• Proceedings of the KIEE Conference
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• summer
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• pp.607-609
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• 2004

A breakdown occurred in power transformer causes interruption of power transmission. Protective relay should be installed in transformer to detect such a fault. Protective relaying algorithm for transformer must be included a function to discriminate between winding fault and inrushing state. Recently, current differential relay is widely used to protect power transformer. However if inrush occurs in transformer, relay can be tripped by judging as internal fault. New algorithms are required in order to such problem. This study proposes a new protective relaying algorithm using Neuro-Fuzzy inference and wavelet. A variety of transformer transient states are simulated by BCTRAN and HYSDT in EMTP. D1 coefficients of differential current are obtained by wavelet transform. D1 coefficients and RMS of 3-phase primary voltage are used to make a target data and are trained by Nwo-Fuzzy algorithm which distinguishes correctly whether internal fault occurs or not within 1/2 after fault detection. It is evaluated that the results obtained by simulations can effectively protect a transformer by contact discriminating between winding fault and inrushing state.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.55.2-55.2
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• 2012

Silicate-carbon stars are characterized by oxygen-rich (O-rich) dust features despite their carbon-rich (C-rich) photospheres. While the origin of silicate-carbon stars has been a mystery ever since their discovery, the most widely accepted hypothesis is that the silicate-carbon stars have a low-luminosity companion and the O-rich material is stored in a circumbinary disk or a circumstellar disk even after the primary star becomes a carbon star. In order to study the properties of circumstellar dust envelopes of silicate-carbon stars, we perform radiative transfer model calculations using RADMC-3D with an axi-symmetric dust density distribution (a disk) as well as a spherically symmetric dust distribution. For various dust envelope models with different shapes and chemistry, we calculate the model spectral energy distributions (SEDs) and compare the model results with the observed SEDs of selected 5 silicate-carbon stars. The Circumstellar disk models are fairly well fitted with the observational data of 5 silicate-carbon stars. We find some evidences that the circumbinary disk model could be a better explanation for the origin of silicate carbon stars than the simple detached silicate dust shell model of the transition phase of the stellar chemistry.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.957-960
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• 1997

A complete quantitative understanding of DT has been difficult because the process represents such s broad field of research. The experimental measurement of tool force is a single area of DT which still covers a wide range of possibilities. Here are numerous parameters of the process which affect cutting forces. There are also many turnable materials of current interest. To obtain information toward a better understanding of the process, a few cutting parameters and materials were selected for detail study. It was decided that free-oxygen copper and 6061-T6 alloy aluminum would be the primary test materials. There are materials which other workers have also used because of there wide use in reflective applications. The experimental phase of the research project began by designing tests to isolate certain cutting parameters. The parameters chosen to study were those that affected the cross-sectional area of the uncut chip. The specific parameters which cause this area to vary are the depth of cut and infeed per revolution, or feedrates. Other parameter such a tool nose radius and surface roughness were investigated as they became relevant to the research.

• Molecular & Cellular Toxicology
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• v.1 no.2
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• pp.87-91
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• 2005

Although 2D-PAGE has been widely used as the primary method for protein separation, difficulties in displaying proteins with an extreme values of isoelectric paint (pI), molecular size and hydrophobicity limit the technique. In addition, time consuming steps involving protein transfer and extraction from the gel-pieces can result in sample loss. Here, we describe a novel protein separation technique with capillary size-exclusion chromatography (CSEC) for rapid protein identification from human plasma. The method includes protein fractionation along with molecular size followed by in-solution tryptic digestion and peptide analysis through reversed phase liquid chromatography (RPLC) coupled to nanoflow electrospray-tandem mass spectrometry (ESI-MS/MS). Tryptic peptides are applied an a $100\;{\mu}m\;i.d.{\times}10mm$ length pre-column and then separated on a $75\;{\mu}m{\times}200mm$ analytical column at -100 nL/min flaw rate. Proteins were identified over the wide ranges of pI (3.7-12.3) when this technique was applied to the analysis of $1-2\;{\mu}L$ of human plasma. This gel-free system provides fast fractionation and may be considered a complementary technique to SDS-PAGE in proteomics.

• Food Science and Biotechnology
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• v.15 no.6
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• pp.948-953
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• 2006

The D-form of lactic acid is frequently detected in fermented foods, and an excessive dietary intake of D-lactic acid may induce metabolic stress in both infants and patients. This work was carried out to determine the prevailing microorganisms relevant to the accumulation of D-lactic acid in kimchi. Leuconostoc (Leuc.) mesenteroides and Leuc. citreum primarily synthesized D-lactate with a small quantity of L-form. Leuc. gelidum and Leuc. inhae evidenced patterns similar to this. Lactobacillus (Lb.) plantarum and Lb. brevis were shown to convert glucose into a balanced mixture of D-/L-lactic acid, whereas Lb. casei principally synthesized L-lactic acid and a very small quantity of D-lactic acid. When kimchi was incubated at 8 or $22^{\circ}C$, D-lactic acid was over-produced than L-form. Leuconostoc was determined as the primary producer between the initial to mid-phase of fermentation and Lb. plantarum or Lb. brevis seemed to boost D-lactic acid content during later stage of acid accumulation.

