• Bulletin of the Korean Chemical Society
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• v.18 no.8
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• pp.896-898
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• 1997

• Bulletin of the Korean Chemical Society
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• v.10 no.5
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• pp.465-466
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• 1989

• Bulletin of the Korean Chemical Society
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• v.16 no.12
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• pp.1143-1145
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• 1995

• Bulletin of the Korean Chemical Society
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• v.18 no.2
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• pp.238-239
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• 1997

• The Korean Journal of Nuclear Medicine
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• v.3 no.1
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• pp.13-18
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• 1969

• Restorative Dentistry and Endodontics
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• v.26 no.5
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• pp.418-435
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• 2001

Root canal preparation process is of utmost importance in successful treatment of root canal. Also, one of the most important purpose of the root canal preparation is to enlarge the root canal three dimensionally without changing the curvature of the root canal However as the curvature of the root canal increases, there are many difficulties involved in formation of optimum root canal. Therefore in order to solve the above mentioned problems, new developments in methods of root canal preparation and equipments for such purposes were made. Recently, vigorous studies about newly introduced engine-driven nickel-ti-tanium rotary file are conducted. As shown in research results to dates, it is well established that the use of nickel-titanium file is better suited for curved root canal than stainless steel file in maintaining the curvature or root canal and reducing the deformation of root canal. However it is also acknowledged that there are a few discrepancies in research results according to protocol, due to failure to remove variables in experiments. In addition, although it is recommended by the manufacturer that the GT rotary file should maintain a low rotational speed of 150~350rpm and 'light pressure' as light as not to break the lead of a pencil, academic studies about the vertical force which is not yet standardized are not sufficiently explored. Therefore, this research devised and utilized a special research equipment to standardize the appropriate range of vertical force for GT rotary file through experiments by breaking of the lead of a pencil as expressed by the manufacturer and to accurately measure factors involved through repeating and recreating the environment of root canal preparation. Forming nine experimental groups by varying the vertical forces (150g. 220g, 300g) and rpm (150rpm, 250rpm, 350rpm), the effects of changing vertical forces and rpm on working efficiency were measured in terms of time expended in root canal preparation by crown-down method using a transparent resin block with 35 degree curvature and GT rotary file (z-test). The following research using this special research equipment that involved nine experimental groups and varying the vertical force for root canal preparation from 300g which is within the normal vertical force range to 700g and 1000g which fall outside the normal rpm range. The results were as follows : 1. Analysis of the experiment results revealed that the time spent in root canal preparation decreased as the vertical forces and rpm increased (p<0.05). Also, the effects of rpm were greater than those of the vertical forces within the normal vertical force range ($\beta$-weight test). 2. Observation of the deformation of GT rotary file revealed that deformation increases in a direct correlation with the vertical force increase and in a reverse correlation with the rpm decrease. In the case of the vertical forces close to the normal range, the probability of GT rotary file deformation were quite different depending on the rpm changes. In the case of greater vertical forces, the occurrences of deformation of the file were more frequent regardless of the rpm changes. 3. Deformation and breakage of file were also commonly observed in the expended time measurement experiments and GT rotary file deformation experiments in which low speed rpm (150rpm) was used and at the curved portion of the resin block.

• Food Science and Biotechnology
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• v.18 no.5
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• pp.1230-1236
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• 2009

Optimum conditions for the freeze-thaw stability (FTS) of mung bean starch (MBS) paste as a main ingredient in omija-eui were investigated. For the optimization of the paste preparation condition, the FTS of MBS prepared by boiling in a shaking water bath (BMSW) or by pressure-cooking in an autoclave (PCMA) were analyzed using a response surface methodology (RSM). In addition, the effects of various additives such as gums, sugars, and emulsifier were evaluated on the FTS of MBS paste prepared under optimal conditions. The predicted maximal FTS of MBS paste prepared by the PCMA method (73%) was higher than that of the paste prepared by the BMSW method (36%). In case of additives, gellan gum and sodium alginate effectively prevented the syneresis of MBS paste in the BMSW method and in the PCMA method, respectively. The use of a fructose fatty acid ester as an emulsifier decreased syneresis in a dose-dependent, while the addition of sugars accelerated syneresis. Consequently, MBS paste for omija-eui preparation may be efficiently prepared by adding sodium alginate and fructose fatty acid ester under the optimal conditions of 4.3% MBS content, $121^{\circ}C$ heating temperature, and $89^{\circ}C$ cooling temperature by pressure-cooking in an autoclave.

• Journal of the Korean Geotechnical Society
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• v.22 no.11
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• pp.151-158
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• 2006

Centrifuge tests have shown that a uniformly placed sand layer will first initiate liquefaction near the surface and that liquefaction will progress downward during shaking. This appears to be in conflict with the overburden stress effect on soil liquefaction (i.e., $K_0$ effect) observed in laboratory testing. This discrepancy can be explained by stress-induced densification at depth which overcomes the effect of confining stress on liquefaction resistance. Stress densification occurs in centrifuge model tests but its effect has generally not been considered when preparing or evaluating centrifuge models. A new centrifuge model preparation method is proposed by considering stress-induced densification upon spin-up. The proposed method can be used to explore $K_0$ effects. The method is supported in this study by numerical predictions.

• Journal of the Korean Ceramic Society
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• v.25 no.2
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• pp.168-172
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• 1988

In order to prevent the PbO vaporization during calcination and to produce the powder of good sinterability, a coprecipitation method for preparing homogeneous Lead-Zirconate-Titanate (PZT) powder from aqueous salt solution is described. In this method, the PZT-ceramics show low calcining and sintering temperature, and they have good sintering and electronic properties.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.579-582
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• 2000

Enantiomerically pure hydroxycarboxylic acids have great potential as chiral building blocks in fine chemicals due to their easily modificable two functional groups. Microbial polyhydroxyalkanoates (PHAs) can have more than one hundred of hydroxycarboxylic acids as monomeric constituents by growing cells under various conditions. All of the monomeric constituents are enantiomerically pure in (R)-conformation if there is a chiral center. Therefore, efficient production of enantiomerically pure hydroxycarboxylic acids by degrading PHAs is possible. In this presentation, we report on the development of a novel method for the preparation of (R)-hydroxybutyric acid by in vivo depolymerization of Polyhydroxybutyrae.