The influence of service temperature on bond between FRP reinforcement and concrete

The interest in fibre reinforced polymer (FRP) reinforcement in construction has considerably increased and especially the application of FRP as externally bonded reinforcement (FRP EBR) has become more and more established. The use of FRP EBR has been adopted world-wide as a very attractive technique for structural strengthening and rehabilitation. At Ghent university, the fire behaviour of slabs and beams strengthened with advanced composites, including the use of fire protection systems, has been investigated. In addition, the behaviour of the FRP-concrete interface at increased temperatures has been considered, as elevated temperatures may occur during service conditions, especially for outdoor applications. According to fib Bulletin 14, the glass transition temperature of the adhesive used to bond the FRP should equal 20°C in excess of the maximum ambient temperature at normal service conditions, and should be at least 45°C. When reaching the glass transition temperature, the properties of the adhesive decrease to a large extend and bond interaction between the concrete and the external FRP reinforcement may be completely lost. To study the bond behaviour at elevated temperatures, a joint test program between the Universities of Ghent and Lecce has been executed, comprising a series of 20 bond tests performed at the Magnel Laboratory for Concrete Research. The present paper will discuss the experimental work and the main test results obtained

Note on the helicity decomposition of spin and orbital optical currents

In the helicity representation, the Poynting vector (current) for a monochromatic optical field, when calculated using either the electric or the magnetic field, separates into right-handed and left-handed contributions, with no cross-helicity contributions. Cross-helicity terms do appear in the orbital and spin contributions to the current. But when the electric and magnetic formulas are averaged ('electric-magnetic democracy'), these terms cancel, restoring the separation into right-handed and left-handed currents for orbital and spin separately.Comment: 10 pages, no figure

A mobility analysis of the occupational status of the graduates of the University of Palermo in an economic crisis context

In such a global economic crisis context, our aims are describing the mobility of the Palermitan graduates in the labour market, identifying the variables that influence most their occupational status and finally outlining a transition probability structure among the states: Work, Search for a Job, Study, Other. The availability of a large amount of longitudinal data provided by the surveys carried out by STELLA (Statistics about Graduates and Labour Market) allowed us to analyze the mobility of the graduates of the University of Palermo among the different occupational states in three different times. We analyze data coming from a disproportionate stratified sample of graduates in 2009, interviewed three different times: one year (2010), three years (2012), five years (2014) after the graduation. To achieve our aim, first we provide a brief descriptive analysis of the main characteristics of the graduates gathered by the three different surveys; secondly we fit a time inhomogeneous multi-state Markov model with piecewise constant intensities; eventually implications from the main results are discussed

Orbital angular momentum induced beam shifts

We present experiments on Orbital Angular Momentum (OAM) induced beam shifts in optical reflection. Specifically, we observe the spatial Goos-H\"anchen shift in which the beam is displaced parallel to the plane of incidence and the angular Imbert-Fedorov shift which is a transverse angular deviation from the geometric optics prediction. Experimental results agree well with our theoretical predictions. Both beam shifts increase with the OAM of the beam; we have measured these for OAM indices up to 3. Moreover, the OAM couples these two shifts. Our results are significant for optical metrology since optical beams with OAM have been extensively used in both fundamental and applied research.Comment: 7 pages, 7 figure

How orbital angular momentum affects beam shifts in optical reflection

It is well known that reflection of a Gaussian light beam ($\text{TEM}_{00}$) by a planar dielectric interface leads to four beam shifts when compared to the geometrical-optics prediction. These are the spatial Goos-H\"{a}nchen (GH) shift, the angular GH shift, the spatial Imbert-Fedorov (IF) shift and the angular IF shift. We report here, theoretically and experimentally, that endowing the beam with Orbital Angular Momentum (OAM) leads to coupling of these four shifts; this is described by a $4 \times 4$ mixing matrix.Comment: v2 Version accepted for publication in Phys. Rev.