• Asian Journal of Atmospheric Environment
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• v.11 no.3
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• pp.153-164
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• 2017

Odor dispersion around a cubic building from rooftop odor emissions was investigated using computational fluid dynamics (CFD). The Shear Stress Transport (here after SST) $k-{\omega}$ model in FLUENT CFD code was used to simulate the flow and odor dispersion around a cubic building. The CFD simulations were performed for three different configurations of cubic buildings comprised of one building, two buildings or three buildings. Five test emission rates were assumed as 1000 OU/s, 2000 OU/s, 3000 OU/s, 4000 OU/s and 5000 OU/s, respectively. Experimental data from wind tunnels obtained by previous studies are used to validate the numerical result of an isolated cubic building. The simulated flow and concentration results of neutral stability condition were compared with the wind tunnel experiments. The profile of streamline velocity and concentration simulation results show a reasonable level of agreement with wind tunnel data. In case of a two-building configuration, the result of emission rate 1000 OU/s illustrates the same plume behavior as a one-building configuration. However, the plume tends to the cover rooftop surface and windward facet of a downstream building as the emission rate increases. In case of a three-building configuration, low emission rates (<4000 OU/s) form a similar plume zone to that of a two-building configuration. However, the addition of a third building, with an emission rate of 5000 OU/s, creates a much greater odorous plume zone on the surface of second building in comparison with a two-building configuration.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.543-551
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• 2021

Changes in gluten surface hydrophobicity, which play an important role in the functional characteristics of protein, were measured according to various protein concentrations, pH levels, electrolytes concentrations, and alginate molecular weights using 8-anilino-1-naphthalene sulfonic acid (ANS) as a fluorescent probe. Gluten surface hydrophobicity decreased as gluten concentration increased, reaching a maximum pH of 7.0. The effects of alginate molecular weights and alginate concentration on the surface hydrophobicity, emulsifying activity index (EAI), and emulsion stability index (ESI) of gluten-sodium alginate dispersion (GAD) were measured. Gluten surface hydrophobicity rapidly increased the asl NaCl concentration of gluten solution up to 300 mM and showed no significant increase above 300 mM. However, gluten surface hydrophobicity notably decreased until the concentration of CaCl₂ and MgCl₂ reached 30 mM, indicating no significant variations above 30 mM. GAD surface hydrophobicity increased as the concentration and molecular weight of sodium alginate increased, however, gluten concentration increased as the GAD surface hydrophobicity decreased. The EAI and ESI of GAD increased as both molecular weight and concentration of sodium alginate increased.

• Macromolecular Research
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• v.11 no.6
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• pp.444-450
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• 2003

Hydrophobically End-capped polyethylene oxide Urethane Resin(HEUR)-associating polymers, HEUR 35(8), HEUR 35(12), and HEUR 35(18), comprise a polyethylene oxide (PEO) having a molecular weight of 35,000 that is end capped with two C$\_$8/H$\_$17/, C$\_$12/H$\_$25/, and C$\_$18/H$\_$37/ alkyl chains, respectively. These associating polymers were synthesized by condensation reactions with polyethylene oxides and alkyl isocyanates. The self-diffusion coefficients of HEUR-associating polymers were measured in aqueous solution by pulsed-gradient spin-echo (PGSE) nuclear magnetic resonance (NMR) spectroscopy. All polymers underwent a decrease in their mean diffusion coefficients as the concentration was increased. However, the dispersion of the diffusion coefficients, ${\beta}$, about the mean fluctuated with changes in concentration. The large dispersion at low concentrations of HEUR 35(8) and HEUR 35(12) is related to the interaction between hydrophobic end groups, and the large dispersion at high concentrations of HEUR 35(18) is correlated with transient network formation. These results are valuable for predicting the associating mechanism of the large aggregates before and after their critical micelle concentration.

• Environmental Engineering Research
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• v.14 no.2
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• pp.111-119
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• 2009

A prototype GIS-based decision support system (DSS) was developed by using a database management system (DBMS), a model management system (MMS), a knowledge-based system (KBS), a graphical user interface (GUI), and a geographical information system (GIS). The method of selecting a dispersion model or a modeling scheme, originally devised by Park and Seok, was developed using our GIS-based DSS. The performances of candidate models or modeling schemes were evaluated by using a single index(statistical score) derived by applying fuzzy inference to statistical measures between the measured and predicted concentrations. The fumigation dispersion model performed better than the models such as industrial source complex short term model(ISCST) and atmospheric dispersion model system(ADMS) for the prediction of the ground level $SO_2$ (1 hr) concentration in a coastal area. However, its coincidence level between actual and calculated values was poor. The neural network models were found to improve the accuracy of predicted ground level $SO_2$ concentration significantly, compared to the fumigation models. The GIS-based DSS may serve as a useful tool for selecting the best prediction model, even for complex terrains.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1851-1856
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• 2003

