• Journal of Institute of Control, Robotics and Systems
• /
• v.5 no.2
• /
• pp.237-247
• /
• 1999

Flight parameters of a light aircraft in normal category named ChangGong-91 we identified from flight tests. Modified Maximum Likelihood Estimation (MMLE) is used to produce aerodynamic coefficients, stability and control derivatives. A Flight Training Device (FTD) has been developed based on the identified flight parameters. Flat earth, rigid body, and standard atmosphere are assumed in the FTD model. Euler angles are adapted for rotational state variables to reduce computational load. Variations in flight Mach number and Reynolds number are assumed to be negligible. Body, stability and inertial axes allow 6 second-order linear differential equations for translational and rotational motions. The equations of motion are integrated with respect to time, resulting in good agreements with flight tests.

• Journal of the Korean Society for Precision Engineering
• /
• v.30 no.4
• /
• pp.409-413
• /
• 2013

A polypropylene film was ablated using a $CO_2$ laser, Ti-sapphire femtosecond laser, and UV nanosecond laser. For modified atmosphere packaging, polypropylene films were ablated by laser pulse with different pulse energies and measured on an optical microscope. Also, we observed the shelf life of a banana contained within packaging of a breathable zipper bag. As a result, we have demonstrated that the breathable film can efficiently extend the shelf life of respiring foods, particularly fresh fruits and vegetables. The development of breathable film laser microfabrication system will more useful for industrial applications.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.13 no.3_4
• /
• pp.97-102
• /
• 2007

A Korean seasoned meat product, seasoned bulgogi was developed in processing and packaging for improved convenience and extended shelf life. The optimal process conditions were found to consist of aging for $20{\sim}30$ hours at $5^{\circ}C$ and air heating for 20 minutes at $210^{\circ}C$ Aging of 24 hours could attain soft texture with little change in pH, color and total aerobic bacterial count. Appropriate drip level could be achieved at air heating of 20 minutes at $210^{\circ}C$, while the air heating at $180^{\circ}C$ could not give suitable level of texture. Modified atmosphere packaging of 60% $CO_2$ and 40% $N_2$ could preserve the product significantly better compared to control of air package and vacuumed package.

• Journal of Engineering Education Research
• /
• v.15 no.6
• /
• pp.34-42
• /
• 2012

Problem solving by homework assignment is a process of practicing what were discussed in classrooms and thus is considered as an essential part of learning procedure in engineering education. We introduced the concept of cooperative learning, Student Teams-Achievement Division(STAD), to improve the students' learning efficiency by in-class problem solving. The instructor explained fundamental concepts, and lecture materials were handed out to compensate for the time of in-class team activity. Brief tests were given after every chapter, and team-based additional credits were given for the improvement comparing the average of previous tests of each student. This attempt of modified STAD was evaluated to have brought about a significant improvement in students' academic achievement, in addition to activating classroom atmosphere.

• Food Science and Biotechnology
• /
• v.14 no.1
• /
• pp.82-88
• /
• 2005

Ethnic Korean onggi earthenwares were fabricated using different clay formulations and glazing treatments. Their permeability properties against oxygen, carbon dioxide, and moisture were measured at $20^{\circ}C$ and examined from the aspect of food preservation. Onggi walls consisted of micropores that offered higher gas and moisture permeation rates when compared with other food packaging materials. Earthenware walls were unique in having $CO_2/O_2$ permeability ratios of 0.60-1.00. Gas and moisture permeabilities were lower, with wall structure having lower porosity and surface glazing. Results revealed onggi jar packages of grape fruits could attain wide range of $O_2$ and $CO_2$ concentrations. Onggi containers present good opportunity to obtain optimum packaging conditions for respiring or ripening products, depending on commodity type.

