• Journal of the Society of Cosmetic Scientists of Korea
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• v.46 no.2
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• pp.133-145
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• 2020

This study utilized nano-liposomes for the purpose of stabilizing and increasing the solubility of biotin, a water-soluble active material with low solubility. The particle size, zeta potential, and polydispersity index were confirmed with a nano zetasizer. It was possible to manufacture nano liposomes at 100 to 250 nm of particle size and -80 to -30 mV of zeta potential. Dialysis membrane method (DMM) was used to measure the capsulation efficiency of biotin in biotin nano-liposomes, and results showed that pH increased biotin nano-liposomes had higher capsulation efficiency than normal biotin nano-liposome. Through this experiment, it was confirmed that the pH has a great influence on the stability of biotin nano-liposomes. In vitro franz diffusion cell method was used to measure in vitro skin absorption rate of biotin nano-liposomes. The shape of the formulation and biotin solubility in nano-liposome was observed by cryogenic transmission electron microscopy (cryo-TEM). Through this study, we confirmed that biotin, which is introduced as closely related to hair health, can be incorporated into a nano-liposome drug delivery system, to make biotin nano-liposome with improved solubility and precipitation problems.

• Journal of the Korean Chemical Society
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• v.60 no.3
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• pp.187-193
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• 2016

In this study, preparation of positively and negatively charged carbon nanotube (CNT)-collagen (CG) hydrogels with pH sensitive characteristic was reported. The positive and negative characteristics of the prepared hydrogels were created by introduction of positively functionalized CNT-NH₂ and negatively functionalized CNT-COOH, respectively, into the collagen hydrogel. The surface charge of CNTs (CNT-NH₂ and CNT-COOH), CG and CNTs/CG hydrogels was measured by Zetasizer. The swelling ratios of CNT-NH₂/CG and CNT-COOH/CG hydrogels in aqueous solution were checked by measuring of weight changes of the hydrogels in the range of pH 2~10. In detail, the positively charged CNT-NH₂/CG hydrogel swelled up to 5% at pH 4 in comparison to the weight at pH 7, while the negatively charged CNT-COOH/CG hydrogel swelled up to 10% at pH 10. The prepared CNT-NH₂/CG and CNT-COOH/CG hydrogels will be very useful as pH sensitive oral drug-delivering systems for gastrointestine (pH ~2) and small intestine (pH ~9), respectively.

• Clean Technology
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• v.17 no.4
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• pp.389-394
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• 2011

A compact adsorption-based process for removal of carbon dioxide and nitrogen from natural gas has been discussed. Among the adsorption-based processes, especially, the pressure swing adsorption (PSA) process has been a suitable unit operation for the purification and separation of gas because of low operation energy and cost. A step cycle is made up of pressurization, feed, equalization, blowdown and rinse. In this work, the PSA process is composed of zeolite 13X and carbon molecular sieve (CMS) for removal of carbon dioxide and nitrogen from mixed gas containing $CH_4/CO_2/N_2$ (75:21:4 vol%). A CMS selectively removes carbon dioxide and a zeolite 13X separates nitrogen from methane. CMS is investigated experimentally due to the high throughput of the faster diffusing component ($CO_2$). The gas composition of top, bottom and feed tank was measured with the gas chromatography (GC) using TCD detector, helium as carrier gas and packed column for analysis of methane, carbon dioxide, and nitrogen.

• Strategy21
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• s.46
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• pp.159-204
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• 2020

