12,333 research outputs found
Non-Linear Stability Analysis of Higher Order Dissipative Partial Differential Equations
We extend the invariant manifold method for analyzing the asymptotics of
dissipative partial differential equations on unbounded spatial domains to
treat equations in which the linear part has order greater than two. One
important example of this type of equation which we analyze in some detail is
the Cahn-Hilliard equation. We analyze the marginally stable solutions of this
equation in some detail. A second context in which such equations arise is in
the Ginzburg-Landau equation, or other pattern forming equations, near a
codimension-two bifurcation
Potential Milk Production in the Point MacKenzie Area of Southcentral Alaska
Point MacKenzie is an area northwest of Anchorage
directly across the Knik Arm of Cook Inlet (Figure
1 ). This area contains a substantial amount of latent
agricultural land and discussion regarding its potential
has been going on for some time. The catalyst which
activated the recent planning process directed at Point
MacKenzie was concern over potential loss of the
southcentral Alaska dairy industry expressed on May
4, 1979, in a letter from Jack Flint, General Manager,
Matanuska Maid, Inc., to Governor Jay Hammond:
"It is my opinion that if we do not take immediate
steps to stabilize this important phase of agriculture,
[the dairy industry] will pass from the scene. I think
that if it should occur, it would be a serious blow to
the State of Alaska, economically and socially. I
believe we should also realize that if the dairy industry
should cease to exist within the state, it is going
to be very difficult to re-establish it."
Mr. Flint's letter and corresponding action by
the Matanuska-Susitna Borough have directed planning
processes of the State of Alaska toward Poinr Mac-
Kenzie. The Alaska Agricultural Action Council,
created by the 1979 state legislature to plan, recommend,
and administer agricultural development projects
on state lands in Alaska, held a meeting in the
Matanuska Valley in September, 1979, and determined
that an economic feasibility study, directed toward
dairy production, should be undertaken for the Point
MacKenzie area. This report is that feasibility study.The information presented in this bulletin is part
of a report prepared for the Agricultural Action
Council of the State of Alaska. The group was formed
in 1979 by legislative action and is chaired by W. I.
"Bob" Palmer, Special Projects Director, Office of
the Governor. The purpose of the group is to plan
and manage agricultural development projects within
the state.
The report on the feasibility of milk production
in the Point MacKenzie Area presented to Governor Hammond through the Alaska Agricultural Action
Council was prepared by the authors of this bulletin
and Dr. Boyd Buxton, Agricultural Economist,
U.S. D.A., stationed at the University of Minnesota at
St. Paul and Dr. Paul Fuglestad, Agricultural Economist,
U.S.D .A., stationed in Anchorage, Alaska, both
of whom are acknowledged with gratitude.
The authors also wish to thank Cathy Warren
who reviewed extensively the tabular data
Geometric Stability Analysis for Periodic Solutions of the Swift-Hohenberg Equation
In this paper we describe invariant geometrical ~structures in the phase
space of the Swift-Hohenberg equation in a neighborhood of its periodic
stationary states. We show that in spite of the fact that these states are only
marginally stable (i.e., the linearized problem about these states has
continuous spectrum extending all the way up to zero), there exist finite
dimensional invariant manifolds in the phase space of this equation which
determine the long-time behavior of solutions near these stationary solutions.
In particular, using this point of view, we obtain a new demonstration of
Schneider's recent proof that these states are nonlinearly stable.Comment: 44 pages, plain tex, 0 figure
Higher Order Modulation Equations for a Boussinesq Equation
In order to investigate corrections to the common KdV approximation to long
waves, we derive modulation equations for the evolution of long wavelength
initial data for a Boussinesq equation. The equations governing the corrections
to the KdV approximation are explicitly solvable and we prove estimates showing
that they do indeed give a significantly better approximation than the KdV
equation alone. We also present the results of numerical experiments which show
that the error estimates we derive are essentially optimal
LoCoH: nonparameteric kernel methods for constructing home ranges and utilization distributions.
