4,091 research outputs found
Investigations using data in Alabama from ERTS-A
There are no author-identified significant results in this report
The statistical analysis of a seiche record
The series analysed consists of 660 15 sec observations of the water level in a rock channel on the Wellington coast. Both correlogram and periodogram were employed in an attempt to isolate possible discrete components of the spectrum and to characterise the continuous component...
Minimal energy control of a nanoelectromechanical memory element
The Pontryagin minimal energy control approach has been applied to minimise the switching energy in a nanoelectromechanical memory system and to characterise global stability of the oscillatory states of the bistable memory element. A comparison of two previously experimentally determined pulse-type control signals with Pontryagin control function has been performed, and the superiority of the Pontryagin approach with regard to power consumption has been demonstrated. An analysis of global stability shows how values of minimal energy can be utilized in order to specify equally stable states
Human response to vibration in residential environments (NANR209), technical report 2: measurement of response
Based on a review of the literature and the best practice guidance available, a social survey questionnaire was developed to measure residents’ self-reported annoyance and to provide data suitable for establishing exposure-response relationships between levels of annoyance and levels of vibration. The development of the questionnaire was influenced by a number of previous studies such as: the social survey questionnaire developed for the NANR172 Pilot Study of this research (Defra, 2007); best practice guidelines for the development of socio-acoustic surveys issued by ICBEN and presented in the current International Standard (Fields et al., 2001; ISO/TS 15666:2003); the Nordtest Method (2001) for the development of socio-vibration surveys, and a peer review of the social survey questionnaire by international experts in the field. In order to avoid influencing responses and reasons for participation in the research, the survey was introduced as a survey of neighbourhood satisfaction. The questionnaire design, through the use of sections, enables new sections to be added to the questionnaire so that specific vibration sources can be investigated in more depth. In addressing the ‘response’ component in the ‘exposure-response’ relationship, the questionnaire was designed to yield interval-level measurement data suitable for analysis with vibration measurement data via two response scales: the five-point semantic and the eleven-point numerical scales. This decision was largely founded upon the ability of the two scales to meet the criteria established by ICBEN (Fields et al., 2001) for socio-acoustic survey design. Detailed procedures were documented, following the field trial of the questionnaire, in terms of the role of the interviewer, the recording of information and the transfer of the data to the relevant database for subsequent analysis and to inform the vibration team responsible for the ‘exposure’ component of this research project
HST Observations of the Double-Peaked Emission Lines in the Seyfert Galaxy Markarian 78: Mass Outflows from a Single AGN
Previous ground based observations of the Seyfert 2 galaxy Mrk 78 revealed a
double set of emission lines, similar to those seen in several AGN from recent
surveys. Are the double lines due to two AGN with different radial velocities
in the same galaxy, or are they due to mass outflows from a single AGN?We
present a study of the outflowing ionized gas in the resolved narrow-line
region (NLR) of Mrk 78 using observations from Space Telescope Imaging
Spectrograph (STIS) and Faint Object Camera (FOC) aboard the Hubble Space
Telescope(HST) as part of an ongoing project to determine the kinematics and
geometries of active galactic nuclei (AGN) outflows. From the spectroscopic
information, we deter- mined the fundamental geometry of the outflow via our
kinematics modeling program by recreating radial velocities to fit those seen
in four different STIS slit positions. We determined that the double emission
lines seen in ground-based spectra are due to an asymmetric distribution of
outflowing gas in the NLR. By successfully fitting a model for a single AGN to
Mrk 78, we show that it is possible to explain double emission lines with
radial velocity offsets seen in AGN similar to Mrk 78 without requiring dual
supermassive black holes.Comment: 22 pages, 7 figures (2 color), accepted for publication in The
Astrophysical Journa
Locally Optimal Control of Quantum Systems with Strong Feedback
For quantum systems with high purity, we find all observables that, when
continuously monitored, maximize the instantaneous reduction in the von Neumann
entropy. This allows us to obtain all locally optimal feedback protocols with
strong feedback, and explicit expressions for the best such protocols for
systems of size N <= 4. We also show that for a qutrit the locally optimal
protocol is the optimal protocol for a given range of control times, and derive
an upper bound on all optimal protocols with strong feedback.Comment: 4 pages, Revtex4. v2: published version (some errors corrected
Thin Animals
Lattice animals provide a discretized model for the theta transition
displayed by branched polymers in solvent. Exact graph enumeration studies have
given some indications that the phase diagram of such lattice animals may
contain two collapsed phases as well as an extended phase. This has not been
confirmed by studies using other means. We use the exact correspondence between
the q --> 1 limit of an extended Potts model and lattice animals to investigate
the phase diagram of lattice animals on phi-cubed random graphs of arbitrary
topology (``thin'' random graphs). We find that only a two phase structure
exists -- there is no sign of a second collapsed phase.
