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For direct time integrations: A comparison of the Newmark and <sub> ρ ∞ </sub> -Bathe schemes
Noh, Gunwoo,Bathe, Klaus-Jü,rgen Elsevier 2019 Computers & structures Vol.225 No.-
<P><B>Abstract</B></P> <P>We consider the unconditionally stable Newmark and <SUB> ρ ∞ </SUB> <B>-</B>Bathe methods for the direct time integration of the finite element equations in structural dynamics and wave propagations. In our evaluation of the Newmark method we consider the parameters δ and α , and in the <SUB> ρ ∞ </SUB> <B>-</B>Bathe method we consider the parameters γ and <SUB> ρ ∞ </SUB> <B>,</B> with 0 < γ < ∞ , γ ≠ 1 and <SUB> ρ ∞ </SUB> ∈ [ - 1 , + 1 ] . We show that the Newmark method as usually used with its δ and α parameters, α = 0.25 <SUP> ( δ + 0.5 ) 2 </SUP> and δ ⩾ 0.5 , is a special case of the <SUB> ρ ∞ </SUB> <B>-</B>Bathe method. We also show that the <SUB> β 1 </SUB> / <SUB> β 2 </SUB> -Bathe method is a special case of the <SUB> ρ ∞ </SUB> <B>-</B>Bathe scheme. The study of the curves of numerical dissipation and dispersion shows that the <SUB> ρ ∞ </SUB> -Bathe method provides effective dissipation and dispersion whereas the Newmark method lacks in that regard. To illustrate our theoretical findings we give the results of some example solutions of structural dynamics and wave propagations. Our study also shows that further research is needed to identify the optimal use of the <SUB> ρ ∞ </SUB> <B>-</B>Bathe scheme and other implicit methods in wave propagation analyses.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We consider the Newmark and <SUB> ρ ∞ </SUB> -Bathe time integrations for dynamic solutions. </LI> <LI> New insights into the Newmark and <SUB> ρ ∞ </SUB> -Bathe methods are presented. </LI> <LI> We show that the Newmark method with α = 0.25 <SUP> ( δ + 0.5 ) 2 </SUP> and δ ⩾ 0.5 is a special case of the <SUB> ρ ∞ </SUB> -Bathe method. </LI> <LI> Some example solutions of structural dynamics and wave propagations are presented to illustrate the theoretical findings. </LI> </UL> </P>
The MITC4+ shell element and its performance
Ko, Yeongbin,Lee, Phill-Seung,Bathe, Klaus-Jü,rgen Elsevier 2016 Computers & structures Vol.169 No.-
<P><B>Abstract</B></P> <P>The objective in this paper is to improve the performance of the 4-node MITC quadrilateral shell finite element, referred to as the MITC4 element (Dvorkin and Bathe, 1984). We propose a new MITC4 shell element, the MITC4+ element, in which the mid-surface membrane strain components are assumed using the concept of the MITC method. The tying membrane strains are obtained from four triangular domains which subdivide the mid-surface of the 4-node quadrilateral shell element. This approach alleviates locking that can happen when the MITC4 shell elements are geometrically distorted in curved geometries. Several basic tests including the isotropy, zero energy mode, and patch tests are performed. Through the solution of various shell problems, the convergence behavior of the MITC4+ shell element is studied to show the improvements reached.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An effective new 4-node shell element is derived from the MITC4 shell element. </LI> <LI> A new assumed membrane strain field is developed to alleviate membrane locking. </LI> <LI> The numerical results show the improved predictive capability. </LI> </UL> </P>
The MITC3+ shell element enriched in membrane displacements by interpolation covers
Jun, Hyungmin,Yoon, Kyungho,Lee, Phill-Seung,Bathe, Klaus-Jü,rgen Elsevier 2018 Computer methods in applied mechanics and engineer Vol.337 No.-
<P><B>Abstract</B></P> <P>In this paper, we significantly improve the membrane behavior of the previously published 3-node triangular MITC3+ shell element through the use of interpolation covers. We give the formulation of the improved MITC3+ element for linear and nonlinear large displacement analyses. The 3-node shell element passes the basic tests, namely the isotropy, patch, and zero energy mode tests, and we illustrate the excellent performance of the element in various standard test problems.</P>
Performance of the MITC3+ and MITC4+ shell elements in widely-used benchmark problems
Ko, Y.,Lee, Y.,Lee, P.S.,Bathe, K.J. Pergamon Press ; Elsevier Science Ltd 2017 Computers & structures Vol.193 No.-
Recently, new 3-node and 4-node MITC shell elements, the MITC3+ and MITC4+ elements, have been proposed. The two shell elements were tested through theoretically well-established convergence studies. In this paper we continue to investigate the performance of the MITC3+ and MITC4+ shell elements in relatively simple but widely adopted benchmark problems. To perform these tests as usually done, the predictive capability of the elements is assessed through point-wise convergence of displacements at specific locations of shell structures. The results obtained using the MITC3+ and MITC4+ shell elements are compared with those found for some other shell elements.
