Coupled electric and magnetic dipole formulation for planar arrays of dipolar particles: metasurfaces with various electric and/or magnetic meta-atoms per unit cell

The optical properties of infinite planar array of scattering particles, metasurfaces and metagratings, are attracting special attention lately for their rich phenomenology, including both plasmonic and high-refractive-index dielectric meta-atoms with a variety of electric and magnetic resonant responses. Herein we derive a coupled electric and magnetic dipole (CEMD) analytical formulation to describe the reflection and transmission of such periodic arrays, including specular and diffractive orders, valid in the spectral regimes where only dipolar multipoles are needed. Electric and/or magnetic dipoles with all three orientations arising in turn from a single or various meta-atoms per unit cell are considered. The 2D lattice Green function is rewritten in terms of a 1D (chain) version that fully converges and can be easily calculated. Modes emerging as poles of such lattice Green function can be extracted. This formulation can be applied to investigate a wealth of plasmonic, all-dielectric, and hybrid metasurfaces/metagratings of interest throughout the electromagnetic spectrum.Comment: 8 pages, 4 figure

Measurements and calibration of the stripline BPM for the ELI-NP facility with the stretched wire method

A methodology has been developed to perform electrical characterization of the stripline BPMs for the future Gamma Beam System of ELI Nuclear Physics facility in Romania. Several prototype units are extensively benchmarked and the results are presented in this paper. The BPM sensitivity function is determined using a uniquely designed motorized test bench with a stretched wire to measure the BPM response map. Here, the BPM feedthroughs are connected to Libera Brilliance electronics and the wire is fed by continuous wave signal, while the two software-controlled motors provide horizontal and vertical motion of the BPM around the wire. The electrical offset is obtained using S-parameter measurements with a Network Analyzer (via the “Lambertson” method) and is referenced to the mechanical offse

Pâturage: une alternative pour la cultures d’orge à faible rendement

An experiment was performed to evaluate the nutritive value of vitreous-grain barley grazed by sheep (instantaneous stocking rate of 66 sheep/ha). Available biomass (2353 kg dry matter (DM)/ha, on average) was determined at the beginning of the experimental period, which lasted for three consecutive weeks, and barley heads, leaves and stems were separated for quantification. Important amounts of Wimmera ryegrass (Lolium rigidum) were also found. Diet selection, intake and digestibility were estimated using the nalkanes technique. Rumen fermentation characteristics and in situ degradation parameters were obtained from rumen cannulated animals. Transit kinetics of barley heads, leaves and stems was also assessed. The proportion of barley heads in the diet consumed was high (0.53 on average) and varied along the grazing period (0.30 in the first, 0.64 in the second and 0.65 in the third week). Wimmera ryegrass was highly selected during the first week of the experimental period (0.7) and much lesser afterwards (0.35). Estimated total DM intake was low (428, 376 and 657 g/day for weeks 1, 2 and 3, respectively), and chan ged with the botanical composition of the paddock and biomass availability. Average DM digestibility of the diet consumed was also low (56%) and decreased as the grazing period advanced (67%, 55% and 47% for weeks 1, 2 and 3, respectively). Rumen pH was, on average, 6.6, whereas ammonia concentration reached a value of 93 mg/l. Proportions of acetic (0.65), propionic (0.15) and butyric (0.15) acids were representative of a rumen environment driven by fibre fermentation. Effective DM degradability of barley heads, leaves and stems was, on average, 81%, 66% and 55%, respectively.Un essai a été mené pour évaluer la valeur nutritive de l’orge en stade de grain vitreux pâturé par les ovins (taux de charge animale instantanée de 66 brebis/ha). La biomasse disponible (2353 kilogrammes de matière sèche (MS)/ha, en moyenne) a été déterminée au début de la période expérimentale, qui a duré trois semaines consécutives, et les épis, les feuilles et les tiges de l’orge ont été séparés pour leur quantification. Des quantités importantes d’ivraie raide (Lolium rigidum) ont été également rencontrées. Le choix alimentaire, les quantités ingérées et la digestibilité du régime ont été estimés en utilisant la technique des nalcanes. Les caractéristiques de fermentation ruminale et les paramètres de dégradation in situ ont été obtenues en utilisant des animaux canulés dans le rumen. La cinétique de passage des épis, des feuilles et des tiges d’orge a été également évaluée. La proportion des épis d’orge dans le régime consommé était élevée (0,53 en moyenne) et variait le long de la période de pâturage (0,30, 0,64 et 0,65 pendant la première, la deuxième et la troisième semaine respectivement). L’ivraie raide a été fortement choisie pendant la première semaine de la période expérimentale (0,7) et beaucoup moins après (0,35). Les quantités ingérées estimées de MS étaient faibles (428, 376 et 657 g/j pendant la 1ère, 2ème et 3ème semaine, respectivement), et changeaient avec la composition botanique et la disponibilité de la biomasse. La digestibilité moyenne de MS du régime consommé était également faible (56%) et diminuait avec la progression de la période du pâturage (67%, 55% et 47% durant la 1ère, 2ème et 3ème semaine, respectivement). Le pH ruminal était, en moyenne, de 6,6, tandis que la concentration en ammoniaque atteignait une valeur 93 de mg/l. Les proportions d’acide acétique (0,65), propionique (0,15) et butyrique (0,15) étaient représentatives d’un milieu ruminal propice d’une fermentation cellulolytique. La dégradabilité effective de la MS des épis, des feuilles et des tiges d‘orge était, en moyenne, 81%, 66% et 55%, respectivement

