• 한국생산제조학회지
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• 제9권1호
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• pp.111-118
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• 2000

Over tightening experiments of the tension-controlled bolts are carried out and the stripping mechanism is reviewed base on the observed results. There are two modes of bolt failure due to the over tightening : one the fracture of the bolt the other the thread stripping Bifurcation between these two modes is rather delicate but it seems being related with the elastic flexibility of the bolt which depends upon the unused thread length. The fracture mode occurs in the bolts with good flexibility while the latter with bad one. According to the ISO Standard some meter coarse threads like M20 and M22 have the same pitch which causes bigger fastener to less resistance in shear and bending compared with the smaller one. however since UNC thread system adapts different pitch for different nominal diameter unified coarse threads show better stripping resistance than their corresponding meter threads.

• The Journal of Advanced Prosthodontics
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• 제1권1호
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• pp.19-25
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• 2009

STATEMENT OF PROBLEM. Primary stability at the time of implant placement is related to the level of primary bone contact. The level of bone contact with implant is affected by thread design, surgical procedure and bone quality, etc. PURPOSE. The aim of this study was to compare the initial stability of the various taper implants according to the thread designs, half of which were engaged to inferior cortical wall of type IV bone(Group 1) and the rest of which were not engaged to inferior cortical wall(Group 2) by measuring the implant stability quotient(ISQ) and the removal torque value(RTV). MATERIAL AND METHODS. In this study, 6 different implant fixtures with 10 mm length were installed. In order to simulate the sinus inferior wall of type IV bone, one side cortical bone of swine rib was removed. 6 different implants were installed in the same bone block following manufacturer s recommended procedures. Total 10 bone blocks were made for each group. The height of Group 1 bone block was 10 mm for engagement and that of group 2 was 13 mm. The initial stability was measured with ISQ value using Osstell $mentor^{(R)}$ and with removal torque using MGT50 torque gauge. RESULTS. In this study, we found the following results. 1. In Group 1 with fixtures engaged to the inferior cortical wall, there was no significant difference in RTV and ISQ value among the 6 types of implants. 2. In Group 2 with fixtures not engaged to the inferior cortical wall, there was significant difference in RTV and ISQ value among the 6 types of implants(P < .05). 3. There was significant difference in RTV and ISQ value according to whether fixtures were engaged to the inferior cortical wall or not(P < .05). 4. Under-drilling made RTV and ISQ value increase significantly in the NT implants which had lower RTV and ISQ value in Group 2(P < .05). CONCLUSIONS. Without being engaged to the inferior cortical wall fixtures had initial stability affected by implant types. Also in poor quality bone, under-drilling improved initial stability.

• 한국비블리아학회지
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• 제32권1호
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• pp.415-442
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• 2021

본 연구는 청소년 메이크업에 관한 유튜브 동영상의 주요 시청자가 청소년이라는 가정하에 청소년 메이크업을 주제로 한 유튜브 동영상과 그에 딸린 댓글 창을 집중적으로 분석한 사례연구이다. 청소년 메이크업에 대한 정보를 제공하는 이와 그 정보를 수용하는 이 사이의 상호작용, 정보를 수용하는 이들 간의 소통, 그 안에서 제기되는 논의의 내용과 토론의 방식 등을 살펴봄으로써 청소년이 소셜 미디어를 이용하는 양상을 알아보고자 하였다. 청소년 메이크업 튜토리얼 영상을 시청하고 댓글 창에 참여한 청소년들 중 상당수는 뷰티 크리에이터의 미모를 찬양하고 부러워하며 그와 적극적으로 소통하고자 하는 모습을 보였다. 청소년이 작성한 댓글에 딸린 답글 타래에서는 답변과 공감 등의 소통 방식을 통해 또래와의 공감대를 형성하고 정보 요구를 해결하였으며, 각자의 경험과 생각을 주고받으며 시야와 사고를 확장하고 있었다. 그러나, 청소년 집단 내에서 상대적 약자인 초등학생에 심각한 언어폭력이 가해지는 등 나이에 따른 힘의 불균형 문제도 나타나고 있었다.

• 한국자동차공학회논문집
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• 제19권2호
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• pp.111-116
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• 2011

Three-dimensional finite element analyses have been performed to improve the durability of bulkhead. To keep pace with design changes and concentrate on regions of interest, SUBMODEL technique in ABAQUS was used for analysis. An analysis was conducted with following load cases: 1) Cap press-fit, 2) Bearing crush, 3) Bolt assembly, 4) Hot assembly, 5) Firing load, 6) Alternating firing load, 7) 2nd hot assembly. Fatigue analysis was done using commercial software FEMFAT and fatigue factors at the interested regions such as bolt tip area, counter bore, breathing hole, honing clearance were calculated and compared to aid design validation. Finite element modeling in the area of thread engagement used a simple constraint equations. Increasing bolt length, to a minimum of 39 mm above joint face gives a better fatigue resistance to the bulkhead. Breathing hole helps not only circulate the air in the crankcase but also fatigue resistance of bulkhead by relieving the stress at the critical locations.

• Journal of Periodontal and Implant Science
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• 제29권1호
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• pp.209-231
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• 1999

Even though titanium(Ti) and its alloys are the most used dental implant materials, there are some problems that Ti wears easily and interferes normal osteogenesis due to the metal ions. Ti coated with bioactive ceramics such as hydroxyapatite has also such problems as the exfoliation or resorption of the coated layer, Recent studies on implant materials have been proceeding to improve physical properties of the implant substrate and biocompatibility of the implant surfaces. The purpose of the present study was to examine the physical property and bone tissue compatibility of bioinert nitrides ion plated Ti, Button type specimens(14mm in diameter, 2.32rrun in height) for the abrasion test and cytotoxicity test and thread type implants(3.75mm in diameter, 6mm in length) for the animal experiments were made from Ti(grade 2) and 316LVM stainless steel. Ti specimens were ion plated with TiN, ZrN by the low temperature arc vapor deposition, and the depth profile of the TiN/Ti, ZrN/Ti ion plated surface was examined by Auger Electron Spectroscopy. Three kind of button type specimens .of TiN/Ti, ZrN/Ti and Ti were used for abrasion test, and HEPAlClC7 cells and CCD cells were cultivated for 4 days with the specimens for cytotoxicity test. Thread type implants of TiN/Ti, ZrN/Ti, Ti, 316LVM were implanted on the femur of 6 adult dogs weighing 10kg-13kg. Two dogs were sacrified for histological examination after 45 days and 90 days, and four dogs were sacrified for the removal torque test of the implant') after 90 days. The removal torque force was measured by Autograph (Shimadzu Co., AGS-1000D series, Japan). Abrasion resistance of TiN/Ti was the highest, and that of ZrN/Ti and Ti were followed. The bioinert nitride ion plated Ti had much better abrasion resistance, compared with Ti, In the cytotoxicity test, the number of both cells were increased in all specimens, and there were no significant difference in cytotoxic reaction among all groups (p>0.1), In histological examination, 316LVM showed the soft tissue engagement in interface between the implant and bone, but the other materials after 45 days noted immature new bone formation in the medullary portion along the implant surface, and those after 90 days showed implant support by new bone formation in both the cortical and the medullary portion, The removal torque force of Tilv/Ti showed significantly higher than that of Ti(p(O,05). The difference in removal torque force between TiN/Ti and ZrN/Ti was not significant(p>0.05), and that of 316LVM was lowest among all groups(p<0.05). These results suggest that bioinert nitrides ion plated Ti can resolve the existing problems of Ti and bioactive ceramics, and it may be clinically applicable to human.