• Journal of the Korean Ceramic Society
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• v.49 no.1
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• pp.37-42
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• 2012

Mass transport near grain boundary in a magnetite bi-crystal has been estimated at 823 K by finite element method. Mass transport near grain boundary strongly depends on the diffusivities along grain boundary. If grain boundary diffusion has the same oxygen activity dependence as lattice diffusion, there is no mass transport between grains and grain boundary. On the other hand, mass transport between grains and grain boundary is observed in the case that grain boundary diffusion has different oxygen activity dependence.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.313-320
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• 2013

The fractional slot windings are widely used in rotating machine in order to increase the flexibility of design and improve the voltage waveform. However, the MMF wave of fractional-slot windings are found to contain unique harmonic component, which are designated as even order space flux harmonics, fractional number flux harmonics, or both. They may cause stray loss and stator core vibration. This paper proposes new winding methods "novel interspersed windings" and "expanded group windings" to reduce these harmonics. The advantages of two proposed windings are verified by using numerical analysis and measurement test of winding model.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.620-625
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• 2018

Pyropia yezoensis is one of the most extensively cultivated seaweeds used as food in Korea. However, the quality and yield of Pyropia farms are frequently affected by outbreaks of thallus discoloration. The objective of this study was to develop a simple and rapid method to evaluate P. yezoensis discoloration caused by nutrient deficiencies. A colorimeter was used to quantify the color of P. yezoensis in nutrient deficient media over 10 days. Quantitative values of lightness (L), redness (a), and yellowness (b) measured with a colorimeter were used as indicators of P. yezoensis discoloration. The vacuoles of P. yezoensis were observed at 4 days and swelled gradually from 6 days onward. The three colorimeter parameters L, a, and b values showed significantly different values with culture period. The lightness (L) value was darker initially, and continued to lighten over culture period. The yellowness (b) value increased, but the redness (a) value decreased throughout this study. The a/b ratio and redness (a) values from the colorimeter were important P. yezoensis color change indicators. The discoloration group of P. yezoensis had quantitative values for parameters of L above 70, a below 2.6, and b above 15.0. The results of this study showed that quantitative colorimetric measurements can be used as tools for simple and rapid detection of P. yezoensis discoloration.

• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.417-430
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• 2003

A new method was developed to prepare microcapsules involving hydrophobic components. A totally new "silicone-resin-polypeptide" was used as the wall materials. The polypeptide was made by hydrolysis of collagen and silk protein and so on, and that was combined with silicone. This microcapsule was easily prepared from silicone-resin-polypeptide in water solution. The ratio of encapsulation in the microcapsule was not only high level as 90％, which had never been reached, but also the particle size could be controlled to obtain very small size (average particle size: 2${\mu}{\textrm}{m}$). Moreover, these microcapsules were resistant to high shearing forces and were stable over a long time period. This stable microcapsule was not crushed in pressure with finger spreading, so the core materials hardly touch the skin directly. Application in cosmetics by using microcapsule involving UV absorbents (2-ethylhexy1-4-methoxycinnamate (OMC) and 4-tert-butyl-4' -methoxydibenzoyl-methane (BMDBM)) was examined. It was possible to apply organic UV absorbents in water-rich formulations without any surfactant by using this microcapsule. This formulation demonstrated a good moisturizing and soft skin feel. Therefore, the microcapsule was applied to hair care products. As a result, the sunscreen hair lotion with microcapsule was able to prevent from damaging and decoloring of hair color by UV rays. As just, it was suggested that this microcapsules were be widely applied in cosmetics.cosmetics.

• Geophysics and Geophysical Exploration
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• v.11 no.1
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• pp.60-67
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• 2008

In this paper we consider an application of the method of electromagnetic (EM) migration to the interpretation of a typical marine controlled-source (MCSEM) survey consisting of a set of sea-bottom receivers and a moving electrical bipole transmitter. Three-dimensional interpretation of MCSEM data is a very challenging problem because of the enormous number of computations required in the case of the multi-transmitter and multi-receiver data acquisition systems used in these surveys. At the same time, we demonstrate that the MCSEM surveys with their dense system of transmitters and receivers are extremely well suited for application of the migration method. In order to speed up the computation of the migration field, we apply a fast form of integral equation (IE) solution based on the multigrid quasi-linear (MGQL) approximation which we have developed. The principles of migration imaging formulated in this paper are tested on a typical model of a sea-bottom petroleum reservoir.

