• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.124-124
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• 2015

Acoustic microscopy and scanning electron microscopy were applied to non-destructively evaluate the hydrogen-induced cracking of API X-80 steels and to find the initiation time of the crack. The API X-80 steel had the average grain size of about $4-10{\mu}m$. The hardness was reduced from 240 to 202 [Hv] after exposing in HIC environment for 2-days. Friction coefficient and wear loss were 0.745 and 0.392 mm, respectively. Empirical equation of corrosion potential and corrosion rate of the steel with HIC time in $5%NaCl-0.5%CH_3COOH$ at $25^{\circ}C$ were $Eh\;(up)=0.06^*t[day]+0.2951$, $Eh(down)=0.376^*t[day]+0.5938$, respectively. HIC grew with micro-size after 1-day exposure. The HIC tended to propagate on the surface with Al, Si, Ti, and Mn.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.249-258
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• 2006

In this paper, deformation capacity of steel moment connections with RHS column was investigated. Initially, non-linear finite element analysis of five bate steel beam models was conducted. The models were designed to have different detail at their beam-to-column connection, so that the flexural moment capacity was different respectively. Analysis results showed 4hat the moment transfer efficiency of the analytical model with RHS-column was poor when comparing to model with WF(Wide flnage)-column due to out-of-plane deformation of the RHS-column flange. The presence of scallop and thin plate of RHS column was also a reason of the decrease of moment transfer efficiency, which would result in a potential fracture of tile steel beam-to-column connections. Further test on beam-to-column connections with RHS column revealed that the moment transfer efficiency of a beam web decreased due to the out-of-plane deformation of column flange, which led to premature failure of the connection.

• Geosciences Journal
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• v.22 no.6
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• pp.891-902
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• 2018

Techniques for more reliable detection of 3D subsurface flow paths are highly important for most water-related geotechnical projects. In this case study, a magnetometric resistivity method with a new approach and state-of-the-art technology ("Willowstick survey") was applied to the testbed dam (YD dam) site, and its applicability was validated by geotechnical investigation techniques including borehole drilling and sampling, Lugeon test, flow direction and velocity test, and seismic tomography. In addition to the magnetometric survey, a 3D electrical resistivity survey was performed independently and the results were compared and discussed. The electrical resistivity survey was effective in detecting groundwater levels, but it was limited in mapping leakage paths. On the other hand, the Willowstick magnetometric survey effectively detected geologic weaknesses (e.g., fault fracture) and potential leakage paths of the dam site foundation rocks. The results of this research are expected to be effective for water infrastructures where leakage is an important issue.

• Journal of Trauma and Injury
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• v.34 no.1
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• pp.57-60
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• 2021

Warfarin is used as part of the treatment of various diseases, and laboratory monitoring of its effects is required. Airway hematoma secondary to warfarin is rare, but can be fatal because of potential airway obstruction. Rapid definitive airway establishment is crucial if airway obstruction is suspected. This complication is more likely to occur in those with elevated coagulation laboratory values. However, we experienced a patient in whom a massive retropharyngeal hematoma caused airway obstruction after a non-severe motor vehicle collision. The patient had been taking warfarin, and had coagulation parameter values within the normal ranges. A major fracture or hemorrhage was not anticipated. Upon examination, a massive retropharyngeal hematoma was noted. Orotracheal intubation failed due to an airway obstruction. Emergency tracheostomy and an operation for hematoma removal were performed. Physicians must always consider the possibility of airway hematoma in warfarin-taking patients with normal coagulation values regardless of the severity of mechanism of injury.

• Archives of Plastic Surgery
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• v.46 no.6
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• pp.589-593
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• 2019

Post-traumatic defects of the distal third of the leg often require skipping a few steps of the well-established reconstructive ladder, due to the limited local reliable reconstructive options. In rare cases, the reconstructive plan and flap choice may encounter challenges when the patient has psychiatric illness affecting compliance with postoperative care. We describe a case of a patient with severe intellectual disability and an open fracture of the distal lower limb. After fracture management and debridement of devitalized tissues, the resultant soft tissue defect was covered with a free gracilis flap. On postoperative day 7, the patient ripped out the newly transplanted flap. The flap was too traumatized for salvage, so a contralateral free gracilis muscle flap was used. The patient showed good aesthetic and functional outcomes at a 1-year follow-up. When planning the postoperative management of patients with psychiatric illness, less complex and more robust procedures may be preferred over a long and complex surgical reconstruction requiring good compliance with postoperative care. The medical team should be aware of the risk of postoperative collapse, focus on the prevention of pain, and be wary of drug interactions. Whenever necessary, free tissue transfer should be performed despite potential compliance issues.

• Journal of the Korean Ceramic Society
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• v.55 no.6
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• pp.556-561
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• 2018

In this study, we performed a microwave sintering (MWS) of $Al_2O_3$ ceramic and $Al_2O_3$-based composites with nominal contents of graphene nanoplatelets (GPLs) of 0.2, 0.4, 0.6, and 0.8 vol%. The GPL dispersion in N-methyl pyrroleketone was optimized to deagglomerate the GPLs without damaging their structure. Dense composites were then obtained by MWS at $1500^{\circ}C$ for 30 min. The effects of different GPL contents on the phase compositions, microstructures, and mechanical properties of the composites were investigated. The microstructures of the composites became finer with the incorporation of the GPLs. The well-dispersed GPL fillers led to higher sintered densities in the composites. The optimal mechanical properties were achieved with 0.4 vol% GPLs. For this sample, the hardness, fracture toughness, and bending strength were $2000kgf/mm^2$, $6.19MPa{\cdot}m^{1/2}$, and 365.10 MPa, respectively. The addition of GPL could improve the microstructure of the $Al_2O_3$ ceramic and has potential to improve the fracture toughness of the ceramics.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.4
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• pp.377-385
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• 2002

