974 research outputs found
Amplification and Increased Duration of Earthquake Motion on Uneven Stress-Free Ground
When a flat stress-free surface (i.e., the ground in seismological
applications) separating air from a isotropic, homogeneous or
horizontally-layered, solid substratum is solicited by a SH plane body wave
incident in the substratum, the response in the substratum is a single
specularly-reflected body wave. When the stress-free condition, equivalent to
vanishing surface impedance, is relaxed by the introduction of a {spatially-
constant, non- vanishing surface impedance}, the response in the substratum is
again a single reflected body wave whose amplitude is less than the one in the
situation of a stress-free ground. When the stress-free condition is relaxed by
the introduction of a a {spatially-modulated surface impedance}, which
simulates the action of an uneven (i.e., not entirely-flat) ground, the
frequency-domain response takes the form of a spectrum of {plane body waves}
and {surface waves} and {resonances} are produced at the frequencies of which
one or several surface wave amplitudes can become large. It is shown, that at
resonance, the amplitude of one, or of several, components of the motion on the
surface can be amplified with respect to the situation in which the surface
impedance is either constant or vanishes. Also, when the solicitation is
pulse-like, the integrated time history of the square of surface displacement
and of the square of velocity can be larger, and the duration of the signal can
be considerably longer, for a spatially-modulated impedance surface than for a
constant, or vanishing, impedance surface.Comment: Third International Symposium on the Effects of Surface Geology on
Seismic Motion, Grenoble, 200
Simulation of seismic response in a city-like environment
We study the seismic response of idealized 2D cities, constituted by non
equally-spaced, non equally-sized homogenized blocks anchored in a soft layer
overlying a hard half space. The blocks and soft layer are occupied by
dissipative media. To simulate such response, we use an approximation of the
viscoelastic modulus by a low-order rational function of frequency and
incorporate this approximation into a first-order-in-time scheme. Our results
display spatially-variable, strong, long-duration responses inside the blocks
and on the ground, which qualitatively match the responses observed in some
earthquake-prone cities of Mexico, France, the USA, etc.Comment: 22 pages, 8 figures, submitted to SDE
Acoustic response of a rigid frame porous medium slab with a periodic set of inclusions
The acoustic response of a rigid frame porous slab with a periodic set of
inclusions is calculated by use of a multipole method. The acoustic properties,
in particular the absorption, of such a structure are then derived and studied.
Numerical results together with a modal analysis show that the addition of a
periodic set of high-contrast inclusions leads to quasi-modes excitation of
both the slab and the gratings, and to a large increase of the acoustic
absorption of the initial slab, this being partly due to the quasi-modes
excitation.Comment: submitted to Journal of Sound and Vibratio
Acoustic identification of a poroelastic cylinder
We show how to cope with the acoustic identification of poroelastic materials
when the specimen is in the form of a cylinder. We apply our formulation, based
on the Biot model, approximated by the equivalent elastic solid model, to a
long bone-like or borehole sample specimen probed by low frequency sound
Preparation and electrical properties of dense micro-cermets made of nickel ferrite and metallic copper
Dense micro-cermets made of nickel ferrites and copper micrometric particles were obtained from partial reduction under hydrogenated atmosphere at 350 C of mixed copper nickel ferrites, and sintering in nitrogen at 980 C. The small copper particles are homogeneous in size and well dispersed in the spinel oxide matrix. No exudation of copper metal was observed after sintering. The micro-cermets prepared are semi-conducting materials with electrical conductivity lying from 44 to 130 S/cm at 980 C. Their overall characteristics make them interesting for inert anodes dedicated to aluminium electrolysis in melted cryolite
Seismic motion in urban sites consisting of blocks in welded contact with a soft layer overlying a hard half space: I. Finite set of blocks
International audienceWe address the problem of the response to a seismic wave of an urban site consisting of non-identical, non-equispaced blocks overlying a soft layer underlain by a hard substratum. The results of a theoretical analysis, appealing to a space-frequency mode-matching (MM) technique, are compared to those obtained by a space-time finite element (FE) technique. The two methods are shown to give rise to the same prediction of the seismic response for and blocks. The mechanism of the interaction between blocks and the ground, as well as that of the mutual interaction between blocks, are studied. It is shown that the presence of a small number of blocks modifies the seismic disturbance in a manner which evokes qualitatively, but not quantitatively, what was observed during the 1985 Michoacan earthquake in Mexico City. Disturbances at a much greater level, induced by a large number of blocks (in fact, a periodic set) are studied in the companion paper
Fast Cars and No Brakes: Autologous Stem Cell Transplantation as a Platform for Novel Immunotherapies
AbstractAutologous stem cell transplantation (ASCT) is indicated in a number of hematologic malignancies, including multiple myeloma, non-Hodgkin lymphoma, and Hodgkin lymphoma. Relapse, however, remains 1 of the main causes of post-ASCT failure, and several strategies are being investigated to decrease the risk of relapse of progression. Recent advances in the treatment of hematological malignancies have included adoptive transfer of genetically modified TÂ cells that express chimeric antigen receptors or TÂ cell receptors, as well the use of checkpoint inhibitors. Early clinical results in nontransplantation patients have been very promising. This review will focus on the use of gene-modified TÂ cells and checkpoint inhibitors in stem cell transplantation
La réalité virtuelle pour initier et contrôler la démarche chez des patients atteints de la maladie de Parkinson
Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal
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