• Journal of Astronomy and Space Sciences
• /
• v.9 no.1
• /
• pp.111-119
• /
• 1992

The IUE archival spectra of VV Cephei were collected to investigate the eclipse nature in the ultraviolet. The temperature of the B star has been determined, as approximately 30000K, based on the flux distributions during egress. Light curves of VV Cephei were reduced from the spectrophotometry of the IUE archival spectra. Three light curves at the center wavelengths of 2350 ${\AA}$, 2550 ${\AA}$ and 2850 ${\AA}$ have been analyzed by the modified Wilson and Devinney light curve program. The radii of the B star and M star were deduced to 0.05 and 0.22 of unit separation, respectively. The UV light curves show an evidence that the light was attenuated by the highly opaque atmosphere of the M star.

• Journal of the Korean Ceramic Society
• /
• v.36 no.5
• /
• pp.459-464
• /
• 1999

A carbon-containing silica glass was prepared from orgaincally modified silicate(Ormosil) by heat treatment in N2 atmosphere after the ormosil was synthesized using sol-gel method. The Ormosil was fabricated from the TEOS as the inorganic component and the PDMS as the organic component. The Ormosil changed to balck-coloured glass by carbon decomposed from the PDMS when the Ormosil was heated to 450$^{\circ}C$ 20hrs. A dense silicon oxycarbide glass with 2.08 g/cm3 was obtained by heating the Ormosil at 1050$^{\circ}C$ 10hrs. The microstructure of the carbon-containing silica glass was observed by SEM and the SiOxC4-x structure was confirmed by XPS measurement. The densification of the glass was studied by measurements of specific surface area linear shrinkage and geometric density.

• Food Science and Biotechnology
• /
• v.15 no.3
• /
• pp.431-436
• /
• 2006

Effects of vacuum packaging and modified atmosphere packaging (MAP) on shelf life of selenium-supplemented chicken meat during refrigerated storage were examined. Body weight and feed efficiency were unaffected by dietary selenium level. Dietary treatments and packaging methods had no significant effects on level of microbial growth, lightness, and metmyoglobin content. MAP decreased purge loss (10.9-34.5%) and lipid oxidation (15.2-15.9%) more efficiently than vacuum packaging. Broiler chicks supplemented with ${\alpha}$-tocopherol or ${\alpha}$-tocopherol + selenium had similar TBA values. Dietary supplementation of 4 and 8 ppm selenium reduced lipid oxidation, and this effect was less significant in MAP breast meat.

• Journal of the Korean Magnetics Society
• /
• v.5 no.5
• /
• pp.745-748
• /
• 1995

Magnetic nanoparticles of iron and iron oxide have been prepared in a modified upward thermal diffusion cloud chamber using pulsed laser evaporation. SEM/TEM studies of these particles reveal a size distribution with a mean diameter of about $60\;{\AA}$. FTIR spectrum measurements are used to investigate the difference in oxidation level between nanoparticles prepared at different partial oxygen pressures. The complex magnetic behaviour of these particles was studied using DC- and AC-susceptibility measurements. All samples exhibit superparamagnetism with blocking temperatures ranging from 50 K to above room temperature. The coercivity fields as well as the dependence of the blocking temperature on measuring frequency have been studied. magnetic anisotropy constants are found to be one order of magnitude higher than is known for the bulk values. The mean particle size estimated from the magnetic data is found to be in perfect agreement with the TEM observations.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.3
• /
• pp.328-332
• /
• 1998

Anionic ring-opening polymerization of 3,4-[(dimethylsilyl)isopropyl]benzo-1,1-dimethyl-1-silacyclopentene in the presence of n-butyllithium and HMPA in THF at - 78 ℃ afforded poly[3,4-(dimethylsilylisopropyl)benzo-1,1-dimethyl-1-silapentene]. The characteristic Si-H stretching frequency in the IR is observed at 2100 cm-1. The polycarbosilane has been modified by chloroplatinic acid catalyzed addition of styrene to the polycarbosilane SiH units. Molecular weights and thermal properties of the polymers were compared. The sol-gel polymerization of 3,4-[(dimethoxysilyl)isopropyl]benzo-1,1-dimethoxy-1-silacyclopentene in the presence of aqueous HCl or NaOH in THF resulted in a cross-linked polysiloxane. The xerogel has a low surface area of 13-14 m2/g and is stable up to about 400 ℃ with only 5% weight loss under a nitrogen atmosphere.