• Journal of Conservation Science
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• v.37 no.6
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• pp.767-777
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• 2021

This study analyzed the microstructures and chemical composition of three samples of bronze mirrors excavated in the Jeollanam-do region, particularly Goheung and Damyang. Under x-ray irradiation, the analysis results confirmed the broken parts and pores caused by cracks, casting, and corrosion. Major and minor elemental analysis were performed on three mirrors by Scanning electron microscopy (SEM) with Energy dispersive x-ray spectrometry (EDS) and Inductively coupled plasma mass spe ctrome try (ICP-MS). The re sult shows that the bronze mirrors containe d Cu-Sn-Pb alloys. Alpha phase and eutectic phase were observed in the microstructure, confirming that the casting was performed without additional heat treatment. Notably, Three bronze mirrors were made early Three Kingdoms period in Korea.

• Conservation Science in Museum
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• v.28
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• pp.1-16
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• 2022

Treatment was performed to conserve the Underwood Typewriter (Hangi 6863) from the collection of the National Hangeul Museum. Since the typewriter was presumably manufactured in the modern or contemporary era and bore patterns of damage such as component loss, corrosion, and paint loss, as well as being made of multiple materials, a condition survey and a scientific analysis were conducted ahead of the conservation treatment in order to carry out appropriate treatments for each material. The analysis confirmed that the typewriter was made of various materials including metal, paint, and rubber, and the conservation treatment was performed in the sequence of removal of contamination, reinforcement, and restoration under conditions where each material was stable. Conservation treatment was completed in a stable state by strengthening the layer of damaged paint and restoring the lost leg. These processes have enabled a better understanding of the materials and characteristics of typewriters manufactured in the early modern era, which is expected to provide basic data for typewriter conservation research to be conducted in the future.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.61-69
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• 2009

Statement of problem: Porcelain veneers have become a popular treatment modality for aesthetic anterior prosthesis. Fitting porcelain veneers in the mouth usually involve a try-in appointment, which frequently results in salivary contamination of fitting surfaces. Purpose: An in vitro study was carried out to investigate the effect of silane treatment timing and saliva contamination on the resin bond strength to porcelain veneer surface. Material and methods: Cylindrical test specimens (n=360) and rectangular test specimens (n=5) were prepared for shear bond test and contact angle analysis. Whole cylindrical specimens divided into 20 groups, each of which received a different surface treatment and/or storage condition. The composite resin cement stubs were light-polymerized onto porcelain adherends. The shear bond strengths of cemented stubs were measured after dry storage and thermocycling (3,000 cycles) between 5 and $55^{\circ}C$. The silane and their reactions were chemically monitored by using Fourier Transform Infrared Spectroscopy analysis (FTIR) and contact angle analysis. One-way analysis of variance (ANOVA) and Dunnett's multiple comparison were used to analyze the data. Results: FT-IR analysis showed that salivary contamination and silane treatment timing did not affect the surface interactions of silane. Observed water contact angles were lower on the saliva contaminated porcelain surface and the addition of 37% phosphoric acid for 20 seconds on saliva contaminated porcelain increased the degree of contact angle. Silane applied to the porcelain, a few days before cementation, resulted in increasing the bond strength after thermocycling. Conclusion: Within the limitation of this study, it can be concluded that it would be better to protect porcelain prosthesis before saliva contamination with silane treatment and to clean the contaminated surface by use of phosphoric acid.

• Progress in Medical Physics
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• v.16 no.4
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• pp.214-219
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• 2005

As part of Korean retinal prosthesis project, we have provided preliminary experimental results regarding voltage parameters for the stimulation of chemically degenerated rabbit retina. Since our APB-treated chemically degenerated retina is only ON-pathway blocked, now we switch our experiments to more appropriate retinal degeneration model, genetically degenerated retina model (RD mouse: rd/rd (C3H/HeJ)). Before studying with RD mouse, we started control experiments with normal SD rat to understand characteristics of retinal ganglion ceil activity with postnatal maturation in rodents. Ganglion cell activities were recorded with 8${\times}$8 multi-electrode array. Moving spontaneous bursts appeared until postnatal day of 15. During pre-eye opening period, no light evoked response appeared. After postnatal day of 2 weeks (post-eye opening period), ON-, OFF- and ON/OFF response appeared. The fractional distributions of ON, OFF, and ON/OFF ganglion cell is about $40\%,\;50\%$, and $5\%$. The percentage ($\%$) of light evoked response in each dorso-temporal, ventral, and dorso-nasal area of eye is about $50\%,\;37.5\%$ and $12.5\%$, respectively. We concluded that the optimal period for experiment in rodent is about postnatal day of 2${\~}$3 weeks.

