Reinforcement of wood with natural fibers

This paper describes an experimental programme which examines the reinforcement in flexure of timber beams with composite materials based on natural fibers in the form of fabrics made from hemp, flax, basalt and bamboo fibers. The industrial use of natural fibers has been continuously increasing since 1990s due to their advantages in terms of production costs, pollution emissions and energy consumption for production and disposal. The technique allows the reinforcement of the intrados of beams, avoiding the dismantling of the overlying part of the structure with significant savings in terms of costs and work time. The test program consists of three phases incorporating 45 beams. The bending tests on the wooden elements made it possible to measure the increase in capacity and stiffness resulting from the composite reinforcement. This was applied to beams, creating different arrangements and using different quantities (number of layers). Despite the diversity of the various tests carried out, the results obtained in some cases showed significant increases in terms of load-carrying capacity and in deflection ductility

Radiative corrections to the excitonic molecule state in GaAs microcavities

The optical properties of excitonic molecules (XXs) in GaAs-based quantum well microcavities (MCs) are studied, both theoretically and experimentally. We show that the radiative corrections to the XX state, the Lamb shift $\Delta^{\rm MC}_{\rm XX}$ and radiative width $\Gamma^{\rm MC}_{\rm XX}$, are large, about $10-30$ of the molecule binding energy $\epsilon_{\rm XX}$, and definitely cannot be neglected. The optics of excitonic molecules is dominated by the in-plane resonant dissociation of the molecules into outgoing 1$\lambda$-mode and 0$\lambda$-mode cavity polaritons. The later decay channel, ``excitonic molecule $\to$ 0$\lambda$-mode polariton + 0$\lambda$-mode polariton'', deals with the short-wavelength MC polaritons invisible in standard optical experiments, i.e., refers to ``hidden'' optics of microcavities. By using transient four-wave mixing and pump-probe spectroscopies, we infer that the radiative width, associated with excitonic molecules of the binding energy $\epsilon_{\rm XX} \simeq 0.9-1.1$ meV, is $\Gamma^{\rm MC}_{\rm XX} \simeq 0.2-0.3$ meV in the microcavities and $\Gamma^{\rm QW}_{\rm XX} \simeq 0.1$ meV in a reference GaAs single quantum well (QW). We show that for our high-quality quasi-two-dimensional nanostructures the $T_2 = 2 T_1$ limit, relevant to the XX states, holds at temperatures below 10 K, and that the bipolariton model of excitonic molecules explains quantitatively and self-consistently the measured XX radiative widths. We also find and characterize two critical points in the dependence of the radiative corrections against the microcavity detuning, and propose to use the critical points for high-precision measurements of the molecule bindingenergy and microcavity Rabi splitting.Comment: 16 pages, 11 figures, accepted for publication in Phys. Rev.

Lampedusa in Berlin : (Im)Mobilität innerhalb des europäischen Grenzregimes

This paper analyses the mobility practices offorced migrants within the European border regime. It investigates the relation between the control and management mechanisms of migration and the attempts of forced migrants to move freely, crisscrossing territorial and juridical borders in Europe. The paper focuses on the experiences of a group of forced migrants, who, after escaping the war in Libya, obtained humanitarian protection in Italy, but because of the current precarious socio-economic conditions in Southern Europe, decided to leave for North European countries. A group settled in Berlin, which gave rise to a protest claiming the right to stay and work against what is foreseen by European Union law. This paper draws on ethnographic work to show the tension between individual desires and practices of free mobility and the structural and juridical constraints implemented by institutions in order to control it and contain it. Focusing on this (im)mobility highlights the internal borders of Europe and how they are continuously challenged by migrant subjects. Three different kinds of mobility emerge across the European space: mobility within national territory, infra-national mobility, and \u201ccommuting-mobility\u201d. In this way, migrant subjects create new geographies and experience the whole European territory as one place: living in Berlin, renewing documents in Milan, attending education courses in Turin, and working seasonally in Sicily or Apulia. Such mobilities are supported by networks of migrants, who continuously move, and their supporters. This suggests a process of \u201cEuropeanisation from below\u201d that continuously challenges EU internal borders

liquid air energy storage as a polygeneration system to solve the unit commitment and economic dispatch problems in micro grids applications

