• 대한두개안면성형외과학회지
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• 제17권1호
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• pp.14-19
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• 2016

Background: Most nasal bone fractures are corrected using non-invasive methods. Often, patients are dissatisfied with surgical outcomes following such closed approach. In this study, we compare surgical outcomes following blind closed reduction to that of ultrasound-guided reduction. Methods: A single-institutional prospective study was performed for all nasal fracture patients (n=28) presenting between May 2013 and November 2013. Upon research consent, patients were randomly assigned to either the control group (n=14, blind reduction) or the experimental group (n=14, ultrasound-guided reduction). Surgical outcomes were evaluated using preoperative and 3-month postoperative X-ray images by two independent surgeons. Patient satisfaction was evaluated using a questionnaire survey. Results: The experimental group consisted of 4 patients with Plane I fracture and 10 patients with Plane II fracture. The control group consisted of 3 patients with Plane I fracture and 11 patients with Plane II fracture. The mean surgical outcomes score and the mean patient dissatisfaction score were found not to differ between the experimental and the control group in Plane I fracture (p=0.755, 0.578, respectively). In a subgroup analysis consisting of Plane II fractures only, surgeons graded outcomes for ultrasound-guided reduction higher than that for the control group (p=0.007). Likewise, among the Plane II fracture patients, those who underwent ultrasound-guided reduction were less dissatisfied than those who underwent blind reduction (p=0.043). Conclusion: Our study result suggests that ultrasound-guided closed reduction is superior to blind closed reduction in those patients with Plane II nasal fractures.

• 터널과지하공간
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• 제21권3호
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• pp.235-243
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• 2011

본 연구에서는 SB발파에서 평활한 최종파단면과 발파손상영역을 제어하고, 동시에 발파진동을 제어하기 위한 목적으로 무장약 균열 유도공을 이용한 제어발파기법을 제안하였다. 무장약 균열유도공의 파단면 제어 유효성을 검토하기 위하여 일반 SB발파와 무장약 균열 유도공 적용한 SB발파에서 암반 내 발생하는 파괴과정을 수치해석법으로 모사하여 파단면을 분석하였다. 제발효과를 높이기 위하여 도폭선에 의한 기폭을 고려하였으며, 무장약 균열 유도공을 중심으로 양쪽에 장약공이 설치된 일자유면 발파로 가정하여 암반의 파괴과정해석을 수행하여 SB발파에서 무장약 균열 유도공에 의한 파단면 형성 기구를 고찰하였다. 결과적으로, 공간격이 40cm 이하에서 무장약 균열 유도공을 사용한 경우가 낮은 파단면 거칠기를 보여 파단면 제어 효과가 있음을 입증 하였다.

• 화약ㆍ발파
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• 제26권1호
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• pp.57-66
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• 2008

발파에서 특정한 방향으로 균열 성장을 제어하는데 장약공 노치가 유효하다는 연구결과가 발표되어오고 있다. 본 연구에서는 장약공의 노치가 파단면 형성에 미치는 영향을 살펴보기 위하여 일반 장약공과 노치 장약공에 의한 파단면의 표면을 비교하였다. 암석시편에 노치를 형성하기 위하여 노치비트시스템이 적용되었다. 파단면의 표면은 디지털 영상 계측법을 적용하여 DEM 모델로 재구성하고, 표면 거칠기 지수를 사용하여 파단면의 거칠기를 평가하였다.

• 대한조선학회논문집
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• 제34권3호
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• pp.61-69
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• 1997

CT 시험편을 사용하여 평면응력 파괴인성치를 산정하는 간단하고 새로운 방법론을 제안하였다. 평면응력 조건하의 균열선단에서 발생하는 좌굴을 방지하는 판을 부착하여 SS304와 SS316의 평면응력 파괴인성치를 정확하게 결정하였다. SS304와 SS316의 피로균열 전파거동이 피로하중 주파수에 미치는 영향을 영상해석법(LAT)을 사용하여 규명하였다.