The random graph model is solved in the thermodynamic limit by saddle point
methods. We observe that the ratio of these saddle point equations give
precisely the fixed points of the recursion relations that appear in the
solution of the model on the Bethe lattice by Henkel and Seno. This explains
the equality of non-universal quantities such as the critical lines for the
Bethe lattice and random graph ensembles.Comment: Latex, 10 pages plus 6 ps/eps figure
Clues to Quasar Broad Line Region Geometry and Kinematics
We present evidence that the high-velocity CIV lambda 1549 emission line gas
of radio-loud quasars may originate in a disk-like configuration, in close
proximity to the accretion disk often assumed to emit the low-ionization lines.
For a sample of 36 radio-loud z~2 quasars we find the 20--30% peak width to
show significant inverse correlations with the fractional radio core-flux
density, R, the radio axis inclination indicator. Highly inclined systems have
broader line wings, consistent with a high-velocity field perpendicular to the
radio axis. By contrast, the narrow line-core shows no such relation with R, so
the lowest velocity CIV-emitting gas has an inclination independent velocity
field. We propose that this low-velocity gas is located at higher
disk-altitudes than the high-velocity gas. A planar origin of the high-velocity
CIV-emission is consistent with the current results and with an accretion
disk-wind emitting the broad lines. A spherical distribution of randomly
orbiting broad-line clouds and a polar high-ionization outflow are ruled out.Comment: 5 Latex pages, 1 figure, accepted for publication in ApJ Letter
Computer model calibration with large non-stationary spatial outputs: application to the calibration of a climate model
Bayesian calibration of computer models tunes unknown input parameters by
comparing outputs with observations. For model outputs that are distributed
over space, this becomes computationally expensive because of the output size.
To overcome this challenge, we employ a basis representation of the model
outputs and observations: we match these decompositions to carry out the
calibration efficiently. In the second step, we incorporate the non-stationary
behaviour, in terms of spatial variations of both variance and correlations, in
the calibration. We insert two integrated nested Laplace
approximation-stochastic partial differential equation parameters into the
calibration. A synthetic example and a climate model illustration highlight the
benefits of our approach
Incentivizing Exploration with Heterogeneous Value of Money
Recently, Frazier et al. proposed a natural model for crowdsourced
exploration of different a priori unknown options: a principal is interested in
the long-term welfare of a population of agents who arrive one by one in a
multi-armed bandit setting. However, each agent is myopic, so in order to
incentivize him to explore options with better long-term prospects, the
principal must offer the agent money. Frazier et al. showed that a simple class
of policies called time-expanded are optimal in the worst case, and
characterized their budget-reward tradeoff.
The previous work assumed that all agents are equally and uniformly
susceptible to financial incentives. In reality, agents may have different
utility for money. We therefore extend the model of Frazier et al. to allow
agents that have heterogeneous and non-linear utilities for money. The
principal is informed of the agent's tradeoff via a signal that could be more
or less informative.
Our main result is to show that a convex program can be used to derive a
signal-dependent time-expanded policy which achieves the best possible
Lagrangian reward in the worst case. The worst-case guarantee is matched by
so-called "Diamonds in the Rough" instances; the proof that the guarantees
match is based on showing that two different convex programs have the same
optimal solution for these specific instances. These results also extend to the
budgeted case as in Frazier et al. We also show that the optimal policy is
monotone with respect to information, i.e., the approximation ratio of the
optimal policy improves as the signals become more informative.Comment: WINE 201
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