Showing papers on "Parametrization published in 1986"
TL;DR: In this article, a variational formulation and computational aspects of a three-dimensional finite-strain rod model, considered in Part I, are presented, which bypasses the singularity typically associated with the use of Euler angles.
Abstract: The variational formulation and computational aspects of a three-dimensional finite-strain rod model, considered in Part I, are presented. A particular parametrization is employed that bypasses the singularity typically associated with the use of Euler angles. As in the classical Kirchhoff-Love model, rotations have the standard interpretation of orthogonal, generally noncommutative, transformations. This is in contrast with alternative formulations proposed by Argyris et al. [5–8], based on the notion of semitangential rotation. Emphasis is placed on a geometric approach, which proves essential in the formulation of algorithms. In particular, the configuration update procedure becomes the algorithmic counterpart of the exponential map. The computational implementation relies on the formula for the exponential of a skew-symmetric matrix. Consistent linearization procedures are employed to obtain linearized weak forms of the balance equations. The geometric stiffness then becomes generally nonsymmetric as a result of the non-Euclidean character of the configuration space. However, complete symmetry is recovered at an equilibrium configuration, provided that the loading is conservative. An explicit condition for this to be the case is obtained. Numerical simulations including postbuckling behavior and nonconservative loading are also presented. Details pertaining to the implementation of the present formulation are also discussed.
986 citations
TL;DR: This investigation investigates systematically the possibilities and the limits of the Skyrme force for reproducing nuclear ground-state properties in a spherical Hartree-Fock calculation by means of least-squares fits of the force parameters to the measured binding energy, diffraction radius, and surface width of eight selected nuclei.
Abstract: We investigate systematically the possibilities and the limits of the Skyrme force for reproducing nuclear ground-state properties in a spherical Hartree-Fock calculation. This investigation is performed by means of least-squares fits of the force parameters to the measured binding energy, diffraction radius, and surface width of eight selected nuclei. Particular emphasis is put on the density dependence of the interaction, which turns out to be determined mainly by the surface width. The least-squares fitting procedure yields the best-fit parameters together with uncertainties on them, and it also allows one to estimate the uncertainties of an extrapolation to other fields, e.g., nuclear matter properties. We also study the contribution of random-phase-approximation correlations to the ground-state properties and their influence on the parameters of the effective interaction. Here, we also compare to giant dipole resonance energies.
199 citations
TL;DR: The central problem is to define a triple of coordinates axes at each point of the trajectory in order to specify the position and orientation of the swept object along the trajectory.
195 citations
TL;DR: In this article, a statistical analysis of a large database of simulated experiments is used to obtain a functional representation for intrinsic physical parameters of a system in terms of the values of the measurements.
Abstract: The method of function parametrization, developed by H. Wind for fast data evaluation in high energy physics, is demonstrated in the context of controlled fusion research. This method relies on a statistical analysis of a large database of simulated experiments in order to obtain a functional representation for intrinsic physical parameters of a system in terms of the values of the measurements. Rapid determination of characteristic equilibrium parameters of a tokamak discharge is shown to be a particularly indicated application. The method is employed on the ASDEX experiment to determine the following parameters of the plasma: position of the magnetic axis, geometric centre, and current centre; minor radius, elongation, and area of the plasma column; a normalized safety factor at the plasma boundary; the Shafranov parameter ?p + ?i/2; the flux difference between the plasma boundary and an external reference value; the position of the lower and upper saddle points, and the intersections of the separatrix with the four divertor plates. The relevant measurements consist of three differential poloidal flux measurements, four poloidal field measurements, the current through the multipole shaping coils, and the total plasma current. Function parametrization supplies a very accurate interpretation of these data, which is now used for on-line data analysis, and which is also sufficiently fast to be suitable for real time control of the plasma.
65 citations
TL;DR: In this article, a linear parametrization of the conditional intensity provides systematic classes of flexible models which are reasonably useful for calculating maximum likelihoods, and seismic activity around Canberra is decomposed into components of evolutionary trend, clustering and periodicity.
