Optical black hole lasers

Using numerical simulations we show how to realise an optical black hole laser, i.e. an amplifier formed by travelling refractive index perturbations arranged so as to trap light between a white and a black hole horizon. The simulations highlight the main features of these lasers: the growth inside the cavity of positive and negative frequency modes accompanied by a weaker emission of modes that occurs in periodic bursts corresponding to the cavity round trips of the trapped modes. We then highlight a new regime in which the trapped mode spectra broaden until the zero-frequency points on the dispersion curve are reached. Amplification at the horizon is highest for zero-frequencies, therefore leading to a strong modification of the structure of the trapped light. For sufficiently long propagation times, lasing ensues only at the zero-frequency modes.Comment: accepted for publication in Classical and Quantum Gravit

Dynamic Behaviour of "Collapsible" Concrete

In this work a particular cement composite material for protection of structures and infrastructures against accidental actions, such as blast or impact, has been investigated. An experimental procedure has been developed in order to assess static and dynamic behaviour of energy absorbing cementitious composites. The granular cementitious composite has been studied focusing attention to compressive strength, high deformation and energy dissipation capacity which are important characteristics for an absorber material. An experimental characterization of the material behaviour under compressive static and dynamic loadings has been carried out. Different deformation velocities have been studied in order to define the material behaviour in a wide range of strain rates. The velocity range up to 0.1 m/s is investigated by means of a universal servo-hydraulic MTS 50 kN testing machine. Some preliminary results have been reported and discussed in the present work.JRC.G.4-European laboratory for structural assessmen

Spatial properties of twin-beam correlations at low- to high-intensity transition

It is shown that spatial correlation functions measured for correlated photon pairs at the single-photon level correspond to speckle patterns visible at high intensities. This correspondence is observed for the first time in one experimental setup by using different acquisition modes of an intensified CCD camera in low and high intensity regimes. The behavior of intensity auto- and cross-correlation functions in dependence on pump-beam parameters including power and transverse profile is investigated.Comment: 6 pages, 4 figures, accepted for publication in Optics Expres

Building Design for safety and sustainability

The issue of sustainability in the building industry is prominent, as this industry causes large impacts on the environment but also it contributes greatly in a socioeconomic perspective of growth. In line with sustainability the purpose of this report is twofold: to provide a comprehensive description of the current state-of-the-art building assessment methods and to contribute towards sustainability and building design optimisation through the introduction of a comprehensive design approach. In the first part of the report the role of the Environmental methods and Footprint schemes is examined, with a further analysis in the Footprint (PEF, OEF) methods introduced by the European Commission, in ascertaining building sustainability. Footprint schemes provide an environmental assessment on a product-level approach. However, a building is better described as a process rather than a product, while considering the interactions involved in the building life-cycle it seems inappropriate to consider building components in isolation. Current environmental assessment methods evaluate buildings over their life-cycle at a later design stage to provide an indication of their environmental performance. The sole aspect of environmental performance cannot provide comparable building solutions, while at this stage the information cannot effectively used in the general design process. A more effective way of achieving building sustainability is to consider and incorporate environmental issues in the early design stage, where the principles of durability, probabilistic reliability and safety of structures are involved. Since these parameters are part of the same whole they need to be designed together. To move towards sustainability, a new integrated-design approach is deemed essential that will allow building assessment in a multi-performance perspective. In the second part, the Sustainable Structural Design (SSD) methodology is presented built on environmental and structural performance parameters based on a life-cycle approach. Emphasis is put on integrating environmental results in the structural performance, which is treated in a probabilistic manner through the introduction of a simplified Performance-Based Assessment method. A global assessment parameter as the result of ecological costs and structural repair and downtime losses is obtained, which allows diverse stakeholder categories to make decisions in a multi-dimensional perspective. The final part of the report is devoted to further research insights. Both resource efficiency opportunities in the building sector and a respective Communication launched by the European Union in July 2014 are discussed.JRC.G.4-European laboratory for structural assessmen

Characterizing the non-classicality of mesoscopic optical twin-beam states

We present a robust tool to analyze nonclassical properties of multimode twin-beam states in the mesoscopic photon-number domain. The measurements are performed by direct detection. The analysis exploits three different non-classicality criteria for detected photons exhibiting complementary behavior in the explored intensity regime. Joint signal-idler photon-number distributions and quasi-distributions of integrated intensities are determined and compared with the corresponding distributions of detected photons. Experimental conditions optimal for nonclassical properties of twin-beam states are identified.Comment: 10 pages, 10 captioned figure

Applicability of the Sustainable Structural Design (SSD) method at urban/regional/national level

