• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2001년도 추계학술발표회
• /
• pp.231-234
• /
• 2001

When constructing subsurface structures and/or wells, the precise estimates of hydraulic parameters must be obtained for operating safety and/or for developing necessary quantity of groundwater. Hydraulic conductivity is mainly subjected to the characteristics of fracture network in the fractured media such as fracture orientation and angle, fracture aperture and frequency, fracture length, interconnectivity of fractures, and filling material, feature of fracture plane. In this study we conducted water injection test at afferent depths on six boreholes drilled in granite of Mt. Geumjeong. hydraulic conductivity was calculated using Moye and Hvorslev methods. The relation between hydraulic conductivity and fracture frequency data obtained from acoustic televiewer and core log were analyzed. The result shows that the correlation between the hydraulic conductivity and the fracture frequency data obtained from acoustic televiewer is better than that with the core log.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 춘계 학술발표회
• /
• pp.58-63
• /
• 2009

Biaxial compression test was conducted on a transversely isotropic synthetic jointed rock model for the understanding of the fracture behaviors of a sedimentary or metamorphic rocks with well developed bedding or foliation in uni-direction. The joint angles employed for the model are 30, 45, and 60 degrees to the horizontal, and the synthetic rock mass was made of early strength cement. From the biaxial compression test, initiation propagation of tensile cracks at norm to the joint angle was found. The propagated tensile cracks eventually developed rock blocks, which was dislodged from the rock mass. Furthermore, the propagation process of the tensile cracks varies with joint angle: lower joint angle model shows more stable and progressive tensile crack propagation. The experiment results were validated from the simulation by using discrete element method PFC 2D. From the simulation, as has been observed from the test, a rock mass with lower joint angle produces wider damage region and rock block by tensile cracks. In addition, a rock model with lower joint angle shows a progressive tensile cracks generation around the opening from the investigation of the interacted tensile cracks.

• 한국세라믹학회지
• /
• 제56권5호
• /
• pp.506-512
• /
• 2019

Although graphene has been successfully grown in large scale via chemical vapor deposition (CVD), it is still questionable whether the mechanical properties of CVD graphene are equivalent to those of exfoliated graphene. In addition, there has been an issue regarding how the tilt angle of the grain boundary (GB) affects the strength of graphene. We investigate the mechanical properties of CVD graphene with nanoindentation from atomic force microscopy and transmission electron microscopy. Surprisingly, the samples with GB angles of 10° and 26° yielded similar fracture stresses of ~ 80 and ~ 79 GPa, respectively. Even for samples with GB exhibiting a wider range, from 0° to 30°, only a slightly wider fracture stress range (~ 50 to ~ 90 GPa) was measured, regardless of tilt angle. The results are contrary to previous studies that have reported that GBs with a larger tilt angle yield stronger graphene film. Such a lack of angle dependence of GB can be attributed to irregular and well-stitched GB structures.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• 제11권1호
• /
• pp.87-92
• /
• 1989

Transbuccal trocar has been an established method of fixation for the bone plate in the case of mandibular angle fracture. Other than extraoral approaches, this transbuccal approach has many advantages in the treatment of the fracture of mandibular angle. These advantages are as follows ; (1) Damage to the facial nerve branches is minimal. (2) Less postoperative scar is formed. (3) Good vision of occlusion can be easily obtained on the entire operation. (4) Shorter operation time is needed. But, in the clinical procedure of plate fixation, it is has a difficulty in manipulation of the plate and correction of position. To solve these problems, we designed and used a trocar tip which can be easily attached to the trocar, and could make an improvement in the clinical procedures.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
• /
• pp.223-225
• /
• 2006

In this study, the graphite/epoxy prepregs were surface-treated using oxygen plasma, and optimal treatment time was determined measuring the contact angle en the prepreg surface. Interlaminar fracture behavior of surface-treated graphite/epoxy composite was compared with that of regular (untreated) graphite/epoxy composites. The results showed that the contact angle was a minimum when treated for 30 minutes. The interlaminar fracture toughness of surface-treated specimen was improved about 15% compared with that of regular specimen.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2002년도 봄 학술발표회 논문집
• /
• pp.173-180
• /
• 2002

The specimens with three discontinuities have been tested in uniaxial compression. The geometry of discontinuities is changed by three different parameters: flaw inclination angle, continuity, and spacing. From the tips of the discontinuities wing and secondary cracks are observed. Wing cracks initially propagate curvilinear direction and follow loading direction after some distance from the tip of the discontinuities. Two different types of secondary cracks have been observed from the study: quasi-coplanar secondary cracks and oblique secondary cracks. From the test nine different types of coalescence are observed and they show a correlation with flaw angle and ligament angle. It is attempted to simulate the observed results by using FROCK(Fractured ROCK). FROCK is a code based on the hybridized DDM(Displacement Discontinuities Method) . It is shown that FROCK has quite potential of modeling of rock fracture processes.

