10,694 research outputs found
Enabling Data-Driven Transportation Safety Improvements in Rural Alaska
Safety improvements require funding. A clear need must be demonstrated to secure funding. For transportation safety, data, especially data about past crashes, is the usual method of demonstrating need. However, in rural locations, such data is often not available, or is not in a form amenable to use in funding applications. This research aids rural entities, often federally recognized tribes and small villages acquire data needed for funding applications. Two aspects of work product are the development of a traffic counting application for an iPad or similar device, and a review of the data requirements of the major transportation funding agencies. The traffic-counting app, UAF Traffic, demonstrated its ability to count traffic and turning movements for cars and trucks, as well as ATVs, snow machines, pedestrians, bicycles, and dog sleds. The review of the major agencies demonstrated that all the likely funders would accept qualitative data and Road Safety Audits. However, quantitative data, if it was available, was helpful
Open string axions and the flavor problem
We consider extensions of the standard model inspired by intersecting D-brane
constructions, in order to address flavor mass textures. We include additional
anomalous gauge symmetries, and scalar fields to break them and to generate
Froggatt-Nielsen mass terms. Green-Schwarz axions are included to cancel mixed
anomalies rendering the models consistent. At low energies, a residual
anomalous global symmetry remains, and its associated pseudo-Goldstone mode
becomes the physical axion, which can be interpreted as an axion arising from
open string modes. General considerations show that such axions are very common
in D-brane models and can be completely incompatible with current bounds.
Astrophysical constraints are placed on the axion both by including neutrino
masses in the Froggatt-Nielsen scheme and considering QCD instanton
contributions to the axion mass. We find simple models where the axion decay
constant is in the allowed range, but only one such minimal model with this
property is free from excessive fine tunings elsewhere. We also note that
generically addressing flavor textures for the CKM matrix leads to
deconstructed extra dimensions.Comment: 30 pages, 2 figures. v2: references added. v3:typos fixe
Infinite dimensional stochastic differential equations of Ornstein-Uhlenbeck type
We consider the operator \sL f(x)=\tfrac12 \sum_{i,j=1}^\infty
a_{ij}(x)\frac{\del^2 f}{\del x_i \del x_j}(x)-\sum_{i=1}^\infty \lam_i x_i
b_i(x) \frac{\del f}{\del x_i}(x). We prove existence and uniqueness of
solutions to the martingale problem for this operator under appropriate
conditions on the , and \lam_i. The process corresponding to
\sL solves an infinite dimensional stochastic differential equation similar
to that for the infinite dimensional Ornstein-Uhlenbeck process
Mapping the dynamic interactions between vortex species in highly anisotropic superconductors
Here we use highly sensitive magnetisation measurements performed using a
Hall probe sensor on single crystals of highly anisotropic high temperature
superconductors to study the dynamic interactions
between the two species of vortices that exist in such superconductors. We
observe a remarkable and clearly delineated high temperature regime that
mirrors the underlying vortex phase diagram. Our results map out the parameter
space over which these dynamic interaction processes can be used to create
vortex ratchets, pumps and other fluxonic devices.Comment: 7 pages, 3 figures, to be published in Supercond. Sci. Techno
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