Anytime Point-Based Approximations for Large POMDPs

The Partially Observable Markov Decision Process has long been recognized as a rich framework for real-world planning and control problems, especially in robotics. However exact solutions in this framework are typically computationally intractable for all but the smallest problems. A well-known technique for speeding up POMDP solving involves performing value backups at specific belief points, rather than over the entire belief simplex. The efficiency of this approach, however, depends greatly on the selection of points. This paper presents a set of novel techniques for selecting informative belief points which work well in practice. The point selection procedure is combined with point-based value backups to form an effective anytime POMDP algorithm called Point-Based Value Iteration (PBVI). The first aim of this paper is to introduce this algorithm and present a theoretical analysis justifying the choice of belief selection technique. The second aim of this paper is to provide a thorough empirical comparison between PBVI and other state-of-the-art POMDP methods, in particular the Perseus algorithm, in an effort to highlight their similarities and differences. Evaluation is performed using both standard POMDP domains and realistic robotic tasks

The Auslander-Gorenstein property for Z-algebras

We provide a framework for part of the homological theory of Z-algebras and their generalizations, directed towards analogues of the Auslander-Gorenstein condition and the associated double Ext spectral sequence that are useful for enveloping algebras of Lie algebras and related rings. As an application, we prove the equidimensionality of the characteristic variety of an irreducible representation of the Z-algebra, and for related representations over quantum symplectic resolutions. In the special case of Cherednik algebras of type A, this answers a question raised by the authors.Comment: 31 page

Dynamical control of quantum state transfer within hybrid open systems

We analyze quantum state-transfer optimization within hybrid open systems, from a "noisy" (write-in) qubit to its "quiet" counterpart (storage qubit). Intriguing interplay is revealed between our ability to avoid bath-induced errors that profoundly depend on the bath-memory time and the limitations imposed by leakage out of the operational subspace. Counterintuitively, under no circumstances is the fastest transfer optimal (for a given transfer energy)

Simulating a dual beam combiner at SUSI for narrow-angle astrometry

The Sydney University Stellar Interferometer (SUSI) has two beam combiners, i.e. the Precision Astronomical Visible Observations (PAVO) and the Microarcsecond University of Sydney Companion Astrometry (MUSCA). The primary beam combiner, PAVO, can be operated independently and is typically used to measure properties of binary stars of less than 50 milliarc- sec (mas) separation and the angular diameters of single stars. On the other hand, MUSCA was recently installed and must be used in tandem with the for- mer. It is dedicated for microarcsecond precision narrow-angle astrometry of close binary stars. The performance evaluation and development of the data reduction pipeline for the new setup was assisted by an in-house computer simulation tool developed for this and related purposes. This paper describes the framework of the simulation tool, simulations carried out to evaluate the performance of each beam combiner and the expected astrometric precision of the dual beam combiner setup, both at SUSI and possible future sites.Comment: 28 pages, 23 figures, accepted for publication in Experimental Astronomy. The final publication is available at http://link.springer.co

Condensate density and superfluid mass density of a dilute Bose gas near the condensation transition

We derive, through analysis of the structure of diagrammatic perturbation theory, the scaling behavior of the condensate and superfluid mass density of a dilute Bose gas just below the condensation transition. Sufficiently below the critical temperature, $T_c$, the system is governed by the mean field (Bogoliubov) description of the particle excitations. Close to $T_c$, however, mean field breaks down and the system undergoes a second order phase transition, rather than the first order transition predicted in Bogoliubov theory. Both condensation and superfluidity occur at the same critical temperature, $T_c$ and have similar scaling functions below $T_c$, but different finite size scaling at $T_c$ to leading order in the system size. Through a simple self-consistent two loop calculation we derive the critical exponent for the condensate fraction, $2\beta\simeq 0.66$.Comment: 4 page

THERMODYNAMIC PROPERTIES TO 6000 DEG K FOR 210 SUBSTANCES INVOLVING THE FIRST 18 ELEMENTS

Thermodynamic properties to 6000-deg kelvin for substances involving first 18 elements in their natural stat

