• 한국재료학회지
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• 제4권7호
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• pp.767-774
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• 1994

The TbFeCo thin films were prepared by the magnetron sputtering system to investigate the effect of the base pressure, film thickness and pre sputtering on the oxidation of the films by analyzing the change of matneto optical properties and by AES depth profile. The films prepared by the facing targets sputtering system represented almost constant magneto optical properties independent of the base pressure resulting from the short flight distance of the sputtered particles. Also, the thin TbFeCo films represented better perpendicular anisotropy as the films thickness increased with pre sputtering. However, it was still needed a deposition rate higher than a certain critical deposition rate to obtain a perfect perpendicular anisotropy even at a very high film thickness.

• 한국환경과학회지
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• 제9권2호
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• pp.165-171
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• 2000

A kinetic study for anion exchange was performed for commercially available Cl- type anion exchange resin in use to remove nitrate in water. The obtained results from the batch reactor were applied to the Langmuir and Freundlich models. The constants for Lagmuir model were qmax =29.82 and b=0.202, and for Freundlich model were K=5.509 and n=1.772. Langmuir model showed betterfit than Frendlich model for the experimental results. Ion exchange reaction rate was also calculated and the the approximate first-order reaction, rate constant k1 was 0.16 L/mg.hr. Effective diffusion coefficient was obtained in the range from $9.67$\times$10^{-8} cm^2/sec$ for initial concentration change, and from $6.09$\times$10^{-7} to 3.98$\times$10^{-6} cm^2/sec$ for reaction temperature change. Activation energy during the diffusion was calculated as 26 kcal/mol.

• 전자공학회논문지B
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• 제33B권8호
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• pp.60-67
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• 1996

In this paper, we propose a new temporal interpolation method based on spatial filtering. Compared with the conventional method, the proposed one may use a few adjacent frames and apply temporal lowpass filtering. To develop this method, we follow the basic approach of sampling rate conversion. Additionally, we use some assumption of video sequence : moving object has constant velocity rigid translational motion. From them, spatial filtering for temporal sampling rate conversion is described. This method has a lot of noise immunity on a motion vector and doesn't make a great difference from the original frame. The interpolated frame shows moderate change even there is a great time difference. This method has exactly same description of motion adaptive spatial filter which has an efficient temporal band-limiting characteristics. It imposes the possibility to make video sequence with good pictural quality.

• 한국전산유체공학회지
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• 제15권4호
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• pp.109-114
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• 2010

In a fan design, CFD analysis, which is very useful for mechanical design relating to the heat and fluid dynamics, is one of the most popular tools. However, since the CFD analysis is conventionally carried out with the constant fan speed condition, the speed change, induced by the air flow rate and motor characteristics, is hardly modeled. And, consequently, the remarkable difference exist between analysis and experimental results. In this paper, we has proposed a method of setting the varying fan speed as a boundary condition considering air flow rate and motor torque-speed characteristics. The effectiveness of the proposed method is verified by comparison with experimental results.

• 소성∙가공
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• 제22권8호
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• pp.450-455
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• 2013

In the current study, a new dynamic recrystallization model for predicting high temperature flow stress is developed based on a physical model and the mean field theory. In the model, the grain aggregate is assumed as a representative volume element to describe dynamic recrystallization. The flow stress and microstructure during dynamic recrystallization were calculated using three sub-models for work hardening, for nucleation and for growth. In the case of work hardening, a single parameter dislocation density model was used to calculate change of dislocation density and stress in the grains. For modeling nucleation, the nucleation criterion developed was based on the grain boundary bulge mechanism and a constant nucleation rate was assumed. Conventional rate theory was used for describing growth. The flow stress behavior of pure copper was investigated using the model and compared with experimental findings. Simulated results by cellular automata were used for validating the model.

• 한국식품영양과학회지
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• 제29권5호
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• pp.807-813
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• 2000

One hundred fifty grams of Korean fermented soybean paste and hot pepper-soybean paste were packaged in glass jar of 232 mL and Sotred at 5, 13, 22 and 30℃. During the storage, the changes in their microbial flora and quality attributes were monitored. Carbon dioxide production rate from the stored pastes were also determined from initial change of CO₂concentration in headspace of the pack. Hot pepper-soybean pate showed much higher CO₂ production rate higher dependence of CO₂ production on temperature compared to soybean paste. Total aerobic bacteria count and lactic acid bacteria count did not change significantly through the storage. Yeast count in soybean paste decreased slowly after initial uprise while that of hot pepper-soybean paste steadily decreased. Surface color of hot pepper paste changed to dark red with slight decrease in 'L' value and slight increase in 'a' and 'b' values, whereas any significant color change was not observed in soy paste. Titratable acidity increased with time with higher increase in soybean paste, but pH stayed at constant level for both pastes. All the rates of quality change were higher with higher temperature. Pressure buildup due to CO₂ production needs to be considered first in designing the packages of the fermented pastes before their color changes and other chemical quality changes.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.69-76
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• 2002

