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991.
The ABS class for linear and nonlinear systems has been recently introduced by Abaffy, Broyden, Galantai and Spedicato. Here we consider various ways of applying these algorithms to the determination of the minimal euclidean norm solution of over-determined linear systems in the least squares sense. Extensive numerical experiments show that the proposed algorithms are efficient and that one of them usually gives better accuracy than standard implementations of the QR orthogonalization algorithm with Householder reflections. 相似文献
992.
K. P. Hadeler Dragan Jukić Kristian Sabo 《Mathematical Methods in the Applied Sciences》2007,30(11):1231-1241
The Michaelis–Menten kinetics is fundamental in chemical and physiological reaction theory. The problem of parameter identification, which is not well posed for arbitrary data, is shown to be closely related to the Chebyshev sum inequality. This inequality yields sufficient conditions for existence of feasible solutions both for nonlinear and for linear least‐squares problems. The conditions are natural and practical as they are satisfied if the data show the expected monotone and concave behaviour. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
993.
Using Hadamard matrices and mutually orthogonal Latin squares, we construct two new quasi-symmetric designs, with parameters 2 − (66,30,29) and 2 − (78,36,30). These are the first examples of quasi-symmetric designs with these parameters. The parameters belong to the families 2 − (2u
2 − u,u
2 − u,u
2 − u − 1) and 2 − (2u
2 + u,u
2,u
2 − u), which are related to Hadamard parameters. The designs correspond to new codes meeting the Grey–Rankin bound. 相似文献
994.
We provide an asymptotically tight, computationally efficient approximation of the joint spectral radius of a set of matrices using sum of squares (SOS) programming. The approach is based on a search for an SOS polynomial that proves simultaneous contractibility of a finite set of matrices. We provide a bound on the quality of the approximation that unifies several earlier results and is independent of the number of matrices. Additionally, we present a comparison between our approximation scheme and earlier techniques, including the use of common quadratic Lyapunov functions and a method based on matrix liftings. Theoretical results and numerical investigations show that our approach yields tighter approximations. 相似文献
995.
We propose a series of quasicontinuum approximations for the simplest lattice model of a fully dynamic martensitic phase transition in one dimension. The approximations are dispersive and include various non-classical corrections to both kinetic and potential energies. We show that the well-posed quasicontinuum theory can be constructed in such a way that the associated closed-form kinetic relation is in an excellent agreement with the predictions of the discrete theory. 相似文献
996.
In this paper, we describe two efficient methods to estimate parameters in nonlinear least squares problems: continuation
and sentinels methods. When the studied system is modeled by differential equations, we have to identify both unknown parameters
and initial conditions. For that, we propose to process in two steps: first identify the unknown parameters, then identify
again using the found results, considering now both the parameters and the initial conditions as unknown.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
997.
The renormalization of the relativistic self-consistent Hartree-Fock approximation is restudied. It is shown that the renormalization
procedure suggested by Bielajew and Serot can be greatly simplified and the renormalization achieved in a way no more complicated
than that of the relativistic self-consistent Fock approximation, if the parameters in the counterterms are allowed to be
density-dependent and the renormalization of the tadpole self-energy is treated appropriately. A transformation relation between
the four- and three-dimensional representation of the baryon self-energy is presented and a self-consistent Hartree-Fock scheme
different from that considered by Bielajew and Serot studied. The renormalized integral equations for the baryon self-energy
which includes effects from the Dirac sea are reformulated in a three-dimensional form. Explicit expressions are derived.
Received: 29 August 1997 / Revised version: 30 April 1998 相似文献
998.
A technique is presented for velocity calculations on the highly distorted node distributions typical of those found in Lagrangian vortex methods. The method solves the partial differential equation for streamfunction directly on the nodes, via a sparse, symmetric system of equations that can be solved using standard iterative solvers. When implemented in a triangulated vortex method, the technique gives computation times which scale as N1.23, where N is the number of nodes. The computation scheme is derived for two‐dimensional problems and applied to the prediction of the evolution of perturbed multipolar vortices. Due to the numerical performance of the method, it has been possible to examine such evolution at higher and lower Reynolds numbers than have been considered in published numerical studies. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
999.
Robust weighting in least-squares fits 总被引:1,自引:0,他引:1
James K.G. Watson 《Journal of Molecular Spectroscopy》2003,219(2):326-328
Spectroscopic data sets often contain a significant number of outliers due to effects such as misassignments, trial assignments, or local perturbations. Standard fitting routines can be made robust to such outliers by the method of iteratively reweighted least squares. It is proposed here that the weight of datum i in a give iteration is given by wi=1/(σi2+αri2), where σi is the standard deviation for the idealized distribution without outliers, and ri is the residual from the previous iteration. The value of α should depend on the fractional number of outliers and the size of their residuals, but a standard value of α=1/3 is suggested for spectroscopic applications. 相似文献
1000.
We compare the overall mean response time (a.k.a. sojourn time) of the processor sharing (PS) and feedback (FB) queues under an M/GI/1 system. We show that FB outperforms PS under service distributions having decreasing failure rates; whereas PS outperforms FB under service distributions having increasing failure rates. 相似文献