• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1711-1721
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• 1992

A nonlinear dissipative dynamical system can often have multiple attractors. In this case, it is important to study the global behavior of the system by determining the global domain of attraction of each attractor. In this paper we study the global behavior of a forced beam with two mode interaction. The governing equation of motion is reduced to two second-order nonlinear nonautonomous ordinary differential equations. When .omega. /=3.omega.$_{1}$ and .ohm.=.omega $_{1}$, the system can have two asymptotically stable steady-state periodic solutions, where .omega./ sub 1/, .omega.$_{2}$ and .ohm. denote natural frequencies of the first and second modes and the excitation frequency, respectively. Both solutions have the same period as the excitation period. Therefore each of them shows up as a period-1 solution in Poincare map. We show how interpolated mapping method can be used to determine the two four-dimensional domains of attraction of the two solutions in a very effective way. The results are compared with the ones obtained by direct numerical integration.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.381-385
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• 1997

A long-term prediction algorithm of geostationary orbit was developed using the analytical method. The perturbation force models include geopotential upto fifth order and degree and luni-solar gravitation, and solar radiation pressure. All of the perturbation effects were analyzed by secular variations, short-period variations, and long-period variations for equinoctial elements such as the semi-major axis, eccentricity vector, inclination vector, and mean longitude of the satellite. Result of the analytical orbit propagator was compared with that of the cowell orbit propagator for the KOREASAT. The comparison indicated that the analytical solution could predict the semi-major axis with an accuracy of better than $pm35$ meters over a period of 3 month.

• Journal of Animal Science and Technology
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• v.58 no.8
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• pp.31.1-31.8
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• 2016

Background: Plasma protein hydrolysates have been shown to possess antioxidant activity. However, no report has yet to examine the antioxidant effects of injection of plasma protein hydrolysates on meat quality. Therefore, in this study, the effects of injection of hydrolysis plasma protein solution on meat quality and storability were investigated in porcine M. longissimus lumborum. Methods: Twelve pigs were randomly selected at a commercial slaughter plant and harvested. Dissected loins were injected with one of five solutions: C- control (untreated), T1- 10 mM phosphate buffer solution (PBS), T2- 10 mM PBS with 0.01 % butylated hydroxytoluene, T3- 10 mM PBS with 5 % plasma proteins, and T4- 10 mM PBS with 5 % hydrolysis plasma proteins. Results: T3 and T4 induced greater reduction in protein content of the loin muscle than other treatments. T2 resulted in the lowest pH as well as highest cooking loss. After a storage period of 3-7 days, both lightness and redness of meat were unaffected by all injection treatments. However, yellowness was significantly elevated by treatment with T4 relative to the control. T4 also resulted in the lowest shear force (a measure of meat toughness), suggesting improvement of texture or tenderness. Further, T4 resulted in the most stable TBARS values during storage, indicating that this treatment might retard rancidity in meat. Conclusion: Injection of porcine M. longissimus lumborum with hydrolysis plasma protein solution could improve overall pork quality, including tenderness and storability.

• Restorative Dentistry and Endodontics
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• v.14 no.2
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• pp.49-64
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• 1989

The purpose of this study was to evaluate the effect of several materials on the healing process of apical wound. Sixteen mandibular premolars obtained from 4 healthy dogs were used for this study. Under general anesthesia, the pulpal chamber of each tooth was opened and the pulps were extirpated. The root canals were then instrumented with H-file and irrigated with physiologic saline solution ; the apices were purposely perforated and enlarged with the engine K-reamer. In the experimental groups, apical wounds were filled with one of calcium hydroxide, hydroxylapatite, and tricalcium phosphate materials, mixture of each materials and physiologic saline solution, with a lentulo spiral. In the control group, apical wounds were not filled with any material. All the root canals were filled by the lateral condensation technique with gutta-percha cone and ZOE sealer. The access opening of all the teeth were closed with amalgam. On the 10, 20, 40 and 60th day after experiment, experimental animals were sacrificed. Segments of jaws, each containing one tooth, were fixed in 10% formalin solution and decalcified in Plank-Rychlo solution. The specimens were embedded in paraffin and serially sectioned to an average thickness of $6{\mu}m$. The sections were stained by hematoxylin-eosin and Masson's trichrome stain method and examined under light microscope. The results were as follows : 1. In the experimental groups, the new bone formations were observed in apical wounds. 2. Fourty days later, apical wounds were healed by granulation tissue in the experimental groups, but were not healed by granulation tissue in the control group, and the healing process of experimental groups were more rapid than that of control group. 3. Sixty days later, chronic inflammation disappeared in the experimental groups, and the materials used showed biologic affinity to the periapical tissue. 4. In all the groups, the resorption of cementum appeared on the 10th and 20th day after experiment, and the deposition of cementum appeared on the 40th and 60th day after experiment, especially showing narrowness of apical foramen due to newly formed cementum in calcium hydroxide group. 5. Calcum hydroxide and tricalcium phosphate particles were gradually resolved, but hydroxylapatite particles were not resolved through the experimental period.

