• 한국결정성장학회지
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• 제32권6호
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• pp.251-261
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• 2022

본 연구에서는 냉간단조공정에서 성형하중과 금형내 응력집중 감소를 위해 자동차 엔진 밸브 스프링 리테이너 제품의 형상최적화를 위한 금형형상 최적설계를 수행하였다. 기존 생산에 사용되는 각 성형공정별 냉간단조 금형에 대한 유한요소해석 시뮬레이션을 통해 절단공정을 포함해 총 6공정으로 구성되어 있는 냉간단조공정 별 단조 프리폼의 성형 시에 발생하는 성형하중과 성형유동 특성을 분석하였으며, 이를 통해 금형 내 응력집중이 발생하는 주요 설계인자를 확인하였다. 상형금형과 하형금형부의 챔퍼(chamfer) 및 에지필렛(edge fillet) 형상을 대상으로 4인자 3수준 설계인자 및 변수 수준을 설정하고, 성형해석 시뮬레이션과 다구찌법을 활용하여 설계인자별 영향도를 분석하여 최적의 최적설계인자를 결정하였다. 본 연구를 통해 얻어진 최적설계변수를 적용하여 엔진밸브 스프링 리테이너의 최적설계 시뮬레이션 결과, 각 프리폼 성형공정별로 최대 36 %, 전체 공정 평균 20 %의 성형하중 감소 효과를 얻을 수 있었다. 엔진의 고효율, 고출력, 고성능화 목표가 지속적으로 높아짐에 따라 고강도 소재의 활용이 많아지게 되어 이에 대응할 수 있는 성형공정 및 금형설계의 최적화가 필요하며, 향후 연구 결과를 활용하여 현업에 적용하여 제품단조성형성 개선 및 금형수명관리를 위한 기술자료로 활용하고자 한다.

• 대한치과보철학회지
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• 제55권3호
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• pp.325-330
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• 2017

단일 치아 상실 시 전부피개관을 유지장치로 사용하는 고정성 보철이나 임플란트를 이용한 치료가 우선적으로 선택되어 사용되고 있다. 하지만 전부 피개관 지대치 형성을 위해서는 건전한 치질을 많이 삭제해야 한다는 단점이 있다. 임플란트의 경우 인접 치아의 손상을 피할 수 있으나 환자의 구강 상태와 전신 상태에 따라 불가능하거나 일정기간 연기해야 하는 경우도 있다. 본 증례에서는 최소한의 치질 삭제로 젊은 환자와 치은 퇴축이 있는 환자의 단일 치아 상실을 수복하기 위해 레진 접착 고정성 보철물을 선택하였다. 모든 환자들이 심미적, 기능적으로 만족하였기에 이를 보고하는 바이다.

• 구강회복응용과학지
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• 제18권3호
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• pp.217-224
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• 2002

The purpose of this study was to evaluate the influence of saliva contamination on the resin bonding of the etched metal retainers. The test samples were made of Verabond, and divided into 3 groups. Retainers in group1 had normally etched metal surfaces. Retainers in group2 had normally etched metal surfaces which were saliva-contaminated for 30 seconds and cleaned with streaming, luke-warm for 1 minute and dried thoroughly. Retainers in group3 had normally etched metal surfaces which were saliva- contaminated for 30 seconds and dried thoroughly without water-cleansing. Each 3 group specimen was watched on SEM. A resin core, 5mm in diameter and 6mm in length, was made of Panavia using Teflon mold on the each specimen. These 3 groups were tested to evaluate shear bond strength, using universal testing machine. The results were as follows : 1. The shear bond strength showed no significant difference between group1 and group2. 2. The shear bond strength showed significant difference between group1 and group3. 3. The shear bond strength significant difference between group2 and group3. 4. Scanning electron microscope photographs of group1 and group2 showed no signs of contamination but of group3 showed somewhat contaminated.

• 전기학회논문지
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• 제64권6호
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• pp.954-959
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• 2015

In this paper, 110kW high output density, high efficiency Permanent Magnet Synchronous Motor which can be applied on tram’s traction system is introduced, along with its output and loss characteristics. The motor model is 2pole 18slot model and its size has been reduced through the high speed for high output density. Especially, structure and retainer sleeve structure is applied to its structure, which is also appropriate for high speed rotation. This kind of structure has eddy current loss problem on the surface of rotor, which must be reduced for high output density design. This study has designed the most optimized additional design parameter in order to improve the output characteristics and efficiency of previous produced 2pole 18 slot 110kW motor model and how the width of airgap affects from the loss perspective is mainly analyzed. Finally, the analysis on the extent of the efficiency improvement effect compared to the previous model has performed through electromagnetic FEM analysis. The influence of airgap flux density distribution has also been thoroughly examined.

• 대한치과보철학회지
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• 제30권2호
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• pp.203-224
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• 1992

The purpose of this study was to evaluate the stress distribution developed in supporting structures by distal extension removable partial denture with 4-types of direct retainer. The direct retainers examined were Akers clasp, RPI clasp, RPA clasp and RPL clasp in bilateral & unilateral free end case. 3-dimensional photoelastic stress analysis was used to record the isochromatic fringe patterns and to calculate the compressive stress at measuring points. The results were as follows. 1. In bilateral free end case, RPI clasp exhibited the similar stress distribution on distal and mesial alveolar crest but Akers clasp exhibited higher stress concentration on distal alveolar crest than mesial alveolar crest. 2. In bilateral free end case, RPA clasp and RPL clasp exhibited the similar stress distribution on distal and mesial alveolar crest and RPL clasp exhibited higher stress concentration on buccal alveolar crest than lingual alveolar crest. 3. Akers clasp produced high stress concentration on residual alveolar ridge distally, but RPI clasp, RPA clasp and RPL clasp produced even stress distribution on residual alveolar ridge. 4. Removable partial denture in unilateral free end case exerted higher stress on abutment tooth root apex than bilateral distal extension removable partial denture.