Abstract Storage technologies play a crucial role in polygeneration plants that attempt to integrate power, thermal and cooling energy systems in order to maximize process efficiency and reduce operating cost. With the increasing penetration of renewable energy into the plant, storage technologies help to dampen the intermittency problem in their energy supply whilst at the same time perform peak shaving to reduce primary energy consumption, thus mitigating pollutant emission. Among the various storage technologies, Liquid Air Energy Storage (LAES) have gathered research interest due to its capability of simultaneously producing electrical and cooling power. Furthermore, unlike Electrochemical Energy Storage (EES) technologies, the LAES lifetime is not heavily dependent on its duty cycle, thus allowing for a calendar life twice or thrice that of EES. In this paper, the economic dispatch of an Eco-building in Singapore has been evaluated using a mixed-integer quadratic programming solver by comparing the adoption of EES and LAES within a capacity range of 300kWh-2000kWh. At the higher end of the capacity range, the LAES configuration results in a higher Net Present Value after 20 years and a shorter time period to obtain the Return of Investment compared to that of EES. At the lower capacity range, both technologies give similar financial returns. Analysis of the results show LAES to be a promising technology to compete with EES in the context of a polygeneration plant and further technology integration is discussed

Resonant nature of phonon-induced damping of Rabi oscillations in quantum dots

Optically controlled coherent dynamics of charge (excitonic) degrees of freedom in a semiconductor quantum dot under the influence of lattice dynamics (phonons) is discussed theoretically. We show that the dynamics of the lattice response in the strongly non-linear regime is governed by a semiclassical resonance between the phonon modes and the optically driven dynamics. We stress on the importance of the stability of intermediate states for the truly coherent control.Comment: 4 pages, 2 figures; final version; moderate changes, new titl

Processus d’évaluation des besoins à l’école québécoise : idéologies linguistiques d’orthophonistes scolaires et sentiment d’in/sécurité linguistique d’élèves plurilingues

Lorsqu’il est mis en œuvre auprès d’élèves issu.e.s de l’immigration ou racisé.e.s, le processus d’évaluation des besoins peut engendrer des phénomènes de sur- ou de sous-représentation de ces élèves en adaptation scolaire. Sachant que les représentations des acteurs et actrices scolaires sur les élèves ont une incidence majeure sur lamise en œuvre de pratiques équitables, cet article vise à dégager les idéologies linguistiques d’orthophonistes scolaires à partir de l’analyse de 21 rapports d’évaluation d’élèves plurilingues. Les résultats montrent que les monolinguismes imposé et assimilationniste, le multilinguisme ségrégationniste ainsi que le plurilinguisme sont présents de manière inégale et différente dans le corpus. La discussion aborde la présence d’idéologies linguistiques fluctuantes entre les participantes et au sein des participantes elles-mêmes ; la faible reconnaissance du répertoire linguistique des élèves et sa cristallisation à travers la langue considérée maternelle, ainsi que les possibles incidences des résultats sur le sentiment d’in/sécurité linguistique des élèves concerné.e.s

A new experimental snow avalanche test site at Seehore peak in Aosta Valley (NW Italian Alps) - Part II: Engineering aspects

The estimate of the effects produced by the impact of a snow avalanche against an obstacle is of the utmost importance in designing safe mountain constructions. For this purpose, an ad-hoc instrumented obstacle was designed and built in order to measure impact forces of small and medium snow avalanches at Seehore peak (NW Italian Alps). The structural design had to consider several specific and unusual demands dictated by the difficult environment. In this article, the new test facility is described from the engineering point of view, discussing the most important aspects of the analyzed problems which were solved before and after the construction. The performance of the instrumented obstacle in the first two operating seasons, and some proposals for future upgrading are eventually illustrate