This study is written to bring the proposal forward for the direction of south korean naval force. The political situation and the circumstance of the world, especially in the area of Pacific Ocean, are changing very rapidly. North Korea has been always the conventional existing intimidator for South Korea since the 6·25-War. Additionally, the strengthening movements of the national defense, which is easily noticed from China and Russia, is also an other part of intimidating countries against South Korea. Those three mentioned countries are continually developing the asymmetrical warfare systems, for example a strategic nuclear weapon. Since the Obama Administration, the Asia-Pacific Rebalancing-Strategy has been changed as an East Asian foreign policy. Nowadays, Trump Administration renamed the 'United States Pacific-Command' to 'United States Indo-Pacific Command'. The purpose of this is not only letting India to participate in american alliance, but also reducing an economic burden, which is often mentioned in USA. West Germany was located in the very similar geopolitical position during the Cold War just like South Korea these days. And that's why the strategy of West German Navy is worthy of notice for south korean naval force to decide its suitable strategy. Most of all, the two most important things to refer to this study are the plan to expand naval air force and the realistic political stand for us to take it. In conclusion, I laid an emphasis on maintenance of 'green-water-navy'. instead of selecting the strategy as a 'blue-water-navy'. The reason I would like to say, is that south korean navy is not available to hold the unnecessary war potential, just like Aircraft-Carrier. However, this is not meaning to let the expansion of naval force carelessly. We must search the best solution in order to maintain the firm peace within the situation. To fulfill this concept, it is mostly very important to maintain the stream of laying down a keel of destroyers, submarines and air-defense-missile, as well as the hight-tech software system, taking a survey of 4th industrial revolution. Research and development for the best solution of future aircraft by south korean navy is likewise necessary. Besides, we must also set the international diplomatic flexibly. As well as maintaining the relationship with US Forces, it is also very important to improve the relationship with other potential allied nation.

• Restorative Dentistry and Endodontics
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• v.28 no.4
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• pp.334-340
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• 2003

This study was performed to evaluate the actual temperature rise on the surface of Buchanan plugger using thermocouple. The heat carrier system 'System B Heatsource'(Model 1005, Analytic Technologies, Redmond, WA, USA) and the Buchanan pluggers of F, FM, M and ML sizes are used for this study. The temperature was set to 200^{\circ}C on digital display and the power level on it was set to 10. Five thermocouples were placed in direct contact with the surface of each size of Buchanan's pluggers at 1 mm increments from the tip to the 4 mm length of shank. The heat control spring was touched for 5 seconds. and the temperature rise on the surface of the pluggers were measured at 1 sec intervals for more than 5 seconds with an accuracy of 0.01 using Data Logger. The data were statistically analyzed by one-way ANOVA. The results were as follows. 1. The position at which the temperature peaked was approximately at 1~2 mm far from the tip of Buchanan plugger (p<0.01). 2. The peak temperature was $215.25{\pm}2.28^{\circ}C$ in F plugger. $185.94{\pm}2.19^{\circ}C$ in FM plugger, $169.51{\pm}9.12^{\circ}C$ in M plugger, and 160.79{\pm}1.27^{\circ}C in ML plugger and the peak temperature was highest in F plugger and followed by. in descending order. FM plugger. M plugger. ML plugger showed the lowest peak temperature (p<0.01). 3. The temperature on the plugger was decreased with the increase of touching time. This results suggest that the actual temperature on the surface of the pluggers does not correlate well with the temperature set on digital display. Heat concentrates around the tip. The larger plugger reveals lower temperature rise relatively.

• Clean Technology
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• v.21 no.4
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• pp.224-228
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• 2015

Phospholipase D (PLD) was immobilized on a submicro-porous membrane through covalent immobilization. The immobilization was conducted on the porous membrane surface with the treatment of polyethyleneimine, glutaraldehyde, and the anhydrase, in sequence. The immobilization was confirmed using X-ray photon spectrometer. The pH values of phosphatidylcholine (PC) dispersion solution with buffer were monitored with respect to time to calculate the catalytic activities of PC for free and immobilized PLD. The catalytic rate constant values for free PLD, immobilized PLD on polystyrene nanoparticles, and immobilized PLD on a porous cellulose acetate membrane were 0.75, 0.64, and 0.52 s^-1, respectively. Reusability was studied up to 10 cycles of PC hydrolysis. The activity for the PLD immobilized on the membrane was kept to 95% after 10 cycles, and comparable to the PLD on the nanoparticles. The stabilities for heat and storage were also investigated for the three cases. The results suggested that the PLD immobilized on the membrane had the least loss rate of the activity compared to the others. From these studies, the porous membrane was feasible as a carrier for the PLD immobilization in the production of phosphatidic acid.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.591-598
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• 2002

