• Korean Journal of Food Science and Technology
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• v.27 no.4
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• pp.537-545
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• 1995

Quality changes of lettuce were studied during storage to investigate the efficiency, cooling properties and the washing and storage effects of immersion-type hydrocooling. As a result of plotting the nondimensionalized lettuce temperature versus cooling time, its cooling rate coefficient was shown to be $-0.365\;min^{-1}{\sim}-0.255\;min^{-1}\;(R^2=0.99{\sim}0.88)$. Rate of weight loss was not significantly (p>0.05) different between lettuces with various treatment conditions during storage at $5^{\circ}C$. However, during storage at $15^{\circ}C$, weight loss of hydrocooled lettuce was lower than that of non-treated lettuce after from 10 to 15 days. Especially, The lettuce packed with PE was more effective than that packed with try in terms of packing condition after hydrocooling. Lettuce pretreated with sterilizing agent, packed with PE vinyl film, removed residual water after hydrocooling had lower decaying rate than any other lettuces. Changes of L and b values in hydrocooled lettuce were slower than those of non-treated one. During changes of chlorophyll content, the initial value, $115.7{\sim}147.3\;mg%$ was decreased to $50{\sim}60%$ after 25 days of storage at $5^{\circ}C$ and within 15 days of storage at $15^{\circ}C$. It could be presumed that the addition of sterilizing agent reduced the initial level of overall total and coliform count and its growth rate during storage. The respiration rate of hydrocooled lettuce at $5^{\circ}C$ was $23.95\;mg{\cdot}CO_2/kg\;hr$, which is 10% of those of non-treated lettuce.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.2
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• pp.174-179
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• 2007

This study was carried out to investigate the effect of Gastrodiae elata Blume fractions on systolic blood pressure and serum lipid profiles in spontaneously hypertensive rats (SHR/NCrj) fed high fat diet. Twenty-four males SHR weighing approximately 160 g were randomly divided into four groups; A (low molecule, GR-1), B (polysaccharide, GR-2), C (protein, GR-3) fractions of G. elata Blume, respectively, and D (high fat diet as control). After orally tube feeding the fractions of G. elata Blume, there were no differences in final body weights among the treatment groups. Diet intake was somewhat high in the control group (D), but there were no significant differences in feed efficiency ratios. In terms of serum lipid profiles, total-cholesterol level was statistically higher in the control group (D) than in G. elata Blume fraction groups (p<0.05). Triglyceride levels of low molecule (A) and polysaccharide (B) groups were lower by 16% and 11%, respectively than that of the control group (D). HDL-cholesterol level was remarkably higher (p<0.05), whereas LDL-cholesterol level was significantly lower (by 25%) in the group B as compared to the control group (D). Atherogenic index (AI) of G. elata Blume fraction groups were significantly lower than in the control group (p<0.05). Reference blood pressure (RBP) showed an average of $180\sim190mmHg$ at 8 weeks old after 3 weeks on feeding high fat diet. Compared with RBP, final blood pressure of treatment groups (35 days after feeding the fractions of G. elata Blume gractions) were decreased by 1.7% (A), 5.5% (B) and 3.6% (C), respectively, but the control group (D) contrarily showed an increase of 2.6%. Especially, final systolic blood pressure of the polysaccharide group (B) was lower by 22 mmHg than that of the control group (D). From these findings, it can be suggested that polysaccharide fraction may improve blood serum lipids and should be considered as effective in lowering of blood pressure.

• Journal of the Korean earth science society
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• v.23 no.4
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• pp.357-368
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• 2002

In this study we have tried to explain the barrel-shaped morphology for young supernova remnants considering the dynamical effects of the ejecta. We consider the magnetic field amplification resulting from the Rayleigh-Taylor instability near the contact discontinuity. We can generate the synthetic radio image assuming the cosmic-ray pressure and calculate the azimuthal intensity ratio (A) to enable a quantitative comparison with observations. The postshock magnetic field are amplified by shearing, stretching, and compressing at the R-T finger boundary. The evolution of the instability strongly depends on the deceleration of the ejecta and the evolutionary stage of the remnant. the strength of the magnetic field increases in the initial phase and decreases after the reverse shock passes the constant density region of the ejecta. However, some memory of the earlier phases of amplification is retained in the interior even when the outer regions turn into a blast wave. The ratio of the averaged magnetic field strength at the equator to the one at the pole in the turbulent region can amount to 7.5 at the peak. The magnetic field amplification can make the large azimuthal intensity ratio (A=15). The magnitude of the amplification is sensitive to numerical resolution. This mens the magnetic field amplification can explain the barrel-shaped morphology of young supernova remnant without the dependence of the efficiency of the cosmic-ray acceleration on the magnetic field configuration. In order for this mechanism to be effective, the surrounding magnetic field must be well-ordered. The small number of barrel-shaped remnants may indicate that this condition rarely occurs.

