A feature selection strategy for the analysis of spectra from a photoacoustic sensing system

In the frame of the EU project CUSTOM, a new sensor system for the detection of drug precursors in gaseous samples is being developed, which also includes an External Cavity-Quantum Cascade Laser Photo Acoustic Sensor (ECQCLPAS). In order to define the characteristics of the laser source, the optimal wavenumbers within the most effective 200 cm -1 range in the mid-infrared region must be identified, in order to lead to optimal detection of the drug precursor molecules in presence of interfering species and of variable composition of the surrounding atmosphere. To this aim, based on simulations made with FT-IR spectra taken from literature, a complex multivariate analysis strategy has been developed to select the optimal wavenumbers. Firstly, the synergistic use of Experimental Design and of Signal Processing techniques led to a dataset of 5000 simulated spectra of mixtures of 33 different gases (including the 4 target molecules). After a preselection, devoted to disregard noisy regions due to small interfering molecules, the simulated mixtures were then used to select the optimal wavenumber range, by maximizing the classification efficiency, as estimated by Partial Least Squares - Discriminant Analysis. A moving window 200 cm -1 wide was used for this purpose. Finally, the optimal wavenumber values were identified within the selected range, using a feature selection approach based on Genetic Algorithms and on resampling. The work made will be relatively easily turned to the spectra actually recorded with the newly developed EC-QCLPAS instrument. Furthermore, the proposed approach allows progressive adaptation of the spectral dataset to real situations, even accounting for specific, different environments

CODICE DI PROCEDURA PENALE

Commento sub artt. 669-670 c.p.p.Commento sistematico agli articoli del codice di procedura penale relativi ai sequestr

Corrugated Waveguide Slow-Wave Structure for THz Travelling Wave Tube

THz applications require sources and amplifiers compact, lightweight and powerful. Vacuum electron devices are the candidate solution. Among others, the Corrugated Waveguide Slow-Wave Structure seems particularly suitable for Traveling Wave Tubes in the THz region. THz vacuum electron devices require high precision technological processes with high aspect ratio such as SU-8 process. However, fabrication tolerances could highly affect the overall performances. Therefore a statistical analysis is fundamental for a reliable design. In this summary it is proposed a method based on an analytical model of the corrugated waveguide together with the Pierce theory, to fastly compute the gain of corrugated waveguide vacuum traveling wave tubes. The method is validated by three-dimensional electromagnetic softwares, both for cold and hot parameters. The proved accuracy and fast computation time make the model suitable for performing the sensitivity analysis of the Corrugated waveguide Vacuum tube to be realized by SU-8 technology process

Optical switching matrix as time domain demultiplexer in photonic ADC

A high speed switching matrix has been developed as a cascade of MZM modulators in LiNbO3. The design of the device has been optimized to reduce the switching power drive and the optical power stability with a Bias control loop system. It has been employed in a wideband photonic ADC as a demultiplexer for the optical pulses generated by a MLL. A low pulse to pulse crosstalk has been achieved and the operation of the photonic ADC has been demonstrated. © 2013 EuMA

Electro-optics poled sol-gel materials doped with heterocycle push-pull chromophores

Hybrid organic–inorganic materials doped with zwitterionic push–pull chromophores with high hyperpolarizability have been synthesized via sol–gel, based on glycidoxypropyltrimethoxysilane (GPTMS) and glycidoxypropylmethyldimethoxysilane (GDMMS). Homogeneous films doped with chromophores, have been obtained using N-hydroxyethylcarbazole as a physical spacer avoiding dye aggregation. The waveguiding properties of the spin-coated doped films electrically poled in N2 atmosphere showing second harmonic generation measurements, have been preliminarily measured by m-line spectroscopy before and after poling; the feasibility of channel waveguiding structures has been demonstrated

Drugs and precursor sensing by complementing low cost multiple techniques: overview of the European FP7 project CUSTOM

A large number of techniques for drug precursors chemical sensing has been developed in the latest decades. These techniques are able to screen and identify specific molecules even at very low concentration in lab environment, nevertheless the objective to build up a system which proves to be easy to use, compact, able to provide screening over a large number of compounds and discriminate them with low false alarm rate (FA) and high probability of detection (POD) is still an open issue. The project CUSTOM, funded by the European Commission within the FP7, deals with stand alone portable sensing apparatus based on multiple techniques, integrated in a complex system with a complimentary approach. The objective of the project is to achieve an optimum trade-off between opposite requirements: compactness, simplicity, low cost, sensitivity, low false alarm rate and selectivity. The final goal is the realization of an optical sensing platform able to detect traces of drug precursors compounds, such as ephedrine, safrole, acetic anhydride and the Benzyl Methyl Ketone (BMK). This is reached by implementing two main sensing techniques: the fluorescence enhanced by the use of specially developed Organic macro-molecules, and a spectroscopic technique in Mid-IR optical range. The fluorescence is highly selective with respect to the target compounds, because it is based on properly engineered fluorescent proteins which are able to bind the target analytes, as it happens in an 'immune-type' reaction. The spectroscopic technique is based on the Photo-Acoustic effect, enhanced by the use of a widely Tunable Quantum Cascade Laser. Finally, the sensing platform is equipped with an air sampling system including a pre-concentrator module based on asorption desorption cycles of a syndiotactic polystyrene polymer.European Commission´s FP

Design and Fabrication of a 1 THz Backward Wave Amplifier

The THz frequency range represents a true challenge for designers, fabrication technologies and characterization systems. So far, huge technological obstacles have prohibited any system realization different from laboratory one. Furthermore, most of the applications in the THz frequency range require a level of power not achievable by optoelectronic devices at room temperature or by solid-state technology. The recent availability of three-dimensional simulators and high aspect ratio micro-fabrication techniques has stimulated a class of vacuum electron devices operating in the THz regime, to get a level of output power to enable applications at these frequencies. The OPTHER (Optically driven THz amplifier) project, funded by the European Community, is on the road to realize the first 1 THz vacuum tube amplifier. Technology at the state of the art has been used for the realization of the parts with dimensions supporting THz frequencies. A backward wave amplifier configuration was chosen to make the parts realizable. A carbon nanotube cold cathode has been considered for electron generation. A thermionic micro electron gun was designed to test the tube. A novel slow-wave structure (SWS), the double corrugated rectangular waveguide, was devised to support a cylindrical electron beam and to guarantee a high interaction impedance with limited losses. Both LIGA and UV SU-8 photolithography have been tested to realize the SWS