• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.1
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• pp.47-53
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• 2011

From recent research, it has revealed that Electroacitve polymer(EAP) has a physical limitation. Carbon nanotube(CNT) is known as the promising material which has excellent electro-mechanical characteristics and is mostly defect-free. It is expected that a successful synthesis of CNT and Nafion known as a primary material for IPMC would make a great improvement on its electro-mechanic feature. In this paper, we suggest the method of synthesis of CNT with Nafion which improves electro-mechanical characteristic. Using mechanical dispersion with Nafion and Isopropyl Alcohol(IPA), we disperse Single-walled carbon nanotubes(SWCNT). For a uniformly layer of CNT, we used a spray gun on a hot plate by a simplified method. In the result, we fabricated a disperse SWCNT/Nafion composite uniformly.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.919-924
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• 2001

The purpose of this study is to prepare the basic data for the development of building board with expanded perlite. Each paste was mixed with four levels of water cement ratio(30, 40, 50, 60%), and expanded perlite was substituted with four levels of substitutive ratio(20, 40, 60, 80%) for the each paste. The physical property, compressive strength, bending strength and thermal conductivity of each cement composite which is made through previously described method were analyzed and the result was as follow. In the case of 80 percent substitutive ratio, the cement composite had a mechanical defect which was resulted from lack of paste content. In the case of 40 and 60percent substitutive ratio, the cement composite had sufficient strength, light weight and low thermal conductivity for application to fire resisting board.

• Corrosion Science and Technology
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• v.16 no.3
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• pp.151-159
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• 2017

The MA8 alloy (formula Mg-Mn-Се) has been shown to have greater corrosion stability than the VMD10 magnesium alloy (formula Mg-Zn-Zr-Y) in chloride-containing solutions by Scanning Vibrating Electrode Technique (SVET) and by optical microscopy, gravimetry, and volumetry. It has been established that the crucial factor for the corrosion activity of these samples is the occurrence of microgalvanic coupling at the sample surface. The peculiarities of the kinetics and mechanism of the corrosion in the local heterogeneous regions of the magnesium alloy surface were investigated by localized electrochemical techniques. The stages of the corrosion process in artificial defects in the coating obtained by plasma electrolytic oxidation (PEO) at the surface of the MA8 magnesium alloy were also studied. The analysis of the experimental data enabled us to determine that the corrosion process in the defect zone develops predominantly at the magnesium/coating interface. Based on the measurements of the corrosion rate of the samples with PEO and composite polymer-containing coatings, the best anticorrosion properties were displayed by the composite polymer-containing coatings.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.26 no.6
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• pp.557-564
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• 2000

The bone graft materials can be grossly divided into autogenous bone, allogenic bone, xenogenic bone, and alloplastic material. Much care was given to other bone graft materials away from autogenous bone due to its additional operation for harvesting, delayed resorption and limitation of quantity. Demineralized freeze-dried bone(DFDB) and hydroxyapatite are the representatives of bone graft materials. As resorbable hydroxyapatite is developed in these days, the disadvantage of nonresorbability can be overcome. So we planned to study on the strength and the bone formation at the rats calvarial defects of DFDB graft and those of the composite graft with DFDB and resorbable hydroxyapatite. We used the 16 male rats weighting range from 250 to 300 gram bred under the same environment during same period. After we made the 6mm diameter calvarial defect, we filled the DFDB in 8 rats and DFDB and resorbable hydroxyapatite in another 8 rats. We sacrificed them at the postoperative 1 month and 2 months with the periostium observed. As soon as the specimens were delivered, we measured the compressive forces to break the normal calvarial area and the newly formed bone in calvarial defect area using Instron(Model Autograph $S-2000^{(R)}$, Shimadzu, Japan). The rest of the specimens were stained with H&E(Hematoxylin & Eosin) and evaluated with the light microscope. So we got the following results. 1. In every rats, there was no significant difference between the measured forces of normal bone area and those of the bone graft area. 2. In 1 month, the measured forces at DFDB graft group were higher than those of the DFDB and resorbable hydroxyapatite composite graft group(P<0.05). 3. In 2 months, there was no significant differences between the measured forces of DFDB graft group and those of the DFDB and resorbable hydroxyapatite composite graft group. 4. In lightmicroscopic examination, most of the grafted DFDB were transformed into bone in 1 month and a large numbers of hydroxyapatite crystal were observed in DFDB and resorbable hydroxyapatite composite graft group in 1 month. 5. Both group showed no inflammatory reaction in 1 month. And hydroxyapatite crystals had a tight junction without soft tissue invagination when consolidated with newly formed bone. 6. In both groups, newly formed bone showed the partial bone remodeling and the lamellar bone structures and some of reversal lines were observed in 2 months. From the above results, it is suggested that DFDB and resorbable hydroxyapatite composite graft group had a better resistance to compressive force in early stage than DFDB graft group, but there would be no significant difference between two groups after some period. And it is suggested that the early stage of bone formation procedure of DFDB and resorbable hydroxyapatite composite graft group was slight slower than that of DFDB graft group, but there would be no significant difference between two groups after some period.

• Structural Monitoring and Maintenance
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• v.10 no.3
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• pp.221-242
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• 2023

Internal and external corrosion are common in pressure pipes used in a variety of industries, often resulting in defects that compromise their integrity. This economically and industrially significant problem calls for both preventive and curative technical solutions to guarantee the reliability of these structures. With this in mind, our study focuses on the influence of composite and metallic patch repairs on the limit loads of pipes, particularly elbows, the critical component of piping systems. To this end, we used the nonlinear extended finite element method (X-FEM) to study elbows, a priori corroded on the internal surface of the extrados section, then repaired with composite and metallic patches. In addition, the effect of the geometry of composite materials and metal patches was examined, in particular the effect of their thickness and material on the increase in limit loads of repaired structures. The results obtained provide information on the effectiveness and optimization of patch repair of corroded elbows, with the aim of increasing their service life.

