• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.816-819
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• 2010

A study on the required propulsion powers at the EAV2 electric propulsion vehicle using power system such as solar cell, fuel cell and secondary cell is conducted, through which the scenario about available supply power is discussed at the optimum propulsion system weight on the specified flight envelope. In the result, it is noticed that propulsion system weight is 7.06kg and fuelcell 500W and secondary cell 100W are available to flight for glider-type electric vehicle with 6m length, 0.35m width.

• Smart Structures and Systems
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• v.21 no.2
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• pp.207-223
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• 2018

In this inquisition, a passive damper namely Stockbridge Damper (SBD) has been introduced to the field of vibration control of Offshore Wind Turbine (OWT) to reduce the earthquake excitations. The dynamic responses of the structure have been analyzed for three recorded earthquakes and the responses have been assessed. To find an optimum SBD, the parameters of damper have been optimized using Response Surface Methodology (RSM) based on Box-Behnken Design (BBD) and Particle Swarm Optimization (PSO). The influence of the design variables of SBD such as the diameter of messenger cable, the length of messenger cable and logarithmic decrement of the damping has been investigated through response variables such as maximum displacement, RMS displacement and frequency amplitude of structure under an artificially generated white noise. After that, the structure with optimized and non-optimized damper has been analyzed with under the same earthquakes. Moreover, the comparative results show that the structure with optimized damper is 11.78%, 18.71%, 11.6% and 7.77%, 7.01%, 10.23% more effective than the structure with non-optimized damper with respect to the displacement and frequency response under the earthquakes. The results show that the SBD can obviously affect the characteristics of the vibration of the OWT and RSM based on BBD and PSO approach can provide an optimum damper.

• Plant Resources
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• v.7 no.3
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• pp.206-210
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• 2004

In order to find out the optimum harvest (dipping) date combined with sowing date on yield and nutrient quality of forage rye which is suitable at the Southern part of Korea, Paldanghomil variety was grown Sep. 2001 to May 2002 at Sunchon National University, and yield and nutrient quality of plant were observed. As harvest date and sowing date were delayed, the plant length was longest, number of leaves per plant was increased in the time of May 20 clipping. Fresh yield was the heaviest in the time of May 20 clipping and Oct. l0 sowing, and the most dry matter yield was the heaviest in the time of May 20 clipping and Oct. 10 sowing. Content of crude protein was the highest and that of crude fiber such as NDF, ADF, hemicellulose, cellulose and lignin were the lowest in the late time of clipping and sowing. Further more IVDMD was high and dry matter yield and digestible dry matter yield were the highest in the time of May 20 dipping and Oct. 10 sowing. Judging from the results reported above, at optimum harvest (dipping) date combined with sowing date for yield and nutrient quality of forage rye seemed to be the time of May 20 clipping and Oct. 10 sowing.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.4
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• pp.279-285
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• 2000

High quality crystals of $YMnO_3$, which is interested in non-volatile memory device application, were grown by the floating zone method. Optimum condition for powder synthesis was established to be $1200^{\circ}C$ for 10 hrs and optimum condition for sintering of $YMnO_3$feed-rod was established to be $1500^{\circ}C$ for 10hrs respectively. It was found from non-seeded growth experiment that $YMnO_3$crystal was grown preferentially to the [1010] orientation. The $YMnO_3$single crystal, which was grown to the direction of perpendicular to C-axis, was typically 5mm in diameter, 50 mm in length and showed dark-blue color.

• Korean Journal of Optics and Photonics
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• v.4 no.1
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• pp.101-107
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• 1993

We carried out the useful theoretical calculation for the optimum design of a 1.48 ${\mu}m$ diode laser pumped E$r^{3+}$ doped fiber amplifier. The model we established is based on the rate equations of three level laser system and the overlap integral between fundamental mode L$P_{01}$ and E$r^{3+}$ doped area. We determined several fiber parameters (N.A., V value, fiber length, E$r^{3+}$ concentration, cutoff wavelength etc.) for the optimum design of a high optical gain. We found that our theoretical results are very useful to the design of E$r^{3+}$ doped fiber used in EDFA.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.245-249
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• 1997

An electro-optic polymer digital optical switch with a coupling region modified for optimum coupling is designed and demonstrated. Its branch waveguide is fabricated by reactive ion etching. Then, the modified coupling region is adiabatically introduced along the propagation direction from the branching point of the two waveguides, and it is implemented by photobleaching after the device fabrication. The structure of the modified coupling region and its refractive index profiles are designed to optimize and mode coupling in the Y-branch waveguide. Therefore, the switching performance of the device was shown to be enhanced with a fixed device length. The measured drive voltage is reduced by more than 30 percents, and the crosstalk is also improved by about 4~6 dB.

