• Journal of Digital Convergence
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• v.19 no.3
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• pp.245-251
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• 2021

This study was to investigate the effect of the new surface treatment method of zirconia on the shear bond strength with resin cement. The zirconia specimens were classified according to the surface treatment. CON: non-treatment, HF: 10 minutes exposure to 9% HF, ZS15: Apply 15% ZrO2 slurry, ZS30: Apply 30% ZrO2 slurry, ZS50: Apply 50% ZrO2 slurry. The resin cement was layered on the surface treated zirconia, and the shear bond strength between the zirconia and the resin cement was measured after thermo-cycling. The statistical methods for shear bond strength were Kruskal-Wallis test, Mann-Whitney U test, and Bonferroni correction(α=.05/10=.005). ZS15, ZS30, and ZS50 groups treated with zirconia slurry showed higher shear bond strength than CON and HF groups(p<.05/10=.005). Within the limits of this study, the surface treatment using zirconia slurry increased the shear bond strength with resin cement. The new surface treatment method complements and improves the limitations of the adhesion of zirconia, so that various clinical applications of zirconia can be expected.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.655-660
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• 2002

Major deterioration in concrete structures are salt attack and carbonation. Especially severe problems due to carbonation occur in tile concrete structures of city, tunnel, underground structures. Cracks in concrete during service life including early age due to hydration heat and/or shrinkage accelerate the diffusion of concrete so that the deterioration is also accelerated. In this study, carbonation depths of both non-cracked concrete and cracked concrete are evaluated and weight change test and TGA are carried out. Through the tests, a relation between water-cement ratio and carbonation depth is derived and also carbonation increase rate is derived in the function of crack width.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.233-238
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• 1998

For substitution for crushed sand, high strength aggregate for cement and concrete using coal ash as a main material was prepared and then compared its physical properties with those of crushed sand. Effect of mix proportion change of raw materials on the property of aggregate was checked. On the basis of these experimental results we are going to comprehend the reutilization of coal ash and utilize a basic data for judging possibility the substitution of crushed sand.

• Computers and Concrete
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• v.9 no.1
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• pp.35-50
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• 2012

The 2D representative volume element (RVE) for softening quasi-brittle materials like concrete is determined. Two alternative methods are presented to determine a size of RVE in concrete subjected to uniaxial tension by taking into account strain localization. Concrete is described as a heterogeneous three-phase material composed of aggregate, cement matrix and bond. The plane strain FE calculations of strain localization at meso-scale are carried out with an isotropic damage model with non-local softening.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.753-756
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• 2005

Recently, the alkali activation of Fly-ash has become a significant field of research because it is possible to use these materials having highly chemical reaction property. Also, the product does not generate CO2 gas, unlike ordinary Portland cement(O.P.C). Therefore, the purpose of this paper is to design for improving mechanical and chemical properties using Fly-ash and Meta-kaolin. And additive(CaO) affected to control the strength behaviors and shrinkage rate.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.247-253
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• 1997

This study performed the experimental research comparing mechanical characteristics of the concrete replaced by the waste glass powder with the non-replaced concrete. The experimental parameters are kinds of the waste glass powder and replacement rate of the waste glass powder on the cement. As as result, the slump value, the flow value and the amount of air were decreased as the waste glass powder replacement rate increased, and the strength was increased when the waste glass powder replacement rate is 5%~15%.

• Proceedings of the Korea Contents Association Conference
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• 2013.05a
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• pp.101-102
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• 2013

시멘트 및 건설산업은 그 제조과정에서 다량의 이산화탄소를 배출하기 때문에 지구온난화 문제를 가속화시키고 있는 것으로 알려져 있다. 따라서 이러한 시멘트를 대체할 수 있는 재료 개발에 많은 연구가 이루어지고 있으며, 철강산업 부산물인 고로슬래그 미분말은 그 중 하나의 재료라 할 수 있다. 고로슬래그 미분말은 물과 직접 반응하지 않으나 알칼리 환경하에서는 물과 반응하여 CSH 수화물을 생성하게 된다. 본 연구에서는 알칼리 자극제를 첨가한 경우의 무시멘트 경화체에 대한 강도 및 수화 특성에 대하여 분석하고자 하였다.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.329-334
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• 1997

Most of domestic pavement were non-permeable. However, in foreign country although it wasn't entirely satisfied, porous pavement was partially utilized with footpaths and soft-roadways. In this study, experiments were carried out to investigate the properties fundamental of porous concrete pavement. As a result of experiments, it was concluded that the coefficient of permeability was increased in proportion to continuous void ratio and decreased in proportion to S/a ratio and unit cement contents. On the other hand, the strength of porous concrete pavement was in inverse proportion to the void ratio.

• Journal of Plant Biology
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• v.28 no.4
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• pp.329-332
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• 1985

A simple new device for obtaining very clear epidermal imprints for light microscopic studies is discussed. This new device is developed from“Britfix”(polystyrene cement) which is non-toxic to the plant organs. It involves direct application of the material on the desired surface of the plant organ to obtain thin, transparent replica. From the present investigation“Britfix”is found to be useful for the study of epidermal anatomy, morphology and physiology. Epidermal imprints can be mounted on the microscope slide without a mounting medium. Permanent slide of these imprints can be kept for any desired period without any deterioration of the replica.

• The Journal of Asian Finance, Economics and Business
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• v.4 no.1
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• pp.5-18
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• 2017

Total debt in the People's Republic of China surged to nearly 290% as a ratio to GDP by the second quarter of 2016, mostly on account of non-financial corporate debt. The outpouring of credit to stem the impact of the global financial crisis accentuated industrial overcapacity in traditional sectors, such as steel, cement, and energy, while feeding asset bubbles in the property, equity and bond markets. At the Chinese corporate level, this has translated into weakened fundamentals and a fall in industrial profits, particularly of SOEs. As debtors struggle to service interest payments, non-performing loans (NPLs) have been on the rise. This paper assesses the financial fragility of the Chinese economy by looking at risk factors in the non-financial sector. We apply quantile regressions to a dataset containing all Chinese listed companies in Standard & Poor's IQ Capital database. We find higher sensitivity over time of corporate leverage to some of its key determinants, particularly for firms at the upper margin of the distribution. In particular, profitability increasingly acts as a curb on corporate leverage. At a time of falling profitability across the Chinese non-financial corporate sector, this eases the brake on leverage and may contribute to its continuing increase.