• Bulletin of the Korean Mathematical Society
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• v.43 no.2
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• pp.443-459
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• 2006

The prey-predator system with a single cross-diffusion pressure is known to possess a local solution with the maximal existence time $T\;{\leq}\;{\infty}$. By obtaining the bounds of $W\array_2^1$-norms of the local solution independent of T we establish the global existence of the solution. And the long-time behaviors of the global solution are analyzed when the diffusion rates $d_1\;and\;d_2$ are sufficiently large.

• Macromolecular Research
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• v.15 no.1
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• pp.10-16
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• 2007

In this work, we prepared epoxy/BMI composites by using N,N'-bismaleimide-4,4'-diphenylmethane (BMI), epoxy resin (diglycidyl ether of bisphenol-A (DGEBA)), and 4,4'-diamino diphenyl methane (DDM). The thermal properties and water sorption behaviors of the epoxy and BMI composites were investigated. For the epoxy/BMI composites, the glass transition and decomposition temperatures both increased with increasing BMI addition, which indicates the effect of BMI addition on improved thermal stability. The water sorption behaviors were gravi-metrically measured as a function of humidity, temperature, and composition. The diffusion coefficient and water uptake decreased and the activation energy for water diffusion increased with increasing BMI content, indicating that the water sorption in epoxy resin, which causes reliability problems in electronic devices, can be diminished by BMI addition. The water sorption behaviors in the epoxy/BMI composites were interpreted in terms of their chemical and morphological structures.

• Korean Journal of Materials Research
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• v.28 no.5
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• pp.286-294
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• 2018

Hot-press forming(HPF) steel can be applied successfully to auto parts because of its superior mechanical properties. However, its resistances to aqueous corrosion and the subsequent hydrogen embrittlement(HE) decrease significantly when the steel is exposed to corrosive environments. Considering that the resistances are greatly dependent on the properties of coating materials formed on the steel surface, the characteristics of the corrosion and hydrogen diffusion behaviors regarding the types of coating material should be clearly understood. Electrochemical polarization and impedance measurements reveal a higher corrosion potential and polarization resistance and a lower corrosion current of the Al-coating compared with Zn-coating. Furthermore, it was expected that the diffusion kinetics of the hydrogen atoms would be much slower in the Al-coating, and this would be due mainly to the much lower diffusion coefficient of hydrogen in the Al-coating with a face-centered cubic structure. The superior surface inhibiting effect of the Al-coating, however, is degraded by the formation of local cracks in the coated layer under severe stress conditions, and therefore further study will be necessary to gain a clearer understanding of the effect of cracks formed on the coated layer on the subsequent corrosion and hydrogen diffusion behaviors.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.177-180
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• 2007

Numerical simulations on the suspended load in the Do jang fish port are carried out. Suspended load is analysed by using the two-dimensional advection-diffusion equation. To describe behaviors of a pollutant in costal zone, a split-operator method is applied to the numerical model. The advection part is first solved by SOWMAC and then the diffusion part is solved by a three-level locally implicit scheme.

• Journal of Technologic Dentistry
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• v.21 no.1
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• pp.15-26
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• 1999

This study was carried out by observing to composition of oxide on the surface of dental porcelain low gold alloy with various Indium additions according to the degassing and analysing the change composition of additional elements In on diffusion behaviors of Porcelain-matal surface. The specimens used were Au-Pd-Ag alloys by small indium addition. These specimens were treated for 10min at $1000^{\circ}C$ in vacuum condition. To investigate the microsturcture of oxidized alloy surface, SEM and EDAX were used, and EPMA were used to investigate the diffusion behaviors of porcelain-metal surface. X-ray diffraction were used to observe the morphological changes in the oxidation zone. The results of this study were obtained as follows ; 1) The hardness of alloy increased with increasing amount of In addition. 2) The formation of oxidation increased with increasing In content after heat treatment. 3) Diffusion of indium elements increased with increasing In content in metal-porcelain surface after firing. 4) The oxidations of alloy surface were mainly $In_2O_3$.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.68-75
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• 2002

The dynamic behaviors of the single vortex and flame-vortex interaction in a $CH_4/Air$ diffusion flame with addition of $CO_2$ were investigated numerically. The numerical method was based on a predictor-corrector for low Mach number flow. A two-step global reaction mechanism was adopted as a combustion model. Through comparison of results by effect of $CO_2$ added either on the fuel or oxidizer side, it was found that the growth of single vortex and entrainment of surrounding fluid by $CO_2$addition on the fuel side are larger than those by $CO_2$ addition on oxidizer side. Also, when $CO_2$ is added on fuel side, flame-vortex interaction becomes more significant than on air side.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2237-2242
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• 2011

Anomalous scaling behaviors such as significantly large growth exponent (${\beta}$) and small reciprocal of dynamic exponent (1/z) values for many molecular crystalline thin films have been reported. In this study, the variation of scaling exponent values and consequent growth behaviors of molecular thin films were more quantitatively analysed using a (1+1)-dimensional surface lateral diffusion model. From these simulations, influence of step edge barriers and grain boundaries of molecular thin films on the various scaling exponent values were elucidated. The simulation results for the scaling exponents were also well consistent with the experimental data for previously reported molecular thin film systems.

• Bulletin of the Korean Chemical Society
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• v.20 no.11
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• pp.1323-1328
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• 1999

Interdiffusion between two partially miscible polymers of similar chemical structures with different molecular weights is characterized theoretically by using the reptation model for the interdiffusion. This model provides more reliable results than the early Rouse model for same molecular weights, compared with the experiments. Furthermore, by introducing the molecular weight ratio R into the reptation model, we can see the dynamic effect of molecular weight on the diffusion behaviors of the asymmetric system. Near the critical point the diffusion behaviors of asymmetric binary polymer mixtures are well characterized by the interfacial width W(t), the mass transport M(t) for the different values of the Flory Χ parameter and different molecular weight ratios ofpolymers of the diffusion couple. These two quantities and composition profiles by this model give betteragreement with experiments.

• Journal of Pharmaceutical Investigation
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• v.29 no.3
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• pp.185-191
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• 1999

The polymeric films containing drug and various excipients were fabricated using aqueous-based $Eudragit^{\circledR}$ RS 30D dispersions. The diffusional behaviors and mechanism of the fabricated polymeric film were investigated using Keshary-Chien diffusion cell. The melatonin was used as a model drug. The diffusion behaviors of drug through the fabricated polymeric films were highly dependent on drug concentration in donor part, polymer contents and drug concentration, and the types of plasticizers and solubilizers. The fabricated polymeric films containing excipients and solubilizers could be applied for the controlled release of poorly water-soluble drug and for the preparation of drug-containing latex films for topical or oral drug delivery.

• Structural Engineering and Mechanics
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• v.60 no.3
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• pp.529-545
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• 2016

In this article, the generalized coupled non-Fickian diffusion-thermoelasticity analysis is carried out using an analytical method. The transient behaviors of field variables, including mass concentration, temperature and displacement are studied in a strip, which is subjected to shock loading. The governing equations are derived using generalized coupled non-Fickian diffusion-thermoelasticity theory, which is based on Lord-Shulman theory of coupled thermoelasticity. The governing equations are transferred to the frequency domain using Laplace transform technique and then the field variables are obtained in analytical forms using the presented method. The field variables are eventually determined in time domain by employing the Talbot technique. The dynamic behaviors of mass concentration, temperature and displacement are studied in details. It is concluded that the presented analytical method has a high capability for simulating the wave propagation with finite speed in mass concentration field as well as for tracking thermoelastic waves. Furthermore, the obtained results are more realistic than that of others.