• Journal of Korean Society of Steel Construction
• /
• v.10 no.3 s.36
• /
• pp.423-435
• /
• 1998

In this paper fatigue strength reduction of butt weld with penetration defect, which can be seen frequently in the steel bridge, was assessed quantitatively. S-N curves were derived and investigated through the constant amplitude fatigue test of fully or partially penetrated welded specimen made of SWS490 steel. The fracture mechanical method was applied in order to calculate the remaining fatigue life of the partially penetrated butt welds. The fatigue limit of the fully penetrated butt welds was higher than that of category A in AASHTO's fatigue design curves, and the slope of S-N curves with 5.57 was stiffer than that of other result for welded part generally accepted as 3. The fatigue strength of the partially Penetrated butt weld was strongly influenced by the size of lack of penetration, D. It decreased drastically with increasing D from 3.9 to 14.7mm. Fracture behaviour of the partially penetrated butt weld is able to be explained obviously from the beach mark test that a semi-elliptical surface crack with small a/c ratio initiates at a internal weld root and propagates through the weld metal. To estimate the fatigue life of the partially penetrated butt weld with fracture mechanics, stress intensity factors K of 3-dimensional semi-elliptical crack were calculated by appling finite elements method and fracture mechanics parameters such as C and m were derived through the fatigue test of CT-specimen. As a result, the fatigue lives obtained by using the fracture mechanical method agreed well with the experimental results. The results were applied to Sung-Su bridge collapsed due to penetration defects in butt weld of vertical member.

• Journal of Korean Society of Steel Construction
• /
• v.9 no.3 s.32
• /
• pp.287-300
• /
• 1997

In this study, an effective application method of AE technique for the detection of fatigue crack in multi-girder steel bridges has been proposed. The applicability has been examined through the laboratory works with bridge model. The proposed analytical method which evaluates the remaining fatigue lives of structural members may improve the rational determination of the priority of inspection for structural members assuming to have fatigue cracks. Laboratory tests for the application of AE technique to steel girder bridges show that the frequency bands of traffic noise are in the range between 10 show that the frequency bands of traffic noise are in the range between 100~200 kHz and the AE signal raised from fatigue cracks is concentrated around 400~500 kHz. Therefore. R30 sensor is proved to be the most suitable for the detection of cracks in steel girder bridges. A linear proportionality between the crack propagation and the frequency of AE signals has been obtained. In addition, an economic and effective source location method for steel girder bridges was studied through experiments.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.10
• /
• pp.825-829
• /
• 2015

Theoretical calculations suggest that the thermoelectric figure of merit (ZT) can be improved by introducing a core-shell heterostructure to a semiconductor nanowire because of the reduced thermal conductivity of the nanowire. To experimentally verify the decrease in thermal conductivity in core-shell nanowires, the thermal conductivity of Ge-SixGe1-x core-shell nanowires grown by chemical vapor deposition (CVD) was measured using suspended microdevices. The silicon composition (Xsi) in the shells was measured to be about 0.65, and the remainder of the germanium in the shells was shown to play a role in decreasing defects originating from the lattice mismatch between the cores and shells. In addition to the standard four-point current- voltage (I-V) measurement, the measurement configuration based on the Wheatstone bridge was attempted to enhance the measurement sensitivity. The measured thermal conductivity values are in the range of 9-13 W/mK at room temperature and are lower by approximately 30 than that of a germanium nanowire with a comparable diameter.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.3
• /
• pp.224-234
• /
• 2019

Waterproof layers are installed in civil engineering structures and bridge construction is commonly finished by applying a layer of regular or asphalt concrete above the waterproof layer. However, asphalt materials are susceptible to melting at high temperature due to its superior temperature sensitivity, and this causes the waterproofing material to melt due to the high temperature of the asphalt concrete, thereby increasing the defect occurrence rate due to the thickness reduction. In this study, tensile strength and elongation of hard and soft type of MMA(Methyl Methacrylate) applied to bridges were compared in accordance to standard performance criteria based on different mixture ratios. Results of comparative testing showed that hard MMA resin can display a satisfactory tensile strength, and soft MMA resin displays satisfactory elongation properties, but as the two resin types are separately used, neither types are able to satisfy the standard requirements outlined in KS F 4932. When the amount of the powder exceeds 56.25% of the total amount, voids are generated on the surface after curing and self leveling was impossible and a heterogeneous surface is formed. Furthermore, when the hard resin: soft resin: powder mixture ratio was set to 15g: 85g: 150g. the tensile strength was $1.5N/mm^2$ and the elongation percentage was 133% which satisfy the tensile performance of KS F 4932.

• Journal of the Korean Institute of Gas
• /
• v.10 no.3 s.32
• /
• pp.20-26
• /
• 2006

The survey team has conducted the on-the-site inspection of 53 bridges to which LNG gas pipelines are attached, to ascertain their level of safety, durability and any defect by adapting a method of computer data input process and precision analysis. In this way, we could estimate an effective corrective action on the defective gas pipelines found through this survey. Our survey team has analyzed carefully these 2 defective lines selectively out of 10 lines, which are considered to be most seriously weak. According to our elaborate analysis these two pipelines go over 70% of the set standard stress based on our Safety Manual Scale. We have taken corrective actions on these lines by repairing/replacing/obsolete damaged lines to ensure the distress of the bridges involved with the pipelines and could secure safety.

