649 research outputs found
A micromechanical model of elastoplastic and damage behavior of a cohesive geomaterial
AbstractThe present study is devoted to the development and validation of a nonlinear homogenization approach of the mechanical behavior of Callovo-Oxfordian argillites. The material is modeled as an heterogeneous composite composed of an elastoplastic clay matrix and of linear elastic or elastic damage inclusions. The macroscopic constitutive law is obtained by adapting the incremental method proposed by Hill [Hill, R., 1965. Continuum micro-mechanics of elastoplastic polycrystals. J. Mech. Phys. Solids 13, 89–101]. The approach consists in formulating the macroscopic tangent operator of the material by considering the nonlinear local behavior of each phase. Due to the matrix/inclusion morphology of the microstructure of the argillite, a Mori–Tanaka scheme is considered for the localization step. The developed model is first compared to Finite Element calculations and then validated and applied for the prediction of the macroscopic stress–strain responses of argillites
Comportement mécanique d'une pâte de ciment pétrolier sous température : Effet de la dégradation chimique
Cette étude présente l'influence d'une dégradation chimique sur le comportement thermo-hydro-mécanique (THM) d'une pâte de ciment pétrolier servant de barrière d'étanchéité dans les puits pétroliers. Afin de caractériser l'évolution du comportement THM avec la dégradation, des essais de compression triaxiale cyclique à différentes pressions de confinement avec une pression interstitielle constante sont réalisés sur le matériau à l'état sain et complètement dégradé par le nitrate d'ammonium, sous température de 90 °C. Les résultats obtenus montrent d'importantes évolutions. Le matériau sain présente une très faible phase élastique et une forte phase plastique évoluant avec le confinement. La résistance à la rupture diminue drastiquement après la dégradation chimique conduisant à une augmentation de la porosité. Le coefficient élastique chute également et évolue peu au cours de l'essai. Par ailleurs, un passage clair d'un comportement fragile à un comportement ductile est constaté avec la dégradation, notamment pour des faibles confinements
Distributed phase-covariant cloning with atomic ensembles via quantum Zeno dynamics
We propose an interesting scheme for distributed orbital state quantum
cloning with atomic ensembles based on the quantum Zeno dynamics. These atomic
ensembles which consist of identical three-level atoms are trapped in distant
cavities connected by a single-mode integrated optical star coupler. These
qubits can be manipulated through appropriate modulation of the coupling
constants between atomic ensemble and classical field, and the cavity decay can
be largely suppressed as the number of atoms in the ensemble qubits increases.
The fidelity of each cloned qubit can be obtained with analytic result. The
present scheme provides a new way to construct the quantum communication
network.Comment: 5 pages, 4 figure
Spontaneous CP Violating Phase as The CKM Matrix Phase
We propose that the CP violating phase in the CKM mixing matrix is identical
to the CP phases responsible for the spontaneous CP violation in the Higgs
potential. A specific multi-Higgs model with Peccei-Quinn (PQ) symmetry is
constructed to realize this idea. The CP violating phase does not vanish when
all Higgs masses become large. There are flavor changing neutral current (FCNC)
interactions mediated by neutral Higgs bosons at the tree level. However,
unlike general multi-Higgs models, the FCNC Yukawa couplings are fixed in terms
of the quark masses and CKM mixing angles. Implications for meson-anti-meson
mixing, including recent data on mixing, and neutron electric dipole
moment (EDM) are studied. We find that the neutral Higgs boson masses can be at
the order of one hundred GeV. The neutron EDM can be close to the present
experimental upper bound.Comment: 16 pages, RevTex. Several typos corrected, and one reference adde
Field Measurements of Terrestrial and Martian Dust Devils
Surface-based measurements of terrestrial and martian dust devils/convective vortices provided from mobile and stationary platforms are discussed. Imaging of terrestrial dust devils has quantified their rotational and vertical wind speeds, translation speeds, dimensions, dust load, and frequency of occurrence. Imaging of martian dust devils has provided translation speeds and constraints on dimensions, but only limited constraints on vertical motion within a vortex. The longer mission durations on Mars afforded by long operating robotic landers and rovers have provided statistical quantification of vortex occurrence (time-of-sol, and recently seasonal) that has until recently not been a primary outcome of more temporally limited terrestrial dust devil measurement campaigns. Terrestrial measurement campaigns have included a more extensive range of measured vortex parameters (pressure, wind, morphology, etc.) than have martian opportunities, with electric field and direct measure of dust abundance not yet obtained on Mars. No martian robotic mission has yet provided contemporaneous high frequency wind and pressure measurements. Comparison of measured terrestrial and martian dust devil characteristics suggests that martian dust devils are larger and possess faster maximum rotational wind speeds, that the absolute magnitude of the pressure deficit within a terrestrial dust devil is an order of magnitude greater than a martian dust devil, and that the time-of-day variation in vortex frequency is similar. Recent terrestrial investigations have demonstrated the presence of diagnostic dust devil signals within seismic and infrasound measurements; an upcoming Mars robotic mission will obtain similar measurement types
