• Restorative Dentistry and Endodontics
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• v.33 no.4
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• pp.397-404
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• 2008

The purpose of this study was to evaluate the effects of MTAD, EDTA and sodium hypochlorite(NaOCl) as final irrigants on coronal leakage resistance to Enterococcus faecalis. Forty extracted human maxillary molars were used in this experiment. The teeth were randomly divided into positive control group (Group 1; n = 5), negative control group (Group 2; n = 5) and three experimental groups (n = 30). In Group 3 (n = 10), the root canals were irrigated with sodium hypochlorite. In Group 4 (n = 10) and 5 (n = 10), the root canals were irrigated with sodium hypochlorite and rinsed with EDTA and MTAD, respectively. The teeth in each group were cleaned and shaped to #40 profile with .04 taper, and obturated with gutta-percha and AH-26 root canal sealer. The coronal portion of each tooth was placed in contact with inoculum of Enterococcus faecalis in Brain Heart Infusion (BHI) culture media. Each root tip was placed in a vial containing sterile culture media. The vials were placed in anaerobic chamber and observed everyday for turbidity for 180 days. Statistical analysis was performed using Fisher's Exact Test. After 180 days, Group 3, 4, and 5 showed 7, 4 and 5 leaking samples respectively. The differences in leakage resistance were not statistically significant among Group 3, 4 and 5.

• Restorative Dentistry and Endodontics
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• v.31 no.4
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• pp.290-299
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• 2006

Objectives: The purpose of this study is to evaluate the effect of ethylene glycol analogs on modulus of elasticity and ultimate tensile strength of moist, demineralized dentin matrix. Methods: Dentin disks 0.5 mrn thick were prepared from mid-coronal dentin of extracted. unerupted, human third molars. 'I' beam and hour-glass shaped specimens were prepared from the disks, the ends protected with nail varnish and the central regions completely demineralized in 0.5M EDTA for 5 days. Ultimate tensile stress (UTS) and low strain modulus of elasticity (E) were determined with specimens immersed for 60 min in distilled water $(H_{2}O)$, ethylene glycol $(HO-CH_{2}-CH_{2}-OH)$, 2-methoxyethanol $(H_{3}CO-CH_{2}-CH_{2}-OH)$, and 1,2-dimethoxyethane $(H_{3}CO-CH_{2}-CH_{3}-OCH_{3})$ prior to testing in those same media. Modulus of elasticity was measured on the same specimens in a repeated measures experimental design. The results were analyzed with a one-way ANOVA on ranks, followed by Dunn's test at ${\alpha}\;=\;0.05$. Regression analysis examined the relationship between UTS or E and hoy's solubility parameter for hydrogen bonding $({\delta}_{h})$ of each solvent. Results: The UTS of demineralized dentin in water, ethylene glycol, 2-methoxyethanol, and 1,2-dimethoxyethane was 24 (3), 30 (5), 37 (6), and 45 (6) MPa, ${\times}$ (SD) N = 10. Low strain E for the same media were 16 (13), 23 (14), 52 (24), and 62 (22) MPa. Regression analysis of UTS vs ${\delta}_{h}$ revealed a significant $(p\;<\;0.0001,\;r\;=\;-0.99,\;R^{2}\;=\;0.98)$ inverse, exponential relationship. A similar inverse relationship was obtained between low strain E vs ${\delta}_{h}\;(p\;<\;0.0005,\;r\;=\;-0.93,\;R^{2}\;=\;0.86)$. Significance: The tensile properties of demineralized dentin are dependent upon the hydrogen bonding ability of polar solvents $({\delta}_{h})$. Solvents with low ${\delta}_{h}$ values may permit new interpeptide H-bonding in collagen that increases its tensile properties. Solvents with high ${\delta}_{h}$ values prevent the development of these new interpeptide H-bonds.

