• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.17-21
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• 2019

The redox flow battery (RFB) is a large-capacity energy storage equipment, and the vanadium redox flow cell is a typical RFB, but VRFB is expensive. Iron-chrome RFBs are economical because they use low-cost active materials, but their low performance is an urgent problem. One of the reasons for the low performance is the crossover of the active materials. In this study, the sulfonated Poly (ether ether ketone) (sPEEK) membrane, which is a hydrocarbon membrane, was used instead of the fluorine membrane to reduce the crossover of the active materials. The chromium ion permeability of the sPEEK membrane was $1.8{\times}10^{-6}cm^2/min$, which was about 1/33 of that of the Nafion membrane. Thus, it was shown that the use of the sPEEK membrane instead of the fluorine membrane could solve the high active material crossover problem. The activation energy of iron diffusion through the sPEEK membrane was 24.9 kJ/mol, which was about 66% of Nafion membrane. And that the e-PTFE support in the polymer membrane reduces the active material crossover through Iron-Chrome Redox Flow Battery (ICRFB).

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.183-187
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• 2007

The magnetron reactive ion etching (RIE) characteristics of polycrystalline (poly) 3C-SiC grown on $SiO_2$/Si substrate by APCVD were investigated. Poly 3C-SiC was etched by $CHF_3$ gas, which can form a polymer as a function of side wall protective layers, with additive $O_2$ and Ar gases. Especially, it was performed in magnetron RIE, which can etch SiC at lower ion energy than a commercial RIE system. Stable etching was achieved at 70 W and the poly 3C-SiC was undamaged. The etch rate could be controlled from $20\;{\AA}/min$ to $400\;{\AA}/min$ by the manipulation of gas flow rates, chamber pressure, RF power, and electrode gap. The best vertical structure was improved by the addition of 40 % $O_2$ and 16 % Ar with the $CHF_3$ reactive gas. Therefore, poly 3C-SiC etched by magnetron RIE can expect to be applied to M/NEMS applications.

• Journal of Pharmaceutical Investigation
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• v.34 no.6
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• pp.491-497
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• 2004

We investigated some important factors which affect the transdermal flux of ketoprofen, a nonsteroidal anti-inflammatory agent, as a first step to provide some basic knowledge for the development of a iontophoretic transdermal patch system. Factors such as current density, polarity, buffer (HEPES) and electrolyte concentration and pH were studied using hairless mouse skin. The effect of poly(L-lysin), which is known to affect the electro-osmotic flow through skin, on flux was also studied. Passive flux was about $20\;{\mu}g/cm^2hr$ at pH 4.0, but was negligible at pH 7.4 where all ketoprofen molecules dissolved are ionized (ketoprofen pKa=5.94). At pH 4.0, application of anodal current increased the flux further above the passive level, however anodal flux at pH 7.4 was much smaller than passive flux at pH 4.0. The application of cathodal current at pH 4.0 increased the average flux to $30-40\;{\mu}g/cm^2hr$, depending on the current density applied. At pH 7.4, cathodal flux was only about $5\;{\mu}g/cm^2hr$. Decrease in buffer and electrolyte concentration increased this cathodal flux about 10 fold. However decrease in HEPES buffer concentration 100 fold did not affect the flux. Anodal flux of acetaminophen was much larger than cathodal flux, indicating that electroosmotic flow can be playing an important role in the flux. Poly(L-lysin) increased the cathodal flux at pH 7.4. These results provide some important insights into the mechanism of transdermal flux of ketoprofen and the role of electroosmotic flow.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.268-271
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• 2008

In order to understand mixing characteristics of the APU combustor, sector combustor which size is 1/6 of the real combustor was manufactured. To see the inner side of combustor, Poly Carbonate material is used as a combustor riner. Turbo blower is used as a air supplying device and valves are used as controling the air flow. Maximum flow rate of the blower is 7 $m^3$/min and maximum inlet velocity is up to 100 m/s.

• Journal of Pharmaceutical Investigation
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• v.33 no.1
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• pp.15-19
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• 2003

The rheological behavior of poloxamer 407 solution as function of concentration and temperature was evaluated by rotational viscometer. The viscosity of poloxamer 407 solution was increased as the concentration of poloxamer 407 and temperature increased. At $4^{\circ}C$, poloxamer 407 solution showed the Newtonian flow characteristics regardless of concentration. Upon increasing temperature the poloxamer solution changed to the pseudoplastic flow pattern. And at gelation temperature, rheological profiles showed the abrupt increase in viscosity. Gelation temperature was decreased as the concentration of poloxamer 407 increased, while it increased as the concentration of poly(ethylene glycol) 4000 increased. Poly(ethylene glycol) might be expected to reduce the driving force for hydrophobic interaction resulting in slow gelation. From the viscoelastic properties of poloxamer gel system, we obtained the storage and loss modulus depending on the shear stress and frequency. And the sol-gel transition temperature was also obtained from the viscoelastic properties of poloxamer 407 gel.

