• Journal of Korean Society of Water and Wastewater
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• v.34 no.3
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• pp.183-190
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• 2020

Although membrane bio-reactor (MBR) has been widely applied for wastewater treatment plants, the membrane fouling problems are still considered as an obstacle to overcome. Thus, many studies and commercial developments on mitigating membrane fouling in MBR have been carried out. Recently, high voltage impulse (HVI) has gained attention for a possible alternative technique for desalting, non-thermal sterilization, bromate-free disinfection and mitigation of membrane fouling. In this study, it was verified if the HVI could be used for mitigation of membrane fouling, particularly the internal pore fouling in MBR. The HVI was applied to the fouled membrane under different conditions of electric fields (E) and contact time (t) of HVI in order to investigate how much of internal pore fouling was reduced. The internal pore fouling resistance (R_f) after HVI induction was reduced as both E and t increased. For example, R_f decreased by 19% when the applied E was 5 kV/cm and t was 80 min. However, the R_f decreased by 71% as the E increased to 15 kV/cm under the same contact time. The correlation between E and t that needed for 20% of R_f reduction was modeled based on kinetics. The model equation, E^1.54t = 1.2 × 10³ was obtained by the membrane filtration data that were obtained with and without HVI induction. The equation states the products of En and t is always constant, which means that the required contact time can be reduced in accordance with the increase of E.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.153-160
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• 2021

Nitrous oxide is a global warming substance and is known as the main cause of the destruction of the ozone layer because its global warming effect is 310 times stronger than carbon dioxide, and it takes 120 years to decompose. Therefore, in this study, we investigated the characteristics of NOx emission from N2O reduction by thermal decomposition of N2O. Bunsen premixed flames were adopted as a heat source to form a high-temperature flow field, and the experimental variables were nozzle exit velocity, co-axial velocity, and N2O dilution rate. NO production rates increased with increasing N2O dilution rates, regardless of nozzle exit velocities and co-axial flow rates. For N2O, large quantities were emitted from a stable premixed flame with suppressed combustion instability (Kelvin Helmholtz instability) because the thermal decomposition time is not sufficient with the relatively short residence time of N2O near the flame surface. Thus, to improve the reduction efficiency of N2O, it is considered effective to increase the residence time of N2O by selecting the nozzle exit velocities, where K-H instability is generated and formed a flow structure of toroidal vortex near the flame surface.

• Korean Journal of Food Science and Technology
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• v.48 no.1
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• pp.36-41
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• 2016

In this study, the effects of intense pulsed light (IPL) treatment on microbial inactivation and quality in rapeseed sprouts were investigated. Untreated rapeseed sprouts exhibit a high level of total aerobic bacteria (TAB) ($1.2{\times}10^7CFU/g$), coliform bacteria (coliform) ($3.3{\times}10^6CFU/g$), and pathogenic E. coli (PE) ($2.1{\times}10^5CFU/g$). The microorganisms found on rapeseed sprouts decreased with exposure to increasing light intensity and treatment time. The greatest reduction in microbial content was observed with a treatment of 1000 V, 5 pps for 10 min, where TAB, coliform, and PE levels decreased to 1.0 log CFU/g, 1.6 log CFU/g, and 1.8 log CFU/g, respectively. In agreement with these data, the microbial inactivation rate increased with the increase in the distance between the light source and the samples during IPL treatment. After IPL treatment of rapeseed sprouts, water content and vitamin C content decreased.

• Korean Journal of Food Science and Technology
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• v.47 no.4
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• pp.486-491
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• 2015

The potential of applying cold plasma (CP) treatments to improve microbiological safety of powdered products has been investigated using infant milk powder (IMP) and onion powder (OP). Among the different kinds of CP-forming gases, He-$O_2$ (99.8:0.2) gas mixture and He gas were most effective in reducing the number of Cronobacter sakazakii in IMP and Bacillus cereus spores in OP, respectively. C. sakazakii counts in IMP decreased by $0.9{\pm}0.1{\log}\;CFU/g$ after CP treatment, and the extent of C. sakazakii inhibition increased in a time-dependent manner. CP treatment at 900 W for 20 min reduced the number of B. cereus spores by ~0.4 log spores/g. Treatments that integrated CP with microwave (MW-CP treatment) as well as those that integrated CP with heat and microwave (H-MW-CP treatment) resulted in a 90% reduction in the number of spores in OP. Thus, CP treatments demonstrated potential for decontaminating foodborne pathogens from powdered products, in combination with heat for improved effect.

• Membrane and Water Treatment
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• v.2 no.3
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• pp.159-173
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• 2011

The air gap membrane distillation (AGMD) process was applied for water desalination. The main objective of the present work was to study the heat and mass transfer mechanism of the process. The experiments were performed on a flat sheet module using aqueous NaCl solutions as a feed. The membrane employed was hydrophobic PTFE of pore size 0.22 ${\mu}m$. A mathematical model is proposed to evaluate the membrane mass transfer coefficient, thermal boundary layers' heat transfer coefficients, membrane / liquid interface temperatures and the temperature polarization coefficients. The mass transfer model was validated by the experimentally and fitted well with the combined Knudsen and molecular diffusion mechanism. The mass transfer coefficient increased with an increase in feed bulk temperature. The experimental parameters such as, feed temperature, 313 to 333 K, feed velocity, 0.8 to 1.8 m/s (turbulent flow region) were analyzed. The permeation fluxes increased with feed temperature and velocity. The effect of feed bulk temperature on the boundary layers' heat transfer coefficients was shown and fairly discussed. The temperature polarization coefficient increased with feed velocity and decreased with temperature. The values obtained were 0.56 to 0.82, indicating the effective heat transfer of the system. The fouling was observed during the 90 h experimental run in the application of natural ground water and seawater. The time dependent fouling resistance can be added in the total transport resistance.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1199-1204
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• 2013

