• Archives of Plastic Surgery
• /
• 제38권1호
• /
• pp.85-88
• /
• 2011

Purpose: Takotsubo cardiomyopathy is a relatively uncommon type of stress-induced cardiomyopathy characterized by transient left ventricular regional wall motion abnormalities. Emotional and physical stresses play a key role in this type of cardiomyopathy in postmenopausal women. The current hypothesis is that the syndrome represents a form of catecholamine surge due to stress or epinephrine-mediated acute myocardial stunning. Methods: A 44-year-old woman had suffered premature ventricular contraction following a cardiogenic shock during a breast augmentation surgery under enflurane anesthesia and tumescent solution infiltration. She was treated with cardiopulmonary resuscitation at a local clinic. Then she was brought to the Emergency Department of the authors' hospital. Results: The woman's echocardiogram showed an ejection fraction of 20~25% with associated basal hyperkinesis and left ventricular apical ballooning. The patient was admitted to the ICU and required inotropic support for two weeks. The patient's condition dramatically improved, and her ejection fraction returned to 70%. Conclusion: It is believed that there were multiple triggering factors of the onset of Takotsubo cardiomyopathy in the woman's social and family history, including infiltration of a large volume of the tumescent solution and VPCs induced by enflurane anesthesia without premedication. The importance of careful history-taking, careful pre-operative consultation on psychological suffering especially for breast surgery, premedication before surgery, patient reassurance, and post-operative psychosocial and emotional assistance was again seen in this case.

• 한국강구조학회 논문집
• /
• 제18권6호
• /
• pp.717-726
• /
• 2006

교량의 보강공법으로 주로 사용되는 외부강봉을 이용한 후인장공법은 적용범위가 넓고 교량의 극한 및 항복에 대한 강성을 증가시켜 휨 보강 효과가 뛰어나지만, 모재접합부의 응력집중, 비효율적인 하중분배, 고정앵커부설치, 유지관리의 어려움 등의 단점이 있다. 본 연구는 기존의 외부강봉을 이용한 후인장공법이 가지는 단점을 보완하고 강판접합공법의 장점을 접목한 새로운 개념의 보강공법으로 커버플레이트의 열변형 특성을 이용한 다단계 프리스트레싱 보강공법을 제안하고자 한다. 커버플레이트의 열변형 특성을 이용한 다단계 프리스트레싱 보강공법은 커버플레이트를 다단계로 가열하여 가열단계별로 거더의 하부플랜지에 고장력볼트로 접합한 뒤, 열원을 제거하여 발생하는 다단계 수축력을 보강에 필요한 프리스트레싱력으로 이용하는 보강공법이다. 커버플레이트의 다단계 프리스트레싱에 의한 보강효과는 커버플레이트의 온도분포와 가열구간에 따라 결정되므로 본 연구에서는 커버플레이트의 열전달 모형실험 및 강거더 모형 실험을 통하여 커버플레이트의 열전달해석과 프리스트레스 도입효과를 분석하였으며, 단경간 강거더 교량을 대상으로 제안된 보강공법의 효율성 및 적용성을 검토하였다.

• 한국초전도ㆍ저온공학회논문지
• /
• 제18권1호
• /
• pp.59-63
• /
• 2016

The superconducting NMR magnets have used cryogen such as liquid helium for their cooling. The conduction cooling method using cryocoolers, however, makes the cryogenic cooling system for NMR magnets more compact and user-friendly than the cryogen cooling method. This paper describes the thermal and structural analysis of a cryogenic conduction cooling system for a 400 MHz HTS NMR magnet, focusing on the magnet assembly. The highly thermo-conductive cooling plates between HTS double pancake coils are used to transfer the heat generated in coils, namely Joule heating at lap splice joints, to thermal link blocks and finally the cryocooler. The conduction cooling structure of the HTS magnet assembly preliminarily designed is verified by thermal and structural analysis. The orthotropic thermal properties of the HTS coil, thermal contact resistance and radiation heat load are considered in the thermal analysis. The thermal analysis confirms the uniform temperature distribution for the present thermal design of the NMR magnet within 0.2 K. The mechanical stress and the displacement by the electromagnetic force and the thermal contraction are checked to verify structural stability. The structural analysis indicates that the mechanical stress on each component of the magnet is less than its material yield strength and the displacement is acceptable in comparison with the magnet dimension.

