• 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 the Korean Society of Safety
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• v.33 no.2
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• pp.8-13
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• 2018

The light weight composite materials have been replacing in high performance structures. The object of this study is to examine the effects of the initial crack location about a delamination in a PVC foam cored sandwich composite that is used for the strength improvement of structures. The initial crack location and fiber laminates thickness were changed with several types. The MMB specimen was used for evaluating the fracture toughness and crack behaviors. The material used in the experiment is a commercial twill carbon prepreg in CFRP material and Airex in PVC foam core. Sandwich laminate composites are composed by PVC foam core layer between CFRP face sheets. The face sheets were fabricated as 2 types of 5 and 8 plies. The initial cracks were located in a PVC form core and the interface of upper CFRP sheet. From the results, the crack initiation was affected with the location of the initial crack inserted in the PVC foam core. Among them, the initial crack at 1/3 of the upper part of the PVC foam core was the most rapid progression. And the critical energy release rate was $0.40kJ/m^2$, which is the lowest value when the initial crack was inserted into the interface between a PVC foam core and CFRP laminated with 5 plies. Meanwhile, the highest value of $1.27kJ/m^2$ was obtained when the initial crack was located at the center line in case of the 8 plies.

• International Journal of Highway Engineering
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• v.7 no.2 s.24
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• pp.1-12
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• 2005

This study was conducted to evaluate effect of geogrid and fabric, which are used underneath the overlaid asphalt pavement for retarding reflection cracking by simulated laboratory test. In this study, an interlayer at the interface between old concrete pavement surface and overlaid asphalt mixture, and polymer-modifier were used as an effort of retarding reflection crack initiation and for strengthening mixture. Five products were used in preparation of asphalt concrete beam specimen which was tack coated on top of jointed concrete block. Simulated Mode I and II fracture test were conducted under wheel loading and results were compared among those products. From the test results, several material and reinforcement combinations were observed to have a significant retardation effect against reflection cracking. The most effectively strengthened pavement against reflection cracking was found to be the LDPE-modifier asphalt mixture with a grid reinforcement at the bottom.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.36-41
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• 2017

In this paper, $Si_3N_4/hBN$ ceramics with various hexagonal boron nitride (hBN) contents (0, 10, 20, or 30 wt%) were fabricated via spark plasma sintering (SPS) at $1500^{\circ}C$, 50MPa, and 10m holding time. The material properties such as the relative density, hardness, and fracture toughness were systematically evaluated according to the hBN content in the $Si_3N_4/hBN$ ceramics. The results show that relative density, hardness, and fracture toughness continuously decreased as the hBN content increased. In addition, peak-step drilling (with tool diameter $500{\mu}m$) was performed to observe the effects of hBN content in micro-hole shape and cutting force. A machined hole diameter of $510{\mu}m$ (entrance) and stable cutting force were obtained at 30 wt% hBN content. Consequently, $Si_3N_4/30wt%$ hBN ceramic is a feasible material upon which to apply semi-conductor components, and this study is very meaningful for determining correlations between material properties and machining performance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.46-54
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• 2013

Two different UHPCCs having different fiber lengths and volume fractions are considered to be applied to bridge decks. The objective of this study is to estimate cracking resistance of the two UHPCCs. The notched beam tests were performed with the UHPCCs, and the relationships between load and CMOD(Crack Mouth Opening Displacement) were obtained from the tests. The tensile stress and crack opening relationships optimally fitting the measured load-CMOD curves were found through the inverse analyses. The UHPCC with 2% volume fraction of 13 mm long fiber has lower fracture energy than the UHPCC with 0.5% and 1.0% volume fractions of 16.3 mm and 19.5 mm long fibers, respectively. It indicates that the latter UHPCC is more effective in uniformly distributing crack formation and reducing crack width.

• Clinics in Shoulder and Elbow
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• v.18 no.2
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• pp.75-79
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• 2015

Background: This retrospective comparative study aims to evaluate the surgical outcomes and complications of two surgical methods for simple fractures of the humeral shaft; minimally invasive anterior plating and open reduction combined with internal fixation. Methods: A total of 26 patients with humeral shaft simple fractures, who had surgery between June 2009 and September 2013 and were followed-up at least 12 months, were included in our analysis. They were divided into two groups; group 1 comprised of 12 patients who underwent minimally invasive anterior plating and group 2 comprised of 14 patients who underwent an open reduction and internal fixation. The clinical outcomes, radiological results, and complications were compared and analyzed. Results: We found that bone union was achieved in all patients, and the mean union periods were $20.7{\pm}3.34$ and $20.3{\pm}3.91$ weeks for groups 1 and 2, respectively. In most patients, we found that shoulder and elbow functions were recovered. At 12 months post-operation, we found that the Korean Shoulder Scoring system, the University of California at Los Angeles score and Mayo elbow performance score were $91.4{\pm}7.97$, $33.4{\pm}1.15$, and $90.8{\pm}2.23$ for group 1, and $95.2{\pm}1.53$, $33.3{\pm}1.43$, and $90.17{\pm}1.85$ for group 2. In terms of complications, we found that 2 patients had radial nerve palsy after open reduction and internal fixation, but all cases spontaneously resolved within 6 months. Complications such as infection and loss of fixation were not reported. Conclusions: Both minimally invasive anterior plating and open reduction with internal fixation produced satisfactory outcomes in the treatment of simple fractures of the humeral shaft.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.544-544
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• 2014

