• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6A
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• pp.625-639
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• 2009

Experimental and analytical studies are performed on the mechanical behavior of concrete-filled tubular(CFT) truss girders for different f/L ratios. Bending tests are conducted on two CFT truss girder specimens to determine fundamental structural characteristics such as the strength and deformation properties. Nonlinear material models for CFT members subjected to an axial compressive force are compared in this paper by using the nonlinear finite element program, ABAQUS. Previous researchers have proposed several nonlinear stress-strain models of confined concrete. In this study, the nonlinear analyses are performed applying several stress-strain models for confined concrete proposed by Mander, Sakino, Han, Susantha and Ellobody, and the results are compared with the experimental results in terms of load-deflection and load-strain relationships. Based on the comparisons of the load-deflection relationships, the models proposed by Mander and Susantha provide a maximum load about 12.0~13.8% higher and that by Sakino gives a maximum load about 7.6% higher than the experimental results. The models proposed by Han and Ellobody give a maximum load only about 0.2~1.2% higher than the test results, showing the best agreement among the proposed stress-strain models. However, the load-strain relations predicted by the existing models generally provide conservative results exhibiting larger strains than the experimental data.

• Applied Biological Chemistry
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• v.26 no.4
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• pp.222-230
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• 1983

This study was designed to develop a process for the immobilization of xylose isomerase(D-xylose ketol isomerase, EC 5.3.1.5) from Streptomyces griseolus previously isolated by the authors and its application on a pilot plant scale for the production of high fructose corn syrup. The biomass which has endo-excreted xylose isomerase was homogenized under a pressure of $500kg/cm^2$ and 90.8% of the enzyme recovery of the native activity was obtained as compared to 54.7% recovery by the lysozyme treatment. Ionic bonding method was adopted for the enzyme immobilization due to its many reported merits. It was found that the porous resins such as Diaion HP 20, Duolite A-7, Amberlite IRA 93 and 94 were effective in immobilizing the enzyme. In addition, it was disclosed that the regeneration form of $BO_4--$ is effective for Amberlite IRA 93 and $HCO_3-$ for Diaion HP 20. Optimal immobilization condition for Amberlite IRA 93 was pH 8.0 and $55^{\circ}C$ yielding 80.6% of immobilization. Activity decay test showed half life of the immobilized enzyme with Amberlite IRA 93 was more than 24 days at $65^{\circ}C$. The carrier was evaluated to be resuable and its result showed the relative immobilization yields were 98.2, 93.3, 90.7 and 87.5%, respectively at second, third, forth and fifth rebinding test of the enzyme on Amberlite IRA 93. Optimal temperature of the immobilized enzyme was slightly lowered and the range widened to $60\sim70^{\circ}C$, while optimal pH moved toward $8.0\sim8.3$ in its isomerization reaction. The trial production result of high fructose corn syrup in pilot scale immobilization showed that one liter of immobilized xylose isomerase (350 IXIU/ml-R) is capable producing about 293l high fructose corn syrup(75% dry substance) in 30 days.

• Restorative Dentistry and Endodontics
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• v.34 no.1
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• pp.61-68
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• 2009

This study was performed to assess the radiopacity of a variety of root canal sealers according to the specification concerning root canal sealers. Ten materials including Tubli-$Seal^{TM}$. Kerr Pulp Canal $Sealer^{TM}$, AH $26^{(R)}$, AH $plus^{(R)}$, AH plus $jet^{TM}$, Ad sea $1^{TM}$. $Sealer^{TM}$, $NOGENOL^{TM}$, ZOB $seal^{TM}$, $Epiphany^{TM}$ and dentin were evaluated in this study. In the first part, densitometric reading of an each step of aluminum step wedge on occlusal film was performed at different voltage and exposure time. In the second part, ten specimens were radiographed simultaneously with an aluminum step wedges on the occlusal films under decided condition. The mean radiographic density values of the materials were transformed into radiopacity expressed equivalent thickness of aluminum (mm Al). The following results were obtained. 1. Among the various conditions, the appropriate voltage and exposure time that meet the requirement density was 60 kVp at 0.2 s 2. All of the materials had greater radiopacity than 3 mm Al requirement of ANSI/ADA specification No. 57 (2000) and ISO No. 6876 (2001) standards. 3. The radiopacity of materials increased as thickness of materials increased. 4. The mm Al value of each specimen at 1mm in thickness has a significant difference in the statistics. It suggests that root canal sealers have a sufficient radiopacity that meet the requirement.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.3
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• pp.419-430
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• 2000

The purpose of this study was to compare the microleakage pattern of preventive resin restoration using conventional composite resin and flowable composite resin that recently developed. 60 sound premolar teeth were allocated to three groups. Flowable composite resin was used for the experimental groups(Group I and II) and conventional resin for the control group(Group III). After composite filling and sealant application, all teeth were thermocycled and evaluated for microleakage under light microscope. Additionally, a variety of voids formed inside restorations were also evaluated. Data were analyzed statistically using Kruskal-Wallis test and/or Mann-Whitney U-test. The results of the present study were as follows. 1. Microleakage found in all samples was only limited to the interface of restoration margin and enamel. 2. The flowable composite resin groups (Group I, II) generally showed less microleakage than control groups (conventional preventive resin restoration) (p<0.05) 3. Various types of voids were observed in most specimens. Especially, there was a tendency for more and larger voids to be found in group I, II than group III (p<0.05).

