95 research outputs found

    Comparing four interaction techniques on a simple structured navigation task using a Head-Mounted Display

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    Virtual Reality (VR) is a scientific and technical domain that can provide mediums to dive users into an interactive 3D computer-generated world. Several processes of immersion bring to user the feeling of having quit the real world and of being present in the virtual environment, physically as well as psychologically (1,2). VR must provide a coherent experience in terms of sensory, cognitive and functional information (2). Fidelity, as the objective degree of exactness with which a system reproduces real-world, is hence a key point to design immersive VR-based systems. Since the 2010’s, low-cost cave automatic virtual environment (3) and many Head-Mounted Display (HMD) are available for immersive VR. However, navigate through 3D environments displayed in HMD is still challenging because it can cause sickness and disorientation. Since techniques based on haptic devices like keyboard and joystick have been extensively explored in the past, the present study aimed to investigate the impact of the navigation technique on performance on a simple traveling-centered task and the user experience with the HMD HTC Vive. Since techniques based on haptic devices like keyboard and joystick have been extensively explored in the past, the present study aimed to investigate the impact of the navigation technique on performance on a simple traveling-centered task and the user experience with the HMD HTC Vive. We compared four continuous navigation techniques: Arms Swinging, Walking-In-Place, Pointing and Touchpad. Results on the learning effect indicated that the repetition was especially beneficial for Directional Touchpad. On the user experience, the results revealed a general discomfort of attendees with the presented systems, but they found themselves competent at the end of the experiment in the accomplishment of the proposed task. Joysticks or directional was associated to a failure in using the gaze to orientate the camera view in virtual reality

    Object recognition by intersection between adapted color histograms

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    Most of object recognition schemes fail in case of illumination changes between the color image acquisitions. One of the most widely used solutions to cope with this problem is to compare the images by means of the intersection between invariant color histograms. Unlike the classical invariant color histograms approach which independently analyzes each image, we consider each pair constituted by the query image and one of the target images constructed during the retrieval. In this paper, we propose a new approach based on color histograms which are adapted to each pair constituted by the query image and one of the target images. These adapted color histograms are determined so that their intersection is high only when the objects contained in the two images are similar. The adapted color histograms processing is based on an original model of illumination changes based on the rank measures of the pixels within the color component images.Dans cet article, nous abordons le problĂšme de la reconnaissance des objets sous Ă©clairage non contrĂŽlĂ© par la recherche de toutes les images d'une base qui contiennent le mĂȘme objet que celui reprĂ©sentĂ© dans une image requĂȘte. Nous nous intĂ©ressons aux problĂšmes soulevĂ©s par les modifications des images couleur consĂ©cutives Ă  des changements d'illuminant. Les images considĂ©rĂ©es dans cet article contiennent un seul objet placĂ© sur un fond uniforme et Ă©clairĂ© avec un illuminant qui diffĂšre d'une image Ă  l'autre. Les mĂ©thodes classiques basĂ©es sur des histogrammes invariants ne fournissent pas des rĂ©sultats satisfaisants en termes de reconnaissance d'objets Ă©clairĂ©s par diffĂ©rents illuminants. Nous proposons de traiter ce problĂšme, non pas en analysant les images de la base indĂ©pendamment les unes des autres, mais en analysant tous les couples constituĂ©s de l'image requĂȘte et de chacune des images candidates. Plus prĂ©cisĂ©ment, nous proposons d'analyser chaque couple d'histogrammes couleur pour comparer le contenu de chaque couple d'images. Pour cela, la procĂ©dure dĂ©termine un couple d'histogrammes couleur dits « spĂ©cifiques » Ă  chaque couple d'histogrammes couleur considĂ©rĂ©, de telle sorte que l'intersection entre ces histogrammes couleur spĂ©cifiques soit Ă©levĂ©e uniquement lorsque les deux objets contenus dans les deux images sont similaires. Cette procĂ©dure est basĂ©e sur une nouvelle hypothĂšse sur les consĂ©quences d'un changement d'illuminant qui ne porte pas directement sur les couleurs des pixels, mais sur les mesures de rang des pixels

    Emergence of Epidemic Neisseria meningitidis Serogroup X Meningitis in Togo and Burkina Faso

