9,909 research outputs found
A land mobile satellite data system
The Telesat Mobile Incorporated (TMI) Mobile Data System (MDS) was developed to apply satellite technology to the transportation industry's requirement for a fleet management system. It will provide two-way messaging and automatic position reporting capabilities between dispatch centers and customers' fleets of trucks. The design was based on the Inmarsat L-Band space segment with system link parameters and margins adjusted to meet the land mobile satellite channel characteristics. The system interfaces with the Teleglobe Des Laurentides earth station at Weir, Quebec. The signaling protocols were derived from the Inmarsat Standard C packet signalling system with unique trucking requirements incorporated where necessary
Bipolar High Field Excitations in Co/Cu/Co Nanopillars
Current-induced magnetic excitations in Co/Cu/Co bilayer nanopillars
(50 nm in diameter) have been studied experimentally at low temperatures
for large applied fields perpendicular to the layers. At sufficiently high
current densities excitations, which lead to a decrease in differential
resistance, are observed for both current polarities. Such bipolar excitations
are not expected in a single domain model of spin-transfer. We propose that at
high current densities strong asymmetries in the longitudinal spin accumulation
cause spin-wave instabilities transverse to the current direction in bilayer
samples, similar to those we have reported for single magnetic layer junctions.Comment: 4 pages, 4 figures+ 2 additional jpg figures (Fig. 2d and Fig. 3)
high resolution figures and recent related articles are available at:
http://www.physics.nyu.edu/kentlab/news.htm
Temperature dependent nucleation and propagation of domain walls in a sub-100 nm perpendicularly magnetized Co/Ni multilayer
We present a study of the temperature dependence of the switching fields in
Co/Ni-based perpendicularly magnetized spin-valves. While magnetization
reversal of all-perpendicular Co/Ni spin valves at ambient temperatures is
typically marked by a single sharp step change in resistance, low temperature
measurements can reveal a series of resistance steps, consistent with
non-uniform magnetization configurations. We propose a model that consists of
domain nucleation, propagation and annihilation to explain the temperature
dependence of the switching fields. Interestingly, low temperature (<30 K) step
changes in resistance that we associate with domain nucleation, have a bimodal
switching field and resistance step distribution, attributable to two competing
nucleation pathways.Comment: 5 pages, 4 figure
Temperature dependence of the switching field distributions in all-perpendicular spin-valve nanopillars
We present temperature dependent switching measurements of the Co/Ni
multilayered free element of 75 nm diameter spin-valve nanopillars. Angular
dependent hysteresis measurements as well as switching field measurements taken
at low temperature are in agreement with a model of thermal activation over a
perpendicular anisotropy barrier. However, the statistics of switching (mean
switching field and switching variance) from 20 K up to 400 K are in
disagreement with a N\'{e}el-Brown model that assumes a temperature independent
barrier height and anisotropy field. We introduce a modified N\'{e}el-Brown
model thats fit the experimental data in which we take a dependence
to the barrier height and the anisotropy field due to the temperature dependent
magnetization and anisotropy energy.Comment: 5 pages, 4 figure
Current Induced Excitations in Cu/Co/Cu Single Ferromagnetic Layer Nanopillars
Current-induced magnetic excitations in Cu/Co/Cu single layer nanopillars
(~50 nm in diameter) have been studied experimentally as a function of Co layer
thickness at low temperatures for large applied fields perpendicular to the
layers. For asymmetric junctions current induced excitations are observed at
high current densities for only one polarity of the current and are absent at
the same current densities in symmetric junctions. These observations confirm
recent predictions of spin-transfer torque induced spin wave excitations in
single layer junctions with a strong asymmetry in the spin accumulation in the
leads.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Producers' Use of Crop Borders for Management of Potato Virus Y (PVY) in Seed Potatoes
Potato virus Y (PVY) is a very serious problem throughout most major seed potato producing states. Seed potato producers in Minnesota and North Dakota were surveyed in early 2005 to assess their perception of the profitability and risks associated with using crop borders to manage PVY in seed lots. Five of the 23 producers responding (a 25% response rate) said they had used crop borders in 2004. These 23 producers entered 152 seed lots into state seed certification programs. On average, producers had less than 0.1 seed lots rejected for PVY based on summer inspection. The average number of seed lots rejected in winter trials was 1.7. Of the 152 seed lots, these producers said they had entered into state seed certification programs, they reported detailed information on 108 lots. Generations 1 and 2 were the most likely generations to be protected by a crop border. Of these 108 seed lots, 104 passed summer inspection for PVY. Seventy-four percent of the 89 lots sent in for the winter test were reported to have passed. The use of crop borders was significant in explaining whether a seed lot had passed the winter test or not. Thirty-one (97%) of the 32 seed lots that were planted within a crop border passed the winter test while 31 (54%) of the 57 seed lots that were not planted with a crop border passed the winter test. No relationship was found between the choice of border crop and passing the winter test. Producers also were asked to state their agreement or disagreement with several statements regarding their knowledge and opinions on use of crop borders.Crop Production/Industries,
Conceptual Model-Based Reasoning for Knowledge-Based Software Project Management
This paper presents a conceptual model for software project management and the power derived from using a conceptual model-based reasoning approach in building intelligent decision-support systems. The Software Project Manager (SPM) has been prototyped in Inference Corporation\u27s Automated Reasoning Tool (ART) on Symbolics artificial intelligence (Al) workstations. This prototype conceptual model is an outgrowth of research con- ducted under the Knowledge-Based Software Project Management project at Lockheed Software Technology Center in Austin, Texas. In this paper, we present an overview of the management model underlying SPM and define the essential concepts and relationships needed to model the project management domain. We then describe the knowledge representation strategy used to implement this conceptual model. Finally, we illustrate the power of using conceptual model-based reasoning in building intelligent decision-support systems for the project management domain
Real World Interpretations of Quantum Theory
I propose a new class of interpretations, {\it real world interpretations},
of the quantum theory of closed systems. These interpretations postulate a
preferred factorization of Hilbert space and preferred projective measurements
on one factor. They give a mathematical characterisation of the different
possible worlds arising in an evolving closed quantum system, in which each
possible world corresponds to a (generally mixed) evolving quantum state. In a
realistic model, the states corresponding to different worlds should be
expected to tend towards orthogonality as different possible quasiclassical
structures emerge or as measurement-like interactions produce different
classical outcomes. However, as the worlds have a precise mathematical
definition, real world interpretations need no definition of quasiclassicality,
measurement, or other concepts whose imprecision is problematic in other
interpretational approaches. It is natural to postulate that precisely one
world is chosen randomly, using the natural probability distribution, as the
world realised in Nature, and that this world's mathematical characterisation
is a complete description of reality.Comment: Minor revisions. To appear in Foundations of Physic
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