Search results for "fluids"
showing 10 items of 1936 documents
The numerical challenges in multiphysical modeling of laser welding with arbitrary Lagrangian-Eulerian method
2018
International audience; The interaction of high power laser beam with metallic materials produces a number of interconnected phenomena that represent a serious challenge for numerical modeling, especially for creation of auto-consistent models. Additional difficulty consists in lack of data on materials properties at the temperatures superior to their melting point. The present work summarizes the numerical challenges in creation and validation of free-surface models using ALE moving mesh coupled with heat transfer equation and Navier-Stokes fluid flow.
Altered (oxidized) C1q induces a rheumatoid arthritis-like destructive and chronic inflammation in joint structures in arthritis-susceptible rats.
1997
Previous studies have identified an altered C1q molecule in synovial fluids from the joints of rheumatoid arthritis patients. We therefore immunized arthritis-susceptible Lewis 1A.AVN rats with either native C1q (C1q nat), altered (oxidized) C1q (C1q ox), or type II collagen (CII, induces arthritis in these animals), in order to induce arthritis. Unlike C1q nat, both CII and C1q ox were able to induce swelling and erythema of joints consistent with an arthritis-like inflammatory reaction. Histopathological evaluation of individual joint sections revealed synovitis, bursitis and tendovaginitis, massive joint destruction, and severe pannus formation. In a time-course study, no differences in …
Ritz Solution for Transient Analysis of Variable-Stiffness Shell Structures
2020
The dynamic response of thin-walled structures is driven by mass and stiffness distribution. As such, variable-stiffness (VS) composites offer opportunities to tune structural dynamic responses. To this extent, efficient analysis tools become increasingly important for structural analysis and design purposes. In this work, an efficient and versatile Ritz method for free vibrations and linear transient analysis of VS doubly curved shell structures is presented. VS shell structures are modeled as an assembly of shell-like domains. The shell kinematics is based on the first-order shear deformation theory, and no further assumption is made on the shallowness or on the thinness of the structure.…
Coronary Stent Strut Fractures: Classification, Prevalence and Clinical Associations
2021
Introduction. The frequency, characteristics and clinical implications of Strut fractures (SFs) remain incompletely understood. Methods and results. A total of 185 (160 patients) newer-generation drug-eluting stents (DES) were imaged. SFs were found in 21 DES (11.4%) and were classified in four patterns: one single stacked strut (41%)
Noise effect in a FitzHugh-Nagumo circuit driven by a bichromatic signal
2013
We analyze the response of a nonlinear circuit exactly ruled by the FitzHugh-Nagumo equations. This circuit is submitted to a bichromatic signal including a high frequency and a low frequency. In absence of noise, we show that for an appropriate amplitude of the high frequency driving, the response of the circuit estimated at the low frequency can be optimized via the phenomenon of vibrational resonance. Next, we show that under certain conditions, noise can contribute to the effect of vibrational resonance. Colored noise is also considered. Our experimental results are confirmed by a numerical analysis.
Noise effect in a sine-Gordon Lattice
2013
International audience; This paper is devoted to the influence of internal noise in a sine-Gordon chain exhibiting the well known nonlinear supratransmission phenomenon. It is shown that spatiotemporal noise can trigger breather modes with a given probability in a range of parameters where they do not occur without noise. A frequency analysis is carried out to quantify the degree of coherence of the emitted breather. It is shown that there exists an appropriate amount of noise which ensures the existence of breather modes with the best coherence.
Johnson-Nyquist Noise Effects in Neutron Electric-Dipole-Moment Experiments
2021
Magnetic Johnson-Nyquist noise (JNN) originating from metal electrodes, used to create a static electric field in neutron electric-dipole-moment (nEDM) experiments, may limit the sensitivity of measurements. We present here the first dedicated study on JNN applied to a large-scale long-measurement-time experiment with the implementation of a co-magnetometry. In this study, we derive surface- and volume-averaged root-mean-square normal noise amplitudes at a certain frequency bandwidth for a cylindrical geometry. In addition, we model the source of noise as a finite number of current dipoles and demonstrate a method to simulate temporal and three-dimensional spatial dependencies of JNN. The c…
Quantum Non-Markovian Piecewise Dynamics from Collision Models
2017
Recently, a large class of quantum non-Markovian piecewise dynamics for an open quantum system obeying closed evolution equations has been introduced [B. Vacchini, Phys. Rev. Lett. 117, 230401 (2016)]. These dynamics have been defined in terms of a waiting-time distribution between quantum jumps, along with quantum maps describing the effect of jumps and the system's evolution between them. Here, we present a quantum collision model with memory, whose reduced dynamics in the continuous-time limit reproduces the above class of non-Markovian piecewise dynamics, thus providing an explicit microscopic realization.
Decoherence without entanglement and quantum Darwinism
2020
It is often assumed that decoherence arises as a result of the entangling interaction between a quantum system and its environment, as a consequence of which the environment effectively measures the system, thus washing away its quantum properties. Moreover, this interaction results in the emergence of a classical objective reality, as described by quantum Darwinism. In this Rapid Communication, we show that the idea that entanglement is needed for decoherence is imprecise. We propose a dynamical mixing mechanism capable of inducing decoherence dynamics on a system without creating any entanglement with its quantum environment. We illustrate this mechanism by introducing a simple and exactl…
Modeling epidemics through ladder operators
2020
Highlights • We propose an operatorial model to describe epidemics. • The model describes well the asymptotic numbers of the epidemics. • Ladder operators are used to model exchanges between the “actors” of the system.