• Computers and Concrete
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• 제1권4호
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• pp.371-388
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• 2004

Our objective is to model static multi-cracking processes in concrete. The explicit dynamic relaxation (DR) method, which gives the solutions of non-linear static problems on the basis of the steady-state conditions of a critically damped explicit transient solution, is chosen to deal with the high geometric and material non-linearities stemming from such a complex fracture problem. One of the common difficulties of the DR method is its slow convergence rate when non-monotonic spectral response is involved. A modified concept that is distinct from the standard DR method is introduced to tackle this problem. The methodology is validated against the stable three point bending test on notched concrete beams of different sizes. The simulations accurately predict the experimental load-displacement curves. The size effect is caught naturally as a result of the calculation. Micro-cracking and non-uniform crack propagation across the fracture surface also come out directly from the 3D simulations.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.150-155
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• 2003

Fractures in the form of micro cracks are commonly found in natural rocks. A rock behaves in a complex way due to fracture; in particular, the anisotropic strength of a rock material is significantly influenced by the presence of these fractures. Therefore, it is essential to understand the failure mechanism of a fractured rock. In this study, a fractured rock is formulated in terms of fabric tensor based on geometric and mechanical simplifications. In this way, position, density and shape of fractures can be determined by the fabric tensor so that rocks containing multi-fractures can successfully be modeled. Also an index to evaluate the degree of anisotropy of a fractured rock is proposed. Hence, anisotropic strength of a rock containing fractures under uniaxial compression condition is estimated through a series of numerical analyses for the multi-fractured model. Numerical investigations are carried out by varying the fracture angle from $0^{\circ}\;to\;90^{\circ}$ and relationship between uniaxial compression strength and the degree of anisotropy is investigated. By comparing anisotropic strength of numerical analysis with analytic solution, this study attempts to understand the failure mechanism of rock containing fractures.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.591-604
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• 2009

This paper presents some important issues in modeling rock behaviour around an underground opening at depth which characterized as stress-induced fractural failure of rock. Unlike other conventional modeling approaches, stress-induced rock failure is highly complex process due to its own heterogeneous and discrete natures. Because of this complexity, many researchers has been struggled to mimic such processes as close as possible to reality with various approaches in both analytical, and numerical approaches for past few decades. Such approaches which are based on continuum mechanics, analytical fracture mechanics, and DEM(Discrete Element Method) were explored in this paper, and fundamental shortcomings for each approaches were illustrated here. In addition, DEM approach using $PFC^{2D}$(Particle Flow Code) was also implemented and illuminated in this paper and discuss the improvement and considerations for the future research.

• Journal of Yeungnam Medical Science
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• 제19권2호
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• pp.73-91
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• 2002

Method of management of the spine injury should be determined, based on the status of neurological injury as well as on the presence of traumatic instability. At the thoracic and lumbar spine, patterns of neurological injury are different from the cervical spine due to their neuro-anatomical characteristics. Especially, at the thoracolumbar junction, neurological injury patterns with their respective prognosis vary from the complete cord injury or conus medullaris syndrome to the cauda equina syndrome according to the injury level. The concept of Holdsworth's instability based on the posterior ligament complex theory has evolved into the current 3-column theory of Denis. Flexion-rotation injury and fracture-dislocation are well known to be unstable that surgical fixation is frequently needed for these injuries. However, there have been some controversies for the stability of burst fractures and their treatment, such as indirect or direct decompression and anterior or posterior approach. In this article, current concepts and management of traumatic instabilities at the thoracic and lumbar spine have been reviewed and summarized.

• Clinics in Shoulder and Elbow
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• 제22권2호
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• pp.113-117
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• 2019

Treating distal humerus fractures, especially those involving intra-articular lesions, is complex and often technically demanding. Although there still exist many controversial issues, the goal of treatment is to establish anatomical stable fixation by restoring the two columns and the articular surface. Universally, a posterior midline incision is applied, and the approach varies according to the further management of the triceps or olecranon. Evidence supports dual plate fixation as the optimal fixation method, and debates regarding appropriate plating configuration are still ongoing. As multiple clinical studies comparing results of parallel and perpendicular plate fixation have shown no actual difference, it is important to place the plates according to the fracture configuration.

• 국제강구조저널
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• 제18권4호
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• pp.1125-1138
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• 2018

During earthquakes, braces behave in complex manners because of the asymmetric response nature of their responses in tension and compression. Hollow structural sections (HSS) have been popularly used for braces due to their sectional efficiency in compression. The purpose of this study is to accurately simulate the cyclic behavior of rectangular HSS braces using a computationally efficient numerical model. A conceptually efficient and simple physical theory model is used as a basis model. To improve the accuracy of the model, cyclic beam growth and buckling load, as well as the incidences of local buckling and brace fracture are estimated using empirical equations obtained from regression analyses using test data on rectangular HSS braces. The accuracy of the proposed model is verified by comparing actual and simulated cyclic curves of brace specimens with various slenderness and width-to-thickness ratios.

