• Korean Journal of Food Science and Technology
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• v.23 no.2
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• pp.217-223
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• 1991

A capillary method was used to evaluate the properties of mass transfer process and diffusion coefficients in the gel food. Amaranth dye was selected as a diffusant material to visualize the degree of diffusion procedure easily. After contacting cylinder containing agar gel with amaramth dye solution for some hours, the gel was cut to five segments by 0.5 cm in length. The diffusant concentration from the segments were measured by the spectrophotometer at 523 nm. Prediction models for the diffused quantities in gel food were established by the regression program of SPSS package program. Generally, diffusion coefficient can be calculated by Fick's second law, however, it will be determined by using numerical analysis method more easily. Finally the diffusion coefficients in this research were calculated by arithmetic mean of the measured values. As raising gel agent concentration, the mean diffusion coefficient tended to decrease because the obstruction effect came to become significant.

• Journal of Internet Computing and Services
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• v.7 no.2
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• pp.93-102
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• 2006

Traditionally, diffusion of telecommunications services has been considerably affected by presence of critical mass and network externalities, and thus shown the so-called late take-off phenomenon. However, as telecommunications network evolves from circuit switching to packet switching, enabling diverse new services such as Internet access, Internet banking and web hosting, it seems this traditional diffusion patterns are changing. By comparing diffusion of the packet-based services with those of circuit-based services and durable goods, we have found the late take-off phenomenon is not involved in diffusion of newly introduced the packet-based services. Moreover, we concluded diffusion of the packet-based services is much faster than that of durable goods, thus showing early take-off phenomenon. Based on this empirical result, we suggest Telcos and ISPs should pay as much attention to the growth state as the introduction stage in order for their packet-based services to be successful in the markets.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.48.4-48.4
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• 2019

We studied the metal-distribution of isolated Milky-way mass galaxy using various hydrodynamic solvers and investigated the difference of the result between AMR and SPH codes. In particle-based codes, physical quantities like mass or metallicity defined in each particle are conserved unless being injected explicitly by the effect of the supernova, whereas in the Eulerian codes the diffusion is simply accomplished by hydro-equation. Therefore, without including explicit physics of diffusion on the SPH- codes, the metal mixing in the galaxy or CGM only can be accomplished by the direct motion of the particles, however, the standard-SPH codes depress the instability of the turbulent fluid mixing. In this work, we simulated under common initial conditions, common gas-physics like cooling-heating models, and star-formation feedback using ENZO(AMR) GIZMO and GADGET-2 codes. We additionally included a metal-diffusion algorithm on the SPH-codes, which follows the subgrid-turbulent mixing model investigated by Shen et al. (2010) and compared the effect of the metal-outflow on the halo region of the galaxy in different hydro-solvers. We also found that for the implementation of the diffusion scheme in the SPH-codes, the existence of a sufficient number of the gas-particles, which is the carrier of the metals, is necessary. So we tested a new initial condition for proper implementation of the diffusion scheme on the SPH simulations. By comparing the metal-contamination of the circumgalactic medium with different hydrodynamics models, we quantify the diffusion strength of AMR codes using diffusion parameterization of the SPH codes and also suggest the calibration solutions in the different behavior of codes in metal-outflow.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.263-270
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• 2020

In this study, the physical mechanism and diffusion effects in aluminium implanted silicon was investigated. For fabricating power semiconductor devices, an aluminum implantation can be used as an emitter and a long drift region in a power diode, transistor, and thyristor. Thermal treatment with O₂ gas exhibited to a remarkably deeper profile than inert gas with N₂ in the depth of junction structure. The redistribution of aluminum implanted through via thermal annealing exhibited oxidation-enhanced diffusion in comparison with inert gas atmosphere. To investigate doping distribution for implantation and diffusion experiments, spreading resistance and secondary ion mass spectrometer tools were used for the measurements. For the deep-junction structure of these experiments, aluminum implantation and diffusion exhibited a junction depth around 20 ㎛ for the fabrication of power silicon devices.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.4
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• pp.403-408
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• 2011