• Journal of Conservation Science
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• v.31 no.1
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• pp.37-46
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• 2015

In the case of adhesives & restoration agents currently being used for the preservation treatment of ceramics and earthenware, epoxy type, cellulose type and cellulose type are mainly being used. However, they are showing various problems such as re-detachment from severe contraction, color change from yellowing, work inconvenience of staining on tools and hand during usage and irreversibility. For the purpose of solving the issues of yellowing and irreversibility of epoxy resin being used to restore ceramics, urethane synthetic resin with low yellowing excellent reversibility has been developed in this study. The adhesive strength of urethane resin that has been developed has excellent properties with 2.07MPa for undiluted solution, which is 1.5 times higher than that of existing material EPO-$TEK301^{(R)}$ 1.21MPa. The result of workability measurement showed that the wear rate of urethane resin (in Talc 50wt%) was 1.09%, which was somewhat higher than that of existing material Quick $Wood^{(R)}$ (1.02%). In addition, its wear rate is two times higher than that of $EPO-TEK301^{(R)}$ (0.41%) and $L30^{(R)}$ (0.39%), thereby showing an advantage in its forming process compared to existing materials. As for the advantage of urethane resin of reversibility experiment, 12 hours after acetone, ethyl alcohol deposition, urethane resin and filler talc were dissolved 100% while showing powdering phenomenon. Compared to 0% reversibility of existing epoxy resin, it has much superior reversibility. The result of UV rays experiment to evaluate its durability showed that ${\Delta}E^*ab$ color change value based on undiluted solution of urethane resin was 2.76 before & after UV rays exposure, which was a decrease by about 7-20 times compared to that of existing resin, thereby minimizing the issue of heterogeneity.

• Korean Journal of Heritage: History & Science
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• v.42 no.1
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• pp.122-142
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• 2009

This study explored all domestic and international theories for maintenance and health enhancement of an old and big tree, and carried out the anatomical survey of the operation part of the tree toward he current status of domestic surgery and the perception survey of an expert group, and drew out following conclusion through the process of suggesting its reform plan. First, as a result of analyzing the correlation of the 67 subject trees with their ages, growth status. surroundings, it revealed that they were closely related to positional characteristic, damage size, whereas were little related to materials by fillers. Second, the size of the affected part was the most frequent at the bough sheared part under $0.09m^2$, and the hollow size by position(part) was the biggest at 'root + stem' starting from the behind of the main root and stem As a result of analyzing the correlation, the same result was elicited at the group with low correlation. Third, the problem was serious in charging the fillers (especially urethane) in the big hollow or exposed root produced at the behind of the root and stem part, or surface-processing it. The benefit by charging the hollow part was analyzed as not so much. Fourth, the surface-processing of fillers currently used (artificial bark) is mainly 'epoxy+woven fabric+cork', but it is not flexible, so it has brought forth problems of frequent cracks and cracked surface at the joint part with the treetextured part. Fifth, the correlation with the external status of the operated part was very high with the closeness, surface condition, formation of adhesive tissue and internal survey result. Sixth, the most influential thing on flushing by the wrong management of an old and big tree was banking, and a wrong pruning was the source of the ground part damage. In pruning a small bough can easily recover itself from its damage as its formation of adhesive tissue when it is cut by a standard method. Seventh, the parameters affecting the times of related business handling of an old and big tree are 'the need of the conscious reform of the manager and related business'. Eighth, a reform plan in an institutional aspect can include the arrangement of the law and organization of the old and big tree management and preservation at an institutional aspect. This study for preparing a reform plan through the status survey of the designated old and big tree, has a limit inducing a reform plan based on the status survey through individual research, and a weak point suggesting grounds by any statistical data. This can be complemented by subsequent studies.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.2
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• pp.273-284
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• 2007