• Journal of The Korean Association For Science Education
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• v.5 no.1
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• pp.49-61
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• 1985

In this study, I compared and analyzed the new and old secondary school science textbooks to find the charateristics of them and the differences between them. The results of the study are the following. Major concepts in the new textbook are almost similar to those in the old one. The-new textbook reinforces the functions of the introudction and checking the result of learning, and presents more and diverse learning materials and reduces the degree of learning difficulty by omitting the several abstract knowledges and mathematical formulas which can be understood through formal operational thinking. The results show that the new textbook is more effective in arousing student's interest and curiosity there fore it increases the efficiency of learning. But the new textbook is less suitable for inquiry because it is mainly composed of explanation and fact rather than experiment and observation. I think that this is the result from the actual approach to the real conditions of school when the curriculum was reformed and the new textbook was written.

• Clean Technology
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• v.20 no.4
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• pp.375-382
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• 2014

This work investigated the plasma-catalytic decomposition of isopropyl alcohol (IPA) and the behavior of the byproduct compounds over monolith-supported metal oxide catalysts. Iron oxide ($Fe_2O_3$) or copper oxide (CuO) was loaded on a monolithic porous ${\alpha}-Al_2O_3$ support, which was placed inside the coaxial electrodes of plasma reactor. The IPA decomposition efficiency itself hardly depended on the presence and type of metal oxides because the rate of plasma-induced decomposition was so fast, but the behavior of byproduct formation was largely affected by them. The concentrations of the unwanted byproducts, including acetone, formaldehyde, acetaldehyde, methane, carbon monoxide, etc., were in order of $Fe_2O_3/{\alpha}-Al_2O_3$ < $CuO/{\alpha}-Al_2O_3$ < ${\alpha}-Al_2O_3$ from low to high. Under the condition (flow rate: $1L\;min^{-1}$; IPA concentration: 5,000 ppm; $O_2$ content: 10%; discharge power: 47 W), the selectivity towards $CO_2$ was about 40, 80 and 95% for ${\alpha}-Al_2O_3$, $CuO/{\alpha}-Al_2O_3$ and $Fe_2O_3/{\alpha}-Al_2O_3$, respectively, indicating that $Fe_2O_3/{\alpha}-Al_2O_3$ is the most effective for plasma-catalytic oxidation of IPA. Unlike plasma-alone processes in which tar-like products formed from volatile organic compounds are deposited, the present plasma-catalyst hybrid system did not exhibit such a phenomenon, thus retaining the original catalytic activity.

• Korean Journal of Environment and Ecology
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• v.20 no.4
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• pp.436-447
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• 2006

Recently, there is increasing demand on enhancing the efficiency of hydro-seed spraying in afforestation for damaged or degraded land including forest road slopes. In this study, we focus on how seed coating and molding may affect seed germination and seedling growth. Plant species used in the study are Lespedeza cyrtobotrya, Indigofera pseudotinctoria, Arudineila hirta, Poa pratensis, and Lolium perenne. The results of seed germination and seedling growth with and without seed coating and molding are analyzed as follows: 1. For all the species and in both seeding with molding covered with soil and seeding without molding in which seeds were over sown, the increment of germination ratio by seed coating method is greater than by non·coating one. Seed coating increases average germination ratios observed in seeding with molding and without molding by 11.2% and 21.4%, respectively. Germination force may decrease from 0.8 to 3.7 days depending on the plant species and the treatments. The $LD_{50}$ decreased by $0.8{\sim}2.6$ days. However, seed coating delays the start of germination by approximate 1 day for all of the observed plants. 2. Seed coating may have the effect of accelerating the growth of stem and leaf and root. The experimental result shows that seed coating leads to 21.7% and 34.8% increment of average stem and leaf growth by seeding with molding and without molding, respectively. In terms of root growth, seeding with molding results in 22.0% increment while seeding without molding produces 26.2% increased root growth. 3: Compared to seeding without molding, germination starts on an average of 1.3 days later in seeding coated seeds with molding. However. the germination ratio is increased by 5%, and germination force and $LD_{50}$ are observed to shorten by 1.0 day and 1.4 days, respectively. Meanwhile, whether seeds are coated or not may be more related with germination and seedling growth in seeding without molding than with those in seeding with molding. 4. In this study, coating materials are examined to look at which ones are better in each treatment. Coating with Vermiculite+Talcum is the most effective in germination and seedling growth for overall plants. Seed coating using Bentonite, Calcium Carbonate, and Calcium Hydroxide shows better results than non-coating does. 5. When seeds are coated, the greatest enhancement of seed germinations was observed in Indigofera pseudotinctoria and, in the case of seedling growth, Lespedeza cyrtobotrya has the most increasing observation value among the 5 examined species. These results may indicate that woody plant seeds, having greater sizes of seeds than ones of grass seeds, may have greater relation with seed coating than grass plant seeds may have. 6. Therefore, if seeds cannot be molded up after hydro-seeding on forest road slopes, it is recommended that seeds for restoration be pre-coated with Vermiculite+Talcum and then be sowed, in order to quickly stabilize the damaged slope and achieve successful afforestation.