Effect of Riffle Height and Spacing of a Sluice Board on Placer Gold Recovery

Sluicing is the preferred mineral processing technique for the treatment of placer gold-bearing alluvium for small scale and artisanal miners in Ghana because sluice board is perceived to be the most cost effective device. However, there are differences in approaches from design to operation.  In this work, about 50 kg of ore was obtained from “Peace School” small scale mining site near the University of Mines and Technology, Tarkwa. It was processed to determine the effects of riffle height and spacing on gold recovery. It was confirmed that, in order to trap a greater percentage of gold particles, the height of the riffle ought to be higher than the suspension height of the gold. The suspension heights of the gold particles of the various operational regimes of the sluice board at superficial velocities of 0.5 m/s, 1.0 m/s, 1.5 m/s and 2.0 m/ were   0.9 cm, 1.2 cm, 1.5 cm and 2.9 cm respectively. Analysis of concentrates showed that, 85.4% of gold was recovered during sluicing at approximately 1.0 cm riffle height.  The lowest recovery was recorded at 0.5 cm riffle height. Gold recovery was also affected by riffles spacing.  For the indicated speeds and the riffle heights the necessary spacing should not be more than 20 cm. The peak recovery was obtained at a riffle height of 1.0 cm but dropped after 20.0 cm spacing. Keywords: Sluice Board, Riffle Height, Gold, Rifle Spacing

A low cost scheme for high precision dual-wavelength laser metrology

A novel method capable of delivering relative optical path length metrology with nanometer precision is demonstrated. Unlike conventional dual-wavelength metrology which employs heterodyne detection, the method developed in this work utilizes direct detection of interference fringes of two He-Ne lasers as well as a less precise stepper motor open-loop position control system to perform its measurement. Although the method may be applicable to a variety of circumstances, the specific application where this metrology is essential is in an astrometric optical long baseline stellar interferometer dedicated to precise measurement of stellar positions. In our example application of this metrology to a narrow-angle astrometric interferometer, measurement of nanometer precision could be achieved without frequency-stabilized lasers although the use of such lasers would extend the range of optical path length the metrology can accurately measure. Implementation of the method requires very little additional optics or electronics, thus minimizing cost and effort of implementation. Furthermore, the optical path traversed by the metrology lasers is identical with that of the starlight or science beams, even down to using the same photodetectors, thereby minimizing the non-common-path between metrology and science channels.Comment: 17 pages, 4 figures, accepted for publication in Applied Optic

The distance to M5 from its RR Lyrae variables

A variation of the Baade-Wesselink method has been applied to four RR Lyrae variables in the moderately metal-poor globular cluster M5. The method developed for the analysis utilizes an effective wavelength for each filter and relies on the accuracy of the calibration of absolute flux for bright standard stars by Oke and Gunn (1983), as well as on the accuracy of the absolute emitted fluxes predicted in the near-infrared by the Kurucz (1979) grid of model stellar atmospheres. The results must be viewed as preliminary thus far due to apparent discrepancies between the photometrically and spectroscopically deduced angular diameter-phase relationships which are most apparent in the part of the cycle immediately following maximum light. This restricts the range of phase that can be used to derive the distance to the variables. The best value obtained for the mean of the 4 RR Lyrae stars in M5 is an absorption-corrected intensity mean absolute V magnitude of +1.05 mag (+0.15, -0.25 mag)

Methodology for environmental assessment of agri-environment schemes: the Agri Environmental Footprint Index

End of project reportAgri-environment schemes pay farmers for the provision of environmental services. Such schemes tend to have multiple measures that deliver multiple environmental objectives, and there is a lack of consistent methodology with which to measure the environmental benefits of such schemes. Funded by EU FP6, the Agri-Environment Footprint project (www.footprint.rdg.ac.uk) aimed to address this challenge, and this report provides results from selected components of the project.European Unio