• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.551-552
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• 2006

The miniature fuel cells have emerged as a promising power source for applications such as cellular phones, small digital devices, and autonomous sensors to embedded monitors or to micro-electro mechanical system (MEMS) devices. Several chemicals run candidate at a fuel in those systems, such as hydrogen. methanol, ethanol, acetic acid, and di-methyl ether (DME). Among them, hydrogen shows most efficient fuel performance. However, there are some difficulties in practical application for portable power sources. Therefore, more recently, there have been many efforts for development of micro-reformer to operate highly efficient micro fuel cells with liquid fuels such as methanol, ethanol, and DME In our experiments, we have integrated a micro-fuel processor system using low temperature co-fired ceramics (LTCC) materials. Our integrated micro-fuel processor system is containing embedded heaters, cavities, and 3D structures of micro- channels within LTCC layers for embedding catalysts (cf. Figs. 1 and 2). In the micro-channels of LTCC, we have loaded $CuO/ZnO/Al_2O_3$ catalysts using several different coating methods such as powder packing or spraying, dipping, and washing of catalyst slurry.

• Transactions on Electrical and Electronic Materials
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• v.11 no.4
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• pp.174-177
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• 2010

We have developed an environment-friendly etching process, an alternative to the dichromic acid etching process, as a pretreatment of acrylonitrile-butadiene-styrene (ABS) plastic for electroless plating. In order to plate ABS plastic in an electroless way, there should be fine holes on the surface of the ABS plastic to enhance mechanically the adhesion strength between the plastic surface and the plate. To make these holes, the surface was coated uniformly with dispersed chemical foaming agents in a mixture of environmentally friendly dispersant and solvent by the methods of dipping or direct application. The solvent seeps into just below the surface and distributes the chemical foaming agents uniformly beneath the surface. After drying off the surface, the surface was heated at a temperature well below the glass transition temperature of ABS plastic. By pyrolysis, the chemical foaming agents made fine holes on the surface. In order to discover optimum conditions for the formation of fine holes, the mixing ratio of the solvent, the dispersant and the chemical foaming agent were controlled. After the etching process, the surface was plated with nickel. We tested the adhesion strength between the ABS plastic and nickel plate by the cross-cutting method. The surface morphologies of the ABS plastic before and after the etching process were observed by means of a scanning electron microscope.

• Journal of Pharmaceutical Investigation
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• v.37 no.1
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• pp.51-55
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• 2007

Solid lipid nanoparticles (SLNs) have been regarded to behave similar to the vegetable oil emulsions because emulsions of lipid melts are formed before lipid droplets being solidified to turn into SLNs. Compared to lipid emulsion, however, it has been more difficult to obtain stable SLNs and needs more extensive considerations on stabilizer and manufacturing process. In the present study, we tried to prepare phosphatidylcholine-based trymyristin (TM) SLNs using high pressure homogenization method and optimize the manufacturing variables such as homogenization pressure, number of homogenization cycles, cooling temperature, co-stabilizer and freeze-drying with cryoprotectants. Nano-sized TM particles could be Prepared using egg Phosphatidylcholine and pegylated phospholipids ($PEG_{2000}$PE) as stabilizers. Based on the optimization study, the dispersion was manufactured by homogenization under the pressure of 100 MPa for more than 5 cycles, and solidifying the intermediately formed lipid melt droplets by dipping in liquid nitrogen followed by thawing at room temperature. In addition, TM SLNs could be freeze-dried and then redispersed easily without significant particle size changes after freeze drying with 10% and 12.5% sucrose or trehalose. The TM SLNs established in this study can be used as delivery system for drugs and cosmetics.

• Horticultural Science & Technology
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• v.29 no.1
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• pp.48-52
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• 2011

This study was conducted to establish the efficient screening system for resistant radish to Fusarium oxysporum f. sp. raphani. Five radish cultivars ('Myoungsan', 'Chungdu', 'Jangsaeng', 'Hannongyeorm', and 'Chungsukungjung') showing different degree of resistance to the fungus were selected. And the development of Fusarium wilt of the cultivars according to several conditions such as root wounding, dipping period of roots in spore suspension, inoculum concentration, and incubation temperature to develop the disease was tested. In distinguishing the resistance degree of the radish cultivars to the disease, non-cut roots were more effective than cut roots. And occurrence of Fusarium wilt of the radish plants increased in the proportion to increase of root-dipping period and spore concentration of the fungus. Thus, optimum conditions to differentiate susceptible and resistant cultivars to the disease were root-dipping period of 0.5 hour and spore concentration of $1{\times}10^7\;conidia{\cdot}mL^{-1}$. Disease severity of Fusarium wilt on the cultivars was changed with incubation temperature and the radish seedlings incubated at $25^{\circ}C$ represented the most difference of resistance and susceptibility to Fusarium wilt. From the above results, we suggest that the efficient screening method for resistant radish to Fusarium oxysporum f. sp. raphani would be to dip non-cut roots of fourteen-day-old radish seedlings in spore suspension of $1{\times}10^7\;conidia{\cdot}mL^{-1}$ for 0.5 hour and to transplant the inoculated plants to plastic pots with fertilized soil, and then to incubate the radish plants at a temperature of $25^{\circ}C$ for development of Fusarium wilt.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.35-41
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• 2013

