• Journal of Korean Neurosurgical Society
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• v.30 no.3
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• pp.319-324
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• 2001

Objectives : The percutaneous vertebroplasty provides a good result in the treatment of osteoporotic vertebral compression fractures. But, the epidural leakage of polymethylmetacrylate(PMMA) after vertebroplasty may decrease the therapeutic effects because of the compression of thecal sac and/or nerve roots. The authors carried out a prospective study to evaluate the causative factors of epidural leakage of PMMA and to assess the influence on the outcome. Methods : This study involved 347 vertebral levels of compression fractures in 159 patients. Among these, the epidural leakages were identified in 92 vertebral levels(26.5%) in 64 patients(40.3%) on post-operative CT scan. Results : The incidence of epidural leakage of PMMA was significantly higher in the level above T7(p=0.001). The large amount of the injected PMMA and the use of an injector also increased the incidence(p=0.03 and p=0.045, respectively). The position of the needle tip in the vertebral body and the pattern of venous drainage did not influence. The immediate post-operative visual analogue scale(VAS) scores and facial scales(FS) were higher in the patients with epidural leakage(p=0.009). But there were no significant differences between the two groups after three months of operation(p=0.541). Conclusions : The incidence of epidural leakage of PMMA after percutaneous vertebroplasty appears to have relationship with the amount of PMMA and the levels injected. The epidural leakage of PMMA reduced the immediate therapeutic effects of vertebroplasty, but did not influence the late outcome. However, the epidural leakage should be avoided because of its potential neurological complications.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.633-642
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• 2008

It's important to measure quantitative properties about thermal-nano behavior of polymer for producing high quality components using Nanoimprint lithography process. Nanoscale indents can be used to make the cells for molecular electronics and drug delivery, slots for integration into nanodevices, and defects for tailoring the structure and properties. In this study, formability of polymethylmetacrylate(PMMA) and polycarbonate(PC) were characterized Polymer has extreme variation in thermo mechanical variation during forming high temperature. Because of heating the polymer, it becomes softer than at room temperature. In this case it is particularly important to study high temperature-induced mechanical properties of polymer. Nanoindenter XP(MTS) was used to measure thermo mechanical properties of PMMA and PC. Polymer was heated by using the heating stage on NanoXP. At CSM(Continuous Stiffness Method) mode test, heating temperature was $110^{\circ}C,120^{\circ}C,130^{\circ}C,140^{\circ}C$ and $150^{\circ}C$ for PMMA, $140^{\circ}C,150^{\circ}C,160^{\circ}C,170^{\circ}C$ and $180^{\circ}C$ for PC, respectively. Maximum indentation depth was 2000nm. At basic mode test, heating temperature was $90^{\circ}C$ and $110^{\circ}C$ for PMMA, $140^{\circ}C,160^{\circ}C$ for PC. Maximum load was 10mN, 20mN and 40mN. Also indented pattern was observed by using SEM and AFM. Mechanical properties of PMMA and PC decreased when temperature increased. Decrease of mechanical properties from PMMA went down rapidly than that of PC.

• Journal of Korean Neurosurgical Society
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• v.30 no.2
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• pp.163-167
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• 2001

Objective : Percutaneous vertebroplasty has recently been introduced as an interesting therapeutic alternative for the treatment of thoracolumbar vertebral body fractures in elderly persons with osteoporosis. The authors present the early results of this method. Method and Material : From July 1999 to April 2000, percutaneous transpedicular technique was used in 20 patients (2 men and 18 women) whose mean age was 67.5 years old(range 59-79) with painful vertebral compression(22) and burst(2) fractures. The interval between fracture and vertebroplasty ranged 1 day to 4 months. The procedure involved percutaneous puncture of the injured vertebra via transpedicular approach under fluoroscopic guidance, followed by injection of polymethylmetacrylate(PMMA) into the vertebral body through a disposable 11-guage Jamshidi needle. Result : The most common cause of fracture was slip down and the most frequent injured level was the twelfth thoracic spine. The procedure was technically successful bilaterally in 18 patients(9 thoracic and 15 lumbar spines) with an average injection amount of 7.7ml PMMA in each level. Seventeen(94.4%) patients reported significant pain relief immediately after treatment. Two leaks of PMMA were detected with postoperative CT in spinal epidural space and extravertebral soft tissue without clinical symptoms. Conclusion : Although this study represents the early results, percutaneous vertebroplasty seems to be valuable tool in the treatment of painful osteoporotic vertebral body fractures in elderly, providing acute pain relief and early mobilization.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.11
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• pp.3630-3638
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• 1996

An experimental study has been conducted to explore the behaviors of the radiative ignition of polymethylmetacrylate(PMMA) in a confined enclosure such as the ignition delay time, PMMA surface temperature, the ignition location and the ignition process. In addition, the effects of hot wall orientation on the ignition delay and PMMA surface temperature were studied. When the hot wall is located at the bottom, ignition delay time is the shortest. Ignition surface temperature becomes the lowest for the hot top wall case. These are due to buoyancy effect. Since the radiative heat flux of hot wall is rather lower than laser source, the ignition is considered to be controlled by the mixing process. Therefore, the ignition location, where appropriate mixture of fuel and oxygen exists, occurs near the hot wall. The flame propagates along the hot wall where there exists sufficient oxygen.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.108-111
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• 2007

