• 대한치과의사협회지
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• 제53권5호
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• pp.360-367
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• 2015

Purpose : The purpose of this study was to evaluate the effect of amount of cantilever in intra-crown according to implant fixture position on mechanical strength of internal conical joint type implant. Materials and Methods : Internal conical joint type implant fixture, abutment screw, abutment was connected and gold alloy prostheses were fabricated and cemented on abutment. For fatigue fracture test, the specimens were loaded to the 350 N, 2,000,000 cycle on 3, 4, 5, and 6 mm off-center of gold alloy prostheses. The fracture pattern of implant component was observed. Results : No fatigue fracture found on 3 and 4 mm group. But initial crack pattern found on 3 specimens of 4 mm group. Fatigue fracture found on all specimens of 5 mm group. But complete fracture was not observed. One specimen of 6 mm group fracture completely. Implant fixture fracture wax not observed. Conclusion : The mechanical failure of implant prostheses increased with the loading area farther from center of implant fixture. To reduce mechanical problem of internal joint type implant, surgical and prosthetic consideration is needed.

• 대한의용생체공학회:의공학회지
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• 제19권5호
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• pp.433-441
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• 1998

본 연구에서는 전부도재관용 도재의 균열전파 양상과 구강환경이 파절강도에 미치는 영향을 평가하기 위해 시행되었다. 도재의 굽힘강도 늘 In-Ceram, IPS-Empress 및 VMK68의 순으로 나타났으며, 수중에서 좌다 기름중에서 더 놀은 강도를 보였다. 비커스 압자 압입부와 압입부를 중심으로 한 파면의 관찰 결과, VMK68 도재의 경우에는 9.8N의 압인하중하에서, IPS-Empress의 경우에는 47.0N의 압입하중하에서 교면에 median crack이 형성되는 양상을 보였으며, 균열이 압자의 압입시에 형성된 벽개면을 따라서 빠르게 성장하여 파괴에 도달한 양상을 보였다. In-Ceram의 경우에는 49.0h의 압임하중하에서 Palmqvlst clack이 형성되는 양상을 보였으며, 알루미나 입자에 의한 균열의 굴곡과 creak bridging으로 인한 강화기전이 관찰되었다.

• 자원환경지질
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• 제33권6호
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• pp.547-556
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• 2000

The purpose of this study is to analyze shear fracture system using landslide location occurred 1998 at Janghung area. For the geological implication, foliation was surveyed and analyzed, and location of landslide, geological structure and topography were constructed into spatial database using GIS. With the constructed spatial database, shear fracture system was assessed by the relation analysis between strike and dip of the foliation and aspect and slope of the topography. We compared strike and dip of foliation and aspect and slope of topography and recognized the typical fracture pattern, strike and dip of joint, that coincided with shear fracture system. The result tells us that foliation of gneiss has geometrical relation to joint or fault that leading landslide. GIS was used to analyze vast data efficiently and the result can be used to assess the landslide susceptibility as important factor.

• Computers and Concrete
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• 제20권3호
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• pp.291-295
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• 2017

Tests on the fracture behavior of CFRP-concrete composite bonded interfaces have been extensively carried out. In this study, a progressive damage model is employed to simulate the fracture behaviors. The crack nucleation, propagation and more other details can be captured by these models. The numerical results indicate the fracture patterns seem to depend on the relative magnitudes of the interface cohesive strength and concrete tensile strength. The fracture pattern transits from the predominated adhesive-concrete interface debonding to the dominated concrete cohesive cracking as the interface cohesive strength changes from lower than concrete tensile strength to higher than that. The numerical results have an agreement with the experimental results.

• 소성∙가공
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• 제10권6호
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• pp.465-470
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• 2001

Hole flanging experiments are performed on flat circular plates with a hole in the center and the flangeability and fracture behaviors of TRIP steels and ferrite-Bainite duplex steels were examined. In the hole flanging, deformation by lip and petalling occurs when plates are struck by punches of various shapes and high circumferential strains induced in the target material cause radial cracking and the subsequent rotation of the affected plate material in a number of symmetric petals. In all cases, failure of the plate was due to lip fracture that results from multiple localized neckings that take place around the hole periphery where straining is most severe and a somewhat regular pattern was observed in a fracture shape. The neck characteristics in flange formation and the transition from the lip to petal mode at which fracture occurs were compared with two materials.

• 대한치과기공학회지
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• 제41권4호
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• pp.279-285
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• 2019

Purpose: The dental CAD / CAM system has been popular with the development of the digital dental industry. Zirconia is a typical material in dental CAD / CAM systems. Zirconia crowns are classified into single layer and double layer. This study is about the double layer crown of zirconia. The surface roughness, bond strength and fracture patterns of the zirconia surface were observed. Methods: Zirconia blocks were cut using a low speed cutter. Sintered to form a plate shape (6mm × 6mm × 3mm). The prepared specimens were surface treated in four ways. Surface roughness and bond strength were measured. And the fracture pattern was observed. Results: Result of surface treatment of zirconia. The surface roughness test results were as ET 2.87 ㎛, ST 2.67 ㎛, LT 2.44 ㎛, AT 2.41 ㎛, CN 2.08 ㎛ order. Bond Strength results were as LT 25.09 MPa, AT 23.27 MPa, ST 21.27 MPa, ET 21.09 MPa, CN 16.12 MPa order. Fracture patterns showed cohesive failure of 25-50% of the bond area. Conclusion: Surface roughness, bond strength and fracture pattern of the zirconia surface were observed. Etching the surface treatment of zirconia materials has been shown to affect the surface roughness. Zirconia special binder treatment has been shown to affect the bond strength improvement.

