• Composites Research
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• 제36권1호
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• pp.59-67
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• 2023

항공우주산업에서 경량화를 위해 사용되는 CFRP 복합재료로 구성된 차체의 충격에 따른 파손은 탑승자의 안전과 직결된다. 따라서 충돌 상황에서 육안으로 확인하기 힘든 재료의 손상거동을 파악하는 것이 중요하며, 이를 구현할 수 있는 유한요소모델을 통한 연구가 필요하다. 본 연구에서는 일방향 적층 복합재료의 충돌 해석에 대해 파손 거동 예측에 적합한 유한요소모델을 구축하였다. 인공신경망 모델을 통해 LS-DYNA에서 제공하는 MAT_54 Enhanced Composite Damage 재료 모델의 교정 파라미터를 역추정하여 획득하였다. 획득한 파라미터에 대한 인공신경망 모델의 결과를 실험결과와 비교하여 신뢰성을 검증하였다. 그 결과, 교정 파라미터의 최적화를 통해 실험에 대한 정확도를 향상시킨 유한요소모델을 구축할 수 있음을 확인하였다.

• 대한토목학회논문집
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• 제35권4호
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• pp.769-777
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• 2015

본 연구에서는 속도 의존성을 나타내는 콘크리트의 인장거동을 모사하기 위하여 유변학적(rheological) 모델을 개발하였고 이를 평가하였다. 일반적으로 외부에서 가해지는 하중 속도가 증가할수록 콘크리트의 물성(강도, 탄성계수, 파괴에너지 등)은 그 크기가 증가한다. 콘크리트의 강도는 다른 물성에 비하여 큰 속도의존성을 나타내고, 압축 하중인 경우보다 인장 하중을 받는 경우 그 속도의존성이 크게 나타난다. 이러한 콘크리트의 속도 의존성을 모사하기 위하여, 기존 RBSN(Rigid-Body-Spring-Network) 모델의 거동을 나타내는 스프링 세트에 대쉬포트(Dashpot)와 같은 점성 요소와 Coulomb 마찰 요소를 조합하였다. 요소의 조합에 따라 세 가지 모델( 1)점탄성, 2)점소성, 3)점탄소성 손상(Damage 모델)을 고려하였고, 이에 대한 구성관계식을 유도하였다. 개발된 해석모델은 직접인장 실험의 응력-변형률 관계곡선과 비교 검증되었고, 이중 점탄소성 손상 모델은 실험결과를 잘 모사할 수 있음을 확인하였다.

• Geomechanics and Engineering
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• 제36권2호
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• pp.167-181
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• 2024

The soil-structure relative stiffness is a key factor affecting the seismic response of underground structures. It is of great significance to study the soil-structure relative stiffness for the soil-structure interaction and the seismic disaster reduction of subway stations. In this paper, the dynamic shear modulus ratio and damping ratio of an inhomogeneous soft soil site under different buried depths which were obtained by a one-dimensional equivalent linearization site response analysis were used as the input parameters in a 2D finite element model. A visco-elasto-plastic constitutive model based on the Mohr-Coulomb shear failure criterion combined with stiffness degradation was used to describe the plastic behavior of soil. The damage plasticity model was used to simulate the plastic behavior of concrete. The horizontal and vertical relative stiffness ratios of soil and structure were defined to study the influence of relative stiffness on the seismic response of subway stations in inhomogeneous soft soil. It is found that the compression damage to the middle columns of a subway station with a higher relative stiffness ratio is more serious while the tensile damage is slighter under the same earthquake motion. The relative stiffness has a significant influence on ground surface deformation, ground acceleration, and station structure deformation. However, the effect of the relative stiffness on the deformation of the bottom slab of the subway station is small. The research results can provide a reference for seismic fortification of subway stations in the soft soil area.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 International Symposium
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• pp.183-199
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• 2002

Reliability.The reliability strongly depended on the CTE of underfill resin..The fractured portion was identical with the maximum plastic equivalent strain..1 % or less value of the maximum plastic equivalent strain certified more than 1000 cycle of TCT life. UFB.Bonding accuracy was confirmed within2$2{\mu}{\textrm}{m}$..The fundamental bondability of UFB was confirmed with no damage around aluminum pads. Some dislocations and vacancies were observed at the interface, however, the atomic level bonding was confirmed. CBB.Dry process was applied to UBM removal.

• Archives of Reconstructive Microsurgery
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• 제23권2호
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• pp.93-96
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• 2014

The microscope is a surgical instrument with wide use in plastic surgeries more often than other departments due to the high rate of microscopic surgeries. Unfortunately, because the microscope is used mainly for digital replantations and free flaps, the utilization rate is low compared to the price and usability of the microscope itself. From September 2013 to March 2014, a foreign body which was untraceable with radiology in a patient who desired surgical exploration (one case), and a foreign body which was detected but was smaller than 3 mm (two cases) were removed using the microscope. All foreign bodies, which were fish bone, thin metals, or wooden objects, matching the history of the patients, were completely removed without damage. There were no complications and patient satisfaction was high through follow-up. We have described the microscope as the last and optimal examination tool in removal of micro foreign bodies. A simple change of thought, so that the microscope can be used as a second diagnostic tool will decrease complications by foreign bodies.

