• Restorative Dentistry and Endodontics
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• v.33 no.4
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• pp.377-388
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• 2008

The aim of the present study is to compare the corrosion tendency using two kinds of NiTi files in the various environmental conditions through the visual examination and electrochemical analysis. ProTaper Universal S2, 21 mm (Dentsply Maillefer, Ballaigues, Switzerland) and Hero 642, 0.06 tapers, size 25, 21 mm (Micromega, Besancon, France) rotary instruments were tested. The instruments were randomly divided into eighteen groups (n = 5) by the immersion temperature, the type of solution, the brand of NiTi rotary instrument and the presence of mechanical loading. Each file was examined at various magnifications using Scanning Electron Microscope (JEOL, Akishima, Tokyo, Japan) equipped with energy dispersive X-ray microanalysis (EDX). EDX was used to determine the components of the endodontic file alloy in corroded and noncorroded areas. The corrosion resistance of unused and used NiTi files after repeated uses in the human teeth was evaluated electrochemically by potentiodynamic polarization test using a potentiostat (Applied Corrosion Monitoring, Cark-in-Cartmel, UK). Solution temperature and chloride ion concentration may affect on passivity of NiTi files. Under the conditions of this in vitro study, the corrosion resistance is slightly increased after clinical use.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4542-4551
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• 2013

Recently, much attention has focused on the study of eco-friendly concrete using recycled by-products for protecting marine ecosystem and durability of concrete exposed to marine condition. This study evaluated the durabilities of 4 different type of concrete mixtures(Control, Marine, Porous, New slag) with the seawater resistance by marine environment exposure experiment and freeze-thaw resistance, resistance to chloride ion penetration considering severe deterioration environment. In this study, we conducted seawater resistance using compressive strength according to the age(7/28/56 days) of specimen and curing conditions(standard(fresh water), tidal, immersion, artificial seawater). The results show that compressive strength of concrete exposed to marine environment exposure condition was lower than those of the standard curing condition. Also, compressive strength of New slag using eco-friendly materials for protecting marine ecosystem was lower than those of other concretes, there is need to improve the performance of New slag. The results for freeze-thaw resistance showed that all mixtures have excellent, but the Porous and New slag were lower than others. Also, the more improved resistance to chloride ion penetration than those of the Marine was measured in the New slag regardless of curing condition.

• The Korean Journal of Malacology
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• v.29 no.3
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• pp.251-258
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• 2013

This study aims to find out a suitable cryoprotective agent (CPA) for cryopreservation and its optimum concentration in order to conduct planned artificial seed production of Pacific oyster, Crassostrea gigas and to preserve superior sperm. For this, we tried to understand toxicity and the effect of cryopreservation by CPA type and concentrations first and then looked into cell damage of the sperm after thawing. Toxicity analysis on the sperm of Pacific oyster according to different CPA and immersion time shows that dimethyl sulfoxide (DMSO) comes first when it comes to survival rate and mobility followed by ethylene glycol (EG), glycerol and methanol. To identify the optimum CPA and its level, filtered seawater was used as a diluent before cryopreservation for 30 days. As a result, cryopreserved sperm of Pacific oyster with 15% of DMSO showed the highest survival rate and activation. Also, we observed the cryopreserved and thawed sperm with Scanning electron micrographs by CPAs and concentrations. Consequently, DSMO showed the lowest cell damage followed by EG, methanol, glycerol and the level was 15, 20, 10, 5% respectively. In a nutshell, it is proven that the optimum CPA and its level is 15% of DMSO.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.1
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• pp.76-84
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• 2019

This study evaluated the microleakage of three restorative materials and three tricalcium silicate-based pulp capping agents. The restorative materials were composite resin (CR), resin-reinforced glass ionomer cement (RMGI), and traditional glass ionomer cement (GIC) and the pulp capping agents were TheraCal $LC^{(R)}$ (TLC), $Biodentine^{(R)}$ (BD), and $ProRoot^{(R)}$ white MTA (WMTA). Additionally, shear bond strengths between the pulp-capping agents and dentine were compared. Class V cavities were made in bovine incisors and classified into nine groups according to the type of pulp-capping agent and final restoration. After immersion in 0.5% fuchsin solution, each specimen was observed with a stereoscopic microscope to score microleakage level. The crowns of the bovine incisors were implanted into acrylic resin, cut horizontally, and divided into three groups. TLC, BD and WMTA blocks were applied on dentine, and the shear bond strengths were measured using a universal testing machine. The microleakage was lowest in TLC + GIC, TLC + RMGI, TLC + CR, and BD + GIC groups and highest in WMTA + RMGI and WMTA + CR groups. The shear bond strength of BD group was the highest and that of WMTA group was significantly lower than the others.

