• Korean Journal of Materials Research
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• v.28 no.7
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• pp.376-380
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• 2018

Microalgae produce not only lipids for biodiesel production but also valuable biochemicals which are often accumulated under cellular stress mediated by certain chemicals. While the microcarriers for the application of drug delivery systems for animal cells are widely studied, their applications into microalgal research or biorefinery are rarely investigated. Here we develope dual-functional magnetic microcapsules which work not only as flocculants for microalgal harvesting but also potentially as microcarriers for the controlled release of target chemicals stimulating microalgae to enhance the accumulation of valuable chemicals. Magnetic microcapsules are synthesized by layer-by-layer(LbL) coating of PSS-PDDA on $Fe_3O_4$ nanoparticle-embedded $CaCO_3$ microparticles followed by removing $CaCO_3$ sacrificial templates. The positively charged magnetic microcapsules flocculate microalgae by electrostatic interaction which are sequentially collected by the magnetophoretic separation. The microcapsules with a polycationic outer layer provide efficient binding sites for negatively charged microalgae and by that means are further utilized as a chemical-delivery and flocculation system for microalgal research and biorefineries.

• Journal of Power Electronics
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• v.18 no.1
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• pp.309-322
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• 2018

The technology of inductive power transfer has been proved to be a promising solution in many applications especially in electric vehicle (EV) charging systems, due to its features of safety and convenience. However, loosely coupled transformers lead to the system efficiency not coming up to the expectation at the present time. Therefore, at first, the magnetic core losses are calculated with a novel magnetic-circuit model instead of the commonly used finite-element-method (FEM) simulations. The parameters in the model can be obtained with a one-time FEM simulation, which makes the calculation process expeditious. When compared with traditional methods, the model proposed in the paper is much less time-consuming and relatively accurate. These merits have been verified by experimental results. Furthermore, with the proposed loss calculation model, the system is optimized by parameter sweeping, such as the operating frequency and winding turns. Specifically, rather than a predesigned switching frequency, a more efficiency-optimized frequency for the series-parallel (SP) compensation topology is detected and a detailed investigation has been presented accordingly. The optimized system is capable of an efficiency that is greater than 93% at a coil separation distance of 200mm and coil dimensions of $600mm{\times}400mm$.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.48-56
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• 2018

A potassium copper hexacyanoferrate (KCuHCF) embedded magnetic hydrogel bead (HCF-Mbead) was synthesized via a facile double crosslinking methods of $Fe^{3+}$ ionic binding and freeze-thaw for effective $Cs^+$ removal. The HCF-Mbead had a hierarchical porous structure facilitating fast access of $Cs^+$ ions to embedded active sites. The adsorbent showed enhanced $Cs^+$ removal properties in terms of capacity (69.2 mg/g), selectivity ($K_d=4{\times}10^4mL/g$, 1 ppm $Cs^+$ in seawater) and stability (>99.5% removal in pH 3~11) with rapid magnetic separation. This study further opens the possibility to develop an efficient material that links the integration of adsorption and recovery.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.3
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• pp.363-372
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• 2020

Anionic radionuclides pose one of the highest risks to the long-term safety assessments of disposal repositories. Therefore, techniques to immobilize and separate such anionic radionuclides are of crucial importance from the viewpoints of safety and waste volume reduction. The main objective of this study is to design a separator with minimum pressure disturbance, based on the concept of a conventional cyclone separator. We hypothesize that the anionic radionuclides can be immobilized onto a nanomaterial-based substrate and that the particles generated in the process can flow via water. These particles are denser than water; hence, they can be trapped within the cyclone-type separator because of its design. We conducted particle tracking analysis using computational fluid dynamics (CFD) for the conventional cyclone separator and studied the effects due to the morphology of the separator. The proposed sandglass-like design of the separator shows promising results (i.e., only one out of 10,000 particles escaped to the outlet from the separation zone). To validate the design, we manufactured a laboratory-scale prototype separator and tested it for iron particles; the efficiency was ca. 99%. Furthermore, using an additional magnetic effect with the separator, we could effectively separate particles with ~100% efficiency. The proposed sandglass-like separator can thus be used for effective separation and recovery of immobilized anionic radionuclides.