• 대한기계학회논문집A
• /
• 제40권12호
• /
• pp.1013-1019
• /
• 2016

CFRP는 탄소섬유를 기반으로 수지를 합침하여 제조된 복합소재로, 높은 비 강도와 경량성을 지녀 다양한 분야들에서 널리 사용되어지고 있다. 특히 일방향 탄소섬유는 적층 각도를 적용할 수 있으며 이때 적용된 적층 각도로 구성된 CFRP는 적층 각도가 없는 것보다 더 높은 강성을 가지고 있다. 본 논문에서는 적층 각도 변화에 따른 CFRP 소형 인장시험편의 크랙 전파와 파괴거동에 관한 것으로, 각 적층 각도에 따른 크랙 성장의 특성을 고찰한다. 적층 각도가 증가함에 따라 최대 응력 값이 작게 나타나고 크랙 전파가 더디게 나타나지만, 적층 각도 $60^{\circ}$를 기점으로 그 응력이 다시 증가되므로 서, 적층 각도에 따른 한계를 보이고 있다. 본 연구결과는 기계구조물의 CFRP사용에 있어 구조물내의 결함이 발생하였을 때의 피로파괴 가능성을 검증하는 자료로 사용될 수 있다고 사료된다.

• 대한족부족관절학회지
• /
• 제13권2호
• /
• pp.118-123
• /
• 2009

Purpose: We wanted to evaluate the relating factors for deformities of the foot after tibial fracture and the outcome of respective surgical treatment. Materials and Methods: We studied thirty-two patients (thirty-five feet) who had foot deformities after tibia fracture. The age, gender, shape, location, concurrent soft tissue injury and operative treatment of tibial fracture were analysed and outcome of the surgical treatment was investigated. Results: Deformities of the foot mostly occurred in open fractures of Gustilo type 3 or closed fracture with severe soft tissue injury. Variable surgical treatments such as simple release, lengthening, Z-plasty and osteotomy were performed. The AOFAS ankle-hind foot scale was improved from average of 37.3 points preoperatively to an average of 77.2 points at the last follow up. The Maryland foot score was from 42.9 to 90.2 and AOFAS Lesser Toe Metatarso-phalangeal interphalangeal scale was from 42.9 to 90.5. Radiological correction was also improved from 21.9 degrees to 7.9 degrees (Meary angle), from 112.2 to 138.5 (Hibb's angle) and from 33.8 to 25.9 (Calcaneal pitch). Conclusion: We proposed that great care should be taken of treatment for the tibial fracture and early detection and proper management of the foot deformities are crucial.

• 대한족부족관절학회지
• /
• 제13권1호
• /
• pp.85-90
• /
• 2009

Purpose: Nonunion of intra-articular fractures of calcaneus is rarely reported complication. We present our experiences with 4 patients (5 cases) treated operatively for nonunion after intra-articular fracture of calcaneus. Materials and Methods: 4 patients (5 cases) with nonunion of intra-articular fracture of calcaneus after operative treatment were followed for 4 years (from 2002 to 2006). For assessment, the American Orthopedic Foot and Ankle Society (AOFAS) ankle-hindfoot score and Visual Analogue Scale (VAS) were assessed for clinical outcome and the union of fracture site, the talocalcaneal height and the angle of talar declination were determined for radiologic outcome. Results: The mean talocalcaneal height was 6.94 cm (range, 5.9${\sim}$7.6 cm) preoperatively and 7.34 cm (range, 6.0${\sim}$8.3 cm) at last follow-up. The mean angle of talar declination was 5.68 degrees (range, 4.6${\sim}$8 degrees) preoperatively and 13.1 degrees (range, 5.7${\sim}$21 degrees) at last follow-up. The mean preoperative AOFAS score and VAS were 20.4 (range, 14${\sim}$36) and 4 (range, 3${\sim}$6), respectively. At last follow-up, these scores improved to a mean of 59.6 (range, 54${\sim}$68) and 3 (range, 2${\sim}$4), respectively. Unions of previous nonunion site of intra-articular fracture of calcaneus were achieved in all 4 patients (5 cases). Conclusion: The reconstructive procedure for nonunion of intra-articular fracture of calcaneus showed good results in terms of bone union, radiologic results and functional improvement than preoperative state. Because the plantar pain for the inferior angular formation in nonunion site may happen, we will pay attention to reduction of fragment.

• 콘크리트학회지
• /
• 제8권6호
• /
• pp.235-243
• /
• 1996

콘크리트의 역학적거동은 다양한 종류의 균열의 발생과 전파에 의하여 영향을 받는다. 최근 고성능 콘크리트의 개발이 이루어지면서 계면파괴와 계면역에서의 균열양상에 대한 연구가 중요한 분야로 부각되고 있다. 탄성이며 균질한 재료에 적용되는 균열전파에 대한 규준은 계면역에서 균열이 진전하는 경우는 유효하지 않으며 이 경우에는 콘크리트에서 균열전파를 예측하기 위하여 구성재료들의 파괴인성과 그들 사이 계면의 파괴인성의상대적인 크기를 고려하여야 한다. 본 논문에서는 계면균열선단에서 계면파괴역학변수인 에너지해방률과 하중위상각을 수치해석방법을 이용하여 구하는 방법과 계면에서의 균열전파의 예측을 위한 에너지해방률에 기초를 둔 파괴규준을 제안하였다. 계면역에서의 균열양상을 조사하기 위하여 계면균열을 가진 이상복합모델에 대한 실험과 수치해석연구를 수행하였으며 대체적으로 실험결과와 규준을 이용하여 예측한 결과가 서로 일치하는 결과를 얻었다.