In this pedagogical article, we present a simple direct matrix method for analytically computing the Jacobian of nonlinear algebraic equations that arise from the discretization of nonlinear integro-differential equations. The method is based on a formulation of the discretized equations in vector form using only matrix-vector products and componentwise operations. By applying simple matrix-bas...

Multiple access interference (MAI) limits the capacity of Direct sequence Code Division Multiple Access (DS-CDMA) systems. In CDMA systems MAI is considered as additive noise and matched filter bank is employed. Traditionally, multiuser detectors a code matched and a multiuser linear filter are used which increases the complexity of the system due to its nature of operation. Multiuser detection...

Performance based seismic design (PBSD) is an alternative to code based approaches to design or evaluation of structures that fail to yield a more direct relationship between a seismic event and the corresponding structural performance of a building; this generally leads to over-conservatism. This paper presents a case study on the alternative procedures used in the performance based design of ...

This paper introduces a nonlinear shrinkage estimator of the covariance matrix that does not require recovering the population eigenvalues first. We estimate the sample spectral density and its Hilbert transform directly by smoothing the sample eigenvalues with a variable-bandwidth kernel. Relative to numerically inverting the so-called QuEST function, the main advantages of direct kernel estim...

An acoustic prediction capability for supersonic axisymmetric jets was developed on the basis of OVERFLOW Navier-Stokes CFD (Computational Fluid Dynamics) code of NASA Langley Research Center. Reynolds-averaged turbulent stresses in the flow fie ld are modeled with the aid of Spalart-Alimaras one-equation turbulence modeL Appropriate acoustic and outflow boundary conditions were implemented to ...

Advanced x-ray radiography machines require that multiple electron beam pulses be delivered to x-ray converter targets over several lines of sight. This can be accomplished using a single accelerator by using a fast kicker to deliver the electron beam pulses to several beamlines. This type of radiography machine requires transport lines with several large achromatic bends in the individual tran...

Low-complexity coding and decoding (Lococode), a novel approach to sensory coding, trains autoassocia-tors (AAs) by Flat Minimum Search (FMS), a recent general method for nding low-complexity networks with high generalization capability. FMS works by minimizing both training error and required weight precision. We nd that as a by-product Lococode separates nonlinear superpositions of sources wi...

In this work, a Fourier solver [McMillan et. al., Comput. Phys. Commun. 181, 715 (2010)] is implemented in the global Eulerian gyrokinetic code GT5D [Y. Idomura et. al., Nucl. Fusion 49, 065029, 2009] and in the global Particle-In-Cell code ORB5 [S. Jolliet et. al., Comput. Phys. Commun 177, 477 (2007)] in order to reduce the memory of the matrix associated with the field equation. This scheme ...

Forward and reverse modes of algorithmic differentiation (AD) transform implementations of multivariate vector functions F : IR → IR as computer programs into tangent and adjoint code, respectively. The reapplication of the same ideas yields higher derivative code. In particular, second derivatives play an important role in nonlinear programming. Second-order methods based on Newton’s algorithm...

A new formalism to describe the spatiotemporal evolution of relativistic Raman backscatter ~RBS! of ultrashort laser pulses in underdense plasma has been developed. This theory is based on an eikonal representation for the RBS field and averaging over the oscillation frequency. Equations are derived for the evolution of the RBS radiation field amplitude and phase and for particle motion in the ...