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( Seung-hyeop Nam ),( Chi-heum Cho ),( Sang-hoon Kwon ),( So-jin Shin ),( Tae-kyu Jang ),( Hye-won Chung ),( Seung-mee Lee ) 대한산부인과학회 2018 대한산부인과학회 학술대회 Vol.104 No.-
Objective: To compare the operative outcomes of patients undergoing either robotic (RH) or laparoscopic single-site hysterectomy (LH) in benign gynecological diseases. Methods: This is a retrospective study comparing perioperative outcomes of RH and LH in benign gynecological diseases including leiomyoma, adenomyosis, carcinoma in situ of cervix and endometrial hyperplasia. Patient demographic data and operative data were abstracted from the electronic charts. Parameters for comparison included total operation time, postoperative hospital stay, conversion and complication. Results: One hundred patients underwent LH between December 2011 and April 2013 and three hundreds patients underwent RH February 2014 to August 2017 at Keimyung University, Daegu, Korea. No significant differences were found in terms of age, body mass index (BMI) and uterus weight. Operative time was similar: 98.3 minutes in RH and 80 in LH. Estimated blood loss was also similar: 100ml in both groups. However, there were 2 cases of conversion in LH when there was no case of conversion in RH. Postoperative hospital stay was 2.8 days in RH and 3 days in LH. No intraoperative complications occurred in both groups. Postoperative complications were 0.65% in RH and 4.9% in LH. Conclusion: This single center experience presents that RH is safe and feasible surgical approach in benign gynecological diseases with comparable outcomes while RH overcomes technical limitations of LH.
980 MPa급 열연강의 신장플랜지성에 미치는 템퍼드 마르텐사이트 기지조직과 입상 베이나이트 복합상의 영향
이주승 ( Ju Seung Lee ),이명진 ( Myung Jin Lee ),도형협 ( Hyeong Hyeop Do ),김성주 ( Seong Ju Kim ),강남현 ( Nam Hyun Kang ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.2
The main goal of the study is to obtain high strength and formability for automotive sheet steels such as wheel and chassis. Ferrite-based steels developed previously exhibited superior stretch-flangeability to 780 MPa and even to 980 MPa grade steels. However, it was difficult to achieve 980 MPa tensile strength sufficiently. To achieve a superior stretch-flangeability and to acquire a sufficiently high strength over 980 MPa, a composition of Fe-Cr-Ti-B was developed for hot rolling. The manufactured steel was coiled for 1 hour at 430, 450, and 470 ℃. Specifically, 998 MPa ultimate tensile strength, 11% total elongation, and a 59% excellent hole expansion ratio were obtained by microstructural constituents of a tempered martensite matrix and granular bainite when the coiling was conducted at 470 ℃. As the coiling temperature varied from 470 to 430 ℃, the fraction of granular bainite decreased and that of tempered martensite increased. Therefore, the deviation of phase fractions between two phases decreased at 470 ℃ coiling. Furthermore, as the hole expansion ratio (HER) increased, the hardness deviation of the two phases decreased. As the HER value increased, the crack propagation path dispersed on the second fracture surface and fracture was significantly delayed. Therefore, hot rolled steels using a tempered martensite matrix and granular bainite had the same behavior of stretch-flangeability with respect to the hardness deviation and crack propagation path as compared with the steels using a ferrite matrix. For high strength steels composed of the tempered martensite matrix and granular bainite, however, the minimal deviation between the two constituent phases was acknowledged as an important factor to increase stretch-flangeability. †(Received May 8, 2013)
Fabrication of Rod-Shaped Photonic Structures Using Self-Assembled Colloidal Particles
Seo, Han-Bok,Hyun, Seung-Hyeop,Hur, Nam-Hwi,Lee, Seung-Yop American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.8
<P>In this paper, we propose a simple self-assembly technique to fabricate rectangular rod-shaped photonic structures with micrometer-scale thickness and width using silica nanoparticles. Colloidal nanoparticles were crystallized from the colloidal suspensions injecting the micro-channels with hydrophilic substrates, and then a lot of rectangular rods were rapidly fabricated with relatively low defects by a rotational drying process. The fabricated micro-rods have a specific structural color and a rectangular cross-section where the width is about 1 similar to 2 times larger than the thickness, which is identical to the gap of the micro-channel. As the gap is decreased, the ratio of the width to the thickness of the rectangular rods and the structural irregularity become increasing.</P>
980 MPa급 열연강의 권취온도와 탄화물 거동에 따른 신장플랜지성
천은준 ( Eun Joon Chun ),이주승 ( Ju Seung Lee ),도형협 ( Hyeong Hyeop Do ),김성주 ( Seong Ju Kim ),최윤석 ( Yoon Suk Choi ),박용호 ( Yong Ho Park ),강남현 ( Nam Hyun Kang ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.7
To analyze the factors on stretch-flangeability for 980 MPa-grade hot-rolled steels, two types of steels (Fe-Cr and Fe-Mo) were manufactured by hot-rolling. Manufactured steels at the low coiling temperature, such as 400 and 500℃, had poor stretch-flangeability due to un-uniformly distributed carbides and a large deviation of interphase hardness. However, when the coiling temperature was set at 650℃ with Fe-Cr steel, 998 MPa of ultimate tensile strength, 19% of total elongation and 65% of the hole expanding ratio were achieved by microstructural constituents of polygonal ferrite (PF) and granular ferrite (GF) dispersed with fine carbides (<50 nm). Therefore, the material to attain 980 MPa with superior formability was the Fe- Cr steel that was precipitation-hardened in polygonal ferrite and granular ferrite at the coiling temperature 650℃.
천은준,이주승,도형협,김성주,박용호,강남현,Chun, Eun-Joon,Lee, Ju-Seung,Do, Hyeong-Hyeop,Kim, Seong-Ju,Park, Yong-Ho,Kang, Nam-Hyun 한국재료학회 2012 한국재료학회지 Vol.22 No.1
Research into the development of high strength (1 GPa) and superior formability, such as total elongation (10%), and stretch-flangeability (50%) in hot-rolled steel was conducted with a thermomechanically controlled hot-rolling process. To improve the overall mechanical properties simultaneously, low-carbon steel using precipitation hardening of Ti-Nb-V multimicroalloying elements was employed. And, ideal microstructural characteristics for the realization of balanced mechanical properties were determined using SEM, EBSD, and TEM analyses. The developed steel, 0.06C-2.0Mn-0.5Cr-0.2(Ti + Nb + V), consisted of ferrite as the matrix phase and second phase of granular bainite with fine carbides (20-50 nm) in both phases. The significant factor of the microstructural characteristics that affect stretch-flangeability was found to be the microstructural homogeneity. The microstructural homogeneity, manifest in such characteristics as low localization of plastic strain and internally stored energy, was identified by grain average misorientation method, analyzed by electron backscattered diffraction (EBSD) and hardness deviation between the phases. In summar, a hot-rolled steel having a composition 0.06C-2.0Mn-0.5Cr-0.2(Ti + Nb + V) demonstrated a tensile strength of 998 MPa, a total elongation of 19%, and a hole expansion ratio of 65%. The most important factors to satisfy the mechanical property were the presence of fine carbides and the microstructural homogeneity, which provided low hardness deviation between the phases.