• Journal of the Korean Orthopaedic Association
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• v.56 no.4
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• pp.341-345
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• 2021

The infrapatellar fat pad (IPFP) is one of three fat pads located about the anterior knee. Injury in this region is relatively common. Damage to the IPFP is caused mostly by an iatrogenic injury from a surgical procedure or repeated small collision trauma. The authors experienced a case of an IPFP injury, that has not been reported in the domestic or international literature. In this case, acute IPFP separation followed by a contusion at the anterior aspect of knee in the kneeling position, confirmed using magnetic resonance imaging. The patient was fully recovered with conservative treatment.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.64.1-64.1
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• 2015

In the present study, we examine the dependence of solar proton peak flux at SOHO and STEREO on 3-D CME parameters (radial speed, angular width, and longitudinal angular separation between its source region and the magnetic footpoints of spacecraft). For this we consider 38 proton enhancements of 16 SEP events observed by SOHO, STEREO-A, and/or B from 2010 August to 2013 June. As a result, we find that the enhancements are strongly dependent on these three parameters. The correlation coefficient between proton peak flux and CME speed is about 0.42 for the cases the footpoints are located inside the lateral boundaries of angular widths, while there is no correlation for the events outside the boundaries. The correlation coefficient between peak flux and angular separation is -0.51. We find that most of strong proton events occur when their angular separations are closer to zero, supporting that most of the proton fluxes are generated near the CME noses rather than their flanks.

• Progress in Superconductivity
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• v.6 no.1
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• pp.32-36
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• 2004

To investigate the influence of strip width and inter-strip separation on the ac loss, arrays of parallel strips with different widths and separations were prepared. Studies on the hysteresis-loss characteristics of multifilamentary YBCO films were performed. The local magnetic field due to magnetization currents is measured by a scanning Hall probe microscope. Based on these results a conceptual design for a low loss YBCO coated conductor is suggested.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.578-582
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• 2000

When the motion of vibrating structure is restrained due to the adjacent objects, the frequencies and the mode shapes of the structure change and its vibration characteristics becomes unpredictable, in general. Although the importance of the study on this type of vibration model increases in many engineering areas, most studies conducted so far are limited to the theoretical study on dynamic responses of the structure with the separation plate, including some experimental works. In the paper, both numerical analyses and experiments are conducted to study the chaotic vibration characteristics and the dynamic response of a fixed-free beam which has restrained motion at the free end by the separation plates. Results are presented for various magnetic forces and gaps between stops.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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• pp.100-103
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• 2003

The magnetoresistance (MR) of $La_{1-\chi}S_{\chi}CoO_{3-\delta}$ films prepared by pulsed-laser deposition were investigated in order to clarify the magnetotransport properties around the metal-insulator transition. For the films in the metallic state ($\chi$ > 0.25), the MR(T) manifests a small peak at the Curie temperature due to the spin-disorder scattering. The transition of the film into the insulating state ($\chi\;\leq$ 0.25) is accompanied by an essential growth of the MR and results in a significant increase in the MR(T) with decreasing temperature, due to a phase separation into the ferromagnetic-metal clusters and the insulating matrix.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.07a
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• pp.47-50
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• 2003

Carbon-silica membranes were Prepared by Pyrolyzing polyimide/silica composite obtained from ill-situ polymerization of alkoxy silanes via sol-gel reaction. In this study, effects of silica content and silica network in polyimide matrix were focused on the gas permeation and separation properties of the final carbon-silica membrane. The membranes prepared were characterized with a field emission scanning electron microscopy (FE-SEM), a solid state $^{29}$ Si nuclear magnetic resonance spectroscopy ($^{29}$ Si-NMR), an electron spectroscopy for chemical analysis (ESCA), a thermogravimetric analysis (TGA) and gas permeation tests.