• Journal of Advanced Marine Engineering and Technology
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• v.21 no.4
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• pp.393-403
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• 1997

In this paper, we proposed an optimal identification method of identifying the membership func¬tions and the fuzzy rules for the stabilization controller of the nonlinear system by RVEGA( Real Variable Elitist Genetic Algo rithm l. Although fuzzy logic controllers have been successfully applied to industrial plants, most of them have been relied heavily on expert's empirical knowl¬edge. So it is very difficult to determine the linguistic state space partitions and parameters of the membership functions and to extract the control rules. Most of conventional approaches have the drastic defects of trapping to a local minima. However, the proposed RVEGA which is similiar to the processes of natural evolution can optimize simulta¬neously the fuzzy rules and the parameters of membership functions. The validity of the RVEGA - based fuzzy controller was proved through applications to the stabi¬lization problems of an inverted pendulum system with highly nonlinear dynamics. The proposed RVEGA - based fuzzy controller has a swing -. up control mode(swing - up controller) and a stabi¬lization one(stabilization controller), moves a pendulum in an initial stable equilibrium point and a cart in an arbitrary position, to an unstable equilibrium point and a center of the rail. The stabi¬lization controller is composed of a hierarchical fuzzy inference structure; that is, the lower level inference for the virtual equilibrium point and the higher level one for position control of the cart according to the firstly inferred virtual equilibrium point. The experimental apparatus was imple¬mented by a DT -- 2801 board with AID, D/A converters and a PC - 586 microprocessor.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.593-597
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• 2003

Multilevel power conversion technology has received increasing attention recently for high power applications. The converters with the technology are suitable for high voltage and high power applications due to their ability to synthesize waveforms with better harmonic spectrum and apply for the high voltage equipment with a limited voltage rating of device. In the family of multilevel inverters, the topologies based on cascaded H-bridges are particularly attractive because of their modularity and simplicity of control. This paper presents multilevel inverter with cascaded H-bridge for large-power motor drives. The main features of this drive 1) reduce harmonic injection 2) can generate near-sinusoidal voltages, 3) have almost no common-mode voltage; 4) are low dv/dt at output voltage; 5)do not generate significant over-voltage on motor terminal; The topology of the developed product is presented and the feasibility study of the inverter on 3300v 1MVA 7-level H-bridge type was tarried out with experiments.

• Journal of Animal Science and Technology
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• v.47 no.2
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• pp.233-242
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• 2005

Effects of supplemental charcoal powder and vitamin A on growth performance, serum profile and carcass characteristics with 24 Hanwoo steers were inves$\ell$ated. The Hanwoo steers were randomly assigned to one of the three dietary treatments: 1) Control(commercial feed), 2) Tl(commercial feed supplemented with 2% charcoal powder and 0.2 % vitamin A), 3) T2(commercial feed with 2 % charcoal powder). In the age 26 month, body weight of control Tl and T2 were 633.8 kg, 621.0 kg, 619.4 kg, respectively, with not significantly different(P> 0.05). The daily weight gain of control was the highest followed by Tl and T2. The contents of vitamin A(retinol) and total cholesterol in the blood of Tl was higher Tl(56.32 $\ell$ / dt, 163.83 mg/ dz) than the other treatment groups(P < 0.05). The average of WBC value in the blood was 6.86-" 9.83 k / ${\mu}\ell$, RBC value was 7.98 - 11.26 k / ${\mu}\ell$ and blood platelet was 236.7 - 287.0 k / ${\mu}\ell$. But The serum profile in blood was not significantly different between control and treatment groups. The carcass grade and characteristics of all treatments in Hanwoo steers were not significantly different except the texture.

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.276-280
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• 2001

The quality of images displayed by using an LC projector is strongly influenced by the cell-gap variations over LC panels, the essential components of the projector. We show that such influence can be relieved by introducing slit patterns in the pixel electrodes in the LC panels. The improvement comes from the compensation of the influence of cell-gap variations by optical anisotropy variations arising from the lateral components of the electric field generated by the slit patterned electrodes. Simulations show that cell-gap tolerance can be increased by more than 50% by introducing the slit patterns. This method can be used in TN mode LC panels, which use LC's with positive dielectric anisotropy. tropy.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.6
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• pp.233-241
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• 2005

The present model of a SF6 arc accounts for the copper vapour contamination from the electrodes inside a Laval nozzle of a circuit breaker. Steady state simulations have been done for the arc with electrode gap of 60mm and DC electric current of 500A, 1000A and 1500A for both cases with and without copper contamination. The effects of electrode polarity are considered for the arc current of 1000A. It was found out that evaporation of copper from the anode results in a cooling of the arc in a region close to the electrodes. The electrical potential across the electrodes is not sensitive to the presence of copper vapour, typically less than $4\%$ difference. Transient analysis has been done in order to obtain the arc properties at current zero. The arc current is increased linearly from -1000 to 0A when the upstream electrode is cathode with constant dI/dt of $27.0A/{\mu}s$ (or decreased linearly from 1000 to 0A when upstream electrode is anode). It has been predicted that the presence of copper vapour reduces the interruption capability of the breaker.

• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.693-699
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• 2000

Casting behavior of Zr(Y,Ce)O2 TZP/Mullite suspension during pressure filtration was investigated to prepare multi-layered Functionally Gradient Materials(FGM). The dispersion stabilities of each layer suspension were investigated by examination of zeta potential and viscosity. The each suspensions with 20 vol.% solid loading and 100 첸 of viscosity was prepared after fix of the dispersing agent (Sodium hexa-meta phosphate) and the binder (Hydroxyethyl cellulose), and then the cakes were formed at the 2.5 MPa~10.0MPa pressure range. The cake thickness of all suspensions was increased with the square root of time at the constant pressure, and the relations between filtration pressure(P)a nd dehydration rate (Q=dh/dt) showed that the flows of filtrates in the consolidated layers were laminar. The permeabilities were nearly constant during filtration, and kozeny constants(Kc) of the suspensions were 4.8~6.7. These valumes were seen as close to 5, which might be homogeneous particle packing during filtration. On the basis of those data, the multi layered compaction with 9 mm thickness and 52.5% green density was prepared by continuous pressure filtration.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.5-10
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• 2002

For fitness-for-service evaluation of high temperature plant components with defects, crack growth life must be assessed properly as indicated in the recent draft of API 579 code. Type 308 stainless steel has been widely used as a field weld material in the petrochemical industry. In this study, creep crack data of type 308 stainless steel are collected and re-analyzed using $C_t$ as a characterizing fracture parameter. A unique da/dt versus $C_t$ relationship was obtained despite of difference of creep deformation constant of the reviewed materials and specimen geometry of the tested specimens. The obtained results can be employed for crack growth life assessment and fitness-for-service evaluation for the cracks in high temperature components. It is also argued that since the effect of creep properties and other material variability on the creep crack growth behavior would be minor the obtained model may be applied for most of the 308 stainless steels.

• Journal of Korean society of Dental Hygiene
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• v.17 no.5
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• pp.889-898
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• 2017

Objectives: This study was conducted in order to identify the various influencing factors of dental caries according to the socio-economic characteristics and oral health behaviors across the life cycle among Koreans. Methods: The data were extracted from the 6th Korea National Health and Nutrition Examination Survey (2013-2015) and a total of 4,871 subjects with ages of 7 and over were selected. The data were analyzed using SPSS 21.0 for ${\chi}^2$-test and multi-logistic regression. Results: Significant differences were observed in the socio-economic characteristics, health behaviors and in the dental caries across the life cycle. The influencing factors of DT includes the type of health insurance (p<0.05) in school aged & adolescence, Oral health examination/year (p<0.01), Residence (p<0.05) in early adults, type of health insurance (p<0.001), Oral health examination/year (p<0.001), use of oral hygiene products (p<0.01) in late Adults, Oral health examination/year (p<0.05) and Gender (p<0.05) in old age. Conclusions: This study suggests that dental health promotion can be enhanced by regular checkup. The government must provide the people with better quality of oral health care and promotion across the life cycle in the near future.

• Transactions of the Society of Information Storage Systems
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• v.3 no.4
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• pp.173-177
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• 2007

A photo-reactive methacrylate monomer having triazine as a core component was examined for photochromic diffractive image formation. Photochromic photopolymer films as a recording media contained a monomer mixture of triazine difunctional metharylate (DT) and ethylene glycol phenyl ether acrylate, binder polymer, photo initiator, and a photochromic spiro-oxazine dye. The content of photochromic dye was changed to examine the effect of photochromophore on diffraction efficiency and real holographic image formation. Holographic recording was performed on the photopolymer film by the combination of reference and probe beam. The diffraction efficiency of the photopolymer film in real-time measurement reached a maximum of $\sim90%$ within 30s. It was highly dependent on the photochromophore contents. After holographic recording, the color of the recorded area was changed under UV light (365 nm) and reversibly bleached to original color upon exposure to a visible light source. Films containing only photochromophore without monomer mixture were not reactive under the recording beam (491nm). Diffractive image formation and mechanism of the holographic recording in the presence of photochromophore will be presented.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.5
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• pp.209-215
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• 2016

In this study, the effect of Nb contents and processing parameters on dynamic recrystallization behaviour of 0.15C-0.2Si-0.5Mn low-carbon steels was investigated. Three kinds of steel specimens with different Nb contents were fabricated and then high-temperature compressive deformation test was conducted by varying reheating temperature (RT), deformation temperature (DT), and strain rate (SR). The Nb2 and Nb4 specimens containing Nb had smaller prior austenite grain size than the Nb0 specimens, presumably due to pinning effect by the formation of carbides and carbonitrides precipitates at austenite grain boundaries. The high-temperature compressive deformation test results showed that dynamic recrystallization behavior was suppressed in the specimens containing Nb as the strain rate increased and deformation temperature decreased because of pinning effect by precipitates, grain boundary dragging effects by solute atoms, although the compressive stress increased with increasing strain rate and decreasing deformation temperature.