The evolution of microstructure and electrical performance in doped Mn-Co and Cu-Mn oxide layers with the extended oxidation time
Mn-Co and Cu-Mn based alloy coatings are deposited on 430 SS by high energy micro-arc alloying process, and then alloy coatings are oxidized at 750 ℃ in air to form the spinel oxides. Some composite oxides, such as Co3O4, Mn2O3 and (Mn,Co)3O4, are formed at the initial stage of oxidation. The single-phase spinel (pure MnCo2O4) without impurity phases is only found on the surface of Co-33Mn-17Cu oxide layer with the extended oxidation time, its area-specific resistance values at 500 ℃ to 800 ℃ are low and close to that of Mn-35Cu oxide layer which mainly composed of Cu1.2Mn1.8O4 spinel
Consequences of temperature fluctuations in observables measured in high energy collisions
We review the consequences of intrinsic, nonstatistical temperature
fluctuations as seen in observables measured in high energy collisions. We do
this from the point of view of nonextensive statistics and Tsallis
distributions. Particular attention is paid to multiplicity fluctuations as a
first consequence of temperature fluctuations, to the equivalence of
temperature and volume fluctuations, to the generalized thermodynamic
fluctuations relations allowing us to compare fluctuations observed in
different parts of phase space, and to the problem of the relation between
Tsallis entropy and Tsallis distributions. We also discuss the possible
influence of conservation laws on these distributions and provide some examples
of how one can get them without considering temperature fluctuations.Comment: Revised version of the invited contribution to The European Physical
Journal A (Hadrons and Nuclei) topical issue about 'Relativistic Hydro- and
Thermodynamics in Nuclear Physics' guest eds. Tamas S. Biro, Gergely G.
Barnafoldi and Peter Va
Numerical modelling of gas flow in a compact clay barrier for DECOVALEX-2019
The mechanisms controlling the movement of gases through geological disposal facilities can be described by models
accounting for (i) diffusion, (ii) two-phase flow, (iii) localised flow pathways and (iv) gas fracturing of the rock. It is therefore
necessary to consider all these phenomena for a better understanding of the processes governing the movement of gases in low
permeability materials. The purpose of Task A in the current phase of the DEvelopment of COupled models and their VALidation
against Experiments (DECOVALEX) project is to better understand the processes governing the advective movement of gas. In this
paper, a synthesis of the ongoing work of eight participating modelling teams is presented. A wide range of 2D and 3D approaches
including (i) continuous strategies assuming different mechanical deformation behaviors, (ii) continuous models with distinct phases
or embedded fractures and (iii) discrete models with different formulations are validated against a gas flow test on pre-compacted
bentonite undertaken by the British Geological Survey. The results of the ongoing work show that after a calibration process, plausible
descriptions of the laboratory experiment can be achieved
Recurrent mutations in the U2AF1 splicing factor in myelodysplastic syndromes
Myelodysplastic syndromes (MDS) are hematopoietic stem cell disorders that often progress to chemotherapy-resistant secondary acute myeloid leukemia (sAML). We used whole-genome sequencing to perform an unbiased comprehensive screen to discover the somatic mutations in a sample from an individual with sAML and genotyped the loci containing these mutations in the matched MDS sample. Here we show that a missense mutation affecting the serine at codon 34 (Ser34) in U2AF1 was recurrently present in 13 out of 150 (8.7%) subjects with de novo MDS, and we found suggestive evidence of an increased risk of progression to sAML associated with this mutation. U2AF1 is a U2 auxiliary factor protein that recognizes the AG splice acceptor dinucleotide at the 3' end of introns, and the alterations in U2AF1 are located in highly conserved zinc fingers of this protein. Mutant U2AF1 promotes enhanced splicing and exon skipping in reporter assays in vitro. This previously unidentified, recurrent mutation in U2AF1 implicates altered pre-mRNA splicing as a potential mechanism for MDS pathogenesis
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