Modified dipole-dipole interaction and dissipation in an atomic ensemble near surfaces

We study how the radiative properties of a dense ensemble of atoms can be modified when they are placed near or between metallic or dielectric surfaces. If the average separation between the atoms is comparable or smaller than the wavelength of the scattered photons, the coupling to the radiation field induces long-range coherent interactions based on the interatomic exchange of virtual photons. Moreover, the incoherent scattering of photons back to the electromagnetic field is known to be a many-body process, characterized by the appearance of superradiant and subradiant emission modes. By changing the radiation field properties, in this case by considering a layered medium where the atoms are near metallic or dielectric surfaces, these scattering properties can be dramatically modified. We perform a detailed study of these effects, with focus on experimentally relevant parameter regimes. We finish with a specific application in the context of quantum information storage,where the presence of a nearby surface is shown to increase the storage time of an atomic excitation that is transported across a one-dimensional chain

A near-infrared spectroscopy study on thermal transitions of PMMA and PMMA/SiO2 nanocomposites

In this work infrared spectroscopy in the near infrared (NIR) range is used to study the dynamics of polymethylmethacrylate (PMMA) as a pure polymer and when it is modified with silica nanoparticles. Different ways of analyzing FT-NIR spectra were explored taking the temperature as the variable of the systems: i) bands shifts in terms of the first moment of the wavenumber; ii) bands shifts in terms of an absorbance ratio method and iii) absorbance variations in terms of the integrated absorbance. The spectroscopic analysis allowed to study thermal transitions in PMMA and PMMA based nanocomposites. In particular the method based on the use of an absorbance ratio is the most sensible to analyze the thermal transitions. All bands considered could be used to detect thermal transitions reflecting how the vibrations of the groups CH2; CH3 and C¼O are affected by changes in the free volume of the PMMA. It seems that the PMMA dynamics is more driven by the lateral groups than the backbone of the polymer. The presence of silica nanoparticles, at least when 1% by weight is used, restrains the PMMA motion increasing the relaxation temperatures that can be associated with the glass transitions

Expected seismic performance of irregular isolated bridges

Bridge structures are usually built on irregular topographical surfaces which create substructures with pier heights of different lengths. Three height irregularity types of typical RC medium length bridges are analyzed aimed at determining the best strength and stiffness parameters of an isolation system. The models were located in a high seismicity zone of Mexico. The isolation system is composed by lead rubber bearings (LRB) located on each pile and abutment. The bridge and isolation parameters conducted to the nonlinear time history analysis (NLTHA) of 169 models. Ten seismic records representative of the subduction zone in the Pacific Coast in Mexico were chosen to carry out the study. The maximum drift pier demands, bending moments and shear forces were analyzed to identify the best isolation properties for improving the bridges’ structural behavior, specially focused on looking for avoiding irregularity concentrations of shear forces on piers. Additionally, the seismic response of the bridges supported on traditional neoprene bearings was carried out

Live Migration Downtime Analysis of a VNF Guest for a Proposed Optical FMC Network Architecture

Fixed Mobile Convergence (FMC) implies use of a shared optical fronthaul network infrastructure able to carry transparently both fixed and mobile traffic including Wi-Fi, Mobile and fixed Ethernet. Network Function Virtualization (NFV) is a main enabler for FMC using a shared infrastructure for fixed and mobile gateways. Live migration, a virtualization key-feature, offers load-balancing, increased energy efficiency, application elasticity and other worthy advantages. This paper presents the evaluation of migrating a VNF over an FMC infrastructure. Our results show that, performing a livemigration over a dedicated connection yielded zero downtime and met a benchmark delay. The following scenario, where the ongoing connection is re-routed on a different optical path, shows the successful completion of the migration with an increase in delay of 2.4 seconds (22% higher than the benchmark) and only 2.1 seconds downtime Fixed Mobile Convergence (FMC) implies use of a shared optical fronthaul network infrastructure able to carry transparently both fixed and mobile traffic including Wi-Fi, Mobile and fixed Ethernet. Network Function Virtualization (NFV) is a main enabler for FMC using a shared infrastructure for fixed and mobile gateways. Live migration, a virtualization key-feature, offers load-balancing, increased energy efficiency, application elasticity and other worthy advantages. This paper presents the evaluation of migrating a VNF over an FMC infrastructure. Our results show that, performing a live migration over a dedicated connection yielded zero downtime and met a benchmark delay. The following scenario, where the ongoing connection is re-routed on a different optical path, shows the successful completion of the migration with an increase in delay of 2.4 seconds (22% higher than the benchmark) and only 2.1 seconds downtime

Stability of relative equilibria with singular momentum values in simple mechanical systems

A method for testing $G_\mu$-stability of relative equilibria in Hamiltonian systems of the form "kinetic + potential energy" is presented. This method extends the Reduced Energy-Momentum Method of Simo et al. to the case of non-free group actions and singular momentum values. A normal form for the symplectic matrix at a relative equilibrium is also obtained.Comment: Partially rewritten. Some mistakes fixed. Exposition improve