• Proceedings of the KIEE Conference
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• 1997.07b
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• pp.682-684
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• 1997

In the design of nonlinear control systems separation principle does not hold. Moreover even an exponentially decaying disturbances can destabilize a nonlinear system and lead to finite escape time from certain initial conditions. So we present a simple output feedback speed controller of induction motors which is designed to minimize the effects of observation error using the Kanellakopoulos et al's interlaced controller-observer design method. Simulation shows that the proposed controller has desired performance like another complex controllers.

• Proceedings of the Membrane Society of Korea Conference
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• 1995.10a
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• pp.58-73
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• 1995

Membrane filtration is a promising technology for efficient solid/liquid separation in water purification. In FY 1991, the Ministry of Health and Welfare, Japanese Government launched a comprehensive research project "MAC 21" for development of membrane technology and its application to public water supply. The project was conducted by the Water Purification Process Association (WPPA), under the supervision of the Institute of Public Health. By the research project from FY 1991 to FY 1993, we confirmed that microfiltration (MF)/ultrafiltration (UF) technology was applicable to water purification and MF/UF was a effective method for the removal of such contaminants as particulate matter and coliforms. The Guideline Committee organized under the Technical Committee prepared a the guidelines on application of membrane system to small-scale public water supplies, based on the results as written above. The guidelines has been published in Dec., 1994 by WPPA.4 by WPPA.

• Journal of Surface Science and Engineering
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• v.24 no.3
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• pp.125-136
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• 1991

a mathematical model is presented to describe the current distribution on a rotaing disk electrode under the galvanostatic pulse conlitions. A numerical technique by finite difference method to the transient convective diffusion equation, coordinate transformation and separation of variables to Laplace equation, and an iterative algorithm to solve the above equations simtltaneously with approximate boundary conditions were developed. An experimental investigated based on copper deposition in a copper sulfate-sulfuric acid system was performed and satisfactory agreement was obtained between expermental and theoretical current distribution. The current distribution of copper deposition is secondary current distribution within the experimental conditions. Dimensionless variables, N and J as well as Wagner number were used to determine the criteria for the uniformity of current distribution.

• Bulletin of the Korean Chemical Society
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• v.24 no.12
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• pp.1805-1808
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• 2003

The simultaneous determination of As(III), As(V), and DMA has been performed by ion chromatography (IC) coupled with inductively coupled plasma-mass spectrometry (ICP-MS). The separation of the three arsenic species was achieved by an anionic separator column (AS 7) with an isocratic elution system. The separated species were directly detected by ICP-MS as an element-selective detection method. The IC-ICP-MS technique was applied for the determination of arsenic species in a NIST SRM 1643d water sample. An As(III) only was detected in the sample. The detection limits of As(III), As(V) and DMA were 0.31, 0.45, and 2.09 ng/mL, respectively. It was also applied for the determination of arsenic species in a human urine obtained by a volunteer, and three arsenic species were identified. The determination of total As in human urines that were obtained from 25 volunteers at the different age was also carried out by ICP-MS.

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.957-960
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• 2003

A method of preparation of magnetite nanoparticles in ordered systems, as in vesicle and microemulsion, consisting of soybean lecithin and water has been introduced. The size of magnetite grain was controlled by the content of soybean lecithin and size of liposomes in the systems. It was found by experiment that magnetite nanoparticles were formed inside the double layer vesicles. The magnetite nanoparticles were separated by magnetic separation and centrifugation and the dispersion of the magnetite nanoparticles prepared at 10% (w/w) soybean lecithin was particularly stable. The formation of pure magnetite nanoparticles was confirmed by analyses of XRD and electron diffraction pattern.

• Bulletin of the Korean Chemical Society
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• v.28 no.5
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• pp.800-804
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• 2007

Cyanobacterial toxins, microcystins are very potent hepatotoxins and their occurrence has been reported all over the world. They could threaten human health when toxic Microcystis occurs in water supply reservoirs. In this study, the effects of several environmental factors on production and degradation of toxins produced by cyanobacteria in Lake Soyang have been studied. A new rapid quantification method of microcystins using fluorescence for a detection signal and a lateral-flow-type immunochromatography as a separation system was used. Culture age, temperature, light intensity, pH, N-nutrient concentration, P-nutrient concentration, iron and zinc concentration were the most importantly examined factors. The toxin content was the highest on 17-18 days and at temperatures between 20℃ and 25℃, and at pH between 8.4 and 8.8.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.102-108
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• 2002

Numerical analysis has been conducted in order to simulate the flow characteristics by tip clearance of turbine cascades. A 3-D Navier-Stokes CFD code based on body-fitted coordinate system, pressure-correction and finite volume method has been used along with a commercial CFD code. The present results have showed that the development and generation of leakage vortex, vortex within tip clearance, etc. are clearly simulated, consistent with the generally known tendency. The leakage vortex occurs mainly by a separation of leakage flow that arises due to a pressure difference between two surfaces of the blade at the tip.

• Journal of computational fluids engineering
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• v.16 no.3
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• pp.22-28
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• 2011

Laminar Flow over an equilateral triangular cylinder is studied for several inflow angles. Under an uniform flow of $Re_d$=50,75,100,125,150, the triangular cylinder is rotated by ${\theta}$=$0^{\circ}$,$15^{\circ}$,$30^{\circ}$,$45^{\circ}$,$60^{\circ}$,$75^{\circ}$,$90^{\circ}$,$105^{\circ}$. The governing equations are solved by the PISO algorithm based on the finite volume method of the unstructured grid system. The effects of the inflow angle on the vortex-shedding flows are investigated. The Strouhal number shows a minimum at ${\theta}$=$60^{\circ}$. It is closely related to the variation of pressure and flow structure induced by the movement of separation points.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.539-544
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• 2013

$Ag@SiO_2@SiO_2$(FITC) nanocomposites were prepared by the simple polyol process and St$\ddot{o}$ber method. Fluorescence enhancement of fluorescein moiety (fluorescein isothiocyanate, FITC) was investigated in the presence of silver nanoparticles in $Ag@SiO_2@SiO_2$(FITC) system with varying thickness (X nm) of first silica shell. Maximum enhancement factor of 4.3 fold was achieved in $Ag@SiO_2@SiO_2$(FITC) structure with the first silica shell thickness of 8 nm and the average separation distance of 11 nm between the surface of silver nanoparticle and fluorescein moiety. The enhancement is believed to be originated from increased excitation rate of fluorescein moiety due to concentrated local electromagnetic field which was improved by interaction of light with silver nanoparticles.

• Bulletin of the Korean Chemical Society
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• v.24 no.5
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• pp.555-558
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• 2003

An enrichment/separation system for atomic absorption spectrometric determinations of Cu(Ⅱ), Fe(Ⅲ), Ni(Ⅱ) and Co(Ⅱ) has been established. The procedure is based on the adsorption of the analytes as calmagite chelates on Chromosorb-102. The effects of some parameters including pH, amount of ligand, salt matrix, flow rates of sample and eluent solutions were investigated. Under optimized conditions, the relative standard deviation of the combined method of sample treatment, preconcentration and determination with FAAS (N=5) is generally lower than 5%. The limit of detection (3σ) was between 6.0-112.9 ㎍/L. The results were used for preconcentration of analytes from some sodium and ammonium salt.