• 대한기계학회논문집
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• 제17권1호
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• pp.27-37
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• 1993

본 연구에서는 공구의 파손 및 마멸량을 검출할 수 있는 시스템을 구축하고자 하였다. CCD(charge coupled device)카메라를 통해 공구형상의 영상을 얻고 이를 PC 로 분석하는 영상처리 기법과, 여기서 계산된 정보를 이용하여 패턴인식 기법으로 공 구의 상태를 판정하는 알고리즘을 개발하였다.

• 터널과지하공간
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• 제31권1호
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• pp.41-51
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• 2021

치밀 저류층의 투과도 증진을 위해 개발된 수압파쇄 기술은 셰일가스와 같은 비전통자원과 심부지열 개발에 필수적인 기술 중 하나이다. 파쇄형태가 단순하고 파쇄효율이 좋지 않은 수압파쇄를 개선하기 위해 다양한 파쇄유체를 이용한 실험적 연구가 진행되었다. 물, N2, CO2 가스를 파쇄유체로 사용하여 치밀 암석에 대한 파쇄형태와 효율성을 분석하였다. 파쇄유체로 물을 일정 주입속도로 주입한 경우 순간적으로 압력이 상승하여 파쇄가 발생하였으나, 파쇄유체로 가스를 주입한 경우 서서히 압력이 증가되면서 물보다 낮은 파쇄압력을 보였다. 3D 단층촬영 기법을 이용하여 물과 가스 주입으로 생성된 균열을 관찰한 결과는 기존 공극부피 대비 파쇄 자극부피가 각각 5.71%(물), 12.72%(N2), 43.82%(CO2) 증가되었다. 또한 파쇄유체의 파쇄 효율성을 검정하기 위한 파쇄 전후 투과도 변화 실험에서는 가스 파쇄에 의해 증가되는 투과도 증가 값이 물을 이용한 파쇄보다 훨씬 높게 측정되었다. 파쇄 이후 인공균열의 생성과 주변응력에 의해 다시 균열이 닫히는 현상을 고려하여 생성된 인공균열에 구속압을 단계별로 증가시켜 투과도 변화를 측정하였다. 구속압이 2MPa에서 10MPa로 증가시켰을 경우 초기 투과도 대비 각각 89%(N2), 50%(CO2) 감소하였다. 본 연구는 가스파쇄기술이 수압파쇄보다 투과도 증진 효과가 크고 이후 주변 응력에 의한 투과도 감소가 적은 것으로 나타났다.

• 대한두개안면성형외과학회지
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• 제17권4호
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• pp.206-210
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• 2016

Background: Zygoma is a major buttress of the midfacial skeleton, which is frequently injured because of its prominent location. Zygoma fractures are classified according to Knight and North based on the direction of anatomic displacement and the pattern created by the fracture. In zygomaticomaxillary complex (ZMC) fracture many incisions (lateral eyebrow, lateral upper blepharoplasty, transconjunctival, subciliary, subtarsal, intraoral, direct percutaneous approach) are useful. We reviewed various approaches for the treatment of ZMC fractures and discussed about incisions and fixation methods. Methods: A retrospective review was conducted of patients with ZMC fracture at a single institution from January 2005 to December 2014. Patients with single zygomatic arch fracture were excluded. Results: The identified 694 patients who were admitted for zygomatic fractures from which 192 patients with simple arch fractures were excluded. The remaining 502 patients consisted of 439 males and 63 females, and total 532 zygomatic bone was operated. Orbital fracture was the most common associated fracture. According to the Knight and North classification the most frequent fracture was Group IV. Most fractures were fixated at two points (73%). Conclusion: We reviewed our cases over 10 years according to fracture type and fixation methods. In conclusion, minimal incision, familiar approach and fixation methods of the surgeon are recommended.

• 대한두개안면성형외과학회지
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• 제10권2호
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• pp.91-96
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• 2009

Purpose: Frontal sinus fractures are relatively less common than other facial bone fractures. They are commonly concomitant with other facial bone fractures. They can cause severe complications but the optimal treatment of frontal sinus fractures remains controversial. Currently, many principles of treatment were introduced variously. The authors present valid and simplified protocols of treatment for frontal sinus fractures based on fracture pattern, nasofrontal duct injury, and complications. Methods: A retrospective chart review was performed on 36 cases of frontal sinus fractures between January, 2004 and January, 2009. The average age of patients was 33.7 years. Fracture patterns were classified by displacement of anterior and posterior wall, comminution, nasofrontal duct injury. These fractures were classified in 4 groups: I. anterior wall linear fractures; II. anterior wall displaced fractures; III. anterior wall displaced and posterior wall linear fractures; IV. anterior wall and posterior wall displaced fractures. Also, assessment of nasofrontal duct injury was conducted with preoperative coronal section computed tomographic scan and intraoperative findings. Patients were treated with various procedures including open reduction and internal fixation, obliteration, galeal frontalis flap and cranialization. Results: 12 patients are group I (33.3 percent), 14 patient were group II (38.8 percent), group III, IV were 5 each (13.9 percent). Frontal sinus fractures were commonly associated with zygomatic fractures (21.8 percent). 9 patients had nasofrontal duct injury. The complication rate was 25 percent (9 patients), including hypoesthesia, slight forehead irregularity, transient cerebrospinal fluid leakage. Conclusion: The critical element of successful frontal sinus fracture repair is precise diagnosis of the fracture pattern and nasofrontal duct injury. The main goal of management is the restoration of the sinus function and aesthetic preservation.