Nanocomposites consisting of Sn nanoparticles and graphene oxide (GO) were electrophoretically deposited onto Cu current collectors that was used for anodes in Li ion batteries (LIBs). In order to optimize the electrochemical performance of nanocomposites as an anode material by controlling the oxygen functionality, the GO was subjected to $O_3$ treatment prior to electrophoretic deposition (EPD). During thermal reduction of the GO in the nanocomposites, the Sn nanoparticles were reduced in size, along with the formation of SnO and/or $SnO_2$ at a small fraction, relying on the oxygen functionalities of the GO. The variation in the duration of time for the $O_3$ irradiation resulted in a small change in total oxygen content, but in a significantly different fraction of each functional group in the GO, which influenced the Sn nanoparticle size and the amount of SnO (and/or $SnO_2$). As a result, the EPD films prepared with the GO that possessed the least amount of carboxylic groups (made by treating GO in an $O_3$ environment for 3 h) showed the best performance, when compared with the nanocomposites composed of untreated GO or GO that was $O_3$-treated for a duration of less than 3 h.

• Economic and Environmental Geology
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• v.27 no.6
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• pp.507-521
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• 1994

Bentonite occurs in the Janggi Conglomerate of Tertiary age and consists mainly of montmorillonite with Mg as predominant interlayer cations. The bentonite was reacted with various concentrations of sulfuric acid (0.8~1.5M) for various reaction time (1-10h) at $103^{\circ}C$. Cation exchange capacity, exchangeable cations, surface area and solid acidity of the original bulk and acid activated bentonites were measured. Chemical analysis, X-ray diffraction, differential thermal analysis and infrared spectroscopy were used to characterize the changes in structure and properties of the acid activated bentonite. The dissolution of octahedral cations occurs not only from the edge of the clay platelets but also throughout the whole clay structure creating vacant octahedral sites. These lattice defects are created by $H^+$ diffused into the smectite layers. The cations leached possibly from the octahedral sheets are adsorbed on the interlayer exchange sites. They are exchanged with hydronium ions again by stronger acid attack. These reactions create wedge-shaped pores resulting in the increase of the surface area and the changes the morphology in the lattice structure.

• Journal of Electrical Engineering and Technology
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• v.6 no.1
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• pp.59-66
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• 2011

This work treat the modeling and simulation of non-linear dynamic behavior of a web winding process during traction. We designate by a winding process any system applying the cycles of unwinding, transport, treatment, and winding to various flat products. This system knows several constraints, such as the thermal effects caused by the frictions, and the mechanical effects provoked by metal elongation, that generates dysfunctions due to the influence of the process conditions. Several controllers are considered, including Proportional-integral (PI) and Backstepping control. This paper presents the study of Backstepping controls strategy of the winding system. Our winding system is simulated in MATLAB SIMULINK environment, the results obtained illustrate the efficiency of the proposed control with no overshoot, and the rising time is improved with good disturbances rejections comparing with the classical control law.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.6
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• pp.1057-1064
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• 2009

This paper introduces a new approach based on a quantum-inspired evolutionary algorithm (QEA) to solve unit commitment (UC) problems. The UC problem is a complicated nonlinear and mixed-integer combinatorial optimization problem with heavy constraints. This paper proposes a bounded quantum evolutionary algorithm (BQEA) to effectively solve the UC problems. The proposed BQEA adopts both the bounded rotation gate, which is simplified and improved to prevent premature convergence and increase the global search ability, and the increasing rotation angle approach to improve the search performance of the conventional QEA. Furthermore, it includes heuristic-based constraint treatment techniques to deal with the minimum up/down time and spinning reserve constraints in the UC problems. Since the excessive spinning reserve can incur high operation costs, the unit de-commitment strategy is also introduced to improve the solution quality. To demonstrate the performance of the proposed BQEA, it is applied to the large-scale power systems of up to 100-unit with 24-hour demand.

• Journal of Acupuncture Research
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• v.38 no.4
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• pp.300-311
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• 2021

Background: So far there is no confidence in the basics of acupoint/meridian phenomena, specifically in spatial and temporal electrical manifestations in the skin. Methods: Using the skin electrodynamic introscopy, the skin areas of 32 × 64 mm² were monitored for spectral electrical impedance landscape with spatial resolution of 1 mm, at 2 kHz and 1 MHz frequencies. The detailed baseline and 2D test-induced 2 kHz-impedance phase dynamics and the 4-parameter time plots of dozens of individual points in the St32-34 regions were examined in a healthy participant and a patient with mild gastritis. Non-thermal stimuli were used: (1) (for the sick subject), microwaves and ultraviolet radiation applied alternately from opposite directions of the meridian; and (2) (for the healthy one) microwaves to St17, and cathodic/anodic stimulation of the outermost St45, alternately. Results: In both cases, the following phenomena have been observed: emergence of in-phase and/or antiphase coherent structures, exceeding the acupoint conditional size of 1 cm; collective movement along the meridian; reversible with a reversed stimulus; counter-directional dynamics of both whole structures and adjacent points; local abnormalities in sensitivity and dynamics of the 1 MHz and 2 kHz parameters indicating existence of different waveguide paths. Conclusion: It is assumed that these findings necessitate reconsideration of some basic methodological issues regarding neurogenic/acupuncture points as spatial and temporal phenomena; this requires development of an appropriate approach for identifying the acuzones patterns. These findings may be used for developing new approaches to personalized/controlled therapy/treatment.