• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.37 no.2
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• pp.122-126
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• 2011

Introduction: In the lateral window approach for a maxillary sinus bone graft, there has been considerable controversy regarding the placement of a barrier membrane over the osteotomy site. In particular, when there is no damage to the Schneiderian membrane, clinicians should decide whether to use a barrier membrane or not, considering the benefits and costs. This study presents the clinical cases to demonstrate that only repositioning the detached window can lead to satisfactory bony healing of the grafted material without using a barrier membrane in the lateral approach for a maxillary sinus bone graft. Materials and Methods: Five consecutive patients were treated with the same surgical procedures. After performing the antrostomy on the lateral maxillary wall using a round carbide bur and diamond bur, the bony window was detached by a gentle levering action. After confirming no perforation of the Schneiderian membrane, the grafting procedure was carried out the detached window of the lateral maxillary wall was repositioned over the grafted material without using a barrier membrane. A gross examination was carried out at the postoperative 6 month re-entry, and the the preoperative and postoperative dental computed tomography (CT) at re-entry were compared. Results: All the procedures in the 5 patients went on to uneventful healing with no complications associated with the bone graft. Satisfactory bone regeneration without the interference of fibrous tissue on the gap between the repositioned window and lateral wall of the maxillary sinus was observed in the postoperative 6 month re-entry. The CT findings at re-entry revealed the, reconstruction of the external cortical plate including repositioned bony window. In addition, the loss of the discontinuity of the lateral maxillary wall was confirmed. Conclusion: This preliminary report showed that the detached window, which was just repositioned on the grafted material, could function as a barrier membrane in the lateral approach for a maxillary sinus bone graft. Therefore additional morphometric and histologic studies will be needed.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.1
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• pp.52-60
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• 2005

Purpose. The intent of this study was to evaluate the effects of curing conditions on self-curing denture base resins to find out proper condition in self-curing resin polymerization. Materials and methods, In this study, 3 commercial self-curing denture base resins are used Vertex SC, Tokuso Rebase and Jet Denture Repair Acrylic. After mixing the self curing resin, it was placed in a stainless steel mold(3$\times$6$\times$60mm). The mold containing the resin was placed under the following conditions: in air at 23$^{\circ}C$; or in water at 23$^{\circ}C$; or in water at 23$^{\circ}C$ under pressure(20psi); or in water at 37$^{\circ}C$ under pressure(20psi) or in water at 50$^{\circ}C$ under pressure(20psi) , or in water at 65$^{\circ}C$ under pressure(20psi), respectively. Also heat-curing denture base resin is polymerized according to manufactures' instructions as control. Fracture toughness was measured by a single edge notched beam(SENB) method. Notch about 3mm deep was carved at the center of the long axis of the specimen using a dental diamond disk driven by a dental micro engine. The flexural test was carried out at a crosshead speed 0.5mm/min and fracture surface were observed under measuring microscope. Results and conclusion . The results obtained were summarized as follows : 1. The fracture toughness value of self-curing denture base resins were relatively lower than that of heat-curing denture base resin. 2. In Vertex SC and Jet Denture Repair Acrylic, higher fracture toughness value was observed in the curing environment with pressure but in Tokuso Rebase, low fracture toughness value was observed but there was no statistical difference. 3. Higher fracture toughness value was observed in the curing environment with water than air but there was no statistical difference. 4. Raising the temperature in water showed the increase of fracture toughness.

• Journal of The Korean Association For Science Education
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• v.35 no.2
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• pp.333-342
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• 2015

This study analyzes the verbal interaction patterns used in a social network activity analysis that appeared in a science inquiry activity of 31 small groups of science-gifted students consisting of 5 members each. The results of this study are as follows: The interaction patterns showed eight types. The most prevalent interaction pattern, type 1, is triangle-shaped, interacting with 3 members out of 5 without a central member. Type 2 is wye form, interacting with 4 members and with one alienated member. Type 3 is diamond-shaped, interacting with 4 members. Type 4 is ray form, interacting with 5 around a central member. Type 5 has an alienated member and interacts with 4 members around the central member. Type 6 is triangle-branched, 4 members linked to the central member. Type 7 is wye form linked all around the central member. Type 8 is wye form with a more complex link than type 7. These can be classified in two. One is the participation-type where the rest of the 4 members are linked to the central member. The other is the alienation-type where a member/members is/are alienated without a central member. The participation-type appeared in 9 groups (29%), type 4, type 6, type 7, and type 8. The alienation-type showed in 22 groups (71%), type 1, type 2, type 3, and type 5. On the basis of this study, we propose that the best number of members in a group is three. It helps prevent a free-riding effect or isolation of members. Also, we deem it more fruitful if there is a member playing a central role in a group.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.4
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• pp.283-292
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• 2007

