29,811 research outputs found
Two-dimensional polymer networks at a mixed boundary: Surface and wedge exponents
We provide general formulae for the configurational exponents of an arbitrary
polymer network connected to the surface of an arbitrary wedge of the
two-dimensional plane, where the surface is allowed to assume a general mixture
of boundary conditions on either side of the wedge. We report on a
comprehensive study of a linear chain by exact enumeration, with various
attachments of the walk's ends to the surface, in wedges of angles and
, with general mixed boundary conditions.Comment: 4 pages, Latex2e, 3 figures, Eur. Phys. J. B macro
Computer Programs for Calculating and Plotting the Stability Characteristics of a Balloon Tethered in a Wind
Computer programs for calculating the stability characteristics of a balloon tethered in a steady wind are presented. Equilibrium conditions, characteristic roots, and modal ratios are calculated for a range of discrete values of velocity for a fixed tether-line length. Separate programs are used: (1) to calculate longitudinal stability characteristics, (2) to calculate lateral stability characteristics, (3) to plot the characteristic roots versus velocity, (4) to plot the characteristic roots in root-locus form, (5) to plot the longitudinal modes of motion, and (6) to plot the lateral modes for motion. The basic equations, program listings, and the input and output data for sample cases are presented, with a brief discussion of the overall operation and limitations. The programs are based on a linearized, stability-derivative type of analysis, including balloon aerodynamics, apparent mass, buoyancy effects, and static forces which result from the tether line
Vector Reflectometry in a Beam Waveguide
We present a one-port calibration technique for characterization of beam
waveguide components with a vector network analyzer. This technique involves
using a set of known delays to separate the responses of the instrument and the
device under test. We demonstrate this technique by measuring the reflected
performance of a millimeter-wave variable-delay polarization modulator
Local u'g'r'i'z' Standard Stars in the Chandra Deep Field-South
Because several observing programs are underway in various spectral regimes
to explore the Chandra Deep Field South (CDF-S), the value of local photometric
standards is obvious. As part of an NOAO Surveys Program to establish
u'g'r'i'z' standard stars in the southern hemisphere, we have observed the
central region of the CDF-S to create local standards for use by other
investigators using these filters. As a courtesy, we present the CDF-S
standards to the public now, although the main program will not finish until
mid-2005.Comment: Accepted by AJ (scheduled for October 2003 issue). 26 pages, 5
tables, 5 figures. High resolution version of Figure 7 available at
http://home.fnal.gov/~dtucker/Southern_ugriz/index.htm
Quantum computers can search rapidly by using almost any transformation
A quantum computer has a clear advantage over a classical computer for
exhaustive search. The quantum mechanical algorithm for exhaustive search was
originally derived by using subtle properties of a particular quantum
mechanical operation called the Walsh-Hadamard (W-H) transform. This paper
shows that this algorithm can be implemented by replacing the W-H transform by
almost any quantum mechanical operation. This leads to several new applications
where it improves the number of steps by a square-root. It also broadens the
scope for implementation since it demonstrates quantum mechanical algorithms
that can readily adapt to available technology.Comment: This paper is an adapted version of quant-ph/9711043. It has been
modified to make it more readable for physicists. 9 pages, postscrip
Indeterminate-length quantum coding
The quantum analogues of classical variable-length codes are
indeterminate-length quantum codes, in which codewords may exist in
superpositions of different lengths. This paper explores some of their
properties. The length observable for such codes is governed by a quantum
version of the Kraft-McMillan inequality. Indeterminate-length quantum codes
also provide an alternate approach to quantum data compression.Comment: 32 page
The Submillimeter Polarization Spectrum of M17
We present 450 {\mu}m polarimetric observations of the M17 molecular cloud
obtained with the SHARP polarimeter at the Caltech Submillimeter Observatory.
Across the observed region, the magnetic field orientation is consistent with
previous submillimeter and far-infrared polarization measurements. Our
observations are centered on a region of the molecular cloud that has been
compressed by stellar winds from a cluster of OB stars. We have compared these
new data with previous 350 {\mu}m polarimetry and find an anti-correlation
between the 450 to 350 {\mu}m polarization magnitude ratio and the ratio of 21
cm to 450 {\mu}m intensity. The polarization ratio is lower near the east end
of the studied region where the cloud is exposed to stellar winds and
radiation. At the west end of the region, the polarization ratio is higher. We
interpret the varying polarization spectrum as evidence supporting the
radiative alignment torque (RAT) model for grain alignment, implying higher
alignment efficiency in the region that is exposed to a higher anisotropic
radiation field.Comment: 24 pages, 10 figure
Parallel-propagating Fluctuations at Proton-kinetic Scales in the Solar Wind are Dominated by Kinetic Instabilities
We use magnetic helicity to characterise solar wind fluctuations at
proton-kinetic scales from Wind observations. For the first time, we separate
the contributions to helicity from fluctuations propagating at angles
quasi-parallel and oblique to the local mean magnetic field, . We
find that the helicity of quasi-parallel fluctuations is consistent with
Alfv\'en-ion cyclotron and fast magnetosonic-whistler modes driven by proton
temperature anisotropy instabilities and the presence of a relative drift
between -particles and protons. We also find that the helicity of
oblique fluctuations has little dependence on proton temperature anisotropy and
is consistent with fluctuations from the anisotropic turbulent cascade. Our
results show that parallel-propagating fluctuations at proton-kinetic scales in
the solar wind are dominated by proton temperature anisotropy instabilities and
not the turbulent cascade. We also provide evidence that the behaviour of
fluctuations at these scales is independent of the origin and macroscopic
properties of the solar wind.Comment: Accepted for publication in ApJL. 6 Pages, 3 figures, 1 tabl
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