19 Matching Results

Search Results

Advanced search parameters have been applied.
in subjects: "Moments Method"  
Results: 1 - 19
open access

Digital simulation and modeling of nonlinear stochastic systems

Description: Digitally generated solutions of nonlinear stochastic systems are not unique, but depend critically on the numerical integration algorithm used. Some theoretical and practical implications of this dependence are examined. The Ito-Stratonovich controversy concerning the solution of nonlinear stochastic systems is shown to be more than a theoretical debate on maintaining Markov properties as opposed to utilizing the computational rules of ordinary calculus. The theoretical arguments give rise to … more
Date: January 1, 1980
Creator: Richardson, J. M. & Rowland, J. R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Moment series for the coefficient of variation in Weibull sampling

Description: For the 2-parameter Weibull distribution function F(t) = 1 - exp(-t/b)/sup c/, t > 0, with c and b positive, a moment estimator c* for c is the solution of the equationGAMMA(1 + 2/c*)/GAMMA/sup 2/ (1 + 1/c*) = 1 + v*/sup 2/ where v* is the coefficient of variation in the form ..sqrt..m/sub 2//m/sub 1/', m/sub 1/' being the sample mean, m/sub 2/ the sample second central moment (it is trivial in the present context to replace m/sub 2/ by the variance). One approach to the moments of c* (Bowman a… more
Date: January 1, 1981
Creator: Bowman, K.O. & Shenton, L.R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Eigenmodes of classical fluids in thermal equilibrium

Description: The eigenmodes of a classical fluid in thermal equilibrium are discussed. For long wavelengths and times, they can be computed from linear hydrodynamic equations. They are then the hydrodynamic modes, in particular, the heat mode, which describes the diffusion of heat in the fluid and two sound modes. For short wavelengths and times they can be derived from linear kinetic operators. For low densities, the linear Boltzmann operator can be employed and the three most important eigenmodes are dire… more
Date: January 1, 1985
Creator: Cohen, E.G.D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Moments in particle-in-cell simulations

Description: The moment equations that form the basis of the BEDLAM simulation code can also be used as a check on Particle-In-Cell (PIC) simulations. Moments can be computed as sums over the macroparticles used in the PIC simulations. These moments should satisfy the moment equations if the simulation is valid. A check has been done to sixth order for two cases: the RFQRZP code, which simulated a radio-frequency quadrupole (RFQ) linac, and the BEAMTRACE code, which simulated the final focusing system in a … more
Date: January 1, 1985
Creator: Berz, M.M. & Lysenko, W.P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Moment code BEDLAM

Description: BEDLAM is a fourth-order moment simulation code. The beam at the input to a linear accelerator is specified as a collection of moments of the phase-space distribution. Then the moment equations, which describe the time evolution of the moments, are numerically integrated. No particles are traced in this approach. The accuracy of the computed distribution, the external forces, and the space-charge forces are computed consistently to a given order. Although BEDLAM includes moments to fourth order… more
Date: January 1, 1985
Creator: Channell, P.J.; Healy, L.M. & Lysenko, W.P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Modeling pollutant dispersion over irregular terrain with second moments and cubic splines

Description: Under ideal conditions, dispersion can be reasonably predicted with analytical methods, such as Gaussian puff/plume theory. However, analytical methods are typically inflexible under variable wind conditions, particularly in cases where dispersion occurs over irregular surfaces. A specific need exists for more detailed study into the effect of surface irregularities on dispersion. The requirement is to establish an accurate and efficient numerical solution algorithm for three-dimensional mesosc… more
Date: January 1, 1978
Creator: Pepper, D. W. & Baker, A. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Neutron slowing down and transport in monoisotopic media with constant cross sections or with a square-well minimum

Description: A specialized moments-method computer code was constructed for the calculation of the even spatial moments of the scalar flux, phi/sub 2n/, through 2n = 80. Neutron slowing-down and transport in a medium with constant cross sections was examined and the effect of a superimposed square-well cross section minimum on the penetrating flux was studied. In the constant cross section case, for nuclei that are not too light, the scalar flux is essentially independent of the nuclide mass. The numerical … more
Date: January 1, 1977
Creator: Peng, W.H.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Mechanisms of fast neutron penetration in thick layers of sodium

Description: A series of computer experiments was carried out to elucidate the penetration mechanisms of fast neutrons through thick layers of sodium such as occur in LMFBR designs. As a one-dimensional approximation of the actual situation, the calculations concentrated mainly on the flux 5 meters from a plane isotropic fission source in an infinite sodium medium. Most of the transport calculations were made with the moments-method code BMT with a 496-energy point grid. Previously developed methods for rec… more
Date: January 1, 1975
Creator: Huang, L. Y.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Moment approach to charged particle beam dynamics

