vivienne Westwood and her political attitude and the influence of her political attitude to her fashion design is analyzed.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.8
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• pp.1427-1438
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• 1997

The art plastique is the part from which designers draw their inspirations to create fashion design. Many designers look for their inspirations from Art Plastique. Since the early 20th century, lots of designers led by Paul Poiret drew their inspirations from Art and co-works with artists. The direct involvement of those artists helped to position Fashion to be an art. Also, these co-works brought the mass media's attention and commercial profit. The most prevalent relationship between the fashion design and art plastique is the reproduction of art such as the 1960s 'Pop Art printed on T-shirts, which can be seen easily todays. After World War ll, art was popularized in a new society where young generation played a major role. Pop Art having image of the freedom and the rejection of tradition was considered as the major trend of 1960s. This study considers reflection of anti-traditionalism, anti-elitism and popularity as the kitsch of Pop. That is the attraction which youth culture looked for from Pop Art and the reason that 60's avast-garde cloth could position itself into the masses. Therefore, this study examines the influence of the kitsch of Pop and the expression of parody upon the major changes in 1960s fashion from which are the mini-look and women's trousers wearing. This study examines Andra Courreges who led 1960s Mini look and Yves Saint Laurent who introduced Pop dress, Smoking look and transparent blouse to find the way which makes it possible for avant garde fashion to have a close relationship with the public and to position itself to be a art.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1652-1656
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• 2014

In this work, we demonstrated a 77 GHz waveguide VCO with transition from WR-12 to WR-10 for anti-collision radar applications. The fabricated waveguide VCO consists of a GaAs-based Gunn diode, a varactor diode, a waveguide transition, and two bias posts for operating as a LPF and a resonator. The cavity is designed for fundamental mode at 38.5 GHz and operated at second hormonic of 77 GHz. The waveguide transition has a 1.86 dB of insertion loss and -30.22 dB of S11 at the center frequency of 77 GHz. The fabricated VCO achieves an oscillation bandwidth of 870 MHz. Output power is from 12.0 to 13.75 dBm and phase noise is -100.78 dBc/Hz at 1 MHz offset frequency from the carrier.

• Journal of the Korean Geographical Society
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• v.38 no.6
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• pp.887-905
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• 2003

In this paper, we first understand the concept of imperialism as a 'a dialectical relation between territorial and capitalistic logics of power', as suggested by Harvey, and its history with three phases, the last of which would be seen as the phase of new imperialism. Secondly, we examine the New Security Strategy of the U.S which can be seen as a reflection of the new imperialism of the U.S. with its neo-conservative Bush administration, and explain the wars in Afghanistan and Iraq as the implementation of the new imperialism. And then we take a close look on the current geopolitical situation of East Asia, especially North and South Korea, Japan and China, in terms of the new imperialist foreign policy of the Bush administration. Finally, we consider the limits of the new imperialism of the U.S. and globally emerging movements of anti-imperialism.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1737-1739
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• 2004

Diamond-like carbon (DLC) films were prepared with RF-PECVD (Plasma Enhanced Chemical Vapor Deposition) method on coming glass and silicon substrates using methane ($CH_4$) and hydrogen ($H_2$) gases. We examined the effects of $CH_4$ to $H_2$ ratios on tribological and optical properties of the DLC films. The structure and surface morphology of the films were examined using Raman spectroscopy and atomic force microscopy (AFM). The hardness of the DLC film was measured with nano-indentor. The optical properties of DLC thin film were investigated by UV/VIS spectrometer and ellipsometry. And also, solar cells were fabricated using DLC as antireflection coating before and after coating DLC on silicon substrate and compared the efficiency.