238 research outputs found
Conceptual mechanization studies for a horizon definition spacecraft attitude control subsystem, phase A, part II, 10 October 1966 - 29 May 1967
Attitude control subsystem for spin stabilized spacecraft for mapping earths infrared horizon radiance profiles in 15 micron carbon dioxide absorption ban
Qualitative and quantitative analysis of stability and instability dynamics of positive lattice solitons
We present a unified approach for qualitative and quantitative analysis of
stability and instability dynamics of positive bright solitons in
multi-dimensional focusing nonlinear media with a potential (lattice), which
can be periodic, periodic with defects, quasiperiodic, single waveguide, etc.
We show that when the soliton is unstable, the type of instability dynamic that
develops depends on which of two stability conditions is violated.
Specifically, violation of the slope condition leads to an amplitude
instability, whereas violation of the spectral condition leads to a drift
instability. We also present a quantitative approach that allows to predict the
stability and instability strength
Chiral Quasicrystalline Order and Dodecahedral Geometry in Exceptional Families of Viruses
On the example of exceptional families of viruses we i) show the existence of
a completely new type of matter organization in nanoparticles, in which the
regions with a chiral pentagonal quasicrystalline order of protein positions
are arranged in a structure commensurate with the spherical topology and
dodecahedral geometry, ii) generalize the classical theory of quasicrystals
(QCs) to explain this organization, and iii) establish the relation between
local chiral QC order and nonzero curvature of the dodecahedral capsid faces.Comment: 8 pages, 3 figure
Isotropic Conductivity of Two-Dimensional Three-Component Symmetric Composites
The effective dc-conductivity problem of isotropic, two-dimensional (2D),
three-component, symmetric, regular composites is considered. A simple cubic
equation with one free parameter for
is suggested whose solutions automatically have all the exactly known
properties of that function. Numerical calculations on four different
symmetric, isotropic, 2D, three-component, regular structures show a
non-universal behavior of with an
essential dependence on micro-structural details, in contrast with the
analogous two-component problem. The applicability of the cubic equation to
these structures is discussed. An extension of that equation to the description
of other types of 2D three-component structures is suggested, including the
case of random structures.
Pacs: 72.15.Eb, 72.80.Tm, 61.50.AhComment: 8 pages (two columns), 8 figures. J. Phys. A - submitte
Noncommutative space and the low-energy physics of quasicrystals
We prove that the effective low-energy, nonlinear Schroedinger equation for a
particle in the presence of a quasiperiodic potential is the potential-free,
nonlinear Schroedinger equation on noncommutative space. Thus quasiperiodicity
of the potential can be traded for space noncommutativity when describing the
envelope wave of the initial quasiperiodic wave.Comment: 9 pages, some refs adde
Glassy Random Matrix Models
This paper discusses Random Matrix Models which exhibit the unusual phenomena
of having multiple solutions at the same point in phase space. These matrix
models have gaps in their spectrum or density of eigenvalues. The free energy
and certain correlation functions of these models show differences for the
different solutions. Here I present evidence for the presence of multiple
solutions both analytically and numerically.
As an example I discuss the double well matrix model with potential where is a random matrix (the
matrix model) as well as the Gaussian Penner model with . First I study what these multiple solutions are in the large
limit using the recurrence coefficient of the orthogonal polynomials.
Second I discuss these solutions at the non-perturbative level to bring out
some differences between the multiple solutions. I also present the two-point
density-density correlation functions which further characterizes these models
in a new university class. A motivation for this work is that variants of these
models have been conjectured to be models of certain structural glasses in the
high temperature phase.Comment: 25 pages, Latex, 7 Figures, to appear in PR
Pure point diffraction and cut and project schemes for measures: The smooth case
We present cut and project formalism based on measures and continuous weight
functions of sufficiently fast decay. The emerging measures are strongly almost
periodic. The corresponding dynamical systems are compact groups and
homomorphic images of the underlying torus. In particular, they are strictly
ergodic with pure point spectrum and continuous eigenfunctions. Their
diffraction can be calculated explicitly. Our results cover and extend
corresponding earlier results on dense Dirac combs and continuous weight
functions with compact support. They also mark a clear difference in terms of
factor maps between the case of continuous and non-continuous weight functions.Comment: 30 page
Geometrical isotropy in perforated plates with subwavelength holes decorated with Archimedean patterns
The design and use of small apertures perforated in opaque plates to control the transmission of ultrasonic waves has been widely studied in recent years. The ultrasonic transmission response of brass plates perforated with Archimedean patterns of subwavelength hole arrays immersed in water is reported, both numerically and experimentally, in this work. It is shown that an increase in the geometrical isotropy of the elementary cells of the Archimedean patterns gives rise to a suppression of both minimum and maximum transmission corresponding to the destructive and constructive interferences, leading to uniformity within the angle-dependent transmitted sound power coefficient. The experimental results are in close agreement with the calculated ones. This property can be used to design ultrasonic devices such as filters and sensors.This work has been supported by the Spanish MICINN (MAT2010-16879) and Generalitat Valenciana (PROM-ETEOII/2014/026).Gómez Lozano, V.; Rubio Michavila, C.; Candelas Valiente, P.; Belmar Ibáñez, F.; Uris Martínez, A. (2015). Geometrical isotropy in perforated plates with subwavelength holes decorated with Archimedean patterns. EPL. 111(3):34002p1-34002p5. https://doi.org/10.1209/0295-5075/111/34002S34002p134002p5111
An ultrametric state space with a dense discrete overlap distribution: Paperfolding sequences
We compute the Parisi overlap distribution for paperfolding sequences. It
turns out to be discrete, and to live on the dyadic rationals. Hence it is a
pure point measure whose support is the full interval [-1; +1]. The space of
paperfolding sequences has an ultrametric structure. Our example provides an
illustration of some properties which were suggested to occur for pure states
in spin glass models
Hybrid photonic-bandgap accelerating cavities
In a recent investigation, we studied two-dimensional point-defected photonic
bandgap cavities composed of dielectric rods arranged according to various
representative periodic and aperiodic lattices, with special emphasis on
possible applications to particle acceleration (along the longitudinal axis).
In this paper, we present a new study aimed at highlighting the possible
advantages of using hybrid structures based on the above dielectric
configurations, but featuring metallic rods in the outermost regions, for the
design of extremely-high quality factor, bandgap-based, accelerating
resonators. In this framework, we consider diverse configurations, with
different (periodic and aperiodic) lattice geometries, sizes, and
dielectric/metal fractions. Moreover, we also explore possible improvements
attainable via the use of superconducting plates to confine the electromagnetic
field in the longitudinal direction. Results from our comparative studies,
based on numerical full-wave simulations backed by experimental validations (at
room and cryogenic temperatures) in the microwave region, identify the
candidate parametric configurations capable of yielding the highest quality
factor.Comment: 13 pages, 5 figures, 3 tables. One figure and one reference added;
minor changes in the tex
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