• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.87-92
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• 2011

This paper describes a study on the permeability reduction of the riverbed ground during urban railway tunnel construction. The research is mainly concentrated on the study of the grouting or injection methods among permeability reduction methods which can be adapted in the riverbed ground. The design technology of grouting methods considering the long term hydro-geological behaviour in the riverbed, was suggested. Two injection methods namely, Natural Durable Stabilizer (N.D.S) and Space-Multi Injection Grouting (S.M.I) methods, were introduced as new approach methods which could be adapted to modify the riverbed ground. In order to evaluate the performance of the improved ground by the N.D.S and S.M.I method, a series of pilot tests including the field and laboratory permeability tests, were carried out in the river crossing tunnel construction sites. The results obtained from pilot test program, were also reviewed. The results, the grouting efficiency of the S.M.I method using the non-alkalimeter silica sol is better than that of N.D.S method using cement. In addition, it is anticipated that the current research results are contributed to develop the grouting design technology.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.2
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• pp.185-194
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• 2018

The objective of this study was to compare the shear bonding strength of zirconia after cleaning the crown contaminated by saliva or blood and determine the effect of thermocycling. 180 specimens were embedded in acrylic resin. 20 Specimens in the positive control group were bonded with resin cement without contamination. 20 Specimens in the negative control group were washed with water for 20 seconds and then dried for 10 seconds. 120 Specimens contaminated by saliva or blood were cleaned by using three cleaning methods: 37% phosphoric acid gel, commercial cleanse, and 2.5% NaOCl. All samples were bonded with resin cement and divided into two subgroups: One was not aged, and the other was tested with 30,000 thermocycling. In both groups contamination by saliva and blood, no statistically significant difference was not found in control, groups cleansed by commercial cleanser and 2.5% NaOCl. When the groups cleansed with water and 37% phosphate gel were compared with the control, significantly low shear bond strength was shown. Thermocycling group showed statistically significantly low shear bond stress compared to the groups without thermocycling. When zirconia was contaminated by saliva or blood, its original shear bond strength could be obtained if it was cleaned with commercial cleanser or 2.5% NaOCl.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.551-557
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• 2007

This paper describes a study on the permeability reduction of the riverbed ground during urban railway tunnel construction. The research is mainly concentrated on the study of the grouting or injection methods among permeability reduction methods which can be adapted in the riverbed ground. Firstly, the various grouting methods are theoretically reviewed and compared based on the previous research papers and case study results. It is also evaluated the grouting methods in view of a safe construction of the river crossing railway tunnel. Baced on the literature review and previous construction data, the design technology of grouting methods considering the long term hydro-geological behaviour in the riverbed, is suggested. Two injection methods namely, Natural Durable Stabilizer(N.D.S) and Space-Multi Injaction Grouting(S.M.I) methods, are introduced as new approach methods which can be adopted to modify the riverbed ground. In order to evaluate the ground that grouted and modified by the N.D.S and S.M.I method, the pilot test programmes including the field and laboratory permeability tests, are carried out in the river crossing tunnel construction sites. The results obtained from pilot test programme, are also reviewed. In conclusion, the grouting efficiency of the S.M.I method using the non-alcalimeter silica sol is better than that of NDS method using cement. In addition, it hopes that the research results are contributed to develop the grouting design technology.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.4
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• pp.509-518
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• 2002

The purpose of this study was to evaluate the bonding of compomer to deciduous dentin which is known to have been developed to improve the weak properties of glass ionomer cement and composite resin. 120 sound primary molars were used for the shear bond strength test and another 24 for the scanning electron microscopic evaluation. Each material was ailed into polyethylene mold attached to exposed dentinal surface($3{\times}4mm$ in diameter) of sample blocks. Shearbond strength was measured using Universal testing machine and data were analyzed statistically with Oneway-ANOVA and Scheffe test. Scanning electron microscopic observation was performed in order to evaluate the pattern of distribution and penetration of resin tags and hybrid layer. Compomer groups(II-V) showed significantly higher bond strength values than glass ionomer group(I)(p<.05). Etching-compomer groups(III, V) showed the significantly higher bond strength than non-etching compomer groups(II, IV)(p<.05), but slightly lower values than composite resin group(VI) with no statistically significant difference(p>.05). No significantly different bond strength was found between compomer groups of different bonding system(p>.05). Scanning electron micrographs showed more irregular distribution of short and thin resin tags in non-etching compomer groups(II, IV) whereas the more regular and intimate distribution of long and thick tags in etching compomer groups(III, V) and composite resin group(VI). The evaluation of hybrid layer also showed more regular formation of thicker layer in etching compomer groups(III, V). Based on the results of present study, the use of compomer as an esthetic restorative material for primary molars might be justified.