Parametric kernel methods currently dominate the literature regarding the construction of animal home ranges (HRs) and utilization distributions (UDs). These methods frequently fail to capture the kinds of hard boundaries common to many natural systems. Recently a local convex hull (LoCoH) nonparametric kernel method, which generalizes the minimum convex polygon (MCP) method, was shown to be more appropriate than parametric kernel methods for constructing HRs and UDs, because of its ability to identify hard boundaries (e.g., rivers, cliff edges) and convergence to the true distribution as sample size increases. Here we extend the LoCoH in two ways: "fixed sphere-of-influence," or r-LoCoH (kernels constructed from all points within a fixed radius r of each reference point), and an "adaptive sphere-of-influence," or a-LoCoH (kernels constructed from all points within a radius a such that the distances of all points within the radius to the reference point sum to a value less than or equal to a), and compare them to the original "fixed-number-of-points," or k-LoCoH (all kernels constructed from k-1 nearest neighbors of root points). We also compare these nonparametric LoCoH to parametric kernel methods using manufactured data and data collected from GPS collars on African buffalo in the Kruger National Park, South Africa. Our results demonstrate that LoCoH methods are superior to parametric kernel methods in estimating areas used by animals, excluding unused areas (holes) and, generally, in constructing UDs and HRs arising from the movement of animals influenced by hard boundaries and irregular structures (e.g., rocky outcrops). We also demonstrate that a-LoCoH is generally superior to k- and r-LoCoH (with software for all three methods available at http://locoh.cnr.berkeley.edu)
Testable polarization predictions for models of CMB isotropy anomalies
Anomalies in the large-scale CMB temperature sky measured by WMAP have been
suggested as possible evidence for a violation of statistical isotropy on large
scales. In any physical model for broken isotropy, there are testable
consequences for the CMB polarization field. We develop simulation tools for
predicting the polarization field in models that break statistical isotropy
locally through a modulation field. We study two different models: dipolar
modulation, invoked to explain the asymmetry in power between northern and
southern ecliptic hemispheres, and quadrupolar modulation, posited to explain
the alignments between the quadrupole and octopole. For the dipolar case, we
show that predictions for the correlation between the first 10 multipoles of
the temperature and polarization fields can typically be tested at better than
the 98% CL. For the quadrupolar case, we show that the polarization quadrupole
and octopole should be moderately aligned. Such an alignment is a generic
prediction of explanations which involve the temperature field at recombination
and thus discriminate against explanations involving foregrounds or local
secondary anisotropy. Predicted correlations between temperature and
polarization multipoles out to l = 5 provide tests at the ~ 99% CL or stronger
for quadrupolar models that make the temperature alignment more than a few
percent likely. As predictions of anomaly models, polarization statistics move
beyond the a posteriori inferences that currently dominate the field.Comment: 17 pages, 15 figures; published in PRD; references adde
An Examination of the Challenges Experienced by Canadian Ice-Hockey Players in the National Hockey League
Semistructured interviews were used in this study to learn about the challenges experienced by four groups of National Hockey League (NHL) players (N=11): prospects (n=3), rookies (n=3), veterans (n=2), and retirees (n=3). The database is comprised of 757 meaning units grouped into 11 contextual challenges pertaining to scouting demands, training camp, increased athletic demands, team expectations, and earning team trust. The veterans spoke mostly of challenges including scouting demands, athletic demands, and team expectations. Retirees considered mostly challenges pertaining to team expectations, athletic demands, lifestyle, media demands, transactions, cross-cultural encounters, and playoffs. An expert panel ensured that the interview guide, data analysis, and the findings represented the participants’ experiences in the NHL. Recommendations for practitioners and researchers working with NHL players are proposed
Impact of reionization on CMB polarization tests of slow-roll inflation
Estimates of inflationary parameters from the CMB B-mode polarization
spectrum on the largest scales depend on knowledge of the reionization history,
especially at low tensor-to-scalar ratio. Assuming an incorrect reionization
history in the analysis of such polarization data can strongly bias the
inflationary parameters. One consequence is that the single-field slow-roll
consistency relation between the tensor-to-scalar ratio and tensor tilt might
be excluded with high significance even if this relation holds in reality. We
explain the origin of the bias and present case studies with various tensor
amplitudes and noise characteristics. A more model-independent approach can
account for uncertainties about reionization, and we show that parametrizing
the reionization history by a set of its principal components with respect to
E-mode polarization removes the bias in inflationary parameter measurement with
little degradation in precision.Comment: 9 pages, 6 figures; submitted to Phys. Rev.
Thermo-mechanical sensitivity calibration of nanotorsional magnetometers
We report on the fabrication of sensitive nanotorsional resonators, which can
be utilized as magnetometers for investigating the magnetization dynamics in
small magnetic elements. The thermo-mechanical noise is calibrated with the
resonator displacement in order to determine the ultimate mechanical torque
sensitivity of the magnetometer.Comment: 56th Annual Conference on Magnetism and Magnetic Material
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