• Structural Engineering and Mechanics
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• 제65권6호
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• pp.699-706
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• 2018

In the present contribution, fracture resistance of U-notched GPPS members under mixed mode I/III loading conditions is assessed by using the Averaged Strain Energy Density (ASED) criterion. This criterion has been founded based on the ASED parameter averaged over a well-defined control volume embracing the notch edge. The validation of the theoretical criterion predictions is evaluated through comparing with the results of a series of mixed mode I/III fracture tests conducted on rectangular-shaped GPPS specimens weakened by a single edge U-notch. A recently developed apparatus for mixed mode I/III fracture experiments is employed for measuring the fracture loads of the specimens. The test samples are fabricated with different notch tip radii with the aim of evaluating the influence of this major feature of the U-notched components on the mixed mode I/III fracture behavior. It is shown that the onset of brittle fracture in U-notched GPPS specimens under various combinations of tension and out-of-plane shear can well be predicted by means of the ASED criterion.

• Restorative Dentistry and Endodontics
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• 제17권1호
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• pp.153-165
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• 1992

Dental composite resin is a kind of the particle - reinforced composite material, and is widely used in recent dental restoration of anterior and posterior tooth region. The purpose of this study was to investigate the fracture behaviour according to volume fractions and external findings of the filler particles for better interpretation of the fracture characteristics of posterior dental composite resins by analytic method of fracture mechanics. The plane strain fracture toughness($K_{IC}$) and Acoustic Emission were determined with three - point bending test using the single edge notch specimen according to the ASTM - E399, and its analyzed data was compared with filler volume fractions derived from the standard ashing test and scanning electron fractographs of each specimen including the unfilled experimental resin as a control. The results were that the value of fracture toughness of the composite resin material was in the range from 0.85 MPa$\sqrt{m}$ to 1.60 MPa$\sqrt{m}$ and was higher than the value of the unfilled experimental resin, and the fracture behaviours dervied from Acoustic Emission analysis show prominent differences according to the volume fraction and the size of filler particles used in each composite resin. The degree of resistance against crack propagation seems to be increase and the fractographs demonstrate the high degree of surface roughness and irregularity according with the increase of fracture toughness value.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제39권5호
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• pp.217-223
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• 2013

Objectives: Buccal fracture of the mandibular proximal bone segment during bilateral sagittal split ramus osteotomy (SSRO) reduces the postoperative stability. The primary aim of this study is to evaluate the effect of this type of fracture on bone healing and postoperative stability after mandibular setback surgery. Materials and Methods: Ten patients who experienced buccal fracture during SSRO for mandibular setback movement were evaluated. We measured the amount of bone generation on a computed tomography scan, using an image analysis program, and compared the buccal fracture side to the opposite side in each patient. To investigate the effect on postoperative stability, we measured the postoperative relapse in lateral cephalograms, immediately following and six months after the surgery. The control group consisted of ten randomly-selected patients having a similar amount of set-back without buccal fracture. Results: Less bone generation was observed on the buccal fracture side compared with the opposite side (P<0.05). However, there was no significant difference in anterior-posterior postoperative relapse between the group with buccal fracture and the control group. The increased mandibular plane angle and anterior facial height after the surgery in the group with buccal fracture manifested as a postoperative clockwise rotation of the mandible. Conclusion: Bone generation was delayed compared to the opposite side. However, postoperative stability in the anterior-posterior direction could be maintained with rigid fixation.

• 한국세라믹학회지
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• 제34권11호
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• pp.1151-1158
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• 1997

Fracture of uni-directional carbon fiber reinforced carbon matrix composite is strongly dependent on the orientation of basal plane in graphite matrix when it is limited within matrix. The orientation of basal planes are vertically stacked to carbon fiber which results in the weakness for applied tensile or shear force in thermosetting resin derived-carbon matrix composite. Microtextural control of the matrix was tried through chemical interaction between metal carbides and furan resin derived-carbon matrix. SiC and TiO2 addition made the orientation disordered. However, porosity increased due to decomposition of SiC. Interfacial bonding could be controlled by TiO2 addition, but carbon fiber was considerably reacted with TiC during thermal treatment higher than 2$600^{\circ}C$. Therefore, it is desirable to control the thermal treatment temperature at which decomposition of SiC was not serious and TiC/C was not formed eutectoid.

