37,070 research outputs found
On the Implementation of Efficient Channel Filters for Wideband Receivers by Optimizing Common Subexpression Elimination Methods
No abstract availabl
Summary of Experimental Meson Physics
A summary of the present experimental status of meson physics is presented.
The presentation includes the new results presented at the MESON06 workshop, as
well as other recent experimental developments in the field.Comment: 15 pages, 6 figures, presented at 9th International Workshop on Meson
Production, Properties and Interaction, Krakow, Poland, June 200
Pinned modes in lossy lattices with local gain and nonlinearity
We introduce a discrete linear lossy system with an embedded "hot spot" (HS),
i.e., a site carrying linear gain and complex cubic nonlinearity. The system
can be used to model an array of optical or plasmonic waveguides, where
selective excitation of particular cores is possible. Localized modes pinned to
the HS are constructed in an implicit analytical form, and their stability is
investigated numerically. Stability regions for the modes are obtained in the
parameter space of the linear gain and cubic gain/loss. An essential result is
that the interaction of the unsaturated cubic gain and self-defocusing
nonlinearity can produce stable modes, although they may be destabilized by
finite amplitude perturbations. On the other hand, the interplay of the cubic
loss and self-defocusing gives rise to a bistability.Comment: Phys. Rev. E (in press
Calibration of shielded microwave probes using bulk dielectrics
A stripline-type near-field microwave probe is microfabricated for microwave
impedance microscopy. Unlike the poorly shielded coplanar probe that senses the
sample tens of microns away, the stripline structure removes the stray fields
from the cantilever body and localizes the interaction only around the
focused-ion beam deposited Pt tip. The approaching curve of an oscillating tip
toward bulk dielectrics can be quantitatively simulated and fitted to the
finite-element analysis result. The peak signal of the approaching curve is a
measure of the sample dielectric constant and can be used to study unknown bulk
materials.Comment: 10 pages, 3 figure
Improved Memoryless RNS Forward Converter Based on the Periodicity of Residues
The residue number system (RNS) is suitable for DSP architectures because of its ability to perform fast carry-free arithmetic. However, this advantage is over-shadowed by the complexity involved in the conversion of numbers between binary and RNS representations. Although the reverse conversion (RNS to binary) is more complex, the forward transformation is not simple either. Most forward converters make use of look-up tables (memory). Recently, a memoryless forward converter architecture for arbitrary moduli sets was proposed by Premkumar in 2002. In this paper, we present an extension to that architecture which results in 44% less hardware for parallel conversion and achieves 43% improvement in speed for serial conversions. It makes use of the periodicity properties of residues obtained using modular exponentiation
A Search for Binary Stars at Low Metallicity
We present initial results measuring the companion fraction of metal-poor
stars ([Fe/H]2.0). We are employing the Lick Observatory planet-finding
system to make high-precision Doppler observations of these objects. The binary
fraction of metal-poor stars provides important constraints on star formation
in the early Galaxy (Carney et al. 2003). Although it has been shown that a
majority of solar metallicity stars are in binaries, it is not clear if this is
the case for metal-poor stars. Is there a metallicity floor below which binary
systems do not form or become rare? To test this we are determining binary
fractions at metallicities below [Fe/H]. Our measurments are not as
precise as the planet finders', but we are still finding errors of only 50 to
300 m/s, depending on the signal-to-noise of a spectrum and stellar atmosphere
of the star. At this precision we can be much more complete than previous
studies in our search for stellar companions.Comment: To appear in conference proceedings,"First Stars III", eds. B.
O'Shea, A. Heger & T. Abel. 3 pages, 5 figure
FIR Filter Implementation by Efficient Sharing of Horizontal and Vertical Common Sub-expressions
No abstract availabl
Sheath ionization model of beam emissions from large spacecraft
An analytical model of the charging of a spacecraft emitting electron and ion beams has been applied to the case of large spacecraft. In this model, ionization occurs in the sheath due to the return current. Charge neutralization of spherical space charge flow is examined by solving analytical equations numerically. Parametric studies of potential large spacecraft are performed. As in the case of small spacecraft, the ions created in the sheath by the returning current play a large role in determining spacecraft potential
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