• Journal of computational fluids engineering
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• v.21 no.4
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• pp.33-39
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• 2016

Generally, thermal analysis of spent fuel storage cask has been conducted using the porous media and effective thermal conductivity model to simplify the structural complexity of spent fuel assemblies. As the fuel assembly is composed of two regions; active fuel region corresponding to UO2 pellets and unactive fuel region corresponding to the top and bottom nozzle, the heat transfer performance can be influenced depending on porous media application at these regions. In this study, numerical analysis on concrete storage cask of spent fuel was performed to investigate heat transfer effects for two cases; one was porous media application only to active fuel region(case 1) and the other one was porous media to whole length of fuel assembly(case 2). Using computational fluid dynamics code, the three dimensional, 1/4 symmetry model was constructed. For two cases, maximum temperatures for each component were evaluated below the allowable limits. For the case 1, maximum temperatures for fuel cladding, neutron absorber and baskets inside the canister were slightly higher than those for the case 2. In particular, even though the helium flows with low velocity due to buoyant forces occurred at the top and bottom of unactive fuel region, treating only active fuel region as the porous media was ineffective in respect of the heat removal performance of concrete storage cask, implying a conservative result.

• The Journal of the Korea Contents Association
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• v.22 no.2
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• pp.187-197
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• 2022

This study examined the effects of game genre, news media with differing political ideologies, and game-related information sources on gamer issue participation by performing a hierarchical regression model, using an online survey on Korean gamers (N=1,362). As a result of the study, playing specific genres of games played a positive role in gamer issue participation. The group behavior or collective action for or against game regulation reported in the liberal/moderate media acted as a mobilization cue for readers and potentially encouraged gamers to take social action. But the conservative media, which used governmental organizations and interest groups as sources of information, had a negative impact on real-life participatory behavior. The biased journalism practice of the mass media on game-related social issues influenced gamers' social and political behavior through corrective action. This study is significant in empirically analyzing the relationship between political ideology, game genre, media use, and gamers' social participation. The current research suggests the improvement of game regulation policy and the need for theoretical and conceptual expansion of game research.

• Restorative Dentistry and Endodontics
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• v.32 no.2
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• pp.87-94
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• 2007

This study was done to evaluate transportation of the apical foramen after 0.5 mm overinstrumentation by ProFile, ProTaper and $K^3$ in simulated resin root canal. Sixty simulated resin root canal with a curvature of J and S-shape were divided into two groups. Each group consisted of three subgroups with 10 blocks according to the instruments used: $ProFile^{(R)},\;ProTaper^{TM},\;and\;K^{3TM}$. Simulated resin root canal was prepared by ProFile, ProTaper and $K^3$ with 300 rpm by the crown-down preparation technique. Pre- and post-instrumentation apical foramen images were overlapped and recorded with Image-analyzing microscope 100X (Camcope, Sometech Inc, Korea). The amounts of difference in width and dimension on overlapped images were measured after reference points were determined by Image Analysis program ($Image-Pro^{(R)}$ Express, Media Cybernetic, USA). Data were analyzed using Kruskal-Wallis and Mann-Whitney U-test. The results suggest that ProFile showed significantly less canal transportation and maintained original apical foramen shape better than $K^3$ and ProTaper.

• Journal of Digital Convergence
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• v.15 no.11
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• pp.85-95
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• 2017

The news media report the pledges of presidential candidates, which have important implications for political communication. This study is to investigate the difference between news coverage on the presidential candidate' s pledge and to discuss its implications. The sampled news from the two newspapers were analyzed for content analysis. Frequency analysis and Chi-square analysis are utilized with SPSS. As results, there was no difference in the tone of the article's headlines, but the difference of the tone between the article content was statistically significant. The results means that the media framing affect on the reader's perception. Follow - up study can be suggested a comparative study of past election candidates 'pledge reports, a network analysis for the news language, and a comparative analysis of newspaper coverage and broadcast coverage.

• The Journal of the Korea Contents Association
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• v.15 no.5
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• pp.179-190
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• 2015

This study discusses on the influential factors of satisfaction in communication by focusing on the political communication phenomenon that is revealed in our society. The acts of political communication and its communication satisfaction are examined by exploring individuals' political inclination and their media usage which are the main influential factors of political communication. An interview survey was conducted on a thousand adults over the age of nineteen who are residing in sixteen cities and provinces nationwide. As a result, a high rate of online media usage was observed among people with progressive political inclination. It showed that the political communication acts of 'writing/communicating' which indicates ons actively posting their personal opinions, has a positive influence on communication satisfaction. On the other hand, the usage of offline media was dominant over people with conservative and neutral political inclination. A passive act of 'reading/watching,' which is to observe other people's opinions, was shown by most of the interviewees. Therefore, it was able to discuss that in order for a harmonious flow of political communication among our society, the understanding of citizens' political characteristic must be preceded and the differentiated political communication using media must be raised accordingly.