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    Serogroup X meningococci (NmX) historically have caused sporadic and clustered meningitis cases in sub-Saharan Africa. To study recent NmX epidemiology, we analyzed data from population-based, sentinel and passive surveillance, and outbreak investigations of bacterial meningitis in Togo and Burkina Faso during 2006–2010. Cerebrospinal fluid specimens were analyzed by PCR. In Togo during 2006–2009, NmX accounted for 16% of the 702 confirmed bacterial meningitis cases. Kozah district experienced an NmX outbreak in March 2007 with an NmX seasonal cumulative incidence of 33/100,000. In Burkina Faso during 2007–2010, NmX accounted for 7% of the 778 confirmed bacterial meningitis cases, with an increase from 2009 to 2010 (4% to 35% of all confirmed cases, respectively). In 2010, NmX epidemics occurred in northern and central regions of Burkina Faso; the highest district cumulative incidence of NmX was estimated as 130/100,000 during March–April. Although limited to a few districts, we have documented NmX meningitis epidemics occurring with a seasonal incidence previously only reported in the meningitis belt for NmW135 and NmA, which argues for development of an NmX vaccine

    Automatic colorimetric calibration of human wounds

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    Contains fulltext : 88431.pdf (publisher's version ) (Open Access)BACKGROUND: Recently, digital photography in medicine is considered an acceptable tool in many clinical domains, e.g. wound care. Although ever higher resolutions are available, reproducibility is still poor and visual comparison of images remains difficult. This is even more the case for measurements performed on such images (colour, area, etc.). This problem is often neglected and images are freely compared and exchanged without further thought. METHODS: The first experiment checked whether camera settings or lighting conditions could negatively affect the quality of colorimetric calibration. Digital images plus a calibration chart were exposed to a variety of conditions. Precision and accuracy of colours after calibration were quantitatively assessed with a probability distribution for perceptual colour differences (dE_ab). The second experiment was designed to assess the impact of the automatic calibration procedure (i.e. chart detection) on real-world measurements. 40 Different images of real wounds were acquired and a region of interest was selected in each image. 3 Rotated versions of each image were automatically calibrated and colour differences were calculated. RESULTS: 1st Experiment: Colour differences between the measurements and real spectrophotometric measurements reveal median dE_ab values respectively 6.40 for the proper patches of calibrated normal images and 17.75 for uncalibrated images demonstrating an important improvement in accuracy after calibration. The reproducibility, visualized by the probability distribution of the dE_ab errors between 2 measurements of the patches of the images has a median of 3.43 dE* for all calibrated images, 23.26 dE_ab for all uncalibrated images. If we restrict ourselves to the proper patches of normal calibrated images the median is only 2.58 dE_ab! Wilcoxon sum-rank testing (p < 0.05) between uncalibrated normal images and calibrated normal images with proper squares were equal to 0 demonstrating a highly significant improvement of reproducibility. In the second experiment, the reproducibility of the chart detection during automatic calibration is presented using a probability distribution of dE_ab errors between 2 measurements of the same ROI. CONCLUSION: The investigators proposed an automatic colour calibration algorithm that ensures reproducible colour content of digital images. Evidence was provided that images taken with commercially available digital cameras can be calibrated independently of any camera settings and illumination features

    Time projection chambers for the T2K near detectors

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    The T2K experiment is designed to study neutrino oscillation properties by directing a high intensity neutrino beam produced at J-PARC in Tokai, Japan, towards the large Super-Kamiokande detector located 295 km away, in Kamioka, Japan. The experiment includes a sophisticated near detector complex, 280 m downstream of the neutrino production target in order to measure the properties of the neutrino beam and to better understand neutrino interactions at the energy scale below a few GeV. A key element of the near detectors is the ND280 tracker, consisting of two active scintillator-bar target systems surrounded by three large time projection chambers (TPCs) for charged particle tracking. The data collected with the tracker is used to study charged current neutrino interaction rates and kinematics prior to oscillation, in order to reduce uncertainties in the oscillation measurements by the far detector. The tracker is surrounded by the former UA1/Nomad dipole magnet and the TPCs measure the charges, momenta, and particle types of charged particles passing through them. Novel features of the TPC design include its rectangular box layout constructed from composite panels, the use of bulk micromegas detectors for gas amplification, electronics readout based on a new ASIC, and a photoelectron calibration system. This paper describes the design and construction of the TPCs, the micromegas modules, the readout electronics, the gas handling system, and shows the performance of the TPCs as deduced from measurements with particle beams, cosmic rays, and the calibration system

