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풍력발전 타워용 종방향 보강 원형단면 강재 쉘의 극한압축강도
안준태,신동구,Ahn, Joon Tae,Shin, Dong Ku 한국강구조학회 2017 韓國鋼構造學會 論文集 Vol.29 No.2
풍력발전 타워용 종방향 보강 원형단면 강재 쉘에 대하여 재료 및 기하학적 비선형 유한요소법(GMNIA)으로 극한압축강도 해석을 수행하였다. 보강 쉘의 반경 대 두께비, 초기변형 형상 및 진폭, 종방향보강재의 면적 및 간격 등의 주요 설계 파라미터가 압축력을 받는 보강 쉘의 극한강도에 미치는 영향을 분석하였으며, DNV 설계기준에 의한 설계좌굴강도와 유한요소해석으로 구한 극한압축강도를 비교하였다. 기하학적 초기결함의 형상은 선형 좌굴해석으로부터 구한 좌굴모드 및 제작 과정에서 용접으로 발생하는 딤플 변형을 고려하였다. 해석 대상 보강 쉘의 반경 대 두께비는 50~200이며, 종방향보강재는 횡비틀림좌굴과 국부좌굴이 발생하지 않도록 DNV 설계기준에 따라 두께와 돌출폭을 결정하였다. Ultimate axial strength of longitudinally stiffened cylindrical steel shells for wind turbine tower was investigated by applying the geometrically and materially nonlinear finite element method. The effects of radius to thickness ratio of shell, shape and amplitude of initial imperfections, area ratio between effective shell and stiffener, and stiffener spacing on the ultimate axial strength of cylindrical shells were analyzed. The ultimate axial strengths of stiffened cylindrical shells by FEA were compared with design buckling strengths specified in DNV-RP-C202. The shell buckling modes obtained from a linear elastic bifurcation FE analysis as well as the weld depression during fabrication specified in Eurocode 3 were introduced in the nonlinear FE analysis as initial geometric imperfections. The radius to thickness ratio of cylindrical shell models was selected to be in the range of 50 to 200. The longitudinal stiffeners were designed according to DNV-RP-C202 to prevent the lateral torsional buckling and local buckling of stiffeners.
안준태,신동구,Ahn, Joon Tae,Shin, Dong Ku 한국강구조학회 2015 韓國鋼構造學會 論文集 Vol.27 No.1
Ultimate flexural buckling strength of cylindrical steel shells for the wind turbine tower structure was investigated by applying the geometrically and materially nonlinear finite element method. The effects of initial imperfection, radius to thickness ratio, and type of steel on the ultimate flexural strength of cylindrical shell were analyzed. The flexural strengths of cylindrical shells obtained by FEA were compared with design flexural strengths specified in Eurocode 3 and AISI. The shell buckling modes recommended in DNV-RP-C202 and the out-of-roundness tolerance and welding induced imperfections specified in Eurocode 3 were used in the nonlinear FE analysis as initial geometrical imperfections. The radius to thickness ratios of cylindrical shell in the range of 60 to 210 were considered and shells are assumed to be made of SM520 or HSB800 steel. 풍력발전 타워용 원형단면 강재 쉘에 대하여 재료 및 기하학적 비선형 유한요소법으로 극한휨강도 해석을 수행하였다. 쉘의 기하학적 초기변형, 반경 대 두께비, 적용 강종 등이 극한휨강도에 미치는 영향을 분석하였으며, Eurocode 3와 AISI 설계기준에 의한 설계휨강도와 유한요소해석으로 구한 극한휨강도를 비교하였다. 비선형 FE 해석에는 DNV-RP-C202에 제시된 쉘의 좌굴모드와 유로코드에 규정된 진원도 허용오차 및 용접에 의한 변형을 기하학적 초기 결함으로 고려하였다. 원통형 쉘의 반경 대 두께비는 60~210 범위를 고려하였으며 SM520과 HSB800 강재로 제작된 것으로 가정하였다.
IEEE802.22 WRAN에 대한 향상된 QoS 구조 제안
조동훈(Dong-Hoon Cho),안준태(Joon-Tae Ahn),박진규(Jin-Kyu Park) 대한전자공학회 2018 대한전자공학회 학술대회 Vol.2018 No.6
In paper, we have proposed a new QoS architecture for IEEE 802.22 WRAN MAC protocol. We also presented a bandwidth allocation and admission control policy for the architecture. The simulation and analytical results show that our architecture may provide QoS support in terms of bandwidth request and allocation for all type of traffic classes.
송용중(Yong Jung Song),윤병선(Byoung Sun Yoon),김현희(Hyun Hee Kim),안준태(Joon Tae Ahn),최석철(Suck Chul Choi),유상영(Sang Young Ryu),김종훈(Jong Hoon Kim),김병기(Byoung Gie Kim),박상윤(Sang Yoon Park),이경희(Kyung Hee Lee) 대한산부인과학회 2001 Obstetrics & Gynecology Science Vol.44 No.12
N/A Objectives : This study is to investigate clinicopathologic characteristics, survival and prognostic factors in patients with Krukenberg tumor of the ovary. Material & Methods : From Jan. 1991 to Dec. 2000, 42 patients with Krukenberg tumor of the ovary were investigated with clinical profiles, such as age, stage, primary sites, clinical symptoms, and survival, retrospectively. Results : A mean age of 42 patients was 44.8 years (range 27-77). Stomach was the most frequent primary site (30/42, 71.4%), followed by colon (7/42, 16.7%) and gallbladder (1/42, 2.4%). In 38 patients, primary sites diagnosed before or after 1 month of diagnosis of Krukenberg tumor of ovary (36/38 cases, 94.7%). The most common feature of patients with Krukenberg tumor of ovary was bilateral abdominal mass. 5-year survival rate of patients with Krukenberg tumor of ovary was 8.94% (95% CI=3.33-14.55) and median survival time was 11 months. Age, bilaterality of tumor, time of diagnosis, presence of ascites and the primary site did not affect the survival. The patients who received post-operative adjuvant chemotherapy had better 3-year survival than those who did not (17.28% vs 10% p=0.03). Conclusion : Krukenberg tumor of the ovary is an aggressive tumor with poor prognosis. Post-operative adjuvant chemotherapy may increase the survival of patients with Krukenberg tumor of the ovary. Further prospective studies for the role of surgery and chemotherapy are needed.