258 research outputs found
A statistical interpretation of the correlation between intermediate mass fragment multiplicity and transverse energy
Multifragment emission following Xe+Au collisions at 30, 40, 50 and 60 AMeV
has been studied with multidetector systems covering nearly 4-pi in solid
angle. The correlations of both the intermediate mass fragment and light
charged particle multiplicities with the transverse energy are explored. A
comparison is made with results from a similar system, Xe+Bi at 28 AMeV. The
experimental trends are compared to statistical model predictions.Comment: 7 pages, submitted to Phys. Rev.
Impact of Roots
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66547/2/10.1177_002193478601600306.pd
Control Law Design for Perching an Agile MAV with Articulated Wings
This paper explores the use of variable wing dihedral and variable wing twist (in conjunction
with a conventional horizontal elevator) to control an aircraft performing a perching
maneuver. A choice of controller architecture wherein the dihedral is employed in the
forward path and the elevator and twist are employed in the feedback path, is considered.
The aircraft is modeled as a multivariable linear time-varying system. A specific perching
trajectory is considered; and the open-loop aircraft is longitudinally unstable for a segment
of this perching trajectory and lateral-directionally unstable for the entire perching trajectory.
A multivariable time-varying controller is designed to efficiently stabilize the aircraft
as well as reject longitudinal-lateral-directional wind disturbances, while closely tracking
the reference perching trajectory
Monitoring changes in human activity during the COVID-19 shutdown in Las Vegas using infrasound microbarometers
While studies of urban acoustics are typically restricted to the audio range, anthropogenic activity also generates infrasound (<20 Hz, roughly at the lower end of the range of human hearing). Shutdowns related to the COVID-19 pandemic unintentionally created ideal conditions for the study of urban infrasound and low frequency audio (20-500 Hz), as closures reduced human-generated ambient noise, while natural signals remained relatively unaffected. An array of infrasound sensors deployed in Las Vegas, NV, provides data for a case study in monitoring human activity during the pandemic through urban acoustics. The array records a sharp decline in acoustic power following the temporary shutdown of businesses deemed nonessential by the state of Nevada. This decline varies spatially across the array, with stations close to McCarran International Airport generally recording the greatest declines in acoustic power. Further, declines in acoustic power fluctuate with the time of day. As only signals associated with anthropogenic activity are expected to decline, this gives a rough indication of periodicities in urban acoustics throughout Las Vegas. The results of this study reflect the city's response to the pandemic and suggest spatiotemporal trends in acoustics outside of shutdowns
Calibration of Plastic Phoswich Detectors for Charged Particle Detection
The response of an array of plastic phoswich detectors to ions of has been measured from =12 to 72 MeV. The detector response has been
parameterized by a three parameter fit which includes both quenching and high
energy delta-ray effects. The fits have a mean variation of with
respect to the data.Comment: 17 pages, 5 figure
Isospin Effects in Nuclear Multifragmentation
We develop an improved Statistical Multifragmentation Model that provides the
capability to calculate calorimetric and isotopic observables with precision.
With this new model we examine the influence of nuclear isospin on the fragment
elemental and isotopic distributions. We show that the proposed improvements on
the model are essential for studying isospin effects in nuclear
multifragmentation. In particular, these calculations show that accurate
comparisons to experimental data require that the nuclear masses, free energies
and secondary decay must be handled with higher precision than many current
models accord.Comment: 46 pages, 16 figure
Multifragment production in Au+Au at 35 MeV/u
Multifragment disintegration has been measured with a high efficiency
detection system for the reaction at . From the event
shape analysis and the comparison with the predictions of a many-body
trajectories calculation the data, for central collisions, are compatible with
a fast emission from a unique fragment source.Comment: 9 pages, LaTex file, 4 postscript figures available upon request from
[email protected]. - to appear in Phys. Lett.
Symmetries and Elasticity of Nematic Gels
A nematic liquid-crystal gel is a macroscopically homogeneous elastic medium
with the rotational symmetry of a nematic liquid crystal. In this paper, we
develop a general approach to the study of these gels that incorporates all
underlying symmetries. After reviewing traditional elasticity and clarifying
the role of broken rotational symmetries in both the reference space of points
in the undistorted medium and the target space into which these points are
mapped, we explore the unusual properties of nematic gels from a number of
perspectives. We show how symmetries of nematic gels formed via spontaneous
symmetry breaking from an isotropic gel enforce soft elastic response
characterized by the vanishing of a shear modulus and the vanishing of stress
up to a critical value of strain along certain directions. We also study the
phase transition from isotropic to nematic gels. In addition to being fully
consistent with approaches to nematic gels based on rubber elasticity, our
description has the important advantages of being independent of a microscopic
model, of emphasizing and clarifying the role of broken symmetries in
determining elastic response, and of permitting easy incorporation of spatial
variations, thermal fluctuations, and gel heterogeneity, thereby allowing a
full statistical-mechanical treatment of these novel materials.Comment: 21 pages, 4 eps figure
Non-Thermal Behavior in Multifragment Decay
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
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