    Precise Measurement of the Neutrino Mixing Parameter theta(23) from Muon Neutrino Disappearance in an Off-Axis Beam

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    New data from the T2K neutrino oscillation experiment produce the most precise measurement of the neutrino mixing parameter theta_{23}. Using an off-axis neutrino beam with a peak energy of 0.6 GeV and a data set corresponding to 6.57 x 10^{20} protons on target, T2K has fit the energy-dependent nu_mu oscillation probability to determine oscillation parameters. Marginalizing over the values of other oscillation parameters yields sin^2 (theta_{23}) = 0.514 +0.055/-0.056 (0.511 +- 0.055), assuming normal (inverted) mass hierarchy. The best-fit mass-squared splitting for normal hierarchy is Delta m^2_{32} = (2.51 +- 0.10) x 10^{-3} eV^2/c^4 (inverted hierarchy: Delta m^2_{13} = (2.48 +- 0.10) x 10^{-3} eV^2/c^4). Adding a model of multinucleon interactions that affect neutrino energy reconstruction is found to produce only small biases in neutrino oscillation parameter extraction at current levels of statistical uncertainty

    Measurement of the intrinsic electron neutrino component in the T2K neutrino beam with the ND280 detector

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    The T2K experiment has reported the first observation of the appearance of electron neutrinos in a muon neutrino beam. The main and irreducible background to the appearance signal comes from the presence in the neutrino beam of a small intrinsic component of electron neutrinos originating from muon and kaon decays. In T2K, this component is expected to represent 1.2% of the total neutrino flux. A measurement of this component using the near detector (ND280), located 280 m from the target, is presented. The charged current interactions of electron neutrinos are selected by combining the particle identification capabilities of both the time projection chambers and electromagnetic calorimeters of ND280. The measured ratio between the observed electron neutrino beam component and the prediction is 1.01 +/- 0.10 providing a direct confirmation of the neutrino fluxes and neutrino cross section modeling used for T2K neutrino oscillation analyses. Electron neutrinos coming from muons and kaons decay are also separately measured, resulting in a ratio with respect to the prediction of 0.68 +/- 0.30 and 1.10 +/- 0.14, respectively