Purpose: To study the concentration distribution and diffusion depth in tinted lenses using the law of diffusion. Methods: The measured values taken from experiments were fitted with the theoretical fitting curve induced on the basis of Fick's second law of diffusion. Results: The fitting curves were in very good agreement with the measured values. As the results, we found the quantitative relationship between mass of dye solution diffused into the tinted lens per unit area and dyeing time, and evaluated concentration distribution of dye in tinted lens, diffusion depth, etc. Conclusions: The dyeing mechanism of tinted lenses can be well described by diffusion theory.

• Fire Science and Engineering
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• v.16 no.3
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• pp.1-7
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• 2002

Diffusion and dispersion of injected $CO_2$gas into the $N_2$ gas flow are complex. In the packed column with porous particles the axial dispersion and the extra-particle mass transport as well as the intra-particle mass transport are involved. The pulse spreads by stationary diffusion during the period of arrested flow. Hence, the effect of axial dispersion, and of entrance and exit, as well as that of intraparticle convection should be eliminated during the period. The effective diffusivity was determined experimentally by using the gas chromatography, which is to arrest the gas flow during the period after injecting the pulse. This experiment method hasn't been used often in the field. Effective diffusivities are raised with temperature increasing, and it is quite satisfied com-pared to literature values. In this study, the calculated data of gaseous chemical for extinguish fires could be helpful to appreciate several physical phenomenons. Also, it could be expected that, the calculated data of this study might be very useful for development of excellent gaseous chemical for extinguish fires and improvement of its efficiency.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.3
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• pp.133-140
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• 2007

A 2-D model of fluid flow, mass transport and electrochemistry is analysed to examine the effect of current density at the current collector depending on active layer thickness of catlyst in polymer elecrolyte fuel cells. The finite element method is used to solve the continuity, potential and Maxwell-Stefan equations in the flow channel and gas diffusion electrode regions. For the material behavior of electrode reactions in the active catalyst layers, the agglomerate model is implemented to solve the diffusion-reaction problem. The calculated model results are described and compared with the different thickness of active catalyst layers. The significance of the results is discussed in the viewpoint of the current collecting capabilities as well as mass transportation phenomena, which is inferred that the mass transport of reactants dictates the efficiency of the electrode in the present analysis.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.73-78
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• 2003

The InP thin films grown by metalorganic chemical vapor deposition (MOCVD) are widely used to optoelectronic devices such as laser diodes, wave-guides and optical modulators. Effects of various parameters controlling film growth rate such as gas-phase reaction rate constant, surface reaction rate constant and mass diffusivity are numerically investigated. Results show that at the upstream region where film growth rate increases with the flow direction, diffusion including thermal diffusion plays an important role. At the downstream region where the growth rate decreases with flow direction, film deposition mechanism is revealed as a mass-transport limited. Mass transport characteristics are also studied using systematic analyses.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.6
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• pp.1171-1178
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• 1992

An experiment was performed to describe the heat and mass transfer occurring between hot waste gas and cold water through direct contact in a direct contact heat exchanger. This model was then used to obtain an equation of overall heat transfer coefficent based on heat exchanger volume. The diffusion heat transfer rate is 2-3 times larger than the convection heat transfer rate as results of condensation of the water vapor contained in the waste gas. The boiler efficiency increases over 10%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.8
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• pp.366-374
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• 2014

Experimental mass transfer data, which were obtained for the $CO_2$-water slug flows in vertical tubes with 2, 5, and 8mm diameters, were analyzed in comparison with the penetration theory. It was found that a penetration model with molecular diffusion coefficient cannot predict the experimental data accurately. An effective diffusion coefficient, which considers enhancement effect of interfacial waves, was suggested to improve prediction. Another empirical factor was also suggested to consider the effect of non-uniform interface velocity. A modified penetration model was found to be capable of predicting the experimental data reasonably well.