• Journal of the Korean Ceramic Society
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• v.55 no.3
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• pp.299-306
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• 2018

In order to improve the hardness of commercial bone china, we suggested a chemical strengthening process and new glaze for its process. New glaze contained about two times more $Na_2O$ and $Al_2O_3$ and had a higher transition temperature than that of commercial frit. Chemical strengthening enhanced the hardness of the new glaze-coated bone china by over 30% compared to that of commercial product. The change of glaze composition influenced potassium ion diffusion distance and depth of strengthened layer during chemical treatment. After chemical strengthening of new glaze-coated bone china, the residual compressive stress inside the glaze was measured and found to be greater than 160 MPa.

• Journal of the Korean Ceramic Society
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• v.56 no.5
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• pp.483-488
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• 2019

We studied whether chemical strengthening can heal the flaws on soda-lime silicate glass. Artificial surface cracks were introduced on the glass by sharp indentation with various loads of 0.1 to 10 N. Then, the glasses with flaws were treated by ion-exchanging in KNO₃ melt. The change in the dimension of the crack on glass was measured by a digital microscope and a scanning electron microscope. The chemical strengthening treatment enhances the strength of the glass with flaws. It is thought that the melted KNO₃ not only forms the depth of the compressed layer of 7.5 ㎛, but also heals the cracks by infiltrating them and expanding the glass on both sides of the cracks. The critical length (2c) of the cracks on soda-lime glass that can be healed by chemical strengthening is 50 ㎛ or less.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.508-513
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• 2015

In order to improve the hardness of commercial bone china, we attempted to control the glost firing temperature and apply a chemical strengthening process. When the glost firing time was longer or its temperature was higher than normal conditions, the hardness was improved by approximately 5%. The chemical strengthening process also enhanced the hardness of the glaze by more than 13% compared with bone china. It is believed that the enhancement of the hardness of the glaze was related to the development of residual compressive stress in the glaze due to 1) the increase in the calcium phosphate phase in the interface layer between the body and the glaze after firing, and 2) the increase of the $K^+$ concentration on the glaze surface during the chemical strengthening process.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.5
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• pp.35-42
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• 2014

Many historical archives have been deteriorated by aging with time. Various kinds of defects such as worm-hole, yellowing, brittleness are observed and their severity was dependent on raw material type, storage condition, and so on. For a long-term use and storage, a proper preservation treatment is required. Many studies on preservation and conservation have been carried out on hanji which was made from mulberry fiber, but there are few concerns on foreign paper. Therefore, aging and chemical strengthening treatment was done on paper made of bamboo and wood fibers depending on aging condition, the type and pickup weight of chemicals and treatment method. When methyl cellulose was treated with impregnation or brushing, the aged paper was strengthened effectively. The strengthening effect by chemicals was dependent on the aged condition of the paper.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.6
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• pp.145-151
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• 2014

The glass used for mobile display windows is required to have high strength. Chemical strengthening by means of ion exchange is widely used glass. The depth of the layer and the compressed stress are affected by tempering temperature and time. The purpose of this study is to investigate the range of DOL and CS, which to less breakage during reliability tests such as the ball drop test, hole drop test, 3-point bending test, drop test, and tumble test with Soda-lime Glass.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.149-158
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• 2010

Recently, numerous construction techniques for repairing and strengthening methods for above ground or air exposed concrete structure have been developed. However repairing and strengthening methods for underwater structural members under continuous loading, such as piers and steel piles need the further development. Therefore, this study develops an aqua epoxy, which can be used for repairing and strengthening of structural members located underwater. Moreover, using the epoxy material and strengthening fibers, a fiber reinforced composite sheet called Aqua Advanced FRP (AAF) for underwater usage is developed. To verify and to obtain properties of the material and the performance of AAF, several tests such as pull-off strength test, bond shear strength test, and chemical resistance test, were carried out. The results showed that the developed aqua epoxy does not easily dissolve in wet conditions and does not create any residual particle during hardening. In spite of underwater conditions, it showed the superior workability, because of the high viscosity over 30,000 cps and adhesion capacity over 2 MPa, which are nearly equivalent to those used in dry conditions. In case of the chemical resistance test, the developed aqua epoxy and composite showed the weight change of about 0.5~1.0%, which verifies the superior chemical resistance.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.501-502
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• 2009

