• Structural Engineering and Mechanics
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• v.75 no.2
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• pp.133-144
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• 2020

This investigation is to study the effect of gravitational field and diffusion on a microstretch thermoelastic medium heating by a non-Gaussian laser beam. The problem was studied in the context of the dual-phase-lag model. The normal mode analysis is used to solve the problem to obtain the exact expressions for the non-dimensional displacement components, the micro-rotation, the stresses, and the temperature distribution. The effect of time parameter, heat flux parameter and gravity response of three theories of thermoelasticity i.e. dual-phase-lag model (DPL), Lord and Shulman theory (L-S) and coupled theory (CT) on these quantities have been depicted graphically for a particular model.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.1
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• pp.17-22
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• 2000

The transient process simplified by the 1-D stretched laminar flame formed at the fuel-oxidizer interface was investigated using the coherent flame sheet model. Under the combustion environment of high temperatures and pressures the results show that the time required to reach the steady state was relatively short compared to the reverse of strain rate. Hence the employment of the tabulation of precalculated steady-flame results in the calculation of turbulent diffusion flames using the coherent flame sheet model is concluded valid, Also upstream temperatures were found to have only a minor effect on the nondimensional flame temperature and nondimensional fuel even through the letter is sensitive to pressure changes.

• Nuclear Engineering and Technology
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• v.14 no.4
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• pp.178-185
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• 1982

Albedo-type boundary condition is incorporated into the finite element formulation of the cubic Hermite polynomials for the two-dimensional solution of the two-group diffusion problem. Two modifications are introduced with respect to the conventional expression for the weak form of the group diffusion equation with the zero flux or zero current boundary condition and the cubic element functions over the boundary nodes. The finite element formulations obtained from those modifications are tested with the two-dimensional ZION problem. The numerical effectiveness of the modifications are examined.

• Nuclear Engineering and Technology
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• v.49 no.1
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• pp.29-42
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• 2017

The purpose of the present study is the presentation of the appropriate element and shape function in the solution of the neutron diffusion equation in two-dimensional (2D) geometries. To this end, the multigroup neutron diffusion equation is solved using the Galerkin finite element method in both rectangular and hexagonal reactor cores. The spatial discretization of the equation is performed using unstructured triangular and quadrilateral finite elements. Calculations are performed using both linear and quadratic approximations of shape function in the Galerkin finite element method, based on which results are compared. Using the power iteration method, the neutron flux distributions with the corresponding eigenvalue are obtained. The results are then validated against the valid results for IAEA-2D and BIBLIS-2D benchmark problems. To investigate the dependency of the results to the type and number of the elements, and shape function order, a sensitivity analysis of the calculations to the mentioned parameters is performed. It is shown that the triangular elements and second order of the shape function in each element give the best results in comparison to the other states.

• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.81-94
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• 1997

In many solute transport studies, either flux or resident concentration has been used. Choice of the concentration mode was dependent on the monitoring device in solute displacement experiments. It has been accepted that no priority exists in the selection of concentration mode in the study of solute transport. It would be questionable, however, to accept the equivalency in the solute transport parameters between flux and resident concentrations in structured soils exhibiting preferential movement of solute. In this study, we investigate how they differ in the monitored breakthrough curves (BTCs) and transport parameters for a given boundary and flow condition by performing solute displacement experiments on a number of undisturbed soil columns. Both flux and resident concentrations have been simultaneously obtained by monitoring the effluent and resistance of the horizontally-positioned TDR probes. Two different solute transport models namely, convection-dispersion equation (CDE) and convective lognormal transfer function (CLT) models, were fitted to the observed breakthrough data in order to quantify the difference between two concentration modes. The study reveals that soil columns having relatively high flux densities exhibited great differences in the degree of peak concentration and travel time of peak between flux and resident concentrations. The peak concentration in flux mode was several times higher than that in resident one. Accordingly, the estimated parameters of flux mode differed greatly from those of resident mode and the difference was more pronounced in CDE than CLT model. Especially in CDE model, the parameters of flux mode were much higher than those of resident mode. This was mainly due to the bypassing of solute through soil macropores and failure of the equilibrium CDE model to adequate description of solute transport in studied soils. In the domain of the relationship between the ratio of hydrodynamic dispersion to molecular diffusion and the peclet number, both concentrations fall on a zone of predominant mechanical dispersion. However, it appears that more molecular diffusion contributes to the solute spreading in the matrix region than the macropore region due to the nonliearity present in the pore water velocity and dispersion coefficient relationship.

