• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.284-284
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• 2006

Electrospray deposited films of poly(vinylidene fluoride) were prepared with various conditions. A model has been developed, which provides the state of the electrosprayed droplet at impact. With a combination of the experimental films and the model calculations, it can be shown that growth rate, the increase of the sprayed solution on the substrate per second, defines the film morphology in electrospray deposition. Growth rate indicates which factors play the main role in the film formation process. The most important factors are liquid flow, surface tension and shear rate. The model can calculate the shear rate and it is shown that PVDF, and most likely polymers in general, has a large range of growth rates, where the morphology only depends on the shear rate of the depositing droplet. This method can also be used to describe electrospray deposition of other compounds.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.703-707
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• 1994

This paper proposes a method of learning control in DC servomotor using a neural network. First we estimate the pulse transfer function of the servo system with an unknown load, then we determine the best gains of I-PD control system using a neural network. Each time the load changes, its best gains of the I-PD control system is computed by the neural network. And the best gains and its pulse transfer function for the case are stored in the memory. According the increase of the set of gains and its pulse transfer function, the learning control system can afford the most suitable I-PD gains instantly.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1966-1971
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• 2005

Though several previous anti-windup techniques have been proposed, they are limited to linear systems or friction is not considered. Thus this paper proposes a compensation scheme for input-constrained robot systems with friction to cope with the windup phenomenon and shows its effectiveness by simulations. Given a feedback linearizing controller for a robot system designed without considering its input constraint, an additional dynamic compensator is proposed to account for the constraint. The dynamic anti-windup is based on the minimization of a reasonable performance index, and properties of the resulting closed-loop are presented.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.493-496
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• 2006

Steel corrosion in concrete is aggravated with the increase of chloride content in concrete. So, there are regulations in the total amount of chloride ions in concrete in Korea and Japan. The purpose of this paper is to propose a resonable method to regulate the amount of chlorides in concrete. In this study, the experimental results showed that it is rather reasonable to regulate the amount of chloride ions in cement than the total amount of the chloride ions in concrete.

• Journal of Ocean Engineering and Technology
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• v.14 no.3
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• pp.46-54
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• 2000

Three dimensional numerical experiments that included the land-use transformation by the large scale reclamation were used to investigate the mesoscale air flow over the coastal regions. In this paper the surface temperature of the inland was determined through the surface heat budget consideration with inclusion of a layer of vegetation. The vertical diffusion coefficients of momentum, heat and specific humidity in the constant flux layer were taken from the Mellor and Yamada(1975). It has shown that the resulting model is able to reproduce the air circulation in coastal regions, and the simulated characteristics agree with the known properties of this circulation. A series of numerical experiments were then carried out to investigate the diurnal response of the air flow to various types of surface inhomogeneities.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1302-1305
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• 2006

We evaluated the usability of two kinds types of recently commercialized e-books through an analysis of their protocols, compared the time required to read an e-book with that for a paper book, and compared text display sizes that were easy to read for aged and young readers, under identical conditions. This showed clear problems with the usability of e-books for aged and young readers. It was found that it took longer for aged readers to read text in an e-book than for young readers, and that the size of text that aged readers found easy to read was different than for young readers.

• The Korean Journal of Ceramics
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• v.5 no.1
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• pp.40-43
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• 1999

In order to investigate Sn substitution sites and interstitial O atoms in tin-doped indium oxide, molecular dynamics (MD) simulations were carried out. There are two kinds of cation sites in $In_2O_3$, namely b-site and d-site. NTP-MD simulations under the condition of 300 K and 0 GPa were performed with two kinds of cells substituted by Sn atoms at each site. The excess oxygen atom accompanied with Sn doping was also taken into consideration. According to the calculations of Sn potential energies in each site, it was revealed that Sn atoms were substituted for b-sites rather than for d-sites. It was also revealed that the interstitial excess oxygen atoms tend to be connected with the Sn atoms substituted for the d-sites Sn rather than for the b-site. There MD simulation results well agreed with the experimental results.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.363-367
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• 1999

New glass ceramics were investigated for the application as substrates to be used in hard disk devices. The glass system to precipitate lithium di-silicate was studied so as to optimize the composition to realize very high surface flatness. The addition of small amount of several metal oxides with high valences had very drastic effects on the microstructure, because they played a role of crystallization agents, and consequently it determined surface flatness even after the polishing process. The possible mechanism changes of crystal growth due to the addition of metal oxides were discussed in relation to the final micro-texture development. The glass ceramics with very high surface flatness(Ra=7.1 $\AA$) was obtained by the addition of the mixture of $P-2O_5 \;and \;MoO_3$ as crystallization agents.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.348-352
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• 1999

Barium uranium sulfides, $BaUS_3$ and $BaU_2B_5$, were synthesized in a single phase by the reactin of $(Ba, UO_2)(NO_3)_2$ at Ba/U=1 and 0.5 with carbon disulfide at 1273 K for 6 h. They crystallized in orthorhombic structure with space group, Pnma. The lattice parameters a, b and c are 7.493, 10.38 and 7.238$\AA$ for $BaUS_3$ and 7.525, 8.475 and 11.858$\AA$ for $BaU_2S_5$, respectively. The electrical conductivity of these compunds increased with increasing temperature above 200K, below which however, it was nearly temperature independent. The Hall coefficient suggested that they are n-type semiconductors.

• Journal of Radiation Protection and Research
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• v.26 no.3
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• pp.133-137
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• 2001

Spatial and time distributions of x-rays and neutrons from Hokkaido University 45 MeV electron linac facility were measured and compared with the calculation. In the calculation, x-rays in a Pb-target were evaluated using the EGS-code. The x-rays and the neutrons from the target to the facility building boundary and skyshine process outside the facility building were simulated with the EGS and the MCNP respectively.