8,178 research outputs found
Are the Kepler Near-Resonance Planet Pairs due to Tidal Dissipation?
The multiple-planet systems discovered by the Kepler mission show an excess
of planet pairs with period ratios just wide of exact commensurability for
first-order resonances like 2:1 and 3:2. In principle, these planet pairs could
have both resonance angles associated with the resonance librating if the
orbital eccentricities are sufficiently small, because the width of first-order
resonances diverges in the limit of vanishingly small eccentricity. We consider
a widely-held scenario in which pairs of planets were captured into first-order
resonances by migration due to planet-disk interactions, and subsequently
became detached from the resonances, due to tidal dissipation in the planets.
In the context of this scenario, we find a constraint on the ratio of the
planet's tidal dissipation function and Love number that implies that some of
the Kepler planets are likely solid. However, tides are not strong enough to
move many of the planet pairs to the observed separations, suggesting that
additional dissipative processes are at play.Comment: 20 pages, including 7 figures; accepted for publication in Ap
Defect Modes in One-Dimensional Granular Crystals
We study the vibrational spectra of one-dimensional statically compressed
granular crystals (arrays of elastic particles in contact) containing defects.
We focus on the prototypical settings of one or two spherical defects
(particles of smaller radii) interspersed in a chain of larger uniform
spherical particles. We measure the near-linear frequency spectrum within the
spatial vicinity of the defects, and identify the frequencies of the localized
defect modes. We compare the experimentally determined frequencies with those
obtained by numerical eigen-analysis and by analytical expressions based on
few-site considerations. We also present a brief numerical and experimental
example of the nonlinear generalization of a single-defect localized mode
Assessment of ultraviolet light disinfection efficiency of advanced wastewater treatment plant effluent
Pilot-scale operation of a 3-bank UV disinfection system for filter effluent from the Clark County Advanced Wastewater Treatment Plant has shown {dollar}\u3e{dollar}4-log removal of seeded MS-2 coliphage at UV dosages of 80-100 milliwatt-seconds per square centimeter (mW-s/cm{dollar}\sp2{dollar}), and consistent removal of fecal and total coliforms to less than 2.2 MPN/100 mL at dosages in the vicinity of 50-80 mW-s/cm{dollar}\sp2{dollar} UV transmittance varied from 40% to 70% over the monitoring period and was strongly correlated with turbidity. No diurnal variations in effluent quality were detected during intensive sampling. Effluent quality was most strongly affected by storm events that change filter operation conditions. Rapid biological fouling occurred on the off-line banks. Inorganic fouling of on-line banks was minimal. Assuming a worst case UV transmittance (%) and required treatment dosage (mW-s/cm{dollar}\sp2),{dollar} treatment capacity of this 30-foot long, 6-lamp system was 0.10 million gallons per day
A Processor Core Model for Quantum Computing
We describe an architecture based on a processing 'core' where multiple
qubits interact perpetually, and a separate 'store' where qubits exist in
isolation. Computation consists of single qubit operations, swaps between the
store and the core, and free evolution of the core. This enables computation
using physical systems where the entangling interactions are 'always on'.
Alternatively, for switchable systems our model constitutes a prescription for
optimizing many-qubit gates. We discuss implementations of the quantum Fourier
transform, Hamiltonian simulation, and quantum error correction.Comment: 5 pages, 2 figures; improved some arguments as suggested by a refere
On the 2:1 Orbital Resonance in the HD 82943 Planetary System
We present an analysis of the HD 82943 planetary system based on a radial
velocity data set that combines new measurements obtained with the Keck
telescope and the CORALIE measurements published in graphical form. We examine
simultaneously the goodness of fit and the dynamical properties of the best-fit
double-Keplerian model as a function of the poorly constrained eccentricity and
argument of periapse of the outer planet's orbit. The fit with the minimum
chi_{nu}^2 is dynamically unstable if the orbits are assumed to be coplanar.
However, the minimum is relatively shallow, and there is a wide range of fits
outside the minimum with reasonable chi_{nu}^2. For an assumed coplanar
inclination i = 30 deg. (sin i = 0.5), only good fits with both of the lowest
order, eccentricity-type mean-motion resonance variables at the 2:1
commensurability, theta_1 and theta_2, librating about 0 deg. are stable. For
sin i = 1, there are also some good fits with only theta_1 (involving the inner
planet's periapse longitude) librating that are stable for at least 10^8 years.
