1,721,196 research outputs found
MLS-based variable-node elements compatible with quadratic interpolation. Part I: Formulation and application for non-matching meshes
No full textTwo-dimensional variable-node elements compatible with quadratic interpolation are developed using the moving least-square (MLS) approximation. The mapping from the parental domain to the physical element domain is implicitly obtained from MLS approximation, with the shape functions and their derivatives calculated and saved only at the numerical integration points. It is shown that the present MLS-based variable-node elements meet the patch test if a sufficiently large number of integration points are employed for numerical integration. The cantilever problem with non-matching meshes is chosen to check the feasibility of the present MLS-based variable-node elements, and the result is compared with that from the lower-order case compatible with linear interpolation. Copyright (c) 2005 John Wiley & Sons, Ltd.Korea Science and Engineering Foundation;contract/grant number:R01-2002-000-00230-
MLS-based variable-node elements compatible with quadratic interpolation. Part II: Application for finite crack element
No full textTwo-dimensional finite 'crack' elements for Simulation of propagating cracks are developed using the moving least-square (MLS) approximation. The mapping from the parental domain to the physical element domain is implicitly obtained from MLS approximation, with the shape functions and their derivatives calculated and saved only at the numerical integration points. The MLS-based variable-node elements are extended to Construct the crack elements, which allow the discontinuity of crack faces and the crack-tip singularity. The accuracy of the crack elements is checked by calculating the stress intensity factor under mode I loading. The crack elements turn out to be very efficient and accurate for simulating crack propagations, only with the minimal amount of element adjustment and node addition as the crack tip moves. Numerical results and comparison to the results from other works demonstrate the effectiveness and accuracy of the present scheme for the crack elements. Copyright (c) 2005 John Wiley & Sons, Ltd.Korea Science and Engineeirng Foundation; contract /grant number :R01-2002-000-00230-
Modelling of Cu thin film growth by MOCVD process in a vertical reactor
No full textTransport phenomena in a vertical reactor for metalorganic chemical vapor deposition (MOCVD) of copper thin films have been analyzed by numerical simulation of the process. The equations of the mathematical model were solved numerically using the Galerkin finite element method, Newton-Raphson iterations and the frontal algorithm for the gas flow structure, temperature distribution and concentration distribution of the reacting species. Deposition rates of copper thin films using Cu(hfac)VTMS as a precursor were estimated from numerical solutions. Standard process conditions were selected as: a reactor pressure of 1 Torr, a substrate temperature and inlet gas temperature of 200 degrees C and 70 degrees C, respectively, and an inlet gas flow rate of 50 sccm. Under standard conditions, the deposition rates of copper were in the range of 160-230 Angstrom/min. The effects of the process conditions, reactor geometry and shower head structure on the deposition rate and thickness uniformity were examined. It has been demonstrated that numerical simulation can be used for improving the film thickness uniformity and the utilization of source gas
A quasicontinuum method for deformations of carbon nanotubes
No full textWe present a coarse-graining computation for deformations of CNTs (carbon nanotubes) via QC (quasicontinuum), particularly targeting analysis of multi-waited carbon nanotubes. Higher order triangular elements are utilized for proper interpolation of atom positions of the CNT on the basis of QC approach. The computing scheme enables one to differentiate between the fully atomistic zone and the coarse-grained zone in the framework of the multiscale computing. Several numerical examples demonstrate the effectiveness and accuracy of the present methodology.This work was supported by the Ministry of Science and Technology of Korea through the National R&D Project for Nano Science and Technology (Grant no. M1-0213-04-0003). The authors would like to acknowledge the support from KISTI (Korea Institute of Science and Technology Information) under "the 6th Strategic Supercomputing Applications Support Program". The use of the computing system of the Supercomputing Center is also greatly appreciated
Mitochondrial distribution and activity in human mature oocytes: GnRH agonist vs antagonist for pituitary downregulation
No full textObjective: To analyze the effects of GnRH agonists versus antagonists on mitochondrial distribution and activity
in human mature oocytes.
Design: Randomized research experimental study.
Setting: Academic basic research laboratory and hospital-based fertility center.
Patient(s): Two hundred twenty-five supernumerary mature oocytes from 44 patients.
Intervention(s): Fluorescent staining and confocal laser scanning microscopy on oocytes after the use of either
GnRH agonist (group A) or GnRH antagonist (group B).
Main Outcome Measure(s): Oocyte mitochondrial distribution pattern and activity using MitoTracker Orange
CMTM Ros.
Result(s): More oocytes showing polarized mitochondrial distribution pattern were found in group A than in
group B (35% vs. 14%). In group B, hCG rather than GnRH agonist, for ovulation induction, resulted in more
oocytes showing heterogeneous (57% vs. 14%), in particular polarized (24% vs. 0) mitochondrial distribution.
In groups A and B, fluorescence intensity did not vary according to mitochondrial distribution pattern. However,
fluorescence intensity was higher in oocytes with polarized and large granules configurations in group B compared
to group A.
Conclusion(s): The GnRH agonist and antagonist may have different effects on oocyte mitochondrial distribution
pattern and activity. The GnRH antagonist may induce mitochondrial hyperactivity, which may be detrimental to
the oocyte. (Fertil Steril 2009;91:249–55. 2009 by American Society for Reproductive Medicine.
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