• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.55-58
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• 2007

To improve the conventional optical chromatography, the continuous particle separator, the cross-type optical chromatography, is fabricated using micro-channel and fiber optics. A laser beam irradiates into the liquid solution containing particles in the perpendicular to the liquid flow direction. The different sized polystyrene latex micro-spheres, $2.0\;{\mu}m\;{\pm}\;0.02\;{\mu}m$, $5.0\;{\mu}m\;{\pm}\;0.05\;{\mu}m$, and $10.0\;{\mu}m\;{\pm}\;0.09\;{\mu}m$ diameter, are separated in cross-type optical chromatography. The separated particles are delivered to down stream in the micro-channel maintaining the retention distance continuously. The measured retention distances for different sized particles well agree with theoretical predictions.

• Journal of the Korean Society of Visualization
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• v.20 no.3
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• pp.67-73
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• 2022

Underwater environmental pollution caused by microplastic particles is considered to be one of the most serious problems in many oceans and countries nearby. Previous academic studies or field technologies tried to remove the micro-sized particles are often energy-consuming and costly, so it is hard to be employed for the actual uses. In this study, the mechanism of removal of micro-sized polyethylene spheres (size in order of 100㎛) using a rising bubble is experimentally investigated. It is found that the particles are either affected by bubble wake, thus translocated close to the water surface, or pushed far away by the surrounding fluid flow, depending on their initial position relative to the bubble. By scrutinizing the visualized behaviors of bubble-particle interaction, we draw the governing parameter, i.e., the polar angle between the particle and the bubble, to determine the effective capturing of the particles with a rising bubble.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.1-5
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• 2022

We presented a micro hemi-sphere structure flexible film to improve the external quantum efficiency (EQE) in OLEDs. The micro hemi-sphere flexible film was fabricated with breath figure (BF) method and replica process. At 45 mg/mL of concentration, the size of the hemi-spheres was approximately 6.2 ㎛ were obtained which are the most circular shape. So, it was possible to yield the best performance with an improvement of 33 % in the EQE and the widest viewing angle ranging from 0° to 70°. As a result, the hemi-sphere film's size and distribution seem to play important roles in enhancing the EQE in OLEDs. Furthermore, the flexible hemi-sphere film based on polymeric materials could offer an effective, large-scale, mass-produced product and a simple process and approach to achieve high efficiency in flexible OLEDs.

• Journal of Sensor Science and Technology
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• v.29 no.3
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• pp.156-161
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• 2020

In this study, hierarchical mesoporous CuO spheres, ZnO flowers, and heterojunction CuO/ZnO nanostructures were fabricated via a facile hydrothermal method. The as-prepared materials were characterized in detail using various analytical methods such as powder X-ray diffraction, micro Raman spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, and transmission electron microscopy. The obtained results are consistent with each other. The H₂S-sensing characteristics of the sensors fabricated based on the CuO spheres, ZnO flowers, and CuO/ZnO heterojunction were investigated at different temperatures and gas concentrations. The sensor based on ZnO flowers showed a maximum response of ~141 at 225 ℃. The sensor based on CuO spheres exhibited a maximum response of 218 at 175 ℃, whereas the sensor based on the CuO/ZnO nano-heterostructure composite showed a maximum response of 344 at 150 ℃. The detection limit (DL) of the sensor based on the CuO/ZnO heterojunction was ~120 ppb at 150 ℃. The CuO/ZnO sensor showed the maximum response to H₂S compared with other interfering gases such as ethanol, methanol, and CO, indicating its high selectivity.

• Carbon letters
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• v.10 no.3
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• pp.181-189
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• 2009

Activated carbon spheres (ACS) were prepared at different heating rates by carbonization of the resole-type phenolic beads (PB) at $950^{\circ}C$ in $N_2$ atmosphere followed by activation of the resultant char at different temperatures for 5 h in $CO_2$ atmosphere. Influence of heating rate on porosity and temperature on carbon structure and porosity of ACS were investigated. Effect of heating rate and temperature on porosity of ACS was also studied from adsorption isotherms of nitrogen at 77 K using BET method. The results revealed that ACS have exhibited a BET surface area and pore volume greater than $2260\;m^2/g$ and $1.63\;cm^3/g$ respectively. The structural characteristics variation of ACS with different temperature was studied using Raman spectroscopy. The results exhibited that amount of disorganized carbon affects both the pore structure and adsorption properties of ACS. ACS were also evaluated for structural information using Fourier Transform Infrared (FTIR) Spectroscopy. ACS were evaluated for chemical composition using CHNS analysis. The ACS prepared different temperatures became more carbonaceous material compared to carbonized material. ACS have possessed well-developed pores structure which were verified by Scanning Electron Microscopy (SEM). SEM micrographs also exhibited that ACS have possessed well-developed micro- and meso-pores structure and the pore size of ACS increased with increasing activation temperature.