The libration semiamplitudes are about 6 deg. for theta_1 and 10 deg. for
theta_2 for the stable good fit with the smallest libration amplitudes of both
theta_1 and theta_2. We do not find any good fits that are non-resonant and
stable. Thus the two planets in the HD 82943 system are almost certainly in 2:1
mean-motion resonance, with at least theta_1 librating, and the observations
may even be consistent with small-amplitude librations of both theta_1 and
theta_2.Comment: 24 pages, including 10 figures; accepted for publication in Ap
Inherent Structures for Soft Long-Range Interactions in Two-Dimensional Many-Particle Systems
We generate inherent structures, local potential-energy minima, of the
"-space overlap potential" in two-dimensional many-particle systems using a
cooling and quenching simulation technique. The ground states associated with
the -space overlap potential are stealthy ({\it i.e.,} completely suppress
single scattering of radiation for a range of wavelengths) and hyperuniform
({\it i.e.,} infinite wavelength density fluctuations vanish). However, we show
via quantitative metrics that the inherent structures exhibit a range of
stealthiness and hyperuniformity depending on the fraction of degrees of
freedom that are constrained. Inherent structures in two dimensions typically
contain five-particle rings, wavy grain boundaries, and vacancy-interstitial
defects. The structural and thermodynamic properties of inherent structures are
relatively insensitive to the temperature from which they are sampled,
signifying that the energy landscape is relatively flat and devoid of deep
wells. Using the nudged-elastic-band algorithm, we construct paths from
ground-state configurations to inherent structures and identify the transition
points between them. In addition, we use point patterns generated from a random
sequential addition (RSA) of hard disks, which are nearly stealthy, and examine
the particle rearrangements necessary to make the configurations absolutely
stealthy. We introduce a configurational proximity metric to show that only
small local, but collective, particle rearrangements are needed to drive
initial RSA configurations to stealthy disordered ground states. These results
lead to a more complete understanding of the unusual behaviors exhibited by the
family of "collective-coordinate" potentials to which the -space overlap
potential belongs.Comment: 36 pages, 16 figure
Inherent Mach-Zehnder interference with "which-way" detection for single particle scattering in one dimension
We study the coherent transport of single photon in a one-dimensional
coupled-resonator-array, "non-locally" coupled to a two-level system. Since its
inherent structure is a Mach-Zehnder interferometer, we explain the destructive
interference phenomenon of the transmission spectrums according to the effect
of which-way detection. The quantum realization of the present model is a
nano-electromechanical resonator arrays with two nearest resonators coupled to
a single spin via their attached magnetic tips. Its classical simulation is a
waveguide of coupled defected cavity array with double couplings to a side
defected cavity.Comment: 5 papges, 4 figure
Integration of a wireless sensor network project for introductory circuits and systems teaching
This paper presents an integration of a wireless sensor network design project in an introductory course about circuits and systems. In the project, students will design a wireless sensor network that constitutes of sensors, for a creative surveillance application. Through a versatile project vehicle, project-oriented learning modules, a comprehensive assessment strategy and public learning communities, students can learn contemporary concepts of circuits and systems from the system perspective, as well as develop ability to design a basic electronic system. © 2013 IEEE.published_or_final_versio
Incorporating Inertia Into Multi-Agent Systems
We consider a model that demonstrates the crucial role of inertia and
stickiness in multi-agent systems, based on the Minority Game (MG). The inertia
of an agent is introduced into the game model by allowing agents to apply
hypothesis testing when choosing their best strategies, thereby reducing their
reactivity towards changes in the environment. We find by extensive numerical
simulations that our game shows a remarkable improvement of global cooperation
throughout the whole phase space. In other words, the maladaptation behavior
due to over-reaction of agents is removed. These agents are also shown to be
advantageous over the standard ones, which are sometimes too sensitive to
attain a fair success rate. We also calculate analytically the minimum amount
of inertia needed to achieve the above improvement. Our calculation is
consistent with the numerical simulation results. Finally, we review some
related works in the field that show similar behaviors and compare them to our
work.Comment: extensively revised, 8 pages, 10 figures in revtex
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