• Korean Journal of Optics and Photonics
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• v.21 no.2
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• pp.82-88
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• 2010

Photopolymer is a material for recording three dimensional holograms containing photo information. Photopolymer has been found to be a proper material due to many advantages such as high DE value, easy processing, and low price. Compositions of PVA, monomer, initiater and photosensitizer were determined by previous experiments and the compositions of $SeO_2$ and $TiO_2$ were considered as variable to find out the effects of $TiO_2$ on DE. The DE values were constant for the varying compositions of $TiO_2$ (0.1 mg~1.0 mg). In other words, $TiO_2$ is not directly effective on the DE values. Composition change experiments from $SeO_2$ 0.1 mg, $TiO_2$ 0.9 mg to $SeO_2$ 0.9 mg, $TiO_2$ 0.1 showed a maximum DE value of 73.75% at a component of $SeO_2$ 0.8 mg, $TiO_2$ 0.2 mg. It seemed that regardless of the amount of $TiO_2$, increasing the amount of $SeO_2$ gently increases DE`s. If nano particles are heavily added, transparent films could not be made due to the separation of particles by the solubility decrease. Photopolymer films could be made with high DE values for an extensive angle range if $TiO_2$ additions were kept minimum and $SeO_2$ additions were kept maximum.

• Korean Journal of Crystallography
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• v.6 no.1
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• pp.1-13
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• 1995

Cr:A12O3 and Ti:A12O3 single crystals were grown by Czochralski method, and the effects of crystal growth parameters such as pulling rate, rotation rate, dopant and growth atmosphere on crystal quality were investigated. And spectroscopic properties including lasing efficiency were also measured. Single crystals, sized of 20mm in diameter and 100-135mm in length, were successfully grown from the seed of <001> direction. With the doping level of 0.5w/o Cr2O3, pulling rate 2.0mm/hr, rotation rate of 30rpm and inert atmosphere by nitrogen gas, high quality crystals of Cr:A12O3 were grown. While in case of Ti:A12O3 crystals, high quality crystals were grown under the conditions of the doping level of 0.25w/o TiO2, pulling rate of 1.5mm/hr, rotation rate of 30rpm and reducing atmosphere by hydrogen - nitrogen mixed gas. It was confirmed that Cr3+ ion which maintains its ionoc valence during growth easily de-bubbled than Ti4+ ion which changes its valence, Fe3+ ion also has do-bubbling effect to Ti:A12O3 crystal and the reducing atmosphere by 90% N2 - 10% H2 mixed gas gave effective result on the changing of Ti4+ to Ti3+ and de-bubbling. As a result of spectroscopic measurements of Cr:A12O3 crystal, 4A2 →4F2 and 4F1 absorption transitions and E →4A2(R1) and 2A →4A2(R2) fluorenscence transitions were confirmed. And it was measured that wavelengths of laser R1 and R2 transitions were 696±5nm and 692±5nm respectively, line width of these transitions were 12A, and life-time of fluorenscence was 152μsec. In case of Ti:A12O3 crystals, it was confirmed that absortion transition of 4T2→4E and fluorescence transition of 4E→4T2 with wide range of 650-1050nm was occured. And 147μsec of life-time of fluorescence, 125.4 of figure of merit and 9% of laser efficience were also measured.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.2
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• pp.182-206
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• 2003