Two-step or one-step bonding systems generally inhibit curing process of dual-cured core build-up resin composite for their adhesive acidity. In addition this dual-cured core build-up resin composite can be applied to dentin of pulp chamber and root at the time that complete the endodontic treatment. The purpose of this investigation was to determine the influence of sodium hypochlorite on rnicrotensile bond strength of dual-cured core build-up resin composite. Extracted human molars were horizontally sectioned with 1mm thickness using low speed diamond saw. After the sectioned specimens were divided into 8 groups, adhesive systems (Clearfil SE-Bond, Prime&Bond NT[2-step, 1-step], Adper Prompt L-Pop) were then applied with or without sodium hypochlorite pretreatment. The treated specimen was filled with dual-cured core build-up resin composite (Luxacore, DMG corp., German). Then light cured for 40 seconds and soaked in $37^{\circ}C$ water bath for 24 hours. After the treated specimen was grinded with 1mm width and measured rnicrotensile bond strength by testing machine. Additionally 8 teeth were prepared for SEM evaluation. The results were as follows. : NaOCl treated groups generally had lower rnicrotensile bond strength but did not show any difference statistically except Adper Prompt L-Pop. When the teeth were treated by NaOCl, though the difference of applied adhesive system, it had no statistically significant difference within the NaOCl treated groups except the relation of between ClearFil SE-Bond adhesive system and Adper Prompt L-Pop adhesive system. In the SEM evaluation, NaOCl treated groups presented relatively long resin tags and incomplete hybrid layer formation generally.

• The Journal of the Korean dental association
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• v.48 no.6
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• pp.469-477
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• 2010

The purpose of this study was to evaluate the effect of two dentin desensitizers and Er,Cr:YSGG laser for dentinal tubule occlusion. Twenty recently extracted single-rooted human teeth were used to obtain root dentinal fragments. The crowns were cut approximately 1mm below the cementum enamel junction(CEJ). A second cut was used to remove the apex of the root. Subsequently, a longitudinal cut was made in order to obtain 2 fragments from each root sample. The cementum from the cervical portion was removed using a high-speed diamond-coated bur in order to expose the dentin. To open dentinal tubules, forty samples were treated with 50% citric acid for 2 min and then rinsed under distilled water for 1 min. These were divided into four groups of ten samples each. The first group served as a control group. In group 2, the samples were irradiated with the Er,Cr:YSGG laser(Waterlase MD, Biolase, USA). In group 3, the samples were treated with Bisblock and ONE-STEP PLUS(Bisco, USA). In group 4, the samples were treated with Gluma comfort bond & Desensitizer(Heraeus Kulzer, Germany). All the samples were examined using Scanning electron microscopy(Hitachi, S-4700, Japan) with two different magnifications(X2000, X5000). These images were assessed by one examiner who was blind to the experimental procedure, using the index of smear layer removal. The distribution of smear layer removal grades was tested using Fisher's exact test. On the order hand, in order to evaluate the occluding effect of two dentin desensitizers and Er,Cr:YSGG laser, the number of exposed dentinal tubules was counted in each group. These were evaluated using the Kruskal-Wallis test with significance predetermined $\alpha$=0.05. There were statistically significant differences between the three groups(Er,Cr:YSGG laser, Bisblock+ONE-STEP PLUS, Gluma comfort bond & Desensitizer) and control group.

• Journal of Platform Technology
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• v.6 no.2
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• pp.10-18
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• 2018

The purpose of this study was to empirically analyze relations between color changes in the product specification and demand changes with price elasticity in the Chinese mobile phone market. In previous studies on price elasticity, the usual analysis units were product categories or SBU within a given product category. Unlike them, the this study set an analysis unit of price elasticity to focus on colors, which are investigated in the research fields of experiential marketing, aesthetic marketing, and cognitive psychology. Actual sales data according to the mobile phone price changes by the color were based on the sales volume of a sales agency at China's largest B2C site. The findings were as follows: first, price elasticity according to the six colors was higher than the absolute value of 1, which means that demands made flexible reactions to price changes. Secondly, there were differences in price elasticity according to the colors. Aroma white color made the smallest increase in sales volume at the same price discount, whereas diamond color made the biggest increase in sales in the same price discount scope. These findings indicate that more profit can be generated in mobile phone sales in China by setting different price discount or increase rates according to colors or producing different amounts of mobile phones according to colors. Distributors or sales agents can have a chance for higher profit by ordering and selling mobile phones in certain colors than others from mobile phone manufacturers. The academic findings indicates that there are differences in preference and price elasticity according to colors under the mobile phone category in the Chinese market, which means that the present study made an academic contribution by proposing a microscopic analysis unit for product price elasticity and expanding its concept.

