18,519 research outputs found
Constraining crystalline color superconducting quark matter with gravitational-wave data
We estimate the maximum equatorial ellipticity sustainable by compact stars
composed of crystalline color-superconducting quark matter. For the
theoretically allowed range of the gap parameter , the maximum
ellipticity could be as large as , which is about 4 orders of
magnitude larger than the tightest upper limit obtained by the recent science
runs of the LIGO and GEO600 gravitational wave detectors based on the data from
78 radio pulsars. We point out that the current gravitational-wave strain upper
limit already has some implications for the gap parameter. In particular, the
upper limit for the Crab pulsar implies that is less than O(20) MeV
for a range of quark chemical potential accessible in compact stars, assuming
that the pulsar has a mass , radius 10 km, breaking strain
, and that it has the maximum quadrupole deformation it can sustain
without fracturing.Comment: Minor changes to match the published versio
High Fidelity State Transfer Over an Unmodulated Linear XY Spin Chain
We provide a class of initial encodings that can be sent with a high fidelity
over an unmodulated, linear, XY spin chain. As an example, an average fidelity
of ninety-six percent can be obtained using an eleven-spin encoding to transmit
a state over a chain containing ten-thousand spins. An analysis of the magnetic
field dependence is given, and conditions for field optimization are provided.Comment: Replaced with published version. 8 pages, 5 figure
Social Game for Building Energy Efficiency: Utility Learning, Simulation, and Analysis
We describe a social game that we designed for encouraging energy efficient
behavior amongst building occupants with the aim of reducing overall energy
consumption in the building. Occupants vote for their desired lighting level
and win points which are used in a lottery based on how far their vote is from
the maximum setting. We assume that the occupants are utility maximizers and
that their utility functions capture the tradeoff between winning points and
their comfort level. We model the occupants as non-cooperative agents in a
continuous game and we characterize their play using the Nash equilibrium
concept. Using occupant voting data, we parameterize their utility functions
and use a convex optimization problem to estimate the parameters. We simulate
the game defined by the estimated utility functions and show that the estimated
model for occupant behavior is a good predictor of their actual behavior. In
addition, we show that due to the social game, there is a significant reduction
in energy consumption
Freeform Extrusion of High Solids Loading Ceramic Slurries, Part II: Extrusion Process Control
Part I of this paper provided a detailed description of a novel fabrication machine for high solids
loading ceramic slurry extrusion and presented an empirical model of the ceramic extrusion
process, with ram velocity as the input and extrusion force as the output. A constant force is
desirable in freeform extrusion processes as it correlates with a constant material deposition rate
and, thus, good part quality. The experimental results in Part I demonstrated that a constant ram
velocity will produce a transient extrusion force. In some instances the extrusion force increased
until ram motor skipping occurred. Further, process disturbances, such as air bubble release and
nozzle clogging that cause sudden changes in extrusion force, were often present. In this paper a
feedback controller for the ceramic extrusion process is designed and experimentally
implemented. The controller intelligently adjusts the ram motor velocity to maintain a constant
extrusion force. Since there is tremendous variability in the extrusion process characteristics, an
on-off controller is utilized in this paper. Comparisons are made between parts fabricated with
and without the feedback control. It is demonstrated that the use of the feedback control reduces
the effect of process disturbances (i.e., air bubble release and nozzle clogging) and dramatically
improves part quality.Mechanical Engineerin
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