2,380 research outputs found
Experimentally observed evolution between dynamic patterns and intrinsic localized modes in a driven nonlinear electrical cyclic lattice
Locked intrinsic localized modes (ILMs) and large amplitude lattice spatial
modes (LSMs) have been experimentally measured for a driven 1-D nonlinear
cyclic electric transmission line, where the nonlinear element is a saturable
capacitor. Depending on the number of cells and electrical lattice damping a
LSM of fixed shape can be tuned across the modal spectrum. Interestingly, by
tuning the driver frequency away from this spectrum an LSM can be continuously
converted into ILMs and visa versa. The differences in pattern formation
between simulations and experimental findings are due to a low concentration of
impurities. Through this novel nonlinear excitation and switching channel in
cyclic lattices either energy balanced or unbalanced LSMs and ILMs may occur.
Because of the general nature of these dynamical results for nonintegrable
lattices applications are to be expected. The ultimate stability of driven aero
machinery containing nonlinear periodic structures may be one example.Comment: 7 pages 7 figure
Notes on Snail Feeding Behavior of Anaxjunius (Drury): (Odonata)
A naiad of Anax junius (Drury), in final instar, preyed upon 47 mature snails, Helisoma trivolvis (Say), during a period of 63 clays. The feeding behavior has potential significance: (1) with respect to biological control of trematode vectoring gastropods; (2) as a mechanism for vectoring trematodes between snails and birds; and (3) in interpreting structural adaptations and perception in immature oclonates
Controlled switching of intrinsic localized modes in a 1-D antiferromagnet
Nearly steady-state locked intrinsic localized modes (ILMs) in the quasi-1d
antiferromagnet (C2H5NH3)2CuCl4 are detected via four-wave mixing emission or
the uniform mode absorption. Exploiting the long-time stability of these locked
ILMs, repeatable nonlinear switching is observed by varying the sample
temperature, and localized modes with various amplitudes are created by
modulation of the microwave driver power. This steady-state ILM locking
technique could be used to produce energy localization in other atomic
lattices.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Lett. v.2 :
clarifications of text and figures in response to comment
Laboratory Measurements of Celestial Solids
Our experimental study has focused on laboratory measurements of the low temperature optical properties of a variety of astronomically significant materials in the infrared and mm-wave region of the spectrum. Our far infrared measurements of silicate grains with an open structure have produced a variety of unusual results: (1) the low temperature mass opacity coefficient of small amorphous 2MgO(central dot)SiO2 and MgO(central dot)2SiO2 grains are many times larger than the values previously used for interstellar grain material; (2) all of the amorphous silicate grains studied possess the characteristic temperature dependent signature associated with two level systems in bulk glass; and (3) a smaller but nonzero two level temperature dependence signature is also observed for crystalline particles, its physical origin is unclear. These laboratory measurements yield surprisingly large and variable values for the mm-wave absorption coefficients of small silicate particles similar to interstellar grains, and suggest that the bulk absorptivity of interstellar dust at these long wavelengths will not be well known without such studies. Furthermore, our studies have been useful to better understand the physics of the two level absorption process in amorphous and crystalline grains to gain confidence in the wide applicability of these results
Generation of Intrinsic Vibrational Gap Modes in Three-Dimensional Ionic Crystals
The existence of anharmonic localization of lattice vibrations in a perfect
3-D diatomic ionic crystal is established for the rigid-ion model by molecular
dynamics simulations. For a realistic set of NaI potential parameters, an
intrinsic localized gap mode vibrating in the [111] direction is observed for
fcc and zinc blende lattices. An axial elastic distortion is an integral
feature of this mode which forms more readily for the zinc blende than for the
fcc structure. Molecular dynamics simulations verify that in each structure
this localized mode may be stable for at least 200 cycles.Comment: 5 pages, 4 figures, RevTeX, using epsf.sty. To be published in Phys.
Rev. B. Also available at http://www.msc.cornell.edu/~kiselev
Intrinsic Localized Modes Observed in the High Temperature Vibrational Spectrum of NaI
Inelastic neutron measurements of the high-temperature lattice excitations in
NaI show that in thermal equilibrium at 555 K an intrinsic mode, localized in
three dimensions, occurs at a single frequency near the center of the spectral
phonon gap, polarized along [111]. At higher temperatures the intrinsic
localized mode gains intensity. Higher energy inelastic neutron and x-ray
scattering measurements on a room-temperature NaI crystal indicate that the
creation energy of the ground state of the intrinsic localized mode is 299 meV.Comment: 17 pages, 5 figures Revised version; final versio
Classification of super domains and super domain walls in permalloy antidot lattices
We study the remanent domain configurations of rectangular permalloy antidot
lattices over a range of lattice parameters. The influence of antidot diameter,
antidot spacing, and the aspect ratio of the lattice on the remanent domain
configuration are investigated by magnetic force microscopy and supported by
micromagnetic simulations. In the remanent state, areas of cells with the same
orientation of average magnetization form magnetic super domains separated by
super domain walls (SDWs). Two types of SDWs are identified. The first type is
characterized by low stray field energy, is linear, and expands over many
lattice constants. In contrast the second type shows high stray field energy
and is situated at kinks of low energy SDWs. Its width can vary from a minimum
of two lattice cells up to several lattice constants, depending on the lattice
parameters. The occurrence and structure of these two types of SDWs as function
of lattice parameters are classified and discussed in terms of the interplay of
stray field and exchange energy.Comment: 6 pages, 7 figure
Product assurance technology for custom LSI/VLSI electronics
The technology for obtaining custom integrated circuits from CMOS-bulk silicon foundries using a universal set of layout rules is presented. The technical efforts were guided by the requirement to develop a 3 micron CMOS test chip for the Combined Release and Radiation Effects Satellite (CRRES). This chip contains both analog and digital circuits. The development employed all the elements required to obtain custom circuits from silicon foundries, including circuit design, foundry interfacing, circuit test, and circuit qualification
- …