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Ballasting plan optimization for operation of a 2D floating dry dock
Kyungho Yoon,김효진,Seungkyun Yeo,Younghwa Hong,Jihye Cha,정현 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.74 No.4
A floating dry dock is an advanced structure that can provide a solution for dry dock space shortages. The critical point in floating dock operation is compensating the deflection caused by a heavy payload by adjusting the water level in the ballast system. An appropriate ballasting plan warrants safe and precise construction on a floating dock. Particularly, in the case of a 2D floating dock, ballasting plan evaluation is crucial due to complex deformation modes. In this paper, we developed a method to calculate the optimal ballasting plan for accurate and precise construction on a 2D floating dock. The finite element method was used for considering the flexibility of the floating dock as well as the construction blocks. Through a gradient-based optimization algorithm, the optimal ballasting plan for the given load condition was calculated in semi-real time (5 min). The present method was successfully used for the actual construction of an offshore structure on the 2D floating dock.
Yoon, Kyungho,Lee, Youngyu,Lee, Phill-Seung Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.4
In this paper, we propose a continuum mechanics based 3-D beam finite element with cross-sectional discretization allowing for warping displacements. The beam element is directly derived from the assemblage of 3-D solid elements, and this approach results in inherently advanced modeling capabilities of the beam element. In the beam formulation, warping is fully coupled with bending, shearing, and stretching. Consequently, the proposed beam elements can consider free and constrained warping conditions, eccentricities, curved geometries, varying sections, as well as arbitrary cross-sections (including thin/thick-walled, open/closed, and single/multi-cell cross-sections). We then study the modeling and predictive capabilities of the beam elements in twisting beam problems according to geometries, boundary conditions, and cross-sectional meshes. The results are compared with reference solutions obtained by analytical methods and solid and shell finite element models. Excellent modeling capabilities and solution accuracy of the proposed beam element are observed.
An efficient warping model for elastoplastic torsional analysis of composite beams
Yoon, Kyungho,Lee, Phill-Seung,Kim, Do-Nyun ELSEVIER (APPLIED SCIENCE) 2017 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.178 No.-
<P><B>Abstract</B></P> <P>In this paper, we present an efficient warping model for nonlinear elastoplastic torsional analysis of composite beams developed based on Benscoter warping theory. A major challenge here is how to account for the evolution of warping functions efficiently as materials yield at various locations at different rates. Here, we propose to describe the warping displacement using a linear combination of two asymptotic warping functions with corresponding warping degrees of freedom. The asymptotic warping functions are calculated only once initially by solving the extended St. Venant equations under two material conditions: purely elastic condition and fully plastic condition when no material point in the cross-section remains elastic. Only the warping degrees of freedom are updated incrementally and iteratively in analysis without evaluating the warping functions again. The proposed warping model demonstrates an excellent performance in several numerical examples despite its simplicity.</P>
Jang, Kyungho,Yoon, Seonghae,Kim, Sung-Eun,Cho, Joo-Youn,Yoon, Seo Hyun,Lim, Kyoung Soo,Yu, Kyung-Sang,Jang, In-Jin,Lee, Howard Dove Medical Press 2014 Drug design, development and therapy Vol.8 No.-
<P><B>Background</B></P><P>Megestrol acetate is an effective treatment for improving appetite and increasing body weight in patients with cancer-associated anorexia. However, Megace<SUP>®</SUP> oral suspension (OS), a micronized formulation of megestrol acetate, has low bioavailability in the fasting state. To overcome this limitation, a nanocrystal formulation has been developed. This study was performed to evaluate the pharmacokinetics and tolerability of the nanocrystal formulation and to compare them with those of Megace<SUP>®</SUP> OS in the fed and fasting states.</P><P><B>Methods</B></P><P>A randomized, open-label, two-treatment, two-period, two-sequence, crossover study was performed in three parts in 93 healthy subjects. A single 625 mg/5 mL oral dose of a nanocrystal formulation was administered in the fasting and fed states (part I). In parts II and III, a single 625 mg/5 mL oral dose of the nanocrystal formulation or Megace<SUP>®</SUP> OS 800 mg/20 mL was given in the fed and fasting states, respectively. Blood samples were collected for up to 120 hours post dose for pharmacokinetic analysis. Tolerability was evaluated throughout the entire study period.</P><P><B>Results</B></P><P>The nanocrystal formulation of megestrol acetate was rapidly absorbed in both the fed and fasting states. In the fed state, systemic exposure was comparable between the nanocrystal formulation of megestrol acetate and Megace<SUP>®</SUP> OS. In the fasting state, however, the peak plasma concentration and area under the plasma concentration-time curve to the last measurable concentration of megestrol acetate was 6.7-fold and 1.9-fold higher, respectively, for the nanocrystal formulation than for Megace<SUP>®</SUP> OS. No serious adverse events were reported.</P><P><B>Conclusion</B></P><P>Systemic exposure to megestrol acetate is less affected by lack of concomitant food intake when it is administered using the nanocrystal formulation. The nanocrystal formulation of megestrol acetate could be more effective in treating patients with cachexia or anorexia.</P>
Kyungho Park,Ahmed Shehta,Jeong-Moo Lee,Suk Kyun Hong,Kyung Chul Yoon,Jae-Hyung Cho,Nam-Joon Yi,Kwang-Woong Lee,Kyung-Suk Suh 한국간담췌외과학회 2019 Annals of hepato-biliary-pancreatic surgery Vol.23 No.4
Backgrounds/Aims: Pure laparoscopic living donor right hemihepatectomy (PLDRH) has been performed in many experienced centers. However, portal vein variations still remain challenging thus disturbing the widespread of PLDRH in many centers. PLDRH when integrated with 3-dimensional laparoscopy and indocyanine green (ICG) near-infrared fluorescence cholangiography is safe and feasible. Methods: We reviewed 19 donors with separated right anterior and right posterior portal veins who underwent living donor right hemihepatectomy between January 2014 and December 2016. We compared the clinical outcomes of PLDRH and conventional open right hemihepatectomy (CDRH). Results: 6 donors (31.6%) underwent PLDRH while 13 donors (68.4%) underwent CDRH. There was no intraoperative complications, transfusions and open conversions in the PLDRH donors. The total operative time was longer in PLDRH (356.5 vs. 244.5 minutes, p=0.003). However, the length of hospital stay (8.5 vs. 9.0 days, p=0.703), blood loss (450.0 vs. 393.6 ml, p=0.557) and complication rate (16.6% vs.27.3%; p=0.327) did not differ between the two groups. Conclusions: PLDRH is safe and feasible in donors with type II and III portal vein variations. Further prospective comparative studies are needed to prove the safety and efficacy of PLDRH.