A new Lagrangian stochastic dispersion model is developed by combining the GLM(generalized Langevin model) and the elliptic relaxation method. Under the physically plausible assumptions a simple analytical solution of elliptic relaxation is obtained. To compare the performance of our model with other model, the statistics of particle velocity as well as concentration are investigated. Numerical simulation results show good agreement with available experimental data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.11
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• pp.735-744
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• 2010

An efficient code has been developed to predict dispersion of indoor air pollutants. The computing capability of the code has been compared with that of a commercial code in a benchmark test. After that, the code has been employed to compute dispersion of a pollutant released from a new furniture, a kind of Sick Building Syndrome(SBS). A sofa which generates formaldehyde is implemented by using an immersed boundary method. Large Eddy Simulation (LES) is employed to obtain time-dependent velocity and concentration fields. LES has been regarded as an academic tool, but the newly-developed code reveals a possibility of application of LES to practical problems, especially dispersion of indoor pollutants.

• Journal of Pharmaceutical Investigation
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• v.27 no.4
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• pp.295-301
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• 1997

Nitrendipine, a slightly soluble calcium channel blocking agent forms a solid dispersion system with $hydroxypropyl-{\beta}-cyclodextrin$, which exhibits better dissolution characteristics than the uncomplexed drug. The dissolution rate of nitrendipine was markedly increased in solid dispersion system in pharmacopeial disintegration media at pH 1.2 and pH 6.8. Four different dosage forms of nitrendipine were administered to rats: (a) nitrendipine in the solution of PEG 400; (b) nitrendipine solid dispersion system with $hydroxypropyl-{\beta}-cyclodextrin$ in a molar ratio of 1:2 by solvent evaporation method and administered in capsule form; (c) physical mixture of nitrendipine with $hydroxypropyl-{\beta}-cyclodextrin$ in a molar ratio of 1:2 and administered in capsule form; (d) nitrendipine alone administered in capsule form. Relative bioavailability after the oral administration of various dosage forms to rats with a dose of 10 mg/kg equivalent to nitrendipine was compared with that of nitrendipine in the solution of PEG 400. The AUC of solid dispersion was significantly bigger than that of nitrendipine powder. $T_{max}$ of solid dispersion was significantly shorter and $C_{max}$ was higher than that of nitrendipine powder. These results indicate that the bioavailability of nitrendipine could be improved markedly by inclusion complexation. An interesting correlation also appears to exist between the in vitro dissolution data and the area under the plasma concentration-time curves.

• Journal of Korea Water Resources Association
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• v.33 no.4
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• pp.407-417
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• 2000

To estimate the longitudinal dispersion coefficient at the downstream of Jungrang-River, the undistorted 1/20 scale hydraulic model was used in this study. Experiments were conducted for dry season discharge, and Rhodamine B was used as a tracer. The relationship curve between concentration and conductivity of Rhodamine B was otained by laboratory test, and the conductivity which was measured in hydraulic model was converted to concentration using this curve. The longitudinal dispersion coefficient was calculated using the relationship between the peak concentration and the time to peak concentration. The results of this study were compared with the calculated values by the empirical equations for the longitudinal dispersion coefficient and with the field data. The results of comparison show that Parker's equation underestimates, and Liu'g equation and Iwasa and Aya's one overestimate, and McQuivey and Keefer's equations, Fischer's one, Magazine's one, and Seo and Cheong's one predict relatively well. The measured data sets were relatively close to the observed ones in natural river. The longitudinal dispersion coefficient at the downstream of Jungrang-River was estimated $10\textrm{m}^2/s$.

• Journal of Korean Society of Water and Wastewater
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• v.7 no.1
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• pp.29-36
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• 1993

The complex nature of low flow mixing in natural channels has been investigated using both laboratory experiments and the numerical solution of a proposed mathematical model that is based on a set of mass balance equations describing the mixing and mass exchange mechanisms. Laboratory experiments, which involved collection of channel geometry, hydraulic, and dye dispersion test data, were conducted in a model of four pool and riffle sequences in a 49-m long tilting flume. The experimental results show that flow over the model pool-riffle sequences is highly non-uniform. Concentration-time curves are significantly skewed with long tails. Comparison between measured and predicted concentration-time curves shows good agreement in the general shape, peak concentration and time to peak. The proposed model shows significant improvement over the conventional one-dimensional dispersion model in predicting natural mixing processes in open channels under low flow conditions through pools and riffles.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.5
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• pp.537-545
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• 2005

A new dispersion model for dense gas is constructed in the Lagrangian framework. Prediction of concentration by the proposed model is compared with measure data obtained in the experiment conducted in Thorney Island in 1984. Two major effects of dense gas dispersion, gravity slumping and stratification effect, are successfully incorporated into LDM (Lagrangian dense gas model). Entrainment effect is naturally modelled by introducing stochastic dispersion model with the effect of turbulence suppression by stratification. Not only various releasing conditions but also complex terrain can be extended to, although proposed model is appropriate for flat terrain.