• Journal of Electrochemical Science and Technology
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• v.15 no.2
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• pp.242-252
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• 2024

To date, methods used to assess the interfacial transition zone (ITZ), which represents the boundary between the aggregate and paste inside concretes, have primarily relied on destructive tests, and non-destructive tests has received little attention until recently. This study assessed the interfaces of concretes with lightweight aggregates based on electrochemical impedance spectroscopy (EIS) for high-strength concretes and examined the possibility of estimating the compressive strength of concretes through non-destructive testing using EIS. The experimental results revealed that the impedance of the hardened cement increased with increasing compressive strength and aggregate density. In particular, when the results of impedance measurement were displayed as a Nyquist plot, the intercept of the x-axis depicting the effective conductivity was proportional to the compressive strength. Furthermore, an equivalent circuit was selected to interpret the correlation between cement aggregates and impedance. Consequently, the compressive strength was found to increase with the value of the resistances of the electrolyte filled in continuous pores in the cement aggregate. And, the pores formed in the ITZ affect this value. The resistance at the ITZ for different aggregates was also obtained, and it was found that the resistance was consistent with the results predicted by SEM images of the ITZ and correlated with the strength of the concretes. The proposed method can be used as a way to easily determine the strength of cement according to differences in aggregate.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.4
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• pp.515-522
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• 1993

The purpose of this study was to evaluate the bond strength of rebase resin to denture base resin. The denture base resins in this study were Premium Super-20(Lang Dental Mfg. Co. Inc., Wheeling, USA) and Lucitone 199(Dentsply International Inc., York, USA). And the rebase resins were Repair Acrylic(Lang Dental Mfg. Co. Inc., Wheeling USA). Toughron Rebase(Miki Chemical Product Co. Ltd., Japan) , Tokuso Rebase(Tokuyama Soda. Co. Ltd., Japan) and Triad VLC Reline Material(Dentsply International Inc., York, USA). The obtained results were as follows : 1. The bond strength of Repair Acrylic to Premium Super-20, and that of Toughron Rebase to Lucitone 199 were the highest. 2. In Premium Super-20 and Lucitone 199, bond strength of all rebase resins had significant differences. 3. The bond strength of Triad VLC Reline Material was inclined to the lowset.

• Journal of the Korean Home Economics Association
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• v.33 no.6
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• pp.179-186
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• 1995

The purpose of this paper was to identify bonding strength by weave (plain weave, twill weave, satin weave) and counts(20 s, 40s) of the face cloth cotton 100% in the course of sewing process using by cotton fabric of adhesive interlining. The results of the study was as follows. 1. With the increased laundry, it revealed that the bonding strength was decreased to some degree regardless of the kinds of face cloth. 2. the bonding strength by the counts of the face cloth appeared in order of 40 s<20 s. 4. It was observed that there are no significant differences on the adhesive strength in the cutting directions which are an inclination warp, weft, bias in this experiment.

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.280-288
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• 1996

The purpose of this study was to assess comparatively the shear bond strength on dentin of four dentin bonding agents used in conjunction with light-curing composite resins. Clearfil New Bond, Scotchbond Multipurpose Dentin Adhesive, All-Bond 2 and X-R Bond were applicated on labial dentin surfaces just below dentin - enamel juction of bovine incisor teeth. After shear bond strength testing with the universal testing machine, the bonding interface of the specimens were observed under light stereomicroscope. Following results were obtained. 1. The shear bond strength was high in the order of B,C,D,A and group B Scotchbond Multipurpose Dentine Adhesive revealed greater bond strength than Clearfil New Bond and X-R Bond. (p<.001) 2. When using ANOVA and Duncan's multiple range test, there were statistical differences among the four groups, except between group Band C,group D and A. 3. There was no relationship between mode of failure and shear bond strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1091-1096
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• 2001

