240 research outputs found
READ @your library Beny Neta (bookmark)
No full textA project of the Dudley Knox Library at the Naval Postgraduate School
READ @your library Beny Neta (poster)
No full textA project of the Dudley Knox Library at the Naval Postgraduate School
A new sixth-order scheme for nonlinear equations
No full textApplied Math. Letters, 25, (2012), 185–189, doi:10.1016/j.aml.2011.08.012.The article of record as published may be located at http://dx.doi.org/10.1016/j.aml.2011.08.012In this paper we present a new efficient sixth-order scheme for nonlinear equations. The method is compared to several members of the family of methods developed by Neta (1979) [B. Neta, A sixth-order family of methods for nonlinear equations, Int. J. Comput. Math. 7 (1979) 157–161]. It is shown that the new method is an improvement over this well known scheme
Software for the staggered and unstaggered Turkel-Zwas schemes for the shallow water equations on the sphere
No full textA linear analysis of the shallow water equations in spherical coordinates for the Turkel-Zwas1 explicit large time-step scheme was presented by Neta, Giraldo and Navon2 as well as the unstaggered1 Turkel-Zwas scheme for the solution of the shallow water equations on the sphere.Approved for public release; distribution is unlimited
Application of Higdon non-reflecting boundary conditions to shallow water models
No full textIn many applications involving wave propagation, problem domains are often very large or unbounded. A common numerical method used to solve such problems is to truncate the domain via artificial boundaries to form a finite computational domain. To accomplish this, Non-Reflecting Boundary Conditions (NRBC's) which minimize spurious wave reflections are imposed. The quality of the solution strongly depends on the properties of both the NRBC and the wave behavior. This dissertation explores the use of Higdon NRBC's to solve shallow water equations (SWE's) in a dispersive environment. A linearized SWE model is developed that includes stratification and advection effects. Initially a single NRBC is used to truncate a semi-infinite channel. Later four NRBC's are used to restrict an infinite plane. In both cases finite rectangular domains are formed. A scheme developed by Neta and Givoli is used to rapidly discretize high-order Higdon NRBC's. Finite difference methods and are used in all numerical schemes, which are solved explicitly when possible. Results will show that Higdon NRBC's can be used effectively to restrict large rectangular domains when solving SWE's that include the before mentioned effects.Approved for public release; distribution is unlimited.Commander, United States Navyhttp://archive.org/details/applicationofhig109451104
Unstructured high-order galerkin-temporal-boundary methods for the klein-gordon equation with non-reflecting boundary conditions
No full textA reduced shallow water model under constant, non-zero advection in infinite domains is considered. High-Order Givoli-Neta (G-N) and Hagstrom-Hariharan (H-H) non-reflecting boundary conditions (NRBCs) are introduced to create a finite computational space and solved using a spectral element formulation with high-order time integration. Numerical examples are used to demonstrate the synergy of using high-order spatial, time and boundary discretizations. Several alternatives are also presented for solving open domain problems. These alternatives include adjustments to the G-N NRBC based on physical arguments as well as formulating the boundary condition for arbitrary domains using unstructured grids. The H-H polar NRBC is also formulated in an unstructured grid setting and extended to include dispersive effects. Results show that by balancing all numerical errors involved, high-order accuracy can be achieved for unbounded channel problems. Further, the adjustments to the G-N and H-H NRBCs to operate in an unstructured grid setting are shown to significantly reduce errors over first order non-reflecting boundary schemes when operating in an open domain configuration.Major, United States Armyhttp://archive.org/details/unstructuredhigh109451052
Parallelization of the Naval Space Surveillance Center (NAVSPASUR) satellite motion model
No full textThe Naval Space Surveillance Center (NAVSPASUR) uses an analytic satellite motion model based on the Brouwer-Lyddane theory to assist in tracking over 6000 objects in orbit around the earth. The satellite motion model is implemented by a Fortran subroutine, PPT2. Due to the increasing number of objects required to be tracked, NAVSPASUR desires a method to reduce the computation time of this satellite motion model. Parallel computing offers one method to achieve this objective. This thesis investigates the parallel computing potential of the MAVSPASUR model using the Intel iPSC/2 hypercube multi-computer. The thesis developed several parallel algorithms for the NAVSPASUR satellite motion model using the various methods of parallelization, applies these algorithms to the hypercube, and reports on each algorithm's potential reduction in computation time. A diskette containing the Fortran software is available upon request from [email protected] for public release; distribution is unlimited.Captain, United States Armyhttp://archive.org/details/parallelizationo109452400
Inferring effective field observables from a discrete model
No full textAspin system on a lattice can usually be modeled at large scales by an effective quantum field theory. A key mathematical result relating the two descriptions is the quantum central limit theorem, which shows that certain spin observables satisfy an algebra of bosonic fields under certain conditions. Here, we show that these particular observables and conditions are the relevant ones for an observer with certain limited abilities to resolve spatial locations as well as spin values. This is shown by computing the asymptotic behaviour of a quantum Fisher information metric as function of the resolution parameters. The relevant observables characterise the state perturbations whose distinguishability does not decay too fast as a function of spatial or spin resolution.The author is grateful to Tobias Osborne for discussions leading to this work. This work was supported by the ERC grants QFTCMPS and SIQS, by the cluster of excellence EXC 201 Quantum Engineering and Space-Time Research, and by the research fund of Hanyang University (HY-2016-2237)
- …
