323,511 research outputs found
25 Gbit/s per user coherent all-optical OFDM for tbit/s-capable PONs
No full textWe propose and test a coherent all-optical orthogonal frequency-division multiplexing (AO-OFDM) system, based on all-optical (de)multiplexing and coherent detection, for multiterabit per second (multi-Tbit/s) passive optical networks (PONs). The proposed approach allows us to greatly increase the downstream data rate per user and extend the standard single-mode fiber reach for future long-reach applications. The compliance with a next-generation PON layout is guaranteed thanks to the exploitation of cyclic arrayed waveguide gratings. Five-user transmission with 12.5 Gbaud quadrature phase shift keying modulation per user (125 Gbit/s downstream capacity per wavelength) over a more than 40 km link has been successfully demonstrated
Balancing sensors and seniors: introducing sensors sensitivity, human sensors and future-self goals
No full textBeing monitored at home as an independent and fit elderly person for the sake of illnesses onset prevention poses big challenges in the design of a meaningful sensors system. In this paper we discuss how a critical understanding of seniors’ felt experience around a predictive sensors system was gained through fieldwork and experience prototyping. Starting from the fieldwork insights, several disruptive opportunity areas for the design of such monitoring systems are elicited and deployed into future scenarios, which explore the possibility of sensors sensitivity attunement; the introduction of the human sensors and the personal setting of future-self goals. The proposed concepts challenge current mainstream research on active ageing, ICT solutions for the elderly population and AI as a black box disjoint from human experience, opening up to a complete new perspective of seniors as agent of their sensors monitoring system
Color transparency effects in exclusive (e,e'p) reactions
No full textcolor transparency is a phenomenon predicted by QCD; it is shown here that it could be possible to study it in exclusive knockout reactions such as (e,e'p) on nuclei
Electroweak structure of the nucleon, meson cloud and light-cone wavefunctions
No full textThe meson-cloud model of the nucleon consisting of a system of three valence quarks surrounded by a meson cloud is applied to study the electroweak structure of the proton and neutron. Light-cone wave functions are derived for the dressed nucleon as pictured to be part of the time a bare nucleon and part of the time a baryon-meson system. Configurations are considered where the baryon can be a nucleon or a Δ and the meson can be a pion as well as a vector meson such as the ρ or the ω. An overall good description of the electroweak form factors is obtained. The contribution of the meson cloud is small and only significant at low Q2. Mixed-symmetry S′-wave components in the wave function are most important to reproduce the neutron electric form factor. Charge and magnetization densities are deduced as a function of both the radial distance from the nucleon center and the transverse distance with respect to the direction of the three-momentum transfer. In the latter case, a central negative charge is found for the neutron. The up and down quark distributions associated with the Fourier transform of the axial form factor have opposite sign, with the consequence that the probability to find an up (down) quark with positive helicity is maximal when it is (anti)aligned with the proton helicity
Numerical stability of the finite element immersed boundary method
No full textsummary:Numerical analysis of a model Stokes interface problem with the homogeneous Dirichlet boundary condition is considered. The interface condition is interpreted as an additional singular force field to the Stokes equations using the characteristic function. The finite element method is applied after introducing a regularization of the singular source term. Consequently, the error is divided into the regularization and discretization parts which are studied separately. As a result, error estimates of order in norm for the velocity and pressure, and of order in norm for the velocity are derived. Those theoretical results are also verified by numerical examples
Nuclear transparency in quasielastic A(e,e ' p): Intranuclear cascade versus eikonal approximation
No full textnuclear transparency is a property due to final-state interactions accompanying the color transparency phenomenon predicted by quantum chromodynamics; it is here explored by means of nucleon knockout reactions and two possible mechanisms to describe the final state interactions of the ejected nucleo
On the hyper-elastic formulation of the immersed boundary method
No full textThe immersed boundary (IB) method is both a mathematical formulation and a numerical method for fluid-structure interaction problems, in which immersed incompressible visco-elastic bodies or boundaries interact with an incompressible fluid. Previous formulations of the IB method were not able to treat appropriately immersed materials of finite, nonzero thickness modeled by general hyper-elastic constitutive laws because of the lack of appropriate transmission conditions between the immersed body and the surrounding fluid in the case of a nonzero jump in normal stress at the solid-fluid interface. (Such a jump does not arise when the solid is comprised of fibers that run parallel to the interface, but typically does arise in other cases, e.g., when the solid contains elastic fibers that terminate at the solid-fluid interface.) We present a derivation of the IB method that takes into account in an appropriate way the missing term. The derivation presented in this paper starts from a separation of the stress that appears in the principle of virtual work. The stress is divided into its fluid-like and solid-like components, and each of these two terms is treated in its natural framework, i.e., the Eulerian framework for the fluid-like stress and the Lagrangian framework for the solid-like stress. We describe how the IB method can be used in conjunction with standard formulations of continuum mechanics models for immersed incompressible elastic materials and present some illustrative numerical experiments
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