• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1382-1385
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• 2003

Deformation on shapes of the hydrogen absorption metal in this paper was investigated on hydrogen absorption-desorption cycling. In order to study this problem, the cold rolled palladium plate and the cold extrusion palladium bar as specimens had been used. By using the electrochemical method, the palladium specimens were cyclically hydrogenated in the 0.1 mol H$_2$SO$_4$ electrolyte. As results, it is noted that the thickness of the plate specimen gradually increased in increasing hydrogenation cycles whereas the width and the length decreased. But both the diameter and the length of the bar specimen increased with increasing hydrogenation cycles. Also, grains in the plate specimen were greatly deformed after hydrogenation cycling whereas internal grains in the bar specimen were pulverized. And deterioration of the hydrogen absorption rate of the bar specimen was lager than the plate specimen.

• 소성∙가공
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• 제3권1호
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• pp.23-37
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• 1994

The upper bound element technique(UBET) is used to analyze the final stage of the axisymmetric forward extrusion. Kinematically admissible velocity field involving curved surface of velocity discontinuity is assumed. The required power to arise the piping defect is obtained and is compared with Aviture's solution a the same condition. Conditions for inception of the cavity and development of the pipe are predicted. The internal radius of the pipe and critical length of billet are also determined. Experiments are carried out for extrusion with lead specimens to investigate the piping phenomena. The theoretically predicted results showed reasonably good agreement with the experimental observation.

• 한국정밀공학회지
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• 제9권2호
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• pp.116-121
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• 1992

The optimal extrusion process for the rate sensitive materials have been developed in this study. The preliminary designs of the die shapes have been carried out to maintain constant strain rate during extrusion and the upper bound approach has been applied to define the process variables (the die entrance velocity and the die length) including the rheology during deformation. The result for the axisymmetric extrusion process has been verified with rigid-viscoplastic finite element analysis. It has been confirmed that the optimal die has wider band of constant strain rate than the conical one does.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.403-406
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• 2006

Internal spline forming using a thin and long tube can cause the buckling and folding during the forming process. In the study, we proposed two different extrusion processes, and we performed the analysis in order to obtain the optimal process according to the length of land part. Using the rigid-plastic finite element simulation, the proposed processes have been compared by checking the deformed shape and stroke-road relation.

• 소성∙가공
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• 제8권2호
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• pp.143-151
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• 1999

The twisting and extrusion process of the product with trapezoidal helical fin from the round billet is developed by the upper bound analysis. The twisting of extruded product is caused by the twisted die surface connecting the die entrance section and the die exit section linearly. In the analysis, the rotational velocity in angular direction is assumed by the multiplication of radial distance and angular velocity. The angular velocity is increased linearly by axial distance from the die entrance. The increase rate of angular velocity is determined by the minimization of plastic work. The results of the analysis show that the angular velocity of the extruded product increases with the die twisting angle, the reduction of area, and decreases with the die length, the friction condition.

• 대한치과의사협회지
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• 제57권11호
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• pp.679-688
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• 2019

A 8-year-old patient presented with a crown-root fracture of the maxillary right central incisor with an oblique subgingival fracture line. A multidisciplinary treatment approach including endodontic treatment, surgical extraction and intraalveolar repositioning was used to gain sufficient crown length of the fractured maxillary incisor. The coronally repositioned maxillary right central incisor was stabilized by a resin wire splint. Apexification using MTA was performed. Resin core and direct resin restoration(Cl IV) on fractured teeth was built up. Clinical and radiographic follow-up of the maxillary right central incisor after 36 months showed no signs of root resorption or pathology and acceptable aesthetics and functions were maintained. Surgical extrusion can be considered as a good treatment modality for young patients.

• 한국재료학회지
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• 제17권6호
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• pp.313-317
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• 2007

In-situ micro-channeled multi tubular solid oxide fuel cell(SOFC) was fabricated using multi-pass extrusion process with out side diameter of 2.7 mm and active length of 5 mm that contained 61 individual cells. Cell materials used in this work were NiO-YSZ (50 : 50 vol.%), 8 mol% yttria-stabilized zirconia(8YSZ), $La_{0.8}Sr_{0.2}MnO_3(LSM)$ as anode, electrolyte, and cathode, respectively. The arrangement of each electrode and electrolyte layer in green bodies showed uniformity and integrity after extrusion and sintering. The XRD analysis confirmed that no reaction phases appeared and the microstructure of the electrolyte was fairly dense (relative density > 96%) after sintering.

