• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.2
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• pp.180-188
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• 2002

Newly developed curing units(plasma arc curing units) operate at relatively high intensity and are claimed to result in optimum properties of composite resin in a short curing time. The purpose of this study was to evaluate the microhardness and microleakage at the resin-tooth interface of two types of composite resins polymerized with visible light and plasma arc curing units. The results from the present study can be summarized as follows 1. Microhardness in each depth was shown to be higher in group AHL than AP3 & AP6. Group ZHL was lower than AP6 at surface(p<0.05) and had no statistically significant difference at 1mm and 2mm(p>0.05). In other depths, group ZHL was higher than ZP3 and ZP6(p<0.05). 2. The incremental reduction in microhardness with depth was shown to be in all group except in surface-1mm of group AHL and $1{\sim}2mm$ of group ZHL(p<0.05). 3. Degree of microleakage in all oops were shown to be higher in gingival margin than occlusal margin but no statistically significant difference(p>0.05). 4. Differences between curing methods in microleakage were shown to be no statistically significant difference(p>0.05). 5. Differences between composite resins in microleakage were shown to be no statistically significant differ once(p>0.05).

• KSBB Journal
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• v.19 no.4
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• pp.269-273
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• 2004

A simple, fast and reproducible quantitative analysis method for sugar concentration composed in oligosaccharide mixture was developed. Two glass TLC plates were prepared per sample. After dipping one plate into the copper bicinchoninate reagent and the other plate into 5% sulfuric acid solution, both plates were baked in microwave oven until sugar spots were developed or the surface temperature of TLC plate becomes 60 to 70 $^{\circ}C$. The corrective factor values [F value =(the value of total sugar concentration converted as glucose unit/the value of reducing sugar concentration converted as glucose unit)/(polymerization degree of sugar)] of different molecular weight sugars were determined. Within the concentration of 0.25∼1.0 $\mu\textrm{g}$ in each sample loaded, the fructose-F (corrective factor value of fructose) was 0.45, yet for the higher concentration (2.5∼7.5 $\mu\textrm{g}$) fructose-F was 1.0. In case of glucose, in the range of 0.5∼7.5 $\mu\textrm{g}$, glucose-F was same as fructose-F, 1.0. However, as the molecular weight of sugar was increased, the F values were decreased in both maltodextrin and isomaltodextrin oligosaccharides in 0.5∼7.5 $\mu\textrm{g}$ of each sample loaded. Interestingly, F values were equal for the same molecular weight sugars, although the structures were different from each other. Using F value of each sugar, we could determine and compare the exact total sugar concentration of different molecular weight maltooligosaccharide and isomaltooligosaccharide. We also could determine if the unknown sugar was a reducing or non-reducing compound by using optimized TLC with microwave oven method.

• Applied Biological Chemistry
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• v.40 no.2
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• pp.95-100
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• 1997

This study was aimed to survey inexpensive and reliable sources of chitinase from the animal origin. The stomach and its content of the broiler, the cod, the yellowtail and ${\beta}-glucuronidase$ from snail gut showed a considerable chitinolytic activity, while those of the bas didn't have any detectable activity. These crude enzymes was found to have both endo- and exochitinase activity. The effects of pH and temperature on the enzyme activity were variable. The hydrolytic products of colloidal chitin by the enzyme preparation from the broiler and the cod were chitooligomers having the degree of polymerization between 3 and 5. Furthermore we observed the chitosanolytic activity from these enzymes. In the degradation of chitosan the chyme of the broiler had the highest activity and ${\beta}-glucuronidase$ from snail gut followed. On the basis of the fact that the by-product of the broiler was not only commercially available but also the most potent in the endochitinase activity and the lowest in the exochitinase activity, we conclude that the gizzard and its chyme are considered as the most suitable source of the industrial chitinase among animals studied in this paper.

• Microbiology and Biotechnology Letters
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• v.32 no.2
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• pp.117-122
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• 2004

Bacillus sp. $\beta$-mannanase was purified by DEAE-sephadex ion exchange column chromatography. The specific activity of the purified enzyme was 21.57 units/$m\ell$ protein, representing an 95.33-folds purification of the original crude extract. The final preparation thus obtained showed a single band on SDS-polyacrylamide gel electrophoresis. The molecular weight was determined to be 38.9 kDa. Guar gum galactomannan was hydrolyzed by the purified $\beta$-mannanase, and then the hydrolysates was separated by activated carbon column chromatography and Sephadex G-25 gel filtration. The main hydrolysates were composed of D.P. (Degree of Polymerization) 5 and 7 galactomannooligosaccharides. To investigate the effects of guar gum galactomannooligosaccharides on in vitro growth of Bifidobacterium longum, B. bifidum, B. infantis, B. adolescentis, B. animalis, and B. breve, Bifidobacterium spp. were cultivated individually on the modified-MRS medium containing carbon source such as D.P. 5 and D.P. 7 galactomannooligosaccharides, respectively B. longum and B. bifidum grew up l0-fold and 9.8-fold more effectively by the treatment of D.P. 5 galactomannooligosaccharides, compared to those of standard MRS medium. Especially, D.P. 5 was more effective than D.P. 7 galactomannooligosaccharide on the growth of Bifidobacterium spp.