• Computers and Concrete
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• v.8 no.2
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• pp.125-142
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• 2011

In the present paper, a numerical simulation method based on mesoscopic composite structure of concrete, the truss network model, is developed to evaluate the diffusivity of concrete in order to account for the microstructure of concrete, the binding effect of chloride ions and the chloride concentration dependence. In the model, concrete is described as a three-phase composite, consisting of mortar, coarse aggregates and the interfacial transition zones (ITZs) between them. The advantage of the current model is that it can easily represent the movement of mass (e.g. water or chloride ions) through ITZs or the potential cracks within concrete. An analytical method to estimate the chloride diffusivity of mortar and ITZ, which are both treated as homogenious materials in the model, is introduced in terms of water-to-cement ratio (w/c) and sand volume fraction. Using the newly developed approaches, the effect of cracking of concrete on chloride diffusion is reflected by means of the similar process as that in the test. The results of calculation give close match with experimental observations. Furthermore, with consideration of the binding capacity of chloride ions to cement paste and the concentration dependence for diffusivity, the one-dimensional nonlinear diffusion equation is established, as well as its finite difference form in terms of the truss network model. A series of numerical analysises performed on the model find that the chloride diffusion is substantially influenced by the binding capacity and concentration dependence, which is same as that revealed in some experimental investigations. This indicates the necessity to take into account the binding capacity and chloride concentration dependence in the durability analysis and service life prediction of concrete structures.

• Computers and Concrete
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• v.20 no.4
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• pp.391-407
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• 2017

Fiber reinforced polymer (FRP) bars have been recently used to reinforce concrete members in flexure due to their high tensile strength and especially in corrosive environments to improve the durability of concrete structures. However, FRPs have a low modulus of elasticity and a linear elastic behavior up to rupture, thus reinforced concrete (RC) components with such materials would exhibit a less ductility in comparison with steel reinforcement at the similar members. There were several studies showed the behavior of concrete beams with the hybrid combination of steel and FRP longitudinal reinforcement by adopting the experimental and numerical programs. The current study presents a numerical and analytical investigation based on the data of previous researches. Three-dimensional (3D) finite element (FE) models of beams by using ANSYS are built and investigated. In addition, this study also discusses on the design methods for hybrid FRP-steel beams in terms of ultimate moment capacity, load-deflection response, crack width, and ductility. The effects of the reinforcement ratio, concrete compressive strength, arrangement of reinforcement, and the length of FRP bars on the mechanical performance of hybrid beams are considered as a parametric study by means of FE method. The results obtained from this study are compared and verified with the experimental and numerical data of the literature. This study provides insight into the mechanical performances of hybrid FRP-steel RC beams, builds the reliable FE models which can be used to predict the structural behavior of hybrid RC beams, offers a rational design method together with an useful database to evaluate the ductility for concrete beams with the combination of FRP and steel reinforcement, and motivates the further development in the future research by applying parametric study.

• Journal of The Korean Astronomical Society
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• v.50 no.6
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• pp.157-165
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• 2017

$H_2O$ maser emission at 22 GHz in the circumstellar envelope is one of the good tracers of detailed physics and kinematics in the mass loss process of asymptotic giant branch stars. Long-term monitoring of an $H_2O$ maser spectrum with high time resolution enables us to clarify acceleration processes of the expanding shell in the stellar atmosphere. We monitored the $H_2O$ maser emission of the semi-regular variable R Crt with the Kagoshima 6-m telescope, and obtained a large data set of over 180 maser spectra over a period of 1.3 years with an observational span of a few days. Using an automatic peak detection method based on least-squares fitting, we exhaustively detected peaks as significant velocity components with the radial velocity on a $0.1kms^{-1}$ scale. This analysis result shows that the radial velocity of red-shifted and blue-shifted components exhibits a change between acceleration and deceleration on the time scale of a few hundred days. These velocity variations are likely to correlate with intensity variations, in particular during flaring state of $H_2O$ masers. It seems reasonable to consider that the velocity variation of the maser source is caused by shock propagation in the envelope due to stellar pulsation. However, it is difficult to explain the relationship between the velocity variation and the intensity variation only from shock propagation effects. We found that a time delay of the integrated maser intensity with respect to the optical light curve is about 150 days.