The alarming data on world climatic change, resources impoverishment and increasing human diseases caused by environmental pollution has encouraged the modern society to feel committed in reducing the environmental issues and to adopt a sustainable approach to every human activity. Sustainability is an ambitious challenge for Europe development and European policy is addressed in investing massive resources for achieving sustainable goals. Construction is one of the most impactful industrial sector because of the high consequences it generates on the society, the environment and the economy. Indeed, building constructions involve social aspects, as safety and comfort, economic aspects, as construction investments and maintenance, and environmental aspects, as energy consumption and emissions. The present study derives from the development of a building design method, called Sustainable Structural Design (SSD) Methodology. This methodology is based on a multi-performance and life cycle-oriented approach, which includes the environmental aspects, related to energy consumption and CO2 emissions, in structural design, performed with a simplified Performance Based Assessment (sPBA) methodology, in order to obtain a global assessment parameter in monetary terms. Moreover, the study derives from the awareness about the structural condition of the European building stock, which is old and, in some cases, far from the structural safety required by the European codes. Thus, a simply applicable methodology, allowing the identification of the territorial areas which need a more urgent intervention is necessary. The application of the SSD methodology at territorial level could allow the inclusion of the main aspects of sustainability, identifying the areas which an intervention could reduce the energy consumptions, the CO2 emissions and the structural losses of the included buildings. Thus, this report aims at studying the applicability of the SSD methodology at territorial level, considering three different area dimensions, as countries, regions and cities, and identifying the right approach for each of them. Consequently, an SSD methodology at territorial level is developed and illustrated.JRC.E.4-Safety and Security of Building

Absolute spectroscopy near 7.8 μm with a comb-locked extended-cavity quantum-cascade-laser

We report for the first time the frequency locking of an extended-cavity quantum-cascade-laser (EC-QCL) to a near-infrared frequency comb. The locked laser source is exploited to carry out molecular spectroscopy around 7.8 μm with a line-centre frequency combined uncertainty of ~63 kHz. The strength of the approach, in view of an accurate retrieval of line centre frequencies over a spectral range as large as 100 cm-1, is demonstrated on the P(40), P(18) and R(31) lines of the fundamental rovibrational band of N2O covering the centre and edges of the P and R branches. The spectrometer has the potential to be straightforwardly extended to other spectral ranges, till 12 μm, which is the current wavelength limit for commercial cw EC-QCLs

Conjugating precision and acquisition time in a Doppler broadening regime by interleaved frequency-agile rapid-scanning cavity ring-down spectroscopy

We propose a novel approach to cavity-ring-down-spectroscopy (CRDS) in which spectra acquired with a frequency-agile rapid-scanning (FARS) scheme, i.e., with a laser sideband stepped across the modes of a high-finesse cavity, are interleaved with one another by a sub-millisecond readjustment of the cavity length. This brings to time acquisitions below 20 s for few-GHz-wide spectra composed of a very high number of spectral points, typically 3200. Thanks to the signal-to-noise ratio easily in excess of 10 000, each FARS-CRDS spectrum is shown to be sufficient to determine the line-centre frequency of a Doppler broadened line with a precision of 2 parts over 1011, thus very close to that of sub-Doppler regimes and in a few-seconds time scale. The referencing of the probe laser to a frequency comb provides absolute accuracy and long-term reproducibility to the spectrometer and makes it a powerful tool for precision spectroscopy and line-shape analysis. The experimental approach is discussed in detail together with experimental precision and accuracy tests on the (30 012) â\u86\u90 (00 001) P12e line of CO2at â\u88¼1.57 μm

Comb-calibrated Nonlinear Spectroscopy Of The Q(1) 1-0 Line Of Molecular Hydrogen

Molecular hydrogen is the subject of intensive theoretical and experimental studies because of its relevance to benchmark quantum electrodynamics models. We report an accurate study of the Q(1) 1-0 line of H$_{2}$ through a nonlinear spectroscopy setup based on Stimulated Raman Scattering (SRS) and comb calibration of the frequency axis. Systematic uncertainties affecting the apparatus, mainly due to pointing instabilities of pump and Stokes beams and to temperature drifts of the gas cell, have been reduced to about 200 kHz, which is comparable to statistical and systematic errors expected from the global fitting of multi-pressure SRS spectra. We performed measurements over two decades of pressure, from 0.05 to 5 bar, using low-pressure spectra to extrapolate the transition frequency of the isolated molecule, and high-pressure spectra to test collisional lineshape models. Our results are likely to be of relevance for a deeper understanding of H$_{2}$ physics and for bringing theory-vs-experiment comparison on the Q(1) 1-0 line-centre frequency below 1 MHz

Exploiting magnetic properties of Fe doping in zirconia

In this study we explore, both from theoretical and experimental side, the effect of Fe doping in ZrO2 (ZrO2:Fe). By means of first principles simulation we study the magnetization density and the magnetic interaction between Fe atoms. We also consider how this is affected by the presence of oxygen vacancies and compare our findings with models based on impurity band and carrier mediated magnetic interaction. Experimentally thin films (~ 20 nm) of ZrO2:Fe at high doping concentration are grown by atomic layer deposition. We provide experimental evidence that Fe is uniformly distributed in the ZrO2 by transmission electron microscopy and energy dispersive X-ray mapping, while X-ray diffraction evidences the presence of the fluorite crystal structure. Alternating gradient force magnetometer measurements show magnetic signal at room temperature, however with low magnetic moment per atom. Results from experimental measures and theoretical simulations are compared.Comment: 8 pages, 9 figures. JEMS 201