• 한국정밀공학회지
• /
• 제27권2호
• /
• pp.130-136
• /
• 2010

For stability analysis of the lumbar spine, the hypothesis presented is that the disc has stress sensors driving feedback mechanism, which could react to the imposed loads by adjusting the contraction of the muscles. Fusion in the motion segment of the lumbar spinal column is believed to alter the stability of the spinal column. To identify this effect finite element (FE) models combined with optimization technique was applied and quantify the role of each muscle and reaction forces in the spinal column with respect to the fusion level. The musculoskeletal FE model was consisted with detailed whole lumbar spine, pelvis, sacrum, coccyx and simplified trunk model. Vertebral body and pelvis were modeled as a rigid body and the rib cage was constructed with rigid truss element for the computational efficiency. Spinal fusion model was applied to L3-L4, L4-L5, L5-S1 (single level) and L3-L5 (two levels) segments. Muscle architecture with 46 local muscles was used as acting directions. Minimization of the nucleus pressure deviation and annulus fiber average axial stress deviation was selected for cost function. As a result, spinal fusion produced reaction changes at each motion segment as well as contribution of each muscle. Longissimus thoracis and psoas major muscle showed dramatic changes for the cases of L5-S1 and L3-L5 level fusion. Muscle force change at each muscle also generated relatively high nucleus pressure not only at the adjacent level but at another level, which can explain disc degeneration pattern observed in clinical study.

• 대한조선학회논문집
• /
• 제58권2호
• /
• pp.66-72
• /
• 2021

As the demand for natural gas that satisfies environmental regulations increases, the quantities of natural gas cargo that carrier can load is also increasing. Natural gas is transported in a liquefied state at -163 ℃ to increase loading efficiency. Among several LNG CCS types, MARK-III types are generally adopted in terms of loading efficiency. The secondary barrier adhesives of the MARK-III, nevertheless, is subjected to tensile stress due to thermal contraction and tension in the environment. In terms of these reasons, local analysis of the adhesive to evaluate the stress state must be carried out. According to previous studies, local analysis is unavailable since material properties for secondary barrier adhesives have not been reported. Thus, in this study, the cryogenic tensile test and coefficient of thermal expansion of epoxy and polyurethane (PU15, PU45), which are most widely used at cryogenic temperatures, were experimentally analyzed. At cryogenic temperature, the mechanical behavior of the polyurethane adhesive was better than epoxy of the adhesive. the joint of FSB and epoxy adhesive of the secondary barrier has the maximum coefficient of thermal expansion difference at 25 ℃ and minimum at -150 ℃, respectively.

• Geomechanics and Engineering
• /
• 제18권4호
• /
• pp.407-415
• /
• 2019

A controlled low strength material (CLSM) is a highly flowable cementitious material used for trench backfilling. However, when applying vertical loads to backfilled trenches, shear failure or differential settlement may occur at the interface between the CLSM and natural soil. Hence, this study aims to evaluate the characteristics of the interface friction between the CLSM and soils based on curing time, gradation, and normal stress. The CLSM is composed of fly ash, calcium sulfoaluminate cement, sand, silt, water, and an accelerator. To investigate the engineering properties of the CLSM, flow and unconfined compressive strength tests are carried out. Poorly graded and well-graded sands are selected as the in-situ soil adjacent to the CLSM. The direct shear tests of the CLSM and soils are carried out under three normal stresses for four different curing times. The test results show that the shear strengths obtained within 1 day are higher than those obtained after 1 day. As the curing time increases, the maximum dilation of the poorly graded sand-CLSM specimens under lower normal stresses also generally increases. The maximum contraction increases with increasing normal stress, but it decreases with increasing curing time. The shear strengths of the well-graded sand-CLSM interface are greater than those of the poorly graded sand-CLSM interface. Moreover, the friction angle for the CLSM-soil interface decreases with increasing curing time, and the friction angles of the well-graded sand-CLSM interface are greater than those of the poorly graded sand-CLSM interface. The results suggest that the CLSM may be effectively used for trench backfilling owing to a better understanding of the interface shear strength and behavior between the CLSM and soils.