Abstract: It is demonstrated that linear parametrization of the conditional intensity provides systematic classes of flexible models which are reasonably useful for calculating maximum likelihoods. To exemplify the modelling, seismic activity around Canberra is decomposed into components of evolutionary trend, clustering and periodicity. The causal relationship between earthquake sequences from two seismic regions is also analysed for a certain Japanese earthquake data set. Some technical aspects of the modelling and calculations are descrnbed.
40 citations
01 Mar 1986-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, a simple approximate formula for the calculation of multiple concentric magnetic shields is derived, which is accurate on the one percent level for all relevant cases, and which replaces the cumbersome recursion procedures used so far.
Abstract: A simple approximate formula is derived for the calculation of multiple concentric magnetic shields, which is accurate on the one percent level for all relevant cases, and which replaces the cumbersome recursion procedures used so far. The new formula allows the parametrization of the problem such that the optimum shield configuration is readily obtained for all applications.
29 citations
TL;DR: In this paper, a non-scaling formula is proposed to describe the multiplicity distribution of particles produced in hadronic collision at high energy, which is the consequence of a dynamical branching model.
23 citations
TL;DR: In this paper, it was shown how all zeros of weight −1 6j coefficients arise as particular cases of a four-parameter family of such zeros, and the parametrization was given explicitly.
Abstract: It is shown how all zeros of weight‐1 6j coefficients arise as particular cases of a four‐parameter family of such zeros. The parametrization is given explicitly.
20 citations
18 citations
TL;DR: In this article, analytical functions which approximate six commonly used standard temperature profiles (the AFGL set, and the 1976 U.S. Standard) are described. These provide a uniform way of rounding off the sharp corners of the original models, and have been used in a recent radiation model intercomparison study.
Abstract: Analytic functions which approximate six commonly used standard temperature profiles (the AFGL set, and the 1976 U.S. Standard) are described. These provide a uniform way of rounding off the sharp corners of the original models, and have been used in a recent radiation model intercomparison study.
18 citations
TL;DR: It is shown that the two distinct approaches to design an adaptive controller for pole placement result in identical error terms.
Abstract: A new parametrization for a linear system is presented. This parametrization is the basis for two approaches to design an adaptive controller for pole placement. One approach is based on parameter estimation and requires sufficient excitation, while the other, the model reference adaptive pole placement, uses a reference model and an augmented error. It is shown that the two distinct approaches result in identical error terms.
TL;DR: In this paper, the authors used the second quantization technique as well as the canonical transformation method to obtain the expression for the electric-dipole (4f-4f)-transition probabilities in a form, which is convenient for the interpretation of the experimental data.
Abstract: The consideration of transfer processes of an electron from ligand to the trivalent lanthanide ion allows to obtain theeffective dipole-moment operator containing the terms having complicated tensor structure. Using the second quantization technique as well as the canonical-transformation method permit to write the expression for the electric-dipole (4f-4f)-transition probabilities in a form, which is convenient for the interpretation of the experimental data. The expression for the transition probabilities contains traditional Ω2, Ω4, and Ω6 parameters as well as four additional D2, D4, L2, and L4 ones being due to the complicated tensorial structure of the electric-dipole moment operator. The microscopic analysis carried out for the Er3+ ion in LaF3, single crystal shows that one can neglect the terms with L2, and L4 parameters. Using the new parametrization scheme containing five parameters (Ω2, Ω4, Ω6, D2, and D4,) the intensity spectroscopic properties of Pr3+ ions in Bi4Ge3O12, single crystal are non-contradictorily described, where the hypersensitive inter-manifold 3II4 3F2 transition is taken into account. On the basis of this parametrization scheme the best description of the experimental data as a whole as well as of the hypersensitive inter-manifold 4I15/12 2H11/2, 4G11/2 transitions of Er3+ ions in Y3Al5O12, Lu3AI5O12, and BaYb2F8 single crystals are also obtained.
[Russian Text Ignored].
TL;DR: In this paper, a model for describing nuclear matter consisting of different multiquark clusters is constructed and a detailed analysis of statistical properties for this mixture is presented over the whole density-temperature plane.
TL;DR: In this paper, a semiclassical study of bubble formation (nucleation) in nuclei at finite temperature is presented, and the effects of the Coulomb interaction and of the density profile parametrization are investigated.