• Journal of Technologic Dentistry
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• v.12 no.1
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• pp.23-45
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• 1990

This study aimed at inquiring into the basic theory on co-operative education, grasping and analyzing the present situation of the junior health college, the present condition of co-operative education and into problem. and seeking to find a solution to activate the co-operative edcation of the junior health colleges. For this purpose this study compared the co-operative education system in our country with that of foreign countries revolving around the related literature to co-operative education, analyzed it, and the pointed out its problem. And this study classified into the solution of establishing co-operative education system, the solution of consolidating the on-the-spot training system, the solution to activate the co-operative education of the junior health college. First this study suggested three methods as a part of establishing co-operative education system as below. 1. The need to set up the ideology concerning co-operative education. 2. The construction of the advisory committee for co-operative education. 3. The establishment of an agency for co-operative education. And this study suggested nine methods as the method of consolidating the on-the-spot training as below. 1. The execution of the basic research for the on-the-spot training. 2. The reorganization of the existing curriculum into the curriculum the industrial organization requires. 3. The establishing of the system in a closer cooperation with the industrial organization for the on-the-spot training. 4. The participation in solving commonly the problems of the industrial organization and in education. 5. The establishing of the guidance system assuming exclusive charge of the on-the-spot training. 6. The submission of the evaluation sheet for the on-the-spot training. 7. The extension of the period of the on-the-spot training and the reorganization of an educational system. 8. The persistent support for the on-the-spot training at the governmental dimension. 9. The securing of the educational dost spent on the on-the-spot training and the imposition of benefits on the industrial organization.

• Journal of Surface Science and Engineering
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• v.54 no.5
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• pp.238-247
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• 2021

PEO (plasma electrolytic oxidation) was applied to modify the surface of AZ31 magnesium alloy in this study. The mixed solution of sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) was used as the electrolyte, and 0 - 0.05 g/L of Ca-GP (Glycerol Phosphate Calcium salt) was added in the electrolyte as an additive. PEO treatment was conducted at a current density of 30mA/cm² for 5 minutes using a DC power supply. The surface properties were identified by SEM, XRD and surface roughness analyses, and the corrosion resistance was evaluated by potentiodynamic polarization and immersion tests. In addition, the biocompatibility was evaluated by immersion test in SBF solution. As the concentration of Ca-GP was increased, the surface morphology was denser and more uniform, and the amount of Ca and the thickness of oxide layer increased. Only Mg peak was observed in XRD analysis due to very thin oxide layer. The corrosion resistance of PEO-treated samples increased with the concentration of Ca-GP in comparision with the untreated sample. In particular, the highest corrosion resistance was identified at the group of 0.04g Ca-GP through potentiodynamic polarization and immersion tests in saline solution (0.9 wt.%NaCl). During the immersion in saline solution, pH rapidly increased at the beginning of immersion period due to rapid corrosion, and then increase rate of pH decreased. However, the pH value in the SBF temporarily increased from 7.4 to 8.5 during the day, then decreased due to the inhibition of corrosion with HA(hydroxyapatite) formation.

• Korean Journal of Clinical Pharmacy
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• v.7 no.1
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• pp.45-49
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• 1997