• Journal of Korea Port Economic Association
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• v.28 no.1
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• pp.229-261
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• 2012

Concerning the political situations of Korea, after the coming of MB Administration the blockades between South and North has been deepened. Because of stopping of the tourism of Diamond Mountain, the Cheonan ship accidents and the ** bombardment of Yeonpyung island, the situation of confrontation of South and North is enlarged. After the death of Kim Jong-il, on 17 Dec. 2011, the new situations are opened in North Korea(NK). On the basis of economic cooperation between South and North, various logistical cooperation of South and North has been progressed. On November of 2002, the 1st Shipping Cooperation Meeting of South and North, which may be a basis of Shipping Agreement has been discussed. And the railway between South and North has been connected. This study, screening the change of South and North conditions, analyzed the tasks and current conditions of South and North logistics based on economic cooperation, with the previous researches and data of South and North Korea. And it grouped and suggested future development directions and practical agenda, after considering the recent changes. Furthermore it proposed the medium-long term logistical system of Korea peninsula and future strategies and vision. To solve the confrontation situations the role of South Korea is more important.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.546-559
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• 1997

The purposes of this study were to evaluate the efficiency of cavity preparation and to determine the incidence of tooth crack when root-end retrograde cavity preparation was done with ultrasonics. 91 distobuccal root-ends of extracted human maxillary first molars were cut by 3 mm perpendicularly to the long axis of tooth using a slow speed diamond saw, retrocavities were prepared using a slow-speed no. 2 round bur as controls, and stainless steel ultrasonic tips of power settings of 1 through 10 as experimentals. Time consumed and the number of strokes used for the cavity preparation were measured and evaluated, and the incidence of tooth cracks was observed under a stereomicroscope. The results were as follows : For the retrograde cavity preparation, time and number of strokes used were decreased as the ultrasonic power setting increased (p<0.001). High power setting of ultrasonics induced significantly more tooth cracks than did the slow-speed bur or low- and medium power setting of ultrasonics (p<0.05). Teeth with previous crack induced significantly more tooth cracks than those without previous one when high power setting of ultrasonics were used for the retrograde cavity preparation (p<0.001). Teeth with initial apical canal size of no. 10 induced significantly more crack than did those with size of no. 15 when low power setting of ultrasonics were used for the retrograde cavity preparation (p<0.05).

• Journal of the Mineralogical Society of Korea
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• v.1 no.2
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• pp.94-103
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• 1988

Diamond anvil cell (DAC) interfaced with a YAG laser heating system has been used to study the phase transformations on perovskite structured titanates ($BaTiO_3$, and $PbTiO_3$) and to synthesize the silicate perovskite phase from the orthopyroxenes of $MgSiO_3$ and $(Mg_{0.87},\;Fe_{0.13})SiO_3$. $BaTiO_3$ and $PbTiO_3$ transform from tetragonal phase to cubic at the pressures of approximately 2.6 GPa and 4.0 GPa at room temperature, respectively. Cubic phases of the both show wide range of stability in the extended in-situ high pressures and high temperature regions. Starting orthoenstatite of $MgSiO_3$ has yielded the perovskite phase as the major structure with ilmenite, gamma-spinel, betta-spinel and stishovite phases at ~38 GPa and ${\sim}1,000^{\circ}C$. $(Mg_{0.87},\;Fe_{0.13})SiO_3$ has shown the perovskite as the major phase with betta-spinel, stishovite and enstatite phases at ~35 GPa and ${\sim}1,000^{\circ}C$. The ilmenite phase does not occur at this condition.

• Environmental and Resource Economics Review
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• v.19 no.2
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• pp.361-382
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• 2010

In 2005, the Korean government decided to postpone the introduction of competition up to 2009 in the power plant service industry. Thus, the purpose of this study is to analyze the efficiency changes and the determinants of international competitiveness of Korean power plant service industry by the comparison between before and after 2006. The sample used in the estimation of efficiency is six firms III Korean power plant service sector for the period of 2003~2008. According to the results, technical efficiency before 2006 (2003~2005) is 0.865 and that after 2005 (2006~2008) is 0.947, which implies that efficiency has been improved after the delay of introduction of competition. In addition, according to the analyses based on the diamond model of Porter using survey data, demand condition has been ranked first in the determinants of international competitiveness. The second and the third important conditions are government and input factor ones. Firm's strategy/structure/competitiveness condition is the most weak condition. Therefore, it would be necessary for firms to improve this condition for competitiveness.