This paper presents a strengthening technique of weakened telegraph pole using an inflating agent to adjust chemical pre-stressing. The strengthening technique increases only resisting capacity and ductility of telegraph but also limited quantity and application ability of FRP. The chemical pre-stressing and the resisting capacity are investigated experimentally. From the results, it is confirmed that it is possible to control the degree of applied pre-stressing by controlling the amount of inflating agent. In addition, the pre-stressing can increase resisting capacity up to three times compared with no pre-stressing.

• Journal of the Korean Ceramic Society
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• v.52 no.2
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• pp.133-136
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• 2015

The outward diffusion of $Na^+$ ions in iron-bearing soda lime silicate glass via oxidation heat treatment before the ion exchange process is artificially induced in order to increase the amount of ions exchanged during the ion exchange process. The effect of the addition process is analyzed through measuring the bending strength, the weight change, and the inter-diffusion coefficient after the ion exchange process. The glass strength is increased when the outward diffusion of $Na^+$ ions via oxidation heat treatment before the ion exchange process is added. For the glass subjected to the additional process, the weight change and diffusion depth increase compared with the glass not subjected to the process. The interdiffusion coefficient is also slightly increased as a result of the additional process.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.3
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• pp.285-293
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• 2015

Objectives: This study was conducted in order to ascertain the important factors for SMEs in managing the risks of chemicals and to suggest a government role in strengthening the responsibility of small and medium enterprises(SMEs) as employers. Methods: About 100 enterprises were surveyed in Incheon. A questionnaire for employers and walk-through surveys by occupational hygienists were performed at each enterprise. Results: The results showed that most employers thought chemicals were not hazardous but chemical management was needed. When employers determine how to manage chemicals, they rely heavily on personal experience and rather less on information from the government or experts. However, if employers think the chemicals are hazardous, they do more to manage the chemicals. Conclusions: When employers think chemicals are hazardous, risk assessment would be an effective tool to control chemical hazards in SMEs. Employers' position on chemical hazards is very important. Since the government is the initiator, it is the government who develops messages for SMEs, such as "Chemicals are hazardous and management can reduce the risk of chemicals." Governmental messages can play an invaluable role in strengthening the responsibility of SME employers to manage chemical hazards.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.4
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• pp.49-58
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• 2011

The maximum drying shrinkage velocity was proposed to verify bulk and stiffness improvement mechanism during drying according to papermaking parameters. It was based on the wet-web shrinkage behavior without the restraint of wet-web during drying, so intact drying impact could be measured. Bulking agent reduced the drying shrinkage and the maximum drying shrinkage velocity, so paper bulk increased and paper strength decreased. When adding cationic starch to stock with the bulking agent for strengthening, the bulk was increased further with additional decreasing of the drying shrinkage and the maximum drying shrinkage velocity. Paper strength also increased except tensile stiffness index with decreasing the drying shrinkage and the maximum drying shrinkage velocity. When using additional strength additives for strengthening of fiber interfaces extended by bulking agent and cationic starch, amphoteric strength additive increased paper stiffness without loss of paper bulk. It was considered that the added amphoteric strength additives were cross-linked to the stretched cationic starch and this cross-linking increased elasticity of fiber-polymer-fiber interfaces without changing the drying behavior. Paper bulk could be increased with decreasing the maximum drying shrinkage velocity. The drying shrinkage of paper also could be controlled by fiber-to-fiber bonding interfaces by the bulking agent. In this case, paper strength including stiffness was decreased by reducing fiber-to-fiber bonding but it could be improved by strengthening fiber-to-fiber interfaces with polymer complex without loss of bulk.