Quality of Service for Information Access

Information is available in many forms from different sources, in distributed locations; access to information is supported by networks of varying performance; the cost of accessing and transporting the information varies for both the source and the transport route. Users who vary in their preferences, background knowledge required to interpret the information and motivation for accessing it, gather information to perform many different tasks. This position paper outlines some of these variations in information provision and access, and explores the impact these variations have on the user’s task performance, and the possibilities they make available to adapt the user interface for the presentation of information

Decay channels and charmonium mass-shifts

The discovery in the last few years of the $X, Y$ and $Z$ states of the extended charmonium family has highlighted the importance of the closeness of decay channels to an understanding of these mesons. We aid this debate by illustrating a simple calculational procedure for including the effect of open and nearby closed channels.Comment: 4 pages, 2 figures Revised version: (1) corrected 2 typos in Table II, (2) additional text in penultimate paragraph to clarify the calculation of mass-shifts for $\eta_c'$ and $\eta_c"$. We thank colleagues for pointing out confusing wording of previous tex

Segmentation ART: A Neural Network for Word Recognition from Continuous Speech

The Segmentation ATIT (Adaptive Resonance Theory) network for word recognition from a continuous speech stream is introduced. An input sequeuce represents phonemes detected at a preproccesing stage. Segmentation ATIT is trained rapidly, and uses a fast-learning fuzzy ART modules, top-down expectation, and a spatial representation of temporal order. The network performs on-line identification of word boundaries, correcting an initial hypothesis if subsequent phonemes are incompatible with a previous partition. Simulations show that the system's segmentation perfonnance is comparable to that of TRACE, and the ability to segment a number of difficult phrases is also demonstrated.National Science Foundation (NSF-IRI-94-01659); Office of Naval Research (N00014-95-1-0409, N00014-95-1-0G57

Pushing the precision limit of ground-based eclipse photometry

Until recently, it was considered by many that ground-based photometry could not reach the high cadence sub-mmag regime because of the presence of the atmosphere. Indeed, high frequency atmospheric noises (mainly scintillation) limit the precision that high SNR photometry can reach within small time bins. If one is ready to damage the sampling of his photometric time-series, binning the data (or using longer exposures) allows to get better errors, but the obtained precision will be finally limited by low frequency noises. To observe several times the same planetary eclipse and to fold the photometry with the orbital period is thus generally considered as the only option to get very well sampled and precise eclipse light curve from the ground. Nevertheless, we show here that reaching the sub-mmag sub-min regime for one eclipse is possible with a ground-based instrument. This has important implications for transiting planets characterization, secondary eclipses measurement and small planets detection from the ground.Comment: Transiting Planets Proceeding IAU Symposium No.253, 2008. 7 pages, 4 figure

Studies of high latitude current systems using MAGSAT vector data

The magnetic disturbance fields caused by global external current systems are considered with particular emphasis on improving the understanding of the physical processes which control high latitude current systems. Following processing the MAGSAT data were routinely plotted in the Universal Time (UT) format as well as in a polar plot format. The H'D'U' coordinate system, was adopted as the standard for representing the MAGSAT residual magnetic field vectors. A data file was generated and the TPOLAR computer code was developed to determine from the orbital elements, the time, latitude, and MLT of the extremum latitude of each transpolar segment of orbit. The precision of the vector data set from MAGSAT prompted an extended exploratory phase for data analysis procedures, modeling techniques and phenomenology

Wave Energy Amplification in a Metamaterial based Traveling Wave Structure

We consider the interaction between a particle beam and a propagating electromagnetic wave in the presence of a metamaterial. We show that the introduction of a metamaterial gives rise to a novel dispersion curve which determines a unique wave particle relationship, via the frequency dependence of the metamaterial and the novel ability of metamaterials to exhibit simultaneous negative permittivity and permeability. Using a modified form of Madey's theorem we find that the novel dispersion of the metamaterial leads to a amplification of the EM wave power

On-board timeline validation and repair : a feasibility study

We report on the progress and outcome of a recent ESAfunded project (MMOPS) designed to explore the feasibility of on-board reasoning about payload timelines. The project sought to examine the role of on-board timeline reasoning and the operational context into which it would fit. We framed a specification for an on-board service that fits with existing practices and represents a plausible advance within sensible constraints on the progress of operations planning. We have implemented a prototype to demonstrate the feasibility of such a system and have used it to show how science gathering operations might be improved by its deployment

High-temperature thermal storage systems for advanced solar receivers materials selections

Advanced space power systems that use solar energy and Brayton or Stirling heat engines require thermal energy storage (TES) systems to operate continuously through periods of shade. The receiver storage units, key elements in both Brayton and Stirling systems, are designed to use the latent heat of fusion of phase-change materials (PCMs). The power systems under current consideration for near-future National Aeronautics and Space Administration space missions require working fluid temperatures in the 1100 to 1400 K range. The PCMs under current investigation that gave liquid temperatures within this range are the fluoride family of salts. However, these salts have low thermal conductivity, which causes large temperature gradients in the storage systems. Improvements can be obtained, however, with the use of thermal conductivity enhancements or metallic PCMs. In fact, if suitable containment materials can be found, the use of metallic PCMs would virtually eliminate the orbit associated temperature variations in TES systems. The high thermal conductivity and generally low volume change on melting of germanium and alloys based on silicon make them attractive for storage of thermal energy in space power systems. An approach to solving the containment problem, involving both chemical and physical compatibility, preparation of NiSi/NiSi2, and initial results for containment of germanium and NiSi/NiSi2, are presented

Studies of high latitude current systems using Magsat vector data

Disturbance fields caused by global external current systems are analyzed in order to gain an improved understanding of the phydical processes which control high latitude current systems and to increase the confidence level in the identification of internal field levels. The basic approach is to: (1) categorize the vector data by those physical parameters important for investigation of external current systems; (2) map the disturbances for appropriate conditions; (3) model the currents which might cause the mapped disturbances; and (4) correlate results with data from other sources. It is concluded that the Magsat data set appears to have remarkably high precision and quality and should permit major advances to be made in modeling current distribution at high latitudes in the ionosphere and magnetosphere