Sensitivity of a Bolometric Interferometer to the CMB power spectrum

Context. The search for B-mode polarization fluctuations in the Cosmic Microwave Background is one of the main challenges of modern cosmology. The expected level of the B-mode signal is very low and therefore requires the development of highly sensitive instruments with low systematic errors. An appealing possibility is bolometric interferometry. Aims. We compare in this article the sensitivity on the CMB angular power spectrum achieved with direct imaging, heterodyne and bolometric interferometry. Methods. Using a simple power spectrum estimator, we calculate its variance leading to the counterpart for bolometric interferometry of the well known Knox formula for direct imaging. Results. We find that bolometric interferometry is less sensitive than direct imaging. However, as expected, it is finally more sensitive than heterodyne interferometry due to the low noise of the bolometers. It therefore appears as an alternative to direct imagers with different and possibly lower systematic errors, mainly due to the absence of an optical setup in front of the horns.Comment: 5 pages, 3 figures. This last version matches the published version (Astronomy and Astrophysics 491 3 (2008) 923-927). Sensitivity of Heterodyne Interferometers modified by a factor of tw

Cosmic Background dipole measurements with Planck-High Frequency Instrument

This paper discusses the Cosmic Background (CB) dipoles observations in the framework of the Planck mission. Dipoles observations can be used in three ways: (i) It gives a measurement of the peculiar velocity of our Galaxy which is an important observation in large scale structures formation model. (ii) Measuring the dipole can give unprecedent information on the monopole (that can be in some cases hard to obtain due to large foreground contaminations). (iii) The dipole can be an ideal absolute calibrator, easily detectable in cosmological experiments. Following the last two objectives, the main goal of the work presented here is twofold. First, we study the accuracy of the Planck-HFI calibration using the Cosmic Microwave Background (CMB) dipole measured by COBE as well as the Earth orbital motion dipole. We show that we can reach for HFI, a relative calibration between rings of about 1% and an absolute calibration better than 0.4% for the CMB channels (in the end, the absolute calibration will be limited by the uncertainties on the CMB temperature). We also show that Planck will be able to measure the CMB dipole direction at better than 1.7 arcmin and improve on the amplitude. Second, we investigate the detection of the Cosmic Far-Infrared Background (FIRB) dipole. Measuring this dipole could give a new and independent determination of the FIRB for which a direct determination is quite difficult due to Galactic dust emission contamination. We show that such a detection would require a Galactic dust emission removal at better than 1%, which will be very hard to achieve.Comment: 10 pages, 13 figures, submitted to A&A, uses aa.sty V5.

Stability of Hematological Parameters in Woodland Caribou (Rangifer tarandus caribou) Blood Stored at 4°C

Eighteen free-ranging female woodland caribou were captured in northern Alberta in January and February 1993. Blood was collected into ethylenediaminetetraacetate (EDTA) tubes which were packaged in coolers containing ice packs, and transported to the laboratory where they arrived within 48 hrs of collection. Complete blood counts (CBC) were performed on five consecutive days to assess the stability of hematological parameters. Average values of hematocrit (HCT), mean cell hemoglobin (MCH), mean cell volume (MCV), red cell distribution width (P-J3W), white blood cell count (WBC), and red blood cell count (RJ3C) remained stable with no statistically significant changes occurring during 5 days of post-collection storage at 4°C. Mean PvBC values exhibited significant differences (p<0.05) between geographic locations. Mean platelet volume (MPV) increased significantly (p<0.001) with storage time, while platelet (PLT) values decreased (p<0.001) over time and were significantly different (p<0.01) between locations. For optimal hematological results, it is recommended that sample analysis be performed within 24 hours of blood collection; however, if caribou blood samples are properly stored at 4°C, useful information may be obtained from stable parameters up to 5 days following collection

A new Aerodynamic traction principle for handling products on an Air Cushion.

