• Membrane Journal
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• v.12 no.4
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• pp.207-215
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• 2002

The hindered diffusion in confined spaces is an important phenomenon to understand in a micro-scale the filtration mechanism determined by the particle motion in membrane pores. Compared to the case of spherical colloids, both the theoretical investigations and the experiments on the hindered diffusion of polyelectrolytes is actually more difficult, due to lots of relevant parameters resulting from the complicated conformational properties of the polyelectrolyte chain. We have successfully performed the Brownian dynamics simulations upon a single polyeiectrolyte confined in a slit-like pore, where a coarse-grained bead-spring model incorporated with Debye-Huckel interaction is properly adopted. For the given sizes of both the polyelectrolyte and the pore width, the hindered diffusion coefficient decreases as the solution ionic concentration decreases. It is evident that a charge effect of the pore wall enhances the hindered diffusion of polyelectrolyte. Simulation results allow us to make sense of the diffusive transport through the micro-pore, which is restricted by the influences of the steric hindrance of polyelectrolytes as well as the electrostatic repulsion between the polyelectrolytes and pore wall.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.10a
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• pp.139-140
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• 1997

1. 서론 : 한외 및 정밀여과의 분리메카니즘에 연관된 물리적 현상에 대해 현재까지 진행된 많은 연구들은, 막기공이 갖는 복잡하고 불규칙한 구조를 단순하고 규칙적인 well-defined 구조인 실린더형이나 슬릿형 기공으로 가정하여 문제를 전개하고 있다. 본래, 다공성 매질(porous media)에서의 유체흐름을 다루는 이론 및 실험연구자들에 의해 제안된 섬유상 매질(fibrous media)에 대한 해석은 계의 미세구조(microstructure)에 추계적 개념을 적용시키려는 최근의 추세에 따라 점차 관심이 높아가고 있다.(생략)

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.4
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• pp.13-23
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• 1984

The purpose of this paper is to develop a numerical model which can be used to compute the suspended load concentration of which the two-dimensional unsteady diffusion equation is able to be solved by the finite difference method using the implicit scheme. The pick-up rate formula from the bottom used in the open channel as a sink source term and the Coleman's empirical formula for the diffusion coefficient were taken, and especially the hindered settling velocity and the vertical velocity of flow due to the periodical tidal motion were taken into account, while the effects of the variables, such as the horizontal and vertical velocities of flow, tidal range, the settling velocity and hindered settling, on the suspened load concentrations have been discussed, comparing the results obtained from the different cases in the simulation conditions.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.91-110
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• 2004

A comprehensive three-dimensional nano-particle tracking technique in micro- and nano-scale spatial resolution using the Total Internal Reflection Fluorescence Microscope (TIRFM) is discussed. Evanescent waves from the total internal reflection of a 488nm argon-ion laser are used to measure the hindered Brownian diffusion within few hundred nanometers of a glass-water interface. 200-nm fluorescence-coated polystyrene spheres are used as tracers to achieve three-dimensional tracking within the near-wall penetration depth. A novel ratiometric imaging technique coupled with a neural network model is used to tag and track the tracer particles. This technique allows for the determination of the relative depth wise locations of the particles. This analysis, to our knowledge is the first such three-dimensional ratiometric nano-particle tracking velocimetry technique to be applied for measuring Brownian diffusion close to the wall.

• Journal of the Korean Society of Visualization
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• v.6 no.2
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• pp.45-50
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• 2008

It has been found that the colony size of bacteria grown on an agar plate decreases with increasing agar gel concentration. Evidenc from recent studies suggests that the bacterial colony dynamics is closely related with the mechanical properties of the substrate. We investigate whether bacterial growth on the agar substrate is controlled mostly by the nutrients' diffusion which is hindered more in porous medium than in solution. The number of bacterial cells in single colonies is found to be inversely correlated with agar concentration. High-resolution live cell imaging at the single bacterium level confirms that the bacterial growth rate is reduced with increasing agar concentration. There is a strong correlation between the slowed diffusion and the reduced number of cells in a high concentration of agar medium.

• Journal of Korea Technology Innovation Society
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• v.1 no.1
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• pp.69-82
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• 1998

As a new medium for knowledge diffusion, E-Journal is expected to be a general type of scholarly communication. However, the techno - economic problems have hindered the advancement of the E-Journal. For the technical aspects, there are problems such as the standardization of document format, automatization of the document preparation, forward and backward link between documents. Also there are necessities for the support of the information infrastructure of digital library and information superhighway. For the economic domain, reengineering of total publishing cycle is considered and the new paradigm of peer review is analyzed. We pointed out that the main difficulties in the diffusion of E-Journal are on the promotion of service and technological advance, not the price and marketing strategy.