• Korean Journal of Heritage: History & Science
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• v.43 no.3
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• pp.334-365
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• 2010

Mother-of-Pearl craftwork sketch involves the whole process of making a piece of work. Therefore, it includes types, forms, sizes, and patterns of the work. Some information about when and by whom those works were manufactured and who ordered them are still found in some sketches. This paper seeks to find out popular types and patterns of the works in each period and its demand and the way of supply by examining the collection of approximately 1700 Mother-of-Pearl craftwork sketches from the period of Japanese colonization up to the present time, which are owned by Mr. Song Bang-wung, Important Intangible Cultural Heritage no.10. Typical patterns of sketches are the hua-jo(花鳥 : Flowers and Birds), the Sakunja(四君子 : Four Gracious Plants), cultural treasures, figures in folk tales, 'Su-bok(壽福)' characters, and landscape. The pattern sketches have changed according to the circumstances of Korean society. During the period of Japanese colonization from the 1920s to the 1940s the manufacture and the supply and demand of Mother-of-Pearl craftworks were controled by the Japanese government. As a result, many of the patterns were adjusted to the Japanese taste. Most of its customers were also Japanese. During the 1950s after Independence the American Military Forces appeared as new customers due to the Korean War. Thus, the traditional Korean patterns to decorate accessories adored by American soldiers gained popularity. Foreign Mother-of-Perls were imported from the late 1960s to the 1970s. They were bigger and more colorful than those of Korean and it enabled the sketches bigger and the patterns more various. The most popular pattern in this period was the pattern of cultural treasures, such as an image of Buddha, metalcraft works, porcelains and pagodas. In terms of a technique, new techniques, such as engraving and rusting were introduced. There was a great demand for Mother-of-Pearl craftworks in the 1970s as people were highly interested in them. They were entirely made to order and there was a large demand from diverse organizations, furniture dealers and individuals. And the Mother-of-Pearl craftwork was in full flourish in the 1970s due to the country's economic development and the growth of national income. Mass production of the works was possible and the professional designers who drew patterns actively worked in this period. The favor of Mother-of-Pearl craftworks declined in the 1980s since the built-in furniture and the Western style of furniture became prevalent due to the change of housing into apartments. But it seemed that the manufacture of Mother-of-Pearl craftworks revived for once the technique of Kunum-jil(끊음질 : cutting and attaching) became popular in Tong-young(統營). After the 1990s, however, the making of Mother-of-Pearl craftworks gradually declined as the need of them decreased. Now it barely maintains its existence by a few artisans.

• Journal of the Mineralogical Society of Korea
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• v.24 no.3
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• pp.235-244
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• 2011

A batch experiment of pyrite oxidation was performed and the surfaces of the reacted pyrite were regularly observed with the scanning electron microscope (SEM) together with the chemical compositions of the solution to help understand the oxidation mechanisms of pyrite by Acidithiobacillus ferrooxidans (Af). The dissolved Fe concentrations clearly indicated that Af experiences the lag and then exponential growth phase. An Af cell was observed to be attached to the surface of pyrite during the lag, implying that a direct leaching by the microbe really happens for the period. It is not certain, however, whether the main mechanism of pyrite oxidation during that time was the direct leaching or not, because there were just a few cells confirmed to be attached and most of the dissolved Fe was Fe(III). The dissolved Fe concentration stayed almost constant from the mid-lag phase to just before the onset of the exponential phase, suggesting that AI needs an adaptation time to switch its oxidation mechanism from one to the other whichever it is during that stage of growth. The moment of Af's cell division was observed by SEM on the surface of pyrite during the lag phase. The corrosion outline around the dividing cell was quite similar to the shape of the cell itself, which implies that the rate of the microbial oxidation is very uneven and the rate when the cell metabolizes should be much faster than that calculated from the concentration variation of the dissolved Fe. The number of etch holes by Af is much higher on the inoculated surfaces, indicating the average rate of pyrite oxidation is also much faster than that of abiotic oxidation. The microbial etch holes on pyrite surface are small and deep, which may influence the transition of the growth phases of Af from lag to exponential.