International audienceThis paper introduces a new aerodynamic traction principle for handling delicate and clean products, such as silicon wafers, glass sheets or flat foodstuff. The product is carried on a thin air cushion and transported along the system by induced air flows. This induced air flow is the indirect effect of strong vertical air-jets that pull the surrounding fluid. The paper provides a qualitative explanation of the operating principles and a description of the experimental device. Very first experimental results with active control are presented. The maximum velocity and acceleration that can be obtained for the considered device geometry meet the requirements for industrial applications

2-DOF Contactless Distributed Manipulation Using Superposition of Induced Air Flows.

International audienceMany industries require contactless transport and positioning of delicate or clean objects such as silicon wafers, glass sheets, solar cell or flat foodstuffs. The authors have presented a new form of contactless distributed manipulation using induced air flow. Previous works concerned the evaluation of the maximal velocity of transported objects and one degreeof- freedom position control of objects. This paper introduces an analytic model of the velocity field of the induced air flow according to the spatial configuration of vertical air jets. Then two degrees-of-freedom position control is investigated by exploiting the linearity property of the model. Finally the model is validated under closed-loop control and the performances of the position control are evaluated

Independent reinforcement learners in cooperative Markov games: a survey regarding coordination problems.

International audienceIn the framework of fully cooperative multi-agent systems, independent (non-communicative) agents that learn by reinforcement must overcome several difficulties to manage to coordinate. This paper identifies several challenges responsible for the non-coordination of independent agents: Pareto-selection, nonstationarity, stochasticity, alter-exploration and shadowed equilibria. A selection of multi-agent domains is classified according to those challenges: matrix games, Boutilier's coordination game, predators pursuit domains and a special multi-state game. Moreover the performance of a range of algorithms for independent reinforcement learners is evaluated empirically. Those algorithms are Q-learning variants: decentralized Q-learning, distributed Q-learning, hysteretic Q-learning, recursive FMQ and WoLF PHC. An overview of the learning algorithms' strengths and weaknesses against each challenge concludes the paper and can serve as a basis for choosing the appropriate algorithm for a new domain. Furthermore, the distilled challenges may assist in the design of new learning algorithms that overcome these problems and achieve higher performance in multi-agent applications

SOaN : un algorithme pour la coordination d'agents apprenants et non communicants.

National audienceL'apprentissage par renforcement dans les systèmes multi-agents est un domaine de recherche très actif, comme en témoignent les états de l'art récents [Busoniu et al., 2008, Sandholm, 2007, Bab & Brafman, 2008, Vlassis, 2007]. Lauer et Riedmiller ont notamment montré que, sous certaines hypothèses, il est possible à des agents apprenants simultanément de coordonner leurs actions sans aucune communication et sans qu'ils perçoivent les actions de leurs congénères [Lauer & Riedmiller, 2000]. Cette propriété est particulièrement intéressante pour trouver des stratégies de coopération dans les systèmes multi-agents de grande taille

A new contactless conveyor system for handling clean and delicate products using induced air flows.

International audienceIn this paper, a new contactless conveyor system based on an original aerodynamic traction principle is described and experimented. This device is able to convey without any contact flat objects like silicon wafer, glass sheets or foodstufff thanks to an air cushion and induced air flows. A model of the system is established and the identification of the parameters is carried out. A closed-loop control is proposed for one dimension position control and position tracking. The PID-controller gives good performances for different reference signals. Its robustness to object change and perturbation rejection are also tested

Coordination of independent learners in cooperative Markov games.

In the framework of fully cooperative multi-agent systems, independent agents learning by reinforcement must overcome several difficulties as the coordination or the impact of exploration. The study of these issues allows first to synthesize the characteristics of existing reinforcement learning decentralized methods for independent learners in cooperative Markov games. Then, given the difficulties encountered by these approaches, we focus on two main skills: optimistic agents, which manage the coordination in deterministic environments, and the detection of the stochasticity of a game. Indeed, the key difficulty in stochastic environment is to distinguish between various causes of noise. The SOoN algorithm is so introduced, standing for “Swing between Optimistic or Neutral”, in which independent learners can adapt automatically to the environment stochasticity. Empirical results on various cooperative Markov games notably show that SOoN overcomes the main factors of non-coordination and is robust face to the exploration of other agents