• Archives of Pharmacal Research
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• v.26 no.6
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• pp.504-510
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• 2003

The aim of this study is to prepare biodegradable microspheres without the use of surfactants or emulsifiers for a novel sustained delivery carriers of protein drugs. A poly($\varepsilon$-caprolactone)/poly(ethylene glycol)/poly($\varepsilon$-caprolactone) (CEC) triblock copolymer was synthesized by the ring-opening of $\varepsilon$-caprolactone with dihydroxy poly (ethylene glycol) to prepare surfactant-free microspheres. When dichloromethane (DCM) or ethyl formate (EF) was used as a solvent, the formation of microspheres did not occur. Although the microspheres could be formed prior to lyophilization under certain conditions, the morphology of microspheres was not maintained during the filtration and lyophilization process. Surfactant-free microspheres were only formed when ethyl acetate (EA) was used as the organic solvent and showed good spherical micro-spheres although the surfaces appeared irregular. The content of the protein in the micro-sphere was lower than expected, probably because of the presence of water channels and pores. The protein release kinetics showed a burst release until 2 days and after that sustained release pattern was showed. Therefore, these observations indicated that the formation of microsphere without the use of surfactant is feasible, and, this the improved process, the protein is readily incorporated in the microsphere.

• Macromolecular Research
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• v.12 no.6
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• pp.564-572
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• 2004

Modem applications could benefit from multifunctional materials having anisotropic optical, electrical, thermal, or mechanical properties, especially when coupled with locally controlled distribution of the directional response. Such materials are difficult to engineer by conventional methods, but the electric field-aided technology presented herein is able to locally tailor electroactive composites. Applying an electric field to a polymer in its liquid state allows the orientation of chain- or fiber-like inclusions or phases from what was originally an isotropic material. Such composites can be formed from liquid solutions, melts, or mixtures of pre-polymers and cross-linking agents. Upon curing, a 'created composite' results; it consists of these 'pseudofibers' embedded in a matrix. One can also create oriented composites from embedded spheres, flakes, or fiber-like shapes in a liquid plastic. Orientation of the externally applied electric field defines the orientation of the field-aided self-assembled composites. The strength and duration of exposure of the electric field control the degree of anisotropy created. Results of electromechanical testing of these modified materials, which are relevant to sensing and actuation applications, are presented. The materials' micro/nanostructures were analyzed using microscopy and X-ray diffraction techniques.

• Tribology and Lubricants
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• v.12 no.4
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• pp.52-59
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• 1996

The results of the electrical contact conductivity of multi-contact spots accounting the surface roughness and the non-conductive films of different origins such as air, water, cutting oil, and machining oil are presented. The array of metal spheres compressed between two flat plates has been used for simulation of the contact behavior of multiple contact of solids, under normal loading. Measurement of electrical contact resistance has been made using the equipment providing the adequate accuracy in the range of micro Ohms. The data on electrical contact resistance have been compared with theoretical predictions using the multiple contact model of constriction resistance. The effect of single spot number and array on conductivity of contact has been evaluated. The results of the experiments show that the contact resistance are closely related to the number of loading cycles, form of surface roughness, and presence of non-conductive films that reduce the size of the real electrical contact spots.

• Journal of Biomedical Engineering Research
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• v.14 no.3
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• pp.209-220
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• 1993

Microspheres are expected to be applied to biomedical areas such as solid-phase immunoassays, drug delivery systems, Immunomagnetic cell separation. To synthesize micro-spheres for biomedical application, "two stage shot growth method" was developed. The uniformity ratio or synthesized microspheres was always smatter than 1.05. And the surface charge density (or the number of ionizable functional groups) of the microspheres synthesized by "two stage shot growth method" was 6-13 times higher than thats of the ml crospheres synthesized by conventional seeded batch copolymerization. As a previous step for biomedical application, adsorption experiments of bovine albumin on microspheres were carried out under various conditions. The maximum adsorbed amount was obtained in the neighborhood of pH 4.5. Isoelectric point of bovine albumin Is pH 5.0, so experimental result shows that it shifted to acid area. The adsorption Isotherm was obtained, the plateau region was always reached at 2.Og/L (bulk concentration of bovine albumin ) . The effect of the kind and the amount of surface functional group was also examined.p was also examined.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.91-110
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• 2004

A comprehensive three-dimensional nano-particle tracking technique in micro- and nano-scale spatial resolution using the Total Internal Reflection Fluorescence Microscope (TIRFM) is discussed. Evanescent waves from the total internal reflection of a 488nm argon-ion laser are used to measure the hindered Brownian diffusion within few hundred nanometers of a glass-water interface. 200-nm fluorescence-coated polystyrene spheres are used as tracers to achieve three-dimensional tracking within the near-wall penetration depth. A novel ratiometric imaging technique coupled with a neural network model is used to tag and track the tracer particles. This technique allows for the determination of the relative depth wise locations of the particles. This analysis, to our knowledge is the first such three-dimensional ratiometric nano-particle tracking velocimetry technique to be applied for measuring Brownian diffusion close to the wall.