Properties of $NaBH_4$ hydrolysis reaction using Co-P-B/FeCrAlloy catalyst and the catalyst durability were studied. Co-P-B/FeCrAlloy catalyst showed low activation energy such as 25.2 kJ/mol in 5 wt% $NaBH_4$ solution, which was similar that of noble metal catalyst. The activation energy increased as the $NaBH_4$ concentration increased. Formation of gel at high concentration of $NaBH_4$ seriously affected hydrogen evolution rate and the catalyst durability. The catalyst loss decreased as reaction temperature increased due to lower gel formation when the concentration of $NaBH_4$ was over 20 wt%. Considering hydrogen generation rate and durability of catalyst, the catalyst supported with FeCrAlloy heat-treated at $1,000^{\circ}C$ without ultra vibration during dipping and calcination after catalyst dipping was best catalyst. To use catalyst more than three times in 25 wt% $NaBH_4$ solution, it should be reacted at higher temperature than $60^{\circ}C$.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.688-697
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• 2014

In this study, electrode bonding technology needed for high density of rechargeable battery is studied, which is recently researched for electric vehicle, the small leisure vessel. For the alternative overcoming the limit of stacking amount able to be stacked by conventional ultrasonic welding, the low temperature bonding method, eligible for minimum of degeneration of chemical activator on the electrode surface which is generated by thermal effect as well as the increase of conductivity and tension strength caused by electrode bonding using filler metal, not using conventional direct heating on the electrode material method, is studied. Specifically to say, recently used more generally the ultrasonic welding and spot welding method are not usable for satisfying stable electric conductivity and bonding strength when much electrode is stacking bonded. If the electrical power is unreasonably increased for the welding, due to the effect of welding temperature, deformation of electrode and activating material degeneration are caused, and after the last packaging, decline of electrical output and generating heat cause to reduce stability of battery. Therefore, in this study, induction heating system bonding method using high frequency heating and differentiated electrode method using filler metal pre-treatment of hot dipping are introduced.

• Korean Journal of Food Science and Technology
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• v.41 no.3
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• pp.245-250
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• 2009

This study examined the optimization of alcohol extraction conditions for maximizing the total polyphenols derived from apple pomace, by response surface methodology (RSM). The effects of four independent variables, including $X_1$ (ratio of solvent to sample content), $X_2$ (dipping time), $X_3$ (extraction time), and $X_4$(extraction temperature), were investigated at five levels using central composite design (CCD). $Y_1$ (yield) and $Y_2$ (total polyphenols) were chosen as dependent variables. The coefficients of determination, $R^2$, were greater than 0.900 (0.9042 and 0.9555). The results showed that the model fit was very significant (p<0.001). The optimum extraction conditions were as follows: 13.00 mL/g for the ratio of solvent to sample content, 89.02 min for dipping time, 180 min for extraction time, and $70^{\circ}C$ for extraction temperature. At these conditions, the predicted total polyphenol content was 29.68 mg catechin equiv./g.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.461-466
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• 1999

The humidity sensor containing ammonium salt was prepared from the copolymer of 2-methacryloxyethyl dimethyl 2-hydroxyethyl ammonium bromide (MDHAB)/MMA/DAEMA = 6/3/1. The humid membrane was fabricated on the gold/alumina electrode by dipping. The impedances were $298k{\Omega},\;11k{\Omega}$, and $2.3k{\Omega}$ at 40%RH, 70%RH and 90%RH, respectively, at $5^{\circ}C$ and the humidity-sensitive characteristics were suitable for low temperature humidity sensor. The temperature-dependent coefficient between $5^{\circ}C$ and $20^{\circ}C$ was found to be $-0.80%RH/^{\circ}C$ and the hysteresis falled in the ${\pm}2%RH$ range. The response time was found to be 38 sec for the relative humidity ranging from 34%RH to 88%RH at $20^{\circ}C$. The reliabilities such as temperature cycle, humidity cycle, high temperature and humidity resistance, electrical load stability, stability of long-term storage and water durability were measured and evaluated for the application as a humidity sensor.

• Horticultural Science & Technology
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• v.16 no.3
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• pp.355-357
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• 1998

Various temperatures and plant growth regulators were assessed to investigate the nature of the dormancy and bud sprouting of stem cutting of Hibiscus syriacus 'Honghwarang'. The bud sprouting was promoted as temperature increased. Under $30^{\circ}C$ condition, stem cuttings began sprouting at 4days after cutting and showed 100% sprouting at 6 days after cutting. With GA or BA treatment, the cuttings started sprouting at 6 days after cuttings under $25^{\circ}C$ condition and reached 65% sprouting, which was not different from the results without hormone treatments. However, ABA dipping under below $25^{\circ}C$ condition resulted in low sprouting, whereas under over $25^{\circ}C$ condition they started sprouting at 6 days after cutting and reached 93% at 12 days after cutting, which indicated that ABA is not effective on inhibition of sprouting under high temperature condition.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.111-120
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• 2000

Recently, metal oxide films such as MgO or ZrO$_2$ have been studied as buffer layers to fabricate the superconductor with preferred orientation and as diffusion barriers to prevent the reaction between superconductor and metal substrate. In this research, we focused fabrication and characterization of MgO and ZrO$_2$ films on textured metal substrates. We fabricated MgO and ZrO$_2$ films on the Ni metal sheets by sol-gel dipping method. The microstrcures of the films were investigated by SEM and AES analyses. The films were coated with different cycles and dryed at 400$^{\circ}$C and 500$^{\circ}$C . The final films were heat-treated at 700$^{\circ}$C, 800$^{\circ}$C, and 1000$^{\circ}$C, in air atmosphere. We investigated the alignment of MgO and ZrO$_2$ films on Ni metal sheets by XRD and pole figure. The grain growth of metal oxide films was improved by the increase of the drying temperature and annealing temperature. The grain growth was increased with the annealing temperature. The alignment of metal oxide films depended on the thickness.