• Journal of Ocean Engineering and Technology
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• v.4 no.2
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• pp.262-262
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• 1990

In order to check the effect of dislocation behavior on creep rate in 12% Chromium steel, 14 samples of different compositions were examined by creep rupture test, and subgrain sizes, distribution of dislocations and precipitates were checked. And, authors reviewed the behaviors of dislocations, the formation and growth of subgrains and precipitates during creep. The results are as the following: 1) Creep rates calculated by .epsilon. over dot = .rho.bv show 10-15% higher values than actual data measured. However, authors conclude that the density and velocity of dislocations together with subgrain size are important factors governing deformation during creep in 12% chromium steel. 2) The values of the strength of obstacles in the mobility of dislocations are more clearly depended on the effective stress in the range of $10{\pm}5kgf/mm^{2}$ and increase with the increase of temperature. 3) Creep rates decrease with the smaller sizes of subgrains formed and can result in the longer creep rupture lives(hours). The smaller subgrains can be made by forming shorter free gliding distances of dislocations with very fine precipitates formed in the matrix during creep by applying proper alloy design. 4) Dislocation mobility gets hindered by precipitates occurring, which are coarsened by the softening process governed by diffusion during long time creep.

• Journal of Ocean Engineering and Technology
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• v.4 no.2
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• pp.112-120
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• 1990

In order to check the effect of dislocation behavior on creep rate in 12% Chromium steel, 14 samples of different compositions were examined by creep rupture test, and subgrain sizes, distribution of dislocations and precipitates were checked. And, authors reviewed the behaviors of dislocations, the formation and growth of subgrains and precipitates during creep. The results are as the following: 1) Creep rates calculated by .epsilon. over dot = .rho.bv show 10-15% higher values than actual data measured. However, authors conclude that the density and velocity of dislocations together with subgrain size are important factors governing deformation during creep in 12% chromium steel. 2) The values of the strength of obstacles in the mobility of dislocations are more clearly depended on the effective stress in the range of $10{\pm}5kgf/mm^{2}$ and increase with the increase of temperature. 3) Creep rates decrease with the smaller sizes of subgrains formed and can result in the longer creep rupture lives(hours). The smaller subgrains can be made by forming shorter free gliding distances of dislocations with very fine precipitates formed in the matrix during creep by applying proper alloy design. 4) Dislocation mobility gets hindered by precipitates occurring, which are coarsened by the softening process governed by diffusion during long time creep.

• Korean Membrane Journal
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• v.3 no.1
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• pp.39-50
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• 2001

The counter-diffusion of two gaseous substances permeating a polymeric membrane has been investigated both experimentally and theoretically. The aim of the study was to find mutual effects, if any, that could influence the permeability and diffusivity data. The experimental data were obtained with an isostatic permeameter operating at ambient pressure and 303 K: helium, nitrogen, carbon dioxide methane were used as permeating gas at different partial pressure; helium or nitrogen as equilibrating or carrier gas. No evident mutual effect of the counter-diffusing gas was observed. The theoretical analysis gave some insight into the phenomena and it was concluded that at near-atmospheric pressures, and in the absence of swelling phenomena no mutual interaction exists. On a theoretical basis any mutual interaction between diffusing and counter-diffusing gases could only occur: i) at high pressures , when the free movement of permeating gas molecules within the polymer is hindered by the counter-diffusing gas; ii) when a large part of the free volume fraction is occupied by the counter--diffusing gas; iii) swelling phenomena modify the structure and free volume fraction of the polymer.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.11
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• pp.887-893
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• 1991

To take advantage of Ti-polycide, when it is contacted with both n+ and p+ active area of silicon, the effects of BF$_2$ on the formation of Ti-silicide were investigated with RTA temperature and dopant concentration. The intermediate phase C49 TiSi$_2$ appeared at $650^{\circ}C$ and the stable phase C54 TiSi2 was formed at $700^{\circ}C$. And the formation of Ti-silicide was hindered by BF$_2$ doping and this trend was decreased with increasing temperature. The out-diffusion phenomena of BF$_2$ into Ti silicide were not observed. And significantly, the native oxide was a chief factor preventing the formation of Ti-silicides.