• Proceedings of the KSME Conference
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• 2000.11a
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• pp.93-98
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• 2000

Unpredictable failures can occur due to the DHC (delayed hydride cracking) or the degradation of fracture toughness by hydride embrittlement in CANDU pressure tube which can result from the absorption of hydrogen or deuterium in the high temperature coolant. To investigate the hydride embrittlement of CANDU Zr-2.5Nb pressure tube, the transverse tensile test and the fracture toughness test were performed from room temperature to $300^{\circ}C$ using three different specimens which have an AR (As Received), 100, and 200 ppm hydrogen. As the amount of absorbed hydrogen was increased, the transverse yield strength and the ultimate tensile strength were also increased. In addition, as the test temperature became higher they were decreased linearly. While, at room temperature, the hydrogenbsorbed specimens represented the embrittlement which resulted in sudden decreasing of fracture toughness, the fracture characteristics became ductile such as AR specimen at high temperatures. Through the observation of fracture surface using SEM, it was found that the stress state of mixed mode could be related to the fissure which was believed to decrease the global fracture toughness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.3
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• pp.455-463
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• 2003

The aim of this study is to investigate the hydrogen embrittlement of Zr-2.5Nb CANDU pressure tube at room temperature. The transverse tensile and fracture toughness tests were performed at various hydrogen concentrations using transverse tensile specimens and CCT (curved compact tension) specimens. These specimens were directly machined from the pressure tube retaining original curvatures. Based on the results of these tests. the hydrogen embrittlement phenomenon was clearly observed and fracture toughness parameters of Zr-2.5Nb pressure tube materials such as, $K_{J(0.2)}$.$J_{ML}$.dJ/da, were dramatically decreased with the increasement of the hydrogen concentration. From microscopic observation by SEM and TEM, it was also revealed that various shapes dimples, fissures and quasi-cleavage were found at the hydrogen-absorbed materials with hydrides while traditional shape dimples were generally located at the as-received materials Through the comparison of the hydride and fissure lengths with the hydrogen concentration the new evaluation method of hydrogen embrittlement was suggested.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.41
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• pp.55.1-55.7
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• 2019

Background: Transverse facial clefts are Tessier's number 7 facial cleft among numbers 1-15 in Tessier's classification of craniofacial malformations, which varies from a simple widening oral commissure to a complete fissure extending towards the external ear. Case presentation: In a patient with a transverse facial cleft, to functionally arrange the orbicularis oris muscle and form the oral commissure naturally, we performed a surgical procedure including orbicularis oris muscle reconstruction and cheiloplasty with Z-plasty. Conclusion: We achieved good results functionally and esthetically by orbicularis oris muscle reconstruction and cheiloplasty with Z-plasty. The surgical modality of our anatomical repair and 3 months follow-up results are presented.

• Journal of Korean Society of Steel Construction
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• v.11 no.1 s.38
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• pp.33-42
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• 1999

In the present study, crack initiation criteria, static failure and tensile mode fatigue behavior for a rail steel are evaluated to assure the railway vehicle's safety. The transverse fissure, which is the most critical damage in the rail, is initiated by the maximum shear stress and its location is subsurface. In addition, the possibility of transition from the shear mode to the mixed mode increases with increasing the length of subsurface crack. Because of the brittleness by the welding, the fracture toughness of the welded part is lower than of the base metal. For low ${\Delta}K$, the stage II fatigue crack growth rates of the welded part is slower than of the base metal but, for high ${\Delta}K$, this different behavior for fatigue crack growth rate is nearly diminished. These trends are more remarkable for low stress ratio, R=0.1. It is believed that this behavior is caused by the change of the microstructure which that of the welded part is coarser than of base metal.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.21 no.3
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• pp.303-311
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• 1999

In adult patients, the corrections of their malocclusion may be more difficult and require longer treatment time due to thicker layer of cortical bone and reduced blood supply. Recently, various methods such as surgery, implant for anchorage and corticotomy have been tried to overcome these problems. Corticotomy is a surgical technique in which a fissure is made through the cortical bone that surrounds a tooth so that the tooth is embedded within a block of bone that is connected to adjacent blocks through only the medullary bone. Technique of corticotomy has been widely used for correction of maxillary transverse deficiency, but hasn't actively in other fields of orthodontics. We applied corticotomies in many types of orthodontic treatment and had satisfactory results. We suggested clinical application of corticotomy in adult orthodontics to reduce treatment period and to achieve better stability after orthodontic treatment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.1039-1047
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• 1999

It is necessary to evaluate the fatigue behavior of rail steel under the multi-axial stress state to assure the railway vehicle's safety. For this purpose, the stress analysis to investigate the crack initiation criteria, static failure and fatigue behavior under mixed-mode are performed. The stress analysis results show that the initiation of the transverse fissure depends on the maximum shear stress below the surface. For the mixed mode, the fatigue crack growth behavior which is represented by the projection crack length and comparative S.I.F, ${\Delta}K_v$, shows the more conservative results. Also, its rate is lower than that of the case of the mode I, and this difference decreases with increasing the stress ratio, R.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.27 no.5
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• pp.488-491
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• 2005

A 3-year-old female, 5kg, Shih-tzu developed an acute onset of depression, disorientation, hypersalivation, nystagmus after falling down 2 meter height place. In plain skull radiography, there was fracture line in the frontal and parietal bones and next day magnetic resonance imaging examination was performed. Magnetic resonance imaging of the brain was performed with 3.0 Tesla unit. Under general anesthesia, the dog was placed in prone with its head positioned in a birdcage coil. Transverse, sagittal and coronal fast spin echo images of the brain were obtained with the following pulse sequences: T1 weighted images (TR = 560 ms and TE = 18.6 ms) and T2 weighted images (TR = 3500 ms and TE = 80 ms). Magnetic resonance imaging showed epidural hematoma in the left frontal area resulting in compression of the adjacent brain parenchyma. Left lateral ventricle was compressed secondarily and the longitudinal fissure shifted to the right, representing mass effect. The lesion was iso-to slightly hyperintense on T1 weighted image and iso-slightly hypointense signal on T2 weighted image. At necropsy, there was a skull fracture and epidural hematoma in the left frontal area. Magnetic resonance imaging of epidural hematoma is reviewed.