Bibliographies thématiques / Conical hollow beam

Littérature scientifique sur le sujet « Conical hollow beam »

Auteur : Grafiati
Publié le 10 mars 2023

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Articles de revues sur le sujet "Conical hollow beam"

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Melnyk, Igor, Sergey Tugay, Volodymyr Kyryk et Iryna Shved. « Methods and algorithm for calculating the focal parameters of a hollow conical electron beam in high-voltage glow discharge electron guns with a focusing magnetic lens ». System research and information technologies, no 3 (18 novembre 2021) : 17–32. http://dx.doi.org/10.20535/srit.2308-8893.2021.3.02.

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The algorithm is considered for calculating the focal distance of a hollow conical electron beam generated by high-voltage glow discharge electron guns with magnetic focusing of the beam in the drift region, as well as a method for calculating the diameter of the focal ring and its thickness for such a beam. The proposed algorithm is based on the theory of electron drift in the field of a focusing magnetic lens and is designed using the methods of discrete mathematics and the minimax analysis. The obtained simulation results made it possible to establish the influence of the magnetic lens current on the focal diameter of a hollow conical electron beam and on its focal ring thickness. It is shown that the change in the focal parameters of a hollow conical electron beam can be effectively provided through the regulation of the magnetic lens current.
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Kim, J. A., K. I. Lee, H. Nha, H. R. Noh et W. Jhe. « Cold Atoms in a Hollow Mirror Trap ». International Journal of Modern Physics B 11, no 28 (10 novembre 1997) : 3311–17. http://dx.doi.org/10.1142/s0217979297001611.

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We present a novel and simple vapour-cell magneto-optical atom trap in a pyramidal and a conical hollow mirror cavity. A single laser beam having modulation sidebands at microwaves is used for cooling, trapping and repumping of rubidium atoms. When the laser is circularly polarized and sent into the hollow region, three pairs of counterpropagating beams are automatically produced therein, having the same polarization configuration as in the conventional six beam magneto-optical trap. The precooled atom sources thus produced may be used to obtain much colder and denser atoms for study of their quantum statistical properties.
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Amoiropoulos, Kostas, Georgia Kioselaki, Nikolaos Kourkoumelis et Aris Ikiades. « Shaping Beam Profiles Using Plastic Optical Fiber Tapers with Application to Ice Sensors ». Sensors 20, no 9 (28 avril 2020) : 2503. http://dx.doi.org/10.3390/s20092503.

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Using either bulk or fiber optics the profile of laser beams can be altered from Gaussian to top-hat or hollow beams allowing enhanced performance in applications like laser cooling, optical trapping, and fiber sensing. Here, we report a method based on multimode Plastic Optical Fibers (POF) long-tapers, to tweak the beam profile from near Gaussian to a hollow beam, by generating surface irregularities on the conical sections of the taper with a heat-and-pull technique. Furthermore, a cutback technique applied on long tapers expanded the output beam profile by more than twice the numerical aperture (NA) of the fiber. The enhanced sensitivity and detection efficiency of the extended profile was tested on a fiber optical ice sensor related to aviation safety.
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Vest, T. A., et M. S. Darlow. « A Modified Conical Beam Element Based on Finite Element Analysis : Experimental Correlations ». Journal of Vibration and Acoustics 112, no 3 (1 juillet 1990) : 350–54. http://dx.doi.org/10.1115/1.2930515.

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A portion of the results from a previous investigation into the structural behavior of hollow conical sections has been used to develop a method of correcting the conical beam element used in modern rotordynamic programs. The modification is made by altering the local value of the Young’s modulus so that the equations used in the conical element produce a bending flexibility which corresponds to that determined from detailed, three-dimensional finite element models. The use of this modification produces substantial improvement in the prediction of the first five natural frequencies of a hollow nonrotating shaft containing two opposed conical sections, for a range of wall thicknesses. The modification exhibits a length dependency which appears to be a main cause of the remaining discrepancies, though it is pointed out that the procedure is only a partial implementation of a more complete hybrid element to be presented later. Static experiments are also discussed, and the verification of a unique behavior characteristic of steep tapered sections is reported.
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Ovchinnikov, Yu B., I. Manek, A. I. Sidorov, G. Wasik et R. Grimm. « Gravito-optical atom trap based on a conical hollow beam ». Europhysics Letters (EPL) 43, no 5 (1 septembre 1998) : 510–15. http://dx.doi.org/10.1209/epl/i1998-00390-9.

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Lee, K. I., J. A. Kim, H. R. Noh et W. Jhe. « Single-beam atom trap in a pyramidal and conical hollow mirror ». Optics Letters 21, no 15 (1 août 1996) : 1177. http://dx.doi.org/10.1364/ol.21.001177.

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Bentley, J., K. B. Alexander et Z. L. Wang. « TEM Z-contrast imaging with wide-angle hollow-cone illumination ». Proceedings, annual meeting, Electron Microscopy Society of America 48, no 4 (août 1990) : 400–401. http://dx.doi.org/10.1017/s0424820100175132.