Ultrasonic tests employing non-ionizing radiation are preferred in nondestructive examinations since they are safe and simple in use. The same principles of the techniques have been taken as valuable tools in medical area for the diagnoses of diseases, in other words, defects of the human body. The paper overviews the principles of the medical diagnosis based on nondestructive ultrasonic tests, and then evaluates experimentally the clinical potential of C scan images not popular in medicine, for detecting the micro fractures of the cortical bone. In the experiment the micro bone fractures were created on the femurs of porks by loading three point bending forces (2-4kN) with the speed of 1 mm/min. As the extent of the fracture was altered, not only X ray images but also ultrasonic C scan images using a focused ultrasonic probe resonated at 25 MHz were obtained. The results showed that ultrasonic C scan images were capable of detecting the micro bone fractures which were not possible to identify by conventional X ray images.

• Journal of Korean Neurosurgical Society
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• v.57 no.2
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• pp.100-107
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• 2015

Objective : To report a minimally invasive treatment option using percutaneous pedicle screw fixation with adjuvant treatment for metastatic thoraco-lumbar and lumbar spinal tumors. Methods : This is a retrospective study of charts of patients with spinal metastases. All were older than 18 years of age and were considered to have more than 3 months of life expectancy. The patients had single or two level lesions, and compression fracture or impending fracture. Exclusion criterion was metastasis showing severe epidural compression with definite neurological symptoms. Usually spinal segments from one level above to below pathology were stabilized. Visual analog scale (VAS) score for pain assessment and Frankel scale for neurological deficit were used, while pre- and post-operative performance status was evaluated using the Eastern Cooperative Oncology Group (ECOG). Results : Twelve patients (nine men, three women; median age 54.29 years) underwent surgery. All patients presented with back pain with/without radicular pain. There were no early complications and perioperative mortalities. Following surgery, a significant difference between average pre- and post-operative VAS scores was found (p=0.003). Overall, 91.8% of patients (11/12) experienced improvement in their ECOG score post-operatively. The mean ambulation time was 196.9 days [95% confidence interval (CI), 86.2-307.6 days; median, 97 days]. During follow-up, nine patients died and the mean overall survival time in enrolled twelve patients was 249.9 days (95% CI, 145.3-354.4 days; median, 176 days). Conclusion : Minimally invasive treatment using percutaneous pedicle screw fixation with adjuvant treatment is a good alternative treatment option for potential instability of the thoraco-lumbar and lumbar spinal metastasis.

• Journal of Korean Orthopaedic Sports Medicine
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• v.4 no.1
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• pp.6-11
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• 2005

Injury of articular cartilage can be classified into acute injury and chronic degenerative osteoarthritis Acute mechanical trauma on articular cartilage causes injuries that are divided into three distinct types based on the depth of injury: microdamage, chondral fracture, osteochondral fracture and each type has different potential of healing response and long-term prognosis. Articular cartilage undergoes degradation in response to a number of stimuli and eventually degenerative osteoarthritic changes will progress. The extent of initial injury to the articular cartilage is the most important factor affecting the long-term outcome of the healing response and other variables such as the size of lesion, site, age, activity level, obesity, limb alignment are also important factors. In this review, the pathophysiology that occurs within articular cartilage after different injuries and the effect of nonsurgical treatment mainly in physicochemical aspect and biological aspect will be discussed.

• Journal of Korean Neurosurgical Society
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• v.63 no.5
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• pp.631-639
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• 2020

Objective : Traditionally, staged surgery has been preferred in the treatment of compound comminuted depressed fracture (FCCD) after traumatic brain injury (TBI) and involves the removal of primarily damaged bone and subsequent cranioplasty. The main reason for delayed cranioplasty was to reduce the risk of infection-related complications. Here, the author performed immediate reconstruction using a titanium mesh in consecutive patients with FCCD after TBI, reported the surgical results, and reviewed previous studies. Methods : Nineteen consecutive patients who underwent single-stage reconstruction with titanium mesh for FCCD of the skull from April 2014 to June 2018 were retrospectively analyzed. The demographic and radiological characteristics of the patients with FCCD were investigated. The characteristics associated with surgery and outcome were also evaluated. Results : The frequency of TBI in men (94.7%) was significantly higher than that in women. Most FCCDs (73.7%) occurred during work, the rest were caused by traffic accidents. The mean interval between TBI and surgery was 7.0±3.9 hours. The median Glasgow coma scale score was 15 (range, 8-15) at admission and 15 (range, 10-15) at discharge. FCCD was frequently located in the frontal (57.9%) and parietal (31.6%) bones than in other regions. Of the patients with FCCDs in the frontal bone, 62.5% had paranasal sinus injury. There were five patients with fractures of orbital bone, and they were easily reconstructed using titanium mesh. These patients were cosmetically satisfied. Postoperatively, antibiotics were used for an average of 12.6 days. The mean hospital stay was 17.6±7.5 days (range, 8-33). There was no postoperative seizure or complications, such as infection. Conclusion : Immediate bony fragments replacement and reconstruction with reconstruction titanium mesh for FCCD did not increase infectious sequelae, even though FCCD involved sinus. This suggests that immediate single-stage reconstruction with titanium mesh for FCCD is a suitable surgical option with potential benefits in terms of cost-effectiveness, safety, and cosmetic and psychological outcomes.