Cooling electrons from 1 K to 400 mK with V-based nanorefrigerators

The fabrication and operation of V-based superconducting nanorefrigerators is reported. Specifically, electrons in an Al island are cooled thanks to hot-quasiparticle extraction provided by tunnel-coupled V electrodes. Electronic temperature reduction down to 400 mK starting from 1 K is demonstrated with a cooling power ~20 pW at 1 K for a junction area of 0.3 micron^2. The present architecture extends to higher temperatures refrigeration based on tunneling between superconductors and paves the way to the implementation of a multi-stage on-chip cooling scheme operating from above 1 K down to the mK regime.Comment: 3+ pages, 4 color figure

Energy harvesting from earthquake for vibration-powered wireless sensors

Wireless sensor networks can facilitate the acquisition of useful data for the assessment and retrofitting of existing structures and infrastructures. In this perspective, recent studies have presented numerical and experimental results about self-powered wireless nodes for structural monitoring applications in the event of earthquake, wherein the energy is scavenged from seismic accelerations. A general computational approach for the analysis and design of energy harvesters under seismic loading, however, has not yet been presented. Therefore, this paper proposes a rational method that relies on the random vibrations theory for the electromechanical analysis of piezoelectric energy harvesters under seismic ground motion. In doing so, the ground acceleration is simulated by means of the Clough-Penzien filter. The considered piezoelectric harvester is a cantilever bimorph modeled as Euler-Bernoulli beam with concentrated mass at the free-end, and its global behavior is approximated by the dynamic response of the fundamental vibration mode only (which is tuned with the dominant frequency of the site soil). Once the Lyapunov equation of the coupled electromechanical problem has been formulated, mean and standard deviation of the generated electric energy are calculated. Numerical results for a cantilever bimorph which piezoelectric layers made of electrospun PVDF nanofibers are discussed in order to understand issues and perspectives about the use of wireless sensor nodes powered by earthquakes. A smart monitoring strategy for the experimental assessment of structures in areas struck by seismic events is finally illustrated

Assessment of the impact of ship emissions on the air quality in Naples

The paper reports the results of a monitoring campaign of SO2, NO2 and Benzene carried out in the port of Naples and inside the nearby urban canopy from 20th January to 8th March 2016. The activity is a continuation of a previous monitoring campaign realized by the authors in 2012. About 40 passive samplers were placed and average concentration in the period for the three pollutants was evaluated. Concentration levels observed are lower than limit values established by European directives both for SO2 and NO2. Benzene in some place of measure exceeded the limit value (5 ìg/m3) that is fixed, however, as annual average. Results have been interpreted by an interpolation algorithm using the software SURFER® obtaining contour maps that show significant differences among the three pollutants. In fact, maximum levels of SO2 occur inside the harbour area, those of NO2 inside the urban area while Benzene maximum average concentrations in the period occur at the boundary between port and urban canopy. This result has been interpreted on the basis of the occurrences of wind direction and speed measured in the same observation period

KGTorrent: A dataset of python jupyter notebooks from kaggle

Computational notebooks have become the tool of choice for many data scientists and practitioners for performing analyses and disseminating results. Despite their increasing popularity, the research community cannot yet count on a large, curated dataset of computational notebooks. In this paper, we fill this gap by introducing KGTorrent, a dataset of Python Jupyter notebooks with rich metadata retrieved from Kaggle, a platform hosting data science competitions for learners and practitioners with any levels of expertise. We describe how we built KGTorrent, and provide instructions on how to use it and refresh the collection to keep it up to date. Our vision is that the research community will use KGTorrent to study how data scientists, especially practitioners, use Jupyter Notebook in the wild and identify potential shortcomings to inform the design of its future extensions

Towards productizing AI/ML Models: An industry perspective from data scientists

The transition from AI/ML models to production-ready AI-based systems is a challenge for both data scientists and software engineers. In this paper, we report the results of a workshop conducted in a consulting company to understand how this transition is perceived by practitioners. Starting from the need for making AI experiments reproducible, the main themes that emerged are related to the use of the Jupyter Notebook as the primary prototyping tool, and the lack of support for software engineering best practices as well as data science specific functionalities