Statement of problem : Successful osseointegration of endosseous threaded implants is dependent on many factors. These may include the surface characteristics and gross geometry of implants, the quality and quantity of bone where implants are placed, and the magnitude and direction of stress in functional occlusion. Therefore clinical quantitative measurement of primary stability at placement and functional state of implant may play a role in prediction of possible clinical symptoms and the renovation of implant geometry, types and surface characteristic according to each patients conditions. Ultimately, it may increase success rate of implants. Purpose : Many available non-invasive techniques used for the clinical measurement of implant stability and osseointegration include percussion, radiography, the $Periotest^{(R)}$, Dental Fine $Tester^{(R)}$ and so on. There is, however, relatively little research undertaken to standardize quantitative measurement of stability of implant and osseointegration due to the various clinical applications performed by each individual operator. Therefore, in order to develop non-invasive experimental method to measure stability of implant quantitatively, the resonance frequency analyzer to measure the natural frequency of specific substance was developed in the procedure of this study. Material & method : To test the stability of the resonance frequency analyzer developed in this study, following methods and materials were used : 1) In-vitro study: the implant was placed in both epoxy resin of which physical properties are similar to the bone stiffness of human and fresh cow rib bone specimen. Then the resonance frequency values of them were measured and analyzed. In an attempt to test the reliability of the data gathered with the resonance frequency analyzer, comparative analysis with the data from the Periotest was conducted. 2) In-vivo study: the implants were inserted into the tibiae of 10 New Zealand rabbits and the resonance frequency value of them with connected abutments at healing time are measured immediately after insertion and gauged every 4 weeks for 16 weeks. Results : Results from these studies were such as follows : The same length implants placed in Hot Melt showed the repetitive resonance frequency values. As the length of abutment increased, the resonance frequency value changed significantly (p<0.01). As the thickness of transducer increased in order of 0.5, 1.0 and 2.0 mm, the resonance frequency value significantly increased (p<0.05). The implants placed in PL-2 and epoxy resin with different exposure degree resulted in the increase of resonance frequency value as the exposure degree of implants and the length of abutment decreased. In comparative experiment based on physical properties, as the thickness of transducer increased, the resonance frequency value increased significantly(p<0.01). As the stiffness of substances where implants were placed increased, and the effective length of implants decreased, the resonance frequencies value increased significantly (p<0.05). In the experiment with cow rib bone specimen, the increase of the length of abutment resulted in significant difference between the results from resonance frequency analyzer and the $Periotest^{(R)}$. There was no difference with significant meaning in the comparison based on the direction of measurement between the resonance frequency value and the $Periotest^{(R)}$ value (p<0.05). In-vivo experiment resulted in repetitive patternes of resonance frequency. As the time elapsed, the resonance frequency value increased significantly with the exception of 4th and 8th week (p<0.05). Conclusion : The development of resonance frequency analyzer is an attempt to standardize the quantitative measurement of stability of implant and osseointegration and compensate for the reliability of data from other non-invasive measuring devices It is considered that further research is needed to improve the efficiency of clinical application of resonance frequency analyzer. In addition, further investigation is warranted on the standardized quantitative analysis of the stability of implant.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.232-239
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• 2009

Statements of the problem: Many denture wearers occasionally use denture adhesives to improve denture retention, stability and chewing efficiency. An ideal denture adhesive is nontoxic, non-irritating, and provides comfort to the oral mucosa. Purpose: The purpose of this study was to evaluate the cytotoxicity and adhesive properties of a selected denture adhesive. Material and methods: To test cytotoxicity of the selected denture adhesive, mouse fibroblast cells were used in MTT testing. Cytotoxicity was examined according to the concentration of the denture adhesive and incubated for 1 to 4 days. To examine adhesive property, a denture base was fabricated on an edentulous dentiform. The adhesive was applied to the denture base, then tensile bond strength was measured, to evaluate the change in retention during 3 days. Results and Conclusion: 1. 1% and 2% concentration denture adhesive cream had no cytotoxicity. 2. The tensile bond strength of the group with both denture adhesive and artificial saliva was significantly higher than that of the group with only denture adhesive(P<.05). The tensile bond strength of the group with denture adhesive was significantly higher than that of with only artificial saliva(P<.05). 3. The tensile bond strength had no significant change during 1 hour, and then gradually decreased. After 1 day, it decrease to half. Within the limitation of this study, the tested denture adhesive had no cytotoxicilty and was effective in improving denture retention. The adhesive strength began to continuously decrease after 1 hour and it decreased to half at 1 day after application.