• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.354-359
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• 2008

Modal characteristics of a cracked beam with a concentrated mass undergoing rotational motion are investigated in this paper. Hybrid deformation variables are employed to derive the equations of motion of a rotating cantilever beam. The flexibility due to crack, which is assumed to be open during the vibration, is calculated basing on a fracture mechanics theory. To obtain more general information, the equations of motion are transformed into a dimensionless form in which dimensionless parameters are identified. The effects of the dimensionless parameters related to the angular speed, the depth and location of a crack and the size and location of a concentrated mass on the modal characteristics of the beam are investigated numerically.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.865-868
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• 2006

In this paper, a dynamic behavior(natural frequency) of a cracked simply supported pipe conveying fluid is presented. 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 Lagrange's equation. The crack section is represented by a local flexibility matrix connecting two undamaged beam 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 study will contribute to the safety test and stability estimation of structures of a cracked pipe conveying fluid.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.1
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• pp.51-56
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• 1989

This study was performed to investigate the effect of defect on fatigue strength under the stress of rotary bending. The specimens were made of low carbon steel having artificial microholes, namely, single micro-hole and two adjacent micro-holes as natural defects, and the effects of the diameter of hole and the distance between the holes on fatigue strength have been investigated. The obtained result can be summarized as follows: 1, The critical defect means the largest size of defect that does not affect fatigue limit, and correspondes to the size of defect leading to final fracture under fatigue limit of smooth specimen. The size of defect which has an effect on fatigue limit is larger than that of critical defect. 2, The defect larger than the critical defect affects fatigue strength for as a kind of size effect, and the physical meaning of size effect of defect is considered same as the one of notch effect.

• Journal of Korean Neurosurgical Society
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• v.56 no.5
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• pp.423-427
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• 2014

Traumatic pseudoaneurysms of the middle meningeal artery (MMA) are rare phenomenon, which are usually associated with head trauma such as an underlying skull fracture. They were usually known to cause acute or delayed epidural hematomas but can be associated with subdural, subarachnoid, or even intracerebral hemorrhage. Sometimes, a high mortality rate was reported in these circumferences. But the natural course of these pseudoaneurysms is not well recognized. The indication and guideline of treatment for pseudoaneurysm are also unclear. This report describes a rare case of angiographically progressive change of traumatic pseudoaneurysm of the middle meningeal artery for one week, which was treated with endovascular embolization.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.3
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• pp.49-55
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• 2010

In this paper, the stability of cracked cantilever T-beams subjected to subtangential follower force is investigated. Also, the effect of subtangential coefficient and crack on the natural frequency of T-beams is presented. 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 values of critical follower force and the stability maps of cantilever T-beams are obtained according to the subtangential coefficient and crack severity. The results of this study will contribute to the safety testing and the stability estimation of cracked T-beams subjected to follower force.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.215-218
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• 2007

In this paper a dynamic behavior(natural frequency) of a cracked cantilever beam subjected to follower force is presented. In addition, an analysis of the flutter and buckling instability of a cracked cantilever beam subjected to a follower compressive load is presented. Based on the Euler-Bernouli beam theory, the equation of motion can be constructed by using the Lagrange's equation. The vibration analysis on such cracked beam is conducted to identify the critical follower force for flutter insstability based on the variation of the first two resonant frequencies of the beam. Besides, the effect of the crack's intensity and location on the flutter follower force is studied. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations.

• Structural Engineering and Mechanics
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• v.25 no.2
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• pp.131-146
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• 2007

This paper presents the results of a study to show how the development of a crack alters the structural behavior of I-shaped steel beams and how this can be used to evaluate nondestructive evaluation techniques. The approach is based on changes in the dynamic behavior. An approximate finite element model for a cracked beam with I-shaped cross-section is developed based on a simplified fracture model. The model is then used to review different damage cases. Damage detection techniques are studied to determine their ability to identify the existence of the crack and to identify its location. The techniques studied are the coordinate modal assurance criterion, the modal flexibility, and the state and the slope arrays.

• Korean Journal of Psychosomatic Medicine
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• v.4 no.1
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• pp.98-108
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• 1996

Korean women are now living almost 1/3 of their life after menopause. Sex-steroid hormone deficiency adversely affect various fields of physical & mental activity and quality of life during this period. Therefore, replacement of deficient hormone is thought to be natural therapeutic modality. Postmenopausal syndrome is recently redefined as an endocrinopathy with both short-and long-term sequelae, as a result of cessation of ovarian function. Hormone replacement therapy taken at or near time of menopause alleviates shot-term acute menopausal symptoms such as vasomotor disturbances and psychological problems. HRT also beneficially affects some of intermediate symptoms such as urogenital atrophy and cutaneous problems. The major benefits of long-term use were reductions in risk of long-term sequelae, that is, total fracture by 50-60%, cardiovascular disease by 50% and cerebrovascular disease by 30-40%, respectively. In addition, HRT may also positively influence Alzheimer's disease, reduce the colorectal cancer risk and increase longevity of the life. In conclusion, all postmenopausal women should consider preventive HRT when there are no contraindications.

• Journal of Korean Neurosurgical Society
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• v.58 no.2
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• pp.147-149
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• 2015

A Schmorl's node is defined as a simple endplate intravertebral herniation resulting from trauma or idiopathic causes. Although Schmorl's nodes have been considered clinically insignificant, they might indicate an active symptomatic process or cause serious complications. In this study, we report an interesting case of complete separation of a vertebral body caused by an untreated Schmorl's node accompanying severe osteoporosis. To our knowledge, this is the first clinical report in the published literature to evaluate the complete separation of a vertebral body associated with a Schmorl's node.

• Structural Engineering and Mechanics
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• v.58 no.1
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• pp.103-119
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• 2016

Multi-storey frame structures are frequently exposed to static and dynamic forces. Therefore analyses of static (buckling) and dynamic stability come into prominence for these structures. In this study, the effects of number of storey, static and dynamic load parameters, crack depth and crack location on the in-plane static and dynamic stability of cracked multi-storey frame structures subjected to periodic loading have been investigated numerically by using the Finite Element Method. A crack element based on the Euler beam theory is developed by using the principles of fracture mechanics. The equation of motion for the cracked multi-storey frame subjected to periodic loading is achieved by Lagrange's equation. The results obtained from the stability analysis are presented in three dimensional graphs and tables.