6,118 research outputs found
Alien Registration- Landry, Emma C. (Solon, Somerset County)
https://digitalmaine.com/alien_docs/4372/thumbnail.jp
Efficient characterization of blinking quantum emitters from scarce data sets via machine learning
Single photon emitters are core building blocks of quantum technologies, with
established and emerging applications ranging from quantum computing and
communication to metrology and sensing. Regardless of their nature, quantum
emitters universally display fluorescence intermittency or photoblinking:
interaction with the environment can cause the emitters to undergo quantum
jumps between on and off states that correlate with higher and lower
photoemission events, respectively. Understanding and quantifying the mechanism
and dynamics of photoblinking is important for both fundamental and practical
reasons. However, the analysis of blinking time traces is often afflicted by
data scarcity. Blinking emitters can photo-bleach and cease to fluoresce over
time scales that are too short for their photodynamics to be captured by
traditional statistical methods. Here, we demonstrate two approaches based on
machine learning that directly address this problem. We present a multi-feature
regression algorithm and a genetic algorithm that allow for the extraction of
blinking on/off switching rates with >85% accuracy, and with >10x less data and
>20x higher precision than traditional methods based on statistical inference.
Our algorithms effectively extend the range of surveyable blinking systems and
trapping dynamics to those that would otherwise be considered too short-lived
to be investigated. They are therefore a powerful tool to help gain a better
understanding of the physical mechanism of photoblinking, with practical
benefits for applications based on quantum emitters that rely on either
mitigating or harnessing the phenomenon
Wind Turbines and Coastal Recreation Demand
We examine the impact of coastal wind turbines on coastal tourism and recreation for residents of the northern CAMA counties in North Carolina. A combination of telephone and web survey data are used to assess the impact of coastal wind farms on trip behavior and site choice. Most of the respondents to our telephone survey claim to support offshore wind energy development, and independent survey data suggest that the observed levels of support may be indicative of the broader population in this region. Overall, we find very little impact of coastal wind turbines on aggregate recreational visitation; loss in consumer surplus associated with wide spread wind development in the coastal zone is insignificant at 55 per household. On average, we find no evidence of aversion to wind farms 4 miles out in the ocean, or for wind farms located in coastal estuaries. For all wind farm scenarios, we find evidence of preference heterogeneityâ some respondents find this appealing while others find it aversive. Key Words: Recreation demand, tourism, renewable energy
Impulse distributions in dense granular flows: signatures of large-scale spatial structures
In this paper we report the results of simulations of a 2D gravity driven,
dissipative granular flow through a hopper system. Measurements of impulse
distributions P(I) on the simulated system show flow-velocity-invariant
behavior of the distribution for impulses larger than the average impulse .
For small impulses, however, P(I) decreases significantly with flow velocity, a
phenomenon which can be attributed exclusively to collisions between grains
undergoing frequent collisions. Visualizations of the system also show that
these frequently colliding particles tend to form increasingly large linear
clusters as the flow velocity decreases. A model is proposed for the form of
P(I), given distributions of cluster size and velocity, which accurately
predicts the observed form of the distribution. Thus the impulse distribution
provides some insight into the formation and properties of these ``dynamic''
force chains.Comment: 4 pages, 4 figure
A new atmospheric aerosol phase equilibrium model (UHAERO): organic systems
In atmospheric aerosols, water and volatile inorganic and organic species are distributed between the gas and aerosol phases in accordance with thermodynamic equilibrium. Within an atmospheric particle, liquid and solid phases can exist at equilibrium. Models exist for computation of phase equilibria for inorganic/water mixtures typical of atmospheric aerosols; when organic species are present, the phase equilibrium problem is complicated by organic/water interactions as well as the potentially large number of organic species. We present here an extension of the UHAERO inorganic thermodynamic model (Amundson et al., 2006c) to organic/water systems. Phase diagrams for a number of model organic/water systems characteristic of both primary and secondary organic aerosols are computed. Also calculated are inorganic/organic/water phase diagrams that show the effect of organics on inorganic deliquescence behavior. The effect of the choice of activity coefficient model for organics on the computed phase equilibria is explored
Going Home: Evacuation-Migration Decisions of Hurricane Katrina Survivors
In the wake of Hurricane Katrina, many evacuees from the Gulf region began the difficult process of deciding whether to rebuild or restart elsewhere. We examine pre-Katrina Gulf residentsâ decision to return to the post-disaster Gulf regionâwhich we call the âreturn migrationâ decision. We estimate two separate return migration models, first utilizing data from a mail survey of individuals in the affected region and then focusing on self-administered questionnaires of evacuees in Houston. Our results indicate that return migration can be affected by household income; age; education level; employment, marital and home ownership status; but the results depend upon the population under consideration. We find no impact of âconnection to placeâ on the return migration decision. While the impact of income is relatively small, we find that the real wage differential between home and host region influences the likelihood of return. Larger implicit costs, in terms of foregone wages for returning, induce a lower likelihood of return. Exploiting this difference at the individual level, we are able to produce estimates of willingness to pay to return home. Average WTP to return home for a sample of relatively poor households is estimated at 3,954 per year.
Granular packings with moving side walls
The effects of movement of the side walls of a confined granular packing are
studied by discrete element, molecular dynamics simulations. The dynamical
evolution of the stress is studied as a function of wall movement both in the
direction of gravity as well as opposite to it. For all wall velocities
explored, the stress in the final state of the system after wall movement is
fundamentally different from the original state obtained by pouring particles
into the container and letting them settle under the influence of gravity. The
original packing possesses a hydrostatic-like region at the top of the
container which crosses over to a depth-independent stress. As the walls are
moved in the direction opposite to gravity, the saturation stress first reaches
a minimum value independent of the wall velocity, then increases to a
steady-state value dependent on the wall-velocity. After wall movement ceases
and the packing reaches equilibrium, the stress profile fits the classic
Janssen form for high wall velocities, while it has some deviations for low
wall velocities. The wall movement greatly increases the number of
particle-wall and particle-particle forces at the Coulomb criterion. Varying
the wall velocity has only small effects on the particle structure of the final
packing so long as the walls travel a similar distance.Comment: 11 pages, 10 figures, some figures in colo
Phonon Band Structure and Thermal Transport Correlation in a Layered Diatomic Crystal
To elucidate the relationship between a crystal's structure, its thermal
conductivity, and its phonon dispersion characteristics, an analysis is
conducted on layered diatomic Lennard-Jones crystals with various mass ratios.
Lattice dynamics theory and molecular dynamics simulations are used to predict
the phonon dispersion curves and the thermal conductivity. The layered
structure generates directionally dependent thermal conductivities lower than
those predicted by density trends alone. The dispersion characteristics are
quantified using a set of novel band diagram metrics, which are used to assess
the contributions of acoustic phonons and optical phonons to the thermal
conductivity. The thermal conductivity increases as the extent of the acoustic
modes increases, and decreases as the extent of the stop bands increases. The
sensitivity of the thermal conductivity to the band diagram metrics is highest
at low temperatures, where there is less anharmonic scattering, indicating that
dispersion plays a more prominent role in thermal transport in that regime. We
propose that the dispersion metrics (i) provide an indirect measure of the
relative contributions of dispersion and anharmonic scattering to the thermal
transport, and (ii) uncouple the standard thermal conductivity
structure-property relation to that of structure-dispersion and
dispersion-property relations, providing opportunities for better understanding
of the underlying physical mechanisms and a potential tool for material design.Comment: 30 pages, 10 figure
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