• Journal of Digital Convergence
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• v.20 no.4
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• pp.575-584
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• 2022

The purpose of this study is to derive interaction types that appear variously in immersive contents through John Dewey's empirical theory, and to explore how the derived types are delivered in real cases. For this reason, two cases of the National Museum of Korea 'Immersive Digital Gallery' and 'Arte Museum Jeju' were analyzed through interaction types derived from the empirical theory. The interaction types derived based on the experience theory are the elements of 'multi-sensory', 'simultaneous experience' and 'sensory expansion'. In both cases, these types appear connected rather than grafted one by one in common. In one direction, 'multi-sensory' leads to 'sensory expansion', and in two directions, 'simultaneous experience' leads to 'sensory expansion'. As such, the core types of communication between technology and humans are not delivered one by one, but a cycle of interaction is formed in multiple ways. Therefore, it can be seen that the interaction type of immersive contents is expanded step by step by fusion of various senses and experiences in various fields, rather than a 1:1 partial delivery method. Based on this, it will be necessary to study how types are expanded and how viewers are affected when interaction is implemented in immersive contents in the future.

• Journal of the Korean GEO-environmental Society
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• v.23 no.3
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• pp.15-22
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• 2022

This study aims to observe the swelling representative rocks in Korea and to suggest improvements in the use of test methods and prior analysis in relation to the weathering of rocks. The swelling test and analysis were performed on the drilling cores obtained for the ground investigation at the domestic highway construction site. For the method of determining the absorption expansion index of rocks, the method proposed in "Standard Methods for Sample Collection and Specimen Preparation" of ISRM and Korean Rock Engineers Standard Rock Test Method was used. The specimen for the measurement of the expansion displacement was cylindrical with a height of 10 cm and a diameter of 5 cm. The existing swelling analysis method evaluates the sensitivity to weathering by using the maximum expansion displacement, but since the classification by bedrock grade is unclear, it is reasonable to use the rate of change of the expansion displacement according to the immersion time. It is necessary to conduct an experiment to distinguish between weathering and fault deterioration. In addition, long-term weathering prediction technology for each cancer type is needed through the expansion displacement analysis of the chemical weathering stage.

• Design Convergence Study
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• v.15 no.2
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• pp.17-35
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• 2016

Along with popularization of smart phone and routinization of social network service, enterprises are using several social network services as a marketing channel to raise brand awareness and conduct PR. Enterprises have been utilizing an element of 'Gamification' representing a functional aspect and emotional pleasure of a game in order to attract users' attention and increase their voluntary participation since the early social network service marketing. However, social network service system contains functional roles of Gamification components rather than they function separately. Hence, this research intends to examine Gamification elements of social network service and characteristics occurred when enterprise uses several social network services as a marketing channel. Besides, it aims at suggesting a marketing guideline for Gamification based on social network that may induce users' interest and increase an immersion effect. Firstly, this study examined concepts and characteristics of social network service and Gamification centered on literature research. Secondly, it summarized a game mechanics, dynamics and a fun type of Gamification components. Thirdly, based on theoretical research, it collected Gamification marketing cases of 5 enterprises including 'Coca Cola Korea', 'Lotte Mart', 'Canon Korea', "Kolon Sports' and 'Uniqlo Korea' that utilize more than 3 of 4 social network services including 'Kakao Story', 'Band', 'Facebook' and 'Instagram' used the most in our nation, analyzing characteristics of Gamification marketing and deriving a suggestion. Finally, it suggested a guideline for Gamification and social network service to build a foundation for a Gamification marketing plan through social network service.

