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

Assessing the impact of banks’ high-tech investments on efficiency. What is the actual relationship direction?

This paper analyses whether there is any relationship between the efficiency level achieved by Euro Area banking groups and their attitude toward high-tech investments proxied by high-tech patents. We measure banking efficiency via Data Envelopment Analysis (DEA). The period considered is the decade between 2012 and 2021. The results obtained show that there is a generally negative relationship between the two topics under investigation. The evidence obtained justifies the importance of an appropriate level of attention by regulators since increasing levels of technological innovation pursued through significant growth in intangible assets, could negatively affect the overall financial system efficiency

Lending activity efficiency. A comparison between fintech firms and the banking sector

The FinTech phenomenon is undoubtedly increasingly changing the morphology of the global financial system, as well as the existing competitive levers in particular sectors, including lending. The aim of this study is to offer a comparative analysis of the level of efficiency exhibited by FinTech firms operating in this sector with that of banks, which have traditionally carried out this activity. We measure efficiency levels by implementing the Stochastic Data Envelopment Analysis (SDEA). The study, referred to 2021, analyses a data set composed of all the Italian FinTech firms engaged in the lending business and all the Italian banks. We find higher efficiency levels for banks compared to FinTech firms. The results are certainly interesting both at corporate level and for regulatory purposes

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

Seeking the Optimal Dimension of Local Administrative Units: A Reflection on Urban Concentration and Changes in Municipal Size

In the search for a better administrative functioning as a key dimension of economic performances, changes in municipal boundaries and the creation (or suppression) of local administrative units reflect a progressive adjustment to a spatially varying population size and density. With intense population growth, municipal size reflects the overall amount (and spatial concentration) of services and infrastructures, being functionally related with agglomeration economies, land availability for building, and specific sociodemographic attributes of local communities. Based on these premises, the intrinsic relationship between settlement expansion, population growth, and municipal size in a metropolitan region of Southern Europe (Attica, hosting the Greater Athens’ area in Central Greece) was investigated in this study over nearly one century as a contribution to a refined investigation of the (changing) organization of local administrative units under a complete metropolitan cycle from urbanization to reurbanization. Based on descriptive statistics, mapping, (parametric and nonparametric) correlation coefficients, and econometric techniques, a quantitative analysis of the relationship between population size and density and municipal area provides pivotal knowledge to policy and planning adjustments toward a more balanced spatial distribution of population and administered land among local government units. Together with a slight decrease in the average municipal size over time, the average population density per municipal unit increased systematically, with a considerable reduction in spatial heterogeneity of settlements. The observed goodness-of-fit of the linear model explaining municipal area with population density, increased significantly over time. Empirical results of our study indicate that municipal size has slowly adjusted to population density across metropolitan areas, determining an imbalanced spatial distribution of resident population and a supposedly less efficient government partition. The recent administrative reform of local authorities in Greece (the so-called ‘Kallikratis’ law) seems to consolidate–rather than rebalance this organizational structure over space, reflecting spatially polarized settlements. Such conditions represent a base for informed analysis of the spatial structure of local administrative units as a pivotal element of economic sustainability and may contribute to the debate on the optimal size of municipalities at both urban and metropolitan scales of governance