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Least-square Fit (least-square + fit)
Selected AbstractsInterface reconstruction with least-square fit and split Eulerian,Lagrangian advectionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2003Ruben Scardovelli Abstract Two new volume-of-fluid (VOF) reconstruction algorithms, which are based on a least-square fit technique, are presented. Their performance is tested for several standard shapes and is compared to a few other VOF/PLIC reconstruction techniques, showing in general a better convergence rate. The geometric nature of Lagrangian and Eulerian split advection algorithms is investigated in detail and a new mixed split Eulerian implicit,Lagrangian explicit (EI,LE) scheme is presented. This method conserves the mass to machine error, performs better than split Eulerian and Lagrangian algorithms, and it is only slightly worse than unsplit schemes. However, the combination of the interface reconstruction with the least-square fit and its advection with the EI,LE scheme appears superior to other existing approaches. Copyright © 2003 John Wiley & Sons, Ltd. [source] Time-resolved investigation of the ,1 ro-vibrational Raman band of H2CO with fs-CARSJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2007A. M. Walser Abstract The technique of femtosecond time-resolved coherent anti-Stokes scattering (fs-CARS) is used to investigate the strongly perturbed ,1 ro-vibrational Raman band of formaldehyde (H2CO). The time-dependent signal is simulated using a ,Watson-'Hamiltonian in A-type reduction and Raman theory for asymmetric rotors. The results are compared with the experimental data. The fs-CARS method measures the evolution of the polarization in a molecular ensemble via superposition of many states and is sensitive to spectral irregularities or line shifts of the involved transitions. ,Coriolis' interactions play a major role in the analysis of the ,1 band of formaldehyde. We successfully simulate the fs-CARS transient signal from the ,1 band of formaldehyde including a model for multiple ,Coriolis' interactions, without the necessity of describing the complete interaction between all the vibrational levels. ,Coriolis' coupling coefficients and energy shifts are derived from the experiment by a least-square fit. The results are discussed and compared to literature values. Copyright © 2006 John Wiley & Sons, Ltd. [source] Conformational analysis of thiopeptides: derivation of sp2 sulfur parameters for the CFF91 force fieldJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2001Tran Trung Tran Abstract When a sulfur atom is used to substitute for the oxygen in peptide bonds, its bulkiness should restrict the conformational space available to an amino acid. This conformational restriction as well as the ability to confer resistance to enzymatic degradation in the body means that thio-substituted amino acids are potentially useful building blocks for drug design. To simulate the effects of thio substitution, force field parameters for sp2 sulfur are required. In this article, parameters for the thioamide group have been derived for the molecular mechanics CFF91 force field (available at http://www.ludwig.edu.au/archive/tran). The bond increment charges were obtained by fitting to ab initio charges and dipoles. The van der Waals parameters were obtained by fitting to high-resolution crystallographic data, and the nonbonded parameters were verified by comparing with experimentally derived lattice energy. The bonded parameters were derived by least-square fits to the ab initio calculated energy surfaces, i.e., conformational energy as well as their first and second derivatives of seven model thioamide molecules. When the sp2 sulfur parameters were tested on a set of seven X-ray crystallographic structures from the Cambridge Structural Database, they satisfactorily reproduced the bond lengths, bond angles, torsional angles, and nonbonded distances of all the crystal structures. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1010,1025, 2001 [source] | ||||||||||