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The readout of negatively charged nitrogen-vacancy centre electron spins is essential for applications in quantum computation, metrology and sensing. Conventional readout protocols are based on the detection of photons emitted from nitrogen-vacancy centres, a process limited by the efficiency of photon collection. We report on an alternative principle for detecting the magnetic resonance of nitrogen-vacancy centres, allowing the direct photoelectric readout of nitrogen-vacancy centres spin state in an all-diamond device. The photocurrent detection of magnetic resonance scheme is based on the detection of charge carriers promoted to the conduction band of diamond by two-photon ionization of nitrogen-vacancy centres. The optical and photoelectric detection of magnetic resonance are compared, by performing both types of measurements simultaneously. The minima detected in the measured photocurrent at resonant microwave frequencies are attributed to the spin-dependent ionization dynamics of nitrogen-vacancy, originating from spin-selective non-radiative transitions to the metastable singlet state.

The design and maintenance of turnouts implies considering a great number of external factors that have an effect on their structural integrity. The proper generalised decomposition (PGD) method is used in this paper to carry out a parametrised study of the vehicle-track interaction in a non-intrusive way. The reduced model is built using a defined domain for some of the influence parameters: the vehicle speed, the wheel/rail friction coefficient and the axle load. A major assumption of the PGD solution is its ability to express quantities of interest in a separated form. One of the goals is to show the relevance of separability in the field of railway dynamics. The example of a switch is chosen as a validation of method. The output of the PGD model is the dissipated energy per metre in the switch rail. The robustness of the reduced model is verified using the complete solution. Probabilistic simulations are carried out in order to explore the possibility of using the PGD solution as a numerical abacus in dynamic simulations of switches and crossings. These first tests show that the PGD solution is a promising reduction model method in railway dynamics. [ABSTRACT FROM AUTHOR]

Les contributions successives de différents auteurs ont permis d'identifier les phénomènes mis en jeu dans la compaction des sédiments, puis de proposer des modélisations mécaniques cohérentes de ce processus. On s'intéresse ici aux non-linéarités géométriques dues à la forte diminution de la porosité: elles imposent de renoncer à employer la déformation de Green-Lagrange linéarisée. On adopte une loi de comportement adaptée aux grandes transformations d'un milieu poreux élastique dont les constituants sont incompressibles pour étudier la diminution de porosité liée aux phénomènes purement mécaniques intervenant dans la compaction. The numerous works devoted to the phenomena involved in the compaction of sediments have led to a good understanding and to mechanically consistent modellings of this process. During compaction, large reduction of porosity occurs and the sediments undergo large strains : in this context, the usual linearized Green-Lagrange strain tensor is no longer relevant. Using the constitutive law of a poroelastic medium (made of incompressible constituents) at large strains, we discuss the influence of geometrical nonlinearities in the study of purely mechanical compaction.

An analysis is presented to study the stability of a shallow masonry tunnel of the Paris metro subjected to the spreading of the vault's supports caused by nearby excavations. FEM numerical computations are carried out using a specifically developed model for the masonry that combines a homogenization technique with a damage model. Calculations display three hinges in the vault. Measures show that the masonry vault may withstand about 2 centimeters of support spreading. Soil–structure interaction analysis shows that the ground reaction is critical to ensure stability. The loss of stiffness and shear strength of the soil next to the sidewalls produces severe deformations and cracks in the structure. Based on the results some thresholds are proposed. The study also presents an analysis on the importance of the constitutive law for masonry and a brief discussion on the use of Eurocodes to investigate the stability of the vault. [ABSTRACT FROM AUTHOR]

Author(s): E. Bustarret (corresponding author) [1, 7]; C. Marcenat (corresponding author) [3, 7]; P. Achatz [1, 3]; J. Kačmarčik [1, 4]; F. Lévy [3]; A. Huxley [3, 8]; L. Ortéga [...]