• Journal of Yeungnam Medical Science
• /
• v.10 no.1
• /
• pp.218-225
• /
• 1993

This is a case report and review of literature that deals with hemifacial microsomia corrected by costochondral graft, Lefort I osteotomy and bilateral intraoral sagittal split ramus osteotomy. Patient, 23 years old female, had visited to treat the esthetic problem due to a deviation of jaw. On the basis of clinical and radiographic examinations, she was diagnosed as hemifacial microsomia. First, costochondral graft was performed to bridge the defect between glenoid fossa and body of mandible. After 11 months, Patient was performed a Lefort I osteotomy and bilateral intraoral sagittal split ramus osteotomy to create a symmetric jaw. Patient was satisfied with final esthetics and there have been no evidence of infection ill now.

• Clinical and Experimental Pediatrics
• /
• v.46 no.6
• /
• pp.597-601
• /
• 2003

Trisomy 9 mosaic syndrome is a rarely reported chromosomal abnormality with high incidence of intrauterine growth retardation and perinatal death. Even a baby lives, he has severe mental retardation and significant malformations. The incidence and severity of malformations and mental retardation correlate with the percentage of trisomic cells in the different tissues. The characteristic craniofacial abnormalitis are narrow bifrontal diameter, up-slanted and short palpebral fissures, a prominent nasal bridge with a short root, a prominent lip covering a receding lower lip, low-set, posteriorly rotated, and misshapen ears. Ventricular septal defect is a main cardiac abnormality. Bony hypoplasia and dislocated hips have been frequently reported. Central nervous system, hepatobiliary, gastrointestinal and genitourinary abnormalities also had been reported. The authors report a baby who had characteristic abnormalities of trisomy 9 mosaicism with narrow temples, up-slanted palpebral fissures, a bulbous nose, thin and protruding upper lip, low set and malformed ears, hyperextended wrist and overlapping fingers. Cytogenetic analysis performed to confirm the chromosomal abnormality revealed trisomy 9, low level mosaic type.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.31 no.1
• /
• pp.120-125
• /
• 2004

Cornelia de Lange syndrome is a disorder of unknown etiology resulting in an syndrome characterized by specific dysmorphic features. Therefore this syndrome is diagnosed only by clinical features and other examinations for diagnostic aim are not effective. There are general growth retardation, mental retardation, hypertrichosis, confluent eye brows, low hair line, broad nasal bridge, anteverted nose tip, malformed limbs, webbing of toes, heart defect, gastroesophageal reflux disease, ear and ocular problems. Features associated oral structures are micrognathia, delayed eruption of teeth, cleft lip, cleft plate, thin upper lip and downturned angles of mouth. These are cases about two children who visited Department of Pediatric Dentistry of Chonbuk National University because of dental caries with Cornelia do Lange syndrome.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.13 no.2
• /
• pp.203-216
• /
• 1991

Nerve allografts as a bridge of regeneration is useful in the repair of peripheral nerve defect resulting from trauma, and leprosy. But immunological rejection and complicated scar formation is an unavoidable problem in the application of allogeneic nerves. This article is intended to study of the regeneration of allogeneic nerve grafts in rats with histopathologically, scanning electron microscopically. 24 adult male Sprague-Dawley rats were used as the experimental animals. A 2cm skin incision was made on the lateral aspects of limb, parallel to femur. Segments of sciatic nerve trunk taken from rats, 10mm was resected at the middle of the thigh, nerve graft was inserted between the ends of gaps with perineural and epineural suture method with 10-0 prolene. Obsrevation was made simultaneously at 3 day, 1, 2, 3, 4, 5, 6, 8 weeks after surgery. The results were as follows. 1. In light and electronic microscopic studies, marked degenerative change of the graft nerves were observed at 2 weeks after surgery. 2. After surgery, blood clot fromation was observed at 3 day, granualtion tissue formation was observed at 2 week, and fibrous tissue proliferation was observed at 3 week. 3. In change of nerve fiber, there were Wallerian degeneration at early stage, decrease in degeneration at 4 week but degeneration of myeline was continuded at 8 week. 4. At 4 week, schwann cells proliferate at its cut ends to join with the distal and proximal stump of the damaged nerve. 5. Fibrous scar tissues are formed at 2 weeks and increased progressively in 8 weeks, which was interrupted the regeneration of grafted nerve.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.27 no.2
• /
• pp.222-228
• /
• 2000

Ectodermal dysplasia is a hereditary disease characterized by a congenital dysplasia of one or more ectodermal structures and their accessory appendages. At least 120 subtypes of ectodermal dysplasia have been reported. The disease is usually transmitted as an X-linked recessive trait in which the gene is carried by the female and manifested in the male. Hypohidrotic ectodermal dysplasia is manifested as a triad of defects that include hypohidrosis, hypotrichosis and hypodontia. The characteristic facial features consist of asteatosis, onchodysplasia, sparse and fine blond hair, prominent forehead, a depressed nasal bridge, thick everted lips. The patient may suffer from dry skin, hyperthermia and unexplained high fever as a result of the deficiency of sweat glands. This case report presents detailed procedures of rehabilitating functional and esthetic defect of a 6-year-old boy with hypohidrotic ectodermal dysplasia along with the review of relevant literatures.