• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1571-1578
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• 2015

The cleaning characteristics of pulse air jet type cleaning system which is widely applied in the industries were identified by utilizing the computational fluid dynamics (CFD) and the cleaning performance in modified shape of dedusting unit was compared in this study. The review on each shape of cleaning part showed that the case of installing the nozzle on the blow tube (Case-3) and the case of installing the double intaking tube to the venturi (Case-4 and Case-5) were more excellent than the structure (Case-1). Also, the optimal venturi shape was designed and examined its applicability to the site in a pilot scale plant. A combined system of a blow tube and a venturi proposed by this study turned out to be very effective for concentrating an cleaning air compared to existing systems, such as using only blow tube and combines the blow tube and venturi. In addition, as a result of installing and testing a venturi proposed by this study, the cleaning frequency and cleaning time were much improved compared to a case of using a commercial venturi that is under use at the industrial sites.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6305-6314
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• 2015

This study presents numerical simulations of mean flow and turbulence structure of an open channel with submerged vegetation. Filtered Navier-Stokes equations are solved using large-eddy simulation (LES). The immersed boundary method (IBM) is employed based on a Cartesian grid. The numerical result is compared with experimental data of Liu et al. (2008) and shows that simulated results coincided reasonably with experimental data within the average error of 10%. Strong vortices are generated at the interface between vegetated and non-vegetated regions with spanwise extent. The generation of turbulence induced by shear at the interface is interfered with wake turbulence, resulting turbulence intensity maximum. Turbulence produced by shear affects the flow in vegetated region and the penetration depth increases with an increase in the submergence ratio. This result can be used to understand sediment transport mechanisms in the vegetated region.

• Membrane Journal
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• v.15 no.1
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• pp.34-43
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• 2005

The poly(vinyl alcohol) (PVA)-based thin film composite nanofiltration (NF) membranes were prepared by coating polysulfone ultrafiltration membranes, sulfonated polyethersulfone and polyamide NF membranes with aqueous PVA solution by a pressurizing method. The PVA was cross-linked with aqueous glutaraldehyde solution. The NF membranes coated with a very low concentration of PVA on all the support membranes was successfully prepared. With increasing the hydrophilicity of the support membranes, the water flux increased. Especially, ζ-potential of negatively charged polyamide NF membrane was reduced by coating the membrane with PVA. A fouling experiment was carried out with positively charged surfactant, humic acid, complex of humic acid and calcium ion and bovine serum albumin. A non-coated polyamide NF membrane was significantly fouled by various foulants. The fouling process when using humic acid and protein occurred at the isoelectric point. There was severe fouling when using humic acid and adding bivalent cations. By coating the polyamide NF membrane with aqueous PVA solution, fouling was reduced. The polyamide NF membrane coated with PVA was resistant to the acidic and basic solution.

• Membrane Journal
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• v.11 no.4
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• pp.170-178
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• 2001

PVC microfiltration membrane was prepared by phase immersion method and applied to membrane bioreactor (MBR) contained activated sludge. The hydrophilicity of membrane and the pore size increase with the amount of additive(PVP) ducting the preparation of membrane. Permeation characteristics and the membrane fouling behavior were investigated by varying the internal environment in MBR using the prepared membranes. When there is a sludge bulking in MBR caused by microorganism, membrane fouling was accumulated. The cake layer resistance, R$_{c}$, of membrane increased in the order of CP-0 > CP-1.0 > CP-1.5. Rc increased up to 3.5~7 fold where the sludge bulking occurred in MBR. CP-1.5 seems to be appropriated membrane on the basis of the surface characteristics and the flux. The average flux of all the test membrane was 12(${\pm}$2) L/$m^2$hr whereas the COD removal efficiency was 98.8%. The ratio of bulking sludge and the type and the size of microorganism in operating MBR accelerate the membrane fouling and flux decline. It is concluded that the characteristic of membrane filtration depends on the hydrophilicity of membrane, the internal environment of MBR reactor and the growth factor of sludge.

• Journal of Radiation Protection and Research
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• v.2 no.1
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• pp.9-16
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• 1977

A simple method has been established for determining RaA, RaB and RaC concentrations in airborne dust. This is to evaluate the concentration from measurement of total alpha activities in three selected-time intervals after an air sample is taken from the membrane filter paper (mean pore size: $0.8{\mu}m$). As a preliminary trial, a time-variation of the concentrations has been determined using the single-filter method at the KAERI site (N. Lat. $37^{\circ}38'$ and E. Long $127^{\circ}15'$), Seoul, Korea. It appears that there is a large variation of the concentrations depending on the sampling time. Generally the highest value was observed in the morning that may coincide with the highest density of atmosphere in a day while the lowest value was obtained around fourteen o'clock.