• Membrane Journal
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• v.26 no.3
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• pp.187-196
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• 2016

Pressure-assisted forward osmosis (PAFO) process has recently been under spotlight for its potential to improve forward osmosis (FO) process performance by applying low hydraulic pressure on the feed side. Structure parameter, one of the governing factors in estimating water flux and solute flux across FO membranes in the solution-diffusion model (S-D model), determines solute resistivity in FO and PAFO processes. This study aims to estimate the trend of structure parameter change with respect to varying additional hydraulic pressure condition in PAFO.

• Resources Recycling
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• v.24 no.5
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• pp.33-39
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• 2015

A basic study was conducted to effectively recover nitric acid from a waste solder stripper by diffusion dialysis using anion exchange membranes. The effects of flow rate, flux ratio, nitrate concentration, and metallic ion types and concentration on the recovery percentage of nitric acid were investigated. The recovery percentage of nitric acid was decreased with the increase of flow velocity. But the recovery percentage of nitric acid was increased as the increase of flux ratio(W/F) and showing a recovery percentage of nitric acid of about 99% at a flux ratio of 1.5 or more. As the increase of nitric acid concentration in feed solution, the recovery percentage of nitric acid was increased up to 3.0M, but in case of greater than 3.0M, the recovery percentage gradually was decreased. Leakage percentage of metallic ions through the membrane were in the order of Pb, Na and Cu but Fe and Sn did not leakaged. As a result of diffusion dialysis using real waste solder stripper at a flow rate of $0.9L/hr-m^2$, W/F = 1.3, a recovery percentage of nitric acid of approximately 94% was gained.

• Journal of Life Science
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• v.31 no.11
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• pp.1004-1009
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• 2021

Angelica gigas Nakai (AGN) has been used in Korean herbal medicine for various pharmacological activities, such as to create antioxidant and skin whitening effects. Decursin and decursinol angelate of AGN extracts can be used as potential active drugs and cosmetic ingredients. This study investigated the possibility of topical delivery of AGN extracts using a manufactured emulsion system. Lotion was formulated by using Tefose^® and paraffin for the oil phase, Kolliphor RH 40 for the surfactant and solubilizing agent-which showed high solubility in water (0.82 mg/ml)-and a water phase with a carbomer. In vitro skin permeation of decursin and decursinol angelate was determined using a Strat-M^® membrane in Franz diffusion cells. Lotion samples as the experimental group (248.08±19.72 ug/cm²) significantly increased the permeation of decursin and decursinol angelate for up to 24 hr compared to the control group (119.18±19.23 ug/cm²). The permeability was also characterized by the flux (penetration rates) and Kp (permeability coefficient) values. The experimental group (17.20±1.23 ug/h/cm² and 5.73±1.39 cm/h^*10^-3) had higher flux and Kp than the control group (8.22±1.24 ug/h/cm² and 2.74±0.51 cm/h^*10^-3). Lotion with decursin and decursinol angelate of AGN extracts could be used for the topical application of drug and cosmetic products.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.295-304
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• 2010

Performance of a landfill liner is evaluated based on leakage rate and mass flux. In this study, the recently utilized double composite liner system, which consists of a geomembrane (GM), a geosynthetic clay liner (GCL), a GM, and a compacted clay layer (61 or 91.5 cm) is compared with other popular composite liners including the single GCL system, the Subtitle D liner system, and the Wisconsin NR500 liner system. The leakage rate through circular and long defects in the GM of the landfill liners is analyzed using numerical models. For the mass flux criterion, the analyses of inorganic contaminant transport through defects in the GM component of liner systems and diffusion of organic compounds through intact landfill liners are conducted using three- and one-dimensional numerical models, respectively. Cadmium and toluene are used in the analyses as a typical inorganic and organic substance, respectively, which will be chemical species encountered during landfill operation. The comparison shows that the double composite liner systems are superior to the other liner systems according to the performance-based evaluation.

• Journal of Astronomy and Space Sciences
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• v.36 no.2
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• pp.45-60
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• 2019

The Earth's outer radiation belt has long received considerable attention mainly because the MeV electron flux in the belt varies often dramatically and at various time scales. It is now widely accepted that the wave-particle interaction is one of the major mechanisms responsible for such flux variations. The wave-particle interaction can accelerate electrons to MeV energies, explaining the observed flux increase events, and can also scatter the electrons' motion into the loss cone, resulting in atmospheric precipitation and thus contributing to flux dropouts. In this paper, we provide a review of the current state of research on relativistic electron scattering and precipitation due to the interaction with electromagnetic ion cyclotron (EMIC) waves in the inner magnetosphere. The review is intended to cover progress made over the last ~15 years in the theory and simulations of various issues, including quasilinear resonance diffusion, nonlinear interactions, nonresonant interactions, effects of finite normal angle on pitch angle scattering, effects due to rising tone emission, and ways to scatter near-equatorial pitch angle electrons. The review concludes with suggestions of a few promising topics for future research.