The effect of the light on the stability of 5-fluorouracil admixture was investigated. Four sets of 5-fluorouracil admixture were prepared using 50 mg/ml injection in $5\%$ dextrose solution in PVC bags and glass bottles: (1) 5-fluorouracil 1 mg/ml concentration in glass bottles, (2) 5-fluorouracil 1 mg/ml in PVC bags, (3) 5-fluorouracil 10 mg/ml in glass bottles, and (4) 5-fluorouracil 10 mg/ml in PVC bags. In each set, one group was protected from the light (control group) and the other group was exposed to the fluorescent light (study group). All admixtures were stored at room temperature for 72 hours. Also, 5-fluorouracil injections (50 mg/ml) were prepared in plastic syringes. Half of the samples of 50 mg/ml concentration were protected from the light (control group) and the other half were exposed to the fluorescent light (study group). These were stored at room temperature for 48 hours. After visual inspection, the pHs of each admixture were determined. The 5-fluorouracil concentrations were measured by high-performance liquid chromatography with UV detection, with 5-bromouracil as an internal standard. Over the study period, no visual changes were observed. The pHs of 5-fluorouracil admixtures were in the range of $8.2\~8.5$. The peak area ratios (5-FU/5-BrU) of 5-fluorouracil admixtures protected from the light were compared with those of the admixtures exposed to the light. There was no statistically significant difference between two groups during the study period (p>0.05). In conclusion, 5-fluorouracil admixtures in $5\%$ dextrose solution exposed to the light were stable for 72 hours.

• Korean journal of food and cookery science
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• v.16 no.1
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• pp.75-83
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• 2000

The effects of salting methods on sensory and microbiological properties of Kakdugi were evaluated during fermentation at 10$\^{C}$ for up to 52 days. Kakdugi samples were prepared by 4 different salting methods at the final salt concentration about 1.5%, which was appropriate for organoleptic quality. The salting methods for radish cubes(2cm size) of Kakdugi included; 1) Treatment S-1: spraying dry salt uniformly onto the radish cubes, at the concentration of about 1.5%(w/w) and cured for 1 hr, 2) Treatment S-5: spraying dry salt uniformly onto the radish cubes, at the concentration of about 1.2%(w/w) and cured for 5 hr, 3) Treatment B-1: brining radish cubes in a 8.5%(w/v) salt solution and cured for 1 hr, 4) Treatment B-5: brining radish cubes in a 4.0%(w/v) salt solution and cured for 5 hr. During the early stage of fermentation, sensory test showed higher scores in the overall acceptability of Kakdugi prepared with salting methods S-1 and S-5 than those with B-1 and B-5. However, the trend of acceptability has been reversed by the treatments B-1 and, more notably, by B-5 at the later stage of fermentation. The counts of lactic acid bacteria increased remarkably and then decreased gradually after the optimum ripening period. The major lactic acid bacteria isolated and identified from Kakdugi were Pediococcus, Streptococcus, Leuconostoc, and Lactobacillus.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.108-113
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• 2007

In this report, stress corrosion cracking generation due to pipe material degradation in the primary stage of the nuclear power plant was investigated. Firstly, after artificially degrading the CF8A steel during 2, 4, and 6 months in actual temperature, $400^{\circ}C,$ assessed corrosion susceptibility of the degraded material following ASTM G5 standard. And next, the S.C.C. tests for the degraded material were conducted under the condition of $60^{\circ}C,$ 2wt.% H2BO3+Li70H solution, 0.8 oy. From the results, Corrosion rates linearly increased with degradation period and solution temperature increase. And both the raw material and the degraded materials were not failed in the S.C.C. test condition. In spite of long time test (about 3,900 hrs) under S.C.C. condition, surface pits or surface corrosion by the electro chemical reaction were not observed. And also, even though the nondestructive DCPD and ACPD methods were applied to on-line monitor the S.C.C. failure processes it was impossible because the surface pits and cracks were not generated.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.887-890
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• 2009

Hydroxyapatite (HAp)-based materials have attracted considerable attention on account of their excellent stability and recrystallization. Nanoscale HAp powders with a mean particle size of 200 nm were used to regenerate the enamel layers of damaged teeth. An artificially scratched tooth was immersed in a nanoscale HAp powder suspension in d.i. water (HAp of 70 wt%) at 37 ${^{\circ}C}$ for a period of 1~3 months. SEM and AFM showed that the scratched surface was ultimately inlaid with HAp after three months and the roughness increased from 2.80 to 5.51. Moreover, the hardness of the neo-generated HAp layer on the crown was similar to that of the innate layer. $Ca^{2+}$ and ${PO_4}^{3-}$ ions from the HAp powders dissolved in d.i. water were precipitated on the tooth to produce cemented pasteson the enamel surface due to its high recrystallizing characteristics, resulting in a hard neo-regenerated HAp layer on the enamel layer. This nanoscale HAp powder solution might be used to heal decayed teeth as well as to develop tooth whitening appliances.