• Polymer(Korea)
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• v.28 no.5
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• pp.433-443
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• 2004

The membranes of the blends of chitosan and polycaprolactarn (PA6) were prepared in formic acid. FT-IR data revealed that hydrogen bonding between amide and hydroxyl groups of chitosan and PA6, respectively, was formed. Thermogravimetric analysis demonstrated that the blend samples contain water. DMA results showed that the dissipation of water in the samples significantly reduced the storage modulus (E'). The mechanical loss tangent (tan $\delta$) data of the blend samples showed the $\beta$d loss peak around $0^{\circ}C$. The blend samples were completely dried in a vacuum and then exposed to high moisture to absorb water which would cause, so called, w-bridges between the molecules. The E' data of these regained samples increased abnormally and additional loss peak appeared on the shoulder of the peak around $50^{\circ}C$. Under dry condition, the samples with a blend ratio of 40/60 for chitosan/PA6 displayed a better miscibility between two components.

• Applied Science and Convergence Technology
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• v.26 no.4
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• pp.70-73
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• 2017

The dielectric constant and loss of poling/non-poling was measured in the $Pb_{1-3x/2}La_x[(Mg_{1/3}Ta_{2/3})_{0.66}Zr_{0.34}]O_3$ samples. The addition of $La^{3+}$ to the $Pb_{1-3x/2}La_x[(Mg_{1/3}Ta_{2/3})_{0.66}Zr_{0.34}]O_3$ did not cause a large change in grain size. But the addition of $La^{3+}$ did show transition temperature, which shifted toward low temperature in the $Pb[(Mg_{1/3}Ta_{2/3})Zr]O_3$ systems. In addition, the dielectric and pyroelectric properties (${\varepsilon}{\sim}20000$, $p{\sim}0.03C/m^2K$) of this system using $La^{3+}$ have been greatly improved. Pyroelectrics $Pb_{0.97}La_{0.02}(Mg_{1/3}Ta_{2/3})_{0.66}Zr_{0.34}]O_3$ system was found to have a relatively high ferroelectric FOMs ($F_V{\sim}0.035m^2/C$, $F_D{\sim}0.52{\times}10^{-4}Pa^{-1/2}$) at room temperature. Spontaneous polarization showed a value of $0.27{\sim}0.35C/m^2$ in the composition added to $La^{3+}$. The piezoelectric constant ($d_{33}=350{\sim}490pC/N$) and electromechanical coupling factor ($k_P=0.25{\sim}0.35$) are obtained in $Pb_{1-3x/2}La_x[(Mg_{1/3}Ta_{2/3})_{0.66}Zr_{0.34}]O_3$ compositions with $La^{3+}$ dopant.

• Journal of the Korean institute of surface engineering
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• v.37 no.5
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• pp.249-252
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• 2004

Effects of HA and TiN coating on the electrochemical characteristics of Ti-6AI-4V alloys for bone plates were investigated using various test methods. Ti-6AI-4V alloys were fabricated by using a vacuum induction furnace and bone plates were made by laser cutting and polishing. HA was made of extracted tooth sintered and then tooth ash was used as HA coating target. The TiN and HA film coating on the surface were carried on using electron-beam physical vapor deposition (EB-PVD) method. The corrosion behaviors of the samples were examined through potentiodynamic method in 0.9% NaCI solutions at $36.5\pm$$1^{\circ}C$ and corrosion surface was observed using SEM and XPS. The surface roughness of TiN coated bone plates was lower than that of tooth ash coated plates. The structure of TiN coated layer showed the columnar structure and tooth ash coated layer showed equiaxed and anisotrophic structure. The corrosion potential of the TiN coated specimen is comparatively high. The active current density of TiN and tooth ash coated alloy showed the range of about $1.0xl0^{-5}$ $A\textrm{cm}^2$, whereas that of the non-coated alloy was$ 1.0xl0^{-4}$ $A\textrm{cm}^2$. The active current densities of HA and TiN coated bone plates were smaller than that of non-coated bone plates in 0.9% NaCl solution. The pitting potential of TiN and HA coated alloy is more drastically increased than that of the non-coated alloy. The pit number and pit size of TiN and HA coated alloy decreased in compared with those of non-coated alloy. For the coated samples, corrosion resistance increased in the order of TiN coated, tooth ash coated, and non-coated alloy.

• Journal of the Korean Institute of Gas
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• v.2 no.3
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• pp.60-69
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• 1998

Methane, the major constituent of natural gas, had been converted to higher hydrocarbons by microwave and radio-frequency plasma in vacuum condition. Methane had been activated to plasma by suppling high energy then converted to ethane, ethylene, acetylene. The direct conversion process of methane had produced few by-products and demanded low-energy. The plasma sources were microwave and radio-frequency. Two types of reactor had been used to activate methane. One is common single tubular-type reactor and the other is series coil-type reactor which used for the first time in this study. To produce more C2 products, methane had been converted by a plasma and catalyst. The results of this study could be used to study mechanism of plasma reaction of methane, design the plant-scale reactor.

• Food Engineering Progress
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• v.13 no.3
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• pp.216-220
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• 2009

The several functional properties of freeze-dried powder of Aloe vera gel was examined as influenced by pre-concentration degrees of the gel solution. As a pre-treatment prior to freeze drying, the gel solution was vacuum-concentrated by three levels (unit: g-water/g-solids) - high (H), 76; medium (M), 119; low (L), 159. In FT-IR spectra, the sample H showed the highest absorbance in the range of 1600-1550 $cm^{-1}$ and 1450-1400 $cm^{-1}$, which corresponded to level of the acetyl group in glucomannan. The sample H of freeze-dried powder was the highest in polysaccharide content, jack bean urease inhibition rate, and FAC (fat adsorption capacity). It could be inferred that the sample H had an effect on Helicobacter pylori inhibition and fat adsorption suppression according to urease inhibition rate and FAC, respectively.

