• Journal of Korean Neurosurgical Society
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• 제29권11호
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• pp.1461-1468
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• 2000

Objective : The aim of this study is to evaluate clinical outcome of anterior screw fixation for type II odontoid fractures for the prliematim of atlanatoaxial mobility. Methods : Between 1995 and 1999, we treated 15 cases of type II odontoid fractures by anterior screw fixation among 44 cases of odontoid fractures. Thece included 14 males and 1 female aged from 23 to 63 years, with a mean age of 39.7 years. The causes of trauma were traffic accident in 13 cases, slip down in 1 and fall down in 1. The fracture type was type II-P in 7 cases, type II-A in 3, type II-N in 2 and type II-A and P in 3. The fracture line was oblique downward and backward in 6 cases, oblique downward and forward in 3 and horizontally in 6. The range of follow up was 4 to 47 months(mean 26.5 months). Results : Adequate reduction and fixation were obtained in 12 cases. Three cases in which fracture type and line were type II-A and oblique downward forward were failed, so posterior transarticular screw fixation was performed. All except 3 failed cases had adequate cervical movement and stability. There were no operative mortality nor morbidity. Conclusion : Anterior screw fixation provides the best anatomical and functional results for type II odontoid fracture with intact transverse ligament when fracture line is horizontal or oblique downward and backward. But it is limited when fracture line is oblique downward and forward.

• 한국터널지하공간학회 논문집
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• 제15권6호
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• pp.547-557
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• 2013

전단응력에 의한 전단강도 및 모드 II 파괴인성은 이산화탄소 지중저장에서의 덮개암 및 주입층의 안정성 평가에 활용되는 중요한 인자들이다. 본 연구에서는 짧은 보 압축시험을 이용하여 코코니노 사암의 전단강도 및 모드 II 파괴인성을 측정하였다. 측정된 평균 전단강도는 23.53 MPa이며, 모드 II 파괴인성은 1.58 MPa${\surd}$m이다. 응력확대계수(stress intensity factor)는 변위외삽법(displacement extrapolation method)을 이용한 유한요소법으로 결정하였다. 또한 이축응력(biaxial stress)과 수분포화(water saturation)가 모드 II 파괴인성에 미치는 영향을 분석하였다. 그 결과 이축응력이 증가할수록 파괴인성도 증가하였고, 완전포화된 시험편의 파괴인성은 건조상태의 파괴인성보다 대략 11.4% 감소하였다.

• 대한의용생체공학회:의공학회지
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• 제31권3호
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• pp.199-209
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• 2010

The locking compression plates-distal femur(LCP-DF) are being widely used for surgical management of the extra-articular complex fractures of the distal femur. They feature locking mechanism between the screws and the screw holes of the plate to provide stronger fixation force with less number of screws than conventional compression bone plate. However, their biomechanical efficacies are not fully understood, especially regarding the number of the screws inserted and their optimal configurations. In this study, we investigated effects of various screw configurations in the shaft and the condylar regions of the femur in relation to structural stability of LCP-DF system. For this purpose, a baseline 3-D finite element (FE) model of the femur was constructed from CT-scan images of a normal healthy male and was validated. The extra-articular complex fracture of the distal femur was made with a 4-cm defect. Surgical reduction with LCP-DF and bone screws were added laterally. To simulate various cases of post-op screw configurations, screws were inserted in the shaft (3~5 screws) and the condylar (4~6 screws) regions. Particular attention was paid at the shaft region where screws were inserted either in clustered or evenly-spaced fashion. Tied-contact conditions were assigned at the bone screws-plate whereas general contact condition was assumed at the interfaces between LCP-DF and bone screws. Axial compressive load of 1,610N(2.3 BW) was applied on the femoral head to reflect joint reaction force. An average of 5% increase in stiffness was found with increase in screw numbers (from 4 to 6) in the condylar region, as compared to negligible increase (less than 1%) at the shaft regardless of the number of screws inserted or its distribution, whether clustered or evenly-spaced. At the condylar region, screw insertion at the holes near the fracture interface and posterior locations contributed greater increase in stiffness (9~13%) than any other locations. Our results suggested that the screw insertion at the condylar region can be more effective than at the shaft during surgical treatment of fracture of the distal femur with LCP-DF. In addition, screw insertion at the holes close to the fracture interface should be accompanied to ensure better fracture healing.

• Geomechanics and Engineering
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• 제17권2호
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• pp.215-225
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• 2019

The mechanical behavior of rock is essential to estimate the capacity and long-term stability of $CO_2$ storage in deep saline aquifers. As the depth of reservoir increases, the pressure and temperature that applied on the rock increase. To answer the question of how the confining pressure and temperature influence the mechanical behavior of reservoir rock, triaxial compression experiments were carried out on brine-saturated sandstone at elevated temperature. The triaxial compressive strength of brine-saturated sandstone was observed to decrease with increasing testing temperature, and the temperature weakening effect in strength enhanced with the increase of confining pressure. Sandstone specimens showed single fracture failures under triaxial compression. Three typical regions around the main fracture were identified: fracture band, damaged zone and undamaged zone. A function was proposed to describe the evolution of acoustic emission count under loading. Finally, the mechanism of elevated temperature causing the reduction of strength of brine-saturated sandstone was discussed.