In the ship structural design, the material cost of hull weight and the overall cost of construction processes should be minimized considering safety and reliability. In the past, minimum weight design has been mainly focused on reducing material cost and increasing dead weight reflect the interests of a ship's owner. But, in the past experience, the minimum weight design has been inevitably lead to increasing the construction cost. Therefore, it is necessary that the designer of ship structure should consider both structural weight and construction cost. In this point of view, multi-objective optimization technique is proposed to design the ship structure in this study. According to the proposed algorithm, the results of optimization were compared to the structural design of actual VLCC(Very Large Crude Oil Carrier). Objective functions were weight cost and construction cost of VLCC, and ES(Evolution Strategies), one of the stochastic search methods, was used as an optimization solver. For the scantlings of members and the estimations of objectives, classification rule was adopted for the longitudinal members, and the direct calculation method, GSDM(Generalized Slope Deflection Method), lot the transverse members. To choose the most economical design point among the results of Pareto optimal set, RFR(Required Freight Rate) was evaluated for each Pareto point, and compared to actual ship.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.35-40
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• 2013

In this study, the influence on the surface passivation properties of crystalline silicon according to silicon wafer thickness, and the correlation with a-Si:H/c-Si heterojunction solar cell performances were investigated. The wafers passivated by p(n)-doped a-Si:H layers show poor passivation properties because of the doping elements, such as boron(B) and phosphorous(P), which result in a low minority carrier lifetime (MCLT). A decrease in open circuit voltage ($V_{oc}$) was observed when the wafer thickness was thinned from $170{\mu}m$ to $50{\mu}m$. On the other hand, wafers incorporating intrinsic (i) a-Si:H as a passivation layer showed high quality passivation of a-Si:H/c-Si. The implied $V_{oc}$ of the ITO/p a-Si:H/i a-Si:H/n c-Si wafer/i a-Si:H/n a-Si:H/ITO stacked layers was 0.715 V for $50{\mu}m$ c-Si substrate, and 0.704 V for $170{\mu}m$ c-Si. The $V_{oc}$ in the heterojunction solar cells increased with decreases in the substrate thickness. The high quality passivation property on the c-Si led to an increasing of $V_{oc}$ in the thinner wafer. Short circuit current decreased as the substrate became thinner because of the low optical absorption for long wavelength light. In this paper, we show that high quality passivation of c-Si plays a role in heterojunction solar cells and is important in the development of thinner wafer technology.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.45-50
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• 2006

Oxygen-deficient anatase and rutile titanium dioxide $(TiO_{2-\delta})$ thin films were prepared by a sol-gel method and their structural, electronic, and magnetic properties were investigated. Both anatase and rutile $TiO_{2-\delta}:Fe$ Fe films exhibited ferromagnetism at room temperature for a limited range of Fe doping. For the same amount of Fe doping, the anatase sample exhibited a higher magnetic moment than the rutile one. Result of conversion electron Mossbauer spectroscopy measurements indicates that $Fe^{3+}$ ions substituting the octahedral $Ti^{4+}$ sites mainly contribute to the room-temperature ferromagnetism. Some of the anatase $TiO_{2-\delta}:Fe$ films exhibited p-type character but the observed feromagnetism turns out to be independent of the hole concentration. The room-temperature ferromagnetism can be explained in terms of a direct ferromagnetic coupling between two neighboring $Fe^{3+}$ ions via an electron trapped in oxygen vacancy in $TiO_{2-\delta}:Fe$.

• Food Science of Animal Resources
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• v.25 no.1
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• pp.92-97
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• 2005

This study was carried out to determine the storage, cryotolerance, heat and drying resistance, when Lactobacillus acidophilus CT 01 isolated from preweaned piglet feces growing at suboptimal temperature. L. acidophilus CT 01 suboptimal temperature incubated for 48 hours had the slowest growth rate at 22℃ but the highest viable cell number after 36 hours at 22℃, with 1.3×10/sup 9/ CFU/mL. In case of 4 and 20℃ storage, the suboptimal temperature incubated groups had a viability higher than the control (p<0.01). The cryotolerance of suboptimal temperature incubated L. acidophilus CT 01 was a higher than the control (p<0.01). When L. acidophilus CT 01 was heat treated at 60℃ for 15 minutes and 30 minutes, the suboptimal temperature incubated L. acidophilus CT 01 at 22℃ had a viability higher more than the control (p<0.01). L. acidophilus CT 01 incubated suboptimal temperature was inoculated by 30% to the carrier, and dried at 50℃ for 12 hours had the highest viability in the suboptimal temperature incubated L. acidophilus CT 01 at 28℃.