Quantification of energy-related parameters for near-fault pulse-like seismic ground motions

An energy-based approach facilitates the explicit consideration of the damage associated with both maximum displacements and cumulative plastic deformations under earthquakes. For structural systems that can undergo pulse-like seismic ground motions close to causative faults, an energy-based approach is deemed especially appropriate with respect to well-established force-or displacement-based strategies. In such a case, in fact, most of the damage is attributable to the dominant pulse-like component, which usually occurs into the velocity time history of the seismic ground motion, thus implying high energy levels imparted to a structural system. In order to enable the implementation of an energy-based approach in the analysis and design of structures under near-fault pulse-like seismic ground motions, this study presents a comprehensive numerical investigation about the influence of seismological parameters and hysteretic behavior on the spectra of the following energy-related parameters: inelastic absolute and relative input energy; input energy reduction factor; hysteretic energy dissipation demand; hysteretic energy reduction factor; dimensionless cumulative plastic deformation ratio. Closed-form approximations are proposed for these spectra, and the numerical values of the corresponding parameters have been also calibrated (with reference to both mean and standard deviation values) as functions of earthquake magnitude, type of hysteretic behavior (i.e., non-degrading or degrading) and ductility level. The outcomes of this study are meant to support the derivation of design spectra for the energy-based seismic design of structures under near-fault pulse-like seismic ground motions

Validation of an Emission Model for a Marine Diesel Engine with Data from Sea Operations

In this study, a model is developed to simulate the dynamics of an internal combustion engine, and it is calibrated and validated against reliable experimental data, making it a tool that can effectively be adopted to conduct emission predictions. In this work, the Ricardo WAVE software is applied to the simulation of a particular marine diesel engine, a four-stroke engine used in the maritime field. Results from the bench tests are used for the calibration of the model. Finally, the calibration of the model and its validation with full-scale data measured at sea are presented. The prediction includes not only the classic engine operating parameters for a comparison with surveys but also an estimate of nitrogen oxide emissions, which are compared with similar results obtained with emission factors. The calibration of the model made it possible to obtain an overlap between the simulation results and real data with an average error of approximately 7% on power, torque, and consumption. The model provides encouraging results, suggesting further applications, such as in the study on transient conditions, coupling of the engine model with the ship model for a complete simulation of the operating conditions, and optimization studies on consumption and emissions. The availability of the emission data during the sea trial and validated simulation results are the strengths and novelties of this work

Novel Scintillating Materials Based on Phenyl-Polysiloxane for Neutron Detection and Monitoring

Neutron detectors are extensively used at many nuclear research facilities across Europe. Their application range covers many topics in basic and applied nuclear research: in nuclear structure and reaction dynamics (reaction reconstruction and decay studies); in nuclear astrophysics (neutron emission probabilities); in nuclear technology (nuclear data measurements and in-core/off-core monitors); in nuclear medicine (radiation monitors, dosimeters); in materials science (neutron imaging techniques); in homeland security applications (fissile materials investigation and cargo inspection). Liquid scintillators, widely used at present, have however some drawbacks given by toxicity, flammability, volatility and sensitivity to oxygen that limit their duration and quality. Even plastic scintillators are not satisfactory because they have low radiation hardness and low thermal stability. Moreover organic solvents may affect their optical properties due to crazing. In order to overcome these problems, phenyl-polysiloxane based scintillators have been recently developed at Legnaro National Laboratory. This new solution showed very good chemical and thermal stability and high radiation hardness. The results on the different samples performance will be presented, paying special attention to a characterization comparison between synthesized phenyl containing polysiloxane resins where a Pt catalyst has been used and a scintillating material obtained by condensation reaction, where tin based compounds are used as catalysts. Different structural arrangements as a result of different substituents on the main chain have been investigated by High Resolution X-Ray Diffraction, while the effect of improved optical transmittance on the scintillation yield has been elucidated by a combination of excitation/fluorescence measurements and scintillation yield under exposure to alpha and {\gamma}-rays.Comment: InterM 2013 - International Multidisciplinary Microscopy Congres