• KSBB Journal
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• v.26 no.1
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• pp.69-77
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• 2011

In this study, poly (L-lactic acid) (PLLA) microparticles containing gemcitabine hydrochloride were prepared by a supercritical fluid process, called aerosol solvent extraction system (ASES), utilizing supercritical carbon dioxide as antisolvent. The influence of process parameters such as temperature, pressure, $CO_2$ and solution flow rate, solution concentration, and feed ratio of drug to polymer on the morphology and characteristics of the microparticles was studied in detail. The gemcitabine-loaded microparticles exhibited a spherical shape with a smooth surface. The entrapment efficiency of gemcitabine increased with increasing temperature, solution concentration and $CO_2$ flow rate and with decreasing drug/polymer feed ratio. The maximum drug loading obtained from the ASES process was found to be about 11%. The ASES-processed PLLA microparticles containing gemcitabine showed a relatively high initial burst due to the presence of surface pores on the microparticles and the poor affinity between drug and polymer.

• Korean Chemical Engineering Research
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• v.44 no.5
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• pp.513-519
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• 2006

We developed two kinds of the microchip for application to electrophoresis based on both glass and quartz employing the MEMS fabrications. The poly-Si layer deposited onto the bonding interface apart from channel regions can play a role as the optical slit cutting off the stray light in order to concentrate the UV ray, from which it is possible to improve the signal-to-noise (S/N) ratio of the detection on a chip. In the glass chip, the deposited poly-Si layer had an important function of the etch mask and provided the bonding surface properly enabling the anodic bonding. The glass wafer including more impurities than quartz one results in the higher surface roughness of the channel wall, which affects subsequently on the microflow behavior of the sample solutions. In order to solve this problem, we prepared here the mixed etchant consisting HF and $NH_4F$ solutions, by which the surface roughness was reduced. Both the shape and the dimension of each channel were observed, and the electroosmotic flow velocities were measured as 0.5 mm/s for quartz and 0.36 mm/s for glass channel by implementing the microchip electrophoresis. Applying the optical slit with poly-Si layer provides that the S/N ratio of the peak is increased as ca. 2 times for quartz chip and ca. 3 times for glass chip. The maximum UV absorbance is also enhanced with ca. 1.6 and 1.7 times, respectively.

• Journal of the Korean Chemical Society
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• v.17 no.1
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• pp.40-46
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• 1973

The afterpolymerization of nylon 6 was carried out in three different reaction conditions, nitrogen flow, sealing and evacuation. The viscosity and reduced weight of polymer were increased by increasing the reaction time and temperature, and viscosity of polymers at constant reaction temperature was decreased as the following order: nitrogen flow >sealing >evacuation. The activation energy of afterpolymerization was 10.5 kcal/mole.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.234-235
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• 2008

The surface flatness of heteroepitaxially grown 3C-SiC thin films is a key factor affecting electronic and mechanical device applications. This paper describes the surface flatness of poly(polycrystalline) 3C-SiC thin films according to Ar flow rates and the geometric structures of reaction tube, respectively. The poly 3C-SiC thin film was deposited by APCVD (Atmospheric pressure chemical vapor deposition) at $1200^{\circ}C$ using HMDS (Hexamethyildisilane : $Si_2(CH_3)_6)$ as single precursor, and 1~10 slm Ar as the main flow gas. According to the increase of main carrier gas, surface fringes and flatness are improved. It shows the distribution of thickness is formed uniformly.

• Journal of the Korean Chemical Society
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• v.39 no.8
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• pp.604-610
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• 1995

The interaction between 3,3'-dipropyl oxacarbocyanine and poly(styrenesulfonate) has been studied by means of absorption and fluorescence spectroscopic methods. The results was interpreted by stacking model. The kinetic studies of the interaction between 3,3'-dipropyl oxacarbocyanine and poly(styrenesulfonate) were carried out by the absorption and fluorescence spectroscopic stopped-flow methods. The observed relaxation effect in DPC-PSS system was described quantitatively by assuming two relaxation processes. The dependence of rate of reaction on the salt concentration of the solution was also studied. The results are consistent with the two-step mechanism.