Ko, Y.,Lee, P.S.,Bathe, K.J. Pergamon Press ; Elsevier Science Ltd 2017 Computers & structures Vol.192 No.-
We present in this paper a new reliable and efficient 4-node quadrilateral element, which we call the 2D-MITC4 element, for two-dimensional plane stress and plane strain solutions of solids using the MITC method. We also present an extension of the element assuming a constant element pressure, which we call the 2D-MITC4/1 element. The elements show a much better predictive capability than the displacement-based element and perform in linear analyses almost as well as the 4-node element with incompatible modes, an enhanced assumed strain (EAS) element. However, unlike when using EAS elements, we do not observe spurious instabilities in geometrically nonlinear solutions. Embedding the new MITC formulation into the previously presented MITC4+ shell element, we improve the membrane behavior of the shell element. The new 2D solid elements and the improved MITC4+ shell element pass all basic tests (the isotropy, zero energy mode and patch tests). We present the finite element solutions of various benchmark problems to illustrate the solution accuracy of the new elements.
A framework of finite element procedures for the analysis of proteins
Sedeh, Reza Sharifi,Yun, Giseok,Lee, Jae Young,Bathe, Klaus-Jü,rgen,Kim, Do-Nyun Elsevier 2018 Computers & structures Vol.196 No.-
<P><B>Abstract</B></P> <P>Large-scale, functional collective motions of proteins and their supra-molecular assemblies occur in a physiological solvent environment at finite temperatures. The solution of these motions with standard molecular dynamics algorithms is computationally hardly possible when considering macromolecules. Much research has focused on alternative approaches that use coarse-graining to model proteins, but mostly in vacuum. In this paper, we incorporate realistically the physical effects of solvent damping into the finite element model of proteins. The proposed framework is based on Brownian dynamics and shown to be effective. An important advantage of the approach is that the computational cost is not dependent on the molecular size, which makes the long-time simulation of macromolecules possible. Using the proposed procedure, we demonstrate the analysis of a macromolecule in solvent—an analysis that has not been achieved before and could not be performed with a molecular dynamics algorithm.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A finite element framework for the analysis of proteins in solvent is newly developed. </LI> <LI> The effect of solvent damping is considered. </LI> <LI> The computational cost of this method is not dependent on the molecular size. </LI> <LI> Through numerical examples, the effectiveness of the method is demonstrated. </LI> </UL> </P>
Hui-Juan Huang-Tiel,Isabella Otto,Klaus Golka,Silvia Selinski,Stephan Koswig,Kathrin Bathe,Steffen Hallmann,Thorsten H. Ecke 대한비뇨의학회 2020 Investigative and Clinical Urology Vol.61 No.3
Purpose: High-dose-rate brachytherapy (HDR-BT) with external beam radiation therapy (EBRT) is a common treatment option for locally advanced prostate cancer. Quality of life is an important factor when discussing therapy options for high-risk prostate cancer. This study evaluated adverse effects and health-related quality of life (HRQOL). Materials and Methods: Ninety male patients (median age, 71 years; range, 50 to 79 years) with high-risk prostate cancer underwent HDR-BT after EBRT between December 2009 and January 2017 with a median follow-up of 43 months. A total of 57 patients (69.5%) answered the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life of Cancer Patients questionnaire (QLQ-C30; ver. 3.0), and 8 patients died during follow-up. In order to put the results of this study in context, we compared the results with reference data from the EORTC QLQ-C30 Scoring Manual. Correlations of prostate-specific antigen (PSA) values, International Prostate Symptom Score, and HRQOL measures were calculated. Results: The study participants reported better physical functioning and better global health compared with the reference data, but worse social, role, and cognitive functioning. We found negative statistically significant correlations between the last-measured PSA value and social functioning (p>0.01), cognitive functioning, pain, and constipation (all p<0.05). Toxicity rates were 10.0% for gastrointestinal and 12.2% for genitourinary adverse effects. All reported complications for toxicity were Grade I. Conclusions: The described therapy results in high biochemical control rates with minimal adverse effects. Compared with reference groups, the HRQOL of this study cohort was acceptable. PSA values during follow-up seem to be a possible indicator to influence HRQOL.
Aidala, C.,Akiba, Y.,Alfred, M.,Andrieux, V.,Aoki, K.,Apadula, N.,Asano, H.,Ayuso, C.,Azmoun, B.,Babintsev, V.,Bagoly, A.,Bandara, N. S.,Barish, K. N.,Bathe, S.,Bazilevsky, A.,Beaumier, M.,Belmont, R. American Physical Society 2018 Physical review letters Vol.120 No.2
<P>During 2015, the Relativistic Heavy Ion Collider (RHIC) provided collisions of transversely polarized protons with Au and Al nuclei for the first time, enabling the exploration of transverse-single-spin asymmetries with heavy nuclei. Large single-spin asymmetries in very forward neutron production have been previously observed in transversely polarized p+p collisions at RHIC, and the existing theoretical framework that was successful in describing the single-spin asymmetry in p+p collisions predicts only a moderate atomic-mass-number (A) dependence. In contrast, the asymmetries observed at RHIC in p+A collisions showed a surprisingly strong A dependence in inclusive forward neutron production. The observed asymmetry in p+Al collisions is much smaller, while the asymmetry in p+Au collisions is a factor of 3 larger in absolute value and of opposite sign. The interplay of different neutron production mechanisms is discussed as a possible explanation of the observed A dependence.</P>