• Journal of IKEEE
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• v.21 no.2
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• pp.123-129
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• 2017

Proton Exchange Membrane Fuel Cell (FEMFC) is a strong candidate for future automobile and power generation because of its high power density, low emission and low operation temperature. The major concerns of the gas diffusion layer (GDL) inside a FEMFC is water management. The GDL is typically comprised of carbon for electrical conductivity and PTFE for Hydrophobicity. In this simulation, GDL flooding was investigated using a simplified approach method of an established equation models(Fick' Law, Darcy, Law, Stefan-Maxwell diffusion). The performance of GDL was shown using result of the inner heat, water density and oxygen density of the cell using model equations. The catalyst layer mode in FEMFC showed results of effectiveness factor, Butler-volmer and hydrogen flux density. These results are interesting because the influence of several factors has been shown and the information will be helpful for fuel cell design.

• International Commerce and Information Review
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• v.19 no.1
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• pp.3-21
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• 2017

As to 'E-Commerce Trade' or 'The Cross Border E-Commerce (CBEC)' which has shown rapid diffusion, Korean government is providing active support on the basis of idea that it has profound impact on increase of export. However, sporadic support propelled by various ministries and agencies are not effective and efficient at all on actual circumstances. Consequently, in order to promote consistency, effectiveness, and efficiency of supporting policy, it is desirable to clarify competent ministry and the duty of cooperation to the other ministries and agencies. For its own sake, it is necessary to amend each existing laws which scattered all over the business territory, or to legislate new enactments. Yet these methods are extremely tough to carry out, therefore, it seems that amending 'Electronic Trade Facilitation Act', which already exist and regulate 'paperless trade' would be a realistic alternative. For the diffusion of Korean CBEC especially export, in this study the author insists that amending this law to promote CBEC is the most reasonable way comparing to other ways with several reference materials.

• Geomechanics and Engineering
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• v.21 no.4
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• pp.357-369
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• 2020

Different from the conventional planar fracture and simplified Newton model, for power-law slurries with a lower water-cement ratio commonly used in grouting engineering, flow model in geological rough fractures is built based on ten standard profiles from Barton (1977) in this study. The numerical algorithm is validated by experimental results. The flow mechanism, grout superiority, and water plugging of pseudo plastic slurry are revealed. The representations of hydraulic grouting properties for JRCs are obtained. The results show that effective plugging is based on the mechanical mechanisms of the fluctuant structural surface and higher viscosity at the middle of the fissure. The formulas of grouting parameters are always variable with the roughness and shear movement, which play a key role in grouting. The roughness can only be neglected after reaching a threshold. Grouting pressure increases with increasing roughness and has variable responses for different apertures within standard profiles. The whole process can be divided into three stationary zones and three transition zones, and there is a mutation region (10 < JRCs < 14) in smaller geological fractures. The fitting equations of different JRCs are obtained of power-law models satisfying the condition of -2 < coefficient < 0. The effects of small apertures and moderate to larger roughness (JRCs > 10.8) on the permeability of surfaces cannot be underestimated. The determination of grouting parameters depends on the slurry groutability in terms of its weakest link with discontinuous streamlines. For grouting water plugging, the water-cement ratio, grouting pressure and grouting additives should be determined by combining the flow conditions and the apparent widths of the main fracture and rough surface. This study provides a calculation method of grouting parameters for variable cement-based slurries. And the findings can help for better understanding of fluid flow and diffusion in geological fractures.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.4
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• pp.449-457
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• 2012

The program/erase (P/E) cyclic endurances including bias temperature instability (BTI) behaviors of Metal-$Al_2O_3$-Nitride-Oxide-Semiconductor (MANOS) memories are investigated in comparison with those of Semiconductor-Oxide-Nitride-Oxide-Semiconductor (SONOS) memories. In terms of BTI behaviors, the SONOS power-law exponent n is ~0.3 independent of the P/E cycle and the temperature in the case of programmed cell, and 0.36~0.66 sensitive to the temperature in case of erased cell. Physical mechanisms are observed with thermally activated $h^*$ diffusion-induced Si/$SiO_2$ interface trap ($N_{IT}$) curing and Poole-Frenkel emission of holes trapped in border trap in the bottom oxide ($N_{OT}$). In terms of the BTI behavior in MANOS memory cells, the power-law exponent is n=0.4~0.9 in the programmed cell and n=0.65~1.2 in the erased cell, which means that the power law is strong function of the number of P/E cycles, not of the temperature. Related mechanism is can be explained by the competition between the cycle-induced degradation of P/E efficiency and the temperature-controlled $h^*$ diffusion followed by $N_{IT}$ passivation.

