• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.155-161
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• 2023

Ion concentration polarization (ICP) is one of the essential important mechanisms for biomolecule preconcentration devices as well as a fundamental transport phenomenon found in electrodialysis, electrochemical cell, etc. The ICP triggered by externally applied voltage enables the biomolecular analyte to be preconcentrated at an arbitrary position by a locally amplified electric field inside the microchannel. Conventional preconcentration methodologies using the ICP have two limitations: uncertain equilibrium position and hydrodynamic instability of preconcentration plug. In this work, a new preconcentration method in the dead-end microchannel around cation exchange membrane was numerically studied to resolve the limitations. As a result, the numerical model showed that the analyte was concentrated at a shock front developed in a geometrically confined dead-end channel. Furthermore, the electrokinetic behaviors for preconcentration dynamics were analyzed by changing microchannel's applied voltage and volumetric charge concentration of microchannel as key parameters to describe the dynamics. This work would provide an effective means for a point-of-care platform that requires ultra-fast preconcentration method.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.216-221
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• 2024

Ion cyclotron range of frequency (ICRF) heating system is an important auxiliary heating method in the experimental Advanced Superconducting Tokamak (EAST). In EAST, several megawatts of power are transmitted with coaxial transmission lines and coupled to the plasma. For the long pulse and high power operation of the ICRF waves heating system, it is very important to effectively control the power and initial phase of the ICRF signals. In this paper, a power and phase feedback control system is described based on field programmable gate array (FPGA) devices, which can realize complicated algorithms with the advantages of fast running and high reliability. The transmitted power and antenna phase are measured by a power and phase detector and digitized. The power and phase feedback control algorithms is designed to achieve the target power and antenna phase. The power feedback control system was tested on a dummy load and during plasma experiments. Test results confirm that the feedback control system can precisely control ICRF power and antenna phase and is robust during plasma variations.

• Analytical Science and Technology
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• v.6 no.4
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• pp.349-357
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• 1993

Analytical methods of thromboxane $B_2(TXB_2)$ using various techniques of Fast Atom Bombardment mass spectrometry (FAB MS) were studied, static FAB condition was investigated to obtain linear response curve using docosanoic acid as a internal standard. For maximum sensitivity, a continuos-flow(CF-) FAB MS by selected-ion monitoring(SIM) with devised sample introduction system, has been developed to quantiate thromboxane $B_2$ in biological sample. Instrumental parameters affecting sensitivity, reproducibility has been studied. The method has been optimized with respect to the eluent, 0.75% glycerol(in EtOH v/v) and flow rate of $3.7{\mu}l/min.$ Under the condition, detection limits were below 10pg in SIM mode and a good linear relationship between dose and response was achieved.

• Food Science of Animal Resources
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• v.36 no.6
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• pp.769-778
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• 2016

In this study, we improved the eggshell-membrane separation process by separating the shell and membrane with EDTA solution, evaluating effects of three different extraction solutions (acetic acid, EDTA, and phosphate solution), and co-purifying multiple eggshell proteins with two successive ion-exchange chromatography procedures (CM Sepharose Fast Flow and DEAE Sepharose Fast Flow). The recovery and residual rates of eggshell and membrane separated by the modified method with added EDTA solution were 93.88%, 91.15% and 1.01%, 2.87%, respectively. Ovocleidin-116 (OC-116) and ovocalyxin-36 (OCX-36) were obtained by loading 50 mM Na-Hepes, pH 7.5, 2 mM DTT and 350 mM NaCl buffer onto the DEAE-FF column at a flow rate of 1 mL/min, ovocleidin-17 (OC-17) was obtained by loading 100 mM NaCl, 50 mM Tris, pH 8.0 on the CM-FF column at a flow rate of 0.5 mL/min. The purities of OCX-36, OC-17 and OC-116 were 96.82%, 80.15% and 73.22%, and the recovery rates were 55.27%, 53.38% and 36.34%, respectively. Antibacterial activity test suggested that phosphate solution extract exhibited significantly higher activity against the tested bacterial strains than the acetic acid or EDTA extract, probably due to more types of proteins in the extract. These results demonstrate that this separation method is feasible and efficient.

• Membrane and Water Treatment
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• v.7 no.1
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• pp.55-70
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• 2016

Microfiltration/ultrafiltration (MF/UF) Adsorptive polyamide-6 (PA-6) membranes were prepared using wet phase inversion process. The prepared PA-6 membranes are characterized by scanning electron microscopy (SEM), porosity and swelling degree. In this study, the membranes performance has examined by adsorptive removal of copper ions from aqueous solutions in a batch adsorption mode. The $PA-6/H_2O$ membranes display sponge like and highly porous structures, with porosities of 41-73%. Under the conditions examined, the adsorption experiments have showed that the $PA-6/H_2O$ membranes had a good adsorption capacity (up to 120-280 mg/g at the initial copper ion concentration ($C_0$) = 680 mg/L, pH7), fast adsorption rates and short adsorption equilibrium times (less than 1.5-2 hrs) for copper ions. The fast adsorption in this study may be attributed to the high porosities and large pore sizes of the $PA-6/H_2O$ membranes, which have facilitated the transport of copper ions to the adsorption. The results obtained from the study illustrated that the copper ions which have adsorbed on the polyamide membranes can be effectively desorbed in an Ethylene dinitrilotetra acetic acid Di sodium salt ($Na_2$ EDTA) solution from initial concentration (up to 92% desorption efficiency) and the PA-6 membranes can be reused almost without loss of the adsorption capacity for copper ions. The results obtained from the study suggested that the $PA-6/H_2O$ membranes can be effectively applied for the adsorptive removal of copper ions from aqueous solutions.