• Archives of Plastic Surgery
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• 제38권3호
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• pp.263-272
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• 2011

Purpose: The human face is the most exposed part of the body, and in patients with simple or complex trauma from traffic accidents, industrial calamities, sports injuries, human assaults, and daily accidents, facial trauma occupies an important portion. The etiology of facial trauma vary on a society's economic, cultural, and environmental status. Methods: Regarding patients who were admitted from between the years 2000 to 2009 at the Hanyang University hospital, the authors studied how the changes in the economic status in the past 10 years of our country influences the incidence of facial bone fractures. Results: In this study, 1) The unemployment rate showed a strong negative relationship with the total number of inpatients with facial bone fractures, the number of male patients, the number of female patients, the number of patients with facial bone fractures caused by fall down, the number of patients who were admitted for shorter than 7 days, and the number of the facial bone fracture patients with their age in the twenties. 2) The consumer price index showed a strong positive relationship with the number of female patients, the number of patients who were admitted for shorter than 7 days, and the number of the facial bone fracture patients with their age in the teens and fifties. Conclusion: Looking at the results of correlation analysis and multiple regression analysis with economic indicators, the unemployment rate showed negative influence to the total number of inpatients with facial bone fractures, and the number of inpatients with facial bone fractures caused by fall down, with statistical significance.

• Archives of Plastic Surgery
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• 제40권5호
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• pp.546-552
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• 2013

Background The zygoma is a major portion of the midfacial contour. When deformity occurs in this area, a reduction should be conducted to correct it. If a sagittal fracture at the temporal root of the zygomatic arch occurs, this also requires reduction, but it is difficult to approach due to its anatomical location, and the possibility of fixation is also limited. Thus, the authors attempted the reduction of sagittal fracture by two- or three-point fixation and the Gillies approach without direct manipulation. The preoperative and postoperative results of the patients were evaluated. Follow-up was performed to establish a treatment guideline. Methods A retrospective study was done with 40 patients who had sagittal fractures at the temporal root of the zygomatic arch from March 2009 to June 2012. Only two- or three-point fixation was performed for the accompanying zygomatic-orbital-maxillary fracture. The Gillies approach was used for complex fractures of the zygomatic arch, while the temporal root of the zygomatic arch was only observed without reduction. Preoperative and postoperative computed tomography and X-ray scans were performed to examine the results. Results The result of the paired t-test on preoperative and postoperative bone gap differences, the depression level, and the degree of temporal protrusion showed a marked decrease in the mean difference at a 95% confidence interval. The results were acceptable. Conclusions In the treatment of sagittal fractures at the temporal root of the zygomatic arch, it is acceptable to use indirect reduction and non-fixation methods. This leads to a satisfactory aesthetic and functional outcome.

• Journal of Trauma and Injury
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• 제31권2호
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• pp.103-106
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• 2018

Fat embolism refers to the presence of fat droplets within the peripheral and lung microcirculation with or without clinical sequelae. However, early diagnosis of fat embolism is very difficult because the embolism usually does not show at the computed tomography as a large fat complex within vessels. Forty-eight-year-old male with pedestrian traffic accident ransferred from a local hospital by helicopter to the regional trauma center by two flight surgeons on board. At the rendezvous point, he had suffered with dyspnea without any airway obstruction sign with 90% of oxygen saturation from pulse oximetry with giving 15 L of oxygen by a reserve bag mask. The patient was intubated at the rendezvous point. The secondary survey of the patient revealed multiple pelvic bone fracture with sacrum fracture, right femur shaft fracture and right tibia head fracture. Abdominal computed tomography was performed in 191 minutes after the injury and fat embolism with Hounsfield unit of -86 in his right common iliac vein was identified. Here is a very rare case that mass of fat embolism was shown within common iliac vein detected in computed tomography. Early detection of the fat embolus and early stabilization of the fractures are essential to the prevention of sequelae such as cerebral fat embolism.

• 대한정형외과 초음파학회지
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• 제6권2호
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• pp.60-64
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• 2013

원위 요골 골절에 대한 수장부 금속판 고정술이 많이 사용되면서, 합병증으로서, 원위 요골 배측 피질골을 관통한 나사못으로 인해 신전건 활막염이나 파열이 발생할 수 있슴이 보고된 바 있다. 그러나, 나사못에 의한 배측 피질골의 관통여부를 표준 방사선 촬영만으로 정확히 평가하기에는 한계가 있다. 저자들은 수장측 금속판 고정술 후 발생한 신전건 건활막염 및 부분 파열이 의심된 환자에 대하여 수술 전 초음파를 이용하여 나사못에 의한 건활막염 및 활막 종괴 형성 소견을 효과적으로 진단하고 수술적 치료를 시행하여 좋은 결과를 얻었기에 이를 보고하고자 한다.