14,996 research outputs found
Estudio de la fisuración de paneles sándwich de yeso laminado y alma de lana de roca = Study of the cracking of sandwich panels of plasterboard and rockwool
Este artÃculo presenta el estudio de la rotura de paneles
sándwich de yeso laminado y lana de roca bajo solicitaciones
de flexo-tracción dentro de su plano. Estos paneles se
emplean para conformar tabiques interiores de edificación
y con frecuencia se fisuran por flechas excesivas en los
forjados. Actualmente no hay modelos de cálculo fiables ni
datos experimentales que permitan estudiar este problema.
Este trabajo presenta los resultados de una campaña
experimental encaminada a caracterizar el comportamiento
en rotura de los paneles sándwich y de sus componentes
individuales. Además, se presenta un modelo cohesivo
con fisura embebida que permite simular el comportamiento
en rotura del panel sándwich conjunto. Por último
se presentan los resultados de los ensayos de fractura en
modo mixto (tracción/cortante) de paneles comerciales y
se reproduce su comportamiento con el modelo cohesivo
propuesto, obteniéndose un buen ajuste. This paper presents the study of plasterboard and rockwool sandwich panels cracking under flexural loading. These panels are usually used to perform interior partition walls and they frequently show cracking pathology due to excessive deflexion of the slabs. There are currently no reliable simulation models and experimental data for the study of this problem. This paper presents the results of an experimental campaign aimed to characterize the fracture behaviour of sandwich panels and their individual
components. In addition, the paper presents a cohesive
model with embedded crack to simulate the fracture behaviour
of the panel. Finally we present the results of tests
for mixed mode fracture (tensile / shear) commercial panels
and their behaviour is reproduced with the cohesive
model proposed, yielding a good fit
Bose-Einstein condensation in antiferromagnets close to the saturation field
At zero temperature and strong applied magnetic fields the ground sate of an
anisotropic antiferromagnet is a saturated paramagnet with fully aligned spins.
We study the quantum phase transition as the field is reduced below an upper
critical and the system enters a XY-antiferromagnetic phase. Using a
bond operator representation we consider a model spin-1 Heisenberg
antiferromagnetic with single-ion anisotropy in hyper-cubic lattices under
strong magnetic fields. We show that the transition at can be
interpreted as a Bose-Einstein condensation (BEC) of magnons. The theoretical
results are used to analyze our magnetization versus field data in the organic
compound - (DTN) at very low temperatures. This is the
ideal BEC system to study this transition since is sufficiently low to
be reached with static magnetic fields (as opposed to pulsed fields). The
scaling of the magnetization as a function of field and temperature close to
shows excellent agreement with the theoretical predictions. It allows
to obtain the quantum critical exponents and confirm the BEC nature of the
transition at .Comment: 4 pages, 1 figure. Accepted for publication in PRB
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Automatic segmentation of centromeres, foci and delineation of chromosomes
The observation of chromosomes has been crucial for our understanding of their structure, function, organization, and evolution of genes and genomes as well as morphological changes during mitotic and meiotic divisions. In this work, we present an automatic algorithm for the segmentation of centromeres and foci of DNA processing proteins, as well as the delineation of convoluted chromosomes. The algorithm is fully automatic and does not require tuning of parameters. Statistical measurements of numbers, areas distance and lengths are provided by the algorithm. The work is preliminary as this algorithm has not been tested on a large database nor used to differentiate between populations, however, it is considered that given it is fully automatic and fast it should be a useful tool for the analysis of chromosomes
Evaluation of the Aerodynamic Effect of a Smooth Rounded Roof on Crosswind Stability of a Train by Wind Tunnel Tests
The advent of high-speed trains led to new issues and constraints for railway network manufacturers and operators. This is the case of crosswind effect, that occurs when train is running in strong wind conditions. The combination of train speed and wind speed generates a relative flow that affects the train stability. Wind tunnel tests on still railway vehicles (relative wind-train velocity in coincidence with absolute wind velocity) are mandatory according to Technical Specification for Interoperability (TSI) to ensure high-speed train safety. However, issues related to the correct evaluation of the full-scale aerodynamic behaviour of the trains can arise. In the present work, aerodynamic force and pressure coefficients measured in wind tunnel tests on a scaled model of ETR1000 high-speed train on single track ballast and rails are presented. The tests were performed in the GVPM wind tunnel of Politecnico di Milano. Results show that different flow behaviours can occur at high yaw angles when the train behaves like a bluff body depending on wind speed used during the test
Plasmon polaritons in photonic superlattices containing a left-handed material
We analyze one-dimensional photonic superlattices which alternate layers of
air and a left-handed material. We assume Drude-type dispersive responses for
the dielectric permittivity and magnetic permeability of the left-handed
material. Maxwell's equations and the transfer-matrix technique are used to
derive the dispersion relation for the propagation of obliquely incident
optical fields. The photonic dispersion indicates that the growth-direction
component of the electric (or magnetic) field leads to the propagation of
electric (or magnetic) plasmon polaritons, for either TE or TM configurations.
Furthermore, we show that if the plasma frequency is chosen within the photonic
zeroth-order bandgap, the coupling of light with plasmons
weakens considerably. As light propagation is forbidden in that particular
frequency region, the plasmon-polariton mode reduces to a pure plasmon mode.Comment: 4 pages, 4 figure
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