2,938 research outputs found
Can the Pioneer anomaly be of gravitational origin? A phenomenological answer
In order to satisfy the equivalence principle, any non-conventional mechanism
proposed to gravitationally explain the Pioneer anomaly, in the form in which
it is presently known from the so-far analyzed Pioneer 10/11 data, cannot leave
out of consideration its impact on the motion of the planets of the Solar
System as well, especially those orbiting in the regions in which the anomalous
behavior of the Pioneer probes manifested itself. In this paper we, first,
discuss the residuals of the right ascension \alpha and declination \delta of
Uranus, Neptune and Pluto obtained by processing various data sets with
different, well established dynamical theories (JPL DE, IAA EPM, VSOP). Second,
we use the latest determinations of the perihelion secular advances of some
planets in order to put on the test two gravitational mechanisms recently
proposed to accommodate the Pioneer anomaly based on two models of modified
gravity. Finally, we adopt the ranging data to Voyager 2 when it encountered
Uranus and Neptune to perform a further, independent test of the hypothesis
that a Pioneer-like acceleration can also affect the motion of the outer
planets of the Solar System. The obtained answers are negative.Comment: Latex2e, 26 pages, 6 tables, 2 figure, 47 references. It is the
merging of gr-qc/0608127, gr-qc/0608068, gr-qc/0608101 and gr-qc/0611081.
Final version to appear in Foundations of Physic
The Newcastle Earthquake Experience: The Human Context and its Implications for Disaster Management
This paper is concerned with the psychological impact of the Newcastle earthquake during the first twelve months after its occurrence and with the implications for disaster management. As most disaster workers are aware, the N.S.W. Disaster Welfare Plan identifies Health Services as being responsible for counselling services following a disaster. Accordingly, following the Newcastle earthquake on 28th December, 1989 the Hunter Area Health Service established a Disaster Counselling Service. This Service involved identified strands for primary counselling, specialist counselling, stress debriefing services and counselling for ethnic communities. A Co-ordinator was appointed to assume responsibility for the overall co-ordination of services. The Disaster Counselling Services Committee was established and consisted of the Co-ordinator, a consultant (a psychiatrist), an Administrative Officer, and Co-ordinators of Primary Counselling Services, Specialist Counselling Services, and Stress Debriefing Services, a Professor of Psychiatry and two staff members from existing Community Health Centres. The Committee's role was to monitor service provision and to discuss issues pertinent to service delivery. The Consultant was responsible for the initial educative process for personnel from Health and other organisations with a view to assisting them to function optimally in their roles dealing with clients. The Administrative Officer was responsible for the smooth day-to-day functioning of the identified strands of the Services
Robot mapping and localisation in metal water pipes using hydrophone induced vibration and map alignment by dynamic time warping
Water is a highly valuable resource so asset management of associated infrastructure is of critical importance. Water distribution pipe networks are usually buried, and so are difficult to access. Robots are therefore appealing for performing inspection and detecting damage to target repairs. However, robot mapping and localisation of buried water pipes has not been widely investigated to date, and is challenging because pipes tend to be relatively featureless. In this paper we propose a mapping and localisation algorithm for metal water pipes with two key novelties: the development of a new type of map based on hydrophone induced vibration signals of metal pipes, and a mapping algorithm based on spatial warping and averaging of dead reckoning signals used to calibrate the map (using dynamic time warping). Localisation is performed using both terrain-based extended Kalman filtering and also particle filtering. We successfully demonstrate and evaluate the approach on a combination of experimental and simulation data, showing improved localisation compared to dead reckoning
Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings
<p>Highly reflective dielectric mirror coatings are critical components in a range of precision optics applications including frequency combs, optical atomic clocks, precision interferometry and ring laser gyroscopes. A key limitation to the performance in these applications is thermal noise, arising from the mechanical loss of the coatings. The origins of the mechanical loss from these coatings is not well understood.</p>
<p>Recent work suggests that the mechanical loss of amorphous Ta2O5 coatings can drop by as much as 40% when it is doped with TiO2. We use a combination of electron diffraction data and atomic modelling using molecular dynamics to probe the atomic structure of these coatings, and examine the correlations between changes in the atomic structure and changes in the mechanical loss of these coatings. Our results show the first correlation between changes in the mechanical loss and experimentally measured changes in the atomic structure resulting from variations in the level of TiO2 doping in TiO2-doped Ta2O5 coatings, in that increased homogeneity at the nearest-neighbour level appears to correlate with reduced mechanical loss. It is demonstrated that subtle but measurable changes in the nearest-neighbour homogeneity in an amorphous material can correlate with significant changes in macroscopic properties.</p>