Energy harvesting technology, which scavenges electric power from ambient, otherwise wasted, energy sources, has been explored to develop self-powered wireless sensors and possibly eliminate the battery replacement cost for wireless sensors. Among ambient energy sources, vibration energy can be converted into electric power through a piezoelectric energy harvester. For the last decade, although tremendous advances have been made in design methodology to maximize harvestable electric power under a given vibration condition, the research in reliability assessment to ensure durability has been stagnant due to the complicated nature of the multiple failure modes of a piezoelectric energy harvester, such as the interfacial delamination, fatigue failure, and dynamic fracture. Therefore, this study presents the first-ever system reliability analysis for multiple failure modes of a piezoelectric energy harvester using the Generalized Complementary Intersection Method (GCIM), while accounts for the energy conversion performance. The GCIM enables to decompose the probabilities of high-order joint failure events into probabilities of complementary intersection events. The electromechanically-coupled analytical model is implemented based on the Kirchhoff plate theory to analyze its output performances of a piezoelectric energy harvester. Since a durable as well as efficient design of a piezoelectric energy harvester is significantly important in sustainably utilizing self-powered electronics, we believe that technical development on system reliability analysis will have an immediate and major impact on piezoelectric energy harvesting technology.

• Archives of Reconstructive Microsurgery
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• v.17 no.2
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• pp.82-86
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• 2008

Purpose: Soft tissue defect can occur on the posterior aspect of the elbow after trauma or fracture fixation. To cover the defect and maintain elbow functions, various flap surgeries including latissimus dorsi muscle flap, lateral arm flap and radial forearm flap can be performed. We present the clinical results of transposition lateral arm flap for coverage of the elbow defect and discuss the cause of posterior soft tissue necrosis after fracture fixation. Materials and Methods: Two patients who had posterior soft tissue defect of the elbow after open reduction of the fractures around the elbow were treated with transposition lateral arm flap. The mean size of skin defect was 20 $cm^2$. The flap was elevated with posterior radial collateral artery pedicle and transposed to the defect area. Donor defect was covered with split thickness skin graft. The elbow was immobilized for 1 week in extended position and active range of motion was permitted. Results: All two cases of transposition lateral arm flap survived without marginal necrosis. The average range of motion of the elbow was 10~115 degrees. Mayo elbow performance score was 72 and Korean DASH score was 23. Conclusion: When elbow fractures are fixed with three simultaneous plates and screws, skin necrosis can occur on the posterior aspect of the elbow around olecranon area. If the size of skin defect is relatively small, transposition lateral arm flap is very useful option for orthopaedic surgeons without microsurgical technique.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.4
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• pp.253-262
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• 2004

Construction of tunnels in a deep crystalline host rock for a potential High-Level Radioactive Waste(HLW) repository inevitably generates an excavation disturbed zone (EDZ). There have been a series of debates on whether a permeability in an EDZ increases or not and what would be the maximum depth of an EDZ. Recent studies show mixed opinions on permeability. However, there has been an international consensus on the thickness of an EDZ; 30 cm for TBM and 1 meter for controlled blast. One of the impacts of an EDZ is on determining the distance between adjacent deposition holes. The void gap by the excavation hinders relaxation of temperature profiles so that the current Korean reference designing distance between holes should be stretched out more to keep the maximum temperature in a buffer region below 100 degrees Celsius. The other impact of an EDZ is on the long-term post closure radiological safety. To estimate the impact, the reference scenario, the well scenario, is chosen. Released nuclides diffuse through a bentonite buffer region experiencing strong sorption and reach a fracture surrounded by a porous medium. Inside a fractured porous region, radionuclides migrate by advection and dispersion with matrix diffusion into a porous medium. Finally, they reach a well assumed to be a source of potable water for local residents. The annual individual dose is assessed on this well scenario to find out the significance of an EDZ. A profound sensitivity study was performed, but all results show that the impact is negligible. Even though the role of an EDZ turns out to be limited on overall safety assessment, still it is worthwhile to study the chemical role of an EDZ, such as a potential source for natural colloids, potential sealing of an open fracture by fine clay particles generated by the process of an EDZ, and alteration of a sorption mechanism by an EDZ in the future.

• Journal of Powder Materials
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• v.11 no.5
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• pp.412-420
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• 2004

The purpose of the present study is to determine an optimum composition using cheaper powders keeping with high performance of hard rock cutting diamond saw blade. With 50Fe-20(Cu . Sn)-30Co specimen, a part of Co was replaced by Ni(5%, 10%, and 15%, respectively). These specimens were hot pressed and sintered for predetermined time at various temperature. Sintering is performed by two different methods of temperature controlled method and specimen dimension controlled method. In order to determine the property of the sintered diamond saw blade, 3 point bending tester, X-ray diffractometer, and SEM were used. As the Co in the bond alloy was replaced by Ni, the hardness of the specimen increased. Thus the 50Fe-20(CuㆍSn)-15Co-15Ni specimen showed the maximum hardness of 104(HRB). The results of 3 point bending test showed that flexure strength decreased along with increase in Ni content. This is attributed to the formation of intermetallic compound(Ni$_{x}$Sn) determined by X-ray diffraction. The fracture surface after 3 point bending test showed that diamond was fractured in the specimen containing 0%, 5%, and 10%Ni, and the fracture occurred at the interface between diamond and matrix in the specimen containing 15%Ni. The cutting ability test showed that the abrasive property was not changed in the specimen containing 0%, 5%, and 10%Ni. The optimum composition determined in this study is 50Fe-20(CuㆍSn)-20Co-10Ni.