• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.3
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• pp.99-106
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• 1998

The performance of the turbofan engine, a medium scale civil aircraft which has been developing in Rep. of Korea, was analyzed and the control scheme for optimization the performance was studied. The dynamic and real-time linear simulation was performed in the previous study The result was that the fuel scedule of the step increase overshoot the limit temperature(3105 $^{\cire}R$) of the high pressure turbine and got small surge margine of the high pressure compressor. Therefore a control scheme such as the LQR(Linear Quadratic Regulator) was applied to optimizing the performance in this studies. The linear model was expected for designing controller and the real time linear model was developed to be closed to nonlinear simulation results. The system matrices were derived from sampling operating points in the scheduled range and then the least square method was applied to the interpolation between these sampling points, where each element of matrices was a function of the rotor speed. The control variables were the fuel flow and the low pressure compressor bleed air. The controlled linear model eliminated the inlet temperature overshoot of the high pressure turbine and obtained maximum surge margins within 0.55. The SFC was stabilized in the range of 0.355 to 0.43.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.1
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• pp.73-80
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• 2008

An hydraulic experiment was carried out in an open channel flume in order to improve the technique of designing shape of the sluice used for tidal power generation, which greatly affects the economical efficiency of the construction of a tidal power plant. To predict the influence of change in the major design parameters relating to the sluice shape on the water discharge capability of the sluice, it was necessary to perform a precise experiment that is discriminated to previous feasibility studies or design projects. For this purpose, by installing various flow straighteners and rectifying structures inside the water supply system and the rectifying tank, the flow in the flume was stabilized as tranquil as possible. In addition, the measuring instruments and the location of installing them were carefully determined so as to minimize the errors intervened during the measurement of water discharge and water level. The method of estimating head difference between upstream and downstream of the sluice was also developed by taking account of the head loss due to the friction at the bottom and side walls in the flume.

• Polymer(Korea)
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• v.29 no.5
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• pp.440-444
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• 2005

An increase in the surface area of drugs by reducing particle sizes from microns to nanometers has been known as an efficient method to improve the bioavailability of water-insoluble drugs. To prevent drug nanoparticles from aggregation during the processes of drug formulation, a limited number of pharmaceutical inactive ingredients such as hydroxypropyl cellulose has been employed as stabilizers or dispersants. In this study, copolymers of hydrophilic and hydrophobic amino acids were synthesized by the ring opening polymerization of their N-carboxyanhydride monomers and evaluated as novel candidates to stabilize the nanoparticles of a water insoluble drug, naproxen. Naproxen nanoparticles stabilized by synthesized amino acid copolymers were successfully prepared in the size of $200\~500nm$ in 60 min by a wet comminution process. Particle size analysis showed that the effective stabilization performance of copolymers required the hydrophobic moiety content to be higher than $10 mol\%$. However, the molecular weight and morphology of copolymers was not the critical parameters in determining the particle size reduction. Their particle size was found to be stable up to 14 days without significant aggregation.

• Korean Journal of Poultry Science
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• v.21 no.4
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• pp.239-247
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• 1994

A study was conducted to investigate the effects of the addition of varied levels of NaCi and phosphates on the physicochernical properties of the breast meat of the spent layers(2 \pm 0.2 kg) which were stabilized for over 24 h before slaughter. Within 1 h after slaughter, breast meats were removed and treated with NaGl(0, 1, 2, 3%) and phosphates(0.25% and 0.5%) using a hot-salted method. The breast meat was stored at 4 \pm $1^{\circ}C$ for 3 d. The results obtained were summarized as follows. 1. The pH values of salt-treated groups were significantly higher than that of the control(P<0.05) ; the higher the salt level, the higher the pH. The pH values were significantly increased in both control and treatment groups during storage(P<0.05). Among salt-treated groups, the 0.5% phosphates level showed significantly high pH(P<0.05) compared to other levels of salt groups. 2. The moisture contents were significantly lower in all salt4reated groups than the control(P<0.05), and showed a negative relationship with the levels of salt. It decreased in control group gradually as the storage period extended, but not significantly changed in salt-treated groups. 3. The shear force values in salt-treated groups were lower than that of the control and showed a negative relationship with salt levels. At a constant level of NaCI, the shear force value was higher in 0.25% phosphates level than in 0.5% level. It decreased in both control and salt-treated groups during storage. 4. The salt treatments tended to increase the sodium content proportionately. The sodium content decreased in both control and salt treatment groups during storage(P<0.05). In addition, the combination of high levels of NaCl and phosphates rather than those of low levels of NaCI and phosphates resulted in elevated levels of sodium. 5. The phosphorus contents in salt-treated groups were higher than that of control. Between 0.5% and 0.25% phosphates levels this value showed significant difference(P<0.05). Its contents in both control and treatment groups were significantly decreased during storage (P<0.05).