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High resolution scanning transmission electron microscopy (STEM) images with contrast sensitive to atomic number (Z-contrast) have been obtained with the use of a high-angle annular detector. The equivalent conventional transmission electron microscopy (TEM) dark-field mode reciprocally related to Z-contrast STEM is wide-angle hollow-cone illumination with an on-axis objective aperture. There are two ways to obtain hollow cone illumination; with an annular condenser aperture or by conically scanning the beam tilt coils. As in the case of STEM Z-contrast imaging, resolution with hollow-cone illumination should theoretically be higher than for phase contrast imaging in the same instrument.Philips CM30/STEM, CM12/STEM, and EM400T/FEG/STEM instruments have been used to investigate this imaging technique. The conical illumination dark-field mode is standard on the CM series and was implemented with a hybrid diffraction unit on the EM400. Commercial (SPI Supplies #1780) copper annular apertures with inner and outer diameters of 600 and 900 μm, respectively, spot welded to suitable supports for use as condenser apertures, resulted in cone angles too small to give good Z-contrast in the microprobe mode, because there is still a large diffraction contrast contribution.
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Dépret, Benoı̂t, Philippe Verkerk et Daniel Hennequin. « Characterization and modelling of the hollow beam produced by a real conical lens ». Optics Communications 211, no 1-6 (octobre 2002) : 31–38. http://dx.doi.org/10.1016/s0030-4018(02)01900-4.

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Rankin, Joanna M. « An Empirical Theory of Pulsar Emission ». International Astronomical Union Colloquium 128 (1992) : 132–39. http://dx.doi.org/10.1017/s0002731600154939.

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AbstractA system of pulsar profile classification is used as a starting point to study the emission characteristics of pulsars. Two types or mechanisms of pulsar radiation are identified which combine geometrically to produce five major species of profile. The core emission, which forms a pencil beam of radiation, is apparently produced close to the stellar surface throughout the entire polar cap region by low γ particles. The conal emission, which consists of a hollow conical beam, then seems to be emitted at heights of 10 to 20 stellar radii by currents of high γ particles travelling along some of the most peripheral of the “open” field lines.
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Burdonsky, I. N., A. L. Velikovich, V. V. Gavrilov, A. Yu Gol'tsov, E. V. Zhuzhukalo, N. G. Kovalsky, M. A. Liberman et M. I. Pergament. « Studies of thin foils acceleration by pulsed laser beam ». Laser and Particle Beams 6, no 2 (mai 1988) : 327–34. http://dx.doi.org/10.1017/s0263034600004080.

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Experimental studies of the ablative acceleration of thin foils as carried out on the “Mishen” device (Nd laser, λ = 1·06μm, 3 nsec pulses) are reported. The plasma corona in the range of power densities 1013–1014 W/cm2 is shown to absorb 80–90% of the laser beam energy, the classical collisional absorption mechanism being the main one. Jet-like and filamentary structures are observed in the laser-plasma interaction; however, the main plasma parameters are found to be independent of the presence (or absence) of such structures. The measured hydrodynamic efficiency of stable ablative acceleration in plane geometry is ≲5%. The production of high-speed cumulative jets with irradiated thin-wall hollow conical targets is reported as an example of a non-traditional ablative acceleration geometry.
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Thèses sur le sujet "Conical hollow beam"

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Wu, Jun-De, et 吳俊德. « A Hollow Conical Beam Finite Element for Rotor Dymanics Analysis ». Thesis, 1996. http://ndltd.ncl.edu.tw/handle/48775392147103513959.

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碩士
國立中央大學
機械工程學系
84
The article is proposed to derive a hollow conical beam finite element formulation especially for large rotor. The shape functions are obtained from the homogeneous solution of the governing equation neglecting dynamic effects. Four illustrative examples demonstrate the performance of this element, and allow comparisons of results with those obtained by elements derived from Greenhill, Bickford and Nelson''s formulations based on polynomial shape function. As the result shown, when the taper gets steeper or complicated,the rate of convergency is increasing. And the effect of gyroscopic donot have much influence on rate of convergency.
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Taglialegne, Luca. « ANALYTICAL STUDY OF STRESS FIELDS IN WIND TURBINE BLADES ». Doctoral thesis, 2018. http://hdl.handle.net/2158/1152810.

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The thesis aims at shedding light on the difference in the stress distribution between prismatic and non-prismatic beams. The approach strategy has being that of drastically simplifying the initial problem in the attempt to identify the relevant governing parameters. The geometry of a real wind turbine blade has been first drastically simplified: from the multi-cellular airfoil to a box girder and to a single web panel. Once solved the simplest problems, the intention has been to gradually reintegrate the complexity of the problem with the aim of applying the obtained results to a real wind turbine blade. The thesis consists of three parts. In the first part some brief information on the technology of wind energy and wind turbines are given. Also, the state of the art of the modeling of non-prismatic beams is discussed, with a particular focus on tapered beams. After some first remarkable results obtained at the beginning of the 20th century, the literature survey shows that only in recent years it has been an increase of interest on the subject. In the second part all the theoretical details that lead to the approach that is subject of the present thesis are deepened. In the third part the results of the application of the strategy proposed to both elementary and more complex geometries are shown, and the final remarks on the 10MW wind turbine blade are discussed.
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Actes de conférences sur le sujet "Conical hollow beam"

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Melnyk, I. V., V. G. Melnyk, B. A. Tugai, S. B. Tuhai, N. I. Mieshkova et A. V. Pochynok. « Simplyfied Universal Analytical Model for Defining of Plasma Boundary Position in the Glow Discharge Electron Guns for Forming Conic Hollow Electron Beam ». Dans 2019 IEEE 39th International Conference on Electronics and Nanotechnology (ELNANO). IEEE, 2019. http://dx.doi.org/10.1109/elnano.2019.8783454.

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