• Restorative Dentistry and Endodontics
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• 제18권1호
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• pp.1-26
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• 1993

The purpose of this study was to investigate the effect of acid etching on the surface appearance and fracture toughness of five glass ionomer cements. Five kinds of commercially available glass ionomer cements including chemical curing filling type, chemical curing lining type, chemical curing metal reinforced type, light curing tilling type and light curing lining type were used for this study. The specimens for SEM study were fabricated by treating each glass ionomer cement with either visible light curing or self curing after being inserted into a rubber mold (diameter 4mm, depth 1mm). Some of the specimens were etched with 37% phosphoric acid for 0, 15, 30, 60, go seconds, at 5 minutes, 1 hour and 1 day after mixing of powder and liquid. Unetched ones comprised the control group and the others were the experimental groups. The surface texture was examined by using scanning electron microscope at 20 kV. (S-2300, Hitachi Co., Japan). The specimens for fracture toughness were fabricated by curing of each glass ionomer cement previously inserted into a metal mold for the single edge notch specimen according to the ASTME399. They were subjected to a three-point bend test after etching for 0, 30, 60, and 90 seconds at 5 minutes-, 1 hour-and 1 day-lapse after the fabrication of the specimens. The plane strain fracture toughness ($K_{IC}$) was determined by three-point bend test which was conducted with cross-head speed of 0.5 mm/min using Instron universal testing machine (Model No. 1122) following seven days storage of the etched specimens under $37^{\circ}C$, 100% humidity condition. Following conclusions were drawn. 1. In unetched control group, crack was present, but the surface was generally smooth. 2. Deterioration of the surface appearance such as serious dissolving of gel matrix and loss of glass particles occured as the etching time was increased beyond 15 s following Immediate etching of chemical curing type of glass ionomer cements. 3. Etching after 1 h, and 1 d reduced surface damage, 15 s, and 30s etch gave rough surface appearance without loss of glass particle of chemical curing type of glass ionomer cements. 4. Light curing type glass ionomer cement was etched by acid, but there was no difference in surface appearances according to various waiting periods. 5. It was found that the value of plane stram fracture toughness of glass ionomer cements was highest in the light curing filling type as $1.79\;MNm^{-1.5}$ followed by the light curing lining type, chemical curing metal reinforced type, chemical curing filling type and chemical curing lining type. 6. The value of plane stram fracture toughness of the chemical curing lining type glass ionomer cement etched after 5 minutes was lower than those of the cement etched after 1 hour or day or unetched (P < 0.05). 7. Light curing glass ionomer cement showed Irregular fractured surface and chemical curing cement showed smooth fractured surface.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제40권
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• pp.36.1-36.5
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• 2018

Background: Botulinum toxin-A (BTX-A) injection into muscle reduces muscular power and may prevent post-operative complication after orthognathic surgery. The purpose of this study was (1) to evaluate BTX-A injection into the masseter muscle on the prevention of plate fracture and (2) to compare post-operative relapse between the BTX-A injection group and the no injection group. Methods: Sixteen patients were included in this study. Eight patients received BTX-A injection bilaterally, and eight patients served as control. All patients received bilateral sagittal split ramus osteotomy for the mandibular setback and additional surgery, such as LeFort I osteotomy or genioplasty. Post-operative plate fracture was recorded. SNB angle, mandibular plane angle, and gonial angle were used for post-operative relapse. Results: Total number of fractured plates in patients was 2 out of 16 plates in the BTX-A injection group and that was 8 out of 16 plates in the no treatment group (P = 0.031). However, there were no significant differences in post-operative changes in SNB angle, mandibular plane angle, and gonial angle between groups (P > 0.05). Conclusions: BTX-A injection into the masseter muscle could reduce the incidence of plate fracture.