It's important to measure quantitative properties about thermal-nano variation conduct of polymer for producing high quality components using NIL process. NanoScale indents can be used ad cells for molecular electronics and drug deliver, slots for integration into nanodevices, and defects for tailoring the structure and properties. In this study, it's to evaluate mechanical characteristic of polymer such as PMMA and PC at high temperature for manufacture of nano/micro size of polymer using indenter at high temperature. At high temperature mechanical properties of polymer have extreme variation. Because heating the polymer, it becomes softer than room temperature. In this case it is especially important to study for mechanical properties of polymer at high temperature.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.26 no.6
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• pp.672-676
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• 2000

One of the current treatment methods for chronic osteomyelitis is removal of the infected and necrotic tissue to reduce the bacterial concentration as much as possible. This is performed concomitantly with antibiotic therapy. Chronic osteomyelitis(C.O.) implies chronic ischemia of the diseased bone. Thus, the treatment for C.O. requires high systemic level of antibiotics. In some cases, however, inherent undesirable adverse effects(for example, nephrotoxicity, ototoxicity, and others) may render this course of treatment difficult. Knowing that residual monomers are released from hardened bone cement, installation of antibiotic-impregnated PMMA(polymethyl-methacrylate) beads in situ have been one of treatment methods of C.O. When introduced into the wound, they established an exceedingly high level of local antibiotics for prolonged period without high systemic level of antibiotics. We experienced favorable results with vancomycin-impregnated PMMA beads for the treatment of C.O. of the mandible. So, we report it with literature reviews.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.384.1-384.1
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• 2014

대면적 그래핀을 합성하는 방법으로 주로 화학기상증작법, SiC 기판을 고온 열처리하는 방법 그리고 최근에는 고체소스를 활용하여 그래핀을 합성하는 방법 등이 보고되고 있다. 이에, 본 연구에서는 폴리머 용액들을 원하는 기판에 스핀코팅하여 건조시킨 후, 후 열처리 공정을 통해 그래핀을 합성하고 물성을 평가해보았다. 그래핀 합성을 위해서 사용된 폴리머 탄소원은 Vinyl계 폴리머 용액으로, polystyrene (PS), polyacrylonitrile (PAN), 그리고 polymethylmetacrylate (PMMA) 등으로 2wt%의 폴리머 용액을 $SiO_2$기판에 스핀 코팅을 하고, 그 위에 Nickel이나 Copper와 같은 catalytic metal을 capping layer로 증착하고, 고진공에서 후열처리 공정에 의해 그래핀을 성장하였다. 이때, 탄소원으로 쓰인 PS, PMMA 폴리머는 pristine graphene 합성을 위해, PAN 폴리머는 질소가 도핑된(n-type) 그래핀 합성을 위해 사용되었다. 그래핀의 물성은 폴리머 종류, 코팅된 두께, 촉매 금속층 종류와 두께, 그리고 후열처리 공정 온도와 시간에 따라서 조절이 가능하였다. 우리는 Raman spectroscopy, AFM, SEM 등을 활용하여 그래핀의 층수, 결함, 표면양상 등을 평가하였고, 또한 전사된 그래핀을 기반으로 제작된 FET의 게이트 전압에 따른 I-V 곡선을 측정하여 캐리어 종류 및 전하 이동도 등을 평가하였다. 더욱 상세한 내용은 프레젠테이션에서 논하겠다.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.423-430
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• 2021

In order to evaluate the fire risk and fire risk rating of wood for construction materials, this study focused on fire performance index-III (FPI-III), fire growth index-III (FGI-III), and fire risk index-IV (FRI-IV) according to Chung's equations-III and -IV. Western red cedar, needle fir, ash, and maple were used as the specimens. The fire characteristics were investigated using a cone calorimeter (ISO 5660-1) equipment on the specimen. The FPI-III measured after the combustion reaction was 0.86 to 12.77 based on polymethylmethacrylate (PMMA). The FGI-III was found to be 0.63 to 5.26 based on PMMA. The fire rating according to the FRI-IV, which is the fire rating index, was 0.05 to 6.12, and the western red cedar was 122.4 times higher than that of the maple. The fire risk rating according to the FRI-IV increased in the order of maple, ash, needle fir, PMMA and western red cedar. The CO peak concentration of all specimens was measured as 103 to 162 ppm, and it was 2.1 to 3.2 times higher than 50 ppm, the permissible exposure limits of the US occupational safety and health administration. Materials such as western red cedar, which have a low bulk density and contain a large amount of volatile organic substances, have a low FPI-III and a high FGI-III, so they have a high fire risk rating.