• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1254-1261
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• 2003

In this paper we present a simple and efficient robust optimal design formulation and its application to a resonant-type micro probe. The basic idea is to use the Gradient Index (GI) to improve robustness of the objective and constraint functions. In the robust optimal design procedure, a deterministic optimization for performance of MEMS structures is followed by design sensitivity analysis with respect to uncertainties such as fabrication errors and change of operating conditions. During the process of deterministic optimization and sensitivity analysis, dominant performance and uncertain variables are identified to define GI. The GI is incorporated as a term of objective and constraint functions in the robust optimal design formulation to make both performance and robustness improved. While most previous approaches for robust optimal design require statistical information on design variations, the proposed GI based method needs no such information and therefore is cost-efficient and easily applicable to early design stages. For the micro probe example, robust optimums are obtained to satisfy the targets for the measurement sensitivity and they are compared in terms of robustness and production yield with the deterministic optimums through the Monte Carlo simulation.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.7
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• pp.29-35
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• 2000

The relationship between calculated hydrogen molecular concentration in fiber core and measured index change during the grating growth is analyzed. The index change increases by ${\sim}2{\times}10^{-5}$ per 100ppm of $H_2$ concentration in standard telecommunication optical fiber and the defects related photosensitivity generate ${\sim}3.8{\times}10^{17}$ per 100ppm of $H_2$.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.10
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• pp.447-450
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• 2003

This paper presents a process optimization of antireflection (AR) coating on crystalline Si solar cells. Theoretical and experimental investigations were performed on a double-layer AR (DLAR) coating of MgF$_2$/CeO$_2$. We investigated CeO$_2$ films as an AR layer because they have a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. RF sputter grown CeO$_2$ film showed strong dependence on a deposition temperature. The CeO$_2$ deposited at 40$0^{\circ}C$ exhibited a strong (111) preferred orientation and the lowest surface roughness of 6.87 $\AA$. Refractive index of MgF$_2$ film was measured as 1.386 for the most of growth temperature. An optimized DLAR coating showed a reflectance as low as 2.04% in the wavelengths ranged from 0.4${\mu}{\textrm}{m}$ to 1.1${\mu}{\textrm}{m}$. We achieved the efficiencies of solar cells greater than 15% with 3.12% improvement with DLAR coatings. Further details on MgF$_2$, CeO$_2$ films, and cell fabrication parameters are presented in this paper.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.12
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• pp.821-825
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• 2015

Anti-reflective (AR) thin film was fabricated on a glass substrate by sol-gel method. The coating solution was synthesized with TEOS (tetraethlyorthosilicate) and poly ethylene glycol (PEG, 4.0 wt%). As the withdrawal speed of coating was changed from 0.1 mm/sec to 0.3 mm/sec, the thickness and refractive index of prepared thin films were changed. The reflectance and transmittance of coating glass fabricated by the withdrawal speed of 0.1 mm/sec were 0.62% and 95.0% in visible light range. The refractive index and thickness of single layer thin film were n= 1.29 and ca. 99.0 nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.593-596
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• 1999

This paper presents a process optimization of antireflectiun (AR) coating on crystalline Si solar cells. Theoretical and experimental investigations were performed on a doble-layer AR(DLAR) coating of MgF$_2$/CeO$_2$, We investigated CeO$_2$ films as an All layer because they hale a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. RF sputter grown CeO$_2$ film showed strong dependence on a deposition temperature. The CeO$_2$ film deposited at 400 $^{\circ}C$ exhibited a strong (111) preferred orientation and the lowest surface roughness of 6.87 $\AA$. Refractive index of MgF$_2$ film was measured as 1.386 for the most of growth temperature. An optimized DLAR coating showed a reflectance as low as 2.04 % in the wavelengths ranged from 0.4 7m to 1.1 7m. We achieved the efficiencies of solar cells greater than 15% with 3.12 % improvement with DLAR coatings . Further details on MgF$_2$, CeO$_2$ films, and cell fabrication Parameters are presented in this paper.