The aim of this study is to provide fundamental informations that make it possible to use a cool stream and a hot stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and a hot stream in each exit of a tube. Also we measured the axial and the radial temperature distribution in internal spare of a tube. From the study, fellowing conclusive remarks 7an be made. First, As the number of nozzles increase, separation point move into the hot exit. Second, When we use guide vane type nozzle, the axial temperature distribution constant over the 0.75 of air mass flow rate radio. Third, When we use Spiral type nozzle, axial and radial temperature distribution in the inner space is higher than another nozzle. Fourth, Axial and radial temperature distribution in the inner space vortex-tube is determined by separation point. And separation point is moved by changing of air mass flow rate ratio. At last, A heating apparatus is possible far vortex-tube to use.

• 한국환경과학회지
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• 제20권1호
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• pp.119-126
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• 2011

In this study, reaction model and reactions rate accelerated by o-iodosobenzoate ion(IB$^{\ominus}$) on hydrolysis reaction of p-nitrophenyl valate(NPV) using ethyl tri-octyl ammonium mesylate(ETAMs) for quaternary ammonium salts, the phase transfer catalysis(PTC) reagent, were investigated. The effect of IB$^{\ominus}$ on hydrolysis reaction rate constant of NPV was weak without ETAMs solutions. Otherwise, in ETAMs solutions, the hydrolysis reactions exhibit higher first order kinetics with respect to the nucleophile, IB$^{\ominus}$, and ETAMs, suggesting that reactions are occurring in small aggregates of the three species including the substrate(NPV), whereas the reaction of NPV with OH$^{\ominus}$ is not catalyzed by ETAMs. Different concentrations of NPV were tested to measure the change of rate constants to investigate the effect of NPV as substrate and the results showed that the effect was weak. This means the reaction would be the first order kinetics with respect to the nucleophile. This behavior for the drastic rate-enhancement of the hydrolysis is referred as 'Aggregation complex model' for reaction of hydrophobic organic ester with o-iodosobenzoate ion(IB$^{\ominus}$) in hydrophobic quarternary ammonium salt(ETAMs) solutions.

• Journal of Welding and Joining
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• 제25권4호
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• pp.42-48
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• 2007

An inert gas atomized NiTiZrSiSn bulk metallic glass feedstock was sprayed onto the copper plate using vacuum plasma spraying process. In order to change the in-flight particle energy, that is, thermal energy, the hydrogen gas flow rate in plasma gas mixture was increased at the constant flow rate of argon gas. Coating and single pass spraying bead were produced with the least feeding rate. Regardless of the plasma gas composition, fully melted through unmelted particle could be observed on the overlay coating. However, the frequency of the unmelted particle number density was increased with the decrease of the hydrogen gas flow rate. The amorphous phase fraction within coating was also affected by the number density of the unmelted particle.

• 천문학회보
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• 제45권1호
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• pp.42.3-42.3
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• 2020

We investigate the observational properties of Wolf-Rayet stars, suggest the constraint of their mass-loss rate and apply our results to the observed progenitor candidates of Type Ib/Ic supernovae (iPTF13bvn and SN 2017ein). For this purpose, we adopt the WR star models with various mass-loss rates and wind terminal velocities. We obtain the high resolution spectra of those models at the pre-supernova phase using the radiative transfer code CMFGEN. We verify the optically faint property of SN Ic progenitors and show that the optical faintness is mainly originated by the high effective temperature at the photosphere. We also show that a simple analytic model for WR winds using a constant opacity can roughly predict the photospheric parameters. We show that the change of the mass-loss rate and the terminal wind velocity critically affects the optical luminosity. We find the optical luminosities of SN Ic progenitor models with our fiducial mass-loss rate prescription are fainter than the detection limits. We also suggest the mass-loss rate of WR stars may not exceed 2 times of our fiducial value by comparing our predictions with the detection limit of SN Ib/Ic progenitors. The directly observed progenitor candidate of iPTF13bvn can be explained by our SN Ib progenitor models. We find that the SN 2017ein progenitor candidate is too bright and too blue to be a SN Ic progenitor.