• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1623-1630
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• 2010

In this study, effective forming methods for reducing the roll-over of a sector tooth, which is a main component of an automotive seat recliner, are proposed. Due to the large amount of roll-over, accurate contact between the inner gear of a sector tooth and the outer gear of a pawl tooth cannot be normally achieved; thus sensitivity and safety for the passengers decrease. To overcome the aforementioned drawback, we investigated the effect of flowcontrol forming methods involving local embossing die, coining punch, and VIC (Variable Inverse Clearance) on the roll-over depth by FE-analysis and an experiment. The results of a fine-blanking experiment for verifying the proposed methods showed that VIC type is decidedly superior from the aspects of reduction of roll-over and tool strength of the sector tooth.

• Journal of dental hygiene science
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• v.22 no.3
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• pp.180-190
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• 2022

Background: Like direct infection from COVID-19, psychological concern about infection could affect health. Concern about COVID-19 infection was associated with individual habits to practice rules for preventing infection. Therefore, this study aimed to check occupational types and whether to practice tooth brushing after lunch depending on the occupation of economic workers and find correlations between concerns about infection due to COVID-19 pandemic and tooth brushing after lunch. Methods: The raw data was from the community health survey conducted in 2020. Among 229,269 adult participants aged 19 years and older, 138,970 economic workers were included in the final analysis. The chi-squared test was used to find differences in psychological concerns due to the COVID-19 pandemic. According to the participants, the rate of practicing tooth brushing after lunch was based on COVID-19-related psychological concerns. Multiple logistic regression analysis was conducted to check the influence of psychological concerns due to the COVID-19 pandemic on the rate of practicing tooth brushing after lunch. Results: According to occupational classifications, professionals and office workers and career soldiers had 1.551- and 1.581-times higher practicing rates than managers, respectively, whereas machine operators, agricultural and fishery sector workers, and daily laborers had lower practicing rates. Regarding COVID-19-related psychological concerns, the group with a lower concern about infection had a 1.076 times higher practicing rate than that with greater concern. The group with greater concern about blame from neighbors had 1.119 times higher practicing rate than that with lower concern. Conclusion: The correlations between higher economic workers' concerns about infection and blame from neighbors and higher recognition of the necessity to prevent COVID-19 and practice tooth brushing after lunch were confirmed. It is necessary to prepare measures for practicing tooth brushing after lunch suitable to the characteristics of occupational types and work environments of economic workers.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.6
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• pp.478-485
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• 2012

In this paper, a new PWM method is proposed to reduce the input current harmonics of 3 phase PWM rectifier. In the conventional carrier comparison PWM method, a triangular wave is generally used as the carrier wave. However, the large d-axis current ripple by the triangle carrier wave may be a source of large input current THD(Total Harmonic Distortion). In this paper, a new carrier comparison PWM method with saw tooth wave is proposed. Depending on the sector where the voltage command vector places, one of the rising or falling saw tooth wave is selected. To reduce the switching losses of the saw tooth carrier PWM, the discontinuous PWM is also presented. The proposed PWM method can reduce the d-axis current ripple as well as the switching losses. The performance of the conventional and proposed PWM methods is verified by the simulation and experimental results.

• Journal of Periodontal and Implant Science
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• v.38 no.2
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• pp.207-214
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• 2008

Purpose: The aim of augmentation of the alveolar ridge is to restore absorbed alveolar ridges for future implant site or esthetic prosthodontic restoration. The present clinical report describes the anterior maxillary augmentation cases using a soft tissue rotated palatal flap, and considers various problems of before and after surgery. Method: First & second patients were treated by vascularized interpositional periosteal-connective tissue(VIP-CT) flap for horizontal soft tissue augmentation. Especially second patient was progressed with bone grafting at the same time. Third patient was treated by the same flap with bone graft and implant placement in single tooth missing premaxillary area. Result: The obtained horizontal augmentation width measured $0.5{\sim}2.7\;mm$. Conclusion: This technique constitutes a viable approach for augmentation the anterior sector of alveolar ridge with the placement of dental implants. But it needs correct diagnosis preparation and careful surgery skill.

