L. Dobrzyński
A5087521827- Particle physics theoretical and experimental studies
- High-Energy Particle Collisions Research
- Quantum Chromodynamics and Particle Interactions
- Particle Detector Development and Performance
- Photonic Crystals and Applications
- Magnetic properties of thin films
- Dark Matter and Cosmic Phenomena
- Photonic and Optical Devices
- Acoustic Wave Phenomena Research
- Magnetic Properties of Alloys
- Cosmology and Gravitation Theories
- Rare-earth and actinide compounds
- Magnetic Properties and Applications
- Plasmonic and Surface Plasmon Research
- Ultrasonics and Acoustic Wave Propagation
- Acoustic Wave Resonator Technologies
- Quantum and electron transport phenomena
- Theoretical and Computational Physics
- Surface and Thin Film Phenomena
- Nuclear Physics and Applications
- Neutrino Physics Research
- Semiconductor Quantum Structures and Devices
- Crystallography and Radiation Phenomena
- Mechanical and Optical Resonators
- Metallic Glasses and Amorphous Alloys
Université de Lille
2011-2024
Institut d'électronique de microélectronique et de nanotechnologie
2011-2024
École Centrale de Lille
2008-2023
Centre National de la Recherche Scientifique
2013-2023
Université Lille Nord de France
2004-2023
Université Polytechnique Hauts-de-France
2005-2023
Laboratoire Leprince-Ringuet
2009-2022
École Polytechnique
2009-2022
National Centre for Nuclear Research
2008-2020
Institute of High Energy Physics
2010-2017
We present the first full band-structure calculations for periodic, elastic composites. For transverse polarization of vibrations we obtain a ``phononic'' band gap which extends throughout Brillouin zone. A complete acoustic or low density states should have important consequences suppression zero-point motion and localization phonons, may lead to improvements in transducers creation vibrationless environment.
We study an elastic composite described by the position-dependent mass density \ensuremath{\rho}(r), longitudinal speed of sound ${\mathit{c}}_{\mathit{l}}$(r), and transverse ${\mathit{c}}_{\mathit{t}}$(r). For a spatially periodic composite---a ``phononic crystal''---we derive eigenvalue equation for frequencies ${\mathrm{\ensuremath{\omega}}}_{\mathit{n}}$(K), where n is serial number band K Bloch wave vector. This applied to special case binary and, further, infinite cylinders that form...
Experimental measurements of acoustic transmission through a solid-solid two-dimensional binary-composite medium constituted triangular array parallel circular steel cylinders in an epoxy matrix are reported. Attention is restricted to propagation elastic waves perpendicular the cylinders. Measured transmitted spectra demonstrate existence absolute stop bands, i.e., band gaps independent direction plane Theoretical calculations structure and using wave expansion finite difference time domain...
Positron annihilation experiments were performed to identify native point defects in n-type GaN bulk crystals as well epitaxial layers. The results show that Ga vacancies are present at concentrations ${10}^{17}--{10}^{18}{\mathrm{cm}}^{\ensuremath{-}3}$ both and negatively charged, their concentration correlates with the intensity of yellow luminescence. We conclude contribute electrical compensation acceptor levels involved luminescence transition.
The propagation of transverse elastic waves both perpendicular and parallel to the laminations infinite semi-infinite periodically layered media is studied. displacement fields dispersion relations for such are obtained analytically, latter solved numerically yield corresponding curves. It shown that a medium its stress-free surface can support shear horizontal acoustic have no counterpart in homogeneous medium. Finally, dynamical Green's function obtained, possible application Brillouin...
We present results of elastic band structure for two-dimensional composite materials, composed periodical square arrays parallel cylinders in a background. reveal, the first time, existence several very large complete gaps material practical interest such as C fibre reinforced epoxy composite. Within these propagation acoustic waves is forbidden. The influence geometry and effect composition on are studied. also compare with those obtained metallic composites W (Al) an Al (W) matrix....
innodata J. O. VASSEUR et al. MAGNON BAND STRUCTURE OF PERIODIC COMPOSITES We calculate the spin-wave spectra of two-dimensional composite materials consisting periodic square arrays parallel cylinders made a ferromagnetic material embedded in background. Each is described by its spontaneous magnetization ${\mathit{M}}_{\mathit{S}}$ and exchange constant A. An external static magnetic field applied along direction both are assumed to be magnetized this field. consider spin-waves propagation...
Transmission of acoustic waves in two-dimensional binary solid/solid composite media composed arrays Duralumin cylindrical inclusions embedded an epoxy resin matrix is studied. The experimental transmission spectrum and theoretical band structure two periodic cylinders organized on a square lattice centred rectangular network are reported. Absolute gaps extending throughout the first Brillouin zone predicted. measured observed to drop noise level frequency intervals reasonable agreement with...
We study theoretically the propagation of elastic waves in two-dimensional composite media composed a square array hollow steel cylinders embedded water using finite-difference time-domain method. These constitute class acoustic band gap materials with narrow pass bands their transmission stop bands. The frequency at which occurs is tunable by controlling inner radius tubular inclusions. effect tube on spectrum semiquantitatively separable from periodicity. A linear defect formed row an...
Elastic waves, polarized in the sagittal plane, are investigated infinite and semi-infinite superlattices made from alternate layers of two isotropic media. By use a transfer-matrix method, we obtain explicit equations for dispersion bulk modes as well surface superlattice. We present few illustrations theory Al-W which relative thicknesses media or thickness layer at varied.
A neutron-scattering experiment to look for spin-wave excitation-energy changes of magnetite at the transition point 119°K showed no such change. During this work we discovered, however, that low-temperature structure gives rise weak extra neutron-diffraction lines can be indexed as (h, k, l±½) in cubic indices. From observed neutron polarization sensitivity intensities and increasing factors with sinθ/λ, conclude reflections are not directly due magnetic ordering (ferrimagnetic spirals or...
The propagation of acoustic waves in a two-dimensional composite medium constituted square array parallel copper cylinders air is investigated both theoretically and experimentally. band structure calculated with the plane wave expansion (PWE) method by imposing condition elastic rigidity to solid inclusions. PWE results are then compared transmission coefficients computed finite difference time domain (FDTD) for thickness samples. In low frequency regime, calculations agree FDTD indicating...
We study theoretically the propagation of acoustic waves through a linear waveguide, created inside two-dimensional phononic crystal, along which side branch (or stub) is attached. The primary effect this resonator to induce zeros transmission in spectrum perfect waveguide. transmittivity exhibits very narrow dips whose frequencies depend upon width and length stub. When gap exists stub may also permit selective frequency gap. have considered crystals constituted by either fluid or solid...