TL;DR: In this paper, a parametrization of the solution of the TFDW variational equations for the density of atoms and diatomic systems is presented, which is a sufficiently simple yet accurate parametrisation.
Abstract: We present a sufficiently simple yet accurate parametrisation of the solution of the TFDW variational equations for the density of atoms and diatomic systems.
TL;DR: In this article, the problem of calculating surface zonal flow using Green's large-scale eddy flux parametrizations in spherical geometry is re-examined and it is shown that the latter performs quite well if QG1 approximations are applied to the Coriolis parameter.
Abstract: The problem of calculating the surface zonal flow using Green's large-scale eddy flux parametrizations in spherical geometry is re-examined. In a 2-level, quasi-geostrophic (QG1) model, low-latitude easterlies and mid-latitude westerlies of reasonable intensity can be obtained by assuming a more realistic baroclinicity than that applied in a study reported by White in 1977. This result also depends on the use of a more realistic value for the latitude average of a certain transfer coefficient; but no detailed treatment of its spatial variation is found to be necessary. Some further solutions are obtained using a strictly inconsistent formulation in which the Coriolis parameter is allowed its true latitude variation in all terms (in contrast to the QG1 model). In line with the conclusions of White's earlier study it seems in this case that detailed specification of the relevant transfer coefficient's spatial variation would be needed in order to produce a realistic surface zonal flow. Regarding the surface flow problem as a test of Green's parametrization scheme, we conclude that the latter performs quite well if QG1 approximations are applied to the Coriolis parameter. However, further refinement of the scheme is evidently required for good performance when these approximations are not applied.
TL;DR: It is shown that there exists a simple parametrization of the MCSCF orbital manifold that is convenient for computer implementation of quasi-Newton optimization schemes.
Abstract: The modern version of the process of removing redundant variables in an MCSCF optimization problem is studied on the basis of the manifold theory. It is shown that there exists a simple parametrization of the MCSCF orbital manifold that is convenient for computer implementation of quasi-Newton optimization schemes. A sequential unconstrained optimization technique for minimizing electronic energy with respect to local coordinates is described.
TL;DR: Application d'un resultat de Holder aux groupes d'iterations. Representation parametrique. Equations fonctionnellsassociees as mentioned in this paper. And,
Abstract: Application d'un resultat de Holder aux groupes d'iterations. Representation parametrique. Equations fonctionnellsassociees
01 Dec 1986
TL;DR: In this article, the properties of a parametrization corresponding to monic ARMA systems with prescribed column degrees are considered, and some properties of such a parameter are discussed.
Abstract: In the paper some properties of a parametrization corresponding to monic ARMA systems with prescribed column degrees are considered
TL;DR: The emphasis of this work is on preserving some behavior of the steady states by incorporating in the parameterized models information concerning the topological structure of the original solutions by formulating the parameterization in terms of the stead...
Abstract: An objective parameterization technique is developed for general nonlinear hydrodynamical systems. The typical structure of hydrodynamical systems, regardless of their complexity, is one in which the rates of change of the dependent variables depend on homogeneous quadratic and linear forms, as well as on inhomogeneous forcing terms. As a prototype of the generic problem containing this typical structure, the parameterization technique is applied to various three component subsets of a five component nonlinear spectral model of forced, dissipative quasi-geostrophic flow in a channel. The results obtained lead to specification of the necessary data coverage requirements for applying the technique in general.
01 Jan 1986
TL;DR: In this paper, the general expression of the nucleon-nucleus optical potential has been obtained using Watson's multiple scattering theory and Wolfenstein's parametrization of the N = Z scattering amplitude.
Abstract: The general expression of the nucleon-nucleus optical potential has been obtained using Watson's multiple scattering theory and Wolfenstein's parametrization of the nucleon-nucleon scattering amplitude. The resulting theoretical potential is non-local and consists of an energy independent central volume plus surface real and imaginary potential and of a Thomas-like spin-orbit term. The analysis has been restricted to N=Z spherical nuclei, so that neither isospin-isospin nor spin-spin interaction have been included.