• 건축역사연구
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• 제11권4호
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• pp.129-142
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• 2002

The Kyeongbok Palace was completely renewed during the reign of King Sejong, the fourth King of the Joseon Dynasty(1392-1910). The repair was done for the two main purpose; one was to obtain the dignity of the main palace of the dynasty, the other was to make the palace suitable for the performing of the various ritual ceremonies. It was under the reign of King Sejong that every detail of the procedure of the royal ritual ceremony. The procedure of ritual ceremony changed the buildings of the palace. The quarter of Sajeong-jeon, King's office, was changed remarkably from the original form as the building became the beginning and ending point of King's moving during the ritual ceremonies. The site of the palace had ill reputation from the point of geomancy since its establishment. King Sejong ignored the rumor and kept the palace as usual. In his later year's, Sejong had tried to build a detached quarter and a Buddhist shrine in the palace. But he had to give up his plan because of the retainer's strong opposition. The original layout of the Kyeongbok Palace could be remained as the King renounced his controversial personal wish. King Sejong deserves a full credit for the establishment of the Kyeongbok Palace as the main palace of the Joseon Dynasty.

• 한국생산제조학회지
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• 제22권2호
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• pp.310-317
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• 2013

In this paper, the contact pressure of the wafer and polishing pad for final polishing process for 300 mm-wafer were investigated through numerical analysis using FEM tool, ANSYS. The distribution of the contact pressure is one of main parameters which affects on the flatness and surface roughness of polished wafers. Two types of polishing head, a hard type head with ceramic disk and a soft type head with air bag were considered. The effects of the deformation and initial shape of table on the contact pressure were also examined. Both heads and tables were modeled as 3D finite element model from solid model, and the material properties of polishing pads and rubber plate for the air-bag head were obtained from tensile tests. The contact pressure deviation on wafer surface was smaller with air bag head than hard type head even when the table had form errors such as convex or concave. From this 3D analysis, it could be concluded that the air-bag head has better uniformity of the contact pressure on wafer. Also, the effects of inner diameter of air bag and radial clearance between wafer and retainer were investigated as view point of contact pressure concentration on the edge of wafer.

• Journal of Periodontal and Implant Science
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• 제45권4호
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• pp.152-155
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• 2015

Purpose: This case report discusses the effect of a root submergence technique on preserving the periodontal tissue at the pontic site of fixed dental prostheses in the maxillary anterior aesthetic zone. Methods: Teeth with less than ideal structural support for fixed retainer abutments were decoronated at the crestal bone level. After soft tissue closure, the final fixed dental prostheses were placed with the pontics over the submerged root area. Radiographic and clinical observations at the pontic sites were documented. Results: The submerged roots at the pontic sites preserved the surrounding periodontium without any periapical pathology. The gingival contour at the pontic site was maintained in harmony with those of the adjacent teeth, as well as the overall form of the arch. Conclusions: The results of this clinical report indicate that a root submergence technique can be successfully applied in pontic site development with fixed dental prostheses, especially in the maxillary anterior esthetic zone.

• Tribology and Lubricants
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• 제28권6호
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• pp.278-282
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• 2012

Various bearings such as deep-groove ball bearings, angular-contact ball bearings, and roller bearings are used to support the load and to lubricate between the shaft and the housing. The bearings of potential rolling systems in a turbo pump are the deep-groove ball bearings as comparing with the bearings with rolling elements such as cylindrical rollers, tapered cylindrical rollers, and needle rollers. The deep-groove ball bearings consist of rolling elements, an inner raceway, an outer raceway and a retainer that maintain separation and help to lubricate the rolling element that is rotating in the raceways. In the case of water-lubricated ball bearings, however, fluid friction between the ball and raceways is affected by the entry direction of flow, rotation speed, and flow rate. In addition, this friction is the key factor affecting the bearing life cycles and reliability. In this paper, the characteristics of flow conditions corresponding to a deep-groove ball bearing are investigated numerically, with particular focus on the friction distribution on the rolling element, in order to extend the analysis to the area that experiences solid friction. A simple analysis model of fluid flow inside the water-lubricated ball bearing is analyzed with CFD, and the flow characteristics at high rotation speeds are presented.

• 대한구순구개열학회지
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• 제12권1호
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• pp.7-20
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• 2009

Orthodontic treatment planning of cleft lip and palate requires consideration of the characteristic features, growth pattern and functional disorders related to cleft lip and palate patients. Tissue deficiencies and constriction of the scar tissue in surgically treated cleft lip and palate results in disturbance of maxillary growth and deficiency of midfacial region with anterior and posterior crossbite. These patients often present congenital missing of teeth, supernumerary teeth, malformed teeth, or ectopic position of teeth, which should be treated by orthodontic treatment by expanding upper arch followed by fixed appliance. Proper use of retainer and continuous follow-up is needed to prevent relapse after orthodontic treatment has finished. Also we have to pay attention to correct speech disorder which is caused by the velopharyngeal insufficiency.