• Journal of the Korean Institute of Gas
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• v.16 no.2
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• pp.18-24
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• 2012

This research seeks to evaluate damage on type II gas cylinder by an acoustic emission test when executing 20000 cycles fatigue test and thereafter burst test. Used gas cylinders in the experimental are three types as follows; one is sound cylinder, others are cylinders which contain longitudinal and transverse artificial defect. The size of artificial defect is a depth of 3 mm, width of 3 mm and length of 50 mm. In the case of the cylinder which artificial defect, unlike the expectation that it will burst in low pressure, the burst pressure of the cylinder did not differ much according to whether or not there were defects. However, when there was longitudinal defect, the location of burst was near the location of defect. This leads to the effect in which the thickness of the composite material becomes thinner according to the length of the longitudinal defect and this is judged to have an effect on the location of initiation and growth of crack in the liner. Also, for the acoustic emission signal, when there is longitudinal defect, the ratio of an event occurring at defect position among overall hits is more than 50 %, and the source location also accords very precisely with defect position.

• Archives of Reconstructive Microsurgery
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• v.10 no.1
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• pp.34-37
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• 2001

The injury on the dorsum of foot is usually manifested in the defect of bone and soft tissue, so its reconstruction requires composite tissue. Free flap satisfies this defect but its indication is determined by the defect size, recipient status and so on. Iliac crest bone and fibular bone are useful bone flap but in more than 8cm defect, fibular flap is more useful. The drawback of fibular free flap is the absence of soft-tissue coverage, so another local flap and myocutaneous flap must be added. Fibula-hemisoleus ostemusculocutaneous free flap has been used for the reconstruction of upper and lower extremity. Its advantages are one stage operation, one donor site and the flexibility of the reconstruction with the use of muscle, bone, and skin. This flap has never been reported for the reconstruction of dorsum of foot. In our case, 20-year-old woman was referred with the 17 cm defect of 1st metatarsal bone and $16{\times}8cm$ sized soft tissue loss on the dorsum of the right foot. We reconstructed successfully the dorsum of foot with fibula-hemisoleus osteomusculocutaneous free flap and the patient can walk without crutches after 6 monthes.

• Archives of Craniofacial Surgery
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• v.11 no.1
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• pp.37-40
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• 2010

Purpose: Reconstruction of eyebrow defects after wide excision of the benign and malignant tumors present a cosmetic challenge to the plastic surgeon. There were several methods for reconstruction of partial eyebrow defect with local flaps except hair bearing composite graft. We introduce simple eyebrow reconstruction with bilateral advancement flap and tattooing on the idea that eyebrow tattooing is popular permanent eyebrow makeup among elderly Korean women. Methods: The flaps were designed on both ends of the eyebrow defect along the upper and lower margin of the eyebrow. Both flaps were cut, undermined and were moved centrally to cover the defect. Both flaps were attached along the vertical suturing line. The rest of each flap was sown with dog-ears revised minimally. Scar lines would be hidden along the natural borders of the eyebrow if possible. The resulting vertical scar finally was covered with hair. After 8 months, eyebrow tattooing would be done to camouflage eyebrow shortening and scar. Results: Partial eyebrow defect was reconstructed successfully with bilateral advancement flap and tattooing. The postoperative scar was inconspicuous and eyebrow looked symmetric. Conclusion: We recommend partial eyebrow reconstruction with bilateral advancement flap and tattooing for the elderly Korean female patients after excision of small tumor in and around eyebrow region.

• Archives of Craniofacial Surgery
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• v.19 no.4
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• pp.254-259
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• 2018

Background: The esthetic and functional outcomes of periorbital defect reconstruction are very important because of the complex anatomy and specialized functions of this region. The orbicularis oculi myocutaneous (OOMC) flap is useful for the reconstruction of periorbital defects. But, according to the location and depth of the defects, the reconstruction using OMC flaps with various techniques is rare. The authors have used various kinds of OOMC flaps in various situations and we present an analysis of our experiences. Methods: From November 2001 to July 2017, we used 36 OOMC flaps to reconstruct 30 periorbital defects in 25 patients. We analyzed the cause of the defect, its location, the type of concomitant surgery, the method of flap movement, and complications. Results: Of the 30 defects, basal cell carcinoma was the most common cause, accounting for 20 cases. When the used OOMC flap was classified according to the location of the defects, the switch flap was used in nine cases among 15 defects of lower eyelid, and the V-Y advancement flap was mainly used for other parts. As surgical methods according to the depth of defect were classified, all cases involving the tarsal plate were reconstructed with a composite graft. In case of skin and muscles, they were reconstructed only with OOMC flap or with full-thickness skin graft. Conclusion: The OOMC flap provides good skin quality that is very similar to that of the defect tissue. Depending on the location and depth of the defect, the OOMC flap may be used properly in a variety of ways to achieve good results.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.1
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• pp.44-48
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• 2011

Maxillary defects are inherently complex because they generally involve more than one midfacial component. In addition, most maxillary defects are composite in nature, and often require bony support, as well as a mucosal lining for reconstruction. Therefore, midfacial bone and soft tissue defects present a unique challenge because they require a complex arrangement of tissues in a relatively limited space. This might be difficult to achieve only with free osteocutaneous flaps. The use of bone grafts allows greater flexibility in a reconstruction but is limited by graft resorption. We report a case of a patient reconstructed with a lateral arm free flap, iliac bone graft, sagital split ramus osteotomy for the reconstruction of a right maxillary defect zygomatico-maxillary defect caused by a zygomatico-maxillary malignant tumor resection.