1,678 research outputs found

    The APX Spectrometer for Martian Missions

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    Obtaining the chemical composition of any planetary body should be a prime science objective of each planetary mission. The APX spectrometer has been designed to provide a detailed and complete chemical composition of all major (except H) and minor elements with high accuracy, in situ and remotely. From such complete analyses a first-order mineralogy of analyzed samples can be deduced. Laboratory studies in the past have shown that rock types (e.g., dunites, basalts, Philippinate 300 sample) were a uniquely in blind test analyses. Such identification is more accurate than can be obtained from any other remote spectroscopic technique. The APX technique is based on three modes of nuclear and atomic interactions of alpha particles with matter resulting in three different energy spectra containing the compositional information. The instrument uses 50 to 100 mCi of Cm-242 or Cm-244 transuranium radioisotopes to provide a monoenergetic beam of alpha particles (6.01 MeV and 5.80 MeV respectively) and solid-state detectors for acquiring the energy spectra

    Optically induced spin gates in coupled quantum dots using the electron-hole exchange interaction

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    We propose a fast optically induced two-qubit \textsc{c-phase} gate between two resident spins in a pair of coupled quantum dots. An excited bound state which extends over the two dots provides an effective electron-electron exchange interaction. The gate is made possible by the electron-hole exchange interaction, which isolates a single transition in the system. When combined with appropriate single qubit rotations, this gate generates an entangled state of the two spins

    An Alpha-p-x Analytical Instrument for Lunar Resource Investigations

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    An instrument using alpha backscattering, alpha-proton nuclear reactions, and x-ray production by alpha particles and other auxiliary sources can be used on lunar landers to provide detailed analytical information concerning the lunar surface material. This information is important scientifically and can be the basis for utilizing efficiently lunar resources to build lunar colonies in the future. This alpha particle instrument uses radioactive isotopes, silicon detectors for the alpha and proton modes, and mercuric iodide detectors operating at room temperature for the x-ray mode. The alpha and proton modes of the instrument can provide an analysis for all elements (except hydrogen) present in amounts greater than about 1 percent by atom. These modes have excellent sensitivity and accuracy for the lighter elements, in particular, directly determining the amount of oxygen in the lunar soil. This is an element of paramount significance for the lunar resource mission. The x-ray mode makes possible a determination of Ti, Fe, and other important metals with even greater accuracy. In general, the x-ray mode provides increased sensitivity for heavier elements, in many cases achieving a sensitivity of several hundred ppm

    Experiments on asteroids using hard landers

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    Hard lander missions to asteroids are examined using the Westphal penetrator study as a basis. Imagery and chemical information are considered to be the most significant science to be obtained. The latter, particularly a detailed chemical analysis performed on an uncontaminated sample, may answer questions about the relationships of asteroids to meteorites and the place of asteroids in theories of the formation of the solar system

    Fast Two-Qubit Gates in Semiconductor Quantum Dots using a Photonic Microcavity

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    Implementations for quantum computing require fast single- and multi-qubit quantum gate operations. In the case of optically controlled quantum dot qubits theoretical designs for long-range two- or multi-qubit operations satisfying all the requirements in quantum computing are not yet available. We have developed a design for a fast, long-range two-qubit gate mediated by a photonic microcavity mode using excited states of the quantum dot-cavity system that addresses these needs. This design does not require identical qubits, it is compatible with available optically induced single qubit operations, and it advances opportunities for scalable architectures. We show that the gate fidelity can exceed 90% in experimentally accessible systems

    A Tonks Giradeau Gas in the Presence of a Local Potential

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    The physics of a Tonks-Giradeau Gas in the presence of a local potential is studied. In order to evaluate the single particle density matrix (SPDM) of the many-body ground state, the Wiger-Jordan transformation is used. The eigenvector with the largest eigenvalue of the SPDM corresponds to the "Bose-Einstein Condensate"(BEC) State. We find that the "BEC" state density at the positon of the local potential decreases, as expected, in the case of a repulsive potential. For an attractive potential, it decreases or increases depending on the strength of the potential. The superfluidity of this system is investigated both numerically and perturbatively. An experimental method for detecting the effect of an impurity in a Tonks-Giradueau gas is discussed.Comment: 14 pages, 5 figure

