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Geometry-dependent MITC method for a 2-node iso-beam element
Lee, Phill-Seung,Noh, Hyuk-Chun,Choi, Chang-Koon Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.2
In this paper, we present an idea of the geometry-dependent MITC method. The simple concept is exemplified to improve a 2-node iso-beam (isoparametric beam) finite element of varying section. We first study the behavior of a standard 2-node iso-beam finite element of prismatic section, which has been widely used with reduced integration (or the equivalent MITC method) in order to avoid shear locking. Based on analytical studies on cantilever beams of varying section, we propose the axial strain correction (ASC) scheme and the geometry-dependent tying (GDT) scheme for the 2-node iso-beam element. We numerically analyze varying section beam problems and present the improved performance by using both ASC and GDT schemes.
이필승(Lee Phill-Seung),노혁천(Noh Hyuk-Chun) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.3A
본 논문에서는 최근 주요 연구들을 토대로 쉘 구조물의 유한요소해석에 대하여 중요한 개념들과 그 연관관계를 고찰한다. 감절점 쉘 유한요소의 수학모델인 기본쉘수학모델을 살펴본다. 쉘 구조물의 두께가 얇아짐에 따라 일어나는 쉘 구조문제의 세가지 극한거동들(휨지배거동, 막지배거동, 혼합지배거동)에 대한 쉘의 점근거동 이론을 소개하고 점근거동을 유한요소해석을 통해 찾아내는 방법을 알아본다. 유한요소해의 오차를 s-norm으로 평가하는 방법을 소개하고 이를 이용하여 쉘 유한요소의 잠김현상이 유한요소해의 수렴곡선에 어떻게 나타나는지 살펴본다. 쉘 구조물의 유한요소해석에서 균일최적수렴의 개념을 논의한다. 마지막으로 이상적인 쉘 유한요소의 조건을 알아보고 쉘 유한요소의 성능평가를 위한 방법론을 제시한다. Based on recent research works, important concepts on the finite element analysis of shell structures and the relations among them are presented in this paper. We review the basic shell mathematical model, which is the underlying mathematical model of the continuum mechanics based shell finite elements. The asymptotic theory of shell structures then is reviewed and we present how to evaluate the asymptotic behavior in finite element solutions. S-norm is introduced as an error measure of finite element solutions and we show "locking" in the convergence curves of shell finite element solutions. We discuss the concept of "uniform optimal convergence" in finite element analysis of shells. We finally summarize requirements on ideal shell finite elements and propose how to perform benchmark tests of shell finite elements.
분리기술 열역학 : 활성탄소섬유 카트리지 휠터에 의한 수중 잔류염소의 흡 탈착 거동
송승필(Seung Phill Song),이재광(Jae Kwang Lee),유승곤(Seung Kon Ryu) 한국화학공학회 2000 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.38 No.2
Cylindrical Activated Carbon Fiber cartridge filters were prepared to investigate their adsorption/desorption behavior of residual chlorine from 2 ppm aqueous solution. From breakthrough profiles, the amount of purified water was 31.5 ton with Activated Carbon Fiber cartridge filter(Activated Carbon Fiber: 100g) while only 8.4 ton with Activated Carbon Fiber/Activated Carbon cartridge filter(Activated Carbon Fiber; 50 g, Activated Carbon: 50 g) at the breakpoint when the breakpoint was fixed to 0.2 ppm(C/C_0=0.1) residual chlorine. The pressure drop through Activated Carbon Fiber and Activated Carbon Fiber/Activated Carbon cartridge filter were 0.2 ㎏_f/㎠ and 2.3 ㎏_f/㎠, respectively, when 120 ton aqueous solution was passing the cartridges at 10ℓ/min flow rate. The desorption of chlorine from fully used cartridges was performed by reverse washing with hot water at 90 ℃. The desorption efficiency of cartridge was determined by comparison the 2nd adsorption capacity of residual chlorine with the 1st adsorption capacity at breakpoint. The desorption efficiency of Activated Carbon Fiber cartridge was 70.5% while that of Activated Carbon Fiber/Activated Carbon cartridge was 36.9%. The desorption efficiency of cartridge increased with the temperature of washing water and decreased with the amount of Activated Carbon charged in cartridge.
Dong-Hwa Lee,Hyo-Jin Kim,Phill-Seung Lee 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.5
In this paper, we present a new method to calculate interface warping functions for the analysis of beams with geometric and material discontinuities in the longitudinal direction. The classical Saint Venant torsion theory is extended to a three-dimensional domain by considering the longitudinal direction. The interface warping is calculated by considering both adjacent cross-sections of a given interface. We also propose a finite element procedure to simultaneously calculate the interface warping function and the corresponding twisting center. The calculated interface warping functions are employed in the continuum-mechanics based beam formulation to analyze arbitrary shape cross-section beams with longitudinal discontinuities. Compared to the previous work by Yoon and Lee (2014a), both geometric and material discontinuities are considered with fewer degrees of freedom and higher accuracy in beam finite element analysis. Through various numerical examples, the effectiveness of the proposed interface warping function is demonstrated.