• The korean journal of orthodontics
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• v.53 no.2
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• pp.106-115
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• 2023

Objective: To evaluate the null hypothesis that there is no difference in a set of clinical predictors of potentially impacted canines between low-risk patients with and without displaced canines. Methods: The normal canine position group consisted of 30 patients with 60 normally erupting canines ranked in sector I (age, 9.30 ± 0.94 years). The displaced canine group comprised 30 patients with 41 potentially impacted canines ranked in sectors II to IV (age, 9.46 ± 0.78 years). Maxillary lateral incisor crown angulation, inclination, rotation, width, height, and shape, as well as palatal depth, arch length, width, and perimeter composed a set of clinical predictors, which were evaluated on digital dental casts. Statistical analyses consisted of group comparisons and variable correlations (p < 0.05). Results: There was a significant association between sex and mesially displaced canines. Unilateral canine displacement was more prevalent than bilateral displacement. The crown of the maxillary lateral incisors was significantly angulated more mesially and rotated mesiolabially in low-risk patients with displaced canines, who also had a shallower palate and shorter anterior dental arch length. Lateral incisor crown angulation and rotation, as well as palatal depth and arch length, were significantly correlated with the canine displacement severity. Conclusions: The null hypothesis was rejected. Maxillary lateral incisor angulation inconsistent with the "ugly duckling" stage as well as a shallow palate and short arch length are clinical predictors that can significantly contribute to the early screening of ectopic canines in low-risk patients.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.44 no.3
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• pp.93-102
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• 2018

Angiogenesis is one of the essential processes that occur during wound healing. It is responsible for providing immunity as well as the regenerative cells, nutrition, and oxygen needed for the healing of the alveolar socket following tooth extraction. The inappropriate removal of formed blood clots causes the undesirable phenomenon of alveolar osteitis (AO) or dry socket. In this review, we aimed to investigate whether enhanced angiogenesis contributes to a more effective prevention of AO. The potential pro- or anti-angiogenic activity of different materials used for the treatment of AO were evaluated. An electronic search was performed in the PubMed, MEDLINE, and EMBASE databases via OVID from January 2000 to September 2016 using the keywords mentioned in the PubMed and MeSH (Medical Subject Headings) terms regarding the role of angiogenesis in the prevention of AO. Our initial search identified 408 articles using the keywords indicated above, with 38 of them meeting the inclusion criteria set for this review. Due to the undeniable role of angiogenesis in the socket healing process, it is beneficial if strategies for preventing AO are directed toward more proangiogenic materials and modalities.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.3
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• pp.149-158
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• 2013

The purpose of this study was to evaluate the shape and impacted pattern of mesiodens and associated complications using three dimensional images produced by dental CBCT. This study was based on the CBCT (CB Mercury, Hitachi, Tokyo, Japan) radiographic view of 280 pediatric patients who visited the Department of Pediatric Dentistry at the Chosun University Dental Hospital with the chief complain of mesiodens during between 2007 and 2012. Impacted mesiodens occurs more frequently in boys than in girls, the ratio being approximately 3.3:1 and most cases were observed between 6 and 8 years of age. The number of mesiodens per patient was 1.38. Majority of the mesiodens were conical (79.5%) in shape and inverted (48.6%) in direction. The mesio-distal position of mesiodens were the most common in middle sector (81.8%), vertical level were the most common near cervical (60.3%), and labio-palatal position were the most common at palatal side of the dental arch (73.8%). 47.5% of mesiodens had complications and common complications associated with mesiodens were displaced tooth and delayed eruptions. The shape, vertical level, and labio-palatal position of mesiodens had correlations with complications. CBCT appears to be an excellent diagnostic tool, providing three dimensional information and accurate images, for diagnosis of impacted mesiodens.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.44-53
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• 2021

As environmental issues have emerged worldwide, emission gas regulations have been strengthened. In the construction machinery sector, studies have been actively conducted to utilize the power source of electric motors owing to the increasing demand for zero emissions. In this study, the gear specifications of an electric axle for construction machinery were selected by considering the specifications of the motor, gear tooth contact pattern, and face load factor. The gear strength evaluation was performed at the system level using the simulation model. The bending and contact strength of the spiral bevel gears and the bending strength of the planetary gear set showed a safety factor of 1 or more. However, the contact strength of the planetary gear set showed a safety factor of 0.92. Conservative results were derived by performing the analysis under the rated load condition of the motor. However, the ratio of the equivalent torque to the rated torque of the motor was 45% or less, hence, it was determined that no difficulties should arise regarding the durability of the axle.