• Journal of dental hygiene science
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• v.6 no.3
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• pp.153-158
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• 2006

Bleaching of vital and nonvital teeth is becoming a more commonly used treatment in the dental office and at home. To improve appearance and remove discoloration, the teeth of specific patients are treated with a variety of bleaching agents. The typical bleaching agents contains carbamide or hydrogen peroxide as the active component. The purpose of the review article was to summarize and discuss the available information concerning the effect of peroxide releasing bleaching agent on dental restorative materials and restorations. Information from all original scientific full papers or reviews listed in PubMed or ISI Web Science were included in the review. Bleaching may exert a negative influence on restorations and restorative materials. Advice is provided based on the current literature to minimize the impact of bleaching treatment on restorative materials and restorations.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.679-686
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• 2005

The corrosion of reinforcement induced by chloride ingress is the main deterioration cause of coastal reinforced concrete structures. In this paper, an experimental study was executed to investigate the effect of the kinds and replacement ratios of mineral admixtures (fly-ash, ground granulated blast-furnace slag silica fume and meta-kaolin), W/B and curing time on chloride diffusion of concrete by long-time immersion test in chloride solution. According to the result, the use of mineral admixtures was effective in improving the resistant to chloride ingress. The chloride penetration depth and diffusion coefficient were decreased as replacement ratios of mineral admixture were increased. The kind and replacement ratio of the mineral admixture are more important than the W/B in reducing the chloride diffusion of concrete. Chloride binding capacity of mineral admixture, which was sequenced in the order of MK

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.606-614
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• 2003

The major cause of deterioration for the concrete bridge decks exposed to de-icing chemicals would be chloride-induced reinforcement corrosion. Thus, in this paper, in order to predict time to corrosion for concrete bridge decks in the urban area, chloride concentration was measured with depth from the surface. A frequency analysis on surface chloride concentration and chloride diffusion coefficient of concrete bridge deck equals 0.192, 29.828 in the scale parameter and 7.899, 1.983 in the shape parameter of gamma distribution. The average value of surface chloride concentration equals 1.5 kg/㎥ and condenses from 1 to 2 kg/㎥ in the level of probability 70%. From the probabilistic results, it is confirmed that 26mm of minimum cover depth in order to target 20 years over is calculated. The countermeasure strategy to extend the service life of concrete bridge deck exposed to de-icing chemicals would be an effective method to increase cover depth and to place high performance concrete, which could lead to reduce the chloride diffusion coefficient and distribution range.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.529-540
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• 2003

Recently, the researches on the durability design of concrete structures have been studied. As the examples, models to evaluate the service life prediction of the structure have been developed. The purpose of this article is to develop the model for predicting remaining service life. The final aim is to provide the user time for repairing the concrete structures. In addition, it makes possible to maintain the concrete structure economically. 70 reservoirs out of the inland concrete structures were selected and concrete structures of their components were surveyed. Two methods were used for measuring carbonation; TG/DTA method and Phenolphtalein indicator and, the value of pH was measured by the pH meter, After deriving correlations of calcium carbonate and used year, duration from completion year to 2002, pH value, and concrete cover depth the model was developed for predicting remaining service life by measuring data as small as possible. The conventional models had been developed on the basis of experiment data obtained from the restricted lab environment like as carbon gas exposure. On the other hand this model was developed on the basis of measuring data obtained from the real field that the complex deterioration actions are occurred such as freezing and thawing, carbonation, steel corrosion, and so on. The reliability of the developed model will be evaluated high in this point and this model can help to maintain concrete structures economically by providing the manager time to repair the deteriorated concrete structures in site of facility management.