• Water for future
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• v.6 no.2
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• pp.30-37
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• 1973

The coefficient of the current meter generally determined by the maker Its coefficient is subject to being changed with time. Therefore the coefficient of the current meter has to be checked up before it is ready to be used Such an inspection is termed a current meter rating The current meter equipped an electronic apparatus and all the others are to be rated in a rating flume. The price current meter which is most widely used for measuring flow velocities ranging between 0.3m/sec and 3.5m/sec has been used in this study. The length of the flume and the optimum range of the rating in the cross section are determined in the range of 20∼120cm deep, 50∼160cm wide of the flume. In this study, the 23 different kinds of the current meter rating enabled us to determine the constants a and b of the following equation. V=an+b(m/sec) where, n is number of revolution per second(n=N/T) V is velocity(v=D/T) The above constant can be determined by the least squares method and plotting, using the velocity(V=D/T) and the number of revolution per second(n=N/T) obtained from the running distance(D), time(T), the number of revolutin(N), and the running number(m). From the experiments the following conclusions are drawn: 1) The rating flume is large enough if the flume is 110∼120cm deep, and 40∼50m long. 2) The optimum depth for rating of a current meter is in the range of h=40∼50cm.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.6
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• pp.553-556
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• 2006

A cis-1,2-dichloroethylene (cis-DCE)-degrading anaerobic bacterium, Clostridium sp. strain KYT-1, was isolated from a sediment sample collected from a landfill site in Nanji-do, Seoul, Korea. The KYT-1 strain is a gram-positive, endospore-forming, motile, rod-shaped anaerobic bacterium, of approximately $2.5{\sim}3.0\;{\mu}m$ in length. The degradation of cis-DCE is closely related with the growth of the KYT-1 strain, and it was stopped when the growth of the KYT-1 strain became constant. Although the pathway of cis-DCE degradation by strain KYT-1 remains to be further elucidated, no accumulation of the harmful intermediate, vinyl chloride (VC), was observed during anaerobic cis-DCE degradation. Strain KYT-1 proved able to degrade a variety of volatile organic compounds, including VC, isomers of DCE (1,1-dichloroethylene, trans-1,2-dichloroethylene, and cis-DCE), trichloroethylene, tetrachloroethylene, 1,2-dichloroethane, 1,1,1-trichloroethane, and 1,1,2-trichloroethane. Strain KYT-1 degraded cis-DCE at a range of temperatures from $15\;to\;37^{\circ}C$, with an optimum at $30^{\circ}C$, and at a pH range of 5.5 to 8.5, with an optimum at 7.0.

• Earthquakes and Structures
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• v.5 no.3
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• pp.261-276
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• 2013

Oil, hysteretic and inertial mass dampers are representatives of passive dampers used for smart enhancement of seismic performance of building structures. Since oil dampers have a nonlinear relief mechanism and hysteretic dampers possess nonlinear restoring-force characteristics, several difficulties arise in the evaluation of buildings including such dampers. The purpose of this paper is to propose a practical method for simultaneous optimal use of such dampers. The optimum design problem is formulated so as to minimize the maximum interstory drift under design earthquakes in terms of a set of damper quantities subject to an equality constraint on the total cost of dampers. The proposed method to solve the optimum design problem is a successive procedure which consists of two steps. The first step is a sensitivity analysis by using nonlinear time-history response analyses, and the second step is a modification of the set of damper quantities based upon the sensitivity analysis. Numerical examples are conducted to demonstrate the effectiveness and validity of the proposed design method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.4
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• pp.298-305
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• 1998

The PVC membrane electrode for measuring perchlorate ion was developed by incorporating various quaternary ammonium sallts. The effect of chemical structure, the content of active material, the kind of plasticizers, and the membrane thickness on the electrode characteristic such as the linear response range and Nernstian slope of the electrode were studied. It was obtained that the effect of the chemical structure of an active material on the electrode characteristics was improved with increasing the alkyl chain length of the quarternary ammonium salts in the ascending order of Aliquat 336P, TOAP, TDAP, and TDDAP. The optimum membrane composition was 9.09wt% of TDDAP, 30.3wt% of PVC, and 60.6wt% of plasticizer(DBP). And the optimum membrane thickness was 0.45mm at this composition. Under the above condition, the linear response range was $10^{-1}~1.2\times10^{-6}$M, and the detection limit was $5.1\times10^{-7}$M with the Nernstian slope of 57mV/decade of activity of perchlorate ion. The electrode potential was stable within the pH range from 4 to 11. The selectivity coefficient was as shown below: $SCN^->I^-NO_3^->Br^->ClO_3^->F^->Cl^->SO_4^{2-}$