가수분해 반응 제어에 의한 TiO₂ 미분말 제조

서동석,이종국,이은구 조선대학교 생산기술연구소 1999 生産技術硏究 Vol.21 No.2

TiO₂ powders were prepared via the sol-gel method using titanium alkoxide. The process for the preparation of TiO₂ powder was studied as a functuion of the molar ratio of water to alkoxide. Microstructure, crystallization behaviour with heat treatment temperature, specific surface area, and particle size were examined using SEM. X-ray diffraction. TG/DSC, BET, and particle size analyser, respectively. The TiO₂ powders showed slightly agglomeration less than 0.5㎛ and the powders transformed amorphous to anatase phase at 450℃.

수산화아파타이트 생체재료의 표면용해 특성

이종국,서동석 조선대학교 생산기술연구소 2003 生産技術硏究 Vol.25 No.1

Grain boundary dissolution and separation of hydroxyapatite (HA) in distilled water were investigated For the preparation of HA ceramics, a laboratory synthesized HA powder with different Ca/P molar ratio was used. After preparing powder compacts, the specimens were sintered at 1200℃ for 2h in air with under moisture protection. Microstructural degradation related to the grain boundary dissolution could be induced by microstructures and composition of HA ceramics.

세리아 안정화 지르코니아 과립분말의 제조 및 소결특성

이종국,서동석,황규홍 조선대학교 생산기술연구소 2000 生産技術硏究 Vol.22 No.1

Stabilized zirconia granule powder was prepared from monoclinic zirconia powder by an addition of ceria and spray-drying method The preparation condition of optimal slurry for nozzle spray-drying was the mixing of 60 vol% zirconia powder containing 12 mol% Ce(NO_3)_3, and 40 % water and milling for 24h in zirconia jar. The slurry was stabilized by the addition of binder (PVA 1Owt%), dispersant(sodium phosphate) 1 wt%, and plasticizer(PEG) 05 wt%. The best spherical granule powder prepared from the condition for the spray-drying is the inlet temperature of 300℃, outlet temperature of 180℃, slurry feeding speed of 850 rpm, and atomizer speed of 40 Hz. The highly dense compact was obtained by the CIP under the pressure of 200 MPa and the sintering at 1500℃ for 2h.

두개골의 3차원 영상 분석을 위한 전산화단층촬영 방법의 비교 : 상층 두께가 3차원 영상의 계측에 미치는 영향

정호걸,김기덕,박혁,김동욱,정해조,김희중,유선국,김용욱,박창서 대한구강악안면방사선학회 2004 Imaging Science in Dentistry Vol.34 No.3

Purpose : To evaluate the quantitative accuracy of three-dimensional (3D) images by means of comparing distance measurements on the 3D images with direct measurements of dry human skull according to slice thickness and scanning modes. Materials and Mathods : An observer directly measured the distance of 21 line items between 12 orthodontic landmarks on the skull surface using a digital vernier caliper and each was repeated five times. The dry human skull was scanned with a Helical CT with various slice thickness (3, 5, 7 mm) and acquisition modes (Conventional and Helical). The same observer measured corresponding distance of the same items on reconstructed 3D images with the internal program of V-works 4.0 (Cybermed Inc., Seoul, Korea). The quantitative accuracy of distance measurements were statistically evaluated with Wilcoxons’ two-sample test. Results : 11 line items in Conventional 3 mm, 8 in Helical 3mm, 11 in Conventional 5 mm, 10 in Helical 5 mm, 5 in Conventional 7 mm and 9 in Helical 7 mm showed no statistically significant difference. Average difference between direct measurements and measurements on 3D CT images was within 2 mm in 19 line items of Conventional 3 mm, 20 of Helical 3 mm, 15 of Conventional 5 mm, 18 of Helical 5 mm, 11 of Conventional 7mm and 16 of Helical 7 mm. Conclusion : Considering image quality and patient’s exposure time, scanning protocol of Helical 5 mm is recommended for 3D image analysis of the skull in CT.

Management of neck contractures by single-stage dermal substitutes and skin grafting in extensive burn patients

Dong-Kook Seo,Dohern Kym,Jun Hur 대한외과학회 2014 Annals of Surgical Treatment and Research(ASRT) Vol.87 No.5

Purpose: Severe neck contracture is a problem that must be resolved by priority. We consider the best contracture treatment to be the full-thickness skin graft. However, clinicians often encounter patients, especially extensive burn patients, who have insufficient donor sites for the full-thickness skin graft. We treated extensive burn patients with neck scar contractures with a split-thickness skin graft (STSG) combined with dermal substitutes. The purpose of this study was to evaluate clinical outcomes of neck contracture treatment in extensive burn patients performing STSG with dermal substitutes as adjuvant treatment. Methods: We analyzed the retrospective clinical and photographic records of 28 patients with severe neck contracture who were admitted to Hallym University Hangang Sacred Heart Hospital, Seoul, Korea, from January 2012 to December 2012. We performed STSG in combination with dermal substitutes to minimize the degree of contracture. Results: The overall take rate of skin to dermal substitutes was 95.9%, and no grafts failed to affect recontracture except in one patient with a partial loss of artificial dermis who underwent a follow-up skin graft without any problems. Excellent/good outcomes were shown in 27 out of 28 patients. Conclusion: In extensive burn patients, skin grafting in combination with dermal substitutes can be an alternative to STSG alone for contracture release.