Generally, in a steel girder and the concrete slab act as a composite structure, the connectors must have adequate strength and stiffness. If there are no horizontal or vertical separations at the interface, the connectors are described as rigid, and complete interaction can be said to exist under these idealized circumstances. In previous study, it was considered that the strength of stud is affected by the stud diameter, height of stud and compressive strength of concrete. The differences between previous study and this study are variables, which are shank diameter of shear connector, the spacing of shear connector, the size of specimen and the row of shear connector. So this paper, as a study on the strength of shear connector with the spacing of shear connector, size of specimen (block-out size), row of shear connector and shank diameter of shear connector resulted from the push-out specimen are conducted with ABAQUS program. It is to investigate the effects of characteristics of these factors. The load-slip relations obtained from the experiments are compared with those of analyses. From these results, the trends of stress are stress estimated and compared with push-out test.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.655-660
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• 2002

The purpose of this study is to analyze void ratio, coefficient of water permeability, and strength characteristics when silica fume and carbon fibers were added in order to improve the strength of porous concrete, and when recycled aggregates were used. Comparing with the case that recycled aggregate was not used, as the replacement ratio of recycled aggregate increased, the differences in void ratios and strength characteristics were decreased. In the case that silica fume was used, the content of 10% silica fume was most effective in improving strength. In the case that carbon fibers were used, the content of 3% carbon fiber were good to achieve the highest flexural strength, and Pan-derived CF was much better than pitch-derived CF in improving these effects.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.89-90
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• 2018

The strength of cement mortar is one of the most important factors in design and construction. Strength can vary widely depending on factors such as water cement ratio, aggregate and materials and curing. In the study, it was found that the standardized method of making the cement mrtar was different from the standard method of preparing the cement mortar by the different process of the cement mortar. I wanted to know the difference. Experiments were carried out to investigate the differences in strength, physical properies and performance depending on the points when the sample were made long in vertical form.

• IE interfaces
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• v.12 no.1
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• pp.150-157
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• 1999

Mini-Mill process has been recently in operation at Pohang steel company, which enables more flexible steel coil production on customer demands. The effects of process parameters in Mini-Mill process need to be analyzed not only to make the process stable but also to improve product quality. This work aims to develop a regression model of Mini-Mill process using accumulated product data such that the process parameter effects on product tensile strength may be analyzed. The analysis shows that tensile strength is influenced mainly by the amount of components such as carbon, manganese, silicon, and sulfur. The effect of temperature is shown to be small. It is concluded that control of the components is much more responsible for both meeting the target and reducing the variation of the product tensile strength. Heat treatment is more useful in compensating tensile strength variations due to thickness differences and improving workability and other quality characteristics. More work is necessary for establishing regression expressions of the process that is reliable and accurate enough to dispense with the off-line inspection of the product tensile strength.

• Journal of Korean Clinical Health Science
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• v.6 no.2
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• pp.1199-1204
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• 2018

Purpose. This study was conducted to find out about the differences in the women's ability to balance women in the movement to strengthen their lower extremities. Methods. The study was a functional reach test and Y Balance test, to examine the static and dynamic balance of women in their 20s who do not have a surgical history at H University. For the strengthening of the lower strength, the lower leg muscles were reinforced by half squats and the thera band movement. The SPSS ver.18.0 Wilcoxon test was used to see the difference in balance as an analysis. Results. The results of the study showed a statistically significant difference in balance ability before and after the intervention. Conclusions. Steady low-strength campaigns can improve muscle strength and balance, and further improve quality of life.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.85-94
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• 1999

It was investigated to evaluate the characteristics of cement-flyash paste which was affected the replacement level, curing method and chemical admixtures. The strength of cement-flyash paste was lower than that of cement paste only and the differences increased with increasing the replacement level. However, in steam curing, the strength of cement-flyash pastes was improved and specially, the early strength was effectively increased. The inclusion of $Na_2SO_4$ increased the early strength of cement-flyash paste. In addition, the strength of concrete including 30% of fly ash and $Na_2SO_4$ has improved and obtained the highest strength compared to other concrete mixes.