Description: We have derived the hierarchy of moment equations that describes the dynamics of charged-particle beams in linear accelerators and can truncate the hierarchy at any level either by discarding higher moments or by a cumulant expansion discarding only correlation functions. We have developed a procedure for relating the density expansion linearly to the moments to any order. The relation of space-charge fields to the density has been derived; and an accurate, systematic, and computationally conve… more
Date: January 1, 1983
Creator: Channell, P.J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Comparison of an exact and moments calculation of reliability

Description: Present methods for calculating the reliability of reactor systems usually assume constant failure rates for individual components of the system. In principle, if the uncertainty in component failure rates can be expressed in terms of a probability density function, then the probability density function for the overall system reliability can be obtained. The system reliability distribution can then be used to calculate confidence bounds, for example. The probability distribution for the system … more
Date: January 1, 1976
Creator: Hockenbury, R. W.; Yeater, M. L.; Hawkins, J. M. & Wilkinson, J. W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Moment invariants for particle beams

Description: The rms emittance is a certain function of second moments in 2-D phase space. It is preserved for linear uncoupled (1-D) motion. In this paper, the authors present new functions of moments that are invariants for coupled motion. These invariants were computed symbolically using a computer algebra system. Possible applications for these invariants are discussed. Also, approximate moment invariants for nonlinear motion are presented.
Date: January 1, 1988
Creator: Lysenko, W. P. & Overley, M. S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

New BEDLAM (BEam Dynamics for Linear Accelerators by Moments)

Description: BEDLAM (BEam Dynamics for Linear Accelerators by Moments) is a 3-D code that simulates bunched ion beams in linear accelerators and beamlines. The BEDLAM beam is described by moments of the phase-space distribution, and the evolution of these moments is what is computed. In this approach, the beam, the external focusing forces, and the space-charge forces are all described consistently to the same order of accuracy. The present version of BEDLAM includes moments up to fourth order (equivalent t… more
Date: January 1, 1990
Creator: Lysenko, W.P. & Channell, P.J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Moment methods for simulation and design

Description: It is often advantageous to describe a particle beam by the moments of its phase-space distribution. This paper relates original work by Sacherer to presently-used linear design codes like TRACE3D and to some recent results. 15 refs., 1 fig.
Date: January 1, 1990
Creator: Lysenko, W.P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Fitting: Subroutine to fit four-moment probability distributions to data

Description: FITTING is a Fortran subroutine that constructs a smooth, generalized four-parameter probability distribution model. It is fit to the first four statistical moments of the random variable X (i.e., average values of X, X{sup 2}, X{sup 3}, and X{sup 4}) which can be calculated from data using the associated subroutine CALMOM. The generalized model is produced from a cubic distortion of the parent model, calibrated to match the first four moments of the data. This four-moment matching is intended … more
Date: January 1, 1995
Creator: Winterstein, S. R.; Lange, C. H. & Kumar, S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Ionization cooling and muon dynamics

Description: Muon colliders potential to provide a probe for fundamental particle physics is very interesting. To obtain the needed collider luminosity, the phase space volume must be greatly reduced within the muon life time. The Ionization cooling is the preferred method used to compress the phase space and reduce the emittance to obtain high luminosity muon beams. The authors note that, the ionization losses results not only in damping, but also heating. They discuss methods used including moments method… more
Date: January 1, 1998
Creator: Parsa, Z.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Evaluation of the discrete complex-image method for a NEC-like moment-method solution

Description: The discrete image approximation for the field of a half-space is tested in the NEC antenna modeling program as an alternative to the interpolation method presently used. The accuracy and speed of the discrete image approximation are examined for varying number of images and approximation contour, and the solution for current is obtained on a horizontal wire approaching the interface.
Date: January 5, 1996
Creator: Burke, G. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Moment series for moment estimators of the parameters of a Weibull density

Description: Taylor series for the first four moments of the coefficients of variation in sampling from a 2-parameter Weibull density are given: they are taken as far as the coefficient of n/sup -24/. From these a four moment approximating distribution is set up using summatory techniques on the series. The shape parameter is treated in a similar way, but here the moment equations are no longer explicit estimators, and terms only as far as those in n/sup -12/ are given. The validity of assessed moments and … more
Date: January 1, 1982
Creator: Bowman, K.O. & Shenton, L.R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
Back to Top of Screen