• International Commerce and Information Review
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• v.5 no.2
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• pp.19-45
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• 2003

The main issues addressed in this paper are as follows : First, this paper makes a distinction among types of e-money, IC card type versus Network type, open-loop type versus closed-loop type, online type versus offline type and accountable type versus unaccountable type, and analysis the clear and accurate criterion. Second, generally speaking, e-money is a claim on originator of e-money and not legal tender, so, delivery of e-money by itself does not relieve of monetary obligation. Between it is not easy to define e-money, by now there are many definitions of e-money, there is a legal uncertainty accordingly and then it is not easy to find proper law applicable to resolve a particular issue. As a result. many problems relating to e-money would be solved through analogical application of the moot proper law among the laws that apply to the cash, check, credit card, or fund transfer after analyzing type of e-money at issue. This paper studies the methods on diffusion of the utilization of electronic money. To diffuse the usage of electronic money, it need; prerequisitely as a basic conditions independence of electronic money, non-reusability, and anonymity. And also as a additional conditions it need; usability in the offline commerce, transferability, divisibility. And now electronic money is used very actively, but still has many Jaw problems such as protections of consumer, law enforcement, supervisory, etc. So electronic money has called as money, but it is sure that electronic money is not a legal tender. So to facilitate the economic function of the electronic monel it is need to supplement the electronic money in the legal sides.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.35-43
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• 2008

Purpose: This review article was written to investigate how the various factors, such as lacrimal thickness, CL's thickness and Dk, affects the influx of $O_2$ diffusion into the cornea. Methods: A mathematical model was proposed to analyze the oxygen diffusion reaching the cornea through the tear layers and contact lens based on Fick's law and the principle of continuity of the diffusion flux through the each layers. Results: The model predicts how the parameters such as the thickness of tear layer on the cornea, both the Dk and thickness of contact lenses etc., affect the oxygen tension at cornea and oxygen flux entering the cornea. Conclusions: It is found that either too flat or too tightly fitted contact lenses can cause the oxygen deficiency at/inside the periphery of the cornea because of the reduction of oxygen flux resulted from too thickened tear layer.

• Journal of The Korean Association For Science Education
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• v.30 no.1
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• pp.80-93
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• 2010

The scope of this study is: (1) to review or summarize the theoretical explanations of diffusion; (2) to investigate the preservice teachers' understanding of diffusion utilizing the inquiry experiment of diffusion that was developed in this study. The data was collected through questionnaires given to 41 preservice teachers in 3 universities and interviews with 20 subjects from this population, who conducted the inquiry experiment. During the experiment, the data was collected from the students' reports and 3 small groups' audio/video recordings. To understand preservice teachers' conceptions, reports, audio/video recordings, questionnaires and interviews were analyzed and discussed with co-workers. The results follow: (1) The differences between effusion and diffusion as well as equal-pressure experiment and equal-flux one on diffusion were discussed; (2) Most preservice teachers understood effusion and diffusion connected to Graham's law of diffusion by rote and have misconceptions about the diffusion process; (3) They observed two kinds of diffusion experiments (equal-pressure and equal-flux) by inquiry experiment, but the majority of them failed to find conceptual differences between these experiments. After the inquiry experiment, about 40% of the samples modified their conceptions about diffusion.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.149-156
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• 2016

The service life in RC (Reinforced Concrete) is very important and it is usually obtained through deterministic method based on Fick's 2nd law and probabilistic method. This paper presents an evaluation of $P_{df}$(durability failure probability) and the related service life considering time-dependent behaviors in chloride diffusion and surface chloride content. For the work, field investigation is performed for RC structures exposed to chloride attack for 3.5~4.5years, focusing tidal zone (6.0 m) and sea shore (9.0 m), respectively. Random variables like cover depth, chloride diffusion coefficient, and surface chloride content are obtained, and $P_{df}$ and the service life are evaluated. Unlike the results from deterministic method using LIFE 365, probabilistic method with time effects on diffusion and surface chloride shows a relatively rapid change in the result, which is a significant reductions of service life in the case with low surface chloride content. For probabilistic evaluation of durability, high surface chloride content over $10.0kg/m^3$ is required and reasonable service life can be derived with consideration of time-dependent diffusion coefficient.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.925-928
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• 2012

The accurate expression for the steady-state velocity of an irreversible enzyme-catalyzed reaction obtained by Shin and co-workers (J. Chem. Phys. 2001, 115, 1455) is generalized to allow for the rebinding of the product. The amplitude of the power-law ($t^{-1/2}$) relaxation of the free- and bound-enzyme concentrations to steady-state values is expressed in terms of the steady-state velocity and the intrinsic (chemical) rate constants. This result is conjectured to be exact, even though our expression for the steady-state velocity in terms of microscopic parameters is only approximate.

• Journal of the Korean Electrochemical Society
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• v.7 no.3
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• pp.155-162
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• 2004

This article covers the fundamentals of percolation phenomenon giving emphasis to the percolation concept involved in disordered electrochemical systems. After a brief discourse on the basic concepts of percolation theory, the geometrical properties and fractality of percolation clusters were presented. Then, anomalous behaviours of diffusion in percolation clusters were explained in terms of the fractal structures of the infinite percolation clusters. Finally, the conductivity-related properties of composite ionic materials were shortly discussed on the basis of percolation theory from practical points of view.