• Special Issue of the Society of Naval Architects of Korea
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• 2015.09a
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• pp.50-55
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• 2015

Application of newly conceptualized Anti-Splash Devices designed for COT vent pipes were studied on a P/V valve located on the upper deck of an oil carrier vessel. Anti-Splash devices are used in the shipbuilding industry in order to avoid oil overflow and spray accidents caused by excess pressure and vacuum condition in the cargo oil tanks. These conditions are caused by the transverse and longitudinal sloshing forces that arise from ship motion during sea voyages. The main issue with existing Anti-Splash device model is flux at the outlet of the Anti-Splash Device, and so, new conceptual models for the Anti-Splash device were developed and compared to existing Anti-Splash device model using CFD analysis. Transient analysis was used to capture the flow and velocity of each model and a comparative analysis was performed between old and new-concept models. This data was used to determine the optimal design parameters in order to develop an optimized Anti-Splash Device. A Factory acceptance test was performed on the new-concept models in order to verify the performance and efficiency against their design requirements and other criterion. The final step performed was to apply the optimized Anti-Splash Device models for COT vent pipes to an actual vessel and verify performance through a seawater cargo operation during a sea voyage as per the ship owner's request. The patent for the aforementioned device was obtained by the Korean Intellectual property Office dated Dec. 18th,2014.

• Korean Journal of Optics and Photonics
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• v.1 no.1
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• pp.46-51
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• 1990

Laser plasma was generated by a 1GW iodine photodissociation laser ($\lambda$=1.315$\mu\textrm{m}$, E=12.7J) whose output beam was focused on a molybdenum target surface. The experiment was conducted in a vacuum chamber under 1D-sTorr and several tens of laser shooting were necessary for sufficient exposure for the PBS resist of 111m thickness. Aluminium was coated on the top of the resist by 0.1$\mu\textrm{m}$ thickness which acts as an X-ray filter to cut off the visible and the ultraviolet lights. A bio-specimen was put directly on the aluminium coated resist and located at a distance of 3 cm from the X-ray source. The replicas of a steel mesh, spider's web. and a red blood cell were obtained by this technique and were observed by Nomarski microscope and SEM. The limitation of its resolution is determined by the X-ray source size and Fresnel diffraction effect, and its theoretical prediction is well matched with the experimental results. In this experiment, a resolution better than 0.1$\mu\textrm{m}$ could be obtained. ained.

• Food Science and Preservation
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• v.15 no.5
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• pp.731-735
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• 2008

The coliform group, Salmonella typhimurium and Staphylococcus were analyzed for eliminating of microorganism spore which could be embeded in honey and eradication of studied for heat resistance of thermoacidophilic bacteria was studied for marketing of honey after producing honey drink. The method for analyzing of heat resistance thermoacidophilic bacteria was membrane-seperated cell culture with $0.45\;{\mu}m$ micro-filter and vacuum aspirator. The results of bacteria, coliform group, Salmonella typhimurium and Staphylococcus was negative, but normal method such as sterilization with electrolyzed water, normal micro-filter, high-temperature heating and microwave did not have effect on heat resistance thermoacidophilic bacteria. Also, absolute type micro-filter of $0.45\;{\mu}m$ and $0.8\;{\mu}m$ microfilteration showed higher effect on heat resistance thermoacidophilic bacteria than micro-filter of normal type, showing negative results at all treatments.

• Tribology and Lubricants
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• v.34 no.6
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• pp.241-246
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• 2018

This research addresses the improvement of tribo-systems, specifically regarding the reduction of friction and wear through tribo-coupling between tetrahedral amorphous carbon (ta-C) with different types of counterpart materials, namely bearing steel (SUJ2), tungsten carbide (WC), stainless steel (SUS304), and alumina ($Al_2O_3$). A second variable in this project is the utilization of different values of duct bias voltage in the deposition of the ta-C coating - 0, 5, 10, 15, and 20 V. The results of this research are expected to determine the optimum duct bias and best counter materials associated with ta-C to produce the lowest friction and wear. Results obtained reveal that the tribo-couple between the ta-C coating and SUJ2 balls produces the lowest friction coefficient and wear rate. In terms of duct bias changes, deposition using 5 V produces the most optimum tribological behavior with lowest friction and wear on the tribo-system. In contrast, the tribo-couple between ta-C with a WC ball causes penetration through the coating surface layer and hence high surface delamination. This study demonstrates that the most effective ta-C coating duct bias is 5 V associated with SUJ2 counter material to produce the lowest friction and wear.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.66-72
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• 2018

A numerical study was conducted to investigate the performance characteristics of a STED with various pressure ratios (PRs) and cone shapes. Due to momentum loss, the pressure in vacuum chamber increased with cone angle for a PR of 75. Also, the STED is started between PRs of 36 and 37 in the case of a cone angle of $15^{\circ}$ and a blockage ratio (BR) of 15%. The results for various PRs and cone shapes are presented, and the optimal cone shape is found to have a cone angle of between $5{\sim}20^{\circ}$ and a BR of between 15~40%.