The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform

Afshin Moradi - One of the best experts on this subject based on the ideXlab platform.

  • Surface plasmon modes of a nanoegg above a substrate.
    The Journal of chemical physics, 2014
    Co-Authors: Afshin Moradi
    Abstract:

    An analytical approach describing the surface plasmon modes of a nanoegg (a nanoshell with a nonconcentric core) above a substrate is presented. The bispherical coordinate system is used for Mathematical Convenience. A general dispersion relation for the coupled modes as function of geometrical characteristics of the system is obtained. In the special case (in the limit of a very large separation between the nanoegg and substrate) dispersion relation of the plasmon modes of an isolated nanoegg is derived. It is shown that the coupled plasmon modes exhibit excellent numerical convergence.

  • Multipole plasmon excitations of C60 dimers.
    The Journal of chemical physics, 2014
    Co-Authors: Afshin Moradi
    Abstract:

    We study the multipole plasmon mode frequencies of a pair of C60 molecules by means of the linearized hydrodynamic theory for electronic excitations on the each C60 surface. We apply the two-center spherical coordinate system for Mathematical Convenience and find an explicit form of the surface plasmon energies. Numerical result shows when approaching the two C60 molecules, the coupling between the bare plasmon modes leads to the appearance of additional modes having energies that are different from those of the isolated C60 molecules.

  • Plasmon hybridization in parallel nano-wire systems
    Physics of Plasmas, 2011
    Co-Authors: Afshin Moradi
    Abstract:

    We apply the plasmon hybridization method to a double-nano-wire system, providing a simple and intuitive description of the plasmon excitations in the system. We apply the two-center cylindrical coordinate system for Mathematical Convenience and find an explicit form of the surface plasmon oscillations, in terms of the interaction between the bare plasmon modes of the individual surfaces of the nano-wires. We present numerical results to display how the plasmon excitations of the system depend on nano-wire separation when there is no angular momentum transfer, i.e., when m = 0.

  • Plasmon hybridization in metallic nanotubes with a nonconcentric core
    Optics Communications, 2009
    Co-Authors: Afshin Moradi
    Abstract:

    Abstract We develop a theory of plasmon excitations in a metallic nanotube with a nonconcentric core using the plasmon hybridization method. We apply the two-center cylindrical coordinate system for Mathematical Convenience and find an explicit form of the dispersion relation for surface plasmons, in terms of interaction between the bare plasmon modes of the individual surfaces of the nanotubes. We present numerical result displaying the effect of the offset distant d of the inner core from the nanotube center, when there is no angular momentum transfer, i.e., m = 0 . For large offsets, the plasmon shifts is strong, but weak for small offset.

R. Tolimieri - One of the best experts on this subject based on the ideXlab platform.

  • The tensor product: a Mathematical programming language for FFTs and other fast DSP operations
    IEEE Signal Processing Magazine, 1992
    Co-Authors: J. Granata, M. Conner, R. Tolimieri
    Abstract:

    The use of the tensor product as a tool for modeling and developing digital signal processing algorithms is discussed. A precise Mathematical definition of the tensor product is established along with several important properties. Special tensor matrices suited for implementation on various computer architectures are then identified. The notion of the stride permutation matrix is introduced as a method of modeling operand addressing. An important connection between tensor matrices and stride permutations is made explicit. By identifying particular tensor matrices suited for implementation on a given machine the tensor product has been transformed from a Mathematical Convenience into an extremely useful tool for matching algorithms to computer architectures. Several design examples in which a tensor matrix multiplication is implemented on several radically different types of computer architectures are presented. >

Jeremiah G. Murphy - One of the best experts on this subject based on the ideXlab platform.

  • Transversely isotropic biological, soft tissue must be modelled using both anisotropic invariants
    European Journal of Mechanics - A Solids, 2013
    Co-Authors: Jeremiah G. Murphy
    Abstract:

    Abstract Skeletal muscles, ligaments and tendons are typically assumed to be incompressible, transversely isotropic, non-linearly hyperelastic materials. If one adopts the phenomenological approach to modelling, then the corresponding strain-energy function can be represented as an arbitrary function of two invariants of the Cauchy–Green strain tensors, representing the isotropic contribution, and two pseudo-invariants, representing the anisotropic contribution. For Mathematical Convenience, dependence on one of these pseudo-invariants is usually dropped. It will be shown here that a necessary consequence of this reduced form of the strain-energy function is that the infinitesimal shear moduli are identical, an assumption that is not supported by experimental data. It will also be shown that a further consequence is that two out of the three shearing modes are identical over the full range of deformation. The conclusion is that transversely isotropic biological, soft tissue must be modelled using both anisotropic invariants.

  • On the volumetric part of strain-energy functions used in the constitutive modeling of slightly compressible solid rubbers
    International Journal of Solids and Structures, 2009
    Co-Authors: Cornelius O. Horgan, Jeremiah G. Murphy
    Abstract:

    A popular model for the finite element simulation of slightly compressible solid rubber-like materials assumes that the strain-energy function can be additively decomposed into a volumetric part and a deviatoric part. Based on Mathematical Convenience, the volumetric part is usually assumed to be a finite polynomial in the volume change. Experimental evidence suggests that for solid rubbers in compression, this polynomial can be taken to be a simple quadratic for moderate deformations and that this function also adequately models the volume change and the stress/stretch relation for materials in simple tension, up to stretches of order 100%. For larger tensile deformations, however, experimental data suggest that the Cauchy stress-volume change relation has an increasingly large slope and therefore a truncated Taylor series expansion is not the most appropriate. A rational function approach is proposed here as an alternative.

David Hilditch - One of the best experts on this subject based on the ideXlab platform.

  • Conformally flat slices of asymptotically flat spacetimes
    Classical and Quantum Gravity, 2020
    Co-Authors: Miguel Duarte, David Hilditch
    Abstract:

    For Mathematical Convenience initial data sets in numerical relativity are often taken to be conformally flat. Employing the dual-foliation formalism, we investigate the physical consequences of this assumption. Working within a large class of asymptotically flat spacetimes we show that the ADM linear momentum is governed by the leading Lorentz part of a boost even in the presence of supertranslation-like terms. Following up, we find that in spacetimes that are asymptotically flat, and admit spatial slices with vanishing linear momentum that are sufficiently close to conformal flatness, any boosted slice can not be conformally flat. Consequently there are no conformally flat boosted slices of the Schwarzschild spacetime. This confirms the previously anticipated explanation for the presence of junk-radiation in Brandt-Bruegmann puncture data.

Frank Nielsen - One of the best experts on this subject based on the ideXlab platform.

  • EUSIPCO - On the Angular Resolution Limit Uncertainty
    2018 26th European Signal Processing Conference (EUSIPCO), 2018
    Co-Authors: Maria Greco, Remy Boyer, Frank Nielsen
    Abstract:

    The Angular Resolution Limit (ARL), denoted by 6, is a key statistical quantity to measure our ability to resolve two closely-spaced narrowband far-field complex sources. In the literature, the ARL, denoted by δ0, is systematically assumed to be perfectly known for Mathematical Convenience. In this work, our knowledge on the ARL is supposed to be only partial, meaning that δ ~N (δ0, σδ2). The degree of uncertainty is quantified by the ratio ξ = δ20/σ2δ. Based on the Chernoff Upper Bound (CUB) on the minimal error probability, we show that the CUB is highly dependent on the degree of uncertainty, ξ. As by-product, the optimal s-value for which the CUB is the tightest upper bound is analytically studied.