Robot localization in water pipes using acoustic signals and pose graph optimization
One of the most fundamental tasks for robots inspecting water distribution pipes is localization, which allows for autonomous navigation, for faults to be communicated, and for interventions to be instigated. Pose-graph optimization using spatially varying information is used to enable localization within a feature-sparse length of pipe. We present a novel method for improving estimation of a robot’s trajectory using the measured acoustic field, which is applicable to other measurements such as magnetic field sensing. Experimental results show that the use of acoustic information in pose-graph optimization reduces errors by 39% compared to the use of typical pose-graph optimization using landmark features only. High location accuracy is essential to efficiently and effectively target investment to maximise the use of our aging pipe infrastructure
Universal behavior of localization of residue fluctuations in globular proteins
Localization properties of residue fluctuations in globular proteins are
studied theoretically by using the Gaussian network model. Participation ratio
for each residue fluctuation mode is calculated. It is found that the
relationship between participation ratio and frequency is similar for all
globular proteins, indicating a universal behavior in spite of their different
size, shape, and architecture.Comment: 4 pages, 3 figures. To appear in Phys. Rev.
Temperature Variation of Ultra Slow Light in a Cold Gas
A model is developed to explain the temperature dependence of the group
velocity as observed in the experiments of Hau et al (Nature {\bf397}, 594
(1999)). The group velocity is quite sensitive to the change in the spatial
density. The inhomogeneity in the density and its temperature dependence are
primarily responsible for the observed behavior.Comment: 12 pages, 4 figure
Just enough structure at the edge of chaos: Agile information system development in practice
Agile information systems development is not well understood and suffers from a lack of sustainable theories, which are based on empirical research of practice. We use a framework that focuses on the ‘edge of chaos’ as the area, where agile information systems development takes place to fill in this gap. Our study identifies for a concrete project under investigation, where the beneficial balance between stability and instability lies. It discusses the circumstances, which influence this balance and the relationships of the elements, which constitute it
The Pioneer Anomaly in the Light of New Data
The radio-metric tracking data received from the Pioneer 10 and 11 spacecraft
from the distances between 20-70 astronomical units from the Sun has
consistently indicated the presence of a small, anomalous, blue-shifted Doppler
frequency drift that limited the accuracy of the orbit reconstruction for these
vehicles. This drift was interpreted as a sunward acceleration of a_P =
(8.74+/-1.33)x10^{-10} m/s^2 for each particular spacecraft. This signal has
become known as the Pioneer anomaly; the nature of this anomaly is still being
investigated.
Recently new Pioneer 10 and 11 radio-metric Doppler and flight telemetry data
became available. The newly available Doppler data set is much larger when
compared to the data used in previous investigations and is the primary source
for new investigation of the anomaly. In addition, the flight telemetry files,
original project documentation, and newly developed software tools are now used
to reconstruct the engineering history of spacecraft. With the help of this
information, a thermal model of the Pioneers was developed to study possible
contribution of thermal recoil force acting on the spacecraft. The goal of the
ongoing efforts is to evaluate the effect of on-board systems on the
spacecrafts' trajectories and possibly identify the nature of this anomaly.
Techniques developed for the investigation of the Pioneer anomaly are
applicable to the New Horizons mission. Analysis shows that anisotropic thermal
radiation from on-board sources will accelerate this spacecraft by ~41 x
10^{-10} m/s^2. We discuss the lessons learned from the study of the Pioneer
anomaly for the New Horizons spacecraft.Comment: 19 pages, 5 figure
Probing the energy bands of a Bose-Einstein condensate in an optical lattice
We simulate three experimental methods which could be realized in the
laboratory to probe the band excitation energies and the momentum distribution
of a Bose-Einstein condensate inside an optical lattice. The values of the
excitation energies obtained in these different methods agree within the
accuracy of the simulation. The meaning of the results in terms of density and
phase deformations is tested by studying the relaxation of a phase-modulated
condensate towards the ground state.Comment: 5 pages, 5 figure
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