The aim of this study was to evaluate the resistance to degradation and to compare the wear resistance characteristics of four esthetic restorative materials in an alkaline solution(0.1N NaOH). The composite resins studied were Composan LCM flow(Promedica, Germany). Clearfil ST(Kuraray medical, Japan), Durafi VS1(Heraeus Kulzer, U.S.A), Point 4(Kerr, U.S.A). The results were as follows : 1. The mass loss of each brand was $1.02{\sim}6.04%$ and highest value in Durafil VS$(6.04{\pm}0.29%)$. 2. The sequence of the degree of degradation layer depth was in descending order by Durafil VS, Clearfil ST, Point 4 and Composan LCM flow. There were significant differences between Point 4, Composan LCM flow and the others (p<0.001). 3. The sequence of the Si loss was in descending order by Clearfil ST, Durafil VS, Composan LCM flow and Point 4. There were significant differences among the materials (p<0.001). 4. On SEM, destruction of bonding between matrix and filler and on CLSM, the depth of degradation layer of specimen surface was observed. 5. The sequence of maximum wear depth was in descending order by Durafil VS, Composan LCM flow, Point 4 and Clearfil ST. There were no significant differences among the materials (p>0.001) 6. The correlation coefficient between Si loss and degradation layer depth (r=0.892, p<0.01) and Si loss and mass loss(r=0.736, p<0.01) were relatively high. These results indicate that hydrolytic degradation, wear and another factor may consider as evaluation factors of composite resins.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.471-479
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• 2001

The purpose of this study was to compare the effect of the high intensity halogen light $(850\sim1000mW/cm^2)$ with that of the conventional halogen light $(400mW/cm^2)$ on the hardness of composite resin. Three resin composites (Z-100, 3M, U.S.A. : Tetric Ceram, Vivadent, Liechtenstein; SureFil, Dentsply, U.S.A.) were filed in the stainless steel moulds which were 4mm in diameter and 2, 3, 4, and 5mm in depth, respectively. They were cured under the four different modes : (1) conventional mode, 40 seconds at $400mW/cm^2$; (2) 'ramp' mode, 10 seconds at 100 to $1000mW/cm^2$ plus 10 seconds at $1000mW/cm^2$; (3) 'boost' mode, 10 seconds at $1000mW/cm^2$; and (4) 'standard' mode, 20 seconds at $850mW/cm^2$. The surface hardnesses of the top and the bottom of the resin samples were measured with a microhardness tester (MXT70, Matsuzawa, Japan). The top surface hardness was not significantly different among the curing modes. The bottom surface hardness was generally the highest in the conventional mode and the lowest in the high intensity boost mode. There was no significant difference in the bottom surface hardness between the conventional mode and the high intensity standard mode in 2mm depth. The results suggest that the curing time of the high intensity halogen light $(850mW/cm^2)$ should be at least 20 seconds to produce the equal level of the bottom surface hardness of 2mm resin composite as compared to the hardness produced by the conventional halogen light $(400mW/cm^2)$.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.190-201
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• 2004

The aim of this study was to evaluate the resistance to degradation and to compare the wear resistance characteristics of four esthetic restorative materials in an alkaline solution. The brands studied were Charmfil, Charmfil flow(composite resin), Compoglass F and PrimaFlow(compomer). The results were as follows: 1. The mass loss were not significantly different among the materials(p>0.05). 2. The sequence of the degree of degradation layer depth was in descending order by Compoglass F, PrimaFlow, Charmfil, and Charmfil flow. There were significant differences between Compoglass F and the others(p<0.05). 3. The sequence of the Si loss was in descending order by Charmfil flow, Charmfil, PrimaFlow, and Compoglass F. There were significant differences among these materials(p<0.05). 4. When observed with SEM, destruction of bonding between matrix and filler was observed and when observed with CLSM, the depth of degradation layer of specimen surface was observed. 5. The sequence of maximum wear depth was in descending order by Comfoglass, PrimaFlow Charmal, and Charmfil flow. There were significant differences among these materials(p<0.05). 6. The correlation coefficient between Si loss and degradation layer depth (r=0.602, p<0.05) Vicker's hardness number and maximum wear depth (r=0.501, p<0.05) were relatively high. These results indicate that wear and hydrolytic degradation may be considered to be evaluation factors of composite resins and compomers.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.3
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• pp.557-568
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• 2005

The aim of this study was to evaluate the resistance to degradation and to compare the wear resistance characteristics of four esthetic restorative materials in an alkaline solution(0.1N NaOH). The brands studied were MetafilCX(Sun medical, Japan) Solitaire 2(Heraeus Kulzer, USA), Composan LCM(Promedica, Germany), DenFil(Vericom, Korea). The results were as follows: 1. The mass loss of each brand was 0.74~7.94% and highest value in Metafil($7.94{\pm}0.39%$). 2. The sequence of the degree of degradation layer depth was in descending order by Metafil, Solitaire 2, DenFil, Composan LCM. There were significant differences between Metafil and the others(p<0.05). 3. The sequence of the Si loss was in descending order by Metafil, Solitaire 2, Composan LCM, DenFil. There were significant differences among the materials(p<0.05). 4. On SEM, destruction of bonding between matrix and filler and on CLSM, the depth of degradation layer of specimen surface was observed. 5. The sequence of maximum wear depth was in descending order by Metafil, Solitaire 2, Composan LCM and DenFil. There were significant differences among the materials(p<0.05). 6. The correlation coefficient between Si loss and degradation layer depth (r=0.491, p<0.05) and Vicker's hardness number and maximum wear depth (r=-0.942, p<0.05) were relatively high. These results indicate that hydrolytic degradation and wear may consider as a evaluation factors of composite resins.