• Structural Engineering and Mechanics
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• v.50 no.2
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• pp.151-161
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• 2014

In this paper, fuel tank of the locomotive ER 24 has been studied. Firstly the behavior of fuel and air during the braking time has been investigated by using a two-phase model. Then, the distribution of pressure on the surface of baffles caused by sloshing has been extracted. Also, the fuel tank has been modeled and analyzed using Finite Element Method (FEM) considering loading conditions suggested by the DIN EN 12663 standard and real boundary conditions. In each loading condition, high stressed areas have been identified. By comparing the distribution of pressure caused by sloshing phenomena and suggested loading conditions, optimization of the tank has been taken into consideration. Moreover, internal baffles have been investigated and by modifying their geometric properties, search of the design space has been done to reach the optimal tank. Then, in order to reduce the mass and manufacturing cost of the fuel tank, Non-dominated Sorting Genetic Algorithm (NSGA-II) and Artificial Neural Networks (ANNs) have been employed. It is shown that compared to the primary design, the optimized fuel tank not only provides the safety conditions, but also reduces mass and manufacturing cost by %39 and %73, respectively.

• Membrane and Water Treatment
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• v.11 no.4
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• pp.237-245
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• 2020

The effects of the mixed two solvents, Dimethylacetamide (DMAc) and Dimethylformamide (DMF), and Polyethylene glycol (PEG) and Polyvinylpyrrolidone (PVP) as additives on performance of Polyvinylidene fluoride (PVDF) membranes were studied. Initially, PEG200 was used as a primary additive at fixed percentage of 5% wt. PVP was then blended with PEG200 in different concentrations. PVDF and DMAc were used as polymer and solvent in the casting solutions, respectively. To control the diffusion rate of PVP in the presence of PEG200 and PVP blend, mixtures of DMAc and DMF were used as the mixed solvent in the casting solutions. Asymmetric PVDF membranes were prepared via phase inversion process in a water bath and the effects of two additives and two solvents on the membrane morphology, pure water flux (PWF), hydrophilicity and rejection (R) were investigated. Attenuated Total Reflection Fourier Transform Infrared Spectra (ATR-FTIR) analysis was used to show the residual PVP on the surface of the membranes. Atomic Force Microscopy (AFM) was utilized to determine roughness of membrane surface. The use of mixed solvents in the casting solution resulted in reduction of PVP diffusion rate and increment of PEG diffusion rate. Eventually, PWF and R values reduced, while porosity and hydrophilicity increased.

• Nuclear Engineering and Technology
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• v.44 no.7
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• pp.709-718
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• 2012

The pressurized water reactor APR1400 adopts DVI (Direct Vessel Injection) for the emergency cooling water in the upper downcomer annulus. The International Standard Problem number 50 (ISP-50) was launched with the aim to investigate thermal hydraulic phenomena during a 50% DVI line break scenario with best estimate codes making use of the experimental data available from the ATLAS facility located at KAERI. The present work describes the calculation results obtained for the ISP-50 using the RELAP5/MOD3.3 system code. The work aims at validation and assessment of the code to reproduce the observed phenomena and investigate about its limitations to predict complicated mixing phenomena between the subcooled emergency cooling water and the two-phase flow in the downcomer. The obtained results show that the overall trends of the main test variables are well reproduced by the calculations. In particular, the pressure in the primary system show excellent agreement with the experiment. The loop seal clearance phenomenon was observed in the calculation and it was found to have an important influence on the transient progression. Moreover, the collapsed water levels in the core are accurately reproduced in the simulations. However, the drop in the downcomer level before the activation of the DVI from safety injection tanks was underestimated due to multi-dimensional phenomena in the downcomer that are not properly captured by one-dimensional simulations.

• Journal of Energy Engineering
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• v.12 no.2
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• pp.93-100
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• 2003

An estimation methodology of the mass and energy (M/E) release due to the main steam line break (MSLB) has been developed with the RETRAN-3D code. In the case of equipment qualification (EQ), the over-estimated temperature would exceed the design limits of some cables or valves. In order to have a more flexible EQ profiles from the MSLB M/E release, the methodology with the best-estimated code was used. The major conditions affecting the MSLB M/E were found to be the initial SG level, heat transfer between primary and secondary sides, power level, operable protection system, main or auxiliary feedwater availability, and break conditions. The RETRAN-3D models were developed for the Kori unit 1 (KRN-1) which is typical two loop Westinghouse (WH) designed plant. Particularly, a detailed model of the steam generators was developed to estimate a more realistic two-phase heat transfer effect of the steam flow. After the modeling, the methodology has been developed through the sensitivity analyses. The M/E release data generated from the analyses have been used as the input to the inside containment pressure and temperature (P/T) analysis. According to the results at the point of view containment P/T, the Kori unit 1 can have more margin of 5∼15 ㎪ in pressure and 8∼15$^{\circ}C$ in temperature.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.112-122
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• 2014

A main steam line break (MSLB) test at the ATLAS facility was simulated using the best-estimate thermal-hydraulic system code, MARS-KS. This has been performed as an activity at the third domestic standard problem for code benchmark (DSP-03) that has been organized by Korea Atomic Energy Research Institute (KAERI). The results of the MSLB experiment and the MARS input data prepared for the previous DSP-02 using the ATLAS facility were provided to participants. The preliminary MSLB simulation using the base input data, however, showed unphysical results in the primary-to-secondary heat transfer. To resolve the problems, some improvements were implemented in the MARS input modelling. These include the use of fine meshes for the bottom region of the steam generator secondary side and proper thermal-hydraulics calculation options. Other input model improvements in the heat loss and the flow restrictor models were also made and the results were investigated in detail. From the results of simulations, the limitations and further improvement areas of the MARS code were identified.