    T2K neutrino flux prediction

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    cited By 15 art_number: 012001 affiliation: Centre for Particle Physics, Department of Physics, University of Alberta, Edmonton, AB, Canada; Albert Einstein Center for Fundamental Physics, Laboratory for High Energy Physics (LHEP), University of Bern, Bern, Switzerland; Department of Physics, Boston University, Boston, MA, United States; Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada; Department of Physics and Astronomy, University of California Irvine, Irvine, CA, United States; IRFU, CEA Saclay, Gif-sur-Yvette, France; Institute for Universe and Elementary Particles, Chonnam National University, Gwangju, South Korea; Department of Physics, University of Colorado at Boulder, Boulder, CO, United States; Department of Physics, Colorado State University, Fort Collins, CO, United States; Department of Physics, Dongshin University, Naju, South Korea; Department of Physics, Duke University, Durham, NC, United States; IN2P3-CNRS, Laboratoire Leprince-Ringuet, Ecole Polytechnique, Palaiseau, France; Institute for Particle Physics, ETH Zurich, Zurich, Switzerland; Section de Physique, DPNC, University of Geneva, Geneva, Switzerland; H. Niewodniczanski Institute of Nuclear Physics PAN, Cracow, Poland; High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan; Institut de Fisica d’Altes Energies (IFAE), Bellaterra (Barcelona), Spain; IFIC (CSIC and University of Valencia), Valencia, Spain; Department of Physics, Imperial College London, London, United Kingdom; INFN Sezione di Bari, Dipartimento Interuniversitario di Fisica, UniversitĂ  e Politecnico di Bari, Bari, Italy; INFN Sezione di Napoli and Dipartimento di Fisica, UniversitĂ  di Napoli, Napoli, Italy; INFN Sezione di Padova, Dipartimento di Fisica, UniversitĂ  di Padova, Padova, Italy; INFN Sezione di Roma, UniversitĂ  di Roma la Sapienza, Roma, Italy; Institute for Nuclear Research, Russian Academy of Sciences, Moscow, Russian Federation; Kobe University, Kobe, Japan; Department of Physics, Kyoto University, Kyoto, Japan; Physics Department, Lancaster University, Lancaster, United Kingdom; Department of Physics, University of Liverpool, Liverpool, United Kingdom; Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, United States; UniversitĂ© de Lyon, UniversitĂ© Claude Bernard Lyon 1, IPN Lyon (IN2P3), Villeurbanne, France; Department of Physics, Miyagi University of Education, Sendai, Japan; National Centre for Nuclear Research, Warsaw, Poland; State University of New York at Stony Brook, Stony Brook, NY, United States; Department of Physics and Astronomy, Osaka City University, Department of Physics, Osaka, Japan; Department of Physics, Oxford University, Oxford, United Kingdom; UPMC, UniversitĂ© Paris Diderot, Laboratoire de Physique NuclĂ©aire et de Hautes Energies (LPNHE), Paris, France; Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, United States; School of Physics, Queen Mary University of London, London, United Kingdom; Department of Physics, University of Regina, Regina, SK, Canada; Department of Physics and Astronomy, University of Rochester, Rochester, NY, United States; III. Physikalisches Institut, RWTH Aachen University, Aachen, Germany; Department of Physics and Astronomy, Seoul National University, Seoul, South Korea; Department of Physics and Astronomy, University of Sheffield, Sheffield, United Kingdom; University of Silesia, Institute of Physics, Katowice, Poland; STFC, Rutherford Appleton Laboratory, Harwell Oxford, Warrington, United Kingdom; Department of Physics, University of Tokyo, Tokyo, Japan; Institute for Cosmic Ray Research, Kamioka Observatory, University of Tokyo, Kamioka, Japan; Institute for Cosmic Ray Research, Research Center for Cosmic Neutrinos, University of Tokyo, Kashiwa, Japan; Department of Physics, University of Toronto, Toronto, ON, Canada; TRIUMF, Vancouver, BC, Canada; Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada; Faculty of Physics, University of Warsaw, Warsaw, Poland; Institute of Radioelectronics, Warsaw University of Technology, Warsaw, Poland; Department of Physics, University of Warwick, Coventry, United Kingdom; Department of Physics, University of Washington, Seattle, WA, United States; Department of Physics, University of Winnipeg, Winnipeg, MB, Canada; Faculty of Physics and Astronomy, Wroclaw University, Wroclaw, Poland; Department of Physics and Astronomy, York University, Toronto, ON, Canada references: Astier, P., (2003) Nucl. 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    Measurement of the neutrino-oxygen neutral-current interaction cross section by observing nuclear deexcitation gamma rays

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    We report the first measurement of the neutrino-oxygen neutral-current quasielastic (NCQE) cross section gamma It is obtained by observing nuclear deexcitation. rays which follow neutrino-oxygen interactions at the Super-Kamiokande water Cherenkov detector. We use T2K data corresponding to 3.01 x 10(20) protons on target. By selecting only events during the T2K beam window and with well-reconstructed vertices in the fiducial volume, the large background rate from natural radioactivity is dramatically reduced. We observe 43 events in the 4-30 MeV reconstructed energy window, compared with an expectation of 51.0, which includes an estimated 16.2 background events. The background is primarily nonquasielastic neutral-current interactions and has only 1.2 events from natural radioactivity. The flux-averaged NCQE cross section we measure is 1.55 x 10(-38) cm(2) with a 68% confidence interval of (1.22, 2.20) x 10(-38) cm(2) at a median neutrino energy of 630 MeV, compared with the theoretical prediction of 2.01 x 10(-38) cm(2)

    First muon-neutrino disappearance study with an off-axis beam

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    We report a measurement of muon-neutrino disappearance in the T2K experiment. The 295-km muon-neutrino beam from Tokai to Kamioka is the first implementation of the off-axis technique in a long-baseline neutrino oscillation experiment
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