• Korean Journal of Food Science and Technology
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• v.26 no.3
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• pp.310-316
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• 1994

The phenolic substances contents of 45 plant foods in Korean diet were determined by different methods. Total phenolics contents by Folin-Denis method were $0.1{\sim}5.8%$ (dry matter basis), in which persimmon leaf, chestnut's inner skin, Chinese quince, walnut, sunflower seed and arrowroot exhibited the higher levels above 2%. Condensed tannin contents by vanillin method were $0{\sim}48%$, in which Chinese quince and chestnut's inner layer gave very high levels. Protein-precipitable phenolic substances ranged from 0.4% to 2.2%, in which chestnut's inner layer, walnut and Chinese quince had the highest content. The ability of phenolics to form precipitate was higher with pepsin and albumin than with trypsin. Among different phenolics content, total phenlolics correlated significantly with protein-precipitable phenolics (r=0.65) and condensed tannin (r=0.56). Chinese quince, chestnut's inner skin and sorghum showed a relatively lower degree of polymerization, as expressed by vanillin/FolinDenis ratio. Processed foods from buckwheat, acorn, mugwort and arrowroot showed a lower content of phenolic substances, suggesting a negligible adverse effect on the bioavailability of food proteins, if any.

• Journal of the Korean Wood Science and Technology
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• v.15 no.4
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• pp.45-58
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• 1987

This study was carried out to improve the physical and mechanical properties of Pupulus alba $\times$ glandulosa treated by the heat and compression. The results obtained were as follows. 1. The specific gravity of the wood was conspicuously increased by the lincreasing of pressing level. 2. The shrinkage of the wood was increased. by the increasing of pressing level. The radial shrinkage was 6.41-8.81%, the tangential shrinkage was 8.98-19.81 %, and the longitudinal shrinkage was 1.46-1.91 %. Comparing to the untreated stock, the rate of increase was 48.7-104.4% in radial direction. 1.7-124.4% in tangential direction and 60.4-109.9% in longitudinal direction, respectively. 3. The rate absorption of 30% compressed stock was Similar to that of untreated stock. but the rate of absorption of 40 % or more compressed stock was increased highly. 4. The thickness swelling of the wood was not changed in radial direction at pressing level, but was conspicuously increased in tangential direction under the pressing level of 40% and 50%. 5. The heat and compression treatment affected on the mechanical properties of the wood. The longitudinal compressive strength was increased under the pressing level of up to 40%, but was decreased under the pressing level of 50%. The bending strength was not changed under the compression percentage of up to 30%, but was decreased under the pressing level of 30% or more. And, the absorbed energy in impact bending was increased to 128% under the pressing level of up to 30%, but was decreased under the pressing level of 30% or more. Conclusionly, the mechanical properties of the wood was improved by the heat and compression treatment, but the strength of the wood was decreased under the pressing level of a certain level or more(in this study, pressing level of 30% or more). This was because of the wood deterioration due to the deformation(shrinkage, crack, failure) of wood tissues induced by the heat and compression treatment, the heat analysis of wood components induced by the heating, and the drop of the degree of polymerization.

• International Journal of Ocean System Engineering
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• v.2 no.3
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• pp.185-194
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• 2012

A Macroscopic combination of two or more distinct materials is commonly referred to as a "Composite Material", having been designed mechanically and chemically superior in function and characteristic than its individual constituent materials. Composite materials are used not only for aerospace and military, but also heavily used in boat/ship building and general composite industries which we are seeing increasingly more. Regardless of the various applications for composite materials, the industry is still limited and requires better fabrication technology and methodology in order to expand and grow. An example of this is that the majority of fabrication facilities nearby still use an antiquated wet lay-up process where fabrication still requires manual hand labor in a 3D environment impeding productivity of composite product design advancement. As an expert in the advanced composites field, I have developed fabrication skills with the use of machinery based on my past composite experience. In autumn 2011, the Korea government confirmed to fund my project. It is the development of a composite sanding machine. I began development of this semi-robotic prototype beginning in 2009. It has possibilities of replacing or augmenting the exhaustive and difficult jobs performed by human hands, such as sanding, grinding, blasting, and polishing in most often, very awkward conditions, and is also will boost productivity, improve surface quality, cut abrasive costs, eliminate vibration injuries, and protect workers from exposure to dust and airborne contamination. Ease of control and operation of the equipment in or outside of the sanding room is a key benefit to end-users. It will prove to be much more economical than normal robotics and minimize errors that commonly occur in factories. The key components and their technologies are a 360 degree rotational shoulder and a wrist that is controlled under PLC controller and joystick manual mode. Development on both of the key modules is complete and are now operational. The Korean government fund boosted my development and I expect to complete full scale development no later than 3rd quarter 2012. Even with the advantages of composite materials, there is still the need to repair or to maintain composite products with a higher level of technology. I have learned many composite repair skills on composite airframe since many composite fabrication skills including repair, requires training for non aerospace applications. The wind energy market is now requiring much larger blades in order to generate more electrical energy for wind farms. One single blade is commonly 50 meters or longer now. When a wind blade becomes damaged from external forces, on-site repair is required on the columns even under strong wind and freezing temperature conditions. In order to correctly obtain polymerization, the repair must be performed on the damaged area within a very limited time. The use of pre-impregnated glass fabric and heating silicone pad and a hot bonder acting precise heating control are surely required.