Lee, Sang-Min,Oh, Dong-Joon,Jung, Im-Deok,Bae, Kong-Myeong,Jung, Phill-Gu,Chung, Kwang-Hyo,Cho, Seung-Jin,Ko, Jong-Soo 한국정밀공학회 2009 International Journal of Precision Engineering and Vol.10 No.3
Nickel micromesh sheets were designed and fabricated and their water-repellent and water-proof abilities were characterized. The network-type microstructures of the micromesh sheets functioned as micro-protrusions of lotus leaves, which allowed the sheets to superhydrophobic. The micromesh enabled the material waves, including sound and light waves, to pass through the microholes, but repelled water. Because of the effects of the micromesh and plasma polymerized fluorocarbon(PPFC) coating, the contact angle of the micromesh sheets was drastically jumped up from $63^{\circ}$ of the non-coated nickel flat film to $140^{\circ}$ of the PPFC-coated nickel micromesh, which modified the nickel sheet from hydrophilic to superhydrophobic. The narrower lattice width in the micromesh was more effective at enhancing the water-repellency. On the other hand, the narrow lattice width weakened the water-proof ability. Reducing the hole size and increasing the lattice width of the micromesh are necessary to improve the water-proof ability.
The strain-smoothed MITC3+ shell finite element
Lee, Chaemin,Lee, Phill-Seung Elsevier 2019 Computers & structures Vol.223 No.-
<P><B>Abstract</B></P> <P>In this paper, we propose the strain-smoothed MITC3+ shell finite element. The membrane strain field of the continuum mechanics based 3-node triangular shell element (MITC3+) is smoothed using the recently developed strain-smoothed element (SSE) method. The strain-smoothed MITC3+ shell element passes basic tests (patch, isotropy and zero energy mode tests) and shows significantly improved membrane behavior in various numerical examples. The major advantage of the SSE method is that no additional degree of freedom is required for solution improvement.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The strain-smoothed MITC3+ shell finite element is proposed. </LI> <LI> The membrane strain of the MITC3+ element is improved using the strain-smoothed element method. </LI> <LI> The strain-smoothed element does not require special smoothing domains and additional DOFs. </LI> <LI> Through various numerical examples, its improved performance is demonstrated. </LI> </UL> </P>
Poor prognosis after conservative surgery in stage I mucinous epithelial ovarian cancer
( Phill Seung Jung ),( Shin Wha Lee ),( Jeong Yeol Park ),( Dai Shik Suh ),( Dae Yeon Kim ),( Jong Hyeok Kim ),( Yong Man Kim ),( Young Tak Kim ),( Joo Hyun Nam ) 대한산부인과학회 2014 대한산부인과학회 학술대회 Vol.100 No.-
목적: To evaluate the oncologic safety and to identify prognostic factor for recurrence in premenopausal women with stage I mucinous epithelial ovarian cancer (mEOC) who underwent conservative surgery. 방법: We enrolled 97 patients who were 1) premenopausal at the time of surgery and 2) confirmed to be the FIGO stage I. The surgical procedure of conservative surgery was unilateral salpingo-oophorectomy with/without contralateral ovarian wedge resection. 결과: The median age was 33 (range: 13-50) years at the time of surgery. Sixty-three (64.9%) patients were stage Ia, and 34 (35.1%) were Ic. Fifty-three (54.6%) patients underwent conservative surgery, and adjuvant chemotherapy was administrated to 61 (62.9%) patients. During 73.7 (range: 7.1-243.5) months of the median follow-up duration, 13 (13.4%) patients recurred and 8 (8.2%) of them died of disease. Among patients who underwent conservative surgery, there were 10 recurrences and the majority of recurred site was intraperitoneal cavity (n=8) with median age of 25 (range: 14-46) and median PFS of 17.8 (range: 5.1-53.3) months. In multivariate analysis, a significantly poorer prognosis was noted in patients who underwent conservative surgery (HR: 6.26, 95% CI: 1.53-25.53, p=0.011) and in patients with high preoperative CA-125 (HR: 1.98, 95% CI: 1.26-3.11, p=0.003). In patients with high preoperative CA-125 (>35U/mL, n=48), conservative surgery caused significantly higher recurrence rate (HR: 5.73, 95% CI: 1.22-27.03, p=0.027). 5-year disease-free survival rate was significantly lower in patients who underwent conservative surgery than in patients who did not (77.7% vs. 94.2%, p=0.047). 결론: In conclusion, conservative surgery might cause the poor prognosis in premenopausal women with stage I mEOCs, particularly with high preoperative CA-125 level. The further multicenter study with larger cohort would be needed to verify the oncologic safety of conservative surgery in mEOCs.