• 대한소아치과학회지
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• 제35권2호
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• pp.305-312
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• 2008

치아의 치관-치근 파절은 치아파절이 치관과 치근에 걸쳐 발생되어 법랑질, 상아질 및 백악질까지 이환된 경우로 정의되며, 치수이환여부에 따라 복잡파절과 비복잡파절로 분류될 수 있다. 치관-치근 파절의 빈도는 유치열에서 2%, 영구치열에서 5%로 나타나며, 보통 상악 전치부에 호발한다. 이러한 치관-치근 파절된 치아의 수복을 위해서는 생물학적 폭경이 유지되어야 한다. 이를 위하여 사용되는 방법은 골삭제 후 치은절제술, 교정적 견인, 외과적 정출 후 수복하는 방법과, 인위적으로 발치하여 근관치료와 수복 후 재식하는 방법 등이 있다. 이중 외과적 정출술은 치아를 발거하여 파절부를 치은 연상으로 이동시켜 재식하는 방법으로서, 이는 치관부 파절편이 임상치근의 1/2 미만인 경우에 적응증이 될 수 있으며, 발견하지 못한 다른 파절편을 직접 시진할 수 있고 때로는 파절선을 순측에 위치시켜 치료시 시야확보 및 접근이 용이하다는 등의 장점이 있다. 본 증례에서는 외상으로 치관-치근 파절된 미완성 치근단의 상악 중절치를 가진 환아에서 외과적 정출술 후 근관치료와 광중합복합레진을 이용한 치관수복을 시행하였으며, 정기적 검진시 양호한 결과가 관찰됨을 확인할 수 있었다.

• 한국가축번식학회지
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• 제19권3호
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• pp.181-189
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• 1995

In this study, methods on fabrication of microtool and setting of micromanipulator were examined and relationship between first polar body extrusion rate and maturation time of follicular oocyte, enulceation rae and repetition of trial, and enucleation rate and maturation period were investigated. The results are as follows: 1. Suitable outside diameter of micropipette tube was 1mm. Holding pipette with less than diameter of oocyte was fitred for manipulation, and zona dissection needle was easily operated when its sharp-point had diameter of about 8 ${\mu}{\textrm}{m}$ and length of 300${\mu}{\textrm}{m}$. The injection pipette with 20~35${\mu}{\textrm}{m}$ outside diameter was adequate for injection of blastomere into perivitelline space. 2. Separation of blastomere was effective when zona pellucida had cut with zonadissection needle and the embryo was pipetted gently with the pipette that had narrower diameter than that of embryo until separation of blastomeres had completed. 3. The extrusion rate of first polar body was 78% during 20~24% hours incubation for maturation. 4. According to repetitions of micromanipulation, the enucleation rate was increased to 85% and the time required for enucleation of a oocyte was shortened to 3 min. 5. The extrusion rate of first polar body and enucleation rate were 82 and 76% respectively, in the group of the oocytes cultured for 22 hours. However in the group cultured for 24 hours, the extrusion rate of first polar body and enucleation rate were 53 and 100% respectively.

• Journal of Korean Neurosurgical Society
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• 제63권2호
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• pp.210-217
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• 2020

Objective : To analyze the accuracy of iliac screws using freehand technique performed by the same surgeon. We also analyzed how the breach of iliac screws was related to the clinical symptoms resulting in revision surgery. Methods : From January 2009 to November 2015, 100 patients (193 iliac screws) were analyzed using postoperative computed tomography scans. The breaches were classified based on the superior, inferior, lateral, and medial iliac wall violation by the screw. According to the length of screw extrusion, the classification grades were as follows : grade 1, screw extrusion <1 cm; grade II, 1 cm ≤ screw extrusion <2 cm; grade III, 2 cm ≤ screw extrusion <3 cm; and grade IV, 3 cm ≤ screw extrusion. We also reviewed the revision surgery associated with iliac screw misplacement. Results : Of the 193 inserted screws, 169 were correctly located and 24 were misplaced screws. There were eight grade I, six grade II, six grade III, and four grade IV screw breaches, and 11, 8, 2, and 3 screws violated the medial, lateral, superior, and inferior walls, respectively. Four revision surgeries were performed for the grade III or IV iliac screw breaches in the lateral or inferior direction with respect to its related symptoms. Conclusion : In iliac screw placement, 12.4% breaches developed. Although most breaches were not problematic, symptomatic violations (2.1%) could result in revision surgery. Notably, the surgeon should keep in mind that lateral or inferior wall breaches longer than 2 cm can be risky and should be avoided.