• 한국화재소방학회:학술대회논문집
• /
• 한국화재소방학회 2008년도 추계학술논문발표회 논문집
• /
• pp.465-470
• /
• 2008

This paper introduces experimental investigates of an electrical accident of the distributing cable termination with simulated badness construction. We prepared two termination kites, one is built-up type, the other is heat contraction type. Also, we manufactured cable termination that have simulated defect by badness construction and measured their insulation characteristics such as ac (35kV, 1min) and impulse (95kV, $1.2{\times}50{\mu}s$) withstand test. The influence of defects such as thickness and the gap between stress-con of housing and semi-conductor on insulating properties of the termination have been studied. The thickness decrease of insulator decreases ac breakdown strength. Dielectric breakdown traces of insulator that is damaged by knife displayed other shape. The gap of between housing and semiconductor deteriorates dielectric strength of insulator seriously.

• 한국구조물진단유지관리공학회 논문집
• /
• 제10권1호
• /
• pp.190-196
• /
• 2006

기존 연구에서 살펴보면, 철근콘크리트구조물에 발생한 화재로 인해 경화된 시멘트 페이스트와 골재의 수축과 팽창의 차이에 따라 조직이 와해되고, 열응력에 의해 균열이 발생하여 내구성이 저하한다. 그래서 성능저하의 정확한 진단은 일반적인 콘크리트구조물에서 방화성능저하의 매커니즘에 관한 기초가 요구되며, 고온에 노출된 콘크리트의 특성에 대한 기초 정보와 데이터는 성능저하의 정확한 진단을 위해 필요하다. 따라서, 본 연구는 다양한 콘크리트 시험체를 제작하여, 고온 환경에서 노출시켜, 폭열을 관찰하고, 공학적인 특성을 평가함으로서 화재피해를 입은 콘크리트구조물 성능저하의 빠르고 정확한 진단을 위한 기초적인 데이터를 제공하고자 한다.

• 한국해양공학회지
• /
• 제17권4호
• /
• pp.31-36
• /
• 2003

In case of this thick rolling-steel for a multistory building, a large oil-drilling structure, a large vessel, a bridge and so on, Lamella Tearing around the welded joint zone is the most serious problems. In order to prevent Lamella Tearing, not only is choice of material important, but also the comprehensive investigation for the structural design and the construction. The Lamella Tearing that is a staircase-shape occurs due to the contraction stress to the thickness direction of the plate and has the character that the cracks progress along the elongated inclusion by rolling. In general, because cracks occur at the heat affected zone and around HAZ, it is necessary to establish the safety and the confidence of the welded structure to restrain the welding defect such as Lamella Tearing. The mechanical approaches are the easier and more economical than the approaches of the material and the construction method. In addition, the appropriate welding profile and the optimum welding condition contribute toward the improvement of the productivity and influence on the standardization of the manufacturing technology.

• 한국가스학회지
• /
• 제6권4호
• /
• pp.17-22
• /
• 2002

LNG는 여러 가지 장점으로 해마다 수요가 크게 늘고 있으며 이에 따른 LNG 저장설비의 건설과 확장 또한 급속도로 증가하고 있다. LNG 저장탱크에서 가장 중요한 요소중의 하나는 스테인레스 조재로 제작된 멤브레인이다. 멤브레인은 LNG 온도에 따른 열수축과 팽창을 흡수하는 주름을 가지고 있는 스테인레스 판으로 안정적 변형과 충분한 파괴강도를 확보하여야 한다. 따라서 본 논문에서는 개발된 Kogas 멤브레인의 변형과 강도를 실험적으로 수행되었고 모든 결과들이 관련 규격을 만족하는 것으로 나타났다.