• Journal of Powder Materials
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• v.26 no.3
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• pp.225-230
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• 2019

To develop Taraxacum platycarpum extract (TP)-loaded particles for tablet dosage form, various TP-loaded particles composed of TP, dextrin, microcrystalline cellulose (MCC), silicon dioxide, ethanol, and water are prepared using a spray-drying method and fluid-bed-drying method. Their physical properties are evaluated using angle of repose, Hausner ratio, Carr's index, hardness, disintegrant time, and scanning electron microscopy. Optimal TP-loaded particles improve flowability and compressibility. Furthermore, 2% silicon dioxide gives increased flowability and compressibility. The formula of TP-loaded fluid-bed-drying particles at a TP/MCC/silicon-dioxide amount of 5/5/0.2 improves the angle of repose, Hausner ratio, Carr's index, hardness, and disintegrant time as compared with the TP-loaded spray-drying particles. The TP-loaded fluid-bed-drying particles considerably improve flowability and compressibility ($35.10^{\circ}$ vs. $40.3^{\circ}$, 0.97 vs. 1.17, and 18.97% vs. 28.97% for the angle of repose, Hausner ratio, and Carr's index, respectively), hardness (11.34 vs. 4.7 KP), and disintegrant time (7.4 vs. 10.4 min) as compared with the TP-loaded spray-drying particles. Thus, the results suggest that these fluid-bed-drying particles with MCC and silicon dioxide can be used as powerful particles to improve the flowability and compressibility of the TP.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.154-157
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• 2011

Hydrogenated silicon nitride deposited by LF-PECVD is commonly used for anti-reflection coating and passivation in silicon solar cell fabrication. The deposition of the optimized silicon nitride on the surface is elemental in crystalline silicon solar cell. In this work, the carrier lifetimes were measured while the thicknesses of $SiN_x$ were changed from 700 ${\AA}$ to 1150 ${\AA}$ with the gas flow of $SiH_4$ as 40 sccm and $NH_3$ as 120 sccm,. The carrier lifetime enhanced as the thickness of $SiN_x$ increased due to improved passivation effect. To study the characteristics of $SiN_x$ with various gas ratios, the gas flow of $NH_3$ was changed from 40 sccm to 200 sccm with intervals of 40 sccm. The thickness of $SiN_x$ was fixed as 1000 ${\AA}$ and the gas flow of $SiH_4$ as 40 sccm. The refractive index of SiNx and the carrier lifetime were measured before and after heat treating at $650^{\circ}C$ to investigate their change by the firing process in solar cell fabrication. The index of refraction of SiNx decreased as the gas ratios increased and the longest carrier lifetime was measured with the gas ratio $NH_3/SiH_4$ of 3.

• Korean Journal of Construction Engineering and Management
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• v.23 no.5
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• pp.98-107
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• 2022

The purpose of this study is to suggest a model for evaluation of a risk based value index for modular design alternatives in plant construction projects. Accordingly, 1) Setting the basic project cost and the scope to apply the module, 2) Evaluating the importance, easiness, and effectiveness index for Engineering, Procurement, Fabrication, transportation, and construction work, 3) Estimating the total project cost by analyzing the risk reserve Step, 4) Comparing the effectiveness index and total project cost for each modular design alternative, it was composed of the steps of deriving RVI. To verify such a model, Plan-A, which applied a module to one process, and Plan-B, which applied a module to three processes, were composed to evaluate RVI.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.696-706
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• 1992

In sheet metal fabrication using NCT(numerically controlled turret), the automatic tool selection for the NCT operation is the major problem to be solved first to improve its production performance. However, the punching tool selection has been done by human experts either manually or semi-automatically. In this paper, we have introduced the shape-index-set to handle the shape of sheet metal parts and developed an algorithm through which one can find easily the successive matching curves between two curve lists, one from the punching tool and the other from the boundaries of the sheet metal part. Based on this algorithm, we have also devised the method that can select automatically the tools to punch out the boundaries of sheet metal parts. The result of several computational experiments shows the successful tool selection without any fail.

• Korean Journal of Materials Research
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• v.12 no.4
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• pp.254-258
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• 2002

To realize channel cross-connecting in optical communications systems, a high speed optical matrix switch was fabricated using z-cut $LiNbO_3$. For switch fabrication was design bending structure and coupling length and four $2{\times}2$ directional couplers were integrated on one substrate far construction of a $4{\times}4$ switch. Single-mode optical waveguides were formed by Ti-diffusion at a wet $O_2$ atmosphere. Ti-diffusion profile, refractive index variation and waveguide morphology were analyzed by Prism coupler and optical microscopy, respectively.