• Food Science of Animal Resources
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• v.20 no.2
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• pp.159-165
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• 2000

Glycomacropeptide(GMP) was purified from cheese whey which is obtaining as a byproduct in cheese producing. Cheese whey was first concentrated 10 times with a ultrafiltration aparratus, and then heated at 95$^{\circ}C$ for 5 min. The concentrated fraction was centrifuged at 20,000$\times$g for 30 min to remove fat layer. The supernatant layer enriched GMP protein was fractionated by ion exchange chromatography on DEAE-Sepharose Fast Flow column. GMP was bound to DEAE resin and eluted with 0.1~0.25 M NaCl when using a linear NaCl gradient from 0 M to 0.5 M. The purified GMP gave a single band of 24 kDa which seems to be trimer molecular weight in SDS-PAGE, and migrated to the same molecular weight with control GMP obtained commercially. Its amino acid composition were consistent with that of standard GMP. About 0.71 g of GMP was recovered from 1 L of cheese whey. These results indicate that glycomacropeptide could be simply purified from cheese whey by using ultrafiltration and DEAE column chromatography.

• Journal of Radiation Protection and Research
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• v.11 no.2
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• pp.104-113
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• 1986

The ion exchange behaviour of the $Cs^{+1},\;Sr^{+2},\;and\;Th^{+4}$ in the system of $Cs^{+1},\;Sr^{+2},\;Th^{+4},\;and\;7Cl^{-}-H^{+}$ from Dowex HCR-W2, was examined in the loading and elution processes. $Th^{+4}$ was slowly adsorbed through the entire contact time between resin and solution and $Cs^{+1}\;and\;Sr^{2+}$ were adsorbed fast for the first few minutes of contact time. Because of the strong affinity of $Th^{+4}$, the longer contact time was allowed, the less amount of $Cs^{+1}\;and\;Sr^{2+}$ was adsorbed on the resin. The peak concentration of the resin phase $Cs^{+1}$ in the solution concentration of $Cs^{+1}:Sr^{+2}:Th^{+4}$ in the ratio of 2 : 2 : 1 in normality with total normality of 0.1N was produced at about 4 minutes of contact time and the peak time for $Sr^{+2}$ was 20 minutes. The loaded ions were eluted using hydrochloric acid. The loaded $Cs^{+1}$ was eluted at the low eluent concentration of less than 0.1N with less than 5% contamination of $Sr^{+2}$. The loaded $Th^{+4}$ was eluted at the high eluent concentration of greater than 1N. The best eluent concentration for eluting $Th^{+4}$ was 4N.

• Journal of the Korean Applied Science and Technology
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• v.30 no.2
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• pp.258-263
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• 2013

New conducting polymers containing heterocyclic ring with carbazole, EDOT and benzobisthiazole were synthesized and characterized by organic spectroscopic methods. Potentiometric ion-selective membrane electrodes (ISMEs) have been extensively used for ion analysis in clinical, environmental, and industeial fields owing to its wide response range (4 to 7 orders of magnitude), no effect of sample turbidity, fast response time, and ease of miniaturization. Considerable attention has been given to alternative use of room temperature vulcanizing (RTV)-type silicone rubber(SR) owing to its strong adhesion and high thermal durability. Unfortunately, the high membrane resistance of SR-based (ISMs)(2 to 3 higher orders of magnitude compared to those of poly(vinyl chloride)(PVC)-based ones) has significantly restricted its application. Herein we demonstrate a new method to reduce membrane resistance via addition of new conducting polymer into the SR-based ISMs.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.931-938
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• 2005

When concrete structures are exposed under marine condition for a long time, the steel in concrete is corroded due to the ingression of chlorides in the seawater. Because the damages of corrosion resulting from the chloride ion are very serious, many researches have been performed. Silver nitrate colormetric method that can measure easily penetration depth of chloride ion has been executed, recent)y. However, characteristics of silver nitrate colormetric method were not fully examined. Therefore, the objective of this paper Is to study the applicability of colormetric method. For the purpose of this, effect factors and reaction mechanism of colormetric method were investigated, and the colormetric method is applied for marine concrete structures. According to the results of silver nitrate colored method, two reactions such as white reaction of AgCl and brown reaction of AgOH were shown when $AgNO_3$ was sprayed in splited section. And velocity constant ratio(K) of two reactions appeared that white reaction, AgCl reacts with the fast speed by 3240. When the colormetric method was applied in concrete, it is reasonable that $AgNO_3$ solution more than 0.05N concentration was sprayed. It is confirmed that the colormetric method is useful tool for estimating the chloride of concrete structures in situ. The average chloride amount of colored parts indicates $0.9kg/m^3$ per concrete unit weight.

• Membrane Journal
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• v.32 no.6
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• pp.442-455
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• 2022

High-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) has been studied as an alternative to low-temperature PEMFC due to its fast activation of electrodes and high resistance to electrode poisoning by carbon monoxide. It is highly required to develop stable PEMs operating at high temperatures even doped by ion-conducting materials for the development of high-performance and durable HT-PEMFC systems. A number of studies have been conducted to develop polybenzimidazole (PBI)-based PEMs for applications in HT-PEMFC due to their high interaction with doped ion-conducting materials and outstanding thermomechanical stability under high-temperature operation. This review focused on the development of PBI-based PEMs showing high performance and durability. Firstly, the characteristic behavior of PBI-based PEMs doped with various ion-conducting materials including phosphoric acid was systematically investigated. And then, a comparison of the physicochemical properties of the PEMs according to the different membrane manufacturing processes was conducted. Secondly, the incorporation of porous polytetrafluoroethylene substrate and/or inorganic composites to PBI matrix to improve the membrane performances was studied. Finally, the construction of cross-linked structures into PBI-based PEM systems by polymer blending method was introduced to improve the PEM properties.