Fasciotomy for the electrical injury

Dong-Kook Seo 대한외과학회 2015 대한외과학회 학술대회 초록집 Vol.2015 No.11

Influence of Starting Powders on Hydroxyapatite Coatings Fabricated by Room Temperature Spraying Method.

Seo, Dong Seok,Lee, Jong Kook,Hwang, Kyu Hong,Hahn, Byung Dong,Yoon, Seog Young American Scientific Publishers 2015 Journal of Nanoscience and Nanotechnology Vol.15 No.8

<P>Three types of raw materials were used for the fabrication of hydroxyapatite coatings by using the room temperature spraying method and their influence on the microstructure and in vitro characteristics were investigated. Starting hydroxyapatite powders for coatings on titanium substrate were prepared by a heat treatment at 1100 °C for 2 h of bovine bone, bone ash, and commercial hydroxyapatite powders. The phase compositions and Ca/P ratios of the three hydroxyapatite coatings were similar to those of the raw materials without decomposition or formation of a new phase. All hydroxyapatite coatings showed a honeycomb structure, but their surface microstructures revealed different features in regards to surface morphology and roughness, based on the staring materials. All coatings consisted of nano-sized grains and had dense microstructure. Inferred from in vitro experiments in pure water, all coatings have a good dissolution-resistance and biostability in water.</P>

문장 의도 분류와 개체명 인식을 활용한 개인정보 검출 및 비식별화 시스템

서동국 ( Dong-kuk Seo ),김건우 ( Gun-woo Kim ),김재영 ( Jae-young Kim ),이동호 ( Dong-ho Lee ) 한국정보처리학회 2020 한국정보처리학회 학술대회논문집 Vol.27 No.2

최근 개인정보가 포함된 비정형 텍스트 문서들이 유출되거나 무분별하게 공개됨으로써 정보의 주체는 물론 기업들까지 피해를 받고 있다. 데이터를 공개 및 활용하기 위해 개인정보 검출 및 비식별화 과정이 필수적이지만 정형 데이터와는 달리 비정형 데이터의 경우 해당 과정을 자동으로 처리하는 데 한계가 있다. 이를 위해 딥러닝 모델들을 사용하여 자동화하려는 연구들이 있었지만 문장 내 단어의 모호성에 대한 고려 없이 단어 개체명 정보에만 의존하여 개인정보를 검출하는 형태로 진행되었다. 따라서 문장 내 단어들 중 식별 대상인 단어들도 비식별화 되어 데이터에 대한 유용성을 저해할 수 있다는 문제점을 남겼다. 본 논문에서는 문장의 의도 정보를 단어의 개체명 학습 과정에 부가적인 정보로 활용하는 개인정보 검출 모델과 개인정보 데이터의 유용성을 고려한 비식별화 기법을 제안한다.

Sintering and Mechanical Property of Tuna Bone-Derived Hydroxyapatite

Seo, Dong Seok,Kim, Yong Gook,Lee, Jong Kook Trans Tech Publications, Ltd. 2010 Advanced materials research Vol.97 No.-

<P>Hydroxyapatite (HA) ceramics derived from tuna bone (THA) was prepared and their mechanical property was investigated with immersion in buffered water. Tuna bones were soaked in 0.1 M of NaOH solution at 80°C for 1 h. After soaking, the bones were calcined at 800°C for 1 h to completely remove organic, and then attritor-milled for 24 h. The powders obtained were cold isostatically pressed and sintered at 1300°C with a dwell time of 1 h. Sintered densities of the THA was about 93%. After polishing, the THA were immersed in buffered water at 37 °C for 3 and 7 days. The THA ceramics consisted of HA and small amount of magnesium oxide. Immersion test revealed that there was no clear evidence of dissolution for the THA which sintered at high temperatures. Vickers hardness test showed that the hardness value of THA ceramics was not changed with immersion time indicating that dense hydroxyapatite from tuna bone was stable in liquid environment.</P>

Preparation of novel fillers, named networked silicas, and their effects of reinforcement on rubber compounds

Seo, Gon,Kaang, Shinyoung,Hong, Chang Kook,Jung, Dong Shin,Ryu, Chang Seok,Lee, Dong Hee John Wiley Sons, Ltd. 2008 Polymer international Vol.57 No.10

<P>BACKGROUND: A new concept for reinforcing silica, named networked silica, was used to achieve enhanced reinforcing performance of silica and to eliminate the disadvantage of ethanol production and precure through coupling reagents in the preparation of silica-reinforced SBR compounds.</P><P>RESULTS: The networked silicas were prepared by connecting silica particles with amine and glycidoxy groups, which had been previously coupled on their surface. The networked silicas compounded in SBR showed a significant enhancement of tensile strength accompanied with a moderate increase in modulus at a high loading of 70 phr even without using any coupling reagents. Their high performance is discussed in relation to their physical and chemical properties investigated using thermogravimetry, infrared spectroscopy, ζ-potential, transmission electron microscopy and nitrogen adsorption methods.</P><P>CONCLUSION: The improved reinforcing performance of networked silicas confirmed their feasibility as reinforcing materials for the manufacture of highly stable tires. The high tensile strength achieved using the networked silicas is probably due to the physical entanglements of rubber molecules with the networks formed among silica particles. Copyright © 2008 Society of Chemical Industry</P>