• Restorative Dentistry and Endodontics
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• v.8 no.1
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• pp.133-137
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• 1982

Radiography is one of the important tool adopted in daily dental practice and medical diagnosis. To visualize soft tissuechange various contrast media has Been introduced. Any cavity or space can be easily determined by increasing the X-ray absorption of the cavity using the radiopaque contrast media which widely employed in medical radiography to show much of the digestive, cardiovascular, pulmonary, and renal system. The essential part of any radiopaque medium is a heavy element that can absoarb most of the X-ray beam. The element must be noninjurious and easily eliminated. Both aqueous and oil suspensions of iodine containing compounds' are available to the dental profession, for example Lipiodol and Dionosil. The study was designed to determine toxic effect of Lipiodol to the vital pulp and to confirm visualization ioprovement in pulp canal. 1. Thin mixture of Calcium hydroxide and Lipiodol was applied to 19 deep vital cavities for 24 hours. Only one case complained slight pain for short time. 2. Cotton pellet over-saturated in Lipiodol was inserted in coronal chamber of which 6 were non vital and 5 were vital. The transference of Lipiodol was not noticed in every case after 24 hours. 5 cases with vital pulp tissue in the canals showed no clinical symptome. 3. Extracted 20 teeth were routinely prepared for endodontic treatment and applied Lipiodol in conjunction with cotton fiber as deep as midportion of the roots. After 24, hours the medicament reached to nearly the end of apex, but there were no evidence of penetration in dentine layer and migrate into ramified canal.

• Journal of Internet Computing and Services
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• v.20 no.2
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• pp.77-91
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• 2019

This paper explores the hyperlink structures of the official websites for the following terrestrial TV networks: ABC(US), BBC(UK), NHK(Japan), and KBS(Korea). These websites were selected and visualized to analyze the hyperlink structure and examine the connection relations among the TV networks. A total of 4378 data was collected through the Voson site and were analyzed with NodeXL. Results shows that NHK's network demonstrates a good network structure at a quite high level, holding more related websites than BBC. We discovered that ABC TV network has the largest effect with the largest number of out-links. Surprisingly, structures of BBC and NHK were quite similar, overcoming geographical and cultural differences. Thus, both TV networks were seen to be progressive and open. On the contrary, ABC and KBS were considered to be relatively conservative. A comprehensive review of the "category points" combination chart revealed that NHK's official website has the widest variety of hyperlinks. The shortest distance of a hyperlink between a website type and a TV network meant that the TV network has a larger number of links to those website types than other TV networks do. The result may provide Internet users to efficiently select TV network web pages according to the types of information they want to find out.

• The Journal of the Convergence on Culture Technology
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• v.8 no.5
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• pp.459-468
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• 2022

This study searched and analyzed news and information on the Korea-U.S. Summit to explore which political agenda is spreading among Korean newspapers and social media. The result of the analysis revealed that, on the one hand, the conservative-leaning newspaper, Chosunilbo, covered the unresolved issue between two countries. The principal source of news was the opposition party. On the other hand, the progressive-leaning newspaper, Kyunghany Sinmun, highlighted President Moon's visit to the United States and described the visit to the United States as an achievement. In this paper, the principal source of news is the ruling party. Both conservative and the progressive newspapers did not present a negative view of the United States. In the case of Chosunilbo, it mentioned that foreign policy priority of President Biden is human rights in North Korea. If the two countries do not solve this issue, the relationship between Korea and the United States will not develop further. Second, I searched YouTube videos about the Korea-U.S. summit and conducted a network analysis to understand the influence of YouTube videos and explore their relationship the each other. The results of the analysis revealed that the 10 most influential videos portrayed the Moon government positively. These videos held the achievement of the visit to the United States in highly esteem and framed it positively, similarly to the progressive newspaper.