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Search Results: 1 - 10 of 223817 matches for " R. Roncin "
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Diffraction of fast atoms and molecules from surfaces
J. R. Manson,Hocine Khemliche,Philippe Roncin
Physics , 2008,
Abstract: Prompted by recent experimental developments, a theory of surface scattering of fast atoms at grazing incidence is developed. The theory gives rise to a quantum mechanical limit for ordered surfaces that describes coherent diffraction peaks whose thermal attenuation is governed by a Debye-Waller factor, however, this Debye-Waller factor has values much larger than would be calculated using simple models. A classical limit for incoherent scattering is obtained for high energies and temperatures. Between these limiting classical and quantum cases is another regime in which diffraction features appear that are broadened by the motion in the fast direction of the scattered beam but whose intensity is not governed by a Debye-Waller factor. All of these limits appear to be accessible within the range of currently available experimental conditions.
Simulation Du Comportement Dynamique Du Voilier
Kostia Roncin
Physics , 2010,
Abstract: A simulator of two sailing boats in interaction is being made in order to provide sportsmen with a reliable analytical tool. We presently describe different models we used. Stationary hydrodynamics efforts have been specially evaluated. Experiences plan method has been implemented to exploit the towing tank tests made in the Fluids Mechanic Laboratory of Ecole Centrale de Nantes. Here are set out partial results of the model we achieved. At last, a simulator example illustrates the possibilities provided.
Image processing for grazing incidence fast atom diffraction: the $β_2$(2x4) reconstruction of the GaAs(001) surface
Maxime Debiossac,Philippe Roncin
Physics , 2015,
Abstract: Grazing incidence fast atom diffraction (GIFAD, or FAD) has developed as a very sensitive technique most suited for well ordered crystalline surfaces. Such high quality surfaces are routinely fabricated in molecular beam epitaxy (MBE) chamber and a GIFAD setup has been installed allowing in situ operation. Focusing here on static condition, i.e. before or after the growth process, the paper describes in details the few steps needed to measure the relative intensities of the diffraction spots. Care is taken to outline the underlying physical assumptions.
Atom beam triangulation of organic layers at 100 meV normal energy: self-assembled perylene on Ag(110) at room temperature
Nataliya Kalashnyk,Philippe Roncin
Physics , 2015,
Abstract: The controlled growth of organic layer on surface is still awaiting for an on-line reliable monitoring that would allow improvement of its quality. We show here that the self-assembly of the perylene monolayer deposited on Ag(110) at room temperature can be tracked with low energy atoms in a regime where the energy perpendicular to the layer is less than 0.1 eV preventing damage to the layer. The image processing required for this triangulation technique with atoms is described in details.
Grazing incidence fast atom diffraction for He atoms impinging on a Ag(110) surface
C. A. Ríos Rubiano,G. A. Bocan,M. S. Gravielle,N. Bundaleski,H. Khemliche,P. Roncin
Physics , 2013,
Abstract: Experimental diffraction patterns produced by grazing scattering of fast helium atoms from a Ag(110) surface are used as a sensitive tool to test both the scattering and the potential models. To describe the elastic collision process we employ the surface eikonal (SE) approximation, which is a semi-classical method that includes the quantum interference between contributions coming from different projectile paths. The projectile-surface potential is derived from an accurate density-functional theory (DFT) calculation that takes into account the three degrees of freedom of the incident projectile. A fairly good agreement between theoretical and experimental momentum distributions is found for incidence along different low-indexed crystallographic directions.
Simulation dynamique du voilier
Kostia Roncin,Jean-Michel Kobus
Physics , 2010,
Abstract: A sailing simulator has been developed from a new point of view. It will rather be for the sailor to use it than for the architect. One boat which characteristics were already known has been chosen. The whole coupled mechanic equations system has been solved. Heave and pitch equations, usually neglected, have been introduced to evaluate each trim of the crew and provide an optimal ride analysis tool. In this paper, efforts models and their determination's method are briefly presented. A tack simulation is shown as a brief overview on the simulator possibilities.
