• Journal of the Society of Naval Architects of Korea
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• v.48 no.1
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• pp.76-83
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• 2011

FCAW(Flux Cored Arc Welding) is a widely used welding method in shipbuilding. It also conducts WPS(Welding Procedure Specification) requested by the classification variations of the factors which affect the quality on the welded area such as thickness of base metal, type of welding wire and shielding gas etc. which has to be satisfied. CO2 is commonly used as a shielding gas for FCAW due to the economic point of view. The amount of shielding gas is stated when classification certify WPS. However, the shielding gas is unnecessarily used at the shipyard leaning only on the welder's experience as there are classification standards for using the shielding gas. It causes production cost to rise. Also recently, CO2 is a main contributor for global warming, and large amounts of CO2 are discharged into the atmosphere during shipbuilding processes without any filtration. Therefore it was confirmed by the security of the welded area as a result of conducting the destructive and non-destructive tests with setting up the factors and the standards by using the Taguchi method. Then the FCAW shielding gas's amounts were calculated precisely when assembling a ship. It will be applied to cost reduction and prevention of environmental pollution at the shipyard.

• Membrane Journal
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• v.13 no.2
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• pp.88-100
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• 2003

A change of filtrate flux in Taylor vortex flow filtration was investigated experimentally by rotating speed of inner cellulose ester membrane cylinder (average pore size: 1.2 ${\mu}m$), slurry concentration, and particle size. The filtrate flux was a direct proportion relation with TMP, but an inverse relation with resistances. A change of cake resistance with time was examined by rotating speed, slurry concentration, and particle size. Initial resistance increased dramatically as raising slurry concentration, and the pseudo-steady state was maintained at high resistance value. However, times to reach the pseudo-steady state did not depend on slurry concentration. The resistance was larger as smaller particle size, because possibility of pore blocking inside membrane could be higher and shear effect should be lower as smaller particle size. A model equation suggested in this study was composed of particle deposition and removal terms, and could confirm well experimental data using average values of experimental coefficients.

• Membrane Journal
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• v.23 no.1
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• pp.45-53
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• 2013

Membrane filtration processes are increasingly popular for drinking water treatment that requires high quality of water. But pre-treatment system (Coagulation/Flocculation/Sedimentation) requires increased footprint and installation cost. In addition, 5~10% of the concentrate are formed. In this study, the pressurized PVDF membrane (ECONITY Co., Ltd.) system was tested with surface water (Han River, South Korea) without pre-treatment. As a result, permeate flux was operated between 1 m/d and 2.4 m/d (at $25^{\circ}C$) without chemical cleaning for one year and membrane permeate turbidity was maintained stably under 0.05 NTU regardless of raw water turbidity. And we studied application of concetrate treatment of pressurized PVDF membrane by submerged PE membrane (ECONITY Co., Ltd.). As a result, we increased recovery of total treatment process to 99.5%.

• Membrane and Water Treatment
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• v.9 no.2
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• pp.69-77
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• 2018

The use of membrane as an innovative technology for water treatment process has now widely been accepted and adopted to replace the conventional water treatment process in increasing fresh water production for various domestic and industrial purposes. In this study, ultrafiltration (UF) membranes with different formulation were fabricated via phase inversion method. The membranes were fabricated by varying the polymer concentration (16 wt%, 18 wt%, 20 wt%, and 21 wt%). A series of tests, such as field emission scanning electron microscope (FESEM), pore size and porosity, contact angle, and zeta potential were performed to characterize the membranes. The membrane performance in terms of permeation flux and rejection were evaluated using a laboratory bench-scale test unit with mine water, lake water and tube well as model feed solution. Long hour filtration study of the membranes provides the information on its fouling property. Few pore blocking mechanism models were proposed to examine the behaviour of flux reduction and to estimate the fouling parameters based on different degree of fouling. 21 wt% PVDF membrane with smaller membrane pore size showed an excellent performance for surface water treatment in which the treated water complied with NWQS class II standard.

• Membrane and Water Treatment
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• v.9 no.2
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• pp.115-121
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• 2018

Artificial neural network (ANN) simulation is used to predict the dynamic change of permeate flux during wheat starch industry wastewater microfiltration with and without static turbulence promoter. The experimental program spans range of a sedimentation times from 2 to 4 h, for feed flow rates 50 to 150 L/h, at transmembrane pressures covering the range of $1{\times}10^5$ to $3{\times}10^5Pa$. ANN predictions of the wastewater microfiltration are compared with experimental results obtained using two different set of microfiltration experiments, with and without static turbulence promoter. The effects of the training algorithm, neural network architectures on the ANN performance are discussed. For the most of the cases considered, the ANN proved to be an adequate interpolation tool, where an excellent prediction was obtained using automated Bayesian regularization as training algorithm. The optimal ANN architecture was determined as 4-10-1 with hyperbolic tangent sigmoid transfer function transfer function for hidden and output layers. The error distributions of data revealed that experimental results are in very good agreement with computed ones with only 2% data points had absolute relative error greater than 20% for the microfiltration without static turbulence promoter whereas for the microfiltration with static turbulence promoter it was 1%. The contribution of filtration time variable to flux values provided by ANNs was determined in an important level at the range of 52-66% due to increased membrane fouling by the time. In the case of microfiltration with static turbulence promoter, relative importance of transmembrane pressure and feed flow rate increased for about 30%.