• Archives of Plastic Surgery
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• 제33권3호
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• pp.392-397
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• 2006

Orbital pseudotumor, also known as idiopathic orbital inflammatory syndrome(IOIS), may have protean clinical manifestations. IOIS should be determined with a diagnosis of exclusion, with evaluation directed toward eliminating other causes of orbital disease. Orbital MRI and CT are the important diagnostic tests, but serologic studies are necessary to exclude a systemic causes. Biopsy is usually not performed currently, as the risk of producing damage to vital structures within the orbital outweighs the benefits. Patients with multiple recurrences, or those unresponsive to therapy, should be treated of biopsy sample extraction. Corticosteroids are the mainstay of therapy and administered for several months to ensure remission. Radiotherapy may be used in patients who fail to respond to steroids or who have a rapidly progressive course. We analysed the data of two patients. There were no specific complications related to this treatment. We discussed the radiologic findings, treatment procedures, and other orbital diseases.

• Archives of Plastic Surgery
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• 제33권4호
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• pp.525-529
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• 2006

Purpose: Facial nerve injury is a rare but feared complication of face lift. Uncertainty as to the depth and vulnerability of the facial nerve in face lift dissection causes some surgeon, particularly novices, to dissect slowly. Excessively thin flaps can be made because of fear of nerve injury, contributing to skin slough. Methods: From September 1998 to February 2003, the authors operated on 34 aging face patients using classical face-lift. We had analysed about quantity of skin removal and degree of elevated flap. The authors have found quantity of skin removal was 1.5-2.0 cm, degree of elevated flap was 40-45 degree on average. Results: The authors performed preauricular pre-excision face-lift technique on 12 aging face patients from July 2003 to Feburary 2005 based on experienced surgery. This technique reduced fear of dissecting skin flap necrosis and facial nerve injury because of firmly attached pre-auricular skin removed in advance. Conclusions: We easily dissected SMAS without visual field disturbance, nerve damage and reduced operation time and bleeding loss compared to classical face-lift.

• Archives of Plastic Surgery
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• 제51권1호
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• pp.67-71
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• 2024

Clavicle fractures are frequent injuries accounting for approximately 4% of all fractures in adults with about 35% occurring in the shoulder region among which midshaft fractures are the most common (>66%). Nonsurgical management is the treatment of choice for most clavicle fractures; however, poor functional and aesthetic outcomes may result from nonunion, symptomatic malunion, and aesthetic impairment which are the most common complications. A young woman was referred to our clinic for a "Step Deformity" resulting after primary, nonsurgical treatment of a midshaft clavicle fracture. Residual deformity was corrected with a novel simple and little invasive approach. Midshaft clavicle fractures typically only require conservative nonsurgical treatment, nevertheless suboptimal outcomes may occur. Selective osteotomies and fixation are deemed too invasive when only cosmetic impairment of the clavicle contour is present without any functional or sensitive damage and most patients are discouraged from undergoing surgery. Thus far, no specific focus on this topic, nor exploration of possible correction can be found in the published literature. These residual deformities may be very noticeable sometimes and cause psychological distress and social life impairment. Despite no related functional impairment, this deformity should still be addressed, to improve patients' quality of life.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 춘계학술대회 논문집
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• pp.190-195
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• 2001

In the present paper computational simulation of a concrete dam is performed to determine the effect of vertical ground motions on earthquake response of concrete dams. Cyclic and dynamic versions of the plastic-damage model proposed by Lee and Fenves are used to represent micro-crack development and crack opening/closing, which is important mechanism in nonlinear damage analysis of concrete structures subject to strong earthquake loading. The result shows that the vertical component of ground motion effects on final crack patterns and consequently, on displacement response.

• Journal of Ship and Ocean Technology
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• 제6권3호
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• pp.1-12
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• 2002

In this paper the results are reported of sixty-nine lateral collision tests, which were performed to investigate the collision resistance of plates. For the tests a collision testing machine of spring-roller conveyer type was designed and fabricated. Using this machine, various plates were tested with different masses and velocities and various headers of the striker. A simple analytical method has also been developed to predict the extent of damage of struck plates due to lateral collision. In the method, it is assumed that the kinetic energy of the striker can be dissipated by the formation of yield lines and membrane tensions in the impacted plate. The calculated predictions of extent of damage using the developed method have been substantiated with the test results, which shows reasonably acceptable correlations.