• 대한치과보철학회지
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• 제42권3호
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• pp.280-293
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• 2004

Statement of problem. Glass fiber post is one of recent developments to accommodate esthetic restoration for endodontically treated teeth. This has many advantages over conventional post system in physical properties, esthetic factor, risk of root and restoration fracture, adhesion to core, radiopacity, removal and retrievabilty, biocompatibility and chemical stability. Purpose. This in vitro study was to evaluate the most suitable type of resin core for the glass fiber post through surveying the fracture modes and the maximum load that fractures the tooth. Material and methods. 50 sound maxillary premolars restored with glass fiber posts($ParaPost^{(R)}$ Fiber White) and different types of resin cores(ParaCore, $Z100^{TM}$, $Rebilda^{(R)}$ and $Admira^{(R)}$) were prepared and loaded to faiure in a universal test machine. The maximum fracture load and fracture mode were investigated in the specimens that were restored with resin and those of metal cast and core. With the data, Wilcoxon rank sum test was used to validate the significance between the test groups, and Tukey' s studentized range test was used to check if there is any significant statistical difference between each test group. Every analysis was approved with 95% reliance. Results. On measuring the maximum fracture load of teeth specimens, there was a significant difference between the maximum fracture loads of the tooth specimens. ParaCore showed the highest mean maximum fracture load followed by $Z100^{TM}$. And, the distribution of fracture mode of tooth specimens showed generally Type D, the three parted fracture of the core around the post was mostly seen(62.5%), and specifically, ParaCore showed 90% and $Z100^{TM}$ showed 100% Type D fracture. Conclusion. Referring to the values of maximum fracture load and mean compressive fracture load, ParaCore and $Z100^{TM}$ had high values and are recommended as tooth colored resin core material for glass fiber post. CLINICAL IMPLICATIONS. This study was carried out intending to be of aid in selecting the appropriate resin core for the glass fiber post. The dual cure type composite resin ParaCore and light cure type composite resin $Z100^{TM}$ have good properties and are recommended as tooth colored resin core material for glass fiber post.

• 한국구조물진단유지관리공학회 논문집
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• 제17권4호
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• pp.30-37
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• 2013

연암 파쇄대는 암반 사면이나 흙막이 공법에서 중요한 요소 중의 하나이지만, 흙막이 벽체의 안정성 연구는 미흡한 실정이다. 따라서 본 연구는 연암 파쇄대에 설치된 조건과 연암 파쇄대에 미설치된 조건에 따른 흙막이 벽체의 거동을 비교 분석하기 위하여 현장 계측데이터와 흙과 구조물의 상호작용을 고려한 유한요소법으로 수치해석 등을 실시하였다. 그 결과 흙막이 벽체에 작용하는 수평변위는 현장 계측결과와 파쇄대 조건의 수치해석 결과와는 거의 일치하는 것으로 나타났으며, 변위 지점 응력분포는 파쇄대 조건에서는 안정측으로 해석되었지만, 파쇄대 미조건에서는 불안정으로 결과가 도출되었다. 이 연구결과를 추후 설계 시 현장의 안전을 최우선으로 한 시공에 적용하는데 목적이 있다.

• 한국소음진동공학회논문집
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• 제20권5호
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• pp.453-459
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• 2010

In this paper, the purpose is to investigate the stability of cracked cantilever T-beams subjected to axial force. In addition, an analysis of the natural frequency of a cracked beams as crack position, crack depth and tip mass is investigated. Based on the Euler-Bernoulli beam theory, the equation of motion is derived by the energy expressions using extended Hamilton's Principle. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. The results of this study will contribute to the safety test and stability estimation of structures of a cracked T-beams subjected to axial force.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.356-359
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• 2007

In this paper, the stability of a rotating cantilever pipe conveying fluid with a crack is investigated by the numerical method. That is, the influences of the rotating angular velocity, mass ratio and crack severity on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating pipe are derived using the Euler beam theory and the Lagrange's equation. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. Generally, the critical flow velocity for flutter is proportional to the angular velocity and the depth of crack. Also, the critical flow velocity and stability maps of the rotating pipe system as a function of mass ratio for the changing each parameter are obtained.

• 한국소음진동공학회논문집
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• 제17권12호
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• pp.1161-1169
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• 2007

In this paper, the dynamic stability of a rotating cantilever pipe conveying fluid with a crack is investigated by the numerical method. That is, the influence of the rotating angular velocity, mass ratio and crack severity on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating cantilever pipe are derived by using extended Hamilton's principle. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of fracture and always opened during the vibrations. Generally, the critical flow velocity for flutter is proportional to the rotating angular velocity of a pipe. Also, the critical flow velocity and stability maps of the rotating pipe system for the variation each parameter are obtained.

• 한국소음진동공학회논문집
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• 제17권1호
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• pp.10-16
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• 2007

In this paper, the dynamic stability of a cracked simply supported pipe conveying fluid is investigated. In addition, an analysis of the flutter and buckling instability of a cracked pipe conveying fluid due to the coupled mode(modes combined) is presented. Based on the Euler-Bernouli beam theory, the equation of motion can be constructed by using the Galerkin method. The crack section is represented by a local flexibility matrix connecting two undamaged pipe segments. The stiffness of the spring depends on the crack severity and the geometry of the cracked section. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. This results of study will contribute to the safety test and a stability estimation of the structures of a cracked pipe conveying fluid.