• Journal of Intelligence and Information Systems
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• v.29 no.4
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• pp.207-228
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• 2023

After COVID-19, organizations have widely adopted platforms such as zoom or developed their proprietary online real-time systems for remote work, with recent forays into incorporating the metaverse for meetings and publicity. While ongoing studies investigate the impact of avatar customization, expansive virtual environments, and past virtual experiences on participant satisfaction within virtual reality or metaverse settings, the utilization of the metaverse as a dedicated workspace is still an evolving area. There exists a notable gap in research concerning the factors influencing the performance of the metaverse as a workspace, particularly in non-immersive work-type metaverses. Unlike studies focusing on immersive virtual reality or metaverses emphasizing immersion and presence, the majority of contemporary work-oriented metaverses tend to be non-immersive. As such, understanding the factors that contribute to the success of these existing non-immersive metaverses becomes crucial. Hence, this paper aims to empirically analyze the factors impacting personal outcomes in the non-immersive metaverse workspace and derive implications from the results. To achieve this, the study adopts the Embodied Social Presence (ESP) model as a theoretical foundation, modifying and proposing a research model tailored to the non-immersive metaverse workspace. The findings validate that the impact of presence on task engagement and task involvement exhibits a moderating effect based on the metaverse platform used. Following interviews with participants engaged in non-immersive metaverse workplaces (specifically Gather Town and Ifland), a survey was conducted to gather comprehensive insights.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.82-90
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• 2009

Statement of problem: Recently, as patients' expectation and interest for esthetics are increasing, concerns of esthetic restoration for removable dentures as well as fixed prosthodontics are also increasing. And the color stability of artificial teeth will affect a long term success rate of the denture. But the stain or discoloration of these artificial teeth as well as denture resin has caused esthetic problem. Purpose: This study was designed to evaluate the influence on color stability of artificial teeth when soy sauce, red pepper paste and coffee which many Koreans have eaten were applied. Material and methods: For artificial teeth type(Endura $Anterio^{(R)}$, Physio $Duracross^{(R)}$, Trubyte $Biotone^{(R)}$) selected for the study, 10 specimens each were soaked into individual beakers of soy sauce, red pepper paste, coffee and distilled water. And $L^*$, $a^*$, $b^*$ value were measured for evaluation of the color difference (${\Delta}E^*$) with spectrophotometer on the 1 day, 1 week, 2 weeks, 4 weeks and 8 weeks after immersion. Results: 1. ${\Delta}E^*$ value of artificial teeth which were soaked in soy sauce and coffee was various according to soaking periods. However there was significant difference between Trubyte $Biotone^{(R)}$ and Physio $Duracross^{(R)}$ in red pepper paste regardless of soaking period(P<.05). 2. Except for 8 weeks of Endura $Anterio^{(R)}$, 4 weeks and 8 weeks of Physio $Duracross^{(R)}$, artificial teeth soaked in red pepper paste regardless of the type had significant difference of ${\Delta}E^*$ value compared with other groups (P<.05). 3. $a^*$, $b^*$ value of Endura $Anterio^{(R)}$ and Trubyte $Biotone^{(R)}$ which were soaked in red pepper paste had significant difference compared with the value of other group(P<.05). Conclusion: Red pepper paste had the greatest effect on color difference of artificial tooth. Physio $Duracross^{(R)}$ showed relatively less color difference than Trubyte $Biotone^{(R)}$ and Endura $Anterio^{(R)}$. But as ${\Delta}E^*$ difference were all less than 3.3, these artificial resin teeth seemed appropriate for clinical use.

• Restorative Dentistry and Endodontics
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• v.23 no.2
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• pp.561-574
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• 1998

The purposes of this study were to observe the difference in the root canal wall after hand instrumentation or engine-driven Ni-Ti instrumentation under the scanning electron microscope, and to evaluate the apical leakage provided by continuous wave of canal filling technique with or without root canal sealer and smear layer. Twenty recently extracted human maxillary anterior teeth were instrumented with K-type files or engine-driven Ni-Ti files, Quantec series 2000$^{TM}$ and irrigated with 5.25% NaOCl alone or 15% EDT A and final flush of 5.25% NaOCl. After the instrumentation and flushing, teeth were split in half with a knife and a mallet. They were then examined with a scanning electron microscope Forty-four recently extracted human maxillary anterior teeth were divided into four groups with and without smear layer and then warm vertical canal filling using System-B with or without sealer. The extent of leakage was scored after immersion in India ink for 1 week. The results were as follows: 1. No significant difference of smear layer was observed between K-type file-instrumented group and engine-driven Ni-Ti file-instrumented group. 2. A group without smear layer showed significantly less apical leakage than a group with smear layer when sealer was used for the canal filling (p<0.01). 3. There was no significant difference between a group without sealer and smear layer and a group without sealer and with smear layer (p<0.01). 4. In groups without smear layer, a group with sealer showed significantly less apical leakage than a group without sealer (p<0.01). 5. When root canals were irrigated with NaOCl alone, a group with sealer showed significantly less apical leakage than a group without sealer (p<0.01).