    Spatio-temporal modelling of extreme storms

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    A flexible spatio-temporal model is implemented to analyse extreme extra-tropical cyclones objectively identified over the Atlantic and Europe in 6-hourly re-analyses from 1979-2009. Spatial variation in the extremal properties of the cyclones is captured using a 150 cell spatial regularisation, latitude as a covariate, and spatial random effects. The North Atlantic Oscillation (NAO) is also used as a covariate and is found to have a significant effect on intensifying extremal storm behaviour, especially over Northern Europe and the Iberian peninsula. Estimates of lower bounds on minimum sea-level pressure are typically 10-50 hPa below the minimum values observed for historical storms with largest differences occurring when the NAO index is positive.Comment: Published in at http://dx.doi.org/10.1214/14-AOAS766 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Intelligent Based Terrain Preview Controller for a 3-axle Vehicle

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    Presented at 13th International Symposium on Advanced Vehicle Control, AVEC'16; Munich 13-16/09/2016The paper presents a six-wheel half longitudinal model and the design of a dual level control architecture. The first (top) level is designed using a Sugeno fuzzy inference feedforward architecture with and without preview. The second level of controllers are locally managing each wheel for each axle. As the vehicle is moving forward the front wheels and suspension units will have less time to respond when compared to the middle and rear units, hence a preview sensor is used to compensate. The paper shows that the local active suspensions together with the Sugeno Fuzzy, (locally optimised using subtractive clustering), Feedforward control strategy is more effective and this architecture has resulted in reducing the sprung mass vertical acceleration and pitch accelerations

    Quantifying how user-interaction can modify the perception of the value of climate information: A Bayesian approach

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    ArticleThis is the final version of the article. Available from Elsevier via the DOI in this record.The growing attention user relevance is receiving in the context of climate services is giving new light to engagement activities. However, while there is an almost unanimous consensus that these are important to the delivery of usable services, there is relatively little quantitative evidence of their impact on the usefulness of the service or its value as perceived by the users and decision-makers. Using a simple Bayesian decision theoretic framework, we have analysed how the perceived value of the service changes as a function of the user’s belief in the accuracy of the forecast. Based on this, we conclude, that, at least for the generic users adopted for our analysis, 30 or more repeated forecasts may be needed to ascertain the real user value of a predictive service. However, we argue that engagement between users and service providers can play a significant role in modifying the perceived accuracy and value of the service, bringing it closer in line with the objective evaluation. This requires feedback from users on both the specific climate information content and its presentation, alongside exploring the user’s attitude to risk. If appropriate engagement can be achieved, this work suggests that it has the potential to alter the overall perceived cost-benefit ratio over a relatively short period of time, enabling users to make best use of the available climate information.This work was supported by the Joint DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). The authors wish to acknowledge all of those who contributed indirectly to the development of the EUPORIAS winter transport prototype (Seasonal Prototype: Risk of Impacts from NAO on Transport; http://sprint.euporias.eu/), through scientific discussion, review, data provision, stakeholder engagement and facilitation: Erika Palin, Adam Scaife, Anca Brookshaw, Alberto Arribas, and the UK Department for Transport-led stakeholder group. The UK Government Department for Transport is acknowledged for providing financial support, in parallel to that received from EUPORIAS, for the SPRINT prototype. EUPORIAS was funded by the European Commission through the 7th Framework Programme for Research, grant agreement 308291

    Nonlinear surface impurity in a semi-infinite 2D square lattice

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    We examine the formation of localized states on a generalized nonlinear impurity located at, or near the surface of a semi-infinite 2D square lattice. Using the formalism of lattice Green functions, we obtain in closed form the number of bound states as well as their energies and probability profiles, for different nonlinearity parameter values and nonlinearity exponents, at different distances from the surface. We specialize to two cases: impurity close to an "edge" and impurity close to a "corner". We find that, unlike the case of a 1D semi-infinite lattice, in 2D, the presence of the surface helps the formation of a localized state.Comment: 6 pages, 7 figures, submitted to PR
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