The Waveform Digitiser of the Double Chooz Experiment: Performance and Quantisation Effects on PhotoMultiplier Tube Signals
Y. Abe,T. Akiri,A. Cabrera,B. Courty,J. V. Dawson,L. F. G. Gonzalez,A. Hourlier,M. Ishitsuka,H. de Kerret,D. Kryn,P. Novella,M. Obolensky,S. Perasso,A. Remoto,R. Roncin
Physics , 2013, DOI: 10.1088/1748-0221/8/08/P08015
Abstract: We present the waveform digitiser used in the Double Chooz experiment. We describe the hardware and the custom-built firmware specifically developed for the experiment. The performance of the device is tested with regards to digitising low light level signals from photomultiplier tubes and measuring pulse charge. This highlights the role of quantisation effects and leads to some general recommendations on the design and use of waveform digitisers.
Une Chaine de Mesure Permettant de Caracteriser la Performance en Voile
Paul Iachkine,Sophie Barré,Kostia Roncin,Jean-Michel Kobus
Physics , 2010,
Abstract: This paper presents the experimental set-up and the analysis tools developed for the performance evaluation in sailing. The measurement system is composed of sensors for the position and attitude of the sail boat, sensors for the wind measurement and some tools for the coach.
Factor structure and internal consistency of the 12-item General Health Questionnaire (GHQ-12) and the Subjective Vitality Scale (VS), and the relationship between them: a study from France
Mare? Salama-Younes, Ali Montazeri, Amany Isma?l, Charles Roncin
Health and Quality of Life Outcomes , 2009, DOI: 10.1186/1477-7525-7-22
Abstract: Using a standard 'forward-backward' translation procedure, the English language versions of the two instruments (i.e. the 12-item General Health Questionnaire and the Subjective Vitality Scale) were translated into French. A sample of adults aged 58–72 years then completed both questionnaires. Internal consistency was assessed by Cronbach's alpha coefficient. The factor structures of the two instruments were extracted by confirmatory factor analysis (CFA). Finally, the relationship between the two instruments was assessed by correlation analysis.In all, 217 elderly adults participated in the study. The mean age of the respondents was 61.7 (SD = 6.2) years. The mean GHQ-12 score was 17.4 (SD = 8.0), and analysis showed satisfactory internal consistency (Cronbach's alpha coefficient = 0.78). The mean VS score was 22.4 (SD = 7.4) and its internal consistency was found to be good (Cronbach's alpha coefficient = 0.83). While CFA showed that the VS was uni-dimensional, analysis for the GHQ-12 demonstrated a good fit not only to the two-factor model (positive vs. negative items) but also to a three-factor model. As expected, there was a strong and significant negative correlation between the GHQ-12 and the VS (r = -0.71, P < 0.001).The results showed that the French versions of the 12-item General Health Questionnaire (GHQ-12) and the Subjective Vitality Scale (VS) are reliable measures of psychological distress and vitality. They also confirm a significant negative correlation between these two instruments, lending support to their convergent validity in an elderly French population. The findings indicate that both measures have good structural characteristics.The General Health Questionnaire (GHQ) was developed in England as a screening instrument to identify psychological distress in primary care settings [1]. It was originally designed as a 60-item instrument but several shortened versions are currently available, including the GHQ-30, the GHQ-28, the GHQ-20 and the GH
High-sensitive Optical Pulse-Shape Characterization using a Beating-Contrast-Measurement Technique
Vincent Roncin,Sylvain Fève,Audrey Millaud,Romain Cramer,Yves Jaou?n,Jean-Claude Simon
Physics , 2014,
Abstract: Ultrahigh-speed optical transmission technology, such as optical time domain multiplexing or optical signal processing is a key point for increasing the communication capacity. The system performances are strongly related to pulse properties. We present an original method dedicated to short pulse-shape characterization with high repetition rate using standard optical telecommunications equipments. Its principle is based on temporal measurement of the contrast produced by the beating of two delayed optical pulses in a high bandwidth photo detector. This technique returns firstly reliable information on the pulse-shape, such as pulse width, shape and pedestal. Simulation and experimental results evaluate the high-sensitivity and the high-resolution of the technique allowing the measurement of pulse extinction ratio up to 20 dB with typical timing resolution of about 100 fs. The compatibility of the technique with high repetition rate pulse measurement offers an efficient tool for short pulse analysis.
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