• Composites Research
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• v.34 no.2
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• pp.108-114
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• 2021

Graphene flakes are generally mass-produced by converting graphene oxide into reduced graphene oxide using chemical or thermal reduction. These graphene flakes can be stacked to form a free-standing graphene paper, which can be used for various applications. However, a graphene paper lacks stretchability, which hinders its application in stretchable devices. In this work, we introduced wrinkles in a graphene paper to make it stretchable. A graphene paper fabricated by vacuum-filtering a graphene dispersion was placed on a pre-stretched adhesive film. When the pre-stretched adhesive film returned to the original state, the graphene paper was wrinkled. The effect of the pre-stretching and wet condition of the graphene papers was experimentally investigated by using scanning electron microscopy. In addition, we observed the change of the period of the wrinkles in the graphene paper depending on the pre-stretching.

• Journal of the Korean GEO-environmental Society
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• v.12 no.10
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• pp.51-56
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• 2011

This study was conducted to investigate the applicability of pulsed electric field (PEF) treatment for the prevention of scaling formation and membrane fouling reduction. To validate the effect of PEF and to identify the mechanism, some experiments with and without PEF treatment were carried out. PEF treatment affected the precipitation of $CaCO_3$ by which $CaCO_3$ particles were actively grown and sedimented. It was confirmed that the calcium ions were decreased as 78% and particle size was grown by PEF treatment. It was also verified that the crystalline structure of $CaCO_3$ was transformed by PEF treatment from Aragonite, which is formed at a high temperature and hard to be removed, to Calcite being stable at room temperature. In PEF treatment, permeate volume and permeation flux were greater than that of without PEF, case while Langelier Index(LI) decreased. From the experiment results, PEF treatment is believed to be an effective method to prevent scaling formation and to mitigate $CaCO_3$ fouling as the pretreatment of membrane filtration.

• Membrane Journal
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• v.31 no.3
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• pp.161-169
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• 2021

As clean water continues to be a demand in this global water crisis, development of separation membrane technology for water purification becomes a necessity. The effectiveness of separation membranes is hindered in the water crisis due to fouling of membranes. To address this problem, the application of patterns on flat membranes via various methods have been recently studied and experimented. Patterned membranes have shown to not only reduce the fouling effects of membranes, but also increase the fluxes depending on the method and materials used. Each application has shown benefits that include, but not limited to, enhanced surface area, higher pure-water permeability, and increased number of filtration cycles. In this review, the effects of patterned membranes against antifouling is summarized and discussed.

• KIPS Transactions on Software and Data Engineering
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• v.11 no.4
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• pp.157-162
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• 2022

Today, most data is stored in a database (DB). In the DB environment, the users requests the DB to find the data they wants. Similarity Query has predicate that explained by a similarity. However, in the process of processing the similarity query, it is difficult to use an index that can reduce the range of processed records, so the cost of calculating the similarity for all records in the table is high each time. To solve this problem, this paper defines a lightweight similarity function. The lightweight similarity function has lower data filtering accuracy than the similarity function, but consumes less cost than the similarity function. We present a method for reducing similarity query processing cost by using the lightweight similarity function features. Then, Chebyshev distance is presented as a lightweight similarity function to the Euclidean distance function, and the processing cost of a query using the existing similarity function and a query using the lightweight similarity function is compared. And through experiments, it is confirmed that the similarity query processing cost is reduced when Chebyshev distance is applied as a lightweight similarity function for Euclidean similarity.

• Membrane Journal
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• v.33 no.1
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• pp.34-45
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• 2023

Two computational intelligence techniques namely artificial neural networks (ANN) and support vector machine (SVM) are employed to model the permeate flux based on seven input variables including time, transmembrane pressure, rotating velocity, the pore diameter of the membrane, dynamic viscosity, concentration and density of the feed fluid. The best-fit model was selected through the trial-error method and the two statistical parameters including the coefficient of determination (R²) and the average absolute relative deviation (AARD) between the experimental and predicted data. The obtained results reveal that the optimized ANN model can predict the permeate flux with R² = 0.999 and AARD% = 2.245 versus the SVM model with R² = 0.996 and AARD% = 4.09. Thus, the ANN model is found to predict the permeate flux with high accuracy in comparison to the SVM approach.