An efficient fluctuating charge model for transition metal complexes

A fluctuating charge model for transition metal complexes, based on the Hirshfeld partitioning scheme, spectroscopic energy data from the NIST Atomic Spectroscopy Database and the electronegativity equalization approach, has been developed and parameterized for organic ligands and their high‐ and low‐spin Fe^II and Fe^III, low‐spin Co^III and Cu^II complexes, using atom types defined in the Momec force field. Based on large training sets comprising a variety of transition metal complexes, a general parameter set has been developed and independently validated which allows the efficient computation of geometry‐dependent charge distributions in the field of transition metal coordination compounds. © 2013 Wiley Periodicals, Inc.     

Guidelines for dynamics‐based parameterization of one‐dimensional cellular automata rule spaces

As paradigmatic complex systems, various studies have been done in the context of one‐dimensional cellular automata (CA) on the definition of parameters directly obtained from their transition rule, aiming at the help they might provide to forecasting CA dynamic behavior. Out of the analysis of the most important parameters available for this end, as well as others evaluated by us, a set of guidelines is proposed that should be followed when defining a parameter of that kind. Based upon the guidelines, a critique of those parameters is made, which leads to a set of five that jointly provide a good forecasting set; two of them were drawn from the literature and three are new ones defined according to the guidelines. By using them as a heuristic in the evolutionary search for CA of a predefined computational behavior, good results have been obtained, exemplified herein by the evolutionary search for CA that perform the Synchronization Task. © 2001 John Wiley & Sons, Inc.     

High‐fidelity aerodynamic shape optimization of modern transport wing using efficient hierarchical parameterization

Aerodynamic shape optimization technology is presented, using an efficient domain element parameterization approach. This provides a method that allows geometries to be parameterized at various levels, ranging from gross three‐dimensional planform alterations to detailed local surface changes. Design parameters control the domain element point locations and, through efficient global interpolation functions, deform both the surface geometry and corresponding computational fluid dynamics volume mesh, in a fast, high quality, and robust fashion. This results in total independence from the mesh type (structured or unstructured), and optimization independence from the flow‐solver is achieved by obtaining gradient information for an advanced gradient‐based optimizer by finite‐differences. Hence, the optimization tool can be used in conjunction with any flow‐solver and/or mesh generator. Results have been presented recently for two‐dimensional aerofoil cases, and shown impressive results; drag reductions of up to 45% were demonstrated using only 22 active design parameters. This paper presents the extension of these methods to three dimensions, with results for highly constrained optimization of a modern aircraft wing in transonic cruise. The optimization uses combined global and local parameters, giving 388 design variables, and produces a shock‐free geometry with an 18% reduction in drag, with the added advantage of significantly reduced root moments. Copyright © 2009 John Wiley & Sons, Ltd.     

Paramfit: Automated optimization of force field parameters for molecular dynamics simulations

The generation of bond, angle, and torsion parameters for classical molecular dynamics force fields typically requires fitting parameters such that classical properties such as energies and gradients match precalculated quantum data for structures that scan the value of interest. We present a program, Paramfit, distributed as part of the AmberTools software package that automates and extends this fitting process, allowing for simplified parameter generation for applications ranging from single molecules to entire force fields. Paramfit implements a novel combination of a genetic and simplex algorithm to find the optimal set of parameters that replicate either quantum energy or force data. The program allows for the derivation of multiple parameters simultaneously using significantly fewer quantum calculations than previous methods, and can also fit parameters across multiple molecules with applications to force field development. Paramfit has been applied successfully to systems with a sparse number of structures, and has already proven crucial in the development of the Assisted Model Building with Energy Refinement Lipid14 force field. © 2014 Wiley Periodicals, Inc.     

Parameterizations of Masks for Tight Affine Frames with Two Symmetric/Antisymmetric Generators

Parameterizations of FIR orthogonal systems are of fundamental importance to the design of filters with desired properties. By constructing paraunitary matrices, one can construct tight affine frames. In this paper we discuss parameterizations of paraunitary matrices which generate tight affine frames with two symmetric/antisymmetric generators (framelets). Based on the parameterizations, several symmetric/antisymmetric framelets are constructed.     

C~2 CONTINUOUS NEARLY ARC-LENGTH PARAMETERIZED CURVE

An efficient method for C~2 nearly arc-length parameterized curve is presented. An idea of approximation for the arc-length function of parametric curve which interpolates CAD data points is discussed. The parameterization is implemented by using parameter transformation. Finally, two numerical examples are given..     

Analysis of Curve Reconstruction by Meshless Parameterization

This paper proposes and analyzes a method called meshless parameterization for reconstructing curves from unordered point samples. The method solves a linear system of equations based on convex combinations so as to map the sampled points into corresponding parameter values, whose natural ordering provides the ordering of the points. Using the theory of M-matrices, we derive natural conditions on the point sample which guarantee the correct ordering. A sufficient condition is that the underlying curve be tangent-continuous and free of self-intersections and that the sample is dense enough.