• Journal of the Korean GEO-environmental Society
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• v.11 no.1
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• pp.5-11
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• 2010

The objective of this study is to evaluate the effect of operational parameters such as rotation speed and vibrating milling time for the fabrication of photocatalytic $TiO_2$ thin film using aerosol deposition methods. $TiO_2$ powders produced in the range of 1,000-3,000 rpm of rotation speed of centrifugal separator are ineffective on the fabrication of $TiO_2$ thin film by aerosol deposition due to the problem of nozzle powder jam. $TiO_2$ powders controlled by vibrating milling had about 420 nm of average diameter after 2 hr of vibrating milling time. The result of XRD analysis indicated that $TiO_2$ powders had a anatase phase. Vibrating milling methods was considered to be an effective pre-treatment process for $TiO_2$ powder control. Consequently $TiO_2$ photocatalytic thin film with dispersion of anatase crystallites controled by vibrating milling was successfully fabricated by aerosol deposition. The permeation flux of $TiO_2$ photocatalytic thin film with the immobilized $TiO_2$ powder was higher than that of suspended $TiO_2$ powder. Therefore, $TiO_2$ photocatalytic thin film promises to be one of the effective methods for enhancing filtration performance for the treatment of organic pollutants.

• Economic and Environmental Geology
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• v.37 no.5
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• pp.499-508
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• 2004

Changwon City first constructed riverbank filtration plants in Book-Myeon and Daesan-Myeon in Korea in the year 2001. This study evaluated hydrogeological characteristics and groundwater flow simulation between the Nakdong River and the fluvial aquifers adjacent to the river in Book-Myeon, Changwon City. The groundwater simulation calculated the influx rate from the Nakdong River and the fluvial aquifers to pumping wells through the riverbank filtration system. The groundwater flow model utilized drilling, grain size analysis, pumping test, groundwater level measurements, river water discharge and rainfall data. Hydraulic heads calculated by the steady-state model closely matched measured heads in pumping and observation wells. According to the transient flow model, using a total pumping amount of 14,000 $m^3$/day, the flux into the pumping wells from the Nakdong River accounts for 8,390 $m^3$/day (60%), 590 $m^3$/day (4%) is from the aquifer in the rectilinea. direction to the Nakdong River, and 5,020 $m^3$/day (36%) is from the aquifer in the parallel direction to the Nakdong River. The particle tracking analysis shows that a particle from the Nakdong River moves toward the pumping wells at a rate of about 1.85 m/day and a particle from the aquifer moves toward the pumping wells at a rate of about 0.75 m/day. This study contributes to surface water/groundwater management modeling, and helps in understanding, how seasonal change affects pumping rates, water quality, and natural recharge.

• Membrane Journal
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• v.16 no.1
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• pp.39-50
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• 2006

Porous chitosan and chitin membranes were prepared by using silica particles as porogen. Membrane preparation was achieved via the following three steps: (1) chitosan film formation by casting an chitosan solution containing silica particles, (2) preparation of porous chitosan membrane by dissolving the silica particles by immersing the film into an alkaline solution and (3) preparation of porous chitin membrane by acetylation of chitosan membrane with acetic anhydride. The optimum preparation conditions which could provide a chitosan and chitin membranes with good mechanical strength and adequate pure water flux were determined. To allow protein affinity, a reactive dye (Cibacron Blue 3GA) was immobilized on porous chitosan membrane. Binding capacities of affinity chitosan and chitin membranes for protein and enzyme were determined by the batch adsorption experiments of BSA protein and lysozyme enzyme. The maximum binding capacity of affinity chitosan membrane for BSA protein is about 22 mg/mL, and that of affinity chitin membrane for lysozyme enzyme is about 26 mg/mL. Those binding capacities are about $several{\sim}several$ tens times larger than those of chitosan and chitin-based hydrogel beads. Those results suggest that the porous chitosan and chitin membranes are suitable in affinity filtration chromatography for large scale separation of proteins.

• Journal of Appropriate Technology
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• v.7 no.1
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• pp.72-81
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• 2021

Gravity-driven membrane (GDM) filtration system based on the nanofiber membrane was investigated. This system can be operated with little energy demand due to a gravitational pressure-driven filtration and biological fouling control strategy. Moreover, the optimal module configuration based on the high permeance of nanofiber membrane can provide a significantly high water productivity. In order to evaluate its applicability potential, the pilot-scale (3000-5000 L/day) systems with nanofiber membranes were operated in developing countries (Kiribati and Tuvalu). Our results showed that the 14-92 L/(m²×h) of the permeate flux was determined indicating a stabilized water productivity. In addition, the permeate water indicated a high removal rate (more than 99.99%) of turbidity and bacteria. Consequently, the system can provide a stabilized water production with safe permeate water quality during long-term operation. These findings exemplify an effective approach to decentralized drinking water treatment for developing countries.

• Membrane and Water Treatment
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• v.1 no.1
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• pp.49-60
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• 2010

In this study, response surface methodology (RSM) was performed in NF membrane process to evaluate the separation efficiency of membrane in the removal of salt and reactive dye by varying different variables such as pressure, temperature, pH, dye concentration and salt concentration. The significant level of both the main effects and the interaction were observed by analysis of variance (ANOVA) approach. Based on the statistical analysis, the results have provided valuable information on the relationship between these variables and the performances of membrane. The rejection of salt was found to be greatly influenced by pressure, pH and salt concentration whereas the dye rejection was relatively constant in between 96.22 and 99.43% regardless of the changes in the variables. The water flux on the other hand was found to be affected by the pressure and salt concentration. It is also found that the model predictions were in good agreement with the experimental data, indicating the validity of these models in predicting membrane performances prior to the real filtration process.