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.351-356
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• 2008

Titania nanoparticles were prepared by controlled hydrolysis of titanium tetraisopropoxide (TTIP) in water-in-oil (W/O) and microemulsion stabilized with a nonionic surfactant, N P-10 (Polyoxyethylene Nonylphenol Ether: $C_9H_{19}C_6H_4(OCH_2CH_2)_{10}OH$)). The nanosized particles prepared in W/O microemulsion were characterized by FT-IR, TEM, XRD, TGA, and DTA. In addition, the photocatalytic degradation of p-nitrophenol has been studied by using a batch reactor in the presence of UV light in order to compare the photocatalytic activity of prepared nanosized titania. The nanaosized titania particles calcined at $300{\sim}600^{\circ}C$ showed an anatase structure, but it transformed to a rutile phase above $700^{\circ}C$ of calacination temperature. With an increase of $W_o$ ratio, the crystallite size increased but photocalytic activity decreased. The titania synthesized at $W_o=5$, R = 2, and calcined at $400{\sim}500^{\circ}C$ showed the highest activity on the photocatalytic degradation of p-nitrophenol.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.83-88
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• 2015

Coating materials used in the electron beam (EB) deposition method, which is being studied as one of the fabrication methods of thermal barrier coating, are exposed to high power electron beam at focused area during the EB deposition. Therefore the coating source for EB process is needed to form as ingot with appropriate density and microstructure to sustain their shape and stable melts status during EB deposition. In this study, we tried to find the optimum powder condition for fabrication of ingot of 8 wt% yttria stabilized zirconia which can be used for EB irradiation. It seems that the ingot, which is fabricated through bi-modal type initial powder mixture which consists of tens of micro and nano size particles, was shown better performance than the ingot which is fabricated using monolithic nanoscale powder when exposed to high power EB.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.1 s.49
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• pp.111-114
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• 2005

This study is about the cosmeceutical products using enzyme induced bio-conversion system. In general, ascorbic acid (AA) has the higher reducing activity and can be used for various purpose in the cosmetics. But it is very unstable in the aqueous system and difficult to maintain its stability in the cosmetics product. 2-O-$\alpha$-D-Glucopyranosyl-L-ascorbic acid (AA2G) is the stabilized form of AA and showed the less whitening activity than AA. In this study, we developed bio-conversion system improving the stability and efficacy of AA2G and AA, respectively. In this system, AA2G (over $80\%$) can be converted to AA and glucose within 30 min. The converted product showed higher anti-tyrosinase activity like AA (AA2G showed no anti tyrosinase activity) and depigmenting activity in the artificial tanning test. From these results, we could conclude this system is a brand new method to increase the activity of AA and maintain its stability.

• Journal of Korean Physical Therapy Science
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• v.28 no.2
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• pp.57-64
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• 2021

Background: During squat exercises, Ankle joint stability during squat movement transfers forces produced by unstable supports or various loads to the leg joints and trunk, reducing the risk of injury; therefore, a reference is needed for correct ankle joint posture during squat exercises. The purpose of this study was to examine the effect of ankle joint stability on quadriceps femoris and hamstring activation during squat exercises. Design: Quasi-experiment one group pretest-posttest design. Methods: The participants in this study were 20 volunteers who performed squat exercises with and without kinesiology tape. We measured quadriceps femoris and hamstring activation using surface electromyography. The ankle joint was stabilized with kinesiology tape using the ankle balance taping (ABT) method. A paired t-test was performed to compare differences between taping conditions. Results: Vastus medialis and vastus lateralis activation were greater following squat exercises with kinesiology tape than without; however, the difference was not significant. Medial and lateral hamstring activation was not significantly different between taping conditions. Conclusion: Although it is difficult to maintain stability using kinesiology tape alone, ankle joint stability is believed to affect quadriceps femoris muscle activity, which increases the effectiveness of the squat exercise.

• Korean Journal of Comparative Education
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• v.18 no.4
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• pp.113-139
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• 2008

The purpose of this study is to analyze the operating case of admission officer system of colleges and universities in USA, and to deduce its implications to Korean colleges and universities. In order to accomplish the purpose of this study, following methodologies were adopted: review on the related literatures, statistical data, and previous studies concerning admission officers of colleges and universities in USA, and in-depth interview with them. Historical and cultural background of university admission system of USA was analyzed. Case study on USA colleges and universities was divided with four parts such as determining factors of admission and admission methods, organization for admission affairs and its number of persons, work of admission officer and admission process, and cost of admission and salary. Implications to Korean colleges and universities were presented with three points such as overall implication, implication on materials for admission process, and implication on managing system of admission. Based on the analysis, discussion and implications, the conclusion and further suggestion of this study are as follows: First, actual authority of admission should be grant to admission officer. Second, not only non-curricular factors but also scholastic factors should be emphasized in role of admission officer. Third, education and training about work of admission officer and unification of criteria for admission should be held. Fourth, admission officers with various occupation background are needed. Fifth, work of admission officers should be extended to various work concerning university entrance. Sixth, cross-checking on marks of over two admission officers is needed. Seventh, in order to stabilize admission process, status of admission officer should be stabilized. Eighth, part-time admission officers are need to employ in season of admission. Ninth, authority of weighting high schools should be grant to admission officers in long term perspective.

• Journal of Korea Entertainment Industry Association
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• v.15 no.2
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• pp.179-189
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• 2021

As the school was in crisis due to the COVID-19, e-Learning was extended. Although it was difficult for everyone, e-Learning were stabilized with the enthusiasm and efforts of school teachers. Online education in Korea, called 'K-edu' is being promoted by school teachers in COVID19, and is considered an important area of future education beyond the post corona. Therefore, analyze the meaning of K-edu experienced by school teachers, studying changes in the educational paradigm in the Post-COVID era is very important in establishing the direction and content of future education. In this study described the K-edu experienced by school teachers in response to Corona 19 as 'changed daily life of school teachers', 'changes in schools', 'difficulties felt by teachers' and 'proposals for K-edu' through the qualitative research method FGI. Based on this, the characteristics of K-edu that changed through COVID-19 were analyzed as 'expansion of educational space', 'expansion of educational form' and 'highlighting the importance of face-to-face education'. Through this study, we hope that K-Edu led by school teachers will serve as a cornerstone for leading the world beyond Korea.