• Bulletin of the Korean Chemical Society
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• v.8 no.2
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• pp.83-88
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• 1987

The Smoluchowski equations with a linear and a parabolic potentials in one-dimensional case are solved for the reflecting boundary condition. Analytic expressions for the long-time behaviors of the remaining probabilities are obtained. These results, together with the previous result for a step potential, show the dependence of the desorption process on the form of potential. The effect of the radiation boundary condition is also investigated for three types of potentials.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.886-891
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• 1995

Electroactive monolayers based on zirconium(Ⅳ) phosphonate film were prepared on gold and tin oxide electrodes by sequential layer-by-layer depostion technique. High transfer coefficient values and surface coverages of surface bound redox molecules were obtained from the electrochemical measurements of heterogeneous electron transfer rates for monolayer modified electrodes. 1,10-Decanediylbis(phosphonic acid) (DBPA) monolayer as insulating barrier was effective in blocking electron transfer. However, these film modified oxide electrode shows voltammetric behavior of diffusion/permeation process taking place at very small exposed area of modified electrode through channels due to structural defects within film when a very fast redox couple such as Ru(NH3)63+ is hired.

• Journal of the Chungcheong Mathematical Society
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• v.36 no.1
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• pp.39-53
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• 2023

In this paper, we consider a delayed ratio-dependent predator-prey reaction-diffusion system with homogenous Neumann boundary conditions. We study the existence of nonnegative solutions and the stability of the nonnegative equilibria to the system. In particular, we provide a sufficient condition for the positive equilibrium to be globally asymptotically stable.

• Journal of the Korean Vacuum Society
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• v.21 no.5
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• pp.242-248
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• 2012

Valence band of a vacuum-reduced $TiO_2$ (001) surface has been carefully examined using synchrotron x-ray photoelectron spectroscopy to investigate variation of the gap state upon oxidation and thermal diffusion of $Ti^{3+}$ interstitials from the bulk. We compare our results with that obtained from $TiO_2$ (110) and aim to address a crystal-face dependency in the oxidation and diffusion rates of $Ti^{3+}$ interstitials. We find very similar behaviors in the oxidation and thermal diffusion rate of $Ti^{3+}$ interstitials between the two crystal faces suggesting a negligible crystal-face dependency in this case.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.522-528
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• 2003

Concrete has been considered as a semi-permanent structural material, because its excellent durability. However, such high durable structure is often attacked by some environmental condition such as chloride diffusion, carbonation and so on. In order to prevent the deterioration behaviors of concrete structures. We estimated durability of concrete when used surface treatment system and coatings by new type inorganic coating materials. Base on the results of chloride ion's diffusion test, the coated cement mortar had smaller transmitted quantity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.5
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• pp.695-702
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• 2002

Nonlinear dynamics of striped diffusion flames, by the diffusional-thermal instability with Lewis numbers sufficiently less than unity, is numerically investigated by examining various two-dimensional flame-structure solutions. The Lewis numbers for fuel and oxidizer are assumed to be identical and an overall single-step Arrhenius-type chemical reaction rate is employed in the model. Particular attention is focused on identifying the flame-stripe solution branches corresponding to each distinct stripe pattern and hysteresis encountered during the transition. At a Damkohler number slightly greater than the extinction Damkohler number, eight-stripe solution first emerges from one dimensional solution. The eight-stripe solution survives Damkohler numbers much smaller than the extinction Damkohler number until the transition to four-stripe solution occurs at the first forward transition Damkohler number. At the second forward transition Damkohler number, somewhat smaller than the first transition Damkohler number, the transition to two-stripe solution occurs. However, anu further transition from two-stripe solution to one-stripe solution is not always possible even if one-stripe solution can be independently accessed for particular initial conditions. The Damkohler number ranges for two-stripe and one-stripe solutions are found to be virtually identical because each stripe is an independent structure if distance between stripes is sufficiently large. By increasing the Damkohler number, the backward transition can be observed. In comparison with the forward transition Damkohler numbers, the corresponding backward transition Damkohler numbers are always much greater, thereby indicating significant hysteresis between the stripe patterns of strained diffusion flames.

• Journal of the Korean Ceramic Society
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• v.34 no.1
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• pp.23-30
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• 1997

Semiconductive SrTiO3 ceramic bodies were prepared by conventional ceramic powder processes in-cluding sintering in a reducing atmosphere. Sodium or potassium ions were diffused from the surface of the sintered bodies into the inner region using thermal diffusion process at 800-120$0^{\circ}C$. The effects of such ther-mal treatments on the electrical and chemical characteristics of the grain boundaries were investigated. The presence of sodium or potassium ions at grain boundaries produces non-linear current-voltage behaviors, electrical boundary potential barriers of 0.1-0.2eV, and threshold voltages of 10-70V. The diffused ions form diffusion layers with thicknesses of 20-50nm near the grain boundaries, reducing the concentration of strontium and oxygen.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.8
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• pp.3005-3027
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• 2015

Spam has become one of the top threats of micro-blogging networks as the representations of rumor spreading, advertisement abusing and malware distribution. With the increasing popularity of micro-blogging, the problems will exacerbate. Prior detection tools are either designed for specific types of spams or not robust enough. Spammers may escape easily from being detected by adjusting their behaviors. In this paper, we present a novel model to quantitatively evaluate information diffusion in micro-blogging networks. Under this model, we found that spam posts differ wildly from the non-spam ones. First, the propagations of non-spam posts mostly result from their followers, but those of spam posts are mainly from strangers. Second, the non-spam posts relatively last longer than the spam posts. Besides, the non-spam posts always get their first reposts/comments much sooner than the spam posts. With the features defined in our model, we propose an RBF-based approach to detect spams. Different from the previous works, in which the features are extracted from individual profiles or contents, the diffusion features are not determined by any single user but the crowd. Thus, our method is more robust because any single user's behavior changes will not affect the effectiveness. Besides, although the spams vary in types and forms, they're propagated in the same way, so our method is effective for all types of spams. With the real data crawled from the leading micro-blogging services of China, we are able to evaluate the effectiveness of our model. The experiment results show that our model can achieve high accuracy both in precision and recall.

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.270-278
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• 2007

PEMFC electrodes with various gas diffusion layers (GDL) were characterized to find out the effect of GDL on fuel cell performance. The physical properties of GDL such as electric conductivity, porosity, air permeability, water flux, PTFE content, etc had close relationship each other and affected on the variation of the cell performance. It was observed that the micro-porous layer (MPL) on carbon paper or cloth changed the physical properties of GDL and changed the cell performance. The variation of cell performance as a function of the physical properties of GDL showed different behaviors according to the amount of current density.

• Journal of the Korean Magnetics Society
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• v.18 no.1
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• pp.32-35
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• 2008

Thermally stable diffusion barrier of tungsten carbon nitride(W-C-N) and of tungsten boron carbon nitride(W-B-C-N) thin films have studied to investigate the impurity behaviors of boron and nitrogen. In this paper we newly deposited tungsten boron carbon nitride(W-B-C-N) thin film for various $W_2B$ target power on silicon substrate. The impurities of the 100nm-thick W-C-N and W-B-C-N thin films provide stuffing effect for preventing the inter-diffusion between W-C-N or W-B-C-N thin films and silicon during the high temperature($700^{\circ}C{\sim}1000^{\circ}C$) annealing process.